Microscopic Origins of Dynamic Mechanical Properties of Filled Rubber Investigated with X-ray Photon Correlation Spectroscopy*

The mechanical properties of nanoparticle filled rubber are largely determined by the structure of the filler network and filler/polymer interactions. These reinforced rubbers have broad commercial utility, such as use in tire tread technology. The dynamic mechanical properties of these systems have a major impact on tire safety and fuel economy. Despite their importance, the connections between microscale filler behavior and macroscale performance are not well understood. Recent developments in X-ray photon correlation spectroscopy (XPCS) allow us to probe the microscale dynamics of filler particle networks and determine how this influences macroscale properties. We have used in-situ XPCS on styrene-butadiene rubber (SBR) filled with silicas of different surface chemistries under dynamic strain to probe the rearrangement of the filler network. We draw connections between the filler/polymer interaction and the resulting network structure, filler dynamics, and macroscopic properties.