Low-bagging (growth) stretch denim yarn production by spinning optimization of cotton-wrapped dual-core elastane and T400 multifilament.

Cotton-wrapped elastane core yarns have been widely used in producing stretch denim fabrics due to their comfortable stretching and recovery, but they suffer from undesirable fabric growth under prolonged or repeated stress. To reduce that problem, an additional semi-elastic multifilament has been incorporated with the elastane core, called dual-core yarn. Herein, it was intended to produce well-engineered dual-core yarns possessing high elasticity with low bagging. Twenty types of cotton-wrapped elastane/T400 multifilament dual-core yarns with different combinations of elastane and T400 tension draft were produced on industrial scale in a spinning mill. Structural parameters, tensile properties and elastic recovery behavior under cyclic loading of the yarns were thoroughly studied. For an optimum combination of elastane/T400 draft, the dual-core yarn attained excellent tenacity and elongation with significantly low evenness, imperfections and hairiness values. More importantly, the results of the cyclic loading study explicitly revealed a remarkable reduction in plastic deformation and stress decay indicating low growth and high resilience of yarn after deformation. The dual-core yarn containing high strength, high elongation and low growth obtained here can have durable stretch jeans with high body movement comfort and long-lasting shape retention.