Master debinding curves for solvent extraction of binders in powder injection molding

Abstract

This study successfully extends the master sintering curve concept to model removal of polymeric binders in powder injection molded bodies. In this demonstration the focus is solvent debinding. Master debinding curves (MDC) were used to estimate the activation energy for debinding. Binder removal curves were developed for solvent extraction of polyethylene glycol (PEG) from injection molded shapes made from silicon nitride doped with yttria and spinel (Si3N4 5% Y2O3 5% MgAl2O4). The extraction for different shapes incorporated a shape parameter in the standard master curve equation, giving activation energy of 12.4 kJ/mol extraction of PEG. Master debinding curves were also developed for wicking debinding. The analysis showed lower activation energies for solvent extraction and wicking compared to thermal debinding. The lower activation energy suggests easier removal by solvent or wicking versus pyrolysis. The study provides a unifying quantitative framework for comparing and predicting the effects of material, process and geometry on binder removal. The master debinding curves can be utilized in design and optimization of binder removal. (C) 2012 Published by Elsevier B.V.