Quantifying Physical Degradation Limits in Synthetic Elastomeric Knits
Thermal setting over 190°C and jet nozzle pressures above 0.30 MPa degrade polyurethane cores, causing permanent set and elasticity loss in synthetic knits.
Unrecovered Elongation
Permanent Set
Mechanical deformation of textile fibers under load consists of both temporary and permanent components. In the performance testing of stretch fabrics, unrecovered elongation represents the percentage of stretch that remains as a permanent strain after the tensile force has been removed. This value determines the extent to which a fabric will sag or deform after being stretched during wear.
When this value is high, the material fails to return to its original dimensions, resulting in baggy elbows or knees.
Garment Fitting
Garment performance in activewear relies on the ability of the fabric to retain its shape after repeated movements. High unrecovered elongation causes the garment to lose its compression and fit over time. This defect is particularly critical in athletic wear and shapewear where constant pressure is required.
Technical specifications for these garments establish strict limits on this parameter.
Test Protocol
Laboratory evaluation utilizes tensile testers to stretch the fabric specimens to a specified percentage and hold them for a set duration. The tester then measures the residual stretch after a recovery period to calculate the unrecovered elongation. This procedure is repeated over multiple cycles to simulate the effects of extended garment wear.
Finishing Influence
Mill processing must use correct heat-setting temperatures to minimize this deformational behavior. Insufficient heat-setting fails to stabilize the elastomeric yarn, which increases the unrecovered elongation of the finished fabric. Proper thermal stabilization is the primary method to control this quality aspect.