Abstract: Based on the independence of pressure(P)temperature(T)specific volume(V) relationship of polymer to processing mode, using the modified double domain Tait state equation, a isovolume pressureholding curve was proposed. The injection pressureholding was simulated using Moldflow software, a cooling pressureholding curve of products was extracted. With such a curve we could transfer the pressuretemperature curve into a pressuretime one. Comparison among various pressureholding modes showed that the quality of products could be significantly improved through isovolume pressureholding method.

Key words: polymer, pressuretemperaturespecific volume relationship, Tait state equation, packing pressure of isosteric