Bicomponents

Bicomponent fibers have also provided a route to self-texturing (self-crimping) fibers. The crimp results from the length differential developed during processing caused by differential shrinkage in the two polymers in side-by-side or eccentric core—sheath configurations (50). 

Eibers spun from two different polyesters placed side-by-side or ia a sheath—core arrangement have found utility (18,35,38,39). Bicomponent fibers produced from PET and a copolymer can be used as a biader fiber. Bicomponent fibers made from PET and PBT homopolymers are used ia apparel appHcations which take advantage of the dyeabiHty and high recovery of the PBT polyester. 

R. Jeffries, Bicomponent Fibers, Merrow Publishing Co., Ltd., Watford Herts, UK, 1978. 

Fig. 2. Ultrafine fibers are produced by spinning bicomponent or biconstituent polymer mixtures, highly stretching such products to ultrafine deniers, and extracting or otherwise removing the undesked matrix carrier to release the desked ultrafine fibers (30). For example, spinning polyester islands in a matrix of polystyrene and then, after stretching, dissolving the polystyrene to leave the polyester fibers cospinning polyester with polyamides, then stretching,...

The open hoUow fiber shape shown ia Figure 13 is made by a unique process requiring bicomponent yam technology (145). A yam is spun with a water-soluble copolyester core and nylon sheath where the core is dissolved out with an alkaH treatment ia fabric dyeiag. 

Fig. 14. Bicomponent spinneret for sheath-core fiber, where A represents copolymer B, homopolymer and D, bicomponent fiber capillary exit. If...

Bicomponent technology has been used to introduce functional and novelty effects other than stretch to nylon fibers. For instance, antistatic yams are made by spinning a conductive carbon-black polymer dispersion as a core with a sheath of nylon (188) and as a side-by-side configuration (189). At 0.1—1.0% implants, these conductive filaments give durable static resistance to nylon carpets without interfering with dye coloration. Conductive materials such as carbon black or metals as a sheath around a core of nylon interfere with color, especially light shades. 

Fig. 15. Bicomponent cross-section forms (a) side by side, (b) concentric sheath core, (c) eccentric sheath core, (d) kidney-shaped sheath core, and (e)...

A characteristic feature of the structure of samples obtained under the conditions of molecular orientation is the presence of folded-chain crystals in addition to ECC. Kawai22 has emphasized that the process of crystallization from the melt under the conditions of molecular orientation can be regarded as a bicomponent crystallization in which, just as in the case of fibrous structures in the crystallization from solutions, the formation of crystals of the packet type (ECC) occurs in the initial stage followed by the crystallization with folding . 

Wunderlich30 and Zubov33 suppose that ECC under high pressures occur as a result of an isothermal thickening of folded-chain lamellae. However, this contradicts the later data of Wunderlich and of Japanese authors31 who have shown that folded-chain crystals (FCC) are formed after ECC, when the melt is cooled. According to Kawai22, crystallization under hydrostatic compression can he considered as a variant of the bicomponent crystallization. 

M.W. Olson G.H- Brice, Bicomponent and Biconstituent Fibers in Ballistic Fabric for Personnel Armor , Rept No USA-NLabs, C/-PLSEL-TR-71-48CE, TS-173, Contract DAA17-70-C-0032, Uniroyal Inc, Wayne (1971)... 

Contact lithography can be used to spatially control the photosubstitution process to form laterally resolved bicomponent films with image resolution below 10 pm. Dramatic changes occur in the colors and redox potentials of such ruthenium(II) complexes upon substitution of chloride for the pyridine ligands (Scheme 1). Striped patterns of variable colors are observed on addressing such films with a sequence of potentials. 

Figure 12.18 Bicomponent fibers before being separated into microfibers...

The types of products that contain PET fibers will expand, especially in areas such as nonwoven fabrics used for disposable items, e.g. industrial fabrics for diapers, disposable wipes, filters, etc. These are products that do not require much hand labor, and are relatively well protected from low labor costs in developing countries. Bicomponent fibers based on PET will become more prevalent as the production technology becomes more widespread, in areas where the bico approach can enhance properties or economics. 

Shiyanovskaya 1, Hepel M (1999) Bicomponent WOs/Xi02 films as photoelectrodes. J Electrochem Soc 146 243-249... 

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