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

• Published in: Polymers Vol. 13; no. 19; p. 3360
• Main Authors: Gorelov, Borys M, Mischanchuk, Oleksandr V, Sigareva, Nadia V, Shulga, Sergey V, Gorb, Alla M, Polovina, Oleksiy I, Yukhymchuk, Volodymyr O
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 30-09-2021; MDPI
• Subjects: Compressive strength; Dielectric loss; dielectric permittivity; Dielectric properties; Dielectrics; Dipoles; Electrochemical analysis; epoxy; Epoxy resins; Graphene; graphene multilayered; Graphite; Heat resistance; Mass spectrometry; Modulus of elasticity; Molecular structure; Morphology; Multilayers; Nanocomposites; Nanoparticles; polymer nanocomposites; Polymers; Positron annihilation; Raman spectroscopy; Scientific imaging; thermal destruction; Thermal stability; dielectric permittivity; graphene multilayered; positron annihilation; epoxy; polymer nanocomposites; thermal destruction
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym13193360

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 (ε1) and the dielectric loss factor (ε2) increased with increasing C over the entire frequency region tested (4 Hz-8 MHz). Increased ε2 is correlated with decreased free volume when increasing C. Physical mechanisms of MLG-epoxy interactions underlying the effects observed are discussed.