Studies on Heterogeneous Degradation of Polypropylene/Talc Composite: Effect of Iron Impurity on the Degradation Behavior

In this study, an effect of iron oxide (Fe2O3) impurity in talc on degradation behavior of polypropylene (PP)/talc composite was studied using a PP/Fe2O3 model composite sample. The thermal oxidative degradation was performed at 100 degrees C. Although the degradation of a pure PP sample hardly occurred at such temperature, the existence of Fe2O3 inciuced the PP degradation. The degraded PP part was formed around the Fe2O3 grain in the PP/Fe2O3 sample. It was found from the optical microscope observation that the degraded PP was able to diffuse only within the PP amorphous part. The analysis of the oxidation distribution on the degraded PP surface was performed employing a scanning electron microscope/electron dispersive spectrometer. The result showed that the PP spots in the vicinity of the Fe2O3 grain were unoxidized during the initial degradation process, and the oxidized PP spots were located at around 6 mu m distance from the Fe2O3 grain. It was concluded that the degradation was initiated microscopically away from the Fe2O3 grain so that the Fe2O3 had both the abilities to accelerate the decomposition of PP hydroperoxide compounds and to reduce the produced radical species into nonradical products. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 167-173, 2010