STUDE OF EFFECT OF DEFLOCCULANTS ON THE RHEOLOGICAL BEHAVIOR OF а-ALUMINA SUSPENSIONS
Comparative studies have been carried out on the effectiveness of various commercially available polyphosphates and polycarboxylate esters used as deflocculants in aqueous suspensions of reactive alumina. Finely dispersed alpha-alumina is prepared by dry grinding of calcined alumina. The resulting powder has a median particle diameter of D50 = 2.4 microns, S (BET) = 1.4 m2/g. The dosage of polycarboxylate esters in suspensions was 0.17 and 0.34 wt.°%, and polyphosphates - 0.10 and 0.25 wt.% by weight of reactive alumina powder. All defloculated suspensions in the shear rate range of less than 20 s-1 can be characterized as non-Newtonian structured liquids having a certain yield strength of T0. With an increase in the shear rate above 20 s-1, the values of the apparent viscosity of all the suspensions studied decrease significantly, and the dependences of т = f(y) become rectilinear. The measured flow curves т = f(y) were satisfactorily approximated by the Casson model. The calculated values of the yield strength т0 allowed us to give a comparative assessment of the degree of flocculation of suspensions with additives of various dispersants. The amount of shut-in water significantly affects the fluidity of reactive alumina suspensions. For a sample defloculated with an additive based on polycarboxylate ether Sinteflou DM50 0.17 wt.%, a decrease in the solid phase content from 84 to 78% increases the fluidity of the suspension by about 4 times.