Abstract: The effect of nozzle temperature, pressure, melt viscosity, and cooling time on the cell size, cell density, and mechanical properties of chemically foamed PP/SiO2 nanocomposites were studied through orthogonal experiments. The Image-Pro software was used to count the cell size. It was found that the nozzle temperature was the most important factor, melt viscosity was the second. The optimal injection processing parameters were nozzle temperature 175 ℃, injection pressure 67.5 MPa, melt viscosity 95 %, and cooling time 35 s, by which an impact strength of 5.45 kJ/m2 ,an average cell diameter of 15.71 m , an cell density was 9.8×106 bubble/cm3 were obtained.

Key words: polypropylene, silica, nanocomposite, microcellular, injection molding, processing parameter