Proceedings (senza ISBN) del ongresso “XIV Congreso Interamericano – III Congreso Argentino de Ingenieria Quimica”, Buenos Aires (RA), 15-18 settembre 1991.
In polymer processing there is a growing need of knowledge about phase bahavior of polymeric mixtures. In particular activity coefficients at infinite dilution of solvents in polymer are useful for evaluating the last step of volatilization of solvents in the drying process.
Correlative and predictive methods are available for the evaluation of activity of solvents in polymeric solutions. Correlative models, such as the well known Flory-Huggins, need specific experimental data for the estimation of parameters. Predictive methods, on the other hand, are based in group contribution and need no specific information about the system. Despite the generality of these methods, they are not able to differentiate among different isomers of the same polymers. In the present work three well characterized polybutadienes differing in structure and in molecular weight were studied. Activity coefficients at infinite dilution of 20 organic compounds of variate polarity were determined at different temperatures by inverse gas chromatography in the three polymers. Flory parameters and infinite dilution partial molar enthalpies were calculated. All the results evidenced the structure differences. Among the polymers these differences were put in evidence also by fitting activity coefficients using the PHCT equation of state.
