THE INFLUENCE OF POWDER LOADING AND BINDER ADDITIVE ON THE PROPERTIESOF ALUMINA INJECTION-MOLDING BLENDS

The effects of powder loading and binder additive on the theology, mou lding, and sintered properties of alumina injection-moulding blends we re studied. The melt viscosity increased with the powder loading, whic h enhanced the defect concentration of the moulded parts when the powd er loading was higher than 0.54 volume fraction. This transitional pow der loading was much smaller than the critical powder loading of 0.65 derived by fitting the theological data with a mathematical model. The low molecular weight acidic binder additives used in this study effec tively reduced the melt viscosity. However, additives that yielded a l arge quantity of burn-out residue deteriorated the sintered properties . A high powder-loading mixture having a low melt viscosity and good p owder dispersion was achieved by eliminating powder agglomerates befor e mixing, and by using an appropriate binder additive.