RUSSELL D. COX
Stephenson Speciality Chemicals, Brookfoot House, Low Lane, Horsforth, Leeds, West Yorkshire, LS18 5PU, United Kingdom

Abstract

The use of emulsions is widespread in the personal care industry. This article collects information distributed through a number of sources to provide an insight into the chemistry employed in the development and manufacture of emulsions. The discussion incorporates some physiochemical aspects of emulsion science including the thermodynamics of emulsion stability and the effects of surfactant geometry upon emulsion formation.

EMULSIONS
An emulsion can be best defined as a dispersion of one material inside another non-miscible phase. Generally for products found in the cosmetics and personal care industries the two phases of an emulsion are termed the oil phase and the aqueous or water phase respectively.
Emulsions can be used as vehicles to deliver active ingredients (be they hydrophobic or hydrophilic in nature) to the surface of the skin. In addition to providing a method for active delivery an emulsion also provides the opportunity to tailor the texture, body and sensory character of the resulting finished product.
There are two main types of emulsions, oil in water (O/W) or water in oil (W/O). The means to determine between these emulsion types will be discussed later in this article. More complex emulsion types may possibly be formed, such as; liquid crystal emulsions, Water in Oil in Water, Oil in Water in Oil (ie an emulsion of a droplet that is itself an emulsion) or biemulsions where multiple droplets of immiscible phases exist in the continuous phase. Foams can also be categorised as emulsions where a gaseous phase is dispersed throughout a liquid co ...