USE OF PHASE DIAGRAMS AND DIFFUSION EQUATIONS TO PREDICT SPONTANEOUS EMULSIFICATION

摘要

When two liquid phases are brought into contact without mixing, diffusion can produce local supersaturation in some locations even though both initial compositions are in single-phase regions. In oil/water/surfactant systems the result is spontaneous emulsification. The use of equilibrium phase diagrams and the diffusion equations to understand when such emulsification occurs will be discussed. Examples will be given for situations where aqueous surfactant solutions contact oil, e.g., in detergency applications, and those where oil containing surfactant contacts water, e.g., emulsifiable concentrates of agricultural chemicals and similar products. The latter phenomenon, often called self-emulsification, has recently been studied with videomicroscopy. In this case spontaneous emulsification yielding oil droplets a few microns in diameter was seen in a variety of systems when diffusion and/or chemical reaction caused inversion of a much larger injected drop from an oil-continuous to a water-continuous phase, leading to local supersaturation in oil.