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Young, P. R.

Publications and source records attributed to Young, P. R..

33 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Polyimides with pendant alkyl groups

The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

Jensen, B. J.↗
NASA NTRS1981

Characterization of initial cure reactions in propargyl and nadic end capped model compounds

Imide model compounds containing propargyl and nadic groups were studied to obtain a fundamental understanding of the reaction of these groups attached to imide oligomers. The initial cure reactions were examined by a variety of characterization techniques including high pressure liquid chromatography, infrared spectroscopy, thermal analyses, and mass spectroscopy. The initial step in the cure of propargyl end capped model compounds probably involved the formation of a new terminal acetylenic group. Configurational changes involving endo/exo isomerism was found in the nadimide model compounds. Nadimide compounds heated in air and in nitrogen appeared to cure by different mechanisms.

Young, P. R.↗
NASA NTRS1980

Characterization of aging effects of LARC-160

Specimens of freshly prepared polyimide precursor resin LARC-160 and resin aged at room temperature up to 45 days were characterized by high-pressure liquid chromatography and several different thermal analyses. Graphite reinforced composites were then fabricated from fresh and aged resin and tested to determine if changes observed by these techniques were significant. It was found that resin aging resulted in greater flow during processing and poorer composite isothermal stability. However, aging did not affect the room-temperature flexural or short-beam-shear strengths of the composites.

Young, P. R.↗
NASA NTRS1980

Analysis of aromatic polyamine mixtures for formulation of LARC-160 resin

An investigation was conducted to identify a potential substitute for the aromatic polyamine mixture, Jeffamine AP-22, currently used to formulate LARC-160 polyimide precursor resin. Jeffamine AP-22 was characterized by high pressure liquid chromatography and mass spectrometry. Eleven different aromatic amines in the mixture were isolated and identified. Subsequent liquid chromatographic analysis of nine additional commercially available aromatic polyamine mixtures identified three candidates that are similar in composition to AP-22.

Young, P. R.↗
NASA NTRS1979

HPLC for quality control of polyimides

High Pressure Liquid Chromatography (HPLC) as a quality control tool for polyimide resins and prepregs are presented. A data base to help establish accept/reject criteria for these materials was developed. This work is intended to supplement, not replace, standard quality control tests normally conducted on incoming resins and prepregs. To help achieve these objectives, the HPLC separation of LARC-160 polyimide precursor resin was characterized. Room temperature resin aging effects were studied. Graphite reinforced composites made from fresh and aged resin were fabricated and tested to determine if changes observed by HPLC were significant.

Young, P. R.↗
NASA NTRS1979

High-pressure liquid chromatography of aromatic amines

Analysis made on commercially available liquid chromatograph demonstrates high-pressure liquid chromatographic conditions for separation of approximately 50 aromatic amines ranging from simple aniline derivatives to complex multiring di- and tri-amines.

Young, P. R.↗
NASA NTRS1977

Integral glass encapsulation for solar arrays

Electrostatic bonding has been used to join silicon solar cells to borosilicate glass without the aid of any organic binders or adhesives. The results of this investigation have been to demonstrate, without question, the feasibility of this process as an encapsulation technique. The potential of ESB for terrestrial solar arrays was clearly shown. The process is fast, reproducible, and produces a permanent bond between glass and silicon that is stronger than the silicon itself. Since this process is a glass sealing technique requiring no organics it makes moisture tight sealing of solar cells possible.

Young, P. R.↗
NASA NTRS1975

Basicity of aromatic amines from liquid chromatographic behavior

A liquid chromatographic investigation was conducted to determine whether the adsorption of weakly basic aromatic amines on slightly acidic silica gel adsorbents could be used to study their relative basicity. Under proper conditions, a linear correlation between pKb and log of capacity factor was observed. This finding may prove useful in helping to predict the relative basicity of closely related aromatic diamines, especially new amines being synthesized for polymer synthesis.

Young, P. R.↗
NASA NTRS1972

Investigation of phase-change coatings for variable thermal control of spacecraft

An investigation was conducted to determine the feasibility of producing a spacecraft coating system that could vary the ratio of its solar absorptance to thermal emittance to adjust automatically for changes in the thermal balance of a spacecraft. This study resulted in a new concept called the phase-change effect which uses the change that occurs in the optical properties of many materials during the phase transition from a crystalline solid to an amorphous material. A series of two-component model coatings was developed which, when placed on a highly reflecting substrate, exhibited a sharp decrease in solar absorptance within a narrow temperature range. A variable thermal control coating can have a significant amount of temperature regulation with the phase-change effect. Data are presented on several crystallite-polymer formulations, their physical and optical properties, and associated phase-change temperatures. Aspects pertaining to their use in a space environment and an example of the degree of thermal regulation attainable with these coatings is also given.

Kelliher, W. C.↗
NASA NTRS1972

Polyimidazopyrrolone model compounds.

Study of model reactions between phthalic anhydride and o-phenylenediamine under conditions analogous to the polymerization and post cyclization of dianhydrides with bis(o-diamines) to form polyimidazopyrrolones (Pyrrones). Solid-state thermal conversion of the amide-acid-amine affords a unique dimeric species containing amide, imide, and benzimidazole functions. It was confirmed that melt techniques lead to disproportionation products. The application of these findings to related polymer syntheses is discussed.

Young, P. R.↗
NASA NTRS1972

Polyimidazopyrrolone model compounds.

The model reactions between phthalic anhydride and o-phenylenediamine were studied under conditions analogous to the polymerization and post-cyclization of dianhydrides with bis(o-diamines) to form polyimidazopyrrolones (Pyrrones). The route from the initial amide-acid-amine to the tetracyclic Pyrrone model when the reactions are conducted in aprotic solvents is highly competitive between isolatable benzimidazole-acid and imide-amine intermediates. Solid-state thermal conversion of the amide-acid-amine affords a unique dimeric species containing amide, imide, and benzimidazole functions. It was confirmed that melt techniques lead to disproportionation products. The application of these findings to related polymer synthesis is discussed.

Young, P. R.↗