Effect of oxidation treatment of multiwalled carbon nanotubes on the mechanical and electrical properties of their epoxy composites

The mechanical and electrical properties of oxidised multiwalled carbon nanotube (MWCNT)/epoxy composites are investigated with respect to the chemical treatment of the nanofiller. Surface modification of the MWCNTs is carried out by treating the as-received material with HCl, H2SO4/H2O2, HNO3, and H2O2/NH4OH under well specified conditions. The strongly oxidised MWCNTs appear to be extremely pure but their perfection is affected by the oxidation treatment. The material oxidised by the mixture of H2O2/NH4OH provides epoxy composites with a higher conductivity than those produced by the other oxidation agents. This is due to the milder impact of the mixture of H2O2/NH4OH on the conductive shells of the nanotubes and also the effective removal of poorly conducting amorphous carbon. Evidence is provided that the induced nanotube damage as a result of oxidative treatment can affect considerably the mechanical and electrical properties of the epoxy composites.