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Results for “Polymer synthesis”

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.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Toughening of BIS maleimide resins: Synthesis and characterization of maleimide terminated poly(arylene ether) oligomers and polymers

Amine functional poly(arylene ether) sulfones were previously reported. Herein, the chemistry was extended to amorphous poly(arylene ether) ketones because of their higher fracture toughness values, relative to the polysulfones. It was demonstrated that the amino functional oligomers undergo a self-crosslinking reaction at temperatures above about 220 C. This produces an insoluble, but ductile network that has excellent resistance. A ketamine structure hypothesis was proposed and verified using solid state magic angle NMR. In most cases, the water generated upon ketamine formation is too low to produce porosity and solid networks are obtained. The stability of the ketamine networks towards hydrolysis is excellent. The chemistry was further demonstrated to be able to crosslink preformed nonfunctional poly(arylene ether) ketones if a difunctional amine was utilized. This concept has the possibility of greatly improving the creep resistance of thermoplastics. Also, a new technique was developed for converting the amine functional oligomers cleanly into maleimide structures. This method involves reacting maleic anhydride with monomeric aminophenols in the presence of solvent mixtures.

Mcgrath, J. E.↗
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 NTRS1990

Preparation Of High-Temperature Reactive Oligomers

Very reactive materials form very-heat-stable polymers. Recent research directed toward synthesis of polyimides soluble in common organic solvents, melt-processable, and thermally curable without evolution of volatile by-products. Diels-Alder polymerization yields compounds that maintain integrities and toughnesses during long exposure times at high temperatures. High-temperature polymers synthesized by use of technique. Films and perhaps fibers fabricated from prepolymer in solution. Major potential at this stage of research limited to aerospace applications.

Ottenbrite, Raphael M.↗
NASA NTRS1982

Ultrahigh molecular weight aromatic siloxane polymers

The condensation of a diol with a silane in toluene yields a silphenylene-siloxane polymer. The reaction of stiochiometric amounts of the diol and silane produced products with molecular weights in the range 2.0 - 6.0 x 10 to the 5th power. The molecular weight of the product was greatly increased by a multistep technique. The methodology for synthesis of high molecular weight polymers using a two step procedure was refined. Polymers with weight average molecular weights in excess of 1.0 x 10 to the 6th power produced by this method. Two more reactive silanes, bis(pyrrolidinyl)dimethylsilane and bis(gamma butyrolactam)dimethylsilane, are compared with the dimethyleminodimethylsilane in ability to advance the molecular weight of the prepolymer. The polymers produced are characterized by intrinsic viscosity in tetrahydrofuran. Weight and number average molecular weights and polydispersity are determined by gel permeation chromatography.

Ludwick, L. M.↗
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 NTRS2004

High Temperature Polymers for use in Fuel Cells

NASA Glenn Research Center (GRC) is currently working on polymers for fuel cell and lithium battery applications. The desire for more efficient, higher power density, and a lower environmental impact power sources has led to interest in proton exchanges membrane fuels cells (PEMFC) and lithium batteries. A PEMFC has many advantages as a power source. The fuel cell uses oxygen and hydrogen as reactants. The resulting products are electricity, heat, and water. The PEMFC consists of electrodes with a catalyst, and an electrolyte. The electrolyte is an ion-conducting polymer that transports protons from the anode to the cathode. Typically, a PEMFC is operated at a temperature of about 80 C. There is intense interest in developing a fuel cell membrane that can operate at higher temperatures in the range of 80 C- 120 C. Operating the he1 cell at higher temperatures increases the kinetics of the fuel cell reaction as well as decreasing the susceptibility of the catalyst to be poisoned by impurities. Currently, Nafion made by Dupont is the most widely used polymer membrane in PEMFC. Nafion does not function well above 80 C due to a significant decrease in the conductivity of the membrane from a loss of hydration. In addition to the loss of conductivity at high temperatures, the long term stability and relatively high cost of Nafion have stimulated many researches to find a substitute for Nafion. Lithium ion batteries are popular for use in portable electronic devices, such as laptop computers and mobile phones. The high power density of lithium batteries makes them ideal for the high power demand of today s advanced electronics. NASA is developing a solid polymer electrolyte that can be used for lithium batteries. Solid polymer electrolytes have many advantages over the current gel or liquid based systems that are used currently. Among these advantages are the potential for increased power density and design flexibility. Automobiles, computers, and cell phones require highly efficient power density for lowering emissions and meeting increasing consumer demands. Many of the solutions can be provided by proton exchange membrane fuel cells and lithium batteries. NASA Glenn Research Center has recognized this need, and is presently engaged in a solution. The goals for the summer include mastering synthesis techniques, understanding the reactions occurring during the synthesis, and characterizing the resulting polymer membranes using NMR, DSC, and TGA for the PEMFC and lithium batteries.

Peplowski, Katherine M.↗
NASA NTRS2003

Research to Significantly Enhance Composites Survivability at 550 F in Oxidative Environments

Methylene dianiline (MDA) and its derivatives have been used in the synthesis of polyimides to yield polymers with characteristic low-density, high tensile strength, improved solubility in organic solvents, low-melt viscosities and high thermal stability (greater than 550 F) in air. Polyimides with such properties are desirable for use in aerospace systems, e.g., jet engines, airframe, missiles, and rockets where weight is critical. Recent research at Prairie View A&M University is focused on developing monomers to generate polyimides with enhanced performance over that of NASA s PMR-15. The objective of this work is to synthesize three ring aromatic diamines which are non-toxic and when reacted with the appropriate dianhydrides will yield polyimides with lower viscosity, improve processability, good retention of mechanical properties, and oxidative stability at high environmental temperatures. Modifications of the three ring aromatic diamines include replacing the methylene linkages with aromatic ethers by nucleophilic aromatic substitution reactions and incorporating mono- and di-substituents to the center aromatic ring. An update of current reactions involved in synthesis efforts to generate three ring aromatic monomers for polyimides with methylene, carbonyl, and ether linkages separating the aromatic moieties will be displayed.

Meador, Michael A.↗
NASA NTRS1973

Polyimide fiber-glass composite resists high temperatures

Composites synthesized from bismaleimide have superior strength and oxidation resistance at elevated temperatures when compared with similar composites prepared with epoxy or silicon polymers of similar cost. Polyimide synthesis technique and processing method yield essentially void-free fiber-glass reinforced composites.

Gilwee, W. J.↗
NASA NTRS1975

Isomer effects on polyimide properties

The effect of structure variation on the solubility and glass-transition temperature of polyimide polymers is investigated. The addition of alkyl substituents to an aromatic ring in the polymer molecule, the reduction in the number of imide rings per average polymer chain-length, and a variation in the symmetry of the polymer molecule are studied. The synthesis of key intermediates for the preparation of the monomers required in this investigation is reported along with progress made in the synthesis of polyimide-precursor amines that contain functional groups to allow for post-cure cross-linking.

Stump, B. L.↗
NASA NTRS1982

Prebiotic organic matter - Possible pathways for synthesis in a geological context

Models for the accretion of the earth, core formation, differentiation of the planet into core, mantle, crust, and atmosphere, and prebiotic synthesis of organic materials are reviewed. The development of the Haldane-Oparin and Urey models is traced, and the effect of accretion time on the outgassing process and the composition of the consequent atmosphere is examined. Model prebiotic atmospheres are calculated, the extent of equilibration of the primitive atmosphere is studied and the evolution of the atmosphere prior to organic chemical evolution is reviewed. Finally, experimental progress in synthesis of biological monomers and polymers under presumed early earth conditions is covered.

Chang, S.↗
NASA NTRS1987

Polyenamines for Films, Coatings, and Adhesives

Easy process makes polymers with good mechanical properties. Synthesis involves Michael-type addition polymerization of two diacetylenic diketones, with various aromatic diamines in m-cresol at 60 to 130 degrees C. Technique provides synthetic route to high-molecular-weight polyenamines with moderate thermal stability and good mechanical properties. Polyenamines produced exhibit potential for use as films, coatings, adhesives, molding compounds, and composite matrices.

Hergenrother, Paul M.↗
NASA NTRS1991

High performance addition-type thermoplastics (ATTs) - Evidence for the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated material and a bismaleimide

Recently, the concept and demonstration of a new versatile synthetic reaction for making a large number of high-performance addition-type thermoplastics (ATTs) were reported. The synthesis shows promise for providing polymers having an attractive combination of easy processability, good toughness, respectable high temperature mechanical performance, and excellent thermo-oxidative stability. The new chemistry involves the reaction of an acetylene-terminated material with a bismaleimide or benzoquinone. In order to clarify the reaction mechanism, model compound studies were undertaken in solutions as well as in the solid state. The reaction products were purified by flash chromatography and characterized by conventional analytical techniques including NMR, FT-IR, UV-visible, mass spectroscopy, and high pressure liquid chromatography. The results are presented of the model compound studies which strongly support the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated compound and a bismaleimide or benzoquinone.

Pater, R. H.↗
NASA NTRS1994

A redox beginning: Which came first phosphoryl, acyl, or electron transfer ?

Thermodynamic and kinetic information available on the synthesis of prebiotic monomers and polymers will be examined in order to illuminate the prebiotic plausibility of polymer syntheses based on (a) phosphoryl transfer that yields phosphodiester polymers, (b) acyl transfer that gives polyamides, and (c) electron transfer that produces polydisulfide or poly(thio)ester polymers. New experimental results on the oxidative polymerization of 2,3-dimercaptopropanol by ferric ions on the surface of ferric hydroxide oxide will be discussed as a chemical model of polymerization by electron transfer. This redox polymerization that yields polymers with a polydisulfide backbone was found to give oligomers up to the 15-mer from 1 mM of 2,3-dimercaptopropanol after one day at 25 C. High pressure liquid chromatography (HPLC) analysis of the oligomers was carried out on an Alltech OH-100 column eluted with acetonitrile-water.

Weber, Arthur L.↗
NASA NTRS2003

High Performance Polymers

This report summarizes results from research on high performance polymers. The research areas proposed in this report include: 1) Effort to improve the synthesis and to understand and replicate the dielectric behavior of 6HC17-PEK; 2) Continue preparation and evaluation of flexible, low dielectric silicon- and fluorine- containing polymers with improved toughness; and 3) Synthesis and characterization of high performance polymers containing the spirodilactam moiety.

Venumbaka, Sreenivasulu R.↗
NASA NTRS1972

Viscoelastic cationic polymers containing the urethane linkage

A method for the synthesis and manufacturing of elastomeric compositions and articles containing quaternary nitrogen centers and condensation residues along the polymeric backbone of the centers is presented. Linear and cross-linked straight chain and block polymers having a wide damping temperature range were synthesized. Formulae for the viscoelastic cationic polymers are presented.

Rembaum, A.↗
NASA NTRSDate not supplied

Forcespun Polymers as Precursors to Boron Nitride Fibers

The need for multifunctional materials in aerospace technologies is currently driving the development of new novel composite materials. Specifically, insulation materials with high thermal conductivity, high electrical resistivity, and are chemically inert are needed for high voltage power applications. Boron nitride (BN) nanomaterials fit these criteria and can be incorporated into composites for further material design. The synthesis of boron nitride through a polymer derived ceramic route allows for the morphology of the resulting BN to be tailored. This is especially beneficial since the polymers can be shaped or spun into fibers prior to the ceramic conversion. This project utilizes the Forcespinning technique to produce boron-containing polymer fibers that are converted to boron nitride through a heat treatment. The chemical compositions and fiber morphologies were studied and reported here.

Boron nitride, Fibers, Forcespinning↗