STABILIZATION OF POLYOLEFINS TO GAMMA-IRRADIATION - ROLE OF THE INITIAL RADICALS

The initial, atypical peroxyl radicals which start the free-radical chain oxidations have been identified in gamma-irradiated polyolefins. These radicals were quantified in total by electron spin resonance and trapped by reaction with nitric oxide at -78-degrees-C to give nitrates which could be individually identified by infrared spectroscopy. Loss in physical properties was correlated with the accumulation of oxidation products formed during post-irradiation storage for polypropylene containing several stabilizer combinations. The best retention of impact strength corresponded to the minimum formation of oxidation products although none of the stabilizer combinations was able to completely suppress the oxidation processes.