Surface Treatment Of Wood Research Articles

Transparent Coating Systems Applied on Spruce Wood and Their Colour Stability on Exposure to an Accelerated Ageing Process

The objective of this study was to investigate the colour stability of spruce wood surfaces treated with coating systems (CS) and exposed to accelerated ageing. The tested CSs were transparent and three-layered; the top layer was modified with ultraviolet (UV) absorbers, while the base layer was modified with lignin stabiliser. Spruce wood surfaces treated with unmodified CSs were not colour-stable during the accelerated ageing process, with the surface exhibiting colour change after just 100 ageing hours. Adding specific UV absorbers into the top layer and lignin stabiliser into the base layer significantly improved the colour stability of the surface-treated wood. In all cases, however, the colour variation associated with ongoing ageing was significant. An additional study task was to determine whether the discolouration of surface-treated wood is caused by the discolouration of the wood substrate alone or also by the CS discolouration. Consequently, there was also the examination of discolouration of the individual coating materials or coating systems applied to glass slides. This testing proved that in the case of wood surface-treated with CS, without lignin stabiliser, the discolouration was the same as that of the substrate, and this was true throughout the whole ageing process. In the case of wood surface-treated with CS, but with lignin stabiliser, there were, in some cases, significant differences in discolouration between surface-treated wood and the wood substrate. These variations were especially evident during the initial 300 ageing hours.

A Review on the Effect of Wood Surface Modification on Paint Film Adhesion Properties

Wood surface treatment aims to improve or reduce the surface activity of wood by physical treatment, chemical treatment, biological activation treatment or other methods to achieve the purpose of surface modification. After wood surface modification, the paint film adhesion performance, gluing performance, surface wettability, surface free energy and surface visual properties would be affected. This article aims to explore the effects of different modification methods on the adhesion of wood coating films. Modification of the wood surface significantly improves the adhesion properties of the paint film, thereby extending the service life of the coating. Research showed that physical external force modification improved the hydrophilicity and wettability of wood by changing its surface structure and texture, thus enhancing the adhesion of the coating. Additionally, high-temperature heat treatment modification reduced the risk of coating cracking and peeling by eliminating stress and moisture within the wood. Chemical impregnation modification utilized the different properties of organic and inorganic substances to improve the stability and durability of wood. Organic impregnation effectively filled the wood cell wall and increased its density, while inorganic impregnation enhanced the adhesion of the coating by forming stable chemical bonds. Composite modification methods combined the advantages of the above technologies and significantly improved the comprehensive properties of wood through multiple modification treatments, showing superior adhesion and durability. Comprehensive analysis indicated that selecting the appropriate modification method was key for different wood types and application environments.

Effects and Modification Mechanisms of Different Plasma Treatments on the Surface Wettability of Different Woods

Plasma treatment of wood surfaces has shown significant effects, but different excitation methods used for different species of wood generally result in varied characteristics of wood surfaces. Secondly, plasma modification greatly enhances the absorption of liquids by wood, but the relationship between liquid absorption and surface wettability is rarely studied. Limited detailed investigation of the modification effects and mechanisms has hindered the large-scale applications of plasma treatment in the wood industry. In this study, two typical plasmas, radio frequency (RF) plasma and gliding arc discharge (GAD) plasma, were employed to treat three species of wood: poplar, black walnut, and sapele. By focusing on changes in the contact angle of the wood surface, an exponential equation fitting method is used to determine the measurement time for contact angles. The research identified that factors contributing to the decrease in contact angle after plasma modification include not only the increase in surface energy but also liquid absorption. SEM and XPS analyses demonstrate that plasma etching accelerated liquid absorption by modifying the surface topography, while the increase in surface energy was due to the addition of oxygen-containing groups. High-valence C=O and O-C=O groups serve as indicators of plasma-induced surface chemical reactions. RF modification primarily features surface etching, whereas GAD significantly increases the active surface groups. Thus, different plasmas, due to their distinct excitation modes, produce diverse modification effects on wood. Considering the various physical and chemical properties of plasma-modified wood surfaces, recommendations for adhesive use on plasma-modified wood are provided.

Investigations of Surface-Treated Wood by a Micro-Indentation Approach: A Short Review and a Case Study

Over the past 50 years, instrumented indentation, in which an indenter tip probes the specimen surface with a regulated force and displacement to characterize its mechanical properties, has evolved. With the development of atomic force microscopy, instrumented nanoindentation has been extensively applied, and instrumented indentation in the micro range (micro-indentation) has been somewhat overshadowed by nanoindentation. However, micro-indentation remains an extremely useful technique that has the potential to investigate various properties of surface treated wood. In the first, overview-type part of the paper, instrumented micro-indentation is described and some examples of its possible applications in the field of wood science and technology are presented. To illustrate the importance of this experimental technique, some results of micro-indentation experiments carried out in our wood surface treatment laboratory are shown in the second part of the paper. The objects of the tests were untreated Scots pine wood and Scots pine wood with surface deposits of SiO2 or ZnO. The differences between the mechanical properties of early and latewood could be clearly distinguished by the micro indentation technique. On the other hand, the influence of ZnO and SiO2 particles on mechanical properties as a function of indentation depth could not be detected by this technique.

The Effect of Hot and Cold Check Tests on Surface Roughness and Glossiness in Varnished Wood Material

In this study, specimens from Scots pine (Pinus sylvestris L.), Anatolian chestnut (Castanea sativa Mill.) and Eastern beech (Fagus orientalis Lipsky) tree species, prepared according to ISO 3129, were conditioned according to TS ISO 13061-1. Cellulosic varnish, water-based varnish, and glass polish varnish were applied to their surfaces in accordance with ASTM-D 3023 principles. In the study, roughness (TS 2495 EN ISO 3274 and TS EN ISO 21920-3) and gloss (according to TS EN ISO 2813) values of the samples were calculated after hot and cold check test. Varnished test specimens prepared in 100 mm × 100 mm ×10 mm dimensions were first kept in drying oven at (50±5) °C for 1 hour, then were kept in conditioning room for 1 hour, and then at (-20±2) °C for 1 hour, according to ASTM D1211-97. These processes were accepted as one cycle, and tests were continued until 15 cycles. Afterward, glossiness was measured as perpendicular and parallel to fibers at 60º with a gloss measurement device, and surface roughness values of Ra and Rz were determined with a surface roughness measuring device. According to the results obtained, Scots pine (Pinus sylvestris L.), Eastern beech (Fagus Orientalis Lipsky), and Anatolian chestnut (Castanea sativa Mill.) varnish-coated wood material surfaces all showed a decrease in gloss values after hot-cold shock effect. While an increase occurred in Rz values of roughness for all wooden surfaces, Ra values roughness increased for Scots pine and chestnut and decreased for eastern beech. Gloss and roughness values of surface-treated wood materials against changing weather conditions can determine usefulness of the surface material used. The findings obtained in this study can be useful to manufacturers who use wooden products in the design of marine vehicles and those who export furniture to countries in different climatic conditions.

Formulation of environmentally robust flame-retardant and superhydrophobic coatings for wood materials

Developing flame-retardant wood with integrated anti-wetting property, self-cleaning and good weatherability, has received intensive attention, which is vital to the rapid advancements in construction and building materials. Here, a superhydrophobic and flame-retardant coating is constructed based on a trinity monocomponent intumescent flame retardant, polydimethylsiloxane resin and modified SiO2 nanoparticles. Such a coating can endow wood materials with high flame retardancy and self-cleaning performances. In comparison to pristine woods, the surface-treated wood shows a self-extinguish behavior in the vertical burning test with an obviously increased limiting oxygen index of 31.0% and UL 94 rating of V0. The peak heat release rate is reduced by 24.4% and the total heat release after surface treatment is decreased to 24.5 MJ/m2. The water-repellency of sample is greatly improved with water contact angle over 154° and slide angle below 5°, exhibiting appreciable resistance to dust contamination. Due to the significant anti-wetting property, the coating can effectively protect the inner flame-retardant layer from water penetration, thereby the treated wood can preserve high flame-retardant performances even after being immersed in water for 24 h. More importantly, the modified wood material can endure different harsh environmental conditions, including high temperatures, UV light irradiation, hydrothermal environment and mechanical impact, without losing the superhydrophobicity or flame retardancy, presenting high weatherability and mechanical robustness. The findings provide an effective approach to prepare high-weatherability fire-safety wood materials that have application potential in outdoor environments.

Physical Chemistry of the Interaction of Cellulose with Lignin during Wood Surface Treatment with a Phosphate Flame Retardant

Physical Chemistry of the Interaction of Cellulose with Lignin during Wood Surface Treatment with a Phosphate Flame Retardant

Cocuring of Epoxidized Soybean Oil-Based Wood Adhesives and the Enhanced Bonding Performance by Plasma Treatment of Wood Surfaces

Cocuring of Epoxidized Soybean Oil-Based Wood Adhesives and the Enhanced Bonding Performance by Plasma Treatment of Wood Surfaces

Durability and Fire Performance of Charred Wood Siding (Shou Sugi Ban)

Shou sugi ban, also known as yakisugi, or just sugi ban, is an aesthetic wood surface treatment that involves charring the surface of dimensional lumber, such as exterior cladding. The goal of this research is to examine the effect of shou sugi ban on the flammability and decay resistance of wood. Several species and variants of commercially available sugi ban were tested. The flammability was examined from the heat release rate curves using the oxygen consumption method and cone calorimeter. Durability was examined with a soil block assay for one white-rot fungus and one brown-rot fungus. The testing showed that the shou sugi ban process did not systematically improve the flammability or durability of the siding.

Study of resistance of thermomodified wood to the influence of natural conditions

It is established that thermal modification provides a decrease in the hydrophobicity of wood. Additional wood surface treatment reduces water absorption factor of 2 and modified sample at a temperature of 220°C – 3 times. Geometric and dimensional stability is improved by 2 times. The effect of heat treatment on the water absorption of wood is slightly smaller - for samples modified at 190 and 220°C for more than 10 hours – 20 %. Additionally, a 20 % deterioration in water absorption can be achieved by applying oil-wax or azure. With increasing temperature modification improves color stability to UV-rays. If the wood after termomodyfikuvannya 160°C color difference ΔE 2 times larger, 190 and 220°C – does not change. Protection after applying azure to the surface is slightly better compared to oil-wax. Thermal modification and finishing paint and varnish materials increases resistance to surface weathering. Therefore, such treatment is appropriate for the protection and aesthetic appeal of wood products.

Plasma Treatment of Thermally Modified and Unmodified Norway Spruce Wood by Diffuse Coplanar Surface Barrier Discharge

This work deals with the treatment of wood surfaces by diffuse coplanar surface barrier discharge (DCSBD) generated at atmospheric pressure. The effect of the distance of the sample from the electrode surface and the composition of the working gas in the chamber was studied. Norway spruce (Picea abies) wood, both unmodified and thermally modified, was chosen as the investigated material. The change in the surface free energy (SFE) of the wood surface was investigated by contact angles measurements. Chemical and structural changes were studied using infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Activation at a 0.15 mm gap from the electrode led in all cases to an increase in the SFE. The largest change in SFE components was recorded for wood thermally modified to 200 °C. At a 1 mm gap from the electrode increase of SFE occurred only when oxygen (O2) and argon (Ar) were used as working gas. Treatment in air and nitrogen (N2) resulted in an anomalous reduction of SFE. With the growing temperature of thermal modification, this hydrophobization effect became less pronounced. The results point out the importance of precise position control during the DCSBD mediated plasma treatment. A slight reduction of SFE on thermally modified spruce was achieved also by short term ultra-violet (UV) light exposure, generated by DCSBD.

Possibilities of Wood Surface Treatment Technologies Utilizing Tribological Phenomena

Possibilities of Wood Surface Treatment Technologies Utilizing Tribological Phenomena

Fabrication of Superhydrophobic Wood Surface by Etching Polydopamine Coating with Sodium Hydroxide

Superhydrophobic treatment of wood surfaces can effectively prevent the contact between the external moisture and wood, which improves the service life of the wood. In this study, different rough surfaces of wood were constructed, derived from the self-polymerization of dopamine (DA) in weak base solution to form a polydopamine (PDA) coating and the deprotonation of the PDA coating in a strong base solution. Furthermore, octadecyltrichlorosilane (OTS) was used as a low-surface-free-energy agent to modify rough surface in order to prepare superhydrophobic woods: Wood@PDA–NaOH–OTS and the Wood@PDA–NaOH/SiO2–OTS. The contact angles (CAs) and sliding angles (SAs) of the resulting superhydrophobic woods were tested. The results showed that the CA and SA of the Wood@PDA–NaOH–OTS were 151° and 4.8°, respectively; the CA and SA of the Wood@PDA–NaOH/SiO2–OTS were 155.1° and 5.0°, respectively. Surface electron microscopy (SEM) images presented that NaOH successfully etched the PDA coating, and the roughness was further improved by adding nano-SiO2. Atomic force microscope images (AFM) revealed that the nano-SiO2 particles could effectively provide nanolevel roughness, which was beneficial to the wood’s superhydrophobic properties. In addition, the obtained superhydrophobic wood possessed strong surface stability and anti-loss property, as well as resistance to acid-base solution and organic solvent.

The influence of selected treatment parameters with atmospheric plasma on the treatment process and wood wettability

The paper presents the use of low-temperature plasma, generated in the air at atmospheric pressure, for treatment of wood surfaces to improve their wettability. For this purpose, a dielectric barrier discharge plasma device with a floating electrode configuration was used. The density and homogeneity of the plasma discharge, formed between the isolated high voltage electrodes and the surface of the spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) wood, was shown to be highly dependent on the size of the gap between the electrode and wood. Topography measurements using a confocal laser microscope showed that exposure of wood to plasma causes changes on its surface at the sub-microscopic level. Measurements of the contact angles of water droplets and water-based coating showed the improved susceptibility to wetting of treated surfaces. Differences in surface wettability were also detected depending on the selected machining parameters: type of wood, workpiece feed speed, the distance between the electrodes, the distance between the electrodes and workpiece, and workpiece thickness.

Wood surface treatment techniques for enhanced solar steam generation

Water vapor is vital both as an energy carrier and as an intermediary state for removing impurities from water. In nature, transpiration occurs when water is transported (against gravity) from the roots to the underside of leaves where it evaporates. Using this process, one large tree can pump and purify 400 L of water each day. Based on trunk cross-sectional area, this corresponds to a water flux range of ∼100–1000 kg/m2day, but based on evaporation area it only corresponds to a rate of ∼0.1 kg/m2day. Compared to industrial mechanisms of producing water vapor (i.e. typical thermal-driven systems have a flux of ∼4000 kg/m2day), natural wood has a relatively low flux. In an effort to boost the flux of sustainable, natural wood, we investigated wood surface modifications, laser carbonization and deposition of gold nanolayers, which achieved an instantaneous evaporation rate of ∼4 kg/m2h—under 3 kW/m2 light intensity, exceeding all previous studies of synthetic materials (including 3.8 kg/m2h reported by Zhou et al. in a 2016 Nature Photonics article) for solar steam generation applications. The cost analysis of different natural and synthetic material-based techniques for solar steam generation indicated that the carbonization and laser treatments are very cost-effective and even the gold coating was comparable to previously reported synthetic materials. Based on these results, we suggest that natural, surface-modified poplar wood could represent a viable alternative to synthetic materials for liquid/vapor separation.

Preparation of Lignin Nanoparticles from Wood Waste for Wood Surface Treatment.

Lignin was isolated from wood wastes comprising Iroko sawdust (IR) and mixed sawdust from Iroko and Norway spruce (IRNS), furnished by a local wood houses producer. The respective acidolysis lignin fractions were structurally characterized using pyrolysis (Py)-GCMS, two-dimensional heteronuclear single quantum correlation nuclear magnetic resonance (2D HSQC NMR), Fourier-transform infrared FTIR and ultraviolet-visible (UV-VIS) spectroscopies, size exclusion chromatography, and standard wet-chemistry methods for Klason lignin and polysaccharides determination. The isolated lignin fractions were subsequently used for the preparation of lignin nanoparticles (LNPs) using a non-solvent method. LNPs were then used for wood surface treatment using a dip-coating technique. The coated wood samples were analyzed by colorimetry and scanning electron microscopy (SEM) before and after artificial weathering experiments in a UV chamber to investigate the UV protection potential of the LNPs coatings. Wood samples dip-coated with LNPs showed promising surface modifications resembling a sort of film of fused LNPs. Coatings made from IR-LNPs and IRNS-LNPs performed significantly better in artificial weathering experiments than uncoated reference samples.

Preparation of Lignin Nanoparticles from Wood Waste for Wood Surface Treatment

Preparation of Lignin Nanoparticles from Wood Waste for Wood Surface Treatment

Dielectric barrier discharge (DBD) plasma pretreatment of lignocellulosic materials in air at atmospheric pressure for their improved wettability: a literature review

AbstractThe treatment of wood surfaces with gas discharges is one of the methods to achieve better surface adhesion properties. Good penetration, spreading and wettability of the applied liquid adhesives and coatings is a crucial factor for their adequate mechanical properties. Plasmas are the result of electrical discharge and can be created in different ways. The plasma treatment (PT) is frequently executed prior to material bonding or coating via the so-called dielectric barrier discharges (DBD) at atmospheric pressure. This literature review summarizes the essential aspects of DBD PTs aiming at a better wettability and surface adhesion. After introduction of the principle of DBD, the individual effects of internal and external parameters of the process will be discussed, which influence the final properties of treated materials.

Influence of Surface Treatment of Wood to the Flame Length and Weight Loss under Load Single-Flame Source

The aim of the paper is reaction of fire of two selected wood (spruce and beech wood). These type of woods are used most in the construction industry both as a lining in outdoor or indoor, on the stairs or in the construction of roof trusses. Experiment was focus on testing reaction of fire on two different types of surfaces and the treated and untreated surfaces. The modified surface was abraded by sandpaper and rough surface was only saw wood. The main objective of this study was to observe and compare the length of the flame spread and weight loss of spruce and beech forest in treated and untreated surfaces when applied Single-flame source on the surface of the material.

Sensory and Emotional Perception of Wooden Surfaces through Fingertip Touch.

Previous studies on tactile experiences have investigated a wide range of material surfaces across various skin sites of the human body in self-touch or other touch modes. Here, we investigate whether the sensory and emotional aspects of touch are related when evaluating wooden surfaces using fingertips in the absence of other sensory modalities. Twenty participants evaluated eight different pine and oak wood surfaces, using sensory and emotional touch descriptors, through the lateral motion of active fingertip exploration. The data showed that natural and smooth wood surfaces were perceived more positively in emotional touch than coated surfaces. We highlight the importance of preserving the naturalness of the surface texture in the process of wood-surface treatment so as to improve positive touch experiences, as well as avoid negative ones. We argue that the results may offer possibilities in the design of wood-based interior products with a view to improving consumer touch experiences.