Vapor-liquid equilibrium of polymer + solvent systems: Experimental data and thermodynamic modeling

The experimental data were modeled with two group contribution models for the activity coefficient, Elbro-FV and UNIFAC-Zhong; the latter method considers the free-volume of molecules of high molecular weight, such as polymers. UNIFAC groups in the literature as well as new groups that were proposed for the monomers were used. The necessary energy interaction parameters between these groups were estimated. There were observed mean deviations between experimental and calculated mass fractions of about 8.5% with Elbro-FV, and about 17% with UNIFAC-Zhong when original groups were used, while there were observed mean deviations of about 7% with Elbro-FV and about 16% with UNIFAC-Zhong when new groups were used. The Elbro-FV model represents the experimental data with better precision in both cases; on the other hand, the data were better correlated with both models when new groups were used.