Stretch yarns

ASTM D 3107 Standard Test Methods for Stretch Properties of Fabrics Woven from Stretch Yarns... 

Non-mineral oil coning oil for use for use on nylon and polyester yarns. Most effective on nylon stretch yarns that are subsequently knitted into apparel containing rubber yarn. 

Bulk shrinkage. A measure of potential stretch and power of stretch yarns or a measure of bulk of textured-set yarns. 

Reinforcing fibers can be modified by physical and chemical methods. Physical methods, such as stretching [22], calandering [23,24], thermotreatment [25], and the production of hybrid yarns [26,27] do not change the chemical composition of the fibers. Physical treatments change structural and surface properties of the fiber and thereby influence the mechanical bondings in the matrix. 

Amine salts of a-sulfonated fatty acids and esters are also used as antistatic agents. Mixtures of alkyl a-sulfo fatty acid ester diethanolamine salts and hexa-decyl stearate or butyl stearate are coated onto nylon yarn after fiber formation and before stretching [97]. Polypropylene can be made antistatic with an amine salt of a-sulfolauric acid [C10H21CH(SO3Na)COO +NH(CH2CH(OH) CH3)3] [98]. 

The main application of spandex (e.g., Lycra ) is for stretched apparel clothing. It is used to make yarns when combined with other natural and synthetic fibres. 

Fig. 71 Lifetime curves as a function of the creep load for nylon 66 yarns with different draw ratios (d.r.). The yarn with a stretch ratio of 5.6 is from a different polymer batch [54]. The drawn lines represent the regression lines of the observed data...

These fibres contain long chains of poly glycols or polyesters between polyurethane blocks. Urethane gets copolymerised with suitable polyol or polyester and then melt spun as monofilament or polyfilament yarn. The urethane blocks are in a randomly disordered fashion in the yarn. When stretched they uncoil and straighten out. 

Unlike nylon, which is highly crystalline, PET fibers are amorphous after spinning. They are like the molecules shown at the top of Figure 22-6 in Chapter 22. In order to make a usable textile yarn or staple fiber our of PET, it must be drawn under conditions that result in orientation and crystallinity. This is accomplished by drawing at temperatures of about 175°F with stretch 300-400%. As with nylon, the conditions of draw (especially... 

The polymer was extruded at 240 C to produce 28-strand multifilament yarn. The yam was hot-stretched and fiber tensile strengths in the range 3-6 g/den (1-2 dpf) could be obtained. The yam was placed on braider bobbins on a 12-carrier machine with 7-ply core. The braid was made with 51 picks per inch and hot-stretched 25% at215 F. 

Film can be heated and/or stretched and cut eventually giving filament-like materials. Unfibrillated slit-film materials are used in weaving sacks and other packaging. Randomly fibrillated slit-film material is used to make twines and ropes, while controlled fibrillated material is used to make yarns for use in carpet backings and furnishing fabrics. 

When nylon is made in industry, it forms as a solid which is melted and forced through small holes (Figure 15.19). The long filaments cool and solid nylon fibres are produced which are stretched to align the polymer molecules and then dried. The resulting yarn can be woven into fabric to make shirts, ties, sheets and parachutes or turned into ropes or racket strings for tennis and badminton rackets. The annual worldwide production of nylon is expected to reach 6 million tonnes by 2015. 

TABLE 19.8 Stretch series of polyethylene terephthalate) yarns (data from Van der Meer, 1970)... 

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