Foaming Behavior and Mechanical Properties of Microcellular PP/SiO2 Composites

Microcellular foamed polypropylene (PP)/SiO2 composites were prepared by using micro-SiO2 and nano-SiO2 particles. The effects of the particle size of SiO2 on the foaming behavior and mechanical properties of the composites were studied based on heterogeneous nucleation theory. The results showed that the silica facilitated the cell nucleation to some extent. The average cell size of 16.3 μm and the cell density of 4.46 × 107 cells/cm3 were achieved for the composite foam at the silica content of 4 wt.%. The plastic deformation of the PP was strongly constrained due to the presence of the nano-silica. The tensile and impact strength of the nano-SiO2 composite foam are larger than those of the micro-SiO2 composite foam due to the high crack propagation resistance in the microcellular PP/nano-SiO2 composite.