Thermooxidative degradation of methyl methacrylate‐graft‐natural rubber

Abstract

Abstract The thermooxidative degradation of methyl methacrylate‐ graft ‐natural rubber (MG) at different heating rates ( B ) has been studied with thermogravimetric analysis in an air environment. The results indicate that the thermooxidative degradation of MG in air is a one‐step reaction. The degradation temperatures increase with B . The initial degradation temperature (T o ) is 0.697 B + 350.7; the temperature at the maximum degradation rate, that is, the peak temperature on a differential thermogravimetry curve ( T p ), is 0.755 B + 368.8; and the final degradation temperature ( T f ) is 1.016 B + 497.4. The degradation rates at T p and T f are not affected by B , and their average values are 46.7 and 99.7%, respectively. The maximum thermooxidative degradation reaction rate, that is, the peak height on a differential thermogravimetry curve ( R p ), increases with B . The relationship between B and R p is R p = 2.12 B + 7.28. The thermooxidative degradation kinetic parameters are calculated with the Doyle model. The reaction energy ( E ) and frequency factor ( A ) change with an increasing reaction degree, and the variational trends of the two kinetic parameters are similar. The values of E and A increase remarkably during the initial stage of the reaction, then keep relevantly steady, and finally reach a peak during the last stage. The velocity constants of the thermooxidative degradation vary with the reaction degree and increase with the reaction temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1227–1232, 2003