## 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

_{0}

_{∞}

_{0}

_{∞}

_{max}s

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'_{0}+A.t^{n}

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

The other inputs are Tanδ at t=0 and t=t_{max}, 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.