Novel isocyanate‐based matrix resins for high temperature composite applications

Abstract Polyoxazolidone composites were prepared from polymeric isocyanate (PAPI 901) and epoxides (Epon 828 and DEN 431) in the presence of an oxazolidone‐forming catalyst, triphenylantimony iodide. The effects of isocyanate to epoxide equivalent ratio, type of epoxide, and amount of fiberglass reinforcement on the composite properties were studied as well as the effects of post‐curing temperature and time. Increasing the fiberglass content of the polyoxazolidone composites resulted in an improvement of the thermal and mechanical strength properties. The heat deflection temperature of all polyoxazolidones was > 250°C. The retention of the tensile strength at 150°C was excellent, ∼90% or higher. Polyoxazolidone composites based on DEN 431 at 1.2 isocyanate to epoxide equivalent ratio with 70 wt.% of fiberglass and post‐cured at 150°C for 48 h exhibited the best properties. According to the results of DMA, TMA and DSC, the maximum operating temperature for polyoxazolidone composites is around 200°C. The TGA data showed that the decomposition temperature was ∼330°C.