Science.gov

Sample records for advanced polymer matrix

  1. Micromechanical characterization of nonlinear behavior of advanced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Chen, J. L.; Sun, C. T.

    1994-01-01

    Due to the presence of curing stresses and oriented crystalline structures in the matrix of polymer matrix fiber composites, the in situ nonlinear properties of the matrix are expected to be rather different from those of the bulk resin. A plane stress micromechanical model was developed to retrieve the in situ elastic-plastic properties of Narmco 5260 and Amoco 8320 matrices from measured elastic-plastic properties of IM7/5260 and IM7/8320 advance composites. In the micromechanical model, the fiber was assumed to be orthotropically elastic and the matrix to be orthotropic in elastic and plastic properties. The results indicate that both in situ elastic and plastic properties of the matrices are orthotropic.

  2. Polymer, metal and ceramic matrix composites for advanced aircraft engine applications

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.; Serafini, T. T.; Dicarlo, J. A.

    1985-01-01

    Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

  3. Study of mould design and forming process on advanced polymer-matrix composite complex structure

    NASA Astrophysics Data System (ADS)

    Li, S. J.; Zhan, L. H.; Bai, H. M.; Chen, X. P.; Zhou, Y. Q.

    2015-07-01

    Advanced carbon fibre-reinforced polymer-matrix composites are widely applied to aviation manufacturing field due to their outstanding performance. In this paper, the mould design and forming process of the complex composite structure were discussed in detail using the hat stiffened structure as an example. The key issues of the moulddesign were analyzed, and the corresponding solutions were also presented. The crucial control points of the forming process such as the determination of materials and stacking sequence, the temperature and pressure route of the co-curing process were introduced. In order to guarantee the forming quality of the composite hat stiffened structure, a mathematical model about the aperture of rubber mandrel was introduced. The study presented in this paper may provide some actual references for the design and manufacture of the important complex composite structures.

  4. Advanced High Temperature Polymer Matrix Composites for Gas Turbine Engines Program Expansion

    NASA Technical Reports Server (NTRS)

    Hanley, David; Carella, John

    1999-01-01

    This document, submitted by AlliedSignal Engines (AE), a division of AlliedSignal Aerospace Company, presents the program final report for the Advanced High Temperature Polymer Matrix Composites for Gas Turbine Engines Program Expansion in compliance with data requirements in the statement of work, Contract No. NAS3-97003. This document includes: 1 -Technical Summary: a) Component Design, b) Manufacturing Process Selection, c) Vendor Selection, and d) Testing Validation: 2-Program Conclusion and Perspective. Also, see the Appendix at the back of this report. This report covers the program accomplishments from December 1, 1996, to August 24, 1998. The Advanced High Temperature PMC's for Gas Turbine Engines Program Expansion was a one year long, five task technical effort aimed at designing, fabricating and testing a turbine engine component using NASA's high temperature resin system AMB-21. The fiber material chosen was graphite T650-35, 3K, 8HS with UC-309 sizing. The first four tasks included component design and manufacturing, process selection, vendor selection, component fabrication and validation testing. The final task involved monthly financial and technical reports.

  5. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  6. Advanced Polymer

    NASA Technical Reports Server (NTRS)

    1992-01-01

    In the mid-1980's, Langley developed a polyimide sulfone, combining desirable properties of two classes of polymers. Composites and other products made from polyimide sulfone can be used with solvents and corrosive fluids, are light weight, low cost and can be easily fabricated for a wide range of industrial uses. High Technology Systems, Inc. obtained a license for the polymer and was awarded a Small Business Innovation Research (SBIR) contract for development in a powder form. Although its principal use is as a matrix resin for composites, the material can also be used as a high temperature structural adhesive for aircraft structures and as a coating for protection from heat and radiation for electronic components.

  7. High-temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    1990-01-01

    Polymers research at the NASA Lewis Research Center has produced high-temperature, easily processable resin systems, such as PMR-15. In addition, the Polymers Branch has investigated ways to improve the mechanical properties of polymers and the microcracking resistance of polymer matrix composites in response to industry need for new and improved aeropropulsion materials. Current and future research in the Polymers Branch is aimed at advancing the upper use temperature of polymer matrix composites to 700 F and beyond by developing new resins, by examining the use of fiber reinforcements other than graphite, and by developing coatings for polymer matrix composites to increase their oxidation resistance.

  8. High Thermal Conductivity Polymer Matrix Composites (PMC) for Advanced Space Radiators

    NASA Technical Reports Server (NTRS)

    Shin, E. Eugene; Bowman, Cheryl; Beach, Duane

    2007-01-01

    High temperature polymer matrix composites (PMC) reinforced with high thermal conductivity (approx. 1000 W/mK) pitch-based carbon fibers are evaluated for a facesheet/fin structure of large space radiator systems. Significant weight reductions along with improved thermal performance, structural integrity and space durability toward its metallic counterparts were envisioned. Candidate commercial resin systems including Cyanate Esters, BMIs, and polyimide were selected based on thermal capabilities and processability. PMC laminates were designed to match the thermal expansion coefficient of various metal heat pipes or tubes. Large, but thin composite panels were successfully fabricated after optimizing cure conditions. Space durability of PMC with potential degradation mechanisms was assessed by simulated thermal aging tests in high vacuum, 1-3 x 10(exp -6) torr, at three temperatures, 227 C, 277 C, and 316 C for up to one year. Nanocomposites with vapor-grown carbon nano-fibers and exfoliated graphite flakes were attempted to improve thermal conductivity (TC) and microcracking resistance. Good quality nanocomposites were fabricated and evaluated for TC and durability including radiation resistance. TC was measured in both in-plan and thru-the-thickness directions, and the effects of microcracks on TC are also being evaluated. This paper will discuss the systematic experimental approaches, various performance-durability evaluations, and current subcomponent design and fabrication/manufacturing efforts.

  9. High Temperature Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    1985-01-01

    These are the proceedings of the High Temperature Polymer Matrix Composites Conference held at the NASA Lewis Research Center on March 16 to 18, 1983. The purpose of the conference is to provide scientists and engineers working in the field of high temperature polymer matrix composites an opportunity to review, exchange, and assess the latest developments in this rapidly expanding area of materials technology. Technical papers are presented in the following areas: (1) matrix development; (2) adhesive development; (3) characterization; (4) environmental effects; and (5) applications.

  10. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    House, E. E.; Hoggatt, J. T.; Symonds, W. A.

    1980-01-01

    The extent to which graphite fibers are released from resin matrix composites that are exposed to fire and impact conditions was determined. Laboratory simulations of those conditions that could exist in the event of an aircraft crash and burn situation were evaluated. The effectiveness of various hybridizing concepts in preventing this release of graphite fibers were also evaluated. The baseline (i.e., unhybridized) laminates examined were prepared from commercially available graphite/epoxy, graphite/polyimide, and graphite/phenolic materials. Hybridizing concepts investigated included resin fillers, laminate coatings, resin blending, and mechanical interlocking of the graphite reinforcement. The baseline and hybridized laminates' mechanical properties, before and after isothermal and humidity aging, were also compared. It was found that a small amount of graphite fiber was released from the graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that several hybrid concepts eliminated this fiber release. Isothermal and humidity aging did not appear to alter the fiber release tendencies.

  11. Polymer Matrix Composite Material Oxygen Compatibility

    NASA Technical Reports Server (NTRS)

    Owens, Tom

    2001-01-01

    Carbon fiber/polymer matrix composite materials look promising as a material to construct liquid oxygen (LOX) tanks. Based on mechanical impact tests the risk will be greater than aluminum, however, the risk can probably be managed to an acceptable level. Proper tank design and operation can minimize risk. A risk assessment (hazard analysis) will be used to determine the overall acceptability for using polymer matrix composite materials.

  12. Advanced fiber/matrix material systems

    NASA Technical Reports Server (NTRS)

    Hartness, J. Timothy

    1991-01-01

    Work completed in Phase 1 of the NASA Advanced Composite Technology program is discussed. Two towpreg forms (commingled yarns and fused powder towpregs) are being characterized under the program. These towpregs will be used to evaluate textile fabrication technologies for advanced aircraft composite structures. The unique characteristic of both of these material forms is that both fiber and matrix resin are handled in a single operation such as weaving, braiding, or fiber placement. The evaluation of both commingled and fused powder towpreg is described. Various polymer materials are considered for both subsonic and supersonic applications. Polymers initially being evaluated include thermoplastic polyimides such as Larc-TPI and New-TPI, thermoplastics such as PEEK and PEKEKK as well as some toughened crosslinked polyimides. Preliminary mechanical properties as well as tow handling are evaluated.

  13. Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix.

    PubMed

    Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

    2015-01-01

    The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion(®) ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg(-1)Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion(®) ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture. PMID:26537781

  14. Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

    2015-11-01

    The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg-1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture.

  15. Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix

    PubMed Central

    Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

    2015-01-01

    The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg−1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture. PMID:26537781

  16. Nanoscale Reinforced, Polymer Derived Ceramic Matrix Coatings

    SciTech Connect

    Rajendra Bordia

    2009-07-31

    The goal of this project was to explore and develop a novel class of nanoscale reinforced ceramic coatings for high temperature (600-1000 C) corrosion protection of metallic components in a coal-fired environment. It was focused on developing coatings that are easy to process and low cost. The approach was to use high-yield preceramic polymers loaded with nano-size fillers. The complex interplay of the particles in the polymer, their role in controlling shrinkage and phase evolution during thermal treatment, resulting densification and microstructural evolution, mechanical properties and effectiveness as corrosion protection coatings were investigated. Fe-and Ni-based alloys currently used in coal-fired environments do not possess the requisite corrosion and oxidation resistance for next generation of advanced power systems. One example of this is the power plants that use ultra supercritical steam as the working fluid. The increase in thermal efficiency of the plant and decrease in pollutant emissions are only possible by changing the properties of steam from supercritical to ultra supercritical. However, the conditions, 650 C and 34.5 MPa, are too severe and result in higher rate of corrosion due to higher metal temperatures. Coating the metallic components with ceramics that are resistant to corrosion, oxidation and erosion, is an economical and immediate solution to this problem. Good high temperature corrosion protection ceramic coatings for metallic structures must have a set of properties that are difficult to achieve using established processing techniques. The required properties include ease of coating complex shapes, low processing temperatures, thermal expansion match with metallic structures and good mechanical and chemical properties. Nanoscale reinforced composite coatings in which the matrix is derived from preceramic polymers have the potential to meet these requirements. The research was focused on developing suitable material systems and

  17. Polymer matrix effects on acid generation

    NASA Astrophysics Data System (ADS)

    Fedynyshyn, Theodore H.; Goodman, Russell B.; Roberts, Jeanette

    2008-03-01

    We have measured the acid generation efficiency with EUV exposure of a PAG in different polymer matrixes representing the main classes of resist polymers as well as some previously described fluoropolymers for lithographic applications. The polymer matrix was found to have a significant effect on the acid generation efficiency of the PAG studied. A linear relationship exists between the absorbance of the resist and the acid generation efficiency. A second inverse relationship exists between Dill C and aromatic content of the resist polymer. It was shown that polymer sensitization is important for acid generation with EUV exposure and the Dill C parameter can be increased by up to five times with highly absorbing non-aromatic polymers, such as non-aromatic fluoropolymers, over an ESCAP polymer. The increase in the Dill C value will lead to an up to five fold increase in resist sensitivity. It is our expectation that these insights into the nature of polymer matrix effects on acid generation could lead to increased sensitivity for EUV resists.

  18. Oriented polymers: A transfer matrix calculation

    NASA Astrophysics Data System (ADS)

    Koo, W. M.

    1995-11-01

    Based on transfer matrix techniques and finite-size scaling, we study the oriented polymer (self-avoiding walk) with nearest neighbor interaction. In the repulsive regime, various critical exponents are computed and compared with exact values predicted recently. The polymer is also found to undergo a spiral transition for sufficiently strong attractive interaction. The fractal dimension of the polymer is computed in the repulsive and attractive regimes and at the spiral transition point. The later is found to be different from that at the collapse transition of the ordinary self-avoiding walk.

  19. Light weight polymer matrix composite material

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

    1988-01-01

    A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750 F in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

  20. Light weight polymer matrix composite material

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

    1991-01-01

    A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

  1. Fracture toughness testing of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.

    1992-01-01

    The experimental techniques and associated data analysis methods used to measure the resistance to interlaminar fracture, or 'fracture toughness', of polymer matrix composite materials are described. A review in the use of energy techniques to characterize fracture behavior in elastic solids is given. An overview is presented of the types of approaches employed in the design of delamination-resistant composite materials.

  2. Oriented nanofibers embedded in a polymer matrix

    NASA Technical Reports Server (NTRS)

    Barrera, Enrique V. (Inventor); Rodriguez-Macias, Fernando J. (Inventor); Lozano, Karen (Inventor); Chibante, Luis Paulo Felipe (Inventor); Stewart, David Harris (Inventor)

    2011-01-01

    A method of forming a composite of embedded nanofibers in a polymer matrix is disclosed. The method includes incorporating nanofibers in a plastic matrix forming agglomerates, and uniformly distributing the nanofibers by exposing the agglomerates to hydrodynamic stresses. The hydrodynamic said stresses force the agglomerates to break apart. In combination or additionally elongational flow is used to achieve small diameters and alignment. A nanofiber reinforced polymer composite system is disclosed. The system includes a plurality of nanofibers that are embedded in polymer matrices in micron size fibers. A method for producing nanotube continuous fibers is disclosed. Nanofibers are fibrils with diameters of 100 nm, multiwall nanotubes, single wall nanotubes and their various functionalized and derivatized forms. The method includes mixing a nanofiber in a polymer; and inducing an orientation of the nanofibers that enables the nanofibers to be used to enhance mechanical, thermal and electrical properties. Orientation is induced by high shear mixing and elongational flow, singly or in combination. The polymer may be removed from said nanofibers, leaving micron size fibers of aligned nanofibers.

  3. Functional Reactive Polymer Electrospun Matrix.

    PubMed

    Agarwal, Vipul; Ho, Dominic; Ho, Diwei; Galabura, Yuriy; Yasin, Faizah; Gong, Peijun; Ye, Weike; Singh, Ruhani; Munshi, Alaa; Saunders, Martin; Woodward, Robert C; St Pierre, Timothy; Wood, Fiona M; Fear, Mark; Lorenser, Dirk; Sampson, David D; Zdyrko, Bogdan; Luzinov, Igor; Smith, Nicole M; Iyer, K Swaminathan

    2016-02-01

    Synthetic multifunctional electrospun composites are a new class of hybrid materials with many potential applications. However, the lack of an efficient, reactive large-area substrate has been one of the major limitations in the development of these materials as advanced functional platforms. Herein, we demonstrate the utility of electrospun poly(glycidyl methacrylate) films as a highly versatile platform for the development of functional nanostructured materials anchored to a surface. The utility of this platform as a reactive substrate is demonstrated by grafting poly(N-isopropylacrylamide) to incorporate stimuli-responsive properties. Additionally, we demonstrate that functional nanocomposites can be fabricated using this platform with properties for sensing, fluorescence imaging, and magneto-responsiveness. PMID:26780245

  4. Advanced Polymer Processing Facility

    SciTech Connect

    Muenchausen, Ross E.

    2012-07-25

    Some conclusions of this presentation are: (1) Radiation-assisted nanotechnology applications will continue to grow; (2) The APPF will provide a unique focus for radiolytic processing of nanomaterials in support of DOE-DP, other DOE and advanced manufacturing initiatives; (3) {gamma}, X-ray, e-beam and ion beam processing will increasingly be applied for 'green' manufacturing of nanomaterials and nanocomposites; and (4) Biomedical science and engineering may ultimately be the biggest application area for radiation-assisted nanotechnology development.

  5. Polymer lasers: recent advances

    NASA Astrophysics Data System (ADS)

    Riedl, T.; Rabe, T.; Görrn, P.; Wang, J.; Weinmann, T.; Hinze, P.; Galbrecht, F.; Scherf, U.; Kowalsky, W.

    2007-09-01

    The development of organic thin film lasers has seen tremendous progress over the past few years. Only a few materials are necessary to allow for continuous wavelength tunability in the spectral region from the UV to the near IR. At the same time, the lasing thresholds of organic thin film lasers have been reduced considerably both due to improved low-loss distributed feedback (DFB) resonator structures and highly efficient gain materials based on guest-host energy transfer. Aside from the as yet open issue of electrical operation of organic lasers, which we will address briefly in this paper, there are numerous applications (e.g. in biotechnology, spectroscopy) where optically driven organic lasers may be the more cost effective and versatile solution. In this context, tunable polymer lasers pumped by compact and inexpensive InGaN laser diodes will be shown. These lasers are based on a modified poly(9,9'-dioctylfluorene) derivative (BN-PFO) containing 12% of -6,6'-(2,2'-octyloxy-1,1'-binaphthyl) spacer groups doped with a few wt% of the stilbene dye 1,4-Bis(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl-benzene (DPAVB). With the same host polymer (BN-PFO) quasi continuous wave operation (up to 5 MHz) can be demonstrated. Highly repetitive lasers are especially desirable for many spectroscopic applications. This regime of operstion is found to be impeded by the photo-physics in doped organic systems where the accumulation of absorptive species in the gain medium leads to piled-up absorption losses and consequently to termination of the lasing process. The presence of the dopand molecules seems to strongly promote the formation and stabilization of the species which we relate to triplet excitons. Therefore, the concentration of the dopand affects the feasibility of quasi-cw operation of thin-film organic lasers. Strategies and results to achieve highly repetitive operation in low-threshold guest-host systems BN-PFO:DPAVB or BN-PFO:poly[2-methoxy-5-(2'-ethylhexyloxy)-1

  6. Thermomechanical fatigue of polymer matrix composites

    SciTech Connect

    Strait, L.H.; Koudela, K.L.; Karasek, M.L.; Amateau, M.F.; Runt, J.P.

    1996-12-31

    The present research was undertaken to evaluate the effects of mechanical constraint on the response of polymer matrix composites during thermal cycling. Analytical and experimental techniques were used to characterize the response of carbon-fiber-reinforced cyanate ester and bismaleimide composites. Cross-ply laminates were subjected to thermal cycles from 24 to 177 C in the unconstrained, fully constrained, and overconstrained conditions. Laminate response, damage mechanisms, and residual compressive properties were characterized for each material and degree of constraint. The results of this research indicate that the level of constraint can have a significant effect on the response of polymer matrix composites during thermal cycling. However, longer-term testing is required to determine if the observed changes in response will ultimately affect the final failure mode and fatigue endurance of the materials.

  7. Multifunctional Nanotube Polymer Nanocomposites for Aerospace Applications: Adhesion between SWCNT and Polymer Matrix

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Wise, Kristopher E.; Kang, Jin Ho; Kim, Jae-Woo; Sauti, Godfrey; Lowther, Sharon E.; Lillehei, Peter T.; Smith, Michael W.; Siochi, Emilie J.; Harrison, Joycelyn S.; Jordan, Kevin

    2008-01-01

    Multifunctional structural materials can enable a novel design space for advanced aerospace structures. A promising route to multifunctionality is the use of nanotubes possessing the desired combination of properties to enhance the characteristics of structural polymers. Recent nanotube-polymer nanocomposite studies have revealed that these materials have the potential to provide structural integrity as well as sensing and/or actuation capabilities. Judicious selection or modification of the polymer matrix to promote donor acceptor and/or dispersion interactions can improve adhesion at the interface between the nanotubes and the polymer matrix significantly. The effect of nanotube incorporation on the modulus and toughness of the polymer matrix will be presented. Very small loadings of single wall nanotubes in a polyimide matrix yield an effective sensor material that responds to strain, stress, pressure, and temperature. These materials also exhibit significant actuation in response to applied electric fields. The objective of this work is to demonstrate that physical properties of multifunctional material systems can be tailored for specific applications by controlling nanotube treatment (different types of nanotubes), concentration, and degree of alignment.

  8. Dynamics of nanoparticles in an entangled polymer matrix

    NASA Astrophysics Data System (ADS)

    Dhakal, Subas; Sureshkumar, Radhakrishna

    2014-03-01

    Quantitative description of the dynamics and rheology of the extracellular polymeric substance (EPS) of bacterial biofilms is still a major challenge due to their structural complexity. Recent experiments suggest that the viscoelasticity of EPS is not governed by entanglements in the polymer matrix. Here, we investigate the microstructure, dynamics and rheology of a Dextran EPS by probing the motion of nanoparticles embedded in the matrix using coarse-grained molecular dynamics simulations. Specifically, these simulations show that for particle diameter D >entanglement length le, the probe particles exhibit normal diffusion, while for D polymer chain dynamics is observed. Results will be discussed in the context of micro-rheology experiments. NSF grants 1049489, 1049454 for the financial support, and Texas Advanced Computing Center (TACC) for providing HPC resources.

  9. Survey of inorganic polymers. [for composite matrix resins

    NASA Technical Reports Server (NTRS)

    Gerber, A. H.; Mcinerney, E. F.

    1979-01-01

    A literature search was carried out in order to identify inorganic, metallo-organic, and hybrid inorganic-organic polymers that could serve as potential matrix resins for advanced composites. The five most promising candidates were critically reviewed and recommendations were made for the achievement of their potential in terms of performance and cost. These generic polymer classes comprise: (1) Poly(arylsil sesquioxanes); (2) Poly(silyl arylene siloxanes); (3) Poly(silarylenes); (4) Poly(silicon-linked ferrocenes); and (5) Poly(organo phosphazenes). No single candidate currently possesses the necessary combination of physicomechanical properties, thermal stability, processability, and favorable economics. The first three classes exhibit the best thermal performance. On the other hand, poly (organo phosphazenes), the most extensively studied polymer class, exhibit the best combination of structure-property control, processability, and favorable economics.

  10. Nanotube reinforced thermoplastic polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Shofner, Meisha Lei

    The inherent high strength, thermal conductivity, and electrical conductivity make nanotubes attractive reinforcements for polymer matrix composites. However, the structure that makes them desirable also causes highly anisotropic properties and limited reactivity with other materials. This thesis isolates these problems in two separate studies aimed at improving mechanical properties with single wall nanotube (SWNT) reinforced thermoplastic polymer composites. The two studies demonstrate the effect of solid freeform fabrication (SFF) and chemical functionalization on anisotropy and limited reactivity, respectively. Both studies showed mechanical property improvements. The alignment study demonstrates a maximum increase of 93% in tensile modulus with single wall nanotubes (SWNTs). The chemical functionalization study shows a larger increase in storage modulus for functionalized SWNTs as compared to purified SVWNTs with respective increases of 9% and 44% in storage modulus. Improved interfacial properties are also observed as a decrease in mechanical damping. Maximum property increases in composites are obtained when nanotubes are aligned, requiring additional processing consideration to the anisotropic structure. Melt spinning and extrusion processing effectively align nanotubes, but the end product of these techniques, composite fibers, requires further processing to be incorporated into finished parts. Extrusion-based SFF is a novel technique for processing nanotube reinforced composites because it allows for the direct fabrication of finished parts containing aligned nanotubes. SFF processing produces parts containing preferentially oriented nanotubes with improved mechanical properties when compared to isotropic composites. Functionalization of the nanotube surface disrupts the rope structure to obtain smaller ropes and promote further interfacial bonding. The chemically inert nature of nanotubes resulting from a structure containing few defects and the

  11. Advanced Integration Matrix Education Outreach

    NASA Technical Reports Server (NTRS)

    Paul Heather L.

    2004-01-01

    The Advanced Integration Matrix (AIM) will design a ground-based test facility for developing revolutionary integrated systems for joint human-robotic missions in order to study and solve systems-level integration issues for exploration missions beyond Low Earth Orbit (LEO). This paper describes development plans for educational outreach activities related to technological and operational integration scenarios similar to the challenges that will be encountered through this project. The education outreach activities will provide hands-on, interactive exercises to allow students of all levels to experience design and operational challenges similar to what NASA deals with everyday in performing the integration of complex missions. These experiences will relate to and impact students everyday lives by demonstrating how their interests in science and engineering can develop into future careers, and reinforcing the concepts of teamwork and conflict resolution. Allowing students to experience and contribute to real-world development, research, and scientific studies of ground-based simulations for complex exploration missions will stimulate interest in the space program, and bring NASA's challenges to the student level. By enhancing existing educational programs and developing innovative activities and presentations, AIM will support NASA s endeavor to "inspire the next generation of explorers.. .as only NASA can."

  12. Bismaleimides and related maleimido polymers as matrix resins

    NASA Technical Reports Server (NTRS)

    Parker, J. A.; Kourtides, D. A.; Fohlen, G. M.

    1985-01-01

    Significant processing and property improvements can be achieved by copolymerization of state-of-the-art bisimides with various vinyl stilbazole derivatives to give both fire resistance and high-temperature properties from hot-melt compositions. Significant improvement in mechanical properties is achieved through these modifications, which may make these new matrix resins ideal candidates for fireworthy secondary graphite composite structures. Phosphorous modifications of maleimido polymers through phosphonate structure and tricyclophosphazene derivatives provide families of new matrix resins for short-time applications in severe thermo-oxidative environments. With further research these may provide matrix resins for long-term thermo-oxidative stability of advanced composites at temperatures up to 400 to 500 C.

  13. Polymer Matrix Composite Lines and Ducts

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.

    2001-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, a task was undertaken to assess the feasibility of making cryogenic feedlines with integral flanges from polymer matrix composite materials. An additional level of complexity was added by having the feedlines be elbow shaped. Four materials, each with a unique manufacturing method, were chosen for this program. Feedlines were to be made by hand layup (HLU) with standard autoclave cure, HLU with electron beam cure, solvent-assisted resin transfer molding (SARTM), and thermoplastic tape laying (TTL). A test matrix of fill and drain cycles with both liquid nitrogen and liquid helium, along with a heat up to 250 F, was planned for each of the feedlines. A pressurization to failure was performed on any feedlines that passed the cryogenic cycling testing. A damage tolerance subtask was also undertaken in this study. The effects of foreign object impact to the materials used was assessed by cross-sectional examination and by permeability after impact testing. At the end of the program, the manufacture of the electron beam-cured feedlines never came to fruition. All of the TTL feedlines leaked heavily before any cryogenic testing, all of the SARTM feedlines leaked heavily after one cryogenic cycle. Thus, only the HLU with autoclave cure feedlines underwent the complete test matrix. They passed the cyclic testing and were pressurized to failure.

  14. Polymer matrix and graphite fiber interface study

    NASA Technical Reports Server (NTRS)

    Adams, D. F.; Zimmerman, R. S.; Odom, E. M.

    1985-01-01

    Hercules AS4 graphite fiber, unsized, or with EPON 828, PVA, or polysulfone sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compression. Quasi-isotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, and wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

  15. Fracture toughness testing of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.

    1992-01-01

    A review of the interlaminar fracture indicates that a standard specimen geometry is needed to obtain consistent fracture toughness measurements in polymer matrix composites. In general, the variability of measured toughness values increases as the toughness of the material increases. This variability could be caused by incorrect sizing of test specimens and/or inconsistent data reduction procedures. A standard data reduction procedure is therefore needed as well, particularly for the tougher materials. Little work has been reported on the effects of fiber orientation, fiber architecture, fiber surface treatment or interlaminar fracture toughness, and the mechanisms by which the fibers increase fracture toughness are not well understood. The little data that is available indicates that woven fiber reinforcement and fiber sizings can significantly increase interlaminar fracture toughness.

  16. Engineered Polymers for Advanced Drug Delivery

    PubMed Central

    Kim, Sungwon; Kim, Jong-Ho; Jeon, Oju; Kwon, Ick Chan; Park, Kinam

    2009-01-01

    Engineered polymers have been utilized for developing advanced drug delivery systems. The development of such polymers has caused advances in polymer chemistry, which, in turn, has resulted in smart polymers that can respond to changes in environmental condition, such as temperature, pH, and biomolecules. The responses vary widely from swelling/deswelling to degradation. Drug-polymer conjugates and drug-containing nano/micro-particles have been used for drug targeting. Engineered polymers and polymeric systems have also been used in new areas, such as molecular imaging as well as in nanotechnology. This review examines the engineered polymers that have been used as traditional drug delivery and as more recent applications in nanotechnology. PMID:18977434

  17. Creep of plain weave polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Gupta, Abhishek

    Polymer matrix composites are increasingly used in various industrial sectors to reduce structural weight and improve performance. Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. Currently, available creep models are limited in scope and have not been validated for any loading orientation and time period beyond the experimental time window. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The ability of the model to predict creep for any orientation of the load is a "first" in this area. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (0°) and off-axis loading (45°). Constant load creep, in the temperature range of 80-240°C and stress range of 1-70% UTS of the

  18. Characterization of Hybrid CNT Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Cano, Roberto J.; Kinney, Megan C.; Pressley, James; Sauti, Godfrey; Czabaj, Michael W.; Kim, Jae-Woo; Siochi, Emilie J.

    2015-01-01

    Carbon nanotubes (CNTs) have been studied extensively since their discovery and demonstrated at the nanoscale superior mechanical, electrical and thermal properties in comparison to micro and macro scale properties of conventional engineering materials. This combination of properties suggests their potential to enhance multi-functionality of composites in regions of primary structures on aerospace vehicles where lightweight materials with improved thermal and electrical conductivity are desirable. In this study, hybrid multifunctional polymer matrix composites were fabricated by interleaving layers of CNT sheets into Hexcel® IM7/8552 prepreg, a well-characterized toughened epoxy carbon fiber reinforced polymer (CFRP) composite. The resin content of these interleaved CNT sheets, as well as ply stacking location were varied to determine the effects on the electrical, thermal, and mechanical performance of the composites. The direct-current electrical conductivity of the hybrid CNT composites was characterized by in-line and Montgomery four-probe methods. For [0](sub 20) laminates containing a single layer of CNT sheet between each ply of IM7/8552, in-plane electrical conductivity of the hybrid laminate increased significantly, while in-plane thermal conductivity increased only slightly in comparison to the control IM7/8552 laminates. Photo-microscopy and short beam shear (SBS) strength tests were used to characterize the consolidation quality of the fabricated laminates. Hybrid panels fabricated without any pretreatment of the CNT sheets resulted in a SBS strength reduction of 70 percent. Aligning the tubes and pre-infusing the CNT sheets with resin significantly improved the SBS strength of the hybrid composite To determine the cause of this performance reduction, Mode I and Mode II fracture toughness of the CNT sheet to CFRP interface was characterized by double cantilever beam (DCB) and end notch flexure (ENF) testing, respectively. Results are compared to the

  19. Advances in shape-memory polymer actuation

    NASA Astrophysics Data System (ADS)

    Leng, Jinsong; Liu, Yanju; Lan, Xin

    2009-03-01

    Shape memory polymer (SMP) is a promising smart material, which is able to perform a large deformation upon applying an external stimulus, such as heat, light and moisture, etc. In recent years, many investigations have been advanced in thermo-responsive SMP actuation, and several novel actuations have been applied in SMP. In this paper, the mechanism and demonstration of three types of SMP actuations (infrared laser, physical swelling effect and electricity) are presented. These novel actuation approaches may help SMP to fully reach its potential application. Firstly, for the infrared laser-activated SMP, it is concerned about the drive of SMP by infrared light. The infrared laser, transmitted through the optical fiber embedded in the SMP matrix, was chosen to drive the SMP. The working frequency of infrared laser was installed in 3-4μm. Moreover, this paper presents a study on the effects of solution on the glass transition temperature (Tg). It shows that the hydrogen bonding of SMP was aroused by the absorbed solution that significantly reduces transition temperature of polymer. In this way, the shape memory effect (SME) can undergo solution-driven shape recovery. Finally, the actuation of two types of electro-active SMP composites filled with electrically conductive powders (carbon black, nickel powers) have been carried out, and the SMP composite can be driven by applying a relatively low voltage.

  20. Strain Rate Dependent Modeling of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Strain rate dependent inelastic constitutive equations have been developed to model the polymer matrix, and have been incorporated into a micromechanics approach to analyze polymer matrix composites. The Hashin failure criterion has been implemented within the micromechanics results to predict ply failure strengths. The deformation model has been implemented within LS-DYNA, a commercially available transient dynamic finite element code. The deformation response and ply failure stresses for the representative polymer matrix composite AS4/PEEK have been predicted for a variety of fiber orientations and strain rates. The predicted results compare favorably to experimentally obtained values.

  1. Polymer Matrix Composites: A Perspective for a Special Issue of Polymer Reviews

    SciTech Connect

    Kessler, Michael R.

    2012-09-04

    Polymer matrix composites, with their high specific strength and stiffness, are used in a wide range of applications from large wind turbine blades to microelectronics. This perspective article provides a brief primer on polymer matrix composites, discusses some of their advantages and limitations, and describes a number of emerging trends in the field. In addition, it introduces four review articles on the topics of recent developments in carbon fibers, natural fiber reinforced composites, evaluation of the interface between the fiber reinforcement and polymer matrix, and carbon nanotube reinforced polymers.

  2. Recent advances in photorefractive polymers

    NASA Astrophysics Data System (ADS)

    Thomas, Jayan; Christenson, C. W.; Lynn, B.; Blanche, P.-A.; Voorakaranam, R.; Norwood, R. A.; Yamamoto, M.; Peyghambarian, N.

    2011-10-01

    Photorefractive composites derived from conducting polymers offer the advantage of dynamically recording holograms without the need for processing of any kind. Thus, they are the material of choice for many cutting edge applications, such as updatable three-dimensional (3D) displays and 3D telepresence. Using photorefractive polymers, 3D images or holograms can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. Absence of a large-area and dynamically updatable holographic recording medium has prevented realization of the concept. The development of a novel nonlinear optical chromophore doped photoconductive polymer composite as the recording medium for a refreshable holographic display is discussed. Further improvements in the polymer composites could bring applications in telemedicine, advertising, updatable 3D maps and entertainment.

  3. Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Wallace, C. J. (Inventor)

    1978-01-01

    An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

  4. Electron beam curing of polymer matrix composites

    SciTech Connect

    Janke, C.J.; Wheeler, D.; Saunders, C.

    1998-01-08

    The purpose of the CRADA was to conduct research and development activities to better understand and utilize the electron beam PMC curing technology. This technology will be used to replace or supplement existing PMC thermal curing processes in Department of Energy (DOE) Defense Programs (DP) projects and American aircraft and aerospace industries. This effort involved Lockheed Martin Energy Systems, Inc./Lockheed Martin Energy Research Corp. (Contractor), Sandia National Laboratories, and ten industrial Participants including four major aircraft and aerospace companies, three advanced materials companies, and three electron beam processing organizations. The technical objective of the CRADA was to synthesize and/or modify high performance, electron beam curable materials that meet specific end-use application requirements. There were six tasks in this CRADA including: Electron beam materials development; Electron beam database development; Economic analysis; Low-cost Electron Beam tooling development; Electron beam curing systems integration; and Demonstration articles/prototype structures development. The contractor managed, participated and integrated all the tasks, and optimized the project efforts through the coordination, exchange, and dissemination of information to the project participants. Members of the Contractor team were also the principal inventors on several electron beam related patents and a 1997 R and D 100 Award winner on Electron-Beam-Curable Cationic Epoxy Resins. The CRADA achieved a major breakthrough for the composites industry by having successfully developed high-performance electron beam curable cationic epoxy resins for use in composites, adhesives, tooling compounds, potting compounds, syntactic foams, etc. UCB Chemicals, the world`s largest supplier of radiation-curable polymers, has acquired a license to produce and sell these resins worldwide.

  5. Redox polymer electrodes for advanced batteries

    DOEpatents

    Gregg, Brian A.; Taylor, A. Michael

    1998-01-01

    Advanced batteries having a long cycle lifetime are provided. More specifically, the present invention relates to electrodes made from redox polymer films and batteries in which either the positive electrode, the negative electrode, or both, comprise redox polymers. Suitable redox polymers for this purpose include pyridyl or polypyridyl complexes of transition metals like iron, ruthenium, osmium, chromium, tungsten and nickel; porphyrins (either free base or metallo derivatives); phthalocyanines (either free base or metallo derivatives); metal complexes of cyclams, such as tetraazacyclotetradecane; metal complexes of crown ethers and metallocenes such as ferrocene, cobaltocene and ruthenocene.

  6. Redox polymer electrodes for advanced batteries

    DOEpatents

    Gregg, B.A.; Taylor, A.M.

    1998-11-24

    Advanced batteries having a long cycle lifetime are provided. More specifically, the present invention relates to electrodes made from redox polymer films and batteries in which either the positive electrode, the negative electrode, or both, comprise redox polymers. Suitable redox polymers for this purpose include pyridyl or polypyridyl complexes of transition metals like iron, ruthenium, osmium, chromium, tungsten and nickel; porphyrins (either free base or metallo derivatives); phthalocyanines (either free base or metallo derivatives); metal complexes of cyclams, such as tetraazacyclotetradecane; metal complexes of crown ethers and metallocenes such as ferrocene, cobaltocene and ruthenocene. 2 figs.

  7. Recent Advances in Simulation of Dendritic Polymers

    SciTech Connect

    Cagin, Tahir; Miklis, Paul J.; Wang, Guofeng; Zamanakos, Georgios; Martin, Ryan; Li, Hao; Mainz, Daniel T.; Nagarajan, V.; Goddard, William A.

    1999-05-11

    Dendrimers and hyperbranched polymers represent a revolution in methodology for directed synthesis of monodisperse polymers with enormous possibility of novel architectures. They demonstrate the ability to attain micelle-like structures with distinct internal and external character. Furthermore, the polyfunctional character of dendrimers allows varied response to environment and promise as selective sensors, carrier for drugs, encapsulation of toxic chemicals and metals. One of the key problems is the characterization of the structures. Theory and simulation can be essential to provide and predict structure and properties. We present some recent advances in theory, modeling and simulation of dendritic polymers.

  8. Ceramic matrix composites -- Advanced high-temperature structural materials

    SciTech Connect

    Lowden, R.A.; Ferber, M.K.; Hellmann, J.R.; Chawla, K.K.; DiPietro, S.G.

    1995-10-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base.

  9. Polymer composites based on gypsum matrix

    NASA Astrophysics Data System (ADS)

    Mucha, Maria; Mróz, Patrycja; Kocemba, Aleksandra

    2016-05-01

    The role of polymers as retarder additives is to prolong the workability connected with setting time of gypsum. Various cellulose derivatives, soluble in water in concentration up to 1,5% by weight were applied taking different water/binder ratio. The hydration process of calcium sulfate hemihydrate (gypsum binder) into dihydrate (gypsum plaster) was observed by setting and calorimetric techniques. Scanning electron microscopy confirmed that the gypsum microstructure was varied when polymers are used. The mechanical properties of gypsum plasters were studied by bending strength test and they are correlated with sample microstructure

  10. Rate Dependent Deformation and Strength Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is being undertaken to develop rate dependent deformation and failure models for the analysis of polymer matrix composite materials. In previous work in this program, strain-rate dependent inelastic constitutive equations used to analyze polymers have been implemented into a mechanics of materials based composite micromechanics method. In the current work, modifications to the micromechanics model have been implemented to improve the calculation of the effective inelastic strain. Additionally, modifications to the polymer constitutive model are discussed in which pressure dependence is incorporated into the equations in order to improve the calculation of constituent and composite shear stresses. The Hashin failure criterion is implemented into the analysis method to allow for the calculation of ply level failure stresses. The deformation response and failure stresses for two representative uniaxial polymer matrix composites, IM7/977-2 and AS4-PEEK, are predicted for varying strain rates and fiber orientations. The predicted results compare favorably to experimentally obtained values.

  11. High Strain Rate Deformation Modeling of a Polymer Matrix Composite. Part 1; Matrix Constitutive Equations

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1998-01-01

    Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this first paper of a two part report, background information is presented, along with the constitutive equations which will be used to model the rate dependent nonlinear deformation response of the polymer matrix. Strain rate dependent inelastic constitutive models which were originally developed to model the viscoplastic deformation of metals have been adapted to model the nonlinear viscoelastic deformation of polymers. The modified equations were correlated by analyzing the tensile/ compressive response of both 977-2 toughened epoxy matrix and PEEK thermoplastic matrix over a variety of strain rates. For the cases examined, the modified constitutive equations appear to do an adequate job of modeling the polymer deformation response. A second follow-up paper will describe the implementation of the polymer deformation model into a composite micromechanical model, to allow for the modeling of the nonlinear, rate dependent deformation response of polymer matrix composites.

  12. Advances in inherently conducting polymers

    SciTech Connect

    Aldissi, M.

    1987-09-01

    The discovery of polyacetylene as the prototype material led to extensive research on its synythesis and characterization. The techniques that emerged as the most important and promising ones are those that dealt with molecular orientation and that resulted in conductivities almost as high as that of copper. The study of dozens of other materials followed. Interest in conducting polymers stems from their nonclassical optical and electronic properties as well as their potential technological applications. However, some of the factors currently limiting their use are the lack of long-term stability and the need to develop conventional low-cost techniques for easy processing. Therefore, research was extended toward solving these problems, and progress has been recently made in that direction. The synthesis of new materials such as stable and easily processable alkylthiophenes, water-soluble polymers, and multicomponent systems, including copolymers and composites, constitutes an important step forward in the area of synthetic metals. However, a full understanding of materials chemistry and properties requires more work in the years to come. Although, few small-scale applications have proven to be successful, long-term stability and applicability tests are needed before their commercial use becomes reality.

  13. INTEGRATED COI S200 - Hi-NiCalon FIBER WITH AN S200 MATRIX (POLYMER MATRIX COMPOSITE - PMC) / AETB 1

    NASA Technical Reports Server (NTRS)

    2003-01-01

    INTEGRATED COI S200 - Hi-NiCalon FIBER WITH AN S200 MATRIX (POLYMER MATRIX COMPOSITE - PMC) / AETB 16 (FOAM CORE) / CARBON REINFORCED CYANOESTER (CERAMIC MATRIX COMPOSITE - CMC) HOT STRUCTURE, PANEL 884-1: SAMPLE 3

  14. INTEGRATED COI S200 - Hi-NiCalon FIBER WITH AN S200 MATRIX (POLYMER MATRIX COMPOSITE - PMC) / AETB 1

    NASA Technical Reports Server (NTRS)

    2003-01-01

    INTEGRATED COI S200 - Hi-NiCalon FIBER WITH AN S200 MATRIX (POLYMER MATRIX COMPOSITE - PMC) / AETB 16 (FOAM CORE) / CARBON REINFORCED CYANOESTER (CERAMIC MATRIX COMPOSITE - CMC) HOT STRUCTURE, PANEL 884-1: SAMPLE 1

  15. Polymer precursors for ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Litt, M. H.; Kumar, K.

    1986-01-01

    The synthesis and characterization of a polycyclohexasilane is reported. Because of its cyclic structure, it is anticipated that this polymer might serve as a precursor to SIC having a high char yield with little rearrangement to form small, volatile cyclic silanes, and, as such, would be of interest as a precursor to SiC composite matrices and fibers, or as a binder in ceramic processing. Several approaches to the synthesis of a bifunctional cyclic monomer were attempted; the most successful of these was metal coupling of PhMeSiCl2 and Me2SiCl2. The procedure gives six-membered ring compounds with all degrees of phenyl substitution, from none to hexaphenyl. The compounds with from 0-2 groups were isolated and characterized. The fraction with degree of phenyl substitution equal to 2, a mixture of cis and trans 1,2-; 1,3-; and 1,4 isomers, was isolated in 32 percent yield. Pure 1,4 diphenyldecamethylcyclohexasilane was isolated from the mixed diphenyl compounds and characterized. Diphenyldecamethylcyclohexasilanes were dephenylated to dichlorodecamethylcyclohexasilanes by treating with H2SO4.NH4Cl in benzene. The latter were purified and polymerized by reacting with sodium in toluene. The polymers were characterized by HPGPC, elemental analysis, proton NMR, and IR. Thermogravimetric analyses were carried out on the polymers. As the yield of residual SiC was low, polymers were heat treated to increase the residual char yield. As high as 51.52 percent residual char yield was obtained in one case.

  16. Polymer matrix electroluminescent materials and devices

    DOEpatents

    Marrocco, III, Matthew L.; Motamedi, Farshad J.; Abdelrazzaq, Feras Bashir; Abdelrazzaq, legal representative, Bashir Twfiq

    2012-06-26

    Photoluminescent and electroluminescent compositions are provided which comprise a matrix comprising aromatic repeat units covalently coordinated to a phosphorescent or luminescent metal ion or metal ion complexes. Methods for producing such compositions, and the electroluminescent devices formed therefrom, are also disclosed.

  17. The secretory granule matrix: a fast-acting smart polymer.

    PubMed

    Nanavati, C; Fernandez, J M

    1993-02-12

    The secretory granule matrix is a miniature biopolymer that consists of a charged polymer network that traps peptides and transmitters when it condenses and releases them on exocytotic decondensation. Models of exocytotic fusion have treated this matrix as a short circuit and have neglected its electrical contributions. This matrix responded to negative voltages by swelling, which was accompanied by a large increase in conductance, and to positive voltages by condensing. Thus, the matrix resembled a diode. The swollen matrix exerted large pressures on the order of 12 bar. The responses took place within milliseconds of the application of the electric field. These findings suggest that matrix decondensation, and therefore product release, is controlled by potential gradients. PMID:8438154

  18. Nanophosphor composite scintillators comprising a polymer matrix

    DOEpatents

    Muenchausen, Ross Edward; Mckigney, Edward Allen; Gilbertson, Robert David

    2010-11-16

    An improved nanophosphor composite comprises surface modified nanophosphor particles in a solid matrix. The nanophosphor particle surface is modified with an organic ligand, or by covalently bonding a polymeric or polymeric precursor material. The surface modified nanophosphor particle is essentially charge neutral, thereby preventing agglomeration of the nanophosphor particles during formation of the composite material. The improved nanophosphor composite may be used in any conventional scintillator application, including in a radiation detector.

  19. Erosion Resistant Coatings for Polymer Matrix Composites in Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Sutter, James K.; Naik, Subhash K.; Horan, Richard; Miyoshi, Kazuhisa; Bowman, Cheryl; Ma, Kong; Leissler, George; Sinatra, Raymond; Cupp, Randall

    2003-01-01

    Polymer Matrix Composites (PMCs) offer lightweight and frequently low cost alternatives to other materials in many applications. High temperature PMCs are currently used in limited propulsion applications replacing metals. Yet in most cases, PMC propulsion applications are not in the direct engine flow path since particulate erosion degrades PMC component performance and therefore restricts their use in gas turbine engines. This paper compares two erosion resistant coatings (SANRES and SANPRES) on PMCs that are useful for both low and high temperature propulsion applications. Collaborating over a multi-year period, researchers at NASA Glenn Research Center, Allison Advanced Developed Company, and Rolls-Royce Corporation have optimized these coatings in terms of adhesion, surface roughness, and erosion resistance. Results are described for vigorous hot gas/particulate erosion rig and engine testing of uncoated and coated PMC fan bypass vanes from the AE 3007 regional jet gas turbine engine. Moreover, the structural durability of these coatings is described in long-term high cycle fatigue tests. Overall, both coatings performed well in all tests and will be considered for applications in both commercial and defense propulsion applications.

  20. Polymer matrix composites research: A survey of federally sponsored programs

    SciTech Connect

    Not Available

    1990-06-01

    This report identifies research conducted by agencies of the federal government other than the Department of Energy (DOE) in the area of advanced polymer matrix composites (PMCs). DOE commissioned the report to avoid duplicating other agencies' efforts in planning its own research program for PMCs. PMC materials consist of high-strength, short or continuous fibers fused together by an organic matrix. Compared to traditional structural metals, PMCs provide greater strength and stiffness, reduced weight and increased heat resistance. The key contributors to PMC research identified by the survey are the Department of Defense (DOD), the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the Department of Transportation (DOT). The survey identified a total of 778 projects. More than half of the total projects identified emphasize materials research with a goal toward developing materials with improved performance. Although an almost equal number of identified materials projects focus on thermosets and thermoplastics receive more attention because of their increased impact resistance and their easy formability and re-formability. Slightly more than one third of projects identified target structures research. Only 15 percent of the projects identified focus on manufacturing techniques, despite the need for efficient, economical methods manufacturing products constructed of PMCs--techniques required for PMCs to gain widespread acceptance. Three issues to be addressed concerning PMCs research are economy of use, improvements in processing, and education and training. Five target technologies have been identified that could benefit greatly from increased use of PMCs: aircraft fuselages, automobile frames, high-speed machinery, electronic packaging, and construction.

  1. Outgassing and dimensional changes of polymer matrix composites in space

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Matthews, R.

    1993-01-01

    A thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites is described. Experimental results derived from a 'control' sample are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples.

  2. Surface characterization of LDEF carbon fiber/polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Grammer, Holly L.; Wightman, James P.; Young, Philip R.; Slemp, Wayne S.

    1995-01-01

    XPS (x-ray photoelectron spectroscopy) and SEM (scanning electron microscopy) analysis of both carbon fiber/epoxy matrix and carbon fiber/polysulfone matrix composites revealed significant changes in the surface composition as a result of exposure to low-earth orbit. The carbon 1s curve fit XPS analysis in conjunction with the SEM photomicrographs revealed significant erosion of the polymer matrix resins by atomic oxygen to expose the carbon fibers of the composite samples. This erosion effect on the composites was seen after 10 months in orbit and was even more obvious after 69 months.

  3. Synthesis and characterization of polymer matrix nanocomposites and their components

    NASA Astrophysics Data System (ADS)

    Burnside, Shelly Dawn

    Herein we present synthesis schemes and characterization results for polymer matrix nanocomposite reinforced with organically modified layered silicates. These host materials with ultrafine dimensions are promising candidates for polymer and have been previously shown to yield substantial property enhancements at low silicate loadings due to their extreme geometry. Siloxane nanocomposites with a variety of nanostructures were formed. Thermal stability, solvent uptake and moduli of the nanocomposites were explores. Exfoliated nanocomposites displayed enhanced properties when compared to unreinforced siloxanes, and at lower volume fraction filler than in conventional composites. Large amounts of bound polymer, polymer affected by the silicate, were found in exfoliated nanocomposites as a result of the extreme geometry of the layered silicate. This bound polymer was related to the dramatic property enhancements in the nanocomposites. The behavior of these nanocomposites is compared to behavior expected from traditional models developed for conventional composites and model elastomeric networks. A lightly brominated polymer has been intercalated into a single crystal of organically exchanged vermiculite. The intercalation was followed using x-ray diffraction by monitoring the gallery height of the vermiculite host. Rutherford Backscattering Spectroscopy, used to confirm polymer intercalation, showed a constant bromine content in the direction normal to the layers. Atomic Force Microscopy images of a cleaved polymer-intercalated crystal showed raised hemispheres on an otherwise flat background. The hemispheres consist of single chains or aggregates of 3-40 polymer chains resulting from relaxations following cleaving. Three component or Hansen solubility parameters (delta) of organically modified layered silicates, the reinforcing agent in polymer matrix nanocomposites presented herein, have been determined. Two experimental techniques, temporal turbidimetry and

  4. Dispersion of Soft Nanoparticles in a Chemically Identical Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Ratnaweera, Dilru; Baskaran, D.; Holley, D.; Ruppel, M.; Mays, J.; Urban, V.; Dadmun, Mark

    2013-03-01

    The mechanical, thermal and rheological properties of polymers can be improved by embedding organic nanoparticles (NPs). However, controlling the dispersion of NPs is often challenging due to thermodynamic and kinetic incompatibilities between particles and matrices. The current work focuses on the dispersion of chemically identical NPs in a polystyrene matrix. These NPs were made through a micro-emulsion technique using styrene and divinylbenzene (DVB) monomers. Polystyrene nanoparticles with controlled interfacial roughness and targeted styrene densities were achieved by controlling DVB volume fraction during synthesis. The dispersion of these NPs in deuterated polystyrene matrices was followed by Small Angle Neutron Scattering as a function of NP concentration and matrix molecular weight. At low NP concentrations, individual NPs are well distributed in the matrix, while aggregates were formed at higher concentrations in high molecular weight polymer matrices. Shape of the aggregates as well as the minimum concentration of NPs required to form aggregates were affected by the surface roughness and softness of the NPs.

  5. Advanced Polymers Containing the Phenyltrifluoroethylidene Connecting Group

    NASA Technical Reports Server (NTRS)

    Alstron, William B.; Sivko, Gloria S.

    2006-01-01

    A new, lower cost fluorinated dianhydride based on the phenyltrifluoroethylidene (3F) connecting linkage was invented by the principal author in the early 1980's. New 3F condensation and addition cured polyimides were synthesized with the newly discovered 3F dianhydride and the previously known 3F diamine. As controls, polyimides based on the somewhat analogous higher cost hexafluoroisopropylidene (6F) linkage were also prepared. The short term thermal oxidative stability (TOS), determined by thermal gravimetric analysis (TGA), and the glass transition temperatures (Tg) of 3F dianhydride polyimides were found to be similar to 6F dianhydride polyimides, but the Tg was slightly higher for 3F diamine polyimides than 6F diamine polyimides. Unfortunately, in real time testing, long term TOS of 3F polymers was clearly inferior to 6F polymers. This was due to a 3 to 5 fold greater rate of loss of trifluoromethyl group from 3F versus 6F linkages. However, at shorter times or lower temperatures, 3F TOS was almost comparable to 6F TOS. The wide scope of the 3F technology was also demonstrated to have distinct unique advantages over 6F technology through the use of the 3F pendant phenyl ring as a synthetic site to introduce other functional groups. These groups have been used for the control or modification of polymer properties; an advantage lacking within 6F technology. The synthetic ease by which 3F can be introduced into various types of monomers has lead to the explosion of advanced 3F polyimides and other high performance advanced 3F polymers in the prior decade of 3F polymer literature as cited herein; covering polyimides, substituted polyimides, at least ten types of nonpolyimide 3F polymer modifications, and also the government's nine 3F U.S. patents and corporations' nine 3F U.S. patents.

  6. Active-matrix polymer displays made with electroluminescent polymers

    NASA Astrophysics Data System (ADS)

    Yu, Gang; Srdanov, Gordana; Zhang, Belinda; Stevenson, Matthew; Wang, Jian; Chen, Peter; Baggao, Erlinda; Macias, Johnny; Sun, Runguang; McPherson, Charlie; Sant, Paul; Innocenzo, Jeffrey; Stainer, Matthew; O'Regan, Marie B.

    2003-09-01

    Active-matrix organic/polyeric light emitting displays (AMOLEDs/AMPLEDs) are of great potentials for high information content display applications. They offer high brightness, fast response time, high image quality (high contrast, high gray levels and small pixel pitch size) and low power consumption. AMPLEDs are ideal for portable electronic devices such as web-phones, personal data assistants, GPS and handhold computers. AMPLEDs are especially suitable for motion picture applications. Since the image pixels consume power only when they are turned on, and only consume the power necessary for their corresponding brightness, video displays made with AMOLED/AMPLED reduce power consumption and extend display lifetime considerably. Motion picture applications also minimize image retention and optimize display homogeneity. In this presentation, we discuss our recent progress on AMPLEDs and compare their performance with that of AMLCD.

  7. Advanced materials based on polymer blends/polymer blend nanocomposites

    NASA Astrophysics Data System (ADS)

    Shikaleska, A. V.; Pavlovska, F. P.

    2012-09-01

    Processability, morphology, mechanical properties and rheological behavior of poly(vinylchloride) (PVC)/poly(ethylmethacrylate) (PEMA) blends and PVC/PEMA/montmorillonite (MMT) composites, prepared by melt processing in a brabender mixer, were studied. Samples were characterized using SEM, mechanical testing, DMTA and a parallel plate rheometer. Plastograms show that there is noticeable drop of fusion times and increase in melt viscosity torque of both, polymer blend and polymer blend nanocomposite, in comparison with those of neat PVC. SEM images show that homogenous dispersions are obtained. Tensile tests indicate that PVC/PEMA and PVC/PEMA/MMT samples have greater tensile strength and elastic modulus and lower elongation compared to PVC. When solid viscoelastic properties are considered (DMTA), slightly higher storage moduli are obtained whereas more prominent increase of storage modulus is observed when nanoclay particles are added in a PVC/PEMA matrix. From the calculated area of tandelta peak of all tested samples, nanocomposites exhibit the lowest damping behavior. Oscillatory measurements in a molten state were used for determining the frequency dependencies of storage G' and loss G" moduli. It was found that G" curves of neat PVC lie above those of G' suggesting that PVC behaves like viscoelastic liquid. Similar results, but with significantly higher values of G' and G" over the whole frequency range for PVC/PEMA blends were obtained. Steady shear measurements show that the presence of PEMA and nanoclay particles increases the shear stress and shear viscosity of neat PVC. In order to define the rheological equations of state the three material functions were determined. According to these functions all samples exhibit shear thinning behavior and the curves obey the power law equation. As rheological behaviour was found to be strongly dependent on blend's micro and macro structure and it is one of the main factors defining the end properties, attempt was

  8. Linear and nonlinear optical processing of polymer matrix nanocomposites

    NASA Astrophysics Data System (ADS)

    DeJournett, Travis J.; Han, Karen; Olasov, Lauren R.; Zeng, Fan W.; Lee, Brennan; Spicer, James B.

    2015-08-01

    This work focuses on the scalable synthesis and processing of nanostructures in polymer matrix nanocomposites (PMNCs) for applications that require photochemical functionality of these nanostructures. An in situ vapor deposition process using various metal and metal oxide precursors has been used to create a range of nanocomposites that display photochromic and photocatalytic behaviors. Under specific processing conditions, these composites consist of discrete nanoparticles distributed uniformly throughout the bulk of an optically transparent polymer matrix. Incorporating other chemical species as supplementary deposition agents in the synthesis process can modify these particles and produce complicated nanostructures with enhanced properties. In particular, work has been carried out to structure nanoparticles using laser irradiation. Starting with metallic or metal oxide nanoparticles in the polymer matrix, localized chemical vapor deposition in the near-particle environment has been carried out using laser irradiation to decompose chemical precursors leading to the formation of secondary structures surrounding the seed nanoparticles. Control of the spatial and temporal characteristics of the excitation source allows for synthesis of nanocomposites with a high degree of control over the location, composition and size of nanoparticles in the matrix and presents the opportunity to produce patterned materials with spatially varying properties.

  9. Analysis of thermal stresses in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, David E.; Griffin, O. H., Jr.

    1989-01-01

    In the present micromechanics study of the thermally-induced stress field which emerges at very low temperatures in the matrix and fibers of continuous fiber-reinforced polymer composites, the results obtained by a specialized FEM analysis are compared to an analytical solution of the composite cylinder model for several composite materials. Attention is given to the influence of microstructural geometry and constituent properties; it is established that the distributions and magnitudes of the thermally-induced stresses are affected by the assumed microstructural geometry of the sample. While matrix stresses are not a strong function of fiber properties, the temperature dependence of the matrix properties significantly affects the magnitudes of thermally-induced matrix stresses.

  10. High Strain Rate Behavior of Polymer Matrix Composites Analyzed

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.

    2001-01-01

    Procedures for modeling the high-speed impact of composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. To characterize and validate material models that could be used in the design of impactresistant engine cases, researchers must obtain material data over a wide variety of strain rates. An experimental program has been carried out through a university grant with the Ohio State University to obtain deformation data for a representative polymer matrix composite for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used to characterize and validate a constitutive model that was developed at the NASA Glenn Research Center.

  11. Electron Beam Curing of Polymer Matrix Composites - CRADA Final Report

    SciTech Connect

    Janke, C. J.; Howell, Dave; Norris, Robert E.

    1997-05-01

    The major cost driver in manufacturing polymer matrix composite (PMC) parts and structures, and one of the elements having the greatest effect on their quality and performance, is the standard thermal cure process. Thermal curing of PMCs requires long cure times and high energy consumption, creates residual thermal stresses in the part, produces volatile toxic by-products, and requires expensive tooling that is tolerant of the high cure temperatures.

  12. Thermal-vacuum response of polymer matrix composites in space

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Matthews, R.

    1993-01-01

    This report describes a thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites. Experimental results derived from 'control' samples are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples. Coefficient of thermal expansion (CTE) data are also presented. In addition, an example is given illustrating the dimensional change of a 'zero' CTE laminate due to moisture outgassing.

  13. Improving photo-stability of conjugated polymer MEH-PPV embedded in solid matrices by purification of the matrix polymer

    NASA Astrophysics Data System (ADS)

    Tian, Yuxi; Sheinin, Vladimir; Kulikova, Olga; Mamardashvili, Nugzar; Scheblykin, Ivan G.

    2014-04-01

    For single molecule spectroscopy (SMS), molecules under study are usually immobilized in a polymer matrix e.g. poly(methyl methacrylate). We show a very significant improvement of the conjugated polymer MEH-PPV photo-stability and decrease of the luminescence impurities concentration when the matrix is purified. We identify benzoyl peroxide (a common radical initiator) as a possible oxidizing agent which residuals in the polymer matrix destroy MEH-PPV. These results show that purification and selection of a matrix obtained by radical-free synthetic technique are of great importance for SMS as well as other technologies using polymer matrices as hosts for light-emitting materials.

  14. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  15. Polydispersity for Tuning the Potential of Mean Force between Polymer Grafted Nanoparticles in a Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Martin, Tyler B.; Dodd, Paul M.; Jayaraman, Arthi

    2013-01-01

    We present an integrated theory and simulation study of polydisperse polymer grafted nanoparticles in a polymer matrix to demonstrate the effect of polydispersity in graft length on the potential of mean force between the grafted nanoparticles. In dense polymer solutions, increasing polydispersity in graft length reduces the strength of repulsion at contact and weakens the attractive well at intermediate interparticle distances, completely eliminating the latter at high polydispersity index. The reduction in contact repulsion is attributable to polydispersity relieving monomer crowding near the particle surface, especially at high grafting densities. The elimination of the midrange attractive well is attributable to the longer grafts in the polydisperse graft length distribution that introduce longer range steric repulsion and alter the wetting of the grafted layer by matrix chains. Dispersion of the grafted particles is stabilized by increased penetration or wetting of the polydisperse grafted layer by the matrix chains. This work demonstrates that at high grafting densities, polydispersity in graft length can be used to stabilize dispersions of grafted nanoparticles in a polymer matrix at conditions where monodisperse grafts would cause aggregation.

  16. Development of advanced polymer nanocomposite capacitors

    NASA Astrophysics Data System (ADS)

    Mendoza, Miguel

    The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, and flexibility. The implementation of high aspect ratio dielectric inclusions such as nanowires into polymer capacitors could lead to further enhancement of its energy density. Therefore, this research effort is focused on the development of a new series of dielectric capacitors composed of nanowire reinforced polymer matrix composites. This concept of nanocomposite capacitors combines the extraordinary physical and chemical properties of the one-dimension (1D) nanoceramics and high dielectric strength of polymer matrices, leading to a capacitor with improved dielectric properties and energy density. Lead-free sodium niobate (NaNbO3) and lead-containing lead magnesium niobate-lead titanate (0.65PMN-0.35PT) nanowires were synthesized following hydrothermal and sol-gel approaches, respectively. The as-prepared nanowires were mixed with a polyvinylidene fluoride (PVDF) matrix using solution-casting method for nanocomposites fabrication. The dielectric constants and breakdown voltages of the NaNbO3/PVDF and 0.65PMN-0.35PT/PVDF nanocomposites were measured under different frequency ranges and temperatures in order to determine their maximum energy (J/cm3) and specific (J/g) densities. The electrical properties of the

  17. Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

    PubMed

    Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

    2013-06-26

    The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica. PMID:23639183

  18. Thermosetting polymer-matrix composites for structural repair applications

    NASA Astrophysics Data System (ADS)

    Goertzen, William Kirby

    2007-12-01

    Several classes of thermosetting polymer matrix composites were evaluated for use in structural repair applications. Initial work involved the characterization and evaluation of woven carbon fiber/epoxy matrix composites for structural pipeline repair. Cyanate ester resins were evaluated as a replacement for epoxy in composites for high-temperature pipe repair applications, and as the basis for adhesives for resin infusion repair of high-temperature composite materials. Carbon fiber/cyanate ester matrix composites and fumed silica/cyanate ester nanocomposites were evaluated for their thermal, mechanical, viscoelastic, and rheological properties as they relate to their structure, chemistry, and processing characteristics. The bisphenol E cyanate ester under investigation possesses a high glass transition temperature, excellent mechanical properties, and unique ambient temperature processability. The incorporation of fumed silica served to enhance the mechanical and rheological properties of the polymer and reduce thermal expansion without sacrificing glass transition or drastically altering curing kinetics. Characterization of the composites included dynamic mechanical analysis, thermomechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy.

  19. [Antioxidant properties of the pollen exine polymer matrix].

    PubMed

    Smirnova, A V; Timoffev, K N; Breĭgina, M A; Matveeva, N P; Ermakov, I P

    2012-01-01

    The antioxidant properties of exine polymer matrix which forms the outer layer of pollen grain wall were studied. The main component of this matrix is sporopollenin - a unique biopolymer resistant to mechanical and chemical damage. The samples of isolated exine, purified from soluble compounds, were studied with EPR using stable nitroxyl radical TEMPO and DMPO spin trap. At the same time, we analyzed changes in fluorescence of DCFH which detected ROS in the solution. It has been established that exine effectively reduces TEMPO radical and eliminates hydroxyl radical. Also, the fluorometric analysis demonstrated that the exine eliminated H2O2, and this ability significantly decreased after treatment of exine with feruloyl esterase or mild alkaline hydrolysis (1M NaOH), i.e. after hydrolysis of hydroxycinnamic acid esters. After harsh hydrolysis (4M NaOH, 170 degrees C) of ethers bonds a large amount of hydroxycinnamic acids has been released, and exines have lost their antioxidant capacity almost completely. The obtained results point to the ability of extracellular polymer matrix of the exine to eliminate free radicals and H2O2 during crucial periods of male gametophyte development. The participation of ferulic acid and, possibly, of other hydroxycinnamic acids of sporopollenin in these processes has been demonstrated. PMID:22594282

  20. Thermosetting Polymer-Matrix Composites for Strucutral Repair Applications

    SciTech Connect

    Goertzen, William Kirby

    2007-12-01

    Several classes of thermosetting polymer matrix composites were evaluated for use in structural repair applications. Initial work involved the characterization and evaluation of woven carbon fiber/epoxy matrix composites for structural pipeline repair. Cyanate ester resins were evaluated as a replacement for epoxy in composites for high-temperature pipe repair applications, and as the basis for adhesives for resin infusion repair of high-temperature composite materials. Carbon fiber/cyanate ester matrix composites and fumed silica/cyanate ester nanocomposites were evaluated for their thermal, mechanical, viscoelastic, and rheological properties as they relate to their structure, chemistry, and processing characteristics. The bisphenol E cyanate ester under investigation possesses a high glass transition temperature, excellent mechanical properties, and unique ambient temperature processability. The incorporate of fumed silica served to enhance the mechanical and rheological properties of the polymer and reduce thermal expansion without sacrificing glass transition or drastically altering curing kinetics. Characterization of the composites included dynamic mechanical analysis, thermomechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy.

  1. Progressive delamination in polymer matrix composite laminates: A new approach

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.

    1992-01-01

    A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive delamination in polymer matrix composite laminates. The damage stages are quantified based on physics via composite mechanics while the degradation of the laminate behavior is quantified via the finite element method. The approach accounts for all types of composite behavior, laminate configuration, load conditions, and delamination processes starting from damage initiation, to unstable propagation, and to laminate fracture. Results of laminate fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach.

  2. Space environmental effects on LDEF low Earth orbit exposed graphite reinforced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    George, Pete

    1992-01-01

    The Long Duration Exposure Facility (LDEF) was deployed on April 7, 1984 in low earth orbit (LEO) at an altitude of 482 kilometers. On board experiments experienced the harsh LEO environment including atomic oxygen (AO), ultraviolet radiation (UV), and thermal cycling. During the 5.8 year mission, the LDEF orbit decayed to 340 kilometers where significantly higher AO concentrations exist. LDEF was retrieved on January 12, 1990 from this orbit. One experiment on board LDEF was M0003, Space Effects on Spacecraft Materials. As a subset of M0003 nearly 500 samples of polymer, metal, and glass matrix composites were flown as the Advanced Composites Experiment M0003-10. The Advanced Composites Experiment is a joint effort between government and industry with the Aerospace Corporation serving as the experiment integrator. A portion of the graphite reinforced polymer matrix composites were furnished by the Boeing Defense and Space Group, Seattle, Washington. Test results and discussions for the Boeing portion of M0003-10 are presented. Experiment and specimen location on the LDEF are presented along with a quantitative summary of the pertinent exposure conditions. Matrix materials selected for the test were epoxy, polysulfone, and polyimide. These composite materials were selected due to their suitability for high performance structural capability in spacecraft applications. Graphite reinforced polymer matrix composites offer higher strength to weight ratios along with excellent dimensional stability. The Boeing space exposed and corresponding ground control composite specimens were subjected to post flight mechanical, chemical, and physical testing in order to determine any changes in critical properties and performance characteristics. Among the more significant findings are the erosive effect of atomic oxygen on leading edge exposed specimens and microcracking in non-unidirectionally reinforced flight specimens.

  3. Nanostructured polymer stable glasses via matrix assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Shepard, Kimberly B.

    Amorphous materials, or glasses, which lack a crystalline structure, are technologically ubiquitous with applications including structural components, pharmaceuticals, and electronic devices. Glasses are traditionally formed by rapid cooling from the melt state, where molecules become kinetically trapped into a non-equilibrium configuration. The temperature at which the material transforms from supercooled liquid to glass is the glass transition temperature. The glass transition temperature is the most important property of amorphous materials, as it determines the range of temperatures where they are fabricated, used and stored. Recent technological developments in which glasses are formed by alternative routes, such as physical vapor deposition and matrix assisted pulsed laser evaporation (MAPLE), enable tunability of Tg and related physical properties. High-Tg glasses formed by these techniques are termed "stable glasses" and exhibit a wide range of exceptional properties. This work focuses on the formation and characterization of stable polymer glasses fabricated via MAPLE. Bulk films (>1 microm thick) of glassy polymers fabricated by MAPLE at slow growth rates (<1 nm/s) and controlled substrate temperature (T sub = 0.85Tg,bulk) have greatly elevated Tg, low density, high enthalpy, increased kinetic stability and a spheroidal nanostructure. We focus on connecting the bulk and nanoscale properties of MAPLE-deposited polymer glasses. Building on molecular dynamics simulations from the literature on the MAPLE process, we experimentally study the origin of nanostructure in our MAPLE-deposited films. We measure the time-of-flight of MAPLE-deposited material, confirming that the velocity is sufficiently low for intact deposition of polymer nanoglobules. The size distribution of polymer nanoglobules fabricated in short MAPLE depositions provides insight into how nanostructured MAPLE films form. Using our atomic force microscopy-based nanoscale dilatometry technique

  4. LDEF results for polymer matrix composite experiment AO 180

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.

    1992-01-01

    This report represents a summary of the results obtained to-date on a polymer matrix composite experiment (AO 180) located at station D-12, about 82 deg off the 'ram' direction. Different material systems comprised of graphite, boron, and aramid (Kevlar) fiber reinforcements were studied. Although previous results were presented on in-situ thermal-vacuum cycling effects, particularly dimensional changes associated with outgassing, additional comparative data will be shown from ground-based tests on control and flight samples. The system employed was fully automated for thermal-vacuum cycling using a laser interferometer for monitoring displacements. Erosion of all three classes of materials due to atomic oxygen (AO) will also be discussed, including angle of incidence effects. Data from this experiment will be compared to published results for similar materials in other LDEF experiments. Composite materials' erosion yields will be presented on an AO design nomogram useful for estimating total material loss for given exposure conditions in low Earth orbit (LEO). Optical properties of these materials will also be compared with control samples. A survey of the damage caused by micrometeoroids/debris impacts will be addressed as they relate to polymer matrix composites. Correlations between hole size and damage pattern will be given. Reference to a new nomogram for estimating the number distribution of micrometeoroid/debris impacts for a given space structure as a function of time in LEO will be addressed based on LDEF data.

  5. Fabrication process of a high temperature polymer matrix engine duct

    NASA Technical Reports Server (NTRS)

    Pratt, R. D.; Wilson, A. J.

    1985-01-01

    The process that was used in the molding of an advanced composite outer by-pass duct planned for the F404 engine is discussed. This duct was developed as a potential replacement for the existing titanium duct in order to reduce both the weight and cost of the duct. The composite duct is now going into the manufacturing technology portion of the program. The duct is fabricated using graphite cloth impregnated with the PMR-15 matrix system.

  6. Dispersion/Aggregation of polymer grafted nanorods in a polymer matrix studied by Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Maia, Joao; Khani, Shaghayegh

    2015-03-01

    Nanorods are incorporated into polymer matrices for fabricating composite materials with enhanced physical and mechanical properties.The final macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the mechanical properties of the nanorod-polymer composites is observed upon formation of a percolating network. One way of controlling the assembly of nanorods in the polymer medium is adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. The recent developments in the computational techniques have paved the road for further understanding of the controlled dispersion and aggregation of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the abovementioned nanocomposites. In DPD, the interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. This works studies the effect of the enthalpic and entropic variables on phase transitions. The main goal is to provide a phase diagram than can be used to guide the experiments in designing new materials.

  7. Advances in mechanistic understanding of release rate control mechanisms of extended-release hydrophilic matrix tablets.

    PubMed

    Timmins, Peter; Desai, Divyakant; Chen, Wei; Wray, Patrick; Brown, Jonathan; Hanley, Sarah

    2016-08-01

    Approaches to characterizing and developing understanding around the mechanisms that control the release of drugs from hydrophilic matrix tablets are reviewed. While historical context is provided and direct physical characterization methods are described, recent advances including the role of percolation thresholds, the application on magnetic resonance and other spectroscopic imaging techniques are considered. The influence of polymer and dosage form characteristics are reviewed. The utility of mathematical modeling is described. Finally, how all the information derived from applying the developed mechanistic understanding from all of these tools can be brought together to develop a robust and reliable hydrophilic matrix extended-release tablet formulation is proposed. PMID:27444495

  8. Progressive fracture of polymer matrix composite structures: A new approach

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.

    1992-01-01

    A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive fracture of polymer matrix composite structures. The damage stages are quantified based on physics via composite mechanics while the degradation of the structural behavior is quantified via the finite element method. The approach account for all types of composite behavior, structures, load conditions, and fracture processes starting from damage initiation, to unstable propagation and to global structural collapse. Results of structural fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach. Parameters and guidelines are identified which can be used as criteria for structural fracture, inspection intervals, and retirement for cause. Generalization to structures made of monolithic metallic materials are outlined and lessons learned in undertaking the development of new approaches, in general, are summarized.

  9. Nanocarbon filler particles in polymer matrix - Nanosized dielectric probe

    NASA Astrophysics Data System (ADS)

    Shevchenko, Vitaliy G.; Polschikov, Sergey V.; Nedorezova, Polina M.; Klyamkina, Alla N.; Aladyshev, Alexander M.

    2014-05-01

    Composite materials of polypropylene, graphene nanoplatelets (GNP) or fullerene C60 were synthesized by in situ polymerization. GNP particles consist of 3 - 5 graphene layers and have aspect ratio 40. In composites with pristine GNP particles their aspect ratio is 110, whereas ultrasonic processing reduces it to 40 - 50. This change of aspect ratio of filler particles and their aggregates results in different properties of composites with pristine and sonicated GNP. Percolation threshold for composites with pristine GNP is 0.25% vol. In composites with sonicated GNP it is 2-3% vol. This is due to reduction in the size of filler particles aggregates and more uniform distribution of particles in polymer matrix after ultrasonic treatment. The presence of nanocarbon filler (GNP or fullerene) makes α-transition, associated with the glass transition of the amorphous phase of polypropylene, clearly resolved. Its intensity increases with the concentration of nanofiller, which acts as a dielectric probe.

  10. Measuring time-dependent diffusion in polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Pilli, Siva P.; Smith, Lloyd V.; Vaithiyalingam, Shutthanandan

    2014-11-01

    Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMCs). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick's Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time-dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60] s , was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C 0, followed by a slow linear increase to the saturation level.

  11. Measuring time-dependent diffusion in polymer matrix composites

    SciTech Connect

    Pilli, Siva Prasad; Smith, Lloyd V.; Shutthanandan, V.

    2014-11-01

    Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMC’s). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick’s Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60]s, was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C0, followed by a slow linear increase to the saturation level.

  12. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  13. Biaxial Yield Surface Investigation of Polymer-Matrix Composites

    PubMed Central

    Ye, Junjie; Qiu, Yuanying; Zhai, Zhi; He, Zhengjia

    2013-01-01

    This article presents a numerical technique for computing the biaxial yield surface of polymer-matrix composites with a given microstructure. Generalized Method of Cells in combination with an Improved Bodner-Partom Viscoplastic model is used to compute the inelastic deformation. The validation of presented model is proved by a fiber Bragg gratings (FBGs) strain test system through uniaxial testing under two different strain rate conditions. On this basis, the manufacturing process thermal residual stress and strain rate effect on the biaxial yield surface of composites are considered. The results show that the effect of thermal residual stress on the biaxial yield response is closely dependent on loading conditions. Moreover, biaxial yield strength tends to increase with the increasing strain rate. PMID:23529150

  14. Polymers as advanced materials for desiccant applications

    SciTech Connect

    Czanderna, A.W.

    1990-12-01

    This research is concerned with solid materials used as desiccants for desiccant cooling systems (DCSs) that process water vapor in an atmosphere to produce cooling. Background information includes an introduction to DCSs and the role of the desiccant as a system component. The water vapor sorption performance criteria used for screening the modified polymers prepared include the water sorption capacity from 5% to 80% relative humidity (R.H.), isotherm shape, and rate of adsorption and desorption. Measurements are presented for the sorption performance of modified polymeric advanced desiccant materials with the quartz crystal microbalance. Isotherms of polystyrene sulfonic acid (PSSA) taken over a 5-month period show that the material has a dramatic loss in capacity and that the isotherm shape is time dependent. The adsorption and desorption kinetics for PSSA and all the ionic salts of it studied are easily fast enough for commercial DCS applications with a wheel rotation speed of 6 min per revolution. Future activities for the project are addressed, and a 5-year summary of the project is included as Appendix A. 34 refs., 20 figs., 3 tabs.

  15. Suppression of Acid Diffusion in Chemical Amplification Resists by Molecular Control of Base Matrix Polymers

    NASA Astrophysics Data System (ADS)

    Yoshimura, Toshiyuki; Shiraishi, Hiroshi; Okazaki, Shinji

    1995-12-01

    Suppression of acid diffusion during post-exposure baking (PEB) of chemical amplification resists is investigated from the standpoint of molecular control of base matrix polymers. Negative-type chemical amplification resists composed of cresol novolak-based matrix polymers, acid-catalyzed crosslinkers of melamine resins, and acid generators of onium salts are prepared. The molecular weight distributions of the base matrix polymers are controlled by means of a precipitation method. The resists are exposed with electron beams in isolated lines to evaluate the acid diffusion characteristics. Dependence of pattern sizes on the PEB time clearly shows that acid diffusion determines the resist pattern sizes based on Fick's law. The diffusion coefficients of resists with base matrix polymers with small polydispersities are smaller than those of resists with base matrix polymers with large polydispersities. Acid diffusion can still be suppressed by applying base matrix polymers with small weight-average molecular weights and small polydispersities. Diffusion coefficients can be further decreased by using base matrix polymers with more p-cresol components. A diffusion mechanism is proposed based on acid diffusion channels composed of active OH-groups and vacancies in the base matrix polymers.

  16. Creep-rupture of polymer-matrix composites. [graphite-epoxy laminates

    NASA Technical Reports Server (NTRS)

    Brinson, H. F.; Griffith, W. I.; Morris, D. H.

    1980-01-01

    An accelerated characterization method for resin matrix composites is reviewed. Methods for determining modulus and strength master curves are given. Creep rupture analytical models are discussed as applied to polymers and polymer matrix composites. Comparisons between creep rupture experiments and analytical models are presented. The time dependent creep rupture process in graphite epoxy laminates is examined as a function of temperature and stress level.

  17. High performance polymers and polymer matrix composites for spacecraft structural applications

    NASA Technical Reports Server (NTRS)

    Bowles, D. E.; Connell, J. W.

    1992-01-01

    A program implemented by NASA Langley Research Center to develop and evaluate new polymers and polymer matrix composites for spacecraft structural applications is examined. Various polymeric films, moldings, and adhesives are evaluated for resistance to atomic oxygen and high energy electron and UV radiation. Thin films from the poly(arylene ether)s containing phenylphosphine oxide groups and the siloxane-epoxies exhibited minor weight loss compared to Kapton polyimide after exposure. Large doses (greater than 10 exp 9 rads) of electron radiation, simulating 30 yr of exposure in GEO, are found to alter the chemical structure of epoxies by both chain scission and cross-linking. The thermal cycling representative of both LEO and GEO environments can cause microcracking in composites which can in turn affect the dimensional stability and produce mechanical property reductions. The processing and fabrication issues associated with precision composite spacecraft components are also addressed.

  18. Advances in biomimetic regeneration of elastic matrix structures

    PubMed Central

    Sivaraman, Balakrishnan; Bashur, Chris A.

    2012-01-01

    Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures. PMID:23355960

  19. Mechanophore activation in a crosslinked polymer matrix via instrumented indentation

    NASA Astrophysics Data System (ADS)

    Davis, Chelsea; Forster, Aaron; Woodcock, Jeremiah; Wang, Muzhou; Gilman, Jeffrey; Material Measurement Laboratory Team

    Recent advances in mechanically-activated fluorophores will enable a host of unique scientific challenges and opportunities to be addressed. Several mechanophores (MPs) in polymers have been reported, yet the specific deformation required to activate these molecules in a bulk polymer network has not been sufficiently specified. In an effort to develop the mechano-activation/deformation relationship of a spirolactam-based MP, scratches were applied to a MP-functionalized glassy crosslinked material at varying normal loads and lateral displacement rates. This experimental design allowed strain and strain rate effects to be decoupled. The fluorescence activation was then observed with a laser scanning confocal microscope. Areas of elastic and plastic deformation as well as brittle fracture were observed within each scratch as the normal loading of the indenter increased. The fluorescence intensity increased with increasing strain. Contact mechanics models are employed to demonstrate that relatively high degrees of strain are required to initiate the ring-opening activation transition within the spirolactam-based MP. These self-reporting damage sensors can be incorporated within polymeric coatings to allow real time structural health monitoring for a myriad of applications.

  20. Enhancing Crystalline Structural Orders of Polymer Semiconductors for Efficient Charge Transport via Polymer-Matrix-Mediated Molecular Self-Assembly.

    PubMed

    Lei, Yanlian; Deng, Ping; Lin, Ming; Zheng, Xuelin; Zhu, Furong; Ong, Beng S

    2016-08-01

    A facile polymer-matrix-mediated molecular self-assembly of polymer semiconductors into highly crystalline orders for efficient charge transport in organic thin-film transistors is demonstrated. Phenomenal enhancements in field-effect mobility of about one order of magnitude and current on/off ratio of two to three orders of magnitude are realized with polyacrylonitrile-incorporated polymer semiconductor compositions via solution deposition. PMID:27168128

  1. Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Liaw, Benjamin; Zeichner, Glenn; Liu, Yanxiong; Bowles, Kenneth J. (Technical Monitor)

    2000-01-01

    The main objective of this NASA FAR project is to conduct ultrasonic assessment of impact-induced damage and microcracking in polymer matrix composites at various temperatures. It is believed that the proposed study of impact damage assessment on polymer matrix composites will benefit several NASA's missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Currently, impact-induced delamination and fracture in 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy were generated in an instrumented drop-weight impact machine. Although only a small dent was produced on the aluminum side when a hemispherical penetrator tup was dropped onto it from a couple of inches, a large ring of delamination at the interface was observed. The delamination damage was often accompanied by severe shattering in the acrylic substratum. Damage patterns in the acrylic layer include radial and ring cracks and, together with delamination at the interface, may cause peeling-off of acrylic material from the sandwich plate. Theory of stress-wave propagation can be used to explain these damage patterns. The impact tests were conducted at various temperatures. The results also show clearly that temperature effect is very important in impact damage. For pure cast acrylic nil-ductile transition (NDT) occurs between 185-195 F Excessive impact energy was dissipated into fracture energy when tested at temperature below this range or through plastic deformation when tested at temperature above the NDT temperature. Results from this study will be used as baseline data for studying fiber-metal laminates, such as GLARE and ARALL for advanced aeronautical and astronautical applications.

  2. Prediction of thermal cycling induced cracking in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Mcmanus, Hugh L.

    1993-01-01

    This report summarizes the work done in the period February 1993 through July 1993 on the 'Prediction of Thermal Cycling Induced Cracking In Polymer Matrix Composites' program. An oral presentation of this work was given to Langley personnel in September of 1993. This document was prepared for archival purposes. Progress studies have been performed on the effects of spatial variations in material strength. Qualitative agreement was found with observed patterns of crack distribution. These results were presented to NASA Langley personnel in November 1992. The analytical methodology developed by Prof. McManus in the summer of 1992 (under an ASEE fellowship) has been generalized. A method for predicting matrix cracking due to decreasing temperatures and/or thermal cycling in all plies of an arbitrary laminate has been implemented as a computer code. The code also predicts changes in properties due to the cracking. Experimental progressive cracking studies on a variety of laminates were carried out at Langley Research Center. Results were correlated to predictions using the new methods. Results were initially mixed. This motivated an exploration of the configuration of cracks within laminates. A crack configuration study was carried out by cutting and/or sanding specimens in order to examine the distribution of cracks within the specimens. These investigations were supplemented by dye-penetrant enhanced X-ray photographs. The behavior of thin plies was found to be different from the behavior of thicker plies (or ply groups) on which existing theories are based. Significant edge effects were also noted, which caused the traditional metric of microcracking (count of cracks on a polished edge) to be very inaccurate in some cases. With edge and configuration taken into account, rough agreement with predictions was achieved. All results to date were reviewed with NASA Langley personnel in September 1993.

  3. Advanced polymer chemistry of organometallic anions

    SciTech Connect

    Chamberlin, R.M.; Abney, K.D.; Balaich, G.J.; Fino, S.A.

    1997-11-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to prepare and characterize new polymers incorporating cobalt dicarbollide. Specific goals were to prepare polymerizable cobalt dicarbollide monomers using the nucleophilic substitution route discovered in laboratories and to establish the reaction conditions required to form polymers from these complexes. This one-year project resulted in two publications (in press), and provided the foundation for further investigations into polymer synthesis and characterization using cobalt dicarbollide and other metallocarboranes. Interest in synthesizing organometallic polymers containing the cobalt bis(dicarbollide) anion is motivated by their possible application as cation exchange materials for the remediation of cesium-137 and strontium-90 from nuclear wastes.

  4. Electron Beam-Cure Polymer Matrix Composites: Processing and Properties

    NASA Technical Reports Server (NTRS)

    Wrenn, G.; Frame, B.; Jensen, B.; Nettles, A.

    2001-01-01

    Researchers from NASA and Oak Ridge National Laboratory are evaluating a series of electron beam curable composites for application in reusable launch vehicle airframe and propulsion systems. Objectives are to develop electron beam curable composites that are useful at cryogenic to elevated temperatures (-217 C to 200 C), validate key mechanical properties of these composites, and demonstrate cost-saving fabrication methods at the subcomponent level. Electron beam curing of polymer matrix composites is an enabling capability for production of aerospace structures in a non-autoclave process. Payoffs of this technology will be fabrication of composite structures at room temperature, reduced tooling cost and cure time, and improvements in component durability. This presentation covers the results of material property evaluations for electron beam-cured composites made with either unidirectional tape or woven fabric architectures. Resin systems have been evaluated for performance in ambient, cryogenic, and elevated temperature conditions. Results for electron beam composites and similar composites cured in conventional processes are reviewed for comparison. Fabrication demonstrations were also performed for electron beam-cured composite airframe and propulsion piping subcomponents. These parts have been built to validate manufacturing methods with electron beam composite materials, to evaluate electron beam curing processing parameters, and to demonstrate lightweight, low-cost tooling options.

  5. Mechanocompatible Polymer-Extracellular-Matrix Composites for Vascular Tissue Engineering.

    PubMed

    Jiang, Bin; Suen, Rachel; Wang, Jiao-Jing; Zhang, Zheng J; Wertheim, Jason A; Ameer, Guillermo A

    2016-07-01

    Small-diameter vascular grafts developed from vascular extracellular matrix (ECM) can potentially be used for bypass surgeries and other vascular reconstruction and repair procedures. The addition of heparin to the ECM improves graft hemocompatibility but often involves chemical cross-linking, which increases ECM mechanical stiffness compared to native arteries. Herein, the importance of maintaining ECM mechanocompatibility is demonstrated, and a mechanocompatible strategy to immobilize heparin onto the ECM via a biodegradable elastomer is described. Specifically, poly(1,8-octamethylene citrate)-co-cysteine is hybridized to the ECM, forming a polymer-ECM composite that allows for heparin immobilization via maleimide-thiol "click" chemistry. Heparinized composites reduce platelet adhesion by >60% in vitro, without altering the elastic modulus of the ECM. In a rat abdominal aortic interposition model, intimal hyperplasia in heparinized mechanocompatible grafts is 65% lower when compared to ECM-only control grafts at four weeks. In contrast, grafts that are heparinized with carbodiimide chemistry exhibit increased intimal hyperplasia (4.2-fold) and increased macrophage infiltration (3.5-fold) compared to ECM-only control grafts. All grafts show similar, partial endothelial cell coverage and little to no ECM remodeling. Overall, a mechanocompatible strategy to improve ECM thromboresistance is described and the importance of ECM mechanical properties for proper in vivo graft performance is highlighted. PMID:27109033

  6. Modeling Woven Polymer Matrix Composites with MAC/GMC

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Arnold, Steven M. (Technical Monitor)

    2000-01-01

    NASA's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) is used to predict the elastic properties of plain weave polymer matrix composites (PMCs). The traditional one step three-dimensional homogertization procedure that has been used in conjunction with MAC/GMC for modeling woven composites in the past is inaccurate due to the lack of shear coupling inherent to the model. However, by performing a two step homogenization procedure in which the woven composite repeating unit cell is homogenized independently in the through-thickness direction prior to homogenization in the plane of the weave, MAC/GMC can now accurately model woven PMCs. This two step procedure is outlined and implemented, and predictions are compared with results from the traditional one step approach and other models and experiments from the literature. Full coupling of this two step technique with MAC/ GMC will result in a widely applicable, efficient, and accurate tool for the design and analysis of woven composite materials and structures.

  7. Phase Behavior of Polymer-Grafted Nanoparticles in a Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Mongcopa, Katrina Irene; Ashkar, Rana; Butler, Paul; Krishnamoorti, Ramanan

    2015-03-01

    We examine the thermodynamic interactions of polystyrene (PS) grafted onto spherical silica nanoparticles blended with a poly(vinyl methyl ether) (PVME) matrix using light, x-ray and neutron scattering techniques. PS/PVME systems are known to exhibit a lower critical solution temperature, with blending thermodynamics greatly affected by the chain length of the components. Thus, we study how enthalpic and entropic effects play a role in the dispersion of PS-grafted nanoparticles in a chemically-distinct matrix, especially as the system approaches a phase boundary. Scattering techniques are used to examine the effect of molecular weight on the blend thermodynamics and concentration fluctuations for such strongly interacting polymer blends. X-ray scattering data and analysis of the structure factor reveal that for a grafted deuterated polystyrene brush (33,000 Da) in a PVME matrix (226,000 Da), an initial dispersion of nanoparticles occurs at low temperatures. The system then gradually transitions to an aggregated state as temperature is increased, suggesting the presence of strong inter-particle interactions that lead to fractal formation as the system approaches a phase boundary. Complementary neutron scattering experiments confirm this phenomenon.

  8. Recent advances in conjugated polymers for light emitting devices.

    PubMed

    Alsalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  9. Recent Advances in Conjugated Polymers for Light Emitting Devices

    PubMed Central

    AlSalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  10. Tuning the wetting-dewetting and dispersion-aggregation transitions in polymer nanocomposites using composition of graft and matrix polymers

    NASA Astrophysics Data System (ADS)

    Martin, Tyler B.; Jayaraman, Arthi

    2016-03-01

    Recent simulation and experimental work on polymer nanocomposites composed of polymer grafted particles and free matrix polymers, where the graft and matrix homopolymers are chemically dissimilar and exhibit lower critical solution temperature behavior with temperature, has shown that wetting to dewetting is a gradual and distinct transition from the sharp particle dispersion-aggregation transition. In this study, using coarse-grained molecular simulations, we demonstrate that the extent of wetting of the grafted polymer layer and the particle dispersion-aggregation transition are tuned using the composition of graft and matrix polymers. Specifically, we study composites where the graft and matrix chains are random copolymers composed of attractive and athermal monomers. We maintain a dense grafting density on the spherical particles of diameter five times the monomer diameter and study matrix lengths five times that of the graft chain length or equal graft and matrix chain lengths. We vary the fraction of attractive monomers in the graft ({f}{{G}}) and matrix ({f}{{M}}) chains, graft-matrix chain composition ratio ({f}{{G}}/{f}{{M}}), and the graft-matrix interaction strength, as characterized by the Flory-Huggins interaction parameter between graft and matrix attractive monomers: {χ }{{GM}}. When {χ }{{GM}} is negative, decreasing {f}{{G}} and/or {f}{{M}} decreases the extent of grafted layer wetting by matrix chains because the enthalpic driving force for wetting is reduced. As the {χ }{{GM}} increases and becomes positive, the extent of wetting decreases gradually till it reaches the wetting of analogous athermal composites. That value of {χ }{{GM}} where the extent of wetting is the same as that of an analogous athermal polymer nanocomposite marks the onset of dispersion-aggregation transition. For symmetric graft and matrix chain compositions ({f}{{G}}={f}{{M}}), the magnitude of {f}{{G}} and {f}{{M}} tunes the overall extent of wetting of the grafted

  11. Advanced Polymer For Multilayer Insulating Blankets

    NASA Technical Reports Server (NTRS)

    Haghighat, R. Ross; Shepp, Allan

    1996-01-01

    Polymer resisting degradation by monatomic oxygen undergoing commercial development under trade name "Aorimide" ("atomic-oxygen-resistant imidazole"). Intended for use in thermal blankets for spacecraft in low orbit, useful on Earth in outdoor applications in which sunlight and ozone degrades other plastics. Also used, for example, to make threads and to make films coated with metals for reflectivity.

  12. Advancing polymers of intrinsic microporosity by mechanochemistry

    DOE PAGESBeta

    Zhang, Pengfei; Jiang, Xueguang; Wan, Shun; Dai, Sheng

    2015-02-20

    Herein, we report a fast (15 min) and solvent-free mechanochemical approach to construct polymers of intrinsic microporosity (PIMs) with high molecular mass and low polydispersity by solid grinding. The enhanced reaction efficiency results from the instantaneous frictional heating and continuous exposure of active sites within those solid reactants.

  13. Effects of physical aging on long-term creep of polymers and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Brinson, L. Catherine; Gates, Thomas S.

    1994-01-01

    For many polymeric materials in use below the glass transition temperature, the long term viscoelastic behavior is greatly affected by physical aging. To use polymer matrix composites as critical structural components in existing and novel technological applications, this long term behavior of the material system must be understood. Towards that end, this study applied the concepts governing the mechanics of physical aging in a consistent manner to the study of laminated composite systems. Even in fiber-dominated lay-ups the effects of physical aging are found to be important in the long-term behavior of the composite. The basic concepts describing physical aging of polymers are discussed. Several aspects of physical aging which have not been previously documented are also explored in this study, namely the effects of aging into equilibrium and a relationship to the time-temperature shift factor. The physical aging theory is then extended to develop the long-term compliance/modulus of a single lamina with varying fiber orientation. The latter is then built into classical lamination theory to predict long-time response of general oriented lamina and laminates. It is illustrated that the long term response can be counterintuitive, stressing the need for consistent modeling efforts to make long term predictions of laminates to be used in structural situations.

  14. Polymer-brush lubrication: a review of recent theoretical advances.

    PubMed

    Kreer, T

    2016-04-13

    This review compiles recent theoretical advances to describe compressive and shear forces of polymer-brush bilayers, which consist of two opposing brushes in contact. Such model systems for polymer-brush lubrication are frequently used as a benchmark to gain insight into biological problems, e.g., synovial joint lubrication. Based on scaling theory, I derive conformational and collective properties of polymer-brush bilayers in equilibrium and out-of-equilibrium situations, such as shear forces in the linear and nonlinear response regimes of stationary shear and under non-stationary shear. Furthermore, I discuss the influence of macromolecular inclusions and electrostatic interactions on polymer-brush lubrication. Comparisons to alternative analytical approaches, experiments and numerical results are performed. Special emphasis is given to methods for simulating polymer-brush bilayers using molecular dynamics simulations. PMID:27029521

  15. E-beam-Cure Fabrication of Polymer Fiber/Matrix Composites for Multifunctional Radiation Shielding

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Jensen, Brian J.; Thibeault, Sheila A.; Hou, Tan-Hung; Saether, Erik; Glaessgen, Edward H.; Humes, Donald H.; Chang, Chie K.; Badavi, Francis F.; Kiefer, Rrichard L.; Adams, Dan O.

    2004-01-01

    Aliphatic polymers were identified as optimum radiation polymeric shielding materials for building multifunctional structural elements. Conceptual damage-tolerant configurations of polyolefins have been proposed but many issues on the manufacture remain. In the present paper, we will investigate fabrication technologies with e-beam curing for inclusion of high-strength aliphatic polymer fibers into a highly cross-linked polyolefin matrix. A second stage of development is the fabrication methods for applying face sheets to aliphatic polymer closed-cell foams.

  16. Advanced Developments in Cyclic Polymers: Synthesis, Applications, and Perspectives

    PubMed Central

    Zhu, Yinghuai; Hosmane, Narayan S

    2015-01-01

    Due to the topological effect, cyclic polymers demonstrate different and unique physical and biological properties in comparison with linear counterparts having the same molecular-weight range. With advanced synthetic and analytic technologies, cyclic polymers with different topologies, e.g. multicyclic polymers, have been reported and well characterized. For example, various cyclic DNA and related structures, such as cyclic duplexes, have been prepared conveniently by click chemistry. These types of DNA have increased resistance to enzymatic degradation and have high thermodynamic stability, and thus, have potential therapeutic applications. In addition, cyclic polymers have also been used to prepare organic–inorganic hybrids for applications in catalysis, e.g. catalyst supports. Due to developments in synthetic technology, highly pure cyclic polymers could now be produced in large scale. Therefore, we anticipate discovering more applications in the near future. Despite their promise, cyclic polymers are still less explored than linear polymers like polyolefins and polycarbonates, which are widely used in daily life. Some critical issues, including controlling the molecular weight and finding suitable applications, remain big challenges in the cyclic-polymer field. This review briefly summarizes the commonly used synthetic methodologies and focuses more on the attractive functional materials and their biological properties and potential applications. PMID:26478835

  17. Structural and functional polymer-matrix composites for electromagnetic applications

    NASA Astrophysics Data System (ADS)

    Wu, Junhua

    This dissertation addresses the science and technology of functional and structural polymer-matrix composite materials for electromagnetic applications, which include electromagnetic interference (EMI) shielding and low observability (Stealth). The structural composites are continuous carbon fiber epoxy-matrix composites, which are widely used for airframes. The functional composites are composites with discontinuous fillers and in both bulk and coating forms. Through composite structure variation, attractive electromagnetic properties have been achieved. With no degradation of the tensile strength or modulus, the shielding effectiveness of the structural composites has been improved by enhancing multiple reflections through light activation of the carbon fiber. The multiple reflections loss of the electromagnetic wave increases from 1.1 to 10.2 dB at 1.0 GHz due to the activation. Such a large effect of multiple reflections has not been previously reported in any material. The observability of these composites has been lowered by decreasing the electrical conductivity (and hence decreasing the reflection loss) through carbon fiber coating. The incorporation of mumetal, a magnetic alloy particulate filler (28-40 mum size), in a latex paint has been found to be effective for enhancing the shielding only if the electrical resistivity of the resulting composite coating is below 10 O.cm, as rendered by a conductive particulate filler, such as nickel flake (14-20 mum size). This effectiveness (39 dB at 1.0 GHz) is attributed to the absorption of the electromagnetic wave by the mumetal and the nickel flake, with the high conductivity rendered by the presence of the nickel flake resulting in a relatively high reflection loss of 15.5 dB. Without the nickel flake, the mumetal gives only 3 dB of shielding and 1.5 dB of reflection loss at 1.0 GHz. Nickel powder (0.3-0.5 mum size) has been found to be an effective filler for improving the shielding of polyethersulfone (PES

  18. High Temperature Degradation Mechanisms in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Cunningham, Ronan A.

    1996-01-01

    Polymer matrix composites are increasingly used in demanding structural applications in which they may be exposed to harsh environments. The durability of such materials is a major concern, potentially limiting both the integrity of the structures and their useful lifetimes. The goal of the current investigation is to develop a mechanism-based model of the chemical degradation which occurs, such that given the external chemical environment and temperatures throughout the laminate, laminate geometry, and ply and/or constituent material properties, we can calculate the concentration of diffusing substances and extent of chemical degradation as functions of time and position throughout the laminate. This objective is met through the development and use of analytical models, coupled to an analysis-driven experimental program which offers both quantitative and qualitative information on the degradation mechanism. Preliminary analyses using a coupled diffusion/reaction model are used to gain insight into the physics of the degradation mechanisms and to identify crucial material parameters. An experimental program is defined based on the results of the preliminary analysis which allows the determination of the necessary material coefficients. Thermogravimetric analyses are carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. Powdered samples are used to eliminate diffusion effects. Tests in both inert and oxidative environments allow the separation of thermal and oxidative contributions to specimen mass loss. The concentration dependency of the oxidative reactions is determined from the tests in pure oxygen. Short term isothermal tests at different temperatures are carried out on neat resin and unidirectional macroscopic specimens to identify diffusion effects. Mass loss, specimen shrinkage, the formation of degraded surface layers and surface cracking are recorded as functions of exposure time. Geometry effects

  19. Advances in Polymer and Polymeric Nanostructures for Protein Conjugation

    PubMed Central

    González-Toro, Daniella C.; Thayumanavan, S.

    2013-01-01

    Linear polymers have been considered the best molecular structures for the formation of efficient protein conjugates due to their biological advantages, synthetic convenience and ease of functionalization. In recent years, much attention has been dedicated to develop synthetic strategies that produce the most control over protein conjugation utilizing linear polymers as scaffolds. As a result, different conjugate models, such as semitelechelic, homotelechelic, heterotelechelic and branched or star polymer conjugates, have been obtained that take advantage of these well-controlled synthetic strategies. Development of protein conjugates using nanostructures and the formation of said nanostructures from protein-polymer bioconjugates are other areas in the protein bioconjugation field. Although several polymer-protein technologies have been developed from these discoveries, few review articles have focused on the design and function of these polymers and nanostructures. This review will highlight some recent advances in protein-linear polymer technologies that employ protein covalent conjugation and successful protein-nanostructure bioconjugates (covalent conjugation as well) that have shown great potential for biological applications. PMID:24058205

  20. Development of Metal Matrix Composites for NASA'S Advanced Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

    The state-of-the-art development of several aluminum and copper based Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The presentation's goal is to provide an overview of NASA-Marshall Space Flight Center's planned and on-going activities in MMC for advanced liquid rocket engines such as the X-33 vehicle's Aerospike and X-34 Fastrac engine. The focus will be on lightweight and environmental compatibility with oxygen and hydrogen of key MMC materials, within each NASA's new propulsion application, that will provide a high payoff for NASA's reusable launch vehicle systems and space access vehicles. Advanced MMC processing techniques such as plasma spray, centrifugal casting, pressure infiltration casting will be discussed. Development of a novel 3D printing method for low cost production of composite preform, and functional gradient MMC to enhanced rocket engine's dimensional stability will be presented.

  1. Advanced composite polymer electrolyte fuel cell membranes

    SciTech Connect

    Wilson, M.S.; Zawodzinski, T.A.; Gottesfeld, S.; Kolde, J.A.; Bahar, B.

    1995-09-01

    A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.

  2. Structural and functional polymer-matrix composites for electromagnetic applications

    NASA Astrophysics Data System (ADS)

    Wu, Junhua

    This dissertation addresses the science and technology of functional and structural polymer-matrix composite materials for electromagnetic applications, which include electromagnetic interference (EMI) shielding and low observability (Stealth). The structural composites are continuous carbon fiber epoxy-matrix composites, which are widely used for airframes. The functional composites are composites with discontinuous fillers and in both bulk and coating forms. Through composite structure variation, attractive electromagnetic properties have been achieved. With no degradation of the tensile strength or modulus, the shielding effectiveness of the structural composites has been improved by enhancing multiple reflections through light activation of the carbon fiber. The multiple reflections loss of the electromagnetic wave increases from 1.1 to 10.2 dB at 1.0 GHz due to the activation. Such a large effect of multiple reflections has not been previously reported in any material. The observability of these composites has been lowered by decreasing the electrical conductivity (and hence decreasing the reflection loss) through carbon fiber coating. The incorporation of mumetal, a magnetic alloy particulate filler (28-40 mum size), in a latex paint has been found to be effective for enhancing the shielding only if the electrical resistivity of the resulting composite coating is below 10 O.cm, as rendered by a conductive particulate filler, such as nickel flake (14-20 mum size). This effectiveness (39 dB at 1.0 GHz) is attributed to the absorption of the electromagnetic wave by the mumetal and the nickel flake, with the high conductivity rendered by the presence of the nickel flake resulting in a relatively high reflection loss of 15.5 dB. Without the nickel flake, the mumetal gives only 3 dB of shielding and 1.5 dB of reflection loss at 1.0 GHz. Nickel powder (0.3-0.5 mum size) has been found to be an effective filler for improving the shielding of polyethersulfone (PES

  3. RAFT technology for the production of advanced photoresist polymers

    NASA Astrophysics Data System (ADS)

    Sheehan, Michael T.; Farnham, William B.; Okazaki, Hiroshi; Sounik, James R.; Clark, George

    2008-03-01

    Reversible Addition Fragmentation Chain Transfer (RAFT) technology has been developed for use in producing high yield low polydispersity (PD) polymers for many applications. RAFT technology is being used to produce low PD polymers and to allow control of the polymer architecture. A variety of polymers are being synthesized for use in advanced photoresists using this technique. By varying the RAFT reagent used we can modulate the system reactivity of the RAFT reagent and optimize it for use in acrylate or methacrylate monomer systems (193 and 193i photoresist polymers) or for use in styrenic monomer systems (248 nm photoresist polymers) to achieve PD as low as 1.05. RAFT polymerization technology also allows us to produce block copolymers using a wide variety of monomers. These block copolymers have been shown to be useful in self assembly polymer applications to produce unique and very small feature sizes. The mutual compatibilities of all the components within a single layer 193 photoresist are very important in order to achieve low LWR and low defect count. The advent of immersion imaging demands an additional element of protection at the solid/liquid interface. We have used RAFT technology to produce block copolymers comprising a random "resist" block with composition and size based on conventional dry photoresist materials, and a "low surface energy" block for use in 193i lithography. The relative block lengths and compositions may be varied to tune solution behavior, surface energy, contact angles, and solubility in developer. The use of this technique will be explored to produce polymers used in hydrophobic single layer resists as well as additives compatible with the main photoresist polymer.

  4. Matrix metalloproteinase-sensitive thermogelling polymer for bioresponsive local drug delivery.

    PubMed

    Garripelli, Vivek Kumar; Kim, Jin-Ki; Son, Sejin; Kim, Won Jong; Repka, Michael A; Jo, Seongbong

    2011-05-01

    Development of a successful bioresponsive drug delivery system requires exquisite engineering of the materials so that they are able to respond to signals stemming from the physiological environment. In this study we propose a new Pluronic(®) based thermogelling system containing matrix metalloproteinase-2 (MMP2) responsive peptide sequences. A novel thermosensitive multiblock co-polymer comprising an MMP2-labile octapeptide (Gly-Pro-Val-Gly-Leu-Ile-Gly-Lys) was synthesized from a Pluronic(®) triblock co-polymer. The polymer was designed to form a thermogel at body temperature and degrade in the presence of MMP overexpressed in a tumor. The synthesized polymer was a multiblock co-polymer with ∼2.5 U of Pluronic(®). The multiblock co-polymer solutions exhibited reverse thermal gelation around body temperature. The gelation temperatures of the multiblock co-polymer solutions were lower than those of the corresponding Pluronic(®) monomer at a particular concentration. The cytotoxicity of the synthesized polymer was lower compared with the monomer. The solubility of the hydrophobic anticancer drug paclitaxel was enhanced in the polymer solutions by micelle formation. The synthesized polymer was preferentially degraded in the presence of MMP. Paclitaxel release was dependent on the enzyme concentration. These findings suggest that the synthesized polymer has potential as a controlled drug delivery system due to its unique phase transition and bioresponsive behavior. PMID:21300184

  5. IUPAC International Symposium on Polymers for Advanced Technologies, Jerusalem, Israel, Aug. 16-21, 1987, Proceedings

    SciTech Connect

    Lewin, M.

    1988-01-01

    The present conference discusses topics in radiation-sensitive, radiation-modified, and cured polymers, polymers of photoconductive, electroconductive, and piezoelectric type, polymers for advanced structures, liquid-crystal polymers, high-performance polymers compounded from flexible macromolecules, polymer networks, polymer blends, and the matching of composites with adhesives. Attention is given to the industrial radiation-curing of polymers, a frequency-analysis of ferroelectricity, liquid crystal polyester fibers, photochromic and thermochromic liquid crystals, diacetylene-based single-crystal fibers, interpenetrating polymer networks, chain-length development in complex epoxy-amine matrices, and a statistical-thermodynamic theory of polymer precipitation fractionation.

  6. Effect of matrix molecular weight on the coarsening mechanism of polymer-grafted gold nanocrystals.

    PubMed

    Jia, Xiaolong; Listak, Jessica; Witherspoon, Velencia; Kalu, E Eric; Yang, Xiaoping; Bockstaller, Michael R

    2010-07-20

    A systematic evaluation of the effect of polymer matrix molecular weight on the coarsening kinetics of uniformly dispersed polystyrene-grafted gold nanoparticles is presented. Particle coarsening is found to proceed via three stages (i.e., atomic-diffusion-based Ostwald ripening (OR), particle-migration-based collision-coalescence, and the subsequent reshaping of particle assemblies). The relative significance of each stage and hence the evolution of particle size and shape have been found to depend sensitively upon time, temperature, and the molecular weight of the host polymer. At temperatures close to the matrix glass-transition temperature, Ostwald ripening has been observed to be dominant on all experimental timescales. With increasing annealing temperature, collision coalescence becomes the dominant mode of coarsening, leading to rapid particle growth. The onset of the latter process is found to be increasingly delayed with increasing molecular weight of the polymer host. Particle coalescence is observed to proceed via two fundamental modes (i.e., diffusion-limited aggregation and growth resulting in the formation of fractal particle clusters and the subsequent recrystallization into more spherical monolithic aggregate structures). Interestingly, particle coarsening in high-molecular-weight matrix polymers is found to proceed significantly faster than predicted on the basis of the bulk polymer viscosity; this acceleration is interpreted to be a consequence of the network characteristics of high-molecular-weight polymers by analogy to the phenomenon of nanoviscosity that has been reported in the context of nanoparticle diffusion within high-molecular-weight polymers. PMID:20575544

  7. Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

    PubMed

    Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

    2015-09-15

    Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format. PMID:26287499

  8. Development of Metal Matrix Composites for NASA's Advanced Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Lee, J.; Elam, S.

    2001-01-01

    The state-of-the-art development of several Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The goal is to provide an overview of NASA-Marshall Space Flight Center's on-going activities in MMC components for advanced liquid rocket engines such as the X-33 vehicle's Aerospike engine and X-34's Fastrac engine. The focus will be on lightweight, low cost, and environmental compatibility with oxygen and hydrogen of key MMC materials, within each of NASA's new propulsion application, that will provide a high payoff for NASA's Reusable Launch Vehicles and space access vehicles. In order to fabricate structures from MMC, effective joining methods must be developed to join MMC to the same or to different monolithic alloys. Therefore, a qualitative assessment of MMC's welding and joining techniques will be outlined.

  9. LS-DYNA Implementation of Polymer Matrix Composite Model Under High Strain Rate Impact

    NASA Technical Reports Server (NTRS)

    Zheng, Xia-Hua; Goldberg, Robert K.; Binienda, Wieslaw K.; Roberts, Gary D.

    2003-01-01

    A recently developed constitutive model is implemented into LS-DYNA as a user defined material model (UMAT) to characterize the nonlinear strain rate dependent behavior of polymers. By utilizing this model within a micromechanics technique based on a laminate analogy, an algorithm to analyze the strain rate dependent, nonlinear deformation of a fiber reinforced polymer matrix composite is then developed as a UMAT to simulate the response of these composites under high strain rate impact. The models are designed for shell elements in order to ensure computational efficiency. Experimental and numerical stress-strain curves are compared for two representative polymers and a representative polymer matrix composite, with the analytical model predicting the experimental response reasonably well.

  10. Implementation of Fiber Substructuring Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2001-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were incorporated into a mechanics of materials based micromechanics method. In the current work, the micromechanics method is revised such that the composite unit cell is divided into a number of slices. Micromechanics equations are then developed for each slice, with laminate theory applied to determine the elastic properties, effective stresses and effective inelastic strains for the unit cell. Verification studies are conducted using two representative polymer matrix composites with a nonlinear, strain rate dependent deformation response. The computed results compare well to experimentally obtained values.

  11. Analytical Modeling of the High Strain Rate Deformation of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

    2003-01-01

    The results presented here are part of an ongoing research program to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric matrix materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical 5 plasticity theory definitions of effective stress and effective plastic strain are modified by applying variations of the Drucker-Prager yield criterion. To verify the revised formulation, the shear and tensile deformation of a representative toughened epoxy is analyzed across a wide range of strain rates (from quasi-static to high strain rates) and the results are compared to experimentally obtained values. For the analyzed polymers, both the tensile and shear stress-strain curves computed using the analytical model correlate well with values obtained through experimental tests. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. In the micromechanics, the unit cell is divided up into a number of independently analyzed slices, and laminate theory is then applied to obtain the effective deformation of the unit cell. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite (composed using the representative polymer analyzed for the correlation of the polymer constitutive equations) for several fiber orientation angles across a variety of strain rates. The computed values compare favorably to experimentally obtained results.

  12. Bridging Microstructure, Properties and Processing of Polymer Based Advanced Materials

    SciTech Connect

    Li, Dongsheng; Ahzi, Said; Khaleel, Mohammad A.

    2012-01-01

    This is a guest editorial for a special issue in Journal of Engineering Materials and Technology. The papers collected in this special issue emphasize significant challenges, current approaches and future strategies necessary to advance the development of polymer-based materials. They were partly presented at the symposium of 'Bridging microstructure, properties and processing of polymer based advanced materials' in the TMS 2011 annual conference meeting, which was held in San Diego, US, on Feb 28 to March 3, 2011. This symposium was organized by the Pacific Northwest National Laboratory (USA) and the Institute of Mechanics of Fluids and Solids of the University of Strasbourg (France). The organizers were D.S. Li, S. Ahzi, and M. Khaleel.

  13. E-Beam Processing of Polymer Matrix Composites for Multifunctional Radiation Shielding

    NASA Technical Reports Server (NTRS)

    Hou, Tan-Hung; Wilson, John W.; Jensen, Brian J.; Thibeault, Sheila A.; Chang, Chie K.; Kiefer, Richard L.

    2005-01-01

    Aliphatic polymers were identified as optimum radiation shielding polymeric materials for building multifunctional structural elements for in-space habitats. Conceptual damage tolerant configurations of polyolefins have been proposed, but many manufacturing issues relied on methods and materials which have sub-optimal radiation shielding characteristics (for example, epoxy matrix and adhesives). In the present approach, we shall investigate e-beam processing technologies for inclusion of high-strength aliphatic polymer reinforcement structures into a highly cross-linked polyolefin matrix. This paper reports the baseline thermo-mechanical properties of low density polyethylene and highly crystallized polyethylene.

  14. Influence of the nanoparticle surface polarity on the flow behavior of polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Hanemann, Thomas

    2012-07-01

    The influence of different nanosized titanias with opposite surface polarity, dispersed in an unsaturated polyester matrix, on the resulting composite flow behaviour like shear rate and load dependent viscosity as well as on the temperature influence was investigated systematically. It is known from composites containing microsized particles that a surface polarity conversion from the original hydrophilic to the polymer-like hydrophobic character allows higher solid loads due to a pronounced viscosity reduction. In this work it was derived from viscosity measurements that a large hydrophobic surface causes a pronounced attractive interaction between the filler and the polymer matrix reducing the maximum accessible filler load in comparison to a similar hydrophilic titania.

  15. 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.

  16. Printing microstructures in a polymer matrix using a ferrofluid droplet

    NASA Astrophysics Data System (ADS)

    Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.

    2016-03-01

    We print complex curvilinear microstructures in an elastomer matrix using a ferrofluid droplet as the print head. A magnetic field moves the droplet along a prescribed path in liquid polydimethylsiloxane (PDMS). The droplet sheds magnetic nanoparticle (MNP) clusters in its wake, forming printed features. The PDMS is subsequently heated so that it crosslinks, which preserves the printed features in the elastomer matrix. The competition between magnetic and drag forces experienced by the ferrofluid droplet and its trailing MNPs highlight design criteria for successful printing, which are experimentally confirmed. The method promises new applications, such as flexible 3D circuitry.

  17. Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Hoy, Robert S.

    2007-03-01

    The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush/brush, brush/melt and melt/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited to identify chain/chain entanglements. We use a new thin-chain PPA technique to eliminate spurious non-entangled inter chain contacts arising from excluded volume. As the grafting density of the brush increases we find that the entanglements of the brush with the melt decrease as the system crosses over from the wet to dry brush regime. Results are compared to brush/brush entanglements in an implicit solvent of varying solvent quality. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  18. Radiation and Thermal Stability of Solid Radwaste After Immobilization in Polymer Matrix - 13504

    SciTech Connect

    Pokhitonov, Yu.; Babain, V.; Strelkov, S.; Kuznetsov, D.; Kelley, Dennis

    2013-07-01

    The paper will illustrate results of the various experiments on radiation and thermal stability of polymer matrixes after solutions solidification including aqueous and organic solutions and mixed waste. It was shown that- after irradiation the specimen and after solidification the mixture with oil and TBP hydrogen has been observed (less 1%) and some others gases have been detected. Results of the performed experiments and the radiation stability data of the polymer compositions allow the conclusion that the technological process of immobilizing the above mentioned aqueous solutions and solutions with organic products into polymers at room temperature is the explosion- and flameproof as well as the storage thereof. (authors)

  19. Symposium Review: Metal and Polymer Matrix Composites at MS&T 2013

    NASA Astrophysics Data System (ADS)

    Gupta, Nikhil; Paramsothy, Muralidharan

    2014-06-01

    This article reflects on the presentations made during the Metal and Polymer Matrix Composites symposium at Materials Science and Technology 2013 (MS&T'13) held in Montreal (Quebec, Canada) from October 27 to 31. The symposium had three sessions on metal matrix composites and one session on polymer matrix composites containing a total of 23 presentations. While the abstracts and full-text papers are available through databases, the discussion that took place during the symposium is often not captured in writing and gets immediately lost. We have tried to recap some of the discussion in this article and hope that it will supplement the information present in the proceedings. The strong themes in the symposium were porous composites, aluminum matrix composites, and nanocomposites. The development of processing methods was also of interest to the speakers and attendees.

  20. Polymer/inorganic nanocomposites with tailored hierarchical structure as advanced dielectric materials

    SciTech Connect

    Manias, Evangelos; Randall, Clive; Tomer, Vivek; Polyzos, Georgios

    2012-01-01

    Most advances and commercial successes of polymer/inorganic nanocomposites rely only on the dispersion of nanoparticles in a polymer matrix. Such approaches leave untapped opportunities where performance can be improved by controlling the larger length-scale structures. Here, we review selected examples where the hierarchical structure (from millimeter to nanometer) is tailored to control the transport properties of the materials, giving rise to marked property enhancements, relevant to dielectric materials for power capacitors. These examples address composite structures that are self-assembled, both at the nm and the micron scales, and, thus, can be produced using standard industrial practices. Specifically, polyethylene (PE) blends or poly(vinylidene fluoride) (PVDF) copolymers are reinforced with nanofillers; these composites are designed with high filler orientation, which yielded marked improvements in electric-field breakdown strength and, consequently, large improvements in their recoverable energy densities.

  1. Protective coatings for high-temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Harding, David R.; Sutter, James K.; Papadopoulos, Demetrios S.

    1993-01-01

    Plasma-enhanced chemical vapor deposition was used to deposit silicon nitride on graphite-fiber-reinforced polyimide composites to protect against oxidation at elevated temperatures. The adhesion and integrity of the coating were evaluated by isothermal aging (371 C for 500 hr) and thermal cycling. The amorphous silicon nitride (a-SiN:H) coating could withstand stresses ranging from approximately 0.18 GPa (tensile) to -1.6 GPa (compressive) and provided a 30 to 80 percent reduction in oxidation-induced weight loss. The major factor influencing the effectiveness of a-SiN:H as a barrier coating against oxidation is the surface finish of the polymer composite.

  2. Development of meniscus substitutes using a mixture of biocompatible polymers and extra cellular matrix components by electrospinning.

    PubMed

    López-Calzada, G; Hernandez-Martínez, A R; Cruz-Soto, M; Ramírez-Cardona, M; Rangel, D; Molina, G A; Luna-Barcenas, G; Estevez, M

    2016-04-01

    Despite the significant advances in the meniscus tissue engineering field, it is difficult to recreate the complex structure and organization of the collagenous matrix of the meniscus. In this work, we developed a meniscus prototype to be used as substitute or scaffold for the regeneration of the meniscal matrix, recreating the differential morphology of the meniscus by electrospinning. Synthetic biocompatible polymers were combined with the extracellular matrix component, collagen and used to replicate the meniscus. We studied the correlation between mechanical and structural properties of the polymer blend as a function of collagen concentration. Fibers were collected on a surface of a rapidly rotating precast mold, to accurately replicate each sectional morphology of the meniscus; different electro-tissues were produced. Detailed XRD analyses exhibited structural changes developed by electrospinning. We achieved to integrate all these electro-tissues to form a complete synthetic meniscus. Vascularization tests were performed to assess the potential use of our novel polymeric blend for promising meniscus regeneration. PMID:26838921

  3. Recent Advances in the Improvement of Polymer Electret Films

    NASA Astrophysics Data System (ADS)

    Erhard, Dominik P.; Lovera, Deliani; von Salis-Soglio, Cosima; Giesa, Reiner; Altstädt, Volker; Schmidt, Hans-Werner

    Polymer electret materials are electrically charged dielectric polymers capable of quasi-permanently retaining their electric field. However, environmental influences such as temperature and humidity reduce their charge stability and restrict applications. Therefore it is of great importance to provide a broad pool of polymer electret materials and to enhance further the charge storage behavior. In this context we report on concepts, measures, and solutions to improve the electret performance of commodity and high performance thermoplastic polymers, which was carried out at the University of Bayreuth in recent years. It is demonstrated that the commodity polymer polypropylene can be manufactured into excellent electret films when certain trisamide additives are incorporated in very low concentrations. Polypropylene can be employed at temperatures up to its continuous service temperature of 70 ∘C. To achieve higher temperature windows we investigated the commodity blend system of poly(phenylene ether) (PPE) and polystyrene (PS). We demonstrate that especially PPE/PS blend films with a composition of 75/25 exhibit remarkably good charge storage retention during the isothermal surface decay (ITPD) tests at 120 ∘C. In addition, the commercially available high performance thermoplastic polyetherimide (PEI) resin containing special phosphorus(III) additives shows very good electret properties at elevated temperatures. These properties can be further enhanced by physical aging; resulting in a charge retention after 24 h at 120 ∘C as high as 95%. The same beneficial effect of physical aging can be used to advance PPE and PPE/PS blends. Polymer electret materials with such charge storage properties have the potential to be employed in microphones, sensor devices, and electret filters.

  4. Laser induced fluorescence imaging of thermal damage in polymer matrix composites

    SciTech Connect

    Fisher, W.G.; Meyer, K.E.; Wachter, E.A.; Perl, D.R.; Kulowitch, P.J.

    1997-06-01

    A simple, fluorescence based imaging system has been developed that is capable of identifying regions of thermal damage in polymer matrix composites (PMCs). These materials are playing an increasingly important role in the production of high performance vehicles and aircraft, where their low weight and high mechanical strength, combined with advancements in manufacturing technology, ensure increased use for a variety of applications. Of particular concern in the aerospace industry is the tendency of some PMC materials to become irreversibly damaged when exposed to elevated temperatures. Traditional nondestructive testing (NDT) techniques are capable of detecting physical anomalies such as cracks and delaminations but cannot detect initial heat damage, which occurs on a molecular scale. Spectroscopic techniques such as laser induced fluorescence provide an attractive means for detecting this type of damage and are amenable to imaging large, irregularly shaped surfaces. In this report the authors describe instrumentation capable of rapidly detecting thermal damage in graphite epoxy components and suggest improvements which will enable this technology to make quantitative judgments concerning the mechanical strength properties of heat damaged specimens.

  5. Automotive applications polymer matrix composites. (Latest citations from Engineered Materials abstracts). NewSearch

    SciTech Connect

    Not Available

    1994-10-01

    The bibliography contains citations concerning the use of polymer matrix composites in automotive body parts, structural frame members, and engine components. Design, manufacturing, and performance considerations are examined. The future of engineered plastics and their role in new products are reviewed. (Contains 250 citations and includes a subject term index and title list.)

  6. Collapse of two-dimensional linear polymers: a transfer matrix calculation of the exponent nu t

    NASA Astrophysics Data System (ADS)

    Derrida, B.; Saleur, H.

    1985-12-01

    Using a transfer matrix technique and finite size scaling, the authors calculate the exponent nu t of two-dimensional polymers at the theta point. They find nu t=0.55+or-0.01 by two slightly different calculations on the square lattice. This value is compared with those which had been previously proposed in the literature.

  7. Determination of Material Parameters for Microbuckling Analysis of Fiber Reinforced Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Romanowicz, M.

    2015-05-01

    This research focuses on studying the effect of the constitutive law adopted for a matrix material on the compressive response of a unidirectional fiber reinforced polymer matrix composite. To investigate this effect, a periodic unit cell model of a unidirectional composite with an initial fiber waviness and inelastic behavior of the matrix was used. The sensitivity of the compressive strength to the hydrostatic pressure, the flow rule and the fiber misalignment angle were presented. The model was verified against an analytical solution and experimental data. Results of this study indicate that a micromechanical model with correctly identified material parameters provides a useful alternative to theoretical models and experimentation.

  8. Recent Advances in Conjugated Polymer Materials for Disease Diagnosis.

    PubMed

    Lv, Fengting; Qiu, Tian; Liu, Libing; Ying, Jianming; Wang, Shu

    2016-02-10

    The extraordinary optical amplification and light-harvesting properties of conjugated polymers impart sensing systems with higher sensitivity, which meets the primary demands of early cancer diagnosis. Recent advances in the detection of DNA methylation and mutation with polyfluorene derivatives based fluorescence resonance energy transfer (FRET) as a means to modulate fluorescent responses attest to the great promise of conjugated polymers as powerful tools for the clinical diagnosis of diseases. To facilitate the ever-changing needs of diagnosis, the development of detection approaches and FRET signal analysis are highlighted in this review. Due to their exceptional brightness, excellent photostability, and low or absent toxicity, conjugated polymers are verified as superior materials for in-vivo imaging, and provide feasibility for future clinical molecular-imaging applications. The integration of conjugated polymers with clinical research has shown profound effects on diagnosis for the early detection of disease-related biomarkers, as well as in-vivo imaging, which leads to a multidisciplinary scientific field with perspectives in both basic research and application issues. PMID:26679834

  9. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  10. Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

    2015-07-01

    The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

  11. High Strain Rate Deformation Modeling of a Polymer Matrix Composite. Part 2; Composite Micromechanical Model

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1998-01-01

    Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this second paper of a two part report, a three-dimensional composite micromechanical model is described which allows for the analysis of the rate dependent, nonlinear deformation response of a polymer matrix composite. Strain rate dependent inelastic constitutive equations utilized to model the deformation response of a polymer are implemented within the micromechanics method. The deformation response of two representative laminated carbon fiber reinforced composite materials with varying fiber orientation has been predicted using the described technique. The predicted results compare favorably to both experimental values and the response predicted by the Generalized Method of Cells, a well-established micromechanics analysis method.

  12. Advanced Ceramic Matrix Composites (CMCs) for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2005-01-01

    Advanced ceramic matrix composites (CMCs) are enabling materials for a number of demanding applications in aerospace, energy, and nuclear industries. In the aerospace systems, these materials are being considered for applications in hot sections of jet engines such as the combustor liner, vanes, nozzle components, nose cones, leading edges of reentry vehicles, and space propulsion components. Applications in the energy and environmental industries include radiant heater tubes, heat exchangers, heat recuperators, gas and diesel particulate filters, and components for land based turbines for power generation. These materials are also being considered for use in the first wall and blanket components of fusion reactors. In the last few years, a number of CMC components have been developed and successfully tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. They include robust fabrication and manufacturing, assembly and integration, coatings, property modeling and life prediction, design codes and databases, repair and refurbishment, and cost. Fabrication of net and complex shape components with high density and tailorable matrix properties is quite expensive, and even then various desirable properties are not achievable. In this presentation, a number of examples of successful CMC component development and testing will be provided. In addition, critical need for robust manufacturing, joining and assembly technologies in successful implementation of these systems will be discussed.

  13. Photovoltaic properties of conjugated polymer/methanofullerene composites embedded in a polystyrene matrix

    NASA Astrophysics Data System (ADS)

    Brabec, C. J.; Padinger, F.; Sariciftci, N. S.; Hummelen, J. C.

    1999-05-01

    Bulk donor-acceptor heterojunctions between conjugated polymers and fullerene derivatives have been utilized successfully for photovoltaic devices showing monochromatic energy conversion efficiencies above 1%. The photovoltaic response of these devices is based on the ultrafast, photoinduced electron transfer from the conjugated polymer to the fullerene [N. S. Sariciftci and A. J. Heeger, Handbook of Organic Conductive Molecules and Polymers, (Wiley, New York, 1997), pp. 413-455]. In this work we present efficiency data of solar cells based on a soluble derivative of p-phenylene vinylene (PPV), poly [2-methoxy, 5-(3',7'-dimethyl-octyloxy)]-p-phenylene vinylene (MDMO-PPV), and a highly soluble methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), embedded into a conventional polymer, polystyrene (PS). By the blending of the optimized donor-acceptor components into the conventional polymer matrix, the percolation threshold for photovoltaic response of the three component systems is found to be determined by percolation of the methanofullerene in the polymer matrix. We present current/voltage data of PS-MDMO-PPV-PCBM devices with various PS concentrations as well as photoinduced absorption studies in the infrared [(PIA) Fourier transform infrared] and light induced electron spin resonance studies on the electron transfer in these composites. At low light intensities, the monochromatic power conversion efficiency ηe and the photon carrier collection efficiency ηc of the PS free device are calculated with 1.5% and 18%, respectively.

  14. Material and structural studies of metal and polymer matrix composites.

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1972-01-01

    Research directed toward the application of fiber composites to aeronautical and space vehicle systems indicates that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

  15. Studies on natural fiber reinforced polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Kapatel, P. M.; Machchhar, A. D.; Kapatel, Y. A.

    2016-05-01

    Natural fiber reinforced composites show increasing importance in day to days applications because of their low cost, lightweight, easy availability, non-toxicity, biodegradability and environment friendly nature. But these fibers are hydrophilic in nature. Thus they have very low reactivity and poor compatibility with polymers. To overcome these limitations chemical modifications of the fibers have been carried out. Therefore, in the present work jute fibers have chemically modified by treating with sodium hydroxide (NaOH) solutions. These treated jute fibers have been used to fabricate jute fiber reinforced epoxy composites. Mechanical properties like tensile strength, flexural strength and impact strength have been found out. Alkali treated composites show better properties compare to untreated composites.

  16. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1972-01-01

    The application of fiber composites to aeronautical and space vehicle systems indicates the following: It appears quite probable that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

  17. A comparison of fiber effects on polymer matrix composite oxidation

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1991-01-01

    A number of thermo-oxidative stability studies addressing the effects of fiber reinforcement on composite thermal stability and influence of geometry on the results of aging studies were performed at NASA-Lewis. The information presented herein, a compilation of some results from these studies, shows the influence of the reinforcement fibers on the oxidative degradation of various PMR-15 composites. Reinforcement of graphite and ceramics were studied and three composite oxidation mechanisms were observed. One was a dominant attack of the reinforcement fiber, the second was the aggressive oxidation of the matrix material, and the third was interfacial degradation.

  18. Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-10-01

    We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

  19. Effect of two hydrophobic polymers on the release of gliclazide from their matrix tablets.

    PubMed

    Hussain, Talib; Saeed, Tariq; Mumtaz, Ahmad M; Javaid, Zeeshan; Abbas, Khizar; Awais, Azeema; Idrees, Hafiz Arfat

    2013-01-01

    Gliclazide is an oral hypoglycemic agent, indicated in non insulin dependent diabetes mellitus and in patients with diabetic retinopathy. It has good tolerability and is a short acting sulfonyl urea that requires large dose to maintain the blood glucose level. So development of a sustained release formulation of gliclazide (GLZ) is required for better patient compliance. This study was conducted to assess the effects of different drug polymer ratios on the release profile of gliclazide from the matrix. Oral matrix tablets of gliclazide were prepared by hot melt method, using pure and blended mixture of glyceryl monostearate (GMS) and stearic acid (SA) in different ratios. In vitro release pattern was studied for 8 h in phosphate buffer media (pH 7.4). Different kinetic models including zero order, first order, Higuchi and Peppas were applied to evaluate drug release behavior. Drug excipient compatibility was evaluated by scanning with DSC and FTIR. Higuchi model was found the most appropriate model for describing the release profile of GLZ and non-Fickian release was found predominant mechanism of drug release. The release of drug from the matrix was greatly controlled by GMS while SA appeared to facilitate the release of drug from matrix tablets. FTIR results showed no chemical interaction between drug and the polymers, and DSC results indicated amorphous state of GLZ and polymers without significant complex formation. The results indicate that matrix tablets of gliclazide using glyceryl monostearate and stearic acid showed marked sustained release properties. PMID:23923399

  20. Fillers for improved graphite fiber retention by polymer matrix composites

    NASA Technical Reports Server (NTRS)

    House, E. E.; Sheppard, C. H.

    1981-01-01

    The results of a program designed to determine the extent to which elemental boron and boron containing fillers added to the matrix resin of graphite/epoxy composites prevent the release of graphite fibers when the composites are exposed to fire and impact conditions are described. The fillers evaluated were boron, boron carbide and aluminum boride. The conditions evaluated were laboratory simulations of those that could exist in the event of an aircraft crash and burn situation. The baseline (i.e., unfilled) laminates evaluated were prepared from commercially available graphite/epoxy. The baseline and filled laminates' mechanical properties, before and after isothermal and humidity aging, also were compared. It was found that a small amount of graphite fiber was released from the baseline graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that the addition of boron and boron containing fillers to the resin matrix eliminated this fiber release. Mechanical properties of laminates containing the boron and boron containing fillers were lower than those of the baseline laminates. These property degradations for two systems: boron (5 micron) at 2.5 percent filler loading, and boron (5 micron) at 5.0 percent filler loading do not appear severe enough to preclude their use in structural composite applications.

  1. Probabilistic simulation of long term behavior in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Shah, A. R.; Singhal, S. N.; Murthy, P. L. N.; Chamis, C. C.

    1995-01-01

    A methodology to compute cumulative probability distribution functions (CDF) of fatigue life for different ratios, r of applied stress to the laminate strength based on first ply failure criteria has been developed and demonstrated. Degradation effects due to long term environmental exposure and mechanical cyclic loads are considered in the simulation process. A unified time-stress dependent multi-factor interaction equation model developed at NASA Lewis Research Center has been used to account for the degradation/aging of material properties due to cyclic loads. Fast probability integration method is used to perform probabilistic simulation of uncertainties. Sensitivity of fatigue life reliability to uncertainties in the primitive random variables are computed and their significance in the reliability based design for maximum life is discussed. The results show that the graphite/epoxy (0/+45/90) deg laminate with ply thickness 0.125 in. has 500,000 cycles life for applied stress to laminate strength ratio of 0.6 and a reliability of 0.999. Also, the fatigue life reliability has been found to be most sensitive to the ply thickness and matrix tensile strength. Tighter quality controls must therefore be enforced on ply thickness and matrix strength in order to achieve high reliability of the structure.

  2. Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures

    NASA Technical Reports Server (NTRS)

    McManus, Hugh L.; Chamis, Christos C.

    1996-01-01

    This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

  3. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  4. Benchmark integration test for the Advanced Integration Matrix (AIM)

    NASA Astrophysics Data System (ADS)

    Paul, H.; Labuda, L.

    The Advanced Integration Matrix (AIM) studies and solves systems-level integration issues for exploration missions beyond Low Earth Orbit (LEO) through the design and development of a ground-based facility for developing revolutionary integrated systems for joint human-robotic missions. This systems integration approach to addressing human capability barriers will yield validation of advanced concepts and technologies, establish baselines for further development, and help identify opportunities for system-level breakthroughs. Early ground-based testing of mission capability will identify successful system implementations and operations, hidden risks and hazards, unexpected system and operations interactions, mission mass and operational savings, and can evaluate solutions to requirements-driving questions; all of which will enable NASA to develop more effective, lower risk systems and more reliable cost estimates for future missions. This paper describes the first in the series of integration tests proposed for AIM (the Benchmark Test) which will bring in partners and technology, evaluate the study processes of the project, and develop metrics for success.

  5. Advancements of molecularly imprinted polymers in the food safety field.

    PubMed

    Wang, Peilong; Sun, Xiaohua; Su, Xiaoou; Wang, Tie

    2016-06-01

    Molecularly imprinted technology (MIT) has been widely employed to produce stable, robust and cheap molecularly imprinted polymer (MIP) materials that possess selective binding sites for recognition of target analytes in food, such as pesticides, veterinary drugs, mycotoxins, illegal drugs and so on. Because of high selectivity and specificity, MIPs have drawn great attention in the food safety field. In this review, the recent developments of MIPs in various applications for food safety, including sample preparation, chromatographic separation, sensing, immunoassay etc., have been summarized. We particularly discuss the advancements and limitations in these applications, as well as attempts carried out for their improvement. PMID:26937495

  6. Recent advances in solid polymer electrolyte fuel cell technology

    SciTech Connect

    Ticianelli, E.A.; Srinivasan, S.; Gonzalez, E.R.

    1988-01-01

    With methods used to advance solid polymer electrolyte fuel cell technology, we are close to obtaining the goal of 1 A/cm/sup 2/ at 0.7. Higher power densities have been reported (2 A/cm/sup 2/ at 0.5 V) but only with high catalyst loading electrodes (2 mg/cm/sup 2/ and 4 mg/cm/sup 2/ at anode and cathode, respectively) and using a Dow membrane with a better conductivity and water retention characteristics. Work is in progress to ascertain performances of cells with Dow membrane impregnated electrodes and Dow membrane electrolytes. 5 refs., 6 figs.

  7. Effect of fiber reinforcements on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1991-01-01

    A number of studies have investigated the thermo-oxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. A compilation of some results from these studies is presented, and this information shows the influence of the reinforcement fibers on the oxidative degradation of various polymer matrix composites. The polyimide PMR-15 was the matrix material that was used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-40R graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. The Celion 6000/PMR-15 bond is very tight but the T-40/PMR-15 bond is less tight. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  8. [LOXOCELES BITE WOUND TREATMENT WITH SYNTHETIC POLYMER MATRIX].

    PubMed

    Navarro Caballero, Ma Ascensión

    2015-05-01

    Loxocelism is a toxic condition produces by the venom inoculated by the bit of the recluse spider (genus Loxosceles). In can appear in two clinical forms: cutaneous loxocelism and viscerocutaneous Ioxocelim. The species Loxoceles rufescens, found in Spain, is responsible of cases of cutaneous loxocelism. Cutaneous loxocelism starts with an itch, later giving rise to intense pain, and it later takes either a more or less severe necrotic form or an edematous form. The latter, with a better prognosis, is the one we focus on here. The diagnosis is clinical. The systemic treatment consists in analgesics, antihistamines, corticosteroids, broad-spectrum antibiotics, and dapsone in severe cases. The local treatment is based on the cleaning and debridement of the wound, and in advanced treatments for complex wounds. It is not uncommon that such wounds require skin grafting. We present the case of an 18-year female bitten by a loxosceles on the dorsal area of the foot. She developed a deep tissue necrosis in the area. She presented systemic complications such as leucocitosis, fever, local infection and cellulitis. Systemic treatment and hospitalization were required, as well as advanced therapeutic care. Finally, cutaneous integrity was restored after 84 days. PMID:26540898

  9. Development of novel graphene and carbon nanotubes based multifunctional polymer matrix composites

    SciTech Connect

    Leung, S. N. Khan, M. O. Naguib, H. E.

    2014-05-15

    This paper investigates strategies to alter the nano-and-microstructures of carbon-based filler-reinforced polymer matrix composites (PMCs). The matrix materials being studied in this work include polyphenylene sulfide (PPS) and liquid crystal polymer (LCP). A set of experiments were performed to investigate various strategies (i) to fabricate a morphological structure within the polymer matrix; (ii) to develop a thermally and electrically conductive network of nano-scaled fillers; and (iii) to produce a thermally conductive but electrically insulative network of hybrid fillers of nano-and-micro scales. The PMCs' structure-to-property relationships, including electrical and thermal properties, were revealed. In particular, the composites' effective thermal conductivities could be increased by as much as 10-folded over the neat polymers. By structuring the embedded electrically conductive pathways in the PMCs, their electrical conductivities could be tailored to levels that ranged from those of electrical insulators to those of semi-conductors. These multifunctional carbon-based filler-reinforced PMCs are envisioned to be potential solutions of various engineering problems. For example, light-weight thermally conductive PMCs with tailored electrical conductivities can serve as a new family of materials for electronic packaging or heat management applications.

  10. Development of novel graphene and carbon nanotubes based multifunctional polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Leung, S. N.; Khan, M. O.; Naguib, H. E.

    2014-05-01

    This paper investigates strategies to alter the nano-and-microstructures of carbon-based filler-reinforced polymer matrix composites (PMCs). The matrix materials being studied in this work include polyphenylene sulfide (PPS) and liquid crystal polymer (LCP). A set of experiments were performed to investigate various strategies (i) to fabricate a morphological structure within the polymer matrix; (ii) to develop a thermally and electrically conductive network of nano-scaled fillers; and (iii) to produce a thermally conductive but electrically insulative network of hybrid fillers of nano-and-micro scales. The PMCs' structure-to-property relationships, including electrical and thermal properties, were revealed. In particular, the composites' effective thermal conductivities could be increased by as much as 10-folded over the neat polymers. By structuring the embedded electrically conductive pathways in the PMCs, their electrical conductivities could be tailored to levels that ranged from those of electrical insulators to those of semi-conductors. These multifunctional carbon-based filler-reinforced PMCs are envisioned to be potential solutions of various engineering problems. For example, light-weight thermally conductive PMCs with tailored electrical conductivities can serve as a new family of materials for electronic packaging or heat management applications.

  11. Damage initiation, progression and failure of polymer matrix composites due to manufacturing induced defects

    NASA Astrophysics Data System (ADS)

    Chowdhury, Khairul Alam

    In polymer matrix composites (PMCs) manufacturing processes can induce defects, e.g., voids, fiber misalignment, irregular fiber distribution in the cross-section and broken fibers. The effects of such defects can be beneficial or deleterious depending on whether they cause failure suppression or enhancement by localized deformation processes e.g., crazing, shear yielding and fiber-matrix debonding. In this study, a computational approach is formulated and implemented to develop solutions for general boundary-value problems for PMC microstructures that accounts for micromechanics-based constitutive relations including fine scale mechanisms of material failure. The defects considered are voids, and the microstructure is explicitly represented by a distribution of fibers and voids embedded in a polymer matrix. Fiber is modeled as a linearly elastic material while the polymer matrix is modeled as an elastic-viscoplastic material. Two distinct models for the matrix behavior are implemented: (i) Drucker-Prager type Bodner model that accounts for rate and pressure-sensitivity, and (ii) improved macromolecular constitutive model that also accounts for temperature dependence, small-strain softening and large-strain hardening. Damage is simulated by the Gearing-Anand craze model as a reference model and by a new micromechanical craze model, developed to account for craze initiation, growth and breakdown. Critical dilatational energy density criterion is utilized to predict fiber-matrix debonding through cavitation induced matrix cracking. An extensive parametric study is conducted in which the roles of void shape, size and distribution relative to fiber in determining damage initiation and evolution are investigated under imposed temperature and strain rate conditions. Results show there are significant effects of voids on microstructural damage as well as on the overall deformational and failure response of composites.

  12. Study on dosimetry characteristics of polymer-CNT nanocomposites: Effect of polymer matrix

    NASA Astrophysics Data System (ADS)

    Malekie, Shahryar; Ziaie, Farhood; Esmaeli, Abdolreza

    2016-04-01

    In this research work, the current density of polymer-carbon nanotube nanocomposite in different weight percentages of nanotubes, over the radiation absorbed dose under a fixed DC voltage for different polymer matrices such as high density polyethylene, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, and polystyrene was investigated via finite element method. The predicted electrical percolation threshold values in different composites were validated by experimental results published by other scientists. The absorbed dose value was considered as multiplying of heat capacity and temperature rise of the composite, regarding the calorimetric approach. Results show that the polymer type having different characteristics of relative permittivity and heat capacity could affect the sensitivity and working dose range of the composite as a dosimeter.

  13. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1973-01-01

    Fiber-reinforced composites and design analysis methods for these materials are being developed because of the vast potential of composites for decreasing weight and/or increasing use temperature capability in aerospace systems. These composites have potential for use in airbreathing engine components as well as aeronautical and space vehicle structures. Refractory wire-superalloy composites for use up to 2200 F or more and metal-matrix composites for lower temperature applications such as aerospace structures and turbojet fan and compressor blades are under investigation and are discussed. The development of a number of resin systems, including the polyimides and polyphenylquinoxalines, is described and their potential for use at temperatures approaching 315 C (600 F) is indicated. Various molecular modifications that improve processability and/or increase thermal and oxidative resistance of the resins are also described. Structural analysis methods are discussed for determining the stresses and deformations in complex composite systems. Consideration is also given to residual stresses resulting from the curing process and to the foreign object damage problem in fan blade applications.

  14. Nanoparticle and Gelation Stabilized Functional Composites of an Ionic Salt in a Hydrophobic Polymer Matrix

    PubMed Central

    Kanyas, Selin; Aydın, Derya; Kizilel, Riza; Demirel, A. Levent; Kizilel, Seda

    2014-01-01

    Polymer composites consisted of small hydrophilic pockets homogeneously dispersed in a hydrophobic polymer matrix are important in many applications where controlled release of the functional agent from the hydrophilic phase is needed. As an example, a release of biomolecules or drugs from therapeutic formulations or release of salt in anti-icing application can be mentioned. Here, we report a method for preparation of such a composite material consisted of small KCOOH salt pockets distributed in the styrene-butadiene-styrene (SBS) polymer matrix and demonstrate its effectiveness in anti-icing coatings. The mixtures of the aqueous KCOOH and SBS-cyclohexane solutions were firstly stabilized by adding silica nanoparticles to the emulsions and, even more, by gelation of the aqueous phase by agarose. The emulsions were observed in optical microscope to check its stability in time and characterized by rheological measurements. The dry composite materials were obtained via casting the emulsions onto the glass substrates and evaporations of the organic solvent. Composite polymer films were characterized by water contact angle (WCA) measurements. The release of KCOOH salt into water and the freezing delay experiments of water droplets on dry composite films demonstrated their anti-icing properties. It has been concluded that hydrophobic and thermoplastic SBS polymer allows incorporation of the hydrophilic pockets/phases through our technique that opens the possibility for controlled delivering of anti-icing agents from the composite. PMID:24516593

  15. Dispersion-Aggregation and Wetting-Dewetting Phase Transitions in Mixtures of Polymer Grafted Nanoparticles and a Chemically Dissimilar Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Martin, Tyler; Mongcopa, Katrina; Ashkar, Rana; Butler, Paul; Krishnamoorti, Ramanan; Jayaraman, Arthi

    Significant efforts have been focused towards controlling morphology of the nanoscale fillers and matrix polymer in polymer nanocomposites as the composite morphology is directly related to the macroscopic properties of that material. For nanocomposites with chemically identical graft and matrix polymers, it is well understood that the polymer grafted particle dispersion to aggregation transition is directly linked to and synonymous with wetting/dewetting of the graft and matrix polymer. Our recent work has focused on exploring composites with chemically different graft and matrix polymers, specifically those with attractive graft-matrix interactions that lead to a dispersed filler state at low temperature and aggregated filler state at high temperatures. We show, using coarse-grained molecular simulations, that the sharp phase transition from dispersed to aggregated states is distinct from the continuous wetting-dewetting transition. The onset of wetting to dewetting occurs at temperatures lower than the dispersion to aggregation transition, and dewetting continues at temperatures above the transition temperature in the aggregated state. Furthermore, the graft and matrix chain composition can be varied to tune the dispersion-aggregation transition temperature and the degree of wetting of the grafted layer. Experiments using SANS and SAXS of deuterated poly(styrene) grafted silica particles in a poly(vinyl methyl ether) matrix show remarkable agreement with our simulations.

  16. Improving Dispersion of Single-Walled Carbon Nanotubes in a Polymer Matrix Using Specific Interactions

    SciTech Connect

    Rasheed, Asif; Dadmun, Mark D; Ivanov, Ilia N; Britt, Phillip F; Geohegan, David B

    2006-01-01

    A novel approach is presented to improve the dispersion of oxidized single-walled carbon nanotubes (SWNTs) in a copolymer matrix by tuning hydrogen-bonding interactions to enhance dispersion. Nanocomposites of single-walled carbon nanotubes and copolymers of styrene and vinyl phenol (PSVPh) with varying vinyl phenol content were produced and examined. The dispersion of the SWNT in the polymer matrix is quantified by optical microscopy and Raman spectroscopy. Raman spectroscopy is also used to investigate preferred interactions between the SWNTs and the copolymers via the shift in the D* Raman band of the SWNTs in the composites. All composites show regions of SWNT aggregates; however, the aggregate size varies with composition of the PSVPh copolymer and the amount of SWNT oxidation. Optimal dispersion of the SWNT is observed in PSVPh with 20% vinyl phenol and oxidized nanotubes, which correlates with spectroscopic evidence that indicates that this system also incorporates the most interactions between SWNT and polymer matrix. These results are in agreement with previous studies that indicate that optimizing the extent of specific interactions between a polymer matrix and nanoscale filler enables the efficient dispersion of the nanofillers.

  17. Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation

    PubMed Central

    2012-01-01

    The present work reports on the gas transport behavior of mixed matrix membranes (MMM) which were prepared from multi-walled carbon nanotubes (MWCNTs) and dispersed within polymers of intrinsic microporosity (PIM-1) matrix. The MWCNTs were chemically functionalized with poly(ethylene glycol) (PEG) for a better dispersion in the polymer matrix. MMM-incorporating functionalized MWCNTs (f-MWCNTs) were fabricated by dip-coating method using microporous polyacrylonitrile membrane as a support and were characterized for gas separation performance. Gas permeation measurements show that MMM incorporated with pristine or functionalized MWCNTs exhibited improved gas separation performance compared to pure PIM-1. The f-MWCNTs MMM show better performance in terms of permeance and selectivity in comparison to pristine MWCNTs. The gas permeances of the derived MMM are increased to approximately 50% without sacrificing the selectivity at 2 wt.% of f-MWCNTs' loading. The PEG groups on the MWCNTs have strong interaction with CO2 which increases the solubility of polar gas and limit the solubility of nonpolar gas, which is advantageous for CO2/N2 selectivity. The addition of f-MWCNTs inside the polymer matrix also improved the long-term gas transport stability of MMM in comparison with PIM-1. The high permeance, selectivity, and long term stability of the fabricated MMM suggest that the reported approach can be utilized in practical gas separation technology. PMID:22953751

  18. Supramolecular polymer adhesives: advanced materials inspired by nature.

    PubMed

    Heinzmann, Christian; Weder, Christoph; de Espinosa, Lucas Montero

    2016-01-21

    Due to their dynamic, stimuli-responsive nature, non-covalent interactions represent versatile design elements that can be found in nature in many molecular processes or materials, where adaptive behavior or reversible connectivity is required. Examples include molecular recognition processes, which trigger biological responses or cell-adhesion to surfaces, and a broad range of animal secreted adhesives with environment-dependent properties. Such advanced functionalities have inspired researchers to employ similar design approaches for the development of synthetic polymers with stimuli-responsive properties. The utilization of non-covalent interactions for the design of adhesives with advanced functionalities such as stimuli responsiveness, bonding and debonding on demand capability, surface selectivity or recyclability is a rapidly emerging subset of this field, which is summarized in this review. PMID:26203784

  19. Durability of a polymer matrix composite: Neural networks approach

    NASA Astrophysics Data System (ADS)

    Al-Haik, Marwan S.

    In this study, the viscoplastic behavior of a carbon-fiber/thixotropic-epoxy matrix composite was investigated through two deferent modeling efforts. The first model is phenomenological in nature and it utilizes the tensile and stress relaxation experiments to predict the creep strain. In the second model, the composite viscoplastic behavior is no longer represented by closed-form constitutive laws, but it is captured by a neural network formulation. The composite was processed and cured using hand lay-up technique together with autoclave curing system. By performing thermomechanical analysis and differential scanning calorimetry, the glass transition temperature of the composite was noticed to degrade. Experiments were performed to examine the tensile, creep, and load relaxation behavior of the composite under different temperatures. It was found that the composite strength and stiffness decrease significantly at elevated temperatures. A phenomenological model was constructed based on the overstress viscoplastic model. In this model, four material's parameters are extracted from tensile and load relaxation tests. These parameters are used by a system of coupled equations to predict the creep strain. The results of the phenomenological model were satisfactory for predicting creep at low temperature conditions, but for the high stress-high temperature regimes, the model failed to predict the creep strain accurately. The neural network model was built directly from the experimental creep tests performed at various stress-temperature conditions. The optimal structure of the neural network was achieved through the universal approximation theory and the dimensionality of the creep problem (stress, temperature, and time). The neural network model was trained to predict the creep strain based on the stress-temperature-time values. The performance of the neural model is captured by the mean squared error between the neural network prediction and the experimental creep

  20. Matrix Metalloproteinase-Sensitive Thermogelling Polymer For Bioresponsive Local Drug Delivery

    PubMed Central

    Garripelli, Vivek Kumar; Kim, Jin-Ki; Son, Sejin; Kim, Won Jong; Repka, Michael A.; Jo, Seongbong

    2011-01-01

    Development of a successful bioresponsive drug delivery system requires exquisite engineering of materials so that they are able to respond to the signals stemming from the physiological environment. In this study, we proposed a new Pluronic® based thermogelling system containing matrix metalloproteinase-2 (MMP2) responsive peptide sequences. A novel thermosensitive multiblock copolymer comprising an MMP2-labile octapeptide (Gly-Pro-Val-Gly-Leu-Ile-Gly-Lys) was synthesized from Pluronic® triblock copolymer. The polymer was designed to form thermogel at body temperature and degrade in presence of MMP overexpressed in the tumor. The synthesized polymer was a multiblock copolymer with ~ 2.5 units of Pluronic®. The multiblock copolymer solutions exhibited a reverse thermal gelation around body temperature. The gelation temperatures of the multiblock copolymer solutions were lower than those of the corresponding Pluronic® monomer at a particular concentration. The cytotoxicity of the synthesized polymer was lower comparing to its monomer. The solubility of hydrophobic anticancer drug, paclitaxel, was enhanced in the polymer solutions via micelle formation. The synthesized polymer was preferentially degraded in presence of MMP. Paclitaxel release was dependent on the enzyme concentration. These findings suggest that the synthesized polymer has the potential as controlled drug delivery system due to its unique phase transition and bioresponsive behavior. PMID:21300184

  1. Nanoparticle-assisted high photoconductive gain in polymer/fullerene matrix

    PubMed Central

    Chen, Hsiang-Yu; Lo, Michael K. F.; Yang, Guanwen; Monbouquette, Harold G.; Yang, Yang

    2014-01-01

    Polymer/inorganic nanocrystal composites1–10 offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility11 and distribution of nanocrystals (NCs) in polymer matrices. Here, a high photoconductive gain has been achieved by blending cadmium telluride (CdTe) nanoparticles (NPs) into a polymer/fullerene matrix followed by a solvent annealing12 process. The NP surface capping ligand, N-phenyl-N’-methyldithiocarbamate, renders the NPs highly soluble in the polymer blend thereby enabling high nanocrystal loadings. An external quantum efficiency (EQE) as high as ~8000% (at 350nm) is reached at −4.5V. Hole-dominant devices coupled with AFM images are studied to uncover the probable mechanism. We observe a higher concentration of CdTe NPs is located near the cathode/polymer interface. These NPs with trapped electrons assist hole injection into the polymer under reverse bias, which contributes to greater than 100% EQE. PMID:18772915

  2. Purification of HIV RNA from serum using a polymer capture matrix in a microfluidic device.

    PubMed

    Root, Brian E; Agarwal, Abhishek K; Kelso, David M; Barron, Annelise E

    2011-02-01

    In this report, we demonstrate the purification of DNA and RNA from a 10% serum sample using an oligonucleotide capture matrix. This approach provides a one-stage, completely aqueous system capable of purifying both RNA and DNA for downstream PCR amplification. The advantages of utilizing the polymer capture matrix method in place of the solid-phase extraction method is that the capture matrix eliminates both guanidine and the 2-propanol wash that can inhibit downstream PCR and competition with proteins for the binding sites that can limit the capacity of the device. This method electrophoreses a biological sample (e.g., serum) containing the nucleic acid target through a polymer matrix with covalently bound oligonucleotides. These capture oligonucleotides selectively hybridize and retain the target nucleic acid, while the other biomolecules and reagents (e.g., SDS) pass through the matrix to waste. Following this purification step, the solution can be heated above the melting temperature of the capture sequence to release the target molecule, which is then electrophoresed to a recovery chamber for subsequent PCR amplification. We demonstrate that the device can be applied to purify both DNA and RNA from serum. The gag region of HIV at a starting concentration of 37.5 copies per microliter was successfully purified from a 10% serum sample demonstrating the applicability of this method to detect viruses present in low copy numbers. PMID:21214255

  3. Purification of HIV RNA from serum using a polymer capture matrix in a microfluidic device

    PubMed Central

    Root, Brian E.; Agarwal, Abhishek K.; Kelso, David M.; Barron, Annelise E.

    2012-01-01

    In this report, we demonstrate the purification of DNA and RNA from a 10% serum sample using an oligonucleotide capture matrix. This approach provides a one-stage, completely aqueous system capable of purifying both RNA and DNA for downstream PCR amplification. The advantages of utilizing the polymer capture matrix method in place of the solid-phase extraction method is that the capture matrix eliminates both guanidine and the isopropanol wash that can inhibit downstream PCR and competition with proteins for the binding sites that can limit the capacity of the device. This method electrophoreses a biological sample (e.g. serum) containing the nucleic acid target through a polymer matrix with covalently bound oligonucleotides. These capture oligonucleotide selectively hybridize and retain the target nucleic acid, while the other biomolecules and reagents (e.g. SDS) pass through the matrix to waste. Following this purification step, the solution can be heated above the melting temperature of the capture sequence to release the target molecule, which is then electrophoresed to a recovery chamber for subsequent PCR amplification. We demonstrate that the device can be applied to purify both DNA and RNA from serum. The gag region of HIV at a starting concentration of 37.5 copies per microliter was successfully purified from a 10% serum sample demonstrating the applicability of this method to detect viruses present in low copy numbers. PMID:21214255

  4. A strain sensor based on an aligned carbon particle string in a UV-cured polymer matrix

    NASA Astrophysics Data System (ADS)

    Høyer, H.; Knaapila, M.; Kjelstrup-Hansen, J.; Liu, X.; Helgesen, G.

    2011-11-01

    We demonstrate micro-mechanical strain sensors by aligning carbon black particles into single wirelike strings in a polymer matrix using an alternating electric field (dielectrophoresis) when the particle fraction is 0.1 vol. %. The strings are stabilized by UV-curing the polymer matrix and characterized electrically and electromechanically. Particle alignment makes the material conductive, and the stretching of such strings in polymer matrices gives a reversible change in resistivity. A gauge factor of about 150 is demonstrated. Nonaligned films containing 12 vol. % of carbon particles in the same polymer are conductive but not sensitive to similar stretching.

  5. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  6. LDEF (Flight), AO180 : The Effect of Space Environment Exposure on the Properties of Polymer Matrix

    NASA Technical Reports Server (NTRS)

    1990-01-01

    LDEF (Flight), AO180 : The Effect of Space Environment Exposure on the Properties of Polymer Matrix Composite Materials, Tray D12 The flight photograph was taken from the Orbiter aft flight deck during the LDEF retrieval. During the mission, the tray surface was at an angle of approximately ninety-eight (98) degrees to the orbital velocity vector and therefore exposed to a lower atomic oxygen flux than if parallel with the velocity vector. A very light stain is present on white paint dots on experiment tray clamps along the lower edge of the tray. The Polymer Matrix Composite Materials experiment has several changes to material colors. The composite containing the aramid (Kevlar) fibers has changed from a yellow to a light brown color and the cylindrical tubes containing the boron and carbon fiber materials have changed from a light green tint to a brown color.

  7. Effect of Cyclic Thermal Loads on Fatigue Reliability in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    1997-01-01

    Technological solutions that will ensure the economic viability and environmental compatibility of a future High Speed Civil Transport plane are currently being sought. Lighter structural materials for both airframe primary structures and engine structure components are being investigated. We believe that such objectives can be achieved through the use of high-temperature composites as well as other conventional, lighter weight alloys. One of the prime issues for these structural components is assured long-term behavior with a specified reliability. An investigation was conducted to describe a computational simulation methodology for predicting fatigue life, reliability, and probabilistic long-term behavior of polymer matrix composites. A unified time-, stress-, and load-dependent Multi- Factor Interaction Equation (MFIE) model developed at the NASA Lewis Research Center was used to simulate the long-term behavior of polymer matrix composites.

  8. Multiscale characterization of chemical–mechanical interactions between polymer fibers and cementitious matrix

    SciTech Connect

    Hernández-Cruz, Daniel; Hargis, Craig W.; Bae, Sungchul; Itty, Pierre A.; Meral, Cagla; Dominowski, Jolee; Radler, Michael J.; Kilcoyne, David A.; Monteiro, Paulo J. M.

    2014-04-01

    Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (lCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowed visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.

  9. Computational Simulation of the High Strain Rate Tensile Response of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2002-01-01

    A research program is underway to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Under these types of loading conditions, the material response can be highly strain rate dependent and nonlinear. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the effective mechanical and thermal response of the composite. To verify the analytical model, tensile stress-strain curves are predicted for a representative composite over strain rates ranging from around 1 x 10(exp -5)/sec to approximately 400/sec. The analytical predictions compare favorably to experimentally obtained values both qualitatively and quantitatively. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results.

  10. Implementation of Laminate Theory Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2000-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were implemented into a mechanics of materials based micromechanics method. In the current work, the computation of the effective inelastic strain in the micromechanics model was modified to fully incorporate the Poisson effect. The micromechanics equations were also combined with classical laminate theory to enable the analysis of symmetric multilayered laminates subject to in-plane loading. A quasi-incremental trapezoidal integration method was implemented to integrate the constitutive equations within the laminate theory. Verification studies were conducted using an AS4/PEEK composite using a variety of laminate configurations and strain rates. The predicted results compared well with experimentally obtained values.

  11. Analysis of Carbon Nanotube Pull-out from a Polymer Matrix

    NASA Technical Reports Server (NTRS)

    Frankland, S. J. V.; Harik, V. M.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    Molecular dynamics (MD) simulations of carbon nanotube (NT) pull-out from a polymer matrix are carried out. As the NT pull-out develops in the simulation, variations in the displacement and velocities of the NT are monitored. The existence of a carbon-ring-based period in NT sliding during pull-out is identified. Linear trends in the NT velocity-force relation are observed and used to estimate an effective viscosity coefficient for interfacial sliding at the NT/polymer interface. As a result, the entire process of NT pull-out is characterized by an interfacial friction model that is based on a critical pull-out force, and an analog of Newton's friction law used to describe the NT/polymer interfacial sliding.

  12. Non linear viscoelasticity applied for the study of durability of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Cardon, A.; Brinson, H. F.; Hiel, C. C.

    1989-01-01

    A methodology is described for the durability analysis of polymer matrix composites, based on nonlinear viscoelasticity theory. The durability analysis is performed on the basis of a certain number of tests carried out on limited and, if possible, short time scale by the use of accelerating factors. The method was applied to thermomatrix composites under uniaxial and biaxial loadings, showing satisfactory agreement between the life-time predictions and the published data on real-time behavior.

  13. Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix.

    PubMed

    Porras, R; Bavykin, D V; Zekonyte, J; Walsh, F C; Wood, R J

    2016-05-13

    Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the 'drop-cast' method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young's modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young's modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM. PMID:27039947

  14. Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

    NASA Astrophysics Data System (ADS)

    Porras, R.; Bavykin, D. V.; Zekonyte, J.; Walsh, F. C.; Wood, R. J.

    2016-05-01

    Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

  15. Sulfur polymer cement as a low-level waste glass matrix encapsulant

    SciTech Connect

    Sliva, P.; Peng, Y.B.; Peeler, D.K.

    1996-01-01

    Sulfur polymer cement (SPC) is being considered as a matrix encapsulant for the Hanford low-level (activity) waste glass. SPC is an elemental sulfur polymer-stabilized thermoplastic that is fluid at 120 {degrees}C to 140{degrees}C. The candidate process would encapsulate the waste glass by mixing the glass cullet with the SPC and casting it into the container. As the primary barrier to groundwater and a key factor in controlling the local environment of the disposal system after it has been compromised, SPC plays a key role in the waste form`s long-term performance assessment. Work in fiscal year 1995 targeted several technical areas of matrix encapsulation involving SPC. A literature review was performed to evaluate potential matrix-encapsulant materials. The dissolution and corrosion behavior of SPC under static conditions was determined as a function of temperature, pH, and sample surface area/solution volume. Preliminary dynamic flow-through testing was performed. SPC formulation and properties were investigated, including controlled crystallization, phase formation, modifying polymer effects on crystallization, and SPC processibility. The interface between SPC and simulated LLW glass was examined. Interfacial chemistry and stability, the effect of water on the glass/SPC interface, and the effect of molten sulfur on the glass surface chemistry were established. Preliminary scoping experiments, involving SPC`s Tc gettering capabilities were performed. Compressive strengths of SPC and SPC/glass composites, both before and after lifetime radiation dose exposure, were determined.

  16. Carbon fiber polymer-matrix structural composites for electrical-resistance-based sensing

    NASA Astrophysics Data System (ADS)

    Wang, Daojun

    This dissertation has advanced the science and technology of electrical-resistance-based sensing of strain/stress and damage using continuous carbon fiber epoxy-matrix composites, which are widely used for aircraft structures. In particular, it has extended the technology of self-sensing of carbon fiber polymer-matrix composites from uniaxial longitudinal loading and flexural loading to uniaxial through-thickness loading and has extended the technology from structural composite self-sensing to the use of the composite (specifically a one-lamina composite) as an attached sensor. Through-thickness compression is encountered in the joining of composite components by fastening. Uniaxial through-thickness compression results in strain-induced reversible decreases in the through-thickness and longitudinal volume resistivities, due to increase in the fiber-fiber contact in the through-thickness direction, and minor-damage-induced irreversible changes in these resistivities. The Poisson effect plays a minor role. The effects in the longitudinal resistivity are small compared to those in the through-thickness direction, but longitudinal resistance measurement is more amenable to practical implementation in structures than through-thickness resistance measurement. The irreversible effects are associated with an increase in the through-thickness resistivity and a decrease in the longitudinal resistivity. The through-thickness gage factor is up to 5.1 and decreases with increasing compressive strain above 0.2%. The reversible fractional change in through-thickness resistivity per through-thickness strain is up to 4.0 and decreases with increasing compressive strain. The irreversible fractional change in through-thickness resistivity per unit through-thickness strain is around -1.1 and is independent of the strain. The sensing is feasible by measuring the resistance away from the stressed region, though the effectiveness is less than that at the stressed region. A one

  17. Impact of polymer matrix on the electromagnetic interference shielding performance for single-walled carbon nanotubes-based composites.

    PubMed

    Liang, Jiajie; Huang, Yi; Li, Ning; Bai, Gang; Liu, Zunfeng; Du, Feng; Li, Feifei; Ma, Yanfeng; Chen, Yongsheng

    2013-02-01

    Composites of acrylonitrile butadiene styrene (ABS), epoxy and soluble cross-linked polyurethane (SCPU) with various loadings of single-walled carbon nanotubes (SWCNTs) were prepared. Their electromagnetic interference (EMI) shielding effectiveness (SE) in the frequency range of 8.2-12.4 GHz (X band) was studied. Well-dispersed SWCNT composites were created in these three representative polymer matrixes. The choice of polymer matrix greatly affects the conductivity, percolation threshold, and EMI shielding properties of the SWCNT/polymer composites. Enhanced EMI SE performances were observed for the composites with better dispersed SWCNTs. Moreover, the EMI SE performances strongly correlated with SWCNT loading in the polymer matrix. The best SWCNT dispersion was achieved in the epoxy matrix: 20-30 dB EMI SE was obtained with 15 wt% SWCNTs. PMID:23646584

  18. Advanced composites: Environmental effects on selected resin matrix materials

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    The effects that expected space flight environment has upon the mechanical properties of epoxy and polyimide matrix composites were analyzed. Environmental phenomena covered water immersion, high temperature aging, humidity, lightning strike, galvanic action, electromagnetic interference, thermal shock, rain and sand erosion, and thermal/vacuum outgassing. The technology state-of-the-art for graphite and boron reinforced epoxy and polyimide matrix materials is summarized to determine the relative merit of using composites in the space shuttle program. Resin matrix composites generally are affected to some degree by natural environmental phenomena with polyimide resin matrix materials less affected than epoxies.

  19. Extracellular matrix-like surfactant polymers containing arginine-glycine-aspartic acid (RGD) peptides.

    PubMed

    Anderson, Eric H; Ruegsegger, Mark A; Murugesan, Gurunathan; Kottke-Marchant, Kandice; Marchant, Roger E

    2004-08-01

    We report on a novel series of biomimetic polymers exhibiting interfacial properties similar to the extracellular matrix. A series of well-defined surfactant polymers were synthesized by simultaneously incorporating arginine-glycine-aspartic acid (RGD) peptide, dextran oligosaccharide, and hexyl ligands with controlled feed ratios onto a poly(vinyl amine) (PVAm) backbone. The peptide sequence was H-GSSSGRGDSPA-NH(2) (Pep) having a hydrophilic extender at the amino terminus and capped carboxy terminus. The peptide-to-dextran (Pep:Dex) ratios were varied to create surfactants having 0, 25, 50, 75, and 100 mol-% peptide relative to dextran. The surfactants were characterized by IR, NMR and atomic force microscopy (AFM) for composition and surface active properties. AFM confirmed full surface coverage of PVAm(Pep)(100%) on graphite, and supported the mechanism of interdigitation of hexyl ligands between surfactant molecules within a specified range of hexyl chain densities. the attachment and growth of human pulmonary artery endothelial cells on the PVAm(Pep)(100%) surface was identical to the fibronectin positive control. Cell adhesion decreased dramatically with decreasing peptide density on the surfactant polymers. Molecular model of a peptide surfactant polymer, consisting of poly(vinyl amine) backbone with peptide, dextran oligosaccharide and hexyl branches coupled to the polymer chain. PMID:15468270

  20. Design and development of advanced adaptive polymer lenses

    NASA Astrophysics Data System (ADS)

    Santiago, Freddie

    The dissertation presented here describes advancements made in adaptive polymer lens design and implementation. Singlets and doublets lenses were constructed for visible, short- wavelength infrared (SWIR), and middle-wavelength infrared (MWIR) applications. The lenses are implemented in a variety of tactical imaging systems to demonstrate their performance. A process was developed that defines the allowable fabrication variables, first for APL singlets and then for APL doublets. A first-order finite element model is described that enables going from an optical design to APL fabrication. This model was then extended to the design of fluidic doublets, which are equivalent to their two-element glass counter-parts. Two constant volume fluidic chambers were enclosed by three flexible membranes resulting in a variable focal length doublet. Chromatic focal shift was then used to compare numerical modeling to experimentally measured results. These same tools, methodology, and process were lastly used in the definition and fabrication of the SWIR and MWIR adaptive polymer lens for tactical systems. Imaging and illumination systems are presented, based on these lensesnotably an adaptive zoom imaging system, in the MWIR. This is the first known instance of such a system in this band.

  1. Influence of interphase morphology on adhesion and composite durability in semicrystalline polymer matrix composites

    SciTech Connect

    Clark, R.L. Jr.; Kander, R.G.

    1996-12-31

    The microstructure of the interphase in semicrystalline polymer matrix composites has a dramatic influence on their mechanical properties. Studies have been performed to alter this region and to correlate various interphase morphologies with changes in fiber-matrix adhesion. A reinforced nylon 66 composite, when subjected to specific thermal histories, contains an interphase composed of transcrystallinity. This region has been altered by coating fibers with a diluent, poly(vinyl pyrrolidone), and/or adding the diluent to the matrix material in very small quantities. Interphase morphology was investigated with optical microscopy, and adhesion was measured using a modified fiber pull-out test. It was found that transcrystallinity increases the interfacial shear strength. The effect different interphase morphologies have on the durability of bulk composite samples is currently under investigation.

  2. Silicon nitride ceramic matrix for CMCs from silane derived Si powders and preceramic polymers

    SciTech Connect

    Rhine, W.E.; Lightfoot, A.; Seyferth, D.; Haggerty, J.S.

    1995-10-01

    Si powders synthesized by the laser pyrolysis of silane can be nitrided at 1,200--1,250 C, producing an improved reaction bonded silicon nitride. This RBSN is a potential matrix for composites since it can be formed at temperatures which do not degrade the strengths of commercially available amorphous ceramic fibers. However, the density of the RBSN matrix has been limited to about 75% using the silane-derived Si powder. Combining Si powders and preceramic polymers offers an approach for increasing the density and mechanical properties of the reaction-formed Si{sub 3}N{sub 4} matrix. The incorporation of polysilazanes inhibited the nitridation oat 1,250 C, but samples could be effectively nitrided at 1,400 C. These higher nitriding temperatures are compatible with SCS-6 and other low-oxygen, crystalline SiC fibers which can be used as reinforcements for ceramic composites.

  3. Full eigenvalues of the Markov matrix for scale-free polymer networks

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongzhi; Guo, Xiaoye; Lin, Yuan

    2014-08-01

    Much important information about the structural and dynamical properties of complex systems can be extracted from the eigenvalues and eigenvectors of a Markov matrix associated with random walks performed on these systems, and spectral methods have become an indispensable tool in the complex system analysis. In this paper, we study the Markov matrix of a class of scale-free polymer networks. We present an exact analytical expression for all the eigenvalues and determine explicitly their multiplicities. We then use the obtained eigenvalues to derive an explicit formula for the random target access time for random walks on the studied networks. Furthermore, based on the link between the eigenvalues of the Markov matrix and the number of spanning trees, we confirm the validity of the obtained eigenvalues and their corresponding degeneracies.

  4. [INVITED] New advances in polymer fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Nogueira, Rogério; Oliveira, Ricardo; Bilro, Lúcia; Heidarialamdarloo, Jamshid

    2016-04-01

    During the last years, fiber Bragg gratings (FBGs) written in polymer optical fibers (POFs) have been pointed as an interesting alternative to silica FBGs for applications in sensors and in optical access networks. In order to use such components in real applications, the manipulation of POFs, as well as the increase of quality in the production of FBGs has to be achieved. In this article some of the recent advances regarding these two aspects are reported and include recent developments to produce smooth POFs end face with high quality, benefiting the current splicing process and the inscription of high quality FBGs in a few seconds. Furthermore, additional characterizations to strain, temperature, pressure, and humidity are also shown.

  5. Effect of Cyclic Thermo-Mechanical Loads on Fatigue Reliability in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Shah, A. R.; Murthy, P. L. N.; Chamis, C. C.

    1996-01-01

    A methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects caused by long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multi-factor interaction relationship developed at NASA Lewis Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability- based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/- 45/90)(sub s) graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.

  6. Temperature Stability and Bioadhesive Properties of Δ9-Tetrahydrocannabinol Incorporated Hydroxypropylcellulose Polymer Matrix Systems

    PubMed Central

    Repka, Michael A.; Munjal, Manish; ElSohly, Mahmoud A.; Ross, Samir A.

    2010-01-01

    The purpose of this study was to determine and compare the bioadhesive profiles of hydroxypropylcellulose (HPC) polymer matrices as a function of Δ9-tetrahydrocannabinol (THC) content. In addition, the effect of processing temperature on the stability of THC and its extent of degradation to cannabinol (CBN) was investigated. A hot-melt cast molding method was used to prepare HPC polymer matrix systems incorporated with THC at 0, 4, 8, and 16 percent. Bioadhesive measurements including peak adhesive force, area under the curve, and elongation at adhesive failure were recorded utilizing the TA.XT2i Texture Analyzer™. Data obtained from these tests at various contact time intervals suggested that the incorporation of THC led to an increase in the bioadhesive strength of the HPC polymer matrices. To determine the stability of THC and the resulting CBN content in the matrices, three different processing temperatures were utilized (120, 160, and 200°C). Post-production High Performance Liquid Chromotography (HPLC) analysis revealed that the processed systems contained at least 94% of THC and the relative percent formation of CBN was 0.5% at 120°C and 0.4% at 160°C compared to 1.6% at 200°C. These findings indicate that the cannabinoid may be a plausible candidate for incorporation into systems utilizing hot-melt extrusion techniques for the development of an effective mucoadhesive transmucosal matrix system for delivery of THC. PMID:16455601

  7. Release of engineered nanomaterials from polymer nanocomposites: the effect of matrix degradation.

    PubMed

    Duncan, Timothy V

    2015-01-14

    Polymer nanocomposites-polymer-based materials that incorporate filler elements possessing at least one dimension in the nanometer range-are increasingly being developed for commercial applications ranging from building infrastructure to food packaging to biomedical devices and implants. Despite a wide range of intended applications, it is also important to understand the potential for exposure to these nanofillers, which could be released during routine use or abuse of these materials so that it can be determined whether they pose a risk to human health or the environment. This article is the second of a pair that review what is known about the release of engineered nanomaterials (ENMs) from polymer nanocomposites. Two roughly separate ENM release paradigms are considered in this series: the release of ENMs via passive diffusion, desorption, and dissolution into external liquid media and the release of ENMs assisted by matrix degradation. The present article is focused primarily on the second paradigm and includes a thorough, critical review of the associated body of peer-reviewed literature on ENM release by matrix degradation mechanisms, including photodegradation, thermal decomposition, mechanical wear, and hydrolysis. These release mechanisms may be especially relevant to nanocomposites that are likely to be subjected to weathering, including construction and infrastructural materials, sporting equipment, and materials that might potentially end up in landfills. This review pays particular attention to studies that shed light on specific release mechanisms and synergistic mechanistic relationships. The review concludes with a short section on knowledge gaps and future research needs. PMID:25397693

  8. Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.

    2014-01-01

    The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

  9. Imaging of Au nanoparticles deeply buried in polymer matrix by various atomic force microscopy techniques.

    PubMed

    Kimura, Kuniko; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2013-10-01

    Recently, some papers reported successful imaging of subsurface features using atomic force microscopy (AFM). Some theoretical studies have also been presented, however the imaging mechanisms are not fully understood yet. In the preceeding papers, imaging of deeply buried nanometer-scale features has been successful only if they were buried in a soft matrix. In this paper, subsurface features (Au nanoparticles) buried in a soft polymer matrix were visualized. To elucidate the imaging mechanisms, various AFM techniques; heterodyne force microscopy, ultrasonic atomic force microscopy (UAFM), 2nd-harmonic UAFM and force modulation microscopy (FMM) were employed. The particles buried under 960 nm from the surface were successfully visualized which has never been achieved. The results elucidated that it is important for subsurface imaging to choose a cantilever with a suitable stiffness range for a matrix. In case of using the most suitable cantilever, the nanoparticles were visualized using every technique shown above except for FMM. The experimental results suggest that the subsurface features buried in a soft matrix with a depth of at least 1 µm can affect the local viscoelasticity (mainly viscosity) detected as the variation of the amplitude and phase of the tip oscillation on the surface. This phenomenon presumably makes it possible to visualize such deeply buried nanometer-scale features in a soft matrix. PMID:23770541

  10. Effect of fiber reinforcement on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1992-01-01

    A number of studies have investigated the thermooxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. The polyimide PMR-15 was the matrix material used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-4OR graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  11. Controlled release evaluation of bacterial fertilizer using polymer composites as matrix.

    PubMed

    Wu, Chin-San

    2008-11-24

    The use of polybutylene succinate (PBSU)/starch-type composite as biodegradable matrix material for the controlled release of bacterial fertilizer was evaluated. The composites were prepared by a melting-blending method and various methods/instruments were applied to characterize composites and PBSU. The mechanical properties of the PBSU/starch composite were worse than PBSU alone because the former had poor compatibility between starch and the polymer matrix. Much better dispersion and homogeneity were observed in the composite when PBSU was replaced by acrylic acid grafted PBSU (PBSU-g-AA), hence leading to better mechanical properties of PBSU-g-AA/starch. Furthermore, PBSU-g-AA/starch was more easily processed. The bacterial fertilizer was encapsulated in PBSU and PBSU-g-AA/starch matrix. Increased blending of starch increased the biodegradability of matrix and the amount and rate of cell release from matrix suggesting that this composite is a promising candidate material for 'controlled release' bacterial fertilizer. PMID:18796320

  12. Optimal Substrate Preheating Model for Thermal Spray Deposition of Thermosets onto Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Tsurikov, A.; Sutter, J. K.

    2003-01-01

    High velocity oxy-fuel (HVOF) sprayed, functionally graded polyimide/WC-Co composite coatings on polymer matrix composites (PMC's) are being investigated for applications in turbine engine technologies. This requires that the polyimide, used as the matrix material, be fully crosslinked during deposition in order to maximize its engineering properties. The rapid heating and cooling nature of the HVOF spray process and the high heat flux through the coating into the substrate typically do not allow sufficient time at temperature for curing of the thermoset. It was hypothesized that external substrate preheating might enhance the deposition behavior and curing reaction during the thermal spraying of polyimide thermosets. A simple analytical process model for the deposition of thermosetting polyimide onto polymer matrix composites by HVOF thermal spray technology has been developed. The model incorporates various heat transfer mechanisms and enables surface temperature profiles of the coating to be simulated, primarily as a function of substrate preheating temperature. Four cases were modeled: (i) no substrate preheating; (ii) substrates electrically preheated from the rear; (iii) substrates preheated by hot air from the front face; and (iv) substrates electrically preheated from the rear and by hot air from the front.

  13. Parts per billion doping and characterization of uranium distribution in an epoxy polymer matrix.

    PubMed

    Mitchell, James W; Carpenter, Steve

    2006-10-01

    Formulating an epoxy polymer provides a broadly applicable method for homogeneously doping a chemically stable, particulate-resistant, and radiation-hardened matrix with virtually any trace elements of interest. In the example reported, control of uranium levels over the range, 15 microg/g-15 ng/g, is demonstrated. Fission track density determinations, referenced to NIST SRMs, indicate +/-5% variations in lateral uranium distributions. Determinations of levels of uranium impurities in commercially available high-purity samples of graphite, fused silica, and aluminum show respective nanogram per gram ranges of 3 +/- 0.1-5 +/- 0.3, 3 +/- 0.8-27 +/- 2, and 113 +/- 11-546 +/- 11. The prepared polymer materials cover 3 orders of magnitude of uranium levels in an ideal matrix. This accomplishes the prerequisite for subsequent investigations of the chemistry occurring at fission fragment-induced damage sites of selected track registering materials as a function of controlled reactive site densities. The matrix also serves as a source of swift heavy ions for creating nanoscale features in dielectric materials. PMID:17007520

  14. Matrix metalloproteinase 9 (MMP-9) and biodegradable polymers in the engineering of a vascular construct

    NASA Astrophysics Data System (ADS)

    Sung, Hak-Joon

    The role of matrix metalloproteinase (MMP)-9 and processing conditions of biodegradable polymer scaffolds has been investigated to optimize engineering vascular constructs. For a small diameter vascular construct, uniform 10 mum thickness of highly porous scaffolds were developed using a computer-controlled knife coater and exploiting phase transition properties of salts. The comparative study of fast vs. slow degrading three-dimensional scaffolds using a fast degrading poly D, L-lactic-glycolic acid copolymer (PLGA) and a slow degrading poly e-caprolactone (PCL) indicated that fast degradation negatively affects cell viability and migration into the scaffold in vitro and in vivo, which is likely due to the fast polymer degradation mediated acidification of the local environment. MMP-9 was crucial for collagen remodeling process by smooth muscle cells (SMC). MMP-9 deficiency dramatically decreased inflammatory cell invasion as well as capillary formation within the scaffolds implanted in vivo. This study reports that the angiogenic response developed within the scaffolds in vivo was related to the presence of inflammatory response. Combinatorial polymer libraries fabricated from blended PLGA and PCL and processed at gradient annealing temperatures were utilized to investigate polymeric interactions with SMC. Surface roughness was also found to correlate with SMC adhesion. SMC aggregation, proliferation, and protein production, were highest in regions that exhibited increased surface roughness, reduced hardness, and decreased crystallinity of the PCL-rich phases. This study revealed a previously unknown processing temperature and blending compositions for two well-known polymers, which optimized SMC interactions.

  15. Sulfur polymer cement as a low-level waste glass matrix encapsulant

    SciTech Connect

    Sliva, P.; Peng, Y.B.; Bunnell, L.R.

    1995-12-31

    Sulfur polymer cement (SPC) is being considered as a matrix encapsulant for the Hanford low-level (activity) waste glass. SPC is an elemental sulfur polymer-stabilized thermoplastic that is fluid at 140{degrees}C. The candidate process would encapsulate the glass by filling the waste container with glass (e.g., as cullet) and backfiring with SPC to form a composite. As the primary barrier to groundwater, SPC plays a key role in the waste form`s long-term performance assessment. Work to date has targeted both the performance characteristics of the SPC alone and its potential influence on the glass. Bulk properties of the glass-SPC composite will be discussed along with glass-SPC interface characteristics. Properties that will be addressed include SPC properties, mechanical strength of the composite and the glass-SPC interface, glass-SPC interface chemistry, glass-SPC aqueous durability, and radiation effects.

  16. Polymer model with annealed dilution on the square lattice: A transfer-matrix study

    NASA Astrophysics Data System (ADS)

    Serra, Pablo; Stilck, Jürgen F.

    1994-02-01

    We study a lattice model for equilibrium polymerization with annealed dilution. The model considered is an Ising lattice-gas monomer-solvent system where the polymers are represented by mutually and self-avoiding walks constrained to pass through sites occupied by monomers. Numerical results on the square lattice using transfer-matrix techniques and finite-size scaling are reported. The values obtained for the tricitical exponent νt are in agreement with the tricritical Ising exponent (8/11) for high values of the monomer fugacity, but the accuracy we obtained does not rule out the possibility of νt being equal to the critical self-avoiding-walk (SAW) value 3/4. Our results indicate that a crossover occurs in the tricritical behavior of the model. This crossover corroborates the equivalence between a particular limit of the diluted model and the self-attracting polymer system proposed recently.

  17. Advanced Ceramic Matrix Composites with Multifunctional and Hybrid Structures

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Morscher, Gregory N.

    2004-01-01

    Ceramic matrix composites are leading candidate materials for a number of applications in aeronautics, space, energy, and nuclear industries. Potential composite applications differ in their requirements for thickness. For example, many space applications such as "nozzle ramps" or "heat exchangers" require very thin (< 1 mm) structures whereas turbine blades would require very thick parts (> or = 1 cm). Little is known about the effect of thickness on stress-strain behavior or the elevated temperature tensile properties controlled by oxidation diffusion. In this study, composites consisting of woven Hi-Nicalon (trademark) fibers a carbon interphase and CVI SiC matrix were fabricated with different numbers of plies and thicknesses. The effect of thickness on matrix crack formation, matrix crack growth and diffusion kinetics will be discussed. In another approach, hybrid fiber-lay up concepts have been utilized to "alloy" desirable properties of different fiber types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the C(sub I)-SiC and SiC(sub f)-SiC composite systems. CVI SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven SiC fiber (Hi-Nicalon (trademark)) layers were fabricated. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites. In addition, shear properties of these composites at different temperatures will also be presented. Other design and implementation issues will be discussed along with advantages and benefits of using these materials for various components in high temperature applications.

  18. In vitro release of ketoprofen from hydrophilic matrix tablets containing cellulose polymer mixtures.

    PubMed

    Vueba, M L; Batista de Carvalho, L A E; Veiga, F; Sousa, J J; Pina, M E

    2013-11-01

    The effect of cellulose ether polymer mixtures, containing both hydroxypropylcellulose (HPC) and hydroxypropylmethylcellulose (HPMC K15M or K100M), on ketoprofen (KTP) release from matrix tablets was investigated. In order to evaluate the compatibility between the matrix components, Raman spectroscopy, scanning electron microscopy (SEM), and X-ray powder diffraction (XRPD) experiments were performed. The results evidence the absence of significant intermolecular interactions that could eventually lead to an incompatibility between the drug and the different excipients. Formulations containing mixtures of polymers with both low and high viscosity grades were prepared by a direct compression method, by varying the polymer/polymer (w/w) ratio while keeping the drug amount incorporated in the solid dispersion constant (200 mg). The hardness values of different matrices were found within the range 113.8 to 154.9 N. HPLC analysis showed a drug content recovery between 99.3 and 102.1%, indicating that no KTP degradation occurred during the preparation process. All formulations attained a high hydration degree after the first hour, which is essential to allow the gel layer formation prior to tablet dissolution. Independent-model dissolution parameters such as t(10%) and t(50%) dissolution times, dissolution efficiency (DE), mean dissolution time (MDT), and area under curve (AUC) were calculated for all formulations. Zero-order, first-order, Higuchi, and Korsmeyer-Peppas kinetic models were employed to interpret the dissolution profiles: a predominantly Fickian diffusion release mechanism was obtained - with Korsmeyer-Peppas exponent values ranging from 0.216 to 0.555. The incorporation of HPC was thus found to play an essential role as a release modifier from HPMC containing tablets. PMID:23094867

  19. Multi-scale mechanism based life prediction of polymer matrix composites for high temperature airframe applications

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Priyank

    A multi-scale mechanism-based life prediction model is developed for high-temperature polymer matrix composites (HTPMC) for high temperature airframe applications. In the first part of this dissertation the effect of Cloisite 20A (C20A) nano-clay compounding on the thermo-oxidative weight loss and the residual stresses due to thermal oxidation for a thermoset polymer bismaleimide (BMI) are investigated. A three-dimensional (3-D) micro-mechanics based finite element analysis (FEA) was conducted to investigate the residual stresses due to thermal oxidation using an in-house FEA code (NOVA-3D). In the second part of this dissertation, a novel numerical-experimental methodology is outlined to determine cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house FEA code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. Double cantilever beam (DCB) experiments were conducted (at UT-Dallas) on both pristine and isothermally aged IM-7/BMI composite specimens to determine the model parameters. The J-Integral based approach was adapted to extract cohesive stresses near the crack tip. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to numerically simulate the DCB experiment. FEA simulation accurately captures the macro-scale behavior (load-displacement history) simultaneously with the micro-scale behavior (crack-growth history).

  20. Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Liaw, Benjamin; Villars, Esther; Delmont, Frantz; Bowles, Kenneth J. (Technical Monitor)

    2001-01-01

    The main objective of this NASA FAR project is to conduct ultrasonic assessment of impact-induced damage and microcracking in polymer matrix composites at various temperatures. It is believed that the proposed study of impact damage assessment on polymer matrix composites will benefit several NASA missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass (for GLARE) and aramid- (for ARALL) fiber-reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating cracks emanating from the impact site

  1. Nanostructural Characteristics and Interfacial Properties of Polymer Fibers in Cement Matrix.

    PubMed

    Shalchy, Faezeh; Rahbar, Nima

    2015-08-12

    Concrete is the most used material in the world. It is also one of the most versatile yet complex materials that humans have used for construction. However, an important weakness of concrete (cement-based composites) is its low tensile properties. Therefore, over the past 30 years many studies were focused on improving its tensile properties using a variety of physical and chemical methods. One of the most successful attempts is to use polymer fibers in the structure of concrete to obtain a composite with high tensile strength and ductility. The advantages of polymer fiber as reinforcing material in concrete, both with regard to reducing environmental pollution and the positive effects on a country's economy, are beyond dispute. However, a thorough understanding of the mechanical behavior of fiber-reinforced concrete requires a knowledge of fiber/matrix interfaces at the nanoscale. In this study, a combination of atomistic simulations and experimental techniques has been used to study the nanostructure of fiber/matrix interfaces. A new model for calcium-silicate-hydrate (C-S-H)/fiber interfaces is also proposed on the basis of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. Finally, the adhesion energy between the C-S-H gel and three different polymeric fibers (poly(vinyl alcohol), nylon-6, and polypropylene) were numerically studied at the atomistic level because adhesion plays a key role in the design of ductile fiber-reinforced composites. The mechanisms of adhesion as a function of the nanostructure of fiber/matrix interfaces are further studied and discussed. It is observed that the functional group in the structure of polymer macromolecule affects the adhesion energy primarily by changing the C/S ratio of the C-S-H at the interface and by absorbing additional positive ions in the C-S-H structure. PMID:26212096

  2. NASA Glenn/AADC-Rolls Royce Collaborated to Measure Erosion Resistance on Coated Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard; Ma, Kong; Horan, Dick; Naik, Subhash; Cupp, Randall

    2003-01-01

    Polymer matrix composites (PMCs) are increasingly used in aerospace and automotive applications because of their light weight and high strength-to-weight ratio relative to metals. However, a major drawback of PMCs is poor abrasion resistance, which restricts their use, especially at high temperatures. Simply applying a hard coating on PMCs to improve abrasion and erosion resistance is not effective since coating durability is short lived (ref. 1). Generally, PMCs have higher coefficients of thermal expansion than metallic or ceramic coatings have, and coating adhesion suffers because of poor interfacial adhesion strength. One technique commonly used to improve coating adhesion or durability is the use of bond coats that are interleaved between a coating and a substrate with vastly different coefficients of thermal expansion. An example of this remedy is the use of bondcoats for ceramic thermal barrier coatings on metallic turbine components (ref. 2). Prior collaborative research between the NASA Glenn Research Center and the Allison Advanced Development Company (AADC) demonstrated that bond coats sandwiched between PMCs and high-quality plasma-sprayed, erosion-resistant coatings substantially improved the erosion resistance of PMCs (ref. 3). One unresolved problem in this earlier collaboration was that there was no easy, accurate way to measure the coating erosion wear scar. Coating wear was determined by both profilometry and optical microscopy. Both techniques are time consuming. Wear measurement by optical microscopy requires sample destruction and does not provide a comprehensive measure of the entire wear volume. An even more subtle, yet critical, problem is that these erosion coatings contain two or more materials with different densities. Therefore, simply measuring specimen mass loss before and after erosion will not provide an accurate gauge for coating and/or substrate volume loss. By using a noncontact technique called scanning optical interferometry

  3. The effect of polymer properties on direct compression and drug release from water-insoluble controlled release matrix tablets.

    PubMed

    Grund, Julia; Koerber, Martin; Walther, Mathias; Bodmeier, Roland

    2014-07-20

    The objective of this study was to identify and evaluate key polymer properties affecting direct compression and drug release from water-insoluble matrices. Commonly used polymers, such as Kollidon(®) SR, Eudragit(®) RS and ethyl cellulose, were characterized, formulated into tablets and compared with regard to their properties in dry and wet state. A similar site percolation threshold of 65% v/v was found for all polymers in dry state. Key parameters influencing polymer compactibility were the surface properties and the glass transition temperature (T(g)), affecting polymer elasticity and particle size-dependent binding. The important properties observed in dry state also governed matrix characteristics and therefore drug release in wet state. A low T(g) (Kollidon(®) SRpolymer (ethyl cellulose). However, release retardation was observed in the same order as matrix integrity (Eudragit(®) RSpolymer need to be considered in polymer design and formulation of controlled-release matrix systems. PMID:24746409

  4. Pprogramming biomaterial bioresorption profile by embedding hydrolytic enzymes on polymer matrix

    NASA Astrophysics Data System (ADS)

    Ganesh, Manoj

    A unique strategy to control bioresorbable polymer lifetime by embedding enzymes in polymer matrices has been developed. Lipase from Candida Antarctica Lipase B (CALB) is surfactant paired enabling it to be organo-soluble and active for hydrolysis of the polymer matrix. The ion-paired lipase prepared by this technique is embedded within the poly(caprolactone) (PCL) matrix. Degradation studies of enzyme embedded PCL films were performed in three different incubation conditions namely i) batch; ii) continuous flow; iii) static (controlled humidity). In our batch studies ion paired CALB (6.5 and 1.65% (w/w)) was reported to degrade the PCL films in 1 day and 18 days respectively. Enzyme-catalyzed degradation of PCL films with embedded CALB (1.6 %-by-wt) under continuous fluid exchange (flow) conditions and in controlled humidity desiccators were also determined. At 0.2 mL/min flow rate, film weight loss reached 85% in 3 days relative to static incubations where 70% degradation occurred in 9 days. However, further increase in flow rate from 0.2 to 0.5 mL/min results in slower weight loss (7 days, 70%) as increased flow rate appears to negatively influence enzyme stability. The removal of degradation products is more efficient leading to formation of a porous matrix where SEM cross sectional images show larger better defined pores under continuous flow conditions. 1.6% CALB-embedded PCL films were incubated in desiccators set at 20, 75 and 95% relative humidity (RH). Water uptake and molecular weight change at 20% RH were insignificant. However, at 75 and 95% RH, by 28 days, %-water content increased to 0.30 and 0.82, and film Mn decreased by 25% to 59300 and 58% to 33900, respectively. From studies performed in embedded enzymatic polymer systems, we have extended our work to develop a new method for micro contact printing (μCP), which involves enzymes that has site-specific recognition domains for the polymer substrates. We have shown that degradation can occur under

  5. Method and apparatus for evaluating structural weakness in polymer matrix composites

    DOEpatents

    Wachter, E.A.; Fisher, W.G.

    1996-01-09

    A method and apparatus for evaluating structural weaknesses in polymer matrix composites is described. An object to be studied is illuminated with laser radiation and fluorescence emanating therefrom is collected and filtered. The fluorescence is then imaged and the image is studied to determine fluorescence intensity over the surface of the object being studied and the wavelength of maximum fluorescent intensity. Such images provide a map of the structural integrity of the part being studied and weaknesses, particularly weaknesses created by exposure of the object to heat, are readily visible in the image. 6 figs.

  6. Method and apparatus for evaluating structural weakness in polymer matrix composites

    DOEpatents

    Wachter, Eric A.; Fisher, Walter G.

    1996-01-01

    A method and apparatus for evaluating structural weaknesses in polymer matrix composites is described. An object to be studied is illuminated with laser radiation and fluorescence emanating therefrom is collected and filtered. The fluorescence is then imaged and the image is studied to determine fluorescence intensity over the surface of the object being studied and the wavelength of maximum fluorescent intensity. Such images provide a map of the structural integrity of the part being studied and weaknesses, particularly weaknesses created by exposure of the object to heat, are readily visible in the image.

  7. Experimental and Numerical Investigations on the Ballistic Performance of Polymer Matrix Composites Used in Armor Design

    NASA Astrophysics Data System (ADS)

    Colakoglu, M.; Soykasap, O.; Özek, T.

    2007-01-01

    Ballistic properties of two different polymer matrix composites used for military and non-military purposes are investigated in this study. Backside deformation and penetration speed are determined experimentally and numerically for Kevlar 29/Polivnyl Butyral and Polyethylene fiber composites because designing armors for only penetration is not enough for protection. After experimental ballistic tests, a model is constructed using finite element program, Abaqus. The backside deformation and penetration speed are determined numerically. It is found that the experimental and numeric results are in agreement and Polyethylene fiber composite has much better ballistic limit, the backside deformation, and penetration speed than those of Kevlar 29/Polivnyl Butyral composite if areal densities are considered.

  8. Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Sutter, James K.; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

    2004-01-01

    The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona road dust impinging at 20 degrees, 60 degrees, and 90 degrees angles at a velocity of 229 meters per second at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.

  9. Processing and characterization of a polymer matrix composite using variable frequency microwave heating

    SciTech Connect

    Fathi, Z.; Garard, R.S.; DeMeuse, M.T.

    1995-12-31

    Variable frequency microwave energy was successfully applied to uniformly heat thermoset polymer matrix composite (PMC) materials consisting of glass-reinforced isocyanate/epoxy mixtures as well as graphite fiber-reinforced epoxy. Results of a series of materials processed via variable frequency microwave energy are compared with computed results from numerical modeling techniques. A finite difference time domain (FDTD) technique provides 2-D models of the electric and thermal field distributions inside the microwave cavity as well as inside the processed materials. The materials` physical and chemical characteristics from the empirical trials are evaluated for both variable and fixed frequency irradiation.

  10. MS&T'13 Symposium Preview: Metal and Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Gupta, Nikhil; Paramsothy, Muralidharan

    2013-08-01

    The Metal and Polymer Matrix Composites symposium at Materials Science & Technology 2013 (MS&T'13) conference is planned to provide a platform to researchers working on various aspects of composite materials and capture the state of the art in this area. The dialogue among leading researchers is expected to provide insight into the future of this field and identify the future directions in terms of research, development, and applications of composite materials. In the 2 day program, the symposium includes 34 presentations, including 10 invited presentations. The contributions have come from 16 different countries including USA, Mexico, Switzerland, India, Egypt, and Singapore.

  11. Polymer matrix composites on LDEF experiments M0003-9 and M0003-10

    NASA Technical Reports Server (NTRS)

    Steckel, Gary L.; Cookson, Thomas; Blair, Christopher

    1992-01-01

    Over 250 polymer matrix composites were exposed to the natural space environment on Long Duration Exposure Facility (LDEF) experiments M0003-9 and 10. The experiments included a wide variety of epoxy, thermoplastic, polyimide, and bismalimide matrix composites reinforced with graphite, glass, or organic fibers. A review of the significant observations and test results obtained to date is presented. Estimated recession depths from atomic oxygen exposure are reported and the resulting surface morphologies are discussed. The effects of the LDEF exposure on the flexural strength and modulus, short beam shear strength, and coefficient of thermal expansion of several classes of bare and coated composites are reviewed. Lap shear data are presented for composite-to-composite and composite-to-aluminum alloy samples that were prepared using different bonding techniques and subsequently flown on LDEF.

  12. Advanced composites: Fabrication processes for selected resin matrix materials

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

  13. The influence of matrix and laser energy on the molecular mass distribution of synthetic polymers obtained by MALDI-TOF-MS

    NASA Astrophysics Data System (ADS)

    Wetzel, Stephanie J.; Guttman, Charles M.; Girard, James E.

    2004-11-01

    The molecular mass distribution (MMD) obtained in synthetic polymer characterization by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) may be biased by preferential desorption/ionization of low mass polymer molecules, preferential ion attachment to larger polymers, or degradation and fragmentation due to the desorption process. In this study we focus on the effect of matrix and laser energy on the MMD of four synthetic polymers of low polydispersity with varying thermal stabilities. The four polymers considered were polystyrene (PS), poly(ethylene glycol) (PEG), poly(methyl methacrylate) (PMMA) and poly(tetrahydrofuran) (PTHF). The matrix in which the polymer is analyzed may also influence the laser energy effect of MALDI and was also considered in this paper. Three common matrixes were considered, dithranol, all trans-retinoic acid (RA) and 2,5-dihydroxybenzoic acid (DHB). Statistical analyses of the molecular mass distributions, obtained by varying laser energy and matrixes, reveal trends that can be used to describe the influences of matrix and laser energy on MALDI-TOF-MS data measurement of synthetic polymers. The statistical analysis revealed that the matrix has a greater effect on the polymer MMD than was expected. Polymers analyzed in DHB yielded lower mass moments than polymers analyzed in RA and dithranol. The effects of laser power on the MMD of the polymers were found to be matrix dependent.

  14. Polymers as advanced materials for desiccant applications, 1988

    SciTech Connect

    Czanderna, A.W.; Neidlinger, H.H.

    1990-09-01

    This report documents work to identify a next-generation, low-cost material with which solar energy or heat from another low-cost energy source can be used for regenerating the water vapor sorption activity of the desiccant. The objective of the work is to determine how the desired sorption performance of advanced desiccant materials can be predicted by understanding the role of the material modifications and material surfaces. The work concentrates on solid materials to be used for desiccant cooling systems and which process water vapor in an atmosphere to produce cooling. The work involved preparing modifications of polystyrene sulfonic acid sodium salt, synthesizing a hydrogel, and evaluating the sorption performances of these and similar commercially available polymeric materials; all materials were studied for their potential application in solid commercial desiccant cooling systems. Background information is also provided on desiccant cooling systems and the role of a desiccant material within such a system, and it includes the use of polymers as desiccant materials. 31 refs., 16 figs., 5 tabs.

  15. Experiments and micromechanical models for creep-rupture in polymer matrix composites: Progress report for period June 15, 1984-June 14, 1987

    SciTech Connect

    Phoenix, S.L.

    1986-12-01

    The research thrust has been to develop micromechanical probability models and conduct critical experiments on the failure of polymer matrix composites under high, sustained loads. Tensile failure of such composites is a complex statistical process involving scattered failure of fibers at flaw sites, and local overloading and failure of neighboring fibers by way of stress transfer through the matrix which may creep and debond in time. Failure results from the subsequent development of a catastrophic crack. These models are ultimately to be used to develop life prediction methodologies, accelerated test techniques, and superior 'microengineered' composites. Recent theoretical progress has included a new recursive formulation which yields a key asymptotic scaling law for strength and lifetime; this is also a new development in modern percolation theory. A key characteristic distribution function results which embodies all local statistical and micromechanical activity, and is now amenable to 'supercomputer' calculation. Progress has also been made in developing a self-similar formulation for micromechanical stress redistribution under a power law creeping matrix. Experimental advances include creep-rupture results for single Kevlar 49 aramid fibers at elevated temperatures, creep-rupture results for graphite fiber/epoxy microcomposites, the development of a single fiber composite test as an advanced technique for studying statistics for fiber strength and fiber/matrix debonding, microindentation techniques for studying matrix creep and debonding, and the development of research equipment for high-precision fabrication of microcomposites.

  16. Experiments and micromechanical models for creep-rupture in polymer matrix composites: Final technical report for period June 15, 1984-June 14, 1987

    SciTech Connect

    Phoenix, S.L.

    1987-06-01

    The research thrust has been to develop micromechanical probability models and conduct critical experiments on the failure of polymer matrix composites under high, sustained loads. Tensile failure of such composites is a complex statistical process involving scattered failure of fibers at flaw sites, and local overloading and failure of neighboring fibers by way of stress transfer through the matrix which may creep and debond in time. Failure results from the subsequent development of a catastrophic crack. These models are ultimately to be used to develop life prediction methodologies, accelerated test techniques, and superior 'microengineered' composites. Recent theoretical progress has included a new recursive formulation which yields a key asymptotic scaling law for strength and lifetime; this is also a new development in modern percolation theory. A key characteristic distribution function results which embodies all local statistical and micromechanical activity, and is now amenable to 'supercomputer' calculation. Progress has also been made in developing a self-similar formulation for micromechanical stress redistribution under a power law creeping matrix. Experimental advances include (1) creep-rupture results for single Kevlar 49 aramid fibers at elevated temperatures, (2) creep-rupture results for graphite fiber/epoxy microcomposites, (3) the development of a single fiber composite test as an advanced technique for studying statistics for fiber strength and fiber/matrix debonding, (4) microindentation techniques for studying matrix creep and debonding, and (5) the development of research equipment for high-precision fabrication of microcomposites.

  17. Matrix effects in nilotinib formulations with pH-responsive polymer produced by carbon dioxide-mediated precipitation.

    PubMed

    Colombo, Stefano; Brisander, Magnus; Haglöf, Jakob; Sjövall, Peter; Andersson, Per; Østergaard, Jesper; Malmsten, Martin

    2015-10-15

    Factors determining the pH-controlled dissolution kinetics of nilotinib formulations with the pH-titrable polymer hydroxypropyl methylcellulose phthalate, obtained by carbon dioxide-mediated precipitation, were mechanistically examined in acid and neutral environment. The matrix effect, modulating the drug dissolution, was characterized with a battery of physicochemical methodologies, including ToF-SIMS for surface composition, SAXS/WAXS and modulated DSC for crystallization characterization, and simultaneous UV-imaging and Raman spectroscopy for monitoring the dissolution process in detail. The hybrid particle formulations investigated consisted of amorphous nilotinib embedded in a polymer matrix in single continuous phase, displaying extended retained amorphicity also under wet conditions. It was demonstrated by Raman and FTIR spectroscopy that the efficient drug dispersion and amorphization in the polymer matrix were mediated by hydrogen bonding between the drug and the phthalate groups on the polymer. Simultaneous Raman and UV-imaging studies of the effect of drug load on the swelling and dissolution of the polymer matrix revealed that high nilotinib load prevented matrix swelling on passage from acid to neutral pH, thereby preventing re-precipitation and re-crystallization of incorporated nilotinib. These findings provide a mechanistic foundation of formulation development of nilotinib and other protein kinase inhibitors, which are now witnessing an intense therapeutic and industrial attention due to the difficulty in formulating these compounds so that efficient oral bioavailability is reached. PMID:26276256

  18. Long-term water-aging of whisker-reinforced polymer-matrix composites.

    PubMed

    Xu, H H K

    2003-01-01

    Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si(3)N(4) and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean +/- SD; n = 6) of 185 +/- 33 MPa, similar to 146 +/- 44 MPa for Si(3)N(4) composite (p = 0.064); both were significantly higher than 67 +/- 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si(3)N(4) composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging. PMID:12508045

  19. An Analysis of Nondestructive Evaluation Techniques for Polymer Matrix Composite Sandwich Materials

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.; Roberts, Gary D.; Binienda, Wieslaw K.; Zheng, Diahua; Averbeck, Timothy; Roth, Donald J.; Jeanneau, Philippe

    2006-01-01

    Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in-field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials and a flat sandwich sample were examined with multiple NDE techniques including thermographic, radiographic, and shearographic methods to investigate damage induced in the blades and flat panel components. Hockey blades used during actual play and a flat polymer matrix composite sandwich sample with damage inserted into the foam core were investigated with each technique. NDE images from the samples were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. Structural elements, damaged regions, and other material variations were detected in the hockey blades with shearography. Each technique s advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

  20. Matrix polymer species have distinct effects on the mechanics of bacterial biofilms

    NASA Astrophysics Data System (ADS)

    Kovach, Kristin; Davis-Fields, Megan; Gordon, Vernita

    2015-03-01

    Biofilms are aggregates of microorganisms embedded in a self-produced extracellular polymer matrix. The matrix confers protection to these microorganisms against mechanical and chemical stresses that they may experience in their environment. The bacterium Pseudomonas aeruginosa is widely used as a model biofilm-forming organism because it is an opportunistic human pathogen common in hospital-acquired infections, in chronic wounds, and in cystic fibrosis lung disease. P. aeruginosa strain PA01 forms biofilms that are primarily structured by the extracellular polysaccharides Pel and Psl. Using bulk rheological measurements, we show that these polysaccharides each play a unique role in the mechanical robustness of the biofilm. Psl increases the elastic storage modulus while Pel increases the ductility of the biofilm. Increased expression of either Psl or Pel increases the yield stress by about the same amount. Identifying the mechanism(s) by which these polymers contribute to the mechanical toughness of the biofilm could allow new approaches to effective biofilm clearance, by revealing targets for disruption that would weaken the biofilm.

  1. Fabrication and characterization of novel polymer-matrix nanocomposites and their constituents

    NASA Astrophysics Data System (ADS)

    Ding, Rui

    Two main issues for the wide application of polymer-matrix nanocomposites need to be addressed: cost-effective processing of high-performance nanomaterials, and fundamental understanding of the nanofiller-polymer interaction related to property changes of nanocomposites. To fabricate inexpensive and robust carbon nanofibers (CNFs) by the electrospinning technique, an organosolv lignin for replacing polyacrylonitrile (PAN) precursor was investigated in this work. Modification of lignin to its butyl ester alters the electrospinnability and the thermal mobility of the lignin/PAN blend precursor fibers, which further affect the thermostabilization and carbonization processes of CNFs. The micromorphology, carbon structure, and mechanical properties of resultant CNFs were evaluated in detail. Lignin butyration reveals a new approach to controlling inter-fiber bonding of CNFs which efficiently increases the tensile strength and modulus of nonwoven mats. A commercial vapor-grown CNF reinforcing of room-temperature-vulcanized (RTV) polysiloxane foam has potential impact on the residual tin catalyst in composites and consequently the aging and the long-term performance of the materials. Elemental spectra and mapping were employed to analyze the distribution and the composition of tin catalyst residues in the CNF/polysiloxane composites. Thermal analysis revealed a significant increase of thermal stability for CNF-filled composites. Further, the glass transition properties of polysiloxane are not evidently influenced by the physical interaction between CNF filler and polysiloxane matrix. Nanocomposites consisting of anthracene, a model polycyclic aromatic hydrocarbon (PAH) compound, and a thermosetting epoxy was matrix was studied to interpret the reinforcing effect on the glass transition temperature ( Tg) by different routes: physical dispersion and/or covalent modification. The molecular dynamics of the relaxation processes were analyzed by broadband dielectric

  2. Carbon fiber polymer-matrix structural composites tailored for multifunctionality by filler incorporation

    NASA Astrophysics Data System (ADS)

    Han, Seungjin

    This dissertation provides multifunctional carbon fiber polymer-matrix structural composites for vibration damping, thermal conduction and thermoelectricity. Specifically, (i) it has strengthened and stiffened carbon fiber polymer-matrix structural composites by the incorporation of halloysite nanotubes, carbon nanotubes and silicon carbide whiskers, (ii) it has improved mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation, (iii) it has increased the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, and (iv) it has enhanced the thermoelectric behavior of carbon fiber polymer-matrix structural composites. Low-cost natural halloysite nanotubes (0.1 microm diameter) were effective for strengthening and stiffening continuous fiber polymer-matrix composites, as shown for crossply carbon fiber (5 microm diameter, ˜59 vol.%) epoxy-matrix composites under flexure, giving 17% increase in strength, 11% increase in modulus and 21% decrease in ductility. They were less effective than expensive multiwalled carbon nanotubes (0.02 microm diameter), which gave 25% increase in strength, 11% increase in modulus and 14% decrease in ductility. However, they were more effective than expensive silicon carbide whiskers (1 microm diameter), which gave 15% increase in strength, 9% increase in modulus and 20% decrease in ductility. Each filler, at ˜2 vol.%, was incorporated in the composite at every interlaminar interface by fiber prepreg surface modification. The flexural strength increase due to halloysite nanotubes incorporation related to the interlaminar shear strength increase. The measured values of the composite modulus agreed roughly with the calculated values based on the Rule of Mixtures. Continuous carbon fiber composites with enhanced vibration damping under flexure are provided by incorporation of fillers between the laminae

  3. Light-triggered conducting properties of a random carbon nanotubes network in a photochromic polymer matrix

    NASA Astrophysics Data System (ADS)

    Castagna, R.; Sciascia, C.; Srimath Kandada, A. R.; Meneghetti, M.; Lanzani, G.; Bertarelli, C.

    2011-10-01

    Photochromic materials reversibly change their colour due to a photochemical reaction that takes place when the material is irradiated with photons of suitable energy. This peculiar feature has been extensively exploited to develop smart sunglasses, filters and inks. With a proper molecular design it is possible to enable modulation not only of colour but also of other properties such as refractive index, dipole moment, nonlinear optical properties or conductivity by a photoswitching of the molecular structure. The approach herein developed consists in modifying, upon irradiation, the properties of a molecular component coupled with the photochromic molecule. In particular, the switching features of photochromic systems are matched with the intriguing peculiar properties of carbon nanotubes (CNTs). A photochromic polyester has been properly synthesised to be used as switching polymer matrix coupled with a network of CNTs. Irradiation of the polymer/CNTs blend results into a light-triggered conductance switching. The reversible electrocyclization of the polymer under UV-vis illumination results into a modification of the inter-tube charge mobility, and accordingly, of the overall resistance of the blend. Solution techniques allow us to obtain blended films with sheet resistance modulation larger than 150%, good thermal stability and fatigue resistance at room conditions, in an easier, faster and scalable way as respect to the single-molecule approach.ÿ

  4. Do the cations in clay and the polymer matrix affect quantum dot fluorescent properties?

    PubMed

    Wei, Wenjun; Liu, Cui; Liu, Jiyan; Liu, Xueqing; Zou, Linling; Cai, Shaojun; Shi, Hong; Cao, Yuan-Cheng

    2016-06-01

    This paper studied the effects of cations and polymer matrix on the fluorescent properties of quantum dots (QDs). The results indicated that temperature has a greater impact on fluorescence intensity than clay cations (mainly K(+) and Na(+) ). Combined fluorescence lifetime and steady-state spectrometer tests showed that QD lifetimes all decreased when the cation concentration was increased, but the quantum yields were steady at various cation concentrations of 0, 0.05, 0.5 and 1 M. Poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and diepoxy resin were used to study the effects of polymers on QD lifetime and quantum yield. The results showed that the lifetime for QDs 550 nm in PEO and PVA was 17.33 and 17.12 ns, respectively; for the epoxy resin, the lifetime was 0.74 ns, a sharp decrease from 24.47 ns. The quantum yield for QDs 550 nm changed from 34.22% to 7.45% and 7.81% in PEO and PVA, respectively; for the epoxy resin the quantum yield was 2.25%. QDs 580 nm and 620 nm showed the same results as QDs 550 nm. This study provides useful information on the design, synthesis and application of QDs-polymer luminescent materials. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26663530

  5. Multi-Scale CNT-Based Reinforcing Polymer Matrix Composites for Lightweight Structures

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh; Mather, Patrick; Rodriguez, Erika

    2013-01-01

    Reinforcing critical areas in carbon polymer matrix composites (PMCs), also known as fiber reinforced composites (FRCs), is advantageous for structural durability. Since carbon nanotubes (CNTs) have extremely high tensile strength, they can be used as a functional additive to enhance the mechanical properties of FRCs. However, CNTs are not readily dispersible in the polymer matrix, which leads to lower than theoretically predicted improvement in mechanical, thermal, and electrical properties of CNT composites. The inability to align CNTs in a polymer matrix is also a known issue. The feasibility of incorporating aligned CNTs into an FRC was demonstrated using a novel, yet commercially viable nanofiber approach, termed NRMs (nanofiber-reinforcing mats). The NRM concept of reinforcement allows for a convenient and safe means of incorporating CNTs into FRC structural components specifically where they are needed during the fabrication process. NRMs, fabricated through a novel and scalable process, were incorporated into FRC test panels using layup and vacuum bagging techniques, where alternating layers of the NRM and carbon prepreg were used to form the reinforced FRC structure. Control FRC test panel coupons were also fabricated in the same manner, but comprised of only carbon prepreg. The FRC coupons were machined to size and tested for flexural, tensile, and compression properties. This effort demonstrated that FRC structures can be fabricated using the NRM concept, with an increased average load at break during flexural testing versus that of the control. The NASA applications for the developed technologies are for lightweight structures for in-space and launch vehicles. In addition, the developed technologies would find use in NASA aerospace applications such as rockets, aircraft, aircraft/spacecraft propulsion systems, and supporting facilities. The reinforcing aspect of the technology will allow for more efficient joining of fiber composite parts, thus offering

  6. Humidity versus photo-stability of metal halide perovskite films in a polymer matrix.

    PubMed

    Manshor, Nurul Ain; Wali, Qamar; Wong, Ka Kan; Muzakir, Saifful Kamaluddin; Fakharuddin, Azhar; Schmidt-Mende, Lukas; Jose, Rajan

    2016-08-21

    Despite the high efficiency of over 21% reported for emerging thin film perovskite solar cells, one of the key issues prior to their commercial deployment is to attain their long term stability under ambient and outdoor conditions. The instability in perovskite is widely conceived to be humidity induced due to the water solubility of its initial precursors, which leads to decomposition of the perovskite crystal structure; however, we note that humidity alone is not the major degradation factor and it is rather the photon dose in combination with humidity exposure that triggers the instability. In our experiment, which is designed to decouple the effect of humidity and light on perovskite degradation, we investigate the shelf-lifetime of CH3NH3PbI3 films in the dark and under illumination under high humidity conditions (Rel. H. > 70%). We note minor degradation in perovskite films stored in a humid dark environment whereas upon exposure to light, the films undergo drastic degradation, primarily owing to the reactive TiO2/perovskite interface and also the surface defects of TiO2. To enhance its air-stability, we incorporate CH3NH3PbI3 perovskite in a polymer (poly-vinylpyrrolidone, PVP) matrix which retained its optical and structural characteristics in the dark for ∼2000 h and ∼800 h in room light soaking, significantly higher than a pristine perovskite film, which degraded completely in 600 h in the dark and in less than 100 h when exposed to light. We attribute the superior stability of PVP incorporated perovskite films to the improved structural stability of CH3NH3PbI3 and also to the improved TiO2/perovskite interface upon incorporating a polymer matrix. Charge injection from the polymer embedded perovskite films has also been confirmed by fabricating solar cells using them, thereby providing a promising future research pathway for stable and efficient perovskite solar cells. PMID:27432518

  7. Recent Advances in Glycerol Polymers: Chemistry and Biomedical Applications

    PubMed Central

    Zhang, Heng

    2015-01-01

    Glycerol polymers are attracting increased attention due to the diversity of polymer compositions and architectures available. This article provides a brief chronological review on the current status of these polymers along with representative examples of their use for biomedical applications. First, we describe the underlying chemistry of glycerol, which provides access to a range of monomers for subsequent polymerizations. We then review the various synthetic methodologies to prepare glycerol-based polymers including polyethers, polycarbonates, polyesters, and so forth. Next, we describe several biomedical applications where glycerol polymers are being investigated including carriers for drug delivery, sealants or coatings for tissue repair, and agents possessing antibacterial activity. Fourth, we describe the growing market opportunity for the use of polymers in medicine. Finally we conclude and summarize the findings, as well as discuss potential opportunities for continued research efforts. PMID:25308354

  8. Implementation and Assessment of Advanced Analog Vector-Matrix Processor

    NASA Technical Reports Server (NTRS)

    Gary, Charles K.; Bualat, Maria G.; Lum, Henry, Jr. (Technical Monitor)

    1994-01-01

    This paper discusses the design and implementation of an analog optical vecto-rmatrix coprocessor with a throughput of 128 Mops for a personal computer. Vector matrix calculations are inherently parallel, providing a promising domain for the use of optical calculators. However, to date, digital optical systems have proven too cumbersome to replace electronics, and analog processors have not demonstrated sufficient accuracy in large scale systems. The goal of the work described in this paper is to demonstrate a viable optical coprocessor for linear operations. The analog optical processor presented has been integrated with a personal computer to provide full functionality and is the first demonstration of an optical linear algebra processor with a throughput greater than 100 Mops. The optical vector matrix processor consists of a laser diode source, an acoustooptical modulator array to input the vector information, a liquid crystal spatial light modulator to input the matrix information, an avalanche photodiode array to read out the result vector of the vector matrix multiplication, as well as transport optics and the electronics necessary to drive the optical modulators and interface to the computer. The intent of this research is to provide a low cost, highly energy efficient coprocessor for linear operations. Measurements of the analog accuracy of the processor performing 128 Mops are presented along with an assessment of the implications for future systems. A range of noise sources, including cross-talk, source amplitude fluctuations, shot noise at the detector, and non-linearities of the optoelectronic components are measured and compared to determine the most significant source of error. The possibilities for reducing these sources of error are discussed. Also, the total error is compared with that expected from a statistical analysis of the individual components and their relation to the vector-matrix operation. The sufficiency of the measured accuracy of the

  9. Immobilization of radioactive and hazardous wastes in a developed sulfur polymer cement (SPC) matrix

    SciTech Connect

    Wagdy, M.; Azim, Abdel; El-Gammal, Belal; Husain, Ahmed

    2007-07-01

    Available in abstract form only. Full text of publication follows: A process has been developed for the immobilization Cs, Sr, Ce, Pb, and Cr in forms that is non-dispersible and could be safely immobilized. The simulated radioactive wastes of Cs, Sr, and Ce, and the hazardous wastes of Cr, and Pb were immobilized in the stable form of sulfur polymer cement (SPC). In this process, the contaminants (in a single form) were added to the sulfur mixture of sulfur and aromatic /or aliphatic hydrocarbons that used as polymerizing agents for sulfur (95% S, and 5% organic polymer by weight). Durability of the fabricated SPC matrices was assessed in terms of their water of immersion, porosity, and compressive strength. The water immersion, and open porosity were found to be less than 2.5% for all the prepared matrices, whereas the compressive strength was in the range between 62.4 and 142.3 Kg.cm{sup -2}, depending on the composition of the prepared matrix. The prepared SPC matrices that characterized by X-ray diffraction (XRD) showed that the different added contaminants were stabilized during the solidification process during their reaction with sulfur and the organic polymer to form the corresponding metal sulfides. Toxicity Characteristic Leaching Procedure (TCLP), and the IAEA standard method have assessed the leachability of the prepared waste matrices. The TCLP results showed that most the concentration of the contaminants released were under their detection limit. The leach index for the investigated metals from the prepared SPC matrices was in the range of 9-11. The order of release of the investigated metals was Sr>Cs>Pb>Cr>Ce for the aliphatic polymer, and Sr>Cr>Pb>Cs>Ce for the aromatic one. The results obtained revealed a high performance for the prepared SPC matrices, as they are of low cost effect, highly available materials, and possessed good mechanical and leaching properties. Key Words: SPC/ Matrices/ Immobilization/ Wastes/ Leachability. (authors)

  10. Nonlinear mechanical behavior of thermoplastic matrix materials for advanced composites

    NASA Technical Reports Server (NTRS)

    Arenz, R. J.; Landel, R. F.

    1989-01-01

    Two recent theories of nonlinear mechanical response are quantitatively compared and related to experimental data. Computer techniques are formulated to handle the numerical integration and iterative procedures needed to solve the associated sets of coupled nonlinear differential equations. Problems encountered during these formulations are discussed and some open questions described. Bearing in mind these cautions, the consequences of changing parameters that appear in the formulations on the resulting engineering properties are discussed. Hence, engineering approaches to the analysis of thermoplastic matrix material can be suggested.

  11. Tissue Engineering: Mechanocompatible Polymer-Extracellular-Matrix Composites for Vascular Tissue Engineering (Adv. Healthcare Mater. 13/2016).

    PubMed

    Jiang, Bin; Suen, Rachel; Wang, Jiao-Jing; Zhang, Zheng J; Wertheim, Jason A; Ameer, Guillermo A

    2016-07-01

    Heparinized mechanocompatible polymer-extracellular matrix (ECM) composites to improve vascular graft performance are presented by J. A. Wertheim, G. A. Ameer, and co-workers on page 1594. Polymer-coated ECM is visualized by the purple color. The composite vascular graft reduced intimal hyperplasia in a rodent model, revealed by α-smooth muscle actin staining (green). The method shows promise for tissue engineering where immobilization of bioactive molecules is desirable. PMID:27384933

  12. A novel approach for FE-SEM imaging of wood-matrix polymer interface in a biocomposite.

    PubMed

    Singh, Adya P; Anderson, Ross; Park, Byung-Dae; Nuryawan, Arif

    2013-01-01

    Understanding the interface between polymer and biomass in composite products is important for developing high performance products, as the quality of adhesion at the interface determines composite properties. For example, with greater stiffness compared to polymer matrix, such as that of high density polyethylene, the wood component enhances stiffness of wood-polymer composites, provided there is good adhesion between composite components. However, in composites made from wood flour (wood particles) and synthetic resins it is often difficult to clearly resolve particle-matrix interfaces in the conventionally employed microscopy method that involves SEM examination of fractured faces of composites. We developed a novel approach, where composites made from high density polyethylene and wood flour were examined and imaged with a FE-SEM (field emission scanning electron microscope) in transverse sections cut through the composites. Improved definition of the interface was achieved using this approach, which enabled a more thorough comparison to be made of the features of the interface between wood particles and the matrix in composites with and without a coupling agent, as it was possible to clearly resolve the interfaces for particles of all sizes, from large particles consisting of many cells down to tiny cell wall fragments, particularly in composites that did not incorporate the coupling agent used to enhance particle adhesion with the matrix polymer. The method developed would be suitable particularly for high definition SEM imaging of a wide range of composites made combining wood and agricultural residues with synthetic polymers. PMID:24063951

  13. Preclinical evaluation of a novel abluminal surface coated sirolimus eluting stent with biodegradable polymer matrix

    PubMed Central

    Doshi, Manish; Galloni, Marco; Vignolini, Christina; Vyas, Ashwin; Chevli, Bhavesh; Sheiban, Imad

    2015-01-01

    Background Second generation of drug eluting stents (DES) has attempted to improve safety using abluminal sirolimus drug delivery with biodegradable polymers matrix. The present preclinical study was designed to investigate the safety and efficacy profile of Abluminus™ stents (SES). This is a new coronary stent with sirolimus and biodegradable polymer matrix coated on abluminal stent and balloon surface. Methods SES were compared with two controls: bare metal stent (BMS) and BMS + polymer coated stents (PC). All devices (40 stents) were implanted in porcine coronary arteries with primary endpoint of endothelialization at 7 days and subsequent histological and morphometric evaluations at 7, 30 and 90 days. Results Early endothelialization at seven days was complete in all stents. Histology at 30 days revealed minimum inflammation in all groups and increased at 90 days in PC group while it was absent at 180 days. Thirty day morphometry showed significantly reduction of neointimal area in Abluminus™ (SES 0.96±0.48 mm2; BMS 1.83±0.34 mm2; PC 1.76±0.55 mm2; P<0.05); after 90 days neointimal area was 1.10±0.54 mm2 for SES; 1.92±0.36 mm2 for BMS; and 1.94±0.48 mm2 for PC; P<0.05). Neointimal thickness at 30 and 90 days respectively was 0.15±0.07 and 0.18±0.10 mm for SES, 0.57±0.08 and 0.61±0.09 mm for BMS and 0.52±0.09 and 0.59±0.08 mm, P<0.001 for PC group. Conclusions The most significant experimental evidence appears to be earlier endothelialization at 7 days for SES which led to safety of the device. Efficacy of the device was also observed by a reduced neointimal thickness and minimized inflammatory score at all follow-ups. Termination of antiplatelet at 30 days has not shown any further complications. Polymer thickness was almost in negligible amount at 180 days with no inflammation. PMID:26331109

  14. Recent advances in joining of aluminium metal matrix composites

    SciTech Connect

    Threadgill, P.L.

    1994-12-31

    Studies have been made of the use of friction welding and gas tungsten arc welding to join several types of SiC particulate reinforced aluminium alloys. The joints have been subjected to detailed metallographic assessment, and some mechanical property data are also reported. Friction welding has been shown to be a very suitable process, and good joints were obtained with relative ease. Although bond line strength in the as-welded condition is less than parent material strength, a full solution treatment and age will restore properties. GTA welding is possible on reinforced 2080 and 7475 sheet materials, using either autogenous welding or a 4047A filler. No evidence for particle/matrix reactions was observed, although SiC particles in the melt zone were often surrounded by eutectic or interdendritic phases. Mechanical properties were variable, but could be significantly improved by postweld heat treatment.

  15. Engineering the Crystalline Morphology of Polymer Thin Films at a Molecular Level via Matrix Assisted Pulsed Laser Evaporation

    NASA Astrophysics Data System (ADS)

    Jeong, Hyuncheol; Arnold, Craig; Priestley, Rodney

    2015-03-01

    Controlling the crystalline morphology of polymeric thin films at a molecular level has been increasingly important due to their potential as the active layer in organic electronics. Typically, the crystalline morphology in films is achieved via thermal annealing or melt-crystallization of spin-cast polymers. This approach often leads to a spherulitic morphology where the crystalline lamellae grow in all directions. Here, we introduce an alternative approach to make crystalline polymer films via Matrix Assisted Pulsed Laser Evaporation (MAPLE). Using polyethylene oxide (PEO) as a model polymer, we show that the preferential orientation of polymer crystals can be controlled during the film growth. By laser-ablating a frozen dilute solution of the desired polymer, MAPLE provides a non-destructive means for the deposition of polymer films. Due to the liquid nature of as-deposited polymers confined in nanodroplets, this technique can exploit the substrate effect on the crystal nucleation and growth of nano-confined polymers during the film growth. Mimicking the epitaxial growth of metallic films, this novel polymer deposition technique may enable the engineering of film properties in a way not achievable in bulk.

  16. Ultra-thin Solid-State Li-Ion Electrolyte Membrane Facilitated by a Self-Healing Polymer Matrix.

    PubMed

    Whiteley, Justin M; Taynton, Philip; Zhang, Wei; Lee, Se-Hee

    2015-11-18

    Thin solid membranes are formed by a new strategy, whereby an in situ derived self-healing polymer matrix that penetrates the void space of an inorganic solid is created. The concept is applied as a separator in an all-solid-state battery with an FeS2 -based cathode and achieves tremendous performance for over 200 cycles. Processing in dry conditions represents a paradigm shift for incorporating high active-material mass loadings into mixed-matrix membranes. PMID:26421754

  17. An NDE approach for characterizing quality problems in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Baaklini, George Y.; Sutter, James K.; Bodis, James R.; Leonhardt, Todd A.; Crane, Elizabeth A.

    1994-01-01

    Polymer matrix composite (PMC) materials are periodically identified appearing optically uniform but containing a higher than normal level of global nonuniformity as indicated from preliminary ultrasonic scanning. One such panel was thoroughly examined by nondestructive (NDE) and destructive methods to quantitatively characterize the nonuniformity. The NDE analysis of the panel was complicated by the fact that the panel was not uniformly thick. Mapping of ultrasonic velocity across a region of the panel in conjunction with an error analysis was necessary to (1) characterize properly the porosity gradient that was discovered during destructive analyses and (2) account for the thickness variation effects. Based on this study, a plan for future NDE characterization of PMC's is presented to the PMC community.

  18. Space environmental effects on polymer matrix composites as a function of sample location on LDEF

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Cool, G. R.; Zimcik, D. G.

    1995-01-01

    This paper presents results on the effect of circumferential location on the variation in solar absorptance (alpha(sub S)) and infrared emittance (epsilon) for five different polymer matrix composites (PMC), and variations in erosion depth due to atomic oxygen (AO) for fourteen different PMC materials. In addition, a chemical content design parameter (gamma) has been found that correlates well with the erosion yield obtained from space flight data and hyperthermal AO tests for hydrocarbon polymeric materials. This parameter defines the ratio of the total number of atoms in a repeat monomer unit to the difference between the total carbon content and the total number of intermolecular oxygen atoms in the same repeat unit.

  19. Transfer matrix approach to the statistical mechanics of single polymer molecules

    NASA Astrophysics Data System (ADS)

    Livadaru, Lucian

    In this work, we demonstrate, implement and critically assess the capabilities and the limitations of the Transfer Matrix (TM) method to the statistical mechanics of single polymer molecules within their classical models. We first show how the TM can be employed with the help of computers, to provide highly accurate results for the configurational statistics of polymers in theta-conditions. We proceed gradually from simple to complex polymer models, analyzing their statistical properties as we vary the model parameters. In the order of their complexity, the polymer models approached in this work are: (i) the freely jointed chain (FJC); (ii) the freely rotating chain (FRC); (iii) the rotational isomeric state (RIS) model with and without energy parameters; (iv) the continuous rotational potential model (for n-alkanes); (v) an interacting chain model (ICM) with virtual bonds for poly(ethylene glycol)(PEG). The Statistical Mechanics of polymer chains is carried out in both the Helmholtz and Gibbs ensembles, depending on the quantities of interest. In the Helmholtz ensemble the polymer's Green function is generally a function of both the spatial coordinates and orientations of chain bonds. In the Gibbs ensemble its arguments are the bond orientations with respect to an applied external force. This renders the latter ensemble more feasible for an accurate study of the mechanical properties of the mentioned models. We adapt the TM method to study statistical and thermodynamical properties of various models, including: chain end distribution functions, characteristic ratios, mean square radius of gyration, Kuhn length, static structure factor, pair correlation function, force-extension curves, Helmholtz and Gibbs free energies. For all cases, the TM calculations yielded accurate results for all these quantities. Wherever possible, we compared our findings to other results, theoretical or experimental in literature. A great deal of effort was focused on precise

  20. Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1985-01-01

    A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

  1. Durability of polymer matrix composites for infrastructure: The role of the interphase

    NASA Astrophysics Data System (ADS)

    Verghese, Kandathil Nikhil Eapen

    1999-12-01

    As fiber reinforced polymer matrix composites find greater use in markets such as civil infrastructure and ground transportation, the expectations placed on these materials are ever increasing. The overall cost and reliability have become the drivers of these high performance materials and have led to the disappearance of resins such as bismaleimides (BMI). cyanate esters and other high performance polyimides and epoxys. In their place polymers, such polyester and vinylester have arisen. The reinforcing fiber scenario has also undergone changes from the high quality and performance assured IM7 and AS4 to cheaper and hybrid systems consisting of both glass and low cost carbon. Manufacturing processes have had their share of changes too with processes such as pultrusion and other mass production techniques replacing hand lay-up and resin transfer molding. All of this has however come with little or no concession on material performance. The motivation of the present research has therefore been to try to improve the properties of these low cost composites by better understanding the constituent materials (fiber and matrix) and the region that lies in-between them namely the interphase. In order to achieve this. working with controls is necessary and the present discourse therefore deals with the AS4 fiber system from Hexcel Corporation and the vinyl ester resin, Derakane 441-400 from The Dow Chemical Company. The following eight chapters sum up the work done thus far on composites made with sized fibers and the above mentioned resin and fiber systems. They are in the form of publications that have either been accepted. submitted or going to be submitted to various peer reviewed journals. The sizings used have been poly(vinylpyrrolidone) PVP and Polyhydroxyether (Phenoxy) thermoplastic polymers and G' an industrial sizing material supplied by Hexcel. A number of issues have been addressed ranging from viscoelastic relaxation to enviro-mechanical durability. Chapter 1

  2. Morphology and kinetic modeling of molecularly imprinted organosilanol polymer matrix for specific uptake of creatinine.

    PubMed

    Ang, Qian Yee; Low, Siew Chun

    2015-09-01

    Molecular imprinting is an emerging technique to create imprinted polymers that can be applied in affinity-based separation, in particular, biomimetic sensors. In this study, the matrix of siloxane bonds prepared from the polycondensation of hydrolyzed tetraethoxysilane (TEOS) was employed as the inorganic monomer for the formation of a creatinine (Cre)-based molecularly imprinted polymer (MIP). Doped aluminium ion (Al(3+)) was used as the functional cross-linker that generated Lewis acid sites in the confined silica matrix to interact with Cre via sharing of lone pair electrons. Surface morphologies and pore characteristics of the synthesized MIP were determined by field emission scanning electron microscopy (FESEM) and Brunauer-Emmet-Teller (BET) analyses, respectively. The imprinting efficiency of MIPs was then evaluated through the adsorption of Cre with regard to molar ratios of Al(3+). A Cre adsorption capacity of up to 17.40 mg Cre g(-1) MIP was obtained and adsorption selectivity of Cre to its analogues creatine (Cr) and N-hydroxysuccinimide (N-hyd) were found to be 3.90 ± 0.61 and 4.17 ± 3.09, respectively. Of all the studied MIP systems, chemisorption was predicted as the rate-limiting step in the binding of Cre. The pseudo-second-order chemical reaction kinetic provides the best correlation of the experimental data. Furthermore, the equilibrium adsorption capacity of MIP fit well with a Freundlich isotherm (R (2) = 0.98) in which the heterogeneous surface was defined. PMID:26163132

  3. Recent advances in research on carbon nanotube-polymer composites.

    PubMed

    Byrne, Michele T; Gun'ko, Yurii K

    2010-04-18

    Carbon nanotubes (CNTs) demonstrate remarkable electrical, thermal, and mechanical properties, which allow a number of exciting potential applications. In this article, we review the most recent progress in research on the development of CNT-polymer composites, with particular attention to their mechanical and electrical (conductive) properties. Various functionalization and fabrication approaches and their role in the preparation of CNT-polymer composites with improved mechanical and electrical properties are discussed. We tabulate the most recent values of Young's modulus and electrical conductivities for various CNT-polymer composites and compare the effectiveness of different processing techniques. Finally, we give a future outlook for the development of CNT-polymer composites as potential alternative materials for various applications, including flexible electrodes in displays, electronic paper, antistatic coatings, bullet-proof vests, protective clothing, and high-performance composites for aircraft and automotive industries. PMID:20496401

  4. Surface indentation and fluid intake generated by the polymer matrix of Bacillus subtilis biofilms.

    PubMed

    Zhang, W; Dai, W; Tsai, Shi-Ming; Zehnder, S M; Sarntinoranont, M; Angelini, T E

    2015-05-14

    Bacterial biofilms are highly structured, surface associated bacteria colonies held together by a cell-generated polymer network known as EPS (extracellular polymeric substance). This polymer network assists in adhesion to surfaces and generates spreading forces as colonies grow over time. In the laboratory and in nature, biofilms often grow at the interface between air and an elastic, semi-permeable nutrient source. As this type of biofilm increases in volume, an accommodating compression of its substrate may arise, potentially driven by the osmotic pressure exerted by the EPS against the substrate surface. Here we study Bacillus subtilis biofilm force generation by measuring the magnitude and rate of deformation imposed by colonies against the agar-nutrient slabs on which they grow. We find that the elastic stress stored in deformed agar is orders of magnitude larger than the drag stress associated with pulling fluid through the agar matrix. The stress exerted by the biofilm is nearly the same as the osmotic pressure generated by the EPS, and mutant colonies incapable of producing EPS exert much lower levels of stress. The fluid flow rate into B. subtilis biofilms suggest that EPS generated pressure provides some metabolic benefit as colonies expand in volume. These results reveal that long-term biofouling and colony expansion may be tied to the hydraulic permeability and elasticity of the surfaces that biofilms colonize. PMID:25797701

  5. Advances in random matrix theory, zeta functions, and sphere packing.

    PubMed

    Hales, T C; Sarnak, P; Pugh, M C

    2000-11-21

    Over four hundred years ago, Sir Walter Raleigh asked his mathematical assistant to find formulas for the number of cannonballs in regularly stacked piles. These investigations aroused the curiosity of the astronomer Johannes Kepler and led to a problem that has gone centuries without a solution: why is the familiar cannonball stack the most efficient arrangement possible? Here we discuss the solution that Hales found in 1998. Almost every part of the 282-page proof relies on long computer verifications. Random matrix theory was developed by physicists to describe the spectra of complex nuclei. In particular, the statistical fluctuations of the eigenvalues ("the energy levels") follow certain universal laws based on symmetry types. We describe these and then discuss the remarkable appearance of these laws for zeros of the Riemann zeta function (which is the generating function for prime numbers and is the last special function from the last century that is not understood today.) Explaining this phenomenon is a central problem. These topics are distinct, so we present them separately with their own introductory remarks. PMID:11058156

  6. Advances in random matrix theory, zeta functions, and sphere packing

    PubMed Central

    Hales, T. C.; Sarnak, P.; Pugh, M. C.

    2000-01-01

    Over four hundred years ago, Sir Walter Raleigh asked his mathematical assistant to find formulas for the number of cannonballs in regularly stacked piles. These investigations aroused the curiosity of the astronomer Johannes Kepler and led to a problem that has gone centuries without a solution: why is the familiar cannonball stack the most efficient arrangement possible? Here we discuss the solution that Hales found in 1998. Almost every part of the 282-page proof relies on long computer verifications. Random matrix theory was developed by physicists to describe the spectra of complex nuclei. In particular, the statistical fluctuations of the eigenvalues (“the energy levels”) follow certain universal laws based on symmetry types. We describe these and then discuss the remarkable appearance of these laws for zeros of the Riemann zeta function (which is the generating function for prime numbers and is the last special function from the last century that is not understood today.) Explaining this phenomenon is a central problem. These topics are distinct, so we present them separately with their own introductory remarks. PMID:11058156

  7. Fabrication of synthetic diffractive elements using advanced matrix laser lithography

    NASA Astrophysics Data System (ADS)

    Škereň, M.; Svoboda, J.; Květoň, M.; Fiala, P.

    2013-02-01

    In this paper we present a matrix laser writing device based on a demagnified projection of a micro-structure from a computer driven spatial light modulator. The device is capable of writing completely aperiodic micro-structures with resolution higher than 200 000 DPI. An optical system is combined with ultra high precision piezoelectric stages with an elementary step ~ 4 nm. The device operates in a normal environment, which significantly decreases the costs compared to competitive technologies. Simultaneously, large areas can be exposed up to 100 cm2. The capabilities of the constructed device will be demonstrated on particular elements fabricated for real applications. The optical document security is the first interesting field, where the synthetic image holograms are often combined with sophisticated aperiodic micro-structures. The proposed technology can easily write simple micro-gratings creating the color and kinetic visual effects, but also the diffractive cryptograms, waveguide couplers, and other structures recently used in the field of optical security. A general beam shaping elements and special photonic micro-structures are another important applications which will be discussed in this paper.

  8. Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix

    NASA Technical Reports Server (NTRS)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor)

    2007-01-01

    The invention provides polymer blends containing polyhydroxyamide and one or more flammable polymers. The polymer blends are flame retardant and have improved durability and heat stability compared to the flammable polymer portion of the blends. Articles containing the polymer blends are also provided.

  9. Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix

    NASA Technical Reports Server (NTRS)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor)

    2011-01-01

    The invention provides polymer blends containing polyhydroxyamide and one or more flammable polymers. The polymer blends are flame retardant and have improved durability and heat stability compared to the flammable polymer portion of the blends. Articles containing the polymer blends are also provided.

  10. Incorporation of Mean Stress Effects into the Micromechanical Analysis of the High Strain Rate Response of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

    2002-01-01

    The results presented here are part of an ongoing research program, to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. A micromechanics approach is employed in this work, in which state variable constitutive equations originally developed for metals have been modified to model the deformation of the polymer matrix, and a strength of materials based micromechanics method is used to predict the effective response of the composite. In the analysis of the inelastic deformation of the polymer matrix, the definitions of the effective stress and effective inelastic strain have been modified in order to account for the effect of hydrostatic stresses, which are significant in polymers. Two representative polymers, a toughened epoxy and a brittle epoxy, are characterized through the use of data from tensile and shear tests across a variety of strain rates. Results computed by using the developed constitutive equations correlate well with data generated via experiments. The procedure used to incorporate the constitutive equations within a micromechanics method is presented, and sample calculations of the deformation response of a composite for various fiber orientations and strain rates are discussed.

  11. A Micromechanical Constitutive Model of Progressive Crushing in Random Carbon Fiber Polymer Matrix Composites

    SciTech Connect

    Lee, H.K.; Simunovic, S.

    1999-09-01

    A micromechanical damage constitutive model is presented to predict the overall elastoplastic behavior and damage evolution in random carbon fiber polymer matrix composites (RFPCs).To estimate the overall elastoplastic damage responses,an effective yield criterion is derived based on the ensemble-volume averaging process and first-order effects of eigenstrains due to the existence of spheroidal (prolate) fibers.The proposed effective yield criterion,to ether with the assumed overall associative plastic flow rule and hardening law, constitutes the analytical foundation for the estimation of effective elastoplastic behavior of ductile matrix composites.First,an effective elastoplastic constitutive dama e model for aligned fiber-reinforced composites is proposed.A micromechanical damage constitutive model for RFPCs is then developed.The average process over all orientations upon overning constitutive field equations and overall yield function for aligned fiber-reinforced composites i s performed to obtain the constitutive relations and effective yield function of RFPCs.The discrete numerical integration algorithms and the continuum tan ent operator are also presented to implement the proposed dama e constitutive model.The dama e constitutive model forms the basis for the pro ressive crushing in composite structures under impact loading.

  12. A micromechanics analysis of the influence of the interface on the performance of polymer-matrix composites

    NASA Technical Reports Server (NTRS)

    Adams, Donald F.

    1986-01-01

    A specially developed two-dimensional finite element micromechanics analysis was used to predict the transverse tensile response of three different carbon fiber-reinforced, polymer matrix unidirectional composites. Experimental data were available for four different fiber sizings. The composites were tested both dry and moisture-conditioned, at room and elevated temperatures. Analytical/experimental correlations are presented and discussed.

  13. A micromechanics analysis of the influence of the interface on the performance of polymer-matrix composites

    NASA Technical Reports Server (NTRS)

    Adams, Donald F.

    1987-01-01

    A specially developed two-dimensional finite element micromechanics analysis was used to predict the transverse tensile response of three different carbon fiber-reinforced, polymer matrix unidirectional composites. Experimental data were available for four different fiber sizings. The composites were tested both dry and moisture-conditioned, at room and elevated temperatures. Analytical/experimental correlations are presented and discussed.

  14. Evaluation of Influence of Various Polymers on Dissolution and Phase Behavior of Carbamazepine-Succinic Acid Cocrystal in Matrix Tablets

    PubMed Central

    Ullah, Majeed; Ullah, Hanif; Murtaza, Ghulam; Mahmood, Qaisar; Hussain, Izhar

    2015-01-01

    The aim of current study was to explore the influence of three commonly used polymers, that is, cellulosics and noncellulosics, for example, Methocel K4M, Kollidon VA/64, and Soluplus, on the phase disproportionation and drug release profile of carbamazepine-succinic acid (CBZ-SUC) cocrystal at varying drug to polymer ratios (1 : 1 to 1 : 0.25) in matrix tablets. The polymorphic phase disproportionation during in-depth dissolution studies of CBZ-SUC cocrystals and its crystalline properties were scrutinized by X-ray powder diffractrometry and Raman spectroscopy. The percent drug release from HPMC formulations (CSH) showed inverse relation with the concentration of polymer; that is, drug release increased with decrease in polymer concentration. On contrary, direct relation was observed between percent drug release and polymer concentrations of Kollidon VA 64/Soluplus (CSK, CSS). At similar polymer concentration, drug release from pure carbamazepine was slightly lower with HPMC formulations than that of cocrystal; however, opposite trend in release rate was observed with Kollidon VA/64 and Soluplus. The significant increase in dissolution rate of cocrystal occurred with Kollidon VA/64 and Soluplus at higher polymer concentration. Moreover, no phase change took place in Methocel and Kollidon formulations. No tablet residue was left for Soluplus formulation so the impact of polymer on cocrystal integrity cannot be predicted. PMID:26380301

  15. Evaluation of Influence of Various Polymers on Dissolution and Phase Behavior of Carbamazepine-Succinic Acid Cocrystal in Matrix Tablets.

    PubMed

    Ullah, Majeed; Ullah, Hanif; Murtaza, Ghulam; Mahmood, Qaisar; Hussain, Izhar

    2015-01-01

    The aim of current study was to explore the influence of three commonly used polymers, that is, cellulosics and noncellulosics, for example, Methocel K4M, Kollidon VA/64, and Soluplus, on the phase disproportionation and drug release profile of carbamazepine-succinic acid (CBZ-SUC) cocrystal at varying drug to polymer ratios (1 : 1 to 1 : 0.25) in matrix tablets. The polymorphic phase disproportionation during in-depth dissolution studies of CBZ-SUC cocrystals and its crystalline properties were scrutinized by X-ray powder diffractrometry and Raman spectroscopy. The percent drug release from HPMC formulations (CSH) showed inverse relation with the concentration of polymer; that is, drug release increased with decrease in polymer concentration. On contrary, direct relation was observed between percent drug release and polymer concentrations of Kollidon VA 64/Soluplus (CSK, CSS). At similar polymer concentration, drug release from pure carbamazepine was slightly lower with HPMC formulations than that of cocrystal; however, opposite trend in release rate was observed with Kollidon VA/64 and Soluplus. The significant increase in dissolution rate of cocrystal occurred with Kollidon VA/64 and Soluplus at higher polymer concentration. Moreover, no phase change took place in Methocel and Kollidon formulations. No tablet residue was left for Soluplus formulation so the impact of polymer on cocrystal integrity cannot be predicted. PMID:26380301

  16. Advanced Proton Conducting Polymer Electrolytes for Electrochemical Capacitors

    NASA Astrophysics Data System (ADS)

    Gao, Han

    Research on solid electrochemical energy storage devices aims to provide high performance, low cost, and safe operation solutions for emerging applications from flexible consumer electronics to microelectronics. Polymer electrolytes, minimizing device sealing and liquid electrolyte leakage, are key enablers for these next-generation technologies. In this thesis, a novel proton-conducing polymer electrolyte system has been developed using heteropolyacids (HPAs) and polyvinyl alcohol for electrochemical capacitors. A thorough understanding of proton conduction mechanisms of HPAs together with the interactions among HPAs, additives, and polymer framework has been developed. Structure and chemical bonding of the electrolytes have been studied extensively to identify and elucidate key attributes affecting the electrolyte properties. Numerical models describing the proton conduction mechanism have been applied to differentiate those attributes. The performance optimization of the polymer electrolytes through additives, polymer structural modifications, and synthesis of alternative HPAs has achieved several important milestones, including: (a) high proton mobility and proton density; (b) good ion accessibility at electrode/electrolyte interface; (c) wide electrochemical stability window; and (d) good environmental stability. Specifically, high proton mobility has been addressed by cross-linking the polymer framework to improve the water storage capability at normal-to-high humidity conditions (e.g. 50-80% RH) as well as by incorporating nano-fillers to enhance the water retention at normal humidity levels (e.g. 30-60% RH). High proton density has been reached by utilizing additional proton donors (i.e. acidic plasticizers) and by developing different HPAs. Good ion accessibility has been achieved through addition of plasticizers. Electrochemical stability window of the electrolyte system has also been investigated and expanded by utilizing HPAs with different heteroatoms

  17. On crack initiation in notched, cross-plied polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Yang, Q. D.; Schesser, D.; Niess, M.; Wright, P.; Mavrogordato, M. N.; Sinclair, I.; Spearing, S. M.; Cox, B. N.

    2015-05-01

    The physics of crack initiation in a polymer matrix composite are investigated by varying the modeling choices made in simulations and comparing the resulting predictions with high-resolution in situ images of cracks. Experimental data were acquired using synchrotron-radiation computed tomography (SRCT) at a resolution on the order of 1 μm, which provides detailed measurement of the location, shape, and size of small cracks, as well as the crack opening and shear displacements. These data prove sufficient to discriminate among competing physical descriptions of crack initiation. Simulations are executed with a high-fidelity formulation, the augmented finite element method (A-FEM), which permits consideration of coupled damage mechanisms, including both discrete cracks and fine-scale continuum damage. The discrete cracks are assumed to be nonlinear fracture events, governed by reasonably general mixed-mode cohesive laws. Crack initiation is described in terms of strength parameters within the cohesive laws, so that the cohesive law provides a unified model for crack initiation and growth. Whereas the cracks investigated are typically 1 mm or less in length, the fine-scale continuum damage refers to irreversible matrix deformation occurring over gauge lengths extending down to the fiber diameter (0.007 mm). We find that the location and far-field stress for crack initiation are predicted accurately only if the variations of local stress within plies and in the presence of stress concentrators (notches, etc.) are explicitly computed and used in initiation criteria; stress redistribution due to matrix nonlinearity that occurs prior to crack initiation is accounted for; and a mixed-mode criterion is used for crack initiation. If these factors are not all considered, which is the case for commonly used failure criteria, predictions of the location and far-field stress for initiation are not accurate.

  18. Do Membranes Dream of Electric Tubes? Advanced Membranes Using Carbon Nanotube - Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    de Lannoy, Charles-Francois Pedro Claude Karolek Ghislain

    Membrane technologies represent an energy efficient, effective solution for treating municipal and commercial waters/wastewaters. Membranes are predominantly polymer-based and despite steady advances in polymeric materials, they continue to suffer from operational problems including biofouling and breakages. This work addresses these two disparate problems by developing novel CNT-polymer nanocomposite materials that contain variously functionalized carbon nanotubes (fCNTs) in low quantities (<0.5wt%). Several strategies have been employed to achieve highly functional CNT-polymer nanocomposite membranes including blend mixing, ionic charge association, and covalent cross-linking with monomer and oligomer constituents. These CNT-polymer nanocomposite membranes were compared to traditional polymer membranes across various properties including increased Young's Modulus, changes in surface hydrophilicity, fine control over molecular weight cut-off and flux, and surface electrical conductivity. Membranes with high surface electrical conductivity were further tested for their anti-biofouling properties. Finally, CNT stability and polymer compatibility were evaluated throughout membrane manufacture, use, and cleaning. The incorporation of CNTs mixed in bulk phase and linked through ionic associations in polymer matrices showed significant (50%) increases in Young's modulus for certain CNT functionalizations and derivatization percent. Membranes formed with high surface electrical conductivity demonstrated almost complete resistance to biofouling (> 95%) in long-term bacterially challenged experiments. CNTs and polymer mixtures that lacked covalent or ionic bonds were susceptible to significant (up to 10%) loss of CNTs during membrane non-solvent gelation and aggressive chemical cleaning treatment. Functionalized carbon nanotubes endow polymer membranes with their unique strength and electrically conductive properties. These added properties were demonstrated to greatly

  19. Recent advances in the chemical modification of unsaturated polymers

    NASA Technical Reports Server (NTRS)

    Schulz, D. N.; Turner, S. R.; Golub, M. A.

    1982-01-01

    The present discussion has the objective to update the most comprehensive reviews on the considered subject and to fill in the gaps of less complete, but more modern treatments. Only simple chemical functionalization or structural modification of unsaturated polymers are covered, and the literature of diene polymer modification since 1974 is emphasized. Attention is given to hydrogenation, halogenation and hydrohalogenation, cyclization, cis-trans isomerization, epoxidation, ene and other cycloaddition reactions, sulfonation, carboxylation, phosphonylation, sulfenyl chloride addition, carbene addition, metalation, and silylation. It is pointed out that modern synthetic reagents and catalysts have been advantageously employed to improve process and/or product quality. Synthetic techniques have been refined to allow the selective modification of specific polymer microstructures or blocks.

  20. Nanometer-sized extracellular matrix coating on polymer-based scaffold for tissue engineering applications.

    PubMed

    Uchida, Noriyuki; Sivaraman, Srikanth; Amoroso, Nicholas J; Wagner, William R; Nishiguchi, Akihiro; Matsusaki, Michiya; Akashi, Mitsuru; Nagatomi, Jiro

    2016-01-01

    Surface modification can play a crucial role in enhancing cell adhesion to synthetic polymer-based scaffolds in tissue engineering applications. Here, we report a novel approach for layer-by-layer (LbL) fabrication of nanometer-size fibronectin and gelatin (FN-G) layers on electrospun fibrous poly(carbonate urethane)urea (PCUU) scaffolds. Alternate immersions into the solutions of fibronectin and gelatin provided thickness-controlled FN-G nano-layers (PCUU(FN-G) ) which maintained the scaffold's 3D structure and width of fibrous bundle of PCUU as evidenced by scanning electron miscroscopy. The PCUU(FN-G) scaffold improved cell adhesion and proliferation of bladder smooth muscles (BSMCs) when compared to uncoated PCUU. The high affinity of PCUU(FN-G) for cells was further demonstrated by migration of adherent BSMCs from culture plates to the scaffold. Moreover, the culture of UROtsa cells, human urothelium-derived cell line, on PCUU(FN-G) resulted in an 11-15 μm thick multilayered cell structure with cell-to-cell contacts although many UROtsa cells died without forming cell connections on PCUU. Together these results indicate that this approach will aid in advancing the technology for engineering bladder tissues in vitro. Because FN-G nano-layers formation is based on nonspecific physical adsorption of fibronectin onto polymer and its subsequent interactions with gelatin, this technique may be applicable to other polymer-based scaffold systems for various tissue engineering/regenerative medicine applications. PMID:26194176

  1. Manufacturing Aspects of Advanced Polymer Composites for Automotive Applications

    NASA Astrophysics Data System (ADS)

    Friedrich, Klaus; Almajid, Abdulhakim A.

    2013-04-01

    Composite materials, in most cases fiber reinforced polymers, are nowadays used in many applications in which light weight and high specific modulus and strength are critical issues. The constituents of these materials and their special advantages relative to traditional materials are described in this paper. Further details are outlined regarding the present markets of polymer composites in Europe, and their special application in the automotive industry. In particular, the manufacturing of parts from thermoplastic as well as thermosetting, short and continuous fiber reinforced composites is emphasized.

  2. Thermoplastic polymer patterning without residual layer by advanced nanoimprinting schemes

    NASA Astrophysics Data System (ADS)

    Park, Hyunsoo; Cheng, Xing

    2009-06-01

    Nanoimprinting is a fast-growing technique for nanoscale patterning. One of the remaining issues in nanoimprinting is the removal of the residual layer after nanoimprinting. Traditionally the residual layer is removed by an oxygen reactive-ion etching (RIE) step. The need for a vacuum environment and dedicated equipment in this step lowers the throughput and increases the cost of the nanoimprinting process. It also prevents the possibility of patterning isolated functional polymers because oxygen RIE destroys the functional materials. In this work, novel nanoimprinting schemes are developed to nondestructively remove the residual layer in thermal nanoimprinting by solvent developing and dewetting. Combined with a transfer-bonding technique, three-dimensional polymer scaffolds are achieved. The techniques developed here eliminate the RIE step in thermal nanoimprinting and are compatible with roller nanoimprinting for large-scale patterning of polymer micro- or nanostructures. The technique also opens up new applications for nanoimprinting in patterning isolated conjugated polymers for organic electronic devices and circuits.

  3. Thermoplastic polymer patterning without residual layer by advanced nanoimprinting schemes.

    PubMed

    Park, Hyunsoo; Cheng, Xing

    2009-06-17

    Nanoimprinting is a fast-growing technique for nanoscale patterning. One of the remaining issues in nanoimprinting is the removal of the residual layer after nanoimprinting. Traditionally the residual layer is removed by an oxygen reactive-ion etching (RIE) step. The need for a vacuum environment and dedicated equipment in this step lowers the throughput and increases the cost of the nanoimprinting process. It also prevents the possibility of patterning isolated functional polymers because oxygen RIE destroys the functional materials. In this work, novel nanoimprinting schemes are developed to nondestructively remove the residual layer in thermal nanoimprinting by solvent developing and dewetting. Combined with a transfer-bonding technique, three-dimensional polymer scaffolds are achieved. The techniques developed here eliminate the RIE step in thermal nanoimprinting and are compatible with roller nanoimprinting for large-scale patterning of polymer micro- or nanostructures. The technique also opens up new applications for nanoimprinting in patterning isolated conjugated polymers for organic electronic devices and circuits. PMID:19468173

  4. Aromatic/aliphatic diamine derivatives for advanced compositions and polymers

    NASA Technical Reports Server (NTRS)

    Delozier, Donovan M. (Inventor); Watson, Kent A. (Inventor); Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor)

    2010-01-01

    Novel compositions of matter comprise certain derivatives of 9,9-dialkyl fluorene diamine (AFDA). The resultant compositions, whether compositions of matter or monomers that are subsequently incorporated into a polymer, are unique and useful in a variety of applications. Useful applications of AFDA-based material include heavy ion radiation shielding components and components of optical and electronic devices.

  5. A Polymer-Extracellular Matrix Composite with Improved Thromboresistance and Recellularization Properties

    PubMed Central

    Jiang, Bin; Akgun, Berke; Lam, Ryan C.; Ameer, Guillermo A.; Wertheim, Jason A.

    2015-01-01

    Organ engineering using decellularized scaffolds is a potential long-term solution to donor organ shortage. However, this technology is severely limited by small vessel thrombosis due to incompletely recellularized vessels, resulting in exposure of extracellular matrix (ECM) components to platelets and clotting factors in flowing blood. To address this limitation, we designed a polymer-ECM composite and demonstrated its potential to reduce thrombosis and facilitate re-endothelialization in a vascular graft model. Rat aortas were decellularized using a sequential combination of weak detergents followed by a nuclease treatment that resulted in 96.5±1.3% DNA removal, while ECM components and mechanical properties were well maintained. A biodegradable and biocompatible elastomer poly (1,8 octanediol citrate) (POC, 1wt%) was infused throughout the ECM at mild conditions (37°C and 45°C) and was functionalized with heparin using carbodiimide chemistry. The polymer-ECM composite significantly reduced platelet adhesion (67.4±8.2% and 82.7±9.6% reduction relative to untreated ECM using one of two processing temperatures, 37°C or 45°C, respectively); inhibited whole blood clotting (85.9±4.3% and 87.0±11.9% reduction relative to untreated ECM at 37°C or 45°C processing temperature, respectively); and supported endothelial cell—and to a lesser extent smooth muscle cell—adhesion in vitro. Taken together, this novel POC composite may provide a solution for thrombosis of small vessel conduits commonly seen in decellularized scaffolds used in tissue engineering applications. PMID:25712388

  6. Recent advances in metathesis-derived polymers containing transition metals in the side chain.

    PubMed

    Dragutan, Ileana; Dragutan, Valerian; Simionescu, Bogdan C; Demonceau, Albert; Fischer, Helmut

    2015-01-01

    This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  7. Recent advances in metathesis-derived polymers containing transition metals in the side chain

    PubMed Central

    Demonceau, Albert; Fischer, Helmut

    2015-01-01

    Summary This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  8. Polymer/Graphene Hybrids for Advanced Energy-Conversion and -Storage Materials.

    PubMed

    Cui, Linfan; Gao, Jian; Xu, Tong; Zhao, Yang; Qu, Liangti

    2016-04-20

    Polymer/graphene-based materials with interesting physical and chemical properties have been attracting considerable attention and have been shown to have great potential as active materials in the field of energy conversion and storage. In this review, we focus on recent significant advances in the fabrication and application of polymer/graphene hybrids as electrocatalysts and electrode materials. Synthetic strategies and application of these materials in energy conversion and storage are presented, particularly in devices such as fuel cells, actuators, and supercapacitors, accompanied with a discussion of the challenges and research directions necessary for the future development of polymer/graphene hybrids. PMID:26878997

  9. Advanced Composites: Mechanical Properties and Hardware Programs for Selected Resin Matrix Materials. [considering space shuttle applications

    NASA Technical Reports Server (NTRS)

    Welhart, E. K.

    1976-01-01

    This design note presents typical mechanical properties tabulated from industrial and governmental agencies' test programs. All data are correlated to specific products and all of the best known products are presented. The data include six epoxies, eight polyimides and one polyquinoxaline matrix material. Bron and graphite are the fiber reinforcements. Included are forty-two summaries of advanced (resin matrix) composite programs in existence in the United States. It is concluded that the selection of appropriate matrices, the geometric manner in which the fibers are incorporated in the matrix and the durability of the bond between fiber and matrix establish the end properties of the composite material and the performance of the fabricated structure.

  10. Smart Materials for Advanced Applications: Self-Decontaminating Polymers, Photofunctional Composites, and Electroconductive Fibers

    NASA Astrophysics Data System (ADS)

    Little, Brian Kevin

    2011-12-01

    Materials capable of providing multifunctional properties controllable by some external stimulus (pH, light, temperature, etc) are highly desirable and obtainable given recent advancements in material science. Development of these so called "Smart" materials spanned across many disciplines of science with applications in industrial areas such as medical, military, security, and environmental. Furthermore, next-generation materials require the ability to not only sense/respond to changes in their external/internal environment, but process information in regards to these changes and adapt accordingly in a dynamic fashion, autonomously, so called "Intelligent" materials. Findings reported in this manuscript detail the synthesis, characterization, and application of smart materials in the following three areas: (1) self-cleaning polymers (2) photoresponsive composites and (3) electroconductive fibers. Self-Cleaning Polymers: Self-decontaminating polymers are unique materials capable of degrading toxic organic chemicals (TOCs). Barriers composed of or coated with our photochemical reactive polymer matrix could be applied to multiple surfaces for defense against TOCs; for example, military garments for protection against chemical warfare agents. This study investigates conditions necessary for formation of peroxides via O2 reduction induced by long-lived, strongly reducing benzophenyl ketyl (BPK) polymer radicals. Photolysis of aqueous solutions composed of sulphonated poly(ether etherketone), SPEEK, and poly(vinyl alcohol), PVA lead to the formation of the BPK radicals. Experiments investigate the formation and decomposition of peroxides in aqueous solutions of SPEEK/PVA under photolysis. Photofunctional Composites: Photoresponsive nanoporous (PN) films and powders were studied and evaluated as possible additives to sensitize the initiation of CH3NO2 via a mechanism involving coalescence of reaction sites. Such materials consist of a 3-D mesoporous silica framework

  11. Density matrix renormalization group studies of the effect of constraint release on the viscosity of polymer melts

    NASA Astrophysics Data System (ADS)

    Paeßens, Matthias; Schütz, Gunter M.

    2002-08-01

    The scaling of the viscosity of polymer melts is investigated with regard to the molecular weight. We present a generalization of the Rubinstein-Duke model, which takes constraint releases into account and calculates the effects on the viscosity by the use of the density matrix renormalization group algorithm. Using input from Rouse theory, the rates for the constraint releases are determined in a self-consistent way. We conclude that shape fluctuations of the tube caused by constraint release are not a likely candidate for improving Doi's crossover theory for the scaling of the polymer viscosity.

  12. Silk-elastin-like protein polymer matrix for intraoperative delivery of an oncolytic vaccinia virus

    PubMed Central

    Price, Daniel L.; Li, Pingdong; Chen, Chun-Hao; Wong, Danni; Yu, Zhenkun; Chen, Nanhai G.; Yu, Yong A.; Szalay, Aladar A.; Cappello, Joseph; Fong, Yuman; Wong, Richard J.

    2016-01-01

    Background Oncolytic viral efficacy may be limited by the penetration of the virus into tumors. This may be enhanced by intraoperative application of virus immediately after surgical resection. Methods Oncolytic vaccinia virus GLV-1h68 was delivered in silk-elastin-like protein polymer (SELP) in vitro and in vivo in anaplastic thyroid carcinoma cell line 8505c in nude mice. Results GLV-1h68 in SELP infected and lysed anaplastic thyroid cancer cells in vitro equally as effectively as in phosphate-buffered saline (PBS), and at 1 week retains a thousand fold greater infectious plaque-forming units. In surgical resection models of residual tumor, GLV-1h68 in SELP improves tumor control and shows increased viral β-galactosidase expression as compared to PBS. Conclusion The use of SELP matrix for intraoperative oncolytic viral delivery protects infectious viral particles from degradation, facilitates sustained viral delivery and transgene expression, and improves tumor control. Such optimization of methods of oncolytic viral delivery may enhance therapeutic outcomes. PMID:25244076

  13. Applications of multifunctional polymer-matrix composites in hybrid heat sinks

    NASA Astrophysics Data System (ADS)

    Leung, Siu N.; Khan, Omer M.; Naguib, Hani E.; Dawson, Francis; Adinkrah, Vincent

    2012-04-01

    Designers of electronic devices and telecommunications equipment have used three-dimensional chip architecture, comprised of a vertically integrated stack of chips, to increase the number of transistors on integrated circuits. These latest chips generate excessive amount of heat, and thus can reach unacceptably high temperatures. In this context, this research aims to develop thermally conductive liquid crystal polymer (LCP)/hexagonal boron nitride (hBN) composite films to replace the traditionally-used Kapton films that satisfy the electrical insulation requirements for the attachment of heat sinks to the chips without compromising the heat dissipation performance. Parametric study was conducted to elucidate the effects of hBN contents on the heat dissipation ability of the composite. The performance of the hybrid heat sinks were experimentally simulated by measuring the temperature distribution of the hybrid heat sinks attached to a 10 W square-faced (i.e., 10 cm by 10 cm) heater. Experimental simulation show that the maximum temperature of the heater mounted with a hybrid heat sink reduced with increased hBN content. It is believed the fibrillation of LCP matrix leads to highly ordered structure, promoting heat dissipation ability of the electrically insulating pad of the hybrid heat sink.

  14. Matrix Reorganization during Uniaxial Drawing of Polymer Single Crystal-Based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Laird, Eric D.; Lenhart, Joseph L.; Strawhecker, Kenneth E.; Bain, Erich D.; Knorr, Daniel B.

    Ultra-high molecular weight polyethylene (UHMWPE) was nonisothermally recrystallized from dilute solution. In this way, the natively entangled UHMWPE powders could be disentangled in a suspension of polymer single crystal (PSC) lamellae. Nanofillers with one or more length scales on the order of the PSC thickness were then mixed in and cosedimented along with these PSCs. After drying out the consolidated wet crystal/filler mixture, the resulting composite could be described as an anisotropic PSC matrix with nanomaterials confined to the interlamellar galleries. Graphene nanoflakes, surface-modified silica nanoparticles, and poly(ethylene oxide) PSCs were all successfully incorporated into UHMWPE mats. It was found that, under certain conditions, the mats could be ultradrawn to draw ratios of 150 or higher, with increasing filler content leading to greater variability in the ultimate draw ratio. The draw behavior was found to be strongly influenced by network shear modulus. AFM modulus maps revealed how the filler materials influenced the organization of filaments in the ultradrawn tapes. These tapes showed excellent mechanical properties, with composites frequently outperforming their neat UHMWPE counterparts in several important categories.

  15. Mechanics of aligned carbon nanotube polymer matrix nanocomposites simulated via stochastic three-dimensional morphology

    NASA Astrophysics Data System (ADS)

    Stein, Itai Y.; Wardle, Brian L.

    2016-01-01

    The promise of enhanced and tailored properties motivates the study of one-dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While CNTs have remarkable theoretical properties, previous work on aligned CNT polymer matrix nanocomposites (A-PNCs) reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs, because the CNTs that comprise the A-PNCs have significant local curvature commonly referred to as waviness. Here we present a simulation framework capable of analyzing 105 wavy CNTs with realistic three-dimensional morphologies to quantify the impact of waviness on the effective elastic modulus contribution of wavy CNTs. The simulation results show that due to the low shear modulus of the reinforcing CNT ‘fibers’, and large (\\gt 50%) compliance contribution of the shear deformation mode, waviness reduces the effective stiffness contribution of the A-CNTs by two to three orders of magnitude. Also, the mechanical property predictions resulting from the simulation framework outperform those previously reported using finite element analysis since representative descriptions of the morphology are required to accurately predict properties of the A-PNCs. Further work to quantify the morphology of A-PNCs in three-dimensions, simulate their full non-isotropic constitutive relations, and predict their failure mechanisms is planned.

  16. Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    1999-01-01

    Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

  17. Reconfigurable optical interleaver modules with tunable wavelength transfer matrix function using polymer photonics lightwave circuits.

    PubMed

    Chen, Changming; Niu, Xiaoyan; Han, Chao; Shi, Zuosen; Wang, Xinbin; Sun, Xiaoqiang; Wang, Fei; Cui, Zhanchen; Zhang, Daming

    2014-08-25

    A transparent reconfigurable optical interleaver module composed of cascaded AWGs-based wavelength-channel-selector/interleaver monolithically integrated with multimode interference (MMI) variable optical attenuators (VOAs) and Mach-Zehnder interferometer (MZI) switch arrays was designed and fabricated using polymer photonic lightwave circuits. Highly fluorinated photopolymer and grafting modified organic-inorganic hybrid material were synthesized as the waveguide core and caldding, respectively. Thermo-optic (TO) tunable wavelength transfer matrix (WTM) function of the module can be achieved for optical routing network. The one-chip transmission loss is ~ 6 dB and crosstalk is less than ~25 dB for transverse-magnetic (TM) mode. The crosstalk and extinction ratio of the MMI VOAs were measured as -15.2 dB and 17.5 dB with driving current 8 mA, respectively. The modulation depth of the TO switches is obtained as ~18.2 dB with 2.2 V bias. Proposed novel interleaver module could be well suited for DWDM optical communication systems. PMID:25321200

  18. A Damage Resistance Comparison Between Candidate Polymer Matrix Composite Feedline Materials

    NASA Technical Reports Server (NTRS)

    Nettles, A. T

    2000-01-01

    As part of NASAs focused technology programs for future reusable launch vehicles, a task is underway to study the feasibility of using the polymer matrix composite feedlines instead of metal ones on propulsion systems. This is desirable to reduce weight and manufacturing costs. The task consists of comparing several prototype composite feedlines made by various methods. These methods are electron-beam curing, standard hand lay-up and autoclave cure, solvent assisted resin transfer molding, and thermoplastic tape laying. One of the critical technology drivers for composite components is resistance to foreign objects damage. This paper presents results of an experimental study of the damage resistance of the candidate materials that the prototype feedlines are manufactured from. The materials examined all have a 5-harness weave of IM7 as the fiber constituent (except for the thermoplastic, which is unidirectional tape laid up in a bidirectional configuration). The resin tested were 977-6, PR 520, SE-SA-1, RS-E3 (e-beam curable), Cycom 823 and PEEK. The results showed that the 977-6 and PEEK were the most damage resistant in all tested cases.

  19. Mechanics of aligned carbon nanotube polymer matrix nanocomposites simulated via stochastic three-dimensional morphology.

    PubMed

    Stein, Itai Y; Wardle, Brian L

    2016-01-22

    The promise of enhanced and tailored properties motivates the study of one-dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While CNTs have remarkable theoretical properties, previous work on aligned CNT polymer matrix nanocomposites (A-PNCs) reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs, because the CNTs that comprise the A-PNCs have significant local curvature commonly referred to as waviness. Here we present a simulation framework capable of analyzing 10(5) wavy CNTs with realistic three-dimensional morphologies to quantify the impact of waviness on the effective elastic modulus contribution of wavy CNTs. The simulation results show that due to the low shear modulus of the reinforcing CNT 'fibers', and large ([Formula: see text]) compliance contribution of the shear deformation mode, waviness reduces the effective stiffness contribution of the A-CNTs by two to three orders of magnitude. Also, the mechanical property predictions resulting from the simulation framework outperform those previously reported using finite element analysis since representative descriptions of the morphology are required to accurately predict properties of the A-PNCs. Further work to quantify the morphology of A-PNCs in three-dimensions, simulate their full non-isotropic constitutive relations, and predict their failure mechanisms is planned. PMID:26636342

  20. A Limited Comparison of the Thermal Durability of Polyimide Candidate Matrix Polymers with PMR-15

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Papadopoulos, Demetrios S.; Scheiman, Daniel A.; Inghram, Linda L.; McCorkle, Linda S.; Klans, Ojars V.

    2003-01-01

    Studies were conducted with six different candidate high-temperature neat matrix resin specimens of varied geometric shapes to investigate the mechanisms involved in the thermal degradation of polyimides like PMR-15. The metrics for assessing the quality of these candidates were chosen to be glass transition temperature (T(sub g)), thermo-oxidative stability, dynamic mechanical properties, microstructural changes, and dimensional stability. The processing and mechanical properties were not investigated in the study reported herein. The dimensional changes and surface layer growth were measured and recorded. The data were in agreement with earlier published data. An initial weight increase reaction was observed to be dominating at the lower temperatures. However, at the more elevated temperatures, the weight loss reactions were prevalent and probably masked the weight gain reaction. These data confirmed the findings of the existence of an initial weight gain reaction previously reported. Surface- and core-dependent weight losses were shown to control the polymer degradation at the higher temperatures.

  1. A stable silicon anode based on the uniform dispersion of quantum dots in a polymer matrix

    NASA Astrophysics Data System (ADS)

    Zhong, Lanlan; Guo, Juchen; Mangolini, Lorenzo

    2015-01-01

    We propose a novel approach to the fabrication of silicon-containing anodes for lithium-ion batteries. Our approach is based on a liquid dispersion comprising of silicon quantum dots, carbon nanotubes and polyvinylpirrolidone (PVP) as a polymer additive. Coating of this dispersion onto copper foil followed by annealing in inert atmosphere allows the realization of a structure with good electrical conductivity, high specific surface area and with a carbon-based coating preventing the direct contact between the silicon particles and the electrolyte. This structure maintains a specific charge capacity of approximately 1000 mAh g-1 for 200 cycles and reaches a coulombic efficiency of 99.8%. The addition of PVP is a simple and scalable way of realizing, after annealing, a carbon-based matrix which surrounds the silicon particles and which greatly enhances the stability of the battery. The proposed process is based on commercially available carbon nanotubes, on silicon quantum dots which are produced using a scalable plasma-enhanced chemical vapour deposition technique, and is compatible with large area coating and processing techniques. The fabrication protocol described in this contribution represents a step towards the successful commercial utilization of silicon-based nanomaterials for energy storage applications.

  2. Development of new and improved polymer matrix resin systems, phase 1

    NASA Technical Reports Server (NTRS)

    Hsu, M. S.

    1983-01-01

    Vinystilbazole (vinylstryrylpyridine) and vinylpolystyrulpyridine were prepared for the purpose of modifying bismaleimide composite resins. Cure studies of resins systems were investigated by differential scanning calorimetry. The vinylstyrylpyridine-modified bismaleimide composite resins were found to have lower cure and gel temperatures, and shorter cure times than the corresponding unmodified composite resins. The resin systems were reinforced with commercially avialable satin-weave carbon cloth. Prepregs were fabricated by solvent or hot melt techniques. Thermal stability, flammability, moisture absorption, and mechanical properties of the composites (such as flexural strength, modulus, tensile and short beam shear strength) were determined. Composite laminates showed substantial improvements in both processability and mechanical properties compared to he bismaleimide control systems. The vinylstyrylpyridine modified bismaleimide resins can be used as advanced matrix resins for graphite secondary structures where ease of processing, fireworthiness, and high temperature stability are required for aerospace applications.

  3. A micro to macro approach to polymer matrix composites damage modeling : final LDRD report.

    SciTech Connect

    English, Shawn Allen; Brown, Arthur A.; Briggs, Timothy M.

    2013-12-01

    Capabilities are developed, verified and validated to generate constitutive responses using material and geometric measurements with representative volume elements (RVE). The geometrically accurate RVEs are used for determining elastic properties and damage initiation and propagation analysis. Finite element modeling of the meso-structure over the distribution of characterizing measurements is automated and various boundary conditions are applied. Plain and harness weave composites are investigated. Continuum yarn damage, softening behavior and an elastic-plastic matrix are combined with known materials and geometries in order to estimate the macroscopic response as characterized by a set of orthotropic material parameters. Damage mechanics and coupling effects are investigated and macroscopic material models are demonstrated and discussed. Prediction of the elastic, damage, and failure behavior of woven composites will aid in macroscopic constitutive characterization for modeling and optimizing advanced composite systems.

  4. Visualization of subsurface nanoparticles in a polymer matrix using resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy.

    PubMed

    Kimura, Kuniko; Kobayashi, Kei; Yao, Atsushi; Yamada, Hirofumi

    2016-10-14

    A visualization technique of subsurface features with a nanometer-scale spatial resolution is strongly demanded. Some research groups have demonstrated the visualization of subsurface features using various techniques based on atomic force microscopy. However, the imaging mechanisms have not yet been fully understood. In this study, we demonstrated the visualization of subsurface Au nanoparticles buried in a polymer matrix 900 nm from the surface using two techniques; i.e., resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy. It was clarified that the subsurface features were visualized by the two techniques as the area with a higher contact resonance frequency and a higher Q-factor than those in the surrounding area, which suggests that the visualization is realized by the variation of the contact stiffness and damping of the polymer matrix due to the existence of the buried nanoparticles. PMID:27607548

  5. Microgravity polymer and crystal growth at the Advanced Materials Center for the Commercial Development of Space

    NASA Technical Reports Server (NTRS)

    Mccauley, Lisa A.

    1990-01-01

    The microgravity research programs currently conducted by the Advanced Materials Center for the Commercial Development of Space (CCDS) are briefly reviewed. Polymer processing in space, which constitutes the most active microgravity program at the Advanced Materials CCDS, is conducted in three areas: membrane processing, multiphase composite behavior, and plasma polymerization. Current work in microgravity crystal growth is discussed with particular reference to the development of the Zeolite Crystal Growth facility.

  6. Effect of monomer composition of polymer matrix on flexural properties of glass fibre-reinforced orthodontic archwire.

    PubMed

    Ohtonen, J; Vallittu, P K; Lassila, L V J

    2013-02-01

    To compare force levels obtained from glass fibre-reinforced composite (FRC) archwires. Specifically, FRC wires were compared with polymer matrices having different dimethacrylate monomer compositions. FRC material (E-glass provided by Stick Tech Ltd, Turku, Finland) with continuous unidirectional glass fibres and four different types of dimethacrylate monomer compositions for the resin matrix were tested. Cross-sectionally round FRC archwires fitting into the 0.3 mm slot of a bracket were divided into 16 groups with six specimens in each group. Glass fibres were impregnated by the manufacturer, and they were initially light-cured by hand light-curing unit or additionally post-cured in light-curing oven. The FRC archwire specimens were tested at 37°C according to a three-point bending test in dry and wet conditions using a span length of 10 mm and a crosshead speed of 1.0 mm/minute. The wires were loaded until final failure. The data were statistically analysed using analysis of variance (ANOVA). The dry FRC archwire specimens revealed higher load values than water stored ones, regardless of the polymer matrix. A majority of the FRC archwires showed higher load values after being post-cured. ANOVA revealed that the polymer matrix, curing method, and water storage had a significant effect (P < 0.05) on the flexural behaviour of the FRC archwire. Polymer matrix composition, curing method, and water storage affected the flexural properties and thus, force level and working range which could be obtained from the FRC archwire. PMID:22058110

  7. Recent Advances in Thermoplastic Puncture-Healing Polymers

    NASA Technical Reports Server (NTRS)

    Gordon, K. L.; Working, D. C.; Wise, K. E.; Bogert, P. B.; Britton, S. M.; Topping, C.C.; Smith, J. Y.; Siochi, E. J.

    2009-01-01

    Self-healing materials provide a route for enhanced damage tolerance in materials for aerospace applications. In particular, puncture-healing upon impact has the potential to mitigate significant damage caused by high velocity micrometeoroid impacts. This type of material also has the potential to improve damage tolerance in load bearing structures to enhance vehicle health and aircraft durability. The materials being studied are those capable of instantaneous puncture healing, providing a mechanism for mechanical property retention in lightweight structures. These systems have demonstrated healing capability following penetration of fast moving projectiles -- velocities that range from 9 mm bullets shot from a gun (approx.330 m/sec) to close to micrometeoroid debris velocities of 4800 m/sec. In this presentation, we report on a suite of polymeric materials possessing this characteristic. Figure 1 illustrates the puncture healing concept. Puncture healing in these materials is dependent upon how the combination of a polymer's viscoelastic properties responds to the energy input resulting from the puncture event. Projectile penetration increases the temperature in the vicinity of the impact. Self-healing behavior occurs following puncture, whereby energy must be transferred to the material during impact both elastically and inelastically, thus establishing two requirements for puncture healing to occur: a.) The need for the puncture event to produce a local melt state in the polymer material and b.) The molten material has to have sufficient melt elasticity to snap back and close the hole. 1,2 Previous ballistic testing studies revealed that Surlyn materials warmed up to a temperature approx.98 C during projectile puncture (3 C higher than it s melting temperature). 1,2 The temperature increase produces a localized flow state and the melt elasticity to snap back thus sealing the hole. Table 1 lists the commercially polymers studied here, together with their physical

  8. Synergistic Effects of Physical Aging and Damage on Long-Term Behavior of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Brinson, L. Cate

    1999-01-01

    The research consisted of two major parts, first modeling and simulation of the combined effects of aging and damage on polymer composites and secondly an experimental phase examining composite response at elevated temperatures, again activating both aging and damage. For the simulation, a damage model for polymeric composite laminates operating at elevated temperatures was developed. Viscoelastic behavior of the material is accounted for via the correspondence principle and a variational approach is adopted to compute the temporal stresses within the laminate. Also, the effect of physical aging on ply level stress and on overall laminate behavior is included. An important feature of the model is that damage evolution predictions for viscoelastic laminates can be made. This allows us to track the mechanical response of the laminate up to large load levels though within the confines of linear viscoelastic constitutive behavior. An experimental investigation of microcracking and physical aging effects in polymer matrix composites was also pursued. The goal of the study was to assess the impact of aging on damage accumulation, in ten-ns of microcracking, and the impact of damage on aging and viscoelastic behavior. The testing was performed both at room and elevated temperatures on [+/- 45/903](sub s) and [02/903](sub s) laminates, both containing a set of 90 deg plies centrally located to facilitate investigation of microcracking. Edge replication and X-ray-radiography were utilized to quantify damage. Sequenced creep tests were performed to characterize viscoelastic and aging parameters. Results indicate that while the aging times studied have limited ]Influence on damage evolution, elevated temperature and viscoelastic effects have a profound effect on the damage mode seen. Some results are counterintuitive, including the lower strain to failure for elevated temperature tests and the catastrophic failure mode observed for the [+/- 45/9O3](sub s), specimens. The

  9. Fast photochromism in polymer matrix with plasticizer and real-time dynamic holographic properties

    NASA Astrophysics Data System (ADS)

    Ishii, Norihito; Abe, Jiro

    2013-04-01

    We have developed a photochromic polymer film for the use of real-time dynamic hologram, fabricated by the plasticized polymer doped with the fast photochromic molecule. The addition of a plasticizer into the conventional polymer is proved to be effective to improve the photochromic performances for the polymer film doped with the fast photochromic molecule that shows instantaneous coloration upon exposure to UV light and rapid fading in the dark. The plasticized photochromic polymers enable the real-time control of the writing and erasing of a holographic grating and show a higher recording sensitivity compared with other organic holographic materials.

  10. Evaluation of a molecularly imprinted polymer for determination of steroids in goat milk by matrix solid phase dispersion.

    PubMed

    Gañán, Judith; Morante-Zarcero, Sonia; Gallego-Picó, Alejandrina; Garcinuño, Rosa María; Fernández-Hernando, Pilar; Sierra, Isabel

    2014-08-01

    A molecularly imprinted polymer-matrix solid-phase dispersion methodology for simultaneous determination of five steroids in goat milk samples was proposed. Factors affecting the extraction recovery such as sample/dispersant ratio and washing and elution solvents were investigated. The molecularly imprinted polymer used as dispersant in the matrix solid-phase dispersion procedure showed high affinity to steroids, and the obtained extracts were sufficiently cleaned to be directly analyzed. Analytical separation was performed by micellar electrokinetic chromatography using a capillary electrophoresis system equipped with a diode array detector. A background electrolyte composed of borate buffer (25mM, pH 9.3), sodium dodecyl sulfate (10mM) and acetonitrile (20%) was used. The developed MIP-MSPD methodology was applied for direct determination of testosterone (T), estrone (E1), 17β-estradiol (17β-E2), 17α-ethinylestradiol (EE2) and progesterone (P) in different goat milk samples. Mean recoveries obtained ranged from 81% to 110%, with relative standard deviations (RSD)≤12%. The molecularly imprinted polymer-matrix solid-phase dispersion method is fast, selective, cost-effective and environment-friendly compared with other pretreatment methods used for extraction of steroids in milk. PMID:24881547

  11. Relationship between activation volume and polymer matrix effects on photochromic performance: bridging molecular parameter to macroscale effect.

    PubMed

    Shima, Kentaro; Mutoh, Katsuya; Kobayashi, Yoichi; Abe, Jiro

    2015-02-19

    Photochromic compounds have attracted attention as ophthalmic lenses because of their reversible color modulation upon irradiation with light. However, the efficiency of the photochromism is strongly affected by their surrounding because of the structural changes concomitant with the photochromism, which causes the decrease in the photochromic performance in the polymer matrix. Therefore, the clarification of the degree of the structural changes is necessary to apply to the ophthalmic lenses. Bridged imidazole dimers are one of the fast photoswitch molecules possessing high photochromic quantum yield and durability. Although the enhancement of the photochromic properties of bridged imidazole dimers has been vigorously studied, the quantitative information about the structural changes has not been revealed in detail. In this study, we investigated the pressure effects on the photochromic properties of bridged imidazole dimers. The activation volume for the thermal back-reaction of the photogenerated biradical species becomes an effective measure to predict the degree of the structural change during the photochromic reaction. We revealed that the smaller activation volume is suitable for keeping the efficient photochromic reaction in the polymer matrix because the photochromic reaction is not affected by the surroundings. These fundamental insights into the molecular dynamics provide valuable information to develop fast photochromic compounds that are suitable for the use in the polymer matrix and pressure sensitive photochromic materials. PMID:25621415

  12. Measurements of Erosion Wear Volume Loss on Bare and Coated Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard J.; Bowman, Cheryl; Ma, Kong; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

    2003-01-01

    An investigation was conducted to examine the erosion behavior of uncoated and coated polymer matrix composite (PMC) specimens subjected to solid particle impingement using air jets. The PMCs were carbon-Kevlar (DuPont, Wilmington, DE) fiber-epoxy resin composites with a temperature capability up to 393 K (248 F). Tungsten carbide-cobalt (WC-Co) was the primary topcoat constituent. Bondcoats were applied to the PMC substrates to improve coating adhesion; then, erosion testing was performed at the University of Cincinnati. All erosion tests were conducted with Arizona road-dust (ARD), impinging at angles of 20 and 90 on both uncoated and two-layer coated PMCs at a velocity of 229 m/s and at a temperature of 366 K (200 F). ARD contains primarily 10-m aluminum oxide powders. Vertically scanning interference microscopy (noncontact, optical profilometry) was used to evaluate surface characteristics, such as erosion wear volume loss and depth, surface topography, and surface roughness. The results indicate that noncontact, optical interferometry can be used to make an accurate determination of the erosion wear volume loss of PMCs with multilayered structures while preserving the specimens. The two-layered (WC-Co topcoat and metal bondcoat) coatings on PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. The tenfold increase in erosion resistance will contribute to longer PMC component lives, lower air friction, reduced related breakdowns, decreased maintenance costs, and increased PMC reliability. The decrease in the surface roughness of the coated vanes will lead to lower air friction and will subsequently reduce energy consumption. Eventually, the coatings could lead to overall economic savings.

  13. Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Gyekanyesi, John (Technical Monitor); Liaw, Benjamin; Villars, Esther; Delmont, Frantz

    2003-01-01

    The main objective of this NASA Faculty Awards for Research (FAR) project is to conduct ultrasonic assessment of impact-induced damage and microcracking in fiber-metal laminated (FML) composites at various temperatures. It is believed that the proposed study of impact damage assessment on FML composites will benefit several NASA's missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass- (for GLARE) and aramid- (for ARALL) fiber reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 2024-T3 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating

  14. Encapsulation of Mentha Oil in Chitosan Polymer Matrix Alleviates Skin Irritation.

    PubMed

    Mishra, Nidhi; Rai, Vineet Kumar; Yadav, Kuldeep Singh; Sinha, Priyam; Kanaujia, Archana; Chanda, Debabrata; Jakhmola, Apurva; Saikia, Dharmendra; Yadav, Narayan Prasad

    2016-04-01

    Mentha spicata L. var. viridis oil (MVO) is a potent antifungal agent, but its application in the topical treatment is limited due to its irritancy and volatility. It was aimed to develop more efficient, chitosan-incrusted MVO microspheres with reduced volatility and lesser irritancy and to dispense it in the form of ointment. Simple coacervation technique was employed to microencapsulate MVO in chitosan matrix. Morphological properties and polymer cross-linking were characterized by scanning electron microscopy and differential scanning calorimetry, respectively. Optimization was carried out on the basis of entrapment efficiency (EE) using response surface methodology. Well-designed microspheres having smooth surface and spherical shape were observed. EE (81.20%) of optimum batch (R21) was found at 1.62% w/v of cross-linker, 5.4:5 of MVO to chitosan ratio and at 1000 rpm. R21 showed 69.38 ± 1.29% in vitro MVO release in 12 h and 96.92% retention of MVO in microspheres even after 8 week. Ointments of PEG 4000 and PEG 400 comprising MVO (F1) and R21 (F2) were developed separately. F2 showed comparatively broader zone of growth inhibition (13.33 ± 1.76-18.67 ± 0.88 mm) and less irritancy (PII 0.5833, irritation barely perceptible) than that of F1. F2 was able to avoid the direct contact of mild irritant MVO with the skin and to reduce its rapid volatility. Controlled release of MVO helped in lengthening the duration of availability of MVO in agar media and hence improved its therapeutic efficacy. In conclusion, a stable and non-irritant formulation with improved therapeutic potential was developed. PMID:26248538

  15. Chitosan based polymer matrix with silver nanoparticles decorated multiwalled carbon nanotubes for catalytic reduction of 4-nitrophenol.

    PubMed

    Alshehri, Saad M; Almuqati, Turki; Almuqati, Naif; Al-Farraj, Eida; Alhokbany, Norah; Ahamad, Tansir

    2016-10-20

    A novel catalyst for the reduction of 4-nitrophenol (4-NP) was prepared using carboxyl group-functionalized multiwalled carbon nanotubes (MWCNTs), polymer matrix, and silver nanoparticles (AgNPs). The AgNPs were prepared by the reduction of silver nitrate by trisodium citrate in the MWCNTs-polymer nanocomposite; the size of the synthesized AgNPs was found to be 3nm (average diameter). The synthesized nanocomposites were characterized using several analytical techniques. Ag@MWCNTs-polymer composite in the presence of sodium borohydride (NaBH4) in aqueous solution is an effective catalyst for the reduction of 4-NP. The apparent kinetics of reduction has a pseudo-first-order kinetics, and the rate constant and catalytic activity parameter were found to be respectively 7.88×10(-3)s(-1)and 11.64s(-1)g(-1). The MWCNTs-polymer nanocomposite renders stability to AgNPs against the environment and the reaction medium, which means that the Ag@MWCNTs-polymer composite can be re-used for many catalytic cycles. PMID:27474552

  16. Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.

    2003-01-01

    Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of

  17. Recent Advances in Targeted Drug Delivery Approaches Using Dendritic Polymers

    PubMed Central

    Bugno, Jason; Hsu, Hao-Jui; Hong, Seungpyo

    2014-01-01

    Since they were first synthesized over 30 years ago, dendrimers have seen rapid translation into various biomedical applications. A number of reports have not only demonstrated their clinical utility, but also revealed novel design approaches and strategies based on the elucidation of underlying mechanisms governing their biological interactions. This review focuses on presenting the latest advances in dendrimer design, discussing the current mechanistic understandings, and highlighting recent developments and targeted approaches using dendrimers in drug/gene delivery. PMID:26221937

  18. Effect of advanced glycation end products, extracellular matrix metalloproteinase inducer and matrix metalloproteinases on type-I collagen metabolism

    PubMed Central

    LI, WANG; LING, WANG; TENG, XIAOMEI; QUAN, CUIXIA; CAI, SHENGNAN; HU, SHUQUN

    2016-01-01

    The aim of the study was to examine the association among advanced glycation end products (AGEs), extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase (MMPs), and investigate whether AGEs affect type I collagen (COL-I) through EMMPRIN or MMPs. A co-culture system with the osteoblast-like cells (MC3T3E1) and mouse RAW264.7 cells was employed to examine the effects of AGE-bovine serum albumin (BSA) (50 mg/l), EMMPRIN antibody (5 mg/l) and AGE-BSA+EMMPRIN antibody separately on COL-I expression for 24 h. Culture media were analyzed for the content of COL-I by ELISA. The effect of different concentrations of AGE-BSA (0, 50, 100, 200 and 400 mg/l) for 24 h was assessed on COL-I levels. Finally, semiquantitative RT-PCR was used to detect the osteoblast COL-I mRNA expression and MMP-2 and MMP-9's PMAO were also measured in the culture medium. COL-I content in the culture medium decreased significantly following treatment with AGE-BSA (P<0.05). EMMPRIN antibody increased COL-I content (P<0.05). EMMPRIN antibody+AGE-BSA increased COL-I significantly (P<0.05). Different concentrations of AGE-BSA increased COL-I mRNA expression significantly compared with the control group (P<0.05), and were enhanced with increasing AGE-BSA concentration (P<0.05). Also MMP-2 and MMP-9 secretion increased significantly (P<0.05), with the increasing AGE-BSA concentration. In conclusion, an increase in AGE levels in vitro stimulates the secretion of EMMPRIN/MMPs, promotes the degradation of COL-I and reduces bone strength. PMID:27284408

  19. Effect of polymer matrix on structure of Se particles formed in aqueous solutions during redox process

    NASA Astrophysics Data System (ADS)

    Suvorova, E. I.; Klechkovskaya, V. V.

    2010-12-01

    Transmission electron microscopy and X-ray energy dispersive microanalysis study of the structure of particles formed during the reduction of Se(IV) to Se(0) in aqueous solutions in the presence of amphiphilic polymers showed the formation of Se/polymer composite particles. The content of carbon inside the particles can be as large as 80 at %. Polymers deeply influence the structure of particles. Depending on polymers, the composite particles may be unstable with time and they spontaneously evolve from Se/polymer composite particles to crystalline particles of monoclinic Se. For the stable ones, addition of bacterial cellulose Acetobacter xylinum gel-film can induce crystallization in the particles which expel the polymeric material. The Se/polymer composite particles and Se crystalline particles exhibit different sensitivity to electron irradiation and stiffness.

  20. Effect of polymer matrix on structure of Se particles formed in aqueous solutions during redox process

    SciTech Connect

    Suvorova, E. I. Klechkovskaya, V. V.

    2010-12-15

    Transmission electron microscopy and X-ray energy dispersive microanalysis study of the structure of particles formed during the reduction of Se(IV) to Se(0) in aqueous solutions in the presence of amphiphilic polymers showed the formation of Se/polymer composite particles. The content of carbon inside the particles can be as large as 80 at %. Polymers deeply influence the structure of particles. Depending on polymers, the composite particles may be unstable with time and they spontaneously evolve from Se/polymer composite particles to crystalline particles of monoclinic Se. For the stable ones, addition of bacterial cellulose Acetobacter xylinum gel-film can induce crystallization in the particles which expel the polymeric material. The Se/polymer composite particles and Se crystalline particles exhibit different sensitivity to electron irradiation and stiffness.

  1. Advances with polymer-free amphilimus-eluting stents.

    PubMed

    CARRIé, Didier

    2016-06-01

    Despite the improved clinical outcomes following the availability of second generation drug eluting stents (DES), percutaneous coronary intervention (PCI) is associated with worse clinical and angiographic outcomes among the patients with diabetes mellitus (DM) than among non-diabetics. The Cre8 Amphilimus-eluting DES is polymer-free, resulting in a reduced inflammatory response and lower risk of stent thrombosis. In a clinical study, it showed equivalent efficacy and safety in diabetic and non-diabetic populations, a unique finding among DES studies. These findings were confirmed in a real-world study, Investig8, and another real-world study, Particip8, is ongoing. The RESERVOIR Clinical Trial recruited patients with DM and showed noninferiority of the Cre8 DES compared to an everolimus eluting DES (EES) in the overall group but showed a statistical superiority of Cre8 in diabetic patients with higher metabolic dysfunctions. The Cre8 DES is therefore a valuable option for this important patient population. PMID:26934663

  2. Advances in ferroelectric polymers for shock compression sensors

    SciTech Connect

    Bauer, F.; Moulard, H.; Samara, G.

    1997-10-01

    Our studies of the shock compression response of PVDF polymer are continuing in order to understand the physical properties under shock loading and to develop high fidelity, reproducible, time-resolved dynamic stress gauges. New PVDF technology, new electrode configurations and piezoelectric analysis have resulted in enhanced precision gauges. Our new standard gauges have a precision of better than 1% in electric charge release under shock up to 15 GPa. The piezoelectric response of shock compressed PVDF gauges 1 mm{sup 2} in active area has been studied and yielded well-behaved reproducible data up to 20 GPa. Analysis of the response of these gauges in the {open_quotes}thin mode regime{close_quotes} using a Lagrangian hydrocode will be presented. P(VDF-TrFE) copolymers exhibit unique piezoelectric properties over a wide range of temperature depending on the composition. Their properties and phase transitions are being investigated. Emphasis of the presentation will be on key results and implications.

  3. Advances on Magnetic Nanocarriers Based on Natural Polymers.

    PubMed

    Muzzalupo, Rita; Tavano, Lorena

    2016-01-01

    The use of nanodevices to transport active compounds like small-molecular drugs, peptides, or genes found an increased attention throughout the different fields of natural sciences. Moreover, recent research trends are focused on the employment of smart nanocarriers able to react on certain internal or external applied stimuli, in order to achieve temporal and site-specific drugs/gene release. In contrast to traditional biodegradable nanocarriers that slowly release drugs inside the cells, these smart nanosystems are able to quickly release or even dump drugs in response to a specific biological signal in the target cancer cells such lower pH, high redox potential or over expression of enzymes or to external stimuli such as temperature, light, ultrasounds and magnetic field. This review gives a brief overview about some types of stimuli-responsive nanocarriers, with the main focus on magnetic fieldresponsive devices obtained from natural polymers. The concept of magnetic field-sensitive nanocarriers, their advantages and disadvantages, the methods of preparation and applications in various fields of drug delivery will be explored, giving an exhaustive collection of the findings of recent investigations. PMID:26861649

  4. Advances in ferroelectric polymers for shock compression sensors

    SciTech Connect

    Bauer, F.; Moulard, H.; Samara, G.

    1998-07-01

    Our studies of the shock compression response of PVDF polymer are continuing in order to understand the physical properties under shock loading and to develop high fidelity, reproducible, time-resolved dynamic stress gauges. New PVDF technology, new electrode configurations and piezoelectric analysis have resulted in enhanced precision gauges. Our new standard gauges have a precision of better than 1{percent} in electrical charge release under shock up to 15 GPa. The piezoelectric response of shock compressed PVDF gauges 1 mm{sup 2} in active area has been studied and yielded well-behaved reproducible data up to 20 GPa. Analysis of the response of these gauges in the {open_quotes}thin mode regime{close_quotes} using a Lagrangian hydrocode will be presented. P(VDF-TrFE) copolymers exhibit unique piezoelectric properties over a wide range of temperature depending on the composition. Their properties and phase transitions are being investigated. Emphasis of the presentation will be on key results and implications. {copyright} {ital 1998 American Institute of Physics.}

  5. The energy release rate of the fiber/polymer matrix interface: Measurement and theoretical analysis

    SciTech Connect

    Hampe, A.; Marotzke, C.

    1995-12-31

    A new method for the experimental determination of the fracture toughness in the fiber matrix interface by means of the single fiber pull out test is presented. To achieve this aim, two problems had to be overcome: the measurement of the compliance of a partial debonded fiber, which necessitates a stable crack propagation, and the determination of the corresponding crack length. Stable crack propagation along the interface of a single fiber is achieved using an advanced test equipment exhibiting an extremely high stiffness. This is obtained by using a piezo translator and a piezo force cell in combination with a very short free fiber length. The experimental data and a theoretical analysis of the pull out process under these conditions reveal, that the commonly used compliant pull out equipment is hiding important details of the force displacement trace and thus leading to a wrong interpretation and wrong results, The most important result is, that in the case of a brittle interfacial fracture the maximal force cannot be used for the determination of an interfacial strength as it is common practice till now.

  6. Transparent oxygen and water vapor barriers for flexible electronics using semi-crystalline polymer matrix thin films

    NASA Astrophysics Data System (ADS)

    Sehgal, Akhil

    Electronic components such as organic light emitting diodes (OLED) and photo-voltaics have been of more focus with the advancement of technology. These electronics are susceptible to degradable in the presence of gases such as water vapor and oxygen. Being that these gases are constituents of the atmosphere and can be found in nearly every environment, certain protocols must take place to mitigate the issues that occur. New generation electronics are sensitive to oxidation and corrosion in the presence of extremely low concentrations of moisture and oxygen and therefore the development and improvements of gas barriers are vital for advancements in electronics technology. The improvements of appliances such as flexible solar cells and OLEDs require barriers that need to be flexible in order to achieve high longevity. The area of research has been focused on designing flexible polymer films with composite nanoparticles and cross-linking agents that have low permeability to moisture and oxygen gas. The polymers studied are in the family of methacrylates. Due to the properties of methacrylate polymers, it has been proposed that they are capable of having efficient barrier properties due to their ability to cross link and form crystalline structures with low chain mobility. The change in intensities of the FTIR peaks of different functional groups indicates the cross-linking and crystallinity of the polymer films. The UV-Vis data indicates high transparency of the films. SEM images of the films show continuous and well cured surfaces with minimal deviations, pores and defects. The addition of cross-linking agents and nanoparticles increased polymerization and cross-linking of the methacrylate polymer chains, therefore increasing inter-chain density and long range order. The incorporation of these additives increased the crystallinity of the films and by decreasing the distances and number of voids between polymer chains along with having minimal sorption sites for gases

  7. Determination of carbon fiber adhesion to thermoplastic polymers using the single fiber/matrix tensile test

    NASA Technical Reports Server (NTRS)

    Bascom, W. D.; Cordner, L. W.; Hinkley, J. L.; Johnston, N. J.

    1986-01-01

    The single fiber adhesion shear test has been adapted to testing the adhesion between carbon fiber and thermoplastic polymers. Tests of three thermoplastics, polycarbonate, polyphenylene oxide and polyetherimide indicate the shear adhesion strength is significantly less than of an epoxy polymer to the same carbon fiber.

  8. Processing of functional polymers and organic thin films by the matrix-assisted pulsed laser evaporation (MAPLE) technique

    NASA Astrophysics Data System (ADS)

    Piqué, A.; Wu, P.; Ringeisen, B. R.; Bubb, D. M.; Melinger, J. S.; McGill, R. A.; Chrisey, D. B.

    2002-01-01

    The matrix-assisted pulsed laser evaporation (MAPLE) technique has been successfully used to deposit highly uniform thin films of various functional materials such as non-linear optical (NLO) organic materials, conductive polymers, luminescent organic molecules and several types of proteinaceous compounds. MAPLE is a laser evaporation technique for growing thin films of organic and polymeric materials which involves directing a pulsed laser beam (λ=193 nm; fluence=0.01-0.5 J cm -2) onto a frozen target (-40 to -160 °C) consisting of a solute polymeric or organic compound dissolved in a solvent matrix. Using MAPLE, thin films of N-(4-nitrophenyl)-( L)-prolinol or NPP, an NLO material; polypyrrole, a conductive polymer; and tris-(8-hydroxyquinoline) aluminum or Alq3, a luminescent organic compound, have been separately deposited with minor (in the case of Alq3) or no degradation (for the NPP and polypyrrole) to their optical and electrical properties. The MAPLE process has also been used to deposit discrete thin film micro-arrays of biotinylated bovine serum albumin (BSA). The deposited BSA films, after washing with a blocking protein and fluorescently tagged streptavidin, fluoresce when exposed to UV. This fluorescence indicates that the biochemical specificity of the transferred biotinylated protein is unaffected by the MAPLE process. These results demonstrate that the MAPLE technique can be used for growing thin films of functional polymer and active biomaterials.

  9. Formulation and Evaluation of Cephalexin Extended-release Matrix Tablets Using Hydroxy Propyl Methyl Cellulose as Rate-controlling Polymer

    PubMed Central

    Vijay, J; Sahadevan, JT; Prabhakaran, R; Gilhotra, R Mehra

    2012-01-01

    The present investigation reports the design and evaluation of six-hour extended release film-coated matrix tablets of cephalexin using different grades of hydrophilic polymer hydroxypropylmethylcellulose (HPMC) employing direct compression method. The preformulation studies performed included the physical compatibility studies, Differential Scanning Calorimetry analysis, drug characterization using Fourier Transform Infra Red spectroscopic analysis and particle size analysis using sieve method. The tablets were evaluated for weight variation, hardness, thickness and friability. Results of the studies indicate that the polymers used have significant release-retarding effect on the formulation. The dissolution profile comparison of the prepared batches P1 to P8 and market preparation (Sporidex AF 375) was done by using Food and Drug Administration-recommended similarity factor (f2) determination. The formulation P8 (10% HPMC K4M, 15% HPMC 15cps) with a similarity factor (f2) of 77.75 was selected as the optimized formulae for scale-up batches. The dissolution data of the best formulation P8 was fitted into zero order, first order, Higuchi and Korsemeyer-Peppas models to identify the pharmacokinetics and mechanism of drug release. The results of the accelerated stability study of best formulation P8 for three months revealed that storage conditions were not found to have made any significant changes in final formulation F3. The release of cephalexin was prolonged for 6 h by using polymer combinations of HPMC and a twice daily matrix tablet was formulated. PMID:22523453

  10. Advanced multi-contrast Jones matrix optical coherence tomography for Doppler and polarization sensitive imaging.

    PubMed

    Ju, Myeong Jin; Hong, Young-Joo; Makita, Shuichi; Lim, Yiheng; Kurokawa, Kazuhiro; Duan, Lian; Miura, Masahiro; Tang, Shuo; Yasuno, Yoshiaki

    2013-08-12

    An advanced version of Jones matrix optical coherence tomography (JMT) is demonstrated for Doppler and polarization sensitive imaging of the posterior eye. JMT is capable of providing localized flow tomography by Doppler detection and investigating the birefringence property of tissue through a three-dimensional (3-D) Jones matrix measurement. Owing to an incident polarization multiplexing scheme based on passive optical components, this system is stable, safe in a clinical environment, and cost effective. Since the properties of this version of JMT provide intrinsic compensation for system imperfection, the system is easy to calibrate. Compared with the previous version of JMT, this advanced JMT achieves a sufficiently long depth measurement range for clinical cases of posterior eye disease. Furthermore, a fine spectral shift compensation method based on the cross-correlation of calibration signals was devised for stabilizing the phase of OCT, which enables a high sensitivity Doppler OCT measurement. In addition, a new theory of JMT which integrates the Jones matrix measurement, Doppler measurement, and scattering measurement is presented. This theory enables a sensitivity-enhanced scattering OCT and high-sensitivity Doppler OCT. These new features enable the application of this system to clinical cases. A healthy subject and a geographic atrophy patient were measured in vivo, and simultaneous imaging of choroidal vasculature and birefringence structures are demonstrated. PMID:23938857

  11. Current Advances in Polymer-Based Nanotheranostics for Cancer Treatment and Diagnosis

    PubMed Central

    2015-01-01

    Nanotheranostics is a relatively new, fast-growing field that combines the advantages of treatment and diagnosis via a single nanoscale carrier. The ability to bundle both therapeutic and diagnostic capabilities into one package offers exciting prospects for the development of novel nanomedicine. Nanotheranostics can deliver treatment while simultaneously monitoring therapy response in real-time, thereby decreasing the potential of over- or under-dosing patients. Polymer-based nanomaterials, in particular, have been used extensively as carriers for both therapeutic and bioimaging agents and thus hold great promise for the construction of multifunctional theranostic formulations. Herein, we review recent advances in polymer-based systems for nanotheranostics, with a particular focus on their applications in cancer research. We summarize the use of polymer nanomaterials for drug delivery, gene delivery, and photodynamic therapy, combined with imaging agents for magnetic resonance imaging, radionuclide imaging, and fluorescence imaging. PMID:25014486

  12. Associative Flow Rule Used to Include Hydrostatic Stress Effects in Analysis of Strain-Rate-Dependent Deformation of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.

    2004-01-01

    designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and the strain-rate dependence of the composite response are due primarily to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. By applying micromechanics techniques along with given fiber properties, one can also determine the effects of the hydrostatic stresses in the polymer on the overall composite deformation response. First efforts to account for the hydrostatic stress effects in the composite deformation applied purely empirical methods that relied on composite-level data. In later efforts, to allow polymer properties to be characterized solely on the basis of polymer data, researchers at the NASA Glenn Research Center developed equations to model the polymers that were based on a non-associative flow rule, and efforts to use these equations to simulate the deformation of representative polymer materials were reasonably successful. However, these equations were found to have difficulty in correctly analyzing the multiaxial stress states found in the polymer matrix constituent of a composite material. To correct these difficulties, and to allow for the accurate simulation of the nonlinear strain-rate-dependent deformation analysis of polymer matrix composites, in the efforts reported here Glenn researchers reformulated the polymer constitutive equations from basic principles using the concept of an associative flow rule. These revised equations were characterized and validated in an

  13. Advanced polymer systems for optoelectronic integrated circuit applications

    NASA Astrophysics Data System (ADS)

    Eldada, Louay A.; Stengel, Kelly M. T.; Shacklette, Lawrence W.; Norwood, Robert A.; Xu, Chengzeng; Wu, Chengjiu; Yardley, James T.

    1997-01-01

    An advanced versatile low-cost polymeric waveguide technology is proposed for optoelectronic integrated circuit applications. We have developed high-performance organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture (NA) and geometry. These materials are formed from highly crosslinked acrylate monomers with specific linkages that determine properties such as flexibility, toughness, loss, and stability against yellowing and humidity. These monomers are intermiscible, providing for precise adjustment of the refractive index from 1.30 to 1.60. Waveguides are formed photolithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser direct-writing. A wide range of rigid and flexible substrates can be used, including glass, quartz, oxidized silicon, glass-filled epoxy printed circuit board substrate, and flexible polyimide film. We discuss the use of these materials on chips and on multi-chip modules (MCMs), specifically in transceivers where we adaptively produced waveguides on vertical-cavity surface-emitting lasers (VCSELs) embedded in transmitter MCMs and on high- speed photodetector chips in receiver MCMs. Light coupling from and to chips is achieved by cutting 45 degree mirrors using excimer laser ablation. The fabrication of our polymeric structures directly on the modules provides for stability, ruggedness, and hermeticity in packaging.

  14. Development of a variable frequency microwave processing system for post-curing of thermoset polymer matrix composite materials. Final report, 1 September 1994-28 February 1995

    SciTech Connect

    Johnson, A.

    1995-02-28

    Using a Variable frequency Microwave Furnace (VFMF) technology, Lambda Technologies has demonstrated the ability to tune to the optimum incident frequency for best coupling into a given material structure (e.g., polymer matrix composite, PMC), and then by sweeping around that incident center frequency, producing uniform energy distribution throughout the cavity and sample volume. Hence, the advantages of microwave energy---enhanced reaction rates, reduced process time, and heat generation at the molecular level---are now obtainable with controlled and uniform results compatible for commercial scale-up. The processing via VFMF is 8 - 10 times faster than conventional processing methods. The advantages of VFMF technology over single frequency microwave technology in achieving the uniform electromagnetic energy distribution required for rapid and reliable processing of advanced polymer composites are systematically demonstrated in the Phase I (Both Glass and Carbon fiber reinforced PMC were investigated). In addition, a numerical modeling program implemented during Phase I provided a foundation for the ability to predict field distribution and temperature profiles in various geometries (plate, disk and cylinder) and materials (glass and graphite fiber reinforced PMCs) when being heated with variable frequency microwave energy.

  15. Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging.

    PubMed

    Crick, Colin R; Noimark, Sacha; Peveler, William J; Bear, Joseph C; Ivanov, Aleksandar P; Edel, Joshua B; Parkin, Ivan P

    2016-01-01

    The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials. PMID:27500449

  16. A process to recover carbon fibers from polymer-matrix composites in end-of-life vehicles

    NASA Astrophysics Data System (ADS)

    Jody, Bassam J.; Pomykala, Joseph A.; Daniels, Edward J.; Greminger, Jessica L.

    2004-08-01

    Because of their high strength-to-weight ratios, carbon-fiber-reinforced polymer-matrix composite (PMC) materials are being evaluated for use in the automotive industry. The major barriers to their widespread use are their relatively high cost and the uncertainty about whether they can be recycled. A process to recover carbon fibers from obsolete PMC materials has been developed at Argonne National Laboratory. The process was tested using PMC samples made with different thermoset or thermoplastic substrates. For most mixtures of PMCs, the process can be energy self-sufficient using the polymer substrate as an energy source. An evaluation of the recovered samples found that the fibers appear to have retained good properties and characteristics and are suitable for short fiber applications. This paper describes the process and the characteristics and properties of the recovered fibers.

  17. Environment enhanced fatigue of advanced aluminum alloys and metal matrix composites

    NASA Technical Reports Server (NTRS)

    Slavik, Donald C.; Gangloff, Richard P.

    1991-01-01

    The environmental fatigue crack propagation behavior of advanced Al-Li-Cu based alloys and metal matrix composites is being characterized. Aqueous NaCl and water vapor, which produce atomic hydrogen by reactions on clean crack surfaces, are emphasized. The effects of environment sensitive crack closure, stress ratio, and precipitate microstructure are assessed. Mechanistic models are sought for intrinsic crack tip damage processes to enable predictions of cracking behavior outside of the data, metallurgical improvements in material cracking resistance, and insight on hydrogen compatibility.

  18. Formulation optimizations for variable DUV resist thickness applications based on the same polymer matrix

    NASA Astrophysics Data System (ADS)

    Schlicht, Karin R.; Maxwell, Brian; Ferri, John E.; Toukhy, Medhat A.

    2001-08-01

    We are investigating strategies of resist optimization for various target thicknesses based on the same polymer. The photo acid generator (PAG) and base levels are optimized for each application thickness. The polymer of choice, used in this work, contained sufficient tertiary-butyl ester groups to provide high dissolution rate after exposure (high Rmas) while its initial dissolution rate in the developer is very low (low Rmin). The polymer structure was also designed to provide a high ratio of carbon to hydrogen atoms to be adequately resistant to plasma etching. Other polymer properties, such as solubility in resist solvents, long shelf life stability, good coating properties, good adhesion to different substrates, low solution viscosity, low coating defects and good wettability are only a few examples of many required characteristics for good resist performance.

  19. ac transport studies in polymers by resistor-network and transfer-matrix approaches: Application to polyaniline

    NASA Astrophysics Data System (ADS)

    Nagashima, H. N.; Onody, R. N.; Faria, R. M.

    1999-01-01

    A statistical model of resistor networks is proposed to describe a polymer structure and to simulate the real and imaginary components of its ac resistivity. It takes into account the polydispersiveness of the material as well as intrachain and interchain charge transport processes. By the application of a transfer-matrix technique, it reproduces ac resistivity measurements carried out with polyaniline films in different doping degrees and at different temperatures. Our results indicate that interchain processes govern the resistivity behavior in the low-frequency region while, for higher frequencies, intrachain mechanisms are dominant.

  20. Interfacial studies of refractory glass-ceramic matrix/advanced SiC fiber-reinforced composites. Annual report, 1 Feb 91-1 Feb 92

    SciTech Connect

    Brennan, J.J.

    1992-04-30

    The main objective of this program is to characterize the chemistry and structure of new advanced small diameter silicon based fibers and how these factors influence the nature of the fiber/matrix interface in refractory glass-ceramic matrix composites. It is the nature of this interface that then determines to a great degree the composite thermal, environmental, and mechanical properties. The fibers under investigation during the second year of this program included the new experimental polymer derived crystalline SiC fibers from Dow Corning Corp., the Si-N-C-O 'Black' fibers from Textron Specialty Materials, as well as the new low oxygen radiation cured Nicalon SiC type fibers from Nippon Carbon Co. Since the availability of all of these fibers was extremely limited, emphasis was placed on the mechanical, chemical, and microstructural characterization of the fibers through tensile testing, SEM of fiber fracture characteristics, scanning Auger depth profiling of fiber surfaces, and TEM of fiber thin sections, as well as their fracture behavior, bonding characteristics, and interfacial compatibility with various glass-ceramic matrix materials. Results of these analyses are discussed. Crystalline SiC fibers, Textron 'Black' fibers, low oxygen Nicalon fibers, SiC fiber/glass-ceramic matrix interfaces, TEM fiber analyses.

  1. Effect of bidispersity in grafted chain length on grafted chain conformations and potential of mean force between polymer grafted nanoparticles in a homopolymer matrix.

    PubMed

    Nair, Nitish; Wentzel, Nathaniel; Jayaraman, Arthi

    2011-05-21

    In efforts to produce polymeric materials with tailored physical properties, significant interest has grown around the ability to control the spatial organization of nanoparticles in polymer nanocomposites. One way to achieve controlled particle arrangement is by grafting the nanoparticle surface with polymers that are compatible with the matrix, thus manipulating the interfacial interactions between the nanoparticles and the polymer matrix. Previous work has shown that the molecular weight of the grafted polymer, both at high grafting density and low grafting density, plays a key role in dictating the effective inter-particle interactions in a polymer matrix. At high grafting density nanoparticles disperse (aggregate) if the graft molecular weight is higher (lower) than the matrix molecular weight. At low grafting density the longer grafts can better shield the nanoparticle surface from direct particle-particle contacts than the shorter grafts and lead to the dispersion of the grafted particles in the matrix. Despite the importance of graft molecular weight, and evidence of non-trivial effects of polydispersity of chains grafted on flat surfaces, most theoretical work on polymer grafted nanoparticles has only focused on monodisperse grafted chains. In this paper, we focus on how bidispersity in grafted chain lengths affects the grafted chain conformations and inter-particle interactions in an implicit solvent and in a dense homopolymer polymer matrix. We first present the effects of bidispersity on grafted chain conformations in a single polymer grafted particle using purely Monte Carlo (MC) simulations. This is followed by calculations of the potential of mean force (PMF) between two grafted particles in a polymer matrix using a self-consistent Polymer Reference Interaction Site Model theory-Monte Carlo simulation approach. Monte Carlo simulations of a single polymer grafted particle in an implicit solvent show that in the bidisperse polymer grafted particles

  2. The NASA "PERS" Program: Solid Polymer Electrolyte Development for Advanced Lithium-Based Batteries

    NASA Technical Reports Server (NTRS)

    Baldwin, Richard S.; Bennett, William R.

    2007-01-01

    In fiscal year 2000, The National Aeronautics and Space Administration (NASA) and the Air Force Research Laboratory (AFRL) established a collaborative effort to support the development of polymer-based, lithium-based cell chemistries and battery technologies to address the next generation of aerospace applications and mission needs. The ultimate objective of this development program, which was referred to as the Polymer Energy Rechargeable System (PERS), was to establish a world-class technology capability and U.S. leadership in polymer-based battery technology for aerospace applications. Programmatically, the PERS initiative exploited both interagency collaborations to address common technology and engineering issues and the active participation of academia and private industry. The initial program phases focused on R&D activities to address the critical technical issues and challenges at the cell level. Out of a total of 38 proposals received in response to a NASA Research Announcement (NRA) solicitation, 18 proposals (13 contracts and 5 grants) were selected for initial award to address these technical challenges. Brief summaries of technical approaches, results and accomplishments of the PERS Program development efforts are presented. With Agency support provided through FY 2004, the PERS Program efforts were concluded in 2005, as internal reorganizations and funding cuts resulted in shifting programmatic priorities within NASA. Technically, the PERS Program participants explored, to various degrees over the lifetime of the formal program, a variety of conceptual approaches for developing and demonstrating performance of a viable advanced solid polymer electrolyte possessing the desired attributes, as well as several participants addressing all components of an integrated cell configuration. Programmatically, the NASA PERS Program was very successful, even though the very challenging technical goals for achieving a viable solid polymer electrolyte material or

  3. Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into Strain Rate Dependent Analyses of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.

    2004-01-01

    A numerical procedure has been developed to investigate the nonlinear and strain rate dependent deformation response of polymer matrix composite laminated plates under high strain rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain rate dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed strain rate dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain rate loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.

  4. Towards Acid-Tolerated Ethanol Dehydration: Chitosan-Based Mixed Matrix Membranes Containing Cyano-Bridged Coordination Polymer Nanoparticles.

    PubMed

    Wu, C-W; Kang, Chao-Hsiang; Lin, Yi-Feng; Tung, Kuo-Lun; Deng, Yu-Heng; Ahamad, Tansir; Alshehri, Saad M; Suzuki, Norihiro; Yamauchi, Yusuke

    2016-04-01

    Prussian blue (PB) nanoparticles, one of many cyano-bridged coordination polymers, are successfully incorporated into chitosan (CS) polymer to prepare PB/CS mixed matrix membranes (MMMs). The PB nanoparticles are uniformly distributed in the MMMs without the collapse of the original PB structure. As-prepared PB/CS MMMs are used for ethanol dehydration at 25 °C in the pervaporation process. The effect of loading PB in CS matrix on pervaporation performance is carefully investigated. The PB/CS membrane with 30 wt% PB loading shows the best performance with a permeate flux of 614 g. m-2 . h-1 and a separation factor of 1472. The pervaporation using our PB/CS membranes exhibits outstanding performance in comparison with the previously reported CS-based membranes and MMMs. Furthermore, the addition of PB allows PB/CS MMMs to be tolerant of acidic environment. The present work demonstrates good pervaporation performance of PB/CS MMMs for the separation of an ethanol/water (90:10 in wt%) solution. Our new system provides an opportunity for dehydration of bioethanol in the future. PMID:27451778

  5. Development of damped metal-matrix composites for advanced structural applications. Technical report

    SciTech Connect

    Updike, C.A.; Bhagat, R.B.

    1990-04-01

    The development of damped metal matrix composite structures for advanced applications has been investigated by the use of two different approaches: (1) the development of metal matrix composites with high intrinsic damping compared to that of the matrix material, and (2) the development of coated metal matrix composites with high structural damping compared to that of the composite substrates. The two different approaches are analyzed in terms of their potential for improved damping and feasibility for structural applications. Damping was measured by the transverse vibration of free-free beams using the bandwidth technique by a laser vibrometer under ambient conditions. The damping measurements were made over a wide range of frequencies (.7 kHz to 25.6 kHz) at low strain amplitudes (10 to the -10 power to 10 to the -7 power). Materials investigated for their tensile stiffness, strength, and damping performance include mechanically alloyed (MA) Aluminum-Magnesium, SiC(p)/Aluminum-Copper (MA), SiC(p)/AL, AL2O3(p)/AL, SiC(W)/AL, planar random Gr/AL, unidirectional Gr/AL and unidirectional SiC(Nicalon)/AL composites. The effects of coatings of high damping metals (nitinol and incramute) on 6061-T6 AL and AL2O3(p)/AL substrates have also been studied. The AL-Mg (MA), SiC(p)/AL (MA), SiC(W)/AL and th AL2O3(p)/AL composites show no significant improvement in damping compared with that of the 6061-T6 AL.

  6. Formulation and in vitro evaluation of theophylline matrix tablets prepared by direct compression: Effect of polymer blends

    PubMed Central

    El-Bagory, Ibrahim; Barakat, Nahla; Ibrahim, Mohamed A.; El-Enazi, Fouza

    2011-01-01

    The deformation mechanism of pharmaceutical powders, used in formulating directly compressed matrix tablets, affects the characteristics of the formed tablets. Three polymers of different deformation mechanisms were tested for their impact on theophylline directly compressed tablets namely Kollidon SR (KL SR, plastic deformation), Ethylcellulose (EC, elastic deformation) and Carnauba wax (CW, brittle deformation) at different compression forces. However, tablets based mainly on KL SR, the plastically deformed polymer (TN1) exhibited the highest hardness values compared to the other formulae which are based on either blends of KL SR with CW, the very brittle deformed polymer. The upper detected force for TN formulae and the lower punch force were found to dependent mainly on the powder deformation. This difference is attributed to the work done during the compression phase as well as the work lost during the decompression phase. Furthermore, the release profiles of TN from formulae TN2 and TN4 that are based on the composition (2KL SR:1EC) and (1KL SR:2EC), respectively, were consistent with different deformation mechanisms of KL SR and EC and on the physicochemical properties like the water absorptive capacity of EC. Upon increasing the weight ratio of KL SR (TN2), the release rate was greatly retarded (39.4%, 37.1%, 35.0% and 33.6% released after 8 h at 5, 10, 15 and 20 kN. PMID:24115902

  7. Patterned structures of in situ size controlled CdS nanocrystals in a polymer matrix under UV irradiation

    NASA Astrophysics Data System (ADS)

    Fragouli, D.; Resta, V.; Pompa, P. P.; Laera, A. M.; Caputo, G.; Tapfer, L.; Cingolani, R.; Athanassiou, A.

    2009-04-01

    A method of in situ formation of patterns of size controlled CdS nanocrystals in a polymer matrix by pulsed UV irradiation is presented. The films consist of Cd thiolate precursors with different carbon chain lengths embedded in TOPAS polymer matrices. Under UV irradiation the precursors are photolyzed, driving to the formation of CdS nanocrystals in the quantum size regime, with size and concentration defined by the number of incident UV pulses, while the host polymer remains macroscopically/microscopically unaffected. The emission of the formed nanocomposite materials strongly depends on the dimensions of the CdS nanocrystals, thus, their growth at the different phases of the irradiation is monitored using spatially resolved photoluminescence by means of a confocal microscope. X-ray diffraction measurements verified the existence of the CdS nanocrystals, and defined their crystal structure for all the studied cases. The results are reinforced by transmission electron microscopy. It is proved that the selection of the precursor determines the efficiency of the procedure, and the quality of the formed nanocrystals. Moreover it is demonstrated that there is the possibility of laser induced formation of well-defined patterns of CdS nanocrystals, opening up new perspectives in the development of nanodevices.

  8. Patterned structures of in situ size controlled CdS nanocrystals in a polymer matrix under UV irradiation.

    PubMed

    Fragouli, D; Resta, V; Pompa, P P; Laera, A M; Caputo, G; Tapfer, L; Cingolani, R; Athanassiou, A

    2009-04-15

    A method of in situ formation of patterns of size controlled CdS nanocrystals in a polymer matrix by pulsed UV irradiation is presented. The films consist of Cd thiolate precursors with different carbon chain lengths embedded in TOPAS polymer matrices. Under UV irradiation the precursors are photolyzed, driving to the formation of CdS nanocrystals in the quantum size regime, with size and concentration defined by the number of incident UV pulses, while the host polymer remains macroscopically/microscopically unaffected. The emission of the formed nanocomposite materials strongly depends on the dimensions of the CdS nanocrystals, thus, their growth at the different phases of the irradiation is monitored using spatially resolved photoluminescence by means of a confocal microscope. X-ray diffraction measurements verified the existence of the CdS nanocrystals, and defined their crystal structure for all the studied cases. The results are reinforced by transmission electron microscopy. It is proved that the selection of the precursor determines the efficiency of the procedure, and the quality of the formed nanocrystals. Moreover it is demonstrated that there is the possibility of laser induced formation of well-defined patterns of CdS nanocrystals, opening up new perspectives in the development of nanodevices. PMID:19420544

  9. Stress-induced fragmentation of multiwall carbon nanotubes in a polymer matrix

    NASA Astrophysics Data System (ADS)

    Wagner, H. D.; Lourie, O.; Feldman, Y.; Tenne, R.

    1998-01-01

    We report the observation of single nanotube fragmentation, under tensile stresses, using nanotube-containing thin polymeric films. Similar fragmentation tests with single fibers instead of nanotubes are routinely performed to study the fiber-matrix stress transfer ability in fiber composite materials, and thus the efficiency and quality of composite interfaces. The multiwall nanotube-matrix stress transfer efficiency is estimated to be at least one order of magnitude larger than in conventional fiber-based composites.

  10. Dielectrophoresis in particle confinement: Aligned carbon particles in polymer matrix below percolation threshold

    NASA Astrophysics Data System (ADS)

    Knaapila, M.; Høyer, H.; Helgesen, G.

    2014-09-01

    We review preparation and properties of confined, aligned string-like particle assemblies formed by dielectrophoresis under alternating electric fields. Particular attention is placed on carbon particles aligned in the oligomer matrix. In these systems the particle fraction is low, below the isotropic percolation threshold. The matrix is polymerized after alignment, which locks the aligned strings in place. Application examples are discussed including particle separation, conductivity enhancement and piezoresistive sensors.

  11. The effect of mixing methods and polymer infiltration and pyrolysis (PIP) cycles on the densification of silicon carbide inert matrix fuel through a polymer precursor route

    NASA Astrophysics Data System (ADS)

    Shih, Chunghao; Tulenko, J. S.; Baney, R. H.

    2011-12-01

    The effect of mixing methods on the fabrication of silicon carbide (SiC) inert matrix fuel through a polymer precursor route was investigated in order to break up the agglomerates of the SiC particles observed in earlier studies. It was found that a high energy shaker mill could effectively break up the agglomerates and thereby achieve a higher pellet density. Moreover, it was found that the pellet density depended less on the pressing pressure, when the particles are well mixed. SEM images showed cracks caused by the springback effect on pellets with a high cold pressing pressure of 600 MPa, but no signs of springback effect were observed for the 200 MPa pressed pellets. The polymer infiltration and pyrolysis (PIP) cycles were used to further increase the pellet density and close the open pores. The first PIP cycle was found to increase the theoretical density of the pellets from 81.2% to 86.0% and close ˜50% of the open pores. The pore size distribution showed that most of the remaining open pores had diameters smaller than 10 nm. The successive second PIP cycle is not as effective on either the density or the pore size distribution because the small pores present before the second PIP cycle made the infiltration process difficult.

  12. Matrix effects on the photochemical fatigue resistance of fulgide doped polymers

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Lafond, Christophe; Pouraghajani, Ozra; Bolte, Michel; Ritcey, Anna-Marie R.; Lessard, Roger A.

    2002-09-01

    Fulgide Aberchrome 670-doped polymer films are studied. The closed form of this chromophore presents a maximum of absorption centered at about 525 nm and is formed upon irradiation of its colorless open form at 365 nm. We have determined the photoreaction rate constants, kUV and kVIS, respectively, for the coloring and bleaching processes. It was found that photochemical fatigue of fulgide doped in the mixture of a cyanoacrylate adhesive with 10% of dioctoepoxy monomer is essentially absent after 40 UV/visible irradiation cycles. We thus report, for the first time, a simple and rapid preparation of dye-doped polymer films in a solvent-free process that shows significant improvements in fatigue behavior. Our previous investigation of conventional polymer matrices prepared by gravity deposition of dilute dye-polymer solutions found losses of 9, 11, 13, and 35% after only 8 UV/visible irradiation cycles, respectively, in polystyrene (PS), cellulose acetate (CA), poly(methyl methacrylate) (PMMA), and polyvinyl carbazole (PVK).

  13. Nonaligned carbon nanotubes partially embedded in polymer matrixes: a novel route to superhydrophobic conductive surfaces.

    PubMed

    Peng, Mao; Liao, Zhangjie; Qi, Ji; Zhou, Zhi

    2010-08-17

    A new method for transforming common polymers into superhydrophobic conductive surfaces, with both a high static water contact angle (approximately 160 degrees) and a low sliding angle (2.0 degrees-4.5 degrees), and a low sheet resistance on the order of 10(1)-10(3) ohms/sq is presented. A layer of multiwalled carbon nanotubes (MWNTs) is first distributed on the surface of a polymer substrate, then by a single step of pressing, the MWNTs are partially embedded inside the substrate surface and form a superhydrophobic coating with a "carpet-" or "hair"-like morphology. The infiltration of polymer melts into the porous MWNT layer follows Darcy's law, and the pressing time greatly influence the morphology and superhydrophobicity. Moreover, the coating can be electrically heated by 20-70 degrees C with a voltage as low as 4-8 V at an electric energy density below 1.6 J/cm(2) and therefore can be used for deicing applications. Hydroxylation and fluoroalkylsilane treatment can greatly improve the stability of the superhydrophobicity of MWNTs. This method is convenient and applicable to a variety of thermoplastic polymers and nonpolymer substrates coated by silicone rubber. PMID:20695606

  14. Novel patternable and conducting metal-polymer nanocomposites: a step towards advanced mutlifunctional materials

    NASA Astrophysics Data System (ADS)

    Rodríguez-Cantó, Pedro J.; Martínez-Marco, Mariluz; Abargues, Rafael; Latorre-Garrido, Victor; Martínez-Pastor, Juan P.

    2013-03-01

    In this work, we present a novel patternable conducting nanocomposite containing gold nanoparticles. Here, the in-situ polymerization of 3T is carried out using HAuCl4 as oxidizing agent inside PMMA as host matrix. During the bake step, the gold salt is also reduced from Au(III) to Au(0) generating Au nanoparticles in the interpenetrating polymer network (IPN) system. We found that this novel multifunctional resist shows electrical conductivity and plasmonic properties as well as potential patterning capability provided by the host matrix. The resulting nanocomposite has been investigated by TEM and UV-Vis spectroscopy. Electrical characterization was also conducted for different concentration of 3T and Au(III) following a characteristic percolation behaviour. Conductivities values from 10-5 to 10 S/cm were successfully obtained depending on the IPN formulation. Moreover, The Au nanoparticles generated exhibited a localized surface plasmon resonance at around 520 nm. This synthetic approach is of potential application to modify the conductivity of numerous insulating polymers and synthesize Au nanoparticles preserving to some extent their physical and chemical properties. In addition, combination of optical properties (Plasmonics), electrical, and lithographic capability in the same material allows for the design of materials with novel functionalities and provides the basis for next generation devices.

  15. Designing a better matrix for solidification/stabilization of hazardous waste with the aid of bagasse (lignin) as a polymer additive to cement

    SciTech Connect

    Bourgeois, J.C.; Kliebert, N.M.; Janusa, M.A.

    1996-10-01

    A significant portion of modem industrial waste is disposed by solidification in cement and slags. Cement has been found to be effective for some heavy metals while ineffective for others. There is a strong need for a better solidification/stabilization matrix that can help solve the hazardous waste disposal problem. Herein, the waste/cement matrix is improved by adding a polymer additive to the matrix. The polymer enhances the encapsulation and penetration of the cement system into the interstitial spaces of the waste. To make the process more economically feasible, the source of polymer was lignin obtained from the large excess of bagasse produced each year from sugar cane processors. The studies were done with lead as the initial heavy metal waste source.

  16. Development of scalable methods for the utilization of multi-walled carbon nanotubes in polymer and metal matrix composites

    NASA Astrophysics Data System (ADS)

    Vennerberg, Danny Curtis

    Multi-walled carbon nanotubes (MWCNTs) have received considerable attention as reinforcement for composites due to their high tensile strength, stiffness, electrical conductivity and thermal conductivity as well as their low coefficient of thermal expansion. However, despite the availability of huge quantities of low-cost, commercially synthesized nanotubes, the utilization of MWCNTs in engineering composites is extremely limited due to difficulties in achieving uniform dispersion and strong interfacial bonding with the matrix. A proven method of enhancing the nanotube-polymer interface and degree of MWCNT dispersion involves functionalizing the MWCNTs through oxidation with strong acids. While effective at laboratory scales, this technique is not well-suited for large-scale operations due to long processing times, poor yield, safety hazards, and environmental concerns. This work aims to find scalable solutions to several of the challenges associated with the fabrication of MWCNT-reinforced composites. For polymer matrix composite applications, a rapid, dry, and cost-effective method of oxidizing MWCNTs with O3 in a fluidized bed was developed as an alternative to acid oxidation. Oxidized MWCNTs were further functionalized with silane coupling agents using water and supercritical carbon dioxide as solvents in order to endow the MWCNTs with matrix-specific functionalities. The effect of silanization on the cure kinetics, rheological behavior, and thermo-mechanical properties of model epoxy nanocomposites were investigated. Small additions of functionalized MWCNTs were found to increase the glass transition temperature, strength, and toughness of the epoxy. In order to achieve composite properties approaching those of individual nanotubes, new approaches are needed to allow for high loadings of MWCNTs. One strategy involves making macroscopic mats of nanotubes called buckypaper (BP) and subsequently infiltrating the mats with resin in processes familiar to

  17. Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach. Degree awarded by Cincinnati Univ.

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    1999-01-01

    Potential gas turbine applications will expose polymer matrix composites to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under extreme conditions. Specifically, analytical methods designed for these applications must have the capability of properly capturing the strain rate sensitivities and nonlinearities that are present in the material response. The Ramaswamy-Stouffer constitutive equations, originally developed to analyze the viscoplastic deformation of metals, have been modified to simulate the nonlinear deformation response of ductile, crystalline polymers. The constitutive model is characterized and correlated for two representative ductile polymers. Fiberite 977-2 and PEEK, and the computed results correlate well with experimental values. The polymer constitutive equations are implemented in a mechanics of materials based composite micromechanics model to predict the nonlinear, rate dependent deformation response of a composite ply. Uniform stress and uniform strain assumptions are applied to compute the effective stresses of a composite unit cell from the applied strains. The micromechanics equations are successfully verified for two polymer matrix composites. IM7/977-2 and AS4/PEEK. The ultimate strength of a composite ply is predicted with the Hashin failure criteria that were implemented in the composite micromechanics model. The failure stresses of the two composite material systems are accurately predicted for a variety of fiber orientations and strain rates. The composite deformation model is implemented in LS-DYNA, a commercially available transient dynamic explicit finite element code. The matrix constitutive equations are converted into an incremental form, and the model is implemented into LS-DYNA through the use of a user defined material subroutine. The deformation response of a bulk polymer and a polymer matrix composite are predicted by finite element analyses. The results

  18. Implementation of an Associative Flow Rule Including Hydrostatic Stress Effects Into the High Strain Rate Deformation Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

    2003-01-01

    A previously developed analytical formulation has been modified in order to more accurately account for the effects of hydrostatic stresses on the nonlinear, strain rate dependent deformation of polymer matrix composites. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical J2 plasticity theory definitions of effective stress and effective inelastic strain, along with the equations used to compute the components of the inelastic strain rate tensor, are appropriately modified. To verify the revised formulation, the shear and tensile deformation of two representative polymers are computed across a wide range of strain rates. Results computed using the developed constitutive equations correlate well with experimental data. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite for several fiber orientation angles across a variety of strain rates. The computed values compare well to experimentally obtained results.

  19. Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

  20. Adjuvant Chemotherapy for Brain Tumors Delivered via a Novel Intra-Cavity Moldable Polymer Matrix

    PubMed Central

    Rahman, Cheryl V.; Smith, Stuart J.; Morgan, Paul S.; Langmack, Keith A.; Clarke, Phil A.; Ritchie, Alison A.; Macarthur, Donald C.; Rose, Felicity R.; Shakesheff, Kevin M.; Grundy, Richard G.; Ruman Rahman

    2013-01-01

    Introduction Polymer-based delivery systems offer innovative intra-cavity administration of drugs, with the potential to better target micro-deposits of cancer cells in brain parenchyma beyond the resected cavity. Here we evaluate clinical utility, toxicity and sustained drug release capability of a novel formulation of poly(lactic-co-glycolic acid) (PLGA)/poly(ethylene glycol) (PEG) microparticles. Methods PLGA/PEG microparticle-based matrices were molded around an ex vivo brain pseudo-resection cavity and analyzed using magnetic resonance imaging and computerized tomography. In vitro toxicity of the polymer was assessed using tumor and endothelial cells and drug release from trichostatin A-, etoposide- and methotrexate-loaded matrices was determined. To verify activity of released agents, tumor cells were seeded onto drug-loaded matrices and viability assessed. Results PLGA/PEG matrices can be molded around a pseudo-resection cavity wall with no polymer-related artifact on clinical scans. The polymer withstands fractionated radiotherapy, with no disruption of microparticle structure. No toxicity was evident when tumor or endothelial cells were grown on control matrices in vitro. Trichostatin A, etoposide and methotrexate were released from the matrices over a 3-4 week period in vitro and etoposide released over 3 days in vivo, with released agents retaining cytotoxic capabilities. PLGA/PEG microparticle-based matrices molded around a resection cavity wall are distinguishable in clinical scanning modalities. Matrices are non-toxic in vitro suggesting good biocompatibility in vivo. Active trichostatin A, etoposide and methotrexate can be incorporated and released gradually from matrices, with radiotherapy unlikely to interfere with release. Conclusion The PLGA/PEG delivery system offers an innovative intra-cavity approach to administer chemotherapeutics for improved local control of malignant brain tumors. PMID:24155955

  1. RBS analysis of the diffusion of nano-size spheres in a polymer matrix

    SciTech Connect

    Cole, D.H. |; Shull, K.R.; Rehn, L.E.; Baldo, P.M.

    1997-08-01

    Rutherford Backscattering Spectrometry (RBS) with 1.5-MeV He ions was employed to measure the depth distribution of gold particles sandwitched between two poly(tert-butyl acrylate) layers following various isothermal annealing treatments; temperatures were kept below 170{degrees}C to prevent degradation of the polymer. Since PTBA also degrades when the ion beam impinges the sample, it was necessary to quantify the mass loss in order to obtain accurate diffusion coefficients. Although the total mass loss was substantial (40-60%), a simple expansion of the energy-to-depth scale was sufficient to account for the beam-induced shrinkage. This result is attributed to the fact that the mass loss occurs very rapidly, and is uniformly distributed through the depth of the sample. The data reveal that the diffusion of the nanometer-size gold particles is substantially slower than is predicted by a simple physical model (Stokes-Einstein) for noninteracting particles. This slowdown is attributed to polymer bridging interactions, in which polymer strands bind to individual metal particles, thereby retarding their diffusion.

  2. Micro and nano composites composed of a polymer matrix and a metal disperse phase

    NASA Astrophysics Data System (ADS)

    Olea Mejia, Oscar Fernando

    Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10%. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices.

  3. Properties of Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Kang, Jin Ho; Grimsley, Brian W.; Ratcliffe, James G.; Siochi, Emilie J.

    2016-01-01

    For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strength- and stiffness-to-weight ratios, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Carbon nanotubes (CNT) offer the potential to enhance the multi-functionality of composites with improved thermal and electrical conductivity. In this study, hybrid CNT/carbon fiber (CF) polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing. Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated.

  4. Microscopic Model of the Metal-Organic Framework/Polymer Interface: A First Step toward Understanding the Compatibility in Mixed Matrix Membranes.

    PubMed

    Semino, Rocio; Ramsahye, Naseem A; Ghoufi, Aziz; Maurin, Guillaume

    2016-01-13

    An innovative computational methodology integrating density functional theory calculations and force field-based molecular dynamics simulations was developed to provide a first microscopic model of the interactions at the metal-organic framework (MOF) surface/polymer interface. This was applied to the case of the composite formed by the polymer of intrinsic microporosity, PIM-1, and the zeolitic imidazolate framework, ZIF-8, as a model system. We found that the structure of the composite at the interface is the result of both the chemical affinity between PIM-1 and ZIF-8 and the rigidity of the polymer. Specifically, there is a preferential interaction between the -CN groups of PIM-1 and the NH terminal functions of the organic linker at the ZIF-8 surface. Additionally, the resulting conformation of the polymer gives rise to interfacial microvoids at the vicinity of the MOF surface. The porosity, rigidity, and density of the interfacial polymer were analyzed and compared to those for the bulk polymer. It was shown that the polymer still feels the impact of the MOF surface even at long distances above 15-20 Å. Further, both the polydispersity of the polymer and the flexibility of the MOF surface were revealed to only slightly affect the properties of the MOF/interface. This work, which delivers a microscopic picture of the MOF surface/polymer interactions at the interface, would lead, in turn, to the understanding of the compatibility in MOF-based mixed-matrix membranes. PMID:26653765

  5. Mechanical properties of several neat polymer matrix materials and unidirectional carbon fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Coguill, Scott L.; Adams, Donald F.

    1989-01-01

    The mechanical and physical properties of three neat matrix materials, i.e., PEEK (polyetheretherketone) thermoplastic, Hexcel F155 rubber-toughened epoxy and Hercules 8551-7 rubber-toughened epoxy, were experimentally determined. Twelve unidirectional carbon fiber composites, incorporating matrix materials characterized in this or earlier studies (with one exception; the PISO(sub 2)-TPI matrix itself was not characterized), were also tested. These composite systems included AS4/2220-1, AS4/2220-3, T500/R914, IM6/HX1504, T300/4901A (MDA), T700/4901A (MDA), T300/4901B (MPDA), T700/4901B (MPDA), APC2 (AS4/PEEK, ICI), APC2 (AS4/PEEK, Langley Research Center), AS4/8551-7, and AS4/PISO(sub 2)-TPI. For the neat matrix materials, the tensile, shear, fracture toughness, coefficient of thermal expansion, and coefficient of moisture expansion properties were measured as a function of both temperature and moisture content. For the unidirectional composites, axial and transverse tensile, longitudinal shear, coefficient of thermal expansion, and coefficient of moisture expansion properties were determined, at room temperature and 100 C.

  6. A green and environment-friendly gel polymer electrolyte with higher performances based on the natural matrix of lignin

    NASA Astrophysics Data System (ADS)

    Gong, Sheng-Dong; Huang, Yun; Cao, Hai-Jun; Lin, Yuan-Hua; Li, Yang; Tang, Shui-Hua; Wang, Ming-Shan; Li, Xing

    2016-03-01

    In order to explore one truly green and environment-friendly gel polymer electrolyte (GPE), the natural biopolymer of lignin is firstly all over the world used as matrix to prepare GPE. The electrolyte membrane based on lignin can be easily fabricated just with lignin, liquid electrolyte and distilled water. Through comprehensive investigation of obtained GPE, it is found that the liquid electrolyte uptake reaches up to 230 wt.%; before 100 °C, GPE does not lose any weight and is thermal stable; at room temperature the ion conductivity is 3.73 mS cm-1; the amazing property of lithium ion transference number is high up to 0.85; GPE expresses complete electrochemical stability before 7.5 V and favorable compatibility with lithium anode; the outstanding cell performance of C-rate and cycle capacity. All these remarkably excellent performances endow lignin with application potential in GPE used in lithium ion batteries (LIBs) with higher performances.

  7. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-09-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  8. Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix.

    PubMed

    Yu, Ji Hoon; Chen, Hung-Shan; Chen, Po-Ju; Song, Ki Hoon; Noh, Seong Cheol; Lee, Jae Myeong; Ren, Hongwen; Lin, Yi-Hsin; Lee, Seung Hee

    2015-06-29

    Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast~5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality. PMID:26191743

  9. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  10. Two-photon excitation of dyes in a polymer matrix by femtosecond pulses from a Ti:sapphire laser

    SciTech Connect

    Meshalkin, Yu P; Myachin, A Yu; Bakhareva, S S; Svetlichnyi, Valerii A; Kopylova, T N; Reznichenko, A V; Dolotov, S M; Ponomarenko, E P

    2003-09-30

    Two-photon fluorescence was observed for 18 organic dyes in a polymethyl methacrylate (PMMA) matrix excited by a femtosecond Ti:sapphire laser. The product of the cross section for two-photon absorption by the quantum yield of fluorescence (two-photon fluorescence cross section) is estimated by comparing it with fluorescence of Rhodamine 6G in ethanol. Using this parameter, dyes are selected that exhibit the most intense fluorescence in PMMA and their concentrations in PMMA are optimised. Coumarin and rhodamine dyes in polymer matrices are proposed for using as visualisers of femtosecond radiation of a Ti:sapphire laser and as detectors in self-triggering systems. (active media. lasers)

  11. Melt Infiltrated Ceramic Matrix Composites for Shrouds and Combustor Liners of Advanced Industrial Gas Turbines

    SciTech Connect

    Gregory Corman; Krishan Luthra; Jill Jonkowski; Joseph Mavec; Paul Bakke; Debbie Haught; Merrill Smith

    2011-01-07

    This report covers work performed under the Advanced Materials for Advanced Industrial Gas Turbines (AMAIGT) program by GE Global Research and its collaborators from 2000 through 2010. A first stage shroud for a 7FA-class gas turbine engine utilizing HiPerComp{reg_sign}* ceramic matrix composite (CMC) material was developed. The design, fabrication, rig testing and engine testing of this shroud system are described. Through two field engine tests, the latter of which is still in progress at a Jacksonville Electric Authority generating station, the robustness of the CMC material and the shroud system in general were demonstrated, with shrouds having accumulated nearly 7,000 hours of field engine testing at the conclusion of the program. During the latter test the engine performance benefits from utilizing CMC shrouds were verified. Similar development of a CMC combustor liner design for a 7FA-class engine is also described. The feasibility of using the HiPerComp{reg_sign} CMC material for combustor liner applications was demonstrated in a Solar Turbines Ceramic Stationary Gas Turbine (CSGT) engine test where the liner performed without incident for 12,822 hours. The deposition processes for applying environmental barrier coatings to the CMC components were also developed, and the performance of the coatings in the rig and engine tests is described.

  12. Advances in the biomedical application of polymer-functionalized carbon nanotubes.

    PubMed

    Soleyman, Rouhollah; Hirbod, Sorina; Adeli, Mohsen

    2015-05-01

    Nowadays, carbon nanotubes (CNTs) have attracted the attention of scientists because of their unique electronic, magnetic, optical, mechanical, and chemical properties. However, their poor solubility in solvents, especially in water, limits their applications in several promising fields such as biomedicine, biomedical imaging, and cancer therapy. The attachment of hydrophilic segments to CNTs is a very efficient method for overcoming this problem. This review covers the latest advances in the synthesis of water-soluble CNTs with an emphasis on the molecular structure of various categories of hydrophilic molecules/macromolecules which have been grafted onto the surface of CNTs. Indeed, from the viewpoint of chemical synthesis, covalent bonding of several water-soluble molecules/macromolecules including small water-soluble organic molecules, linear, hyperbranched and dendritic polymers/biopolymers, glycoconjugate molecules/polymers as well as biomolecules onto the surface of CNTs has been deeply surveyed. Moreover, the most recent and interesting bio-applications of polymer-functionalized water-soluble CNTs have been properly reviewed. PMID:26222588

  13. Survivability of Affordable High Temperature Polymer Matrix Composites for Propulsion Engine Components

    NASA Technical Reports Server (NTRS)

    Dean, Derrick; Haque, Anwar; Vaidya, Uday; Meador, Michael A. (Technical Monitor)

    2003-01-01

    PMR-type polyimides are regarded as state of the art high temperature polymers, due to their excellent thermo-mechanical properties and thermo-oxidative stability. One of their drawbacks, however is the inability to process them using cost-effective processing methods such as Resin Transfer Molding (RTM) and Resin Film Infusion (RFI). Development of low viscosity, high temperature polymers has been the subject of intense research. Recently, a new generation of low viscosity polyimides were synthesized by the introduction of twisted biphenyl or binapthyl groups into the backbone. This report details the progress for Year 1, which has involved acquiring samples and initiating Phases I and II of the proposed research. Specifically, studies of the process-property relationships of a series of polymers using oligomers based on 2,3,3' ,4'-biphenyltertracarboxylic dianhydride (PBDA) and a mixture of a diamine, BAX and a triamine, 1,3,5-Tris (4-aminophenoxybenzene), TAB, where the amount of TAB was varied have been initiated. The sample containing 10 percent TAB possesses a slightly higher degree of crystalline order versus that of the 20 percent TAB sample, based on x-ray diffraction studies of the b-staged oligomers. Both systems lose all of the crystalline order upon curing, however. The chemorheology has been studied as a function of the TAB content. While the magnitude of the viscosity is essentially the same for both systems, the cure kinetics of the 10 percent TAB system is faster than that for the 20 percent TAB system. The sample exhibits a melting-recrystallization-remelting behavior before the crosslinking commences. Correlation of other kinetic parameters, such as the activation energies for curing, the Tg and mechanical properties to the structure of these systems is underway. Future studies will involve characterization of mechanical and thermal properties of the pure resins and the fabrication of fiber reinforced composites using these materials.

  14. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  15. Sulfur polymer cement as a low-level waste glass matrix encapsulant. Part 1: Thermal processing

    SciTech Connect

    Sliva, P.; Peng, Y.B.; Bunnell, L.R.; Peeler, D.K.; Feng, X.; Martin, P.; Turner, P.J.

    1996-08-01

    Sulfur polymer cement (SPC) is a candidate material to encapsulate low-level waste (LLW) glass. Molten SPC will be poured into a LLW glass cullet-filled canister, surrounding the glass to act as an additional barrier to groundwater intrusion. This paper covers the first part of a study performed at Pacific Northwest National Laboratory concerned with the fundamental aspects of embedding LLW glass in SPC. Part one is a study of the SPC itself. Variations in SPC properties are discussed, especially in relation to long-term stability and controlling crystallization in a cooling canister.

  16. Advances in Ceramic Matrix Composite Blade Damping Characteristics for Aerospace Turbomachinery Applications

    NASA Technical Reports Server (NTRS)

    Min, James B.; Harris, Donald L.; Ting, J. M.

    2011-01-01

    For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the one-piece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming with blisk construction, however, is that blisks may be prone to high cycle fatigue due to their structural response to high vibration environments. Use of ceramic composites is expected to provide some internal damping to reduce the vibratory stresses encountered due to unsteady flow loads through the bladed turbine regions. A goal of our research was to characterize the vibration viscous damping behavior of C/SiC composites. The vibration damping properties were measured and calculated. Damping appeared to decrease with an increase in the natural frequency. While the critical damping amount of approximately 2% is required for typical aerospace turbomachinery engines, the C/SiC damping at high frequencies was less than 0.2% from our study. The advanced high-performance aerospace propulsion systems almost certainly will require even more damping than what current vehicles require. A purpose of this paper is to review some work on C/SiC vibration damping by the authors for the NASA CMC turbine blisk development program and address an importance of the further investigation of the blade vibration damping characteristics on candidate CMC materials for the NASA s advanced aerospace turbomachinery engine systems.

  17. Mechanical properties and XRD studies of silicon carbide inert matrix fuel fabricated by a low temperature polymer precursor route

    NASA Astrophysics Data System (ADS)

    Shih, Chunghao; Rohbeck, Nadia; Gopalakrishnan, Karthik; Tulenko, James S.; Baney, Ronald H.

    2013-01-01

    The mechanical properties of silicon carbide (SiC) inert matrix fuel (IMF) pellets fabricated by a low temperature (1050 °C) polymer precursor route were evaluated at room temperature. The Vickers hardness was mainly related to the chemical bonding strength between the amorphous SiC phase and the β-SiC particles. The biaxial fracture strength with pre-notch and fracture toughness were found to be mostly controlled by the pellet density. The maximum Vickers hardness, biaxial fracture strength with pre-notch and fracture toughness achieved were 5.6 GPa, 201 MPa and 2.9 MPa m1/2 respectively. These values appear to be superior to the reference MOX or UO2 fuels. Excellent thermal shock resistance for the fabricated SiC IMF was proven and the values were compared to conventional UO2 pellets. XRD studies showed that ceria (PuO2 surrogate) chemically reacted with the polymer precursor during sintering, forming cerium oxysilicate. Whether PuO2 will chemically react in a similar manner remains unclear.

  18. PES mixed matrix nanofiltration membrane embedded with polymer wrapped MWCNT: Fabrication and performance optimization in dye removal by RSM.

    PubMed

    Ghaemi, Negin; Madaeni, Sayed S; Daraei, Parisa; Rajabi, Hamid; Shojaeimehr, Tahereh; Rahimpour, Farshad; Shirvani, Bita

    2015-11-15

    MWCNTs were wrapped by poly(sodium 4-styrenesulfonate) (PSS), and different amounts of raw and polymer wrapped MWCNTs were implemented to fabricate PES mixed matrix membranes by phase inversion method. Success of wrapping was probed by FTIR spectroscopy, and prepared membranes were characterized by SEM, AFM, porosity, and water contact angle measurements. Response surface methodology (RSM) was employed to optimize the permeate flux and dye removal efficiency of membranes with three variables of concentration, pH of dye solution, and membrane composition. A response surface (RS) with a D-optimal design was defined to build the mathematical model, minimize the number of experiments, and investigate the effect of parameters on the response. Adequacy of the obtained model was confirmed by means of variance analysis and additional experiments. Based on observed and predicted results, wrapping CNTs by PSS improved permeation flux and dye removal efficiency of MMMs. Validity of model was verified according to the good agreement between predicted and experimental results. Membrane mixed with 0.1 wt.% polymer wrapped MWCNTs offered the highest permeation flux as well as dye removal efficiency. According to the model response, in order to achieve a higher dye removal, an acidic pH and a moderate dye solution concentration are recommended. Additionally, basic solution pH (9.0) and a dilute dye solution are suggested to reach a higher permeation flux. PMID:26022851

  19. Nondestructive Determination of Heat/Fire Damage to Polymer- Matrix Composites Using Obliquely Insonified Ultrasonic Waves

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.; Mal, A.; Lih, S.

    1995-01-01

    Heat and fire damage to composite structures cause loss of strength that cannot be detected by current NDE methods unless physical damage occurs. Further, there is a lack of fundamental understanding of the mechanism of damage from thermal exposure of organic matrix composites to elevated temperatures. Information compiled from field reports and lab experiments increasingly suggests that there is material degradation and it is not necessarily involved with the introduction of physical defects. In recent years, various researchers examined the potential to identifying thermal degradation to organic matrix composites prior to delamination. The methods that were used include: ultrasonics, backscattered X-ray, eddy current, thermography, drift and LPF spectroscopies, acousto-ultrasonics and hardness testing. None of these methods were able to correlate NDE results with loss of mechanical properties.

  20. An antibacterial coating based on a polymer/sol-gel hybrid matrix loaded with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Rivero, Pedro José; Urrutia, Aitor; Goicoechea, Javier; Zamarreño, Carlos Ruiz; Arregui, Francisco Javier; Matías, Ignacio Raúl

    2011-12-01

    In this work a novel antibacterial surface composed of an organic-inorganic hybrid matrix of tetraorthosilicate and a polyelectrolyte is presented. A precursor solution of tetraethoxysilane (TEOS) and poly(acrylic acid sodium salt) (PAA) was prepared and subsequently thin films were fabricated by the dip-coating technique using glass slides as substrates. This hybrid matrix coating is further loaded with silver nanoparticles using an in situ synthesis route. The morphology and composition of the coatings have been studied using UV-VIS spectroscopy and atomic force microscopy (AFM). Energy dispersive X-ray (EDX) was also used to confirm the presence of the resulting silver nanoparticles within the thin films. Finally the coatings have been tested in bacterial cultures of genus Lactobacillus plantarum to observe their antibacterial properties. It has been experimentally demonstrated that these silver loaded organic-inorganic hybrid films have a very good antimicrobial behavior against this type of bacteria.

  1. Additional results on space environmental effects on polymer matrix composites: Experiment A0180

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.

    1992-01-01

    Additional experimental results on the atomic oxygen erosion of boron, Kevlar, and graphite fiber reinforced epoxy matrix composites are presented. Damage of composite laminates due to micrometeoroid/debris impacts is also examined with particular emphasis on the relationship between damage area and actual hole size due to particle penetration. Special attention is given to one micrometeoroid impact on an aluminum base plate which resulted in ejecta visible on an adjoining vertical flange structure.

  2. Erosion Coatings for High-Temperature Polymer Composites: A Collaborative Project With Allison Advanced Development Company

    NASA Technical Reports Server (NTRS)

    Sutter, James K.

    2000-01-01

    The advantages of replacing metals in aircraft turbine engines with high-temperature polymer matrix composites (PMC's) include weight savings accompanied by strength improvements, reduced part count, and lower manufacturing costs. Successfully integrating high-temperature PMC's into turbine engines requires several long-term characteristics. Resistance to surface erosion is one rarely reported property of PMC's in engine applications because PMC's are generally softer than metals and their erosion resistance suffers. Airflow rates in stationary turbine engine components typically exceed 2.3 kg/sec at elevated temperatures and pressures. In engine applications, as shown in the following photos, the survivability of PMC components is clearly a concern, especially when engine and component life-cycle requirements become longer. Although very few publications regarding the performance of erosion coatings on PMC's are available particularly in high-temperature applications the use of erosion-resistant coatings to significantly reduce wear on metallic substrates is well documented. In this study initiated by the NASA Glenn Research Center at Lewis Field, a low-cost (less than $140/kg) graphite-fiber-reinforced T650 35/PMR 15 sheet-molding compound was investigated with various coatings. This sheet-molding compound has been compression molded into many structurally complicated components, such as shrouds for gas turbine inlet housings and gearboxes. Erosion coatings developed for PMC s in this study consisted of a two-layered system: a bondcoat sprayed onto a cleaned PMC surface, followed by an erosion-resistant, hard topcoat sprayed onto the bondcoat as shown in following photomicrograph. Six erosion coating systems were evaluated for their ability to withstand harsh thermal cycles, erosion resistance (ASTM G76 83 "Standard Practice for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets") using Al2O3, and adhesion to the graphite fiber polyimide

  3. Evolution of stress and deformations in high-temperature polymer matrix composites during thermo-oxidative aging

    NASA Astrophysics Data System (ADS)

    Pochiraju, K. V.; Tandon, G. P.; Schoeppner, G. A.

    2008-03-01

    This paper presents a model-based analysis of thermo-oxidative behavior in high-temperature polymer matrix composite (HTPMC) materials. The thermo-oxidative behavior of the composite differs from that of the constituents as the composite microstructure, the fiber/matrix interphase/interface behavior and damage mechanisms introduce anisotropy in the diffusion and oxidation behavior. Three-dimensional Galerkin finite element methods (GFEM) that model the thermo-oxidative layer growth with time are used together with homogenization techniques to analyze lamina-scale behavior using representative volume elements (RVEs). Thermo-oxidation-induced shrinkage is characterized from dimensional changes observed during aging in inert (argon) and oxidative (air) environments. Temperature-dependent macro-scale (bulk) mechanical testing and nano-indentation techniques are used for characterizing the effect of oxidative aging on modulus evolution. The stress and deformation fields in a single ply unidirectional lamina are studied using coupled oxidation evolution and non-linear elastic deformation analyses. Deformation and stress states are shown as a function of the aging time. While the thermo-oxidative processes are controlled by diffusion phenomenon in neat resin, the onset and propagation of damage determines the oxidative response of an HTPMC.

  4. Tuning the performance of direct methanol fuel cell membranes by embedding multifunctional inorganic submicrospheres into polymer matrix

    NASA Astrophysics Data System (ADS)

    Wang, Jingtao; Zhang, Han; Jiang, Zhongyi; Yang, Xinlin; Xiao, Lulu

    A series of surface functionalized silica submicrospheres by distillation-precipitation polymerization were embedded into chitosan (CS) matrix to fabricate the hybrid membranes for direct methanol fuel cell (DMFC). SEM characterization indicated that the submicrospheres could disperse homogenously within the CS matrix via tuning the polymer/particle and particle/particle interfacial interactions. The incorporation of sulfonated silica and carboxylated silica led to the reduced fractional free volume (FFV), whereas the incorporation of quaternary aminated silica resulted in increased FFV in the hybrid membranes, which was confirmed by the free volume characteristics analysis using positron annihilation lifetime spectroscopy (PALS). The correlation between methanol crossover and FFV was established: the hybrid membranes with lower FFV displayed higher methanol resistance. Meanwhile, the correlation between the proton acceptor/donor capability and proton conductivity in the hybrid membranes was established. Compared with sulfonated silica and quaternary aminated silica, carboxylated silica possessed the optimum matching in proton acceptor and donor capabilities. Therefore, the membrane embedded with carboxylated silica displayed the highest proton conductivity. In particular, embedding carboxylated silica simultaneously reduced the methanol permeability by 63% and increased the proton conductivity by 40% in comparison with pure CS membrane.

  5. Schottky diodes between Bi{sub 2}S{sub 3} nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

    SciTech Connect

    Saha, Sudip K.; Pal, Amlan J.

    2015-07-07

    We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi{sub 2}S{sub 3} nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi{sub 2}S{sub 3} nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells.

  6. Schottky diodes between Bi2S3 nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Saha, Sudip K.; Pal, Amlan J.

    2015-07-01

    We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi2S3 nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi2S3 nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells.

  7. Quantum efficiency of PAG decomposition in different polymer matrices at advanced lithographic wavelengths

    NASA Astrophysics Data System (ADS)

    Fedynyshyn, Theodore H.; Sinta, Roger F.; Mowers, William A.; Cabral, Alberto

    2003-06-01

    The Dill ABC parameters for optical resists are typically determined by measuring the change in the intensity of transmitted light at the wavelength of interest as a function of incident energy. The effectiveness of the experiment rests with the fact that the resist optical properties change with exposure and that the optical properties are directly related to the concentration of PAG compound. These conditions are not typically satisfied in CA resists and thus C is unobtainable by this method. FT-IR spectroscopy can directly measure changes in the photoactive species by isolating and measuring absorbance peaks unique to the photoactive species. We employed the ProABC software, specially modified to allow FT-IR absorbance input, to extract ABS parameters through a best fit of the lithography model to experimental data. The quantum efficiency of PAG decomposition at 157-, 193-, and 248-nm was determined for four diazomethane type PAGs in four different polymer matrices. It was found that both the Dill C parameter and the quantum efficiency for all PAGs increased as wavelength decreased, but that the magnitude of the increase was strongly dependent on the polymer matrix.

  8. Accumulation of Extracellular Matrix in Advanced Lesions of Canine Distemper Demyelinating Encephalitis.

    PubMed

    Seehusen, Frauke; Al-Azreg, Seham A; Raddatz, Barbara B; Haist, Verena; Puff, Christina; Spitzbarth, Ingo; Ulrich, Reiner; Baumgärtner, Wolfgang

    2016-01-01

    In demyelinating diseases, changes in the quality and quantity of the extracellular matrix (ECM) may contribute to demyelination and failure of myelin repair and axonal sprouting, especially in chronic lesions. To characterize changes in the ECM in canine distemper demyelinating leukoencephalitis (DL), histochemical and immunohistochemical investigations of formalin-fixed paraffin-embedded cerebella using azan, picrosirius red and Gomori`s silver stain as well as antibodies directed against aggrecan, type I and IV collagen, fibronectin, laminin and phosphacan showed alterations of the ECM in CDV-infected dogs. A significantly increased amount of aggrecan was detected in early and late white matter lesions. In addition, the positive signal for collagens I and IV as well as fibronectin was significantly increased in late lesions. Conversely, the expression of phosphacan was significantly decreased in early and more pronounced in late lesions compared to controls. Furthermore, a set of genes involved in ECM was extracted from a publically available microarray data set and was analyzed for differential gene expression. Gene expression of ECM molecules, their biosynthesis pathways, and pro-fibrotic factors was mildly up-regulated whereas expression of matrix remodeling enzymes was up-regulated to a relatively higher extent. Summarized, the observed findings indicate that changes in the quality and content of ECM molecules represent important, mainly post-transcriptional features in advanced canine distemper lesions. Considering the insufficiency of morphological regeneration in chronic distemper lesions, the accumulated ECM seems to play a crucial role upon regenerative processes and may explain the relatively small regenerative potential in late stages of this disease. PMID:27441688

  9. Accumulation of Extracellular Matrix in Advanced Lesions of Canine Distemper Demyelinating Encephalitis

    PubMed Central

    Seehusen, Frauke; Al-Azreg, Seham A.; Raddatz, Barbara B.; Haist, Verena; Puff, Christina; Spitzbarth, Ingo; Ulrich, Reiner; Baumgärtner, Wolfgang

    2016-01-01

    In demyelinating diseases, changes in the quality and quantity of the extracellular matrix (ECM) may contribute to demyelination and failure of myelin repair and axonal sprouting, especially in chronic lesions. To characterize changes in the ECM in canine distemper demyelinating leukoencephalitis (DL), histochemical and immunohistochemical investigations of formalin-fixed paraffin-embedded cerebella using azan, picrosirius red and Gomori`s silver stain as well as antibodies directed against aggrecan, type I and IV collagen, fibronectin, laminin and phosphacan showed alterations of the ECM in CDV-infected dogs. A significantly increased amount of aggrecan was detected in early and late white matter lesions. In addition, the positive signal for collagens I and IV as well as fibronectin was significantly increased in late lesions. Conversely, the expression of phosphacan was significantly decreased in early and more pronounced in late lesions compared to controls. Furthermore, a set of genes involved in ECM was extracted from a publically available microarray data set and was analyzed for differential gene expression. Gene expression of ECM molecules, their biosynthesis pathways, and pro-fibrotic factors was mildly up-regulated whereas expression of matrix remodeling enzymes was up-regulated to a relatively higher extent. Summarized, the observed findings indicate that changes in the quality and content of ECM molecules represent important, mainly post-transcriptional features in advanced canine distemper lesions. Considering the insufficiency of morphological regeneration in chronic distemper lesions, the accumulated ECM seems to play a crucial role upon regenerative processes and may explain the relatively small regenerative potential in late stages of this disease. PMID:27441688

  10. Observations of coarsening of air voids in a polymer-highly-soluble crystalline matrix during dissolution

    NASA Astrophysics Data System (ADS)

    Karakosta, Eleni; Jenneson, Paul M.; Sear, Richard P.; McDonald, Peter J.

    2006-07-01

    A combination of magnetic resonance imaging and x-ray microcomputed tomography has been used to visualize the development of the internal micro-structure within compressed tablets made from a combination of insoluble particles (Eudragit, a polymer) and soluble particles (diltiazem hydrochloride, a drug), during dissolution in water. Air voids in the tablet are seen to coarsen. The size distribution of the air voids is well fitted by a log-normal distribution with a mean size that grows linearly with time. There is evidence for both diffusion of voids and sudden collapse of individual voids, presumably as they coalesce. The behavior of the voids is studied and compared with models of coarsening; the implications for tablet dissolution are considered.

  11. New high temperature cross linking monomers. [for polymer matrix composite materials

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1978-01-01

    Several PMR-polyimide resins capable of being processed at a maximum temperature of 232 C to 288 C without sacrifice of high temperature capability were developed. Four monomethyl esters were synthesized and characterized for use in the crosslinking studies. The infrared and DSC studies of each crosslinker suggested that curing could be accomplished at 288 C. However, fabrication of dense, void free polymer specimens required a temperature of 316 C and a pressure of 0.69 MPa (100 psi). Crosslinkers were evaluated in Celion 6000/PMR polyimide composites. These composites were characterized at RT, 288 C and 316 C initially and after isothermal aging at 288 C and 316 C for several hundred hours. The results suggest that both PMR systems are promising candidates as matrices for addition type polyimide composites. It is demonstrated that alternate crosslinkers are feasible, but mechanisms to lower the crosslinking temperature must be developed to provide lower temperature processing PMR-type polyimides.

  12. Improving processing and toughness of a high performance composite matrix through an interpenetrating polymer network. VI

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H.

    1990-01-01

    The use of a semiinterpenetrating polymer network (SIPN) of the high-performance polyimide NR-150B2 to reduce brittleness and improve processability in the highly crosslinked acetylene-terminated polyimides Thermid LR-600, AL-600, MC-600, and FA-700 is described. The theoretical basis of the SIPN process is reviewed; the preparation and characterization of the neat SIPN resins and unidirectional graphite-fiber composites are explained; and the results are presented in extensive tables, graphs, and micrographs and discussed in detail. Significant increases in fracture energy were observed with SIPN, from 93 J/sq m for unmodified LR-600 to 283-603 J/sq m for the SIPN materials; the room-temperature flexural strength of the unidirectional composites also increased, from 1344 MPa for an unmodified MC-600 composite to 2020-1751 MPa for the SIPN composites. The potential applicability of SIPN-based composites to aerospace structures and electronic components is indicated.

  13. Improving processing and toughness of a high performance composite matrix through an interpenetrating polymer network. VI

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H.

    1990-01-01

    A simultaneous semi-interpenetrating polymer network (semi-IPN) concept is presented which combines easy-to-process, but brittle, thermosetting polyimides with tough, but difficult to process, linear thermoplastic polyimides. The combination results in a semi-IPN with the easy processability of a thermoset and good toughness of a thermoplastic. Four simultaneous semi-IPN systems were developed from commercially available NR-150B2 combined with each of the four Thermid materials (LR-600, AL-600, MC-600, and FA-700). It is concluded that there is a significant improvement in resin fracture toughness of Thermid-polyimide-based semi-IPN systems and some improvement in composite microcracking resistance compared to Thermid LR-600. Excellent composite mechanical properties have been achieved. These new semi-IPN materials have the potential to be used as composite matrices, adhesives, and molding materials.

  14. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  15. Three-Dimensional Nanoporous Cellulose Gels as a Flexible Reinforcement Matrix for Polymer Nanocomposites.

    PubMed

    Shi, Zhuqun; Huang, Junchao; Liu, Chuanjun; Ding, Beibei; Kuga, Shigenori; Cai, Jie; Zhang, Lina

    2015-10-21

    With the world's focus on utilization of sustainable natural resources, the conversion of wood and plant fibers into cellulose nanowhiskers/nanofibers is essential for application of cellulose in polymer nanocomposites. Here, we present a novel fabrication method of polymer nanocomposites by in-situ polymerization of monomers in three-dimensionally nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solution. The NCG have interconnected nanofibrillar cellulose network structure, resulting in high mechanical strength and size stability. Polymerization of the monomer gave P(MMA/BMA)/NCG, P(MMA/BA)/NCG nanocomposites with a volume fraction of NCG ranging from 15% to 78%. SEM, TEM, and XRD analyses show that the NCG are finely distributed and preserved well in the nanocomposites after polymerization. DMA analysis demonstrates a significant improvement in tensile storage modulus E' above the glass transition temperature; for instance, at 95 °C, E' is increased by over 4 orders of magnitude from 0.03 MPa of the P(MMA/BMA) up to 350 MPa of nanocomposites containing 15% v/v NCG. This reinforcement effect can be explained by the percolation model. The nanocomposites also show remarkable improvement in solvent resistance (swelling ratio of 1.3-2.2 in chloroform, acetone, and toluene), thermal stability (do not melt or decompose up to 300 °C), and low coefficients of thermal expansion (in-plane CTE of 15 ppm·K(-1)). These nanocomposites will have great promising applications in flexible display, packing, biomedical implants, and many others. PMID:26397710

  16. Longtime Durability of PMR-15 Matrix Polymer at 204, 260, 288, and 316 C

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Papadopoulos, Demetrios S.; Inghram, Linda L.; McCorkle, Linda S.; Klan, Ojars V.

    2001-01-01

    Isothermal weight loss studies at the Glenn (Lewis) Research Center were conducted at four temperatures (204, 260, 288, and 316 C) with specimens of varied geometric shapes to investigate the mechanisms involved in the thermal degradation of PMR-15. Both neat resin behavior and composite behaviors were studied. Two points of interest in these studies are the role(s) of oxygen in the mechanisms involved in the thermo-oxidative degradation of these composite materials and the dimensional changes that occur during their useable lifetime. Specimen dimensional changes and surface layer growth were measured and recorded. It was shown that physical and chemical changes take place as a function of time and location in PMR-15 neat resin and composites as aging takes place in air at elevated temperatures. These changes initiate at the outer surfaces of both materials and progress inward following the oxygen as it proceeds by diffusion into the central core of each material. Microstructural changes cause changes in density, material shrinkage (strains), glass transition temperature, dimension, dynamic shear modulus, and compression properties. These changes also occur slowly dividing the polymer material into two distinct parts: a visibly undamaged core section between two visibly damaged surface layers. The surface layer has a significant effect on compression properties of thinner specimens, but the visibly undamaged core material controls these properties for specimens having eight or more plies. It was demonstrated that there are three different mechanisms involved in the degradation of PMR-15 during aging at elevated temperatures. These are a weight gain, a small weight fraction bulk material weight loss, and a large mass fraction weight loss concentrated at the surface of the polymer or composite. At the higher temperatures (260 C and above), the surface loss predominates. Below 260 C, the surface loss and the bulk core loss become more equivalent. Between 175 and 260 C

  17. Relationship between voids and interlaminar shear strength of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Frimpong, Stephen

    1991-01-01

    The effect of voids on the interlaminar shear strength of a polyimide matrix composite system is described. The AS4 graphite/PMR-15 composite was chosen for study because this system can be readily processed by using the standard specified cure cycle to produce void-free composites and because preliminary work in this study had shown that the processing parameters of this resin matrix system can be altered to produce cured composites of varying void contents. Thirty-eight 12-ply unidirectional composite panels were fabricated for this study. A significant range of void contents (0 to 10 percent) was produced. The panels were mapped, ultrasonically inspected, and sectioned into interlaminar shear, flexure, and fiber content specimens. The density of each specimen was measured and interlaminar shear and flexure strength measurements were then made. The fiber content was measured last. The results of these tests were evaluated by using ultrasonic results, photomicrographs, statistical methods, theoretical relationships derived by other investigators, and comparison of the test data with the Integrated Composite Analyzer (ICAN) computer program developed at the Lewis Research Center for predicting composite ply properties. The testing is described in as much detail as possible in order to help others make realistic comparisons.

  18. Advances in the design of macroporous polymer scaffolds for potential applications in dentistry

    PubMed Central

    Braschler, Thomas M.; Renaud, Philippe

    2013-01-01

    A paradigm shift is taking place in medicine and dentistry from using synthetic implants and tissue grafts to a tissue engineering approach that uses degradable porous three-dimensional (3D) material hydrogels integrated with cells and bioactive factors to regenerate tissues such as dental bone and other oral tissues. Hydrogels have been established as a biomaterial of choice for many years, as they offer diverse properties that make them ideal in regenerative medicine, including dental applications. Being highly biocompatible and similar to native extracellular matrix, hydrogels have emerged as ideal candidates in the design of 3D scaffolds for tissue regeneration and drug delivery applications. However, precise control over hydrogel properties, such as porosity, pore size, and pore interconnectivity, remains a challenge. Traditional techniques for creating conventional crosslinked polymers have demonstrated limited success in the formation of hydrogels with large pore size, thus limiting cellular infiltration, tissue ingrowth, vascularization, and matrix mineralization (in the case of bone) of tissue-engineered constructs. Emerging technologies have demonstrated the ability to control microarchitectural features in hydrogels such as the creation of large pore size, porosity, and pore interconnectivity, thus allowing the creation of engineered hydrogel scaffolds with a structure and function closely mimicking native tissues. In this review, we explore the various technologies available for the preparation of macroporous scaffolds and their potential applications. PMID:24455437

  19. Rate dependent stress-strain behavior of advanced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1991-01-01

    The formulation of an elastic/viscoplastic constitutive model which was used to predict the measured behavior of graphite/thermoplastic and graphite/bismaleimide composite materials at elevated temperature is described. The model incorporates the concepts of overstress and effective strain/strain to provide a simple formulation which was able to account for material behavior under monotonic tension or compression loads over a temperature range of 23 to 200 C. Observed behavior such as stress relaxation and steady state creep, in off-axis tension and compression tests, were predicted by the model. Material constants required by the model were extracted from simple off-axis test data.

  20. Clearance Kinetics and Matrix Binding Partners of the Receptor for Advanced Glycation End Products

    PubMed Central

    Milutinovic, Pavle S.; Englert, Judson M.; Crum, Lauren T.; Mason, Neale S.; Ramsgaard, Lasse; Enghild, Jan J.; Sparvero, Louis J.; Lotze, Michael T.; Oury, Tim D.

    2014-01-01

    Elucidating the sites and mechanisms of sRAGE action in the healthy state is vital to better understand the biological importance of the receptor for advanced glycation end products (RAGE). Previous studies in animal models of disease have demonstrated that exogenous sRAGE has an anti-inflammatory effect, which has been reasoned to arise from sequestration of pro-inflammatory ligands away from membrane-bound RAGE isoforms. We show here that sRAGE exhibits in vitro binding with high affinity and reversibly to extracellular matrix components collagen I, collagen IV, and laminin. Soluble RAGE administered intratracheally, intravenously, or intraperitoneally, does not distribute in a specific fashion to any healthy mouse tissue, suggesting against the existence of accessible sRAGE sinks and receptors in the healthy mouse. Intratracheal administration is the only effective means of delivering exogenous sRAGE to the lung, the organ in which RAGE is most highly expressed; clearance of sRAGE from lung does not differ appreciably from that of albumin. PMID:24642901

  1. Clearance kinetics and matrix binding partners of the receptor for advanced glycation end products.

    PubMed

    Milutinovic, Pavle S; Englert, Judson M; Crum, Lauren T; Mason, Neale S; Ramsgaard, Lasse; Enghild, Jan J; Sparvero, Louis J; Lotze, Michael T; Oury, Tim D

    2014-01-01

    Elucidating the sites and mechanisms of sRAGE action in the healthy state is vital to better understand the biological importance of the receptor for advanced glycation end products (RAGE). Previous studies in animal models of disease have demonstrated that exogenous sRAGE has an anti-inflammatory effect, which has been reasoned to arise from sequestration of pro-inflammatory ligands away from membrane-bound RAGE isoforms. We show here that sRAGE exhibits in vitro binding with high affinity and reversibly to extracellular matrix components collagen I, collagen IV, and laminin. Soluble RAGE administered intratracheally, intravenously, or intraperitoneally, does not distribute in a specific fashion to any healthy mouse tissue, suggesting against the existence of accessible sRAGE sinks and receptors in the healthy mouse. Intratracheal administration is the only effective means of delivering exogenous sRAGE to the lung, the organ in which RAGE is most highly expressed; clearance of sRAGE from lung does not differ appreciably from that of albumin. PMID:24642901

  2. Preparation and characterization of an advanced collagen aggregate from porcine acellular dermal matrix.

    PubMed

    Liu, Xinhua; Dan, Nianhua; Dan, Weihua

    2016-07-01

    The objective of this study was to extract and characterize an advanced collagen aggregate (Ag-col) from porcine acellular dermal matrix (pADM). Based on histological examination, scanning electron microscopy (SEM) and atomic force microscope (AFM), Ag-col was composed of the D-periodic cross-striated collagen fibrils and thick collagen fiber bundles with uneven diameters and non-orientated arrangement. Fourier transform infrared (FTIR) spectra of pADM, Ag-col and Col were similar and revealed the presence of the triple helix. Circular dichroism (CD) analysis exhibited a slightly higher content of α-helix but inappreciably less amount of random coil structure in Ag-col compared to Col. Moreover, imino acid contents of pADM, Ag-col and Col were 222.43, 218.30 and 190.01 residues/1000 residues, respectively. From zeta potential analysis, a net charge of zero was found at pH 6.45 and 6.11 for Ag-col and Col, respectively. Differential scanning calorimetry (DSC) study suggested that the Td of Ag-col was 20°C higher than that of Col as expected, and dynamic mechanical analysis (DMA) indicated that Ag-col possessed a higher storage modulus but similar loss factor compared to Col. Therefore, the collagen aggregate from pADM could serve as a better alternative source of collagens for further applications in food and biological industries. PMID:27039117

  3. Preparation and nonlinear characterization of zinc selenide nanoparticles embedded in polymer matrix

    NASA Astrophysics Data System (ADS)

    Sharma, Mamta; Tripathi, S. K.

    2012-09-01

    Nanocomposites of ZnSe nanoparticles embedded in polyvinyl alcohol (PVA) matrix have been prepared by in-situ synthesis. ZnSe/PVA nanocomposites are characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV/Vis spectra. The nanocomposite structure is confirmed by the blue-shift of the absorption edge. The nonlinear refractive index and two-photon absorption (TPA) coefficient are measured by the Z-scan technique using low power CW He-Ne laser light. The results show that the ZnSe nanocomposite films show large optical nonlinearity and the magnitude of the third-order nonlinear susceptibility χ(3) is calculated to be 2.62×13-11 m2/V2.

  4. Modeling the Stress Transfer between Carbon Nanotubes and a Polymer Matrix during Cyclic Deformation

    NASA Astrophysics Data System (ADS)

    Kao, C. C.; Young, R. J.

    Raman spectroscopy was used in this study to investigate the cyclic deformation behavior of the single-walled carbon nanotubes (SWNTs)/epoxy composites. The stress transfer between the nanotube and epoxy resin has been followed through the stress-induced variation of the G' Raman band position of the nan-otubes. A hysteresis loop was found between the loading and unloading cycles and its size decreased with the increase of the deformation cycles. The energy dissipated in the composite and at the interface between the nanotube and matrix has been modeled from the loop area. The amount of interface damaged for each loading cycle was further predicted from the estimated dissipation energy.

  5. Cheap glass fiber mats as a matrix of gel polymer electrolytes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Yusong; Wang, Faxing; Liu, Lili; Xiao, Shiyin; Yang, Yaqiong; Wu, Yuping

    2013-11-01

    Lithium ion batteries (LIBs) are going to play more important roles in electric vehicles and smart grids. The safety of the current LIBs of large capacity has been remaining a challenge due to the existence of large amounts of organic liquid electrolytes. Gel polymer electrolytes (GPEs) have been tried to replace the organic electrolyte to improve their safety. However, the application of GPEs is handicapped by their poor mechanical strength and high cost. Here, we report an economic gel-type composite membrane with high safety and good mechanical strength based on glass fiber mats, which are separator for lead-acid batteries. The gelled membrane exhibits high ionic conductivity (1.13 mS cm-1), high Li+ ion transference number (0.56) and wide electrochemical window. Its electrochemical performance is evaluated by LiFePO4 cathode with good cycling. The results show this gel-type composite membrane has great attraction to the large-capacity LIBs requiring high safety with low cost.

  6. Cheap glass fiber mats as a matrix of gel polymer electrolytes for lithium ion batteries

    PubMed Central

    Zhu, Yusong; Wang, Faxing; Liu, Lili; Xiao, Shiyin; Yang, Yaqiong; Wu, Yuping

    2013-01-01

    Lithium ion batteries (LIBs) are going to play more important roles in electric vehicles and smart grids. The safety of the current LIBs of large capacity has been remaining a challenge due to the existence of large amounts of organic liquid electrolytes. Gel polymer electrolytes (GPEs) have been tried to replace the organic electrolyte to improve their safety. However, the application of GPEs is handicapped by their poor mechanical strength and high cost. Here, we report an economic gel-type composite membrane with high safety and good mechanical strength based on glass fiber mats, which are separator for lead-acid batteries. The gelled membrane exhibits high ionic conductivity (1.13 mS cm−1), high Li+ ion transference number (0.56) and wide electrochemical window. Its electrochemical performance is evaluated by LiFePO4 cathode with good cycling. The results show this gel-type composite membrane has great attraction to the large-capacity LIBs requiring high safety with low cost. PMID:24216756

  7. Nanocomposite scaffold fabrication by incorporating gold nanoparticles into biodegradable polymer matrix: Synthesis, characterization, and photothermal effect.

    PubMed

    Abdelrasoul, Gaser N; Farkas, Balazs; Romano, Ilaria; Diaspro, Alberto; Beke, Szabolcs

    2015-11-01

    Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532nm laser, known as the photothermal effect. PMID:26249594

  8. Cheap glass fiber mats as a matrix of gel polymer electrolytes for lithium ion batteries.

    PubMed

    Zhu, Yusong; Wang, Faxing; Liu, Lili; Xiao, Shiyin; Yang, Yaqiong; Wu, Yuping

    2013-01-01

    Lithium ion batteries (LIBs) are going to play more important roles in electric vehicles and smart grids. The safety of the current LIBs of large capacity has been remaining a challenge due to the existence of large amounts of organic liquid electrolytes. Gel polymer electrolytes (GPEs) have been tried to replace the organic electrolyte to improve their safety. However, the application of GPEs is handicapped by their poor mechanical strength and high cost. Here, we report an economic gel-type composite membrane with high safety and good mechanical strength based on glass fiber mats, which are separator for lead-acid batteries. The gelled membrane exhibits high ionic conductivity (1.13 mS cm(-1)), high Li(+) ion transference number (0.56) and wide electrochemical window. Its electrochemical performance is evaluated by LiFePO4 cathode with good cycling. The results show this gel-type composite membrane has great attraction to the large-capacity LIBs requiring high safety with low cost. PMID:24216756

  9. Advanced two-photon photolithography for patterning of transparent, electrically conductive ionic liquid-polymer nanostructures

    NASA Astrophysics Data System (ADS)

    Bakhtina, Natalia A.; MacKinnon, Neil; Korvink, Jan G.

    2016-04-01

    A key challenge in micro- and nanotechnology is the direct patterning of functional structures. For example, it is highly desirable to possess the ability to create three-dimensional (3D), conductive, and optically transparent structures. Efforts in this direction have, to date, yielded less than optimal results since the polymer composites had low optical transparency over the visible range, were only slightly conductive, or incompatible with high resolution structuring. We have previously presented the novel cross-linkable, conductive, highly transparent composite material based on a photoresist (IP-L 780, OrmoComp, or SU-8) and the ionic liquid 1-butyl-3-methylimidazolium dicyanamide. Material patterning by conventional and two-photon photolithography has been demonstrated as proof-of-concept. Aiming to increase the resolution and to extend the spectrum of exciting applications we continued our research into identifying new ionic liquid - polymer composites. In this paper, we report the precise 3D single-step structuring of optically transparent and electrically conductive ionic liquid - polymer nanostructures with the highest spatial resolution (down to 150 nm) achieved to date. This was achieved via the development of novel cross-linkable composite based on the photoresist IP-G 780 and the ionic liquid 1-butyl-3-methylimidazolium dicyanamide. The successful combination of the developed material with the advanced direct laser writing technique enabled the time- and cost-saving direct manufacturing of transparent, electrically conductive components. We believe that the excellent characteristics of the structured material will open a wider range of exciting applications.

  10. Advancements in fabrication process of microelectrode array for a retinal prosthesis using Liquid Crystal Polymer (LCP).

    PubMed

    Jeong, Joonsoo; Shin, Soowon; Lee, Geun Jae; Gwon, Tae Mok; Park, Jeong Hoan; Kim, Sung June

    2013-01-01

    Liquid Crystal Polymer (LCP) has been considered as an alternative biomaterial for implantable biomedical devices primarily for its low moisture absorption rate compared with conventional polymers such as polyimide, parylene and silicone elastomers. A novel retinal prosthetic device based on monolithic encapsulation of LCP is being developed in which entire neural stimulation circuitries are integrated into a thin and eye-conformable structure. Micromachining techniques for fabrication of a LCP retinal electrode array have been previously reported. In this research, however, for being used as a part of the LCP-based retinal implant, we developed advanced fabrication process of LCP retinal electrode through new approaches such as electroplating and laser-machining in order to achieve higher mechanical robustness, long-term reliability and flexibility. Thickened metal tracks could contribute to higher mechanical strength as well as higher long-term reliability when combined with laser-ablation process by allowing high-pressure lamination. Laser-thinning technique could improve the flexibility of LCP electrode. PMID:24110931

  11. Thermo-mechanical fatigue of polymer matrix composites. Ph.D. Thesis

    SciTech Connect

    Strait, L.H. Jr.

    1994-01-01

    This research was undertaken to evaluate the effects of mechanical constraint on the response of polymer composites during thermal cycling. Analytical and experimental techniques were used to characterize the response of carbon fiber reinforced cyanate ester (IM6/BT3008) and bismaleimide (IM7/5250-4) composites. Cross-ply laminates were subjected to thermal cycles from 24 to 177 C in the unconstrained, fully-constrained and over-constrained conditions. Laminate response, damage mechanisms and residual compressive properties were characterized. Predicted ply stress distributions are significantly different for the various degrees of constraint and are highly sensitive to temperature-dependent lamina properties and laminate stress free temperature. Predictions of laminate response correlate well with experimental results. Deviations are apparent at elevated temperature which are attributed to the effects of time-dependent deformation. Changes in laminate response are observed during thermal cycling of IM6/BT3008 in the unconstrained and fully-constrained conditions. The changes are attributed to time-dependent deformation in the 90 deg plies which leads to changes in the ply stress distribution and ultimately to transverse microcracking. Microcracking initiates more rapidly for fully-constrained laminates due to higher 90 ply stresses which result in more time-dependent deformation per cycle. With continued cycling, microcrack densities converge and become equivalent after 1000 cycles. The ply stress distribution in over-constrained laminates is substantially different from those in unconstrained and fully-constrained laminates. Time-dependent deformation in the 90 deg plies results in changes in the ply stress distribution but does not significantly alter the laminate response. The microcrack density in over constrained laminates is equivalent to that in unconstrained and fully constrained laminates after 1000 cycles.

  12. Protein-resistant polymer coatings obtained by matrix assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Rusen, L.; Mustaciosu, C.; Mitu, B.; Filipescu, M.; Dinescu, M.; Dinca, V.

    2013-08-01

    Adsorption of proteins and polysaccharides is known to facilitate microbial attachment and subsequent formation of biofilm on surfaces that ultimately results in its biofouling. Therefore, protein repellent modified surfaces are necessary to block the irreversible attachment of microorganisms. Within this context, the feasibility of using the Poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether (PEG-block-PCL Me) copolymer as potential protein-resistant coating was explored in this work. The films were deposited using Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique that allows good control of composition, thickness and homogeneity. The chemical and morphological characteristics of the films were examined using Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements and Atomic Force Microscopy (AFM). The FTIR data demonstrates that the functional groups in the MAPLE-deposited films remain intact, especially for fluences below 0.5 J cm-2. Optical Microscopy and AFM images show that the homogeneity and the roughness of the coatings are related to both laser parameters (fluence, number of pulses) and target composition. Protein adsorption tests were performed on the PEG-block-PCL Me copolymer coated glass and on bare glass surface as a control. The results show that the presence of copolymer as coating significantly reduces the adsorption of proteins.

  13. Dilation and degradation of the brain extracellular matrix enhances penetration of infused polymer nanoparticles

    PubMed Central

    Neeves, Keith B.; Sawyer, Andrew J.; Foley, Conor P.; Saltzman, W. Mark; Olbricht, William L.

    2007-01-01

    This study investigates methods of manipulating the brain extracellular matrix (ECM) to enhance the penetration of nanoparticle drug carriers in convection-enhanced delivery (CED). A probe was fabricated with two independent microfluidic channels to infuse, either simultaneously or sequentially, nanoparticles and ECM-modifying agents. Infusions were performed in the striatum of the normal rat brain. Monodisperse polystyrene particles with a diameter of 54 nm were used as a model nanoparticle system. Because the size of these particles is comparable to the effective pore size of the ECM, their transport may be significantly hindered compared with the transport of low molecular weight molecules. To enhance the transport of the infused nanoparticles, we attempted to increase the effective pore size of the ECM by two methods: dilating the extracellular space and degrading selected constituents of the ECM. Two methods of dilating the extracellular space were investigated: co-infusion of nanoparticles and a hyperosmolar solution of mannitol, and pre-infusion of an isotonic buffer solution followed by infusion of nanoparticles. These treatments resulted in an increase in the nanoparticle distribution volume of 50% and 123%, respectively. To degrade hyaluronan, a primary structural component of the brain ECM, a pre-infusion of hyaluronidase (20,000 U/mL) was followed after 30 min by infusion of nanoparticles. This treatment resulted in an increase in the nanoparticle distribution of 64%. Our results suggest that both dilation and enzymatic digestion can be incorporated into CED protocols to enhance nanoparticle penetration. PMID:17920047

  14. Thermal/Mechanical Durability of Polymer-Matrix Composites in Cryogenic Environments

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Whitley, Karen S.; Grenoble, Ray W.; Bandorawalla, Tozer

    2003-01-01

    In order to increase the reliability of the next generation of space transportation systems, the mechanical behavior of polymeric-matrix composite (PMC) materials at cryogenic temperatures must be investigated. This paper presents experimental data on the residual mechanical properties of a carbon fiber polymeric composite, IM7/PETI-5 as a function of temperature and aging. Tension modulus and strength were measured at room temperature, -196 C, and -269 C on five different specimens ply lay-ups. Specimens were preconditioned with one set of coupons being isothermally aged for 576 hours at -184 C, in an unloaded state. Another set of corresponding coupons were mounted in constant strain fixtures such that a constant uniaxial strain was applied to the specimens for 576 hours at -184 C. A third set was mechanically cycled in tension at -184 C. The measured properties indicated that temperature, aging, and loading mode can all have significant influence on performance. Moreover, this influence is a strong function of laminate stacking sequence. Thermal-stress calculations based on lamination theory predicted that the transverse tensile ply stresses could be quite high for cryogenic test temperatures. Microscopic examination of the surface morphology showed evidence of degradation along the exposed edges of the material because of aging at cryogenic temperatures. ________________

  15. Thermal/Mechanical Response of a Polymer Matrix Composite at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Whitley, Karen S.; Gates, Thomas S.

    2003-01-01

    In order for polymeric-matrix composites to be considered for use as structural materials in the next generation of space transportation systems, the mechanical behavior of these materials at cryogenic temperatures must be investigated. This paper presents experimental data on the residual mechanical properties of a carbon-fiber polymeric composite, IM7/PETI-5, both before and after aging. Both tension and compression modulus and strength were measured at room temperature, -196C, and -269 C on five different laminate configurations. One set of specimens was aged isothermally for 576 hours at -184 C in an unconstrained state. Another set of corresponding specimens was aged under constant uniaxial strain for 576 hours at -184 C. Based on the experimental data presented, it is shown that trends in stiffness and strength that result from changes in temperature are not always smooth and consistent. Moreover, it is shown that loading mode and direction are significant for both stiffness and strength, and aging at cryogenic temperature while under load can alter the mechanical properties of pristine, un-aged laminates made of IM7/PETI-5 material.

  16. Advanced insulations for refrigerator/freezers: The potential for new shell designs incorporating polymer barrier construction

    SciTech Connect

    Griffith, B.T.; Arasteh, D.

    1992-11-01

    The impending phase-out of chlorofluorocarbons (CFCs) used to expand foam insulation, combined with requirements for increased energy efficiency, make the use of non-CFC-based high performance insulation technologies increasingly attractive. The majority of current efforts are directed at using advanced insulations in the form of thin, flat low-conductivity gas-filled or evacuated orthogonal panels, which we refer to as Advanced Insulation Panels (AIPs). AIPs can be used in composite with blown polymer foams to improve insulation performance in refrigerator/freezers (R/Fs) of conventional design and manufacture. This AIP/foam composite approach is appealing because it appears to be a feasible, near-term method for incorporating advanced insulations into R/Fs without substantial redesign or retooling. However, the requirements for adequate flow of foam during the foam-in-place operation impose limitations on the allowable thickness and coverage area of AIPs. This report examines design alternatives which may offer a greater increase in overall thermal resistance than is possible with the use of AIP/foam composites in current R/F design. These design alternatives generally involve a basic redesign of the R/F taking into account the unique requirements of advanced insulations and the importance of minimizing thermal bridging with high thermal resistance insulations. The focus here is on R/F doors because they are relatively simple and independent R/F components and are therefore good candidates for development of alterative designs. R/F doors have significant thermal bridging problems due to the steel outer shell construction. A three dimensional finite difference computer modeling exercise of a R/F door geometry was used to compare the overall levels of thermal resistance (R-value) for various design configurations.

  17. Final Technical Report - Advanced Optical Sensors to Minimize Energy Consumption in Polymer Extrusion Processes

    SciTech Connect

    Susan J. Foulk

    2012-07-24

    Project Objective: The objectives of this study are to develop an accurate and stable on-line sensor system to monitor color and composition on-line in polymer melts, to develop a scheme for using the output to control extruders to eliminate the energy, material and operational costs of off-specification product, and to combine or eliminate some extrusion processes. Background: Polymer extrusion processes are difficult to control because the quality achieved in the final product is complexly affected by the properties of the extruder screw, speed of extrusion, temperature, polymer composition, strength and dispersion properties of additives, and feeder system properties. Extruder systems are engineered to be highly reproducible so that when the correct settings to produce a particular product are found, that product can be reliably produced time after time. However market conditions often require changes in the final product, different products or grades may be processed in the same equipment, and feed materials vary from lot to lot. All of these changes require empirical adjustment of extruder settings to produce a product meeting specifications. Optical sensor systems that can continuously monitor the composition and color of the extruded polymer could detect process upsets, drift, blending oscillations, and changes in dispersion of additives. Development of an effective control algorithm using the output of the monitor would enable rapid corrections for changes in materials and operating conditions, thereby eliminating most of the scrap and recycle of current processing. This information could be used to identify extruder systems issues, diagnose problem sources, and suggest corrective actions in real-time to help keep extruder system settings within the optimum control region. Using these advanced optical sensor systems would give extruder operators real-time feedback from their process. They could reduce the amount of off-spec product produced and

  18. A Probabilistic Risk Analysis (PRA) of Human Space Missions for the Advanced Integration Matrix (AIM)

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.; Dillon-Merrill, Robin L.; Thomas, Gretchen A.

    2003-01-01

    The Advanced Integration Matrix (AIM) Project u7ill study and solve systems-level integration issues for exploration missions beyond Low Earth Orbit (LEO), through the design and development of a ground-based facility for developing revolutionary integrated systems for joint human-robotic missions. This paper describes a Probabilistic Risk Analysis (PRA) of human space missions that was developed to help define the direction and priorities for AIM. Risk analysis is required for all major NASA programs and has been used for shuttle, station, and Mars lander programs. It is a prescribed part of early planning and is necessary during concept definition, even before mission scenarios and system designs exist. PRA cm begin when little failure data are available, and be continually updated and refined as detail becomes available. PRA provides a basis for examining tradeoffs among safety, reliability, performance, and cost. The objective of AIM's PRA is to indicate how risk can be managed and future human space missions enabled by the AIM Project. Many critical events can cause injuries and fatalities to the crew without causing loss of vehicle or mission. Some critical systems are beyond AIM's scope, such as propulsion and guidance. Many failure-causing events can be mitigated by conducting operational tests in AIM, such as testing equipment and evaluating operational procedures, especially in the areas of communications and computers, autonomous operations, life support, thermal design, EVA and rover activities, physiological factors including habitation, medical equipment, and food, and multifunctional tools and repairable systems. AIM is well suited to test and demonstrate the habitat, life support, crew operations, and human interface. Because these account for significant crew, systems performance, and science risks, AIM will help reduce mission risk, and missions beyond LEO are far enough in the future that AIM can have significant impact.

  19. Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric study of bis(imidazole-1-carboxylate) endfunctionalized polymers,.

    PubMed

    Kéki, Sándor; Nagy, Miklós; Deák, György; Zsuga, Miklós; Herczegh, Pál

    2003-02-01

    A detailed Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric (MALDI-TOF MS) investigation of polyethylene glycol (PEG), polypropylene glycol (PPG) and polyisobutylene (PIB) bis(imidazole-1-carboxylate) esters is reported. The MS spectra of PPG and PIBb is (imidazole-1-carboxylate) esters recorded in the reflectron mode showed the presence of two additional series of peaks compared to those recorded in the linear mode, while in the case of PEG bis(imidazole-1-carboxylate) only one additional peak series appeared in the reflectron MS spectra. These additional series were attributed to the formation of fragment ions by the loss of one and two end groups in the first field-free region of the instrument. The neutral losses for the three polymers were also supported by using the post-source decay method (PSD). The observation of decreasing mass difference between the adjacent peaks from two series of polymeric ions with the increase of oligomer mass indicates the presence of PSD ions in a reflectron MALDI spectrum. The relationship between the mass of the precursor ions and those of the PSD ions and neutral loss are also discussed. PMID:12596703

  20. Optimal Topology and Experimental Evaluation of Piezoelectric Materials for Actively Shunted General Electric Polymer Matrix Fiber Composite Blades

    NASA Technical Reports Server (NTRS)

    Choi, Benjamin B.; Duffy, Kirsten; Kauffman, Jeffrey L.; Kray, Nicholas

    2012-01-01

    NASA Glenn Research Center, in collaboration with GE Aviation, has begun the development of a smart adaptive structure system with piezoelectric (PE) transducers to improve composite fan blade damping at resonances. Traditional resonant damping approaches may not be realistic for rotating frame applications such as engine blades. The limited space in which the blades reside in the engine makes it impossible to accommodate the circuit size required to implement passive resonant damping. Thus, a novel digital shunt scheme has been developed to replace the conventional electric passive shunt circuits. The digital shunt dissipates strain energy through the load resistor on a power amplifier. General Electric (GE) designed and fabricated a variety of polymer matrix fiber composite (PMFC) test specimens. Investigating the optimal topology of PE sensors and actuators for each test specimen has revealed the best PE transducer location for each target mode. Also a variety of flexible patches, which can conform to the blade surface, have been tested to identify the best performing PE patch. The active damping control achieved significant performance at target modes. This work has been highlighted by successful spin testing up to 5000 rpm of subscale GEnx composite blades in Glenn s Dynamic Spin Rig.

  1. Study of optical and structural properties of CdSe quantum dot embedded in PVA polymer matrix

    SciTech Connect

    Tyagi, Chetna Sharma, Ambika

    2015-08-28

    To enhance the properties and applicability of devices it is essential to incorporate semiconductor nanoparticles into polymer matrix. This introduces a new branch of science which includes device fabrications such as gas sensors, nonlinear optics, catalysis etc. Herein, we have synthesized CdSe/PVA nanocomposite (NC) material using wet chemical synthesis technique. The XRD studies revealed the formation of crystalline structure of CdSe nanoparticles (NP’s) and PVA NC’s with an average size of 100 nm and 5 nm respectively. Energy band gap is determined using UV-VIS Spectroscopy. A red shift in the absorption edge of CdSe/PVA NC is observed with respect to CdSe Np’s, The photoluminescence spectra also show red shift for CdSe/PVA NC as compared to CdSe NP’s Thus the use of CdSe/PVA for solar cell application would be more preferable than CdSe NP’s.

  2. Embedded optical fibres as strain sensors in polymer matrix fibre composites: The influence of adhesion in strain transfer

    NASA Astrophysics Data System (ADS)

    Ekroth, M.

    1994-06-01

    Optical fibers can serve as strain sensors embedded in load carrying polymer matrix fiber composites. The aim of the study was to investigate the influence of chemical bonding between the optical fiber, its protective polyimide coating and the surrounding composite, in strain transfer from the composite to the optical fiber. The degree of adhesion was determined by measuring the force during debonding and pull-out of the optical fiber from the composite. Debonding occurred between the quartz fiber and the coating for both untreated and ammonia modified fibers. The PTFE coated fibers debonded between the coating and the composite. The modified fibers debonded at a lower applied load than the untreated fibers. The strain during tensile loading was measured both with conventional resistance strain gages mounted on the specimen surfaces, and optically with a Mach-Zehnder-interferometer. The optically measured strains, obtained with the untreated fiber and the modified fibers, were all in good agreement with the response from the resistance strain gages. It is concluded that the chemical bonding between the quartz fiber/coating/composite consequently has little or no influence on the strain transfer. Internal stresses (mechanical pressure and friction forces) arising from the laminate fabrication process are sufficient for strain transfer.

  3. Advanced polymer PV system: PVMaT 4A1 annual report, September 1995--September 1996

    SciTech Connect

    Hanoka, J; Chleboski, R; Farber, M; Fava, J; Kane, P; Martz, J

    1997-06-01

    Purpose of this subcontract was to produce lower module and systems costs through the innovative use of polymeric materials. The Innovative Mounting System (IMS) was developed and testing begun during the first year of this contract. IMS reduces the cost of installed PV systems by reducing labor and materials costs both in the factory and in field installation. It incorporates several advances in polymers, processing methods and product design. An advanced backskin material permits elimination of the conventional Al perimeter frame by protecting and sealing the edge and by direct bonding of multifunctional mounting bars. Electrical interconnection is easier and more reliable with a new junction box. Feasibility of a non-vacuum, high-throughput lamination method was also demonstrated, involving a novel transparent encapsulant with UV stabilization package that can be laminated in air and which should lead to longer field life than conventional designs. The first-year program culminated in the fielding of prototype products with the new encapsulant, backskin, junction box, frameless edge seal, and IMS. Feedback and marketing information from potential customers were solicited. Result promises a $0.50/watt manufacturing and system cost reductions as well as increased system lifetime. The second year will complete refinement and test of the encapsulant and backskin, complete the new lamination method, and refine product designs.

  4. Advanced Polymer Technology for Containing and Immobilizing Strontium-90 in the Subsurface - 8361

    SciTech Connect

    K. Baker; G. Heath; C. Scott; A. Schafer; S. Bryant; M. Sharma; C. Huh; S. K. Choi

    2008-02-01

    Many Department of Energy (DOE) sites, including Idaho and Hanford, have heavy metals and/or radionuclides (e.g. strontium-90) present that are strongly adsorbed in the vadose zone, but which nevertheless are propagating toward the water table. A key challenge for immobilization of these contaminants is bringing the chosen amendment or remediation technology into contact with the contaminated porous medium, while ensuring that contaminated water and colloids do not escape. This is particularly challenging when the subsurface geology is complex and highly heterogeneous, as is the case at many DOE sites. The Idaho National Laboratory (INL) in collaboration with the University of Texas at Austin (UT) has conducted research sponsored through the DOE Office of Environmental Management (EM) Advanced Remediation Technologies Phase I program that successfully demonstrated application of a novel, pH-triggered advanced polymer for creating a physical barrier that prevents heavy metals and radionuclides in vadose zone soil and soil-pore water from migrating to the groundwater. The focus of this paper is on the column and sandbox experiments conducted by researchers at the Idaho National Laboratory in support of the Phase I program objectives. Proof of these concepts provides a technology basis for confining or isolating a volume of contaminated groundwater, to be implemented in future investigations at the Vadose Zone Research Park (VZRP) at INL.

  5. Joint Strength Control at the Fiber/Matrix Interface during the Production of Polymer Composite Materials Reinforced with High Performance Fibers

    NASA Astrophysics Data System (ADS)

    Kudinov, Vladimir V.; Korneeva, Natalia V.

    2010-06-01

    The paper presents the results obtained in the study of the joint strength between polymer matrix and high performance polyethylene fiber. The fiber/matrix joints simulate the unit cell of the fiber-reinforced composite materials. Effect of heat treatment on the composite properties at the interface was estimated by a multifilament wet-pull-out method. It was found that the joint strength may be increased with the help of extra heart treatment. Both the energy to peak load and the energy to failure for CM joints at various stages of loading were determined.

  6. Computer Simulation of Spatial Arrangement and Connectivity of Particles in Three-Dimensional Microstructure: Application to Model Electrical Conductivity of Polymer Matrix Composite

    NASA Technical Reports Server (NTRS)

    Louis, P.; Gokhale, A. M.

    1996-01-01

    Computer simulation is a powerful tool for analyzing the geometry of three-dimensional microstructure. A computer simulation model is developed to represent the three-dimensional microstructure of a two-phase particulate composite where particles may be in contact with one another but do not overlap significantly. The model is used to quantify the "connectedness" of the particulate phase of a polymer matrix composite containing hollow carbon particles in a dielectric polymer resin matrix. The simulations are utilized to estimate the morphological percolation volume fraction for electrical conduction, and the effective volume fraction of the particles that actually take part in the electrical conduction. The calculated values of the effective volume fraction are used as an input for a self-consistent physical model for electrical conductivity. The predicted values of electrical conductivity are in very good agreement with the corresponding experimental data on a series of specimens having different particulate volume fraction.

  7. Biological Matrix Effects in Quantitative Tandem Mass Spectrometry-Based Analytical Methods: Advancing Biomonitoring

    PubMed Central

    Panuwet, Parinya; Hunter, Ronald E.; D’Souza, Priya E.; Chen, Xianyu; Radford, Samantha A.; Cohen, Jordan R.; Marder, M. Elizabeth; Kartavenka, Kostya; Ryan, P. Barry; Barr, Dana Boyd

    2015-01-01

    The ability to quantify levels of target analytes in biological samples accurately and precisely, in biomonitoring, involves the use of highly sensitive and selective instrumentation such as tandem mass spectrometers and a thorough understanding of highly variable matrix effects. Typically, matrix effects are caused by co-eluting matrix components that alter the ionization of target analytes as well as the chromatographic response of target analytes, leading to reduced or increased sensitivity of the analysis. Thus, before the desired accuracy and precision standards of laboratory data are achieved, these effects must be characterized and controlled. Here we present our review and observations of matrix effects encountered during the validation and implementation of tandem mass spectrometry-based analytical methods. We also provide systematic, comprehensive laboratory strategies needed to control challenges posed by matrix effects in order to ensure delivery of the most accurate data for biomonitoring studies assessing exposure to environmental toxicants. PMID:25562585

  8. Facile synthesis of hydrophilic polyamidoxime polymers as a novel solid-phase extraction matrix for sequential characterization of glyco- and phosphoproteomes.

    PubMed

    Wang, Jiaxi; Wang, Yanan; Gao, Mingxia; Zhang, Xiangmin; Yang, Pengyuan

    2016-02-11

    Selective enrichment of glycopeptides or phosphopeptides with great biological significance is essential for high-throughput mass spectrometry analysis. However, most previously reported methods only focused on enriching either glycopeptides or phosphopeptides rather than enriching them both. In this work, for the first time, a facile route was developed for the synthesis of polyamidoxime polymers with intrinsic hydrophilic skeletons and attractive long chain structure. The polyamidoxime materials (co-PAN) were synthesized from polyacrylonitrile (PAN) precursor and were successfully used for selective enrichment of glycopeptides. After that, co-PAN as a matrix functionalized with titanium ions (co-PAN@Ti(4+)) could efficiently enrich phosphopeptides. The performances of the polymers for sequential selective and effective enrichment of glycopeptides and phosphopeptides were evaluated with standard peptide mixtures and human serum. Moreover, the efficiency of enrichment of the material was still retained after being used repeatedly. These results demonstrated that the polymers showed great potential in the practical application of proteomics. PMID:26803004

  9. Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

  10. Exploiting metal-organic coordination polymers as highly efficient immobilization matrixes of enzymes for sensitive electrochemical biosensing.

    PubMed

    Fu, Yingchun; Li, Penghao; Bu, Lijuan; Wang, Ting; Xie, Qingji; Chen, Jinhua; Yao, Shouzhuo

    2011-09-01

    We report on the exploitation of metal-organic coordination polymers (MOCPs) as new and efficient matrixes to immobilize enzymes for amperometric biosensing of glucose or phenols. A ligand, 2,5-dimercapto-1,3,4-thiadiazole (DMcT), two metallic salts, NaAuCl(4) and Na(2)PtCl(6), and two enzymes, glucose oxidase (GOx) and tyrosinase, are used to demonstrate the novel concept. Briefly, one of the metallic salts is added into an aqueous suspension containing DMcT and one of the enzymes to trigger the metal-organic coordination reaction, and the yielded MOCPs-enzyme biocomposite (MEBC) is then cast-coated on an Au electrode for biosensing. The aqueous-phase coordination polymerization reactions of the metallic ions with DMcT are studied by visual inspection as well as some spectroscopic, microscopic, and electrochemical methods. The thus-prepared glucose and phenolic biosensors perform better in analytical performance (such as sensitivity and limit of detection) than those prepared by the conventional chemical and/or electrochemical polymerization methods and most of the reported analogous biosensors, as a result of the improved enzyme load/activity and mass-transfer efficiency after using the MOCPs materials with high adsorption/encapsulation capability and unique porous structure. For instance, the detection limit for catechol is as low as 0.2 nM here, being order(s) lower than those of most of the reported analogues. The enzyme electrode was also used to determine catachol in real samples with satisfactory results. The emerging MOCPs materials and the suggested aqueous-phase preparation strategy may find wide applications in the fields of bioanalysis, biocatalysis, and environmental monitoring. PMID:21780824

  11. Mechanical properties and in vivo behavior of a biodegradable synthetic polymer microfiber - extracellular matrix hydrogel biohybrid scaffold

    PubMed Central

    Hong, Yi; Huber, Alexander; Takanari, Keisuke; Amoroso, Nicholas J.; Hashizume, Ryotaro; Badylak, Stephen F.; Wagner, William R.

    2011-01-01

    A biohybrid composite consisting of extracellular matrix (ECM) gel from porcine dermal tissue and biodegradable elastomeric fibers was generated and evaluated for soft tissue applications. ECM gel possesses attractive biocompatibility and bioactivity with weak mechanical properties and rapid degradation, while electrospun biodegradable poly(ester urethane)urea (PEUU) has good mechanical properties but limited cellular infiltration and tissue integration. A concurrent gel electrospray/polymer electrospinning method was employed to create ECM gel/PEUU fiber composites with attractive mechanical properties, including high flexibility and strength. Electron microscopy revealed a structure of interconnected fibrous layers embedded in ECM gel. Tensile mechanical properties could be tuned by altering the PEUU/ECM weight ratio. Scaffold tensile strengths for PEUU/ECM ratios of 67/33, 72/28 and 80/20 ranged from 80–187 kPa in the longitudinal axis (parallel to the collecting mandrel axis) and 41–91 kPa in the circumferential axis with 645–938% breaking strains. The 72/28 biohybrid composite and a control scaffold generated from electrospun PEUU alone were implanted into Lewis rats, replacing a full-thickness abdominal wall defect. At 4 wk, no infection or herniation was found at the implant site. Histological staining showed extensive cellular infiltration into the biohybrid scaffold with the newly developed tissue well integrated with the native periphery, while minimal cellular ingress into the electrospun PEUU scaffold was observed. Mechanical testing of explanted constructs showed evidence of substantial remodeling, with composite scaffolds adopting properties more comparable to the native abdominal wall. The described elastic biohybrid material imparts features of ECM gel bioactivity with PEUU strength and handling to provide a promising composite biomaterial for soft tissue repair and replacement. PMID:21303718

  12. Development of a Subcell Based Modeling Approach for Modeling the Architecturally Dependent Impact Response of Triaxially Braided Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.; Kohlman, Lee W.

    2016-01-01

    Understanding the high velocity impact response of polymer matrix composites with complex architectures is critical to many aerospace applications, including engine fan blade containment systems where the structure must be able to completely contain fan blades in the event of a blade-out. Despite the benefits offered by these materials, the complex nature of textile composites presents a significant challenge for the prediction of deformation and damage under both quasi-static and impact loading conditions. The relatively large mesoscale repeating unit cell (in comparison to the size of structural components) causes the material to behave like a structure rather than a homogeneous material. Impact experiments conducted at NASA Glenn Research Center have shown the damage patterns to be a function of the underlying material architecture. Traditional computational techniques that involve modeling these materials using smeared homogeneous, orthotropic material properties at the macroscale result in simulated damage patterns that are a function of the structural geometry, but not the material architecture. In order to preserve heterogeneity at the highest length scale in a robust yet computationally efficient manner, and capture the architecturally dependent damage patterns, a previously-developed subcell modeling approach where the braided composite unit cell is approximated as a series of four adjacent laminated composites is utilized. This work discusses the implementation of the subcell methodology into the commercial transient dynamic finite element code LS-DYNA (Livermore Software Technology Corp.). Verification and validation studies are also presented, including simulation of the tensile response of straight-sided and notched quasi-static coupons composed of a T700/PR520 triaxially braided [0deg/60deg/-60deg] composite. Based on the results of the verification and validation studies, advantages and limitations of the methodology as well as plans for future work

  13. Thermo- and pH-responsive polymer brushes-grafted gigaporous polystyrene microspheres as a high-speed protein chromatography matrix.

    PubMed

    Qu, Jian-Bo; Xu, Yu-Liang; Liu, Jun-Yi; Zeng, Jing-Bin; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo

    2016-04-01

    Dual thermo- and pH-responsive chromatography has been proposed using poly(N-isopropylacrylamide-co-butyl methacrylate-co-N,N-dimethylaminopropyl acrylamide) (P(NIPAM-co-BMA-co-DMAPAAM)) brushes grafted gigaporous polystyrene microspheres (GPM) as matrix. Atom transfer radical polymerization (ATRP) initiator was first coupled onto GPM through Friedel-Crafts acylation with 2-bromoisobutyryl bromide. The dual-responsive polymer brushes were then grafted onto GPM via surface-initiated ATRP. The surface composition, gigaporous structure, protein adsorption and dual-responsive chromatographic properties of the matrix (GPM-P(NIPAM-co-BMA-co-DMAPAAM) were characterized in detail. Results showed that GPM were successfully grafted with thermoresponsive cationic polymer brushes and that the gigaporous structure was well maintained. A column packed with GPM-P(NIPAM-co-BMA-co-DMAPAAM presented low backpressure, good permeability and appreciable thermo-responsibility. By changing pH of the mobile phase and temperature of the column in turn, the column can separate three model proteins at the mobile phase velocity up to 2528cmh(-1). A separation mechanism of this matrix was also proposed. All results indicate that the dual thermo- and pH-responsive chromatography matrix has great potentials in 'green' high-speed protein chromatography. PMID:26947166

  14. Ultrafast, efficient separations of large-sized dsDNA in a blended polymer matrix by microfluidic chip electrophoresis: a design of experiments approach.

    PubMed

    Sun, Mingyun; Lin, Jennifer S; Barron, Annelise E

    2011-11-01

    Double-stranded (ds) DNA fragments over a wide size range were successfully separated in blended polymer matrices by microfluidic chip electrophoresis. Novel blended polymer matrices composed of two types of polymers with three different molar masses were developed to provide improved separations of large dsDNA without negatively impacting the separation of small dsDNA. Hydroxyethyl celluloses with average molar masses of ∼27  kDa and ∼1  MDa were blended with a second class of polymer, high-molar mass (∼7  MDa) linear polyacrylamide. Fast and highly efficient separations of commercially available DNA ladders were achieved on a borosilicate glass microchip. A distinct separation of a 1-kb DNA extension ladder (200-40,000  bp) was completed in 2  min. An orthogonal design of experiments was used to optimize experimental parameters for DNA separations over a wide size range. We find that the two dominant factors are the applied electric field strength and the inclusion of a high concentration of low-molar mass polymer in the matrix solution. These two factors exerted different effects on the separations of small dsDNA fragments below 1  kbp, medium dsDNA fragments between 1 and 10  kbp, and large dsDNA fragments above 10  kbp. PMID:22009451

  15. Advances in solid polymer electrolyte fuel cell technology with low-platinum-loading electrodes

    NASA Technical Reports Server (NTRS)

    Srinivasan, Supramaniam; Ticianelli, E. A.; Derouin, C. R.; Redondo, A.

    1987-01-01

    The Gemini Space program demonstrated the first major application of fuel cell systems. Solid polymer electrolyte fuel cells were used as auxiliary power sources in the spacecraft. There has been considerable progress in this technology since then, particularly with the substitution of Nafion for the polystyrene sulfonate membrane as the electrolyte. Until recently the performance was good only with high platinum loading (4 mg/sq cm) electrodes. Methods are presented to advance the technology by (1) use of low platinum loading (0.35 mg/sq cm) electrodes; (2) optimization of anode/membrane/cathode interfaces by hot pressing; (3) pressurization of reactant gases, which is most important when air is used as cathodic reactant; and (4) adequate humidification of reactant gases to overcome the water management problem. The high performance of the fuel cell with the low loading of platinum appears to be due to the extension of the three dimensional reaction zone by introduction of a proton conductor, Nafion. This was confirmed by cyclic voltammetry.

  16. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Henshaw, J.

    1983-01-01

    Methods of improving the fire resistance of graphite epoxy composite laminates were investigated with the objective of reducing the volume of loose graphite fibers disseminated into the airstream as the result of a high intensity aircraft fuel fire. Improvements were sought by modifying the standard graphite epoxy systems without significantly negating their structural effectiveness. The modifications consisted primarily of an addition of a third constituent material such as glass fibers, glass flakes, carbon black in a glassy resin. These additions were designed to encourage coalescense of the graphite fibers and thereby reduce their aerodynamic float characteristics. A total of 38 fire tests were conducted on thin (1.0 mm) and thick (6.0 mm) hybrid panels.

  17. Hybridized polymer matrix composite

    NASA Technical Reports Server (NTRS)

    Stern, B. A.; Visser, T.

    1981-01-01

    Under certain conditions of combined fire and impact, graphite fibers are released to the atmosphere by graphite fiber composites. The retention of graphite fibers in these situations is investigated. Hybrid combinations of graphite tape and cloth, glass cloth, and resin additives are studied with resin systems. Polyimide resins form the most resistant composites and resins based on simple novolac epoxies the least resistant of those tested. Great improvement in the containment of the fibers is obtained in using graphite/glass hybrids, and nearly complete prevention of individual fiber release is made possible by the use of resin additives.

  18. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    London, A.

    1981-01-01

    Design approaches and materials are described from which are fabricated pyrostatic graphite/epoxy (Gr/Ep) laminates that show improved retention of graphite particulates when subjected to burning. Sixteen hybridized plus two standard Gr/Ep laminates were designed, fabricated, and tested in an effort to eliminate the release of carbon (graphite) fiber particles from burned/burning, mechanically disturbed samples. The term pyrostatic is defined as meaning mechanically intact in the presence of fire. Graphite particulate retentive laminates were constructed whose constituent materials, cost of fabrication, and physical and mechanical properties were not significantly different from existing Gr/Ep composites. All but one laminate (a Celion graphite/bis-maleimide polyimide) were based on an off-the-shelf Gr/Ep, the AS-1/3501-5A system. Of the 16 candidates studied, four thin (10-ply) and four thick (50-ply) hybridized composites are recommended.

  19. Effects of Molecular Structure in Macroscopic Mechanical Properties of an Advanced Polymer (LARC(sup TM)-SI)

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Hinkley, Jeffrey A.; Whitley, Karen S.; Gates, Thomas S.

    2004-01-01

    Mechanical testing of an advanced polymer resin with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The elastic properties, inelastic elongation behavior, and notched tensile strength all as a function of molecular weight and test temperature were determined. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature.

  20. Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Stackpoole, Margaret Mary

    Use of preceramic polymers offers many advantages over conventional ceramic processing routes. Advantages include being able to plastically form the part, form a pyrolized ceramic material at lower temperatures and form high purity microstructures which are tailorable depending on property requirements. To date preceramic polymers are mostly utilized in the production of low dimensional products such as fibers since loss of volatiles during pyrolysis leads to porosity and large shrinkage (in excess of 30%). These problems have been partially solved by use of active fillers (e.g. Ti, Cr, B). The reactive filler converts to a ceramic material with a volume expansion and this increases the density and reduces shrinkage and porosity. The expansion of the reactive filler thus compensates for the polymer shrinkage if the appropriate volume fraction of filler is present in a reactive atmosphere (e.g. N2 or NH3). This approach has resulted in structural composites with limited success. The present research investigates the possibility of using filled preceramic polymers to form net shaped ceramic composite materials and to investigate the use of these unique composite materials to join and coat ceramics and ceramic composites. The initial research focused on phase and microstructural development of bulk composites from the filled polymer/ceramic systems. A processing technique was developed to insure consistency between different samples and the most promising filler/polymer choices for this application have been determined. The processing temperatures and atmospheres have also been optimized. The work covers processing and characterization of bulk composites, joints and coatings. With careful control of processing near net shape bulk composites were fabricated. Both ambient and high temperature strength and fracture toughness was obtained for these composite systems. The potential of using reactively filled preceramic polymers to process joints and coatings was also

  1. Recent advances in solid polymer electrolyte fuel cell technology with low platinum loading electrodes

    NASA Technical Reports Server (NTRS)

    Srinivasan, Supramaniam; Manko, David J.; Enayatullah, Mohammad; Appleby, A. John

    1989-01-01

    High power density fuel cell systems for defense and civilian applications are being developed. Taking into consideration the main causes for efficiency losses (activation, mass transport and ohmic overpotentials) the only fuel cell systems capable of achieving high power densities are the ones with alkaline and solid polymer electrolyte. High power densities (0.8 W/sq cm at 0.8 V and 1 A/sq cm with H2 and O2 as reactants), were already used in NASA's Apollo and Space Shuttle flights as auxiliary power sources. Even higher power densities (4 W/sq cm - i.e., 8 A sq cm at 0.5 V) were reported by the USAF/International Fuel Cells in advanced versions of the alkaline system. High power densities (approximately 1 watt/sq cm) in solid polymer electrolyte fuel cells with ten times lower platinum loading in the electrodes (i.e., 0.4 mg/sq cm) were attained. It is now possible to reach a cell potential of 0.620 V at a current density of 2 A/sq cm and at a temperature of 95 C and pressure of 4/5 atm with H2/O2 as reactants. The slope of the linear region of the potential-current density plot for this case is 0.15 ohm-sq cm. With H2/air as reactants and under the same operating conditions, mass transport limitations are encountered at current densities above 1.4 A/sq cm. Thus, the cell potential at 1 A/sq cm with H2/air as reactants is less than that with H2/O2 as reactants by 40 mV, which is the expected value based on electrode kinetics of the oxygen reduction reaction, and at 2 A/sq cm with H2/air as reactant is less than the corresponding value with H2/O2 as reactants by 250 mV, which is due to the considerably greater mass transport limitations in the former case.

  2. Development and testing of new biologically-based polymers as advanced biocompatible contact lenses

    SciTech Connect

    Bertozzi, Carolyn R.

    2000-06-01

    Nature has evolved complex and elegant materials well suited to fulfill a myriad of functions. Lubricants, structural scaffolds and protective sheaths can all be found in nature, and these provide a rich source of inspiration for the rational design of materials for biomedical applications. Many biological materials are based in some fashion on hydrogels, the crosslinked polymers that absorb and hold water. Biological hydrogels contribute to processes as diverse as mineral nucleation during bone growth and protection and hydration of the cell surface. The carbohydrate layer that coats all living cells, often referred to as the glycocalyx, has hydrogel-like properties that keep cell surfaces well hydrated, segregated from neighboring cells, and resistant to non-specific protein deposition. With the molecular details of cell surface carbohydrates now in hand, adaptation of these structural motifs to synthetic materials is an appealing strategy for improving biocompatibility. The goal of this collaborative project between Prof. Bertozzi's research group, the Center for Advanced Materials at Lawrence Berkeley National Laboratory and Sunsoft Corporation was the design, synthesis and characterization of novel hydrogel polymers for improved soft contact lens materials. Our efforts were motivated by the urgent need for improved materials that allow extended wear, and essential feature for those whose occupation requires the use of contact lenses rather than traditional spectacles. Our strategy was to transplant the chemical features of cell surface molecules into contact lens materials so that they more closely resemble the tissue in which they reside. Specifically, we integrated carbohydrate molecules similar to those found on cell surfaces, and sulfoxide materials inspired by the properties of the carbohydrates, into hydrogels composed of biocompatible and manufacturable substrates. The new materials were characterized with respect to surface and bulk hydrophilicity, and

  3. Selection of polymer binders and fabrication of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Haggerty, John S.; Lightfoot, A.; Sigalovsky, J.

    1993-01-01

    The topics discussed include the following: effects of solvent and polymer exposures on nitriding kinetics of high purity Si powders and on resulting phase distributions; effects of solvent and polymer exposures on Si Surface Chemistry; effects of solvent and polymeric exposures on nitriding kinetics; and fabrication of flexural test samples.

  4. Ceramic matrix composite applications in advanced liquid fuel rocket engine turbomachinery

    NASA Technical Reports Server (NTRS)

    Brockmeyer, Jerry W.

    1992-01-01

    Fiber-reinforced ceramic matrix composites have been identified with properties suitable for near term applications. Conceptual design studies indicate the feasibility of applying C/SiC, and subelements were manufactured that verify selected fabrication features and key material properties. Tests and inspection of these subelements confirmed their capabilities.

  5. Implementation of advanced matrix corrections for active interrogation of waste drums using the CTEN instrument

    SciTech Connect

    Melton, S.; Estep, R.; Hollas, C.

    1998-12-31

    The combined thermal/epithermal neutron instrument (CTEN) was designed at Los Alamos to improve measurement accuracy and mitigate self shielding effects inherent in the differential dieaway technique (DDT). A major goal in this research effort has been the development of a calibration technique that incorporates recently developed matrix and self-shielding corrections using data generated from additional detectors and new acquisition techniques. A comprehensive data set containing both active and passive measurements was generated using 26 different matrices and comprising a total of 1,400 measurements. In all, 31 flux-and-matrix-dependent parameters, 24 positional parameters, two dieaway times, and a correlated ratio were determined from each of the over 1,400 measurements. A reduced list of matrix indicators, prioritized using the alternating conditional expectation (ACE) algorithm, was used to train a neural network using a generalized regression technique (GRNN) to determine matrix- and position-corrected calibration factors. This paper describes the experimental, analytical, and empirical techniques used to determine the corrected calibration factor for an unknown waste drum. Results from a range of cases are compared with those obtained using a mobile DDT instrument and traditional DDT algorithms.

  6. Advanced Process Model for Polymer Pyrolysis and Uranium Ceramic Material Processing

    SciTech Connect

    Wang, Xiaolin; Zunjarrao, Suraj C.; Zhang, Hui; Singh, Raman P.

    2006-07-01

    Silicon carbide (SiC) based uranium ceramic material can be fabricated as hosts for ultra high temperature applications, such as gas-cooled fast reactor fuels and in-core materials. A pyrolysis-based material processing technique allows for the fabrication of SiC based uranium ceramic materials at a lower temperature compared to sintering route. Modeling of the process is considered important for optimizing the fabrication and producing material with high uniformity. This study presents a process model describing polymer pyrolysis and uranium ceramic material processing, including heat transfer, polymer pyrolysis, SiC crystallization, chemical reactions, and species transport of a porous uranium oxide mixed polymer. Three key reactions for polymer pyrolysis and one key reaction for uranium oxide polymer interaction are established for the processing. Included in the model formulation are the effects of transport processes such as heat-up, polymer decomposition, and volatiles escape. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Processing of a sample with certain geometry is simulated. The effects of heating rate, particle size and volume ratio of uranium oxide and polymer on porosity evolution, species uniformity, reaction rate are investigated. (authors)

  7. Polymer-based metal nano-coated disposable target for matrix-assisted and matrix-free laser desorption/ionization mass spectrometry.

    PubMed

    Bugovsky, Stefan; Winkler, Wolfgang; Balika, Werner; Koranda, Manfred; Allmaier, Günter

    2016-07-15

    The ideal MALDI/LDI mass spectrometry sample target for an axial TOF instrument possesses a variety of properties. Primarily, it should be chemically inert to the sample, i.e. analyte, matrix and solvents, highly planar across the whole target, without any previous chemical contact and provide a uniform surface to facilitate reproducible measurements without artifacts from previous sample or matrix compounds. This can be hard to achieve with a metal target, which has to be extensively cleaned every time after use. Any cleaning step may leave residues behind, may change the surface properties due to the type of cleaning method used or even cause microscopic scratches over time hence altering matrix crystallization behavior. Alternatively, use of disposable targets avoids these problems. As each possesses the same surface they therefore have the potential to replace the conventional full metal targets so commonly employed. Furthermore, low cost single-use targets with high planarity promise an easier compliance with GLP guidelines as they alleviate the problem of low reproducibility due to inconsistent sample/matrix crystallization and changes to the target surface properties. In our tests, polymeric metal nano-coated targets were compared to a stainless steel reference. The polymeric metal nano-coated targets exhibited all the performance characteristics for a MALDI MS sample support, and even surpassed the - in our lab commonly used - reference in some aspects like limit of detection. The target exhibits all necessary features such as electrical conductivity, vacuum, laser and solvent compatibility. PMID:27038744

  8. The use of novel biodegradable, optically active and nanostructured poly(amide-ester-imide) as a polymer matrix for preparation of modified ZnO based bionanocomposites

    SciTech Connect

    Abdolmaleki, Amir; Mallakpour, Shadpour; Borandeh, Sedigheh

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer A novel biodegradable and nanostructured PAEI based on two amino acids, was synthesized. Black-Right-Pointing-Pointer ZnO nanoparticles were modified via two different silane coupling agents. Black-Right-Pointing-Pointer PAEI/modified ZnO BNCs were synthesized through ultrasound irradiation. Black-Right-Pointing-Pointer ZnO particles were dispersed homogeneously in PAEI matrix on nanoscale. Black-Right-Pointing-Pointer The effect of ZnO nanoparticles on the properties of synthesized polymer was examined. -- Abstract: A novel biodegradable and nanostructured poly(amide-ester-imide) (PAEI) based on two different amino acids, was synthesized via direct polycondensation of biodegradable N,N Prime -bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide and N,N Prime -(pyromellitoyl)-bis-L-phenylalanine diacid. The resulting polymer was characterized by FT-IR, {sup 1}H NMR, specific rotation, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. The synthesized polymer showed good thermal stability with nano and sphere structure. Then PAEI/ZnO bionanocomposites (BNCs) were fabricated via interaction of pure PAEI and ZnO nanoparticles. The surface of ZnO was modified with two different silane coupling agents. PAEI/ZnO BNCs were studied and characterized by FT-IR, XRD, UV/vis, FE-SEM and TEM. The TEM and FE-SEM results indicated that the nanoparticles were dispersed homogeneously in PAEI matrix on nanoscale. Furthermore the effect of ZnO nanoparticle on the thermal stability of the polymer was investigated with TGA and DSC technique.

  9. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Estili, Mehdi; Sakka, Yoshio

    2014-12-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  10. Zirconia-magnesia inert matrix fuel and waste form: Synthesis, characterization and chemical performance in an advanced fuel cycle

    NASA Astrophysics Data System (ADS)

    Holliday, Kiel Steven

    There is a significant buildup in plutonium stockpiles throughout the world, because of spent nuclear fuel and the dismantling of weapons. The radiotoxicity of this material and proliferation risk has led to a desire for destroying excess plutonium. To do this effectively, it must be fissioned in a reactor as part of a uranium free fuel to eliminate the generation of more plutonium. This requires an inert matrix to volumetrically dilute the fissile plutonium. Zirconia-magnesia dual phase ceramic has been demonstrated to be a favorable material for this task. It is neutron transparent, zirconia is chemically robust, magnesia has good thermal conductivity and the ceramic has been calculated to conform to current economic and safety standards. This dissertation contributes to the knowledge of zirconia-magnesia as an inert matrix fuel to establish behavior of the material containing a fissile component. First, the zirconia-magnesia inert matrix is synthesized in a dual phase ceramic containing a fissile component and a burnable poison. The chemical constitution of the ceramic is then determined. Next, the material performance is assessed under conditions relevant to an advanced fuel cycle. Reactor conditions were assessed with high temperature, high pressure water. Various acid solutions were used in an effort to dissolve the material for reprocessing. The ceramic was also tested as a waste form under environmental conditions, should it go directly to a repository as a spent fuel. The applicability of zirconia-magnesia as an inert matrix fuel and waste form was tested and found to be a promising material for such applications.

  11. Properties of advanced fibers for reinforcing metal and ceramic matrix composites

    SciTech Connect

    Porter, J.

    1993-12-31

    The mechanical properties of ceramic reinforcing fibers need to be well characterized before their incorporation into composite materials. Critical fiber properties include strength and Weibull modulus, bundle strength, modulus and creep resistance. Important composite properties include thermochemical stability, interface debond energy and interfacial sliding resistance. Tailoring these interfacial properties by fiber coating can, in turn, influence fiber properties. Methods of measuring strength related properties are addressed and the results of a computer simulation to assess the quality of measured data statistically are presented. The readily available monofilament fibers are mostly chemically vapor deposited (CVD) silicon carbide. Current aerospace programs have identified the need for new ceramic fibers as enabling materials for their success. Alternate fibers such as sapphire are therefore currently under development with several objectives including: a CTE greater than that of SiC, higher strength and creep resistance, and chemical stability in new candidate matrices. The strength of a ceramic fiber is statistical, being determined by the largest flaw in the flaw population of the tested length of fiber. In a brittle matrix material such as an intermetallic, for toughening by continuous fiber reinforcement, fibers need to exhibit pull-out during matrix crack propagation. However, the stress distribution along a bridging fiber has a maximum in the crack plane and for fiber failure to occur away from the crack plane, a prerequisite for pull-out, a weak link must also exist away from the crack plane.

  12. Atomic step-and-terrace surface of polyimide sheet for advanced polymer substrate engineering.

    PubMed

    Tan, G; Shimada, K; Nozawa, Y; Kaneko, S; Urakami, T; Koyama, K; Komura, M; Matsuda, A; Yoshimoto, M

    2016-07-22

    Typical thermostable and flexible polyimide polymers exhibit many excellent properties such as strong mechanical and chemical resistance. However, in contrast to single-crystal substrates like silicon or sapphire, polymers mostly display disordered and rough surfaces, which may result in instability and degradation of the interfaces between thin films and polymer substrates. As a step toward the development of next-generation polymer substrates, we here report single-atom-layer imprinting onto the polyimide sheets, resulting in an ultrasmooth 0.3 nm high atomic step-and-terrace surface on the polyimides. The ultrasmooth polymer substrates are expected to be applied to the fabrication of nanostructures such as superlattices, nanowires, or quantum dots in nanoscale-controlled electronic devices. We fabricate smooth and atomically stepped indium tin oxide transparent conducting oxide thin films on the imprinted polyimide sheets for future use in organic-based optoelectronic devices processed with nanoscale precision. Furthermore, toward 2D polymer substrate nanoengineering, we demonstrate nanoscale letter writing on the atomic step-and-terrace polyimide surface via atomic force microscopy probe scratching. PMID:27284690

  13. Atomic step-and-terrace surface of polyimide sheet for advanced polymer substrate engineering

    NASA Astrophysics Data System (ADS)

    Tan, G.; Shimada, K.; Nozawa, Y.; Kaneko, S.; Urakami, T.; Koyama, K.; Komura, M.; Matsuda, A.; Yoshimoto, M.

    2016-07-01

    Typical thermostable and flexible polyimide polymers exhibit many excellent properties such as strong mechanical and chemical resistance. However, in contrast to single-crystal substrates like silicon or sapphire, polymers mostly display disordered and rough surfaces, which may result in instability and degradation of the interfaces between thin films and polymer substrates. As a step toward the development of next-generation polymer substrates, we here report single-atom-layer imprinting onto the polyimide sheets, resulting in an ultrasmooth 0.3 nm high atomic step-and-terrace surface on the polyimides. The ultrasmooth polymer substrates are expected to be applied to the fabrication of nanostructures such as superlattices, nanowires, or quantum dots in nanoscale-controlled electronic devices. We fabricate smooth and atomically stepped indium tin oxide transparent conducting oxide thin films on the imprinted polyimide sheets for future use in organic-based optoelectronic devices processed with nanoscale precision. Furthermore, toward 2D polymer substrate nanoengineering, we demonstrate nanoscale letter writing on the atomic step-and-terrace polyimide surface via atomic force microscopy probe scratching.

  14. Serum Matrix Metalloproteinase-7 is an independent prognostic biomarker in advanced bladder cancer

    PubMed Central

    2014-01-01

    Background Urine markers have been studied extensively but there is a lack of blood prognostic markers in bladder cancer. MMP-7 is produced by stromal cells and by tumor cells and is overexpressed in a variety of epithelial and mesenchymal tumors. In this study, we assessed with an immunoassay we developed, the prognostic value of serum MMP-7 in a series of patients with advanced bladder cancer. Methods Serum samples were collected from 56 patients with advanced bladder cancer who were treated at the Montpellier Cancer Institute between March 2003 and December 2004. MMP-7 was quantified in serum samples by using a homogeneous sandwich fluoroimmunoassay we developed based on the time resolved amplified cryptate emission (TRACE) technology. Results The median overall survival of the study population was 2.2 years (95% CI, 1.4 to 3.0) with 1- and 5-year survival rates of 73% (95% CI, 59% to 82%) and 25% (95% CI, 14% to 37%), respectively. High MMP-7 serum levels were associated with poor survival. Using a cut-off value of 11.5 ng/mL, the median overall survival was 3.0 years (95% CI, 1.5 to 5.1) for patients with MMP-7 serum level <11.5 ng/mL and 1.3 years (95% CI, 0.8 to 2.5) for patients with serum level ?11.5 ng/mL. Multivariate analysis identified high MMP-7 serum concentration as an independent prognostic factor for survival in patients with advanced bladder cancer (R?=?2.1, 95% CI, 1.1 to 4.4). Conclusions Our results show that the MMP-7 serum concentration is an independent prognostic factor in patients with locally advanced and or metastatic bladder cancer. PMID:25984271

  15. Durability and CMAS Resistance of Advanced Environmental Barrier Coatings Systems for SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2015-01-01

    Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. This paper will emphasize advanced environmental barrier coating developments for SiCSiC turbine airfoil components, by using advanced coating compositions and processing, in conjunction with mechanical and environment testing and durability validations. The coating-CMC degradations and durability in the laboratory simulated engine fatigue-creep and complex operating environments are being addressed. The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will be discussed. The results help understand the advanced EBC-CMC system performance, aiming at the durability improvements of more robust, prime-reliant environmental barrier coatings for successful applications of the component technologies and lifing methodologies.

  16. Recent Advances in the Analysis of Macromolecular Interactions Using the Matrix-Free Method of Sedimentation in the Analytical Ultracentrifuge

    PubMed Central

    Harding, Stephen E.; Gillis, Richard B.; Almutairi, Fahad; Erten, Tayyibe; Kök, M. Şamil; Adams, Gary G.

    2015-01-01

    Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or “hetero”-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10−12 M to 10−1 M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions. PMID:25756246

  17. Recent advances in solid polymer electrolyte fuel cell technology with low platinum loading electrodes

    NASA Technical Reports Server (NTRS)

    Srinivasan, Supramaniam; Manko, David J.; Koch, Hermann; Enayetullah, Mohammad A.; Appleby, A. John

    1989-01-01

    Of all the fuel cell systems only alkaline and solid polymer electrolyte fuel cells are capable of achieving high power densities (greater than 1 W/sq cm) required for terrestrial and extraterrestrial applications. Electrode kinetic criteria for attaining such high power densities are discussed. Attainment of high power densities in solid polymer electrolyte fuel cells has been demonstrated earlier by different groups using high platinum loading electrodes (4 mg/sq cm). Recent works at Los Alamos National Laboratory and at Texas A and M University (TAMU) demonstrated similar performance for solid polymer electrolyte fuel cells with ten times lower platinum loading (0.45 mg/sq cm) in the electrodes. Some of the results obtained are discussed in terms of the effects of type and thickness of membrane and of the methods platinum localization in the electrodes on the performance of a single cell.

  18. Efficient upconversion polymer-inorganic nanocomposite thin film emitters prepared by the double beam matrix assisted pulsed laser evaporation (DB-MAPLE)

    NASA Astrophysics Data System (ADS)

    Darwish, Abdalla M.; Burkett, Allan; Blackwell, Ashley; Taylor, Keylantra; Walker, Vernell; Sarkisov, Sergey; Koplitz, Brent

    2014-09-01

    We report on fabrication and investigation of optical and morphological properties of highly efficient (a quantum yield of 1%) upconversion polymer-inorganic nanocomposite thin film emitters prepared by the new technique of double beam matrix assisted pulsed laser evaporation (DB-MAPLE). Polymer poly(methyl methacrylate) (PMMA) host was evaporated on a silicon substrate using a 1064-nm pulsed laser beam using a target made of frozen (to the temperature of liquid nitrogen) solution of PMMA in chlorobenzene. Concurrently, the second 532-nm pulsed beam from the same laser was used to impregnate the polymer host with the inorganic nanoparticulate made of the rare earth upconversion compounds NaYF4: Yb3+, Er3+, NaYF4: Yb3+, Ho3+, and NaYF4: Yb3+, Tm3+. The compounds were initially synthesized using the wet process, baked, and compressed in solid pellet targets. The proposed DB-MAPLE method has the advantage of making highly homogeneous nanocomposite films with precise control of the doping rate due to the optimized overlapping of the plumes produced by the ablation of the organic and inorganic target with the infrared and visible laser beams respectively. X-ray diffraction, electron and atomic force microscopy, and optical fluorescence spectroscopy indicated that the inorganic nanoparticulate preserved its crystalline structure and upconversion properties (strong emission in green, red, and blue bands upon illumination with 980-nm laser diode) after being transferred from the target in the polymer nanocomposite film. The produced films can be used in applications varying from the efficiency enhancement of the photovoltaic cells, optical sensors and biomarkers to anti-counterfeit labels.

  19. Threaded molecular wires as building blocks for advanced polymer blends: WPLEDs, ultra-broadband optical amplifiers, multi color lasers

    NASA Astrophysics Data System (ADS)

    Brovelli, Sergio; Mroz, Marta; Sforazzini, Giuseppe; Virgili, Tersilla; Meinardi, Franco; Paleari, Alberto; Anderson, Harry L.; Lanzani, Guglielmo; Cacialli, Franco

    2011-03-01

    The ability to produce semiconducting polymer blends with white emission spectra, large emission cross sections and broad optical gain is critical to their application in white PLEDs, lasers and broadband amplifiers. Cyclodextrin-encapsulation is an effective means of suppressing detrimental intermolecular interactions, and energy transfer (ET) channels in polymer blends, thus enabling fabrication of white-PLEDs. We show that all such properties combine into a high impact photonic application: ultra-broad optical gain and two-color lasing in a binary polyrotaxane blend. We study the ultrafast photophysics of a blend of a conventional and an encapsulated polyfluorene. The morphology is investigated by microRaman imaging, AFM, and fluorescence lifetime microscopy. We ascribe the ultra-broad optical gain (>850 meV), and the simultaneous ASE for both constituents, to the dual effect of reduced polaron formation and suppressed ET. Our results demonstrate that polyrotaxanes could realistically represent the building blocks for advanced polymer blends with highly controlled optical properties, for applications in solid state lightning, lasers and photovoltaic technologies.

  20. Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices.

    PubMed

    Vázquez, Mercedes; Paull, Brett

    2010-06-01

    This review critically summarises recent novel and advanced achievements in the application of monolithic materials and related porous polymer gels in micro-fluidic devices appearing within the literature over the period of the last 5 years (2005-2010). The range of monolithic materials has developed rapidly over the past decade, with a diverse and highly versatile class of materials now available, with each exhibiting distinct porosities, pore sizes, and a wide variety of surface functionalities. A major advantage of these materials is their ease of preparation in micro-fluidic channels by in situ polymerisation, leading to monolithic materials being increasingly utilised for a larger variety of purposes in micro-fluidic platforms. Applications of porous polymer monoliths, silica-based monoliths and related homogeneous porous polymer gels in the preparation of separation columns, ion-permeable membranes, preconcentrators, extractors, electrospray emitters, micro-valves, electrokinetic pumps, micro-reactors and micro-mixers in micro-fluidic devices are discussed herein. Procedures used in the preparation of monolithic materials in micro-channels, as well as some practical aspects of the micro-fluidic chip fabrication are addressed. Recent analytical/bioanalytical and catalytic applications of the final micro-fluidic devices incorporating monolithic materials are also reviewed. PMID:20493286

  1. Advanced ceramic matrix composite materials for current and future propulsion technology applications

    NASA Astrophysics Data System (ADS)

    Schmidt, S.; Beyer, S.; Knabe, H.; Immich, H.; Meistring, R.; Gessler, A.

    2004-08-01

    Current rocket engines, due to their method of construction, the materials used and the extreme loads to which they are subjected, feature a limited number of load cycles. Various technology programmes in Europe are concerned, besides developing reliable and rugged, low cost, throwaway equipment, with preparing for future reusable propulsion technologies. One of the key roles for realizing reusable engine components is the use of modern and innovative materials. One of the key technologies which concern various engine manufacturers worldwide is the development of fibre-reinforced ceramics—ceramic matrix composites. The advantages for the developers are obvious—the low specific weight, the high specific strength over a large temperature range, and their great damage tolerance compared to monolithic ceramics make this material class extremely interesting as a construction material. Over the past years, the Astrium company (formerly DASA) has, together with various partners, worked intensively on developing components for hypersonic engines and liquid rocket propulsion systems. In the year 2000, various hot-firing tests with subscale (scale 1:5) and full-scale nozzle extensions were conducted. In this year, a further decisive milestone was achieved in the sector of small thrusters, and long-term tests served to demonstrate the extraordinary stability of the C/SiC material. Besides developing and testing radiation-cooled nozzle components and small-thruster combustion chambers, Astrium worked on the preliminary development of actively cooled structures for future reusable propulsion systems. In order to get one step nearer to this objective, the development of a new fibre composite was commenced within the framework of a regionally sponsored programme. The objective here is to create multidirectional (3D) textile structures combined with a cost-effective infiltration process. Besides material and process development, the project also encompasses the development of

  2. Advanced High-Temperature Engine Materials Technology Progresses

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The objective of the Advanced High Temperature Engine Materials Technology Program (HITEMP) at the NASA Lewis Research Center is to generate technology for advanced materials and structural analysis that will increase fuel economy, improve reliability, extend life, and reduce operating costs for 21st century civil propulsion systems. The primary focus is on fan and compressor materials (polymer-matrix composites - PMC's), compressor and turbine materials (superalloys, and metal-matrix and intermetallic-matrix composites - MMC's and IMC's), and turbine materials (ceramic-matrix composites - CMC's). These advanced materials are being developed in-house by Lewis researchers and on grants and contracts.

  3. Responsive Biomaterials: Advances in Materials Based on Shape-Memory Polymers.

    PubMed

    Hardy, John G; Palma, Matteo; Wind, Shalom J; Biggs, Manus J

    2016-07-01

    Shape-memory polymers (SMPs) are morphologically responsive materials with potential for a variety of biomedical applications, particularly as devices for minimally invasive surgery and the delivery of therapeutics and cells for tissue engineering. A brief introduction to SMPs is followed by a discussion of the current progress toward the development of SMP-based biomaterials for clinically relevant biomedical applications. PMID:27120512

  4. Effects of dispersion and interfacial modification on the macroscale properties of TiO2 polymer matrix nanocomposites

    PubMed Central

    Hamming, Lesley M.; Qiao, Rui; Messersmith, Phillip B.; Brinson, L. Catherine

    2009-01-01

    This paper quantifies how the quality of dispersion and the quality of the interfacial interaction between TiO2 nanoparticles and host polymer independently affect benchmark properties such as glass transition temperature (Tg), elastic modulus and loss modulus. By examining these composites with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM), we were able to demonstrate changes in properties depending on the adhesive/wetting or repulsive/dewetting interactions the nanoparticles have with the bulk polymer. We further quantified the dispersion of TiO2 nanoparticles in polymethylmethacrylate (PMMA) matrices by a digital-optical method and correlated those values to the degree of Tg depression compared to neat PMMA. Samples with the same weight percent of nanoparticles but better dispersion showed larger shifts in Tg. PMID:20161273

  5. Cross-linked κ-carrageenan polymer/zinc nanoporous composite matrix for expanded bed application: Fabrication and hydrodynamic characterization.

    PubMed

    Mohsenkhani, Sadaf; Jahanshahi, Mohsen; Rahimpour, Ahmad

    2015-08-21

    Expanded bed adsorption (EBA) is a reliable separation technique for the purification of bioproducts from complex feedstocks. The specifically designed adsorbent is necessary to form a stable expanded bed. In the present work, a novel custom-designed composite matrix has been prepared through the method of water-in-oil emulsification. In order to develop an adsorbent with desirable qualities and reduce the costs, κ-carrageenan and zinc powder were used as the polymeric skeleton and the densifier, respectively. The prepared composite matrix was named as KC-Zn. Optical microscope (OM) and scanning electron microscope (SEM) were applied to characterize the morphology and structure of prepared composite matrix. These analyses approved good spherical shape and porous structure with nano-scale pores in the range of about 60-180nm. The results from the particle size analyzer (PSA) revealed that all the KC-Zn beads followed logarithmic normal size distribution with the range of 50-350μm and average diameter of 160-230μm, respectively. Main physical properties of KC-Zn matrices were measured as a function of zinc powder ratio to κ-carrageenan slurry, which showed an appropriate wet density in the range of 1.39-2.27g/ml, water content of 72.67-36.41% and porosity of 98.07-80.24%, respectively. The effects of matrix density and liquid phase viscosity on hydrodynamic behavior of prepared matrix have been investigated by residence time distribution (RTD) experiments in an expanded bed. The results indicated that in a constant liquid velocity as the matrix density was increased, the expansion factor of bed decreased and the axial mixing coefficient increased. Moreover, an enhancement in the fluid viscosity led to an increase in the bed expansion and a decrease in the stability of expanded bed. Therefore using a matrix with higher density seems necessary to face viscous feedstocks. All the results demonstrated that proper physical properties and hydrodynamic characteristics

  6. Parmacokinetic evaluation of ibuprofen controlled release matrix tablets using hydrophilic Eudragit® polymer and co-excipients.

    PubMed

    Bakhsh, Sattar; Khan, Gul Majid; Menaa, Farid; Khan, Barkat Ali

    2015-09-01

    The present study was conducted to formulate controlled release dosage forms containing Ibuprofen with Eudragit® S 100 polymer. The tablets were formulated at three different ratios with the polymer to investigate the effect of different concentrations of polymer on in vitro drug release patterns/kinetics and in vivo absorption/pharmacokinetics. Pre-formulation studies were conducted including bulk density, tapped density, compressibility index, Hausner ratio and angle of repose. In vitro studies were conducted using phosphate buffer (pH 7.4) as dissolution medium. In vivo performance was evaluated using albino rabbits. Physico-chemical characteristics (i.e. dimensional tests, weight variation, hardness, friability and drug content determination) fell in the USP acceptable limits. The compressibility index was found to range between 12.02 ± 0.01% and 18.66 ± 0.03%, the Hausner ratio varied between 1.02 ± 0.01 and 1.19 ± 0.10 and the angle of repose ranged from 15.19 ± 0.01 to 24.52 ± 0.10, all indicating better flow properties than the bulk-reference standard. Both bulk and tapped densities also fell in the USP acceptable range. Ibuprofen market tablets showed Tmax of 2.1 ± 0.4h, which was significantly (P-value <0.05) lower compared to that of the reference standard (i.e. 4.09 ± 1.3h). Ibuprofen test formulation has a half-life (t1/2) of 16.9 ± 2.5h, which was significantly (P-value<0.001) higher compared to that of the reference standard (i.e. 9.23 ± 2.9h). Eudragit® S 100 polymers can be used efficiently to develop directly compressed prolonged release tablets. PMID:26408874

  7. Identification of transformation products during advanced oxidation of diatrizoate: Effect of water matrix and oxidation process.

    PubMed

    Azerrad, Sara P; Lütke Eversloh, Christian; Gilboa, Maayan; Schulz, Manoj; Ternes, Thomas; Dosoretz, Carlos G

    2016-10-15

    Removal of micropollutants from reverse osmosis (RO) brines of wastewater desalination by oxidation processes is influenced by the scavenging capacity of brines components, resulting in the accumulation of transformation products (TPs) rather than complete mineralization. In this work the iodinated contrast media diatrizoate (DTZ) was used as model compound due to its relative resistance to oxidation. Identification of TPs was performed in ultrapure water (UPW) and RO brines applying nonthermal plasma (NTP) and UVA-TiO2 as oxidation techniques. The influence of main RO brines components in the formation and accumulation of TPs, such as chloride, bicarbonate alkalinity and humic acid, was also studied during UVA-TiO2. DTZ oxidation pattern in UPW resulted similar in both UVA-TiO2 and NTP achieving 66 and 61% transformation, respectively. However, DTZ transformation in RO brines was markedly lower in UVA-TiO2 (9%) than in NTP (27%). These differences can be attributed to the synergic effect of RO brines components during NTP. Moreover, reactive species other than hydroxyl radical contributed to DTZ transformation, i.e., direct photolysis in UVA-TiO2 and direct photolysis + O3 in NTP accounted for 16 and 23%, respectively. DTZ transformation led to iodide formation in both oxidation techniques but it further oxidized to iodate by ozone in NTP. In total 14 transformation products were identified in UPW of which 3 were present only in UVA-TiO2 and 2 were present exclusively in NTP; 5 of the 14 TPs were absent in RO brines. Five of them were new and were denoted as TP-474A/B, TP-522, TP-586, TP-602, TP-628. TP-522 (mono-chlorinated) was elucidated only in presence of high chloride titer-synthetic water matrix in NTP, most probably formed by active chlorine species generated in situ. TPs accumulation in RO brines was markedly different in comparison to UPW. This denotes the influence of RO brines components in the formation of reactive species that could further attack

  8. Relationship between Surface Properties and In Vitro Drug Release from a Compressed Matrix Containing an Amphiphilic Polymer Material.

    PubMed

    Yarce, Cristhian J; Pineda, Diego; Correa, Clara E; Salamanca, Constain H

    2016-01-01

    The performance of compressed tablet drug delivery systems made using polymeric materials depend on multiple factors, such as surface properties like contact angle, surface free energy and water absorption rate, besides the release mechanisms driven by the kind of polymer used. Hence, it should be possible to establish a relationship between the surface properties and the drug release kinetics. Compressed tablets with different proportions of poly(maleic acid-alt-octadecene) potassium salt (0%, 10%, 20%, 30% and 40%) were prepared. Blends of a model drug (ampicillin trihydrate) and the polymer material were analyzed by DSC. The surface properties of the tablets were determined by the sessile drop method, while the surface energy was determined using the semi-empirical Young-Dupre, Neumann and OWRK models. The release profiles were determined simulating in vitro conditions (buffer solutions pH 1.2 and pH 7.4 with ionic strength of 1.5 M at 37 °C (310.15 K)). A kinetic analysis of the dissolution profiles using different models (zero order, first order, Higuchi and Korsmeyer-Peppas) was realized. The results showed a significant effect of the proportion of polymer in both the surface properties of the tablets and the dissolution release, indicating a relationship between the kinetic and thermodynamic properties. PMID:27347979

  9. Thermosetting polyimide resin matrix composites with interpenetrating polymer networks for precision foil resistor chips based on special mechanical performance requirements

    NASA Astrophysics Data System (ADS)

    Wang, X. Y.; Ma, J. X.; Li, C. G.; Wang, H. X.

    2014-04-01

    Based on interpenetrating networks (IPNs) different macromolecular materials such as epoxy, phenolic, and silicone resin were chosen to modify thermosetting polyimide (TSPI) resin to solve the lack of performance when used for protecting precision foil resistor chips. Copolymerization modification, controlled at curing stage, was used to prepare TSPI composites considering both performance and process requirements. The mechanical properties related to trimming process were mainly studied due to the special requirements of the regularity of scratch edges caused by a tungsten needle. The analysis on scratch edges reveals that the generation and propagation of microcracks caused by scratching together with crack closure effect may lead to regular scratch traces. Experiments show that the elongation at break of TSPI composites is the main reason that determines the special mechanical properties. The desired candidate materials should have proper hardness and toughness, and the specific mechanical data are that the mean elongation at break and tensile strength of polymer materials are in the range of 9.2-10.4% and 100-107 MPa, respectively. Possible reasons for the effect of the modifiers chosen on TSPI polymers, the reaction mechanisms on modified TSPI resin and the IPN structure in TSPI composite polymers were discussed based on IR and TG analysis.

  10. Quantitative bone matrix density measurement by water- and fat-suppressed proton projection MRI (WASPI) with polymer calibration phantoms.

    PubMed

    Cao, Haihui; Ackerman, Jerome L; Hrovat, Mirko I; Graham, Lila; Glimcher, Melvin J; Wu, Yaotang

    2008-12-01

    The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water- and fat-suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density. The phantom contained a specifically designed poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend, whose MRI properties (T(1), T(2), and resonance linewidth) were similar to those of solid bone matrix (collagen, tightly bound water, and other immobile molecules), minimizing the need to correct for differences in T(1) and/or T(2) relaxation between the phantom and the subject. Cortical and trabecular porcine bone specimens were imaged using WASPI with the calibration phantom in the field of view (FOV) as a stable intensity reference. Gravimetric and amino acid analyses were carried out on the same specimens after WASPI, and the chemical results were found to be highly correlated (r(2) = 0.98 and 0.95, respectively) to the WASPI intensity. By this procedure the WASPI intensity can be used to obtain the true bone matrix mass density in g cm(-3). PMID:19025909

  11. Application of high performance computing to automotive design and manufacturing: Composite materials modeling task technical manual for constitutive models for glass fiber-polymer matrix composites

    SciTech Connect

    Simunovic, S; Zacharia, T

    1997-11-01

    This report provides a theoretical background for three constitutive models for a continuous strand mat (CSM) glass fiber-thermoset polymer matrix composite. The models were developed during fiscal years 1994 through 1997 as a part of the Cooperative Research and Development Agreement, "Application of High-Performance Computing to Automotive Design and Manufacturing." The full derivation of constitutive relations in the framework of the continuum program DYNA3D and have been used for the simulation and impact analysis of CSM composite tubes. The analysis of simulation and experimental results show that the model based on strain tensor split yields the most accurate results of the three implemented models. The parameters used in the models and their derivation from the physical tests are documented.

  12. Recent advances with generalized entropy theory of glass-formation in polymers

    NASA Astrophysics Data System (ADS)

    Freed, Karl

    The generalized entropy theory (GET) of glass-formation in polymers is a combination of the lattice cluster theory (LCT) for the configurational entropy density with the Adam-Gibbs (AG) theory for the structural relaxation time. A greatly simplified form of the GET (whose expression for the free energy is roughly double that of Flory-Huggins theory) accurately reproduces the four characteristic temperatures of glass-formation (the onset, crossover, glass transition, and Kauzmann temperatures) of the full GET to within 4K for a series of models of polymers composed of semi-flexible chains having the structure of poly(n-alpha olefins). The theory is now simple enough to be used in courses in polymer physics. Although the successes of the GET provide a strong validation of the final form of the AG theory provided the configurational entropy is used, the physical basis of the AG theory has remained an enigma. Hence, we have developed a new, more general, statistical mechanical derivation of AG theory that explains the previously perplexing observations that the string-like elementary excitations have the mass and temperature dependence of systems undergoing equilibrium self-assembly. This work is supported by the (U.S.) Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE- SC0008631.

  13. Fibre prestressed composites: A study of the influences of fibre prestressing on the mechanical properties of polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Motahhari, Siamak

    1998-12-01

    the fibre prestressed composites were a linear, increasing function of the prestressing level. Furthermore, a new method was introduced to measure the shrinkage of the polymeric resins. By the use of this method, the shrinkage of the epoxy resin was measured for the three curing temperatures, previously used to fabricate the samples. The tests were carried out on the un-reinforced polymer. In the next step, some experiments were arranged to investigate the contribution of the resin shrinkage to the formation of the residual stresses in the reinforced polymer. To achieve this goal, a bi-layer composite-neat polymer bar was made. The residual strain of the polymer was calculated by the measurement of the deflection of the bar. Comparison of the residual strain of the polymer in the bi-layer sample with the shrinkage of the polymer in the un-reinforced sample revealed that only 3.3% of the shrinkage of the resin contributes to form the residual stresses in the bi-layer sample. The stress free temperature of the bi-layer sample, the temperature at which the deflection of the sample disappeared, was determined by re-heating the sample and measuring the deflection of the sample at the same time. This temperature was the point below which the stresses were formed in the composite. The stress free temperature was found to be much lower than the curing temperature which usually was taken as stress free temperature.

  14. Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: Recent Advances and Future Directions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2016-01-01

    This presentation briefly reviews the SiC/SiC major environmental and environment-fatigue degradations encountered in simulated turbine combustion environments, and thus NASA environmental barrier coating system evolution for protecting the SiC/SiC Ceramic Matrix Composites for meeting the engine performance requirements. The presentation will review several generations of NASA EBC materials systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. This paper will also focus on the performance requirements and design considerations of environmental barrier coatings for next generation turbine engine applications. The current development emphasis is placed on advanced NASA candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be briefly discussed.

  15. A dual-ion imprinted polymer embedded in sol-gel matrix for the ultra trace simultaneous analysis of cadmium and copper.

    PubMed

    Bali Prasad, Bhim; Jauhari, Darshika; Verma, Archana

    2014-03-01

    In simultaneous determination of group of elements, there are inter-metallic interactions which result in a non-linear relationship between the peak current and ionic concentration for each of the element, at bare (unmodified) electrode. To resolve this problem, we have resorted, for the first time, to develop a modified pencil graphite electrode using a typical ion imprinted polymer network (dual-ion imprinted polymer embedded in sol-gel matrix (inorganic-organic hybrid nano-material)) for the simultaneous analysis of a binary mixture of Cd(II) and Cu(II) ions, without any complication of inter-metallic interactions and competitive bindings, in real samples. The adequate resolution of differential pulse anodic stripping voltammetry peaks by 725 mV (cf, 615 mV with unmodified electrode), without any cross-reactivity and the stringent detection limits as low as, 0.050 and 0.034 ng mL(-1) (S/N=3) for Cd(II) and Cu(II) ions, respectively by the proposed sensor can be considered useful for the primitive diagnosis of several chronic diseases in clinical settings. PMID:24468388

  16. Mechanical, Electromagnetic, and X-ray Shielding Characterization of a 3D Printable Tungsten-Polycarbonate Polymer Matrix Composite for Space-Based Applications

    NASA Astrophysics Data System (ADS)

    Shemelya, Corey M.; Rivera, Armando; Perez, Angel Torrado; Rocha, Carmen; Liang, Min; Yu, Xiaoju; Kief, Craig; Alexander, David; Stegeman, James; Xin, Hao; Wicker, Ryan B.; MacDonald, Eric; Roberson, David A.

    2015-08-01

    Material-extrusion three-dimensional (3D) printing has recently attracted much interest because of its process flexibility, rapid response to design alterations, and ability to create structures "on-the-go". For this reason, 3D printing has possible applications in rapid creation of space-based devices, for example cube satellites (CubeSat). This work focused on fabrication and characterization of tungsten-doped polycarbonate polymer matrix composites specifically designed for x-ray radiation-shielding applications. The polycarbonate-tungsten polymer composite obtained intentionally utilizes low loading levels to provide x-ray shielding while limiting effects on other properties of the material, for example weight, electromagnetic functionality, and mechanical strength. The fabrication process, from tungsten functionalization to filament extrusion and material characterization, is described, including printability, determination of x-ray attenuation, tensile strength, impact resistance, and gigahertz permittivity, and failure analysis. The proposed materials are uniquely advantageous when implemented in 3D printed structures, because even a small volume fraction of tungsten has been shown to substantially alter the properties of the resulting composite.

  17. Delamination toughness characterization of out-of-autoclave vacuum-bag-only polymer matrix composites enhanced by z-aligned carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Brewer, John S.

    Brewer, John S., M. S., University of South Alabama, May 2015. Delamination Toughness Characterization of Out-of-Autoclave Vacuum-Bag-Only Polymer Matrix Composites Enhanced by z-aligned Carbon Nanofibers. Chair of Committee: Kuang-Ting Hsiao, Ph.D. In the last few decades, the use of composite materials has revolutionized materials manufacturing. Now, carbon fiber materials are at the forefront of engineering and manufacturing technology. One of the chief failure modes of composite materials is delamination. For this reason, this study employed the Mode-I Interlaminar Fracture Toughness Test (ASTM D 5528-01) to characterize how the inclusion of z-aligned carbon nanofibers (CNF) in Carbon Fiber Reinforced Polymers (CFRP) affects delamination strength. CFRP with z-aligned CNF in concentrations of 0.3% and 0.6% by weight were compared to control CFRP samples and CFRP samples modified with 0.3 weight percent unaligned CNF. The largest improvement was seen in the 0.3 weight percent aligned composite with a mean interlaminar fracture toughness increase of over 35%, while the uncertainty was decreased. A standard deviation of 3.3% was observed which equates to an uncertainty value 30% better than the control samples. Data and microscopy are included and discussed.

  18. Advanced composites X

    SciTech Connect

    1994-12-31

    In the past ten years, high volume, high performance applications of advanced composites in transportation have grown substantially. The 10th annual ASM/ESD Advanced Composites Conference and Exposition presents the latest developments in composite applications and technologies with over 70 papers presented. The conference is organized in tracks covering body, chassis, powertrain and infrastructure applications, material sciences, manufacturing processes and recycling. Polymer composite and metal matrix composite technologies are included throughout. Body sessions feature adhesive bonding, analysis and test methods and crash energy absorption. The Chassis sessions showcase polymer and metal composite applications. The Powertrain/Propulsion track includes emerging materials as well as design and processing case studies. The Materials Science track features papers on new materials, their performance and theoretical treatment. Manufacturing Processes sessions cover process, modelling, fiber preforming and emerging manufacturing methods. The Infrastructure and Recycling track includes a panel discussion of infrastructure applications and technical papers on the recycling of polymer composites and nondestructive testing.

  19. A novel promising biomolecule immobilization matrix: synthesis of functional benzimidazole containing conducting polymer and its biosensor applications.

    PubMed

    Uzun, Sema Demirci; Unlu, Naime Akbasoglu; Sendur, Merve; Kanik, Fulya Ekiz; Timur, Suna; Toppare, Levent

    2013-12-01

    In order to construct a robust covalent binding between biomolecule and immobilization platform in biosensor preparation, a novel functional monomer 4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2-yl)benzaldehyde (BIBA) was designed and successfully synthesized. After electropolymerization of this monomer, electrochemical and spectroelectrochemical properties were investigated in detail. To fabricate the desired biosensor, glucose oxidase (GOx) was immobilized as a model enzyme on the polymer coated graphite electrode with the help of glutaraldehyde (GA). During the immobilization step, an imine bond was formed between the free amino groups of enzyme and aldehyde group of polymer. The surface characterization and morphology were investigated to confirm bioconjugation by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) at each step of biosensor fabrication. The optimized biosensor shows good linearity between 0.02mM and 1.20mM and a low limit of detection (LOD) of 2.29μM. Kinetic parameters Km(app) and Imax were determined as 0.94mM and 10.91μA, respectively. The biosensor was tested for human blood serum samples. PMID:23973906

  20. A new solid polymer electrolyte incorporating Li10GeP2S12 into a polyethylene oxide matrix for all-solid-state lithium batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Yanran; Wu, Chuan; Peng, Gang; Chen, Xiaotian; Yao, Xiayin; Bai, Ying; Wu, Feng; Chen, Shaojie; Xu, Xiaoxiong

    2016-01-01

    Li10GeP2S12 (LGPS) is incorporated into polyethylene oxide (PEO) matrix to fabricate composite solid polymer electrolyte (SPE) membranes. The lithium ion conductivities of as-prepared composite membranes are evaluated, and the optimal composite membrane exhibits a maximum ionic conductivity of 1.21 × 10-3 S cm-1 at 80 °C and an electrochemical window of 0-5.7 V. The phase transition behaviors for electrolytes are characterized by DSC, and the possible reasons for their enhanced ionic conductivities are discussed. The LGPS microparticles, acting as active fillers incorporation into the PEO matrix, have a positive effect on the ionic conductivity, lithium ion transference number and electrochemical stabilities. In addition, two kinds of all-solid-state lithium batteries (LiFeO4/SPE/Li and LiCoO2/SPE/Li) are fabricated to demonstrate the good compatibility between this new SPE membrane and different electrodes. And the LiFePO4/Li battery exhibits fascinating electrochemical performance with high capacity retention (92.5% after 50 cycles at 60 °C) and attractive capacities of 158, 148, 138 and 99 mAh g-1 at current rates of 0.1 C, 0.2 C, 0.5 C and 1 C at 60 °C, respectively. It is demonstrated that this new composite SPE should be a promising electrolyte applied in solid state batteries based on lithium metal electrode.

  1. Advanced Aromatic Polymers with Excellent Antiatomic Oxygen Performance Derived from Molecular Precursor Strategy and Copolymerization of Polyhedral Oligomeric Silsesquioxane.

    PubMed

    Wang, Pei; Tang, Yusheng; Yu, Zhen; Gu, Junwei; Kong, Jie

    2015-09-16

    In this contribution, the advanced aromatic polymers with excellent antiatomic oxygen (AO) performance were designed and synthesized using molecular precursor strategy and copolymerization of polyhedral oligomeric silsesquioxane (POSS). A soluble poly(p-phenylene benzobisoxazole) (PBO) precursor, that is, TBS-PBO (tert-butyldimethylsilyl was denoted as TBS), was designed to overcome the poor solubility of PBO in organic solvents. Then the new copolymer of TBS-PBO-POSS was synthesized by the copolymerization of TBS-PBO and POSS, which possessed good solubility and film-forming ability in common organic solvents, such as N-methylpyrrolidone, N,N-dimethylacetamide, and dimethyl sulfoxide. More importantly, the TBS-PBO-POSS films exhibited outstanding antiatomic oxygen properties because of the incorporation of POSS monomers with cagelike structure into the main chain of copolymer, which drastically reduced the AO-induced erosion owing to the formation of the passivating silica layer on the surface of polymers. When the TBS-PBO-POSS films were exposed to AO effective fluences of 1.5495×10(20) atom cm(-2) (5 h) and 4.6486×10(20) atom cm(-2) (15 h), the relative mass loss was merely 0.19% and 0.41%, respectively. This work provides a new perspective and efficient strategy for the molecular design of aromatic heterocyclic polymers possessing excellent combination properties including processing convenience and antioxidative and mechanical properties, which can be employed as potential candidates to endure the aggressive environment encountered in low earth orbits. PMID:26322523

  2. Fabrication of Ruthenium Nanoparticles in Porous Organic Polymers: Towards Advanced Heterogeneous Catalytic Nanoreactors.

    PubMed

    Mondal, John; Kundu, Sudipta K; Hung Ng, Wilson Kwok; Singuru, Ramana; Borah, Parijat; Hirao, Hajime; Zhao, Yanli; Bhaumik, Asim

    2015-12-21

    A novel strategy has been adopted for the construction of a copolymer of benzene-benzylamine-1 (BBA-1), which is a porous organic polymer (POP) with a high BET surface area, through Friedel-Crafts alkylation of benzylamine and benzene by using formaldehyde dimethyl acetal as a cross-linker and anhydrous FeCl3 as a promoter. Ruthenium nanoparticles (Ru NPs) were successfully distributed in the interior cavities of polymers through NaBH4, ethylene glycol, and hydrothermal reduction routes, which delivered Ru-A, Ru-B, and Ru-C materials, respectively, and avoided aggregation of metal NPs. Homogeneous dispersion, the nanoconfinement effect of the polymer, and the oxidation state of Ru NPs were verified by employing TEM, energy-dispersive X-ray spectroscopy mapping, cross polarization magic-angle spinning (13)C NMR spectroscopy, and X-ray photoelectron spectroscopy analytical tools. These three new Ru-based POP materials exhibited excellent catalytic performance in the hydrogenation of nitroarenes at RT (with a reaction time of only ≈ 30 min), with high conversion, selectivity, stability, and recyclability for several catalytic cycles, compared with other traditional materials, such as Ru@C, Ru@SiO2, and Ru@TiO2, but no clear agglomeration or loss of catalytic activity was observed. The high catalytic performance of the ruthenium-based POP materials is due to the synergetic effect of nanoconfinement and electron donation offered by the 3D POP network. DFT calculations showed that hydrogenation of nitrobenzene over the Ru (0001) catalyst surface through a direct reaction pathway is more favorable than that through an indirect reaction pathway. PMID:26572500

  3. Photo-Curable Polymer Blend Dielectrics for Advancing Organic Field-Effect Transistor Applications

    SciTech Connect

    S Kim; K Hong; M Jang; J Jang; J Anthony; H Yang; C Park

    2011-12-31

    A solution method of photo-curable and -patternable polymer gate dielectrics was introduced by using blend solutions of poly(4-dimethylsilyl styrene) (PDMSS) and poly(melamine-co-formaldehyde) acrylate (PMFA). The fabrication was optimized to produce a smooth hydrophobic gate dielectric with good insulating and solvent-resistant properties. On the optimized PDMSS/PMFA blend gate dielectric, pentacene could grow into highly ordered structure, showing high electric performances for the resulting OFETs, as well as PTCDI-C13 and TES-ADT.

  4. Hot Melt Extruded Amorphous Solid Dispersion of Posaconazole with Improved Bioavailability: Investigating Drug-Polymer Miscibility with Advanced Characterisation

    PubMed Central

    Amin, Purnima

    2014-01-01

    Invasive antifungal infections are reasons for morbidity and mortality in immunogenic patients worldwide. Posaconazole is a most promising antifungal agent against all types of invasive infections with high % of cure rate. The marketed suspension formulation has low bioavailability and is needed to be taken with food. In this paper, PCZ hot melt extruded amorphous solid dispersion (SD) with immediate release and improved bioavailability was prepared using Soluplus (Sol) as primary carrier for solubilization. Surfactants such as PEG 400, Lutrol F27, Lutrol F68, and TPGS are also used in combination with Soluplus to improve the physicochemical performance of the formulation when it comes in contact with GI (gastrointestinal) fluid. Drug-polymer miscibility of SD was investigated using advanced techniques. In the in vivo study, the AUC(0–72) and Cmax of PCZ/Soluplus were 11.5 and 11.74 time higher than those of pure PCZ. The formulation of the extrudate SD had an AUC(0–72) and Cmax higher than those with the commercial capsule (Noxafil). Molecular dynamic (MD) simulation studies were carried out using in silico molecular modelling to understand the drug-polymer intermolecular behaviour. The results of this research ensure enhanced dissolution and bioavailability of the solid dispersion of PCZ prepared by HME compared with the PCZ suspension. PMID:25143935

  5. Engineered glycated amino dendritic polymers as specific nonviral gene delivery vectors targeting the receptor for advanced glycation end products.

    PubMed

    Giron-Gonzalez, M Dolores; Morales-Portillo, Arturo; Salinas-Castillo, Alfonso; Lopez-Jaramillo, F Javier; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco; Salto-Gonzalez, Rafael

    2014-06-18

    The receptor for advanced glycation end products (RAGE) is involved in diabetes or angiogenesis in tumors. Under pathological conditions, RAGE is overexpressed and upon ligand binding and internalization stimulates signaling pathways that promote cell proliferation. In this work, amino dendritic polymers PEI 25 kDa and alkylated derivatives of PAMAM-G2 were engineered by the nonenzymatic Maillard glycation reaction to generate novel AGE-containing gene delivery vectors targeting the RAGE. The glycated dendritic polymers were easily prepared and retained the capability to bind and protect DNA from endonucleases. Furthermore, while glycation decreased the transfection efficiency of the dendriplexes in CHO-k1 cells which do not express RAGE, glycated dendriplexes acted as efficient transfection reagents in CHO-k1 cells which stably express recombinant RAGE. In addition, preincubation with BSA-AGEs, a natural ligand of the RAGE, or dansyl cadaverine, an inhibitor of the RAGE internalization, blocked transfection, confirming their specificity toward RAGE. The results were confirmed in NRK and RAW264.7 cell lines, which naturally express the receptor. The glycated compounds retain their transfection efficiency in the presence of serum and promote in vivo transfection in a mouse model. Accordingly, RAGE is a suitable molecular target for the development of site-directed engineered glycated nonviral gene vectors. PMID:24852962

  6. Insight into Pathologic Abnormalities in Congenital Semilunar Valve Disease Based on Advances in Understanding Normal Valve Microstructure and Extracellular Matrix

    PubMed Central

    Stephens, Elizabeth H.; Kearney, Debra L.; Grande-Allen, K. Jane

    2011-01-01

    Congenitally diseased valves are relatively frequent causes of significant morbidity and mortality. Pathology descriptions of such valves have primarily focused on gross structural features including the number of leaflets or commissures (bicuspid/bicommissural valve) and alterations in the contour, thickness and consistency of the leaflets (dysplastic valve). Functional correlates of these pathologic alterations are valvar stenosis, insufficiency or both. Further characterization of the microstructural abnormalities seen in these malformed valves may not only provide insight into the correlation of distinct pathologies with their respective pathogenesis and clinical sequelae, but also may prove pivotal in uncovering new avenues for therapeutic interventions and prevention regimens. This review summarizes microstructural findings in congenital semilunar valve disease (CSVD) and discusses their relevance in light of recent advances in knowledge of normal valve microstructure, biology, and function. Specifically, the biological and mechanical roles of various matrix components and their interactions are discussed in the context of CSVD. Indeed, recent research in normal valves adds significant insight into CSVD, and raises many hypotheses that will need to be addressed by future studies. PMID:21349746

  7. Influence of the Shell Thickness and Ratio Between Core Elements on Photostability of the CdTe/CdS Core/Shell Quantum Dots Embedded in a Polymer Matrix.

    PubMed

    Doskaliuk, Nataliia; Khalavka, Yuriy; Fochuk, Petro

    2016-12-01

    This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polymer film containing CdTe/CdS quantum dots leads to a significant decrease in the photoluminescence intensity together with the "blue shift" of the photoluminescence peak energy associated with quantum dot photooxidation. The mechanisms of the CdTe/CdS core/shell quantum dot photooxidation and photomodification in a polymer matrix are discussed. We have found a correlation between the photostability of the quantum dots and the CdS shell thickness as well as the ratio of core elements. PMID:27102905

  8. Influence of the Shell Thickness and Ratio Between Core Elements on Photostability of the CdTe/CdS Core/Shell Quantum Dots Embedded in a Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Doskaliuk, Nataliia; Khalavka, Yuriy; Fochuk, Petro

    2016-04-01

    This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polymer film containing CdTe/CdS quantum dots leads to a significant decrease in the photoluminescence intensity together with the "blue shift" of the photoluminescence peak energy associated with quantum dot photooxidation. The mechanisms of the CdTe/CdS core/shell quantum dot photooxidation and photomodification in a polymer matrix are discussed. We have found a correlation between the photostability of the quantum dots and the CdS shell thickness as well as the ratio of core elements.

  9. An investigation of tensile damage behavior of X5230/T800 polymer matrix composites through in-situ tensile testing in SEM

    SciTech Connect

    Zhang, S.J.; Zhang, H.Q.; Delale, F.; Liaw, B.M.; Bode, J.H.

    1994-12-31

    Dog bone tensile specimens made of 8-ply X5230/T800 polymer matrix composites with [0{degree}/+45{degree}/0{degree}/{minus}45{degree}]{sub s}, arrangement and 57% fiber volume fraction have been subjected to tensile loading either along or perpendicular to the 0{degree} fiber direction at various temperatures. The tests were conducted inside an enlarged specimen chamber of a Hitachi S-2400 scanning electron microscope (SEM). During the test, the upper surface of the specimen in the gage section area was closely monitored through the screen of the SEM and the images revealing the intermediate tensile damage events on the surface and the edge of the specimen were captured in-situ either by using a Polaroid camera or a thermal print processor. When loading was applied parallel to the 0{degree} fiber direction at room temperature, damage started in the 0{degree} ply in the form of fiber breaking, followed by multiple fiber braiding in the 0{degree} ply, delamination between O{degree} and {+-}45{degree} plies, matrix cracking along the fiber direction in the {+-}45{degree} plies and the eventual failure of the specimen. No matrix cracks in the 0{degree} ply were observed for tests in room temperature. However, when tested at 1OO C, interface cracks were found in the 0{degree} ply and the failure load decreases substantially. When the loading was applied perpendicular to the 0{degree} fiber direction, no damage was observed in the 0{degree} ply until failure. A finite element model which incorporates the observed damage progression and based on the microstructure of the composite was also developed.

  10. Enhancement in dose sensitivity of polymer gel dosimeters composed of radiation-crosslinked gel matrix and less toxic monomers

    NASA Astrophysics Data System (ADS)

    Hiroki, A.; Yamashita, S.; Taguchi, M.

    2015-01-01

    Polymer gel dosimeters based on radiation-crosslinked hydroxypropyl cellulose gel were prepared, which comprised 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol #400 dimethacrylate (9G) as less toxic monomers and tetrakis (hydroxymethyl) phosphonium chloride (THPC) as an antioxidant. The dosimeters exposed to 60Co γ-rays became cloudy at only 1 Gy. The irradiated dosimeters were optically analyzed by using a UV- vis spectrophotometer to evaluate dose response. Absorbance of the dosimeters linearly increased in the dose range from 0 to 10 Gy, in which dose sensitivity increased with increasing 9G concentration. The dose sensitivity of the dosimeters with 2 wt% HEMA and 3 wt% 9G was also enhanced by increment in THPC.

  11. Conductive Polymer-Coated VS4 Submicrospheres As Advanced Electrode Materials in Lithium-Ion Batteries.

    PubMed

    Zhou, Yanli; Li, Yanlu; Yang, Jing; Tian, Jian; Xu, Huayun; Yang, Jian; Fan, Weiliu

    2016-07-27

    VS4 as an electrode material in lithium-ion batteries holds intriguing features like high content of sulfur and one-dimensional structure, inspiring the exploration in this field. Herein, VS4 submicrospheres have been synthesized via a simple solvothermal reaction. However, they quickly degrade upon cycling as an anode material in lithium-ion batteries. So, three conductive polymers, polythiophene (PEDOT), polypyrrole (PPY), and polyaniline (PANI), are coated on the surface to improve the electron conductivity, suppress the diffusion of polysulfides, and modify the interface between electrode/electrolyte. PANI is the best in the polymers. It improves the Coulombic efficiency to 86% for the first cycle and keeps the specific capacity at 755 mAh g(-1) after 50 cycles, higher than the cases of naked VS4 (100 mAh g(-1)), VS4@PEDOT (318 mAh g(-1)), and VS4@PPY (448 mAh g(-1)). The good performances could be attributed to the improved charge-transfer kinetics and the strong interaction between PANI and VS4 supported by theoretical simulation. The discharge voltage ∼2.0 V makes them promising cathode materials. PMID:27377263

  12. Support for the Advanced Polymers Beamline at the National Synchrotron Light Source

    SciTech Connect

    Hsiao, Benjamin S

    2008-10-01

    The primary focus of the X27C beamline is to investigate frontier polymer science and engineering problems with emphasis on real-time studies of structures, morphologies and dynamics from atomic, nanoscopic, microscopic to mesoscopic scales using simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The scientific merit of this project is as follows. Currently, many unique sample chambers for in-situ synchrotron studies, developed by the PI (B. Hsiao) and Co-PI (B. Chu), are available for general users of X27C at NSLS. These instruments include a gel/melt spinning apparatus, a continuous fiber drawing apparatus, a tensile stretching apparatus, a high pressure X-ray cell using supercritical carbon dioxide, a parallel plate strain-controlled shear stage and a dynamic rheometer for small-strain oscillatory deformation study. Based on the use of these instruments in combination with synchrotron X-rays, many new insights into the relationships between processing and structure have been obtained in recent years. The broader impact of this project is as follows. The X27C beamline is the first synchrotron facility in the United States dedicated to chemistry/materials research (with emphasis on polymers). The major benefit of this facility to the materials community is that no extensive synchrotron experience and equipment preparation are required from general users to carry out cutting-edge experiments.

  13. Towards modelling of stochastic kinetics for process related to photochromic dye semi-intercalation in DNA-based polymer matrix

    NASA Astrophysics Data System (ADS)

    Mitus, Antoni C.; Pawlik, Grzegorz; Kordas, Wojciech; Mysliwiec, Jaroslaw; Miniewicz, Andrzej; Kajzar, Francois; Rau, Ileana; Grote, James G.

    2011-09-01

    The semi-intercalation of an azo-dye Disperse Red 1 (DR1) molecule into a biopolymeric material made of deoxyribonucleic acid (DNA) complexed with the cationic surfactant hexadecyltrimethyl-ammonium chloride (CTMA) formulated recently1-3 has successfully explained the main experimental results4 of laser dynamic inscription of diffraction gratings: short response time, low diffraction efficiency, single-exponential kinetics and flat wavelength dependence.5 In this paper we generalize the analytic model of Ref.2 to account for a more realistic dynamics of DNA-CTMA matrix. To this end we extend the model of paper5 by including into it probabilistic features of local free volume in DNA matrix which characterize, in a simple way, the spatial distribution of local voids which, in turn play the central role for the kinetics of photoinduced trans-cis-trans cycles of DR1 dye under the polarized laser light illumination. We discuss a stochastic master equation which generalizes the simple model of Ref.2 and address briefly the topic of non-exponential grating inscription in modelling and in recent experiments.

  14. An investigation into the drug release from ibuprofen matrix tablets with ethylcellulose and some poly-acrylate polymers.

    PubMed

    Tabandeh, Hosseinali; Mortazavi, Seyed Alireza

    2014-05-01

    This study was performed to achieve sustained-release Ibuprofen matrix tablets with a zero-order release kinetic while most of the previous formulations have shown Higuchi release kinetic. Considering the results from previous studies, ethyl cellulose, Carbopol 934P, Carbopol 974P, and Pemulen TR-1 were used at different amounts for preparation of the tablets by direct compression. The release profiles were studied in a two-stage release test using non-linear regression analysis. Carbopols 934P and 974P could not sustain the release adequately while Pemulen TR-1 had too strong sustaining effect. Therefore, combination formulations were considered and studied. The release profiles of ethyl cellulose formulation and the combination formulation consisting Carbopol 934P and Pemulen TR-1 best fitted in Higuchi model, although the zero-order model was not completely rejected. However, the kinetic model of release from the combination formulation consisting Carbopol 974P and Pemulen TR-1 changed to zero-order indicating the most constant release rate among formulations. This was speculated to be due to some erosion of the gel, as well as some interaction of the hydrophobic chain of Pemulen TR-1 with Ibuprofen. Therefore, this formulation is suggested for directly compressed sustained-release matrix tablets of Ibuprofen with a more constant release rate. PMID:24811808

  15. In vitro Evaluation of the Effect of Combination of Hydrophilic and Hydrophobic Polymers on Controlled Release Zidovudine Matrix Tablets.

    PubMed

    Ganesh, S; Radhakrishnan, M; Ravi, M; Prasannakumar, B; Kalyani, J

    2008-01-01

    The aim of the present study was to prepare and characterize controlled-release matrix tablets of zidovudine using hydrophilic HPMC K4 M or Carbopol 934 alone or in combination with hydrophobic ethyl cellulose. Release kinetics was evaluated by using USP XXIV dissolution apparatus No.2 (paddle) type. Scanning electron microscopy was used to visualize the effect of dissolution medium on matrix tablet surface. The in vitro results of controlled - release zidovudine tablets were compared with conventional marketed tablet Zidovir. The in vitro drug release study revealed that HPMC K4 M or Carbopol 934 preparation was able to sustain the drug release near to 6 hours. Combining HPMC K4 M or Carbopol 934 with ethyl cellulose sustained the drug release for nearly 12 h. The in vitro evaluation showed that the drug release may be by diffusion along with erosion. Results suggest that the developed controlled-release tablets of zidovudine could perform therapeutically better than marketed dosage forms, leading to improve efficacy, controlling the release and better patient compliance. PMID:20046771

  16. Free Radical Addition Polymerization Kinetics without Steady-State Approximations: A Numerical Analysis for the Polymer, Physical, or Advanced Organic Chemistry Course

    ERIC Educational Resources Information Center

    Iler, H. Darrell; Brown, Amber; Landis, Amanda; Schimke, Greg; Peters, George

    2014-01-01

    A numerical analysis of the free radical addition polymerization system is described that provides those teaching polymer, physical, or advanced organic chemistry courses the opportunity to introduce students to numerical methods in the context of a simple but mathematically stiff chemical kinetic system. Numerical analysis can lead students to an…

  17. Utilizing advanced polymerization techniques for simplifying polymer grafting from silica colloidal crystal substrates

    NASA Astrophysics Data System (ADS)

    Yerneni, Charu K.

    Polyacrylamide has been well established as a biocompatible material when Polyacrylamide gel electrophoresis (PAGE) came into existence in the 1960s. Under aqueous buffer conditions it becomes non-adsorptive to proteins and due to its molecular level pore forming nature could be used in size based biomolecule separations. Since then considerable research has been done to explore the non-adsorptive nature of polyacrylamide on a platform or substrate. Attempts were made to grow polyacrylamide chains from silica as a substrate which can then be used in various protein separation techniques. Based on an ionic polymerization method which was used for gel casting in PAGE, polymers were grown on silica gel. Though considerable thickness could be achieved, polymerization was not just confined to the surface. Therefore a rigid polymer brush layer could not be achieved. Atom transfer radical polymerization (ATRP) method showed the solution to this problem. Polymer brush layers with acceptable thickness could now be achieved for growing polyacrylamide from silica gel. Yet it still suffered from several disadvantages such as the need of an inert atmosphere for polymerization and limited thickness. Many developments have taken place in the past decade which led to improvements in substrate and polymerization methods. This research used non porous sub-micron silica as the substrate and AGET ATRP (Activator generated electron transfer atom transfer radical polymerization) for surface grafting polyacrylamide. Non porous submicron silica has been shown to be a better stationary phase substrate for protein separations than conventional substrates. AGET ATRP enables polymerization to be performed under ambient conditions and in water based solutions which gives thicknesses much higher than conventional ATRP. Data from various analytical techniques showed that within the experimental range the polymerization is linear and has decent control. This means silica nanoparticles coated with

  18. Interfaces in polymer, ceramic, and metal matrix composites; Proceedings of the Second International Conference on Composite Interfaces (ICCI-II), Cleveland, OH, June 13-17, 1988

    SciTech Connect

    Ishida, H.

    1988-01-01

    The present conference on interfacial factors in advanced composite materials discusses such topics in their development status and properties as silane coupling, the electrochemical and plasma-surface treatment of carbon fibers, fiber surface-analytical techniques, polymer molecular scale characterization by atom-probe field-ion microscopy, the study of carbon fiber-epoxy resin interface interactions by means of labeling techniques, and the surface tailoring of SiC by ion implantation. Also discussed are developments in laser light-scattered photoelasticity, microstructural evolutions under heat treatment and radiation damage, TEM for composites, the interfaces of carbon fiber-reinforced Al composites, the influence of the interface on macroscopic composite properties, and the status of the theoretical understanding of composite interfaces.

  19. Molecularly designed lipid microdomains for solid dispersions using a polymer/inorganic carrier matrix produced by hot-melt extrusion.

    PubMed

    Adler, Camille; Schönenberger, Monica; Teleki, Alexandra; Kuentz, Martin

    2016-02-29

    Amorphous solid dispersions have for many years been a focus in oral formulations, especially in combination with a hot-melt extrusion process. The present work targets a novel approach with a system based on a fatty acid, a polymer and an inorganic carrier. It was intended to adsorb the acidic lipid by specific molecular interactions onto the solid carrier to design disorder in the alkyl chains of the lipid. Such designed lipid microdomains (DLM) were created as a new microstructure to accommodate a compound in a solid dispersion. Vibrational spectroscopy, X-ray powder diffraction, atomic force microscopy as well as electron microscopic imaging were employed to study a system of stearic acid, hydroxypropylcellulose and aluminum magnesium silicate. β-carotene was used as a poorly water-soluble model substance that is difficult to formulate with conventional solid dispersion formulations. The results indicated that the targeted molecular excipient interactions indeed led to DLMs for specific compositions. The different methods provided complementary aspects and important insights into the created microstructure. The novel delivery system appeared to be especially promising for the formulation of oral compounds that exhibit both high crystal energy and lipophilicity. PMID:26721729

  20. Click Grafting of Alkyne-containing Vinyl Polymers onto Biosynthesized Extracellular Matrix Protein Containing Azide Functionality and Adhesion Control of Human Umbilical Vein Endothelial Cells

    PubMed Central

    Yamada, Tomoki

    2015-01-01

    In vivo incorporation of a phenylalanine (Phe) analogue, p-azidophenylalanine (p-N3Phe) into an artificial extracellular matrix protein (aECM-CS5-ELF) was accomplished using a bacterial expression host that harbors the mutant phenylalanyl-tRNA synthetase (PheRS) with an enlarged binding pocket, in which the Ala294Gly/Thr251Gly mutant PheRS (PheRS**) was expressed under the control of T7 promoters. In this study, biosynthesized aECM-CS5-ELF containing p-N3Phe (aECM-CS5-ELF-N3) was coupled with alkyne-containing vinyl polymers prepared via controlled radical polymerization of three vinyl monomers, (styrene, acrylamide, and N-isopropylacrylamide) using a trithiocarbonate as the RAFT agent. Grafting of the vinyl polymers onto the aECM was accomplished via a copper-catalyzed alkyne-azide click reaction. The lower critical transition temperature (LCST) was evaluated, as well as the solubility in aqueous and organic media, which are dependent on the incorporation ratio of p-N3Phe and species of graft chains, in which the LCST behavior was altered remarkably when poly(N-isopropylacrylamide) moieties were attached as side chains. Circular dichroism measurements indicate conformational change was not induced by the grafting. Specific adhesion of human umbilical vein endothelial cells (HUVECs) onto the aECM-CS5-ELF-N3-graft-poly(N-isopropylacrylamide) composite surface and subsequent temperature-sensitive detachment were also demonstrated. PMID:26294960