Effect of side-wall functionalisation of multi-walled carbon nanotubes on the thermo-mechanical properties of epoxy composites

Abstract

In this work, a novel functionalisation was carried out by grafting carboxyl-terminated poly(acrylonitrile-co-butadiene) on the side-walls of multi-walled carbon nanotubes to prepare MWCNT-g-CTBN. The functionalized nanotubes were characterized by XPS, Raman spectroscopy, and TGA and the surface morphology was analyzed by transmission electron microscopy. The dispersion behavior of the MWCNT/epoxy nanosuspension was carefully analyzed by transmission optical microscopy (TOM) and rheology. The MWCNT-g-CTBN was added to the diglycidyl ether of bisphenol A-type epoxy to prepare MWCNT-g-CTBN/epoxy composites. Incorporation of CTBN-grafted MWCNTs in epoxy matrix imparted tremendous improvement in mechanical strength as well as fracture toughness when compared with pristine MWCNT/epoxy composites. The mechanism for this improvement in mechanical properties is attributed to the increase in interfacial strength between nanotubes and the epoxy matrix through chemical bonding. The toughening mechanism that leads to the enhancement in the fracture toughness of the nanocomposites was assessed with the help of Field Emission Scanning Electron Microscopy (FESEM). Dynamic mechanical analysis of the MWCNT-g-CTBN/epoxy composite revealed an increase in the T_g of the epoxy phase as well as an increase in modulus due to the enhancement in stiffness of the material.