High temperature epoxide resin formulations

The rapid advances being made in the airborne instrument field necessitates the use of higher temperature electrical insulating materials which will withstand severe thermal ageing and cycling, humidity, salt spray, fungus, vibration and MIL-L-7808 diester type oils. This paper covers the formulation and evaluation of high-temperature encapsulating and impregnating resins. The resins considered were conventional bisphenol A types (Epon 828), epoxide novolacs (Dow DEN 438 and Dow X2638.1) and Epoxide 201 and 207 (Union Carbide). The catalysts considered were pyromellitic dianhydride, phthalic anhydride, maleic anhydride, Nadic methyl anhydride and hexahydro-phthalic anhydride.