A modified Thermodynamic model for prediction thermodynamic and rheological properties of polymer solutions

In this study a new thermodynamic model based on m-fluid theory and local surface fraction has been proposed. The new model has combinatorial and residual terms for correlation phase behavior of polymer solutions. Flory-Huggins model has been used for combinatorial term and the modified local composition model proposed by Pazuki et al. converted to local area fraction has been used to residual term. The new model has been developed for correlation and prediction of phase behavior, vapor-liquid equilibria and liquid-liquid equilibria, of polymer solutions and results are compared with the UNIQUAC-FV model. The comparisons show that the new model has good agreement between experimental and theoretical results. Also thermodynamic and rheological properties of polymer-solvent systems such as density of solution, excess enthalpy and viscosity have been calculated by the proposed model. Of course the new model and Eyring model are combined for predictio n viscosity of polymer solutions. The results of new model are compared with the Wilson model proposed by Sadeghi and the NRTL model proposed by Chen. From new model the excess volume is evaluated so we can predict density of polymer solutions. The results of density from new model compared by Poly-Wilson and Poly- NRTL models and show lesser deviation than those models. Also the new model is used to predict excess enthalpy of polymer solutions. The results of new model compared with Poly-Wilson and Poly-NRTL models. The results shows the new model have better accuracy for predicting of excess enthalpy of polymer solutions. The average absolute deviations of thermodynamic properties show that the proposed model has suitable accuracy for correlation and prediction of polymer solution properties. Some diagrams for excess enthalpy, density and viscosity are shown.

Keywords:

Polymer solution , Local surface fraction , Thermodynamic and rheological properties , Gibbs free energy