Simple activity coefficient model for the prediction of solvent activities in polymer solutions

A new simple activity coefficient model for the prediction of solvent activities in polymer solutions is presented. The model consists of two terms, a recently proposed “combined” combinatorial-free-volume term by Elbro et al. and the residual term of UNIFAC. The linear temperature-de-pendent parameter table for UNIFAC, recently developed by Hansen et al., is used.

The ability of the new model to predict solvent activity coefficients at infinite dilution for many different polymer-solvent systems is shown. Considering the significant errors often found in the experimental measurements of these coefficients and the scatter of the experimental data, the obtained results are very good: they compare favorably with the UNIFAC-FV model by Oishi and Prausnitz and they are better than the two rather complicated and recently developed equations of state proposed for polymer solutions by High and and Chen et al.