Interfacial tension in polymer blends

Theoretical models of the interfacial tension coefficient in polymer blends, v₁₂, were evaluated. A new working relation was derived that makes it possible to compute v₁₂ from the chemical structure of two 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 v₁₂ for 46 blends were found to follow the experimental ones with a reasonable scatter of ± 36%. Next, the experimental methods of v₁₂-measurements were critically examined. Although many have been developed for low viscosity Newtonian fluids, most are irrelevant to industrial polymeric systems. For the present studies two were selected. Values of v₁₂ were measured using the so-called “capillary breakup method,” and a newly developed method based on the retraction rate of deformed drop.