Influence of measuring conditions on the thixotropy of hydrotalcite-like/montmorillonite suspension

The influence of the measuring conditions on the thixotropy of suspensions, which were made up of hydrotalcite-like compounds (HTlc) and Na-montmorillonite (MT), was studied. Usually, the structure recovery at rest after preshear is considered the fundamental thixotropic process. And the recovery process was performed under the steady shear experiments, then the thixotropic type can be judged according to the recovery process. In this paper, the influence of rest time (ts) and the shear rate (γ̇) on the recovery process was studied. Three kinds of HTlc/MT suspension were studied, their mass ratios of HTlc to MT, which were signed as R (e.g. R=WHTlc/WMT), were 0.013, 0.051, 0.091, respectively. It is found the HTlc/MT suspension with R=0.013 showed positive thixotropy at ts=0, but it changed to negative one with the increase of ts. The suspension with R=0.051 transformed from complex thixotropy at low γ̇ or positive thixotropy at high γ̇ into negative one with the increase of ts. The suspension with R=0.091 behaved as complex thixotropy when γ̇ is 1022 s−1, and it behaved as negative thixotropy when γ̇ is 10 s−1. Whereas, the suspension transformed from negative thixotropy to the weak complex one as the increase of ts when γ̇ is 170 or 341 s−1. For all the systems, the equilibrium viscosity decreased gradually with ts at the low γ̇, but the equilibrium viscosity increased with ts at high γ̇ because of the memory effect. The mechanism has been discussed.