The influence of the blowing agent addition and injection molding parameters on the structure of polypropylene moldings

The results of studies of the influence of the content of the applied blowing agent and injection molding parameters on the structure of polypropylene (PP) moldings have been presented. The studies were carried out on neat polypropylene (Moplen) as well as on polypropylene incorporated with 0.125—0.5 wt. % of the endothermic chemical blowing agent — Hydrocerol CF40E (Fig. 1). The experiments were carried out based on the Statistica 8.0 factorial design model with the Design of Experiments (DOE) module (Table 1, Fig. 4). Changes were made in four independent variable injection molding parameters namely: the concentration of blowing agent (c), mold temperature (Tf), melt temperature (Tw) and injection velocity (vw). The studies confirm a vital influence of the amount of the blowing agent and injection molding parameters on the structure of the moldings (Table 2, Figs. 5—12). The expected microcellular porous structure enhancing mechanical properties was achieved by applying a low injection and mold temperature and 0.5 wt. % of the blowing agent.