Investigation of poly(carbosilane arylacetylene)s with thermal oxidation resistance

The aerospace industry demands a resin matrix with excellent thermal oxidation resistance for advanced composites. A series of poly(carbosilane arylacetylene)s (PCSAs) resins with high silicon content were synthesized via arylacetylene Grignard reagents with polychlorocarbosilane polycondensation in this study. The cured PCSAs were obtained by heating at 150 °C for 2 h, 170 °C for 2 h, 210 °C for 2 h, and 250 °C for 4 h. The temperature at which PCSAs lose 5% weight (T_d5) is approximately 600 °C under a nitrogen atmosphere. The cured PCSAs do not exhibit a glass transition temperature in the range of 50 °C ∼ 450 °C. The cured PCSAs demonstrate outstanding thermal oxidation resistance, with a T_d5 of approximately 560 °C under the air atmosphere. The cured PCSA with high silicon content can retain up to 75% of its weight when exposed to flowing air for 480 h at 300 °C. The retention of mechanical properties of carbon fiber cloth reinforced PCSAs composites (CF/PCSAs) improves with increasing silicon content after 100 h of thermal aging under flowing air at 300 °C. The increase in silicon content is beneficial for reducing surface cracking of cured resins and preventing internal matrix oxidation. Moreover, cured PCSAs can serve as a precursor to be pyrolyzed at 1500 °C to form β-SiC crystal. These results suggest that PCSAs are suitable as a heat-resistant matrix for advanced composites.