Accelerated laboratory weathering of polypropylene composites filled with synthetic silicon-based compounds

Abstract

Non-functionalized and n-alkyl functionalized polyhedral oligomeric silsesquioxanes (POSS), siloxane-silsesquioxane resins and the sol-gel silicas were for the first time examined as possible UV-stabilizers and/or antioxidants in polypropylene (PP). The obtained composites were subjected to the accelerated laboratory weathering tests. The influence of the weathering conditions on the structure and properties of the PP materials was evaluated on the basis of the results from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) studies. It was found that weathering resistance of the PP materials was strongly depended on the kind of the silicon-based filler used. Functionalized silsesquioxanes and siloxane-silsesquioxane resins improved weathering resistance of the PP materials, most probably because of its uniform dispersion in polymer, and thus, they could be considered as antioxidant additives. The changes in structural characteristics influenced thermal properties of the PP composites. It was revealed that the addition of the n-alkyl functionalized POSS and siloxane-silsesquioxane resins caused less significant changes in the melting and crystallization behaviour of PP materials.