Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. This material is used very widely in clothing.

Elastane fibres, better known under their trade names, Lycra and Dorlastan, represent a further high point in the development of man-made fibres. Invented in 1937 in Germany, elastane has properties not found in nature, the most important being an extraordinary elasticity. Compared to rubber, elastane has both greater tear resistance and durability and a tension capacity two or three times greater, at a third of the weight. Elastane is used in all areas where a high degree of permanent elasticity is required, as, for example, in tights, sportswear, swimwear, corsetry, and in woven and knitted fabrics. When stretched, it always reverts to its original form. Elastane thus is a prerequisite for fashionable or functional apparel which is intended to cling to the body, while at the same time remaining comfortable.