Spandex fabric is any fabric that contains spandex, the elastic manufactured fibre that United States law defines as a long-chain synthetic polymer made of at least 85% segmented polyurethane (16 CFR 303.7(k)). The same fibre is called elastane in the European Union and in the ISO list of fibre names, and LYCRA® is one maker’s trademark for it, so spandex, elastane and Lycra describe one material. Spandex material is almost never used on its own: a small share, from a few per cent in stretch cotton yarns to 20% or more in swimwear, is knitted or woven with cotton, nylon or polyester so that the fabric stretches and springs back. The fibre is made by reacting a long, soft polyether or polyester chain with a diisocyanate and a diamine in a solvent, then dry-spinning that solution into fine continuous filaments.
Last verified: 17 October 2026. Figures are taken from the regulation, patent, paper or museum record named beside them; the sources are listed at the end. Percentages of spandex are by weight of the total fibre.
Spandex fabric at a glance
| Question | Short answer | Source |
|---|---|---|
| What is it? | A manufactured elastic fibre of at least 85% segmented polyurethane | 16 CFR 303.7(k); EU Regulation 1007/2011, Annex I |
| Natural or synthetic? | Synthetic: a manufactured fibre made from a synthetic polymer | 16 CFR 303.7(k) |
| Other names | Elastane (EU and ISO); LYCRA® and other trademarks | EU Annex I; FTC, 63 FR 7508 (1998) |
| How far it stretches | Breaks at about 500 to 700% elongation; the EU definition requires rapid, substantial recovery after being stretched to three times its length | CAMEO, Museum of Fine Arts, Boston; EU Annex I |
| How it is made | By dry spinning a polymer solution, or by reaction spinning | US EPA, AP-42 §6.9 |
| Share in the cited fabrics and yarns | 5% in a cotton/elastane knitting yarn and 4 to 8% in denim core-spun yarns cited below; 20 to 41% in nine swimwear fabrics | Sitotaw and Gedion 2020; Helali et al.; Potočić Matković et al. 2024 |
| US label below 5% | May still be named, because it has a functional significance; the rule’s own example is “96 percent Acetate, 4 percent Spandex” | 16 CFR 303.3(a) |
| Label tolerance | 3 percentage points of the total fibre weight, in both the US and the EU | 16 CFR 303.43(a); EU Article 20(3) |
| A known weakness in use | Chlorine: pool water slowly degrades it | CAMEO; Potočić Matković et al. 2024 |
| Invented | At DuPont by the chemist Joseph Shivers; “Fiber K” in 1958 | The LYCRA Company; National Inventors Hall of Fame |
Spandex, elastane and Lycra: one fibre, three names
Spandex is the generic name the US Federal Trade Commission gives the fibre in its Textile Rules: “a manufactured fiber in which the fiber-forming substance is a long chain synthetic polymer comprised of at least 85 percent of a segmented polyurethane” (16 CFR 303.7(k)). The word is usually explained as a rearrangement of “expands” (CAMEO, Museum of Fine Arts, Boston).
Elastane is the name in the European Union’s list of fibre names: an elastofibre of at least 85% by mass of a segmented polyurethane which, stretched to three times its original length and released, recovers rapidly and substantially to its initial length (Regulation (EU) No 1007/2011, Annex I, No 43). It is also the name in ISO 2076, the international list of man-made fibre names. Since 1998 the FTC has accepted the ISO names on US labels and said in so many words that “elastane” may be used as an alternative to “spandex” (63 FR 7508, 13 February 1998).
LYCRA® is a trademark, not a fibre type. DuPont gave the name to its spandex; the business passed to Koch Industries with DuPont’s Invista fibres business in 2004 (National Inventors Hall of Fame), and The LYCRA Company has traded as a standalone company since 2019 (The LYCRA Company). Other trademarks for the same generic fibre have included Dorlastan, Glospan and Cleerspan (CAMEO).
| Name | What kind of name | Where it is used on labels | Source |
|---|---|---|---|
| Spandex | Generic fibre name | United States | 16 CFR 303.7(k) |
| Elastane | Generic fibre name | European Union; ISO list; accepted in the US as an alternative | EU Annex I, No 43; 63 FR 7508 |
| LYCRA® | Trademark of one producer | Anywhere, but only next to the generic name | 16 CFR 303.17(a) |
Spandex is one member of a wider family of elastic fibres. The FTC also defines rubber and elastoester, and the EU list adds elastodiene, elastomultiester and elastolefin; the site’s page on elastomeric fibres compares them.
What is spandex material made of?
Spandex is a segmented polyurethane: each long molecule alternates soft, flexible segments with short, stiff ones. The soft segment is usually a polyether or polyester chain, and the hard segment is made of urethane or urea units (CAMEO). The two behave very differently: in one DuPont patent the soft segments melt below 60 °C and the hard segments above 200 °C, and the balance between them sets the fibre’s character. Too little hard segment and the fibre has low recovery power; too much and it loses elongation (EP 0 343 985, priority 1988). In the DuPont dry-spinning patent read for this page, the hard segments make up only 7 to 13% of the polymer’s weight (US 5,362,432).
- Is spandex a natural fibre? No. It is a manufactured fibre made from a synthetic polymer (16 CFR 303.7(k)). It was developed to replace natural rubber thread.
- Is spandex polyester? No. Polyester has its own generic name and definition (16 CFR 303.7(c)). The confusion is understandable: the soft segment inside some spandex is a polyester chain, and spandex is very often blended with polyester.
- Is spandex polyurethane? Yes, in the sense that at least 85% of it is a segmented polyurethane. Not every polyurethane is spandex: the EU list keeps “polyurethane” fibre and “elastane” as separate entries.
How spandex is made
The US Environmental Protection Agency’s account of synthetic fibre plants describes two spandex processes in use in the United States: dry spinning, and reaction spinning (AP-42, section 6.9, Synthetic Fiber, 1990, reformatted 1995). Dry spinning is the one described in most detail, and the steps below combine that account with the DuPont patent.
- Make the soft segment. Tetrahydrofuran, the principal raw material, has its ring opened and is polymerised into a low-molecular-weight polyether glycol (EPA).
- Cap it. The glycol is reacted with an excess of a diisocyanate, MDI in the patent, at a capping ratio generally of 1.6 to 2.0, leaving a prepolymer with reactive isocyanate ends (EPA; US 5,362,432).
- Extend the chain. The prepolymer is reacted with a diamine in a solvent, which builds the hard urea segments and the long chain; a monoamine is added as a stabiliser. The solvent is dimethylformamide in the EPA’s account; the patent lists dimethylacetamide, dimethylformamide or N-methylpyrrolidone.
- Dry-spin. The solution, 32 to 38% polymer by weight in the patent’s claims, is pumped through spinneret holes into a spin cell, where the solvent evaporates and leaves solid filaments of 6 to 25 decitex each. The patent winds them up at 550 metres a minute or faster.
- Wind and recover the solvent. The yarn is wound onto bobbins straight after spinning. Solvent in the spin-cell exhaust is condensed and recovered, at up to 99% in the EPA’s account (EPA).
Reaction spinning works the other way round. A polyester polyol is reacted with excess diisocyanate to make the prepolymer, which is pumped through spinnerets into a bath of ethylenediamine in toluene; the chains cross-link after the fibre has formed, and the fibre is then dried in an oven, lubricated and wound (EPA).
For process parameters such as dope solids, wind-up speed and the hard-segment share, the patent figures above are one producer’s preferred ranges for one polymer, not an industry norm. Spin-cell temperatures were not given in the documents read for this page, so none are quoted.
Properties of spandex
| Property | Value | Source |
|---|---|---|
| Elongation at break | 500 to 700% | CAMEO |
| Stretch claimed by the producer of LYCRA® fibre | “Up to 500% of its original length”, returning to shape repeatedly | The LYCRA Company |
| Recovery (definition) | Recovers rapidly and substantially after being stretched to three times its length | EU Annex I, No 43 |
| Tenacity | 0.5 to 1.5 g/denier | CAMEO |
| Density | 1.20 to 1.25 g/cm³ | CAMEO |
| Moisture regain | 0.3 to 1.2% | CAMEO |
| Agreed allowance for fibre-content calculation | 1.50% (cotton 8.50%, polyester 1.50%) | EU Annex IX |
| Resistance | Resists sunlight and body oils; slowly degraded by pool chlorine | CAMEO |
| Burning | Urethane burns with a bright flame and little smoke | CAMEO |
Spandex is not a strong fibre, at 0.5 to 1.5 g/denier, and it takes up little moisture. In fabrics it is almost always covered or wrapped by another yarn, or knitted alongside one, as the next section shows.
Spandex yarn forms: bare, covered, air-covered and core-spun
Spandex reaches the fabric in one of a handful of yarn forms. Which one is used decides how the spandex is protected, how the fabric looks and how its share is calculated.
| Form | How it is made | Where it is used |
|---|---|---|
| Bare | The spandex filament itself, fed under tension beside a ground yarn | Plated knits such as cotton/spandex single jersey (worked example below) |
| Covered (single or double) | A filament yarn is wrapped round the stretched spandex; the covering yarn must first be wound on flanged bobbins, so it is a two-step process (Rieter, 7 September 2020) | Compared with air covering by Rieter; end uses not given in the sources read |
| Air-covered | Spandex and a filament run together through an air jet that intermingles them at intervals; typically 30 to 50 times faster than conventional covering (Rieter) | Elastic denim, mainly in the weft; hosiery |
| Core-spun | The stretched spandex is fed into the ring frame, where staple fibres (cotton in Helali et al.) cover it completely | Stretch denim weft (Helali et al.); see core-spun yarn |
| Plied | Spandex twisted together with a spun yarn | The 95/5 cotton/elastane knitting yarn in Sitotaw and Gedion 2020 |
In plated, covered and core-spun yarns the spandex is fed stretched, so each metre of ground yarn uses only 1 ÷ draft metres of spandex from the package. That is why the spandex share depends on the spandex denier divided by the draft: doubling the draft halves the share, just as halving the denier does, as the worked example shows.
How much spandex is in a spandex blend?
The share of spandex follows the job the fabric does. The figures below come from fabrics that were measured or specified in the cited work; they are examples, not limits.
| Fabric or yarn | Spandex share | Other fibre | Source |
|---|---|---|---|
| Labelling example in the US rule | 4% | 96% acetate | 16 CFR 303.3(a) |
| Knitting yarn for single jersey, pique, fleece, rib and interlock | 5% (40 denier elastane plied with 35s Ne cotton, giving a 28s Ne yarn) | 95% combed cotton | Sitotaw and Gedion, JTATM 11(2), 2020 |
| Cotton-covered elastane core-spun yarns spun industrially as denim weft | 4 to 8% of the yarn, the range the study spun (less of the whole fabric, if the warp has none) | Cotton sheath | Helali et al., IJFTR 48(4), Table 1 |
| Nine swimwear fabrics available on the market | 20 to 41% (eight of the nine between 20 and 29%) | Polyamide (eight fabrics) or polyester (one) | Potočić Matković et al., Polymers 16, 2024, Table 1 |
| Plated cotton single jersey, worked below | 6.06% | Cotton | The site’s plating ratio calculator |
More spandex is not simply better. In the cotton knit study, the 5% elastane fabrics had lower bursting strength and higher abrasion resistance than the same structures in 100% cotton, and pilling resistance rose in some structures and fell in others (Sitotaw and Gedion 2020).
Worked example: the spandex percentage of a plated knit
Take a single jersey plated in every course with 30s Ne cotton and 40 denier bare spandex fed at a draft of 3.5. Cotton of 30s Ne is 590.5 ÷ 30 = 19.68 tex; 40 denier is 40 ÷ 9 = 4.44 tex. For each metre of cotton the machine takes in 1 ÷ 3.5 = 0.286 m of spandex, which weighs 4.44 × 0.286 = 1.27 mg against the cotton’s 19.68 mg. Spandex share = 1.27 ÷ (19.68 + 1.27) = 6.06%. The plating ratio calculator, with these inputs, shows 6.06%.
The draft is set at the spandex feed. If the draft drifts during the run, the share in the cloth moves away from the planned figure. The next section shows what that means for the label.
Labelling a spandex blend: 98% cotton 2% spandex and other labels
A label such as “98% cotton, 2% spandex” gives each fibre’s share of the total fibre weight. Three rules decide what the label may say.
- Small shares. In the US, a fibre under 5% must normally be called “other fiber”, but a fibre with “a clearly established and definite functional significance” may be named, and the rule’s example is “96 percent Acetate, 4 percent Spandex” (16 CFR 303.3(a)). That is why 2% spandex appears on labels. In the EU every fibre is listed in descending order; a fibre of up to 5% may be grouped as “other fibres” only where it cannot easily be stated at the time of manufacture (Regulation 1007/2011, Article 9).
- Trademarks. “LYCRA®” may appear on a US label only next to the generic name, in type of equal size, as in “4% LYCRA® spandex” (16 CFR 303.17(a)). The site’s page on labelling a trademarked fibre sets out the EU and US label side by side.
- Tolerance. The stated share may differ from a laboratory result by up to 3 percentage points of the total fibre weight, not 3% of the stated figure: a fibre labelled 40% may be anywhere from 37 to 43% (16 CFR 303.43(a)). The EU allows the same 3% in relation to the total weight of fibres (Article 20(3)). A product labelled as made wholly of one fibre gets no tolerance in the US (303.43(c)).
Worked check. The knit above is labelled “94% cotton, 6% spandex”. A test then finds 95.2% cotton and 4.8% spandex, because the draft drifted. The deviation is 1.2 points, inside the 3-point band, with 1.8 points to spare; the fibre content tolerance calculator, with these figures, shows the same margin. A test result of 2.9% spandex would be 3.1 points out, and the label would need correcting.
Stretch and recovery: how a spandex fabric is tested
What a buyer cares about is not the fibre’s 500% but the fabric’s stretch and how much of it comes back. A stretch test measures a marked length three times: relaxed, extended and after release. Stretch is the extension as a share of the starting length; growth (permanent set) is what has not come back; recovery is the share of the extension that has. The methods are set out in ASTM D3107 for fabrics woven from stretch yarns, ASTM D2594/D2594M for knits of low power and ASTM D4964 for elastic fabrics on a tensile tester.
Example: a 250 mm mark stretches to 375 mm and returns to 260 mm. Stretch = 125 ÷ 250 = 50%; growth = 10 ÷ 250 = 4%; recovery = (125 − 10) ÷ 125 = 92%. The elastic stretch and recovery calculator, written for elastic tape but working the same arithmetic, shows elongation 50%, permanent set 4% and elastic recovery 92% for these lengths.
Caring for spandex fabric
Follow the care label first: in the US a garment’s care label must give the regular care it needs (16 CFR 423.6(b)), and the label is written for the whole garment, not for the spandex alone. The fibre’s own weak point is chlorine. Pool chlorine degrades spandex slowly (CAMEO), and in a 2024 study the breaking force of nine swimwear fabrics left in chlorinated outdoor pool water fell by 12.4% after 200 hours and by 65.7% after 300 hours (Potočić Matković et al.). Rinsing swimwear in clean water after a swim shortens its time in chlorine, and chlorine bleach is best kept away from any spandex blend.
Washing temperatures and dryer settings vary with the other fibres in the blend; the earlier version of this page gave a single temperature without a source, and it has been withdrawn.
Who invented spandex?
Spandex was invented at DuPont by the chemist Joseph C. Shivers, who joined the company in 1946 and worked on Orlon and Dacron polyester before looking for a synthetic replacement for the rubber threads in foundation garments (National Inventors Hall of Fame). The producer’s history dates his “Fiber K” to 1958 and its first use, in form-fitting intimate apparel, to 1960 (The LYCRA Company); the Hall of Fame says only “during the 1950s”, and inducted Shivers in 2018 for US Patent 3,023,192.
Is spandex sustainable?
Conventional spandex is made from tetrahydrofuran, a diisocyanate and a diamine and spun from an organic solvent, which plants condense and recover (EPA). Producers are working on alternatives. The LYCRA Company reports producing samples of 50% recycled LYCRA® fibre and starting industrial composting trials in 2023, and launching a renewable fibre made with corn in 2025 (The LYCRA Company). These are the producer’s statements; no independent figure on biodegradability or recycling rates was found for this page.
Spandex questions
Is elastane the same as spandex?
Yes. Both are generic names for a fibre of at least 85% segmented polyurethane: spandex in US law, elastane in the EU and ISO lists. The FTC has accepted “elastane” as an alternative to “spandex” on US labels since 1998.
What is the difference between Lycra and spandex?
LYCRA® is a trademark of The LYCRA Company for its spandex; spandex is the fibre type. A US label that uses the trademark must put the generic name beside it, as in “LYCRA® spandex”.
Is spandex a natural or synthetic fiber?
Synthetic. It is a manufactured fibre made from a synthetic polymer, a segmented polyurethane. It was developed at DuPont to replace natural rubber thread.
Does spandex contain polyester?
Not as a separate fibre. The soft segment inside some spandex is a polyester chain (in others it is a polyether), but on a label spandex and polyester are different fibres, and a polyester/spandex fabric contains both.
What does 98% cotton 2% spandex mean, and will it shrink?
It means 2% of the fibre weight is spandex, added for stretch and recovery. US rules let spandex be named below 5% because it has a functional purpose. Shrinkage depends on the fibres and on how the fabric was finished; the care label is the guide.
What is spandex used for?
Wherever a fabric must stretch and recover: swimwear, leotards and activewear, hosiery, intimate apparel and shapewear, stretch denim and surgical stockings. In each it is blended with another fibre, such as nylon, polyester or cotton.
Sources
- US Federal Trade Commission, Rules and Regulations under the Textile Fiber Products Identification Act, 16 CFR Part 303: sections 303.3, 303.7(c) and (k), 303.17 and 303.43, read through the eCFR on 17 October 2026; and the 1998 final rule, 63 FR 7508, on ISO names and “elastane”.
- Regulation (EU) No 1007/2011 on textile fibre names and labelling: Articles 9 and 20, Annex I (No 43, elastane) and Annex IX (agreed allowances).
- US Environmental Protection Agency, AP-42, Chapter 6.9, Synthetic Fiber (9/90, reformatted 1/95): spandex dry-spun and reaction-spun process descriptions.
- E. I. du Pont de Nemours and Co., US 5,362,432, Process for dry spinning spandex (priority 2 April 1993); E. I. du Pont de Nemours and Co., EP 0 343 985 A2, Spandex fiber with copolymer soft segment (priority 26 May 1988).
- Museum of Fine Arts, Boston, CAMEO: Spandex fiber, with its references (Joseph, Introductory Textile Science; Cook, Handbook of Textile Fibres).
- National Inventors Hall of Fame, Joseph C. Shivers Jr.; The LYCRA Company, history of LYCRA® fiber.
- V. M. Potočić Matković, I. Salopek Čubrić and K. Krstović, “The Impact of Chlorinated Water and Sun Exposure on the Durability and Performance of Swimwear Materials”, Polymers 16 (2024) 3050, doi:10.3390/polym16213050.
- D. B. Sitotaw and R. K. Gedion, “Performance Characteristics of Knitted Fabrics Made from 100% Cotton and Cotton/Elastane Blended Yarns”, Journal of Textile and Apparel, Technology and Management 11(2), 2020.
- H. Helali, A. Babay, B. Jaouachi and M. Chikhrouhou, “Developing a rheological model for predicting stress relaxation behavior of cotton-covered elastane core-spun yarns”, Indian Journal of Fibre and Textile Research 48(4) (2023), 409–418, doi:10.56042/ijftr.v48i4.7644.
- Rieter, Covering Yarn: Faster Elastic Yarn Production with Air Covering, media release, 7 September 2020.
How this page is kept
Last verified: 17 October 2026. Definitions, labelling rules and tolerances are read from the US Code of Federal Regulations and the EU textile regulation themselves; the manufacturing steps from the US EPA’s process description and a DuPont patent; fibre properties from the Museum of Fine Arts, Boston’s CAMEO record; blend shares from the papers named beside them; and the history from the National Inventors Hall of Fame and the producer’s own account, which is marked as such. The worked examples use the site’s plating ratio, fibre content tolerance and elastic stretch and recovery calculators, and each prefilled link was opened to check that it shows the figures quoted. This page was rewritten on this date; the earlier version’s unsourced stretch, recovery and washing-temperature figures, its market forecasts and its list of journal home pages offered as citations were removed. Spotted an error? Tell us through the contact page and it will be corrected.
