EFFECTS OF STERIC AND HYDROPHOBIC FORCES ON THE RHEOLOGICAL PROPERTIES OF ZRO2 SUSPENSIONS

The effect of pH on the how behavior of ZrO2 suspensions containing po lyacrylic and octanoic acids was evaluated. In the flocculated pH regi me, the flow behavior is highly shearthinning and can be described by a power-law model. The shearthinning behavior increases with increasin g degree of flocculation. Maximum shearthinning was observed at the ze ro zeta potential condition. Hydrophobic interaction arising from adso rbed octanoic acid was found to enhance the shearthinning behavior. No such enhancement was observed for adsorbed polyacrylic acid. It was a lso illustrated that the viscosity-pH behavior is a mirror image of th e yield stress-pH behavior. A quantitative particle-pair interactions model incorporating steric and hydrophobic interactions was proposed t o explain the effects of polyacrylic and octanoic acids on the maximum yield stress.