Calculation of liquid-liquid phase separation in a ternary system of a polymer in a mixture of a solvent and a nonsolvent

The Saatchi-Edalat theory for three-component systems is used to calculation of liquid-liquid phase separation in a ternary system of polymer in a mixture of a solvent and a nonsolvent. This correlation predicts NRTL parameters of polymer solution within the range of acceptable accuracy. We applied proposed correlation for ij to calculating activity coefficient. The results are showing good agreements between experimental data and calculated activity coefficient. Binodals are calculated for polymer/solvent/nonsolvent systems which are used in the preparation of asymmetric ultrafiltration or reverse osmosis membranes: cellulose acetate/solvent/water. Although knowledge of the interaction parameters for all compositions in the ternary system is rather poor, fairly good agreement has been found between calculated and experimentally found miscibility gaps when the solvent/nonsolvent parameter is taken to be concentration dependent and the other parameters, the polymer/solvent and the polymer/nonsolvent interaction parameter, are vary with temperature and degree of polymerization. The most important advantage of using presented method is decreasing minimum number of experimental data's is needed to calculation of the polymer/solvent and the polymer/nonsolvent interaction parameter. In this method we just need to know one infinity activity coefficient for each polymer/solvent and the polymer/nonsolvent systems to calculation of the polymer/solvent and the polymer/nonsolvent interaction parameter.