Search NASA⌕ Search

SEARCH · Search NASA

Results for “Polymer glasses”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Highly stretchable ionically crosslinked acrylate elastomers inspired by polyelectrolyte complexes

Dynamic bonds are a powerful approach to tailor the mechanical properties of elastomers and introduce shape-memory, self-healing, and recyclability. Among the library of dynamic crosslinks, electrostatic interactions among oppositely charged ions have been shown to enable tough and resilient elastomers and hydrogels. In this work, we investigate the mechanical properties of ionically crosslinked ethyl acrylate-based elastomers assembled from oppositely charged copolymers. Using both infrared and Raman spectroscopy, we confirm that ionic interactions are established among polymer chains. We find that the glass transition temperature of the complex is in between the two individual copolymers, while the complex demonstrates higher stiffness and more recovery, indicating that ionic bonds can strengthen and enhance recovery of these elastomers. We compare cycles to increasing strain levels at different strain rates, and hypothesize that at fast strain rates ionic bonds dynamically break and reform while entanglements do not have time to slip, and at slow strain rates ionic interactions are disrupted and these entanglements slip significantly. Further, we show that a higher ionic to neutral monomer ratio can increase the stiffness, but its effect on recovery is minimal. Lastly, taking advantage of the versatility of acrylates, ethyl acrylate is replaced with the more hydrophilic 2-hydroxyethyl acrylate, and the latter is shown to exhibit better recovery and self-healing at a cost of stiffness and strength. The design principles uncovered for these easy-to-manufacture polyelectrolyte complex-inspired bulk materials can be broadly applied to tailor elastomer stiffness, strength, inelastic recovery, and self-healing for various applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Chain dynamics of alternating polymers P(C n EG 4 )

Alternating or sequence defined polymers attract the attention of an increasing number of researchers recently. Due to their different blocks, they are very customizable and material properties can be tuned. In this publication, we present dynamical studies with focus on polymer dynamics, investigated by rheology and fast field cycling (FFC) NMR. The molecular weight dependencies of the relaxation time and zero-shear viscosity could hint to entanglement effects; however, the spectral shape of the viscoelastic data resembles the polymer dynamics of unentangled melts. Furthermore, taking both techniques into account, i.e. rheology and FFC NMR leads to the conclusion that the relaxation spectra of the alternating polymer are similar to those of linear polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Validation of Advanced Photovoltaic Module Materials and Processes by Combined-Accelerated Stress Testing (C-AST)

Tessolar module technology was developed to allow the incorporation of 5 incremental module material innovations. Combined, these innovations may improve the efficiency and durability of the standard silicon cell module. The innovations evaluated are: electrically conductive adhesive (ECA) replacing soldering of tabbing ribbons, light-capturing ribbon (LCR), silicone encapsulant, 2 mm front glass with backsheet, and a polymer-composite module frame. Tessolar-constructed individually encapsulated cells incorporating the material innovations are used to assemble 60-cell modules. 2 x 2 cell mini-modules of the same materials were produced for combined-accelerated stress testing (C-AST). C-AST results demonstrate that the 2 x 2 cell mini-module of Tessolar construction out-performed mini-modules using both ECA with EVA and standard solder with EVA constructions in power production over 108 cycles of testing.

14 SOLAR ENERGY↗
DOE OSTI2023

Theory and Implementation of the Spectacular Nonlinear Viscoelastic Constitutive Model

This report is a comprehensive guide to the nonlinear viscoelastic Spectacular model, which is an isotropic, thermo-rheologically simple constitutive model for glass-forming materials, such as amorphous polymers. Spectacular is intermediate in complexity to the previous PEC and SPEC models (Potential Energy Clock and Simplified Potential Energy Clock models, respectively). The model form consists of two parts: a Helmholtz free energy functional and a nonlinear material clock that controls the rate of viscoelastic relaxation. The Helmholtz free energy is derived from a series expansion about a reference state. Expressions for the stress and entropy functionals are derived from the Helmholtz free energy following the Rational Mechanics approach. The material clock depends on a simplified expression for the potential energy, which itself is a functional of the temperature and strain histories. This report describes the thermo-mechanical theory of Spectacular, the numerical methods for time-integrating the model, model verification for its implementation in LAMÉ, a user guide for its implementation in LAMÉ, and ideas for future work. A number of appendices provide supplementary mathematical details and a description of the procedure used to derive the simplified potential energy from the full expression for the potential energy. The goal of this report is create a convenient point-of-entry for engineers who wish to learn more about Spectacular, but also to serve as a reference manual for advanced users of the model.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Absorption Of Gases By Glassy Polymers

Report discusses solubility of gas in glassy polymer, both above and below glass-transition temperature (Tg). Thermodynamic arguments brought to bear on previously-developed mathematical models, result being new model that enables calculation of infinite-dilution partial molar volume of solvent in glass or liquid solvent from data on pressure, volume, and temperature of solute in equilibrium with solvent.

Fedors, Robert F.↗
NASA NTRS1995

Poly(Arylene Ether)s Containing Pendent Ethynyl Groups

Poly(arylene ether)s containing pendent ethynyl groups synthesized. Offer advantage over linear poly(arylene ether)s in upon heating, pendent ethynyl groups react to form cross-linked molecular structures exhibiting greater resistance to solvents and higher glass-transition temperatures and tensile moduli. Polymers useful as adhesives, moldings, films, and matrices of composite materials.

Hergenrother, Paul M.↗
NASA NTRS2001

Testing and Optimization of Electrically Conductive Spacecraft Coatings

This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.

Mell, R. J.↗
NASA NTRS2004

Lithium Polymer Electrolytes and Solid State NMR

Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for participation on a variety of other projects, including aero-gels and carbon graphite mat en als. The goals of the polymer electrolyte research are to improve the physical properties of the polymers. This includes improving conductivity, durability, and expanding the temperature range over which it is effective. Currently, good conductivity is only present at high temperatures. My goals are to experiment with different arrangements of rods and coils to achieve these desirable properties. Some of my experiments include changing the number of repeat units in the polymer, the size of the diamines, and the types of coil. Analysis of these new polymers indicates improvement in some properties, such as lower glass transition temperature; however, they are not as flexible as desired. With further research we hope to produce polymers that encompass all of these properties to a high degree.

Berkeley, Emily R.↗
NASA NTRS2010

Micromechanics Modeling of Composites Subjected to Multiaxial Progressive Damage in the Constituents

The high-fidelity generalized method of cells composite micromechanics model is extended to include constituent-scale progressive damage via a proposed damage model. The damage model assumes that all material nonlinearity is due to damage in the form of reduced stiffness, and it uses six scalar damage variables (three for tension and three for compression) to track the damage. Damage strains are introduced that account for interaction among the strain components and that also allow the development of the damage evolution equations based on the constituent material uniaxial stress strain response. Local final-failure criteria are also proposed based on mode-specific strain energy release rates and total dissipated strain energy. The coupled micromechanics-damage model described herein is applied to a unidirectional E-glass/epoxy composite and a proprietary polymer matrix composite. Results illustrate the capability of the coupled model to capture the vastly different character of the monolithic (neat) resin matrix and the composite in response to far-field tension, compression, and shear loading.

Bednarcyk, Brett A.↗
NASA NTRS2021

Meta-aerogels: Auxetic Shape-memory Polyurethane Aerogels

Shape-memory poly(isocyanurate-urethane) (PIR-PUR) aerogels are low-density monolithic nanoporous solids that remember and return to their permanent shape through a heating actuation step. Herein, through structural design at the macro scale, the shape-memory response is augmented with an auxetic effect manifested by a negative Poisson’s ratio of approximately -0.8 at 15% compressive strain. Thus, auxetic shape-memory PIR-PUR monoliths experience volume contraction upon compression at a temperature above the glass transition temperature of the base polymer (Tg ~ 30 °C), and they can be stowed indefinitely in that temporary shape by cooling below Tg. By heating back above Tg, the compressed/shrunk form expands back to their original shape/size. This technology is relevant to a broad range of industries spanning the commercial, aeronautical, and aerospace sectors. The materials are referred to as meta-aerogels and their potential applications include minimally invasive medical devices, soft robotics, and in situations where volume is at a premium, as for example for storage of deployable space structures and planetary habitats during transport to the point of service.

Sadeq Malakooti↗
NASA NTRS2005

New Fiber Reinforced Waterless Concrete for Extraterrestrial Structural Applications

Commercial use of sulfur concrete on Earth is well established, particularly in corrosive, e.g., acid and salt, environments. Having found troilite (FeS) on the Moon raises the question of using extracted sulfur as a lunar construction mate: iii an attractive alternative to conventional concrete as it does not require water For the purpose of this paper it is assumed that lunar ore is mined, refined, and the raw sulfur processed with appropriate lunar regolith to form, for example, brick and beam elements. Glass fibers produced from regolith were used as a reinforcement to improve the mechanical properties of the sulfur concrete. Glass fibers and glass rebar were produced by melting the lunar regolith simulant. Lunar regolith stimulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline 46100 high temperature MoSi2 furnace at melting temperatures of 1450 to 1600G. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The viability of sulfur concrete as a construction material for extraterrestrial application is presented. The mechanical properties of the glass fiber reinforced sulfur concrete were investigated.

Toutanji, H.↗
DOE OSTI2023

Laser Welded Edge Seals for Polymer-Free Glass/Glass Modules

This presentation covers fs lasers which enable crack-free and stress-free glass/glass welds. Welds are nearly as strong as the glass (KI, weld ~ KI, glass) and static load test passed, enabling: 1) polymer-free; 2) hermetically sealed; and 3) recyclable modules. Next steps are: 1) follow-on funding; 2) develop feed throughs (metal/glass welds already achieved for other devices); and 3) weld mini modules for further IEC module testing.

DuraMAT↗
NASA NTRS1976

Thermoplastic polymers for improved fire safety

The thermochemical and flammability characteristics of some typical thermoplastic materials currently in use and others being considered for use in aircraft interiors are described. The properties studied included (1) thermomechanical properties such as glass transition and melt temperature, (2) changes in polymer enthalpy by differential scanning calorimetry, (3) thermogravimetric analysis in anaerobic and oxidative environments, (4) oxygen index, (5) smoke evolution, (6) relative toxicity of the volatile products of pyrolysis, and (7) selected physical properties. The generic polymers that were evaluated included: acrylonitrile butadiene styrene, bisphenol A polycarbonate, 9,9 bis (4-hydroxyphenyl) fluorene polycarbonatepoly (dimethyl siloxane) block polymer, phenolphthalein bisphenol A polycarbonate, phenolphthalein polycarbonate, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyaryl sulfone, chlorinated polyvinyl chloride homopolymer, polyvinyl fluoride, and polyvinylidene fluoride. Processing parameters, including molding characteristics of some of the advanced polymers, are described. Test results and relative ranking of some of the flammability, smoke, and toxicity properties are presented.

Kourtides, D. A.↗
DOE OSTI2022

Microparticle Impact Testing at High Precision, Higher Temperatures, and with Lithographically Patterned Projectiles

Abstract In the first decade of high‐velocity microparticle impact research, hardly any modification of the original experimental setup has been necessary. However, future avenues for the field require advancements of the experimental method to expand both the impact variables that can be quantitatively assessed and the materials and phenomena that can be studied. This work explores new design concepts for the launch pad (the assembly that launches microparticles upon laser ablation) that can address the root causes of many experimental challenges that may limit the technique in the future. Among the design changes contemplated, the substitution of a stiff glass launch layer for the standard elastomeric polymer layer offers a number of improvements. First, it facilitates a reduction of the gap between launch pad and target from hundreds to tens of micrometers and thus unlocks a reproducibility in targeting a specific impact location better than the diameter of the test particle itself (±1.75 µm for SiO 2 particles 7.38 µm in diameter). Second, the inert glass surface enables experiments at higher temperatures than previously possible. Finally—as demonstrated by the launch of thin‐film Au disks—a launch pad made of materials standard in microfabrication paves the way to facile microfabrication of advanced impactors.

36 MATERIALS SCIENCE↗