EFFECT OF PROCESSING CONDITIONS ON SHRINKAGE IN INJECTION-MOLDING

A systematic study on the effect of processing conditions on mold shri nkage was undertaken for seven common thermoplastic polymers. It turne d out that the holding pressure was always the key parameter. The effe ct of the melt temperature is slightly less important. Injection veloc ity and mold temperature do not show a general trend for all polymers. It was shown that at least for amorphous polymers a simple thermoelas tic model could describe all experimental results. For semi-crystallin e materials the model overpredicts shrinkage.