ABSTRACT:The thermal degradation behaviors of polymethylphenylsilsesquioxane/epoxy resin (PMPSQ/EP) systems were investigated by thermogravimetric analysis (TGA) under nonisothermal conditions in nitrogen atmosphere. During nonisothermal degradation, Kissinger's and Flynn-Wall-Ozawa's methods were both used to analyze the thermal degradation process. The results showed that a remarkable increase of activation energy was observed in the presence of PMPSQ, which indicated that the addition of PMPSQ retarded the thermal degradation of EP.Flynn-Wall-Ozawa's method further revealed that PMPSQ significantly increased the activation energy of EP thermal degradation especially in the early and final stage of thermal degradation process, which illustrated that the PMPSQ stabilized the char layer and improved the flame retardancy of EP.