Abstract
During the polymer processing stage, polymer volume changes with phase transition from molten state to solid state. The molten state can be assumed as an equilibrium state. At this stage, the change of volume is function of time and pressure. The phase transition (from melt to solid) can be regarded as a non-equilibrium state. At this stage, the change of volume is related to its time history. For example, the rate of cooling and pressure change will have major effect on the change of volume. In practical polymer processing process, most theoretical models were based on equilibrium state to describe the change of volume during the process such as injection molding. As described above, the change of polymer phase (from melt to solid) is a non-equilibrium process, the equilibrium theory can not adequately describe the change of volume during the phase transition. Therefore an adequately non-equilibrium PVT model is very important for studying the polymer processing process such as in injection molding. The purpose of this work is to explore an adequate nonequilibrium theory to explain the relationship between temperature, volume and pressure of polymer under non-equilibrium process. There are three major approaches to model the P-V-T relationship of the non-equilibrium process: Non-equilibrium thermodynamic model such as KROGT equation. Secondary, base on free volume theory. Third, base on viscoelasticity of polymer material, such as Ko-Bogue equation and K-BKZ equation. This work was based on the combination of non-equilibrium thermodynamic and viscoelasticity of polymer material, In this work, experimental data were used to exam and modify the theoretical models. By doing so, a non-equilibrium P-V-T mode was developed. By using the result of this work, the change of volume during polymer processing can be described more. Therefore the thermal stress, dimension and warpage can be precisely predict by using CAE program for injection molding process.