Classical and recent free-volume models for polymer solutions: A comparative evaluation

H.R. Radfarnia, Georgios Kontogeorgis, C. Ghotbi, V. Taghikhani

Research output: Contribution to journalJournal articleResearchpeer-review


In this work, two "classical" (UNIFAC-FV, Entropic-FV) and two "recent" free-volume (FV) models (Kannan-FV, Freed-FV) are comparatively evaluated for polymer-solvent vapor-liquid equilibria including both aqueous and non-aqueous solutions. Moreover, some further developments are presented here to improve the performance of a recent model, the so-called Freed-FV First, we propose a modification of the Freed-FV model accounting for the anomalous free-volume behavior of aqueous systems (unlike the other solvents, water has a lower free-volume percentage than polymers). The results predicted by the modified Freed-FV model for athermal and non-athermal polymer systems are compared to other "recent" and "classical" FV models, indicating an improvement for the modified Freed-FV model for aqueous polymer solutions. Second, for the original Freed-FV model, new UNIFAC group energy parameters are regressed for aqueous and alcohol solutions, based on the physical values of the van der Waals volume and surface areas for both FV-combinatorial and residual contributions. The prediction results of both "recent" and "classical" FV models using the new regressed energy parameters are significantly better, compared to using the classical UNIFAC parameters, for VLE of aqueous and alcohol polymer systems.
Original languageEnglish
JournalFluid Phase Equilibria
Issue number1
Pages (from-to)63-69
Publication statusPublished - 2007


  • polymer solutions
  • aqueous solutions
  • free-volume


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