Abstract

Most elastomeric fibers are currently produced from either natural rubber or segmented polyurethane polymers. The elastic properties or rubber fibers derive from chemical cross-links formed by vulcanization of either sheets or extruded threads. The segmented polyurethanes, called spandex fibers, are linear block copolymers with relatively long weakly interacting segments that are interconnected by shorter blocks in which intermolecular interactions are strong. Rubber fibers are formed either by slitting vulcanized sheets or by extruding latex into a coagulation bath followed by heating to vulcanize. Spandex fibers are most commonly formed by passing polymer solution through a spinneret followed by removal of solvent; certain spandex compositions can be formed into fibers by melt extrusion. These fibers are normally blended with hard fibers such as nylon, polyester, or cotton to form fabrics with desirable stretch and recovery characteristics. Stabilizers must be included with elastomeric fibers to provide adequate protection from exposure to heat, sunlight, atmospheric pollutants, and active chlorine materials. The unique properties and availability in fine sizes compared to rubber has recently allowed extensive penetration of spandex fibers into hosiery and sportswear markets.