Regenerated fibres cellulosic

As the chain modulus of a polymer cannot be altered in a spinning process, a larger fibre modulus can only be obtained by improving the orientation of the chains and by an increase of the shear modulus g. However, there is one exception. After dissolving native cellulose fibres with the cellulose I conformation and a chain modulus of 138 GPa into a solution, the regenerated fibres obtained by spinning of this solution and subsequent coagulation always have the cellulose II chain conformation with a chain modulus of 88 GPa [26]. 

Cotton and Other Cellulosic Fibres. The dominant natural cellulosic fibre is cotton, the other natural cellulosic fibres, or bast fibres, include flax, linen, jute and ramie. The so-called regenerated fibres, which include viscose, modal fibres and lyoceU (Tencel), are made by various chemical treatments of cellulosic substrates. The dyeing and printing of cellulosic fibres and materials is carried out using, in decreasing order of scale and importance, reactive, direct and vat dyes. ... 

Injection of the viscous solution of cellulose xanthate into an acidic (H2SO4) bath regenerates the cellulose by the reverse of this reaction, as a film or a fibre depending on the process. The result is known as cellophane if it is a film or viscose rayon if it is a fibre. 

The methods used for the cellulosic regenerated fibres are the same as those for cotton, with the exception that there is less colouring matter to remove and the severity of the process can be decreased. Thus 1 g per litre of available chlorine will always be sufficient and bleaching must be carried out cold with sodium hvpochlorite. A 015 to 0-3 per cent w/w hydrogen peroxide liquor is used and approximately lb per 100 lb of sodium chlorite would be required. The amount of alkali must be reduced when bleaching... 

Majumdar, A., Mukhopadhyay, S., Yadav, R., 2010. Thermal properties of knitted fabrics made from cotton and regenerated bamboo cellulosic fibres. Int. J. Therm. Sci. 49 (10), 2042-2048. 

The refractive indices of native and regenerated cellulose at ideal orientation and in the isotropic condition (reduced to a density of 1.520) are collected in Table 8 (The percentage of crystalline matter is practically equal in aU regenerated fibres). 

In agreement with the foregoing, it could be shown experimentally that the double refraction of regenerated fibres changed if their crystalline portion (consistii of the crystalline modification cellulose II) was transformed into another modification (cellulose IV) without chai ir the orientation of the fibre These effects, which impose certain restrictions as to the possibility of quantitative evaluation of orientation from optical measurements, arise from the influence of the internal field (cf. p. 586). 

With the aid of equations (33) and (34) the orientation factor and the average angle of orientation of uniaxially oriented cellulose objects can be computed, if their birefringence is measured. This may be of some use in botanical work and in fibre research. It is necessary, however, to use the correct values of % and n jj. For practical purposes it will be sufficient to discriminate between native cellulose and regenerated cellulose. Further, the moisture content must be taken into account. The figures of % and n y for the usual density of 1.555 in native and 1.520 in regenerated fibres, adjusted to the usual regain at 65 % rel. humidity which the fibres attain if first swollen in water and then conditioned in air of this humidity, arc listed in Table 9. 

Fibres added to the bituminous mixtures are natural, synthetic or regenerated fibres, such as cellulose, mineral (asbestos), metallic (iron) (Gottschall and Hollnsteiner 1985) and carbon, fibreglass or polymer fibres. 

A different approach aimed at elaborating composite materials for microwave technology called upon the coating of cellulose fibres with a metal like copper [12]. Finally, magnetically active cellulose-based composites have also been described [13] by the incorporation of barium ferrite into a regenerated fibre structure. 

Advantages over wool are claimed to be (a) more uniform stmctnre, (b) sconring not reqnired and (c) high affinity for dyestuffs. Disadvantages are loss of strength (np to 50%) on wetting and poor resistance to bacterial attack. Such regenerated fibres have not yet proved to be commercially successful as textiles but show more promise in the field of simulated meat products (Section 12.4) [10]. The co-extrusion of casein and cellulose has been tried [11]. 

According to a novel method, enzymatic modification of cellulose by increasing the alkaline solubility enables the manufacturing of regenerated fibres without any derivative or organic solvent. It has been proved that by using certain specific compositions of cellulolytic enzymes (a controlled ratio of endoglucanases to cellobiohydrolases) it is possible to obtain directly... 

A second process for producing regenerated cellulose fibre was introduced in 1897 in Germany. In this method, cellulose is treated with an ammoniacal solution of cupric hydroxide (Cu(NH3)4(OH)2) to form a soluble complex. The solution is then spun into dilute sulphuric acid to regenerate the cellulose. This process is relatively expensive because of the need to recover copper. However, the product, called cuprammonium rayon, is still made on a limited scale because of its pleasing appearance and feel. 

Regenerated fibres from cellulose - R on and viscose are regenerated cellulosic fibres. The issue that is often brought up about regenerated fibres is that the processing uses harsh chemicals and is environmentally damaging. Tencel is considered a more environment-friendly regenerated fibre, and it has different properties from rayon. Lyocell/ Tencel is a cellulose-based fabric from farmed trees. 

Cellulose can be regenerated into textile fibres (Cellulose II) through the dissolution and then precipitation into filaments. The viscose and the Lyocell process are the two main... 

B. V. Hettich, "Regenerated Cellulose Fibres—Technology foi the Future," 30th Annual TPIMeeting 1980. 

This material has been known for many years, being used originally in the making of electric lamp filaments. In principle vulcanised fibre is produced by the action of zinc chloride on absorbent paper. The zinc chloride causes the cellulosic fibres to swell and be covered with a gelatinous layer. Separate layers of paper may be plied together and the zinc chloride subsequently removed to leave a regenerated cellulose laminate. 

Cellulose may be solubilised by treatment with sodium hydroxide and carbon disulfide. It can be regenerated by acidification of the solution. This is the basis of the production of regenerated cellulose fibre, so-called viscose rayon , which is a major textile fibre. The technique is also used for the production of continuous cellulose-derived film, so-called cellophane (from cellulose and diaphane , the latter being French for transparent). 

Most cotton is bleached with peroxide, by far the greater proportion by continuous methods. Synthetic fibres seldom require bleaching, but where it is necessary either peroxide or chlorite bleaches are recommended. Most regenerated cellulosic fabrics are only bleached... 

Table 12.12 Metal content of regenerated cellulosic fibres [146]...

Fixation in 6-12 hours with a mixture of sodium hydroxide and trisodium orthophosphate, a metering device being necessary. This method is recommended for regenerated cellulosic fibres. This formulation contains the same total amount of alkali as method (1) with the same bath stability, but may be preferred where some buffering capacity is required and sodium silicate is undesirable. 

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