The equation of state of polymers

In this study, several equations of state are presented for polymers in the liquid state, i.e. above the melting point, or above the glass transition for amorphous polymers. The numerous empirical and theoretical equations of state that have been developed for polymers constitute more or less precise analysis functions for pressure, volume and temperature (PVT) data, and form the basis of methods for predicting the PVT of mixtures or solutions, particularly at low pressures. Most of these equations require several fitting parameters determined from experimental data. They can be divided into two categories: some are phenomenological, others are based on considerations of statistical thermodynamics. Equations of state in the first category are empirical representations of volumetric data. The majority of equations in this first group correspond to isothermal compressibility equations of state.