Surface Properties of Beech Wood after CO2 Laser Engraving

Abstract

The paper deals with the properties of a beech wood surface treated by CO2 laser engraving. The studied concerns were the discoloration, changes to morphology assessed through roughness and waviness parameters, and surface wetting with standard liquids (water and diiodomethane), with the aim of determining the wood surface free energy. The results have confirmed that the studied properties of the beech wood surface varied significantly, which were affected by the laser beam power P and raster density n. With increasing P and n, the lightness L* (expressed in CIE L*a*b* color space) decreased significantly. We also observed significant variation in the color coordinates a* and b*. At 8% laser power, the roughness and waviness parameters measured parallel as well as perpendicular to the grain increased proportionally with the increasing raster density. However, 4% laser power was not associated with distinct changes. Increasing the raster density reduced beech wood surface wetting equally with water and with diiodomethane. This was reflected in the higher contact angle values. The wood surface exhibited higher hydrophobicity at 4% laser power. At this power, the increasing raster density was reflected in the decreasing surface free energy, due to its polar component decrease. At 8% laser power, the changes in surface free energy were very minor from the practical viewpoint. The results suggest a potential good adhesion between film-forming materials and wood. However, the gluing performance may be negatively affected by the high roughness attained at 8% laser power and at higher raster densities.

Trends in Chemical Wood Surface Improvements and Modifications: A Review of the Last Five Years

“…As the name implies, the carbonization methods revolve around charring the surface of wood to modify its properties. The use of CO 2 lasers with radiation doses up to 75 J/cm 2 was studied in several publications, as well as its effect on the tensile strength of adhesives, the resistance to molds of the treated wood and its surface free energy [225][226][227]. The authors found that high radiation doses would increase the wood surface blackening, as a result of the carbonization, as well as its resistance to molds.…”

“…However, this method also involves the generation of HF as a by-product, which undermines the safety aspect. Methods relying on the carbonization of wood like CO 2 laser irradiation [225][226][227], one-sided charring [228][229][230] and blow-torch combustion [231] improved the resistance to biodegradation and the water sorption properties of the treated wood, although its appearance was notably affected (blackened) by the charring.…”

Prediction of surface roughness of CO2 laser modified poplar wood via response surface methodology

“…However, the roughness did not show any changes with increasing the period of treatment to 3 hours (Kaygin et al 2014). Kúdela et al (2020) investigated the effects of hot-press on surface roughness of eucalyptus wood. Thermally modified eucalyptus wood surface became rougher with the increasing of temperature, but the pressure had opposite effect on surface roughness.…”

“…During laser modification, the color, surface morphology of wood will be changed, which have strong effects on the wooden material subsequent processing performance. Kúdela et al (2020) investigated the surface properties of CO 2 laser engraved beech wood. Results showed that the surface roughness increased significantly at 8 % laser power (12 W), and the values of Ra, Rq, Rz, and Rt increased with the increasing of raster density.…”

Optimization of Parameters for the Cutting of Wood-Based Materials by a CO2 Laser

“…The application of lasers in the furniture industry for automated cutting processes us also well-known [11,12]. In addition to cutting, CO 2 lasers are also used for the irradiation or engraving of a wood surface [13][14][15][16][17]. The main advantages of the laser cutting of wood in comparison with conventional cutting methods are the highly precise cut, flexibility to start and finish cutting at any point of the board, narrow kerf width (0.1-0.3 mm compared to saw cut of 3-6 mm), and extremely smooth surfaces [18][19][20][21][22][23].…”