Effects of oxidative conditions on properties of multi-walled carbon nanotubes in polymer nanocomposites

This study investigates the effects of the oxidizing conditions on the properties of the multi-walled carbon nanotubes (MWNTs). MWNTs have been oxidized using a mixture of sulfuric and nitric acids. The time and temperature of the oxidation process of MWNTs were varied to understand the critical process and the changes in properties of the MWNTs. The morphologies of MWNTs oxidized under various conditions were observed with a scanning electron microscopy (SEM) and a transmission electron microscope (TEM). The length of MWNTs decreased dramatically when the refluxing time and temperature were increased. Based on the experimental results a phenomenological model is suggested that predicts the average length of MWNTs as a function of oxidation time and temperature. The results suggest that it is possible to obtain the desired average length of MWNTs by controlling the effective parameters of the oxidation process. The damages in the wall of the MWNTs were monitored through TEM to understand the attrition in length of the MWNT. Further, better dispersion was observed in the MWNTs/PP nanocomposites with the shorter length of MWNTs.