Miscible Blends of Poly(siloxane Imide) Segmented Copolymers and Polybenzimidazole as Potential High Performance Aerospace Materials

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Abstract
Compatible blends of high performance engineering thermoplastics have been investigated for aerospace applications, where stability in an aggressive atomic oxygen environment is of significant concern. The blends were comprised of polyimide homopolymers and poly(siloxane imide) segmented copolymers based upon benzophe-none tetracarboxylic dianhydride (BTDA) and m-diaminodiphenyl sulfone, and polybenzimidazole (PBI). The blends exhibited glass transition temperatures in excess of 300°C, and significantly reduced water sorption relative to PBI. Conversion of the siloxane surface to an inorganic, oxidation resistant silicate in the presence of atomic oxygen accounted for the enhanced stability of siloxane-containing blends to a simulated low earth orbit environment.