Influence of deagglomeration and carboxymethyl cellulose binders on rheological behaviour of kaolin suspensions

The influence of adding two carboxymethyl cellulose (CMC) binder/thickening agents with different molecular weights on the rheological behaviour of kaolin suspensions has been investigated in the presence of ammonium polycarbonate as dispersant. Ball milling performed deagglomeration of the kaolin. The suspensions were prepared at different solid contents from 20 to 45 vol.%, and the rheological measurements were made on these suspensions (nondiluted systems) and compared with those performed on suspensions containing the same solid volume fractions but derived from a more concentrated one (45 vol.%) by adding the required amounts of water (diluted systems). The experimental results showed that at given solid loading, diluted systems are less viscous and pack better than nondiluted ones. This indicates that in the range of solid concentration studied, increasing the solid volume fraction enhances deagglomeration of kaolin particles. The rheological effects of adding CMC binder/thickening agents strongly depended on the amount added, molecular weight (M-W), and the suspension preparation procedure. The strong thickening effect was generally observed for the higher M-W CMC, followed by the mixture of both, although a different sequence has been observed for the more concentrated and nondiluted systems. Slip casting experiments were also performed in order to correlate the flow characteristics of the suspensions with their ability towards packing. (C) 2003 Elsevier B.V. All rights reserved.