Thermal stability of organofunctional polysiloxanes

The thermal stability of cured samples of organofunctional polysiloxanes including glycidyloxypropyl polysiloxane (GSLX160), aminopropyl polysiloxane (ASLX160), methacryloxypropyl polysiloxane (MSLX160) and vinyl polysiloxane (VSLX160) was investigated. The thermal degradation kinetics for GSLX160, ASLX160 and MSL160 were determined by the model-fitting method with the aid of a deconvolution technique. For GSLX160, Stage 1 was attributed to polycondensation. The thermal degradation process was described by nucleation mechanism, followed by multi-molecular decay law (reaction-controlled) in Stage 2. By contrast, it was reaction-controlled mechanism that characterized the thermal degradation process in Stage 3. For ASLX160, three stages including four processes (i.e., one polycondensation and three thermal decomposition processes characterized by reaction-controlled mechanisms) were identified. As to MSLX160, thermal degradation processes in both Stages 1 and 2 were characterized by nucleation mechanism, followed by reaction-controlled mechanism. In contrast, reaction-controlled mechanism for the thermal decomposition involved in Stage 3 was the best choice.