Spinning dry-wet

Filled Fibers. Interest in the encapsulation of specific active materials (e g., activated charcoal, enzymes, drugs) led to the development of encapsulation spinning, usually employing a wet- or dry wet-spinning process. 

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]. 

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

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. 

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

Besides CNTs, another ID carbon nanostructure is carbon nanoflbers. For example, Shen et al. [156] prepared a series of hierarchical porous carbon libers with a BET surface area of 2,231 m g and a pore volume of 1.16 cm g. In this synthesis method, the polyacrylonitrile (PAN) nanofibers (prepared by dry-wet spinning) were selected as precnrsors, and pre-oxidation and chemical activation were involved to get the developed porosities. This type of material contained a large amount of nitrogen-containing groups (N content >8.1 wt%) and consequently basic sites, resulting in a faster adsorption rate and a higher adsorption capacity for CO2 than the commercial zeolite 13X that is conventionally used to capture CO2, in the presence of H2O (Fig. 2.27). 

The cross-sections of two types of spinnerets are given in figure III - 8. In dry-wet spinning the dimensions of the spinneret are very important since the fiber dimensions are mainly determined by these. The fiber dimensions are more or less fixed after immersion in the coagulation bath. 

Figure III 8. Cross-section of three types of spinnerets (A) used for melt spinning and dryspinning, (B) used for wet spinning and dry-wet spinning and (C) triple spinneret used for wet spinning.

In melt spinning and dry-spinning the dimensions of the spinneret are less crucial Decause the fiber dimensions are mainly determined by the ratio of the extrusion rate and tearing-rate. The spinning rate in melt spinning (thousands of meters per minute) is much. -ugher than that used in the dry-wet spin process (meters per minute). 

Membrane surfaces can also be modified by heat treatment. The PES HFMs were prepared by dry-wet spinning method and heated in an oven at 120,150, and 180°C. The membrane shrank by heating. It was noticed that pore size decreased from 8.16 nm for untreated hollow fiber to 3.8 nm with 1 minute heating and then increased to about 6 nm with 5 min heating at 150°C. With an increase in heating temperature, the pore size of the membrane decreases [77,78]. Charkoudian et al. reported increased levels of protein adsorbed in thermally treated poly-acrylamide-modified PVDF microporous membranes in comparison to thermally untreated polyacrylate-modified membranes [79]. 

Trimethylsilyl (TMS) substituent was introduced to polypherylene oxide (PPO) with n-BuLi is a catalyst Homogeneous hollow fibers were sprm by the dry-wet spinning method [65]. 

The ratio of initial fiber velocity to the take-up drum velocity, called the draw ratio or jet stretch (JS), is equal to unity. First part of this study is focused on the preparation of PAN hollow fiber membrane during dry/wet spinning process. Table 5.1 shows the condition of dry/wet spinning process used during this study. 

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