HLD–NAC and the Formation and Stability of Emulsions Near the Phase Inversion Point

Abstract

It is well-known that surfactant–oil–water (SOW) emulsions undergo substantial changes in drop size (10-fold or more) and stability (up to 4 orders of magnitude) near the phase inversion point. Predicting these changes is important in numerous applications. However, the complex connection between composition, formulation properties, and hydrodynamic conditions limits the ability to predict the outcome of emulsification and demulsification processes. To address this gap, the hydrophilic–lipophilic deviation (HLD) was used to quantify the proximity to the inversion point, considering the composition of the formulation, temperature, and electrolyte concentration. The net-average-curvature (NAC) equations combined with the HLD predicted the density, interfacial tension, interfacial rigidity, and viscosity for the sodium dihexyl sulfosuccinate (SDHS)–toluene–water system. The predicted properties were incorporated in hydrodynamic models to predict the initial emulsion drop size. The calculated properties and i...