Effects of C_nTAB Chain Length and Concentration on the Rheological Properties of Aqueous Suspensions of Alkylated Alumina Powders

Abstract

Alumina particles have successfully been alkylated via a condensation reaction between surface hydroxide sites and different, long chain alcohol molecules, specifically decanol, dodecanol, and octadecanol. These hydrophobic particles have been successfully dispersed in water using different C n TAB surfactant molecules, where n 5 10, 12, 14, 16. The effect of the length of the surfactant molecule and its concentration was quantified with rheological experiments. Rheology and conductivity measurements were used to determine the minimum amount of the surfactant needed to disperse the alkylated powder. Slurries formulated with the alkylated powder and the proper amount of C n TAB exhibited Newtonian rheology for n ! 10. n potential measurements showed that the surface charge on the particles was always positive confirming that the C n TAB molecules, with a positive head group, surrounded the alkylated particles. Such powder did not have an isoelectric point. In addition, the Newtonian behavior of the alkylated-alumina/C n TAB slurry systems were independent of pH.