Covalent Functionalization of Multi-Walled Carbon Nanotubes Surface via Chemical Treatment.

Due to the strong hydrophobic and van der Waals interactions between individual carbon nanotubes (CNTs), these particles easily aggregate with themselves. When CNTs were introduced into a polymer matrix as a filler, aggregations formed that can adversely affect the mechanical and thermal properties of polymer/CNTs composites. To prevent aggregation, covalent functionalizations via chemical treatments using H₂SO₄/HNO₃, H₂O₂/H₂O and a silane coupling agent(STX)-glycidoxypropyltrimethoxysilane, GPTMS) on the CNTs were chosen in this study. Moreover, the effect of the functional groups on the solubility of CNTs in tetrahydrofuran (THF) was investigated. The surface-modified multi-walled carbon nanotubes (MWCNTs) were also characterized and compared with pristine MWCNTs using several techniques. Morphology changes in surfacemodified MWCNTs were observed by Raman spectroscopy and Field-Emission Scanning Electron Microscopy (FE-SEM) images. Qualitative analyses of the functional groups on the surface-modified MWCNTs were performed by Fourier Transform Infrared Spectroscopy (FT-IR). Additionally, quantitative analyses were performed by X-Ray Photoelectron Spectroscopy (XPS), Energy Dispersive Spectroscopy (EDS), a titration method and Thermogravimetric analysis (TGA).