Investigation on Electrical Conductivity and EMI Shielding Efficiency of Modified Epoxy-Exfoliate Graphite Composites

The use of epoxy-graphene composites by advanced processing techniques and three roll mill dispersions resulted in 40 dB of electromagnetic interference (EMI) shielding efficiency in the range of 8-18 GHz. Since ac conductivity did not increase up to 5 wt.% of graphene nanoplatelets (GNPs), the polymer matrix was modified with eight layers of woven carbon fabric to increase the ac conductivity. The use of carbon fabric resulted in enhanced ac conductivity of 70 S/m and EMI shielding efficiency of 60 dB at 8 GHz, which slowly decreased to 50 dB at 18 GHz. Further enhancement in the ac conductivity of the composite to 90 S/m was realized by the integration of 1 wt.% of graphene to the epoxy matrix with carbon fabric. The EMI shielding efficiency of the composite improved to 80 dB at 8 GHz, and 70 dB at 18 GHz. Significant enhancement of EMI shielding efficiency was achieved owing to the higher ac conductivity. Absorption was the dominant EMI shielding mechanism due to the inherent ac conductivity of carbon layers which also helped in the minimal increase of attenuation by reflection.