Science.gov

Sample records for elastomeric gasket materials

  1. [Elastomeric impression materials].

    PubMed

    Anagnostopoulos, T; Tsokas, K

    1990-01-01

    A review of the literature on elastomeric impression materials, is presented in this paper. The article mentions the composition and the most important properties of the elastomeric impression materials used in dental practice. The clinical significance of these materials, physical and mechanical properties are also emphasized. In addition some new elastomeric impression materials with improved properties and a new (experimental) light-cured impression material, are mentioned. Another part of this article is the biocompatibility of these materials. In the end the great significance of handling is outlined. PMID:2130039

  2. Fluorinated elastomeric materials

    DOEpatents

    Lagow, Richard J.; Dumitru, Earl T.

    1986-11-04

    This invention relates to a method of making perfluorinated elastomeric materials, and to materials made by such methods. In the full synthetic scheme, a partially fluorinated polymeric compound, with moieties to prevent crystallization, is created. It is then crosslinked to a desired degree, then perfluorinated. Various intermediate materials, such as partially fluorinated crosslinked polymers, have useful properties, and are or may become commercially available. One embodiment of this invention therefore relates to perfluorination of a selected partially fluorinated, crosslinked material, which is one step of the full synthetic scheme.

  3. Fluorinated elastomeric materials

    DOEpatents

    Lagow, Richard J.; Dumitru, Earl T.

    1990-02-13

    This invention relates to a method of making perfluorinated elastomeric materials, and to materials made by such methods. In the full synthetic scheme, a partially fluorinated polymeric compound, with moieties to prevent crystallization, is created. It is then crosslinked to a desired degree, then perfluorinated. Various intermediate materials, such as partially fluorinated crosslinked polymers, have useful properties, and are or may become commercially available. One embodiment of this invention therefore relates to perfluorination of a selected partially fluorinated, crosslinked material, which is one step of the full synthetic scheme.

  4. [Elastomeric impression materials].

    PubMed

    Levartovsky, S; Folkman, M; Alter, E; Pilo, R

    2011-04-01

    Elastomeric impression materials are in common use. The impression taken should be highly precise, thus, requiring specific care when manipulatingthese materials. There are 4 groups of elastomers; polysulfide, condensation silicone, addition silicone and polyether; each differ in their setting mechanism and their physical and chemical properties. This review elaborates the major properties of elastomers and its implications on their use. The impression material is inserted into the patient's mouth in a viscous state and transforms into viscoelastic state, upon withdrawal, influencing the residual deformation. The requirements are minimal residual deformation or maximal elastic recovery. As the mouth is a wet environment a major consideration is hydrophilicity. The wettability which is estimated by measuring either the contact angle of a droplet of water and the substrate post setting or the contact angle of a droplet of impression material and the wet tooth pre setting, determines the interaction of the material with both mouth fluids and gypsum. As the primary end target is to obtain a model depicting accurately the oral details, an attention to the impressions' compatibility with gypsum should also be given. Many studies were conducted to get a thorough understanding of the hydrophilic properties of each material, and the mechanism utilized, such as surfactants in hydrophilic PVS. Polyether is the only material that is truly hydrophilic; it exhibits the lowest contact angle, during and after setting. Recent studies show that during setting the Polyether hydrophilicity is increased compared to the condition after setting. Dimensional stability, a crucial property of the impression, is affected by the physical and chemical attributes of the material, such as its tear strength. Polysulfide has the highest tear strength. Tear Strength is affected by two major parameters, viscosity, a built-in property, and how fast the impression is pulled out of the mouth, the

  5. Friction and abrasion of elastomeric materials

    NASA Technical Reports Server (NTRS)

    Gent, A. N.

    1975-01-01

    An abrasion apparatus is described. Experimental measurements are reported for four representative elastomeric materials, including a typical high-quality tire tread material and a possible replacement material for aircraft tire treads based on transpolypentenamer (TPPR). Measurements are carried out at different levels of frictional work input, corresponding to different severities of wear, and at both ambient temperature and at 100 C. Results indicate the marked superiority in abrasion resistance of the material based on TPPR, especially at 100 C, in comparison with the other materials examined.

  6. Wettability of nonaqueous elastomeric impression materials.

    PubMed

    Chai, J Y; Yeung, T C

    1991-01-01

    The wettability of eight nonaqueous elastomeric impression materials was studied by comparing their contact angles. The materials included three polyethers (one of which was light activated), three hydrophilic poly(vinyl siloxanes), one conventional poly(vinyl siloxane), and one poly(vinyl siloxane) putty. Extracted teeth were prepared to approximate the roughness of a tooth preparation. Contact angles were measured at different time intervals after the start of mixing but were not shown to be significant. The nonhydrophilic poly(vinyl siloxane) materials and the poly(vinyl siloxane) putty were found to be significantly less wettable. PMID:1817528

  7. The development and testing of asbestos-free gasket materials

    SciTech Connect

    Mallow, W.A. )

    1992-01-01

    Of the 27 vendors contacted, 11 submitted asbestos-free gasket materials for thermal analysis followed by hydrostatic pressure testing, steam pressure testing, and fire testing. Virtually all were acceptable up to 400 C (air-free), and most were stable to 700 C. Several can be used to over 900 C in air or gases, since they are ceramic. Several graphitic gaskets are serviceable to 900 C in absence of air. Several performed well in steam pressure testing to 315 C, requiring a single adjustment in bolt/flange pressure after pressurization. Many acquired a compression set and consequent slight pressure loss, but responded well to bolt tightening. All except one are made of compressed ceramic or graphite fiber with 0-35 wt% binder, hence was inelastic but malleable/compressible. The large number of ceramic-and graphitic-based gasket materials obviated the need for further development; efforts were concentrated on critical evaluation of the off-the-shelf available materials, in comparison with asbestos.

  8. 46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... other equivalent material fitted with gaskets and clamping devices. 42.15-30 Section 42.15-30 Shipping... equivalent material fitted with gaskets and clamping devices. (a) Hatchway coamings. At positions 1 and 2 the... equivalent material fitted with gaskets and clamping devices shall be as specified in § 42.15-25(a)(1)....

  9. 46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... other equivalent material fitted with gaskets and clamping devices. 42.15-30 Section 42.15-30 Shipping... equivalent material fitted with gaskets and clamping devices. (a) Hatchway coamings. At positions 1 and 2 the... equivalent material fitted with gaskets and clamping devices shall be as specified in § 42.15-25(a)(1)....

  10. Hydrophilicity of unset and set elastomeric impression materials.

    PubMed

    Rupp, Frank; Geis-Gerstorfer, Jurgen

    2010-01-01

    The aim of this study was to compare the initial hydrophilicity of unset and set elastomeric impression materials. Initial water contact angles were studied on thin unset and set films of one polyether and six polyvinyl siloxane (PVS) impression materials using high-resolution drop shape analysis at drop ages of 1 and 3 seconds. All unset PVS materials were very hydrophobic initially but showed different kinetics of hydrophilization. In contrast, the unset polyether was more hydrophilic initially but lacked distinct hydrophilization. All impression materials showed statistically significant contact angle differences between unset and set surfaces (P < .05). Dependent on the drop age, two PVS materials reached or exceeded the hydrophilicity of the polyether (P < .05). It can be concluded that studies on the wetting behavior of elastomeric impression materials should consider both the experimental drop age and set and unset material surfaces. PMID:21209992

  11. Evaluation of dimensional stability of autoclavable elastomeric impression material.

    PubMed

    Surendra, G P; Anjum, Ayesha; Satish Babu, C L; Shetty, Shilpa

    2011-03-01

    Impressions are important sources of cross contamination between patients and dental laboratories. As a part of infection control impressions contaminated with variety of micro-organisms via blood and oral secretions should be cleaned and disinfected or sterilized before being handled in dental laboratory. The purpose of this study was to determine the effect of autoclaving on dimensional stability of elastomeric impression material (polyvinyl siloxane-Affinis). In this in vitro study standardized stainless steel die as per ADA specification number 19 was fabricated. Polyvinyl siloxane (Affinis) light body and putty viscosity elastomeric impression materials were used. A total of 40 impressions of the stainless steel die were made and numeric coding system was used to identify the samples. Measurements were made using a measuring microscope. Distance between the cross lines CD and C'D' reproduced in the impression were measured before autoclaving, immediately after autoclaving and 24 hours after autoclaving and dimensional change was calculated. The data obtained was subjected to statistical analysis. The mean difference in dimensional change between the three groups was not statistically significant (P > 0.05). However the results revealed that there was higher mean dimensional change immediately after autoclaving when compared to the other 2 time intervals. It is desirable to delay the casting of an autoclavable elastomeric impression material by about 24 hours. Though disinfection of impression is routinely followed autoclaving of impression is an effective method of sterilization. PMID:22379308

  12. Soft hydrogel materials from elastomeric gluten-mimetic proteins

    NASA Astrophysics Data System (ADS)

    Bagheri, Mehran; Scott, Shane; Wan, Fan; Dick, Scott; Harden, James; Biomolecular Assemblies Team

    2014-03-01

    Elastomeric proteins are ubiquitous in both animal and plant tissues, where they are responsible for the elastic response and mechanical resilience of tissues. In addition to fundamental interest in the molecular origins of their elastic behaviour, this class of proteins has great potential for use in biomaterial applications. The structural and elastomeric properties of these proteins are thought to be controlled by a subtle balance between hydrophobic interactions and entropic effects, and in many cases their characteristic properties can be recapitulated by multi-block protein polymers formed from repeats of short, characteristic polypeptide motifs. We have developed biomimetic multi-block protein polymers based on variants of several elastomeric gluten consensus sequences. These proteins include constituents designed to maximize their solubility in aqueous solution and minimize the formation of extended secondary structure. Thus, they are examples of elastic intrinsically disordered proteins. In addition, the proteins have distributed tyrosine residues which allow for inter-molecular crosslinking to form hydrogel networks. In this talk, we present experimental and simulation studies of the molecular and materials properties of these proteins and their assemblies.

  13. Long-time dynamic compatibility of elastomeric materials with hydrazine

    NASA Technical Reports Server (NTRS)

    Coulbert, C. D.; Cuddihy, E. F.; Fedors, R. F.

    1973-01-01

    The tensile property surfaces for two elastomeric materials, EPT-10 and AF-E-332, were generated in air and in liquid hydrazine environments using constant strain rate tensile tests over a range of temperatures and elongation rates. These results were used to predict the time-to-rupture for these materials in hydrazine as a function of temperature and amount of strain covering a span of operating times from less than a minute to twenty years. The results of limited sheet-folding tests and their relationship to the tensile failure boundary are presented and discussed.

  14. Substitute materials to replace asbestos in refinery-service gaskets and packings

    SciTech Connect

    Thomas, S.F.; McKillop, G.R.

    1986-05-26

    Refiners have been able to successfully replace asbestos in many packing and gasket applications. The changeover has been driven by health concerns, refusal of product liability insurance to suppliers, and supplier concern over long-term availability of asbestos. A great deal of purchasing and engineering effort is currently being expended to qualify and convert nonasbestos materials for gaskets and packings. The task has been complicated by a lack of objective performance criteria in existing industry standards. The majority of industry standards has specified the use of asbestos-based products because operating experience has shown they work. The specification criteria which do exist typically are valid for comparing competitive asbestos products only, and do not correlate well when applied to unrelated materials. The task of reliably and safely operating a refinery without asbestos-based gasketing and packing is progressing on three fronts: 1. Replacement with products based on materials such as flexible graphite and poly tetra fluoro ethylene (PTFE). Performance characteristics are well known, and sufficient historical operating data exist. The initial cost of these materials is typically higher than asbestos-based products. 2. Trials and replacement with ''new'' materials such as Aramid or glass-fiber-based sheet materials and braided packing, or mica/graphite-filled, spiral-wound gaskets. The performance characteristics of these materials are not well known in comparison to asbestos.

  15. Performance testing of elastomeric seal materials under low and high temperature conditions: Final report

    SciTech Connect

    BRONOWSKI,DAVID R.

    2000-06-01

    The US Department of Energy Offices of Defense Programs and Civilian Radioactive Waste Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. The report presents the results of low- and high-temperature tests conducted on 27 common elastomeric compounds.

  16. Molecular engineering of high-performance elastomeric materials

    NASA Astrophysics Data System (ADS)

    Deng, Shengwei; Falk, Michael

    2013-03-01

    Polyurethane is a typical elastomeric material and among the most versatile materials today. It is a linear block copolymer consisting of alternating soft and hard segments with phase separation due to thermodynamic segmental incompatibility. Inspired by the hierarchical structure of spider silk, this kind of block copolymer can be synthesized with two distinct blocks that can differ in their propensity to crystallize. Either the soft or hard segments can be amorphous or semicrystalline. Recent experiments indicate that crystallizable segments lead to higher tensile strength and that systems with crystalline hard segment exhibit better stiffness, strength and mechanical toughness. Here we implement molecular dynamics simulation to investigate the influence of block architectures on mechanical properties and molecular chain movement.

  17. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

    PubMed Central

    De Angelis, Francesco; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

  18. Development and Evaluation of Elastomeric Materials for Geothermal Applications

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Kalfayan, S. H.; Reilly, W. W.; Yavrouian, A. H.; Mosesman, I. D.; Ingham, J. D.

    1979-01-01

    A material was formulated having about 250-350 psi tensile strength and 30-80 percent elongation at 260 C for at least 24 hours in simulated brine. The relationship between these laboratory test results and sealing performance in actual or simulated test conditions is not entirely clear; however, it is believed that no conventional formation or casing packer design is likely to perform well using these materials. The synthetic effort focused on high temperature block copolymers and development of curable polystyrene. Procedures were worked out for synthesizing these new materials. Initial results with heat-cured unfilled polystyrene 'gum' at 260 C indicate a tensile strength of about 50 psi. Cast films of the first sample of polyphenyl quinoxaline-polystyrene block copolymer, which has 'graft-block' structure consisting of a polystyrene chain with pendant polyphenyl quinoxaline groups, show elastomeric behavior in the required temperature range. Its tensile strength and elongation at 260 C were 220-350 psi and 18-36 percent, respectively. All of these materials also showed satisfactory hydrolytic stability.

  19. Recent developments in PVRC gasket testing

    SciTech Connect

    Hsu, K.H.; Payne, J.R.; Derenne, M.

    1996-12-01

    For the past 15--20 years, a major research program aimed at solving the problem of leakage of gasketed flanged joints has been undertaken by the Pressure Vessel Research Council (PVRC). This program has resulted in greatly enhanced understanding of the leakage phenomena of a flanged joint and improvements of the ASME Code design procedures. The PVRC bolted flanged program has been organized into six areas: (1) implement PVRC gasket constants and test procedure development; (2) issue a flange design guidelines report considering items such as modeling, tightness, transients, relaxation, etc.; (3) flange rating parameters for standard flanges; (4) design parameters for ASME joints; (5) gasket testing for temperature behavior data and test method developments; and (6) flanged joint assembly and interaction effects. This paper presents an update of the recent developments in the area of gasket testing; specifically, testing on flexible graphite gaskets, elastomeric sheet gaskets, and fugitive emissions gasket characteristics with various types of fluids are described.

  20. Comparison of Dimensional Accuracies Using Two Elastomeric Impression Materials in Casting Three-dimensional Tool Marks.

    PubMed

    Wang, Zhen

    2016-05-01

    The purpose of this study was to evaluate two types of impression materials which were frequently used for casting three-dimensional tool marks in China, namely (i) dental impression material and (ii) special elastomeric impression material for tool mark casting. The two different elastomeric impression materials were compared under equal conditions. The parameters measured were dimensional accuracies, the number of air bubbles, the ease of use, and the sharpness and quality of the individual characteristics present on casts. The results showed that dental impression material had the advantage of special elastomeric impression material in casting tool marks in crime scenes; hence, it combined ease of use, dimensional accuracy, sharpness and high quality. PMID:27122422

  1. Elastomeric Polypeptides

    PubMed Central

    van Eldijk, Mark B.; McGann, Christopher L.

    2013-01-01

    Elastomeric polypeptides are very interesting biopolymers and are characterized by rubber-like elasticity, large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Their useful properties have motivated their use in a wide variety of materials and biological applications. This chapter focuses on elastin and resilin – two elastomeric biopolymers – and the recombinant polypeptides derived from them (elastin-like polypeptides and resilin-like polypeptides). This chapter also discusses the applications of these recombinant polypeptides in the fields of purification, drug delivery, and tissue engineering. PMID:21826606

  2. Development of an impact noise reduction method by the adding of a small thickness elastomeric material

    NASA Astrophysics Data System (ADS)

    Arz, Jean-Pierre

    The starting point of this Ph.D. is the industrial issue submitted to the ETS by the company Bombardier Recreational Products (BRP) of the noise reduction of the tracked drive mechanism of snowmobiles. The overall goal of is to develop a method to predict the impact noise reduction obtained by the adding of an elastomeric layer specimen of small thickness between the impacting body and the impacted structure which is a complex structure (i.e. a structure whose geometry is complex and whose composition involves several materials). To reach this overall goal, three specific goals have been fixed: (1) characterize the behavior under impact of different small thickness elastomeric layers; (2) predict the impact force generated when an elastomeric layer is added on a complex vibrating structure; and (3) validate experimentally the whole method by applying it to the impact noise reduction of a bar of the snowmobile track. To reach the first specific goal (characterize the behavior under impact of different small thickness elastomeric layers), a specific experimental characterization method has been developed. Firstly, an experimental device has been realized to submit the elastomeric layer specimens to the reproducible impact conditions of an impact hammer. The measurement of the penetration depth of the hammer into the elastomeric layer is achieved by recording its motion with a high-speed camera and by detecting its position by further analysis on the individual images. Secondly, the experimental curves obtained are analyzed to point out their main characteristics and choose an appropriate impact model. Thirdly, the contact force parameters are estimated from the experimental results and from the impact model. Using this method, eight impacted elastomeric specimens have been characterized. The results show that a more precise characterization than hardness is obtained. To reach the second specific goal (predict the impact force generated when an elastomeric layer is

  3. Developments in new aircraft tire tread materials. [fatigue life of elastomeric materials

    NASA Technical Reports Server (NTRS)

    Yager, T. J.; Mccarty, J. L.; Riccitiello, S. R.; Golub, M. A.

    1976-01-01

    Comparative laboratory and field tests were conducted on experimental and state-of-the-art aircraft tire tread materials in a program aimed at seeking new elastomeric materials which would provide improved aircraft tire tread wear, traction, and blowout resistance in the interests of operational safety and economy. The experimental stock was formulated of natural rubber and amorphous vinyl polybutadiene to provide high thermal-oxidative resistance, a characteristic pursued on the premise that thermal oxidation is involved both in the normal abrasion or wear of tire treads and probably in the chain of events leading to blowout failures. Results from the tests demonstrate that the experimental stock provided better heat buildup (hysteresis) and fatigue properties, at least equal wet and dry traction, and greater wear resistance than the state-of-the-art stock.

  4. Methodology for Evaluating Raw Material Changes to RSRM Elastomeric Insulation Materials

    NASA Technical Reports Server (NTRS)

    Mildenhall, Scott D.; McCool, Alex (Technical Monitor)

    2001-01-01

    The Reusable Solid Rocket Motor (RSRM) uses asbestos and silicon dioxide filled acrylonitrile butadiene rubber (AS-NBR) as the primary internal insulation to protect the case from heat. During the course of the RSRM Program, several changes have been made to the raw materials and processing of the AS-NBR elastomeric insulation material. These changes have been primarily caused by raw materials becoming obsolete. In addition, some process changes have been implemented that were deemed necessary to improve the quality and consistency of the AS-NBR insulation material. Each change has been evaluated using unique test efforts customized to determine the potential impacts of the specific raw material or process change. Following the evaluations, the various raw material and process changes were successfully implemented with no detectable effect on the performance of the AS-NBR insulation. This paper will discuss some of the raw material and process changes evaluated, the methodology used in designing the unique test plans, and the general evaluation results. A summary of the change history of RSRM AS-NBR internal insulation is also presented.

  5. Characterization of elastomeric materials with application to design

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1986-01-01

    Redesign of the Space Shuttle Solid Booster has necessitated re-evaluation of the material used in the field joint O-ring seals. The viscoelastic characteristics of five candidate materials were determined. The five materials are: two fluorocarbon compounds, two nitrile compounds, and a silicon compound. The materials were tested in a uniaxial compression test to determine the characteristic relaxation functions. These tests were performed at five different temperatures. A master material curve was developed for each material from the experimental data. The results are compared to tensile relaxation tests. Application of these results to the design analysis is discussed in detail.

  6. Development and evaluation of elastomeric materials for geothermal applications

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Kalfayan, S. H.; Reilly, W. W.; Ingham, J. D.

    1978-01-01

    A material for a casing packer for service for 24 hours in a geothermal environment was developed by synthesis of new elastomers and formulation of available materials. Formulation included use of commercial elastomer gumstocks and also crosslinking of plastic (high Tg) materials. Fibrous reinforcement of fluorocarbon rubbers was emphasized. Organic fiber reinforcement did not increase hot properties significantly. Glass fiber reinforcement gave significant increase in tensile properties. Elongation was reduced, and the glass-reinforced composition examined so far did not hold up well in the geothermal environment. Colloidal asbestos fibers were also investigated. A few experiments with polyphenyl ether gave material with low tensile and high compression set. Available high styrene SBR compositions were studied. Work to date suggests that new synthetic polymers will be required for service in geothermal environments.

  7. High k dielectric elastomeric materials for low voltage applications

    NASA Astrophysics Data System (ADS)

    Walder, C.; Molberg, M.; Opris, D. M.; Nüesch, F. A.; Löwe, C.; Plummer, C. J. G.; Leterrier, Y.; Månson, J.-A. E.

    2009-03-01

    In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already observed for blends of an olefin based thermoplastic elastomer and PANI.

  8. Effects of atomic oxygen and ultraviolet radiation on candidate elastomeric materials for long duration missions. Test series no.1

    NASA Technical Reports Server (NTRS)

    Linton, R. C.; Finckenor, M. M.; Kamenetzky, R. R.; Gray, P.

    1993-01-01

    Research was conducted at MSFC on the behavior of elastomeric materials after exposure to simulated space environment. Silicone S383 and Viton V747 samples were exposed to thermal vacuum, ultraviolet radiation, and atomic oxygen and then evaluated for changes in material properties. Characterization of the elastomeric materials included weight, hardness, optical inspection under normal and black light, spectrofluorescence, solar absorptance and emittance, Fourier transform infrared spectroscopy, and permeability. These results indicate a degree of sensitivity to exposure and provided some evidence of UV and atomic oxygen synergism.

  9. The Effect of Disinfectants and a Surface Wetting Agent on the Wettability of Elastomeric Impression Materials: An In Vitro Study

    PubMed Central

    Lad, Pritam P; Gurjar, Minal; Gunda, Sachin; Gurjar, Vivek; Rao, Nandan K

    2015-01-01

    Background: This study was carried out to evaluate the effect of two commercially available chemical disinfectants namely sodium hypochlorite and glutaraldehyde and a surface wetting agent on the wettability of three high precision elastomeric impression materials, addition silicone, condensation silicone and polyether. Materials and Methods: Three different types of elastomeric impression materials commonly used in prosthodontic practice were selected. The glutaraldehyde and sodium hypochloride solutions were employed to disinfect the impressions made with the above-mentioned elastomeric impression materials. True Blue surface wetting agent was selected. GBX contact angle analyzer was used to measure advancing and receding contact angle. Results: The results of this study have demonstrated that the polyether impression material was the most hydrophilic of all the materials, followed by hydrophilic addition silicone. Condensation silicone was least hydrophilic. All materials showed improvement in the wettability when a topical surfactant was used. Conclusion: The short term disinfection of the three elastomeric impression materials does not affect the wettability of these impression materials. PMID:26124605

  10. The thermal and mechanical properties of a low density elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1973-01-01

    Thermal and mechanical properties data were obtained for a low density elastomeric resin based ablation material with phenolic-glass honeycomb reinforcement. Data were obtained for the material in the charred and uncharred state. Ablation material specimens were charred in a laboratory furnace at temperatures in the range from 600 K to 1700 K to obtain char specimens representative of the ablation char layer formed during reentry. These specimens were then used to obtain effective thermal conductivity, heat capacity, porosity, and permeability data at the char formation temperature. This provided a boxing of the data which enables the prediction of the transient response of the material during ablation. Limited comparisons were made between the furnace charred specimens and specimens which had been exposed to simulated reentry conditions.

  11. Utilizing stretch-tunable thermochromic elastomeric opal films as novel reversible switchable photonic materials.

    PubMed

    Schäfer, Christian G; Lederle, Christina; Zentel, Kristina; Stühn, Bernd; Gallei, Markus

    2014-11-01

    In this work, the preparation of highly thermoresponsive and fully reversible stretch-tunable elastomeric opal films featuring switchable structural colors is reported. Novel particle architectures based on poly(diethylene glycol methylether methacrylate-co-ethyl acrylate) (PDEGMEMA-co-PEA) as shell polymer are synthesized via seeded and stepwise emulsion polymerization protocols. The use of DEGMEMA as comonomer and herein established synthetic strategies leads to monodisperse soft shell particles, which can be directly processed to opal films by using the feasible melt-shear organization technique. Subsequent UV crosslinking strategies open access to mechanically stable and homogeneous elastomeric opal films. The structural colors of the opal films feature mechano- and thermoresponsiveness, which is found to be fully reversible. Optical characterization shows that the combination of both stimuli provokes a photonic bandgap shift of more than 50 nm from 560 nm in the stretched state to 611 nm in the fully swollen state. In addition, versatile colorful patterns onto the colloidal crystal structure are produced by spatial UV-induced crosslinking by using a photomask. This facile approach enables the generation of spatially cross-linked switchable opal films with fascinating optical properties. Herein described strategies for the preparation of PDEGMEMA-containing colloidal architectures, application of the melt-shear ordering technique, and patterned crosslinking of the final opal films open access to novel stimuli-responsive colloidal crystal films, which are expected to be promising materials in the field of security and sensing applications. PMID:25243892

  12. Gasket with pushrod retainer

    DOEpatents

    Knudsen, Julian R.; Welch, Christopher B.

    2005-04-26

    In an engine having a rocker member adapted to rock about an axis intermediate the rocker member and a pushrod extending from a lower body to an upper body and engaging an end of the rocker member, a gasket for sealing the lower body to the upper body is provided. The gasket includes a sealing portion adapted to substantially seal at least a portion of the upper body to the lower body, and a pushrod support portion extending outwardly from the sealing portion adapted to engage the pushrod. At least a portion of the pushrod support portion engaging the pushrod is constructed from a material that is softer than the material of the pushrod.

  13. Elastomeric optical fiber sensors and method for detecting and measuring events occurring in elastic materials

    DOEpatents

    Muhs, Jeffrey D.; Capps, Gary J.; Smith, David B.; White, Clifford P.

    1994-01-01

    Fiber optic sensing means for the detection and measurement of events such as dynamic loadings imposed upon elastic materials including cementitious materials, elastomers, and animal body components and/or the attrition of such elastic materials are provided. One or more optical fibers each having a deformable core and cladding formed of an elastomeric material such as silicone rubber are embedded in the elastic material. Changes in light transmission through any of the optical fibers due the deformation of the optical fiber by the application of dynamic loads such as compression, tension, or bending loadings imposed on the elastic material or by the attrition of the elastic material such as by cracking, deterioration, aggregate break-up, and muscle, tendon, or organ atrophy provide a measurement of the dynamic loadings and attrition. The fiber optic sensors can be embedded in elastomers subject to dynamic loadings and attrition such as commonly used automobiles and in shoes for determining the amount and frequency of the dynamic loadings and the extent of attrition. The fiber optic sensors are also useable in cementitious material for determining the maturation thereof.

  14. 46 CFR 98.30-8 - Gaskets and lining.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Gaskets and lining. 98.30-8 Section 98.30-8 Shipping... Gaskets and lining. No person may transfer a hazardous material to or from a portable tank on board a vessel unless each gasket and the lining of the portable tank are made of a material that is—...

  15. 46 CFR 98.30-8 - Gaskets and lining.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Gaskets and lining. 98.30-8 Section 98.30-8 Shipping... Gaskets and lining. No person may transfer a hazardous material to or from a portable tank on board a vessel unless each gasket and the lining of the portable tank are made of a material that is—...

  16. Development and Evaluation of High Temperature Gaskets for Hypersonic and Reentry Applications

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Shpargel, Tarah

    2007-01-01

    A wide variety of flexible gasket compositions were developed and tested at high temperatures. The gasket material system has high temperature capability. GRABER sealants were very effective in sealing machined ACC-4 composite surfaces. The gasket composition do not bond strongly with the ACC-4 substrate materials. The density of gasket materials can be tailored to show appropriate compressibility.

  17. Effects of material composition on the ablation performance of low density elastomeric ablators

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.; Kabana, W. P.

    1973-01-01

    The ablation performance of materials composed of various concentrations of nylon, hollow silica spheres, hollow phenolic spheres, and four elastomeric resins was determined. Both blunt-body and flat-panel specimens were used, the cold-wall heating-rate ranges being 0.11 to 0.8 MW/sq m, respectively. The corresponding surface pressure ranges for these tests were 0.017 to 0.037 atmosphere and 0.004 to 0.005 atmosphere. Some of the results show that (1) the addition of nylon significantly improved the ablation performance, but the nylon was not compatible with one resin system; (2) panel and blunt-body specimen data do not show the same effect of phenolic sphere content on ablation effectiveness; and (3) there appears to be an optimum concentration of hollow silica spheres for good ablation performance. The composition of an efficient, nonproprietary ablator for lifting body application is identified and the ablation performance of this ablator is compared with the performance of three commercially available materials.

  18. Biodegradable and elastomeric poly(glycerol sebacate) as a coating material for nitinol bare stent.

    PubMed

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters. PMID:24955369

  19. Biodegradable and Elastomeric Poly(glycerol sebacate) as a Coating Material for Nitinol Bare Stent

    PubMed Central

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters. PMID:24955369

  20. Thiol-Ene functionalized siloxanes for use as elastomeric dental impression materials

    PubMed Central

    Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

    2014-01-01

    Objectives Thiol- and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies. Methods Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The Tg, storage modulus, and creep behavior are determined by DMA. Results Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy. Significance Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and ‘click’ nature. PMID:24553250

  1. 46 CFR 56.25-15 - Gaskets (modifies 108.4).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Gaskets (modifies 108.4). 56.25-15 Section 56.25-15... APPURTENANCES Pipe Flanges, Blanks, Flange Facings, Gaskets, and Bolting § 56.25-15 Gaskets (modifies 108.4). (a) Gaskets shall be made of materials which are not injuriously affected by the fluid or by temperature....

  2. 46 CFR 56.25-15 - Gaskets (modifies 108.4).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Gaskets (modifies 108.4). 56.25-15 Section 56.25-15... APPURTENANCES Pipe Flanges, Blanks, Flange Facings, Gaskets, and Bolting § 56.25-15 Gaskets (modifies 108.4). (a) Gaskets shall be made of materials which are not injuriously affected by the fluid or by temperature....

  3. The thermal and mechanical properties of a low-density glass-fiber-reinforced elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1974-01-01

    An evaluation of the thermal and mechanical properties was performed on a molded low-density elastomeric ablation material designated as Material B. Both the virgin and charred states were examined to provide meaningful inputs to the design of a thermal protection system. Chars representative of the flight chars formed during ablation were prepared in a laboratory furnace from 600 K to 1700 K and properties of effective thermal conductivity, heat capacity, porosity and permeability were determined on the furnace chars formed at various temperature levels within the range. This provided a boxing of the data which will enable the prediction of the transient response of the material during flight ablation.

  4. Nuclear power plant accident simulations of gasket materials under simultaneous radiation plus thermal plus mechanical stress conditions

    SciTech Connect

    Gillen, K.T.; Malone, G.M.

    1997-07-01

    In order to probe the response of silicone door gasket materials to a postulated severe accident in an Italian nuclear power plant, compression stress relaxation (CSR) and compression set (CS) measurements were conducted under combined radiation (approximately 6 kGy/h) and temperature (up to 230{degrees}C) conditions. By making some reasonable initial assumptions, simplified constant temperature and dose rates were derived that should do a reasonable job of simulating the complex environments for worst-case severe events that combine overall aging plus accidents. Further simplification coupled with thermal-only experiments allowed us to derive thermal-only conditions that can be used to achieve CSR and CS responses similar to those expected from the combined environments that are more difficult to simulate. Although the thermal-only simulations should lead to sealing forces similar to those expected during a severe accident, modulus and density results indicate that significant differences in underlying chemistry are expected for the thermal-only and the combined environment simulations. 15 refs., 31 figs., 15 tabs.

  5. Elastomeric member

    DOEpatents

    Hoppie, Lyle O.

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16) disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section (74), and transition end sections (76, 78), attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the elastomeric member (16), a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing (14). Each of the transition sections (76, 78) are received within and bonded to a woven wire mesh sleeve (26, 28) having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve (26, 28) also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle.

  6. Elastomeric member

    DOEpatents

    Hoppie, L.O.

    1985-07-30

    An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond there between. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

  7. Serpentine metal gasket

    DOEpatents

    Rothgeb, Timothy Moore; Reece, Charles Edwin

    2009-06-02

    A metallic seal or gasket for use in the joining of cryogenic fluid conduits, the seal or gasket having a generally planar and serpentine periphery defining a central aperture. According to a preferred embodiment, the periphery has at least two opposing elongated serpentine sides and two opposing arcuate ends joining the opposing elongated serpentine sides and is of a hexagonal cross-section.

  8. Flame resistant elastic elastomeric fibers

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Massucco, A. A.

    1972-01-01

    Development of materials to improve flame resistance of elastic elastomeric fibers is discussed. Two approaches, synthesis of polyether based urethanes and modification of synthesized urethanes with flame ratardant additives, are described. Specific applications of both techniques are presented.

  9. Fiber gasket and method of making same

    DOEpatents

    Bruck, Gerald Joseph; Alvin, Mary Anne; Smeltzer, Eugene E.

    2003-01-01

    A gasket (1) is made by repetitively spirally winding a fiber (3) back on itself in a closed path. The gasket (1) so made has a multi-layer spiral winding (1) formed in a loop (5). The fiber (3) can be wound at a constant wrap rate to form a gasket with a uniform cross-section around the loop. Alternatively, the wrap rate can be varied, increased to increase cross-sectional bulk, and decreased to reduce cross-section bulk around the loop (5). Also, the spiral winding (7) can be applied over a core (13) of either strands of the fiber (3) or a dissimilar material providing a desired property such as resiliency, stiffness or others. For high temperature applications, a ceramic fiber (3) can be used. The gasket (1) can have any of various geometric configurations with or without a core (13).

  10. A Comparative Evaluation of the Dimensional Stability of Three Different Elastomeric Impression Materials after Autoclaving – An Invitro Study

    PubMed Central

    Thota, Kiran Kumar; Ravuri, Rajyalakshmi; Tella, Suchita

    2014-01-01

    Aim of the Study: The purpose of the study was to determine the effect of autoclaving on the dimensional stability of three different elastomeric impression materials at three different time intervals. Materials and Methods: Standardized stainless steel master die as per ADA specification number 19 was fabricated. The impression materials used for the study were condensation silicone (GP1), addition silicone (GP2) and polyether (GP3). A total of 45 samples of the stainless steel die were made (n = 45), that is 15 samples for each group. Impression materials were mixed according to the manufacturer’s instructions and were loaded into the mold to make an impression of the die. Impressions were identified with the help of numerical coding system and measurements were made using stereomicroscope (MAGNUS MSZ-Bi) of 0.65x magnification with the help of image analysis software (IMACE PRO-INSIGHT VERSION.The results were subjected to statistical analysis using one way analysis of variance and student t-test for comparison between the groups. Results: Within the limitations of the study statistically significant dimensional changes were observed for all the three impression materials at three different time intervals but this change was not clinically significant. Conclusion: It is well-known fact that all impressions should be disinfected to avoid possible transmission of infectious diseases either by direct contact or cross contamination. Immersion and spray disinfection as well as various disinfection solutions have been tested and proven to be effective for this purpose. But for elastomeric impression materials these methods have proven to be ineffective as they do not prevent cross contamination among the dental team. So autoclaving was one of the most effective sterilization procedure for condensation silicone and addition silicone. Since polyether is hydrophilic it is better to disinfect the impressions as recommended by the manufacturer or by immersion or spray

  11. Experience with gasket testing according to new DIN standards

    SciTech Connect

    Kockelmann, H.; Bartonicek, J.; Hirschvogel, A.

    1996-12-01

    In 1995 new DIN standards were published containing gasket factor definitions, gasket testing procedures and requirements as a basis for technical delivery conditions. The gasket factors in DIN 28090 are consistent with those in the design rules for bolted flanged connections laid down in DIN EN 1591. Both standards together are an advanced and reliable tool for strength analysis and tightness assessment for bolted flanged connections. The new DIN standards contain new features in detail: gasket factors are related to tightness classes allowing tightness classification of flanged joints; time and temperature effects are regarded by means of high temperature longterm aging leakage tests; and gasket material degradation due to chemical attack is covered by means of chemical resistance tests. Verification of gasket testing according to the new DIN standards by means of tests on real flanged joints is under way.

  12. A thermo-mechanically coupled theory for fluid permeation in elastomeric materials: Application to thermally responsive gels

    NASA Astrophysics Data System (ADS)

    Chester, Shawn A.; Anand, Lallit

    2011-10-01

    An elastomeric gel is a cross-linked polymer network swollen with a solvent, and certain gels can undergo large reversible volume changes as they are cycled about a critical temperature. We have developed a continuum-level theory to describe the coupled mechanical deformation, fluid permeation, and heat transfer of such thermally responsive gels. In discussing special constitutive equations we limit our attention to isotropic materials, and consider a model based on a Flory-Huggins model for the free energy change due to mixing of the fluid with the polymer network, coupled with a non-Gaussian statistical-mechanical model for the change in configurational entropy—a model which accounts for the limited extensibility of polymer chains. We have numerically implemented our theory in a finite element program. We show that our theory is capable of simulating swelling, squeezing of fluid by applied mechanical forces, and thermally responsive swelling/de-swelling of such materials.

  13. 30 CFR 18.27 - Gaskets.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Gaskets. 18.27 Section 18.27 Mineral Resources... Gaskets. A gasket(s) shall not be used between any two surfaces forming a flame-arresting path except as follows: (a) A gasket of lead, elastomer, or equivalent will be acceptable provided the gasket does...

  14. 30 CFR 18.27 - Gaskets.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Gaskets. 18.27 Section 18.27 Mineral Resources... Gaskets. A gasket(s) shall not be used between any two surfaces forming a flame-arresting path except as follows: (a) A gasket of lead, elastomer, or equivalent will be acceptable provided the gasket does...

  15. Thermal performance of 625-kg/cu m elastomeric ablative materials on spherically blunted 0.44-radian cones

    NASA Technical Reports Server (NTRS)

    Champman, A. J.

    1972-01-01

    Spherically blunted 0.44-radian (25 deg) half-angle conical models coated with elastomeric ablative materials were tested in supersonic arc-heated wind tunnels to evaluate performance of the ablators over a range of conditions typical of lifting entry. Four test conditions were combinations of stagnation point-heat transfer rates of 2.3 and 4.5 MW/m2 and stagnation pressures of 20 and 2kN/m2. Afterbody values of heat transfer rate and pressure were 0.05 to 0.20 of stagnation point values. Stagnation enthalpy varied from 4.4 to 25 MJ/kg (1900 to 11000 Btu/lbm) and free-stream Mach number was in a range from 3.5 to 4. Ablative materials retained the spherical nose shape throughout tests at the lower heat transfer level, but receded, assuming a flattened nose shape, during tests at the high heat transfer level. The residue layer that formed on the conical after-body was weak, friable, and extensively cracked. The reference ablative material, which contained phenolic microspheres, generally retained the conical shape on the model afterbody. However, a modified ablator, in which phenolic microspheres were replaced with silica microspheres, deformed and separated from the undegraded material, and thereby produced a very uneven surface. Substrate temperatures and ablator recession were in good agreement with values computed by a numerical analysis.

  16. Elastomeric polypeptide-based biomaterials

    PubMed Central

    Li, Linqing; Charati, Manoj B.; Kiick, Kristi L.

    2011-01-01

    Elastomeric proteins are characterized by their large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Motivated by their unique mechanical properties, there has been tremendous research in understanding and manipulating elastomeric polypeptides, with most work conducted on the elastins but more recent work on an expanded set of polypeptide elastomers. Facilitated by biosynthetic strategies, it has been possible to manipulate the physical properties, conformation, and mechanical properties of these materials. Detailed understanding of the roles and organization of the natural structural proteins has permitted the design of elastomeric materials with engineered properties, and has thus expanded the scope of applications from elucidation of the mechanisms of elasticity to the development of advanced drug delivery systems and tissue engineering substrates. PMID:21637725

  17. Flame resistant elastic elastomeric fiber

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S.; Massucco, A. A.; Sidman, K. R.

    1974-01-01

    Compositions exhibit elastomeric properties and possess various degrees of flame resistance. First material polyurethane, incorporates halogen containing polyol and is flame resistant in air; second contains spandex elastomer with flame retardant additives; and third material is prepared from fluorelastomer composition of copolymer of vinylidene fluoride and hexafluoropropylene.

  18. Determination of spring modulus for several types of elastomeric materials (O-rings) and establishment of an open database for seals

    SciTech Connect

    McMurtry, W.M.; Hohnstreiter, G.F.

    1995-12-31

    Seals that provide the containment system interface between the packaging body and closure must function in high and low temperature environments, under dynamic and static loading conditions, and with different types of contained media. It is one of the most critical elements in the container since the container fails to meet regulations if the seal does not function properly. A research and testing program for seal materials was initiated at Sandia in 1988 with the goal of characterizing the behavior of seal materials commonly used in packages conditions as specified in the regulations (NRC IOCFR Part 71) and American National Standards Institute (ANSI) 14.5. The performance of elastomeric seals in undeformed closures at both high and low temperatures has been investigated (Bronowski 1995). Work has begun with this program to determine the response of elastomeric seals to fast acting dynamic deformations`` in the closure. The response of elastomeric o-ring seals during closure movements due to long-term deformations has already been characterized. What has not been well characterized are short-term closure movements with durations of only a few milliseconds that result in the so called ``burp`` release. Methods for generating this type of response in a repeatable manner had not been developed and standard leak detection equipment does not have a fast enough response time to measure these transient events. One factor which affects the length of the burp is the ability of the o-ring to quickly close the gap to prevent a significant leak. The dynamic characteristics of the elastomeric o-ring material including the dynamic spring modulus and internal damping are directly related to its ability to quickly close the gap. A set of tests designed to determine the dynamic properties for various material types and durometers (hardness) of elastomers that were both lubricated and dry at ambient temperature were conducted.

  19. Elastomeric load sharing device

    NASA Technical Reports Server (NTRS)

    Isabelle, Charles J. (Inventor); Kish, Jules G. (Inventor); Stone, Robert A. (Inventor)

    1992-01-01

    An elastomeric load sharing device, interposed in combination between a driven gear and a central drive shaft to facilitate balanced torque distribution in split power transmission systems, includes a cylindrical elastomeric bearing and a plurality of elastomeric bearing pads. The elastomeric bearing and bearing pads comprise one or more layers, each layer including an elastomer having a metal backing strip secured thereto. The elastomeric bearing is configured to have a high radial stiffness and a low torsional stiffness and is operative to radially center the driven gear and to minimize torque transfer through the elastomeric bearing. The bearing pads are configured to have a low radial and torsional stiffness and a high axial stiffness and are operative to compressively transmit torque from the driven gear to the drive shaft. The elastomeric load sharing device has spring rates that compensate for mechanical deviations in the gear train assembly to provide balanced torque distribution between complementary load paths of split power transmission systems.

  20. Properties of a new polyether urethane dimethacrylate photoinitiated elastomeric impression material.

    PubMed

    Craig, R G; Hare, P H

    1990-01-01

    The photoinitiated impression material is supplied premixed as a light-bodied material in a light-tight plastic syringe and as a heavy-bodied material in a tube. The impression material has excellent physical, mechanical, and clinical qualities with noteworthy long working times, short setting times, dimensional stability, accuracy, high tear strength, good wettability, biocompatibility, and ease of cold disinfection without loss of quality. The impression material is also compatible with gypsum and silver or copper metallizing baths. Accurate casts can be obtained by means of either a double-impression technique or a double-mix technique. PMID:2295985

  1. A New Method for Evaluating Elastomeric Materials for Use in High Pressure Oxygen

    NASA Technical Reports Server (NTRS)

    Jordan, Scott M.

    2001-01-01

    The seal configuration tester (SCT) developed at the Stennis Space Center (SSC) was designed to replicate the intended application of different seat and seal materials in a high pressure oxygen system and assess the wearibility of those materials. Statistical models were used to test the reliability of the SCT in its intended application, and the tests showed very consistent measurements over time, indicating that the device was working as intended. Other statistical designs were used to test different O-ring materials in a high-pressure oxygen system. Those tests indicated that the SCT could be used to rank the performance of O-ring materials in certain environments. The results indicated that some cheaper materials performed as well as, if not better than, other more expensive materials. Different lubrications were integrated in the testing as well and had a significant impact on the performance of the materials. Testing of seat materials is the next stage of this project. An augmentation grant (JAG) was obtained to further this experimental testing at the Stennis Space Center. This part of the project is ongoing at this time and therefore there are no significant accomplishments with respect to seat materials as of yet.

  2. The effect of tray selection on the accuracy of elastomeric impression materials.

    PubMed

    Gordon, G E; Johnson, G H; Drennon, D G

    1990-01-01

    This study evaluated the accuracy of reproduction of stone casts made from impressions using different tray and impression materials. The tray materials used were an acrylic resin, a thermoplastic, and a plastic. The impression materials used were an additional silicone, a polyether, and a polysulfide. Impressions were made of a stainless steel master die that simulated crown preparations for a fixed partial denture and an acrylic resin model with cross-arch and anteroposterior landmarks in stainless steel that typify clinical intra-arch distances. Impressions of the fixed partial denture simulation were made with all three impression materials and all three tray types. Impressions of the cross-arch and anteroposterior landmarks were made by using all three tray types with only the addition reaction silicone impression material. Impressions were poured at 1 hour with a type IV dental stone. Data were analyzed by using ANOVA with a sample size of five. Results indicated that custom-made trays of acrylic resin and the thermoplastic material performed similarly regarding die accuracy and produced clinically acceptable casts. The stock plastic tray consistently produced casts with greater dimensional change than the two custom trays. PMID:2404101

  3. A summary of laboratory testing performed to characterize and select an elastomeric O-ring material to be used in the redesigned solid rocket motors of the space transportation system

    NASA Technical Reports Server (NTRS)

    Turner, J. E.

    1993-01-01

    An elastomeric O-ring material is used in the joints of the redesigned solid motors (RSRM's) of the National Space Transportation System (NSTS). The selection of the O-ring material used in the RSRM's was a very thorough process that included efforts by NASA's Marshall Space Flight Center and the Langley Research Center, and the Thiokol Corporation. One of the efforts performed at MSFC was an extensive in-house laboratory test regime to screen potential O-ring materials and ultimately to characterize the elastomeric material that was chosen to be used in the RSRM's. The laboratory tests performed at MSFC are summarized.

  4. Flight and ground tests of a very low density elastomeric ablative material

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Chapman, A. J., III

    1972-01-01

    A very low density ablative material, a silicone-phenolic composite, was flight tested on a recoverable spacecraft launched by a Pacemaker vehicle system; and, in addition, it was tested in an arc heated wind tunnel at three conditions which encompassed most of the reentry heating conditions of the flight tests. The material was composed, by weight, of 71 percent phenolic spheres, 22.8 percent silicone resin, 2.2 percent catalyst, and 4 percent silica fibers. The tests were conducted to evaluate the ablator performance in both arc tunnel and flight tests and to determine the predictability of the albator performance by using computed results from an existing one-dimensional numerical analysis. The flight tested ablator experienced only moderate surface recession and retained a smooth surface except for isolated areas where the char was completely removed, probably following reentry and prior to or during recovery. Analytical results show good agreement between arc tunnel and flight test results. The thermophysical properties used in the analysis are tabulated.

  5. Embedded strain gauges for condition monitoring of silicone gaskets.

    PubMed

    Schotzko, Timo; Lang, Walter

    2014-01-01

    A miniaturized strain gauge with a thickness of 5 µm is molded into a silicone O-ring. This is a first step toward embedding sensors in gaskets for structural health monitoring. The signal of the integrated sensor exhibits a linear correlation with the contact pressure of the O-ring. This affords the opportunity to monitor the gasket condition during installation. Thus, damages caused by faulty assembly can be detected instantly, and early failures, with their associated consequences, can be prevented. Through the embedded strain gauge, the contact pressure applied to the gasket can be directly measured. Excessive pressure and incorrect positioning of the gasket can cause structural damage to the material of the gasket, which can lead to an early outage. A platinum strain gauge is fabricated on a thin polyimide layer and is contacted through gold connections. The measured resistance pressure response exhibits hysteresis for the first few strain cycles, followed by a linear behavior. The short-term impact of the embedded sensor on the stability of the gasket is investigated. Pull-tests with O-rings and test specimens have indicated that the integration of the miniaturized sensors has no negative impact on the stability in the short term. PMID:25014099

  6. Embedded Strain Gauges for Condition Monitoring of Silicone Gaskets

    PubMed Central

    Schotzko, Timo; Lang, Walter

    2014-01-01

    A miniaturized strain gauge with a thickness of 5 µm is molded into a silicone O-ring. This is a first step toward embedding sensors in gaskets for structural health monitoring. The signal of the integrated sensor exhibits a linear correlation with the contact pressure of the O-ring. This affords the opportunity to monitor the gasket condition during installation. Thus, damages caused by faulty assembly can be detected instantly, and early failures, with their associated consequences, can be prevented. Through the embedded strain gauge, the contact pressure applied to the gasket can be directly measured. Excessive pressure and incorrect positioning of the gasket can cause structural damage to the material of the gasket, which can lead to an early outage. A platinum strain gauge is fabricated on a thin polyimide layer and is contacted through gold connections. The measured resistance pressure response exhibits hysteresis for the first few strain cycles, followed by a linear behavior. The short-term impact of the embedded sensor on the stability of the gasket is investigated. Pull-tests with O-rings and test specimens have indicated that the integration of the miniaturized sensors has no negative impact on the stability in the short term. PMID:25014099

  7. Application of gasket performance data for design and operation of low emissions, high-reliability gasketed joints

    SciTech Connect

    Waterland, A.F. III

    1996-07-01

    The MTI project No. 47, Test Methods for Non-Asbestos Gasket Materials, opened everyone`s eyes to the breadth of performance and use information for gasket materials. What the MTI has started has resulted in a quiet revolution in gasketing, and just in time. Today`s emissions and reliability mandates have created a situation whereby gasket materials can no longer be selected and designed into systems simply through practicable experience and personnel judgment. A defined engineering approach is required. Based on the work initiated by the MTI and furthered by groups such as ASME and PVRC, there now exists extensive performance data for all gasketing materials. This presentation addresses the existence and usage of the various MTI and PVRC-type performance data as a tool for initial material selection. With this background, a novel simplification to the future ASME code procedure is introduced which allows for a simple yet accurate means of applying this widely available data to an emissions` control program at the plant level.

  8. Evaluation of Force Degradation Pattern of Elastomeric Ligatures and Elastomeric Separators in Active Tieback State

    PubMed Central

    Mohammadi, Amir; Mahmoodi, Farhang

    2015-01-01

    Background and aims. The purpose of this study was to evaluate initial force and force decay of commercially available elastomeric ligatures and elastomeric separators in active tieback state in a simulated oral environment. Materials and methods. A total of 288 elastomeric ligatures and elastomeric separators from three manufacturers (Dentaurum, RMO, 3M Unitek) were stretched to 100% and 150% of their original inner diameter. Force levels were measured initially and at 3-minute, 24-hour, and 1-, 2-, 3- and 4-week intervals. Data were analyzed by univariate analysis of variance and a post hoc Tukey test. Results. The means of initial forces of elastomeric ligatures and separators from three above-mentioned companies, when stretched to 100% of their inner diameters, were 199, 305 and 284 g, and 330, 416, 330 g; when they were stretched to 150% of their inner diameters the values were 286, 422 and 375 g, and 433, 540 and 504 g, respectively. In active tieback state, 11-18% of the initial force of the specimens was lost within the first 3 minutes and 29-63% of the force decay occurred in the first 24 hours; then force decay rate decreased. 62-81% of the initial force was lost in 4 weeks. Although force decay pattern was identical in all the products, the initial force and force decay of Dentaurum elastomeric products were less than the similar products of other companies (P<0.05). Under the same conditions, the force of elastomeric separators was greater than elastomeric ligatures of the same company. Conclusion. Regarding the force pattern of elastomeric ligatures and separators and optimal force for tooth movement, many of these products can be selected for applying orthodontic forces in active tieback state. PMID:26889363

  9. Evaluation of Force Degradation Pattern of Elastomeric Ligatures and Elastomeric Separators in Active Tieback State.

    PubMed

    Mohammadi, Amir; Mahmoodi, Farhang

    2015-01-01

    Background and aims. The purpose of this study was to evaluate initial force and force decay of commercially available elastomeric ligatures and elastomeric separators in active tieback state in a simulated oral environment. Materials and methods. A total of 288 elastomeric ligatures and elastomeric separators from three manufacturers (Dentaurum, RMO, 3M Unitek) were stretched to 100% and 150% of their original inner diameter. Force levels were measured initially and at 3-minute, 24-hour, and 1-, 2-, 3- and 4-week intervals. Data were analyzed by univariate analysis of variance and a post hoc Tukey test. Results. The means of initial forces of elastomeric ligatures and separators from three above-mentioned companies, when stretched to 100% of their inner diameters, were 199, 305 and 284 g, and 330, 416, 330 g; when they were stretched to 150% of their inner diameters the values were 286, 422 and 375 g, and 433, 540 and 504 g, respectively. In active tieback state, 11-18% of the initial force of the specimens was lost within the first 3 minutes and 29-63% of the force decay occurred in the first 24 hours; then force decay rate decreased. 62-81% of the initial force was lost in 4 weeks. Although force decay pattern was identical in all the products, the initial force and force decay of Dentaurum elastomeric products were less than the similar products of other companies (P<0.05). Under the same conditions, the force of elastomeric separators was greater than elastomeric ligatures of the same company. Conclusion. Regarding the force pattern of elastomeric ligatures and separators and optimal force for tooth movement, many of these products can be selected for applying orthodontic forces in active tieback state. PMID:26889363

  10. Sealing Force Increasing of ACM Gasket through Electron Beam Radiation

    NASA Astrophysics Data System (ADS)

    dos Santos, D. J.; Batalha, G. F.

    2011-01-01

    Rubber is an engineering material largely used as sealing parts, in form of O-rings, solid gaskets and liquid gaskets, materials applied in liquid state with posterior vulcanization and sealing. Stress relaxation is a rubber characteristic which impacts negatively in such industrial applications (rings and solid gaskets). This work has the purpose to investigate the use of electron beam radiation (EB) as a technology able to decrease the stress relaxation in acrylic rubber (ACM), consequently increasing the sealing capability of this material. ACM samples were irradiated with dose of 100 kGy and 250 kGy, its behavior was comparatively investigated using, dynamic mechanical analysis (DMA) and compression stress relaxation (CSR) experiments. The results obtained by DMA shown an increase of Tg and changes in dynamic mechanical behavior.

  11. Conductive elastomeric extensometer

    NASA Technical Reports Server (NTRS)

    Gause, R. L.; Glenn, C. G. (Inventor)

    1974-01-01

    An extensometer was used for measuring surface area changes of the human body caused by expansion and contraction of the body. A relatively thin and wide strain responsive conductive elastomeric band was adapted for application to a part of the body, such as around a limb or the trunk of the body. The elastomeric band is incorporated as a resistor in a balanced bridge circuit. Expansion or contraction of the portion of the body on which the elastomeric band is applied causes a change in the resistance of the band and a resultant imbalance of the bridge circuit. The output of the amplifier in volts is suitable for proving the desired reading through a recorder, oscilloscope or voltmeter.

  12. Filter holder and gasket assembly for candle or tube filters

    DOEpatents

    Lippert, T.E.; Alvin, M.A.; Bruck, G.J.; Smeltzer, E.E.

    1999-03-02

    A filter holder and gasket assembly are disclosed for holding a candle filter element within a hot gas cleanup system pressure vessel. The filter holder and gasket assembly includes a filter housing, an annular spacer ring securely attached within the filter housing, a gasket sock, a top gasket, a middle gasket and a cast nut. 9 figs.

  13. Filter holder and gasket assembly for candle or tube filters

    DOEpatents

    Lippert, Thomas Edwin; Alvin, Mary Anne; Bruck, Gerald Joseph; Smeltzer, Eugene E.

    1999-03-02

    A filter holder and gasket assembly for holding a candle filter element within a hot gas cleanup system pressure vessel. The filter holder and gasket assembly includes a filter housing, an annular spacer ring securely attached within the filter housing, a gasket sock, a top gasket, a middle gasket and a cast nut.

  14. Highly tunable elastomeric silk biomaterials

    PubMed Central

    Partlow, Benjamin P.; Hanna, Craig W.; Rnjak-Kovacina, Jelena; Moreau, Jodie E.; Applegate, Matthew B.; Burke, Kelly A.; Marelli, Benedetto; Mitropoulos, Alexander N.; Omenetto, Fiorenzo G.

    2014-01-01

    Elastomeric, fully degradable and biocompatible biomaterials are rare, with current options presenting significant limitations in terms of ease of functionalization and tunable mechanical and degradation properties. We report a new method for covalently crosslinking tyrosine residues in silk proteins, via horseradish peroxidase and hydrogen peroxide, to generate highly elastic hydrogels with tunable properties. The tunable mechanical properties, gelation kinetics and swelling properties of these new protein polymers, in addition to their ability to withstand shear strains on the order of 100%, compressive strains greater than 70% and display stiffness between 200 – 10,000 Pa, covering a significant portion of the properties of native soft tissues. Molecular weight and solvent composition allowed control of material mechanical properties over several orders of magnitude while maintaining high resilience and resistance to fatigue. Encapsulation of human bone marrow derived mesenchymal stem cells (hMSC) showed long term survival and exhibited cell-matrix interactions reflective of both silk concentration and gelation conditions. Further biocompatibility of these materials were demonstrated with in vivo evaluation. These new protein-based elastomeric and degradable hydrogels represent an exciting new biomaterials option, with a unique combination of properties, for tissue engineering and regenerative medicine. PMID:25395921

  15. A finite strain thermo-viscoelastic constitutive model to describe the self-heating in elastomeric materials during low-cycle fatigue

    NASA Astrophysics Data System (ADS)

    Ovalle Rodas, C.; Zaïri, F.; Naït-Abdelaziz, M.

    2014-03-01

    A thermo-visco-hyperelastic constitutive model, in accordance with the second thermodynamics principle, is formulated to describe the self-heating evolution in elastomeric materials under cyclic loading. The mechanical part of the model is based upon a Zener rheological representation in which the specific free energy potential is dependent on an added internal variable, allowing the description of the time-dependent mechanical response. The large strain mechanical behavior is described using a Langevin spring, while the continuous stress-softening under cyclic loading is taken into account by means of a network alteration kinetics. The thermo-mechanical coupling is defined by postulating the existence of a dissipation pseudo-potential, function of the viscous dilatation tensor. The proposed model is fully three-dimensional and is implemented into a finite element code. The model parameters are identified using experimental data obtained on a styrene-butadiene rubber under a given strain rate for different strain conditions. Predicted evolutions given by the model for other strain rates are found in good agreement with the experimental data.

  16. Modeling the low-cycle fatigue behavior of visco-hyperelastic elastomeric materials using a new network alteration theory: Application to styrene-butadiene rubber

    NASA Astrophysics Data System (ADS)

    Ayoub, G.; Zaïri, F.; Naït-Abdelaziz, M.; Gloaguen, J. M.

    2011-02-01

    Although several theories were more or less recently proposed to describe the Mullins effect, i.e. the stress-softening after the first load, the nonlinear equilibrium and non-equilibrium material response as well as the continuous stress-softening during fatigue loading need to be included in the analysis to propose a reliable design of rubber structures. This contribution presents for the first time a network alteration theory, based on physical interpretations of the stress-softening phenomenon, to capture the time-dependent mechanical response of elastomeric materials under fatigue loading, and this until failure. A successful physically based visco-hyperelastic model is revisited by introducing an evolution law for the physical material parameters affected by the network alteration. The general form of the model can be basically represented by two parallel networks: a nonlinear equilibrium response and a time-dependent deviation from equilibrium, in which the network parameters become functions of the damage rate (defined as the ratio of the applied cycle over the applied cycle to failure). The mechanical behavior of styrene-butadiene rubber was experimentally investigated, and the main features of the constitutive response under fatigue loading are highlighted. The experimental results demonstrate that the evolution of the normalized maximum stress only depends on the damage rate endured by the material during the fatigue loading history. The average chain length and the average chain density are then taken as functions of the damage rate in the proposed network alteration theory. The new model is found to adequately capture the important features of the observed stress-strain curves under loading-unloading for a large spectrum of strain and damage levels. The model capabilities to predict variable amplitude tests are critically discussed by comparisons with experiments.

  17. Novel rhenium gasket design for nuclear resonant inelastic x-ray scattering at high pressure

    SciTech Connect

    Tanis, Elizabeth A.; Giefers, Hubertus; Nicol, Malcolm F.

    2008-02-15

    For the first time, a highly absorbing element, rhenium, has been proven to be a strong, reliable, and safe gasket material for achieving high pressure in nuclear resonant inelastic x-ray scattering (NRIXS) experiments. Rhenium foil was cut into rectangular slices and in order to reduce absorption, the elevated imprint due to preindenting of the gasket is removed using electrical discharge machining. By utilizing this novel gasket design, transmission losses were mitigated while performing NRIXS experiments conducted on the {sup 119}Sn and {sup 57}Fe Moessbauer isotopes.

  18. Elastomeric actuator devices for magnetic resonance imaging

    NASA Technical Reports Server (NTRS)

    Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)

    2008-01-01

    The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

  19. Gaskets of teflon-bonded EPDM halt leakage from acid lines - low sealing force design eliminates flange distress

    SciTech Connect

    Walker, I.S.; Gaines, A.

    1987-11-01

    The W.R. Grace Chemical Division plant in Lake Charles, LA had to stop producing catalysts for the oil refining industry whenever a piping system for 98% sulfuric acid developed a leak. Gaskets of a nonasbestos material were being used between the flanges of the steel pipe lined with TFE or polypropylene. The flange bolts were kept tight, but the gaskets usually failed to maintain a leaktight seal with the acid at 60 psi for more than a few weeks or months. The acid lines had to be drained before the faulty gasket could be replaced, and production downtime would range from one to three hours. In July 1986, the plant decided to try a chemical resistant gasket of Teflon molded and bonded to a core of Shore A 65-66 durometer EPDM rubber in the acid lines. The resilient gasket also has patented double convex rings on both faces for optimum sealing with only one-eighth the bolt tightening torque commonly required with flat-faced gaskets. The low sealing force requirement prolongs the life of the gasket, eliminates plastic cold flow at the flange of lined steel pipe, and avoids stresses that can damage thermoplastic and fiberglass piping systems. The gasket has a temperature range of {minus}4 to 210{degree}F and is available in 1/2 through 12 inch sizes that conform to ANSI B16.1 flange dimensions. Alternative gasket materials are Kynar PVDF-bonded EPDM and EPDM without a fluoropolymer laminate. The Teflon-bonded EPDM gaskets eliminated unscheduled catalyst production downtime due to leakage from the sulfuric acid piping system. The plant maintains an inventory of the low torque gasket, but has never had to replace any that have been in service since July 1986.

  20. Method for making an elastomeric member with end pieces

    DOEpatents

    Hoppie, L.O.; McNinch, J.H. Jr.; Nowell, G.C.

    1984-10-23

    A molding process is described for molding an elongated elastomeric member with wire mesh sleeves bonded to the ends. A molding preform of elastomeric material is positioned within a seamless mold cylinder, and the open ends of the wire mesh sleeves are mounted to end plug assemblies slidably received into the mold cylinder and positioned against the ends of the preform. A specialized profile is formed into surfaces of the respective end plug assemblies and by heating of the mold, the ends of the elastomeric preform are molded to the profile, as well as bonded to the reinforcing wire mesh sleeves. Vacuum is applied to the interior of the mold to draw outgassing vapors through relief spaces there through. The completed elastomeric member is removed from the mold cylinder by stretching, the consequent reduction in diameter enabling ready separation from the mold cylinder and removal thereof. 9 figs.

  1. Method for making an elastomeric member with end pieces

    DOEpatents

    Hoppie, Lyle O.; McNinch, Jr., Joseph H.; Nowell, Gregory C.

    1984-01-01

    A molding process for molding an elongated elastomeric member (60) with wire mesh sleeves (16) bonded to the ends (14). A molding preform (10) of elastomeric material is positioned within a seamless mold cylinder (26), and the open ends of the wire mesh sleeves (16) are mounted to end plug assemblies (30) slidably received into the mold cylinder (26) and positioned against the ends (14) of the preform (10). A specialized profile is formed into surfaces (44) of the respective end plug assemblies (30) and by heating of the mold (26), the ends (14) of the elastomeric preform (10) are molded to the profile, as well as bonded to the reinforcing wire mesh sleeves (16). Vacuum is applied to the interior of the mold to draw outgassing vapors through relief spaces therethrough. The completed elastomeric member (60) is removed from the mold cylinder (26) by stretching, the consequent reduction in diameter enabling ready separation from the mold cylinder (26) and removal thereof.

  2. Integrated-fin gasket for palm cubic-anvil high pressure apparatus

    SciTech Connect

    Cheng, J.-G.; Matsubayashi, K.; Nagasaki, S.; Hisada, A.; Hirayama, T.; Uwatoko, Y.; Hedo, M.; Kagi, H.

    2014-09-15

    We described an integrated-fin gasket technique for the palm cubic-anvil apparatus specialized for the high-pressure and low-temperature measurements. By using such a gasket made from the semi-sintered MgO ceramics and the tungsten-carbide anvils of 2.5 mm square top, we successfully generate pressures over 16 GPa at both room and cryogenic temperatures down to 0.5 K. We observed a pressure self-increment for this specific configuration and further characterized the thermally induced pressure variation by monitoring the antiferromagnetic transition temperature of chromium up to 12 GPa. In addition to enlarge the pressure capacity, such a modified gasket also improves greatly the surviving rate of electrical leads hanging the sample inside a Teflon capsule filled with the liquid pressure-transmitting medium. These improvements should be attributed to the reduced extrusion of gasket materials during the initial compression.

  3. Influence of Custom Trays, Dual-Arch Passive, Flexed Trays and Viscosities of Elastomeric Impression Materials on Working Dies

    PubMed Central

    Kohli, Shivani; Kalsi, Rupali

    2016-01-01

    Introduction Dual arch impression technique signifies an essential improvement in fixed prosthodontics and has numerous benefits over conventional impression techniques. The accuracy of working dies fabricated from dual arch impression technique remains in question because there is little information available in the literature. Aim This study was conducted to compare the accuracy of working dies fabricated from impressions made from two different viscosities of impression materials using metal, plastic dual arch trays and custom made acrylic trays. Materials and Methods The study samples were grouped into two groups based on the viscosity of impression material used i.e. Group I (monophase), whereas Group II consisted of Dual Mix technique using a combination of light and heavy body material. These were further divided into three subgroups A, B and C depending on the type of impression tray used (metal dual arch tray, plastic dual arch tray and custom made tray). Measurements of the master cast were made using profile projector. Descriptive statistics like mean, Standard Deviation (SD) were calculated for all the groups. One way analysis of variance (ANOVA) was used for multiple group comparisons. A p-value of 0.05 or less was considered statistically significant. Results The gypsum dies obtained with the three types of impression trays using two groups of impression materials were smaller than the master models in dimensions. Conclusion The plastic dual arch trays produced dies which were the least accurate of the three groups. There was no significant difference in the die dimensions obtained using the two viscosities of impression materials. PMID:27437342

  4. Manifold gasket accommodating differential movement of fuel cell stack

    SciTech Connect

    Kelley, Dana A.; Farooque, Mohammad

    2007-11-13

    A gasket for use in a fuel cell system having at least one externally manifolded fuel cell stack, for sealing the manifold edge and the stack face. In accordance with the present invention, the gasket accommodates differential movement between the stack and manifold by promoting slippage at interfaces between the gasket and the dielectric and between the gasket and the stack face.

  5. Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Ethanol-blended Gasoline

    SciTech Connect

    Kass, Michael D; Pawel, Steven J; Theiss, Timothy J; Janke, Christopher James

    2012-07-01

    In 2008 Oak Ridge National Laboratory began a series of experiments to evaluate the compatibility of fueling infrastructure materials with intermediate levels of ethanol-blended gasoline. Initially, the focus was elastomers, metals, and sealants, and the test fuels were Fuel C, CE10a, CE17a and CE25a. The results of these studies were published in 2010. Follow-on studies were performed with an emphasis on plastic (thermoplastic and thermoset) materials used in underground storage and dispenser systems. These materials were exposed to test fuels of Fuel C and CE25a. Upon completion of this effort, it was felt that additional compatibility data with higher ethanol blends was needed and another round of experimentation was performed on elastomers, metals, and plastics with CE50a and CE85a test fuels. Compatibility of polymers typically relates to the solubility of the solid polymer with a solvent. It can also mean susceptibility to chemical attack, but the polymers and test fuels evaluated in this study are not considered to be chemically reactive with each other. Solubility in polymers is typically assessed by measuring the volume swell of the polymer exposed to the solvent of interest. Elastomers are a class of polymers that are predominantly used as seals, and most o-ring and seal manufacturers provide compatibility tables of their products with various solvents including ethanol, toluene, and isooctane, which are components of aggressive oxygenated gasoline as described by the Society of Automotive Engineers (SAE) J1681. These tables include a ranking based on the level of volume swell in the elastomer associated with exposure to a particular solvent. Swell is usually accompanied by a decrease in hardness (softening) that also affects performance. For seal applications, shrinkage of the elastomer upon drying is also a critical parameter since a contraction of volume can conceivably enable leakage to occur. Shrinkage is also indicative of the removal of one or more

  6. Evaluation of the effect of elastomeric damping material on the stability of a bearingless main rotor system

    NASA Technical Reports Server (NTRS)

    Sheffler, M.; Staley, J.; Warmbrodt, W.

    1980-01-01

    The considered investigation was conducted in connection with a contract to design, fabricate, and test a prototype bearingless main rotor (BMR) system. Part of the design process involved an aeroelastic stability investigation in a wind tunnel. Attention is given to a description of model testing, model test results, the description of the full scale wind tunnel configuration, full scale test results, and aspects of correlation with theory. It was found that the complex geometry of the BMR, with 12.5 degrees of nose-up prepitch at the hub and 2.5 degrees of tip-up predroop at the blade attachment clevis, is required to achieve a stable configuration. Subsequent model testing showed that a constrained layer of elastomer material could increase stability at all rotor speeds and collectives tested for a flat strap configuration.

  7. Adhesiveless Transfer Printing of Ultrathin Microscale Semiconductor Materials by Controlling the Bending Radius of an Elastomeric Stamp.

    PubMed

    Cho, Sungbum; Kim, Namyun; Song, Kwangsun; Lee, Jongho

    2016-08-01

    High-performance electronic devices integrated onto unconventional substrates provide opportunities for use in diverse applications, such as wearable or implantable forms of electronic devices. However, the interlayer adhesives between the electronic devices and substrates often limit processing temperature or cause electrical or thermal resistance at the interface. This paper introduces a very simple but effective transfer printing method that does not require an interlayer adhesive. Controlling the bending radius of a simple flat stamp enables picking up or printing of microscale semiconductor materials onto rigid, curvilinear, or flexible surfaces without the aid of a liquid adhesive. Theoretical and experimental studies reveal the underlying mechanism of the suggested approach. Adhesiveless printing of thin Si plates onto diverse substrates demonstrates the capability of this method. PMID:27458878

  8. Investigation of extrusion failures of PTFE-based gaskets in chemical plant service

    SciTech Connect

    Winter, J.R.; Keywood, S.S.

    1996-12-01

    PTFE-based gaskets in chemical plant service typically fail in an extrusion mode, sometimes referred to as blowout. Test work previously published by Monsanto indicated that correctly installed PTFE-based gaskets have pressure performance far exceeding system pressure ratings. These results have since been confirmed by extensive testing at the Montreal based Ecole Polytechnique Tightness Testing and Research Laboratory (TTRL), funded by a consortium of gasket users and manufacturers. With the knowledge that properly installed gaskets can withstand system pressures in excess of 1,000 psig [6,894 kPa], failures at two chemical plants were re-examined. This analysis indicates that extrusion type failures can be caused by excessive internal pressures, associated with sections of pipe having an external source of heat coincident with a blocked flow condition. This results in high system pressures which explain the extrusion type failures observed. The paper discusses details of individual failures and examines methods to prevent them. Other causes for extrusion failures are reviewed, with a recommendation that stronger gasket materials not be utilized to correct problems until it is verified that excessive pressure build-up is not the problem. Also summarized are the requirements for proper installation to achieve the potential blowout resistance found in these gaskets.

  9. Apparatus for cutting elastomeric materials

    NASA Technical Reports Server (NTRS)

    Corbett, A. B.

    1974-01-01

    Sharp thin cutting edge is held in head of milling machine designed for metal working. Controls of machine are used to position cutting edge in same plane as vibrating specimen. Controls then are operated, making blade come into contact with specimen, to cut it into shapes and sizes desired. Cut surfaces appear mirror-smooth; vibrating mechanism causes no visible striations.

  10. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    PubMed Central

    Pithon, Matheus Melo; Ferraz, Caio Souza; Rosa, Francine Cristina Silva; Rosa, Luciano Pereira

    2015-01-01

    OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60) (20 KGy) gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination), Group 2 (70°GL alcohol), Group 3 (autoclave), Group 4 (ultraviolet), Group 5 (peracetic acid) and Group 6 (glutaraldehyde). After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL), and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05). CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties. PMID:26154462

  11. 46 CFR 64.23 - Gasket and lining.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Gasket and lining. 64.23 Section 64.23 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS Standards for an MPT § 64.23 Gasket and lining. Each gasket and lining must be made...

  12. 46 CFR 64.23 - Gasket and lining.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Gasket and lining. 64.23 Section 64.23 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS Standards for an MPT § 64.23 Gasket and lining. Each gasket and lining must be made...

  13. Robust and Soft Elastomeric Electronics Tolerant to Our Daily Lives.

    PubMed

    Sekiguchi, Atsuko; Tanaka, Fumiaki; Saito, Takeshi; Kuwahara, Yuki; Sakurai, Shunsuke; Futaba, Don N; Yamada, Takeo; Hata, Kenji

    2015-09-01

    Clothes represent a unique textile, as they simultaneously provide robustness against our daily activities and comfort (i.e., softness). For electronic devices to be fully integrated into clothes, the devices themselves must be as robust and soft as the clothes themselves. However, to date, no electronic device has ever possessed these properties, because all contain components fabricated from brittle materials, such as metals. Here, we demonstrate robust and soft elastomeric devices where every component possesses elastomeric characteristics with two types of single-walled carbon nanotubes added to provide the necessary electronic properties. Our elastomeric field effect transistors could tolerate every punishment our clothes experience, such as being stretched (elasticity: ∼ 110%), bent, compressed (>4.0 MPa, by a car and heels), impacted (>6.26 kg m/s, by a hammer), and laundered. Our electronic device provides a novel design principle for electronics and wide range applications even in research fields where devices cannot be used. PMID:26218988

  14. Adhesive, elastomeric gel impregnating composition

    DOEpatents

    Shaw, David Glenn; Pollard, John Randolph; Brooks, Robert Aubrey

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  15. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler

    PubMed Central

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-01-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated. PMID:27221079

  16. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler

    NASA Astrophysics Data System (ADS)

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-05-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated.

  17. Elastomeric Cellular Structure Enhanced by Compressible Liquid Filler.

    PubMed

    Sun, Yueting; Xu, Xiaoqing; Xu, Chengliang; Qiao, Yu; Li, Yibing

    2016-01-01

    Elastomeric cellular structures provide a promising solution for energy absorption. Their flexible and resilient nature is particularly relevant to protection of human bodies. Herein we develop an elastomeric cellular structure filled with nanoporous material functionalized (NMF) liquid. Due to the nanoscale infiltration in NMF liquid and its interaction with cell walls, the cellular structure has a much enhanced mechanical performance, in terms of loading capacity and energy absorption density. Moreover, it is validated that the structure is highly compressible and self-restoring. Its hyper-viscoelastic characteristics are elucidated. PMID:27221079

  18. Liquid-Oxygen-Compatible Cement for Gaskets

    NASA Technical Reports Server (NTRS)

    Elmore, N. L.; Neale, B. C.

    1984-01-01

    Fluorelastomer and metal bonded reliably by new procedure. To cure fluoroelastomer cement, metal plate/gasket assembly placed in vacuum bag evacuated to minimum vacuum of 27 inches (69 cm) of mercury. Vacuum maintained throughout heating process and until assembly returns to ambient room temperature. Used to seal gaskets and O-rings or used to splice layers of elastomer to form non-standard sized O-rings. Another possible use is to apply protective, liquid-oxygen-compatible coating to metal parts.

  19. Non-flammable elastomeric fiber from a fluorinated elastomer and containing an halogenated flame retardant

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S. G.; Sidman, K. R.; Massucco, A. A. (Inventor)

    1976-01-01

    Flame retardant elastomeric compositions are described comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives. Methods are described for preparing fibers of the flame retardant elastomeric materials and articles of manufacture comprised of the flame retardant clastomeric materials and non elastic materials such as polybenzimidazoles, fiberglass, nylons, etc.

  20. Indium Foil Serves As Thermally Conductive Gasket

    NASA Technical Reports Server (NTRS)

    Eastman, G. Yale; Dussinger, Peter M.

    1993-01-01

    Indium foil found useful as gasket to increase thermal conductance between bodies clamped together. Deforms to fill imperfections on mating surfaces. Used where maximum temperature in joint less than melting temperature of indium. Because of low melting temperature of indium, most useful in cryogenic applications.

  1. Process for spinning flame retardant elastomeric compositions. [fabricating synthetic fibers for high oxygen environments

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S.; Sidman, K. R.; Massucco, A. A. (Inventor)

    1978-01-01

    Flame retardant elastomeric compositions comprised of either spandex type polyurethane having halogen containing polyols incorporated into the polymer chain, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives were developed. Methods are described for preparing fibers of the flame retardant elastomeric materials and manufactured articles as well as nonelastic materials such as polybenzimidazoles, fiberglass, and nylons, for high oxygen environments.

  2. Recent buckling experiences with spiral wound flexible graphite filled gaskets

    SciTech Connect

    Mueller, R.T.

    1996-12-01

    Given the long and successful history of spiral wound asbestos filled gaskets as widely used in petrochemical plants and refineries, the evolution to flexible graphite filled spiral wound gaskets was expected to be relatively straightforward. For the most part, the transition to flexible graphite has occurred with relatively good success consistent with its improved sealing performance. However, recent experiences reported with buckling type instability problems of flexible graphite filled spiral wound gaskets warrants another look at the industry practices covering this type of gasket. The paper presents findings from 2 different but related instability problems involving spiral would flexible graphite filled gaskets. The first involved Class 1500 and 2500 spiral wound gaskets fitted with inner retaining rings which suffered severe inward buckling with initial boltup. The second experience pertains to Class 600 and lower gaskets supplied without inner retaining rings. Gaskets supplied in both cases complied fully with ASME B16.20 requirements, which highlights possible inadequacies in this standard for spiral wound gaskets. Efforts have been initiated to work with manufacturers in their assessment of fundamental design considerations and with appropriate Code committees to address apparent deficiencies discovered with the industry standards for this type of gasket.

  3. The effect upon friction of the degradation of orthodontic elastomeric modules.

    PubMed

    Edwards, Ian Robert; Spary, David John; Rock, William Peter

    2012-10-01

    Orthodontic elastomeric modules are susceptible to degradation and deformation after time in the mouth. The aims of this study were to determine whether degradation of elastomeric modules significantly affects friction during sliding mechanics and to investigate whether there is a difference in the behaviour of elastomeric modules after storage in both in vivo and in vitro environments. An Instron testing machine was used to determine the friction generated by elastomeric modules on 0.019 × 0.025 inch stainless steel archwires at 4 degrees of bracket tip. Four brands of modules were tested straight from the packet (n = 15), after storage in artificial saliva (n = 15), and after being in patients' mouths (n = 32). Modules were tested after 24 hours, 1 week, and 6 weeks after storage in both in vivo and in vitro. Analysis of variance revealed that the degradation of elastomeric modules had a variable affect upon friction and that each storage medium produced a distinct pattern of frictional resistance. Modules stored in artificial saliva experienced a significant reduction in friction (P < 0.001) while modules collected from patients' mouths produced similar friction to modules tested straight from the packet. TP Super Slick® modules under dry test conditions produced significantly greater friction than the other three types of test modules (P < 0.001). The structure and surface characteristics of elastomeric modules may affect frictional resistance when a bracket slides along an archwire. These effects vary according to time, storage medium, and brand of elastomeric material. PMID:21771803

  4. Polyprotein of GB1 is an ideal artificial elastomeric protein

    NASA Astrophysics Data System (ADS)

    Cao, Yi; Li, Hongbin

    2007-02-01

    Naturally occurring elastomeric proteins function as molecular springs in their biological settings and show mechanical properties that underlie the elasticity of natural adhesives, cell adhesion proteins and muscle proteins. Constantly subject to repeated stretching-relaxation cycles, many elastomeric proteins demonstrate remarkable consistency and reliability in their mechanical performance. Such properties had hitherto been observed only in naturally evolved elastomeric proteins. Here we use single-molecule atomic force microscopy techniques to demonstrate that an artificial polyprotein made of tandem repeats of non-mechanical protein GB1 has mechanical properties that are comparable or superior to those of known elastomeric proteins. In addition to its mechanical stability, we show that GB1 polyprotein shows a unique combination of mechanical features, including the fastest folding kinetics measured so far for a tethered protein, high folding fidelity, low mechanical fatigue during repeated stretching-relaxation cycles and ability to fold against residual forces. These fine features make GB1 polyprotein an ideal artificial protein-based molecular spring that could function in a challenging working environment requiring repeated stretching-relaxation. This study represents a key step towards engineering artificial molecular springs with tailored nanomechanical properties for bottom-up construction of new devices and materials.

  5. Flexible ceramic gasket for SOFC generator

    DOEpatents

    Zafred, Paolo; Prevish, Thomas

    2009-02-03

    A solid oxide fuel cell generator (10) contains stacks of hollow axially elongated fuel cells (36) having an open top end (37), an oxidant inlet plenum (52), a feed fuel plenum (11), a combustion chamber (94) for combusting reacted oxidant/spent fuel; and, optionally, a fuel recirculation chamber (106) below the combustion chamber (94), where the fuel recirculation chamber (94) is in part defined by semi-porous fuel cell positioning gasket (108), all within an outer generator enclosure (8), wherein the fuel cell gasket (108) has a laminate structure comprising at least a compliant fibrous mat support layer and a strong, yet flexible woven layer, which may contain catalytic particles facing the combustion chamber, where the catalyst, if used, is effective to further oxidize exhaust fuel and protect the open top end (37) of the fuel cells.

  6. Modeling friction phenomena and elastomeric dampers in multibody dynamics analysis

    NASA Astrophysics Data System (ADS)

    Ju, Changkuan

    the behavior of the elastomeric damper based on a continuum mechanics approach: the configuration of the damper is modeled using a finite element approach, and material behavior is represented by a set of nonlinear constitutive laws and material parameters. The validated finite element model of the elastomeric damper is then coupled with a comprehensive, multibody dynamics analysis code to predict the behavior of complex systems featuring elastomeric components, for example, rotorcraft with elastomeric lead-lag dampers.

  7. Gasket and snap ring installation tool

    DOEpatents

    Southerland, Jr., James M.; Barringer, Jr., Curtis N.

    1994-01-01

    A tool for installing a gasket and a snap ring including a shaft, a first plate attached to the forward end of the shaft, a second plate slidably carried by the shaft, a spring disposed about the shaft between the first and second plates, and a sleeve that is free to slide over the shaft and engage the second plate. The first plate has a loading surface with a loading groove for receiving a snap ring and a shoulder for holding a gasket. A plurality of openings are formed through the first plate, communicating with the loading groove and approximately equally spaced about the groove. A plurality of rods are attached to the second plate, each rod slidable in one of the openings. In use, the loaded tool is inserted into a hollow pipe or pipe fitting having an internal flange and an internal seating groove, such that the gasket is positioned against the flange and the ring is in the approximate plane of the seating groove. The sleeve is pushed against the second plate, sliding the second plate towards the first plate, compressing the spring and sliding the rods forwards in the openings. The rods engage the snap ring and urge the ring from the loading groove into the seating groove.

  8. Gasket and snap ring installation tool

    SciTech Connect

    Southerland, J.M. Jr.; Barringer, C.N. Jr.

    1994-09-06

    A tool is disclosed for installing a gasket and a snap ring including a shaft, a first plate attached to the forward end of the shaft, a second plate slidably carried by the shaft, a spring disposed about the shaft between the first and second plates, and a sleeve that is free to slide over the shaft and engage the second plate. The first plate has a loading surface with a loading groove for receiving a snap ring and a shoulder for holding a gasket. A plurality of openings are formed through the first plate, communicating with the loading groove and approximately equally spaced about the groove. A plurality of rods are attached to the second plate, each rod slidable in one of the openings. In use, the loaded tool is inserted into a hollow pipe or pipe fitting having an internal flange and an internal seating groove, such that the gasket is positioned against the flange and the ring is in the approximate plane of the seating groove. The sleeve is pushed against the second plate, sliding the second plate towards the first plate, compressing the spring and sliding the rods forwards in the openings. The rods engage the snap ring and urge the ring from the loading groove into the seating groove. 6 figs.

  9. Gasket and snap ring installation tool

    SciTech Connect

    Southerland, J.M., Sr.; Barringer, C.N., Sr.

    1993-08-23

    This invention is comprised of a tool for installing a gasket and a snap ring including a shaft, a first plate attached to the forward end of the shaft, a second plate slidably carried by the shaft, a spring disposed about the shaft between the first and second plates, and a sleeve that is free to slide over the shaft and engage the second plate. The first plate has a loading surface with a loading groove for receiving a snap ring and a shoulder for holding a gasket. A plurality of openings are formed through the first plate, communicating with the loading groove and approximately equally spaced about the groove. A plurality of rods are attached to the second plate, each rod slidable in one of the openings. In use, the loaded tool is inserted into a hollow pipe or pipe fitting having an internal flange and an internal seating groove, such that the gasket is positioned against the flange and the ring is in the approximate plane of the seating groove. The sleeve is pushed against the second plate, sliding the second plate towards the first plate, compressing the spring and sliding the rods forwards in the openings. The rods engage the snap ring and urge the ring from the loading groove into the seating groove.

  10. Gasket Assembly for Sealing Mating Surfaces

    NASA Technical Reports Server (NTRS)

    Bryant, Melvin A., III (Inventor)

    2003-01-01

    A pair of substantially opposed mating surfaces are joined to each other and sealed in place by means of an electrically-conductive member which is placed in proximity to the mating surfaces. The electrically-conductive member has at least one element secured thereto which is positioned to contact the mating surfaces, and which softens when the electrically-conductive member is heated by passing an electric current therethrough. The softened element conforms to the mating surfaces, and upon cooling of the softened element the mating surfaces are joined together in an effective seal. Of particular significance is an embodiment of the electrically-conductive member which is a gasket having an electrically-conductive gasket base and a pair of the elements secured to opposite sides of the gasket base. This embodiment is positioned between the opposed mating surfaces to be joined to each other. Also significant is an embodiment of the electrically-conductive member which is an electrically-conductive sleeve having an element secured to its inner surface. This embodiment surrounds cylindrical members the bases of which are the substantially opposed mating surfaces to be joined, and the element on the inner surface of the sleeve contacts the outer surfaces of the cylindrical members.

  11. Comparison of Contamination of Low-Frictional Elastomeric Rings with That of Conventional Elastomeric Rings by Streptococcus mutans - An In-vivo Study

    PubMed Central

    Mogra, Subraya; Shetty, V. Surendra; Shetty, Siddarth; Jose, Nidhin Philip

    2015-01-01

    Introduction: The presence of brackets and ligatures has been shown to be related to an increase in gingival inflammation and increased risk of decalcification. The various measures were taken to reduce the plaque accumulation and also lot of efforts were made by manufacturers that reduced the binding friction between the ligature rings and arch wire that facilitated easy sliding of the tooth through the wire. The low frictional ligatures rings manufactured by different manufacturers presumed to attract fewer bacteria due to greater reduction in surface roughness. Our study aimed to evaluate whether the low frictional elastomeric rings accumulate fewer bacteria than conventional ligature rings. Materials and Methods: Thirty patients (15 males and 15 females) who underwent fixed appliance therapy were selected. The study was done using split-mouth design. In each volunteer, synergy low frictional elastomeric rings were tied to brackets bonded to the maxillary premolar on the right side and mandibular premolar on the left side. Conventional elastomeric rings that served as control group were tied to the contralateral teeth, with the same design. Samples were collected after four weeks (28 days) and cultured for bacteria Streptococcus mutans. Results: There was no statistical difference between Streptococcus mutans count in low frictional elastomeric rings with that of conventional rings. Conclusion: We concluded that adherence of Streptococcus mutans is similar in both synergy low frictional elastomeric rings and conventional clear elastomeric rings and thus the manufacturer’s claim of minimal bacterial adherence was discarded. PMID:26023638

  12. Elastic proteins and elastomeric protein alloys.

    PubMed

    Aghaei-Ghareh-Bolagh, Behnaz; Mithieux, Suzanne M; Weiss, Anthony S

    2016-06-01

    The elastomeric proteins elastin and resilin have been used extensively in the fabrication of biomaterials for tissue engineering applications due to their unique mechanical and biological properties. Tropoelastin is the soluble monomer component of elastin. Tropoelastin and resilin are both highly elastic with high resilience, substantial extensibility, high durability and low energy loss, which makes them excellent candidates for the fabrication of elastic tissues that demand regular and repetitive movement like the skin, lung, blood vessels, muscles and vocal folds. Combinations of these proteins with silk fibroin further enhance their biomechanical and biological properties leading to a new class of protein alloy materials with versatile properties. In this review, the properties of tropoelastin-based and resilin-based biomaterials with and without silk are described in concert with examples of their applications in tissue engineering. PMID:26780495

  13. 46 CFR 56.30-35 - Gasketed mechanical couplings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Gasketed mechanical couplings. 56.30-35 Section 56.30-35 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Selection and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a)...

  14. 46 CFR 56.30-35 - Gasketed mechanical couplings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Gasketed mechanical couplings. 56.30-35 Section 56.30-35 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Selection and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a) This section applied to pipe fittings...

  15. 46 CFR 56.30-35 - Gasketed mechanical couplings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Gasketed mechanical couplings. 56.30-35 Section 56.30-35 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Selection and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a)...

  16. 46 CFR 56.30-35 - Gasketed mechanical couplings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Gasketed mechanical couplings. 56.30-35 Section 56.30-35 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Selection and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a)...

  17. 46 CFR 56.30-35 - Gasketed mechanical couplings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Gasketed mechanical couplings. 56.30-35 Section 56.30-35 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Selection and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a)...

  18. Hydrostatic low-range pressure applications of the Paris–Edinburgh cell utilizing polymer gaskets for diffuse X-ray scattering measurements

    PubMed Central

    Chapman, Karena W.; Chupas, Peter J.; Kurtz, Charles A.; Locke, Darren R.; Parise, John B.; Hriljac, Joseph A.

    2007-01-01

    The use of a polymeric Torlon (polyamide–imide) gasket material in a Paris–Edinburgh pressure cell for in situ high-pressure X-ray scattering measurements is demonstrated. The relatively low bulk modulus of the gasket allows for fine control of the sample pressure over the range 0.01–0.42 GPa. The quality of the data obtained in this way is suitable for Bragg and pair distribution function analysis. PMID:19461850

  19. Partial-Vacuum-Gasketed Electrochemical Corrosion Cell

    NASA Technical Reports Server (NTRS)

    Bonifas, Andrew P.; Calle, Luz M.; Hintze, Paul E.

    2006-01-01

    An electrochemical cell for making corrosion measurements has been designed to prevent or reduce crevice corrosion, which is a common source of error in prior such cells. The present cell (see figure) includes an electrolyte reservoir with O-ring-edged opening at the bottom. In preparation for a test, the reservoir, while empty, is pressed down against a horizontal specimen surface to form an O-ring seal. A purge of air or other suitable gas is begun in the reservoir, and the pressure in the reservoir is regulated to maintain a partial vacuum. While maintaining the purge and partial vacuum, and without opening the interior of the reservoir to the atmosphere, the electrolyte is pumped into the reservoir. The reservoir is then slowly lifted a short distance off the specimen. The level of the partial vacuum is chosen such that the differential pressure is just sufficient to keep the electrolyte from flowing out of the reservoir through the small O-ring/specimen gap. Electrochemical measurements are then made. Because there is no gasket (and, hence, no crevice between the specimen and the gasket), crevice corrosion is unlikely to occur.

  20. Seal Materials Compatible with the Electroplating Solvent Used in Constellation-X Mirrors

    NASA Technical Reports Server (NTRS)

    Pei, Xiong-Skiba

    1999-01-01

    The existing gasket seals used in electroplating of the Constellation-X mirrors are difficult to assemble, and the current seal material is hydrophobic and too thick. The combination of the above problems result in: 1) non-uniform plating; 2) defect sites such as pits on the mirror edges; 3) "bear claws" on the edges of the mandrels and mirrors causing difficulties in shell-mirror separations; and 4) leakage of the plating solution past the seals into the mandrel causing chemical etching of the mandrel interior. This paper reports the results of this summer study in searching for alternate seal materials chemically compatible with the electroplating solvent. Fifteen common elastomeric rubber seal materials made-by Parker Seals were investigated including butyl, ethylene propylene, fluorosilicone, nitrile, Viton fluorocarbon, and silicone. Test results showed that Viton fluorocarbon compounds as a group were superior to the other tested compounds for chemical compatibility with the plating bath.

  1. Sealability of API R, RX, and BX ring gaskets

    SciTech Connect

    Fowler, J.R.

    1995-12-31

    This report presents work done to determine the sealability limits of API R, RX, and BX gaskets. The work included finite element modeling and full scale testing. The research teaches that bolt stresses of 15 to 30 ksi are necessary to seat the gaskets. If these seating loads are not achieved, the gaskets will likely leak at design pressure, particularly for gas service. If the flanges are properly madeup, the sealability limits in API Bulletins 6AF and 6AF2 are too conservative and can be eliminated for non cyclic service.

  2. Airborne asbestos exposures associated with gasket and packing replacement: a simulation study of flange and valve repair work and an assessment of exposure variables.

    PubMed

    Madl, Amy K; Devlin, Kathryn D; Perez, Angela L; Hollins, Dana M; Cowan, Dallas M; Scott, Paul K; White, Katherine; Cheng, Thales J; Henshaw, John L

    2015-02-01

    A simulation study was conducted to evaluate worker and area exposure to airborne asbestos associated with the replacement of asbestos-containing gaskets and packing materials from flanges and valves and assess the influence of several variables previously not investigated. Additionally, potential of take home exposures from clothing worn during the study was characterized. Our data showed that product type, ventilation type, gasket location, flange or bonnet size, number of flanges involved, surface characteristics, gasket surface adherence, and even activity type did not have a significant effect on worker exposures. Average worker asbestos exposures during flange gasket work (PCME=0.166 f/cc, 12-59 min) were similar to average worker asbestos exposures during valve overhaul work (PCME=0.165 f/cc, 7-76 min). Average 8-h TWA asbestos exposures were estimated to range from 0.010 to 0.062 f/cc. Handling clothes worn during gasket and packing replacement activities demonstrated exposures that were 0.71% (0.0009 f/cc 40-h TWA) of the airborne asbestos concentration experienced during the 5 days of the study. Despite the many variables considered in this study, exposures during gasket and packing replacement occur within a relatively narrow range, are below current and historical occupational exposure limits for asbestos, and are consistent with previously published data. PMID:25445297

  3. REVIEW OF ENERGY EFFICIENCY OF REFRIGERATOR/FREEZER GASKETS

    EPA Science Inventory

    The report gives results of an investigation of the significance of heat leakage through gaskets in household refrigerator/freezers, explores different design features, and suggests further study if necessary. The report gives results of an extensive literature review, interviews...

  4. REVIEW OF ENERGY EFFICIENCY OF REFRIGERATOR/FREEZER GASKETS

    EPA Science Inventory

    The report gives results of an investigation of the significance of heat leakage through gaskets in household refrigerator/freezers, explores different design features, and suggests further study if necessary. he report gives results of an extensive literature review, interviews ...

  5. Chemical Stability of Telavancin in Elastomeric Pumps☆

    PubMed Central

    Sand, Patrick; Aladeen, Traci; Kirkegaard, Paul; LaChance, Dennis; Slover, Christine

    2015-01-01

    solutions examined. All decreases in telavancin concentration were ≤2.7%. Comparison of each test sample solution to the corresponding glass control indicated no loss of active drug due to absorption by the elastomeric material of the pumps. The greatest increase in the amount of total degradants observed over the 8-day period was ~0.7 w/w%. Conclusions The results of this study indicate that telavancin remains chemically stable when diluted in the Intermate Infusion System and the Homepump Eclipse elastomeric pumps and stored at 2°C to 8°C for up to 8 days protected from light at the concentration range and dilution schemes evaluated. PMID:26649079

  6. DEVELOPMENT OF REMOTE HANFORD CONNECTOR GASKET REPLACEMENT TOOLING FOR DWPF

    SciTech Connect

    Krementz, D.; Coughlin, Jeffrey

    2009-05-05

    The Defense Waste Processing Facility (DWPF) requested the Savannah River National Laboratory (SRNL) to develop tooling and equipment to remotely replace gaskets in mechanical Hanford connectors to reduce personnel radiation exposure as compared to the current hands-on method. It is also expected that radiation levels will continually increase with future waste streams. The equipment is operated in the Remote Equipment Decontamination Cell (REDC), which is equipped with compressed air, two master-slave manipulators (MSM's) and an electro-mechanical manipulator (EMM) arm for operation of the remote tools. The REDC does not provide access to electrical power, so the equipment must be manually or pneumatically operated. The MSM's have a load limit at full extension of ten pounds, which limited the weight of the installation tool. In order to remotely replace Hanford connector gaskets several operations must be performed remotely, these include: removal of the spent gasket and retaining ring (retaining ring is also called snap ring), loading the new snap ring and gasket into the installation tool and installation of the new gasket into the Hanford connector. SRNL developed and tested tools that successfully perform all of the necessary tasks. Removal of snap rings from horizontal and vertical connectors is performed by separate air actuated retaining ring removal tools and is manipulated in the cell by the MSM. In order install a new gasket, the snap ring loader is used to load a new snap ring into a groove in the gasket installation tool. A new gasket is placed on the installation tool and retained by custom springs. An MSM lifts the installation tool and presses the mounted gasket against the connector block. Once the installation tool is in position, the gasket and snap ring are installed onto the connector by pneumatic actuation. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and

  7. Evaluation of surface detail reproduction, dimensional stability and gypsum compatibility of monophase polyvinyl-siloxane and polyether elastomeric impression materials under dry and moist conditions

    PubMed Central

    Vadapalli, Sriharsha Babu; Atluri, Kaleswararao; Putcha, Madhu Sudhan; Kondreddi, Sirisha; Kumar, N. Suman; Tadi, Durga Prasad

    2016-01-01

    Objectives: This in vitro study was designed to compare polyvinyl-siloxane (PVS) monophase and polyether (PE) monophase materials under dry and moist conditions for properties such as surface detail reproduction, dimensional stability, and gypsum compatibility. Materials and Methods: Surface detail reproduction was evaluated using two criteria. Dimensional stability was evaluated according to American Dental Association (ADA) specification no. 19. Gypsum compatibility was assessed by two criteria. All the samples were evaluated, and the data obtained were analyzed by a two-way analysis of variance (ANOVA) and Pearson's Chi-square tests. Results: When surface detail reproduction was evaluated with modification of ADA specification no. 19, both the groups under the two conditions showed no significant difference statistically. When evaluated macroscopically both the groups showed statistically significant difference. Results for dimensional stability showed that the deviation from standard was significant among the two groups, where Aquasil group showed significantly more deviation compared to Impregum group (P < 0.001). Two conditions also showed significant difference, with moist conditions showing significantly more deviation compared to dry condition (P < 0.001). The results of gypsum compatibility when evaluated with modification of ADA specification no. 19 and by giving grades to the casts for both the groups and under two conditions showed no significant difference statistically. Conclusion: Regarding dimensional stability, both impregum and aquasil performed better in dry condition than in moist; impregum performed better than aquasil in both the conditions. When tested for surface detail reproduction according to ADA specification, under dry and moist conditions both of them performed almost equally. When tested according to macroscopic evaluation, impregum and aquasil performed significantly better in dry condition compared to moist condition. In dry

  8. Understanding Mechanical Response of Elastomeric Graphene Networks.

    PubMed

    Ni, Na; Barg, Suelen; Garcia-Tunon, Esther; Macul Perez, Felipe; Miranda, Miriam; Lu, Cong; Mattevi, Cecilia; Saiz, Eduardo

    2015-01-01

    Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls. PMID:26348898

  9. Understanding Mechanical Response of Elastomeric Graphene Networks

    NASA Astrophysics Data System (ADS)

    Ni, Na; Barg, Suelen; Garcia-Tunon, Esther; Macul Perez, Felipe; Miranda, Miriam; Lu, Cong; Mattevi, Cecilia; Saiz, Eduardo

    2015-09-01

    Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls.

  10. Elastomeric Photopolymers: Shaping Polymer Gels with Light

    NASA Astrophysics Data System (ADS)

    Kornfield, Julia

    2008-03-01

    Polymer gels that possess a latent ability to change shape, which can be triggered in a spatially resolved manner using light---``elastomeric photopolymers''---have been developed to meet the need for materials that can be reshaped without direct contact, e.g., to non-invasively adjust an implanted lens in the human eye. The physics of diffusion and swelling in elastomers are applied to create a transparent silicone suitable for making a foldable intraocular lens that can be reshaped using near ultraviolet light. A crosslinked silicone matrix dictates the initial shape of the lens, while ``macromers''--short silicone chains with polymerizable end groups—and photoinitiator enable shape adjustment using light: polymerization of the macromer in the irradiated regions, followed by diffusion of free macromer causes local swelling. To predict shape change directly from irradiation profile, a theoretical treatment is presented that captures 1. shape change with no external forces, 2. coupling between diffusion and deformation, and 3. connection between thermodynamics, constitutive equations and equations of motion. Using continuum mechanics complemented with thermodynamics within the auspices of the finite element method, we develop a steady-state model which successfully captures the coupling between diffusion and deformation. Parameter values are drawn from our prior experimental studies of the mechanical properties, equilibrium swelling, penetrant diffusivities and interaction parameters in systematically varied polydimethylsiloxane (PDMS) networks and acrylate endcapped PDMS macromers. Preliminary computational studies show qualitative agreement with experimentally observed phenomena.

  11. Understanding Mechanical Response of Elastomeric Graphene Networks

    PubMed Central

    Ni, Na; Barg, Suelen; Garcia-Tunon, Esther; Macul Perez, Felipe; Miranda, Miriam; Lu, Cong; Mattevi, Cecilia; Saiz, Eduardo

    2015-01-01

    Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls. PMID:26348898

  12. 49 CFR 178.356-2 - Materials of construction and other requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... specification 20PF-1 top section. (b) Gaskets must be as follows: (1) Inner liner flange—Neoprene rubber of 30 to 60 type A durometer hardness or other equivalent gasket material which is compatible with...

  13. 49 CFR 178.356-2 - Materials of construction and other requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... specification 20PF-1 top section. (b) Gaskets must be as follows: (1) Inner liner flange—Neoprene rubber of 30 to 60 type A durometer hardness or other equivalent gasket material which is compatible with...

  14. Strain-induced crystallization in elastomeric polymer networks prepared in solution and sol-gel derived high-temperature organic-inorganic hybrid materials

    NASA Astrophysics Data System (ADS)

    Premachandra, Jagath Kumara

    Cross-linking polymer chains in solution should bring about fewer inter-chain entanglements in the resulting network. The subsequent drying of this network should compress the chains into a "super-contracted" state. The opposing effects of these changes on strain-induced crystallization in cis-1,4-polyisoprene networks formed in solution were investigated. Higher elongations were required to achieve strain-induced crystallinity in the networks prepared at higher dilutions, suggesting that in this regard the compressed states of the chains was more important than their reduced entangling. The constrained-junction theory was applied to strain-induced crystallization in the above networks. The stress-strain isotherms generated from this theory were in satisfactory agreement with experiment. It was found that the constraint parameter kappa decreases with increase in dilution during cross-linking mainly due to the fact that cross-linking in solution decreases chain interpenetration. The dependence of hydrolysis and condensation of gamma-ureidopropyltrimethoxysilane on pH in the water-methanol system at 23sp°C was investigated by FTIR spectroscopy. Quantitative analysis of rates of hydrolysis showed that gamma-ureidopropyltrimethoxysilane is most stable in the water-methanol system at pH 7.7. The rate of overall condensation of silanols produced by the hydrolysis was qualitatively analyzed. These silanol groups are relatively more stable around pH 4.87. The mechanical properties, thermal stability and water absorption of high-temperature sulfopolybenzobisthiazole-silica hybrid materials were investigated. The use of a bonding agent N,N-diethylaminopropyltrimethoxysilane facilitated the interfacial bonding between the organic and inorganic phases in these materials prepared through the sol-gel process. Tensile modulus, thermal stability and the resistant to water absorption were increased with increase in silica content in the resulting composites

  15. Photocrosslinkable and elastomeric hydrogels for bone regeneration.

    PubMed

    Thakur, Teena; Xavier, Janet R; Cross, Lauren; Jaiswal, Manish K; Mondragon, Eli; Kaunas, Roland; Gaharwar, Akhilesh K

    2016-04-01

    Nanocomposite biomaterials are extensively investigated for cell and tissue engineering applications due their unique physical, chemical and biological characteristics. Here, we investigated the mechanical, rheological, and degradation properties of photocrosslinkable and elastomeric nanocomposite hydrogels from nanohydroxyapatite (nHAp) and gelatin methacryloyl (GelMA). The addition of nHAp resulted in a significant increase in mechanical stiffness and physiological stability. Cells readily adhere and proliferate on the nanocomposite surfaces. Cyclic stretching of cells on the elastomeric nanocomposites revealed that nHAp elicited a stronger alignment response in the direction of strain. In vitro studies highlight enhanced bioactivity of nanocomposites as determined by alkaline phosphate (ALP) activity. Overall, the elastomeric and photocrosslinkable nanocomposite hydrogels can be used for minimally invasive therapy for bone regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 879-888, 2016. PMID:26650507

  16. Elastomeric member for energy storage device

    DOEpatents

    Hoppie, Lyle O.; Chute, Richard

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16), disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section, transition end sections, and is attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the member, a substantially uniform diameter assembly results to minimize the required volume of the surrounding housing (14). During manufacture, woven wire mesh sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle. Each sleeve (26, 28) contracts with the contraction of the associated transition section to maintain the bond therebetween.

  17. Blends of thermoplastic and elastomeric matrices with liquid crystalline polymers

    SciTech Connect

    Roggero, A.; Pedretti, U.; La Mantia, F.P.

    1995-12-01

    Liquid crystalline polymers (LCPs) present a unique balance of properties and, when added to thermoplastic (TP) or elastomeric (EL) matrices, can impart to the relevant blends specific properties that can be utilized for specific applications. As regards TP/LCP blends, the proclivity of LCPs to form fibrous structures and their low melt viscositiy allowed to obtain blends reinforced and easier to process than the pure TPs: particularly, depending on the LCP-TP structures and on the processing parameters, materials with improved processability, high modulus, enhanced impact strength and creeping resistance were obtained. As regards EL/LCP blends, that based on fluoroelastomers were in depth investigated and offered outstanding properties.

  18. Coevolutionary extremal dynamics on gasket fractal

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung Eun; Sung, Joo Yup; Cha, Moon-Yong; Maeng, Seong Eun; Bang, Yu Sik; Lee, Jae Woo

    2009-11-01

    We considered a Bak-Sneppen model on a Sierpinski gasket fractal. We calculated the avalanche size distribution and the distribution of distances between subsequent minimal sites. To observe the temporal correlations of the avalanche, we estimated the return time distribution, the first-return time, and the all-return time distribution. The avalanche size distribution follows the power law, P(s)∼s, with the exponent τ=1.004(7). The distribution of jumping sites also follows the power law, P(r)∼r, with the critical exponent π=4.12(4). We observe the periodic oscillation of the distribution of the jumping distances which originated from the jumps of the level when the minimal site crosses the stage of the fractal. The first-return time distribution shows the power law, P(t)∼t, with the critical exponent τ=1.418(7). The all-return time distribution is also characterized by the power law, P(t)∼t, with the exponent τ=0.522(4). The exponents of the return time satisfy the scaling relation τ+τ=2 for τ⩽2.

  19. Elastomeric organic material for switching application

    SciTech Connect

    Shiju, K. E-mail: pravymon@gmail.com Praveen, T. E-mail: pravymon@gmail.com Preedep, P. E-mail: pravymon@gmail.com

    2014-10-15

    Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes.

  20. Recombinant Exon-Encoded Resilins for Elastomeric Biomaterials

    PubMed Central

    Qin, Guokui; Rivkin, Amit; Lapidot, Shaul; Hu, Xiao; Arinus, Shira B.; Dgany, Or; Shoseyov, Oded; Kaplan, David L.

    2011-01-01

    Resilin is an elastomeric protein found in specialized regions of the cuticle of most insects, providing outstanding material properties including high resilience and fatigue lifetime for insect flight and jumping needs. Two exons (1 and 3) from the resilin gene in Drosophila melanogaster were cloned and the encoded proteins expressed as soluble products in Escherichia coli. A heat and salt precipitation method was used for efficient purification of the recombinant proteins. The proteins were solution cast from water and formed into rubber-like biomaterials via horseradish peroxidase-mediated cross-linking. Comparative studies of the two proteins expressed from the two different exons were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichrosim (CD) for structural features. Little structural organization was found, suggesting structural order was not induced by the enzyme-mediateed dityrosine cross-links. Atomic Force Microscopy (AFM) was used to study the elastomeric properties of the uncross-linked and cross-linked proteins. The protein from exon 1 exhibited 90% resilience in comparison to 63% for the protein from exon 3, and therefore may be the more critical domain for functional materials to mimic native resilin. Further, the cross-linking of the recombinant exon 1 via the citrate-modified photo-Fenton reaction was explored as an alternative dityrosine mediated polymerization method and resulted in both highly elastic and adhesive materials. The citrate-modified photo-Fenton system may be suitable for in-vivo applications of resilin biomaterials. PMID:21963157

  1. Recombinant exon-encoded resilins for elastomeric biomaterials.

    PubMed

    Qin, Guokui; Rivkin, Amit; Lapidot, Shaul; Hu, Xiao; Preis, Itan; Arinus, Shira B; Dgany, Or; Shoseyov, Oded; Kaplan, David L

    2011-12-01

    Resilin is an elastomeric protein found in specialized regions of the cuticle of most insects, providing outstanding material properties including high resilience and fatigue lifetime for insect flight and jumping needs. Two exons (1 and 3) from the resilin gene in Drosophila melanogaster were cloned and the encoded proteins expressed as soluble products in Escherichia coli. A heat and salt precipitation method was used for efficient purification of the recombinant proteins. The proteins were solution cast from water and formed into rubber-like biomaterials via horseradish peroxidase-mediated cross-linking. Comparative studies of the two proteins expressed from the two different exons were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichrosim (CD) for structural features. Little structural organization was found, suggesting structural order was not induced by the enzyme-mediated di-tyrosine cross-links. Atomic Force Microscopy (AFM) was used to study the elastomeric properties of the uncross-linked and cross-linked proteins. The protein from exon 1 exhibited 90% resilience in comparison to 63% for the protein from exon 3, and therefore may be the more critical domain for functional materials to mimic native resilin. Further, the cross-linking of the recombinant exon 1 via the citrate-modified photo-Fenton reaction was explored as an alternative di-tyrosine mediated polymerization method and resulted in both highly elastic and adhesive materials. The citrate-modified photo-Fenton system may be suitable for in vivo applications of resilin biomaterials. PMID:21963157

  2. Elastomeric PGS scaffolds in arterial tissue engineering.

    PubMed

    Lee, Kee-Won; Wang, Yadong

    2011-01-01

    Cardiovascular disease is one of the leading cause of mortality in the US and especially, coronary artery disease increases with an aging population and increasing obesity. Currently, bypass surgery using autologous vessels, allografts, and synthetic grafts are known as a commonly used for arterial substitutes. However, these grafts have limited applications when an inner diameter of arteries is less than 6 mm due to low availability, thrombotic complications, compliance mismatch, and late intimal hyperplasia. To overcome these limitations, tissue engineering has been successfully applied as a promising alternative to develop small-diameter arterial constructs that are nonthrombogenic, robust, and compliant. Several previous studies have developed small-diameter arterial constructs with tri-lamellar structure, excellent mechanical properties and burst pressure comparable to native arteries. While high tensile strength and burst pressure by increasing collagen production from a rigid material or cell sheet scaffold, these constructs still had low elastin production and compliance, which is a major problem to cause graft failure after implantation. Considering these issues, we hypothesized that an elastometric biomaterial combined with mechanical conditioning would provide elasticity and conduct mechanical signals more efficiently to vascular cells, which increase extracellular matrix production and support cellular orientation. The objective of this report is to introduce a fabrication technique of porous tubular scaffolds and a dynamic mechanical conditioning for applying them to arterial tissue engineering. We used a biodegradable elastomer, poly (glycerol sebacate) (PGS) for fabricating porous tubular scaffolds from the salt fusion method. Adult primary baboon smooth muscle cells (SMCs) were seeded on the lumen of scaffolds, which cultured in our designed pulsatile flow bioreactor for 3 weeks. PGS scaffolds had consistent thickness and randomly distributed macro

  3. Elastomeric member and method of manufacture therefor

    DOEpatents

    Hoppie, L.O.

    1985-12-10

    An energy storage device is disclosed consisting of a stretched elongated elastomeric member disposed within a tubular housing, which elastomeric member is adapted to be torsionally stressed to store energy. The elastomeric member is configured in the relaxed state with a uniform diameter body section, and transition end sections, attached to rigid end piece assemblies of a lesser diameter. The profile and deflection characteristic of the transition sections are such that upon stretching of the elastomeric member, a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing. Each of the transition sections are received within and bonded to a woven wire mesh sleeve having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves are forced against a forming surface and bonded to the associated transition section to provide the correct profile and helix angle. 12 figs.

  4. Elastomeric member and method of manufacture therefor

    DOEpatents

    Hoppie, Lyle O.

    1985-01-01

    An energy storage device (10) is disclosed consisting of a stretched elongated elastomeric member (16) disposed within a tubular housing (14), which elastomeric member (16) is adapted to be torsionally stressed to store energy. The elastomeric member (16) is configured in the relaxed state with a uniform diameter body section (74), and transition end sections (76, 78), attached to rigid end piece assemblies (22, 24) of a lesser diameter. The profile and deflection characteristic of the transition sections (76, 78) are such that upon stretching of the elastomeric member (16), a substantially uniform diameter assembly results, to minimize the required volume of the surrounding housing (14). Each of the transition sections (76, 78) are received within and bonded to a woven wire mesh sleeve (26, 28) having helical windings at a particular helix angle to control the deflection of the transition section. Each sleeve (26, 28) also contracts with the contraction of the associated transition section to maintain the bond therebetween. During manufacture, the sleeves (26, 28) are forced against a forming surface and bonded to the associated transition section (76, 78) to provide the correct profile and helix angle.

  5. 33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Standards § 183.536 Seals and gaskets in fuel filters and strainers. (a) (b) Each gasket and each...

  6. 33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Standards § 183.536 Seals and gaskets in fuel filters and strainers. (a) (b) Each gasket and each...

  7. 33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Standards § 183.536 Seals and gaskets in fuel filters and strainers. (a) (b) Each gasket and each...

  8. 33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Standards § 183.536 Seals and gaskets in fuel filters and strainers. (a) (b) Each gasket and each...

  9. 33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF... Standards § 183.536 Seals and gaskets in fuel filters and strainers. (a) (b) Each gasket and each...

  10. 10. Detail of center hangar doors and canvas gasket, dock ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Detail of center hangar doors and canvas gasket, dock no. 493. View to southwest. - Offutt Air Force Base, Looking Glass Airborne Command Post, Nose Docks, On either side of Hangar Access Apron at Northwest end of Project Looking Glass Historic District, Bellevue, Sarpy County, NE

  11. Elastomeric binders for electrodes. [in secondary lithium cells

    NASA Technical Reports Server (NTRS)

    Yen, S. P. S.; Shen, D. H.; Somoano, R. B.

    1983-01-01

    The poor mechanical integrity of the cathode represents an important problem which affects the performance of ambient temperature secondary lithium cells. Repeated charge of a TiS2 cathode may give rise to stresses which disturb the electrode structure and can contribute to capacity loss. An investigation indicates that the use of an inelastic binder material, such as Teflon, aggravates the problem, and can lead to electrode disruption and poor TiS2 particle-particle contact. The feasibility of a use of elastomers as TiS2 binder materials has, therefore, been explored. It was found that elastomeric binders provide an effective approach for simplifying rechargeable cathode fabrication. A pronounced improvement in the mechanical integrity of the cathode structure contributes to a prolonged cycle life.

  12. Effects of gasket on coupled plastic flow and strain-induced phase transformations under high pressure and large torsion in a rotational diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Feng, Biao; Levitas, Valery I.

    2016-01-01

    Combined plastic flow and strain-induced phase transformations (PTs) under high pressure in a sample within a gasket subjected to three dimensional compression and torsion in a rotational diamond anvil cell (RDAC) are studied using a finite element approach. The results are obtained for the weaker, equal-strength, and stronger high-pressure phases in comparison with low-pressure phases. It is found that, due to the strong gasket, the pressure in the sample is relatively homogenous and the geometry of the transformed zones is mostly determined by heterogeneity in plastic flow. For the equal-strength phases, the PT rate is higher than for the weaker and stronger high-pressure phases. For the weaker high-pressure phase, transformation softening induces material instability and leads to strain and PT localization. For the stronger high-pressure phase, the PT is suppressed by strain hardening during PT. The effect of the kinetic parameter k that scales the PT rate in the strain-controlled kinetic equation is also examined. In comparison with a traditional diamond anvil cell without torsion, the PT progress is much faster in RDAC under the same maximum pressure in the sample. Finally, the gasket size and strength effects are discussed. For a shorter and weaker gasket, faster plastic flow in radial and thickness directions leads to faster PT kinetics in comparison with a longer and stronger gasket. The rates of PT and plastic flows are not very sensitive to the modest change in a gasket thickness. Multiple experimental results are reproduced and interpreted. Obtained results allow one to design the desired pressure-plastic strain loading program in the experiments for searching new phases, reducing PT pressure by plastic shear, extracting kinetic properties from experiments with heterogeneous fields, and controlling homogeneity of all fields and kinetics of PTs.

  13. Practical Usage of Effect of Cold Weldability of Metals in Joint of Plastically Deformable Gasket and Flanges of Detachable Joint of Fuel Pipe-Line

    NASA Astrophysics Data System (ADS)

    Danchenko, V. G.

    2002-01-01

    The performed investigations of the character of changing the leakage of control gas through flange connections in the process of drawing- up the bolts in to calculation moment and subsequent lowering of bolt loading to zero have shown the following. Gradual reduction of leakage through a gasket occurs in the process of increasing the tightening torque up to its complete absence. But there is no leakage through the unloaded gasket after untwisting all nuts and removal of fastening bolts from flanges. The performed analysis has shown that this effect is caused by cold weldability of the gasket with flanges; this is a result of flowing of its material into microrough holes of contact surfaces of flanges at plastic deformation with formation of strong and dense contact. Some technological methods of formation of undetachable joint have been developed for practical application of this effect. According to one of those methods, drawing- up the gasket is performed with the help of flanges preliminarily. Those bolts are substituted by less strong standard bolts for drawing- up by less moment after achievement of stress needed. Method of pressurization of the joint is more effective when technological detachable flanges and bolts are used for reduction of the gasket up to its plastic state. Those flanges and bolts are removed after drawing- up; after that standard flanges are loaded by the moment used for reception of effort only from pressure of operational medium in the pipe- line (Qoper.m.) because drawing- up of the gasket by effort (Qeff.) that provides its plastic state, is already achieved. Then we exclude the first component (Qeff.) in dependence which is known from technical literature: Qdraw. = Qeff . + Qoper .m. = qFgas. + PFpip. (1), and the final formula for calculation of the effort of drawing- up the joint (in which drawing- up the gasket with provision of cold weldability is carried out preliminarily before drawing- up the standard bolts) is expressed in

  14. Characterization of a Crosslinked Elastomeric-Protein Inspired Polypeptide.

    PubMed

    Bochicchio, Brigida; Bracalello, Angelo; Pepe, Antonietta

    2016-08-01

    Materials inspired by natural proteins have a great appeal in tissue engineering for their biocompatibility and similarity to extracellular matrix (ECM). Chimeric polypeptides inspired by elastomeric proteins such as silk, elastin, and collagen are of outstanding interest in the field. A recombinant polypeptide constituted of three different blocks, each of them having sequences derived from elastin, resilin, and collagen proteins, was demonstrated to be a good candidate as biomaterial for its self-assembling characteristics and biocompatibility. Herein, taking advantage of the primary amine functionalities present in the linear polypeptide, we crosslinked it with 1,6-hexamethylene-diisocyanate (HMDI). The characterization of the obtained polypeptide was realized by CD spectroscopy, AFM, and SEM microscopies. The obtained results, although not conclusive, demonstrate that the crosslinked polypeptide gave rise to porous networks, thin nanowires, and films not observable for the linear polypeptide. Chirality 28:606-611, 2016. © 2016 Wiley Periodicals, Inc. PMID:27403636

  15. Elastomeric polymer light-emitting devices and displays

    NASA Astrophysics Data System (ADS)

    Liang, Jiajie; Li, Lu; Niu, Xiaofan; Yu, Zhibin; Pei, Qibing

    2013-10-01

    The emergence of devices that combine elasticity with electronic or optoelectronic properties offers exciting new opportunities for applications, but brings significant materials challenges. Here, we report the fabrication of an elastomeric polymer light-emitting device (EPLED) using a simple, all-solution-based process. The EPLED features a pair of transparent composite electrodes comprising a thin percolation network of silver nanowires inlaid in the surface layer. The resulting EPLED, which exhibits rubbery elasticity at room temperature, is collapsible, and can emit light when exposed to strains as large as 120%. It can also survive repeated continuous stretching cycles, and small stretching is shown to significantly enhance its light-emitting efficiency. The fabrication process is scalable and was readily adapted for the demonstration of a simple passive matrix monochrome display featuring a 5 × 5 pixel array.

  16. Confinement of elastomeric block copolymers via forced assembly coextrusion.

    PubMed

    Burt, Tiffani M; Keum, Jong; Hiltner, Anne; Baer, Eric; Korley, Lashanda T J

    2011-12-01

    Forced assembly processing provides a unique opportunity to examine the effects of confinement on block copolymers (BCPs) via conventional melt processing techniques. The microlayering process was utilized to produce novel materials with enhanced mechanical properties through selective manipulation of layer thickness. Multilayer films consisting of an elastomeric, symmetric block copolymer confined between rigid polystyrene (PS) layers were produced with layer thicknesses ranging from 100 to 600 nm. Deformation studies of the confined BCP showed an increase in ductility as the layer thickness decreased to 190 nm due to a shift in the mode of deformation from crazing to shear yielding. Postextrusion annealing was performed on the multilayer films to investigate the impact of a highly ordered morphology on the mechanical properties. The annealed multilayer films exhibited increased toughness with decreasing layer thickness and resulted in homogeneous deformation compared to the as-extruded films. Multilayer coextrusion proved to be an advantageous method for producing continuous films with tunable mechanical response. PMID:22124208

  17. Testing the influence of various conditions on the migration of epoxidised soybean oil from polyvinylchloride gaskets.

    PubMed

    Hanušová, Kristýna; Rajchl, Aleš; Votavová, Lenka; Dobiáš, Jaroslav; Steiner, Ingrid

    2013-01-01

    Epoxidised soybean oil (ESBO) is widely used as a plasticiser and stabiliser mainly in food contact materials on the base of polyvinylchloride (PVC), especially in the gaskets of jar lids. PVC gaskets containing 10-37% of ESBO were prepared by the baking of PVC plastisols at various process temperatures (180-240°C) in the laboratory. ESBO migration into olive oil and 3% acetic acid was studied at various temperatures (4°C, 25°C, 40°C and 60°C) during a storage time up to 12 months. ESBO released into food simulants was transmethylated, derivatised and analysed by gas chromatography-mass spectrometry (GC/MS). The effect of food processing, i.e. pasteurisation (80°C and 100°C) and sterilisation (125°C) on ESBO migration was also evaluated. The results were critically assessed with respect to the test conditions of specific migration in accordance with the current European Union legislation (Regulation (EU) No. 10/2011). The levels of ESBO migration found confirmed that the test conditions (i.e. 40°C or 60°C, 10 days) representing contact in the worst foreseeable use scenario seem to be insufficient for the simulation of ESBO migration during long-term storage and thus do not provide satisfactory objective results. PMID:23978228

  18. Accuracy and consistency of modern elastomeric pumps.

    PubMed

    Weisman, Robyn S; Missair, Andres; Pham, Phung; Gutierrez, Juan F; Gebhard, Ralf E

    2014-01-01

    Continuous peripheral nerve blockade has become a popular method of achieving postoperative analgesia for many surgical procedures. The safety and reliability of infusion pumps are dependent on their flow rate accuracy and consistency. Knowledge of pump rate profiles can help physicians determine which infusion pump is best suited for their clinical applications and specific patient population. Several studies have investigated the accuracy of portable infusion pumps. Using methodology similar to that used by Ilfeld et al, we investigated the accuracy and consistency of several current elastomeric pumps. PMID:25140510

  19. Method of making hollow elastomeric bodies

    NASA Technical Reports Server (NTRS)

    Broyles, H. F.; Moacanin, J.; Cuddihy, E. F. (Inventor)

    1976-01-01

    Annular elastomeric bodies having intricate shapes are cast by dipping a heated, rotating mandrel into a solution of the elastomer, permitting the elastomer to creep into sharp recesses, drying the coated mandrel and repeating the operation until the desired thickness has been achieved. A bladder for a heart assist pump in which a cylindrical body terminating in flat, sharp horizontal flanges fabricated by this procedure has been subjected to over 2,500 hours of simulated life conditions with no visible signs of degradation.

  20. Elastomeric biodegradable polyurethane blends for soft tissue applications.

    PubMed

    Fromstein, J D; Woodhouse, K A

    2002-01-01

    Four biodegradable polyurethane blends were made from segmented polyurethanes that contain amino acid-based chain extender and diisocyanate groups. The soft segments of these parent polyurethanes were either polyethylene oxide (PEO) or polycaprolactone (PCL) diols. The blends were developed to investigate the effect of varying soft segment compositions on the overall morphological, mechanical, and degradative properties of the materials, with a view to producing a family of materials with a wide range of properties. The highly hydrophilic PEO material was incorporated to increase the blend's susceptibility to degradation, while the PCL polyurethane was selected to provide higher moduli and percent elongations (strains) than the PEO parent materials can achieve. All four blends were determined to be semi-crystalline, elastomeric materials that possess similarly shaped stress-strain curves to that of the PCL-based parent polyurethane. As the percent composition of PEO polyurethane within the blend increased, the material became weaker and less extensible. The blends demonstrated rapid initial degradation in buffer followed by significantly slower, prolonged degradation, likely corresponding to an initial loss of primarily PEO-containing polymer, followed by the slower degradation of the PCL polyurethane. All four blends were successfully formed into three-dimensional porous scaffolds utilizing solvent casting/particulate leaching methods. Since these new blends possess a range of mechanical and degradation properties and can be shaped into three-dimensional objects, these materials may hold potential for use in soft tissue engineering scaffold applications. PMID:12160300

  1. Experiences with new European standards for calculation of flanged joints including necessary gasket factors

    SciTech Connect

    Bartonicek, J.; Kockelmann, H.; Schoeckle, F.

    1996-12-01

    The correct function of a flanged joint in a given construction (flanges, bolts) and with given loads (pressure, temperature, additional forces) depends on the following: (1) choice of the gasket for the operation environment; (2) determination of the gasket stress for assembly conditions; and (3) gasket stress in operation, i.e., the conditions when leakage has to be minimized. For the correct choice of a gasket it is necessary to have gasket factors available, as given by DIN 28090 (Sept. 95) together with the test procedures. These gasket factors determine the tightening characteristics as well as the deformation capability of the gaskets. Furthermore, these gasket factors must be available for use in calculations. On the basis of calculations a stress analysis (i.e. a limitation of the stresses in flanges and bolts) must be possible as well as the determination of the bolt forces for the assembly state and of the gasket stress for operating conditions. This is one of the goals of the standard pr DIN EN 1591. The paper first introduces the actual European standards. Calculations are reviewed using test data from special test rigs and from real flanged joints. The calculations were made according to DIN 2505 (initial German standard for flanged joints) and pr DIN EN 1591. Additionally, 2D and 3D Finite Element analysis calculations were performed.

  2. Evaluation of shear mounted elastomeric damper

    NASA Technical Reports Server (NTRS)

    Zorzi, E.; Walton, J.

    1982-01-01

    Viton-70 elastomeric shear mounted damper was built and tested on a T-55 power turbine spool in the rotor's high speed balancing rig. This application of a shear mounted elastomeric damper demonstrated for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear damper design was selected because it was compatible with actual gas turbine engine radial space constraints, could accommodate both the radial and axial thrust loads present in gas turbine engines, and was capable of controlled axial preload. The shear damper was interchangeable with the production T-55 power turbine roller bearing support so that a direct comparison between the shear damper and the production support structure could be made. Test results show that the Viton-70 elastomer damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing up to the maximum rotor speed of 16,000 rpm. Excellent correlation between the predicted and experienced critical speeds, mode shapes and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

  3. NCO-5 Technician Cuts Finger while Cutting Gasket Material

    SciTech Connect

    Trujillo, Stanley; Schreiber, Stephen Bruce; Mcneel, John Worth; Monsalve-Jones, Robert A.; Welsh, Mark; Ortega, Greg N.; Martinez, Xavier Baltazar; Padilla, Ruby A.

    2015-12-10

    As part of the ADPSM Safety Improvement Plan, the WSST has established a subcommittee for a Learning Team. The purpose of a Learning Team is to transfer and communicate the information into operational feedback and improvement. We want to pay attention to the small things that go wrong because they are often early warning signals and may provide insight into the health of the whole system.

  4. Windows based computer program for gasket determination based on two different calculation procedures

    SciTech Connect

    Bernard, F.; Borovnicar, I.; Ghirlanda, M.

    1996-12-01

    The windows based computer program for gasket calculation was presented. C++ computer language was used. On the basis of experimental results and data sets available in the literature and calculated with the help of FSA and PVRC method, the assembly parameters were determined. The result is DONIT TESNITI Diskette, a smart tool to select gaskets on the basis of service conditions and tightness requirements.

  5. Rubber and alumina gaskets retain vacuum seal in high temperature EMF cell

    NASA Technical Reports Server (NTRS)

    Hesson, J. C.

    1966-01-01

    Silicone rubber gasket and an alumina gasket retain a vacuum inside a high temperature EMF cell in which higher and lower density liquid metal electrodes are separated by an intermediate density fused salt electrolyte. This innovation is in use on a sodium bismuth regenerable EMF cell in which the fused salts and metals are at about 500 deg to 600 deg C.

  6. Elastomeric composites based on carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Araby, Sherif; Meng, Qingshi; Zhang, Liqun; Zaman, Izzuddin; Majewski, Peter; Ma, Jun

    2015-03-01

    Carbon nanomaterials including carbon black (CB), carbon nanotubes (CNTs) and graphene have attracted increasingly more interest in academia due to their fascinating properties. These nanomaterials can significantly improve the mechanical, electrical, thermal, barrier, and flame retardant properties of elastomers. The improvements are dependent on the molecular nature of the matrix, the intrinsic property, geometry and dispersion of the fillers, and the interface between the matrix and the fillers. In this article, we briefly described the fabrication processes of elastomer composites, illuminated the importance of keeping fillers at nanoscale in matrices, and critically reviewed the recent development of the elastomeric composites by incorporating CB, CNTs, and graphene and its derivatives. Attention has been paid to the mechanical properties and electrical and thermal conductivity. Challenges and further research are discussed at the end of the article.

  7. Anisotropic dewetting on stretched elastomeric substrates.

    PubMed

    Qiao, L; He, L H

    2008-08-01

    We study the instability of a very thin liquid film resting on a uniformly stretched soft elastomeric substrate driven by van der Waals forces. A linear stability analysis shows that the critical fluctuation wavelength in the tensile direction is larger than those in the other directions. The magnitudes of the critical wavelengths are adjustable in the sense that they depend on the principal stretch of the substrate. For example, when the principal stretch of the substrate varies from 1.0 (unstretched) to 3.0, the range of the critical wavelength in the tensile direction increases by 7.0% while that normal to the tensile direction decreases by 8.7%. Therefore, the phenomenon may find potential applications in creating tunable topographically patterned surfaces with nano- to microscale features. PMID:19230211

  8. Friction of soft elastomeric wrinkled surfaces

    NASA Astrophysics Data System (ADS)

    Rand, Charles J.; Crosby, Alfred J.

    2009-09-01

    We evaluate the sliding of a rigid spherical lens over a surface-wrinkled, elastomeric substrate. Sliding is conducted both parallel and perpendicular to the aligned surface wrinkles, and the sliding force is compared to the required sliding forces on nonwrinkled surfaces. We evaluate the effects of wrinkle dimensions and applied normal force on the sliding resistance. A simple Bowden-Tabor friction model can describe the dependence of the sliding force on normal load, with different coefficients of friction associated with the nonwrinkled and wrinkled surfaces both perpendicular and parallel. The aspect ratio of the wrinkles has a secondary effect on the sliding force. We associate the changes in friction to changes in the tangential stiffness and fracture angle caused by the surface wrinkles.

  9. Flame Arrival Measurement By Instrumented Spark Plug or Head Gasket

    Energy Science and Technology Software Center (ESTSC)

    1995-04-10

    PLUGBIN was developed to support Sandia technologies involving instrumented head gaskets and spark plugs for engine research and development. It acquires and processes measurements of flame arrival and pressure from a spark ignition. Flame arrival is determined from analog ionization-probe or visible-emission signals, and/or digitial signals from a dedicated flame arrival measurement processor. The pressure measurements are analyzed to determine the time of peak pressure and the time to burn 10 and 90 percent ofmore » the charge. Histograms are then calculated and displayed for each measurement.« less

  10. The characteristic of blind flanged bolted joints with full-face gaskets

    SciTech Connect

    Sawa, Toshiyuki

    1996-12-01

    In this paper, the characteristics of blind flanged bolted joints with full-face gaskets such as the contact stress distributions and the variation of axial bolt force are analyzed using axisymmetrical theory of elasticity. The effect of Young`s modulus of gaskets, the gasket thickness and the bolt pitch circle diameter on the contact stress distribution are clarified by the numerical calculations. In the experiments, the contact stress distributions were measured by sensitive films when the gasket is asbestos. Variations of axial bolt force are measured using strain gages. The internal pressure is observed when the internal fluid starts to leak. The numerical results are in fairly good agreement with the experimental results. Discussions are made on the sealing performance of gaskets used in these experiments.

  11. Gasket performance of SWG in ROTT and short term estimation at elevated temperature

    SciTech Connect

    Asahina, M.; Nishida, T.; Yamanaka, Y.

    1996-12-01

    This paper deals with the sealability at room temperature and the durability at elevated temperature of SWG (spiral wound gasket). The fillers in the gasket specimens are chosen as newly developed non-asbestos, asbestos and flexible graphite. The effects of inner and outer rings inserted in the gasket specimens on the new PVRC gaskets constants are examined by using the ROTT test procedure (room temperature tightness test). The durability of SWG at elevated temperature is estimated by using the weight loss of filler and the stress-deflection curve of SWG obtained after aging at elevated temperatures. As a result, the sealability and the durability of newly developed non-asbestos SWG is the same as asbestos SWG, and the durability of flexible graphite SWG at elevated temperatures in this method conform to the boundary temperature in field and it is shown that this method is available to estimate the durability of gaskets at elevated temperatures.

  12. Elastomeric Conducting Polyaniline Formed Through Topological Control of Molecular Templates.

    PubMed

    Ding, Hangjun; Zhong, Mingjiang; Wu, Haosheng; Park, Sangwoo; Mohin, Jacob W; Klosterman, Luke; Yang, Zhou; Yang, Huai; Matyjaszewski, Krzysztof; Bettinger, Christopher John

    2016-06-28

    A strategy for creating elastomeric conducting polyaniline networks is described. Simultaneous elastomeric mechanical properties (E < 10 MPa) and electronic conductivities (σ > 10 S cm(-1)) are achieved via molecular templating of conjugated polymer networks. Diblock copolymers with star topologies processed into self-assembled elastomeric thin films reduce the percolation threshold of polyaniline synthesized via in situ polymerization. Block copolymer templates with star topologies produce elastomeric conjugated polymer composites with Young's moduli ranging from 4 to 12 MPa, maximum elongations up to 90 ± 10%, and electrical conductivities of 30 ± 10 S cm(-1). Templated polyaniline films exhibit Young's moduli up to 3 orders of magnitude smaller compared to bulk polyaniline films while preserving comparable bulk electronic conductivity. Flexible conducting polymers have prospective applications in devices for energy storage and conversion, consumer electronics, and bioelectronics. PMID:27175931

  13. Material morphology and electrical resistivity differences in EPDM rubbers.

    SciTech Connect

    Yang, Nancy Y. C.; Domeier, Linda A.

    2008-03-01

    Electrical resistance anomalies noted in EPDM gaskets have been attributed to zinc-enriched surface sublayers, about 10-{micro}m thick, in the sulfur cured rubber material. Gasket over-compression provided the necessary connector pin contact and was also found to cause surprising morphological changes on the gasket surfaces. These included distributions of zinc oxide whiskers in high pressure gasket areas and cone-shaped features rich in zinc, oxygen, and sulfur primarily in low pressure protruding gasket areas. Such whiskers and cones were only found on the pin side of the gaskets in contact with a molded plastic surface and not on the back side in contact with an aluminum surface. The mechanisms by which such features are formed have not yet been defined.

  14. The effect of dietary pigmentation on the esthetic appearance of clear orthodontic elastomeric modules

    PubMed Central

    Talic, Nabeel F; Almudhi, Abdullazez A

    2016-01-01

    Objective: To compare the stain resistance of three types of clear elastomeric modules exposed to several common dietary substances through the assessment of the perception of a group of dentists to discoloration using visual analog scale (VAS). Materials and Methods: Elastomeric modules from Unitek (AU), Ormco (OR), and dentaurum (DE) were immersed in the following food substances: Coffee, black tea, chocolate, energy drink, ketchup, and Coca-Cola for 72 h. VAS was used to reflect the module staining severity. Results: Significant difference was found among the three types of modules examined in this study. OR modules showed the least mean staining ratings by the examiners. There was no statistical difference in the staining properties between AU and DE modules. Coffee and tea showed higher staining potential as compared to all staining media. Furthermore, there was no difference in the staining characteristics of coffee and black tea. Conclusions: Coffee and tea are strong staining media that should be avoided by patients who opted to have esthetic appliances for their orthodontic treatment. Elastomeric modules manufactured by AU showed higher staining optical properties as compared to the other two companies, which could be related to the manufacturing processing of these modules. PMID:27127754

  15. Long-term compression effects on elastomeric O-ring behavior

    NASA Technical Reports Server (NTRS)

    Clinton, R. G.; Turner, J. E.

    1990-01-01

    This paper discusses the results of testing performed on elastomeric seal materials that had been under compression for extended periods of time. Elastomeric seals used in the Space Shuttle redesigned solid rocket motors can experience compression times of up to six months. These seals must be capable of sealing internal motor pressure upon ignition. The tests described herein were performed in order to verify that the seals, which had experienced long-term compression could seal throughout motor operation. Testing was divided into two phases: (1) dynamic high pressure testing, and (2) resiliency testing. Dynamic testing was performed using specialized test fixtures that allowed simulation of the field joint movements during initial motor operation along with high pressure gas. Resiliency testing was performed using specialized test fixtures that also simulated field joint movements and also had the ability to measure the sealing force of the O-ring. Results from all testing indicated that the current elastomeric seals used in the redesigned solid rocket motors will seal during motor operations in the currently defined launch environments.

  16. The application of elastomeric connector for multi-channel electrophysiological recordings.

    PubMed

    Szabó, Imre; Máthé, Kálmán; Tóth, Attila; Hernádi, István; Czurkó, András

    2002-02-15

    Interest in recording multi-channel electrophysiological data from behaving animals is rapidly growing, and many laboratories tend to record a large number of EEG and/or multi-unit channels, despite the limitation of the size of the headpiece that a small behaving animal can carry. A common drawback of these experiments, therefore, is the relatively large size of even the smallest, commercially available, high-density micro-connectors for the headset. To overcome this problem, we suggest the application of elastomeric or silicone inter-rubber connectors, that are widely used in electronics. The elastomeric or "zebra" connector consists of alternating thin strips of layered electrically conductive and non-conductive materials. The conductive strips provide electrical connections between uninsulated contact surfaces of printed circuit boards such as the connector plate of the micro-drive, that holds the brain electrode wires, and the preamplifier board of the recording system. In the present paper, we provide technical details of the design of this type of connector-sets and discuss common issues arising from their use. By comparing the applicability of two designs, we aim to demonstrate the simplicity, reliability and durability of the elastomeric inter-rubber connectors in electrophysiological experiments on freely moving laboratory animals. PMID:11850041

  17. Solvent-resistant elastomeric microfluidic devices and applications

    NASA Astrophysics Data System (ADS)

    van Dam, Robert Michael

    Microfluidics is increasingly being used in many areas of biotechnology and chemistry to achieve reduced reagent volumes, improved performance, integration, and parallelism, among other advantages. Though early devices were based on rigid materials such as glass and silicon, elastomeric materials such as polydiznethylsiloxane (PDMS) are rapidly emerging as a ubiquitous platform for applications in biotechnology. This is due, in part, to simpler fabrication procedures and to the ability to integrate mechanical microvalves at vastly greater densities. For many applications in the areas of chemical synthesis and analysis, however, PDMS cannot replace glass and silicon due to its incompatibility with many solvents and reagents. Such areas could benefit tremendously from the development of an elastomeric microfluidic device technology that combines the advantages of PDMS with the property of solvent resistance. Simplified fabrication could increase the accessibility of microfluidics, and the possibility of dense valve integration could lead to significant advances in device sophistication. Applications could be more rapidly developed by design re-use due to the independence of mechanical valves on fluid properties (unlike electrokinetic pumping), and the property of permeability could enable novel fluidic functions for accessing a broader range of reactions than is possible in glass and silicon. The first half of this thesis describes our strategies and efforts to develop this new enabling technology. Several approaches are presented in Chapter 3, and two particularly successful ones, based on new elastomers (FNB and PFPE), are described in Chapters 4 and 5. Chapter 6 describes a novel method of fabricating devices from 3D molds that could expand the range of useful clastomers. The second half of this thesis discusses microfluidic combinatorial synthesis and high throughput screening-applications that take particular advantage of the ability to integrate thousands of

  18. Elastomeric and soft conducting microwires for implantable neural interfaces.

    PubMed

    Kolarcik, Christi L; Luebben, Silvia D; Sapp, Shawn A; Hanner, Jenna; Snyder, Noah; Kozai, Takashi D Y; Chang, Emily; Nabity, James A; Nabity, Shawn T; Lagenaur, Carl F; Cui, X Tracy

    2015-06-28

    Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young's modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young's modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications. PMID:25993261

  19. Elastomeric and soft conducting microwires for implantable neural interfaces

    PubMed Central

    Kolarcik, Christi L.; Luebben, Silvia D.; Sapp, Shawn A.; Hanner, Jenna; Snyder, Noah; Kozai, Takashi D.Y.; Chang, Emily; Nabity, James A.; Nabity, Shawn T.; Lagenaur, Carl F.; Cui, X. Tracy

    2015-01-01

    Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young’s modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young’s modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications. PMID:25993261

  20. Elastomeric gradients: a hedge against stress concentration in marine holdfasts?

    PubMed Central

    Waite, J Herbert; Vaccaro, Eleonora; Sun, Chengjun; Lucas, Jared M

    2002-01-01

    The byssal threads of marine mussels are elastomeric fibres with a great capacity for absorbing and dissipating energy. Up to 70% of the total absorbed energy can be dissipated in the byssus. Because byssal threads attach the mussel to hard inert surfaces in its habitat, they must combine the need to be good shock absorbers with appropriate matching of Young's modulus between living tissue and a hard sub-stratum such as stone - stiffnesses that can differ by five orders of magnitude. Recent data suggest that improved modulus matching and decreased stress concentration between different portions of the byssus is achieved by the use of protein gradients. Protein gradients in byssal threads are constructed using natural macromolecular chimeras having a central collagenous domain, variable flanking modules and histidine-rich amino and carboxy termini. Stiff silk-like flanking modules prevail distally, while at the animal end, rubbery modules resembling elastin predominate. In between the two thread ends there is a mix of both module types. The histidine-rich termini provide metal binding/cross-linking sites, while collagen domains may confer self-assembly on all parts of the structure. A graded axial distribution of flanking modules is expected to moderate stress concentration in joined materials having disparate moduli. PMID:11911771

  1. Charge Effects on Mechanical Properties of Elastomeric Proteins

    NASA Astrophysics Data System (ADS)

    Kappiyoor, Ravi; Balasubramanian, Ganesh; Dudek, Daniel; Puri, Ishwar

    2012-02-01

    Several biological molecules of nanoscale dimensions, such as elastin and resilin, are capable of performing diverse tasks with minimal energy loss. These molecules are efficient in that the ratio of energy output to energy consumed is very close to unity. This is in stark contrast to some of the best synthetic materials that have been created. For example, it is known that resilin found in dragonflies has a hysteresis loss of only 0.8% of the energy input while the best synthetic rubber made to date, polybutadiene, has a loss of roughly 20%.We simulate tensile tests of naturally occurring motifs found in resilin (a highly hydrophilic protein), as well as similar simulations found in reduced-polarity counterparts (i.e. the same motif with the charge on each individual atom set to half the natural value, the same motif with the charge on each individual atom set to zero, and a motif in which all the polar amino acids have been replaced with nonpolar amino acids). The results show a strong correlation between charge and extensibility. In order to further understand the effect of properties such as charge on the system, we will run simulations of elastomeric proteins such as resilin in different solvents.

  2. A spun elastomeric graft for dialysis access.

    PubMed

    Drasler, W J; Wilson, G J; Stenoien, M D; Jenson, M L; George, S A; Dutcher, R G; Possis, Z C

    1993-01-01

    A new composite vascular graft was developed using electrostatic spinning technology. The graft is primarily microfibrous polydimethylsiloxane spun onto a mandrel; a small diameter polyester yarn provides additional strength while minimizing wall thickness, and a helical bead provides crush and kink resistance. Eighteen grafts were implanted in a mongrel canine arteriovenous shunt model for 12 months. The grafts were implanted in femoral artery to femoral vein loops and were cannulated using three pairs of 16 gauge dialysis needles per week. Grafts were evaluated during each puncture session, and also followed using angiography. Histologic study of explanted grafts, regional lymph nodes, and lungs was performed. The grafts provided excellent handling and puncture characteristics, with no bleeding through the graft wall at puncture sites. Cumulative patency of these punctured grafts was 88% at 6 months and 80% at 1 year. Histologic study showed external fibroconnective tissue encapsulation of the grafts, with tissue growth through the interstices of the graft consisting of a microvascular network surrounded predominantly by histiocytes, many multinucleated foreign body giant cells, with some fibroblasts and collagen formation also present. Little luminal thrombus was seen at puncture sites in the patent grafts, and there was no evidence of pulmonary thromboemboli. This new elastomeric graft shows excellent promise for dialysis access; similar grafts under development may also find application for small diameter peripheral vascular reconstruction. PMID:8324257

  3. Regenerative braking through elastomeric energy storage

    NASA Astrophysics Data System (ADS)

    Hoppie, L. O.

    The project goals are to improve the energy density and fatigue life of the elastomeric units through elastomer formulations and fabrication technique research, and to verify that a compact method of attachment is feasible in full-size units. Samples of a new compound have shown an improvement of 100% in energy density as compared with the previous compound. The energy density, hysteresis loss, and fatigue life of fullsize units fabricated with this compound will be measured during the project. Molding techniques commonly used within the rubber industry give rise to surface flaws on the finished energy storage units, and these surface flaws have been indentified as sources of subsequent fatigue failure. A molding technique aimed at minimizing surface flaws will be investigated during this project. Small-scale energy storage units were used to carry out a comparison of compact attachment concepts. One concept has been selected and will be incorporated into full-size units for test and evaluation during this project.

  4. Elastomeric composites with tuned electromagnetic characteristics

    NASA Astrophysics Data System (ADS)

    Wheeland, Sara; Bayatpur, Farhad; Amirkhizi, Alireza V.; Nemat-Nasser, Sia

    2013-01-01

    This paper presents a novel elastomeric composite that exhibits a deformation-induced change in chirality. Previous efforts primarily dealt with a coil array in air without chiral tuning. Here, a composite is created that consists of an array of parallel, metallic helices of the same handedness embedded in a polymer matrix. The chiral response of the composite depends on pitch, coil diameter, wire thickness and coil spacing; however, pitch has the greatest effect on electromagnetic performance. The present study explores this effect by using helical elements to construct a chiral medium that can be mechanically stretched to adjust pitch. This adjustment directly affects the overall chirality of the composite. A prototype sample of the composite, fabricated for operation between 5.5-12.5 GHz, demonstrates repeatable elastic deformation. Using a transmit/receive measurement setup, the composite scattering response is measured over the frequency interval. The results indicate substantial tuning of chirality through deformation. An increase in axial strain of up to 30% yields a ˜18% change in axial chirality.

  5. Development of a snubber type magnetorheological fluid elastomeric lag damper for helicopter stability augmentation

    NASA Astrophysics Data System (ADS)

    Ngatu, Grum T.

    Most advanced helicopter rotors are typically fitted with lag dampers, such as elastomeric or hybrid fluid-elastomeric (FE) lag dampers, which have lower parts counts, are lighter in weight, easier to maintain, and more reliable than conventional hydraulic dampers. However, the damping and stiffness properties of elastomeric and fluid elastomeric lag dampers are non-linear functions of lag/rev frequency, dynamic lag amplitude, and operating temperature. It has been shown that elastomeric damping and stiffness levels diminish markedly as amplitude of damper motion increases. Further, passive dampers tend to present severe damping losses as damper operating temperature increases either due to in-service self-heating or hot atmospheric conditions. Magnetorheological (MR) dampers have also been considered for application to helicopter rotor lag dampers to mitigate amplitude and frequency dependent damping behaviors. MR dampers present a controllable damping with little or no stiffness. Conventional MR dampers are similar in configuration to linear stroke hydraulic type dampers, which are heavier, occupy a larger space envelope, and are unidirectional. Hydraulic type dampers require dynamic seal to prevent leakage, and consequently, frequent inspections and maintenance are necessary to ensure the reliability of these dampers. Thus, to evaluate the potential of combining the simplicity and reliability of FE and smart MR technologies in augmenting helicopter lag mode stability, an adaptive magnetorheological fluid-elastomeric (MRFE) lag damper is developed in this thesis as a retrofit to an actual fluid-elastomeric (FE) lag damper. Consistent with the loading condition of a helicopter rotor system, single frequency (lag/rev) and dual frequency (lag/rev at 1/rev) sinusoidal loading were applied to the MRFE damper at varying temperature conditions. The complex modulus method was employed to linearly characterize and compare the performance of the MRFE damper with the

  6. Synthesis and Characterization of Elastomeric Heptablock Terpolymers Structured by Crystallization

    SciTech Connect

    Alfonzo, C.Guillermo; Fleury, Guillaume; Chaffin, Kimberly A.; Bates, Frank S.

    2010-12-07

    We report the synthesis and characterization of fully saturated hydrocarbon block copolymer thermoplastic elastomers with competitive mechanical properties and attractive processing features. Block copolymers containing glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were produced in a CEC-P-CEC heptablock architecture, denoted XPX, by anionic polymerization and catalytic hydrogenation. The X blocks contain equal volume fractions of C and E, totaling 40%-60% of the material overall. All the XPX polymers are disordered above the melt temperature for E (T{sub m,E} {approx_equal} 95 C) as evidenced by SAXS and dynamic mechanical spectroscopy measurements. Cooling below T{sub m,E} results in crystallization of the E blocks, which induces microphase segregation of E, C, and P into a complex morphology with a continuous rubbery domain and randomly arranged hard domains as shown by TEM. This mechanism of segregation decouples the processing temperature from the XPX molecular weight up to a limiting value. Tensile mechanical testing (simple extension and cyclic loading) demonstrates that the tensile strength (ca. 30 MPa) and strain at break (>500%) are comparable to the behavior of CPC triblock thermoplastic elastomers of similar molecular weight and glass content. However, in the CPC materials, processability is constrained by the order-disorder transition temperature, limiting the applications of these materials. Elastic recovery of the XPX materials following seven cycles of tensile deformation is correlated with the fraction of X in the heptablock copolymer, and the residual strain approaches that of CPC when the fraction of hard blocks f{sub X} {le} 0.39.

  7. Effect of Commonly Used Beverage, Soft Drink, and Mouthwash on Force Delivered by Elastomeric Chain: A Comparative In Vitro Study

    PubMed Central

    Kumar, Kiran; Shetty, Sharath; Krithika, M J; Cyriac, Bobby

    2014-01-01

    Background: The objective was to evaluate and compare the effect of Coca-Cola®, tea, Listerine® mouthwash on the force delivered by elastomeric chain in vitro. Materials and Methods: Four specimen groups (distilled water, Coca-Cola®, tea, Listerine® mouthwash) with a total sample size of 480 specimens. A specimen is described as a four link grey close elastomeric chain. Jigs, each with a series of pins set 25 mm apart, was used to hold stretched elastomeric chains at a constant length. These jigs allowed for complete submersion of the elastomeric chain in a water bath throughout the test period, as well as the dipping of elastomeric chains in respective control and test solutions. For 60 s, twice a day, groups were exposed to the respective solutions, the two daily exposure was separated by 9 h and force measurements were taken at six time points during the experiment, that is, 1 h, 24 h, 7 days, 14 days, 21 days, and 28 days. Force measurements were made by Instron machine by a single blinded examiner with the help of a second examiner. Results: It was found out that there was highly significant difference between groups control, Coca-Cola®, Listerine®, and tea as well as there was highly significant (p < 0.01) between time periods. Group versus time was also highly significant (p < 0.01). For all groups substantial amount of force decay occurred until 7 days. The control group reached plateau between 7 and 14 days and then suddenly decreased from 14 days to 28 days. The Coca-Cola® and the Listerine® group reached a plateau between 7 and 21 days then decrease between 21 and 28 days. The tea group showed plateau phase between 7 and 28 days. After 28 days in the control group, 25% force decay occurred while the test groups force decay of 30-50% occurred. Conclusion: Coca-Cola®, Listerine® mouthwash, and tea cause an increase in force decay of elastomeric chains over time. Tea caused highest force decay followed by Listerine® and Coca-Cola® when compared

  8. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40 Applicability; description...

  9. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40 Applicability; description...

  10. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  11. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  12. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) ASBESTOS MANUFACTURING POINT SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40...

  13. Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance.

    PubMed

    Sanders, Joan E; Nicholson, Brian S; Zachariah, Santosh G; Cassisi, Damon V; Karchin, Ari; Fergason, John R

    2004-03-01

    The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products. PMID:15558371

  14. Evaluation of the durability of elastomeric easy-release coatings

    NASA Astrophysics Data System (ADS)

    Christiaen, Anne-Claire

    1998-12-01

    Novel coatings have been designed to solve problems associated with biofouling of marine structures, particularly ship hulls. The best candidates to date are multilayered coatings incorporating silicone rubber technology. These materials are efficient because they exhibit excellent release properties. However, they are very soft and tend to be more susceptible to various forms of mechanical damage. Fundamental analysis of the durability of these coatings has been done using standard laboratory tests. Simulative studies are essential to screen candidates as well as to predict the true life of the systems. The goal of this project was to develop a testing protocol for the evaluation of the durability of elastomeric easy release coatings and to implement it on selected candidate coatings. A brushing apparatus was designed and built to simulate the cleaning processes of ship hulls. Wear was measured with profilometry. The proposed methodology is valuable to study the processes of wear of the coatings, to screen various materials and to identify parameters, either functional or material, which would directly affect their durability. Two groups of candidate coatings were tested: the EXS series and the NRL series. The EXS series samples showed better wear resistance than the NRL series samples and showed no dependence on the rotational speed of the brushes. The NRL series samples showed that increasing the sliding speed resulted in a decrease in wear. An increase in the applied load resulted in increased wear for both sample series. The effect of coating thickness was also investigated and discrimination between the proposed coatings could not be established because the tips of the bristles were sharp and irregular. Scratches matching the path of the brush bristles were observed in the wear scars of both sample types under all load and speed conditions. The NRL samples also exhibited ridges perpendicular to the sliding direction similar to the abrasion pattern.

  15. Simulated Body Fluid Nucleation of Three-Dimensional Printed Elastomeric Scaffolds for Enhanced Osteogenesis.

    PubMed

    Castro, Nathan J; Tan, Wilhelmina Nanrui; Shen, Charlie; Zhang, Lijie Grace

    2016-07-01

    Osseous tissue defects caused by trauma present a common clinical problem. Although traditional clinical procedures have been successfully employed, several limitations persist with regards to insufficient donor tissue, disease transmission, and inadequate host-implant integration. Therefore, this work aims to address current limitations regarding inadequate host tissue integration through the use of a novel elastomeric material for three-dimensional (3D) printing biomimetic and bioactive scaffolds. A novel thermoplastic polyurethane-based elastomeric composite filament (Gel-Lay) was used to manufacture porous scaffolds. In an effort to render the scaffolds more bioactive, the flexible scaffolds were subsequently incubated in simulated body fluid at various time points and evaluated for enhanced mechanical properties along with the effects on cell adhesion, proliferation, and 3-week osteogenesis. This work is the first reported use of a novel class of flexible elastomeric materials for the manufacture of 3D printed bioactive scaffold fabrication allowing efficient and effective nucleation of hydroxyapatite (HA) leading to increased nanoscale surface roughness while retaining the bulk geometry of the predesigned structure. Scaffolds with interconnected microfibrous filaments of ∼260 μm were created and nucleated in simulated body fluid that facilitated cell adhesion and spreading after only 24 h in culture. The porous structure further allowed efficient nucleation, exchange of nutrients, and metabolic waste removal during new tissue formation. Through the incorporation of osteoconductive HA, human fetal osteoblast adhesion and differentiation were greatly enhanced thus setting the tone for further exploration of this novel material for biomedical and tissue regenerative applications. PMID:27298115

  16. Alloy 825 and 718 gasket corrosion in deep water (500 m) connections

    SciTech Connect

    Amen, C.; Howl, R.; Oldfield, J.W.

    1999-11-01

    Corrosion has been observed on a number of alloy 718 (UNS N07718) and alloy 825 (UNS N08825) gaskets from subsea connections. The gaskets were in contact with either weld overlaid alloy 625 (UNS N06625) or super duplex stainless steel hubs (UNS S32750). A few hubs also showed some limited corrosion in regions where severe gasket corrosion had occurred. Corrosion was more prevalent on jumpers that had been exposed to sea water for a few months at alloy 718 (UNS N07718) gaskets in contact with alloy 625 (UNS N06625) weld overlay. General observations were that short term exposures of up to 20 days did not result in corrosion but longer exposures of 40--50 days resulted in severe attack. A program of work was carried out to determine the reason for the observed attack and to suggest ways of avoiding it in the future. This paper describes the findings of the study.

  17. A review on the cords & plies reinforcement of elastomeric polymer matrix

    NASA Astrophysics Data System (ADS)

    Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

    2016-06-01

    Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

  18. Influence of elastomeric seal plate surface chemistry on interface integrity in biofouling-prone systems: Evaluation of a hydrophobic "easy-release" silicone-epoxy coating for maintaining water seal integrity of a sliding neoprene/steel interface

    NASA Astrophysics Data System (ADS)

    Andolina, Vincent L.

    The scientific hypothesis of this work is that modulation of the properties of hard materials to exhibit abrasion-reducing and low-energy surfaces will extend the functional lifetimes of elastomeric seals pressed against them in abrasive underwater systems. The initial motivation of this work was to correct a problem noted in the leaking of seals at major hydropower generating facilities subject to fouling by abrasive zebra mussel shells and extensive corrosion. Similar biofouling-influenced problems can develop at seals in medical devices and appliances from regulators in anesthetic machines and SCUBA diving oxygen supply units to autoclave door seals, injection syringe gaskets, medical pumps, drug delivery components, and feeding devices, as well as in food handling equipment like pasteurizers and transfer lines. Maritime and many other heavy industrial seal interfaces could also benefit from this coating system. Little prior work has been done to elucidate the relationship of seal plate surface properties to the friction and wear of elastomeric seals during sliding contacts of these articulating materials, or to examine the secondary influence of mineralized debris within the contacting interfaces. This investigation utilized the seal materials relevant to the hydropower application---neoprene elastomer against carbon steel---with and without the application of a silicone-epoxy coating (WearlonRTM 2020.98) selected for its wear-resistance, hydrophobicity, and "easy-release" capabilities against biological fouling debris present in actual field use. Analytical techniques applied to these materials before and after wear-producing processes included comprehensive Contact Angle measurements for Critical Surface Tension (CA-CST) determination, Scanning Electron Microscopic inspections, together with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-Ray Fluorescence (XRF) measurements for determination of surface texture and inorganic composition, Multiple

  19. Development of UHV compatible machined diamond profile gaskets for INDUS-2

    NASA Astrophysics Data System (ADS)

    Yadav, D. P.; Shiroman, R.; Shukla, S. K.; Kotaiah, S.

    2008-05-01

    Ultra High Vacuum (UHV) compatible demountable joints are needed in Indus-2 (2.5 GeV, 300mA) electron storage ring for connecting Al-alloy vacuum chambers (homogeneous joints) as well as Al-alloy vacuum chambers to well proven stainless steel components like beam diagnostic components and RF-shielded bellow assemblies (heterogeneous joints). Bakeable & reliable diamond profile Al-alloy gaskets have been developed for Helium leak rate less than 2×10-10 Std. CC/sec, which eliminated the need of any Al to SS transition pieces onto the Aluminium vacuum chambers. Salient features of these gaskets are: high reliability, low cost, reduced flange thickness, self alignment, ease in installation, less torque requirement, formability to non-circular shape & ultra cleanliness. These diamond profile gaskets were machined from extruded Al-alloy 6061-T5 pipes using specially developed high-speed steel formed cutting tools. Thermal cyclic tests were carried to check the reliability of these gaskets. No leaks were found even after several bakeouts at 150°C. Non-circular metallic gaskets like the one used in UHV gate valve bonnet seal can also be manufactured using specially developed formed toolings. This paper describes basic design philosophy, manufacturing process and testing details of these gaskets.

  20. Physiologic Compliance in Engineered Small-diameter Arterial Constructs Based on an Elastomeric Substrate

    PubMed Central

    CRAPO, PETER M.; WANG, YADONG

    2009-01-01

    Compliance mismatch is a significant challenge to long-term patency in small-diameter bypass grafts because it causes intimal hyperplasia and ultimately graft occlusion. Current engineered grafts are typically stiff with high burst pressure but low compliance and low elastin expression. We postulated that engineering small arteries on elastomeric scaffolds under dynamic mechanical stimulation would result in strong and compliant arterial constructs. Compare properties of engineered arterial constructs based on biodegradable polyester scaffolds composed of either rigid poly(lactide-co-glycolide) (PLGA) or elastomeric poly(glycerol sebacate) (PGS). Adult baboon arterial smooth muscle cells (SMCs) were cultured in vitro for 10 days in tubular, porous scaffolds. Scaffolds were significantly stronger after culture regardless of material, but the elastic modulus of PLGA constructs was an order of magnitude greater than that of porcine carotid arteries and PGS constructs. Deformation was elastic in PGS constructs and carotid arteries but plastic in PLGA constructs. Compliance of arteries and PGS constructs were equivalent at pressures tested. Altering scaffold material from PLGA to PGS significantly decreased collagen content and significantly increased insoluble elastin content in constructs without affecting soluble elastin concentration in the culture medium. PLGA constructs contained no appreciable insoluble elastin. This research demonstrates that: (1) substrate stiffness directly affects in vitro tissue development and mechanical properties; (2) rigid materials likely inhibit elastin incorporation into the extracellular matrix of engineered arterial tissues; and (3) grafts with physiologic compliance and significant elastin content can be engineered in vitro after only days of cell culture. PMID:19962188

  1. Mechanical-property changes of structural composite materials after low-temperature proton irradiation: Implications for use in SSC magnet systems

    SciTech Connect

    Morena, J.; Snead, C.L. Jr.; Czajkowski, C.; Skaritka, J.

    1993-07-01

    Longterm physical, mechanical, electrical, and other properties of advanced composites, plastics, and other polymer materials are greatly affected by high-energy proton, neutron, electron, and gamma radiation. The effects of high-energy particles on materials is a critical design parameter to consider when choosing polymeric structural, nonstructural, and elastomeric matrix resin systems. Polymer materials used for filled resins, laminates, seals, gaskets, coatings, insulation and other nonmetallic components must be chosen carefully, and reference data viewed with caution. Most reference data collected in the high-energy physics community to date reflects material property degradation using other than proton irradiations. In most instances, the data were collected for room-temperature irradiations, not 4.2 K or other cryogenic temperatures, and at doses less than 10{sup 8}--10{sup 9} Rad. Energetic proton (and the accompanying spallation-product particles) provide good simulation fidelity to the expected radiation fields predicted for the cold-mass regions of the SSC magnets, especially the corrector magnets. The authors present here results for some structural composite materials which were part of a larger irradiation-characterization of polymeric materials for SSC applications.

  2. Plaque retention on elastomeric ligatures. An in vivo study

    PubMed Central

    CONDÒ, R.; CASAGLIA, A.; CONDÒ, S.G.; CERRONI, L.

    2013-01-01

    SUMMARY Fixed orthodontic appliances make it difficult to maintain the oral hygiene, resulting in plaque accumulation. Retention of bacterial plaque, represents a risk for white spot lesions and development of periodontal disease. Aim Purpose of this study was to determine in vivo the retention of plaque on three different elastic ligatures, in comparison with stainless steel ligature, to determine a possible association between type of ligatures and accumulation of microorganisms. Material and Methods three elastic ligation systems were analyzed for plaque retention: ring-shape, clear, latex ligatures (Leone® Spa), ring-shape, grey, polyurethane ligatures (Micerium® Spa) and grey, polyurethane, Slide low-friction ligatures (Leone® Spa), compared with stainless steel ligatures (Leone® Spa) used as control. Forthy orthodontic patients undergoing fixed orthodontic therapy were selected. A sample for each type of ligature were applied inside the oral cavity of each subject. Samples were kept in the oral cavity for 28 days, ligating 0.16 X 0.22 stainless steel archwire to stainless steel orthodontic premolars brackets. The presence of bacterical slime was quantified by spectrophotometric method (crystal violet-Bouin’s fixative) and morphological observations was evaluated by Scanning Electron Microscopy (SEM). Results From analysis of bacterical slime emerges that all the elastics showed a low plaque retention, especially if compared to the group of steinless steel ligatures, that presented a greater plaque adhesion, statistically significant compared to the Slide group (r<0.0002) and the two elastic groups (r<0.0001). This study reported no significant difference between the Slide ligatures and the traditional elastic ligatures as regards the retention of plaque. SEM images showed presence of cocci, rods and few filamentous organisms and an interbacterial matrix in all observed samples. Conclusion Elastomeric ligatures showed a significant lower susceptibility

  3. Stability of colistimethate sodium in a disposable elastomeric infusion device.

    PubMed

    Abdulla, Alan; van Leeuwen, Roelof W F; de Vries Schultink, Aurelia H M; Koch, Birgit C P

    2015-01-01

    Infections of the respiratory tract with Pseudomonas aeruginosa in cystic fibrosis patients are frequently treated with colistimethate sodium (CMS). For the intravenous administration of CMS a disposable elastomeric pump is a convenient option. To date, there are no data available on the chemical stability of CMS solutions stored in elastomeric pumps. We evaluated the chemical stability of 0.8 mg/mL solutions of CMS by measuring the degradation over a period of 7 days. Test samples were prepared by diluting CMS with saline solution (0.9%). The preparations were transferred to 100-mL elastomeric pumps and stored at 4 °C. The chemical stability was measured by a high-performance liquid chromatography method with UV detection. There was no degradation of CMS (<0.5% of CMS present as colistin) for at least 3 day at 4 °C, and after 7 days all test samples remained chemically stable (<5% of CMS present as colistin). Since colistin formed in pharmacy-compounded CMS solutions prior to administration may cause toxicity, we advise that the solution should be used before the hydrolysis of CMS occurs. Therefore, we recommend that the 0.8 mg/mL solution of CMS can be stored for up to 3 days at 4 °C in an elastomeric pump. PMID:25863116

  4. Effect of modified elastomeric binders on the electrochemical properties of silicon anodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Tao; Yang, Juan-yu; Lu, Shi-gang

    2012-08-01

    Silicon has been investigated intensively as a promising anode material for rechargeable lithium-ion batteries. The choice of a binder is very important to solve the problem of the large capacity fade observed along cycling. The effect of modified elastomeric binders on the electrochemical performance of crystalline nano-silicon powders was studied. Compared with the conventional binder (polyvinylidene fluoride (PVDF)), Si electrodes using the elastomeric styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (SCMC) combined binder show an improved cycling performance. The reversible capacity of the Si electrode with the SCMC/SBR binder is as high as 2221 mA·h/g for 30 cycles in a voltage window between 0.005 and 2 V. The structure changes from SEM images of the silicon electrodes with different binders were used to explore the property improvement.

  5. Resilin-PEG Hybrid Hydrogels Yield Degradable Elastomeric Scaffolds with Heterogeneous Microstructure.

    PubMed

    McGann, Christopher L; Akins, Robert E; Kiick, Kristi L

    2016-01-11

    Hydrogels derived from resilin-like polypeptides (RLPs) have shown outstanding mechanical resilience and cytocompatibility; expanding the versatility of RLP-based materials via conjugation with other polypeptides and polymers would offer great promise in the design of a range of materials. Here, we present an investigation of the biochemical and mechanical properties of hybrid hydrogels composed of a recombinant RLP and a multiarm PEG macromer. These hybrid hydrogels can be rapidly cross-linked through a Michael-type addition reaction between the thiols of cysteine residues on the RLP and vinyl sulfone groups on the multiarm PEG. Oscillatory rheology and tensile testing confirmed the formation of elastomeric hydrogels with mechanical resilience comparable to aortic elastin; hydrogel stiffness was easily modulated through the cross-linking ratio. Macromolecular phase separation of the RLP-PEG hydrogels offers the unique advantage of imparting a heterogeneous microstructure, which can be used to localize cells, through simple mixing and cross-linking. Assessment of degradation of the RLP by matrix metalloproteinases (MMPs) illustrated the specific proteolysis of the polypeptide in both its soluble form and when cross-linked into hydrogels. Finally, the successful encapsulation and viable three-dimensional culture of human mesenchymal stem cells (hMSCs) demonstrated the cytocompatibility of the RLP-PEG gels. Overall, the cytocompatibility, elastomeric mechanical properties, microheterogeneity, and degradability of the RLP-PEG hybrid hydrogels offer a suite of promising properties for the development of cell-instructive, structured tissue engineering scaffolds. PMID:26646060

  6. Mechanically tissue-like elastomeric polymers and their potential as a vehicle to deliver functional cardiomyocytes.

    PubMed

    Xu, Bing; Li, Yuan; Fang, Xiya; Thouas, George A; Cook, Wayne D; Newgreen, Donald F; Chen, Qizhi

    2013-12-01

    One of the major challenges in the field of biomaterials engineering is the replication of the non-linear elasticity observed in soft tissues. In the present study, non-linearly elastic biomaterials were successfully fabricated from a chemically cross-linked elastomeric poly(glycerol sebacate) (PGS) and thermoplastic poly(L-lactic acid) (PLLA) using the core/shell electrospinning technique. The spun fibrous materials, containing a PGS core and PLLA shell, demonstrated J-shaped stress-strain curves, and having ultimate tensile strength, rupture elongation, and stiffness constants respectively comparable to muscle tissue properties. In vitro evaluations also showed that PGS/PLLA fibrous biomaterials possess excellent biocompatibility, capable of supporting human stem-cell-derived cardiomyocytes over several weeks in culture. Therefore, the core/shell electrospun elastomeric materials provide a new potential scaffold to support cells in the therapy of a wide range of soft tissues exposed to cyclic deformation, such as tendon, ligament, cardiac or smooth muscle and lung epithelium. PMID:24125905

  7. Thermal stress analysis of pipe flange connections with raised-face gasket subjected to heat conduction

    SciTech Connect

    Sawa, Toshiyuki; Kotani, Kenichi

    1996-12-01

    This paper deals with thermal stress analysis of a pipe flange connection with a raised-face gasket subjected to heat conduction. In the analysis, pipe flange, hubs of the flanges and a raised-face gasket are replaced by finite hollow cylinders. When the inner surface is subjected to heat conduction due to contained fluid and the outer surface are kept at a constant temperature, temperature distribution of the connection is analyzed. Using the temperature distribution, thermoelastic displacement potential is determined. Thermal stresses and displacements are analyzed by using the thermoelastic displacement potential and axisymmetrical theory of elasticity. Experiments are performed. The analytical results are in fairly good agreement with the experimental results concerning the variation of axial bolt force and the axial strain at the hubs of pipe flange. In the numerical calculations, the effects of the ratios of Young`s modulus and the gasket thickness between the flanges and the gaskets on the contact stress distribution are examined. As the results, it is seen that the thermal stress at the inner surface increases with a decrease of the ratio of Young`s modulus and that it increases with a decrease of the gasket thickness.

  8. Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa

    SciTech Connect

    Meier, Thomas; Haase, Jürgen

    2015-12-15

    Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al{sub 2}O{sub 3}), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures.

  9. Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa.

    PubMed

    Meier, Thomas; Haase, Jürgen

    2015-12-01

    Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al2O3), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures. PMID:26724046

  10. Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa

    NASA Astrophysics Data System (ADS)

    Meier, Thomas; Haase, Jürgen

    2015-12-01

    Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al2O3), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures.

  11. Ultraviolet light crosslinking of poly(trimethylene carbonate) for elastomeric tissue engineering scaffolds.

    PubMed

    Bat, Erhan; Kothman, Bas H M; Higuera, Gustavo A; van Blitterswijk, Clemens A; Feijen, Jan; Grijpma, Dirk W

    2010-11-01

    A practical method of photocrosslinking high molecular weight poly(trimethylene carbonate)(PTMC) is presented. Flexible, elastomeric and biodegradable networks could be readily prepared by UV irradiating PTMC films containing pentaerythritol triacrylate (PETA) and a photoinitiator. The network characteristics, mechanical properties, wettability, and in vitro enzymatic erosion of the photocrosslinked PTMC films were investigated. Densely crosslinked networks with gel contents up to 98% could be obtained in this manner. Upon photocrosslinking, flexible and tough networks with excellent elastomeric properties were obtained. To illustrate the ease with which the properties of the networks can be tailored, blends of PTMC with mPEG-PTMC or with PTMC-PCL-PTMC were also photocrosslinked. The wettability and the enzymatic erosion rate of the networks could be tuned by blending with block copolymers. Tissue engineering scaffolds were also fabricated using these flexible photocrosslinkable materials. After crosslinking, the fabricated PTMC-based scaffolds showed inter-connected pores and extensive microporosity. Human mesenchymal stem cell (hMSC) culturing studies showed that the photocrosslinked scaffolds prepared from PTMC and PTMC/PTMC-PCL-PTMC blends are well-suited for tissue engineering applications. PMID:20739060

  12. Antimicrobial Effect of Zataria Multiflora Extract in Comparison with Chlorhexidine Mouthwash on Experimentally Contaminated Orthodontic Elastomeric Ligatures

    PubMed Central

    Aghili, Hossein; Jafari Nadoushan, Abbas Ali; Herandi, Vahid

    2015-01-01

    Objectives: Long-term use of orthodontic appliances and fixation ligatures creates a favorable environment for the accumulation of oral normal microflora and increases the risk of enamel demineralization and periodontal disease. The aim of this study was to compare the antimicrobial effects of Zataria Multiflora extract and 0.2% chlorhexidine (CHX) mouthwash on experimentally contaminated orthodontic elastomeric ligatures. Materials and Methods: In this lab trial study, Iranian and foreign-made elastomeric ligatures were experimentally contaminated in Streptococcus mutans, Enterococcus faecalis and Candida albicans suspensions. Ligatures were then decontaminated using 0.2% CHX as the control, 0.5 mg/ml Zataria multiflora extract mouthwashes as the test and phosphate buffered saline (PBS) as the negative control for one hour. Antimicrobial properties of both solutions were evaluated by comparing the mean viable bacterial cell count on both rings after decontamination, using SPSS version 15 software. Results: The mean viable bacterial cell count on Iranian ligatures was greater than that on foreign-made ligatures before disinfection (P=0.001), however this difference for C. albicans was not statistically significant (P=0.061). Chlorhexidine mouthwash completely eliminated all tested microorganisms attached to both elastomeric rings, but Zataria extract was only capable of completely eliminating C. albicans from both ligatures. Statistically significant differences were found in viable bacterial counts on both ligatures before and after disinfection with Zataria extract (P=0.0001). Conclusion: Zataria multiflora extract has antimicrobial properties and can be used for disinfection of elastomeric ligatures. In vivo studies are required to evaluate the efficacy of the incorporation of this herbal extract in mouthwashes for orthodontic patients. PMID:26005448

  13. Thin graphite bipolar plate with associated gaskets and carbon cloth flow-field for use in an ionomer membrane fuel cell

    DOEpatents

    Marchetti, George A.

    2003-01-03

    The present invention comprises a thin graphite plate with associated gaskets and pieces of carbon cloth that comprise a flow-field. The plate, gaskets and flow-field comprise a "plate and gasket assembly" for use in an ionomer membrane fuel cell, fuel cell stack or battery.

  14. Soft materials with recoverable shape factors from extreme distortion states

    DOE PAGESBeta

    Goff, Jonathan; Sulaiman, Santy; Arkles, Barry; Lewicki, James P.

    2016-01-20

    We present elastomeric polysiloxane nanocomposites with elongations of >5000% (more than 3× greater than any previously reported material) with excellent shape recovery. Highly deformable materials are desirable for the fabrication of stretchable implants and microfluidic devices. No crosslinking or domain formation is observed by a variety of analytical techniques, suggesting that their elastomeric behavior is caused by polymer chain entanglements.

  15. Bending a beam by a generalized ideal elastomeric gel

    PubMed Central

    Cai, Shengqiang

    2015-01-01

    A hybrid beam with a gel layer bonded on the top of an elastic non-swellable substrate has been commonly adopted to make various sensors and actuators. Usually, different models need to be developed for the hybrid beam when different gels are used in the system. In this article, based on the generalized ideal elastomeric gel model, we formulate a unified relationship between the swelling of hydrogels and the bending curvature of the elastic beam, which is independent of specific swelling mechanisms of gels. We further illustrate that the equations derived in the article can be used to validate the ideal elastomeric gel model and measure the elasticity of polymer networks of the gels. PMID:25792965

  16. Assessing patient preference for two types of elastomeric infusion device.

    PubMed

    Dodd, Susan

    Home administration of antibiotic therapy to cystic fibrosis patients is one of many applications for the use of elastomeric infusion devices. Patient acceptability can significantly affect adherence to complex drug regimens with concordance being a concern in this patient population. While patient acceptance is often cited as a factor in pump selection, patient preference has not been assessed within a particular class of infusion device. The objective of this study was to assess patient preference for one type of elastomeric infusion device (Baxter Intermate--hard-shelled design) or another (Fresenius Kabi Eclipse--soft-shelled design). Twenty-four patients entered the study. 20/24 (83%) patients expressed a preference for the Eclipse, while 4/24 (17%) stated no preference for either device. The Eclipse device was found to be much more favourable in terms of comfort and discreetness. Patient preference should therefore be given significant consideration in order to maximize concordance with drug regimens. PMID:18026019

  17. Interaction of Reinforced Elastomeric Bearings in Bridge Construction

    NASA Astrophysics Data System (ADS)

    Nittmannová, Ľubica; Magura, Martin

    2016-03-01

    The aim of this paper is to demonstrate the behavior of reinforced elastomeric bearings under various loads. They are made of special types of bearings. The experimental verification of these special bearings has been tested on various types of loading. The results of the experimental measurements are compared with the results of the numerical modeling and calculations according to the standard assumptions in STN EN 1337-3. In the conclusion, the results are summarized for the selected types of bearings.

  18. Generation and detection of gigahertz surface acoustic waves using an elastomeric phase-shift mask

    NASA Astrophysics Data System (ADS)

    Li, Dongyao; Zhao, Peng; Zhao, Ji-Cheng; Cahill, David G.

    2013-10-01

    We describe a convenient approach for measuring the velocity vSAW of surface acoustic waves (SAWs) of the near-surface layer of a material through optical pump-probe measurements. The method has a lateral spatial resolution of <10 μm and is sensitive to the elastic constants of the material within ≈300 nm of the surface. SAWs with a wavelength of 700 nm and 500 nm are generated and detected using an elastomeric polydimethylsiloxane phase-shift mask which is fabricated using a commercially available Si grating as a mold. Time-domain electromagnetics calculations show, in agreement with experiment, that the efficiency of the phase-shift mask for generating and detecting SAWs decreases rapidly as the periodicity of the mask decreases below the optical wavelength. We validate the experimental approach using bulk and thin film samples with known elastic constants.

  19. Compressible elastomeric aerogels of hexagonal boron nitride and single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Joo Jeong, Yeon; Islam, Mohammad F.

    2015-07-01

    Lightweight porous ceramic materials that can recover their shapes after mechanical deformation have numerous applications. However, these types of materials tend to be highly fragile and often crack when compressed. Here, we report on the fabrication and characterization of highly porous, freestanding composites of hexagonal boron nitride (h-BN) and single-walled carbon nanotubes (SWCNTs) of density 13-15 mg mL-1, which corresponds to a volume fraction of 0.009, that were mechanically robust and recovered their original shape even after uniaxially compressing them by more than 50%. We made these porous elastomeric composites using a solution based assembly process that involved first shaping SWCNTs into porous networks of density ~7 mg mL-1 (volume fraction ~0.005) followed by coatings of SWCNT networks with 6-8 mg mL-1 of h-BN (volume fraction ~0.003-0.004). The h-BN coating strengthened the underlying SWCNT networks, likely via reinforcement of the nodes between the SWCNTs, resulting in an increase in Young's modulus by ~100% compared to that of SWCNT networks alone. Surprisingly, SWCNT networks, which were initially highly fragile, became elastomeric after h-BN coating, even though porous structures solely from h-BN are very brittle. Our fabrication approach preserves the morphology of the underlying networks, allowing for fabrication of various shapes and sizes of porous composites of h-BN and SWCNTs. Finally, our fabrication scheme is robust and facile for the preparation of porous composites of diverse ceramic materials and SWCNTs using the appropriate ceramic-precursor.Lightweight porous ceramic materials that can recover their shapes after mechanical deformation have numerous applications. However, these types of materials tend to be highly fragile and often crack when compressed. Here, we report on the fabrication and characterization of highly porous, freestanding composites of hexagonal boron nitride (h-BN) and single-walled carbon nanotubes (SWCNTs) of

  20. In-use Stability of Ceftaroline Fosamil in Elastomeric Home Infusion Systems and MINI-BAG Plus Containers.

    PubMed

    Bhattacharya, Sisir; Parekh, Satish; Dedhiya, Mahendra

    2015-01-01

    The objective of this study was to determine in-use stability of ceftaroline fosamil infusion solution of concentrations up to 12 mg/mL in elastomeric home infusion system prefilled with 0.9% Sodium Chloride Injection USP or 5% Dextrose Injection USP and MINI-BAG Plus Container delivery devices prefilled with 0.9% sodium chloride injection. In-use ceftaroline fosamil infusion solution (12 mg/mL) was prepared for elastomeric home infusion systems (Homepump Eclipse, Baxter Intermate, and AccuRx Elastomeric Pump) pre-filled with either 0.9% sodium chloride injection or 5% dextrose; or Baxter MINI-BAG Plus Containers pre-filled with 0.9% Sodium Chloride Injection USP (4 mg/mL to 12 mg/mL ceftaroline fosamil in final solution). The systems were stored refrigerated for 24 hours followed by up to 6 hours of storage at room temperature. Samples were analyzed at various time points for assay and degradation product by a validated stability-indicating high-performance liquid chromatography method. In-use ceftaroline fosamil infusion solution, ranging from 4-mg/mL to a maximum of 12-mg/mL concentration, in elastomeric home infusion systems prefilled with 0.9% sodium chloride injection or 5% dextrose, and MINI-BAG Plus Containers prefilled with 0.9% sodium chloride injection were chemically stable for up to 24 hours refrigerated at 2°C to 8°C (36°F to 46°F) and up to 6 hours at room temperature and had acceptable compatibility with material used. Ceftaroline fosamil (4 mg/mL to 12 mg/mL) maintains its potency for up to 24 hours refrigerated at 2°C to 8°C (36°F to 46°F) and up to 6 hours of storage at room temperature upon reconstitution in infusion solution with 0.9% sodium chloride or 5% dextrose when used in elastomeric home infusion system and MINI-BAG Plus Containers delivery devices prefilled with 0.9% sodium chloride injection. PMID:26775451

  1. Compressible elastomeric aerogels of hexagonal boron nitride and single-walled carbon nanotubes.

    PubMed

    Jeong, Yeon Joo; Islam, Mohammad F

    2015-08-14

    Lightweight porous ceramic materials that can recover their shapes after mechanical deformation have numerous applications. However, these types of materials tend to be highly fragile and often crack when compressed. Here, we report on the fabrication and characterization of highly porous, freestanding composites of hexagonal boron nitride (h-BN) and single-walled carbon nanotubes (SWCNTs) of density 13-15 mg mL(-1), which corresponds to a volume fraction of 0.009, that were mechanically robust and recovered their original shape even after uniaxially compressing them by more than 50%. We made these porous elastomeric composites using a solution based assembly process that involved first shaping SWCNTs into porous networks of density ∼7 mg mL(-1) (volume fraction ∼0.005) followed by coatings of SWCNT networks with 6-8 mg mL(-1) of h-BN (volume fraction ∼0.003-0.004). The h-BN coating strengthened the underlying SWCNT networks, likely via reinforcement of the nodes between the SWCNTs, resulting in an increase in Young's modulus by ∼100% compared to that of SWCNT networks alone. Surprisingly, SWCNT networks, which were initially highly fragile, became elastomeric after h-BN coating, even though porous structures solely from h-BN are very brittle. Our fabrication approach preserves the morphology of the underlying networks, allowing for fabrication of various shapes and sizes of porous composites of h-BN and SWCNTs. Finally, our fabrication scheme is robust and facile for the preparation of porous composites of diverse ceramic materials and SWCNTs using the appropriate ceramic-precursor. PMID:26161911

  2. Manikin-based performance evaluation of elastomeric respirators against combustion particles.

    PubMed

    He, Xinjian; Yermakov, Michael; Reponen, Tiina; McKay, Roy T; James, Kelley; Grinshpun, Sergey A

    2013-01-01

    This study investigated the effects of faceseal leakage, breathing flow, and combustion material on the overall (non-size-selective) penetration of combustion particles into P-100 half and full facepiece elastomeric respirators used by firefighters. Respirators were tested on a breathing manikin exposed to aerosols produced by combustion of three materials (wood, paper, and plastic) in a room-size exposure chamber. Testing was performed using a single constant flow (inspiratory flow rate = 30 L/min) and three cyclic flows (mean inspiratory flow rates = 30, 85, and 135 L/min). Four sealing conditions (unsealed, nose-only sealed, nose and chin sealed, and fully sealed) were examined to evaluate the respirator faceseal leakage. Total aerosol concentration was measured inside (C(in)) and outside (C(out)) the respirator using a condensation particle counter. The total penetration through the respirator was determined as a ratio of the two (P = C(in) / C(out)). Faceseal leakage, breathing flow type and rate, and combustion material were all significant factors affecting the performance of the half mask and full facepiece respirators. The efficiency of P-100 respirator filters met the NIOSH certification criteria (penetration ≤0.03%); it was not significantly influenced by the challenge aerosol and flow type, which supports the current NIOSH testing procedure using a single challenge aerosol and a constant airflow. However, contrary to the NIOSH total inward leakage (TIL) test protocol assuming that the result is independent on the type of the tested aerosol, this study revealed that the challenge aerosol significantly affects the particle penetration through unsealed and partially sealed half mask respirators. Increasing leak size increased total particle penetration. The findings point to some limitations of the existing TIL test in predicting protection levels offered by half mask elastomeric respirators. PMID:23442086

  3. 21 CFR 177.1210 - Closures with sealing gaskets for food containers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... incorporated by reference in accordance with 5 U.S.C. 522(a) and 1 CFR part 51. Copies are available from the... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Closures with sealing gaskets for food containers. 177.1210 Section 177.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND...

  4. 21 CFR 177.1210 - Closures with sealing gaskets for food containers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Closures with sealing gaskets for food containers. 177.1210 Section 177.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic Components of Single...

  5. 21 CFR 177.1210 - Closures with sealing gaskets for food containers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Viscometer),” which is incorporated by reference in accordance with 5 U.S.C. 522(a) and 1 CFR part 51. Copies... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Closures with sealing gaskets for food containers. 177.1210 Section 177.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND...

  6. 21 CFR 177.1210 - Closures with sealing gaskets for food containers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... incorporated by reference in accordance with 5 U.S.C. 522(a) and 1 CFR part 51. Copies are available from the... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Closures with sealing gaskets for food containers. 177.1210 Section 177.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND...

  7. 21 CFR 177.1210 - Closures with sealing gaskets for food containers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... incorporated by reference in accordance with 5 U.S.C. 522(a) and 1 CFR part 51. Copies are available from the... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Closures with sealing gaskets for food containers. 177.1210 Section 177.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND...

  8. Assessment of airborne asbestos exposure during the servicing and handling of automobile asbestos-containing gaskets.

    PubMed

    Blake, Charles L; Dotson, G Scott; Harbison, Raymond D

    2006-07-01

    Five test sessions were conducted to assess asbestos exposure during the removal or installation of asbestos-containing gaskets on vehicles. All testing took place within an operative automotive repair facility involving passenger cars and a pickup truck ranging in vintage from late 1960s through 1970s. A professional mechanic performed all shop work including engine disassembly and reassembly, gasket manipulation and parts cleaning. Bulk sample analysis of removed gaskets through polarized light microscopy (PLM) revealed asbestos fiber concentrations ranging between 0 and 75%. Personal and area air samples were collected and analyzed using National Institute of Occupational Safety Health (NIOSH) methods 7400 [phase contrast microscopy (PCM)] and 7402 [transmission electron microscopy (TEM)]. Among all air samples collected, approximately 21% (n = 11) contained chrysotile fibers. The mean PCM and phase contrast microscopy equivalent (PCME) 8-h time weighted average (TWA) concentrations for these samples were 0.0031 fibers/cubic centimeters (f/cc) and 0.0017 f/cc, respectively. Based on these findings, automobile mechanics who worked with asbestos-containing gaskets may have been exposed to concentrations of airborne asbestos concentrations approximately 100 times lower than the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 0.1 f/cc. PMID:16730109

  9. Response of elastomeric packaging components to a corrosive simulant mixed waste

    SciTech Connect

    Nigrey, P.J.; Dickens, T.G.

    1997-10-01

    The purpose of hazardous and radioactive materials packaging is to enable these materials to be transported without posing a threat to the health or property of the general public. To achieve this aim, regulations in the US have been written establishing general design requirements for such packagings. While no regulations have been written specifically for mixed waste packaging, regulations for the constituents of mixed wastes, i.e., hazardous and radioactive substances, have been codified by the US Department of Transportation and the US Nuclear Regulatory Commission. Based on these national requirements, a Chemical Compatibility Testing Program was developed in the Transportation Systems Department at SNL. In this paper, the authors present the results of Part B of the second phase of this testing program. The first phase screened five liner materials and six seal materials towards four simulant mixed wastes. Part A of the second phase involved the comprehensive testing of five candidate liner materials to an aqueous Hanford Tank simulant mixed waste. Part B involved similar testing on elastomeric materials, ethylene-propylene and butadiene-acrylonitrile rubber. The comprehensive testing protocol involved exposing the respective materials to a matrix of four gamma radiation doses ({approximately}1, 3, 6, and 40 kGy), three temperatures (18, 50, and 60 C), and four exposure times (7, 14, 28, and 180 days). Following their exposure to these combinations of conditions, the materials were evaluated by measuring six material properties. These properties were specific gravity, dimensional changes, hardness, vapor transport rates, compression set, and mechanical properties.

  10. Seismic response analyses of base isolated structures with high damping elastomeric bearings

    SciTech Connect

    Wang, C.Y.; Tang, Y.; Chang, Y.W.; Seidensticker, R.W. ); Marchertas, A.H. )

    1991-01-01

    Seismic response analysis of base-isolated structures with high damping elastomeric bearings is described. Emphasis is placed on the adaptation of a nonlinear constitutive model for the isolation bearing together with the treatment of foundation embedment for the soil-structure-interaction analysis. The constitutive model requires six input parameters derived from bearing experimental data under sinusoidal loading. The characteristic behavior of bearing, such as the variation of shear modulus and material damping with the change of maximum shear deformation, can be captured closely by the formulation. In the treatment of soil embedment a spring method is utilized to evaluate the foundation input motion as well as soil stiffness and damping. The above features have been incorporated into a three-dimensional system response program, SISEC, developed at Argonne National Laboratory. Sample problems are presented to illustrate the relative response of isolated and unisolated structures. 11 refs., 12 figs.

  11. Flame resistant elastomeric polymer development. [for use in space shuttle instrument packaging

    NASA Technical Reports Server (NTRS)

    Howarth, J. T.; Sheth, S. G.; Sidman, K. R.

    1975-01-01

    Elastomeric products were developed for use in the space shuttle program, and investigations were conducted to improve the properties of elastomers developed in previous programs, and to evaluate the possibility of using lower-cost general purpose polymers. Products were fabricated and processed on conventional processing equipment; these products include: foams based on fluorinated rubber flame-retarded compounds with a density of 20-30 pounds/cubic foot for use as padding and in helmets; foams based on urethane for use in instrument packaging in the space shuttle; flexible and semi-rigid films of fluorinated rubber and neoprene compounds that would not burn in a 70% nitrogen, 30% oxygen atmosphere, and in a 30% nitrogen, 70% oxygen atmosphere, respectively for use in packaging or in laminates; coated fabrics which used both nylon and Kelvar fabric substrates, coated with either fluorinated or neoprene polymer compositions to meet specific levels of flame retardancy; and other flame-resistant materials.

  12. PRELIMINARY REPORT: EFFECTS OF IRRADIATION AND THERMAL EXPOSURE ON ELASTOMERIC SEALS FOR CASK TRANSPORTATION AND STORAGE

    SciTech Connect

    Verst, C.; Skidmore, E.; Daugherty, W.

    2014-05-30

    A testing and analysis approach to predict the sealing behavior of elastomeric seal materials in dry storage casks and evaluate their ability to maintain a seal under thermal and radiation exposure conditions of extended storage and beyond was developed, and initial tests have been conducted. The initial tests evaluate the aging response of EPDM elastomer O-ring seals. The thermal and radiation exposure conditions of the CASTOR® V/21 casks were selected for testing as this cask design is of interest due to its widespread use, and close proximity of the seals to the fuel compared to other cask designs leading to a relatively high temperature and dose under storage conditions. A novel test fixture was developed to enable compression stress relaxation measurements for the seal material at the thermal and radiation exposure conditions. A loss of compression stress of 90% is suggested as the threshold at which sealing ability of an elastomeric seal would be lost. Previous studies have shown this value to be conservative to actual leakage failure for most aging conditions. These initial results indicate that the seal would be expected to retain sealing ability throughout extended storage at the cask design conditions, though longer exposure times are needed to validate this assumption. The high constant dose rate used in the testing is not prototypic of the decreasingly low dose rate that would occur under extended storage. The primary degradation mechanism of oxidation of polymeric compounds is highly dependent on temperature and time of exposure, and with radiation expected to exacerbate the oxidation.

  13. Life prediction of elastomeric and thermoplastic components

    SciTech Connect

    Stevenson, A.

    1994-12-31

    Life prediction tests for polymeric materials have been in use for a considerable period of time. However there are still fundamental problems with their usage and interpretation in terms of engineering performance. In particular, it is not yet in general possible to relate the rate of change of physical properties that arise as a consequence of chemical aging to the rate of change in the underlying chemical structure or morphology. Also, different physical properties may change at different rates and these materials are generally non-linear. This renders accelerated life prediction testing potentially unreliable. This paper reviews this general problem area and discusses advances which need to be made with respect to the roles of the permeation of fluids, mechanical fatigue crack growth and time dependent changes. Illustrative examples are discussed of both thermoplastics and crosslinked elastomers. Finally, a general scheme is discussed for future research in this area, related to the development of interactive numerical modelling.

  14. Micromechanical damage and fracture in elastomeric polymers

    NASA Astrophysics Data System (ADS)

    Heyden, Stefanie

    This thesis aims at a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. The failure model is motivated by post-mortem fractographic observations of void nucleation, growth and coalescence in polyurea stretched to failure, and accounts for the specific fracture energy per unit area attendant to rupture of the material. Furthermore, it is shown that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by means of fractional strain-gradient elasticity. Optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely the critical energy-release rate of the material, and micromechanical parameters pertaining to the elasticity and strength of the polymer chains, and to the strain-gradient elasticity regularization, are derived. Based on optimal scaling laws, it is shown how the critical energy-release rate of specific materials can be determined from test data. In addition, the scope and fidelity of the model is demonstrated by means of an example of application, namely Taylor-impact experiments of polyurea rods. Hereby, optimal transportation meshfree approximation schemes using maximum-entropy interpolation functions are employed. Finally, a different crazing model using full derivatives of the deformation gradient and a core cut-off is presented, along with a numerical non-local regularization model. The numerical model takes into account higher-order deformation gradients in a finite element framework. It is shown how the introduction of non-locality into the model stabilizes the effect of strain localization to small volumes in materials undergoing softening. From an investigation of craze formation in the limit of large deformations, convergence studies verifying scaling properties of both local- and non-local energy

  15. Mechanically durable and highly conductive elastomeric composites from long single-walled carbon nanotubes mimicking the chain structure of polymers.

    PubMed

    Ata, Seisuke; Kobashi, Kazufumi; Yumura, Motoo; Hata, Kenji

    2012-06-13

    By using long single-walled carbon nanotubes (SWNTs) as a filler possessing the highest aspect ratio and small diameter, we mimicked the chain structure of polymers in the matrix and realized a highly conductive elastomeric composite (30 S/cm) with an excellent mechanical durability (4500 strain cycles until failure), far superior to any other reported conductive elastomers. This exceptional mechanical durability was explained by the ability of long and traversing SWNTs to deform in concert with the elastomer with minimum stress concentration at their interfaces. The conductivity was sufficient to operate many active electronics components, and thus this material would be useful for practical stretchable electronic devices. PMID:22546049

  16. Drilling fluids based on a mixture of a sulfonated thermoplastic polymer and a sulfonated elastomeric polymer

    SciTech Connect

    Turner, S.R.; Lundberg, R.D.; Peiffer, D.G.; Thaler, W.A.; Walker, T.O.

    1984-01-10

    The present invention relates to mixtures of sulfonated thermoplastic polymers and sulfonated elastomeric polymers which function as viscosification agents when added to oil-based drilling muds which are the fluids used to maintain pressure, cool drill bits, and lift cuttings from the holes in the drilling operation for oil and gas wells. The sulfonated thermoplastic and elastomeric polymers both have about 5 to about 200 meq. of sulfonate groups per 100 grams of the sulfonated thermoplastic or elastomeric polymers, wherein the sulfonated groups are neutralized with a metallic cation or an amine or ammonium counterion. A polar cosolvent can optionally be added to the mixture of oil drilling mud and sulfonated thermoplastic and elastomeric polymers, wherein the polar cosolvent increases the solubility of the sulfonated thermoplastic and elastomeric polymer in the oil drilling mud by decreasing the strong ionic interactions between the sulfonate groups of the sulfonated polymers.

  17. Mechanics of precisely controlled thin film buckling on Elastomeric substrate.

    SciTech Connect

    Sun, Y.; Jiang, H.; Rogers, J.; Huang, Y.; Arizone State Univ.; Beckman Inst.; University of Illinois Urbana-Champaign

    2007-01-01

    Stretchable electronics has many important and emerging applications. Sun et al. [Nature Nanotech. 1, 201 (2006)] recently demonstrated stretchable electronics based on precisely controlled buckle geometries in GaAs and Si nanoribbons on elastomeric substrates. A nonlinear buckling model is presented in this letter to study the mechanics of this type of thin film/substrate system. An analytical solution is obtained for the buckling geometry (wavelength and amplitude) and the maximum strain in buckled thin film. This solution agrees very well with the experiments, and shows explicitly how buckling can significantly reduce the thin film strain to achieve the system stretchability.

  18. Buckling dynamics of a solvent-stimulated stretched elastomeric sheet.

    PubMed

    Lucantonio, Alessandro; Roché, Matthieu; Nardinocchi, Paola; Stone, Howard A

    2014-04-28

    When stretched uniaxially, a thin elastic sheet may exhibit buckling. The occurrence of buckling depends on the geometrical properties of the sheet and the magnitude of the applied strain. Here we show that an elastomeric sheet initially stable under uniaxial stretching can destabilize when exposed to a solvent that swells the elastomer. We demonstrate experimentally and computationally that the features of the buckling pattern depend on the magnitude of stretching, and this observation offers a new way for controlling the shape of a swollen homogeneous thin sheet. PMID:24668079

  19. Elastomer degradation sensor using a piezoelectric material

    DOEpatents

    Olness, Dolores U.; Hirschfeld, deceased, Tomas B.

    1990-01-01

    A method and apparatus for monitoring the degradation of elastomeric materials is provided. Piezoelectric oscillators are placed in contact with the elastomeric material so that a forced harmonic oscillator with damping is formed. The piezoelectric material is connected to an oscillator circuit,. A parameter such as the resonant frequency, amplitude or Q value of the oscillating system is related to the elasticity of the elastomeric material. Degradation of the elastomeric material causes changes in its elasticity which, in turn, causes the resonant frequency, amplitude or Q of the oscillator to change. These changes are monitored with a peak height monitor, frequency counter, Q-meter, spectrum analyzer, or other measurement circuit. Elasticity of elastomers can be monitored in situ, using miniaturized sensors.

  20. Hierarchically UVO patterned elastomeric and thermoplastic structures

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Kulkarni, Manish; Marshall, Allan; Karim, Alamgir

    2014-03-01

    We demonstrate a simple yet versatile method to fabricate tunable hierarchical micro-nanostructures on flexible Poly(dimethylsiloxane) (PDMS) elastomer and thermoplastic polymer surface by a two-step process. Nanoscale patterned PDMS was obtained by imprinting compact disc (CD)/digital video disc (DVD) patterns. The second micro pattern was superposed by selective densification of PDMS by exposing to ultraviolet-ozone radiation (UVO) through micro-patterned TEM grid as a mask. The nanoscale patterns are preserved through UVO exposure step leading to formation of deep hierarchical patterns, so that for a 19 um square mesh, the micro pattern has a depth of 600nm with 6h PDMS UVO exposure time. This simple method can be promoted to fabricate hierarchical structures of thermoplastic materials (such as polystyrene), from which the mechanism of capillary imprinting and thermal stability of hierarchical patterns are investigated. This study is potentially important to various applications ranging from biomimetic scaffolds to solar cell.

  1. Three-Dimensional Elastomeric Scaffolds Designed with Cardiac-Mimetic Structural and Mechanical Features

    PubMed Central

    Neal, Rebekah A.; Jean, Aurélie; Park, Hyoungshin; Wu, Patrick B.; Hsiao, James; Engelmayr, George C.; Langer, Robert

    2013-01-01

    Tissue-engineered constructs, at the interface of material science, biology, engineering, and medicine, have the capacity to improve outcomes for cardiac patients by providing living cells and degradable biomaterials that can regenerate the native myocardium. With an ultimate goal of both delivering cells and providing mechanical support to the healing heart, we designed three-dimensional (3D) elastomeric scaffolds with (1) stiffnesses and anisotropy mimicking explanted myocardial specimens as predicted by finite-element (FE) modeling, (2) systematically varied combinations of rectangular pore pattern, pore aspect ratio, and strut width, and (3) structural features approaching tissue scale. Based on predicted mechanical properties, three scaffold designs were selected from eight candidates for fabrication from poly(glycerol sebacate) by micromolding from silicon wafers. Large 20×20 mm scaffolds with high aspect ratio features (5:1 strut height:strut width) were reproducibly cast, cured, and demolded at a relatively high throughput. Empirically measured mechanical properties demonstrated that scaffolds were cardiac mimetic and validated FE model predictions. Two-layered scaffolds providing fully interconnected pore networks were fabricated by layer-by-layer assembly. C2C12 myoblasts cultured on one-layered scaffolds exhibited specific patterns of cell elongation and interconnectivity that appeared to be guided by the scaffold pore pattern. Neonatal rat heart cells cultured on two-layered scaffolds for 1 week were contractile, both spontaneously and in response to electrical stimulation, and expressed sarcomeric α-actinin, a cardiac biomarker. This work not only demonstrated several scaffold designs that promoted functional assembly of rat heart cells, but also provided the foundation for further computational and empirical investigations of 3D elastomeric scaffolds for cardiac tissue engineering. PMID:23190320

  2. Elastically stretchable thin film conductors on an elastomeric substrate

    NASA Astrophysics Data System (ADS)

    Jones Harris, Joyelle Elizabeth

    Imagine a large, flat screen television that can be rolled into a small cylinder after purchase in the store and then unrolled and mounted onto the wall of a home. The electronic devices within the television must be able to withstand large deformation and tensile strain. Consider a robot that is covered with an electronic skin that simulates human skin. The skin would enable the machine to lift an elderly person with care and sensitivity. The skin will endure repeated deformation with the highest tensile strains being experienced at the robot's joints. These applications and many others will benefit from stretchable electronic circuitry. While several different methods have been employed to create stretchable electronics, all methods use a common tool -- stretchable conductors. Therefore, the goal of this thesis work was to fabricate elastically stretchable conductors that can be used in stretchable electronics. We deposited Au thin films on an elastomeric substrate, and the resulting conductors remained electrically continuous when stretched by 30% and more. We developed photolithographic processes that can be used to pattern elastically stretchable conductors with a 10 mum resolution. We fabricated bi-level stretchable conductors that are separated by an elastomeric insulator and are electrically connected through via holes in the insulator. We applied our bi-level conductors to create a stretchable resistor-inductor-capacitor (RLC) circuit with a tunable resonant frequency. We also used stretchable conductors to measure action potentials in biological samples. This thesis describes the fabrication and application of our elastically stretchable conductors.

  3. Viscoelastic and elastomeric active matter: Linear instability and nonlinear dynamics

    NASA Astrophysics Data System (ADS)

    Hemingway, E. J.; Cates, M. E.; Fielding, S. M.

    2016-03-01

    We consider a continuum model of active viscoelastic matter, whereby an active nematic liquid crystal is coupled to a minimal model of polymer dynamics with a viscoelastic relaxation time τC. To explore the resulting interplay between active and polymeric dynamics, we first generalize a linear stability analysis (from earlier studies without polymer) to derive criteria for the onset of spontaneous heterogeneous flows (strain rate) and/or deformations (strain). We find two modes of instability. The first is a viscous mode, associated with strain rate perturbations. It dominates for relatively small values of τC and is a simple generalization of the instability known previously without polymer. The second is an elastomeric mode, associated with strain perturbations, which dominates at large τC and persists even as τC→∞ . We explore the dynamical states to which these instabilities lead by means of direct numerical simulations. These reveal oscillatory shear-banded states in one dimension and activity-driven turbulence in two dimensions even in the elastomeric limit τC→∞ . Adding polymer can also have calming effects, increasing the net throughput of spontaneous flow along a channel in a type of drag reduction. The effect of including strong antagonistic coupling between the nematic and polymer is examined numerically, revealing a rich array of spontaneously flowing states.

  4. Thermoplastic vulcanizates: new materials of choice.

    PubMed

    Severyns, K

    2000-03-01

    Increasingly, thermoplastic vulcanizates of ethylene propylene diene monomer rubber-polypropylene are being specified for medical applications. This article describes their properties and advantages over thermoset rubbers and other conventional medical elastomeric materials. PMID:10915490

  5. “Pop-slide” patterning: Rapid fabrication of microstructured PDMS gasket slides for biological applications

    PubMed Central

    Ramji, Ramesh; Khan, Nafeesa T; Muñoz-Rojas, Andrés; Miller-Jensen, Kathryn

    2015-01-01

    We describe a “pop-slide” patterning approach to easily produce thin film microstructures on the surface of glass with varying feature sizes (3 μm – 250 μm) and aspect ratios (0.066 – 3) within 45 minutes. This low cost method does not require specialized equipment while allowing us to produce micro structured gasket layers for sandwich assays and could be readily applied to many biological applications. PMID:26949529

  6. Estimate for the fractal dimension of the Apollonian gasket in d dimensions.

    PubMed

    Farr, R S; Griffiths, E

    2010-06-01

    We adapt a recent theory for the random close packing of polydisperse spheres in three dimensions [R. S. Farr and R. D. Groot, J. Chem. Phys. 131, 244104 (2009)] in order to predict the Hausdorff dimension dA of the Apollonian gasket in dimensions 2 and above. Our approximate results agree with published values in two and three dimensions to within 0.05% and 0.6%, respectively, and we provide predictions for dimensions 4-8. PMID:20866417

  7. Storage containers for radioactive material

    DOEpatents

    Groh, Edward F.; Cassidy, Dale A.; Dates, Leon R.

    1981-01-01

    A radioactive material storage system for use in the laboratory having a flat base plate with a groove in one surface thereof and a hollow pedestal extending perpendicularly away from the other surface thereof, a sealing gasket in the groove, a cover having a filter therein and an outwardly extending flange which fits over the plate, the groove and the gasket, and a clamp for maintaining the cover and the plate sealed together, whereby the plate and the cover and the clamp cooperate to provide a storage area for radioactive material readily accessible for use or

  8. Storage containers for radioactive material

    DOEpatents

    Groh, E.F.; Cassidy, D.A.; Dates, L.R.

    1980-07-31

    A radioactive material storage system is claimed for use in the laboratory having a flat base plate with a groove in one surface thereof and a hollow pedestal extending perpendicularly away from the other surface thereof, a sealing gasket in the groove, a cover having a filter therein and an outwardly extending flange which fits over the plate, the groove and the gasket, and a clamp for maintaining the cover and the plate sealed together. The plate and the cover and the clamp cooperate to provide a storage area for radioactive material readily accessible for use or inventory. Wall mounts are provided to prevent accidental formation of critical masses during storage.

  9. Z-Pinch Wire-Electrode Contact Resistance Studies Using Weighted and Soft Metal Gasket Contacts*

    NASA Astrophysics Data System (ADS)

    Gomez, M. R.; Zier, J. C.; Thurtell, A. F.; French, D. M.; Gilgenbach, R. M.; Tang, W.; Lau, Y. Y.

    2008-11-01

    The contact made between z-pinch wires and electrodes has a significant effect on both the energy deposited in the wires and the uniformity of the expansion profile of the wires. We have shown that using soft metal gaskets can improve wire-electrode contact significantly over typical weighted contacts. Images of wire expansion profile and wire plasma emission will be presented for single and double wire shots on a 16 kA, 100 kV 4-stage Marx bank with 150 ns risetime. Bench resistance measurements for aluminum, stainless steel, and tungsten wires with diameters ranging from 7.5 um to 30 um will be presented. These measurements utilized both soft metal gasket contacts (gaskets include: indium, silver, aluminum, tin, and lead) and double-ended wire weight contacts (weights ranged from 0.4 g to 1.9 g). *This research was supported by U. S. DoE through Sandia National Laboratories award document numbers 240985, 768225, 790791 and 805234 to the University of Michigan. MRG supported by NNSA Fellowship and JCZ supported by NPSC Fellowship sponsored by Sandia National Labs.

  10. Determination of design gasket assembly stress with the new constants -- Exact Method

    SciTech Connect

    Guizzo, A.C.

    1996-12-01

    The PVRC task force, working to determine the new design procedure for bolted flange connections, has done a great job in developing a theory based on extensive experimental work, but they are still striving to determine an adequate way to establish a calculation procedure, using the concepts behind the new gasket constants. The current draft of the new code describes the Convenient Method for doing a calculation. The results obtained by using this procedure are different from the ones obtained with the Flexible Method, an alternative calculation procedure that requires iteration to find what would be the lowest and therefore the optimum bolt load. As in some situations this iterative procedure shows no convergence, attempts are being made to modify the Convenient Method so that it would result in design bolt load figures closer to the optimum. This paper proposes and describes a direct approach for calculating the assembly stress to be applied on the gasket using the new constants concept. It proposes also the introduction of ``d`` the Tp exponent as a fourth constant and the utilization of the actual gasket diameter in the Tp calculation. Comparisons are made between these proposals and the current calculation procedure.

  11. From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials

    PubMed Central

    D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R.; Sacks, Michael S.

    2014-01-01

    In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics. PMID:25128869

  12. Strain-induced phase transformation under compression in a diamond anvil cell: Simulations of a sample and gasket

    NASA Astrophysics Data System (ADS)

    Feng, Biao; Levitas, Valery I.; Ma, Yanzhang

    2014-04-01

    Combined high pressure phase transformations (PTs) and plastic flow in a sample within a gasket compressed in diamond anvil cell (DAC) are studied for the first time using finite element method. The key point is that phase transformations are modelled as strain-induced, which involves a completely different kinetic description than for traditional pressure-induced PTs. The model takes into account, contact sliding with Coulomb and plastic friction at the boundaries between the sample, gasket, and anvil. A comprehensive computational study of the effects of the kinetic parameter, ratio of the yield strengths of high and low-pressure phases and the gasket, sample radius, and initial thickness on the PTs and plastic flow is performed. A new sliding mechanism at the contact line between the sample, gasket, and anvil called extrusion-based pseudoslip is revealed, which plays an important part in producing high pressure. Strain-controlled kinetics explains why experimentally determined phase transformation pressure and kinetics (concentration of high pressure phase vs. pressure) differ for different geometries and properties of the gasket and the sample: they provide different plastic strain, which was not measured. Utilization of the gasket changes radial plastic flow toward the center of a sample, which leads to high quasi-homogeneous pressure for some geometries. For transformation to a stronger high pressure phase, plastic strain and concentration of a high-pressure phase are also quasi-homogeneous. This allowed us to suggest a method of determining strain-controlled kinetics from experimentation, which is not possible for weaker and equal-strength high-pressure phases and cases without a gasket. Some experimental phenomena are reproduced and interpreted. Developed methods and obtained results represent essential progress toward the understanding of PTs under compression in the DAC. This will allow one optimal design of experiments and conditions for synthesis of new

  13. Seismic isolation of nuclear power plants using elastomeric bearings

    NASA Astrophysics Data System (ADS)

    Kumar, Manish

    Seismic isolation using low damping rubber (LDR) and lead-rubber (LR) bearings is a viable strategy for mitigating the effects of extreme earthquake shaking on safety-related nuclear structures. Although seismic isolation has been deployed in nuclear structures in France and South Africa, it has not seen widespread use because of limited new build nuclear construction in the past 30 years and a lack of guidelines, codes and standards for the analysis, design and construction of isolation systems specific to nuclear structures. The nuclear accident at Fukushima Daiichi in March 2011 has led the nuclear community to consider seismic isolation for new large light water and small modular reactors to withstand the effects of extreme earthquakes. The mechanical properties of LDR and LR bearings are not expected to change substantially in design basis shaking. However, under shaking more intense than design basis, the properties of the lead cores in lead-rubber bearings may degrade due to heating associated with energy dissipation, some bearings in an isolation system may experience net tension, and the compression and tension stiffness may be affected by the horizontal displacement of the isolation system. The effects of intra-earthquake changes in mechanical properties on the response of base-isolated nuclear power plants (NPPs) were investigated using an advanced numerical model of a lead-rubber bearing that has been verified and validated, and implemented in OpenSees and ABAQUS. A series of experiments were conducted at University at Buffalo to characterize the behavior of elastomeric bearings in tension. The test data was used to validate a phenomenological model of an elastomeric bearing in tension. The value of three times the shear modulus of rubber in elastomeric bearing was found to be a reasonable estimate of the cavitation stress of a bearing. The sequence of loading did not change the behavior of an elastomeric bearing under cyclic tension, and there was no

  14. Elastomeric Polymer Resonant Waveguide Grating based Pressure Sensor

    PubMed Central

    Song, Fuchuan; Xie, Antonio Jou; Seo, Sang-Woo

    2014-01-01

    In this paper, we demonstrate an elastomeric polymer resonant waveguide grating structure to be used as a pressure sensor. The applied pressure is measured by optical resonance spectrum peak shift. The sensitivity - as high as 86.74pm/psi or 12.58pm/kPa - has been experimentally obtained from a fabricated sensor. Potentially, the sensitivity of the demonstrated sensor can be tuned to different pressure ranges by the choices of elastic properties and layer thicknesses of the waveguide and cladding layers. The simulation results agree well with experimental results and indicate that the dominant effect on the sensor is the change of grating period when external pressure is applied. Based on the two-dimensional planar structure, the demonstrated sensor can be used to measure applied surface pressure optically, which has potential applications for optical ultrasound imaging and pressure wave detection/mapping. PMID:25419447

  15. Gold-Tipped Elastomeric Pillars for Cellular Mechanotransduction

    PubMed Central

    Ghassemi, S.; Rossier, O.; Sheetz, M. P.; Wind, S. J.; Hone, J.

    2010-01-01

    We describe a technique for the fabrication of arrays of elastomeric pillars whose top surfaces are treated with selective chemical functionalization to promote cellular adhesion in cellular force transduction experiments. The technique involves the creation of a rigid mold consisting of arrays of circular holes into which a thin layer of Au is deposited while the top surface of the mold and the sidewalls of the holes are protected by a sacrificial layer of Cr. When an elastomer is formed in the mold, the Au adheres to the tops of the molded pillars. This can then be selectively functionalized with a protein that induces cell adhesion, while the rest of the surface is treated with a repellent substance. An additional benefit is that the tops of the pillars can be fluorescently labeled for improved accuracy in force transduction measurements. PMID:20526428

  16. Adhesion of elastomeric surfaces structured with micro-dimples

    NASA Astrophysics Data System (ADS)

    Nanni, Gabriele; Fragouli, Despina; Ceseracciu, Luca; Athanassiou, Athanassia

    2015-01-01

    Topography has a dominant role in determining the adhesion properties of a surface. In this work we explore how arrays of micron-sized dimples can alter the adhesion performance of elastomeric surfaces. We study the effect of the dimple surface coverage, showing that the dimples act both as passive suction devices, allowing to exceed the adhesion performance of untextured surfaces, and crack-like defects, generating stress concentration at the edge of the contact area between the surface of the sample and a flat surface. Interestingly, our results reveal that the suction effect generated by the negative pressure produced by the dimples can be effectively tuned by adjusting their depth. These findings have significant relevance for the fabrication of adhesive systems in which selective adhesion to objects with small difference in weight is required.

  17. Damage of Elastomeric Matrix Composites (EMC-rubbers) Under Static Loading Conditions: Experimental and Numerical Study

    NASA Astrophysics Data System (ADS)

    Ayari, F.; Bayraktar, E.; Zghal, A.

    2011-01-01

    Elastomeric matrix composites (EMC-rubbers) are considered as isotropic hyper elastic incompressible materials under static loading conditions. As a rubber material element cannot be extended to an infinite stretch ratio, a damage mechanism at large strain is considered. The phenomenon of cavitation plays an important role in the damage of EMCs and influences the toughening mechanism of rubber-modified plastics. Indeed, cavitation in elastomers is thought to be initiated from flaws, which grow primarily due to a hydrostatic tensile stress and ahead of the crack; there will not only be a high stress perpendicular to the plane of the crack but also significant stress components in the other direction. However, there exists historically much discussion on the evolution of the cavitation in elastomers under monotonic and/or static solicitation. Mainly, cavitation instability occurs when the stress levels are sufficiently high so that the void expansion rate becomes infinitely large. Many research works have been performed to understand the effects of rubber cavitation on toughening of plastics. In fact, the cavitation phenomenon is not well known in detail. The most popular idea states that the cavitation is related to the existence of the gas bubbles trapped in the material during the production stage and the growing of the cavities would then be the result of the growing gas bubbles. Further, instable failure mechanism at the end of the cavitation is not well known too.

  18. Shape-Memory Polymers Based on Fatty Acid-Filled Elastomeric Ionomers

    NASA Astrophysics Data System (ADS)

    Izzo, Elise; Weiss, Robert

    2009-03-01

    Shape memory polymers (SMPs) have applications as medical devices, actuators, sensors, artificial muscles, switches, smart textiles, and self-deployable structures. All previous design of SMPs has involved synthesizing new polymers or modifying existing polymers. This paper describes a new type of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts (FAS). Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and various amounts of a FAS (e.g., zinc stearate, zinc oleate, and various aliphalic acids). Nanophase separation of the metal sulfonate groups provided the ``permanent'' crosslinks, while sub-microscopic crystals of the low molecular weight FAS provided a physical crosslink needed for the temporary shape. The material was deformed above the melting point of the FAS and the new shape was fixed by cooling the material while under stress to below the melting point of the FAS. Polar interactions between the ionomer and the FAS stabilized the dispersion of the FAS in the polymer and provided the continuity between the phases that allowed the crystals of the FAS to provide a second network of physical crosslinks. The temporary shape was erased and the material returned to the primary shape by heating above the melting point of the FAS.

  19. Damage of Elastomeric Matrix Composites (EMC-rubbers) Under Static Loading Conditions: Experimental and Numerical Study

    SciTech Connect

    Ayari, F.

    2011-01-17

    Elastomeric matrix composites (EMC-rubbers) are considered as isotropic hyper elastic incompressible materials under static loading conditions. As a rubber material element cannot be extended to an infinite stretch ratio, a damage mechanism at large strain is considered. The phenomenon of cavitation plays an important role in the damage of EMCs and influences the toughening mechanism of rubber-modified plastics. Indeed, cavitation in elastomers is thought to be initiated from flaws, which grow primarily due to a hydrostatic tensile stress and ahead of the crack; there will not only be a high stress perpendicular to the plane of the crack but also significant stress components in the other direction. However, there exists historically much discussion on the evolution of the cavitation in elastomers under monotonic and/or static solicitation. Mainly, cavitation instability occurs when the stress levels are sufficiently high so that the void expansion rate becomes infinitely large. Many research works have been performed to understand the effects of rubber cavitation on toughening of plastics. In fact, the cavitation phenomenon is not well known in detail. The most popular idea states that the cavitation is related to the existence of the gas bubbles trapped in the material during the production stage and the growing of the cavities would then be the result of the growing gas bubbles. Further, instable failure mechanism at the end of the cavitation is not well known too.

  20. Designing an elastomeric binder for large-volume-change electrodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chen, Zonghai

    It is of commercial importance to develop high capacity negative and positive electrode materials for lithium-ion batteries to meet the energy requirements of portable electronic devices. Excellent capacity retention has been achieved for thin sputtered films of amorphous Si, Ge and Si-Sn alloys even when cycled to 2000 mAh/g and above, which suggests that amorphous alloys are capable of extended cycling. However, PVDF-based composite electrodes incorporating a-Si0.64Sn0.36/Ag powder (10 wt% silver coating) (˜10mum) still suffer from severe capacity fading because of the huge volumetric changes of a-Si0.64Sn0.36/Ag during charge/discharge cycling. It is the objective of this thesis to understand the problem scientifically and to propose practical solutions to solve this problem. Mechanical studies of binders for lithium battery electrodes have never been reported in the literature. The mechanical properties of commonly used binders, such as poly(vinylidene fluoride) (PVDF), haven't been challenged because commercially used active materials, such as LiCoO2 and graphite, have small volumetric changes (<10%) during charge/discharge cycling. However, the recently proposed metallic alloys have huge volumetric changes (up to 250%) during cycling. In this case, the mechanical properties of the binder become critical. A tether model is proposed to qualitatively understand the capacity fading of high-volume-change electrodes, and to predict the properties of a good binder system. A crosslinking/coupling route was used to modify the binder system according to the requirements of the tether model. A poly(vinylidene fluoride-tetrafluoroethylenepropylene)-based elastomeric binder system was designed to successfully improve the capacity retention of a-Si0.64 Sn0.36/Ag composite electrodes. In this thesis, it has also proven nontrivial to maximize the capacity retention of large-volume-change electrodes even when a fixed elastomeric binder system was used. The parameters that

  1. Application of the time-temperature superposition principle to the mechanical characterization of elastomeric adhesives for crash simulation purposes

    NASA Astrophysics Data System (ADS)

    Rauh, A.; Hinterhölzl, R.; Drechsler, K.

    2012-05-01

    In the automotive industry, finite element simulation is widely used to ensure crashworthiness. Mechanical material data over wide strain rate and temperature ranges are required as a basis. This work proposes a method reducing the cost of mechanical material characterization by using the time-temperature superposition principle on elastomeric adhesives. The method is based on the time and temperature interdependence which is characteristic for mechanical properties of polymers. Based on the assumption that polymers behave similarly at high strain rates and at low temperatures, a temperature-dominated test program is suggested, which can be used to deduce strain rate dependent material behavior at different reference temperatures. The temperature shift factor is found by means of dynamic mechanical analysis according to the WLF-equation, named after Williams, Landel and Ferry. The principle is applied to the viscoelastic properties as well as to the failure properties of the polymer. The applicability is validated with high strain rate tests.

  2. Evaluation of the effect of different stretching patterns on force decay and tensile properties of elastomeric ligatures

    PubMed Central

    Aminian, Amin; Nakhaei, Samaneh; Agahi, Raha Habib; Rezaeizade, Masoud; Aliabadi, Hamed Mirzazadeh; Heidarpour, Majid

    2015-01-01

    Background: There have been numerous researches on elastomeric ligatures, but clinical conditions in different stages of treatment are not exactly similar to laboratory conditions. The aim of this in vitro study was to simulate clinical conditions and evaluate the effect of three stretching patterns on the amount of force, tensile strength (TS) and extension to TS of the elastomers during 8 weeks. Materials and Methods: Forces, TS and extension to TS of two different brands of elastomers were measured at initial, 24 h and 2, 4, and 8-week intervals using a testing machine. During the study period, the elastomers were stored in three different types of jig (uniform stretching, 1 and 3 mm point stretching) designed by the computer-aided design and computer-aided manufacturing technique in order to simulate the different stages of orthodontic treatment. Results: The elastomeric ligatures under study exhibited a similar force decay pattern. The maximum force decay occurred during the first 24 h (49.9% ± 15%) and the amount of force decay was 75.7% ± 8% after 8 weeks. In general, the TS decreased during the study period, and the amount of extension to TS increased. Conclusion: Although the elastic behavior of all ligatures under study was similar, the amount of residual force, TS and extension to TS increased in elastomers under point stretching pattern. PMID:26759597

  3. Biodegradable, Elastomeric, and Intrinsically Photoluminescent Poly(Silicon-Citrates) with high Photostability and Biocompatibility for Tissue Regeneration and Bioimaging.

    PubMed

    Du, Yuzhang; Xue, Yumeng; Ma, Peter X; Chen, Xiaofeng; Lei, Bo

    2016-02-01

    Biodegradable polymer biomaterials with intrinsical photoluminescent properties have attracted much interest, due to their potential advantages for tissue regeneration and noninvasive bioimaging. However, few of current biodegradable polymers possess tunable intrinsically fluorescent properties, such as high photostability, fluorescent lifetime, and quantum field, and strong mechanical properties for meeting the requirements of biomedical applications. Here, by a facile one-step thermal polymerization, elastomeric poly(silicone-citrate) (PSC) hybrid polymers are developed with controlled biodegradability and mechanical properties, tunable inherent fluorescent emission (up to 600 nm), high photostability (beyond 180 min for UV and six months for natural light), fluorescent lifetime (near 10 ns) and quantum yield (16%-35%), high cellular biocompatibility, and minimal inflammatory response in vivo, which provide advantages over conventional fluorescent dyes, quantum dots, and current fluorescent polymers. The promising applications of PSC hybrids for cell and implants imaging in vitro and in vivo are successfully demonstrated. The development of elastomeric PSC polymer may provide a new strategy in synthesizing new inorganic-organic hybrid photo-luminescent materials for tissue regeneration and bioimaging applications. PMID:26687865

  4. Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis

    NASA Technical Reports Server (NTRS)

    Sreekantamurthy, Thammaiah; Turner, Travis L.; Moore, James B.; Su, Ji

    2014-01-01

    Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

  5. Thermoviscoplastic behaviors of anisotropic shape memory elastomeric composites for cold programmed non-affine shape change

    NASA Astrophysics Data System (ADS)

    Mao, Yiqi; Robertson, Jaimee M.; Mu, Xiaoming; Mather, Patrick T.; Jerry Qi, H.

    2015-12-01

    Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape upon activation by an external stimulus. Most SMPs require programming at above their transition temperatures, normally well above the room temperature. In addition, most SMPs are programmed into shapes that are affine to the high temperature deformation. Recently, a cold-programmed anisotropic shape memory elastomeric composite was developed and showed interesting low temperature stretching induced shape memory behavior. There, simple, uniaxial stretching at low temperature transformed the composites into curled temporary shapes upon unloading. The exact geometry of the curled state depended on the microstructure of the composite, and the curled shape showed no affinity to the deformed shape. Heating the sample recovered the sample back to its original shape. This new composite consisted of an elastomeric matrix reinforced by aligned amorphous polymer fibers. By utilizing the plastic-like behavior of the amorphous polymer phase at low temperatures, a temporary shape could be fixed upon unloading since the induced plastic-like strain resists the recovery of the elastomer matrix. After heating to a high temperature, the permanent shape was recovered when the amorphous polymer softened and the elastomer matrix contracted. To set a theoretical foundation for capturing the cold-programmed shape memory effects and the dramatic non-affine shape change of this composite, a 3D anisotropic thermoviscoelastic constitutive model is developed in this paper. In this model, the matrix is modeled as a hyperelastic solid, and the amorphous phase of the fibrous mat is considered as a nonlinear thermoviscoplastic solid, whose viscous flow resistance is sensitive to both temperature and stress. The plastic-deformation like behavior demonstrated in the fiber is treated as nonlinear viscoplasticity with extremely high viscosity or long relaxation time at zero-stress state at low temperature. The

  6. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

    PubMed Central

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  7. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

    PubMed

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  8. Influence of elastomeric seal plate surface chemistry on interface integrity in biofouling-prone systems: Evaluation of a hydrophobic "easy-release" silicone-epoxy coating for maintaining water seal integrity of a sliding neoprene/steel interface

    NASA Astrophysics Data System (ADS)

    Andolina, Vincent L.

    The scientific hypothesis of this work is that modulation of the properties of hard materials to exhibit abrasion-reducing and low-energy surfaces will extend the functional lifetimes of elastomeric seals pressed against them in abrasive underwater systems. The initial motivation of this work was to correct a problem noted in the leaking of seals at major hydropower generating facilities subject to fouling by abrasive zebra mussel shells and extensive corrosion. Similar biofouling-influenced problems can develop at seals in medical devices and appliances from regulators in anesthetic machines and SCUBA diving oxygen supply units to autoclave door seals, injection syringe gaskets, medical pumps, drug delivery components, and feeding devices, as well as in food handling equipment like pasteurizers and transfer lines. Maritime and many other heavy industrial seal interfaces could also benefit from this coating system. Little prior work has been done to elucidate the relationship of seal plate surface properties to the friction and wear of elastomeric seals during sliding contacts of these articulating materials, or to examine the secondary influence of mineralized debris within the contacting interfaces. This investigation utilized the seal materials relevant to the hydropower application---neoprene elastomer against carbon steel---with and without the application of a silicone-epoxy coating (WearlonRTM 2020.98) selected for its wear-resistance, hydrophobicity, and "easy-release" capabilities against biological fouling debris present in actual field use. Analytical techniques applied to these materials before and after wear-producing processes included comprehensive Contact Angle measurements for Critical Surface Tension (CA-CST) determination, Scanning Electron Microscopic inspections, together with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-Ray Fluorescence (XRF) measurements for determination of surface texture and inorganic composition, Multiple

  9. DEVELOPMENT OF REMOTE HANFORD CONNECTOR GASKET REPLACEMENT TOOLING FOR THE SAVANNAH RIVER SITE'S DEFENSE WASTE PROCESSING FACILITY

    SciTech Connect

    Krementz, D

    2007-11-27

    The Savannah River Site's (SRS) Defense Waste Processing Facility (DWPF) requested development of tooling for remote replacement of gaskets in mechanical Hanford connectors. The facility has compressed air supply, two master-slave manipulators (MSM's) and a lightweight robotic arm for operation of the remote tools. The Savannah River National Laboratory (SRNL) developed and tested multiple tools to perform the gasket replacement tasks. Separate pneumatic snap-ring removal tools that use the connector skirt as a reaction surface were developed for removal of the snap ring and spent gasket on both vertical and horizontal Hanford connectors. A pneumatic tool that clamps and centers on the jumper pipe ID was developed to simultaneously install the new gasket and snap ring. A pneumatic snap-ring-loading tool was developed that compresses the snap ring and places it in a groove in the installation tool. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and vents the tools as needed. The entire system has been successfully tested using MSM's to manipulate the various tools. Deployment of the entire system is expected during FY08. The Hanford connector gasket replacement tooling has been successfully tested using MSM's to manipulate the various tools. Nitric acid is used in many of the decontamination processes performed in the REDC, where the tooling will be deployed. Although most of the tool components were fabricated/purchased with nitric acid and radioactive service in mind, some of the prototype parts must be replaced with parts that are more compatible with nitric acid/radioactive service. Several modifications to the various tools are needed to facilitate maintenance and replacement of failed components. Development of installation tools for replacement of 1-inch, 2-inch and multi-hole gaskets is being considered. Deployment of the existing system in the DWPF REDC is expected during FY

  10. Static and cyclic mechanical loading of mesenchymal stem cells on elastomeric, electrospun polyurethane meshes.

    PubMed

    Cardwell, Robyn D; Kluge, Jonathan A; Thayer, Patrick S; Guelcher, Scott A; Dahlgren, Linda A; Kaplan, David L; Goldstein, Aaron S

    2015-07-01

    Biomaterial substrates composed of semi-aligned electrospun fibers are attractive supports for the regeneration of connective tissues because the fibers are durable under cyclic tensile loads and can guide cell adhesion, orientation, and gene expression. Previous studies on supported electrospun substrates have shown that both fiber diameter and mechanical deformation can independently influence cell morphology and gene expression. However, no studies have examined the effect of mechanical deformation and fiber diameter on unsupported meshes. Semi-aligned large (1.75 μm) and small (0.60 μm) diameter fiber meshes were prepared from degradable elastomeric poly(esterurethane urea) (PEUUR) meshes and characterized by tensile testing and scanning electron microscopy (SEM). Next, unsupported meshes were aligned between custom grips (with the stretch axis oriented parallel to axis of fiber alignment), seeded with C3H10T1/2 cells, and subjected to a static load (50 mN, adjusted daily), a cyclic load (4% strain at 0.25 Hz for 30 min, followed by a static tensile loading of 50 mN, daily), or no load. After 3 days of mechanical stimulation, confocal imaging was used to characterize cell shape, while measurements of deoxyribonucleic acid (DNA) content and messenger ribonucleic acid (mRNA) expression were used to characterize cell retention on unsupported meshes and expression of the connective tissue phenotype. Mechanical testing confirmed that these materials deform elastically to at least 10%. Cells adhered to unsupported meshes under all conditions and aligned with the direction of fiber orientation. Application of static and cyclic loads increased cell alignment. Cell density and mRNA expression of connective tissue proteins were not statistically different between experimental groups. However, on large diameter fiber meshes, static loading slightly elevated tenomodulin expression relative to the no load group, and tenascin-C and tenomodulin expression

  11. Elastomeric fluorescent POF for partial discharge detection: recent progress

    NASA Astrophysics Data System (ADS)

    Siebler, Daniel; Hohberg, Michaela; Rohwetter, Philipp; Brusenbach, Roy; Plath, Ronald

    2015-09-01

    We present recent progress in our development of fibre-optic sensors for the detection of partial discharge (PD) in silicone cable accessories, based on detecting related low-level optical emission. We experimentally show that the sensitive optical detection of PD can dramatically enhance the performance of conventional electrical PD measurement in electromagnetically noisy environments, and that it can yield high sensitivity and specificity even when no synchronous electrical PD measurement is conducted. This is demonstrated using a real-scale model of a high voltage cable accessory with a surface-attached conventional thermoplastic fluorescent polymer optical fibre (F-POF) sensor. In order to increase light collection efficiency, as a prerequisite for a commercially competitive implementation using cost-efficient detectors, sensing fibres will have to be integrated into the silicone rubber insulation, close to the potential origin of PD-induced damage. This is the rationale for our efforts to develop elastomeric fluorescent sensing fibres, tailored to the requirements of the application. We discuss specific challenges to be tackled and report on the successful implementation of all-silicone rubber fluorescent POF, to our best knowledge for the first time.

  12. Impact-Induced Glass Transition in Elastomeric Coatings

    NASA Astrophysics Data System (ADS)

    Roland, C. M.

    2013-03-01

    When an elastomer layer is applied to the front surface of steel, the resistance to penetration by hard projectiles increases significantly. It is not obvious why a soft polymer should affect this property of metals, and most rubbers do not. However, we have found that a few are very effective; the requirement is that the polymer undergo a viscoelastic phase transition upon impact. This means that the frequency of its segmental dynamics correspond to the impact frequency. The latter is estimated as the ratio of the projectile velocity to the coating thickness, and is on the order of 105 s-1 for the experiments herein. Our data and a non-linear dynamics finite-element analysis offer support for this resonance condition as a primary mechanism underlying the penetration-resistance of elastomer-coated metal substrates. The impact-induced phase transition causes large energy absorption, decreasing the kinetic energy of the impacting projectile. However, this energy absorption only accounts for about half the enhanced stopping power of the elastomer/steel bilayer. An additional mechanism is lateral spreading of the impact force, resulting from the transient hardening of the elastomeric during its transition to the glassy state - the modulus of the rubber increases 1000-fold over a time period of microseconds. The penetration-resistance is a very nonlinear function of the coating thickness. Moreover, tests on various metals show that hardness is the principal substrate parameter controlling the contribution of the coating. This work was supported by the Office of Naval Research.

  13. Biocide squirting from an elastomeric tri-layer film

    NASA Astrophysics Data System (ADS)

    Sonntag, Philippe; Hoerner, Pierre; Cheymol, André; Argy, Gilles; Riess, Gérard; Reiter, Günter

    2004-05-01

    Protective layers typically act in a passive way by simply separating two sides. Protection is only efficient as long as the layers are intact. If a high level of protection has to be achieved by thin layers, complementary measures need to be in place to ensure safety, even after breakage of the layer-an important issue in medical applications. Here, we present a novel approach for integrating a biocide liquid into a protective film (about 300-500 μm thick), which guarantees that a sufficient amount of biocide is rapidly released when the film is punctured. The film is composed of a middle layer, containing the liquid in droplet-like compartments, sandwiched between two elastomeric boundary layers. When the film is punctured, the liquid squirts out of the middle layer. A theoretical model was used to determine the size and density of droplets that are necessary to ensure a sufficient quantity of biocide is expelled from an adequately elastic matrix to provide protection at the site of damage. We demonstrate the utility of this approach for the fabrication of surgical gloves.

  14. An analysis of pipe flange connections using epoxy adhesives/anaerobic sealant instead of gaskets

    SciTech Connect

    Sawa, T.; Sasaki, R.; Yoneno, M.

    1995-11-01

    This paper deals with the strength and the sealing performance of pipe flange connections combining the bonding force of adhesives with the clamping force of bolts. The epoxy adhesives or anaerobic sealants are bonded at the interface partially instead of gaskets in pipe flange connections. The stress distribution in the epoxy adhesives (anaerobic sealant), which governs the sealing performance, and the variations in axial bolt force are analyzed, using an axisymmetrical theory of elasticity, when an internal pressure is applied to a connection in which two pipe flanges are clamped together buy bolts and nuts with an initial clamping force after being joined by epoxy adhesives or anaerobic sealant. In addition, a method for estimating the strength of the combination connection is demonstrated. Experiments are performed and the analytical results are consistent with the experimental results concerning the variation in axial bolt force and the strength of combination connections. It can be seen that the strength of connections increases with a decrease in the bolt pitch circle diameter. Furthermore, it is seen that the sealing performance of such combination connections in which the interface is bonded partially is improved over that of pipe flange connections with metallic gaskets.

  15. Fabrication and characterization of heparin-grafted poly-L-lactic acid-chitosan core-shell nanofibers scaffold for vascular gasket.

    PubMed

    Wang, Ting; Ji, Xuyuan; Jin, Lin; Feng, Zhangqi; Wu, Jinghang; Zheng, Jie; Wang, Hongyin; Xu, Zhe-Wu; Guo, Lingling; He, Nongyue

    2013-05-01

    Electrospun nanofibers were widely studied to be applied as potential materials for tissue engineering. A new technology to make poly-l-lactic acid/chitosan core/shell nanofibers from heterologous solution by coaxial electrospinning technique was designed for vascular gasket. Chitosan surface was cross-linked by genipin and modified by heparin. Different ratios of PLA/CS in heterologous solution were studied to optimize the surface morphology of fibers. Clean core-shell structures formed with a PLA/CS ratio at 1:3. Superior biocompatibility and mechanical properties were obtained by optimizing the core-shell structure morphology and surface cross-linking of chitosan. UE7T-13 cells grew well on the core-shell structure fibers as indicated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) results and scanning electron microscopy (SEM) images. Compared with the pure PLA fiber meshes and commercial vascular patch, PLA/CS core-shell fibers had better mechanical strength. The elastic modulus was as high as 117.18 MPa, even though the yield stress of the fibers was lower than that of the commercial vascular patch. Attachment of red blood cell on the fibers was evaluated by blood anticoagulation experiments and in vitro blood flow experiments. The activated partial thromboplastin time (APTT) and prothrombin time (PT) value from PLA/CS nanofibers were significantly longer than that of pure PLA fibers. SEM images indicated there were hardly any red blood cells attached to the fibers with chitosan coating and heparin modification. This type of fiber mesh could potentially be used as vascular gasket. PMID:23586670

  16. Microstructured elastomeric surfaces with reversible adhesion and examples of their use in deterministic assembly by transfer printing

    PubMed Central

    Kim, Seok; Wu, Jian; Carlson, Andrew; Jin, Sung Hun; Kovalsky, Anton; Glass, Paul; Liu, Zhuangjian; Ahmed, Numair; Elgan, Steven L.; Chen, Weiqiu; Ferreira, Placid M.; Sitti, Metin; Huang, Yonggang; Rogers, John A.

    2010-01-01

    Reversible control of adhesion is an important feature of many desired, existing, and potential systems, including climbing robots, medical tapes, and stamps for transfer printing. We present experimental and theoretical studies of pressure modulated adhesion between flat, stiff objects and elastomeric surfaces with sharp features of surface relief in optimized geometries. Here, the strength of nonspecific adhesion can be switched by more than three orders of magnitude, from strong to weak, in a reversible fashion. Implementing these concepts in advanced stamps for transfer printing enables versatile modes for deterministic assembly of solid materials in micro/nanostructured forms. Demonstrations in printed two- and three-dimensional collections of silicon platelets and membranes illustrate some capabilities. An unusual type of transistor that incorporates a printed gate electrode, an air gap dielectric, and an aligned array of single walled carbon nanotubes provides a device example. PMID:20858729

  17. 75 FR 47027 - In the Matter of: Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-04

    ... COMMISSION In the Matter of: Certain Devices Having Elastomeric Gel and Components Thereof; Notice of... States after importation of certain devices having elastomeric gel and components thereof by reason of... CFR 210.10 (2010). Scope of Investigation: Having considered the complaint, the U.S....

  18. 75 FR 64742 - In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-20

    ... Austin, Texas (``ILF''). 75 FR 47027 (Aug. 4, 2010). The complaint alleges violations of section 337 of... COMMISSION In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of... having elastomeric gel and components thereof by reason of infringement of certain claims of U.S....

  19. Measurement of oil film thickness for application to elastomeric Stirling engine rod seals

    NASA Technical Reports Server (NTRS)

    Krauter, A. I.

    1981-01-01

    The rod seal in the Stirling engine has the function of separating high pressure gas from low or ambient pressure oil. An experimental apparatus was designed to measure the oil film thickness distribution for an elastomeric seal in a reciprocating application. Tests were conducted on commercial elastomeric seals having a 76 mm rod and a 3.8 mm axial width. Test conditions included 70 and 90 seal durometers, a sliding velocity of 0.8 m/sec, and a zero pressure gradient across the seal. An acrylic cylinder and a typical synthetic base automotive lubricant were used. The experimental results showed that the effect of seal hardness on the oil film thickness is considerable. A comparison between analytical and experimental oil film profiles for an elastomeric seal during relatively high speed reciprocating motion showed an overall qualitative agreement.

  20. Elastomeric Seal Performance after Terrestrial Ultraviolet Radiation Exposure

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Oravec, Heather A.; Mather, Janice L.; Taylor, Shawn C.; Dunlap, Patrick H.

    2015-01-01

    Ultraviolet radiation was evaluated to determine its negative effects on the performance of elastomeric gas pressure seals. The leak rates of the silicone elastomer S0383-70 O-ring test articles were used to quantify the degradation of the seals after exposure to vacuum-ultraviolet and/or middle-to-near-ultraviolet wavelength radiation. Three groups of seals were exposed in terrestrial facilities to 115-165 nm wavelength radiation, 230-500 nm wavelength radiation, or both spectrums, for an orbital spaceflight equivalent of 125 hours. The leak rates of the silicone elastomer S0383-70 seals were quantified and compared to samples that received no radiation. Each lot contained six samples and statistical t-tests were used to determine the separate and combined influences of exposure to the two wavelength ranges. A comparison of the mean leak rates of samples exposed to 115-165 nm wavelength radiation to the control specimens showed no difference, suggesting that spectrum was not damaging. The 230-500 nm wavelength appeared to be damaging, as the mean leak rates of the specimens exposed to that range of wavelengths, and those exposed to the combined 115-165 nm and 230-500 nm spectrums, were significantly different from the leak rates of the control specimens. Most importantly, the test articles exposed to both wavelength spectrums exhibited mean leak rates two orders of magnitude larger than any other exposed specimens, which suggested that both wavelength spectrums are important when simulating the orbital environment.

  1. Thermally tailored gradient topography surface on elastomeric thin films.

    PubMed

    Roy, Sudeshna; Bhandaru, Nandini; Das, Ritopa; Harikrishnan, G; Mukherjee, Rabibrata

    2014-05-14

    We report a simple method for creating a nanopatterned surface with continuous variation in feature height on an elastomeric thin film. The technique is based on imprinting the surface of a film of thermo-curable elastomer (Sylgard 184), which has continuous variation in cross-linking density introduced by means of differential heating. This results in variation of viscoelasticity across the length of the surface and the film exhibits differential partial relaxation after imprinting with a flexible stamp and subjecting it to an externally applied stress for a transient duration. An intrinsic perfect negative replica of the stamp pattern is initially created over the entire film surface as long as the external force remains active. After the external force is withdrawn, there is partial relaxation of the applied stresses, which is manifested as reduction in amplitude of the imprinted features. Due to the spatial viscoelasticity gradient, the extent of stress relaxation induced feature height reduction varies across the length of the film (L), resulting in a surface with a gradient topography with progressively varying feature heights (hF). The steepness of the gradient can be controlled by varying the temperature gradient as well as the duration of precuring of the film prior to imprinting. The method has also been utilized for fabricating wettability gradient surfaces using a high aspect ratio biomimetic stamp. The use of a flexible stamp allows the technique to be extended for creating a gradient topography on nonplanar surfaces as well. We also show that the gradient surfaces with regular structures can be used in combinatorial studies related to pattern directed dewetting. PMID:24697617

  2. Elastomeric Properties of Poly(glycerol sebacate) (PGS) Based Nanoparticle Composites

    NASA Astrophysics Data System (ADS)

    Chung, Hyun-Joong; Li, Xinda; Hong, Albert T.-L.

    2014-03-01

    Owing to the unique combination of biocompatible, biodegradable, and elastomeric properties, poly(glycerol sebacate) and their derivatives are an emerging class of biomaterials for soft tissue replacement, drug delivery, tissue adhesive, and hard tissue regeneration. The mechanical properties of the polyester have been tailored to match a wide range of target organs, ranging from cardiac muscle to bones, by manipulating the process parameters to modulate cross-linking density. In the present study, we applied nanoparticles and cross-linking agents to further optimize their elastomeric properties. Especially, the study aims to enhance the practically important, but less studied, property of tear resistance. Microscopic origin of the property enhancement is discussed.

  3. The effects of 2% alkaline glutaraldehyde solution on the elastic properties of elastomeric chain.

    PubMed

    Jeffries, C L; von Fraunhofer, J A

    1991-01-01

    The effect of two proprietary alkaline gluteraldehyde solutions on the strength (failure load) and the required displacement or stretching to achieve a force of 500g was studied for six types of elastomeric chains. The effect of disinfection (short-term exposure) and sterilization (long-term exposure) as well as repeated immersion cycles on these parameters was evaluated. The findings showed that exposure to gluteraldehyde solution affected the strength and the distention required to deliver a force of 500g of certain elastomeric chains. However, the resultant changes were relatively small and are probably insignificant in the clinical setting. PMID:1901464

  4. Locally auxetic behavior of elastomeric polypropylene on the 100 nm length scale.

    PubMed

    Franke, Mechthild; Magerle, Robert

    2011-06-28

    We observe unexpected locally auxetic behavior in elastomeric polypropylene, a semicrystalline polymer with a natural microstructure and a low degree of crystallinity. Our series of scanning force microscopy images show the nanomechanical deformation processes that occur upon stretching a thin film of elastomeric polypropylene. Upon uniaxial stretching, the angle between epitaxially grown lamella branches remains constant and the lamellae elongate, resulting in locally auxetic behavior (negative Poisson's ratio) on the 100-nanometer scale. This mechanism causing auxetic behavior, which was previously proposed on the basis of geometric arguments, appears to be an intrinsic property of certain semicrystalline polymers. PMID:21495686

  5. A fundamental study of the modification of elastomeric poly(dimethylsiloxane) and silicon surfaces using polymers and their applications in patterning

    NASA Astrophysics Data System (ADS)

    Ell, John Randall

    A fundamental study of the polymer functionalization of flat elastomeric poly(dimethylsiloxane) (PDMS) and Silcon wafers is described. Using polymer grafting methodologies such as "grafting onto" and "grafting from" a functional substrate, the development of a novel pattern miniaturization protocol and method for nanoparticle patterning was achieved. Currently, a general strategy for the poly(ethylene glycol) (PEG) functionalization of Silastic RTV elastomeric substrates does not exist in the literature. Our preliminary attempts with the functionalization of elastomeric PDMS suffered from a lack of effective surface functionalization control, primarily as a result of literature inconsistencies and inadequate surface characterization. Therefore, we performed in-depth and quantitative surface analysis of the surface functionality of the elastic PDMS substrates that were used to adopt a modified functionalization strategy. The end result was the development of a dynamic material where the surface energy could be manipulated through simple mechanical stretching. A new miniaturization protocol, referred to as high-efficiency stepwise contraction and adsorption nanolithography (hSCAN), was demonstrated. A thin film of elastomeric precursor was first cast on a stretched substrate. A designed microstructure was then imprinted and the precursor layer was subsequently cured. The microstructure was miniaturized after the substrate relaxed to its original length. The miniaturized structures can be used as stamps to transfer materials onto a designated support or as molds to produce the structure on another stretched substrate for further miniaturization. The patterning of materials by microcontact printing has been improved with the development of hSCAN. Optical disc media polycarbonate discs were used as master molds in the hSCAN miniaturization protocol with promising results. CD's, DVD's and even Blue-ray polycarbonate discs were miniaturized, and < 100 nm features were

  6. Structural evaluation of Marman V-band coupling and flange with conoseal gasket

    NASA Technical Reports Server (NTRS)

    Oates, J. H.

    1972-01-01

    Results are described of a development test program directed at evaluating the structural capabilities of the Marman V-band coupling and flange with conoseal gasket. The intended end use was for the 75K NERVA flight engine propellant lines. Of major importance in the structural evaluation was the ability to predict stresses throughout the assembly for a variety of loading conditions. Computer finite element analysis was used to predict these stresses but, for the subject configuration, large uncertainties were introduced in modeling the complex geometry and boundary conditions. The purpose of the structural tests was to obtain actual stresses and deflections for correlation with, and updating of the finite element model. Results of the incomplete test program are inconclusive with respect to determining suitability for use on the NERVA engine.

  7. Radiation Effects on Polymer Properties

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.; Winslow, J. W.

    1987-01-01

    Report compiles data on effects of radiation on physical properties of synthetic organic materials. Emphasis on materials of interest to nuclear-equipment and nuclear-reactor designers. Data covers five categories of polymeric materials: Insulators, elastomeric seals and gaskets, lubricants, adhesives, and coatings. More than 250 materials represented.

  8. Comparison of canine retraction by in vivo method using four brands of elastomeric power chain

    PubMed Central

    Kanuru, Ravi Krishna; Azaneen, Mustafa; Narayana, Veera; Kolasani, Balaram; Indukuri, Ravikishore Reddy; Babu, P Firoz

    2014-01-01

    Objective: To investigate the amount of space closure by movement of canines into the extraction spaces using four brands of elastomeric power chains (EPCs) by intraoral application with pre-adjusted appliance for 6 weeks. Materials and Methods: The sample size calculation was based on the studies of Boester and Johnston and also with repeated measures analysis of variance (ANOVA) continuous data for force degradation, standard deviation of 24.9 g, and also from a pilot study, which totaled to around 17 patients with a mean age of 20 ± 2 years and receiving fixed orthodontic treatment that required retraction of canines into the premolar extraction spaces in all four dental arch quadrants. Four brands of EPCs, namely the Ormco, 3M Unitek, Rocky Mountain, and Highland, which were closed-link with five loops delivering less than or equal to 250 g were used. The rates of canine retraction were measured between the attachment points on the canine bracket hook and first molar hook using a Mitutoyo Digital Vernier Caliper at the time of first application, after 3 weeks of use, and at the end of 6 weeks of use, and were subjected to statistical calculations. Results: The distances recorded from canine retraction were similar with slight differences noticed in the four brands of EPCs. However, no statistically significant difference was observed in relation to the EPCs. Conclusion: Although all brands of the EPCs produced space closure of canines, it was observed that not much of a significant difference existed among the products tested. PMID:25452925

  9. Elastomeric and mechanically stiff nanocomposites from poly(glycerol sebacate) and bioactive nanosilicates.

    PubMed

    Kerativitayanan, Punyavee; Gaharwar, Akhilesh K

    2015-10-01

    Poly(glycerol sebacate) (PGS) has been proposed for tissue engineering applications owing to its tough elastomeric mechanical properties, biocompatibility and controllable degradation. However, PGS shows limited bioactivity and thus constraining its utilization for musculoskeletal tissue engineering. To address this issue, we developed bioactive, highly elastomeric, and mechanically stiff nanocomposites by covalently reinforcing PGS network with two-dimensional (2D) nanosilicates. Nanosilicates are ultrathin nanomaterials and can induce osteogenic differentiation of human stem cells in the absence of any osteogenic factors such as dexamethasone or bone morphogenetic proteins-2 (BMP2). The addition of nanosilicate to PGS matrix significantly enhances the mechanical stiffness without affecting the elastomeric properties. Moreover, nanocomposites with higher amount of nanosilicates have higher in vitro stability as determined by degradation kinetics. The increase in mechanical stiffness and in vitro stability is mainly attributed to enhanced interactions between nanosilicates and PGS. We evaluated the in vitro bioactivity of nanocomposite using preosteoblast cells. The addition of nanosilicates significantly enhances the cell adhesion, support cell proliferation, upregulate alkaline phosphates and mineralized matrix production. Overall, the combination of high mechanically stiffness and elastomericity, tailorable degradation profile, and the ability to promote osteogenic differentiation of PGS-nanosilicate can be used for regeneration of bone. PMID:26297886

  10. Synthetic Organic Materials in Nuclear Powerplants

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.; Winslow, J. W.

    1985-01-01

    Report aids plant designers and qualification engineers in ensuring that organic materials in nuclear powerplants will perform satisfactorily in such safety-related equipment as insulation on motor windings, pump diaphragms, motor and pump lubricants, and pump seals and gaskets. Report provides information for service that may include both mild and harsh nuclear environments.

  11. Standard operating procedure (SOP) for the quantitative determination of organic silicon compounds at the surface of elastomeric sealants

    NASA Astrophysics Data System (ADS)

    Gross, Th; Treu, D.; Unger, W.

    2001-07-01

    Elastomeric sealants may contain organic silicon compounds. The use of these sealants for housings for electronic components is harmful for the reliability of electric contacts inside. In order to prevent electronic components from malfunction, quality control of elastomeric sealants is required. An analytical procedure developed to fulfil this requirement was developed. It is based on electron spectroscopy for chemical analysis (ESCA). Information on the silicon compounds existing at the surface of elastomeric sealants is provided by this method. Silicon in organic and inorganic compounds can be differentiated with the help of Si 2p photoelectron spectra. Quantitative results can be obtained too. The uncertainty budget of the quantitative procedure is estimated.

  12. Phase separation and mechanical properties of an elastomeric biomaterial from spider wrapping silk and elastin block copolymers.

    PubMed

    Muiznieks, Lisa D; Keeley, Fred W

    2016-10-01

    Elastin and silk spidroins are fibrous, structural proteins with elastomeric properties of extension and recoil. While elastin is highly extensible and has excellent recovery of elastic energy, silks are particularly strong and tough. This study describes the biophysical characterization of recombinant polypeptides designed by combining spider wrapping silk and elastin-like sequences as a strategy to rationally increase the strength of elastin-based materials while maintaining extensibility. We demonstrate a thermo-responsive phase separation and spontaneous colloid-like droplet formation from silk-elastin block copolymers, and from a 34 residue disordered region of Argiope trifasciata wrapping silk alone, and measure a comprehensive suite of tensile mechanical properties from cross-linked materials. Silk-elastin materials exhibited significantly increased strength, toughness, and stiffness compared to an elastin-only material, while retaining high failure strains and low energy loss upon recoil. These data demonstrate the mechanical tunability of protein polymer biomaterials through modular, chimeric recombination, and provide structural insights into mechanical design. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 693-703, 2016. PMID:27272259

  13. Gecko gaskets for self-sealing and high-strength reversible bonding of microfluidics.

    PubMed

    Wasay, A; Sameoto, D

    2015-07-01

    We report in this work a novel reversible bonding technique for elastomeric microfluidic devices by integrating gecko-inspired dry adhesives with microfluidic channels which greatly enhances the bonding strength of reversibly sealed channels. The concept is applicable to nearly any elastomer and can be used to bond against any smooth surface which allows for van der Waals interactions. It does not require any solvents or glues or sources for plasma activation or thermal-compressive loading to aid the bonding process and is achievable at zero extra cost. We also demonstrate a quick fabrication technique involving soft master thermo-compressive molding of these microfluidic devices with thermoplastic elastomers. The resultant devices can be used for both pressure driven and non-pressure driven flows. We report the maximum contained pressure of these devices manufactured from two grades of styrene ethylene butylene styrene (SEBS) by conducting a burst pressure test with various substrates. PMID:26016928

  14. Compositional GC-FID analysis of the additives to PVC, focusing on the gaskets of lids for glass jars.

    PubMed

    Biedermann-Brem, Sandra; Biedermann, Maurus; Fiselier, Katell; Grob, Koni

    2005-12-01

    A gas chromatographic (FID) method is described which aims at the quantitative compositional analysis of the additives in plasticized PVC, particularly the plastisols used as gaskets for lids of glass jars. An extract of the PVC is analysed directly as well as after transesterification to ethyl esters. Transesterification enables the analysis of epoxidized soya bean and linseed oil (ESBO and ELO) as well as polyadipates. For most other additives, the shifts in the chromatogram resulting from transesterification is used to confirm the identifications made by direct analysis. In the gaskets of 69 lids from the European market used for packaging oily foods, a broad variety of plastisol compositions was found, many or possibly all of which do not comply with legal requirements. In 62% of these lids, ESBO was the principal plasticizer, whereas in 25% a phthalate had been used. PMID:16356892

  15. Reinforced polyquinoxaline gasket and method of preparing the same. [resistant to ionizing radiation and liquid hydrogen temperatures

    NASA Technical Reports Server (NTRS)

    Vanauken, R. (Inventor)

    1974-01-01

    A gasket or seal resistant to ionizing radiation and liquid hydrogen temperatures is made up of a laminated polyquinoxaline resin-fiberglass cloth body portion and a molded polyquinoxaline encapsulating film. The laminated body is prepared by stacking thin sheets of the resin alternately with fiberglass cloth and heating the assembly under pressure with the temperature, pressure and resin film thickness being controlled so that only partial impregnation of the fiberglass cloth is produced. The encapsulating resin film is preheated at about 300 f and applied to the laminate body by molding at a temperature of about 625 F. The molded gasket is then deflashed and post-cured by heating at 675 to 700 F.

  16. Novel elastomeric fibrous networks produced from poly(xylitol sebacate)2:5 by core/shell electrospinning: fabrication and mechanical properties.

    PubMed

    Li, Yuan; Thouas, George A; Chen, Qizhi

    2014-12-01

    Fabrication of nonlinear elastic materials that resemble biological tissues remains a challenge in biomaterials research. Here, a new fabrication protocol to produce elastomeric fibrous scaffolds was established, using the core/shell electrospinning technique. A prepolymer of poly(xylitol sebacate) with a 2:5mol ratio of xylitol:sebacic acid (PXS2:5) was first formulated, then co-electrospun with polyvinyl alcohol (PVA - 95,000Mw). After cross-linking of core polymer PXS2:5, the PVA shells were rinsed off in water, leaving a porous elastomeric network of PXS2:5 fibres. Under aqueous conditions, the PXS2:5 fibrous scaffolds exhibited stable, nonlinear J-shaped stress-strain curves, with large average rupture elongation (76%) and Young׳s modulus (~1.0MPa), which were in the range of muscle tissue. Rupture elongation of PXS2:5 was also much higher when electrospun, compared to 2D solid sheets (45%). In direct contact with cell monolayers under physiological conditions, PXS2:5 scaffolds were as biocompatible as those made of poly-l-lactic acid (PLLA), with improvements over culture medium alone. In conclusion, the newly developed porous PXS2:5 scaffolds show tissue-like mechanical properties and excellent biocompatibility, making them very promising for bioengineering of soft tissues and organs. PMID:25243671

  17. Survey of phthalate levels in Italian oily foods contained in glass jars with PVC gaskets.

    PubMed

    Sannino, A

    2009-01-01

    A method based on gas chromatography/tandem mass spectrometry was used to assess levels of twelve phthalates in 50 samples of oily foods packed in glass jars with metal closure obtained from a retail market. The amounts of di-methyl phthalate, di-ethyl phthalate, di-propyl phthalate, di-butyl phthalate, di-pentyl phthalate, benzyl butyl phthalate, di-cyclohexyl phthalate, di-n-octyl phthalate, di-isononyl phthalate and di-isodecyl phthalate in all samples analysed were less than the limit of quantification (LOQ). Di-(2-ethylhexyl) phthalate was detected in 20 samples in the range from 0.1 to 6 mg kg(-1) with an average of 1.0 mg kg(-1), and it exceeded the specific migration limit (SML) of 1.5 mg kg(-1) in five cases with an average of 3.0 mg kg(-1). Di-isobutyl phthalate was found in four samples at 0.1-0.4 mg kg(-1). The PVC gaskets used for the lids were negative for all tested phthalates, suggesting that the contamination of the foods originated from other sources, e.g. olive oil. PMID:24785180

  18. Roll to plate printed stretchable silver electrode using single walled carbon nanotube on elastomeric substrate.

    PubMed

    Jung, Minhun; Noh, Jinsoo; Kim, Junseok; Kim, Donghwan; Cho, Gyoujin

    2013-08-01

    Stretchable electronics may open new applications in display, sensors and actuators. To attain the stretchable electronics, the ink formulation should be compatible with elastomeric substrates. Here, we present the formulation of silver nanoparticles and single walled carbon nanotubes (SWNTs) for printing stretchable silver electrodes on the elastomeric substrates. Highly conductive stretchable electrodes can be printed directly on the poly(styrene-b-butadiene-b-styrene) (PSBS) substrates by roll to plate (R2P) gravure printer. During the stretching test, R2P printed silver based stretchable electrodes show the high conductivity of 1000 S cm(-1) at 0.27 wt% of SWNT loading. Furthermore, the resistance of the printed silver electrode was not changed up to 15% of tensile strain. PMID:23882805

  19. Increasing pumping efficiency in a micro throttle pump by enhancing displacement amplification in an elastomeric substrate

    NASA Astrophysics Data System (ADS)

    Fujiwara, T.; Johnston, I. D.; Tracey, M. C.; Tan, C. K. L.

    2010-06-01

    Fluid transport is accomplished in a micro throttle pump (MTP) by alternating deformation of a micro channel cast into a polydimethylsiloxane (PDMS) elastomeric substrate. The active deformation is achieved using a bimorph PZT piezoelectric disc actuator bonded to a glass diaphragm. The bimorph PZT deflects the diaphragm as well as alternately pushing and pulling the elastomer layer providing displacement amplification in the PDMS directly surrounding the micro channel. In order to improve pumping rates we have embedded a polymethylmethacrylate (PMMA) ring into the PMDS substrate which increases the magnitude of the displacement amplification achieved. FEM simulation of the elastomeric substrate deformation predicts that the inclusion of the PMMA ring should increase the channel deformation. We experimentally demonstrate that inclusion of a PMMA ring, having a diameter equal to that of the circular node of the PZT/glass/PDMS composite, increases in the throttle resistance ratio by 40% and the maximum pumping rate by 90% compared to an MTP with no ring.

  20. Pattern transfer printing by kinetic control of adhesion to an elastomeric stamp

    DOEpatents

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao

    2011-05-17

    The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of `soft adhesion` to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

  1. The effect of nonlinear elastomeric lag damper characteristics on helicopter rotor dynamics

    NASA Technical Reports Server (NTRS)

    Felker, Fort F.; Lau, Benton H.; Mclaughlin, Stacey; Johnson, Wayne

    1987-01-01

    Many helicopters use elastomeric lag dampers to prevent ground resonance and aeromechanical instability in hover and forward flight. Recent experimental results have shown that when the damper motion occurs at two superimposed frequencies, which is characteristic of operation in forward flight, the damper properties are not well-predicted by a superposition of the damper properties at each of the motion frequencies. This paper presents experimental data obtained with an elastomeric damper while it was undergoing single- and dual-frequency motion. The effect of the nonlinear dual-frequency damper characteristics on predicted rotor aeromechanical stability in forward-flight operation in a wind tunnel was evaluated using the comprehensive rotorcraft analysis program called CAMRAD.

  2. A pillar-based microfilter for isolation of white blood cells on elastomeric substrate

    PubMed Central

    Alvankarian, Jafar; Bahadorimehr, Alireza; Yeop Majlis, Burhanuddin

    2013-01-01

    Our goal is to design, fabricate, and characterize a pillar-based microfluidic device for size-based separation of human blood cells on an elastomeric substrate with application in the low-cost rapid prototyping of lab-chip devices. The single inlet single outlet device is using parallel U-shape arrays of pillars with cutoff size of 5.5 μm for trapping white blood cells (WBCs) in a pillar chamber with internal dead-volume of less than 1.0 μl. The microstructures are designed to limit the elastomeric deformation against fluid pressures. Numerical analysis showed that at maximum pressure loss of 15 kPa which is lower than the device conformal bonding strength, the pillar elastomeric deformation is less than 5% for flow rates of up to 1.0 ml min−1. Molding technique was employed for device prototyping using polyurethane methacrylate (PUMA) resin and polydimethylsiloxane (PDMS) mold. Characterization of the dual-layer device with beads and blood samples is performed. Tests with blood injection showed that ∼18%–25% of WBCs are trapped and ∼84%–89% of red blood cells (RBCs) are passed at flow rates of 15–50 μl min−1 with a slight decrease of WBCs trap and improve of the RBCs pass at higher flow rates. Similar results were obtained by separation of mixed microspheres of different size injected at flow rates of up to 400 μl min−1. Tests with blood samples stained by fluorescent gel demonstrated that the WBCs are accumulated in the arrays of pillars that later end up to blockage of the device. Filtration results of using elastomeric substrate present a good consistency with the trend of separation efficiencies of the similar silicon-based filters. PMID:24403994

  3. EPDM - Silicone blends - a high performance elastomeric composition for automotive applications

    SciTech Connect

    Mitchell, J.M.

    1987-01-01

    Styling and design changes have dramatically altered performance requirements for elastomers. High performance engines with electronic fuel injection have increased temperatures under the hood. Therefore, high performance elastomers are required to meet today's service conditions. New technology has been developed to compatibilize EPDM and silicone into high performance elastomeric compositions. These blends have physical, electrical and mechanical properties, for 175/sup 0/C service. Formulations are discussed for applications which require heat and weather resistance.

  4. Process for the preparation of fluorine containing crosslinked elastomeric polytriazine and product so produced

    NASA Technical Reports Server (NTRS)

    Rosser, R. W.; Korus, R. A. (Inventor)

    1980-01-01

    Crosslinking elastomeric polytriazines are prepared by a 4 step procedure which consists of (1) forming a poly(imidoylamidine) by the reaction, under reflux conditions, of anhydrous ammonia with certain perfluorinated alkyl or alkylether dinitriles; (2) forming a linear polytriazine by cyclizing the imidoylamidine linkages by reaction with certain perfluorinated alkyl or alkylether acid anhydrides or halides; (3) extending the linear polytriazine chain by further refluxing in anhydrous ammonia; and (4) heating to cyclize the new imidoylamidine and thereby crosslink the polymer.

  5. Investigation of the recycling of tires to elastomeric requirements by techniques of thermal compression

    NASA Astrophysics Data System (ADS)

    Nadal Gisbert, Antonio V.

    In this work is investigated the recycling of tires to elastomeric requirements by thermal compression. The production of recycled products is carried out starting from the powder, of elastomeric nature, coming from the grinding of used tires denominated GTR (Ground Tire Rubber) of different grain size, although the fundamental objective is the recycling of powder of 0,2mm grain size. The process of forming used for obtaining the recycled product is thermal compression, due to its simplicity and low cost. The composition of the powder has been analyzed and also the influence, on the elastomeric characteristics of the recycled product, of different parameters: Grain size, compact pressure, temperature, time, thickness of the recycled product and combination of sizes. At last we give an hypothesis that justifies the mechanism that gives cohesion to the powder GTR and allows their recycling. We also have carried out an analysis of the investigation lines, at the present, on the recycling of tires in general and an economic study of the viability of the recycled product in front of present products in the market, agglomerated with polyurethane, that have their application in using it in different types of floors.

  6. Structure/property relations of elastomeric hybrid organic-inorganic composites

    NASA Astrophysics Data System (ADS)

    Miller, Thomas Michael

    Hybrid organic-inorganic composites have been synthesized by the sol-gel processing of triethoxysilane end functionalized poly(tetramethylene oxide) and tetraethxoysilane. The resulting transparent materials are elastomeric gels crosslinked by an amorphous polysilicate phase. Elementary rubber-elasticity theory in conjunction with dynamic mechanical spectroscopy was applied to these seemingly nonideal networks to quantify the change in phase interaction induced by aging the benchmark acid catalyzed gels in a basic solution of 70% ethylamine in water. The change in the average molar mass between crosslinks explained the previously published mechanical and dynamic mechanical results. Furthermore, the application of this theory to these seemingly nonideal networks resulted in network parameters that were in excellent agreement with traditional equilibrium swelling estimates. The work was then extended by utilizing this ethylamine solution to catalyze the sol-gel reaction in-situ. The effect of this change in catalyst upon the oxygen diffisivity of the hybrids as a function of polysilicate loading was investigated using a luminescence based approach. While the diffusivity of the acid catalyzed gels decreased with increasing loading, the base catalyzed gels did not indicating that the polysilicate domains resulting from the base catalysis possess considerable porosity. However, the pores appear to be much too small for Knudsen diffusion, a commonly observed gas separation mechanism in porous ceramic membranes. To investigate the influence of polysilicate network polarity and spatial distribution, the sol-gel processing of the hybrids was adjusted to produce two classes of gels. One exhibited a more discrete polysilicate phase possessing greater network connectivity and reduced silanol content than the other. This was accomplished by using dimethylformamide in place of tetrahydrofuran as the organic solvent constituent of the sol. Poly(methacrylic acid

  7. Effect of soft metal gasket contacts on contact resistance, energy deposition, and plasma expansion profile in a wire array Z pinch

    NASA Astrophysics Data System (ADS)

    Gomez, M. R.; Zier, J. C.; Gilgenbach, R. M.; French, D. M.; Tang, W.; Lau, Y. Y.

    2008-09-01

    Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire and the electrode in an aluminum wire Z pinch by more than an order of magnitude over the best weighted contact case. Clamping a gasket over a Z-pinch wire compresses the wire to the electrode with a greater normal force than possible with wire weights. Average contact resistance was reduced from the range of 100-3000 Ω (depending on wire weight mass) to 1-10 Ω with soft metal gaskets. Single wire experiments (13 μm Al 5056) on a 16 kA, 100 kV Marx bank showed an increase in light emission (97%) and emission volume (100%) of the plasma for the reduced contact resistance cases. The measured increases in plasma volume and light emission indicate greater energy deposition in the ablated wire. Additionally, dual-wire experiments showed plasma edge effects were significantly decreased in the soft metal gasket contact case. The average height of the edge effects was reduced by 51% and the width of the edge effects was increased by 40%, thus the gasket contact case provided greater axial uniformity in the plasma expansion profile of an individual wire.

  8. Comparison of frictional resistance between self-ligating and conventional brackets tied with elastomeric and metal ligature in orthodontic archwires

    PubMed Central

    Leite, Vanessa Vieira; Lopes, Murilo Baena; Gonini Júnior, Alcides; de Almeida, Marcio Rodrigues; Moura, Sandra Kiss; de Almeida, Renato Rodrigues

    2014-01-01

    Objective To compare the frictional resistance between self-ligating and conventional brackets tied to different types of wire. Material and Methods Abzil Kirium Capelozza (Pattern I) and Easy Clip (Roth prescription) incisor brackets were used. An elastomeric ligature or a ligating wire 0.10-in was used to ligate the wire to the Abzil bracket. Three types of orthodontic archwire alloys were assessed: 0.016-in NiTi wire, 0.016 x 0.021-in NiTi wire and 0.019 x 0.025-in steel wire. Ten observations were carried out for each bracket-archwire angulation combination. Brackets were mounted in a special appliance, positioned at 90 degrees in relation to the wire and tested in two angulations. Frictional test was performed in a Universal Testing Machine at 5 mm/min and 10 mm of displacement. The means (MPa) were submitted to ANOVA and Tukey's test set at 5% of significance. The surfaces of wires and brackets were observed at SEM. Results Steel-tied brackets (16.48 ± 8.31) showed higher means of frictional resistance than elastomeric-tied brackets (4.29 ± 2.16 ) and self-ligating brackets (1.66 ± 1.57) (P < 0.05), which also differed from each other (P < 0.05). As for the type of wire, 0.019 x 0.025-in steel wire (5.67 ± 3.97) showed lower means (P < 0.05) than 0.16-in NiTi wire (8.26 ± 10.92) and 0.016 x 0.021-in NiTi wire (8.51 ± 7.95), which did not differ from each other (P > 0.05). No statistical differences (P > 0.05) were found between zero (7.76 ± 8.46) and five-degree (7.19 ± 7.93) angulations. Conclusions Friction was influenced not only by the type of bracket, but also by the ligating systems. Different morphological aspects were observed for the brackets and wires studied PMID:25162575

  9. To improve the flame resistance of spandex elastic elastomeric fiber

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Strength characteristics of fibers were improved to pass the 70% oxygen/30% nitrogen specification. Spinning techniques and information about incorporating these fibers in fabric structures using wrapping materials of Beta Fiberglas, Nomex, and PBI were developed.

  10. Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface

    PubMed Central

    MEHDI, Ghalem; BELARBI, Abderrahmane; MANSOURI, Bensmaine; AZARI, Zitouni

    2015-01-01

    Objective This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant® implant type in order to minimize stress concentration in the bone-implant interface. Material and Methods This study investigated 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis. Results Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively. Conclusion The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant® implant system. PMID:25760271

  11. Bond Percolation on a NON-P.C.F. SIERPIŃSKI Gasket, Iterated Barycentric Subdivision of a Triangle, and Hexacarpet

    NASA Astrophysics Data System (ADS)

    Lougee, D.; Steinhurst, B.

    2016-05-01

    We investigate bond percolation on the iterated barycentric subdivision of a triangle, the hexa-carpet, and the non-p.c.f. Sierpinski gasket. With the use of known results on the diamond fractal, we are able to bound the critical probability of bond percolation on the non-p.c.f. gasket and the iterated barycentric subdivision of a triangle from above by 0.282. We then show how both the gasket and hexacarpet fractals are related via the iterated barycentric subdivisions of a triangle: the two spaces exhibit duality properties although they are not themselves dual graphs. Finally, we show the existence of a non-trivial phase transition on all three graphs.

  12. Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis

    SciTech Connect

    Chou, I.-M.; Bassett, W.A.; Anderson, A.J.; Mayanovic, R.A.; Shang, L.

    2009-03-25

    Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 {micro}m in diameter and - 50 {micro}m deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90{sup o} angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 {micro}m, a pressure of 76 MPa at 500 C was maintained for 2 h with no change in the original fluid density.

  13. Elasto-Plastic FEM Stress Analysis and Mechanical Characteristics of Pipe Flange Connections with Non-Asbestos Gaskets under Internal Pressure

    NASA Astrophysics Data System (ADS)

    Takagi, Yoshio; Omiya, Yuya; Kobayashi, Takashi; Sawa, Toshiyuki

    The effects of the nominal diameter of pipe flange connections with non-asbestos spiral wound gaskets(SWG) under internal pressure on the mechanical characteristics such as the contact gasket stress distribution which governs the sealing performance, the load factor and the hub stress of the connections were evaluated. The stresses in the connections with the nominal diameters from 3” to 24” under internal pressure are analyzed using the elasto-plastic(EP) FEM analysis taking account the hysteresis and non-linearity of deformation behavior of the non-asbestos SWG. As a result, it is found that the variations in the contact gasket stress distributions are substantial due to the flange rotation in the connections with the larger nominal diameter. Leakage tests were conducted to measure the axial bolt forces (the load factor) and the hub stress. The results obtained from the EP-FEM analyses are fairly consistent with the experimental results concerning the variation in the axial bolt forces (the load factor) and the hub stress. Using the obtained contact gasket stress distributions and the fundamental relationship between the amount of leakage and the contact gasket stress, the amount of the leakage of the connections is estimated. It is observed that the sealing performance of the connections with larger nominal diameter is worse than that of the connection with smaller nominal diameter because of the flange rotation. The estimated results are in a fairly good agreement with the measured results. The difference in the hub stress between the EP-FEM and ASME code is demonstrated and the differences in the load factor and the sealing performance of the connections are shown between the asbestos and non-asbestos gaskets.

  14. Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis

    USGS Publications Warehouse

    Chou, I.-Ming; Bassett, William A.; Anderson, Alan J.; Mayanovic, Robert A.; Shang, L.

    2008-01-01

    Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 ??m in diameter and ???50 ??m deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 ??C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 ??C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90?? angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 ??m, a pressure of 76 MPa at 500 ??C was maintained for 2 h with no change in the original fluid density. ?? 2008 American Institute of Physics.

  15. Baseline and Lifetime Assessments for DC745U Elastomeric Components

    SciTech Connect

    Maxwell, R S; Chinn, S C; Herberg, J; Harvey, C; Alviso, C; Vance, A; Cohenour, R; Wilson, M; Solyom, D

    2004-12-20

    The silicone elastomer Dow Corning DC 745U is used in two major components in the W80. We have investigated a number of issues concerning this material. Our studies have accomplished a baseline study of the chemical composition of DC745 and LLNL now has a good understanding of the chemical composition of this material. DC745 crystallizes within the system STS. Two potential means identified to mitigate the risk associated with this phenomenon are to (1) change material formulation and (2) predose the parts to {approx} 25 MRad {gamma}-radiation. A candidate material identified by Gordon Spellman has been studied for composition and the lack of crystallization within the STS has been verified. A sensitivity study of the effects of relevant aging mechanisms also has been performed. The extent of aging due to radiation exposure or elevated temperatures is minimal over the expected course of the LEP. In addition, since the DC745 parts are expected to be replaced at rebuild, the aging clock is essentially being reset. No significant aging issues seem likely to develop for these parts. DC745 parts are also subject to permanent deformation in service. Our studies have shown that the deformation is likely due to incomplete mixing of the raw gum stock and the curing agent at production. This results in areas of low crosslink density that are subject to a higher degree of compression set in service. We have identified two production diagnostic tools based on Nuclear Magnetic Resonance spectroscopy to prescreen the parts at production at KCP. These studies are concluded with specific recommendation for changes to core surveillance for this part based on the chemical knowledge we have gained from this study.

  16. Impact of Different Standard Type A7A Drum Closure-Ring Practices on Gasket Contraction and Bolt Closure Distance– 15621

    SciTech Connect

    Ketusky, Edward; Blanton, Paul; Bobbitt, John H.

    2015-03-11

    The Department of Energy, the Savannah River National Laboratory, several manufacturers of specification drums, and the United States Department of Transportation (DOT) are collaborating in the development of a guidance document for DOE contractors and vendors who wish to qualify containers to DOT 7A Type A requirements. Currently, the effort is focused on DOT 7A Type A 208-liter (55-gallons) drums with a standard 12-gauge bolted closure ring. The U.S. requirements, contained in Title 49, Part 178.350 “Specification 7A; general packaging, Type A specifies a competent authority review of the packaging is not required for the transport of (Class 7) radioactive material containing less than Type A quantities of radioactive material. For Type AF drums, a 4 ft. regulatory free drop must be performed, such that the drum “suffers maximum damage.” Although the actual orientation is not defined by the specification, recent studies suggest that maximum damage would result from a shallow angle top impact, where kinetic energy is transferred to the lid, ultimately causing heavy damage to the lid, or even worse, causing the lid to come off. Since each vendor develops closure recommendations/procedures for the drums they manufacture, key parameters applied to drums during closing vary based on vendor. As part of the initial phase of the collaboration, the impact of the closure variants on the ability of the drum to suffer maximum damage is investigated. Specifically, closure testing is performed varying: 1) the amount of torque applied to the closure ring bolt; and, 2) stress relief protocol, including: a) weight of hammer; and, b) orientation that the hammer hits the closure ring. After closure, the amount of drum lid gasket contraction and the distance that the closure bolt moves through the closure ring is measured.

  17. Leakage Through a Channel Formed by a Gasket, a Sealing Surface, and a Filament Trapped Between Them

    NASA Technical Reports Server (NTRS)

    Russell, John; Adams, Frederick

    1996-01-01

    Plumbing for the transport of liquid Hydrogen or liquid Oxygen at the Kennedy Space Center (KSC) is very critical. Every piece of hardware for handling such a hazardous cryogen is subject to testing prior to installation and use. Safe, realistic testing of all such hardware is prohibitively expensive, which leads, perforce, to expidients such as: (1) lead testing with non-flammable tracer fluids (e.g, liquid nitrogen) and (2) leak testing with room temperature tracer fluids (e.g. liquid helium). Such expedients undermine the realism of the tests. If however, one could apply rational fluid dynamics methods to derive a general analytical expression with which one could relate the throughput of gaseous Helium through a given leak channel to the throughput of liquid Hydrogen through the same channel, then one could recover much of the information that one would otherwise forfeit through these expedients. These facts lead to the following questions: (1) What would be an example of a generic flaw in a gasket?; and (2) How can one calculate the flow of fluid in it? The report addresses these questions. It considers a particular leak geometry, namely one formed by a gasket, a sealing surface, and a filament trapped between them (so that the cross section of the leak channel is a flat bottomed curvilinear triangle, two sides of which are circular arcs and which has cusps on all three corners).

  18. 46 CFR 53.05-3 - Materials (modifies HG-401.2).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets... 46 Shipping 2 2010-10-01 2010-10-01 false Materials (modifies HG-401.2). 53.05-3 Section 53.05-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING...

  19. 46 CFR 53.05-3 - Materials (modifies HG-401.2).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets... 46 Shipping 2 2012-10-01 2012-10-01 false Materials (modifies HG-401.2). 53.05-3 Section 53.05-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING...

  20. 46 CFR 53.05-3 - Materials (modifies HG-401.2).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets... 46 Shipping 2 2014-10-01 2014-10-01 false Materials (modifies HG-401.2). 53.05-3 Section 53.05-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING...

  1. 46 CFR 53.05-3 - Materials (modifies HG-401.2).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets... 46 Shipping 2 2011-10-01 2011-10-01 false Materials (modifies HG-401.2). 53.05-3 Section 53.05-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING...

  2. 46 CFR 53.05-3 - Materials (modifies HG-401.2).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets... 46 Shipping 2 2013-10-01 2013-10-01 false Materials (modifies HG-401.2). 53.05-3 Section 53.05-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING...

  3. Elastomeric microposts integrated into microfluidics for flow-mediated endothelial mechanotransduction analysis.

    PubMed

    Lam, Raymond H W; Sun, Yubing; Chen, Weiqiang; Fu, Jianping

    2012-04-24

    Mechanotransduction is known as the cellular mechanism converting insoluble biophysical signals in the local cellular microenvironment (e.g. matrix rigidity, external mechanical forces, and fluid shear) into intracellular signalling to regulate cellular behaviours. While microfluidic technologies support a precise and independent control of soluble factors in the cellular microenvironment (e.g. growth factors, nutrients, and dissolved gases), the regulation of insoluble biophysical signals in microfluidics, especially matrix rigidity and adhesive pattern, has not yet been achieved. Here we reported an integrated soft lithography-compatible microfluidic methodology that could enable independent controls and modulations of fluid shear, substrate rigidity, and adhesive pattern in a microfluidic environment, by integrating micromolded elastomeric micropost arrays and microcontact printing with microfluidics. The geometry of the elastomeric micropost array could be regulated to mediate substrate rigidity and adhesive pattern, and further the elastomeric microposts could be utilized as force sensors to map live-cell subcellular contractile forces. To illustrate the general application of our methodology, we investigated the flow-mediated endothelial mechanotransduction process and examined specifically the involvement of subcellular contractile forces in the morphological realignment process of endothelial cells under a sustained directional fluid shear. Our results showed that the cytoskeletal contractile forces of endothelial cells were spatiotemporally regulated and coordinated to facilitate their morphology elongation process along the direction of flow. Together, our study provided an integrated microfluidic strategy to modulate the in vitro cellular microenvironment with both defined soluble and insoluble signals, and we demonstrated its application to investigate quantitatively the involvement of cytoskeletal contractile forces in the flow

  4. On the source of entropic elastomeric force in polypeptides and proteins: Backbone configurational vs. side-chain solvational entropy

    SciTech Connect

    Luan, Chihao; Jaggard, J.; Harris, R.D.; Urry, D.W. )

    1989-01-01

    At physiological temperature in water, the relaxed state of the protein, elastin, and model elastomeric sequential polypeptides derived from this biological elastomer is the result of an inverse temperature transition. At lower temperatures, say at 20{degree}C, the hydrophobic side chains of the elastomers are hydrated with a low-entropy net of water. Following Flory and colleagues, thermoelasticity studies suggests that these polypeptide elastomers are dominantly entropic elastomers above the temperature of the inverse temperature transition. A central question becomes the source of the entropic elastomeric force. On stretching, hydrophobic side chains become exposed to water, resulting in an exothermic reaction of hydrophobic hydration. The issue addressed by the present report is whether this decrease in solvent entropy on stretching might make a major contribution to the entropic elastomeric restoring force. It has previously been argued that the free energy of solvation can be made very small by a 30% ethylene glycol (EG):70% water solvent mixture. This is demonstrated here using the repeating pentapeptide sequence of elastin (Val{sup 1}-Pro{sup 2}-Gly{sup 3} -Val{sup 4}-Gly{sup 5}){sub n} or poly(VPGVG) and its {gamma}-irradiation cross-linked elastomeric matrix. Differential scanning calorimetry of the inverse temperature transition of poly(VPGVG) shows the endothermic heat of the transition to become very small in EG/H{sub 2}O when compared with H{sub 2}O alone, which also indicates a very small entropy change for the transition on exposure of the hydrophobic side chains to the EG/H{sub 2}O solvent mixture. A similar result is found for the crosslinked elastomeric matrix. Significantly, however, in spite of the lower heats for hydrophobic solvation, the elastic modulus and the entropic elastomeric forces generated are greater in EG/H{sub 2}O.

  5. Modelling the self-assembly of elastomeric proteins provides insights into the evolution of their domain architectures.

    PubMed

    Song, Hongyan; Parkinson, John

    2012-01-01

    Elastomeric proteins have evolved independently multiple times through evolution. Produced as monomers, they self-assemble into polymeric structures that impart properties of stretch and recoil. They are composed of an alternating domain architecture of elastomeric domains interspersed with cross-linking elements. While the former provide the elasticity as well as help drive the assembly process, the latter serve to stabilise the polymer. Changes in the number and arrangement of the elastomeric and cross-linking regions have been shown to significantly impact their assembly and mechanical properties. However, to date, such studies are relatively limited. Here we present a theoretical study that examines the impact of domain architecture on polymer assembly and integrity. At the core of this study is a novel simulation environment that uses a model of diffusion limited aggregation to simulate the self-assembly of rod-like particles with alternating domain architectures. Applying the model to different domain architectures, we generate a variety of aggregates which are subsequently analysed by graph-theoretic metrics to predict their structural integrity. Our results show that the relative length and number of elastomeric and cross-linking domains can significantly impact the morphology and structural integrity of the resultant polymeric structure. For example, the most highly connected polymers were those constructed from asymmetric rods consisting of relatively large cross-linking elements interspersed with smaller elastomeric domains. In addition to providing insights into the evolution of elastomeric proteins, simulations such as those presented here may prove valuable for the tuneable design of new molecules that may be exploited as useful biomaterials. PMID:22396636

  6. Optical Manipulation of Shape-Morphing Elastomeric Liquid Crystal Microparticles Doped with Gold Nanocrystals

    SciTech Connect

    Sun, Y. R.; Evans, J. S.; Lee, T.; Senyuk, B.; Keller, P.; He, S. L.; Smalyukh, I. I.

    2012-06-11

    We demonstrate facile optical manipulation of shape of birefringent colloidal microparticles made from liquid crystal elastomers. Using soft lithography and polymerization, we fabricate elastomeric microcylinders with weakly undulating director oriented on average along their long axes. These particles are infiltrated with gold nanospheres acting as heat transducers that allow for an efficient localized transfer of heat from a focused infrared laser beam to a submicrometer region within a microparticle. Photothermal control of ordering in the liquid crystal elastomer using scanned beams allows for a robust control of colloidal particles, enabling both reversible and irreversible changes of shape. Possible applications include optomechanics, microfluidics, and reconfigurable colloidal composites with shape-dependent self-assembly.

  7. Non-aqueous emulsions stabilized by block copolymers: application to liquid disinfectant-filled elastomeric films.

    PubMed

    Riess, Gérard; Cheymol, André; Hoerner, Pierre; Krikorian, Raffi

    2004-05-20

    The emulsifying and stabilization efficiency of polybutadiene-b-poly(ethylene oxide) and poly(ter butylstyrene)-poly(ethylene oxide) diblock copolymers is examined in non-aqueous emulsions. These emulsions are formed by a dispersion of polyethylene glycol mixed with a cationic surfactant acting as a biocide, in a continuous phase of a thermoplastic elastomer (SEBS) dissolved in methylcyclohexane. Emulsions with controlled droplet size and excellent stability could be obtained, which by solvent evaporation lead to elastomeric films containing droplets of confined disinfecting liquids. PMID:15072927

  8. In vivo performance of a phospholipid-coated bioerodable elastomeric graft for small-diameter vascular applications

    PubMed Central

    Soletti, Lorenzo; Nieponice, Alejandro; Hong, Yi; Ye, Sang-Ho; Stankus, John J.; Wagner, William R.; Vorp, David A.

    2011-01-01

    There remains a great need for vascular substitutes for small-diameter applications. The use of an elastomeric biodegradable material, enabling acute antithrombogenicity and long-term in vivo remodeling, could be beneficial for this purpose. Conduits (1.3 mm internal diameter) were obtained by electrospinning biodegradable poly(ester urethane)urea (PEUU), and by luminally immobilizing a non-thrombogenic, 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer. Platelet adhesion was characterized in vitro after contact with ovine blood. The conduits were implanted as aortic interposition grafts in the rat for 4, 8, 12, and 24 weeks. Surface treatment resulted in a 10-fold decrease in platelet adhesion compared to untreated material. Patency at 8 weeks was 92% for the coated grafts compared to 40% for the non-coated grafts. Histology at 8 and 12 weeks demonstrated formation of cellularized neotissue consisting of aligned collagen and elastin. The lumen of the grafts was confluent with cells qualitatively aligned in the direction of blood flow. Immunohistochemistry suggested the presence of smooth muscle cells in the medial layer of the neotissue and endothelial cells lining the lumen. Mechanically, the grafts were less compliant than rat aortas prior to implantation (4.5 ± 2.0 × 10–4 mmHg–1 vs. 14.2 ± 1.1 × 10–4 mmHg–1, respectively), then after 4 weeks in vivo they approximated native values, but subsequently became stiffer again at later time points. The novel coated grafts exhibited promising antithrombogenic and mechanical properties for small-diameter arterial revascularization. Further evaluation in vivo will be required to demonstrate complete remodeling of the graft into a native-like artery. PMID:21171163

  9. Prediction of service lifetimes of elastomeric seals during radiation ageing

    NASA Astrophysics Data System (ADS)

    Burnay, S. G.; Hitchon, J. W.

    1985-04-01

    Measurements have been made on fluoropolymer seals of leakage rates, sealing force and compression set over a limited range of temperature and irradiation conditions to compare these techniques for their effectiveness in determining seal lifetimes. The results obtained indicate that the use of compression set tests in the routine assessment of seal performance is justified. Compression set measurements have been made on a polyurethane and a fluoropolymer over a range of temperature and radiation dose rates. The time-temperature superposition principle has been used to determine the thermal and dose rate shift factors aT, aR and activation energy Ea for both materials. Determination of the functional dependence of aT, aR and Ea on the dose rate enables realistic lifetime predictions to be made even when dose rate effects and temperature-radiation synergism are present.

  10. Biodegradabilite et proprietes energetiques d'elastomeres azotures

    NASA Astrophysics Data System (ADS)

    Lavoie, Jonathan

    The interest for polymer materials has steadily increased in the last decades and the use of polymer materials has been increasing ever since. These polymers are used in a vast range of applications from civil to military (Colclough et al., 1994; Nair & Laurencin, 2007; Sansone et al., 2012). This demand for polymer materials resulted in the development of various polymers with a wide range of properties depending on the desired application. In the field of propellants, this interest led to the development of glycidyl azide polymer (GAP) and other similar materials. Growing environmental concerns has led to a demand for more environmentally friendly polymers. This demand so far has been increasing and shows no sign of following a different trend for the next years. This demand is in part due to the presence of non-recyclable polymers, for which end of life can be problematic. At the same time, another problematic arose: the soil contamination originating from repeated military training as well as the subsequent contamination of water supplies by rain water seeping into the ground absorbing part of the contaminants (Dontsova, Pennington, Hayes, imunek, & Williford, 2009; M. R. Walsh, Thiboutot, Walsh, & Ampleman, 2012). This phenomenon incurs large decontamination costs and can result in the abandonment of training grounds due to contamination (Michael R. Walsh, Walsh, & Hewitt, 2010). The compounds responsible for the contamination of military training grounds are in part present in elastomers used as binders for propellants. The binders are non-biodegradable as well. In order to make greener propellants, it is not only necessary to replace the contaminants by non-contaminant materials, but also necessary to replace the binder by using new biodegradable materials. Glycidyl azide polymer, a commonly used energetic polymer in binders is non-biodebradable and as such unburned residue will accumulate in the environment. The main objective of this work is to develop new

  11. Towards development of lignin reinforced elastomeric compounds with reduced energy dissipation

    NASA Astrophysics Data System (ADS)

    Bahl, Kushal

    This research deals with development of lignin as reinforcing filler for elastomeric compounds. Lignins are naturally abundant and cost competitive wood derivatives possessing strong mechanical properties and offering reactive functional groups on their surfaces. The presence of the functional groups imparts polarity to the lignin molecules and makes them incompatible with non-polar elastomers. Also, the large particle size of lignin does not produce desired mechanical reinforcement. The present study deals with solving the outstanding issues associated with the use of lignin as fillers for polymeric compounds. In addition, the work specifically focuses on producing rubber compounds with reduced energy dissipation via partial replacement of carbon black with lignin. The first part of this study is devoted to suppression of the polarity of lignin and achievement of compatibility with rubber matrix via modification of lignosulfonates (LS) with cyclohexylamine (CA). CA reduces the polarity of lignin via interactions originating from proton transfer and hydrogen bonding. X-ray Photoelectron Spectroscopy (XPS) confirms the attachment of CA on the surfaces of lignin. The mechanical properties of rubber compounds increase substantially along with improvement in cure properties and increase in crosslink density in the presence of LS particles modified with CA. The tensile strength and storage modulus show an increase by 45% and 41% respectively. The values of the 100% modulus and elongation at break also improve by 35% and 60% respectively. The second part of this study exploits the non-covalent interactions between lignin and carbon black (CB) for the design of novel hybrid filler particles exhibiting lower energy loss in rubber compounds. The hybrid fillers offer unique morphology consisting of coating layers of lignin on carbon black particle aggregates. It is found that such coating layers are formed due to pi-pi interactions between lignin and carbon black. Raman

  12. Transient dynamic mechanical properties of resilin-based elastomeric hydrogels

    PubMed Central

    Li, Linqing; Kiick, Kristi L.

    2014-01-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (<15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

  13. Buckling of Dielectric Elastomeric Plates for Electrically Active Microfludic Pumps

    NASA Astrophysics Data System (ADS)

    Holmes, Douglas; Tavakol, Behrouz; Bozlar, Michael; Froehlicher, Guillaume; Stone, Howard; Aksay, Ilhan

    2013-11-01

    Fluid flow can be directed and controlled by a variety of mechanisms within industrial and biological environments. Advances in microfluidic technology have required innovative ways to control fluid flow on a small scale, and the ability to actively control fluid flow within microfluidic devices is crucial for advancements in nanofluidics, biomedical fluidic devices, and digital microfluidics. In this work, we present a means for microfluidic control via the electrical actuation of thin, flexible valves within microfluidic channels. These structures consist of a dielectric elastomer confined between two compliant electrodes that can be actively and reversibly buckle out of plane to pump fluids from an applied voltage. The out-of-plane deformation can be quantified using two parameters: net change in surface area and the shape of deformation. Change in surface area depends on the voltage, while the deformation shape, which significantly affects the flow rate, is a function of voltage, and the pressure and volume of the chambers on each side of the thin plate. The use of solid electrodes enables a robust and reversible pumping mechanism that will have will enable advancements in rapid microfluidic diagnostics, adaptive materials, and artificial muscles.

  14. Encoding Gaussian curvature in glassy and elastomeric liquid crystal solids

    PubMed Central

    Mostajeran, Cyrus; Ware, Taylor H.; White, Timothy J.

    2016-01-01

    We describe shape transitions of thin, solid nematic sheets with smooth, preprogrammed, in-plane director fields patterned across the surface causing spatially inhomogeneous local deformations. A metric description of the local deformations is used to study the intrinsic geometry of the resulting surfaces upon exposure to stimuli such as light and heat. We highlight specific patterns that encode constant Gaussian curvature of prescribed sign and magnitude. We present the first experimental results for such programmed solids, and they qualitatively support theory for both positive and negative Gaussian curvature morphing from flat sheets on stimulation by light or heat. We review logarithmic spiral patterns that generate cone/anti-cone surfaces, and introduce spiral director fields that encode non-localized positive and negative Gaussian curvature on punctured discs, including spherical caps and spherical spindles. Conditions are derived where these cap-like, photomechanically responsive regions can be anchored in inert substrates by designing solutions that ensure compatibility with the geometric constraints imposed by the surrounding media. This integration of such materials is a precondition for their exploitation in new devices. Finally, we consider the radial extension of such director fields to larger sheets using nematic textures defined on annular domains. PMID:27279777

  15. Interactions between sealing materials and lubricating oil additives

    SciTech Connect

    Winkenbach, R.; Von Arndt, E.M.; Mindermann, H.

    1987-01-01

    Due to the increasingly higher application demands, engine and transmission manufactures are today using lubrication oils with more and more additives. The result is that seal materials are being damaged when exposed to such conditions and such additives. This paper shows the effects of basic oils with, and without, additives on elastomeric materials such as NBR, ACM, MVQ and FPM.

  16. Roofing: Workbook and Tests. Common Roofing and Waterproofing Materials and Equipment.

    ERIC Educational Resources Information Center

    California State Dept. of Education, Sacramento. Bureau of Publications.

    This workbook on materials and equipment is one of a series of nine individual units of instruction for roofing apprenticeship classes in California. The workbook covers eight topics: production of bitumens and asphaltic roofing materials; built-up roofing materials and adhesives; asphaltic products and rigid roofing materials; elastomeric and…

  17. Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes

    PubMed Central

    Paek, Jungwook; Cho, Inho; Kim, Jaeyoun

    2015-01-01

    Microscale soft-robots hold great promise as safe handlers of delicate micro-objects but their wider adoption requires micro-actuators with greater efficiency and ease-of-fabrication. Here we present an elastomeric microtube-based pneumatic actuator that can be extended into a microrobotic tentacle. We establish a new, direct peeling-based technique for building long and thin, highly deformable microtubes and a semi-analytical model for their shape-engineering. Using them in combination, we amplify the microtube’s pneumatically-driven bending into multi-turn inward spiraling. The resulting micro-tentacle exhibit spiraling with the final radius as small as ~185 μm and grabbing force of ~0.78 mN, rendering itself ideal for non-damaging manipulation of soft, fragile micro-objects. This spiraling tentacle-based grabbing modality, the direct peeling-enabled elastomeric microtube fabrication technique, and the concept of microtube shape-engineering are all unprecedented and will enrich the field of soft-robotics. PMID:26066664

  18. Degradation of different elastomeric polymers in simulated geothermal environments at 300°C

    SciTech Connect

    Sugama, Toshifumi; Pyatina, Tatiana; Redline, Erica Marie; McElhanon, James R.; Blankenship, Douglas A.

    2015-07-17

    This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300 °C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO2-rich geo-brine fluid, and, 5) heat–cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus. The reliability of the O-rings to maintain their integrity depended on the elastomeric polymer composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This study discusses the degradation mechanisms of the polymers under the aforementioned conditions.

  19. A new UV-curing elastomeric substrate for rapid prototyping of microfluidic devices

    NASA Astrophysics Data System (ADS)

    Alvankarian, Jafar; Yeop Majlis, Burhanuddin

    2012-03-01

    Rapid prototyping in the design cycle of new microfluidic devices is very important for shortening time-to-market. Researchers are facing the challenge to explore new and suitable substrates with simple and efficient microfabrication techniques. In this paper, we introduce and characterize a UV-curing elastomeric polyurethane methacrylate (PUMA) for rapid prototyping of microfluidic devices. The swelling and solubility of PUMA in different chemicals is determined. Time-dependent measurements of water contact angle show that the native PUMA is hydrophilic without surface treatment. The current monitoring method is used for measurement of the electroosmotic flow mobility in the microchannels made from PUMA. The optical, physical, thermal and mechanical properties of PUMA are evaluated. The UV-lithography and molding process is used for making micropillars and deep channel microfluidic structures integrated to the supporting base layer. Spin coating is characterized for producing different layer thicknesses of PUMA resin. A device is fabricated and tested for examining the strength of different bonding techniques such as conformal, corona treating and semi-curing of two PUMA layers in microfluidic application and the results show that the bonding strengths are comparable to that of PDMS. We also report fabrication and testing of a three-layer multi inlet/outlet microfluidic device including a very effective fluidic interconnect for application demonstration of PUMA as a promising new substrate. A simple micro-device is developed and employed for observing the pressure deflection of membrane made from PUMA as a very effective elastomeric valve in microfluidic devices.

  20. Multi-stimuli-responsive elastomeric opal films: processing, optics, and applications

    NASA Astrophysics Data System (ADS)

    Schäfer, Christian G.; Gallei, Markus; Hellmann, Götz P.; Biesalski, Markus; Rehahn, Matthias

    2013-09-01

    A new strategy to build large-scale solvent-responsive elastomeric opal films that are candidates for a wide range of optical sensor applications is reported. Hard-soft core-interlayer-shell (CIS) beads were used to prepare paper-supported elastomeric opal films with remarkably distinct iridescent reflection colors. Extrusion and compression molding of the CIS beads directly on the top of a highly porous paper sheet followed by UV cross-linking led to polymer-paper composite films with a high tensile strength and an outstanding solvent resistivity. Due to the high porosity of the paper sheets used, these composites could be easily swollen by various solvents. The swelling changed the crystalline lattice of the opals which provoked a tremendous photonic band gap shift and also enhanced the brilliance of these colors. After deswelling, the original opal structure was totally restored which means that the shift of the photonic band gap was completely reversible. This approach can become the basis for a whole family of polymer-based soft sensors with a fascinating optical response.

  1. Locally-tailored structure of an elastomeric substrate for stretchable circuits

    NASA Astrophysics Data System (ADS)

    Park, Chan Woo; Jung, Soon Won; Na, Bock Soon; Oh, Ji-Young; Park, Nae-Man; Lee, Sang Seok; Bon Koo, Jae

    2016-02-01

    We demonstrate a new process for fabricating a hybrid elastomeric polydimethylsiloxane (PDMS) substrate, which can provide a high ratio (as large as ∼50) of the elastic modulus between the active device region and the interconnect area, as well as a locally tailored surface profile for each region. For this process, a Si master mold with a dual surface profile is prepared, where locally flat regions are distributed within a wavy-surfaced area. The stiffer elastomeric islands for active devices are formed on the flat regions by photolithography of a photo-patternable and hard PDMS layer (E ∼ 160 MPa), over which a soft PDMS layer (E ∼ 2 to 3 MPa) is casted. By releasing the whole PDMS layer from the mold, a hybrid silicone substrate with stiff and flat islands embedded within a soft and wavy matrix is obtained. In this hybrid structure, active devices located on the stiff regions can provide high reliability under stretched conditions, while most strain is accommodated by wavy interconnects within the soft area. Such beneficial effects are demonstrated by organic thin film transistors produced on the hybrid substrate.

  2. Optical fiber sensor for pressure measurement based on elastomeric membrane and macrobending loss

    NASA Astrophysics Data System (ADS)

    Ribeiro, Livia A.; Rosolem, Joao B.; Dini, Danilo C.; Floridia, Claudio; Bezerra, Edson W.; Cezar, Fabio A.; Loichate, Marcelo D.; Durelli, Anderson S.

    2012-04-01

    We propose a fiber optic sensor array based on bend loss assessed by optical time domain reflectometry (OTDR). The sensor mechanism is based on optical fiber bending loss compressed by external pressure. An elastomeric surface is applied to the sensor in order to communicate external pressure to the fiber coil and also, this make sensor able to deal with degradation coming from aggressive environments. The sensing system proposed is able to monitor liquid or gas pressure in different environments, such as water, oil, alcohols, some diluted acids and others, depending only of elastomeric membrane choice. In order to protect the sensor stage against environmental degradation a plastic packaging was chosen. Bend loss measurements is taken concerning the number of fiber loops involved in the sensor, pump signal wavelength and temporal width. This long for the best parameters in the sensor construction. The specific case of the sensor applied to water percolation monitoring from embankment damns is detailed in this paper; for this application the sensor array have a number of at least six stages totally independent each other, in such a way that each stage can be developed to monitor a specific environment. Sensors have shown good performance in field tests, reaching work range from 0.1 to 0.6 atm with 0.05 atm of precision.

  3. Regional anaesthesia elastomeric pump performance after a single use and subsequent refill: a laboratory study.

    PubMed

    Grant, C R K; Fredrickson, M J

    2009-07-01

    Ambulatory local anaesthetic delivery systems are often limited by a short effective duration of infusion. Prolonging nerve blockade by substituting a new pump as recommended by the manufacturers, represents a substantial consumable item cost ($US 300-500). We therefore evaluated the flow delivery performance of 31 single model elastomeric devices (all with a 2 ml.h(-1) background and 5 ml every hour bolus capability) that had been filled, used in clinical practice and then refilled in the laboratory. For the second infusion, there was a pattern of over-infusion (< 10 ml.h(-1)) in the first hour; however, all pumps depreciated to < 150% of predicted by the second hour. The subsequent performance of all pumps was not only within safe limits, but also predominantly within the range (background infusion +/- 15%, bolus +10/-20%) specified by the manufacturer for primary infusion. We conclude that this elastomeric regional anaesthesia pump design performs satisfactorily after having been refilled following a single previous use. PMID:19624633

  4. Evaluation of a disposable, elastomeric infusion device in the home environment.

    PubMed

    Rich, D S

    1992-07-01

    The use of a disposable, elastomeric infusion device was evaluated in 55 patients receiving home antimicrobial therapy. During a 30-day period, all patients referred to five service centers to receive home antimicrobial therapy for at least one week were enrolled in the study. Pharmacists used an automated pump to fill 110-mL, 100-mL/hr elastomeric devices (Homepump; Block Medical, Carlsbad, CA). Nurses trained patients to use the device. Nurses and pharmacists completed an evaluation form for each patient. Fifty-five patients received a total of 1938 doses; a fresh device was used to administer each dose. Nurses described patient teaching for the device as easy (51) or no different from that for other devices (4). Patient acceptance was reported to be good in 54 patients and poor in 1 patient. A total of 91 restarts were required; 36 patients needed more than one restart. The failure rate of the device was 1.6%; 25 of 44 reported problems occurred in devices that were frozen and thawed before use. The Homepump was determined to be an acceptable device for the intermittent infusion of small-volume antimicrobial solutions in the home environment because of its low failure rate and high degree of patient and nursing preference; its drawbacks include high cost and slowed infusion rates for units that are not thawed properly after freezing. PMID:1621729

  5. A highly sensitive and flexible pressure sensor with electrodes and elastomeric interlayer containing silver nanowires.

    PubMed

    Wang, Jun; Jiu, Jinting; Nogi, Masaya; Sugahara, Tohru; Nagao, Shijo; Koga, Hirotaka; He, Peng; Suganuma, Katsuaki

    2015-02-21

    The next-generation application of pressure sensors is gradually being extended to include electronic artificial skin (e-skin), wearable devices, humanoid robotics and smart prosthetics. In these advanced applications, high sensing capability is an essential feature for high performance. Although surface patterning treatments and some special elastomeric interlayers have been applied to improve sensitivity, the process is complex and this inevitably raises the cost and is an obstacle to large-scale production. In the present study a simple printing process without complex patterning has been used for constructing the sensor, and an interlayer is employed comprising elastomeric composites filled with silver nanowires. By increasing the relative permittivity, εr, of the composite interlayer induced by compression at high nanowire concentration, it has been possible to achieve a maximum sensitivity of 5.54 kPa(-1). The improvement in sensitivity did not sacrifice or undermine the other features of the sensor. Thanks to the silver nanowire electrodes, the sensor is flexible and stable after 200 cycles at a bending radius of 2 mm, and exhibits outstanding reproducibility without hysteresis under similar pressure pulses. The sensor has been readily integrated onto an adhesive bandage and has been successful in detecting human movements. In addition to measuring pressure in direct contact, non-contact pressures such as air flow can also be detected. PMID:25588044

  6. In situ mechanical characterization of square microfabricated elastomeric membranes using an improved microindentation

    NASA Astrophysics Data System (ADS)

    Liu, Kuo-Kang; Khoo, Hwa Seng; Tseng, Fan-Gang

    2004-02-01

    A testing method has been developed for in situ mechanical characterizations of square microfabricated elastomeric membranes, using a tailored microindentation instrument. Such a depth-sensing microindentation system, incorporated with a long-focal microscope for capturing the side view image, provides accurate load-displacement measurements and complete profiles of deformed membranes. The deformations of square silicon rubber membranes with various thicknesses were examined under different degrees of external central microindentation forces. These membranes were integrated and supported by SU-8 photoresist frames, with openings of 2 mm×2 mm. A theoretical model was applied to quantitatively correlate the membrane elasticity to the measured compliance under such indentation. Through comparing the simulated and experimental results, the average values of Young's modulus for these membranes were reasonably extracted and determined. Viscoelasticity of the membranes used was acknowledged; however, it showed no significant effect on the determination of the Young's modulus of the membranes in the current work. The good agreement between the experimental results and the theoretical analyses demonstrates the successful in situ mechanical characterizations of microfabricated elastomeric films, particularly for the square shape membrane, which is the most common structure or component for microfabricated devices.

  7. Elastomeric nanocomposite scaffolds made from poly (glycerol sebacate) chemically crosslinked with carbon nanotubes

    PubMed Central

    Patel, Alpesh; Dolatshahi-Pirouz, Alireza; Zhang, Hongbin; Rangarajan, Kaushik; Iviglia, Giorgio; Shin, Su-Ryon; Hussain, Mohammad Asif

    2015-01-01

    Carbon nanotube (CNT)-based nanocomposites often possess properties such as high stiffness, electrical conductivity, and thermal stability and have been studied for various biomedical and biotechnological applications. However, the current design approaches utilize CNTs as physical filler, and thus, the true potential of CNT-based nanocomposites has not been achieved. Here, we introduce a general approach of fabricating stiff, elastomeric nanocomposites from poly(glycerol sebacate) (PGS) and CNTs. The covalent crosslinking between the nanotubes and polymer chains resulted in novel property combinations that are not observed in conventional nanocomposites. The addition of 1% CNTs resulted a five-fold increase in the tensile modulus and a six-fold increase in compression modulus compared with PGS alone, which is far superior to the previously reported studies for CNT-based nanocomposites. Despite significant increase in mechanical stiffness, the elasticity of the network was not compromised and the resulting nanocomposites showed more than 94% recovery. This study demonstrates that the chemical conjugation of CNTs to a PGS backbone results in stiff and elastomeric nanocomposites. Additionally, in vitro studies using human mesenchymal stem cells (hMSCs) indicated that the incorporation of CNTs to PGS network significantly enhanced the differentiation potential of the seeded hMSCs rendering them potentially suitable for applications ranging from scaffolding in musculoskeletal tissue engineering to biosensors in biomedical devices. PMID:26146547

  8. Degradation of different elastomeric polymers in simulated geothermal environments at 300°C

    DOE PAGESBeta

    Sugama, Toshifumi; Pyatina, Tatiana; Redline, Erica Marie; McElhanon, James R.; Blankenship, Douglas A.

    2015-07-17

    This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300 °C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO2-rich geo-brine fluid, and, 5) heat–cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus. The reliability of the O-rings to maintain their integrity depended on the elastomeric polymermore » composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This study discusses the degradation mechanisms of the polymers under the aforementioned conditions.« less

  9. Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes.

    PubMed

    Paek, Jungwook; Cho, Inho; Kim, Jaeyoun

    2015-01-01

    Microscale soft-robots hold great promise as safe handlers of delicate micro-objects but their wider adoption requires micro-actuators with greater efficiency and ease-of-fabrication. Here we present an elastomeric microtube-based pneumatic actuator that can be extended into a microrobotic tentacle. We establish a new, direct peeling-based technique for building long and thin, highly deformable microtubes and a semi-analytical model for their shape-engineering. Using them in combination, we amplify the microtube's pneumatically-driven bending into multi-turn inward spiraling. The resulting micro-tentacle exhibit spiraling with the final radius as small as ~185 μm and grabbing force of ~0.78 mN, rendering itself ideal for non-damaging manipulation of soft, fragile micro-objects. This spiraling tentacle-based grabbing modality, the direct peeling-enabled elastomeric microtube fabrication technique, and the concept of microtube shape-engineering are all unprecedented and will enrich the field of soft-robotics. PMID:26066664

  10. Highly stretchable electric circuits from a composite material of silver nanoparticles and elastomeric fibres

    NASA Astrophysics Data System (ADS)

    Park, Minwoo; Im, Jungkyun; Shin, Minkwan; Min, Yuho; Park, Jaeyoon; Cho, Heesook; Park, Soojin; Shim, Mun-Bo; Jeon, Sanghun; Chung, Dae-Young; Bae, Jihyun; Park, Jongjin; Jeong, Unyong; Kim, Kinam

    2012-12-01

    Conductive electrodes and electric circuits that can remain active and electrically stable under large mechanical deformations are highly desirable for applications such as flexible displays, field-effect transistors, energy-related devices, smart clothing and actuators. However, high conductivity and stretchability seem to be mutually exclusive parameters. The most promising solution to this problem has been to use one-dimensional nanostructures such as carbon nanotubes and metal nanowires coated on a stretchable fabric, metal stripes with a wavy geometry, composite elastomers embedding conductive fillers and interpenetrating networks of a liquid metal and rubber. At present, the conductivity values at large strains remain too low to satisfy requirements for practical applications. Moreover, the ability to make arbitrary patterns over large areas is also desirable. Here, we introduce a conductive composite mat of silver nanoparticles and rubber fibres that allows the formation of highly stretchable circuits through a fabrication process that is compatible with any substrate and scalable for large-area applications. A silver nanoparticle precursor is absorbed in electrospun poly (styrene-block-butadiene-block-styrene) (SBS) rubber fibres and then converted into silver nanoparticles directly in the fibre mat. Percolation of the silver nanoparticles inside the fibres leads to a high bulk conductivity, which is preserved at large deformations (σ ~ 2,200 S cm-1 at 100% strain for a 150-µm-thick mat). We design electric circuits directly on the electrospun fibre mat by nozzle printing, inkjet printing and spray printing of the precursor solution and fabricate a highly stretchable antenna, a strain sensor and a highly stretchable light-emitting diode as examples of applications.

  11. Highly stretchable electric circuits from a composite material of silver nanoparticles and elastomeric fibres.

    PubMed

    Park, Minwoo; Im, Jungkyun; Shin, Minkwan; Min, Yuho; Park, Jaeyoon; Cho, Heesook; Park, Soojin; Shim, Mun-Bo; Jeon, Sanghun; Chung, Dae-Young; Bae, Jihyun; Park, Jongjin; Jeong, Unyong; Kim, Kinam

    2012-12-01

    Conductive electrodes and electric circuits that can remain active and electrically stable under large mechanical deformations are highly desirable for applications such as flexible displays, field-effect transistors, energy-related devices, smart clothing and actuators. However, high conductivity and stretchability seem to be mutually exclusive parameters. The most promising solution to this problem has been to use one-dimensional nanostructures such as carbon nanotubes and metal nanowires coated on a stretchable fabric, metal stripes with a wavy geometry, composite elastomers embedding conductive fillers and interpenetrating networks of a liquid metal and rubber. At present, the conductivity values at large strains remain too low to satisfy requirements for practical applications. Moreover, the ability to make arbitrary patterns over large areas is also desirable. Here, we introduce a conductive composite mat of silver nanoparticles and rubber fibres that allows the formation of highly stretchable circuits through a fabrication process that is compatible with any substrate and scalable for large-area applications. A silver nanoparticle precursor is absorbed in electrospun poly (styrene-block-butadiene-block-styrene) (SBS) rubber fibres and then converted into silver nanoparticles directly in the fibre mat. Percolation of the silver nanoparticles inside the fibres leads to a high bulk conductivity, which is preserved at large deformations (σ ≈ 2,200 S cm(-1) at 100% strain for a 150-µm-thick mat). We design electric circuits directly on the electrospun fibre mat by nozzle printing, inkjet printing and spray printing of the precursor solution and fabricate a highly stretchable antenna, a strain sensor and a highly stretchable light-emitting diode as examples of applications. PMID:23178335

  12. 76 FR 13434 - In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-11

    ... supplemented, of ] Interactive Life Forms, LLC of Austin, Texas (``ILF''). 75 FR 47027 (Aug. 4, 2010). The... add two respondents and correct the identification of two original respondents. 75 FR 64742 (Oct. 20... COMMISSION In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...

  13. Development of a low-cost, modified resin transfer molding process using elastomeric tooling and automated preform fabrication

    NASA Technical Reports Server (NTRS)

    Doane, William J.; Hall, Ronald G.

    1992-01-01

    This paper describes the design and process development of low-cost structural parts made by a modified resin transfer molding process. Innovative application of elastomeric tooling to increase laminate fiber volume and automated forming of fiber preforms are discussed, as applied to fabrication of a representative section of a cruise missile fuselage.

  14. Semicarbazide is a minor thermal decomposition product of azodicarbonamide used in the gaskets of certain food jars.

    PubMed

    Stadler, Richard H; Mottier, Pascal; Guy, Philippe; Gremaud, Eric; Varga, Natalia; Lalljie, Sam; Whitaker, Richard; Kintscher, Jurgen; Dudler, Vincent; Read, Wendy A; Castle, Laurence

    2004-03-01

    Evidence is presented for the first time showing that semicarbazide (SEM) is a minor thermal decomposition product of the blowing agent azodicarbonamide (ADC). A novel direct analytical method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) has been developed to determine SEM in foamed polyvinyl chloride (PVC) seals of metal lids, as well as in commercially available ADC. The direct LC-MS/MS method for gaskets entails extraction of the gaskets in hot water, addition of ((15)N(2)(13)C)-SEM as internal standard, and injection of an aliquot directly into the LC-MS system, achieving good sensitivity (S/N = 348 for 2 ng injected on-column) and monitoring three characteristic mass transitions (m/z 76-->31; 76 -->44; 76-->59). Semicarbazide can be detected in thermally treated ADC, reaching up to 0.93 mmol mol(-1) at 220 degrees C, as determined by the direct LC-MS/MS method. This new method is also compared to the classical derivatization method using 2-nitrobenzaldehyde (2-NBA) that is routinely employed to determine SEM as an indicator of the usage of the antimicrobial drug nitrofurazone, the use of which is not authorized in the European Union (EU). Both methods revealed proportional results, with approx. 3-fold higher levels recorded by the direct SEM approach, probably due to differences in the extraction procedures used. A limited survey of plastic seals from used press twist and twist-off metal lids on food jars (non-foamed and foamed) revealed levels of SEM ranging from 2 to 8689 microg kg(-1)(average = 1593 microg kg(-1), n= 57 determinations). PMID:14978533

  15. Molecular modeling of the elastomeric properties of repeating units and building blocks of resilin, a disordered elastic protein.

    PubMed

    Khandaker, Md Shahriar K; Dudek, Daniel M; Beers, Eric P; Dillard, David A; Bevan, David R

    2016-08-01

    The mechanisms responsible for the properties of disordered elastomeric proteins are not well known. To better understand the relationship between elastomeric behavior and amino acid sequence, we investigated resilin, a disordered rubber-like protein, found in specialized regions of the cuticle of insects. Resilin of Drosophila melanogaster contains Gly-rich repetitive motifs comprised of the amino acids, PSSSYGAPGGGNGGR, which confer elastic properties to resilin. The repetitive motifs of insect resilin can be divided into smaller partially conserved building blocks: PSS, SYGAP, GGGN and GGR. Using molecular dynamics (MD) simulations, we studied the relative roles of SYGAP, and its less common variants SYSAP and TYGAP, on the elastomeric properties of resilin. Results showed that SYGAP adopts a bent structure that is one-half to one-third the end-to-end length of the other motifs having an equal number of amino acids but containing SYSAP or TYGAP substituted for SYGAP. The bent structure of SYGAP forms due to conformational freedom of glycine, and hydrogen bonding within the motif apparently plays a role in maintaining this conformation. These structural features of SYGAP result in higher extensibility compared to other motifs, which may contribute to elastic properties at the macroscopic level. Overall, the results are consistent with a role for the SYGAP building block in the elastomeric properties of these disordered proteins. What we learned from simulating the repetitive motifs of resilin may be applicable to the biology and mechanics of other elastomeric biomaterials, and may provide us the deeper understanding of their unique properties. PMID:26851528

  16. Properties of aircraft tire materials

    NASA Technical Reports Server (NTRS)

    Dodge, Richard N.; Clark, Samuel K.

    1988-01-01

    A summary is presented of measured elastomeric composite response suitable for linear structural and thermoelastic analysis in aircraft tires. Both real and loss properties are presented for a variety of operating conditions including the effects of temperature and frequency. Suitable micro-mechanics models are used for predictions of these properties for other material combinations and the applicability of laminate theory is discussed relative to measured values.

  17. Caracterisation de l'effet du vieillissement en milieu aqueux sur les proprietes mecaniques de composites a matrice elastomere

    NASA Astrophysics Data System (ADS)

    Favre, Audrey

    Rubber composites are widely used in several engineering fields, such as automotive, and more recently for inflatable dams and other innovative underwater applications. These rubber materials are composed by an elastomeric matrix while the reinforcing phase is a synthetic fabric. Since these components are expected to operate several years in water environment, their durability must be guaranteed. The use of rubber materials immersed in water is not new, in fact, these materials have been studied for almost one century. However, the knowledge on reinforced rubber composites immersed several years in water is still limited. In this work, investigations on reinforced rubbers were carried out in the framework of a research project in partnership with Alstom and Hydro-Quebec. The objective of this study was to identify rubber composites that could be used under water for long periods. Various rubber composites with ethylene-propylene-diene monomer (EPDM), silicone, EPDM/silicone and polychloroprene (Neoprene) matrices reinforced with E-glass fabric were studied. Thus, these materials were exposed to an accelerated ageing at 85 °C underwater for periods varying from 14 to 365 days. For comparison purposes, they were also immersed and aged one year at room temperature (21 °C). The impact of accelerated aging was estimated through three different characterization methods. Scanning electron microscopy (SEM) was first used to assess the quality of fiber-matrix interface. Then, water absorption tests were performed to quantify the rate of water absorption during immersion. Finally the evolution of the mechanical properties was followed by the determination of Young's modulus (E) and ultimate stress (sigmau) using a dedicated traction test. This analysis allowed to point out that the quality of the fiber-matrix interface was the main factor influencing the drop of the mechanical properties and their durability. Moreover, it was noticed that this interface could be improved

  18. Elastomeric Capture Microparticles (ECmuPs) and Their use with Acoustophoresis to Perform Affinity Capture Assays

    NASA Astrophysics Data System (ADS)

    Cushing, Kevin Wallace

    This dissertation describes the development of elastomeric capture microparticles (ECmicroPs) and their use with acoustophoresis to perform affinity capture assays. ECμPs that function as negative acoustic contrast particles were developed by crosslinking emulsion-based droplets composed of commercially available silicone precursors followed by functionalization with avidin/biotin reagents. The size distribution of the ECμPs was very broad or narrow depending on the emulsion system that was used during the synthesis process. Elastomeric particles exhibited a very broad size distribution when a bulk-emulsion process was used; however, when microfluidic systems were utilized, their size distribution became comparatively narrow. The functionalization of elastomeric particles was accomplished by the non-specific adsorption of avidin protein followed by bovine serum albumin (BSA) blocking and bio-specific adsorption of a biotinylated-capture antibody. Polydisperse ECμPs were functionalized to bind prostate specific antigen (PSA) or IgG-phycoerythrin (PE) in aqueous media (buffer, plasma, blood); whereas monodisperse ECμPs were functionalized to bind a high density lipoprotein in the aqueous media. Polydisperse ECμPs functionalized to bind PSA in a physiological buffer (PBS pH 7.4) demonstrated nanomolar detection using flow cytometry analysis; whereas ECμPs functionalized to bind IgG-PE demonstrated picomolar detection in 10% porcine plasma. ECμPs have a specific density of ~1.03 and are more compressible than their surrounding aqueous media; which allowed the ECμPs to exhibit negative acoustic contrast properties under an ultrasonic acoustic standing wave field. The negative acoustic contrast property of ECμPs was advantageously utilized in an IgG-PE assay conducted in 0.1% whole porcine blood. The ligand-bound ECμPs suspended in the diluted blood sample were flowed through an acoustofluidic device where the application of an ultrasonic acoustic standing wave

  19. Post-buckling analysis for the precisely controlled buckling of thin film encapsulated by elastomeric subsrates.

    SciTech Connect

    Jiang, H.; Sun, Y.; Rogers, J. A.; Huang, Y.; Arizona State Univ.; Univ. of Illinois; Northwestern Univ.

    2008-04-01

    The precisely controlled buckling of stiff thin films (e.g., Si or GaAs nano ribbons) on the patterned surface of elastomeric substrate (e.g., poly(dimethylsiloxane) (PDMS)) with periodic inactivated and activated regions was designed by Sun et al. [Sun, Y., Choi, W.M., Jiang, H., Huang, Y.Y., Rogers, J.A., 2006. Controlled buckling of semiconductor nanoribbons for stretchable electronics. Nature Nanotechnology 1, 201-207] for important applications of stretchable electronics. We have developed a post-buckling model based on the energy method for the precisely controlled buckling to study the system stretchability. The results agree with Sun et al.'s (2006) experiments without any parameter fitting, and the system can reach 120% stretchability.

  20. A highly sensitive and flexible pressure sensor with electrodes and elastomeric interlayer containing silver nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Jiu, Jinting; Nogi, Masaya; Sugahara, Tohru; Nagao, Shijo; Koga, Hirotaka; He, Peng; Suganuma, Katsuaki

    2015-02-01

    The next-generation application of pressure sensors is gradually being extended to include electronic artificial skin (e-skin), wearable devices, humanoid robotics and smart prosthetics. In these advanced applications, high sensing capability is an essential feature for high performance. Although surface patterning treatments and some special elastomeric interlayers have been applied to improve sensitivity, the process is complex and this inevitably raises the cost and is an obstacle to large-scale production. In the present study a simple printing process without complex patterning has been used for constructing the sensor, and an interlayer is employed comprising elastomeric composites filled with silver nanowires. By increasing the relative permittivity, εr, of the composite interlayer induced by compression at high nanowire concentration, it has been possible to achieve a maximum sensitivity of 5.54 kPa-1. The improvement in sensitivity did not sacrifice or undermine the other features of the sensor. Thanks to the silver nanowire electrodes, the sensor is flexible and stable after 200 cycles at a bending radius of 2 mm, and exhibits outstanding reproducibility without hysteresis under similar pressure pulses. The sensor has been readily integrated onto an adhesive bandage and has been successful in detecting human movements. In addition to measuring pressure in direct contact, non-contact pressures such as air flow can also be detected.The next-generation application of pressure sensors is gradually being extended to include electronic artificial skin (e-skin), wearable devices, humanoid robotics and smart prosthetics. In these advanced applications, high sensing capability is an essential feature for high performance. Although surface patterning treatments and some special elastomeric interlayers have been applied to improve sensitivity, the process is complex and this inevitably raises the cost and is an obstacle to large-scale production. In the present

  1. Transition to an elastomeric infusion pump in home care: an evidence-based approach.

    PubMed

    Broadhurst, Daphne

    2012-01-01

    A fatal overdose of a chemotherapeutic agent delivered to a patient via an electronic infusion device served as a stark reminder of the risks that infusion therapy poses to patients and health care providers and as the impetus for a strategy to optimize safe and efficient delivery of home infusion therapy. The Academic Center for Evidence-Based Practice Star Model of Knowledge Transformation was used as the evidence-based framework for the implementation of a portable infusion pump that supports home infusion of high-risk medications, leading to increased patient and caregiver satisfaction. Evaluation of this implementation supports the use of an elastomeric infusion device for a high-risk therapy. PMID:22498484

  2. Elastomeric Polymer Multilayer Thin Film with Sustainable Gas Barrier at High Strain.

    PubMed

    Xiang, Fangming; Givens, Tara M; Ward, Sarah M; Grunlan, Jaime C

    2015-08-01

    Most gas barrier thin films suffer from cracking or plastic deformation when stretched, leading to significant loss of barrier. In an effort to make a stretchable gas barrier, which maintains low permeability when exposed to cyclic strain, we prepared layer-by-layer assemblies of tannic acid (TA) and poly(ethylene oxide) (PEO). A 40-bilayer (344 nm-thick) TA/PEO assembly maintained its oxygen transmission rate (6X lower than the 1.6 mm-thick rubber substrate) after being stretched 100%. This submicron coating maintains a barrier 4X lower than the thick rubber substrate even after being strained 20X at 100%. These highly elastomeric assemblies are potentially useful for light-weighting inflatable devices. PMID:26196671

  3. Printing transferable components using microstructured elastomeric surfaces with pressure modulated reversible adhesion

    DOEpatents

    Menard, Etienne; Rogers, John A.; Kim, Seok; Carlson, Andrew

    2016-08-09

    In a method of printing a transferable component, a stamp including an elastomeric post having three-dimensional relief features protruding from a surface thereof is pressed against a component on a donor substrate with a first pressure that is sufficient to mechanically deform the relief features and a region of the post between the relief features to contact the component over a first contact area. The stamp is retracted from the donor substrate such that the component is adhered to the stamp. The stamp including the component adhered thereto is pressed against a receiving substrate with a second pressure that is less than the first pressure to contact the component over a second contact area that is smaller than the first contact area. The stamp is then retracted from the receiving substrate to delaminate the component from the stamp and print the component onto the receiving substrate. Related apparatus and stamps are also discussed.

  4. A rheology model of soft elastomeric capacitor for Weigh-In-Motion application

    NASA Astrophysics Data System (ADS)

    Kollipara, Venkata Dharmateja

    As a result of fast growing industry, there is an increase in traffic congestion and deterioration of transportation inventory. Real-time traffic characterisation could be used to amoliorate the efficiency of our transportation system. Weigh-In-Motion (WIM) systems offer the advantages of vehicle classification, speed measurement, in addition to weight measurement while vehicles are moving. In this thesis, state-of-the-art WIM systems are discussed and limitations of current technologies are identified. A Soft Elastomeric Capacitor (SEC) that works as a large scale surface strain gauge is introduced to address the limitations in existing techniques and investigated for its applicability as a WIM sensor. Though the novel SEC has potential advantages, the relationship axial strain-to-stress needs to be modeled to enable its utilization as a WIM sensor. A Zener model is selected and modified by the addition of a slider to characterize the polymer behavior. An overstress approach is used to study the resultant stress-strain response owing to its simplicity and computational benefits. Since the overstress approach is data-driven, an experimental testing scheme is used to identify the model parameters. The tests comprise three types of applied strain loading: multi step relaxation, simple relaxation and cyclic compression. Specimens with varying stiffness are employed for these tests. Numerical simulations for the cyclic compression loading are presented to assess the model performance. The model is found to be capable of reproducing the experimental data with an absolute maximum error value of 0.085 MPa for slow loading rate tests and 0.175 MPa for high loading rate tests. Comparative studies are completed to investigate the impact of patch stiffness on the mechanical behavior of the soft elastomeric capacitor patches. It is observed that as stiffness decreases, the nonlinearity in stress-strain response increases

  5. Radiation data definitions and compilation for equipment qualification data bank

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.; Winslow, J. W.

    1986-01-01

    Dose definitions, physical properties, mechanical properties, electrical properties, and particle definitions are listed for insulators and dielectrics, elastomeric seals and gaskets, lubricants, adhesives, and coatings.

  6. 46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Hatchways closed by weathertight covers of steel or... Conditions of Assignment of Freeboard § 42.15-30 Hatchways closed by weathertight covers of steel or other... height above the deck of hatchway coamings fitted with weathertight hatch covers of steel or...

  7. 46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Hatchways closed by weathertight covers of steel or... Conditions of Assignment of Freeboard § 42.15-30 Hatchways closed by weathertight covers of steel or other... height above the deck of hatchway coamings fitted with weathertight hatch covers of steel or...

  8. 46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Hatchways closed by weathertight covers of steel or... Conditions of Assignment of Freeboard § 42.15-30 Hatchways closed by weathertight covers of steel or other... height above the deck of hatchway coamings fitted with weathertight hatch covers of steel or...

  9. Correlation of elastomer material properties from small specimen tests and scale-size bearing tests

    SciTech Connect

    Kulak, R.F.; Hughes, T.H.

    1994-06-01

    Tests were performed on small-size elastomer specimens and scale-size laminated elastomeric bearings to correlate the material properties in shear between the two types of tests. An objective of the tests was to see how well the material properties that were determined from specimen tests could predict the response of scale-size laminated elastomeric bearings. Another objective was to compare the results of specimen test and scale-size bearing test conducted by different testing organizations. A comparison between the test results from different organizations on small specimens showed very good agreement. In contrast, the correlation of scale-size bearing tests showed differences in bearing stiffness.

  10. An Effective Lift-Off Method for Patterning High-Density Gold Interconnects on an Elastomeric Substrate**

    PubMed Central

    Guo, Liang; DeWeerth, Stephen P.

    2012-01-01

    High-resolution, high-density gold interconnects are effectively patterned on an elastomeric substrate. A 3cm cable of ten gold wires with 10μm width and 20μm pitch is achieved, successfully demonstrating density increases of more than one order of magnitude from previously established work. Many applications in the fields of stretchable electronics and conformable neural interfaces will benefit from these fabrication developments. PMID:21104803

  11. Compilation of current literature on seals, closures, and leakage for radioactive material packagings

    SciTech Connect

    Warrant, M.M.; Ottinger, C.A.

    1989-01-01

    This report presents an overview of the features that affect the sealing capability of radioactive material packagings currently certified by the US Nuclear Regulatory Commission. The report is based on a review of current literature on seals, closures, and leakage for radioactive material packagings. Federal regulations that relate to the sealing capability of radioactive material packagings, as well as basic equations for leakage calculations and some of the available leakage test procedures are presented. The factors which affect the sealing capability of a closure, including the properties of the sealing surfaces, the gasket material, the closure method and the contents are discussed in qualitative terms. Information on the general properties of both elastomer and metal gasket materials and some specific designs are presented. A summary of the seal material, closure method, and leakage tests for currently certified packagings with large diameter seals is provided. 18 figs., 9 tabs.

  12. Highly Sensitive, Flexible, and Wearable Pressure Sensor Based on a Giant Piezocapacitive Effect of Three-Dimensional Microporous Elastomeric Dielectric Layer.

    PubMed

    Kwon, Donguk; Lee, Tae-Ik; Shim, Jongmin; Ryu, Seunghwa; Kim, Min Seong; Kim, Seunghwan; Kim, Taek-Soo; Park, Inkyu

    2016-07-01

    We report a flexible and wearable pressure sensor based on the giant piezocapacitive effect of a three-dimensional (3-D) microporous dielectric elastomer, which is capable of highly sensitive and stable pressure sensing over a large tactile pressure range. Due to the presence of micropores within the elastomeric dielectric layer, our piezocapacitive pressure sensor is highly deformable by even very small amounts of pressure, leading to a dramatic increase in its sensitivity. Moreover, the gradual closure of micropores under compression increases the effective dielectric constant, thereby further enhancing the sensitivity of the sensor. The 3-D microporous dielectric layer with serially stacked springs of elastomer bridges can cover a much wider pressure range than those of previously reported micro-/nanostructured sensing materials. We also investigate the applicability of our sensor to wearable pressure-sensing devices as an electronic pressure-sensing skin in robotic fingers as well as a bandage-type pressure-sensing device for pulse monitoring at the human wrist. Finally, we demonstrate a pressure sensor array pad for the recognition of spatially distributed pressure information on a plane. Our sensor, with its excellent pressure-sensing performance, marks the realization of a true tactile pressure sensor presenting highly sensitive responses to the entire tactile pressure range, from ultralow-force detection to high weights generated by human activity. PMID:27286001

  13. n-Propylpyridinium chloride-modified poly(dimethylsiloxane) elastomeric networks: preparation, characterization, and study of metal chloride adsorption from ethanol solutions.

    PubMed

    Pissetti, Fábio L; Magosso, Herica A; Yoshida, Inez V P; Gushikem, Yoshitaka; Myernyi, Sergiy O; Kholin, Yuriy V

    2007-10-01

    An n-propylpyridinium chloride-modified PDMS elastomeric network, PDMS/Py(+)Cl(-), was prepared from linear PDMS chains containing Si(CH(3))(2)OH end-groups cross-linked by 3-chloropropyltrimethoxysilane and posterior reaction with pyridine. PDMS/Py(+)Cl(-) material was structurally characterized by infrared spectroscopy (IR) and solid state (13)C and (29)Si NMR. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 450 K. The ion-exchange capacity of the PDMS/Py(+)Cl(-) was 0.65 mmol g(-1). Metal halides, MCl(z) [M=Fe(3+), Cu(2+), and Co(2+)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes MCl(z+n)(n-). The nature of the anionic complex structure was proposed by UV-vis diffuse reflectance spectra. The species adsorbed were FeCl(-)(4), CuCl(2-)(4), and CoCl(2-)(4). The specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. The trend in affinities of PDMS/Py(+)Cl(-) for the metal halides were found to be FeCl(3)>CuCl(2) approximately CoCl(2). PMID:17582428

  14. An Overview of Advanced Elastomeric Seal Development and Testing Capabilities at NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Dunlap, Patrick H., Jr.

    2014-01-01

    NASA is developing advanced space-rated elastomeric seals to support future space exploration missions to low Earth orbit, the Moon, near Earth asteroids, and other destinations. This includes seals for a new docking system and vehicle hatches. These seals must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them, and seal adhesion forces must be low to allow the sealed interface to be separated when required (e.g., during undocking or hatch opening). NASA Glenn Research Center has developed a number of unique test fixtures to measure the leak rates and compression and adhesion loads of candidate seal designs under simulated thermal, vacuum, and engagement conditions. Tests can be performed on full-scale seals with diameters on the order of 50 in., subscale seals that are about 12 in. in diameter, and smaller specimens such as O-rings. Test conditions include temperatures ranging from -238 to +662F (-150 to +350C), operational pressure gradients, and seal-on-seal or seal-on-flange mating configurations. Nominal and off-nominal conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features and capabilities of each test apparatus and provides an overview of advanced seal development activities at NASA Glenn.

  15. Fabrication of elastomeric scaffolds with curvilinear fibrous structures for heart valve leaflet engineering.

    PubMed

    Hobson, Christopher M; Amoroso, Nicholas J; Amini, Rouzbeh; Ungchusri, Ethan; Hong, Yi; D'Amore, Antonio; Sacks, Michael S; Wagner, William R

    2015-09-01

    Native semi-lunar heart valves are composed of a dense fibrous network that generally follows a curvilinear path along the width of the leaflet. Recent models of engineered valve leaflets have predicted that such curvilinear fiber orientations would homogenize the strain field and reduce stress concentrations at the commissure. In the present work, a method was developed to reproduce this curvilinear fiber alignment in electrospun scaffolds by varying the geometry of the collecting mandrel. Elastomeric poly(ester urethane)urea was electrospun onto rotating conical mandrels of varying angles to produce fibrous scaffolds where the angle of fiber alignment varied linearly over scaffold length. By matching the radius of the conical mandrel to the radius of curvature for the native pulmonary valve, the electrospun constructs exhibited a curvilinear fiber structure similar to the native leaflet. Moreover, the constructs had local mechanical properties comparable to conventional scaffolds and native heart valves. In agreement with prior modeling results, it was found under quasi-static loading that curvilinear fiber microstructures reduced strain concentrations compared to scaffolds generated on a conventional cylindrical mandrels. Thus, this simple technique offers an attractive means for fabricating scaffolds where key microstructural features of the native leaflet are imitated for heart valve tissue engineering. PMID:25771748

  16. Rapid micropatterning of cell lines and human pluripotent stem cells on elastomeric membranes.

    PubMed

    Paik, Isha; Scurr, David J; Morris, Bryan; Hall, Graham; Denning, Chris; Alexander, Morgan R; Shakesheff, Kevin M; Dixon, James E

    2012-10-01

    Tissue function during development and in regenerative medicine completely relies on correct cell organization and patterning at micro and macro scales. We describe a rapid method for patterning mammalian cells including human embryonic stem cells (HESCs) and induced pluripotent stem cells (iPSCs) on elastomeric membranes such that micron-scale control of cell position can be achieved over centimeter-length scales. Our method employs surface engineering of hydrophobic polydimethylsiloxane (PDMS) membranes by plasma polymerization of allylamine. Deposition of plasma polymerized allylamine (ppAAm) using our methods may be spatially restricted using a micro-stencil leaving faithful hydrophilic ppAAm patterns. We employed airbrushing to create aerosols which deposit extracellular matrix (ECM) proteins (such as fibronectin and Matrigel™) onto the same patterned ppAAm rich regions. Cell patterns were created with a variety of well characterized cell lines (e.g., NIH-3T3, C2C12, HL1, BJ6, HESC line HUES7, and HiPSC line IPS2). Individual and multiple cell line patterning were also achieved. Patterning remains faithful for several days and cells are viable and proliferate. To demonstrate the utility of our technique we have patterned cells in a variety of configurations. The ability to rapidly pattern cells at high resolution over macro scales should aid future tissue engineering efforts for regenerative medicine applications and in creating in vitro stem cell niches. PMID:22511037

  17. Fabrication of elastomeric scaffolds with curvilinear fibrous structures for heart valve leaflet engineering

    PubMed Central

    Hobson, Christopher M.; Amoroso, Nicholas J.; Amini, Rouzbeh; Ungchusri, Ethan; Hong, Yi; D’Amore, Antonio; Sacks, Michael S.; Wagner, William R.

    2015-01-01

    Native semi-lunar heart valves are composed of a dense fibrous network that generally follows a curvilinear path along the width of the leaflet. Recent models of engineered valve leaflets have predicted that such curvilinear fiber orientations would homogenize the strain field and reduce stress concentrations at the commissure. In the present work, a method was developed to reproduce this curvilinear fiber alignment in electrospun scaffolds by varying the geometry of the collecting mandrel. Elastomeric poly(ester urethane)urea was electrospun onto rotating conical mandrels of varying angles to produce fibrous scaffolds where the angle of fiber alignment varied linearly over scaffold length. By matching the radius of the conical mandrel to the radius of curvature for the native pulmonary valve, the electrospun constructs exhibited a curvilinear fiber structure similar to the native leaflet. Moreover, the constructs had local mechanical properties comparable to conventional scaffolds and native heart valves. In agreement with prior modeling results, it was found under quasi-static loading that curvilinear fiber microstructures reduced strain concentrations compared to scaffolds generated on a conventional cylindrical mandrels. Thus, this simple technique offers an attractive means for fabricating scaffolds where key microstructural features of the native leaflet are imitated for heart valve tissue engineering. PMID:25771748

  18. Probing Mechanoregulation of Neuronal Differentiation by Plasma Lithography Patterned Elastomeric Substrates

    NASA Astrophysics Data System (ADS)

    Nam, Ki-Hwan; Jamilpour, Nima; Mfoumou, Etienne; Wang, Fei-Yue; Zhang, Donna D.; Wong, Pak Kin

    2014-11-01

    Cells sense and interpret mechanical cues, including cell-cell and cell-substrate interactions, in the microenvironment to collectively regulate various physiological functions. Understanding the influences of these mechanical factors on cell behavior is critical for fundamental cell biology and for the development of novel strategies in regenerative medicine. Here, we demonstrate plasma lithography patterning on elastomeric substrates for elucidating the influences of mechanical cues on neuronal differentiation and neuritogenesis. The neuroblastoma cells form neuronal spheres on plasma-treated regions, which geometrically confine the cells over two weeks. The elastic modulus of the elastomer is controlled simultaneously by the crosslinker concentration. The cell-substrate mechanical interactions are also investigated by controlling the size of neuronal spheres with different cell seeding densities. These physical cues are shown to modulate with the formation of focal adhesions, neurite outgrowth, and the morphology of neuroblastoma. By systematic adjustment of these cues, along with computational biomechanical analysis, we demonstrate the interrelated mechanoregulatory effects of substrate elasticity and cell size. Taken together, our results reveal that the neuronal differentiation and neuritogenesis of neuroblastoma cells are collectively regulated via the cell-substrate mechanical interactions.

  19. Static characterization of a soft elastomeric capacitor for non destructive evaluation applications

    SciTech Connect

    Saleem, Hussam; Laflamme, Simon; Zhang, Huanhuan; Geiger, Randall; Kessler, Michael; Rajan, Krishna

    2014-02-18

    A large and flexible strain transducer consisting of a soft elastomeric capacitor (SEC) has been proposed by the authors. Arranged in a network setup, the sensing strategy offers tremendous potential at conducting non-destructive evaluation of large-scale surfaces. In prior work, the authors have demonstrated the performance of the sensor at tracking strain history, localizing cracks, and detecting vibration signatures. In this paper, we characterize the static performance of the proposed SEC. The characterization includes sensitivity of the signal, and temperature and humidity dependences. Tests are conducted on a simply supported aluminum beam subjected to bending as well as on a free standing sensor. The performance of the SEC is compared against off-the-shelf resistance-based strain gauges with resolution of 1 με. A sensitivity of 1190 pF/ε is obtained experimentally, in agreement with theory. Results also show the sensor linearity over the given level of strain, showing the promise of the SEC at monitoring of surface strain.

  20. Characterisation and evaluation of soft elastomeric actuators for hand assistive and rehabilitation applications.

    PubMed

    Yap, Hong Kai; Lim, Jeong Hoon; Nasrallah, Fatima; Cho Hong Goh, James; Yeow, Chen-Hua

    2016-01-01

    Various hand exoskeletons have been proposed for the purposes of providing assistance in activities of daily living and rehabilitation exercises. However, traditional exoskeletons are made of rigid components that impede the natural movement of joints and cause discomfort to the user. This paper evaluated a soft wearable exoskeleton using soft elastomeric actuators. The actuators could generate the desired actuation of the finger joints with a simple design. The actuators were characterised in terms of their radius of curvature and force output during actuation. Additionally, the device was evaluated on five healthy subjects in terms of its assisted finger joint range of motion. Results demonstrated that the subjects were able to perform the grasping actions with the assistance of the device and the range of motion of individual finger joints varied from subject to subject. This work evaluated the performance of a soft wearable exoskeleton and highlighted the importance of customisability of the device. It demonstrated the possibility of replacing traditional rigid exoskeletons with soft exoskeletons that are more wearable and customisable. PMID:27007297

  1. Development and evaluation of elastomeric hollow fiber membranes as small diameter vascular graft substitutes.

    PubMed

    Mercado-Pagán, Ángel E; Kang, Yunqing; Findlay, Michael W; Yang, Yunzhi

    2015-04-01

    Engineering of small diameter (<6mm) vascular grafts (SDVGs) for clinical use remains a significant challenge. Here, elastomeric polyester urethane (PEU)-based hollow fiber membranes (HFMs) are presented as an SDVG candidate to target the limitations of current technologies and improve tissue engineering designs. HFMs are fabricated by a simple phase inversion method. HFM dimensions are tailored through adjustments to fabrication parameters. The walls of HFMs are highly porous. The HFMs are very elastic, with moduli ranging from 1-4MPa, strengths from 1-5MPa, and max strains from 300-500%. Permeability of the HFMs varies from 0.5-3.5×10(-6)cm/s, while burst pressure varies from 25 to 35psi. The suture retention forces of HFMs are in the range of 0.8 to 1.2N. These properties match those of blood vessels. A slow degradation profile is observed for all HFMs, with 71 to 78% of the original mass remaining after 8weeks, providing a suitable profile for potential cellular incorporation and tissue replacement. Both human endothelial cells and human mesenchymal stem cells proliferate well in the presence of HFMs up to 7days. These results demonstrate a promising customizable PEU HFMs for small diameter vascular repair and tissue engineering applications. PMID:25686982

  2. Elastomeric composites with high dielectric constant for use in Maxwell stress actuators

    NASA Astrophysics Data System (ADS)

    Szabo, Jeffrey P.; Hiltz, Johnathan A.; Cameron, Colin G.; Underhill, Royale S.; Massey, Jason; White, Brian; Leidner, Jacob

    2003-07-01

    Electroactive polymer actuators that utilize the Maxwell stress effect have generated considerable interest in recent years for use in applications such as artificial muscles, sensors, and parasitic energy capture. In order to maximize performance, the dielectric layer in Maxwell stress actuators should ideally have a high dielectric constant and high dielectric breakdown strength. In this study, the effect of high dielectric constant fillers on the electrical and mechanical properties of thin elastomeric films was examined. The fillers studied included the inorganic compounds titanium dioxide (TiO2), barium titanate (BaTiO3), and lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3-PbTiO). A high dielectric constant filler based on a polymeric conjugated ligand-metal complex, poly(copper phthalocyanine), was also synthesized and studied. Maxwell stress actuators fabricated with BaTiO3 dispersed in a silicone elastomer matrix were evaluated and compared with unfilled systems. A model was presented which relates filler volume fraction to actuation stress, strain, and elastic energy density at fields below dielectric breakdown. The model and experimental results suggest that for the case of strong filler particle-elastomer matrix interaction, actuation strain decreases with increasing filler content.

  3. Caterpillar locomotion-inspired valveless pneumatic micropump using a single teardrop-shaped elastomeric membrane.

    PubMed

    So, Hongyun; Pisano, Albert P; Seo, Young Ho

    2014-07-01

    This paper presents a microfluidic pump operated by an asymmetrically deformed membrane, which was inspired by caterpillar locomotion. Almost all mechanical micropumps consist of two major components of fluid halting and fluid pushing parts, whereas the proposed caterpillar locomotion-inspired micropump has only a single, bilaterally symmetric membrane-like teardrop shape. A teardrop-shaped elastomeric membrane was asymmetrically deformed and then consecutively touched down to the bottom of the chamber in response to pneumatic pressure, thus achieving fluid pushing. Consecutive touchdown motions of the teardrop-shaped membrane mimicked the propagation of a caterpillar's hump during its locomotory gait. The initial touchdown motion of the teardrop-shaped membrane at the centroid worked as a valve that blocked the inlet channel, and then, the consecutive touchdown motions pushed fluid in the chamber toward the tail of the chamber connected to the outlet channel. The propagation of the touchdown motion of the teardrop-shaped membrane was investigated using computational analysis as well as experimental studies. This caterpillar locomotion-inspired micropump composed of only a single membrane can provide new opportunities for simple integration of microfluidic systems. PMID:24812661

  4. Development and evaluation of elastomeric hollow fiber membranes as small diameter vascular graft substitutes

    PubMed Central

    Mercado-Pagán, Ángel E.; Kang, Yunqing; Findlay, Michael W.; Yang, Yunzhi

    2015-01-01

    Engineering of small diameter (<6 mm) vascular grafts (SDVGs) for clinical use, remains a significant challenge. Here, elastomeric polyester urethane (PEU)-based hollow fiber membranes (HFM) are presented as an SDVG candidate to target the limitations of current technologies and improve tissue engineering designs. HFMs are fabricated by a simple phase inversion method. HFM dimensions are tailored through adjustments to fabrication parameters. The walls of HFMs are highly porous. The HFMs are very elastic, with moduli ranging from 1–4 MPa, strengths from 1–5 MPa, and max strains from 300–500%. Permeability of the HFMs varies from 0.5–3.5×10−6 cm/s, while burst pressure varies from 25 to 35 psi. The suture retention forces of HFMs are in the range of 0.8 to 1.2 N. These properties match those of blood vessels. A slow degradation profile is observed for all HFMs, with 71 to 78% of the original mass remaining after 8 weeks, providing a suitable profile for potential cellular incorporation and tissue replacement. Both human endothelial cells and human mesenchymal stem cells proliferate well in the presence of HFMs up to 7 days. These results demonstrate a promising customizable PEU HFMs for small diameter vascular repair and tissue engineering applications. PMID:25686982

  5. Elimination of stick-slip of elastomeric sutures by radiofrequency glow discharge deposited coatings.

    PubMed

    Griesser, H J; Chatelier, R C; Martin, C; Vasic, Z R; Gengenbach, T R; Jessup, G

    2000-01-01

    Fine elastomeric sutures intended for cardiovascular surgery can exhibit "stick-slip" behavior as they are pulled through tissue; the resulting oscillatory force can damage delicate tissue or cause sutures to snap. To eliminate this undesirable effect, sutures were surface-modified using a radiofrequency glow discharge in a vapor of either hexamethyldisiloxane or hexamethyldisilazane, to produce a thin polymeric coating on the suture. The same coatings were also deposited onto aluminized tape to facilitate their characterization by measurement of air/water contact angles and by X-ray photoelectron spectroscopy. Coatings from both monomers were found to be very hydrophobic. The hexamethyldisiloxane glow discharge coatings underwent negligible oxidation when stored in air, and thus remained stable over a shelf-life period akin to what may be required of sutures. The hexamethyldisilazane glow discharge coatings, in contrast, incorporated substantial amounts of oxygen over a 3-month period. The coatings did not measurably alter the tensile properties of the sutures. The frictional properties of coated sutures were assessed by measuring the dynamic friction between the suture and ovine myocardium. Both coatings were effective in removing the inherent stick-slip behavior of polybutester sutures in this model. The coatings remained intact after several passes and proved to be robust and efficacious under various strain regimes. PMID:10813763

  6. Analysis of longitudinal seismic response of bridge with magneto-rheological elastomeric bearings

    NASA Astrophysics Data System (ADS)

    Li, Rui; Li, Xi; Wu, Yueyuan; Chen, Shiwei; Wang, Xiaojie

    2016-04-01

    As the weakest part in the bridge system, traditional bridge bearing is incapable of isolating the impact load such as earthquake. A magneto-rheological elastomeric bearing (MRB) with adjustable stiffness and damping parameters is designed, tested and modeled. The developed Bouc-Wen model is adopted to represent the constitutive relation and force-displacement behavior of an MRB. Then, the lead rubber bearing (LRB), passive MRB and controllable MRB are modeled by finite element method (FEM). Furthermore, two typical seismic waves are adopted as inputs for the isolation system of bridge seismic response. The experiments are carried out to investigate the different response along the bridge with on-off controlled MRBs. The results show that the isolating performance of MRB is similar to that of traditional LRB, which ensures the fail-safe capability of bridge with MRBs under seismic excitation. In addition, the controllable bridge with MRBs demonstrated the advantage of isolating capacity and energy dissipation, because it restrains the acceleration peak of bridge beam by 33.3%, and the displacement of bearing decrease by 34.1%. The shear force of the pier top is also alleviated.

  7. Biodegradable, elastomeric coatings with controlled anti-proliferative agent release for magnesium-based cardiovascular stents.

    PubMed

    Gu, Xinzhu; Mao, Zhongwei; Ye, Sang-Ho; Koo, Youngmi; Yun, Yeoheung; Tiasha, Tarannum R; Shanov, Vesselin; Wagner, William R

    2016-08-01

    Vascular stent design continues to evolve to further improve the efficacy and minimize the risks associated with these devices. Drug-eluting coatings have been widely adopted and, more recently, biodegradable stents have been the focus of extensive evaluation. In this report, biodegradable elastomeric polyurethanes were synthesized and applied as drug-eluting coatings for a relatively new class of degradable vascular stents based on Mg. The dynamic degradation behavior, hemocompatibility and drug release were investigated for poly(carbonate urethane) urea (PCUU) and poly(ester urethane) urea (PEUU) coated magnesium alloy (AZ31) stents. Poly(lactic-co-glycolic acid) (PLGA) coated and bare stents were employed as control groups. The PCUU coating effectively slowed the Mg alloy corrosion in dynamic degradation testing compared to PEUU-coated, PLGA-coated and bare Mg alloy stents. This was confirmed by electron microscopy, energy-dispersive x-ray spectroscopy and magnesium ion release experiments. PCUU-coating of AZ31 was also associated with significantly reduced platelet adhesion in acute blood contact testing. Rat vascular smooth muscle cell (rSMC) proliferation was successfully inhibited when paclitaxel was released from pre-loaded PCUU coatings. The corrosion retardation, low thrombogenicity, drug loading capacity, and high elasticity make PCUU an attractive option for drug eluting coating on biodegradable metallic cardiovascular stents. PMID:27085049

  8. An Overview of Advanced Elastomeric Seal Development and Testing Capabilities at NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Dunlap, Patrick H.

    2014-01-01

    NASA is developing advanced space-rated elastomeric seals to support future space exploration missions to low Earth orbit, the Moon, near Earth asteroids, and other destinations. This includes seals for a new docking system and vehicle hatches. These seals must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them, and seal adhesion forces must be low to allow the sealed interface to be separated when required (e.g., during undocking or hatch opening). NASA Glenn Research Center has developed a number of unique test fixtures to measure the leak rates and compression and adhesion loads of candidate seal designs under simulated thermal, vacuum, and engagement conditions. Tests can be performed on full-scale seals with diameters on the order of 50 in., subscale seals that are about 12 in. in diameter, and smaller specimens such as O-rings. Test conditions include temperatures ranging from -238 to 662 F (-150 to 350 C), operational pressure gradients, and seal-on-seal or seal-on-flange mating configurations. Nominal and off-nominal conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features and capabilities of each type of test apparatus and provides an overview of advanced seal development activities at NASA Glenn.

  9. An Overview of Advanced Elastomeric Seal Development and Testing Capabilities at NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Dunlap, Patrick H., Jr.

    2014-01-01

    NASA is developing advanced space-rated elastomeric seals to support future space exploration missions to low Earth orbit, the Moon, near Earth asteroids, and other destinations. This includes seals for a new docking system and vehicle hatches. These seals must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them, and seal adhesion forces must be low to allow the sealed interface to be separated when required (e.g., during undocking or hatch opening). NASA Glenn Research Center has developed a number of unique test fixtures to measure the leak rates and compression and adhesion loads of candidate seal designs under simulated thermal, vacuum, and engagement conditions. Tests can be performed on fullscale seals with diameters on the order of 50 in., subscale seals that are about 12 in. in diameter, and smaller specimens such as O-rings. Test conditions include temperatures ranging from -238 to 662degF (-150 to 350degC), operational pressure gradients, and seal-on-seal or seal-on-flange mating configurations. Nominal and off-nominal conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features and capabilities of each type of test apparatus and provides an overview of advanced seal development activities at NASA Glenn.

  10. Elastomeric PDMS Planoconvex Lenses Fabricated by a Confined Sessile Drop Technique.

    PubMed

    Ekgasit, S; Kaewmanee, N; Jangtawee, P; Thammacharoen, C; Donphoongpri, M

    2016-08-10

    The ubiquity of high quality smartphones at affordable prices not only accelerated the social penetration in the global population but also promoted nontraditional usage of smartphones as point-of-care medical diagnostic devices, sensors, and portable digital microscopes. This paper reveals a simple, rapid, cost-effective, and template-free technique for mass-scale production of an elastomeric PDMS (ePDMS) planoconvex lens capable of converting a smartphone into a portable digital microscope. By taking advantage of the resistance to spreading of liquid by a sharp edge, highly stable spherical cap of viscous liquid PDMS (lPDMS) on a smooth PMMA circular disk was fabricated. The axisymmetric spreading of lPDMS under the gravitational force and interfacial tension force enable the formation of spherical cap with a certain radius of curvature. A thermal treatment at 80 °C for 30 min cured the spherical cap lPDMS into a bubble-free ePDMS planoconvex lens. Lenses with focal lengths of 55.2-3.4 mm could be reproducibly fabricated by adjusting the volume of dispensed lPDMSs and diameter of PMMA disks. High-resolution panoramic microscope images without a distortion of small cylindrical object could be constructed on-the-fly using the imbedded smartphone app. Applications of the smartphone digital microscope equipped with an ePDMS planoconvex lens for imaging of micro printings, gun shot residues, cylindrical objects, and bullet toolmarks were explored. PMID:27419266

  11. Anisotropic reversible piezoresistivity in magnetic-metallic/polymer structured elastomeric composites: modelling and experiments.

    PubMed

    Mietta, José Luis; Tamborenea, Pablo I; Martin Negri, R

    2016-01-14

    Structured elastomeric composites (SECs) with electrically conductive fillers display anisotropic piezoresistivity. The fillers do not form string-of-particle structures but pseudo-chains formed by grouping micro-sized clusters containing nanomagnetic particles surrounded by noble metals (e.g. silver, Ag). The pseudo-chains are formed when curing or preparing the composite in the presence of a uniform magnetic field, thus pseudo-chains are aligned in the direction of the field. The electrical conduction through pseudo-chains is analyzed and a constitutive model for the anisotropic reversible piezoresistivity in SECs is proposed. Several effects and characteristics, such as electron tunnelling, conduction inside the pseudo-chains, and chain-contact resistivity, are included in the model. Experimental results of electrical resistance, R, as a function of the normal stress applied in the direction of the pseudo-chains, P, are very well fitted by the model in the case of Fe3O4[Ag] microparticles magnetically aligned while curing in polydimethylsiloxane, PDMS. The cross sensitivity of different parameters (like the potential barrier and the effective distance for electron tunnelling) is evaluated. The model predicts the presence of several gaps for electron tunnelling inside the pseudo-chains. Estimates of those parameters for the mentioned experimental system under strains up to 20% are presented. Simulations of the expected response for other systems are performed showing the influence of Young's modulus and other parameters on the predicted piezoresistivity. PMID:26477664

  12. Semicrystalline thermoplastic elastomeric polyolefins: Advances through catalyst development and macromolecular design

    PubMed Central

    Hotta, Atsushi; Cochran, Eric; Ruokolainen, Janne; Khanna, Vikram; Fredrickson, Glenn H.; Kramer, Edward J.; Shin, Yong-Woo; Shimizu, Fumihiko; Cherian, Anna E.; Hustad, Phillip D.; Rose, Jeffrey M.; Coates, Geoffrey W.

    2006-01-01

    We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90% elastic recovery at strains of 100% or less. An isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene pentablock copolymer was synthesized that also shows exceptional elastomeric properties. Notably, microphase separation is not necessary in the semicrystalline isotactic polypropylenes to achieve good mechanical performance, unlike commercial styrenic thermoplastic elastomers. PMID:17032769

  13. Static characterization of a soft elastomeric capacitor for non destructive evaluation applications

    NASA Astrophysics Data System (ADS)

    Saleem, Hussam; Laflamme, Simon; Zhang, Huanhuan; Geiger, Randall; Kessler, Michael; Rajan, Krishna

    2014-02-01

    A large and flexible strain transducer consisting of a soft elastomeric capacitor (SEC) has been proposed by the authors. Arranged in a network setup, the sensing strategy offers tremendous potential at conducting non-destructive evaluation of large-scale surfaces. In prior work, the authors have demonstrated the performance of the sensor at tracking strain history, localizing cracks, and detecting vibration signatures. In this paper, we characterize the static performance of the proposed SEC. The characterization includes sensitivity of the signal, and temperature and humidity dependences. Tests are conducted on a simply supported aluminum beam subjected to bending as well as on a free standing sensor. The performance of the SEC is compared against off-the-shelf resistance-based strain gauges with resolution of 1 μɛ. A sensitivity of 1190 pF/ɛ is obtained experimentally, in agreement with theory. Results also show the sensor linearity over the given level of strain, showing the promise of the SEC at monitoring of surface strain.

  14. Characterization of a soft elastomeric capacitive strain sensor for fatigue crack monitoring

    NASA Astrophysics Data System (ADS)

    Kong, Xiangxiong; Li, Jian; Laflamme, Simon; Bennett, Caroline; Matamoros, Adolfo

    2015-04-01

    Fatigue cracks have been one of the major factors for the deterioration of steel bridges. In order to maintain structural integrity, monitoring fatigue crack activities such as crack initiation and propagation is critical to prevent catastrophic failure of steel bridges due to the accumulation of fatigue damage. Measuring the strain change under cracking is an effective way of monitoring fatigue cracks. However, traditional strain sensors such as metal foil gauges are not able to capture crack development due to their small size, limited measurement range, and high failure rate under harsh environmental conditions. Recently, a newly developed soft elastomeric capacitive sensor has great promise to overcome these limitations. In this paper, crack detection capability of the capacitive sensor is demonstrated through Finite Element (FE) analysis. A nonlinear FE model of a standard ASTM compact tension specimen is created which is calibrated to experimental data to simulate its response under fatigue loading, with the goal to 1) depict the strain distribution of the specimen under the large area covered by the capacitive sensor due to cracking; 2) characterize the relationship between capacitance change and crack width; 3) quantify the minimum required resolution of data acquisition system for detecting the fatigue cracks. The minimum resolution serves as a basis for the development of a dedicated wireless data acquisition system for the capacitive strain sensor.

  15. Tissue-to-Cellular Deformation Coupling in Cell-Microintegrated Elastomeric Scaffolds

    NASA Astrophysics Data System (ADS)

    Stella, J. A.; Liao, J.; Hong, Y.; Merryman, W. D.; Wagner, W. R.; Sacks, M. S.

    Long term efficacy of tissue replacements or regenerative therapies rely on the critical processes of cell proliferation and differentiation, the production of organized matrix, and concurrent tissue remodeling or growth. Recent studies have shown that mechanical and chemical factors modulate cell function which has profound implications on tissue growth and remodeling. As such, creating engineered tissue replacement options requires a detailed command of the complex, dynamic, and reciprocal interactions which occur at the cell-ECM interface. To gain a better understanding of the coupled tissue-cellular deformation response, we propose the use of cell-microintegrated elastomeric scaffolds which provide a unique platform to investigate cellular deformations within a three dimensional fibrous scaffold. Scaffold specimens micro-integrated with vascular smooth muscle cells (VSMC) were subjected to controlled biaxial stretch with 3D cellular deformations and local fiber micro-architecture simultaneously quantified. Interestingly, local cellular deformations exhibited a non-linear deformation response with scaffold strain which was attributed to unique microarchitectural morphologies. Local scaffold microstructural changes induced by macro-level applied strain dominated cellular deformations, so that monotonic increases in scaffold strain do not necessitate similar levels of cellular deformation. This result has fundamental implications when attempting to elucidate the events of de-novo tissue development and remodeling in engineeredtissues.

  16. Extrusion resistance of elastomers and plastic materials

    SciTech Connect

    Kosty, J.

    1984-02-01

    In today's oil production equipment, sealing systems are required to withstand high pressures and temperatures without extruding. The variety of seal shapes and of operating conditions makes it necessary to characterize the extrusion resistance of seal materials so that the component design engineer can select the proper seal system for the application. This paper will present a unique test method for measuring the extrusion characteristics of elastomeric and thermoplastic seal material at various temperature, pressure, and gap conditions. Data will be presented to illustrate the effect of elastomeric extrusion of seals of different sizes and the effect of concentric and eccentric gaps. Data will also be presented for acceptable extrusion characteristics of thermoplastic backups.

  17. A Bi-Layered Elastomeric Scaffold for Tissue Engineering of Small-Diameter Vascular Grafts

    PubMed Central

    Soletti, Lorenzo; Hong, Yi; Guan, Jianjun; Stankus, John J.; El-Kurdi, Mohammed S.; Wagner, William R.; Vorp, David A.

    2011-01-01

    A major barrier in the development of a clinically-useful small-diameter tissue engineered vascular graft (TEVG) is the scaffold component. Scaffold requirements include matching the mechanical and structural properties with those of native vessels and optimizing the microenvironment to foster cell integration, adhesion, and growth. We have developed a small-diameter, bi-layered, biodegradable, elastomeric scaffold based on a synthetic, biodegradable elastomer. The scaffold incorporates a highly porous inner layer, allowing cell integration and growth, and an external, fibrous reinforcing layer deposited by electrospinning. Scaffold morphology and mechanical properties were assessed, quantified, and compared to those of native vessels. Scaffolds were then seeded with adult stem cells via a rotational vacuum seeding device to obtain a TEVG, cultured in dynamic conditions for 7 days, and evaluated for cellularity. The scaffold showed a firm integration of the two polymeric layers with no delaminations. Mechanical properties were physiologically-consistent showing anisotropy, elastic modulus (1.4±0.4 MPa), and ultimate tensile stress (8.3±1.7 MPa) comparable with native vessels. Compliance and suture retention force were 4.6±0.5×10−4 mmHg−1 and 3.4±0.3 N, respectively. Seeding resulted in a rapid, uniform, bulk integration of cells, with a seeding efficiency of 92±1%. The scaffolds maintained a high level of cellular density throughout dynamic culture. This approach, combining artery-like mechanical properties and a rapid and efficient cellularization, might contribute to the future clinical translation of TEVGs. PMID:19540370

  18. Pre-treatment of synthetic elastomeric scaffolds by cardiac fibroblasts improves engineered heart tissue.

    PubMed

    Radisic, Milica; Park, Hyoungshin; Martens, Timothy P; Salazar-Lazaro, Johanna E; Geng, Wenliang; Wang, Yadong; Langer, Robert; Freed, Lisa E; Vunjak-Novakovic, Gordana

    2008-09-01

    Native myocardium consists of several cell types, of which approximately one-third are myocytes and most of the nonmyocytes are fibroblasts. By analogy with monolayer culture in which fibroblasts were removed to prevent overgrowth, early attempts to engineer myocardium utilized cell populations enriched for cardiac myocytes (CMs; approximately 80-90% of total cells). We hypothesized that the pre-treatment of synthetic elastomeric scaffolds with cardiac fibroblasts (CFs) will enhance the functional assembly of the engineered cardiac constructs by creating an environment supportive of cardiomyocyte attachment and function. Cells isolated from neonatal rat ventricles were prepared to form three distinct populations: rapidly plating cells identified as CFs, slowly plating cells identified as CMs, and unseparated initial population of cells (US). The cell fractions (3 x 10(6) cells total) were seeded into poly(glycerol sebacate) scaffolds (highly porous discs, 5 mm in diameter x 2-mm thick) using Matrigeltrade mark, either separately (CM or CF), concurrently (US), or sequentially (CF pre-treatment followed by CM culture, CF + CM), and cultured in spinner flasks. The CF + CM group had the highest amplitude of contraction and the lowest excitation threshold, superior DNA content, and higher glucose consumption rate. The CF + CM group exhibited compact 100- to 200-mum thick layers of elongated myocytes aligned in parallel over layers of collagen-producing fibroblasts, while US and CM groups exhibited scattered and poorly elongated myocytes. The sequential co-culture of CF and CM on a synthetic elastomer scaffold thus created an environment supportive of cardiomyocyte attachment, differentiation, and contractile function, presumably due to scaffold conditioning by cultured fibroblasts. When implanted over the infarcted myocardium in a nude rat model, cell-free poly(glycerol sebacate) remained at the ventricular wall after 2 weeks of in vivo, and was vascularized. PMID

  19. Tensile Properties and Small-Angle Neutron Scattering Investigation of Stereoblock Elastomeric Polypropylene

    SciTech Connect

    Pople, John A

    2002-08-06

    Elastomeric polypropylene (ePP) produced from unbridged 2-arylindene metallocene catalysts was studied by uniaxial tensile and small-angle neutron scattering (SANS) techniques. The ePP can be separated into three fractions by successive boiling-solvent fractionation method to yield: a low-tacticity fraction soluble in ether (ES), an intermediate-tacticity fraction soluble in heptane (HS), and a high-tacticity fraction insoluble in heptane (HI). Tensile properties of ePP were compared to its solvent fractions, and the role of each solvent fraction residing within ePP was investigated by blending 5 weight % deuterated fraction with ePP. The tensile properties of each fraction vary considerably, exhibiting properties from a weak gum elastomer for ES, to a semi-crystalline thermoplastic for HI. The intermediate-tacticity HS fraction exhibits elastic properties similar to the parent elastomer (ePP). In the melt at 160 C, SANS shows that all deuterated fractions are homogeneously mixed with ePP in a one-phase system. At 25 C upon a slow cooling from the melt, the low-tacticity fraction is preferentially segregated in the amorphous domains induced by different crystallization temperatures and kinetics of the deuterated ES and high-tacticity components. The high-tacticity component within ePP (dHI-ePP) retains its plastic properties in the blend. Despite its low crystallinity ({le} 2%), the low-tacticity fraction can co-crystallize with the crystalline matrix. The dES-ePP shows little or no relaxation when held under strain and recovers readily upon the release of stress.

  20. An air-pressure-free elastomeric valve for integrated nucleic acid analysis by capillary electrophoresis

    NASA Astrophysics Data System (ADS)

    Jung, Wooseok; Barrett, Matthew; Brooks, Carla; Rivera, Andrew; Birdsell, Dawn N.; Wagner, David M.; Zenhausern, Frederic

    2015-12-01

    We present a new elastomeric valve for integrated nucleic acid analysis by capillary electrophoresis. The valve functions include metering to capture a designated volume of biological sample into a polymerase chain reaction (PCR) chamber, sealing to preserve the sample during PCR cycling, and transfer of the PCR-products and on-chip formamide post-processing for the analysis of DNA fragments by capillary gel electrophoresis. This new valve differs from prior art polydimethylsiloxane (PDMS) valves in that the valve is not actuated externally by air-pressure or vacuum so that it simplifies a DNA analysis system by eliminating the need for an air-pressure or vacuum source, and off-cartridge solenoid valves, control circuit boards and software. Instead, the new valve is actuated by a thermal cycling peltier assembly integrated within the hardware instrument that tightly comes in contact with a microfluidic cartridge for thermal activation during PCR, so that it spontaneously closes the valve without an additional actuator system. The valve has bumps in the designated locations so that it has a self-alignment that does not require precise alignment of a valve actuator. Moreover, the thickness of the new valve is around 600 μm with an additional bump height of 400 μm so that it is easy to handle and very feasible to fabricate by injection molding compared to other PDMS valves whose thicknesses are around 30-100 μm. The new valve provided over 95% of metering performance in filling the fixed volume of the PCR chamber, preserved over 97% of the sample volume during PCR, and showed very comparable capillary electrophoresis peak heights to the benchtop assay tube controls with very consistent transfer volume of the PCR-product and on-chip formamide. The new valve can perform a core function for integrated nucleic acid analysis by capillary electrophoresis.

  1. Elastomeric high-mineral content hydrogel-hydroxyapatite composites for orthopedic applications

    PubMed Central

    Song, Jie; Xu, Jianwen; Filion, Tera; Saiz, Eduardo; Tomsia, Antoni P.; Lian, Jane B.; Stein, Gary S.; Ayers, David C.; Bertozzi, Carolyn R.

    2009-01-01

    The design of synthetic bone grafts that mimic the structure and composition of bone and possess good surgical handling characteristics remains a major challenge. We report the development of poly(2-hydroxyethyl methacrylate) (pHEMA)-hydroxyapatite (HA) composites termed “FlexBone” that possess osteoconductive mineral content approximating that of human bone yet exhibit elastomeric properties enabling the press-fitting into a defect site. The approach involves crosslinking pHEMA hydrogel in the presence of HA using viscous ethylene glycol as a solvent. The composites exhibit excellent structural integration between the apatite mineral component and the hydroxylated hydrogel matrix. The stiffness of the composite and the ability to withstand compressive stress correlate with the microstructure and content of the mineral component. The incorporation of porous aggregates of HA nanocrystals rather than compact micrometer-sized calcined HA effectively improved the resistance of the composite to crack propagation under compression. Freeze-dried FlexBone containing 50 wt % porous HA nanocrystals could withstand hundreds-of-megapascals compressive stress and >80% compressive strain without exhibiting brittle fractures. Upon equilibration with water, FlexBone retained good structural integration and withstood repetitive moderate (megapascals) compressive stress at body temperature. When subcutaneously implanted in rats, FlexBone supported osteoblastic differentiation of the bone marrow stromal cells pre-seeded on FlexBone. Taken together, the combination of high osteoconductive mineral content, excellent organic-inorganic structural integration, elasticity, and the ability to support osteoblastic differentiation in vivo makes FlexBone a promising candidate for orthopedic applications. PMID:18546185

  2. Elastomeric free-form blood vessels for interconnecting organs on chip systems.

    PubMed

    Zhang, Weijia; Zhang, Yu Shrike; Bakht, Syeda Mahwish; Aleman, Julio; Shin, Su Ryon; Yue, Kan; Sica, Marco; Ribas, João; Duchamp, Margaux; Ju, Jie; Sadeghian, Ramin Banan; Kim, Duckjin; Dokmeci, Mehmet Remzi; Atala, Anthony; Khademhosseini, Ali

    2016-04-26

    Conventional blood vessel-on-a-chip models are typically based on microchannel-like structures enclosed within bulk elastomers such as polydimethylsiloxane (PDMS). However, these bulk vascular models largely function as individual platforms and exhibit limited flexibility particularly when used in conjunction with other organ modules. Oftentimes, lengthy connectors and/or tubes are still needed to interface multiple chips, resulting in a large waste volume counterintuitive to the miniaturized nature of organs-on-chips. In this work, we report the development of a novel form of a vascular module based on PDMS hollow tubes, which closely emulates the morphology and properties of human blood vessels to integrate multiple organs-on-chips. Specifically, we present two templating strategies to fabricate hollow PDMS tubes with adjustable diameters and wall thicknesses, where metal rods or airflow were employed as the inner templates, while plastic tubes were used as the outer template. The PDMS tubes could then be functionalized by human umbilical vein endothelial cells (HUVECs) in their interior surfaces to further construct elastomeric biomimetic blood vessels. The endothelium developed biofunctionality as demonstrated by the expression of an endothelial biomarker (CD31) as well as dose-dependent responses in the secretion of von Willebrand factor and nitric oxide upon treatment with pharmaceutical compounds. We believe that with their clear advantages including high optical transparency, gas permeability, and tunable elasticity matching those of native blood vessels, these free-form PDMS vascular modules can supplement bulk vascular organoids and likely replace inert plastic tubes in integrating multiple organoids into a single microfluidic circuitry. PMID:26999423

  3. On the mobility of iron particles embedded in elastomeric silicone matrix

    NASA Astrophysics Data System (ADS)

    Rabindranath, R.; Böse, H.

    2013-02-01

    In this contribution the rheological and magnetorheological properties of different polydimethylsiloxane (PDMS) based magnetorheological elastomers (MRE) are presented and discussed. In order to investigate the mobility of the iron particles with respect to the rheological characteristics, the iron particles were silanized with vinyltrimethoxysilane to enable a reaction between the modified particle and the cross-linking agent of the silicone elastomer. In addition, the vinyl-functionalized particles were further modified by the coupling of the superficial vinyl groups with a long-chain hydride terminated PDMS, which enables a reaction pathway with the vinyl terminated PDMS. On the other hand, the iron particles were treated with surfactants such as fatty acids, calcium and aluminum soaps, respectively, prior to vulcanization in order to increase the mobility of the iron particles in the elastomeric matrix. It was found, that both, the modification with the long-chain hydride terminated PDMS as well as the treatment with surfactants lead to an increase of the storage modulus G', the loss modulus G" and the loss factor tan δ in the magnetic field. It is concluded that both modifications, the coupling with long-chain hydride terminated PDMS as well as the treatment with surfactants, provide a greater mobility of the iron particles and hence a greater friction represented by the increase of the loss factor tan δ. Consequently it is assumed that untreated iron particles are less mobile in the rubber matrix due to covalent bonding with the silicone components, most likely due to the reaction of the hydroxyl groups on the metal surface with the silane groups of the cross-linking agent.

  4. Evaluation of various generic types of building sealants against ASTM C-920, standard specification for elastomeric joint sealants

    SciTech Connect

    Fiorillo, A.R.

    1996-12-31

    A number of sealant manufacturers suggest that although they supply primers for their sealants, in many cases the primers may not be necessary. They usually suggest running a test on the substrates the sealants are to be used with to determine if the primers are needed. This paper will discuss the results of testing several commercially available polysulfide, silicone and polyurethane sealants against ASTM C-920, Standard Specification for Elastomeric Joint Sealants. Morar, plate glass and anodized aluminum were used as the substrates. Where manufacturers supplied primers, the sealant was tested with and without their primer. Where the manufacturer did not recommend primers, testing was only doe without a primer.

  5. Synthesis, characterization, and paclitaxel release from a biodegradable, elastomeric, poly(ester urethane)urea bearing phosphorylcholine groups for reduced thrombogenicity.

    PubMed

    Hong, Yi; Ye, Sang-Ho; Pelinescu, Anca L; Wagner, William R

    2012-11-12

    Biodegradable polymers with high elasticity, low thrombogenicity, and drug loading capacity continue to be pursued for vascular engineering applications, including vascular grafts and stents. A biodegradable elastomeric polyurethane was designed as a candidate material for use as a drug-eluting stent coating, such that it was nonthrombogenic and could provide antiproliferative drug release to inhibit smooth muscle cell proliferation. A phosphorylcholine containing poly(ester urethane) urea (PEUU-PC) was synthesized by grafting aminated phosphorylcholine onto backbone carboxyl groups of a polyurethane (PEUU-COOH) synthesized from a soft segment blend of polycaprolactone and dimethylolpropionic acid, a hard segment of diisocyanatobutane and a putrescine chain extender. Poly(ester urethane) urea (PEUU) from a soft segment of polycaprolactone alone was employed as a control material. All of the synthesized polyurethanes showed high distensibility (>600%) and tensile strengths in the 20-35 MPa range. PEUU-PC experienced greater degradation than PEUU or PEUU-COOH in either a saline or lipase enzyme solution. PEUU-PC also exhibited markedly inhibited ovine blood platelet deposition compared with PEUU-COOH and PEUU. Paclitaxel loaded in all of the polymers during solvent casting continued to release for 5 d after a burst release in a 10% ethanol/PBS solution, which was utilized to increase the solubility of the releasate. Rat smooth muscle cell proliferation was significantly inhibited in 1 wk cell culture when releasate from the paclitaxel-loaded films was present. Based on these results, the synthesized PEUU-PC has promising functionality for use as a nonthrombogenic, drug eluting coating on metallic vascular stents and grafts. PMID:23035885

  6. Synthesis, Characterization, and Paclitaxel Release from a Biodegradable, Elastomeric, Poly(ester urethane)urea Bearing Phosphorylcholine Groups for Reduced Thrombogenicity

    PubMed Central

    Hong, Yi; Ye, Sang-Ho; Pelinescu, Anca L.; Wagner, William R.

    2013-01-01

    Biodegradable polymers with high elasticity, low thrombogenicity, and drug loading capacity continue to be pursued for vascular engineering applications, including vascular grafts and stents. A biodegradable elastomeric polyurethane was designed as a candidate material for use as a drug-eluting stent coating, such that it was nonthrombogenic and could provide antiproliferative drug release to inhibit smooth muscle cell proliferation. A phosphorylcholine containing poly(ester urethane) urea (PEUU-PC) was synthesized by grafting aminated phosphorylcholine onto backbone carboxyl groups of a polyurethane (PEUU-COOH) synthesized from a soft segment blend of polycaprolactone and dimethylolpropionic acid, a hard segment of diisocyanatobutane and a putrescine chain extender. Poly(ester urethane) urea (PEUU) from a soft segment of polycaprolactone alone was employed as a control material. All of the synthesized polyurethanes showed high distensibility (>600%) and tensile strengths in the 20–35 MPa range. PEUUPC experienced greater degradation than PEUU or PEUU-COOH in either a saline or lipase enzyme solution. PEUU-PC also exhibited markedly inhibited ovine blood platelet deposition compared with PEUU-COOH and PEUU. Paclitaxel loaded in all of the polymers during solvent casting continued to release for 5 d after a burst release in a 10% ethanol/PBS solution, which was utilized to increase the solubility of the releasate. Rat smooth muscle cell proliferation was significantly inhibited in 1 wk cell culture when releasate from the paclitaxel-loaded films was present. Based on these results, the synthesized PEUU-PC has promising functionality for use as a nonthrombogenic, drug eluting coating on metallic vascular stents and grafts. PMID:23035885

  7. Materialism.

    PubMed

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website. PMID:26301463

  8. Advanced materials for geothermal energy processes

    SciTech Connect

    Kukacka, L.E.

    1985-08-01

    The primary goal of the geothermal materials program is to ensure that the private sector development of geothermal energy resources is not constrained by the availability of technologically and economically viable materials of construction. This requires the performance of long-term high risk GHTD-sponsored materials R and D. Ongoing programs described include high temperature elastomers for dynamic sealing applications, advanced materials for lost circulation control, waste utilization and disposal, corrosion resistant elastomeric liners for well casing, and non-metallic heat exchangers. 9 refs.

  9. Migration of epoxidised soybean oil from PVC gaskets of commercial lids: simulation of migration under various conditions and screening of food products from Czech markets.

    PubMed

    Hanušová, Kristýna; Vrbík, Karel; Rajchl, Aleš; Dobiáš, Jaroslav; Sosnovcová, Jitka

    2015-01-01

    Previous studies have shown that a large number of polyvinylchloride (PVC) lid gaskets exceed the existing migration limits for epoxidised soybean oil (ESBO) and correct prediction of ESBO release into food therefore appears to be a difficult issue. ESBO migration from PVC gaskets of metal closures into food simulants and food products from the Czech market is evaluated during a survey in 2009 and subsequently one in 2012 to assess progress in lid manufacturing and official testing conditions. ESBO migration from lids into various food simulants was studied at various temperatures (25, 40 and 60°C) during storage times up to 12 months. ESBO released into food simulants or food products was transmethylated, derivatised and analysed by GC-MS. The levels of ESBO migration in foodstuffs in 2012 exceeded the specific migration limit (SML) in fewer products in comparison with the previous survey. However, most of the products were analysed at a time far from the expiry date and exceedance of the SML at the end of the product shelf life is not therefore excluded. More severe test conditions (60°C for 10 days) for specific migration given by the current European Union legislation (Regulation (EU) No. 10/2011) still seem to be insufficient for the simulation of ESBO migration during long-term storage. PMID:25685888

  10. [Use of new elastomeric pumps and PCA in postoperative pain control in thoraco-abdominal surgery].

    PubMed

    Testa, G; Borzomati, V; Costantini, D; De Chiara, A; Picarazzi, A; Capelli, O

    1996-01-01

    36 patients submitted to interventions for thoraco-abdominal surgery has been submitted to antalgic post-operatory therapy with elastomeric pump at a continuous intravenous infusion and patient controlled analgesia (PCA). The patients have been randomized in three groups. The patients of the 1 degree group received 30 minutes before of the end of the surgical intervention 30 mg of Ketorolac. At the end of the anesthesia came started an infusion of 150 mg of Ketorolac (5 vials) in 60 ml of isotonic chlorinated solution at the rate of 0.5 ml/h. The pump had besides the capability of disperse a maximum of 4 bolus/ h, everyone of 0.5 ml, on demand of the patient. The 2 degrees group received a solution containing 60 ml of Morphine in 60 ml of isotonic chlorinated solution with the same formality of administration. The 3 degrees group (placebo) received 60 ml of isotonic chlorinated solution in pumps from infusion and Ketorolac intramuscular on demand. To the times T0 (awakening), T1 (3 h), T2 (6h), T3 (12 h), T4 (24 h), T5 (30 h, was collected algometrical consequences according to VAS (Visual Analogous Scale of Sc modification of the PA increase, FC, FR, SatO2.. The obtained results have highlighted like in the 1 degree group, to the 1 degree algometric consequence (T0), there is a good sedative effect on the pain (intensity of the middle low pain 3.70 +/- 1.64); this antalgic effect has also continued in the other consequences effected in the post-operatory. In the 2 degree group to the awakening (T0), the pain was middle-tall (5.50 +/- 2.32) and an expressive reduction appeared at the time T2 (3.60 +/- 1.35 P < 0.005). In the 3 degrees group have not recorded a diminution of the pain if not after 24 hours from the end of the intervention deposit the intramuscular antalgic therapy. In conclusion, the system infusion + PCA represents an indubitable advantage in comparison with the traditional antalgic therapy as for concern the entity of the reduction of the pain as

  11. [Diagnostics and planning of orthodontic treatment of patients with crowded teeth position with the use of elastomeric correcting splints].

    PubMed

    Arsenina, O I; Riakhovskiĭ, A N; Safarova, N M

    2011-01-01

    3D scanning of plaster jaw models and further processing of the received data in editing program for three dimensional models Rapid Form 2006 Basis is one of the used methods of diagnostics of patients with crowded teeth position (measurement of anthropometric parameters of jaw models, dental arches symmetry, sizes and forms of dentitions). On 3D jaw models with crowded teeth position there were planned trajectories of gradual single tooth displacement in such a way that to move them in new correct position. Prescribing determined step with which the tooth would be moved there was made a series of individual plastic jaw models corresponding to each stage of treatment by stereolithographic method. On the received models there was made a series of elastomeric correcting splints producing some pressure upon teeth and making for their displacement. PMID:21512472

  12. Elastomeric inverse moulding and vacuum casting process characterization for the fabrication of arrays of concave refractive microlenses

    NASA Astrophysics Data System (ADS)

    Desmet, L.; Van Overmeire, S.; Van Erps, J.; Ottevaere, H.; Debaes, C.; Thienpont, H.

    2007-01-01

    We present a complete and precise quantitative characterization of the different process steps used in an elastomeric inverse moulding and vacuum casting technique. We use the latter replication technique to fabricate concave replicas from an array of convex thermal reflow microlenses. During the inverse elastomeric moulding we obtain a secondary silicone mould of the original silicone mould in which the master component is embedded. Using vacuum casting, we are then able to cast out of the second mould several optical transparent poly-urethane arrays of concave refractive microlenses. We select ten particular representative microlenses on the original, the silicone moulds and replica sample and quantitatively characterize and statistically compare them during the various fabrication steps. For this purpose, we use several state-of-the-art and ultra-precise characterization tools such as a stereo microscope, a stylus surface profilometer, a non-contact optical profilometer, a Mach-Zehnder interferometer, a Twyman-Green interferometer and an atomic force microscope to compare various microlens parameters such as the lens height, the diameter, the paraxial focal length, the radius of curvature, the Strehl ratio, the peak-to-valley and the root-mean-square wave aberrations and the surface roughness. When appropriate, the microlens parameter under test is measured with several different measuring tools to check for consistency in the measurement data. Although none of the lens samples shows diffraction-limited performance, we prove that the obtained replicated arrays of concave microlenses exhibit sufficiently low surface roughness and sufficiently high lens quality for various imaging applications.

  13. Synthesis and Characterization of Elastin-Mimetic Hybrid Polymers with Multiblock, Alternating Molecular Architecture and Elastomeric Properties

    PubMed Central

    Grieshaber, Sarah E.; Farran, Alexandra J. E.; Lin-Gibson, Sheng; Kiick, Kristi L.; Jia, Xinqiao

    2009-01-01

    We are interested in developing elastin–mimetic hybrid polymers (EMHPs) that capture the multiblock molecular architecture of tropoelastin as well as the remarkable elasticity of mature elastin. In this study, multiblock EMHPs containing flexible synthetic segments based on poly(ethylene glycol) (PEG) alternating with alanine-rich, lysine-containing peptides were synthesized by step-growth polymerization using α,ω-azido-PEG and alkyne-terminated AKA3KA (K = lysine, A = alanine) peptide, employing orthogonal click chemistry. The resulting EMHPs contain an estimated three to five repeats of PEG and AKA3KA and have an average molecular weight of 34 kDa. While the peptide alone exhibited α-helical structures at high pH, the fractional helicity for EMHPs was reduced. Covalent cross-linking of EMHPs with hexamethylene diisocyanate (HMDI) through the lysine residue in the peptide domain afforded an elastomeric hydrogel (xEMHP) with a compressive modulus of 0.12 MPa when hydrated. The mechanical properties of xEMHP are comparable to a commercial polyurethane elastomer (Tecoflex SG80A) under the same conditions. In vitro toxicity studies showed that while the soluble EMHPs inhibited the growth of primary porcine vocal fold fibroblasts (PVFFs) at concentrations ≥0.2 mg/mL, the cross-linked hybrid elastomers did not leach out any toxic reagents and allowed PVFFs to grow and proliferate normally. The hybrid and modular approach provides a new strategy for developing elastomeric scaffolds for tissue engineering. PMID:19763157

  14. Controle sismique d'un batiment en acier de 1 etage par amortisseurs elastomeres et contreventements en Chevron

    NASA Astrophysics Data System (ADS)

    Girard, Olivier

    Actuellement, le principe de dimensionnement a la capacite est fortement utilise dans le domaine du genie parasismique. De maniere simplifiee, cette methode de dimensionnement consiste a dissiper l'energie injectee a une structure lors d'une secousse sismique par la deformation inelastique d'un element structural sacrificiel. Cette methode de dimensionne-ment permet d'obtenir des structures economiques, car cette dissipation d'energie permet de reduire substantiellement les efforts qui se retrouvent a l'interieur de la structure. Or, la consequence de ce dimensionnement est la presence de degats importants a la structure qui suivent a la secousse sismique. Ces degats peuvent engendrer des couts superieurs aux couts d'erection de la structure. Bien entendu, sachant que les secousses sismiques d'importances sont des phenomenes rares, l'ingenieur est pret a accepter ce risque afin de diminuer les couts initiaux de construction. Malgre que cette methode ait permis d'obtenir des constructions economiques et securitaires, il serait interessant de developper un systeme qui permettrait d'obtenir des performances de controle des efforts sismiques comparables a un systeme dimensionne selon un principe de dimensionnement a la capacite sans les consequences negatives de ces systemes. En utilisant les principes d'isolation a la base, il a ete possible de developper un systeme de reprise des forces sismiques (SRFS). qui permet d'obtenir un controle des efforts sismiques concurrentiels tout en gardant une structure completement elastique. Ce systeme consiste u inserer un materiel elastomere entre l'assemblage de la poutre et des contreventements a l'interieur d'un cadre contrevente conventionnel. Cette insertion permet de diminuer substantiellement la rigidite laterale du batiment, ce qui a pour consequence d'augmenter la valeur de la periode fondamentale du batiment dans lequel ces cadres sont inseres. Ce phenomene est appele le saut de periode. Ce saut de periode permet de

  15. NASA Materials Research for Extreme Conditions

    NASA Technical Reports Server (NTRS)

    Sharpe, R. J.; Wright, M. D.

    2009-01-01

    This Technical Memorandum briefly covers various innovations in materials science and development throughout the course of the American Space program. It details each innovation s discovery and development, explains its significance, and describes the applications of this material either in the time period discovered or today. Topics of research include silazane polymers, solvent-resistant elastomeric polymers (polyurethanes and polyisocyanurates), siloxanes, the Space Shuttle thermal protection system, phenolic-impregnated carbon ablator, and carbon nanotubes. Significance of these developments includes the Space Shuttle, Apollo programs, and the Constellation program.

  16. Materials

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Schoeppner, Gregory A.

    2006-01-01

    NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

  17. Low-cost encapsulation materials for terrestrial solar cell modules

    NASA Technical Reports Server (NTRS)

    Cuddihy, E. F.; Baum, B.; Willis, P.

    1979-01-01

    The paper presents the findings of material surveys intended to identify low cost materials which could be functional as encapsulants (by 1986) for terrestrial solar cell modules. Economic analyses have indicated that in order to meet the low cost goal of $2.70 per sq m, some or all of the following material technologies must be developed or advanced: (1) UV screening outer covers; (2) elastomeric acrylics; (3) weatherproofing and waterproofing of structural wood and paper products; (4) transparent UV stabilizers for the UV-sensitive transparent pottants; and (5) cost-effective utilization of silicone and fluorocarbon materials.

  18. Nonlinear analysis of r.c. framed buildings retrofitted with elastomeric and friction bearings under near-fault earthquakes

    NASA Astrophysics Data System (ADS)

    Mazza, Mirko

    2015-12-01

    Reinforced concrete (r.c.) framed buildings designed in compliance with inadequate seismic classifications and code provisions present in many cases a high vulnerability and need to be retrofitted. To this end, the insertion of a base isolation system allows a considerable reduction of the seismic loads transmitted to the superstructure. However, strong near-fault ground motions, which are characterised by long-duration horizontal pulses, may amplify the inelastic response of the superstructure and induce a failure of the isolation system. The above considerations point out the importance of checking the effectiveness of different isolation systems for retrofitting a r.c. framed structure. For this purpose, a numerical investigation is carried out with reference to a six-storey r.c. framed building, which, primarily designed (as to be a fixed-base one) in compliance with the previous Italian code (DM96) for a medium-risk seismic zone, has to be retrofitted by insertion of an isolation system at the base for attaining performance levels imposed by the current Italian code (NTC08) in a high-risk seismic zone. Besides the (fixed-base) original structure, three cases of base isolation are studied: elastomeric bearings acting alone (e.g. HDLRBs); in-parallel combination of elastomeric and friction bearings (e.g. high-damping-laminated-rubber bearings, HDLRBs and steel-PTFE sliding bearings, SBs); friction bearings acting alone (e.g. friction pendulum bearings, FPBs). The nonlinear analysis of the fixed-base and base-isolated structures subjected to horizontal components of near-fault ground motions is performed for checking plastic conditions at the potential critical (end) sections of the girders and columns as well as critical conditions of the isolation systems. Unexpected high values of ductility demand are highlighted at the lower floors of all base-isolated structures, while re-centring problems of the base isolation systems under near-fault earthquakes are

  19. Waste handling: A study of tributyl phosphate compatibility with nonmetallic materials

    SciTech Connect

    Jenkins, C.F.; Briedenbach, P.J.

    1989-01-01

    The need for numerous seals, plastic tubing, instrument components, and miles of plastic pipe for transferring process waste streams containing tributyl phosphate (TBP) and petroleum solvents led to an investigation of compatibility. TBP is a solvent for many plastics and elastomers and causes softening, crazing, or cracking of most nonmetallics tested. In this regard it may be considered an external plasticizer for some polymers. TBP also is a surfactant in aqueous solution. Dimension changes and property changes associated with softening will preclude the use of some materials as gaskets. Teflon/trademark/ and Kalrez/trademark/ gaskets appear to be compatible with TBP. Mixed results were obtained with EPDM elastomers, but EPDM O-rings are less costly than Kalrez/trademark/ and are being applied in some areas. Exposure of CPVC rigid piping led to crazing and, ultimately, catastrophic stress cracking, thus precluding its use in the waste services described. High-density polyethylene and PVDF plastic piping were unaffected by the test exposures and are useable for process and process waste service. Applications include 25-30 miles of polyethylene pipe and a large number of EPDM gaskets in the filter assembly of an effluent treatment system at the Savannah River Plant. 3 refs., 7 figs., 3 tabs.

  20. An experimental investigation of the damping contribution of an elastomeric ablator on aluminum beams

    NASA Technical Reports Server (NTRS)

    Howell, W. E.

    1974-01-01

    Damping results are presented for an elastometric ablation material bonded to an aluminum alloy substrate. Tests were conducted on aluminum beams 0.159, 0.318, and 0.476 cm thick, and with and without an ablator. Ablation-material thickness varied from 0.159 to 0.953 cm. Comparative damping data were obtained by using variations of the free-free beam technique with strain gages and piezoelectric transducers. Of the two test arrangements employed, the technique using strain gages produced results that indicated less restraint of the beams. Ablation material, in thicknesses less than 1 cm, substantially increased the damping parameter of the aluminum beams.

  1. Heat shrinkability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Chaki, T. K.; Bhowmick, Anil K.

    2000-11-01

    The heat shrinkability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditrimethylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrinkability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrinkability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

  2. Load and stability measurements on a soft-inplane rotor system incorporating elastomeric lead-lag dampers

    NASA Technical Reports Server (NTRS)

    Weller, W. H.

    1977-01-01

    An experimental investigation was conducted of the dynamic response and inplane stability associated with a new soft-inplane helicopter rotor. The unique feature of this rotor was the use of an internal elastomeric damper to restrain the blade inplane motion about the lead-lag hinge. The properties of the elastomer were selected to provide both a nominal first inplane frequency ratio of 0.65 and sufficient damping to eliminate the need for additional external damping sources to prevent ground resonance on a typical fuselage structure. For this investigation a 1/5-scale aeroelastic model was used to represent the rotor. The four-blade model had a diameter of 3.05 m (10 ft) and a solidity of 0.103. The first out-of-plane frequency ratio was 1.06. The model was tested in hover and in forward flight up to an advance ratio of 0.45. At each forward speed the rotor lift was varied up to simulated maneuver conditions. The measured rotor loads and response were within acceptable limits, and no adverse response qualities were observed. Moderate out-of-plane hub moments were measured, even for zero lift, to indicate the beneficial control power available for this design. Blade inplane stability testing indicated that the rotor system damping remained at moderate levels throughout the operating envelope.

  3. Seismic vulnerability assessment of a steel-girder highway bridge equipped with different SMA wire-based smart elastomeric isolators

    NASA Astrophysics Data System (ADS)

    Hedayati Dezfuli, Farshad; Shahria Alam, M.

    2016-07-01

    Shape memory alloy wire-based rubber bearings (SMA-RBs) possess enhanced energy dissipation capacity and self-centering property compared to conventional RBs. The performance of different types of SMA-RBs with different wire configurations has been studied in detail. However, their reliability in isolating structures has not been thoroughly investigated. The objective of this study is to analytically explore the effect of SMA-RBs on the seismic fragility of a highway bridge. Steel-reinforced elastomeric isolators are equipped with SMA wires and used to isolate the bridge. Results revealed that SMA wires with a superelastic behavior and re-centering capability can increase the reliability of the bearing and the bridge structure. It was observed that at the collapse level of damage, the bridge isolated by SMA-HDRB has the lowest fragility. Findings also showed that equipping NRB with SMA wires decreases the possibility of damage in the bridge while, replacing HDRB with SMA-HDRB; or LRB with SMA-LRB increases the failure probability of the system at slight, moderate, and extensive limit states.

  4. A design of backing seat and gasket assembly in diamond anvil cell for accurate single crystal x-ray diffraction to 5 GPa

    NASA Astrophysics Data System (ADS)

    Komatsu, K.; Kagi, H.; Yasuzuka, T.; Koizumi, T.; Iizuka, R.; Sugiyama, K.; Yokoyama, Y.

    2011-10-01

    We designed a new cell assembly of diamond anvil cells for single crystal x-ray diffraction under pressure and demonstrate the application of the cell to the crystallographic studies for ice VI and ethanol high-pressure (HP) phase at 0.95(5) GPa and 1.95(2) GPa, respectively. The features of the assembly are: (1) the platy anvil and unique-shaped backing seat (called as "Wing seat") allowing the extremely wide opening angle up to ±65°, (2) the PFA-bulk metallic glass composite gasket allowing the easy attenuation correction and less background. Thanks to the designed assembly, the Rint values after attenuation corrections are fairly good (0.0125 and 0.0460 for ice VI and ethanol HP phase, respectively), and the errors of the refined parameters are satisfactory small even for hydrogen positions, those are comparable to the results which obtained at ambient conditions. The result for ice VI is in excellent agreement with the previous study, and that for ethanol HP phase has remarkable contributions to the revision to its structure; the H12 site, which makes gauche molecules with O1, C2, and C3 sites, may not exist so that only trans conformers are present at least at 1.95(2) GPa. The accurate intensities using the cell assembly allow us to extract the electron density for ethanol HP phase by the maximum entropy method.

  5. Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior

    SciTech Connect

    Soreto Teixeira, S.; Graça, M. P. F.; Costa, L. C.; Dionisio, M.; Ilcíkova, M.; Mosnacek, J.; Spitalsky, Z.; Krupa, I.

    2014-12-14

    Lithium ferrite (LiFe{sub 5}O{sub 8}) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe{sub 5}O{sub 8} crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li{sub 2}O-Fe{sub 2}O{sub 3} powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer and of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between −73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10{sup −2}) that can be considered interesting for technological applications.

  6. Elastomeric electrospun scaffolds of poly(L-lactide-co-trimethylene carbonate) for myocardial tissue engineering.

    PubMed

    Mukherjee, Shayanti; Gualandi, Chiara; Focarete, Maria Letizia; Ravichandran, Rajeswari; Venugopal, Jayarama Reddy; Raghunath, Michael; Ramakrishna, Seeram

    2011-07-01

    In myocardial tissue engineering the use of synthetically bioengineered flexible patches implanted in the infarcted area is considered one of the promising strategy for cardiac repair. In this work the potentialities of a biomimetic electrospun scaffold made of a commercial copolymer of (L)-lactic acid with trimethylene carbonate (P(L)LA-co-TMC) are investigated in comparison to electrospun poly(L)lactic acid. The P(L)LA-co-TMC scaffold used in this work is a glassy rigid material at room temperature while it is a rubbery soft material at 37 °C. Mechanical characterization results (tensile stress-strain and creep-recovery measurements) show that at 37 °C electrospun P(L)LA-co-TMC displays an elastic modulus of around 20 MPa and the ability to completely recover up to 10% of deformation. Cell culture experiments show that P(L)LA-co-TMC scaffold promotes cardiomyocyte proliferation and efficiently preserve cell morphology, without hampering expression of sarcomeric alpha actinin marker, thus demonstrating its potentialities as synthetic biomaterial for myocardial tissue engineering. PMID:21617996

  7. Structure and Mechanical Behavior of Elastomeric Multiblock Terpolymers Containing Glassy, Rubbery, and Semicrystalline Blocks

    SciTech Connect

    Zuo, Feng; Alfonzo, C. Guillermo; Bates, Frank S.

    2012-11-14

    Multiblock copolymers containing glassy poly(cyclohexylethylene) (C), rubbery poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were synthesized by sequential anionic polymerization of styrene, isoprene, and butadiene followed by catalytic hydrogenation. The resulting CECPCEC (denoted XPX) and CECP (XP) multiblock copolymers each contain 50 vol % of P and equal amounts of C and E. These materials have been studied by dynamic mechanical spectroscopy (DMS), transmission electron microscopy (TEM), small- and wide-angle X-ray scattering (SAXS and WAXS), differential scanning calorimetry (DSC), and tensile deformation to characterize the morphology, phase behavior, and mechanical properties. Microphase separation in these compounds is induced by crystallization of E and/or chemical incompatibility between the three blocks, leading to a new type of morphology which contains continuous region of P and continuous region of microphase-separated X, resulting in mechanically resilient materials. High molecular weight block copolymers microphase separate with two different length scales associated with segregation between C and E and X and P. These structural features produce a nonclassical scaling relationship for the C-E domain spacing, d {approx} N{sup 0.31}, where N is the degree of polymerization of CEC portion. The role of semicrystalline E domains during uniaxial deformation has been exposed with WAXS experiments, which support a two-step mechanism involving recoverable and nonrecoverable deformation to different extents. Strain hardening is observed in double-anchored XPX, but not in single-anchored XP, at large tensile strains.

  8. Buckling Instability of Dielectric Elastomeric Plates for Soft, Bio-Compatible Microfluidic Pumps

    NASA Astrophysics Data System (ADS)

    Tavakol, Behrouz; Bozlar, Michael; Froehlicher, Guillaume; Punckt, Christian; Stone, Howard A.; Aksay, Ilhan; Holmes, Douglas

    2013-03-01

    Dielectric elastomers are well-known for their superior stretchability and permittivity. A fully-clamped thin elastomer will buckle when it is compressed by applying sufficient electric potentials to its sides. When embedded within soft, silicone rubbers, these advanced materials can provide a means for a bio-compatible pumping mechanism that can be used to inject bio-fluids with desired flow rates into microfluidic devices, tissues, and organs of interest. We have incorporated a dielectric film that is sandwiched between two thin, flexible, solid electrodes into a microfluidic device and utilized a voltage-induced out-of-plane buckling instability for pumping of fluids. We experimentally quantify the voltage-induced plate buckling and measure the fluid flow rate when the structure is embedded in a microchannel. Additionally, we offer an analytical prediction that uses plate buckling theory to estimate the flow rate as a function of applied voltage.

  9. Printing Three-Dimensional Heterogeneities in the Elastic Modulus of an Elastomeric Matrix.

    PubMed

    Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K

    2016-05-01

    We present a rapid and controllable method to create microscale heterogeneities in the 3D stiffness of a soft material by printing patterns with a ferrofluid ink. An ink droplet moved through a liquid polydimethylsiloxane (PDMS) volume using an externally applied magnetic field sheds clusters of magnetic nanoparticles (MNPs) in its wake. By varying the field spatiotemporally, a well-defined three-dimensional curvilinear feature is printed that contains MNP clusters. Subsequent cross-linking of the PDMS preserves the feature in place after the magnetic field is removed. Since the ferrofluid ink interferes with the cross-linking of PDMS, a 3D print containing ink density variations leads to corresponding spatial deviations in the elastic modulus of the matrix. The modulus is mapped in the experiments with atomic force microscopy. This rapid method to print 3D heterogeneities in soft matter promises the ability to mimic mechanical variations that occur in natural biomaterials. PMID:27088326

  10. Fabrication and characterization of elastomeric polyester/carbon nanotubes nanocomposites for biomedical application.

    PubMed

    Meng, Z X; Zheng, W; Ding, M H; Zhou, H M; Chen, X Q; Chen, J C; Liu, M K; Zheng, Y F

    2011-04-01

    A novel biodegradable polymer elastomer nanocomposite composing of poly(1,8-octanediol-citrate) (POC) polymer matrix and carbon nanotubes (CNTs) additive was successfully fabricated and systematically investigated using Fourier transform infrared (FT-IR), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), tensile test, incubation and cytotoxicity tests. It was found that the addition of CNTs in POC elastomer did not result in any noticeable change in its chemical structure and the amorphous state. However, the tensile strength and elongation at break were greatly improved by the addition of CNTs in POC polymer matrix. It revealed that the swelling ratio and percentage of weight loss of POC/CNTs nanocomposite were lower, compared with the pure POC material. Moreover, the adsorption amount of bovine serum albumin (BSA) increased with an increase of the CNTs mass content in POC matrix revealing the enhanced hydrophilicity of POC/CNTs nanocomposites contributed by the carboxyl of the CNTs. Additionally, the cytotoxicity tests with L929 cell line revealed that the experimental POC/CNTs nanocomposites possessed good in vitro biocompatibility. PMID:21776679

  11. Integrated elastomeric components for autonomous regulation of sequential and oscillatory flow switching in microfluidic devices

    NASA Astrophysics Data System (ADS)

    Mosadegh, Bobak; Kuo, Chuan-Hsien; Tung, Yi-Chung; Torisawa, Yu-Suke; Bersano-Begey, Tommaso; Tavana, Hossein; Takayama, Shuichi

    2010-06-01

    A critical need for enhancing the usability and capabilities of microfluidic technologies is the development of standardized, scalable and versatile control systems. Electronically controlled valves and pumps typically used for dynamic flow regulation, although useful, can limit convenience, scalability and robustness. This shortcoming has motivated the development of device-embedded non-electrical flow-control systems. Existing approaches to regulate operation timing on-chip, however, still require external signals such as timed generation of fluid flow, bubbles, liquid plugs or droplets or an alteration of chemical compositions or temperature. Here, we describe a strategy to provide device-embedded flow switching and clocking functions. Physical gaps and cavities interconnected by holes are fabricated into a three-layer elastomer structure to form networks of fluidic gates that can spontaneously generate cascading and oscillatory flow output using only a constant flow of Newtonian fluids as the device input. The resulting microfluidic substrate architecture is simple, scalable and should be applicable to various materials. This flow-powered fluidic gating scheme brings the autonomous signal processing ability of microelectronic circuits to microfluidics where there is the added diversity in current information of having distinct chemical or particulate species and richness in current operation of having chemical reactions and physical interactions.

  12. Transparent, elastomeric and tough hydrogels from poly(ethylene glycol) and silicate nanoparticles.

    PubMed

    Gaharwar, Akhilesh K; Rivera, Christian P; Wu, Chia-Jung; Schmidt, Gudrun

    2011-12-01

    The structures and mechanical properties of both physically and covalently cross-linked nanocomposite hydrogels made from poly(ethylene glycol) (PEG) and silicate nanoparticles (Laponite RD) are investigated. Injectable nanocomposite precursor solutions can be covalently cross-linked via photopolymerization. The resulting hydrogels are transparent and have interconnected pores, high elongation and toughness. These properties depend on the hydrogel composition, polymer-nanoparticle interactions and degree of cross-linking (both physical and covalent). Covalent cross-linking of polymer chains leads to the formation of an elastic network, whereas physical cross-linking between nanoparticles and polymer chains induces viscoelastic properties. At high deformations covalent bonds may be broken but physical bonds rebuild and to some extent self-heal the overall network structure. Addition of silicate also enhances the bioactivity and adhesiveness of the hydrogel as these materials stick to soft tissue as well as to hard surfaces. In addition, MC3T3-E1 mouse preosteoblast cells readily adhere and spread on nanocomposite hydrogel surfaces. Collectively, the combinations of properties such as elasticity, stiffness, interconnected network, adhesiveness to surfaces and bio-adhesion to cells provide inspiration and opportunities to engineer mechanically strong and elastic tissue matrixes for orthopedic, craniofacial and dental applications. PMID:21839864

  13. High friction on ice provided by elastomeric fiber composites with textured surfaces

    NASA Astrophysics Data System (ADS)

    Rizvi, R.; Naguib, H.; Fernie, G.; Dutta, T.

    2015-03-01

    Two main applications requiring high friction on ice are automobile tires and footwear. The main motivation behind the use of soft rubbers in these applications is the relatively high friction force generated between a smooth rubber contacting smooth ice. Unfortunately, the friction force between rubber and ice is very low at temperatures near the melting point of ice and as a result we still experience automobile accidents and pedestrian slips and falls in the winter. Here, we report on a class of compliant fiber-composite materials with textured surfaces that provide outstanding coefficients of friction on wet ice. The fibrous composites consist of a hard glass-fiber phase reinforcing a compliant thermoplastic polyurethane matrix. The glass-fiber phase is textured such that it is aligned transversally and protruding out of the elastomer surface. Our analysis indicates that the exposed fiber phase exhibits a "micro-cleat" effect, allowing for it to fracture the ice and increase the interfacial contact area thereby requiring a high force to shear the interface.

  14. Mechanically tunable aspheric lenses via additive manufacture of hanging elastomeric droplets for microscopic applications

    NASA Astrophysics Data System (ADS)

    Fuh, Yiin-Kuen; Chen, Pin-Wen; Lai, Zheng-Hong

    2016-07-01

    Mechanically deformable lenses with dynamically tunable focal lengths have been developed in this work. The fabricated five types of aspheric polydimethylsiloxane (PDMS) lenses presented here have an initial focal length of 7.0, 7.8, 9.0, 10.0 and 10.2 mm. Incorporating two modes of operation in biconvex and concave-convex configurations, the focal lengths can be tuned dynamically as 5.2-10.2, 5.5-9.9, 6.6-11.9, 6.1-13.5 and 6.6-13.5 mm respectively. Additive manufacturing was utilized to fabricate these five types of aspheric lenses (APLs) via sequential layering of PDMS materials. Complex structures with three-dimensional features and shorter focal lengths can be successfully produced by repeatedly depositing, inverting and curing controlled PDMS volume onto previously cured PDMS droplets. From our experiments, we empirically found a direct dependence of the focal length of the lenses with the amount (volume) of deposited PDMS droplets. This new mouldless, low-cost, and flexible lens fabrication method is able to transform an ordinary commercial smartphone camera into a low-cost portable microscope. A few microscopic features can be readily visualized, such as wrinkles of ladybird pupa and printed circuit board. The fabrication technique by successively applying hanging droplet and facile mechanical focal-length-tuning set-up can be easily adopted in the development of high-performance optical lenses.

  15. Structure and Dynamics of Elastomeric Multiblock Terpolymers containing Glassy, Rubbery and Semicrystalline Blocks.

    SciTech Connect

    Zuo, Feng; Alfonzo, C. Guillermo; Bates, F. S.

    2011-01-01

    Multiblock copolymers containing glassy poly-(cyclohexylethylene) (C), rubbery poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were synthesized by sequential anionic polymerization of styrene, isoprene, and buta-diene followed by catalytic hydrogenation. The resulting CECP-CEC (denoted XPX) and CECP (XP) multiblock copolymers each contain 50 vol % of P and equal amounts of C and E. These materials have been studied by dynamic mechanical spectroscopy (DMS), transmission electron microscopy (TEM), small- an wide-angle X-ray scattering (SAXS and WAXS), di!erential scanning calorimetry (DSC), and tensile deformation to characterize the morphology, phase behavior, and mechanical properties. Microphase separation in these compounds is induced by crystallization of Eand/or chemical incompatibility between the three blocks, leading to a new type of morphology which contains continuous region of P and continuous region ofmicrophase-separated X, resulting inmechanically resilientmaterials.Highmolecular weight block copolymers microphase separate with two di!erent length scales associated with segregation between C and E and X and P. These structural features produce a nonclassical scaling relationship for the C!E domain spacing, d ! N0.31, where N is the degree of polymerization of CEC portion. The role of semicrystalline E domains during uniaxial deformation has been exposed withWAXS experiments, which support a two-stepmechanisminvolving recoverable and nonrecoverable deformation to di!erent extents. Strain hardening is observed in double-anchored XPX, but not in single-anchored XP, at large tensile strains.

  16. Synthesis and characterization of conductive, biodegradable, elastomeric polyurethanes for biomedical applications.

    PubMed

    Xu, Cancan; Yepez, Gerardo; Wei, Zi; Liu, Fuqiang; Bugarin, Alejandro; Hong, Yi

    2016-09-01

    Biodegradable conductive polymers are currently of significant interest in tissue repair and regeneration, drug delivery, and bioelectronics. However, biodegradable materials exhibiting both conductive and elastic properties have rarely been reported to date. To that end, an electrically conductive polyurethane (CPU) was synthesized from polycaprolactone diol, hexadiisocyanate, and aniline trimer and subsequently doped with (1S)-(+)-10-camphorsulfonic acid (CSA). All CPU films showed good elasticity within a 30% strain range. The electrical conductivity of the CPU films, as enhanced with increasing amounts of CSA, ranged from 2.7 ± 0.9 × 10(-10) to 4.4 ± 0.6 × 10(-7) S/cm in a dry state and 4.2 ± 0.5 × 10(-8) to 7.3 ± 1.5 × 10(-5) S/cm in a wet state. The redox peaks of a CPU1.5 film (molar ratio CSA:aniline trimer = 1.5:1) in the cyclic voltammogram confirmed the desired good electroactivity. The doped CPU film exhibited good electrical stability (87% of initial conductivity after 150 hours charge) as measured in a cell culture medium. The degradation rates of CPU films increased with increasing CSA content in both phosphate-buffered solution (PBS) and lipase/PBS solutions. After 7 days of enzymatic degradation, the conductivity of all CSA-doped CPU films had decreased to that of the undoped CPU film. Mouse 3T3 fibroblasts proliferated and spread on all CPU films. This developed biodegradable CPU with good elasticity, electrical stability, and biocompatibility may find potential applications in tissue engineering, smart drug release, and electronics. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2305-2314, 2016. PMID:27124702

  17. Resorbable elastomeric networks prepared by photocrosslinking of high-molecular-weight poly(trimethylene carbonate) with photoinitiators and poly(trimethylene carbonate) macromers as crosslinking aids.

    PubMed

    Bat, Erhan; van Kooten, Theo G; Feijen, Jan; Grijpma, Dirk W

    2011-05-01

    Resorbable and elastomeric poly(trimethylene carbonate) (PTMC) networks were efficiently prepared by photoinitiated crosslinking of linear high-molecular-weight PTMC. To crosslink PTMC films, low-molecular-weight PTMC macromers with methacrylate end groups were synthesized and used as crosslinking aids. By exposing PTMC films containing only photoinitiator (Irgacure(®) 2959) or both photoinitiator and PTMC macromers to ultraviolet light, PTMC networks with high gel contents (87-95%) could be obtained. The crosslink density could be readily varied by adjusting the irradiation time or the amount of crosslinking aid used. The formed networks were flexible, with low elastic modulus values ranging from 7.1 to 7.5MPa, and also showed excellent resistance to creep in cyclic tests. In vitro experiments showed that the photocrosslinked PTMC networks could be eroded by macrophages, and upon incubation in aqueous cholesterol esterase enzyme- or potassium dioxide solutions. The rate of surface erosion of photocrosslinked PTMC networks was significantly lower than that observed for films prepared from linear PTMC. These resorbable PTMC elastomeric networks are compatible with cells and may find application in tissue engineering and controlled release. PMID:21232640

  18. Rumen metabolism and absorption of a /sup 14/C-labelled elastomeric copolymer and its value as a roughage substitute for cattle

    SciTech Connect

    Bartley, E.E.; Meyer, R.M.; Call, E.P.

    1981-05-01

    Several synthetic elastomeric and plastomeric polymers were tested for suitability as artificial roughages. They were fed to rumenfistulated cattle fed grain only. Several of the polymers were regurgitated, remasticated and reswallowed, and they formed thin strands of intermeshed fiber that produced a large, loosely woven hay-like mass that floated on the rumen contents. An elastomeric polymer consisting of copolymers of 80 to 90% ethylene and 10 to 20% propylene, with a tensile strength at yield of 45.7 kg/cm2, a hardness of 30 units (Shore D hardness scale) and a tensile strength at 300% elongation of 51.0 kg/cm2, was selected for further testing. The copolymer was fed at about 90 g/head daily for 127 days to cattle fed grain only. At slaughter, rumens contained an average of 8.0 kg copolymer (dry basis). Cattle fed the copolymer had healthier rumen papillae and epithelia of the abomasum and small intestines than did control animals fed grain only. Using /sup 14/C-labeled copolymer, we found that the copolymer was not degraded by rumen microorganisms or acid-pepsin solution. When /sup 14/C-labeled copolymer was fed to milking cows, no /sup 14/C activity was found in milk, blood or urine. Upon slaughter, about 100% of the /sup 14/C activity was recovered from digesta and feces. We concluded that the copolymer was not absorbed from the digestive tract.

  19. Advanced materials and biochemical processes for geothermal applications

    SciTech Connect

    Kukacka, L.E.; van Rooyen, D.; Premuzic, E.T.

    1987-04-01

    Two Geothermal Technology Division (GTD)-sponsored programs: (1) Geothermal Materials Development, and (2) Advanced Biochemical Processes for Geothermal Brines, are described. In the former, work in the following tasks is in progress: (1) high temperature elastomeric materials for dynamic sealing applications, (2) advanced high temperature (300/sup 0/C) lightweight (1.1 g/cc) well cementing materials, (3) thermally conductive composites for heat exchanger tubing, (4) corrosion rates for metals in brine-contaminated binary plant working fluids, and (5) elastomeric liners for well casing. Methods for the utilization and/or the low cost environmentally acceptable disposal of toxic geothermal residues are being developed in the second program. This work is performed in two tasks. In one, microorganisms that can interact with toxic metals found in geothermal residues to convert them into soluble species for subsequent reinjection back into the reservoir or to concentrate them for removal by conventional processes are being identified. In the second task, process conditions are being defined for the encapsulation of untreated or partially biochemically treated residues in Portland cement-based formulations and the subsequent utilization of the waste fractions in building materials. Both processing methods yield materials which appear to meet disposal criteria for non-toxic solid waste, and their technical and economic feasibilities have been established.

  20. MCU MATERIALS COMPATIBILITY WITH CSSX SOLVENT

    SciTech Connect

    Fondeur, F

    2006-01-13

    The Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) plans to use several new materials of construction not previously used with CSSX solvent. SRNL researchers tested seven materials proposed for service in seal and gasket applications. None of the materials leached detectable amounts of components into the CSSX solvent during 96 hour tests. All are judged acceptable for use based on their effect on the solvent. However, some of the materials adsorbed solvent or changed dimensions during contact with solvent. Consultation with component and material vendors with regard to performance impact and in-use testing of the materials is recommended. Polyetheretherketone (PEEK), a material selected for use in contactor bearing seals, did not gain weight or change dimensions on contact with CSSX solvent. Analysis of the solvent contacted with this material showed no impurities and the standard dispersion test gave acceptable phase separation results. The material contains a leachable hydrocarbon substance, detectable on exposed surfaces, that did not adversely contaminate the solvent within the limits of the testing. We recommend contacting the vendor to determine the source and purpose of this component, or, alternatively, pursue the infrared analysis of the PEEK in an effort to better define potential impacts.

  1. 49 CFR 178.360-4 - Closure devices.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... be closed by a securely bolted flange and leak-tight gasket. Each flange must be welded or brazed to... torque of no more than twice the force necessary to seal the selected gasket. Gasket material must...

  2. 49 CFR 178.360-4 - Closure devices.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... securely bolted flange and leak-tight gasket. Each flange must be welded or brazed to the body of the 2R... twice the force necessary to seal the selected gasket. Gasket material must be capable of...

  3. Cryogenic loading of large volume presses for high-pressure experimentation and synthesis of novel materials

    SciTech Connect

    Lipp, M J; Evans, W J; Yoo, C S

    2005-01-21

    We present an efficient easily implemented method for loading cryogenic fluids in a large volume press. We specifically apply this method to the high-pressure synthesis of an extended solid derived from CO using a Paris-Edinburgh cell. This method employs cryogenic cooling of Bridgman type WC anvils well insulated from other press components, condensation of the load gas within a brass annulus surrounding the gasket between the Bridgman anvils. We demonstrate the viability of the described approach by synthesizing macroscopic amounts (several milligrams) of polymeric CO-derived material, which were recovered to ambient conditions after compression of pure CO to 5 GPa or above.

  4. 78 FR 17350 - Foreign-Trade Zone 262-Southaven (Desoto County), Mississippi; Notification of Proposed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-21

    ..., hoses, gaskets, seals, guards, boots, covers), articles of leather, felt seals, paper and paperboard labels/seals/gaskets/boxes/containers, printed materials, textile carrying cases, sweatshirts,...

  5. The effect of configuration on strength, durability, and handle of Kevlar fabric-based materials

    NASA Technical Reports Server (NTRS)

    Reuter, L. L.; Munson, J. B.

    1977-01-01

    Five Kevlar based laminates and three Kevlar based coated materials were designed, hand made, and tested against comparative conventional Dacron based materials for strength, peel, tear, puncture, creases, and handle. Emphasis was placed on evaluating geometric orientation of constituents, use of elastomeric film in place of high modulus films, and the use of flying thread loom bias reinforcement of Kevlar yarns. Whereas, the performance of the Kevlar laminates was severely degraded by crease effects, significant gains in overall performance factors were shown for the coated Kevlar materials.

  6. Analytical investigations on elastomeric shells of new Poly Implant Prothèse (PIP) breast and from sixteen cases of surgical explantation.

    PubMed

    Beretta, Giangiacomo; Panseri, Sara; Manzo, Alessandra; Hamid, Rufaida; Richards, Adrian; Malacco, Matteo

    2014-09-01

    In this study we have analysed the chemical composition of the extractable components from the elastomeric shells from n=27 explanted implants (n=16 patients), n=2 new PIP implants, and from explanted Eurosilicone and McGhan implants (n=2 for each brand). Empty elastomeric PIP shells (n=2) were also available for analysis. Prostheses were explanted between 2011 and 2012, after 3-11 years of implantation. Patients presented pre- and post-operation complications of different degrees. First we evaluated the micro-structural features of the shells by phase contrast microscopy, and compared the results with those obtained using attenuated total reflectance infrared spectroscopy (ATR-FT-IR), head space gas chromatography coupled to mass spectrometry (HS-GC-MS) and GC-MS in direct injection mode. The results of these studies confirm and explain the conclusion of previous international investigations that evidenced a linear decrease of rupture rate for prostheses implanted after 2006. The analytical identification of a series of UV sensitive radical photo-initiators (0.1%-0.2% w/w), belonging to the benzophenone family, in the shells of new and explanted prostheses produced after 2006 (associated with a strong smell absent in those produced earlier), in parallel to (ii) the removal of the anti bleed barrier from their manufacturing procedure (introduced after 2001), strongly suggested that from 2007, the PIP company used a polymerisation process different from that declared, probably as a consequence of the first reports of rupture problems. In addition, the HS-GC-MS experiments demonstrated that at body temperature the diffusivity of low molecular weight (LMW) silicones present in the PIP filler silicone is significantly higher than that of LMW silicones in an approved implant. PMID:24915531

  7. Advanced process control and novel test methods for PVD silicon and elastomeric silicone coatings utilized on ion implant disks, heatsinks and selected platens

    SciTech Connect

    Springer, J.; Allen, B.; Wriggins, W.; Kuzbyt, R.; Sinclair, R.

    2012-11-06

    Coatings play multiple key roles in the proper functioning of mature and current ion implanters. Batch and serial implanters require strategic control of elemental and particulate contamination which often includes scrutiny of the silicon surface coatings encountering direct beam contact. Elastomeric Silicone Coatings must accommodate wafer loading and unloading as well as direct backside contact during implant plus must maintain rigid elemental and particulate specifications. The semiconductor industry has had a significant and continuous effort to obtain ultra-pure silicon coatings with sustained process performance and long life. Low particles and reduced elemental levels for silicon coatings are a major requirement for process engineers, OEM manufacturers, and second source suppliers. Relevant data will be presented. Some emphasis and detail will be placed on the structure and characteristics of a relatively new PVD Silicon Coating process that is very dense and homogeneous. Wear rate under typical ion beam test conditions will be discussed. The PVD Silicon Coating that will be presented here is used on disk shields, wafer handling fingers/fences, exclusion zones of heat sinks, beam dumps and other beamline components. Older, legacy implanters can now provide extended process capability using this new generation PVD silicon - even on implanter systems that were shipped long before the advent of silicon coating for contamination control. Low particles and reduced elemental levels are critical performance criteria for the silicone elastomers used on disk heatsinks and serial implanter platens. Novel evaluation techniques and custom engineered tools are used to investigate the surface interaction characteristics of multiple Elastomeric Silicone Coatings currently in use by the industry - specifically, friction and perpendicular stiction. These parameters are presented as methods to investigate the critical wafer load and unload function. Unique tools and test

  8. Advanced process control and novel test methods for PVD silicon and elastomeric silicone coatings utilized on ion implant disks, heatsinks and selected platens

    NASA Astrophysics Data System (ADS)

    Springer, J.; Allen, B.; Wriggins, W.; Kuzbyt, R.; Sinclair, R.

    2012-11-01

    Coatings play multiple key roles in the proper functioning of mature and current ion implanters. Batch and serial implanters require strategic control of elemental and particulate contamination which often includes scrutiny of the silicon surface coatings encountering direct beam contact. Elastomeric Silicone Coatings must accommodate wafer loading and unloading as well as direct backside contact during implant plus must maintain rigid elemental and particulate specifications. The semiconductor industry has had a significant and continuous effort to obtain ultra-pure silicon coatings with sustained process performance and long life. Low particles and reduced elemental levels for silicon coatings are a major requirement for process engineers, OEM manufacturers, and second source suppliers. Relevant data will be presented. Some emphasis and detail will be placed on the structure and characteristics of a relatively new PVD Silicon Coating process that is very dense and homogeneous. Wear rate under typical ion beam test conditions will be discussed. The PVD Silicon Coating that will be presented here is used on disk shields, wafer handling fingers/fences, exclusion zones of heat sinks, beam dumps and other beamline components. Older, legacy implanters can now provide extended process capability using this new generation PVD silicon - even on implanter systems that were shipped long before the advent of silicon coating for contamination control. Low particles and reduced elemental levels are critical performance criteria for the silicone elastomers used on disk heatsinks and serial implanter platens. Novel evaluation techniques and custom engineered tools are used to investigate the surface interaction characteristics of multiple Elastomeric Silicone Coatings currently in use by the industry - specifically, friction and perpendicular stiction. These parameters are presented as methods to investigate the critical wafer load and unload function. Unique tools and test

  9. Enabling Desktop Nanofabrication with the Targeted Use of Soft Materials

    NASA Astrophysics Data System (ADS)

    Eichelsdoerfer, Daniel James

    This thesis focuses on the application of soft materials to scanning probe-based molecular printing techniques, such as dip-pen nanolithography (DPN). The selective incorporation of soft materials in place of hard materials in traditional cantilever-based scanning probe lithography (SPL) systems not only enables the deposition of a broader range of materials, but also dramatically lowers the cost while simultaneously increasing the throughput of SPL. Chapter 1 introduces SPL and DPN, and highlights a few recent advances in using DPN to control surface chemical functionality at the nanoscale. In addition to introducing the material deposition capabilities of DPN, Chapter 1 introduces the development of the cantilever-free architecture, a relatively recent paradigm shift in high-throughput SPL. Furthermore, an in-depth synthetic methodology for making the most widely used cantilever-free tip arrays, consisting of elastomeric nanoscale pens adhered to an elastomeric backing layer on a glass slide, is included as an appendix. Chapter 2 discusses the synthesis of metal and metal oxide nanoparticles at specified locations by using DPN to deposit the precursors dispersed in a polymer matrix; after deposition, the precursors are annealed to form single nanoparticles. This work builds on previous soft material-based advances in DPN by utilizing the polymer as a "nanoreactor" to synthesize the desired nanoparticles, where the precursors can diffuse and coalesce into a single nanoparticle within each spot. The process of precursor aggregation and single nanoparticle formation is studied, and it is found that metal precursors follow one of three pathways based upon their reduction potential. Chapter 3 is the first of three chapters that highlights the power of soft materials in the cantilever-free architecture. In particular, Chapter 3 examines the role of the elastomeric backing layer as a compliant spring whose stiffness (as measured by the spring constant, k) can be tuned

  10. High resolution PFPE-based molding High resolution PFPE-based molding High resolution PFPE-based molding techniques for nanofabrication of high pattern density sub-20 nm features: A fundamental materials approach

    SciTech Connect

    Williams, Stuart S; Samulski, Edward; Lopez, Renee; Ruiz, Ricardo; DeSimone, Joseph; Retterer, Scott T

    2010-01-01

    ABSTRACT. Described herein is the development and investigation of PFPE-based elastomers for high resolution replica molding applications. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface energies (<25 mN/m). Using practically relevant large area master templates, we show that the resolution of the molds is strongly dependant upon the elastomeric mold modulus. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus composite molds were able to effectively replicate the nano-grating structures without cracking or tear-out defects that typically occur with high modulus elastomers.

  11. Controlling cell-material interactions with polymer nanocomposites by use of surface modifying additives

    NASA Astrophysics Data System (ADS)

    Poole-Warren, L. A.; Farrugia, B.; Fong, N.; Hume, E.; Simmons, A.

    2008-11-01

    Polymer nanocomposites (NC) are fabricated by incorporating well dispersed nanoscale particles within a polymer matrix. This study focuses on elastomeric polyurethane (PU) based nanocomposites, containing organically modified silicates (OMS), as bioactive materials. Nanocomposites incorporating chlorhexidine diacetate as an organic modifier (OM) were demonstrated to be antibacterial with a dose dependence related to both the silicate loading and the loading of OM. When the non-antibacterial OM dodecylamine was used, both cell and platelet adhesion were decreased on the nanocomposite surface. These results suggest that OM is released from the polymer and can impact on cell behaviour at the interface. Nanocomposites have potential use as bioactive materials in a range of biomedical applications.

  12. Filament-wound composite vessels material technology

    NASA Technical Reports Server (NTRS)

    Lark, R. F.

    1973-01-01

    Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

  13. Survey of materials for hydrazine propulsion systems in multicycle extended life applications

    NASA Technical Reports Server (NTRS)

    Coulbert, C. D.; Yankura, G.

    1972-01-01

    An assessment is presented of materials compatibility data for hydrazine monopropellant propulsion systems applicable to the Space Shuttle vehicle missions. Materials were evaluated for application over a 10-yr/100-mission operational lifetime with minimum refurbishment. A general materials compatibility rating for a broad range of materials and several propellants based primarily on static liquid propellant immersion testing and an in-depth evaluation of hydrazine decomposition as a function of purity, temperature, material, surface conditions, etc., are presented. The most promising polymeric material candidates for propellant diaphragms and seals appear to have little effect on increasing hydrazine decomposition rates, but the materials themselves do undergo changes in physical properties which can affect their 10-yr performance in multicycle applications. The available data on these physical properties of elastomeric materials as affected by exposure to hydrazine or related environments are presented.

  14. Mechanical Properties of Cellular Materials

    SciTech Connect

    Solem, J.C.; Dienes, J.K.

    1999-07-09

    The authors calculated the stress-strain relation for elastomeric foam from an ab initio theory, which shows that the plateau and densification regions should be described by a hyperbola. The theory seems to agree reasonably well with experiment.

  15. Mechanically Active Electrospun Materials

    NASA Astrophysics Data System (ADS)

    Robertson, Jaimee M.

    Electrospinning, a technique used to fabricate small diameter polymer fibers, has been employed to develop unique, active materials falling under two categories: (1) shape memory elastomeric composites (SMECs) and (2) water responsive fiber mats. (1) Previous work has characterized in detail the properties and behavior of traditional SMECs with isotropic fibers embedded in an elastomer matrix. The current work has two goals: (i) characterize laminated anisotropic SMECs and (ii) develop a fabrication process that is scalable for commercial SMEC manufacturing. The former ((i)) requires electrospinning aligned polymer fibers. The aligned fibers are similarly embedded in an elastomer matrix and stacked at various fiber orientations. The resulting laminated composite has a unique response to tensile deformation: after stretching and releasing, the composite curls. This curling response was characterized based on fiber orientation. The latter goal ((ii)) required use of a dual-electrospinning process to simultaneously electrospin two polymers. This fabrication approach incorporated only industrially relevant processing techniques, enabling the possibility of commercial application of a shape memory rubber. Furthermore, the approach had the added benefit of increased control over composition and material properties. (2) The strong elongational forces experienced by polymer chains during the electrospinning process induce molecular alignment along the length of electrospun fibers. Such orientation is maintained in the fibers as the polymer vitrifies. Consequently, residual stress is stored in electrospun fiber mats and can be recovered by heating through the polymer's glass transition temperature. Alternatively, the glass transition temperature can be depressed by introducing a plasticizing agent. Poly(vinyl acetate) (PVAc) is plasticized by water, and its glass transition temperature is lowered below room temperature. Therefore, the residual stress can be relaxed at room

  16. Polyurethanes: versatile materials and sustainable problem solvers for today's challenges.

    PubMed

    Engels, Hans-Wilhelm; Pirkl, Hans-Georg; Albers, Reinhard; Albach, Rolf W; Krause, Jens; Hoffmann, Andreas; Casselmann, Holger; Dormish, Jeff

    2013-09-01

    Polyurethanes are the only class of polymers that display thermoplastic, elastomeric, and thermoset behavior depending on their chemical and morphological makeup. In addition to compact polyurethanes, foamed variations in particular are very widespread, and they achieve their targeted properties at very low weights. The simple production of sandwich structures and material composites in a single processing step is a key advantage of polyurethane technology. The requirement of energy and resource efficiency increasingly demands lightweight structures. Polyurethanes can serve this requirement by acting as matrix materials or as flexible adhesives for composites. Polyurethanes are indispensable when it comes to high-quality decorative coatings or maintaining the value of numerous objects. They are extremely adaptable and sustainable problem solvers for today's challenges facing our society, all of which impose special demands on materials. PMID:23893938

  17. Investigation of test methods, material properties, and processes for solar cell encapsulants. Eighteenth quarterly progress report, August 12-November 12, 1980

    SciTech Connect

    Willis, P. B.; Baum, B.; Davis, M.

    1980-12-01

    The goal of this program is to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. A survey was made of elastomers for use as gaskets for the photovoltaic module. Of the wide variety of materials examined EPDM offered the optimum combination of low compression set and low cost. The preference for EPDM is borne out by its long history of use as an automobile gasket. The commercial availability of materials that would be useful for sealants between the edge of the module and the gasket was investigated. Butyl sealants have the best combination of physical properties, low cost and a well-documented history of performance. A preferred composition has not yet been identified. One laminating type pottant ethylene/methyl acrylate copolymer (EMA), and two casting polymers, polybutyl acrylate and polyurethane, have been under investigation this past quarter. An EMA formulation has been developed which is easily extrudable and cures to a high gel content. So far only one commercial US source (Quinn) of aliphatic polyurethane has been located. Work is continuing to improve reaction rate as well as to eliminate source(s) of bubble formation during module fabrication. Considerable effort was spent in developing an improved polybutyl acrylate casting formulation providing high gel. Many viable curing systems are now available: however, the best formulation considering physical properties, freedom from bubbles as well as cure time utilizes Lupersol II (aliphatic peroxide) initiator. This initiator gives the desired gel after 20 minute cure at 45/sup 0/C or 12 minute cure at 55/sup 0/C.

  18. Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover

    SciTech Connect

    Ghaemi, F. Tony

    2011-09-10

    Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3 {mu}m, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)10.1117/1.3251343], while further information on the four science cameras can be found at http://www.msss.com.

  19. Engineered 3D bioimplants using elastomeric scaffold, self-assembling peptide hydrogel, and adipose tissue-derived progenitor cells for cardiac regeneration

    PubMed Central

    Soler-Botija, Carolina; Bagó, Juli R; Llucià-Valldeperas, Aida; Vallés-Lluch, Ana; Castells-Sala, Cristina; Martínez-Ramos, Cristina; Fernández-Muiños, Teresa; Chachques, Juan Carlos; Pradas, Manuel Monleón; Semino, Carlos E; Bayes-Genis, Antoni

    2014-01-01

    Contractile restoration of myocardial scars remains a challenge with important clinical implications. Here, a combination of porous elastomeric membrane, peptide hydrogel, and subcutaneous adipose tissue-derived progenitor cells (subATDPCs) was designed and evaluated as a bioimplant for cardiac regeneration in a mouse model of myocardial infarction. SubATDPCs were doubly transduced with lentiviral vectors to express bioluminescent-fluorescent reporters driven by constitutively active, cardiac tissue-specific promoters. Cells were seeded into an engineered bioimplant consisting of a scaffold (polycaprolactone methacryloyloxyethyl ester) filled with a peptide hydrogel (PuraMatrix™), and transplanted to cover injured myocardium. Bioluminescence and fluorescence quantifications showed de novo and progressive increases in promoter expression in bioactive implant-treated animals. The bioactive implant was well adapted to the heart, and fully functional vessels traversed the myocardium-bioactive implant interface. Treatment translated into a detectable positive effect on cardiac function, as revealed by echocardiography. Thus, this novel implant is a promising construct for supporting myocardial regeneration. PMID:24936221

  20. Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover.

    PubMed

    Ghaemi, F Tony

    2011-09-10

    Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3 μm, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)], while further information on the four science cameras can be found at http://www.msss.com. PMID:21946992

  1. Condition monitoring methods applied to degradation of chlorosulfonated polyethylene cable jacketing materials.

    SciTech Connect

    Assink, Roger Alan; Gillen, Kenneth Todd; Bernstein, Robert; Celina, Mathias Christopher

    2005-05-01

    Three promising polymer material condition monitoring (CM) methods were applied to eight commercial chlorosulfonated polyethylene cable jacket materials aged under both elevated temperature and high-energy radiation conditions. The CM methods examined, cross-sectional modulus profiling, solvent uptake and NMR T{sub 2} relaxation time measurements of solvent-swelled samples, are closely related since they are all strongly influenced by the changes in overall crosslink density of the materials. Each approach was found to correlate well with ultimate tensile elongation measurements, the most widely used method for following degradation of elastomeric materials. In addition approximately universal failure criteria were found to be applicable for the modulus profiling and solvent uptake measurements, independent of the CSPE material examined and its degradation environment. For an arbitrarily assumed elongation 'failure' criterion of 50% absolute, the CSPE materials typically reached 'failure' when the modulus increased to {approx}35 MPa and the uptake factor in p-xylene decreased to {approx}1.6.

  2. Use of a sub-gasket and soft gas diffusion layer to mitigate mechanical degradation of a hydrocarbon membrane for polymer electrolyte fuel cells in wet-dry cycling

    NASA Astrophysics Data System (ADS)

    Ishikawa, Hiroshi; Teramoto, Takeshi; Ueyama, Yasuhiro; Sugawara, Yasushi; Sakiyama, Yoko; Kusakabe, Masato; Miyatake, Kenji; Uchida, Makoto

    2016-09-01

    The mechanical durability of hydrocarbon (HC) membranes, used for polymer electrolyte fuel cells (PEFCs), was evaluated by the United States Department of Energy (USDOE) stress protocol involving wet-dry cycling, and the degradation mechanism is discussed. The HC membrane ruptured in the edge region of the membrane electrode assembly (MEA) after 300 cycles due to a concentration of the mechanical stress. Post-test analysis of stress-strain measurements revealed that the membrane mechanical strain decreased more than 80% in the edge region of the MEA and about 50% in the electrode region, compared with the pristine condition. Size exclusion chromatography (SEC) indicated that the average molecular weight of the HC polymer increased slightly, indicating some cross-linking, while the IEC decreased slightly, indicating ionomer degradation. As a result of two types of modifications, a sub-gasket (SG) and a soft gas diffusion layer (GDL) in the MEA edge region, the mechanical stress decreased, and the durability increased, the membrane lasting more than 30,000 cycles without mechanical failure.

  3. Functional and multifunctional polymers: Materials for smart structures

    SciTech Connect

    Arnold, S.; Li, J.; Pratt, L.; Khan, I.M.

    1995-12-01

    A number of functional and multifunctional polymeric systems with potential applications in smart structures will be discussed. The synthesis, characterization and some applications of the microphase separated mixed (electronic and ionic) conductive or MIEC block copolymers will be presented. One such series is poly[3-methylthiophene-co-3-octylthiophene)-block-{omega}-methoxyocta(oxyethylene) methacrylate] block copolymers. Applications of these polymers are in synthetic muscles, electromagnetic shielding materials, membranes for biological electron transfer processes. A new class of proccessible and electroactive polymers, copolymers of (3-methyl or 3-phenyl)thiophene and (3-oligodimethy)siloxane)thiophene will be reported. These polymers have applications in electrorheological fluids and synthetic muscles. Also, a easier methodology for preparing highly ionic conductive and elastomeric solid polymer electrolytes by blending commercial polymers will be discussed. Application of these materials are in electrochromic windows and solid state microelectromechanical devices.

  4. 40 CFR 1060.240 - How do I demonstrate that my emission family complies with evaporative emission standards?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... least 2 percent of the fuel tank's overall wall thickness with any of the following gasket and fuel-cap characteristics: (i) No nonmetal gaskets or fuel caps. (ii) All nonmetal gaskets and fuel caps made from low-permeability materials. (iii) Nonmetal gaskets and fuel caps that are not made from low-permeability...

  5. 40 CFR 1060.240 - How do I demonstrate that my emission family complies with evaporative emission standards?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... least 2 percent of the fuel tank's overall wall thickness with any of the following gasket and fuel-cap characteristics: (i) No nonmetal gaskets or fuel caps. (ii) All nonmetal gaskets and fuel caps made from low-permeability materials. (iii) Nonmetal gaskets and fuel caps that are not made from low-permeability...

  6. Comparison of Raman spectroscopy vs. high performance liquid chromatography for quality control of complex therapeutic objects: model of elastomeric portable pumps filled with a fluorouracil solution.

    PubMed

    Bourget, Philippe; Amin, Alexandre; Vidal, Fabrice; Merlette, Christophe; Lagarce, Frédéric

    2014-03-01

    This study compares the performance of a reference method of HPLC to Raman spectroscopy (RS) for the analytical quality control (AQC) of complex therapeutic objects. We assessed a model consisting of a widely used anticancer drug, i.e., 5-fluorouracil, which was compounded in a complex medical device, i.e., an elastomeric portable infusion pump. In view of the main objective, the two methods provided excellent results for the analytical validation key criteria, i.e., trueness, precision and accuracy, ranging from 7.5 to 50mg/mL and in either isotonic sodium or 5% dextrose. The Spearman and Kendall correlation tests (p-value<1×10(-15)) and the statistical studies performed on the graphs confirm a strong correlation in the results between RS and the standard HPLC under the experimental conditions. The selection of a spectral interval between 700 and 1400cm(-1) for both the characterization and quantification by RS was the result of a gradual process optimization, combining matrix and packaging responses. In this new application, we demonstrate at least eight benefits of RS: (a) operator safety, (b) elimination of disposables, (c) elimination of analysis waste, which contributes to the protection of the environment, (d) a fast analytical response of less than 2min, (e) the ability to identify the solubilizing phase, (f) reduction of the risk of errors because no intrusion or dilution are needed, (g) negligible maintenance costs and (h) a reduction in the budget dedicated to technician training. Overall, we indicate the potential of non-intrusive AQC performed by RS, especially when the analysis is not possible using the usual techniques, and the technique's high potential as a contributor to the safety of medication. PMID:24463044

  7. Comparison of Simulated Workplace Protection Factors Offered by N95 and P100 Filtering Facepiece and Elastomeric Half-Mask Respirators against Particles of 10 to 400 nm

    PubMed Central

    He, Xinjian; Vo, Evanly; Horvatin, M; Liu, Y; Bergman, M; Zhuang, Z

    2015-01-01

    This study compared the simulated workplace protection factors (SWPFs) between NIOSH-approved N95 respirators and P100 respirators, including two models of filtering facepiece respirator (FFR) and two models of elastomeric half-mask respirator (EHR), against sodium chloride particles (NaCl) in a range of 10 to 400 nm. Twenty-five human test subjects performed modified OSHA fit test exercises in a controlled laboratory environment with the N95 respirators (two FFR models and two EHR models) and the P100 respirators (two FFRs and two EHRs). Two Scanning Mobility Particle Sizers (SMPS) were used to measure aerosol concentrations (in the 10–400 nm size range) inside (Cin) and outside (Cout) of the respirator, simultaneously. SWPF was calculated as the ratio of Cout to Cin. The SWPF values obtained from the N95 respirators were then compared to those of the P100 respirators. SWPFs were found to be significantly different (P<0.05) between N95 and P100 class respirators. The 10th, 25th, 50th, 75th and 90th percentiles of the SWPFs for the N95 respirators were much lower than those for the P100 models. The N95 respirators had 5th percentiles of the SWPFs > 10. In contrast, the P100 class was able to generate 5th percentiles SWPFs > 100. No significant difference was found in the SWPFs when tested against nano-size (10 to 100 nm) and large-size (100 to 400 nm) particles. Overall, the findings suggest that the two FFRs and two EHRs with P100 class filters provide better performance than those with N95 filters against particles from 10 to 400 nm, supporting current OSHA and NIOSH recommendations. PMID:26273701

  8. Nanoprobe measurements of materials at megabar pressures.

    SciTech Connect

    Wang, L.; Ding, Y.; Yang, W.; Liu, W.; Cai, Z.; Kung, J.; Shu, J.; Hemley, R. J.; Mao, W. L.; Mao, H.; Carnegie Inst.; National Cheng Kung Univ.; Stanford Univ.; SLAC National Accelerator Lab.

    2010-01-01

    The use of nanoscale x-ray probes overcomes several key limitations in the study of materials up to multimegabar (> 200) pressures, namely, the spatial resolution of measurements of multiple samples, stress gradients, and crystal domains in micron to submicron size samples in diamond-anvil cells. Mixtures of Fe, Pt, and W were studied up to 282 GPa with 250-600 nm size synchrotron x-ray absorption and diffraction probes. The probes readily resolve signals from individual materials, between sample and gasket, and peak pressures, in contrast to the 5-{micro}m-sized x-ray beams that are now becoming routine. The use of nanoscale x-ray beams also enables single-crystal x-ray diffraction studies in nominally polycrystalline samples at ultrahigh pressures, as demonstrated in measurements of (Mg,Fe)SiO{sub 3} postperovskite. These capabilities have potential for driving a push toward higher maximum pressures and further miniaturization of high-pressure devices, in the process advancing studies at extreme conditions.

  9. Micromechanics and constitutive models for soft active materials with phase evolution

    NASA Astrophysics Data System (ADS)

    Wang, Binglian

    Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

  10. Laser 3D printing with sub-microscale resolution of porous elastomeric scaffolds for supporting human bone stem cells.

    PubMed

    Petrochenko, Peter E; Torgersen, Jan; Gruber, Peter; Hicks, Lucas A; Zheng, Jiwen; Kumar, Girish; Narayan, Roger J; Goering, Peter L; Liska, Robert; Stampfl, Jürgen; Ovsianikov, Aleksandr

    2015-04-01

    A reproducible method is needed to fabricate 3D scaffold constructs that results in periodic and uniform structures with precise control at sub-micrometer and micrometer length scales. In this study, fabrication of scaffolds by two-photon polymerization (2PP) of a biodegradable urethane and acrylate-based photoelastomer is demonstrated. This material supports 2PP processing with sub-micrometer spatial resolution. The high photoreactivity of the biophotoelastomer permits 2PP processing at a scanning speed of 1000 mm s(-1), facilitating rapid fabrication of relatively large structures (>5 mm(3)). These structures are custom printed for in vitro assay screening in 96-well plates and are sufficiently flexible to enable facile handling and transplantation. These results indicate that stable scaffolds with porosities of greater than 60% can be produced using 2PP. Human bone marrow stromal cells grown on 3D scaffolds exhibit increased growth and proliferation compared to smooth 2D scaffold controls. 3D scaffolds adsorb larger amounts of protein than smooth 2D scaffolds due to their larger surface area; the scaffolds also allow cells to attach in multiple planes and to completely infiltrate the porous scaffolds. The flexible photoelastomer material is biocompatible in vitro and is associated with facile handling, making it a viable candidate for further study of complex 3D-printed scaffolds. PMID:25522214

  11. Novel nanocomposite technologies for dynamic monitoring of structures: a comparison between cement-based embeddable and soft elastomeric surface sensors

    NASA Astrophysics Data System (ADS)

    Ubertini, Filippo; Laflamme, Simon; Ceylan, Halil; Materazzi, Annibale Luigi; Cerni, Gianluca; Saleem, Hussam; D'Alessandro, Antonella; Corradini, Alessandro

    2014-04-01

    The authors have recently developed two novel solutions for strain sensing using nanocomposite materials. While they both aim at providing cost-effective solutions for the monitoring of local information on large-scale structures, the technologies are different in their applications and physical principles. One sensor is made of a cementitious material, which could make it suitable for embedding within the core of concrete structures prior to casting, and is a resistor, consisting of a carbon nanotube cement-based transducer. The other sensor can be used to create an external sensing skin and is a capacitor, consisting of a flexible conducting elastomer fabricated from a nanocomposite mix, and deployable in a network setup to cover large structural surfaces. In this paper, we advance the understanding of nanocomposite sensing technologies by investigating the potential of both novel sensors for the dynamic monitoring of civil structures. First, an in-depth dynamic characterization of the sensors using a uniaxial test machine is conducted. Second, their performance at dynamic monitoring of a full-scale concrete beam is assessed, and compared against off-the-shelf accelerometers. Experimental results show that both novel technologies compare well against mature sensors at vibration-based structural health monitoring, showing the promise of nanocomposite technologies for the monitoring of large-scale structural systems.

  12. An Analysis of the Macroscopic Tensile Behavior of a Nonlinear Nylon Reinforced Elastomeric Composite System Using MAC/GMC

    NASA Technical Reports Server (NTRS)

    Assaad, Mahmoud; Arnold, Steven M.

    1999-01-01

    A special class of composite laminates composed of soft rubbery matrices and stiff reinforcements made of steel wires or synthetic fibers is examined, where each constituent behaves in a nonlinear fashion even in the small strain domain. Composite laminates made of piles stacked at alternating small orientation angles with respect to the applied axial strain are primarily dominated by the nonlinear behavior of the reinforcing fibers. However; composites with large ply orientations or those perpendicular to the loading axis, will approximate the behavior of the matrix phase and respond in even a more complex fashion for arbitrarily stacked piles. The geometric nonlinearity due to small cord rotations during loading was deemed here to have a second order effect and consequently dropped from any consideration. The user subroutine USRMAT within the Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC), was utilized to introduce the constituent material nonlinear behavior. Stress-strain behavior at the macro level was experimentally generated for single and multi ply composites comprised of continuous Nylon-66 reinforcements embedded in a carbon black loaded rubbery matrix. Comparisons between the predicted macro composite behavior and experimental results are excellent when material nonlinearity is included in the analysis. In this paper, a brief review of GMC is provided, along with a description of the nonlinear behavior of the constituents and associated constituent constitutive relations, and the improved macro (or composite) behavior predictions are documented and illustrated.

  13. Physics-Based Simulation and Experiment on Blast Protection of Infill Walls and Sandwich Composites Using New Generation of Nano Particle Reinforced Materials

    NASA Astrophysics Data System (ADS)

    Irshidat, Mohammad

    A critical issue for the development of nanotechnology is our ability to understand, model, and simulate the behavior of small structures and to make the connection between nano structure properties and their macroscopic functions. Material modeling and simulation helps to understand the process, to set the objectives that could guide laboratory efforts, and to control material structures, properties, and processes at physical implementation. These capabilities are vital to engineering design at the component and systems level. In this research, experimental-computational-analytical program was employed to investigate the performance of the new generation of polymeric nano-composite materials, like nano-particle reinforced elastomeric materials (NPREM), for the protection of masonry structures against blast loads. New design tools for using these kinds of materials to protect Infill Walls (e.g. masonry walls) against blast loading were established. These tools were also extended to cover other type of panels like sandwich composites. This investigation revealed that polymeric nano composite materials are strain rate sensitive and have large amount of voids distributed randomly inside the materials. Results from blast experiments showed increase in ultimate flexural resistance achieved by both unreinforced and nano reinforced polyurea retrofit systems applied to infill masonry walls. It was also observed that a thin elastomeric coating on the interior face of the walls could be effective at minimizing the fragmentation resulting from blast. More conclusions are provided with recommended future research.

  14. Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric

    PubMed Central

    Liang, Jiajie; Li, Lu; Chen, Dustin; Hajagos, Tibor; Ren, Zhi; Chou, Shu-Yu; Hu, Wei; Pei, Qibing

    2015-01-01

    Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm2 V−1 s−1, on/off ratio of 103–104, switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays. PMID:26173436

  15. Frictional force released during sliding mechanics in nonconventional elastomerics and self-ligation: An in vitro comparative study

    PubMed Central

    Kumar, Davender; Dua, Vinay; Mangla, Rajat; Solanki, Ravinder; Solanki, Monika; Sharma, Rekha

    2016-01-01

    Aim and Objectives: The aim of this study is to evaluate the frictional forces generated by five different orthodontic brackets when used in combination with stainless steel (SS), titanium molybdenum alloy (TMA), and nickel-titanium (NiTi) archwires in dry conditions at physiological temperature. Materials and Methods: Five different types of maxillary upper right side self-ligating brackets (SLBs) (Damon 3MX, Smart Clip and Carriere LX) and conventional SS brackets (Mini 2000, Optimum Series and Victory Series) with a slot size 0.022 inch were coupled with 0.016” NiTi and 0.019 × 0.025” SS/titanium molybdenum alloy (TMA) archwires. Tests were carried out for each group of the bracket-wire combination at physiological temperature and in the dry state. Frictional forces were measured by Instron universal testing machine. Results: SLB showed lower fictional values in comparison with elastic ligatures. Frictional force increased proportionally to the wire size; TMA and NiTi archwires presented higher frictional resistance than SS archwires. Conclusion: SS brackets tied with conventional ligatures produced high and low friction when ligated with SLBs with passive clip. PMID:27433047

  16. Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric

    NASA Astrophysics Data System (ADS)

    Liang, Jiajie; Li, Lu; Chen, Dustin; Hajagos, Tibor; Ren, Zhi; Chou, Shu-Yu; Hu, Wei; Pei, Qibing

    2015-07-01

    Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ~30 cm2 V-1 s-1, on/off ratio of 103-104, switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays.

  17. Effect of temperature and gap opening rate on the resiliency of candidate solid rocket booster O-ring materials

    NASA Technical Reports Server (NTRS)

    Lach, Cynthia L.

    1992-01-01

    In the redesign of the Space Shuttle solid rocket motor following the Challenger accident, the field and nozzle-to-case joints were designed to minimize gap opening caused by internal motor pressurization during ignition. The O-ring seals and glands for these joints were designed both to accommodate structural deflections and to promote pressure assisted sealing. The resiliency behavior of several candidate O-ring materials was evaluated for the effects of temperature and gap opening rates. The performance of three of the elastomeric materials was tested under the specific redesign gap opening requirement. Dynamic flexure conditions unique to launch produce low frequency vibrations in the gap opening. The effect of these vibrations on the ability of the O-ring to maintain contact with the sealing surface was addressed. The resiliency of the O-ring materials was found to be extremely sensitive to variations in temperature and gap opening rate. The top three elastomeric materials tracked the simulated solid rocket booster (SRB) field joint deflection at 75 and 120 F. The external tank/SRB attach strut load vibrations had a negligible effect on the ability of the O-ring to track the simulated SRB field joint deflection.

  18. An elastomeric patch derived from poly(glycerol sebacate) for delivery of embryonic stem cells to the heart.

    PubMed

    Chen, Qi-Zhi; Ishii, Hikaru; Thouas, George A; Lyon, Alexander R; Wright, Jamie S; Blaker, Jonny J; Chrzanowski, Wojciech; Boccaccini, Aldo R; Ali, Nadire N; Knowles, Jonathan C; Harding, Siân E

    2010-05-01

    We hypothesize that a combinatorial approach of ventricle constraint and stem cell therapy would offer a greater benefit for the treatment of heart failure than either strategy alone. A heart patch would serve two therapeutic purposes: biomechanical support and cell delivery. In this study, we describe a hybrid heart patch engineered from a synthetic elastomer, poly(glycerol sebacate) (PGS), supplemented with cardiomyocytes differentiated from human embryonic stem cells (hESCs). In line with two therapeutically relevant considerations, i.e. biocompatibility and cell delivery efficiency, the PGS was (a) pre-conditioned in culture medium for 6 days, and (b) prepared without gelatin coatings to facilitate detachment and delivery of cardiomyocytes following patch implantation. Following pre-conditioning under physiological conditions, the PGS patch material without gelatin coating was found to satisfactorily support cardiomyocyte viability and attachment, with active cell beating for periods of longer than 3 months until interrupted. Dynamic culture studies revealed that cells detached more efficiently from the uncoated surface of PGS than from gelatin-coated PGS. No significant differences were detected between the beating rates of human embryonic stem cell-derived cardiomyocytes on tissue culture plate and the pre-conditioned and gelatin-uncoated PGS. PGS patches sutured over the left ventricle of rats in vivo remained intact over a 2 week period without any deleterious effects on ventricular function. We conclude that PGS is a suitable biomaterial for stem cell-based regeneration strategies to restore cardiomyocyte function, and the hybrid heart patch engineered under optimal conditions would be a promising support device for the cardiac repair. PMID:20153041

  19. Replication of microchannel structures in WC-Co feedstock using elastomeric replica moulds by hot embossing process.

    PubMed

    Sahli, M; Gelin, J-C; Barrière, T

    2015-10-01

    Hot embossing is a net shaping process that is able to produce the micro-components of polymers with intrinsic and complex shapes at lower cost compared with machining and injection moulding. However, the emboss of hard metals, such as WC-Co, is more challenging due to their high thermal conductivity and ease of agglomeration. Thus, a WC-Co alloy mixed with a wax-based binder feedstock was selected. The formed feedstock exhibited pseudo-plastic flow and was successfully embossed (green part). Here, we developed a novel process that is used to replicate polymer microfluidic chips while simultaneously reducing the channel surface roughness of the mould insert, yielding optical-grade (less than 100 nm surface roughness) channels and reservoirs. This paper concerns the replication of metallic microfluidic mould inserts in WC-Co and the parameters associated with feedstock formation via a hot embossing process. A suitable formulation for micro-powder hot embossing has been established and characterised by thermogravimetric analyses and measurements of mixing torques to verify and quantify the homogeneity of the proposed feedstocks. The relative density of the samples increased with processing temperature, and almost fully dense materials were obtained. In this work, the effects of the sintering temperature on the physical properties were systematically analysed. The evolution of the metal surface morphology during the hot embossing process was also investigated. The results indicate that the feedstock can be used to manufacture micro-fluidic die mould cavities with a low roughness, proper dimensions and good shape retention. The shrinkage of the sintered part was approximately 19-24% compared with that of the brown part. PMID:26117760

  20. Correlation of electrical reactor cable failure with materials degradation

    SciTech Connect

    Stuetzer, O.M.

    1986-03-01

    Complete circuit failure (shortout) of electrical cables typically used in nuclear power plant containments is investigated. Failure modes are correlated with the mechanical deterioration of the elastomeric cable materials. It is found that for normal reactor operation, electrical cables are reliable and safe over very long periods. During high temperature excursions, however, cables pulled across corners under high stress may short out due to conductor creep. Severe cracking will occur in short times during high temperatures (>150/sup 0/C) and in times of the order of years at elevated temperatures (100/sup 0/C to 140/sup 0/C). A theoretical treatment of stress distribution responsible for creep and for cracking by J.E. Reaugh of Science Applications, Inc. is contained in the Appendix. 29 refs., 32 figs.

  1. Open-access dielectric elastomer material database

    NASA Astrophysics Data System (ADS)

    Vertechy, R.; Fontana, M.; Stiubianu, G.; Cazacu, M.

    2014-03-01

    Dielectric Elastomer Transducers (DETs) are deformable capacitors that can be used as sensors, actuators and generators. The design of effective and optimized DETs requires the knowledge of a set of relevant properties of the employed Dielectric Elastomer (DE) material, which make it possible to accurately predict their electromechanical dynamic behavior. In this context, an open-access database for DE materials has been created with the aim of providing the practicing engineer with the essential information for the design and optimization of new kinds of DET. Among the electrical properties, dielectric susceptibility, dielectric strength and conductivity are considered along with their dependence on mechanical strain. As regards mechanical behavior, experimental stress-strain curves are provided to predict hyperelasticity, plasticity, viscosity, Mullins effect and mechanical rupture. Properties of commercial elastomeric membranes have been entered in the database and made available to the research community. This paper describes the instrumentations, experimental setups and procedures that have been employed for the characterization of the considered DE materials. To provide an example, the experimental data acquired for a commercially available natural rubber membrane (OPPO Band Red 8012) are presented.

  2. Experimental performance of an ablative material as an external insulator for a hypersonic research aircraft

    NASA Technical Reports Server (NTRS)

    Puster, R. L.; Chapman, A. J.

    1977-01-01

    An ablative material composed of silica-filled elastomeric silicone was tested to evaluate its thermal and structural performance as an external insulator, or heat shield, for a hypersonic research aircraft. The material was also tested to determine whether it would form a durable char layer when initially heated and thereafter function primarily as an insulator with little further pyrolysis or char removal. Aerothermal tests were representative of nominal Mach 6 cruise conditions of the aircraft, and additional tests were representative of Mach 8 cruise and interference heating conditions. Radiant heating tests were used to simulate the complete nominal Mach 6 surface-temperature history. The silica char that formed during aerothermal tests was not durable. The char experienced a general and preferential surface recession, with the primary mechanism for char removal being erosion. Tests revealed that radiant heating is not a valid technique for simulating aerodynamic heating of the material.

  3. Elastomer actuators: systematic improvement in properties by use of composite materials

    NASA Astrophysics Data System (ADS)

    Molberg, Martin; Leterrier, Yves; Plummer, Christopher J. G.; Löwe, Christiane; Opris, Dorina M.; Clemens, Frank; Månson, Jan-Anders E.

    2010-04-01

    Dielectric elastomer actuators (DEAs) have attracted increasing attention over the last few years owing to their outstanding properties, e.g. their large actuation strains, high energy density, and pliability, which have opened up a wide spectrum of potential applications in fields ranging from microengineering to medical prosthetics. There is consequently a huge demand for new elastomer materials with improved properties to enhance the performance of DEAs and to overcome the limitations associated with currently available materials, such as the need for high activation voltages and the poor long-term stability. The electrostatic pressure that activates dielectric elastomers can be increased by higher permittivity of the elastomer and thus may lead to lower activation voltages. This has led us to consider composite elastomeric dielectrics based on thermoplastic elastomers or PDMS, and conductive polyaniline or ceramic (soft doped PZT) powder fillers. The potential of such materials and strategies to counter the adverse effects of increased conductivity and elastic modulus are discussed.

  4. Novel methods and self-reinforced composite materials for assessment and prevention of mechanically assisted corrosion in modular implants

    NASA Astrophysics Data System (ADS)

    Ouellette, Eric S.

    effectively insulate CoCrMo/Ti6Al4V alloy interfaces during cyclic fretting motion at contact stresses similar to those that might be experienced in modular taper junctions. SRC-PEEK and SRC-PE reduced fretting currents by approximately two orders of magnitude as compared to metal-metal interfaces, and sliding mechanics for SRC-PEEK lined samples were similar to metal-metal interfaces, while SRC-PE samples created a much lower COF at the interface. Finally, SRC-PEEK and SRC-PE gaskets were created to sleeve the trunnions of modular tapers and insulate the head from the trunnion. Cyclic fretting corrosion techniques were employed to assess the ability of SRCs to reduce or prevent the onset of fretting corrosion in the modular taper junction. In a set of three short-term tests assessing the effects of incremented cyclic loads, frequencies, and working electrode potential, SRC lined samples prevented the onset of fretting corrosion and had significantly lower currents than severely corroding metal-metal samples. In long-term million cycle cyclic fretting corrosion testing, the SRC gaskets did not experience failure at any point throughout the test and did not allow for the onset of corrosion currents. Inspection of the gaskets following all testing confirmed that the SRC gaskets withstood the high contact stresses and abrasive fretting motion experienced during the cyclic tests performed, indicating that SRC-PEEK and SRC-PE may be suitable candidates as new materials to prevent the onset of fretting corrosion in modular taper junctions.

  5. 46 CFR 153.530 - Special requirements for alkylene oxides.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... types 416 and 442; and (2) Steel. (b) Except as provided in paragraph (c) of this section, gaskets must... materials are generally found unsatisfactory for gaskets, packing, insulation, and similar uses in alkylene... materials, and gasket materials. (3) Materials containing oxides of magnesium, such as mineral wools....

  6. Sealing Materials for Use in Vacuum at High Temperatures

    NASA Technical Reports Server (NTRS)

    Pettit, Donald R.; Camarda, Charles J.; Lee Vaughn, Wallace

    2012-01-01

    Sealing materials that can be applied and left in place in vacuum over a wide range of temperatures (especially temperatures of a few thousand degrees Celsius) have been conceived and investigated for potential utility in repairing thermal-protection tiles on the space shuttles in orbit before returning to Earth. These materials are also adaptable to numerous terrestrial applications that involve vacuum processing and/or repair of structures that must withstand high temperatures. These materials can be formulated to have mechanical handling characteristics ranging from almost freely flowing liquid-like consistency through paste-like consistency to stiff puttylike consistency, and to retain these characteristics in vacuum until heated to high curing temperatures. A sealing material of this type can be formulated to be used in any of several different ways for example, to be impregnated into a high-temperature-fabric patch, impregnated into a high-temperature-fabric gasket for sealing a patch, applied under a patch, or applied alone in the manner of putty or wallboard compound. The sealing material must be formulated to be compatible with, and adhere to, the structural material(s) to be repaired. In general, the material consists of a vacuum-compatible liquid containing one or more dissolved compound(s) and/or mixed with suspended solid particles. Depending on the intended application, the liquid can be chosen to be of a compound that can remain in place in vacuum for a time long enough to be useful, and/or to evaporate or decompose in a controlled way to leave a useful solid residue behind. The evaporation rate is determined by proper choice of vapor pressure, application of heat, and/or application of ultraviolet light or other optical radiation. The liquid chosen for the original space shuttle application is a commercial silicone vacuum-pump oil.

  7. Evaluation of Ion Exchange Materials in K Basin Floor Sludge and Potential Solvents for PCB Extraction from Ion Exchange Materials

    SciTech Connect

    Schmidt, A.J.; Klinger, G.S.; Bredt, P.R.

    1999-04-10

    Approximately 73 m{sup 3} of heterogeneous solid material, ''sludge,'' (upper bound estimate, Packer 1997) have accumulated at the bottom of the K Basins in the 100 K Area of the Hanford Site. This sludge is a mixture of spent fuel element corrosion products, ion exchange materials (organic and inorganic), graphite-based gasket materials, iron and aluminum metal corrosion products, sand, and debris (Makenas et al. 1996, 1997). In addition, small amounts of polychlorinated biphenyls (PCBs) have been found. These small amounts are significant from a regulatory standpoint. Ultimately, it is planned to transfer the K Basins sludge to the Hanford double shell tanks (DSTs). Chemical pretreatment is required to address criticality issues and the destruction or removal of PCBs before the K Basin sludge can be transferred to the DSTs. Eleven technologies have been evaluated (Papp 1997) as potential pretreatment methods. Based on the evaluations and engineering studies and limited testing, Fluor Daniel Hanford recommended solvent washing of the K Basin sludge, followed by nitric acid dissolution and, potentially, peroxide addition (FDH 1997). The solvent washing (extraction) and peroxide addition would be used to facilitate PCB removal and destruction. Following solvent extraction, the PCBs could be distilled and concentrated for disposal as a low-level waste. The purpose of the work reported here was to continue investigating solvent extraction, first by better identifying the ion exchange materials in the actual sludge samples and then evaluating various solvents for removing the PCBs or possibly dissolving the resins. This report documents some of the process knowledge on ion exchange materials used and spilled in the K Basins and describes the materials identified from wet sieving KE Basin floor and canister sludge and the results of other analyses. Several photographs are included to compare materials and illustrate material behavior. A summary of previous tests on

  8. Space Environment Effects on Silicone Seal Materials

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III; Daniels, Christopher C.; Dever, Joyce A.; Miller, Sharon K.; Waters, Deborah L.; Finkbeiner, Joshua R.; Dunlap, Patrick H.; Steinetz, Bruce M.

    2010-01-01

    A docking system is being developed by the NASA to support future space missions. It is expected to use redundant elastomer seals to help contain cabin air during dockings between two spacecraft. The sealing surfaces are exposed to the space environment when vehicles are not docked. In space, the seals will be exposed to temperatures between 125 to -75 C, vacuum, atomic oxygen, particle and ultraviolet radiation, and micrometeoroid and orbital debris (MMOD). Silicone rubber is the only class of space flight-qualified elastomeric seal material that functions across the expected temperature range. NASA Glenn has tested three silicone elastomers for such seal applications: two provided by Parker (S0899-50 and S0383-70) and one from Esterline (ELA-SA-401). The effects of atomic oxygen (AO), UV and electron particle radiation, and vacuum on the properties of these three elastomers were examined. Critical seal properties such as leakage, adhesion, and compression set were measured before and after simulated space exposures. The S0899-50 silicone was determined to be inadequate for extended space seal applications due to high adhesion and intolerance to UV, but both S0383-70 and ELA-SA-401 seals were adequate.

  9. Grant Writing without Blowing a Gasket

    ERIC Educational Resources Information Center

    Vandenbroek, Alicia

    2010-01-01

    In today's economic downturn budget cut is becoming more and more common. Even libraries seen as a vital part of the educational process are subject to reductions because districts are suffering financially. The answer? Grants. They aren't a perfect solution, but there is a lot of financial support available for those who ask. Besides the monetary…

  10. High-resolution PFPE-based molding techniques for nanofabrication of high-pattern density, sub-20 nm features: a fundamental materials approach.

    PubMed

    Williams, Stuart S; Retterer, Scott; Lopez, Rene; Ruiz, Ricardo; Samulski, Edward T; DeSimone, Joseph M

    2010-04-14

    Several perfluoropolyether (PFPE)-based elastomers for high-resolution replica molding applications are explored. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface tension values (<25 mN/m). Using large area (>4 in.(2)) master templates, we experimentally show the relationship between mold resolution and material properties such as modulus and surface tension for materials used in this study. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus PFPE tetramethacrylate (TMA) composite molds were able to effectively replicate the nanograting structures without cracking or tear-out defects that typically occur with high modulus elastomers. PMID:20178369

  11. Compatibility of refrigerants and lubricants with elastomers

    SciTech Connect

    Hamed, G.R.; Seiple, R.H.

    1992-07-01

    Information contained in this reporters designed to assist the air-conditioning and refrigeration industry in the selection of suitable elastomeric gasket and seal materials that will prove useful in various refrigerant and refrigeration lubricant environments. Swell measurements have been made on approximately 50% of the proposed elastomers (94 total)in both the lubricant (7 total) and refrigerant (10 total) materials. Swell behavior in the these fluids have been determined using weight and in situ diameter measurements for the refrigerants and weight, diameter and thickness measurements for the lubricants. Weight and diameter measurements are repeated after 2 hours and 24 hours for samples removed from the refrigerant test fluids and 24 hours after removal from the lubricants.

  12. Compatibility of refrigerants and lubricants with elastomers. Quarterly report, 1 April 1992--30 June 1992

    SciTech Connect

    Hamed, G.R.; Seiple, R.H.

    1992-07-01

    Information contained in this reporters designed to assist the air-conditioning and refrigeration industry in the selection of suitable elastomeric gasket and seal materials that will prove useful in various refrigerant and refrigeration lubricant environments. Swell measurements have been made on approximately 50% of the proposed elastomers (94 total)in both the lubricant (7 total) and refrigerant (10 total) materials. Swell behavior in the these fluids have been determined using weight and in situ diameter measurements for the refrigerants and weight, diameter and thickness measurements for the lubricants. Weight and diameter measurements are repeated after 2 hours and 24 hours for samples removed from the refrigerant test fluids and 24 hours after removal from the lubricants.

  13. Orthodontic materials research and applications: part 2. Current status and projected future developments in materials and biocompatibility.

    PubMed

    Eliades, Theodore

    2007-02-01

    The purpose of this 2-part opinion article was to project the developments expected to occur in the next few years in orthodontic materials research and applications. Part 1 reviewed developments in bonding to enamel. Part 2 looks at other orthodontic materials applications and explores emerging research strategies for probing the biological properties of materials. In the field of metallic brackets, expansion of the use of titanium alloys with improved hardness and nickel-free steels with better corrosion resistance and increased hardness is expected. Manufacturing techniques might be modified to include laser-welding methods and metal injection molding. Esthetic bracket research will involve the synthesis of high-crystallinity biomedical polymers with increased hardness and stiffness, decreased water sorption, and improved resistance to degradation. New plastic brackets might incorportate ceramic wings. Fiber-reinforced composite archwires, currently experimental, could soon be commercially available, and long-term applications of shape-memory plastics might become viable. Advancements in elastomeric materials will result in polymers with reduced relaxation, broader use of fluoride-releasing elastomers with decreased relaxation, and large-scale film coating of elastomers to decrease reactivity, water sorption, and degradation. Finally, biocompatibility assessments will incorporate testing of potential endocrinological action. New polymer formulations might be tested in adhesive and plastic bracket manufacturing, based on benzoic ring-free monomers to avoid the adverse effects of the estrogenic molecule bisphenol-A. PMID:17276868

  14. 49 CFR 192.275 - Cast iron pipe.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... leak clamps. (b) Each mechanical joint in cast iron pipe must have a gasket made of a resilient material as the sealing medium. Each gasket must be suitably confined and retained under compression by...

  15. 49 CFR 173.323 - Ethylene oxide.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... and gaskets must be constructed of materials which are compatible with ethylene oxide and do not lower... the lading. (h) Neoprene, natural rubber and asbestos gaskets are prohibited. All packing and...

  16. 49 CFR 173.323 - Ethylene oxide.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... and gaskets must be constructed of materials which are compatible with ethylene oxide and do not lower... the lading. (h) Neoprene, natural rubber and asbestos gaskets are prohibited. All packing and...

  17. 49 CFR 192.275 - Cast iron pipe.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... leak clamps. (b) Each mechanical joint in cast iron pipe must have a gasket made of a resilient material as the sealing medium. Each gasket must be suitably confined and retained under compression by...

  18. 46 CFR 151.50-10 - Alkylene oxides.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... valves, gauges, thermometers, or any similar devices. Gaskets shall be constructed of spirally wound stainless steel with “Teflon” or other suitable material. All packing and gaskets shall be constructed...

  19. 49 CFR 178.504 - Standards for steel drums.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... mechanically seamed or welded in place. Gaskets or other sealing elements must be used with closures unless the.... Gaskets or other sealing elements must be used with all removable heads. (7) If materials used for...

  20. 30 CFR 20.9 - Class 2 lamps.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... contact, except enclosures requiring glass, in which case glass-to-metal joints are permitted. Gaskets, if... paris are not acceptable as material for gaskets. For enclosures having an unoccupied volume (air...