Various thermodynamic functions can be derived from the equations of state using standard thermodynamic relations. This work presents a review of several equations of state, for polystyrene in the liquid state. These equations provide accurate volume to analyze PVT data, also, provide valuable thermodynamic information and can be used to predict the properties of polymer blends and solutions. Perhaps the most common empirical representation of polymeric PVT data is that of the Tait equation. Using this equation, we have provided experimental data for isobaric expansion coefficient, isothermal compressibility, and internal pressure. An alternative to empirical representation of PVT behavior is to develop a theoretical model, starting from an understanding of the forces that exist between molecules. Average deviations between experimental and calculated specific volumes, isobaric expansion coefficient, isothermal compressibility, and internal pressure were determined and an overall average deviation was calculated for polystyrene. Table 1 compares the performance of the various theories.

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