What are the types of surfactants? How surfactants work?
Surfactant is widely used in the fine chemical industry. It refers to a substance that can significantly reduce the surface tension of the target solution. It has fixed hydrophilic and lipophilic groups and can be oriented on the surface of the solution. Common surfactants are anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants.
Cationic surfactants are mainly nitrogen-containing organic amine derivatives. Since the nitrogen atom in the molecule contains lone pair electrons, it can combine with the hydrogen in the acid molecule by hydrogen bond, so that the amino group is positively charged.
Cationic Surfactant Classification
According to the chemical structure of cationic surfactants, it can be mainly divided into four types: amine salt type, quaternary ammonium salt type, heterocyclic type and loxane salt type.
1. Amine salt type: It is the general name of primary amine salt, secondary amine salt and tertiary amine salt surfactant. Their properties are very similar, mainly the salt formed by aliphatic amine and inorganic acid, which is only soluble in acidic solution. Under alkaline conditions, amine salts easily react with bases to generate free amines and reduce their solubility, so the scope of use is limited.
2. Quaternary ammonium salt type: It is the most important variety of cationic surfactant, and its properties and preparation methods are different from those of amine salt type. Such surfactants are soluble in both acidic and alkaline solutions, have a series of excellent properties, and are compatible with other types of surfactants, so they are widely used.
3. Heterocyclic type: The heterocyclic rings contained in the cationic surfactant molecule are mainly nitrogen-containing morpholine rings, pyridine rings, imidazole rings, piperazine rings and quinoline rings.
4. Halal salt type: Cationic surfactants can be classified into surfactants containing N, P, As, S, I and other elements according to the difference of heteroatoms, but this classification method is rarely used. According to the atoms carrying positive charges, cationic surfactants also include salts, sulfonium salts, iodine salts, and salt compounds.
Cationic Surfactant use
Cationic surfactants have good sterilization, softening, antistatic and anti-corrosion effects and certain emulsifying and wetting properties, and are often used for special purposes such as fungicides, fiber softeners and antistatic agents.
Anionic surfactants are a class of products with the longest development history, the largest output and the largest variety of surfactants. Anionic surfactants are divided into sulfonates and sulfates according to the structure of their hydrophilic groups, which are the main categories of anionic surfactants at present. The various functions of surfactants are mainly manifested in changing the properties of the surface of the liquid, the liquid-liquid interface and the liquid-solid interface, among which the surface (interface) of the liquid is the most important.
Anionic surfactant Types
1. Carboxylate: an anionic surfactant whose hydrophilic group is a carboxyl group, including potassium, sodium, ammonium and triethanolammonium salts of higher fatty acids. The surface-active moiety after ionization in water is the fatty acid anion.
2. Sulfuric acid ester salt: Sulfuric acid is a dibasic acid that can generate sulfuric acid monoester and sulfuric diester when esterification occurs with alcohols. The salt formed by neutralization of sulfuric acid monoester and alkali is called sulfate salt.
3. Phosphate ester salts: Alkyl phosphate ester salts include alkyl phosphoric acid mono- and diester salts, as well as phosphoric acid mono- and diester salts of fatty alcohol polyoxyethylene ethers and phosphoric acid mono- and diester salts of alkylphenol polyoxyethylene ethers . The most common are mono- and diester salts of alkyl phosphates.
4. Sulfonate: After ionization in water, the anion that generates surface activity as sulfonate (R-S03) is called sulfonate type anionic surfactant. Commonly used products are sodium dioctyl succinate sulfonate (Aloso-OT), sodium dodecylbenzene sulfonate and sodium glycocholate. Its water solubility and acid resistance, calcium and magnesium salt resistance are slightly worse than sulfate, but it is not easy to hydrolyze in acidic solution.
Amphoteric surfactants refer to surfactants that have two ionic properties at the same time. However, the so-called double-sided surfactants refer to surfactants composed of anions and cations, that is, there is a cation at one end of the hydrophilic group. And anion, is a surfactant that combines the two together.
Zwitterionic Surfactant use
1. Water treatment in tap water industry, high turbidity water purification, sedimentation, coal washing, mineral processing, metallurgy, iron and steel industry, zinc, aluminum processing industry, electronics industry, etc.
2. It is widely used in petroleum industry, oil production, drilling mud, waste mud treatment, preventing water channeling, reducing friction, enhancing oil recovery and tertiary oil recovery.
3. It is used as a sizing agent for textiles, with stable sizing performance, less sizing, low fabric breakage rate, and smooth cloth surface.
4. Used in the paper industry, one is to improve the retention rate of fillers and pigments. In order to reduce the loss of raw materials and pollution to the environment; the second is to improve the strength of the paper (including dry strength and wet strength), in addition, the use of PAM can also improve the tear resistance and porosity of the paper to improve visual and printing properties
5. Used in food and tea wrapping paper, other industries, food industry, used for cane juice clarification and syrup phosphorus float extraction in the production of cane sugar and beet sugar.
Non-ionic surfactants refer to molecules with ether groups as the main hydrophilic groups in the molecule, which do not dissociate in aqueous solutions, and whose surface activity is reflected by neutral molecules. Nonionic surfactants have high surface activity, good solubilization, washing, antistatic, calcium soap dispersion and other properties, less irritation, and excellent wetting and washing functions.
Nonionic surfactant use
Nonionic surfactants are mainly used in the production of daily industrial products for the production of detergents, cosmetics, medicines, etc. The main components in soaps and detergents are non-ionic surfactants, which remove dirt from solid surfaces through their good wetting, solubilizing, and emulsifying effects during the washing process.
Surfactants in cosmetics
Surfactant can make the immiscible oil phase and water phase mixed together to form a relatively stable dispersion system, that is, emulsion. The role played by surfactants in emulsion is called emulsification. We call surfactants that play an emulsifying role as emulsifiers. Therefore, there are surfactants in the creams and lotions we use every day.
The so-called emulsification means that the most common creams and moisturizing lotions in skin care products contain both oil-soluble ingredients and a lot of water. They are compounds produced by two types of chemical substances: oil-soluble ingredients and water. But why do we see neither the droplets inside nor the water seeping out under the human eye? This is because they have already produced a well-proportioned dispersion management system, that is, oil-soluble components are uniformly dispersed in water in the form of fine liquids, or water is uniformly dispersed in oil-soluble components in the form of fine liquids. The former is called oil-in-water, and the latter is called water-in-oil. These types of skin care products are called solvent-based skin care products, which are the most common type of skin care products. As everyone knows, under all normal conditions, oil and water are miscible with each other. After the mixing is terminated, the oil and water are restored to the level state, and a stable and uniform decentralized management system cannot be achieved. The oil-soluble components and water can often produce a well-mixed dispersed management system. Because of the addition of surfactants, the unique structure of the surfactants can make the two types of chemical substances, oil and water, which are miscible, evenly distributed. Mixed together, and produce a relatively stable dispersion management system, that is, the solvent, the effect that the surfactant fully exerts in the solvent is called emulsification. We call the surfactant that fully exerts the emulsification effect. It is a demulsifier. Therefore, there are surfactants in the creams and moisturizing lotions that everyone usually uses.
Surfactants can increase the solubility of some insoluble or insoluble substances in water, so that they can be completely dissolved in water, and finally form a transparent state. This effect is called solubilization. Agents are also called solubilizers.
Surfactants can expand the solubility of some insoluble or insoluble water-soluble chemicals in water, so that they can be completely dissolved in water, and finally produce a completely transparent situation. Solubilizing surfactants are also called solubilizers. For example, you want to add an oil-soluble ingredient with very good skin care properties to the fully transparent toner, but the oil cannot be dissolved in water, and only floats on the surface of the toner in the form of small droplets. At this time, everyone The solubilization effect of surfactants can be used. According to the addition of surfactants, the oil-soluble ingredients are very well dissolved in the softening water, and the product finally shows an excellent transparent appearance. However, it must be noted that the amount of oil-soluble components dissolved by solubilization is relatively limited, and many oil-soluble components cannot be completely dissolved in water according to the solubilization method. Therefore, with the increase of oil-soluble ingredients, the amount of surfactants must also be increased, and the oil-soluble ingredients and water are formed into an emulsion, which is why some toners are not completely transparent and milky white, because the skin care plants inside There are many oil components, and the surfactant will be the reason for the water emulsion.
3. Cleaning effect
The most extensive and practical basic feature of surfactants is the effect of washing and decontamination. Sodium lauryl sulfate is a commonly used raw material in cleaning series of cosmetics, which can make the skin achieve a good cleaning effect. Amphoteric surfactants imidazoline, cocamidopropyl betaine and amino acids are mild cleaning surfactants, and are indispensable components for the preparation of high-end face wash products, hair care shampoos and baby shampoos.
The phenomenon that surfactants make water-insoluble substances form particles in water and are uniformly dispersed is called dispersion, which maximizes the effects of powdered whitening, concealer and sunscreen.
5. Wetting effect
Cosmetics are inseparable from the wetting effect of surfactants, and biosurfactants have achieved remarkable results in this regard. As an important component of biological cells, phospholipids play an important role in cell metabolism and cell membrane permeability | bioregulation, and have good moisturizing and permeability to human skin. Sophorolipid biosurfactants have a peculiar affinity for the skin, which can make the skin feel soft and moist.
6. Foam effect
The formation of foam is mainly due to the directional adsorption of the active agent, which is caused by the reduction of the surface tension between the gas and liquid phases. Generally, low molecular weight active agents are easy to foam, high molecular weight active agents have less foam, yellow myristate has the highest foamability, and sodium stearate has the worst foamability. For example, sodium alkyl benzene sulfonate has strong foaming properties. Commonly used foam stabilizers include fatty alcohol amides, carboxymethyl cellulose, etc., and foam inhibitors include fatty acids, fatty acid esters, polyethers, etc. and other nonionic surfactants.
Some surfactants have very good cleaning and polyurethane foaming effects. Soaps that everyone knows very well are a very common type of surfactants. Activating agent) to achieve the effect of cleaning and polyurethane foaming. Some cleansers also fully exert the cleaning effect according to the soap ingredients inside, but the soap ingredients have strong cleaning power, which is very easy to cause the skin to de-oil, and the irritation is slightly stronger. , so dry skin and sensitive skin are not suitable for the application of such cleansing products. In addition, the products such as body wash, shampoo, hand sanitizer, and whitening toothpaste are all surfactants that give full play to their cleaning and polyurethane foaming effects.