Elastane yarns in the textile industry;
It can be used plain or coated with another type of fiber.
Plain (Naked) Elastane Yarns
It can be used directly after being obtained as a result of fiber spinning from polymer melt. They are monofilament or multifilament yarns. The usage area in textile is very limited. They are used in some knit fabrics. Due to its high price, the plain use of elastane fibers is avoided.
Coated Elastane Yarns
In order to respond to the various needs of the textile industry in an economical way, elastane fibers have been used in combination with different yarn and fiber types. By wrapping various fibers on elastane in filament form, covered elastane threads are obtained. Elastane-containing combined yarns produced for these purposes have properties that vary according to the type of components that make up the yarn and the systems used in production. It is possible to examine the elastane-containing combined yarn production methods in four main groups.
>>>>> Covering method
>>>>> Air-covering method
>>>>> twist method
>>>>> Core-spun method
The coating process is a process based on winding the inelastic filament or short staple yarn onto the elastane filament in the center. The elastane filament, which will remain in the center of the yarn, is passed through the hollow spindle and wrapped with the covering yarn, which is extracted from a special bobbin on the hollow spindle.
The winding of the winding thread on the spandex core can be single or double layer.
Elastane-containing combined yarns produced according to the single-ply winding method have a twisting (tangling) tendency caused by the effect of winding applied in one direction. This tendency may adversely affect the textile processes in which such combined yarns will be used. In order to reduce this negative tendency on the combined yarn, it is necessary to apply heat treatment (fixing) to the yarn. Fixing process it is usually in the form of heat treatment of the produced combined yarns in an autoclave in bobbins. However, heat treatment can also be done using hot plates during the winding process, if desired. The temperature and time the fibers are exposed to during heat treatment affect the flexibility of the yarn.For this reason, these two factors should be determined by considering the end-use place of the produced yarn.
In the production of combined yarn with the double winding method, both the feeding of the elastane and the pulling and winding of the combined yarn are similar to the single winding method. Unlike the single-ply winding system, this system uses two hollow spindles that rotate in opposite directions with respect to each other. In this way, elastane is wound diagonally by the covering threads. (in Z and S directions). Two group windings in opposite directions; It is possible to call it as inner and outer winding. The outer winding compensates for the twisting effect on the combined yarn produced by the effect of the first winding. The balancing of this force on the combined yarn is achieved by coordinating the number of turns of the upper spindle forming the outer winding with the number of turns of the lower spindle forming the inner winding. Therefore, there is no need for heat treatment (fixing) in such cross-wound combined yarns. The turn difference between the inner and outer windings varies depending on the tension of the elastane yarn and the desired elongation ability. The yarns obtained by the coating method are used for stretch trousers, sportswear, socks, etc. They are used to add flexibility to various woven and knitted products.
Air-covering Method Air-covering Method
In the air coating principle, after the filament yarn is taken from the bobbin, it passes over the rollers and comes to the drafting area. Here, it is subjected to a drawing process at varying rates according to the filament type. Compressed air is blown to the filament yarn at a wide angle from the opposite side in the combination section following the drafting area. With the effect of compressed air, the filament yarn separates into individual filaments and the filaments enter into a rotational movement and are twisted on each other and on the elastane. In this way, elastane-containing combined yarn emerges with the formation of periodic connection points between elastane and filament yarn. These connection points continue along the yarn in a periodic fashion. It can be used in yarns spun from staple fibers instead of filament in the system. Since the warp threads are exposed to periodic elongation during shedding and tamping during the weaving process, there are unwinding in the connection points of the elastomeric thread and the warp threads cling to each other, making the weaving process difficult and reducing its efficiency. Because of these problems, it is more efficient to use the yarns produced by this method only as weft yarn in weaving.
In the air coating principle, after the filament yarn is taken from the bobbin, it passes over the rollers and comes to the drafting area. Here, it is subjected to a drawing process at varying rates according to the filament type. Compressed air is blown to the filament yarn at a wide angle from the opposite side in the combination section following the drafting area. With the effect of compressed air, the filament yarn separates into individual filaments and the filaments enter into a rotational movement and are twisted on each other and on the elastane. In this way, elastane-containing combined yarn emerges with the formation of periodic connection points between elastane and filament yarn. These connection points continue along the yarn in a periodic fashion. It can be used in yarns spun from staple fibers instead of filament in the system.
Since the warp threads are exposed to periodic elongation during shedding and tamping during the weaving process, there are unwinding in the connection points of the elastomeric thread and the warp threads cling to each other, making the weaving process difficult and reducing its efficiency. Because of these problems, it is more efficient to use the yarns produced by this method only as weft yarn in weaving.
The production of elastane-containing yarn by the twisting method can be examined under four sub-titles. While elastane is used bare in three of them, it is possible to use bare elastane or elastic combined yarn as an elastic component in the two for one process.
These methods are;
>>>>> Twisting on the ring machine (Elasto-twist)
>>>>> Two for one
>>>>> Hollow spindle technique
>>>>> Siro-spun technique
Ring Twisting Machine
The basis of twisting in the ring machine is to cover the elastomer fiber (in three layers) with two-ply staple fiber yarn. Three separate threads rotate between the traveler and the ring at the same time, making the coating. The ram speed is limited in the system. When working at high speeds, there may be gaps in the cop formation and the low amount of yarn wound on the cop is the reasons why the system is not used much.
In the process, pre-wound bobbins are placed in the creel of the machine. The elastane fiber is fed into the system with the help of the upper feeding roller and combined with the other two yarns. Short staple yarns and elastane pass through the lower feed roller together and are twisted by the rotation of the traveler and spindle and wound onto the cop.
The system is a technique that does not require much investment cost compared to other techniques and allows the use of a wide variety of raw materials during production. In this way, it is a system that provides the opportunity to produce yarn in different colors and numbers. There is no obligation to use elastane naked in the system. The coating process takes place in two stages as folding and twisting. During the folding stage, the exposed elastomer fiber is combined with other normal yarns and folded. After the folding process comes the twisting process. The folded yarn bobbin is placed on the hollow spindle. The yarns taken from the bobbin are passed through the spindle. Then, these yarns pass through the balloon breaker via the yarn exit channel under the spindle and reach the winding unit. In each revolution of the spindle, a twist is given to the yarn in the spindle, while at the same time a twist is given in the balloon region. These two twists are given to the yarn in the same direction and simultaneously. Thus, the yarn receives two twists in one turn of the spindle.
Hollow Spindle Technique
In this system, yarn obtained as a result of combining three different materials is in question. Here, there is an elastomeric filament called the core, a parallel staple fiber bundle surrounding this filament, and a winding filament that wraps these two materials and gives them grip.
The sliver consisting of previously parallelized and staple fibers is fed into the drafting unit of the system. After the necessary thinning is achieved, it is fed into the hollow spindle carrying the winding filament by the attraction effect. At the same time, the elastomeric core, which will form the core of the yarn, is fed directly into the hollow spindle. At the spindle entrance, the fed elastomeric core filament is mixed between the staple fiber bundle and passed through the hollow spindle that rotates around its axis and also carries the winding filament. During this transition, the winding filament is wound on these two materials in a helical structure.
This system is especially suitable for working with long staple fibers. This process has been developed in order to provide savings in production by eliminating the folding and twisting stages.
In the system, the production of elastic combined yarn (twisting and adding elastane) takes place in a single step. Two separate rovings are fed on the machine parallel to each other in the system. Elastomer fiber is fed between the rovings coming to the pre-drawing cylinder after being drawn and the elastane and fibers leaving the pre-drawing cylinder are coiled with the help of ring and traveler.
Elastane-containing core yarn consists of two concentric fiber bundles. The first of these is the core of elastane with high elasticity, and the other is the outer layer consisting of a bundle of staple fibers wound on this core. Such combined yarns are known in the industry as “elastic core yarns” or “elastic core-spun yarns”.
Spinning systems in which the core yarn structure is obtained can be listed as follows:
>>>>> ring spinning
>>>>> friction spinning
>>>>> Tandem (air jet + friction) spinning
>>>>> Repco selfil
The most common spinning system in which the core yarn structure is produced is the ring spinning system. Although core yarn structure can be obtained with other spinning methods, these systems are not used much in industry. In core yarn production, filament core, staple fiber core or elastane core can be used in the yarn center. However, since elastane core and discrete outer layer were studied in the thesis study, elastane cored core yarn was emphasized.
Elastane Core Core Yarn Production on OE Rotor Machine
The basic principle in the OE rotor spinning system is to open the fiber group fed to the machine as a single fiber, then collect it regularly and bring it into yarn form. In open-end spinning, the fiber feed is reduced until it becomes a single fiber. The fibers in the fiber sliver are carried by the air stream. The fibers are attached to the free yarn tail, freed from internal stresses. In this way, with the help of a kind of twist obtained by the rotation of the rotor, the yarn is obtained and wound into bobbins. In order to produce elastane core core yarn in OE rotor machines, the rotor, in which the fibers are fed, must be opened and brought into a special form.
Elastane Core Core Yarn Production on Vortex Spinning Machine
In the vortex spinning system, the fibers coming out of the drafting system are sucked into the spiral opening at the entrance of the jet, in which a high-speed air swirl is formed, and take a taut position. In this way, the other open ends of the fibers entering through the spiral opening in the jet are rotated around the hollow spindle by means of the air vortex. These rotated fibers are wrapped around the fibers in a tight structure in the jet, and thus the yarn formed is pulled down through the jet. In order to produce elastane-containing yarn in the Vortex machine, a special mechanism is required to feed the elastane into the jet under a certain tension. The elastane fiber fed into the middle of the jet is completely wrapped with the winding fibers so that it remains in the center. In the system, the elastane fiber in the center does not get twisted, as the winding fibers are provided to wrap on the elastane thanks to the high air flow. Therefore, the vortex yarn does not suffer from the problems caused by the core yarn being damaged under the torsional force. In addition, the decrease in yarn strength caused by this reason is reduced.
Elastane Core Core Yarn Production in Ring Machine
The production of elastane core core yarn in the ring machine is carried out on standard ring spinning machines modified to process bare elastane.
The short staple fibers fed into the machine in the form of roving and the elastane filament combine with each other at the nip point of the front roller pair of the drafting system. In order to produce elastic core yarn in the ring spinning system, elastane feeding unit (feeding rollers) and “V-grooved spandex guide” must be added to the ring spinning machine. The tension (drawing) ratio applied to the elastane filament determines the elastane ratio in the core yarn produced and the elasticity of the core yarn. The draft value applied between the Elastana drive rollers and the front rollers of the drafting system is determined by the ratio of the surface velocities of these two rollers to each other. In practical applications, the shrinkage value of the elastane filament is between 3-4. As the draft value increases, the elastane ratio in the elastic combined yarn produced will decrease.
In order to ensure that the elastane is well encapsulated by the short staple fibers during the process, a greater amount of twist is given to the structure than in normal conventional ring spinning. The amount of twist to be given to the elastic core yarn depends on the type of short staple fibers used, the number of core yarn produced and the end use area. The twist value given to the elastic core yarn produced should be at a rate that ensures that the short staple fibers do not slip on the elastane. Elastic core yarns to be used in weaving are given more twist than those to be used in knitting, just as in the production of classical ring yarn.
Elastic core yarn production systems should have yarn monitoring elements. If the spandex breaks during production, the roving feeding must also stop. Otherwise, areas that do not contain elastane will form on the core yarn produced. This is one of the major problems encountered in the production of elastane yarn. In general, all kinds of natural and chemical fibers with short or long fibers can be used in the production of elastic core yarn. The amount of elastane in the structure of elastic core yarns varies between 3-20%. The use of fibers with very different structures and properties offers wide design possibilities to fabric manufacturers who will use the elastic core yarns produced. Elastic core yarns, which are wound on bobbins produced in modified ring spinning machines, are wound as bobbins in conventional winding machines. However, due to the high elasticity of these yarns, care should be taken to work at low winding tension. Elastic core yarns to be used in knitting machines are generally waxed during the winding process.
Since the elastic core yarns produced have more twist than normal, a fixation process is usually applied to prevent untwisting and tangling. However, the fixation process should be done at low temperatures in order to preserve the physical properties of the elastane in the structure. In order to prevent the elastane from shortening in the produced yarn and forming non-uniform voluminous knots around the staple fiber, heavier travelers should be used in the modified ring spinning system compared to the travelers used in the production of a normal ring yarn of the same number. Being heavy on the clasps will put more traction on the elastic thread in the bracelet than usual. Elastic core yarn manufacturers should determine the most suitable traveler weight to be used during the process by trial way, since the travelers being too heavy will cause elastane breaks.
Usage Areas of Elastane Containing Yarns
Elastane has an important place in the textile industry thanks to the comfort, flexibility, full adaptation to the human body, comfort and functionality it adds to the yarn and therefore to the fabric. Among the fashion trends exhibited especially after the 2000s, there is almost no design without elastane products. Among the classical usage areas of elastane textile products are men's and women's socks, leisure wear, underwear products, sportswear, evening dresses, corsets, swimwear and medical textiles. Elastane textile products are also preferred for clothes used in sports that involve a lot of activity and require a high degree of body movement, except for classical areas. For example, a garment used in skiing should have the ability to stretch between 35-50% at various points. It is possible to provide this flexibility with elastane textile products.
Elastane yarns have very high elasticity and resilience (springing) ability. These yarns add considerable elasticity to the fabric and clothing, even at low usage rates of 3-5% of the elastane in it. Extra features that elastane yarns add to the fabric;
>>>>> Neat and pleasant appearance in clothes,
>>>>> Increase in clothing comfort,
>>>>> The shape dimensions given to the clothes are more permanent,
>>>>> Less wrinkling tendency
>>>>> It's a lot of freedom of movement.
In addition to these features, elastane textile products continue to be used and preferred in almost every field, especially thanks to its perfect compatibility with the human body, extremely well wrapping the body, extreme sensitivity to body movements, being durable and long-lasting, preventing deformation and loosening, and thin and silky attitude. .