Effect of Substituted Phenylnadimides on Processing and Properties of PMR (Polymerization of Monomeric Reactants) Polyimide Composites

Three nitrophenylnadimide cure initiators and two phenylnadimides (without nitros) were evaluated as additives to PMR-15 resins and Celion 6000 graphite fiber composites. The results of a resin screening study eliminated all of the additives except 3-nitrophenylnadide (NO2PN) for use as a low temperature curing additive for PMR-15. Thus, No2Pn and the two control additives were investigated in PMR-15 formulations from which Celion 6000 graphite fiber/PMR-15 composites were processed both with low temperature (274 C) and normal (316 C) cure cycles. Comparisons of the two processing cycles, the resultant glass transition temperatures (Tg), the ambient, 274 and 316 C composite mechanical properties determined before and after 316 C posture, the 316 C thermo-oxidative weight losses and the retention of 316 C composite mechanical properties are presented. Empirical correlations of the type and amount of nadimide additives with processing parameters, Tg, composite mechanical properties, composite thermo-oxidative stability and long term retention of 316 degree C composite mechanical properties are also presented. It was shown that PMR-15 composites could be fabricated using a low temperature (274 C) with nitrophenylnadimide additives.