Polyaniline/carbon nanotube hybrids modified with ionic liquids as anticorrosive additive in epoxy coatings

Abstract

Polyaniline (PAni) doped with dodecylbenzene sulfonic acid was prepared by inverse emulsion polymerization of aniline (Ani) in toluene medium in the presence of unmodified and modified carbon nanotube (CNT). Two different imidazolium based ionic liquids (IL), such as, 1-methyl-3-butyl imidazolium tetrafluorate (bmim.BF4) and (1-(1-methyl-3-imidazole) butane-4-sulfonate) as zwitterion IL (mimbutylSO3) modified with dodecylbenzene sulfonic acid were used to disperse CNT and assist the polymerization of Ani. The presence of IL gave rise to PAni.IL and PAni.IL/CNT hybrid composites with superior electrical conductivity when compared with PAni and PAni/CNT without IL. PAni and the CNT-based hybrids were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). 1 wt% of the synthesized hybrids were formulated with epoxy resin and applied on AISI 1020 carbon steel plates to investigate the corrosion resistance of the coating using electrochemical impedance spectroscopy (EIS) technique. The epoxy coating loaded with PAni/CNT hybrid materials displayed outstanding anti-corrosion properties when compared with those loaded with PAni. The hybrid conducting additive prepared in the presence of bmim.BF4 provided the highest anti-corrosion performance of the corresponding epoxy coating. Moreover, the corrosion resistance increased with immersion time. The complex viscosity of the dispersions and dynamic-mechanical analysis (DMA) as well as differential scanning calorimetry (DSC) of the epoxy-based networks were also evaluated.