The use of pressurized water pellets in injection molding to improve dimensional consistency while decreasing cycle time

In injection molding, cycle time, and dimensional stability are critical factors for process economics and product quality. In this paper, we discuss a new process/molding method developed by our group to improve dimensional stability while decreasing cycle time with minimum effect on mechanical properties. Pellets were prepared by compounding a water carrier particle, (Activated Carbon /AC) via extrusion, followed by a batch pressurizing process at a controlled pressure and temperature to allow a small amount of water to be absorbed into the pellets. Results show that the cycle time, sink marks and warpage are reduced without a major effect on the mechanical properties. A simplified diffusion model is proposed to better understand the loss of water in the pellet as a function of time and estimate raw material stability.