THERMAL-DEGRADATION OF GAMMA-IRRADIATED POLYMERS .2. POLYMETHACRYLONITRILE

The effect of gamma-irradiation on the thermal stability of polymethacrylonitrile has been examined for doses from 20 to 300 kGy. It has been found that, on irradiation, small amounts of hydrogen cyanide, methane and hydrogen are evolved. The effect of irradiation is to raise slightly the temperature required for release of volatile products from the polymer. Pure polymethacrylonitrile degrades thermally to give monomer and traces of hydrogen cyanide, isobutene and propane. The irradiated polymer, unlike the pure unirradiated material, discolours on heating, the amounts of these trace products increase and ammonia and carbon dioxide are formed in addition to the monomer. The reactions which occur during irradiation and subsequent thermal degradation are discussed.