Critical thickness in binder removal process for injection molded compacts

The conception of the critical thickness was presented through the analysis of debinding kinetics. It was found that there was a critical compact thickness, at which the kinetic controlling step during debinding transforms from liquid diffusion control to vapor transportation control. When the critical thickness is large, the temperature can be increased relative rapidly during the initial stage of debinding. The debinding time can be shortened. While the critical thickness is small, the temperature should be increased slowly during the initial stage of debinding to avoid defects such as blister, crack and deformation, etc. The larger the critical thickness, the more easily the binder removal process can be carried out. The effects of the powder particle size, the debinding temperature and the powder loading on the critical thickness were investigated. The critical thickness is proportional to the particle size. The larger the powder particle is, the larger the critical thickness is. The critical thickness is inversely proportional to the holding temperature. The higher the holding temperature is, the smaller the critical thickness is. The critical thickness is inversely proportional to the powder loading. The higher the powder loading is, the smaller the critical thickness is. (C) 2003 Elsevier B.V. All rights reserved.