Nonlinear Viscoelastic Behavior of Silica-Filled Natural Rubber Nanocomposites

The nonlinear viscoelastic behavior of the composites of natural rubber filled with surface-modified nanosilica was studied with reference to silica loading. The effect of temperature on the nonlinear viscoelastic behavior has been investigated. It was observed that Payne effect becomes more pronounced at higher silica loading. The filler characteristics such as particle size, specific surface area, and the surface structural features were found to be the key parameters influencing the Payne effect. A nonlinear decrease in storage modulus with increasing strain was observed for unfilled compounds also. The results reveal that the mechanism includes the breakdown of different networks namely the filler−filler network, the weak polymer−filler network, the chemical network, and the entanglement network. The model of variable network density proposed by Maier and Goritz has been applied to explain the nonlinear behavior. The activation energy of desorption was calculated and found to be within the range of Van der Waal’s interaction energy. The model fits well with the experimental results.