Injection moulding of alumina with partially water soluble binder system and solvent debinding kinetics

A partially water soluble binder system was successfully derived and tested for injection moulding of alumina powder. The major binder of the binder system was comprised of poly(2-ethly-2-oxaline) and polyethylene glycol and these constituents formed the water soluble fraction of the system. The rheological properties of the feedstock were investigated systematically over a temperature range of 120 to 160 degrees C and a shear rate range of 100 to 1000 s(-1). Binder removal was accomplished using a two stage process. The water soluble constituents were removed by water leaching. The remaining binder constituents were removed by thermal pyrolysis. The solvent debinding kinetics of the water leaching process were studied as a function of temperature, ranging from 40 to 80 degrees C. Solvent debinding is a two stage process consisting of dissolution and diffusion. In this study, dissolution was the rate limiting step during the first stage of water leaching over a leaching time of 90 min at 40 degrees C. As the process proceeds, it is shown that diffusion becomes the rate limiting step.