Nonlinear Rheology of Model Filled Elastomers

Submitted to large sinusoidal strains, filled elastomers not only show a decrease in their storage modulus - the Payne effect, but also a nonlinear behavior - their response is not sinusoidal anymore and involves strain-stiffening. We show in this study that the two effects can be separated thanks to large amplitude oscillatory shear experiments. The stress signal of filled elastomers consisting of a dispersion of silica particles into a polymeric matrix was decomposed into an elastic and a viscous part and we could observe simultaneously the Payne effect and a strain-stiffening phenomenon. We showed that the strain-stiffening was correlated with the Payne effect but came from various intricated effects. It most probably also has its origins in the finite extensibility of the polymer chains confined between solid particles, where the strain is larger. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2490-2496, 2010