The Linear-Nonlinear Dichotomy Behavior for Filled Rubbers in LOAS

Filled rubbers display an unusual linear-nonlinear dichotomy of their rheological responses under large amplitude oscillatory shears, where the amplitude of stress output deviates strongly from the linear dependence of strain, but the time-dependence of stress remains sinusoidal. Increasing the cross-linking density in the rubber matrix tends to favor this quasi-sinusoidal responses. Rising the usage of processing oil in a rubber compound tends to disfavor this dichotomy behavior. Varying the amount of reinforcement fillers seems to be ineffective, as long as the filler loading exceeds its percolation threshold. These observations suggest that the topological structure of polymer chain network in the matrix plays an important role in the linear-nonlinear dichotomy rheology. The agglomeration of fillers and the overall characteristics of the fractal structures of filler clusters may have a less important influence on this phenomenon. A summary of recent research activities at Tongji on this subject will be given.