Comprehensive Analysis of pvT Rheological Testing for Mechanical, Thermal and Thermodynamic Property Evaluation of Soft Polymers

This article presents a comprehensive review of polymer pressure-volume-temperature (pvT) behavior, which is fundamental to polymer physics and processing. It details the derivation of critical thermal, mechanical and thermodynamic properties, specifically, isothermal compressibility, isobaric thermal expansion coefficients, melt thermal conductivity, and isothermal entropy change, directly from empirical pvT data. Through a critical analysis of the piston-dilatometric method (both isothermal and isobaric modes), this study validates pvT testing as a versatile and indispensable method for simulating industrial manufacturing processes, such as injection molding, where the accurate prediction of specific volume, shrinkage, and warpage is crucial. While acknowledging limitations in capturing subtle solid-state transitions due to non-equilibrium effects in glassy or semi-crystalline states, the review highlights the high accuracy of the method in capturing the solid and melt behaviors of polymers. Key technical aspects, including the influence of cooling rates, pressure-dependent phase transitions, and the utilization of equation of the state, are discussed to provide a thorough overview of polymer material characterization.