Enhancement of electrical conduction mechanisms and analysis of dielectric relaxations in hybrid graphite/MWCNT-reinforced pentafunctional epoxy nanocomposites

In this work, hybrid epoxy nanocomposites were developed from a pentafunctional epoxy resin, namely pentaglycidyl ether pentabisphenol A of phosphorus (PGEPBAP), crosslinked with methylene dianiline (MDA). Four samples were investigated: the neat epoxy matrix (PGEPBAP–MDA), epoxy reinforced with 1 wt% graphite (Gt), epoxy reinforced with 1 wt% Gt and 0.5 wt% multi-walled carbon nanotubes (MWCNT), and epoxy reinforced with 1 wt% Gt and 1 wt% MWCNT. Thermal analysis by differential thermal analysis (DTA) revealed significant changes in the glass transition behavior of the nanocomposites compared with the neat matrix. Raman spectroscopy confirmed the successful incorporation of Gt and MWCNT fillers into the epoxy network through the characteristic D-, G-, and D*-bands. The surface morphology of the nanocomposites was examined using scanning electron microscopy (SEM). The DC conductivity at 350 K increased from 1.57 × 10 −9 to 2.8 × 10 −8 (Ω·m) −1 , indicating a significant change in electrical conduction of the nanocomposite upon the addition of 0.5 wt% of MWCNT. The conduction mechanism was analyzed using a modified form of Jonscher’s universal power law, showing good agreement with the Correlated Barrier Hopping (CBH) model. The α-relaxation and Maxwell–Wagner–Sillars (MWS) interfacial polarization observed in the electric modulus spectra were successfully fitted using the Havriliak–Negami model. Furthermore, the temperature dependence of the relaxation time and DC conductivity was interpreted using Arrhenius behavior. The results demonstrate that the combined incorporation of Gt and MWCNT enhances electrical performance and alters the relaxation dynamics of the epoxy nanocomposites.