Elastomeric fibers properties

Uses Softener for soft hand and stretch and recovery props., for knit goods and hosiery containing elastomeric fibers Properties Liq. 

The physical characteristics of current commercial mbber and spandex fibers are summarized ia Table 1. Typical stress—straia curves for elastomeric fibers, hard fibers, and hard fibers with mechanical stretch properties ate compared ia Eigute 1. 

Solvent Resistance. Elastomeric fibers tend to swell in certain organic solvents mbber fibers swell in hydrocarbon solvents such as hexane. Spandex fibers become highly swollen in chlorinated solvents such as tetrachloroethylene [127-18-4] (Perclene). Although the physical properties of spandex fibers return to normal after the solvent evaporates, considerable amounts of its stabilizers may have been extracted. Therefore, the development of stabilizers that are more resistant to solvent extraction has become important as solvent scouring during mill processing replaces aqueous scouring at many mills, especially in Europe (26). 

Block copolymers have become commercially valuable commodities because of their unique stmcture—property relationships. They are best described in terms of their appHcations such as thermoplastic elastomers (TPE), elastomeric fibers, toughened thermoplastic resins, compatibilizers, surfactants, and adhesives (see Elastot rs, synthetic—thermoplastic). 

Property of polymer e, elastomeric /, fiber- or film-forming p, powdery. 

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. 

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. 

Spandex fibers are elastomeric fibers that are >85 % segmented polyurethane formed through reaction of a diisocyanate with polyethers or polyesters and subsequent crossl inking of polyurethane units. The spandex fibers resemble rubber in both stretch and recovery properties, but are far superior to mbber in their resistance to sunlight, heat, abrasion, oxidation, oils, and chemicals. They find the widest use of any of the elastomeric fibers. 

In 1970, anidex fibers were introduced as an elastomeric fiber by Rohm and Haas with the trade name Anim. Anidex fibers are defined as fibers containing polymers that are at least 50%of one or more polymerized acrylate esters. Anidex fibers are formed through emulsion copolymerization of acrylate esters with reactive crosslinkable comonomers such as N-methyl ol-acrylamide. The resulting copolymer emulsion is mixed with a filler and wet spun to form a fiber which is heated to crosslink the polymer chains and provide the necessary elastomeric properties. The morphology and elastomeric action of the fiber resemble spandex and rabber, but anidex generally has a lower elongation at break than these fibers. It has a round... 

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

Mechanical Properties. Properties of typical grades of PBT, either as unfiUed neat resin, glass-fiber fiUed, and FR-grades, are set out in Table 8. This table also includes impact-modified grades which incorporate dispersions of elastomeric particles inside the semicrystalHne polyester matrix. These dispersions act as effective toughening agents which greatly improve impact properties. The mechanisms are not fiiUy understood in all cases. The subject has been discussed in detail (171) and the particular case of impact-modified polyesters such as PBT has also been discussed (172,173). 

Copolymers of S-caprolactone and L-lactide are elastomeric when prepared from 25% S-caprolactone and 75% L-lactide, and rigid when prepared from 10% S-caprolactone and 90% L-lactide (47). Blends of poly-DL-lactide and polycaprolactone polymers are another way to achieve unique elastomeric properties. Copolymers of S-caprolactone and glycoHde have been evaluated in fiber form as potential absorbable sutures. Strong, flexible monofilaments have been produced which maintain 11—37% of initial tensile strength after two weeks in vivo (48). 

The properties of elastomeric materials are also greatly iafluenced by the presence of strong interchain, ie, iatermolecular, forces which can result ia the formation of crystalline domains. Thus the elastomeric properties are those of an amorphous material having weak interchain iateractions and hence no crystallisation. At the other extreme of polymer properties are fiber-forming polymers, such as nylon, which when properly oriented lead to the formation of permanent, crystalline fibers. In between these two extremes is a whole range of polymers, from purely amorphous elastomers to partially crystalline plastics, such as polyethylene, polypropylene, polycarbonates, etc. 

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