The addition of nano-scale fillers to a rubber profoundly changes the mechanical properties. We describe small- and large-amplitude oscillatory measurements of nanoparticle-filled rubbers and some model filled materials. The effect of fillers at various concentrations on the small-amplitude modulus includes an unusual inverse size dependence for small particles that asymptotes to the expected particle size-independent scaling for larger particles. The large-amplitude elastic response can be reduced to master curves that depend only on the maximum amplitude of the deformation, hence the mechanical response to oscillatory loading is insensitive to frequency.
