Bicomponent fiber spinning

In another approach, filaments containing two polymers that do not adhere to each other are spun and then split. One may, for example, spin a bicomponent fiber of nylon that has several filaments of polyester embedded. After a fabric containing bicomponent filaments has been woven, it is treated to split the components, thus converting the original filament to several smaller filaments. Deniers of the order of 0.1 can be achieved by this ingenious method. In the last method, instead of... 

Bicomponent fibers A fiber made by spinning two compositions concurrently in each capillary of the spinneret. 

An interesting variation of the bicomponent fiber idea is the use of air or micropores as the second phase. These fibers have found use in biomedical applications as filter media in artificial kidneys. Robinson has reviewed some recent patents in this area, as well as in the other segments of polymer extrusion, spinning, and processing (34). 

The first commercial microfibers were produced in Japan [76] in the 1970s and were made by spinning a bicomponent fiber with polyester fibrils dispersed in a matrix polymer in the islands in a sea configuration [77]. This was drawn into fibers and processed into fabric and finally the matrix polymer was dissolved, leaving tiny polyester fibrils. These were processed into a synthetic suede material marketed as Ultrasuede. The polyester fibrils were extremely fine, less than 1 pm in diameter. The process was expensive, but the product was successful. At the same time, numerous variations on this theme later followed. One ingenious idea by Sato and coworkers used was a blend of PET in a PET-sulfoisophthalate copolymer rich in SOsNa groups, which dissolved readily in aqueous base leaving the unaffected PET. 

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. 

Spinning of a PVA mixture with some other polymers has been studied by a number of researchers, and properties of the bicomponent fibers are reported mostly in patents. There is a classical report by Kawakami on the mixed-spinning of PVA [135]. 

A bicomponent fiber of PVC and PVA is produced by spinning a mixture of a polyvinyl chloride emulsion and an aqueous solution of PVA. This process is called emulsion spinning. The fiber is produced by Kohjin Company under the trade name of Cordelan. The fiber s generic name is polychlal. 

Emulsion-spinning to prepare bicomponent fiber from the emulsified polymer is different from that used to obtain single-component fiber. In the latter case, a polymer dissolved in the dispersed medium during spinning is completely removed from the final fiber therefore, it cannot affect the properties of the product. In the bicomponent fibers, the two polymers, one in the dispersed medium and the other in the dispersed phase, remain in the final fiber and modify its properties. 

Mechanical Properties of Bicomponent Fibers Prepared by Emulsion-Spinning of Mixtures of PVA and Emulsions of Various Polymers... 

Bicomponent fibers of PVC/PVA are prepared by emulsion-spinning and contain about 40% PVC (see Section 4.4.3). 

Toray and Asahi have reported new types of bicomponent fibers that employ more than two functional components. Toray, for example, has announced the development of a water-repellent, antipilling, bicomponent fiber for the sport sweater market [544]. This product, which derives its water repellency by the addition of a fluorine-type resin, exhibits an exceptionally soft handle along with long-lasting water repellency. Asahi has developed a three-component fiber that is made by spinning one polymer as a continuous phase and intermittently... 

Figure 9.4. Results of melt-spinning a simple bicomponent fiber. Light and dark portions represent different polymer materials. Note the ballooning effect (the die-swell phenomenon) as the blend leaves the common capillary. Since the pressure drop in the common capillary must be the same for each component, careful regulation of the homopolymer capillary diameters is necessary to obtain the desired result.

What are known as bicomponent fibers can additionally be made by wet, dry, and emulsion spinning, as well as by melt spinning, but more rarely... 

In this study Polycaprolactone (PCL, 80 kDa) and coUagen (type I) extracted from calf skin were used as the materials. The solvents employed for preparing samples were gladal acetic acid with pyridine for pure PCL scaffolds and 1,1,1,2,2,2-HFIP for both collagen and PCL for the bicomponent fiber scaffolds. The spinning conditions used and the structures produced are indicated in Table 2.4. 

While theoretically one can propose a combination of any two or more thermoplastic polymers in order to spin a bicomponent fiber, in actual practice, the... 

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