Mechanically stable superhydrophobic surface fabricated by self-growth of ZnO nanoflowers on vulcanized silicone rubber

The development of superhydrophobic materials in practical applications has been severely hindered by the complexity of manufacturing and the sensitivity to mechanical contact. In order to prepare a mechanically durable flexible super-hydrophobic surface on the surface of a flexible substrate (vulcanized silicone rubber), using the reversible characteristics of the swelling process of vulcanized silicone rubber and the improved sol-gel method, the silicone rubber sheet was swelled with a n-butylamine aqueous solution in advance, and then immersed in zinc nitrate/ethanol solution. Due to the cross-diffusion, contact and reaction between zinc nitrate and n-butylamine aqueous solution on the surface of silicone rubber, ZnO nanoflowers were grown in-situ on the rubber surface. The construction of the superhydrophobic rough structure came from the synergistic effect of zinc nitrate and n-butylamine, with static contact angle and rolling angle being (158±1.5)° and (4.5±0.5)° respectively. SEM images show that ZnO nanosheets of 100-200 nm in thickness are generated and the ZnO nanosheets are “embedded”, not just “deposited” on the rubber surface, which improves the mechanical durability. By adding a silane coupling agent γ-aminopropyltriethoxysilane (KH550) to the silicone rubber compounds, the interface interaction between the ZnO nanosheets and the rubber matrix is further improved. Even with 300 times of linear wear, it could still maintain superhydrophobic and exhibit excellent mechanical stability. Moreover, after 500 cycles of bending deformation, its hydrophobicity hardly changes, which solves the problem of superhydrophobic coating falling off when the substrate is bent and deformed. High mechanical stability and simple preparation process endow the superhydrophobic rubber a high application prospect.