The effect of particle wettability on the of rheology particulate suspensions with capillary force

Abstract

We examined the dependence of the rheology of capillary suspensions on particle wettability using model ternary liquid/liquid/particle mixtures. Experiments were conducted using silica particles suspended in a majority liquid phase, to which a small minority of a second liquid was added. Silane modification was used to realize three different particle wettabilities ranging from particles being fully-wettable by the minority fluid, to being almost completely non-wettable by the minority liquid. In all three cases, the ternary suspensions showed solid-like behavior, with the yield stress and modulus decreasing as particles became less wettable towards the minority fluid. In all three cases, the minority liquid was found to induce particle aggregation into percolating networks which are responsible for the solid-like rheology. Our results suggest two reasons why the solid-like properties of such suspensions diminish as the particles become less wetting by the minority fluid: because particle network relies on multi-particle capillary clusters (rather than pair-wise meniscus binding), and because a certain fraction of particles become too non-wettable to participate in the network.