Preparation and Properties of Multiwalled Carbon Nanotube/Waterborne Polyurethane Superhydrophobic Conductive Coatings Using Electrostatic Spraying

Traditional waterborne polyurethane (WPU) coatings were difficultly applied in the field of hydrophobic coatings because of the poor electrical conductivity, wear resistance and corrosion resistance. Thus, fillers including the polytetrafluoroethylene (PTFE) emulsion and multiwalled carbon nanotubes (MWCNTs) were added to the WPU in this work. Then, the MWCNTs/WPU superhydrophobic conductive coatings with micro-rough surfaces were prepared using electrostatic spraying owing to the synergistic effect of the low surface energy arising from PTFE with the micro-rough structure produced by the MWCNTs. It was concluded that the friction coefficient of the coating was reduced and its wear resistance was improved owing to the addition of PTFE. However, both of its adhesion and corrosion resistance were decreased as the PTFE content rose. To make the adhesion of the coating to the steel substrate meet the requirement, the PTFE content should be 50% less than the WPU content. Remarkably, when the mass ratio of the WPU, PTFE and MWCNTs was 7:3:0.2, the structure and combination property of the obtained coating were the best among all the coatings. Its volume resistivity, water contact angle (WCA) and adhesion were, respectively, 2.3 × 104 (Ω·cm), 154° and 5.01 MPa. Moreover, both of its wear resistance and corrosion resistance were greater than those of the pure WPU coating.