Study on the thermal behaviors of polyhedral oligomeric octaphenylsilsesquioxane (OPS)

Polyhedral oligomeric octaphenylsilsesquioxane (OPS) is usually used to improve the oxidative stability, thermal stability and fire-retardant property of polymers. Due to the divergences in the thermal decomposition of the OPS according to thermogravimetric analysis (TGA), a comprehensive study of the thermal behaviors of OPS under air and nitrogen atmospheres was carried out. Sublimation of OPS was proved. Due to the OPS sublimating, the TGA results of OPS depended on the sample mass used in the TGA tests. Two mass loss steps were found under nitrogen, while three steps were found under air. The mass loss of the 1st step was mainly caused by the sublimation of OPS under air and nitrogen. Sublimation of OPS, detachment of phenyl groups and destruction of caged structures happened in the 2nd step under both atmospheres. In the 3rd step under air atmosphere, the residual organic part of the sample was oxidated into carbon monoxide and carbon dioxide.