Effects of silica particle size on the structure and properties of polypropylene/silica composites foams

In this study, we prepared organically modified silica materials with various particle sizes, in the ranges of micrometer and nanometer, and their polypropylene (PP) composites. The PP micro/nanocomposites were then molded through conventional and microcellular injection molding processes. The effects of silica particle sizes on the structure, mechanical and rheological properties were investigated. The results showed that PP/silica nanocomposites provide better tensile strength than that of foamed nanocomposites. The addition of silica also increased the tensile strength of the nanocomposites, but decreased the tensile strength of microcomposites. Therefore, the tensile strength of PP/silica nanocomposites is better than that of PP/silica microcomposites. The silica particles helped the nanocomposites to develop small cells in the foaming process. Rheological results indicated an increase in the viscosity with the addition of nano silica and micro silica to PP. The viscosity increase for the silica nanocomposites was found greater than that of microcomposites at the same filler content.