The kinetics and mechanisms of the thermal degradation of poly(methyl methacrylate) studied by thermal analysis-Fourier transform infrared spectroscopy

The kinetics and mechanisms of thermal degradation of poly(methyl methacrylate) (PMMA) have been studied to demonstrate the usefulness of thermal analysis-Fourier transform infrared spectroscopy (TA-FTIR) as a qualitative and quantitative kinetic tool to study the thermal degradation of polymers. From the dependence of the rate of thermal degradation of PMMA on molecular weight at low degradation temperatures, it was concluded that thermal degradation was initiated by a mixture of chain end and random chain scission initiation, followed by depropagation and first-order termination. Random scission is attributed to pre-oxidation of the polymer on storage at room temperature. At higher temperatures, a change in molecular weight dependence was observed, related to depropagation to the end of the polymer chain. The thermal degradation of PMMA also leads to the production of char, which was produced by the elimination of methoxycarbonyl side-chains. The amount of char produced increased with increasing concentration of end-groups and temperature.