Kinetics of imidization and crosslinking in PMR-polyimide resin
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Lauver, R. W.↗
Engineering topics
Lauver, R. W.
Publications and source records attributed to Lauver, R. W..
Kinetics of imidization and crosslinking in PMR-polyimide resin
Infrared spectroscopy and differential scanning calorimetry were employed to study the imidization and crosslinking kinetics of norbornenyl-capped, addition-type polyimide resins (designated PMR for polymerization of monomer reactants). The spectral and thermal analyses were performed on resin specimens which had been isothermally aged at temperatures appropriate for imidization (120 to 204 C) and crosslinking (275 to 325 C). Imidization occurs rapidly (approximately 0.01/min) at short times, while at times longer than approximately 0.5 hour, the rate decreases significantly (approximately 0.0001/min). The crosslinking reaction exhibits first order kinetics during the initial portion of the reaction and its rate appears to be limited by the reversion of the norbornenyl Diels-Alder adduct. The total heat evolved per mole of endcap during crosslinking shows an inverse dependence on the molecular weight of the imide prepolymers. This reflects the effect of endcap dilution and decreased mobility of the larger oligomers.
Lauver, R. W.↗
Solar selective surfaces
Method consists of applying high absorptance coating onto thin film or foil of low emittance material. Thin film surface is then bonded to collector panel surface.
Mcdonald, G.↗
Effect of ester impurities in PMR-polyimide resin
Spectral and chomatographic studies were conducted which established the presence of tri- and tetraester impurities in aged monomer solutions employed in fabrication of PMR-polyimide resin composites. The equilibrium constant and apparent rate of the esterification were determined. It was demonstrated, using differential scanning calorimetry, that the ortho-ester moiety of these impurities does not completely react at typical cure conditions. It is concluded that voids formed in composites fabricated with aged monomer solution are due to gaseous decomposition products evolved by ester impurities and/or unreacted amine during elevated temperature post-cure treatment.
Lauver, R. W.↗