The importance of crystal morphology on the viscosity of concentrated suspensions of kaolins

The effects of particle morphology on the rheological behavior of high-solids kaolin suspensions were investigated using low shear (Brookfield) and high shear (Hercules) viscometers. The kaolin samples used were: a well-crystallized platy kaolinite from the Rio Capim, Brazil; a spherical halloysite from Spokane, Washington; and a tubular halloysite from Guoshan, Fujian Province, China. The spherical halloysite showed the lowest viscosity, followed by the platy kaolinite and the tubular halloysite. It is postulated that halloysite affects kaolin rheology through modification of particle interactions during flow of high concentration suspensions.