ESR investigations in the degradation PS/PP (80/20) blend with 20wt% from SBS, under gamma irradiation, after of 5 years of storage in air.

Abstract

The additives are intended to increase the lifetime of the polymers. However the exposition to nuclear radiations and the oxidative atmosphere storage induces chemical changes of the additives added to macromolecules which generate modifications in its physical and chemical properties that affect the stability of these materials. In this paper our attention is focused on the degradationprocesses induced by ageing and gamma irradiation on polystyrene/polypropylene (PS/PP) (80/20) blends with and without compatibilizer styrene-butadiene-styrene (triblock SBS) at 20wt%after 5 years of air storage irradiated with gamma rays from a 60Co source at a dose rate of 4.8 kGy/h and at a integral irradiation dose of 10, 25 and 50 kGy in the presence of air at room temperature (RT =298ºK). The effect of ageing and gamma irradiation on the polymers studied was measured by electron spinresonance (ESR) spectroscopy 7 days after the gamma irradiation. The dependence of resonance line, Hpp, the resonance line shape, K, and the free radical concentration (S%) versus integral dose, is investigated. The free radicals concentration, S%, has been estimated, for a group of single lines characterized by the same giromagnetic factor, g. The nature of the free radicals is discussed.