Graphene related materials as effective additives for electrical and electromagnetic performance of epoxy nanocomposites

The use of graphene as its ideal form remains an unsolved engineering and industrial challenge, which has led to the exploration of a range of materials called graphene related materials (GRM). Among GRM, graphene nanoplatelets (GNP) are highlighted to improve the general properties of polymers in nanocomposites. Other forms of GRM, such as nanographite and reduced graphene oxide (rGO), are also widely used. This work evaluated the effect caused by the addition of four types of GRM on the electrical, electromagnetic interference shielding efficiency (EMI SE), and Reflectivity (RL) behavior in the epoxy matrix. The nanocomposites with 5, 10, 15, 20, and 30 wt% of GRM were prepared by mechanical mixing of nanoparticles into the epoxy resin. The samples were characterized by Raman spectroscopy, scanning electron microscopy, X-ray diffraction, impedance spectroscopy, EMI SE, and reflectivity. A mathematical tool was also used to estimate the optimum thickness of samples to obtain the maximum reflection loss data. The performance evaluation at elevated GRM contents (20 and 30 wt%) had presented unique outcomes, not previously reported in the literature, which were observed aside from a deep study of the electrical and reflectivity behavior. According to the morphological analyses, each GRM studied presented different average thickness dispersion and lateral sizes. The functionalized graphene nanoplatelets with a higher aspect ratio (G4) achieved electrical percolation in the epoxy matrix for lower content (10 wt%), due to its better dispersibility into the matrix. The composition with 30 wt% of GNP (G2) also with small average thickness and lateral size, but without functionalization achieved the best electrical conductivity (10(-4) S/cm) and EMI SE properties (similar to 20 dB), the G2 nanocomposites presented some GNP were stacked closely and aligned (as a cluster), which had activated an absorptive shielding component and increased the conductivity of the G2 pathways. The composition with 15 wt% of rGO(G3) presented promising reflection loss values RL <-12 dB and 1.3 GHZ wide for a thickness of 7.5 mm (simulated and validated), which was related to the best dissipation due to oxygen defects presence.