Textile fibers are called flexible, durable bodies with small transverse dimensions, limited length, suitable for the manufacture of textiles.
Textile fibers are divided into two classes: natural and chemical. Based on the origin of the fiber-forming substance, natural fibers are divided into three subclasses: plant, animal and mineral origin, chemical fibers are divided into two subclasses: artificial and synthetic.
Artificial fiber- chemical fiber made from natural high-molecular substances.
Synthetic fiber- chemical fiber made from synthetic high-molecular substances.
Fibers can be elementary or complex.
Elementary- a fiber that does not divide in the longitudinal direction without destruction (cotton, linen, wool, viscose, nylon, etc.). Complex fiber consists of longitudinally bonded elementary fibers.
Fibers are the starting material for the manufacture of textile products and can be used both in natural and mixed forms. The properties of fibers affect the technological process of processing them into yarn. Therefore, it is important to know the basic properties of fibers and their characteristics: thickness, length, crimp. The thickness of the products obtained from them depends on the thickness of the fibers and yarn, which affects their consumer properties.
Yarn made from thin synthetic fibers is more prone to pilling - the formation of rolled fibers on the surface of the material. The longer the fibers, the more even in thickness and stronger the yarn made from them.
Natural fibers
Cotton- These are the fibers that cover the seeds of cotton plants. Cotton is an annual plant 0.6-1.7 m high, growing in areas with a hot climate. The main substance (94-96%) that makes up cotton fiber is cellulose. Under a microscope, cotton fiber of normal maturity looks like a flat ribbon with a corkscrew crimp and a channel filled with air inside. One end of the fiber on the side where it is separated from the cotton seed is open, the other, which has a conical shape, is closed.
The amount of fiber depends on its degree of maturity.
Cotton fiber is inherently crimped. Fibers of normal maturity have the greatest crimp - 40-120 crimps per 1 cm.
The length of cotton fibers ranges from 1 to 55 mm. Depending on the length of the fibers, cotton is divided into short-staple (20-27 mm), medium-staple (28-34 mm) and long-staple (35-50 mm). Cotton with a length of less than 20 mm is called unspun, i.e., it is impossible to make yarn from it. There is a certain relationship between the length and thickness of cotton fibers: the longer the fibers, the thinner they are. Therefore, long-staple cotton is also called fine-staple cotton; it has a thickness of 125-167 millitex (mtex). The thickness of medium-staple cotton is 167–220 mtex, short-staple cotton is 220–333 mtex.
The thickness of the fibers is expressed in terms of linear density in hexes. Tex shows how many grams a piece of fiber 1 km long weighs. Millitex = mg/km.
The choice of spinning system (yarn production) depends on the length and thickness of the fibers, which in turn affects the quality of the yarn and fabric. Thus, from long-staple (fine-fiber) cotton, thin, even in thickness, with low hairiness, dense, strong yarn of 5.0 tex and above is obtained, used for the manufacture of high-quality thin and light fabrics: cambric, voile, volte, combed satin, etc.
Medium-fiber cotton is used to produce medium- and above-average yarn linear density 11.8-84.0 tex, from which the bulk of cotton fabrics are produced: calico, calico, calico, carded satin, corduroy, etc.
From short-fiber cotton, loose, thick, uneven in thickness, fluffy, sometimes with foreign impurities, yarn is obtained - 55-400 tex, used for the production of flannel, paper, flannel, etc.
Cotton fiber has numerous positive properties. It has high hygroscopicity (8-12%), so cotton fabrics have good hygienic properties.
The fibers are quite strong. A distinctive feature of cotton fiber is its increased wet tensile strength by 15-17%, which is explained by a doubling of the cross-sectional area of the fiber as a result of its strong swelling in water.
Cotton has high heat resistance - fiber destruction does not occur up to 140°C.
Cotton fiber is more resistant to light than viscose and natural silk, but in terms of light resistance it is inferior to bast and wool fibers. Cotton is highly resistant to alkalis, which is used in finishing cotton fabrics (finishing - mercerization, treatment with caustic soda solution). At the same time, the fibers swell greatly, shrink, become uncrimped, smooth, their walls thicken, the channel narrows, strength increases, and shine increases; the fibers are better dyed, holding the dye firmly. Due to its low elasticity, cotton fiber has high creasing, high shrinkage, and low resistance to acid. Cotton is used to make fabrics for various purposes, knitwear, non-woven fabrics, curtains, tulle and lace products, sewing threads, braid, laces, ribbons, etc. Cotton fluff is used in the production of medical, clothing, and furniture wool.
Bast fibers obtained from stems, leaves or fruit shells various plants. Stem bast fibers are flax, hemp, jute, kenaf, etc., leaf fibers are sisal, etc., fruit fibers are coir, obtained from the covering of coconut shells. Of the bast fibers, flax fibers are the most valuable.
Linen - An annual herbaceous plant, it has two varieties: long flax and curly flax. Fibers are obtained from fiber flax. The main substance that makes up bast fibers is cellulose (about 75%). Associated substances include: lignin, pectin, fatty wax, nitrogenous, coloring, ash substances, water. Flax fiber has four to six edges with pointed ends and characteristic strokes (shifts) in individual areas resulting from mechanical influences onto the fiber upon receipt.
Unlike cotton, flax fiber has relatively thick walls, a narrow channel, closed at both ends; The surface of the fiber is more even and smooth, so linen fabrics are less likely to get dirty than cotton fabrics and are easier to wash. These properties of flax are especially valuable for linen fabrics. Flax fiber is also unique in that, with high hygroscopicity (12%), it absorbs and releases moisture faster than other textile fibers; it is stronger than cotton, elongation at break is 2-3%. The content of lignin in flax fiber makes it resistant to light, weather, and microorganisms. Thermal destruction of the fiber does not occur up to + 160°C. The chemical properties of flax fiber are similar to cotton, that is, it is resistant to alkalis, but not resistant to acids. Due to the fact that linen fabrics have their natural, quite beautiful silky shine, they are not subjected to mercerization.
However, flax fiber is highly wrinkled due to low elasticity and is difficult to bleach and dye.
Due to its high hygienic and strength properties, flax fibers are used to produce linen fabrics (for underwear, table linen, bed linen), and summer suit and dress fabrics. At the same time, about half of linen fabrics are produced in a mixture with other fibers, a significant part of which is semi-linen underwear fabrics with cotton yarn at the base.
Canvas, fire hoses, cords, shoe threads are also made from flax fibers, and coarser fabrics are made from flax tows: bags, canvas, tarpaulins, sailcloths, etc.
Hemp obtained from the annual hemp plant. The fibers are used to produce ropes, ropes, twines, packaging and bagging fabrics.
Kenaf, jute get from annual plants families of mallow and linden. Kenaf and jute are used to produce bag and container fabrics; used for transporting and storing moisture-intensive goods.
Wool - fiber from the removed hair of sheep, goats, camels, rabbits and other animals. Wool removed by shearing in the form of a single hairline is called fleece. Wool fibers are composed of the protein keratin, which, like other proteins, contains amino acids.
Under a microscope, wool fibers can be easily distinguished from other fibers - their outer surface is covered with scales. The scaly layer consists of small plates in the form
cone-shaped rings strung on top of each other and represents keratinized cells. The scaly layer is followed by the cortical layer, the main one, on which the properties of the fiber and products made from them depend. The fiber may also have a third layer, the core layer, consisting of loose, air-filled cells. Under a microscope, the peculiar crimp of the wool fibers is also visible. Depending on what layers are present in the wool, it can be of the following types: fluff, transitional hair, awn, dead hair.
Pooh- thin, highly crimped, silky fiber without a core layer. Transitional hair has an intermittent, loose core layer, due to which it is uneven in thickness, strength, and has less crimp.
Ost And dead hair have a large core layer, are characterized by great thickness, lack of crimp, increased rigidity and fragility, and low strength.
Depending on the thickness of the fibers and the uniformity of the composition, wool is divided into fine, semi-fine, semi-coarse and coarse. Important indicators of the quality of wool fiber are its length and thickness. The length of wool affects the technology for obtaining yarn, its quality and the quality of finished products. From long fibers (55-120 mm) combed (worsted) yarn is obtained - thin, even in thickness, dense, smooth.
From short fibers (up to 55 mm), hardware (cloth) yarn is obtained, which, unlike worsted, is thicker, loose, fluffy, with uneven thickness.
The properties of wool are unique in their own way - it is characterized by high feltability, which is explained by the presence of a scaly layer on the surface of the fiber.
Thanks to this property, felt, cloth fabrics, felt, blankets, and felted shoes are made from wool. Wool has high heat-protective properties and is highly elastic. Alkalies have a destructive effect on wool; it is resistant to acids. Therefore, if wool fibers containing plant impurities are treated with an acid solution, then these impurities dissolve, and the wool fibers remain pure. This process of cleaning wool is called carbonization.
The hygroscopicity of wool is high (15-17%), but unlike other fibers it slowly absorbs and releases moisture, remaining dry to the touch. In water it swells greatly, and the cross-sectional area increases by 30-35%. Moistened fiber in a stretched state can be fixed by drying; when re-moistened, the length of the fiber is restored again. This property of wool is taken into account during the wet-heat treatment of garments made from woolen fabrics for stretching and stretching their individual parts.
Wool is a fairly strong fiber with a high elongation at break; when wet, fibers lose 30% strength. The disadvantage of wool is its low heat resistance - at temperatures of 100-110°C, the fibers become brittle, stiff, and their strength decreases.
From fine and semi-fine wool, both in pure form and mixed with other fibers (cotton, viscose, nylon, lavsan, nitron), worsted and fine cloth dress, suit, coat fabrics, non-woven fabrics, knitwear, scarves, blankets are produced. ; from semi-rough and coarse - coarse cloth coat fabrics, felted shoes, felt.
Goat down is used mainly for the production of scarves, knitwear and some dress, suit, and coat fabrics; camel hair- for the production of blankets and national products. Lower quality fabrics, felted shoes, nonwovens, construction felt.
Natural silk in terms of its properties and cost, it is the most valuable textile raw material. It is obtained by unwinding cocoons formed by silkworm caterpillars. The most widespread and valuable silk is the silkworm, which accounts for 90% of world silk production.
The homeland of silk is China, where the silkworm was cultivated 3000 BC. e. The production of silk goes through the following stages: the silkworm butterfly lays eggs (grena), from which caterpillars hatch about 3 mm long. They feed on mulberry leaves, hence the name silkworm. After a month, the caterpillar, having accumulated natural silk, through the silk-secreting glands located on both sides of the body, wraps itself in a continuous thread of 40-45 layers and forms a cocoon. Winding the cocoon lasts 3-4 days. Inside the cocoon, the caterpillar turns into a butterfly, which, having made a hole in the cocoon with an alkaline liquid, comes out of it. Such a cocoon is unsuitable for further unwinding. Cocoon threads are very thin, so they are unwound simultaneously from several cocoons (6-8), connecting them into one complex thread. This thread is called raw silk. The total length of the unwinding thread is on average 1000-1300 m.
The scrap remaining after unwinding the cocoon (a thin shell that cannot be unwinded, containing about 20% of the length of the thread), rejected cocoons are processed into short fibers, from which silk yarn is obtained.
Of all natural fibers, natural silk is the lightest fiber and, along with its beautiful appearance, has high hygroscopicity (11%), softness, silkiness, and low creasing.
Natural silk has high strength. The breaking load of silk when wet is reduced by approximately 15%. Natural silk is resistant to acids, but not to alkalis, has low light fastness, relatively low heat resistance (100-110°C) and high shrinkage. Silk is used to make dress and blouse fabrics, as well as sewing threads, ribbons, and laces.
Chemical fibers are obtained by chemical processing of natural (cellulose, proteins, etc.) or synthetic high-molecular substances (polyamides, polyesters, etc.).
The technological process of manufacturing chemical fibers consists of three main stages - obtaining a spinning solution, forming fibers from it and finishing the fibers. The resulting spinning solution enters dies - metal caps with small holes (Fig. 6) - and flows out of them in the form of continuous streams that dry or wet method(air or water) solidify and turn into elementary threads.
The shape of the holes of the spinnerets is usually round, and to obtain profiled threads, spinnerets with holes in the form of a triangle, polyhedron, stars, etc. are used.
When producing short fibers, spinnerets with a large number of holes are used. Elementary threads from many spinnerets are combined into one bundle and cut into fibers required length, which corresponds to the length of natural fibers. The formed fibers are subjected to finishing.
Depending on the type of finish, the fibers are white, dyed, shiny or matted.
Man-made fibers
Artificial fibers are obtained from natural high-molecular compounds - cellulose, proteins, metals, their alloys, silicate glasses.
The most common artificial fiber is viscose, produced from cellulose. For the production of viscose fiber, wood pulp, mainly spruce pulp, is usually used. The wood is split and processed chemical reagents, converted into a spinning solution - viscose.
Viscose fibers They are produced in the form of complex threads and fibers, their application is different.
Viscose fiber is hygienic, has high hygroscopicity (11-12%), products made from viscose absorb moisture well; it is resistant to alkalis; The heat resistance of viscose fiber is high.
But viscose fiber has disadvantages:
- due to low elasticity, it wrinkles greatly;
— high fiber shrinkage (6-8%);
— when wet, it loses strength (up to 50-60%). It is not recommended to rub or twist the products.
Other artificial fibers used include acetate and triacetate fibers.
Metal threads are monofilaments of round or flat cross-section made of aluminum foil, copper and its alloys, silver, gold and other metals. Alunit (Lurex) is a metal thread made of aluminum foil, coated on both sides with a protective antioxidant film.
Synthetic fibers
Synthetic fibers are obtained from natural, low-molecular substances (monomers), which are converted into high-molecular substances (polymers) through chemical synthesis.
Polyamide (nylon) fibers obtained from caprolactam polymer, a low-molecular crystalline substance produced from coal or oil. In other countries, nylon fibers are called differently: in the USA, England - nylon, in Germany - dederon.
Polyester fibers(lavsan) is produced under various names: in England and Canada - terylene, in the USA - dacron, in Japan - polyester. The presence of valuable consumer properties of polyester fibers has led to their widespread use in textile, knitting, and artificial fur production.
Polyacrylonitrile fibers(acrylic, nitron): in the USA - orlon, in England - kurtel, in Japan - cashmilon. Nitron fiber in its properties and appearance resembles wool. Fibers in their pure form and mixed with wool are used to produce dress and suit fabrics, artificial fur, various knitwear, and curtains and tulle products.
Polyvinyl chloride (PVC), chlorine fiber is produced from a solution of polyvinyl chloride resin in dimethylformamide (PVC) and from chlorinated polyvinyl chloride. These fibers differ significantly from other synthetic fibers: as a result of their low thermal conductivity, they have a high thermal insulation ability, do not burn, do not rot, and are very resistant to chemical influences.
Polyurethane fibers. By processing polyurethane resin, spandex or lycra fiber is obtained, produced in the form of monofilament. It is characterized by high elasticity, its elongation is up to 800%. It is used instead of rubber core in the production of women's toiletries and high-stretch knitwear.
Alunite- metal threads made of aluminum foil, coated with a polymer film that protects the metal from oxidation. To strengthen it, alunit is twisted with nylon threads.
Hardware cotton yarn- fluffy, loose, thick yarn obtained from short fibers, characterized by low strength.
Hardware wool yarn- produced using a hardware system from short-fiber wool and waste (spinning waste) with a thickness of 42-500 tex, loose, fluffy, uneven in thickness and strength.
Reinforced thread- a textile thread that has a complex structure consisting of a braided core, i.e. the axial thread is wrapped or tightly braided with fibers or other threads.
Asbestos fiber- mineral fiber found in rocks. The longest fibers (10 mm or more) are processed into yarn used for the production of technical fabrics, tapes, cords, used mainly for thermal insulation.
Acetate fiber- artificial fiber, obtained from solutions of partially saponified secondary cellulose acetate in acetate using a dry method (pressing through a spinneret and drying).
Viscose fiber- an artificial fiber produced from wood cellulose, converted by chemical transformations into a viscous liquid (viscose), which is pressed through spinnerets and reduced to cellulose hydrate.
Restored (regenerated) wool—an additional source of raw materials for light industry. It is obtained from scraps of yarn during spinning and weaving, from scraps of woolen fabrics and knitwear in sewing production, and from waste raw materials (used fabrics and knitwear). Used in small quantities (20-35%) in a mixture with regular wool and with the addition of 10-30% synthetic fiber to reduce production costs.
High bulk yarn- yarn, the additional volume of which is obtained by chemical and/or heat treatment.
Combed cotton yarn- thin, smooth, even-in-thickness yarn obtained from long-staple cotton is characterized by the greatest strength.
Combed (worsted) wool yarn- thin, smooth, produced from long-fiber wool using a combed spinning system, thickness 15.5-42 tex.
Coarse wool- heterogeneous wool, consisting mainly of guard hairs with a thickness of 41 microns or more. Obtained by shearing sheep of coarse-wool breeds (Caucasian, Tushino, etc.).
Jute, kenaf- fibers obtained from the stems of plants of the same names, reaching a height of 3 m or more. Dry stems contain up to 21% fiber, used for technical, packaging, furniture fabrics and carpets. The largest sown areas are in India and Bangladesh.
Crimped fiber- natural or chemical fiber with crimp.
Artificial fiber (thread)- a chemical fiber (thread) made as a result of a production process from natural polymers through chemical processing.
Carded cotton yarn- a thick, uneven yarn obtained from medium-length cotton. Used for the production of cotton fabrics.
Combination thread- a textile thread consisting of complex threads or monofilaments, or complex threads that differ in chemical composition or structure, different in fibrous composition and structure.
Complex thread- a textile thread consisting of two or more longitudinally connected and twisted elementary fibers.
Crepe thread- characterized by high (crepe) twist. To obtain natural silk crepe, 2-5 threads of raw silk are twisted to 2200-3200 kr/m, and then they are steamed to fix the twist. Crepe from complex chemical threads is obtained by twisting one thread up to 1500-200 cr/m. Due to the high twist, fabrics made from crepe threads are characterized by significant elasticity, rigidity, and roughness.
twisted thread- a textile thread twisted from one or more textile threads.
Twisted yarn- a textile thread twisted from two or more yarns.
Linen- bast fiber obtained from the stems of a plant of the same name. Fiber flax with a long (up to 1 m) and thin (1-2 mm in diameter) stem is cultivated for fiber.
Bast fiber- long prosenchymal cells in the stems of various plants, devoid of part of the contents of the plant stem. Fibers from bast crops (flax, nettle, hemp, etc.) are used to produce yarn.
Wet-spun linen yarn- produced with a thickness of 24-200 tex from long fiber and tow, while the roving (a semi-finished flax product) - thin and uniform in thickness - is wetted before spinning.
Dry-spun linen yarn- produced from flax fiber and tow, uneven in thickness, 33-666 tex.
Lurex- a thread in the form of a shiny narrow metal strip covered with foil or a metallized film.
Copper-ammonia fiber— produced from a solution of cellulose in a copper-ammonia complex, its properties are close to viscose. Production is limited, as it is associated with significant copper consumption (50 g per 1 kg of fiber).
Multi-twist thread- a twisted thread of two or more textile threads, one of which is single-twist, twisted together in one or more twisting operations.
Modified thread (fiber)- textile thread (fiber) with specified specific properties, obtained by additional chemical or physical modification.
Mooskrep- double twist thread. Mooskrep from natural silk is produced by twisting a crepe thread with 2-3 threads of raw silk. Mooscrep from artificial threads is obtained by caning and subsequent twisting of crepe thread and flat twist thread. The second twist is made in the direction of the crepe thread at approximately 200 cr/m. The crepe thread is a core thread, and the raw silk thread or a flat twist thread is a surge thread that wraps around the core thread.
Muslin- thin thread of medium twist. Natural silk muslin is produced by twisting one thread of raw silk up to 1500-1800 cr/m, followed by steaming to fix the twist. Muslin from a complex chemical thread (viscose, acetate, nylon) is produced by twisting the thread up to 600-800 cr/m.
Maron (nylon), melan (lavsan)- tensile threads, obtained like high-tensile threads, by chemical treatment, but with additional heat treatment with some stretching. As a result of this, the spiral-shaped tortuosity characteristic of elastic turns into a sinusoidal one and is fixed in this state. The threads are soft, fluffy, elongation 30-50%.
Natural fiber- textile fiber natural origin.
Natural silk- a product of the secretion of the silk glands of silkworm caterpillars - the protein substance fibroin - in the form of a thin continuous thread curled into a cocoon. At the moment the cocoon is formed, the caterpillars secrete two thin silks, which harden when exposed to air. At the same time, the protein substance sericin is released, which glues the mulberries together.
Heterogeneous thread- textile thread consisting of fibers of different nature.
Single thread- an untwisted, untwisted thread or an untwisted twisted thread that received a twist in one twisting operation.
Single twist thread- a twisted thread made of two or more single strands twisted together in a single twisting operation.
Uniform thread- a textile thread consisting of textile fibers of the same nature.
Uniform yarn- yarn consisting of fibers of one type.
Hemp— is produced from an annual tall hemp plant. Hemp is divided into filament hemp (thin), used for making yarn, industrial hemp (thick, coarse), from which technical fabrics are produced, and rope hemp, used for ropes.
Trace yarn- yarn with alternating thickening and thinning.
Film textile thread- a flat filament thread obtained by splitting a textile film or extruding in the form of a strip.
Polyacrylonitrile fiber (nitron)- a synthetic fiber formed from solutions of polyacrylonitrile or copolymers containing more than 85% (by weight) acrylonitrile using a wet or dry method. Produced under the following trade names: orlon, acrylon (USA), cashmilon (Japan), dralon (Germany), etc.
Polyamide fiber- synthetic fiber formed from melts of polyamides. It is made from polycaprolactam under the following trade names: nylon (Russia), nylon (Japan), perlon, dederon (Germany), amelan (Japan), etc.
Polyvinyl alcohol fiber- synthetic fiber, formed from solutions of polyvinyl alcohol, is produced in many countries under the following names: vinol (Russia), vinylon, kuralon (Japan), vinalon (DPRK), etc.
Polyvinyl chloride fiber- synthetic fiber formed from solutions of polyvinyl chloride, perchlorovinyl resin or vinyl chloride copolymers using a dry or wet method; is produced in the form of continuous threads or staple fibers under the following trade names: chlorin, saran, vignon (USA), roville (France), Teviron (Japan), etc.
Polynose fiber- a type of viscose fiber with a high degree of orientation of macromolecules in the structure and homogeneity of the structure in the cross section, as a result of which it has high strength and low elongation.
Polypropylene fiber- a synthetic fiber molded from a melt of polypropylene. Due to its low density, it is used for the manufacture of non-sinking ropes, nets, filter and upholstery materials; staple polypropylene fibers - for the production of blankets, fabrics, and outerwear. Textured (high volume) polypropylene fibers are used primarily in the carpet industry. They are produced under various trade names: Herculon (USA), Ulstrene (Great Britain), Found (Japan), Mercalone (Italy), etc.
Polyester fiber (lavsan)- synthetic fiber formed from a melt of polyethylene terephthalate (synthesis of petroleum distillation products). Technical thread made from polyester fibers is used in the manufacture of conveyor belts, drive belts, ropes, sails, etc. Monofilament is used to make nets for paper-making machines, strings for rackets, etc. High-volume thread is obtained using the “false twist” method.
Semi-coarse wool- consists of transitional hair fibers and relatively thin awn fibers with a thickness of 35-40 microns. They get it from fine-fleece-coarse-wool sheep (Zadonsky, steppe, Volga, etc.).
Semi-fine wool- uniform wool, consisting of coarse fibers, 25-35 microns thick, classified as fluff or transitional hair. Obtained by shearing semi-fine fleece sheep (precut, Kazakh, Kuibyshev, etc.).
Yarn- a textile thread consisting of fibers of limited length (natural or staple chemical), connected into a long thread by spinning (orientation and twisting of the fibers).
Yarn with neps- yarn with spun inclusions of fibers of a different color or type.
Rami- fiber produced from perennial grasses and shrubs of the nettle family, containing up to 21% of durable silky fiber in dry stems.
Fleece- a continuous layer obtained by shearing sheep, consisting of tufts of wool firmly held next to each other - staples.
Siblon- modified durable viscose fiber with uniform properties of both external and internal layers, achieved by cellulose regeneration at low temperatures precipitation bath and fiber flow out at high temperature (95 ° C).
Synthetic fiber (thread)- chemical fiber (thread), made from synthetic fiber-forming polymers (polyamide, polyester, etc.).
Blended yarn- yarn consisting of two or more types of fibers.
Spandex— polyurethane monofilament with high elongation — up to 700-800%.
Glass threads- threads obtained by pressing molten glass mass through thin holes. The flowing streams, cooling, turn into flexible threads. The main application is thermal and electrical insulation, filters.
Harsh yarn- gray-yellow yarn without any finishing.
Textile tape (roving)- a set of longitudinally oriented staple fibers of a given linear density without twist, intended for subsequent machining(pulling, twisting).
Textile monofilament thread (monofilament thread)- a filament thread used for the direct production of textiles.
Textile thread- a textile product of unlimited length and relatively small cross-section, consisting of textile fibers and/or filaments, with or without twist.
Textile fiber- a thin, flexible, extended body of limited length, suitable for making yarn and threads.
Textured thread- a crimped textile thread, the structure of which is additional treatments has increased specific volume and extensibility.
Heat-fixed thread (fiber)- textile thread (fiber) subjected to heat or thermal moisture treatment in order to bring its structure to an equilibrium state.
Fine wool- uniform wool, consisting only of fluff fibers, up to 25 microns thick, with fine uniform crimp, soft, elastic, of the same length. It is obtained from fine-wool sheep (Merino, Tsigai) and is used for high-quality fabrics and knitwear.
Triacetate fiber— obtained from solutions of triacetyl cellulose in a mixture of methylene chloride and alcohol by a dry method.
Troweled thread- a textile thread consisting of two or more threads connected without twisting.
Shaped thread- a textile thread that has periodically repeating local changes in structure in the form of knots, loops and coloring.
Fibrillated film thread- a film textile thread with longitudinal cuts, having transverse connections between fibrils. Fibrils in this case are structural elements with a fineness of the same order as that of textile fibers.
Chemical fiber (thread)- textile fiber (thread) obtained as a result of a production process from artificial, synthetic polymers or inorganic substances.
Cotton— fibers from the surface of cotton seeds, an annual shrub that grows in warm climates. There are long-staple cotton (34-50 mm), medium-staple cotton (24-35 mm) and short-staple cotton (up to 27 mm).
Raw cotton- raw material from cotton gins, contains a large amount of cotton seeds, covered with cotton fiber, with admixtures of leaves, parts of bolls, etc.
Silk yarn— made from natural silk waste (scraping of defective cocoons), which is cleaned of impurities, boiled and split into individual fibers (up to 7 tex).
Silk base- double twist thread of 2-4 threads of raw silk. First, threads of raw silk are twisted to the left at 400-600 cr/m, and then 2-3 such threads are caned and twisted to the right at 480-600 cr/m. With secondary reverse twist, the primary twist is slightly reduced, resulting in a soft twisted thread.
Raw silk- a product of unwinding cocoons on special cocoon winding machines, where several (4-9) threads folded together are wound on a reel.
Silk weft- a flat twist thread obtained by twisting 2-5 or more threads of raw silk with a flat twist (125 twists per 1 m). The thread is soft, even, smooth, 9.1-7.1 tex thick.
Wool- hair fibers of various animals: sheep, goats, camels, etc.
Staple fiber- an elementary fiber of limited length, which is obtained by cutting a tow of chemical fibers.
Staple fiber in bulk- a random mass of elementary fibers of limited length.
Elastic- (from the Greek Elastos - flexible, viscous) highly extensible textured threads with high (up to 40%) elongation, spiral crimp and fluffiness. It is produced on “false torsion” machines by imparting a twist of 2500-3000 kr/m to the thread and then removing the resulting internal stresses in a heat chamber (150-180 °C). As a result, the thread takes the shape of a spiral. Elastic is used to make hosiery.
Elementary thread (filament)- a single textile thread of practically unlimited length, considered as infinite.
Elemental fiber- textile fiber, which is a single, indivisible element.
Natural fibers depending on chemical composition are divided into two subclasses: organic (plant and animal origin) and mineral fibers of plant origin: cotton, flax, hemp, jute, kenaf, kendyr, ramie, rope, sisal, etc.
Fibers of animal origin: wool of sheep, goats, camels and other animals, natural silk of mulberry and oak silkworms.
Mineral fibers include asbestos,
Chemical fibers are divided into two subclasses: artificial and synthetic.
Artificial fibers are divided into organic (viscose fiber, acetate, triacetate, copper-ammonia, mtilon B, siblon, polynose, etc.) and inorganic (glass and metal fibers and threads).
Synthetic fibers, depending on the nature of the starting materials, are divided into polyamide (nylon, anide, enant), polyester (lavsan), polyacrylonitrile (nitron), polyolefin (polypropylene, polyethylene), polyurethane (spandex), polyvinyl alcohol (vinol), polyvinyl chloride (chlorine), fluorine-containing (fluorlon), as well as polyformaldehyde, polybutylene terephthalate, etc.
Man-made fibers
Viscose fiber is the most natural of all chemical fibers, obtained from natural cellulose. Depending on the purpose, viscose fibers are produced in the form of threads, as well as staple (short) fibers with shiny or matte surface. The fiber has good hygroscopicity (35-40%), light resistance and softness. The disadvantages of viscose fibers are: a large loss of strength when wet, easy creasing, insufficient resistance to friction and significant shrinkage when moistened. These disadvantages are eliminated in modified viscose fibers (polinose, siblon, mtilon), which are characterized by significantly higher dry and wet strength, greater wear resistance, less shrinkage and increased crease resistance.
Siblon, compared to conventional viscose fiber, has a lower degree of shrinkage, increased crease resistance, wet strength and alkali resistance. Mtilan has antimicrobial properties and is used in medicine as threads for temporary fastening of surgical sutures. Viscose fibers are used in the production of clothing fabrics, underwear and outerwear, both in pure form and in a mixture with other fibers and threads.
Acetate and triacetate fibers are obtained from cotton pulp. Fabrics made from acetate fibers are very similar in appearance to natural silk, have high elasticity, softness, good drape, low creasing, and the ability to transmit ultraviolet rays. Hygroscopicity is less than that of viscose, so they become electrified. Fabrics made from triacetate fiber have low creasing and shrinkage, but lose strength when wet. Due to their high elasticity, the fabrics retain their shape and finishes (corrugated and pleated) well. High heat resistance allows you to iron fabrics made of acetate and triacetate fibers at 150-160°C.
Fibers are long flexible and strong substances of limited length and small transverse dimensions, suitable for the manufacture of yarn and textiles. We talk about what natural and synthetic fiber is in the article.
Fiber classification
Fiber classification:
- natural – fibers of plant origin (cotton, flax - polysaccharides (carbohydrates) having the composition (C 6 H 10 O 5)x) and animal origin (wool, silk - protein substances consisting of long polypeptide chains).
- chemical , which are divided into artificial fibers and synthetic fibers. Artificial fibers are obtained from chemical processing products of natural polymers (cellulose), for example, viscose, copper-ammonia, acetate fiber. Synthetic fibers are obtained by chemical treatment synthetic polymers. For example, nylon and nylon (polyamide fibers), lavsan (polyester fibers).
Synthetic fiber
Synthetic fibers include polyamide , polyester, polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride, polypropylene, and many others. The former include substances such as nylon, anide, and enant. The main characteristics of these fibers are tensile strength and abrasion resistance. However, there are also disadvantages: low hygroscopicity, low heat resistance and high electrification. This fiber is used in the production of knitwear, threads, lace, ropes and fishing nets.
Rice. 1. Polyamide fibers.
Polyamide fiber does not tolerate high temperatures. If it is heated to 160 degrees, the strength decreases sharply down to 50%.
TO polyester fibers include lavsan, dacron, terylene. Fiber has both advantages and disadvantages. Disadvantages include increased rigidity and strong electrification. Lavsan is often used to make fabric for household purposes.
Rice. 2. Polyester fibers.
TO polyacrylonitrile fibers include, for example, nitron, orlon. Nitron by external signs resembles wool. Nitron is very durable and elastic, and these properties are retained regardless of whether it is wet or dry. However, in terms of abrasion resistance, nitron is inferior to polyamide and polyester fibers.
TO polyvinyl chloride fibers include chlorine. Compared to other synthetic fibers, it is less durable, less resilient and less abrasion resistant.
Rice. 3. Polyvinyl chloride fibers.
Chlorine has the ability to accumulate electrostatic charges, which is why it is used for the production of medicinal linen
Polyvinyl alcohol fibers include, for example, vinol. A distinctive feature of this material is its high hygroscopicity; these fibers are easily dyed with dyes and are used for the production of knitwear, fabric and carpets.
What have we learned?
All existing fibers can be divided into 2 classes: chemical and natural. synthetic fibers are classified as chemical fibers. They are divided into polyester, polyamide, polyvinyl chloride and many others. The article also presents examples of synthetic fibers.
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Synthetic Fibers are fibers that produce the synthesis of simple molecules. Synthetic fibers include: lavsan, nitron, nylon, chlorine, vinol, polyethylene, polypropylene and other fibers. Depending on the raw material, the following polymers are obtained: polyamide, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polyurethane. The peculiarity of the creation of chemical fiber is that the formation process is also its spinning.
Polyamide fibers. The most widely used polyamide nylon fibers. The starting raw material for the production of nylon fiber is benzene And phenol(products of coal processing). Processed in chemical plants into caprolactane. Capron resin is processed from capronolactan. This is a melt that is pressed through a slot from the die and comes out in the form of thin streams that solidify when blown with air. One machine can have 60 - 100 dies. Depending on the type of chemical fiber, the spinneret has a different number of holes of different sizes. The fibers are stretched, twisted, and treated with hot water to fix the structure. Methods have also been developed for producing hollow nylon fiber, which is profiled and highly shrinkable. It is used for the manufacture of hosiery fabric, knitwear, sewing threads and technical purpose. Manufacturing processes anida And enanta similar to the production of nylon fiber.
Properties polyamide fibers: lightness, elasticity, high tensile strength, high chemical resistance, frost resistance, resistance to microorganisms and mold. The fibers dissolve in concentrated acids and phenol.
Burning fibers with a bluish flame forming a melted brown ball at the end.
Refers to polyamide silk- which is used for the manufacture of light dress and blouse fabrics and megalop- chemically modified fiber, hygroscopic, durable, abrasion-resistant, gives the fabric an increased shimmering shine. Polyamide profiled thread - trilobal used for silk-type fabrics that are similar in appearance to natural silk.
Polyester fibers. Lavsan produced from petroleum products. Does not change its properties when wet.
Properties lavsan fibers: light, elastic, moth-resistant, resistant to decay, destroyed by acids and alkalis, hygroscopicity is very low 0.4%. During wet heat treatment, the temperature is maintained at 140ºС. When brought into the flame, lavsan melts, then slowly burns with a yellow, smoky flame.
Polyurethane fibers. According to their own physical and mechanical properties refers to elanomers, i.e. has high elastic recovery rates. Elongation at break 600% - 800%. When the load is removed, elasticity is immediately restored by 90%, and after a minute - 95%. These fibers are low hygroscopic - 1 - 1.5%, heat-resistant, abrasion-resistant, and dye well. They are used for the manufacture of knitwear, tapes in sports corsetry, and medical elastic products.
Polyacrylonitrine fibers(PAN). Nitron It is produced from products of processing of coal, oil and gas. Softer and silkier to the touch than lavsan and nylon. The strength is more than half that of nylon and lavsan fibers. Elongation at break 16 - 22%, hygroscopicity 1.5%.
Nitron has a number of valuable properties: resistant to mineral acids, alkalis, organic solvents during dry cleaning, resistant to bacteria, mold, moths. In terms of heat-protective properties, nitron is superior to wool. At a temperature of 200 - 250 ° C, nitron softens. Burns with a bright, smoky flame with flashes.
Polyvinyl chloride fibers (PVC). Chlorine produced from ethylene or acetylene. It is resistant to water, acids, alkalis, oxidizing agents, does not rot, and has no shine.
According to heat-shielding properties not inferior to wool. Strength when wet does not change, and has low resistance to light weather. Wet heat treatment - at 70%. Disadvantage: low heat resistance. Chlorine does not burn, does not support combustion, and when added to the flame, a dusty smell is felt and it sinteres. Chlorine is electrified, therefore it is used for medical linen, as well as for producing embossed silk fabrics, artificial fur and workwear fabrics (fishermen, foresters, firefighters, etc.).
Resistance to aggressive environments, high mechanical strength, elasticity and other valuable qualities have made synthetic fibers indispensable for modern textile production.
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) using the 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, besides 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 chemicalization program 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 focused all their efforts on creating new polymers with high performance characteristics, and methods of 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 inorganic acids and various organic solvents. It is an ideal 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 explained by 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, 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 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 item machines, gears, bearing shells, etc. Russian industry produces artificial fiber that is even stronger than nylon, for example, ultra-strong acetate silk, which is stronger than steel wire. This silk is for one square millimeter withstands 126 kg, 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 include polyamide, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polypropylene, etc.
Polyamide fibers(nylon, anide, enanth). The fibers are cylindrical in 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. Adding 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 slightly lower than that of polyamide fibers (40-50 cN/tex), the elongation at break is within 20-25%, and strength is not lost when wet. Unlike nylon, lavsan is destroyed when exposed to acids and alkalis; its hygroscopicity is lower than nylon (0.4%). When brought into the flame, lavsan melts and 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 low 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 in a mixture with wool, cotton, linen and viscose fiber, which gives the products increased abrasion resistance and elasticity
Rice. 9. Longitudinal view and cross section of synthetic fibers:
a) nylon; b) lavsan; c) nitron; d) chlorine
and crease resistance. It is also successfully used in the production of non-woven fabrics, sewing threads, curtains and tulle products, technical fabrics and cord. Complex lavsan threads are subjected to texturing, as a result of which they better absorb moisture and retain heat.
Polyacrylonitrile fibers (nitron, orlon). In appearance, nitron resembles wool. Its surface is smooth (Fig. 9, V) with an irregular cross-sectional shape with jagged edges (dumbbell-shaped and close to it).
Nitron is distinguished by high strength (32-39cN/tex), which does not change when wet, and elasticity. Products made from it retain their shape quite well after washing. 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 with strong electrification. Nitron fiber also has the best light resistance, low thermal conductivity, that is, good heat-shielding properties and therefore is often used in mixtures with wool and in its pure form for suit and coat materials.
Nitron burns in flashes, emitting a haze of black soot. After combustion ends, 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 base, carpets, blankets and fabrics for technical purposes.
Polyvinyl chloride fibers(chlorine) (Fig. 9, G). Compared to 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, nonflammability, and nonflammability.
Chlorine, when brought to a flame, chars, but does not burn, releasing the smell of chlorine.
Chlorine has the ability to accumulate electrostatic charges, which is why it is used to make medicinal underwear. Chlorine is also used in the manufacture of fabrics for workwear, as it is resistant to water and microorganisms.
PVC fiber, like chlorine, belongs to polyvinyl chloride fibers, but unlike chlorine it is the strongest (26-36cN/tex), more elastic and light-resistant. It is used in the production of knitted and curtain-tulle products, blankets, decorative fabrics, batting, carpets, rugs, rugs and other products.
Polyvinyl alcohol fibers and threads. The threads are formed from a solution using the wet method. Moreover, depending on the spinning conditions 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 repeated deformation. Vinol is quite elastic and characterized by high heat resistance. The temperature of softening and the beginning of fiber decomposition 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 sets them apart from all synthetic fibers, is their high hygroscopicity, due to the presence of a large number of hydroxyl groups in the 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 costume and dress products. These fibers are easily dyed with cellulose fiber dyes. They are used in a mixture with cotton and 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 with porous fibrous structures, as well as in the production of guipure (instead of natural silk). Polyvinyl alcohol threads are used in medicine for temporary fastening of surgical sutures.
The presence of hydroxyl groups allows for chemical modification of these fibers, especially by the 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 –SNSN 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 fairly high strength and tensile elongation values. Polyolefin fibers and threads are characterized by high resistance to acids and alkalis, and are not inferior in terms of chemical resistance to chlorine. Their resistance to abrasion is lower than that of polyamide threads, especially polypropylene.
The heat resistance of polyolefin threads is low. At a temperature of 80°C, polyethylene thread loses about 80% of its original strength. The hygroscopicity of the threads is almost zero, so dyeing them is possible only with the introduction of pigment into the polymer before molding. Low hygroscopicity is also associated with significant electrification of these threads. The density of polyethylene and polypropylene threads is very low, so products made from them do not sink in water.
Polyolefin fibers are used mainly for technical purposes, as well as in a mixture with hydrophilic fibers (cotton, wool, viscose, etc.) in the production of materials for outerwear, shoes, and decorative fabrics.
Polyurethane threads. Currently, there is a fairly large range of materials using polyurethane (elastane) threads (spandex, lycra, etc.). The threads are cylindrical in shape with a round cross-section, amorphous. A feature of all polyurethane threads is their high elasticity: their elongation at break is 800%, the proportion of elastic and elastic deformation is 92-98%. Therefore, materials containing polyurethane threads have good elastic properties and wrinkle little. It was this feature that determined the area of their use. Spandex is used mainly in the manufacture of elastic products. These threads are used to produce fabrics and knitted fabrics for household use, for sportswear, as well as hosiery. Polyurethane threads have insufficient strength (6–7 cN/tex) and heat resistance. When exposed to temperatures above 100°C, threads lose their elastic properties. Therefore, they are produced mainly with a braid that protects them. Polyurethane threads also have very low hygroscopicity (0.8–0.9%), which also limits their use in pure form.
To specifically change the properties of chemical fibers, they are chemically modified. different 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-flammable, 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 phenylon, vnivlon (or SHM - ultra-high modulus), oxalone, arimid T, Kevlar, etc. were obtained. By special processing of polyacrylonitrile and viscose fibers, high-strength, chemical-resistant, heat-resistant fibers were obtained carbon They have unique properties. Under conditions of prolonged heating (at temperatures of 400°C or more) they retain their mechanical properties and are non-flammable. Used in various fields of technology (astronautics, aviation and chemical engineering, etc.)
More detailed information about the production and structure of chemical fibers is given in the textbook.
