Role of Glassy Bridges on the Mechanics of Filled Rubbers under Pressure

We address the question of the equivalent role of the pressure and temperature on the mechanical properties of highly filled elastomers. It is well-known that in polymer matrixes the equivalence of temperature and pressure results from free volume variations. Our measurements performed on phenylated polydimethylsiloxane (PDMS) chains filled with silica particles show that a temperature-pressure superposition property is still observed in both linear and nonlinear regimes in these systems. However, the temperature-pressure equivalence involves coefficients that are 2 orders of magnitude larger than those in nonreinforced matrixes. We suggest that the mechanical response of the filled elastomers is controlled by the shape of the rigid network made by fillers that are connected by rigid polymer bridges. In this frame, we provide quantitative evidence that the macroscopic behavior of reinforced elastomers is controlled by the variation in the degree of the confinement of polymer chains between particle surfaces.