ELEMENTARY RADICAL FORMATION AND CONVERSION PROCESSES IN GAMMA-IRRADIATED POLYVINYLCHLORIDE

In the reported experiments, elementary processes of gamma -irradiated polyvinylchloride (PVC) have been investigated by both electron spin resonance (ESR) and optical absorption measurements. On irradiating PVC film with gamma rays at minus 196 degree C, alkyl-type radicals are produced. When the PVC film is warmed to room temperature, the radicals convert to polyenyl type. gamma Irradiation of PVC film containing biphenyl (Ph//2) or pyrene (Py) at minus 196 degree C yields the corresponding radical cation. The relative ESR peak heights of the radicals decrease and the G values for the formation of cation radicals increase with increasing additive concentrations. These facts indicate that energy is transferred from the precursor of the radicals to the additive. In the case of PVC film containing Py, the Py cation radical decreases and the cyclohexadienyl-type radical from Py is produced by thermal annealing. A possible mechanism for radical formation and conversion is proposed.