Influence of Surface Densification of Wood on its Dynamic Wettability and Surface Free Energy

Treatment of wood with atmospheric plasma discharge: study of the treatment process, dynamic wettability and interactions with a waterborne coating

“…Among wood modification methods to protect the wood, thermal modification (Welzbacher and Scheiding 2011) can be performed by exposing wood to temperatures between 200 and 260°C, in an inert atmosphere, at atmospheric (Esteves et al 2008) or reduced pressures (Humar et al 2017;Surini et al 2012). This causes a loss of hydroxyl groups in lignin and hemicelluloses, which lowers both the dispersion and polar components of the surface free energy (SFE) (Gérardin et al 2007;Petrič et al 2007;Petrič et al 2013). In turn, this makes the wood turn dark brown and more hydrophobic (Tjeerdsma et al 1998).…”

“…Wettability measurements with various probe liquids enable to quantify the wettability of wood surfaces with coatings and glues alike (Hakkou et al 2005;Petrič et al 2013;Wålinder and Gardner 1999). When studying the interface between wood and coating, two basic systems are to be considered: the interface between a solid and a liquid (1), and the interface of two solids with different physical and chemical properties (2) (Liptáková et al 2000).…”

“…Density, porosity, grain direction, surface roughness, chemical heterogeneity, MC, polarity, capillary flow and the adsorption of the test liquid, sample freshness, are all parameters of the wood surface that influence on its SFE (Wålinder and Johanson 2001;Wålinder and Ström 2001). Considering all these parameters, dynamic CA analysis is therefore relevant when studying wood surfaces, since it is not limited by surface absorption and chemical heterogeneity (De Meijer et al 2000;Gardner et al 1991;Moghaddam et al 2014;Petrič et al 2013;Shen et al 1998;Shupe et al 1998). The result of dynamic CA measurement is a detected force in relation to time of measurement, manifested in the form of hysteresis.…”