Untreated Wood Research Articles

Fixation of Tripotassium Citrate Flame Retardant Using a Sorbitol and Citric Acid Wood-Modification Treatment

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.

Role of Lignin in Moisture Interactions of Cellulose Microfibril Structures in Wood

Wood is a complex, multi‐component material with a variety of applications. The properties of wood are especially sensitive to its moisture content and comprehending wood–water interactions is thus paramount. Understanding of the moisture interactions of the wood polysaccharide components, cellulose microfibrils and hemicelluloses, is improving. However, the role of lignin remains less clear. In this work, X‐ray scattering measurements were carried out on delignified spruce undergoing a desorption‐adsorption cycle, and the results were compared to previous data from untreated wood. In addition, a molecular model of the cell wall nanostructure, including the main chemical components, was used to support the experimental results. Based on the small‐angle scattering, delignification affects the arrangement of cellulose microfibrils in the cell wall by increasing their packing distance. Wide‐angle scattering shows that delignification has no substantial effect on the cellulose crystal structure and how it changes with moisture. Both the scattering results and simulations suggest that lignin is a passive, rather than an active participant in the moisture response of microfibril bundles in wood cell walls. Small‐angle scattering from fully wet delignified wood reveals a contribution that can be assigned to aligned nanometer scale pores which close during drying.

Evaluations of the deterioration characteristics of thermally treated wood samples from Corymbia citriodora and Eucalyptus urophylla caused by marine wood borers

The low natural durability properties of some types of wood indicate the need for treatments to enhance the resistance of these materials to biological decay. In the sea, this resistance is necessary due to the actions of wood-boring mollusks and crustaceans. These treatments must be effective without harming the environment. Wood thermal treatment should be evaluated for this purpose. Therefore, the aim of this study was to evaluate the deterioration characteristics of thermally treated wood samples from Corymbia citriodora and Eucalyptus urophylla under the actions of marine wood borers. A method was proposed to aid in this assessment. Ten samples of these woods, both untreated and thermally treated, were submerged in the sea, each at a depth of 2.5 meters, for five months. After this period, the external borehole number, mass loss, and central flat lesion parameters of the samples were evaluated. Both the thermally treated and untreated wood samples of C. citriodora showed less deterioration than those of E. urophylla, with fewer boreholes, smaller lesioned areas, and lower mass losses. Compared with untreated wood and E. urophylla wood, thermally treated C. citriodora wood exhibited some resistance to marine wood borers. It was concluded that C. citriodora wood was naturally more resistant to marine wood borers than E. urophylla wood. Moreover, thermal treatment increased the boring resistance of C. citriodora wood while increasing the susceptibility of E. urophylla wood. The digital measurement of flat lesions was proven to be an auxiliary and promising method for evaluating the deterioration process.

Evaluating the Effectiveness of Cellulose-Based Surfactants in Expandable Graphite Wood Coatings.

This study deals with the design of modern environmentally friendly and non-toxic flame retardants based on expandable graphite 25 K + 180 (EG) modified by cellulose ethers (Lovose TS 20, Tylose MH 300, Klucel H) and nanocellulose (CNC) that are biocompatible with wood and, therefore, are a prerequisite for an effective surfactant for connecting EG to wood. The effectiveness of the formulations and surfactants was verified using a radiant heat source test. The cohesion of the coating to the wood surface and the cohesion of the expanded graphite layer were also assessed. The fire efficiency of the surfactants varied greatly. Still, in combination with EG, they were all able to provide sufficient protection-the total relative mass loss was, in all cases, in the range of 7.38-7.83% (for untreated wood it was 88.67 ± 1.33%), and the maximum relative burning rate decreased tenfold compared to untreated wood, i.e., to 0.04-0.05%·s-1. Good results were achieved using Klucel H + EG and CNC + EG formulations. Compared to Klucel H, CNC provides significantly better cohesion of the expanded layer, but its high price increases the cost of the fireproof coating.

Deactivation of chromated copper arsenate as a catalyst in smouldering of wood

Chromated copper arsenate (CCA) is a preservative treatment that enhances the biodegradation resistance of wood, essential for prolonging the service life of exterior infrastructure. However, the susceptibility of CCA-treated wood to smouldering combustion presents a significant challenge, as the metals present in the CCA catalyze the smouldering. In this work, we examined the oxidative behaviour of char produced from CCA-treated wood through dynamic thermogravimetric analysis. There was a gradual decrease in the catalytic activity of the CCA as temperature increased, particularly above 400 °C. At this stage, lignin undergoes secondary pyrolysis, and thermal decomposition of CCA complexes occurs. The thermal decomposition of CCA-treated wood at temperatures above 650 °C was similar to that of untreated wood, indicating the possible deactivation of the CCA. The agglomeration of species containing Cu or Cr above 650 °C might be responsible for the deactivation. This process is influenced by simultaneous lignin pyrolysis and decomposition of CCA complexes, which are also likely contributors to the loss of CCA's catalytic activity. This research introduced a novel experimental approach to assess the catalytic effects of CCA on char oxidation at elevated temperatures, offering valuable insights into CCA deactivation and its implications for fire safety. It also contributes to the development of potential modifications to CCA formulations aimed to reduce smouldering in wildfire-prone regions.

Pristine Wood‐Supported Electrodes With Intrinsic Superhydrophilic/Superaerophobic Surface Intensify Hydrogen Evolution Reaction

AbstractWood, as a renewable material, has been regarded as an emerging substrate for self‐supporting electrodes in large‐scale water electrolysis due to numerous merits such as rich pore structure, abundant hydroxyl groups, etc. However, poor conductivity of wood can greatly suppress the performance of wood‐based electrodes. Carbonization process can improve wood's conductivity, but the loss of hydroxyl groups and the required high energy consumption are the drawbacks of such a process. Here, a facile strategy is developed to prepare pristine wood‐supported electrode (Ni‐NiP/W) for enhanced hydrogen evolution reaction (HER); this improves electrical conductivity of wood while retaining its excellent intrinsic properties. The preparation process involves the deposition of copper on the untreated wood followed with the loading of Ni‐NiP catalyst at room temperature. Encouragingly, the Ni‐NiP/W exhibits conductive and inherited pristine wood's superhydrophilic and superaerophobic properties, that effectively boost mass and charge transfer. It demonstrates high activity and excellent stability in acidic, alkali, and seawater conditions as well as high current densities of up to 2000 mA cm−2; particularly a record‐low HER overpotential of 206 mV in acidic conditions at 1000 mA cm−2. This work fully unlocks the admiring potential of pristine wood as superior substrate for high‐performance electrochemical electrodes.

Acetylation of Aspen and Alder Wood - Preliminary Tests

An experimental study of the physical and mechanical properties of untreated and acetylated wood was conducted. The effect of acetylation on wood density was investigated. It was established that the density of the samples generally decreases after acetylation. As the level of acetylation increases, the fiber saturation point decreases in both conifers and hardwoods. Acetylation of wood helps to reduce the sorption properties of wood. The amount of swelling was analyzed. For untreated wood (aspen and alder), the volume swelling index is at the level of 7.5 %. Acetylation contributes to the stability of the geometric dimensions of structures, as the volume swelling index for aspen decreased by 4 times, for alder – by 2 times. An increase in the amount of swelling along the fibers is observed in all samples. Regarding the nature of the destruction of the samples during compression, the aspen (both untreated and acetylated) only crumples without visible signs of destruction. In some samples of alder, partial exfoliation is visible. It was found that acetylation has an ambiguous effect on the mechanical properties of wood of both species.

CARACTERÍSTICAS ACÚSTICAS DA MADEIRA DE ROXINHO (<i>PELTOGYNE SP.</i>) TRATADA TERMICAMENTE

The present research aimed to develop products for the musical instruments market using wood modified through heat treatments. Initially, a survey of wood traditionally used in musical instruments, or their parts was carried out. Subsequently, bibliographic research about the wood modification treatments was produced to know the technical limits and their characteristics and to identify which of these can be applied in Brazilian woods, being then chosen as the technique of heat treatment with the application of temperatures of 160ºC and 200ºC carried out in laboratory ovens. From this, the musical instrument xylophone was chosen as a test product to evaluate the use of the chosen technique of modification for the roxinho wood (Peltogyne sp.). Thus, the musical instrument was designed and produced with untreated wood and treated with the mentioned temperatures and evaluated the mass loss, specific gravity, resonance frequency, sound propagation velocity and dynamic modulus of elasticity (MOEd). The results indicated that the treatment with the temperatures used increased the sound propagation velocity and the MOEd, even with the decrease in the apparent density. The production of the product also showed a significant gain in relation to the final timbre when compared to untreated wood. Thus, the use of temperature at 160ºC is indicated as a technological product that can increase the final quality of the musical instrument.

Effect of Polyethylene Glycol with Different Molecular Weights on the Properties of Mytilaria laosensis Timber

Mytilaria laosensis, a common fast-growing tree species in southern China, boasts excellent growth speed and attractive color and texture. However, due to its short growth cycle and high proportion of juvenile wood, it typically exhibits poor dimensional stability and low strength, which significantly limits its practical applications. This study uses vacuum impregnation to modify M. laosensis wood with polyethylene glycol (PEG), focusing on the effects and mechanisms of PEG with different molecular weights on wood properties. The results indicate that PEG enters the wood cell walls through capillary action and diffusion, forming hydrogen bonds with the free hydroxyl groups on cellulose and hemicellulose, which keeps the cell walls swollen and enhances dimensional stability. Post modification, the dimensional stability of M. laosensis wood improved, with an anti-swelling efficiency ranging from 61.43% to 71.22%, showing an initial increase followed by a decrease with increasing PEG molecular weight. The optimal PEG molecular weight for anti-swelling efficiency was 1500 Da, achieving 71.22%. The flexural modulus of elasticity and flexural strength of the treated wood also first decreased and then increased with increasing PEG molecular weight. Among them, the PEG1000-treated material showed the best performance, with the flexural modulus of elasticity increased by about 29% and the flexural strength increased by about 5% compared to untreated wood. Additionally, PEG, having a higher pyrolysis temperature than wood, raised the initial pyrolysis temperature and maximum pyrolysis rate temperature of M. laosensis wood, thus improving its thermal stability. These findings provide scientific evidence and technical support for the efficient utilization and industrialization of M. laosensis wood, promoting its widespread application and industrial development.

Surface Characteristics and Artificial Weathering Resistance of Oil-Based Coatings on the Chemically and Thermally Modified Short-Rotation Teak Wood.

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.

Эксплуатационные характеристики древесно-полимерных композитов на основе ацетилированного древесного наполнителя

The demand for composite materials is growing every year. In this regard, the competitiveness of a particular product is determined primarily by the price-quality ratio. The most rational option for the production of wood-filled composites is using the materials with the increased performance characteristics. To date, it is the performance characteristics of modern composite materials that are the most significant, not only for final consumers, but also for manufacturers. In this regard, to improve performance characteristics in the production of wood-filled composites, various methods of pre-treatment of wood are used – thermal modification, acetylation, furfulation, ultra-high-frequency processing, alkali treatment, the use of various additives, etc. A promising way to improve the physical and mechanical properties of wood-filled materials is acetylation, whose mechanism consists in the formation of acetyl groups in wood during processing. To reduce production costs and the cost of the final product, it is possible to use a cheaper precursor (for example, icy acetic acid instead of acetic anhydride) with the possibility of intensifying the impregnation process. This article presents the results of obtaining wood-filled composites based on acetylated birch wood flour with its various proportions in the composition. The effect of introducing acetylated wood filler into the composition on the performance properties of composites (abradability, frost-resistance, flexural strength) has been evaluated in comparison with control samples made from untreated birch wood flour. The effect of acetylation with glacial acetic acid on the structure of birch wood flour has been characterized using Fourier-transform infrared spectroscopy. The IR-spectra of the control and acetylated samples contain absorption bands belonging to the corresponding groups of cellulose and lignin of hardwoods. The abradability and frost-resistance coefficients for a wood-filled composite based on acetylated birch wood flour are on average 1.5–2 times lower for all compositions compared to control samples. The results of the research allow us to conclude that acetylation of wood flour as a method of pre-treatment of the filler in order to improve the performance characteristics of the final product is promising for implementation in the production of wood-filled materials.

Properties of patula pine plywood using phenolic resin-impregnated veneers

Having observed the need for structural panels for external use, it is important to study methods of treating wood from new forest species, with less harmful products. In this sense, veneers of Pinus patula wood were subjected to immersion treatment in phenolic resin diluted in water at 5% solids content for one minute, and subsequently used to produce plywood panels using phenol-formaldehyde resin, with a weight of 160 g /m² in single line. The experimental design included four types of panels: fresh veneers glued with 35% resin solids content, treated veneers glued with 12%, 23% and 35% resin solids content. The physical-mechanical properties of the panels were compared with the parameters defined by the Brazilian Association of the Mechanically Processed Wood Industry (ABIMCI) and the Brazilian Association of Technical Standards (ABNT). The panels produced presented apparent density and bonding quality results below the minimum recommendations established in these technical parameters, in addition to water absorption higher than the values found in research with other pine species. However, veneer panels treated with phenolic resin showed better bonding quality than untreated panels for the same resin solids content. In less severe conditions, such as in the wet bonding test, the use of 23% resin solids content maintained bonding quality compared to 35% untreated wood. Therefore, further studies are suggested on the use of wood veneers treated with phenol and to reduce the resin solids content for to reduce costs and harmful effects on the environment.

New insights into the influencing mechanisms of hemicellulose removal on dynamic wood-water interactions characterized with low-field NMR

Hemicellulose, one of the most hygroscopic components, highly affected wood properties and wood-water interactions. To get more knowledge about the effects of hemicellulose on wood, this study changed hemicellulose content of wood through hydro-thermal removal of about 8 %, 20 % and 70 %. The dynamic cell water state and distribution during 384 h water absorption and air drying were characterized with low-field nuclear magnetic resonance technique (LFNMR). During water absorption, wood with less hemicellulose initially had higher and faster moisture increase, consisting of more free water in cell lumina and some large voids in cell walls than bound water in cell walls. The highest ratio of free water to bound water reached over 4.5, which was higher than that of untreated wood by over 15 %. This was because hemicellulose removal changed wood-water interaction environments suggested by SEM, FTIR and N2 absorption analysis. Specifically, hemicellulose removal enriched porous structures, especially the mesopore in cell walls. Although sorption sites decreased after hemicellulose removal, increased water paths and water accommodations played a more important role during initial water absorption. Besides, hemicellulose removal facilitated wood air drying, and the decreased moisture included more free water than bound water. This was because the enriched water paths accelerated water exchange, and sorption site decrease after hemicellulose loss reduced wood attraction to water molecules. Therein, the bound water leaving was generally slower than free water for hydrogen bond interaction with wood. The T2 s of bound water and free water were both shortened after hemicellulose removal, possibly because mesopore diameter reduction tightened wood-water bonding. This study provided new insights into understanding role of hemicellulose removal in dynamic wood-water interactions and facilitating development of wood processing technology.

FeP nanoparticle embedded in N,P-doped 3D porous wood-derived carbon aerogel for oxygen reduction reaction

Metal-air batteries require the exploration of affordable electrocatalysts with exceptional catalytic performance for oxygen reduction reactions (ORR). One of the powerful ways to develop highly active and robust oxygen electrocatalysts is to load transition metal compounds onto a highly porous carbon aerogel. Here, we report a cell wall nanoengineering strategy to transform natural balsa wood into a wood-derived carbon aerogel (WCA), following by loading FeP nanoparticles inside the hierarchical N, P-doped WCA for ORR electrocatalysts. Wood nanotechnology is applied to manipulate the microstructure of the porous carbon aerogel with low-tortuosity, multichannel, and aligned pore, which benefits to the electron transportation for boosting the ORR. Under 0.1 M KOH conditions, the initial potential, half wave potential and limit current of FeP@N,P-WCA are 0.95 V, 0.84 V, and 5.20 mA cm−2 respectively, which are much higher than that of untreated wood and comparable to commercial Pt/C. The aqueous Zn-air batteries assembled with this catalyst exhibit a remarkable specific capacity of 775.5 mA h g−1 and better charge-discharge cycling stability. The excellent electrocatalytic activity demonstrated by FeP@N,P-WCA for ORR is attributed to the inherent tri-pathway (lumen, pit, and ray cell) porous structure of wood, the high conductivity and specific surface area of WCA (584.2 m2 g−1), and the highly dispersed FeP nanoparticles. This work provides a structural design concept for achieving high electrocatalytic biobased WCA reactors by combining wood nanotechnology and electrocatalysts chemistry for energy storage and conversion.

Superhydrophobic coatings reduce human bacterial foodborne pathogen attachment to woods used in fresh produce harvest and postharvest packing

Wood is reportedly more difficult to maintain in hygienic condition versus other food contact materials, yet its use in produce packing and retail warrants efforts to reduce the risk of microbial pathogen contamination and attachment. This study characterized antifouling capabilities of fluorinated silanes applied to wood used in fresh edible produce handling to render the wood superhydrophobic and less supportive of bacterial pathogen attachment. Pine and oak cubic coupon surfaces were treated with 1% (w/w) silane or left untreated. Treated and untreated coupons were inoculated with Salmonella enterica or Listeria monocytogenes and held to facilitate pathogen attachment for 1, 4, or 8 h. Silane treatment of wood produced significant reductions in the proportions of strongly attaching cells for both pathogens versus loosely attaching cells (P < 0.01). Salmonella attachment demonstrated a dependency on wood treatment; silane-treated wood supported a lower fraction of strongly adhering cells (1.87 ± 1.24 log CFU/cm2) versus untreated wood (3.72 ± 0.67 log CFU/cm2). L. monocytogenes demonstrated significant declines in strongly attaching cells during extended exposure to silane-treated wood, from 7.59 ± 0.14 to 5.27 ± 0.68 log CFU/cm2 over 8 h post-inoculation. Microscopic analysis demonstrated silane treatment increased the surface roughness of both woods, leading to superhydrophobic conditions on wood surfaces, consequently decreasing strong attachment of pathogenic bacteria.

Artificial-weathering test requirements for fire-retardant-treated wood to reproduce optimal chemical retention and moisture conditions

Despite the increasing outdoor use of fire-retardant-treated wood, methods for predicting its service life remain poorly established. With the aim of establishing a method to predict chemical losses from fire-retardant-treated (FRT) wood caused by humid atmospheres and rain outdoors, this study examined the preferable conditions for artificial-weathering tests and demonstrated the acceleration coefficients in these tests (i.e., the ratio of equivalent time to reach the same retention of chemicals in artificial weathering and outdoors) based on the EN927-6 standard. To determine the moisture absorption and desorption levels of FRT exposed to outdoor conditions, an outdoor exposure experiment was conducted. The moisture content was higher in the FRT wood than in untreated wood, regardless of the type of coating, and ranged between 11% (in March) and 50% (in September) of the untreated wood’s weight. EN927-6 artificial weathering tests were performed on two groups of specimens with initial moisture contents of 0% and 25%. Retention rates of fire-retardant chemicals after a 2520-h test were compared with those retrieved from 4-year outdoor exposure reported elsewhere. Comparison of these two experiments demonstrated that the acceleration coefficients were 4.1–11.3 in the case of specimens with 0% initial moisture content and 5.1–11.4 in the case of specimens with 25% initial moisture content. The higher initial moisture content produced a more uniform acceleration coefficient. Nevertheless, larger acceleration coefficients were derived from specimens with penetrating or semi-film-forming coatings in both cases. The relationships between the uniformity of this acceleration coefficient and the initial moisture content are discussed from the moisture absorption experiment under constant temperature and humidity and under condensation conditions.

Evidence to support phytosanitary policies–the minimum effective heat treatment parameters for pathogens associated with forest products

Research on reducing the movement of pests on wood products has led to several options for safer trade including heat treatment of wood to mitigate pests. In this study, pathogenic organisms commonly regulated in the trade of forest products were tested to determine the minimum heat dose (temperature and time) required to cause mortality. The mycelial stage of tree pathogens, Heterobasidion occidentale, Grosmannia clavigera, Bretziella fagacearum, Phytophthora cinnamomi, P. lateralis, P. ramorum and P. xmultiformis, which may be found in untreated wood products, were tested in vitro using the Humble water bath with parameters simulating the rate of heat applied to wood in a commercial kiln. RNA detection using reverse transcription real-time PCR was used to validate pathogen mortality following treatment for: P. ramorum, P. lateralis, P. cinnamomi, P. xmultiformis and G. clavigera. The lethal temperature for all pathogens ranged from 44 to 50°C for a 30-min treatment duration. Using this method to evaluate heat treatment for other forest product pests is recommended to accurately identify the minimum dose required to support phytosanitary trade. With more data potentially lower heat treatment applications may be recommended under specific conditions to produce more efficient and economical heat treatment schedules and reduce environmental impacts.

Decay and Termite Resistance of Wood Modified by High-Temperature Vapour-Phase Acetylation (HTVPA), a Simultaneous Acetylation and Heat Treatment Modification Process.

High-temperature vapour-phase acetylation (HTVPA) is a simultaneous acetylation and heat treatment process for wood modification. This study was the first investigation into the impact of HTVPA treatment on the resistance of wood to biological degradation. In the termite resistance test, untreated wood exhibited a mass loss (MLt) of 20.3%, while HTVPA-modified wood showed a reduced MLt of 6.6-3.2%, which decreased with an increase in weight percent gain (WPG), and the termite mortality reached 95-100%. Furthermore, after a 12-week decay resistance test against brown-rot fungi (Laetiporus sulfureus and Fomitopsis pinicola), untreated wood exhibited mass loss (MLd) values of 39.6% and 54.5%, respectively, while HTVPA-modified wood exhibited MLd values of 0.2-0.9% and -0.2-0.3%, respectively, with no significant influence from WPG. Similar results were observed in decay resistance tests against white-rot fungi (Lenzites betulina and Trametes versicolor). The results of this study demonstrated that HTVPA treatment not only effectively enhanced the decay resistance of wood but also offered superior enhancement relative to separate heat treatment or acetylation processes. In addition, all the HTVPA-modified wood specimens prepared in this study met the requirements of the CNS 6717 wood preservative standard, with an MLd of less than 3% for decay-resistant materials.

Effect of changes in surface visual properties of heat-treated wood on the psychological preference

Heat treatment of wood is an attractive, environmentally friendly modification, which can change surface visual properties of wood including color and grain, but it is unclear how heat-treated wood is perceived and evaluated compared with untreated wood. In this paper, Chinese fir was heat-treated at 160, 180, 200, or 220 °C for 2 or 4 h. The changes of wood surface color and grain contrast were measured. A subjective questionnaire and eye-tracking technology were used for psychological evaluation. The results showed that changes in the visual properties of heat-treated wood had a significant effect on psychological preference—heat-treated wood was generally more preferred than the untreated, particularly at 200 °C for 4 h. Grain contrast and hue played an important role in the preference for heat-treated wood. The preference gave people the positive psychological impression of warmth, weight, cost, prevalence, and comfort. Eye-tracking analysis showed that Chinese fir heat-treated at about 200 °C with high hue value and clear grain contrast was easier to gain more visual attention. The results would have a high technical reference value for the heat-treated wood in product visual design.

Laser-induced graphene formation on different wood species: Dependence of electronic performance on intrinsic features of certain types of wood

Conductive, 3D, porous graphene can be produced with a CO2 laser from a large variety of materials, including wood, at room temperature, and under inert atmosphere or after treatment for fire protection. Here, we investigated the suitability for direct conversion of 46 typical European and Asian woods into laser-induced graphene (LIG), without pre-treatment. The LIG was characterized by resistance measurements to determine if a conductive layer had formed, and via Raman spectroscopy. Here, we show, for the first time, that it is possible to produce LIG on certain woods under atmospheric conditions without additional fire protection treatment. We determined that the ability to produce LIG on untreated, natural wood under ambient atmosphere is favoured overall by a high density and a diffuse-porous xylem structure, as well as a high soluble lignin content. Some of these characteristics are similar to those required for high yields in char production. Problematic for the production of LIG-based electronics is the presence of pronounced growth rings, or other geometric wood features, with density variations, which can be reduced using specific cuts with minimized growth rings and absence of rays. This is the first time that untreated wood has been directly converted into LIG using a conventional CO2 laser and ambient atmosphere. Our results represent a further step towards the development of a new generation of sustainable electronics relying on natural materials.