Fluid Phase Equilibria 202 (2002) 367–383 Revision of UNIFAC group interaction parameters of group contribution models to improve prediction results of vapor–liquid equilibria for solvent–polymer systems Gede Wibawa, Shigeki Takishima, Yoshiyuki Sato, Hirokatsu Masuoka ∗ Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan Received 20 February 2002; accepted 13 May 2002 Abstract The objective of this work was to improve the accuracy of group contribution models for prediction of solvent activities in polymer solutions by revising UNIFAC group interaction parameters using a wide range of vapor–liquid equilibrium (VLE) data of solvent–polymer systems. The group contribution models considered in this work were UNIFAC-FV, Entropic-FV, GK-FV and UNIFAC-ZM models. A total of 142 systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from non-polar to polar substances were considered to optimize 46 pairs of group interaction parameters. Data considered were split up into systems containing alkane and cycloalkane, aromatic, and polar solvents. For athermal systems, the UNIFAC-FV model gave the best results. Therefore, the model was used in optimizing the group parameters. Revised group interaction parameters were found to improve the reliability of VLE predictions in solvent–polymer systems. A significant improvement of prediction results was achieved by UNIFAC-FV model from 20.0 to 10.8% absolute average deviation (AAD) in solvent activities for systems containing polar solvents and from 16.7 to 10.9% AAD for all systems. The prediction results of GK-FV and UNIFAC-ZM models were also improved. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Group contribution; UNIFAC model; Solubility; Vapor–liquid equilibria; Polymer; Activity coefficient 1. Introduction A quantitative description of vapor–liquid equilibrium (VLE) is important to make proper design for processes directed to polymer devolatilization as is required to meet environment, health and safety regulations. Since the structures of polymer solutions are more complicated than low molecular fluid ∗ Corresponding author. Tel.: +81-82-4-247721; fax: +81-82-4-247721. E-mail address: masuoka@hiroshima-u.ac.jp (H. Masuoka). 0378-3812/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0378-3812(02)00140-1