Jan Graczyk

Rheology and Extrudability of Ceramic Compounds

Many ceramic products are made by extruding materials which are not extrudable in their original state and must be made so by appropriate treatment and by incorporating various additives which adjust their rheology or flow properties. The properties that are of importance for extrusion can, in fact, be characterized and quantified by means of rheological measurements. Capillary rheometry especially enables many different extrudability tests to be carried out, ranging from simple suitability tests to complex determinations of properties in order to achieve optimum processes and products.

Wall Slip Behavior of Alumina-Silicone Oil Pastes During Extrusion

In this work, the applicability of two rheological characterization methods to determine the wall slip velocity during extrusion of alumina/silicone oil pastes has been examined. The results are compared with those obtained using another more recently developed technique called the color marking method. These methods were used to determine the wall slip behavior of model pastes as a function of solids concentration, shear stress and extrudate velocity.

Kapillarrheometrie von Aluminiumoxid-Silikonöl-Suspensionen

Kapillarrheometrische Messungen an konzentrierten Suspensionen von Aluminiumoxidhydroxid in einem Silikonol werden beschrieben. Die Abmessungen der Extrusionsdusen wurden variiert. Die Schubspannungsfunktionen und die Druckverluste an einer plotzlichen Querschnittsveranderung wurden ermittelt. Die Einflusse der Eigenschaften der festen Phase (Partikelgrose, Partikelgrosenverteilung, Partikelform) und deren Konzentration (40–65 Gew.-%) auf das Fliesverhalten der Suspensionen wurden untersucht. The capillary rheometry measurements of concentrated suspensions of aluminum oxide hydroxide in silicon oil are described. The dimension of the extrusion dies was varied. The shear-stress curves and the pressure drop at sudden reduction of the cross section were ascertained. The influence of the properties of the solid phase (particle size, particle size distribution, particle geometry) and the concentration of the solid phase (40–65 wt.-%) on the flow behavior of the suspension were also investigated.