Impact of milling conditions on the effectiveness of chemical additives in suspension preparation

Electrosteric and electrostatic stabilization of a commercially available boehmite powder in water was investigated for the purpose of performing milling experiments to reduce the particle size to the nanoscale range. The effect of commercially available dispersing agents based on polyacrylic acid as well as nitric and acetic acid on the particle properties in aqueous slips was assessed by electroacoustic measurements in comparison with rheological tests. Adsorption of the polyelectrolyte was investigated through measurement of the chemical oxygen demand (COD) in the background solution for detection of the amount of additive adsorbed on the particle surface and ATR-FTIR measurements for analysis of the adsorption mechanism of the polyacrylate. Milling resulted in a significant loss of the stabilizing effect of the commercial polyacrylic deflocculant Dispex HDN due to the application of mechanical energy. The reason for this was studied and the feasibility of milling of the boehmite powder in a ball mill determined.