Mazda

What and how are rubber (tires) made from? For your car wheels. Rubber composition and its production

Elastic materials have been familiar to man since ancient times. They were then used mainly for domestic purposes. Today, without rubber and caoutchouc, it is difficult to imagine the development of industry, transport and construction and communications, and the daily life of people.

What came first

Even before Europeans discovered America, the Indians who lived there used rubber. It was obtained from tropical hevea juice. The dried juice was smoked, producing a waterproof and elastic material. It was used to make water containers, toys, and religious objects. Primitive shoes and clothing were made from it.

In the middle of the 18th century, travelers brought rubber to Europe. However, for a long time they could not find a way to use it. Except for pencil erasers. Because it dried out and hardened, it was thought to have no prospects for practical use. In the next century, waterproof fabrics, bags and overshoes appeared, which hardened in cold weather and became soft in warm weather.

A hundred years after the appearance of rubber in the Old World, a method was invented that made it possible to make the elasticity of this material stable. It got the name vulcanization. Its essence is mixing raw rubber with sulfur and further heating this mixture. The resulting product became known as rubber. It began to be widely used as a sealant and electrical insulator. At the beginning of the twentieth century, due to the growing demand for rubber, the problem of producing synthetic rubbers in industrialized countries was solved.

Where does latex go?

Natural rubber is extracted from rubber trees that grow in tropical forests or on special plantations. Such a tree begins to produce sap after seven years. To do this, a spiral-shaped depression is made on it with a knife, through which the flowing white juice, called latex, enters the container. After a few hours, about one and a half hundred grams are collected. After thickening and drying, lumps of natural rubber form. This procedure can be carried out once every two days.

Total natural rubber in the world reaches 40% in the overall production and consumption of all types of rubbers. It is approximately 9 million tons.

Raw rubber dissolves in gasoline, forming rubber glue, and other organic solvents. After vulcanization, it only swells and does not dissolve.

In addition to gasoline, it dissolves in benzene, chloroform, carbon disulfide and other hydrocarbons. It is practically insoluble and does not swell in alcohol, water and acetone.

More than half of natural rubber is used to produce tires. Large-scale production has been organized in the countries of Southeast Asia (Vietnam, Indonesia, Malaysia and Thailand).

How rubber is made

Both elastic materials are inextricably linked. Rubber is obtained from natural or synthetic rubber through vulcanization. A filler is added, which is most often carbon black. Heated to 130-160 degrees rubber begins to interact with sulfur. During this technological process, rubber molecules are stitched into a single network using sulfur atoms. This dramatically increases its elasticity, hardness, and strength qualities. Swelling and solubility are regulated by organic solvents.

In addition to sulfur, metal oxides, amine-type compounds, catalysts that speed up the process, and other chemical components are used for vulcanization. They provide the necessary plasticity, anti-aging properties and other performance qualities. As a result, rubber turns into rubber. Depending on the sulfur content, a material of varying degrees of elasticity is formed. The softest rubber is the one with the minimum sulfur content, and the hardest is the one in which it makes up a third or more.

When manufacturing rubber, it is given certain qualities for the production of products from it:

Acid resistance.
stability in aggressive environments.
Oil and petrol resistance.
resistance against high and low temperatures.
Ozone resistance.
Electrical conductivity, etc.

Rubber is widely used for the manufacture of tires for vehicles, various hoses and seals, conveyor belts, household, hygiene and medical products.

What are the similarities and differences

Rubber and caoutchouc are similar primarily in their elasticity and the fact that they can be recycled. Their differences are more significant.

Raw rubber:

Not suitable for industrial production. No more than 1% of extracted natural rubber is used in the world. Mainly in the form of rubber cement.
It has low strength and high stickiness, which is very noticeable at high temperatures. In the cold it hardens and breaks. It acquires useful qualities only after vulcanization.
At room temperature, its aging begins, resulting in a loss of strength and elasticity.
When the temperature rises to 200 degrees, it decomposes to form low molecular weight hydrocarbons.
Dissolves in organic solvents such as gasoline.
Serves as a raw material for rubber production.

Rubber obtained as a result of vulcanization of rubbers is used for the mass production of many thousands of different products.

It is made from:

Tires for vehicles and aircraft.
A variety of seals used in industry and construction, various types of equipment.
Electrical insulating materials.
Drive belts, hoses for supplying liquids.
Floor coverings and insulating plates.
Rubber shoes and waterproof clothing.
Means of protection against chemical, radiation and bacteriological exposure (suits, gloves, boots, etc.).
Products of medical equipment and hygiene.
Accessories for clothing, etc.

Rubber is an elastic polymer material, a product of processing natural or synthetic isoprene or diene rubber.

The transformation of rubber into rubber occurs through vulcanization. In this case, linear polymer molecules enter into a chemical reaction with sulfur, and sulfide bridges are formed between neighboring molecules. The polymer acquires a spatial structure. By changing the structure, the elasticity, strength, wear resistance and other technological characteristics of the material are significantly increased.

Achieving the best possible combination of mechanical and physical properties during the rubber manufacturing process is known as the vulcanization optimum.

The production process includes the following stages:

formation of a vulcanization network,
induction stage,
reversion.

Depending on the required properties of the final product, various additives are introduced into the reaction mixture: carbon black, chalk, plasticizers, softeners. To improve the performance qualities of finished rubber products, organic additives, in particular peroxides and oligoether acrylates, have recently been increasingly used.

There are cold and hot vulcanization. In the production of sealants, the cold vulcanization method is used at temperatures within 20...30 degrees. Hot vulcanization is carried out at temperatures of 140... 300 degrees.

In rubber production, various catalysts are used, which affect not only the reaction rate, but also the quality of the rubber. Thiazoles and substituted sulfonamides are most often used in industry. Sulfonamides ensure the integrity of the product, while thiazoles increase the resistance of the material to thermal-oxidative aging.

In addition to cold and hot vulcanization, there is a method called sulfur vulcanization, which is used in the production of rubber with increased wear resistance for the manufacture of tires and some types of shoes.

Rubber Applications

Approximately half of all rubber production is destined for tire production. The rest is used as various types of insulation, for the manufacture of parts for various machines and mechanisms, in the shoe industry, electrical engineering, medical equipment production, instrument making, etc.

Useful products made from recycled rubber

Today, humanity is able to largely reproduce its needs for rubber. This potential is contained not just in waste, but in waste that has nowhere to go. Even Russia, rich in natural resources, is beginning to understand its benefits here

Crumb rubber can be used to make high-quality coatings used in a wide variety of places, including in the country, children's and sports grounds

Danger of waste

During the rubber production process, oxides of sulfur, nitrogen, carbon, soot particles, resorcinol, ethylene, formaldehyde and a number of other aggressive and toxic compounds enter the atmosphere.

Rubber waste, for example, used rubber, is no less dangerous. tires, insulation elements and other rubber products. As rubber is left in the open air, it gradually breaks down, releasing into the environment volatile components and heavy metals.

In places where there is a large accumulation of used tires, mouse-like rodents and some insects that settle in the cavities of tires multiply intensively. These animals are carriers of dangerous diseases and also cause direct harm to agricultural production and a number of adjacent industries. The largest amount of rubber waste is nothing more than worn-out tires; this is the most large-tonnage and voluminous waste entering landfills around the world.

Methods for recycling rubber products

In developed countries, more and more attention is being paid to the development and improvement of technologies for the recycling of rubber products, in particular.

Slightly worn tires are repaired by retreading. Products unsuitable for repair are subject to disposal using various technologies, which can be divided into 3 groups:

Methods that do not affect the physical and chemical properties of the material. This is primarily a rough crushing of used products. The resulting crumbs are subject to burial or are used as a filler for certain types of concrete, asphalt, or as raw materials for the production of rubber tiles and similar materials.
Methods leading to partial destruction of the spatial structure of the material and partial destruction of rubber, which include the production of tire reclaim. The regenerate is returned to the tire production cycle and replaces part of the primary raw material.
Thermal methods of rubber destruction. This group includes pyrolysis and combustion. A more progressive method of thermal recycling is pyrolysis, which allows one to obtain thermal and electrical energy from rubber waste, valuable components for the chemical industry and to minimize the amount of pressure on the environment.

The use of rubber products in various industries makes it possible to reduce the cost of the final product, reduce the amount of harmful emissions into the atmosphere, soil and water, and also reduce the energy intensity of the main production.

Rubber composition and its production

TO category:

Automotive operating materials

Rubber composition and its production

The main component of rubber is rubber: its content in rubber products is approximately 50...60% by weight. In rubber, the molecules are long threads twisted into balls and entangled with each other. This structure of rubber determines its main feature - elasticity. When rubber is stretched, its molecules gradually straighten, returning to their previous state after the load is removed. However, if the stretch is too great, the molecules are irreversibly displaced relative to each other and the rubber ruptures.

At first, only natural rubber was used in rubber products, which was obtained from the milky sap (latex) of the rubber tree - the Brazilian Hevea. In 1932, for the first time in the world, synthetic rubber was synthesized in our country, which soon became the main raw material for the manufacture of rubber products. Currently, dozens of varieties of synthetic rubbers are produced for this purpose.

The most widely used are styrene rubbers C KMC (butadiene-methylstyrene) and SKS (butadiene-styrene). These rubbers are superior to natural rubber. wear resistance, but are inferior to it in elasticity, heat and frost resistance.

In the production of tires, isoprene (SKI-3) and butadiene (SKV) rubbers are used. SKI-3 rubber is close in properties to natural rubber, SKV rubber is highly wear-resistant. Chloroprene (nairit) and nitrile (SKN) rubbers have good oil and petrol resistance. They are used to make parts that come into contact with petroleum products: hoses, cuffs, etc.

In the manufacture of tubes and the sealing layer of tubeless tires, butyl rubber is used, which is characterized by high gas impermeability.

Natural or synthetic rubber forms the basis of the rubber mixture or “raw” rubber, which itself, due to its low strength, finds limited use - mainly for the manufacture of adhesives and sealing gaskets. To increase the strength of rubbers, the process of vulcanization is used - the chemical bonding of rubber molecules with sulfur atoms. During the vulcanization process, which occurs at a temperature of 130 ... 140 ° C, sulfur molecules combine with linear rubber molecules, forming bridges between them (Fig. 59). The result is vulcanized rubber, which is an elastic material.

The amount of sulfur used during vulcanization is determined by the strength and elasticity requirements of the material. As the sulfur concentration increases, the strength of rubber increases, but at the same time its elasticity decreases. Therefore, in rubbers intended for the manufacture of automobile tubes and tires, the addition of sulfur is limited to 1...3% of the total rubber content. With a sulfur content of 40...60%, rubber turns into a solid material - ebonite.

To ensure the required strength and wear resistance of rubber, especially those intended for the manufacture of tires, fillers are used. The main filler is soot, which is powdered carbon with particle sizes of 0.03...0.25 microns. Modern rubbers contain a significant amount of soot - from 30 to 70% in relation to the rubber contained. With the introduction of soot, the strength of rubber increases by more than an order of magnitude. For the production of colored rubber, so-called white carbon black (silica and other products) is used. Along with carbon black, inactive fillers are used to increase the volume of the rubber mixture without deteriorating its properties (exhausted chalk, asbestos flour, etc.).

Rice. 1. Structure of vulcanized rubber

To facilitate mixing of the components of the rubber mixture, plasticizers or softeners are introduced into it - usually liquid or solid petroleum products. In order to slow down the aging process, as well as to increase the endurance of rubber under repeated deformations, antioxidants are added. Special chemicals are used as antioxidants that bind oxygen penetrating into the rubber. Neozone D and Santoflex A are used as such substances. Accelerator additives are used to accelerate vulcanization. The production of porous sponge rubber is achieved using special pore-forming agents.

To increase the strength of a number of rubber products (car tires, drive belts, high-pressure hoses, etc.), rubber is reinforced with fabric or metal reinforcement. For example, one of the most important and expensive products - car tires - uses polyamide (nylon), viscose or metal cords.

The main stage of the technological process for preparing rubber is mixing, which ensures complete and uniform distribution in the rubber of all contained ingredients (components), the number of which can reach up to 15. Mixing is carried out in rubber mixers, usually in two stages. First, an auxiliary mixture is prepared without sulfur and accelerators, then at the second stage sulfur and accelerators are introduced. The resulting rubber mixtures are used for the manufacture of relevant parts and for rubberizing the cord. In the latter case, to ensure sufficient bond strength between the cord and rubber, the cord must be impregnated with latexes and resins. The final operation is vulcanization, after which the rubber product is suitable for use.

When repairing car tires and inner tubes using the hot vulcanization method, types of raw rubber such as layer, tread and tube rubber are widely used. In this case, to ensure the required quality of repair, along with high temperature, the vulcanization process must take place under a certain pressure, provided using various devices.

RUBBER AND RUBBER
Rubber is a substance obtained from rubber-bearing plants, growing mainly in the tropics and containing a milky fluid (latex) in the roots, trunk, branches, leaves or fruits or under the bark. Rubber is a product of vulcanization of rubber-based compositions. Latex is not a plant sap, and its role in the life of the plant is not fully understood. Latex contains particles that coagulate into a solid elastic mass called raw or unprocessed rubber.
SOURCES OF NATURAL RUBBER
Raw natural rubber comes in two types:
1) wild rubber, extracted from trees, bushes and vines growing naturally;
2) plantation rubber, extracted from trees and other plants cultivated by humans. During the 19th century. The entire mass of raw rubber for industrial use was wild rubber, extracted by tapping Hevea brasiliensis in the equatorial tropical forests of Latin America, from trees and vines in equatorial Africa, on the Malay Peninsula and the Sunda Islands.

PROPERTIES OF RUBBER
Crude rubber, intended for subsequent industrial use, is a dense amorphous elastic material with a specific gravity of 0.91-0.92 g/cm3 and a refractive index of 1.5191. Its composition varies among different latexes and plantation preparation methods. The results of a typical analysis are presented in the table.
Rubber hydrocarbon is polyisoprene, a hydrocarbon polymer chemical compound having the general formula (C5H8)n. Exactly how rubber hydrocarbons are synthesized in wood is unknown. Unvulcanized rubber becomes soft and sticky in warm weather and brittle in cold weather. When heated above 180° C in the absence of air, rubber decomposes and releases isoprene. Rubber belongs to the class of unsaturated organic compounds that exhibit significant chemical activity when interacting with other reactive substances. Thus, it reacts with hydrochloric acid to form rubber hydrochloride, and also with chlorine by addition and substitution mechanisms to form chlorinated rubber. Atmospheric oxygen acts on rubber slowly, making it hard and brittle; ozone does the same thing faster. Strong oxidizing agents, such as nitric acid, potassium permanganate and hydrogen peroxide, oxidize rubber. It is resistant to alkalis and moderately strong acids. Rubber also reacts with hydrogen, sulfur, sulfuric acid, sulfonic acids, nitrogen oxides and many other reactive compounds, forming derivatives, some of which have industrial applications. Rubber is insoluble in water, alcohol or acetone, but swells and dissolves in benzene, toluene, gasoline, carbon disulfide, turpentine, chloroform, carbon tetrachloride and other halogenated solvents, forming a viscous mass used as an adhesive. Rubber hydrocarbon is present in latex in the form of a suspension of tiny particles, the size of which ranges from 0.1 to 0.5 microns. The largest particles are visible through an ultramicroscope; they are in a state of continuous motion, which can illustrate a phenomenon called Brownian motion. Each rubber particle carries a negative charge. If a current is passed through the latex, then such particles will move to the positive electrode (anode) and be deposited on it. This phenomenon is used in industry to coat metal objects. On the surface of rubber particles there are adsorbed proteins that prevent the latex particles from approaching each other and their coagulation. By replacing the substance adsorbed on the surface of the particle, you can change the sign of its charge, and then rubber particles will be deposited on the cathode. Rubber has two important properties that determine its industrial use. In the vulcanized state, it is elastic and, after stretching, returns to its original shape; in the unvulcanized state it is plastic, i.e. flows under the influence of heat or pressure. One property of rubbers is unique: when stretched, they heat up, and when compressed, they cool. Instead, rubber contracts when heated and expands when cooled, demonstrating a phenomenon called the Joule effect. When stretched by several hundred percent, the rubber molecules are oriented to such an extent that its fibers give an X-ray pattern characteristic of a crystal. The molecules of rubber extracted from Hevea have a cis configuration, while the molecules of balata and gutta percha have a trans configuration. Being a poor conductor of electricity, rubber is also used as an electrical insulator.
RUBBER PROCESSING AND RUBBER PRODUCTION
Plasticization. One of the most important properties of rubber - plasticity - is used in the production of rubber products. To mix rubber with other rubber compound ingredients, it must first be softened, or plasticized, by mechanical or thermal treatment. This process is called rubber plasticization. T. Hancock's discovery in 1820 of the possibility of plasticizing rubber was of great importance for the rubber industry. His plasticizer consisted of a spiked rotor rotating in a spiked hollow cylinder; this device was manually driven. In the modern rubber industry, three types of similar machines are used before introducing other rubber components into the rubber. These are a rubber grinder, a Banbury mixer and a Gordon plasticizer. The use of granulators - machines that cut rubber into small granules or plates of uniform size and shape - facilitates dosing operations and controlling the rubber processing process. The rubber is fed into the granulator upon exiting the plasticizer. The resulting granules are mixed with carbon black and oils in a Banbury mixer to form a masterbatch, which is also granulated. After processing in a Banbury mixer, it is mixed with vulcanizing agents, sulfur and vulcanization accelerators.
Preparation of rubber mixture. A chemical compound of rubber and sulfur alone would have limited practical use. To improve the physical properties of rubber and make it more suitable for use in various applications, it is necessary to modify its properties by adding other substances. All substances mixed with rubber before vulcanization, including sulfur, are called rubber compound ingredients. They cause both chemical and physical changes in the rubber. Their purpose is to modify hardness, strength and toughness and increase resistance to abrasion, oil, oxygen, chemical solvents, heat and cracking. Different compounds are used to make rubber for different applications.
Accelerators and activators. Certain chemicals called accelerators, when used in conjunction with sulfur, reduce curing time and improve the physical properties of rubber. Examples of inorganic accelerators are white lead, litharge (lead monoxide), lime and magnesia (magnesium oxide). Organic accelerators are much more active and are an important part of almost any rubber compound. They are added to the mixture in a relatively small proportion: usually from 0.5 to 1.0 parts per 100 parts of rubber is sufficient. Most accelerators are fully effective in the presence of activators such as zinc oxide, and some require an organic acid such as stearic acid. Therefore, modern rubber compound formulations usually include zinc oxide and stearic acid.
Softeners and plasticizers. Softeners and plasticizers are usually used to reduce the time of preparation of the rubber mixture and lower the temperature of the process. They also help disperse the ingredients of the mixture, causing the rubber to swell or dissolve. Typical softeners are paraffin and vegetable oils, waxes, oleic and stearic acids, pine tar, coal tar and rosin.
Strengthening fillers. Certain substances strengthen rubber, giving it strength and resistance to wear. They are called strengthening fillers. Carbon black (gas) in finely ground form is the most common strengthening filler; it is relatively cheap and is one of the most effective substances of its kind. The tread rubber of a car tire contains approximately 45 parts carbon black to 100 parts rubber. Other commonly used strengthening fillers are zinc oxide, magnesium carbonate, silica, calcium carbonate and some clays, but all are less effective than carbon black.
Fillers. In the early days of the rubber industry, even before the advent of the automobile, certain substances were added to rubber to reduce the cost of the products obtained from it. Hardening was not yet of great importance, and such substances simply served to increase the volume and mass of rubber. They are called fillers or inert rubber ingredients. Common fillers are barite, chalk, some clays and diatomaceous earth.
Antioxidants. The use of antioxidants to maintain the desired properties of rubber products during their aging and use began after World War II. Like vulcanization accelerators, antioxidants are complex organic compounds that, at a concentration of 1-2 parts per 100 parts of rubber, prevent the growth of rubber hardness and brittleness. Exposure to air, ozone, heat and light is the main cause of rubber aging. Some antioxidants also protect rubber from damage due to bending and heat.
Pigments. Strengthening and inert fillers and other rubber compound ingredients are often called pigments, although real pigments are also used to impart color to rubber products. Zinc and titanium oxides, zinc sulfide and lithopone are used as white pigments. Crown yellow, iron oxide pigment, antimony sulfide, ultramarine and lamp black are used to give various color shades to products.
Calendering. Once the raw rubber is plasticized and mixed with rubber compound ingredients, it is further processed before vulcanization to shape it into the final product. The type of treatment depends on the application of the rubber product. Calendering and extrusion are widely used at this stage of the process. Calenders are machines designed for rolling rubber mixture into sheets or coating fabrics with it. A standard calender usually consists of three horizontal rollers stacked one above the other, although four-shaft and five-shaft calenders are used for some applications. Hollow calender rolls have a length of up to 2.5 m and a diameter of up to 0.8 m. Steam and cold water are supplied to the rolls to control the temperature, the selection and maintenance of which is crucial to obtain a quality product with a constant thickness and a smooth surface. Adjacent shafts rotate in opposite directions, with the rotation speed of each shaft and the distance between the shafts precisely controlled. The calender is used to coat fabrics, coat fabrics, and roll out the rubber mixture into sheets.
Extrusion. The extruder is used to form pipes, hoses, tire treads, pneumatic tire tubes, automotive gaskets and other products. It consists of a cylindrical steel body equipped with a heating or cooling jacket. A screw that fits tightly to the body feeds the unvulcanized rubber mixture, preheated on the rollers, through the body to the head, into which a replaceable molding tool is inserted, which determines the shape of the resulting product. The product emerging from the head is usually cooled by a stream of water. Pneumatic tire tubes come out of the extruder as a continuous tube, which is then cut to the required length. Many products, such as gaskets and small tubing, come out of the extruder in their final shape and are then cured. Other products, such as tire treads, come out of the extruder as straight blanks, which are subsequently applied to and vulcanized to the tire body, changing their original shape.
Curing. Next, it is necessary to vulcanize the workpiece to obtain a finished product suitable for use. Vulcanization is carried out in several ways. Many products are given their final shape only at the vulcanization stage, when the rubber mixture enclosed in metal molds is exposed to temperature and pressure. Car tires, after being assembled on a drum, are molded to the desired size and then vulcanized in grooved steel molds. The molds are placed one on top of the other in a vertical vulcanizing autoclave, and steam is released into a closed heater. An air bag of the same shape as the tire tube is inserted into the unvulcanized tire blank. Air, steam, hot water are released into it through flexible copper tubes, individually or in combination with each other; These pressure transfer fluids push the tire carcass apart, forcing the rubber to flow into the shaped recesses of the mold. In modern practice, technologists are striving to increase the number of tires vulcanized in separate vulcanizers called molds. These casting molds have hollow walls that allow internal circulation of steam, hot water, and air to transfer heat to the workpiece. At the specified time, the molds open automatically. Automated vulcanizing presses have been developed that insert a cooking chamber into a tire blank, vulcanize the tire, and remove the cooking chamber from the finished tire. The cooking chamber is an integral part of the vulcanization press. Tire tubes are vulcanized in similar molds that have a smooth surface. The average vulcanization time for one chamber is about 7 minutes at 155° C. At lower temperatures, the vulcanization time increases. Many smaller products are cured in metal molds that are placed between parallel platens in a hydraulic press. The press plates are hollow inside to provide steam access for heating without direct contact with the product. The product receives heat only through a metal mold. Many products are vulcanized by heating in air or carbon dioxide. Rubberized fabric, clothing, raincoats and rubber shoes are vulcanized in this way. The process is usually carried out in large horizontal vulcanizers with a steam jacket. Dry heat vulcanized rubber compounds usually contain less sulfur to prevent some of the sulfur from escaping onto the surface of the product. To reduce the vulcanization time, which is usually longer than with open steam or press vulcanization, accelerator substances are used. Some rubber products are vulcanized by immersion in hot water under pressure. The rubber sheet is wound between layers of muslin on a drum and vulcanized in hot water under pressure. Rubber bulbs, hoses, and wire insulation are vulcanized in open steam. Vulcanizers are usually horizontal cylinders with tightly fitting lids. Fire hoses are vulcanized with steam from the inside and thus act as their own vulcanizers. The rubber hose is pulled inside the braided cotton hose, connecting flanges are attached to them, and steam is injected under pressure into the workpiece for a specified time. Vulcanization without heat can be carried out using sulfur chloride S2Cl2 by either immersion in a solution or exposure to vapor. Only thin sheets or items such as aprons, bathing caps, finger guards or surgical gloves are vulcanized in this way because the reaction is rapid and the solution does not penetrate deeply into the workpiece. Additional treatment with ammonia is necessary to remove the acid formed during the vulcanization process.
HARD RUBBER
Hard rubber products differ from soft rubber products mainly in the amount of sulfur used in vulcanization. When the amount of sulfur in a rubber compound exceeds 5%, vulcanization results in hard rubber. The rubber compound can contain up to 47 parts of sulfur per 100 parts of rubber; this produces a hard and tough product, called ebonite, because it is similar to ebony (black) wood. Hard rubber products have good dielectric properties and are used in the electrical industry as insulators, such as switchboards, plugs, sockets, telephones and batteries. Pipes, valves and fittings made using hard rubber are used in areas of the chemical industry where corrosion resistance is required. The manufacture of children's toys is another source of hard rubber consumption.
SYNTHETIC RUBBER
The synthesis of rubber that occurs in wood has never been done in a laboratory. Synthetic rubbers are elastic materials; they are similar to the natural product in chemical and physical properties, but differ from it in structure. Synthesis of an analogue of natural rubber (1,4-cis-polyisoprene and 1,4-cis-polybutadiene). Natural rubber, obtained from Hevea brasiliensis, has a structure consisting of 97.8% 1,4-cis-polyisoprene:

The synthesis of 1,4-cis-polyisoprene has been carried out in several different ways using stereostructure-controlling catalysts, and this has enabled the production of various synthetic elastomers. The Ziegler catalyst consists of triethylaluminum and titanium tetrachloride; it causes isoprene molecules to combine (polymerize) to form giant molecules of 1,4-cis-polyisoprene (polymer). Likewise, lithium metal or alkyl and alkylene lithium compounds, such as butyllithium, serve as catalysts for the polymerization of isoprene to 1,4-cis-polyisoprene. Polymerization reactions with these catalysts are carried out in solution using petroleum hydrocarbons as solvents. Synthetic 1,4-cis-polyisoprene has the properties of natural rubber and can be used as its substitute in the production of rubber products.
see also PLASTICS. Polybutadiene, consisting of 90-95% 1,4-cis isomer, has also been synthesized via stereostructure-regulating Ziegler catalysts such as triethylaluminum and titanium tetraiodide. Other stereostructure-controlling catalysts, such as cobalt chloride and aluminum alkyl, also produce polybutadiene with a high (95%) content of the 1,4-cis isomer. Butyllithium is also capable of polymerizing butadiene, but produces polybutadiene with a lower (35-40%) content of the 1,4-cis isomer. 1,4-cis-polybutadiene has extremely high elasticity and can be used as a filler in natural rubber. Thiokol (polysulfide rubber). In 1920, while trying to make a new antifreeze from ethylene chloride and sodium polysulfide, J. Patrick instead discovered a new rubber-like substance, which he called thiokol. Thiokol is highly resistant to gasoline and aromatic solvents. It has good aging characteristics, high tear resistance and low gas permeability. Although not a true synthetic rubber, it is nevertheless used for the manufacture of special-purpose rubbers.
Neoprene (polychloroprene). In 1931, DuPont announced the creation of a rubber-like polymer, or elastomer, called neoprene. Neoprene is made from acetylene, which in turn is made from coal, limestone and water. Acetylene is first polymerized to vinyl acetylene, from which chloroprene is produced by adding hydrochloric acid. Next, chloroprene is polymerized to neoprene. In addition to being oil-resistant, neoprene has high heat and chemical resistance and is used in hoses, pipes, gloves, and machine parts such as gears, gaskets, and drive belts. Buna S (SBR, styrene butadiene rubber). Buna S synthetic rubber, referred to as SBR, is produced in large jacketed reactors, or autoclaves, that are charged with butadiene, styrene, soap, water, a catalyst (potassium persulfate) and a chain growth regulator (mercaptan). Soap and water serve to emulsify the butadiene and styrene and bring them into close contact with the catalyst and chain growth regulator. The contents of the reactor are heated to approximately 50 ° C and stirred for 12-14 hours; During this time, as a result of the polymerization process in the reactor, rubber is formed. The resulting latex contains rubber in small particle form and has a milky appearance, much like natural latex extracted from wood. The latex from the reactors is treated with a polymerization interrupter to stop the reaction and an antioxidant to preserve the rubber. It is then purified from excess butadiene and styrene. To separate (by coagulation) rubber from latex, it is treated with a solution of sodium chloride (table salt) in acid or a solution of aluminum sulfate, which separates the rubber in the form of fine crumbs. Next, the crumbs are washed, dried in an oven and pressed into bales. Of all the elastomers, SBR is the most widely used. Most of it goes to the production of car tires. This elastomer has properties similar to natural rubber. It is not oil resistant and exhibits low chemical resistance in most cases, but has high impact and abrasion resistance.
Latexes for emulsion paints. Styrene-butadiene latexes are widely used in emulsion paints, in which the latex forms a mixture with the pigments of conventional paints. In this application, the styrene content of the latex must exceed 60%.
Low temperature oil-extended rubber. Low temperature rubber is a special type of SBR rubber. It is produced at 5°C and provides better tire wear resistance than standard SBR produced at 50°C. Tire wear resistance is further enhanced if the low temperature rubber is given high impact strength. To do this, certain petroleum oils called petroleum softeners are added to the base latex. The amount of oil added depends on the required impact strength value: the higher it is, the more oil is added. The added oil acts as a hard rubber softener. Other properties of oil-extended low-temperature rubber are the same as those of ordinary low-temperature rubber.
Buna N (NBR, butadiene acrylonitrile rubber). Along with Buna S, an oil-resistant type of synthetic rubber called perbunan, or Buna N, was also developed in Germany. The main component of this nitrile rubber is also butadiene, which copolymerizes with acrylonitrile by essentially the same mechanism as SBR. NBR grades differ in the content of acrylonitrile, the amount of which in the polymer varies from 15 to 40% depending on the purpose of the rubber. Nitrile rubbers are oil resistant to a degree corresponding to their acrylonitrile content. NBR was used in military equipment where oil resistance was required, such as hoses, self-sealing fuel cells, and vehicle structures.
Butyl rubber. Butyl rubber, another synthetic rubber, was discovered in 1940. It is remarkable for its low gas permeability; A tire tube made of this material retains air 10 times longer than a tube made of natural rubber. Butyl rubber is made by polymerizing isobutylene obtained from petroleum with a small addition of isoprene at a temperature of -100 ° C. This polymerization is not an emulsion process, but is carried out in an organic solvent, such as methyl chloride. The properties of butyl rubber can be greatly improved by heat treating a masterbatch of butyl rubber and carbon black at temperatures ranging from 150 to 230° C. Butyl rubber has recently found new use as a tire tread material due to its good driving characteristics, lack of noise and excellent traction. Butyl rubber is incompatible with natural rubber and SBR and therefore cannot be mixed with them. However, once chlorinated to chlorobutyl rubber, it becomes compatible with natural rubber and SBR. Chlorobutyl rubber retains low gas permeability. This property is exploited in the manufacture of CBR/natural rubber blended products, or SBR, which are used to produce the inner liner of tubeless tires.
Ethylene propylene rubber. Ethylene-propylene copolymers can be produced in a wide range of compositions and molecular weights. Elastomers containing 60-70% ethylene are vulcanized with peroxides and produce a vulcanizate with good properties. Ethylene propylene rubber has excellent weather and ozone resistance, high heat, oil and wear resistance, but also high breathability. This rubber is made from cheap raw materials and has numerous industrial applications. The most widely used type of EPDM is EPDM (diene comonomer). It is mainly used for making wire and cable sheaths, single-ply roofing and as an additive for lubricating oils. Its low density and excellent ozone and weather resistance lead to its use as a roofing material.
Vistanex. Vistanex, or polyisobutylene, is an isobutylene polymer, also produced at low temperatures. It is similar in properties to rubber, but unlike rubber it is a saturated hydrocarbon and, therefore, cannot be vulcanized. Polyisobutylene is ozone resistant.
Korosil. Korosil, a rubber-like material, is a plasticized polyvinyl chloride made from vinyl chloride, which in turn is obtained from acetylene and hydrochloric acid. Korosil is remarkably resistant to oxidizing agents, including ozone, nitric and chromic acids, and is therefore used for the internal lining of tanks to protect them from corrosion. It is impervious to water, oils and gases and is therefore used as a coating for fabrics and paper. Calendered material is used in the production of raincoats, shower curtains and wallpaper. Low water absorption, high electrical strength, non-flammability and high aging resistance make plasticized polyvinyl chloride suitable for the manufacture of wire and cable insulation.
Polyurethane. A class of elastomers known as polyurethanes are used in the production of foams, adhesives, coatings and molded products. The production of polyurethanes includes several stages. First, a polyester is prepared by reacting a dicarboxylic acid, such as adipic acid, with a polyhydric alcohol, in particular ethylene glycol or diethylene glycol. The polyester is treated with a diisocyanate, for example toluylene-2,4-diisocyanate or methylene diphenylene diisocyanate. The product of this reaction is treated with water and a suitable catalyst, in particular n-ethylmorpholine, to obtain an elastic or flexible polyurethane foam. By adding diisocyanate, molded products are obtained, including tires. By varying the ratio of glycol to dicarboxylic acid during the polyester production process, polyurethanes can be made that are used as adhesives or processed into rigid or flexible foams or molded products. Polyurethane foams are fire-resistant, have high tensile strength, and very high tear and abrasion resistance. They exhibit exceptionally high load-bearing capacity and good aging resistance. Vulcanized polyurethane rubbers have high tensile strength, abrasion, tear and aging resistance. A process was developed to produce polyurethane rubber based on polyether. This rubber behaves well at low temperatures and is resistant to aging.
Organosilicon rubber. Organosilicon rubbers have no equal in their suitability for use in a wide temperature range (from -73 to 315° C). For vulcanized silicone rubbers, a tensile strength of about 14 MPa has been achieved. Their aging resistance and dielectric characteristics are also very high.
Hypalon (chlorosulfoethylene rubber). This chlorosulfonated polyethylene elastomer is produced by treating polyethylene with chlorine and sulfur dioxide. Vulcanized Hypalon is extremely ozone and weather resistant and has good thermal and chemical resistance.
Fluorinated elastomers. Elastomer kel-F is a copolymer of chlorotrifluoroethylene and vinylidene fluoride. This rubber has good heat and oil resistance. It is resistant to corrosive substances, non-flammable and suitable for use in the range from -26 to 200 ° C. Viton A and fluorel are copolymers of hexafluoropropylene and vinylidene fluoride. These elastomers have excellent resistance to heat, oxygen, ozone, weathering and sunlight. They have satisfactory low temperature performance and are suitable for use down to -21°C. Fluorine-containing elastomers are used in applications where resistance to heat and oils is required.
Specialized elastomers. Specialized elastomers with a variety of physical properties are produced. Many of them are very expensive. The most important of these are acrylate rubbers, chlorosulfonated polyethylene, ether copolymers, epichlorohydrin polymers, fluorinated polymers and thermoplastic block copolymers. They are used to make seals, gaskets, hoses, wire and cable sheaths and adhesives.
see also

Tire production technology begins with its development using a special computer program that draws various modifications of the tire tread and profile. Using the program, the behavior of each tire option on the road is calculated in various situations. Then, those tires that perform best in simulated road tests are hand-cut on a machine and tested in real road conditions. Then the technical indicators of each tested tire are compared with the best indicators of existing tires of a similar class, if necessary, they are fine-tuned and the product is put into mass production.

Stages of car tire production

1. Production of rubber mixture

The first stage of creating any tire is the production of a rubber compound, the composition of which is individual for each manufacturing company and kept in strict confidence. This is due to the fact that the quality of the tire’s rubber determines its technical characteristics, such as:

level of adhesion to the road surface;
reliability;
work resource.

Raw materials and consumables

Tire production technology requires the presence of many different components, materials and chemical compounds without which the very existence of car tires is impossible. In this article we will list only the most basic of these components.

All this is achieved thanks to the work of chemists who select and combine components and their content in rubber in accordance with their own experience and computer data. As a rule, the quality of rubber depends on the correct dosage of components, since its composition is no secret to anyone and includes the following components:

rubber, which forms the basis of the rubber mixture, which can be either synthetic or more expensive isoprene. As practice shows, Russian rubber is considered the best in the world and is still used by the most famous foreign manufacturing companies to manufacture their products;
industrial soot, also known as carbon black, which gives rubber its characteristic color and is responsible for its strength and wear resistance, since it is the soot that performs the molecular compound during the vulcanization process;
silicic acid, which is an analogue of soot in the manufacture of tires by foreign manufacturers and increases the level of adhesion of the tire to the wet road surface;
oils and resins, which are auxiliary components and act as rubber softeners.
vulcanizing agents, in particular sulfur and vulcanization activators.

2.
Production of tire components

Tire production technology provides for such a production stage as the manufacture of tire components, which consists of several parallel processes such as:

3. Car tire assembly and vulcanization

Tire assembly is the third stage of production and is performed on an assembly drum by sequentially layering the carcass, bead and tread layers with the sidewalls of the tire on top of each other, followed by a vulcanization procedure.

Car tire production technology, video review:

Other similar articles to Car tire production technology

The production of molded rubber goods is carried out using pressing equipment, with the help of which vulcanized rubber is converted into parts.

A hydraulic press is the main type of equipment for making rubber parts. The principle of operation of a hydraulic press is that a liquid under pressure and enclosed in a closed vessel exerts equal pressure on the walls of the vessel.

Getting into the working cylinder of the press and filling it, the liquid presses with equal force on the bottom of the cylinder, its walls, as well as on the end surface of the plunger inserted into the cylinder.

Hydraulic presses for rubber goods are equipment in which the working process is carried out thanks to a liquid under pressure.

Products made by molding are widely used in instrument and machine-building enterprises, where parts are constantly cut from raw and sheet rubber, which is subjected to vulcanization and pressing.

The process of preparation USING HYDRAULIC PRESSES.

First, preparation for work is carried out, i.e. The molds are heated to 150 ± 5°, and then they are lubricated with a special solution.
After drying and lubricating, the mold is ready for laying reinforcement and raw rubber. If open molds are used during pressing, the reinforcement is placed in the sockets, and the rubber takes up the remaining space. When using injection molds, the reinforcement is still placed in them, and a loading chamber is reserved for raw rubber.
To press reinforced parts, a specific pressure of 50-60 MPa is required; for non-reinforced parts, 25-30 MPa is sufficient.
Vulcanization consists of holding the rubber blank and fittings on a press for 0.5-1 hour, and the temperature should be at least 145 ± 3°. Its duration, as well as the operating temperature, must be selected empirically or experimentally, since these values depend on the configuration and wall thickness of the part, as well as the brand of rubber being processed.
Having completed the vulcanization operation, it is necessary to remove the mold from the press, disassemble it, remove the finished part, clean the working equipment, place new reinforcement with raw rubber in it for the manufacture of the next part.
To trim the resulting flash, special scissors or notches are used. All details must be checked by specialists from the technical control department (QC).

What is rubber

In addition to complex substances like polyethylenes, which are high-molecular polymers, there is a class of chemicals that is formed by conjugated dienes.

After the polymerization process of dienes, new chemical substances with a high molecular structure are formed, called rubbers.

Rubber was already known at the end of the 15th century in North America. It was the Indians at that time who used it to make shoes, unbreakable things and dishes. And then they obtained it from the sap of the Hevea plant, which was called “tears of the tree.”

As for the Europeans, about rubber learned for the first time only at the time of the discovery of America. It was Christopher Columbus who first learned about its properties and production. In Europe, rubber could not find use for a long time. In 1823, it was first proposed to use this material for the manufacture of waterproof raincoats and clothing. The fabric was impregnated with rubber and an organic solvent, thus acquiring water-resistant properties. But, of course, a drawback was also noticed, which was that the fabric impregnated with rubber stuck to the skin in hot weather, and cracked in cold weather.

The difference between rubber and rubber

10 years after first use natural rubber and a more detailed study of its chemical and physical properties, it was proposed to introduce rubber into calcium and magnesium oxides. And 5 years later, after studying the properties of a heated mixture of lead and sulfur oxides with rubber, we learned get rubber. Myself the process of converting rubber into rubber called vulcanization.

Of course, rubber is different from rubber.

Rubber is a “cross-linked” polymer that is capable of straightening and folding again when stretched and under mechanical load. Rubber- these are also “cross-linked” macromolecules that do not crystallize when cooled and do not melt when heated. Thereby rubber– a more versatile material than rubber, and is able to maintain its mechanical and physical properties over a wider temperature range.

At the beginning of the 20th century, when the first car appeared, the demand for rubber increased significantly. At the same time, the demand for natural rubber, since at that time all rubber was made from the sap of tropical trees. For example, to obtain a ton of rubber, it was necessary to process almost 3 tons of tropical trees, while more than 5 thousand people were simultaneously employed, and such a mass of rubber could only be obtained in a year.

That's why, rubber and natural rubber were considered quite expensive material.

Only at the end of the 20s did the Russian scientist S.V. Lebedev. During a chemical reaction, the polymerization of 1,3 butadiene on a sodium catalyst, samples of the first sodium-butadiene synthetic rubber were obtained.

By the way, from the 8th grade physics course we probably first became acquainted with ebonite stick. But what is ebonite. As it turns out, ebonite is a derivative of the vulcanization process rubber: if sulfur is added during the vulcanization of rubber (about 32% by weight), then the result is a solid material - this material is ebonite!

One of the fairly cheap ways to obtain 1,3 butadiene is to obtain it from ethyl alcohol. But it was only in the 30s that industrial production of rubber was established in Russia.

In the mid-30s of the 20th century, they learned to produce copolymers representing polymerized 1,3-butadiene. The chemical reaction was carried out in the presence of styrene or some other chemicals. Soon, the resulting copolymers began to rapidly replace rubbers, which were previously widely used for the production of tires. Styrene-butadiene rubber is widely used for the production of passenger car tires, but for heavy vehicles - trucks and airplanes, it was used natural rubber(or synthetic isoprene).

In the middle of the 20th century, after obtaining the new Ziegler-Natta catalyst, synthetic rubber, which in its elasticity and strength properties is significantly higher than all previously known rubbers, polybutadiene and polyisoprene were obtained. But as it turned out, to everyone’s surprise, the received synthetic rubber its properties and structure are similar to natural rubber! And by the end of the 20th century, natural rubber was almost completely replaced by synthetic rubber.

Properties of rubber

Everyone knows that materials can expand when heated. In physics there are even coefficients of thermal expansion; each material has its own coefficient. Solids, gases, and liquids are susceptible to expansion. But what if the temperature increased by several tens of degrees?! For solid bodies, we will not feel any changes (although they exist!). As for high-molecular compounds, such as polymers, their change immediately becomes noticeable, especially if we are talking about elastic polymers that can stretch well. Noticeable, and also with a completely opposite effect!

Back in the early 19th century, English scientists discovered that a stretched tourniquet of several strips natural rubber When heated, it decreased (compressed), but when cooled, it expanded. The experience was confirmed in the mid-19th century.

You yourself can easily repeat this experiment by hanging a weight on a rubber band. She will stretch under his weight. Then blow it with a hairdryer and see how it shrinks from the temperature!

Why is this happening?! This effect can be applied Le Chatelier's principle, which states that if you influence a system that is in equilibrium, this will lead to a change in the equilibrium of the system itself, and this change will be counteracted by external force factors. That is, if the harnesses are not stretched under the influence of a load rubber(the system is in equilibrium) act with a hairdryer (external influence), then the system will go out of balance (the tourniquet will compress), and compression - the action is directed in the opposite direction from the gravity of the load!

If the rope is stretched very sharply and strongly, it will heat up (the heating may not be noticeable to the touch); after stretching, the system will tend to assume an equilibrium state and gradually cool down to ambient temperature. If the rubber bundles are also sharply compressed, they will cool down and then heat up to an equilibrium temperature.

What happens when rubber deforms?

During the studies, it turned out that from the point of view of thermodynamics, no change in internal energy occurs at different positions (bends) of these rubber bundles.

But if you stretch it, then the internal energy increases due to the increase in the speed of movement of the molecules inside the material. From the course of physics and thermodynamics it is known that a change in the speed of movement of the molecules of a material (for example, rubber) is reflected in the temperature of the material itself.

further, the stretched rubber bundles will gradually cool down, since moving molecules will give up their energy, for example, to hands and other molecules, that is, there will be a gradual equalization of energy inside the material between molecules (entropy will be close to zero).

And now that our rubber bundle has reached ambient temperature, we can remove the load. What happens in this case?! At the moment the load is removed, the rubber molecules still have a low level of internal energy (they shared it during stretching!). The rubber contracted - from the point of view of physics, work was done due to its own energy, that is, its own internal energy (thermal) was expended to return to its original position. It is natural to expect that the temperature should drop - which in fact happens!

Rubber- as already mentioned, a highly elastic polymer. Its structure consists of randomly arranged long carbon chains. The fastening of such chains to each other is carried out using sulfur atoms. The carbon chains are normally twisted, but if the rubber is stretched, the carbon chains will unwind.

You can do an interesting experiment with rubber bands and a wheel. Instead of bicycle spokes, use rubber bands in a bicycle wheel. Suspend such a wheel so that it can rotate freely. If all the harnesses are equally stretched, then the bushing in the center of the wheel will be located strictly along its axis. Now let’s try to heat some part of the wheel with hot air. We will see that the part of the harness that has heated up will shrink and move the bushing in its direction. In this case, the center of gravity of the wheel will shift and, accordingly, the wheel will turn around. After its displacement, the following bundles will be exposed to hot air, which in turn will lead to their heating and again to the rotation of the wheel. This way the wheel can rotate continuously!

This experience confirms the fact that when heated rubber And rubber will shrink, and when cooled, will stretch!

Synthetic rubber

C page 1

Synthetic rubbers are less susceptible to swelling than natural rubbers in the presence of oil and most solvents.

Synthetic rubbers are widely used for the manufacture of seals that prevent oil leakage from gearbox housings. Although gear oil specifications sometimes contain requirements that limit the amount of swelling and other damage for certain grades of rubber from which seals are made, it is almost impossible to predict the behavior of these materials under various operating conditions.

Synthetic rubber is worse than natural rubber in terms of tear resistance, but swells less when in contact with oil than natural rubber.

Synthetic rubbers are much more resistant to ultraviolet rays.

Light does not have a noticeable effect on the surface of the wood, but prolonged use of parts made of wood when irradiated with ultraviolet rays can lead to some changes in the surface layers of the wood.

Synthetic rubber SKN-40 (nitrile butadiene rubber) is also a gasoline-resistant material and can be used for lining tanks.

Conventional synthetic rubbers or blends of Buna N, Buna S, neoprene, butyl, caoutchouc and natural rubber have characteristics that allow parts to be molded using standard equipment. However, more recently developed synthetic rubbers, as well as most silicone materials, have 3 - 5% greater shrinkage than standard rubbers. In these cases, the O-rings, molded from new materials on existing equipment, have dimensions 3 - 5% smaller than those required by the standard. Materials with high shrinkage are silicones, Viton, fluorinated silicones and polyacrylates.

Synthetic rubber breaks much more easily than natural rubber.

The brand of synthetic rubber used for fabric-rubber cuffs depends on the working environment and temperature. The most common base polymers are polychloroprene, Buna N, Buna S, butyl and Viton. Polychloroprene and Buna N are used for sealing oils, Buna S for water, butyl for sealing phosphoric acid esters. Viton is used in conditions of high operating temperatures.

Synthetic rubber seals can operate in an oil environment at peripheral speeds on the friction surface of up to 20 m/sec. However, it is not recommended to use high speeds and temperatures unless absolutely necessary, as this reduces the reliability of the seal.

Balls made of synthetic rubber are made hollow. A valve / is installed in the housing, through which liquid is pumped so that the diameter of the ball exceeds the internal diameter of the pipe by 2%.

Synthetic rubber seals can operate at peripheral speeds on the friction surface of up to 20 m/sec, and in some cases up to 25 m/sec. Depending on the type of rubber, they may also be suitable for working at friction surface temperatures above 150 C. For example, silicone rubber cuffs allow temperatures of 180 C at a speed of 25 m/sec.

The coefficient of friction between synthetic rubber and metal generally increases with speed. The friction coefficient depends little on the cleanliness of the surface being sealed, but surface cleanliness significantly affects the wear of seals.