Thermodynamic Analysis of Hydrolyzed Polyurethane Filament Failure during Dyeing
Hydrolytic polyurethane breakdown during high-temperature dyeing occurs via acid-catalyzed ester cleavage, requiring polyether backbones and strict pH control.
Unrecovered Work Set
Elastic Deficit
Energy lost during the loading and unloading cycle of a stretched elastomeric specimen represents the non-recoverable work in synthetic yarns. More precisely, unrecovered work set measures the portion of deformation energy that is dissipated as heat or consumed by plastic flow. This parameter helps apparel manufacturers predict how well stretch garments will maintain their shape after repeated wear.
Deformation Energy
When a yarn is stretched, it absorbs energy as polymer chains straighten and slide past one another. Part of this energy is returned when the yarn retracts, while the remaining energy is lost due to internal molecular friction. A high unrecovered set indicates that the internal structure has undergone permanent plastic deformation.
This energy loss is particularly pronounced in garments that are subjected to high extension rates.
Yarn Retraction
Poor elastic recovery in stretch fabrics results directly from a high value of this energy loss metric. Fabrics that cannot return to their original dimensions show bagging at knees and elbows after a short period of use. The yarn loses its tightness, which alters the fit and comfort of the garment.
Tensile testing machines measure this value by calculating the area between the extension and retraction curves. This area represents the mechanical energy converted to heat during the stretch cycle.
Production Quality
Optimizing the heat-setting temperature during textile finishing reduces the energy lost during subsequent stretching. Regular dynamic cycle testing of fabrics ensures that the unrecovered set remains within acceptable bounds for premium sportswear.