Influence of microemulsion phases on the preparation of fine-disperse emulsions

Emulsions which are used in cosmetics and for technical applications must fulfil certain requirements concerning fine-dispersity and long-term stability. In practice, besides mechanical energy input the phase behavior of the emulsion system may be utilized to obtain optimal emulsification results. -water emulsions stabilized with nonionic emulsifiers can show a temperature induced phase inversion from an oil-in-water to a water-in-oil type. During phase inversion often a microemulsion phase is passed which is connected with ultralow interfacial tensions between the oily and aqueous phase. Due to this ultralow interfacial tension finely dispersed emulsions with long-term stability can be produced by phase inversion emulsification without high energy input. The review presents important basic properties of the fatty alcohol ethoxylates in oil/water systems and their effects on the emulsifying behavior. ystematic study of emulsion and microemulsion phase behavior certain rules have been established which allow the preselection of optimal emulsification routes and optimal emulsifier/oil combinations. On the basis of these rules an algorithm is described, which is used for the calculation of optimal emulsified mixtures for cosmetic and technical emulsions.