Fibres flexibility

The changes in fibre flexibility may affect not only the rigidity of the fibre but also the local plasticity of the cell wall, and this may be important in determining the ease with which the inter-fibre hydrogen bonds are formed during drying. Pulp types also differ in... 

Figure 9.2 shows that, during recycling of chemically delignified (Kraft) pulp fibres, irreversible pore closure within the cell wall takes place which leads to a reduction in their cell wall water content as measured by the fibre saturation point (see Chapter 5). The net effect of this is a loss in fibre flexibility which, in turn, leads to less effective inter-fibre bonding. 

Electricity, electrical household appliances electrical cables, optical fibres, flexible telephone cables, inlet and outlet cable channels... 

Because of such behaviour the CTMP pulps are generally used at higher freeness levels than TMP pulps. Freeness although a useful index of papermaking quality is a complex parameter and is dependent on both fibre flexibility and fines content. 

The major effects of refining (Page, 1989 Smook, 1989) on individual fibres are summarized in Table 13.1. The first effect is the partial removal of the primary cell wall. Removal of this wall exposes the secondary wall and promotes hydration and fibre flexibility. The further action of fibrillation involves loosening of the fibrils and the raising of finer micro-fibrils... 

The fibres usually have a log-normal distribution in length, with a mean value of the order of a few mm, depending on the type of pulp. The width of the fibres shows a normal distribution around a mean value of typically tens of microns. Apart from the dimensions of the fibres, the flexibility plays an important role in the formation characteristics. Increasing the wet fibre flexibility will affect both the fibre packing and bonding, and the more flexible the fibres are in a system, then the lower the tendency to flocculate. Despite the high aspect ratio of the fibres, typically 20-50, each fibre in the sheet only penetrates one or two fibre thicknesses and the structure of the paper sheet should therefore be characterized as layered rather than felted. 

Suprasec MPR Suprasec ML 20 Pure MDI. High performance elastomers. Shoe-soling. Spandex fibres. Flexible coatings. Thermoplastics. 

Bastiaansen, C.W.M. (1997) High-modulus and high-strength fibres based on flexible macromolecules, in Processing of Polymers, ed. Meijer, H.E.H. Materials Science and Technology, A Comprehensive Treatment, vol. 18, eds. Cahn, R.W., Haasen, P. and Kramer, E.J. (VCH, Weinheim) p. 551. 

OT1442 A fibre optic sensor for flexible pipeline and riser integrity momtonng... 

Figure 12.30 Potential uses of polyphosphazenes (a) A thin film of a poly(aminophosphazene) sueh materials are of interest for biomedical applications, (b) Fibres of poly[bis(trifluoroethoxy)phosphazene] these fibres are water-repellant, resistant to hydrolysis or strong sunlight, and do not burn, (c) Cotton cloth treated with a poly(fluoroalkoxyphosphazene) showing the water repellaney eonferred by the phosphazene. (d) Polyphosphazene elastomers are now being manufaetured for use in fuel lines, gaskets, O-rings, shock absorbers, and carburettor eomponents they are impervious to oils and fuels, do not bum, and remain flexible at very low temperatures. Photographs by eourtesy of H. R. Allcock (Pennsylvania State University) and the Firestone Tire and Rubber Company.

Heating mantles. These consist of a flexible knitted fibre glass sheath which fits snugly around a flask and contains an electrical heating element which operates at black heat. The mantle may be supported in an aluminium case which stands on the bench, but for use with suspended vessels the mantle is supplied without a case. Electric power is supplied to the heating element through a control unit which may be either a continuously variable transformer or a thyristor controller, and so the operating temperature of the mantle can be smoothly adjusted... 

As it has been shown lately, insertion of a small quantity (5—15% of the copolymer weight) of ISP monomeric units into the PAN macfomolecules results in an appreciable decrease of stiffness and in an increase of flexibility of the chain, which makes it possible to improve considerably the fatigue properties of usual PAN fibres30. In addition to that, by inserting a comparatively large amount (25—30%) of flexible ISP monomeric units into the copolymer one can decrease substantially the yield temperature of PAN, which makes it possible to spin fibres from thermoplastic state31. ... 

Insertion of flexible blocks into the stiff polymer chain of PAN ensures the possibility of raising the resistance of modified PAN fibres to multiple deformations and, especially, increases significantly the abrasive resistance of fibres made of block copolymers. 

Hence, the main aim of the technological process in obtaining fibres from flexible-chain polymers is to extend flexible-chain molecules and to fix their oriented state by subsequent crystallization. The filaments obtained by this method exhibit a fibrillar structure and high tenacity, because the structure of the filament is similar to that of fibres prepared from rigid-chain polymers (for a detailed thermodynamic treatment of orientation processes in polymer solutions and the thermokinetic analysis of jet-fibre transition in longitudinal solution flow see monograph3. ... 

Nylons 6,6 and 6 are the ones usually employed as textile fibres. Where individual monofilaments are used, such as in brushes, sports equipment, or surgical sutures, nylons 6,10 and 11 tend to be used, because of their greater flexibility and water resistance. All nylons can be injection moulded and the resulting articles have found widespread use in engineering applications, such as bearings and gears. 

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