Abstract
A brief review on the rheology of particulate filled plastics in relation to their processability was given, and then the blow molding of particulate filled polypropylene was discussed.
The rheological properties of polypropylene melt filled with various fine particles were studied. The fillers were white carbons, magnesium carbonate, calcium carbonate, talc, and glass beads. It was found that the shear viscosity at low shear rate increased and the steady-state elasticity decreased by the filling. At the same time, the die swell and the melt fracture were suppressed. The most noticeable effects were observed with white carbons. It was inferred that by the filling the parison draw-down should decrease and the high-speed moldability should improve in the blow molding.
To confirm the prediction, the blow moldability of white carbon filled polypropylene was evaluated by use of an actual blow molding machine. With filling of white carbons, the critical temperature, below which the skin roughness of the parison occurred, was reduced and hence the high-speed moldability was improved. The die swell and the draw-down decreased, and hence the parison approached an ideal form.
