emulsiune

An emulsiune, also known as an emulsion, is a heterogeneous mixture composed of two immiscible liquids in which one liquid forms droplets dispersed in the other. The liquid that forms the dispersed droplets is called the dispersed phase, while the surrounding liquid is the continuous phase. Emulsions require an emulsifier, surfactant, or stabilizing particles to reduce interfacial tension and prevent droplets from coalescing.

Common types are oil-in-water (O/W), where oil droplets are dispersed in water, and water-in-oil (W/O), where water droplets are dispersed in oil. More complex systems include multiple emulsions such as water-in-oil-in-water and oil-in-water-in-oil, and Pickering emulsions stabilized by solid particles.

Stability depends on droplet size, interfacial film, and interactions among droplets. Emulsifiers can be surfactants, natural emulsifiers like proteins and lecithin, or solid particles (Pickering). Methods to create emulsions include mechanical stirring, high-shear homogenization, phase inversion, and ultrasonication. Factors such as temperature, pH, ionic strength, and shear influence stability and rheology.

Emulsions have wide applications in food (mayonnaise, vinaigrette, milk), cosmetics (creams, lotions), pharmaceuticals (drug delivery), and industry (paints, coatings). They are also used in controlled-release systems and as proxies in research on interfacial phenomena.

Common instability modes include creaming or sedimentation, coalescence, flocculation, and Ostwald ripening. Characterization often involves measuring droplet-size distribution, zeta potential, and rheology to assess stability and texture.