Mold Filling And Curing Studies In Reaction Injection Molding

Reaction Injection Molding (RIM), a new kind of polymer processing method, has found wide applications since it was developed in the late of 1960's. RIM involves mixing of two low viscosity, highly reactive chemical components and injection of the mixture into a mold where it polymerizes and solidifies. Since unreacted components with low viscosity are injected, there is no need to head the materials and the pressures in the mole are low. Large parts can be produced with relatively low injection pressures and low consumption of thermal energy.This paper deals with mold filling and curing step in the RIM. Because mold filling and curing step in the RIM are complex polymer processes involving flow of viscous fluid, reaction and heat transfer, it is very difficult to conveniently model them. Although simple models do not incorporate details of the complicated mixing and reaction processes that occur in RIM, relatively simple models are significant in simple mold geometry.Urethane chemical system were the earliest materials developed for RIM and also are the materials used most widely in the current time. Polyurethanes and polyreas are the two important kinds of urethane chemical system. Polyurethanes can be divided into crosslinking and phase separation by their structure. The products made of Polyureas has better ultimate mechanical properties than polyurethanes and contain inner mold release. This paper mainly studies the processes of phase separation polyurethanes.