In injection moulding of alumina the binder components interacted with the alumina powder by a Lewis acid-base reaction. Among the binder components used, stearic acid played a major role in determining the process behaviour even though its composition was only 4 wt% of the total binder (1.8 vol% of the formulation including powder). The effects of the chemisorbed stearic acid due to the Lewis acid-base interaction were a reduction of the apparent viscosity by a factor of 20, minimized separation of binder from the powder during moulding, but a higher content of binder burnout residue than in the carbonyl-iron system.