A STUDY OF THERMAL OXIDATIVE AND THERMAL MECHANICAL DEGRADATION OF POLYPROPYLENE

A study of the mechanism of thermal oxidative and thermal mechanical degradation of isotactic polypropylene (PP) is reported. Size exclusion liquid chromatography has been applied to the study of molar mass distribution (MMD) of samples of PP under oxidative degradation in the presence of an incorporated organic peroxide and of samples subjected to repeated extrusion. The change in MMD of the samples of PP under controlled oxidative degradation at 230-degrees-C is explained by a random chain scission mechanism and those of the samples of PP extruded repeatedly from an extruder at 280-degrees-C can be elucidated by a mechanism of mechanical chain scission with a threshold degree of polymerization 2L, below which the chain will not undergo scission. The value of L was found to be around 500.