Fiber twist

Cotton is seed hairs that protect the seeds in their pods from desiccation in the dry season and from moisture in the rainy season. Under the microscope, cotton appears as a collapsed, tubelike fiber twisted at irregular intervals. In its natural state it repels water because of a waxy substance covering the fiber. Once the wax has been removed, cotton becomes the most absorbent fiber known to man. Cotton is cellulose it withstands moderate alkaline conditions but is easily affected by acids. Because of twist in the fiber, cotton lacks glossiness. Mercerization, a chemical process, gives luster to cotton fiber by straightening the twist. 

Yams from the three Etowah examples exhibit greater variation from each other than do those of the Tunacunnhee. Although the basis for most of the yams is a two-ply, S-twisted unit, the ways in which the units vary affect the resulting fabric structure (see Table IV). The simplest expression is found in the crumpled fabric bundle (No. 840, Burial 57) where two-ply, S-twisted yams are used in both systems (Figure 11). Both sets of yam exhibit a medium degree of twist (25-45°) and are derived from separate fibers twisted together. The System A yam measures 0.175 mm, whereas the System B yam is 0.135 mm. The yams are uniformly brown. 

Object Yarn System Fiber Twist Yam Unit1 Direction of Twist0 Degree of Twist... 

Multifilament cloths are constmcted of a bundle of fibers twisted together. Only synthetic materials are available in this form, since long continuously extruded fibers must be used. Spun fabrics are composed of short sections of bound fibers of varying length. Retention of small particles is increased as the number of fibers or filaments in a bundle increases. The greater the amount of twist in the yam, the more tightly packed the fabric, which contributes to retention. This twist will also increase the weight of the fabric and frequently extends filter cloth lifetime. 

Figure 8-28. A hair fiber illustrating a fiber twist at higher magnification than Figure 8-27. Light micrograph kindly provided by John T. Wilson.

Twist increases the effect of cohesion in the yarn and the yarn strength will increase up to a point where any additional twist starts to break the fibers. Twisted yams can be doubled by plying two yarns, normally of opposite twist, to obtain a further increase in strength. If the yarns are the same twist, the product can be twist Kvely and when relaxed, any excessive twist will cause the doubled yam to snarl and curl up on itself. 

The SEM was used to show yams, composed of fibers twisted together, woven into a fabric (Fig. 5.9). Important features of the fabric, Tiand and coverage, relate to the yarn geometry which can make a thick and comfortable fabric or a thin, uniform and open stmcture. Tilted side views... 

Major industrial applications of fibers are in the production of tire cords and belts. Tire cords are composed of yams of polymer fiber, twisted together into cords, which are coated with... 

Figure 4. Marine Silk 33707 deep cracks along areas of fiber twisting.

Fiber is the basic element of fabrics and other textile structure [1]. A fiber is typically defined as a material having a length at least 100 times its diameter. These can be natural, such as cellulose or wool, or synthetic, such as nylon. A textile is any product made from fibers [1]. This includes nonwoven fabrics such as felt, in which wool fibers are physically interlocked by a suitable combination of mechanical work, chemical action, moisture, and heat [1] and woven fabrics in which yams are interlaced perpendicular to each other. Yarns are made of fibers twisted together in a continuous strand. 

Fig. 4.3 (A) Schematic of conductive metal fiber twisted with the natural or synthetic fibers. From Swiss Shield. (B) Twisted metal wire The metal wire is twisted around the polymer yam.

As a result of the reduction of fiber twists and destmction of the crystal region, the weak-link effect of cellulose is also reduced, increasing the breaking stress of the fabric. In sirmmary, the LA treatment can increase fabric strength and dimensional stabihty. However, the fabric appearance will not be improved simply as a result of LA treatment. 

Yoshida, K., Kurose, T., Nakamura, R., Noda, J., and Goda, K., Effect of yarn structure on mechanical properties of natural fiber twisted yarns and green composites reinforced with the twisted yarn, J. Soc. Mater. Sci. Jpn., 61 (2), 111-118 (2012) (in Japanese). 

Fig. 4.3 (A) Schematic of conductive metal fiber twisted with the natural or synthetic fibers. From Swiss Shield. (B) Twisted metal wire The metal wire is twisted around the polymer yam. (C) Metal fibers The conductive yam consists of metal multtfilament. (B) and (C) from Lxicher, I., 2006. Technologies for System-on-TextUe Integration. Available at http //e-collection.library. ethz.ch/view/eth 28457 (accessed 20.01.14). (D) Conductive winding yams wound around an elastic core yarn in S- and Z-direction. From Schwarz, A., Kazani, I., et al., 2011. Electro-conductive and elastic hybrid yams— the effects of stretching, cyclic straining and washing on their electro-conductive properties. Mater. Des. 32 (8), 4247-4256.

The SEM was used to show yarns, composed of fibers twisted together, woven into a fabric (Fig. 5.9), and can be compared to an optical microscopy (OM) view of a similar fabric (see Fig. 5.1B). Important features of the fabric, hand and coverage, relate to the yarn geometry, which can make a thick and comfortable fabric or a thin, uniform, and open structure. Tilted side views can be used to count the number and the length of protruding surface hairs, which are known to affect the feel or hand of the fabric and its mechanical properties [46, 47]. The complex subject of fabric wear... 

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