Superposed nonlinear rheological behavior in filled elastomers

Abstract

In the present work, the rheological properties of a number of filled elastomers under oscillatory shear conditions are investigated. In both linear and nonlinear regimes, the relationships between moduli (G′ and G) and strain amplitude (γ₀) in response to the frequency change display constant shifts along the vertical direction, leading to a striking superposition of the curves. We show that this superposition via a change of its independent-variables can directly lead to a strain-rate frequency superposition. The underlying principle is that the measured dynamical properties can be separated into a linear viscoelastic frequency-dependent part and a nonlinear strain-dependent part. This frequency-deformation separability is experimentally valid for various rubber compounds that differ widely in the polymer structure, the chemical composition, and the type of the filler as well as the shape, the average size, and the distribution of the particles.