Studies were performed to investigate the effects of partial substitution of tetraamine crosslinking agents for diamine reactants on the thermomechanical properties of PMR polyimide resins and graphite fiber-reinforced composites. The effect of tetraamine content on isothermal weight loss, glass transition, and softening temperatures of neat resin samples is discussed. Composites were fabricated using PMR methodology. Monomeric solution of various stoichiometric ratios were used to impregnate Hercules HTS graphite fiber. The mechanical property retention characteristics of the composites at 316° C (600° F) are described.
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