Dimensional Behavior
The contraction of synthetic fibers when exposed to elevated temperatures during processing or laundry cycles affects the final dimensions of garments. This physical change, known as thermal shrinkage, occurs when the polymer chains return to their disorganized state after being stretched during spinning. It is a measurable value for heat-sensitive materials.
Internal Stress
Heat releases the internal stresses locked inside the fiber during extrusion and drawing. When the temperature exceeds the glass transition point of the polymer, the molecular bonds loosen and allow the fiber to contract. This contraction increases yarn density but decreases the length of the fabric.
Measurement Method
Laboratory testing requires heating a fabric sample of known dimensions in a hot air oven or a heated liquid bath for a set period to simulate industrial finishing. The differences in length and width before and after exposure measure the thermal shrinkage percentage of the material directly. This standardized test helps mill operators adjust yarn tension during weaving to avoid deformation.
Process Control
Heat-setting fabrics under high tension at a temperature above the expected laundry temperature stabilizes the structure against future changes. This preventive step ensures that the finished garments do not change size when washed by the consumer.
