Role of Nitrogen-Oxygen Plasma Functionalization of Carbon Nanotubes in Epoxy Nanocomposites

Carbon nanotubes (CNTs) functionalization was carried out with radio frequency plasma in different working gas Ar/O-2 and Ar/O-2/N-2 at different plasma powers to synthesize epoxy nanocomposites. After the CNT's had been treated, the Fourier transform infrared (FTIR) spectroscopy showed an additional peak at 1,740 cm(-1), attributed to carboxylic groups, corroborating the X-ray photoelectron spectroscopy that shows attachment of oxygen groups, which indicates CNTs' functionalization. Raman shows an increase in the I-D/I-G ratio, attributed to an increased number of defects, in agreement with transmission electron microscope images that show a nanocoating on CNTs' surfaces. Functionalization carried out with low power plasma makes also some C-N bonds possible, preserving the aromatic carbons of the CNTs' structure. Nanocomposites showed better dispersion and distribution for samples with CNTs treated by Ar/O-2/N-2 plasma. Furthermore, there was a decrease in T-g when compared with neat epoxy, especially for samples with more nitrogen atoms attached to the CNTs. Mechanical properties presented an improvement, which is specially related to a better phase interaction led by the nitrogen presence on the CNTs' surface. (C) 2018 Society of Plastics Engineers