Morphology evolution during injection molding: Effect of packing pressure

Injection molding is one of the most widely employed methods for manufacturing polymeric products. The final properties and then the quality of an injection molded part are to a great extent affected by morphology. Thus, the prediction of microstructure formation is of technological importance, also for optimizing processing variables. In this work, some injection molding tests were performed with the aim of studying the effects of packing pressure on morphology distribution. The resulting morphology of the moldings was characterized and it was compared with previous results gathered on samples obtained by applying a lower holding pressure. Furthermore, the molding tests were simulated by means of a code developed at University of Salerno. The results obtained show that on increasing holding pressure the molecular orientation inside the samples increases, and simulations show that this is due mainly to the increase of relaxation time caused by the higher pressures. On discussing the simulation results, some considerations are made on the effects of pressure on crystallization kinetics and on rheology. (c) 2007 Elsevier Ltd. All rights reserved.