Elastane, also known as Spandex or Lycra, is a synthetic fiber prized for its remarkable stretch and ability to return to its original shape. This man-made material is widely used in clothing to enhance textile elasticity, allowing garments to move with the body and provide flexibility and comfort.
The Chemical Building Blocks
Elastane is primarily composed of polyurethane, a long-chain polymer. This synthetic fiber is technically known as a polyether-polyurea copolymer. The structure of elastane is characterized by a combination of “soft” and “hard” segments within its polymer chains. The soft segments are long-chain polyether-glycol units, which provide the fiber’s flexibility and elastic recovery. These amorphous segments allow for significant stretching.
Conversely, the hard segments are derived from diisocyanate monomers. These rigid segments create cross-links within the polymer structure, giving the fiber its strength and ability to return to its initial form after being stretched. The precise ratio of these soft and hard segments is carefully controlled during production, as it directly influences the final elastomeric properties of the fiber. This combination forms a block copolymer, where the distinct segments are linked to create a material that is both highly elastic and durable.
Turning Components into Fiber
The manufacturing process of elastane typically begins with creating a prepolymer by mixing macroglycol with a diisocyanate monomer in a controlled reaction vessel. The prepolymer then undergoes a chain extension reaction, often involving a diamine acid, before being diluted with a solvent to create a spinnable solution.
The most prevalent method for transforming this solution into usable elastane fibers is dry spinning, accounting for approximately 95% of global production. In this process, the polymer solution is extruded through tiny holes in a device called a spinneret. As the fine streams emerge, they enter a heated chamber containing nitrogen and solvent gas, which causes the solvent to evaporate and the liquid polymer to solidify into continuous filaments. These solidified strands are then bundled, twisted, and treated with a finishing agent to prevent sticking, before being wound onto spools.
The Unique Properties of Elastane
Elastane’s chemical structure and manufacturing process give it unique properties. Its most notable is superior elasticity, allowing it to stretch significantly—often 5 to 8 times its original length—and then fully recover its shape. This high degree of stretch and recovery provides garments with flexibility and a comfortable, body-hugging fit.
Beyond its stretch, elastane offers durability and resilience. It resists degradation from common factors like body oils, perspiration, and detergents, contributing to the longevity of clothing. Elastane also helps prevent garments from sagging or losing their shape over time, even after repeated wearing and washing. These properties make it a valuable addition to textiles where flexibility, comfort, and shape retention are desired.