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°C. Although the degradation of a pure PP sample hardly occurred at such temperature, the existence of Fe₂O₃ induced 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 μm 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. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010