Modeling of morphology evolution in the injection molding process of thermoplastic polymers

Abstract

A thorough analysis of the effect of operative conditions of injection molding process on the morphology distribution inside the obtained moldings is performed, with particular reference to semi-crystalline polymers. The paper is divided into two parts: in the first part, the state of the art on the subject is outlined and discussed; in the second part, an example of the characterization required for a satisfactorily understanding and description of the phenomena is presented, starting from material characterization, passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the moldings. In particular, fully characterized injection molding tests are presented using an isotactic polypropylene, previously carefully characterized as far as most of properties of interest. The effects of both injection flow rate and mold temperature are analyzed. The resulting moldings morphology (in terms of distribution of crystallinity degree, molecular orientation and crystals structure and dimensions) are analyzed by adopting different experimental techniques (optical, electronic and atomic force microscopy, IR and WAXS analysis). Final morphological characteristics of the samples are compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.