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“Michelin” from dandelions. Americans pull mass-produced tires from Russian dandelions Experimental methodology

Rubbers are high-molecular compounds that are used to produce rubbers, hard rubber and varnishes, adhesives, and binders. Rubbers have a linear structure, high elasticity, and a wide range of operating temperatures. At a temperature of 100°C they become brittle, and at a temperature of 200°C they liquefy (Table 8.6).

Natural rubber (NR) is obtained from the milky sap of tropical rubber plants. The juice is treated with acids and then the resulting product is rolled.

Synthetic rubbers (SR) are obtained by polymerization of unsaturated compounds. Depending on the type of source material and the conditions of their processing, rubbers with different properties and durability are produced (Table 8.7).

Rubber and ebonite are products of rubber vulcanization. It is carried out in the presence of vulcanizing substances (often sulfur, metal oxides)

at elevated temperatures. Depending on the amount of vulcanizer introduced, soft rubber (2-L% 8), semi-hard (12-20% 8) and hard rubber (30-50% 8) are obtained. The latter is called ebonite.

Rubbers have a unique ability to reverse deformation combined with high elasticity and strength,

resistance to abrasion, exposure to aggressive environments, gas and water resistance.

Styrene-butadiene rubber (SBR) is a copolymer of butadiene and styrene. Ebonites based on it are characterized by high chemical resistance. They are resistant in dry and wet chlorine, in concentrated acetic acid up to 65 °C, and can be used for a long time in 36% hydrochloric acid up to 80 °C.

Butadiene-nitrile rubber (SKN) is a copolymer of butadiene and acrylic acid nitrile. Rubbers based on it have gasoline and oil resistance, high resistance to abrasive wear and high heat resistance (up to 100 ° C).

Chloroprene rubber is called nairite. The main raw materials for its production are cheap and accessible gases - acetylene and hydrogen chloride.

Nairites dissolve in organic solvents and produce low-viscosity and concentrated solutions that can easily be applied to the surface to be protected. Unvulcanized Nairite coatings are thermoplastic. They soften at temperatures above 40°C. If they are kept for several days in a solution of sulfuric acid or sodium chloride at 60-70° C, the coating vulcanizes and acquires the properties of rubber. Such coatings have good aging resistance and can work in acids, alkalis and salt solutions up to 70 °C. Can withstand short-term heating up to 90-95 °C.

Gumming is the coating of chemical equipment with rubber or ebonite. The inner surface of the apparatus is covered with one, two or more layers of raw sheet rubber, followed by vulcanization. Vulcanization is carried out in special boilers heated by live steam. It can be done by filling the apparatus with boiling water, aqueous solutions of salts having a boiling point above 100°C. When heated, the raw rubber mixture turns into strong, elastic rubber. Coverings made of chloroprene rubber protect pipelines, electrolyzers, and tanks.

Raw rubber in railway tanks undergoes self-vulcanization without heating, which is completed within a month in summer.

Ebonites have good adhesion to metal. This property is used to create a two-layer coating, which is often used in chemical plants. The bottom layer is made of ebonite, and the top layer is made of soft rubber. Such coatings are resistant to hydrochloric, hydrofluoric, acetic, citric acids, alkalis and salt solutions up to 65 °C. They are destroyed only in strong

oxidizing environments - in concentrated sulfuric acid and nitric acid.

As an example, consider the protection of heat exchange equipment with rubber coatings. Thin and bakelite coatings on steel pipes of heat exchangers protect steel quite well from corrosion. But they do not protect it from erosion and intense water-abrasive wear. Meanwhile, some of the heat exchange equipment is subject to severe wear under the influence of water with suspended mechanical solid particles. In this case, reliable protection against corrosive and abrasive wear can only be achieved with the help of rubber coatings. Nairite coatings have shown good protective properties. Some factories in Russia and the USA have experience in operating such heat exchangers (Fig. 8.6).

It should only be taken into account that a rubberized heat exchanger will have a reduced heat transfer coefficient compared to a heat exchanger without a protective coating.

Butzhkauchuk is a product of co-polymerization of iso-butylene and isoprene. It is characterized by inertness to aggressive media, high gas impermeability and low water swelling. Rubbers based on it resist the action of some organic solvents.

Silicone rubbers have high heat resistance up to 250-300 °C and frost resistance up to -50-1-60 °C. Their disadvantage is their relatively low corrosion resistance.

Fluororubbers are unsurpassed materials in terms of chemical resistance and heat resistance. Products based on them can be used in highly aggressive environments and oxidizing agents up to a temperature of 200 °C. The disadvantage of this type of rubber is its high shrinkage, which makes it difficult to use for protecting chemical equipment.

Alcadienes

HEVEA BRAZILIAN

(Hevea brasiliensis)

Rubber plants

A rubber extractor coagulating the collected latex by first collecting it on a stick and then holding it over a vat of smoke

Rubber processing on a plantation in Eastern Cameroon

Rubbers- natural or synthetic materials characterized by elasticity, water resistance and electrical insulating properties, from which rubber is obtained through special processing. Natural rubber is obtained from a milky-white liquid called latex, - milky sap of rubber plants.

In technology, rubber is used to make tires for vehicles, airplanes, and bicycles; Rubbers are used for electrical insulation, as well as for the production of industrial goods, medical devices and latex mattresses.

Chemical properties

1928

Diene syntheses (Diels-Alder reaction)

Rubber

Vulcanization of rubber

Natural and synthetic rubbers are used mainly in the form of rubber, as it has significantly higher strength, elasticity and a number of other valuable properties. To obtain rubber, rubber is vulcanized. Many scientists have worked on the vulcanization of rubber.

In 1834, the German chemist Ludersdorff first discovered that rubber could be made solid by treating it with a solution of sulfur in turpentine.

American merchant Charles Goodyear was one of the unsuccessful entrepreneurs who spent his entire life chasing wealth. He became interested in the rubber business and, sometimes remaining penniless, persistently searched for a way to improve the quality of rubber products. Goodyear discovered a method for producing non-sticky, durable and elastic rubber by mixing rubber with sulfur and heating.

In 1843, Hancock, independently of Goodyear, found a way to vulcanize rubber by immersing it in molten sulfur, and a little later Parkes discovered the possibility of producing rubber by treating rubber with a solution of semichloride sulfur ( cold vulcanization).

The Englishman Robert William Thomson, who invented the “patent air wheels” in 1846, and the Irish veterinarian John Boyd Denlob, who stretched a rubber tube onto the wheel of his young son’s bicycle, had no idea that they thereby marked the beginning of the use of rubber in the tire industry.

Modern rubber production technology is carried out in the following stages:

From a mixture of rubber with sulfur, fillers (carbon black is a particularly important filler) and other substances, the desired products are formed and subjected to heating. Under these conditions, sulfur atoms attach to the double bonds of rubber macromolecules and “cross-link” them, forming disulfide “bridges.” As a result, a giant molecule is formed, having three dimensions in space - like length, width and thickness. The polymer acquires a spatial structure:

Such rubber will, of course, be stronger than unvulcanized rubber. The solubility of the polymer also changes: rubber, although slowly, dissolves in gasoline, rubber only swells in it. If you add more sulfur to rubber than is needed to form rubber, then during vulcanization the linear molecules will be “cross-linked” in very many places, and the material will lose its elasticity and become hard - the result will be ebonite. Before the advent of modern plastics, ebonite was considered one of the best insulators.

Vulcanized rubber has greater strength and elasticity, as well as greater resistance to temperature changes than unvulcanized rubber; rubber is impermeable to gases, resistant to scratching, chemical attack, heat and electricity, and also shows a high coefficient of sliding friction with dry surfaces and a low coefficient with wet ones.

Vulcanization accelerators improve the properties of vulcanizers, reduce vulcanization time and consumption of basic raw materials, and prevent over-vulcanization. Inorganic compounds (magnesium oxide MgO, lead oxide PbO and others) and organic compounds are used as accelerators: dithiocarbamates (dithiocarbamic acid derivatives), thiurams (dimethylamine derivatives), xanthates (xanthogenic acid salts) and others.

Accelerator activators vulcanization facilitates the interaction reactions of all components of the rubber mixture. Basically, zinc oxide ZnO is used as activators.

Antioxidants(stabilizers, antioxidants) are introduced into the rubber mixture to prevent “aging” of the rubber.

Fillers- increase the physical and mechanical properties of rubber: strength, wear resistance, abrasion resistance. They also help to increase the volume of raw materials, and, consequently, reduce rubber consumption and reduce the cost of rubber. Fillers include various types of soot (carbon black), mineral substances (chalk CaCO 3, BaSO 4, gypsum CaO 2H 2O, talc 3MgO 4SiO 2 2H 2O, quartz sand SiO 2).

Plasticizers(softeners) - substances that improve the technological properties of rubber, facilitate its processing (reduce the viscosity of the system), and provide the opportunity to increase the content of fillers. The introduction of plasticizers increases the dynamic endurance of rubber and “abrasion” resistance. Oil refining products (fuel oil, tar, paraffins), substances of plant origin (rosin), fatty acids (stearic, oleic) and others are used as plasticizers.

The strength and insolubility of rubber in organic solvents are related to its structure. The properties of rubber are also determined by the type of raw material. For example, rubber made from natural rubber is characterized by good elasticity, oil resistance, wear resistance, but at the same time is not very resistant to aggressive environments; rubber made from SKD rubber has even higher wear resistance than from NK. SKS styrene butadiene rubber improves wear resistance. Isoprene rubber SKI determines the elasticity and tensile strength of rubber, and chloroprene rubber determines its resistance to oxygen.

In Russia, the first large enterprise in the rubber industry was founded in St. Petersburg in 1860, later called “Triangle” (since 1922 - “Red Triangle”). Other Russian factories of rubber products were founded after him: “Kauchuk” and “Bogatyr” in Moscow, “Provodnik” in Riga and others.

Application of rubber in industrial products

Rubber is of great economic importance. Most often it is used not in its pure form, but in the form of rubber. Rubber products are used in technology for insulating wires, making various tires, in the military industry, in the production of industrial goods: shoes, artificial leather, rubberized clothing, medical products...

Rubber is a highly elastic, durable compound, but less ductile than rubber. It is a complex multicomponent system consisting of a polymer base (rubber) and various additives.

The largest consumers of rubber technical products are the automotive industry and agricultural engineering. The degree of saturation with rubber products is one of the main signs of perfection, reliability and comfort of mass types of engineering products. The mechanisms and assemblies of modern cars and tractors contain hundreds of items and up to a thousand pieces of rubber parts, and simultaneously with the increase in the production of machines, their rubber capacity increases.

Types of rubber and their application

Depending on the structure, rubber is divided into non-porous (monolithic) and porous.

Non-porous rubber made on the basis of butadiene rubber. It has high abrasion resistance. The wear life of sole rubber is 2-3 times longer than the wear life of sole leather. The tensile strength of rubber is less than that of natural leather, but the elongation at break is many times higher than that of natural sole leather. Rubber does not allow water to pass through and practically does not swell in it.

Conventional non-porous rubber is used to make molded soles, overlays, heels, half heels, heels and other parts of the bottom of shoes.

Porous rubbers used as soles and platforms for spring-autumn and winter shoes.

Leather-like rubber- this is rubber for the bottom of shoes, made on the basis of rubber with a high styrene content (up to 85%). The increased styrene content gives rubbers hardness, as a result of which it is possible to reduce their thickness to 2.5-4.0 mm while maintaining good protective functions.

The performance properties of leather-like rubber are similar to those of natural leather. It has high hardness and ductility, which allows you to create a shoe footprint of any shape. Leather-like rubber stains well when finishing shoes. It has high wear resistance due to good abrasion resistance and resistance to repeated bending. The wear life of shoes with soles made of leather-like rubber is 179-252 days in the absence of crumbling in the toe.

The disadvantage of this rubber is its low hygienic properties: high thermal conductivity and lack of hygroscopicity and air tightness.

Leather-like rubber is produced in three varieties: non-porous structure with a density of 1.28 g/cm3, porous structure with a density of 0.8-0.95 g/cm3, and porous structure with a fibrous filler, the density of which is not higher than 1.15 g /cm 3. Porous rubbers with fibrous fillers are called “ leather fiber" These rubbers are similar in appearance to genuine leather. Thanks to the fiber filler, their heat-shielding properties increase, they are lightweight, elastic, and have a good appearance. Leather-like rubbers are used as soles and heels in the manufacture of summer and spring-autumn shoes using the adhesive fastening method.

Transparent rubber is a translucent material with a high content of natural rubber. It is distinguished by high abrasion resistance and hardness, and is superior in wear resistance to all types of rubber. Transparent rubbers are produced in the form of molded soles (together with heels), with deep corrugation on the running side.

A type of transport rubber is Styronip containing more rubber. Styronip's resistance to repeated bending is more than three times higher than that of conventional non-porous rubber. Styronip is used in the manufacture of shoes using the adhesive fastening method.

The disadvantage of porous rubber is the ability to shrink and also crumble in the toe part upon impact. To increase the hardness of porous rubbers, polystyrene resins are introduced into their composition.

Currently, the production of new types of porous rubbers has been mastered: porocrepa And vulcanite. Porokrep has a beautiful color, elasticity, and increased strength. Vulcanite is a porous rubber with fibrous fillers, which has high wear resistance and good heat protection. Porous rubbers are used as soles for spring, autumn and winter shoes. A method of producing raw rubber blanks in the form of a continuous strip of the desired thickness and width. Calendering improves the physical and chemical properties of the rubber mixture; the consumption of rubber mixtures and the quality of products depend on it.

Rubbers are natural or synthetic materials characterized by elasticity, water resistance and electrical insulating properties, from which rubber is obtained through special processing. Natural rubber is obtained from a milky-white liquid called latex, the milky sap of rubber plants.

Natural rubber is obtained by coagulating the milky sap (latex) of rubber plants. The main component of rubber is polyisoprene hydrocarbon (91-96%). Natural rubber is found in many plants that do not form one specific botanical family. Depending on the tissues in which rubber accumulates, rubber plants are divided into:

Parenchymal - rubber in roots and stems;

Chlorenchyma - rubber in the leaves and green tissues of young shoots.

Latex - rubber in milky juice.

Herbaceous latex rubber-bearing plants from the Asteraceae family (Kok-sagyz, Crimea-sagyz and others), growing in the temperate zone, including the southern republics, containing rubber in small quantities in the roots, are of no industrial importance.

What is synthetic rubber? These are synthetic polymers that can be processed into rubber by vulcanization and make up the bulk of elastomers. Which city produces rubber in Russia? For example, in Togliatti, Krasnoyarsk.

Synthetic rubber is a high-polymer, rubber-like material. It is obtained by polymerization or copolymerization of butadiene, styrene, isoprene, neoprene, chlorprene, isobutylene, acrylic acid nitrile. Like natural rubbers, synthetic ones have long macromolecular chains, sometimes branched, with an average molecular weight of hundreds of thousands and even millions. Polymer chains in synthetic rubber in most cases have double bonds, due to which, during vulcanization, a spatial network is formed, and the resulting rubber acquires characteristic physical and mechanical properties.

Usually, the classification and naming of rubbers according to the monomers used to obtain them (isoprene, butadiene, etc.) or according to the characteristic group (atoms) in the main chain or side groups (urethane, polysulfide, etc.) is accepted. Synthetic rubbers are also divided according to characteristics , for example, by content of fillers (filled and unfilled), by molecular weight (consistency) and release form (solid, liquid, powder). Some synthetic rubbers are produced in the form of aqueous dispersions - synthetic latexes. A special group of rubbers consists of thermoplastic elastomers.

Some types of synthetic rubbers (for example, polyisobutylene, silicone rubber) are completely saturated compounds, therefore organic peroxides, amines and other substances are used for their vulcanization. Certain types of synthetic rubbers are superior to natural rubber in a number of technical properties.

Based on their area of application, synthetic rubbers are divided into general purpose and special purpose rubbers. General purpose rubbers include rubbers with a set of sufficiently high technical properties (strength, elasticity, etc.) suitable for mass production of a wide range of products. Special-purpose rubbers include rubbers with one or more properties that ensure the fulfillment of special requirements for the product and performance under often extreme operating conditions.

General purpose rubbers: isoprene, butadiene, styrene butadiene, etc.

Rubbers for special purposes: butyl rubber, ethylene propylene rubber, chloroprene rubber, fluorine rubber, urethane rubber, etc. Many do not know that chloroprene rubber was produced in the USSR and ask the question - in which city is rubber produced now? Unfortunately, chloroprene rubber was produced in Armenia at the Nairit plant, which has been shut down for several years.

In technology, rubber is used to make tires for vehicles, airplanes, and bicycles; Rubbers are used for electrical insulation, as well as for the production of industrial goods and medical devices.

1. Natural rubber

Rubber has been around for as long as nature itself. The fossilized remains of rubber trees that have been found are about three million years old. Europeans first encountered natural rubber five centuries ago, and in the United States rubber goods became popular in the 1830s, with rubber bottles and shoes made by South American Indians being sold in large quantities. In 1839, American inventor Charles Goodyear discovered that heating rubber with sulfur eliminated its unfavorable properties. He placed a piece of rubber-covered cloth on the stove, on which a layer of sulfur was applied. After some time, he discovered a leather-like material - rubber. This process was called vulcanization. The discovery of rubber led to its widespread use: by 1919, more than 40,000 different rubber products were put on the market.

Natural rubber plants

The word “rubber” comes from two words in the Tupi-Guarani language: “kau” - tree, “uchu” - to flow, cry. “Caucho” is the juice of the Hevea plant, the first and most important rubber plant. Europeans added just one letter to this word. Among the herbaceous plants of Russia there are the familiar dandelion, wormwood and euphorbia, which also contain milky sap.

Latex trees are of industrial importance because they not only accumulate rubber in large quantities, but also easily give it away; of these, the most important is the Brazilian Hevea (Hevea brasiliensis), which, according to various estimates, produces from 90 to 96% of the world's natural rubber production.

Crude rubber from other plant sources is usually contaminated with resin impurities that must be removed. These raw rubbers contain gutta-percha, a product of certain tropical trees of the sapotaceae family.

Rubber plants grow best no further than 10° from the equator to the north and south. Therefore, this 1,300-kilometer-wide strip on either side of the equator is known as the “rubber belt.” Here rubber is extracted and sold to all countries of the world.

Physical and chemical properties of natural rubber

Natural rubber is an amorphous solid capable of crystallizing.

Natural untreated (crude) rubber is a white or colorless hydrocarbon.

It does not swell and does not dissolve in water, alcohol, acetone and a number of other liquids. Swelling and then dissolving in fatty and aromatic hydrocarbons (gasoline, benzene, ether and others) and their derivatives, rubber forms colloidal solutions that are widely used in technology.

Natural rubber is homogeneous in its molecular structure, distinguished by high physical properties, as well as technological ones, that is, the ability to be processed on the equipment of rubber industry factories.

A particularly important and specific property of rubber is its elasticity (elasticity) - the ability of rubber to restore its original shape after the cessation of the forces that caused the deformation. Rubber is a highly elastic product; under the influence of even small forces, it has a reversible tensile deformation of up to 1000%, and for ordinary solids this value does not exceed 1%. The elasticity of rubber is maintained over a wide temperature range, and this is its characteristic property. But when stored for a long time, rubber hardens.

At a liquid air temperature of -195°C it is hard and transparent; from 0° to 10°C it is brittle and already opaque, and at 20°C it is soft, elastic and translucent. When heated above 50 °C, it becomes plastic and sticky; at a temperature of 80 °C natural rubber loses its elasticity; at 120 °C - turns into a resin-like liquid, after which it hardens it is no longer possible to obtain the original product. If the temperature is raised to 200-250 °C, the rubber decomposes to form a number of gaseous and liquid products.

Rubber is a good dielectric; it has low water and gas permeability. Rubber is insoluble in water, alkali and weak acids; in ethyl alcohol its solubility is low, but in carbon disulfide, chloroform and gasoline it first swells and then dissolves. Easily oxidized by chemical oxidizing agents, slowly by atmospheric oxygen. The thermal conductivity of rubber is 100 times less than the thermal conductivity of steel.

Along with elasticity, rubber is also plastic - it retains its shape acquired under the influence of external forces. The plasticity of rubber, which manifests itself during heating and mechanical processing, is one of the distinctive properties of rubber. Since rubber has elastic and plastic properties, it is often called a plasto-elastic material.

When natural rubber is cooled or stretched, it undergoes a transition from an amorphous to a crystalline state (crystallization). The process does not happen instantly, but over time. In this case, in the case of stretching, the rubber is heated due to the released heat of crystallization. Rubber crystals are very small; they lack clear edges and a specific geometric shape.

At a temperature of about -70 °C, rubber completely loses its elasticity and turns into a glassy mass.

In general, all rubbers, like many polymeric materials, can be in three physical states: glassy, highly elastic and viscous. The highly elastic state for rubber is most typical.

Rubber easily enters into chemical reactions with a number of substances: oxygen (O2), hydrogen (H2), halogens (Cl2, Br2), sulfur (S) and others. This high reactivity of rubber is due to its unsaturated chemical nature. The reactions take place especially well in rubber solutions, in which the rubber is in the form of molecules of relatively large colloidal particles.

Almost all chemical reactions lead to changes in the physical and chemical properties of rubber: solubility, strength, elasticity and others. Oxygen and, especially, ozone, oxidize rubber already at room temperature. Introducing themselves into complex and large rubber molecules, oxygen molecules break them into smaller ones, and the rubber, destructuring, becomes brittle and loses its valuable technical properties. The oxidation process also underlies one of the transformations of rubber - its transition from a solid to a plastic state.

Composition and structure of natural rubber

Natural rubber (NR) is a high molecular weight unsaturated hydrocarbon, the molecules of which contain a large number of double bonds; its composition can be expressed by the formula (C5H8)n (where the value of n ranges from 1000 to 3000); it is a polymer of isoprene.

Natural rubber is found in the milky sap of rubber-bearing plants, mainly tropical ones (for example, the Brazilian Hevea tree). Another natural product, gutta-percha, is also a polymer of isoprene, but with a different molecular configuration.

A long rubber molecule could be observed directly using modern microscopes, but this is not possible because the chain is too thin: its diameter corresponds to the diameter of one molecule. If a rubber macromolecule is stretched to the limit, it will have the appearance of a zigzag, which is explained by the nature of the chemical bonds between the carbon atoms that make up the skeleton of the molecule.

The units of a rubber molecule cannot rotate freely in any direction, but only to a limited extent - only around single bonds. Thermal vibrations of the links cause the molecule to bend, while its ends are brought closer together in a calm state.

When rubber is stretched, the ends of the molecules move apart and the molecules are oriented in the direction of the tensile force. If the force that caused the stretching of the rubber is removed, the ends of its molecules come closer together again and the sample takes on its original shape and size.

A rubber molecule can be thought of as a round, open spring that can be greatly stretched by spreading its ends apart. The released spring returns to its previous position. Some researchers imagine the rubber molecule in the form of a springy spiral. Qualitative analysis shows that rubber consists of two elements - carbon and hydrogen, that is, it belongs to the class of hydrocarbons.

The initially accepted formula for rubber was C 5 H 8, but it is too simple for such a complex substance as rubber. Determination of molecular weight shows that it reaches several hundred thousand (150,000 - 500,000). Rubber is therefore a natural polymer.

It has been experimentally proven that the macromolecules of natural rubber mainly consist of residues of isoprene molecules, and natural rubber itself is a natural polymer cis-1,4-polyisoprene.

The natural rubber molecule consists of several thousand initial chemical groups (links) connected to each other and in continuous vibrational-rotational motion. Such a molecule is similar to a tangled ball, in which its constituent threads in places form regularly oriented sections.

The main product of rubber decomposition is a hydrocarbon, the molecular formula of which is unambiguous with the simplest formula of rubber. We can assume that rubber macromolecules are formed by isoprene molecules. There are similar polymers that do not exhibit the same elasticity as rubber. What explains this special property?

Rubber molecules, although they have a linear structure, are not elongated in a line, but are repeatedly bent, as if rolled into balls. When the rubber is stretched, such molecules straighten, and the rubber sample becomes longer. When the load is removed, due to internal thermal movement, the molecule links return to their previous folded state, and the size of the rubber is reduced. If the rubber is stretched with a sufficiently large force, then not only the molecules will straighten, but also they will shift relative to each other - the rubber sample may tear.

2. Synthetic rubber

In Russia there were no known natural sources for obtaining natural rubber, and rubber was not imported to us from other countries, and they did not yet know what synthetic rubber was. And so, on December 30, 1927, 2 kg of divinyl rubber was obtained by polymerizing 1,3-butadiene under the influence of sodium. Since 1932, industrial production of 1,3-butadiene began, and rubber production from 1,3-butadiene.

The raw material for the synthesis of butadiene is ethyl alcohol. The production of butadiene is based on the reactions of dehydrogenation and dehydration of alcohol. These reactions occur simultaneously when alcohol vapor is passed over a mixture of appropriate catalysts. Butadiene is purified from unreacted ethyl alcohol and numerous byproducts and subjected to polymerization.

In order to force the monomer molecule to connect with each other, they must first be excited, that is, brought to a state where they become capable of mutual attachment as a result of the opening of double bonds. This requires the expenditure of a certain amount of energy or the participation of a catalyst.

During catalytic polymerization, the catalyst is not part of the resulting polymer and is not consumed, but is released at the end of the reaction in its original form. As a catalyst for the synthesis of butadiene rubber, S. V. Lebedev chose metallic sodium, first used for the polymerization of unsaturated hydrocarbons by the Russian chemist A. A. Krakau.

A distinctive feature of the polymerization process is that the molecules of the original substance or substances combine with each other to form a polymer, without releasing any other substances.

The most important types of synthetic rubber

The above-mentioned butadiene rubber (SBR) comes in two types: stereoregular and non-stereoregular. Stereoregular butadiene rubber is used mainly in the production of tires (which are superior to tires made of natural rubber in terms of wear resistance), non-stereoregular butadiene rubber is used for the production, for example, of acid- and alkali-resistant rubber and hard rubber.

Currently, the chemical industry produces many different types of synthetic rubbers that are superior to natural rubber in some properties. In addition to polybutadiene rubber (SBR), copolymer rubbers are widely used - products of co-polymerization (copolymerization) of butadiene with other unsaturated compounds, for example, with styrene (SKS) or acrylonitrile (SKN). In the molecules of these rubbers, butadiene units alternate with units of styrene and acrylonitrile, respectively.

Styrene-butadiene rubber is characterized by increased wear resistance and is used in the production of car tires, conveyor belts, and rubber shoes.

Nitrile butadiene rubbers are petrol and oil resistant and are therefore used, for example, in the production of oil seals.

Vinylpyridine rubbers are products of copolymerization of diene hydrocarbons with vinylpyridine, mainly butadiene with 2-methyl-5-vinylpyridine.

Rubbers made from them are oil-, petrol- and frost-resistant, and adhere well to various materials. They are mainly used in the form of latex to impregnate tire cords.

In Russia, the production of synthetic polyisoprene rubber (SRI), which is similar in properties to natural rubber, has been developed and put into production. Rubbers made from SKI are characterized by high mechanical strength and elasticity. SKI serves as a substitute for natural rubber in the production of tires, conveyor belts, rubber, footwear, medical and sports products.

Organosilicon rubbers, or silicone rubbers, are used in the production of wire and cable sheaths, blood transfusion tubes, prostheses (for example, artificial heart valves), etc. Liquid silicone rubbers are sealants.

Polyurethane rubber is used as the basis for the wear resistance of rubber.

Chloroprene rubbers are polymers of chloroprene (2-chloro-1,3-butadiene) with properties similar to natural rubber; they are used in rubbers to increase weather, petrol and oil resistance.

Foamed rubber finds its application. Various types of rubbers undergo foaming. There is also inorganic synthetic rubber - polyphosphonitrile chloride.

3. Rubber

Vulcanization of rubber

Modern rubber production technology is carried out in the following stages:

1. Production of semi-finished products:

Hanging rubbers and ingredients;

Rubber plasticization;

Rubberizing fabrics, calendering, extrusion;

Cutting rubberized fabrics and rubber sheets, assembling products from semi-finished products.

2. Vulcanization, after which finished rubber products are obtained from raw rubber mixtures.

The solubility of the polymer also changes: rubber, although slowly, dissolves in gasoline, rubber only swells in it. If you add more sulfur to rubber than is needed to form rubber, then during vulcanization the linear molecules will be “cross-linked” in many places, and the material will lose elasticity and become hard - you will get ebonite. Before the advent of modern plastics, ebonite was considered one of the best insulators.

Vulcanization accelerators improve the properties of vulcanizers, reduce vulcanization time and consumption of basic raw materials, and prevent overvulcanization. Inorganic compounds (magnesium oxide MgO, lead oxide PbO and others) and organic compounds are used as accelerators: dithiocarbamates (dithiocarbamic acid derivatives), thiurams (dimethylamine derivatives), xanthates (xanthogenic acid salts) and others.

Activators of vulcanization accelerators facilitate the interaction reactions of all components of the rubber mixture. Basically, zinc oxide ZnO is used as activators.

Antioxidants (stabilizers, antioxidants) are introduced into the rubber mixture to prevent “aging” of the rubber.

Fillers - increase the physical and mechanical properties of rubber: strength, wear resistance, abrasion resistance. They also help to increase the volume of raw materials, and, consequently, reduce rubber consumption and reduce the cost of rubber. Fillers include various types of soot (carbon black), mineral substances (chalk CaCO3, BaSO4, gypsum, talc, quartz sand SiO2).

Plasticizers (softeners) are substances that improve the technological properties of rubber, facilitate its processing (reduce the viscosity of the system), and provide the opportunity to increase the content of fillers. The introduction of plasticizers increases the dynamic endurance of rubber and “abrasion” resistance. Oil refining products (fuel oil, tar, paraffins), substances of plant origin (rosin), fatty acids (stearic, oleic) and others are used as plasticizers.

The strength and insolubility of rubber in organic solvents are related to its structure. The properties of rubber are also determined by the type of raw material. For example, rubber made from natural rubber is characterized by good elasticity, oil resistance, wear resistance, but at the same time is not very resistant to aggressive environments; rubber made from SKD rubber has even higher wear resistance than from NK. SKS styrene-butadiene rubber improves wear resistance. Isoprene rubber SKI determines the elasticity and tensile strength of rubber, and chloroprene rubber determines its resistance to oxygen.

In which city is rubber produced and when did its production begin? In Russia, the first large manufacturing enterprise in the rubber industry was founded in St. Petersburg in 1860, later called “Triangle” (since 1922 - “Red Triangle”). After him, other Russian factories of rubber products (RTI) were founded: “Kauchuk” and “Bogatyr” in Moscow, “Provodnik” in Riga and others.

Application of rubber in industrial products

Rubber is a highly elastic, durable compound, but less ductile than rubber. It is a complex multicomponent system consisting of a polymer base (rubber) and various additives.

The largest consumers of rubber technical products are the automotive industry and agricultural engineering. The degree of saturation with rubber products is one of the main signs of perfection, reliability and comfort of mass types of engineering products. The mechanisms and units of modern cars and tractors contain hundreds of items and up to a thousand pieces of rubber parts, and simultaneously with the increase in the production of machines, their rubber capacity increases.

Types of rubber and their application

Depending on the structure, rubber is divided into non-porous (monolithic) and porous.

Non-porous rubber is made on the basis of butadiene rubber. It has high abrasion resistance. The wear life of plantar rubber is 2-3 times longer than the wear life of plantar leather. The tensile strength of rubber is less than that of natural leather, but the elongation at break is many times higher than that of natural sole leather. Rubber does not allow water to pass through and practically does not swell in it.

Rubber is inferior to leather in terms of frost resistance and thermal conductivity, which reduces the heat-protective properties of shoes. And finally, rubber is absolutely air- and vapor-tight. Non-porous rubber can be sole, leather-like, and transparent. Conventional non-porous rubber is used to make molded soles, overlays, heels, half heels, heels and other parts of the bottom of shoes.

Porous rubbers are used as soles and platforms for spring, autumn and winter shoes.

Leather-like rubber is rubber for the bottom of shoes, made on the basis of rubber with a high styrene content (up to 85%). The increased styrene content gives rubbers hardness, as a result of which it is possible to reduce their thickness to 2.5-4.0 mm while maintaining good protective functions. The performance properties of leather-like rubber are similar to those of natural leather. It has high hardness and ductility, which allows you to create a shoe footprint of any shape. Leather-like rubber stains well when finishing shoes. It has high wear resistance due to good abrasion resistance and resistance to repeated bending.

The wear life of shoes with soles made of leather-like rubber is 179-252 days in the absence of chipping in the toe. The disadvantage of this rubber is its low hygienic properties: high thermal conductivity and lack of hygroscopicity and air tightness.

Leather-like rubber is produced in three varieties: non-porous structure with a density of 1.28 g/cm3, porous structure with a density of 0.8-0.95 g/cm3, and porous structure with a fibrous filler, the density of which is not higher than 1.15 g/cm3 . Porous rubbers with fibrous fillers are called leather fiber. These rubbers are similar in appearance to genuine leather. Thanks to the fiber filler, their heat-shielding properties increase, they are lightweight, elastic, and have a good appearance. Leather-like rubbers are used as soles and heels in the manufacture of summer and spring-autumn shoes using the adhesive fastening method.

Transparent rubber is a translucent material with a high content of natural rubber. It is distinguished by high abrasion resistance and hardness, and is superior in wear resistance to all types of rubber. Transparent rubbers are produced in the form of molded soles (together with heels), with deep corrugation on the running side. A type of transparent rubber is styronip, which contains a larger amount of rubber. Styronip's resistance to repeated bending is more than three times higher than that of conventional non-porous rubber. Styronip is used in the manufacture of shoes using the adhesive fastening method.

Rubber with a porous structure has closed pores, the volume of which, depending on the type of rubber, ranges from 20 to 80% of its total volume. These rubbers have a number of advantages compared to non-porous rubbers: increased softness, flexibility, high shock-absorbing properties, and elasticity. The disadvantage of porous rubber is the ability to shrink and also crumble in the toe part upon impact. To increase the hardness of porous rubbers, polystyrene resins are introduced into their composition.

Currently, the production of new types of porous rubbers has been mastered: porocrep and vulcanite. Porokrep has a beautiful color, elasticity, and increased strength. Vulcanite is a porous rubber with fibrous fillers, which has high wear resistance and good heat protection. Porous rubbers are used as soles for spring, autumn and winter shoes.

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Some tire companies rely on innovative compound materials, while others change the physical structure of products in 3D format. An example of this is Goodyear tires based on soybean oil, Pirelli products made from Nizhnekamsk varieties of isoprene and divinylstyrene rubbers, and Bridgestone models for all-wheel drive SUVs. What's better?

Goodyear: Soybean oil benchmark

Goodyear is increasing the environmental friendliness of its tires. Leading engineer Voloshinek said that last year there was a serial launch of products where the protector is made on the basis of soybean oil. Thanks to innovation, the share of petroleum products was reduced by 60%. Models from the all-season Assurance WeatherReady line began to meet new environmental standards, while their technical characteristics became better adapted to a wide range of temperatures.

Initially, soybean oil was considered as an additive to rubber compounds. But after the Ford concern with the Soybean Council received significant results using soy products, the company's specialists deepened and accelerated research in this area. Thanks to triglycerides, oil-based mixtures have become a complete substitute for compound bases.

Thermoplasticity, elasticity and energy-saving mixing

For all-season products, the thermoplasticity indicator is important, since the adhesion of the tire contact zone with wet, dry, snowy, and ice-covered track surfaces directly depends on the characteristics of the rubber. Usually it is not possible to avoid deterioration of any indicators. Therefore, the optimal balance between tire and road adhesion determined the choice of soybean oil.

The elasticity of soybean oil-based tires, their plasticity, and cost-effectiveness compared to petroleum products have become other driving factors for replacement. Easy mixing of the oil with the components of the compound, which includes silicon dioxide and polymers, is due to the reduced viscosity and the presence of polyunsaturated fatty acids.

Mixing requires less energy than when using petroleum products. The company is considering the use of high oleic oil, which is used in the food industry. Experiments are now being carried out to determine its quality and suitability for tire production.

Instead of natural rubber for tires - artificial from Tatarstan

The petrochemical complex of Tatarstan has become a gold mine for entrepreneurs. Due to rising prices for natural rubber, its high-quality substitutes are increasingly of interest to tire manufacturers. That is why the Nizhnekamskneftekhim company signed a long-term contract in December 2017 for the supply of artificial rubber to the Pirelli concern.

Minnikhanov, President of Tatarstan, noted that over 10 years the volume of Pirelli supplies has increased 3 times. Now Nizhnekamsk and Italians cooperate not only on manufactured products, but are jointly developing promising types of rubber planned for mass production. Due to the fact that Pirelli is one of the five largest tire manufacturers (19 factories, supplies to 160 countries), the need for synthetic rubber and plastic will allow the production capacity of Nizhnekamskneftekhim to be maximally loaded.

It is planned to expand the production of SKI-3 isoprene rubber to 330 thousand tons per year. In the near future, until 2021, we will increase the production of all types of artificial rubber to a million tons. Azat Bikmurzin, head of Tatneftekhiminvest Holding, reports that in 2 years they will synthesize 60 thousand tons of divinylstyrene rubber for the production of new generation tires. This will include 5 brands designed for tires of different types and seasons.

Bridgestone tires for all-wheel drive crossovers and SUVs

The company focused on the exterior of its products. It released a new studless winter tire Blizzak DM-Z3З. The innovative option is designed for owners of all-wheel drive vehicles. The difference between the new model and the old ones is the complex combination of microscopic pores and special microgrooves, which enhance protection against aquaplaning and prevent sliding on ice. The contact of the tread with the road surface is accompanied by the absorption of moisture (the “sponge” effect), after which it is removed through a micro-drainage system.

The tread is equipped with edges and lamellas in 3D format, which have support inserts to prevent their deformation. Thanks to these innovations, the pressure in the contact zone is optimized and distributed evenly. The edge of the 3D block enhances the tire's grip on sections of the road with crumbling snow and ice, which enhances the passage of the section.

The search for cheap raw materials for production prompted the company to begin building a laboratory in Mecklenburg (Germany) for the cultivation of Russian dandelion, its subsequent use in the tire industry instead of natural rubber. It is expected that the cost of launching the project will be 35 million euros, and the milky juice of dandelion will successfully replace the juice of hevea from tropical regions. An important role is played by reducing the cost of transporting raw materials and eliminating the burning of tropical plantations to expand the areas for growing rubber trees.

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