Insights into the high-temperature degradation mechanism of the methylpolysiloxane-B4C composite

Before siloxane resin matrix composites could be successfully used as ablative materials, their mechanism of high-temperature degradation must be investigated in depth. In this study, degradation mechanism, ablation resistance and degradation kinetics of both methylpolysiloxane and the methylpolysiloxane - B4C (10 wt%) composite were investigated.. The presence of B4C resulted in a higher final sample mass in thermogravimetric tests in synthetic air up to 1500C (85% vs 81%), while during ablation tests it reduced linear and mass ablation rates by 45% and 54%, respectively. The XRD and SEM/EDS studies provided an estimate of the phase contributions formed as a result of exposure to corrosive conditions. The effect of the presence of powders on the amount of SiO2 glassy phase, beta-SiC crystalline phase and free carbon precipitates formed is apparent.