The activity of the surfactant refers to its ability to reduce the surface or interface tension on the interface. There are two types of surfactant molecules: hydrophilic head and hydrophobic tail group. When the surfactant is dissolved in the water, its hydrophilic head is facing the water phase, and the hydrophobic tail group faces air or oil. This arrangement makes the surfactant molecules form a adsorption layer on the liquid-gas or liquid-liquid interface.
Due to the special structure of the surfactant molecule, hydrophilic heads can form hydrogen bonds or charge with water molecules, and hydrophobic tail groups can contact oil molecules or air. This adsorption layer can reduce the surface tension of the liquid interface and make the interface more stable. The activity of the surfactant depends on the degree of lowering the surface tension on the interface.
By reducing the surface tension, the surfactant can improve the moisture and lubrication of the liquid, promote emulsification and decentralization, enhance the stability of the emulsion, and provide foamability. Surface active agents with high activity can more effectively reduce the surface tension and have better dispersion, emulsification and cleaning capabilities.
In cosmetics, the activity of surfactants is crucial to the function and performance of the product. Different types of surfactants have different activity, so you need to choose the appropriate surfactant according to specific applications and needs to achieve the expected effect.