Enhanced breakdown strength of epoxy composites by constructing dual-interface charge barriers at the micron filler/epoxy matrix interface

For the advanced energy systems with ultra-high voltage and frequency, in order to improve the thermal conductivity, arc resistance and mechanical strength of epoxy-based dielectric materials, the addition of micron inorganic fillers is necessary. However, this will inevitably degrade their breakdown strength. In this work, the example of constructing dual-interface charge barriers by optimizing molecular structure at micron filler/epoxy matrix interface to capture charge and then enhance the breakdown strength of epoxy composites is reported. Results show that the Al2O3@PVDF-6/BPA system with optimized interfacial structure exhibits the breakdown strength of AC and DC voltages of 37.5 and 67.8 kV/mm, respectively, far outperforming current epoxy composites containing micron fillers. The charge trapping effects in the dual-interface charge barriers are comprehensively investigated, which is confirmed to be the reason for the improved breakdown strength. In particular, the construction of dual-interface charge barriers hardly sacrifices the thermal and mechanical properties of epoxy composites. This work unveils a scalable approach to exploring satisfied dielectric epoxy composites by dual-interface charge barriers construction at the micron filler/epoxy matrix interface. [Display omitted] •A dual-interface charge barrier was constructed at micron filler/epoxy matrix interface to capture charge and then enhance the breakdown strength of epoxy composites.•The dual-interface charge barrier is highly efficient in restricting electric charge migration and reducing electron kinetic energy.•Al2O3@PVDF-6/BPA system exhibits the breakdown strength of AC and DC voltages of 37.5 and 67.8 kV/mm, respectively.•The construction of dual-interface charge barrier hardly sacrifices the thermal and mechanical properties of epoxy composites.