Kinetic modelling of binder removal in powder-based compacts

Binder burnout kinetics has been simulated using a “shrinking core” model for powder compacts and powder/fibre compacts. The model takes into account polymer decomposition, monomer diffusion in the core region and gaseous transport in the porous outer layer. Both cylindrical and plate compact geometries were considered. It is noted that a relatively longer time of debinding is required for the plate geometry. Experimental results with cylindrical powder compacts showed good agreement with the model prediction. The effects of compact size and shrinkage, fibre volume fraction and orientation on the burnout kinetics have been studied. It was found that the burnout time is increased with compact size and by compact shrinkage. Fibres aligned perpendicularly to the removal direction require the longest burnout time, while fibres aligned parallel to the removal direction provide faster diffusion paths along their surfaces and facilitate the burnout process. For all the cases, a higher fibre volume fraction leads to a more significant effect.