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Protective effect of the phenyl group in γ‐irradiated compatible blends of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

1984; Wiley; Volume: 29; Issue: 2 Linguagem: Inglês

10.1002/app.1984.070290202

1097-4628

Tuan Q. Nguyen, H. H. Kausch,

Polymer Nanocomposites and Properties

Abstract The sensitivity to radiation of mixtures of poly(methyl methacrylate) (PMMA) and polystyrene‐co‐acrylonitile) (SAN) was studied over the entire range of composition. Polystyrene‐co‐acrylonitrile, like polystyrene, is highly resistant to ionizing radiation, having a small G x value for crosslinking (0.077) and an even smaller G s value for main chain scission (0.055). In contrast, PMMA degrades readily under irradiation (with G s = 1.2). In γ‐irradiated blends, the behavior of each polymer is largely influenced by the presence of the other component. Gel formation in SAN is impeded by PMMA, as a result of a decrease in G x , and a concomitant increase in the ratio G s / G x . Flexural strength measurements, along with molecular weight determinations by gel permeation chromatography, demonstrated that SAN had a marked protective effect on PMMA by decreasing G s (chain scission). This protective effect was not observed in earlier experiments with PMMA–PS blends, in spite of its chemical similarity to the system PMMA–SAN. The difference in behavior between PMMA–PS and PMMA–SAN may be explained on the basis of polymer compatibility. PMMA and SAN form a compatible pair, whereas PMMA and PS are incompatible; thus the short range protective effect of the phenyl groups in PS is inhibited.