What precautions need to be taken while heat setting of knit fabrics blended with Lycra/Spandex/Elastane?

How dimensional stability and heat setting relate to each other? Lycra/ Spandex/ Elastane/ Dorlastan are brand names of the synthetic Polyurethane based Elastomeric fibres. Discussions on any of them would be applicable to the others. Knitwear, with its unique structure permits easy stretch in different directions Thus it is able to take the shape of the body of the wearer. But the stretch is not capable of returning to its original dimensions fully and thus during repeated wear it would progressively loose its intended and desired dimensional shape Inclusion of Lycra in the blend, due its more ‘true’ elasticity (to stretch and return to original dimensions) compensates this inherent deficiency and assists in maintaining the dimensional stability continuously . Understanding Heat Setting In general, synthetic polymer filaments / fibres though having tenacity and elastic properties lack dimensional stability when subjected to action of heat. Twisted or doubled filaments also have a ...  more