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 inter est in predicting miscibility in polymer - polymer systems. Such measu rements present, however, working difficulties, so a reliable indirect approach has been attempted. The enthalpy of mixing DELTAH(m) is obta ined by application of Hess law to heat of solution measurement for bl ends and their components in a common solvent. For SAN/PMMA blend, cor responding to the weight ratio 50:50, the experiments were performed b y the Hess law approach at 29.4 and 49.3-degrees-C on dilute polymer s olutions, for various concentrations, getting very good correlation da ta. This le-ads to a negative value of the interaction parameter FH(ch i(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 m ixtures.