Probing floc structure by ultrasonic spectroscopy, viscometry, and creaming measurements

Information about the structural organization of droplets within flocculate d monodisperse emulsions was obtained using ultrasonic spectroscopy, dynami c shear rheometry, and creaming-rate measurements. The ultrasonic attenuati on and velocity spectra (from 1 to 150 MHz), apparent viscosity (from 0.01 to 1 Pa), and creaming rate of a series of nonflocculated, 14 vol% silicone oil-in-water emulsions stabilized by SDS were measured at 25 degrees C. Me asurements were then repeated after the droplets had been flocculated by ad ding either SDS micelles (0-80 mM) or NaCl (0-400 mM) to the aqueous phase. Differences in the ultrasonic, rheological, and creaming properties of the flocculated emulsions were interpreted in terms of differences in the spat ial distribution of the droplets within the flocs. By combining ultrasound, rheological, and creaming measurements, it was possible to obtain informat ion about flee structure that was not available using each technique indivi dually.