Stretch Control
Kinematic relationship in yarn spinning determines the level of prestretch applied to the elastic filament before it is wrapped in sheath fibers. Spinning mills adjust the elastane core draft ratio to control the final elasticity and recovery properties of the composite yarn. A higher ratio stretches the core more, which yields a highly elastic yarn that shrinks the fabric tightly after finishing.
This parameter governs the density, weight, and stretch of the resulting fabric, making it a critical control point for elastic denim and sportswear.
Fabric Behavior
Woven structures made with high draft ratios exhibit excellent shape retention and high power. If the elastane core draft ratio is too low, the yarn lacks the retraction force needed to bring the fabric back to its original width. This results in saggy garments that do not fit the wearer properly.
Spinning Efficiency
Excessive draft ratios during ring spinning can lead to frequent core breaks on the machine. The elastane core draft ratio must be optimized to prevent the filament from snapping under high draft tension. This balance maintains high machine efficiency and reduces production downtime.
Measurement Verification
Testing laboratories measure the raw yarn length and compare it to the recovered length of the extracted core to verify the drafted value. The elastane core draft ratio is calculated from the unextended and fully extended core states. This verification prevents batch-to-batch variation in finished fabric stretch.
