Thixotropic Behavior of Oil-in-Water Emulsions Stabilized with Ethoxylated Amines at Low Shear Rates

Abstract

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimOil-in-water (O/W) emulsification is a lubricating pipeline method based on the reduction of the energy frictional loss produced during viscous flow. The flow behavior of heavy O/W emulsions formulated with nonionic surfactants is described. The effects of pH and salinity of the aqueous phase on droplet diameter, stability, and apparent viscosity of O/W emulsions were evaluated. The low-shear Couette flow of O/W emulsions displayed intense shear-thinning and thixotropic behavior. Thixotropy was associated to the droplet deformation energy caused by shear rate changes. The droplet deformation and alignment led to the apparent viscosity reduction compared to the fluid at rest. Thixotropic behavior is supposed to balance between the breakdown and recovery of droplet ordered structures. Emulsion formulation parameters were influenced by the aqueous phase pH, enabling to manage the emulsion properties. The droplet mean diameter of < 18 µm resulted in very stable emulsions.