engleski

Liquid-liquid equilibrium calculations for polymer solutions using the new segmental interaction model

The segmental interaction model containing the combinatorial, free-volume and energetic contributions to the excess Gibbs energy for correlation/prediction of liquid-liquid equilibria (LEE) of polymer solutions has been developed G.Bogdanić, J.Vidal, 16th European Seminar on Applied Thermodynamics, Pont-a-Mouson, France, 1997, Proceedings, p.73; E.Panagou, J.Vidal, G.Bogdanić, Polym.Bull., 40,117-123(1998).The energetic contribution is based on the solution of segment concept. The groups are defined as the polymer or copolymer segments (repeating units) or solvent molecules, as is usually done when applying the mean field theory. Group activity coefficients are calculated through the UNIQUAC model. The informations used to determine the parameters include the experimental LLE data, the densities of the solvent and the polymer at the temperature of the mixture, the van der Waals volumes for the calculation of the free volume-combinatorial contribution, and the molecular surface parameters of the segments for the application of the UNIQUAC model. Previous application of the model was related to the LLE correlation/prediction of nonpolar and moderately polar systems and the present work shows that the extension to a system with strong specific interactions is possible. The lower and upper critical solution temperatures as well as the closed loop diagrams for numerous systems are correlated/predicted, using weakly temperature dependent UNIQUAC parameters. The main limitation is probably the immediate proximity of the critical point of the solvent, where the excess volume of the solution cannot be described.

LLE; correlation; prediction; segmental interaction model; polymer solutions

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