MODIFYING THE TAIT EQUATION WITH COOLING-RATE EFFECTS TO PREDICT THE PRESSURE-VOLUME-TEMPERATURE BEHAVIORS OF AMORPHOUS POLYMERS - MODELINGAND EXPERIMENTS

Cooling-rate effects play an important role in polymer processing beca use the materials experience rapid cooling when transferring from melt states to solid states. The traditional Tait equation has been used w idely in representing the volumetric behaviors of polymers as a functi on of temperature and pressure, but not of cooling rate. Based on the dependence of glass-transition temperature on cooling rate (i.e., thet a = dT(g)/d log \q\), the volumetric dependence on cooling rate is emp loyed in this work to modify the traditional Tait P-V-T equation to be come a time-dependent P-V-T model. The physical meanings of the tradit ional Tait equation parameters are interpreted and, thereby, parameter s in the new model are derived according to the material constant thet a. The controlled cooling-rate measurements of polymeric volumetric da ta have been performed in this work to verify the validity of the prop osed model. Additionally, the material parameter theta, calculated fro m the measured data of polystyrene (PS) (Chi-Mei PG-33) in this work, equals 2.85 K, which is close to 2.86 K calculated from the Greiner-Sc hwarzl work. Furthermore, a comparison of the predicted results with t he experimental data both in this work and from literature is discusse d under different pressures and various cooling rates. The results hav e indicated that the proposed non-equilibrium P-V-T model closely corr elates with experimental data.