Nanoparticle Avalanches in Filled Rubber

Nanoparticle reinforced rubbers have broad commercial utility, such as use in tire tread technology. However, the complex microscale behavior of the filler particle network and the resulting macroscopic properties are not well understood. Recent X-ray Photon Correlation Spectroscopy (XPCS) experiments performed in-situ on rubbers under strain reveal previously undescribed filler network behavior which is not considered in current physical models of these materials. Rubbers under strain exhibit temporally heterogeneous dynamics, i.e. the particles which constitute the filler network show abrupt speeding up and slowing down, akin to the dynamics of granular systems such as sand and snowpack which exhibit avalanche-like behavior. These nanoparticle “avalanches” significantly influence macroscopic properties such as stress relaxation and the storage modulus of filled rubber. Further, the addition of silane coupling agents to filled rubber and resultant bound rubber layers generated on the filler particle surface strongly suppress the intermittency of the filler dynamics. 

We thank Dynasol Group for funding and sample preparation. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-

AC02-06CH11357.