Fibre structure rayon

Error Analysis. The difficulties encountered in resolving peak profiles from each other, and at the same time determining the background scatter, call to question the extent of the error involved in this type of analysis, given that the final resolution appears realistic in the light of known information about the structure of the material. The problem of error in profile resolution has been considered (14) in terms of the equatorial trace of a viscose rayon fibre specimen which is similar to Fortisan, Figure 5 ... 

Carbon fibres are manufactured from rayon and polyacrylonitrile. Carbon fibres can be heated up to 1500°C and contains up to 95% of elemental carbon. Graphite fibres can be heated above 2500 C with 99% carbon. The formation of carbon fibres from polyacrylonitrile is outlined in Fig. 1 -34. Carbon fibres are used in the aerospace industry, in compressor blade to jet engines, helicopter rotor- blades, aircraft fuselage structures, golf-club shafts, cross-bows for archery and in high speed reciprocating parts in loom. 

Viscose rayon is inherently a weak fibre, particularly when wet, therefore it is highly susceptible to damage if enzymatic hydrolysis is not controlled. The enzymatic hydrolysis of viscose fibres causes a decrease of the intrinsic viscosity from 250 to 140 ml/g and an increase in crystallinity from 29 to 39% after 44 h [34]. Strong changes of the structure, however, are not typical for the enzymatic hydrolysis of cellulosic materials. Neither cotton nor wood pulp show an essential decrease of the DP during enzymatic hydrolysis [35-37]. The kinetics of the enzymatic hydrolysis of regenerated cellulose fibres before and after acid prehydrolysis changes the kinetics from a monophasic to a biphasic first order reaction [38]. 

Think of a naturally occurring fibre, and it is odds-on that it will be made of cellulose. Cotton, flax, wood, paper, even rayon hre all cellulose the hairs of the cotton seed plant, in particular, are over ninety per cent pure cellulose. There is more of it in the world than any other organic chemical, for it forms the structural framework on which plants (and some bacteria) are constructed. 

NH4][N03] and [NH4]2[HP04] (which has the benefit of supplying both N and P nutrients) [NH4]2[S04] accounts for a smaller portion of the market. The remaining 12% of NH3 produced was used in the synthetic fibre industry (e.g. nylon-6, nylon-6,6 and rayon), manufacture of explosives (see structures 14.1 and 14.2), resins and miscellaneous chemicals. 

Morey appears to have been the first to make use of this phenomenon to obtain information about the distribution of orientations of the structural units of the polymer. Most of his observations were made using fluorescent molecules incorporated in natural fibres such as ramie, cotton and flax, but some measurements were made on rayons. He used unpolarised ultra-violet light to excite the fluorescence and expressed his results in terms of a percentage orientation defined as... 

Shinohara and Tanzawa examined the effect of orientation on the dynamic properties of viscose rayon films and fibres. (Only an abstract of their studies appears to be available in English.) Making the assumption that the structure was polycrystalline they deduced a relation between extensional and shear moduli in terms of an orientation factor tan d for each modulus was found to be independent of orientation. 

There has been little analytical modelling of the mechanical properties of this group of fibres. Hearle (1967) treated the wet and dry properties of rayon fibres in terms of the composite models shown in Fig. 12 by following the well-known mixture laws. The series structure. Fig. 12a, which is dominated by the soft component, averages the strains at the same stress, and the parallel structure. Fig. 12c, which is dominated by the stiff component, averages stresses at the same strain. The stress for the micellar. Fig. 12b, form is somewhat arbitrarily placed in a mid-way position. In the wet state. Fig. 12d, the component stress-strain curves are assumed to be linear, with a high... 

The early history of polymers is really the conversion of natural polymers into useful materials. Examples include the vulcanization of rubber (Goodyear, 1839), celluloid (which is plasticized cellulose nitrate—Hyatt, 1868), and cellulose-derived fibres, e.g. cuprammonia rayon (Despeisses, 1890) and viscose rayon (Cross, Bevan and Beadle, 1892). The first truly synthetic polymer, that is, one made from laboratory chemicals, was Bakelite (Bakeland, 1907). This was made from phenol and formaldehyde. Bakeland probably did not know the chemical structure of the Bakelite, but he did realize that organic chemicals containing multiple functionality yielded insoluble materials. The various phenol-formaldehyde resins (PF), e.g. Bakelite and novolacs, were thus obtained in an empirical manner. 

The structural models for anisotropic polymeric carbon are compared in fig.9 with the isotropic types as discussed before. The first model was developed by ROLAND (26) for rayon based stress graphitized fibres (the early THORNEL-type fibres of UNION CARBIDE) from small angle scattering, electron diffraction and TEM. The idea of ribbon like polyaromatics was introduced by him. 

Mitsubishi Rayon Co. has reported the development of heat-storage and electrically conductive acrylic fibres with electrical conductivity > 10 S/cm and clothes for winter clothing and sportswear. These bicomponent fibres comprise a core-sheath structure, a core of P(AN/MA/Sod. methaUyl sulphonate) containing 15-70vol% white electrical conductive ceramic particles (e.g. W-P) and P (acrylonitrile/vinyl acetate) as a sheath. 

Boltzmann and his students showed that the superposition principle was valid for inorganic glasses. Leaderman carried out experiments to check its validity for oriented fibres such as rayon, silk and nylon 6,6. He found marked deviations from the Boltzmann principle under many conditions. He correctly attributed this behaviour to the fact that these crystalline substances when subjected to a load often undergo further orientation and crystallization and at the end of the loading experiment they are structurally different from the starting material. The Boltzmann principle can only be expected to apply to such materials at extremely small loads, and temperatures at which further crystallization does not occur. On the other hand, it has been found that many polymeric materials, particularly non-crystalline systems, do show linear viscoelastic behaviour at small strains. 

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