Twisting fiber direction

UL Underwriter s Laboratories Z-twist twisting fiber direction... 

The optical character of chalcedony is distinct from that expected for the normally uniaxial mineral, quartz, and signals the fibrous nature of a particular sample. The direction of fiber elongation is often parallel to the [1120] crystallographic direction of the quartz structure (Fig. 2.19A), but other fiber directions have also been determined within a single sample (Frondel, 1985). The presence of helically twisted fibers are suspected from the variations in extinction and birefringence noted along the fiber length (Fig. 2.19C). More detailed information on the optical or other physical and chemical properties of quartz and its many varieties can be found in volume 3 of Palache et al. (1962) and in Frondel (1985). 

In hair, horn, muscle, fingernail, and porcupine quill there are very long protein molecules with the alpha-helix structure extending in the fiber direction (along the length of a hair, sideways in a fingernail). They are not exactly parallel to one another, but are twisted around one another to form ropes of three or seven alpha helixes. 

Folded yarn Also known as ply twisting, formed from two or more yams twisted together to increase strength and/or improve appearance. Spun staple fiber yams are ply twisted in direction opposite to spinning twist to give resultant composite yarn with virtually zero twist. 

Filament. Eully drawn flat yams and partially oriented (POY) continuous filament yams are available in yam sizes ranging from about 3.3—33.0 tex (30—300 den) with individual filament linear densities of about 0.055 to 0.55 tex per filament (0.5—5 dpf). The fully drawn hard yams are used directly in fabric manufacturing operations, whereas POY yams are primarily used as feedstock for draw texturing. In the draw texturing process, fibers are drawn and bulked by heat-setting twisted yam or by entangling filaments with an air jet. Both textured and hard yams are used in apparel, sleepwear, outerwear, sportswear, draperies and curtains, and automotive upholstery. 

PVA fiber ropes are widely used in fishing and on ships, because of excellent weather resistance, coiling property, ease of handling, twist stabihty, etc. For this purpose spun yams obtained directly from tow by the Pedok spinning system are used. 

It is tapered for a short length at the tip, and along its entire length the dried fiber is twisted frequently the direction of twist reverses occasionally... 

Nylons belong to the class of polymers known as engineering polymers that is, they are strong, tough, and heat resistant. We can readily extrude and mold nylons to form a wide variety of useful objects, such as tubing, furniture casters, and automotive air intake ducts. Nylons are commonly spun into filaments or fibers. These can be used directly, or braided, or twisted to form threads, yarns, cords, and ropes, which may be further woven to make fabrics. In their fibrous forms, nylons are used in carpets, backpacks, and hosiery. 

Electron microscopic examination of the gel-like precipitates obtained on recrystallization of these soaps from several common solvents showed that neither the concentration of the solution nor the polarity of the solvent played a role in determining the direction of the twist for the fibers of a particular sample. These results, together with later studies involving divalent metal soaps (98,99),... 

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