Fibers bicomponent

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

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. 

Since disperse dyes diffuse very slowly into PES fibers, efforts have been made to increase the rate of dye strike by chemical or physical alteration of the fiber. The fiber is also modified to reduce the pilling tendency, to increase shrinkage and elasticity, and to reduce flammability. Such modified fibers exhibit improved dye receptivity. Fibers with improved dyeability can be dyed with disperse dyes at boiling temperature without a carrier or with basic dyes when they are modified with acidic components (5-sulfoisophthalic acid). Fibers of this type are used if dyeing cannot be carried out easily above 100°C (e.g., in the case of floor coverings, articles made of PES-wool blends, stretch materials, and cord). Strongly crimped PES bicomponent fibers are produced for special purposes. These fibers are normally also dyeable at the boil and without a carrier [136, 137, 138],... 

The principle that is the basis for bicomponent fibers usually is likened to that which underlies the bicomponent metal strips often used in temperature controllers. With the latter, differential-thermal expansion of the two joined components results in a bending of the thermal element. With fibers, moisture usually is the agent that acts upon the two side-by-side portions. Differential swelling or shrinkage causes the fiber to be brought into... 

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... 

Data obtained in the EDS analyses are listed in Table I. The fiber standards (primarily organic ) gave broad EDS spectra. No heavy elemental composition was indicated in silk, and only a small quantity of calcium could be detected in linen. No elemental maps could be obtained for silk or linen. The EDS spectra of wool reflected its sulfur content. In some of the samples, the somewhat higher concentration of sulfur in one-half of the cross section, which is expected of this naturally bicomponent fiber, was apparent (7). In other samples, the differentiation was not clear. 

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). 

Figure 1. SEMofPAA/PVA bicomponent fibers (bar = 2 pm) electrospunfrom 6 wf/o total polymer concentration at varying COOH/OH molar ratio (a) 3.5,...

Table 1. Properties of PAA/PVA mixture solutions and the average diameters of the bicomponent fibers.

Figure 2. SEM (bar = 2 fm) ofPAA/PVA bicomponent fibers (COOH/OH molar ratio = 0.97) cross-linked at different temperatures for 5 min, immersed in water for 24 hrs and dried in vacuum at ambient temperature (a) 14(fC and (b) 12(fC.

In their study of partially absorbable vascular grafts made of bicomponent fibers having a polypropylene core and polyglycolide sheath. King and coworkers showed that the absorbable sheath mediates considerably the tissue response to the graft. ... 

Partially Absorbable Bicomponent Fibers for Vascular Grafts... 

Of course with most types of bicomponent fiber, the measurement of birefringence is not possible because of the interference of the different polymer groups along the fiber axis. Also, with deeply dyed fibers, the results if obtainable are unreliable because of the interference from the dye molecule. 

There are many patents (U.S. PatentNo. 3,671,379 U.S. Patent No. 6,692,687 B2) that disclose bicomponent polyester fibers wherein one of the components is PTT and the other is PET. US 2004-222544 Al describes the preparation of bicomponent fibers... 

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