Emulsification refers to two liquids (such as oil and water) that are not in phase with each other. One of the liquids is uniformly dispersed into another liquid with very small particles (particle size of 10-8~10-5m). Emulsion. Dispersing oil droplets into water is called oil-in-water emulsion (O/W), and water droplets are dispersed in oil, which is called water-in-oil emulsion liquid (W/O). A surfactant that can help emulsification is called an emulsifier. Surfactants used as emulsifiers have both stabilizing and protective effects.
The emulsifier has the effect of lowering the interfacial tension between the two liquids to stabilize the mixed system. Because when oil (or water) is dispersed into many tiny particles in water (or oil), the contact area between them is enlarged, resulting in an increase in the energy level of the system and an unstable state. When an emulsifier is added, the lipophilic group of the emulsifier molecule is adsorbed on the surface of the oil droplet particles and the hydrophilic group is extended into the water, and a hydrophilic molecular film is formed on the surface of the oil droplet to form a hydrophilic molecular film. It reduces the energy level of the system and reduces the attraction between the oil droplets, preventing the oil droplets from being aggregated and then re-divided into two layers.
The aligning molecular film formed by the surfactant on the surface of the oil droplet is a strong protective film that prevents oil droplets from colliding and accumulating. If it is an oriented molecular film formed by an ionic surfactant, the oil droplets are also charged with the same kind of electric charge, so that the mutual repulsion is increased to prevent the oil droplets from aggregating in frequent collisions.