Ultrasonic study of oil/water emulsions stabilized with nonionic block copolymers

Abstract

An increment in sound velocity at 2 MHz has been observed as the emulsion globule size decreases with time in a water, toluene, and polyoxethylene (POE)—polyoxypropylene (POP) block copolymer system. The observed effect depends on the copolymer concentration and is largest for the block copolymer composed of 50% POE–50% POP moieties. A general acoustical treatment taking into account viscous loss in the emulsions globules as well as surrounding liquid and heat conduction across the interface fails to explain the observed velocity increment. Aqueous solutions of the above copolymer shows association effects as evidenced by a break in the sound velocity versus concentration curve at approximately 15 g/l. [Work supported by ONR.]