Hollow fibers, fabrics

Wang KL and Cussler EL, Baffled membrane modules made with hollow fiber fabric. Journal of Membrane Science 1993, 85, 265-278. Prasad R, Runkle CJ, and Shuey HF, Method of making spiral-wound hollow fiber membrane fabric cartridges and modules having flow-directing baffles, US Patent 5,264,171, 1993. 

Fig. 3 Schematic of hollow fiber fabrication by dry-wet spinning process. (Spinneret details courtesy of T.S. Chung, National University of Singapore.)...

Others have introduced hehcaUy wound or patterned fiber lay-up in the bundle geometries as a means for controlling and preserving the shell-side flow patterns within the module [27]. The use of hollow-fiber fabrics has also been proposed as a means for precision spacing of the hollow-fibers within the membrane module [28-31]. Many of these are assembled around a central mandrel that also serves as a fluid conduit for feed introduction or product or permeate withdrawal. Modules assembled in this fashion also accommodate distributors and baffles inserted within the fiber pack to aid in the direction and control of the flow sheU-side flow pattern. 

S.R. WiCKRAMASINCHE, M.J. SeMMENS, E. L. CussLER, Hollow-fiber modules made with hollow-fiber fabric. J. Membrane Science 84 (1993) 1-14. 

Feng et al. [32] studied the morphology of the inner and outer surfaces of hollow fibers fabricated from poly(etherimide) by TM-AFM. The hollow fibers were fabricated by the dry-wet phase inversion method at two different bore fluid flow rates, 0.1 and 0.4 mLmin and their effect on the surface morphology was investigated. The average pore sizes on the inner surface were 39.8 and 81.9 nm, respectively, for 0.1 and 0.4 mLmin while those on the outer surface were 218.4 and 93.4, respectively, for 0.1 and 0.4 mLmin h It is interesting to note that the pore size increased with an increase in the bore fluid flow rate at the inner surface, while the opposite was the case at the outer surface. 

Khulbe et al. [4] conducted an AFM study of the cross section of UF poly(ether-imide) hollow fibers, fabricated by the dry-wet spinning method at various air gaps. 

Figure 6.11 shows the cross section of the wall of a hollow fiber fabricated at a 30-cm air gap. There are layers of nodules in rows, but in the middle there is a long. 

Figure 6.12a-c shows the AFM images near the inner surface, middle section, and near the outer surface, respectively, of the hollow fiber fabricated at a 70-cm air gap. Figure 6.12d-f shows the three-dimensional AFM images near the inner surface, middle section, and near the outer surface, respectively, of the same hollow fiber. The arrow in Fig. 6.12a shows the direction from the inner surface toward the outer surface. Fig. 6.12a suggests that nodules are in a row, in the direction perpendicular to the arrow, and are compacted in comparison with the middle section (Fig. 6.12b) and with the area near the outer surface (Fig. 6.12c). The area near the outer surface seems very coarse, and the nodules are fused with each other. The dark space indicates the pores. Similar AFM pictures were obtained for the other studied membranes. The surprising observation is that the nodules are not at random as reported by Fujii et al. [13], but ahgned to the angular direction. The AFM picture of the middle section is very similar to those observed by Fujii et al. [13] in the middle section of Cuprophan, PMMA B-1, and PAN hollow fiber membranes when studied by FE-SEM technique.

Khulbe et al. [4] also measured the nodule sizes (the average of at least 20 measurements) at the inner surface, at the areas near the inner surface, in the middle section and near the outer surface, and at the outer surface for hollow fibers fabricated at different air gaps. Table 6.1 summarizes the results. 

In summary, the following observations were made on the morphology of the PEI hollow fibers fabricated by the dry-wet spinning technique ... 

Polyacrylonitrile hollow fibers fabricated at Gulf South Research Institute were used. Their hydraulic permeability was 9x 10 cm/s atm, the wall thickness 50 /x, the inside diameter 200 microns and the wall micropore diameter about 100 A. Hollow fibers (150) assembled in bundles with a total surface area of 140 cm were washed first with water, and then with methanol and dried by passing nitrogen gas through them for one hour. They were immersed in a mixture of 4-VP and a,co-dihaloalkane (2 1 molar). The reaction was permitted to proceed for 10 days in case of dibromo ethane and 2 days in the case of dibromohexane. A cross section of a typical fiber is shown in Figure 5. 

Hollow-fiber fabrication methods can be divided into two classes (62,63). The most common is solution spinning, in which a 20-30% polymer solution is extruded and precipitated into a bath of a nonsolvent, generally water. Solution spinning allows fibers with the asymmetric Loeb-Sourirajan structure to be made. An alternative technique is melt spinning, in which a hot polymer melt is extruded from an appropriate die and is then cooled and solidified in air or a quench tank. Melt-spun fibers are usually relatively dense and have lower fluxes than solution-spim 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. 

Alternate Hollow Fiber Geometries, Hollow Fiber Fabric,... 

FIGURE 4.4(c) A module containing a woven hollow fiber fabric mounted diagonally in an open-ended box. (From S. R. Wickramasinghe, M. J. Semmens, and E. L. Cussler, J. Membr. Sci., 84, 1, 1993. With permission.)... 

Liu, S., Li, K., and Hughes, R. (2004). Preparation of SrCeo.psYbo. 05O3 a perovsldfe for use as a membrane material in hollow fiber fabrication. Mater. Res. Bull. 39, 119. 

Emerging R D on PVDF Hollow-Fiber Fabrication Technology.232... 

EMERGING R D ON PVDF HOLLOW-FIBER FABRICATION TECHNOLOGY... 

Y.K. Ong and T.S. Chung. (2012). High performance dual-layer hollow fiber fabricated via novel immiscibility induced phase separation (I2PS) process for dehydration of ethanol, J. Memb. Sci. 421-122 271-282. 

Y. Li and T.S. Chung, Exploration of highly sulfonated polyethersulfone (SPES) as a membrane material with the aid of dual-layer hollow fiber fabrication technology for protein separation. Journal of Membrane Science 309(1/2) (2008) 45-55. 

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