Effects of surface ageing on wettability, surface chemistry, and adhesion of wood

Surface Free Energy and Dynamic Wettability of Differently Machined Poplar Woods

“…With respect to this, obtained results should be regarded with caution in their absolute value, but it should be noted that the objective of this study is to demonstrate the machined of woods surfaces with differently machined processes, so this approach seems to be suitable. Different methods for the determination of equilibrium contact angle that can be used to calculate the surface free energy of wood have been presented (Cao et al 2005;Gindl et al 2004;Jennings et al 2006;Liptakova and Kudela 1994). In this study, the relative equilibrium contact angle (which is the intercept value of the regress line of contact angle values over time, the value at t = 0 was taken to simulate the value of the equilibrium contact angle) was utilized to calculate the surface free energy of the wood samples, because many authors had indicated that the contact angle obtained by this method could evaluated the surface free energy of wood material successfully (Cao et al 2005;Cao and Kamdem 2007;Maldas and Kamdem 1998;Mamiński et al 2009;Nzokou and Kamdem 2004).…”

“…The lower surface free energy may have caused the higher initial contact angle. Many authors have indicated that the percentage of carbon on wood surface increases and oxygen percentage decreases with time, and the aging of a wood surface causes a decrease in the polar character of the wood surface and an increase in its hydrophobic character (Gardner et al 1991, Gindl et al 2004, Sernek et al 2004.…”

“…The wettability of wood is an important parameter that provides a series of information on the interaction between the wood surface and liquids (such as water, coating, and adhesives) (Gray 1962;Elbez 1978;Gardner et al 1991;Gindl et al 2004;Rathke and Sinn 2013), which also has a significant influence on the bonding strength of wood composites. Adequate wetting of the wood surface by an aqueous resin solution is a fundamental requirement for a generation of strong adhesive joints (Hse 1972;Jennings et al 2005).…”

“…Gardner et al studied the dynamic wetting behavior of different wood species using the dynamic contact angle method and studied and compared the methods for calculating surface free energy as well (Gardner et al 1991;Wålinder and Gardner 2002). Gindl et al (2004) determined that the effect of aging time on surface free energy is significant using the contact angle measurements combined with X-ray photoelectron spectroscopy. They also concluded that the acidity of wood compared with surface energy components is a good relative measure for the classical acidity and pH value between different wood species.…”

Wettability of Sanded and Aged Fast-growing Poplar Wood Surfaces: I. Surface Free Energy

“…3, one can also conclude that the surface free energy of aged wood was larger than that of fresh wood, in accordance with the contact angle trend, in which the contact angle for aged wood samples was larger than that for fresh wood samples. Therefore, the data obtained by the Zisman method (Timmons and Zisman 1968) might be unsuitable, as indicated in many studies (Gardner 1996;Gindl et al 2004;Maldas and Kamdem 1998) and by the following empirical statement: "Lower surface free energy would have a higher contact angle, and meanwhile, higher surface free energy would have a lower contact angle" (Baldan 2012).…”