Elucidation of the Mechanism Underlying the Payne Effect in Filler-Reinforced Rubber Using in-operando X-ray Photon Correlation Spectroscopy

Our relentless pursuit of improved vehicle performance and safety is driving in-depth research into advanced tire technology. A critical issue in the industry is a significant decrease in the storage modulus under cyclic loading, often attributed to the Payne effect. There is growing evidence that mechanical reinforcement occurs when fillers are bridged by polymer chains adsorbed on filler surfaces, forming percolating structures. The Payne effect is therefore expected to be related to the breaking of polymer-mediated bridges under local stress. However, the understanding of the structures and dynamics of filler networks remains challenging due to the lack of experimental tools capable of providing the information at the relevant length and time scales. Here, we employ XPCS with oscillatory deformation to study the evolution of the structures and dynamics of the filler network and the mechanical properties. Crosslinked silica (SiO₂, 17 nm diameter) filled polybutadiene (PB, Mw= 200 kg/mol) rubber was used. In addition, a silane coupling agent (bis(triethoxysilylpropyl)polysulfide) was added. A relationship between the structural and dynamic irreversibility of the filler network and the nonlinear mechanical property as a function of strain magnitude will be discussed.