Thermal stability enhancement mechanism of poly(dimethylsiloxane) composite by incorporating octavinyl polyhedral oligomeric silsesquioxanes

摘要

The effects of octavinyl polyhedral oligomeric silsesquioxane (Vi-POSS), silica (SiO_2), and octaphenyl POSS (Ph-POSS) on the thermal stability of poly(dimethylsiloxane) (PDMS) were studied using thermal gravimetric analysis. The decomposition mechanism of the PDMS/Vi-POSS composite was proposed by crosslinking density measurement, decomposition residues and volatiles analysis. The results showed that the Vi-POSS had significant effect on enhancing the thermal stability of PDMS. The decomposition mechanism of PDMS was changed by the chemical incorporation of Vi-POSS, but SiO_2 and Ph-POSS had few effects on the polymer decomposition process, because they were mixed by simple physical blending. The cyclic depolymerization of PDMS, which produced many cyclic oligomers at relatively low temperature, was suppressed by the heavily crosslinked network in the PDMS/Vi-POSS composite. The scissions of carbon-carbon, silicon-carbon and carbon-hydrogen bonds took place at higher temperature, releasing hydrogen, methane, ethylene and ethane, left behind siliconoxycarbide and some free carbon at 800℃.