Combined study of structure and dynamics in simplified industrial nanocomposites silica/SBR
Résumé
Since 1992 and the apparition of highly dispersible silica as a nanofiller in the green-tire formulation, the structure and dynamics of precipitated silica-SBR nanocomposites produced by solid phase mixing is of a great interest for manufacturers. In this work, we make use of SAXS and TEM to investigate the organization of silica nanoparticles (Rsi 10nm) varying the filler fraction while dynamics is studied by broadband dielectric spectroscopy (BDS) and rheology. The structural analysis of such complex materials revealed a multi-scale filler organization based on a 3D fractal network built up from aggregates made of nanoparticles [1]. The characteristics (size, average aggregation number, compacity...) of such aggregates are extracted from a combined analysis of SAXS and TEM data taking into account the aggregate polydispersity (Nagg50, 35%). Jointly with mechanical experiments, this analysis enables us to estimate the critical aggregation volume fraction at which the network fully percolates (Figure 1a). In the same context, the ionic conductivity () measured by BDS at high temperature displays a jump from 12.7% of silica that we associate with the percolation threshold observed in rheology (Figure 1b). Moreover, at lower temperatures, a Maxwell-Wagner-Sillars process related to the charges blocked at the interface between silica and polymer is observed at temperatures higher than the glass transition in the nanocomposites.