Mechanical, thermal and morphological behaviour of the polystyrene/polypropylene (80/20) blend, irradiated with γ-rays at low doses (0-70 kGy)

The effect of low doses (0-70 kGy) of gamma irradiation on the mechanical, morphological and thermal behaviour, at room temperature and in the presence of oxygen, of a polystyrene/polypropylene (PS/PP) blend (80/20) with and without compatibilizer (block SBS) at 7.5 wt.% has been studied, to solve different problems related to the radiation stability of polymeric articles and purposeful radiation-induced modifications of polymeric materials. The effect of gamma irradiation on the tensile behaviour of the PS/PP blend (80/20) with and without SBS indicates that the blends present a high irradiation resistance at low doses (less than or equal to 70 kGy); this implies that adding PP to PS to modify its mechanical behaviour is a proper procedure, since PS is one of the most stable polymers regarding radiation, and very large doses are required to produce any noticeable change. Therefore, with an irradiation dose ranging between 0 and 70 kGy, PP is protected against a strong oxidative degradation (chain scission), which coincides with the values of the relative concentration of radicals obtained through EPR. In addition, according to the thermal studies, T-g shows no variations which could point to changes in the PS structure in the blends; however, variations in T-f of PP of the blends were detected, which lead us to conclude that PP shows chain scission degradation. It can be inferred that this decrease in fusion temperature occurs in the blends at irradiation doses (greater than or equal to 50kGy) higher than that of non-compatibilized PP (greater than or equal to 10kGy). (C) 2003 Elsevier Science Ltd. All rights reserved.