Quantifying the 3D multiscale dispersion structure of nanofillers in polymer nanocomposites by combining 3D-STEM and Synchrotron Radiation X-ray CT

Abstract

In this study, a method for quantifying the 3D multiscale dispersion structure of nanofillers including nano-sized primary filler nanoparticles, nano-to sub-micron-sized agglomerates, and micron-sized filler networks in rubber nanocomposites was established for the first time by combining 3D-Scanning Transmission Electron Microscopy (3D-STEM) in a High-angle Annular Dark Field mode and Synchrotron Radiation X-ray CT. By using this method, a model of multiscale dispersion structure of silica (SiO2) in hydrogenated nitrile butadiene rubber (HNBR) nanocomposites with different SiO2-HNBR interactions (If-r) was established. Interestingly, when the content of SiO2 is near the percolation threshold, as the If-r increases, the homogeneity of SiO2 increases, the compactness of SiO2 agglomerates decreases, and the branching degree of SiO2 agglomerates increases, resulting in higher branching degree and connectivity of filler networks. Furthermore, it was firstly revealed that the stronger Payne effect directly correlate with the higher connectivity of filler networks, rather than the higher homogeneity of nanofillers.