Extrusion-cast membrane

Currently, Nation is available in two forms extrusion-cast membranes and polymer dispersions. Nation polymer dispersions are used in the formulation of GDEs and reinforced membranes. Nation 117 is 7 mils thick (1 mil = 25.4 ttm) but can be obtained thinner. Table 1 illustrates the current offering of Nation from DuPont [75]. A number of excellent review articles exist that describe the structure, morphology, physical properties, and applications ofNation [56,76-81]. 

Other, more recently developed, uses include microwave oven parts, transparent pipelines, chemical plant pumps and coffee machine hot water dispensers. One exceptional use has been to produce, by an extrusion moulding process, very large rollers for textile finishing for use where cast nylons cannot meet the specification. Also of growing interest are medical equipment applications that may be repeatedly steam-sterilised at 134°C, filtration membranes and cartridges for ink-jet printers. 

Porous membranes have been prepared by leaching an additive from films and tubes of PCL (64,72). The procedure involves extrusion or casting blends of PCL and Pluronic F68, the latter being an FDA-approved oxyethylene-co-oxypropylene triblock copolymer. Treatment of the phase-separated blend with aqueous acetone or aqueous alcohols causes both swelling of the polymer and extraction of the Pluronic F68. The induced pore size and void volume may be controlled by the time, temperature, and solvent composition. 

The porous structure of ceramic supports and membranes can be first described using the lUPAC classification on porous materials. Thus, macroporous ceramic membranes (pore diameter >50 nm) deposited on ceramic, carbon, or metallic porous supports are used for cross-flow microfiltration. These membranes are obtained by two successive ceramic processing techniques extrusion of ceramic pastes to produce cylindrical-shaped macroporous supports and slip-casting of ceramic powder slurries to obtain the supported microfiltration layer [2]. For ultrafiltration membranes, an additional mesoporous ceramic layer (2 nm<pore diameter <50 nm) is deposited, most often by the solgel process [11]. Ceramic nanofilters are produced in the same way by depositing a very thin microporous membrane (pore diameter <2 nm) on the ultrafiltration layer [4]. Two categories of micropores are distinguished the supermicropores >0.7 nm and the ultramicropores <0.7 nm. 

Polysar H DM. iiles/Pdysar Rubber] EPDM polymers for iig. mdding, hose and ptc e extrusion, sponge and cast coring, roofing membranes, black sidewalls. 

Polysar EPDM. [Miles/Pedysar Rubber] EPDM pedymns fro inj. medding, hose and prriBle extrusion, qxxige a cast curing, roofing membranes, black sidewalls. 

Membranes used in microfiltration, reverse osmosis, dialysis, and gas separation are usually prepared by the wet-extrusion process, since it can be used to produce almost every membrane morphology. In the process, homogeneous solutions of the polymers are made in solvent and nonsolvent mixtures, while phase inversion is achieved by any of the several processes, such as solvent evaporation, exposure to excess nonsolvent, and thermal gelation. In most formulations, polymer solutions of 15-40 wt% concentration are cast or spun and subsequently coagulated in a bath containing a nonsolvent (usually water). 

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