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Acetylation is a breakthrough in wood modification and has been established on industrial scale. However, concerns have been raised regarding the stability of acetylated wood under elevated temperatures, particularly during post hot-pressing processes to manufacture products such as laminated veneer lumber (LVL). At around 150 °C, the added acetyl groups might cleave off ("de-acetylation") and by that release sorption sites for water. This would increase the moisture uptake of the modified wood. In this study, the impact of hot-pressing at 150 °C on the stability of acetylated beech veneers and LVL was investigated. Fourier transform infrared (FTIR) spectroscopy showed that the chemical composition of acetylated veneers seemed to be unaffected after the heat treatment. Dynamic vapor sorption (DVS) analysis and long-term storing over saturated salt-solutions in miniature climate chambers, indicated no de-acetylation on the basis of negligible changes in wood-water interactions. The number of hydroxyl groups of heat-treated acetylated samples was similar to that of not heat-treated ones, indicating the persistence of the effects of acetylation. By the present study, a certain resilience of acetylated wood towards elevated temperature, like it may occur during hot-pressing of acetylated veneers, became apparent and illustrated the thermal stability of this chemical modification approach. [ABSTRACT FROM AUTHOR]

Wood modification has been explored in various ways to enhance dimensional stability and reduce flammability, with a focus on environmentally friendly treatments to meet market demands. This study aimed to investigate the efficacy of new, potential fire-retardant materials. Specifically, the study examined the combination of tripotassium citrate (TPC), a water-soluble and bio-based fire retardant, with sorbitol and citric acid (SorCA), an eco-friendly thermosetting resin previously studied. While TPC is known to control combustion, its application in wood modification has not been thoroughly researched. To assess the fixation and flammability of these fire retardants, tests were conducted on Scots Pine (Pinus sylvestris L.), including chemical analysis, dimensional stability, mechanical properties, flame retardancy, and leaching tests. The combination of SorCA and TPC showed high weight percent gain (WPG) values; however, leaching and anti-swelling efficiency (ASE) tests revealed challenges in fixation stability. The dynamic mechanical properties were reduced, whereas the static strength values were in the same range compared with untreated wood. While TPC exhibited high flame retardancy prior to leaching, its efficacy diminished post-leaching, underscoring challenges in fixation and the need for improved retention strategies. Bunsen burner tests conducted on leached specimens indicated enhanced performance even under severe leaching conditions as per the EN 84:2020 procedure. However, cone calorimetry measurements showed less favorable outcomes, emphasizing the necessity for further investigation into optimizing TPC retention and enhancing treatment efficacy. [ABSTRACT FROM AUTHOR]

The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future. [ABSTRACT FROM AUTHOR]

The combination of different wood-modification technologies to obtain improved performance is increasingly receiving attention in research. In this study, Scots pine (Pinus sylvestris) sapwood was impregnated with furfuryl alcohol (FFA) in pure aqueous 20, 40, and 60% solution strength without adding any catalyst. In a second step, the FFA was polymerized while simultaneously performing thermal modification in a closed system at 130, 150, or 180 °C. After leaching and ageing tests, the nine different combinations were tested in use class 4 applications (in contact with or very close to the ground and frequently wet) according to CEN/TS 15083-2 (2005) decay laboratory test. It was noted that even the minimum-intensity combination of 20% FFA at 130 °C resulted in maximum durability class (DC) 1 performance. On the contrary, DC 4 was assigned to thermally modified control samples, even at the maximum intensity of thermal modification. Similarly, for FFA modifications, previous research has suggested that an uptake of 35% solution strength is required to obtain an adequate durability performance in use class 4 applications. High levels of resistance against termites were also noted by corresponding termite lab tests. Moisture studies showed the combined treatments resulted in improved stability and reduced moisture uptakes. Thus, the results obtained by this study revealed synergistic performance effects, which originate from the combined thermo-chemical modification approach, and which were higher than simple accumulation of the individual performance of purely thermally or chemically modified wood. Thus, the presented findings have provided positive implications for industrial applications of thermo-chemical modification techniques and offers an array of new research opportunities.

The combination of different wood-modification technologies to obtain improved performance is increasingly receiving attention in research. In this study, Scots pine (Pinus sylvestris) sapwood was impregnated with furfuryl alcohol (FFA) in pure aqueous 20, 40, and 60% solution strength without adding any catalyst. In a second step, the FFA was polymerized while simultaneously performing thermal modification in a closed system at 130, 150, or 180 °C. After leaching and ageing tests, the nine different combinations were tested in use class 4 applications (in contact with or very close to the ground and frequently wet) according to CEN/TS 15083-2 (2005) decay laboratory test. It was noted that even the minimum-intensity combination of 20% FFA at 130 °C resulted in maximum durability class (DC) 1 performance. On the contrary, DC 4 was assigned to thermally modified control samples, even at the maximum intensity of thermal modification. Similarly, for FFA modifications, previous research has suggested that an uptake of 35% solution strength is required to obtain an adequate durability performance in use class 4 applications. High levels of resistance against termites were also noted by corresponding termite lab tests. Moisture studies showed the combined treatments resulted in improved stability and reduced moisture uptakes. Thus, the results obtained by this study revealed synergistic performance effects, which originate from the combined thermo-chemical modification approach, and which were higher than simple accumulation of the individual performance of purely thermally or chemically modified wood. Thus, the presented findings have provided positive implications for industrial applications of thermo-chemical modification techniques and offers an array of new research opportunities. [ABSTRACT FROM AUTHOR]

The emergence of transparent wood as a viable alternative to traditional glass has sparked considerable interest in recent research endeavors. Despite advancements, challenges persist in the delignification methods and wood species utilized in prior studies. Therefore, this study delves into the potential of Brazilian eucalyptus wood for transparent wood production through the kraft pulping process. Delignification was carried out in a laboratory setting, replicating the kraft process with varying reaction times (15, 30, 45, and 60 min). The resulting delignified wood veneers were impregnated with a pre-polymerized PMMA solution. The study encompassed various analyses, including UV-Vis spectroscopy, colorimetry, SEM, optical microscopy, and mechanical property evaluations. The results revealed intriguing trends in terms of transparency, color changes, microstructural modifications, and mechanical properties as a function of delignification time. This work presents valuable insights into the transformative potential of eucalyptus wood, offering a deeper understanding of the interplay between wood modification and PMMA impregnation. [ABSTRACT FROM AUTHOR]

No matter where we reside, the issue of greenhouse gas emissions impacts us all. Their influence has a disastrous effect on the earth's climate, producing global warming and many other irreversible environmental impacts, even though it is occasionally invisible to the independent eye. Phase change materials (PCMs) can store and release heat when it is abundant during the day (e.g., from solar radiation), for use at night, or on chilly days when buildings need to be heated. As a consequence, buildings use less energy to heat and cool, which lowers greenhouse gas emissions. Consequently, research on thermally active medium-density fiberboard (MDF) with PCMs is presented in this work. MDF is useful for interior design and furniture manufacturing. The boards were created using pine (Pinus sylvestris L.) and spruce (Picea abies L.) fibers, urea–formaldehyde resin, and PCM powder, with a phase transition temperature of 22 °C, a density of 785 kg m−3, a latent heat capacity of 160 kJ kg−1, a volumetric heat capacity of 126 MJ m−3, a specific heat capacity of 2.2 kJ kgK−1, a thermal conductivity of 0.18 W mK−1, and a maximum operating temperature of 200 °C. Before resination, the wood fibers were divided into two outer layers (16%) and an interior layer (68% by weight). Throughout the resination process, the PCM particles were solely integrated into the inner layer fibers. The mats were created by hand. A hydraulic press (AKE, Mariannelund, Sweden) was used to press the boards, and its operating parameters were 180 °C, 20 s/mm of nominal thickness, and 2.5 MPa for the maximum unit pressing pressure. Five variants of MDF with a PCM additive were developed: 0%, 5%, 10%, 30%, and 50%. According to the study, scores at the MOR, MOE, IB, and screw withdrawal resistance (SWR) tests decreased when PCM content was added, for example, MOE from 3176 to 1057 N mm−2, MOR from 41.2 to 11.5 N mm−2, and IB from 0.78 to 0.27 N mm−2. However, the results of the thickness swelling and water absorption tests indicate that the PCM particles do not exhibit a substantial capacity to absorb water, retaining the dimensional stability of the MDF boards. The thickness swelling positively decreased with the PCM content increase from 15.1 to 7.38% after 24 h of soaking. The panel's thermal characteristics improved with the increasing PCM concentration, according to the data. The density profiles of all the variations under consideration had a somewhat U-shaped appearance; however, the version with a 50% PCM content had a flatter form and no obvious layer compaction on the panel surface. Therefore, certain mechanical and physical characteristics of the manufactured panels can be enhanced by a well-chosen PCM addition. [ABSTRACT FROM AUTHOR]

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Thermal modification processes are environmentally friendly methods used to improve certain properties of wood. Currently, wood from thinning of young plantations of Nothofagus alpina (raulí) in Chile is being evaluated to obtain value before the plantation has reached maturity. The objective of this paper was to assess selected properties of thermally modified wood of young (14- to 25-years-old) N. alpina wood that comes from thinning of two sites with intensive silviculture and one similar to a secondary growth forest. To achieve this, non-destructive tests were carried out to measure some chemical-crystalline characteristics, as well as physical and mechanical properties; the differences between the 25%, 50%, and 75% distance from pith to the bark in each site was studied. The modification temperatures used were 170, 190, and 210 ℃. The results show that thinning wood from N. alpina can be thermally modified with favorable results, thus presenting an option to obtain value while the plantation reaches maturity, particularly the thinning wood from the intensive forestry regimes, which presented most homogeneous results, especially at the modification temperature of 190 ℃. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the fire resistance of silver fir (Abies alba L.) and European ash (Fraxinus excelsior) boards charred using the traditional yakisugi method and to compare the results with the fire resistance of non-charred boards as a reference and exploit its potential as a material with fire protection properties. After the boards were surface-charred on one side, specimens with different char thicknesses, resulting from their different position in the chimney, were selected from each wood species and subjected to analysis. Specimens with dimensions of 250 × 90 mm underwent a small flame test, those of 220 × 170 mm received indirect flame exposure by constant heat flux radiation from an infra-red emitter and those of 600 × 600 mm were subjected to a fire resistance test according to EN 1363-1:2020. The results of the small flame tests showed statistically significant fire resistance enhancement of specimens with 6 and 3 mm char-layer thickness in fir and ash wood, respectively, and a 110% and 75% improvement when compared to reference specimens. The constant heat flux radiation tests did not reveal any significant differences between the reference and charred specimens. The up-scaled fire resistance test, in which an assembled panel was exposed to flame, also indicated significant improvement. The reference burn-through time of fir and ash specimens was improved significantly with increasing char layer thickness, resulting in 10%–26% of fire resistance improvement for fir and 5%–12% for ash wood specimens. These results, based on the tests performed, suggest that the one-sided surface-charring of wood can enhance its fire resistance; however, this was mostly achieved in boards with the thickest char layer in both wood species studied and not all fire resistance indicators were considered. Further in-depth studies are required to better understand the complex behaviour of charred wood in response to fire. [ABSTRACT FROM AUTHOR]

The goal of this study is to comprehensively evaluate the natural weathering performance of three wood species representing hardwood and softwood modified with the acetylation process. Alder (Alnus glutinosa L.), beech (Fagus sylvatica L.), and radiata pine (Pinus radiata D. Don) were characterised by various techniques to determine the aesthetical, chemical, and physical changes. The overall aesthetic performance of the investigated species was similar, with all showing a change in appearance after 9 months of exposure. However, the multi-sensor approach used for characterisation revealed differences in weathering behaviour related to surface erosion, wettability, and changes in chemical composition between the investigated species. An increase in the surface roughness observed for both hardwoods was associated with the erosion of the wood surface and the leaching of photodegraded chemical components. On the contrary, values of Sa remained relatively constant for acetylated radiata pine. Acetylated pine wood exhibited lower susceptibility to bleaching at the initial stage of the weathering process (3 months) and represented a more constant CIE L* compared to the investigated hardwood species. The contact angle measured with water gradually decreased in the case of acetylated radiata pine for up to six months, then it plateaued with a slight oscillation around 15°. For both hardwood species, the big drop was observed already after three months, followed by rather similar values. The PCA of IR spectra highlighted different mechanisms in the weathering of acetylated softwood and hardwood. The acetylated hardwood samples showed higher thermal stability than acetylated radiata pine. Experimental findings provide a comprehensive understanding of the long-term performance of acetylated wood, which directly influences its practical applications by enhancing design strategies, maintenance planning, product development, market acceptance, and overall sustainability. Performed tests have demonstrated the potential of underutilised hardwood species, enhanced through the acetylation process, to serve as alternative cladding materials to commonly used acetylated radiata pine. [ABSTRACT FROM AUTHOR]

Humins are heterogeneous and polydisperse furanic macromolecules derived from sugar biorefinery. Improving wood properties by humination has become of interest recently. This study examined the photodegradation stability of European pine sapwood microveneers modified with humins at different concentrations of citric acid (CA) and succinic acid (SA) as reaction catalysts, e.g., 1.5 %, 3 %, and 4.5 % wt.%. The photostability of huminated wood was assessed after 48 h, 96 h, and 144 h of exposure to the accelerated weathering test by means of mass loss and finite-span tensile strength. The results were compared with unmodified and also unweathered samples. The FT-IR spectroscopy showed apparent changes in the chemical structure of wood by humination modifications. The weight percentage gains of the samples increased with increasing the concentration of the catalyst. While no differences were observed between the samples after two weeks of the water leaching. The strength losses of weathered microveneers were, however, mostly reduced by humin-based formulas containing catalysts, where the microveneers modified with 1.5 % and 3 % CA showed respectively 32 % and 41 % lower strength loss values than the unmodified samples after 144 h of weathering. Overall, the results showed a high potential for humins to protect wood against photodegradation. [ABSTRACT FROM AUTHOR]

Wood is a natural material that presents a great variation in its structural and aesthetic properties. To extend the service life of wood and its products many treatments have been developed. Considering the negative impacts of various conventional wood preservatives, the development of economically viable new or alternative technologies with low toxicity is in progress. Nanotechnology is been portrayed as one of the solutions complimenting conventional wood preservatives due to various aspects. The main goal of this review is to present the role of nanotechnology in wood protection with different end user applications and also it covers the perks over conventional wood preservatives. Commercialization of nanoparticles in wood protection is also discussed in light of safety concerns. [ABSTRACT FROM AUTHOR]

Nowadays, the protection of wood is becoming more important with the increasing demand for durable wood, in addition to its limited accessibility. One possible way to increase the durability is the use of nanoparticles, which can be effective even with a low intake of active ingredients. However, avoiding their leaching is a challenge. A possible solution to leaching is the use of silica aerogel as a fixative. This study investigated the use of mesoporous silica aerogel against the leaching of different nanoparticles under laboratory conditions. Tests were performed involving beech (Fagus sylvatica) and Scots pine (Pinus sylvestris) sapwood, using Trametes versicolor as a white rot and Coniophora puteana as a brown rot fungus. The results show that the subsequent treatment of the wood with mesoporous silica aerogel effectively fixed the nanoparticles in wood. The durability of the samples without aerogel significantly decreased as a result of leaching, whereas the resistance of the samples treated with aerogel decreased only slightly. However, the silica aerogel modification itself caused the leaching of silver nanoparticles, which is a limitation in the use of this method for the fixation of nanoparticles. [ABSTRACT FROM AUTHOR]

Wood's vulnerability to combustion compromises its structural integrity during fire incidents, primarily due to a decrease in effective cross-section area. This study investigates the efficacy of impregnation Chinese fir lumbers with a 30 % concentration of borate-containing phenol–formaldehyde resin, coupled with a 30 % compression treatment, employed as exposed side laminas for glulam columns. Full-scale glulam columns underwent one-sided fire exposure to assess the impact of the modified laminas. Results reveal a significant increase in column ignition time by 55–195 s, due to the combined treatment. The charring rate of columns containing a single modified lamina in the fire-side zone decreased from 0.733 to 0.552 mm/min after 60 min of fire exposure and further reduced from 0.503 to 0.351 mm/min after 120 min fire exposure for double modified laminas. Compared to the control, glulam columns containing a single modified lamina showcased a 31 % increase in residual bearing capacity at 60 min fire exposure duration and a 62.1 % increase at 120 min with double modified laminas. ABAQUS simulation results corroborated experimental findings, highlighting substantial enhancement in fire resistance achieved due to the modified laminas in the fire-side zone.

Wood can be a suitable alternative to energy-intensive materials in various applications. Nevertheless, its susceptibility to weathering and decay has significantly hindered the broad adoption of the most commercially significant wood species. While current solutions do tackle certain challenges, they often come with disadvantages like high costs, environmental risks, and/or inefficiencies. Nanotechnology-based methods can be employed to mitigate these weaknesses and create durable, sustainable wood materials. In this review, we delve into cutting-edge advancements in the development of biodeterioration-resistant wood through innovative nanotechnology approaches. These methods usually involve the application of nanomaterials, either possessing biocidal properties or serving as carriers for biocides. We systematically describe these approaches and compare them to conventional wood modification methods. Additionally, this review provides a brief overview of the prevalent biodeteriorating organisms and their mechanisms of action, which notably impact the development and choice of a suitable strategy for wood modification/treatment. Given the requirements of biodeteriorating organisms for growth and wood degradation, it is expected that the new nanotechnology-based approaches to enhance wood durability may provide innovative broad-spectrum biocidal nanosystems. These systems can simultaneously induce alterations in the physicochemical properties of wood, thereby constraining the availability of the growth requirements. These alterations can efficiently inhibit the biodeterioration process by decreasing water absorption, restricting access to the wood components, and reducing void spaces within the wood structure. Finally, this review highlights the new opportunities, challenges, and perspectives of nanotechnology methods for biodeterioration-resistant wood, through which some techno-economic, environmental and safety aspects associated with these methods are addressed.

This study was conducted to synthesize magnetic wood through the ex situ impregnation method of magnetite nanoparticles and analyze its physical properties and characterization. The process was initiated with the synthesis of magnetite nanoparticles by the co-precipitation method and the nano-magnetite was successfully synthesized with a particle distribution of 17–233 nm at an average size of 75 nm. Furthermore, the impregnation solution consisted of three different levels of magnetite nanoparticles dispersed in furfuryl alcohol, untreated and furfurylated wood for comparison. Sengon wood (Falcataria moluccana Miq.) was also used due to its low physical properties. The impregnation process was conducted by immersing the samples in the solution at a vacuum of −0.5 bar for 30 min, followed by a pressure of 1 bar for 2 h. There was also an improvement in the physical properties, such as weight percent gain, bulking effect, anti-swelling efficiency and density, while the water uptake continued to decrease. Additionally, magnetite nanoparticles appeared in wood microstructure image, supported by the result of ferrum content in chemical element analysis. The results showed that chemical change analysis proved the presence of Fe–O functional group cross-linked with wood polymer. The diffractogram also reported the appearance of magnetite nanoparticles peak and a decrease in crystallinity due to an increase in the concentration. Based on the analysis, sengon wood was classified as a superparamagnetic material with soft magnetic characteristics and the optimum treatment was furfurylated-magnetite 12.5% wood.

To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture. [ABSTRACT FROM AUTHOR]

Wood can be a suitable alternative to energy-intensive materials in various applications. Nevertheless, its susceptibility to weathering and decay has significantly hindered the broad adoption of the most commercially significant wood species. While current solutions do tackle certain challenges, they often come with disadvantages like high costs, environmental risks, and/or inefficiencies. Nanotechnology-based methods can be employed to mitigate these weaknesses and create durable, sustainable wood materials. In this review, we delve into cutting-edge advancements in the development of biodeterioration-resistant wood through innovative nanotechnology approaches. These methods usually involve the application of nanomaterials, either possessing biocidal properties or serving as carriers for biocides. We systematically describe these approaches and compare them to conventional wood modification methods. Additionally, this review provides a brief overview of the prevalent biodeteriorating organisms and their mechanisms of action, which notably impact the development and choice of a suitable strategy for wood modification/treatment. Given the requirements of biodeteriorating organisms for growth and wood degradation, it is expected that the new nanotechnology-based approaches to enhance wood durability may provide innovative broad-spectrum biocidal nanosystems. These systems can simultaneously induce alterations in the physicochemical properties of wood, thereby constraining the availability of the growth requirements. These alterations can efficiently inhibit the biodeterioration process by decreasing water absorption, restricting access to the wood components, and reducing void spaces within the wood structure. Finally, this review highlights the new opportunities, challenges, and perspectives of nanotechnology methods for biodeterioration-resistant wood, through which some techno-economic, environmental and safety aspects associated with these methods are addressed. [ABSTRACT FROM AUTHOR]

A Pinuselliottii wood was thermally modified at 200 °C for 2 h and then treated by in situ polymerization with furfuryl alcohol (FA) using a vacuum-pressure process to investigate the influence of furfurylation on a thermally treated wood. The presence of poly(furfuryl alcohol) (PFA) was confirmed by micrographs (SEM and CLSM), which also showed that it reached internal spaces between cracks originated in the previous heat treatment. Chemical changes from furfurylation were detected by infrared spectroscopy, especially in the previously thermally treated wood. The wood modified by the combined thermorretification/furfurylation treatment presented similar esthetic attributes compared to the furfurylated wood. Compared to the isolated treatments, the combined treatment caused an increase of 150–260% in the evaluated mechanical properties and 5–10% in thermal stability. The two-step treated pine wood also showed higher levels of surface and bulk hydrophobicity and resistance against white-rot fungus. [ABSTRACT FROM AUTHOR]

With the rapid development of modern society, our demand for energy is increasing. And the extensive use of fossil energy has triggered a series of problems such as an energy crisis and environmental pollution. A moisture-enabled electric generator (MEG) is a new type of energy conversion method, which can directly convert the ubiquitous moisture in the air into electrical energy equipment. It has attracted great interest for its renewable and environmentally friendly qualities. At present, most MEGs still have low power density, strong dependence on high humidity, and high cost. Herein, we report the development of a high-efficiency MEG based on a lignocellulosic fiber frame with high-power-density, all-weather, and low-cost characteristics using a simple strategy that optimizes the charge transport channel and ion concentration difference. The MEG devices we manufactured can generate the open-circuit voltage of 0.73 V and the short-circuit current of 360 μA, and the voltage can still reach 0.6 V at less than 30% humidity. It is possible to drive commercial electronic devices such as light-emitting diodes, electronic displays, and electronic calculators by simply connecting several electric generators in series. Biomass-based moisture-enabled electric generation has a low cost, is easy to integrate on a large scale, and is green and pollution-free, providing clean energy for low-humidity or high-electricity-cost areas. [ABSTRACT FROM AUTHOR]

Acetylation is a wood modification used to increase the durability. Although it is known that the wood moisture content is lowered, the exact mechanisms behind the increased durability are not known. However, since fungi need water in different locations for different purposes the location and state of water is most probably of importance in addition to the total moisture content. In a previous study, we used targeted acetylation to alter the wood–water interactions in different parts of the wood structure in water saturated and hygroscopic moisture states. The main range for fungal degradation is, however, between these moisture ranges. This study investigated the effect of targeted acetylation on location, state and amount of water at non-saturated, high moisture states using the pressure plate technique. Specimens were modified using acetic anhydride by two approaches: (1) uniform modification (2) interface modification acting on the cell wall-lumen interface. They were then conditioned to eight moisture states between 99.64 and 99.98% relative humidity in both absorption and desorption and the location and state of water was studied using Low Field Nuclear Magnetic Resonance, X-ray computed tomography and Differential Scanning Calorimetry. Capillary water was present at all the included moisture states for all specimen types, but the amounts of capillary water in absorption were small. Increasing degree of interface modification increased the amount of capillary water compared to untreated wood. In addition, the uniformly modified wood often had higher amounts of capillary water than the untreated wood. The amount of cell wall water was decreased by uniform modification, but slightly or not reduced by the interface modification. The combination of targeted modification and conditioning to high well-defined moisture states thus gave very different amounts of capillary water and cell wall water depending on the conditioning history (absorption or desorption) and choice of modification. This opens new possibilities for designing materials and moisture states for fungal degradation experiments of wood. [ABSTRACT FROM AUTHOR]

This study was conducted to synthesize magnetic wood through the ex situ impregnation method of magnetite nanoparticles and analyze its physical properties and characterization. The process was initiated with the synthesis of magnetite nanoparticles by the co-precipitation method and the nano-magnetite was successfully synthesized with a particle distribution of 17–233 nm at an average size of 75 nm. Furthermore, the impregnation solution consisted of three different levels of magnetite nanoparticles dispersed in furfuryl alcohol, untreated and furfurylated wood for comparison. Sengon wood (Falcataria moluccana Miq.) was also used due to its low physical properties. The impregnation process was conducted by immersing the samples in the solution at a vacuum of −0.5 bar for 30 min, followed by a pressure of 1 bar for 2 h. There was also an improvement in the physical properties, such as weight percent gain, bulking effect, anti-swelling efficiency and density, while the water uptake continued to decrease. Additionally, magnetite nanoparticles appeared in wood microstructure image, supported by the result of ferrum content in chemical element analysis. The results showed that chemical change analysis proved the presence of Fe–O functional group cross-linked with wood polymer. The diffractogram also reported the appearance of magnetite nanoparticles peak and a decrease in crystallinity due to an increase in the concentration. Based on the analysis, sengon wood was classified as a superparamagnetic material with soft magnetic characteristics and the optimum treatment was furfurylated-magnetite 12.5% wood. [ABSTRACT FROM AUTHOR]

The dimensional stabilisation of wood using thermosetting resins relies on the resin uptake into the cell walls. This study tested if a conditioning step after the impregnation and before the final heat-curing enhances the cell wall uptake to improve dimensional stabilisation without increasing the chemical consumption. Small blocks of Scots pine sapwood were vacuum-impregnated with an aqueous melamine formaldehyde solution and conditioned at 33, 70, or 95 % RH for up to 1 week before drying and curing the blocks at 103 °C. However, the conditioning step decreased the cell wall bulking and the moisture exclusion effect compared to the immediate heat curing of the impregnated samples. Analyses of the resin-treated samples by scanning electron microscopy, IR spectroscopy and confocal Raman microspectroscopy provided evidence of wood hydrolysis and polycondensation of the resin within the cell lumen during the conditioning step. Hydrolysis and removal of wood constituents may have counterbalanced the cell wall bulking of the resin. Polycondensation of the resin in the lumen increased its molecule size, which could have hindered the cell wall diffusion of the resin. [ABSTRACT FROM AUTHOR]

In this research, acetylation was applied under industrial conditions to improve the properties of Turkey oak and Pannonia poplar wood. Both species are potential "climate winners" in Hungary, yet they are currently underused due their low durability and poor dimensional stability. The acetylation modification process may be a suitable method to improve their properties. In order to verify the effectiveness of the process, comparative chemical analyses (cellulose, hemicelluloses, lignin, extractives, ash, buffering capacity, and pH) of the untreated and acetylated heartwood and sapwood were carried out for both species for the first time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was also used to support the evaluation of the chemical analyses. The weight percent gain was 11.54% for poplar and 0.94% for Turkey oak, indicating poor treatment efficiency for the latter. The cellulose, hemicelluloses, and lignin contents changed significantly in poplar, with the highest change (+81%) induced by acetylating the hemicelluloses. Only the alpha-cellulose content decreased significantly in Turkey oak, presumably due to the degradation of the non-crystalline part of the cellulose. Acetylation may improve the resistance of Pannonia poplar against moisture, weather, decay, and wood-boring insects, but the process parameters need to be optimized in order to prevent degradation and discoloration in poplar. Turkey oak was found to be less suitable for acetylation due to its low permeability and tendency to crack. [ABSTRACT FROM AUTHOR]

The circular economy forces societies to take actions aimed at giving post-consumer products a "second life". As we know, wood is perfect for this. Moreover, reusing wood helps keep carbon in circulation, thus limiting its emissions into the atmosphere. It turns out that extensive research on determining the durability of wood is very useful and valuable for one more reason. Well, they can be used to create a model to determine the usefulness of wood, which has only apparently lost its utility value during many years of exposure to external factors. The research subject was samples of wood impregnated with protection agents and modified, originating from many years of field tests. The aim of the research was to correlate the results of wood durability determined after a period of exposure in open space with the results of determining the potential usefulness of such wood. On this basis, a model for determining the value of post-consumer wood was created. As a main result of post-consumer wood analysis, the high durabilities against C. puteana with mass loss below 3% were noticed for acetylated, furfurylated, and CCA-treated wood. Moreover, high color stabilities (ΔE < 10) were observed for thermowood and furfurylated wood. [ABSTRACT FROM AUTHOR]

When wood is thermally modified, several chemical reactions take place that change the chemical and physical properties of the wood. These changes correlate with the degree of modification, which is mostly a function of the temperature and duration of modification, and consequently with the mass loss during this process. There is a lack of standardised quality control to verify the degree of heat treatment of wood and thus its quality. One of the possible methods to check the degree of thermal modification of a particular type of wood is thermogravimetry (TG). It is based on the assumption that processes that did not take place during thermal modification continue when the TG experiment is carried out. In this method, calibration curves have to be established based on TG measurements of standard samples that have been thermally modified at different temperatures and whose mass loss during modification is known. The calibration curves show the mass loss during the TG measurement as a function of the mass loss during the previous thermal modification. The course of thermal decomposition during the TG measurements is influenced by many parameters, such as the mass of the sample, the heating rate, the atmosphere in which the measurement takes place, and the shape of the crucible in which the sample is placed. In this paper, the influence of these parameters on the calibration curves was investigated. We have focused on oak wood. The best parameters result in a calibration curve with the largest correlation coefficient R2 and the highest slope of the line k. On this basis, we can determine the mass loss during the thermal modification of unknown samples of the same wood species under the same measurement conditions. [ABSTRACT FROM AUTHOR]

Silver fir (Abies alba L.) wood samples were charred on one surface using an enhanced version of the traditional Japanese Yakisugi method. The 15 charred boards obtained from five charring chimneys were divided into three different zones and investigated for their physical properties. The density profile, water absorption after 24 h of water submersion, and Brinell hardness were analyzed. In general, the temperature-time regime, which causes inside surface carbonization, was more evident at the bottom than at the top of the chimney. The density profile of the specimens revealed that the surface charring treatment decreased the surface density of the wood significantly. A gradient was visible from 383 kg/m² at the bottom to 424 kg/m² at the top. Water absorption measurements showed that a thicker carbonized layer could take up more water as a result of increased porosity. While 3,684 g/m² were absorbed at the bottom, the top accounted for only 2,533 g/m². Furthermore, with increasing thickness of the charred layer, the hardness gradually decreased. The average of the charred specimens reached only 3.2% of the hardness of the uncharred back side of the specimens.

Natural and thermally modified Pine, Ash, and Acacia woods were exposed in two different environments: urban and maritime/industrial. The weathering effects were evaluated during 24 months regarding color, chemical, and structural changes. In all wood species, thermal modification induced color, chemical, and structural changes. All woods became darker (Pine ΔL*: −32.01; Ash ΔL*: −36.83; Acacia ΔL*: −27.50), total extractives content increased (Pine: 19 %; Ash: 32 % and Acacia: 18 %), and the samples presented deformation and damaged cells. Total lignin was not significantly changed, although there were detected changes in lignin, namely the reduction of G-units in Pine (≈2 %) and reduction of S/G ratio in Acacia (≈0.04 %). Ash remained almost the same. After weathering, modified woods suffered fewer color changes, indicating that the thermal modification could improve the resistance to color change. Acacia wood, when exposed to maritime/industrial conditions, revealed a higher color change (ΔE: 35.7 at 24 months) when compared with urban conditions (ΔE: 23.5 at 24 months). Delignification, possibly caused by photodegradation, occurred in all wood samples, and the loss of extractive happened, perhaps caused by rain. Modified woods were slightly less resistant to weathering in maritime/industrial environments. Some structural damage, namely cracked cells, the appearance of molds, blue staining, and particle deposition, was observed. The thermal modification enables color stabilization but does not seem to improve the weathering resistance in all studied wood species. Exposure to the different environments did not lead to significant differences in the morphology and chemical composition of the three natural and modified wood species.

Cultural property and art objects often contain metallic or ceramic materials that can react corrosively with compounds like formic and acetic acid from the ambient air. For this reason, only materials that cannot damage the cultural property by gaseous escaping substances are used for the construction of museum showcases. Due to its chemical composition, wood is excluded as a construction material in museums. In this study, three wood species, beech (Fagus sylvatica L), alder (Alnus), and walnut (Juglans regia), were treated with different concentrations of NaOH solutions to limit their corrosion potential to the extent that the treated wood could be used for the construction of museum display cases. The Oddy accelerated corrosion test, which has established itself as a proven test method for determining the suitability of materials in museums, offers a test method for measuring the corrosion potential of materials. The results show that all three types of wood pass the Oddy test by treatment with a 3% NaOH solution, whereas all untreated samples had to be classified as unsuitable for use in museums, as expected, according to the underlying evaluation scheme. [ABSTRACT FROM AUTHOR]

Wood is a commonly used material in construction. However, its application is limited due to its flammability. Modification of wood with phenol-formaldehyde resin (PF) can improve many of its inherent properties, but does not upgrade its fire resistance. To address this issue, Scots pine (Pinus sylvestris L.) sapwood was impregnated with a low molecular weight PF resin and phosphate-based flame retardant (FR). The fixation of the FR was evaluated using an accelerated ageing procedureaccording to the EN 84 standard (CEN 2020: EN 84 (2020) Wood Preservatives – Accelerated Ageing of Treated Wood Prior to Biological Testing - Leaching Procedure (Brussels, Belgium: European Committee for Standardization)). The thermal stability, flammability and heat release of treated wood were analysed before and after a leaching test. The combination of PF and FR treatment significantly improved the thermal stability, reduced flammability and decreased the heat release, as evidenced by a 82% and 86% reduction in total heat release within 600 s compared to untreated wood and pure PF-treated wood, respectively. The improved fire performance was also observed for the leached wood. [ABSTRACT FROM AUTHOR]

This study aimed to reveal the changes in Fe concentration and colour in the wood obtained from selected tree species: Pinus sylvestris L., Picea abies (L.) H. Karst., Pseudotsuga menziesii (Mirb.) Franco, Juglans regia L., and Acer platanoides L. at different stages of the hydrothermal treatment with additive Fe2O3 in combination with tannic acid. The study results showed that wood obtained from deciduous and coniferous trees responded slightly differently to the duration of treatment, and the temperature applied. In all cases, the higher Fe concentrations were found the outer wood layers, which directly contacted the modifying solvent. In deeper wood layers, Fe concentrations gradually decreased. Higher Fe concentration determined darkening of the colour. The longer treatment time and the higher temperature caused the higher Fe concentrations in all wood layers. For the most reliable and efficient technological process, the treatment temperature could be optimised up to 90°C, when the wood is exposed to the solvent made of water with the addition of Fe2O3 and tannic acid. The duration of the full hydrothermal process could be optimised up to 120 h for the wood from coniferous species, and it could be prolonged up to 150–240 h for deciduous species. [ABSTRACT FROM AUTHOR]

The quality control of thermally modified wood and identifying heat treatment intensity using nondestructive testing methods are critical tasks. This study used near-infrared (NIR) spectroscopy and machine learning modeling to classify thermally modified wood. NIR spectra were collected from the surfaces of untreated and thermally treated (at 170 °C, 212 °C, and 230 °C) western hemlock samples. An explainable machine learning approach was practiced using a TreeNet gradient boosting machine. No dimensionality reduction was performed to better explain the feature ranking results obtained from the model and provide insight into the critical wavelengths contributing to the performance of classification models. NIR spectra in the ranges of 1100–2500 nm, 1400–2500 nm, and 1700–2500 nm were fed into the TreeNet model, which resulted in classification accuracy values (test data) of 94.35%, 89.29%, and 84.52%, respectively. Feature ranking analysis revealed that when using the range of 1100–2500 nm, the changes in wood color resulted in the highest variation in NIR reflectance amongst treatments. As a result, associated features were given higher importance by TreeNet. Limiting the wavelength range increased the significance of features related to water or wood chemistry; however, these predictive models were not as accurate as the one benefiting from the impact of wood color change on the NIR spectra. The developed framework could be applied to different applications in which NIR spectra are used for wood characterization and quality control to provide improved insights into selected NIR wavelengths when developing a machine learning model. [ABSTRACT FROM AUTHOR]

Silver fir (Abies alba L.) wood samples were charred on one surface using an enhanced version of the traditional Japanese Yakisugi method. The 15 charred boards obtained from five charring chimneys were divided into three different zones and investigated for their physical properties. The density profile, water absorption after 24 h of water submersion, and Brinell hardness were analyzed. In general, the temperature-time regime, which causes inside surface carbonization, was more evident at the bottom than at the top of the chimney. The density profile of the specimens revealed that the surface charring treatment decreased the surface density of the wood significantly. A gradient was visible from 383 kg/m² at the bottom to 424 kg/m² at the top. Water absorption measurements showed that a thicker carbonized layer could take up more water as a result of increased porosity. While 3,684 g/m² were absorbed at the bottom, the top accounted for only 2,533 g/m². Furthermore, with increasing thickness of the charred layer, the hardness gradually decreased. The average of the charred specimens reached only 3.2% of the hardness of the uncharred back side of the specimens. [ABSTRACT FROM AUTHOR]

Although cross-linking modification by polycarboxylic acid greatly improves dimensional stability and decay resistance, it causes severe brittleness and rigidity in wood. Introducing polyols into the cross-linking network could improve the flexibility of the modified wood, however, the related research is limited, especially the relationship between the strength and the reaction. In this study, poplar wood was modified by cross-linking with 1,2,3,4-butanetetracarboxylic acid (BTCA). D-sorbitol (SO) and sucrose (SU) used as the polyols were introduced to the modification system to esterify with BTCA. The physical and mechanical properties of the resulting wood were investigated. The effect mechanism and microstructure of the wood were also examined. The findings demonstrated that a cross-linked structure was formed in wood with increased ester bonds and ample polymer filling in the lumens. SU has lower leachability than SO. Although the incorporation of polyols has lowered anti-swelling efficiency, the reduction of modulus of rupture caused by BTCA treatment could be redeemed by reducing the degree of cross-linking between BTCA and wood components, especially SO-BTCA treatment. The addition of polyols has slight impact on the modulus of elasticity of BTCA treated wood. [ABSTRACT FROM AUTHOR]

Beech is an important tree species in Europe. This study aimed to elucidate the influence of four molecular weights of phenol formaldehyde (PF) resin (266, 286, 387, and 410 g/mol) on the sorption behavior of unmodified and modified beech wood samples using a dynamic vapor sorption (DVS) apparatus. The variations in the environmental relative humidity and moisture content (MC) of the samples were recorded, and the DVS isotherms were plotted from the equipment. During the sorption process, the MC of the modified samples decreased in comparison to that of the unmodified samples, and both apparently decreased with the increasing molecular weight of the PF resin. The DVS isotherm hysteresis plot illustrated a reduction in sorption hysteresis for the modified wood with varying PF resins compared to the unmodified samples. Based on the DVS isotherm adsorption and desorption plots, the decrease in the equilibrium of the MC can be attributed to there being fewer sorption sites in the modified samples, which exhibited the lowest hygroscopicity. Overall, the moisture sorption mechanism for both types of samples was clarified, highlighting a clear correlation between the molecular weight of the applied PF resin and its influence on moisture sorption behavior. [ABSTRACT FROM AUTHOR]

Wood surface charring is a treatment method commonly employed to enhance weather protection and aesthetic appearance of building exteriors. This study aims to investigate the differences between two wood surface charring processes: the traditional Japanese method known as Yakisugi and an alternative charring technique industrially manufactured with a gas burner. The objective of the study was to assess whether a thicker layer after Yakisugi treatment has any advantages over a thinner layer after the alternative process. Vibrational spectroscopy techniques including UV resonance Raman (UVRR) and Fourier transform infrared (FTIR) spectroscopy, were utilized in conjunction with X-ray-micro-CT analysis. The findings revealed that ATR-FTIR spectroscopy detected the degradation of carbohydrates and changes in lignin within the charred surface, although both processes exhibited similar vibrational contributions. In contrast, UVRR spectroscopy provided insights into the carbonized layers, revealing spectral differences indicating variations in temperature during the charring processes. X-ray micro-CT analysis visually highlighted significant differences in the coal layers, suggesting distinct combustion profiles. Remarkably, the macrostructure of wood treated with Yakisugi remained intact despite a thicker charred layer compared to the alternative charring techniques. However, further investigations are required to assess the weather stability of the alternative charring method for a comprehensive understanding. [ABSTRACT FROM AUTHOR]

Rubber wood often exhibits dimensional instability during use, which seriously hinders its widespread application. In order to enhance the dimensional stability of rubber wood, a two-step method was employed in this study to modify rubber wood using two plant-derived compounds, namely sucrose and tung oil. Samples treated alone with sucrose or tung oil were also prepared. The water absorption, dimensional stability, and thermal stability of modified and untreated wood were evaluated. The results show that wood samples treated with 30% sucrose and tung oil had excellent water resistance and dimensional stability based on the synergistic effect of sucrose and tung oil. After 384 h of immersion, the 30% sucrose and tung oil group presented a reduction in water absorption by 76.7% compared to the control group, and the anti-swelling efficiency was 57.85%, which was 66.81% higher than that of the tung oil treatment alone. Additionally, the leaching rate of the 30% sucrose and tung oil group decreased by 81.27% compared to the sample modified with the 30% sucrose solution alone. Simultaneously, the 30% sucrose and tung oil group showed better thermal stability. Therefore, this study demonstrates that the synergistic treatment of modified rubber wood by sucrose and tung oil is an eco-friendly, economical, and highly efficient approach with the potential to expand the range of applications of rubber wood products. [ABSTRACT FROM AUTHOR]

The goal of this study was the fixation of water-soluble polyethylene glycol (PEG) into the wooden cell wall. The dimensional stability of beech wood (Fagus sylvatica) modified with PEG400 and various carboxylic acids (1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid (CA), malic acid, pyromellitic acid, tartaric acid, L-glutamic acid hydrochloride, ethylene diamine tetraacetic acid disodium salt dihydrate, trans-aconitic acid, maleic acid and itaconic acid) was examined. Investigations of anti-swelling efficiency (ASE), weight-percent gain (WPG) and bulking effect were made. Both the highest dimensional stabilization (values of ASE at the end of examination between 37 and 40%) and the best fixation of the chemicals in the wood (total loss of WPG between 37 and 38%) were achieved with combinations of BTCA/PEG and CA/PEG. The variants impregnated without PEG had lower bulking values. Successful modification of wood seems to be possible with BTCA, CA and malic acid in combination with PEG400. [ABSTRACT FROM AUTHOR]