Avaliação reológica experimental do comportamento tixotrópico de uma solução de laponita-RD®

Abstract

The present work presents the methodology and results obtained for the study of a thixotropic fluid, Laponita-RD® solution. The objectives of this work were the formulation of a stable solution of the material and the evaluation of the behavior of this fluid in four distinct possible conditions: (a) before the breakdown of the gelled structure; (b) alongside the breakdown; and (c) after the breakdown. The project corroborates measuring methods of the yield stress, in other words, the minimum shear stress required to start a flow, with hair gel, considered an ideal viscoplastic fluid. The critic stresses for several tests were validated and, on oscillatory tests, a direct dependency on the stress amplitude rate was observed. The Laponite-RD® showed critical stresses around a magnitude of ten times less and the thixotropic level of this material when compared to the one measured for the hair gel is expressively higher with respect to the percentage difference of the areas under the curves of the shear rate ramp experiments. The shear rate steps tests evaluated the viscosity as a function of the time. The results unveiled the formulated solution presets repeatability for steady state values and the dynamic of build up and down processes.