Superamphiphobic coatings with coralline-like structure enabled by one-step spray of polyurethane/carbon nanotube composites

This paper describes a facile one-step approach to prepare superamphiphobic coatings with a coralline-like structure. The coatings were fabricated by spray casting nanocomposites composed of fluorinated multi-walled carbon nanotubes (MWCNTs) and fluorinated polyurethane (PU), in which MWCNTs created both microscale and nanoscale roughness, while fluorinated PU acts as a low surface energy binder. The resulting coatings require no additional surface treatments with commonly used low surface energy materials and exhibit inherent superamphiphobicity with contact angles of 162 degrees and 152 degrees for water and n-hexadecane, respectively. Parameters including the content of MWCNTs in the composites and the proportion of toluene in the solvent were studied in detail to optimize the fabrication process. The Cassie and Wenzel wetting models were employed to discuss the superamphiphobic nature of the coatings. Importantly, the coatings were casted and cured under mild and ambient conditions and can be applied to a variety of substrates of large size. Coatings with excellent superamphiphobicity on A4 paper, cotton fabric, and polyethylene terephthalate film were demonstrated for proof-of-concept purposes.