engleski

A segmental interaction model for polymer-solvent systems or polymer blends : liquid-liquid equilibria : correlation and prediction

It is well known that liquid-liquid equilibria calculation is very sensitive to components' properties, as well as to the parameters that have been used for their prediction. Furthermore, for polymer solutions or polymer blends, experimental evidence shows that the usual group contribution methods cannot take into account steric constraints depending on the structure of isomeric repeating units. Also, specific features, such as the usual occurrence of lower critical solution temperatures should be considered. The method that will be presented here starts from the "Entropic free-volume" model developed by Elbro et al. (1990), but defines the so-called residual term through a UNIFAC Iike method. 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 (ten Brinke et al., I983), and the recently method proposed by Chen (1993). In the present work, group activity coefficients are calculated through the UNIQUAC model. The validity of the method should be evaluated through the following conditions: prediction of LCST; interaction parameters between repeating units independent of the number of repeating units and of the copolymer composition; interaction parameters weakly dependent on temperature. In spite of the paucity of experimental data, the method has been successfully applied to correlation and prediction of liquid-liquid equilibria, and lower critical solution temperature of the polystyrene, ploy(n-butylmethacrylate) and poly(n-butylmethacrylate-co-styrene) solutions in methyl ethyl ketone, and the previously stated conditions are shown to be fulfilled. /Lit. H.S. Elbro, Aa. Fredenslund and P. Rasmussen, Macromolecules, 23(1990)4707-4714; G. ten Brinke, F.E. Karasz and W.J. MacKnight, Macromolecules,16(1983*1827-1832; C.C. Chen, Fluid Phase Equilibria, 83(1993)301-312./

liquid-liquid equilibria; correlation; prediction; segmental interaction model for polymer-solvent system

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