Carbon nanotube (CNT) reinforced epoxy nanocomposites have been reported to possess increased thermal, mechanical and electrical properties. This impact of CNTs can be attributed to the novel carbon-carbon architecture that offers a notably high aspect ratio; an attribute that makes them excellent candidates for use as strengthening materials. However, recent publications have reported that CNTs tend to bundle up even at lower weight reinforcement and form agglomerates that eventually lead to the deleterious consequences on the nanocomposites. Much has been done to improve the dispersion of the CNT in the polymer matrix; in fact, two approaches: i.e. the mechanical dispersion of CNT and functionalization of the surface of the CNT, have shown promising results.
To this note, functionalization of the surface of CNT has been done with a goal of achieving proper dispersion as well as providing the better interface between CNT and polymer matrix. Unfortunately, to date, no published studies have reported on the effects of chemical functionalization and mechanical dispersion of carbon nanotube reinforced epoxy resins.
To this end, Oklahoma State University scientists, Dr. Kunal Mishra and Professor Raman P. Singh from the School of Mechanical and Aerospace Engineering investigated the consolidated effect of mechanical dispersion, and chemical functionalization on mechanical and thermal properties of the CNT reinforced epoxy resin. They focused on assessing the influence of chemical functionalization on the mechanical properties of CNT reinforced nanocomposites at micro or nano scale. Their work is currently published in the research journal, Composites Part B.
In brief, their approach involved the chemical functionalization of the CNT via silane treatment. Silane modification was done first by acid treatment on ball-milled CNT followed by chemical treatment of amine-based silane. The two scholars then performed mechanical dispersion of CNT in the epoxy inside the planetary ball mill. Finally, the mechanical properties of ball-milled and silane modified CNT reinforced epoxy was characterized in terms of fracture toughness and tensile modulus.
The authors, using the Fourier transform infrared spectroscopy (FTIR) spectra, were able to establish that the silane chemically interacted with the CNT and epoxy resin. Additionally, they noted that the ball milled CNTs showed some degree of exfoliation. Further, they reported that the silane-modified CNT/epoxy showed an increase of 38% and 42% compared to the neat resin for fracture toughness and tensile modulus values respectively.
In summary, an in-depth investigation of the effects of chemical functionalization, and mechanical dispersion of carbon nanotube reinforced epoxy resin was presented. Mishra and Singh reported that the increase in mechanical properties for silane modified CNT/epoxy was due to the excellent adhesion between CNT-matrix as well as significant dispersion of CNT in the epoxy resin provided by silane molecule as observed from Transmission electron microscopy (TEM) images. Furthermore, Atomic force microscopy indentation on the nanocomposites was seen to exhibit the presence of CNT agglomerates through adhesion and corresponding modulus map at the nanoscale level. Lastly, the presence of CNT exhibited increase in glass transition temperature which corresponded to the better interfacial adhesion between epoxy and CNT.
“This study will be extremely useful for the researchers who wants to reinforce CNT in the polymer system for various applications as improving the interfacial adhesion drastically enhances the properties of the CNT-polymer nanocomposites.” Said Dr. Kunal Mishra in a statement to Advances in Engineering.
Kunal Mishra, Raman P. Singh. Effect of APTMS modification on multiwall carbon nanotube reinforced epoxy nanocomposites. Composites Part B, volume 162 (2019) page 425–432.Go To Composites Part B