Cell Formation and Dimensional Stability According to Molding Conditions in Foam Injection Molding of PP Using a Chemical Blowing Agent

Foam injection molding was performed by adding a chemical blowing agent to PP to form a cell inside the plastic specimen. Cell formation, cell density, and dimensions of the specimen were observed while changing the injection temperature, injection speed, and back pressure of the heating cylinder. The higher the injection temperature, the better the cell formation, and the formation of the cell was the best when the injection speed was the highest at the high injection temperature. The cell density was very high when the back pressure in the heating cylinder of the injection molding machine was low, however the generation of cells significantly decreased as the back pressure increased. In the case of foam injection molding using a chemical blowing agent, it was very important not only to prevent the generated gas from escaping out of the mold during filling stage, but also to prevent it from escaping from the heating cylinder to the outside. The dimensions of the foamed specimens were very stable regardless of cell density variations in various molding conditions.