Simultaneously strengthening, toughening, and conductivity improving for epoxy at ultralow carbonaceous filler content by constructing 3D nanostructures and sacrificial bonds

The combination of high strength, great toughness, and excellent electrical properties for conductive polymer composites is essential for their practical applications. Herein, we demonstrate a strategy to improve simultaneously the strength, toughness, and the electrical conductivity of epoxy resin. This strategy involves constructing compact 3D tannin non-covalent modified graphene/multi-walled carbon nanotube (MWCNT) hybrid network and introducing sacrificial bonds. As a result, with only 0.01 wt% the hybrid filler, the tensile strength, Young's modulus, elongation at break, the mode-I fracture toughness (K_IC), and strain energy release rates (G_IC) of the epoxy resin were increased by 23.3%, 44.6%, 41.2%, 114.6%, and 219.3%, respectively. This filler loading is 10 and 15 times lower to obtain comparable improvement in tensile strength and K_IC compared with the lowest content reported to date. The composites also display excellent electrical properties in terms of an ultralow percolation threshold (~0.076 wt%).