Textile fibers. Textile fibers and threads

Classification of textile threads

Monofilament is a single-strand thread that does not divide in the longitudinal direction without breaking, suitable for direct use in textiles.

A filament thread consists of two or more elementary threads joined together by twisting or gluing. A filament is a single thread that is an integral part of a complex thread or tow. The filament cannot be used as a monofilament.

Yarn is a thread consisting of fibers connected by twisting or gluing.

Twisted thread is a thread twisted from two or more filament threads, yarns, or both.

Shaped thread - a thread that has periodically repeating local changes in structure (nodules, loops, thickenings, etc.) and color.

Reinforced thread - special kind heterogeneous threads obtained by wrapping a core component with forced threads or fibers.

Textured thread is a thread whose structure has been modified by additional processing to increase specific volume or elongation.

Based on the type of raw material used, yarn is divided into homogeneous and mixed, and threads into homogeneous and heterogeneous. Homogeneous threads and yarn consist of fibers of the same type of raw material, mixed yarn - from a mixture of fibers of different types of raw materials, heterogeneous thread - from threads of different types of raw materials.

Threads and yarn are made from natural and chemical (artificial and synthetic) fibers. Natural fiber has natural origin(vegetable, animal, mineral). Chemical fibers are made from natural or synthetic high molecular weight substances. These include artificial fibers obtained from natural high-molecular substances. Synthetic fibers are made from synthetic high molecular weight substances.

Cotton, linen, wool yarn and natural silk are produced from natural fibers.

Cotton yarn is produced in gray, dyed and melange (obtained from dyed cotton).

Linen yarn is produced using a wet and dry spinning system. Yarn made from flax fiber, depending on the finishing method, can be raw, boiled, bleached and dyed.

Wool yarn is produced using combed and machine spinning systems. Depending on the linear density of the wool fiber, combed yarn is divided into finely combed, coarsely combed and semi-combed, and hardware yarn is divided into finely combed and coarsely combed. A significant portion of wool yarn is double-twisted.

Natural silk is obtained by unwinding the cocoons of mulberry and oak silkworms in the form of complexly glued threads (raw silk). In addition, they produce twisted natural silk with a different number of twists: with regular twist - up to 600 kr/m and crepe twist - up to 3200 kr/m. Silk yarn is made from waste obtained from processing natural silk.

Man-made fibers include viscose, acetate, triacetate and copper-ammonia. Artificial fibers are also used in pure form and mixed with natural ones.

Synthetic fibers, depending on the chemical structure, are divided into several types: polyamide (nylon, anide, enanth), polyester (lavsan), polyacrylonitrile (nitrone), polyolefin (polypropylene, polyethylene), etc., from which threads and staple fiber are made to produce homogeneous and mixed yarn. Threads made from synthetic fibers have increased strength, resistance to abrasion and repeated loads.

Polyamide and polyester fibers, which have low thermoplasticity, are more often than other fibers used to make textured threads, which are characterized by increased bulk, fluffiness and softness. The structure of textured threads is changed mechanically (twisting, pressing, crimping, knitting) and fixed by heat treatment. Textured threads include: elastic (spirally crimped), corrugated (flat crimped), ajilon (spatially crimped), taslan (looped), as well as melan, maron, etc.

The article uses materials from the textbook “Materials Science of Garment Production” (authors B. A. Buzov, T. A. Modestova, N. D. Alymennova)

It is a thin, flexible and durable body of considerable length; used for the manufacture of textile products - fabrics, knitwear, non-woven materials, etc. directly or after pre-treatment.

There are textile threads original, primary and secondary. The original textile threads include threads that do not divide in the longitudinal direction without breaking: elementary (chemical, natural, including raw silk, and mineral), monofilament (chemical), as well as narrow strips of paper, film, etc.

Unlike filaments, monofilament directly used for the production of products - thin stockings, nets, etc. To primary textile threads include yarn produced from textile fibers, filament threads consisting of a bundle of (two or more) elementary threads connected by twisting or other means, as well as cut textile threads obtained by twisting strips.

The yarn can be plain, shaped, textured (high volume) and reinforced.

Textile threads are called shaped, the structure of which periodically changes through the formation of thickenings, loops, etc. Textured threads are textile threads whose structure is modified to increase volume or stretchability. Secondary textile threads include twisted threads, usually obtained by twisting several primary ones. Recycled textile threads are also produced textured and shaped.

In addition, textile threads can be homogeneous in composition - from one type of material (for example, cotton yarn, wool, viscose, etc.), mixed - from a mixture of fibers (linen-lavsan yarn, etc.) and heterogeneous (twisted acetate-viscose filament threads). Textile threads obtained by twisting yarn and filament threads are called combined.

A wide variety of textile threads is achieved by using additional operations and processes during their production (for example, singeing, dyeing, bleaching). Textile threads are also used for the manufacture of artificial furs and duplicated materials; some types of textile threads are used to produce sewing threads, filters for chemical industry, ropes, etc.

Lit. see under art. Textile fibers. G. N. Kukin
Source: Great Soviet Encyclopedia

Fiber classification

Taking into account classification characteristics, fibers are divided into:

natural

chemical.

TO natural fibers include fibers of natural (plant, animal, mineral) origin: cotton, flax, wool and silk. Chemical fibers are fibers manufactured in factories. In this case, chemical fibers are divided into artificial and synthetic.

Artificial fibers are obtained from natural high-molecular compounds that are formed during the development and growth of fibers (cellulose, fibroin, keratin). Fabrics made from artificial fibers include: acetate, viscose, staple, modal. These fabrics are highly breathable, remain dry for a very long time and are pleasant to the touch. Today, all these fabrics are actively used by manufacturers of hosiery products, and, thanks to the latest technologies, can replace natural ones.

Synthetic fibers are obtained by synthesis from natural low-molecular compounds (phenol, ethylene, acetylene, methane, etc.) as a result of polymerization or polycondensation reactions, mainly from products of oil, coal and natural gases.

Types of threads

Fibers are the basis for the manufacture of filaments, which, depending on the method of joining, are then produced into many other filaments. The following types of threads are distinguished:

single– a thread that does not divide longitudinally without breaking and can be directly used in the production of textiles (often called monofilament). Monofilaments are obtained from synthetic fibers, they usually have a round cross-section, and, depending on the thickness, monofilaments can be used in the production of light, thin fabrics for blouses and heavy ones for interlining materials.

comprehensive- a thread consisting of two or more elementary threads connected to each other by twisting or gluing

twisted- a thread obtained by twisting two or more filament threads, yarn, or both together

yarn- a thread consisting of fibers interconnected by twisting during the spinning process.

In modern textile production, a wide range of threads of various structures is used. In addition to classical types of yarn, complex, combined threads and monofilaments, film threads and thread-like knitted, woven, braided textile products (chains, cords, ribbons, braid, etc.) are used.

Textile thread is a textile product of unlimited length and relatively small cross-section, consisting of textile fibers and (or) filaments (GOST 13784-94). The structural elements of a textile thread can be connected by gluing, twisting, or, in the case of filament threads, without twisting.

Classification and types of textile threads(diagram 1.2). All textile threads can be divided into the following groups: monofilament threads, complex threads, yarn, film threads and combined threads. According to their fibrous composition, they can be homogeneous, consisting of one type of fiber or threads, or heterogeneous

(in the case of yarn - mixed), consisting of fibers or threads of different chemical compositions.

Depending on the number of folds and twisting operations, single, caned, single-twist and multi-twist threads are distinguished. Single thread - it is an untwisted or twisted thread obtained in a single spinning operation. Troweled thread consists of two or more single strands joined without twisting. Single twist thread consists of two or more single strands twisted in one operation. Multi-twist thread obtained by one or more twisting operations of two or more textile threads, at least one of which is single-twist.

Monofilament. Textile monofilament, or monofilament thread, is a filament of sufficient thickness and strength to be suitable for the manufacture of textile material. Natural monofilament is horsehair, which is used in the manufacture of cushioning materials. Chemical monofilaments are made from synthetic polymers (most often polyamide). They have a round or flat profiled cross section. In the latter case, due to the presence of flat edges, the threads acquire increased shine.

Monofilaments include metallic threads. In ancient times they were made of gold and silver. Currently, they are produced by drawing (pulling) from copper or its alloys or by cutting aluminum foil into strips. A thin layer of gold or silver and a protective film are applied to the surface of such threads. The most famous metal threads: portage- round thread; flattened - flat thread in the form of a ribbon; gimmick- a spiral thread obtained from fiber or rolled wool. Lurex, or alunit, - ribbons 1 - 2 mm wide made of aluminum foil coated with color (often gold or silver) with polyester film. The disadvantages of these threads are their low strength, fragility and rigidity.

Monofilaments also include film threads obtained by cutting a polymer film or extruding in the form of a strip. Films can be transparent or opaque, colored or coated with metal (gold, silver, bronze, mother-of-pearl, etc.). Sometimes film threads are slightly softened and deformed by heat treatment, creating the effects of surface unevenness.

Metal and film monofilaments are most often used as underlays to create decorative effects in appearance textile materials.

Complex threads. Complex threads (multifilament) are a textile thread consisting of two or more elementary threads, the length of which is equal to or slightly greater than the length of the complex thread.

In structure simple complex threads the elementary threads are located more or less parallel to each other, so the surface of the threads is even and smooth (Fig. 1.11, A).

Twisted chemical filament yarns- these are primary filament threads obtained from manufacturing plants, consisting of parallel or weakly twisted elementary threads. They have a smooth, even surface.

Twisted complex threads can be single-twisted or multi-twisted (Fig. 1.11, b). Depending on the degree of twist, threads are distinguished: flat twist (up to 230 kr./m), medium twist - muslin (230-900 kr./m) and high twist - crepe (1500 - 2500 kr./m). The elementary threads in the structure of twisted threads are located along helical lines, and therefore turns are noticeable on the surface of the threads, the density of which and the angle of inclination relative to the longitudinal axis increase as the degree of twist increases. Crepes are distinguished by significant rigidity, elasticity and unbalanced twist, which causes them to wriggle and twist in a free state, forming twists.

Complex threads from natural silk can be obtained by gluing and twisting. When several silk cocoons are unwound, they stick together to form a thread ( Raw silk). Fluctuations in the shape and size of silks, their unequal tension when unwinding from cocoons, uneven distribution of sericin over the surface and, consequently, gluing density significantly affect the uniformity of the structure of raw silk. Twisted threads are obtained by single or double twisting from mulberries from which seri-zinc has been largely removed. Depending on the degree of twist, silk threads can be

Low twist (silk weft), medium twist (muslin) and high twist (crepe). With double torsion you get silk base.

Textured thread is a chemical complex thread with a structure modified by additional processing (Fig. 1.11, c, d). Elementary threads have a stable crimp, due to which textured threads are characterized by increased volume, looseness and porosity. Materials made from textured threads have good drapability, dimensional stability and hygienic properties. A distinctive feature of textured threads is increased elongation (up to 400%) with a high proportion of reversible deformation. Thanks to this, products made from them retain their shape well. According to the classification proposed by F.K. Sadykova, textured threads are divided into three types according to their elongation at break: normal elongation (up to 30%), increased or medium elongation (30-100%) and high elongation (more than 100%).

Majority existing methods texturing is based on mechanical action on complex threads (torsion, corrugation, pressing, etc.) with simultaneous heating to stabilize changes in the shape of elementary threads. Therefore, thermoplastic threads (polyamide, polyester, triacetate) are most often subjected to texturing. The most common texturing method is the false twist method. The primary filament thread is twisted up to 2000-4000 cr/m, followed by thermal fixation of the twist. When the thread is untwisted to its original state, the elementary threads, under the influence of internal stresses, trying to maintain a fixed shape, bend and take on a complex spatial shape. The complex thread acquires greater fluffiness, volume and high elongation. Using this method, highly elastic polyamide threads of the type elastic(see Fig. 1.11, V). To obtain threads with increased elongation, the twist value is reduced to 2000-2500 cr/m and the threads are subjected to secondary heat treatment after untwisting. This reduces the internal tension of the structure and fixes the curved shape of the filaments, resulting in reduced elongation. High tensile threads include: polyamide - maron, polyester - Malan(see Fig. 1.11, d), Belan.

Flat crimp of elementary threads can be obtained by corrugating a complex thread of small twist (up to 100 cr./m) in a heat chamber. This textured thread has high volume, but less elongation than threads obtained using the false twist method. In our country, threads are obtained using this method corrugated

The knitting method of producing crimped threads involves [unraveling a pre-heat-fixed knitted fabric. One of the advantages of this method is the ability to regulate the stretchability, crimp, and fluffiness of the threads by changing the parameters of the fabric structure.

The method of drawing along an edge is that when a steel plate or knife is pulled along a heated edge, the thread is subjected to severe deformation. The side adjacent to the edge is compressed, and the opposite side is stretched. During continuous movement, the thread constantly turns with its outer side towards the blade, which leads to alternating areas of tensile and compressive deformation along its entire length. Next, the thread is cooled and additionally heat-fixed. As a result, individual elementary threads take on the appearance of a coiled spring with different directions of turns. In Russia, using this method, they produce a thread called rilon. Abroad, this method was called eji-lon (after the name of the thread).

The aerodynamic method of changing the structure of complex threads is based on the effect of air flow on them in a special chamber. A stream of air separates and bends the elementary threads into loops and entangles them with each other. Distinguish pneumatic - connected threads, having a compact structure, and pneumatic - textured threads, having increased volume and (or) extensibility (GOST 27244-93). The aerodynamic method makes it possible to obtain textured threads not only from thermoplastic, but also from other types of chemical threads (viscose, acetate). Abroad, such threads have a common name Taslan, in Russia - aeron(Fig. 1.11, d).

The group of textured threads includes complex threads obtained from bicomponent elementary threads with stable crimp.

Yarn. This textile thread, made from staple fibers, usually by twisting (GOST 13784 - 94).

Yarn is produced from natural fibers (cotton, flax, wool, silk) and chemical staple fibers (viscose, polyester, polyamide, polyacrylonitrile, etc.). Depending on the fiber composition, the yarn can be homogeneous, Consisting of fibers of the same type, and mixed- from a mixture of two or more types of fibers. Homogeneous or mixed yarn made from multi-colored fibers is called melange. When creating mixed yarn, the composition of the mixture and its proportions are selected in such a way as to make maximum use of the positive properties of the constituent fibers and neutralize the negative properties. When mixing natural and chemical fibers, take into account the consistency of their sizes (thickness and length) and shape (crimp, profile, roughness). For example, when mixing wool and chemical fibers, the latter must have a stable crimp. Therefore, bicom - porous fibers are often used in these mixtures.

Based on their structure, yarn is distinguished between single, caned and twisted. Single yarn is formed on spinning machines when twisting elementary fibers. Spun yarn consists of two or more folded threads that are not twisted together. This gives the yarns greater balance than single or twisted yarns, which is why they are often used in knitting. Twisted yarn obtained by twisting two or more threads. Single twist yarn is spun from two or three single strands of equal length. Multi-twist yarn is obtained as a result of two or more successive twisting processes; More often than not, two single-twist yarns are connected. When producing twisted yarn, it is desirable that the direction of twisting be opposite to the twist of the constituent threads. In this case, during the final twist, the component threads are untwisted until they are secured by turns of repeated twist. As a result, the component threads bend around each other, arranged in spiral turns, and form a dense, rounded thread, evenly filled with fibers.

The formation of yarn from the fibrous mass occurs during the spinning process - the most ancient method of producing textile threads. The classical process of spindle spinning consists of a number of operations: loosening and scuffing, carding, leveling and drawing, pre-spinning and spinning. The main purpose of these operations is to divide the fibrous mass into individual fibers, clean them of impurities and dust, mix them evenly, straighten them to one degree or another and orient them in the longitudinal direction, form a thread of the required thickness and give it the necessary twist. At the first stage, the fibrous mass, which is often supplied in the form of compressed bales, is separated into small shreds under the impact of disintegrants and scrapers and cleaned of impurities and dust. There are two types of carding operations: carding and combing. In carding, fiber scraps are combed using needle-shaped (carded) surfaces into individual fibers, which removes remaining impurities, tangled fiber scraps and partially short fibers. The combed fibrous canvas is formed into a rope called tape. Subsequently, the tapes are repeatedly folded and stretched, as a result of which the tapes are aligned in thickness, fibers are straightened and oriented in the longitudinal direction. The strips are subjected to a combing operation, and in addition to straightening and orienting the fibers, short fibers are combed out. In the process of pre-

GO spinning slivers are stretched and lightly twisted to form straight lines Tsu. The final spinning is carried out on ring spinning machines, on which the roving is drawn-thin to the required thickness and acquires its final twist. Depending on the set of operations and the number of their repetitions, three main spinning methods are distinguished: hardware, carded and combed.

The hardware spinning process is the shortest. After loosening and fraying, the fibrous mass is subjected to two or three carding, after which the fibrous web is divided into strips and rolled (twisted) into roving and then converted into yarn on a spinning machine. Hardware yarn It is produced from short-fiber cotton, wool and a mixture of them with chemical fibers. In addition, fibers from spinning waste and regenerated fibers (from scrap) are added to them. The structure of hardware yarn is loose. It consists of slightly straightened and slightly oriented fibers (Fig. 1.12, A). The yarn has increased porosity and, therefore, good heat-insulating properties, which are important for winter clothing. Cotton hardware yarn is produced with a linear density of 85 - 250 tex and is used for the manufacture of flannel and cotton cloth. Woolen and wool blend hardware yarn has a linear density of 50-300 tex; It is used to make drapes, cloth, coat fabrics, and, less commonly, costume and dress fabrics.

The card spinning system includes all operations except combing. Carded yarn It is produced from medium-fiber cotton and chemical fibers, from a mixture of cotton or viscose with cottonized linen and synthetic fibers. Carded yarn consists of relatively straightened and oriented fibers, which are arranged along helical lines, moving from the center to the periphery and back (Fig. 1.12, b). The structure of the yarn is somewhat unbalanced, since the tension of the fibers located in the outer layers is greater than in the central ones. Carded yarn is not always uniform in thickness, which in turn can cause uneven twist distribution and the appearance of twists and loops. Cotton carded yarn has a somewhat fleecy surface
due to the protruding ends of the fibers. Yarn made from chemical fibers of uniform length and thickness has a smoother surface and is more uniform in thickness and twist. Carded yarn is produced with a linear density of 15 - 85 tex and is used for the manufacture of fabrics, knitted fabrics and some types of non-woven fabrics.

The comb spinning system lasts the longest; it includes all types of operations: loosening, carding, repeated folding and drawing of ribbons, combing, in which short fibers are combed out, pre-spinning and spinning. Combed yarn It is produced from long-fiber cotton, flax, long fibers of fine, semi-coarse and coarse wool, silk fibers. The structure of combed yarn is the most ordered; straightened and longitudinally oriented fibers are evenly distributed along the length and cross-section of the yarn. When spun, the fibers are arranged in spirals and tightly wrap around each other. The surface of combed yarn is smooth and less fleecy than that of carded yarn.

Combed yarn from cotton, chemical and mixed fibers is produced with a linear density of 6-20 tex and is used in the production of blouses, shirts, dresses, raincoats, suit fabrics and knitted fabrics. Woolen and wool blend combed yarn from fine wool has a linear density of 19 - 42 tex and is used for the manufacture of worsted dress, suit and coat fabrics and outer knitwear. From semi-coarse and coarse wool mixed with chemical fibers, combed yarn with a surface density of 28 - 84 tex is obtained. Combed linen yarn is most often produced with a linear density of 30-170 tex and is used in the production of table and bed linen.

In addition to classical types of spinning, spindleless spinning systems (pneumo-mechanical, electrostatic, etc.) have become widespread in yarn production. Most often, rotor spinning is used, which is based on the principle of mechanical and aerodynamic influence on the fibers. Fibers from the sliver are fed by an air stream into the spinning chamber, which rotates at a frequency of 30,000 rpm. By centrifugal force, the fibers are pressed against the walls of the chamber, grouped in a gutter in the form of a fibrous sliver, twisted and exited the chamber in the form of yarn.

Due to the peculiarities of molding rotor yarn has a layered structure with different densities of fibers in the cross section (Fig. 1.12, V). The highest density of the central layer decreases towards the outer layers. This leads to a decrease in yarn strength. Compared to carded yarn, pneumatic yarn has higher twist (by 10 - 15%) and bulk (by 10%) and lower surface hairiness. Materials made from rotor-mechanical yarn are more resistant to abrasion, have greater elasticity and wrinkle resistance compared to materials made from ring-spun yarn. Rotor spinning yarn is produced from |l3 cotton, cotton flax, chemical and mixed fibers.

High bulk yarn obtained from a mixture of fibers of different shrinkage, increased elongation (30% or more), bulkiness, Fluffiness and the softness of which is achieved due to shrinkage of aasti fibers as a result of chemical or heat treatment. High-volume yarn can be obtained by aerodynamic processing, as a result of which the air flow loosens the structure and increases its volume.

■ Film threads. Elementary filaments in the form of film ribbons are obtained either by cutting the film or forwarding NH from the melt, followed by drawing and heat setting. Complex film threads twisted from elementary film threads of small width.

, Fibrillated film thread is a film textile thread with longitudinal stratification into fibrils, Having connections between each other. The structure of such threads is voluminous and fluffy.

Combined threads. The structure of combined threads is formed by combining two or more threads of different types, structure and fibrous composition. There are many options for such combinations. Combined threads can consist of yarns of different fibrous composition and (or) structure; from complex threads of different chemical composition and (or) structure; from yarn and filament thread; from monofilament, textured thread and yarn; from complex and textured thread, etc. (GOST 13784-94). Combined threads can be single-twisted or multi-twisted. They can be divided into simple, reinforced and shaped threads.

Simple combined threads obtained by connecting the constituent threads of approximately the same length. Various combinations of delivery threads make it possible to create a variety of combined threads that differ in structural parameters, physical characteristics, mechanical properties and appearance, which, in turn, expands the range of textile materials produced from these threads.

Reinforced threads have a core tightly entwined, braided or covered evenly along the entire length with fibers or other threads. Used as a core different kinds yarn and filament threads, polyurethane monofilaments or multifilament threads (spandex, lycra), rubber core, etc.

^wssssssssssss^mmmmm^ IN

Rice. 1.13. Reinforced threads: A - with external winding; b - with elastic rod; V - chenille

Reinforced threads have several options for production and structure.

The classic type of reinforced thread is a core thread of any kind, wrapped in one or two layers with a cover thread of a different composition (Fig. 1.13, A). This allows you to combine in one thread the properties inherent in the constituent threads. For example, using a chemical filament thread as a core thread and a covering thread made from natural fibers, a strong elastic thread with good hygienic properties is obtained. If highly elastic threads (lycra, spandex, rubber vein) are used as the core, which are in a stretched state during twisting, then after removing the load, a high-volume, fluffy elastic thread is obtained (Fig. 1.13.6). A type of reinforced thread is mooscrepe, which is a crepe twist thread entwined with a flat twist thread. The shrinkage of the core gives the surface of the thread volume and fluffiness.

Another type of reinforced thread has a core in the form of yarn or filament thread, evenly covered with fibers. Such threads are produced by an aerodynamic method by supplying fibers with an air flow into the thread torsion zone, where they are captured by the core thread and firmly fixed in its structure. A variant of such threads is a core thread covered with pneumatically entangled elementary threads.

Velor threads, or chenille, consist of a core single-twist thread, in which many short fibers are fixed perpendicular to the longitudinal axis, creating a velvety surface of the thread (Fig. 1.13, c).

Flocked threads are obtained by applying chopped pile in an electrostatic field to a core thread, previously coated with glue. By adjusting the tension of the core thread and the voltage on the electrodes, you can achieve a uniform radial arrangement of the fibers on the surface of the thread.

Shaped threads - textile threads that have periodically repeating local changes in structure or color (Fig. D. 14). In fancy threads, the core thread is wrapped around a surge or effect thread (sometimes several) of greater length than the main one. The local effects that occur in fancy threads and determine their name are very numerous and varied. These can be round or oblong nodules (nodular thread); small loops in the form of rings (loop); large fluffy loops (boucle); alternation of noticeable thickened and thin areas (overtraced); periodic change in the density and "inclination of the turns of the surge thread around the core (spiral); 1®spun lumps of colored fibers (neps); alternation of spirals and loose multi-colored knots (ponge), etc. There are ((shaped threads with sections of film woven into the structure "Threads. Flocked shaped threads have a pile on the surface, (Different in length, thickness, color, density of arrangement. Thanks to shaped threads, textile materials with a varied surface texture are obtained. Shaped threads can be produced by the method of pneumatic entangling of complex threads, with periodic formation of loops on the surface threads, j" B Lately Sometimes, when creating textile materials, thread-like textile products in the form of ribbons, braids, cords, etc., obtained by knitting, weaving or braiding, are used as threads. The greatest variety is found among “knitted” threads (Fig. 1.15), the simplest of which are produced in the form of a ribbed chain or a ribbon of wasp-knitted weave. In reinforced knitted threads, the role of the core is played by a chain into which perpendicularly located pieces of fibers can be woven (flat one-sided

Nii and double-sided “brush”, chenille), spun threads, pneumatically connected fibers. Based on knitted threads, a variety of shaped threads are created: looped, knotted, bouclé, with a neps effect, with shaped weaving of film monofilaments, ribbons made of non-woven adhesive or thermally bonded fabrics, etc.

Main characteristics of the structure and properties of textile threads. The main structural characteristics of textile threads include linear density, twist direction, twist, twist factor and twist amount.

The thickness of textile threads can be determined by linear dimensions and cross-sectional area measured under a microscope. However, often the complex shape of the cross-section, the presence of channels, voids and different densities of elementary fibers make it difficult to correctly assess the thickness of the threads. Therefore, linear density, which has the conventional name tex (from the word textile), has been adopted as a standard characteristic of thickness.

Linear density represents the ratio of the mass of the thread T, mg, to its length L, m:

There are nominal, nominal-calculated, and actual linear densities.

Nominal Tn is called the linear density of the thread designed for release. It is used in calculating the structural parameters of textile materials. Nominal-calculated density Tr caned and twisted threads are calculated by summing the linear density of the constituent threads, using the following formulas:

If threads of the same linear density are connected,

Tr = Tnp,

Where n is the number of constituent threads;

If threads of different linear densities are connected,

Tr = G, + T2 + ... + T„,

Where Ть Т2, ..., Т„ - linear densities of constituent threads;

For multi-twist thread

Tr = 7> +T2, or Tr =(G[ + T2) +(G3 + G4).

When twisting threads, the length of the constituent threads is shortened, the amount of which is called twisting U, %. Ras - ■The linear density of twisted threads, taking into account twisting, is determined by the formula

Tr. To = 1007^/(100 - U).

The actual linear density Гф is determined experimentally by weighing pieces of thread and calculating using the formula

Tf= X m/Y, L,

Where ^t is the total mass of thread segments, mg; ^L - total length of segments, m.

F When determining the linear density of textured nylons, their length is measured under tension (5 ± 1) mN/tex (GOST 18447.1-90).

The standards for all types of textile threads regulate the permissible deviation of the actual linear density from the nominal or nominal calculated density, as well as the coefficients of variation of the linear density along the length of the thread.

In the regulatory and technical documentation, an indirect designation of thread fineness has been preserved - metric numberN.M., m/y:

N.M.= L/m.

The metric number is the inverse characteristic of lily density: TNK = 1000.

If the density of the fiber substance y, mg/mm3 is known, it is possible to determine the cross-sectional area of ​​the thread S, mm2, based on Dependency

5=0,00177/, Central Committee nominal thread diameter dyc L, mm,

Cross-sectional area values S and nominal diameter of the yshte Dycn, calculated taking into account the density of the fiber substance y, ((characterize the conditional cross-section of the thread, in which the fibers fit tightly to each other and within the fibers themselves and there are no pores and voids between them. In real textile threads there are voids due to the loose arrangement of fibers in the yarn AND elementary threads in complex threads, depending on the degree of their crimp and orientation, as well as due to the presence of longitudinal channels and micropores in the elementary fibers and threads themselves. Therefore, the actual cross-sectional dimensions of textile threads are characterized by the calculated thread diameter Dp, mm, when determining which the average density is used, i.e. the mass of a unit volume of threads measured along the outer contour, 8, mg/mm3:

Dp = 0.0357V778.

Approximate values ​​of linear density T, density y and average density of 8 main types of threads are given in table. 1.3.

Twisting is the main method of producing yarn from short fibers, complex and combined yarns. The degree of twisting of the threads is assessed by the following characteristics.

The direction of twist characterizes the location of the turns of the peripheral layer of the thread: when right twist(Z) the components of the thread are directed from left to top to right, with left twist(S) - from right to top to left (Fig. 1.16). To obtain balanced and strong threads, the twist directions during the first and subsequent twisting processes must be opposite.

When twisting, the fibers of the peripheral layer of the thread are arranged along helical lines with a given angle of torsion)