Surfactants: The cleaning core of shampoo and laundry detergent
Surfactants: The cleaning core of shampoo and laundry detergent
Among the cleaning products in daily life, shampoo and laundry detergent are our commonly used products. They can effectively remove dirt from hair and clothes, keeping them fresh and clean. Surfactants play a key role behind this. Let's discuss in detail the specific effects of surfactants in shampoo and laundry detergent.
1. Shampoo
Cleaning and decontamination: Hair will absorb dust and grease in daily exposure, and the grease secreted by the sebaceous glands will also combine with pollutants in the air to form stubborn dirt. The surfactants in shampoo, such as sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) in anionic surfactants, have a unique molecular structure. One end is hydrophilic and the other end is lipophilic, which can act like a "bridge" to allow water and oil to interact. The lipophilic end combines with the grease and dirt on the hair, and the hydrophilic end combines with water. Under the mechanical force generated by rubbing, the grease and dirt are wrapped and dispersed in the water, and are taken away with the water when rinsing, achieving hair cleaning.
Foaming effect: Rich and dense foam is one of the characteristics of high-quality shampoo, thanks to surfactants. Surfactants reduce the surface tension of water, making it easier for air to disperse in water to form bubbles, and a film of surfactant molecules arranged in a directional manner is formed around the bubbles to enhance the stability of the bubbles. Consumers often think that rich foam means strong cleaning power, which is not entirely correct, but the foam can better cover the hair, prolong the contact time between the surfactant and the dirt, and assist in cleaning.
Conditioning function: Cationic surfactants such as quaternary ammonium salt compounds are often used in shampoos. The surface of hair is negatively charged, and cationic surfactants are positively charged and can be adsorbed on the surface of hair to form a protective film. It reduces friction between hair, making hair soft and easy to comb, especially for damaged hair, it can fill the damage to the hair scales and make the hair smooth and shiny. In addition, some zwitterionic surfactants such as cocamidopropyl betaine have a certain conditioning effect while cleaning, and are less irritating to the skin.
Solubilization and dispersion: Functional ingredients such as plant extracts and vitamins are often added to shampoos, some of which are difficult to dissolve in water. Nonionic surfactants, such as polyoxyethylene surfactants, can solubilize these insoluble ingredients in the system, making them evenly dispersed, ensuring that the active ingredients act evenly on the hair during use to exert their effects.
2. Laundry detergent
Strong decontamination: Laundry detergent should deal with a variety of stains on clothes, such as oil stains, sweat stains, blood stains, etc. Anionic surfactants are the main force, such as sodium dodecylbenzene sulfonate, which has excellent decontamination ability and can quickly reduce the surface tension of water, allowing laundry detergent to penetrate into the fiber of clothing and decompose and remove dirt. At the same time, non-ionic surfactants such as fatty alcohol polyoxyethylene ether cooperate with it to enhance the emulsification and dispersion ability of oily stains, emulsify large oil droplets into small oil droplets and disperse them in water to prevent oil stains from reattaching to clothing.
Anti-redeposition: When washing clothes, dirt is separated from the clothes and dispersed in the water. If it is not controlled, it may be re-deposited back to the clothes. When cleaning clothes, anionic surfactants will adsorb on the surface of clothes to form a protective film, so that the dirt with the same charge repel each other and it is difficult to attach to clothes again. Some special polymer surfactants also have this function, such as sodium carboxymethyl cellulose, which can improve the dispersion stability of dirt in water and ensure that the clothes are clean after washing.
Softness and anti-static: Cationic surfactants can give clothes a soft effect in laundry detergent. It adsorbs on the surface of clothing fibers, reduces the friction coefficient between fibers, and makes the clothes feel soft. At the same time, cationic surfactants can neutralize the static electricity generated by clothing during friction, reduce the phenomenon of static electricity adsorbing dust, keep clothing clean, and reduce problems such as clothing entanglement and deformation caused by static electricity.
Low-temperature washing performance: Modern life is fast-paced, and people hope to save time and energy by washing at low temperatures. The cloud point characteristics of non-ionic surfactants make them play an important role in low-temperature washing. At low temperatures, non-ionic surfactants can maintain good solubility and surface activity, effectively reduce water surface tension, and ensure that laundry detergent can still penetrate clothing fibers and remove dirt at low temperatures to meet consumer needs.