Thixotropy Of Suspensions Research Articles

A Study on the Thixotropy of Egyptian Bentonite Suspensions

The rheology behavior of water bentonite suspensions has been studied through recording the viscosity measurements to study the thixotropy of the suspensions using local Egyptian bentonite at 5.0%, 6.40%, and 7.5.0% concentrations in the a presence of different salt concentration as 0.0 M, 0.01 M, and 0.1 M NaCl according to API stander, rheological data was calculated by viscometer, deriving first the D0 curve, from 600 to 3 rpm, followed by a typical thixotropic loop, getting the U curve from 3 to 600 rpm, and then the D curve from 600 to 3 rpm. Three rheograms have been derived for each suspension after intensive preshearing, from high to low, from low to high, and from high to low shear rates. Positive thixotropy is observed for all suspensions at 0.0 M and 0.01 M but not at 0.1 M salt concentrations. Thixotropic indexes computed from the normal thixotropic loop, low to high to low shear rates, have been computed and vary from positive to negative. The higher the bentonite concentration, the higher the index for the suspensions with no salt, while in the presence of salt, variations of the thixotropy index are obtained with the degree of variation dependent on bentonite concentration and salt concentration The suspension with no salt and 0.01 M salt exhibited thixotropy, estimated from the D0-U curves, while the 0.1-M suspensions showed no thixotropy. Thixotropy indices vary and depend on bentonite type and concentration and on the presence and amount of salt.

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

Abstract 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 ( γ ) 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 γ or positive thixotropy at high γ into negative one with the increase of ts. The suspension with R=0.091 behaved as complex thixotropy when γ is 1022 s−1, and it behaved as negative thixotropy when γ is 10 s−1. Whereas, the suspension transformed from negative thixotropy to the weak complex one as the increase of ts when γ is 170 or 341 s−1. For all the systems, the equilibrium viscosity decreased gradually with ts at the low γ , but the equilibrium viscosity increased with ts at high γ because of the memory effect. The mechanism has been discussed.

Influence of Electrolytes on the Thixotropy of Ferric Aluminum Magnesium Hydroxide‐Montmorillonite Suspensions

The thixotropy of suspensions consisting of ferric aluminum magnesium hydroxide (Fe‐Al‐Mg‐MMH) and Na‐montmorillonite (MT) is examined with special emphasis on the influence of electrolytes. When NaCl or MgCl2 is added into the Fe‐Al‐Mg‐MMH/MT suspension, the thixotropy of the suspension may change (if positive) from positive and complex into negative, but NaCl or MgCl2 can't alter the thixotropic type of a negatively thixotropic suspension. When AlCl3 was added to positive thixotropic system can be transformed to a complex one, whereas a complex and negative thixotropic suspension remains unchanged, for additions less than 0.01 mol/L; when the addition level of AlCl3 increases, all types of thixotropic systems are changed to non‐thixotropic. In addition, NaCl and MgCl2 make the initial viscosity measured after cessation of intensive shearing increase, but the value of the viscosity decreased rapidly with time. The equilibrium viscosity of the suspension decreased gradually with increasing concentrations of NaCl and MgCl2 in the suspension. With increasing concentration of AlCl3, the equilibrium viscosities of the positive thixotropic suspension and the complex thixotropic suspension increase at first, but decrease later, and the equilibrium viscosity of negative thixotropic suspensions decrease gradually.