Fluoropolymer membranes applications

While several niche applications for OD have been identified, the commercial acceptance of the technology has been hampered by the nonavailability of a suitable membrane-membrane module combination. Fluoropolymer membranes, such as PTFE and PVDF, have been shown to provide superior flux performance, but are still unavailable in hollow fiber form with a suitable thickness for use in OD applications. The inherently low flux of OD requires fhaf membranepacking density be maximized for effective operation, and hence the available flat-sheet form of perfluoro-carbon membranes is unsuitable for commercial use. Four-port hollow fiber modules that provide excellent fluid dynamics are currently available, but only low-flux polypropylene membranes are utilized. 

Fluoropolymers can be readily processed into membranes which have found applications in ultrafiltration, microfiltration, wastewater treatment, protein adsorption and separation, proton conduction, stimuli-responsive and controlled deliveries, and biotechnology [6-10]. However, the practical applications of fluoropolymer membranes are limited to some extent by their hydrophobic and inert surface properties. 

The practical applications of fluoropolymer membranes especially in the areas of purification and separation related to potable water production, wastewater treatment and bioprocessing, have been limited to some extent by their hydrophobic and inert surface properties. Among the different modification techniques, graft copolymerization of hydrophilic monomers, or inimers for further surface reactions, from fiuoropolymers has been useful and effective in improving the physicochemical properties of the parent fluoropolymer with minimum alteration of their desirable bulk properties. Apart from fiilly fluorinated polymers, most of the partially fluorinated polymers can dissolve in polar organic solvents, such as Ai,Ai-dimethylformamide (DMF), A,A-dimethylacetamide (DMAc), NMP, and dimethyl sulfoxide (DMSO), but are insoluble in water, alcohols, and hydrocarbons. 

Membranes UF membranes consist primarily of polymeric structures (polyethersulfone, regenerated cellulose, polysulfone, polyamide, polyacrylonitrile, or various fluoropolymers) formed by immersion casting on a web or as a composite on a MF membrane. Hydrophobic polymers are surface-modified to render them hydrophilic and thereby reduce fouling, reduce product losses, and increase flux [Cabasso in Vltrafiltration Membranes and Applications, Cooper (ed.). Plenum Press, New York, 1980]. Some inorganic UF membranes (alumina, glass, zirconia) are available but only find use in corrosive applications due to their high cost. 

As was noted above, functional fluoropolymers produced by copolymerization of fluoroolefins with functional PFAVE have several unique properties, with the main disadvantage of these materials being the extremely high cost of functional monomers and the resulting high cost of the functional polymers produced from them. The fact that they are so expensive limits their wider industrial application in other fields such as catalysis and membrane separation, except for chlorine-alkali electrolysis and fuel cells, where the only suitable materials are fully fluorinated polymers because of the extreme conditions associated with those processes. 

The great value of the unique characteristics of fluorinated polymers in the development of modern industries has ensured an increasing technological interest since the discovery of the first fluoropolymer, poly(chlorotrifluoro-ethylene) in 1934. Hence, their fields of applications are numerous paints and coatings [10] (for metals [11], wood and leather [12], stone and optical fibers [13, 14]), textile finishings [15], novel elastomers [5, 6, 8], high performance resins, membranes [16, 17], functional materials (for photoresists and optical fibers), biomaterials [18], and thermostable polymers for aerospace. 

OD applications are those fabricated from nonpolar polymers with low surface free energies. The most commonly used OD membrane materials are polyolefins, such as polyethylene and polypropylene, and fluoropolymers, such as polytetrafiuoroethylene (PTFE) and polyvinylidine difiuoride (PVDF). ... 

This chapter presents the preparation and properties of fluorosilicones and some specialty fluoropolymers. The development of various kinds of novel fluorosilicones for membrane-based applications, as well as their fabrication and modification methods, is also described. 

Since the middle 1970 s, KYNAR resins have also been used for the manufacture of microporous and ultrafiltration membranes. KYNAR fluoropolymer was selected for this application because it is resistant to many chemicals both at room temperature and elevated temperature. Because PVDF is approved by the Federal Drug Administration (FDA) for articles or components of articles intended for repeated use in contact with food, KYNAR filters and fluid handling systems are being used by the chemical and the food industry and are also being used by the semiconductor industry as well as in biomedical applications The latter two applications require particularly inert materials that will not contaminate the fluid with trace contaminants, and KYNAR PVDF does meet these extreme purity requirements. 

These amorphous fluoropolymers are chemically as well as thermally stable, soluble in fluorinated solvents, have low dielectric constants, and the films are transparent. They have unique properties compared to traditional fluoropolymers. The amorphous polymers have high potential in many applications. The following are representative examples that are being pursued polymer waveguides [24,25], pellicles used in the photolithographic reproduction of semiconductor integrated circuits [26], insulators and hydrophobic surfaces for electrowetting [27,28], polymer optical fibers [29,30], and membranes for gas separations [31-33], Here, we describe two examples of the use of the amorphous perfiuorinated polymers optical fibers and gas separation membranes. 

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