Spinning methods

Having mentioned fibre spinning it is appropriate to describe briefly the techniques of wet spinning and dry spinning. For detailed accounts the 

TYPICAL TENSILE PROPERTIES OF ULTRA-HIGH MODULUS ORGANIC FIBRES 

Polymer C is an aromatic-alipliatic ordered copolyamide containing refpeating units of the general formula  

Polymer F is the ordered copolymer produced by the reaction of the diamine below and terephthaloyl chloride H2N 3 CONHNHCO CONHNHCO NH  

Polymer G is the aromatic polyhydrazide from terephthalic dihydrazide and terephthaloyl chloride -t-NHNHCO CONHNHCO CO.  

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One of the principal problems in early commercialization of acryUc fibers was the lack of a suitable spinning method. The polymer caimot be melt spun, except possibly at high pressure in the presence of water. Solution spinning was the only feasible commercial route. However, hydrogen bonding between... 

The thickness of amorphous alloys is dependent upon production methods. Rapid quenching from the liquid state, which is the most widely used method, produces generally thin amorphous alloy sheets of 10-30 tm thickness. This has been called melt spinning or the rotating wheel method. Amorphous alloy powder and wire are also produced by modifications of the melt spinning method. The corrosion behaviour of amorphous alloys has been studied mostly using melt-spun specimens. 

U.S. market trends in, 2 722t Carbon-nanotube spinning method,... 

Fiber type (spinning method) Specific strength (GPa/SGor N/tex1 ) Specific modulus (GPa/SG or N/tex) Electrical conductivity (S/m) Thermal conductivity (W/mK)... 

NMR. NMR analyses were performed on selected samples using dipolar dephasing and off magic angle spinning methods developed at the University of Utah (18-22). This work was performed at the University of Utah under the direction of Professor Ronald Pugmire. The technique allows quantitative analysis of functional groups in the solid coals and chars. 

In most of the previous work with polyimide fibers, the fibers were spun from poly(amic acid) precursors, which were thermally imidized in the fiber form. However, high degrees of imidization were not achieved. Thus, tensile properties of these polymers were not as good as those of high-performance fibers. Work in our laboratories has shown that when the fibers are spun directly from preimidized polymers, it is possible to achieve tensile properties that are as good or even better than those of poly(p-phenyleneterephthalamide) (PPTA or Kevlar ) fibers. For example, fibers have been prepared from m-cresol solutions of BPDA-PFMB using a dry-jet wet-spinning method. The as-spun fibers were then extensively drawn and annealed above 400°C to achieve excellent mechanical properties. 

There are three conventional synthetic liber spinning methods that can he applied to the production of hollovv-liher membranes melt spinning, solution (well spinning, and a combination of these lirst two methods, dry-jet vvei spinning... 

The cross-polarization, magic-angle spinning method (CP MAS) has been applied by Myhre and Yannoni50 to cation 19 in the solid state at very low temperatures using 13C NMR spectroscopy. In the initial study, no convincing evidence for a frozen 2-butyl cation was obtained even at — 190°C. However, subsequently they managed to freeze out the equilibration of the 2-butyl cation (19) at —223°C.62 It behaves like a normal secondary trivalent carbocation. 

A bisphenol A imprinted PES hollow fibre membrane obtained by the dry-wet spinning method was shown to be an interesting alternative to a flat sheet membrane because of its higher surface area [228]. 

Matsumoto, K., Uejima, H., Iwasaki, T., Sano, Y., and Sumino, H. "Studies on regenerated protein fibers 3. Production of regenerated silk fibroin fiber by the self-dialyzing wet spinning method". J. Appl. Polym. Sci. 60(4), 503-511 (1996). 

Ohgo, K., Zhao, C.H., Kobayashi, M., and Asakura, T. "Preparation of non-woven nanofibers of Bombyx mori silk, Sarnia cynthia ricini silk and recombinant hybrid silk with electro-spinning method". Polymer 44(3), 841-846 (2003). 

Extended-chain polyethylene fiber became available commercially in 1984 when DSM, a Dutch firm in the Netherlands, introduced Dyneema , and Mitsui Petrochemicals in Japan announced Tekmilon . Allied Signal of the United States entered the field in 1985 when it introduced Spectra fibers. These materials are characterized by very high strength and modulus, which are achieved by the use of ultrahigh molecular weight polyethylene spun by the gel spinning method into fibers having extended-chain structures and near perfect orientation. 

Gel Spinning. In general, the purpose for which the gel spinning method is used is to produce an as-spun fiber that contains a loose... 

Production. Recognition that the shish-kebab fibers produced by the surface-growth procedure result from the deformation of a gel-like entangled network layer at the rotor surface led to the development of gel-spun polyethylene fibers. The fiber is made by the solution spinning method. The polymer is... 

An alternate way of wet spinning is also possible. Acetate fibers are spun by mixing the isolated reaction product with acetone and water. The spinning solution is formed into filaments by evaporating the solvent and coagulating the acetate in a manner similar to that for triacetate (i.e., by the dry-spinning method). 

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