HIGH-ENERGY RADIATION EFFECTS ON HALOGENATED BUTYL RUBBERS

The effect of high energy radiation on halogenated butyl rubbers was s tudied using electron spin resonance and nuclear magnetic resonance sp ectroscopies and gas chromatography. During high energy irradiation, m ost of the radicals were found to be generated on the halogenated isop rene units. A higher radiation yield for scission was observed in chlo rinated butyl rubber than in brominated butyl rubber. This is due to t he ready abstraction of hydrogen from the main chain by the chlorine r adicals to give main-chain radicals which are known to contribute to s cission in butyl rubbers. However, in both polymers, crosslinking pred ominates over scission up to a limiting dose.