Spandex | Properties and Manufacturing Process

Spandex is a synthetic fibre or fabric made from a polymer containing polyurethane, used in the manufacture of elastic clothing. It is lightweight, soft, strong and very stretchable. In fact, spandex fibre was developed as an alternative to rubber but has a better quality than it. The name Lycra has also come to be a synonymous of spandex.

Lycra-Spandex Confusion

Lycra is the trademark name for the spandex, created by DuPont and subsequently sold to multinational corporation, Invista. Spandex is the generic name for the elastic fibre category, as defined by the U.S. Federal Trade Commission. The two terms are often used interchangeably in everyday speech, though there are some minor differences between Lycra and generic spandex.

Spandex Fibre Characteristics

• Can be stretched repeatedly and still recover to very near its original length and shape
• Generally, can be stretched more than 500% without breaking
• Stronger, more durable and higher retractive force than rubber
• Lightweight, soft, smooth, supple
• In garments, provides a combination of comfort and fit, prevents bagging and sagging
• Heat-settable — facilitates transforming puckered fabrics into flat fabrics, or flat fabrics into permanent rounded shapes
• Dyeable
• Resistant to deterioration by body oils, perspiration, lotions or detergents
• Abrasion resistant
• When fabrics containing spandex are sewn, the needle causes little or no damage from “needle cutting” compared to the older types of elastic materials
• Available in fibre diameters ranging from 10 denier to 2500 denier
• Available in clear and opaque lusters

Manufacturing Process of Spandex Fibre

Spandex fibres are produced in four different ways including melt extrusion, reaction spinning, solution dry spinning, and solution wet spinning. Each of these methods involve the initial step of reacting monomers to produce a prepolymer. Then the prepolymer is reacted further, in various ways, and drawn out to produce a long fibre. Since solution dry spinning is used to produce over 90% of the world's spandex fibres, it is described.

1. The first step in the production of spandex is the production of the prepolymer. This is done by mixing a macroglycol with a diisocyanate monomer. The compounds are mixed in a reaction vessel and under the right conditions they react to form a prepolymer. Since the ratio of the component materials produces fibres with varying characteristics, it is strictly controlled. A typical ratio of glycol to diisocyanate may be 1:2.
2. In dry spinning fibre production, the prepolymer is further reacted with an equal amount of diamine. This is known as a 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. It can then be pumped into the fibre production cell.
3. The spinning solution is pumped into a cylindrical spinning cell where it is cured and converted into fibres. In this cell, the polymer solution is forced through a metal plate, called a spinneret, which has small holes throughout. 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. These conditions cause the liquid polymer to chemically react and form solid strands.
4. As the fibres exit the cell, a specific amount of the solid strands are bundled together to produce the desired thickness. This is done with a compressed air device that twists the fibres together. In reality, each fibre of spandex is made up of many smaller individual fibres that adhere to one another due to the natural stickiness of their surface.
5. The fibres are then treated with a finishing agent. This may be magnesium stearate or another polymer such as poly(dimethyl-siloxane). These finishing materials prevent the fibres from sticking together and aid in textile manufacture. After this treatment, the fibres are transferred through a series of rollers onto a spool. The windup speed of the entire process can be anywhere from 300-500 mi (482.7-804.5 km) per minute depending on the thickness of the fibres.
6. When the spools are filled with fibre, they are put into final packaging and shipped to textile manufacturers and other customers. Here, the fibres may be woven with other fibres such as cotton or nylon to produce the fabric that is used in clothing manufacture. This fabric can also be dyed to produce a desired color.

Spandex Fibre Uses

• Garments where comfort and fit are desired: hosiery, swimsuits, aerobic/exercise wear, ski pants, golf jackets, disposable diaper, waist bands, bra straps and bra side panels
• Compression garments: surgical hose, support hose, bicycle pants, foundation garments
• Shaped garments: bra cups

Spandex Fibre Care Tips

• Hand or machine wash in lukewarm water
• Do not use chlorine bleach on any fabric containing spandex. Use oxygen or sodium perborate type bleach
• Rise thoroughly
• Drip dry. If machine dried, use low temperature
• Ironing, if required, should be done rapidly. Do not leave the iron too long in one position. Use low temperatures setting.