EXTRUSION AND FORMABILITY OF CERAMIC PAST ES

Numerous complicated catalyst geometries are produced by extrusion of plastic ceramic materials. The demands on the precision of the forming process and the formability of the materials are extremely high. At a first glance, plastic ceramic materials seem to be concentrated solid -liquid suspensions. Rheometric methods, in particular capillary rheom etry, are especially suitable for testing of these materials. However, the flow processes occurring during extrusion are very complex, with many special effects such as slip, shear-thinning, shear hardening, hi gh entrance pressure loss. Viscosity functions are not material functi ons. However, in spite of these difficulties, capillary rheometry, whe n critically applied, is a most advantageous tool in the purposeful de velopment of easily extrudable ceramic materials. Correlation of the r heometric test results with the extrusion process during the productio n of honeycomb geometries is presented using aluminium oxide ceramics as an example.