Bismaleimide/Preceramic Polymer Blends for Hybrid Material Transition Regions. Part 2. Incorporating Compatibilizers.

摘要

The problem of phase separation in polycarbosilane-Matrimid thermoset blends designed for thermal protection applications was addressed in this task. The compatibilizers synthesized via a hydrosilylation-deprotection sequence were primarily based upon a polymer structure with a nonpolar carbosilane unit and a polar bisphenol A moiety. Besides the homopolymer, block copolymers with varying polycarbosilane and bisphenol A blocks were prepared. Curing studies on Starfire resin-Matrimid blends using 1-5% compatibilizer were performed followed by morphological characterization of the cured resin. The compatibilizer effectiveness was assessed by domain size, and distribution in cured specimens was examined by scanning electron microscopy. The compositions that were more effective in minimizing phase separation were relatively more polar and were comprised of a larger fraction of phenolic functional units. The blend incorporating 5% of the compatibilizer with the largest fraction of the polar bisphenol A unit was highly effective in providing a homogeneous distribution of domains of fairly uniform size (5 mm or less).