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Why Are There Surfactants In Cosmetics?
Jun 11, 2018

There are a wide variety of cosmetics, from cleansing milk, bath dew, to the maintenance of moisturizing cream, essence, and then to the beauty of perfume, lip gloss, and so on, almost everyone will use. Careful people may also pay attention to the composition list of cosmetics, and see what we smear on our faces every day. If there is some understanding of cosmetics, we will notice that, although the ingredients of different cosmetics vary, except for water, it is mainly moisturizing agent, antiseptic, effective component and surface active agent. Moisturizer for moisturizing, effective ingredients are the key to play the role of cosmetics, preservatives make the product have a certain shelf life, then what is the effect of the surface active agent? Don't underestimate the surfactants, because they are an integral part of cosmetics.

Surfactants - we are two sides

Surfactant (surfactant) refers to a class of compounds that can reduce the surface tension of liquids, or the interfacial tension of liquid, liquid and solid phases. Its English name, surfactant, is the synthetic word of the surface active agent [1], indicating that "surfactant is a substance that can enhance the activity of the surface (or interface)".

Soap commonly used in daily life is a typical surfactant. Soap can be used to wash oil stains on clothing and skin, but it is not easy to wash off with water, because oil is insoluble in water. So, why can soap wash oil stains?  This is due to the "two sides" characteristic of surfactant. The composition of soap is a fatty acid metal salt, which is easily soluble in water. We call it "hydrophilic group"; the other is difficult to dissolve in water and is easily soluble in oil. We call it "hydrophobic group" or "Pro oil group". Because of this special structure, soap can be plunged into the water one by one and the other end into oil. In this way, the water pulls the soap molecules, the soap molecules pull the oil again, and pulls the grease stains off the clothes.

Surfactant molecules have hydrophilic groups and lipophilic groups at the same time, which is also called "amphiphilic". Because of the properties of the surfactant, at the appropriate concentration, they form a micelle (micelle) [1] in the water: the hydrophilic head is attracted by the water, and the tail of the oil is repelled by the water. In the process of washing clothes, oil stains are pulled into the micelle by the oil affinity group, and the whole micelle is carried away by water. If they are in an oily environment, they can form inverse micelle, that is, the inside and outside of the head. These micelles play an important role in cosmetics.