A chemically robust and self-healing superhydrophobic polybenzoxazine coating without fluorocarbon resin modification: Fabrication and failure mechanism

The decaying mechanism of air cushion on superhydrophobic surfaces deserves further investigation upon immersion conditions, which could contribute to a clear understanding to the non-wettability deterioration process. In this work, we constructed a chemically robust and self-healing superhydrophobic coating by spraying method of polybenzoxazine (PBA) particles and polydimethylsiloxane (PDMS) paste, without further modification by low surface-energy and toxic fluorocarbon resin. The size of PBA particles was regulated by adjusting the ball-milling rate to obtain a mixture of micro-nano particles, then the PBA particles were blended with PDMS and sprayed on a mild steel plate to fabricate all-organic superhydrophobic coatings. Laser confocal microscope and FT-IR spectra verified that the hierarchical micro-nano topography on PBA/PDMS coatings contributed more than the low surface-energy modification to the superhydrophobicity. Even after the superhydrophobicity of PBA/ PDMS coating was damaged due to deterioration of the micro-nano structures, it could be easily healed by surface friction on the PBA/PDMS coatings thanks to its three-dimensional superhydrophobic property. Visualization monitoring on the air cushion trapped on PBA/PDMS coatings demonstrated that it failed from several points initially, then expanding to local up to the whole surface finally. It is expected that this work may provide a promising fabrication strategy of superhydrophobic coatings, as well as a preliminary understanding of the mechanism of superhydrophobicity loss.