Pressing, Casting and Extrusion

To make membranes or typically membrane supports possessing relatively large pores (i.e., diameters larger than 1 pm), traditional polymer or ceramic shape forming 

After air drying, the film is separated from the substrate and stamped to the desired shape and dimensions. This is followed by burning out the organic matter at a temperature of, say, 400-500 C and then sintering at a much higher temperature. A solid content approaching 70% and an excess of the binders (e.g., 20% by weight) to increase 

In the case of tape casting a membrane on a porous support, the membrane thickness and the quality of the support surface appear to be important issues. It has been found that alumina, but not titania or zirconia, can be tape cast into crack-free membranes on porous supports and any defect on the support surface (e.g., a protrusion or cavity) can yield a deposit layer that is either bare or cracked [Simon et al., 1991]. Alumina membranes have b tape cast on top of tape cast alumina supports. Borosilicate glass, but not silica, membranes have also been tape cast [Winnick, 19 ). 

The constituent particles, various binders and other additives used for making porous supports or membranes have been shown to affect the plastic properties of the extrusion paste. The plastic properties, in turn, have significant impacts on the final support and membrane characteristics [Shkrabina et al., 1995a and 1995b]. 

The paste is then forced through a die at a given speed which is controlled by the piston pressure. Some details of this process have been given in the literature (e.g., Schleinitz [1981]). Sometimes painstaking care and seemingly repetitive procedures are taken to ensure that the membranes so produced arc crack- and pinhole-free, dimensionally 

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