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

Surfactants have a polar (asymmetric) molecular structure, are able to adsorb at the interface between two media and reduce the free surface energy of the system. Quite minor additions of surfactants can change the surface properties of the particles and give the material new qualities. The action of surfactants is based on the phenomenon of adsorption, which simultaneously leads to one or two opposite effects: a decrease in the 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). Molecular radicals consist of groups that are related in their properties to solvent molecules, and of functional groups with properties that are sharply different from them. These are polar hydrophilic groups, having pronounced valence bonds and having a certain effect on wetting, lubricating and other actions associated with the concept of surface activity . In this case, the stock of free energy decreases with the release of heat as a result of adsorption. Hydrophilic groups at the ends of non-polar hydrocarbon 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 secondary valence bonds. Hydrophobic interactions exist independently of intermolecular forces, being an additional factor contributing to the convergence, "sticking together" of non-polar groups or molecules. The adsorption monomolecular layer of surfactant molecules is oriented by the free ends of hydrocarbon chains from

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

The effectiveness of a particular surfactant additive depends on physical and chemical properties material. A surfactant that has an effect in one chemical system may have no effect or the opposite effect in another. In this case, the surfactant concentration is very important, which determines the degree of saturation of the adsorption layer. Sometimes high-molecular compounds exhibit an action similar to surfactants, although they do not change the surface tension of water, such as polyvinyl alcohol, cellulose derivatives, starch, and even biopolymers (protein compounds). The action of surfactants can be exerted by electrolytes and substances insoluble in water. Therefore, it is very difficult to define the concept of "surfactant". In a broad sense, this concept refers to any substance that, in small quantities, noticeably changes the surface properties of the dispersed system.

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

- wetting agents, defoamers and foaming 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/m2;

– dispersants, peptizers;

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

- detergents that have all the properties of surfactants.

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

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

Nonionic surfactants contain non-ionizable end groups with a high affinity for the dispersion medium (water), which usually include oxygen, nitrogen, and sulfur atoms. Anionic surfactants are compounds in which a long hydrocarbon chain of molecules with a low affinity for the dispersion medium is part of the anion formed in 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. Anionic surfactants include salts of carboxylic acids, alkyl sulfates, alkyl sulfonates, etc. Cationic substances form cations containing a long hydrocarbon radical in aqueous solutions. For example, 1-, 2-, 3- and 4-substituted ammonium, etc. Examples of such substances can be amine salts, ammonium bases, etc. Sometimes a third group of surfactants is distinguished, which includes amphoteric electrolytes and ampholytic substances, which, depending on by the nature of the dispersed phase, they can exhibit both acidic and basic properties. Ampholytes are insoluble in water, but 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. Gel-like shells on solid particles arising due to surfactants as a result of different orientations of polar and non-polar groups can cause various effects: liquefaction; stabilization; dispersion; defoaming; binding, plasticizing and lubricating action.

A surfactant has a positive effect only at a certain concentration. There are very different opinions on the issue of the optimal amount of surfactants to be introduced. P. A. Rebinder points out that for particles

1–10 µm required amount Surfactant should be 0.1-0.5%. Other sources give values of 0.05–1% or more for different fineness. For ferrites, it was found that for the formation of a monomolecular layer during dry grinding of surfactants, it is necessary to take at the 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 surfactants in each case should be selected experimentally.

In the technology of ceramic SEMs, four areas of application of surfactants can be distinguished, which make it possible to intensify physical and chemical changes and transformations in materials and control them during 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 physical and chemical disperse systems (suspensions, slurries, 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 dispersed systems, etc. are important;

– control of flame formation processes when spraying suspensions upon obtaining the specified dimensions, shape and dispersion of the spray plume;

– an increase in the plasticity of molding masses, especially those obtained under the influence of elevated temperatures, and the density of manufactured blanks as a result of the introduction of a complex of binders, plasticizers and lubricants.

Surfactants (surfactant) - chemical compounds, which, 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 phase boundary - this is the derivative of surface tension with respect to surfactant concentration as C tends to zero. However, surfactants have a solubility limit (the so-called critical micelle concentration or CMC), with the achievement of which, when a surfactant is added to a solution, the concentration at the phase boundary remains constant, but at the same time, self-organization of surfactant molecules in a bulk solution occurs (micelle formation or aggregation). As a result of this aggregation, so-called micelles are formed. hallmark micelle formation is the turbidity of the surfactant solution. Aqueous solutions of surfactants, during micelle formation, also acquire a bluish tint (gelatinous tint) due to the refraction of light by micelles.

Methods for determining CMC:

Surface tension method
Method for measuring the contact angle with TV. or liquid surface(contact angle)
Spindrop/Spinning drop method

Surfactant structure

Surfactant classification

Ionic surfactants
- Cationic surfactants
- Anionic surfactants
Nonionic surfactants
- Alkyl polyglucosides
- Alkylpolyethoxylates

The impact of surfactants on the environment

Surfactants are divided into those that are rapidly destroyed in 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 the retention of CO 2 in a body of water. Only a few surfactants are considered safe (alkylpolyglucosides), since their degradation products are carbohydrates. However, when surfactants are adsorbed on the surface of earth/sand particles, the degree/rate of their degradation decreases many times over. Since almost all surfactants used in industry and household, have a 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 body.

Surfactants in the oceans

According to some reports, surfactants, adsorbed on the surface of water in reservoirs, increase the absorption of radar signal waves. In other words, radars and satellites are worse at capturing the signal from underwater objects 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 cleaning products, soap, for the care of premises, dishes, clothes, things, cars, etc. In 2007, more than 1 million tons of synthetic detergents, mainly - washing powders.
Cosmetics. The main use of surfactants in cosmetics is shampoos, where the content of surfactants can reach tens of percent of the total volume. Surfactants are also used in small amounts in toothpaste, lotions, tonics, and other products.
Textile industry. Surfactants are mainly used to remove static electricity on the fibers of synthetic fabric.
leather industry. Protection leather goods from light damage and sticking.
Paint industry. Surfactants are used to reduce surface tension, which ensures that the paint material easily penetrates into small depressions on the treated surface and fills them while displacing another substance (for example, water) from there.
Paper industry. Surfactants are used to separate ink and boiled pulp in the recycling of used paper. 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 the 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 to form emulsions. They are used to increase the efficiency of transporting nutrients to plants through membrane walls.
Food industry. The surfactant is used in ice cream, chocolate, whipped cream and dressings for salads and other dishes.
Oil production. Surfactants are used to hydrophobize the bottomhole formation zone (BFZ) in order to increase oil recovery.

surface-active substance- 3.19 superficial active substance: 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 … Dictionary-reference book of terms of normative and technical documentation

Surfactant term English term surfactant Surfactant synonyms Abbreviations Associated terms amphoteric surfactant, hydrophobic interaction, dispersion, colloid chemistry, critical micelle concentration,… … encyclopedic Dictionary nanotechnology

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

surface-active substance- paviršinio aktyvumo medžiaga statusas T sritis chemija apibrėžtis Medžiaga, kuri adsorbuojasi fazių sąlytyje ir sumažina paviršiaus įtemptį. santrumpa(os) PAM atitikmenys: engl. surface active substance; surfactant superficially active ... ... Chemijos terminų aiskinamasis žodynas

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

Substance capable of being adsorbed at an interface (e.g. liquid and gas) and reducing it surface tension; P. a. in. are used, for example, as detergents, in the preparation of aqueous dispersions ... Big Medical Dictionary

low foaming surfactant- — Topics oil and gas industry EN low foaming surfactant … Technical Translator's Handbook

See Antiatelectic Factor... Big Medical Dictionary

In relation to the non-polar phase (gas, hydrocarbon, non-polar surface of a solid body), a hydrocarbon radical is possessed, which is pushed out of the polar medium. In an aqueous solution of a surfactant, an adsorption surfactant is formed at the boundary with hydrocarbon radicals oriented towards . As it becomes saturated, the (ions) of the surfactant, condensing in the surface layer, are located perpendicular to the surface (normal orientation).

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

where is the affinity (free energy of interaction) of the non-polar part of the surfactant to the hydrocarbon (b is a dimensionless parameter depending on the nature of the surfactant, is the free energy of interaction per one CH 2 group, v is the number of CH 2 groups in the hydrocarbon radical), a -affinity of the polar group for . For colloidal surfactants (b + or , where the indices m correspond to the minimum affinity values at which the colloidal properties of the surfactant begin to manifest themselves. The minimum number of carbons in the radical for different types colloidal surfactants lies in the range of 8-12, i.e. colloidal surfactants have a fairly large hydrocarbon radical. At the same time, 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 20th century D. Davis developed the HLB scale with values from 0 to 40. Surfactants with lipophilic properties have low HLB values, those with hydrophilic properties have high ones. Each group included in the surfactant is assigned a group number. When these numbers are added together, HLB is obtained by the formula:

HLB = hydrophilic group numbers + 4 hydrophobic group numbers + 7.

Although the concept of HLB is rather formal, it allows one to determine the areas of application of surfactants. So, for the formation of water / oil, HLB lies in the range of 3-6, oil / water yes-8-16, for wetting agents - 7-9, for agents - 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 nonionic polyglycol group. Depending on the pH value, they exhibit the properties of cationic or anionic surfactants. At certain pH values, naz. , Surfactants exist in the form of zwitterions. The ionization constants of acidic and basic groups of truly soluble amphoteric surfactants are very low, but cation-oriented and anion-oriented zwitterions are most common. The cationic group is usually a primary, secondary or tertiary ammonium group, residue or. In principle, instead of N m. b. S, P, As, etc. The anionic groups are carboxyl, sulfonate, sulfoether or phosphate groups.

According to chem. structure and some similarity of properties, ampholytic surfactants are divided into 5 main. 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. The same group includes alkylamino-phenylcarboxylic acids RNHC 6 H 4 COOH; alkylaminocarboxylic acids with a primary, secondary or tertiary amino group RCH (NH 2) COOH, RCH (NHR) COOH, R(CH 3)NCH 2 COOH; with an intermediate hydroxyl, ether, 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 bases. groups: a) alkylbetaines -C-alkylbetaines RCH COO - and N-alkylbetaines RN + (CH 3) 2 CH 2 COO - ; b) sulfite-, sul-pho-, sulfate- and phosphate betaines 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 alkylimidazolines, in which 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 structure and methods of synthesis, betaine surfactants are isolated, including carboxy-, sulfo-, sulfate- or sulfoester group [formula IX; R "= (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 ionized groups provides these compounds have good colloid-chemical and sanitary-hygienic properties.

4) Alkylaminoalkane sulfonates and sulfates (AAAC 1 and AAAC 2 respectively). Anionic reference. substances easily pass into the zwitterionic form, which makes it possible to isolate them in their pure form. The ionization constant of the acid group is much greater than the basic group, so they are used in alkaline environment. However, in the case of several main groups and in the presence of other hydrophilic groups next to the acid group, these substances are similar in properties and areas of application to ampholytic surfactants and have a bactericidal effect. Depending on the ionization constants, 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 amine-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; conn. 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, sulfatyr. chitin); step products, fatty acids; derivatives obtained by introducing carboxyl and diethanolaminoethyl groups; synthetic, which combine structural features all the above groups of amphoteric surfactants (see, for example, formulas XII-XVI).

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

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

Surfactants are used in more than 100 industries National economy. Most of the produced surfactants are used as part of the environment, in the production of fabrics and products based on synthetic. and natural fibers. Large consumers of surfactants include petroleum, chemical. industry, construction industry. materials and a number of others. The most important applications of surfactants:

Drilling with mud and reversible water/oil. To regulate the aggregative stability and rheological characteristics of solutions, high-molecular water-soluble surfactants, polyacrylamide, etc. are used, calcium is added to nature. and synthetic. fatty acids (C 16 -C 18 and above), alkylaromatic. , alkylamines, alkylamidoamines, alkylimidazolines;

Enhanced oil recovery through micellar flooding (ethoxylated and alkylaromatic sulfonates);

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

Regulation of iron and manganese (soaps of natural and synthetic fatty acids, higher aliphatic amines), rare (alkylarsonic and alkylphosphonic acids, alkylaromatic 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 affect the amount of surface tension. In the process of interaction of liquid molecules, cohesive forces are formed between them. This force will be different in the surface and inner (deep) layers. Considering the state of the liquid, it is easy to establish that the particles that are directed into the system, with different sides surrounded by the same molecules that affect them. The resultant of all forces that act on such a molecule is zero. Therefore, liquids have the smallest surface area for a given volume. This is clearly manifested in the spherical shape of the droplets. The presence of impurities of various compounds in liquids determines the magnitude of surface tension.

The structure of surfactant molecules

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

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

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

Surfactants: harm and benefit

The surface tension has great value for intestinal absorption. For example, fats, as well as lipids, enter the alimentary tract in the form of droplets. The latter are emulsified in the small intestine with the help of bile acids. Only after that these fats are hydrolyzed by lipolytic enzymes. Soaps (surfactants) are often added to insecticides to increase effectiveness. The manipulation allows insecticides to better interact with the surface of the body of insects. However, surfactants have not only positive, but also negative effects on the body. For example, shampoo contains very harmful foaming agents (surfactants), such as sodium and ammonium lauryl sulfate, ammonium and sodium laureth sulfate. There is an opinion that these components have a carcinogenic effect.

Surfactants (surfactants) are chemical substances, which are able to concentrate at the phase boundaries and reduce the surface (interfacial) tension. Surfactants are used in pharmaceutical and cosmetic products, in the production of shampoos and foaming agents.

Chemical structure of surfactants

A surfactant molecule consists of a hydrophobic hydrocarbon radical and a hydrophilic polar (functional) group, i.e. the molecule is amphiphilic, as a result of which it has a high adsorption capacity. For example, in a water/oil emulsion, at the phase boundary, the hydrophilic group of the surfactant molecule is oriented towards water, and the hydrocarbon part is towards oil. At the same time, the interfacial tension decreases, which ensures the stabilization of oil droplets in water.

The detergent action 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 fat and solid particles, envelop and facilitate their transfer into the washing solution. Surfactants facilitate the spreading of water or products based on them over the skin surface by reducing interfacial tension.

Types of Surfactants

The classification of surfactants is based on the division, depending on the nature of the polar group: non-ionic, which do not dissociate into ions in water, and ionic, which, depending on the charge formed during dissociation 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 an ordinary cation. Anionic surfactant emulsifiers are very effective:

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

An example of an anionic surfactant that is often used in cosmetic formulations such as detergents is sodium lauryl ethoxysulfate (INCI nomenclature "Sodium Laureth Sulfate"). It is obtained by sulfation of saturated or unsaturated primary higher alcohols, followed by neutralization with sodium hydroxide, ammonia or triethanolamine. It is often produced in the form of a pasty mass containing up to 70% of the main substance.

Cationic surfactants, when dissolved in water, 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 are less effective than anionic emulsifiers, since they reduce surface tension to a lesser extent. But they exhibit bactericidal activity by interacting with cellular proteins of bacteria. Cationic surfactants are actively used in hair care products (shampoos, conditioners, hair conditioners). Aliphatic cationic surfactants with one and two hydrocarbon tails are good antistatic agents and are used in hair cosmetics.

Amphoteric surfactants, depending on the pH of the medium, behave in an alkaline environment as anionic or in an acidic environment as cationic. Their molecules contain functional groups that can have both negative and positive charges. Such surfactants are well compatible with cationic and anionic ones. Amphoteric surfactants are dermatologically gentle on the skin, which is why they are often used in children's "no tears" shampoos and products for sensitive skin. So, for example, in combination with an anionic surfactant sodium lauryl sulfate, almost completely soften its dermatological rigidity. Amphoteric surfactants have good foaming properties.

Betaines are one of the varieties of amphoteric surfactants. They belong to soft and high-foam surfactants. The amphoteric surfactant cocamidopropyl betaine (Dehiton / Betadet) is included in the composition of cosmetics in the production of shampoos, gels and cream gels, liquid soap, cleansing bath foams. This surfactant contributes to the compatibility of the cosmetic product with the skin, while improving the viscosity and foaming of this product. Thus, Dechiton, especially in children's foaming products, is an emollient component and contributes to the safety of using a detergent.

Non-ionic (non-ionic) surfactants are surfactants that do not form ions when dissolved in water. 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, as well as co-surfactants, foam stabilizers, wetting agents, etc. Fatty acid diethanolamides can be cited as an example of a nonionic surfactant. They are used in the production of shampoos and foaming detergents in an amount of up to 3% as a refatting agent, foam stabilizer and thickener.

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

Surfactants used in the cosmetic industry must comply with the Unified Sanitary and Epidemiological and hygiene requirements to goods subject to sanitary and epidemiological supervision (control).

Benefits of using surfactants:

lead to the stabilization of the dispersed system, make it impossible for the particles of the dispersed phase to stick together and coagulate;
facilitate the process of dispersion and obtaining cosmetic compositions;
improve the wettability and spreadability of cosmetic substances on the skin;
provide stability of reverse emulsions;
as part of foaming detergents, they improve their foaming and increase the stability of the foam during use.

Literature

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

Fundamentals of cosmetic chemistry. Basic provisions and modern ingredients. Ed. Puchkova T.V. 2011, pp.122-133.

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