Emulsions - Recent Advances in Understanding

Surfactant Science Group, Department of Chemistry, University of Hull, 

This chapter reviews the progress in the understanding of emulsions over the last ten years or so. The emphasis is on the factors affecting the type and subsequent stability of emulsions, and on the associated properties of surface-active molecules adsorbed at the oil-water interface. The field of emulsions is a vast area and so the literature covered is selective rather than comprehensive. 

An emulsion may be defined as an opaque, heterogeneous system of two immiscible liquid phases ( oil and water ) where one of the phases is dispersed in the other as drops of microscopic or colloidal size (typically around 1 pm). There are two kinds of simple emulsions, oil-in-water (O/W) and water-in-oil (W/O), depending on which phase comprises the drops. Emulsions made by agitation of the pure immiscible liquids are very unstable and break rapidly to the bulk phases. Such emulsions may be stabilised by the addition of surface-active material which protects the newly formed drops from re-coalescence. An emulsifier is a surfactant which facilitates emulsion formation and aids in stabilisation through a combination of stfrface activity and possible structure formation at the interface. 

The chapter is organised into the following sections Emulsion Type and the System Hydrophile-Lipophile Balance (HLB), Phase Inversion, Emulsion Stability, Gel Emulsions, and Forces between Oil-Water Interfaces. 

2 Emulsion lype and the System Hydrophile-Lipophile Balance 

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