Elastomeric yams

Block copolymers -A-A-A-A-A-A-B-B-B-B- Styrene-butadiene diblock copolymers Styrene-butad iene-styrene triblock copolymers Polyurethane multiblock copolymers (elastomeric yams)... 

The yarn elasticity plays a minor role, unless the elasticity of the yam is very low or very high (high-elastic false twist yarns, elastomeric yams). 

Looking back on the history of sportswear evolution, it is easy to see that not only professional athletes but also average sports enthusiasts have searched for wearable clothes that enable them to elevate their body strength and realize their sports potential. The invention of elastic fiber has delivered multiple advances in the sportswear industry. Nowadays, sportswear characteristics with elastic fiber, including compression, freedom of movement, and comfort, are essential for athletes in most sports. Recently, some new elastic fibers with improving properties and functions have been developed, applied, or have large potential applications in the sportswear industry. In this chapter, the recent developments of elastomeric fibers, elastomeric yams, and fabrics used in sportswear are introduced and discussed. 

Common varieties of elastomeric yams in sportswear include covered and core elastomeric yam for high stretch requirements and textured yam for low to medium elasticity applications. The processing technology for making elastomeric yams is mainly based on conventional methods such as core spinning, cover twisting, and air texturing. 

Using spandex as the center core, and different types of outer yams, different types of elastomeric yams can be created offering soft feeling and multiple functionalities. The spandex is given complete protection by the outside fibers, which lengthens fabric life. 

There are different methods employed for the production of elastomeric yams. Some of the commercial methods and further advancements in these technologies are briefly introduced below. 

Core yam and cover yam with elastomeric fiber as the core shows lower elongation than that of the fiber itself. Usually, the draw ratio of the elastomeric fiber is from 2 to less than 4 when spinning as a core yam. Even with the elongation decrease, other mechanical properties have been improved such as tenacity, antifriction, hand feeling, and other functions such as moisture management. The elastomeric yams greatly increase the process ability and wearability of bare elastomeric fiber itself. These yams also are another important basis for functional sportswear design besides the elastomeric fibers. 

Special requirements for warp knitting include the following (1) a device is required for proper density and even tension of elastomeric yams in producing elastomeric fabrics with repeatable results in stretch, recovery, modulus, shrinkage, and elastic fiber content (2) yam let-off must be electronic or electromechanical for best fabric control and reproducibility (3) special selvage holders (pullers), fabric hot-wire slitters. 

Testing for elastomeric fabrics is not similar to that used for rigid fabrics because the slight tension variation of elastomeric yams affects the final fabric properties. Normally, an ahysteresis curve is produced when a force is applied to an elastomeric fabric... 

Surgical hosiery Polyamide, polyester, cotton, elastomeric yams Knitted... 

All the structures except crepe bandage have elastomeric material in different ratios. Further, the placement of the elastomeric yam in the fabric also varies in ach type of structure. The effect of creep and the fabric to fabric friction is clearly observed in pressure profile of the bandages. 

In this study two material groups were chosen and numbered from 1 to 4. For number 1 and 2 bamboo, polypropylene and elastomeric yams, for number 3 and 4 soybean, polyester and elastomeric yams were used. The linear density of all yams were 100 tex. Midtiaxial warp knitted structures were produced fiom these yams, directions of the yams are given in Table 1. Finally multiaxial warp knitted bandages were stitched with polyester thread for the structural integrity. 

The name of the elastomeric yam used in this work is Gippe, the core of this yam is elastomeric yam the outer surface of the yam is twisted by cotton fibre. 

Fibre types apart from elastomeric yam do not affect the elastic properties of the bandages. 

The tubes as woven were set by putting them through a two-phase heat-treatment process. In the first step, the grafts were heated to 60°C for 15 min in an agitating water bath. This caused the structures to reach their jam point by allowing the elastomeric yams to fully relax and achieve... 

This summary relates to woven structures but the principles also apply to knitted, especially of warp constructions. The primary materials considered are polyester and elastomeric yams. 

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