CHARACTERIZATION OF SUBMICRON ALUMINA DISPERSIONS WITH POLY(METHACRYLIC ACID) POLYELECTROLYTE

Colloidal dispersion of two submicron alumina powders (A-16SG and APA- 0.2) and their mixtures were investigated in an aqueous suspension wit h and without dispersant (ammonium salt of poly(methacrylic acid), PMA AN). The zeta-potential and isoelectric point (iep) of the powders in aqueous solution were determined in the presence of the dispersant and electrolyte (NaCl). The adsorption of dissociated PMAA(-) on alumina powders was determined via the titration technique. The dispersant was observed to exert a strong influence on the surface potential, flowin g behaviors and packing densities of the aluminas. The results showed that the dispersion conditions were strongly affected by factors inclu ding the solid concentration of submicron alumina particles, the pH va lue and the concentration of PMAAN in the suspensions, and that these three factors were cross-influencing, A reaction model at the interfac e of alumina-solution was developed, based on the dissociation of PMAA N and the adsorption of surface hydrocarboxyl groups on alumina surfac e.