Journal of the European Ceramic Society vol:18 issue:8 pages:1001-1009
The article is devoted to the numerical simulation of the thermal debinding process during powder injection moulding. The model of the binder removal incorporates both main transport mechanisms during debinding, namely, the diffusion of the low molecular weight component and the forced or capillar flow of the binder. Optimization of the heating regimes is proposed to be based on the prediction of the internal stress distribution in the workpiece. Internal pressure is induced by the swelling of the binder during thermal degradation of the polymer or its shrinkage, accompanying the loss of the low molecular weight component. Calculations were accomplished for poly-alphamethylstyrene as organic vehicle for which sufficient data are available. The stress distribution and damage conditions were assessed in the case of a cylindrical and a slab shaped workpiece. The results of the modelling correspond well with experimental data. They confirm that damage during thermal debinding can be explained as a result of the development of internal stresses due to imbalance between degradation of the polymer and outward transportation of resulting products. (C) 1998 Elsevier Science Limited. All rights reserved.