Regenerated fibres

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. 

It is a solvent spun fibre in which the cellulose is directly dissolved keeping the eellulose much closer to that found in nature. The fibre is sourced from Forest Stewardship Council (FSC) certified forests, and the processing is done in a elosed-loop system where very little pollution escapes into the 

There are potential risks assoeiated with using bamboo as a polymer souree for rayon, sinee there is currently a laek of transpareney in the supply ehain. It is not always elear which type of bamboo is used for fibre, where it is grown, how it is eultivated, how it is harvested, etc. To date, there is no known organie eertification of bamboo. 

The proeess to make viseose or rayon fibre fi om bamboo is the same proeess used to produee viseose/rayon from any other plant source. The eellulose is extraeted from the bamboo, and then mixed with chemicals to convert the plant pulp into textile quality fibre. This proeess can be very polluting unless it is earefully eontrolled, and can be influenced by the age and eondition of the equipment as well as whether there is any by-product recycling or effluent treatment. 

Note that in most eountries, the fibre cannot be ealled bamboo, only rayon or viseose from bamboo. 

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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. ... 

Marsano, E., Corsini, P., Arosio, C., Boschi, A., Mormino, M., and Freddi, G. "Wet spinning of Bombyx mori silk fibroin dissolved in N-methyl morpholine N-oxide and properties of regenerated fibres". Int. J. Biol. Macromol. 37(4), 179-188 (2005). 

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... 

For synthetic and regenerated fibres, the fibre production (primary spinning) is mainly made by melt spinning (polyester, nylon etc.), dry spinning (elastane etc.) or wet spinning (viscose, lyocell etc.). Lenzing AG has produced carbon footprints of viscose and lyocell fibres and compared these with other fibres (Shen and Patel, 2008 Shen et al., 2010 Terinte et al., 2014 Van der Velden et al., 2014). The production of natural fibres via agriculture or forestry has been studied elsewhere (e.g. Sandin et al., 2013). 

Inherently flame retardant, conventional synthetic and regenerated fibres... 

The rayon samples indicated I and II differ from each other by the degree of their orientation II being better orientated than I). Mercerised native fibres (fibres previously treated with sodium hydroxide) take an intermediate position between native cotton and regenerated fibres so does woodpulp (not included in the table). 

The totals of 6% and 12% respectively correspond to the water content reached by native and regenerated fibres at nearly 60% rel. humidity upon absorption. 

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]. 

Besides the high performance fibres used in the OS layer, flame-retardant-treated natural and regenerated fibres such as wool and cellu-losic fibres might also be used to make the thermal insulation liner. Some commercially available TL materials for firefighters clothing are shown in Table 3.8. 

The use of protective barrier products is not limited to the operating theatre and is found throughout the healthcare institutions. The range of fibre types is large and goes from natural fibres, (eg. cotton) to regenerated fibres (e.g. viscose) to synthetic fibres (e.g. polyester, polypropylene and polyethylene). The manufactured products are mostly woven, nonwoven or knitted. 

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