Elastan
Spandex or elastane is a highly elastic synthetic fibre that is used to increase the elasticity of fabrics. However, the fibre is only added to the fabrics - usually between 2 and 30 percent in the case of clothing.
According to the European Textile Labelling Act, a fibre is described as elastane as soon as it consists of at least 85% polyurethane - this substance ensures the strength of the fibres. Polyethylene glycol gives the synthetic fibre its high elasticity.
Elastane can be stretched to three times its length and more and then returns to its original shape (very dimensionally stable).
The higher the elastane content, the better the stretch: while it can be up to 30 per cent in a swimming costume, for example, just two per cent is enough for jeans to fit comfortably and have the stretch properties popular with trousers. It is also crease-resistant, lightweight and very tear-resistant.