Evaluation of the degradation effect on the processability of high molecular weight polypropylene

One way to improve the processability of high molecular weight and melt strength of Polypropylene (PP) is reducing its molecular weight by chain scission with increase of flow index. Nevertheless, the more significant occurrence of chain scission in its structure, further improved its processability is at expense of physical properties. It is well known that the high energy radiation creates free radicals in the polymer chains that subsequently stabilize forming structures. These structures composed by low molecular weight chains and by grafted, branched and crosslinked chains modify the physical and chemical properties of the polymer, depending of their distribution. The low molecular weight chains become from the degradation process by high energy irradiation, which decreases the melt strength and improves its processability. So, this work has the objective to evaluate the degradation of the high molecular weight PP using different irradiation doses. Two kinds of PP samples were utilized. The first one, without additive, presented a flow index of 1.9 g/10 min, and the second, additivated with 0.2 wt % of antioxidant phenolic, Irganox 1010, with a flow index of 0.9 g/10 min. These samples were irradiated with doses of 12.5 and 20.0 kGy. The results of flow index and melt strength obtained with these two kinds of samples showed the antioxidant and the radiation action. (author)