From a textile point of view, the elasticity of elastic fibers is related to its special molecular structure, and its elongation can reach several times or more, and it can quickly recover after stretching. In general, elastic fibers refer to synthetic fibers with high elongation at break, close to 100% elastic recovery ability, and very low initial modulus.
The earlier national standard GB/T 4146-1984 "Textile Terminology Chemical Fiber Part" defines elastic fiber as: synthetic fiber with high elongation and high resilience, which can be quickly and basically restored to its original length when it is stretched to three times the original length and then relaxed.
This definition specifies that the tensile factor of the elastic fiber is three times the original length. The current national standard GB/T 4146.1-2009 "Textiles -- Chemical fibers – Part 1: genus names" does not give a specific definition of elastic fibers, but describes the main characteristics of polyurethane elastic fibers and polyolefin elastic fibers.
The American Society for Testing and Materials (ASTM) defines an elastomer as a material that can be repeatedly stretched to at least 2 times its original length at room temperature and can quickly return to its original length after external force is released. This definition is broad and refers specifically to elastic fibers.
ISO 2076:2013(E): Textiles-Man-made fibres-Generic names also do not give a definition of elastane, but describe the properties of different elastane fibres.