Lycra is a brand name for elastane, which is a highly elastic synthetic fabric. ... Unlike many other types of synthetic fabrics, Lycra is highly resistant to heat, and it was quickly recognized as an excellent addition to heat-sensitive synthetics like polyester and nylon. Like other polyurethane materials, Lycra fabric is a polymer, which means that it is composed of long chains of monomers that are connected with a special type of acid.