Deformational Behavior of Rubber in a Variable Speed “Mooney” Rheometer

Because the Mooney Rheometer is widely used and accepted in the laboratory and the plant a closer examination of what it measures is warranted. Although the steady torque value has been converted to steady-state viscosity, the “Mooney torque—time curve” has not been reduced to fundamental parameters. This work, carried out with SBR 1500, treats the initial torque rise as the shear stress-strain behavior analogous to tensile stress-strain. A master curve was constructed from such data obtained at various speeds using a principle of corresponding states. The master curve closely resembles the steady-state viscosity curve and at high shear rates joins the complex viscosity curve measured with the Rheovibron. In addition the use of the transient data enables one to extend the low shear end of the viscosity-rate curve by two decades. The peaks of the torque—time curves strongly suggest that they represent failure points of the material.