Calorimetric analysis of an isotactic polypropylene gamma-irradiated in vacuum

The molecular modifications induced in an isotactic polypropylene gamma-irr adiated in vacuum under a complete set of experimental conditions were stud ied by means of calorimetric analysis. In a previous paper [1], the influen ce of the irradiation parameters, the total absorbed dose, D, and the dose rate, I, was analyzed and a simple kinetic model based on the rates of the main reactions occurring during irradiation, i.e. beta-scission, addition t o double bonds and termination, was also discussed. It is now shown how the rmal analysis confirms the model forecasts and in particular the existence of the 'inversion conditions': below them the main effect is molecular degr adation, while above them the main effects are chain-branching and cross li nking.