Search Results (71)

Spruce wood is a natural polymeric material, consisting of cellulose, lignin, hemicelluloses and other secondary components, which gives it a unique chemical footprint and architecture. Varnishes are used in musical instruments to protect the wood against humidity variations, wood being a hygroscopic material, but also to protect the wood from dirt. The varnishes used both to protect the wood from resonance and to ensure a special aesthetic appearance are either polymeric varnishes (nitrocellulose, oil-based) or volatile solvents (spirit). In this study, the color changes, the surface morphology and the chemical spectrum produced by three types of varnishes, applied in 5, 10 and 15 layers, on resonance spruce plates were analyzed. The results revealed significant changes in the color parameters: the lightness decreased by approximately 17% after the first layer, by 50% after 5 layers, by 65% after 10 layers and by 70% after 15 layers. The color parameters are most influenced by the anatomical quality of spruce wood (annual ring width and earlywood/latewood ratio) in the case of oil-based varnishes and least influenced in the case of nitrocellulose varnishes. The chemical fingerprint was determined by FTIR spectrum analysis, which revealed that the most pronounced absorptions were the double band 2926–2858 cm⁻¹, corresponding to aliphatic methylene and methyl groups (asymmetric and symmetrical C-H stretch), and the bands at 1724 cm⁻¹ (oil-based varnish), 1722 cm⁻¹ (nitrocellulose varnish) and 1708 cm⁻¹ (spirit varnish), all assigned to non-conjugated carbonyl groups in either carboxylic acids, esters aldehydes or ketones. The novelty of the study lies in the comparative analysis of three types of varnishes used in the musical instrument industry, applied to samples of spruce resonance wood with different macroscopic characteristics in three different layer thicknesses. Full article

This paper presents the effect of wood treatment with cellulose nanofibers on its parameters. The wettability, color changes (also after UV+IR radiation), equilibrium moisture content and mechanical parameters of wood treated with cellulose nanofibers (CNF) in three concentrations (0.5, 1 and 2%) were determined. Wood treatment with CNF increased the wettability of its surface, as evidenced by lower values of the contact angle (24.3–56.3 degrees) compared to untreated wood (98.3 degrees). The SEM images indicated the formation of cellulose nanofiber networks on the wood surface, especially in the case of 2% CNF-treated wood, which formed a well-adhered and homogenous film. Wood treated with 0.5% CNF showed a lower total color change (∆E*) value (1.9) after aging compared to untreated wood (2.9), indicating that the color changes in the treated wood were very small and recognizable only to an experienced observer, while the color differences in the control wood were recognizable to an inexperienced observer. Furthermore, CNF showed no negative effect on the strength parameters of the treated wood and only slightly affected the equilibrium moisture content for both sorption phases over the entire relative humidity range compared to control samples. The results prove the effective use of cellulose nanofibers in wood treatment, which can be an ecological and non-toxic component of wood protection systems. Full article

The new wood–plastic composites (WPC) biocomposites, a promising blend of poly(lactic acid) (PLA) and lignocellulosic fillers, are the subject of our study. We used bark and sawdust at 40, 50, and 60% as PLA fillers. The innovative use of ion implantation to modify the surface properties of the produced composites could have significant implications. Argon ions were used in three dosages (1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷ cm⁻²) at an accelerating voltage of 60 kV. The modified composites were then analyzed for changes in surface wettability, surface energy, and color. Our findings demonstrate that the dosage of argon ion implantation and the filler used have a profound impact on the properties of the modified surfaces. In general, ion implantation enhances the surface wettability of composites and pure PLA, with the recorded relationships being more pronounced in composites containing higher proportions of lignocellulosic fillers. Furthermore, the implantation of ions on the surface of composites induces changes in their color, opening up new possibilities for the field of materials science. Full article

This study explores the effects of calcium carbonate (CaCO₃) mineralization on radiata pine wood, focusing on artificial weathering performance, mold resistance, and mechanical and adhesion properties. CaCO₃ mineralization demonstrated significant improvements in wood’s resistance to environmental degradation, reducing color changes and inhibiting mold growth. Despite these benefits, the process showed limited impact on mechanical properties and adhesive performance. The study utilized a novel gaseous diffusion method for mineralization, which has been proven to provide effective fire-retardant protection at low weight gain. The mineralized samples used for the weathering, mold, and adhesion tests achieved an average weight gain of 15%, while those used to assess changes in mechanical properties and density 18%. The findings suggest that while CaCO₃ enhances surface durability, further research is needed to optimize mechanical and adhesive properties, potentially integrating additional treatments. This work highlights the potential of CaCO₃ mineralization for sustainable wood applications, offering insights into its practical implications and future research directions. Full article

Thermal modification improves the properties of wood, especially its stability and durability. We thermally treated spruce wood with the Thermowood process at three temperatures (160 °C, 180 °C, and 210 °C) and subjected it to accelerated aging in wet mode. We evaluated the chemical composition (wet chemistry, infrared spectroscopy), color, surface morphology, and wetting of the wood surface with water. Thermal treatment caused a significant decrease in hemicelluloses (up to 72.39% at a temperature of 210 °C), which initiated an increase in the content of more resistant wood components—cellulose and lignin. With accelerated aging, the hemicellulose content decreased by another 5%. The most significant differences between the infrared spectra of thermally modified wood before and after exposure to accelerated aging were in the absorption bands of lignin (1509 and 1596 cm⁻¹) and in the region of carbonyl groups between 1800 and 1630 cm⁻¹. Thermal treatment also caused a change in the color of the wood to dark brown; the overall color difference ΔE increased several times. The thermal-induced shortening of polysaccharide fibers and reduction in their width were even more manifested during accelerated aging. This work contains new knowledge about the properties critical for the reuse of thermally modified wood after accelerated aging, simulating the end of its life cycle. Full article

This study evaluates the chemical, physical, mechanical, and biological properties of untreated and heat-treated Cryptomeria japonica (Thunb ex L.f.) D.Don wood from the Azores, Portugal. Heat treatment was performed at 212 °C for 2 h following the Thermo-D class protocol. Chemical analysis revealed an increase in ethanol soluble extractives and lignin content after heat treatment, attributed to hemicellulose degradation and condensation reactions. Dimensional stability improved significantly, as indicated by reduced swelling coefficients and higher anti-swelling efficiency (ASE), particularly in the tangential direction. Heat-treated wood demonstrated reduced water absorption and swelling, enhancing its suitability for applications requiring dimensional stability. Mechanical tests showed a decrease in bending strength by 19.6% but an increase in the modulus of elasticity (MOE) by 49%, reflecting changes in the wood’s structural integrity. Surface analysis revealed significant color changes, with darkening, reddening, and yellowing, aligning with trends observed in other heat-treated woods. Biological durability tests indicated that both untreated and treated samples were susceptible to subterranean termite attack, although heat-treated wood exhibited a higher termite mortality rate, suggesting potential long-term advantages. This study highlights the impact of heat treatment on Cryptomeria japonica wood, emphasizing its potential for enhanced stability and durability in various applications. Full article

This study examined the degradation of oil paint coatings on wood under UV light and heat, focusing on three drying oils: tung oil (TO), linseed oil (LO), and walnut oil (WO). Model coatings were prepared with malachite pigment on rubber wood, then exposed to 240 h of UV light at temperatures of 40 °C, 50 °C, and 60 °C. The results showed that tung oil (TO) was the most prone to degradation. After exposure to 60 °C, the lightness (L value) of TO decreased from 51.44 to 50.98, while LO and WO maintained higher lightness. The color differences (ΔE) for TO, LO, and WO were 3.08, 3.26, and 2.87, respectively. Gloss measurements revealed that TO had the lowest initial gloss (3.87 GU), while WO had the highest gloss value. After UV exposure, all three coatings showed a decrease in gloss to varying degrees. Fourier transform infrared spectroscopy (FTIR) analysis confirmed oxidative degradation in TO, characterized by increased hydroxyl and carbonyl bands, while LO and WO exhibited better chemical stability. Scanning electron microscopy (SEM) images revealed that the surface of TO was the roughest, while the WO surface was the smoothest. After UV exposure, the surface of TO became significantly rougher, while the WO coating showed almost no changes, maintaining better structural integrity. The results suggest that LO and WO are more resilient to UV light and thermal stress, making them more suitable for protecting wooden products. Full article

The multi-layered and multi-material structures of a violin’s surface varnish film make it more challenging to comprehensively understand the patterns of sound quality changes during the coating process. Using an alcohol varnish coating technique on one or both sides of the wood, along with a combination of micro-morphology, material characterization, and vibration signal processing, this study traced and analyzed the changes in the acoustic vibration properties of Norway spruce wood during the coating process. The results showed that the acoustic characteristics of the coated wood tended to change in an unfavorable direction throughout the coating process, and the specific dynamic elastic modulus (E_sp) of the final single- and double-sided coating varied by −1.77% and −6.07%, respectively. The loss angle tangent (tanδ) had the opposite trend, with rates of change of 20.76% and 30.42%. The sizing and priming treatments in the pretreatment stage had some positive effects on the acoustic properties of the wood specimens. Additionally, significant changes in acoustic vibration performance parameters began to be highlighted at the color paint stage (p < 0.05). These insights provide reference data for the improvement of violin acoustic performance and the simplification of the coating process. Full article

This study investigated the effects of adding fluorine components to a new wood surface treatment technology called high-speed friction (hereinafter, “HSF”), which rubs wood surfaces at high speeds with a smooth metal surface. The changes in the color, surface roughness, and water contact angle of the spruce surface were evaluated. HSF treatment was performed using a stainless-steel tool coated with polytetrafluoroethylene and an uncoated tool. In addition, fluorinated oil was added as a pretreatment for HSF. The results showed that the spruce surface became darker in color when subjected to HSF. In particular, the brightness of the spruce surface was significantly reduced when rubbed with the uncoated tool. However, the addition of fluorine components to the tool surface and pretreatment suppressed blackening. Surface roughness decreased after HSF treatment; in particular, a smoother wood surface could be formed under the conditions in which fluorine components were added to the tool and wood surface. The contact angle on the spruce surface after HSF treatment improved compared to that without treatment, and it was found that a water-repellent surface with a maximum contact angle of 110° could be formed after HSF treatment with the addition of fluorine components to the tool and wood surface. Full article

This research aimed to examine the effects of a deep impregnation technique (Royal process) and surface coating using a linseed oil-based product, enhanced with small amounts of brown and grey pigments, on the natural and artificial weathering of wood. The treated and reference samples underwent natural weathering for five years and artificial weathering for 1900 h. Changes in color and surface roughness were assessed during weathering. For the artificially weathered samples, liquid water absorption was measured both before and after exposure. The impregnated and coated samples gradually lost their brown color, turning grey over time. More pronounced differences were observed during natural weathering, with the coated samples showing greater structural changes on the wood surface. In contrast, impregnated samples slowed down structural alterations compared to the reference samples. Both treatments effectively reduced water absorption before weathering, although this effect diminished after exposure. The treatments did not significantly impact the fire resistance of spruce and beechwood. Full article

This study investigated the closed-loop recycling of 3D-printed wood fiber (WF)-filled polylactic acid (PLA) composites via fused filament fabrication (FFF). The WF–PLA composites (WPCs) were extruded into WPC filaments (WPC_fs) to produce FFF-printed WPC parts (WPC_ps). The printed WPC_ps were reprocessed three times via extrusion and 3D-printing processes. The tensile properties and impact strengths of the WPC_fs and WPC_ps were determined. To further investigate the impact of closed-loop recycling on the surface morphology, crystallinity, and molecular weight of WPC_fs, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), respectively, were used. After closed-loop recycling, the surface morphology of the WPC_fs became smoother, and a decrease in the pore sizes was observed; however, the tensile properties (tensile strength and elongation at break) deteriorated. With increasing numbers of recycling iterations, the molecular weight of the PLA matrix decreased, while an increase in crystallinity was observed due to the recrystallization of the low-molecular-weight PLA molecules after recycling. According to the SEM images of the recycled WPCps, their layer heights were inconsistent, and the layers were rough and discontinuous. Additionally, the color difference (ΔE*) of the recycled WPC_ps significantly increased. Compared with those of the WPC_ps after recycling them only once, the tensile strength, elongation at break, and impact strength of the WPC_ps noticeably decreased after recycling them twice. Considering the changes in various properties of the WPC_fs and WPC_ps, the FFF-printed WPC parts can be reprocessed only once through 3D printing. Full article

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the increase in crystallinity observed in the case of birch was more significant than in the case of pine. FT-IR analyses of pine samples impregnated with graphene oxide showed changes in intensity in the absorption bands of 400–600, 700–1500 cm⁻¹, and 3200–3500 cm⁻¹ and a peak separation of 1102 cm⁻¹, which may indicate new C-O-C connections. In the case of birch, only some differences were noticed related to the vibrations of the OH group. The proposed modification also affects changes in the color of the wood surface, with earlywood containing more graphene oxide than latewood. Analysis of scanning electron microscope images revealed that graphene oxide adheres flat to the cell wall. Considering the differences in the anatomical structure of both wood species, the research showed a statistically significant difference in water absorption and retention of graphene oxide in wood cells. Graphene oxide does not block the flow of water in the wood, as evidenced by the absorbability of the working liquid at the level of 580–602 kg/m³, which corresponds to the value of pure water absorption by wood in the impregnation method using a single negative pressure. In this case, higher graphene oxide retention values were obtained for pine wood. Full article

Although linseed oil (LO) has been used in wood protection for centuries, research continues to develop new and more effective formulations and treatment approaches. In the future, growing interest in LO use could be expected due to its cost and environmental friendliness. This review summarizes recent research (from 2000 onwards) on the use of LO in wood protection, published in peer-reviewed scientific journals and included in the online publication databases Scopus or Web of Science. The studies cover surface and impregnation treatments of various wood substrates using different LO formulations, including chemically modified LO and the use of LO as a base for the development of biofinish and as a medium for thermal modification of wood, as well as research into the mechanisms behind the changes in wood properties due to treatment methods and interaction with LO formulations. Although the improvement of wood hydrophobicity and biodurability dominates, other aspects such as weathering and color stability, adhesion, and environmental safety are included in these studies. In general, almost all of the studies show a greater or lesser potency of the proposed approaches to provide benefits in wood protection; however, the level of innovation and practical feasibility varies. Full article

Improving the durability of short-rotation wood can be achieved through chemical and thermal modification. Chemical and thermal modification can have an impact on the physicochemical properties of wood, which can affect wood’s surface characteristics and its resistance to weathering. The purpose of this study was to investigate the surface characteristics and artificial weathering resistance of chemically and thermally modified short-rotation teak wood coated with linseed oil (LO)-, tung oil (TO)-, and commercial oil-based coatings consisting of a mixture of linseed oil and tung oil (LT) and commercial oil-based polyurethane resin (LB) coatings. The short-rotation teak woods were prepared in untreated and treated with furfuryl alcohol (FA), thermal treatment (HT) at 150 and 220 °C, and combination of glycerol–maleic anhydride (GMA) impregnation with thermal treatment at 150 and 220 °C. The surface characteristics measured were surface free energy, wettability, Persoz hardness, bonding quality, and color changes before and after artificial weathering exposure. The results showed that chemical and thermal modifications treatment tended to reduce total surface free energy (SFE), hardness, wettability, and bonding quality. FA and GMA at 220 °C treatments provided homogenization effect on surface characteristics, especially in total SFE and wettability. The total SFE of untreated wood ranged from 45.00 to 51.13 mN/m, and treated wood ranged from 40.58 to 50.79 mN/m. The wettability of oil-based coating according to K-value ranged from 0.20 to 0.54. TO presented better photostability than LO. Short-rotation teak wood coated with oil-based commercial coatings presented better weathering resistance compared to pure natural drying oil. Commercial oil-based coatings provided better weathering protection for the chemically and thermally modified teak wood. The application of oil-based coatings on chemically and thermally modified short-rotation teak is being considered for the development of a better wood-protection system. Full article

Two types of microcapsules were added to the coating separately. The specifications of the poplar board were 50 mm × 50 mm × 8 mm. The antibacterial rate of the poplar board surface gradually increased with the increase in the microcapsule content, and the antibacterial activity for Staphylococcus aureus was slightly higher than that against Escherichia coli. Influenced by the change in the wood grain’s color on the poplar board itself, both microcapsules had no significant effect on the chromaticity value and color difference of the poplar board surface, as well as the reflectance of the visible light band. The glossiness decreased with the increase in the microcapsule content, and the gloss loss rate increased with the increase in the microcapsule content. With the increase in the microcapsule content, the hardness of the poplar board surface in both groups increased slightly, and the roughness increased gradually. The adhesion of the poplar board surface coating with melamine-resin-coated pomelo peel flavonoid microcapsules was slightly reduced, and the impact resistance was not significantly affected. Chitosan-coated pomelo peel flavonoid microcapsules had no significant effect on the adhesion of the poplar board surface coating, and the impact resistance increased slightly when the content of microcapsules was higher. Comprehensively, the poplar board coating with 9.0% chitosan-coated pomelo peel flavonoid microcapsules had a better overall performance, with antibacterial activities for Escherichia coli and Staphylococcus aureus of 70.6% and 77.6%, respectively. The color difference was 6.70, the gloss loss rate was 53.9%, the reflectivity was 50.60%, the hardness was H, the adhesion was grade 1, the impact resistance was grade 2, and the roughness was 2.10 μm. The results provide technical references for the application of antibacterial microcapsules of pomelo peel flavonoids on the surface of wood materials. Full article