Polyethylene hollow fiber membranes

Polyethylene glycols, 10 637, 665 in cosmetic molded sticks, 7 840t Polyethylene hollow fiber membranes, 16 21... 

Jian-Mei, L., et al. Microporous polypropylene and polyethylene hollow fiber membranes. Part 3. Experimental studies on membrane distillation for desalination. Desalination, 115, 153, 2003. 

MAT Matsuyama, H., Hayashi, K., Maki, T., Teramoto, M., and Kubota, N., Effect of polymer density on polyethylene hollow fiber membrane formation via thermally induced phase separation, J. Appl. Polym. Sci., 93,471, 2004. 

Sawada Y, Fuji R, Iqami I et al. The adsorption of endotoxin molecules in a microporous polyethylene hollow fiber membranes. J Hyg 1986 97 97-102. 

Sawada Y, Fujii R, Igami I et al. Removal of endotoxin from water by microfiltration through a microporous polyethylene hollow fiber membrane. Appl Environ Microbiol 1986 51 813-820. 

Du Pont does not currently market Permasep permeators for gas separations. They did, however, in the B-1 Permasep permeator, introduce the first commercial, hollow fiber permeator for gas separations. This permeator employed hollow fibers of polyethylene terephthalate as the membrane. Later, permeators having aramid hollow fiber membranes were field tested for hydrogen separations. Du Pont is presently actively engaged in research for the development of membrane technology for a wide variety of applications. 

Experimental. The hollow fiber membranes used for this study were Naflon 811, which Is a copolymer of polysulfonyl fluoride vinyl ether and polytetrafiuoroethylene, and sulfonated and/or quaternated derivatives of polyethylene (kindly supplied by Dr. E. Korngold from Ben Gurlon University In Israel). The aqueous alcohol solutions studied thus far are those of methanol, ethanol and 2-propanol. The separations were accomplished via the pervaporatlon process as described In Reference 9. Counter Ions were replaced In the hollow fiber by soaking the permeator for twenty four hours In 1 molar solutions of the pertinent Ions. For example, experiments were conducted with Na as a counter Ion. When this set of experiments was finished, the sodium was exchanged by Ll etc. Each data point shown In Figure 14 consists of 6 to 10 measurements taken over a time period of 8 hours. Re-runs with the various counter Ions proved that the intrinsic properties of the membrane remain unchanged and the permeability measurements are reproducible. 

The various modifications of the polyethylene Ion-exchange hollow fiber membranes also proved that here we have a workable concept. From this family of special Interest membranes, results were obtained for anion-exchange hollow fiber membranes. Separation factors of 83, 18 and 3.5 were obtained for feed mixtures of 2-propanol, ethanol and methanol, respectively (each feed mixture was composed of 20 wt.X alcohol and the separation was conducted at 23°C). 

A DEA group was appended onto a polyethylene porous hollow-fiber membrane with a density of 2.2 mmol per gram of the resultant DEA-EA fiber. The inner and outer diameters of the hollow fiber were 2.4 and 4.4 mm, respectively. The liquid permeability, i.e., the permeation rate per unit of inside surface area, of the DEAEA fiber for the buffer was maintained at 50% of that of the original hollow fiber. Volume swelling of the porous hollow fiber accompanied by graft polymerization prevented the graft chains from filling the pores. 

Low-density polyethylene and polypropylene in the form of flat-sheet and hollow-fiber membranes are used in plasmapheresis and as oxygenators in the heart-lung machine. Other materials commonly used in plasmapheresis are cellulose acetate, polycarbonate, and polysulfone [129]. 

Al-Obeidani et al. [93] reported on the development of more effective and economical procedures for cleaning polyethylene hollow fiber MF membranes that have been used for removing oil from contaminated seawater. In their study, alkaline cleaning showed higher recovery of operating cycle time but lower permeate flux recovery than acid cleaning. 

Al-Obeidani, S., Al-Hinai, H., Goosen, M.F.A., Sablani, S., Taniguchi, Y., and Okamura, H. 2008. Chemical cleaning of oU contaminated polyethylene hollow fiber microfiltration membranes. J Membr Sci. 307 299-308. 

Li et al. (2003) proposed the use of polyethylene (PE) and polypropylene (PP) hollow-fiber membranes for desalination by DCMD and VMD. The hollow-fiber membranes were prepared by the melt-extruded/cold-stretching method. Compared to PP hollow-fiber membranes, higher water fluxes have been obtained for the PE membranes in both DCMD and VMD. This was attributed to the larger pore size of the PE membranes. The highest permeate flux reported was 0.8 L/m h in DCMD and about 4 L/m h in VMD. 

S. Wongchitphimon, R. Wang, R. Jiraratananon, L. Shi, and C.H. Loh. (2011). Effect of polyethylene glycol (PEG) as an additive on the fabrication of polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) asymmetric microporous hollow fiber membranes,... 

From outward appearance membrane contactors look similar to other membrane devices. However, functionally the membranes used in contactors are very different. They are mostly nonselective and microporous. Membrane contactors can be made out of flat sheet membranes and there are some commercial apphcations. Most common commercial membrane contactors are, however, made from small-diameter microporous hollow fiber (or capillary) membranes with fine pores (illustrated in Figure 2.1) that span the hoUow fiber wall from the fiber inside surface to the fiber outside surface. The contactor shown as an example in Figure 2.1 resembles a tube-in-sheU configuration with inlet/outlet ports for the shell side and tube side. The membrane is typically made up of hydrophobic materials such as Polypropylene, Polyethylene, PTFE, PFA, and PVDF. 

Polyolefins. Low density polyethylene and polypropylene have been developed as sheet and hollow fiber mlcroporous membranes, respectively, for use In plasmapheresis. Polyethylene Is made porous by stretching the annealed film ( ), while polypropylene la made porous by coextruding hollow fibers with a leachable plasticizer. Neither membrane has been prepared with small pore dimensions suitable for protein rejection. These polyolefin membranes are characterized by good chemical stability, but require special surfactant treatments to make them wettable. Their low deformation temperature precludes the use of steam sterilization. Because they are extruded without the usual antl-oxldants and stabilizers, their stability la lower than Injection molding formulations of the same polymer. 

Ethylene has been separated from ethane by a silver nitrate solution passing countercurrent in a hollow fiber poly-sulfone.165 This separation has also been performed with the silver nitrate solution between two sheets of a polysilox-ane.166 A hydrated silver ion-exchanged Nafion film separated 1,5-hexadiene from 1-hexene with separation factors of 50-80.167 Polyethylene, graft-polymerized with acrylic acid, then converted to its silver salt, favored isobutylene over isobutane by a factor of 10. Olefins, such as ethylene, can be separated from paraffins by electroinduced facilitated transport using a Nafion membrane containing copper ions and platinum.168 A carbon molecular sieve made by pyrolysis of a polyimide, followed by enlargement of the pores with water at 400 C selected propylene over propane with an a-valve greater than 100 at 35°C.169... 

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