Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part II. LaRC‐RP41

Recently, we reported on the interpenetrating polyimide network (IPN) approach to develop tough and microcracking resistant high temperature matrix resins for use in aircraft/aerospace structural components. One such polymer developed is designated LaRC‐RP40. This new simultaneous semi‐IPN was prepared from easy‐to‐process but brittle crosslinking PMR‐15 and tough but difficult‐to‐process linear NR‐150B2. Significantly improved toughness, microcracking resistance, and glass transition temperature over PMR‐15 were realized from the combination. These property improvements were achieved without compromising ease of processing, high temperature mechanical performance, and cost effectiveness compared to PMR‐15. These results encouraged us to further explore this approach for the development of a wider range of polymers of basic technological and economic interest. In the present work, we combine crosslinking PMR‐15 and linear LaRC‐TPI to provide a new sequential semi‐2‐IPN called LaRC‐RP41. The physical and mechanical properties of the neat resin and composite reinforced with graphite fibers are presented. The phase morphology and phase stability of the neat resin and composite studied by various techniques are also discussed.