Experimental Clues of Soft Glassy Rheology in Strained Filled Elastomers

Tensile stress-relaxation measurements have been performed on a series of cross-linked filled elastomers. The fillers are chosen to investigate the effect of the filler-filler and the filler-matrix interactions on the time dependence of the tensile relaxation modulus E(t) after UP and DOWN jumps. For the carbon black-filled sample (strong filler-elastomer interaction) E(t) decreases as log(t) when the strain epsilon is strictly larger than 0.2 and reached by UP jumps. For the silica-filled samples in the same conditions, and for all samples after a DOWN jump, including epsilon =0.2, the experimental data can be fitted with a power law equation characterized by the exponent m. Thus, in all cases, |dE(t)/dt| scales as t(-) with ? m + 1. Pertinence of the soft glassy rheology model for interpreting these results is examined. It is shown that could be equivalent to the effective noise temperature x and related to the polymer chain mobility. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 647-656