  This paper exposes an extension of an activation model previously published
by the authors. When particles arranged along the compression axis of a sheared
suspension, they may overcome the electrostatic repulsion and form force chains
associated with shear thickening. A percolation based consideration, allows an
estimation of the impact of the force chains on a flowing suspension. It
suggests that, similar to mode-coupling models, the suspension becomes unstable
before the critical stress evaluated from the activation model is reached. The
theory is applicable only to discontinuous shear thickening, and the
predictions are compared with results from two experimental studies on aqueous
suspensions of inorganic oxides; in one of them hydration repulsion and in the
other hydrophobic attraction can be expected. It is shown that the
incorporation of non-DLVO forces greatly improve predictions of the shear
thickening instability.
