Uncovering the structure-dynamics-property relationship of reinforced rubbers

Tires are a key component of automotive supply chains, and as the only vehicle part that touches the road, they contribute greatly to vehicle safety and fuel efficiency. In this presentation, we aim to establish the structure-dynamics-property relationship of a model rubber under the driving conditions using in operando X-ray Photon Correlation Spectroscopy (XPCS) experiments. Cross-linked silica (SiO₂)-filled polybutadiene (PB, M_w=200 kg/mol) served as a rational model, featuring 17 nm-size fillers with volume fractions of 0.05-0.3, compounded with silane coupling agents, sulfur, and standard vulcanization agents in the PB matrix. Since automobile tires are typically subjected to cyclic applied stress, the so-called speckle echo XPCS measurements under repetitive tensile were performed at room temperature to capture the irreversible rearrangements of fillers associated with the yielding of a material. We captured speckle patterns and compared them at given strain amplitudes and oscillation frequencies from which one-time correlation functions were determined in the directions parallel and perpendicular to the stretching direction. We will discuss the effects of filler loadings and the magnitudes of strain on a connection between the “nanoscopic” irreversibility of filler rearrangements and macroscopic nonlinear deformation.