The thermal transformation process and mechanical strength evolution of ceramifiable silicone composites

Abstract

Ceramifiable silicone composites have promising prospect due to their outstanding thermal protection performance. However, the indistinct thermal transformation process at various temperatures, may be an inevitable bottleneck for the improvement of mechanical strength. Herein, ceramifiable silicone composites (flexural strength over 8 Mpa at 1400 °C) were fabricated and their thermal transformation process was demonstrated by the analysis of composition evolution of the released gases and residual solids. Concretely, the ceramifiable silicone composites modified by octa-aminopropyl polyhedral oligosilsesquioxane (8AP-POSS) could reduce porosity and enhance mechanical properties by decreasing the release rate of gas. At high temperature, the phase composition evolution and microstructure change of formed ceramics did contribute to the adhesion of residues. Based on the above analysis of thermal transformation process from polysiloxane to silica polymorphs, a novel mechanism namely temperature-gradient phase evolution mechanism (TGPEM) was proposed. The research results contribute to the preparation of high-performance silicone composites.