Structural and Dipole-Relaxation Processes in Epoxy–Multilayer Graphene Composites with Low Filler Content

Multilayered graphene nanoplatelets (MLGs) were prepared from thermally expanded graphite flakes using an electrochemical technique. Morphological characterization of MLGs was performed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Raman spectroscopy (RS), and the Brunauer–Emmett–Teller (BET) method. DGEBA-epoxy-based nanocomposites filled with synthesized MLGs were studied using Static Mechanical Loading (SML), Thermal Desorption Mass Spectroscopy (TDMS), Broad-Band Dielectric Spectroscopy (BDS), and Positron Annihilation Lifetime Spectroscopy (PALS). The mass loading of the MLGs in the nanocomposites was varied between 0.0, 0.1, 0.2, 0.5, and 1% in the case of the SML study and 0.0, 1.0, 2, and 5% for the other measurements. Enhancements in the compression strength and the Young’s modulus were obtained at extremely low loadings ([Formula: see text] 0.01%). An essential increase in thermal stability and a decrease in destruction activation energy were observed at [Formula: see text] 5%. Both the dielectric permittivity ([Formula: see text]) and the dielectric loss factor ([Formula: see text]) increased with increasing [Formula: see text] over the entire frequency region tested (4 Hz–8 MHz). Increased [Formula: see text] is correlated with decreased free volume when increasing [Formula: see text]. Physical mechanisms of MLG–epoxy interactions underlying the effects observed are discussed.