Influence of the irradiation parameters on the molecular modifications of an isotactic polypropylene gamma-irradiated under vacuum

Isotactic polypropylene was irradiated under vacuum in a complete set of experimental conditions. The influence of the irradiation parameters, total absorbed dose, D, and dose rate, I, was analysed in order to verify the theoretical predictions of a simple kinetic model, already presented (Sarcinelli L, Valenza A, Spadaro G. Polymer 1997,38:2307), based on the rates of the main reactions occurring during irradiation, i.e. beta-scission, addition to double bonds and termination. The concentration of free radicals and double bonds formed during irradiation is detected together with a comparison to their dependence on the irradiation parameters. A quantitative determination of the "inversion curve", forecasted by the model, i.e. an implicit function of D and I, which gives the dose values enhancing chain branching and molecular weight increase at fixed dose rate and vice versa, was also performed. (C) 2000 Elsevier Science Ltd. All rights reserved.