Synthetic fibers include polyamide, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polypropylene, etc.
Polyamide fibers(kapron, anide, enanth). The fibers have a cylindrical shape, their cross section depends on the shape of the die hole through which the polymers are pressed (Fig. 9, a).
Polyamide fibers are distinguished by high tensile strength (40-70 cN/tex), resistant to abrasion, repeated bending, have high chemical resistance, frost resistance, and resistance to microorganisms. Their main disadvantages are low hygroscopicity (3.5-5%) and light resistance, high electrification and low heat resistance; when heated to 160 ° C, their strength decreases by almost 50%. As a result of rapid "aging", they turn yellow in the light, become brittle and hard. The fibers burn with a bluish flame, forming a brown solid ball at the end.
Polyamide fibers and threads are widely used in the production of hosiery and knitwear, sewing threads, haberdashery products (braids, ribbons), lace, ropes, fishing nets, conveyor belts, cord, technical fabrics, as well as in the production of household fabrics in mixtures with other fibers and threads. The addition of 10–20% polyamide staple fibers to natural ones dramatically increases the wear resistance of products.
polyester fibers(lavsan, terylene, dacron). In cross section, lavsan has the shape of a circle (Fig. 9, b).The tensile strength of lavsan is somewhat lower than that of polyamide fibers (40-50cN / tex), breaking elongation is within 20-25%, strength is not lost in the wet state. Unlike nylon, lavsan is destroyed by the action of acids and alkalis on it, its hygroscopicity is lower than that of nylon (0.4%). When brought into the flame, lavsan melts, slowly burns with a yellow smoky flame. The fiber is heat-resistant, has low thermal conductivity and high elasticity, which makes it possible to obtain products from it that retain their shape well; have little shrinkage. The disadvantages of the fiber are its increased rigidity, the ability to form pilling on the surface of products and strong electrification.
Lavsan is widely used in the production of household fabrics mixed with wool, cotton, linen and viscose fiber, which gives the products increased resistance to abrasion, elasticity
Rice. 9. Longitudinal view and cross section of synthetic fibers:
a) kapron; b) lavsan; c) nitrone; d) chlorine
and invincibility. It is also successfully used in the production of non-woven fabrics, sewing threads, curtains, technical fabrics and cord. Complex lavsan threads are subjected to texturing, as a result of which they absorb moisture better and retain heat.
Polyacrylonitrile fibers (nitron, orlon). In appearance, nitron resembles wool. Its surface is smooth (Fig. 9, in) with an irregular cross-sectional shape with jagged edges (dumbbell-shaped and close to it).
Nitron is characterized by high strength (32-39cN/tex), which does not change when wet, and elasticity. Products from it after washing retain their shape quite well. Nitron is not damaged by moths and microorganisms, and is highly resistant to nuclear radiation. In terms of abrasion resistance, nitron is inferior to polyamide and polyester fibers. In addition, it is characterized by low hygroscopicity (1.5%), which limits its use in the production of linen fabrics, strong electrical conductivity. The nitron fiber also has the best light fastness, low thermal conductivity, that is, good heat-shielding properties, and therefore is often used in blends with wool and in its pure form for suit and coat materials.
Nitron burns in flashes, emitting a smoke of black soot. After the end of burning, a dark, easily crushed lump is formed. Nitron is used in the production of outer knitwear, dress fabrics, as well as fur on a knitted and fabric basis, carpets, blankets and technical fabrics.
PVC fibers(chlorin) (Fig. 9, G). Compared with other synthetic fibers and cotton, it is less durable (12-14 cN / tex), less elastic, less resistant to abrasion, has low hygroscopicity (0.1%), low resistance to light weather, low heat resistance (70 °C). It is characterized by high chemical resistance, incombustibility, non-flammability.
Chlorine, when brought to a flame, chars, but does not burn, while releasing the smell of chlorine.
Chlorine has the ability to accumulate electrostatic charges, so it is used to make medical underwear. Chlorine is also used in the manufacture of fabrics for overalls, as it is resistant to water and microorganisms.
PVC fiber, as well as chlorin, belongs to polyvinyl chloride fibers, however, unlike chlorin, it is the most durable (26-36 cN / tex), more elastic and light resistant. It is used in the production of knitted and curtain-tulle products, blankets, decorative fabrics, batting, carpets, blankets, rugs and other products.
Polyvinyl alcohol fibers and threads. The filaments are spun from the solution by the wet method. Moreover, depending on the conditions of molding and subsequent acetylation, threads with varying degrees of strength and water resistance are obtained: from water-soluble to hydrophobic.
Insoluble polyvinyl alcohol fibers produced in our country are called vinol. They have many positive properties: strength, high resistance to abrasion, light weather, chemical reagents, and multiple deformations. Vinol is quite elastic, characterized by high heat resistance. The temperature of softening and the beginning of the decomposition of the fibers is 220°C. Vinol burns with a yellowish flame; after the burning stops, a solid lump of light brown color is formed.
A distinctive feature of polyvinyl alcohol fibers, which distinguishes them from all synthetic fibers, is their high hygroscopicity, due to the presence of a large number of hydroxyl groups in polymer macromolecules. In terms of hygroscopicity, polyvinyl alcohol fibers are close to cotton, which makes it possible to use it in the production of materials for linen and products of a costume and dress range. These fibers are well dyed with dyes for cellulose fibers. They are used in a mixture with cotton, wool for the production of fabrics, knitwear, carpets, etc.
A water-soluble variety of polyvinyl alcohol fibers is used in the textile industry as an auxiliary (removable) fiber in the production of openwork products, thin fabrics, materials of porous fibrous structures, as well as in the manufacture of guipure (instead of natural silk). Polyvinyl alcohol threads are used in medicine for temporary fastening of surgical sutures.
The presence of hydroxyl groups makes it possible to carry out chemical modification of these fibers, especially by the method of synthesis of graft copolymers, due to which it is possible to create fibers and threads with specific properties: fire-resistant, bactericidal, ion-exchange, etc.
Polyolefin fibers and threads. From the group of polyolefins, polypropylene is used for the production of fibers [– CH 2 –CHSN 3 –] n and polyethylene [– CH 2 –CH 2 –] n medium and low pressure.
Polyolefin fibers can be spun from polymer melts or solutions, followed by drawing and heat setting.
Polypropylene and polyethylene threads have sufficiently high tensile strength and elongation values. Polyolefin fibers and threads are characterized by high resistance to acids, alkalis, they are not inferior in terms of chemical resistance to chlorine. Their resistance to abrasion is lower than that of polyamide yarns, especially polypropylene ones.
The heat resistance of polyolefin yarns is low. At a temperature of 80 ° C, a polyethylene thread loses about 80% of its original strength. The hygroscopicity of the threads is almost zero, so they can be dyed only with the introduction of a pigment into the polymer before spinning. Significant electrification of these threads is also associated with low hygroscopicity. The density of polyethylene and polypropylene threads is very low, so products made from them do not sink in water.
Polyolefin fibers are mainly used for technical purposes, as well as mixed with hydrophilic fibers (cotton, wool, viscose, etc.) in the production of materials for outerwear, footwear, and decorative fabrics.
polyurethane threads. Currently, there is a fairly large range of materials using polyurethane (elastane) threads (spandex, lycra, etc.). Threads have a cylindrical shape with a round cross section, amorphous. A feature of all polyurethane threads is their high elasticity: their breaking elongation is 800%, the proportion of elastic and elastic deformations is 92-98%. Therefore, materials containing polyurethane yarns have good elastic properties and little wrinkle. It is this feature that determined the scope of their use. Spandex is mainly used in the manufacture of elastic products. With the use of these threads, fabrics and knitted fabrics for household use, for sportswear, as well as hosiery are produced. Polyurethane yarns have insufficient strength (6–7 cN/tex) and heat resistance. When exposed to temperatures above 100°C, the threads lose their elastic properties. Therefore, they are produced mainly by a braid protecting them. Polyurethane threads also have a very low hygroscopicity (0.8-0.9%), which also limits their use in pure form.
For a directed change in the properties of chemical fibers, their chemical modification is carried out in various ways. In order to expand the use of chemical fibers and threads in various fields of technology, high-strength, high-modulus (low-stretch), heat-resistant, non-combustible, light-resistant and other types of fibers with special properties have been created. Thus, by introducing aromatic units (benzene rings) into the polyamide chain molecule, high-strength and heat-resistant fibers such as phenylone, vnivlon (or SVM - ultra-high-modulus), oxalon, arimid T, Kevlar, etc. were obtained. High-strength, chemical-resistant, heat-resistant carbon . They have unique properties. Under conditions of prolonged heating (at a temperature of 400°C or more), they retain their mechanical properties and are non-combustible. They are used in various fields of technology (cosmonautics, aviation and chemical engineering, etc.)
More detailed information about the preparation and structure of chemical fibers is given in the textbook.
Synthetic fibers
chemical fibers obtained from synthetic polymers. Synthetic fibers are either spun from a polymer melt ( polyamide, polyester, polyolefin), or from a polymer solution ( polyacrylonitrile, PVC, polyvinyl alcohol) by dry or wet method. Synthetic fibers are produced in the form of textile and cord threads, monofilament, as well as staple fiber. The variety of properties of the initial synthetic polymers makes it possible to obtain synthetic fibers with different properties, while the possibilities for varying the properties of artificial fibers are very limited, since they are formed from almost one polymer ( cellulose or its derivatives). Synthetic fibers are characterized by high strength, water resistance, wear resistance, elasticity and resistance to chemicals.
Since 1931, apart from butadiene rubber, there were no synthetic fibers and polymers, and for the manufacture of fibers, the only materials known at that time based on a natural polymer - cellulose - were used.
Revolutionary changes came in the early 1960s, when, after the announcement of the well-known chemicalization program for 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 the understanding came that polymers and fibers based on them are sometimes better than traditionally used natural materials - they are lighter, stronger, more heat-resistant, able to work in aggressive environments. Therefore, chemists and technologists directed all their efforts to the creation of new polymers with high performance characteristics and methods for their processing. And they achieved results in this business, sometimes surpassing the results of similar activities of well-known foreign firms.
In the early 1970s, Kevlar (USA) fibers, amazing in their strength, appeared abroad, a little later - Twaron (Netherlands), technora (Japan) and others made from aromatic polymers, collectively called aramids. On the basis of such fibers, various composite materials were created, which began to be successfully used for the manufacture of critical parts of aircraft and missiles, as well as tire cord, bulletproof vests, 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 knows that in the same years, Russian chemists and technologists independently created aramid fiber terlon, which is not inferior in its properties to foreign analogues. And then here methods were developed for obtaining SVM and Armos fibers, the strength of which exceeds the strength of Kevlar by one and a half times, and the specific strength (that is, the 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 underway to create a polymer fiber with a strength of up to 600 kg/mm2.
Another class of polymers suitable for producing high-strength fibers are liquid crystal aromatic polyesters, that is, polymers that have the properties of crystals in the liquid state. Fibers based on them are characterized not only by the advantages of aramid fibers, but also by high radiation resistance, as well as resistance to inorganic acids and various organic solvents. It is an ideal material for reinforcing rubber and creating highly filled composites; based on it, 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 crystal polymers themselves serve as reinforcing components.
The molecules of ordinary polymers contain, in addition to carbon, also atoms of other elements - hydrogen, oxygen, nitrogen. But now methods have been developed for obtaining fibers that are, in fact, pure polymeric carbon. Such fibers have record strength (over 700 kg/mm2) and stiffness, as well as extremely low coefficients of thermal expansion, high resistance to wear and corrosion, high temperatures and radiation. This makes it possible to successfully use them for the manufacture of composite materials - carbon fiber reinforced plastics, used in the most critical structural units of high-speed aircraft, rockets and spacecraft.
The use of carbon fiber is economically very profitable. Per unit weight of a product made from it, you need to spend 3 times less energy than a product made of steel, and 20 times less than titanium. A ton of CFRP can replace 10-20 tons of high-alloy steel. The carbon fiber pump turbine, which is suitable for pumping mineral acids at temperatures up to 150°C, is half the price and lasts six times longer. The complexity of manufacturing parts of complex configuration is also reduced.
The production of synthetic fibers is developing at a faster pace than the production of artificial fibers. This is due to the availability of raw materials and the rapid development of the raw material base, the lower labor intensity of production processes, and especially the variety of properties and high quality of 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 the world production of synthetic fibers amounted to 3,760,300 tons. t(about 51.6% of the total output of chemical fibers). For the first time, the production of synthetic fibers on an industrial scale was organized in the mid-30s. 20th century in the USA and Germany.
Kapron
Fiber from polyamide resins is called kapron and anid in our country, they almost do not differ in their quality from one another.
Kapron or kapron fiber is a white-transparent, very durable substance. The elasticity of capron is much higher than silk. Kapron refers to polyamide fibers. Nylon is made synthetically in our factories and from our materials. Feedstock derivatives of amino acids. Capron can be considered as a product of the intramolecular interaction of the carboxyl group and the amino group of the 6-aminohexanoic acid molecule:
Simplified, the transformation of caprolactam into a 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, passed through spinnerets. The jets of polymer are cooled by a stream of cold air and turn into fibers, which are twisted to form filaments.
After that, the capron is subjected to additional chemical treatment. The strength of capron depends on the technology and care of production. The finished capron is white-transparent and very durable material. Even a nylon thread with a diameter of 0.1 mm can withstand 0.55 kilograms.
Abroad, synthetic fiber of the kapron type is called perlon and nylon. Kapron is produced in several varieties; crystal-clear nylon is more durable than opaque with a dull yellowish or milky tint.
Along with high strength, nylon fibers are characterized by resistance to abrasion, the action of repeated deformation (bends).
Nylon fibers do not absorb moisture, so they do not lose strength when wet. But kapron fiber also has disadvantages. It is not very resistant to the action of acids. Capron macromolecules undergo hydrolysis at the site of amide bonds. The heat resistance of capron is also relatively low. when heated, its strength decreases, at 2150C melting occurs.
Products from capron, and in combination with capron, have already become common in our everyday life. From kapron threads sew clothes that are much cheaper than clothes made from natural materials. Fishing nets, fishing line, filter materials, cord fabric are made from kapron. The carcasses of auto and aircraft tires are made from cord fabric. Tires with nylon cord are more durable than viscose and cotton cord tires. Nylon resin is used to produce plastics, which are used to make various machine parts, gears, bearing shells, etc. The Russian industry produces artificial fiber even stronger than nylon, for example, heavy-duty acetate silk, which surpasses steel wire in its strength. This silk can withstand 126 kg per square millimeter, and steel wire - 110 kg.
Lavsan
Lavsan (polyethylene terephthalate) representative of polyesters. It is a polycondensation product of ethylene glycol dihydric alcohol HO-CH2CH2-OH and dibasic acid - terephthalic (1,4-benzenedicarboxylic) acid HOOC-C6H4-COOH (usually not terephthalic acid itself is used, but its dimethyl ester). The polymer belongs to linear polyesters and is obtained in the form of a resin. The presence of polar groups O-CO- regularly located along the chain of the macromolecule leads to an increase in intermolecular interactions, imparting rigidity to the polymer. Macromolecules in it are arranged randomly, in
Synthetic fabrics - guests from the future
Lightweight, strong, durable and beautiful synthetic materials are gaining a stronger position in today's textile market. For high performance and low cost, synthetic fabrics are called the fabric of the future.
In the minds of many people, the axiom "Natural fabrics are good, but synthetics are bad" is clearly deposited. At the same time, most refer to synthetics as all materials, except for cotton, linen, silk and wool.
It is important to know! All non-natural fabrics are divided into two large groups - artificial and synthetic. The first are made from natural components - cellulose, proteins, glass. Synthetic materials are based only on polymers that do not exist in nature.
Synthetic fibers are obtained during the synthesis of ethylene, benzene or phenol, produced from natural gas, oil and coal.
The history of synthetic fabrics began a little more than half a century ago, when, shortly before World War II, the leading chemist of the American DuPont factory, Wallace Carothers, synthesized a new material called nylon.
This shiny, smooth fabric, pleasant to the touch, immediately turned out to be in demand for the production of ladies' stockings. During the war years, nylon was used for the needs of the army, it was used to make fabric for parachutes and camouflage nets.
Already in the late 40s - early 50s of the twentieth century, the era of synthetics began - nylon, nitron, anide, polyester and other fibers appeared on the textile market.
The chemical industry does not stand still, and now the number of synthetic fabrics has exceeded a hundred. Modern technologies make it possible to obtain materials with already predetermined properties.
Classification of synthetic fibers
Fabrics made from synthetic fibers vary depending on the raw materials used in the manufacture. All modern materials can be divided into several types.
Polyamide fibers
This group includes nylon, capron, anid and others. Most often used for the production of household and technical products.
They are distinguished by high tensile and tear strength: nylon thread is 3-4 times stronger than cotton thread. Resistant to abrasion, fungi and microbes.
The main disadvantages are low hygroscopicity, high electrification, resistance to sunlight. With a long service life, they turn yellow and become brittle.
polyester fibers
The most prominent representative of this group of synthetic materials is lavsan, which resembles fine wool in appearance. In some countries, lavsan is known as terylene or dacron.
Lavsan fibers, added to wool, provide products with strength and reduce their wrinkling.
The disadvantage of lavsan is its low hygroscopicity and relative rigidity. In addition, the fabric is highly electrified.
It is used for tailoring suits, dresses, skirts, as well as for the production of artificial fur.
Polyurethane fibers
The main advantage of these fibers is elasticity and high tensile strength. Some of them can stretch, increasing 5-7 times.
Fabrics made from polyurethane - spandex, lycra - are durable, elastic, do not wrinkle and perfectly fit the body.
Negative sides: they do not pass air well, they are non-hygroscopic, they have low heat resistance. Used in the production of knitted fabrics for sewing outerwear, tracksuits, hosiery.
Polyolefin fibers
These cheapest synthetic threads are made from polyethylene and polypropylene. The main use is the production of carpets, technical materials.
Fabrics, which include polyolefin fibers, have increased strength, wear resistance, do not deteriorate when exposed to mold or various microorganisms.
The disadvantages include significant shrinkage during washing, as well as instability to high temperatures.
Interesting fact! Not so long ago, the main advantage of polyolefin fibers was discovered - their ability to repel water, while remaining dry. Due to this, the fibers are used in the production of water-repellent products - tents, raincoat fabric, etc.
Synthetic doesn't mean bad
For all their “unnaturalness”, synthetic fabrics have a number of significant advantages:
- Durability. Unlike "naturals", synthetics are absolutely not subject to rotting, mold, fungi or various pests.
- Color fastness. Thanks to a special technology in which the fabric is first bleached and then dyed, synthetics retain their color stability for many years.
- Lightness and airiness. Synthetic fabrics weigh several times less than their natural counterparts.
- Wrinkle resistance. Products made of chemical fibers do not wrinkle when worn and perfectly retain their shape. Synthetic clothes can be hung on hangers without fear of stretching.
- Low cost. Since the production of these fabrics is based on inexpensive raw materials, products made from them are available to any category of buyers.
In addition, a wide variety of synthetic fabrics allows everyone to choose the material based on their requirements and taste.
Not without flaws
Although the modern chemical industry is developing by leaps and bounds, trying to improve the properties of synthetic materials, it is still not possible to get rid of some of the negative aspects.
List of the main disadvantages of synthetics:
- Reduced hygroscopicity. Synthetic clothing does not absorb moisture well, heat transfer is disturbed, the human body sweats.
- Absorption of odors. Some types of fabrics are able to accumulate unpleasant odors in themselves and distribute them until the next wash.
- The likelihood of an allergy. People with a tendency to allergic reactions may experience skin irritation after contact with synthetics.
- Toxicity. Unfortunately, cheap synthetic materials are not always safe for health. It is not recommended to buy such clothes, especially for small children.
If clothing made from 100% synthetics can cause understandable concerns among buyers, then adding chemical fibers to natural fabrics only improves their properties, making them safer and more environmentally friendly.
Important! Materials made of mixed fibers are elastic, do not wrinkle when worn, do not require ironing, do not cause allergies in people with sensitive skin.
Briefly about the most famous synthetic fabrics
The most common synthetic materials include:
- Acrylic. The raw material for this fabric is obtained from natural gas. According to its properties, acrylic is close to natural wool. It retains heat well, so outerwear is often sewn from it. It is not afraid of moths, does not fade in the sun and retains the brightness of the color for a long time.
The main disadvantage of acrylic is the formation of pellets with prolonged wear.
- . The industrial production of this fabric was established in the 80s of the last century. In terms of softness and comfort in wearing, fleece is comparable to natural wool or fur.
The fabric is very light, elastic, breathable, perfectly retains heat. Fleece is easy to care for: it can be washed in a typewriter and does not need to be ironed. Fleece clothing is great for walking, outdoor activities, as materials for dressing gowns and pajamas.
The only drawback of this material is its ability to electrify.
- Polyester. By themselves, polyester fibers are stiff and difficult to color. However, in combination with cotton or linen, they acquire completely different qualities: softness, elasticity, resistance to moisture and high temperatures.
Thanks to these qualities, polyester fabrics are the best material for sewing curtains, curtains, home textiles - tablecloths, bedspreads, napkins.
In addition, the smoothness and silkiness of polyester is used in the manufacture of women's underwear.
- . The fabric was developed in Japan and first saw the light of day in 1975. The fiber is so thin that a skein of yarn 100 kilometers long weighs only five grams.
Microfiber is easy to wash, dries quickly, holds its shape for a long time and retains its color. It perfectly absorbs moisture, so most often they make household goods from it: napkins, rags, towels, etc.
Every year the range of synthetic fabrics is growing, they are acquiring new and more perfect characteristics, trying to satisfy the needs of the most demanding customers.
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Some natural cellulose fibers are processed and processed for specific uses. Well-known fibers such as viscose, acetate, etc. are obtained by processing various natural polymers.
The first man-made fibers that were developed and manufactured used polymers of natural origin, more precisely cellulose, which is a raw material available in large quantities in the plant kingdom.
Cellulose is a natural polymer that makes up the living cells of all vegetation. It is the material at the center of the carbon cycle and the most abundant and renewable biopolymer on the planet.
Cotton sheets and wood pulp, viscose, copper ammonium silk, cellulose acetate (secondary and triacetate), polynose, high wet modulus (HMW) fibre.
- Cellulose is one of the many polymers found in nature.
- Wood, paper and cotton contain cellulose. Cellulose is an excellent fiber.
- Cellulose is made up of repeating units of monomeric glucose.
- The three types of regenerated cellulose fibers are viscose, acetate and triacetate, which are derived from the cell walls of short cotton fibers called linters.
- Paper, for example, is almost pure cellulose.
Viscose
The word "viscose" was originally applied to any fiber made from cellulose and therefore contained cellulose acetate fibers. However, the definition of viscose was described in 1951 and now includes textile fibers and fibers composed of regenerated cellulose, excluding acetate.
- Viscose is a regenerated cellulose fibre.
- It is the first man-made fiber.
- It has a jagged round shape with a smooth surface.
- When wet, viscose loses 30-50% of its strength.
- Viscose is formed from natural polymers and therefore is not a synthetic fiber, but an artificial regenerated cellulose fiber.
- The fiber is sold as rayon.
- There are two main varieties of viscose fiber, namely viscose and copper ammonium.
Acetate
Derived fiber in which the fiber-forming substance is cellulose acetate. Acetate is obtained from cellulose by refining cellulose from wood pulp with acetic acid and acetic anhydride in the presence of sulfuric acid.
Characteristics of acetate fiber:
- Luxurious to the touch and look
- Wide range of colors and glosses
- Excellent drape and softness
- Relatively fast drying
- Resistant to shrinkage, moths and powdery mildew
Special dyes have been developed for acetate because it does not accept dyes commonly used for cotton and viscose.
Acetate fibers are manufactured fibers in which the fiber-forming substance is cellulose acetate. Cellulose ethers triacetate and acetate are formed by acetylation of cotton linters or wood pulp using acetic anhydride and an acid catalyst in acetic acid.
Acetate and triacetate fibers are very similar in appearance to viscose with consistent strength. Elements and triacetates are moderately stiff fibers and have good flexural and deformation resilience, especially after heat treatment.
The abrasion resistance of acetate and triacetate is poor and these fibers cannot be used in applications requiring high abrasion and wear resistance; however, the abrasion resistance of these fibers is excellent. Although acetate and triacetate are moderately absorbent, their absorption cannot be compared to pure cellulose fibers. To the touch, acetate fabrics are somewhat softer and more flexible than triacetate. The fabrics of both fibers have excellent drape characteristics. Acetate and triacetate fabrics have a pleasant appearance and a high degree of sheen, but the sheen of these fabrics can be modified by adding a matting agent.
Both acetate and triacetate are susceptible to attack by a number of household chemicals. Acetate and triacetate are attacked by strong acids and bases and oxidizing bleaches. Acetate has only a slight resistance to sunlight, while the solar resistance of triacetate is higher. Both fibers have good heat resistance below their melting points.
Acetate and triacetate cannot be dyed with dyes used for cellulose fibers. These fibers can be satisfactorily dyed with disperse dyes at moderate to high temperatures, producing crisp, vibrant hues. Acetate and triacetate dry quickly and can be dry cleaned.
Synthetic fibers began to be produced industrially in 1938. At the moment, there are already several dozen of them. All of them have in common 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 spinning or spinning solution is prepared. They are molded from a solution or melt, and they are only then subjected to finishing.
Varieties
Depending on the features that characterize the structure of macromolecules, synthetic fibers are usually divided into heterochain and carbochain. The former include those obtained from polymers, in whose macromolecules, in addition to carbon, there are other elements - 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 of carbon atoms. This group includes polyvinyl chloride, polyacrylonitrile, polyolefin, polyvinyl alcohol and fluorine-containing.
The polymers that serve as the basis for obtaining heterochain fibers are obtained by polycondensation, and the product is molded from melts. Carbochains are obtained by 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
Such a word as siblon turns out to be completely unfamiliar to many, but earlier on clothing labels one could see the abbreviation VVM, under which a high-modulus viscose fiber was hidden. At that time, it seemed to manufacturers 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 looks.
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 in its pure form. Its largest amount is found in cotton - about 98%, but excellent threads are obtained from cotton fibers even without it. Therefore, for the production of cellulose, wood is more often used, in particular coniferous, where it contains 40-50%, and the rest is unnecessary components. They are required to be disposed of in synthetic fibers.
Process of creation
Synthetically, fibers are produced in stages. At the first stage, the cooking process is carried out, during which all excess substances are transferred from wood chips into the solution, and long polymer chains are broken down into separate fragments. Naturally, only hot water is not enough here, various reagents are added: natrons and others. Only pulping with the addition of sulphates makes it possible to obtain pulp that is suitable for the production of siblon, since it contains fewer impurities.
When the pulp is already digested, 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 and then you first need to prepare a spinning solution. Cellulose is a solid that is not easy to dissolve. Therefore, it is usually converted into a water-soluble dithiocarbonic acid ester. The process of transformation into this substance is quite lengthy. First, the cellulose is treated with hot alkali, followed by squeezing, while unnecessary elements pass into the solution. After squeezing, the mass is crushed, and then placed in special chambers, where pre-ripening begins - the cellulose molecules are almost halved due to oxidative degradation. Next, the alkali cellulose reacts with carbon disulfide, which makes it possible to obtain xanthate. This is an orange-colored dough-like mass, an ester of dithiocarbonic acid and the starting material. This solution was called "viscose" because of its viscosity.
Next comes filtration 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 like young honey - yellow and viscous. On this, the spinning solution is completely ready.
Obtaining fibers
The solution is forced through the dies. the fibers are not simply spun in the traditional way. This operation is difficult to compare with a simple textile, it would be more correct to say that it is a chemical process that allows millions of streams of liquid viscose to become solid fibers. On the territory of Russia, viscose and siblon are obtained 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, less shrinkage and wrinkling. And the differences in the production processes of viscose and siblon appear at the moment when the newly "born" synthetic fibers appear 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 the ether, resulting in pure cellulose fibers. If it is necessary to obtain a siblon, an ester that partially hinders the hydrolysis of the ester is added to the bath, so the threads will contain residual xanthate. And what does it give? The fibers are then stretched and shaped. When there are xanthate residues in the polymer fibers, it turns out to stretch the polymer cellulose chains along the axis of the fiber, and not arrange them randomly, which is typical for ordinary viscose. After drawing, the bundle of fibers is cut into spatulas 2-10 millimeters long. After a few more procedures, the fibers are pressed into bales. A ton of wood is enough to produce 500 kilograms of pulp, from which 400 kilograms of siblon fiber will be produced. Pulp spinning is carried out for about two days.
What's next for the siblon?
In the 1980s, these synthetic fibers were used as additions to cotton to make the threads spin better and not break. Siblon was used to make substrates for artificial leather, and it was also used in the manufacture 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, so great hopes are pinned on siblon. Only the demand for it is not yet particularly great, since almost no one buys fabrics and clothes of domestic production.
Polymer fibers
They are usually divided into natural, synthetic and artificial. Natural are those fibers, the formation of which is carried out in natural conditions. They are usually classified according to their origin, which determines their chemical composition, into animals and plants. The first are composed of protein, namely carotene. It's silk and wool. The latter are composed of cellulose, lignin and hemicellulose.
Man-made synthetic fibers are obtained by chemical processing of 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. As a feedstock in this process, polymer fibers are used, 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 are able to have a high degree of strength, a significant value in relation to elongation, elasticity, resistance to multiple loads, low residual deformations and rapid recovery after removal of the load. That is why, in addition to being used in textiles, they were used as reinforcing elements during the manufacture of composites, and all this made it possible to make 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, combined, the structure of which is the 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, as there are now a huge number of new fibers.
