Fiber swelling

Solvent Resistance. Elastomeric fibers tend to swell in certain organic solvents mbber fibers swell in hydrocarbon solvents such as hexane. Spandex fibers become highly swollen in chlorinated solvents such as tetrachloroethylene [127-18-4] (Perclene). Although the physical properties of spandex fibers return to normal after the solvent evaporates, considerable amounts of its stabilizers may have been extracted. Therefore, the development of stabilizers that are more resistant to solvent extraction has become important as solvent scouring during mill processing replaces aqueous scouring at many mills, especially in Europe (26). 

Both mechanical and chemical action promote ink detachment from cellulose fibers during pulping. Mechanical action includes interfiber abrasion and fiber flexing and bending. Chemical action includes fiber swelling and surfactant-promoted ink particle emulsification and solubilization. 

Uses. The largest use for sodium thiocyanate is as the 50—60 wt % aqueous solution, as a component of the spinning solvent for acryUc fibers (see Fibers, acrylic Acrylonitrile polymers). Other textile appHcations are as a fiber swelling agent and as a dyeing and printing assist. A newer commercial use for sodium thiocyanate is as an additive to cement in order to impart early strength to concrete (376). 

Temperature. No dye transfer takes place below 40°C, above which, because the fiber swells, the rate of dyeing increases. 

Acid dyes can be ptinted on acetate, produciag prints with very good wetfastness and exceptional brightness. The print paste contains a solvent, urea, and ammonium thiocyanate, as a fiber swelling agent to aid ia diffusion of the dye. Again, fixation and scouting foUow the procedures for polyamide. 

Fiber swelling, in paper pulping, 21 434 Fiber volume fraction, 26 775, 776 Fiber-wall morphology, 16 3-5, 11 Fiber width (FW), 18 148 Fibrates, 5 145... 

Refining and Fractionation. These processes are used to alter and select cellulose properties so the final sheet has the desired properties (51). Properties of recycled fibers differ from those of fibers prepared directly from wood. For example, recovered chemical fibers have lower freeness, an apparent viscosity leading to different water drainage characteristics on paper machines. Recovered fibers also have increased apparent density, lower sheet strength, increased sheet opacity, inferior fiber—fiber bonding properties, lower fiber swelling, lower fiber flexibility, lower water retention, reduced fiber fibrillation, and much lower internal fiber delamination. 

The cotton fiber is hydrophilic and porous. Upon immersion in liquid water, the cotton fiber swells and its internal pores fill with water. Pure cotton holds a substantial percentage of its dry weight in water under conditions of centrifugation. The amount of liquid water held depends upon the severity of the centrifugation used in testing. This is approximately 30% for the water of imbibition [281] or 50% for the water retention value [282]. Centrifugation conditions are less severe in the latter case. 

Stone et al. [63] reported that a never-dried cellophane sample was more swollen (2.5 ml/g) than a rayon yam (1.2 ml/g) or super tire cord (0.76 ml/ g) cellulose. The maximum pore sizes decreased in the order cellophane (200 A) > rayon (1(X) A) > tire cord (50 A). Drying was shown to significantly reduce fiber swelling and pore size, especially for cellophane samples. 

Hydroxyl Reactivity. Tables 5 and 6 summarize the relative reactivities of hydroxyl groups observed in partial etherification of cellulose. Besides a distinctly high selectivity of the C6 OH group in tritylation, the relative reactivity of the 2-OH and 6-OH groups was considerably affected by the alkylation conditions, such as fiber swelling and the nature of etherifying conditions. 

Figure 2). Silk fibers swell 192 in cross-sectional area, whereas linen swells 472 (6). Fiber swelling is limited by the interchain forces holding the polymers together in the crystalline areas only when these forces are broken in degradation processes can the fiber swell more. Water is attracted by the peptide bonds of silk and by the cellulosic hydroxyls of linen. The first monolayer of water adsorbed by each polymer molecule is directly adsorbed and thus is tightly held in association with the polymer chain. Subsequent layers of water molecules are indirectly attached and thus are loosely held in association with other water molecules. 

Chlorobenzene is used as a solvent for pesticide formulations, in auto parts degreasing, and in the manufacture of adhesives, paints, polishes, waxes, pharmaceuticals, and natural rubber. It is a chemical intermediate in the production of diphenyl oxide, diisocyanates, and nitrochlorobenzene. It has also been used as a fiber-swelling agent and as a dye carrier in textile processing. 

Lindstrom H, Harris P, Sorensson CT and Evans R (2004) Stiffness and wood variation in 3-year old Pinus radiata clones. Wood Science and Technology, 38 579-97 Lindstrom T (1986) The concept and measurement of fiber swelling. In Bristow AJ and Kolsseth P (eds), Paper structure and properties. Marcel Dekker, New York, 75-97 Littleford TW (1978) Flexural properties of dimension lumber from western Canada. VP-X-179. Environment Canada, Forestry Directorate and Western Forest Products Laboratory, Vancouver, BC... 

Ogiwara, Kubota, and Yasunaga (23) have examined the effect of fiber swelling, photosensitizer, and solvent on photo-induced graft polymerization of methyl methacrylate on vinyl, nylon 6, and polyester fibers. Solvent-induced swelling of fiber as well as the presence of certain sensitizers were found to increase photo-induced grafting through enhancement of radical formation on the fibers. 

Recently Swift [120] and others have provided evidence that the nonkeratin portions of hair are also important to fiber swelling. For example. Swift demonstrated by the penetration of fluorescent-labeled proteins in water that a large-order swelling occurs in the nonkeratin regions of hair. The diametral swelling of hair by water from the dry state is about 14 to 16%. On the other hand. X-ray diffraction measurement of inter-intermediate filament separation distances indicates that swelling of only 5.5% occurs... 

Cross-link density of the fibers Fiber swelling Reaction time... 

The rate of penetration generally increases with increasing temperature and fiber swelling, whereas it decreases with increasing cross-link density and... 

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