Elastane

Elastane — marketed as Spandex in North America and Lycra® (DuPont/Invista) globally — is produced by dry spinning a segmented polyurethane-polyurea block copolymer. The polymer's alternating soft (polyether) and hard (polyurea) segments create a molecular spring that recovers from elongation of 500–800% with minimal force — a property no natural fiber approaches. In apparel, elastane is rarely used as a primary fiber; instead, 2–7% elastane blended with cotton, nylon, or polyester transforms the base fabric's hand and movement characteristics without substantially altering its appearance or care requirements. Higher percentages (15–40%) are used in compression garments, swimwear, and performance activewear where active compression or full-range-of-motion stretch is required. Elastane degrades under chlorine bleach, repeated hot-water washing, and prolonged UV exposure — factors that limit garment life in stretch fabrics not formulated with UV stabilizers.