Wettability modification of heat-treated wood (HTW) via cold atmospheric-pressure nitrogen plasma jet (APPJ)

The modification of heat-treated wood (HTW) wettability by cold atmospheric-pressure nitrogen plasma jet (APPJ) for several treatment durations has been investigated. The effects of the modification were assessed by measurement of the advancing contact angle (ACA) of water along with determination of surface free energy. Additionally, the morphology and chemical changes of the HTW surface were characterized by scanning electron microscope (SEM) and FTIR spectroscopy. As expected, the measurements demonstrated that the ACA decreased proportionally with treatment time of APPJ. The optimal treatment time was 20 s. Clear etching traces are visible on the SEM images of HTW surfaces. The roughness of HTW increased after plasma treatment. FTIR spectra demonstrate that OH, C=O, and COOH groups are formed on the HTW surfaces. All these modifications are beneficial for the HTW wettability, which leads to better bonding strength of HTW.