Improved dielectric properties of polymer-based composites with carboxylic functionalized multiwalled carbon nanotubes

The biggest issues in the preparation of carbon nanotube (CNT)-reinforced composites reside in efficient dispersion of CNT into polymer matrix. In our work, a simple acid treatment method was adopted to obtain carboxylic functionalized multiwalled nanotubes (MWNTs), thus improving the dispersion of CNT and interaction between particles and polymer matrix. X-ray photoelectron spectroscopy and Fourier transform infrared showed that the carboxylic groups were introduced onto the surface of MWNTs. The Raman spectroscopy showed that the amorphous carbon materials and impurities decreased after acid treatment. The electrical and dielectric properties of the Polyamide-11 (PA11)-based composites filled with pristine multiwalled nanotubes (p-MWNTs) and carboxylic functionalized multiwalled nanotubes (c-MWNTs) were investigated. The biggest dielectric constant of PA11/c-MWNTs composites, which was about twice as high as that of PA11/p-MWNTs composites at room temperature and 103 Hz (345–610), was obtained, accompanied by a lower dielectric loss. The formation of abundant microcapacitors and improved interfacial polarization effect by improving the dispersion of MWNTs in the composites via carboxylic functionalization was the main reason for the excellent dielectric properties of PA11/c-MWNTs composites.