Influence of dispersant structure on the rheological properties of highly-concentrated zirconia dispersions

Twelve dispersants with different molecular structure features have been compared for their ability to produce low-viscosity suspensions of yttria-stabilised zirconia in organic media. The relationship between the molecular structures and their influence on the rheological properties of YSZ was studied. The effectiveness of a dispersant is mainly determined by its ability to adsorb onto the surface of the powder dispersed in the organic medium, and adsorption of a dispersant was found to be strongly promoted if a chelate ring could be formed with the powder surface. Rheological measurements showed that Solsperse3000, a pentastearic acid oligomer, was the best dispersant for the powder in question. This is explained in terms of the longer chain length of the surfactant molecule. The effectiveness of this dispersant was investigated in five different organic media. Solid loadings up to 52.5 and 55 vol.% with submicron- and micron-powder, respectively, could be reached using Solsperse3000 as the dispersant and terpineol as the organic medium.