Abstract: Superhydrophobic coatings with high flexibility and mechanical durability can well address many practical application problems. To this end, we proposed and fabricated a kind of bio-based superhydrophobic (multi-walled carbon nanotubes) CNT@PU (polyurethane) coatings. It was demonstrated that the CNT@PU coatings with 64% soft segment content possessed the preferable bonding strength (5B) with metal substrates. The multi-walled carbon nanotubes, as additive materials, were used to construct the microscopic structures of the coating surfaces, which made polyurethane surface superhydrophobic (water contact angle being 156.9?, and water sliding angle being 
4.3?). Furthermore, the high bonding strength between CNT and coating matrix led to robust mechanical durability of superhydrophobic CNT@PU coatings, and the coatings remained superhydrophobicity after 10 cycles of abrasion under 100 g load pressure. Also, the superhydrophobic coatings could well resist 5 cycles of tape-peeling action, and presented outstanding flexibility. The superhydrophobic CNT@PU coatings with high flexibility and mechanical durability could be applied to various substrates suggesting their big potential in future real-world application. 

Key words: bio-based PU, superhydrophobic coatings, high flexibility, mechanical durability