Spandex (elastan, Lycra®)

Spandex, Lycra, or elastane are synthetic fibers known for their exceptional elasticity. It is stronger and more durable than natural rubber. It is a copolymer of polyester-polyurethane, invented in 1958 by the chemist Joseph Shivers at Benger's lab of DuPont in Waynesboro, Virginia. When this company was introduced in 1962, it revolutionized many areas of the clothing industry.

The name "spandex" is an anagram of the word "expand". It is the preferred name in North America; in continental Europe, it refers to variants of "elastane," i.e., Élasthanne (France), Elastan (Germany), elastano (Spain), elastam (Italy), and elastan (Netherlands), Brazil, Argentina, Australia, New Zealand, and Israel primarily as Lycra. Brands for spandex include Lycra (produced by Koch subsidiary Invista (formerly part of DuPont), Elaspan (also Invista), Acepora (Taekwang), Creora (Hyosung), INVIYA (Indorama Corporation), ROICA and Dorlastan (Asahi Kasei) Linel (Fillattice) and ESPA (Toyobo).

Spandex fibers are produced by four different methods: melt extrusion, reaction spinning, dry spinning, and wet spinning. All these methods involve an initial step of reacting monomers to form a prepolymer. Once the prepolymer is created, it is further reacted in various ways to produce fibers.

The dry spinning method is used to produce more than 94.5% of world's spandex fibers, and the process involves five steps:

1. The first step is producing the prepolymer. This is done by mixing macroglycol with a diisocyanate monomer. These two compounds are combined in a reaction vessel to form the prepolymer. The typical ratio of glycol to diisocyanate is 1:2.
2. The prepolymer is then reacted with an equal amount of diamine. This reaction is known as the chain extension reaction. The resulting solution is diluted with a solvent (DMAc) to produce a spinning solution. The solvent helps make the solution thinner and easier to handle, and it can then be pumped into a fiber production cell.
3. The spinning solution is pumped into a cylindrical spinning cell, where it is hardened and transformed into fibers. In this cell, the polymer solution is forced through a metal plate called a spinneret. This causes the solution to be aligned in strands of liquid polymer. As the strands pass through the cell, they are heated in the presence of nitrogen and solvent gas. This process causes the liquid polymer to react chemically and form solid strands.
4. As the fibers exit the cell, a number of solid strands are bundled together to produce the desired thickness. Each spandex fiber is composed of many smaller individual fibers that adhere to each other due to the natural stickiness of their surface.
5. The resulting fibers are then treated with a finishing agent, which can be magnesium stearate or another polymer. This treatment prevents the fibers from sticking together and aids in textile production. The fibers are then wound onto a spool via a series of rollers.

Thanks to its elasticity and strength (expanding up to five times its original length), spandex is incorporated into a wide range of garments, especially in leather clothing. The advantage of spandex is its remarkable strength and elasticity and the ability to recover its original shape after stretching and dries faster than regular fabrics.