Oxidation fronts in polypropylene as studied by imaging chemiluminescence

摘要

The oxidation of isotactic polypropylene (PP) films containing three different commercial stabilisers has been studied at 150℃ in air using imaging chemiluminescence (ICL). The oxidation was initiated using unstabilised PP powder, UV-irradiation or copper. It was shown that the initiated local oxidation spread as a propagating oxidation front in the stabilised PP films. By comparing the speed with which the propagating oxidation front spread, the performance of different stabilisers could be assessed. Furthermore, the influences of temperature, antioxidant concentration and sample thickness on the front speed were compared. The advantage of this technique is a controlled initiation of the oxidation that minimises the influence of weak points in the films. Furthermore, the experimental time is considerably shortened. The position of the oxidation front has been monitored using both ICL and infrared- microscopy. It was concluded that the technique is effective when evaluating stabiliser performance. Furthermore, it allows the study of oxidation phenomena such as oxidative spreading. The technique was also applied to polyamide 6, however, in this poly- mer the oxidation did not show the same spreading behaviour.