Regenerated fiber

Interest in the manufacture of different forms of rayon has resulted in the production of regular rayon, hollow viscose, spun-dyed filaments and staple rayon, crimped rayon and surface modified fibers, high tenacity rayon and high wet modulus (polynosic) rayon fibers. In chemical composition, viscose rayon and cotton are alike they are both cellulose. 

The differences between regular and high-tenacity rayon are to be found in the degree of degradation of the cellulose which has occurred during preparation of the viscose, the degree of crystallization, the size of the crystallites, the degree of orientation and the fine structure and uniformity of the filament. 

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Again, irrespective of the hardware the chemistry is consistent. The partially regenerated fiber from the spinning machine is contaminated with sulfuric acid, 2inc sulfate, sodium sulfate, carbon disulfide, and the numerous incompletely decomposed by-products of the xanthation reactions. The washing and drying systems must yield a pure cellulose fiber, suitably lubricated for the end use, and dried to a moisture level of around 10%. 

Manufactured fibers produced from natural organic polymers are either regenerated or derivative. A regenerated fiber is one which is formed when a natural polymer or its chemical derivative is dissolved and extmded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber-formation process. A derivative fiber is one which is formed when a chemical derivative of the natural polymer is prepared, dissolved, and extmded as a continuous filament, and the chemical nature of the derivative is retained after the fiber-formation process. 

The man-made fibers are classified into two different categories, regenerated fibers and synthetic fibers, depending on the way in which they are prepared. 

Manual code system, in searching patent literature, 18 223-225 Manual of Classification, 18 209 Manuals of Policies and Procedures (MAPPs), 13 688 Manufactured carbon, 4 735 Manufactured fibers, 11 165, 174-175 24 613-614, 616-618. See also Regenerated fibers Synthetic fibers olefin, 11 231-242 regenerated cellulose, 11 247 Manufactured graphite, 4 735 Manufactured products, nanotechnology and, 17 44-45 Manufactured water, 26 96 Manufacturing... 

See also Rayon Regenerated fibers alternative solvent routes for,... 

F. V. Bright, T. A. Betts, and K. S. Litwiler, Regenerable fiber-optic-based immunosensor, Anal. Chem. 62, 1065-1069 (1990). 

These thermotropic cellulose derivatives are of course of interest from the viewpoint of their structure and properties and might be considered for such applications as chiroptical filters. However, they are unlikely to be considered for fiber formation and certainly not for regenerated fibers, as essenti dly they are ethers of cellulose and desubstitution woiild be difficult. Pawlowski et al. (I2fi) prepared a series of cellulose derivatives, namely phenylacetoxy, 4-meflioxyphenyl-acetoxy-, and p-tolylacetoxy cellulose and tnmethylsilyl cellulose that... 

An elaborate study by Ramer etal. (2000) finally documented a functional regeneration of sensory axon (Ramer et al., 2000). Not only were specific behavioral tests corresponding to the regenerated fiber phenotypes used, but they also confirmed their findings by reinjury of the regenerated fibers to demonstrate their capability for participation in functional recovery. 

Flexible media may be woven or unwoven. Filter media, woven from cotton, wool, synthetic and regenerated fibers, and glass and metal fibers, are used as septa in cake filtration. Cotton is the most widely used natural fiber, nylon is predominant among synthetic fibers. Terylene is a useful medium for acid filtration. Penetration and cake discharge are influenced by twisting and plying of fibers and by the adoption of various weaves such as duck and twill. The choice of a particular cloth often depends on the chemical nature of the slurry. 

Among the best-known nonderivatizing solvent systems is a combination between copper, alkali, and ammonia termed Schweizer s reagent. Solutions of cuprammonium hydroxide have been used for both analytical and industrial cellulose dissolution. Regenerated fibers with silk-like appearance and dialysis membrane have been (and partially continue to be) industrial products on the basis of cellulose dissolution in cuprammonium hydroxide. The success of this solvent is based on the ability of copper and ammonia to complex with the glycol functionality of cellulose as shown inO Fig. 11. Because of the potential side reactions (oxidation and crosslinking, Norman compound formation), alternatives to both ammonia as well as copper have been developed. Cuen and cadoxen are related formulations based on the use of ethylene diamine and cadmium, respectively. The various combinations of alkali, ammonia. 

Whereas cotton represents the purest form of cellulose, wood contributes the vast majority of it. Depending on end use, paper, board or chemical grade, wood conversion to some type of cellulose-rich fiber amounts to about 200 x 10 t/a a worldwide [29]. This compares to about 15 X 10 t/a cotton [13]. Only a minor amount, ca. 7 x 10 t/a, of high-purity cellulose is used for chemical purposes, mainly regenerated fibers (viscose rayon, lyocell) and derivatives (esters, ethers). Smaller amounts are also used for hydrocolloids [microcrystalline cellulose (MCC)]. 

Qualification of different cellulose sources for the various end use applications is determined on the basis of purity, molecular size, and a-cellulose content, a-cellulose refers to the portion of cellulose insoluble in 18% aqueous sodium hydroxide. Whereas the content of noncellulosic polysaccharides has proven to be a hindrance to the clarity of cellulose esters (determined as haze in otherwise clear films), a-cellulose content is important for the spinnability of cellulose solutions into regenerated fibers, and for viscosity characteristics of cellulose ethers. Molecular weights play an important role in various cellulose ethers. 

There is much evidence that the metabolic patterns of such immature muscle cells differ from those of mature fibers. The presence of substantial numbers of regenerating fibers in diseased muscle could therefore be responsible for biochemical changes in such muscle. This again emphasizes the importance of considering all biochemical changes within the framework of the morphological alterations. 

The cause of the elevated rate of protein turnover in dystrophic muscle is as yet unknown. It is not clear, for example, whether it can be accounted for by the presence of regenerating fibers or whether, on the other hand, an increased turnover precedes or accompanies degeneration of the mature fibers. The decreased rate of protein synthesis in de-nervated muscle, in which regeneration is not normally seen, would suggest that regeneration may be largely responsible for the accelerated synthesis of protein in dystrophic muscle. 

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