Surface Free Energy and Dynamic Wettability of Differently Machined Poplar Woods

Abstract

The surface free energy and dynamic wettability of wood are important to the performance of its adhesive bonding strength. In this work, the surface free energy of poplar wood samples machined with different processes were calculated by the OWRK (geometric mean) and vOCG (acid-base) methods, and the dynamic wettability of adhesives on wood samples was studied using the S-D wetting model. The results indicate that the contact angles of reference liquids on rotary wood samples were greater than those on planed or sawn wood, and the rotary wood samples were more hydrophobic. The effect of surface roughness on contact angle was insignificant compared with surface structure morphology. The total surface free energy was almost the same for the planed and sawn wood, as calculated by the OWRK and vOCG methods, and the surface free energy of rotary wood samples was lower than that of planed or sawn wood samples. The initial and equilibrium contact angle increased as the viscosity of adhesive increased for all the wood samples, and the contact angles of rotary wood samples were greater than those of planed or sawn wood; however, the K-value was lower. The wettability of the loose side was higher than that of the tight side. Contact angles decreased when surface free energy increased, while the K-value increased.

Wettability and surface free energy on heat-treated Pinus sp. and Erisma sp. woods

“…Surface free energy (γ) was calculated by considering the solid (S)-liquid(L) interactions in equilibrium with the vapor phase. Total surface energy (γ t ) was obtained as a sum of non-polar, dispersive (d), and polar (p) contributions (LAMPROU et al, 2010), and the values of θ were related to γ via the Owens-Wendt-Rabel-Kaeble (OWRK) approach (QIN et al, 2015;QIN et al, 2014;VÁZQUEZ et al, 2011), Equation (1): where γ L p and γ L d are the polar and dispersive components of γ t , and can be calculated from the values of θ in water (W), ethylene glycol (E), formamide (F), and diiodomethane (D) using a commercial spread sheet software program. Since there are two unknowns, γ L p and γ L d , in Equation (1), at least two liquids are necessary to be used in the calculation; one with a predominant polar component and the other, with a predominant dispersive component.…”

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“…Oleh karena itu, proses pembasahan antara kayu dan cairan lebih menarik untuk diketahui dibandingkan dengan sudut kontak statis yang diukur beberapa detik setelah proses pembasahan. Salah satu metode untuk mendapatkan proses ini adalah sessile drop method (Staicopolus, 1962;Gardner, 2006;Qin, et al, 2014).…”

Cambios en la mojabilidad en superficies de maderas tratadas térmicamente: Angulo de contacto y energía libre superficial

“…La Ecuación 5 es conocida como el método de análisis de Owens-Wendt-Rabel-Kaelble (OWRK) para hallar la pendiente y el intercepto de la recta: (Qin et al 2014, Qin et al 2015, Vázquez et al 2011.…”

“…En estudios sobre maderas, por ejemplo, diferentes combinaciones de líquidos de prueba se han empleado: agua/diyodometano (Qin et al 2014), agua/diyodometano/formamida (Qin et al 2015) y agua/diyodometano/formamida/ etilenglicol (Vázquez et. al.…”

“…El proceso de mojabilidad de una superficie por un líquido es complejo, debido a la formación de una interface sólido/líquido, difusión del líquido dentro del sólido y penetración del líquido en el interior del sólido a través de la superficie (Qin et al 2014). Los valores de q sólo pueden ser obtenidos en una situación de equilibrio, teniendo en cuenta factores como las características propias de la madera, los valores de s γ y la viscosidad del líquido extendido sobre la superficie sólida (Qin et al 2014). Erisma.…”