Wool fiber

Flame-Retardant Treatments For Wool. Although wool is regarded as a naturally flame-resistant fiber, for certain appHcations, such as use in aircraft, it is necessary to meet more stringent requirements. The Zirpro process, developed for this purpose (122,123), is based on the exhaustion of negatively charged zirconium and titanium complexes on wool fiber under acidic conditions. Specific agents used for this purpose are potassium hexafluoro zirconate [16923-95-8] [16923-95-8] K ZrF, and potassium hexafluoro titanate [16919-27-0], K TiF. Various modifications of this process have been... 

Textile Finishing. Polyethyleneimine-A/-methylolurea derivatives improve the crease and wear resistance of cotton (429,430). The adhesion between individual wool fibers is improved by pretreatment with amines, which leads to improved shrink resistance (431). An antimicrobial finish can be appHed to cotton by using a combination of PEI and ureas to bind zinc pyrithione to the fabric (432). After wool has been provided with a flameproof finish using fluorozirconate or fluorotitanate, the wool can be neutralized with PEI (433). Conventional neutralizing agents caimot be used for this purpose since they impair the flameproof characteristics of the impregnated fabric. 

Nonwoven Cards. Modem, high speed cards designed to produce nonwoven webs show evidence of either a cotton or wool fiber-processing heritage and have processing rate capabiUties comparable to those of gametts. Contemporary nonwoven cards are available in widths up to 5 m and are configured with one or two main cylinders, roUer or stationary tops, one or two doffers, or various combinations of these principal components. 

Novel finishes have been developed from the traditional chlorination of wool (180). One, the IWS soft-handle process, gives an extremely soft hand to the wool fibers and reduces the prickly effect when wool is worn next to the skin (181). The other, the soft-handle luster treatment, improves the luster. This improvement is most apparent in knitted wool jersey fabrics. 

Gross-Sectional Shape. Fibers vary in cross-sectional shape both naturally and by design (1,2,19). Whereas wool fibers are essentially round, cotton fibers are eUiptical or kidney-shaped. In synthetic fibers, the cross-sectional shape is deterrnined by the method of spinning and the shape of the spinnerette hole through which the fiber is extmded (3,22). 

Wool fibers consist of cells, where battened ovedapping cuticle cells form a protective sheath around cortical cells. In some coarser fibers, a central vacuolated medullary cell type may be present. 

Fig. 1. Schematic of the stmcture of a fine Merino wool fiber.

The cortex comprises the main bulk and determines many mechanical properties of wool fibers (see Fig. 1). Cortical cells are long, polyhedral, and... 

Table 6. The Effect of Moisture Content on the Physical Properties of Wool Fibers at 25°C ...

Fig. 4. The stress—strain curves of a wool fiber at different relative humidities.

The efficiency of the vegetable matter (burr and seeds) removal mechanism depends on the carefiil maintenance of settings and speeds and the level of drying of the scouted wool (86). The butt wastes contain wool fiber. Butt, together with fiber which has dropped beneath the card, may be carbonized and used in the woolen system. 

Wool fibers have a very complex morphological stmcture. They can be considered as biological composite materials, in which the various regions are both chemically and physically different (87). Fine wool fibers contain two types of cell those of the internal cortex and those of the external cuticle. 

An alternative approach is to physicaUy separate the FWA from the wool fiber by incorporating the whitener into a suitable surface polymer treatment for wool fabric (119). The photostabUity of these fabrics is significantly better than conventional FWA treatments, being similar to bleached wool. 

Three forms of set may be conferred to wool fibers. (/) Cohesive set is imparted when the fibers are dried under strain or set in steam and is lost when the fibers are relaxed in water at room temperature. (2) Temporary set is imparted at higher temperatures and is lost when the fibers are wet out in hot (70°C) water. (2) Permanent set is imparted in boiling water and in high pressure steam, and is stable to release in hot water. 

In addition to the restrictions on their mobiHty caused by steric and polar interactions between chemical groups, the protein molecules in wool fibers are covalentiy cross-linked by disulfide bonds. Permanent setting only occurs if these disulfide bonds are also rearranged to be in equiHbrium with the new shape of the fiber. Disulfide bond rearrangement occurs only at high temperature (>70° C) in wet wool and at even higher temperatures (above 100°C) in... 

Fig. 7. Electron micrographs showiag (a) an untreated wool fiber and (b) a wool fiber treated with cblorine-Hercosett.

Fig. 8. Electron micrograph of Merino wool fibers in a fabric that have been treated with a typical shrink-resistance polymer, showing fiber—fiber bond...

Lucas and Porter (U.S. Patent 3,370,401, 1967) developed a fiber-bed scrubber in which the gas and scrubbing liquid flow vertically upward through a fiber bed (Fig. 17-55). The beds tested were composed of knitted structures made from fibers with diameters ranging From 89 to 406 [Lm. Lucas and Porter reported that the fiber-bed scrubber gave substantially higher efficiencies than did venturi-type scrubbers tested with the same dust at the same gas pressure drop. In similar experiments, Semrau (Semrau and Lunn, op. cit.) also found that a fiber-bed contactor made with random-packed steel-wool fibers gave higher efficiencies than an orifice contactor. However, there... 

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