Forms, fibres

In 1891, British chemistry Cross and Bevan discovered that wood pulp when treated with sodium hydroxide solution and carbon disulphide, gets converted into cellulose xanthate. When cellulose xanthate is dissolved in caustic soda solution it gives a viscous solution that could be spun to form fibres called Viscose Rayon. Rayon is produced in large scale today in many countries including India. Rayon (also know as viscose) is in fact regenerated cellulose. 

Optical fibres need to be free of impurities such as transition metal ions (see Chapter 8) and conventional methods of preparing silica glasses are inadequate. The sol-gel process is one way of forming fibres of sufficient purity (chemical vapour deposition. Section 3.7, is another). These processes use volatile compounds of silicon which are more easily purified, for example by fractional distillation, than silica. It is possible to produce silica fibres using a method similar to that studied in the nineteenth century, but with the geldrying time reduced from a year to a few days. Liquid silicon alkoxide (Si(OR)4), where R is methyl, ethyl, or propyl, is hydrolysed by mixing with water. 

Another class consists of extrusion immediately followed by an additional stage. This includes blow moulding, film blowing, quenched film forming, fibre spinning, and extrusion coating. 

Lafon-Lafourcade, S., Peynaud, E. (1974) Sur Faction antibacterienne del anhidride sulfureux sous forme fibre et sous forme combinee. Conn. Vigne Vin, 8, 187-203. 

Pavlov et al.98 observed that partially hydrolyzed. cellulose-PAN copolymers lend themselves to dyeing by add and direct dyes. Unfortunately, the products fail to form fibres suitable for textile industry because of their poor mechanical properties. 

Ability of forming fibres with the thermodynamic stable orientation of macromolecules along the fiber axis (and consequently with high strength and high modulus)... 

The octopus -porphyrin 16, with four long alkyl chains and zwitterionic head groups on both the upper and lower surfaces of tetraphenylporphyrin, binds together in water to form fibres of monomolecular thickness. Only the substituents interact, with a minimal effect on the UV/VIS spectra most importantly the fluorescence of the fibres was strong. Such TPP-derived fibres constitute ideal antipodes to the bilayers whose chromophores are not widely removed from each other. Another consequence of this special environment is the reversible formation of oxygen adducts of the corresponding heme fibres. 

We referred earlier to the silylation of silicates to give trimethylsilyl derivatives corresponding to the Si—0—Si systems in the original minerals. A development of this idea is to treat chrysotile with a mixture of HCl and ClSi(CH3)3 when the Mg and OH ions are stripped off the outside of the layer and replaced by -OSi(CH3)3, giving a gel which on treatment with water forms a fibrous mass of ribbons. When dry these curl up to form fibres similar in shape to those of the original chrysotile. ... 

Coincidence of polymers synthesis or forming fibres from them with dyeing is progressive method in technological and economic respects by which fibres in complete marketable state may be produced directly at the chemical fibres factory. 

Pectin, guar and glucomannans are examples of gel-forming fibres, whereas cellulose, lignins and seed coats are examples of nonsoluble fibres. The non-soluble fibres bind water and swell and keep water in the intestine, while the gel-forming fibres are degraded, which make them unsuitable as laxatives. 

A thermoplastic composition containing a polyolefin and an additive is melted and extraded through multiple orifices to form streams of molten composition, which are cooled to form fibres. The additive is an antimicrobial siloxane quaternary... 

Diequatorially linked polypyranose structures form fibres when the polysaccharides are undecorated - indeed, oligosaccharides beyond a degree of polymerisation of 6 become almost water insoluble. When, however, the backbone chain is substituted ( decorated ), as it is in the plant hemicelluloses, the decoration interferes with the parallel packing of the chains and much more soluble polymers result. 

Fig. 34. AFM-images of insulin amyloid-fibres adsorbed on a mica surface. The left picture shows "normal" linear, temperature-induced (60 °C, incubation time 1 day) fibres of "indefinite" length and a diameter ranging between 8 and 15 tun. In contrast, the image on the right shows that under high hydrostatic pressure conditions (60°C, 1500 bar, incubation time 22 h), the protein is able to form fibres of a different topology Amyloids of a unique circular morphology are observed here (width 35-42 nm, the radius of340-420 nm is the most abundant among the ring-shaped stmctures observed) [138].

Talc [14807-96-6], not containing asbesti-form fibres (Vol. 42,Suppl. 7 1987) Tannic acid [1401-55-4] and tannins (Vol. 10, Suppl. 7 1987)... 

Major applications Available in film, moulded and extruded forms, fibres and lacquers. 

Cellulose is a linear pi,4 glucan which readily forms fibres and it occurs in plants, animal, fungi and bacteria, but there is nothing to suggest that its biosynthesis is very similar in all of these. 

In a similar study, Sen et formed fibre-based membranes. They were spun from SWNT dispersed in either polystyrene or polyurethane with a 3 cm needle-plate gap. In this work, the solution was pumped slowly out of a needle under application of 15 kV. Spinning was continued for 1 h until the counterelectrode was covered in a membrane built up from the spun fibres. 

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