(1) Emulsification and demulsification. The emulsification effect of surfactants is one of the most widely used properties of surfactants. For example, emulsifiers play an important role in cosmetics, food, textiles, papermaking, metal cutting fluids, paints, pesticides, medicines, etc. Various types of surfactants can be used as emulsifiers, but nonionic surfactants and anionic surfactants are more commonly used. Emulsification is the process by which two immiscible liquids form an emulsion. An emulsion refers to a liquid that is insoluble or has very little solubility. Droplets of a certain size are dispersed in two liquids, forming an obviously stable suspension. For two immiscible liquids, a stable emulsion cannot be formed by mechanical stirring. To form an obviously stable emulsion, a third component must be added. This third component is a surfactant, generally called an emulsifier.
(2) Solubilization effect. After surfactants form micelles in an aqueous solution, they have the ability to significantly increase the solubility of water-insoluble organic matter, and the solution is transparent at this time. This effect of the micelles is called solubilization. Surfactants that can produce solubilization are called solubilizers, and organic substances that are solubilized are called solubilized substances. If you continue to add the solubilized substance to the solubilized liquid, after reaching the quantitative level, the solution becomes transparent and becomes milky. This emulsion is an emulsion. Add surfactant to this emulsion and the solution becomes Be transparent and colorless. Although this change is continuous, emulsification and solubilization are essentially different. Solubilization can significantly reduce the chemical potential of the solubilized substance and make the system more stable. That is, solubilization is thermodynamically stable. As long as the external conditions remain unchanged, the system does not change with time. Emulsification is thermodynamically unstable.
(3) Washing effect. Washing can be defined as the process of removing dirt from a solid surface immersed in some medium, usually water. In this process, detergent is used to weaken the adhesion between the dirt and the solid surface, and external force is applied, including mechanical stirring or manual washing, to separate the dirt from the solid surface and suspend it in the medium, and then wash the dirt. Water has better wettability on natural fibers, cotton, wool, etc., but worse on man-made fibers. Surfactants can reduce the surface tension of water and reduce its contact angle. Therefore, the wetting of fibers is easier to achieve under the action of detergents.
