Résumé
Rubber-based nanocomposites prepared by solid-phase mixing with precipitated silica or carbon black are typically strongly aggregated systems with different levels of spatial organization, as highlighted by our group in the past [1, 2]. Our strategy is to investigate such systems based on the study of simplified industrial samples with ingredients limited to a strict minimum. Small-angle X-ray scattering (SAXS) can then be used to study the filler microstructure in rubber nanocomposites with different filler loading. The size and mass of primary particles and small aggregates are determined using a model of inter-aggregate polydisperse hard sphere interactions based on a correlation hole analysis. Another key feature of rubber nanocomposites is the influence of filler surfaces on polymer dynamics, and an original application of dielectric spectroscopy to measure the adsorption isotherm of coating agents on silica embedded in the polymer matrix will be presented. [3] A major advance was then to couple SAXS measurements on synchrotron beamlines with in-situ shear rheology to provide microstructural evidence for macroscopic rheological effects, which leads to disruption of the filler network and subsequent flocculation. The Payne effect has been characterized in rubber nanocomposites filled with carbon black, but with only small signatures in the scattering under oscillatory shear. In parallel, we have also coupled shear rheology with fast acquisition dielectric measurements to follow the change in electrical conductivity due to the destruction/formation of conductive pathways.