Construction and properties of epoxy resin‐based conductive and thermally conductive composites with electromagnetic shielding function

Abstract The construction of 3D networks enhanced filler utilization in conductive composites, but heat‐induced liquefaction of solid epoxy resins hindered internal 3D structure formation. This study prepared semi‐cured epoxy particles (S‐E12‐RGs) by mixing and pre‐curing E12 epoxy with a curing agent. S‐E12‐RGs were combined with liquid epoxy E51, curing additives, and ethylenediamine‐modified nickel‐coated graphite (ENCG), and then hot‐pressed into 3D composites. The crosslinking of S‐E12‐RGs prevented ENCG's inward migration, which promoted its selective dispersion in the E51 phase. With only 15 wt% nickel‐coated graphite (NCG), the conductivity increased by 7 orders of magnitude compared to direct filling. At 25 wt% ENCG, the composites achieved a conductivity of 23.81 S/m, a thermal conductivity of 0.557 W/(m K), and an EMI shielding of 35 dB. Furthermore, DMA‐digital multimeter analysis showed that ΔR/R₀ was less than 0.27 from 35 to 70°C at 0.1–50 Hz, which demonstrated excellent operational stability. Highlights A 3D network was formed in the thermosetting matrix via specific methods. The cross‐linked S‐E12‐RGs promoted ENCG's selective dispersion in the E51 phase. The composite exhibited high electrical conductivity at low filler content. The material maintained stability within a specific temperature and frequency range.