Examining Parameters of Surface Quality Performance of Paulownia Wood Materials Modified by Thermal Compression Technique

Abstract

The aim of this study was to evaluate the effect of thermal compression process on some surface properties of paulownia solid wood materials. The widest surface of wood samples was mechanically compressed at high temperatures. The duration was 45 min. Four different process combinations were created, including two temperatures (150 °C and 170 °C) and two pressure levels (20 bar and 22.5 bar). The surface roughness, wettability and color properties of treated and untreated samples were compared. The roughness properties, both parallel and perpendicular to grain direction, were determined according to JIS B 0601:1994 standard. The contact angle changes of water dripped to the surface were measured according to time. For color properties, a spectrophotometer was used according to CIE L*a*b* system. The color changes were classified according to a grading method from literature. The most remarkable results on wettability were observed. The contact angle values significantly increased with this method. Although higher temperature increased the contact angle values, higher pressures did not change the values. When the surface roughness values were generally considered, this technique could decrease the values up to 40 % ratio according to the control group. Only the combination of 150 °C and 20 bar did not significantly change the values. Lastly, the results of color properties showed that all treatment parameters significantly affected total color change values of samples. Grading results were similar and the color change of modified samples graded as the lowest color difference, except with the combination of 150 °C and 20 bar. The combination of 170 °C and 22.5 bar (highest treatment conditions) significantly changed all color characteristics of samples, except b* parameter. The results of this research showed that mechanical thermal compression method could change surface properties of this fast-growing species.

Effect of Bleaching and Hot-Pressing Conditions on Mechanical Properties of Compressed Wood

“…Thus, the CW density change by the bleaching steps was not significant. The water contact angle (WCA) of the heat-treated CW increases the hydrophobic properties [24,25]. The authors indicated the effects of different heat treatments and compacted surfaces of CW.…”

Durability and wettability of varnishes on the modified and aged surfaces of short rotation teak wood

“…The parameters used to characterise the wood surface properties are surface roughness and surface free energy (SFE) (Qin et al, 2014). Surface roughness is an important factor in determining surface quality, especially wettability (Akgul et al, 2012;Ayrilmis et al, 2009;Candan et al, 2010Candan et al, , 2012Candan et al, , 2021aCandan et al, , 2021bDarmawan et al, 2017;Dundar et al, 2008;Dundar et al, 2014;Unsal et al, 2010Unsal et al, , 2011Demir and Aydin, 2019). Parameters to determine the interaction between the wood surface and the coating material (wettability) can also be analysed by observing the thermodynamic wetting parameters, such as the SFE (Wålinder, 2002).…”

Influence of Wood Surface Preparation on Roughness, Wettability and Coating Adhesion of Unmodified and Thermally Modified Wood

“…Thermally modified wood is shown to have lower hygroscopicity, liquid water uptake, changed acidity, and anatomical structure (Jirouš-Rajković and Miklečić, 2019). It has also been shown that thermal modification has influence on the surface roughness and wettability of wood and wood-based materials (Candan et al, 2010;Unsal et al, 2011;Candan et al, 2012;Candan et al, 2021a). Thermal modification was shown to reduce the wettability and surface roughness of rowan (Sorbus aucuparia L.) wood (Candan et al, 2021b).…”