The role of filler type in the photo-oxidation behaviour of micro- and nano-filled polypropylene

The rising interest in polymer nanocomposites leads also to an increasing concern for their photo-oxidation resistance. The main properties and photo-oxidation behaviour of polypropylene-based microcomposites and nanocomposites were investigated. The results show that the use of nanosized calcium carbonate may lead to a higher photo-oxidation rate than that of pristine polypropylene, in a way that is comparable to organo-modified nanoclays. It is also observed that nanosized calcium carbonate causes higher photodegradation rates than microsized calcium carbonate. The main reasons for the increased photo-oxidation rates when using organo-modified nanoclays include the presence of iron ions, the degradation of the organo-modifier and the formation of acidic sites on nanoclay layers, while in the case of calcium carbonate the main reasons are related to the achieved morphology and structure. The presence of calcium carbonate, especially when nanosized, significantly modifies the distribution of photo-oxidation products in comparison to clay-filled nanocomposites. (C) 2011 Society of Chemical Industry