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At least 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Thermally conductive polymers

A thermally conductive polymer is provided having physical and chemical properties suited to use as a medium for potting electrical components. The polymer is prepared from hydroquinone, phenol, and formaldehyde, by conventional procedures employed for the preparation of phenol-formaldehyde resins. While the proportions of the monomers can be varied, a preferred polymer is formed from the monomers in a 1:1:2.4 molar or ratio of hydroquinone:phenol:formaldehyde.

Byrd, N. R.↗
NASA NTRS1973

Novel polymers and method of preparing same

Polymers are prepared with terminal functional groups by reacting a compound selected from the group consisting of lithium p-lithiophenoxide and tetrabutylammonium p-lithiophenoxide as an initiator with material such as butadiene. The resulting functionally terminated new polymers are then capable of reacting with coupling agents to form star polymers.

Hirshfield, S. M.↗
NASA NTRS1973

The atomic nature of polymer-metal interactions in adhesion, friction and wear

Adhesion experiments with polytetra-fluoroethylene (PTFE) and polyimide contacting tungsten indicate that the polymers bond chemically to the clean metal surface. Polymer chain fragments which transfer to the surface of tungsten in field ion microscopy adhesion studies are highly oriented. Auger emission spectroscopy of PTFE transfer films to various metal surfaces indicates that the PTFE is bonded to the metal surface via the carbon atom. With PTFE in sliding contact with different orientations of aluminum, metal orientation is found to influence surfaces in sliding. The lowest friction and least amount of surface damage is detected on the highest atomic density (111) plane. The friction process itself can initiate polymer film formation from simple organic molecules.

Buckley, D. H.↗
NASA NTRS1974

The atomic nature of polymer-metal interactions in adhesion, friction and wear

The adhesion, friction, and wear behavior of the solid polymers PTFE and polyimide in contact with various metals were studied using field ion microscopy, Auger emission spectroscopy, and scanning electron microscopy. Results indicate that the polymers will transfer to a clean tungsten surface on simple tough contact, forming a chemical bond. With PTFE, it is hypothesized that the bonding is of the carbon to the metal surface, while with the polyimide, both oxygen and carbon bonding to the tungsten surface are possible. In sliding contact, the friction process itself can initiate polymer film formation. The formation of such films has been suggested as a form of extreme pressure lubrication.

Buckley, D. H.↗
NASA NTRS1975

New urea-absorbing polymers for artificial kidney machines

Etherified polymer is made from modified cellulose derivative which is reacted with periodate. It will absorb 2 grams of urea per 100 grams of polymer. Indications are that polymers could be used to help remove uremic wastes in artificial kidneys, or they could be administered orally as therapy for uremia.

Mueller, W. A.↗
NASA NTRS1974

Quinoxaline polymers and copolymers derived from 1, 4-BIS(1'-napthalenyloxayl) benzene

A route for the synthesis of a new monomer, 1,4-bis(1'-naphthalenyl)-oxayl benzene, was devised, and six polymers and copolymers were prepared from this monomer, 1,4-bis(phenyloaxaly)benzene, 3,3'-diaminobenzidine and 3,3',4,4'-tetraaminobenzophenone. Thermogravimetric analysis showed that decomposition of these quinoxaline polymers and copolymers sets in at about 500 C but does not become significant in an inert atmosphere below 600 C. Oxidation becomes significant at about 550 C and the phenylquinoxaline homopolymer is somewhat more oxidation resistant than is the 1-naphthalenylquinoxaline homopolymer. Stress-relaxation measurements showed that, with two exceptions, the homopolymers and copolymers exhibited two second-order transition temperatures, one at about 204.4 C (400 F) and the other at about 315.6 C (600 F). No gross differences in the high temperature plasticity was observed between the naphthalenyl- and the phenyl-quinoaxaline homopolymers. Work was begun on a method for cross-linking polyquinoxalines. A new monomer, p-(methyloxaly)benzil, was synthesized, and model reaction studies showed that cross-linking of 2-methylquinoxaline polymers by a Michael condensation with dimaleimides will probably occur.

Port, W. S.↗
NASA NTRS1975

Molecular weight: Property relationships of high performance polymers used for adhesives and composites

Degradation of high performance polyimide precursor resins was investigated by measuring the molecular weight of the polymers in solution, using a membrane osmometer. It was found that polyimide precursor resins composed of BTDA and ODPA combined with DABP and MDA were unstable in DMAC. The degradation rate was found to depend upon the chemical nature of the isomeric diamine and the geometric structure about the amide linkage. The polymers of DABP were less susceptible to degradation than those of MDA and p,p'-compounds were more stable than m,m'-compounds. These results suggest that degradation is correlated with the basicity of the diamine. That is, the rate of the degradation reaction increases with the basicity of the diamine group in the polyimide precursor resin. The presence of water and a higher temperature increased the degradation rate of the polymers.

Kranbuehl, D.↗
NASA NTRS1976

Investigation of structure-property relationships in systematic series of novel polymers

Solid state transitions in polymeric materials was associated with the onset of sub-molecular motions of the polymer chains. Although these were considered to be intramolecular in general, the local environment of the polymer molecule exerts a strong influence through, for example, the effects of crystallinity, polarity and diluents. The manner of specimen preparation and previous history also affect transitions. The transitions are considered to arise when sufficient free volume is available to permit the occurrence of these side chain and backbone reorientations. The glass transition is the principal transition of amorphous polymeric materials and is associated with the onset of long range segmental motion of the polymer backbone. The various types of shorter range motion occurring below the glass transition have been catalogued.

Gillham, J. K.↗
NASA NTRS1976

Quinoxaline polymers and copolymers derived from 1,4-bis(1'-naphthalenyloxalyl)benzene and their graphite composites

Experimental studies were performed with new polyquinoxalines and their graphite composites. Four polymers were synthesized, and then were characterized with respect to their inherent viscosity, elemental chemical analysis, mechanical, and thermodynamic properties. Structural formulas of the polymers and their precursors are given; methods of synthesis are described; and specifically examined was the preparation of polymers from 3,3' diamino-benzidine from 1,4- and 1,3- bis ((1'-napthalenyl) oxalyl) benzene respectively. Also considered was the preparation of polyquinoxalines from poly (p-benzil), and 1,2- aryldiamines.

Port, W. S.↗
NASA NTRS1976

Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors

The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

Hsu, M. T. S.↗
NASA NTRS1976

Polyphosphazenes - New polymers with inorganic backbone atoms

Unique and useful properties of the class of nonhydrocarbon, nonhalocarbon, nonsilicone polymers known as polyphosphazenes are discussed at length. These polymers, with molecular weights to 4 million (degree of polymerization 15,000), can be fabricated as tubes, fibers, woven fabrics, flexible films, or plates, and many variants are stable to attack by water, bases, aqueous acids, jet fuels, oils, hydraulic fluids, gasoline, or other hydrocarbons. Rubbery polymers with these properties can be fashioned into flexible hose, fuel hose, gaskets, or O-rings. Since they do not provoke clotting reactions in blood, and reveal no carcinogenic effects to date, they are considered for internal prosthetic applications (replacement bone, temporary skin, heart valves), as biodegradable suturing material, as carriers for slow release of drugs, and as carriers for chemotherapeutic agents against cancers.

Allcock, H. R.↗
NASA NTRS1977

Thermochemical characterization of polymers for improved fire safety

Apparatus has been constructed for studying the thermal decomposition of polymers as a function of temperature. Such data is needed to evaluate the toxic threat presented by polymeric materials under fire conditions such as the smoldering fire of the type that occurs in closed areas such as coat closets in which anaerobic decomposition of polymers occurs. The apparatus allows the products of thermal decomposition to be collected and analyzed by infrared spectrometry and mass spectrometry. Data obtained from dog hair, an aromatic polyamide, polyphenylene sulfide, and polybenzimidazole are presented. It was found that significant amounts of toxic gas were evolved from dog hair at temperatures as low as 250 C, while temperatures in excess of 500 C were necessary in order for the evolution of toxic gas from the aromatic polymers to become significant.

Lerner, N. R.↗
NASA NTRS1978

Synthesis of thermally stable polymers

The reaction of bis triazo linediones with divinyl esters and substituted styrenes was investigated. Twenty new polymers were derived via reaction of two previously synthesized bis triazol linediones and four new bis atriazol linediones with eight styrenes. The structure and polymer properties of these thermally stable polymers was examined. The reaction of triazo linediones with enol esters was also considered.

Butler, G. B.↗
NASA NTRS1980

Relating viscosity to polymer concentration

Equation developed by VanDijk and first applied to viscosity of Newtonian suspension of rigid particles by Eilers is rearranged to yield intrinsic viscosity as explicit function of polymer concentration in polymer solvent system. Experiments have shown relationship valid for polymer solutions having relative viscosities ranging from 1 to 100.

Fedors, R. F.↗
NASA NTRS1979

Survey of inorganic polymers

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.

Gerber, A. H.↗
NASA NTRS1979

Mechanical and chemical effects of ion-texturing biomedical polymers

To determine whether sputter etching may provide substantial polymer surface texturing with insignificant changes in chemical and mechanical properties, an 8 cm beam diameter, electron bombardment, argon ion source was used to sputter etch (ion-texture process) nine biomedical polymers. The materials included silicone rubber, 32% carbon impregnated polyolefin, polyoxymethylene, polytetrafluoroethylene, ultrahigh molecular weight (UHMW) polyethylene, UHMW polyethylene with carbon fibers (10%), and several polyurethanes (bioelectric, segmented, and cross linked). Ion textured microtensile specimens of each material except UHMW polyethylene and UHMW polyethylene with 10% carbon fibers were used to determine the effect of ion texturing on tensile properties. Scanning electron microscopy was used to determine surface morphology changes, and electron spectroscopy for chemical analysis was used to analyze the near surface chemical changes that result from ion texturing. Ion energies of 500 eV with beam current densities ranging from 0.08 to 0.19 mA/sq cm were used to ion texture the various materials. Standard microtensile specimens of seven polymers were exposed to a saline environment for 24 hours prior to and during the tensile testing. The surface chemical changes resulting from sputter etching are minimal in spite of the often significant changes in the surface morphology.

Weigand, A. J.↗
NASA NTRS1979

Lunar building materials: Some considerations on the use of inorganic polymers

The use of inorganic polymer systems synthesized from the available lunar chemical elements, viz., silicon, aluminum, and oxygen to make adhesives, binders, and sealants needed in the fabrication of lunar building materials and the assembly of structures is considered. Inorganic polymer systems, their background, status, and shortcomings, and the use of network polymers as a possible approach to synthesis are examined as well as glassy metals for unusual structural strength, and the use of cold-mold materials as well as foam-sintered lunar silicates for lightweight shielding and structural building materials.

Lee, S. M.↗
NASA NTRS1978

Thermochemical and flammability properties of some thermoplastic and thermoset polymers - A review

The thermochemical and flammability properties of thermoplastic and thermoset polymers are discussed. The results of a thermogravimetric analysis of the polymers conducted on a DuPont 950 thermogravimetric analyzer using both nitrogen and air atmospheres are presented. Experimental data on smoke evolution are given, and the methodology for assessing the relative toxicity of the pyrolysis effluents is described. The values obtained from the flammability tests are compared with the stoichiometric char yield, and it is shown that the ignition tendency of the polymers is a linear function of the resin char yield

Kourtides, D. A.↗