Kinetic model for the thermal degradation of poly(methylphenylsiloxane)

The kinetics of the thermal degradation of polymethylphenylsiloxane (PMPS) were investigated by dynamic thermogravimetric analysis. The thermal degradation of PMPS has two processes: "unzipped degradation" and,,rearranged degradation". The corresponding kinetic parameters of the two stages were determined using the Kissinger and Friedman methods respectively. The results showed that the value of the activation energy (E) obtained from the Friedman method was in good agreement with that obtained by the Kissinger method. For "unzipped degradation", E was 164.2 kJ/mol and 168.2 kJ/mol, and for "rearranged degradation", E was 228.6 kJ/mol and 232.0 kJ/mol. The Arrhenius pre-exponential factor (A) and reaction order (n) for the two stages were also discussed. A kinetic model was built by using the obtained kinetic parameters, and the results obtained by the model were in good agreement with the measured value.