Abstract
Waterborne polyurethane (WPU) coatings hold advantages of good toughness, low cost and environmental protection. However, the low water contact angle (WCA), poor wear and corrosion resistance make them unsuitable for application in the superhydrophobic coatings such as antipollution flashover coatings for transmission lines, self-cleaning coatings for outdoor equipment and waterproof textiles. A series of superhydrophobic WPU composites (SHWPUCs) with micro-rough surface structure was prepared by electrostatic spraying nano-SiO2 particles on WPU composites with low surface energy. It showed that as the hydrophobic system content rose the WCAs of the composites first increased and then remained stationary; however, the adhesion and corrosion resistance first increased and then decreased. An appropriate addition of the hydrophobic system content would lead to a dense coating structure, but an excessive addition could increase the interfaces in the coating and then reduce the coating performance. When the mass ratio of the WPU dispersion, polytetrafluoroethylene (PTFE) particles and modified polydimethylsiloxane was 8:0.3:0.4, 10 g/m2 nano-SiO2 particles were sprayed on the uncured coating surface to construct the SHWPUC with a WCA of 156°. Compared with pure WPU coating, its adhesion and corrosion resistance increased by 12.5% and one order of magnitude, respectively; its wear rate decreased by 88.8%.
Highlights
Protective coatings with superhydrophobicity have a widespread application in the fields of antipollution flashover coatings applied in transmission lines, self-cleaning coatings applied in outdoor equipment and waterproof cloth, etc. [1,2,3]
LSWPUC, #2 LSWPUC, #3 LSWPUC and #4 LSWPUC were 83◦, 107◦, 110◦, 112◦ and 113◦, respectively, stating that the low surface energy coating was successfully prepared by the incorporation of the hydrophobic system of M-PDMS/PTFE
When the M-PDMS/PTFE system content was below 8.05 wt % (#3 M-PDMS/PTFE system vs. M-PDMS/PTFE/Waterborne polyurethane (WPU) system), the water contact angle (WCA) of the LSWPUCs first increased and remained stationary as the M-PDMS/PTFE system content rose
Summary
Protective coatings with superhydrophobicity have a widespread application in the fields of antipollution flashover coatings applied in transmission lines, self-cleaning coatings applied in outdoor equipment and waterproof cloth, etc. [1,2,3]. Waterborne polyurethane (WPU) coatings with water as the dispersion medium are basically low cost, solvent-free, non-toxic and non-flammable, in addition, they will not pollute the environment and can avoid safety problems during production and application compared with solvent-based PU coatings [5] Polar groups such as –COOH and –OH in the molecular chains of WPU can produce crosslinking polymerization reactions under certain conditions [6,7,8], it could strengthen the coating structure and enhance the adhesion to the substrates. The incorporation of nano-SiO2 particles to the coating with low surface energy can construct the micro-rough surface structure, increasing the strength of polymer materials, and improve the wear resistance and corrosion resistance of the coating [22,23,24]. This may provide a useful reference for the design, preparation and application of superhydrophobic waterborne coatings
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