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

摘要

Isotactic polypropylene was irradiated under vacuum in a complete set of experimental conditions. The influence of the irradia- tion 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 reac- tions occurring during irradiation, i.e. β-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.