A cost effective strategy to fabricate STA@PF@Cu2O hierarchical structure on wood surface: aimed at superhydrophobic modification

Cuprous oxide nanoparticles (Cu2O NPs), phenol formaldehyde (PF) resin, and stearic acid (STA) were used to fabricate hierarchical core/shell structures to endow wood with superhydrophobic function, in which the preparation of Cu2O NPs and the synthesis of PF were carried out simultaneously in one system. The Cu2O NPs with the shape of a symmetrical tetrahexahedron were prepared in this work, and this novel shape is beneficial for creating a superhydrophobic surface. A relatively rough structure in micro/nanoscale was formed on the wood surface after being sprayed with PF@Cu2O coating, which played a vital role in the fabrication of superhydrophobic wood surfaces, as expected. Morphological analysis and surface free energy calculations verified that STA reduced the surface free energy. Application of 12 layers of PF@Cu2O coating followed by 2 h immersion in STA ethanol solution produced wood surfaces with low water permeability and high water contact angles of 153.3°, 153.2°, 150.5° on cross, radial, and tangential sections, respectively. Abrasion tests coupled with subsequent exposure to acidic and alkaline conditions indicated that the coating was resistant to both mechanical wear and chemical degradation. This two-step coating strategy used inexpensive ingredients and could have potential to application as water repellency protection of wood timber.