EQUILIBRIUM-CONSTANTS AND THE PREDICTION OF MISCIBILITY WINDOWS FOR POLYMER BLENDS CONTAINING POLY(TETRAFLUOROETHYLENE-ALT-VINYL ALCOHOL)

Theoretical calculations of miscibility windows for binary polymer ble nds in which one component is an essentially alternating copolymer of tetrafluoroethylene and vinyl alcohol (FVOH) are reported. FVOH has an inherently low solubility parameter [almost-equal-to 6.2 (cal. cm-3)0 .5] that is outside the range commonly encountered in miscible polymer blends and thus represents a stringent test of the predictive capabil ities of an association model we have used in previous work. The appli cation of this model requires that we determine dimensionless equilibr ium constants describing the self-association of a model compound 3,4- pentafluorobutan-2-ol (PFB) at 25-degrees-C from infrared spectroscopi c data. Analogous equilibrium constants for FVOH were scaled from thos e of PFB by taking into account differences in the molar volume of the model and the specific repeat of the copolymer (see M. M. Coleman, J. F. Graf, and P. C. Painter: Specific Interactions and the Miscibility of Polymer Blends, Technomic, Lancaster, PA, 1991). Equilibrium const ants describing the inter-association of FVOH with ester type carbonyl groups were obtained from spectroscopic studies of miscible blends wi th poly (ethyl methacrylate). These equilibrium constant values were t hen used to calculate theoretical miscibility windows for the complete range of blends of FVOH with polymethacrylates, ethylene-co-methyl ac rylate, styrene-co-methyl acrylate, and ethylene-co-vinyl acetate copo lymers. Experimental results performed in our laboratories confirm the general validity of the predicted miscibility windows.