Improvement of an Entropic-FV model based on solubility parameters for prediction of vapor-liquid equilibria of solvent-polymer systems

In this work, a modified Entropic-Free-Volume (FV) model was proposed for improved accuracy in the prediction of vapor-liquid equilibria (VLE) for solvent-polymer systems. The model was developed by combining an Entropic-FV combinatorial term with a residual term derived from the enthalpy of mixing determined from solubility parameters. Since solubility parameters can be predicted by group contribution models and extensive group parameters are available, the present model can be applied to a wide range of solvent-polymer systems. The accuracy of the present model was tested with finite-concentration VLE data for 16 polymers and 36 solvents composing a large variety of solvent-polymer systems including polar and nonpolar solvents and polymers. The data considered were divided into three categories: systems containing nonpolar, polar without hydrogen bonding and polar with hydrogen bonding solvents. The present model gave good accuracy for all solvent categories. In comparison with the original Entropic-FV model, the present model achieved significant improvements, reducing average absolute deviations in solvent activities from 7.3% to 2.9%, 8.8% to 2.2% and 18.5% to 3.0% for systems containing nonpolar, polar and polar-with-hydrogen bonding solvents, respectively.