STUDY OF THE INFLUENCE OF PRO-OXIDANT ADDITIVES DURING THE OXODEGRADATION OF POLYPROPYLENE AND HIGH IMPACT POLYSTYRENE FILMS

Abstract

This article investigates the influence of pro-oxidant additives on the accelerated degradation of samples of polypropylene homopolymer (PPh), polypropylene copolymer (PPc) and high impact polystyrene (HIPS). Extruded films were prepared with two amounts of a pro-oxidant (0% and 3% w/w). The films were subjected to air oven aging (60 °C) tests for 100 days. The chemical and physical changes induced by aging were monitored by: Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and tensile tests. For accelerated degradation,a complete loss of mechanical properties (i.e., strain at break) was obtained although at different exposure times. DSC values of Tc, Tm and Tg were shown to be the most sensitive parameters since they evidenced early structural changes during degradation. HIPS samples with 3% prooxidant exhibited increased susceptibility to oxidative degradation.For all materials with prodegradant additive signals characteristics of carbonyls and hydroxyl functional groups were observed by FTIR analysis