How Spandex Elastic Fibers Are Chemically Engineered
DuPont's 1960 patent for a stretchy, durable synthetic fiber made from segmented polymers, which became the foundation for modern Spandex.
Original patent title: “Elastic filaments of linear segmented polymers”
DuPont's 1960 patent for a stretchy, durable synthetic fiber made from segmented polymers, which became the foundation for modern Spandex. Granted to EI Du Pont de Nemours and Co in 1960 with 2 claims and 71 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
The patent describes a synthetic filament that combines high elasticity with durability. It achieves this by using a segmented copolymer structure, specifically alternating soft ether segments for stretch and hard urea/urethane segments for strength. The claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → defines the material by its physical performance: it must recover more than 90% of its original length after being stretched and maintain its tension (low stress decay) over time. This specific chemical arrangement allows the fiber to act like rubber but remain stable at temperatures above 150 degrees Celsius.
The gap
What does this patent NOT cover?
- Does not cover non-segmented polymers or simple rubber-based elastic materials.
- Does not cover fibers that exhibit high stress decay (losing tension quickly) above 20%.
- Does not cover polymers with an inherent viscosity below 1.0, as these lack sufficient molecular weight for fiber formation.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The innovation was the 'segmented' architecture: by alternating soft, flexible chains with rigid, interlocking chemical segments, the material mimics the properties of natural rubber without its tendency to degrade or lose shape.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Lycra brand spandex
Athletic compression leggings
Swimsuits
Elastic waistbands in denim
Why it matters
The bigger picture
This patent introduced the world to the chemistry of Spandex (Lycra). It enabled the mass production of garments that could stretch and snap back, fundamentally changing the design of athletic wear, swimwear, and intimate apparel.
Filed
January 31, 1955
Granted
March 22, 1960
Market context
Who's building on this
Companies in this space
The technology is now a commodity produced by major chemical manufacturers like The Lycra Company, Hyosung TNC, and various global textile suppliers. These companies continue to refine the polymer chemistry to improve moisture-wicking and heat-resistance properties.
Market impact
This patent created the multi-billion dollar synthetic elastic fiber market. It allowed clothing manufacturers to move away from rigid fabrics and natural rubber, leading to the rise of modern performance apparel and the 'athleisure' fashion category.
Claim 1 — Plain English
What this patent covers
The patent describes a synthetic filament that combines high elasticity with durability. It achieves this by using a segmented copolymer structure, specifically alternating soft ether segments for stretch and hard urea/urethane segments for strength. The claim defines the material by its physical performance: it must recover more than 90% of its original length after being stretched and maintain its tension (low stress decay) over time. This specific chemical arrangement allows the fiber to act like rubber but remain stable at temperatures above 150 degrees Celsius.
The clever bit
The innovation was the 'segmented' architecture: by alternating soft, flexible chains with rigid, interlocking chemical segments, the material mimics the properties of natural rubber without its tendency to degrade or lose shape.
What it does not cover
- Does not cover non-segmented polymers or simple rubber-based elastic materials.
- Does not cover fibers that exhibit high stress decay (losing tension quickly) above 20%.
- Does not cover polymers with an inherent viscosity below 1.0, as these lack sufficient molecular weight for fiber formation.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Early stage
Citation count
37/40
Highly cited
Claim breadth
1/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$43K – $138K
Midpoint $86K · expired or expiring · industry ×2.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
2 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Walter, S. (1960). How Spandex Elastic Fibers Are Chemically Engineered (U.S. Patent No. 2,929,804). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/2929804/spandex-lycra-elastic-fiber
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Spandex Elastic Fibers Are Chemically Engineered cover?
DuPont's 1960 patent for a stretchy, durable synthetic fiber made from segmented polymers, which became the foundation for modern Spandex.
Who owns patent US 2929804?
EI Du Pont de Nemours and Co owns this patent, granted in 1960.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 2929804 cited by?
This patent has been cited by 71 later patents that build on its ideas.
What problem does this patent solve?
This patent introduced the world to the chemistry of Spandex (Lycra). It enabled the mass production of garments that could stretch and snap back, fundamentally changing the design of athletic wear, swimwear, and intimate apparel.
What does this patent NOT cover?
Does not cover non-segmented polymers or simple rubber-based elastic materials.
Same assignee
More from EI Du Pont de Nemours and Co
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