emulsionsystem

An emulsion system, or emulsion, is a heterogeneous mixture in which droplets of one immiscible liquid are dispersed throughout another liquid that is the continuous phase. Emulsions are typically stabilized by an emulsifier or stabilizing particles to reduce interfacial tension and to prevent droplet coalescence. The properties of an emulsion depend on the dispersed-phase fraction, droplet size distribution, interfacial tension, and the rheology of the continuous phase. Emulsions are usually kinetically stable, meaning they persist for a time but are not thermodynamically stable.

Common types include oil-in-water (O/W) emulsions, where oil droplets are dispersed in water, and water-in-oil (W/O) emulsions, where water droplets are dispersed in oil. More complex forms include multiple emulsions (such as W/O/W and O/W/O) and microemulsions or nanoemulsions, which differ in stability and droplet size. Emulsifiers can be small-molecule surfactants, polymers, or solid particles (as in Pickering emulsions), and they work by orienting at the oil–water interface to lower interfacial tension and to create a protective interfacial film.

Stability is influenced by factors such as creaming or sedimentation, flocculation, coalescence, and Ostwald ripening. Stabilization strategies include selecting appropriate emulsifiers, optimizing the phase ratio, adding thickeners, and using solid particles to form Pickering emulsions. Emulsion systems are prepared by high-energy methods (homogenization, ultrasonication) or low-energy methods (phase inversion). They are characterized by droplet size analysis, rheology, and interfacial properties. Applications span food, cosmetics, pharmaceuticals, agriculture, and petrochemicals.