What Is Lycra (Spandex)?

How is Lycra (spandex) made?

Spandex is made by building a long-chain polyurethane with alternating soft and hard segments and then extruding it as filaments. According to C&EN, the soft, rubbery segments are made from polyester or polyether polyols and give the stretch, while the hard segments, usually urethanes or urethane-ureas, give strength and limit plastic flow, so the fibre holds its shape. The American Fiber Manufacturers Association (AFMA) describes a multi-step proprietary process that forms this segmented block copolymer, which is extruded either as a single monofilament or as many fine filaments joined into one threadline.

Hidden inside other yarns

For most applications, elastane is blended with other materials through core spinning, according to a 2025 study in RSC Applied Polymers. In core spinning, a roving of polyamide (nylon) or polyester is twisted around an elastane core. The elastane sits at the centre of the yarn, wrapped by the sheath fibre.

From Fiber K to Lycra

DuPont scientist Joseph C. Shivers invented the company’s spandex fibre in 1959 after about a decade of research, according to C&EN. It was first designated Fiber K; DuPont then chose the trade name Lycra. AFMA records 1959 as the first US commercial production of spandex, by DuPont. Its first job was replacing rubber in women’s foundation garments, followed in the 1960s by soft-support pantyhose and other intimate apparel.

What is the difference between Lycra, spandex and elastane?

They are the same type of fibre: Lycra is a trade name, spandex is the generic name in US rules, and elastane is the generic name in the EU and in the international standard ISO 2076.

What are the properties of spandex?

Spandex stretches a long way and comes back: AFMA says it can generally stretch more than 500 per cent without breaking and recover to very near its original length, and C&EN and the 2025 RSC study both give a figure of up to 600 per cent.

• Recovery. AFMA says it can be stretched repeatedly and still return to very near its original length and shape.
• Compared with rubber. AFMA describes it as stronger, more durable and with higher retractive force than rubber; C&EN adds that it is lighter than rubber thread.
• Resistance. Unlike rubber, it is not broken down by body oils, perspiration, lotions or detergents (C&EN, AFMA). AFMA also lists it as abrasion resistant, and names shaped garments such as bra cups among its uses.
• Small amounts do the work. The 2025 RSC study notes that stretch fabrics with about 1–5 per cent elastane stay comfortable without losing tear strength.

How is spandex measured?

Spandex yarn is measured by linear density, which the 2025 RSC study expresses in denier: the weight in grams of 9,000 metres of fibre. The study notes that denier can be adjusted to balance elasticity against tenacity (strength).

Content labels are not required to give the denier. The number you can read is the share of spandex in the fabric. Around 1–5 per cent gives comfort stretch, per the RSC study, and C&EN reported in 1999 that spandex is rarely more than 20 per cent of a garment’s fibre content.

How does spandex appear on a clothing label?

Spandex appears on a content label by its generic name and percentage by weight: “spandex” or “elastane” in the US, “elastane” in the EU, with a trade name such as Lycra allowed only next to that generic name.

United States

• A textile label must give fibre content, country of origin and the identity of the manufacturer or dealer, which may be a registered identification number (RN) instead of a name (FTC).
• Spandex is defined in 16 CFR 303.7 as a manufactured fibre of a long-chain synthetic polymer with at least 85 per cent segmented polyurethane. The same section adopts the ISO 2076 names, and the FTC says either “spandex” or “elastane” may be used.
• A fibre under 5 per cent of the weight is normally listed as “other fiber”. It may be named if it has a clear functional significance at that amount. The regulation’s own example is “96 percent Acetate, 4 percent Spandex”, and the FTC says the purpose does not have to be stated.
• A fibre trademark may appear on a content label only next to the generic name, for example “20% Lycra® Spandex” (FTC).
• Elastic material that is part of the basic fabric need not be counted if it covers no more than 20 per cent of the product’s surface area; the content is then followed by “exclusive of elastic” (FTC).

European Union

• Regulation (EU) No 1007/2011 allows only the fibre names listed in its Annex I. Elastane is entry 43: an elastofibre of at least 85 per cent segmented polyurethane that recovers rapidly after being stretched to three times its length.
• The label must give the name and percentage by weight of every fibre in descending order (Article 9), with a 3 per cent manufacturing tolerance (Article 20).
• Trade marks may be placed immediately before or after the fibre composition (Article 16), so “Lycra” can sit next to “elastane”.
• Elastic threads and bands added at specific and limited points are left out of the composition, as are extra elastic yarns in sock cuffs and the waist belt of tights (Annex VII).

How do you tell good spandex stretch from poor?

Good spandex stretch recovers: pull the fabric, let go, and it should close straight back to its original size, because recovery is the property the fibre is there to supply.

1. Read the percentage. A T-shirt knitted in jersey and labelled “95% cotton, 5% elastane” sits in the 1–5 per cent comfort range the RSC study describes. C&EN reported in 1999 that spandex was rarely more than 20 per cent of a garment’s fibre content.
2. Check the trade name has a partner. On a US content label, “Lycra” should sit beside “spandex” or “elastane” with a percentage. A content label that shows only a trade name falls short of the FTC rule.
3. Do the stretch-and-release test. Take a waistband, the seat of stretch jeans or the knee of leggings. Pull it crosswise firmly, hold for a second and let go. The fabric should spring back flat. If it returns slowly or stays wavy, the garment is not getting the recovery that AFMA and the EU definition describe.
4. Read “exclusive of elastic” correctly. Under US rules it means elastic material that is part of the basic fabric, covering no more than 20 per cent of the surface, was left out of the fibre content (FTC). Check the main fibre list to see whether the rest of the fabric also contains spandex.
5. Look at the care label. AFMA advises against chlorine bleach for spandex. A spandex blend whose care label allows chlorine bleach contradicts that advice.

How do you care for spandex?

Wash spandex by hand or machine in lukewarm water, rinse well, skip chlorine bleach and dry it with little or no heat, AFMA advises.

• Bleach. If you need one, AFMA suggests an oxygen or sodium perborate bleach instead of chlorine.
• Drying. Drip-dry, or tumble on a low heat setting.
• Ironing. If needed, iron quickly on a low setting and do not leave the iron in one place.
• Label first. AFMA also says to follow the garment’s own care label.

Is spandex sustainable?

Spandex makes garments harder to recycle: the authors of a 2025 RSC Applied Polymers study write that standard mechanical recycling is ineffective for core-spun elastane, because it clogs machinery and gets in the way of recovering the outer fibres.

Chemical separation is difficult too. The same study points to elastane’s resistance to most organic solvents and its strong adhesion to the sheath fibres. Its authors conclude that, with current recycling limits, elastane-containing apparel must be discarded regardless of blend composition.

The study itself tested a chitosan finish on elastane fibres, intended to make the fibre easier to recover; this is laboratory research.