On the Surface Tension and its Temperature Variation in Film-Forming Polymers

Abstract A thermal gradient bar has been used for convenient measurements of γc and dγc/dT in complex polymers used as film-formers. The technique yields both γc and its temperature variation in one experimental sequence well suited for rapid, routine applications. Surface tension data have been obtained for a styrene-acrylic terpolymer, and these have also been used to characterize the compatibility of external plasticizers for the polymer. The surface tension approach has shown that glyceryl dibenzoate, though compatible with the polymer at temperatures above ∼70°C becomes incompatible at use temperatures, and exudes to the polymer film surface. Measurements of moisture sensitivity in plasticized polymer samples have confirmed the incompatibility and illustrated one of the applications to which the gradient bar and its data generation potential may be put.