Spandex fibres

Whilst the crystalline fibres and their thermoplastic counterparts are no longer of importance, elastic polyurethane fibres, commonly known as spandex fibres, are of significance. These will be considered further in Section 27.4.1. 

One partieular form of thermoplastic polyurethane elastomers is the elastic fibre known as spandex fibre. Like the usual thermoplastic rubbers these materials consist of hard and soft segments but to qualify for the term spandex by the US Federal Trade Commission the polymer used should contain at least 85% of segmented polyurethane. The first commercial material of this type was introduced by Du Pont in 1958 (Lycra). Several other similar materials have since been introduced including Dorlastan (Bayer), Spanzelle (Courtaulds) and Vyrene (US Rubber). 

Spandex fibres, because of their higher modulus, tensile strength and resistance to oxidation, as well as their ability to be produced at finer deniers, have made severe inroads into the natural rubber latex thread market. They have also enabled lighter weight garments to be produced. Staple fibre blends with non-elastic fibres have also been introduced. 

Spandex fibres have dogbone to rounder cross-section and tend to be larger in... 

The most important polyols obtained by cationic catalysis are PTHF homopolymers with a MW of 600-3000 daltons used for PU elastomers and spandex fibres. The THF-... 

As a general rule, for linear polymers all the properties, such as tensile strength, elongation, elasticity, melting points, glass transition temperature (Tg), modulus and increase of the MW, increase up to a limited value, where all the properties remain practically constant. This behaviour is valuable for linear polymers, in our particular case in linear polyurethanes (PU elastomers, spandex fibres, etc). 

Thus, from high MW diols (MW = 1000-4000 daltons) polyethers (polyalkyleneoxides, polytetrahydrofuran (PTHF)), polyesters, polycarbonates (PC), polybutadienes, etc., by the reaction with diisocyanates [toluene diisocyanate (TDI), or pure diphenyl methane diisocyanate (MDI)], high MW linear polyurethanes are obtained (no crosslinking), with high elasticity (polyurethane elastomers, spandex fibres, some adhesives and sealants, etc). 

The resulting solutions are frequently used for processing spandex fibres, coatings, adhesives, synthetic leathers etc. 

EMVISTA, the owner of the LYCRA brand, has introduced the first commercial offering of a bio-derived spandex— the stretchy fabric commonly found in swimwear and sportswear. The company says approximately 70% by weight of the new LYCRA bio-derived spandex fibre comes from a renewable source made from dextrose derived from com. The use of a renewable feedstock in the making of this new LYCRA bio-derived fibre results in a lower CO2 emission footprint than spandex produced using traditional raw materials. 

Ibrahim, S.M., 1968. Mechanics of form-persuasive garments based on spandex fibres. Text. 

The designers during the early nineteenth century were limited to the fibres, yams and fabrics of that period. These were all natural fibres, which included cotton, flax and protein fibres such as wool and silk. By the middle of the century, other fibres were making their mark on the scene—synthetic fibres were created, such as polyamide, known by its commercial name of nylon. This was followed by polyester and many other synthetic materials, including acetates and spandex fibres, which we know today as Lycra (Figure 6.1). 

Suprasec MPR Suprasec ML 20 Pure MDI. High performance elastomers. Shoe-soling. Spandex fibres. Flexible coatings. Thermoplastics. 

Although these polyethers produced good foams they were rather expensive and were soon displaced by the cheaper propylene oxide-based polyethers. However, these polymers of tetrahydrofuran (commonly called poly(oxytetra-methylene) glycol) now find use in the preparation of polyurethane elastomers and spandex fibres. (See Chapter 14.)... 

Hydroxy-terminated polyethers have now assumed a dominant role in the commercial production of polyurethanes. The most widely used polyethers are derivatives of propylene oxide and these polymers are described in Section 8.4.3.1. Linear, glycol-initiated propylene oxide polymers and propylene oxide-ethylene oxide block copolymers find some use in the preparation of elastomers. Polyether triols of relatively high molecular weight (about 3000) are extensively used for the production of flexible foams whilst polyols of low molecular weight (about 500) are used for rigid foams and surface coatings. Poly(oxytetramethylene) glycols prepared from tetrahydrofuran (Section 8.4.6) are used for the preparation of elastomers and spandex fibres. 

Polyurethane fibres of a kind different to those described above have become important within the last decade these are elastomeric fibres, which are commonly called spandex fibres. These products are made either by solution spinning or by reaction spinning. In the first process, a hydroxy-terminated polyester (e.g., an adipate) or polyether (e.g., poly(oxytetramethylene) glycol) is treated with an excess of diisocyanate (e.g., tolylene diisocyanate) to give an isocyanate-terminated pre-polymer similar to those used for cast elastomers (Section 14.6.1). The pre-polymer is dissolved in a strongly polar solvent (e.g., dimethylformamide) and treated with an aliphatic diamine or hydrazine to effect chain extension with hydrazine the following reaction occurs ... 

Spandex fibres have replaced natural rubber elastomeric fibres in various... 

Thermally insulative undergarments from blends of metal containing spandex and other fibres have been produced. A blend containing 15% spandex fibres having alumina, silica, titania and Pt at 10 82 3 5 wt. ratio, and 85% cotton showed heat conductivity 4.906 x 10 " W/cm°C and heat retention 28.6%. A ladies stocking of a blend " comprising 6.4% spandex fibres containing alumina, silica, titania and Pt at 10 82 3 5 wt. ratio, 24.1 % acrylic fibres and 13.5% nylon fibres also showed heat conductivity 3.525 X lO W/cm C and heat retention 42.3%. 

Suwanii Kk, Thermally insulative stockings from blends of metal containing spandex fibres and other fibres , JP 06,41,801,15 Feb 1994, Chem. Abstr., 1994,120, 325666m. 

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