Studies on the thermal stability of F- and non-F-containing ladder polyepoxysilsesquioxanes by TGA–FTIR

The thermal stability of non-F- (LPS-I) and F- (LPS-II) containing ladder polyepoxysilsesquioxanes under air and nitrogen was studied by DSC, TGA and TGA–FTIR techniques. The thermally curing temperature for LPS-II is about 20 °C higher than that for LPS-I. Both LPS-I and LPS-II exhibits higher thermal stability under air and nitrogen as observed from TGA, where the decomposition temperatures at 5 and 10% weight loss were above 425 and 480 °C, respectively. Under nitrogen, the higher decomposition temperature and residue from TGA was attributed to the gradual cleavage of C–Si and C–C bonds and high stability of F-containing side-chains (non-broken). Because of the weight gain from the oxidation of silsesquioxanes (RSiO3/2) to silica (SiO2), and gradual cleavage of F-containing side-chains, LPS-II exhibits higher decomposition temperature under air environment than under nitrogen. These phenomena detected from TGA could be observed directly from TGA–FTIR stack plots. As combined techniques for the evolved gas analysis, TGA–FTIR played an important role in explaining the phenomena of degradation related to the change of polymer chain structures during heating.