False-twist texturing

In false twist texturing (FTT), shown schematically in Figure 7, a device twists yam upstream of its location as the threadline passes across a heater, and the yam untwists downstream from the device and is wound up. If the yam is not heated downstream from the twist device, it has bulk and high elasticity (stretch). If the yam is heated downstream from the twist device, it has bulk, but much less stretch. FTT machines initially used two steps to sequentially draw and texture. Later machines combined those steps to simultaneously draw and texture (92). Initial machines used pin spindles as the false twist device. Texturing speeds were about 150 m/min and slowly increased to about 300 m/min. As POY quaUty and stmctural stabiUty improved, new... 

The air jet textured yam process is based on overfeeding a yam into a turbulent air jet so that the excess length forms into loops that are trapped in the yam stmcture. The air flow is unheated, turbulent, and asymmetrically impinges the yam. The process includes a heat stabilization zone. Key process variables include texturing speed, air pressure, percentage overfeed, filament linear density, air flow, spin finish, and fiber modulus (100). The loops create visual and tactile aesthetics similar to false twist textured and staple spun yams. 

Commercial textured yams cover a range of yam sizes and end uses. The 1.7—3.3-tex (15—30 denier) yams for hosiery are false-twist-textured, as is the 4.4—22.2-tex (40—200 denier) yams for apparel. The 56—333-tex (500—3000 denier) yams for carpets, upholstery, and soft-sided luggage are air- and fluid-jet-textured. 

Crimp rigidity test. A form of crimp rigidity test used in the UK for the testing of false-twist textured nylon yarns. 

False-twist texturing depends on setting fibers in a kind geometry and then changing to another, which generates elongation that can be recovered by bulking. Another method is to set fibers in the required crimped form. This was the basis for stuffer-box and other methods. 

The most important recent development, applied for the manufacture of about 90% of textured filaments, utilizes a process based on torsion mechanical-thermal procedures. The operation consists of three basic steps high-twist twisting, fixation of the twist, and detwisting of the twist. In the process known as false-twist texturing, these three procedures are carried out in one process step. Rather detailed descriptions of this procedure are given... 

Schematic of two of the most popular texturing processes used for manufactured yarns (a) the air-jet texturing process and (b) the false-twist texturing process. (Courtesy, College ofTextiles, N. C. State Univ.)... 

This is the most widely used texturing process and accounts for about 90% of the textured filament yarn market. In this technique (Fig. 1.6b), twist is inserted into a heated multifilament yarn running at high speed. The yarn is cooled in the twisted state, so that the twist geometry is set, and then the yarn is untwisted. The insertion of twist distorts the fibers, strains the bonds within them, and causes them to break when heat is supplied. Cooling the yarn in the distorted state allows new bonds to form and stabilize the distorted configuration. In false-twist texturing, fiat, fully drawn multifilament yarn is twisted and passed over a heater maintained at a temperature well... 

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