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 (C <= 0.01%). An essential increase in thermal stability and a decrease in destruction activation energy were observed at C <= 5%. Both the dielectric permittivity (epsilon(1)) and the dielectric loss factor (epsilon(2)) increased with increasing C over the entire frequency region tested (4 Hz-8 MHz). Increased epsilon(2) is correlated with decreased free volume when increasing C. Physical mechanisms of MLG-epoxy interactions underlying the effects observed are discussed.

Automated summary

Multilayered graphene nanoplatelets (MLGs) were prepared using an electrochemical technique from thermally expanded graphite flakes. The morphological characterization and studies on DGEBA-epoxy-based nanocomposites filled with MLGs showed enhancements in compression strength, Young's modulus, thermal stability, and dielectric properties at varying loadings. Discussions on the physical mechanisms of MLG-epoxy interactions underlying the observed effects were also included in the study.