Wednesday, November 18, 2020
Materials Engineering and Sciences Division (08) (PreRecorded+)
Velidanda S. Tanmay1, Anukta Datta1, Grace Tan1, Sumanth N. Jamadagni2, Geoffrey Reynolds3 and Ronald G. Larson1, (1)Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, (2)Computational Chemistry, Modeling, and Simulation, The Procter & Gamble Company, West Chester, OH, (3)Corporate Analytical Sciences, The Procter & Gamble Company, West Chester, OH
We report a thorough rheological characterization of a lamellar system consisting of a mixture of a cationic surfactant-behentrimonium methosulfate, a fatty alcohol mixture of cetyl and stearyl alcohol and water at surfactant/fatty alcohol mole fractions ranging from 0.1-0.6 and water mass fractions of 85% to 97%. Rheological measurements unveiled interesting signatures of these fluids such as its highly pronounced shear hysteresis behavior, memory of the highest shear subjected to it and a solid-like creep response with the existence of an apparent “yield-stress”.
Particle-image velocimetry showed that these systems develop fracture planes and shear bands at low shear rates of 0.001 s-1 and evolve to a complete plug flow at higher rates starting from 0.01 s-1. The tendency to slip even after the usage of serrated geometries confirmed that we cannot apply the traditional definition of “viscosity” to these systems. Further experiments with parallel plates at different gaps for fixed velocity and fixed shear rates independently showed the viscosity to be gap-dependent and exhibiting some characteristics of solid-like friction. Thus, this work sheds light on the rheo-tribological signatures of lamellar gels and its relevance on the rheological measurements which governs the formulation and processing of these commercial cosmetic emulsions.
Extended Abstract: File Not Uploaded
