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.
Example of spandex
Spandex leggings as casual wear
"Spandex" is a generic name and not derived from the chemical name of the fiber, which most manufactured fibers are, but an anagram of the word expands. "Spandex" is the preferred name in North America; elsewhere it is referred to as "elastane".
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).
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.
Solution dry spinning
Step 1: The first step is to produce the prepolymer. This is done by mixing a macroglycol with a diisocyanate monomer. The two compounds are mixed together in a reaction vessel to produce a prepolymer. A typical ratio of glycol to diisocyanate is 1:2. 
Step 2: The prepolymer is further reacted with an equal amount of diamine. This reaction is known as chain extension reaction. The resulting solution is diluted with a solvent to produce the spinning solution. The solvent helps make the solution thinner and more easily handled and then can be pumped into the fiber production cell.
Step 3: The spinning solution is pumped into a cylindrical spinning cell where it is cured and converted 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 a nitrogen and solvent gas. This process causes the liquid polymer to chemically react and form solid strands. 
Step 4: As the fibers exit the cell, an amount of solid strands are bundled together to produce the desired thickness. Each fiber of spandex is made up of many smaller individual fibers that adhere to one another due to the natural stickiness of their surface. 
Step 5: The resulting fibers are then treated with a finishing agent. This can be magnesium stearate or another polymer. This process prevents the fibers sticking together and aids in textile manufacture. The fibers are then transferred through a series of rollers onto a spool.
Step 6: When the spools are filled with fiber, they are put into final packaging and shipped to textile manufacturers.
Spandex fiber characteristics
Spandex is classified as an elastomeric fiber. An elastomer is a natural or synthetic polymer that, at room temperature, can be stretched and expanded to twice its original length. After removal of the tensile load it will immediately return to its original length. Along with spandex, rubber and anidex (no longer produced in the United States) are considered elastomeric fibers. Spun from a block copolymer, these fibers exploit the high crystallinity and hardness of polyurethane segments, yet remain "rubbery" due to alternating segments of polyethylene glycol.
This yields the following combination of materials properties:
* can be stretched over 500% without breaking
* able to be stretched repetitively and still recover original length
* abrasion resistant
* poor strength, but stronger and more durable than rubber
* soft, smooth, and supple
* resistant to body oils, perspiration, lotions, and detergents
* no static or pilling problem
* very comfortable
* easily dyed
Major spandex fiber uses
* Apparel and clothing articles where stretch is desired, generally for comfort and fit, such as:
o athletic, aerobic, and exercise apparel
o swimsuits/bathing suits
o competitive swimwear
o netball bodysuits
o brassiere straps and bra side panels
o ski pants
o disco jeans
o skinny jeans
* Compression garments such as:
o surgical hose
o support hose
o cycling shorts
o wrestling singlet
o one piece rowing suits
o foundation garments
o motion capture suits
* Shaped garments such as bra cups
* Home furnishings, such as microbead pillows
In clothing it usually appears as a small percentage of total material. In North America it is rare in men's cheaper clothing, but prevalent in women's. It is used more often in women's as their clothes are usually more form-fitting. It is usually mixed with a greater percentage of one other textile such as cotton, polyester, or others. This keeps the reflection of light reduced to being hardly noticeable.
Spandex in popular culture
In comic books, superheroes and superheroines commonly wear costumes thought to be made of spandex. However, early superhero comics predate the invention of spandex (Superman-1938, Batman-1939, Captain America-1941). Printing processes for early color comics only rendered images with distinctly separate solid blocks of color well. Overprinting and color mixing yielded inconsistent results and bad looking muddy colors.
Because spandex is skintight, as many superhero costumes appear to be drawn, and because spandex is almost exclusively made in the same bright solid colors as the early Golden Age comics, the after-the-fact assumption of spandex composition was made. The same assumption of costume composition is also made for latex / rubber garments, which are also solid in colour and skin-tight.
While spandex is frequently assumed and sometimes ackowledged to be the material in superhero costumes, it is not always the case. In Marvel Comics, for example, many superhero and supervillain costumes are made of a material called "unstable molecules", which is capable of stretching to far more than twice its length as well as having many other unique (and physically impossible, in the real world) properties. Captain America's costume is not made of an elastic material at all, but is rather chain mail or scale armor.
In Japan, spandex is the common material for costumes used in the popular Super Sentai series (known overseas as Power Rangers). The first use of the material was in 1983's Kagaku Sentai Dynaman.
 '70s/'80s rock/metal
During the 1970s and 1980s, spandex leggings rose in popularity amongst many rock and heavy metal bands, particularly British NWOBHM and American glam metal bands. The main reasons for this massive, almost universal, embracement of spandex amongst rock/metal bands was because spandex retained its stretchy, tight fitting quality, even after extended wear. Denim jeans and leather strides tended to sag and wear, while spandex did not. Also, the stretchiness of the material did not constrict musicians' movement onstage, allowing them to perform high kicks, or to rest their feet on monitors. Some of the rock/metal bands who used spandex leggings included Queen, Ratt, Van Halen, Mötley Crüe, Judas Priest, Scorpions, Iron Maiden, Saxon, Whitesnake, Bon Jovi and Twisted Sister. By the end of the 1980s and the decline of glam metal, and metal in general, with the advent of grunge, spandex fell out of fashion and many older glam bands found themselves being referred to as 'Spandex Jockeys'.
 70s/80s country
While glam metal bands were getting into the spandex craze, so were many glam-oriented Country stars, especially women like Dolly Parton, Margo Smith, and Dottie West. Dottie West is probably the best-known out of any Country singer for wearing spandex outfits on stage.