Rheo-physical characterization of microstructure and flow behavior of concentrated surfactant solutions

Effects of shear-induced crystallization on the complex viscosity of lamellar-structured concentrated surfactant solutions

“…Interestingly, the flow behavior and viscosity at 20 1C, 35 1C, and 90 1C across the range of shear rates examined were very similar with slight deviations at the highest applied shear rates that were most likely due to shear-induced flow instabilities. 23 The presence of significant flow instabilities in rotational experiments 23 was a key driving factor for utilizing oscillatory tests in this study. The apparent viscosity of a polymer or surfactant solution typically will increase with decreasing temperature.…”

“…23 At the highest concentration, the presence of significant flow instabilities such as wall slip, shear banding, and plug flow was detected. 23,32 An industrial workhorse used extensively in cleaning product formulations, 33 aqueous solutions of anionic SLES were chosen because they can easily recreate the raw feedstocks and microstructures often observed in consumer products. Even though SLES is a common component of many commercial products, there has been limited published research on its flow behavior, temperature dependence, and phase evolution in pure systems.…”

“…20,21 Interestingly, the apparent viscosity of the more concentrated lamellar phase is often lower than that of the less concentrated hexagonal phase. 22,23 Due to its microstructure of closely packed cylindrical micelles, the high-viscosity hexagonal phase can be very difficult to process and is generally avoided by industrial formulators. 24 In contrast, the lamellar phase has a microstructure composed of stacked parallel surfactant bilayers which flows easily when exposed to shear forces and requires less energy inputs during processing.…”

“…24 In contrast, the lamellar phase has a microstructure composed of stacked parallel surfactant bilayers which flows easily when exposed to shear forces and requires less energy inputs during processing. 22,23…”

Special issue devoted to novel trends in rheology

“…This issue includes nine manuscripts which demonstrate the power of multiple particle tracking microrheology to characterize cell mobility in a biological phenomenon as fundamental as wound healing (Daviran and Schultz 2019), and the use of microfluidic flows to quantify how confinement on bacteria has a significant effect on the behavior of a solution of active swimmers (Liu et al 2019). The current focus in rheology on complex fluid systems is seen through studies quantifying how the detailed surface chemistry of clay particles alters the interfacial layer between oil and water in emulsions and can be used to control the interfacial and bulk rheology of water-oil emulsions (Hong et al 2019), how complex structures in seemingly simple surfactant solutions demonstrate the need for caution in interpreting rheology and informing processing (Caicedo-casso et al 2019), and the ability to use composition to control rheology of block copolymer solutions (Qavi and Foudazi 2019). Polymeric materials maintain importance in the field, and we see the potential trade-off between processability and association strength in ionomers and other associating polymer systems through nonlinear extensional properties (Hinton and Alvarez 2019) and how the concentration of ions in polyacid solutions impact the solgel transition through syneresis on rheology and flow behavior (Han et al 2019).…”