Modelling Thixotropy Using a Novel Structural Kinetics Approach: Basis and Application to a Solution of Iota Carrageenan

A new methodology for modelling the thixotropy of inelastic fluids is described and its application demonstrated. In order to validate the model, data from two measurement protocols are compared and shown to give coherent results. The structural kinetics approach uses a reduced structural variable, λ, which has values between zero, when the structure is totally broken down, and one, when the structure is complete. The new approach is applied to the thixotropy of a solution of iota carrageenan, a well known food hydrocolloid. Solutions were sheared before testing in order to eliminate their viscoelasticity. The measurement protocols used were: (1) stress jumps from above and below each shear stress tested, and (2) triangular ramp‐up/ramp down stress profiles, often called hysteresis loops. The first series of measurements was used to determine the equilibrium structure and kinetics of structural build‐up and breakdown at each shear stress. This data completely determines the parameters in the thixotropic model and allows prediction of the samples response to any stress/time profile. Without using any additional parameters, this model was then used to predict the shape of the hysteresis loops in the second series of measurements. The agreement between the predictions and measurements was very good, provided that the experimental data was first corrected for the efects of inertia and the finite gap‐width of the rheometer.