Rheological predictions of dispersion of powder in ceramic injection molding mixtures.

The process variables of mixing to improve the dispersion of powder in ceramic injection molding mixtures were examined for mixtures consisting of polyethylene and different kinds of ceramic powders. The dispersion in the mixtures mixed under various conditions was evaluated using the dynamic rheological measurements of the mixtures. The degree of dispersion in the mixtures was highly influenced by the mixing temperature and mixing speed of the mixer. With increasing mixing temperature the viscosity of the mixtures increased, and the degree of dispersion in the mixtures reduced as the particle size became smaller. On the other hands, dispersion in the mixtures was improved with decreasing mixing temperature. This improvement in the dispersion resulted from the increase in the mixing strength of the mixer to break down agglomerates with increasing viscosity of the matrix. Increasing the mixing speed was also a processing parameters that improved the dispersion of powder in the mixtures. Furthermore, a simple rheological model was proposed to evaluate the mixing strength of the mixer to disperse the particles as a function of particle size and particle concentration.