Processing-relevant relationships between the microstructure and flow behavior of concentrated surfactant solutions were determined by a combination of basic rheological experiments, rheo-flow velocimetry tests, and flow birefringence measurements. The most common surfactant microstructures found in liquid soaps and other consumer care products—spherical, worm-like, and hexagonally packed micelles and lamellar structures—were recreated by varying the concentration of sodium laureth sulfate in water from 20 to 70 wt% and adding salt in some cases. It was found that common features of flow curves, such as power-law shear thinning behavior, resulted from a wide variety of material responses including shear-induced wall slip in micellar samples and plug flow in lamellar samples. Knowledge of key processing-structure-property relationships for concentrated solutions will allow engineers to develop more efficient industrial workflows for the scalable manufacturing of materials and feedstocks with reduced economic and environmental costs.
Surfactant pastes, Shear thinning, Ultrasonic speckle velocimetry, Birefringence, Phase behavior
Date of this Version
Caicedo-Casso, Eduard & Bice, Jason & Nielsen, Lisa & Sargent, Jessica & Lindberg, Seth & Erk, Kendra. (2019). Rheo-physical characterization of microstructure and flow behavior of concentrated surfactant solutions. Rheologica Acta. 58. 10.1007/s00397-019-01147-x.