What do you mean by false twist stretch yarn? What are its categories?

False twist elastic yarn is the use of polyester, nylon and other synthetic fibers have the characteristics of thermoplastic, in the fiber twist, curl deformation heated to fix the state of its twist, curl down, to obtain loose, good elasticity and no twist of the elastic wire, because the wire slightly torque and no twist, better elasticity, and therefore called it false twist elastic wire.

　　There are five main types of false twist elastic yarn

　　(1)

　　General false twist yarn

　　That is, the fiber is twisted and shaped by a twist, the yarn maintains the twisted state with the elasticity, but no twist. The traditional finishing method that adopts the above three-step method, while the current one-step method in the false twist elastic yarn machine to complete. Its fiber has better twist and elasticity, so it can develop crepe fabrics and stretch fabrics with better crepe effect.

　　(2)

　　Solid twist false twist yarn

　　In order to make the product get comfortable effect due to the loose of false twist elastic yarn and at the same time have a more desirable gathering to make the fabric get a good weaving effect, people then put a sure twist on the false twist elastic yarn machine, thus forming a solid twist false twist elastic yarn. At present, solid twist false twist elastic yarn can be completed on the false twist a real twist one-step method to add elastic machine.

　　(3)

　　Bamboo yarn

　　False twist elastomeric yarn and other monofilament blends and twisting, due to the gap overfeed, so that the surface of the blended fiber with a regular bamboo section, this bamboo section is completely covered by the skin, and non-bamboo section for the skin and core wire twisted side by side, this is the market development of bamboo yarn (Figure 9). There are more than 10 varieties developed, such as white polyester FDY (full stretch yarn) for the skin yarn, white polyester FDY for the core yarn, mainly reflecting the bamboo section convex effect of the knotted section Liz, common specifications are 240dtex/60f.

　　Cationic polyester FDY is the skin yarn and white polyester FDY is the core yarn, mainly reflecting the cationic color absorption effect of bamboo knots, the common specifications are 222dtex/54f, 226dtex/60f. White polyester FDY is the skin yarn and white nylon FDY is the core yarn, mainly reflecting the white effect of bamboo knots, the common specifications are 222dtex/56f (200 denier/56f), 222dtex/56f, 222dtex/56f, 222dtex/56f. 56f), 222dtex/60f ( 200 denier/60f). The length of bamboo section of bamboo yarn ranges from 1 to 15cm, and the number of bamboo sections per meter can be adjusted within 3 to 10. The tightness of bamboo sections can be held tightly without slipping, and can also be held loosely and produce slippage.

　　(4)

　　Uneven false twist yarn

　　MOY (medium speed spinning) polyester, or POY (pre-oriented yarn, high-speed spinning) polyester as raw material, in a one-step machine by drafting and false twist made. In the stretching section due to the different stretching and coarse details of the strip, the false twist section of the strip deformation to achieve both coarse and fine appearance and loose properties, the production of coarse details of the elastic yarn is called uneven false twist yarn.

　　Because of the false twist deformation machine innovation improved to agree to two kinds of raw materials through the double silk channel at the same time to feed the finishing, thus increasing the variety of products, such as long thick knots and short details of uneven polyester yarn for the skin, and FDY (full stretch yarn) polyester for the core, the network and the formation of raw materials, there can be 1 ~ 3 per meter, no length of 2 ~ 6cm thick knots.

　　The raw material formed by the network with short thick knots and long details of uneven polyester yarn as the skin and FDY polyester as the core. Cationic polyester with short thick knots and long details as the skin, FDY polyester as the core, the raw material formed by the network, with short thick knots cationic polyester and short thick knots general polyester side by side, the raw material formed by the network, etc.

　　(5)

　　Mixed twist false twist yarn

　　In the twisting and untwisting areas of the silk strip finishing, two types of twist are formed, so that in general, the positive and negative twist cancel out and "no twist", while in the local part of the silk strip there is a positive and negative twist, thus forming a mixed twist false twist deformation of the silk (Figure 10), which has a single-stranded type and mixed fiber type.

　　Single-stranded type is a monofilament mixed twist false twist silk, in the silk strip with a twist section due to the fiber tightly wrapped and presents a finer twist section, while the non-twist section is loose and coarse section, twist section and the length of the coarse section can be adjusted. Mixed fiber type immediately two kinds of monofilament mixed twist false twist yarn for combination, in order to form a two-color effect, different shrinkage effect, and the formation of two kinds of fiber irregular polyester, cationic polyester and color yarn and other three combinations.