Degradation of some poly(methylphenylsiloxane)-poly(methyl methacrylate) interpenetrating polymer networks

Thermal degradation of poly(methylphenylsiloxane)-poly(methyl methacrylate) interpenetrating polymer networks (PMPS-PMMA IPNs) was studied by using thermogravimetric analysis (TGA), and compared with an unmodified poly(methyl methacrylate) (PMMA) network. The deconvoluted differential thermal gravimetry (DTG) curve of the PMMA-network showed three peaks, and that of PMPS-PMMA IPNs showed more than three peaks. The 5% weight loss temperature of IPNs approximately increases with increasing PMPS-network content, while the temperature of the maximum weight loss is not influenced by PMPS-network content. The average activation energies E-a,E-av of IPNs for degradation are evaluated. The value of E-a,E-av of IPNs in initial thermal degradation is less than that of PMMA-network, whereas E-a,E-av of IPNs in initial thermo-oxidative degradation is higher than that of PMMA-network. (C) 1999 Elsevier Science Ltd. All rights reserved.