Oxidation fronts in polypropylene as studied by imaging chemiluminescence

The oxidation of isotactic polypropylene (PP) films containing three differ ent commercial stabilisers has been studied at 150 degreesC in air using im aging chemiluminescence (ICL). The oxidation was initiated using unstabilis ed PP powder, W-irradiation or copper. It was shown that the initiated loca l oxidation spread as a propagating oxidation front in the stabilised PP fi lms. By comparing the speed with which the propagating oxidation front spre ad, the performance of different stabilisers could be assessed. Furthermore , the influences of temperature, antioxidant concentration and sample thick ness on the front speed were compared. The advantage of this technique is a controlled initiation of the oxidation that minimises the influence of wea k points in the films. Furthermore, the experimental time is considerably s hortened. The position of the oxidation front has been monitored using both ICL and infrared microscopy. It was concluded that the technique is effect ive when evaluating stabiliser performance. Furthermore, it allows the stud y of oxidation phenomena such as oxidative spreading. The technique was als o applied to polyamide 6, however, in this polymer the oxidation did not sh ow the same spreading behaviour. (C) 2001 Elsevier Science Ltd. All rights reserved.