Solvent de-binding of water-soluble binder in powder injection moulding
(State Key Laboratoryfor Powder Metallurgy,Central South University of Technology, Changsha 410083, P.R.China)
Abstract: The solvent debinding of water-soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent debinding rate. After studying the debinding of a green part with a thickness of 4.26mm, it was found that, the debinding rate of polyethylene glycol(PEG) in water and alcohol was high initially, and then decreased; however, it would increase with temperature increasing. At room temperature, the dissolution rate of PEG in water was higher than that in alcohol, but the latter would be much faster with temperature increasing because the debinding activation energy in alcohol was 51.44 kJ·mol-1·K-1, much higher than 24.23 kJ· mol-1·K-1 in water. With a green part thickness larger than 4.26mm, the debinding was controlled by diffusion; but with that smaller than 2.36 mm, the debinding was controlled by both dissolution and diffusion.
Key words: powder injection moulding; water-soluble binders; solvent debinding