Spandex or elastane is a synthetic fiber known for its exceptional elasticity. It is stronger and more durable than rubber, its major non-synthetic competitor. It was invented in 1959 by DuPont chemist Joseph Shivers. When first introduced it revolutionized many areas of the clothing industry.

"Spandex" is a generic name and not derived from the chemical name of the fiber, which most manufactured fibers are, but derived by shifting around the letters in the word expands.Kadolph, Sara J. Textiles. "Spandex" is the preferred name in North America; elsewhere it is referred to as "elastane".Fact: date=August 2008

The most famous brand name associated with spandex is Lycra, a trademark of Invista (formerly part of DuPont). Such is the prominence of the Lycra brand that it has become a genericised trademark in many parts of the world, used to describe any kind of spandex. Invista discourages such use, protecting its trademark vigorously.

Other spandex trademarks include Elaspan (also Invista's), ROICA & Dorlastan (Asahi Kasei) and Linel (Fillattice).

Chemical composition and molecular arrangement

Spandex is a block copolymer of polyurethane and polyethylene glycol.

Spandex consists of rigid and flexible segments in the polymer chain. The flexible segments give the fiber the stretch and the rigid segments hold the chain together. When force is applied, the folded flexible segments straighten out and then return to their original position when the force is removed. The proportions of flexible and rigid segments in the polymer chain determine the amount of stretch.

Physical structure of fiber

Spandex is produced as monofilament or fused multifilament yarns in a variety of deniers. Monofilaments are round in cross section. Multifilaments are partly fused together at intervals and are found in fibers with deniers of 40 and above. The deniers of a spandex fiber range from 20 to 4300 and are determined by what the product use will be. 20 denier spandex, for example, is used in lightweight support hosiery, in which a large amount of stretch is necessary for the product's use and durability. Coarser yarns, with a denier of 1500 to 2240, have less stretch capacity and can be used for support hosiery tops, swimwear, and foundation garments.

Spandex fiber production

Spandex fibers are produced in four different ways including melt extrusion, reaction spinning, solution dry spinning, and solution wet spinning. All of these methods include the initial step of reacting monomers to produce a prepolymer. Once the prepolymer is formed it is reacted further in various ways and drawn out to produce a long fiber. The solution dry spinning method is used to produce over 90% of the world's spandex fibers."How spandex is made" from How Products Are Made