RHEOLOGICAL CHARACTERISATION OF SHEAR THICKENING TIO2 SUSPENSIONS IN LOW MOLECULAR POLYMER SOLUTION [Review]

摘要

The rheological behavior of titanium dioxide (rutile) suspensions has been investigated under steady shear conditions in order to study the influence of disperse phase concentration. The solid particles were dispersed in a Newtonian vehicle, made of epoxy and acrylic resins dissolved in a solvent mixture at different solid volume fractions Phi, ranging from 0.16 to 0.40 (the values do not take account of resin components). The suspensions examined exhibit a Newtonian plateau at very low shear stresses and shear thinning behavior in low and moderately high shear stress re ions. At a solids volume fraction Phi higher than 0.20, the onset of shear thickening behavior is observed in the highest shear stress region. For these suspensions, time-dependent effects can be assumed negligible even at the highest particle concentration examined and the shear-dependent behavior is almost reversible as is usually found for stabilised suspensions. A satisfactory fitting of both shear-thinning and shear-thickening behavior is given for the suspensions examined by modified versions of the Krieger/Dougherty and Cross equations. Accordingly, the critical shear stresses and shear rates for the relevant conditions are defined. A thorough analysis of the whole data set clearly shows that the modified filers equation provides the best correlation for the concentration dependence of relative viscosity, on condition that shear stress is used as a proper reference quantity instead of shear rate. (C) 1997 Elsevier Science S.A. [References: 36]