Staple yams

Spandex Fibers. Spandex fibers are suppHed for processing into fabrics in four basic forms as outlined in Table 3. Bare yams are suppHed by the manufacturer on tubes or beams and can be processed on conventional textile equipment with the aid of special feed and tension devices. In covered yams, the spandex fibers are covered with one or two layers of an inelastic filament or staple yam the hard yam provides strength and rigidity at full extension, which faciUtates knitting and weaving. 

Fig. 1. Schematic drawings of five types of geotextile fibers (a) monofilament, (b) multifilament, (c) staple fibers, (d) staple yam, and (e) sHt film.

Most of the textured apparel and industrial yams are woven or knitted directly into fabric. The carpet BCF yams can be tufted directly off package into loop pile or velvet constmctions. For the textured saxony constmctions, the BCF and the spun staple yams must be ply-twisted and heat-set. The heat-setting temperature for nylon-6 and nylon-6,6 is 180—220°C in hot—dry atmosphere, and 120—140°C in saturated steam. The yams are twist-set in pressurized autoclaves or continuously on the Superba and Suesson machines (121). Before setting the twist, the yam is heated and relaxed for predevelopment of the bulk. 

Because fiber frictional properties are so important in the conversion of staple yams to spun yams, ASTM D2612 has been designed to measure the cohesive force encountered in the drafting or fiber alignment of sHver and top under static conditions. This frictional force is affected by surface lubrication, linear density, surface configuration, fiber length, and fiber crimp. 

Other Fiber Deformations. Deformations such as bending, torsion, shear, and compression are of practical importance in textile apphcations. Bending and twisting of yams, both influential in the development of bulk and stretch in filament yams, are also important in the production of staple yams. Bending characteristics are important in cmsh resistance in carpets. Bending and shear are factors that influence the hand and drape of apparel fabrics, whereas compression influences the recovery of fabrics after such processes as winding. 

Relative scales of the spinning processes for staple and filament products are depicted in Table 12.1. The industrial filament process is intermediate to the staple and textile filament processes, in terms of both spinning throughput and fiber orientation uniformity (here measured by spun birefringence level). Industrial yarns must be uniform enough to be drawn to much higher tenacity levels than staple yams, but are not dyed and therefore not subject to the more demanding uniformity requirements of textile yams. 

Modified Cross Sections. Nylon filaments are spun in a variety of cross-section shapes that include the conventional round to irregular solid and hollow shapes (Fig. 13). The cross-section shape is an important variant in designing the functionality and luster of fibers. The round cross section is used for strength in industrial applications and for subdued luster in apparel and upholstery. The multilobal cross sections are used to enhance bulk and for bright luster in both BCF and spun staple yams for carpets and upholstery. The grooves in the multilobal shapes also enhance moisture transport by wicking water through capillary action. Flat-sided ribbon-like cross sections provide cover in apparel applications. 

Septa may be made of metal, natural, or synthetic yams. Plain, twill, and dutch weaves are available in the metal cloths. In the natural and synthetic fiber cloths, plain, twill, chain, and satin weaves in monofilament, multifilament, and staple yams have been used. 

Cybulska M, Goswani B C and MacAlister D III, Failure mechanism in staple yams . Textile Research Journal, 2001,71, 1087-1094. 

Spiui staple yams are reported to shrink less than comparable fabric woven firom filament yams [Bosley, 1977]. This follows the slipping action of short fibres, one over the other, without major change in the overall yam dimension. 

The mechanical properties of split film yams are comparable to that of filament yam or staple yam. Melt spun filaments exhibit a circular and highly uniform cross-section. Film-based fibers have rectangular, lemon-type or a banana-type cross-section and larger diameter variation. These differences result in changes of softness, handling, resilience, bulk and fiber to fiber friction. The main applications of split fibers are summarized in Table 2. 

Cotton/viscose rayon Staple yam Leno weave... 

Shedding (1) The operation of forming a shed in weaving. (2) A loss of nominal length staple at any process in a staple yam plant. 

Twist n (1) Atextile term, the number oftums (360°) per unit length that a multifilament yam, staple yam, or other structure is turned or twisted around its longitudinal axis into a stable stmcture. (2) The unintended, progressive spiraling seen in some protmded products. 

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