Enhanced atmospheric pressure corona-based weakly ionized plasma was investigated to modify surface properties of wood materials. The plasma was generated using a point-to-point bare electrode geometry without dielectric barriers. The gas-phase admixture used in this work was argon and acetylene. Wood fibers were processed in the post-discharge region outside of the harsh corona environment. Return corona emanating into the high-voltage gap from the grounded screen was utilized to effectively activate acetylene molecules near the substrate. Scanning electron microscopy was used to study the surface morphology of the treated and untreated substrates. The treated wood material was observed to contain on their surface nano- and micro-nodules of plasma-polymerized acetylene. Capillary rise measurements confirmed changes in the surface wettability of the substrates. The water capillary rise rate and diffusion coefficient were reduced by about 37% and 57%, respectively, for a 15-min treatment of ponderosa pine wood flour.

The paper aims at the investigation of atmospheric pressure weakly ionized plasmas with argon and acetylene to deposit plasma-polymerized coatings on wood veneers (birch, maple), cellulose paper, and pine wood flour to modify their surface properties, in particular their topography and wettability. The treatment was performed in a reactor containing an array of high-voltage needles and a grounded metallic mesh as electrodes. The deposition occurred in the discharge downstream of the plasma region. The plasma-polymerized acetylene deposits form spherical nodules on the surface of the substrates and change their wettability from hydrophilic to hydrophobic. The water contact angles of the veneer were determined with a goniometer. The capillary rise was combined with the Washburn equation to assess the change in hydrophilicity of the plasma-treated wood flour.