INTERFACIAL-TENSION IN POLYMER BLENDS

Theoretical models of the interfacial tension coefficient in polymer b lends, nu(12), were evaluated. A new working relation was derived that makes it possible to compute nu(12) from the chemical structure of tw o polymers. The calculations involve determination of the dispersive, polar and hydrogen-bonding parts of the solubility parameter from the tabulated group and bond contributions. The computed values of nu(12) for 46 blends were found to follow the experimental ones with a reason able scatter of +/- 36%. Next, the experimental methos of nu(12)-measu rements were critically examined. Although many have been developed fo r low viscosity Newtonian fluids, most are irrelevant to industrial po lymeric systems. For the present studies two were selected. Values of nu(12) were measured using the so-called ''capillary breakup method,'' and a newly developed method based on the retraction rate of deformed drop.