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.

What it 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.

What it doesn't 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.

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.

Why it matters

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.

Real-world examples

• 1.Lycra brand spandex
• 2.Athletic compression leggings
• 3.Swimsuits
• 4.Elastic waistbands in denim