A simple sterategy for improving mechanical characterisitcs of carbon nanotube-epoxy composite through functionalization of carbon nanotubes by epoxy chains

Abstract

A simple strategy was implemented for functionalization of multiwall carbon nanotubes (MWCNTs) by diglycidyl ether of bisphenol A (DGEBA) to enhance the dispersibility and hereby compatibility of MWCNTs in the epoxy matrix. Figure 1 schematically illustrates the functionalization procedure. As it can be seen, MWCNTs were firstly functionalized by ethylenediamine (EDA) to generate amine moieties on their surface. Then, these amine moieties reacted with oxirane rings of DGEBA chains to fulfill the functionalization of MWCNTs by DGEBA.<br><br>Functionalization of MWCNTs was characterized qualitatively by Fourier transform infrared spectroscopy (FT-IR) and quantitatively using thermogravimetric analysis (TGA). Morphology studies were also performed using scanning electron microscope to investigate the dispersibility of MWCNTs in the epoxy matrix. Moreover, the mechanical properties of MWCNT-epoxy composites were assessed to evaluate the effect of grafted DGEBA chains on compatibility of MWCNTs with epoxy resin.<br><br>The characteristics of DGEBA chains were detected on FT-IR spectra of functionalized-MWCNTs and the functionalization degree was also calculated from the weight loss percentage in TGA. SEM observations revealed that the dispersibility of functionalized MWCNTs has notably increased compared to pristine MWCNTs. This better dispersibility and compatibility of functionalized MWCNTs led to considerable improvements in mechanical properties of composites. Compared to pristine MWCNT-epoxy, composite reinforced by functionalized MWCNT represent more than 55% increase in tensile strength values. Young\\'s modulus also experienced similar improvements (70%) after functionalization of MWCNTs by DGEBA chains. These enhancements in mechanical characteristics of MWCNT-epoxy composites can be attributed to robust mechanical interlocking between MWCNTs and epoxy matrix. Grafted DGEBA chains on MWCNTs are able to react with the hardner of epoxy matrix and consequently covalently bind the MWCNTs to the matrix.