Processing multi-channel alumina membranes by tape casting latex-based suspensions

Tape casting has been used to produce thin, multi-channel alumina ceramic membranes using aqueous-based suspensions with latex as the binder. Three different kinds of latex binders, vinyl/acrylic, vinyl acetate/acrylic and acrylic/styrene latexes, each plasticized with dibutyl-o-phthalate or glycerol, were evaluated in terms of their slurry rheology and green tape mechanical properties. The results showed that the different binder systems had a substantial effect on the rheology of the system as a function of the dispersant concentration; the acrylic/styrene system proving to be the most useful. As a plasticizer, glycerol was not found to be effective; however, dibutyl-o-phthalate was much more successful, particularly in the acrylic/styrene system where it enabled the strain-to-failure of the green tape to be doubled with only a modest decrease in tensile strength. As expected, both binder content and sintering temperature significantly affected the final porosity and fracture strength of the ceramic membranes; 15 wt.% binder and a sintering temperature of 1500 °C were found to yield a membrane with a porosity of ∼40% and strength of ∼95 MPa. Simple multi-channel substrates could be easily assembled by bonding strips of the green tapes together with the ceramic slurry. Adhesion between the tapes was excellent with no interface being observed and on sintering no warping or deformation occurred.