Reinforced Polymers for High-Temperature Microwave Applications

The rapid progress of aerospace technology relative to ultrahigh-speed aircraft has necessitated a reevaluation of electronic insulation with respect to high-temperature environments. A description of the processes that contribute to polymer degradation is presented to alert the electronic system's engineer to the possible insulation problems arising from high frequency and elevated temperatures. Glass-and quartz-fabric-reinforced polymers are evaluated for application in high-temperature microwave systems. Polyester, diallyl isophthalate, diolefin, epoxy, silicone, polyimide, and poly-benzimidazole laminating systems were investigated. The molding capabilities and laminating conditions of these materials in prepreg form are reviewed with respect to degree of porosity and production difficulty that may be encountered in molding thin, intricately designed parts. To determine the suitability of these laminates for high-temperature ure environments, consideration is given to weight loss and flexural strength as a function of temperature and thermal aging. The compatibility of these composites in microwave applications is determined by measuring their dielectric constant and dissipation actor at 1010 Hz and at various operating temperatures.