Artificial fibers. Among chemical fibers In terms of production volume, artificial viscose fiber ranks first. The main substance for producing viscose fiber is wood cellulose and cheap available chemicals. The advantage of viscose fiber is its high economic efficiency its production and processing. Thus, when producing 1 kg of viscose yarn, labor costs are 2-3 times lower than the costs of producing the same yarn from cotton and 4.5-5 times lower than the production of 1 kg of wool yarn.
Viscose fiber is produced in various lengths and thicknesses. The thickness of the elementary fiber of viscose silk ranges from 0.5 to 0.2 tex.
Viscose fibers have sufficient strength, but when wet their strength drops to 50-60%. Their disadvantage is the ability to shrink, that is, to shorten in length, especially after washing the products.
These fibers have high hygienic properties, as they are characterized by their ability to absorb moisture well. Viscose fibers are heat-resistant.
When heated, they do not soften and can withstand heating up to 150° without destruction. With more high temperatures ah (175-200°) the process of fiber decomposition begins.
Viscose fibers with enhanced properties are called polynose. Their properties are similar to cotton fiber.
Other artificial fibers are produced from cotton or wood cellulose - copper-ammonia and acetate.
Copper-ammonia fiber is similar in properties to viscose fiber. It is produced in small quantities, since its production is much more expensive than the production of other artificial fibers. It is mainly used in mixtures with wool.
Acetate fibers come in two types: diacetate and triacetate. Diacetate fibers are usually called acetate. Acetate fibers have sufficient strength. Their breaking elongation is 18-25%. The tensile strength of acetate fiber in the wet state is reduced by 40-50%, and triacetate fiber by 10-15%. Acetate fiber absorbs approximately 6.5% moisture, and triacetate fiber absorbs no more than 1-1.5%.
Acetate fibers in their properties occupy an intermediate position between artificial and synthetic fibers.
Unlike viscose fibers, acetate fibers are thermoplastic and at a temperature of 140-150° they begin to deform.
The use of acetate fibers mixed with viscose fibers can significantly reduce the creasing of products. Acetate fibers are not dyed with dyes used for dyeing viscose fibers, therefore the use of acetate fibers in a mixture with viscose fibers allows you to create various color effects and enhance the front surface of the fabric.
Other artificial fibers used in fabric production are glass and metal; metal threads are used to give fabrics different decorative effects; they are called alunit, lurex, metlon, etc.
Synthetic fibers. Of the synthetic fibers, the most widely used are polyamide fibers, which include nylon, anide, enant and other fibers. In our country, among polyamide fibers, nylon fiber takes first place. To obtain it, caprolactam resin is used, which is obtained by chemical synthesis from relatively simple organic substances.
Polyamide fibers have a number of valuable properties: high tensile strength, elasticity and exceptional abrasion resistance.
The advantage of polyamide fibers is their high resistance to abrasion and repeated deformation.
Synthetic fibers
For thousands of years, humanity has used natural fibers of plant (linen, cotton, hemp) and animal (wool, silk) origin for its needs. In addition, they used mineral materials, such as asbestos.
Fabrics produced from these fibers were used to make clothing, technical needs, etc.
Due to the growth of the world's population, natural fibers have become scarce. That is why the need for their substitutes arose.
The first attempt to produce silk artificially was made in 1855 by the Frenchman Audemart, based on nitrocellulose. In 1884, the French engineer G. Chardonnay developed a method for producing artificial fiber - nitro silk, and since 1890, widespread production of artificial silk was organized using the nitrate method with the formation of threads using spinnerets. The one that began in the 90s of the 19th century turned out to be especially effective. production of silk from viscose. Subsequently, this method became most widespread, and now viscose silk accounts for approximately 85% of the world's production of artificial fiber. In 1900, world production of viscose silk was 985 tons, in 1930 - about 200 thousand tons, and in 1950, production of viscose silk reached almost 1600 thousand tons.
In the 1920s, the production of silk acetate (from cellulose acetate) was mastered. By appearance acetate silk is almost indistinguishable from natural silk. It is low hygroscopic and, unlike viscose silk, does not wrinkle. Acetate silk is widely used in electrical engineering as insulating material. Later, a method was discovered for producing extremely strong acetate fiber (a cord with a cross-section of 1 cm2 can withstand a load of 10 tons).
Based on the successes of chemistry throughout the 20th century. A powerful artificial fiber industry was created in the USSR, England, France, Italy, the USA, Japan and other countries.
On the eve of the First World War, only 11 thousand tons of artificial fiber were produced worldwide, and 25 years later, the production of artificial fiber pushed aside the production of natural silk. If in 1927 the production of viscose and acetate silk was about 60 thousand tons, then in 1956 world products artificial - viscose and acetate - fibers exceeded 2 million tons.
The difference between natural, artificial and synthetic fibers is as follows. Natural (natural) fiber is completely created by nature itself, artificial fiber is made by human hands, and synthetic fiber is created by man in chemical plants. In the synthesis of synthetic fibers, more complex high-molecular compounds are obtained from simpler substances, while artificial materials are formed due to the destruction of much more complex molecules (for example, fiber molecules when producing methyl alcohol by dry distillation of wood).
In 1935, the American chemist W. Carothers discovered nylon - the first synthetic fiber. Carothers initially worked as an accountant, but later became interested in chemistry and attended the University of Illinois. Already in his third year he was assigned to lecture on chemistry. In 1926, Harvard University elected him professor of organic chemistry.
In 1928, Carothers' fate took a sharp turn. The largest chemical concern Dupont de Nemours invited him to head the organic chemistry laboratory. created for him ideal conditions: large staff employees, most modern equipment, freedom in choosing research topics.
This was due to the fact that a year earlier the concern had adopted a strategy for theoretical research, believing that they will ultimately bring significant practical benefit, and therefore profit.
And so it happened. Carothers' laboratory, studying the polymerization of monomers, after three years of hard work achieves outstanding success - they obtain a chloroprene polymer. Based on it, in 1934, the DuPont concern began industrial production of one of the first types of synthetic rubber - polychloroprene (neoprene), whose qualities could successfully replace scarce natural rubber.
However, Carothers considered the main goal of his research to be the production of a synthetic substance that could be converted into fiber. Using the polycompensation method, which he studied while still at Harvard University, Carothers in 1930 obtained a polyester as a result of the interaction of ethylene glycol and sebacic acid, which, as it turned out later, was easily drawn into fiber. This was already a great achievement. However practical application this substance could not have, since it was easily softened by hot water.
Numerous further attempts to obtain commercial synthetic fiber were unsuccessful, and Carothers decided to stop working in this direction. The concern's management agreed to close the program. However, the head of the chemical department opposed this outcome of the matter. With great difficulty, he convinced Carothers to continue his research.
Rethinking the results of his work in search of new ways to continue it, Carothers turned his attention to recently synthesized polymers containing amide groups in the molecule - polyamides. This choice turned out to be extremely fruitful. Experiments have shown that some polyamide resins, squeezed through a spinneret made from a thin medical syringe, form threads from which fiber can be made. The use of new resins seemed very promising.
After new experiments, Carothers and his assistants on February 28, 1935 obtained polyamide, from which it was possible to produce strong, elastic, elastic, water-resistant fiber. This resin, isolated as a result of the reaction of hexamethylenediamine with adipic acid, followed by heating the resulting salt (AG) in a vacuum, was named “polymer 66”, since the starting products contained 6 carbon atoms. Since they worked on the creation of this polymer simultaneously in New York and London, the fiber from it was called “nylon” - after the initial letters of these cities. Textile experts have found it suitable for commercial yarn production.
Within two next years DuPont scientists and engineers developed in laboratory conditions technological processes production of polymer intermediates and nylon yarn and constructed a chemical pilot plant.
On February 16, 1937, nylon was patented. After many experimental cycles, in April 1937, fiber was obtained for an experimental batch of stockings. In July 1938, construction of the pilot plant was completed.
On April 29, 1937, three days after Carothers turned 41, he died from drinking potassium cyanide. The outstanding researcher was haunted by the obsession that he had failed as a scientist.
Nylon cost $6 million to develop, more than any other public product. (For comparison, the United States spent $2.5 million on television development.)
Externally, nylon resembles natural silk and approaches it in terms of chemical structure. However, in terms of its mechanical strength, nylon fiber is approximately three times superior to viscose silk, and natural silk is almost twice as strong.
DuPont Company long time strictly guarded the secret of the nylon production process. And she even made the necessary equipment for this herself. Both employees and wholesale sellers of the goods were required to sign a non-disclosure agreement regarding “nylon secrets”.
The first commercial product to hit the market were toothbrushes with nylon bristles. Their production began in 1938. Nylon stockings were demonstrated in October 1939, and in early 1940, Wilmington began producing nylon fiber, which knitting factories purchased to make stockings. Thanks to a mutual agreement between trading firms, stockings from competing manufacturers appeared on the market on the same day: May 15, 1940.
Mass production of nylon products began only after World War II, in 1946. And although many other polyamides have appeared since then (nylon, perlon, etc.), nylon is still widely used in the textile industry.
If in 1939 world production of nylon was only 180 tons, then in 1953 it reached 110 thousand tons.
In the 50s of the last century, ship blade propellers for small and medium-tonnage ships were made from nylon plastic.
In the 40–50s of the XX century. Other synthetic polyamide fibers also appeared. Thus, nylon was the most common in the USSR. Cheap phenol produced from coal tar is used as a feedstock for its production. From 1 ton of phenol you can get about 0.5 tons of resin, and from it you can make nylon in quantities sufficient to make 20–25 thousand pairs of stockings. Capron is also obtained from petroleum products.
In 1953, for the first time in the world in the USSR, a polymerization reaction between ethylene and carbon tetrachloride was carried out on a pilot industrial scale and the starting product for industrial production enant fibers The scheme for its production was developed by a team of scientists under the leadership of A. N. Nesmeyanov.
In terms of basic physical and mechanical properties, enant was not only not inferior to other known polyamide fibers, but was also in many ways superior to nylon and nylon.
In the 50s–60s. last century, the production of polyester and polyacrylonitrile synthetic fibers began.
Polyester fibers are formed from a melt of polyethylene terephthalate. They have excellent heat resistance, retaining 50% strength at 180°C, and are fire and weather resistant. Resistant to solvents and pests: moths, mold, etc. Polyester fiber thread is used for the manufacture of conveyor belts, drive belts, ropes, sails, fishing nets, hoses, and as a base for tires. Monofilament is used to produce nets for paper machines and strings for rackets. In the textile industry, thread from polyester fibers is used to make knitwear, fabrics, etc. Polyester fibers include lavsan.
Polyacrylonitrile fibers are similar in properties to wool. They are resistant to acids, alkalis, and solvents. They are used to make outerwear, carpets, and fabrics for suits. Mixed with cotton and viscose fiber, polyacrylonitrile fibers are used to make linen, curtains, and tarpaulins. In the USSR, these fibers were produced under the trade name nitron.
Many synthetic fibers are produced by forcing a melt or solution of polymer through spinnerets 50 to 500 micrometers in diameter into a chamber of cold air, where the strands solidify and become fiber. The continuously formed thread is wound onto a bobbin.
Acetate fibers are cured in hot air to evaporate the solvent, while viscose fibers are cured in precipitation baths with special liquid reagents. Drawing of fibers on bobbins during formation is used to ensure that the chain polymer molecules take on a clearer order.
The properties of fibers are affected different methods: by changing the extrusion speed, composition and concentration of substances in the bath, changing the temperature of the spinning solution, bath or air chamber, varying the size of the die opening.
An important characteristic of the strength properties of a fiber is the breaking length at which the fiber breaks under the influence of its own gravity.
For natural cotton fiber it varies from 5 to 10 km, acetate silk - from 12 to 14, natural - from 30 to 35, viscose fiber - up to 50 km. Fibers made from polyesters and polyamides have great strength. For example, nylon has a breaking length of up to 80 km.
Synthetic fibers have replaced natural fibers in many areas. The total volume of their production is almost equal.
This text is an introductory fragment.Modern technologies have affected all spheres of human life. The best example of how they are developing is the textile industry: humanity has learned to produce synthetic fabrics.
Viscose is a type of artificial fabric made from cellulose. This type of canvas is obtained by processing wood raw materials. Synthetic fabrics are made from polymers obtained through chemical reactions. The raw materials for the material are petroleum products, coal, gas. As a rule, sportswear or things necessary for use in extreme situations are made from synthetic fabrics.
Advantages and disadvantages of synthetic fabrics
Synthetic material has its advantages and disadvantages. Despite the abundance of natural fabrics, there are a number of advantages of synthetic material.
- Lightness of fabric. Unlike natural materials, synthetic fabric is lightweight.
- Durability. Clothing made from synthetic material is less susceptible to wear and tear and retains color fastness well. This is achieved through special processing of matter. That's why things can be worn for a long time without fear of them fading. However, some species deteriorate when exposed to ultraviolet rays.
- Fast drying. Almost all synthetic materials do not absorb much moisture, and drying does not take much time.
- Price. Low price material is achieved due to the low cost of the original product. It is profitable for enterprises to produce such fabrics, which is why their production volumes are increasing every year.
The industry is developing every day. Fabric manufacturers can change the characteristics of the fabric taking into account the wishes of large customers.
The biggest disadvantage of such materials is that they can negatively affect health. Synthetic fabric becomes electrified due to the fact that it accumulates static electricity. A person may have an individual tolerance for this tissue. It practically does not absorb moisture, therefore, it is not a very hygienic material. Synthetics are not breathable, so underwear made from polyester or spandex is not very comfortable for everyday use.
On the other hand, in bad weather, synthetic fabric will be extremely useful - it can protect a person from precipitation better than natural fabric.
Production Features
First patent for manufacturing synthetic fabric was registered back in 1930. First, they learned to isolate polyvinyl chloride fibers, then German scientists were able to obtain polyamide. This material became known as . Its production was put on the assembly line only in 1939.
In the Soviet Union, synthetic clothing began to be produced only in the late 60s. At first it was simply a cheap substitute for natural fabric. Only many years later they found proper use for it: they began to produce workwear that was distinguished by high wear resistance characteristics and could protect a person from unfavorable factors environment.
Artificial and synthetic materials differ in the specifics of production, as well as in the cost of raw materials. Synthetics are not required high costs. When making fabric, fiber is synthesized from low molecular weight compounds. To produce a material, the raw material must be melted or dissolved. Afterwards, the thread can be separated from the viscous material. The thread can be single, complex or twisted in the form of a tourniquet. Also, individual parts of clothing and shoes can be made from the molten material.
What are synthetic textiles made from?
Today there are many types of synthetic fibers. Specialists are constantly producing new varieties of material. However, for convenience, they are divided into two groups, each of which has its own characteristics.
Carbon chain synthetics
Hydrocarbons are used in its production. This variety combines the following list of fabrics:
- polyethylene;
- polyacrylonitrile;
- polypropylene;
- polyvinyl chloride;
- polyvinyl alcohol.
Heterochain synthetics
This type of fabric is made not only from hydrocarbons, but also from other chemical elements. These can be nitrogen, chlorine, fluorine. Elements help improve the characteristics of matter.
This group includes the following fabrics:
- polyurethane.
- polyamide.
Thanks to these substances, things based on heterochain synthetics are added to usual characteristics additional qualities that are indispensable when sewing workwear.
Types and names of synthetic fabrics
So, the textile industry at this stage of its development makes it possible to obtain the most different types synthetic matter. But how not to get confused in such an assortment and find out which fabric meets all the necessary criteria? Let's give brief characteristics the most popular varieties of synthetics.
- Lavsan
Has high wear resistance. The fabric does not shrink and can withstand strong temperature changes, up to + 115 degrees. Keeps its shape for a long time. The material is hard to the touch and does not allow water to pass through. The canvas is most often used in the manufacture of curtains. Much less often it is added to natural raw materials for the production of costumes - this allows to increase the wear resistance of products.
- Fleece
Made from synthetic fiber. In appearance it resembles natural wool. Very soft, warm material. It is elastic and breathable. The material is easy to care for, easy to wash and clean. The main thing is that it does not need to be dried and ironed for a long time, which significantly saves time. The fabric is often used in the production of children's clothing. The disadvantage is the rapid loss of shape due to the fact that when everyday wear the thing is stretched. Fleece can accumulate static electricity.
- Polysatin
Made with the addition of cotton or polyester. The material has a number of advantages. It is easy to wash, does not wrinkle, does not lose shape, and has a shiny surface. It is often used in the production of bedding sets, curtains, and for furniture upholstery. Fashionable and popular bed sheets“with a 3D effect” are often made from of this type fabrics.
- Acrylic
This is a fabric that looks like wool, but it is much more practical than natural fiber. Retains its shape for a long time and does not allow moisture to pass through. The material is not susceptible ultraviolet rays, easy to clean, does not shrink. It is also used in combination with wool.
Acrylic is used for sewing outerwear. In combination with wool, it is also used to make children's mattresses, since this fabric is not able to absorb water. When combined with natural fibers, it gives things strength. Acrylic does not form pellets and is able to hold its shape for a long time. However, it also has a small drawback - things made from this fabric are highly electrified. Acrylic is often added to knitting threads.
- Dyneema and Spectra
In this group, there are two types of fibers - polyethylene and polypropylene. They are the lightest in the synthetic fabric category. Such a canvas cannot be drowned in water. It is heat resistant. The material cannot be stretched and is resistant to any weather changes.
Withstands temperatures up to +115 degrees. Widely used in the production of tourist and specialized clothing, for example for fishermen, skiers, rock climbers, and hunters. The material is also used for hosiery products. However, for this purpose, fabric made from natural fibers must be taken.
Bottom line
Every year, the production of products made from synthetic fabrics is growing due to the fact that the raw materials are cheap. The functional characteristics of products and their appearance are also improved.
Synthetic items have high heat-protective properties. They have low hygroscopicity, high hydrophobicity and are quite durable. They may not be as comfortable as natural fibers. There is a lot of controversy about their safety for health. But the above properties allow them to remain among the promising options for use in the textile industry.
Synthetic fibers
chemical fibers obtained from synthetic polymers. Synthetic fibers are formed either from a polymer melt ( polyamide, polyester, polyolefin), or from a polymer solution ( polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol) dry or wet method. Synthetic fibers are produced in the form of textile and cord threads, monofilament, and staple fiber. The variety of properties of the original synthetic polymers makes it possible to obtain synthetic fibers with different properties, while the ability to vary the properties of artificial fibers is very limited, since they are formed from almost the same polymer ( cellulose or its derivatives). Synthetic fibers are characterized by high strength, water resistance, wear resistance, elasticity and resistance to chemical reagents.
Since 1931, apart from butadiene rubber, there were no synthetic fibers or polymers, and the only materials known at that time based on a natural polymer, cellulose, were used to make fibers.
Revolutionary changes came in the early 60s, when, after the announcement of the well-known program for the chemicalization of the national economy, the industry of our country began to master the production of fibers based on polycaproamide, polyesters, polyethylene, polyacrylonitrile, polypropylene and other polymers.
At that time, polymers were considered only cheap substitutes for scarce natural raw materials - cotton, silk, wool. But soon it became clear that polymers and fibers based on them are sometimes better than traditionally used natural materials - they are lighter, stronger, more heat-resistant, and capable of working in aggressive environments. Therefore, chemists and technologists have focused all their efforts on creating new polymers with high performance characteristics and methods for their processing. And we achieved results in this matter that sometimes exceeded the results of similar activities of well-known foreign companies.
In the early 70s, Kevlar (USA) fibers, amazingly strong in their strength, appeared abroad, a little later - Twaron (Netherlands), Technora (Japan) and others made from aromatic polymers, collectively called aramids. Based on such fibers, various composite materials were created, which were successfully used for the manufacture of critical parts of aircraft and missiles, as well as tire cord, body armor, fire-retardant clothing, ropes, drive belts, conveyor belts and many other products.
These fibers were widely advertised in the world press. However, only a narrow circle of specialists know that in those same years, Russian chemists and technologists independently created terlon aramid fiber, which is not inferior in its properties to its foreign analogues. And then methods for producing SVM and Armos fibers were developed here, the strength of which exceeds the strength of Kevlar by one and a half times, and the specific strength (that is, strength per unit weight) exceeds the strength of high-alloy steel by 10-13 times! And if the tensile strength of steel is 160-220 kg/mm2, now work is actively underway to create polymer fiber with a strength of up to 600 kg/mm2.
Another class of polymers suitable for producing high-strength fibers are liquid crystalline aromatic polyesters, that is, polymers that have the properties of crystals in the liquid state. Fibers based on them have not only the advantages of aramid fibers, but also high radiation resistance, as well as resistance to exposure inorganic acids and various organic solvents. This perfect material for reinforcing rubber and creating highly filled composites; On its basis, samples of light guides were created, the quality of which corresponds to the highest world level. And the immediate task is the creation of so-called molecular composites, that is, composite materials in which the molecules of liquid crystalline polymers themselves serve as reinforcing components.
Molecules of conventional polymers contain, in addition to carbon, also atoms of other elements - hydrogen, oxygen, nitrogen. But now methods have been developed for producing fibers that are, in fact, pure polymer carbon. Such fibers have record strength (over 700 kg/mm2) and rigidity, as well as extremely low coefficients of thermal expansion, high resistance to wear and corrosion, high temperatures and radiation. This allows them to be successfully used for the manufacture of composite materials - carbon fiber reinforced plastics, used in the most critical structural components of high-speed aircraft, rockets and spacecraft.
The use of carbon fiber plastic turns out to be very economically profitable. Per unit weight of a product made from it, you need to spend 3 times less energy than a product made from steel, and 20 times less than from titanium. A ton of carbon fiber can replace 10-20 tons of high-alloy steel. A pump turbine made of carbon fiber and suitable for pumping mineral acids at temperatures up to 150°C is half the price and lasts six times longer. The labor intensity of manufacturing parts with complex configurations is also reduced.
The production of synthetic fibers is developing at a faster pace than the production of man-made fibers. This is due to the availability of raw materials and the rapid development of the raw material base, less labor intensity production processes and especially the variety of properties and high quality synthetic fibers. In this regard, synthetic fibers are gradually replacing not only natural, but also artificial fibers in the production of some consumer goods and technical products.
In 1968, world production of synthetic fibers amounted to 3,760.3 thousand. T(about 51.6% of the total production of chemical fibers). The first production of synthetic fibers on an industrial scale was organized in the mid-30s. 20th century in the USA and Germany.
Capron
In our country, fiber made from polyamide resins is called nylon and anide; their quality is almost the same.
Nylon or nylon fiber is a white-transparent, very durable substance. The elasticity of nylon is much higher than silk. Nylon is a polyamide fiber. Nylon is produced synthetically in our factories and from our materials. Feedstock: amino acid derivatives. Capron can be considered as a product of the intramolecular interaction between the carboxyl group and the amino group of the 6-aminohexanoic acid molecule:
In a simplified way, the transformation of caprolactam into the polymer from which nylon fiber is produced can be represented as follows:
Caprolactam in the presence of water is converted into 6-aminohexanoic acid, the molecules of which react with each other. As a result of this reaction, a high-molecular substance is formed, the macromolecules of which have a linear structure. Individual polymer units are 6-aminohexanoic acid residues. The polymer is a resin. To obtain fibers, it is melted and passed through dies. The polymer jets are cooled by a flow of cold air and turn into fibers, which when twisted form threads.
After this, nylon is subjected to additional chemical treatment. The strength of nylon depends on the technology and care of production. The final finished nylon is white-transparent and very durable material. Even a nylon thread with a diameter of 0.1 millimeters can withstand 0.55 kilograms.
Abroad, synthetic fibers such as nylon are called perlon and nylon. Nylon is produced in several varieties; crystal-transparent nylon is more durable than opaque nylon with a cloudy yellowish or milky tint.
Along with high strength, nylon fibers are characterized by resistance to abrasion and repeated deformation (bending).
Nylon fibers do not absorb moisture, so they do not lose strength when wet. But nylon fiber also has disadvantages. It is not very resistant to acids; nylon macromolecules undergo hydrolysis at the site of amide bonds. The heat resistance of nylon is also relatively low. when heated, its strength decreases, and melting occurs at 2150C.
Products made from nylon, and in combination with nylon, have already become common in our everyday life. Clothing is made from nylon threads, which costs much less than clothes made from natural materials. Nylon is used to make fishing nets, fishing line, filter materials, and cord fabric. The frames of car and aircraft tires are made from cord fabric. Tires with nylon cord are more wear-resistant than tires with viscose and cotton cord. Nylon resin is used to produce plastics from which various machine parts, gears, bearing shells, etc. are made. Russian industry produces artificial fiber even stronger than nylon, for example, ultra-strong acetate silk, which is stronger than steel wire. This silk can withstand 126 kg per square millimeter, and steel wire - 110 kg.
Lavsan
Lavsan (polyethylene terephthalate) representative of polyesters. This is a polycondensation product of dihydric alcohol ethylene glycol HO-CH2CH2-OH and dibasic acid - terephthalic (1,4-benzenedicarboxylic) acid HOOC-C6H4-COOH (usually not terephthalic acid itself, but its dimethyl ether is used). The polymer belongs to linear polyesters and is obtained in the form of a resin. The presence of polar O-CO- groups regularly located along the macromolecule chain leads to increased intermolecular interactions, imparting rigidity to the polymer. The macromolecules in it are arranged randomly, in
Synthetic fibers began to be produced industrially in 1938. At the moment, there are already several dozen species of them. What all of them have in common is that the starting material is low molecular weight compounds that are converted into polymers through chemical synthesis. By dissolving or melting the resulting polymers, a molding or spinning solution is prepared. They are formed from a solution or melt, and then they are subjected to finishing.
Varieties
Depending on the features that characterize the structure of macromolecules, synthetic fibers are usually divided into heterochain and carbon chain. The first include those obtained from polymers, in whose macromolecules, in addition to carbon, other elements are present - nitrogen, sulfur, oxygen and others. These include polyester, polyurethane, polyamide and polyurea. Carbon-chain synthetic fibers are characterized by the fact that their main chain is built from carbon atoms. This group includes polyvinyl chloride, polyacrylonitrile, polyolefin, polyvinyl alcohol and fluorine-containing ones.
The polymers that serve as the basis for the production of heterochain fibers are obtained through polycondensation, and the product is formed from melts. Carbon chains are obtained through chain polymerization, and the formation usually occurs from solutions, in rare cases from melts. You can consider one synthetic polyamide fiber, which is called siblon.
Creation and application
A word like siblon is completely unfamiliar to many, but earlier on clothing labels one could see the abbreviation VVM, under which was hidden high-modulus viscose fiber. At that time, manufacturers thought that such a name would look prettier than siblon, which could be associated with nylon and nylon. The production of synthetic fibers of this type is carried out from the Christmas tree, no matter how fabulous it may look.
Peculiarities
Siblon appeared in the early 70s of the last century. It is an improved viscose. At the first stage, cellulose is obtained from wood, it is isolated into pure form. The largest amount of it is found in cotton - about 98%, but cotton fibers make excellent threads even without this. Therefore, wood is more often used to produce cellulose, in particular coniferous, where it contains 40-50%, and the rest is unnecessary components. They need to be disposed of in synthetic fibers.
Process of creation
Synthetic fibers are produced in stages. At the first stage, the cooking process is carried out, during which wood shavings all excess substances are moved into the solution, and long polymer chains are also broken down into separate fragments. Naturally, one does not make do with just hot water; various reagents are added: natron and others. Only cooking with the addition of sulfates makes it possible to obtain cellulose, which is suitable for the production of siblon, since fewer impurities remain in it.
When the cellulose has already been boiled, it is sent for bleaching, drying and pressing, and then moved to where it is needed - this is the production of paper, cellophane, cardboard and fibers, that is, what happens to it next?
Post-processing
If you want to get synthetic ones, then you first need to prepare a spinning solution. Cellulose is solid, which is not easy to dissolve. Therefore, it is usually converted into a water-soluble dithiocarbonate ester. The process of transformation into this substance is quite lengthy. First, the cellulose is treated with hot alkali, followed by squeezing, in which unnecessary elements pass into the solution. After pressing, the mass is crushed and then placed in special chambers, where pre-ripening begins - the cellulose molecules are shortened by almost half due to oxidative destruction. Next, the reaction of alkali cellulose with carbon disulfide occurs, which makes it possible to obtain xanthate. This is a mass orange color, similar to dough, an ester of dithiocarbonic acid and the original substance. This solution was called “viscose” due to its viscosity.
Next, filtering occurs to remove the last impurities. Dissolved air is released by “boiling” the ether in a vacuum. All these operations lead to the fact that xanthate becomes similar to young honey - yellow and viscous. At this point the spinning solution is completely ready.
Obtaining fibers
The solution is forced through dies. fibers are not simply spun traditional way. This operation is difficult to compare with a simple textile one; it would be more correct to say that this is a chemical process that allows millions of streams of liquid viscose to become solid fibers. In Russia, viscose and siblon are produced from cellulose. The second type of fiber is one and a half times stronger than the first, is characterized by greater resistance to alkalis, fabrics made from it are hygroscopic, and have a lower degree of shrinkage and creasing. And the differences in the production processes of viscose and siblon appear at the moment when newly “born” synthetic fibers end up in the precipitation bath after the spinnerets.
Chemistry to help
To obtain viscose, sulfuric acid is poured into the bath. It is designed to decompose ether, resulting in pure cellulose fibers. If it is necessary to obtain siblon, an ester is added to the bath, which partially interferes with hydrolysis, so the threads will contain residual xanthate. And what does this give? Next, the fibers are stretched and molded. When there are xanthate residues in the polymer fibers, it is possible to stretch the polymer cellulose chains along the axis of the fiber, and not arrange them chaotically, which is typical for ordinary viscose. After drawing, the fiber bundle is cut into spatulas 2-10 millimeters long. After several more procedures, the fibers are pressed into bales. A ton of wood is enough to produce 500 kilograms of cellulose, from which 400 kilograms of siblon fiber will be produced. Spinning of cellulose takes approximately two days.
What do they do next with the siblon?
In the eighties, these synthetic fibers were used as additives to cotton to make the threads spin better and not tear. Substrates for artificial leather were made from siblon, and it was also used in the production of asbestos products. At that time, technologists were not interested in creating something new; they needed as much fiber as possible to implement their plans.
And in the West at that time, high-modulus viscose fibers were used to produce fabrics that were cheap and durable compared to cotton, but at the same time absorbed moisture well and breathed. Now Russia does not have its own cotton regions left, so high hopes are placed on siblon. But the demand for it is not particularly high yet, since fabrics and clothes domestic production Almost no one is buying now.
Polymer fibers
They are usually divided into natural, synthetic and artificial. Natural fibers are those fibers that are formed in natural conditions. They are usually classified according to their origin, which determines them chemical composition, animals and plants. The former consist of protein, namely carotene. These are silk and wool. The latter consist of cellulose, lignin and hemicellulose.
Man-made synthetic fibers are obtained by chemically processing polymers that exist in nature. These include acetate, viscose, alginate and protein fibers. The raw material for their production is sulfate or sulfite wood pulp. Man-made fibers are produced in the form of textile and cord threads, as well as in the form of staple fiber, which is processed together with other fibers in the production of various fabrics.
Synthetic polyamide fiber is obtained from artificially derived polymers. The starting raw material in this process is polymer fibers formed from flexible macromolecules of a slightly branched or linear structure, having a significant mass - more than 15,000 atomic mass units, as well as a very narrow molecular weight distribution. Depending on the type, synthetic fibers can have a high degree of strength, significant elongation, elasticity, resistance to multiple loads, low permanent deformation and rapid recovery after removal of the load. That is why, in addition to their use in textiles, they were used as reinforcing elements during the manufacture of composites, and all this was made possible by the special properties of synthetic fibers.
Conclusion
In the last few years, one can observe a very steady increase in the number of advances in the development of new polymer fibers, in particular, para-aramid, polyethylene, heat-resistant, composite, core-shell, heterocyclic polymers, which include various particles, for example, silver or other metals. Now the material nylon is no longer the height of engineering, since there are now a huge number of new fibers.