Drying and Debinding Behavior of Extruded Pipes Containing a Water-Based Binder

Abstract

Zirconia, stainless steel powders and their composite powders have been extruded using an aqueous solution of a water-soluble polymer, hydroxypropyl methylcellulose (HPMC) as a binder. The powder-binder mixtures were extruded into pipes by a multi-billet coextrusion technique. The drying and debinding behavior of the extruded pipes was experimentally verified. The pore sizes and their distribution in dried extrudates obtained from composite powders depend to a large extent on the mixing proportion of the two powders. The pores due to evaporation of the moisture in the drying process accelerate the elimination of the HPMC polymer by promoting the diffusion of oxygen and degraded products. The presence of some oxygen is necessary in order to remove the HPMC polymer completely. The HPMC may be removed during the heating period of sintering operations without any special debinding treatments, provided some oxygen is present.