WOemulsies
WOemulsies, also called water-in-oil emulsions, are emulsions in which water droplets are dispersed in a continuous oil phase. The oil phase is typically a nonpolar or slightly polar liquid such as mineral oil, silicone oil, or natural esters; water is the dispersed phase. Droplet sizes commonly range from submicron to a few micrometers and can influence texture and rheology. These emulsions form when lipophilic surfactants reduce interfacial tension and align at the water–oil interface with a low hydrophilic-lipophilic balance (HLB). Common stabilizers include Span series (sorbitan esters) and other oil-soluble emulsifiers, often combined with thickeners or waxes to improve physical stability and viscosity.
Preparation typically involves high-energy methods (high-shear mixing, rotor-stator homogenization, ultrasonic emulsification) or low-energy approaches (phase-inversion methods)
Stability concerns include coalescence of water droplets, Ostwald ripening, and phase inversion after dilution or heating.