Determination of surface activity for different groups pav. Surface-active substance

Surfactants have a polar (asymmetric) structure of molecules that can adsorb at the interface of two media and lower the free surface energy of the system. Completely minor surfactant additives can change the surface properties of the particles and give the material new qualities. The effect of surfactant is based on the phenomenon of adsorption, which leads simultaneously to one or two opposite effects: reduction of interaction between particles and stabilization of the interface between them due to the formation of an interfacial layer. Most surfactants are characterized by a linear structure of molecules, the length of which significantly exceeds the transverse dimensions (Fig. 15). Molecule radicals consist of groups related in their properties to solvent molecules, and from functional groups with properties that are sharply different from them. These are polar hydrophilic groups, having pronounced valence bonds and having a definite impact on wetting, lubricating and other actions related to the concept of surface activity . This decreases the stock of free energy with the release of heat as a result of adsorption. The hydrophilic groups at the ends of hydrocarbon non-polar chains can be hydroxyl - OH, carboxyl - COOH, amino - NH 2, sulfo - SO and other strongly interacting groups. Functional groups are hydrophobic hydrocarbon radicals characterized by side valence bonds. Hydrophobic interactions exist independently of intermolecular forces, being an additional factor contributing to the convergence, “sticking” of non-polar groups or molecules. The adsorption monomolecular layer of surfactant molecules with the free ends of hydrocarbon chains is oriented from

the surface of the particles and makes it non-wettable, hydrophobic.

The effectiveness of the action of a surfactant additive depends on the physicochemical properties of the material. A surfactant that produces an effect in one chemical system may not have any effect or, obviously, the opposite effect in another. It is very important the concentration of surfactants, which determines the degree of saturation of the adsorption layer. Sometimes, high-molecular compounds exhibit a similar effect to surfactants, although they do not alter the surface tension of water, such as polyvinyl alcohol, cellulose derivatives, starch, and even biopolymers (protein compounds). The effect of surfactant may have electrolytes and substances that are insoluble in water. Therefore, to define the concept of "surfactant" is very difficult. In a broad sense, this concept refers to any substance that in small quantities significantly changes the surface properties of a dispersed system.

The classification of surfactants is very diverse and in some cases contradictory. There have been several attempts at classification according to various criteria. According to Rebinder, all surfactants according to the mechanism of action are divided into four groups:

- wetting, defoamers and blowing agents, i.e., active at the liquid-gas interface. They can reduce the surface tension of water from 0.07 to 0.03–0.05 J / m 2;

- dispersants, peptizers;

- stabilizers, adsorption plasticizers and thinners (viscosity reducers);

- detergent substances with all the properties of surfactants.

Abroad, the classification of surfactants according to their functional purpose is widely used: thinners, wetting agents, dispersants, deflocculants, frothers and defoamers, emulsifiers, stabilizers of disperse systems. Binders, plasticizers and lubricants are also distinguished.

According to the chemical structure, surfactants are classified depending on the nature of hydrophilic groups and hydrophobic radicals. The radicals are divided into two groups - ionic and non-ionic, the first can be anionic and cationic.

Nonionic surfactants contain non-ionizing end groups with high affinity for the dispersion medium (water), which usually include oxygen, nitrogen, and sulfur atoms. Anionic surfactants - compounds in which a long hydrocarbon chain of molecules with low affinity for a dispersion medium is part of the anion formed in an aqueous solution. For example, COOH is a carboxyl group, SO 3 H is a sulfo group, OSO 3 H is an ether group, H 2 SO 4, etc. The anionic surfactants include carboxylic acid salts, alkyl sulfates, alkyl sulfonates, etc. Cationic substances form in aqueous solutions cations containing a long hydrocarbon radical. For example, 1-, 2-, 3-, and 4- substituted ammonium, and others. Examples of such substances can be salts of amines, ammonium bases, etc. Sometimes a third group of surfactants is distinguished, which includes amphoteric electrolytes and ampholytic substances, which, depending on from the nature of the dispersed phase can exhibit both acidic and basic properties. Ampholytes are insoluble in water, but are active in non-aqueous media, such as oleic acid in hydrocarbons.

Japanese researchers propose a classification of surfactants according to their physicochemical properties: molecular weight, molecular structure, chemical activity, etc. The gel-like shells on solid particles arising from surfactants as a result of different orientations of the polar and non-polar groups can cause various effects: dilution; stabilization; dispersion; defoaming; binding, plasticizing and lubricating actions.

Positive effect of surfactant has only a certain concentration. On the issue of the optimal amount of surfactant administered, there are very diverse opinions. P. A. Rebinder indicates that for particles

1–10 µm the required amount of surfactant should be 0.1–0.5%. In other sources, values \u200b\u200bof 0.05–1% or more are given for different dispersity. For ferrites, it was found that for the formation of a monomolecular layer with a dry grinding of surfactants, it is necessary to take a rate of 0.25 mg per 1 m 2 of the specific surface of the initial product; for wet grinding - 0.15–0.20 mg / m 2. Practice shows that the concentration of surfactant in each case should be chosen experimentally.

The technology of ceramic SEM can distinguish four areas of use of surfactants, which allow to intensify the physico-chemical changes and transformations in materials and to manage them in the process of synthesis:

- intensification of the processes of fine grinding of powders to increase the dispersion of the material and reduce the grinding time when the specified dispersion is achieved;

- regulation of the properties of physicochemical dispersed systems (suspensions, slips, pastes) in technological processes. Here, the processes of liquefaction (or a decrease in viscosity with an increase in fluidity without a decrease in moisture content), stabilization of rheological characteristics, defoaming in disperse systems, etc, are important;

- management of the process of flare formation during spraying of suspensions upon receipt of specified sizes, shape and dispersion of the spray pattern;

- an increase in the plasticity of the molding masses, especially those obtained when exposed to elevated temperatures, and the density of the manufactured blanks as a result of the introduction of a complex of binders, plasticizers and lubricants.

Surface Active Agents (Surfactant) - chemical compounds that, concentrating on the interface, cause a decrease in surface tension.

The main quantitative characteristic of surfactants is surface activity - the ability of a substance to reduce surface tension at the interface is the derivative of surface tension with respect to surfactant concentration when C tends to zero. However, surfactant has a limit of solubility (the so-called critical micelle concentration or CMC), with the achievement of which, when adding a surfactant to a solution, the concentration at the interface remains constant, but at the same time, self-organization of the surfactant molecules in the bulk solution (micelle formation or aggregation) occurs. As a result of this aggregation, so-called micelles are formed. A distinctive feature of micelle formation is the clouding of the surfactant solution. Aqueous solutions of surfactants, when micelle formation also acquire a bluish tint (gelatinous tint) due to the refraction of light by micelles.

Methods for determining CMC:

Surface tension method
The method of measuring the contact angle with TV. or liquid surface (Contact angle)
Spindrop / Spinning drop method

Surfactant structure

Surfactant classification

Ionogenic surfactants
- Cationic Surfactants
- Anionic Surfactants
Nonionic surfactants
- Alkylpolyglucosides
- Alkyl polyethoxylates

The impact of surfactants on the environment

Surfactants are divided into those that are rapidly destroyed in the environment and those that are not destroyed and can accumulate in organisms in unacceptable concentrations. One of the main negative effects of surfactants in the environment is a decrease in surface tension. For example, in the ocean, a change in surface tension leads to a decrease in CO 2 retention in the body of water. Only a few surfactants are considered safe (alkyl polyglucosides), since their degradation products are carbohydrates. However, when adsorbing surfactant on the surface of particles of earth / sand, the degree / speed of their degradation decreases many times. Since almost all surfactants used in industry and households have positive adsorption on particles of earth, sand, clay, under normal conditions they can release (desorb) heavy metal ions held by these particles, and thereby increase the risk of these substances entering the human organism.

Surfactant in the world ocean

According to some surfactants, adsorbed on the surface of water in reservoirs increases the absorption of the waves of the radar signal. In other words, radar and satellites worse pick up the signal from objects under water in water bodies with a certain concentration of surfactants.

Areas of use

Detergents. The main use of surfactants is as an active component of detergents and cleaners, soap, for the care of premises, dishes, clothes, things, cars, etc. In 2007, Russia produced more than 1 million tons of synthetic detergents, mainly detergents .
Cosmetics. The main use of surfactants in cosmetics - shampoos, where the content of surfactants can reach tens of percent of the total. Also surfactants are used in small quantities in toothpaste, lotions, tonic and other products.
Textile industry. Surfactants are mainly used to remove static electricity on the fibers of synthetic fabric.
Leather industry. Protection of leather products from light damage and sticking.
Paint industry. Surfactants are used to reduce surface tension, which provides easy penetration of the paint material into small depressions on the treated surface and their filling, displacing another substance (for example, water) from there.
Paper industry. Surfactants are used to separate the ink and boiled pulp in the processing of used paper. The surfactant molecules are adsorbed on the ink pigment. The pigment becomes hydrophobic. Next, the air is passed through a solution of pigment and cellulose. Air bubbles are adsorbed on the hydrophobic part of the surfactant and particles of ink pigment float to the surface. See flotation.
Metallurgy. Surfactant emulsions are used to lubricate rolling mills. Reduce friction. Withstand high temperatures at which oil burns.
Plant protection. Surfactants are widely used in agronomy and agriculture for the formation of emulsions. Used to increase the efficiency of transportation of nutrients to plants through the membrane walls.
Food industry. Surfactant is used in ice cream, chocolate, whipped cream and sauces for salads and other dishes.
Oil production. Surfactants are used to hydrophobicize the bottomhole formation zone (PPP) in order to increase oil recovery.

surface-active substance - 3.19 surfactant: Mineral or organic additives introduced into the mixture to increase the adhesion of the binder to the surface of the stone material or to control the formation processes in the mixture. A source … Vocabulary-reference terms of regulatory and technical documentation

The term surfactant The term in English surfactant Synonyms of surfactants Abbreviations Related terms amphoteric surfactant, hydrophobic interaction, dispersion, colloidal chemistry, critical micelle concentration, ... Encyclopedic Dictionary of Nanotechnology

surface-active substance - aktyvioji paviršiaus medžiaga statusas T sritis Standartizacija ir metrologija apibrėžtis Medžiaga, kuri terpta skysčio ar kietojo kūno paviršių sumažina to paviršiaus įtemptį. atitikmenys: angl. surface active substance; surfactant vok. ... ... Penkiakalbis aiškinamasis metrologijos terminų žodynas

surface-active substance - paviršinio aktyvumo medžiaga statusas t sritis chemija apibrėžtis Medžiaga, kuri adsorbuojasi fazi slytyje ir sumažina paviršiaus temptį. santrumpa (os) PAM atitikmenys: angl. surface active substance; surfactant rus. superficially active ... ... Chemijos terminų aiškinamasis žodynas

surface-active substance - aktyvioji paviršiaus medžiaga statusas T sritis fizika atitikmenys: angl. surface active substance; surfactant vok. grenzflächenaktiver Stoff, m; oberflächenaktiver Stoff, m; Tensid, n rus. surface active substance, n pranc. agent tensio ... ... Fizikos terminų žodynas

A substance capable of adsorbing at the interface (for example, liquid and gas) and lowering its surface tension; P. and. at. are used, for example, as detergents, in the preparation of aqueous dispersions ... Big Medical Dictionary

low foaming surfactant - - Topics in the oil and gas industry en low foaming surfactant ... Technical Translator's Guide

See Antiatelectic Factor ... Big Medical Dictionary

In relation to the non-polar phase (gas, hydrocarbon, non-polar surface of a solid), there is a hydrocarbon radical that is pushed out of the polar medium. In an aqueous surfactant solution, an adsorption is formed at the interface with hydrocarbon radicals oriented to the side. As it is saturated (ions) surfactant, compacted in the surface layer, arranged perpendicular to the surface (normal orientation).

Depending on the state of the surfactant in the solution, conditionally distinguish between truly soluble (molecularly dispersed) and colloidal surfactants. The convention of such a division is that the same surfactant can belong to both groups depending on the conditions and chemical. nature (polarity) of the solvent. Both groups of surfactants are adsorbed on the phase boundaries, i.e. they are manifested in solutions, while the bulk properties associated with the onset of the colloidal (micellar) phase are manifested only by colloidal surfactants. These surfactant groups differ in the value of the dimensionless quantity, which is called. hydrophilic-lipophilic balance (HLB) and is determined by the ratio:

where is the affinity (free interaction energy) of the non-polar part of the surfactant to the hydrocarbon (b-dimensionless parameter depending on the nature of the surfactant, -freedom interaction energy per CH 2 group, v is the number of CH 2 groups in the hydrocarbon radical), a - affinity of the polar group k. For colloidal surfactants (b + or, where the indices m correspond to the minimum affinity values \u200b\u200bat which the colloidal properties of surfactants begin to manifest. The minimum number of carbon in the radical for different types of colloidal surfactants lies between 8 and 12, that is, colloidal surfactants have a rather large hydrocarbon radical. However, colloidal surfactants must also have true solubility in, i.e., the polarity of the hydrophilic group must also be sufficiently high. This corresponds to the condition:

In the beginning. 60s. 20 in. D. Davis developed the HLB scale with values \u200b\u200bfrom 0 to 40. Surfactants with lipophilic properties have low HLB values, with hydrophilic-high values. Each group is included in the surfactant is assigned a group number. When adding these numbers get HLB by the formula:

HLB \u003d hydrophilic group numbers + 4-hydrophobic group numbers + 7.

Although the concept of HLB is quite formal, it allows you to determine the scope of the surfactant. So, for the formation of water / oil HLB is in the range of 3-6, oil / yes-8-16, for wetting agents-7-9, for funds-13-15.

Amphoteric (ampholytic) surfactants contain a hydrophilic radical and a hydrophobic part capable of being an acceptor or donor depending on the pH of the solution. Typically, these surfactants include one or more basic and acidic groups, and may also contain a non-ionic polyglycolic group. Depending on the pH value, they exhibit the properties of cation-active or anion-active surfactants. At some pH values, called , Surfactants exist in the form of zwitterions. The ionization constants of acidic and basic groups of truly soluble amphoteric surfactants are very low, however, cation-oriented and anion-oriented zwitterion are most common. As the cationic group, the primary, secondary or tertiary ammonium group is usually used, the residue or. In principle, instead of N m. B. S, P, As, etc. Anionic groups are carboxyl, sulphonate, sulfoether or phosphate groups.

By chemical structure and some similarity of properties ampholytic surfactants are divided into 5 DOS. groups: 1) alkylaminocarboxylic acids RNH (CH 2) n COOH; The alkyl radical is usually normal (straight-chain), but if it is located between the amine group and the carboxyl group, it sometimes has a branched character. Alkylamino-phenylcarboxylic acids RNHC 6 H 4 COOH; alkylaminocarboxylic acids with primary, secondary or tertiary amino group RCH (NH 2) COOH, RCH (NHR) COOH, R (CH 3) NCH 2 COOH; with an intermediate hydroxyl, ester, ester, amide or sulfoamide group; substances with two or more amino and amido groups, with several amino and hydroxyl groups.

2) Alkyl betaines are the most important group of zwitterionic surfactants. They can be divided into 5 DOS. groups: a) alkyl betaines-C-alkyl betaines RCH COO - and N-alkyl betaines RN + (CH 3) 2 CH 2 COO -; b) sulphite-, sul-foo-, sulphate- and phosphate betaine RN + (CH 3) 2 CH 2 CH 2 RN + (CH 3) 2 CH 2 CH 2, RC 6 H 4 CH 2 N + (CH 3) 2 CH 2 CH 2 RN + (CH 3) 2 CH 2 CH (OH) CH 2 OP; c) amidobetaines RCONH (CH 2) 3 N + (CH 3) 2 COO -; d) ethoxylated RN + [(C 2 H 4 O) p H] [(C 2 H 4 O) g H] CH 2 COO -; e) other zwitterionic surfactants.

3) Derivatives of alkyl imidazolines, in which the anionic and cationic groups have approximately the same ionization constants (formulas VII and VIII), where R is alkyl C 7 -C 17, R "-H, Na, CH 2 COOM (M-metal). By betaine surfactants, including a carboxy, sulfo, sulphate or sulfoester group, are distinguished in the structure and methods of synthesis [formula IX; R "\u003d (CH 2) n COO -, (CH 2) 3, CH 2 CH (OH) CH 2] and other ("non-betaine") imidazoline surfactants [formula X; R "\u003d CH 2 COONa, (CH 2) 2 N (CH 2 COOH) 2, (CH 2) 2 N \u003d \u003d CHC 6 H 4 SO 3 H, (CH 2) 2 OSO 3 H]. The balance of the ionized groups ensures these compounds have good colloid-chemical and sanitary-hygienic properties.

4) Alkylaminoalkanesulfonates and sulfates (AAAC 1 and AAAC 2 respectively). Anionic landmark. substances easily transform into the zwitterionic form, which allows them to be isolated in pure form. The ionization constant of the acid group is much larger than the main one, so they are used in an alkaline medium. However, in the case of several main groups, and in the presence of other hydrophilic groups near the acid group, these substances are similar in properties and applications to ampholytic surfactants and have a bactericidal effect. Depending on the ionization constants, it is possible to distinguish AAAC 1 RN (R ") - R: -SO 3 M, AAAC 2 RN (R") - R: - OSO 3 M, derivatives of aromatic amino sulfonic acids RR "N-Ar-SO 3 M, aminosulfonates with N in heterocycles (formula XI), aminophosphates, aminophosphonates and other amino-containing compounds of the type RR "R: P (O) (OH) 2, RR" R "" OP (O) (OH) 2, where R and R " -long and short hydrocarbon radicals, R: -short divalent radical; Comm. RN (CH 2 CH 2 SO 3 Na) 2. Their difference is a good ability to disperse calcium and resistance to.

5) Polymeric ampholytic surfactants: natural (proteins, nucleic acids, etc.); modified natural (oligomeric hydrolysates, sulfatir. chitin); staged foods, fatty acids; derivatives obtained by the introduction of carboxyl and diethanolaminoethyl groups; synthetic, which combine the structural features of all the above groups of amphoteric surfactants (see, for example, formulas XII-XVI).

The use of surfactants.The global production of surfactants is 2-3 kg per capita per year. Approximately 50% of the surfactants produced are used for (detergents and cleaning products, cosmetics), the rest in industry and with. x-ve. Simultaneously with the annual growth of surfactant production, the ratio between their use in everyday life and industry is changing in favor of industry.

The use of surfactants is determined by them, the structure of the adsorption layers and the bulk properties of the solutions. Surfactants of both groups (truly soluble and colloidal) are used as dispersants for drilling hard rocks (hardness reducer), for improving, lowering and wear, oil recovery rates, etc. Dr. an important aspect of the use of surfactants - the formation and destruction,. Surfactants are widely used for regulation and stability with a liquid dispersion medium (aqueous and organic). Micellar systems formed by surfactants in both aqueous and non-aqueous media are widely used, for which it is not the surface activity of surfactants that is important and not the properties of their adsorbers. layers, and bulk properties: pronounced anomalies with an increase in surfactant until the formation, for example in an aqueous medium, crystallization. structures of solid or solid-shaped structures (in based on petroleum oils).

Surfactants are used in more than 100 sectors of the economy. Most of the surfactants produced are used in the composition of the Wed-in, in the production of textiles and products based on synthetic. and prir. fibers. The major consumers of surfactants include oil, chemical. industry, industry builds. materials and a number of others. The most important surfactant applications are:

Drilling with clay solutions and reversible water / oil. To regulate the aggregative stability and rheological characteristics of the solutions, high-molecular-weight water-soluble surfactants, polyacrylamide, etc. are used, and calcium sources are introduced into it. and synthetic fatty acids (C 16 -C 18 and above), alkyl aromatic. alkylamines, alkylamido amines, alkyl imidazolines;

Enhance oil recovery by micellar flooding (ethoxylated and alkylaromatic sulfonates);

Antioxidant, extreme pressure and other additives in the production of the miner. oils (synthetic soaps. fatty acids, petroleum, hydroxyethyl. alcohols) and plastic. lubricants (derivatives, arylamines, alkyl and aryl phosphates);

Regulation with iron and manganese (soaps of natural and synthetic fatty acids, higher aliphatic amines), rare (alkylaronic and alkylphosphonic acids, alkyl aromatic sulfonates);

Emulsion, production and other vinyl (carboxymethylcellulose, poly, synthetic. Fatty acids, alkyl sulfates, and alkylphenols);

Chemical production fibers (hydroxyethyl. and amides, and, higher and acids);

Mechanical restoration

Surfactants are compounds that influence the amount of surface tension. In the process of interaction of liquid molecules between them are formed adhesion forces. This force will be different in the surface and internal (deep) layers. Considering the state of the liquid, it is easy to establish that the particles that are directed into the system are surrounded from different sides by the same molecules that affect them. The resultant of all the forces that act on such a molecule is zero. Therefore, liquids have the smallest surface at a given volume. This is clearly manifested in the spherical shape of the droplets. The presence of impurities of various compounds in liquids causes the magnitude of the surface tension.

The structure of surfactant molecules

Particles of fatty acids and alcohols consist of two parts, which have different properties, so these compounds are often called diphilic structures. One part of the molecule is represented by a hydrocarbon chain, and the other is represented by different functional groups (amino, hydroxyl, carboxyl, sulfo). The longer the hydrocarbon chain, the stronger the particles will be expressed, they will interact less with water.

Surfactants of organic origin: proteins, soaps, alcohols, ketones, aldehydes, tannids, ketones, etc. Surface-inactive substances do not affect surface tension (starch, glucose, fructose).

Nonionic surfactants (nonionic surfactants) are high-molecular biocompounds that do not form ions in water. These substances enter water bodies together with industrial (chemical, textile, household use (use of various household products), as well as waste from agricultural land (herbicides, fungicides, insecticides, and folios as emulsifiers).

Surfactants: harm and benefits

Surface tension is of paramount importance for the absorption processes in the intestine. For example, fats and lipids in the alimentary canal come in the form of drops. The latter are emulsified in the small intestine with the help of bile acids. Only after this, these fats are hydrolyzed by lipolytic enzymes. Very often, soap (surfactants) is added to increase the effectiveness of insecticides. The manipulation allows insecticides to interact better with the surface of the body of insects. However, surfactants have not only positive but also negative effects on the body. For example, the shampoo contains very harmful blowing agents (surfactants), such as sodium and ammonium lauryl sulfate, ammonium and sodium laureth sulfate. It is believed that these components have a carcinogenic effect.

Surface-active substances (surfactants) are such chemicals that are able to concentrate on the phase boundaries and reduce the surface (interfacial) tension. Surfactants are used in pharmaceuticals and cosmetics, in the manufacture of shampoos and foam detergents.

Chemical structure of surfactants

The surfactant molecule consists of a hydrophobic hydrocarbon radical and a hydrophilic polar (functional) group, i.e. the molecule is diphilic, as a result of which it has a high adsorption capacity. For example, in a water / oil emulsion at the interface, the hydrophilic group of the surfactant molecule is oriented toward water, and the hydrocarbon portion toward oil. And the interfacial tension at the same time decreases, which provides stabilization of oil droplets in water.

The detergent effect of surfactants is based on the fact that the surface-active ingredients of lotions, shampoos, soaps are adsorbed on the surface of such contaminants as grease and solid particles, envelop and facilitate their transfer to the washing solution. Surfactants facilitate the spreading of water on the skin surface or products based on them by reducing the interfacial tension.

Types of surfactants

The classification of surfactants is based on the division depending on the nature of the polar group: non-ionic, not dissociating in water into ions, and ionic, which, depending on the charge formed during dissociation of ion in water, are divided into: anionic, cationic, amphoteric.

Anionic surfactants, when dissolved in water, form negatively charged ions with a long hydrocarbon chain (organic anions) and a common cation. Anionic surfactant emulsifiers are very effective:

when creating oil / water emulsions;
when dispersing a number of powdered materials;
when used in foaming agents to ensure high foaming in hard water.

An example of anionic surfactant, which is often used in cosmetic formulations, in particular detergents, is sodium lauryl ethoxide (according to INCI nomenclature “Sodium Laureth Sulfate”). It is produced by sulphating saturated or unsaturated primary higher alcohols, followed by neutralization with sodium alkali, ammonia or triethanolamine. Often made in the form of a pasty mass containing up to 70% of the basic substance.

When dissolved in water, cationic surfactants form positively charged ions (organic cations) and a low molecular weight anion. Cationic surfactants include salts of fatty amines and quaternary ammonium bases. Cationic emulsifiers, compared with anionic, less effective because they reduce the surface tension to a lesser extent. But they show bactericidal activity, interacting with the cellular proteins of bacteria. Cationic surfactants are widely used in hair care products (shampoos, conditioners, conditioners for hair). Aliphatic cationic surfactants with one and two hydrocarbon tails are good antistatic agents and are used in cosmetics for hair.

Amphoteric surfactants, depending on the pH of the medium, behave in an alkaline medium as anion-active or in an acidic medium as cation-active. In their molecules, there are functional groups that can have both negative and positive charge. Such surfactants are well compatible with cationic and anionic. Amphoteric surfactants act dermatologically on the skin, which is why they are often used in children's shampoos without tears and for sensitive skin. For example, in combination with anionic surfactant sodium lauryl sulfate, its dermatological rigidity is almost completely softened. Amphoteric surfactants have good foaming.

Betains are one of the varieties of amphoteric surfactants. They belong to the soft and highly foamed surfactants. Amphoteric surfactant cocamidopropyl betaine (Dechiton / Betadet) is included in cosmetics in the production of shampoos, gels and cream-gels, liquid soap, cleansing bath foams. This surfactant contributes to the compatibility of cosmetics with the skin, while improving the viscosity and foaming of this tool. Thus, Dehiton, especially in children's washing-up products, is an emollient component and contributes to the safety of using detergent.

Non-ionic (non-ionic) surfactants are surfactants that, when dissolved in water, do not form ions. They, in comparison with anionic ones, having a weaker foaming ability, have a milder effect on the skin. Such surfactants are often used as emulsifiers, dispersants, solubilizers, and also as co-surfactants, foam stabilizers, wetting agents, etc. An example of a non-ionic surfactant is fatty acid diethanolamides. Used in the manufacture of shampoos and foaming agents in an amount up to 3% as a perezhiruyuschey additive, foam stabilizer and thickener.

In Russian-made shampoos, various combinations of surfactants are used depending on the purpose of the cosmetic product to achieve the required consumer properties and improve the quality.

Surfactants used in the cosmetic industry must comply with the Unified sanitary-epidemiological and hygienic requirements for goods subject to sanitary-epidemiological supervision (control).

The advantages of using surfactants:

lead to the stabilization of the dispersed system, make it impossible for the sticking and coagulation of the particles of the dispersed phase;
facilitate the dispersion process and the preparation of cosmetic compositions;
improve the wettability and flowability of cosmetic substances on the skin;
ensure the stability of inverse emulsions;
in the composition of the washing means they improve their foaming and increase the stability of the foam during use.

Literature

Surfactants and compositions. Directory. Edited by M.Yu. Pletnev 2002. - pp.40-44.

Basics of cosmetic chemistry. Basic positions and modern ingredients. Ed. Puchkova T.V. 2011, p.122-133.

Explanatory Dictionary of Cosmetics and Perfumery v.1 Finished products 2nd ed. 2004. p.20.