Tension Decay
Viscoelastic rate process in polymer science governs the decay of internal tension in a stretched material held at a constant elongation. In textile processing, stress relaxation kinetics determine how fast a yarn or fabric releases its internal stresses during heat-setting or winding. When a synthetic fiber is stretched and held, its molecular chains rearrange to relieve the tension, causing the measured force to drop over time.
This decay rate is highly dependent on temperature, moisture, and the polymer chemistry, making it a critical factor in dimensional stabilization.
Processing Effect
High relaxation rates are beneficial in processes like winding, where they reduce the yarn tension before package formation. If stress relaxation kinetics are too slow, the high residual tension can cause packages to bulge or deform. This issue is managed by controlling the tension during winding.
Temperature Dependence
Elevated temperatures accelerate the molecular rearrangements that drive relaxation. This temperature dependence is exploited during fabric heat-setting, where high heat allows the stress relaxation kinetics to complete in seconds. This speed ensures high productivity on the finishing line.
Quality Testing
Tensile testers with load cells measure the tension drop of a sample over a fixed period. This test helps labs analyze the relaxation behavior of different elastic yarns. This testing ensures that yarns used in compression garments have the correct long-term hold.
