Analysis of the mechanical, thermal and morphological behaviour of polypropylene compounds with sisal fibre and wood flour, irradiated with gamma rays

We report a study of the mechanical, thermal and morphological behaviour of blends of polypropylene filled with wood flour and sisal fibre (at 60/40 and 80/20 compositions, respectively), subjected to different doses of gamma irradiation (10, 25, 30, 50, 60 and 70 kGy), at room temperature and in the presence of oxygen. In addition, studies were carried out by infrared spectroscopy and electronic paramagnetic resonance to analyse the formation of radicals or functional groups influencing the behaviour of the irradiated compounds. Low irradiation doses improve the mechanical behaviour of the compounds under study (PP/wood flour, PP/sisal fibre). Thermal stability is acceptable and radical concentration in these materials is low. It was also demonstrated that it is possible to use low irradiation doses to modify the characteristics of PP and filler, which means a number of advantages: no chemical reagents are required and there are no residual polluting by-products or tedious post-treatment. Gamma-irradiation, therefore, is a promising technology to modify these composites in industry. (C) 2002 Elsevier Science Ltd. All rights reserved.