Plasma Treatments to Improve the Bonding of Thermo-Treated Cherry Wood

Thermal treatment can significantly improve the dimensional stability of wood, but it will decrease the bonding strength. In this work, the bonding strength of thermo-treated cherry wood boards was improved by plasma treatment. The change of wettability, surface morphology, and surface chemical property of cherry wood before and after plasma treatment was investigated by water contact angle measurement, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The plasma treatment significantly improved the wettability of thermo-treated cherry wood by decreasing its water contact angle from 109.95 degrees to 53.18 degrees. N-2 or O-2 was used as the plasma atmosphere, and it was found that N-2 plasma treatment afforded cherry wood a rougher surface. The AFM roughness of cherry wood was increased from 19 nm to 31.9 nm after N-2 plasma treatment. XPS results revealed an additional C-N group for N-2 plasma treatment and the content of C=O, O-C-O, and O-C=O increased for O-2 plasma treatment, respectively, indicating that the surface chemical property of cherry wood was modified. Due to the surface character, the bonding strength increased by 21.17% for N-2 plasma treatment and 15.32% for O-2 plasma treatment.