An electron paramagnetic resonance study of PP and PP/SBS blends irradiated with gamma rays

Electron paramagnetic resonance (EPR) measurements of Polypropylene (PP) and its blends with a Styrene Butadiene-Styrene (SBS) copolymer in 10, 20, 30 and 40 wt.% of SBS were carried out. The samples were irradiated in the 0 less than or equal to D less than or equal to 100 kGy range at a dose rate of 4.8 kGy/h. Typical spectra indicative of the formation of peroxy and alkyl radicals were obtained. The dynamics of formation and recombination of radicals in these samples could be explained using a mixed zero and first order generation-recombination fit of the total spin concentration as a function of the integral dose. The time dependence of the spin concentration was studied assuming a mixed first order fit in the decay process. The parameters obtained from the fitting are interpreted in terms of the rate of formation of free radicals at the irradiation time and in terms of the decay time of the total free radical concentration. (C) 2004 Elsevier B.V. All rights reserved.