Fiber spinning structuring

Fiber spinning, 11 174, 175, 170-171 carbon-nanotube, 13 385-386 methods of, 16 8 models of, 11 171-172 of polyester fibers, 20 12-15 Fiber structure, of aromatic polyamides, 19 727... 

Another feature of high-speed spinning is that the fiber macro structure becomes non-uniform, with more orientation and crystallinity near the fiber surface than in the interior. This is a result of non-uniform solidification, where rapid cooling generates a lower temperature and higher viscosity at the surface. This leads to an oriented surface skin which supports the spinning stress, while higher temperatures within the interior allow more relaxation and disorientation. 

Table 13.1 Intrinsic viscosity and molecular weight data for the three characterized polymers (cf. Figure 13.2) [13]. From Some effects of the rheological properties of PET on spinning line profile and structure developed in high-speed spinning , Perez, G., in High-Speed Fiber Spinning, Ziabicki, A. and Kawai, H. (Eds), 1985, pp. 333-362, copyright (1985 John Wiley Sons, Inc.). Reprinted by permission of John Wiley Sons, Inc.

Shimizu, J., Okui, N. and Kikutani, T Simulation of dynamics and structure formation, in High-Speed Fiber Spinning, Ziabicki, A. and Kawai, H. (Eds), Wiley, New York, 1985, pp. 173-201. 

These solvents include tetrahydrofuran (THF), 1,4-dioxane, chloroform, dichloromethane, and chlorobenzene. The relatively broad solubility characteristics of PSF have been key in the development of solution-based hollow-fiber spinning processes in the manufacture of polysulfone asymmetric membranes (see Hollow-fibermembranes). The solvent list for PES and PPSF is short because of the propensity of these polymers to undergo solvent-induced crystallization in many solvents. When the PES structure contains a small proportion of a second bisphenol comonomer, as in the case of RADEL A (Amoco Corp.) polyethersulfone, solution stability is much improved over that of PES homopolymer. 

The mathematical formulation of the fiber-spinning process is meant to simulate and predict the hydrodynamics of the process and the relationship between spinning conditions and fiber structure. It involves rapid extensional deformation, heat transfer to the surrounding quenching environment, air drag on the filament surface, crystallization under rapid axial-orientation, and nonisothermal conditions. 

Fig. 14.11 Schematic representation of fiber spinning process simulation scheme showing the multiple scale simulation analysis down to the molecular level. This is the goal of the Clemson University-MIT NSF Engineering Research Center for Advanced Engineering Fibers and Films (CAEFF) collaboration. CAEFF researchers are addressing fiber and film forming and structuring by creating a multiscale model that can be used to predict optimal combinations of materials and manufacturing conditions, for these and other processes.

Ha, S.W., Tonelli, A.E., and Hudson, S.M. "Structural studies of Bombyx mori silk fibroin during regeneration from solutions and wet fiber spinning". Biomacromolecules 6(3), 1722-1731 (2005). 

High-Performance Carbon Fiber (HPCF) from Hydrogenated Pitch. Alicyclic molecular structure and the extent of hydrogen transfer between molecules have been progressively recognized as important factors to control the properties of the precursor pitch for fiber spinning. Three experimental methods of pitch preparation were explored as our understanding of pitch chemistry was developed. 

We already have reported on the replacement of the terephthalic acid with kinked diphenylether dicarboxylic acids (4). 3,4 - and 4,4 -Dicarboxydiphenylether (3,4 -0 and 4,4 -0) were synthesized and all-aromatic polyesters were prepared represented by structure 1. These polyesters were thermotropic with melt transitions decreasing to about 200°C with increasing replacement of the terephthalic acid with the kinked monomers. The polymers generally were thermally stable without measurable weight loss until well over 400°C. We wish here to supplement our previous studies with rheological measurements and fiber spinning of the polymers, including some measurements of fiber properties. 

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