APPLICATION OF AN EQUIVALENT STRAIN AT EQUAL STRESS PRINCIPLE TO THE DYNAMIC HYSTERESIS OF CARBON-BLACK-LOADED AND OIL-EXTENDED SBR.

Rubber hysteresis is the mechanical energy that is lost or dissipated as heat during deformation of the material. Addition of carbon black to a gum stock increases the hysteresis by an amount depending on the type and loading of carbon black. In the reported investigation, a principle of equivalent strain at equal stress has been applied to dynamic measurements of hysteresis. At 24 degree C and 25% ptp dynamic strain, the relation of hysteresis to strain amplitude and the equivalence principle lead to an expression which describes the measured hysteresis of SBR-1712 filled with a wide variety of carbon black types and loadings to within about plus or minus 25%. At 105 degree C and 25% strain, the exerimental results are much larger than the theory predicts. The deviations of the results from the theoretical predictions which are not described by the rate of change of elastic modulus with strain amplitude appear to be a function of carbon black surface area, structure, and loading.