Spinning methods fiber

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... 

HoUow-fiber fabrication methods can be divided into two classes (61). The most common is solution spinning, in which a 20—30% polymer solution is extmded and precipitated into a bath of a nonsolvent, generally water. Solution spinning allows fibers with the asymmetric Loeb-Soufirajan stmcture to be made. An alternative technique is melt spinning, in which a hot polymer melt is extmded from an appropriate die and is then cooled and sohdified in air or a quench tank. Melt-spun fibers are usually relatively dense and have lower fluxes than solution-spun fibers, but because the fiber can be stretched after it leaves the die, very fine fibers can be made. Melt spinning can also be used with polymers such as poly(trimethylpentene), which are not soluble in convenient solvents and are difficult to form by wet spinning. 

Fig. 8.9 Different methods for spinning CNT fibers and scanning electron micrographs of representative samples, (a) Wet spinning of nanocarbons dispersed in liquid, (b) drawing from a forest of aligned CNTs and (c) direct spinning from the gas phase during CNT synthesis by CVD. Images from references [53,59, 60, 61,62], With kind permission from AMS (2000, 2013), Elsevier (2007, 2011), Wiley (2010).

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)... 

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. 

Fig. 12.14 Effect of the method of measurement on the value of D/Do for HDPE. Curve 1, frozen extrudates Curve 2, extrudates annealed at 160°C in hot silicon oil Curve 3, photographs of extrudates emerging from capillary Curve 4, photographs of extrudates in hot silicon oil. [Reprinted by permission from J. L. White and J. F. Roman, Extrudate Swell During the Melt Spinning of Fibers-Influence of Rheological Properties and Take-up Force, J. Appl. Polym. Sci., 20, 1005 (1976).]...

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). 

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). 

Polyurethane fibers (elastanes) can be made via either of the following two ways. In the first technique, the PU is first synthesized using the prepolymer method, and then the PU is spun from solution (approximately 30% PU) to form a filament or yarn. The yarn can either be collected as one long strand or be cut as it is collected. The second method, called reactive spinning, involves synthesizing the polyurethane and forming the filament all at the same time using a reactive bath to spin the fibers. ... 

Transmet Corporation manufactures flakes by a Rapid Solidification Technology. There are two variations of this method Melt spin and Spinning cup methods. In the Melt spin method, molten metal of any composition (pure metal or alloy) is driven through an orifice and the shape formed in the orifice (continuous sheet) is rapidly cooled on a chilling block. This metal sheet is cut into segments in the form of flakes (square and rectangular), flat fibers, and ribbons of desired... 

The ability of a polymer to be spun into a fiber has been considered a proof of the concept of polymer processability for many years. Wanga et al. [72] have prepared enzymatically synthesized PANI fibers. First, the water-soluble and conductive form of PANI was synthesized using SPS as template and HRP as catalyst. Later, the resulting aqueous dispersion was used to prepare fibers by using a dry-spinning method. The microstructure, mechanical properties, and electrical conductivity of these fibers were improved by traditional fiber techniques such as hot drawing. 

The physical properties of the polymer often dictate the spinning method that must be used for fiber formation. For example, if the melt temperature is above the thermal degradation temperature, the polymers cannot be melt spun. Such polymers must be liquified with... 

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