AbstractThis 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. Increasing filler content produced significant and reproducible reductions of the cycle time. Such effects were especially pronounced with the high thermal conductivity fillers. The cooling process was also treated theoretically, starting from the heat conduction equation and producing a fully satisfactory description of the experimental data. Furthermore, the value of the thermal diffusivity, exemplified by the HDPE/MgO compounds, was in good agreement with the values obtained from current composite expressions.
展开▼
