Strain dependent hysteresis in nanoparticle aggregate dispersions visualized to explain origin of the Payne Effect and Spectral Hole Burning in cross-linked filled rubber

Filled rubbers are composite materials containing two interpenetrating phases: crosslinked elastomers, and a ‘filler’ consisting of nanoparticle particle aggregates. The nanoparticle aggregates form a system-spanning subnetwork that reinforces the elastomer network and introduces a new energy loss mechanism at low strains of only 1-5%. This loss mechanism, known as the Payne Effect, is one of the mechanical hallmarks of filled rubbers and is a major contributor to rolling friction in tires. We create a transparent model system to study the strain dependent hysteresis of nanoparticle aggregates. With this system we can directly observe microstructural changes of filler particle aggregates during in situ shear deformation. We complement these observations with bulk rheological tests, including spectral hole burning, to gain new insight into the microscopic structural changes that occur during cyclic deformation.