Development of polyimide materials for use in solar energy systems. Final report, August 1, 1978-July 31, 1979

Abstract

A program to optimize and characterize improved insulation materials for solar energy systems is described. Two separate and distinct products have been studied, a lightweight flexible insulating foam and a high density, rigid, load bearing insulating foam. These products are derived from a polyimide resin, the formulations and processes for which were developed under NASA-JSC sponsored programs. These materials are non-burning and do not emit measurable quantities of smoke or toxic by-products. Candidate resins were selected on the basis of cost, expected foam insulating and weatherability properties and ease of production. Critical characterization parameters were established for the flexible insulating foam in the form of environmental exposure resistance, thermal conductivity and hydrolytic stability. Studies initiated to improve the exposure resistance included additive studies, using reinforcements and UV absorbers, and postcure and densification studies. Optimum resin formulations, foam densities and foam structures were identified on the basis of the exposure, thermal conductivity, and microwave testing. Two candidate materials were selected and fully characterized for physical and thermal properties. This resulted in the selection of a final candidate material. The rigid foam was optimized through a glass reinforcement and process parameter study. This work was characterized on the basis of low cost, ease of production and the critical property requirement of compressive strength. The result of these studies was an optimized glass strand/microballoon reinforced foam which was then fully characterized for physical and thermal properties. Samples of both the flexible and rigid polyimide insulating materials were then prepared and submitted to DOE.