X-ray Photon Correlation Spectroscopy Study of Filled Rubber Under Dynamic Strain Reveals New Details of the Connection Between Filler Network Change and Filler Surface Chemistry*

Despite the broad commercial utility of nanoparticle reinforced rubbers, connections between microscale filler behavior and macroscale performance are not well understood. XPCS allows us to probe the microscale breakdown and reformation of the filler network, which are responsible for the fuel efficiency and traction of tire tread compounds. We report results of dynamic strain XPCS experiments on two silica-filled rubbers, one with a silane coupling agent and one without. The silane coupling agent suppresses filler breakdown and pushes the onset of irreversible agglomerate breakdown towards larger strains. For a high surface area silica, we find that filler network breakdown alone cannot explain energy dissipation. We can explain this behavior by considering the structure and debonding of bound rubber layers. These results show that the combination of XPCS and DMA is a powerful method for understanding how the microscopic filler behavior dictates the dynamic mechanical properties of rubber.