Hollow fiber preparation

Slow release formulations incorporate nonpersistent compounds, eg, methyl parathion, insect growth regulators, and sex pheromones, in a variety of granular, laminated, microencapsulated, and hollow-fiber preparations. 

FIGURE 25.31 SEM images of sintered hollow fiber prepared by phase inversion spinning from 0.3 pm AljOj particles (a) cross-section (b) membrane wall (c) membrane snrface. (From Liu, S., and Li, K., J. Membr. ScL, 218, 269, 2003.)... 

Fig.435a-d. AFM images at four different sites of the surface of hollow fiber prepared at 1 -cm air gap a and b at scan 3 pm (top surface) and c and d at scan 1 pm (three-dimensional images). Reprinted from [61]. Copyright 2003, with kind permission from Elsevier... 

Table 4.10. Average distance between the rows of nodular aggregates (inner surface) and average diameter of the nodular aggregates on the inner and outer surfece of the hollow fibers prepared at different air gaps...

Feng et al. [32] measured the pore sizes of PEI hollow fibers prepared at different air gaps by AFM and the solute transport technique. The results are given in Table 5.11. The table also shows that the pore sizes determined by AFM are always larger than those calculated from solute transport data. 

Figure 10.34. Cross sections of hollow fibers prepared by coaxial spinning having two, three, four and five channels, respectively. The scale bars are 100 run [64]...

For unsupported polymeric membranes (i.e. hollow fibers), spinning parameters are cracial factors that must be controlled during hollow fiber preparation. These parameters include the amount and types of polymer, solvents, and additives mixed irrto the spimung dope, the dope and bore fluid flow rates, the fibre take-up velocity, the air gap distance (unless wet spinning is used), and the coagulant bath temperature [31,71]. The main challenges in hollow fiber spinning, as proposed by Puri [72], are ... 

Hollow-fiber preparation requires a polymeric dope of suitable viscosity, usually a few thousand of centipoises. As a consequence, the polymer and additive concentrations in the dope are usually higher, thus affecting porosity and pore size. Furthermore, this could result in non-Newtonian rheological behavior [36]. There are three main methods for preparing hollow fibers and eapillaries, namely, wet spinning, melt spinning, and dry spinning [37],... 

PVDF-Ti02 composite hollow fibers exhibit superior hydrophilicity and mechanical properties as compared with the pristine PVDF hollow fibers. The composite hollow fibers prepared through the Ti02 sol-gel technique were observed to have better particle dispersion and interaction between the particle-polymer matrixes. Yuliwati et al. [94] observed that the addition of a small amount (1.95 wt%) of TiOj can greatly improve the performance of PVDF-Ti02composite hollow fibers. The aforementioned composite hollow fibers possess smaller pore sizes coupled with higher hydrophilicity and porosity. 

SPPO coated on PEI hollow fibers prepared from PEI (22.5 wt%)/DMAc(76.0 wt%)/LiN03(1.5 wt%) solution... 

Pesek, S.C. and W.J.Koros, Aqueous Quenched Asymmetric Polysulfone Hollow Fibers Prepared by Dry/Wet Phase Separation , J. Membr. Sci., 88, 1-19, (1994). Scott, J., Hollow Fibers - Manufacture and Applications , Edited by J. Scott, Noyes Data Corporation, New Jersey, U.S.A., (1981). 

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