Ferrofluid with clustered iron nanoparticles: Slow relaxation of rheological properties under joint action of shear flow and magnetic field

The influence of vinegar concentrations on the rheological properties of 40% (w/w)sunflower oil-in-water emulsions stabilized with 7% (w/w) gelatinized bambara groundnut flour (BGNF) was investigated. The rheological properties of interest were steady shear, time dependent and viscoelastic characteristics. Rheological characterizations of the emulsions were carried out using a shear rate controlled rheometer. Both emulsions with and without vinegar were pseudoplastic, thixotropic and viscoelastic fluids. Vinegar however, significantly (p < 0.05) affected 
rheological properties of BGNF-stabilized emulsion. Vinegar in the emulsion decreased extent of thixotropy, pseudo plasticity and viscoelasticity of BGNF-stabilized emulsions. The results indicated that the rheological properties of BGNF-stabilized emulsion can be controlled and manipulated using vinegar however, the presence of vinegar in BGNF-stabilized emulsion may be deleterious to 
the emulsion. The result provided the information to understand the influence of vinegar on the rheological properties of BGNF-stabilized emulsions for product and process development.

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Rheological Properties of Sunflower Oil-in-Water Emulsion Containing Vinegar, Stabilized with Gelatinized Bambara Groundnut Flour

A phenomenological model for dispersed systems which exhibit complex rheological behaviour such as shear and time-dependent viscosity, yield stress, and elasticity is proposed. The model extends the Quemeda model to describe the viscosity function with a structural parameter λ which varies according to different kinetic orders of particle aggregation and segregation. The transient stress response is obtained by solving an instantaneous Maxwell model with an assumed shear modulus functionG of the same form as the viscosity function η. Accuracy of the proposed model is verified experimentally with the results obtained for two oil (creosote)/water emulsions. The model that gives the best fit of experimental data appears to be the one with kinetic ordersn=m=2.

Fang Tunan

Papers

Steady-shear viscosity and transient stress response for elasto-thixotropic fluids