engleski

A segmental interaction model for liquid-liquid equilibrium calculations for polymer solutions

A segment-based thermodynamic model, containing the combinatorial, free-volume and energetic contributions to the excess Gibbs energy for correlation/prediction of liquid-liquid equilibrium (LEE) of polymer solutions has been developed ?1, 4? and in this work is fully presented. The model is derived from the entropic free-volume (entropic-FV) model proposed by Elbro et al. ?5?, following the idea to associate the nonideality of polymer -solvent mixture with polymer segment - solvent interaction parameters. The energetic contribution is based to the individual segments (repeating units) of polymer or copolymer and solvent molecule interactions, as it is done when applying the mean field theory ?6?. Segment activity coefficients are calculated through the UNIQUAC model. In the present state of development 29 binary segmental interaction parameters have been estimated. The capability of the model is demonstrated with successful representation of LLE correlation/prediction for more than 60 polymer-solvent systems. The model is capable to correlate and to predict with satisfactory accuracy the most common types of phase diagrams of LLE of polymer solutions (i.e. phase diagrams of the UCST, LCST, combined UCST and LCST, and "hourglass" types) and provides a thermodynamic framework to describe the LLE phase behavior of polymer solutions, using weakly temperature dependent UNIQUAC parameters.

liquid-liquid equilibrium; polymer solutions; polymer solutions; correlation; prediction

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