The effect of liquids on the dynamic properties of carbon black filled natural rubber as a function of pre-strain

A free oscillation technique has been adopted to measure the dynamic storag e and loss moduli of carbon black filled natural rubber materials. These te sts are conducted with small oscillations that are superimposed on a range of tensile pre-strains. Tn addition, the effect of temperature on the dynam ic moduli is measured as well as the effect of swelling the materials to va rious extents by liquids with a range of viscosity. It is observed that the dynamic storage and loss moduli do not depend strongly on the pre-strain a t small pre-strains. At higher pre-strains there is a marked increase in bo th the storage and the loss moduli. An increase in temperature causes a dra matic reduction in both the storage and loss moduli. The dynamic behaviour of the filled rubbers when swollen can be approximately ascribed to the com bined effects of a reduction in the modulus of the rubber matrix (caused by the swelling action) and a reduction in the effective volume fraction of t he filler. The liquids used had a range of viscosity of more than a factor of a thousand. Despite this, the loss moduli of the swollen rubbers varied by only about a factor of two. This insensitivity could be understood in te rms of a previously developed theory, based on free volume considerations. (C) 2000 Elsevier Science Ltd. All rights reserved.