MEASUREMENTS OF CYCLE TIME IN INJECTION-MOLDING OF FILLED THERMOPLASTICS

This study presents the results of measurements of the sealing and cooling periods of the injection molding cycle of filled thermoplastics, both periods constituting a major part of the cycle. The compounds used were based on HDPE, PP, and PS. The fillers were calcium carbonate, carbon black, and magnesium oxide. The latter two materials were chosen for their high thermal conductivity. The sealing time was determined by a gravimetric method, while the measurement of the cooling time was based on the assessment of the recovery of the ejector marks for samples ejected after varying times of cooling. The cooling process was also treated theoretically, starting from the heat conduction equation and producing a fully satisfactory description of the experimental data.