Search NASA⌕ Search

SEARCH · Search NASA

Results for “polymer stability”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Some final conclusions and supporting experiments related to the search for organic compounds on the surface of Mars

The Viking molecular analysis experiment has demonstrated the absence (within the detection limits which range from levels of parts per million to below parts per billion) of organic substances in the Martian surface soil at the two Viking landing sites. Laboratory experiments with sterile and nonsterile antarctic samples further demonstrate the capability and reliability of the instrument. The circumstances under which organic components could have escaped detection, such as inaccessibility or extreme thermal stability of organic polymers, are discussed but are found to be unlikely. The inability of the instrument to detect free oxygen evolved from soil samples is pointed out.

Biemann, K.↗
NASA NTRS1985

Nonyellowing Polycarbonate for Outdoor Use

Two-step photochemical process prevents yellowing of polycarbonate plastics. Use of polycarbonate plastics growing in windows, aircraft glazing, and streetlight globes. New photochemical process causes formation of stabilizers bound to polymer chains and therefore cannot be leached out.

Gupta, A.↗
NASA NTRS1984

Polymerizable ultraviolet stabilizers

Polymerizable ultraviolet stabilizers were examined. The objective was to synthesize polymerizable UV monomers, and to incorporate polymerizable UV stabilizers (benzotriazoles) into polymers.

Gomez, P.↗
NASA NTRS1990

Dielectric Coating For Hot-Film Flow Sensors

Very-thin-film dielectric coating stable over range of temperatures developed. This dielectric coating, combination of fused silica and thermoplastic polymer, has sufficient stability to withstand stresses placed upon it by cycling to and from cryogenic temperatures. Coating tailored to meet almost any criterion of roughness height. Useful for research in application of hot-film sensors to airfoils.

Hopson, Purnell, Jr.↗
NASA NTRS1990

Low dielectric fluorinated poly(phenylene ether ketone) film and coating

The present invention relates to film and coating materials prepared from novel fluorinated poly(phenylene ether ketones). A fluorinated poly(phenylene ether ketone) is prepared by reacting a bisphenol with 1,1,1,3,3,3 hexafluoro-2,2-bis 4-(4-halobenzoyl) phenyl propane (wherein halo is fluoro or chloro), which is a novel monomer formed as the reaction product of halobenzene (wherein halo is fluoro or chloro) and 1,1,1,3,3,3 hexafluoro-2,2-bis (p-chloro formyl phenyl) propane. Especially beneficial results of this invention are that films and coating materials prepared from the novel fluorinated poly(phenylene ether ketone) are essentially optically transparent/colorless and have a lower dielectric constant than otherwise comparable, commercially available poly(phenylene ether ketones). Moreover, unlike the otherwise comparable commercially available materials, the novel fluorinated poly(phenylene ether ketones) of the present invention can be solution cast or sprayed to produce the films and coatings. Furthermore, the long term thermal stability of the polymers of the present invention is superior to that of the commercially available materials.

Cassidy, Patrick E.↗
NASA NTRS1997

Galactic and Solar Cosmic Ray Shielding in Deep Space

An analysis of the radiation hazards in support of NASA deep space exploration activities is presented. The emphasis is on materials required for radiation protection shielding. Aluminum has been found to be a poor shield material when dose equivalent is used with exposure limits for low Earth orbit (LEO) as a guide for shield requirements. Because the radiation issues are cost related-the parasitic shield mass has high launch costs, the use of aluminum as a basic construction material is clearly not cost-effective and alternate materials need to be developed. In this context, polyethylene is examined as a potentially useful material and demonstrates important advantages as an alternative to aluminum construction. Although polyethylene is useful as a shield material, it may not meet other design criteria (strength, stability, thermal); other polymer materials must be examined.

Wilson, John W.↗
NASA NTRS2002

Preliminary Evaluation of Polyarylate Dielectric Films for Cryogenic Applications

Polymeric materials are used extensively on spacecraft and satellites in electrical power and distribution systems, as thermal blankets and optical surface coatings, as well as mechanical support structures. The reliability of these systems when exposed to the harsh environment of space is very critical to the success of the mission and the safety of the crew in manned-flight ventures. In this work, polyarylate films were evaluated for potential use as capacitor dielectrics and wiring insulation for cryogenic applications. Two grades of the film were characterized in terms of their electrical and mechanical properties before and after exposure to liquid nitrogen (-196 C). The electrical characterization consisted of capacitance and dielectric loss measure Cents in the frequency range of 50 Hz to 100 kHz, and volume and surface resistivities. The mechanical measurements performed included changes in tensile (Young's modulus, elongation-at-break, and tensile strength) and structural properties (dimensional change, weight, and surface morphology). The preliminary results, which indicate good stability of the polymer after exposure to liquid nitrogen, are presented and discussed.

Patterson, Richard L.↗
NASA NTRS2004

Organic Modification of a Layered Silicate by Co-Ion Exchange of an Alkyl Ammonium and a Mono-Protonated Diamine

Co-Ion exchange of the interlayer cations of a layered silicate with a mono-protonated aromatic diamine and an alkyl ammonium ion into the silicate galleries. The presence of the alkyl ammonium ion provides low oligomer melt viscosity during processing. The presence of the diamine allows chemical reaction between the silicate surface modification and the monomers. This reaction strengthens the polymer silicate interface, and ensures irreversible separation of the individual silicate layers. Improved polymer thermal oxidative stability and mechanical properties are obtained.

Sandi G Campbell↗
NASA NTRS1990

Ladder polymers for use as high temperature stable resins or coatings

An object of the invention is to synthesize a new class of ladder and partial ladder polymers. In accordance with the invention, the new class of ladder and partial ladder polymers are synthesized by polymerizing a bis-dienophile with a bis-diene. Another object of the invention is to provide a fabricated, electrically conducting, void free composite comprising the new class of the ladder and partial ladder polymers described above. The novelty of the invention relates to a new class of ladder and partial ladder polymers and a process for synthesizing these polymers. These polymers are soluble in common organic solvents and are characterized with a unique dehydration property at temperatures of 300 to 400 C to provide thermo-oxidatively stable pentiptycene units along the polymeric backbone. These polymers are further characterized with high softening points and good thermo-oxidative stability properties. Thus these polymers have potential as processable, matrix resins for high temperature composite applications.

Meador, Mary Ann↗
NASA NTRS1983

New polymers for composites: A summary of research on polystyrylpyridines

Styrylpyridine and its derivatives are studied. The synthesis, characterization, and thermal stability of styrylpyridine based polymers are discussed, as well as the preparation of a diglycidyl ester of styrylpridine. Also discussed are the preparation of polyarylates, and styrylpyridine based polytriazines and prepolymers.

Pearce, E. M.↗
NASA NTRS1995

Evaluation of high temperature polymers

The purpose of this paper is to identify and develop arc-track resistant insulation materials that can operate reliably at 300 C. In the first phase, high performance polymers are evaluated based on structure, thermal stability and electrical properties. Next, the polymers are ranked according to performance and experimental characterization. Then, experimental evaluations in wire configuration are conducted. And selection is made based on performance and commerical potential.

Jayaraj, K.↗
NASA NTRS1991

Effects of high pressure nitrogen on the thermal stability of SiC fibers

Polymer-derived SiC fibers were exposed to nitrogen gas pressures of 7 and 50 atm at temperatures up to 1800 C. The fiber weight loss, chemical composition, and tensile strength were then measured at room temperature in order to understand the effects of nitrogen exposure on fiber stability. High pressure nitrogen treatments limited weight loss to 3 percent or less for temperatures up to 1800 C. The bulk Si-C-O chemical composition of the fiber remained relatively constant up to 1800 C with only a slight increase in nitrogen content after treatment at 50 atm; however, fiber strength retention was significantly improved. To further understand the effects of the nitrogen atmosphere on the fiber stability, the results of previous high pressure argon treatments were compared to those of the high pressure nitrogen treatments. High pressure inert gas can temporarily maintain fiber strength by physically inhibiting the evolution of gaseous species which result from internal reactions. In addition to this physical effect, it would appear that high pressure nitrogen further improved fiber temperature capability by chemically reacting with the fiber surface, thereby reducing the rate of gas evolution. Subsequent low pressure argon treatments following the initial nitrogen treatments resulted in stronger fibers than after argon treatment alone, further supporting the chemical reaction mechanism and its beneficial effects on fiber strength.

Jaskowiak, Martha H.↗
NASA NTRS1987

Lanthanide-containing polyimides

The preparation of a variety of lanthanide-containing polyimide films is described, and results of their characterization are presented. The properties investigated include the glass transition temperature, thermooxidative stability, magnetic susceptibility, and electrical conductivity of the polymer. Films containing lanthanide chlorides, fluorides, and sulfides are flexible, but those containing lanthanide nitrates are extremely brittle. The addition of lanthanide acetates and acetylacetonates caused immediate gelation of two of the synthesis-mixture ingredients. It was found that, in general, the addition of lanthanide to the polyimide increases the density and glass transition temperature of the polymer but slightly decreases the thermooxidative stability.

Stoakley, D. M.↗
NASA NTRS1992

Residual thermal stresses in composites for dimensionally stable spacecraft applications

An overview of NASA LaRC's research on thermal residual stresses and their effect on the dimensional stability of carbon fiber reinforced polymer-matrix composites is presented. The data show that thermal residual stresses can induce damage in polymer matrix composites and significantly affect the dimensional stability of these composites by causing permanent residual strains and changes in CTE. The magnitude of these stresses is primarily controlled by the laminate configuration and the applied temperature change. The damage caused by thermal residual stresses initiates at the fiber/matrix interface and micromechanics level analyses are needed to accurately predict it. An increased understanding of fiber/matrix interface interactions appears to be the best approach for improving a composite's resistance to thermally induced damage.

Bowles, David E.↗
NASA NTRS1991

Preparation of atomic oxygen resistant polymeric materials

Polyphenyl quinoxalines (PPQs) are an important family of high performance polymers that offer good chemical and thermal stability coupled with excellent mechanical properties. These aromatic heterocyclic polymers are potentially useful as films, coatings, adhesives, and composite materials that demand stability in harsh environments. Our approach was to prepare PPQs with pendent siloxane groups using the appropriate chemistry and then evaluate these polymers before and after exposure to simulated atomic oxygen. Either monomer, the bis(o-diamine)s or the bis(alpha-diketone)s can be synthesized with a hydroxy group to which the siloxane chain will be attached. Several novel materials were prepared.

Tortorelli, Victor J.↗