Dielectric & Dynamic response of emergent hierarchical filler networks in polymer nanocomposites*

Commercial nanocomposites such as tire compounds are composed of dispersions of carbon black/silica mass fractal aggregates in an elastomer/oil blend, the performance of which is related to the nano-aggregate network structure, the interfacial chemical affinity and extent of dispersion based on accumulated strain. These composites display a complex hierarchical structure intimately tied to their inherent incompatibility and processing history. On the nanoscale carbon black displays primary particles aggregated into mass fractal aggregates that percolate locally above about 5wt.% into a network cluster. In the linear viscoelastic regime, this network dictates the high-frequency response.¹ At higher concentrations near 20wt.% the local aggregated clusters agglomerate into a micron-scale mass fractal network associated with electrical conductivity that influence the gel-like dynamic response at low frequencies.² The impact of the inherent particle structure, the attributes of the nano-scale and meso-scale networks on the dynamic and electrical moduli of these systems was explored using different industrial grade carbon blacks.

¹K. Rishi et al., Macromolecules 51, 7893 (2018)
²H. H. Winter et al., Colloid Polym. Sci. 266, 494 (1988)