Wood Surface Research Articles

The Hydrophilicity of Samama Wood Surface Quality after Boron, Methyl Methacrylate Impregnation, and Heat Treatment

Indicators of surface roughness and surface-free energy can represent the improvement in wood surface quality. In this study, those two indicators were used to determine the change in the samama (Anthocephalus macrophyllus) wood surface following two modification steps, namely impregnation and heat treatment. The first step was boron impregnation in two forms applied separately, i.e., boric acid and borax. The second step was impregnation of methyl methacrylate followed by heat treatment at 90°C and 180°C. Surface roughness was determined following the ISO 4287:1997 standard, and surface free energy was analyzed using the Rabel Method. The results showed that the radial surface of samama wood naturally had a lower roughness than the tangential surface. Impregnation with boric acid, borax, and methyl methacrylate increased the wood surface roughness. However, heat treatment at 180°C tended to smooth the rough surface. Total surface free energy was altered after borax and methyl methacrylate impregnation. However, heat treatment seemingly withdrew the alteration. The polar components and dispersion contributed to total surface free energy with different compositions. In this study, the change in surface roughness was not congruent with the change in total surface free energy. Keywords: boron, heat treatment, impregnation, samama, surface free energy

Light-Induced Colour Changes in Wood Surfaces in Indoor Conditions Determined by an Artificial Accelerated Test: Influence of Wood Species and Coating Materials

Stabilising the natural colour of wood species exposed to light in indoor conditions is a challenge that could be better addressed based on a deeper understanding of the occurring phenomena and influencing factors. This paper investigates comparatively the light-induced colour changes for three hardwood species, namely, European maple (Acer pseudoplatanus L.), European ash (Fraxinus excelsior L.) and European walnut (Juglans regia L.), as well as the influence of finishing with three types of clear, colourless waterborne lacquers: acrylic-polyurethane (F1), acrylic (F2) and polyurethane (F3) on their colour stability. Colour measurements in the CIELab system in conjunction with an artificial accelerated ageing test under the action of UV-VIS radiation, simulating natural light passing through window glass, and two types of test samples were employed to highlight the influence and contributions of the wood substrate and of the coating films to the global colour modifications. Coating films applied on 1 mm clear glass slides were employed as a sort of “detachable” finish for this purpose. Direct exposure to UV-VIS light caused visible colour changes for both uncoated and coated wood surfaces, the values of the calculated colour differences (ΔE) after a 72 h exposure being dependant on both the wood species and the coating material. Excepting two situations for walnut, statistically significantly higher colour differences were obtained for the uncoated samples: maple (9.36 units), ash (8.39 units), walnut (6.20 units), compared to the coated ones: maple (4.92–5.71 units), ash (2.25–3.94 units), walnut (4.74–7.70 units). The wood substrates underlying the coating films were found to bring the maximum contribution to the overall colour changes in the clear coated surfaces, while the coating films employed in this research demonstrated a fairly good colour stability to UV-VIS light exposure, with maximum colour changes (∆E) up to only 1.30 units. Overall, the wood species and the type of coating were found as influencing factors in interaction with the light-induced colour changes in wood surfaces in indoor conditions.

Impact of surface finishing technology on slip resistance of oak lacquer wood floorboards with distinct gloss levels

ABSTRACT The choice of surface finishing technology for floorboards can significantly influence the risk of slipping. This study aimed to assess the impact of surface finishing technology on the likelihood of slippage, focusing on lacquered floorboards made of northern red oak (Quercus rubra L.). Four finishing methods were applied to the floorboard surfaces, with the primary distinction between the tested variants being the level of glossiness in the top layer, ranging from 3 to 20 gloss units (GU). To evaluate slip risk, tests were conducted using the British portable skid resistance tester (BSRT), providing numerical values in the form of the British pendulum number (BPN) and the slip resistance value (SRV) for qualitative comparisons. The analyses revealed that depending on the type of lacquered wood surface layer, the difference in BPN could vary from 46% to 77% for dry tests and from 48% to 60% for wet tests. Matte lacquer finishes, specifically at 19 GU, exhibited the smallest slip risk, while glossy finishes (4 GU) demonstrated the greatest slip risk, especially when the surface was wet. In terms of wet test results, the least slip risk, regardless of wood grain direction, was observed for variant No. 4 (low glossiness at 4 GU), with an SRV value ranging from 51 to 53. Conversely, variant No. 1 (high gloss at a mean of 19 GU) recorded the poorest slip resistance properties, with an SRV between 29 and 31. These findings suggest that matte lacquer finishes generally provide a safer option compared to glossy finishes, and the inclusion of brushing during production can enhance slip resistance. Furthermore, the direction of the wood grain was identified as a contributing factor to slip risk, with a 0° grain orientation presenting the highest risk. These insights can be valuable for flooring manufacturers and installers in selecting and applying finishes that effectively minimize the risk of slipping. These findings can be used by flooring manufacturers and installers to select and apply finishes that minimize slip hazard.

Study of Selective Modification Effect of Constructed Structural Color Layers on EUROPEAN Beech Wood Surfaces

In this study, the brush method was used to construct structural color layers on the surface of European beech wood, which has wide rays. The purpose was to expand the research on the structural color modification of wood surfaces and to promote its industrial application. By comparing the structural color layers constructed through brushing on beech wood and glass surfaces, the construction speed on the wood surface was significantly faster than that on the glass surface, which was mainly attributed to the porous structure and hydrophilicity of the wood, which made the solvents to be absorbed quickly, greatly improving construction efficiency. At the same time, the wide-ray regions of the European beech wood showed distinct and excellent structural color modification effects. This specific effect was not only reflected in faster construction speeds than other regions, but also in a complete and full-color block. Moreover, by changing the particle size, raw material, and structure of the microspheres, and by brushing several times, the special construction phenomenon and decorative effect still existed. By characterizing the surface morphology and roughness of beech wood, it was found that the surface of the wide rays was flatter than other anatomical structural regions, which was more conducive to the self-assembly of microspheres and the formation of a structural color layer. The results of this study will help to advance the development of technologies such as structural color-selective modification of wood surfaces.

Assessment of color and contact angle changes in waterborne stained wood under natural weathering condition of South Korea’s summer climate

This study aimed to develop a waterborne stain (WBS) that protects against weathering and increases resistance of wood to fungi when exposed to heavy rainfall. The WBS was prepared using an antibacterial agent, insect repellent, and copper nanoparticle solution (CN) as a surface coating agent. The WBS was applied on larch and hemlock wood, and changes in color and wettability due to natural and artificial weathering were evaluated. A gray-blue spot developed on the untreated wood surface within 30 d of outdoor exposure, which then spread over the entire wood surface, and the wood eventually turned black. Resistance to fungi increased when CN alone was applied; however, the CN surface was oxidized and turned gray after 30 d and 90 d for larch and hemlock, respectively. The water contact angle was increased due to leaching. The application of CN followed by WBS prevented wood discoloration under ultraviolet light and the wood showed excellent weathering resistance capacity. The prevention of wood discoloration and resistance to fungi by CN were confirmed, which could guide the development of a paint that can prolong protection from weathering of wood exposed to heavy rainfall events.

Fabrication of Mildew-Resistant Wood with Multi-Functional Properties Based on In Situ Growth of Metal-Organic Frameworks.

Wood is easily affected by decay fungi, mildew fungi, insects, water, UV, and other factors when used outdoors. In particular, mildew on the surface of wood negatively affects the appearance and practical use of wood or wood-based engineered products. In recent years, as a class of popular crystalline materials, metal-organic frameworks (MOFs) have been widely applied in electrochemistry, adsorption, anti-mildew efforts, and other areas. In this study, we first grew a Co-based metal-organic framework (Co-MOF) in situ on a wood surface and subsequently converted the Co-MOF in situ into a cobalt-nickel double hydroxide layer, which formed micro- and nanohierarchical composite structures on the wood surface. The low surface energy of the CoNi-DH@wood was further modified via impregnation with sodium laurate to obtain the superhydrophobic wood (CoNi-DH-La@wood). We characterized the microstructure, chemical composition, water contact angle, and anti-mold properties of the CoNi-DH-La@wood using SEM, XRD, XPS, water contact angle tests, and anti-fungal tests. The SEM, XRD, and XPS results confirmed that the metal-organic framework was coated on the wood surface, with the long-chain sodium laurate grafted onto it. The CoNi-DH-La@wood had a water contact angle of 151°, demonstrating excellent self-cleaning ability. In addition, the fabricated superhydrophobic balsa wood exhibited excellent chemical and environment stability. Lastly, the CoNi-DH-La@wood exhibited excellent anti-mildew properties in a 30-day anti-mildew test because the superhydrophobic coating was successfully coated on the wood surface. In summary, this work presents an attractive strategy for obtaining wood with superhydrophobic properties at room temperature, thereby endowing the wood or wood-based engineered products with excellent anti-mildew properties.

“APPROXIMATE” WIGGLE-MATCH DATING APPLIED TO EARLY AMERICAN MUSEUM OBJECTS

ABSTRACT Wiggle-match dating of tree-ring sequences is particularly promising for achieving high-resolution dating across periods with reversals and plateaus in the calibration curve, such as the entire post-Columbian period of North American history. Here we describe a modified procedure for wiggle-match dating that facilitates precise dating of wooden museum objects while minimizing damage due to destructive sampling. We present two case studies, a dugout canoe and wooden trough, both expected to date to the 18th–19th century. (1) Tree rings were counted and sampled for dating from exposed, rough cross-sections in the wood, with no or minimal surface preparation, to preserve these fragile objects; (2) dating focused on the innermost and outermost portions of the sequences; and (3) due to the crude counting and sampling procedures, the wiggle-match was approximated using a simple ordered Sequence, with gaps defined as Intervals. In both cases, the outermost rings were dated with precision of 30 years or better, demonstrating the potential of wiggle-match dating for post-European Contact canoes and other similar objects.

Differential Etching of Rays at Wood Surfaces Exposed to an Oxygen Glow Discharge Plasma.

Basswood samples were exposed to oxygen glow-discharge plasmas for 30 min, and etching of radial and tangential longitudinal surfaces was measured. It was hypothesized that there would be a positive correlation between etching and plasma energy, and differential etching of wood surfaces because of variation in the microstructure and chemical composition of different woody tissues. Etching at the surface of basswood samples was examined using profilometry. Light and scanning electron microscopy were used to examine the microstructure of samples exposed to plasma. There was a large effect of plasma energy on etching of basswood surfaces, and radial surfaces were etched to a greater extent than tangential surfaces. However, rays at radial surfaces were more resistant to etching than fibers, resulting in greater variation in the etching of radial versus tangential surfaces. The same phenomenon occurred at radial surfaces of balsa wood, jelutong and New Zealand white pine subjected to plasma etching. The possible reasons for the greater resistance of rays to plasma etching are explored, and it is suggested that such differential etching of wood surfaces may impose a limitation on the use of plasma to precisely etch functional patterns at wood surfaces (raised pillars, grooves), as has been done with other materials.

Sustainable cellulose nanofiber/hydrophobic silica nanoparticle coatings with robust hydrophobic and water-resistant properties for wood substrates

Hydrophobization of wood is pivotal for enhancing the utility of wood products. Traditional hydrophobic coatings, primarily petrochemical-based, are now being replaced by environmentally friendly silane-coupled inorganic nanoparticles. However, these alternatives face challenges like poor dispersion stability and weak wood surface adhesion. Our research introduces cellulose nanofibers (CNFs) into the condensation process of silica nanoparticles, creating a CNFs/silica nanoparticle composite. This composite exhibits remarkable dispersion stability and adjustable viscosity, leading to an improved hydrophobic silica/CNFs coating. Its versatility allows for various application methods, including spray, dip, and brush coating. Remarkably, the composite maintains a water contact angle of about 151°, demonstrating excellent water repellency, even with hydrophilic CNFs. The CNFs also enhance the interaction with wood surfaces, boosting the durability of the coating. This innovative approach not only improves storage stability and workability but also ensures uniform hydrophobicity and durable coating formation. Our findings suggest that CNFs derived from lignocellulosic biomass could ultimately be incorporated into environmentally friendly wood coating materials, significantly improving the shortcomings of conventional hydrophobic coatings while reducing dependence on petroleum-based products.

A new strategy for the preparation of wood-epoxy resin composites reinforced with controllable osmotic interfaces

As a multifunctional material, wood is widely used in interior decoration and construction engineering. The full-cell process of impregnating monomers into wood pores cavity in situ is one of the most common wood modification methods. However, this approach is time-consuming, material-wasting, and not environmentally friendly. In this study, we proposed a simple strategy to directly convert wood into high-performance composites by controlling wood surface penetration through resin pre-curing. A slight amount of resin used was sufficient to penetrate the wood surfaces, and the weight percent gain (WPG) of 11.45 %. High energy efficiency was achieved by simple temperature control (60 °C/120 °C). In addition, this method can rapidly produce wood composites with ultra-low density (0.51 g/cm3) and ultra-high specific bending strength (284 MPa·cm3g−1) in a very short time (4 h and 30 min). The results showed that the problem of excessive resin penetration was effectively solved by the pre-curing process, which enriched the gradient distribution of resin from the surface to the bottom of the wood and significantly improved the material properties. This efficient and environmentally friendly preparation strategy makes natural wood a low-cost, low-density, high-strength engineering material, which broadens the application of wood composites in construction engineering and interior decoration.

Recent Advances in Bio-Based Wood Protective Systems: A Comprehensive Review

This review emphasizes the recent ongoing shift in the wood coating industry towards bio-based resources and circular economy principles, promoting eco-friendly alternatives. In addressing wood’s vulnerabilities, this study investigates the use of natural compounds and biopolymers to enhance wood coatings. These materials contribute to protective matrices that safeguard wood surfaces against diverse challenges. Essential oils, vegetable oils, and bio-based polymers are explored for their potential in crafting eco-friendly and durable coating matrices. Furthermore, this review covers efforts to counter weathering and biological decay through the application of various natural compounds and extracts. It evaluates the effectiveness of different bio-based alternatives to traditional chemical preservatives and highlights promising candidates. This review also delves into the incorporation of sustainable pigments and dyes into wood coatings to enhance both protective and aesthetic qualities. Innovative pigments are able to provide visually appealing solutions in line with sustainability principles. As the wood coating industry embraces bio-based resources and the circular economy, researchers are actively developing protective solutions that encompass the coating matrix, preservatives, bio-based fillers, and natural-pigment dyes. This review showcases the continuous efforts of academia and industry to enhance wood coatings’ effectiveness, durability, and sustainability, while maintaining their aesthetic appeal.

Revealing the behavior and mechanism of surfactant-assisted liquid permeability in Poplar wood

Wood is a sustainable and porous resource that can be utilized to fabricate advanced functional materials. However, the low permeability of liquids within wood poses a challenge to widespread adoption and implementation of technology for producing wood-based functional materials. Surfactants are capable of reducing surface tension of liquids, thus holding promise for enhancing liquid permeability in wood. The effect of four surfactants (JFC-U, Tween 80, OP-10, DDAC) on liquid absorption of copper ethanolamine (CE) in wood was investigated under room temperature and pressure. Surfactants effectively increased liquid absorption of wood up to 2.3 times and weight percent gain by up to 5.8 times compared with that of CE control. The improvement effect of surfactants resulted from three aspects: significantly improved liquid wetting on wood surface, enhanced penetration of liquid in cell lumen, and promoted molecular movement within cell wall. Their contributions varied with the structure of surfactants. Surfactants with linear structure showing significantly reduced surface tension, and cationic surfactants exhibiting high adsorption capacity on wood surface both demonstrated superior efficacy in increasing liquid permeability. This study explored the mechanisms by which surfactants affect liquid permeability within wood, while also provided guidance to select effective surfactants to assist wood impregnation.

Enhancing the durability of reversible wettability on larch wood surfaces through optimized pretreatment methods

The development of superhydrophobic layers on wood is attracting plenty of scientific attention lately in the field of functional wood modification. However, the ability to resist mechanical wear is essential to improve the durability of the functional surface through simple treatment. Hot water, acid, and alkali were initially used to pre-treat larch wood samples, followed by a hydrothermal procedure to deposit zinc oxide (ZnO) nanostructures on the surface of the pretreated wood. Wood that has been pure water hydrothermally processed has a more distinctive ZnO structure with a compact arrangement and rod structure. After pretreatment, the surface contact angle of ZnO wood was greater than 150°, showing excellent superhydrophobic property, while the surface of directly loaded ZnO wood did not. Most importantly, in the test of wear resistance, hot water pretreated ZnO wood showed the optimized performance. The densely packed ZnO nanorods generated by hydrothermal pretreatment exhibit a more stable bond with the wood surface, thereby enhancing the mechanical stability of the wood to some extent both in the sandpaper wear and the tape tearing test. The superhydrophobic modified wood surface also had outstanding self-cleaning talents, which can also easily switch between light and heat caused a reversible shift in the surface wettability. This study offers insight into wood functionalization and addresses the endurance of surface changes on biomass materials.

Lightweight reinforced wood beams through compression of its surface layers combined with the removal of lignin and hemicellulose

When wood is used as a stressed component of building materials, the parts most prone to failure are the upper and lower surfaces which can be called the weak structure. In a hydrothermal environment, lignin and hemicellulose in wood readily soften and dissolve, thus leading to their designation as the weak structure. The weak structures results in the wood having a low strength. In this paper, the sandwich beam material can be obtained by two steps from the skin self-reinforcement method, whereby the weak structure of the wood surface was removed by the delignification, and then the wood surface was densified. The authenticity of the sandwich structure is proved by a scanning electron microscope (SEM) and density profile analysis. When the moisture content (MC) is 10 %–12 % and the mass loss ratio is 23.04 %, the optimal resilience of the sandwich beam is only 1 %, the maximum modulus of rupture (MOR) and modulus of elasticity (MOE) are 1.42 and 2.1 times greater than those of natural wood, respectively. This finding shows that our method strengthens the weak structure of natural wood, which has good flexural performance and springback ratio.

Short wavelength light absorption and conversion films containing carbon nanodots for light damage prevention

The carbon nanodots (CNDs) can absorb short wavelength light and enable excited electrons to achieve light conversion to long wavelength emission by radiative transition, while accompanying the non-radiative transition of excited electrons, in order to block the short wavelength light. The CNDs were prepared from chitosan as the carbon source, and then mixed with polyvinyl alcohol (PVA) to prepare CNDs-based optical blocking films (CND-OBFs) containing different proportions of CNDs. Images were clearly visible through CND-OBFs under both close and long-distance observation, demonstrating good transparency. The CND-OBFs were shown to block both UV light from sunlight and harmful blue light from computers, mobile phones and white light-emitting diodes. The CND-OBFs can thus be used to effectively block short wavelength light. Samples of wood were covered with different CND-OBFs and the wood surfaces were then irradiated with UV light (340 nm, 80 W). The results show that different CND-OBFs block short wavelength light to different extents; CND-OBF containing 15.7 % CNDs can completely block short wavelength light through absorption and conversion, protecting the wood samples from discoloration. This work provides a new research approach in which CNDs are used to protect wood by blocking short wavelength light.

Effect of temperature on the dynamic wettability of Chinese fir wood: integrative consideration of surface spreading, penetration and evaporation

Abstract Wood wettability, the process of liquid interaction with wood surfaces, is influenced by wood surface chemistry, structure, ambient conditions, and temperature. Understanding how temperature impacts wood wettability is crucial for high-temperature manufacturing processes. In this study, the sessile drop method was employed to explore the dynamic wettability of Chinese fir wood using three different liquids (water, glycerol and polyvinyl acetate (PVAc)) across a range of temperatures (25, 40, 60 and 80 °C). By considering spreading, penetration and evaporation, we revealed that the dynamic wettability of Chinese fir was strongly dependent on temperature and the type of liquid. Temperature elevation enhances wettability, leading to reduced contact angles and increased penetration ratios. Water exhibited the highest wettability, followed by glycerol, with PVAc being the least wetting agent. Notably, after 180 s of wetting at 80 °C, the measured contact angles were 0° for water, 45° for glycerol, and 120° for PVAc. When accounting for evaporation, the penetration of water decreased from 57 % to 47 % (25 °C) and 100 % to 62 % (80 °C). The activation energies for the penetration of water and PVAc into Chinese fir exhibited variations, with values of 35.3 and 158.3 kJ/mol, respectively. These comprehensive wetting results, covering spreading, penetration and evaporation, provide valuable insights into wood–water and wood–adhesive interactions, particularly when exposed to high-temperature conditions.

Study on biodegradation mechanism of Fusarium solani NK-NH1 on the hull wood of the Nanhai No. 1 shipwreck.

The Nanhai No. 1 shipwreck is an ancient wooden ship in the Southern Song Dynasty. Currently, serious challenges of microbial diseases exist on the hull wood. This study aimed to obtain microbial samples from the ship hull in December 2021 and analyze the microbial diseases through scanning electron microscopy and high-throughput sequencing to preserve the Nanhai No. 1 shipwreck. The biodegradation mechanism of diseased microorganisms was explored through whole genome sequencing and the detection of enzyme activity and gene expression levels of diseased microorganisms under different conditions. The results showed that there was obvious fungal colonization on the surface of the hull wood and Fusarium solani NK-NH1 was the dominant disease fungus on the surface. NK-NH1 has strong cellulose and lignin degradation ability. Its whole genome size is 52,389,955 bp, and it contains 17,402 genes. It has a variety of key enzyme genes involved in cellulose and lignin degradation. The NK-NH1 dominant degrading enzyme lignin peroxidase has the highest enzyme activity at pH = 4, NaCl concentration of 30%, and FeSO4 concentration of 50 mg/L, while laccase has the highest enzyme activity at pH = 4, NaCl concentration of 10%, and FeSO4 concentration of 100 mg/L. The above research results prove that NK-NH1 is a key fungus to the biodegradation of ship hull wood when it is exposed to air, low pH, high salt, and rich in sulfur iron compounds. This study provides a theoretical basis for the preservation of the Nanhai No. 1 shipwreck.

Fabrication of bulk superhydrophobic wood by grafting porous poly(divinylbenzene) to wood structure using isocyanatoethyl methacrylate.

Superhydrophobic treatment of wood can effectively reduce the interaction between wood and moisture, avoiding deformation, cracking, mould, and other defects caused by water absorption, which can extend the service life of wood and broaden the application field. Currently, the poor abrasion resistance of superhydrophobic wood is a crucial problem limiting its widespread application, and the preparation of superhydrophobic wood with robustness, abrasion resistance, and chemical resistance remains a huge challenge. In this work, robust bulk superhydrophobic wood with excellent abrasion resistance and chemical durability was fabricated by synthesizing porous poly(divinylbenzene) in wood cell cavities using graft copolymerization and solvothermal methods. The contact angles and rolling angles on the superhydrophobic wood surface were approximately 156° and 3°, respectively. Superhydrophobicity was carried through the entire structure of the wood. Even after severe damage by abrasion and sawing, as well as tests with organic solvents and harsh environments, the superhydrophobic properties of wood remained stable. Meanwhile, the superhydrophobic wood exhibited great self-cleaning and antifouling properties. In addition, the water uptake and dimensional stability of the wood were significantly improved. This work developed a simple, efficient, and durable strategy for the fabrication of superhydrophobic wood with robustness, abrasion resistance, and chemical resistance, which was expected to be applied to the wood industry to achieve the high-value applications of wood products and extend their service life.

Fully bio-based water-resistant wood coatings derived from tree bark.

Surface protection is essential when using wood as a construction material. However, the industry lacks sustainable alternatives to replace the presently dominant fossil-based synthetic water-resistant coatings. Here, we show a fully bio-based wood surface protection system using components sourced from birch bark and spruce bark, inspired by the natural barrier function of bark in trees. The coating formulation contains suberinic acids and spruce bark polyphenols, resulting in a waterborne suspension that is safe and easy to apply to wood. The polyphenols play a dual role in the formulation as they stabilize the water-insoluble suberinic acids and serve as nanofillers in the thermally cured coating, enabling the adjustment of the mechanical properties of the resulting coating. When applied to spruce wood, the coating formulation with 10% polyphenol and 90% suberinic acids achieved a water absorption value of 100 g m-2 after 72 hours of water exposure, demonstrating superior performance compared to an alkyd emulsion coating. We conclude that instead of combusting tree bark, it can serve as a valuable resource for wood protection, closing the circle in the wood processing industry.

The Prospect of Artificial Intelligence-Based Wood Surface Inspection: A Review

The Prospect of Artificial Intelligence-Based Wood Surface Inspection: A Review