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Surfactants (surfactants)- chemical compounds that, concentrating on the interface, cause a decrease in surface tension.

Due to their detergent, wetting, emulsifying, dispersing and other valuable properties, surfactants are widely used in the production of detergents and cleaners, cosmetics and pharmaceuticals. Latex. rubber. polymers. Chemical plant protection products, textiles, leather and paper, building materials, corrosion inhibitors, in the extraction, transportation and processing of oil, etc. Most of the surfactants (estimated at 55-60%) are used for the production of synthetic detergents (SMC).

Currently used synthetic surfactants (surfactants) are divided into 4 classes:

• anionic surfactants - compounds that dissociate in aqueous solutions with the formation of anions that cause surface activity. Among them, linear alkylbenzenesulfonate, sulfates and sulfoesters of fatty acids are of the greatest importance;
• amphoteric (ampholytic) surfactants - compounds that ionize in aqueous solutions and behave depending on the conditions (mainly on the pH of the medium), i.e., in an acidic solution they exhibit the properties of cationic surfactants, and in an alkaline solution - anionic surfactants. Among the main amphoteric surfactants, alkyl betaines, alkyl amino carboxylic acids, alkyl imidazoline derivatives, alkyl amino alkane sulfonates should be noted.
• nonionic surfactants Compounds that dissolve in water without being ionized. The solubility of nonionic surfactants in water is determined by the presence of functional groups in them. As a rule, they form nitrates in aqueous solution due to the occurrence of hydrogen bonds between water molecules and oxygen atoms of the polyethylene glycol part of the surfactant molecule. These include: polyglycol esters of fatty alcohols and acids, polyglycol esters of fatty acid amides, acylated or alkylated polyglycol ethers of alkyl amides.
• cationic surfactants - compounds that dissociate in an aqueous solution with the formation of cations that determine the surface activity. Among cationic surfactants, quaternary ammonium compounds, imidazalines, and fatty amines are of the greatest importance.

The main raw materials for large-tonnage production of surfactants are products of oil refining and petrochemical synthesis: low molecular weight and higher paraffins, olefins, synthetic fatty acids, higher fatty alcohols, alkyl derivatives of benzene and phenol, ethylene oxide, etc.

It is known that the first surfactant - soap - has been "living" for almost 4000 years, but in the 50s it lost its position to detergents and cleaners based on alkylbenzenesulfonate. Nevertheless, 9 million tons of soap are consumed annually in the world. Thus, soap remains the most common surfactant in the world, followed by ABS. Soap, according to strategic marketing estimates, has been in the so-called “saturation phase” for many years. The “phase of degeneration” will surely never come as long as humanity lives.

Surfactants in cosmetics

The concept of "Cosmetics" combines a wide range of various products intended for the care of hair and the human body. These are hair shampoo and liquid soap; hair dyes; hair care products after washing; rinses, balms, etc.; cosmetic creams for the face, body, hands, including therapeutic and prophylactic effects.

Modern shampoos are multi-functional products that contain various ingredients that provide softness, stability, foaming, improving the appearance and neck of the hair.
The basis of the raw materials of shampoos are surface-active substances (surfactants), as well as various useful additives, including biologically active ones.
Anionic substances are used as the main surfactants, which provide a sufficient washing effect and foaming while being gentle on the skin and hair.

For conventional commercial shampoos anionic surfactants (alkyl sulfates and alkyl ether sulfates)
In order to obtain “soft” shampoos, alkyl amidoether sulfates, sulfosuccinates, and, to a lesser extent, isothionates, sarcosinates, etc., are used in a mixture with them.
Auxiliary surfactants include amphoteric, non-ionic and cationic substances. They are necessary in shampoo formulations to increase the compatibility of basic surfactants with skin and hair, increase foaming properties, regulate viscosity, and reduce the degreasing effect. For this purpose, imidazoline derivatives, betaines, alkylolamides, and amine oxides are widely used.
Alkylolamides, glycol ethers of fatty alcohols are used as solubilizers for the introduction of fragrances and other hydrophobic components (oils, biologically active substances).

Cationic, non-ionic surfactants, beta-ines are used as conditioning agents that remove static electricity and facilitate combing dry and wet hair.

The most effective antistatic agents are cationic surfactants - quaternary ammonium compounds, although there are problems of incompatibility with anionic surfactants. However, in a mixture with non-ionic and amphoteric substances, it is possible to achieve the desired effect and maintain the stability of the finished product.
Amine oxides, oxyesters of alkyl phosphates are also used to soften hair, reduce their electrification.

A separate group among shampoos, liquid soaps, bath foams are especially “soft” formulations intended for children and adults with sensitive skin, i.e., formulations of increased softness in terms of skin impact. Here the requirements for raw materials are especially high. Most often, a mixture of alkyl ether sulfates with amphoteric surfactants - imidazoline derivatives, as well as betaines and monoalkyl sulfosuccinates is used as the active principle. The same base is used in anti-dandruff and medicated shampoos.

Anionic surfactants

The main types of surfactants used in the composition of SMS are alkyl benzene sulfonates with a linear alkyl chain (LABS) and derivatives of C12-C15 alcohols (ethoxylates, sulfates, ethoxysulfates of alcohols). LABS and alcohol sulfates, along with soap, are anionic surfactants, alcohol ethoxylates are nonionic (nonionic) surfactants.

Non-ionic surfactants

The second important type of surfactant for SMS are non-ionic surfactants obtained by oxyethylation of higher fatty alcohols or alkylphenols.

The most commonly used non-ionic surfactants are fatty alcohol hydroxyethylates, which can be based on both linear and branched alcohols. If ethoxylates based on long chain alcohols (C12-C15) are more used in CMC formulations for laundries due to their better detergency, then it is preferable to use ethoxylates based on short chain alcohols (C9-C11) for cleaning hard surfaces. These ethoxylates are distinguished by better wetting ability and contact angle with respect to hard surfaces. In general, non-ionic surfactants, due to the variability of their base and the degree of hydroxyethylation or propoxylation, can be ideally tailored to a specific task. They generally outperform anionic surfactants in both cleaning and degreasing action and emulsify more or less oils and fats depending on the usage profile.

Amphoteric surfactants

Of the group of amphoteric surfactants, betaine derivatives (for example, cocaminopropyl betaine) are most often used. In combination with anionic surfactants, they improve foaming ability and increase the safety of formulations, and when combined with cationic polymers, they enhance the positive effect of silicones and polymers on hair and skin. These derivatives are obtained from natural raw materials, so they are quite expensive components.

We offer such surfactants (surfactants):

Nonionic surfactants

Compounds that dissolve in water without forming ions are called non-ionic. Their group is represented by polyglycol and polyglycol esters of fatty alcohols (for example, feystenside - Disodium Laurethsulfosuccinate - a fluid liquid consisting of citric acid and fatty alcohols). Non-ionic surfactants are obtained by oxyethylation of vegetable oils (castor, wheat germ, flax, sesame, cocoa, calendula, parsley, rice, St. John's wort). Non-ionic surfactants exist only in liquid or paste form, therefore they cannot be contained in solid detergents (soaps, powders).

Aqueous solutions of fatty acid esters are a dispersion micellar solution, which is often called "smart soap" because it emulsifies dirt and grease, removing them from the surface of the skin and hair without damaging the protective mantle.

Properties of non-ionic surfactants

This type of surfactant makes the detergent soft, safe, environmentally friendly (biodegradability of non-ionic tensides is 100%). They stabilize soap suds, have mild thickening properties, have a bradykinase and polishing effect, restoring the outer layers of the epidermis and hair, and help to activate the action of therapeutic additives of the cleansing preparation.

This is the most promising and rapidly developing class of surfactants. At least 80-90% of these surfactants are obtained by adding ethylene oxide to alcohols, alkylphenols, carboxylic acids, amines, and other compounds with reactive hydrogen atoms. Polyoxyethylene ethers of alkylphenols are the most numerous and widespread group of nonionic surfactants, including more than a hundred trade names, the most well-known preparations are OP-4, OP-7 and OP-10. Typical raw materials are octyl-, ionyl- and dodecylphenols; cr. In addition, cresols, cresol acid, β-naphthol, etc. are used. If an individual alkylphenol is taken into the reaction, the finished product is a mixture of surfactants of the total f-ly RC6H4O (CH2O) mH, where m is the degree of oxyethylation, depending on the molar ratio of the initial components.

All surfactants. can be divided into two categories according to the type of systems they form when interacting with a dissolving medium. One category includes micelle-forming surfactants. in., to the other - not forming micelles. In solutions of micelle-forming surfactants c. above the critical micelle concentration (CMC), colloidal particles (micelles) appear, consisting of tens or hundreds of molecules (ions). Micelles reversibly decompose into individual molecules or ions upon dilution of a solution (more precisely, a colloidal dispersion) to a concentration below the CMC.

Thus, solutions of micelle-forming surfactants. occupy an intermediate position between true (molecular) and colloidal solutions, therefore they are often called semi-colloidal systems. Micellar surfactants include all detergents, emulsifiers, wetting agents, dispersants, etc.

Surface activity is conveniently assessed by the largest decrease in surface tension divided by the corresponding concentration - CMC in the case of micelle-forming surfactants. Surface activity is inversely proportional to CMC:

The formation of micelles occurs in a narrow range of concentrations, which becomes narrower and more defined as the hydrophobic radicals lengthen.

The simplest micelles of typical semi-colloidal surfactants, for example. fatty salts to - t, at concentrations not too exceeding CMC, have a spheroidal shape.

An increase in the surfactant concentration of anisometric micelles is accompanied by a sharp increase in the structural viscosity, leading in some cases to gelation, i.e. complete loss of fluidity.

action of detergents. Soap has been known for thousands of years, but it is only relatively recently that chemists have understood why it has detergent properties. The dirt removal mechanism is essentially the same for soap and synthetic detergents. Let's take it as an example of table salt, conventional soap, and sodium alkylbenzenesulfonate, one of the first synthetic detergents.

When dissolved in water, table salt dissociates into positively charged sodium ions and negatively charged chloride ions. Soap, i.e. sodium stearate (I), substances similar to it, as well as sodium alkylbenzenesulfonate (II) behave in a similar way: they form positively charged sodium ions, but their negative ions, unlike the chloride ion, consist of about fifty atoms.

Soap (I) can be represented by the formula Na+ and C17H35COO-, where 17 carbon atoms with hydrogen atoms attached to them are stretched out in a winding chain. Sodium alkylbenzenesulfonate (Na+ C12H25C6H4SO3-) has about the same number of carbon and hydrogen atoms. However, they are not located in the form of a winding chain, as in soap, but in the form of a branched structure. The significance of this difference will become clear later. For the washing action, it is important that the hydrocarbon part of the negative ion is insoluble in water. However, it is soluble in fats and oils, and it is thanks to fat that dirt sticks to things; and if the surface is completely free of grease, dirt does not linger on it.

The negative ions (anions) of soap and alkylbenzenesulfonate tend to concentrate at the interface between water and fat. The water soluble negative end remains in the water while the hydrocarbon portion is immersed in the fat. In order for the interface to be the largest, the fat must be present in the form of tiny droplets. As a result, an emulsion is formed - a suspension of droplets of fat (oil) in water (III).

If there is a film of fat on a solid surface, then upon contact with water containing detergent, the fat leaves the surface and passes into the water in the form of tiny droplets. Soap and alkylbenzenesulfonate anions are at one end in water and at the other end in fat. Dirt held by a film of grease is removed by rinsing. So in a simplified form, you can imagine the action of detergents.

Any substance that tends to collect at an oil-water interface is called a surfactant. All surfactants are emulsifiers because they promote the formation of an oil-in-water emulsion, i.e. "mixing" oil and water; all of them have detergent properties and form foam - after all, foam is like an emulsion of air bubbles in water. But not all of these properties are expressed in the same way. There are surfactants that lather profusely but are weak detergents; there are also those that almost do not foam, but are excellent detergents. Synthetic detergents are synthetic surfactants with particularly high detergency. In the industry, the term "synthetic detergent" generally means a composition including a surfactant, bleaches and other additives.

Soaps, alkylbenzenesulfonates and many other detergents, where exactly the anion dissolves in fats, are called anionic. There are also surfactants in which the cation is fat-soluble. They are called cationic. A typical cationic detergent, alkyldimethylbenzylammonium (IV) chloride is a quaternary ammonium salt containing nitrogen bonded to four groups. The chloride anion always remains in water, which is why it is called hydrophilic; hydrocarbon groups associated with a positively charged nitrogen are lipophilic. One of these groups, C14H29, is similar to the long hydrocarbon chain in soap and alkylbenzene sulfonate, but it is attached to the positive ion. Such substances are called "reverse soaps". Some of the cationic detergents have strong antimicrobial activity; they are used as part of detergents intended not only for washing, but also for disinfection. However, if they cause eye irritation, then when they are used in aerosol formulations, this circumstance should be reflected in the instructions on the label.

Another type of detergent is non-ionic detergents. The fat-soluble group in the detergent (V) is something like the fat-soluble groups in alkylbenzenesulfonates and soaps, and the remainder is a long chain containing many oxygen atoms and an OH group at the end, which are hydrophilic. Typically, non-ionic synthetic detergents exhibit high detergency but low lather.

Surfactants (Synthetic Surface Active Substances) are an extensive group of compounds, different in their structure, belonging to different classes. These substances are able to be adsorbed on the phase interface and consequently lower the surface energy (surface tension). Depending on the properties exhibited by surfactants when dissolved in water, they are divided into anionic substances (the active part is the anion), cationic (the active part of the molecules is the cation), ampholytic and non-ionic, which are not ionized at all.

It is no secret that the main active ingredients of washing powders are surface-active substances (surfactants). In truth, these active chemical compounds, when they enter the body, destroy living cells by disrupting the most important biochemical processes.

The future of synthetics? Apparently yes. In confirmation of this, surfactants are being improved more and more, there are so-called non-ionic surfactants, the biodegradability of which reaches 100%. They are more effective at low temperatures, which is important for gentle wash cycles. Since many man-made fibers cannot withstand high temperatures. In addition, washing in colder water saves energy, which is more relevant every day. Unfortunately, most non-ionic surfactants are liquid or pasty and are therefore used in liquid and pasty detergents. In powdered SMS, nonionic surfactants are introduced in the form of additives of 2-6% wt. Important advantages of synthetic surfactants are that they do not form calcium and magnesium salts that are poorly soluble in water. This means that they wash equally well in both soft and hard water. The concentration of synthetic detergents, even in soft water, can be much lower than soaps made from natural fats.

Probably, from household chemicals, we know the most synthetic detergents. In 1970, for the first time in the world, synthetic detergents (SMC) were produced more than ordinary natural soap. Every year its production is decreasing, while the production of SMS is continuously increasing.

For example, in our country, the dynamics of growth in the production of SMS can be displayed by the following data: in 1965 they were produced 106 thousand tons, in 1970 - 470 thousand tons, and in 1975 almost one million tons will be produced.

Why is the production of natural, sound soap, which faithfully served a person for many years, falling so much? It turns out he has a lot of flaws.

Firstly, soap, being a salt of a weak organic acid (more precisely, a salt formed by a mixture of three acids - palmitic, margaric and stearic) and a strong base - sodium hydroxide, hydrolyzes in water: xia (i.e. split by it) into acid and alkali. The acid reacts with hardness salts and forms new salts, already insoluble in water, which fall out in the form of a sticky white mass on clothes, hair, etc. This not very pleasant phenomenon is well known to anyone who has tried washing or bathing in hard water.

Another product of hydrolysis - alkali - destroys the skin (degreases it, leads to dryness and the formation of painful cracks) and reduces the strength of the fibers that make up various tissues. Polyamide fibers (kapron, nylon, perlon). are destroyed by soap especially intensively.

Secondly, soap is a relatively expensive product, since its production requires food raw materials - vegetable or animal fats.

There are other, less significant shortcomings of this until recently, completely indispensable substance in everyday life.

Unlike natural soaps, synthetic detergents have undoubted advantages: greater washing power, hygiene and economy.

About 500 names of synthetic detergents are now known on the international market, produced in the form of powders, granules, flakes, pastes, liquids.

The production of SMS gives a great economic effect. Experiments have shown that one ton of synthetic detergents replaces 1.8 tons of 40% laundry soap made from valuable food raw materials. It is estimated that one ton of CMS saves 750 kg of vegetable fats for the food industry.

The use of SMS in the household can reduce labor costs for hand and machine washing by 15-20% * At the same time, the strength and initial consumer properties of the fabric (whiteness, color brightness, elasticity) are much better than when using ordinary laundry soap.

It must be said that SMS is intended not only for washing clothes. There are special products for washing and cleaning various household items, synthetic toilet soaps, hair washing shampoos, foaming bath additives, into which biostimulants are introduced that have a tonic effect on the body.

The main component of all these products is a synthetic surfactant, the role of which is the same as that of an organic salt in ordinary soap.

However, chemists have long known that an individual substance, no matter how universal it may be, cannot satisfy all the requirements placed on it. Small additions of other accompanying substances help to find very useful qualities in this basic substance. That is why all modern SMS are not individual surfactants, but compositions that may include bleaches, fragrances, foam regulators, biologically active substances and other components.

The second most important component of modern synthetic detergents are condensed, or polymeric, phosphates (polyphosphates). These substances have a number of useful properties: they form water-soluble complexes with metal ions present in water, which prevents the appearance of insoluble mineral salts that occur when washing with ordinary soap; increase the detergent activity of surfactants; prevent sedimentation of suspended particles of dirt on the washed surface; cheap to manufacture.

All these properties of polyphosphates make it possible to reduce the content of the more expensive main component, surfactant, in SMS.

As a rule, any synthetic detergent includes a fragrance - a substance with a pleasant smell, which is transferred to the laundry when using SMS.

Nearly all SMSs contain a substance called sodium carboxymethyl cellulose. It is a high molecular weight synthetic product, soluble in water. Its main purpose is to be, along with phosphates, an antiresorptive, i.e. prevent dirt from settling on already washed fibers.

Most of them have a number of advantages over soap, which has long been used for this purpose. So, for example, surfactants dissolve well and foam even in hard water. The potassium and magnesium salts formed in hard water do not worsen the washing action of surfactants and do not form a white coating on the hair.

The main active ingredients of all washing powders, the so-called. Surfactants (surfactants) are extremely active chemical compounds. Possessing some chemical affinity with certain components of human and animal cell membranes, surfactants, when ingested, accumulate on cell membranes, covering their surface with a thin layer and, at a certain concentration, can cause disturbances in the most important biochemical processes occurring in them, disrupt the function and integrity itself. cells.

In experiments on animals, scientists have found that surfactants significantly change the intensity of redox reactions, affect the activity of a number of important enzymes, and disrupt protein, carbohydrate and fat metabolism. Surfactant anions are especially aggressive in their actions. They can cause gross violations of the immune system, the development of allergies, damage to the brain, liver, kidneys, and lungs. This is one of the reasons Western European countries impose strict restrictions on the use of a-surfactants (anionic surfactants) in laundry detergent formulations. At best, their content should not exceed 2-7%. In the West, more than 10 years ago, they abandoned the use of powders containing phosphate additives in everyday life. In the German, Italian, Austrian, Dutch and Norwegian markets, only phosphate-free detergents are sold. In Germany, the use of phosphate powders is prohibited by federal law. In other countries, such as France, Great Britain, Spain, in accordance with government decisions, the content of phosphates in SMS is strictly regulated (no more than 12%).

The presence of phosphate additives in powders leads to a significant increase in the toxic properties of a-surfactants. On the one hand, these additives create conditions for more intense penetration of a-surfactants through intact skin, promote enhanced degreasing of the skin, more active destruction of cell membranes, and sharply reduce the barrier function of the skin. Surfactants penetrate into the microvessels of the skin, are absorbed into the blood and distributed throughout the body. This leads to a change in the physicochemical properties of the blood itself and a violation of immunity. A-surfactants have the ability to accumulate in organs. For example, 1.9% of the total amount of a-surfactants that got on unprotected skin settles in the brain, 0.6% in the liver, etc. They act like poisons: in the lungs they cause hyperemia, emphysema, in the liver they damage the function of cells, which leads to an increase in cholesterol and intensifies the phenomena of atherosclerosis in the vessels of the heart and brain, disrupts the transmission of nerve impulses in the central and peripheral nervous systems.

But this does not exhaust the harmful effects of phosphates - they are a great threat to our environment. Getting after washing along with sewage into water bodies, phosphates are taken to act as fertilizers. The "harvest" of algae in reservoirs begins to grow by leaps and bounds. Algae, decomposing, release huge amounts of methane, ammonia, hydrogen sulfide, which destroy all life in the water. Overgrowth of reservoirs and clogging of slowly flowing waters leads to gross violations of the ecosystems of reservoirs, deterioration of oxygen exchange in the hydrosphere and creates difficulties in providing the population with drinking water. It is also for this reason that many countries have legally banned the use of phosphate SMS.

The traditional disadvantage of surfactants is harshness, expressed in skin irritation, dryness and discomfort after using shampoo or shower gel.

The skin of the hands, in contact with active chemical solutions of washing powders, become the main conductor of the penetration of hazardous chemical agents into the human body. A-surfactants actively penetrate even through intact skin of the hands and, with the assistance of phosphates, enzymes and chlorine, intensively disinfect it. Restoration of normal fat content and moisture of the skin occurs no earlier than after 3-4 hours, and with repeated use due to the accumulation of the harmful effect, the lack of fatty skin coating is felt within two days. The barrier functions of the skin are reduced, and conditions are created for intensive penetration into the body of not only a-surfactants, but also any toxic compounds - bacteriological toxins, heavy metals, etc. After several washes with phosphate powders, skin inflammations - dermatitis often develop. The pipeline of pathological immune reactions is launched.

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 the physicochemical properties of the 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 effect 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 disperse 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 dispersed 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 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. 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, the required amount of 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 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 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. A distinctive feature of 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:

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

Surfactant structure

Surfactant classification

• Ionic surfactants
  • Cationic surfactants
  • Anionic surfactants
  • Amphoteric

• Nonionic surfactants
  • Alkyl polyglucosides
  • Alkylpolyethoxylates

Effect of surfactants on environmental components

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 the retention of CO 2 and oxygen in the 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 households 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 organism.

Areas of use

Bibliography

• Abramzon A. A., Gaevoy G. M. (ed.) Surfactants. - L.: Chemistry, 1979. - 376 p.
• Parshikova T. V. Surfactants as a factor in the regulation of algae development. - Kyiv: Phytosociocenter, 2004. - 276 p. (in Ukrainian) ISBN 966-306-083-8 .
• Ostroumov S. A. Biological effects when exposed to surfactants on organisms. - M.: MAKS-Press, 2001. - 334 p. ISBN 5-317-00323-7.
• Stavskaya S. S., Udod V. M., Taranova L. A., Krivets I. A. Microbiological purification of water from surface-active substances. - Kyiv: Nauk. Dumka, 1988. - 184 p. ISBN 5-12-000245-5.

see also

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See what "Surfactants" are in other dictionaries:

- (a. surfactants; n. grenzflachenaktive Stoffe, oberflachenaktive Stoffe; f. substances tensio actives; and. surfac tantes), substances with an asymmetric mol. structure, the molecules of which have an amphiphilic structure, i.e. contain lyophilic and ... ... Geological Encyclopedia

Substances capable of accumulating (condensing) on ​​the contact surface of two bodies, called the phase separation surface, or interfacial surface. On the interfacial surface P. a. in. form a layer of high concentration adsorption ... ... Great Soviet Encyclopedia

Surfactants (surfactants) detergents - substances that reduce surface tension. By influencing the boundary layers of cells, they disrupt the functions of the cytoplasmic membrane and, as a result, are able to retard growth ... ... Dictionary of microbiology

Substances capable of being adsorbed on the interface between two phases, lowering its surface tension. To P. a. in. include organic connections with an asymmetric mol. structure, molecules to ryh contain at. groups that differ sharply in character ... ... Physical Encyclopedia

- (surfactant) chemical compounds capable of adsorbing at the interface, one of which is usually water, and reduce surface tension. Surfactant molecules consist of a hydrocarbon radical (from 4 to 20 CH2 groups) and a polar group (OH, COOH, ... ... Big Encyclopedic Dictionary

surfactants- Surfactants Things wah that can be adsorbed on the interface and cause a decrease in surface. (interfacial) tension. Typical surfactants - organic. compounds whose molecules contain lyophilic and lyophobic (usually hydrophilic and hydrophobic) at ... Technical Translator's Handbook

Surfactants.- 0.10.4.2. Surfactants. It is allowed to use surfactants in accordance with title= Highways for the preparation of asphalt mixtures. Source … Dictionary-reference book of terms of normative and technical documentation

surfactants- abbr. Surfactants Surfactants (detergents) are substances that are adsorbed on the interface and cause a decrease in interfacial tension. General chemistry: textbook / A. V. Zholnin ... Chemical terms

surfactants- See surface-active substances (surfactants) ... Encyclopedic Dictionary of Metallurgy

surfactants- Surfactants - substances that can concentrate on the interface and reduce the surface (interfacial) tension. They have wetting, emulsifying, detergent and other valuable properties. They are divided into ionic and non-ionic. Among… … Textile glossary

Surfactants are classified according to a number of criteria:

• ? the ability to form ions and the charge of ions;
• ? mechanism of action:
• ? solubility in water and oils.

Classification of surfactants according to their ability to form ions and the charge of ions. All surfactants are divided into two large groups: ionic compounds, which, when dissolved in water, dissociate into ions, and nonionic, which do not dissociate into ions.

Depending on which ions (positive or negative) cause surface activity ionic surfactants, those. respectively, cations or anions, they are divided into cationic, anionic and amphoteric (having two bipolar functional groups).

Anionic surfactants are active in alkaline solutions, cationic - in acid solutions, amphoteric - in both.

Anionic surfactants dissociate in alkaline solutions to form anions:

surfactant anion

Cationic surfactants, when dissociated in acid solutions, form cations:

1ShN 2 S1 1ShN5 + SG.

surfactant cation

Amphoteric surfactants contain two functional groups, one of which is acidic, the other is basic, for example, carboxyl (COOH) and amino group (1CHN 2):

1ShN (CH 2) p COOH-KMN (CH 2) p COOH KMN 2 (CH 2) „COOH.

in an alkaline environment in an acidic environment

To anionic surfactant relate:

• ? carboxylic acids (11COOH) and their salts (KCOOMe);
• ? alkyl sulfates (K080 2 0Me), as well as substances containing other types of anionic hydrophilic groups, such as phosphates (salts of phosphoric acids).

To cationic surfactant includes a number of substances. The main group is represented by amines - nitrogen-containing compounds, which are the products of substitution of one or three hydrogen atoms in ammonia T^H3 with organic radicals II. According to the number of substituted hydrogen atoms, primary (1ShN 2), secondary (K 2 1

To amphoteric surfactant include proteins containing groups: -COO and -MH3. Schematically, an amphoteric surfactant molecule can be represented as

NSZhiz-P-SOO.

Nonionic surfactants, dissolving in water, they do not form ions. The group of nonionic surfactants includes products of oxyethylation of long-chain fatty acids, alcohols, amines; lignosulfonic acids, etc. The solubility of nonionic surfactants in water is due to functional groups that have a strong affinity for it.

Of considerable interest for practice are cream-organic surfactants, which include low-molecular compounds that have a silicon-carbon bond (81-C) in the molecule, and functional groups that ensure their chemical interaction with the surface of various materials. The mechanism of interaction of organosilicon surfactants with materials is as follows: their functional groups interact both with the functional groups of the material and with water adsorbed on its surface. In this case, silanols are formed, which are easily condensed and give a polyorganosiloxane film chemically bonded to the surface of the material. The most accessible and effective of these surfactants are alkyl-chlorosilanes of the K lg 81C1 g/ type.

Classification of surfactants according to the mechanism of action. P.A. Rebinder divided all surfactants, taking into account their different action in dispersed systems, into four groups.

To first group low molecular weight surfactants are assigned, giving true solutions in water, for example, alcohols. They are weak wetting agents and defoamers.

Co. second group include surfactants, dispersants and emulsifiers. They do not form complex structures either in the volume of solutions or in surface boundary layers. However, being adsorbed on the surface of the interacting substance, they effectively reduce the surface tension of the liquid or the surface energy of the solid, which greatly facilitates the process of formation of new surfaces, i.e. dispersion in this environment. The use of surfactants of this group is of great practical importance when grinding stone materials and obtaining homogeneous building compositions. These surfactants include fatty acids, their water-soluble salts, cationic bases and salts, as well as organosilicon compounds.

AT third group combined surfactants, which are good stabilizers. These surfactants have relatively low surface activity due to the symmetrical distribution of polar and nonpolar groups in the molecules. However, they can form structural gel-like protective shells with a hydrophilic surface, which prevents particle aggregation: coagulation and coalescence 1 .

Surfactants of this group are good plasticizers. In the form of very small additives, they "thinn" (plasticize) structures, reducing their strength and structural viscosity, which makes it possible to reduce the water demand of building mixtures. Using these surfactants in cement mortars and concretes, it is possible to move to rigid and at the same time homogeneous mixtures without increasing the water-cement ratio (W / C) to maintain the required workability of the mixtures. In general, such additives increase the density of concrete, which increases its strength and durability, and also allows you to save (Yu ... 20%) of cement. Such additives provide uniform air entrainment of concrete mixtures and the formation of closed porosity in them due to the uniform distribution of small air bubbles that do not merge with each other. This significantly increases the frost resistance of concrete.

Surfactants of this group also bring great practical benefits in the technology of obtaining bitumen-mineral materials:

Increase the adhesion of bitumen to mineral aggregates (sand and gravel). This effect is achieved by hydrophobization of mineral surfaces as a result of chemical adsorption of surfactants. The surface of siliceous (acidic) mineral materials (granites, sandstones) is hydrophobized with cationic surfactants, and the surface of mineral materials from carbonate rocks (limestones, dolomites) with anionic surfactants, for example, higher fatty acids (the mechanisms for such an increase in adhesive interaction are shown in Fig. 1.21 );

coagulation (from lat. coagulatio - coagulation, thickening) - enlargement of solid particles in dispersed systems.

Coalescence (from lat. coalesce - grow together, connect) - the merging of liquid drops when they come into contact.

Rice. 1.21.

various rocks:

a- siliceous (acidic) rock; b - carbonate rock

• ? provide uniform mixing of the asphalt mix;
• ? strengthen, stabilize soils used as a constructive layer of pavement.

Fourth group Surfactants are substances with high surface activity, wetting and hydrophobic effects. They are effective emulsifiers and emulsion stabilizers. This group includes soaps of fatty acids and amines.

Classification of surfactants by solubility in water and oils. In some cases, the classification of surfactants into water-soluble, water-oil-soluble and oil-soluble is applied. The solubility of surfactants in a particular medium is determined, as noted earlier, by the molecular structure: the number and activity of polar functional groups and the length of the hydrocarbon radical.