Crimp bicomponent yarns

The bicomponent fiber technology began in the 1960s on polyester and polyamide fibers. This technology encompasses a vast variety of polymers, filament shapes, and processes. As recent examples, Howe et al. [394], Wu [395], and Talley et al. [396] have disclosed spin-texture processes for the preparation of self-crimped polyamide bicomponent fibers. DuPont [397] disclosed the method for high-speed spinning bicomponent fibers. The use of a bicomponent yarn with another yarn to form a composite yarn bundle has been taught by Stevenson et al. [398] and others. 

The core-sheath (c-s) configuration is adaptable because many different polymers may be applied as a sheath over a solid polyester core, thus giving a variety of modified surface properties while maintaining all the major fiber and textile properties of PET. An early patent by Shima and coworkers uses an eccentric core-sheath configuration to achieve spiral crimp in a yarn [67]. A recent patent by Chang and coworkers discloses the use of side-side or eccentric c-s bicomponent fibers to achieve a self-crimping yarn made from polytrimethylene terephthalate, where one component is a melt-blend of PTT with a small amount of polystyrene [68]. 

Talley, A. Wilkie, A.E. Buchanan, K.H. A self-set yarn made from bicomponent fibers forms helical crimps that lock in twist and form bulk, U.S. Patent 6,158,204, December 12, 2000. 

One interesting, simple bicomponent fiber is made from two types of nylon. If the polymers are selected to have different coefficients of expansion, the resultant fiber will curl or crimp on cooling. This characteristic imparts bulk and stretchiness to the yarn made from the fibers. 

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