Self-bulking fiber

Side-side bicomponent fibers can be used to produee self-bulking yarns. Two PET polymers of different molecular weights, spun as a side-side heterofil, produce a self-bulking fiber... 

SPS/nylon blends have been used to form bicontinuous, self-bulking fibers resulting from melt spinning joined melt streams, one of which comprises SPS, and the other a melt spinnable polymer other than SPS (e.g., nylon 66) [49]. More typically, SPS has been used as an additive in nylon 6 to form carpet fibers that match the morphology and hence the luster and softness of natural fibers such as wool. This technology is described briefly below. 

Bicomponent fiber (BCF) comprises two polymers of different chemical or physical properties. In either case, due to their constitutional variance, the two polymers possess different extendibility characteristics. These differences become evident on heating in air or on exposure to hot water. Both treatments cause the development of bulk. Both polymers are extruded from a common spinneret to form a single filament. Depending on the characteristics of the two polymers, the bicomponent fiber can provide functional properties such as thermal bonding, self bulking, unique cross sections, and achieve functionality of special polymers... 

The side-side configuration is usually used to impart crimp to the fiber. If formed from fiber materials with differing shrinkage characteristics, and treated after fiber formation to develop the shrinkage, the differential lengths will cause the fibers to contract into a helical shape and develop three-dimensional crimp. Such self-crimping fibers provide a different type of bulk and hand than do conventionally crimped fibers. 

The systems discussed up to now all showed chiral susceptibilities that were of the same order of magnitude or smaller than the achiral susceptibility components. The system that we discuss in this section has chiral susceptibilities that dominate the nonlinear optical response.53 The material is a chiral helicenebisquinone derivative shown in Figure 9.22. In bulk samples, the nonracemic, but not the racemic, form of the material spontaneously organizes into long fibers clearly visible under an optical microscope. These fibers comprise columnar stacks of helicene molecules.54,55 Similar columnar stacks self-assemble in appropriate solvents, such as n-dodecane, when the concentration exceeds 1 mM. This association can be observed by a large increase in the circular dichroism (CD) of the solutions. 

Flex. [CNCInt l.] Self-crosslinking polymers imparts hand and bulk to cellulose or synthetic fibers. 

Use of an appropriate cladding material will permit a fiber s core to etch faster than its clad. When such an etch is carried out on a fiber-optic bundle, the result is a bundle tip with one well per fiber. Remarkably, when the tip is brought into contact with a suspension of well-sized beads, self-assembly occurs to yield a bead-filled array. While this bulk self-assembly process is not really akin to the molecular assembly processes of current academic interest, the result is perhaps equally striking. The atomic force micrographs (AMF) shown in Fig. 7 reveal an etched bundle tip with 4-pm wells being filled by 3.5-pm polystyrene beads. Experience reveals that many types of bead material will self-assemble into etched bundle tips. 

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. 

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