Molecular Alignment
Molecular alignment in elastomer polymers describes the stretching and parallel arrangement of the flexible polyether or polyester chains under external tension. During fabric stretching, soft segment orientation occurs as the coiled, amorphous regions of the elastane yarn uncoil and align along the axis of extension. This orientation is highly reversible, allowing the molecules to return to their random, high-entropy coiled state when the stretching force is released.
It provides the high stretch and low modulus that make polyurethane fibers comfortable in apparel applications.
Thermal Stabilization
When elastane fabrics are heat-set on a stenter frame, the polymer chains are warmed to allow stress relaxation. This process locks the soft segment orientation in a new state, setting the fabric width and reducing shrinkage. Careful temperature control ensures that this setting does not destroy the elastane.
Mechanical Recovery
If the soft segments cannot return to their unoriented state, the fabric exhibits poor elastic recovery. This failure can happen if the polymer chains become entangled or cross-linked during chemical finishing. This loss of elasticity results in baggy garments that lose their shape.
Analysis Technique
X-ray diffraction and infrared spectroscopy allow researchers to measure the degree of soft segment orientation in fibers under stress. These tests help fiber manufacturers design polymers with better stretch profiles. This research leads to more durable elastic yarns for heavy-wear garments.
