Degradation of polymer mixtures—Part 10: The thermal degradation of blends of polyacrylonitrile and poly(methyl methacrylate)

Although the thermal degradation of polyacrylonitrile (PAN) is unchanged by blending with poly(methyl methacrylate) (PMMA), the degradation of PMMA is profoundly altered in the presence of PAN. The low temperature phase of the reaction is hindered although monomer is still the predominating product. At higher temperatures the monomer production gives way to the appearance of methanol, carbon dioxide, carbon monoxide and chain fragments which incorporate a variety of carbonyl structures.These results are interpreted in terms of initial reaction of methyl methacrylate units with the ammonia formed by degradation of the PAN. The amide-ester copolymer thus formed undergoes a complex degradation process at higher temperatures which includes inter unit cyclisations, chain fragmentation and the formation of methanol and oxides of carbon. Mechanisms are proposed and discussed.