ABSTRACT
Injection molding, one of the most widely used methods of polymer processing, is characterized by high production rates and accurately sized products. In the process polymer melt flows through a runner system and gates; it is then injected into a cold mold, packed under high pressure, and cooled until solid. During the process the polymer undergoes simultaneous mechanical and thermal influences in the fluid, rubbery, and glassy states. For semicrystalline polymers this process is further complicated by crystallization, which in turn determines crystalline morphology. These effects introduce orientation, residual stresses, and shrinkage in the injection-molded products, which affect the physical and mechanical properties, dimensional stability and appearance of the finished product. So it is quite important to better understand the factors governing the orientation, residual stress, and shrinkage during molding.
