High temperature lifetime of polyimide/poly(silsesquioxane)-like hybrid films

Abstract

Decomposition kinetics in thermogravimetric analysis (TGA) and dynamic mechanical relaxation in dynamic mechanical analysis (DMA) are used to study the high temperature lifetime of the new type of polyimide/poly(silsesquioxane)-like (PI/PSSQ-like) hybrid films, which are designed to form three-dimensional structures with linear polyimide blocks and a crosslinked PSSQ-like structure. Both TGA and DMA analysis reveal that the PI/PSSQ-like hybrid films have a longer lifetime (are more reliable) with regard to their thermal and mechanical characteristics than that of pure PI. Even just 2 wt% of p-aminophenyltrimethoxysilane (APTS) in a PI/PSSQ-like hybrid film can significantly improve the service lifetime by as much as at least four times in a TGA decomposition kinetic study. The dynamical relaxation data are well fitted to the calculated WLF (Williams-Landel-Ferry) master curves. In a series of X-PIS (PI modified with APTS) hybrid films, decreasing the PI block chain length increases the decomposition activation energy, lifetime (in both TGA and DMA) and relaxation modulus. In a series of X-PIS-y-PTS [PI modified with APTS and phenyltrimethoxysilane (PTS)] films, the decomposition activation energy and lifetime (in TGA) increase with the PTS content. Interestingly, the dynamic mechanical relaxation modulus of 10000-PIS-100-PTS film is lower than that of the corresponding 10000-PIS film at frequency > 10(2) rad/sec, but higher at frequency < 10(2) rad/sec. The 10000-PIS-100-PTS has a lower relaxation time than the 10000-PIS at the modulus 5x10(8) Pa, but the relaxation time of the former becomes higher at 5x10(7) Pa.