Prediction of Liquid-Liquid Equilibrium for Binary Polymer Solutions with Simple Activity Coefficient Models

Georgios M. Kontogeorgis, Ana Saraiva, Aage Fredenslund, Dimitrios P. Tassios*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


Liquid-liquid equilibrium predictions for binary polymer solutions using four simple UNIFAC-based activity coefficient models are presented in this work. The four models are the original UNIFAC, the new UNIFAC recently developed in Lyngby, a modified Flory-Huggins model, and the recently developed entropic-FV model. All four models are purely predictive, since they are based on the group-contribution approach. They employ existing UNIFAC group interaction parameter tables, which have been estimated from vapor-liquid equilibrium data of mixtures with exclusively low molecular weight compounds. The investigated models are capable of predicting UCST qualitatively well, but only the modified Flory-Huggins and the entropic-FV models can predict LCST (near the critical temperature of the solvent) and are, thus, able to describe the combined UCST/LCST behavior often found in polymer solutions. In particular, the entropic-FV model can represent the five types of phase diagrams which are most often encountered in polymer solutions, including closed loops and hourglass type. Furthermore, the predictions with the entropic-FV model are in several cases (especially for nonpolar solutions) semiquantitatively correct and generally far more accurate than those provided by the classical UNIFAC models.

Original languageEnglish
JournalIndustrial and Engineering Chemistry Research
Issue number5
Pages (from-to)1823-1834
Publication statusPublished - 1995


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