Waxy oils: Deformation-dependent materials

Waxy oils are thermal and shear dependent materials as the initial and final cooling temperatures, cooling rate, shear rate applied during the cooling and the aging time affect the rheological properties of the material. As reported in recent papers, the waxy oil equilibrium flow curve is not only a function of thermal and shear histories but also of the maximum shear rate imposed on the sample. In the current work, the effect of the shear history on the flow curve of model waxy oils is revisited by carrying out controlled shear rate experiments in rotational rheometers. The experiments consisted of imposing different shear rate plateaus for different times so as to provide the same total shear deformation. The same flow curve was obtained. These findings change the perspectives for proposals of new constitutive equations of these materials.