The thermal degradation of copolymers of methyl methacrylate and acrylonitrile

Abstract

The thermal degradation of four methyl methacrylate/acrylonitrile copolymers with molar ratios 410/1, 40/1, 16/1 and 8/1 has been studied at 280°. Volatilization of the copolymers to give a mixture of the constituent monomers is accompanied by a rapid decrease in the molecular weight of the residue. The same mol. wt. vs. % volatilization relationship is observed for all four copolymers. The rate of decrease of molecular weight and the rate of volatilization are more rapid the smaller the acrylonitrile content of the copolymer. These findings are interpreted in terms of random scission in the methyl methacrylate segments of the copolymer molecules, followed by depolymerization of the resulting radicals. Previous experiments, carried out at 220° on the 410/1 and 40/1 copolymers, have been reinterpreted in order to give a unified picture of the reaction at the two temperatures.