Modeling Polymer Systems Using the Perturbed-Chain Statistical Associating Fluid Theory Equation of State

The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is applied to binary and ternary mixtures of polymers, solvents, and gases. The three pure-component parameters required for nonassociating molecules were identified for six polymer compounds. The phase equilibrium of polymer systems, which often involves high-pressure liquid−liquid mixtures as well as vapor−liquid mixtures at lower pressures, was investigated. Using a constant binary interaction parameter (kij), the PC-SAFT equation of state gives good correlations of the appropriate phase behavior over wide ranges of conditions. Comparisons to an earlier version of SAFT reveal an improvement of the proposed model.