Preparation of oleic acid modified multi-walled carbon nanotubes for polystyrene matrix and enhanced properties by solution blending

Effective surface modification of multi-walled carbon nanotubes (MWCNTs) by covering with oleic acid was carried out via the covalent interaction between the hydroxymethylated MWCNTs and the organic long-chained molecules of oleic acid in xylene. The oleic acid modified MWCNTs were characterized through FT-IR spectroscopy, X-ray photoelectron spectrometer, transmission electron microscope, thermogravimetry and dispersion test to confirm that the well dispersed, robust and functional oleic acid had been introduced on the surface of the pristine MWCNTs without sacrificing the original morphological structure obviously. Additionally, the nanocomposites consisting of oleic acid modified MWCNTs and a polystyrene (PS) matrix were fabricated by solution blending method. The structure and morphology of the oleic acid modified MWCNTs/PS nanocompsites were characterized through X-ray diffraction and scanning electron microscopy (SEM). The SEM images showed that the functionalized MWCNTs had a very well dispersion in the matrix. Moreover, the thermal stability and electronic conductivity presented improvements with the filler concentration increased. Meanwhile, the nanocomposites possessed a high dielectric constant with a comparatively low dielectric loss before the MWCNTs concentration up to 1.5 wt%.