The behavior of thermosetting compounds in injection molding cavities

The thermo‐mechanical history of thermosetting compounds in injection molding cavities influences the ultimate properties of molded articles and affects both moldability and the productivity of the process. Mathematical modeling is an attractive approach for obtaining information regarding the thermo‐mechanical history of the compound in the cavity. In order to obtain useful mathematical models of the thermoset injection molding process, it is necessary to have information regarding the kinetics and heats of reaction during cure; the rheological, thermal, and PVT properties of the thermosetting compound; and the variation of these properties with operating variables and the degree of cure. The paper outlines a model of the thermoset injection molding process in simple rectangular or semi‐circular cavities. Methods are described for the experimental determination of the various physical and chemical properties of thermosets, which are required for modeling purposes. The results obtained in conjunction with the characterization of an epoxy system are illustrated. Finally, the paper demonstrates the results of mathematical modeling of the injection molding process for a commercial epoxy molding compound in a semi‐circular cavity, and shows that reasonable agreement is obtained between model predictions and experimental data.