Thermal-Oxidation-Resistant Poly(Carborane-Silane) for Protective Coatings Under Harsh Environments

Thermal-oxidation-resistant polymers are critical for devices/components used under harsh environments where high temperature and an oxidative atmosphere lead to degradation and failure of polymeric parts. Herein, vinyl-containing poly­(carborane-silane) (VCP) with good thermal-oxidative stability has been prepared through vinyl-modified m-carborane and silane. The cured VCP (c-VCP) could resist high temperature in both inert and oxidative atmospheres. In comparison to traditional carborane-siloxane copolymers, c-VCP aimed at lowering the oxygen content and simultaneously increasing the boron content, allowing maximum ability to capture oxygen atoms. In an oxidative atmosphere, the formation of the boron oxide layer brought nearly 45% weight gain rather than a weight decrease, which protected the matrix from thermal-oxidative degradation. The mechanism of thermal-oxidative degradation was also investigated based on Flynn–Wall–Ozawa method. The boron oxide layer increased the degradation activation energy (E a) and hindered direct contact of inner materials with oxygen atoms. When the carbon fibers were coated with c-VCP, the char yield could be increased from 0 to 57 wt % at 1000 °C in air, which demonstrated that c-VCP coating could effectively protect carbon fiber from oxidation at high temperature in air, also indicating potential applications as anti-thermal-oxidative materials for harsh environments.