The effect of zinc bromide on the thermal degradation of poly(methyl methacrylate): Part 1—Thermal analysis studies and general nature of the interaction |
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Authors: | IC McNeill RC McGuiness |
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Institution: | Chemistry Department, University of Glasgow, Glasgow G12 8QQ, Scotland, Great Britain |
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Abstract: | The degradation behaviour of several different blends of poly(methyl methacrylate) (PMMA) and zinc bromide, under programmed heating to 500°C, has been studied using thermal volatilisation analysis and spectroscopic investigation of the volatile degradation products. The samples were in the form of films cast from a common solution of the components in acetone; these films are found to be transparent, indicating compatibility of PMMA and ZnBr2. From studies of the visible spectra of cobalt bromide, PMMA and blends of PMMA with CoBr2, it has been argued that complex formation occurs between the polymer and the transition metal halides: structures are suggested.When degraded alone, PMMA gives only monomer as the degradation product. In the blends with ZnBr2 (or with CoBr2), the polymer becomes considerably less stable and the pattern of degradation becomes very complex, with a range of volatile products, of which methyl bromide, carbon dioxide and methanol are the major constituents; carbon monoxide and methane are also formed. It is proposed that complex formation facilitates the release of methyl bromide as the first stage of breakdown, with the formation of zinc methacrylate units in the polymer chain; depolymerisation is prevented or severely inhibited, depending on the amount of ZnBr2 present. |
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