Degradation of polymer blends—III. Radiolysis of blends of poly(methyl methacrylate) with styrene-acrylonitrile copolymers

Abstract

The radiolysis at low dose of poly(methyl methacrylate) (PMMA), styrene-acrylonitrile copolymers (SAN) containing 36 wt% acrylonitrile and their blends, have been studied in vacuo and in air. Study of the molecular weight distributions of PMMA and SAN by gel permeation chromatography indicates that the mechanisms of degradation of both components are modified in the blend. The G-value for main chain scission of PMMA is lower in the blend than in pure PMMA and decreases with increasing SAN content. Main chain scission and crosslinking occur simultaneously in pure SAN and in the blends. The latter process is predominant in pure SAN irradiated in vacuo while the former dominates in the other cases. The G-value for chain scission of SAN increases with increasing PMMA content. This interactive degradation process is discussed in relation to the mechanism previously proposed for the radiolysis of PMMA.