EVALUATION OF THE FLORY-HUGGINS INTERACTION PARAMETER FOR POLY(STYRENE-CO-ACRYLO-NITRILE) AND POLY(METHYLMETHACRYLATE) BLEND FROM ENTHALPY OF MIXING MEASUREMENTS

A direct determination of enthalpy of mixing (DELTAH(mix)) is of interest in predicting miscibility in polymer - polymer systems. Such measurements present, however, working difficulties, so a reliable indirect approach has been attempted. The enthalpy of mixing DELTAH(m) is obtained by application of Hess law to heat of solution measurement for blends and their components in a common solvent. For SAN/PMMA blend, corresponding to the weight ratio 50:50, the experiments were performed by the Hess law approach at 29.4 and 49.3-degrees-C on dilute polymer solutions, for various concentrations, getting very good correlation data. This le-ads to a negative value of the interaction parameter FH(chi(1,2)) and by DELTAG(mix) diagram it is possible to make a comparison for each temperature in accordance with the LCST behaviour of these mixtures.