Characterization of thixotropic materials and modification of the Weissenberg rheogoniometer

A Weissenberg Rheogoniometer, Model R-18, was modified to give complete rheological curves without resetting the gearbox and generate hysteresis loops for time-dependent, non-Newtonian materials. This modified instrument was used to analyze a number of materials. Standard Newtonian and known time-independent, non-Newtonian materials were studied to insure the accuracy of the instrument. Results indicated that the instrument would reproduce known viscosities of these materials, give consistent results, and not display inherent hysteresis loops with non-thixotropic materials. Materials known and suspected to be thixotropic: silicone grease-oil mixture, montmorillonite clay, and blood were tested. All displayed the characteristic hysteresis loop usually associated with thixotropic materials. The Huang rheological equation was tested on the thixotropic materials. Having 5 constants which must be evaluated, the final equation with parameters can accurately generate a hysteresis loop for a thixotropic material. It can also generate multiple hysteresis loops using the same 5 constants