Anomalous shear viscosity–temperature behaviour of jojoba oil/LDH-stearate suspensions

• LDH-stearate suspensions in jojoba oil form weak gels above 20 wt.%.
• When shear is applied the structure breaks down and bulk flow results.
• The shear viscosity shows unusual temperature dependence.
• It more than doubles when temperature increases from 25 °C to about 40 °C.
• The explanation lies in a temperature-driven delamination of the clay sheets.

Stearate intercalated layered double hydroxide was synthesized by reacting the corresponding carbonate form with a large excess of stearic acid. Thermal analysis, FTIR, XRD and SEM–EDS characterization indicated the formation of a highly crystalline bilayer-intercalated product. The composition of the inorganic portion showed high variability in the Al:Mg atom ratio. This suggests that the crystals comprised stacks of randomly interstratified layers that varied in compositions from one close to magnesium stearate to one similar to aluminium distearate. The rheology of the jojoba oil suspensions containing this material showed strong shear thinning behaviour and also an anomalous temperature dependence.

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