Hollow fine fiber membrane cross section

Hollow fine fiber RO modules are membranes formed into very small-diameter tubes, with an outside diameter of about 85 microns and an inside diameter of about 42 microns.15 The fibers resemble human hair and can be as flexible. The membrane "skin" or thin film is on the outside of the fiber. This skin is about 0.1 to 1 micron thick.13 Figure 4.29 shows a cross section of such a fiber. 

Figure 4.29 Cross section of a hollow fine fiber RO membrane.

Fujii et al. [13] studied morphological structures of the cross section of various hollow fibers and fiat sheet membranes by high-resolution field emission scanning electron microscopy. Figure 6.8 shows a cross-sectional structure of a flat sheet cellulose acetate RO membrane. The layer near the top surface is composed of a densely packed monolayer of polymeric spheres, which is supported by a layer formed with completely packed spheres. The contours of the spheres in the top layer can be observed. The middle layer is also composed of loosely packed and partly fused spheres, which are larger than the spheres in the surface layer. In the middle layer, there are many microvoids, the sizes of which are the same as the spheres. The layer near the bottom is denser than the middle layer, and the spheres are deformed and fused. Interstitial void spaces between the spheres, which may be called microvoids, are clearly observed. This structure seems common for the flat sheet as well as the hollow fiber membranes. For example. Fig. 6.9 shows a cross section of a hollow fiber made of PMMA B-2 (a copolymer containing methyl methacrylate and a small amount of sulfonate groups). The inside surface layer is composed of the dense structure of compactly packed fine polymeric particles. The particle structure of the middle layer... 

Hollow-Fiber Membrene A photograph of the cross section of the PVDF hollow-fiber membrane and an SEM image of the surface of the PVDF hollow-fiber membrane are shown in Figures 5.19a and 5.19b, respectively. On the external surface of the PVDF hollow-fiber membrane, a number of uniform and fine pores open, through which raw water is filtered. 

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