Synthetic polymeric fibres

As mentioned above, synthetic polymeric fibres can be identified by the IR microscope once sufficiently isolated or, by use of their melting point, by the hot stage microscope or DSC. In the case of DSC, some quantification data can be obtained from the size of the melting endotherm providing standards are available. 

The first successful synthetic fibre. The term is applied to any long-chain synthetic polymeric amide and the best known commercial type is nylon 66 produced by the condensation polymerisation of adipic acid with hexamethylene diamine. 

Exploratory investigations (Freeman et al., 1991, 1993) of the use of more highly ordered polymeric precursors have shown that there remains considerable scope for the development of novel activated chars from synthetic textile fibres. For example, carbon dioxide breakthrough measurements revealed that activated carbons prepared from Kevlar interacted much more strongly with C02 than rayon-based chars. Thus, the latter showed very little ability to separate air and C02, in marked contrast to the Kevlar-derived materials. 

Natural fibres incorporated in synthetic polymeric matrices (mainly polypropylene) had a real industrial success natural additives like lignin were also used. 

Laser irradiation of polymeric fibres can be used to generate a morphological modification at the surface of the irradiated regions. The normally smooth surface of synthetic fibres can be modified by this technique to form a regular, ripple-like, structure, which has a significant effect on the physical properties of the fibre, e.g. adhesion of particles and coatings, wetting properties and optical appearance (Knittel and SchoUmeyer, 1998). 

S.6 Other Natural and Synthetic Polymeric Reinforcing Fibres... 

The most common fibre problem is its sensitivity to alkali attack. This is a particular concern for glass, and for some natural and synthetic polymeric (organic) fibres. The most common and direct test is to expose the fibres to cement extract solutions at different temperatures, and to test the strength of the fibres before and after ageing. Since there is uncertainty as to how well the extract solution represents the actual pore solution in the cementitious matrix, various alternatives have been developed, in which the fibres are cast in a block of cement, and the whole assembly is tested before and after exposure to hot water [102]. 

Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

In addition to plastics materials, many fibres, surface coatings and rubbers are also basically high polymers, whilst in nature itself there is an abundance of polymeric material. Proteins, cellulose, starch, lignin and natural rubber are high polymers. The detailed structures of these materials are complex and highly sophisticated in comparison the synthetic polymers produced by man are crude in the quality of their molecular architecture. 

Perhaps the most notable application of the Beckmann rearrangement is in the industrial production of 8-caprolactam from cyclohexanone (or its oxime), which is used as monomer for the polymerization to a polyamide for the production of synthetic fibres (for example, nylon 6). Furthermore, Beckmann rearrangement provides a facile route for the... 

If crystallisation and orientation go together, the strength can be further improved. The strongest polymeric materials (synthetic fibres) are oriented crystalline polymers. 

The best known products of macromolecular chemistry are plastics, synthetic rubber and fibres. The world average per capita consumption of plastics exceeded 8 kg (44 kg in the USA and in Japan). The production of synthetic fibres and rubber exceeds the production of the natural materials. A large proportion of these substances is produced by polymerization. 

The initial drive for acrylonitrile (AN) production (6.2 Mt/a in 2004 worldwide) was the discovery, in the late 1930s, of the synthetic rubber Buna N. Today nitrile rubbers represent only a minor outlet for AN which is utilized primarily for polymerization to give textile fibres (50%) and ABS resins (24%), and for dimerization to adiponitrile (10%). Early industrial processes depended on the addition of hydrogen cyanide to acetylene or to ethylene oxide, followed by the dehydration of intermediate ethylene cyanohydrin. Both processes are obsolete and are now supplanted by the ammoxidation of propylene (Equation 34) introduced in 1960 by Standard Oil of Indiana (Sohio). The reason for the success stems from the effectiveness of the catalyst and because propylene,... 

The chemical weak spots and the corresponding types of damage vary greatly with synthetic fibres depending on their structure. Thus they are described in the next section in relation to the type of fibre. However, a general difference in chemical stability exists between fibres formed by polymerization or polycondensation. At extreme pH values polycondensate fibres are hydrolytically degraded, for example... 

The pioneer in the field of truly synthetic fibres was Carothers, who demonstrated that two comparatively simple compounds derived from phenol, namely, hexamethylenediamine and adipic acid, could be caused to polymerize to form a potentially fibrous polymer. This was spun into yarn which was successfully placed on the market as nylon. Shortly afterwards ethylene glycol and terephthalic acid were condensed to a polymer from which Terylene or Dacron was made. Ethylene is a by-product in the cracking of petroleum and is the starting point in the manufacture of vinyl chloride and acrlyonitrile, from which Vinyon and the various polyacrylonitrile fibres respectively are spun. 

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