Viscoelastic Stress Relaxation Profiles in Heat Set Polyurethane Stretch Wovens
Controlled stenter dwell at 185-195°C stabilizes polyurethane hard segments to minimize viscoelastic force decay and garment bagging in stretch wovens.
Fabric Bagging
Residual Distortion
Progressive deformation of a textile material characterized by localized three-dimensional bulging after repeated or prolonged loading. Fabric bagging represents a failure of a knitted or woven structure to recover its original flat shape following stress at joints like elbows or knees. It is a time-dependent mechanical property tied to both fibre elasticity and yarn mobility.
Structural Response
Inter-yarn friction and polymer relaxation determine the severity of the distortion observed during wear. When fabric bagging develops, the internal stresses in the yarns are not sufficient to overcome the frictional forces holding the displaced fibres in their new positions. Laboratory evaluation often involves a ball-burst tester or a specialized device that measures the residual height of the bulge.
Materials with high spandex content generally resist this type of permanent aesthetic degradation.
Garment Utility
Shape retention affects the perceived quality and longevity of tight-fitting apparel like leggings or performance sportswear.
Recovery Measurement
Testing protocols quantify the volume or height of the protrusion after a specific relaxation period. This value indicates how fabric bagging will behave under real-world conditions over several hours of use. Garments that maintain their profile after cyclic loading pass the performance threshold for premium activewear.