Reactive extrusion processing of polypropylene/SiO2 nanocomposites by in situ synthesis of the nanofillers: Experiments and properties

The concept of a lab-scale developed in situ sol–gel batch process for fabrication of polypropylene (PP)/silica nanocomposites based on a solvent-free silica precursor polymer, a hyperbranched polyalkoxysiloxane (PAOS), has been transferred to a continuous industrially applicable extrusion process. To achieve a suitable process set-up for the continuous in situ synthesis of nanofillers in the PP melt, process parameters are varied. The influence of process parameters on precursor conversion, size and distribution of the formed silica particles and the mechanical properties of the resulting PP nanocomposites is determined. In addition, these materials are compared to conventional silica composites based on melt mixing process. It was found, that a PAOS conversion to silica particles of more than 90% could be realised using a hexadecyl-modified PAOS of 12.5% degree of modification (C16(12.5%)-PAOS) at the given process set-up. Well distributed, small silica particles without any agglomeration were yield in the resulting composites in comparison to application of silica powder.