Science.gov

Sample records for rheological properties

  1. Rheological properties of defense waste slurries

    SciTech Connect

    Ebadian, M.A.

    1998-01-01

    The major objective of this two-year project has been to obtain refined and reliable experimental data about the rheological properties of melter feeds. The research has involved both experimental studies and model development. Two experimental facilities have been set up to measure viscosity and pressure drop. Mathematical models have been developed as a result of experimental observation and fundamental rheological theory. The model has the capability to predict the viscosity of melter slurries in a range of experimental conditions. The final results of the investigation could be used to enhance the current design base for slurry transportation systems and improve the performance of the slurry mixing process. If successful, the cost of this waste treatment will be reduced, and disposal safety will be increased. The specific objectives for this project included: (1) the design, implementation, and validation of the experimental facility in both batch and continuous operating modes; (2) the identification and preparation of melter feed samples of both the SRS and Hanford waste slurries at multiple solids concentration levels; (3) the measurement and analysis of the melter feeds to determine the effects of the solids concentration, pH value, and other factors on the rheological properties of the slurries; (4) the correlation of the rheological properties as a function of the measured physical and chemical parameters; and (5) transmission of the experimental data and resulting correlation to the DOE site user to guide melter feed preparation and transport equipment design.

  2. Aggregate of nanoparticles: rheological and mechanical properties

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Wu, Xiaojun; Yang, Wei; Zhai, Yuanming; Xie, Banghu; Yang, Mingbo

    2011-12-01

    The understanding of the rheological and mechanical properties of nanoparticle aggregates is important for the application of nanofillers in nanocompoistes. In this work, we report a rheological study on the rheological and mechanical properties of nano-silica agglomerates in the form of gel network mainly constructed by hydrogen bonds. The elastic model for rubber is modified to analyze the elastic behavior of the agglomerates. By this modified elastic model, the size of the network mesh can be estimated by the elastic modulus of the network which can be easily obtained by rheology. The stress to destroy the aggregates, i.e., the yield stress ( σ y ), and the elastic modulus ( G') of the network are found to be depended on the concentration of nano-silica ( ϕ, wt.%) with the power of 4.02 and 3.83, respectively. Via this concentration dependent behavior, we can extrapolate two important mechanical parameters for the agglomerates in a dense packing state ( ϕ = 1): the shear modulus and the yield stress. Under large deformation (continuous shear flow), the network structure of the aggregates will experience destruction and reconstruction, which gives rise to fluctuations in the viscosity and a shear-thinning behavior.

  3. Rheological Properties of Iron Oxide Based Ferrofluids

    NASA Astrophysics Data System (ADS)

    Devi, M.; Mohanta, D.

    2009-06-01

    In the present work, we report synthesis and magneto-viscous properties of cationic and anionic surfactant coated, iron oxide nanoparticles based ferrofluids. Structural and morphological aspects are revealed by x-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. We compare the rheological/magneto-viscous properties of different ferrofluids for various shear rates (2-450 sec-1) and applied magnetic fields (0-100 gauss). In the absence of a magnetic field, and under no shear case, the ferrofluid prepared with TMAH coated particle is found to be 12% more viscous compared to its counterpart. The rheological properties are governed by non-Newtonian features, and for a definite shear rate, viscosity of a given ferrofluid is found to be strongly dependent on the applied magnetic field as well as nature of the surfactant.

  4. Nanoparticles in Polymers: Assembly, Rheology and Properties

    NASA Astrophysics Data System (ADS)

    Rao, Yuanqiao

    Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties. Jeff Munro, Stephanie Potisek, Phillip Hustad; all of the Dow Chemical Company are co-authors.

  5. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    SciTech Connect

    Chuanping Li

    2004-12-19

    Colloidal processing is an effective and reliable approach in the fabrication of the advanced ceramic products. Successful colloidal processing of fine ceramic powders requires accurate control of the rheological properties. The accurate control relies on the understanding the influences of various colloidal parameters on the rheological properties. Almost all research done on the rheology paid less attention to the interactions of particle and solvent. However, the interactions of the particles are usually built up through the media in which the particles are suspended. Therefore, interactions of the particle with the media, the adsorbed layers on the particle surface, and chemical and physical properties of media themselves must influence the rheology of the suspension, especially for the dense suspensions containing nanosized particles. Relatively little research work has been reported in this area. This thesis addresses the rheological properties of nanometric alumina aqueous suspensions, and paying more attention to the interactions between particle and solvent, which in turn influence the particle-particle interactions. Dense nanometric alumina aqueous suspensions with low viscosity were achieved by environmentally-benign fructose additives. The rheology of nanometric alumina aqueous suspensions and its variation with the particle volume fraction and concentration of fructose were explored by rheometry. The adsorptions of solute (fructose) and solvent (water) on the nanometric alumina particle surfaces were measured and analyzed by TG/DSC, TOC, and NMR techniques. The mobility of water molecules in the suspensions and its variation with particle volume fractions and fructose additive were determined by the {sup 17}O NMR relaxation method. The interactions between the nanometric alumina particles in water and fructose solutions were investigated by AFM. The results indicated that a large number of water layers were physically bound on the particles' surfaces

  6. Rheological properties of sulfoacetate derivatives of cellulose.

    PubMed

    Chauvelon, Gaëlle; Doublier, Jean-Louis; Buléon, Alain; Thibault, Jean-François; Saulnier, Luc

    2003-04-01

    Water-soluble cellulose acetate sulfate derivatives (CAS) have been prepared through chemical reaction involving sulfuric acid as a catalyst. These CAS have been obtained from cellulosic materials of different origins (pure cellulose, wheat bran, maize bran) and their rheological behavior in salt-free aqueous solution has been estimated in dilute and semi-dilute regime using dynamic viscoelastic and viscosity measurements. Influence of concentration, temperature of solubilization and temperature of measurement has been investigated. Weak gel-like properties were exhibited at elevated concentration (typically above 7-8 g/L). These systems also exhibited thixotropic properties: the structure was partly broken down upon shearing and recovered at rest. They also displayed thermoreversibility with large hysteresis, the melting temperature being approximately 15 degrees C higher than the temperature at which gelation took place. These overall observations clearly indicate that these distinctive properties arise from intermolecular association of the macromolecular chains of the cellulose derivative. PMID:12668095

  7. Rheological properties of a vesicle suspension.

    PubMed

    Guedda, M; Benlahsen, M; Misbah, C

    2014-11-01

    The rheological behavior of a dilute suspension of vesicles in linear shear flow at a finite concentration is analytically examined. In the quasispherical limit, two coupled nonlinear equations that describe the vesicle orientation in the flow and its shape evolution were derived [Phys. Rev. Lett. 96, 028104 (2006)PRLTAO0031-900710.1103/PhysRevLett.96.028104] and serve here as a starting point. Of special interest is to provide, for the first time, an exact analytical prediction of the time-dependent effective viscosity η_{eff} and normal stress differences N_{1} and N_{2}. Our results shed light on the effect of the viscosity ratio λ (defined as the inner over the outer fluid viscosities) as the main controlling parameter. It is shown that η_{eff},N_{1}, and N_{2} either tend to a steady state or describe a periodic time-dependent rheological response, previously reported numerically and experimentally. In particular, the shear viscosity minimum and the cusp singularities of η_{eff},N_{1}, and N_{2} at the tumbling threshold are brought to light. We also report on rheology properties for an arbitrary linear flow. We were able to obtain a constitutive law in a closed form relating the stress tensor to the strain rate tensor. It is found that the resulting constitutive markedly contrasts with classical laws known for other complex fluids, such as emulsions, capsule suspensions, and dilute polymer solutions (Oldroyd B model). We highlight the main differences between our law and classical laws. PMID:25493791

  8. Using Ultrasound to Measure Mud Rheological Properties

    NASA Astrophysics Data System (ADS)

    Maa, P. Y. P. Y.; Kwon, J. I.; Park, K. S.

    2015-12-01

    In order to predict the dynamic responses of newly consolidated cohesive sediment beds, a better understanding of the material rheological properties (bulk density, ρ, kinematic viscosity, ν, and shear modulus, G, assuming mud is a simple Voigt viscoelastic model) of these sediment beds is needed. An acoustic approach that uses a commercially available 250 kHz shear wave transducer and tone-burst waves has been developed to measure those properties. This approach uses a 86.3 mm long delay-line (DL) to separate the generated pressure and shear waves, and measures the reflected shear waves as well as the reflected pressure waves caused at the interface between the delay line and the mud to interpret these properties. By using materials (i.e., air, water, olive oil, and honey) with available rheological properties to establish a calibration relationship between the information carried by the measured reflected waves and those given material properties, the mud properties as well as thνe change of these properties during consolidation can be interpreted. Using jelly pudding as a check, a value of G ≈ 12310 N/m2 and ν ≈ 5 x 10-5 m2/s were estimated. For the consolidating kaolinite bed (with zero salinity and initial suspended sediment concentration about 420 g/cm3), the measurements show that the shear modulus developed after about 40 hours and approached a value on the order of 15000 N/m2 after about 100 hours. The initial kinematic viscosity was about 5 x 10-4 m2/s, and it decreased slowly with time and approached a low plateau between 10-6 and 10-7 m2/s after 300 hours. The measured bulk density showed a small increasing rate during the entire consolidation period, except at a short period between 80 and 90 hours after consolidation. Results from this study suggest a promising approach for developing an in-situ instrument to measure mud properties, as well as many other materials in other industries.

  9. Rheological properties of heavy oils and heavy oil emulsions

    SciTech Connect

    Khan, M.R.

    1996-06-01

    In this study, the author investigated the effects of a number of process variables such as shear rate, measurement temperature, pressure, the influence of pretreatment, and the role of various amounts of added water on the rheology of the resulting heavy oil or the emulsion. Rheological properties of heavy oils and the corresponding emulsions are important from transportation and processing standpoints.

  10. Rheological Properties and Transfer Phenomena of Nanofluids

    NASA Astrophysics Data System (ADS)

    Jung, Kang-min; Kim, Sung Hyun

    2008-07-01

    This study focused on the synthesis of stable nanofluids and investigation of their rhelogical properties and transfer phenomena. Nanofluids of diamond/ethylene glycol, alumina/transformer oil and silica/water were made to use in this study. Rheological properties of diamond nanofluids were determined at constant temperature (25 °C) using a viscometer. For the convective heat transfer experiment, alumina nanofluid passed through the plate heat exchanger. CO2 absorption experiment was conducted in a bubble type absorber containing silica nanofluid. Diamond nanofluid showed non-Newtonian behaviors under a steady-shear flow except the case of very low concentration of solid nanoparticles. The heat transfer coefficient of alumina nanofluid was higher than that of base fluid. One possible reason is that concentration of nanoparticles at the wall side is higher than that of microparticles. Silica nanofluid showed that both average CO2 absorption rate and total absorption amount enhanced than those of base fluid. The stably suspended nanoparticles create a mesh-like structure. That structure arrangement cracks the gas bubble and increases the surface area.

  11. Biodegradable compounds: Rheological, mechanical and thermal properties

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  12. Dynamic and rheological properties of soft biological cell suspensions

    PubMed Central

    Yazdani, Alireza; Li, Xuejin

    2016-01-01

    Quantifying dynamic and rheological properties of suspensions of soft biological particles such as vesicles, capsules, and red blood cells (RBCs) is fundamentally important in computational biology and biomedical engineering. In this review, recent studies on dynamic and rheological behavior of soft biological cell suspensions by computer simulations are presented, considering both unbounded and confined shear flow. Furthermore, the hemodynamic and hemorheological characteristics of RBCs in diseases such as malaria and sickle cell anemia are highlighted. PMID:27540271

  13. THERMAL AND RHEOLOGICAL PROPERTIES OF LUPINUS ALBUS FLOUR MEAL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is very little research done in the area of structure and function relationships of lupin meal or lupin native protein. The scope of this work is to study lupin's native proteins thermal and rheological properties in whole meal. The effect of pH and heat treatment on the thermal properties o...

  14. THERMAL AND RHEOLOGICAL PROPERTIES OF LUPINUS ALBUS FLOUR MEAL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research on the structure and function relationships of lupin meal or lupin native protein is limited. The scope of this work is to study lupin's native proteins' thermal and rheological properties in whole meal. The effect of pH and heat treatment on the thermal properties of lupin meal was studi...

  15. Rheological Properties of Enzymatically Isolated Tomato Fruit Cuticle.

    PubMed Central

    Petracek, P. D.; Bukovac, M. J.

    1995-01-01

    Rheological properties were determined for cuticular membranes (CMs) enzymatically isolated from mature tomato (Lycopersicon esculentum Mill. cv Pik Red) fruit. The cuticle responded as a viscoelastic polymer in stress-strain studies. Both CM and dewaxed CM expanded and became more elastic and susceptible to fracture when hydrated, suggesting that water plasticized the cuticle. Dewaxing of the CM caused similar changes in elasticity and fracturing, indicating that wax may serve as a supporting filler in the cutin matrix. Exposure of the cuticle to the surfactant Triton X-100 did not significantly affect its rheological properties. PMID:12228622

  16. Pasting and rheological properties of quinoa-oat composites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quinoa (Chenopodium, quinoa) flour, known for its essential amino acids, was composited with oat products containing ß-glucan known for lowering blood cholesterol and preventing heart disease. Quinoa-oat composites were developed and evaluated for their pasting and rheological properties by a Rapid ...

  17. Rheological properties of simulated debris flows in the laboratory environment

    USGS Publications Warehouse

    Ling, Chi-Hai; Chen, Cheng-lung; Jan, Chyan-Deng

    1990-01-01

    Steady debris flows with or without a snout are simulated in a 'conveyor-belt' flume using dry glass spheres of a uniform size, 5 or 14 mm in diameter, and their rheological properties described quantitatively in constants in a generalized viscoplastic fluid (GVF) model. Close agreement of the measured velocity profiles with the theoretical ones obtained from the GVF model strongly supports the validity of a GVF model based on the continuum-mechanics approach. Further comparisons of the measured and theoretical velocity profiles along with empirical relations among the shear stress, the normal stress, and the shear rate developed from the 'ring-shear' apparatus determine the values of the rheological parameters in the GVF model, namely the flow-behavior index, the consistency index, and the cross-consistency index. Critical issues in the evaluation of such rheological parameters using the conveyor-belt flume and the ring-shear apparatus are thus addressed in this study.

  18. Rheological Properties of Liquid and Particle Stabilized Foam

    NASA Astrophysics Data System (ADS)

    Özarmut, A. Ö.; Steeb, H.

    2015-04-01

    In Earth-Pressure-Balance (EPB) tunnelling the excavated ground is used as face support medium to prevent surface settlements. In general, the excavated ground (e.g. for cohesionless soils) does not exhibit suitable conditions to support the tunnelling face. This technical challenge can be solved by adding conditioning agents that are mainly foams. In order to physically understand the rheological properties of the (added) liquid foam and the foam-soil (foam-particle) mixture and to comprehend its influence on the soil, advanced rheological investigations are necessary. Therefore, rheological experiments such as flow curve tests have been performed to determine the effective yield stress. Since the morphology, i.e. the microstructure of the foam accounts for effective rheological properties, size, shape and distribution of the cells of the foam and particle-laden foam were characterized in detail applying imaging techniques. In order to perform the above mentioned experiments, polymer- stabilised shaving foam seems to be a good replacement of tunnelling foam and suitable for laboratory tests due to its time stability, characteristic length scales of the microstructure and accessibility. Glass beads (of different diameter and volume fractions, i.e. specific surface areas) are used to investigate the effective material behaviour of foam-particle mixtures. The experimental results are compared with yield stress models of modified Herschel-Bulkley- Papanastasiou type.

  19. Rheological properties of kaolin and chemically simulated waste

    SciTech Connect

    Selby, C.L.

    1981-12-01

    The Savannah River Laboratory is conducting tests to determine the best operating conditions of pumps used to transfer insoluble radioactive sludges from old to new waste tanks. Because it is not feasible to conduct these tests with real or chemically simulated sludges, kaolin clay is being used as a stand-in for the solid waste. The rheology tests described herein were conducted to determine whether the properties of kaolin were sufficiently similar to those of real sludge to permit meaningful pump tests. The rheology study showed that kaolin can be substituted for real waste to accurately determine pump performance. Once adequately sheared, kaolin properties were found to remain constant. Test results determined that kaolin should not be allowed to settle more than two weeks between pump tests. Water or supernate from the waste tanks can be used to dilute sludge on an equal volume basis because they identically affect the rheological properties of sludge. It was further found that the fluid properties of kaolin and waste are insensitive to temperature.

  20. Rheological and thermal properties of PP-based WPC

    NASA Astrophysics Data System (ADS)

    Mazzanti, V.; Mollica, F.; El Kissi, N.

    2014-05-01

    Wood Plastic Composite (WPC) has attracted great interest in outdoor building products for the reduced cost and the possibility of using recycled materials. Nevertheless the material shows two problems: the large viscosity due to the presence of high concentrations of filler and the degradation of cellulose during processing The aim of this work was to investigate the rheological and thermal properties of WPC. The material used for the experiments was a commercial PP-based WPC compound, with different concentrations of natural fibers (30, 50, 70% wt.). The thermal properties were studied to check for degradation of natural fibers during the subsequent rheological tests. Analyzing the storage and loss moduli and the complex viscosity curves obtained using a parallel plate rheometer it was possible to observe some features related to the viscoelastic nature of the composite.

  1. Rheological properties of polyolefin composites highly filled with calcium carbonate

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Fierro, Annalisa; Jakubowska, Paulina; Sterzynski, Tomasz

    2016-05-01

    In this paper the rheological properties of highly filled polyolefin composites (HFPCs) have been investigated. Calcium carbonate (CaCO3), with stearic acid modified surface, was used as filler. Ternary compounds have been obtained by the inclusion of a CaCO3/polypropylene master batch into the high density polyethylene matrix. The highly filled polyolefin composites with CaCO3 content in the range between 40 and 64 wt% have been prepared in the molten state using a single-screw extruder, the temperature of the extrusion die was set at 230°C. The melt rheological properties of the HFPCs have been extensively investigated both in oscillatory and steady shear flow.

  2. Shape Oscillations of Gas Bubbles With Newtonian Interfacial Rheological Properties

    NASA Technical Reports Server (NTRS)

    Nadim, Ali

    1996-01-01

    The oscillation frequency and damping rate for small-amplitude axisymmetric shape modes of a gas bubble in an ideal liquid are obtained, in the limit when the bubble interface possesses Newtonian interfacial rheology with constant surface shear and dilatational viscosities. Such results permit the latter surface properties to be measured by analyzing experimental data on frequency shift and damping rate of specific shape modes of suspended bubbles in the presence of surfactants.

  3. Rheology and Wetting Properties of Fluxes for Flip Chip Packages

    NASA Astrophysics Data System (ADS)

    Wang, Jinlin

    2008-07-01

    The rheological properties, wettability, and fluxability of fluxes for flip chip packages were studied. The flux viscosity showed significant decrease from room temperature to the peak reflow temperature. The viscosity of fluxes decreased after kneading process. One of the reasons of the viscosity decrease for some fluxes during the kneading is the moisture uptake. The tackiness of the fluxes increased with both applied load and retraction speed.

  4. The effect of temperature on rheological properties of endodontic sealers

    PubMed Central

    Rai, Roshni U.; Singbal, Kiran P.; Parekh, Vaishali

    2016-01-01

    Aim: The purpose of this study was to investigate temperature-dependent rheological properties of three endodontic sealers MTA Fillapex (Angelus, Brazil), AH Plus (Dentsply, Germany), and EndoREZ (Ultradent, USA). Materials and Methods: Five samples of each group of endodontic sealers (n = 30) were freshly mixed and placed on the plate of a rheometer (MCR 301, AntonPaar, Physica) and examined at 25°C and 37°C temperature, respectively. Rheological properties of the sealers were calculated according to the loss modulus (G″), storage modulus (G′), loss factor (Tan δ), and complex viscosity (η*) using dynamic oscillatory shear tests. Results: Statistical analysis (Wilcoxon signed-rank test) demonstrated that MTA Fillapex exhibited higher loss modulus (G″ > G′) and a crossover region. AH Plus and EndoREZ had a higher storage modulus (G′ > G″) at both temperatures. Loss factor (Tan δ) of MTA Fillapex was the highest compared to AH Plus, followed by EndoREZ. With a temperature change from 25°C to 37°C, MTA Fillapex exhibited a decrease while AH Plus exhibited an increase and, EndoREZ exhibited the least change, in complex viscosity (η*). Conclusions: EndoREZ exhibited better rheological properties compared to the other two test sealers. PMID:27099414

  5. Tuneable Rheological Properties of Fluorinated Pickering Emulsions

    NASA Astrophysics Data System (ADS)

    Chacon Orellana, Laura Andreina; Riechers, Birte; Caen, Ouriel; Baret, Jean-Christophe

    Pickering emulsions are an appealing approach to stabilize liquid-liquid dispersions without surfactants. Recently, amphiphilic silica nanoparticles have been proposed as an alternative to surfactants for droplet microfluidics applications, where aqueous drops are stabilized in fluorinated oils. This system, proved to be effective in preventing the leakage of resorufin, a model dye that was known to leak in surfactant-stabilized drops. The overall capabilities of droplet-based microfluidics technology is highly dependent on the dynamic properties of droplets, interfaces and emulsions. Therefore, fluorinated pickering emulsions dynamic properties need to be characterized, understood and controlled to be used as a substitute of already broadly studied emulsions for droplet microfluidics applications. In this study, fluorinated pickering emulsions have been found to behave as a Herschel Bulkley fluid, representing a challenge for common microfluidic operations as re-injection and sorting of droplets. We found that this behavior is controlled by the interaction between the interfacial properties of the particle-laden interface and the bulk properties of the two phases

  6. Rheological Properties of Quasi-2D Fluids in Microgravity

    NASA Technical Reports Server (NTRS)

    Stannarius, Ralf; Trittel, Torsten; Eremin, Alexey; Harth, Kirsten; Clark, Noel; Maclennan, Joseph; Glaser, Matthew; Park, Cheol; Hall, Nancy; Tin, Padetha

    2015-01-01

    In recent years, research on complex fluids and fluids in restricted geometries has attracted much attention in the scientific community. This can be attributed not only to the development of novel materials based on complex fluids but also to a variety of important physical phenomena which have barely been explored. One example is the behavior of membranes and thin fluid films, which can be described by two-dimensional (2D) rheology behavior that is quite different from 3D fluids. In this study, we have investigated the rheological properties of freely suspended films of a thermotropic liquid crystal in microgravity experiments. This model system mimics isotropic and anisotropic quasi 2D fluids [46]. We use inkjet printing technology to dispense small droplets (inclusions) onto the film surface. The motion of these inclusions provides information on the rheological properties of the films and allows the study of a variety of flow instabilities. Flat films have been investigated on a sub-orbital rocket flight and curved films (bubbles) have been studied in the ISS project OASIS. Microgravity is essential when the films are curved in order to avoid sedimentation. The experiments yield the mobility of the droplets in the films as well as the mutual mobility of pairs of particles. Experimental results will be presented for 2D-isotropic (smectic-A) and 2D-nematic (smectic-C) phases.

  7. Hanford Waste Physical and Rheological Properties: Data and Gaps - 12078

    SciTech Connect

    Kurath, D.E.; Wells, B.E.; Huckaby, J.L.; Mahoney, L.A.; Daniel, R.C.; Burns, C.A.; Tingey, J.M.; Cooley, S.K.

    2012-07-01

    The retrieval, transport, treatment and disposal operations associated with Hanford Tank Wastes involve the handling of a wide range of slurries. Knowledge of the physical and rheological properties of the waste is a key component to the success of the design and implementation of the waste processing facilities. Previous efforts to compile and analyze the physical and rheological properties were updated with new results including information on solids composition and density, particle size distributions, slurry rheology, and particle settling behavior. The primary source of additional data is from a recent series of tests sponsored by the Hanford Waste Treatment and Immobilization Plant (WTP). These tests involved an extensive suite of characterization and bench-scale process testing of 8 waste groups representing approximately 75% of the high-level waste mass expected to be processed through the WTP. Additional information on the morphology of the waste solids was also included. Based on the updated results, a gap analysis to identify gaps in characterization data, analytical methods and data interpretation was completed. (authors)

  8. Hanford Waste Physical and Rheological Properties: Data and Gaps

    SciTech Connect

    Kurath, Dean E.; Wells, Beric E.; Huckaby, James L.; Mahoney, Lenna A.; Daniel, Richard C.; Burns, Carolyn A.; Tingey, Joel M.; Cooley, Scott K.

    2012-03-01

    The retrieval, transport, treatment and disposal operations associated with Hanford Tank Wastes involve the handling of a wide range of slurries. Knowledge of the physical and rheological properties of the waste is a key component to the success of the design and implementation of the waste processing facilities. Previous efforts to compile and analyze the physical and rheological properties were updated with new results including information on solids composition and density, particle size distributions, slurry rheology, and particle settling behavior. The primary source of additional data is from a recent series of tests sponsored by the Hanford Waste Treatment and Immobilization Plant. These tests involved an extensive suite of characterization and bench-scale process testing of 8 waste groups representing approximately 75% of the high-level waste mass expected to be processed through the WTP. Additional information on the morphology of the waste solids was also included. Based on the updated results, a gap analysis to identify gaps in characterization data, analytical methods and data interpretation was completed.

  9. The Rheological Properties of the Biopolymers in Synovial Fluid

    NASA Astrophysics Data System (ADS)

    Krause, Wendy E.; Klossner, Rebecca R.; Wetsch, Julie; Oates, Katherine M. N.; Colby, Ralph H.

    2005-03-01

    The polyelectrolyte hyaluronic acid (HA, hyaluronan), its interactions with anti-inflammatory drugs and other biopolymers, and its role in synovial fluid are being studied. We are investigating the rheological properties of sodium hyaluronate (NaHA) solutions and an experimental model of synovial fluid (comprised of NaHA, and the plasma proteins albumin and γ-globulins). Steady shear measurements on bovine synovial fluid and the synovial fluid model indicate that the fluids are highly viscoeleastic and rheopectic (stress increases with time under steady shear). In addition, the influence of anti-inflammatory agents on these solutions is being explored. Initial results indicate that D-penicillamine and hydroxychloroquine affect the rheology of the synovial fluid model and its components. The potential implications of these results will be discussed.

  10. Preparation of Magnetorheological Fluid and Study on Its Rheological Properties

    NASA Astrophysics Data System (ADS)

    Kolekar, Shreedhar

    2014-04-01

    The present paper focuses on preparation and process of the magnetorheological (MR) fluid whose carrier fluid is silicone-based oil and its additive is the commercial grease with different concentration of iron particles. General properties of MR fluid are discussed and rheological properties like shear rate, shear stress, viscosity of MR fluid can be found by using cone-and-plate sensor system-type rheometer. The result shows that shear stress as a function of magnetic flux density and viscosity does not strictly scale with iron loading.

  11. Rheological and dielectric properties of different gold nanoparticle sizes

    PubMed Central

    2011-01-01

    Background Gold nanoparticles (GNPs) have found themselves useful for diagnostic, drug delivery and biomedicine applications, but one of the important concerns is about their safety in clinical applications. Nanoparticle size has been shown to be an extremely important parameter affecting the nanoparticle uptake and cellular internalization. The rheological properties assume to be very important as it affects the pressure drop and hence the pumping power when nano-fluids are circulated in a closed loop. The rheological and dielectric properties have not been documented and identified before. The aim of the present study was to investigate the rheology and the dielectric properties of different GNPs sizes in aqueous solution. Methods 10, 20 and 50 nm GNPs (Product MKN-Au, CANADA) was used in this study. The rheological parameters were viscosity, torque, shear stress, shear rate, plastic viscosity, yield stress, consistency index, and activation energy. These rheological parameters were measured using Brookfield LVDV-III Programmable rheometer supplied with temperature bath and controlled by a computer. Results The shear stress and shear rate of GNPs have shown a linear relationship and GNPs exhibited Newtonian behaviour. The GNPs with larger particle size (50 nm) exhibited more viscosity than those with smaller particle sizes (10 and 20 nm). Viscosity decreased with increasing the temperature for all the examined GNP sizes. The flow behaviour index (n) values were nearly ≤ 1 for all examined GNP sizes. Dielectric data indicated that the GNPs have strong dielectric dispersion in the frequency range of 20-100 kHz. The conductivity and relaxation time decreased with increasing the GNP size. Conclusions This study indicates that the GNP size has considerable influence on the viscosity of GNPs. The strong dielectric dispersion was GNP size dependent. The decrease in relaxation time might be attributed to increase in the localized charges distribution within the medium

  12. Investigating the rheological properties of native plant latex.

    PubMed

    Bauer, Georg; Friedrich, Christian; Gillig, Carina; Vollrath, Fritz; Speck, Thomas; Holland, Chris

    2014-01-01

    Plant latex, the source of natural rubber, has been of interest to mankind for millennia, with much of the research on its rheological (flow) properties focused towards industrial application. However, little is known regarding the rheology of the native material as produced by the plant, a key factor in determining latex's biological functions. In this study, we outline a method for rheological comparison between native latices that requires a minimum of preparatory steps. Our approach provides quantitative insights into the coagulation mechanisms of Euphorbia and Ficus latex allowing interpretation within a comparative evolutionary framework. Our findings reveal that in laboratory conditions both latices behave like non-Newtonian materials with the coagulation of Euphorbia latex being mediated by a slow evaporative process (more than 60 min), whereas Ficus appears to use additional biochemical components to increase the rate of coagulation (more than 30 min). Based on these results, we propose two different primary defensive roles for latex in these plants: the delivery of anti-herbivory compounds (Euphorbia) and rapid wound healing (Ficus). PMID:24173604

  13. Investigating the rheological properties of native plant latex

    PubMed Central

    Bauer, Georg; Friedrich, Christian; Gillig, Carina; Vollrath, Fritz; Speck, Thomas; Holland, Chris

    2014-01-01

    Plant latex, the source of natural rubber, has been of interest to mankind for millennia, with much of the research on its rheological (flow) properties focused towards industrial application. However, little is known regarding the rheology of the native material as produced by the plant, a key factor in determining latex's biological functions. In this study, we outline a method for rheological comparison between native latices that requires a minimum of preparatory steps. Our approach provides quantitative insights into the coagulation mechanisms of Euphorbia and Ficus latex allowing interpretation within a comparative evolutionary framework. Our findings reveal that in laboratory conditions both latices behave like non-Newtonian materials with the coagulation of Euphorbia latex being mediated by a slow evaporative process (more than 60 min), whereas Ficus appears to use additional biochemical components to increase the rate of coagulation (more than 30 min). Based on these results, we propose two different primary defensive roles for latex in these plants: the delivery of anti-herbivory compounds (Euphorbia) and rapid wound healing (Ficus). PMID:24173604

  14. Rheological and Tribological Properties of Complex Biopolymer Solutions

    NASA Astrophysics Data System (ADS)

    Klossner, Rebecca Reese

    2011-12-01

    The rheological and tribological properties of an experimental synovial fluid model were investigated in order to determine the solution dynamics of the three most abundant macromolecules present in synovial fluid, the fluid that lubricates freely moving (synovial) joints. These components, hyaluronic acid (HA) and the plasma proteins, albumin and gamma-globulins are combined in a phosphate buffered saline solution (PBS) and subjected to steady shear rheology testing, as well as nanoindenter-based scratch testing, which allows for the study of the lubrication properties of the experimental synovial fluid model. Steady shear experiments, where the shear rate was increased from low to high, and then decreased from high to low, showed hysteresis in only protein containing solutions, whereas samples of HA in PBS behaved as a "typical" polyelectrolyte in solution. Subsequent rheological experiments on the synovial fluid model exhibited an increase in viscosity at low shear stresses, indicating that a structure was present at these low shear stresses, which was not found at higher shear stresses. This result is in agreement with studies conducted on the same model which show unusual rheological behavior at low shear rates. Low shear stresses can cause modifications to the external protein surface, resulting in their unfolding and creating many opportunities for the molecules to reorder themselves. As the proteins reorder themselves, the newly exposed hydrophobic patches will have a tendency to aggregate together, creating a network within the fluid, and, in turn causing the observed increased viscosity at low shear stresses. Additionally, an anti-inflammatory drug, hydroxychloroquine (HCQ) was added to the solutions. This addition diminishes the protein aggregation process substantially. Finally, the HA component of the synovial fluid model was replaced with a neutral polymer in order to examine the role of HA in synovial fluid. As suspected, the HA appears to have

  15. Rheological and thermal properties of polylactide/silicate nanocomposites films.

    PubMed

    Ahmed, Jasim; Varshney, Sunil K; Auras, Rafeal

    2010-03-01

    Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 degrees C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G') of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (T(g)) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the T(g) of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. PMID:20492249

  16. RHEOLOGICAL PROPERTIES & MOLECULAR WEIGHT DISTRIBUTIONS OF FOUR PERFLUORINATED THERMOPLASTIC POLYMERS

    SciTech Connect

    Hoffman, D M; Shields, A L

    2009-02-24

    Dynamic viscosity measurements and molecular weight estimates have been made on four commercial, amorphous fluoropolymers with glass transitions (Tg) above 100 C: Teflon AF 1600, Hyflon AD 60, Cytop A and Cytop M. These polymers are of interest as binders for the insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) because of their high density and Tg above ambient, but within a suitable processing range of TATB. As part of this effort, the rheological properties and molecular weight distributions of these polymers were evaluated.

  17. Terahertz correlation spectroscopy infers particle velocity and rheological properties.

    PubMed

    Rees, Eric J; Su, Ke; Zeitler, Axel

    2016-07-15

    Correlation spectroscopy is an analytical technique that can identify the residence time of reflective or fluorescent particles in a measurement spot, allowing particle velocity or diffusion to be inferred. We show that the technique can be applied to data measured with a time-domain terahertz sensor. The speed of reflectors such as silica ballotini or bubbles can thus be measured in fluid samples. Time-domain terahertz sensors can therefore be used, for the first time, to measure rheological properties of optically opaque fluids that contain entrained reflectors, such as polyethylene beads. PMID:27420517

  18. The influence of additives on rheological properties of limestone slurry

    NASA Astrophysics Data System (ADS)

    Jaworska, B.; Bartosik, A.

    2014-08-01

    Limestone slurry appears in the lime production process as the result of rinsing the processed material. It consists of particles with diameter smaller than 2 mm and the water that is a carrier of solid fraction. Slurry is directed to the settling tank, where the solid phase sediments and the excess water through the transfer system is recovered for re-circulation. Collected at the bottom of the tank sludge is deposited in a landfill located on the premises. Rheological properties of limestone slurry hinder its further free transport in the pipeline due to generated flow resistance. To improve this state of affairs, chemical treatment of drilling fluid, could be applied, of which the main task is to give the slurry properties suitable for the conditions encountered in hydrotransport. This treatment consists of applying chemical additives to slurry in sufficient quantity. Such additives are called as deflocculants or thinners or dispersants, and are chemical compounds which added to aqueous solution are intended to push away suspended particles from each other. The paper presents the results of research allowing reduction of shear stress in limestone slurry. Results demonstrate rheological properties of limestone slurry with and without the addition of modified substances which causes decrease of slurry viscosity, and as a consequence slurry shear stress for adopted shear rate. Achieving the desired effects increases the degree of dispersion of the solid phase suspended in the carrier liquid and improving its ability to smooth flow with decreased friction.

  19. Particle size dependent rheological property in magnetic fluid

    NASA Astrophysics Data System (ADS)

    Wu, Jie; Pei, Lei; Xuan, Shouhu; Yan, Qifan; Gong, Xinglong

    2016-06-01

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe3O4 nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field.

  20. Correlation of chitosan's rheological properties to its ability to electrospin

    NASA Astrophysics Data System (ADS)

    Krause, Wendy E.; Queen, Hailey A.; Klossner, Rebecca R.; Coughlin, Andrew J.

    2007-03-01

    Chitosan, derived from chitin found in the exoskeleton of crustaceans, has been investigated extensively for use in biomedical applications ranging from drug delivery to scaffolds for tissue engineering. Therefore, forming nanofibers of this linear polysaccharide is desirable for use in such applications, because the nanofibers can be tailored to mimic the size and porosity of the extracellular matrix. Electrostatic spinning (electrospinning) is a convenient method to produce nonwoven mats of nanofibers. The ability of the solutions to successfully electospin is closely correlated with the rheological properties of the solutions. Chitosan is challenging to electrospin due to its relatively high viscosity at modest concentrations. Solutions of chitosan blended with poly(ethylene oxide) (PEO) have been electrospun successfully with freshly prepared solutions. If the blended solutions are stored, they do not readily electrospin. Moreover, chitosan/PEO blend solutions show a drastic decrease in zero shear rate viscosity over time, which can be attributed to phase separation. The challenges associated with electrospinning charged biopolymers (chitosan is cationic) will be discussed in terms of their rheological properties. Successes and failures will be highlighted and compared results for readily electrospun neutral polymers.

  1. Interplay between electrical and rheological properties of viscoelastic inks

    NASA Astrophysics Data System (ADS)

    Yu, Milim; Ahn, Kyung Hyun; Lee, Seung Jong

    2016-04-01

    We investigated the effect of the interaction between the electrical and rheological properties of the ink in electrodydrodynamic (EHD) printing process by designing model systems that control both the electrical conductivity and the viscoelasticity of the ink to observe how they affect the Taylor cone jet formation. The results demonstrate that the initial voltage at which the Taylor cone jet first appears and the final voltage at which the jet becomes unstable increase at higher electrical conductivity as the conical shape with large surface area is formed and grants stability at higher conductivity. Increased viscosity and elasticity also lead to the similar result: increase in the initial and final voltages, which can be attributed to the slower charge transport that minimizes the stabilizing effect of the inks' electrical conductivity. In addition, we use two dimensionless variables (dimensionless flow rate and dimensionless voltage) to make an operating window map of the EHD process. Through this map, the processing condition for the Taylor cone jet zone can be predicted with respect to the effect of the interplay between the electrical and rheological properties of the ink.

  2. Influence of cell properties on rheological characterization of microalgae suspensions.

    PubMed

    Zhang, Xinru; Jiang, Zeyi; Chen, Liang; Chou, Aihui; Yan, Hai; Zuo, Yi Y; Zhang, Xinxin

    2013-07-01

    The influences of algal cell size and surface charge on rheological properties of microalgae suspensions were investigated. The effective viscosity of two microalgae suspensions, i.e., the freshwater Chlorella sp. and the marine Chlorella sp., was measured as a function of their volume fractions in the range of 0.70-4.31%. The hydrodynamic diameters of the freshwater Chlorella sp. and the marine Chlorella sp. were measured to be 3.13 and 6.00 μm, respectively. The Zeta potentials of these two algal cells were measured to be -23.73 and -81.81 mV, respectively. The intrinsic viscosities of these two microalgae suspensions were further determined to be 24.7 and 16.1, respectively. Combining with theoretical models, these results indicated that the algal cell size has a predominant effect over cell surface charge in affecting rheological properties of microalgae suspensions. Smaller algal cells result in a higher effective viscosity of the microalgae suspension. PMID:23665517

  3. Structure and rheological properties in alkali aluminosilicate melts

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Neuville, Daniel

    2010-05-01

    Rheological properties of silicate melts govern both magma ascension from the mantle to the surface of the earth and volcanological eruptions styles and behaviors. In this mind, it is very important to understand which parameters influence these properties. Up to now, we know for example that viscosity of silicate melts is dependent of temperature, pressure and chemical composition. In this work, we will focus on the Na2O-K2O-Al2O3-SiO2 system, which is of a prime importance because it deals with a non-negligible part of natural melts like haplogranitic rhyolitic alkali magmas. We will first present our viscosity measurements and some modelisation concepts based on the Adam and Gibbs theory. From configurational entropy theory we obtain some macroscopic information's that we can link to the structure of glasses and melts. In this mind, we have investigated them with Raman and NMR spectroscopies. These spectroscopies provide information on speciation and polymerization of glasses and melts. We will present and discuss structural and rheological variations as a function of temperature and chemical change.

  4. Molecular simulation of rheological properties using massively parallel supercomputers

    SciTech Connect

    Bhupathiraju, R.K.; Cui, S.T.; Gupta, S.A.; Cummings, P.T.; Cochran, H.D.

    1996-11-01

    Advances in parallel supercomputing now make possible molecular-based engineering and science calculations that will soon revolutionize many technologies, such as those involving polymers and those involving aqueous electrolytes. We have developed a suite of message-passing codes for classical molecular simulation of such complex fluids and amorphous materials and have completed a number of demonstration calculations of problems of scientific and technological importance with each. In this paper, we will focus on the molecular simulation of rheological properties, particularly viscosity, of simple and complex fluids using parallel implementations of non-equilibrium molecular dynamics. Such calculations represent significant challenges computationally because, in order to reduce the thermal noise in the calculated properties within acceptable limits, large systems and/or long simulated times are required.

  5. Pre-cooked Fiber-enriched Wheat Flour Obtained by Extrusion: Rheological and Functional Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Functional and rheological properties of different process conditions of extruded wheat flour with 0%, 10%, 20% and 30% fiber levels were studied in the production of cookies and tortillas. Functional and rheological properties were evaluated using Rapid Visco Analyzer and Mixograph equipment. Resul...

  6. Waxy soft white wheat: extrusion characteristics and thermal and rheological properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Waxy wheat flour was analyzed for its thermal and rheological properties and extruded to understand its processing characteristics. Comparisons were made with normal soft white wheat flour to identify extrusion differences under the same conditions. The thermal and rheological properties through Rap...

  7. Filamin-A and Rheological Properties of Cultured Melanoma Cells

    PubMed Central

    Coughlin, Mark F.; Puig-de-Morales, Marina; Bursac, Predrag; Mellema, Matthew; Millet, Emil; Fredberg, Jeffrey J.

    2006-01-01

    Here we report the rheological properties of cultured hsFLNa (filamin-A)-expressing (FIL+) and hsFLNa-deficient (FIL−) melanoma cells. Using magnetic twisting cytometry over a wide range of probing frequencies, and targeting either cortical or deeper cytoskeletal structures, we found that differences in stiffness of FIL+ versus FIL− cells were remarkably small. When probed through deep cytoskeletal structures, FIL+ cells were, at most, 30% stiffer than FIL− cells, whereas when probed through more peripheral cytoskeletal structures FIL− cells were not different except at very high frequencies. The loss tangent, expressed as an effective cytoskeletal temperature, was systematically greater in FIL− than FIL+ cells, but these differences were small and showed that the FIL+ cells were only slightly closer to a solidlike state. To quantify cytoskeletal remodeling, we measured spontaneous motions of beads bound to cortical cytoskeletal structures and found no difference in FIL+ versus FIL− cells. Although mechanical differences between FIL+ and FIL− cells were evident both in cortical and deeper structures, these differences were far smaller than expected based on measurements of the rheology of purified actin-filamin solutions. These findings do not rule out an important contribution of filamin to the mechanical properties of the cortical cytoskeleton, but suggest that effects of filamin in the cortex are not exerted on the length scale of the probe used here. These findings would appear to rule out any important contribution of filamin to the bulk mechanical properties of the cytoplasm, however. Although filamin is present in the cytoplasm, it may be inactive, its mechanical effects may be small compared with other crosslinkers, or mechanical properties of the matrix may be dominated by an overriding role of cytoskeletal prestress. PMID:16387775

  8. Tribological and Rheological Properties of a Synovial Fluid Model

    NASA Astrophysics Data System (ADS)

    Klossner, Rebecca; Liang, Jing; Krause, Wendy

    2010-03-01

    Hyaluronic acid (HA) and the plasma proteins, albumin and globulins, are the most abundant macromolecules in synovial fluid, the fluid that lubricates freely moving joints. In previous studies, bovine synovial fluid, a synovial fluid model (SFM) and albumin in phosphate buffered saline (PBS) were observed to be rheopectic---viscosity increases over time under constant shear. Additionally, steady shear experiments have a strong shear history dependence in protein-containing solutions, whereas samples of HA in PBS behaved as a ``typical'' polyelectrolyte. The observed rheopexy and shear history dependence are indicative of structure building in solution, which is most likely caused by protein aggregation. The tribology of the SFM was also investigated using nanoindenter-based scratch tests. The coefficient of frictions (μ) between the diamond nanoindenter tip and a polyethylene surface was measured in the presence of the SFM and solutions with varied protein and HA concentrations. The lowest μ is observed in the SFM, which most closely mimics a healthy joint. Finally, an anti-inflammatory drug, hydroxychloroquine, was shown to inhibit protein interactions in the SFM in rheological studies, and thus the tribological response was examined. We hypothesize that the rheopectic behavior is important in lubrication regimes and therefore, the rheological and tribological properties of these solutions will be correlated.

  9. Rheological properties of ovalbumin hydrogels as affected by surfactants addition.

    PubMed

    Hassan, Natalia; Messina, Paula V; Dodero, Veronica I; Ruso, Juan M

    2011-04-01

    The gel properties of ovalbumin mixtures with three different surfactants (sodium perfluorooctanoate, sodium octanoate and sodium dodecanoate) have been studied by rheological techniques. The gel elasticities were determined as a function of surfactant concentration and surfactant type. The fractal dimension of the formed structures was evaluated from plots of storage modulus against surfactant concentration. The role of electrostatic, hydrophobic and disulfide SS interactions in these systems has been demonstrated to be the predominant. The viscosity of these structures tends to increase with surfactant concentration, except for the fluorinated one. Unfolded ovalbumin molecules tend to form fibrillar structures that tend to increase with surfactant concentration, except for the fluorinated one. This fact has been related to the particular nature of this molecule. PMID:21262258

  10. Novel formulations of ballistic gelatin. 1. Rheological properties.

    PubMed

    Zecheru, Teodora; Său, Ciprian; Lăzăroaie, Claudiu; Zaharia, Cătălin; Rotariu, Traian; Stănescu, Paul-Octavian

    2016-06-01

    Ballistic gelatin is the simulant of the human body during field tests in forensics and other related fields, due to its physical and mechanical similarities to human trunk and organs. Since the ballistic gelatin used in present has important issues to overcome, an alternative approach is the use of gelatin-polymer composites, where a key factor is the insertion of biocompatible materials, which replicate accurately the human tissues. In order to be able to obtain an improved material in terms of mechanical performances by an easy industrial-scale technology, before the verification of the ballistic parameters by shooting in agreement with military standards, one of the best and cheapest solutions is to perform a thorough check of their rheological properties, in standard conditions. PMID:27139038

  11. Dynamic elastic properties of magneto-rheological slurries

    NASA Astrophysics Data System (ADS)

    Donado, F. F.; Mendoza, M. E. M. E.; Carrillo, J. L.

    2001-06-01

    We study the propagation of elastic perturbations in magneto-rheological slurries of iron particles dispersed in glycerine. The complexity of these systems is revealed in the fibrillar structure acquired under the application of a magnetic field. Recently, it has been reported the observation of two different low frequency modes of propagation. One of these modes has been associated to the propagation of the perturbation through the fluid medium. The other one has been qualitatively explained as the propagation of the elastic perturbation through the suspended particles. This second mode appears when a magnetic field is applied to the slurry. The propagation speed for both modes depends on the field intensity and on the properties of the magnetic particles. Theoretically, we analyze these modes and calculate the sound velocity. We obtain a quantitative good agreement with the experimental results.

  12. New insights on the rheological properties of a rocksalt

    NASA Astrophysics Data System (ADS)

    Speranza, G.; Vinciguerra, S.; Di Genova, D.; Romano, C.; Vona, A.; Mollo, S.; Iarocci, A.

    2013-12-01

    The importance and economic interest on rocksalt deposits and salt bodies are well known and extensively studied. The physical and mechanical properties of salt have a profound influence on the tectonics as well as they are considered to be vital for applicative purposes such as mining, petroleum and nuclear waste storage. However, previous scientific works have mainly focused on synthetic rocksalt or commercial salt, whereas natural salt facies have been scarcely investigated. In this view, we present new data on the role of natural heterogeneities (i.e., relative abundance of primary salt crystals and impurities) on the rheological parameters of a rocksalt. This rock belongs to the Saline di Volterra formation (Volterra basin, Tuscany, central Italy) that was deposited during the Messinian Salinity Crisis. The 49-metre-thick salt sequence (intersected by the S1113 borehole of the Solvay company) is characterized by a high salt facies variability. In particular, three end-members have been recognized: the first contains abundant primary salt crystals, with minor or no recrystallizazion; the second member is extensively recrystallized, with scarce primary crystal remnants; the third shows a great abundance of clay impurities. Rheological parameters, such as static and dynamic Young's Modulus and coefficient of linear expansion, were measured for the three rocksalt end-members throughout P and S seismic velocities, uniaxial compressive strength and thermal expansion measurements. Seismic velocity has been measured on cubic samples with a side ranging from 4 to 7 cm. A clear effect of the salt facies was found: the average velocity is faster in mostly recrystallized salt samples (4500 m/s), slower in primary salt-rich samples (4300 m/s), and intermediate (4350 m/s) in presence of clay impurities. Dynamic Young's Modulus calculated on velocities (average value ≈ 38 GPa) mirrors this behavior, with lowest values related to primary salt. The anisotropic effect induced

  13. Rheological and morphological properties of graphene-epoxy nanocomposites

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Raimondo, Marialuigia; Lafdi, Khalid; Guadagno, Liberata

    2016-05-01

    In this paper the rheological and morphological properties of an epoxy resin filled with graphene-based nanoparticles have been investigated. Two samples of partially exfoliated graphite (pEG) and carboxylated partially exfoliated graphite (CpEG), differing essentially for the content of carboxylated groups, are used. The percentage of exfoliated graphite is slightly different for the two samples: 56% for pEG and and 60% for CpEG. Exfoliated graphite is prepared using traditional acid intercalation followed by a sudden treatment at high temperature (900°C). The epoxy matrix is prepared by mixing a tetrafunctional precursor with a reactive diluent which produces a significant decrease in the viscosity of the epoxy precursor so that the dispersion step of nanofillers in the matrix can easily occur. The hardener agent, the 4,4-diaminodiphenyl sulfone (DDS), is added at a stoichiometric concentration with respect to all the epoxy rings. The inclusion of the pEG and CpEG samples in the formulated epoxy mixture significantly modifies the rheological behaviour of the mixture itself. The epoxy mixture, indeed, shows a Newtonian behavior; on the contrary the complex viscosity of the nanocomposites clearly shows a shear thinning behavior at 3 wt % of pEG content and at 0.75 wt% of CpEG content. The increase in complex viscosity with the increasing of pEG and CpEG content is mostly caused by a dramatic increase in the storage modulus of the nanocomposites. All the graphene-based epoxy mixtures are cured by a two-stage curing cycles: a first isothermal stage is carried out at the lower temperature of 125°C for 1 hour and, then, a second isothermal stage at the higher temperature of 200°C for 3 hours. The different morphology shown by the two pEG and CpEG samples is consistent with the difference in the percentage of exfoliation degree and well correlates with the rheological behavior of investigated graphene-epoxy nanocomposites.

  14. Dynamic light scattering for measuring microstructure and rheological properties of food

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years there has been significant interest in the determination of microstructural and rheological properties of viscoelastic food materials and their formulations. This is because the arrangement (architecture) of the micro­ and nano­components, size distribution, and rheological (mechanic...

  15. Rheological properties of living cytoplasm: endoplasm of Physarum plasmodium.

    PubMed

    Sato, M; Wong, T Z; Allen, R D

    1983-10-01

    Magnetic sphere viscoelastometry, video microscopy, and the Kamiya double chamber method (Kamiya, N., 1940, Science [Wash. DC], 92:462-463.) have been combined in an optical and rheological investigation of the living endoplasm of Physarum polycephalum. The rheological properties examined were yield stress, viscosity (as a function of shear), and elasticity. These parameters were evaluated in directions perpendicular; (X) and parallel (Y) to the plasmodial vein. Known magnetic forces were used for measurements in the X direction, while the falling ball technique was used in the Y direction (Cygan, D.A., and B. Caswell, 1971, Trans. Soc. Rheol. 15:663-683; MacLean-Fletcher, S.D., and T.D. Pollard, 1980, J. Cell Biol., 85:414-428). Approximate yield stresses were calculated in the X and Y directions of 0.58 and 1.05 dyn/cm2, respectively. Apparent viscosities measured in the two directions (eta x and eta y) were found to fluctuate with time. The fluctuations in eta x and eta y were shown, statistically, to occur independently of each other. Frequency correlation with dynamoplasmograms indicated that these fluctuations probably occur independently of the streaming cycle. Viscosity was found to be a complex function of shear, indicating that the endoplasm is non-Newtonian. Plots of shear stress vs. rate of shear both parallel and perpendicular to the vein, showed that endoplasm is not a shear thinning material. These experiments have shown that living endoplasm of Physarum is an anisotropic viscoelastic fluid with a yield stress. The endoplasm appears not to be a homogeneous material, but to be composed of heterogeneous domains. PMID:6619187

  16. SOME RHEOLOGICAL PROPERTIES OF AQUEOUS PEANUT FLOUR DISPERSIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological behaviors of aqueous peanut flour dispersions were characterized across a range of conditions, including controlled heating and cooling rates under both large and small-strain deformations. Fat content of the dry flours influenced rheological characteristics, as dispersions of highe...

  17. Rheological and microstructural properties of porcine gastric digesta and diets containing pectin or mango powder.

    PubMed

    Wu, Peng; Dhital, Sushil; Williams, Barbara A; Chen, Xiao Dong; Gidley, Michael J

    2016-09-01

    Hydrated polysaccharides and their assemblies are known to modulate gastric emptying rate due to their capacity to change the structural and rheological properties of gastric contents (digesta). In the present study, we investigated the rheological and microstructural properties of gastric digesta from pigs fed with diets incorporating mango powder or pectin, and compared results with those from hydrated diets of the same water content, in order to investigate the origins for rheological changes in the pig stomach. All of the hydrated diets and gastric digesta were particle-dominated suspensions, generally showing weak gel or more solid-like behavior with the storage modulus (G') always greater than loss modulus (G") under small deformation oscillatory measurements, and with small deformation viscosity greater than steady shear viscosity (i.e. non-Cox-Merz superposition). Although significant rheological differences were observed between the hydrated diets, rheological parameters for gastric digesta were similar for all diets, indicative of a rheological homeostasis in the pig stomach. Whilst the addition of gastric mucin (20mg/mL) to control and mango diets altered the rheology to match the gastric digesta rheology, the effect of mucin on the pectin-containing diet was negligible. The viscous effect of pectin also hindered the action of alpha amylase as observed from relatively less damaged starch granules in pectin digesta compared to mango and control digesta. Based on the experimental findings that the rheology of gastric digesta differs from hydrated diets of the same water content, the current study revealed composition-dependent complex behavior of gastric digesta in vivo, suggesting that the rheology of food products or ingredients may not necessarily reflect the rheological effect when ingested. PMID:27185134

  18. Effect of thermal modification on rheological properties of polyethylene blends

    SciTech Connect

    Siriprumpoonthum, Monchai; Nobukawa, Shogo; Yamaguchi, Masayuki; Satoh, Yasuo; Sasaki, Hiroko

    2014-03-15

    We examined the effects of thermal modification under flow field on the rheological properties of linear low-density polyethylene (LLDPE) with high molecular weight, low-density polyethylene (LDPE), and their blends, without thermal stabilizer. Although structural changes during processing are not detected by size extrusion chromatography or nuclear magnetic resonance spectroscopy, linear viscoelastic properties changed greatly, especially for the LLDPE. A cross-linking reaction took place, leading to, presumably, star-shaped long-chain branches. Consequently, the modified LLDPE, having high zero-shear viscosity, became a thermorheologically complex melt. Moreover, it should be noted that the drawdown force, defined as the uniaxial elongational force at a constant draw ratio, was significantly enhanced for the blends. Enhancement of elongational viscosity was also detected. The drawdown force and elongational viscosity are marked for the thermally modified blend as compared with those for the blend of thermally modified pure components. Intermolecular cross-linking reactions between LDPE and LLDPE, yielding polymers with more than two branch points per chain, result in marked strain-hardening in the elongational viscosity behavior even at small strain. The recovery curve of the oscillatory modulus after the shear modification is further evidence of a branched structure.

  19. Rheological properties of myometrium: experimental quantification and mathematical modeling.

    PubMed

    Jelen, Karel; Lopot, Frantisek; Budka, Stepán; Novácek, Vít; Sedlácek, Radek

    2008-08-01

    This work answers some questions related to detection of rheological properties of soft tissues exemplified in myometrium, stressed by external tensile force. In the first stage of the experiment the tissue samples were ciclically stressed and response loops were recorded. This test proved severe plastical deformation of samples, which is not usually being stated for living tissues. In addition to course, growth and stabilizing this deformation also energetical losses of individual hysteresis loops of the response were evaluated. In the second stage of the experiment the tissue samples were exposed to a loading force changed in step-wise manner in four steps. The sample response to each force step was processed and evaluated separately to obtain basic properties of used model. In next step, the changes in model characteristics were obtained and evaluated for each element in subsequent force steps. By reason of following easier interpretation, the quite simple visco-elastic model, defined by differential equation with analytic solution, is used. The results prove necessary to introduce in model both spring and damper constants dependent on the magnitude of the loading force and one damper with even time dependent constant. The interindividual variability of characteristic values of the model elements is surprisingly low. On the other side, they are strongly dependent on load magnitude. Complete mathematical model of uterine wall tissue is obtained by amending the principal equation by formulas describing changes in individual components of the model. PMID:18766144

  20. A study of dilational rheological properties of polymers at interfaces.

    PubMed

    Cao, Xulong; Li, Yang; Jiang, Shengxiang; Sun, Huanquan; Cagna, Alain; Dou, Lixia

    2004-02-15

    Viscoelastic properties of two polymers, partially hydrolyzed polyacrylamide and partially hydrolyzed modified polyacrylamide, widely used in chemical flooding in the petroleum industry, were investigated at three interfaces, water-air, water-dodecane, and water-crude oil, by means of a dilational method provided by I.T. Concept, France, at 85 degrees C. Polymer solutions were prepared in brine with 10,000 mg/l sodium chloride and 2000 mg/l calcium chloride. It has been shown that the viscoelastic modulus increases with the increment of polymer concentration in the range of 0-1500 mg/l at the water-air interface. Each polymer shows different viscoelatic behavior at different interfaces. Generally speaking, values of the viscoelastic modulus (E), the real part (E'), and the imaginary part (E") at the crude oil-water interface for each polymer are lower than at the air-water or water-dodecane interface. The two polymers display different interfacial properties at the same interface. Polymer No. 2 gives more viscous interfaces than polymer No. 1. All the information obtained from this paper will be helpful in understanding the interfacial rheology of ultra-high-molecular-weight polymer solutions. PMID:14697692

  1. Simulation and experimental study of rheological properties of CeO2-water nanofluid

    NASA Astrophysics Data System (ADS)

    Loya, Adil; Stair, Jacqueline L.; Ren, Guogang

    2015-10-01

    Metal oxide nanoparticles offer great merits over controlling rheological, thermal, chemical and physical properties of solutions. The effectiveness of a nanoparticle to modify the properties of a fluid depends on its diffusive properties with respect to the fluid. In this study, rheological properties of aqueous fluids (i.e. water) were enhanced with the addition of CeO2 nanoparticles. This study was characterized by the outcomes of simulation and experimental results of nanofluids. The movement of nanoparticles in the fluidic media was simulated by a large-scale molecular thermal dynamic program (i.e. LAMMPS). The COMPASS force field was employed with smoothed particle hydrodynamic potential (SPH) and discrete particle dynamics potential (DPD). However, this study develops the understanding of how the rheological properties are affected due to the addition of nanoparticles in a fluid and the way DPD and SPH can be used for accurately estimating the rheological properties with Brownian effect. The rheological results of the simulation were confirmed by the convergence of the stress autocorrelation function, whereas experimental properties were measured using a rheometer. These rheological values of simulation were obtained and agreed within 5 % of the experimental values; they were identified and treated with a number of iterations and experimental tests. The results of the experiment and simulation show that 10 % CeO2 nanoparticles dispersion in water has a viscosity of 2.0-3.3 mPas.

  2. Rheological Properties of Aqueous Suspensions of Chitin Crystallites

    PubMed

    Li; Revol; Marchessault

    1996-11-10

    Rheologically, suspensions of chitin crystallites are found to behave as other molecular liquid crystalline polymers (LCPs). The average hydrodynamic diameter of the crystallites in the suspension at pH 4 is determined to be approximately 80 nm using dynamic light scattering. Conductimetric and pH titration results show that the pKa of the crystallites is 6.3, which is the same as that reported for chitosan. In combination with phase diagrams, flow properties of isotropic, biphasic, and anisotropic chitin suspensions were investigated. For isotropic suspensions, a classical shear thinning behavior of rodlike particles is observed. In the case of biphasic suspensions, a two-regime curve is observed where tactoids first orient, deform, and then break up under a shearing force. Similar to other LCPs, a three-regime flow curve is found for the anisotropic suspensions. The viscosity-concentration curve exhibits a maximum at the phase separation concentration, and this maximum is less distinct with a decrease of the ionic strength. Secondary electroviscous effects due to strong particle-particle interactions influence the viscosity of the suspensions at higher concentrations. PMID:8954679

  3. Chain-configuration dependent rheological properties in transient networks

    NASA Astrophysics Data System (ADS)

    Sing, Michelle; Wang, Zhen-Gang; McKinley, Gareth; Olsen, Bradley

    2014-03-01

    Complex associative networks capable of shear thinning followed by recovery on the order of seconds are of interest as injectable biomaterials. However, there is a limited understanding of the molecular mechanisms that contribute to rheological properties such as the network's yield stress and rate of self-healing. Here we present a transient network theory for associative physical gels arising from the chemical kinetic form of the Smoluchowski Equation capable of modeling the full chain end-to-end distance distribution while tracking the fraction of looped, bridged, and free chain configurations in the gel. By varying the equilibrium association rate relative to the material relaxation time, we are able to track the evolution of loop and bridge chain fraction as the system undergoes stress instabilities. We have evidence that these instabilities result from non-monotonic trends in loop and bridge chain fraction when the end group association rate is high relative to the dissociation rate. This behavior provides insight into the complex kinetic interactions responsible for certain mechanical behaviors while serving as a valuable predictive tool for gel design. Institute for Soldier Nanotechnologies, Department of Defense National Defense Science and Engineering Fellowship Program

  4. Silk Fibroin Degradation Related to Rheological and Mechanical Properties.

    PubMed

    Partlow, Benjamin P; Tabatabai, A Pasha; Leisk, Gary G; Cebe, Peggy; Blair, Daniel L; Kaplan, David L

    2016-05-01

    Regenerated silk fibroin has been proposed as a material substrate for biomedical, optical, and electronic applications. Preparation of the silk fibroin solution requires extraction (degumming) to remove contaminants, but results in the degradation of the fibroin protein. Here, a mechanism of fibroin degradation is proposed and the molecular weight and polydispersity is characterized as a function of extraction time. Rheological analysis reveals significant changes in the viscosity of samples while mechanical characterization of cast and drawn films shows increased moduli, extensibility, and strength upon drawing. Fifteen minutes extraction time results in degraded fibroin that generates the strongest films. Structural analysis by wide angle X-ray scattering (WAXS) and Fourier transform infrared spectroscopy (FTIR) indicates molecular alignment in the drawn films and shows that the drawing process converts amorphous films into the crystalline, β-sheet, secondary structure. Most interesting, by using selected extraction times, films with near-native crystallinity, alignment, and molecular weight can be achieved; yet maximal mechanical properties for the films from regenerated silk fibroin solutions are found with solutions subjected to some degree of degradation. These results suggest that the regenerated solutions and the film casting and drawing processes introduce more complexity than native spinning processes. PMID:26756449

  5. Rheological and microstructural properties of the chia seed polysaccharide.

    PubMed

    Timilsena, Yakindra Prasad; Adhikari, Raju; Kasapis, Stefan; Adhikari, Benu

    2015-11-01

    Chia seed polysaccharide (CSP) was extracted from chia (Salvia hispanica) seeds, and its rheological and microstructural properties in aqueous solutions were studied. CSP solution exhibited Newtonian and shear thinning flow patterns depending on shear rate when the concentration was ≤0.06% (w/v). CSP solutions at concentrations >0.06% (w/v) exhibited strong shear thinning behaviour within the shear rate tested (0.001-300s(-1)). The transition from dilute to semi-dilute regime occurred at a critical concentration (C*) of 0.03gdL(-1). The intrinsic viscosity was high (∼16dLg(-1)) and concentration dependence of zero shear viscosity in the semi-dilute regime followed η0∝C(2.7) relationship. The storage modulus (G') was higher than the loss modulus (G″) at all experimental frequencies and their frequency dependence was negligible at all tested concentrations. Apparent shear viscosity was smaller than dynamic complex viscosity at equivalent values of deformation and G' varied with the square of concentration indicating a gel-like behaviour in CSP solutions within 0.02-3.0% (w/v) concentrations. Controlled acid hydrolysis of purified CSP yielded various low molecular fractions with fairly uniform polydispersity giving a Mark-Houwink-Sakurada relationship of intrinsic viscosity equaling to 1.52×10(-4) (molecular weight)(0.803) (dLg(-1)). PMID:26416236

  6. Rheological and biochemical properties of Solanum lycocarpum starch.

    PubMed

    Di-Medeiros, Maria Carolina B; Pascoal, Aline M; Batista, Karla A; Bassinello, Priscila Z; Lião, Luciano M; Leles, Maria Inês G; Fernandes, Kátia F

    2014-04-15

    This study was conducted to evaluate the rheological and physicochemical properties of Solanum lycocarpum starch. The thermogravimetric analysis of S. lycocarpum starch showed a typical three-step weight loss pattern. Microscopy revealed significant changes in the granule morphology after hydrothermal treatment. Samples hydrothermally treated at 50°C for 10 min lost 52% of their crystallinity, which was recovered after storage for 7 days at 4°C. However, samples hydrothermally treated at 65°C were totally amorphous. This treatment was sufficient to completely disrupt the starch granule, as evidenced by the absence of an endothermic peak in the DSC thermogram. The RVA of S. lycocarpum starch revealed 4440.7cP peak viscosity, 2660.5cP breakdown viscosity, 2414.1cP final viscosity, 834.3cP setback viscosity, and a pasting temperature of 49.6°C. The low content of resistant starch (10.25%) and high content of digestible starch (89.78%) in S. lycocarpum suggest that this starch may be a good source for the production of hydrolysates, such as glucose syrup and its derivatives. PMID:24607161

  7. Colloids on the frontier of ferrofluids. Rheological properties.

    PubMed

    López-López, Modesto T; Gómez-Ramírez, Ana; Rodríguez-Arco, Laura; Durán, Juan D G; Iskakova, Larisa; Zubarev, Andrey

    2012-04-17

    This paper is devoted to the steady-state rheological properties of two new kinds of ferrofluids. One of these was constituted by CoNi nanospheres of 24 nm in diameter, whereas the other by CoNi nanofibers of 56 nm in length and 6.6 nm in width. These ferrofluids were subjected to shear rate ramps under the presence of magnetic fields of different intensity, and the corresponding shear stress values were measured. From the obtained rheograms (shear stress vs shear rate curves) the values of both the static and the dynamic yield stresses were obtained as a function of the magnetic field. The magnetoviscous effect was also obtained as a function of both the shear rate and the magnetic field. The experimental results demonstrate that upon magnetic field application these new ferrofluids develop yield stresses and magnetoviscous effects much greater than those of conventional ferrofluids, based on nanospheres of approximately 10 nm in diameter. Besides some expected differences, such as the stronger magnetorheological effect in the case of ferrofluids based on nanofibers, some intriguing differences are found between the rheological behaviors of nanofiber ferrofluids and nanosphere ferrofluid. First, upon field application the rheograms of nanofiber ferrofluids present N-shaped dependence of the shear stress on the shear rate. The decreasing part of the rheograms takes place at low shear rate. These regions of negative differential viscosity, and therefore, unstable flow is not observed in the case of nanosphere ferrofluids. The second intriguing difference concerns the curvature of the yield stress vs magnetic field curves. This curvature is negative in the case of nanosphere ferrofluid, giving rise to saturation of the yield stress at medium field, as expected. However, in the case of nanofiber ferrofluid this curvature is positive, which means a faster increase of the yield stress with the magnetic field the higher the magnitude of the latter. These interesting

  8. Different macro- and micro-rheological properties of native porcine respiratory and intestinal mucus.

    PubMed

    Bokkasam, Harish; Ernst, Matthias; Guenther, Marco; Wagner, Christian; Schaefer, Ulrich F; Lehr, Claus-Michael

    2016-08-20

    Aim of this study was to investigate the similarities and differences at macro- and microscale in the viscoelastic properties of mucus that covers the epithelia of the intestinal and respiratory tract. Natural mucus was collected from pulmonary and intestinal regions of healthy pigs. Macro-rheological investigations were carried out through conventional plate-plate rheometry. Microrheology was investigated using optical tweezers. Our data revealed significant differences both in macro- and micro-rheological properties between respiratory and intestinal mucus. PMID:27311353

  9. Rheological properties comparison between polymer bonded explosives (PBX) and its simulant

    NASA Astrophysics Data System (ADS)

    Naeun, Lee; Youngdae, Kim; Jaehan, Song; Sangkeun, Han; Jeongseob, Shim; Keundeuk, Lee; Sangmook, Lee; Jaewook, Lee

    2016-03-01

    Polymer bonded explosive(PBX) is a composite in which energetic material is highly filled in a polymer binder matrix. For safety reason, however, in experimental studies, corresponding material (Dechlorane) which has similar density and melting point was used. To apply for real system, a comparison of properties of composite filled with energetic material and corresponding material is needed. Not only components of composite like filler, binder and plasticizer but also filler content and distributive properties are important factors determining properties of simulant. Unlike previous low filled PBX, properties of highly filled PBX is greatly influenced by filler content. Rheological properties of composite filled with energetic material and corresponding material can be compared by analyzing effects of filler properties - e.g., mean particle size, particle size distribution and particle shape, etc. - on rheological properties. Rheological properties of two composites of various content over than 50wt% have been investigated by using rotational rheometer with parallel plate.

  10. Rheological properties of peptide-based hydrogels for biomedical and other applications†

    PubMed Central

    Yan, Congqi; Pochan, Darrin J.

    2011-01-01

    Peptide-based hydrogels are an important class of biomaterials finding use in food industry and potential use in tissue engineering, drug delivery and microfluidics. A primary experimental method to explore the physical properties of these hydrogels is rheology. A fundamental understanding of peptide hydrogel mechanical properties and underlying molecular mechanisms is crucial for determining whether these biomaterials are potentially suitable for biotechnological uses. In this critical review, we cover the literature containing rheological characterization of the physical properties of peptide and polypeptide-based hydrogels including hydrogel bulk mechanical properties, gelation mechanisms, and the behavior of hydrogels during and after flow. PMID:20422104

  11. Relationship between electrical and rheological properties of sewage sludge - Impact of temperature.

    PubMed

    Ségalen, C; Dieudé-Fauvel, E; Clément, J; Baudez, J C

    2015-04-15

    Rheological properties are key criteria for sewage sludge management but are difficult to determine in situ. Because the literature often links rheological characteristics to surface charges of particles that interact, the underlying electrostatic interactions could be key characteristics explaining the rheological behavior of sludge. This paper analyzed the impact of temperature on both rheological and electrical properties. Both liquid and solid properties appear to be related to electrical impedance spectroscopy measurements because they obey the same relationships with the same activation energies. Infinite viscosity follows an Arrhenius law with temperature, whereas the storage modulus shows VTF (Vogel-Tamman-Fulcher) behavior. Sludge electrical behavior can be modeled by an equivalent 2-branch parallel circuit whose respective impedances follow Arrhenius and VTF relationships. More interestingly, resistors are proportional to (dissipative) viscous characteristics, whereas capacitances are proportional to the (storage) elastic modulus. These similarities and relationships underlie the same interactions that seem to be involved in both rheological and electrical properties. These interdependences are quite logical but open new insights into sludge characterization. PMID:25634652

  12. Effects of rheological properties on ice-templated porous hydroxyapatite ceramics.

    PubMed

    Zhang, Yan; Zhou, Kechao; Bao, Yinxiang; Zhang, Dou

    2013-01-01

    Freeze casting of aqueous suspension was investigated as a method for fabricating hydroxyapatite (HA) porous ceramics with lamellar structures. The rheological properties of HA suspensions employed in the ice-templated process were investigated systematically. Well aligned lamellar pores and dense ceramic walls were obtained successfully in HA porous ceramics with the porosity of 68-81% and compressive strength of 0.9-2.4 MPa. The results exhibited a strong correlation between the rheological properties of the employed suspensions and the morphology and mechanical properties of ice-templated porous HA ceramics, in terms of lamellar pore characteristics, porosities and compressive strengths. The ability to produce aligned pores and achieve the manipulation of porous HA microstructures by controlling the rheological parameters were demonstrated, revealing the potential of the ice-templated method for the fabrication of HA scaffolds in biomedical applications. PMID:25428079

  13. THE RHEOLOGICAL PROPERTIES OF WHEAT PROTEIN ISOLATE PROLITE TM 200 SUSPENSIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Linear and non-linear rheological properties of wheat protein isolate PROLITE TM 200 suspensions were investigated as a function of concentration and pH. Linear dynamic viscoelastic properties for PROLITE TM 200 were strongly dependent on concentration and pH. The higher the concentration, the str...

  14. Modification of rheological, thermal and functional properties of tapioca starch using gum arabic

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The addition of gum arabic (GA) to native tapioca starch (TS) to modify the functionality of TS was investigated. GA is well known for its stabilizing, emulsifying, and thickening properties. The effects of adding GA (0.1-1.0%) on pasting, rheological and solubility properties of TS (5%) were analy...

  15. Gelatins as rock analogs: a systematic study of their rheological and physical properties

    NASA Astrophysics Data System (ADS)

    Corbi, F.; di Giuseppe, E.; Funiciello, F.; Ranalli, G.; Mojoli, G.

    2009-04-01

    The choice of an analog material for laboratory scale models of tectonic processes is subject to conditions of geometric, kinematic, and dynamic similarity. In the crust/lithosphere system, rheological layering is a consequence of both compositional layering and the variations of temperature with depth. It is therefore important to search for model materials which scale properly and reproduce in the laboratory the whole spectrum of rheological behavior, from brittle to viscoelastic to viscous. The rheological and physical properties of a wide range of gelatins, in both gel- and sol-state, are systematically investigated as functions of temperature, composition, concentration, ageing and applied strain rate. Several types of rheometric tests (amplitude sweep, frequency sweep, temperature sweep) and flow tests are used to obtain storage and loss moduli, strength properties, viscoelastic range, and fluid viscosity. Other physical properites (density and thermal parameters) are also measured and compiled. The rheological variability of gelatins appears promising for their potential use as analog materials to model crustal and lithospheric deformation. As an example, the rheological and physical properties of pig skin 2.5%wt at 10°C are analyzed, and found to satisfy the scaling requirements for experimental models of crustal deformation.

  16. The effect of structural and rheological properties on blood flow distributions in capillary networks

    NASA Astrophysics Data System (ADS)

    Goldman, Daniel

    2001-11-01

    In various tissues microvascular structure, both geometric and topological, has been shown to be an important determinant of microcirculatory hemodynamics. In addition, blood rheology affects flow and hematocrit distributions in the microcirculation. Here we study steady-state hemodynamics in capillary networks modeled on the three-dimensional structure of the hamster cheek pouch retractor muscle. Capillary diameter is fixed while other structural properties are varied and an ensemble of similar random networks is generated for each parameter set. Using an experimentally derived two-phase continuum model for the flow of blood plasma and red cells, we investigate the effects of network size and topology on blood flow distributions and their variability. We also use typical capillary network structures to examine the importance of rheological effects under varying conditions. Our results indicate the relative importance of microvascular structure and blood rheology in determining the hemodynamic properties of capillary networks in striated muscle.

  17. Development and rheological properties of ecological emulsions formulated with a biosolvent and two microbial polysaccharides.

    PubMed

    Trujillo-Cayado, L A; Alfaro, M C; Muñoz, J; Raymundo, A; Sousa, I

    2016-05-01

    The influence of gum concentration and rhamsan/welan gum ratio on rheological properties, droplet size distribution and physical stability of eco-friendly O/W emulsions stabilized by an ecological surfactant were studied in the present work. The emulsions were prepared with 30wt% α-pinene, a terpenic solvent and an ecological alternative for current volatile organic compounds. Rheological properties of emulsions showed an important dependence on the two studied variables. Flow curves were fitted to the Cross model and no synergistic effect between rhamsan and welan gums was demonstrated. Emulsions with submicron mean diameters were obtained regardless of the gum concentration or the rhamsan/welan ratio used. Multiple light scattering illustrated that creaming was practically eliminated by the incorporation of polysaccharides. The use of rhamsan and welan gums as stabilizers lead to apparent enhancements in emulsion rheology and physical stability. PMID:26826979

  18. Rheological and Mechanical Properties of Crosslinked Block Copolymer Nanofiber and Polystyrene Blends.

    NASA Astrophysics Data System (ADS)

    Ma, Sungwon; Thio, Yonathan

    2009-03-01

    The mechanical and rheological properties of blends of crosslinked and uncrosslinked poly(styrene)-b-poly(isoprene) copolymer with commercially available polystyrene were studied. Cylindrical morphology of PS-b-PI copolymer was employed for generating nanofiber morphology. Cold vulcanization process using sulfur monochloride (S2Cl2) was used to preserve the morphology. Blends of uncrosslinked PS-b-PI copolymer with neat polystyrene were also prepared. Both blend samples were prepared by solvent casting method with the filler contents varying between 0.5 and 10 wt%. The mechanical and rheological properties were characterized and the microstructures of the fiber and the systems were imaged. The dynamic moduli (G' and G'') of the crosslinked system increased with increasing the fiber content compared to the uncrosslinked system. The results were compared to the rheological model by fitting to Cross-Williamson. This blend study indicated critical volume concentration of nanofiber between 5 and 10 wt% of nanofiber content.

  19. Rheological Properties of a Biological Thermo-Hydrogel Produced from Soybean Oil Polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of a newly developed biological thermo-hydrogel made from vegetable oil were investigated. The material named HPSO-HG is a hydrolytic product of polymerized soybean oil (PSO). HPSO-HG exhibited viscoelastic behavior above 2% (wt.%) at room temperature and viscous fluid b...

  20. Rheological properties of a biological thermo-responsive hydrogel produced from soybean oil polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of a newly developed biological thermo-hydrogel made from vegetable oil were investigated. The material named HPSO-HG is a hydrolytic product of polymerized soybean oil (PSO). HPSO-HG is a thermo-responsive gel, and it exhibited viscoelastic behavior above 2% (wt.%) at roo...

  1. Effect of salt on the functional and rheological properties of fresh Queso Fresco

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Queso Fresco (QF), a high-moisture fresh Hispanic-style cheese, typically contains 1.5 to 2.0% salt that gives it a distinct salty flavor and helps control spoilage microorganisms. This study investigated the contribution of salt to the functional and rheological properties of QF to provide the basi...

  2. Effect of salt on the chemical, functional, and rheological properties of Queso Fresco during storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The contribution of salt to the functional and rheological properties of Queso Fresco (QF), a high-moisture fresh Hispanic-style cheese, was investigated to provide the basis for developing a low-salt version. QF was manufactured in triplicate from pasteurized, homogenized milk using a commercial pr...

  3. Effect of Hydrothermal Treatment on the Physicochemical, Rheological, and Oil-Resistant Properties of Rice Flour

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice flour was thermo-mechanically modified by steam jet-cooking and the physico-chemical and rheological properties of the resulting product were characterized. Then, its performance in frying batters was evaluated as an oil barrier. Compared to native rice flour, the steam jet-cooked rice flour ...

  4. Rheological and pasting properties of buckwheat (Fagopyrum esculentum Moench) flours with and without jet-cooking

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pasting, rheological and water-holding properties of buckwheat (Fagopyrum esculentum) flour obtained from whole achenes separated into three particle sizes, and three commercial flours (Fancy, Supreme and Farinetta) were measured with or without jet-cooking. Fancy had instantaneous paste viscosity ...

  5. The Rheological Properties of Poly(Vinyl Alcohol) Gels from Rotational Viscometry

    ERIC Educational Resources Information Center

    Hurst, Glenn A.; Bella, Malika; Salzmann, Christoph G.

    2015-01-01

    A laboratory experiment was developed to follow the gelation of a polyvinyl alcohol (PVA) solution upon addition of borax by using rotational viscometry. The rheological properties of the gel were examined, measuring the dependence of viscosity and shear stress on the shear rate. Time-dependent studies were also conducted in which the viscosity of…

  6. Rheological properties of reactive extrusion modified waxy starch and waxy starch-polyacrylamide copolymer gels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of modified waxy starch and waxy starch-polyacrylamide graft copolymers prepared by reactive extrusion were investigated. Both materials can absorb huge amount of water and form gels. The modified waxy starch and waxy starch-polyacrylamide graft copolymer gels all exhibite...

  7. Rheological Properties of Aqueous Dispersions of Amylose-Sodium Palmitate Complexes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A wide range of materials with applications as thickeners and as dispersants for lipids can be formed from aqueous dispersions of amylose helical inclusion complexes with sodium palmitate. This work examines the range of rheological properties that can be obtained by preparing materials under a var...

  8. Rheological properties of a biological thermo-responsive hydrogel produced from soybean oil polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of a newly developed biological thermo-hydrogel made from vegetable oil were investigated. The material named HPSO-VI is a hydrolytic product of polymerized soybean oil (PSO). HPSO-VI exhibited viscoelastic behavior above 2% (wt. %) at room temperature and viscous fluid ...

  9. Pasting and rheological properties of ß-glucan-enriched hydrocolloids from oat bran concentrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pasting and rheological properties of four oat hydrocolloids with different contents of ß-glucan (Nutrim10, C-Trim20, C-Trim30, and C-Trim50) were characterized and compared with oat bran concentrate (OBC) and ß-Glucan 95%. C-Trim30 and C-Trim50 had significantly higher water holding capacities comp...

  10. Effects of sorghum flour addition on chemical and rheological properties of hard white winter wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was carried out to investigate the chemical and rheological properties of different blends prepared using hard white winter wheat and whole or decorticated sorghum. Whole and decorticated sorghum were used to replace 5, 10, 15, and 20% of wheat flour. Wheat samples had higher protein, moi...

  11. Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties the starch graftpolyacrylamide product when a gel is formed in water...

  12. Rheological properties of the product slurry of the Nitrate to Ammonia and Ceramic (NAC) process

    SciTech Connect

    Muguercia, I.; Yang, G.; Ebadian, M.A.; Lee, D.D.; Mattus, A.J.; Hunt, R.D.

    1995-03-01

    The Nitrate to Ammonia and Ceramic (NAC) process is an innovative technology for immobilizing the liquid from Low Level radioactive Waste (LLW). An experimental study was conducted to measure the rheological properties of the pipe flow of the NAC product slurry. Test results indicate that the NAC product slurry has a profound rheological behavior. At low solids concentration, the slurry exhibits a typical dilatant fluid (or shear thinning)fluid. The transition from dilatant fluid to pseudo-plastic fluid will occur at between 25% to 30% solids concentration in temperature ranges of 50--80{degree}C. Correlation equations are developed based on the test data.

  13. Effects of ripening on rheological properties of avocado pulp (Persea americana mill. Cv. Hass)

    NASA Astrophysics Data System (ADS)

    Osorio, F.; Roman, A.; Ortiz, J.

    2015-04-01

    Avocado (Persea americana Mill) Hass variety is the most planted in Chile with a greater trade prospect. The aim of this study was to investigate the effect of maturity on rheological properties of Chilean Avocado Hass pulp. Fresh unripe avocados were washed and peeled, cut and stored at 3 different times; a portion was treated at 5°C and the other was treated at 20°C until it reached 2 lb puncture pressure. During maturation changes would develop due to temperature and time, with internal cellular structure changes. Preliminary results of the rheological characteristics of avocado puree show a Bingham plastic behavior.

  14. Rheological Properties of Silica Nanoparticles in Brine and Brine-Surfactant Systems

    NASA Astrophysics Data System (ADS)

    Pales, Ashley; Kinsey, Erin; Li, Chunyan; Mu, Linlin; Bai, Lingyun; Clifford, Heather; Darnault, Christophe

    2016-04-01

    Rheological Properties of Silica Nanoparticles in Brine and Brine-Surfactant Systems Ashley R. Pales, Erin Kinsey, Chunyan Li, Linlin Mu, Lingyun Bai, Heather Clifford, and Christophe J. G. Darnault Department of Environmental Engineering and Earth Sciences, Laboratory of Hydrogeoscience and Biological Engineering, L.G. Rich Environmental Laboratory, Clemson University, Clemson, SC, USA Nanofluids are suspensions of nanometer sized particles in any fluid base, where the nanoparticles effect the properties of the fluid base. Commonly, nanofluids are water based, however, other bases such as ethylene-glycol, glycerol, and propylene-glycol, have been researched to understand the rheological properties of the nanofluids. This work aims to understand the fundamental rheological properties of silica nanoparticles in brine based and brine-surfactant based nanofluids with temperature variations. This was done by using variable weight percent of silica nanoparticles from 0.001% to 0.1%. Five percent brine was used to create the brine based nanofluids; and 5% brine with 2CMC of Tween 20 nonionic surfactant (Sigma-Aldrich) was used to create the brine-surfactant nanofluid. Rheological behaviors, such as shear rate, shear stress, and viscosity, were compared between these nanofluids at 20C and at 60C across the varied nanoparticle wt%. The goal of this work is to provide a fundamental basis for future applied testing for enhanced oil recovery. It is hypothesized that the addition of surfactant will have a positive impact on nanofluid properties that will be useful for enhance oil recovery. Differences have been observed in preliminary data analysis of the rheological properties between these two nanofluids indicating that the surfactant is having the hypothesized effect.

  15. Rheological and structural properties of sea cucumber Stichopus japonicus during heat treatment

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Xue, Dongmei; Zhang, Zhaohui; Xu, Jiachao; Xue, Changhu

    2005-07-01

    Changes in tissue structure, rheological properties and water content of raw and heated sea cucumber meat were studied. Sea cucumber Stichopus japonicus was heated at 25°C , 70°C and 100°C water for 5 min. The structural changes were observed using a light microscope and the rheological parameters (rupture strength, adhesive strength and deformation) determined using a texture meter. Microscopic photograph revealed that the structural change of heated meat was greater than that of raw meat. The rupture strength, adhesive strength and deformation of raw meat were smaller than those of the heated meat. Meanwhile, rheological parameters showed positive correlation with heating temperature. These changes are mainly caused by thermal denaturation and gelatinization of collagen during heating. These changes were also evidenced in observations using a light microscope and differential scanning calorimetry.

  16. Rheological properties of wood polymer composites and their role in extrusion

    NASA Astrophysics Data System (ADS)

    Duretek, I.; Schuschnigg, S.; Gooneie, A.; Langecker, G. R.; Holzer, C.

    2015-04-01

    The influence of the rheological behaviour of PP based wood plastic composites (WPC) has been investigated in this research by means of a high pressure capillary rheometer incorporating dies having different geometries. The rheological experiments were performed using slit and round dies. The influence of moisture content on the flow properties of the WPC has been investigated as well. It was observed that higher moisture contents lead to wall slippage effect. Furthermore, measured viscosity data have been used in flow simulation of an extrusion profile die. Also, the influence of different rheological models on the simulation results is demonstrated. This research work presents a theoretical and experimental study on the measurement and prediction of the die pressure in the extrusion process of wood-plastic composite (WPC).

  17. Effect of Cephalaria syriaca addition on rheological properties of composite flour

    NASA Astrophysics Data System (ADS)

    Karaoðlu, M. M.

    2012-10-01

    The study was carried out to investigate the effect of whole and defatted Cephalaria syriaca flour on the rheological properties of composite flours that used in bran bread production. Cephalaria syriaca products were used to replace 0.25, 0.75, 1.25, 1.75, and 2.25% of wheat-wheat bran composite flour, and its rheological and fermentative properties were measured by farinograph, extensograph and rheofermentometre. The data showed that the rheological parameters of flours were greatly modified by addition of Cephalaria syriaca. The rheological properties of wheatwheat bran composite flour added with whole and defatted Cephalaria syriaca flour were considerably improved with regard to especially extensograph characteristics such as dough resistance, area (energy), ratio number and rheofermentometer parameters such as Hm, T1, Tx, volume loss and gas retention, as compared to control. However addition of Cephalaria syriaca products adversely affected the farinograph characteristics. Generally, these effects of both whole and defatted Cephalaria syriaca flour increased, as the addition level increased. Maximum Tx, gas retention and area (energy) of dough were obtained from wheat-wheat bran composite flour added with 1.75% whole Cephalaria syriaca flour, while the highest dough stability was at addition level of 0.25% whole Cephalaria syriaca flour.

  18. Effect of pH on Rheological Properties of Dysphagia-Oriented Thickened Water

    PubMed Central

    Yoon, Seung-No; Yoo, Byoungseung

    2016-01-01

    Flow and dynamic rheological properties of thickened waters prepared with commercial food thickeners were investigated at different pH levels (3, 4, 5, 6, and 7). The commercial xanthan gum (XG)-based thickener (thickener A) and starch-based thickener (thickener B), which have been commonly used in a domestic hospital and nursing home for patients with swallowing difficulty (dysphagia) in Korea, were selected in this study. Thickened samples with both thickeners at different pH levels showed high shear-thinning flow behaviors (n=0.08~0.22). Thickened samples at pH 3 showed higher n values and lower consistency index (K) values when compared to those at other pH levels. The K values of thickener A increased with an increase in pH level, while the n values decreased, showing that the flow properties greatly depended on pH. There were no noticeable changes in the K values of thickener B between pH 4 and 7. At pH 3, the thickened water with thickener A showed a higher storage modulus (G′) value, while that with thickener B showed a lower G′. These rheological parameters exhibited differences in rheological behaviors between XG-based and starch-based thickeners, indicating that the rheological properties of thickened waters appear to be greatly influenced by the acidic condition and the type of food thickener. Appropriately selecting a commercial food thickener seems to be greatly important for the preparation of thickened acidic fluids with desirable rheological properties for safe swallowing. PMID:27069910

  19. Effect of pH on Rheological Properties of Dysphagia-Oriented Thickened Water.

    PubMed

    Yoon, Seung-No; Yoo, Byoungseung

    2016-03-01

    Flow and dynamic rheological properties of thickened waters prepared with commercial food thickeners were investigated at different pH levels (3, 4, 5, 6, and 7). The commercial xanthan gum (XG)-based thickener (thickener A) and starch-based thickener (thickener B), which have been commonly used in a domestic hospital and nursing home for patients with swallowing difficulty (dysphagia) in Korea, were selected in this study. Thickened samples with both thickeners at different pH levels showed high shear-thinning flow behaviors (n=0.08~0.22). Thickened samples at pH 3 showed higher n values and lower consistency index (K) values when compared to those at other pH levels. The K values of thickener A increased with an increase in pH level, while the n values decreased, showing that the flow properties greatly depended on pH. There were no noticeable changes in the K values of thickener B between pH 4 and 7. At pH 3, the thickened water with thickener A showed a higher storage modulus (G') value, while that with thickener B showed a lower G'. These rheological parameters exhibited differences in rheological behaviors between XG-based and starch-based thickeners, indicating that the rheological properties of thickened waters appear to be greatly influenced by the acidic condition and the type of food thickener. Appropriately selecting a commercial food thickener seems to be greatly important for the preparation of thickened acidic fluids with desirable rheological properties for safe swallowing. PMID:27069910

  20. Buckwheat and Millet Affect Thermal, Rheological, and Gelling Properties of Wheat Flour.

    PubMed

    Wu, Kao; Gan, Renyou; Dai, Shuhong; Cai, Yi-Zhong; Corke, Harold; Zhu, Fan

    2016-03-01

    Buckwheat (BF) and millet (MF) are recommended as healthy foods due to their unique chemical composition and health benefits. This study investigated the thermal and rheological properties of BF-WF (wheat flour) and MF-WF flour blends at various ratios (0:100 to 100:0). Increasing BF or MF concentration led to higher cold paste viscosity and setback viscosity of pasting properties gel adhesiveness, storage modulus (G') and loss modulus (G″) of dynamic oscillatory rheology, and yield stress (σ0 ) of flow curve of WF. BF and MF addition decreased peak viscosity and breakdown of pasting, gel hardness, swelling volume, and consistency coefficient (K) of flow curve of WF. Thermal properties of the blends appeared additive of that of individual flour. Nonadditive effects were observed for some property changes in the mixtures, and indicated interactions between flour components. This may provide a physicochemical basis for using BF and MF in formulating novel healthy products. PMID:26890337

  1. Electrical and rheological properties of sewage sludge--Impact of the solid content.

    PubMed

    Ségalen, C; Dieudé-Fauvel, E; Baudez, J C

    2015-10-01

    Sludge treatment is a multistep process during which sludge is mixed, pumped, thickened and dewatered. The total solid content (TSC) increases from a few grams to more than a hundred grams per liter and as underlined by the existing literature, rheological characteristics are key criteria for sludge management. However, these characteristics remain difficult to be determined in-situ and professionals are looking for alternative techniques to evaluate them. In that context, the potential of electrical measurements has been highlighted (Dieudé-Fauvel et al., 2009, 2014). This paper investigates the additional benefits of correlating both rheological and electrical properties for sludge characterization within the range of 1-23%TSC. On a rheological point of view, results are consistent with previous literature. In parallel, electrical impedance spectroscopy allowed us to define an equivalent electrical circuit to model the sludge electrical signature. Results highlight that the circuit parameters follow two regimes according to the range of solid content, similarly to rheological properties. This work opens new insights about sludge characterization and treatment monitoring. PMID:26304590

  2. Pectin from Abelmoschus esculentus: optimization of extraction and rheological properties.

    PubMed

    Chen, Yi; Zhang, Jian-Guo; Sun, Han-Ju; Wei, Zhao-Jun

    2014-09-01

    Response surface methodology (RSM) was applied to optimize the parameters of pectin extraction from okra pods. The extracted okra pectin was then investigated by steady-shear and oscillatory rheological measurements. Statistical analysis showed that the linear term of the liquid-solid ratio, the quadratic term of the pH, and the linear term of the extraction time showed highly significant effects on pectin yield. The optimal extraction conditions that maximized the pectin yield within the experimental range of the variables researched were a pH of 3.9, an extraction time of 64 min, an extraction temperature of 60°C, and a liquid-solid ratio of 42:1. Under these conditions, the pectin yield was predicted to be 2.71%. At a liquid-solid ratio less than 2.5% w/w in aqueous solution, the pectin extracted from okra presented non-Newtonian shear-thinning behavior and could be well described by the Cross model. The okra pectin showed predominantly viscous responses (G'

  3. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions.

    PubMed

    Zhou, Ling; He, Hui; Li, Mei-Chun; Song, Kunlin; Cheng, H N; Wu, Qinglin

    2016-11-20

    The present work describes the isolation of cellulose nanoparticles (CNs) with different morphologies and their influence on rheological properties of CN and CN-poly (vinyl alcohol) (PVA) suspensions. Cottonseed hulls were used for the first time to extract three types of CNs, including fibrous cellulose nanofibers, rod-like cellulose nanocrystals and spherical cellulose nanoparticles through mechanical and chemical methods. Rheology results showed that the rheological behavior of the CN suspensions was strongly dependent on CN concentration and particle morphology. For PVA/CN systems, concentration of PVA/CN suspension, morphology of CNs, and weight ratio of CN to PVA were three main factors that influenced their rheology behaviors. This research reveals the importance of CN morphology and composition concentration on the rheological properties of PVA/CN, providing new insight in preparing high performance hydrogels, fibers and films base on PVA/CN suspension systems. PMID:27561516

  4. Rheological and physical properties of spray-dried mucilage obtained from Hylocereus undatus cladodes.

    PubMed

    García-Cruz, E E; Rodríguez-Ramírez, J; Méndez Lagunas, L L; Medina-Torres, L

    2013-01-01

    This study examines the rheological behavior of reconstituted spray-dried mucilage isolated from the cladodes of pitahaya (Hylocereus undatus), the effects of concentration and its relationship with physical properties were analyzed in reconstituted solutions. Drying process optimization was carried out through the surface response method, utilizing a factorial 2(3) design with three central points, in order to evaluate yield and rheological properties. The reconstituted mucilage exhibited non-Newtonian shear-thinning behavior, which adequately fit the Cross model (R(2)>0.95). This dynamic response suggests a random coil configuration. The steady-shear viscosity and dynamic response are suitably correlated through the Cox-Merz rule, confirming the mucilage's stability of flow. Analysis of the physical properties of the mucilage (Tg, DTP, and particle morphology) explains the shear-thinning behavior. PMID:23044149

  5. Measurement of the Rheological Properties of High Performance Concrete: State of the Art Report

    PubMed Central

    Ferraris, Chiara F.

    1999-01-01

    The rheological or flow properties of concrete in general and of high performance concrete (HPC) in particular, are important because many factors such as ease of placement, consolidation, durability, and strength depend on the flow properties. Concrete that is not properly consolidated may have defects, such as honeycombs, air voids, and aggregate segregation. Such an important performance attribute has triggered the design of numerous test methods. Generally, the flow behavior of concrete approximates that of a Bingham fluid. Therefore, at least two parameters, yield stress and viscosity, are necessary to characterize the flow. Nevertheless, most methods measure only one parameter. Predictions of the flow properties of concrete from its composition or from the properties of its components are not easy. No general model exists, although some attempts have been made. This paper gives an overview of the flow properties of a fluid or a suspension, followed by a critical review of the most commonly used concrete rheology tests. Particular attention is given to tests that could be used for HPC. Tentative definitions of terms such as workability, consistency, and rheological parameters are provided. An overview of the most promising tests and models for cement paste is given.

  6. Finite element analysis and simulation of rheological properties of bulk molding compound (BMC)

    NASA Astrophysics Data System (ADS)

    Ergin, M. Fatih; Aydin, Ismail

    2013-12-01

    Bulk molding compound (BMC) is one of the important composite materials with various engineering applications. BMC is a thermoset plastic resin blend of various inert fillers, fiber reinforcements, catalysts, stabilizers and pigments that form a viscous, molding compound. Depending on the end-use application, bulk molding compounds are formulated to achieve close dimensional control, flame and scratch resistance, electrical insulation, corrosion and stain resistance, superior mechanical properties, low shrink and color stability. Its excellent flow characteristics, dielectric properties, and flame resistance make this thermoset material well-suited to a wide variety of applications requiring precision in detail and dimensions as well as high performance. When a BMC is used for these purposes, the rheological behavior and properties of the BMC is the main concern. In this paper, finite element analysis of rheological properties of bulk molding composite material was studied. For this purpose, standard samples of composite material were obtained by means of uniaxial hot pressing. 3 point flexural tests were then carried out by using a universal testing machine. Finite element analyses were then performed with defined material properties within a specific constitutive material behavior. Experimental and numerical results were then compared. Good correlation between the numerical simulation and the experimental results was obtained. It was expected with this study that effects of various process parameters and boundary conditions on the rheological behavior of bulk molding compounds could be determined by means of numerical analysis without detailed experimental work.

  7. Determinations of molecular weight and molecular weight distribution of high polymers by the rheological properties

    NASA Technical Reports Server (NTRS)

    Huang, J. Y.; Hou, T. H.; Tiwari, S. N.

    1989-01-01

    Several methods are reviewed by which the molecular weight (MW) and the molecular weight distribution (MWD) of polymeric material were determined from the rheological properties. A poly(arylene ether) polymer with six different molecular weights was used in this investigation. Experimentally measured MW and MWD were conducted by GPC/LALLS (gel permeation chromatography/low angle laser light scattering), and the rheological properties of the melts were measured by a Rheometric System Four rheometer. It was found that qualitative information of the MW and MWD of these polymers could be derived from the viscoelastic properties, with the methods proposed by Zeichner and Patel, and by Dormier et al., by shifting the master curves of the dynamic storage modulus, G', and the loss modulus, G'', along the frequency axis. Efforts were also made to calculate quantitative profiles of MW and MWD for these polymers from their rheological properties. The technique recently proposed by Wu was evaluated. It was found that satisfactory results could only be obtained for polymers with single modal distribution in the molecular weight.

  8. Rheological properties, molecular distribution, and microstructure of Fortunella margarita (Lour.) swingle polysaccharides.

    PubMed

    Zeng, Hongliang; Zhang, Yi; Jian, Yeye; Tian, Yuting; Miao, Song; Zheng, Baodong

    2015-04-01

    Fortunella margarita polysaccharides (FMPS) are one of the main bioactive components of F. margarita. The activity is related to their rheological properties and structure. The objective of this study was to investigate the relationship between rheological properties, molecular distribution, and microstructure of crude FMPS (C-FMPS) and purified FMPS (P-FMPS). The results showed that both of solutions were shear-thinning pseudoplastic fluids with flow properties in line with the Power Law model. The pseudoplasticity of P-FMPS was stronger compared to C-FMPS. Additionally, the molecular weight and polydispersity of P-FMPS were greater, whereas the molecular radius was less compared to C-FMPS. The surface of C-FMPS was rough and dense whereas P-FMPS displayed a smooth network structure by environment scanning electron microscopy. According to confocal laser scanning microscopy, C-FMPS dispersed in the medium without connected network, whereas the network of P-FMPS was unevenly distributed in the medium and the shape was compact and smooth. The molecular distribution and microstructure of P-FMPS were attributed to the purification process while rearrangement and aggregation of polysaccharide molecules took place, which resulted in the significant difference of rheological properties between C-FMPS and P-FMPS. PMID:25716133

  9. A comparison of calculated and measured rheological properties of crystallising lavas in the field and in the laboratory

    NASA Technical Reports Server (NTRS)

    Pinkerton, Harry; Norton, Gill

    1993-01-01

    Models of most magmatic processes, including realistic models of planetary lava flows require accurate data on the rheological properties of magma. Previous studies suggest that field and laboratory rheological properties of Hawaiian lavas can be calculated from their physico-chemical properties using a non-Newtonian rheology model. The present study uses new measurements of the rheological properties of crystallizing lavas to show that this is also true for lavas from Mount Etna. Rheological measurements on quenched Etna basalts were made in a specially designed furnace using a Haake Rotovisco viscometer attached to a spindle which has been designed to eliminate slippage at the melt-spindle interface. Using this spindle, we have made measurements at lower temperatures than other workers in this field. From these measurements, Mount Etna lavas are Newtonian at temperatures above 1120 C and they are thixotropic pseudoplastic fluids with a yield strength at lower temperatures. The close agreement between calculated and measured rheology over the temperature range 1084 - 1125 C support the use of the non-Newtonian rheology model in future modeling of planetary lava flows.

  10. Effect of Maltodextrins on the Rheological Properties of Potato Starch Pastes and Gels

    PubMed Central

    Juszczak, Lesław; Gałkowska, Dorota; Fortuna, Teresa

    2013-01-01

    The study examines the effects of maltodextrins saccharified to various degrees on some rheological properties of potato starch dispersions. Pasting characteristics, flow curves, and mechanical spectra were determined for native potato starch and for its blends with potato maltodextrins having dextrose equivalents (DE) of 10.5, 18.4, and 26.5. The results showed that medium-saccharified maltodextrin (DE = 18.4) gave the strongest effect, manifesting itself as a considerable reduction in the viscosity at pasting, a decrease in apparent viscosity during flow, and a decrease in the storage and loss moduli. Addition of high-(DE = 26.5) or low-(DE = 10.5) saccharified maltodextrins had a markedly smaller effect on the rheological properties of starch. The differences in the effects produced by the maltodextrins are closely connected to the degree of polymerisation of the maltooligosaccharides in the systems. PMID:26904612

  11. Influence of molecular weight on structure and rheological properties of microcrystalline chitosan mixtures.

    PubMed

    Lewandowska, Katarzyna

    2015-08-01

    In the present work, the atomic force microscopy (AFM) studies and rheological properties of aqueous solutions of microcrystalline chitosan (MCCh), polyacrylamide (PAM) and their mixtures at different weight ratios have been investigated. Flow measurements were carried out using on solutions of native polymers and their mixtures with various weight fractions of components. It has been observed that the polymer solutions and their mixtures exhibited the non-Newtonian behavior with shear-thinning and/or shear-thickening areas. Rheological parameters from power law and activation energy of viscous flow are determined and discussed. The AFM images showed difference in surface properties films for the native polymers and their mixtures. The roughness of the mixtures increases with the increase of MCCh content. This may indicate a strong interaction between the polymeric components. PMID:26014140

  12. Rheological and physical properties of gelatin suspensions containing cellulose nanofibers for potential coatings.

    PubMed

    Andrade, Ricardo D; Skurtys, Olivier; Osorio, Fernando; Zuluaga, Robin; Gañán, Piedad; Castro, Cristina

    2015-07-01

    Rheological and physical properties of edible coating formulations containing gelatin, cellulose nanofibers (CNFs), and glycerol are characterized. Measured properties are analyzed in order to optimize edible coating thickness. Results show that coating formulations density increases linearly with gelatin concentration in presence of CNFs. Surface tension decreases with either gelatin or CNF concentration increases. Power law model well described the rheological behavior of edible coating formulations since determination coefficient was high (R(2 )> 0.98) and standard error was low (SE < 0.0052). Formulations showed pseudoplastic (shear-thinning) flow behavior and no time-dependent features were observed. The flow behavior index was not significantly affected by any factor. Consistency coefficient increases with gelatin concentrations but it decreases with glycerol concentrations. PMID:24831643

  13. The rheological properties of beta amyloid Langmuir monolayers: Comparative studies with melittin peptide.

    PubMed

    Caruso, Benjamín; Ambroggio, Ernesto E; Wilke, Natalia; Fidelio, Gerardo Daniel

    2016-10-01

    We determined the rheological properties of β-amyloid Langmuir films at the air/water interface, a peptide whose interfacial structure is extended β-sheet, and compared them with those of films composed of Melittin (Mel), which adopts an α-helical conformation at neutral pH. To determine the dilatational and shear moduli we evaluated the response of pure peptide monolayers to an oscillatory anisotropic compressive work. Additionally, a micro-rheological characterization was performed by tracking the diffusion of micrometer sized latex beads onto the interface. This technique allowed us the detection of different rheological behaviour between monolayers presenting a low shear response. Monolayers of the β-sheet structure-adopting peptides, such as β-amyloid peptides, exhibited a marked shear (elastic) modulus even at low surface pressures. In contrast, Mel monolayers exhibited negligible shear modulus and the micro-rheological shear response was markedly lower than that observed for either Aβ1-40 or Aβ1-42 amyloid peptides. When Mel monolayers were formed at the interface of an aqueous solution at pH 11, we observed an increase in both the lateral stability and film viscosity as detected by a slower diffusion of the latex beads, in keeping with an increase in β-sheet structure at this high pH (verified by ATR and FT-IR measurements). We suggest that the interactions responsible for the marked response upon shear observed for β-amyloid peptide monolayers are the hydrogen bonds of the β-sheet structure that can form an infinite planar network at the interface. Conversely, α-helical Mel peptide lack of these inter-molecular interactions and, therefore the shear contribution was negligible. We propose that the secondary structure is important for modulating the rheological behavior of short peptide monolayers regardless of the mass density or surface charge at the surface. PMID:27318963

  14. Salt matters: How salt affects the rheological and physical properties of gelatine for analogue modelling

    NASA Astrophysics Data System (ADS)

    Brizzi, S.; Funiciello, F.; Corbi, F.; Di Giuseppe, E.; Mojoli, G.

    2016-06-01

    Gelatine is extensively used as analogue material for the easiness to tune its physical and rheological properties. The addition of salt to gelatine is generally adopted to increase the density of the material, improving the scaling of the models. However, the way the addition of salt changes the rheological properties of gelatine is generally underestimated. Here, we investigate both rheological and physical properties (i.e., density and transparency) of type A pig-skin 2.5 wt.% gelatine at T = 10 °C as a function of salt concentration, cNaCl, and ageing time. We established a standard preparation recipe and measuring protocol, yielding to uniform samples with reproducible behaviour. Rheometric measurements show that the presence of salt weakens the gelatine structure, with a decrease of both material rigidity and viscosity as cNaCl increases. Salted gelatine behaviour moves from viscoelastic to dominantly elastic as the ageing time increases. Density and cloudiness also increase with cNaCl. Finally, we present results from subduction interplate seismicity models performed with pure and salted gelatines, showing that the modified material may improve the modelling performance and open new perspectives in experimental tectonics.

  15. Rheological properties of magnetorheological polishing fluid featuring plate-like iron particles

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Choi, Seung-Bok

    2014-10-01

    In this work, magnetorheological polishing fluid (MRP) rheological properties are experimentally investigated for bi-disperse suspension of plate-like iron particles and non-magnetic abrasive particles dispersed in carrier fluid to see the influence of small-sized non-magnetic particle on the large-size Mr fluid. As a first step, structural and morphology of iron plate-like particles are described in details. The rheological properties are then characterized using magnetorheometer. Particle size and volume fraction of both particles play an important role during the breaking and reforming the structure under application of magnetic field which influence on the rheological properties of MRP fluid. Three different constitutive models, such as the Bingham, Herschel-Bulkley and Casson equations are considered to evaluate their predictive capability of apparent viscosity of proposed MRP fluid. The yield stress increases with increasing magnetic field strength. The results obtained from three models show that the flow index exhibits shear thinning behavior of fluid. A comparative work between the model results and experimental results is also undertaken.

  16. Thermal and rheological properties of biodegradable poly[(butylene succinate)-co-adipate] nanocomposites.

    PubMed

    Bandyopadhyay, Jayita; Maity, Arjun; Khatua, Bhanu Bhusan; Ray, Suprakas Sinha

    2010-07-01

    The thermal and rheological properties of clay-containing poly[(butylene succinate)-co-adipate] (PBSA) nanocomposites are reported. The nanocomposites of PBSA with various weight percentages of organically modified montmorillonite (OMMT) loadings have been prepared by melt-mixing in a batch-mixer. The melting and crystallization behaviours of PBSA and its nanocomposites have been studied using differential scanning calorimeter (DSC). The melt-state rheological properties of pure PBSA and its nanocomposites containing different amounts of OMMT have been studied in detail. The reason for this is that the rheological responses of any nanofilled polymeric materials are strongly related by their dispersed structure and the interfacial characteristic. Results show that the structural strength of all samples remains constant in the examined time interval at an experimental temperature. The dominant viscous behaviour of pure PBSA is getting suppressed up to a certain OMMT loading (4 wt%). Nanocomposite containing 5 wt% OMMT is showing almost "at the gel point" behaviour, suggesting that the material is behaving near the borderline between liquid and solid; while nanocomposite containing 6 wt% OMMT is showing the gel character. The dispersed structure of the clay particles in the PBSA matrix was studied by scanning transmission electron microscopy (STEM). Results show that the stacked and intercalated silicate layers are nicely dispersed in the case of all nanocomposites. However, with a systematic increase in OMMT loading, the dispersed clay structure of the nanocomposites changes from a highly delaminated to a flocculated and then to a stacked-intercalated structure. In the case of all nanocomposites, melt-state rheological properties are in good agreement with the STEM observations. PMID:21128399

  17. Rheological properties of peanut oil-diesel fuel blends

    SciTech Connect

    Goodrum, J.W.; Law, S.E.

    1982-07-01

    Basic physical properties of peanut oil-diesel fuel blends were experimentally determined to help establish suitability for use in compression-ignition engines. For volumetric proportions of peanut oil ranging in 20 percent increments from 0 percent to 100 percent, the continuously varying properties at 21/sup 0/C were found to range as follows: heating value - 45.8 to 40.3 MJ/kg; specific gravity - 0.848 to 0.915; surface tension - 28.3 to 35.6 mN/m; and kinematic viscosity - 3.8 to 7.0 cSt. Dynamic viscosity measured as a function of shear rate over a 0/sup 0/C to 80/sup 0/C temperature range indicated nonNewtonian flow properties at shear rates less than 3/s.

  18. Rheological properties of aqueous solutions of biopolymeric hyaluronan

    NASA Astrophysics Data System (ADS)

    Szwajczak, Elzbieta

    2004-09-01

    Aqueous solutions of hyaluronic acid (hyaluronan, HA) were studied. The HA compound is a natural polysaccharide, bipolymer. It plays an important role in numerous biological processes as a component of the extracellular matrix, connective tissues and, especially, human and animal synovial joints. Natural and artificial solutions of the HA have demonstrated the viscoelastic nature. These properties are shown to be related to the microstructure parameters (bulk concentration, molecular weight) and external parameters (temperature, stress, shear rate). We emphasize the role of the flow properties of polymeric systems. It is found a liquid crystalline "order" can be "induced" during the material flow. The dynamic properties, such as the elastic shear modulus and viscous shear modulus, are given. These results are discussed in relation to the postulated function of hyaluronic acid in synovial joint and with respect to possibilities o their application in medicine and pharmacology.

  19. Rheological and Functional Properties of Catfish Skin Protein Hydrolysates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Catfish skin is an abundant and underutilized resource that can be used as a unique protein source to make fish skin hydrolysates. The objectives of this study were to: isolating soluble and insoluble proteins from hydrolyzed catfish skin and study the chemical and functional properties of the prote...

  20. Rheological and textural properties of pulse starch gels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The properties of starch gels from black beans, chickpeas, lentils and navy beans were investigated. Differences were shown between starch sources, and effect of starch concentration was studied. Navy bean starch had the highest peak and final viscosities in pasting tests, while black bean starch h...

  1. Oats Protein Isolate: Thermal, Rheological, Surface & Functional Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oat protein isolate (OPI) was extracted in 0.015 N NaOH in a 10:1 ratio solvent:flour and was precipitated by adjusting the pH to 4.5 and freeze-dried. The thermal properties of OPI were determined using Differential Scanning Calorimetry (DSC). OPI with 6% moisture content exhibited a glass transi...

  2. BARLEY PROTEIN ISOLATE: THERMAL, FUNCTIONAL, RHEOLOGICAL AND SURFACE PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Barley protein isolate (BPI) was prepared using hexane-defatted commercial barley flour. BPI was extracted in 0.05 N NaOH in a 10:1 ratio solvent:flour. The BPI was precipitated by adjusting the pH to 4.5 and freeze-dried. The thermal properties of the BPI were determined by Modulated Differentia...

  3. Rheological properties of natural waters with regard to plankton thin layers. A short review

    NASA Astrophysics Data System (ADS)

    Jenkinson, Ian R.; Sun, Jun

    2010-11-01

    The science of Rheology is painted with a broad brush, and the structure of matter is reviewed from the scales of the electron to those of a manufactured or a biologically produced article. The development of theory and measurements of viscosity and other rheological properties is then reviewed, and it is shown that values have been derived without regard to the scales of most ocean processes. After introducing the scales of length, time and stress, we show how measurements and the young theory of non-compression thalassorheology have developed over the last 25 years or so. Seawater viscosity is comprised of a Newtonian, perfectly dispersed component contributed by the water and salts, plus a non-Newtonian, less well dispersed component due to more or less lumpy organic exopolymeric substances (EPS) derived mainly from phytoplankton. The rheological properties (excess viscosity) may be expressed as an empirical coefficient and three exponents: the first for abundance; the second for dependence of excess viscosity on shear rate; and the third for its dependence on length scale. We also show the conditions (generally speaking, high EPS abundance, low shear stress, and small length scale), where excess viscosity is most often likely to be non-trivial relative to water viscosity.

  4. Rheological properties and tunable thermoplasticity of phenolic rich fraction of pyrolysis bio-oil.

    PubMed

    Sahaf, Amir; Laborie, Marie-Pierre G; Englund, Karl; Garcia-Perez, Manuel; McDonald, Armando G

    2013-04-01

    In this work we report on the preparation, characterization, and properties of a thermally treated lignin-derived, phenolic-rich fraction (PRF) of wood pyrolysis bio-oil obtained by ethyl acetate extraction. The PRF was characterized for viscoelastic and rheological behavior using dynamic mechanical analysis (DMA) and cone and plate rheology. A unique thermoplastic behavior was evidenced. Heat-treated PRFs acquire high modulus but show low temperatures of thermal flow which can be systematically manipulated through the thermal pretreatment. Loss of volatiles, changes in molecular weight, and glass transition temperature (Tg) were investigated using thermogravimetric analysis (TGA), mass spectrometry (MS), and differential scanning calorimetry (DSC), respectively. Underlying mechanisms for the thermal and rheological behavior are discussed with regard to interactions between pyrolytic lignin nanoparticles present in the system and the role of volatile materials on determining the properties of the material resembling in several aspects to colloidal suspension systems. Low thermal flow temperatures and reversible thermal effects can be attributed to association of pyrolytic lignin particles due to intermolecular interactions that are easily ruptured at higher temperatures. The thermoplastic behavior of PRF and its low Tg is of particular interest, as it gives opportunities for application of this fraction in several melt processing and adhesive technologies. PMID:23424996

  5. Effect of β-cyclodextrin on Rheological Properties of some Viscosity Modifiers.

    PubMed

    Rao, G Chandra Sekhara; Ramadevi, K; Sirisha, K

    2014-01-01

    Cyclodextrins are a group of novel excipients, extensively used in the present pharmaceutical industry. Sometimes they show significant interactions with other conventional additives used in the formulation of dosage forms. The effect of β-cyclodextrin on the rheological properties of aqueous solutions of some selected viscosity modifiers was studied in the present work. β-cyclodextrin showed two different types of effects on the rheology of the selected polymers. In case of natural polymers like xanthan gum and guar gum, enhanced apparent viscosity was found and in case of semi-synthetic polymers like sodium carboxymethyl cellulose and methyl cellulose, reduction in apparent viscosity was found. β-cyclodextrin was included at 0.5, 1 and 2% w/v concentrations into the polymeric solutions. These findings are useful in the adjustment of concentrations of viscosity modifiers during the formulation of physically stable disperse systems. PMID:25593389

  6. Influence of the nanotube oxidation on the rheological and electrical properties of CNT/HDPE composites

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Somma, Elvira; Valentino, Olga; Simon, George; Neitzert, Heinz-Christoph

    2016-05-01

    Rheological and electrical properties of nanocomposites based on multi-walled carbon nanotubes (MWNTs) and high density polyethylene (HDPE), prepared by melt mixing in a micro-twin screw extruder, have been investigated. The effect of MWNT concentration (0.5 and 2.5 wt %) and nanotube surface treatment (oxidative treatment in a tubular furnace at 500°C for 1 hr in a 95% nitrogen, 5% oxygen atmosphere) has been analyzed. It has been found that the sample conductivity with oxidation of the nanotubes decreases more than 2 orders of magnitude. Scanning electron microscopy showed good adhesion and dispersion of nanotubes in the matrix, independently of the surface treatment. Electrical and rheological measurements revealed that the oxidative treatment, causing some reduction of the MWNT quality, decreases the efficiency of the nanotube matrix interaction.

  7. Rheological properties and antitumor activity of schizophyllan produced with solid-state fermentation.

    PubMed

    Zhong, Kui; Liu, Liya; Tong, Litao; Zhong, Xin; Wang, Qiang; Zhou, Sumei

    2013-11-01

    Schizophyllan (SPG) was produced by the fungus Schizophyllum commune under solid-state fermentation conditions in this study. SPG was physically characterized and its rheological properties and antitumor effects on S180 tumors in vivo were evaluated. SPG is a neutral polysaccharide with three main fractions, and the major fraction comprises 55.5%, with an average molecular weight 4.65 × 10(7) Da. Steady shear rheological measurements showed the typical pseudoplastic flow behavior of SPG at the experimental concentrations. The power law model was used to fit the shear curves of SPG and both its viscosity and consistency indices changed regularly as the concentration increased. SPG solution showed different viscoelastic behaviors at different concentrations: typical viscoelastic behavior was observed at lower concentrations, whereas solid-like behavior was observed at higher concentrations. Experimental doses of SPG exerted extreme antitumor effects in vivo, and the maximum inhibition rate was almost 70%. PMID:23973493

  8. Effect of high hydrostatic pressure on rheological and thermophysical properties of murtilla (Ugni molinae Turcz) berries.

    PubMed

    Lemus-Mondaca, Roberto; Ah-Hen, Kong; Vega-Gálvez, Antonio; Zura-Bravo, Liliana

    2016-06-01

    Effects of high hydrostatic pressure (HHP) on rheological and thermophysical properties of murtilla berries were evaluated after pressure treatments for 5 min between 100 and 500 MPa. Differential scanning calorimetry was employed to measure specific heat capacity. HHP caused a significant decrease in specific heat and density, while thermal diffusivity did not changed significantly. Thermal conductivity showed a slight increase upon HHP treatment. Apparent viscosity increased significantly above 200 MPa HHP treatment. Apparent viscosity of treated samples between 200 and 400 MPa did not differ significantly and the increase was significant at 500 MPa. Herschel-Bulkley, Bingham and Ostwald de Waele models were used to describe the rheological behaviour of murtilla purée, and Ostwald de Waele model gave the best fit for the experimental data. PMID:27478228

  9. Effects of Iron Oxides on the Rheological Properties of Cementitious Slurry

    SciTech Connect

    Chung, Chul-Woo; Chun, Jaehun; Wang, Guohui; Um, Wooyong

    2014-04-02

    Iron oxide has been considered a promising host for immobilizing and encapsulating radioactive 99Tc (t1/2=2.1x105 year), which significantly enhances the stability of 99Tc within a cementitious waste form. However, the flow behavior of cementitious slurry containing iron oxide has never been investigated to ensure its workability, which directly influences the preparation and performance of the cementitious waste form monolith. Variation in the rheological properties of the cementitious slurry were studied using rheometry and ultrasonic wave reflection to understand the effects of various iron oxides (magnetite, hematite, ferrihydrite, and goethite) during the cement setting and stiffening processes. The rheological behavior significantly varied with the addition of different chemical compounds of iron oxides. Complementary microscopic characteristics such as colloidal vibration currents, morphology, and particle size distributions further suggest that the most adverse alteration of cement setting and stiffening behavior caused by the presence of goethite may be attributed to its acicular shape.

  10. The rheological properties of polysaccharides sequentially extracted from peony seed dreg.

    PubMed

    Shi, Jun-Jun; Zhang, Jian-Guo; Sun, Yu-Han; Xu, Qi-Xin; Li, Ling; Prasad, Chandan; Wei, Zhao-Jun

    2016-10-01

    The peony seed dreg polysaccharides (PSDPs) were sequentially extracted using hot buffer (HBSS), chelating agent (CHSS), dilute alkaline (DASS) and concentrated alkaline (CASS). The rheological properties of PSDPs were investigated by steady-shear and oscillatory rheological measurements. The four PSDPs fractions in solution exhibited typical non-Newtonian and shear-thinning behavior. The viscosity of HBSS was higher than the rest. While the viscosity value of all PSDPs solution decreased at acid pH (4.0) and alkaline pH (10.0), in the presence of Ca(2+) and high temperature (90°C), it increased in the presence of Na(+) and following freezing. The modulus G' and G" of all PSDPs solution were increased with increasing oscillation frequency ranging between 0.01 and 100Hz at each concentration. In all four cases, the crossover of G' and G" values decreased gradually with increasing concentration of samples. PMID:27311505

  11. Two-dimensional magnetic property measurement for magneto-rheological elastomer

    NASA Astrophysics Data System (ADS)

    Zeng, Jianbin; Guo, Youguang; Li, Yancheng; Zhu, Jianguo; Li, Jianchun

    2013-05-01

    Magneto-rheological elastomer (MRE) is a new kind of smart material. Its rheological properties can be altered and controlled in a real time manner when it is applied an external magnetic field. For calculating magnetic properties of MRE material, usually Maxwell-Garnet equation is used to acquire an approximately effective permeability. This equation treats the magnetic property of particles as linear. However, when the applied magnetic field is alternating or rotating, the nonlinearity of magnetic property and magnetic hysteresis cannot be neglected. Hence, the measurement and modelling of the magnetic properties under alternating and rotating magnetic fields are essential to explore new applications of the material. This paper presents the investigation on the magnetic hysteresis properties of MRE material under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations. A kind of MRE material, consisting of 70% carbonyl iron particles, 10% silicone oil, and 20% silicone rubber, was used to investigate the magnetic properties. The diameter of carbonyl iron particles is 3-5 μm. The measurement results, such as the relations between magnetic field intensity (H) and magnetic flux density (B) under different magnetic field excitations on the MRE sample, have been obtained and analyzed. These data would be useful for design and analysis of MRE smart structures like MR dampers.

  12. Effective Rheological Properties in Semi-dilute Bacterial Suspensions.

    PubMed

    Potomkin, Mykhailo; Ryan, Shawn D; Berlyand, Leonid

    2016-03-01

    Interactions between swimming bacteria have led to remarkable experimentally observable macroscopic properties such as the reduction in the effective viscosity, enhanced mixing, and diffusion. In this work, we study an individual-based model for a suspension of interacting point dipoles representing bacteria in order to gain greater insight into the physical mechanisms responsible for the drastic reduction in the effective viscosity. In particular, asymptotic analysis is carried out on the corresponding kinetic equation governing the distribution of bacteria orientations. This allows one to derive an explicit asymptotic formula for the effective viscosity of the bacterial suspension in the limit of bacterium non-sphericity. The results show good qualitative agreement with numerical simulations and previous experimental observations. Finally, we justify our approach by proving existence, uniqueness, and regularity properties for this kinetic PDE model. PMID:27025378

  13. To the theory of rheological properties of magnetopolymer suspensions.

    PubMed

    Zubarev, Andrey Yu

    2013-10-28

    This paper deals with the theoretical study of the magnetorhelogical properties of dilute suspensions of polymer coils with ferromagnetic nanoparticles adsorbed on the macromolecules. The analysis shows that, under an applied magnetic field, these coils elongate in the field direction and swell. Both these factors lead to a significant increase in the effective viscosity of the system. Estimates show that in the magnetopolymer compositions, strong magnetoviscous effects are expected even though in standard ferrofluids these effects are negligible. PMID:26029780

  14. Study of rheological properties of polymeric liquids by using multiple-mode models

    NASA Astrophysics Data System (ADS)

    Jiang, Bangwu

    Knowledge of the rheological properties of non-Newtonian fluids is critical for modeling in polymer-processing equipment such as injection molders, extruders, and blow molders. Rheological measurements can be obtained through standard flows, such as shear flow and elongational flow. In our research, we modeled the rheological properties of polymeric fluids in several types of experiments: transient and steady shear flow, small amplitude oscillatory shear flow, transient elongational flow, and step-strain shear flow. The accuracy of modeling calculations depends critically on the performance of the rheological model used. Since most non-Newtonian media exhibit not just one, but a whole spectrum of relaxation times; therefore multiple relaxation modes models were used in our research. One of the coupled linear relaxation models, the Two Coupled Maxwell Modes (TCMM) Model, was used to describe quantitatively shear-thickening behavior. A full parameterization of the TCMM Model provided a thorough understanding of the significance of the model parameters and a clear insight into the peculiar behavior of shear thickening in dilute polymer solutions. The primary part of the research focused on models with linear springs. A typical, industrial-grade, low-density polyethylene polymer was studied using three types of multi-mode models. The data from small amplitude oscillatory shear flow and steady shear flow were fitted to obtain the parameters of the different models. Then the predictions for the other standard flows mentioned in the first paragraph were compared with experimental data. Overall evaluations of model performance were presented in detail. Finally, we tested the effects of spring type on the performance of the models described above. We replaced the linear elastic springs in all of the prior models with nonlinear springs to determine whether this would improve model performance in elongational flow. The Finitely-Extensible Nonlinear Elastic Spring Model was

  15. Correlation of average hydrophobicity, water/air interface surface rheological properties and foaming properties of proteins.

    PubMed

    Medrano, A; Abirached, C; Araujo, A C; Panizzolo, L A; Moyna, P; Añón, M C

    2012-04-01

    A comparative study on the behavior in the air-water interface of β-lactoglobulin, α-lactoalbumin, glycinin and β-conglycinin was performed. The behavior at the interface was evaluated by equilibrium surface tension and surface rheological properties of adsorbed films. There were significant differences (α ≤ 0.05) in the values of the constants of adsorption to the interface of the four proteins. The glycinin had the slowest rate of adsorption, due to its low average hydrophobicity, low molecular flexibility and large molecular size. Smaller proteins like β-lactoglobulin and α-lactoalbumin tended to greater equilibrium pressure values than the larger proteins because of its higher rate of adsorption to the interface. The foam capacity of proteins showed a positive correlation with the average hydrophobicity; the maximal retained liquid volume or the initial rate of passage of liquid to foam were significantly lower (α ≤ 0.05) when protein was glycinin. The dilatational modulus of glycinin was the lowest, which implies lowest resistance to disruption of the film. Glycinin protein has lower proportion of gravitational drainage and higher disproportionation having perhaps a less resistant film. In conclusion, β-conglycinin and whey proteins showed a similar behavior, so β-conglycinin might be the best soybean protein to replace milk proteins in food formulations. PMID:22414931

  16. [Development of technology, of rheological and biopharmaceutical properties of new gel].

    PubMed

    Mekhralieva, S Dzh

    2013-04-01

    The purpose of this research is the development of technology for preparation of hydrogel Glysotrical and study its rheological and biopharmaceutical characteristics. Based on gel-forming chitosan, PEG-400, glycerol and Tween-80 a new composition of hydrogel - Glysotrical was developed. Rheological properties of Glysotrical, as well as biopharmaceutical properties of artificial (cellophane) and natural membrane (chicken and pork skin) were investigated by dialysis. Rheological properties of different concentrations of chitosan solution and gel Glysotrical prepared on their basis were studied. It was determined that gel derived from the 5% solution of chitosan meets the technological requirements (pH-5,5-6,0, melting point-75,0±1,07°C, dynamic viscosity - 890,6 ± 3,57 cps). Rheological properties of the hydrogel Glysotrical, prepared on the basis of a multi-component composition in different temperatures (20, 40, 60°C) were identified. It was found that shear of helium drug (458 H/m2, 355 H/m2) at 20° and 40°C is lower, and the value of dynamic viscosity (912spz, 602spz) higher than that of chitosan gel; the hydrogel is stable at 20° and 40°C. High kinetic activity of hydrogel with Tween-80 is observed. During 5 hours membrane maximum quantity of routine diffusion from helium mass into dialysate in cellophane is 57,54 ±0,51%; in normal skin chicken - 20,04±0,55%; in the skin of chicken treated with 2% citric acid - 23,14±0,45%; normal pig skin - 12,64±0,09%; in the skin of pigs, treated with acid - 15,08± 0,11%. The study showed that the gel Glysotrical at 10-22°C is maintained for 2 years. Physico-chemical, rheological, technological and biopharmaceutical research showed that 4% gel Glysotrical was good in treatment of dermatological diseases. PMID:23676493

  17. Viscoelastic properties of magneto- and electro-rheological fluids

    SciTech Connect

    Weiss, K.D.; Carlson, J.D.; Nixon, D.A.

    1994-12-31

    This paper examines the transition area between elastic and viscous behavior for a conventional electrorheological (ER) fluid and a state-of-the-art magnetorheological (MR) fluid through the use of oscillatory rheometry techniques. A comparison between the yield behavior (strain and stress) measured for these two different types of controllable fluids is presented. The data obtained for MR fluids represents the initial characterization of the pre-yield properties exhibited by this type of material. Finally, a recommendation as to a key area for future R and D is highlighted.

  18. Rheological regional properties of brain tissue studied under cyclic creep/ recovery shear stresses

    NASA Astrophysics Data System (ADS)

    Boudjema, F.; Lounis, M.; Khelidj, B.; Bessai, N.

    2015-04-01

    The rheological properties of brain tissue were studied by repeated creep-recovery shear tests under static conditions for different regions. Corpus callosum CC, Thalamus Th and Corona radiata CR. Non-linear viscoelastic model was also proposed to characterize the transient/steady states of shear creep results. From the creep-recovery data it was obvious that the brain tissues show high regional anisotropy. However. the both samples exhibit fluid viscoelastic properties in the first shear stress cycle of 100 Pa, while this behaviour evolutes to solid viscoelastic with cyclic effect.

  19. Correlation of stability/rheology relationship with coal: Properties and chemical additives

    SciTech Connect

    Ohene, F.

    1992-02-19

    Coal-water slurries have the potential of a near term replacement for fuel oil. In order to gain the fundamental understanding of the preparation and handling of coal-water slurries, experiments were performed to identify the relationship between the coal content of a given coal-water slurry and its physical and chemical properties. The objectives of this program were: Investigate the relationship between the chemical and physical properties of coal and the rheology of coal-water slurry Define procedures for evaluating and preparing coal water slurries for a particular coal candidate, based on the characteristic coal properties Develop improved methods of screening surfactants used in coal-water slurry preparation Perform experiments designed to investigate the effect of characteristic coal properties on slurry quality, by examining the effect of the individual coal properties on slurry quality Develop a statistical formulation to predict the coal content of a given coal water slurry content based on the coal characteristic properties.

  20. Effect of colloidal silica on rheological properties of common pharmaceutical excipients.

    PubMed

    Majerová, Diana; Kulaviak, Lukáš; Růžička, Marek; Štěpánek, František; Zámostný, Petr

    2016-09-01

    In pharmaceutical industry, the use of lubricants is mostly based on historical experiences or trial and error methods even these days. It may be demanding in terms of the material consumption and may result in sub-optimal drug composition. Powder rheology enables more accurate monitoring of the flow properties and because the measurements need only a small sample it is perfectly suitable for the rare or expensive substances. In this work, rheological properties of four common excipients (pregelatinized maize starch, microcrystalline cellulose, croscarmellose sodium and magnesium stearate) were studied by the FT4 Powder Rheometer, which was used for measuring the compressibility index by a piston and flow properties of the powders by a rotational shear cell. After an initial set of measurements, two excipients (pregelatinized maize starch and microcrystalline cellulose) were chosen and mixed, in varying amounts, with anhydrous colloidal silicon dioxide (Aerosil 200) used as a glidant. The bulk (conditioned and compressed densities, compressibility index), dynamic (basic flowability energy) and shear (friction coefficient, flow factor) properties were determined to find an optimum ratio of the glidant. Simultaneously, the particle size data were obtained using a low-angle laser light scattering (LALLS) system and scanning electron microscopy was performed in order to examine the relationship between the rheological properties and the inner structure of the materials. The optimum of flowability for the mixture composition was found, to correspond to empirical findings known from general literature. In addition the mechanism of colloidal silicone dioxide action to improve flowability was suggested and the hypothesis was confirmed by independent test. New findings represent a progress towards future application of determining the optimum concentration of glidant from the basic characteristics of the powder in the pharmaceutical research and development. PMID:27163240

  1. [Rheological properties of human bronchial secretions: demonstration of proline-rich polypeptides and their role (author's transl)].

    PubMed

    Bailleul, V; Richet, C; Hayem, A; Degand, P

    1977-01-17

    Human bronchial secretions were examined for chemical components and rheological properties. Proline-rich polypeptides (PRP) obtained by ultrasonic treatment and by contact with a cationic resin (AG 50WX2) were purified by gel-filtration chromatography and high-voltage electrophoresis. The chemical composition of these components allowed a classification according to their proline, glycine, glutamic acid and lysine contents. Rheological experiments suggest a biological role for the PRP in the fibrillar structure of sputum. PMID:12892

  2. Rheology and hydrodynamic properties of Tolypocladium inflatum fermentation broth and its simulation.

    PubMed

    Benchapattarapong, N; Anderson, W A; Bai, F; Moo-Young, M

    2005-07-01

    A physico-chemical, two phase simulated pseudoplastic fermentation (SPF) broth was investigated in which Solka Floc cellulose fibre was used to simulate the filamentous biomass, and a mixture of 0.1% (w/v) carboxymethyl cellulose (CMC) and 0.15 M aqueous sodium chloride was used to simulate the liquid fraction of the fermentation broth. An investigation of the rheological behaviour and hydrodynamic properties of the SPF broth was carried out, and compared to both a fungal Tolypocladium inflatum fermentation broth and a CMC solution in a 50 L stirred tank bioreactor equipped with conventional Rushton turbines. The experimental data confirmed the ability of the two phase SPF broth to mimic both the T. inflatum broth bulk rheology as well as the mixing and mass transfer behaviour. In contrast, using a homogeneous CMC solution with a similar bulk rheology to simulate the fermentation resulted in a significant underestimation of the mass transfer and mixing times. The presence of the solid phase and its microstructure in the SPF broth appear to play a significant role in gas holdup and bubble size, thus leading to the different behaviours. The SPF broth seems to be a more accurate simulation fluid that can be used to predict the bioreactor mixing and mass transfer performance in filamentous fermentations, in comparison with CMC solutions used in some previous studies. PMID:15744504

  3. Thixoforming of an ECAPed Aluminum A356 Alloy: Microstructure Evolution, Rheological Behavior, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Campo, Kaio Niitsu; Zoqui, Eugênio José

    2016-04-01

    Thixoforming depends upon three aspects: (a) solid to liquid transformation; (b) size and morphology of the remaining solid phase in the semisolid state, and (c) the effect of both input factors on rheology of the semisolid slurry. The aluminum A356 alloy presents an ideal solid to liquid transformation, but the solidification process generates coarse aluminum dendrites surrounded by eutectic. In this regard, Equal Channel Angular Pressing (ECAP) has great potential as a method for manufacturing thixotropic raw material due to its grain refining effect. Therefore, the microstructure evolution and rheological behavior in the semisolid state of an ECAPed aluminum A356 alloy were investigated. Samples were heated up to 853 K (580 °C) and held for 0, 30, 60, 90, 210, and 600 seconds at this temperature. The isothermal heat treatment caused the globularization of the solid phase without any significant microstructure coarsening. Compression tests were carried out at the same temperature and holding times using an instrumented mechanical press. Apparent viscosities values close to 250 Pa s were obtained, revealing the exceptional rheological behavior of the produced samples. The thixoformed material also presented good mechanical properties, with high yield and ultimate tensile strength values (YS = 110/122 MPa, UTS = 173/202), and good ductility (E = 6.9/7.5 pct). These results indicate that the production of the A356 alloy via the ECAP process increases its thixoformability.

  4. Morphology evolution and rheological properties of polybutadiene/polyisoprene blend after the cessation of steady shear.

    PubMed

    Liu, Wei; Dong, Xia; Zou, Fasheng; Yang, Jian; Wang, Dujin; Han, Charles C

    2013-09-21

    The morphology evolution and rheological response of a near-critical composition polybutadiene/polyisoprene blend after the cessation of steady shear was studied with an ARES rheometer and a shear light scattering photometer equipped with an optical microscope in this work. The relationship between the morphology of the blend during the relaxation after the cessation of steady shear with different shear rates and their corresponding rheological properties was successfully established. It was found that the different shear-induced morphologies under steady shear would relax to the equilibrium states via varied mechanisms after the shear cessation. The average size of the dispersed domains in the coarsening process was influenced by the pre-shear history. The results indicated that the pre-shear history could slow down the growth rate of phase domains during the coarsening process. It had effect on the coarsening mechanism on the early stage of relaxation after the cessation of very strong shear when the homogenization effects were strong, but no effect on the late stage. The storage modulus G' increased significantly in the breakup process of the string-like phase. After all the string-like structures were broken up into small ellipsoids, then G' gradually decreased and finally approached to an invariant value. The characteristic rheological behavior can be attributed to the different structure on the relaxation process. PMID:24070308

  5. Rheological properties of granular materials - Critical parameters and mixing rules

    NASA Astrophysics Data System (ADS)

    Vasilenko, Alisa Victoria

    2011-12-01

    Granular materials can be found at any stage of processing in many industries, such as food, pharmaceuticals, catalysts, and chemicals. These materials exhibit a variety of flow patterns, and their state and behavior differ from application to application. Since there is a lack of fundamental understanding of particulate or powder behavior, multiple problems can be encountered during routine manufacturing. Scale-up can also be a challenge, as the lack of constitutive equations for granular materials forces most scaleup efforts to follow the trial-and-error route. Powder characterization measurements are employed as both a selection tool and a predictive method for the material's process performance. Therefore, it plays a very important role in process and product development. The numerous existing methods used to characterize the flow properties of powders are mostly application-specific and it is not clear how they correlate with each other or with process performance. Moreover, understanding the relationships between the material properties and the processing conditions is necessary for a successful design of a continuous manufacturing system, which has been a major focus for pharmaceutical industry in the recent years. Before such changes can be implemented, a better understanding of fundamental physical phenomena governing powder flow behavior must be developed. In this work we study particulate/powder flow behavior experimentally using several characterization methods, including the Gravitational Displacement Rheometer (an avalanching tester), the rotational shear cell, and the compressibility tester. We establish the variables of interest through correlative comparison and study the differences and similarities between the methods in order to investigate particulate/powder flow behavior during processing and characterization. A mixing rule for principal stresses is developed through investigation of shear behavior of binary mixtures in a shear cell. In order

  6. Rheological properties of a reentrant nematic liquid crystal.

    PubMed

    Ananthaiah, J; Rajeswari, M; Sastry, V S S; Dabrowski, R; Dhara, Surajit

    2012-07-01

    We report experimental studies on small angle light scattering (SALS), and rheodielectric and electrorheological properties of a binary mixture of octyloxy cyanobiphenyl and hexyloxy cyanobiphenyl liquid crystals. The mixture exhibits nematic (N) to smectic-A (SmA) phase transitions, and then again to a reentrant nematic (N(R)) phase transition. Rapid shear thinning in the quenched samples in the low shear rate region in the N and SmA phases observed from SALS experiments is attributed to the realignment of the director within the domains. The domains are elongated along the shear direction at higher shear rates. The temperature variation of the effective viscosity and static dielectric constant reveals the changes in the director orientation across N-SmA-N(R) phase transitions. At a steady shear rate the effective viscosity increases with the electric field in all the phases and saturates at much higher fields. It also exhibits two anomalous peaks across N-SmA-N(R) phase transitions beyond a particular field. The shear modulus of the SmA phase in an intermediate field is significantly larger than that measured at both low and high fields. This enhanced viscoelasticity of the SmA phase is argued to originate from the increased dislocation density. PMID:23005440

  7. Rheological properties of a reentrant nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Ananthaiah, J.; Rajeswari, M.; Sastry, V. S. S.; Dabrowski, R.; Dhara, Surajit

    2012-07-01

    We report experimental studies on small angle light scattering (SALS), and rheodielectric and electrorheological properties of a binary mixture of octyloxy cyanobiphenyl and hexyloxy cyanobiphenyl liquid crystals. The mixture exhibits nematic (N) to smectic-A (SmA) phase transitions, and then again to a reentrant nematic (NR) phase transition. Rapid shear thinning in the quenched samples in the low shear rate region in the N and SmA phases observed from SALS experiments is attributed to the realignment of the director within the domains. The domains are elongated along the shear direction at higher shear rates. The temperature variation of the effective viscosity and static dielectric constant reveals the changes in the director orientation across N-SmA-NR phase transitions. At a steady shear rate the effective viscosity increases with the electric field in all the phases and saturates at much higher fields. It also exhibits two anomalous peaks across N-SmA-NR phase transitions beyond a particular field. The shear modulus of the SmA phase in an intermediate field is significantly larger than that measured at both low and high fields. This enhanced viscoelasticity of the SmA phase is argued to originate from the increased dislocation density.

  8. Effect of Carboxymethylation on the Rheological Properties of Hyaluronan.

    PubMed

    Wendling, Rian J; Christensen, Amanda M; Quast, Arthur D; Atzet, Sarah K; Mann, Brenda K

    2016-01-01

    Chemical modifications made to hyaluronan to enable covalent crosslinking to form a hydrogel or to attach other molecules may alter the physical properties as well, which have physiological importance. Here we created carboxymethyl hyaluronan (CMHA) with varied degree of modification and investigated the effect on the viscosity of CMHA solutions. Viscosity decreased initially as modification increased, with a minimum viscosity for about 30-40% modification. This was followed by an increase in viscosity around 45-50% modification. The pH of the solution had a variable effect on viscosity, depending on the degree of carboxymethyl modification and buffer. The presence of phosphates in the buffer led to decreased viscosity. We also compared large-scale production lots of CMHA to lab-scale and found that large-scale required extended reaction times to achieve the same degree of modification. Finally, thiolated CMHA was disulfide crosslinked to create hydrogels with increased viscosity and shear-thinning aspects compared to CMHA solutions. PMID:27611817

  9. Stabilization and Control of Rheological Properties of Fe2O3/Al(OH)(3)-rich Colloidal Slurries Under High Ionic Strength and pH

    SciTech Connect

    Chun, Jaehun; Poloski, Adam P.; Hansen, E. K.

    2010-08-01

    Controlling the stability and rheological properties of colloidal slurries has been an important but challenging issue for various applications such as cosmetics, ceramic processing, and nuclear waste treatment. For example, at the Department of Energy (DOE) Hanford and Savannah River sites, operation of the waste treatment facilities with increased solids loading affects waste processing rates but impacts the rheological properties. We investigated various rheological modifiers on a Fe2O3-rich nuclear waste simulant, characterized by high ionic strength and pH, in order to reduce rheological properties of the colloidal slurry. Rheological modifiers change particle interactions in colloidal slurries; they mainly alter the electrostatic and steric interactions between particles, leading to a change in rheological properties. Weak acid type rheological modifiers strengthen electrostatic repulsion whereas nonionic/polymer surfactant type rheological modifiers introduce a steric repulsion. Using rheological analysis, it was found that citric acid and polyacrylic acid are good rheological modifiers for the simulant tested, effectively reducing yield stresses by as much as 70%. Further analysis supports that addition of such rheological modifiers increases the stability of the slurry. Binding cations in bulk solution and adsorption on the surface of the particles are identified as a reasonable working mechanism for citric acid and polyacrylic acid.

  10. The effects of salt on rheological properties of asphalt after long-term aging.

    PubMed

    Yu, Xin; Wang, Ying; Luo, Yilin; Yin, Long

    2013-01-01

    Limited studies in recent years have shown that asphalt pavement subject to seawater in coastal regions or deicing salt in cold regions may be seriously damaged after being soaked in saline water for a long time. However, there is limited research into the influence of salt on rheological properties of asphalt after long-term aging. In this study, rheological properties of unmodified and polymer-modified asphalt after long-term aging were tested after being soaked in different concentrations of salt (0.3%~5%) for different durations (1 day~30 days). Orthogonal array based on the Taguchi method was used for experimental design. The frequency sweep tests were performed on the specimens of aged asphalt after being soaked for complex modulus and phase angle master curves and ultimate fatigue temperature. BBR tests were performed for stiffness. The test results indicate that saline water appears to reduce low temperature properties and fatigue resistance properties and improved high temperature properties of aged asphalt, and it also affects the sensitivity of complex modulus and phase angles at low frequencies. PMID:24459450

  11. The Effects of Salt on Rheological Properties of Asphalt after Long-Term Aging

    PubMed Central

    Yu, Xin; Luo, Yilin; Yin, Long

    2013-01-01

    Limited studies in recent years have shown that asphalt pavement subject to seawater in coastal regions or deicing salt in cold regions may be seriously damaged after being soaked in saline water for a long time. However, there is limited research into the influence of salt on rheological properties of asphalt after long-term aging. In this study, rheological properties of unmodified and polymer-modified asphalt after long-term aging were tested after being soaked in different concentrations of salt (0.3%~5%) for different durations (1 day~30 days). Orthogonal array based on the Taguchi method was used for experimental design. The frequency sweep tests were performed on the specimens of aged asphalt after being soaked for complex modulus and phase angle master curves and ultimate fatigue temperature. BBR tests were performed for stiffness. The test results indicate that saline water appears to reduce low temperature properties and fatigue resistance properties and improved high temperature properties of aged asphalt, and it also affects the sensitivity of complex modulus and phase angles at low frequencies. PMID:24459450

  12. Effect of cream fermentation on microbiological, physicochemical and rheological properties of L. helveticus-butter.

    PubMed

    Ewe, Joo-Ann; Loo, Su-Yi

    2016-06-15

    The primary objective of this study was to evaluate the physicochemical and rheological properties of butter produced by Lactobacillus helveticus fermented cream. The incorporation of putative probiotic - the L. helveticus, to ferment cream prior to butter production was anticipated to alter the nutritional composition of butter. Changes in crude macronutrients and the resultant modification relating to textural properties of butter induced upon metabolic activities of L. helveticus in cream were focused in this research. Fermented butter (LH-butter) was produced by churning the cream that was fermented by lactobacilli at 37 °C for 24 h. Physicochemical analysis, proximate analysis and rheology properties of LH-butter were compared with butter produced using unfermented cream (control). LH-butter showed a significantly (P<0.05) higher fat content and acid value; lower moisture and ash; and was softer than the control. Cream fermentation modified nutritional and textural properties of butter in which LH-butter contained higher health beneficial unsaturated fatty acids than the control and thus rendered the product softer. Its enrichment with probiotics could thus further enhance its functional property. PMID:26868544

  13. Organic Carbon Influences on Soil Particle Density and Rheological Properties

    SciTech Connect

    Blanco-Canqui, H; Lal, Rattan; Post, W M.; Izaurralde, R Cesar C.; Shipitalo, M. J.

    2006-07-01

    Soil particle density (rs) is not routinely measured and is assumed to range between 2.60 and 2.70 Mgm23 or to be a constant (2.65 Mgm23) when estimating essential properties such as porosity, and volumetric water and air relations. Values of rs for the same soil may, however, differ significantly from the standard range due to management induced changes in soil organic carbon (SOC) concentrations. We quantified the rs and Atterberg limits of a Rayne silt loam for five long-term (.22 yr) moldboard-plowed continuous corn (Zea mays L.; MP), no-till continuous corn (NT), no-till continuous corn with beef cattle manure (NTm), pasture, and forest systems.We also assessed the relationships of SOC concentration with rs and the Atterberg limits and the impact of rs on soil porosity. Mean rs across NT, NTm, and pasture (2.35 Mg m23) was |7% lower than that for MP in the 0- to 10-cm soil depth (2.52 Mg m23, P , 0.01). Forest had the lowest rs of all soils (1.79 Mg m23). The NTm caused a greater reduction in rs and a greater increase in SOC concentration, liquid limit (LL), plastic limit (PL), and plasticity index (PI) than NT. Surface soils under MP had the highest rs and rb and the lowest SOC concentration, LL, PL, and PI. The SOC concentration was correlated negatively with rs (r 2 5 0.75) and positively with Atterberg limits (r 2 . 0.64) at .20-cm depth. Estimates of soil porosity for NT, NTm, and pasture using the constant rs overestimated the ''true'' porosity by 12% relative to that using the measured rs.

  14. Changes in Saliva Rheological Properties and Mucin Glycosylation in Dry Mouth.

    PubMed

    Chaudhury, N M A; Shirlaw, P; Pramanik, R; Carpenter, G H; Proctor, G B

    2015-12-01

    Saliva is vital for the maintenance of normal oral physiology and mucosal health. The loss of salivary function can have far-reaching consequences, as observed with dry mouth, which is associated with increased orodental disease, speech impairment, dysphagia, and a significant negative effect on quality of life. The timely diagnosis of oral dryness is vital for the management of orodental disease and any associated often-undiagnosed systemic disease (e.g., Sjögren syndrome). Our aim was to investigate differences in mucin glycoproteins and saliva rheological properties between sufferers and nonsufferers of dry mouth in order to understand the relationship between saliva composition, rheological properties, and dryness perception and provide additional potential diagnostic markers. All patients exhibited objective and subjective oral dryness, irrespective of etiology. Over half of the patients (n = 20, 58.8%) had a saliva secretion rate above the gland dysfunction cutoff of 0.1 mL/min. Mucin (MUC5B and MUC7) concentrations were generally similar or higher in patients. Despite the abundance of these moisture-retaining proteins, patients exhibited reduced mucosal hydration (wetness) and significantly lower saliva spinnbarkeit (stringiness), suggesting a loss of the lubricating and retention/adhesion properties of saliva, which, at least partially, are associated with mucin glycoproteins. Over 90% of patients with dry mouth (DMPs) consistently had unstimulated whole mouth saliva (UWMS) spinnbarkeit below the proposed normal cutoff (10 mm). Further analysis of mucins revealed the reduced glycosylation of mucins in DMPs compared to healthy controls. Our data indicate that UWMS mucin concentrations are not reduced in dry mouth but that the mucin structure (glycosylation) is altered. UWMS from DMPs had reduced spinnbarkeit, the assessment of which, in conjunction with sialometry, could improve sensitivity for the diagnosis of dry mouth. Additionally, it may be useful to

  15. Rheological and mechanical properties of polyamide 6 modified by electron-beam initiated mediation process

    NASA Astrophysics Data System (ADS)

    Shin, Boo Young; Kim, Jae Hong

    2015-07-01

    Polyamide (PA6) has been modified by electron-beam initiated mediator process to improve drawbacks of PA6. Glycidyl methacrylate (GMA) was chosen as a reactive mediator for modification process of PA6. The mixture of the PA6 and GMA was prepared by using a twin-screw extruder, and then the mixture was exposed to electron-beam irradiation at various doses at room temperature. The modified PA6 were characterized by observing rheological and mechanical properties and compared virgin PA6. Thermal properties, water absorption, and gel fraction were also investigated. Tight gel was not found even when PA6 was irradiated at 200 kGy. Complex viscosity and storage modulus of PA6 were remarkably increased by electron-beam irradiation with medium of GMA. Maximum increase in complex viscosity was 75 times higher than virgin PA6 at 0.1 rad/s when it was irradiated at 200 kGy with the GMA. Mechanical properties were also improved without scarifying of processability. The reaction mechanisms for the mediation process with the reactive mediator of GMA were estimated to elucidate the cause of significantly enhanced rheological and mechanical properties without loss of thermoplasticity.

  16. Laboratory procedures and data reduction techniques to determine rheologic properties of mass flows

    USGS Publications Warehouse

    Holmes, R.R., Jr.; Huizinga, R.J.; Brown, S.M.; Jobson, H.E.

    1993-01-01

    Determining the rheologic properties of coarse- grained mass flows is an important step to mathematically simulate potential inundation zones. Using the vertically rotating flume designed and built by the U.S. Geological Survey, laboratory procedures and subsequent data reduction have been developed to estimate shear stresses and strain rates of various flow materials. Although direct measurement of shear stress and strain rate currently (1992) are not possible in the vertically rotating flume, methods were derived to estimate these values from measurements of flow geometry, surface velocity, and flume velocity.

  17. Regulation of dispersity and rheological properties of high-viscosity crudes

    SciTech Connect

    Nadirov, N.K.; Zhumasheva, K.S.; Burkitbaev, S.M.; Antoshkin, A.S.

    1988-03-01

    The degree of dispersity and the rheological properties of blended crudes from the Mangyshlak peninsula were studied. High-wax crudes from the Uzen' and Zhetybai fields and high-aromatic crudes from the Kalamkas and Karazhanbas fields were blended. The degree of dispersity was determined by laser correlation spectroscopy. Dynamic viscosity was determined under various shear stresses in a rotating viscometer. Variations of the ratios of components in the mixed crudes gave complex variations of viscosity. The transition from a highly aromatic crude to a waxy crude through a series of blends was accompanied by a change in the dynamic viscosity from monotonic to extremal.

  18. Rheological properties of ammonia-water liquids and crystal-liquid slurries - Planetological applications

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.; Croft, S. K.; Lunine, J. I.; Lewis, J. S.

    1991-01-01

    The laboratory-measured viscosities of liquid mixtures representative of the variety of cryovolcanic substances of the icy satellites are presently noted to be much greater than could be expected on the assumption that end-member molecules are noninteractive; this observation is supported by others concerning molar volumes and vapor pressure relations, which indicate the presence of strong molecular-interaction forces that fundamentally affect the mixtures' physical properties. Since the rheological effects of partial crystallization parallel the characteristics of silicate lavas, icy satellite cryovolcanic morphologies are similarly interpretable with allowances for differences in surface gravities and lava densities.

  19. Rheological properties and the mechanism of a viscous flow of aqueous pectin solutions

    NASA Astrophysics Data System (ADS)

    Netesova, G. A.; Kotov, V. V.; Bodyakina, I. M.; Lukin, A. L.

    2012-09-01

    The rheological properties and mechanisms of a viscous flow of diluted apple pectin solutions are investigated. It is found that the rise in solution viscosity upon an increase in concentration and a drop in temperature is, along with the corresponding degree to which the interaction between pectin molecules and solvent is reduced, associated with the processes of structuring. The entropy of a viscous flow of pectin solutions is found to be positive: it grows with a rise in concentration is virtually temperature independent. It is established that the entropy factor makes the main contribution to the free energy value of a viscous flow.

  20. Using Micromechanical Resonators to Measure Rheological Properties and Alcohol Content of Model Solutions and Commercial Beverages

    PubMed Central

    Paxman, Rosemary; Stinson, Jake; Dejardin, Anna; McKendry, Rachel A.; Hoogenboom, Bart W.

    2012-01-01

    Micromechanic resonators provide a small-volume and potentially high-throughput method to determine rheological properties of fluids. Here we explore the accuracy in measuring mass density and viscosity of ethanol-water and glycerol-water model solutions, using a simple and easily implemented model to deduce the hydrodynamic effects on resonating cantilevers of various length-to-width aspect ratios. We next show that these measurements can be extended to determine the alcohol percentage of both model solutions and commercial beverages such as beer, wine and liquor. This demonstrates how micromechanical resonators can be used for quality control of every-day drinks. PMID:22778654

  1. Foam stability: the effect of surface rheological properties on the lamella rupture

    SciTech Connect

    Djabbarah, N.F.; Wasan, D.T.

    1985-06-01

    The purpose of this study is to assess the influence of surface rheological properties in the stabilization of thin liquid surfactant films. A direct relationship is established between the lamella rupture time and the trends in surface viscosity and elasticity. A procedure was employed in preparing sodium lauryl sulfate-lauryl alcohol solutions. Surface tension, surface viscosity, and surface elasticity were measured. No preferred direction for the lamella rupture was found, but the spacing of the lamella depended on the gas flow rate, the surfactant system, and concentration of surfactant.

  2. Estimates of rheologic properties for flows on the Martian volcano Ascraeus Mons

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R.

    1985-01-01

    Morphological measurements on six well-defined volcanic flows near the summit of the Martian volcano Ascraeus Mons were used to calculate the yield strength and viscosity of the lavas. The results are similar to values obtained for flows on other Martian and terrestrial shield volcanoes. Calculated viscosities are generally higher than measured viscosities for basaltic lavas but considerably smaller than rhyolite or dacite viscosities. The estimated rheologic properties of the Martian flows are most consistent with basaltic or basaltic andesite lavas, but some individual flows could consist of more evolved lavas.

  3. Effect of inulin on rheological and thermal properties of gluten-free dough.

    PubMed

    Juszczak, Lesław; Witczak, Teresa; Ziobro, Rafał; Korus, Jarosław; Cieślik, Ewa; Witczak, Mariusz

    2012-09-01

    The aim of the study was to evaluate the influence of inulins with varying degree of polymerization on rheological and thermal properties of gluten-free starch-based dough. The share of inulin reduced the values of consistency coefficient, as well as storage and loss moduli, and increased creep compliance. Inulin preparation with the highest average degree of polymerization had the strongest impact on viscoelastic properties of the obtained dough. The presence of inulin also caused a significant decrease of viscosity upon pasting, and an increase of gelatinization temperatures TOg, TP1g, TP2g, and TEg. Addition of inulin had no effect on gelatinization enthalpy (ΔHg), while it strongly reduced the enthalpies of retrograded amylopectin after storage. Water binding properties of inulin seem to be the key factor, responsible for modification of dough properties, because they influence solvent availability for other constituents of such system. PMID:24751052

  4. The effect of gum tragacanth on the rheological properties of salep based ice cream mix.

    PubMed

    Kurt, Abdullah; Cengiz, Alime; Kahyaoglu, Talip

    2016-06-01

    The influence of concentration (0-0.5%, w/w) of gum tragacanth (GT) on thixotropy, dynamic, and creep-recovery rheological properties of ice cream mixes prepared with milk or water based were investigated. These properties were used to evaluate the viscoelastic behavior and internal structure of ice cream network. The textural properties of ice cream were also evaluated. Thixotropy values of samples were reduced by increasing GT concentration. The dynamic and creep-recovery analyses exhibited that GT addition increased both ice cream elastic and viscous behaviors. The increasing of Burger's model parameters with GT concentration indicated higher resistance network to the stress and more elastic behavior of samples. The applying of Cox-Merz rule is possible by using shift factor (α). GT also led to an increase in Young's modulus and the stickiness of ice creams. The obtained results highlighted the possible application of GT as a valuable member to promote structural properties of ice cream. PMID:27083350

  5. Functional and rheological properties of amaranth albumins extracted from two Mexican varieties.

    PubMed

    Silva-Sánchez, C; González-Castañeda, J; de León-Rodríguez, A; Barba de la Rosa, A P

    2004-01-01

    The functional and rheological properties of amaranth albumins isolates extracted from two new Mexican varieties were determined. Functional properties tested were protein solubility, foaming, water and oil absorption capacities, emulsifying activity, and emulsion stability. The maximum solubility values for both amaranth albumins were found above pH 6 and values were compared to the solubility of egg albumins. Albumins from amaranth showed excellent foaming capacity and foaming stability at pH 5, suggesting that this protein could be used as whipping agents as egg albumins, also the water and oil absorption capacities reached their maximum values at acidic pH, suggesting that amaranth albumins could be appropriate in preparation of acidic foods. The rheological test based on farinograms and alveograms showed that wheat flour supplemented with 1% amaranth albumins improves the dough properties due to higher mixing stability and the bread had better crumb characteristics. In addition of the known high nutritional values of amaranth albumins, our results indicate the high potential for use of these proteins as an ingredient in food preparations. PMID:15678726

  6. [EFFICACY OF SURGICAL TREATMENT OF VARICOSE DISEASE, DEPENDING ON ADSORPTION-RHEOLOGIC PROPERTIES OF BLOOD].

    PubMed

    Grihn, V K; Kondratenko, P G; Melekhovets, Yu V; Sinyachenko, Yu O; Sinyachenko, O V

    2015-05-01

    Physico-chemical adsorption-rheological properties of venous blood in patients, suffering varicose disease of the lower extremities, and their impact on efficacy of various methods of surgical treatment were studied. Conduction of endovasal laser coagulation in combination with crossectomy have promoted enhancement of operative treatment efficacy in patients in initial terms of observation (in 1 week), in 1 month a complete occlusion of the vein was noted more rarely. Efficacy of a small--power laser ablation with irradiation power of 10 W and less in 4 weeks postoperatively is higher, than of surgical treatment with a laser irradiation power 15 W. In a varicose disease of the lower extremities there were observed the raising of the blood volume toughness, superficial relaxation and superficial stress on background of reduction of the toughness--elasticity module, superficial toughness and superficial elasticity. Crossectomy conduction did not influence the integral dynamics of adsorption--rheological properties of venous blood, but in 1 month after endovasal laser coagulation a normalization of physicchemical parameters of blood was noted. Application of laser irradiation of the 10 W power and less promotes inhibition of the relaxation properties of venous blood; a prognostic meaning owes initial value of the blood volume toughness. PMID:26419035

  7. Effect of frying on the rheological and chemical properties of palm oil and its blends.

    PubMed

    Siddique, Bazlul Mobin; Muhamad, Ida Idayu; Ahmad, Anees; Ayob, Afizah; Ibrahim, Mahamad Hakimi; Ak, Mohd Omar

    2015-03-01

    The aim of this research was to determine the changes in the physicochemical properties of palm oil and its blends by FTIR and rheological measurements. Application of heat produces some chemical compounds as impurities and even toxic compounds in oils and fats that give absorbance at different region. FTIR spectra of pure palm olein shows an absorbance at 3002 cm(-1) whereas other pure oils show maximum absorption at around 3007 cm(-1) due to C-H stretching vibration of cis-double bond (=C-H). By blending of high unsaturated oils with palm olein, a clear shift of 3007 cm(-1) band to 3005 cm(-1) occurs. Viscosity of palm olein was found higher among all oils while it subsequently and substantially reduced by blending with other oils. Since it is a function of temperature, viscosity of pure oils and their blends decreases with the increase of temperature. The loss modulus (G''), for all oil blends before and after frying, in rheological experiment was found higher for all oils than the storage modulus (G'), therefore, the viscous property was found higher than elastic property of oils and blends. However, the critical stress for all oil blends was found higher than that of pure oils. PMID:25745212

  8. Potential contribution of microbial communities in technical ceramics for the improvement of rheological properties

    NASA Astrophysics Data System (ADS)

    Moreira, Bernardino; Miller, Ana Z.; Santos, Ricardo; Monteiro, Sílvia; Dias, Diamantino; Neves, Orquídia; Dionísio, Amélia; Saiz-Jimenez, Cesareo

    2014-05-01

    Several bacterial and fungal species naturally occurring in ceramic raw materials used in construction, such as Aspergillus, Penicillium and Aureobasidium, are known to produce exopolysaccharides (EPS). These polymers excreted by the cells are of widespread occurrence and may confer unique and potentially interesting properties with potential industrial uses, such as viscosity control, gelation, and flocculation, during ceramic manufacturing. In this study, the microbial communities present in clay raw materials were identified by both cultural methods and DNA-based molecular techniques in order to appraise their potential contribution to enhance the performance of technical ceramics through the use of EPS. Mineralogical identification by X- Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy of the clay raw materials, as well as characterization of rheological properties of ceramic slips were also performed. Microbial EPS production and its introduction into ceramic slips will be then carried out in order to evaluate their effects on the rheological properties of the ceramic slips, powders and conformed bodies. Some positive aspects related to the use of EPS are: reduction of the environmental impact caused by synthetic organic additives, reduction of production costs, as well as the costs related with operator protection systems, gaseous effluent treatments, complex landfill, among others.

  9. Effect of exo-polysaccharide concentration in the rheological properties and settling ability of activated sludge.

    PubMed

    Akkache, S; Seyssiecq, I; Roche, N

    2013-01-01

    The non-Newtonian properties of activated sludge (AS) suspension lead to transfer limitations (oxygen, substrate...) and operation difficulties in Waste Water Treatment Plants (WWTP). The current approach involves assuming the sludge behaves like water on a rheological point of view, and then oversizing pumping and aeration devices, which represent over 60% of the operating cost in WWTP. The objective of this work is to understand the effect of bioflocculation on the rheological properties and the settling ability of AS suspensions, by means of variations in concentration of exo-cellular polysaccharides. Experiments have been conducted in a 20 L laboratory scale bioreactor at a constant retention time of 20 days and with a total suspended solid concentration between 15 and 20 g L(-1). The bioreactor was fed with a synthetic substrate at a constant mass loading rate of 0.3 kg(DCO) kg(-1)(TSS) d(-1). Our results show that increasing the exo-polysaccharide (EPS) concentration from 10 to 80 mg g(-1)(TSS) leads to an increase in shear-thinning properties of AS. An improvement of the settling ability is also obtained, at least when the EPSs increase from 10 to 45 mg g(-1)(TSS). Above 45 mg g(-1)(TSS) of adsorbed polysaccharides, the settling ability seems to decrease again. PMID:24617058

  10. The crosslinking degree controls the mechanical, rheological, and swelling properties of hyaluronic acid microparticles.

    PubMed

    Shimojo, Andréa Arruda Martins; Pires, Aline Mara Barbosa; Lichy, Rafael; Rodrigues, Ana Amélia; Santana, Maria Helena Andrade

    2015-02-01

    Viscosupplements, used for treating joint and cartilage diseases, restore the rheological properties of synovial fluid, regulate joint homeostasis and act as scaffolds for cell growth and tissue regeneration. Most viscosupplements are hydrogels composed of hyaluronic acid (HA) microparticles suspended in fluid HA. These microparticles are crosslinked with chemicals to assure their stability against enzyme degradation and to prolong the action of the viscosupplement. However, the crosslinking also modifies the mechanical, swelling and rheological properties of the HA microparticle hydrogels, with consequences on the effectiveness of the application. The aim of this study is to correlate the crosslinking degree (CD) with these properties to achieve modulation of HA/DVS microparticles through CD control. Because divinyl sulfone (DVS) is the usual crosslinker of HA in viscosupplements, we examined the effects of CD by preparing HA microparticles at 1:1, 2:1, 3:1, and 5:1 HA/DVS mass ratios. The CD was calculated from inductively coupled plasma spectrometry data. HA microparticles were previously sized to a mean diameter of 87.5 µm. Higher CD increased the viscoelasticity and the extrusion force and reduced the swelling of the HA microparticle hydrogels, which also showed Newtonian pseudoplastic behavior and were classified as covalent weak. The hydrogels were not cytotoxic to fibroblasts according to an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. PMID:24828883

  11. Rheological properties of PP/CaCO3 micron-nano composite blends processing based on elongation rheology via vane extruder

    NASA Astrophysics Data System (ADS)

    Benhao, Kang; Rongyuan, Chen; Guizhen, Zhang; Zhitao, Yang; Jinping, Qu

    2016-03-01

    This work aimed to study, for the first time, the rheological properties of the melt blending of PP/micron-CaCO3 and PP/nano-CaCO3 composite processing based on elongation rheology by a novel vane extruder to toughen PP. The rheological behavior of the blends was studied by capillary rheometer. The results show that: PP/CaCO3 Micron-nano copolymer blends are pseudo plastic fluid. The apparent viscosity initially increases with the increasing of feller. The change of the apparent viscosity also depends on the filler type which proves difference when the blends are on the low shear rate. When the shear rate is low, the apparent shear viscosity of micron-nano composite material is more sensitive to shear rate. For PP/micron-CaCO3 composite blend, the non-Newtonian index shows a trend of gradually increasing. In PP/nano-CaCO3 composite blend, the non-Newtonian index changed little in general with the increase of nano-filler content.

  12. Effect of storage duration on the rheological properties of goose liquid egg products and eggshell membranes.

    PubMed

    Kumbar, V; Nedomova, S; Trnka, J; Buchar, J; Pytel, R

    2016-07-01

    In practice, goose eggs are increasingly used and, therefore, the rheological properties have to be known for processing. The eggs of geese (Landes Goose, Anser anser f. domestica) were stored for one, 2, 3, 4, 6, and 8 wk at a constant temperature 4°C. First of all, the egg quality parameters were described in terms of egg weight, egg weight loss, egg shape index, yolk height, albumen height, yolk index, albumen index, and Haugh units. In the next step the rheological behavior of liquid egg products (egg yolk, albumen, and whole liquid egg) was studied using a concentric cylinder viscometer. Flow curves of all liquid egg products exhibited non-Newtonian shear thinning behavior. This behavior can be described using the Herschel-Bulkley model and for technical application using the Ostwald-de Waele model. The effect of the storage duration on the rheological behavior is different for the different liquid egg products. With the exception of very low shear rates, the viscosity of the egg yolk as well as of the whole liquid egg decreases with storage time. At lower shear rates there is a tendency toward increased albumen viscosity with storage duration. The storage duration also affects the mechanical properties of the eggshell membrane. This effect has been evaluated in terms of the ultimate tensile strength, fracture strain, and fracture toughness. All these parameters increased with the loading rate, but decreased during the egg storage. These mechanical phenomena should be respected, namely in the design of the egg model for the numerical simulation of the egg behavior under different kinds of the mechanical loading. PMID:26994202

  13. Estimating rheological properties of lava flows using high-resolution time lapse imaging

    NASA Astrophysics Data System (ADS)

    James, M. R.; Applegarth, L. J.; Pinkerton, H.; Fryer, T.

    2011-12-01

    During effusive eruptions, property and infrastructure can be threatened by lava flow inundation. In order to maximise the effectiveness of the response to such an event, it is necessary to be able to reliably forecast the area that will be affected. One of the major controls on the advance of a lava flow is its rheology, which is spatially and temporally variable, and depends on many underlying factors. Estimating the rheological properties of a lava flow, and the change in these over space and time is therefore of the utmost importance. Here we report estimates of rheological properties made from geometric and velocity measurements on integrated topographic and image data using the method of Ellis et al. (2004) (Ellis B, Wilson L & Pinkerton H (2004) Estimating the rheology of basaltic lava flows. Lunar & Planetary Science XXXV Abst. 1550). These are then compared to the viscosity predicted from composition and temperature by the GRD model (Giordano D, Russell JK, & Dingwell DB (2008) Viscosity of Magmatic Liquids: A Model. Earth & Planetary Science Letters, 271, 123-134). During the 13 May 2008 - 6 July 2009 eruption of Mt Etna, Sicily, lava flows were emplaced into the Valle del Bove, reaching a maximum length of >6 km. Towards the end of the eruption, multiple channelized aa flows were active simultaneously, reaching tens to hundreds of metres in length. Flow lifetimes were of the order hours to days. In the last month of the eruption, we installed a Canon EOS 450D camera at Pizzi Deneri, on the north side of the Valle del Bove, to collect visible images at 15-minute intervals. On one day, topographic data (using a Riegl LPM-321 terrestrial laser scanner) and thermal images (using a FLIR Thermacam S40) were also collected from this location. The fronts of some of the larger flows were tracked through the time lapse image sequence. Using knowledge of the camera imaging geometry, the pixel tracks were reprojected onto the topographic surface to determine flow

  14. New insight into rheology and flow properties of complex fluids with Doppler optical coherence tomography

    PubMed Central

    Haavisto, Sanna; Koponen, Antti I.; Salmela, Juha

    2014-01-01

    Flow properties of complex fluids such as colloidal suspensions, polymer solutions, fiber suspensions and blood have a vital function in many technological applications and biological systems. Yet, the basic knowledge on their properties is inadequate for many practical purposes. One important reason for this has been the lack of effective experimental methods that would allow detailed study of the flow behavior of especially opaque multi-phase fluids. Optical Coherence Tomography (OCT) is an emerging technique capable of simultaneous measurement of the internal structure and motion of most opaque materials, with resolution in the micrometer scale and measurement frequency up to 100 kHz. This mini-review will examine the recent results on the use of Doppler-OCT in the context of flows and rheological properties of complex fluids outside biomedical field. PMID:24904920

  15. Effect of ripening and heat processing on the physicochemical and rheological properties of pepper pectins.

    PubMed

    Ramos-Aguilar, Olivia P; Ornelas-Paz, José de Jesús; Ruiz-Cruz, Saul; Zamudio-Flores, Paul B; Cervantes-Paz, Braulio; Gardea-Béjar, Alfonso A; Pérez-Martínez, Jaime D; Ibarra-Junquera, Vrani; Reyes-Hernández, Jaime

    2015-01-22

    Water-, chelator-, and alkali-soluble pectins were isolated from raw and heat-processed Jalapeño peppers (green and red) and their physiochemical and rheological properties were determined. The yield, tristimulus color, degree of methyl esterification, monosaccharide composition, molecular weights distribution, and protein content depended on ripening and heat processing. The viscosity properties of pectins were independent of ripening. The water-soluble pectin was the most abundant pectin. Pectins from grilled peppers showed the lowest L* values. The alkali-soluble pectin showed the highest protein content. The content of xylose, rhamnose, and mannose in pectins was highly altered by tested factors. The degree of methyl esterification of pectins ranged from 26.8 to 91.6%. The peak Mw of the main fraction of tested pectins was sequentially reduced by ripening and heat processing. Pectins from raw peppers showed the best viscosity properties. PMID:25439875

  16. Correlation of stability/rheology relationship with coal properties and chemical additives

    SciTech Connect

    Ohene, F.

    1991-01-01

    Four coal samples PSOC 1339, 1472, 1531 and 1572 are being used to test the fundamental relationship between coal properties and slurryability. Coal properties that have been examined in order to develop a relationship between slurry quality and the coal properties are: The Equilibrium moisture, Ash Content, Volatile Matter, Carbon Content, Oxygen Content, HG Index, Fixed Carbon and Particle Size Distribution and Hydrophobicity Index. The difference between the sums of hydrogen (H), carbon (C), sulfur (S) and oxygen (O), Nitrogen (N), Moisture (M), ash (A) were determined for each coal and assigned as the hydrophobicity index. In order to test the validity of the relationship in equation 1, zeta potential measurements and rheological characterization of several slurries prepared from PSOC-1339 and 1527 were made. 5 refs., 2 figs., 3 tabs.

  17. The Effect of Rheological Parameters on the Ballistic Properties of Shear Thickening Fluid (STF)-Kevlar Composites

    NASA Astrophysics Data System (ADS)

    Wetzel, Eric D.; Lee, Y. S.; Egres, R. G.; Kirkwood, K. M.; Kirkwood, J. E.; Wagner, N. J.

    2004-06-01

    The addition of colloidal shear thickening fluids (STFs) to Kevlar fabrics has been shown to enhance the ballistic penetration resistance of the fabric, under conditions of low velocities and small target sizes. It is believed that this improvement in ballistic properties is related to the resistance of the STF to deformation at high strain rates, since the addition of Newtonian fluids to Kevlar fabric does not improve ballistic performance. However, the precise role of the STF, and its rheological properties, in the ballistic defeat process are not known. In this study, ballistic and rheological experiments are performed to determine the effect of fluid viscosity, particle loadings, and particle size and shape on the behavior of STF-Kevlar composites. These results will be help to determine which rheological parameters are most critical to achieving enhanced composite properties.

  18. EFFECT OF IONIC STRENGTH AND PH ON THE THERMAL AND RHEOLOGICAL PROPERTIES OF SOY PROTEIN-AMYLOPECTIN BLEND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effect of amylopectin (AP), moisture content, pH, and buffer molarity on the thermal properties of milled defatted soy flour (MDF) and Soy Protein Isolate (SPI) were studied by Differential Scanning Calorimetry (DSC), and the rheological properties of effect of AP on MDF were also investigated. ...

  19. The physico-chemical properties of chia seed polysaccharide and its microgel dispersion rheology.

    PubMed

    Goh, Kelvin Kim Tha; Matia-Merino, Lara; Chiang, Jie Hong; Quek, Ruisong; Soh, Stephanie Jun Bing; Lentle, Roger G

    2016-09-20

    The polysaccharide gel layer surrounding hydrated chia seeds was extracted using water and isolated by ethanol precipitation. The freeze-dried sample consisted of ∼95% non-starch polysaccharides (35% w/w neutral soluble fraction and 65% w/w negatively charged insoluble fraction). The soluble polysaccharide fraction has molar mass, root-mean square radius and intrinsic viscosity of ∼5×10(5)g/mol, 39nm and 719mL/g, respectively. The whole polysaccharide (included soluble and insoluble fractions) when dispersed in water showed presence of irregular shape, fibrous microgel particles with an average size (D4,3) of ∼700μm. Rheological measurements indicated a 'weak' viscoelastic gel and strong shear dependent properties even at low concentration (0.05% w/w). The viscosity of the dispersion was fairly resistant to variations in temperatures (20-80°C), pH (4-12), ionic strengths (0.01-0.5M NaCl) and cation types (MgCl2, CaCl2, NaCl and KCl). The swollen microgel particles dispersed in soluble polysaccharide continuous phase provided complex and potentially useful rheological properties in food systems. PMID:27261754

  20. Rapid heating of Alaska pollock and chicken breast myofibrillar proteins as affecting gel rheological properties.

    PubMed

    Liu, Wenjie; Stevenson, Clint D; Lanier, Tyre C

    2013-07-01

    Surimi seafoods (fish/poikilotherm protein) in the U.S.A. are typically cooked rapidly to 90+°C, while comminuted products made from land animals (meat/homeotherm protein) are purposely cooked much more slowly, and to lower endpoint temperatures (near 70 °C). We studied heating rate (0.5, 25, or 90 °C/min) and endpoint temperature (45 to 90 °C) effects on rheological properties (fracture, small strain) of washed myofibril gels derived from fish (Alaska pollock) compared with chicken breast at a common pH (6.75). This was contrasted with published data on gelation kinetics of chicken myosin over the same temperature range. Heating rate had no effect on fracture properties of fish gels but slow heating did yield somewhat stronger, but not more deformable, chicken gels. Maximum gel strength by rapid heating could be achieved within 5 min holding after less than 1 min heating time. Dynamic testing by small strain revealed poor correspondence of the present data to that published for gelling response of chicken breast myosin in the same temperature range. The common practice of reporting small-strain rheological parameters measured at the endpoint temperature was also shown to be misleading, since upon cooling, there was much less difference in rigidity between rapidly and slowly heated gels for either species. PMID:23646872

  1. Sugar Profile, Mineral Content, and Rheological and Thermal Properties of an Isomerized Sweet Potato Starch Syrup

    PubMed Central

    Dominque, Brunson; Gichuhi, Peter N.; Rangari, Vijay; Bovell-Benjamin, Adelia C.

    2013-01-01

    Currently, corn is used to produce more than 85% of the world's high fructose syrup (HFS). There is a search for alternative HFS substrates because of increased food demand and shrinking economies, especially in the developing world. The sweet potato is a feasible, alternative raw material. This study isomerized a high glucose sweet potato starch syrup (SPSS) and determined its sugar profile, mineral content, and rheological and thermal properties. Rheological and thermal properties were measured using a rheometer and DSC, respectively. Sweet potato starch was hydrolyzed to syrup with a mean fructose content of 7.6 ± 0.4%. The SPSS had significantly higher (P < 0.05) mineral content when compared to commercial ginger and pancake syrups. During 70 days of storage, the SPSS acted as a non-Newtonian, shear-thinning liquid in which the viscosity decreased as shear stress increased. Water loss temperature of the SPSS continually decreased during storage, while pancake and ginger syrups' peak water loss temperature decreased initially and then increased. Further and more detailed studies should be designed to further enhance the fructose content of the syrup and observe its stability beyond 70 days. The SPSS has the potential to be used in human food systems in space and on Earth. PMID:26904593

  2. Coarse-grained red blood cell model with accurate mechanical properties, rheology and dynamics.

    PubMed

    Fedosov, Dmitry A; Caswell, Bruce; Karniadakis, George E

    2009-01-01

    We present a coarse-grained red blood cell (RBC) model with accurate and realistic mechanical properties, rheology and dynamics. The modeled membrane is represented by a triangular mesh which incorporates shear inplane energy, bending energy, and area and volume conservation constraints. The macroscopic membrane elastic properties are imposed through semi-analytic theory, and are matched with those obtained in optical tweezers stretching experiments. Rheological measurements characterized by time-dependent complex modulus are extracted from the membrane thermal fluctuations, and compared with those obtained from the optical magnetic twisting cytometry results. The results allow us to define a meaningful characteristic time of the membrane. The dynamics of RBCs observed in shear flow suggests that a purely elastic model for the RBC membrane is not appropriate, and therefore a viscoelastic model is required. The set of proposed analyses and numerical tests can be used as a complete model testbed in order to calibrate the modeled viscoelastic membranes to accurately represent RBCs in health and disease. PMID:19965026

  3. Rheological, thermo-mechanical, and baking properties of wheat-millet flour blends.

    PubMed

    Aprodu, Iuliana; Banu, Iuliana

    2015-07-01

    Millet has long been known as a good source of fiber and antioxidants, but only lately started to be exploited by food scientists and food industry as a consequence of increased consumer awareness. In this study, doughs and breads were produced using millet flour in different ratios (10, 20, 30, 40, and 50%) to white, dark, and whole wheat flour. The flour blends were evaluated in terms of rheological and thermo-mechanical properties. Fundamental rheological measurements revealed that the viscosity of the flour formulations increases with wheat flour-extraction rate and decreases with the addition of millet flour. Doughs behavior during mixing, overmixing, pasting, and gelling was established using the Mixolab device. The results of this bread-making process simulation indicate that dough properties become critical for the flour blends with millet levels higher than 30%. The breads were evaluated for volume, texture, and crumb-grain characteristics. The baking test and sensory evaluation results indicated that substitution levels of up to 30% millet flour could be used in composite bread flour. High levels of millet flour (40 and 50%) negatively influenced the loaf volume, crumb texture, and taste. PMID:24837596

  4. Opposite rheological properties of neuronal microcompartments predict axonal vulnerability in brain injury

    NASA Astrophysics Data System (ADS)

    Grevesse, Thomas; Dabiri, Borna E.; Parker, Kevin Kit; Gabriele, Sylvain

    2015-03-01

    Although pathological changes in axonal morphology have emerged as important features of traumatic brain injury (TBI), the mechanical vulnerability of the axonal microcompartment relative to the cell body is not well understood. We hypothesized that soma and neurite microcompartments exhibit distinct mechanical behaviors, rendering axons more sensitive to a mechanical injury. In order to test this assumption, we combined protein micropatterns with magnetic tweezer rheology to probe the viscoelastic properties of neuronal microcompartments. Creep experiments revealed two opposite rheological behaviors within cortical neurons: the cell body was soft and characterized by a solid-like response, whereas the neurite compartment was stiffer and viscous-like. By using pharmacological agents, we demonstrated that the nucleus is responsible for the solid-like behavior and the stress-stiffening response of the soma, whereas neurofilaments have a predominant contribution in the viscous behavior of the neurite. Furthermore, we found that the neurite is a mechanosensitive compartment that becomes softer and adopts a pronounced viscous state on soft matrices. Together, these findings highlight the importance of the regionalization of mechanical and rigidity-sensing properties within neuron microcompartments in the preferential damage of axons during traumatic brain injury and into potential mechanisms of axonal outgrowth after injury.

  5. Opposite rheological properties of neuronal microcompartments predict axonal vulnerability in brain injury

    PubMed Central

    Grevesse, Thomas; Dabiri, Borna E.; Parker, Kevin Kit; Gabriele, Sylvain

    2015-01-01

    Although pathological changes in axonal morphology have emerged as important features of traumatic brain injury (TBI), the mechanical vulnerability of the axonal microcompartment relative to the cell body is not well understood. We hypothesized that soma and neurite microcompartments exhibit distinct mechanical behaviors, rendering axons more sensitive to a mechanical injury. In order to test this assumption, we combined protein micropatterns with magnetic tweezer rheology to probe the viscoelastic properties of neuronal microcompartments. Creep experiments revealed two opposite rheological behaviors within cortical neurons: the cell body was soft and characterized by a solid-like response, whereas the neurite compartment was stiffer and viscous-like. By using pharmacological agents, we demonstrated that the nucleus is responsible for the solid-like behavior and the stress-stiffening response of the soma, whereas neurofilaments have a predominant contribution in the viscous behavior of the neurite. Furthermore, we found that the neurite is a mechanosensitive compartment that becomes softer and adopts a pronounced viscous state on soft matrices. Together, these findings highlight the importance of the regionalization of mechanical and rigidity-sensing properties within neuron microcompartments in the preferential damage of axons during traumatic brain injury and into potential mechanisms of axonal outgrowth after injury. PMID:25820512

  6. Co-solvent effects on drag reduction, rheological properties and micelle microstructures of cationic surfactants.

    PubMed

    Zhang, Ying; Schmidt, Judith; Talmon, Yeshayahu; Zakin, Jacques L

    2005-06-15

    Some quaternary cationic surfactants, when mixed with a counterion, are known to self-assemble into threadlike micelles in water. Such behavior causes drastic changes in rheological properties of even very dilute solutions, allowing them to be used as drag reducing agents (DRA) in turbulent pipe flow circulating systems, such as district cooling/heating systems. Surfactant self-assembly is a physicochemical phenomenon whose character depends on surfactant nature and concentration, nature of the solvent, temperature and type and concentration of counterions. This study investigates drag reduction (DR) and rheological properties of two cationic surfactants, Ethoquad O/12 (oleyl bis(hydroxyethyl)methylammonium chloride) and Ethoquad O/13 (oleyl tris(hydroxyethyl) ammonium acetate), with excess salicylate counterion (NaSal), in mixed solvents containing 0 to 28 wt% ethylene glycol (EG) and water. The addition of EG to the solvent had greater effects on solutions' DR ability, shear viscosity, apparent extensional viscosity and viscoelasticity at 25 degrees C than at approximately 0 degrees C. Cryo-TEM images show threadlike micelle in these systems. DR at low temperatures in solutions containing moderate amount of EG can be utilized in a new approach to energy saving in district cooling systems using EG-water based mixtures as the cooling fluids. PMID:15897088

  7. Rheological properties of phosphorylated exopolysaccharide produced by Sporidiobolus pararoseus JD-2.

    PubMed

    Han, Mei; Du, Chao; Xu, Zhi-Yuan; Qian, He; Zhang, Wei-Guo

    2016-07-01

    The exopolysaccharide (EPS) produced by Sporidiobolus pararoseus JD-2 contained about 2.0% phosphorus and its zeta potential was -30mV at pH 6.0. This indicated that it was an anionic polymer. In steady shear measurements, there was a Newtonian plateau in low shear rates, but power-law behavior exhibited at high shear rates. So Williamson model was used to study the flow character of the EPS solutions. This phenomenon was according to its high molecular weight and entanglement networks. Considering the EPS was an anionic polymer, the influence of added salts on apparent viscosity of EPS were studied. Different NaCl concentrations had little effect on the viscosity of the EPS, but high concentrations of CaCl2 increased the viscosity of EPS significantly. EPS solutions showed inapparent thixotropic properties in stress growth and thixotropic loop experiment. According to the flow curve results and oscillatory shear results obtained, the rheological properties of EPS solutions were closer to that of entanglement network system, like carboxy methyl cellulose rather than weak gel structure such as xanthan gum. The EPS had the function to enhance immunological functions. Understanding the rheological characteristics of EPS was essential to exploit the functionality of this EPS in different food or medicine systems. PMID:27090573

  8. Dissipative particle dynamics simulation on the rheological properties of heavy crude oil

    NASA Astrophysics Data System (ADS)

    Wang, Sibo; Xu, Junbo; Wen, Hao

    2015-11-01

    The rheological properties of heavy crude oil have a significant impact on the production, refining and transportation. In this paper, dissipative particle dynamics (DPD) simulations were performed to study the effects of the addition of light crude oil and emulsification on the rheological properties of heavy crude oil. The simulation results reflected that the addition of light crude oil reduced the viscosity effectively. The shear thinning behaviour of crude oil mixtures were becoming less distinct as the increase of the mass fraction of light crude oil. According to the statistics, the shear had an influence on the aggregation and spatial orientation of asphaltene molecules. In addition, the relationship between the viscosity and the oil mass fraction was investigated in the simulations of emulsion systems. The viscosity increased with the oil mass fraction slowly in oil-in-water emulsions. When the oil mass fraction was higher than 50%, the increase became much faster since systems had been converted into water-in-oil emulsions. The equilibrated morphologies of emulsion systems were shown to illustrate the phase inversion. The surfactant-like feature of asphaltenes was also studied in the simulations.

  9. Sugar Profile, Mineral Content, and Rheological and Thermal Properties of an Isomerized Sweet Potato Starch Syrup.

    PubMed

    Dominque, Brunson; Gichuhi, Peter N; Rangari, Vijay; Bovell-Benjamin, Adelia C

    2013-01-01

    Currently, corn is used to produce more than 85% of the world's high fructose syrup (HFS). There is a search for alternative HFS substrates because of increased food demand and shrinking economies, especially in the developing world. The sweet potato is a feasible, alternative raw material. This study isomerized a high glucose sweet potato starch syrup (SPSS) and determined its sugar profile, mineral content, and rheological and thermal properties. Rheological and thermal properties were measured using a rheometer and DSC, respectively. Sweet potato starch was hydrolyzed to syrup with a mean fructose content of 7.6 ± 0.4%. The SPSS had significantly higher (P < 0.05) mineral content when compared to commercial ginger and pancake syrups. During 70 days of storage, the SPSS acted as a non-Newtonian, shear-thinning liquid in which the viscosity decreased as shear stress increased. Water loss temperature of the SPSS continually decreased during storage, while pancake and ginger syrups' peak water loss temperature decreased initially and then increased. Further and more detailed studies should be designed to further enhance the fructose content of the syrup and observe its stability beyond 70 days. The SPSS has the potential to be used in human food systems in space and on Earth. PMID:26904593

  10. Effect of lactobionic acid on the acidification, rheological properties and aroma release of dairy gels.

    PubMed

    Ribeiro, Jéssica C Bigaski; Granato, Daniel; Masson, Maria Lucia; Andriot, Isabelle; Mosca, Ana Carolina; Salles, Christian; Guichard, Elisabeth

    2016-09-15

    The food industry is investigating new technological applications of lactobionic acid (LBA). In the current work, the effect of lactobionic acid on the acidification of dairy gels (pH 5.5 and 6.2), rheological properties using a double compression test, sodium mobility using (23)Na NMR technique and aroma release using headspace GC-FID were studied. Our results showed that it is possible to use LBA as an alternative to glucono-δ-lactone (GDL) for the production of dairy gels with a controlled pH value. Small differences in the rheological properties and in the amount of aroma volatile organic compounds that were released in the vapour phase, but no significant difference in the sodium ion mobility were obtained. The gels produced with LBA were less firm and released less volatile aroma compounds than the gels produced with GDL. The gels at pH 6.2 were firmer than those at pH 5.5 and had a more organised structure around the sodium ions. PMID:27080885

  11. Relating foam and interfacial rheological properties of β-lactoglobulin solutions.

    PubMed

    Lexis, M; Willenbacher, N

    2014-12-28

    We have determined bulk rheology of β-lactoglobulin (BLG) foams and surface viscoelasticity of corresponding protein solutions by varying pH as well as type, valency and concentration of the added salt in a wide range. Foam rheology was characterized by the storage modulus G0, the apparent yield stress τy, and the critical strain γc,foam defining the cessation of the linear viscoelastic response. These quantities were determined at gas volume fractions ϕ between 82% and 96%. Surface viscoelasticity was characterized in shear and dilation, corresponding shear and dilational moduli G, E' as well as the critical stress τc,surface and strain γc,surface marking the onset of non-linear response in oscillatory surface shear experiments were determined at fixed frequency. Beyond the widely accepted assumption that G0 and τy are solely determined by the Laplace pressure within the droplets and the gas volume fraction we have found that both quantities strongly depend on corresponding interfacial properties. G0 increases linearly with G and even stronger with E', τy varies proportional to τc,surface and γc,foam scales linearly with γc,surface. Furthermore, deviations from these simple scaling laws with significantly higher reduced G0 and τy values are observed only for foams at pH 5 and when a trivalent salt was added. Then also the dependence of these quantities on ϕ is unusually weak and we attribute these findings to protein aggregation and structure formation across the lamellae than the dominating bulk rheology. PMID:25363684

  12. Evaluation of rheological properties and swelling behaviour of sonicated scleroglucan samples.

    PubMed

    Ansari, Siddique Akber; Matricardi, Pietro; Meo, Chiara Di; Alhaique, Franco; Coviello, Tommasina

    2012-01-01

    Scleroglucan is a natural polysaccharide that has been proposed for various applications. However there is no investigation on its property variations when the molecular weight of this polymer is reduced. Scleroglucan was sonicated at two different polymer concentrations for different periods of time and the effect of sonication was investigated with respect to molecular weight variations and rheological properties. Molar mass, estimated by viscometric measurements, was drastically reduced already after a sonication for a few min. Sonicated samples were used for the preparation of gels in the presence of borate ions. The effect of borax on the new samples was investigated by recording the mechanical spectra and the flow curves. A comparison with the system prepared with the dialysed polymer was also carried out. The anisotropic elongation, observed with tablets of scleroglucan and borax, was remarkably reduced when the sonicated samples were used for the preparation of the gels. PMID:22367024

  13. Effect of whey and casein protein hydrolysates on rheological, textural and sensory properties of cookies.

    PubMed

    Gani, Adil; Broadway, A A; Ahmad, Mudasir; Ashwar, Bilal Ahmad; Wani, Ali Abas; Wani, Sajad Mohd; Masoodi, F A; Khatkar, Bupinder Singh

    2015-09-01

    Milk proteins were hydrolyzed by papain and their effect on the rheological, textural and sensory properties of cookies were investigated. Water absorption (%) decreased significantly as the amount of milk protein concentrates and hydrolysates increased up to a level of 15 % in the wheat flour. Dough extensibility decreased with inrease in parental proteins and their hydrolysates in wheat flour, significantly. Similarly, the pasting properties also varied significantly in direct proportion to the quantity added in the wheat flour. The colour difference (ΔE) of cookies supplemented with milk protein concentrates and hydrolysates were significantly higher than cookies prepared from control. Physical and sensory characteristics of cookies at 5 % level of supplementation were found to be acceptable. Also the scores assigned by the judges for texture and colour were in good agreement with the measurements derived from the physical tests. PMID:26344985

  14. Rheological and textural properties of microemulsion-based polymer gels with indomethacin.

    PubMed

    Froelich, Anna; Osmałek, Tomasz; Kunstman, Paweł; Roszak, Rafał; Białas, Wojciech

    2016-01-01

    In this paper, we present novel microemulsion (ME)-based semisolid polymer gels designed for topical administration of poorly water soluble non-steroidal anti-inflammatory drugs. Indomethacin (IND) was used as a model compound. The ME consisted of castor oil, water, Tween®80 as a surfactant and ethanol as cosurfactant. To obtain the desired consistency of the formulations Carbopol®960 was applied as a thickening agent. The aim of the study was to analyze in detail the mechanical properties of the obtained systems, with special attention paid to the features crucial for topical application. The rheological and textural experiments performed for samples with and without the incorporated drug clearly indicate that flow characteristics, viscoelastic properties and texture profiles were affected by the presence of IND. Novel semisolid formulations with IND described for the first time in this paper can be considered as an alternative for commercially available conventional topical dosage forms. PMID:26204348

  15. Characterizing the rheological properties of thermoplastic elastomers (TPE) by thermomechanical analysis

    SciTech Connect

    Penn, J.

    1993-12-31

    The increasing demand for products with qualities of functional performance of rubber coupled with ease of processability have enabled thermoplastic elastomers (TPE) to be used more often in traditional application usually reserved for natural and synthetic rubbers. The economic advantages of TPE of few steps to manufacture, processed on less costly equipment that also allows for faster production than versus slow-cycling, capital intensive rubber processing equipment and recyclability for scrap have enhanced its appeal to manufacturers. However, TPE are relatively new to some manufacturers that are unaware of the attributes of this class of materials. The study conducted will characterize the rheological properties of TPE to exhibit the stiffness or hardness, damping factors and other mechanical properties.

  16. Use of a capillary rheometer to evaluate the rheological properties of microcrystalline cellulose and silicified microcrystalline cellulose wet masses.

    PubMed

    Luukkonen, P; Newton, J M; Podczeck, F; Yliruusi, J

    2001-03-23

    The influence of microcrystalline cellulose (MCC) type and water content on the rheological properties of the wet powder masses were studied using two different MCC grades (Avicel and Emcocel) and silicified microcrystalline cellulose (SMCC, Prosolv). A ram extruder was used as a capillary rheometer and unique flow curves for each cellulose grade and moisture content were derived. In addition, the elastic parameters of recoverable shear and compliance were determined. From different flow curve models evaluated, it was not possible to obtain clear evidence, which model best described the rheological properties of each cellulose grade at each water level. Furthermore, the residuals were shear rate dependent, which indicates that the models do not perfectly agree with physical properties of the wet masses. The elastic properties of wet masses increased with increasing water content and decreased with increasing shear stresses. SMCC grade proved to be more elastic than the simple MCC grades at each moisture content. Thus, the rheological properties of MCC and SMCC wet masses were different and changed with water content. Consequently, it was not possible to achieve similar rheological properties between different grades of cellulose by altering the water content of the wet mass. PMID:11274816

  17. The characterizations of rheological, electrokinetical and structural properties of ODTABr/MMT and HDTABr/MMT organoclays

    SciTech Connect

    Isci, S. Uslu, Y.O.; Ece, O.I.

    2009-05-15

    In the present paper, we have investigated as a function of surfactant concentration the rheological (yield value, plastic viscosity) and electrokinetic (mobility, zeta potential) properties of montmorillonite (MMT) dispersions. The influence of surfactants (Octadeccyltrimethylammonium bromide, ODTABr and Hexadecyltrimethylammonium bromide, HDTABr) on dispersions of Na-activated bentonite was evaluated by rheological and electrokinetic measurements, and X-ray diffraction (XRD) studies. The interactions between clay minerals and surfactants in water-based Na-activated MMT dispersions (2 wt.%) were examined in detail using rheologic parameters, such as viscosity, yield point, apparent and plastic viscosity, hysteresis area, and electrokinetic parameters of mobility and zeta potentials, and XRD also analyses helped to determine swelling properties of d-spacings. MMT and organoclay dispersions showed Bingham Plastic flow behavior. The zeta potential measurements displayed that the surfactant molecules hold on the clay particle surfaces and the XRD analyses displayed that they get into the basal layers.

  18. Rheological Principles for Food Analysis

    NASA Astrophysics Data System (ADS)

    Daubert, Christopher R.; Foegeding, E. Allen

    Food scientists are routinely confronted with the need to measure physical properties related to sensory texture and processing needs. These properties are determined by rheological methods, where rheology is a science devoted to the deformation and flow of all materials. Rheological properties should be considered a subset of the textural properties of foods, because the sensory detection of texture encompasses factors beyond rheological properties. Specifically, rheological methods accurately measure "force," "deformation," and "flow," and food scientists and engineers must determine how best to apply this information. For example, the flow of salad dressing from a bottle, the snapping of a candy bar, or the pumping of cream through a homogenizer are each related to the rheological properties of these materials. In this chapter, we describe fundamental concepts pertinent to the understanding of the subject and discuss typical examples of rheological tests for common foods. A glossary is included as Sect. 30.6 to clarify and summarize rheological definitions throughout the chapter.

  19. Effect of cellulose nanocrystals (CNCs) on crystallinity, mechanical and rheological properties of polypropylene/CNCs nanocomposites

    NASA Astrophysics Data System (ADS)

    Bagheriasl, D.; Carreau, P. J.; Dubois, C.; Riedl, B.

    2015-05-01

    Rheological and mechanical properties of polypropylene (PP)/CNCs nanocomposites were compared with those of nanocomposites containing poly(ethylene-co-vinyl alcohol) as a compatibilizer. The nanocomposites were prepared by a Brabender internal mixer at CNC contents of 5 wt%. The compression molded nanocomposite dog-bones and disks were characterized regarding their tensile and dynamic rheological behavior, respectively. The complex viscosity of the nanocomposites samples containing the compatibilizer were increased, slightly, compared to the non-compatibilized nanocomposite samples. Moreover, an overshoot in the transient start-up viscosity of the compatibilized nanocomposite was observed. The Young modulus of the nanocomposite samples containing the compatibilizer were increased up to ca. 37% compared to the neat PP. The elongation at break was decreased in all PP/CNC nanocomposite samples, but less for the nanocomposite samples containing the compatibilizer. The crystalline content of the PP in the nanocomposites and also the crystallization temperature were increased after compatibilization. These results could be ascribed to the efficiency of the poly(ethylene-co-vinyl alcohol) as a compatibilizer that favors a better dispersion and wetting of the hydrophilic CNCs within the hydrophobic PP.

  20. Effects of Momordica charantia L. on the Blood Rheological Properties in Diabetic Patients

    PubMed Central

    França, Eduardo Luzía; Ribeiro, Elton Brito; Scherer, Edson Fredulin; Cantarini, Déborah Giovanna; Pessôa, Rafael Souza; França, Fernando Luzía; Honorio-França, Adenilda Cristina

    2014-01-01

    An evaluation of the rheological properties and the effects of Momordica. charantia L. (M. charantia) nanoparticles and polyethylene glycol (PEG) microspheres adsorbed with M. charantia nanoparticles on the blood of hyperglycemic patients is presented. Blood samples were collected according to glycemic status: normoglycemic (N = 56) and hyperglycemic (N = 26). General and hematological characteristics were determined. Blood rheological parameters were determined at room temperature and under a temperature scan. We determined the effects on whole blood viscosity of treatment with an extract of M. charantia, PEG, or PEG microspheres adsorbed with plant extract. The viscosity of the blood of hyperglycemic patients is greater than that of normoglycemic patients. Nanoparticles of M. charantia extracts lowered blood viscosity at equivalent rates in normo- and hyperglycemic individuals. PEG microspheres did not reduce blood viscosity in hyperglycemic individuals. However, PEG microspheres adsorbed with nanofraction extracts of M. charantia reduced blood viscosity. These data suggest that the effects of diabetes on the viscosity of the blood should be considered. The use of a nanoparticles extract of M. charantia and its adsorption on PEG microspheres may represent an alternative for the control and treatment of blood disorders in diabetic patients. PMID:24672797

  1. Influence of Anti-inflammatory Drugs on the Rheological Properties of Synovial Fluid and Its Components

    NASA Astrophysics Data System (ADS)

    Krause, Wendy E.; Klossner, Rebecca R.; Liang, Jing; Colby, Ralph H.

    2006-03-01

    The polyelectrolyte hyaluronic acid (HA, hyaluronan), its interactions with anti-inflammatory drugs and other biopolymers, and its role in synovial fluid are being studied. We are investigating the rheological properties of sodium hyaluronate (NaHA) solutions and an experimental model of synovial fluid (comprised of NaHA, and the plasma proteins albumin and γ-globulins). Steady shear measurements on bovine synovial fluid, the synovial fluid model, and plasma protein solutions indicate that the fluids are rheopectic (stress increases with time under steady shear). In addition, the influence of anti-inflammatory agents on these solutions is being explored. Initial results indicate that D-penicillamine and hydroxychloroquine (HCQ) affect the rheology of the synovial fluid model and its components. While HCQ has no effect on the viscosity of NaHA solutions, it inhibits/suppresses the observed rheopexy of the synovial fluid model and plasma protein solutions. In contrast, D-penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions,---reducing the zero shear rate viscosity of a 3 mg/mL NaHA (in phosphate buffered saline) by ca. 40% after 44 days. The potential implications of these results will be discussed.

  2. The effect of nanoparticle permeation on the bulk rheological properties of mucus from the small intestine.

    PubMed

    Wilcox, M D; Van Rooij, L K; Chater, P I; Pereira de Sousa, I; Pearson, J P

    2015-10-01

    The effectiveness of delivering oral therapeutic peptides, proteins and nucleotides is often hindered by the protective mucus barrier that covers mucosal surfaces of the gastrointestinal (GI) tract. Encapsulation of active pharmaceutical ingredients (API) in nanocarriers is a potential strategy to protect the cargo but they still have to pass the mucus barrier. Decorating nanoparticles with proteolytic enzymes has been shown to increase the permeation through mucus. Here we investigate the effect of poly(acrylic acid) (PAA) nanoparticles decorated with bromelain (BRO), a proteolytic enzyme from pineapple stem, on the bulk rheology of mucus as well as non-decorated poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Porcine intestinal mucus from the small intestine was incubated for 30min in the presence of PLGA nanoparticles or polyacrylic nanoparticles decorated with bromelain (PAA-BRO). The effect of nanoparticles on the rheological properties, weight of gel, released glycoprotein content from mucus as well as the viscosity of liquid removed was assessed. Treatment with nanoparticles decreased mucus gel strength with PAA-BRO reducing it the most. PAA-BRO nanoparticles resulted in the release of increased glycoprotein from the gel network whereas mucus remained a gel and exhibited a similar breakdown stress to control mucus. Therefore it would be possible to use bromelain to increase the permeability of nanoparticles through mucus without destroying the gel and leaving the underlying mucosa unprotected. PMID:25758122

  3. Universal Scaling of Linear and Nonlinear Rheological Properties of Semidilute and Concentrated Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Larson, Ronald; Heo, Youngsuk

    2008-03-01

    We examine the validity of the de Gennes ``blob'' concept in predicting linear and nonlinear rheological properties of semidilute polystyrene solutions in tricresyl phosphate (TCP). At a fixed value of rescaled concentration c/ce where ce is the entanglement concentration, below a critical value of around 2.0 for our polystyrene/TCP solutions, linear and nonlinear rheological functions superimpose after the modulus and the frequency (or shear rate) of each solution are respectively normalized with the concentration-dependent plateau modulus and the equilibration time obtained from the de Gennes scaling relationships using the literature value of the solvent-quality exponent 0.53. However, once the polymer volume fraction exceeds the ``swelling volume fraction, above which the polymer takes on a random walk configuration on all length scales even in a good solvent, this universal scaling breaks down and the polymer conformation appears to be governed by Colby-Rubinstein's scaling laws for theta solutions. We estimate that all polybutadiene solutions in phenyl octane (a good solvent) from the work of Colby et al. are above the swelling concentration and can be scaled using theta solvent scaling laws for concentrations ranging all the way up to the melt, showing universal behavior of melts and solutions above the swelling concentration.

  4. Microwave-induced synthesis of carboxymethyl hemicelluloses and their rheological properties.

    PubMed

    Peng, Xin-Wen; Ren, Jun-Li; Zhong, Lin-Xin; Cao, Xue-Fei; Sun, Run-Cang

    2011-01-26

    In this article, a facile, rapid, and efficient method was developed for the preparation of carboxymethyl hemicelluloses using microwave-induced organic reaction enhancement chemistry. The influences of the factors including reaction time, temperature, and the amount of sodium monochloroacetate and sodium hydroxide on the degree of substitution (DS) of the products were investigated. The rheological properties and the chemical structure of the resulting polymers were also studied. It was found that microwave irradiation could significantly promote the chemical reaction efficiency and accelerate the carboxymethylation of hemicelluloses with sodium monochloroacetate. Therefore, carboxymethyl hemicelluloses with higher DS of 1.02 could be obtained in much shorter time scales as compared to the conventional heating method. Results from rheological analysis indicated that carboxymethyl hemicellulose solutions exhibited shear-thinning behavior in the range of shear rates tested and showed lower viscosity and modulus in comparison with those of the native hemicelluloses due to lower molecular weight and the role of carboxymethyl groups in reducing the entanglements between hemicelluloses chains. PMID:21166416

  5. Intraluminal mapping of tissue viscoelastic properties using laser speckle rheology catheter (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Hosoda, Masaki; Tshikudi, Diane M.; Nadkarni, Seemantini K.

    2016-03-01

    A number of disease conditions including coronary atherosclerosis, peripheral artery disease and gastro-intestinal malignancies are associated with alterations in tissue mechanical properties. Laser speckle rheology (LSR) has been demonstrated to provide important information on tissue mechanical properties by analyzing the time scale of temporal speckle intensity fluctuations, which serves as an index of tissue viscoelasticity. In order to measure the mechanical properties of luminal organs in vivo, LSR must be conducted via a miniature endoscope or catheter. Here we demonstrate the capability of an omni-directional LSR catheter to quantify tissue mechanical properties over the entire luminal circumference without the need for rotational motion. Retracting the catheter using a motor-drive assembly enables the reconstruction of cylindrical maps of tissue mechanical properties. The performance of the LSR catheter is tested using a luminal phantom with mechanical moduli that vary in both circumferential and longitudinal directions. 2D cylindrical maps of phantom viscoelastic properties are reconstructed over four quadrants of the coronary circumference simultaneously during catheter pullback. The reconstructed cylindrical maps of the decorrelation time constants easily distinguish the different gel components of the phantom with different viscoelastic moduli. The average values of decorrelation times calculated for each gel component of the phantom show a strong correspondence with the viscoelastic moduli measured via standard mechanical rheometry. These results highlight the capability for cylindrical mapping of tissue viscoelastic properties using LSR in luminal organs using a miniature catheter, thus opening the opportunity for improved diagnosis of several disease conditions.

  6. Evaluation of antioxidant, rheological, physical and sensorial properties of wheat flour dough and cake containing turmeric powder.

    PubMed

    Park, S H; Lim, H S; Hwang, S Y

    2012-10-01

    The effects of addition of turmeric powder (0%, 2%, 4%, 6% and 8%) were examined in order to obtain an antioxidant-enriched cake with good physico-chemical and sensorial properties. The rheological properties of doughs were evaluated using dynamic rheological measurements. Physical properties, curcumin content, radical scavenging activity (RSA-DPPH assay) and sensory analysis (hedonic test) of the supplemented cake were determined. Addition of turmeric powder up to 8% caused significant changes on dough characteristics and on cake rheological properties. The highest curcumin (203 mg/kg) and RSA-DPPH activity (45%) were achieved in the cake having the highest percentage of turmeric powder (8%); however, this sample showed the worst results regarding the rheological properties. Moreover, by sensory evaluation this cake sample was not acceptable. A 6% substitution of wheat flour with turmeric powder showed acceptable sensory scores which were comparable to those of 0-4% turmeric cakes. This indicated that up to 6% level of turmeric powder might be included in cake formulation. PMID:23144239

  7. Some Mineral Physics Observations Pertinent to the Rheological Properties of Super-Earths

    NASA Astrophysics Data System (ADS)

    Karato, S.

    2010-12-01

    Both orbital and thermal evolution of recently discovered super-Earths (terrestrial planets whit mass exceeding that of Earth) depends critically on the rheological properties of their mantle. Although direct experimental studies on rheological properties are unavailable under the conditions equivalent to the deep mantles of these planets (~1 TPa and ~5000 K), a review of key materials science observations suggests that the deep mantle of these planets have much lower viscosity than most of the shallower regions of these planets. The key observations are: (i) phase transformations likely occur under these conditions including the B1 to B2 transition in MgO (1) and the dissociation of MgSiO3 into two oxides (MgO and SiO2) (2), (ii) the systematics in high-temperature creep show that materials with NaCl (B1) structures have much smaller viscosity than other oxides compared at the same normalized conditions (3), and (iii) diffusion coefficients in most of materials have a minimum at certain pressure and above that pressure it increases with pressure (due to mechanism transition) (4). In addition, a review of existing studies also shows that the ionic solids with B2 (CsCl) structure have larger diffusion coefficients than their B1 counter parts. Furthermore, if metallization transition occurs in any of these materials, delocalized electrons will further weaken the material. All of these observations or concepts suggest that even though the viscosity of a planet (below the asthenosphere) increases with depth in the relatively shallow regions, viscosity likely starts to decrease with depth below some critical depth (>~2000 km). The inferred low viscosity of super-Earths implies a large tidal dissipation and relatively rapid orbital evolution. Also such a rheological properties likely promote a layered mantle convection that enhances a weak deep mantle and retards the thermal evolution. 1. A. R. Oganov, M. J. Gillan, G. D. Price, Journal of Chemical Physics 118, 10174

  8. PAA/PEO comb polymer effects on the rheological property evolution in concentrated cement suspensions

    NASA Astrophysics Data System (ADS)

    Kirby, Glen Harold

    We have studied the behavior of polyelectrolyte-based comb polymers in dilute solution and on the rheological property evolution of concentrated Portland cement suspensions. These species consisted of charge-neutral, poly(ethylene oxide) (PEO) "teeth" grafted onto a poly(acrylic acid) (PAA) "backbone" that contains one ionizable carboxylic acid group (COOH) per monomer unit. As a benchmark, our observations were compared to those obtained for pure cement pastes and systems containing pure polyelectrolyte species, i.e., sulfonated naphthalene formaldehyde (SNF) and poly(acrylic acid) (PAA). The behavior of PAA/PEO comb polymers, SNF, and PAA in dilute solution was studied as a function of pH in the absence and presence of mono-, di-, and trivalent counterions. Light scattering and turbidity measurements were carried out to assess their hydrodynamic radius and stability in aqueous solution, respectively. PAA experienced large conformational changes as a function of solution pH and ionic strength. Moreover, dilute solutions of ionized SNF and PAA species became unstable in the presence of multivalent counterions due to ion-bridging interactions. PAA/PEO solutions exhibited enhanced stability relative to pure polyelectrolytes under analogous conditions. The charge neutral PEO teeth shielded the underlying PAA backbone from ion-bridging interactions. In addition, such species hindered conformational changes in solution due to steric interactions between adjacent teeth. A new oscillatory shear technique was developed to probe the rheological property evolution of concentrated cement systems. The rheological property evolution of ordinary and white Portland cement systems were studied in the absence and presence of pure polyelectrolytes and PAA/PEO comb polymers with a wide range of PAA backbone molecular weight, PEO teeth molecular weight, and acid:imide ratio. Cement-PAA suspensions experienced rapid irreversible stiffening and set at 6 min due to ion

  9. Effects of chelating agents on the rheological property of cervical mucus.

    PubMed

    Lee, Chi H; Wang, Yicheng; Shin, Sang-Chul; Chien, Yie W

    2002-06-01

    As an ongoing effort to elucidate the mechanisms involved in the calcium-dependent fertility regulation process, the viscoelastic properties of the mucus obtained from lamb cervix and human semen, as well as their water and total protein contents after exposure to EDTA, a chelating agent, or Nonoxynol-9 (N-9), a spermicidal agent, were examined. The viscosity was measured using a Cone Plate Digital Viscometer, while the water and total protein contents were determined by the lyophilization process and the Lowry method, respectively. The significant changes in the rheological properties of mucus, such as its viscosity and the water content, upon exposure to EDTA were demonstrated. The viscosity of cervical mucus and human semen were significantly increased by EDTA treatment (as compared to the controls): lamb cervical mucus (2.9 +/- 0.3 vs. 2.2 +/- 0.3 cps) and human semen (5.0 +/- 0.3 vs. 4.3 +/- 0.3 cps), respectively. The hydration rate was decreased by EDTA treatment as compared with the control (93.6 +/- 0.7 vs. 96.8 +/- 0.8%). Among tested samples, the reduction in the percentage of sperm penetration through the cervical mucus was the highest in the mucus containing EDTA, which had the lowest water content (93.6 +/- 0.7%), indicating that there is a positive relationship between the hydration rate of the cervical mucus and its ability to permit the penetration of spermatozoa. This result indicates that spermicidal activity exerted by high concentrations of EDTA is in part due to its effect on the rheological properties of cervical mucus or semen. PMID:12127644

  10. Effects of the low-temperature thermo-alkaline method on the rheological properties of sludge.

    PubMed

    Wang, Ruikun; Zhao, Zhenghui; Yin, Qianqian; Liu, Jianzhong

    2016-07-15

    Municipal sewage sludge (hereafter referred to as sludge) in increasing amounts is a serious threat to the environment and human health. Sludge is difficult to dispose because of its complex properties, such as high water content, viscosity, and hazardous compound concentration. The rheological properties of sludge also significantly influence treatment processes, including stirring, mixing, pumping, and conveying. Improving the rheological properties and reducing the apparent viscosity of sludge are conducive to economic and safe sludge treatment. In this study, the low-temperature thermo-alkaline (LTTA) method was used to modify sludge. Compared with the original sludge with an apparent viscosity at 100 s(-1) (η100) of 979.3 mPa s, the sludge modified under 90 °C-Ca(OH)2-1 h and 90 °C-NaOH-1 h conditions exhibited lower η100 values of 208.7 and 110.8 mPa s respectively. The original sludge exhibited a pseudoplastic behavior. After modification, the pseudoplastic behavior was weakened, and the sludge gradually tended to behave as Newton fluids. The hysteresis loop observed during the shear rate cycle was mainly caused by the viscoelasticity of the sludge. The hysteresis loop area (Hla) reflected to a certain extent the energy required to break the elastic solid structure of the sludge. The larger the Hla, the more energy was needed. However, this result should be evaluated comprehensively by considering other sludge parameters, such as yield stress and apparent viscosity. Hla may also reflect the damage degree of the sludge structure after shearing action. The irreversible destruction of the structure during shearing may also increase Hla. PMID:27082259

  11. A comparison of field-dependent rheological properties between spherical and plate-like carbonyl iron particles-based magneto-rheological fluids

    NASA Astrophysics Data System (ADS)

    Tan Shilan, Salihah; Amri Mazlan, Saiful; Ido, Yasushi; Hajalilou, Abdollah; Jeyadevan, Balachandran; Choi, Seung-Bok; Azhani Yunus, Nurul

    2016-09-01

    This work proposes different sizes of the plate-like particles from conventional spherical carbonyl iron (CI) particles by adjusting milling time in the ball mill process. The ball mill process to make the plate-like particles is called a solid-state powder processing technique which involves repeated welding, fracturing and re-welding of powder particles in a high-energy ball mill. The effect of ball milling process on the magnetic behavior of CI particles is firstly investigated by vibrating sample magnetometer. It is found form this investigation that the plate-like particles have higher saturation magnetization (about 8%) than that of the spherical particles. Subsequently, for the investigation on the sedimentation behavior the cylindrical measurement technique is used. It is observed from this measurement that the plate-like particles show slower sedimentation rate compared to the spherical particles indicating higher stability of the MR fluid. The field-dependent rheological properties of MR fluids based on the plate-like particles are then investigated with respect to the milling time which is directly connected to the size of the plate-like particles. In addition, the field-dependent rheological properties such as the yield stress are evaluated and compared between the plate-like particles based MR fluids and the spherical particles based MR fluid. It is found that the yield shear stress of the plate-like particles based MR fluid is increased up to 270% compared to the spherical particles based MR fluid.

  12. Antioxidant, functional and rheological properties of optimized composite flour, consisting wheat and amaranth seed, brewers' spent grain and apple pomace.

    PubMed

    Awolu, Olugbenga Olufemi; Osemeke, Richard Onyemaechi; Ifesan, Beatrice O Temilade

    2016-02-01

    Consumer's interest in functional food has continued to increase due to its potential health benefits. This study therefore is aimed at developing a functional wheat based flour comprising, amaranth (Amaranthus hypochondriacus) seed, brewers' spent grain and apple pomace. The statistical analyses were carried out using response surface methodology (RSM). For the experimental design, the composite flour components were the variables while the proximate and mineral compositions were the responses. After the statistical optimisation process, the best three blends were chosen for further analyses; determination of antioxidant, functional and rheological properties. From the results, the best blends were Runs 11, 13 and 19, with percentages composition of wheat, amaranth seed, brewers, spent grain and apple pomace of 65 %, 30 %, 2 %, 3 %; 60.43 %, 29.68 %, 4.1 %, 5.79 % and 81.94 %, 6.75 %, 3.39 %, 7.92 % respectively. The ANOVA, R(2) and R(2) adjusted values for the proximate and mineral compositions showed that the composite flours were statistically satisfactory. The results also indicated that the antioxidant, functional and rheological properties of the three best blends showed good and acceptable nutritional and rheological properties. Composite flours with acceptable and excellent nutritional composition, functional properties and rheological behaviour can be obtained from composite blends consisting wheat, amaranth seed, brewers, spent grain and apple pomace flours. PMID:27162395

  13. EFFECT OF PROTEIN COMPOSITION OF WHEAT FLOUR MILL STREAMS ON DOUGH RHEOLOGICAL PROPERTIES AND BREAD CRUMB CHARACTERISTICS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flour mill streams, obtained from three samples of Nekota, a hard red winter wheat, were used in this study. The objective was to assess the contribution of protein composition on dough rheological properties and bread crumb characteristics of bread made from the mill streams. Flour proteins were fr...

  14. Short Communication: Rheological properties of blood serum of rats after irradiation with different gamma radiation doses in vivo.

    PubMed

    Abdelhalim, Mohamed Anwar K; Moussa, Sherif Aa; Ms, Al-Ayed

    2016-01-01

    The blood serum rheological properties open the door to find suitable radio-protectors and convenient therapy for many cases of radiation exposure. The present study aimed to investigate the rheological properties of rat blood serum at wide range of shear rates after whole body irradiation with different gamma radiation doses in vivo. Healthy male rats were divided into five groups; one control group and 4 irradiated groups. The irradiation process was carried out using Co60 source with dose rate of 0.883cG/sec. Several rheological parameters were measured using Brookfield LVDV-III Programmable rheometer. A significant increase in viscosity and shear stress was observed with 25 and 50Gy corresponding to each shear rate compared with the control; while a significant decrease observed with 75 and 100Gy. The viscosity exhibited a Non-Newtonian behaviour with the shear rate while shear stress values were linearly related with shear rate. The decrease in blood viscosity might be attributed to changes in molecular weight, pH sensitivity and protein structure. The changes in rheological properties of irradiated rats' blood serum might be attributed to destruction changes in the haematological and dimensional properties of rats' blood products. PMID:27005501

  15. Rheological properties of water-coal slurries based on brown coal in the presence of sodium lignosulfonates and alkali

    SciTech Connect

    D.P. Savitskii; A.S. Makarov; V.A. Zavgorodnii

    2009-07-01

    The effect of the oxidized surface of brown coal on the structural and rheological properties of water-coal slurries was found. The kinetics of structure formation processes in water-coal slurries based on as-received and oxidized brown coal was studied. The effect of lignosulfonate and alkali additives on the samples of brown coal was considered.

  16. Impact of the substitution of rice bran on rheological properties of dough and in the new product development.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice bran is a nutrient-rich co-product of the rice milling industries. The impact of adding 2-20% rice bran in wheat flour on the rheological behavior of the dough was investigated using the instruments, Farinograph, Consistograph, and Alveograph. The changes in physico-chemical properties were fo...

  17. A comparison of physical and rheological properties of Arrowtooth Flounder protein made using three different extraction processes.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soluble(s) and insoluble(s) fish protein powders were made from arrowtooth flounder (AF) fillets using three methods, which were heating and fractionation (HF), enzymatic hydrolysis (EH), and alkali protein extraction (AE). The AF powders were compared and physical, chemical and rheological properti...

  18. Probing the micro-rheological properties of aerosol particles using optical tweezers

    NASA Astrophysics Data System (ADS)

    Power, Rory M.; Reid, Jonathan P.

    2014-07-01

    The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst

  19. Effect of texture on rheological properties: the case of ɛ-Fe (Invited)

    NASA Astrophysics Data System (ADS)

    Merkel, S.; Gruson, M.; Tomé, C. N.; Nishiyama, N.; Wang, Y.

    2009-12-01

    Lattice preferred orientations (LPO) are known to affect the physical properties of materials. However, in most high pressure deformation experiments, LPO are ignored when interpreting the measured stress-strain curves. In addition, stress measurements in those experiments are complicated by the effect of plastic deformation on the measured lattice strains(1). Here, we present a new interpretation of the results obtained on hcp-iron at up to 19 GPa and 600 K in the deformation-DIA(2). In those experiments, five independent stress-strain curves were obtained on axial shortening with a ductile behavior of the sample for all. Stress were studied using results of monochromatic X-ray diffraction and the elastic theory of lattice strains(3). However, measured stresses were inconsistent with a change of behavior after 4% axial strain, particularly for strains measured on the 0002 line. We use elasto-plastic self consistent modeling(1) to show that this change of behavior is due to the evolution of LPO in the sample. With compression, 10-10 planes in hcp-iron align parallel to the compression direction and this affects the rheological behavior of the sample, which can not be summarized in a simple average law. We will also discuss the implication of those results for the extraction of polycrystalline rheological properties for materials with non-random lattice preferred orientations and how this could affect our understanding of the Earth deep interior. 1- S. Merkel, C.N. Tomé, H.-R Wenk, A modeling analysis of the influence of plasticity on high pressure deformation of hcp-Co, Phys. Rev. B, 79, 064110 (2009) 2- N. Nishiyama, Y. Wang, M. L. Rivers, S. R. Sutton, D. Cookson, Rheology of e-iron up to 19 GPa and 600 K in the D-DIA, Geophys. Res. Lett., 34, L23304 (2007) 3- A. K. Singh, C. Balasingh, H. K. Mao, R. J. Hemley, J. Shu, Analysis of lattice strains measured under non-hydrostatic pressure, J. Appl. Phys., 83, 7567-7575 (1998)

  20. Rheological and electrical properties of polystyrene/multi-walled carbon nanotube nanocomposites prepared by latex technology

    NASA Astrophysics Data System (ADS)

    Kang, Myung Hwan; Lee, Seong Jae

    2012-06-01

    The nanocomposites of monodisperse polystyrene (PS) particles and multi-walled carbon nanotubes (MWNTs) were prepared by latex technology to provide good dispersion of nanotubes in polymer matrix. Two kinds of monodisperse PS particles were synthesized either by emulsion polymerization or by dispersion polymerization. The MWNTs were dispersed in deionized water and mixed with the PS particles, and then PS/MWNT nanocomposites were prepared by freeze-drying and subsequent compression molding. Rheological and electrical properties of these nanocomposites were investigated. Pronounced effect of MWNT incorporation was observed, resulting in larger modulus at lower frequencies when compared to neat PS. The nanocomposite prepared under ultrasonication showed the optimum results providing good dispersion of MWNTs and high electrical conductivity. The effect of PS particle size on electrical conductivity was found to be dependent on the MWNT content incorporated.

  1. The effect of curdlan on the rheological properties of restructured ribbonfish (Trichiurus spp.) meat gel.

    PubMed

    Wu, Chunhua; Yuan, Chunhong; Chen, Shiguo; Liu, Donghong; Ye, Xingqian; Hu, Yaqin

    2015-07-15

    The influence of curdlan at different levels, as well as the method of addition, on the viscoelastic characteristics of ribbonfish meat gel was investigated. From a small amplitude oscillatory shear analysis (SAOA), a variety of viscoelastic parameters were established and identified to measure the intensity of the interactions between curdlan and protein in the fish meat gel network structure. The results of water holding capacity, texture, sensory property and microstructure analyses were strongly in agreement with the rheology data, suggesting that SAOA might be an appropriate method for the industrial assessment of the quality of fish meat gel. Additionally, the recombination mechanism of the complex system formed by the fish protein and curdlan was also clarified. Compared with the irreversible curdlan gel samples, the addition of reversible curdlan gel to the fish meat gel formed a much denser cross-linked interpenetrating structure, which led to a more stable and ordered three-dimensional gel complex. PMID:25722158

  2. Steady and Dynamic Shear Rheological Properties of Buckwheat Starch-galactomannan Mixtures

    PubMed Central

    Choi, Dong Won; Chang, Yoon Hyuk

    2012-01-01

    This study investigated the effects of galacomannans (guar gum, tara gum, and locust bean gum) on the rheological properties of buckwheat starch pastes under steady and dynamic shear conditions. The power law and Casson models were applied to describe the flow behavior of the buckwheat starch and galactomannan mixtures. The values of the apparent viscosity (ηa,100), consistency index (K), and yield stress (σoc) for buckwheat starch-galactomannan mixtures were significantly greater than those for the control, indicating that there was a high synergism of the starch with galactomannans. The magnitudes of storage modulus (G′) and loss modulus (G″) for the starch-galactomannan mixtures increased with increasing frequency (ω). The dynamic moduli (G′, G″), and complex viscosity (η*) for the buckwheat starch-galactomannan mixtures were significantly higher than those for the control. PMID:24471083

  3. Molecular weight degradation and rheological properties of schizophyllan under ultrasonic treatment.

    PubMed

    Zhong, Kui; Zhang, Qi; Tong, Litao; Liu, Liya; Zhou, Xianrong; Zhou, Sumei

    2015-03-01

    Molecular weight degradation effects of schizophyllan (SPG) under ultrasonic treatments were investigated in this study. The degradation product was treated by alcohol fractional precipitation technology, and the molecular weight and rheological properties of ultrasonic-treated SPG (USPG) fractions were evaluated. Average molecular weight of SPG decreased significantly after ultrasonic treatments, and degradation product had more narrow distribution of molecular weight. The molecular weight degradation kinetics of SPG is adequately described by a second-order reaction. USPG fractions with different molecular weight were obtained by fractional precipitation for final alcohol concentration fractions 0-40%, 40-60% and 60-80%, respectively. USPG fractions had near-Newtonian flow behaviors, and USPG₈₀% exhibited viscous responses over the entire accessible frequency range. Therefore, ultrasonic treatment is a viable modification technology for SPG and other polymer materials with high molecular weight. PMID:25263766

  4. Influence of cementitious additions on rheological and mechanical properties of reactive powder concretes

    NASA Astrophysics Data System (ADS)

    Zenati, A.; Arroudj, K.; Lanez, M.; Oudjit, M. N.

    2009-11-01

    Following needs of concrete market and the economic and ecological needs, several researchers, all over the world, studied the beneficial effect which the incorporation of the mineral additions in Portland cement industry can bring. It was shown that the incorporation of local mineral additions can decrease the consumption of crushing energy of cements, and reduce the CO2 emission. Siliceous additions, moreover their physical role of filling, play a chemical role pozzolanic. They contribute to improving concrete performances and thus their durability. The abundance of dunes sand and blast furnace slag in Algeria led us to study their effect like cementitious additions. The objective of this paper is to study the effect of the incorporation of dunes sand and slag, finely ground on rheological and mechanical properties of reactive powder concretes containing ternary binders.

  5. Characterization of wami tilapia (Oreochromis urolepis hornorum) skin gelatin: microbiological, rheological and structural properties.

    PubMed

    Alfaro, Alexandre Da Trindade; Fonseca, Gustavo Graciano; Balbinot, Evellin; Prentice, Carlos

    2014-07-01

    Gelatin was extracted from the skin of tilapia (Oreochromis urolepis hornorum) and its microbiological, rheological and structural properties were characterized. The tilapia skin gelatin presented typical molecular weight distribution of type I collagen with contents of imino acids (proline + hydroxyproline) of 21.67%. Gel strength and viscosity values were 221 ± 5.68 g and 5.98 ± 0.34 cP, respectively, with the maturation time of 18 ± 1 h, and both parameters increased with the maturation time. Melting and gelling points of 25 degrees C and 21 degrees C, respectively, were obtained for tilapia skin gelatin. The gelatin presented microbiological standards in accordance with the Brazilian Legislation. PMID:23751549

  6. Effect of various superplasticizers on rheological properties of cement paste and mortars

    SciTech Connect

    Masood, I.; Agarwal, S.K. )

    1994-01-01

    The effect of eight commercial superplasticizers including one developed from Cashew Nut Shell Liquid (CNSL) at CBRI on the rheological properties viz. viscosity and flow of cement paste and mortars have been investigated. The viscosity measurements have been made at various shear rates (5--100 rpm). It is found that at higher rates (100 rpm) even with the low concentration of superplasticizers (0.1), the viscosity of the cement paste is more or less the same as that obtained with 0.6 % dosages of SPs at lesser shear rates. The effect of split addition (delayed addition) of superplasticizers on viscosity of cement paste and 1:3 cement sand mortar have also been studied. A decrease in viscosity due to split addition has been observed in the cement paste and there is an increase of 15--20 % in flow of mortars.

  7. Rheological and volumetric properties of TiO2-ethylene glycol nanofluids

    PubMed Central

    2013-01-01

    Homogeneous stable suspensions obtained by dispersing dry TiO2 nanoparticles in pure ethylene glycol were prepared and studied. Two types of nanocrystalline structure were analyzed, namely anatase and rutile phases, which have been characterized by scanning electron microscopy. The rheological behavior was determined for both nanofluids at nanoparticle mass concentrations up to 25%, including flow curves and frequency-dependent storage and loss moduli, using a cone-plate rotational rheometer. The effect of temperature over these flow curve tests at the highest concentration was also analyzed from 283.15 to 323.15 K. Furthermore, the influence of temperature, pressure, nanocrystalline structure, and concentration on the volumetric properties, including densities and isobaric thermal expansivities, were also analyzed. PMID:23763850

  8. Rheological properties of purified illite clays in glycerol/water suspensions

    NASA Astrophysics Data System (ADS)

    Dusenkova, I.; Malers, J.; Berzina-Cimdina, L.

    2015-04-01

    There are many studies about rheological properties of clay-water suspensions, but no published investigations about clay-glycerol suspensions. In this work apparent viscosity of previously purified illite containing clay fraction < 2 μm and glycerol/water suspensions were investigated. Carbonates were removed by dissolution in hydrochloric and citric acids and other non-clay minerals were almost totally removed by centrifugation. All obtained suspensions behaved as shear-thinning fluids with multiple times higher viscosity than pure glycerol/water solutions. Reduction of clay fraction concentration by 5% decreased the apparent viscosity of 50% glycerol/water suspensions approximately 5 times. There was basically no difference in apparent viscosity between all four 50% glycerol/water suspensions, but in 90% glycerol/water suspensions samples from Iecava deposit showed slightly higher apparent viscosity, which could be affected by the particle size distribution.

  9. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    NASA Astrophysics Data System (ADS)

    Wu, Z. X.; Li, L. F.; Li, J. W.; Huang, C. J.; Tan, R.; Tu, Y. P.

    2014-01-01

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  10. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    SciTech Connect

    Wu, Z. X.; Huang, C. J.; Li, L. F.; Li, J. W.; Tan, R.; Tu, Y. P.

    2014-01-27

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  11. Influence of Plasticizer Amount on Rheological and Hydration Properties of CEM II Type Portland Cements

    NASA Astrophysics Data System (ADS)

    Šeputytė-Juciké, J.; Pundienė, I.; Kičaitė, A.; Pranckevičienė, J.

    2015-11-01

    The article analyzes the effect of plasticizer (based on polycarboxilates) amount (0.3 - 1.2% wt. of cement) on the rheological and hydration properties of two Portland cements pastes: CEM II/A-S 42.5N and CEM II/A-LL 42.5N. Increase of plasticizer amount reduces viscosity of CEM II/A-LL 42.5N cement paste from 3 to 12 times, where viscosity of CEM II/A-S 42.5N cement paste reduces from 5 to 20 times. The optimum plasticizer dose (0.3%) in case of CEM II/A-S 42.5N and (1.2%) in case of CEM II/A-LL 42.5N was established. Calorimetry studies have shown that plasticizer reduces the wetting heat release rate in CEM II/A-LL 42.5N cement twice and in CEM II/A-S 42.5N cement - by 25%. Plasticizer prolongs the maximum heat release rate time by 16 h in CEM II/A-LL 42.5N samples and reduces heat release rate by 19%. In CEM II/A-S 42.5N cement samples plasticizer prolongs maximum heat release rate time by 14.5 h and increases heat release rate by 15%. The goal of this study is to analyze the effect of the dosage of the most widely used plasticizer on solubility characteristics, rheological and hydration properties of two cements CEM II/A-S 42.5N and CEM II/A-LL 42.5N to establish the optimum dose of plasticizer in cements pastes.

  12. Physicochemical, thermal and rheological properties of starches isolated from malting barley varieties.

    PubMed

    Pycia, Karolina; Gałkowska, Dorota; Juszczak, Lesław; Fortuna, Teresa; Witczak, Teresa

    2015-08-01

    The aim of this work was to characterize physicochemical, thermal and rheological properties of starches isolated from malting barley varieties. The analyzed starches contained 19.6-25.2 g of amylose, 42.47-70.67 mg of phosphorus, 0.50-1.26 g of protein and 0.10-0.61 g of fat per 100 g of starch dry mass. The clarity of the 1 % (w/w) starch pastes ranged from 5.4 to 9.8 %. Values of the characteristic gelatinization temperatures were in the ranges of 56.5-58.5 °C, 61.2-63.0 °C and 66.7-68.7 °C, respectively for TO, TP and TE, whereas values of gelatinization enthalpy were from 6.49 to 9.61 J/g. The barley starches showed various tendency to retrogradation, from 24.52 to 44.22 %, measured as R = ∆HR/∆HG value. The pasting curves showed differences in pasting characteristics of the barley starches, where values of peak (PV) and final (FV) viscosities were 133-230 mPa·s and 224-411 mPa·s, respectively. The barley starch pastes exhibited non-Newtonian, shear thinning flow behaviour and thixotropy phenomenon. After cooling the starch gels showed different viscoelastic properties, however, most of them behaved like weak gels (tan δ = G″/G' > 0.1). Significant linear correlations between the parameters of pasting characteristic and some rheological parameters were found. PMID:26243900

  13. Changes of rheologic properties of blood in experimental animals irradiated with low-energy lasers

    NASA Astrophysics Data System (ADS)

    Turczynski, Boleslaw; Cieslar, Grzegorz; Sieron, Aleksander; Adamek, Mariusz

    1995-03-01

    The effect of infrared laser radiation on viscosity of serum and blood in experimental animals was investigated. The experiment was carried out on 30 male guinea pigs weighing 280 - 320 g. Fifteen animals composed a group irradiated with laser, the other 15 animals made up a control group in which no irradiation was made. A semiconductive laser generating infrared radiation (wavelength -- 904 nm, frequency -- 800 Hz, pulse duration -- 200 ns, mean power - - 8.7 mW) was used. The right infracostal region of the animal was irradiated 3 minutes daily for 15 consecutive days. After the end of the experiment in the obtained blood and serum the measurement of hematocrit and rheologic examination was made in the temperature of 310 K. The estimation of viscosity of whole blood was made by means of low-gradient viscosimeter `low shear,' for shearing velocities: D1 equals 0.116 s-1 and D2 equals 4.59 s-1. The viscosity of serum was estimated using Ubbelohd's microviscosimeter. A significant increase of whole blood viscosity measured for shearing velocity D1 was obtained in irradiated animals as compared to the controls. No statistically significant differences in viscosity of whole blood at clotting speed D2, viscosity of serum and hematocrit were observed between both groups of animals. The obtained data prove a distinct effect of low-energy laser radiation on rheologic properties of blood in experimental animals. The increase of whole blood viscosity, observed only at low shearing velocities, is probably related to the changes of structural and functional properties of cell membranes of erythrocytes resulting in a decrease of aggregation.

  14. Rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H2O2 pretreatment.

    PubMed

    Liu, Jibao; Yu, Dawei; Zhang, Jian; Yang, Min; Wang, Yawei; Wei, Yuansong; Tong, Juan

    2016-07-01

    The rheological behavior of sludge is of serious concern in anaerobic digestion. This study investigated the rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H2O2 pretreatment (MW-H2O2). The results showed that MW-H2O2 pretreatment resulted in the improvement of sludge flowability and weakening of its viscoelastic properties. Further positive effects on the rheological properties of digested sludge during anaerobic digestion were observed. The flowability was improved with a low level of apparent viscosity. The decrease of the consistency index and increase of the flow behavior index indicated that the strength of the inner structures and non-Newtonian flow characteristics of digested sludge weakened. Both the storage modulus (G') and loss modulus (G″) decreased, indicating that the viscoelastic behavior became weak. These effects were possibly attributed to the changes of the digested sludge micro-structures, such as extracellular polymeric substances (EPS). This study concluded that anaerobic digestion for treating sewage sludge combined with pretreatment is a more favorable option than single anaerobic digestion from the perspective of rheology. PMID:27085155

  15. Chemical and rheological properties of exopolysaccharides produced by four isolates of rhizobia.

    PubMed

    Moretto, Cristiane; Castellane, Tereza Cristina Luque; Lopes, Erica Mendes; Omori, Wellington Pine; Sacco, Laís Postai; Lemos, Eliana Gertrudes de Macedo

    2015-11-01

    The rheological, physicochemical properties, emulsification and stability of exopolysaccharides (EPSs) from four rhizobia isolates (LBMP-C01, LBMP-C02, LBMP-C03 and LBMP-C04) were studied. The EPS yields of isolates under these experimental conditions were in the range of 1.5-6.63gL(-1). The LBMP-C04 isolate, which presented the highest EPS production (6.63gL(-1)), was isolated from Arachis pintoi and was identified as a Rhizobium sp. strain that could be explored as a possible potential source for the production of extracellular heteropolysaccharides. All polymers showed a pseudoplastic non-Newtonian fluid behavior or shear thinning property in aqueous solutions. Among the four EPS tested against hydrocarbons, EPS LBMP-C01 was found to be more effective against hexane, olive and soybean oils (89.94%, 82.75% and 81.15%, respectively). Importantly, we found that changes in pH (2-11) and salinity (0-30%) influenced the emulsification of diesel oil by the EPSs. EPSLBMP-C04 presented optimal emulsification capacity at pH 10 (E24=53%) and 30% salinity (E24=27%). These findings contribute to the understanding of the influence of the chemical composition, physical properties and biotechnology applications of rhizobial EPS solutions their bioemulsifying properties. PMID:26234581

  16. Mechanical, Rheological and Thermal Properties of Polyethylene (PE)/Clay Nanocomposite for Rotomolded Containers

    NASA Astrophysics Data System (ADS)

    Jamshidi, Shadi

    Polyethylene (PE) is widely used to make bulk containers via rotational molding process. Adding 2 wt % and 4 wt % organo-modified clay improved the thermal, barrier and mechanical properties of PE. Clay layers create a tortuous path against the permeant, yielding better barrier properties. Due to the non-polar hydrophobic nature of PE and polar hydrophilic structure of clay minerals, a compatibilizer (PE-g-Maleic Anhydride) was required to enhance the dispersion level of clay in the matrix. In this study High Density Polyethylene (HDPE) and Linear Low Density Polyethylene (LLDPE) layered silicate nanocomposites were melt-compounded with two concentrations of organo-modified clay (2 and 4 weight %). The interaction between nanoclay, compatibilizer and rotomolding grade of PE were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), mechanical and rheological tests. The XRD results revealed an enhanced basal spacing of layered silicates within both LLDPE nanocomposites at low nanoclay loadings, in agreement with the TEM observations; TEM images showed a uniformly dispersed layered silicates. Through thermal and rheological characterization techniques, the results illustrated that the thermal resistance, elastic and viscous modulus of nanocomposites improved significantly with incorporation of layered silicates. Analyzing all the data showed enhanced properties of LLDPE nanocomposites, which can be attributed to a strong interfacial interaction between the compatibilizer with LLDPE backbone and LLDPE matrices compared with HDPE matrices. The influence of in-house organo-modification of layered silicates on the properties of nanocomposites was compared to that of nanocomposites prepared with commercially available nanoclay (Cloisite 20A). LLDPE nanocomposites prepared by the in-house organo-modified clay showed better mechanical properties, elastic and viscous modulus due to good dispersion of layered silicates as determined by the XRD

  17. Effect of the rheological properties of carbon nanotube dispersions on the processing and properties of transparent conductive electrodes.

    PubMed

    Maillaud, Laurent; Poulin, Philippe; Pasquali, Matteo; Zakri, Cécile

    2015-06-01

    Transparent conductive films are made from aqueous surfactant stabilized dispersions of carbon nanotubes using an up-scalable rod coating method. The processability of the films is governed by the amount of surfactant which is shown to alter strongly the wetting and viscosity of the ink. The increase of viscosity results from surfactant mediated attractive interactions between the carbon nanotubes. Links between the formulation, ink rheological properties, and electro-optical properties of the films are determined. The provided guidelines are generalized and used to fabricate optimized electrodes using conductive polymers and carbon nanotubes. In these electrodes, the carbon nanotubes act as highly efficient viscosifiers that allow the optimized ink to be homogeneously spread using the rod coating method. From a general point of view and in contrast to previous studies, the CNTs are optimally used in the present approach as conductive additives for viscosity enhancements of electronic inks. PMID:25961667

  18. Rheological properties of somen noodles--a traditional Japanese wheat product.

    PubMed

    Katagiri, Mina; Kitabatake, Naofumi

    2010-01-01

    We investigated the rheological properties of the Japanese wheat product tenobe somen noodles manufactured using a unique traditional process-"Te-nobe (hand-stretched)." In an extension test, the maximum resistance to extension (R(max)) and extensibility until rupture (Erup) of boiled somen noodles were measured on a Texture Analyzer in the tension test mode and compared with those of machine-made somen noodles. The R(max) and Erup values per unit cross-sectional area were significantly higher for boiled tenobe somen noodles than for machine-made somen noodles, clearly indicating the higher resistance to extension and extensibility of the former. A compression test performed using the Texture Analyzer in the biting-test mode revealed that although the maximum force of compression (F(max)) was lower for boiled tenobe somen noodles than for machine-made somen noodles, the former had more characteristic texture than the latter, which was shown by comparing the force-deformation curve of each somen noodle. Scanning electron microscopy revealed differences between dried tenobe and machine-made somen noodles, which may reflect their rheological differences. Lateral and sectional micrographs of tenobe somen noodles showed regular arrays of starch granules and gluten networks, and some air spaces. Tenobe somen noodles exhibited significantly higher dityrosine content than the flour used for their manufacture, indicating that tyrosine residues in gluten proteins cross-link during the manufacturing process; however, the dityrosine content in tenobe somen noodles were not higher than that in machine-made somen noodles. PMID:20492166

  19. Fault properties, rheology and interseismic deformation in Southern California from high-precision space geodesy

    NASA Astrophysics Data System (ADS)

    Lindsey, Eric Ostrom

    This dissertation presents the collection and processing of dense high-precision geode- tic data across major faults throughout Southern California. The results are used to inform numerical models of the long-term slip rate and interseismic behavior of these faults, as well as their frictional and rheological properties at shallow depths. The data include campaign surveys of dense networks of GPS monuments crossing the faults, and Interferometric Synthetic Aperture Radar (InSAR) observations from ENVISAT. Using a Bayesian framework, we first assess to what extent these data constrain relative fault slip rates on the San Andreas and San Jacinto faults, and show that the inferred parameters depend critically on the assumed fault geometry. We next look in detail at near-field observations of strain across the San Jacinto fault, and show that the source of this strain may be either deep anomalous creep or a new form of shallow, distributed yielding in the top few kilometers of the crust. On the San Andreas fault, we show that this type of shallow yielding does occur, and its presence or absence is controlled by variations in the local normal stress that result from subtle bends in the fault. Finally, we investigate shallow creep on the Imperial fault, and show that thanks to observations from all parts of the earthquake cycle it is now possible to obtain a strong constraint on the shallow frictional rheology and depth of the material responsible for creep. The results also suggest activity on a hidden fault to the West, whose existence has been previously suggested but never confirmed.

  20. Formulation and Comparative Study of Rheological Properties of Loaded and Unloaded Ethanol-Based Gel Propellants

    NASA Astrophysics Data System (ADS)

    Jyoti, Botchu V. S.; Baek, Seung Wook

    2015-04-01

    The current trend in the area of highly energetic storable liquid rocket propellant research is to develop environmentally friendly gelled/metallized systems and to explore the feasibility of their application in rocket engines. The idea stems from the fact that the conversion of a conventional liquid propellant to a gelled state and its subsequent metallization has the potential to significantly enhance the performance and density-specific impulse. The gelation of liquid fuels could be induced at a critical gellant concentration of as low as 8 wt% for the pure ethanol case and as low as 4 and 6 wt% for metallized ethanol depending on the metal type. Furthermore, the gel formed should be thixotropic. Metallized gels using 20 wt% Al and B metal powders could also be formulated. These metallized (Al and B) ethanol gel systems showed a reduction in the critical gellant concentration depending on the degree of metallization. The rheological properties of metallized and nonmetallized ethanol gels using methyl cellulose (MC) as a gelling agent at different ambient temperatures (283.15, 293.15, 303.15, 313.15, and 323.15 K) were experimentally investigated in this study. The gel fuels were rheologically characterized using a rheometer at shear rates ranging from 1 to 12 s-1 and 1 to 1,000 s-1. Metallized and nonmetallized ethanol gels were found to be thixotropic in nature. The apparent viscosity and yield stress (for shear rate range 1 to 12 s-1) of gels were observed to significantly decrease at higher ambient temperatures and as the gellant and metal particle concentrations decreased. The thixotropic behavior was found to be a strong function of the Al and B metal particle concentration for all test temperatures at shear rate ranges from 1 to 12 s-1 and 1 to 1,000 s-1. It was also a function of the MC concentration at a shear rate range of 1 to 1,000 s-1.

  1. Probing the rheological properties of supported thin polystyrene films by investigating the growth dynamics of wetting ridges.

    PubMed

    Zuo, Biao; Tian, Houkuan; Liang, Yongfeng; Xu, Hao; Zhang, Wei; Zhang, Li; Wang, Xinping

    2016-07-13

    Despite its importance in the processing of nanomaterials, the rheological behavior of thin polymer films is poorly understood, partly due to the inherent measurement challenges. Herein, we have developed a facile method for investigating the rheological behavior of supported thin polymeric films by monitoring the growth of the "wetting ridge"-a microscopic protrusion on the film surface due to the capillary forces exerted by a drop of ionic liquid placed on the film surface. It was found that the growth dynamics of the wetting ridge and the behavior of polystyrene rheology are directly linked. Important rheological properties, such as the flow temperature (Tf), viscosity (η), and terminal relaxation time (τ0) of thin polystyrene films, can be derived by studying the development of the height of the wetting ridge with time and the sample temperature. Rheological studies using the proposed approach for supported thin polystyrene (PS) films with thickness down to 20 nm demonstrate that the PS thin film exhibits facilitated flow, with reduced viscosity and lowered viscous temperature and a shortened rubbery plateau, when SiOx-Si was used as the substrate. However, sluggish flow was observed for the PS film supported by hydrogen-passivated silicon substrates (H-Si). The differences in enthalpic interactions between PS and the substrates are the reason for this divergence in the whole-chain mobility and flow ability of thin PS films deposited on SiOx-Si and H-Si surfaces. These results indicate that this approach could be a reliable rheological probe for supported thin polymeric films with different thicknesses and various substrates. PMID:27355155

  2. Rheological and ultrastructural properties of bovine vaginal fluid obtained at oestrus.

    PubMed

    Rutllant, J; López-Béjar, M; Santolaria, P; Yániz, J; López-Gatius, F

    2002-07-01

    The properties of cervical-vaginal fluid are under strict hormonal control: and in mammals in which semen is deposited in the anterior vagina, changes produced in these properties can result in a lower or higher resistance to sperm motion. The aim of this study was to determine whether the structural organization of bovine vaginal fluid is related to its rheological properties. Vaginal fluid samples were collected from 41 cows at oestrus: 20 at the middle of oestrus (between 8 and 12 h after starting) and 21 at the end of oestrus (between 18 and 22 h). Flow behaviour was determined using a viscosimeter, and the ultrastructural analysis was performed by scanning electron microscopy. Six samples showed newtonian behaviour: three collected at the middle and three collected at the end of oestrus. Newtonian samples had dense and compact matrices arranged as membranes with rough, irregular surfaces, and sparse, thin filaments (< 150 nm). Non-newtonian samples collected at the end of oestrus (n = 18) had a higher (P = 0.016) consistency index (K = 944 +/- 229 mPa.s(n)) than those collected at the middle of oestrus (n = 17; K = 237 +/- 84 mPa.s(n)). Thick filaments (> 700 nm) that were either randomly arranged with thinner filaments forming a mesh or heavily cross-linked by thin filaments (50-150 nm) were observed in all non-newtonian samples collected at the end of oestrus, while medium-diameter filaments (between 200 and 500 nm) forming loose networks were observed in non-newtonian samples collected at the middle of oestrus. These findings indicate a close relationship between the molecular organization of the structural elements of bovine vaginal fluid and its rheological behaviour. Vaginal fluid dramatically reduces its mechanical barrier effect during the course of oestrus but always appears to maintain its three-dimensional filamentous structure. The images of vaginal fluid showing newtonian behaviour would appear to support previous results, suggesting that this

  3. Dilution of microbicide gels with vaginal fluid and semen simulants: effect on rheological properties and coating flow.

    PubMed

    Lai, Bonnie E; Xie, Yao Quan; Lavine, Michael L; Szeri, Andrew J; Owen, Derek H; Katz, David F

    2008-02-01

    Microbicides are agents applied topically to the vagina to prevent HIV transmission. Microbicide products formulated as semi-solid dosage forms or "gels" coat vulnerable tissue to deliver active ingredients. Effective microbicide delivery vehicles must have appropriate rheological properties to ensure appropriate deployment in vivo. Microbicide products become diluted by fluids in the vagina after application; dilution affects vehicle rheological properties and mechanics of vaginal distribution, thus affecting efficacy. To simulate the changes that might occur after application, this study analyzed the effects of small dilutions (10-30%) with vaginal fluid and semen simulants on three semi-solid vaginal formulations: a cellulose lubricant (KY Jelly), a polyacrylic acid moisturizer (Replens), and a carrageenan prototype microbicide (Carraguard). Rheological behavior was characterized using cone-and-plate rheometry. Data were fitted to either the power-law, Carreau, or Herschel-Bulkley model. Rheological parameters from these fits were input to models of coating flow due squeezing, and the simulated area coated output from these models was used to compare the responses of the different formulations to the two diluents for varying degrees of dilution. There were differences in the responses of the three materials to dilution. Even small dilutions altered the rank order of vaginal coating rates compared to the undiluted formulations. PMID:17724667

  4. The Field-Dependent Rheological Properties of Magnetorheological Grease Based on Carbonyl-Iron-Particles

    NASA Astrophysics Data System (ADS)

    Mohamad, N.; Mazlan, S. A.; Ubaidillah; Choi, Seung-Bok; Nordin, M. F. M.

    2016-09-01

    This paper presents dynamic viscoelastic properties of magnetorheological (MR) grease under variation of magnetic fields and magnetic particle fractions. The tests to discern the field-dependent properties are undertaken using both rotational and oscillatory shear rheometers. As a first step, the MR grease is developed by dispersing the carbonyl iron (CI) particles into grease medium with a mechanical stirrer. Experimental data are obtained by changing the magnetic field from 0 to 0.7 T at room temperature of 25 °C. It is found that a strong Payne effect limits the linear viscoelastic region of MR grease at strains above 0.1%. The results exhibit a high dynamic yield stress which is equivalent to Bingham plastic rheological model, and show relatively good MR effect at high shear rate of 2000 s‑1. In addition, high dispersion of the magnetic particles and good thermal properties are proven. The results presented in this work directly indicate that MR grease is a smart material candidate that could be widely applicable to various fields including vibration control.

  5. Tailoring the optical and rheological properties of an epoxy acrylate based host-guest system

    NASA Astrophysics Data System (ADS)

    Gleißner, Uwe; Hanemann, Thomas

    2014-05-01

    Polymers with individually adjusted optical and rheological properties are gaining more and more importance in industrial applications like in information technology. To modify the refractive index n, an electron-rich organic dopant is added to a commercially available polymer based resin. Changes in viscosity for applications like ink-jet printing can be achieved by using a comonomer with suitable properties. Therefore we used a commercially available epoxy acrylate based UV-curable polymer matrix to investigate the influence of ethylene glycol dimethacrylate (EGDMA) on viscosity and phenanthrene on refractive index. Refractive index was measured at a wavelength of 589 nm and 20 °C using an Abbe refractometer. As a result the change in viscosity decreased linearly from 47 Pa·s to 4 mPa·s which is a more suitable region for inkjet printing. However, the refractive index decreased at the same time from 1.548 to 1.514. Adding phenanthrene the refractive index increased linearly from 1.548 up to 1.561. It was shown that both, viscosity and refractive index can be successfully adjusted in a wide range depending on desired properties.

  6. Thermal and Rheological Properties of Water-based Ferrofluids and Their Applicability as Quenching Media

    NASA Astrophysics Data System (ADS)

    Župan, Josip; Renjo, Marijana Majić

    Water-based ferrofluids present a new energy transfer fluid with tunable properties. Previous research has shown the increase in thermal conductivity of water-based nanofluids with the addition of iron oxide. Such increased thermal properties show great potential for use in heat transfer. In this paper, several nanofluids were prepared with two step method. Iron (II, III) oxide nanoparticles with average paerticle size less than 50 nm were added to deionized water in following concentration: 0.01, 0.1, 0.5 and 1 g/L. Their thermal and rheological properties were measured at 20, 40 and 60 °C. Results showed increase in thermal conductivity and viscosity with increase in the addition of nanoparticles at all three temperature levels. The biggest increase was observed at 20 °C. For this research, all of the prepared nanofluids were tested as immersion quenching liquid according to ISO 9950 standard. Besides still conditions, quenching experiments were conducted under the magnetic field at two levels, 500 and 1000 Gauss. The magnetic field effect was least present at 60 °C with almost no influence on the cooling curve and cooling rates. At lower temperature levels quenching under the magnetic field shortened the full film boiling phase and increased the maximum cooling rate.

  7. Turkish Tombul hazelnut (Corylus avellana L.) protein concentrates: functional and rheological properties.

    PubMed

    Tatar, F; Tunç, M T; Kahyaoglu, T

    2015-02-01

    Turkish Tombul hazelnut consumed as natural or processed forms were evaluated to obtain protein concentrate. Defatted hazelnut flour protein (DHFP) and defatted hazelnut cake protein (DHCP) were produced from defatted hazelnut flour (DHF) and defatted hazelnut cake (DHC), respectively. The functional properties (protein solubility, emulsifying properties, foaming capacity, and colour), and dynamic rheological characteristics of protein concentrates were measured. The protein contents of samples varied in the range of 35-48 % (w/w, db) and 91-92 % (w/w, db) for DHF/DHC and DHFP/DHCP samples, respectively. The significant difference for water/fat absorption capacity, emulsion stability between DHF and DHC were determined. On the other hand, the solubility and emulsion activity of DHF and DHC were not significantly different (p > 0.05). Emulsion stability of DHFP (%46) was higher than that of DHCP (%35) but other functional properties were found similar. According to these results, the DHCP could be used as DHFP in food product formulations. The DHFP and DHCP samples showed different apparent viscosity at the same temperature and concentration, the elastic modulus (G' value) of DHPC was also found higher than that of DHFP samples. PMID:25694714

  8. Physicochemical and rheological properties of starch and flour from different durum wheat varieties and their relationships with noodle quality.

    PubMed

    Kaur, Amritpal; Shevkani, Khetan; Katyal, Mehak; Singh, Narpinder; Ahlawat, Arvind Kumar; Singh, Anju Mahendru

    2016-04-01

    Starch and flour properties of different Indian durum wheat varieties were evaluated and related to noodle-making properties. Flours were evaluated for pasting properties, protein characteristics (extractable as well as unextractable monomeric and polymeric proteins) and dough rheology (farinographic properties), while starches were evaluated for granule size, thermal, pasting, and rheological properties. Flour peak and final viscosities related negatively to the proportion of monomeric proteins but positively to that of polymeric proteins whereas opposite relations were observed for dough rheological properties (dough-development time and stability). Starches from varieties with higher proportion of large granules showed the presence of less stable amylose-lipids and had more swelling power, peak viscosity and breakdown viscosity than those with greater proportion of small granules. Noodle-cooking time related positively to the proportion of monomeric proteins and starch gelatinization temperatures but negatively to that of polymeric proteins and amylose content. Varieties with more proteins resulted in firmer noodles. Noodle-cohesiveness related positively to the proportion of polymeric proteins and amylose-lipids complexes whereas springiness correlated negatively to amylose content and retrogradation tendency of starches. PMID:27413243

  9. Nanoscale Properties of Rocks and Subduction Zone Rheology: Inferences for the Mechanisms of Deep Earthquakes

    NASA Astrophysics Data System (ADS)

    Riedel, M. R.

    2007-12-01

    Grain boundaries are the key for the understanding of mineral reaction kinetics. More generally, nanometer scale processes involved in breaking and establishing bonds at reaction sites determine how and at which rate bulk rock properties change in response to external tectonic forcing and possibly feed back into various geodynamic processes. A particular problem is the effects of grain-boundary energy on the kinetics of the olivine-spinel phase transformation in subducting slabs. Slab rheology is affected in many ways by this (metastable) mineral phase change. Sluggish kinetics due to metastable hindrance is likely to cause particular difficulties, because of possible strong non-linear feedback loops between strain-rate and change of creep properties during transformation. In order to get these nanoscale properties included into thermo-mechanical models, reliable kinetic data is required. The measurement of grain-boundary energies is, however, a rather difficult problem. Conventional methods of grain boundary surface tension measurement include (a) equilibrium angles at triple junction (b) rotating ball method (c) thermal groove method, and others (Gottstein & Shvindlerman, 1999). Here I suggest a new method that allows for the derivation of grain-boundary energies for an isochemical phase transformation based on experimental (in-situ) kinetic data in combination with a corresponding dynamic scaling law (Riedel and Karato, 1997). The application of this method to the olivine-spinel phase transformation in subducting slabs provides a solution to the extrapolation problem of measured kinetic data: Any kinetic phase boundary measured at the laboratory time scale can be "scaled" to the correct critical isotherm at subduction zones, under experimentelly "forbidden" conditions (Liou et al., 2000). Consequences for the metastability hypothesis that relates deep seismicity with olivine metastability are derived and discussed. References: Gottstein G, Shvindlerman LS (1999

  10. Rheological and interfacial properties at the equilibrium of almond gum tree exudate (Prunus dulcis) in comparison with gum arabic.

    PubMed

    Mahfoudhi, Nesrine; Sessa, Mariarenata; Ferrari, Giovanna; Hamdi, Salem; Donsi, Francesco

    2016-06-01

    Almond gum contains an arabinogalactan-type polysaccharide, which plays an important role in defining its interfacial and rheological properties. In this study, rheological and interfacial properties of almond gum and gum arabic aqueous dispersions were comparatively investigated. The interfacial tension of almond gum and gum arabic aqueous dispersions was measured using the pendant drop method in hexadecane. The asymptotic interfacial tension values for almond gum were significantly lower than the corresponding values measured for gum arabic, especially at high concentration. Rheological properties were characterized by steady and oscillatory tests using a coaxial geometry. Almond gum flow curves exhibited a shear thinning non-Newtonian behavior with a tendency to a Newtonian plateau at low shear rate, while gum arabic flow curves exhibited such behavior only at high shear rate. The influence of temperature (5-50  ℃) on the flow curves was studied at 4% (m/m) gum concentration and the Newtonian viscosities at infinite and at zero shear rate, for gum arabic and almond gum, respectively, were accurately fitted by an Arrhenius-type equation. The dynamic properties of the two gum dispersions were also studied. Both gum dispersions exhibited viscoelastic properties, with the viscous component being predominant in a wider range of concentrations for almond gum, while for gum arabic the elastic component being higher than the elastic one especially at higher concentrations.The rheological and interfacial tension properties of almond gum suggest that it may represent a possible substitute of gum arabic in different food applications. PMID:26163565

  11. Rheological properties, gelling behavior and texture characteristics of polysaccharide from Enteromorpha prolifera.

    PubMed

    Qiao, Leke; Li, Yinping; Chi, Yongzhou; Ji, Yinglu; Gao, Yan; Hwang, Hueymin; Aker, Winfred G; Wang, Peng

    2016-01-20

    Polysaccharide from Enteromorpha prolifera (PE) which is the most common green algae is gradually becoming an attractive candidate with novel functions by virtue of its unique chemical and physicochemical properties. The infrared spectrum (FT-IR) of PE confirmed that it is a distinctive, sulfated heteropolysaccharide. Dynamic rheology was systematically conducted to investigate the effect of concentration, temperature, pH, and electrolytes on PE. The flow behavior testing verified its pseudoplastic character. A closed hysteresis loop was obtained when the PE concentration reached 10 g/L. For the phase angel (tanδ) was always less than 1, the solid-like behavior of PE is also found at 10-14 g/L PE in the linear viscoelastic region (LVR). Furthermore, study on its potential gelling behavior showed that 16 g/L PE could form a gel and had well textural properties. The unique functional groups and characteristics of PE provided the possibility to apply into food industry. PMID:26572475

  12. Some physicochemical and rheological properties of starch isolated from avocado seeds.

    PubMed

    Chel-Guerrero, Luis; Barbosa-Martín, Enrique; Martínez-Antonio, Agustino; González-Mondragón, Edith; Betancur-Ancona, David

    2016-05-01

    Seeds from avocado (Persea americana Miller) fruit are a waste byproduct of fruit processing. Starch from avocado seed is a potential alternative starch source. Two different extraction solvents were used to isolate starch from avocado seeds, functional and rheological characteristics measured for these starches, and comparisons made to maize starch. Avocado seed powder was suspended in a solution containing 2 mM Tris, 7.5 mM NaCl and 80 mM NaHSO3 (solvent A) or sodium bisulphite solution (1500 ppm SO2, solvent B). Solvent type had no influence (p>0.05) on starch properties. Amylose content was 15-16%. Gelatinization temperature range was 56-74 °C, peak temperature was 65.7 °C, and transition enthalpy was 11.4-11.6J/g. At 90 °C, solubility was 19-20%, swelling power 28-30 g water/g starch, and water absorption capacity was 22-24 g water/g starch. Pasting properties were initial temperature 72 °C; maximum viscosity 380-390 BU; breakdown -2 BU; consistency 200 BU; and setback 198 BU. Avocado seed starch dispersions (5% w/v) were characterized as viscoelastic systems, with G'>G″. Avocado seed starch has potential applications as a thickening and gelling agent in food systems, as a vehicle in pharmaceutical systems and an ingredient in biodegradable polymers for food packaging. PMID:26800900

  13. Rheological properties of polymer melts in confined shear flow from dynamic Monte Carlo simulations.

    NASA Astrophysics Data System (ADS)

    Dorgan, John

    2007-03-01

    The viscoelastic properties of dense polymer melts in shear flow are examined using dynamic Monte Carlo simulation for plate spacings less than 10 times the molecular radius of gyration. The coarse graining methodology employed consists of the cooperative motion algorithm of Pakula and a derived biasing technique based on previous studies of Binder and Baushnagel. For relatively large plate spacings and slow flows, a uniform linear velocity profile is obtainable. Use of the Kramers form for entropic springs allows the calculation of stress in the simulation providing a means for exploring rheological properties including viscosity and normal stress differences. Results are in excellent agreement with well-established experimental facts; a shear thinning viscosity is obtained, the first normal stress difference increases with shear rate, and the first normal stress coefficient decreases with shear rate. Evidence of entanglements are present for longer chain lengths. For fast flows, the linear velocity profile is lost and shear banding is observed. A non-monotonic stress with shear rate is found in conjunction with the shear banding and mechanistically this is attributable to a cohesive failure with an excess of chain ends being found at the slip plane. Results for variable plate spacings shed some insight into novel confinement effects that are being exploited in emerging areas of nanotechnology.

  14. Self-assembly of cationic multidomain peptide hydrogels: supramolecular nanostructure and rheological properties dictate antimicrobial activity†

    PubMed Central

    Jiang, Linhai; Xu, Dawei; Sellati, Timothy J.

    2016-01-01

    Hydrogels are an important class of biomaterials that have been widely utilized for a variety of biomedical/medical applications. The biological performance of hydrogels, particularly those used as wound dressing could be greatly advanced if imbued with inherent antimicrobial activity capable of staving off colonization of the wound site by opportunistic bacterial pathogens. Possessing such antimicrobial properties would also protect the hydrogel itself from being adversely affected by microbial attachment to its surface. We have previously demonstrated the broad-spectrum antimicrobial activity of supramolecular assemblies of cationic multi-domain peptides (MDPs) in solution. Here, we extend the 1-D soluble supramolecular assembly to 3-D hydrogels to investigate the effect of the supramolecular nanostructure and its rheological properties on the antimicrobial activity of self-assembled hydrogels. Among designed MDPs, the bactericidal activity of peptide hydrogels was found to follow an opposite trend to that in solution. Improved antimicrobial activity of self-assembled peptide hydrogels is dictated by the combined effect of supramolecular surface chemistry and storage modulus of the bulk materials, rather than the ability of individual peptides/peptide assemblies to penetrate bacterial cell membrane as observed in solution. The structure–property–activity relationship developed through this study will provide important guidelines for designing biocompatible peptide hydrogels with built-in antimicrobial activity for various biomedical applications. PMID:26524425

  15. Effects of intravenous furosemide on mucociliary transport and rheological properties of patients under mechanical ventilation

    PubMed Central

    Kondo, Cláudia Seiko; Macchionne, Mariângela; Nakagawa, Naomi Kondo; de Carvalho, Carlos Roberto Ribeiro; King, Malcolm; Saldiva, Paulo Hilário Nascimento; Lorenzi-Filho, Geraldo

    2002-01-01

    The use of intravenous (IV) furosemide is common practice in patients under mechanical ventilation (MV), but its effects on respiratory mucus are largely unknown. Furosemide can affect respiratory mucus either directly through inhibition of the NaK(Cl)2 co-transporter on the basolateral surface of airway epithelium or indirectly through increased diuresis and dehydration. We investigated the physical properties and transportability of respiratory mucus obtained from 26 patients under MV distributed in two groups, furosemide (n = 12) and control (n = 14). Mucus collection was done at 0, 1, 2, 3 and 4 hours. The rheological properties of mucus were studied with a microrheometer, and in vitro mucociliary transport (MCT) (frog palate), contact angle (CA) and cough clearance (CC) (simulated cough machine) were measured. After the administration of furosemide, MCT decreased by 17 ± 19%, 24 ± 11%, 18 ± 16% and 18 ± 13% at 1, 2, 3 and 4 hours respectively, P < 0.001 compared with control. In contrast, no significant changes were observed in the control group. The remaining parameters did not change significantly in either group. Our results support the hypothesis that IV furosemide might acutely impair MCT in patients under MV. PMID:11940271

  16. Rheology, structure, and properties of new phosphate glass/polymer hybrids

    NASA Astrophysics Data System (ADS)

    Urman, Kevin Leonard

    Physical modification of structure and properties via polymer blending and reinforcement is a common practice in the plastics industry and has a large economic advantage over synthesizing new polymeric materials to fulfill new material needs. Despite the large amount of interest in polymer blends and composites, the currently available commercial materials cannot satisfy the growing need for new advanced materials. This need is being addressed in part by inorganic/organic hybrid materials. By blending low-TG phosphate glasses with polymeric materials, a new class of inorganic/organic hybrids can be created. These hybrids can be processed conventionally with glass loadings of up to 60% by volume or 90% by weight, making it possible to obtain significant improvements in properties that are impossible to achieve from classical polymer blends and composites. This class of inorganic/organic hybrids containing both the inorganic low-TG phosphate glass (Pglass) and the organic polymer are very unique materials because both hybrid components are fluid during processing. Thereby, providing the ability to tailor both the hybrid morphology and properties in unprecedented ways through carefully controlled processing. This dissertation discusses the continuing research into low-Tg tin fluorophosphate glass blended with commodity resins. The specific resins of interest are low density polyethylene (LDPE), polyamide 12, and polyamide 6. The shear rheology and the extensional flow characteristics of LDPE hybrids were studied to understand hybrid behavior under flow characteristics typical of many polymer processing techniques. The elongational flow was also utilized to generate unique morphologies, enhance crystallinity, and to alter polymer chain orientation. The extension of this field into interacting commodity resins like polyamide 12 and polyamide 6 yielded new hybrids with unprecedented properties. Polyamide 12 hybrids were used to build the first processing/structure/property

  17. Rheological properties of erythrocytes in patients suffering from erysipelas. Examination with LORCA device.

    PubMed

    Biesiada, Grazyna; Krzemień, Joanna; Czepiel, Jacek; Teległów, Aneta; Dabrowski, Zbigniew; Spodaryk, Krzysztof; Mach, Tomasz

    2006-01-01

    The rheological properties of erythrocytes: elongation and the aggregation, as well as basic peripheral blood parameters: RBC number, hematocrit, MCV, MCH, MCHC reticulocytes, fibrinogen level, ESR, and glucose level were studied in a group of erysipelas patients. The concentration of malonyl dialdehyde (MDA) in erythrocytes was also measured, as an indicator of oxidative stress exerted. The study involved 18 erysipelas patients and 18 healthy subjects. The rheological properties and the aggregation of erythrocytes were studied with the use of a LORCA instrument (Laser-assisted Optical Rotational Cell Analyser). Differences were found in elongation index (EI) between the blood control (C) and patients (P), with an increase of this value only at 0.58 Pa shear stress and at 1.13 Pa shear stress. Upstroke were used as the indexes of RBC deformability, and the following aggregation parameters: intensity of light scattering in the prior disaggregation (Isc dis) - C - 43.0 au (arbitrary units), P - 44.8 au, time when cells are round and not aggregated (Isc top) - C - 51.6 au, P - 49.3 au, the amplitude of aggregation, the difference between Isc max and Isc min (AMP) - C - 39.9 au, P - 28.7 au, aggregation index (AI) - C - 64.6%, P - 70.0%, time for reach one half of the maximum aggregation (t(1/2)) - C - 2.0 s, P - 1.5 s, threshold shear stress, the lowest force that breaks the aggregation formed (Y(thr)) in P exceed 170% control group were measured. A decrease in the elasticity of erythrocytes in erysipelas patients was associated with the simultaneous increase of MDA - C - 0.08 nM/mgHb, P - 0.11 nM/mgHb content in the membranes of red blood cells. Basic peripheral blood parameters studied in patients with erysipelas did not differ significantly from the control group except for WBC, fibrinogen (C - 3.8 g/l, P - 7.8 g/l), and ESR (C - 6.1 mm/h, P - 45.4 mm/h) which were significantly higher. PMID:16614462

  18. Effect of Crumb Rubber and Warm Mix Additives on Asphalt Aging, Rheological, and Failure Properties

    NASA Astrophysics Data System (ADS)

    Agrawal, Prashant

    Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening.

  19. Modelling the rheological properties of sludge during anaerobic digestion in a batch reactor by using electrical measurements.

    PubMed

    Dieudé-Fauvel, E; Héritier, P; Chanet, M; Girault, R; Pastorelli, D; Guibelin, E; Baudez, J C

    2014-03-15

    Anaerobic digestion is a significant process leading to biogas production and waste management. Despite this double interest, professionals still face a lack of efficient tools to monitor and manage the whole procedure. This is especially true for rheological properties of the material inside the reactor, which are of major importance for anaerobic digestion management. However, rheological properties can hardly be determined in-situ and it would be very helpful to determine indicators of their evolution. To solve this problem, this paper investigates the evolution of sewage sludge rheological and electrical properties during the anaerobic digestion in a batch reactor. We especially focus on apparent viscosity and complex impedance, measured by electrical impedance spectroscopy. Both of them can be modelled by a linear combination of raw sludge and inoculum properties, weighted by time-dependent coefficients. Thus, by determining digested sludge electrical signature, it is possible to obtain those coefficients and model sludge apparent viscosity. This work offers many theoretical and practical prospects. PMID:24419207

  20. Structural Features of Alkaline Extracted Polysaccharide from the Seeds of Plantago asiatica L. and Its Rheological Properties.

    PubMed

    Yin, Jun-Yi; Chen, Hai-Hong; Lin, Hui-Xia; Xie, Ming-Yong; Nie, Shao-Ping

    2016-01-01

    Polysaccharide from the seeds of Plantago asiatica L. has many bioactivities, but few papers report on the structural and rheological characteristics of the alkaline extract. The alkaline extracted polysaccharide was prepared from seeds of P. asiatica L. and named herein as alkaline extracted polysaccharide from seeds of P. asiatica L. (PLAP). Its structural and rheological properties were characterized by monosaccharide composition, methylation, GC-MS and rheometry. PLAP, as an acidic arabinoxylan, was mainly composed of 1,2,4-linked Xylp and 1,3,4-linked Xylp residues. PLAP solution showed pseudoplastic behavior, and weak gelling properties at high concentration. Sodium and especially calcium ions played a significant role in increasing the apparent viscosity and gel strength. PMID:27608001

  1. Self-assembly of cationic multidomain peptide hydrogels: supramolecular nanostructure and rheological properties dictate antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Jiang, Linhai; Xu, Dawei; Sellati, Timothy J.; Dong, He

    2015-11-01

    Hydrogels are an important class of biomaterials that have been widely utilized for a variety of biomedical/medical applications. The biological performance of hydrogels, particularly those used as wound dressing could be greatly advanced if imbued with inherent antimicrobial activity capable of staving off colonization of the wound site by opportunistic bacterial pathogens. Possessing such antimicrobial properties would also protect the hydrogel itself from being adversely affected by microbial attachment to its surface. We have previously demonstrated the broad-spectrum antimicrobial activity of supramolecular assemblies of cationic multi-domain peptides (MDPs) in solution. Here, we extend the 1-D soluble supramolecular assembly to 3-D hydrogels to investigate the effect of the supramolecular nanostructure and its rheological properties on the antimicrobial activity of self-assembled hydrogels. Among designed MDPs, the bactericidal activity of peptide hydrogels was found to follow an opposite trend to that in solution. Improved antimicrobial activity of self-assembled peptide hydrogels is dictated by the combined effect of supramolecular surface chemistry and storage modulus of the bulk materials, rather than the ability of individual peptides/peptide assemblies to penetrate bacterial cell membrane as observed in solution. The structure-property-activity relationship developed through this study will provide important guidelines for designing biocompatible peptide hydrogels with built-in antimicrobial activity for various biomedical applications.Hydrogels are an important class of biomaterials that have been widely utilized for a variety of biomedical/medical applications. The biological performance of hydrogels, particularly those used as wound dressing could be greatly advanced if imbued with inherent antimicrobial activity capable of staving off colonization of the wound site by opportunistic bacterial pathogens. Possessing such antimicrobial properties would

  2. Effects of reducing fat content on the proteolytic and rheological properties of Cheddar-like caprine milk cheese

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High-moisture Cheddar-like cheeses made from caprine milk containing 3.6, 2.0, 1.0, and 0.1-0.5% fat were manufactured and their proteolytic and rheological properties compared after 1, 3, and 6 mo of aging at 4 deg C. The full-fat (FF), reduced fat (RF), low-fat (LF), and non-fat (NF) cheeses conta...

  3. Impact of high pressure treatment on functional, rheological, pasting, and structural properties of lentil starch dispersions.

    PubMed

    Ahmed, Jasim; Thomas, Linu; Taher, Ayoub; Joseph, Antony

    2016-11-01

    Lentil starch (LS) dispersions (flour to water 1:4w/w) were subjected to high pressure (HP) treatment at 0.1, 400, 500 and 600MPa for 10min, followed by evaluation on the functional, particle size, rheological, pasting, and structural properties of post-process samples. Water holding capacity of pressurized starch increased with the pressure intensity due to increase in damaged starch. The amount of resistant starch increased from 5 to 6.8% after pressure treatment at 600MPa. An increase in starch granule particle size (196-207μm) was obvious after HP treatment. The lentil starch was completely gelatinized after pressure treatment at 600MPa for 10min as evidenced from differential scanning calorimetry, rheometry, X-ray diffraction (XRD) and scanning electron microscopy observation. The elastic modulus, G' of lentil starch gel was less frequency dependent, and higher in magnitude at high pressure (>500MPa) than at lower pressure range (≤400MPa). XRD analysis revealed the disappearance of two diffraction peak intensities at 14.86° and 22.82° at 600MPa for 10min, which confirms the transformation of crystalline to amorphous region of lentil starch. Pasting properties were significantly influenced by the pressure treatment especially at 600MPa, resulting in a considerable decrease in peak viscosity, breakdown and final viscosity, and an increase in peak time. It can be inferred that the functional properties of pressure-treated LS are mainly based on the structural destruction of granules. PMID:27516314

  4. The Effect of Physiologically Relevant Additivies on the Rheological Properties of Concentrated Pluronic Copolymer Gels

    SciTech Connect

    Jiang,J.; Li, C.; Lombardi, J.; Colby, R.; Rigas, B.; Rafailovich, M.; Sokolov, J.

    2008-01-01

    The high concentration triblock copolymer poly(ethylene oxide)99-poly(propylene oxide)69-poly(ethylene oxide)99 (Pluronic F127) aqueous solutions with the addition of different components commonly used in physiologically relevant applications were characterized by rheological measurements, differential scanning calorimetry (DSC) and small angle X-ray/neutron scattering. The sol-gel transition temperature, as well as the storage modulus of the F127 solution depend both on the concentration of polymer and of clay. Above the gel transition, the storage modulus of the solutions increased with clay concentration. Yield strain is independent of polymer and clay concentrations. Two different kinds of inorganic salts, sodium chloride (NaCl) and calcium chloride (CaCl2) were added into the polymer and polymer-clay solutions. The sol-gel transition temperature decreased noticeably, but the storage modulus decreased only a small amount with increasing concentration of inorganic salts. Addition of salts to polymer-clay solutions resulted in precipitation of the clays which decreased the modulus. No effect on the mechanical properties was observed with the addition of common serum proteins. However, addition of 0.5-10% glucose decreased the transition temperature between 3 and 7 , without significantly affecting the modulus. The depression of the transition temperature by glucose was similar to that found with salts and indicated that the mechanism, namely competition for water, may be similar.

  5. Rheological properties and formation mechanism of DC electric fields induced konjac glucomannan-tungsten gels.

    PubMed

    Wang, Lixia; Jiang, Yaoping; Lin, Youhui; Pang, Jie; Liu, Xiang Yang

    2016-05-20

    Konjac glucomannan-tungsten (KGM-T) hydrogel of electrochemical reversibility was successfully produced under DC electric fields in the presence of sodium tungstate. The structure and the effects of sodium tungstate concentration, KGM concentration, voltage and electric processing time on the rheological properties of the gels were investigated. pH experiments showed that KGM sol containing Na2WO4·2H2O in the vicinity of the positive electrode became acidic and the negative electrode basic after the application of DC electric fields. Under acid conditions, WO4(2-) ions transformed into isopoly-tungstic acid ions. FTIR and Raman studies indicated that isopoly-tungstic acid ions absorbed on KGM molecular chain and cross-linked with -OH groups at C-6 position on sugar units of KGM. Frequency sweep data showed with increasing sodium tungstate concentration, voltage, and electric processing time, the viscoelastic moduli, i.e., the storage and the loss moduli of the gel increased, whereas an increase in KGM concentration led to a decrease in gel viscoelastic moduli. The temperature sweep measurements indicated the obtained gel exhibited high thermal stability. Finally, the mechanism of gel formation was proposed. Our work may pave the way to use DC electric fields for the design and development of KGM gels as well as polysaccharide gels. PMID:26917402

  6. The effect of spherical nanoparticles on rheological properties of bi-dispersed magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Kannappan, K. Thiruppathi; Laherisheth, Zarana; Parekh, Kinnari; Upadhyay, R. V.

    2015-06-01

    In the present investigation, the rheological properties of bi-dispersed magnetorheological (MR) fluid based on Fe3O4 nanosphere and microsphere of iron particles are experimentally investigated. The MR fluid is prepared by substituting nanosphere of 40nm Fe3O4 particles in MR fluids having microsphere iron particles (7-8 μm). Three different weight fractions (0%, 1% and 3%) of nanosphere-microsphere MR fluids are synthesized. In the absence of the magnetic field, substitution of magnetic nanosphere decreases the viscosity lower than without substituted sample at high as well as low shear rate. Upon the application of the magnetic field, the particles align along the direction of the field, which promotes the yield stress. Here too the yield stress value decreases with magnetic nanosphere substitution. This behaviour is explain based on the inter-particle interaction as well as formation of nanosphere cloud around the magnetic microsphere, which effectively reduces the viscosity and works as weak point when chains are formed. Variation of dynamic yield stress with magnetic field is explained using microscopic model. In any event such fluid does not sediment and is not abrasive so it could be useful if not too high yield stress is needed.

  7. Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets.

    PubMed

    Mehrali, Mohammad; Sadeghinezhad, Emad; Latibari, Sara Tahan; Kazi, Salim Newaz; Mehrali, Mehdi; Zubir, Mohd Nashrul Bin Mohd; Metselaar, Hendrik Simon Cornelis

    2014-01-01

    In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems. PMID:24410867

  8. Effect of colloidal aggregation on the sedimentation and rheological properties of tank waste

    SciTech Connect

    Rector, D.R.; Bunker, B.C.

    1995-09-01

    Tank farm experience and work performed under the Tank Waste Treatment Science task of the Tank Waste Remediation System (TWRS) Pretreatment Technology Development Project indicate that colloidal interactions can have an enormous impact on tank waste processing. This report provides the theoretical and experimental background required to understand how such agglomeration phenomena control the sedimentation and theological behavior of colloidal tank wastes. First, the report describes the conditions under which the colloidal particles present in tank sludge are expected to aggregate. Computational models have been developed to predict solution conditions leading to agglomeration, and to predict the rate and size of aggregate growth. The models show that tank sludge should be heavily agglomerated under most baseline processing conditions. Second, the report describes models used to predict sedimentation rates and equilibrium sediment density profiles based on knowledge of agglomerate structures. The sedimentation models provide a self-consistent picture that explains the apparent discrepancies between bench-top experiments and tank-farm experience. Finally, both discrete and empirical models are presented that can be used to rationalize and predict the rheological properties of colloidal sludge suspensions. In all cases, model predictions are compared and contrasted with experimental results. The net results indicate that most of the observed behaviors of real sludges can be predicted, understood, and perhaps ultimately controlled by understanding a few key central concepts regarding agglomeration phenomena.

  9. Textural, Rheological and Sensory Properties and Oxidative Stability of Nut Spreads—A Review

    PubMed Central

    Shakerardekani, Ahmad; Karim, Roselina; Ghazali, Hasanah Mohd; Chin, Nyuk Ling

    2013-01-01

    Tree nuts are rich in macro and micronutrients, phytochemicals, tocopherols and phenolic compounds. The development of nut spreads would potentially increase the food uses of nuts and introduce consumers with a healthier, non-animal breakfast snack food. Nut spreads are spreadable products made from nuts that are ground into paste. Roasting and milling (particle size reduction) are two important stages for the production of nut spreads that affected the textural, rheological characteristic and overall quality of the nut spread. Textural, color, and flavor properties of nut spreads play a major role in consumer appeal, buying decisions and eventual consumption. Stability of nut spreads is influenced by its particle size. Proper combination of ingredients (nut paste, sweetener, vegetable oil and protein sources) is also required to ensure a stable nut spread product is produced. Most of the nut spreads behaved like a non-Newtonian pseudo-plastic fluid under yield stress which help the producers how to start pumping and stirring of the nut spreads. Similar to other high oil content products, nut spreads are susceptible to autoxidation. Their oxidation can be controlled by application of antioxidants, using processing techniques that minimize tocopherol and other natural antioxidant losses. PMID:23429239

  10. Protein-free cress seed (Lepidium sativum) gum: Physicochemical characterization and rheological properties.

    PubMed

    Razmkhah, Somayeh; Razavi, Seyed Mohammad Ali; Mohammadifar, Mohammad Amin; Ale, Marcel Tutor; Gavlighi, Hassan Ahmadi

    2016-11-20

    Protein-free cress seed gum (PFCSG) was obtained by precipitation of crude cress seed gum (CSG) with ethanol followed by treatment with protease. Molecular weight, moisture, ash and uronic acids content decreased after elimination of protein. Elimination of protein improved significantly rheological properties and thermal stability of cress seed gum. Mechanical spectra of the CSG and PFCSG were classified as weak gels and PFCSG showed stronger and more elastic network structure. The gum dispersions exhibited strong shear-thinning behavior which was described satisfactory by the Herschel-Bulkley and Moore models. Protein-free cress seed gum had higher apparent and intrinsic viscosities than the crude gum. CSG indicated lower hysteresis loop area, but degree of structural recovery of the samples showed no significant difference. The main decomposition of PFCSG started above 213°C with two peaks (at 261.72°C and 306.58°C) and initial decomposition temperature of CSG was 190.21°C with one peak at 258.28°C. DSC results coincided with those observed by thermogravimetric analysis. Enzyme treatment lowered the surface activity of CSG. PMID:27561467

  11. Rheological property and stress development during drying of tape-cast ceramic layers

    SciTech Connect

    Lewis, J.A.; Blackman, K.A.; Ogden, A.L.; Payne, J.A.; Francis, L.F.

    1996-12-01

    Rheological property and stress development of tape-cast ceramic layers derived from nonaqueous alumina (Al{sub 2}O{sub 3})-poly(vinyl butyral) (PVB) suspensions were observed during drying. Casting suspensions exhibited strong shear-thinning behavior, with a low shear Newtonian plateau apparent viscosity >10{sup 2}Pa{center_dot}s. The apparent suspension viscosity displayed a power-law dependence on the Al{sub 2}O{sub 3} volume fraction during the initial stage of drying ({le}30% solvent loss). Stress development, measured by a cantilever deflection method, and parallel weight loss measurements were performed during the drying of tape-cast layers and pure binder coatings. Maximum drying stresses ({sigma}{sub max}) of 1.37--0.77 MPa were observed for plasticized tapes cast at gap heights of 150--400 {micro}m. In contrast, nonplasticized tapes of similar thickness displayed a more gradual stress increase, with {sigma}{sub max} values approximately an order of magnitude higher than their plasticized counterparts. The stress histories of the corresponding binder coatings were quite similar to the tape-cast layers, albeit slightly lower {sigma}{sub max} values were observed. Stresses decayed beyond {sigma}{sub max} with a logarithmic time dependence to an almost constant value of 0.2--0.4 MPa for the plasticized tapes. Based on these observations, process methodologies have been offered to minimize stress development and retention in tape-cast ceramic layers.

  12. Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

    PubMed Central

    2014-01-01

    In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems. PMID:24410867

  13. Rheological properties of ultrasound treated apple, cranberry and blueberry juice and nectar.

    PubMed

    Simunek, Marina; Jambrak, Anet Režek; Dobrović, Slaven; Herceg, Zoran; Vukušić, Tomislava

    2014-12-01

    Ultrasound is non-thermal food processing technique that has been used in food processing very extensively for the last 10 years. The objective of this study was to investigate the effect of high power ultrasound and pasteurization on rheological properties (n and k) of apple, cranberry and blueberry juice and nectar. Samples were treated according the experimental design, with high power sonicator at ultrasound frequency of 20 kHz under various conditions (treatment time, temperature of sample and amplitude). Thermosonication and sonicaton of juice and nectar samples have been performed. It was found that all samples of untreated, pasteurized and ultrasonically treated apple, cranberry and blueberry juices and nectars shows non-Newtonian dilatant fluid characteristics (n > 1). The interaction of treatment time and temperature of sample (BC) and temperature (C) of sample of apple juice had statistically significant effect on flow behavior index (n) for ultrasound treated apple juice. Interaction of treatment time and temperature of sample (BC) has statistically significant effect on the flow behavior index (n) for blueberry nectar. Also, there is statistically significant effect of temperature (C) of sample on consistency coefficient (k) for ultrasound treated apple juice. PMID:25477626

  14. The effect of spherical nanoparticles on rheological properties of bi-dispersed magnetorheological fluids

    SciTech Connect

    Kannappan, K. Thiruppathi; Laherisheth, Zarana; Parekh, Kinnari; Upadhyay, R. V.

    2015-06-24

    In the present investigation, the rheological properties of bi-dispersed magnetorheological (MR) fluid based on Fe{sub 3}O{sub 4} nanosphere and microsphere of iron particles are experimentally investigated. The MR fluid is prepared by substituting nanosphere of 40nm Fe{sub 3}O{sub 4} particles in MR fluids having microsphere iron particles (7-8 μm). Three different weight fractions (0%, 1% and 3%) of nanosphere-microsphere MR fluids are synthesized. In the absence of the magnetic field, substitution of magnetic nanosphere decreases the viscosity lower than without substituted sample at high as well as low shear rate. Upon the application of the magnetic field, the particles align along the direction of the field, which promotes the yield stress. Here too the yield stress value decreases with magnetic nanosphere substitution. This behaviour is explain based on the inter-particle interaction as well as formation of nanosphere cloud around the magnetic microsphere, which effectively reduces the viscosity and works as weak point when chains are formed. Variation of dynamic yield stress with magnetic field is explained using microscopic model. In any event such fluid does not sediment and is not abrasive so it could be useful if not too high yield stress is needed.

  15. Rheological Properties and Electrospinnability of High-Amylose Starch in Formic Acid.

    PubMed

    Lancuški, Anica; Vasilyev, Gleb; Putaux, Jean-Luc; Zussman, Eyal

    2015-08-10

    Starch derivatives, such as starch-esters, are commonly used as alternatives to pure starch due to their enhanced mechanical properties. However, simple and efficient processing routes are still being sought out. In the present article, we report on a straightforward method for electrospinning high-amylose starch-formate nanofibers from 17 wt % aqueous formic acid (FA) dispersions. The diameter of the electrospun starch-formate fibers ranged from 80 to 300 nm. The electrospinnability window between starch gelatinization and phase separation was determined using optical microscopy and rheological studies. This window was shown to strongly depend on the water content in the FA dispersions. While pure FA rapidly gelatinized starch, yielding solutions suitable for electrospinning within a few hours at room temperature, the presence of water (80 and 90 vol % FA) significantly delayed gelatinization and dissolution, which deteriorated fiber quality. A complete destabilization of the electrospinning process was observed in 70 vol % FA dispersions. Optical micrographs showed that FA induced a disruption of starch granule with a loss of crystallinity confirmed by X-ray diffraction. As a result, starch fiber mats exhibited a higher elongation at break when compared to brittle starch films. PMID:26192477

  16. The rheological properties of bamboo cellulose pulp/ionic liquid system

    NASA Astrophysics Data System (ADS)

    Zhang, Y. F.; Zhang, P. R.; Wu, J.; Jia, Q. X.; Liu, X. Y.

    2016-07-01

    In this study, two kinds of spinning solutions were prepared by dissolving bamboo cellulose pulp into 1-ethyl-3-methyl imidazole chloride salt ([EMIM] Cl) and 1-butyl-3-methyl imidazole diethyl phosphate salt ([BMIM]DEP) ionic liquids, respectively. Furthermore, the rotational rheometer was used to test the steady-state rheological properties of above as-prepared spinning solutions. The research results show that both of these two ionic liquids exhibit better solubility to the bamboo cellulose pulp. The apparent viscosities(ηa) decrease with the increased temperature(T) and shear rate(γ) and increase with the increased concentration. The non-Newtonian index(n) declined with the increase of both shear rate and concentration, as well as increased with the build-up temperature. The structural viscosity index(Δη) increased with the increased concentration and tended to decrease with temperature rise. Meanwhile, viscous flow activation energy(Eη) decreases with the increased share rate as well as the concentration. According to the results, it can be seen that the bamboo cellulose pulp/[EMIM]Cl with the concentration of 6% at 70°C exhibits better spinnability.

  17. The effect of particle size on hydrolysis reaction rates and rheological properties in cellulosic slurries.

    PubMed

    Dasari, Rajesh K; Eric Berson, R

    2007-04-01

    The effect of varying initial particle sizes on enzymatic hydrolysis rates and rheological properties of sawdust slurries is investigated. Slurries with four particle size ranges (33 microm < x < or = 75 microm, 150 microm < x < or = 180 microm, 295 microm < x < or = 425 microm, and 590 microm < x < or = 850 microm) were subjected to enzymatic hydrolysis using an enzyme dosage of 15 filter paper units per gram of cellulose at 50 degrees C and 250 rpm in shaker flasks. At lower initial particle sizes, higher enzymatic reaction rates and conversions of cellulose to glucose were observed. After 72 h 50 and 55% more glucose was produced from the smallest size particles than the largest size ones, for initial solids concentration of 10 and 13% (w/w), respectively. The effect of initial particle size on viscosity over a range of shear was also investigated. For equivalent initial solids concentration, smaller particle sizes result in lower viscosities such that at a concentration of 10% (w/w), the viscosity decreased from 3000 cP for 150 microm < x < or = 180 microm particle size slurries to 61.4 cP for 33 microm < x < or = 75 microm particle size slurries. Results indicate particle size reduction may provide a means for reducing the long residence time required for the enzymatic hydrolysis step in the conversion of biomass to ethanol. Furthermore, the corresponding reduction in viscosity may allow for higher solids loading and reduced reactor sizes during large-scale processing. PMID:18478396

  18. Effect of d-allulose on rheological properties of chicken breast sausage.

    PubMed

    Hadipernata, M; Ogawa, M; Hayakawa, S

    2016-09-01

    d-Allulose (Alu), a rare sugar, was applied to chicken breast sausage as a sucrose (Suc) substitute. The ratio (w/w) of Alu to Suc in sugar that was added to the sausage batter was 0/1 (A0S1), 3/7 (A3S7), 7/3 (A7S3), and 1/0 (A1S0). The total amount of Suc used was 2.5% of the weight of minced chicken breast meat. Substituting Suc with Alu did not affect water content, cooking loss, breaking stress, breaking strain, and modulus of elasticity of chicken breast sausage, but a 100% substitution with Alu caused a 10% decrease in viscosity and a 31% decrease in expressible water. A significant difference appeared in the rheological properties of elasticity, viscosity, and water-holding capacity of chicken breast sausage frozen-stored (-20°C) for 90 d. Particularly, the modulus of elasticity for A1S0 chicken breast sausage was 19% higher than that of the control A0S1 chicken breast sausage, suggesting that Alu appreciably reduced the deterioration in elasticity that is caused by long-term frozen storage of sausage. The quality improvement of frozen-stored chicken breast sausage demonstrates the feasibility and benefits of the application of Alu to frozen foods. PMID:27118866

  19. Evolution of the rheological and microstructural properties of olivine aggregates during dislocation creep under hydrous conditions

    NASA Astrophysics Data System (ADS)

    Tasaka, Miki; Zimmerman, Mark E.; Kohlstedt, David L.

    2016-01-01

    Since hydrogen plays an important role in dynamic processes in Earth's mantle, we conducted torsion experiments to shear strains of 0.6 to 5.0 on Fe-bearing olivine aggregates [(Mg0.5Fe0.5)2SiO4: Fo50] under hydrous conditions at T = 1200°C and P = 300 MPa. We deformed samples to high enough strains that a steady state microstructures were achieved, which allowed us to investigate the evolution of both the rheological and microstructural properties. The stress exponent of n ≈ 5.0 and the grain size exponent of p ≈ 0 determined by fitting the strain rate, stress, and grain size data indicate that our samples deformed by dislocation creep. Fourier transform infrared spectroscopy measurements on embedded olivine single crystals demonstrated that our samples were saturated with hydrogen during the deformation experiments. The lattice preferred orientation (LPO) of olivine changes as a function of strain due to competition among three slip systems: (010)[100], (100)[001], and (001)[100]. Observed strain weakening can be attributed to geometrical softening associated with development of LPO, which reduces the stress by ~1/3 from its peak value in constant strain rate experiments. The geometrical softening coefficient determined in this study is an important constraint for modeling and understanding dynamical processes in the upper mantle under hydrous conditions.

  20. Rheological and functional properties of heat moisture treated pearl millet starch.

    PubMed

    Sharma, Monika; Yadav, Deep N; Singh, Ashish K; Tomar, Sudhir K

    2015-10-01

    Pearl millet (Pennisetum typhoides) starch was subjected to heat moisture treatment (HMT) at different moisture levels i.e., 20 % (HMT-20), 25 % (HMT-25) & 30 % (HMT-30) for 8 h at 110 °C and evaluated for changes in rheological, thermal, functional and morphological properties. Peak, breakdown, cool paste and setback viscosity decreased, while pasting temperature increased after HMT. Shear stability of HMT-30 sample was maximum (stability ratio 0.54). Highest (33.5 Pa) G' value was observed for native and lowest (14.8 Pa) for HMT-25 sample. Yield and flow point of starch gels also decreased after HMT, indicating softer gels and higher spreadability. HMT increased gelatinization temperature from 62.59 °C for native to 84.05 °C for HMT-30. Resistant starch content increased about three times in HMT-30 sample (7.07 %) as compared to native. Swelling power and solubility decreased after HMT. HMT also induced cavity and some dents on starch granules surface. PMID:26396395

  1. Rheological properties of a polysaccharide from floral mushrooms cultivated in Huangshan Mountain.

    PubMed

    Xu, Jin-Long; Zhang, Jing-Cheng; Liu, Yong; Sun, Han-Ju; Wang, Jun-Hui

    2016-03-30

    A polysaccharide fraction (FMPS) was isolated from floral mushrooms cultivated in Huangshan Mountain, and the rheological properties of FMPS in aqueous solutions were investigated. The FMPS solution showed shear-thinning behavior at 25°C. Dynamic viscoelastic tests revealed that G' and G″ exhibited strong dependences on the concentration and temperature. The FMPS/water system exhibited sol and weak gel behavior with the change of concentration and temperature. The exponent n of G'∼ω(n) and tan δ also exhibited strong dependences on the concentration and temperature. The gel point (cgel) of FMPS solution was 1.16×10(-2)g/mL at 15°C, and the Tgel of 1.4×10(-2)g/mL FMPS solution was 20.6°C. Dynamic frequency sweep measurements indicated that the FMPS gel system was stable in the selected range of frequency. The heating-cooling process proved that the sol-gel transition of FMPS in aqueous solutions was thermally reversible. PMID:26794945

  2. Injectable gels of anionic collagen:rhamsan composites for plastic correction: preparation, characterization, and rheological properties.

    PubMed

    de Paula, Márcio; Goissis, Gilberto; Martins, Virgínia C A; da Silva Trindade, José Carlos

    2005-11-01

    The present article describes the preparation and characterization of anionic collagen gels obtained from porcine intestinal submucosa after 72 h of alkaline treatment and in the form of rhamsan composites to develop injectable biomaterials for plastic reconstruction. All materials were characterized by SDS/polyacrylamide gel electrophoresis, infrared spectroscopy, thermal stability, potentiometric titration, rheological properties, and fluidity tests. Biocompatibility was appraised after the injection of anionic collagen: rhamsan composites at 2.5% in 60 North Folk rabbits. Independently of processing, the collagen's secondary structure was preserved in all cases, and after 72 h of hydrolysis the collagen was characterized by a carboxyl group content of 346+/-9, which, at physiological pH, corresponds to an increase of 106+/-17 negative charges, in comparison to native collagen, due to the selective hydrolysis of asparagine and glutamine carboxyamide side chain. Rheological studies of composites at pH 7.4 in concentrations of 2, 4, and 6% (in proportions of 75:1 and 50:1) showed a viscoelastic behavior dependent on the frequency, which is independent of concentration and proportion. In both, the concentration of the storage modulus always predominated over the loss modulus (G'>G'' and delta<45 degrees ). The results from creep experiments confirmed this behavior and showed that anionic collagen:rhamsan composites at pH 7.4 in the proportion of 50:1 are less elastic and more susceptible to deformation in comparison to gels in the proportion of 75:1, independent of concentration. This was further confirmed by flow experiments, indicating that the necessary force for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic collagen, was significantly smaller and with a smooth flow. Biocompatibility studies showed that the tissue reaction of anionic collagen:rhamsan composites at 2.5% in the proportion of 75:1 was compatible with the application

  3. Rheological properties of milk gels formed by a combination of rennet and glucono-delta-lactone.

    PubMed

    Lucey, J A; Tamehana, M; Singh, H; Munro, P A

    2000-08-01

    The effects of heat treatment of milk, and a range of rennet and glucono-delta-lactone (GDL) concentrations on the rheological properties, at small and large deformation, of milk gels were investigated. Gels were made from reconstituted skim milk at 30 degrees C, with two levels each of rennet and GDL. Together with controls this gave a total of sixteen gelation conditions, eight for unheated and eight for heated milk. Acid gels made from unheated milks had low storage moduli (G') of < 20 Pa. Heating milks at 80 degrees C for 30 min resulted in a large increase in the G' value of acid gels. Rennet-induced gels made from unheated milk had G' values in the range approximately 80-190 Pa. However, heat treatment severely impaired rennet coagulation: no gel was formed at low rennet levels and only a very weak gel was formed at high levels. In gels made with a combination of rennet and GDL unusual rheological behaviour was observed. After gelation, G' initially increased rapidly but then remained steady or even decreased, and at long ageing times G' values increased moderately or remained low. The loss tangent (tan delta) of acid gels made from heated milk increased after gelation to attain a maximum at pH approximately 5.1 but no maximum was observed in gels made from unheated milk. Gels made by a combination of rennet and GDL also exhibited a maximum in tan delta, indicating increased relaxation behaviour of the protein-protein bonds. We suggest that this maximum in tan delta was caused by a loosening of the intermolecular forces in casein particles caused by solubilization of colloidal calcium phosphate. We also suggest that in combination gels made from unheated milk a low value for the fracture stress and a high tan delta during gelation indicated an increased susceptibility of the network to excessive large scale rearrangements. In contrast. combination gels made from heated milk formed firmer gels crosslinked by denatured whey proteins and underwent fewer large

  4. Antimicrobial, Rheological, and Thermal Properties of Plasticized Polylactide Films Incorporated with Essential Oils to Inhibit Staphylococcus aureus and Campylobacter jejuni.

    PubMed

    Ahmed, Jasim; Hiremath, Nikhil; Jacob, Harsha

    2016-02-01

    Polylactide (PLA) is the most mature biobased and biodegradable polymer. Due to its inherent brittleness, the polymer cannot be used as a packaging material without plasticizer. An attempt was made to develop antimicrobial plasticized PLA film by incorporating polyethylene glycol (PEG) and 3 essential oils (EO), namely cinnamon, garlic, and clove by solvent casting method. Physical, thermal, and rheological properties of those films were evaluated for practical applications whereas the antimicrobial properties were tested against Staphylococcus aureus and Campylobacter jejuni-pathogens related to poultry industry. Both PEG and EOs led to the formation of flexible PLA/PEG/EO films with significant drop in the glass transition temperature (Tg ), and mechanical property. Time-temperature superposition (TTS) principle was employed to melt rheology of EO-based films at selected temperature, and rheological moduli superimposed well in an extended frequency range. Among EOs, cinnamon and clove oil-based films (PLA/PEG/CIN and PLA/PEG/CLO) exhibited a complete zone of inhibition against C. jejuni at the maximum concentration (1.6 mL per 2 g PLA/PEG blend) whereas the garlic oil-based film (PLA/PEG/GAR) had the lowest activity. PMID:26749466

  5. Determination of linear viscoelastic properties of an entangled polymer melt by probe rheology simulations

    NASA Astrophysics Data System (ADS)

    Karim, Mir; Indei, Tsutomu; Schieber, Jay D.; Khare, Rajesh

    2016-01-01

    Particle rheology is used to extract the linear viscoelastic properties of an entangled polymer melt from molecular dynamics simulations. The motion of a stiff, approximately spherical particle is tracked in both passive and active modes. We demonstrate that the dynamic modulus of the melt can be extracted under certain limitations using this technique. As shown before for unentangled chains [Karim et al., Phys. Rev. E 86, 051501 (2012), 10.1103/PhysRevE.86.051501], the frequency range of applicability is substantially expanded when both particle and medium inertia are properly accounted for by using our inertial version of the generalized Stokes-Einstein relation (IGSER). The system used here introduces an entanglement length dT, in addition to those length scales already relevant: monomer bead size d , probe size R , polymer radius of gyration Rg, simulation box size L , shear wave penetration length Δ , and wave period Λ . Previously, we demonstrated a number of restrictions necessary to obtain the relevant fluid properties: continuum approximation breaks down when d ≳Λ ; medium inertia is important and IGSER is required when R ≳Λ ; and the probe should not experience hydrodynamic interaction with its periodic images, L ≳Δ . These restrictions are also observed here. A simple scaling argument for entangled polymers shows that the simulation box size must scale with polymer molecular weight as Mw3. Continuum analysis requires the existence of an added mass to the probe particle from the entrained medium but was not observed in the earlier work for unentangled chains. We confirm here that this added mass is necessary only when the thickness LS of the shell around the particle that contains the added mass, LS>d . We also demonstrate that the IGSER can be used to predict particle displacement over a given timescale from knowledge of medium viscoelasticity; such ability will be of interest for designing nanoparticle-based drug delivery.

  6. Rheological properties of glutaraldehyde-crosslinked collagen solutions analyzed quantitatively using mechanical models.

    PubMed

    Tian, Zhenhua; Duan, Lian; Wu, Lei; Shen, Lirui; Li, Guoying

    2016-06-01

    Understanding the rheological behavior of collagen solutions crosslinked by various amounts of glutaraldehyde (GTA) [GTA/collagen (w/w)=0-0.1] is fundamental either to design optimized products or to ensure stable flow. Under steady shear, all the samples exhibited pseudoplasticity with shear-thinning behavior, and the flow curves were well described by Ostwald-de Waele model and Carreau model. With increased amounts of GTA, the viscosity increased from 6.15 to 168.54 Pa·s at 0.1s(-1), and the pseudoplasticity strengthened (the flow index decreased from 0.549 to 0.117). Additionally, hysteresis loops were evaluated to analyze the thixotropy of the native and crosslinked collagen solutions, and indicated that stronger thixotropic behavior was associated with higher amount of GTA. Furthermore, the values of apparent yield stress were negative, and a flow index <1 for all the systems obtained via Herschel-Bulkley model confirmed that the native and crosslinked collagen solutions belonged to pseudoplastic fluid without apparent yield stress. However, the increment of dynamic denaturation temperature determined by dynamic temperature sweep was not obvious. The viscoelastic properties were examined based on creep-recovery measurements and then simulated using Burger model and a semi-empirical model. The increase in the proportion of recoverable compliance (instantaneous and retardant compliance) reflected that the crosslinked collagen solutions were more resistant to the deformation and exhibited more elastic behavior than the native collagen solution, accompanied by the fact that the compliance value decreased from 39.317 to 0.152 Pa(-1) and the recovery percentage increased from 1.128% to 87.604%. These data indicated that adjusting the amount of GTA could be a suitable mean for manipulating mechanical properties of collagen-based biomaterials. PMID:27040190

  7. Modeling and experimental investigation of rheological properties of injectable poly(lactide ethylene oxide fumarate)/hydroxyapatite nanocomposites.

    PubMed

    Sarvestani, Alireza S; Jabbari, Esmaiel

    2006-05-01

    Injectable multiphasic polymer/ceramic composites are attractive as bioresorbable scaffolds for bone regeneration because they can be cross-linked in situ and are osteoconductive. The injectability of the composite depends on the nanoparticle content and the energetic interactions at the polymer/particle interface. The objective of this research was to determine experimentally the rheological properties of the PLEOF/apatite composite as an injectable biomaterial and to compare the viscoelastic response with the predictions of a linear elastic dumbbell model. A degradable in situ cross-linkable terpolymer based on low molecular weight poly(L-lactide) and poly(ethylene oxide) linked by unsaturated fumarate groups is synthesized. The poly(L-lactide-co-ethylene oxide-co-fumarate) (PLEOF) terpolymer interacts with the surface of the apatite nanoparticles by polar interactions and hydrogen bonding. A kinetic model is developed that takes into account the adsorption/desorption of polymer chains to/from the nanoparticle surface. Rheological properties of the aqueous dispersion of PLEOF terpolymer reinforced with nanosized hydroxyapatite (HA) particles are investigated using mechanical rheometry. To this end, we performed a series of rheological experiments on un-cross-linked PLEOF reinforced with different volume fractions of HA nanoparticles. The results demonstrate that the observed nonlinear viscoelasticity at higher shear rates is controlled by the energetic interactions between the polymer chains and dispersed particle aggregates and by the rate of the adsorption/desorption of the chains to/from the surface of the nanoparticles. PMID:16677041

  8. The influence of zinc on the blood serum of cadmium-treated rats through the rheological properties.

    PubMed

    Moussa, Sherif Aa; Alaamer, Abdulaziz; Abdelhalim, Mohamed A K

    2016-01-01

    The blood rheological properties serve as an important indicator for the early detection of many diseases. This study aimed to investigate the influence of zinc (Zn) on blood serum of cadmium (Cd) intoxication-treated male rats through the rheological properties. The rheological parameters were measured in serum of control, Cd, and Cd+Zn groups at wide range of shear rates (225-1875 s(-1)). The rat blood serum showed a non-significant change in cadmium-treated rats' %torque and shear stress at the lower shear rates (200-600 s(-1)) while a significant increase was observed at the higher shear rates (650-1875 s(-1)) compared with the control. The rat blood serum viscosity increased significantly in the Cd-treated group at each shear rate compared with the control. The viscosity and shear rate exhibited a non-Newtonian behavior for all groups. The increase in blood serum viscosity in Cd-treated male rats might be attributed to destruction or changes in the non-clotting proteins, and other blood serum components. In Cd+Zn-treated rats, the rat blood serum viscosity values returned nearer to the control values at each shear rate. Our results confirmed that Zn displaced Cd or compete with the binding sites for Cd uptake. PMID:26492072

  9. Rheological and functional properties of composite sweet potato - wheat dough as affected by transglutaminase and ascorbic acid.

    PubMed

    Ndayishimiye, Jean Bernard; Huang, Wei-Ning; Wang, Feng; Chen, Yong-Zheng; Letsididi, Rebaone; Rayas-Duarte, Patricia; Ndahetuye, Jean Baptiste; Tang, Xiao-Juan

    2016-02-01

    Effect of transglutaminase (TGM) and ascorbic acid (AA) on composite sweet potato - wheat dough functional and rheological properties was studied. Partial substitution of wheat flour with sweet potato flour at the level of 20 % significantly (P ≤ 0.05) reduced glutenin, gliadin, dough stability, protein weakening, storage modulus (G') and viscous modulus (G″). Mixolab revealed that both TGM and AA treated dough had stability and protein weakening closed to wheat dough (control), with TGM treated dough having the highest values. TGM Introduced new cross-link bonds as shown by the change of amino acid concentration, leading to an increase in storage modulus (G') and viscous modulus (G″), with G' being higher at all levels of TGM concentration. The opposite was observed for composite dough treated with AA as measured by controlled - stress rheometer. TGM treatment increased glutenin and gliadin content. Compared with the control, dough treated with AA exhibited high molecular weight of polymers than TGM treated dough. The results indicate that the TGM and AA modification of the mixolab and dynamic rheological characteristics (G' and G″) dependent on the changes of GMP, glutenin, gliadin and protein weakening in the composite dough. TGM and AA treatment could improve functional and rheological properties of sweet potato - wheat dough to levels that might be achieved with normal wheat bread. However, it's extremely important to optimize the concentrations of both additives to obtain the optimum response. PMID:27162397

  10. Rheological properties essential for the atomization of Coal Water Slurries (CWS). Final report, September 1, 1991--July 31, 1995

    SciTech Connect

    Ohene, F.

    1995-12-31

    The objective of this study was to understand the effect of low shear, high shear rheology, viscoelastic, and extensional properties on the atomization of CWS. In the atomization studies, the mean drop size of the CWS sprays were determined at various air-to-CWS ratios using a Malvern 2600 particle size analyzer and a Delavan Solid Cone Atomizing Nozzle. Solids-loading, coal particle size distributions, and chemical additives were varied in order to determine the significant properties that influence CWS atomization. A correlation of the mass mean droplet size with high shear, viscoelastic and extensional behaviors were made in order to determine the influence of these parameters on CWS atomization.

  11. Rheology of hyaluronate.

    PubMed

    Bothner, H; Wik, O

    1987-01-01

    Solutions containing high molecular weight hyaluronate at concentrations around 10 mg/ml exhibit interesting rheological properties due to formation of a highly entangled network of flexible polysaccharide molecules. We have performed an extensive study of the rheological properties of hyaluronate solutions as a function of concentration and molecular weight. In this paper we review some basic rheological concepts, and discuss the rheological properties of hyaluronate solutions at high concentrations and medium to high molecular weights (1-5 million). The bulk viscosity (zero shear viscosity) of hyaluronate solutions is strongly dependent both on concentration and molecular weight. A 2-fold increase in concentration or molecular weight results in a 10-fold increase in bulk viscosity. For application in body compartments, the concentration of hyaluronate cannot be increased much above 10 mg/ml due to the highly non-ideal colloid osmotic behaviour of hyaluronate. High viscosity hyaluronate solutions must therefore be based on high molecular weight material. PMID:3481162

  12. Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum.

    PubMed

    Wang, Shibin; Tang, Hongbiao; Guo, Jianchun; Wang, Kunjie

    2016-08-20

    pH is an important factor affecting the performance of polymer fluid. The rheological properties of hydroxypropyl guar gum (HPG) base fluid and the structural strength, rheological properties, viscoelastic properties and thixotropy properties of HPG gel depend largely on the pH values. For the base fluid, an apparent viscosity-increasing effect was observed over the pH range from 7 to 11, and the apparent viscosity gradually decreased at pH 11.5-14, exhibiting electrostatic repulsion behavior and steric effects. For the HPG gel, at pH 7-12.5, the gel possessed higher apparent viscosity, higher elastic modulus (G'), lower tanδ (the ratio of the viscous modulus to the elastic modulus) and an "8"-shaped hysteresis loop, indicating stronger gel structure strength and the elastic dominant property. At pH 13-13.5, the gel samples exhibited the transition from a pseudoplastic fluid to a Newtonian fluid, and their viscosity, elastic modulus decreased but tanδ increased with the increase in pH values, exhibiting gradually weakened elastic properties. When the pH was 14, the gel mainly exhibited viscous characteristics. PMID:27178952

  13. [In vivo effects of plasma substitutes on the rheologic properties of blood].

    PubMed

    Donner, M; De Wachter, P; Cauchois, G; Gentils, M; Kurtz, M; Laxenaire, M C; Stoltz, J F

    1993-01-01

    The objective was to investigate in vivo the rheological effects of plasma substitutes (fluid gelatin, dextran 40, dextran 60, hydroxyethylstarch). The study was performed during a hypervolemic hemodilution in 60 adult volunteers who underwent an odontological surgery. Two control groups were infused with Ringer-Lactate or 4% human albumin. Each patient was infused with 500 ml of plasma substitute or control fluid. Blood samples were obtained at four different times: prior to (t0) and immediately after (t1) the infusion, then 3 hours (t2) and 24 hours (t3) after the hemodilution. At t1 and t2, plasma viscosity did not present important variations, except for the group infused with dextran 60 where a significant increase in plasma viscosity was observed. Blood viscosity and erythrocyte aggregation measurements were performed at hematocrit 40% to determine the intrinsic properties of substitute and eliminate the effects of hemodilution. Blood viscosity at high shear rates underwent minor variations in all groups. In contrast, blood viscosity at low shear rate and aggregation parameters exhibited important variations which markedly depended on the used substitute. The infusion of Ringer-Lactate, albumin and dextran 40 induced a significant decrease in blood viscosity and in erythrocyte aggregation. With dextran 60 and gelatin, blood viscosity and erythrocyte aggregation increased. Finally, the infusion with hydroxyethylstarch did not present important differences as compared to the results recorded at t0. Twenty for hours after the infusion, it should be noted an increase in plasma fibrinogen, probably due to surgery, which caused an increase in erythrocyte aggregation in all groups.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7688783

  14. Evaluation of mechanical and rheological properties of metronidazole gel as local delivery system.

    PubMed

    Jelvehgari, Mitra; Montazam, Hassan

    2011-06-01

    Rosacea is a chronic multifactorial vascular skin disorder that affects about 10 percent of the general population. Metronidazole is an effective antibiotic in the treatment of moderate-to severe rosacea. Metronidazole is a suitable drug in cases of resistance to tetracycline or erythromycin, but it has also been shown that oral metronidazole may increase the side effects (e.g., peripheral neuropathy). Oral metronidazole should not be used for more than three months, and hence topical metronidazole gel is the best therapeutic choice in rosacea (especially during pregnancy). This study examined the mechanical (adhesiveness, cohesiveness, extrudability, spreadability, homogeneity) and rheological (viscosity), skin irritant and drug release properties of different metronidazole gel formulations that contain anionic emulsifying wax, glycerin and lactic acid in different proportions. The release studies were conducted using Franz diffusion cells and Silastic membrane as a barrier. The results indicated that gel compressibility, hardness, and adhesiveness, are the factors that influence the ease of gel removal from the container, ease of gel application onto the mucosal membrane, and gel bioadhesion. The findings showed that there exists a strong negative correlation between the spreadability of a formulation and its cohesiveness, the spreadability of a formulation is inversely proportional to its cohesiveness. However, sorbitol solution (70%) concentration was not significantly correlated with drug release. In addition, drug release was significantly reduced as the concentration of anionic emulsifying wax increased and the concentration of lactic acid decreased. The maximum metronidazole release was achieved at a pH of 4-6. Data obtained from in vitro release studies were fitted to various kinetic models and high correlation was obtained in the Higuchi and first order models. The results showed that all the gel formulations showed good extrudability, viscosity

  15. Insoluble calcium content and rheological properties of Colby cheese during ripening.

    PubMed

    Lee, M-R; Johnson, M E; Govindasamy-Lucey, S; Jaeggi, J J; Lucey, J A

    2010-05-01

    Colby cheese was made using different manufacturing conditions (i.e., varying the lactose content of milk and pH values at critical steps in the cheesemaking process) to alter the extent of acid development and the insoluble and total Ca contents of cheese. Milk was concentrated by reverse osmosis (RO) to increase the lactose content. Extent of acid development was modified by using high (HPM) and low (LPM) pH values at coagulant addition, whey drainage, and curd milling. Total Ca content was determined by atomic absorption spectroscopy, and the insoluble (INSOL) Ca content of cheese was measured by the cheese juice method. The rheological and melting properties of cheese were measured by small amplitude oscillatory rheometry and UW-Melt Profiler, respectively. There was very little change in pH during ripening even in cheese made from milk with high lactose content. The initial (d 1) cheese pH was in the range of 4.9 to 5.1. The INSOL Ca content of cheese decreased during the first 4 wk of ripening. Cheeses made with the LPM had lower INSOL Ca content during ripening compared with cheese made with HPM. There was an increase in melt and maximum loss tangent values during ripening except for LPM cheeses made with RO-concentrated milk, as this cheese had pH <4.9 and exhibited limited melt. Curd washing reduced the levels of lactic acid produced during ripening and resulted in significantly higher INSOL Ca content. The use of curd washing for cheeses made from high lactose milk prevented a large pH decrease during ripening; high rennet and draining pH values also retained more buffering constituents (i.e., INSOL Ca phosphate), which helped prevent a large pH decrease. PMID:20412897

  16. Effect of VA and MWNT contents on the rheological and physical properties of EVA

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Ho; Lee, Seungwon; Kim, Byoung Chul; Shin, Bong-Seob; Jeon, Jong-Young; Chae, Dong Wook

    2016-02-01

    Ethylene vinyl acetate (EVA) copolymers with two different VA contents (15 and 33 wt.%, denoted by EVA15 and EVA33, respectively) were melt compounded with multi-walled carbon nanotubes (MWNTs) and the effect of VA and nanotube contents on the rheological, thermal and morphological properties was investigated. The addition of nanotubes into both EVAs increased the onset temperature of crystallization and broadened the peak, but further addition from 3 wt.% slightly decreased the temperature with increasing nanotube contents. In the wide angle X-ray diffraction patterns the peak of EVA15 was little affected by the presence of nanotubes but that of EVA33 slightly shifted to higher degree and became sharper with increasing nanotube contents. Dynamic viscosity (η') increased with nanotube contents giving abrupt increase at 2 wt.% nanotubes. Loss tangent decreased with increasing nanotube contents exhibiting the plateau-like behavior over most of the frequency range from 2 wt.% nanotubes. In the Casson plot, yield stress increased with nanotube content and its increasing extent was more notable for more VA content. In the Cole-Cole plot, the presence of nanotubes from 2 wt.% gave rise to the deviation from the single master curve by decreasing the slope. The deviated extent of EVA33 became more remarkable with increasing nanotube contents than that of EVA15. The stress-strain curve showed that more improved tensile modulus and yield stress were achieved by the introduction of MWNTs for EVA 33 than for EVA15. Tensile strength of EVA33 increased with increasing nanotube contents, while that of EVA15 decreased.

  17. Effect of ultrafiltration process on physico-chemical, rheological, microstructure and thermal properties of syrups from male and female date palm saps.

    PubMed

    Makhlouf-Gafsi, Ines; Baklouti, Samia; Mokni, Abir; Danthine, Sabine; Attia, Hamadi; Blecker, Christophe; Besbes, Souhail; Masmoudi, Manel

    2016-07-15

    This study investigates the effect of the ultrafiltration process on physicochemical, rheological, microstructure and thermal properties of syrups from male and female date palm sap. All the studied syrups switched from pseudoplastic rheological behaviour (n=0.783) to Newtonian behaviour (n∼1) from 10 to 50 °C respectively and present similar thermal profiles. Results revealed that the ultrafiltration process significantly affects the rheological behaviour of the male and female syrups. These differences on rheological properties are attributed to the variation of chemical composition between sap and sap permeate syrups. Furthermore, the effect of temperature on viscosity of the syrups was investigated during heating and cooling processes at the same shear rate (50s(-1)). This study provides idea of the stability of the syrup by evaluating the area between heating and cooling curves. Actually, the syrup prepared from male sap permeate is the most stable between the four studied syrups. PMID:26948603

  18. Rheological Properties of PET/PC Immiscible Polymer Blends: Effect of Catalysts and Stabilizers

    NASA Astrophysics Data System (ADS)

    Souad, Mbarek; Christian, Carrot; Mohamed, Jaziri; Yvan, Chalamet; Boubaker, Elleuch

    2008-07-01

    The rheology of PET/PC blends obtained by melt reactive blending using various transesterification catalysts has been measured in the melt at 260 °C in dynamic oscillatory shear flow. The thermal stability in the melt of PET/PC blends is a key limitation of the measurement time especially in presence of transesterification catalysts. For long residence time, a noticeable decrease of the viscosity is observed. This decrease is attributed to thermal degradation promoted by exchange reactions. The efficiency of phosphite and phenolic stabilizers, alone or in combination, has been assessed from the rheological measurements. The results show that the effectiveness of phenolic species is more important than that of phosphites. The addition of 0.3 wt-% of Irganox 1010 delays the decrease of the rheological characteristics for 10 minutes.

  19. Correlation of stability/rheology relationship with coal: Properties and chemical additives. Final technical report, September 1988--November 1991

    SciTech Connect

    Ohene, F.

    1992-02-19

    Coal-water slurries have the potential of a near term replacement for fuel oil. In order to gain the fundamental understanding of the preparation and handling of coal-water slurries, experiments were performed to identify the relationship between the coal content of a given coal-water slurry and its physical and chemical properties. The objectives of this program were: Investigate the relationship between the chemical and physical properties of coal and the rheology of coal-water slurry Define procedures for evaluating and preparing coal water slurries for a particular coal candidate, based on the characteristic coal properties Develop improved methods of screening surfactants used in coal-water slurry preparation Perform experiments designed to investigate the effect of characteristic coal properties on slurry quality, by examining the effect of the individual coal properties on slurry quality Develop a statistical formulation to predict the coal content of a given coal water slurry content based on the coal characteristic properties.

  20. Influence of calcium fortification on physical and rheological properties of sucrose-free prebiotic milk chocolates containing inulin and maltitol.

    PubMed

    Konar, Nevzat; Poyrazoglu, Ender Sinan; Artik, Nevzat

    2015-04-01

    In the present study, chocolates were investigated that had been prepared according to the composition specified as a result of this previous work (9.00 % w/w inulin and 34.0 % w/w maltitol) Certain physical (particle size distribution [PSD], brightness, chroma, water activity and hardness) and rheological features of the samples resulting from the addition of calcium carbonate in different quantities (300, 450, 600, 750 and 900 mg calcium carbonate to 100 mg milk chocolate) were studied. Both the Herschel-Bulkley and Casson models were used to investigate the rheological findings. It was determined by comparing certain rheological (rate index, Casson yield stress and Casson viscosity) and physical (chroma and hardness) parameters that samples containing 409.5 mg calcium (nearly 41.0 % of the RDA of calcium) per 100 g chocolate did not show significant differences from samples from the control group. Furthermore, these calcium-containing samples were shown to exhibit positive differences in other physical properties (brightness and water activity) that could be noteworthy and significant with respect to visual quality and shelf life. PMID:25829583

  1. The effects of temperature, organic matter and time-dependency on rheological properties of dry anaerobic digested swine manure.

    PubMed

    Liu, Gang-Jin; Liu, Yi; Wang, Zhi-Yong; Lei, Yun-Hui; Chen, Zi-Ai; Deng, Liang-Wei

    2015-04-01

    An efficient way to avoid the pollution of swine wastewater is the application of dry anaerobic digestion, which needs rheological parameter for stirring and pipe designing. The rheological properties of this kind of sludge have been studied for many decades, yet their effects only solid concentration has been investigated widely. In this paper, the influences of temperature, organic and time-dependency on the efficiency of anaerobic digested swine manure were studied. The viscosity decreased with temperature arranged from 10 to 60 °C which caused increase in protein from 7.18 to 8.49 g/kg. 60 °C can make the digested swine manure with TS from 16.6% to 21.5% reach to the same rheology state. The added peptone decreased the viscosity because of its function of water-reducing admixture and air entraining mixture. Time-dependent experiment showed the decrease of shear stress over time. The first and the second yield stress of dry anaerobic digested swine manure were evaluated through time-dependent model. PMID:25616554

  2. Rheological Properties of Nanoparticle Silica-Surfactant Stabilized Crude Oil Emulsions: Influence of Temperature, Nanoparticle Concentration and Water Volume Fraction"

    NASA Astrophysics Data System (ADS)

    Kinsey, Erin; Pales, Ashley; Li, Chunyan; Mu, Linlin; Bai, Lingyun; Clifford, Heather; Darnault, Christophe

    2016-04-01

    Oil in water emulsions occur during oil extraction due to the presence of water, naturally-occurring surface-active agents and mechanical mixing in pipelines or from oil spillage. Emulsions present difficulties for use of oil in fuel and their rheological properties are important to treat environmental impacts of spills. The objective of this study is to assess the rheological characteristics of oil in water emulsions stabilized by 5% NaCl brine, Tween 20 surfactant and silica nanoparticles to gain knowledge about the behavior of oil flow in pipelines and characterize them for environmental applications. Rheological behaviors such as shear rate, shear stress, and viscosity of Prudhoe Bay crude oil emulsions were analyzed with varying percent of water volume fractions (12.5, 25 and 50%), varying weight percent of silica nanoparticles (0.001, 0.01 and 0.1 weight %), with and without 2 CMC Tween 20 nonionic surfactant. Emulsions with varying water volume fractions were analyzed at 20, 40 and 60 degrees Celsius. Flow curve analysis of the emulsions was performed using an Anton-Paar rheometer. Preliminary findings indicate that increased temperature and increasing the concentration of nanoparticles both produced lower shear stress and that the addition of surfactant decreased the viscosity and shear stress of the emulsions.

  3. The effect of polymer-surfactant interaction on the rheological properties of surfactant enhanced alkaline flooding formulations

    SciTech Connect

    French, T.R.; Josephson, C.B.

    1993-02-01

    Surfactant-enhanced, lower pH (weak) alkaline chemicals are effective for mobilizing residual oil. Polymer is used for mobility control because if mobility control is lost, then oil recovery is reduced. The ability to maintain mobility control during surfactant-alkaline flooding can be adversely affected by chemical interaction. In this work, interaction between polymers and surfactants was shown to be affected by pH, ionic strength, crude oil, and the properties of the polymers and surfactants. Polymer-surfactant interaction (phase separation, precipitation, and viscosity loss) occurred between most of the polymers and surfactants that were tested. Polymer-surfactant interaction is difficult to eliminate, and no method was found for completely eliminating interaction. Polymer-surfactant interaction occurred at optimal salinity and below optimal salinity. Polymer-surfactant interaction had an adverse effect on polymer rheology; however, the adverse effect of interaction on polymer rheology was lessened when oil was present. Increasing the pH of chemical systems further reduced the adverse effects of interaction on polymer rheology.

  4. Rheological property of mafic schist and geological interpretation to the subduction dynamics

    NASA Astrophysics Data System (ADS)

    Okazaki, K.; Hirth, G.

    2013-12-01

    To understand the spatial and temporal distribution of deformation (e.g., underplating and exhumation of metamorphic rocks) and earthquakes in subduction zones, it is important to constrain the rheological properties of metamorphic rocks (i.e., altered oceanic crust and sediments), and how they evolve during metamorphic reactions following hydration, carbonation and dehydration of the down-going slab. Metamorphism of oceanic crust has stimulated hypotheses on the relationship between intra-slab earthquakes and slab-wedge coupling along plate boundaries in subduction zone. While it is well known that metamorphisms have important effects on material circulation and arc volcanisms at subduction system, it remains unclear how the formation of metamorphic minerals followed by fluid release on the subduction dynamics influences rheology. Past experimental studies on mafic metamorphic rocks were mostly concentrated on phase equilibrium of mineral, thus there are very few reports on the mechanical data for these metamorphic rocks. We conducted triaxial deformation experiments on a mafic greenschist using Griggs-type solid pressure-medium apparatus installed in Brown University. Mafic schist (chlorite - amphibole - epidote - albite schist) containing calcite and quartz veins from Sambagawa metamorphic belt (Japan), which is metamorphosed at the condition of nearly the corner of mantle wedge in hot subduction (1 GPa of pressure and 520C of temperature), was used as experimental samples for typical metamorphic rocks composing oceanic crust in warm subduction zones. Constant strain rete experiments and strain rate step experiment were conducted at 1.0 GPa of confining pressure, 400 ~ 500C of temperature and 10-5 ~ 5×10-7 1/s of strain rate. At stable conditions of samples (1 GPa of confining pressure and 400 and 500C of temperature), differential stresses were higher than 1 GPa. Microstructure of recovered samples showed backing and several localized shear zones. Although

  5. The influence of particle size on the rheological properties of plate-like iron particle based magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Choi, Seung-Bok

    2015-01-01

    This work is devoted to the dependence of particle size on magnetorheological properties of magnetorheological fluid (MRF) consisting of plate-like iron particles suspended in a carrier liquid with two aspects. One aspect is to study the influence of the particle size on the rheological properties of the MRF, and the other is to investigate the influence of small-sized particles on the large-sized MRF. In order to achieve this goal, firstly, two different types of MR suspensions have been constituted by a plate-like iron particle; one is small with an average particle size of 2 μm in diameter, and the other is large with an average particle size of 19 μm in diameter. In this work, these are denoted as S-MRF and L-MRF, respectively. Secondly, in order to check the influence of the small particle size of the large-sized MR fluid, three different weight fractions of bidisperse MRF samples are prepared. The structural and morphology of plate-like iron particles are described in detail. The magnetic properties of these MR fluids are carried out at room temperature using the magnetometer, followed by the investigation on the field-dependent rheological properties of these MR fluids. It is observed that in both the S-MRF and L-MRF, the yield stress and viscosity is increased by the increasing particle size, which directly shows a correlation with the fluid magnetization. It is also identified from the test of the bidisperse MRF samples that the yield and viscosity depend on the weight fraction due to the magnetostatic interaction between the two different sizes of particles. Based on the rheological properties, some figures of merit are derived for the proposed MRF samples, which are important in the design of the application device. The sedimentation experiments for MRF samples are performed to check the stability of the MRF each day. With the basic rheological properties and sedimentation experiments, it is clearly demonstrated that the bidisperse MR suspension with a

  6. Effect of high-pressure homogenisation on rheological properties of rennet-induced skim milk and standardised milk gels.

    PubMed

    Lodaite, Kristina; Chevalier, François; Armaforte, Emanuele; Kelly, Alan L

    2009-08-01

    The effects of high-pressure homogenisation (HPH) in the pressure range 100-300 MPa on the gel formation and rheological properties of rennet-induced skim milk (0.08%, fat, w/w) and standardised milk (3.60% fat, w/w) gels at pH 6.60 were studied. The average casein micelle size in skim milk was significantly reduced and the gel formation time decreased when skim milk was subjected to the pressures of 200 and 300 MPa. The storage modulus of rennet-induced skim milk gels at 2700 s after rennet addition was higher for samples homogenised at higher pressures, which contained smaller casein particles. HPH had little effect on the large deformation properties of rennet-induced skim milk gels. The gel formation time of renneted standardised milk was significantly reduced as a result of HPH, while the storage modulus of rennet-induced milk gels 2700 s after rennet addition increased with increasing homogenising pressure. The apparent fracture stress was slightly higher for standardised milk gels formed from HPH-treated milk, whereas the apparent strain at fracture was lower, than that of unhomogenised milk. In conclusion, HPH treatment influenced gel formation processes of skim milk and its small-deformation rheological properties, mainly through modification of casein micelles. HPH also significantly affected the gel formation process of standardised milk gels and its rheological properties as a result of an increase in volume fraction of aggregating particles, while the particle size was of lesser importance. PMID:19445828

  7. Slow Release of Permanganate from Injectable Fumed Silica Gel: Rheological Properties and Release Dynamics

    NASA Astrophysics Data System (ADS)

    Yang, S.; Zhong, L.; Oostrom, M.; Li, G.

    2014-12-01

    ISCO (In Situ Chemical Oxidation) has been proved to be a useful remediation technology in destroying most prevalent aqueous organic contaminants. For permanganate (MnO4-) in particular, the chemistry of degradative oxidation is well established for cleaning up groundwater containing trichloroethene (TCE) and tetrachloroethene (PCE). However the long-term effectiveness of the application of this oxidant has been questioned due to the observed post remediation rebound of contaminant concentrations. To improve the efficiency of ISCO using MnO4-under specific site conditions, the technology of emplacing slow-releasing permanganate in an aquifer has been studied. We have developed an injectable slow-release permanganate slurry/gel (ISRPG) by mixing KMnO4 with fumed silica in water. Ideally, the slurry/gel forms would release low concentration of MnO4- by diffusion to maintain a desired concentration level of the agent within the chemically active zone. We have investigated the properties and tested the application of this ISRPG in laboratory studies. Rheological study indicated ISRPG has high viscosity and shear thinning property. The viscosity of silica gel could be lowered by mechanical mixing thus making it easy for subsurface injection. Batch tests revealed that MnO4- was diffused from ISRPG and the gel did not disperse but maintained its initial shape. In column experiments we showed that permanganate release covered 6 times more effluent pore volumes when ISRPG was injected compared to MnO4- solution injection. We also observed TCE degradation by released MnO4-, and the remedial performance occurred over a much longer timeframe with ISRPG compared to MnO4- solution injection. In 2-D flow cell tests we demonstrated that water flows around the injected gel, carrying MnO4- diffused out from the gel and forming a downstream oxidant plume, while the gel was stationary. ISRPG slowly released low concentrations of permanganate to maintain a predetermined level of the

  8. Rheological and biological properties of a hydrogel support for cells intended for intervertebral disc repair

    PubMed Central

    2012-01-01

    Background Cell-based approaches towards restoration of prolapsed or degenerated intervertebral discs are hampered by a lack of measures for safe administration and placement of cell suspensions within a treated disc. In order to overcome these risks, a serum albumin-based hydrogel has been developed that polymerizes after injection and anchors the administered cell suspension within the tissue. Methods A hydrogel composed of chemically activated albumin crosslinked by polyethylene glycol spacers was produced. The visco-elastic gel properties were determined by rheological measurement. Human intervertebral disc cells were cultured in vitro and in vivo in the hydrogel and their phenotype was tested by reverse-transcriptase polymerase chain reaction. Matrix production and deposition was monitored by immuno-histology and by biochemical analysis of collagen and glycosaminoglycan deposition. Species specific in situ hybridization was performed to discriminate between cells of human and murine origin in xenotransplants. Results The reproducibility of the gel formation process could be demonstrated. The visco-elastic properties were not influenced by storage of gel components. In vitro and in vivo (subcutaneous implants in mice) evidence is presented for cellular differentiation and matrix deposition within the hydrogel for human intervertebral disc cells even for donor cells that have been expanded in primary monolayer culture, stored in liquid nitrogen and re-activated in secondary monolayer culture. Upon injection into the animals, gels formed spheres that lasted for the duration of the experiments (14 days). The expression of cartilage- and disc-specific mRNAs was maintained in hydrogels in vitro and in vivo, demonstrating the maintenance of a stable specific cellular phenotype, compared to monolayer cells. Significantly higher levels of hyaluronan synthase isozymes-2 and -3 mRNA suggest cell functionalities towards those needed for the support of the regeneration of

  9. Effect of sucrose and pectin addition on physical, chemical, thermal and rheological properties of frozen/thawed pineapple pulps

    NASA Astrophysics Data System (ADS)

    Conceição, Márcia Cavalcante; Fernandes, Tatiana Nunes; Prado, Mônica Elisabeth Torres; de Resende, Jaime Vilela

    2012-09-01

    Pectin (0-1.0 g/100 mL) and sucrose (0-20 g/100 mL) were added to pineapple pulp to improve their rheological properties, thermal properties and stability after freezing and thawing processes. The properties of the mixes were characterized before and after freezing and thawing. Samples were frozen at -20°C, and the freeze concentration was evaluated every 60 min. The thawing rate was evaluated at 19°C and quantified by photographic editing and image analysis software. The thawing rates and values for the freeze concentration were leveled out at pectin concentrations above 0.5 g/100 mL pectin, which indicated that pectin functions to maintain structural homogeneity during freezing. In the thawed samples, the plastic viscosity values were leveled out from pectin concentrations (0.25-0.75 g/100 mL) as the sucrose concentration increased when compared to unfrozen samples. The differences between the rheological parameters of the unfrozen and frozen/thawed pulps, the higher yield stress values after thawing were attributed to the size of suspended particles in the pulp. Applications can specify formulations of frozen products containing pectin, where these properties can be handled after thawing the product.

  10. Non-local rheological properties of granular flows near a jamming limit.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.; Malloggi, F.; Clement, E.; Materials Science Division; Univ. of California at San Diego; CNRS-ESPCI Univ.

    2008-01-01

    We study the rheology of sheared granular flows close to a jamming transition. We use the approach of partially fluidized theory (PFT) with a full set of equations extending the thin layer approximation derived previously for the description of the granular avalanches phenomenology. This theory provides a picture compatible with a local rheology at large shear rates [G. D. R. Midi, Eur. Phys. J. E 14, 341 (2004)] and it works in the vicinity of the jamming transition, where a description in terms of a simple local rheology comes short. We investigate two situations displaying important deviations from local rheology. The first one is based on a set of numerical simulations of sheared soft two-dimensional circular grains. The next case describes previous experimental results obtained on avalanches of sandy material flowing down an incline. Both cases display, close to jamming, significant deviations from the now standard Pouliquen's flow rule [O. Pouliquen, Phys. Fluids 11, 542 (1999); 11, 1956 (1999)]. This discrepancy is the hallmark of a strongly nonlocal rheology and in both cases, we relate the empirical results and the outcomes of PFT. The numerical simulations show a characteristic constitutive structure for the fluid part of the stress involving the confining pressure and the material stiffness that appear in the form of an additional dimensionless parameter. This constitutive relation is then used to describe the case of sandy flows. We show a quantitative agreement as far as the effective flow rules are concerned. A fundamental feature is identified in PFT as the existence of a jammed layer developing in the vicinity of the flow arrest that corroborates the experimental findings. Finally, we study the case of solitary erosive granular avalanches and relate the outcome with the PFT analysis.

  11. Rheological and tribological properties of carbon nanotube/thermoplastic nanocomposites incorporating inorganic fullerene-like WS2 nanoparticles.

    PubMed

    Díez-Pascual, Ana M; Naffakh, Mohammed; Marco, Carlos; Ellis, Gary

    2012-07-12

    The rheological and tribological properties of single-walled carbon nanotube (SWCNT)-reinforced poly(phenylene sulphide) (PPS) and poly(ether ether ketone) (PEEK) nanocomposites prepared via melt-extrusion were investigated. The effectiveness of employing a dual-nanofiller strategy combining polyetherimide (PEI)-wrapped SWCNTs with inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles for property enhancement of the resulting hybrid composites was evaluated. Viscoelastic measurements revealed that the complex viscosity η, storage modulus G', and loss modulus G″ increased with SWCNT content. In the low-frequency region, G' and G″ became almost independent of frequency at higher SWCNT loadings, suggesting a transition from liquid-like to solid-like behavior. The incorporation of increasing IF-WS2 contents led to a progressive drop in η and G' due to a lubricant effect. PEEK nanocomposites showed lower percolation threshold than those based on PPS, ascribed to an improved SWCNT dispersion due to the higher affinity between PEI and PEEK. The SWCNTs significantly lowered the wear rate but only slightly reduced the coefficient of friction. Composites with both nanofillers exhibited improved wear behavior, attributed to the outstanding tribological properties of these nanoparticles and a synergistic reinforcement effect. The combination of SWCNTs with IF-WS2 is a promising route for improving the tribological and rheological performance of thermoplastic nanocomposites. PMID:22697425

  12. Effect of ultrasonic pretreatment on physicochemical characteristics and rheological properties of soy protein/sugar Maillard reaction products.

    PubMed

    Zhao, Cheng-Bin; Zhou, Lin-Yi; Liu, Jin-Yang; Zhang, Yao; Chen, Yang; Wu, Fei

    2016-05-01

    Maillard reaction products (MRPs) of soybean protein isolate (SPI) and sugars (glucose and maltose) were prepared by heating in the aqueous dispersion at 95 °C for 15 min with ultrasonic pretreatment (ultrasonic power of 200 W) for 20 min. Effect of ultrasonic pretreatment on physicochemical characteristics and rheological properties of SPI/sugar MRPs was investigated. SPI/sugar MRPs prepared with ultrasonic pretreatment had higher degree of glycation (DG), lower browning and less compact tertiary conformation than that with non-ultrasonic pretreatment. Surface hydrophobicity (H0), particle size and rheological properties were measured by fluorescence spectrophotometry, laser particle size analysis and dynamic oscillatory rheometry, respectively. Glycation reduced H0 and particle size as well as weaken the gel network formed by the acidification of GDL. However, ultrasound increased H0 and decreased particle size. This is desirable for the formation of acid-induced gel structure. The ultrasonic pretreatments reduced/eliminate the weakening effect of glycation on the gel network of SPI/sugar MRPs, and even improved the gel properties. PMID:27407200

  13. Biodegradable blends of poly (lactic acid) (PLA) / polyhydroxybutrate (PHB) copolymer and its effects on rheological, thermal and mechanical properties

    NASA Astrophysics Data System (ADS)

    Sood, Nitin K.

    Poly (Lactic acid) is the most important plastic derived from the renewable resources. PLA based products have extensively been used in the medical industry. However, PLA has a few disadvantages such as inherent brittleness and low toughness despite a high modulus. A focus of this experiment was to study the improvement in toughness of PLA and to study the changes in thermal and rheological properties by blending PLA with a PHB copolymer. Where, PLA and PHB copolymer were melt blended using a twin screw Brabender extruder in the ratios of 100/0, 70/30, 50/50, 30/70, 0/100. Further, the blends were injection molded into tensile bar and impact bars for mechanical testing. Rheological properties were studied using a Galaxy capillary rheometer for melt viscosities and temperature dependence indicated a shear-thinning behavior along with power law model and consistency index. Blends were characterized to study the phase model using a differential scanning calorimetric (DSC), showed two separate phases. Mechanical properties were analyzed using a Tensile and Izod impact test indicating decrease in elastic modulus with increase in toughness and elongation as the PHB copolymer content was increased in the blend.

  14. A study of the kinetic, dielectric, and rheological properties of thermosetting resins used in pultruded polymer composites

    NASA Astrophysics Data System (ADS)

    Shanku, Reshma

    A comprehensive analysis has been conducted of the curing behavior of AOC VIBRINRTM E-606-6 (medium reactivity isophthalic), E-964 (high reactivity isophthalic), and P-341 (highest reactivity) polyester resins, and Shell EPON 9310 resin/EPON 9360 curing agent/EPON 537 accelerator resin system using calorimetric, dielectric, and rheological methods. The unsaturated polyester resins were cured with two different catalysts at three levels of concentration. Calorimetry and dielectrometry were employed to obtain polyester resin curing properties for the resin formulations studied. Rheological characterization of selected polyester resin formulations and the EPON 9310 resin system were also conducted. Kinetic parameters for all resin formulations were determined using a differential scanning calorimeter (DSC) by dynamic and isothermal methods. The dynamic and isothermal kinetic parameters obtained were used to generate heat flow values which were compared to the experimental DSC heat flow recorded; kinetic parameters that accurately modeled the pultrusion process were selected. The kinetic parameters were used in a numerical model to predict temperatures and degrees of cure under pultrusion processing conditions. The results obtained from the in-situ dielectric tests conducted on the pultruder in the Composites Material Laboratory at the University of Mississippi were compared to the degree of cure predictions from the numerical model and the experimental degree of cure from calorimetric analysis. Prior to the in-situ pultrusion studies, small quantities of resin formulations were tested for their dielectric cure properties when heated in an oven simulating pultrusion processing temperatures and rate of heating. This technique allowed small quantities of resins to be tested for degrees of cure. It was determined that such screening tests can be effectively conducted and can aid in pultrusion process planning. Complex viscosity profiles until gelation were generated for

  15. Gum tragacanth dispersions: Particle size and rheological properties affected by high-shear homogenization.

    PubMed

    Farzi, Mina; Yarmand, Mohammad Saeed; Safari, Mohammad; Emam-Djomeh, Zahra; Mohammadifar, Mohammad Amin

    2015-08-01

    The effect of high-shear homogenization on the rheological and particle size characteristics of three species of gum tragacanth (GT) was detected. Dispersions were subjected to 0-20 min treatment. Static light scattering techniques and rheological tests were used to study the effect of treatment. The results showed that the process caused a decrease in particle size parameters for all three species, but interestingly, the apparent viscosities increased. The highest increase of apparent viscosity was found for solutions containing Astragalus gossypinus, which possessed the highest insoluble fraction. The viscoelastic behaviors of dispersions were also significantly influenced by the process. Homogenization caused an increase in both G' and G″, in all three species. The alterations seem to be highly dependent on GT species and structure. The results could be of high importance in the industry, since the process will lead to textural modifications of food products containing GT. PMID:25987462

  16. Correlation of stability/rheology relationship with coal properties and chemical additives

    SciTech Connect

    Ohene, F.

    1990-01-01

    A methodology has been developed in order to determine the influence of individual particle size fractions on coal water slurry rheology. This involves the determination of the packaging concentrations and rheology of the separate particle size fractions; {minus}400 mesh, {minus}400/325, {minus}325/270, {minus}270/200 mesh, {minus}200/140 mesh, {minus}140/100 mesh and {minus}100/80 mesh as a function of solids loading. The packaging concentrations of the separate particle size fractions and that of several blends of these sizes have been determined. The packaging concentrations were determined from particle size distribution measurements and a program based on truncated log-normal distribution which has been developed at the Adelphi Center for Energy Studies. 5 refs., 7 figs., 10 tabs.

  17. Properties of starch-polyglutamic acid (PGA) graft copolymer prepared by microwave irradiation - the Fourier transform infrared spectroscopy (FTIR) and rheology studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of waxy starch-'-polygutamic acid (PGA) graft copolymers were investigated. The starch-PGA copolymers absorbed water and formed gels, which exhibited concentration-dependent viscoelastic solid properties. Higher starch-PGA concentrations resulted in stronger viscoelastic p...

  18. Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures.

    PubMed

    Yuan, Zaiwu; Qin, Menghua; Chen, Xiushan; Liu, Changcheng; Li, Hongguang; Hao, Jingcheng

    2012-06-26

    We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by

  19. Effects of κ-carrageenan on rheological properties of dually modified sago starch: Towards finding gelatin alternative for hard capsules.

    PubMed

    Fakharian, Mohammad-Hassan; Tamimi, Nasser; Abbaspour, Hossein; Mohammadi Nafchi, Abdorreza; Karim, A A

    2015-11-01

    Composite sago starch-based system was developed and characterized with the aim to find an alternative to gelatin in the processing of pharmaceutical capsules. Dually modified (Hydrolyzed-Hydroxypropylated) sago starches were combined with κ-carrageenan (0.25, 0.5, 0.75, and 1%). The rheological properties of the proposed composite system were measured and compared with gelatin as reference material. Results show that combination of HHSS12 (Hydrolysed-hydroxypropylated sago starch at 12h) with 0.5% κ-carrageenan was comparable to gelatin rheological behavior in pharmaceutical capsule processing. The solution viscosity at 50 °C and sol-gel transition of the proposed composite system were comparable to those of gelatin. The viscoelastic moduli (G' and G") for the proposed system were lower than those of gelatin. These results illustrate that by manipulation of the constituents of sago starch-based composite system, a suitable alternative to gelatin can be produced with comparable properties and this could find potential application in pharmaceutical capsule industry. PMID:26256336

  20. The effect of NaCl on the rheological properties of suspension containing spray dried starch nanoparticles.

    PubMed

    Shi, Ai-min; Li, Dong; Wang, Li-jun; Adhikari, Benu

    2012-11-01

    The effect of NaCl on the rheological properties of suspensions containing spray dried starch nanoparticles produced through high pressure homogenization and emulsion cross-linking technique was studied. Rheological properties such as continuous shear viscosity, viscoelasticity and creep-recovery were measured. NaCl (5-20%, w/w) was found to lower viscosity quite significantly (p<0.05), enhance the heat stability and weaken their gelling behavior compared to starch-only suspension. NaCl reduced both the storage and loss moduli of suspension within the frequency range (0.1-10 rads/s) studied. However, NaCl brought higher speed of reduction on the storage modulus than on the loss modulus, which resulted into large increase in loss angle. The creep-recovery behavior of suspension was affected by NaCl and the recovery rate was highest (86%) at 15% NaCl. The Cross, the Power law and the Burger's models followed the experimental viscosity, storage and loss moduli, and creep-recovery data well with R(2)>0.97. PMID:22944412

  1. Investigation of the effects of hydroalcoholic solutions on textural and rheological properties of various controlled release grades of hypromellose.

    PubMed

    Missaghi, Shahrzad; Fegely, Kurt A; Rajabi-Siahboomi, Ali R

    2009-01-01

    Hypromellose (hydroxypropyl methylcellulose, HPMC) matrices are widely used in the formulation of sustained release dosage forms. The integrity and performance of an HPMC matrix formulation depends on rapid hydration and gel formation upon ingestion. Due to the recent alert issued by the Food and Drug Administration regarding the potential negative influence of alcoholic beverages on extended release (ER) formulations, several researchers have evaluated the potential influence of hydroalcoholic media on drug release from ER dosage forms. It has been reported that HPMC matrix formulations do not show "dose dumping" in hydroalcoholic media. The purpose of this study was a fundamental investigation on the effect of hydroalcoholic solutions (0-40% v/v ethanol) on textural and rheological properties of different viscosity grades of neat HPMC, as the functional ingredient within a hydrophilic matrix. In general, hydroalcoholic solutions had little effect on gel formation and mechanical properties of hydrated compacts, while the rheological behavior of HPMC showed dependency on the ethanol content of such solutions. PMID:19148758

  2. Thermal, tensile and rheological properties of high density polyethylene (HDPE) processed and irradiated by gamma-ray in different atmospheres

    SciTech Connect

    Ferreto, H. F. R. E-mail: ana-feitoza@yahoo.com.br; Oliveira, A. C. F. E-mail: ana-feitoza@yahoo.com.br; Parra, D. F. E-mail: ablugao@ipen.br; Lugão, A. B. E-mail: ablugao@ipen.br; Gaia, R.

    2014-05-15

    The aim of this paper is to investigate structural changes of high density polyethylene (HDPE) modified by ionizing radiation (gamma rays) in different atmospheres. The gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical-chemical and mechanical properties. Gamma irradiation originates free radicals which can induce chain scission or recombination, providing its annihilation, branching or crosslinking. This polymer was irradiated with gamma source of {sup 60}Co at doses of 5, 10, 20, 50 or 100 kGy at a dose rate of 5 kGy/h. The changes in molecular structure of HDPE, after gamma irradiations were evaluated using thermogravimetric analysis (TGA) and tensile machine and oscillatory rheology. The results showed the variations of the properties depending on the dose at each atmosphere.

  3. Preparation of BAP Composite Particles and Their Effects on Rheological Properties of HTPB/B/AP Slurries

    NASA Astrophysics Data System (ADS)

    Yun-Fei, Liu; Yu, Chen; Liang, Shi; Wei-Shang, Yao

    2014-04-01

    Composite particles (BAP) of boron (B) coated with ammonium perchlorate (AP) were prepared by recrystallization and their structures were characterized using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and laser particle size analyses. The results indicated that AP was well coated on the boron surface. The effects of different contents of BAP coated with different amounts of AP on the rheological properties of HTPB/B/AP composite slurries were also studied. The results show that addition of BAP distinctly decreased the slurries' viscosities and improved their processing properties, which were more obvious when 9.73% AP was coated on the surface of boron and the amount of BAP was 20%.

  4. Rheological properties of long-chain branched chlorinated poly(isobutylene-co-isoprene)-graft-polybutadiene terpolymers (CIIR-g-BR)

    NASA Astrophysics Data System (ADS)

    Sendorek, Jerzy (George)

    Anionically polymerized "living" polybutadiene (BR) was grafted onto chlorinated poly(isobutylene-co-isoprene) (CIIR) to form a series of elastomeric graft copolymers (CIIR-g-BR) of comb-type, long-chain branching structure (LCB) with systematically varying length and number of branches. A comprehensive program of analytical characterization of the structure and morphology of these materials using SEC/DRI-DV, NMR, FT-IR, DSC, TGA, TEM and other techniques, was designed to determine all relevant structural variables and parameters, as well as to exclude the presence of the potential compositional interferences (gel, residual solvent, unattached branch parent polymer, etc.) for intended correlations between branching structure and rheological properties. The principal branching characteristics of comb-like long-chain branched structures were derived from the stoichiometry of the grafting reaction, confirmed by compositional analysis using a combination of NMR/FT-IR/SEC and supplemented by SEC characterization of the parent linear polymers constituting the backbone (CIIR) and the branch of the graft (BR), respectively. Linear viscoelastic properties of these materials were determined by a Rheometrics Mechanical Spectrometer (RMS-800) using small amplitude, dynamic (sinusoidal oscillatory) shear. These measurements were supplemented by Rubber Process Analyzer (RPA 2000sp{TM}) testing in a comparable range of strain amplitudes, frequencies and temperatures. Stress relaxation experiments, following small amplitude step-strain in shear, complemented the dynamic mechanical measurement. Non-linear viscoelastic properties in shear were investigated in a series of isothermal strain and frequency sweeps using large strain (up to 800%) oscillations (RPA 2000), and by stress following a large-amplitude (˜75%) step shear strain, using the Dynamic Stress Relaxometer (DSR). An insight into the morphology of the grafts by means of the TEM and DSC has been compared to the results of

  5. Effects of added plasmin on the formation and rheological properties of rennet-induced skim milk gels.

    PubMed

    Srinivasan, M; Lucey, J A

    2002-05-01

    Elevated plasmin enzyme activity has been suggested as a likely cause of impaired functional properties that occur in milk from cows either in their late-lactational period or that are experiencing mastitis. However, there are conflicting reports on the impact of plasmin on rennet coagulation properties of milk. The effects of added plasmin on the rheological properties, at small and large deformation, of rennet-induced gels were investigated. The microstructure of rennet-induced gels was studied, using confocal scanning laser microscopy. Porcine plasmin was added to reconstituted milk, and samples were incubated at 37 degrees C for between 0.5 to 8 h. The hydrolysis reaction was terminated using soybean trypsin inhibitor. The extent of degradation of caseins was determined with SDS-PAGE. The extent of breakdown of alpha(s)- and beta-caseins increased with incubation time with plasmin. Storage modulus of rennet gels decreased linearly with increasing degradation of caseins. There was an increase in the loss tangent parameter of the gels with increasing casein degradation, indicating a more liquid-like gel character. Gelation time decreased until approximately 3 h of incubation with plasmin (when the amounts of intact alpha(s)- and beta-caseins were approximately 46 and 50%, respectively); thereafter, gelation time increased considerably. Yield stress of rennet-induced gels decreased with increasing casein breakdown. When the level of casein hydrolysis was high (<40% of intact caseins), the microstructure of rennet-induced gels was drastically altered. Even when there were low levels of casein hydrolysis, the rheological properties of rennet gels were altered, which could have negative impacts on cheese yield and texture. PMID:12086040

  6. The effect of deamidation on the structural, functional, and rheological properties of glutelin prepared from Akebia trifoliata var. australis seed.

    PubMed

    Lei, Li; Zhao, Qiang; Selomulya, Cordelia; Xiong, Hua

    2015-07-01

    The characteristics of glutelin samples from Akebia trifoliata var. australis seeds (AG) that had been deamidated by malic acid (MDAG) and by citric acid (CDAG) were investigated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed high-molecular-weight subunits that were degraded into smaller fragments, and FTIR indicated a decrease in the number of β-sheet groups and an increase in the amount of β-turns in the deamidated samples. These results could be caused by the cleaving of partial disulfide bonds to form new sulfhydryl groups during deamidation. Citric acid was found to be more effective at deamidation and hydrolysis, resulting in a higher solubility and emulsifying activity for CDAG, and MDAG also exhibited some improvement in terms of surface hydrophobicity and emulsion ability. Rheology showed that the gelation point for deamidated samples was increased, and the gel network was strengthened. The amounts of essential amino acids that were well-preserved and the improved solubility, emulsification, and rheology properties of AG after acid-heating deamidation show that this technique can be useful for treating other plant-based food ingredients in the future. PMID:25704689

  7. Effect of liposomes on rheological and syringeability properties of hyaluronic acid hydrogels intended for local injection of drugs.

    PubMed

    El Kechai, Naila; Bochot, Amélie; Huang, Nicolas; Nguyen, Yann; Ferrary, Evelyne; Agnely, Florence

    2015-06-20

    The aim of this work was to thoroughly study the effect of liposomes on the rheological and the syringeability properties of hyaluronic acid (HA) hydrogels intended for the local administration of drugs by injection. Whatever the characteristics of the liposomes added (neutral, positively or negatively charged, with a corona of polyethylene glycol chains, size), the viscosity and the elasticity of HA gels increased in a lipid concentration-dependent manner. Indeed, liposomes strengthened the network formed by HA chains due to their interactions with this polymer. The nature and the resulting effects of these interactions depended on liposome composition and concentration. The highest viscosity and elasticity were observed with liposomes covered by polyethylene glycol chains while neutral liposomes displayed the lowest effect. Despite their high viscosity at rest, all the formulations remained easily injectable through needles commonly used for local injections thanks to the shear-thinning behavior of HA gels. The present study demonstrates that rheological and syringeability tests are both necessary to elucidate the behavior of such systems during and post injection. In conclusion, HA liposomal gels appear to be a promising and versatile formulation platform for a wide range of applications in local drug delivery when an injection is required. PMID:25882015

  8. Effect of ball milling energy on rheological and thermal properties of amaranth flour.

    PubMed

    Roa, Diego F; Baeza, Rosa I; Tolaba, Marcela P

    2015-12-01

    Pearled amaranth grains obtained by abrasive milling were processed by planetary ball milling to produce amaranth flours. The influence of milling energy on rheological and thermal behavior of amaranth flour dispersions and stability during 24 h storage at 4 °C were investigated based on a factorial design. The rheological behavior of flour dispersions (4 % and 8 % w/v) was determined using a rotational viscometer, while gelatinization degree was determined by differential scanning calorimetry as a measure of structural changes.The power law model was found to be suitable in expressing the relationship between shear stress and shear rate. Flour dispersions showed a pseudoplastic behavior. However this character decreased with the storage being dependent on flour concentration and milling energy. A decrease of the consistency index and an increase of the flow behavior index were observed as a result of the increasing milling energy. Gelatinization enthalpy decrease showed the loss of crystalline structure due to ball milling. Amaranth flour dispersions presented increasing stability during storage. It was observed, that the stability changed with the concentration of amaranth flours.Thus, more stable dispersions were obtained as the flour concentration increased. The highly milled sample was the most stable sample during the storage. PMID:26604420

  9. Changes in the rheological properties of blood vessel tissue remodeling in the course of development of diabetes.

    PubMed

    Liu, S Q; Fung, Y C

    1992-01-01

    Rheological properties of blood vessels are expected to change in disease process if the structure of the vessel wall changes. This is illustrated in diabetes, which can be induced in rat by a single injection of Streptozocin. One of the rheological properties of the blood vessel is the stress-strain relationship. The nonlinear stress-strain relationship of arteries is best expressed as derivations of a strain-energy function. In this paper, the stress-strain relations are measured and the coefficients in the strain energy function of arteries are determined for diabetic and control rats. The meaning of these coefficients are explained. The influence of diabetes on the elastic property of the arteries is expressed by the changes of these coefficients. A point of departure of the present paper from all other blood vessel papers published so far is that all strains used here are referred to the zero-stress state of the arteries, whereas all other papers refer strains to the no-load state. The existence of a large difference between the zero-stress state and no-load state of arteries is one of our recent findings. We have explained that the use of zero-stress state as a basis of strain measurements reveals that the in vivo circumferential stress distribution is quite uniform in the vessel wall at the homeostatic condition. It also makes the strain energy function much more accurate than those in which the residual stress is ignored. Using these new results, the stress and strain distribution in normal and diabetic arteries are presented. PMID:1306372

  10. Influence of chemical extraction on rheological behavior, viscoelastic properties and functional characteristics of natural heteropolysaccharide/protein polymer from Durio zibethinus seed.

    PubMed

    Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

    2012-01-01

    In recent years, the demand for a natural plant-based polymer with potential functions from plant sources has increased considerably. The main objective of the current study was to study the effect of chemical extraction conditions on the rheological and functional properties of the heteropolysaccharide/protein biopolymer from durian (Durio zibethinus) seed. The efficiency of different extraction conditions was determined by assessing the extraction yield, protein content, solubility, rheological properties and viscoelastic behavior of the natural polymer from durian seed. The present study revealed that the soaking process had a more significant (p < 0.05) effect than the decolorizing process on the rheological and functional properties of the natural polymer. The considerable changes in the rheological and functional properties of the natural polymer could be due to the significant (p < 0.05) effect of the chemical extraction variables on the protein fraction present in the molecular structure of the natural polymer from durian seed. The natural polymer from durian seed had a more elastic (or gel like) behavior compared to the viscous (liquid like) behavior at low frequency. The present study revealed that the natural heteropolysaccharide/protein polymer from durian seed had a relatively low solubility ranging from 9.1% to 36.0%. This might be due to the presence of impurities, insoluble matter and large particles present in the chemical structure of the natural polymer from durian seed. PMID:23203099

  11. Utilization of tartary buckwheat bran as a source of rutin and its effect on the rheological and antioxidant properties of wheat-based products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tartary buckwheat bran, a by-product of buckwheat flour production was utilized as a source of rutin, and the extracted rutin-enriched material (REM) was used to fortify wheat-based foods of which rheological and antioxidant properties were characterized. REM contained a high content of rutin (29.6 ...

  12. Effect of cocoa butter replacement with a beta-glucan-rich hydrocolloid (C-trim30) on the rheological and tribological properties of chocolates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cocoa butter in chocolates was replaced with C-trim30 (5, 10, 15% by weight), a beta-glucan-rich hydrocolloid containing elevated amount of beta-glucan (32%, db). Then, the effects of the C-trim30 on the rheological, tribological, and textural properties of chocolates were investigated. The viscos...

  13. Influence of Chemical Extraction on Rheological Behavior, Viscoelastic Properties and Functional Characteristics of Natural Heteropolysaccharide/Protein Polymer from Durio zibethinus Seed

    PubMed Central

    Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

    2012-01-01

    In recent years, the demand for a natural plant-based polymer with potential functions from plant sources has increased considerably. The main objective of the current study was to study the effect of chemical extraction conditions on the rheological and functional properties of the heteropolysaccharide/protein biopolymer from durian (Durio zibethinus) seed. The efficiency of different extraction conditions was determined by assessing the extraction yield, protein content, solubility, rheological properties and viscoelastic behavior of the natural polymer from durian seed. The present study revealed that the soaking process had a more significant (p < 0.05) effect than the decolorizing process on the rheological and functional properties of the natural polymer. The considerable changes in the rheological and functional properties of the natural polymer could be due to the significant (p < 0.05) effect of the chemical extraction variables on the protein fraction present in the molecular structure of the natural polymer from durian seed. The natural polymer from durian seed had a more elastic (or gel like) behavior compared to the viscous (liquid like) behavior at low frequency. The present study revealed that the natural heteropolysaccharide/protein polymer from durian seed had a relatively low solubility ranging from 9.1% to 36.0%. This might be due to the presence of impurities, insoluble matter and large particles present in the chemical structure of the natural polymer from durian seed. PMID:23203099

  14. Empirical rheology and pasting properties of soft-textured durum wheat (Triticum turgidum ssp. durum) and hard-textured common wheat (T. aestivum)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Puroindoline (PIN) proteins are the molecular basis for wheat kernel texture classification and affect flour milling performance. This study aimed at investigating the effect of PINs on kernel physical characteristics and dough rheological properties of common wheat (Alpowa cv, soft wheat) and durum...

  15. The effect of epoxidized soybean oil on mechanical and rheological properties of poly(butylene succinate)/lignin via vane extruder

    NASA Astrophysics Data System (ADS)

    Liu, Huanyu; Huang, Zhaoxia; Qu, Jinping; Meng, Cong

    2016-03-01

    Epoxidized Soybean Oil (ESO) have been used as the compatilizer in the Poly (butylene succinate)/lignin (PBS/lignin) composites. Compatibilized composites were fabricated by a novel vane extruder (VE) which can generate global and dynamic elongational flow. The effects of ESO on the mechanical, rheological properties and morphology of PBS/lignin were studied. The results indicated that the use of ESO had plasticizing effect on the matrix PBS while the addition reduced tensile strength. From SEM micrographs it could be clearly observed that there was a better interfacial adhesion between lignin and matrix. Meanwhile, rheological tests showed the incorporation of ESO improved its Newtonian behavior and can enhance PBS's flexibility.

  16. Effect of a New Antioxidant Enoxifol on Platelet Aggregation and Blood Rheological Properties in Rats with Experimental Diabetes Mellitus.

    PubMed

    Kucheryavenko, A F; Spasov, A A; Anisimova, V A

    2016-04-01

    Effect of a new antioxidant enoxifol exhibiting antiplatelet activity in vitro and in vivo on hemostasis parameters was assessed in laboratory rats with experimental diabetes mellitus. Gliclazide, a hypoglycemic agent with antiplatelet properties, and pentoxifylline, a preparation improving blood rheology, were used as the reference drugs. Enoxifol produced a pronounced inhibitory effect on platelet aggregation in rats with experimental diabetes comparable to the effect of gliclazide and decreased blood viscosity thus demonstrating a significant effect comparable to that of pentoxifylline. In view of the fact that oxidative stress is a pathogenetic components of vascular complications in diabetes, it can be assumed that improvement of hemostasis parameters under the effect of enoxifol is determined by its antiplatelet and antioxidant activities. PMID:27165061

  17. Rheological properties of concentrated solutions of gelatin in an ionic liquid 1-ethyl-3-methylimidazolium dimethyl phosphate.

    PubMed

    Horinaka, Jun-Ichi; Okamoto, Arisa; Takigawa, Toshikazu

    2016-10-01

    Rheological properties of gelatin solutions were examined in concentrated regions. Gelatin species from porcine skin and from bovine bone were dissolved in an ionic liquid 1-ethyl-3-methylimidazolium dimethyl phosphate. The dynamic viscoelasticity data for the solutions exhibited rubbery plateaus, indicating the existence of entanglement coupling between gelatin chains in the solutions. From the analogy with rubber elasticity, assuming that the molecular weight between entanglements (Me) is the average mesh size of the entanglement network, Me for gelatin in the solutions were determined from the heights of the rubbery plateaus. Then the value of Me in the molten state (Me,melt), a material constant reflecting the chemical structure of polymer species, for gelatin was estimated to be 8.7×10(3). Compared to synthetic polyamides whose Me,melt were known, Me,melt for gelatin was significantly larger, which could be explained by the densely repeating amide bonds composing gelatin. PMID:27311506

  18. Effect of incorporation of antioxidants on the chemical, rheological, and sensory properties of probiotic petit suisse cheese.

    PubMed

    Pereira, E P R; Cavalcanti, R N; Esmerino, E A; Silva, R; Guerreiro, L R M; Cunha, R L; Bolini, H M A; Meireles, M A; Faria, J A F; Cruz, A G

    2016-03-01

    This work investigated the effect of the addition of different antioxidants (ascorbic acid, glucose oxidase, cysteine, and jabuticaba extract) on the rheological and sensorial properties of the probiotic petit suisse cheese. Absence of influence of the antioxidants at the physico-chemical characteristics of the petit suisse cheese was observed. Overall, the petit suisse cheeses presented weak gel characteristics and behaved as pseudoplastic material, except for control. All treatments exhibited a thixotropic non-Newtonian behavior; however, higher hysteresis area was obtained for control sample, which indicates that antioxidants incorporated to petit suisse had a protective effect on the typical thixotropic behavior of the Quark gel. The commercial sample presented higher scores for all aspects by consumers, whereas the probiotic petit suisse samples presented opposite behavior. Projective mapping was able to generate a vocabulary where the sample containing jabuticaba skin extract obtained by supercritical extraction was characterized by the panelists as presenting grape flavor and purple color. PMID:26805976

  19. Rheological properties in discotic liquid crystalline phases of 2,3,7,8,12,13-hexa(n-tetradecanoyloxy)truxene.

    PubMed

    Negita, Keishi; Kawano, Chiharu; Moriya, Keiichi

    2004-08-01

    Measurements of rheological properties, including the electrorheological effect, are made in liquid crystalline phases, discotic nematic (ND) and discotic disordered rectangular columnar (Drd) phases, of 2,3,7,8,12,13-hexa(n-tetradecanoyloxy)truxene. It is found that the fluidity of the ND phase is Newtonian and an application of high electric field perpendicular to the flow direction (velocity gradient direction) causes a decrease of the viscosity. These results indicate that a flow alignment of the director occurs with its orientation near the velocity gradient direction and the signs of the Leslie coefficients alpha2 and alpha3 are positive. From the temperature dependence of alpha2, instability of the flow alignment structure in ND and Drd phases is also discussed. PMID:15447504

  20. Influence of different purification and drying methods on rheological properties and viscoelastic behaviour of durian seed gum.

    PubMed

    Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

    2012-09-01

    The aim of the present study was to investigate the effects of different purification and drying methods on the viscoelastic behaviour and rheological properties of durian seed gum. The results indicated that the purified gum A (using isopropanol and ethanol) and D (using hydrochloric acid and ethanol) showed the highest and lowest viscosity, respectively. Four drying techniques included oven drying (105 °C), freeze drying, spray drying and vacuum oven drying. In the present work, all purified gums exhibited more elastic (gel-like) behaviour than the viscous (liquid-like) behaviour (G″

  1. Influence of substitution on the rheological properties and gelation of hydroxyethyl cellulose solution in NaOH-water solvent.

    PubMed

    Wang, Wencong; Li, Faxue; Yu, Jianyong; Navard, Patrick; Budtova, Tatiana

    2015-06-25

    The rheological properties of hydroxyethyl cellulose (HEC) with a low molar substitution (MS) dissolved in 8wt% NaOH-water were studied as a function of solution temperature, polymer concentration and molar substitution. Special attention was paid to gelation kinetics. Similar to cellulose dissolved in alkali or ionic liquids, the intrinsic viscosity of HEC decreased with temperature increase, indicating a decrease of solvent thermodynamic quality. The gelation time of HEC solutions decreased exponentially with temperature but the kinetics is much slower than the gelation of microcrystalline cellulose solutions in the same solvent. Higher molar substitution leads to slower gelation. The small amount of introduced hydroxyethyl groups prevented cellulose aggregation thus increasing solution stability. PMID:25839797

  2. Rheological properties of the soft-disk model of two-dimensional foams.

    PubMed

    Langlois, Vincent J; Hutzler, Stefan; Weaire, Denis

    2008-08-01

    The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel-Bulkley relation, normal stress effects (dilatancy), and localization in the presence of wall drag. We show that even a model that incorporates only linear viscous effects at the local level gives rise to nonlinear (power-law) dependence of the limit stress on strain rate. With wall drag, shear localization is found. Its nonexponential form and the variation of localization length with boundary velocity are well described by a continuum model in the spirit of Janiaud etal [Phys. Rev. Lett. 97, 038302 (2006)]. Other results satisfactorily link localization to model parameters, and hence tie together continuum and local descriptions. PMID:18850830

  3. Rheological properties and thermal conductivity of AlN-poly(propylene glycol) suspensions

    NASA Astrophysics Data System (ADS)

    Wozniak, Maciej; Rutkowski, Pawel; Kata, Dariusz

    2016-01-01

    Nanofluids have recently attracted researches' attention as a new generation of heat-transferring fluids used in heat exchangers and for energy storage. Also aluminium nitride is commonly known for its considerable heat conductivity, as high as 320 W/(m K). Because of that, the compound might be a preferable dispersed phase of heat-transferring fluids. This presented studies are focused on nano-AlN-poly(propylene glycol) dispersions which can be applied as potential cooling fluids. The rheological response of the suspensions on shearing and their thermal conductivity in the function of solids concentration and temperature were measured and discussed. The most desired result of the studies is to produce dispersions with Newtonian-like flow at increased temperature and at higher shear rate. All the aforementioned parameters conjugated with significant thermal conductivity of such nanofluids could predispose them to be used as effective cooling media.

  4. Comparison of the effects of different heat treatment processes on rheological properties of cake and bread wheat flours.

    PubMed

    Bucsella, Blanka; Takács, Ágnes; Vizer, Viktoria; Schwendener, Urs; Tömösközi, Sándor

    2016-01-01

    Dry and hydrothermal heat treatments are efficient for modifying the technological-functional and shelf-life properties of wheat milling products. Dry heat treatment process is commonly used to enhance the volume of cakes. Hydrothermal heat treatment makes wheat flours suitable as thickener agents. In this study, cake and bread wheat flours that differed in baking properties were exposed to dry (100 °C, 12 min) and hydrothermal (95 °C, 5 min, 5-20 l/h water) heat treatments. Rheological differences caused by the treatments were investigated in a diluted slurry and in a dough matrix. Dry heat treatment resulted in enhanced dough stability. This effect was significantly higher in the cake flour than the bread flour. Altered viscosity properties of the bread flour in the slurry matrix were also observed. The characteristics of hydrothermally treated samples showed matrix dependency: their viscosity increases in the slurry and decreases in the dough matrix. These results can support us to produce flour products with specific techno-functional properties. PMID:26213066

  5. Influence of amine-grafted multi-walled carbon nanotubes on physical and rheological properties of PMMA-based nanocomposites

    SciTech Connect

    Kim, Ki-Seok; Park, Soo-Jin

    2011-11-15

    In this work, poly(methyl methacrylate) (PMMA) was grafted onto amine treated multi-walled carbon nanotubes (NH-MWNTs) and the physical and rheological properties of the NH-MWNTs-g-PMMA nanocomposites were investigated. The graft reaction of NH-MWNTs and the PMMA matrix was confirmed from the change of the N{sub 1S} peaks, including those of amine oxygen and amide oxygen, by X-ray photoelectron spectroscopy (XPS). The thermal and mechanical properties of the NH-MWNT-g-PMMA nanocomposites were enhanced by the graft reaction between NH-MWNTs and PMMA matrix. In addition, the viscosity of the nanocomposites was increased with the addition of NH-MWNTs. Storage (G') and loss modulus (G'') were significantly increased by increase in the NH-MWNT content compared to acid-treated MWNTs/PMMA nanocomposites. This increase was attributed to the strong interaction by the grafting reaction between NH-MWNTs and the PMMA matrix. - Graphical abstract: This describes the increase of mechanical properties in NH-MWNTs-g-PMMA hybrid composites with different NH-MWNT contents. Highlights: > Aminized carbon nanotubes are used as reinforcement for poly(methylmethacrylate). > Poly(methylmethacrylate) is grafted on aminized carbon nanotubes by thermal reaction. > Grafting of carbon nanotubes and polymer provide enhanced physical properties. > It was due to the strong interaction between carbon nanotubes and polymer matrix.

  6. Effect of Mineralogy on the Rheological Properties of Olivine, Othopyroxene and Olivine/Orthopyroxene Mixtures at High Temperature and Pressure

    NASA Astrophysics Data System (ADS)

    Homburg, J. M.; Mei, S.; Kohlstedt, D. L.

    2013-12-01

    To better understand the influence of mineralogy on the rheological properties of the upper mantle, we have carried out a series of triaxial compressive creep experiments on olivine/orthopyroxene mixtures under high pressures (~6 GPa) and high temperatures (1373 - 1473 K) under anhydrous conditions. Experiments were performed using the deformation-DIA (D-DIA) apparatus on beamline X17B2 at the National Synchrotron Light Source at Brookhaven National Laboratory. Samples of three mineralogical compositions (olivine, orthopyroxene and 50:50 volumetric ratio of olivine:orthopyroxene) were prepared from fine-grained (~10 μm) mineral separates of San Carlos olivine and orthopyroxene. Orthopyroxene and olivine/orthopyroxene samples were cold pressed to attain a cylinder ~1 mm in length and 1.1 mm in diameter. The cold pressed sample was then stacked with a hot-pressed olivine sample of similar size and assembled with alumina pistons, a boron nitride sleeve and graphite resistance heater into a 6.2-mm edge length cubic pressure medium. Nickel disks were placed at the ends of both samples to act as strain markers. During each experiment, in-situ stress and strain measurements were obtained from X-ray diffraction and radiography, respectively. After annealing the samples at the pressure/temperature conditions of deformation for ~2 hours to insure compaction of the cold pressed sample, experiments were conducted at constant strain rates between 2.2x10^-5 and 3.3x10^-5 s^-1 up to axial strains of 5 to 20%. The orthopyroxene and olivine/orthopyroxene mixture deformed at approximately the same rate with the mixed phase system displaying some weakening relative to the single-phase system. This observation suggests that orthopyroxene may be controlling sample behavior in the mixed phase material. In contrast, the orthopyroxene and olivine/orthopyroxene samples crept ~ 2 - 3 times faster than olivine. This contrast in rheological behavior was observed at lower temperatures

  7. Rheology and interfacial properties of aqueous solutions of the diblock polyelectrolyte poly(styrene-block-acrylic acid)

    NASA Astrophysics Data System (ADS)

    Kimerling, Abigail

    In aqueous solutions diblock polyelectrolytes with amphiphilic character form aggregate structures, which affect physical properties such as viscosity, elasticity, surface tension, and film hydrophilicity. Potential applications for diblock polyelectrolyte solutions include coatings, inks, oil recovery agents, personal care products, and biomaterials. By varying the diblock polyelectrolyte and solution properties, the solutions can be tuned to meet the needs of particular applications. The research objective was to identify the influences of block length, pH, and ionic strength on the rheological and interfacial properties of poly(styrene- b-acrylic acid) (PS-PAA) solutions. Six polymers with varied PS and PAA block lengths were examined, all at 1.0 wt% in aqueous solutions. The hydrophobicity of the PS block causes the formation of spherical micelles in aqueous solutions. Increasing the solution pH ionizes the PAA block, which leads to an increase in micelle corona thickness due to repulsions between chains. Major trends observed in the rheological and interfacial properties can be understood in terms of expected changes in the micelle size and interfacial self-assembly with pH, ionic strength, and block length. Addition of NaOH was found to increase the solution pH and initially led to increases in solution viscosity, elasticity, surface tension, and film hydrophilicity. This effect was attributed to creation of larger micelles and greater inter-micellar repulsions as the PAA chain became more fully charged. However, when the concentration of NaOH exceeded a critical value, the solution viscosity, elasticity, and film hydrophilicity decreased. It is believed this was due to charge shielding by excess sodium ions, leading to shrinkage of the micelle corona and smaller micelles. Increasing the PS-PAA solution ionic strength by adding NaCl also provided charge shielding, as observed by decreases in solution viscosity and elasticity. Increasing the length of either

  8. Rheology of Active Gels

    NASA Astrophysics Data System (ADS)

    Chen, Daniel

    2015-03-01

    Active networks drive a diverse range of critical processes ranging from motility to division in living cells, yet a full picture of their rheological capabilities in non-cellular contexts is still emerging, e.g., How does the rheological response of a network capable of remodeling under internally-generated stresses differ from that of a passive biopolymer network? In order to address this and other basic questions, we have engineered an active gel composed of microtubules, bidirectional kinesin motors, and molecular depletant that self-organizes into a highly dynamic network of active bundles. The network continually remodels itself under ATP-tunable cycles of extension, buckling, fracturing, and self-healing. Using confocal rheometry we have simultaneously characterized the network's linear and non-linear rheological responses to shear deformation along with its dynamic morphology. We find several surprising and unique material properties for these active gels; most notably, rheological cloaking, the ability of the active gel to drive large-scale fluid mixing over several orders of flow magnitude while maintaining an invariant, solid-like rheological profile and spontaneous flow under confinement, the ability to exert micro-Newton forces to drive persistent directed motion of the rheometer tool. Taken together, these results and others to be discussed highlight the rich stress-structure-dynamics relationships in this class of biologically-derived active gels.

  9. Cooling rate effects on the microstructure, solid content, and rheological properties of organogels of amides derived from stearic and (R)-12-hydroxystearic acid in vegetable oil.

    PubMed

    Toro-Vazquez, Jorge F; Morales-Rueda, Juan; Torres-Martínez, Adriana; Charó-Alonso, Miriam A; Mallia, V Ajay; Weiss, Richard G

    2013-06-25

    Using safflower oil as the liquid phase, we investigated the organogelation properties of stearic acid (SA), (R)-12-hydroxystearic acid (HSA), and different primary and secondary amides synthesized from SA and HSA. The objective was to establish the relationship between the gelator's molecular structure, solid content, and gels' microstructure that determines the rheological properties of organogels developed at two cooling rates, 1 and 20 °C/min. The results showed that the presence of a 12-OH group in the gelator molecule makes its crystallization kinetics cooling rate dependent and modifies its crystallization behavior. Thus, SA crystallizes as large platelets, while HSA crystallizes as fibers forming gels with higher solid content, particularly at 20 °C/min. The addition to HSA of a primary or a secondary amide bonded with an alkyl group resulted in gelator molecules that crystallized as fibrillar spherulites at both cooling rates. Independent of the cooling rate, gels of HSA and its amide derivatives showed thixotropic behavior. The rheological properties of the amide's organogels depend on a balance between hydrogen-bonding sites and the alkyl chain length bonded to the amide group. However, it might also be associated with the effect that the gelators' molecular weight has on crystal growth and its consequence on fiber interpenetration among vicinal spherulites. These results were compared with those obtained with candelilla wax (CW), a well-known edible gelling additive used by the food industry. CW organogels had higher elasticity than HSA gels but lower than the gels formed by amides. Additionally, CW gels showed similar or even higher thixotropic behavior than HSA and the amide's gels. These remarkable rheological properties resulted from the microstructural organization of CW organogels. We concluded that microstructure has a more important role determining the organogels' rheology than the solid content. The fitting models developed to describe the

  10. Rheological Properties of Ascending Magma at a Basaltic Andesitic System: Puy De La Vache, France As a Case Study

    NASA Astrophysics Data System (ADS)

    Sanchez, L.; Sehlke, A.; Harris, A. J. L.; Whittington, A. G.; Menand, T.

    2014-12-01

    Eruptions at basaltic andesitic systems are often characterized by effusive behavior. However, an increasing number of examples around the World indicate that these magmas, with low degrees of differentiation and basic compositions, have the capacity to produce explosive eruptions; thus presenting a considerable hazard. Volcanoes in the Chaîne des Puys (France), more specically the Puy de la Vache volcano, are good examples of explosive activity at basaltic andesitic centers. A combination of factors can explain this behavior: high magma ascent rate, high content of dissolved gases and high crystal contents. The latter leads to an increase in magma viscosity. The rheological properties of the magma control the eruptive style; viscosity itself strongly depends on composition, temperature, crystal fraction and vesicularity. In particular, an increase in crystal content may drastically change the composition of the residual melt and adds rigid particles to the mixture, inducing a complex strain rate dependence. Here, we are interested in the rheology of basaltic andesitic magmas as a function of crystal content. To quantify the effect of crystals on the viscosity, we measured the stress-strain relationship of the remelted Puy de la Vache lava by concentric cylinder viscometry at super and subliquidus conditions. Concurrently, we performed a textural analysis to determine the crystal fraction at each temperature. We also measured viscosities close to the glass transition using a parallel plate viscometer. We then compared the measured viscosities with those obtained from calculations using existing models. With the experimentally obtained stress-strain rate relationship of the magma at different temperatures and crystal fractions, our goal is to design a model where viscosity varies across the conduit depending on the shear stress and strain rate conditions. This will allow us to characterize the potential explosive behavior of basaltic to andesitic magmas.

  11. Effect of nano-alumina concentration on the mechanical, rheological, barrier and morphological properties of guar gum.

    PubMed

    Savvashe, Prashant; Kadam, Pravin; Mhaske, Shashank

    2016-04-01

    In this work, nano-alumina was utilized as a reinforcing agent for guar gum, with an aim to improve its performance properties; especially, mechanical and barrier i.e. water vapor transmission rate (WVTR). Films were prepared by the process of solution casting. Concentration of nano-alumina was varied as 0, 1, 3, 5 and 7 parts per hundred parts of resin (phr) in guar gum. The prepared pristine and guar gum/alumina nano-composite films were characterized for mechanical, puncture, x-ray diffraction, barrier, rheological and morphological properties. Tensile strength, Young's modulus, puncture strength, viscosity and crystallinity increased; whereas, WVTR, elongation at break (%) and damping factor decreased with increased concentration of nano-alumina in guar gum. However, optimized improvement in the performance properties were determined for 5 phr nano-alumina loaded guar gum polymer matrix, attributed to its better dispersion and interaction into the guar gum polymer chains due to the hydrophilic nature of both the materials. Above 5 phr concentration nano-alumina started forming aggregates, as evident from scanning electron microscopy. PMID:27413221

  12. Blood Thixotropy in Patients with Sickle Cell Anaemia: Role of Haematocrit and Red Blood Cell Rheological Properties

    PubMed Central

    Vent-Schmidt, Jens; Waltz, Xavier; Romana, Marc; Hardy-Dessources, Marie-Dominique; Lemonne, Nathalie; Billaud, Marie; Etienne-Julan, Maryse; Connes, Philippe

    2014-01-01

    We compared the blood thixotropic/shear-thinning properties and the red blood cells’ (RBC) rheological properties between a group of patients with sickle cell anaemia (SS) and healthy individuals (AA). Blood thixotropy was determined by measuring blood viscosity with a capillary viscometer using a “loop” protocol: the shear rate started at 1 s−1 and increased progressively to 922 s−1 and then re-decreased to the initial shear rate. Measurements were performed at native haematocrit for the two groups and at 25% and 40% haematocrit for the AA and SS individuals, respectively. RBC deformability was determined by ektacytometry and RBC aggregation properties by laser backscatter versus time. AA at native haematocrit had higher blood thixotropic index than SS at native haematocrit and AA at 25% haematocrit. At 40% haematocrit, SS had higher blood thixotropic index than AA. While RBC deformability and aggregation were lower in SS than in AA, the strength of RBC aggregates was higher in the former population. Our results showed that 1) anaemia is the main modulator of blood thixtropy and 2) the low RBC deformability and high RBC aggregates strength cause higher blood thixotropy in SS patients than in AA individuals at 40% haematocrit, which could impact blood flow in certain vascular compartments. PMID:25502228

  13. The influence of nanodiamond on the oxygenation states and micro rheological properties of human red blood cells in vitro

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Chung; Tsai, Lin-Wei; Perevedentseva, Elena; Chang, Hsin-Hou; Lin, Ching-Hui; Sun, Der-Shan; Lugovtsov, Andrei E.; Priezzhev, Alexander; Mona, Jani; Cheng, Chia-Liang

    2012-10-01

    Nanodiamond has been proven to be biocompatible and proposed for various biomedical applications. Recently, nanometer-sized diamonds have been demonstrated as an effective Raman/fluorescence probe for bio-labeling, as well as, for drug delivery. Bio-labeling/drug delivery can be extended to the human blood system, provided one understands the interaction between nanodiamonds and the blood system. Here, the interaction of nanodiamonds (5 and 100 nm) with human red blood cells (RBC) in vitro is discussed. Measurements have been facilitated using Raman spectroscopy, laser scanning fluorescence spectroscopy, and laser diffractometry (ektacytometry). Data on cell viability and hemolytic analysis are also presented. Results indicate that the nanodiamonds in the studied condition do not cause hemolysis, and the cell viability is not affected. Importantly, the oxygenation/deoxygenation process was not found to be altered when nanodiamonds interacted with the RBC. However, the nanodiamond can affect some RBC properties such as deformability and aggregation in a concentration dependent manner. These results suggest that the nanodiamond can be used as an effective bio-labeling and drug delivery tool in ambient conditions, without complicating the blood's physiological conditions. However, controlling the blood properties including deformability of RBCs and rheological properties of blood is necessary during treatment.

  14. Modification of Polymer Rheological Properties Through the Incorporation of Functionlized Nanoparticles

    NASA Astrophysics Data System (ADS)

    Xavier, Jean Harry; Sokolov, Jonathan; Rafailovich, Miriam; Goldstein, Lauren; Maller, Abigail

    2003-03-01

    Polymer rheology can best be controlled when addressed at the segmental level of the polymer molecule. We show that a critical dimension, Ro, exists between the radius of added nanoparticles and the polymer chain which separates a regime whereby the particles increase the internal free volume or reinforce the chain. We blended Au, Pd, and POSS nanoparticles (3-12nm) with polymers (Mw=100K-4M) and measured the glass transition and viscosity as a function of Ro. Transmission Electron Microscopy (TEM) was used to study filler size and aggregation. The effect of fillers in Tg of PS was studied using Shear Modulation Force Microscopy (SMFM). The dynamics of diffusion of fillers into the PS matrix were studied using Second Ion Mass Spectrometer (SIMS) and Neutron Reflectivity (NR) techniques will be reported. The effect of substrate interactions will be examined by comparing the results in supported and free standing films. References: 1. S.Ge, M.H. Rafailovich, J. Sokolov.Physical Review Letter, Vol. 85, 2340-2343, 9/19/2000. Support from the NSF MRSEC is gratefully acknowledged.

  15. A comparison of the sensory and rheological properties of molecular and particulate forms of xanthan gum☆

    PubMed Central

    Abson, Rachael; Gaddipati, Sanyasi R.; Hort, Joanne; Mitchell, John R.; Wolf, Bettina; Hill, Sandra E.

    2014-01-01

    A particulate form of xanthan gum was prepared by extrusion cooking. The temperature dependence of the viscosity of this form shows similarities to starch with an increase in viscosity to a maximum with increasing temperature as a result of the swelling of the particles. The rheology and mixing behaviour with water of the particulate and conventional molecular forms of xanthan were compared with a modified starch. The particulate xanthan products mixed rapidly with water in a similar way to ungelatinised starch, whereas conventional molecular xanthan systems mixed poorly. Using an experienced sensory panel, model tomato products thickened with the three systems were compared at equal shear viscosities. The panel could not discriminate between the tomato flavour of the three products, but found that the xanthan products were perceived as being significantly thicker. These observations were consistent with previous work. Salt perception for both xanthan products was poorer than for the starch thickened systems. A hypothesis to explain why xanthan does not fit into the previously postulated link between mixing and perception is presented. PMID:24591753

  16. A comparison of the sensory and rheological properties of molecular and particulate forms of xanthan gum.

    PubMed

    Abson, Rachael; Gaddipati, Sanyasi R; Hort, Joanne; Mitchell, John R; Wolf, Bettina; Hill, Sandra E

    2014-03-01

    A particulate form of xanthan gum was prepared by extrusion cooking. The temperature dependence of the viscosity of this form shows similarities to starch with an increase in viscosity to a maximum with increasing temperature as a result of the swelling of the particles. The rheology and mixing behaviour with water of the particulate and conventional molecular forms of xanthan were compared with a modified starch. The particulate xanthan products mixed rapidly with water in a similar way to ungelatinised starch, whereas conventional molecular xanthan systems mixed poorly. Using an experienced sensory panel, model tomato products thickened with the three systems were compared at equal shear viscosities. The panel could not discriminate between the tomato flavour of the three products, but found that the xanthan products were perceived as being significantly thicker. These observations were consistent with previous work. Salt perception for both xanthan products was poorer than for the starch thickened systems. A hypothesis to explain why xanthan does not fit into the previously postulated link between mixing and perception is presented. PMID:24591753

  17. In situ determination of rheological properties and void fraction: Hanford Waste Tank 241-SY-103

    SciTech Connect

    Shepard, C.L.; Stewart, C.W.; Alzheimer, J.M.; Terrones, G.; Chen, G.; Wilkins, N.E.

    1995-11-01

    This report presents the results of the operation of the void fraction instrument (VFI) and ball rheometer in Hanford Tank 241-SY-103. The two instruments were deployed through risers 17C and 22A in July and August 1995 to gather data on the gas content and rheology of the waste. The results indicate that the nonconvective sludge layer contains up to 12% void and an apparent viscosity of 104 to 105 cP with a yield strength less than 210 Pa. The convective layer measured zero void and had no measurable yield strength. Its average viscosity was about 45 cP, and the density was less than 1.5 g/cc. The average void fraction was 0.047 {plus_minus} 0.015 at riser 17C and 0.091 {plus_minus} 0.015 at riser 22A. The stored gas volume based on these void fraction measurements is 213 {plus_minus} 42 M{sup 3} at 1 atmosphere.

  18. A Study on the Rheological Properties of Recycled Rubber-Modified Asphalt Mixtures

    PubMed Central

    Karacasu, Murat; Er, Arzu

    2015-01-01

    Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber-modified asphalt (RMA) concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress-strain response of traffic-induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost. PMID:25695096

  19. Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fazelabdolabadi, Babak; Khodadadi, Abbas Ali; Sedaghatzadeh, Mostafa

    2015-08-01

    The application of functionalized/unfunctionalized (multi-walled) carbon nanotubes (CNT) was investigated in the context of formulating nano-based drilling fluids from water/oil-based fluid templates. CNT functionalization was attempted by applying hydrophilic functional groups onto the surface of the nanotubes via acid treatment. Experimental data were collected for thermal conductivity, viscosity/yield point, and filtrate amount in all samples. The time evolution of thermal conductivity was studied, as well as the effects of temperature and CNTs volume fraction on the parameter. Scanning electron microscopy (SEM) was used to monitor CNTs dispersion quality. The thermal conductivity results unveil considerable enhancements, by as much as 23.2 % (1 % vol. functionalized CNT) in CNT-water-based case at ambient temperature, with extended improvement of 31.8 % at an elevated temperature of 50 °C. Corresponding results for the CNT-oil-based case exhibit an improvement in thermal conductivity by 40.3 % (unfunctionalized) and 43.1 % (functionalized) and 1 % volume fraction of CNT. The rheological results follow an analogous improvement trend. For the CNT-oil-based case, the filtration tests conducted at 138 °C and 500 (psi) show a 16.67 % reduction in filtrate amount (1 % vol. CNT). The time evolution of thermal conductivity was found to nearly equalize (at an amount of 9.7 %) after 100 h of sample preparation in both functionalized and unfunctionalized CNT-oil-based cases.

  20. A study on the rheological properties of recycled rubber-modified asphalt mixtures.

    PubMed

    Karacasu, Murat; Okur, Volkan; Er, Arzu

    2015-01-01

    Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber-modified asphalt (RMA) concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress-strain response of traffic-induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost. PMID:25695096

  1. Effect of frozen storage on the proteolytic and rheological properties of soft caprine milk cheese.

    PubMed

    Van Hekken, D L; Tunick, M H; Park, Y W

    2005-06-01

    Freezing and long-term frozen storage had minimal impact on the rheology and proteolysis of soft cheese made from caprine milk. Plain soft cheeses were obtained from a grade A goat dairy in Georgia and received 4 storage treatments: fresh refrigerated control (C), aged at 4 degrees C for 28 d; frozen control (FC), stored at -20 degrees C for 2 d before being thawed and aged in the same way as C cheese; and 3-mo frozen (3MF), or 6-mo frozen (6MF), stored at -20 degrees C for 3 or 6 mo before being thawed and aged. Soft cheeses had fragile textures that showed minimal change after freezing or over 28 d of aging at 4 degrees C. The only exceptions were the FC cheeses, which, after frozen storage and aging for 1 d at 4 degrees C, were significantly softer than the other cheeses, and less chewy than the other frozen cheeses. Moreover, after 28 d of aging at 4 degrees C, the FC cheeses tended to have the lowest viscoelastic values. Slight variation was noted in protein distribution among the storage treatment, although no significant proteolysis occurred during refrigerated aging. The creation and removal of ice crystals in the cheese matrix and the limited proteolysis of the caseins showed only slight impact on cheese texture, suggesting that frozen storage of soft cheeses may be possible for year-round supply with minimal loss of textural quality. PMID:15905426

  2. Rheological and Mechanical Property Measurements of PMDI foam at Elevated Temperatures.

    SciTech Connect

    Nemer, Martin B.; Brooks, Carlton F.; Bion Shelden; Soehnel, Melissa Marie; Barringer, David Alan

    2014-10-01

    A study was undertaken to determine the viscosity of liquefied 20 lb/ft 3 poly methyl ene diisocyanate (PMDI) foam and the stress required to puncture solid PMDI foam at elevated temperatures. For the rheological measurements th e foam was a priori liquefied in a pressure vessel such that the volatiles were not lost in the liquefaction process. The viscosity of the liquefied PMDI foam was found to be Newtonian with a power law dependence on temperature log 10 ( m/Pa s) = 20.6 - 9.5 log 10 (T/degC) for temperatures below 170 degC. Above 170 degC, the viscosity was in the range of 0. 3 Pa s which is close to the lower measurement limit ([?] 0.1 Pa s) of the pressurized rheometer. The mechanical pressure required to break th rough 20lb/ft 3 foam was 500 - 800 psi at temperatures from room temperature up to 180 degC . The mechanical pressure required to break through 10 lb/ft 3 was 170 - 300 psi at temperatures from room temperature up to 180 degC. We have not been able to cause gas to break through the 20 lb/ft 3 PMDI foam at gas pressures up to 100 psi.

  3. Determination of Interfacial Rheological Properties through Microgravity Oscillations of Bubbles and Drops

    NASA Technical Reports Server (NTRS)

    Nadim, Ali; Rush, Brian M.

    2000-01-01

    This report summarizes our derivations of analytical expressions for the frequencies and damping constants for small-amplitude axisymmetric shape oscillations of a liquid drop suspended in an immiscible fluid host in microgravity. In particular, this work addresses large Reynolds number shape oscillations and focuses on the surface rheological effects that arise from the presence of insoluble surfactants at the interface. Parameters characterizing viscous effects from the bulk phases, surface viscous effects, Marangoni effects from the surface advection and diffusion of surfactants, and the Gibbs elasticity are all considered and analyzed to determine the relative importance of each contribution. Supplementing the analytical treatment for small-amplitude oscillations, a numerical boundary integral equation formulation is developed for the study of large-amplittide axisymmetric oscillations of a drop in vacuum. The boundary integral formulation is an extension of classical potential flow theory and approximately accounts for viscous effects in the bulk fluid as well as the surface viscous and Marangoni effects resulting from an insoluble surfactant contaminating the interface. Theoretical and numerical results are presented for four distinct cases. These, range from the case when the effects of the surfactants are 'negligible' to 'large' when compared to the viscous effects in the bulk phases. The feasibility of the non-contact measurement of the surface parameters, using experimental observations for the oscillation frequencies and damping constants of drops and bubbles, is discussed.

  4. Graphene networks with low percolation threshold in ABS nanocomposites: selective localization and electrical and rheological properties.

    PubMed

    Gao, Chong; Zhang, Shimin; Wang, Feng; Wen, Bin; Han, Chunchun; Ding, Yanfen; Yang, Mingshu

    2014-08-13

    Acrylonitrile-butadiene-styrene resin (ABS)/graphene nanocomposites were prepared through a facile coagulation method. Because the chemical reduction of graphene oxide was in situ conducted in the presence of ABS at the dispersion stage, the aggregation of the graphene nanosheets was avoided. It was shown by transmission electron microscopy that the graphene nanosheets were selectively located and homogeneously dispersed in the styrene-acrylonitrile (SAN) phase. The electrical conductivity and linear viscoelastic behavior of the nanocomposites were systematically studied. With increasing filler content, graphene networks were established in the SAN phase. Consequently, the nanocomposites underwent a transition from electrical insulator to conductor at a percolation threshold of 0.13 vol %, which is smaller than that of other ABS composites. Such a low percolation threshold results from extreme geometry, selective localization, and homogeneous dispersion of the graphene nanosheets in SAN phase. Similarly, the rheological response of the nanocomposites also showed a transition to solid-like behavior. Due to the thermal reduction of graphene nanosheets and structure improvement of graphene networks, enhanced electrical conductivity of the nanocomposites was obtained after annealing. PMID:24969179

  5. Effects of dietary triglycerides on rheological properties of human red blood cells (abstract).

    PubMed

    Cicha, I; Suzuki, Y; Tateishi, N; Maeda, N

    2004-01-01

    Atherogenic diets rich in saturated fat and cholesterol influence the blood viscosity and red blood cell (RBC) aggregability, the parameters associated with increased risk of circulatory disorders. However, little is known about the effect of triglycerides, which are the major dietary lipid form in humans, on blood rheology. Therefore, we studied the effects of postprandial plasma triglyceride levels on human RBC indices, hematological parameters, RBCs aggregation velocity and whole blood viscosity. For this purpose, whole blood was collected 2 hours after high-fat or low-fat meal. Proteins, triglycerides and cholesterol levels of plasma were analysed, and RBCs rouleaux formation rate was measured in 70% autologous plasma using a low-shear rheoscope. There were no significant differences in hematological parameters, RBC indices, whole blood viscosity, plasma protein and cholesterol content between high-fat and low-fat blood samples. However, a significant increase in rouleaux formation rate was observed in samples with high postprandial triglyceride levels, when compared with low-triglyceride samples. Plasma triglyceride levels correlated significantly with rouleaux formation rate. In conclusion, these results suggest that diet-dependent alterations of plasma triglyceride levels as well as possible changes in the cell membrane lipid composition lead to RBC hyperaggregability. PMID:15258358

  6. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This work aims to extract and characterize fibrous, rod-like and spherical cellulose nanoparticles (CNs) from cottonseed hull and to investigate the structure-morphology-rheology relationships. The rheological behavior of poly(vinyl alcohol) (PVA)/CNs suspensions was also examined to guide the solve...

  7. Mathematical model of microbicidal flow dynamics and optimization of rheological properties for intra-vaginal drug delivery: Role of tissue mechanics and fluid rheology.

    PubMed

    Anwar, Md Rajib; Camarda, Kyle V; Kieweg, Sarah L

    2015-06-25

    Topically applied microbicide gels can provide a self-administered and effective strategy to prevent sexually transmitted infections (STIs). We have investigated the interplay between vaginal tissue elasticity and the yield-stress of non-Newtonian fluids during microbicide deployment. We have developed a mathematical model of tissue deformation driven spreading of microbicidal gels based on thin film lubrication approximation and demonstrated the effect of tissue elasticity and fluid yield-stress on the spreading dynamics. Our results show that both elasticity of tissue and yield-stress rheology of gel are strong determinants of the coating behavior. An optimization framework has been demonstrated which leverages the flow dynamics of yield-stress fluid during deployment to maximize retention while reaching target coating length for a given tissue elasticity. PMID:25798760

  8. Effect of chain extension on rheology and tensile properties of PHB and PHB-PLA blends

    NASA Astrophysics Data System (ADS)

    Bousfield, Glenn

    Poly(3-hydroxybutyrate), referred to as PHB, is a bacterially-synthesized and biodegradable polymer which is being considered as a substitute for non-biodegradable bulk polymers like polypropylene. PHB is naturally extremely isotactic and naturally has a very high degree of crystallinity, resulting in a stiff but brittle material. The stability of PHB crystals also means that the melting point of the polymer is approximately 170°C, high with respect to similar polymers. For instance, the melting point of poly(4-hydroxybutyrate) is only 53°C (Saito, Nakamura, Hiramitsu, & Doi, 1996). Above 170°C, PHB is subject to a thermomechanical degradation mechanism, meaning that the polymer cannot be melted without degrading. One possible solution to the problem of degradation is to add a chain extender to the molten polymer to increase average molecular weight to counteract the molecular weight lost to degradation. In this work, a variety of chain extenders (JoncrylRTM ADR 4368-C, pyromellitic dianhydride, hexamethylene diisocyanate, polycarbodiimide) were compounded with a random copolymer of 98 mol% 3-hydroxybutyrate and 2 mol% 3-hydroxyvalerate (referred to as PHB) in concentrations ranging from 0.25% to 4%, to determine which chain extender functionality worked best with PHB. Molecular weight change was inferred from torque monitored during compounding, and from complex viscosity determined from parallel-plate rheology. None of the chain extenders changed the rate of degradation of PHB, although Joncryl increased the complex viscosity of the polymer. PHB was also blended with Poly(L-lactic acid), referred to as PLLA in PHB/PLLA ratios of 100/0, 75/25, 50/50, 25/75 and 0/100, to determine the effect of blending on the thermal stability of PHB. Again, thermal stability was determined by monitoring torque during compounding and by measuring complex viscosity through parallel-plate rheology. Blends in which PHB was the more abundant phase, as well as the 50% PHB/50% PLA

  9. Spray dried melon seed milk powder: physical, rheological and sensory properties.

    PubMed

    Zungur Bastıoğlu, Aslı; Tomruk, Dilara; Koç, Mehmet; Ertekin, Figen Kaymak

    2016-05-01

    Melon seed milk (MSM) powder was produced by aiming to get alternative vegetable milk from crushed Kırkağaç (Cucumis melo subsp. melo cv. Kırkağaç) and Çeşme (C. melo subsp. melo cv. Çeşme) type melon seeds. MSM was converted to powder form via spray dryer at inlet air temperature of 150 °C, air flow rate of 473 l · h(-1), aspiration ratio of 24 m(3) · h(-1)and feed flow rate of 8 ml · min(-1) in order to extend the shelf life and usage area. The moisture content and water activity of samples changed in range of 2.1 to 2.4 % and 0.260 to 0.310, respectively. Bulk densities and the tapped densities of powders were ranged from 340 to 360 kg · m(-3) and 730 and 740 kg · m(-3). MSM powders showed poor flow behavior as determined from Carr Index. The particle densities of powders ranged between and 1069 kg · m(-3). Wettability time of powders was found as 7 s. The Bingham model was the best model fitted to rheological data of MSM beverages. Sensory evaluation test results showed that, the beverage obtained from reconstituted Kırkağaç powder achieved the highest score by panelists. PMID:27407206

  10. Development of probiotic dairy beverages: rheological properties and application of mathematical models in sensory evaluation.

    PubMed

    Castro, W F; Cruz, A G; Bisinotto, M S; Guerreiro, L M R; Faria, J A F; Bolini, H M A; Cunha, R L; Deliza, R

    2013-01-01

    Strawberry-flavored probiotic dairy beverages (2% vol/vol Lactobacillus acidophilus) were produced using 0, 20, 35, 50, 65, and 80% (vol/vol) whey in their formulations. Mathematical models (survival analysis, minimal significant difference, and mean global acceptance) were used to identify the optimal (sensorially) whey concentration in probiotic beverages. Fifty-five consumers evaluated acceptance of the beverages using hybrid 9-point hedonic scales. In addition, Lb. acidophilus were enumerated and pH was determined. Rheological behavior is an important characteristic for the processing and sensory acceptance of dairy beverages, varying with the presence of additives, fermentation process (time, bacterial strain), and whey concentrations used. All beverages presented minimal counts of 8 log cfu/mL of Lb. acidophilus, and pH ranged from 4.09 to 4.14. Increasing the whey content increased the fragility of the gel structure, probably because of the replacement of casein by whey proteins, once the concentrations of other ingredients in formulation were fixed. Whey content had a significant effect on acceptance of the probiotic dairy beverages; beverages with whey contents greater than 65% resulted in lower acceptance by consumers. The model of mean global acceptance presented 2 solutions with high sensory scores: beverages with 12 and 65% whey, the latter being of interest because it allows greater use of the whey by-product. The Weibull distribution presented a prediction of whey concentration of 49%, with higher sensory acceptance. The methodologies used in this research were shown to be useful in determining the constituents of food formulations, especially for whey-based probiotic beverages. PMID:23102956

  11. Effect of gum tragacanth on rheological and physical properties of a flavored milk drink made with date syrup.

    PubMed

    Keshtkaran, Maryam; Mohammadifar, Mohammad Amin; Asadi, Gholam Hassan; Nejad, Reza Azizi; Balaghi, Sima

    2013-08-01

    Date syrup as a nutritional additive and safe alternative to added sugar is one of the best choices for milk flavoring. In this study, a flavored milk beverage was formulated using date syrup for flavoring the product and gum tragacanth to obtain an acceptable mouth feel. Steady shear and dynamic oscillatory rheological properties of the samples contained 3 concentrations (0, 0.1, 0.2, and 0.3%, wt/wt) of 2 types of gum tragacanth (Astragalus gossypinus and Astragalus rahensis) which at 3°C, were studied. Particle size distribution and colorimetric assays were determined by laser diffractometry and using reflection spectrometer, respectively. Sensory analysis was performed with 25 semitrained panelists, using a 5-point hedonic scale. The results showed that viscoelastic properties, flow behavior parameters, particle size, and color parameters (L*, a*, and b*, where L* represents lightness, a* represents the redness/greenness quality of the color, and b* represents the yellowness and blueness quality of the colors) were significantly affected by the concentration of the gum tragacanth and the severity of this effect was influenced by the type of gum. The use of appropriate type and concentration of gum tragacanth in date milk formulation can improve the texture and mouth feel by affecting on particle size and the flow behavior of this product. PMID:23746580

  12. Rheological, baking, and sensory properties of composite bread dough with breadfruit (Artocarpus communis Forst) and wheat flours.

    PubMed

    Bakare, Adegoke H; Osundahunsi, Oluwatooyin F; Olusanya, Joseph O

    2016-07-01

    The rheological (Pasting, farinograph, and alveograph) properties of wheat flour (WF) replaced with breadfruit four (05-40%) was analyzed. Baking and sensory qualities of the resulting bread were evaluated. Differences in baking properties of loaves produced under laboratory and industrial conditions were analyzed with t-test, whereas ANOVA was used for other analyses. Peak and final viscosities in the composite blends (CB) ranged from 109.20 to 114.06 RVU and 111.86 to 134.40 RVU, respectively. Dough stability decreased from 9.15 to 0.78 min, whereas farinograph water absorption increased 59.7-65.9%. Alveograph curve configuration ratio increased from 1.27 to 7.39, whereas specific volume (Spv) of the loaves decreased from 2.96 to 1.32 cm(3)/g. The Spv of WF loaves were not significantly different (P > 0.05) from that of the 5% CB, whereas production conditions had no significant effects on absorbed water (t = 0.532, df = 18 P = 0.3005), weight loss during baking (t = 0.865, df = 18, P = 0.199), and Spv (t = 0.828, df = 14.17, P = 0.211). The sensory qualities of the 5% blend were not significantly different from the WF. PMID:27386107

  13. Rheological properties of styrene-butadiene rubber filled with electron beam modified surface treated dual phase fillers

    NASA Astrophysics Data System (ADS)

    Shanmugharaj, A. M.; Bhowmick, Anil K.

    2004-01-01

    The rheological properties of styrene-butadiene rubber (SBR) loaded with dual phase filler were measured using Monsanto Processability Tester (MPT) at three different temperatures (100°C, 110°C and 130°C) and four different shear rates (61.3, 306.3, 613, and 1004.5 s -1). The effect of electron beam modification of dual phase filler in absence and presence of trimethylol propane triacrylate (TMPTA) or triethoxysilylpropyltetrasulphide (Si-69) on melt flow properties of SBR was also studied. The viscosity of all the systems decreases with shear rate indicating their pseudoplastic or shear thinning nature. The higher shear viscosity for the SBR loaded with the electron beam modified filler is explained in terms of variation in structure of the filler upon electron beam irradiation. Die swell of the modified filler loaded SBR is slightly higher than that of the unmodified filler loaded rubber, which is explained by calculating normal stress difference for the systems. Activation energy of the modified filler loaded SBR systems is also slightly higher than that of the control filler loaded SBR system.

  14. Impact of particle size distribution on rheological and textural properties of chocolate models with reduced fat content.

    PubMed

    Do, T-A L; Hargreaves, J M; Wolf, B; Hort, J; Mitchell, J R

    2007-11-01

    With an increasing consumption of lipids nowadays, decreasing the fat content in food products has become a trend. Chocolate is a fat-based suspension that contains about 30%wt fat. Reducing fat content causes an increase in the molten chocolate viscosity. This leads to 2 major issues: difficulties in the process and a loss of eating quality in the final product, reported to have poor in-mouth melting properties, remain hard, and difficult to swallow. Literature shows that optimizing the particle size distribution (PSD), that is, having one with an increased packing fraction, can decrease the viscosity of highly concentrated suspensions. This study focuses on the impact of the PSD and fat content on the rheological properties, melting behavior, and hardness of chocolate models (dispersions of sugar in fat). We show that optimizing the PSD while reducing the fat content to a critical amount (22%wt) can decrease the viscosity of the molten material and reduce the hardness of the crystallized chocolate models. Melting in the mouth, characterized by an in vitro collapse speed, is faster for the samples with an optimized PSD. The decrease in the viscosity by optimizing the PSD in systems with a constant fraction of medium phase is based on the decrease of interparticle contact, reducing the particle aggregates strength, and structure buildup during flow or meltdown. In its crystallized state, the particle network is less interconnected, providing less resistance to breakage and meltdown. PMID:18034724

  15. The influence of hydrogen, deformation geometry, and grain size on the rheological properties of olivine at upper mantle conditions

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob A.

    Many important geophysical processes, including mantle convection and the associated movement of Earth's tectonic plates, are strongly dependent upon the rheological properties of Earth's upper mantle. Olivine is the most abundant mineral in the upper mantle and therefore largely controls the mechanical behavior of this region of Earth's interior. Many experimental investigations have been carried out to study the rheological properties of olivine single crystals, synthetically produced aggregates, and naturally occurring mantle rocks at asthenospheric temperatures. In contrast, relatively few studies have focused on measuring the rheological properties of olivine deforming at lithospheric temperatures. Furthermore, there are several unanswered questions about the microphysical processes that control deformation of olivine at upper mantle conditions. One outstanding question in the field of rock and mineral physics is Do different microphysical processes control the rate of deformation of olivine at asthenospheric compared to lithospheric mantle conditions? To address this question we carried out direct shear experiments on olivine single crystals at temperatures that span the transition from lithospheric to asthenospheric mantle conditions. The results of these experiments, which are presented in Chapter 2, demonstrate that the dependence of strain rate upon stress transitions from a power-law relationship at high temperatures to an exponential dependence at lower temperatures. This transition in rheological behavior is consistent with deformation that is controlled by the climb of dislocations at high-temperature conditions and deformation that is controlled by the glide of dislocations at low-temperature conditions. Furthermore, the direct shear geometry allows for isolation of the (001)[100] and (100)[001] dislocation slip systems, which cannot be individually activated in triaxial compression. At high-temperature conditions, crystals oriented for shear on the

  16. Modulation of the rheological and mucoadhesive properties of thermosensitive poloxamer-based hydrogels intended for the rectal administration of quinine.

    PubMed

    Koffi, A A; Agnely, F; Ponchel, G; Grossiord, J L

    2006-03-01

    The aim of this work was to formulate and characterize thermosensitive gels based on poloxamer 407, a thermosensitive polymer, and hydroxypropylmethylcellulose (HPMC), a bioadhesive polymer, intended for the rectal delivery of quinine in children. In order to avoid the macroscopic phase separation between the two polymers it was necessary to add propanediol-1,2. After the formulation of stable ternary systems, their rheological properties were studied as a function of temperature. It was thus possible to obtained the gelation temperature of the systems as well as their elastic modulus, G', at 37 degrees C. It appeared that HPMC in the presence of propanediol-1,2 had a synergistic effect on the gelation of poloxamer 407. Tests on the rabbit rectal mucous membrane, founded on a technique of traction of the adhesive/adhered joint, made it possible to characterize the bioadhesive properties of the gels by measuring the work of adhesion, W, and the maximum detachment force, F(max). Over small concentration ranges of poloxamer and HPMC, very important variations of the viscoelastic and mucoadhesives properties were observed. It was shown that the viscoelastic and the bioadhesive properties were tightly correlated. Indeed, an empirical equivalence relation was established between the shear frequency and the rate of deformation in traction and allowed to describe all our samples by a master curve. This master curve would make it possible to predict the values of W at various rates of traction by the simple non-destructive measurement of the elastic modulus, G', at an equivalent shear frequency. PMID:16356700

  17. The effect of crystal plasticity and mineral stability on the rheological properties of magma during spine extrusion at Unzen, Japan

    NASA Astrophysics Data System (ADS)

    Wallace, Paul A.; Kendrick, Jackie E.; Lavallée, Yan; Ashworth, James D.; Mariani, Elisabetta; von Aulock, Felix W.; Coats, Rebecca; Miwa, Takahiro

    2016-04-01

    The presence of crystals in silicic magmas is known to have a significant effect on the rheological properties inducing a non-Newtonian response. Plastic deformation of the crystalline phase in magmatic suspensions is believed to be partially responsible for this characteristic behaviour via accommodating strain, but little has been investigated on its role in volcanic processes. The spine extrusion following the final stages of endogenous growth of the 1991-95 lava dome eruption at Unzen volcano, Japan, has provided a unique opportunity to investigate the contribution of the different deformation mechanisms and varying petrological phenomena associated with magma ascent. The spine forms a shear zone consisting of four structurally discrete units over a 6 m transect including: gouge (1), a heavily sheared zone (2) to a moderately sheared zone (3), and an undeformed magmatic core (4). Here we report the first systematic study of the microstructures, mineralogy, crystal stability, geochemistry and crystal size distribution across this shear zone. The spine samples are porphyritic dacites with varying abundance of phenocrysts (20-30 vol.%), dominantly plagioclase, hornblende and biotite with minor quartz. The groundmass contains the same mineralogy plus pyroxene, magnetite and ilmenite. The microlites (35 vol.%) show a strong trachytic texture in areas of high shear, providing evidence of strain localisation. Brittle deformation is evident across the spine, with the higher sheared samples showing more crystal size reduction of the phenocrysts. By performing high-temperature (900° C) uniaxial compressive strength tests at constant strain rates (10‑5 and 10‑3 s‑1), it can be inferred that crystals play a key role in the rheological properties, by forming a rigid but weak network that serves to partition stress and thus localise strain within the flowing melt. Electron backscatter diffraction (EBSD) enables the identification of crystal plasticity in both

  18. The effect of binders on the rheological properties and the microstructure formation of lithium-ion battery anode slurries

    NASA Astrophysics Data System (ADS)

    Lim, Sanghyuk; Kim, Sunhyung; Ahn, Kyung Hyun; Lee, Seung Jong

    2015-12-01

    There have been many efforts to enhance the performance and the stability of Li-ion battery. It is crucial to develop a new material as well as to understand the mechanism of microstructure formation of the electrode in order to enhance the performance of the battery. In this study, the effect of sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) on the microstructure formation as well as on the rheological properties in the aqueous anode slurries is investigated. The graphite particles aggregate with each other due to their hydrophobicity and form a gel structure in an aqueous slurry. Both CMC and SBR induce the dispersion of the graphite particles by adsorbing onto the graphite surface. In the graphite/CMC/SBR slurry, the SBR can affect the dispersion of the graphite particles at low CMC concentration, while the microstructure is not changed regardless of added SBR at high CMC concentration because the SBR cannot adsorb on the graphite surface due to the presence of CMC. The microstructure of the slurry is also confirmed by the cryo-SEM images. Understanding the role of the binders on the microstructure formation will be helpful for the effective design of the battery slurries.

  19. Textural and rheological properties of Pacific whiting surimi as affected by nano-scaled fish bone and heating rates.

    PubMed

    Yin, Tao; Park, Jae W

    2015-08-01

    Textural and rheological properties of Pacific whiting (PW) surimi were investigated at various heating rates with the use of nano-scaled fish bone (NFB) and calcium chloride. Addition of NFB and slow heating improved gel strength significantly. Activity of endogenous transglutaminase (ETGase) from PW surimi was markedly induced by both NFB calcium and calcium chloride, showing an optimal temperature at 30°C. Initial storage modulus increased as NFB calcium concentration increased and the same trend was maintained throughout the temperature sweep. Rheograms with temperature sweep at slow heating rate (1°C/min) exhibited two peaks at ∼ 35°C and ∼ 70°C. However, no peak was observed during temperature sweep from 20 to 90°C at fast heating rate (20°C/min). Protein patterns of surimi gels were affected by both heating rate and NFB calcium concentration. Under slow heating, myosin heavy chain intensity decreased with NFB calcium concentration, indicating formation of ε-(γ-glutamyl) lysine cross-links by ETGase and NFB calcium ion. PMID:25766799

  20. The effect of soluble salt in bone ash and other factors on the rheological properties of bone china bodies

    NASA Astrophysics Data System (ADS)

    Cheng, Shifan

    A dynamic stress rheometric technique was developed to determine the plasticity of bone china bodies. In addition, the effect of natural variations of commercial bone ash on the rheology and processability of bone china was examined. The plasticity was then related to the floc characteristics of the body. In carrying out this study the physical and colloidal characteristics of a wide range of commercial bone ash batches were determined. The effect of washing bone ash on the properties of bone ash was also determined. The preparation of bone china body followed accepted industrial processing. The extent of flocculation of the bone china body was determined using the Carmen-Kozeny model for filter pressed cakes. Dynamic mechanical analyses were conducted on all samples using a dynamic stress rheometer using a of parallel plate geometery. Stress sweep analyses were used to determine the linear viscoelastic range for other tests and the loss factor of the sample. Frequency sweep analyses were run to obtain the instantaneous modulus as the measurement of plasticity. Creep test analyses were carried out to find the steady viscosity. Mean relaxation time was calculated out from the measured instantaneous modulus and steady viscosity.

  1. Niosomes and discomes for ocular delivery of naltrexone hydrochloride: morphological, rheological, spreading properties and photo-protective effects.

    PubMed

    Abdelkader, Hamdy; Wu, Zimei; Al-Kassas, Raida; Alany, Raid G

    2012-08-20

    Naltrexone hydrochloride (NTX) is a promising treatment for corneal disorders linked to diabetes mellitus (diabetic keratopathy). However, NTX has a major stability problem due to autoxidation, which is likely to hinder its formulation as eye drops for treatment of diabetic keratopathy. In this study, in-house developed NTX non-ionic surfactant vesicles (niosomes and discomes) were evaluated for their spreading, rheological properties and their ability to impede the inevitable autoxidation of NTX in aqueous solutions. The measured contact angles and spreading coefficients for niosomes reflected significantly (P<0.05) better wetting and spreading abilities than the aqueous vehicle. The prepared niosomes were significantly more viscous (P<0.05) than the aqueous solution. The lipid content, size and composition of niosomes are the main factors affecting the viscosity of niosomal dispersions. Exposure of NTX solution to artificial daylight illumination (10,000 lux) can produce extensive degradation of NTX due to oxidation. The prepared formulations were able to significantly (P<0.05) protect the encapsulated NTX from the photo-induced oxidation compared with free NTX solutions. The investigated niosomes lend themselves as a potential ocular delivery modality for NTX. PMID:22595640

  2. Porous gravity currents: A survey to determine the joint influence of fluid rheology and variations of medium properties

    NASA Astrophysics Data System (ADS)

    Ciriello, Valentina; Longo, Sandro; Chiapponi, Luca; Di Federico, Vittorio

    2016-06-01

    We develop a model to grasp the combined effect of rheology and spatial stratifications on two-dimensional non-Newtonian gravity-driven flow in porous media. We consider a power-law constitutive equation for the fluid, and a monomial variation of permeability and porosity along the vertical direction (transverse to the flow) or horizontal direction (parallel to the flow). Under these assumptions, similarity solutions are derived in semi-analytical form for thin gravity currents injected into a two-dimensional porous medium and having constant or time-varying volume. The extent and shape of the porous domain affected by the injection is significantly influenced by the interplay of model parameters. These describe the fluid (flow behaviour index n), the spatial heterogeneity (coefficients β, γ, δ, ω for variations of permeability and porosity in the horizontal or vertical direction), and the type of release (volume exponent α). Theoretical results are validated against two sets of experiments with α = 1 (constant inflow) conducted with a stratified porous medium (simulated by superimposing layers of glass beads of different diameter) and a Hele-Shaw analogue for power-law fluid flow, respectively. In the latter case, a recently established Hele-Shaw analogy is extended to the variation of properties parallel to the flow direction. Comparison with experimental results shows that the proposed model is able to capture the propagation of the current front and the current profile.

  3. Investigation into the physicochemical stability and rheological properties of beta-carotene emulsion stabilized by soybean soluble polysaccharides and chitosan.

    PubMed

    Hou, Zhanqun; Gao, Yanxiang; Yuan, Fang; Liu, Yuwei; Li, Chunlin; Xu, Duoxia

    2010-08-11

    In this study, the possibility of producing stable O/W emulsions incorporating beta-carotene in oil droplets surrounded by multiple-layer interfacial membranes has been demonstrated. Emulsions were prepared using a two-stage process by homogenization, which relied on the adsorption of chitosan to anionic droplets coated with soybean soluble polysaccharides (SSPS). Results showed that the zeta-potential, particle size, and rheological properties of emulsions were greatly dependent on the chitosan concentration. The electrical charge on the droplets increased from -34 to 58.2 mV as the chitosan concentration was increased from 0 to 2 wt %, which indicated that chitosan adsorbed to the droplet surfaces. The mean particle diameter of the emulsions increased dramatically with the rise of chitosan concentration from 0 to 0.33 wt %, indicating the formation of large aggregated structures. At chitosan concentrations above 0.33 wt %, the mean particle diameter of emulsions decreased and reached a minimum value of 0.79 mum at a chitosan concentration of 0.5 wt %. Dynamic oscillatory shear tests indicated that the viscoelastic behavior could be enhanced by the adsorption of chitosan onto the SSPS-coated droplet surfaces. Chitosan concentration had a significant (p < 0.05) impact on the stability of beta-carotene. The least degradation occurred in the emulsion with chitosan concentration of 0.5%. These results implied that the physicochemical stability of beta-carotene emulsions has been improved by the adsorption of chitosan. PMID:20681649

  4. Effect of gamma irradiation on the thermal and rheological properties of grain amaranth starch

    NASA Astrophysics Data System (ADS)

    Kong, Xiangli; Kasapis, Stefan; Bao, Jinsong; Corke, Harold

    2009-11-01

    Physical properties of starch from two cultivars of gamma-irradiated grain amaranth with different amylose content were investigated. Pasting viscosities decreased continuously with the increase in dosages of irradiation. Furthermore, different irradiation dosages resulted in modification of the thermal properties and crystallinity of starch. Dynamic oscillation on shear was also employed, temperature and frequency sweeps showed that changes in storage modulus and loss modulus were significant, with Tibet Yellow producing more elastic gels as compared to Hy030 at different irradiation dosages.

  5. Rheology of aqueous foams

    NASA Astrophysics Data System (ADS)

    Dollet, Benjamin; Raufaste, Christophe

    2014-10-01

    Aqueous foams are suspensions of bubbles inside aqueous phases. Their multiphasic composition leads to a complex rheological behavior that is useful in numerous applications, from oil recovery to food/cosmetic processing. Their structure is very similar to the one of emulsions, so that both materials share common mechanical properties. In particular, the presence of surfactants at the gas-liquid interfaces leads to peculiar interfacial and dissipative properties. Foam rheology has been an active research topics and is already reported in several reviews, most of them covering rheometry measurements at the scale of the foam, coupled with interpretations at the local scale of bubbles or interfaces. In this review, we start following this approach, then we try to cover the multiscale features of aqueous foam flows, emphasizing regimes where intermediate length scales need to be taken into account or regimes fast enough regarding internal time scales so that the flow goes beyond the quasi-static limit. xml:lang="fr"

  6. A Theoretical Study of some Rheological Properties of the Aggregation of the Molecules Deoxy- Hemoglobin S

    NASA Astrophysics Data System (ADS)

    Mensah, Francis; Grant, Julius; Thorpe, Arthur

    2010-02-01

    Sickle cell disease is a serious public health problem that affects many people worldwide. In this paper, the Langevin equation is used for hemoglobin's aggregation in sickle cell anemia. Several parameters are explored such as the time-dependent deformation of the aggregates whose plot gives a sigmoid, the time-dependent expressions obtained for the coefficient of viscosity and the elastic modulus which characterize the aggregation of the sickle hemoglobin. Other properties such as the viscoelastic and the elasto-thixotropic properties of the sickle hemoglobin polymer are also described. An attempt is made to approach the polymerization process in terms of a dynamical system. )

  7. Rheological properties of mudflows associated with the spring 1980 eruptions of Mount St. Helens volcano, Washington

    SciTech Connect

    Fink, J.H.; Malin, M.C.; D'Alli, R.E.; Greeley, R.

    1981-01-01

    Rhelogoical properties of three recent mudflows at Mount St. Helens were estimated using technique developed for deterimining the properties of debris flows based on the geometry of their deposits. Calculated yield strengths of 1100, 1000, and 400 Pa, maximum flow velocities of 10 to 31 m/s, volumetric flow rates of 300 to 3400 m/sup 3//s, and plastic viscosities of 20 to 320 Ps-s all compare favorably with measured and estimated values cited in the literature. A method for determining likely sites of future mudflow initiation based on these data is outlined.

  8. Rheological Model and Mechanical Properties of Hard Nanocoatings in Numerical Nanoindentation Test

    NASA Astrophysics Data System (ADS)

    Kopernik, M.; Pietrzyk, M.

    2007-04-01

    The objective of the work is development of the method, which is based on inverse analysis principles, and which allows determination of material model for lower material layer in the hard nanocoatings system. Hardness of such a system is additionally calculated in the paper. Design of block diagram of inverse analysis for the identification of mechanical properties of hard nanocoating is the main part of the solution. The method for the identification of mechanical properties of the layers is described in detail. Results of calculations are presented and discussed.

  9. Effect of hydrostatic high-pressure processing on the chemical, functional, and rheological properties of starter-free Queso Fresco.

    PubMed

    Van Hekken, D L; Tunick, M H; Farkye, N Y; Tomasula, P M

    2013-10-01

    Queso Fresco (QF), a popular high-moisture, high-pH Hispanic-style cheese sold in the United States, underwent high-pressure processing (HPP), which has the potential to improve the safety of cheese, to determine the effects of this process on quality traits of the cheese. Starter-free, rennet-set QF (manufactured from pasteurized, homogenized milk, milled before hooping, and not pressed) was cut into 4.5- × 4.5- × 15-cm blocks and double vacuum packaged. Phase 1 of the research examined the effects of hydrostatic HPP on the quality traits of fresh QF that had been warmed to a core temperature of 20 or 40 °C; processed at 200, 400, or 600 MPa for 5, 10, or 20 min; and stored at 4 °C for 6 to 8d. Phase 2 examined the long-term effects of HPP on quality traits when QF was treated at 600 MPa for 3 or 10 min, and stored at 4 or 10 °C for up to 12 wk. Warming the QF to 40 °C before packaging and exposure to high pressure resulted in loss of free whey from the cheese into the package, lower moisture content, and harder cheese. In phase 2, the control QF, regardless of aging temperature, was significantly softer than HPP cheeses over the 12 wk of storage. Hardness, fracture stress, and fracture rigidity increased with length of exposure time and storage temperature, with minor changes in the other properties. Queso Fresco remained a bright white, weak-bodied cheese that crumbled and did not melt upon heating. Although high pressures or long processing times may be required for the elimination of pathogens, cheese producers must be aware that HPP altered the rheological properties of QF and caused wheying-off in cheeses not pressed before packaging. PMID:23972497

  10. Effects of multi-walled carbon nanotubes on rheological and physical properties of polyamide-based thermoplastic elastomers

    NASA Astrophysics Data System (ADS)

    Bae, Won-Sik; Kwon, Oh Joo; Kim, Byoung Chul; Chae, Dong Wook

    2012-09-01

    The polyamide-based thermoplastic elastomers (Pebax®) were melt compounded with multi-walled carbon nanotubes (MWNTs: 0.25˜5 wt%) and the variation of rheological and physical properties with MWNT contents was investigated. The crystallization temperature (Tc) of the nanocomposites with 0.5 wt% MWNTs was most increased by ca. 8oC, but it was decreased by further addition. In addition, the presence of MWNTs broadened the Tc peak with increasing nanotube contents. In contrast, the melting behavior was little influenced by the presence of MWNTs for all compositions. The incorporation of MWNTs increased the complex viscosity with MWNT contents and the abrupt increase was observed from 1 wt%. In addition, lower Newtonian flow region became disappearing with increasing MWNT contents, exhibiting notable shear thinning behavior from 1 wt% loading. Storage modulus was increased with MWNT contents in a similar manner to viscosity. Casson plot demonstrated a non-zero positive intercept for all the samples. In particular, the abrupt increase of yield stress was observed from 1 wt% loading. In the Cole-Cole plot, the nanocomposites gave a deviated curve from pure Pebax and the slope was decreased with increasing MWNT contents. The relaxation time calculated from viscoelastic parameters was increased with nanotube contents, but the increasing extents were reduced with increasing frequency. From 2 wt% MWNTs, the electrical conductivity was observed, indicating that the electrical percolation existed between 1.5 and 2 wt%. At 0.25 wt% loading the tensile strength was slightly increased, but it was gradually decreased by further addition. The introduction of MWNTs increased the tensile modulus with nanotube contents. In addition, ductile properties were reduced with increasing MWNT contents, resulting in low toughness.

  11. Polyesters Based on Linoleic Acid for Biolubricant Basestocks: Low-Temperature, Tribological and Rheological Properties

    PubMed Central

    Abdullah, Bashar Mudhaffar; Zubairi, Saiful Irwan; Huri, Hasniza Zaman; Hairunisa, Nany; Yousif, Emad; Basu, Roma Choudhury

    2016-01-01

    Presently, plant oils which contain high percentage of linoleic acid 1 are perceived to be a viable alternative to mineral oil for biolubricant applications due to their biodegradability and technical properties. In order to get biodegradable lubricant, triester derivatives compounds (1–5) were synthesized and characterized. The processes involved were monoepoxidation of linoleic acid 2, oxirane ring opening 3, esterification 4 and acylation 5. The structures of the products were confirmed by FTIR, 1H and 13C-NMR and LC-MS. The results that showed lowest temperature properties were obtained for triester 5, with a pour point value (PP) of -73°C, highest onset temperature (260°C) and lowest volatility at 0.30%. Viscosity index (VI) increased for the ester’s synthetic compounds (2, 3, 4, 5), while the PP decreased. This behavior is the result of the increase of the chain length of the branching agents. Triester based linoleic acid has improved properties such as low-temperature and tribological properties. These results will make it feasible for plant oil to be used for biolubricants, fuels in chain saws, transmission oil and brake fluid. PMID:27008312

  12. Rheological properties of a biological thermo-responsive hydrogel prepared from vegetable oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydrogel is a colloidal gel in which water is the dispersion medium. The unique properties of hydrogels make this kind of materials have many utilization potentials, such as drug delivery, gene therapy, wound care products, breast implant materials, cosmetic products, and tissue engineering. Hydroge...

  13. Influence of Deacetylation on the Rheological Properties of Xanthan-Guar Interactions in Dilute Aqueous Solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An oscillating capillary rheometer was used to investigate the effects of xanthan deacetylation on the viscoelastic properties and intrinsic viscosity of xanthan and guar mixtures in dilute aqueous solutions. Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xan...

  14. Polyesters Based on Linoleic Acid for Biolubricant Basestocks: Low-Temperature, Tribological and Rheological Properties.

    PubMed

    Abdullah, Bashar Mudhaffar; Zubairi, Saiful Irwan; Huri, Hasniza Zaman; Hairunisa, Nany; Yousif, Emad; Basu, Roma Choudhury

    2016-01-01

    Presently, plant oils which contain high percentage of linoleic acid 1 are perceived to be a viable alternative to mineral oil for biolubricant applications due to their biodegradability and technical properties. In order to get biodegradable lubricant, triester derivatives compounds (1-5) were synthesized and characterized. The processes involved were monoepoxidation of linoleic acid 2, oxirane ring opening 3, esterification 4 and acylation 5. The structures of the products were confirmed by FTIR, 1H and 13C-NMR and LC-MS. The results that showed lowest temperature properties were obtained for triester 5, with a pour point value (PP) of -73°C, highest onset temperature (260°C) and lowest volatility at 0.30%. Viscosity index (VI) increased for the ester's synthetic compounds (2, 3, 4, 5), while the PP decreased. This behavior is the result of the increase of the chain length of the branching agents. Triester based linoleic acid has improved properties such as low-temperature and tribological properties. These results will make it feasible for plant oil to be used for biolubricants, fuels in chain saws, transmission oil and brake fluid. PMID:27008312

  15. Rheology of emulsions.

    PubMed

    Derkach, Svetlana R

    2009-10-30

    The review is devoted to the historical and modern understanding of rheological properties of emulsions in a broad range of concentration. In the limiting case of dilute emulsions, the discussion is based on the analogy and differences in properties of suspensions and emulsions. For concentrated emulsions, the main peculiarities of their rheological behaviour are considered. Different approaches to understand the concentration dependencies of viscosity are presented and compared. The effects of non-Newtonian flow curves and the apparent transition to yielding with increasing concentration of the dispersed phase are discussed. The problem of droplet deformation in shear fields is touched. The highly concentrated emulsions (beyond the limit of closest packing of spherical particles) are treated as visco-plastic media, and the principle features of their rheology (elasticity, yielding, concentration and droplet size dependencies) are considered. A special attention is paid to the problem of shear stability of drops of an internal phase starting from the theory of the single drop behaviour, including approaches for the estimation of drops' stability in concentrated emulsions. Polymer blends are also treated as emulsions, though taking into account their peculiarities due to the coexistence of two interpenetrated phases. Different theoretical models of deformation of polymer drops were discussed bearing in mind the central goal of predictions of the visco-elastic properties of emulsions as functions of the properties of individual components and the interfacial layer. The role of surfactants is discussed from the point of view of stability of emulsions in time and their special influence on the rheology of emulsions. PMID:19683219

  16. Physical Property and Rheological Testing of Actual Transuranic Waste from Hanford Single-Shell Tanks

    SciTech Connect

    Tingey, Joel M. ); Gao, Johnway ); Delegard, Calvin H. ); Bagaasen, Larry M. ); Wells, Beric E. )

    2003-08-25

    Composites of sludge from Hanford tanks 241-B-203 (B-203), 241-T-203 (T-203), 241-T-204 (T-204), and 241-T-110 (T-110) were prepared at the Hanford 222-S Laboratory and transferred to the Radiochemical Processing Laboratory at the Pacific Northwest National Laboratory (PNNL) for measurement of the composites' physical properties. These tank composites were prepared from core samples retieved from these tanks. These core samples may not be representative of the entire contents of the tank but provide some indication of the properties of the waste in these underground storage tanks. Dilutions in water were prepared from the composite samples. The measurements included paint filter tests, viscosity, shear strength, settling and centrifuging behavior, a qualitative test of stickiness, total solids concentration, and extrusion tests to estimate shear strength.

  17. [Rheologic properties of some pharmaceutical excipients in drug forms and cosmetic preparation technology].

    PubMed

    Tsagareishvili, G V; Bashura, A A; Alekseeva, M A; Bashura, G S

    2012-06-01

    The establishment of mechanisms and principles of the formation of deformation (fracture) of spatial structure of bentonite solutions and various solutions and disperse systems is one or the most important problems of modern pharmaceutical technology. The article presents the results of a long-term research of influence of high-molecular compounds and surfactants on the properties of designed dosage drug forms and cosmetic preparation. Research data, as the basis for drug combinations "gel" with dekamitoksin, extract Aesculus hippocastanum L and probiotics. PMID:22859452

  18. Rheological properties, shape oscillations, and coalescence of liquid drops with surfactants

    NASA Technical Reports Server (NTRS)

    Apfel, R. E.; Holt, R. G.

    1990-01-01

    A method was developed to deduce dynamic interfacial properties of liquid drops. The method involves measuring the frequency and damping of free quadrupole oscillations of an acoustically levitated drop. Experimental results from pure liquid-liquid systems agree well with theoretical predictions. Additionally, the effects of surfactants is considered. Extension of these results to a proposed microgravity experiment on the drop physics module (DPM) in USML-1 are discussed. Efforts are also underway to model the time history of the thickness of the fluid layer between two pre-coalescence drops, and to measure the film thickness experimentally. Preliminary results will be reported, along with plans for coalescence experiments proposed for USML-1.

  19. Effect of Porcine Collagen Peptides on the Rheological and Sensory Properties of Ice Cream.

    PubMed

    Li, Liying; Kim, Jae-Hyeong; Jo, Yeon-Ji; Min, Sang-Gi; Chun, Ji-Yeon

    2015-01-01

    The effects of low molecular-weight collagen peptides derived from porcine skin were investigated on the physicochemical and sensorial properties of chocolate ice cream. Collagen peptides less than 1 kDa in weight were obtained by sub-critical water hydrolysis at a temperature of 300℃ and a pressure of 80 bar. Ice cream was then prepared with gelatin powder and porcine skin hydrolysate (PSH) stabilizers mixed at seven different ratios (for a total of 0.5 wt%). There was no significant difference in color between the resulting ice cream mixtures. The increase in apparent viscosity and shear thinning of the ice cream was more moderate with PSH added than with gelatin. Moreover, the samples containing more than 0.2 wt% PSH had enhanced melting resistance, while the mixture with 0.2 wt% PSH had the lowest storage modulus at -20℃ and the second highest loss modulus at 10℃, indicating that this combination of hydrocolloids leads to relatively softer and creamier chocolate ice cream. Among the seven types of ice creams tested, the mixture with 0.2 wt% PSH and 0.3 wt% gelatin had the best physicochemical properties. However, in sensory evaluations, the samples containing PSH had lower chocolate flavor scores and higher off-flavor scores than the sample prepared with just 0.5 wt% gelatin due to the strong off-flavor of PSH. PMID:26761823

  20. Effect of molecular characteristics of Konjac glucomannan on gelling and rheological properties of Tilapia myofibrillar protein.

    PubMed

    Jian, Wenjie; Wu, Huayi; Wu, Lanlan; Wu, Yunhui; Jia, Lina; Pang, Jie; Sun, Yuan-Ming

    2016-10-01

    Konjac glucomannan (KGM) is an important gelling agent in composite gels. This study aimed to investigate the effects of KGM molecular characteristics (molecular weight, size and conformation) on gelling properties of Tilapia myofibrillar protein (TMP). In this work, TMP composite gels were prepared under neutral pH with varying KGM (native KGM, 10kGy-KGM, 20kGy-KGM, and 100kGy-KGM) of different molecular characteristics. Native KGM, 10kGy-KGM, and 20kGy-KGM exerted negative effect on gel strength or whiteness of TMP gels. Interestingly 100kGy-KGM improved gelling properties and whiteness of TMP gels. Such effects presented by varying KGM were attributed the physical filling behaviors and the interaction between KGM and TMP. These behaviors or interactions are resulted from different molecular size and conformation. Smaller molecular size (root-mean square radius, Rz 20.2nm) and approximated spherical conformation in 100kGy-KGM enhanced its interaction with TMP and maintained its compact and smooth structure, but the larger molecular size (Rz≥40.2nm) and random coil conformation in other KGMs inhibited part of actins from gelling and deteriorated the network structure. Our study provided principle knowledge to understand the structure-functions relationships of KGM-TMP composite gels. These results can be used to provide theoretical guidance for surimi gel processing. PMID:27312609

  1. Thermal, Morphological and Rheological Properties of Rigid Polyurethane Foams as Thermal Insulating Materials

    SciTech Connect

    Kim, Ji Mun; Han, Mi Sun; Kim, Youn Hee; Kim, Woo Nyon

    2008-07-07

    The polyurethane foams (PUFs) were prepared by polyether polyols, polymeric 4,4'-diphenylmethane diisocyanate (PMDI), silicone surfactants, amine catalysts and cyclopentane as a blowing agent. Solid and liquid type fillers were used as a nucleating agent to decrease a cell size of the PUFs as well as improve the thermal insulating properties of the PUFs. The PUFs were prepared by adding solid and liquid type fillers in the range of 1 to 3 wt%. For the liquid type fillers, the cell size of the PUFs showed minimum and found to decrease compared the PUF without adding fillers. Also, thermal conductivity of the PUFs with adding fillers showed minimum. For the solid type fillers, cell size and thermal conductivity of the PUFs were observed to decrease with the filler content up to 3 wt%. From these results, it is suggested that the thermal insulating property of the PUFs can be improved by adding fillers as a nucleating agent. Also, storage and loss modulus of the PUFs will be presented to study gelling points of the PUFs.

  2. Effect of Porcine Collagen Peptides on the Rheological and Sensory Properties of Ice Cream

    PubMed Central

    2015-01-01

    The effects of low molecular-weight collagen peptides derived from porcine skin were investigated on the physicochemical and sensorial properties of chocolate ice cream. Collagen peptides less than 1 kDa in weight were obtained by sub-critical water hydrolysis at a temperature of 300℃ and a pressure of 80 bar. Ice cream was then prepared with gelatin powder and porcine skin hydrolysate (PSH) stabilizers mixed at seven different ratios (for a total of 0.5 wt%). There was no significant difference in color between the resulting ice cream mixtures. The increase in apparent viscosity and shear thinning of the ice cream was more moderate with PSH added than with gelatin. Moreover, the samples containing more than 0.2 wt% PSH had enhanced melting resistance, while the mixture with 0.2 wt% PSH had the lowest storage modulus at -20℃ and the second highest loss modulus at 10℃, indicating that this combination of hydrocolloids leads to relatively softer and creamier chocolate ice cream. Among the seven types of ice creams tested, the mixture with 0.2 wt% PSH and 0.3 wt% gelatin had the best physicochemical properties. However, in sensory evaluations, the samples containing PSH had lower chocolate flavor scores and higher off-flavor scores than the sample prepared with just 0.5 wt% gelatin due to the strong off-flavor of PSH. PMID:26761823

  3. Effect of coated and uncoated ground flaxseed addition on rheological, physical and sensory properties of Taftoon bread.

    PubMed

    Roozegar, M H; Shahedi, M; Keramet, J; Hamdami, N; Roshanak, S

    2015-08-01

    Flaxseed is used to fortify bread. In order to reduce cyanogenic glycosides compounds of flaxseed, ground flaxseed was incubated at 30 °C and heated in a kitchen microwave oven. The cyanogenic compounds of flaxseed were reduced to 13.4 %. Treated ground flaxseed was coated with Arabic gum solution containing ascorbic acid and hydrogenated fat and was stored at 25 °C for 80 days in order to prevent oxidation of flaxseed oil. Results showed that oxidation in coated samples was lower than that in control samples and that there was a significant difference between them (p < 0.01). Coated and uncoated ground flaxseed was added to wheat flour in 5, 15 and 25 % levels in order to produce fortified Taftoon bread. Rheological, physical and organoleptic tests were carried out in order to evaluate dough and bread properties. Results showed that with increasing coated and uncoated ground flaxseed percentages, a decrease in water absorption and an increase in stability, dough development and relaxation time of dough occurred. The lowest water absorption was observed by adding 25 % coated ground flaxseed with hydrogenated fat. The highest dough development and dough stability time were observed by adding 25 % coated ground flaxseed with Arabic gum. Results indicated that coated and uncoated ground flaxseed has a good effect on decreasing the staling rate compared to the control bread. Results of organoleptic test showed that bread with 5 and 15 % coated and uncoated ground flaxseed had better acceptability. PMID:26243931

  4. Mechano-rheological properties of the murine thrombus determined via nanoindentation and finite element modeling.

    PubMed

    Slaboch, Constance L; Alber, Mark S; Rosen, Elliot D; Ovaert, Timothy C

    2012-06-01

    Deep vein thrombosis, pulmonary embolism, and abdominal aortic aneurysms are blood-related diseases that represent a major public health problem. These diseases are characterized by the formation of a thrombus (i.e., blood clot) that either blocks a major artery or causes an aortic rupture. Identifying the mechanical properties of thrombi can help determine when these incidents will occur. In this investigation, a murine thrombus, formed from platelet-rich plasma, calcium, and thrombin, was nanoindented and the elastic modulus was estimated via elastic contact theory. This information was used as input to an inverse finite element simulation, which determined optimal values for the elastic modulus and viscosity of the thrombus using a viscoelastic material model. A sensitivity analysis was also performed to determine which material parameters have the greatest affect on the simulation. Results from this investigation demonstrate the feasibility of the mechanical characterization of a murine thrombus using nanoindentation. PMID:22520420

  5. Alkali and Acid Solubilization Effects on Rheological Properties of Horse Mackerel Muscle Proteins

    NASA Astrophysics Data System (ADS)

    Campo-Deaño, L.; Tovar, C. A.

    2008-07-01

    Influence of the acid (Type A) and alkali (Type B) solubilization of muscle proteins in the viscoelastic properties of surimi and surimi gels made from horse mackerel (Trachurus trachurus) muscle were evaluated. Stress and frequency sweep tests showed that surimi from method B presents higher viscoelastic moduli, lowest values of phase angle and minimum viscoelastic moduli dependence with frequency than surimi A. These results show a high inicial protein aggregation in surimi B, that could explain the greater firmness and hardness of this sample, showing a more compact network structure. From static and dynamic tests, gel developed from alkali solubilization resulted in higher gel strength and more rigid network than that from acidic pH, despite the incial protein aggregation of surimi B its protein keeps better gelation capacity. The less structural quality of GA gel is likely due to the more lipid content on the surimi as compared to alkali treatment.

  6. Thermodynamic and rheological properties of solid-liquid systems in coal processing. Final technical report

    SciTech Connect

    Kabadi, V.N.

    1995-06-30

    The work on this project was initiated on September 1, 1991. The project consisted of two different tasks: (1) Development of a model to compute viscosities of coal derived liquids, and (2) Investigate new models for estimation of thermodynamic properties of solid and liquid compounds of the type that exist in coal, or are encountered during coal processing. As for task 1, a model for viscosity computation of coal model compound liquids and coal derived liquids has been developed. The detailed model is presented in this report. Two papers, the first describing the pure liquid model and the second one discussing the application to coal derived liquids, are expected to be published in Energy & Fuels shortly. Marginal progress is reported on task 2. Literature review for this work included compilation of a number of data sets, critical investigation of data measurement techniques available in the literature, investigation of models for liquid and solid phase thermodynamic computations. During the preliminary stages it was discovered that for development of a liquid or solid state equation of state, accurate predictive models for a number of saturation properties, such as, liquid and solid vapor pressures, saturated liquid and solid volumes, heat capacities of liquids and solids at saturation, etc. Most the remaining time on this task was spent in developing predictive correlations for vapor pressures and saturated liquid volumes of organic liquids in general and coal model liquids in particular. All these developments are discussed in this report. Some recommendations for future direction of research in this area are also listed.

  7. Surface rheology and foaming properties of sodium oleate and C12(EO)6 aqueous solutions.

    PubMed

    Beneventi, Davide; Pugh, Robert J; Carré, Bruno; Gandini, Alessandro

    2003-12-01

    The dynamic surface tension (DST) and the surface viscoelastic modulus of sodium oleate aqueous solutions at different concentrations were measured using an image analysis tensiometer based on the oscillating bubble technique. The diffusion coefficient of oleate moieties was calculated from DST measurements and the surface viscoelastic modulus using the Langmuir-Szyszkowski and the diffusion-controlled adsorption models. The viscoelastic moduli obtained from model calculations were compared with the corresponding experimental values. The diffusion coefficient of C(12)(EO)(6) in water and the parameters of the Langmuir-Szyszkowski adsorption isotherm were taken from the literature and used to calculate the surface viscoelastic modulus of its aqueous solutions at different concentrations. The foaming properties of both C(12)(EO)(6) and sodium oleate solutions, viz., the foam conductance and the water volume fraction in the foam, were measured using a commercial Foamscan device. Foaming experiments with C(12)(EO)(6) and sodium oleate solutions were carried out either under static conditions; i.e., the foam conductance and the water volume fraction were measured as a function of time after the generation of a fixed volume of foam, or under dynamic conditions; i.e., the foam conductance and the water volume fraction were measured during foam formation. The variations in the foam permeability as a function of surfactant concentration were related to the viscoelastic properties of the air/water interface and to the presence of micelles in the foam films. With foams in which the water volume fraction was higher than 0.05, the foam electrical conduction could be described using a simple parallel resistor model and their conductance measurements were related to the foam water volume fraction. The results related to water drainage under static conditions were used to interpret water drainage under dynamic conditions. Preliminary conjectures on the influence of foam

  8. Rheological properties of bi-dispersed magnetorheological fluids based on plate-like iron particles with application to a small-sized damper

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Xuan Phu, Do; Choi, Seung-Bok

    2014-05-01

    In this study, the rheological properties and an application of bi-dispersed magnetorheological fluid (MRF) based on plate-like iron particles are experimentally investigated. A bi-dispersed MR Fluid is prepared using two different micron-scale sizes of plate-like iron particles. In the absence of a magnetic field, the properties of the fluid are isotropic. Upon the application of a magnetic field, the magnetized particles form a chain aligned in the direction of the field, which promotes the appearance of a yield stress. The reversible transition from solid to liquid is the basic requirement of MR applications. Due to the anisotropy in the shape and formation of a less compact structure in the iron plate-like particles, weak sedimentation and good redispersibility of the proposed MR fluid are created. The physical properties of the proposed MR fluids are evaluated and applied to the design of a small-sized controllable MR vibration damper, which can be used for vibration control of a washing machine. The MR damper is a semi-active device that dissipates energy during vibration motion to increase the stability of the application system. Three different weight fractions of the bi-dispersed MR fluids are prepared, and their rheological properties are presented and discussed. Based on their rheological properties, the figures of merit of the proposed MR fluids are derived. A comparison of these figures of merit gives the nominal behavior of the MR fluids, which are important in the design of the application device. A stability test is also performed to check the settling rate of MR fluids per day. The change in damping force due to the problem of particles settling in the MRF and the field-dependent damping force are measured with the MR damper operated just after filling the MRF and with the MR damper operated after waiting for 48 h after filling. With basic rheological properties and outstanding mechanical properties, it is clearly demonstrated that the proposed MR

  9. Graphene networks and their influence on free-volume properties of graphene-epoxidized natural rubber composites with a segregated structure: rheological and positron annihilation studies.

    PubMed

    He, Canzhong; She, Xiaodong; Peng, Zheng; Zhong, Jieping; Liao, Shuangquan; Gong, Wei; Liao, Jianhe; Kong, Lingxue

    2015-05-14

    Epoxidized natural rubber-graphene (ENR-GE) composites with segregated GE networks were successfully fabricated using the latex mixing combined in situ reduced technology. The rheological behavior and electrical conductivity of ENR-GE composites were investigated. At low frequencies, the storage modulus (G') became frequency-independent suggesting a solid-like rheological behavior and the formation of GE networks. According to the percolation theory, the rheological threshold of ENR-GE composites was calculated to be 0.17 vol%, which was lower than the electrical threshold of 0.23 vol%. Both percolation thresholds depended on the evolution of the GE networks in the composites. At low GE concentrations (<0.17 vol%), GE existed as individual units, while a "polymer-bridged GE network" was constructed in the composites when GE concentrations exceeded 0.17 vol%. Finally, a "three-dimensional GE network" with percolation conductive paths was formed with a GE concentration of 0.23 vol%, where a remarkable increase in the conductivity of ENR-GE composites was observed. The effect of GE on the atom scale free-volume properties of composites was further studied by positron annihilation lifetime spectroscopy and positron age momentum correlation measurements. The motion of ENR chains was retarded by the geometric confinement of "GE networks", producing a high-density interfacial region in the vicinity of GE nanoplatelets, which led to a lower ortho-positronium lifetime intensity and smaller free-volume hole size. PMID:25881784

  10. The effect of polymer-surfactant interaction on the rheological properties of surfactant enhanced alkaline flooding formulations. [Phase separation, precipitation and viscosity loss

    SciTech Connect

    French, T.R.; Josephson, C.B.

    1993-02-01

    Surfactant-enhanced, lower pH (weak) alkaline chemicals are effective for mobilizing residual oil. Polymer is used for mobility control because if mobility control is lost, then oil recovery is reduced. The ability to maintain mobility control during surfactant-alkaline flooding can be adversely affected by chemical interaction. In this work, interaction between polymers and surfactants was shown to be affected by pH, ionic strength, crude oil, and the properties of the polymers and surfactants. Polymer-surfactant interaction (phase separation, precipitation, and viscosity loss) occurred between most of the polymers and surfactants that were tested. Polymer-surfactant interaction is difficult to eliminate, and no method was found for completely eliminating interaction. Polymer-surfactant interaction occurred at optimal salinity and below optimal salinity. Polymer-surfactant interaction had an adverse effect on polymer rheology; however, the adverse effect of interaction on polymer rheology was lessened when oil was present. Increasing the pH of chemical systems further reduced the adverse effects of interaction on polymer rheology.

  11. Probing of field-induced structures and tunable rheological properties of surfactant capped magnetically polarizable nanofluids.

    PubMed

    Felicia, Leona J; Philip, John

    2013-01-01

    Oil-based nanofluid containing surfactant-capped magnetite nanoparticles are synthesized by a simple coprecipitation approach, and their magnetorheological properties are studied for different magnetic field strengths and volume fractions. We observe a distinct "plateau-like region" in the shear thinning viscosity curve, under an external magnetic field, possibly due to a peculiar alignment of the chains with respect to the field direction where the structure is stable against fragmentation. The observed plateau regime is reminiscent to that of kinetically arrested gel networks. Interestingly, such a plateau regime has been observed only above certain critical magnetic field when the dipolar interaction strength is much greater than the thermal energy where the aggregation becomes a nonequilibrium transport-limited process. The good collapse of specific viscosity data against Mason number for different magnetic field strengths onto a single curve suggests the dominance of hydrodynamic and magnetic forces on thermal force above a certain magnetic field strength. The observed increase in both static and dynamic yield stresses under the magnetic field confirms the formation of columnar structures that hinder the flow behavior. The hysteresis observed in the magnetic sweep experiments shows the inability of the chains to relax within the measurement time. The dynamic measurements confirm that the field-induced structures impart elastic behavior to the dispersion, which is found to increase with magnetic field and saturates at higher field strengths. PMID:23210900

  12. Amaranth proteins foaming properties: Film rheology and foam stability - Part 2.

    PubMed

    Bolontrade, Agustín J; Scilingo, Adriana A; Añón, María C

    2016-05-01

    In this work the influence of pH and ionic strength on the stability of foams prepared with amaranth protein isolate was analyzed. The behaviour observed was related to the physico-chemical and structural changes undergone by amaranth protein as a result of those treatments. The results obtained show that foams prepared at acidic pH were more stable than the corresponding to alkaline pH. At pH 2.0 the foams presented higher times and more volumes of drainage. This behaviour is consistent with the characteristics of the interfacial film, which showed a higher viscoelasticity and a greater flexibility at acidic pH than alkaline pH value, which in turn increased by increasing the concentration of proteins in the foaming solution. It is also important to note that the presence of insoluble protein is not necessarily detrimental to the properties of the foam. Detected changes in the characteristics of the interfacial film as in the foam stability have been attributed to the increased unfolding, greater flexibility and net charge of amaranth proteins at acidic conditions. PMID:25497160

  13. Structural characterisation and rheological properties of a polysaccharide from sesame leaves (Sesamum radiatum Schumach. & Thonn.).

    PubMed

    Nep, E I; Carnachan, S M; Ngwuluka, N C; Kontogiorgos, V; Morris, G A; Sims, I M; Smith, A M

    2016-11-01

    A polysaccharide from the leaves of Sesamum radiatum was extracted by maceration in deionized water followed by ethanol precipitation then chemically and physically characterised. Monosaccharide composition and linkages were determined by high performance anion exchange chromatography (HPAEC), gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy respectively. Sesamum gum was composed of glucuronic acid, mannose, galactose, and xylose with trace quantities of glucose, rhamnose and arabinose. Proton and (13)C NMR spectroscopy, and linkage analysis revealed a glucuronomannan based structure comprising a backbone of →4)-β-d-GlcpA-(1→2)-α-d-Manp-(1→ with side-chains of galactose and xylose. Hydrated sesamum gum displayed temperature independent viscoelastic properties with no thermal hysteresis. Intrinsic viscosity was determined to be 3.31 and 4.40dLg(-1) in 0.1M NaCl and deionised water respectively, while the critical concentration was determined to be 0.1% w/v. The characterisation performed in this study will help direct potential applications of this material in foods and pharmaceuticals. PMID:27516302

  14. Effect of some essential oils on rheological properties of wheat flour dough.

    PubMed

    Ozcan, Mehmet Musa

    2009-03-01

    The effects of summer savory (Satureja hortensis L.), majorana (Origanum vulgare L.), sage (Salvia triloba L), rosemary (Rosmarinus officinalis L.), pickling herb (Echinophora tenuifolia L.) and laurel (Laurus nobilis L.) essential oils on extensograph and farinograph characteristics of wheat flour doughs were determined. Also, some chemical properties (moisture content, ash content, wet gluten content, sedimentation value and falling number) were established. The results show that resistance to extension, maximum resistance, ratio number (minimum) and ratio number (maximum) values were increased by S. hortensis oil addition during the proving time. Extensibility values of S. hortensis, O. vulgare and S. triloba at 90 min of proving time were found lower that than those of other proving times (except S. triloba at 135 min). According to the extensograph results, rosemary, pickling herb and laurel oils allowed higher extensibility and energy, and lower resistance to extension and maximum resistance (Brabender Unit Line). The farinograph water absorption (500 farinograph units) varied from 63.6 to 64.7. The development time of dough with rosemary oil was the same as the control group. Stabilities of dough with savory sater, majorana and sage oil were found lower that those of both control and other oils. As a result, rosemary, pickling herb and laurel oils had an advantage on the extensograph and farinograph characteristics of wheat flour dough. PMID:18608558

  15. Effect of dextran and dextran sulfate on the structural and rheological properties of model acid milk gels.

    PubMed

    Pachekrepapol, U; Horne, D S; Lucey, J A

    2015-05-01

    with 0.5% DS exhibited larger pores than the control gels. This study demonstrated that low concentrations of uncharged DX did not significantly affect the rheological properties of model acid milk gels; high concentrations of DX resulted in earlier gelation, possibly caused by depletion-induced attractions between casein particles, which altered the microstructure and created weaker gels. At pH values <4.6, negatively charged DS produced stiff casein gels, which might be due to attractive crosslinking by electrostatic interactions between DS and caseins at pH values below the isoelectric pH of casein (i.e., positively charged casein regions interacted with negatively charged DS molecules). PMID:25747831

  16. EMG Activity of Masseter Muscles in the Elderly According to Rheological Properties of Solid Food

    PubMed Central

    Kang, Au Jin; Kang, Si Hyun; Seo, Kyung Mook; Park, Hyoung Su; Park, Ki-Hwan

    2016-01-01

    Objective To assess the impact of aging on masticatory muscle function according to changes in hardness of solid food. Methods Each of fifteen healthy elderly and young people were selected. Subjects were asked to consume cooked rice, which was processed using the guidelines of the Universal Design Foods concept for elderly people (Japan Care Food Conference 2012). The properties of each cooked rice were categorized as grade 1, 2, 3 and 4 (5×103, 2×104, 5×104, and 5×105 N/m2) respectively. Surface electromyography (sEMG) was used to measure masseter activity from food ingestion to swallowing of test foods. The raw data was normalized by the ratio of sEMG activity to maximal voluntary contraction and compared among subjects. The data was divided according to each sequence of mastication and then calculated within the parameters of EMG activities. Results Intraoral tongue pressure was significantly higher in the young than in the elderly (p<0.05). Maximal value of average amplitude of the sequence in whole mastication showed significant positive correlation with hardness of food in both young and elderly groups (p<0.05). In a comparisons between groups, the maximal value of average amplitude of the sequence in whole mastication and peak amplitude in whole mastication showed that mastication in the elderly requires a higher percentage of maximal muscle activity than in the young, even with soft foods (p<0.05). Conclusion sEMG data of the masseter can provide valuable information to aid in the selection of foods according to hardness for the elderly. The results also support the necessity of specialized food preparation or products for the elderly. PMID:27446781

  17. Rheological properties of suspensions of interacting rodlike FD-virus particles

    NASA Astrophysics Data System (ADS)

    Graf, Christian; Kramer, Hansgerd; Deggelmann, Martin; Hagenbüchle, Martin; Johner, Christian; Martin, Christoph; Weber, Reinhart

    1993-03-01

    Low shear (γ˙=1 s-1) and shear rate dependent (1 s-1<γ˙<100 s-1) viscosity measurements on aqueous suspensions of rodlike FD-virus particles (length=880 nm, diameter=9 nm) below and above the overlap concentration c* =1 particle/length3 are presented. Properties like intrinsic viscosity [η], the virus concentration and shear rate dependence of η are studied in deionized (``saltfree'') suspensions and in the presence of NaCl, where the Coulomb interaction between the particles is totally screened. In the latter case, [η] is in excellent agreement with theoretical predictions [A. R. Altenberger and J. S. Dahler, Macromolecules 18, 1700 (1985); R. M. Davis and W. B. Russel, Macromolecules 20, 518 (1987)]. As a function of the virus concentration, η follows certain power laws in c. The observed exponents depend here on the applied shear rate. In the low shear region, η(c) can be described by the well known Huggins behavior. An attempt to fit the data by the popular stretched exponential form failed. The variation of η with shear rate is compared with available theories [M. Doi and S. F. Edwards, The Theory of Polymer Dynamics (Clarendon, Oxford, 1986); A. R. Altenberger and J. S. Dahler, Macromolecules 18, 1700 (1985); J. S. Dahler, S. Fesciyan, and N. Xystris, Macromolecules 16, 1673 (1983)]. A theory of Hess [Z. Naturforsch. Teil A 35, 915 (1980)] allows us to evaluate the concentration dependent values of the rotational diffusion constant Drot from the η(γ˙) data which are found to be in very good agreement with the values of Drot, obtained by electric or magnetic birefringence [H. Kramer, M. Deggelmann, C. Graf, M. Hagenbüchle, C. Johner, and R. Weber, Macromolecules 25, 4325 (1992); J. F. Maguire and J. P. McTague, Phys. Rev. Lett. 45, 1891 (1980); H. Nakamura and K. Okano, Phys. Rev. Lett. 50, 186 (1983)]. For strong Coulomb interaction among the suspended viruses no adequate theory is available. Therefore, the data achieved under these conditions

  18. The influence of alkaline earth metal equilibria on the rheological, melting and textural properties of Cheddar cheese.

    PubMed

    Cooke, Darren R; McSweeney, Paul L H

    2013-11-01

    The total calcium content of cheese, along with changes in the equilibrium between soluble and casein (CN)-bound calcium during ripening can have a major impact on its rheological, functional and textural properties; however, little is known about the effect of other alkaline earth metals. NaCl was partially substituted with MgCl2 or SrCl2 (8·7 and 11·4 g/kg curd, respectively) at the salting stage of cheesemaking to study their effects on cheese. Three cheeses were produced: Mg supplemented (+Mg), Sr supplemented (+Sr) and a control Cheddar cheese. Ca, Mg and Sr contents of cheese and expressible serum obtained therefrom were determined by atomic absorption spectroscopy. Addition of Mg2+ or Sr2+ had no effect on % moisture, protein, fat and extent of proteolysis. A proportion of the added Mg2+ and Sr2+ became CN-bound. The level of CN-bound Mg was higher in the +Mg cheese than the control throughout ripening. The level of CN-bound Ca and Mg decreased during ripening in all cheeses, as did % CN-bound Sr in the +Sr cheese. The presence of Sr2+ increased % CN-bound Ca and Mg at a number of ripening times. Adding Mg2+ had no effect on % CN-bound Ca. The +Sr cheese exhibited a higher G' at 70 °C and a lower LTmax than the control and +Mg cheeses throughout ripening. The +Sr cheese had significantly lower meltability compared with the control and +Mg cheeses after 2 months of ripening. Hardness values of the +Sr cheese were higher at week 2 than the +Mg and control cheeses. Addition of Mg2+ did not influence the physical properties of cheese. Supplementing cheese with Sr appeared to have effects analogous to those previously reported for increasing Ca content. Sr2+ may form and/or modify nanocluster crosslinks causing an increase in the strength of the para-casein matrix. PMID:24124804

  19. Supramolecular structure, phase behavior and thermo-rheological properties of a poly (L-lactide-co-ε-caprolactone) statistical copolymer.

    PubMed

    Ugartemendia, Jone M; Muñoz, M E; Santamaria, A; Sarasua, J R

    2015-08-01

    PLAcoCL samples, both unaged, termed PLAcoCLu, and aged over time, PLAcoCLa, were prepared and analyzed to study the phase structure, morphology, and their evolution under non-quiescent conditions. X- ray diffraction, Differential Scanning Calorimetry and Atomic Force Microscopy were complemented with thermo-rheological measurements to reveal that PLAcoCL evolves over time from a single amorphous metastable state to a 3 phase system, made up of two compositionally different amorphous phases and a crystalline phase. The supramolecular arrangements developed during aging lead to a rheological complex behavior in the PLAcoCLa copolymer: Around Tt=131 °C thermo-rheological complexity and a peculiar chain mobility reduction were observed, but at T>Tt the thermo-rheological response of a homogeneous system was recorded. In comparison with the latter, the PLLA/PCL 70:30 physical blend counterpart showed double amorphous phase behavior at all temperatures, supporting the hypothesis that phase separation in the PLAcoCLa copolymer is caused by the crystallization of polylactide segment blocks during aging. PMID:25933171

  20. Influence of pH and temperature on the rheological properties of aqueous dispersions of starch-sodium palmitate complexes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aqueous dispersions of high-amylose corn starch were steam jet cooked and blended with aqueous solutions of sodium palmitate to form amylose inclusion complexes. The rheology of dispersions of these complexes was examined. Acetic acid was added to reduce the pH, converting complexed sodium palmita...

  1. To Evaluate the Effect of Solvents and Different Relative Humidity Conditions on Thermal and Rheological Properties of Microcrystalline Cellulose 101 Using METHOCEL™ E15LV as a Binder.

    PubMed

    Jagia, Moksh; Trivedi, Maitri; Dave, Rutesh H

    2016-08-01

    The solvent used for preparing the binder solution in wet granulation can affect the granulation end point and also impact the thermal, rheological, and flow properties of the granules. The present study investigates the effect of solvents and percentage relative humidity (RH) on the granules of microcrystalline cellulose (MCC) with hydroxypropyl methyl cellulose (HPMC) as the binder. MCC was granulated using 2.5% w/w binder solution in water and ethanol/water mixture (80:20 v/v). Prepared granules were dried until constant percentage loss on drying, sieved, and further analyzed. Dried granules were exposed to different percentage RH for 48 h at room temperature. Powder rheometer was used for the rheological and flow characterization, while thermal effusivity and differential scanning calorimeter were used for thermal analysis. The thermal effusivity values for the wet granules showed a sharp increase beginning 50% w/w binder solution in both cases, which reflected the over-wetting of granules. Ethanol/water solvent batches showed greater resistance to flow as compared to the water solvent batches in the wet granule stage, while the reverse was true for the dried granule stage, as evident from the basic flowability energy values. Although the solvents used affected the equilibration kinetics of moisture content, the RH-exposed granules remained unaffected in their flow properties in both cases. This study indicates that the solvents play a vital role on the rheology and flow properties of MCC granules, while the different RH conditions have little or no effect on them for the above combination of solvent and binder. PMID:26729530

  2. Rheology of pig skin gelatine: Defining the elastic domain and its thermal and mechanical properties for geological analogue experiment applications

    NASA Astrophysics Data System (ADS)

    van Otterloo, Jozua; Cruden, Alexander R.

    2016-06-01

    Gelatine is a viscoelastic polymer that has been employed widely in geological analogue experiments to study processes related to the elastic behaviour of rocks such as tensile fracturing, seismicity and magma intrusion. However, the elastic domain of this material has not yet been clearly defined by rheological tests. Here we describe the rheology and define the elastic domain of 250 bloom/20 mesh pigskin gelatine at concentrations ≤ 10 wt.% and temperatures of 5-25 °C; however, these results are strongly comparable with gelatine of 245-260 bloom. New equations are given for the shear and elastic moduli in relationship to temperature and gelatine concentration. It is found that at concentrations ≤ 3 wt.% the tested gelatine is best described by a rheological model composed of a combination of Kelvin-Voight and Maxwell elements and, therefore, is not suitable to model elastic behaviour in geological analogue experiments. At higher concentrations it is best described by a simpler viscoelastic model comprising a single Maxwell element. In order to ensure that geological analogue experiments remain within the elastic domain where the elastic component is far greater than the viscous component, strain rates should range between 0.1 and 10 s- 1 and temperature values should be < 15 °C. With a Poisson's ratio of ~ 0.45 for concentrations > 3 wt.% analogue experiments using gelatine approximate the elastic behaviour of natural rocks more closely than previously assumed.

  3. High-water-content mouldable polyvinyl alcohol-borax hydrogels reinforced by well-dispersed cellulose nanoparticles: dynamic rheological properties and hydrogel formation mechanism.

    PubMed

    Han, Jingquan; Lei, Tingzhou; Wu, Qinglin

    2014-02-15

    Cellulose nanoparticle (CNP) reinforced polyvinyl alcohol-borax (PB) hydrogels were produced via a facile approach in an aqueous system. The effects of particle size, aspect ratio, crystal structure, and surface charge of CNPs on the rheological properties of the composite hydrogels were investigated. The rheological measurements confirmed the incorporation of well-dispersed CNPs to PB system significantly enhanced the viscoelasticity and stiffness of hydrogels. The obtained free-standing, high elasticity and mouldable hydrogels exhibited self-recovery under continuous step strain and thermo-reversibility under temperature sweep. With the addition of cellulose I nanofibers, a 19-fold increase in the high-frequency plateau of storage modulus was obtained compared with that of the pure PB. CNPs acted as multifunctional crosslinking agents and nanofillers to physically and chemically bridge the 3D network hydrogel. The plausible mechanism for the multi-complexation between CNPs, polyvinyl alcohol and borax was proposed to understand the relationship between the 3D network and hydrogel properties. PMID:24507286

  4. Rheological properties of native silk fibroins from domestic and wild silkworms, and flow analysis in each spinneret by a finite element method.

    PubMed

    Moriya, Motoaki; Roschzttardtz, Frederico; Nakahara, Yusuke; Saito, Hitoshi; Masubuchi, Yuichi; Asakura, Tetsuo

    2009-04-13

    Silkworms can produce strong and tough fibers at room temperature and from an aqueous solution. Therefore, it seems useful to study the mechanism of fiber formation by silkworms for development of synthetic polymers with excellent mechanical properties. The rheological behaviors of native silk dopes stored in the silk glands of Bombyx mori and Samia cynthia ricini were clarified, and flow simulations of the dopes in each spinneret were performed with a Finite Element Method. Dynamic viscoelastic measurements revealed that silk fibroin stored in silk glands forms a transient network at room temperature, and that the molecular weight for the network node corresponds to the molecular weight of a heterodimer of H-chain and L-chain (B. mori) and a homodimer of H-chains (S. c. ricini), respectively. Also, each dope exhibited zero-shear viscosity and then shear thinning like polymer melts. In addition, shear thickening due to flow-induced crystallization was observed. The critical shear rate for crystallization of B. mori dopes was smaller than that of S. c. ricini dopes. From the flow simulation, it is suggested that domestic and wild silkworms are able to crystallize the dopes in the stiff plate region by controlling shear rate using the same magnitude of extrusion pressure despite differences in rheological properties. PMID:19317399

  5. Deformation rates and localization of an active fault system in relation with rheological and frictional slip properties: The Corinth Rift case

    NASA Astrophysics Data System (ADS)

    El Arem, S.; Lyon-Caen, H.; Bernard, P.; Garaud, J. D.; Rolandone, F.; Briole, P.

    2012-04-01

    The Gulf of Corinth in Greece has attracted increasing attention because of its seismically active complex fault system and considerable seismic hazard. It is one of the most active extensional regions in the Mediterranean area. However, there are still open questions concerning the role and the geometry of the numerous active faults bordering the basin, as well as the mechanisms governing the seismicity. The Corinth Rift Laboratory (CRL http://crlab.eu) project is based on the cooperation of various European institutions that merge their efforts to study fault mechanics and related hazards in this natural laboratory with 10 destructive earthquakes per century (Magnitude > 6), among which 4 in the selected region of CRL. This active rift continues to open over 10-12 Km of width at a rate of 1:5 cm=yr. Most of the faults of the investigated area are in their latest part of cycle, so that the probability of at least one moderate to large earthquake (Magnitude = 6 to 6:7) is very high within a few decades. In the first part of this work, two-dimensional finite element models of a fault system is considered to estimate the effects of the crust rheological parameters on the stress distribution, the horizontal and vertical deformation in the vicinity of the faults, and the plastic deformation localization. We consider elasto-visco-plastic rheology with a power law viscosity for dislocation creep modelling and the Drucker-Prager yield criterion for plasticity. We investigate the rheological properties of the crust and examine their compatibility with both horizontal and vertical GPS observations recorded during campaigns conducted in the last twenty years. The second part is devoted to simulations involving rate and slip history friction laws for earthquake occurence prediction and seismogenic depth approximation. The case of a single fault is examined first, then two active faults are considered to highlight the effect of their interactions on the seismic cycle

  6. Statistical modelling of the rheological and mucoadhesive properties of aqueous poly(methylvinylether-co-maleic acid) networks: Redefining biomedical applications and the relationship between viscoelasticity and mucoadhesion.

    PubMed

    Jones, David S; Laverty, Thomas P; Morris, Caoimhe; Andrews, Gavin P

    2016-08-01

    Poly(methylvinylether-co-maleic acid) (PMVE/MA) is commonly used as a component of pharmaceutical platforms, principally to enhance interactions with biological substrates (mucoadhesion). However, the limited knowledge on the rheological properties of this polymer and their relationships with mucoadhesion has negated the biomedical use of this polymer as a mono-component platform. This study presents a comprehensive study of the rheological properties of aqueous PMVE/MA platforms and defines their relationships with mucoadhesion using multiple regression analysis. Using dilute solution viscometry the intrinsic viscosities of un-neutralised PMVE/MA and PMVE/MA neutralised using NaOH or TEA were 22.32±0.89dLg(-1), 274.80±1.94dLg(-1) and 416.49±2.21dLg(-1) illustrating greater polymer chain expansion following neutralisation using Triethylamine (TEA). PMVE/MA platforms exhibited shear-thinning properties. Increasing polymer concentration increased the consistencies, zero shear rate (ZSR) viscosities (determined from flow rheometry), storage and loss moduli, dynamic viscosities (defined using oscillatory analysis) and mucoadhesive properties, yet decreased the loss tangents of the neutralised polymer platforms. TEA neutralised systems possessed significantly and substantially greater consistencies, ZSR and dynamic viscosities, storage and loss moduli, mucoadhesion and lower loss tangents than their NaOH counterparts. Multiple regression analysis enabled identification of the dominant role of polymer viscoelasticity on mucoadhesion (r>0.98). The mucoadhesive properties of PMVE/MA platforms were considerable and were greater than those of other platforms that have successfully been shown to enhance in vivo retention when applied to the oral cavity, indicating a positive role for PMVE/MA mono-component platforms for pharmaceutical and biomedical applications. PMID:27085044

  7. Precursory surface deformation expected from a strike-slip fault model into which rheological properties of the lithosphere are incorporated

    NASA Astrophysics Data System (ADS)

    Yamashita, Teruo; Ohnaka, Mitiyasu

    1992-09-01

    Yamashita, T. and Ohnaka, M., 1992. Precursory surface deformation expected from a strike-slip fault model into which rheological properties of the lithosphere are incorporated. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 179-199. Earthquake prediction is one of the important problems with which seismologists are confronted. Much observational effort has been made to detect precursory surface deformation before earthquake occurrence. However, the physical mechanism to generate such precursory deformation is not fully understood. We, in this paper, theoretically study the growth process of strike-slip fault from nucleation to instability and a possibility to detect precursory surface deformation. Analyses are made on the basis of a breakdown zone crack model, which has been successfully applied in many aspects of earthquake rupture. We specifically attempt to simulate earthquake occurrence at the San Andreas fault, California, taking account of geological and geophysical conditions there. The most important parameters of the breakdown zone crack model will be the peak shear stress σ p near the crack tip, the sliding frictional stress σ f, and the critical slip displacement Dc. For the depth variation of these parameters we assume a three-layer model, which is composed of a brittle upper layer, a plastic lower layer and an intervening semibrittle layer. We model the depth variations of σ p and σ f, modifying the shear resistance profile appropriate for the San Andreas fault obtained by Sibson. The depth distribution of Dc is assumed to be constant D0 in the brittle layer and to increase exponentially with depth in the semibrittle and plastic layers on the basis of the study of Ohnaka; the depth distribution of Dc is described by two parameters, D0 and S, the latter standing for the increase rate of Dc in the lower two layers. Since there appears to exist much

  8. The effect of mineral fillers on the rheological, mechanical and thermal properties of halogen-free flame-retardant polypropylene/expandable graphite compounds

    NASA Astrophysics Data System (ADS)

    Mattausch, Hannelore; Laske, Stephan; Hohenwarter, Dieter; Holzer, Clemens

    2015-05-01

    In many polyolefin applications, such as electrical cables or automotive applications, the fire protection is a very important task. Unfortunately flame-retardant polymeric materials are often halogenated and form toxic substances in case of fire, which explains the general requirement to reduce the halogen content to zero. Non-halogenated, state-of-the-art flame retardants must be incorporated into the polymer in very high grades (> 40 wt%) leading to massive decrease in mechanical properties and/or processability. In this research work halogen-free flame-retardant polypropylene (PP) /expandable graphite (EG) were filled with minerals fillers such as layered silicates (MMT), magnesium hydroxide (MgOH), zeolite (Z) and expanded perlite (EP) in order to enhance the flame-retardant effect. The rheological, mechanical and thermal properties of these materials were investigated to gain more fundamental knowledge about synergistic combinations of flame-retardants and other additives. The rheological properties were characterized with a rotational rheometer with plate-plate setup. The EG/EP/PP compound exhibited the highest increase in viscosity (˜ 37 %). As representative value for the mechanical properties the Young's modulus was chosen. The final Young's modulus values of the twofold systems gained higher values than the single ones. Thermo gravimetric analysis (TGA) was utilized to investigate the material with respect to volatile substances and combustion behavior. All materials decomposed in one-step degradation. The EG filled compounds showed a significant increase in sample weight due to the expansion of EG. The combustion behavior of these materials was characterized by cone calorimeter tests. Especially combinations of expandable graphite with mineral fillers exhibit a reduction of the peak heat release rate during cone calorimeter measurements of up to 87% compared to pure PP.

  9. Effects of rhythmic exercise performed to music on the rheological properties of blood in women over 60 years of age.

    PubMed

    Marchewka, Anna; Filar-Mierzwa, Katarzyna; Dąbrowski, Zbigniew; Teległó, Aneta

    2015-01-01

    The aim of this study was to analyze the effects of motor rehabilitation, in the form of rhythmic exercise to music, on the rheological characteristics of blood in older women. The study included 30 women (65-80 years of age), and the control group was comprised of 10 women of corresponding age. Women from the experimental group were subjected to a five-month rehabilitation program, in the form of rhythmic exercise performed to music (three 30-minute sessions per week); women from the control group were not involved in any regular physical activity. Blood samples from all the women were examined for hematological, rheological, and biochemical parameters prior to the study and five months thereafter. The rehabilitation program was reflected by a significant improvement of erythrocyte count and hematocrit. Furthermore, an improvement of erythrocyte deformability was observed by lower shear stress levels, while no significant changes were noted by the higher shear stress values. The rehabilitation resulted in a marked decrease of the aggregation amplitude while no significant changes were observed in aggregation index and total aggregation half-time. Additionally, the training regimen was reflected by a significant increase in the plasma viscosity, while no significant changes in fibrinogen levels were noted. PMID:24169095

  10. Rheological properties of the lower crust and upper mantle beneath Baja California: a microstructural study of xenoliths from San Quintin

    NASA Astrophysics Data System (ADS)

    Van der Werf, Thomas F.; Chatzaras, Vasileios; Tikoff, Basil; Drury, Martyn R.

    2016-04-01

    Baja California is an active transtensional rift zone, which links the San Andreas Fault with the East Pacific Rise. The erupted basalts of the Holocene San Quintin volcanic field contain xenoliths, which sample the lower crust and upper mantle beneath Baja California. The aim of this research is to gain insight in the rheology of the lower crust and the upper mantle by investigating the xenolith microstructure. Microstructural observations have been used to determine the dominant deformation mechanisms. Differential stresses were estimated from recrystallized grain size piezometry of plagioclase and clinopyroxene for the lower crust and olivine for the upper mantle. The degree of deformation can be inferred from macroscopic foliations and the deformation microstructures. Preliminary results show that both the lower crust and the upper mantle have been affected by multiple stages of deformation and recrystallization. In addition the dominant deformation mechanism in both the lower crust and the upper mantle is dislocation creep based on the existence of strong crystallographic preferred orientations. The differential stress estimates for the lower crust are 10-29 MPa using plagioclase piezometry and 12-35 MPa using clinopyroxene piezometry. For the upper mantle, differential stress estimates are 10-20 MPa. These results indicate that the strength of the lower crust and the upper mantle are very similar. Our data do not fit with the general models of lithospheric strength and may have important implications for the rheological structure of the lithosphere in transtensional plate margins and for geodynamic models of the region.

  11. Bioactive constituents in liposomes incorporated in orange juice as new functional food: thermal stability, rheological and organoleptic properties.

    PubMed

    Marsanasco, Marina; Piotrkowski, Bárbara; Calabró, Valeria; Del Valle Alonso, Silvia; Chiaramoni, Nadia S

    2015-12-01

    Liposomes were developed with bioactive constituents (omega-3, omega-6, tocopherol) incorporated in acid food. They were made of soy phosphatidylcholine (SPC) allowing the encapsulation of antioxidant vitamin C (VC) and tocopherol. Stearic acid (SA) or calcium stearate (CaS) was added as a bilayer stabilizer. The structural and oxidative stability of the liposomes were studied considering the heat effect of pasteurization. Size was analyzed by light scattering; shape and structure were studied by optical and transmission electron microscopy, respectively. Membrane packing was studied with merocyanine 540. Surface charge and oxidative stability were analyzed by zeta potential and ORAC method, respectively. The liposomes showed significant stability in all of the parameters mentioned above and an important protective effect over thermolabile VC. To confirm their applicability in food, the rheological behavior and a sensory evaluation of liposomes with vitamin C and bioactive constituents were studied. The sensory evaluation of liposomes in orange juice was performed by the overall acceptability and triangular tests with 40 and 78 potential consumers, respectively. The incorporation of all liposomal formulation did not change the acceptability of orange juice. Noteworthy, SPC and SPC:SA systems had rheological behavior similar to a Newtonian fluid whereas that SPC:CaS presented a pseudoplastic one, both considered excellent for larger scale production. From all the obtained results, we can conclude that these liposomal formulations are suitable for food industry applications, incorporating bioactive constituents and generating functional orange juice that conserves its bioactivity after pasteurization. PMID:26604355

  12. Influence of rheological and frictional slip properties on fault mechanics, deformation rates and localization phenomena: The Corinth Rift case

    NASA Astrophysics Data System (ADS)

    El Arem, Saber; Lyon-Caen, Helene; Bernard, Pascal; Garaud, Jean-Didier; Rolandone, Frederique; Briole, Pierre

    2013-04-01

    The Gulf of Corinth in Greece is one of the most active extensional regions in the Mediterranean area. However, there are still open questions concerning the role and the geometry of the numerous active faults bordering the basin, as well as the mechanisms governing the seismicity. In geodynamics, advances in understanding complex physical processes such as lithospheric deformation or faulting mechanics rely increasingly on the development of sophisticated numerical modeling able to quantify the influence of the unknown rheological parameters and involved complex phenomena. In the framework of the Corinth Rift Laboratory (CRL http://crlab.eu) project, this work is devoted to the exploration of some aspects of fault mechanics. We start by considering a two-dimensional numerical model of one single normal fault slipping continuously embeded in an elastic-viscoplastic media. In this case, the effects of rheological and geometrical parameters on the deformation localization, on the horizontal and vertical surface deformation velocities are examined. The openning and uplift rates at different extension periods are compared to the GPS velocities measured in the CRL region. This comparaison allows to constrain the upper crust rheological parameters as well as their variation with depth . We then introduce a second fault, antithetic to the first one, for a more realistic representation of the CRL region where faults dipping north and south bordering the gulf of Corinth are clearly identified. The effect of the antithetic fault in accommodating the lithospheric extension is discussed. Also, changes in the distribution of the frictional-plastic deformation as well as in the onshore and offshore topography are highlighted. The last part of this work is dedicated to the study of a fault zone over multiple seismic cycles. Long term deformation obtained from a continuously sliping fault model is compared to that obtained from the superposition of seismic cycles and the fine

  13. Effects of endogenous small molecular compounds on the rheological properties, texture and microstructure of soymilk coagulum: Removal of phytate using ultrafiltration.

    PubMed

    Wang, Ruican; Guo, Shuntang

    2016-11-15

    This study aims to clarify the roles played by endogenous small molecular components in soymilk coagulation process and the properties of gels. Soymilk samples with decreasing levels of small molecules were prepared by ultrafiltration, to reduce the amount of phytate and salts. CaSO4-induced coagulation process was analyzed using rheological methods. Results showed that removal of free small molecules decreased the activation energy of protein coagulation, resulting in accelerated reaction and increased gel strength. However, too fast a reaction led to the drop in storage modulus (G'). Microscopic observation suggested that accelerated coagulation generated a coarse and non-uniform gel network with large pores. This network could not hold much water, leading to serious syneresis. Endogenous small molecules in soymilk were vital in the fine gel structure. Coagulation rate could be controlled by adjusting the amount of small molecules to obtain tofu products with the optimal texture. PMID:27283662

  14. Effect of Ca(2+), Fe(2+) and Mg(2+) on rheological properties of new food matrix made of modified cell wall polysaccharides from apple.

    PubMed

    Mierczyńska, Joanna; Cybulska, Justyna; Sołowiej, Bartosz; Zdunek, Artur

    2015-11-20

    A new food matrix made of modified cell wall polysaccharides (MPS) from apple pomace was developed. In this experiment, an effect of metal divalent ions: calcium, magnesium and iron ions on rheological properties of MPS was studied. An increase of Ca(2+) or Fe(2+) concentration in MPS suspensions significantly increased viscosity as well as elastic (G') and viscous (G″) moduli. Contrary, Mg(2+) addition caused a significant decrease of viscosity, G' and G″. Herschel-Bulkley's model fitted to shear stress vs. shear strain (flow curves) showed that calcium and iron ions increased pseudoplasticity and viscosity proportionally to concentration. The addition of any studied metal ions to MPS increased thixotropic effect. A temperature at the gel point increased when concentration increased to 9mM, then the gel points appeared at lower temperatures again for higher concentrations. This study showed that the MPS is an effective texture modifier with a controlled function by metal ions. PMID:26344313

  15. Effect of virgin coconut meal (VCM) on the rheological, micro-structure and baking properties of cake and batter.

    PubMed

    Srivastava, Yashi; Semwal, Anil Dutt

    2015-12-01

    Virgin coconut meal (VCM) cakes were prepared by replacing refined wheat flour (maida) (5 to 20 % level) to check its effect on chemical, textural and rheological attributes of cake. The addition of VCM significantly (p ≤ 0.05) increased redness (a*), yellowness (b*) while reduced lightness (L*) of cakes. The incorporation of VCM affects the hardness, adhesiveness gumminess and chewiness of cake. The effect of flour replacement with VCM increased the viscosity of batter which leads to increase in consistency index and lower the shearthining behavior. The viscoelastic behavior of cake batter in which elastic modulus (G') and viscous modulus (G") both were decreased with the increase in percentage of VCM. The differential scanning calorimetry (DSC) analysis revealed that the onset (To), end set (Tc) and enthalpy of gelatinization (ΔH) increased with the increased level of VCM. PMID:26604385

  16. Properties of Ductile Shear Zones Below Strike-Slip Faults: Insights From Numerical Experiments Incorporating Laboratory-Derived Rheologies (Invited)

    NASA Astrophysics Data System (ADS)

    Fialko, Y. A.; Takeuchi, C. S.

    2013-12-01

    We investigate the long-term evolution of stress and strain in a ductile substrate driven by far-field plate motion and slip on a vertical transform fault cutting through the brittle crust. Numerical models that incorporate laboratory-derived power-law rheologies with Arrhenius temperature dependence, viscous dissipation, and conductive heat transfer give rise to long-lived fault "roots" that localize deformation below the brittle-ductile transition. Strain localization in the viscoelastic medium in this case results from thermomechanical coupling and power law dependence of strain rate on stress. For conditions corresponding to the San Jacinto and San Andreas Faults in Southern California, the predicted width of the shear zone in the lower crust is a few kilometers; this shear zone accommodates more than 50% of the far-field plate motion. Coupled thermomechanical models predict a single-layer lithosphere in case of "dry" composition of the lower crust and upper mantle, and a "jelly sandwich" lithosphere in case of "wet" composition. Deviatoric stress in the lithosphere in our models is relatively insensitive to the water content, the far-field loading rate, and the fault strength, and is of the order of 102 MPa. Furthermore, stress in the lithosphere is found to inversely correlate with the velocity of relative plate motion. Somewhat surprisingly, we find that the thermally-activated shear zones have little effect on postseismic relaxation. In particular, the presence of such zones does not change the polarity of vertical displacements in cases of rheologies that are able to generate robust postseismic transients. We conclude that additional (to thermomechanical coupling) mechanisms of strain localization are required for a viscoelastic model to produce a vertical deformation pattern similar to that due to afterslip on a deep extension of a fault. Possible candidates include dynamic grain re-crystallization, and fabric development (mylonitization).

  17. Relating natural heterogeneities and rheological properties of rocksalt: New insights from microstructural observations and petrophyisical parameters on Messinian halites from the Italian Peninsula

    NASA Astrophysics Data System (ADS)

    Speranza, Giulio; Vona, Alessandro; Vinciguerra, Sergio; Romano, Claudia

    2016-01-01

    The importance and economic interest of rocksalt as well as its influence on tectonics and applicative purposes such as mining, hydrocarbons extraction, and nuclear waste storage are well known. Careful characterization of physical and chemical properties of rocksalt is fundamental as the rocksalt behavior may influence its potential use for applicative purposes. Mechanical and rheological properties of rocksalt have been extensively studied in the past. However, the role of natural heterogeneities within rocksalt and their effect on salt rheology have not been investigated quantitatively. Here we present a comprehensive salt facies study on Messinian rocksalt from several Italian sites (Volterra Basin, Tuscany, Caltanissetta Basin, Sicily and Crotone Basin, Calabria). Four salt facies end members have been identified and analyzed by optical analyses. The main facies-defining characteristics resulted to be the primary salt crystal abundance, crystal size, roundness and orientation, as well as the clay inclusion contents. Three out of four facies were placed on an evolutionary path from an "immature," with respect to the deformation history, to a "mature," rocksalt. So we observed, with increasing rocksalt maturity, a progressive disappearing of primary crystal remnants, increasing crystals elongation and iso-orientation and decreasing in crystal size. This trend has been confirmed by differential stress calculation from subgrain size. Through seismic waves velocity measurements and uniaxial compressive runs, specific salt facies were tested. Results of the investigations demonstrate that the facies parameters have a distinct influence on the rocksalt petrophysical parameters like P- and S-waves velocity, dynamic and static Young Modulus, elastic limit, and strain at peak. Finally, this study allowed to suggest the subdivision of Volterra's salt sequence in three different units that have been subjected to variable deformation degree in response to the different

  18. Rheological properties, oxidative stability, and tocopherol content during storage of fried dough made with Silky fowl egg: comparison with hen egg.

    PubMed

    Toyosaki, T

    2010-05-01

    Eggs from Silky fowl and White Leghorn hens were used to prepare fried dough. The rheological properties, lipid oxidative stability, and trans, trans-2,4-decadienal and tocopherol content of fried dough made with Silky fowl egg were compared with dough made with hen egg. The fried dough was stored in a glass bottle at 50 degrees C in the dark for 12 d. The fried dough made with Silky fowl egg showed little change in hardness and adhesion for 12 d at 50 degrees C. However, in the fried dough made with hen egg, hardness increased drastically and adhesion decreased. The fried dough made with Silky fowl egg showed restricted generation of hydroperoxides during 12 d in storage at 50 degrees C. In contrast, the fried dough made with hen egg showed an increased amount of hydroperoxides during the 12-d storage. The lowest concentration of trans, trans-2,4-decadienal was observed in fried dough made with Silky fowl egg, whereas the concentration of trans, trans-2,4-decadienal in fried dough made with hen egg was significantly increased. Total tocopherols in fried dough made with Silky fowl egg were degraded 23.3 mg/100 g of fried dough by the end of the experimental period at 50 degrees C. In contrast, total tocopherols in the fried dough made with hen egg were degraded 40 mg/100 g of fried dough. The ratio of unsaturated fatty acids to saturated fatty acids decreased and the hydroperoxide content increased with storage time. The unsaturated fatty acid:saturated fatty acid ratio and hydroperoxide and tocopherol contents were lower in fried dough made with Silky fowl egg than in that made with hen egg, indicating decreased lipid oxidation. The present experiment suggests that the use of Silky fowl egg could improve the rheological properties, oxidative stability, and trans, trans-2,4-decadienal and tocopherol contents of fried dough. PMID:20371854

  19. Experimental constraints on the rheology and mechanical properties of lava erupted in the Holuhraun area during the 2014 rifting event at Bárðarbunga, Iceland

    NASA Astrophysics Data System (ADS)

    Lavallee, Yan; Kendrick, Jackie; Wall, Richard; von Aulock, Felix; Kennedy, Ben; Sigmundsson, Freysteinn

    2015-04-01

    A fissure eruption began at Holuhraun on 16 August 2014, following magma drainage from the Bárðarbunga volcanic system (Iceland). Extrusion initiated as fire fountaining along a segment of the fracture and rapidly localised to a series of small, aligned cones containing a lava lake that over spilled at both ends, feeding a large lava field. The lava composition and flow behaviour put some constraints on its rheology and mechanical properties. The lava erupted is a nearly aphyric basalt containing approximately 2-3% plagioclase with traces of olivine and pyroxene in a quenched groundmass composed of glass and 20-25% microlites. The transition from fire fountaining to lava flow leads to lava with variable vesicularities; pyroclasts expelled during fire fountaining reach up to 80% vesicles whilst the lava contain up to 45% vesicles. Textures in the lava vary from a'a to slabby pahoehoe, and flow thicknesses from several meters to few centimetres. Tension gashes, crease structures and shear zones in the upper lava carapace reveal the importance of both compressive and tensional stresses. In addition, occasional frictional marks at the base of the lava flow as well as bulldozing of sediments along the flow hint at the importance of frictional properties of the rocks during lava flow. Flow properties, textures and failure modes are strongly dependent on the material properties as well as the local conditions of stress and temperature. Here we expand our field observation with preliminary high-temperature experimental data on the rheological and mechanical properties of the erupted lava. Dilatometric measurements are used to constrain the thermal expansion coefficient of the lava important to constrain the dynamics of cooling of the flow. Micropenetration is further employed to determine the viscosity of the melt at super-liquidus temperature, which is compared to the temperature-dependence of viscosity as constrained by geochemistry. Lastly, uniaxial compression and

  20. Evolution of nano-rheological properties of Nafion¯ thin films during pH modification by strong base treatment: A static and dynamic force spectroscopy study

    NASA Astrophysics Data System (ADS)

    Eslami, Babak; López-Guerra, Enrique A.; Raftari, Maryam; Solares, Santiago D.

    2016-04-01

    Addition of a strong base to Nafion® proton exchange membranes is a common practice in industry to increase their overall performance in fuel cells. Here, we investigate the evolution of the nano-rheological properties of Nafion thin films as a function of the casting pH, via characterization with static and dynamic, contact and intermittent-contact atomic force microscopy (AFM) techniques. The addition of KOH causes non-monotonic changes in the viscoelastic properties of the films, which behave as highly dissipative, softer materials near neutral pH values, and as harder, more elastic materials at extreme pH values. We quantify this behavior through calculation of the temporal evolution of the compliance and the glassy compliance under static AFM measurements. We complement these observations with dynamic AFM metrics, including dissipated power and virial (for intermittent-contact-mode measurements), and contact resonance frequency and quality factor (for dynamic contact-mode measurements). We explain the non-monotonic material property behavior in terms of the degree of ionic crosslinking and moisture content of the films, which vary with the addition of KOH. This work focuses on the special case study of the addition of strong bases, but the observed mechanical property changes are broadly related to water plasticizing effects and ionic crosslinking, which are also important in other types of films.

  1. Rheology of concentrated biomass

    NASA Astrophysics Data System (ADS)

    Samaniuk, J. R.; Wang, J.; Root, T. W.; Scott, C. T.; Klingenberg, D. J.

    2011-12-01

    Economic processing of lignocellulosic biomass requires handling the biomass at high solids concentration. This creates challenges because concentrated biomass behaves as a Bingham-like material with large yield stresses. Here we employ torque rheometry to measure the rheological properties of concentrated lignocellulosic biomass (corn stover). Yield stresses obtained using torque rheometry agree with those obtained using other rheometric methods, but torque rheometry can be used at much larger solids concentration (weight fractions of insoluble solids greater than 0.2). Yield stresses decrease with severity of hydrolysis, decrease when water-soluble polymers are added (for nonhydrolyzed biomass), and increase with particle length. Experimental results are qualitatively consistent with those obtained from particle-level simulations.

  2. Rheological properties of binary and ternary protein-polysaccharide co-hydrogels and comparative release kinetics of salbutamol sulphate from their matrices.

    PubMed

    Saxena, Anita; Kaloti, Mandeep; Bohidar, H B

    2011-03-01

    Rheological properties of binary (AgarGelA and AgarGelB) and ternary (AgarGelAB and GelABAgar) co-hydrogels of agar (polysaccharide) with gelatin A and gelatin B (proteins) were studied to investigate their differential viscoelastic behavior. Two sets of rheological experiments, isochronal temperature and isothermal frequency sweep, were performed and the storage modulii, G' was measured which could be correlated to the gel strengths. Two separate peaks at 70°C and 35°C, corresponding to melting temperatures of agar and gelatin gels respectively, were obtained when derivative of G' with respect to temperature, dG'/dT was plotted against temperature which clearly showed the presence of two separate networks of gelatin and agar interconnected to each other. The results revealed that AgarGelAB was the strongest and AgarGelA was the weakest gel among all the gels studied. In order to see the effect of gel microstructure on drug encapsulation and release behavior, a model drug salbutamol was encapsulated in various gel matrices and the release of the same was seen in phosphate buffer pH 7.4, in simulated gastric fluid pH 1.2 (SGF) and in simulated intestinal fluid pH 6.8 (SIF) media. The drug release behavior universally followed sigmoidal kinetics invariant of gel composition. It is concluded that the hydrogel microstructure influenced the release behavior and best release, in all the three media, could be found with binary gel, AgarGelB, and ternary gel, AgarGelAB. Finally, microstructure of these gels is proposed. PMID:21108963

  3. Pressure-Induced Slip-System Transition in Forsterite: Single-Crystal Rheological Properties at Mantle Pressure and Temperature

    SciTech Connect

    Raterron,P.; Chen, J.; Li, L.; Weidner, D.; Cordier, P.

    2007-01-01

    Deformation experiments were carried out in a Deformation-DIA high-pressure apparatus (D-DIA) on oriented Mg2SiO4 olivine (Fo100) single crystals, at pressure (P) ranging from 2.1 to 7.5 GPa, in the temperature (T) range 1373-1677 K, and in dry conditions. These experiments were designed to investigate the effect of pressure on olivine dislocation slip-system activities, responsible for the lattice-preferred orientations observed in the upper mantle. Two compression directions were tested, promoting either [100] slip alone or [001] slip alone in (010) crystallographic plane. Constant applied stress ({sigma}) and specimen strain rates (Formula) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of the run products reveals that dislocation creep assisted by dislocation climb and cross slip was responsible for sample deformation. A slip transition with increasing pressure, from a dominant [100]-slip to a dominant [001]-slip, is documented. Extrapolation of the obtained rheological laws to upper-mantle P, T, and {sigma} conditions, suggests that [001]-slip activity becomes comparable to [100]-slip activity in the deep upper mantle, while [001] slip is mostly dominant in subduction zones. These results provide alternative explanations for the seismic anisotropy attenuation observed in the upper mantle, and for the 'puzzling' seismic-anisotropy anomalies commonly observed in subduction zones.

  4. Rheological properties of suspensions containing cross-linked starch nanoparticles prepared by spray and vacuum freeze drying methods.

    PubMed

    Shi, Ai-min; Li, Dong; Wang, Li-jun; Adhikari, Benu

    2012-11-01

    The rheological behavior of suspensions containing vacuum freeze dried and spray dried starch nanoparticles was investigated to explore the effect of these two drying methods in producing starch nanoparticles which were synthesized using high pressure homogenization and mini-emulsion cross-linking technique. Suspensions containing 10% (w/w) spray dried and vacuum freeze dried nanoparticles were prepared. The continuous shear viscosity tests, temperature sweep tests, the frequency sweep and creep-recovery tests were carried out, respectively. The suspensions containing vacuum freeze dried nanoparticles showed higher apparent viscosity within shear rate range (0.1-100 s(-1)) and temperature range (25-90 °C). The suspensions containing vacuum freeze dried nanoparticles were found to have more shear thinning and less thixotropic behavior compared to those containing spray dried nanoparticles. In addition, the suspensions containing vacuum freeze dried particles had stronger elastic structure. However, the suspensions containing spray dried nanoparticles had more stiffness and greater tendency to recover from the deformation. PMID:22944440

  5. Rheology of biological macromolecules

    NASA Astrophysics Data System (ADS)

    Ariyaratne, Amila Dinesh

    Proteins have interesting mechanical properties in addition to the remarkable functionality. For example, Guanylate kinase is an enzyme that catalyzes Guano- sine monophosphate (GMP) to Guanosine diphosphate (GDP) conversion and this enzyme is approximately 5 nm in size. A gold nano particle of similar size shows linear elasticity for strains up to ˜ 0.1% and shows plastic deformation beyond that, whereas the enzyme Guanylate kinase can have strains up to 1 % with reversible deformation. Our experiments show many different regimes of the mechanical response before the plastic deformation of these proteins. In this dissertation, I study the materials properties of two classes of proteins, an ion channel protein and a transferase, which is a globular protein. The experimental techniques to study the materials properties of these proteins were uniquely developed at the Zocchi lab. Therefore, we were able to observe previously unknown characteristics of these folded proteins. The mechanical properties of the voltage gated potassium channel KvAP was studied by applying AC depolarizing voltages. This technique gave new information about the system that was not seen in the previous studies. These previous experiments were based on applying DC depolarizing voltage steps across the membrane to study the ionic current. By monitoring the ionic current at different depolarizing voltage steps, the DC gating process of the channel could be under- stood. We probed the channel using AC depolarizing signals instead of DC pulses and the ionic current revealed new behaviors, which cannot be predicted with the DC response. We found that the conformational motion of the voltage sensing domain of the ion channel shows internal dissipation. Further, a new non linearity in the dissipation parameter was found in which the dissipation parameter increased with the shear rate of the applied force. Previous studies at the Zocchi lab used a nano rheology experiment on the protein Guanylate

  6. Relating facies and rheological properties of rocksalt: new insights from physical properties and microstructural observations on Messinian halite of Italian Peninsula.

    NASA Astrophysics Data System (ADS)

    Speranza, Giulio; Vinciguerra, Sergio; Mollo, Silvio; Iarocci, Alessandro

    2014-05-01

    The importance and economic interest on rocksalt deposits and salt bodies are well known and extensively studied. However, previous scientific works have mainly focused on synthetic rocksalt or commercial salt, whereas the role of natural heterogeneities and their effect on salt rheology have been not investigated quantitatively. Here we present a comprehensive salt facies study including salt samples from Volterra Basin, northern Italy, Caltanissetta Basin, Sicily and Crotone Basin, southern Italy. Throughout optical and images analyses on thin sections we identified four salt facies, that have been named as "green", "blue", "black" and "red" depending on the relationships between primary and secondary salt, recrystallization and deformation. The "green" facies has a great abundance in primary salt remnants (around 20% in volume) rich in primary fluid inclusions and rather rounded crystals (average roundness is 0,6) with no preferred orientation. Thus is considered the less deformed and recrystallized end member. Proceeding toward increasing salt deformation, primary salt remnants are gradually dissolved. Secondary salt is formed and a progressive decrease in average crystals size, increase in crystals elongation and preferred orientation can be observed. So, we identified the "black" facies, with much less primary salt remnants (around 10% in volume), more elongated (average roundness is 0,4) and smaller (average area 1,6 mm2) crystals showing a clear preferred orientation. Then, the "red" facies has been analyzed, being the most deformed salt end member, with almost no primary salt remnants and even smaller (average crystals area is 0,5mm2), very elongated crystals (average roundness is 0,4) also with a neat preferred orientation. The "blue" facies cannot be placed on this evolutionary path, being made up of totally recrystallized but only very slightly deformed (roundness is 0,6) and bigger (average area is 4,9 mm2) crystals with no preferred orientation

  7. Time domain analysis of the weighted distributed order rheological model

    NASA Astrophysics Data System (ADS)

    Cao, Lili; Pu, Hai; Li, Yan; Li, Ming

    2016-05-01

    This paper presents the fundamental solution and relevant properties of the weighted distributed order rheological model in the time domain. Based on the construction of distributed order damper and the idea of distributed order element networks, this paper studies the weighted distributed order operator of the rheological model, a generalization of distributed order linear rheological model. The inverse Laplace transform on weighted distributed order operators of rheological model has been obtained by cutting the complex plane and computing the complex path integral along the Hankel path, which leads to the asymptotic property and boundary discussions. The relaxation response to weighted distributed order rheological model is analyzed, and it is closely related to many physical phenomena. A number of novel characteristics of weighted distributed order rheological model, such as power-law decay and intermediate phenomenon, have been discovered as well. And meanwhile several illustrated examples play important role in validating these results.

  8. The impact of fermentation with exopolysaccharide producing lactic acid bacteria on rheological, chemical and sensory properties of pureed carrots (Daucus carota L.).

    PubMed

    Juvonen, Riikka; Honkapää, Kaisu; Maina, Ndegwa H; Shi, Qiao; Viljanen, Kaarina; Maaheimo, Hannu; Virkki, Liisa; Tenkanen, Maija; Lantto, Raija

    2015-08-17

    Fermentation with lactic acid bacteria (LAB) offers a natural means to modify technological and nutritional properties of foods and food ingredients. This study explored the impact of fermentation with different exopolysaccharide (EPS) producing LAB on rheological, chemical and sensory properties of puréed carrots in water, as a vegetable model, with the focus on texture formation. The screening of 37 LAB strains for starter selection revealed 16 Lactobacillus, Leuconostoc and Weissella strains capable of EPS (dextran, levan, and/or β-glucan) production in the carrot raw material. Fermentations with five out of six selected EPS producers modified perceived texture of the liquid carrot model (p<0.05). The formation of low-branched dextran correlated with perceived thickness, whereas the production of β-glucan correlated with perceived elasticity. Low-branched dextran producing Weissella confusa and Leuconostoc lactis strains produced thick texture accompanied by pleasant odour and flavour. The fermentation with the selected EPS-producing LAB strains is a promising clean label approach to replace hydrocolloid additives as texturizers in vegetable containing products, not only carrot. PMID:26001525

  9. Comparison of observed rheological properties of hard wheat flour dough with predictions of the Giesekus-Leonov, White-Metzner and Phan-Thien Tanner models

    NASA Technical Reports Server (NTRS)

    Dhanasekharan, M.; Huang, H.; Kokini, J. L.; Janes, H. W. (Principal Investigator)

    1999-01-01

    The measured rheological behavior of hard wheat flour dough was predicted using three nonlinear differential viscoelastic models. The Phan-Thien Tanner model gave good zero shear viscosity prediction, but overpredicted the shear viscosity at higher shear rates and the transient and extensional properties. The Giesekus-Leonov model gave similar predictions to the Phan-Thien Tanner model, but the extensional viscosity prediction showed extension thickening. Using high values of the mobility factor, extension thinning behavior was observed but the predictions were not satisfactory. The White-Metzner model gave good predictions of the steady shear viscosity and the first normal stress coefficient but it was unable to predict the uniaxial extensional viscosity as it exhibited asymptotic behavior in the tested extensional rates. It also predicted the transient shear properties with moderate accuracy in the transient phase, but very well at higher times, compared to the Phan-Thien Tanner model and the Giesekus-Leonov model. None of the models predicted all observed data consistently well. Overall the White-Metzner model appeared to make the best predictions of all the observed data.

  10. Differences in the rheological properties and mixing compatibility with heparinoid cream of brand name and generic steroidal ointments: The effects of their surfactants.

    PubMed

    Kitagawa, Shuji; Yutani, Reiko; Kodani, Rhu-Ichi; Teraoka, Reiko

    2016-01-01

    Most steroidal ointments contain propylene glycol (PG) and surfactants, which improve the solubility of corticosteroids in white petrolatum. Surfactants aid the uniform dispersal of PG within white petrolatum. Since the surfactants used in generic ointments are usually different from those used in brand name ointments, we investigated the effects of surfactants on the rheological properties of three brand name ointments and six equivalent generic ointments. We detected marked differences in hardness, adhesiveness, and spreadability among the ointments. Further examinations of model ointments consisting of white petrolatum, PG, and surfactants revealed that the abovementioned properties, especially hardness and adhesiveness, were markedly affected by the surfactants. Since steroidal ointments are often admixed with moisturizing creams prior to use, we investigated the mixing compatibility of the ointments with heparinoid cream and how this was affected by their surfactants. We found that the ointments containing glyceryl monostearate demonstrated good mixing compatibility, whereas those containing non-ionic surfactants with polyoxyethylene chains exhibited phase separation. These results were also consistent with the findings for the model ointments, which indicates that the mixing compatibility of steroidal ointments with heparinoid cream is determined by the emulsifying capacity of the surfactants in their oily bases. PMID:26958460

  11. Differences in the rheological properties and mixing compatibility with heparinoid cream of brand name and generic steroidal ointments: The effects of their surfactants

    PubMed Central

    Kitagawa, Shuji; Yutani, Reiko; Kodani, Rhu-ichi; Teraoka, Reiko

    2016-01-01

    Most steroidal ointments contain propylene glycol (PG) and surfactants, which improve the solubility of corticosteroids in white petrolatum. Surfactants aid the uniform dispersal of PG within white petrolatum. Since the surfactants used in generic ointments are usually different from those used in brand name ointments, we investigated the effects of surfactants on the rheological properties of three brand name ointments and six equivalent generic ointments. We detected marked differences in hardness, adhesiveness, and spreadability among the ointments. Further examinations of model ointments consisting of white petrolatum, PG, and surfactants revealed that the abovementioned properties, especially hardness and adhesiveness, were markedly affected by the surfactants. Since steroidal ointments are often admixed with moisturizing creams prior to use, we investigated the mixing compatibility of the ointments with heparinoid cream and how this was affected by their surfactants. We found that the ointments containing glyceryl monostearate demonstrated good mixing compatibility, whereas those containing non-ionic surfactants with polyoxyethylene chains exhibited phase separation. These results were also consistent with the findings for the model ointments, which indicates that the mixing compatibility of steroidal ointments with heparinoid cream is determined by the emulsifying capacity of the surfactants in their oily bases. PMID:26958460

  12. Bio-nanocomposite films reinforced with cellulose nanocrystals: Rheology of film-forming solutions, transparency, water vapor barrier and tensile properties of films.

    PubMed

    El Miri, Nassima; Abdelouahdi, Karima; Barakat, Abdellatif; Zahouily, Mohamed; Fihri, Aziz; Solhy, Abderrahim; El Achaby, Mounir

    2015-09-20

    This study was aimed to develop bio-nanocomposite films of carboxymethyl cellulose (CMC)/starch (ST) polysaccharide matrix reinforced with cellulose nanocrystals (CNC) using the solution casting method. The CNC were extracted at the nanometric scale from sugarcane bagasse via sulfuric acid hydrolysis and used as reinforcing phase to produce CMC/ST-CNC bio-nanocomposite films at different CNC loading levels (0.5-5.0 wt%). Steady shear viscosity and dynamic viscoelastic measurements of film-forming solution (FFS) of neat CMC, CMC/ST blend and CMC/ST-CNC bio-nanocomposites were evaluated. Viscosity measurements revealed that a transition from Newtonian behavior to shear thinning occurred when CNC were added. The dynamic tests confirmed that all FFS have a viscoelastic behavior with an entanglement network structure, induced by the hydrogen bonding. In regard to the cast film quality, the rheological data showed that all FFS were suitable for casting of films at ambient temperature. The effect of CNC addition on the optical transparency, water vapor permeability (WVP) and tensile properties of bio-nanocomposite films was studied. It was found that bio-nanocomposite films remain transparent due to CNC dispersion at the nanoscale. The WVP was significantly reduced and the elastic modulus and tensile strength were increased gradually with the addition of CNC. Herein, the steps to form new eco-friendly bio-nanocomposite films were described by taking advantage of the combination of CMC, ST and CNC. The as-produced films exhibited good optical transparency, reduced WVP and enhanced tensile properties, which are the main properties required for packaging applications. PMID:26050901

  13. Effects of cold water swimming on blood rheological properties and composition of fatty acids in erythrocyte membranes of untrained older rats.

    PubMed

    Teległów, Aneta; Dabrowski, Zbigniew; Marchewka, Anna; Tabarowski, Zbigniew; Bilski, Jan; Jaśkiewicz, Jerzy; Gdula-Argasińska, Joanna; Głodzik, Jacek; Lizak, Dorota; Kepińska, Magdalena

    2011-01-01

    This is the first report on the effects of a single bout of swimming to exhaustion in cold water on rat erythrocyte deformability, aggregation and fatty acid composition in erythrocyte membranes. The results indicate that there was a significant decrease in body temperature of experimental rats swimming in water at 4 degrees C and 25 degrees C when compared to the control. Erythrocyte aggregation indices did not change after swimming in water at 4 degrees C whereas erythrocyte deformability increased at shear stress 1,13 [Pa] and 15,96 [Pa]. Physical effort performed in water at 4 degrees C when compared to the control group resulted in an increase in monounsaturated and polyunsaturated n-3 fatty acid content in erythrocyte membranes that influenced the increase in their fluidity and permeability even though that of polyunsaturated n-6 fatty acids decreased. Physical effort performed in 25 degrees C water resulted in an increase in saturated fatty acid content and a decrease in all polyunsaturated fatty acids and polyunsaturated n-6 fatty acids when compared to the control group. Swimming of untrained old rats in cold water affected rheological properties oferythrocytes in a negligible way while changes in the fatty acid composition of erythrocyte membranes were more pronounced. PMID:22195477

  14. Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

    NASA Astrophysics Data System (ADS)

    Bigikocin, Erman; Mert, Behic; Alpas, Hami

    2011-09-01

    Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.

  15. Self-Assembly and Rheological Properties of a Pseudogemini Surfactant Formed in a Salt-Free Catanionic Surfactant Mixture in Water.

    PubMed

    Li, Yan; Li, Hongguang; Chai, Jinling; Chen, Mengjun; Yang, Qiao; Hao, Jingcheng

    2015-10-20

    The surface and bulk properties of bola-type dicarboxylic acid (sebacic acid, SA) and zwitterionic surfactant tetradecyldimethylamine oxide (C14DMAO) mixtures in aqueous solutions were studied. Surface tension measurements indicate a pronounced synergistic effect between SA and C14DMAO. In bulk aqueous solutions, rich phase behavior was observed with a varied SA-to-C14DMAO ratio (ρ) and a total surfactant concentration. Typically at ρ = 0.5, a novel pseudogemini surfactant (C14-S-C14) forms, driven by electrostatic interaction and hydrogen bonding. The C14-S-C14/H2O system exhibits rich phase behavior induced by the transition of aggregates. With increasing concentration of C14-S-C14, one can observe a viscous L1 phase, an L1/Lα two-phase region where a birefringent Lα phase is on the top of an L1 phase, a single Lα phase, and finally a mixture of an Lα phase and a precipitate. Microstructures formed in the Lα phases were determined by freeze-fracture transmission electron microscopy (FF-TEM) and cryogenic-transmission electron microscopy (cryo-TEM) observations. Polymorphic aggregation behavior was observed with the formation of a variety of bilayer structures including unilamellar vesicles, onions, and open and hyperbranched bilayers. Rheological measurements showed that the Lα phases are viscoelastic and sensitive to temperature where a quick loss of viscoelasticity was observed at elevated temperature. PMID:26406939

  16. Influence of drug content, type of semi-solid vehicle and rheological properties on the skin penetration of the model drug fludrocortisone acetate.

    PubMed

    Nagelreiter, C; Raffeiner, S; Geyerhofer, C; Klang, V; Valenta, C

    2013-05-01

    Throughout Europe, topical creams containing corticosteroids are diluted with various neutral cream bases to meet the specific needs of patients. Even though this practice has been common for years, its effect has not been thoroughly investigated and so the effectiveness of the diluted topical steroidal creams is difficult to predict. In the present study, the model drug fludrocortisone acetate was incorporated into three cream bases of different hydrophilicity that are commonly used in Austria. Different final drug concentrations were chosen for comparative studies. Additionally, a semi-solid preparation developed by our group was investigated for comparison. These formulations were tested in diffusion and tape stripping experiments. Diffusion cell studies showed that changes in drug concentration do not necessarily change the skin permeation behaviour in vitro. The tape stripping protocol was successfully optimised for investigation of semi-solid preparations to provide reproducible and accurate results despite the challenges of investigating semi-solid formulations. The results showed that tape stripping experiments are more suitable to elucidate subtle differences between formulations. The composition of the cream bases exhibited stronger effects on the skin penetration of the steroidal drug irrespective of its concentration than the rheological properties. No correlation between formulation viscosity and skin penetration was found. PMID:23541986

  17. Rheological Properties of Aqueous Acid Solutions of Chitosan: Experiment and Calculations of the Viscometric Functions on the Basis of a Mesoscopic Model

    NASA Astrophysics Data System (ADS)

    Shipovskaya, A. B.; Abramov, A. Yu.; Pyshnograi, G. V.; Aziz, Al Joda Hyder Nadom

    2016-05-01

    The rheological properties of chitosan solutions in acetic acid at 20°C in the range of polymer concentrations from 0.5 to 8 mass% and acid concentrations from 2 to 70% have been investigated. With the use of a modified Vinogradov-Pokrovskii model based on the microstructural approach to the description of polymer fluid dynamics, numerical solutions of gradient dependences of viscometric functions of aqueous acid solutions of chitosan have been obtained. It has been established that the numerical solution describes with good accuracy the experimental viscosity rheograms. The values of the highest Newton viscosity ηmax have been calculated. The concentration modes of semidiluted and concentrated solutions have been determined by the dependence of ηmax on the polymer concentration, and the range of concentrations in which the mass transfer mechanism changes and a fluctuation network is formed has been found. It has been shown that the concentration of acetic acid practically does not influence the structure and character of flow of chitosan solutions, the formation concentration of a network, and the efficiency of its labile nodes.

  18. Stimuli-responsive chitosan/poly (N-isopropylacrylamide) semi-interpenetrating polymer networks: effect of pH and temperature on their rheological and swelling properties.

    PubMed

    Fernández-Gutiérrez, Mar; Fusco, Sabato; Mayol, Laura; San Román, Julio; Borzacchiello, Assunta; Ambrosio, Luigi

    2016-06-01

    The aim of this work was to synthesize semi-interpenetrating polymer networks (semi-IPNs) by free radical polymerization of N-isopropylacrylamide [poly (NIPAAm)], in the presence of chitosan (CHI), and to study the effect of pH and temperature changes on their rheological and swelling properties. The semi-IPNs are thermally stable up to about 400 °C and the presence of CHI increases the thermal degradation rate compared to bare poly (NIPAAm). The prepared systems presents a well-defined porosity and proved to be non-toxic, in vitro, on human embryonic skin fibroblast, thus offering appropriate support for cell proliferation. The semi-IPNs present, at physiological pH, swelling degrees well below those of the pure poly (NIPAAm). Differently, at acidic pH, the CHI macromolecules are protonated and become much more permeable to the diffusion of water giving a swelling degree that approaches that of bare poly (NIPAAm). The viscoelastic moduli of the semi-IPNs increase as a function of pH while the LCST remain unchanged. Moreover, the semi-IPNs viscoelastic moduli increase with the increase of CHI content and, in particular, the difference between the elastic modulus before and after the sol/gel transition is higher for the semi-IPN than for bare poly (NIPAAm) just at about physiological conditions. PMID:27138966

  19. Brownian dynamics simulation of orientational behavior, flow-induced structure, and rheological properties of a suspension of oblate spheroid particles under simple shear

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takehiro; Suga, Takanori; Mori, Noriyasu

    2005-08-01

    Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level.

  20. Brownian dynamics simulation of orientational behavior, flow-induced structure, and rheological properties of a suspension of oblate spheroid particles under simple shear.

    PubMed

    Yamamoto, Takehiro; Suga, Takanori; Mori, Noriyasu

    2005-08-01

    Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level. PMID:16196575

  1. Effect of high-pressure treatment on the structural and rheological properties of resistant corn starch/locust bean gum mixtures.

    PubMed

    Hussain, Raza; Vatankhah, Hamed; Singh, Ajaypal; Ramaswamy, Hosahalli S

    2016-10-01

    In this study, effects of a 30min high pressure (HP) treatment (200-600MPa) at room temperature on the rheological, thermal and morphological properties of resistant corn starch (RS) (5% w/w) and locust bean gum (LBG) (0.25, 0.50 and 1.0% w/v) dispersions were evaluated. Results showed that the storage modulus (G'), loss modulus (G''), and apparent viscosity values of starch/gum (RS/LBG) mixtures were enhanced with an increase pressure level, and demonstrated a bi-phasic behavior. HP treated RS/LBG samples were predominantly either solid like (G'>G'') or viscous (G''>G'), depending on the pressure level and LBG concentrations. Differential scanning calorimetry (DSC) analysis of the pressurized mixtures showed a major effect on gelatinization temperatures (To, Tp,), and it was observed that RS/LBG mixtures gelatinized completely at ≥400MPa with a 30min holding time. Confocal laser scanning microscopy (CLSM) images confirmed that at 600MPa, RS/LBG mixtures retained granular structures and their complete disintegration was not observed even at the endpoint of the gelatinization. PMID:27312641

  2. On the cytoskeleton and soft glassy rheology.

    PubMed

    Mandadapu, Kranthi K; Govindjee, Sanjay; Mofrad, Mohammad R K

    2008-01-01

    The cytoskeleton is a complex structure within the cellular corpus that is responsible for the main structural properties and motilities of cells. A wide range of models have been utilized to understand cytoskeletal rheology and mechanics (see e.g. [Mofrad, M., Kamm, R., 2006. Cytoskeletal Mechanics: Models and Measurements. Cambridge University Press, Cambridge]). From this large collection of proposed models, the soft glassy rheological model (originally developed for inert soft glassy materials) has gained a certain traction in the literature due to the close resemblance of its predictions to certain mechanical data measured on cell cultures [Fabry, B., Maksym, G., Butler, J., Glogauer, M., Navajas, D., Fredberg, J., 2001. Scaling the microrheology of living cells. Physical Review Letters 87, 14102]. We first review classical linear rheological theory in a concise fashion followed by an examination of the soft glassy rheological theory. With this background we discuss the observed behavior of the cytoskeleton and the inherent limitations of classical rheological models for the cytoskeleton. This then leads into a discussion of the advantages and disadvantages presented to us by the soft glassy rheological model. We close with some comments of caution and recommendations on future avenues of exploration. PMID:18402964

  3. Control of the rheological properties of clay nanosheet hydrogels with a guanidinium-attached calix[4]arene binder.

    PubMed

    Lee, Ji Ha; Kim, Chaelin; Jung, Jong Hwa

    2015-10-21

    A 1,3-alternate calix[4]arene derivative 1 possessing four guanidinium moieties was synthesized as a molecular binder. The clay nanosheet (CNS) hydrogels were prepared upon addition of 1 and sodium polyacrylate (ASSP), and their mechanical properties were measured by rheometry. CNS hydrogels prepared by combining calix[4]arene 1 with dispersed CNSs surrounded by ASSPs showed an enhancement of mechanical properties such as viscosity and elasticity. PMID:26327603

  4. Effect of lime content on the processing conditions of cooked maize tortillas: changes of thermal, structural, and rheological properties

    NASA Astrophysics Data System (ADS)

    Alvarado-Gil, Juan J.; Vargas, Helion; Sanchez-Sinencio, F.; Gonzalez-Hernandez, J.; Miranda, L. C.

    1997-02-01

    Basic data on thermal, dielectric, and IR spectral properties of cooked tortillas were investigated with the major aim to understand the role of lime, Ca(OH)2, incorporated during the alkaline cooking process. The data are further supplemented by x-ray diffraction and texture measurements. The changes in the thermal diffusivities, measured by the photoacoustic technique, as well as the changes in texture, x-ray patterns, dielectric, and IR spectral properties are presented as a function of the lime concentration. The results show strong evidence that there is a marked concentration of lime (around 0.2%) above and below which different behavior patterns of the measured properties of tortilla were observed. In particular, the results for the dielectric constant and thermal diffusivity provide strong evidences for enhanced starch crosslinking taking place for lime content close to 0.2%.

  5. Western Canadian coking coals -- Thermal rheology and coking quality

    SciTech Connect

    Leeder, W.R.; Price, J.T.; Gransden, J.F.

    1997-12-31

    Methods of predicting coke strength developed from the thermal rheological properties of Carboniferous coals frequently indicate that Cretaceous coals would not make high quality coke -- yet both types of coals produce coke suitable for the iron blast furnace. This paper will discuss the reasons why Western Canadian coals exhibit lower rheological values and how to predict the strength of coke produced from them.

  6. Critical laminar shear-temperature effects on the nano- and mesoscale structure of a model fat and its relationship to oil binding and rheological properties.

    PubMed

    Acevedo, Nuria C; Block, Jane M; Marangoni, Alejandro G

    2012-01-01

    This article reports on the effect of laminar shear on structural and mechanical properties of physical mixtures of fully hydrogenated soybean oil (FHSO) in soybean oil (SO). Blends were crystallized statically and under laminar shear rates of 30 and 240 s(-1) at different wall temperatures (-10, 0, 20 degrees C). The micro- and nanocrystalline structures were characterized using Polarized Light Microscopy (PLM), and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Rheological analysis was used to determine changes in mechanical properties. Oil-binding capacity was analyzed through the measurement of the oil lost from the fat samples (OL). Shearing greatly affected the structure at the nano- and mesoscale. At low shear rates, blends displayed the largest increase in crystal size with an increase in wall temperature at both the nano- and mesoscale. On the other hand, at shear rates of 240 s(-1), the effect of crystallization temperature was observed only at the nanoscale since no changes in meso-crystal sizes were observed at different temperatures. Crystallization under laminar shear promoted the growth of spherical crystalline particles at the mesoscale, called here "solid-lipid meso-particles". Crystallization under higher shear rates led to the formation of a weak network with low oil-binding capacity and promoted the asymmetric growth of nanoplatelets. In statically crystallized blends, nanoplatelets had an aspect ratio of -2, while in sheared blends this value increased significantly. These results revealed the existence of critical shear rate values above which strong alterations in the structure of the solid crystalline network took place. Shearing also affected the material's strength. Laminar shear induced a decrease in elastic modulus and yield stress values which was more pronounced at higher shear rate-temperature combinations. Shear-temperature combinations were successfully used to structure fats at the nano and mesoscale. PMID:23234167

  7. Rheological Characterization Of Nano-Composite Hydrogels

    NASA Astrophysics Data System (ADS)

    Lombardi, Jack

    Engineered Polymer hydrogels and hydrogels from Bio macromolecules have visco-elastic properties that can be measured using Oscillatory Shear Rheology. Manipulation and measurement of physical properties in gels including F-127 Pluronic Block Co-Polymer and Poly(N-isopropylacrylamide)-Clay are shown through OSR by addition of salts, clays and glucose at physiological levels. Rheological analysis of f-127 illustrates changes in G' reduction with phase transition temperature. Measurements also indicate physical changes due to the aforementioned additives vary as a function of the gel physical and chemical structure. In particular, non-enzymatic glycation is shown to change the modulus of elasticity in both of the gels tested. Rheological analysis is also interpreted to produce a reduction In gel mesh size in the PNIPA -clay gels due to a possible co-solvency between phases of varying degrees of hydration.

  8. Rheological properties of magnetorheological suspensions based on core-shell structured polyaniline-coated carbonyl iron particles

    NASA Astrophysics Data System (ADS)

    Sedlačík, M.; Pavlínek, V.; Sáha, P.; Švrčinová, P.; Filip, P.; Stejskal, J.

    2010-11-01

    The sedimentation caused by the high density of suspended particles used in magnetorheological fluids is a significant obstacle for their wider application. In the present paper, core-shell structured carbonyl iron-polyaniline particles in silicone oil were used as a magnetorheological suspension with enhanced dispersion stability. Bare carbonyl iron particles were suspended in silicone oil to create model magnetorheological suspensions of different loading. For a magnetorheological suspension of polyaniline-coated particles the results show a decrease in the base viscosity. Moreover, the polyaniline coating has a negligible influence on the MR properties under an external magnetic field B. The change in the viscoelastic properties of magnetorheological suspensions in the small-strain oscillatory shear flow as a function of the strain amplitude, the frequency and the magnetic flux density was also investigated.

  9. Magma rheology variation in sheet intrusions (Invited)

    NASA Astrophysics Data System (ADS)

    Magee, C.; O'Driscoll, B.; Petronis, M. S.; Stevenson, C.

    2013-12-01

    transmitted into the inclusions during magma flow. We suggest that this represents a modification of the magma dynamics from Newtonian-like to Bingham-like behaviour. Furthermore, the spatial restriction of inclusions within the sheet intrusions suggest that subtle variations in magma rheology may partition apparently continuous intrusions, perhaps affecting lateral mixing and the longevity of discrete sheet segments. Detailed fabric analysis of other inclusion-free intrusions in the Ardnamurchan Central Complex supports this interpretation. Our results highlight that the crystalline cargo of a magma can result in temporal and spatial variations in magma rheology. This can partition coalesced magma bodies into ';zones' characterised by different magma properties, potentially affecting the location of magma flow pathways or even eruption sites.

  10. Mechanical, rheological, and bioactivity properties of ultra high-molecular-weight polyethylene bioactive composites containing polyethylene glycol and hydroxyapatite.

    PubMed

    Ahmad, Mazatusziha; Uzir Wahit, Mat; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

    2012-01-01

    Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50 phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

  11. Mechanical, Rheological, and Bioactivity Properties of Ultra High-Molecular-Weight Polyethylene Bioactive Composites Containing Polyethylene Glycol and Hydroxyapatite

    PubMed Central

    Ahmad, Mazatusziha; Wahit, Mat Uzir; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

    2012-01-01

    Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50 phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

  12. Effect of acidification and heating on the rheological properties of oil-water interfaces with adsorbed milk proteins.

    PubMed

    Mellema, M; Isenbart, J G

    2004-09-01

    The behavior of casein and whey proteins at the oil-water interface was studied using a dynamic drop tensiometer (DDT). The dilational modulus of the interface was measured for aqueous solutions of skim milk powder (SMP) and whey protein concentrate (WPC) with various additions (salt, calcium, lactose) and (order of) various processing steps. Acidification or heating was performed before or after creation of the interface. The elastic properties of oil-water interfaces with adsorbed milk proteins could partly determine the rate of partial coalescence and resulting product instability. For WPC, preacidification slows down the adsorption, but the modulus is not affected. This is probably because, although the whey proteins change conformation more slowly at the interface, still a homogeneous film is formed. If postacidification is applied, coarsening of the protein film leads to loss of interfacial rigidity. Preheating of the aqueous phase with WPC leads to denaturation and aggregation, but the aggregates formed are still surface active and give high moduli. If preheating of a WPC solution is followed by postacidification, the resulting modulus is high (approximately 60 mN/m). The oil-water interfacial properties of SMP are only minimally affected by preheating or by choice of powder (low, medium, or high heat). At low pH, however, aggregates are formed that are less surface active, and interfacial moduli are lower. If measurements are performed at high temperature (i.e., if postheating is applied), for both SMP and WPC systems, moduli became much lower (approximately 10 mN/m). This is probably because of accelerated rearrangements, leading to the formation of inhomogeneous film structures. PMID:15375034

  13. Structural properties of films and rheology of film-forming solutions of chitosan gallate for food packaging.

    PubMed

    Wu, Chunhua; Tian, Jinhu; Li, Shan; Wu, Tiantian; Hu, Yaqin; Chen, Shiguo; Sugawara, Tatsuya; Ye, Xingqian

    2016-08-01

    The chitosan gallates (CG) were obtained by free-radical-initiated grafting of gallic acid (GA) onto chitosan (CS) in this work. The chemical structures of the CG were corroborated by UV-vis, GPC and (1)H NMR analysis. The grafting reaction was accompanied with a degradation of the CS molecule. The shear-thinning flow behavior of CG film-forming solutions (CG FFS) decreased with the grafting amount of GA into CS chain, while the CG FFS grafted at a lower GA value behaved like a networks containing entangled or cross-linked polymer chains with a more elastic behavior. The increasing of GA grafting onto the CS chain led to a reduction of tensile strength, elongation at break and water resistance in the corresponding films, but increases in the antioxidant and antimicrobial activities were observed. The microstructure of the film was investigated using scanning electron and atomic force microscope, and the results were closely related to the observed film properties. PMID:27112845

  14. Thermodynamic and rheological properties of solid-liquid systems in coal processing. Quarterly technical report, October 1--December 31, 1994

    SciTech Connect

    Kabadi, V.N.; Ilias, S.

    1995-10-01

    The objective of this project is to develop a model for solid-liquid equilibria and a model for viscosities of the products of coal liquefaction processes. The same characterization procedure and representation by continuous distributions as used in previous work on vapor-liquid equilibria and excess enthalpies of coal liquids will be used. Models when fully developed will give the solid-liquid phase equilibrium properties and viscosities as factors of temperature and pressure for known molecular weight distribution and structural characterization of the coal liquid. To accomplish this well, the project requires three tasks: (1) Solid-Liquid phase equilibrium model development; (2) Experimental Viscosity Measurements; and (3) Viscosity Model Development. The work on development of a predictive model for saturated liquid volumes of coal model compounds has been completed. A manuscript has been prepared for submission to AIChE Journal. A copy of the manuscript is attached. Work on extending the viscosity model to coal derived liquids is continuing and progress on this work will be included in the next report.

  15. Development of an in situ method to define the rheological properties of slurries and sludges stored in underground tanks

    SciTech Connect

    Heath, W.O.

    1987-04-01

    A method for measuring the in situ flow properties of high-level radioactive waste (HLW) sludges has been developed at Pacific Northwest Laboratory, along with a preconceptual design for a shear vane device that can be installed in underground HLW storage tanks and used to make those measurements remotely. The data obtained with this device will assist in the design of mixing equipment used to resuspend and remove HLW sludges from their storage tanks for downstream processing. This method is also suitable for remotely characterizing other types of waste sludges and slurries. Commonly available viscometric methods were adapted to allow characterization of sludge samples in the laboratory such that the laboratory and in-tank data can be directly compared (scaled up). Procedures for conducting measurements and analyzing the results in terms of useful mathematical models describing both start-up and steady-state flow behavior are presented, as is a brief tutorial on the types of flow behavior that can be exhibited by tank sludges. 30 refs., 36 figs., 14 tabs.

  16. Impact of Rheological Modifiers on Various Slurries Supporting DOE Waste Processing

    SciTech Connect

    Chun, Jaehun; Bredt, Paul R.; Hansen, Erich; Bhosale, Prasad S.; Berg, John C.

    2010-03-11

    Controlling the stability and subsequent rheological properties of slurries has been an important but challenging issue in nuclear waste treatment, one that previous research has yet to sufficiently address. At the Hanford and Savannah River sites, operation of the waste treatment facilities at increased solids loading reduces the evaporative load on the melter systems and thereby increases waste processing rates. However, at these higher solids loadings, increased slurry rheology becomes a significant processing issue. The current study evaluates the use of several rheological modifiers to alleviate increased slurry rheology at high waste solids concentrations. Rheological modifiers change particle interactions in slurry. For colloidal slurries, modifiers mainly alter the electrostatic and steric interactions between particles, leading to a change in slurry rheology. Weak organic acid type rheological modifiers strengthen electrostatic repulsion whereas nonionic/polymer surfactant type rheological modifiers introduce a steric repulsion. We investigated various rheological modifiers using high level waste (HLW) nuclear waste simulants characterized typically by high ionic strength and a wide range of pH from 4 to 13. Using rheological analysis, it was found that citric acid and polyacrylic acid would be good rheological modifiers for the HLW simulants tested, effectively reducing slurry rheology by 40% or more. Physical insights into the mechanisms driving stabilization by these rheological modifiers will be discussed.

  17. Rheology of interfacial protein-polysaccharide composites

    NASA Astrophysics Data System (ADS)

    Fischer, P.

    2013-05-01

    The morphology and mechanical properties of protein adsorption layers can significantly be altered by the presence of surfactants, lipids, particles, other proteins, and polysaccharides. In food emulsions, polysaccharides are primarily considered as bulk thickener but can under appropriate environmental conditions stabilize or destabilize the protein adsorption layer and, thus, the entire emulsion system. Despite their ubiquitous usage as stabilization agent, relatively few investigations focus on the interfacial rheology of composite protein/polysaccharide adsorption layers. The manuscript provides a brief review on both main stabilization mechanisms, thermodynamic phase separation and electrostatic interaction and discusses the rheological response in light of the environmental conditions such as ionic strength and pH.

  18. Polymers with customizable optical and rheological properties based on an epoxy acrylate based host-guest system

    NASA Astrophysics Data System (ADS)

    Gleiβner, U.; Hobmaier, J.; Hanemann, T.

    2015-09-01

    We report an easy way to tune the optical refractive index and viscosity of an epoxy acrylate-based host-guest system which can be used for the fabrication of optical waveguides. This allows fast and precise modification of the material system for different replication methods like hot embossing, inkjet printing or spin coating. To modify the refractive index n, an electron-rich organic dopant such as phenanthrene is added to a commercially available reactive polymer based resin. Moreover, changes in viscosity can be achieved by using a comonomer with suitable properties like benzyl methacrylate (BMA). We used a commercially available UV-curable epoxy acrylate based polymer matrix to investigate both the influence of phenanthrene and of benzyl methacrylate. First, mixtures of the pure polymer and benzyl methacrylate with a ratio of 30, 50, and 80 wt% benzyl methacrylate were produced. Second, phenanthrene was added with 5 and 10 wt%, respectively. All components were mixed and then polymerized by UV-irradiation and with a thermal postcure. The viscosity of the mixtures decreased at 20°C linearly from 1.5 Pa·s (30 wt%) to 8 mPa·s (80 wt%), whereas the refractive index decreased at the same time by a small amount from 1.570 to 1.568 (@589 nm, 20 °C). By adding phenanthrene refractive index increased to a maximum of n = 1.586 (50 wt% BMA, 10 wt% phenanthrene). Abbe numbers for the compositions without phenanthrene ranged from 35 to 38.

  19. Rheological characterization of an artificial synovial fluid.

    PubMed

    Casentini, G; Di Paola, L; Marrelli, L; Palma, F

    2005-07-01

    Rheological measurements on two classes of artificial synovial fluids have been carried out in the attempt to get a suitable but cheap lubricant for wear tests of prosthetic materials. Fluids of both classes are solutions of hyaluronic acid (HA) that, for one class, is dissolved into a simple Ringer solution whereas, for the other class, into a mixture of human serum and Ringer solution. Similar rheological properties have been observed for both classes of fluids. Experimental results have been interpreted by two classical models that are commonly used in the literature to describe the rheological behavior of colloidal systems and of polymer solutions with high entanglement density, respectively. The quality of correlations shows that, at high HA concentrations, entangled structures are largely present and cannot be neglected. PMID:16049905

  20. Gelation of edible blue-green algae protein isolate (Spirulina platensis Strain Pacifica): thermal transitions, rheological properties, and molecular forces involved.

    PubMed

    Chronakis, I S

    2001-02-01

    Proteins isolated from blue-green algae Spirulina platensis strain Pacifica were characterized by visible absorption, differential scanning calorimetry (DSC), viscometry, and dynamic oscillatory rheological measurements. Unique thermal unfolding, denaturation, aggregation, and gelation of the algal protein isolate are presented. DSC analysis showed that thermal transitions occur at about 67 and 109 degrees C at neutral pH. Calcium chloride stabilized the quaternary structure against denaturation and shifted the transitions at higher temperatures. Viscometric studies of Spirulina protein isolate as a function of temperature showed that the onset of the viscosity increase is closely related to the dissociation-denaturation process. Lower viscosities were observed for the protein solutions dissolved at pH 9 due to an increased protein solubility. Solutions of Spirulina protein isolate form elastic gels during heating to 90 degrees C. Subsequent cooling at ambient temperatures caused a further pronounced increase in the elastic moduli and network elasticity. Spirulina protein isolate has good gelling properties with fairly low minimum critical gelling concentrations of about 1.5 and 2.5 wt % in 0.1 M Tris buffer, pH 7, and with 0.02 M CaCl(2) in the same buffer, respectively. It is suggested that mainly the interactions of exposed hydrophobic regions generate the molecular association, initial aggregation, and gelation of the protein isolate during the thermal treatment. Hydrogen bonds reinforce the network rigidity of the protein on cooling and further stabilize the structure of Spirulina protein gels but alone are not sufficient to form a network structure. Intermolecular sulfhydryl and disulfide bonds were found to play a minor role for the network strength of Spirulina protein gels but affect the elasticity of the structures formed. Both time and temperature at isothermal heat-induced gelation within 40-80 degrees C affect substantially the network formation and

  1. Micro-heterogeneity and micro-rheological properties of high-viscosity barley beta-glucan solutions studied by diffusion wave spectroscopy (DWS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soluble fiber ß-glucan is one of the key dietary material in healthy food products known for reducing serum cholesterol levels. The micro-structural heterogeneity and micro-rheology of high-viscosity barley ß-glucan solutions were investigated by the diffusion wave spectroscopy (DWS) technology. By ...

  2. Reducing fat levels in cheddar-like goat cheese: impact on proteolysis and rheological properties over 6 months of refrigerated storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development of low-fat goat cheeses that appeal to health conscious consumers requires information on how the reduction of fat affects the quality traits of the cheese, such as its proteolysis and rheology. Goat milk samples containing 3.6, 2.0, 1.0, and <0.5% fat were processed into full-fat (F...

  3. Influence of drug incorporation, temperature and storage time on the pH, textural and rheological properties of different poloxamer hydrogels.

    PubMed

    Almeida, Hugo; Amaral, Maria Helena; Lobão, Paulo; Lobo, José Manuel Sousa

    2013-12-01

    In recent years, Poloxamers had attracted a particular interest in the design of dermal and transdermal delivery systems in order to improve or retard drug permeation through the skin. In the present study, the influence of different parameters, such as, temperature, storage time, type of polymer (Lutrol(®) F-127 and Lutrol(®) F-108) and the addition of two types of drugs (ibuprofen and hydrocortisone) in the pH, texture and rheological behavior of topical pharmaceutical formulations containing poloxamers was assessed. In fact, the type of polymer used in the preparation of the hydrogels, the type of drug incorporated, the temperature and the storage time caused changes in the pH, texture and rheological behavior of topical formulations containing Lutrol(®) F-127 and Lutrol(®) F-108. Lutrol(®) F-127 hydrogels showed higher values of pH, firmness, adhesiveness and viscosity than Lutrol(®) F-108 hydrogels. The chemical nature of the drugs incorporated in these poloxamer hydrogels influence the pH of the preparations. Low percentages of drug incorporated into both types of hydrogels didn't affect significantly their textural and rheological characteristics. The hydrogels prepared with Lutrol(®) F- 127 proved to be more resistant to temperature variations, maintaining their rheological behavior over time. PMID:23886320

  4. Blood Rheology in Marine Mammals

    PubMed Central

    Castellini, Michael A.; Baskurt, Oguz; Castellini, Judith M.; Meiselman, Herbert J.

    2010-01-01

    The field of blood oxygen transport and delivery to tissues has been studied by comparative physiologists for many decades. Within this general area, the particular differences in oxygen delivery between marine and terrestrial mammals has focused mainly on oxygen supply differences and delivery to the tissues under low blood flow diving conditions. Yet, the study of the inherent flow properties of the blood itself (hemorheology) is rarely discussed when addressing diving. However, hemorheology is important to the study of marine mammals because of the critical nature of the oxygen stores that are carried in the blood during diving periods. This review focuses on the essential elements of hemorheology, how they are defined and on fundamental rheological applications to marine mammals. While the comparative rationale used throughout the review is much broader than the particular problems associated with diving, the basic concepts focus on how changes in the flow properties of whole blood would be critical to oxygen delivery during diving. This review introduces the reader to most of the major rheological concepts that are relevant to the unique and unusual aspects of the diving physiology of marine mammals. PMID:21423386

  5. Rheological Modifier Testing with DWPF Process Slurries

    SciTech Connect

    MICHAEL, STONE

    2004-02-01

    Rheological modification agents were tested on simulated SRAT and SME products to determine if a suitable agent could be found for the DWPF process slurries. The agents tested were dispersants that lower the rheological properties of slurries by preventing agglomerization. Dolapix CE64, an ethylene glycol, and Disperse-Ayd W28, a polyacrylate, were the most effective dispersants tested. Further evaluation and testing should be performed on Dolapix CE64 and Disperse-Ayd W28 to determine if implementation is possible in DWPF. The initial phase of future work will include optimization of the rheology modifier by the Illinois Institute of Technology (IIT) and development of a maximum concentration limit for the rheology modifiers. IIT has been commissioned to evaluate the properties of these chemicals to determine if the chemical makeup can be optimized to enhance the properties of these modifiers. An initial concentration limit based upon the DWPF flammability limit and other constraints should be calculated to determine the potential downstream impacts.

  6. Magneto-rheological defects and failures: A review

    NASA Astrophysics Data System (ADS)

    Wahid, SA; Ismail, I.; Aid, S.; Rahim, MSA

    2016-02-01

    Magneto-rheological fluid is the colloidal suspension of micron sized magnetic particles in a carrier fluid where defects and failures occur at many circumstances. This paper presents a review on defects and failures of magneto-rheological fluid in engineering applications. The most significant defect is hard cake which developed due to re-dispersion difficulties of remnant particles magnetization, leaving the magneto-rheological fluid ineffective. Clumping effect on the other hand is a separation of carrier fluid from the magnetic particles when magneto-rheological fluid is being exposed to higher magnetic field for an extended period of time. As clumping occurred, it leads to Fluid Particle Separation (FPS) which is believed altering the strength distribution of magneto-rheological fluid and therefore reducing the squeezing force. Another significant failure is magnetic particles oxidation of the magneto-rheological fluid. This paper also will discuss on stability problems which is the most challenged issue in magneto-rheological fluid technology. With the comprehensive review in this paper, researcher can design materials of magneto-rheological fluid for better properties.

  7. Microgravity Foam Structure and Rheology

    NASA Technical Reports Server (NTRS)

    Durian, Douglas J.

    1997-01-01

    To exploit rheological and multiple-light scattering techniques, and ultimately microgravity conditions, in order to quantify and elucidate the unusual elastic character of foams in terms of their underlying microscopic structure and dynamics. Special interest is in determining how this elastic character vanishes, i.e. how the foam melts into a simple viscous liquid, as a function of both increasing liquid content and shear strain rate. The unusual elastic character of foams will be quantified macroscopically by measurement of the shear stress as a function of static shear strain, shear strain rate, and time following a step strain; such data will be analyzed in terms of a yield stress, a static shear modulus, and dynamical time scales. Microscopic information about bubble packing and rearrangement dynamics, from which these macroscopic non-Newtonian properties presumably arise, will be obtained non-invasively by novel multiple-light scattering diagnostics such as Diffusing-Wave Spectroscopy (DWS). Quantitative trends with materials parameters, such as average bubble size, and liquid content, will be sought in order to elucidate the fundamental connection between the microscopic structure and dynamics and the macroscopic rheology.

  8. Surface shear rheology of saponin adsorption layers.

    PubMed

    Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Edward; Stoyanov, Simeon D

    2012-08-21

    Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial biological activities. The molecular mechanisms behind these unusual properties are unknown, and, therefore, the saponins have attracted significant research interest in recent years. In our previous study (Stanimirova et al. Langmuir 2011, 27, 12486-12498), we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 ± 30 mN/m. In this Article, we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins, which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibit purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, a single master curve describes the data for the viscoelastic creep compliance versus deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases, and the adsorption layers eventually transform into viscous ones. The experimental creep-recovery curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers. PMID:22830458

  9. Development of Alternative Rheological Measurements for DWPF Slurry Samples (U)

    SciTech Connect

    Koopman, D. c.

    2005-09-01

    Rheological measurements are used to evaluate the fluid dynamic behavior of Defense Waste Processing Facility, DWPF, slurry samples. Measurements are currently made on non-radioactive simulant slurries using two state-of-the-art rheometers located at the Aiken County Technical Laboratory, ACTL. Measurements are made on plant samples using a rheometer in the Savannah River National Laboratory, SRNL, Shielded Cells facility. Low activity simulants or plant samples can be analyzed using a rheometer located in a radioactive hood in SRNL. Variations in the rheology of SB2 simulants impacted the interpretation of results obtained in a number of related studies. A separate rheological study was initiated with the following four goals: (1) Document the variations seen in the simulant slurries, both by a review of recent data, and by a search for similar samples for further study. (2) Attempt to explain the variations in rheological behavior, or, failing that, reduce the number of possible causes. In particular, to empirically check for rheometer-related variations. (3) Exploit the additional capabilities of the rheometers by developing new measurement methods to study the simulant rheological properties in new ways. (4) Formalize the rheological measurement process for DWPF-related samples into a series of protocols. This report focuses on the third and fourth goals. The emphasis of this report is on the development and formalization of rheological measurement methods used to characterize DWPF slurry samples. The organization is by rheological measurement method. Progress on the first two goals was documented in a concurrent technical report, Koopman (2005). That report focused on the types and possible causes of unusual rheological behavior in simulant slurry samples. It was organized by the sample being studied. The experimental portion of this study was performed in the period of March to April 2004. A general rheology protocol for routine DWPF slurry samples, Koopman

  10. 77 FR 25406 - Consortium on “Concrete Rheology: Enabling Metrology (CREME)”: Membership Fee Update

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-30

    ... National Institute of Standards and Technology Consortium on ``Concrete Rheology: Enabling Metrology (CREME... NIST/Industry Consortium on Concrete Rheology: Enabling Metrology (CREME)''. The notice stated that... consortium is to predict the pumpability of a grout/mortar or a concrete from the rheological properties...

  11. Rheology of planetary ices

    SciTech Connect

    Durham, W.B.; Kirby, S.H.; Stern, L.A.

    1996-04-24

    The brittle and ductile rheology of ices of water, ammonia, methane, and other volatiles, in combination with rock particles and each other, have a primary influence of the evolution and ongoing tectonics of icy moons of the outer solar system. Laboratory experiments help constrain the rheology of solar system ices. Standard experimental techniques can be used because the physical conditions under which most solar system ices exist are within reach of conventional rock mechanics testing machines, adapted to the low subsolidus temperatures of the materials in question. The purpose of this review is to summarize the results of a decade-long experimental deformation program and to provide some background in deformation physics in order to lend some appreciation to the application of these measurements to the planetary setting.

  12. Rheologically interesting polysaccharides from yeasts

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Nelson, G. A.; Cathey, C. A.; Fuller, G. G.

    1989-01-01

    We have examined the relationships between primary, secondary, and tertiary structures of polysaccharides exhibiting the rheological property of friction (drag) reduction in turbulent flows. We found an example of an exopolysaccharide from the yeast Cryptococcus laurentii that possessed high molecular weight but exhibited lower than expected drag reducing activity. Earlier correlations by Hoyt showing that beta 1 --> 3, beta 2 --> 4, and alpha 1 --> 3 linkages in polysaccharides favored drag reduction were expanded to include correlations to secondary structure. The effect of sidechains in a series of gellan gums was shown to be related to sidechain length and position. Disruption of secondary structure in drag reducing polysaccharides reduced drag reducing activity for some but not all exopolysaccharides. The polymer from C. laurentii was shown to be more stable than xanthan gum and other exopolysaccharides under the most vigorous of denaturing conditions. We also showed a direct relationship between extensional viscosity measurements and the drag reducing coefficient for four exopolysaccharides.

  13. Morphology and Rheology of Polymer/Liquid Crystal Blends

    NASA Astrophysics Data System (ADS)

    Yu, Wei; Wu, Youjun; Zhou, Chixing

    2008-07-01

    The morphology and rheology of immiscible polymer blends has been the subjects of many researches. It is well known that the properties of blends depend on the rheology of components fluids as well as the properties of interface. For blends composed of isotropic fluids, the capillary number, defined as the ratio between the shear stress and the interfacial stress, controls the behaviors of dispersed droplet under flow field. When one component becomes an anisotropic fluid, it is expected that the anisotropic interfacial properties would greatly affect the properties of the blends. The effect of anisotropic properties of interface between a polymer and a liquid crystal (LC) on the steady and transient behavior of morphological evolution and rheology properties is the main interest of the present work. The deformation and relaxation behavior of a LC droplet immersed in a polymer matrix is investigated and compared with the predictions of our recent model.

  14. Rheology of giant micelles

    NASA Astrophysics Data System (ADS)

    Cates, M. E.; Fielding, S. M.

    2006-12-01

    Giant micelles are elongated, polymer-like objects created by the self-assembly of amphiphilic molecules (such as detergents) in solution. Giant micelles are typically flexible, and can become highly entangled even at modest concentrations. The resulting viscoelastic solutions show fascinating flow behaviour (rheology) which we address theoretically in this article at two levels. First, we summarize advances in understanding linear viscoelastic spectra and steady-state nonlinear flows, based on microscopic constitutive models that combine the physics of polymer entanglement with the reversible kinetics of self-assembly. Such models were first introduced two decades ago, and since then have been shown to explain robustly several distinctive features of the rheology in the strongly entangled regime, including extreme shear thinning. We then turn to more complex rheological phenomena, particularly involving spatial heterogeneity, spontaneous oscillation, instability and chaos. Recent understanding of these complex flows is based largely on grossly simplified models which capture in outline just a few pertinent microscopic features, such as coupling between stresses and other order parameters such as concentration. The role of ‘structural memory’ (the dependence of structural parameters such as the micellar length distribution on the flow history) in explaining these highly nonlinear phenomena is addressed. Structural memory also plays an intriguing role in the little-understood shear thickening regime, which occurs in a concentration regime close to but below the onset of strong entanglement, and which is marked by a shear-induced transformation from an inviscid to a gelatinous state.

  15. The Rheology of Concentrated Suspensions

    SciTech Connect

    Andreas Acrivos

    2004-09-07

    Research program on the rheological properties of flowing suspensions. The primary purpose of the research supported by this grant was to study the flow characteristics of concentrated suspensions of non-colloidal solid particles and thereby construct a comprehensive and robust theoretical framework for modeling such systems quantitatively. At first glance, this seemed like a modest goal, not difficult to achieve, given that such suspensions were viewed simply as Newtonian fluids with an effective viscosity equal to the product of the viscosity of the suspending fluid times a function of the particle volume fraction. But thanks to the research findings of the Principal Investigator and of his Associates, made possible by the steady and continuous support which the PI received from the DOE Office of Basic Energy Sciences, the subject is now seen to be more complicated and therefore much more interesting in that concentrated suspensions have been shown to exhibit fascinating and unique rheological properties of their own that have no counterpart in flowing Newtonian or even non-Newtonian (polymeric) fluids. In fact, it is generally acknowledged that, as the result of these investigations for which the PI received the 2001 National Medal of Science, our understanding of how suspensions behave under flow is far more detailed and comprehensive than was the case even as recently as a decade ago. Thus, given that the flow of suspensions plays a crucial role in many diverse physical processes, our work has had a major and lasting impact in a subject having both fundamental as well as practical importance.

  16. Rheological behaviour of heated potato starch dispersions

    NASA Astrophysics Data System (ADS)

    Juszczak, L.; Witczak, M.; Ziêba, T.; Fortuna, T.

    2012-10-01

    The study was designed to investigate the rheological properties of heated potato starch dispersions. Water suspensions of starch were heated at 65, 80 or 95°C for 5, 15, 30 or 60 min. The dispersions obtained were examined for granule size distribution and rheology. It was found that the starch dispersions significantly differed in both respects. The mean diameters of starch granules were largest for the dispersion heated at 65°C and smallest for that heated at 95°C. As the heating temperature was raised, the yield stresses and consistency coefficients decreased, while the flow behaviour indexes and Casson plastic viscosities increased. There were also differences in the viscoelastic properties of the dispersions: for those heated at 65°C the storage and loss moduli increased with heating time whereas for those heated at 80°C both moduli decreased.

  17. Measurements and models of cytoskeletal rheology

    NASA Astrophysics Data System (ADS)

    Kamm, Roger

    2006-11-01

    Much attention has recently focused on understanding the rheology of living cells and reconstituted actin gels using a variety of experimental methods (e.g., single- and multi-particle tracking, magnetic twisting cytometry, AFM indentation) and several different models or descriptors (e.g., biopolymer models, tensegrity, cellular solids, power-law rheology), but the debate continues regarding the fundamental basis for the experimental observations. Our recent studies examine the time-dependent behavior of neutrophils as they deform to enter a narrow channel with capillary-scale dimensions. A sudden drop in the shear modulus is observed, followed by recovery to pre-deformation values in < 1 minute. These rheological changes coincide with a reduction in f-actin content and a transient increase in calcium ion concentration [Ca^++], and the change in storage modulus can be prevented by calcium chelation, suggesting that these observations are causally linked. Cells lacking the ability to increase [Ca^++] also become activated more rapidly following deformation, and the time to activation is independent of intracellular strain rates, contrary to experiments lacking the chelating agent. To better understand these processes and the nature of cytoskeletal rheology in general, we have developed a Brownian dynamics model for cytoskeletal self-assembly and subsequent rheological measurement by single particle tracking. Cross-linking proteins are included possessing a range of properties that lead to a variety of cytoskeletal structures from a fine, homogeneous mesh to a structure containing large stress fibers of varying thickness. These results are described in a multi-dimensional phase space that takes into account the geometry, dimensions and stiffness of the cross-linkers.

  18. Rheological Changes in Refrigerated Dough During Storage in Relation to Proteins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Refrigerated dough is a flour-based, unbaked product that is stored between 4-7 ºC. The aim of this work was to study the rheological properties of refrigerated dough during storage and determine their correlations with dough proteins. Rheological properties were determined using texture analyzer an...

  19. Anomalous rheological behavior of long glass fiber reinforced polypropylene

    NASA Astrophysics Data System (ADS)

    Kim, Dong Hak; Lee, Young Sil; Son, Younggon

    2012-12-01

    Dynamic rheological properties of PP-based long glass fiber-reinforced thermoplastics (LFT) were investigated. Weight fractions of the glass fibers investigated in the present study ranged from 0.15 to 0.5, which are higher than those of previous studies. We observed very abnormal rheological behavior. Complex viscosity (η*) of the LFT increased with the glass fiber content up to 40 wt. %. However, the η* with a weight fraction of 0.5 is observed to be lower than that of LFT with a weight fraction of 0.4 in spite of higher glass fiber content. From various experiments, we found that this abnormal behavior is analogous to the rheological behavior of a lyotropic liquid crystalline polymer solution and concluded that the abnormal rheological behavior for the LFT is attributed to the formation of a liquid crystal- like structure at high concentrations of long glass fibers.

  20. Review Of Rheology Models For Hanford Waste Blending

    SciTech Connect

    Koopman, D. C.; Stone, M.

    2013-09-26

    The area of rheological property prediction was identified as a technology need in the Hanford Tank Waste - waste feed acceptance initiative area during a series of technical meetings among the national laboratories, Department of Energy-Office of River Protection, and Hanford site contractors. Meacham et al. delivered a technical report in June 2012, RPP-RPT-51652 ''One System Evaluation of Waste Transferred to the Waste Treatment Plant'' that included estimating of single shell tank waste Bingham plastic rheological model constants along with a discussion of the issues inherent in predicting the rheological properties of blended wastes. This report was selected as the basis for moving forward during the technical meetings. The report does not provide an equation for predicting rheological properties of blended waste slurries. The attached technical report gives an independent review of the provided Hanford rheological data, Hanford rheological models for single tank wastes, and Hanford rheology after blending provided in the Meacham report. The attached report also compares Hanford to SRS waste rheology and discusses some SRS rheological model equations for single tank wastes, as well as discussing SRS experience with the blending of waste sludges with aqueous material, other waste sludges, and frit slurries. Some observations of note: Savannah River Site (SRS) waste samples from slurried tanks typically have yield stress >1 Pa at 10 wt.% undissolved solids (UDS), while core samples largely have little or no yield stress at 10 wt.% UDS. This could be due to how the waste has been processed, stored, retrieved, and sampled or simply in the differences in the speciation of the wastes. The equations described in Meacham's report are not recommended for extrapolation to wt.% UDS beyond the available data for several reasons; weak technical basis, insufficient data, and large data scatter. When limited data are available, for example two to three points, the equations