ABSTRACT
Abstract This work examines the adhesion properties of sugar maple (Acer saccharum) and black spruce (Picea mariana) wood surfaces following their exposure to a dielectric barrier discharge at atmospheric pressure. Freshly sanded wood samples were treated in Ar, O2, N2 and CO2-containing plasmas and then coated with a waterborne urethane/acrylate coating. In the case of black spruce wood, pull-off tests showed adhesion improvement up to 35% after exposure to a N2/O2 (1:2) plasma for 1 s. For the same exposure time, adhesion improvements on sugar maple wood up to ∼25% were obtained in Ar/O2 (1:1) and CO2/N2 (1:1) plasma mixtures. Analysis of the wettability with water contact angle measurements indicate that the experimental conditions leading to adhesion improvement are those producing more hydrophobic wood surfaces. In the case of sugar maple samples, X-ray photoelectron spectroscopy investigations of the near-surface chemical composition indicate an increase of the O/C ratio due to the formation of functional groups after exposure to oxygen-containing plasmas. It is believed that a combination of structural change (induced by UV radiation, metastable particles impingement, or both) and chemical change due to surface oxidation is responsible for the observed surface modification of black spruce and sugar maple wood samples.
