Effect of cooling rate and shear‐induced crystallization on the pressure–specific volume–temperature diagram of isotactic polypropylene

Abstract

Abstract Rectangular plates were injection molded with isotactic polypropylene. At a pressure of 1300 bar the mold was sealed mechanically in the gate. After the injection and compression phase the internal pressure decay has been calculated using the pressure–specific volume–temperature diagram and compared with measurements. The calculation method is described. The pvT diagram determined on stationary melt at a low cooling rate yields no good approximations of the measured values. It is shown which modifications of the pvT diagram are necessary to obtain a better description of the melt behavior under injection molding conditions. At the end of the cooling phase, the calculated pressure differs from the measured pressure. The reason is the volume change of the mold caused by the high internal pressure.