The use of pressurized water pellets and supercritical nitrogen in injection molding

In injection molding, cycle time, and warpage are critical factors for process economics and product quality. This work focuses on reducing cycle time, and warpage by utilizing water containing polymer pellets. Pellets were prepared by compounding a water carrier particle, (Activated Carbon /AC or Tubular Nanoclay/ NC) via extrusion, followed by a batch pressurizing process at a controlled pressure and temperature to allow a small amount of water be absorbed into the pellets. Water containing polymer/micro particle pellets were molded with and without the addition of supercritical nitrogen to further decrease the cycle time and minimize warpage. Preliminary results showed that the cycle time and part warpage could be reduced without a major effect on the mechanical properties when the water content was low. In this study, it was found that the effect of water is more beneficial than that of nitrogen.