Electromagnetic interference shielding and dielectric properties of graphene nanoplatelets/epoxy composites in the x-band frequency range

Materials with electromagnetic interference (EMI) shielding capabilities are crucial to reduce electromagnetic radiation pollution. This study investigates the EMI shielding and the dielectric properties of epoxy-based nanocomposites incorporating graphene nanoplatelets (GNPs) of varying surface area (750, 500 and 300 m2/g). Sonication during preparation and casting play significant roles in exfoliating and uniformly dispersing the GNPs in the epoxy matrix. EMI shielding properties are measured using the reflection–transmission method in the X-band frequency range, and dielectric properties are calculated using the Nicolson–Ross–Weir method. Complex permittivity, AC conductivity and EMI shielding performance increase with increasing GNP surface area and concentration, with maximum increase in properties over neat epoxy at 17 wt% 750 m2/g GNPs. The dominant observed shielding mechanism is reflection. However, at higher concentrations of the 750 m2/g GNPs, the material acts as a lossy medium with increasing absorptivity. The formation of conductive networks and interfacial polarization play a significant role in enhancing the real and imaginary parts of the permittivity and shielding performance.