Interfacial nanomechanical properties and chain segment dynamics of fibrillar silicate/elastomer nanocomposites

For fiber reinforced rubber composites, the interface is the most critical factor affecting the stress transfer efficiency and the ultimate reinforcing effect. In this study, we investigated the interfacial interaction of three kinds of fibrillar silicate (FS) filled natural rubber (NR) composites via a combination of quantitative nanomechanical technique of atomic force microscopy (AFM-QNM) and broadband dielectric spectroscopy (BDS) measurements. The force-deformation curves at nanoscale of these composites was revealed to quantitatively obtain the interfacial thickness and Young's modulus, and the Johnson-Kendall-Robert (JKR) contact model was used to fit the force-deformation curves to verify the reliability of the AFM-QNM results. The interfacial thickness of these composites with double-layer structure was further verified by High Resolution Transmission Electron Microscope (HRTEM) directly. The BDS results indicate that apart from the bulklike alpha-relaxation, a slower alpha(inf)-relaxation by 1-2 orders of magnitude than bulklike alpha-relaxation was observed in these nanocomposites attributed to restricted segmental relaxation of interfacial NR chains by FS, and the relaxation times of these composites agree well with the results of interfacial thickness and Young's modulus. An in-depth analysis of the interfacial interaction mechanism of these FS/NR composites was given. This study helps us to deep understand the interface of nanofiber reinforced composites, and it provides guidance for the interfacial design of high performance rubber composites.