What is a surfactant? What role does it play in cosmetics?

     Surfactant is a substance with a very special chemical structure and is widely used in the cosmetics industry. It is an auxiliary ingredient in cosmetic raw materials. Although not used in large quantities, it plays a significant role and is used in most products such as facial cleansers, body lotions, skin creams, shampoos, conditioners, toothpaste, etc. It plays a wide range of roles in cosmetics, mainly including emulsification, washing, foaming, solubilization, sterilization, antistatic, dispersion, etc. Here we will elaborate on its four main functions.

(1) Emulsification

      What is emulsification? It is well known that our most commonly used creams, lotions and other skin care products contain both oily ingredients and a large amount of water. They are mixtures of oily ingredients and water, but why can't we see the oil droplets or the seeping water in them to the naked eye? This is because they have formed a very uniform dispersion system, that is, the oily ingredients are evenly dispersed in water in the form of tiny droplets, or the water is evenly dispersed in the oily ingredients in the form of tiny droplets. The former is called oil-in-water, and the latter is called oil-in-water. This type of cosmetic is called an emulsion cosmetic. It is one of the most common types of cosmetics. However, under normal circumstances, oil and water are immiscible. After stirring stops, oil and water return to a层ed state and cannot achieve a stable and uniform dispersion system. The oily components in emulsion products such as creams and lotions can form a well-mixed dispersion system with water because surfactants are added. The special structure of the surfactant enables the immiscible oil and water to mix evenly and form a relatively stable dispersion system, that is, the emulsion. The function of the surfactant in the emulsion is called emulsification, and the surfactant that performs emulsification is called an emulsifier. So, surfactants are present in the creams, lotions and emulsions we use daily.

(2) Washing and foaming effects

      Some surfactants have excellent washing and foaming effects. Soaps, which are very familiar to everyone, are a commonly used type of surfactant. The soaps we use the soap components (surfactants) in them to achieve cleaning and foaming effects. Some cleansing cleansers also work through the soap components in them, but the soap components have stronger cleaning power. It can easily cause the skin to lose fat and is slightly irritating, so dry and sensitive skin should not use this type of cleansing product. In addition, surfactants are used in products such as bath gels, shampoos, hand sanitizers and toothpaste for cleansing and foaming.

(3) Solubilizing effect

      Surfactants can increase the solubility of substances that are insoluble or poorly soluble in water, causing them to dissolve completely in water and eventually form a transparent state. This process is called solubilization, and the surfactants that perform solubilization are also called solubilizers. For example, we want to add an oily component that is very moisturizing to a clear toner, but the oil cannot dissolve in water and can only float on the surface of the toner in the form of small oil droplets. At this point, we can take advantage of the solubicity of the surfactant by adding the surfactant to make the oily component dissolve well in the toner, resulting in a good transparent appearance of the product. It should be noted, however, that the amount of oily ingredients that can be dissolved through solubilization is limited, and large amounts of oily ingredients are difficult to be completely dissolved in water through solubilization. So, as the oiliness increases, the amount of surfactant also needs to be increased to emulsify the oiliness with the water, which is why some toners are opaque and milky white, because they contain more moisturizing oils and the surfactant emulsifies them with the water.

      Surfactants can be classified into four major types based on their structural characteristics: anionic, cationic, amphoteric, and nonionic. Among them, anionic surfactants have better washing and foaming effects and are mostly used in cleaning products; Cationic surfactants are good at killing bacteria, antistatic and softening hair, and are often used in conditioners; Amphoteric surfactants have a weaker washing effect but a better foaming, stabilizing and thickening effect. They are often used to assist anionic surfactants in cleansing products to enhance the cleansing effect and reduce irritation. Nonionic surfactants, which are good at emulsifying and solubilizing, are less irritating and are often used in creams, lotions and water-based products that require solubilization.