Elucidating the particle concentration-dependent flow behavior of aqueous TiO2 suspensions based on polymer dispersant structures and interparticle surface distances

Abstract

Flowing behavior of concentrated aqueous TiO2 suspensions was evaluated in relation to the structure of polymeric dispersants, their adlayer thickness on particle surface, and particle concentrations. Comb-type polymeric dispersants comprising polyethylene glycol-based side chains with different combinations of unit number and side chain length were investigated. Based on particle concentration–apparent viscosity curves of the suspensions with TiO2 nanoparticles saturated with dispersants, maximum packing fraction and polymer adlayer thickness were estimated through the Krieger–Dougherty model. When the steric repulsive force of polymer dispersant dominated van der Waals attractive forces, the flow curves of the suspension exhibited hysteresis characteristics as the average particle surface distance approached the adlayer thickness of polymer dispersants. Additionally, by introducing the concept of relative surface distance, which is the average particle surface distance divided by the adlayer thickness, the particle concentration dependency of the suspension viscosities with different dispersants followed a unified trend.