Thixotropic Recovery

Quick Start

Thixotropic recovery (return of a pre-sheared system to its low-shear value) can be analysed via a low-frequency, low-strain oscillatory analysis.

Thixotropic Recovery

Power law n
tmax s
Log(G or η)

One way of examining thixotropy is via a Thixotropy Hysteresis loop using rotational viscometry. The method here is to provide a strong rotational pre-shear then use a gentle oscillation ~1Hz and low strain (typically 1-2%) to measure the recovery of G', G'' and (therefore) η*. The basic rule seems to be that recovery follows a low power law. If the value of (say) G' after high shear is G'0 and fully recovered is G', then at time t, G' is given by a power-law equation:

G't = G'

Such an equation doesn't give a levelling out to G' so for pragmatic purposes the graph assumes that G' is reached at 3.tmax, the maximum timescale used in the experiment. This means that A=G'/(3.tmax)n

The other inputs are Tanδ at t=0 and t=tmax, with an assumed power-law change from one to the other

The complex viscosity, η* is G* multiplied by the oscillation frequency, assumed to be 1Hz.