Thermal Modification Of Wood Research Articles

Colorimetria e propriedades químicas da madeira de Parkia pendula e Simarouba amara modificada termicamente

ABSTRACT The thermal modification of wood is a process that alters its chemical composition, aiming to improve technological properties such as dimensional stability, reduction of equilibrium moisture content, homogeneity, or color. In this context, this study aimed to evaluate the colorimetry and chemical properties of the wood of Parkia pendula (angelim-saia) and Simarouba amara (marupá) that was thermally modified by different methods. Three treatments were evaluated: T1 (pre-treatment in an oven for one hour at 120 °C and treatment in an oven at 180 °C for three hours); T2 (pre-treatment in an autoclave at 125 °C for three hours under 1.2 kgf cm-2 and treatment in an oven at 180 °C for three hours); and T3 (without pre-treatment, with sample treatment in vegetable oil). The thermally modified wood was evaluated in relation to untreated wood for structural chemical composition (extractives, lignin, holocellulose and ash content), colorimetric parameters defined through the CIELAB (Commission Internationale de l´Eclairage) system and total color variation. We detected a significant increase in extractives content and a decrease in holocellulose and lignin content in T3 for both species, which can be explained by the impregnation of oil in the wood samples. The thermal modification caused the surface darkening of the wood of both species, which was more pronounced in P. pendula. Despite the colorimetric change, there was no chemical damage to the wood.

Comparison on thermally modified beech wood in different mediums: Morphology, chemical change and water-related properties

Thermal modification has been proved to be an effective approach to improve the dimensional stability of wood, while different processes of thermal modification often resulted in various efficacy. In this study, the morphology, chemical structure, crystallinity, pore size distribution, and some water-related properties were investigated in order to explore the effect of different mediums (vacuum, nitrogen, steam and air) on thermally modified wood (TMW). It was found that heating medium plays an important role in thermal modification of wood. At both 180 and 210 ℃, the general severity of thermal modification is in the following order: air > steam > nitrogen > vacuum. Accordingly, the highest dimensional stability appeared in air TMW, and then steam, nitrogen, and vacuum. It seemed that the water-related properties were primarily affected by the extent of decomposition of the amorphous polysaccharides, but showed no direct relationship with the pore structure. Lignin changed greatly for TMW treated in steam at 180 ℃ and all TMW treated at 210 ℃, by showing more uniform distribution in all cell wall layers. It might be resulted from the migration of lignin fragments after depolymerization, the formation of pseudo lignin from holocellulose, and the increased relative lignin content in secondary wall. The changes on pore structure and lignin structure might have significant effect on other wood properties.

Chromophores' Contribution to Color Changes of Thermally Modified Tropical Wood Species.

This work examines the effect of thermal modification temperature (180, 200, and 220 °C) in comparison with reference (untreated) samples on selected optical properties of six tropical wood species-Sp. cedar (Cedrala odorata), iroko (Chlorophora excelsa), merbau (Intsia spp.), meranti (Shorea spp.), padouk (Pterocarpus soyauxii), and teak (Tectona grandis). The main goal is to expand the existing knowledge in the field of wood thermal modification by understanding the related degradation mechanisms associated with the formation of chromophoric structures and, above all, to focus on the change in the content of extractive substances. For solid wood, the CIELAB color space parameters (L*, a*, b*, and ΔE*), yellowness (Y), ISO brightness, and UV-Vis diffuse reflectance spectra were obtained. Subsequently, these wood samples were extracted into three individual solvents (acetone, ethanol, and ethanol-toluene). The yields of the extracted compounds, their absorption spectra, and again L*, a*, b*, ΔE*, and Yi parameters were determined. With increasing temperatures, the samples lose brightness and darken, while their total color difference grows (except merbau). The highest yield of extractives (mainly phenolic compounds, glycosides, and dyes) from thermally modified samples was usually obtained using ethanol. New types of extractives (e.g., 2-furaldehyde, lactones, formic acid, some monomer derivatives of phenols, etc.) are already created around a temperature of 180 °C and may undergo condensation reactions at higher temperatures. For padouk, merbau, teak, and partially iroko modified at temperatures of 200 and 220 °C, there was a detected similarity in the intensities of their UV-Vis DR spectra at the wavelength regions corresponding to phenolic aldehydes, unsaturated ketones, quinones, stilbenes, and other conjugated carbonyl structures. Overall, a statistical assessment using PCA sorted the samples into five clusters. Cluster 3 consists of almost all samples modified at 200 and 220 °C, and in the other four, the reference and thermally modified samples at 180 °C were distributed. The yellowness of wood (Y) has a very high dependence (r = 0.972) on its brightness (L*) and the yellowness index of the extractives in acetone Yi(Ac), whose relationship was described by the equation Y = -0.0951 × Y(Ac) + 23.3485.

Fine dust after sanding untreated and thermally modified spruce, oak, and meranti wood

Airborne wood dust poses health and safety risks in the construction and furniture industry. The study verified whether the thermal modification affects the share of fine wood dust particles (< 10 μm) generated during spruce, oak, and meranti wood sanding. The experimental research involved nine material variants, including three wood species in three states: untreated, thermally modified at 160 °C, and thermally modified at 220 °C). To collect at least 200 g of each dust sample, a belt sander with P80 sandpaper and a belt speed of 10 m/s was used, along with a dust collector. The collected dust was then separated into fractions using a set of sieves with aperture sizes of 2000, 1000, 500, 250, and 125 μm. A laser particle sizer was employed to measure the sizes of dust particles in the under-sieve fraction (dust with particle sizes smaller than 125 μm). The under-sieve fraction was decomposed into three subfractions, with particle sizes: <2.5, 2.5-4.0, and 4.0–10 μm. Surprisingly the results indicate that sanding dust from thermally modified wood generates a lower average mass share of potentially harmful fine particle fractions than dust from untreated wood. Oak dust contained a higher mass share of fine particles compared to the spruce and meranti dust samples. Dust from thermally modified oak and meranti wood had a lower content of harmful particle fractions than dust from untreated wood. The average mass shares of these dust fractions for modified wood at 160 and 220 °C showed no statictically significant differences (p < 0.05). Conversely, spruce dust had a low content of fine fractions because spruce particles exhibit a more irregular elongated shape. The study considered the extreme temperatures of 160 and 220 °C used in the thermal modification of wood. Therefore, the above statements are assumed to be valid for all intermediate thermo-modification temperatures.

Effect of High-Temperature Paraffin Impregnation on the Properties of the Amorphous Cellulose Region Based on Molecular Dynamics Simulation

A paraffin–cellulose composite model was created using Materials Studio software, establishing a cellulose chain with a polymerization degree of 20 and paraffin molecules. A theoretical foundation for the research of wood heat treatment was established by explaining the changes in macroscopic qualities, such as mechanical properties, water absorption, etc., from a microscopic point of view. The model tended to a stable state with lower energy through geometric optimization and kinetic relaxation. The dynamics simulation was run based on this condition at a total of five different temperatures: 100 °C, 150 °C, 170 °C, 190 °C, and 210 °C. The energy balance, paraffin molecular diffusion coefficients, cell parameters and densities, hydrogen bonding numbers and mechanical parameters of the paraffin–cellulose composite model were analyzed. The results demonstrated that the paraffin diffusion range increased with temperature, and the paraffin diffusion coefficient was greatest at 210 °C, which also resulted in the maximum cell volume, the lowest density, and the lowest water absorption at this temperature. On the other hand, the paraffin–cellulose hybrid model had the most hydrogen bonds and the most stable system at 100 °C. The mechanical properties of the amorphous cellulose region of wood are influenced by temperature. According to the calculation of Lamé constants, with the system’s temperature rise, Young’s modulus (E) and shear modulus (G) were maximum at 100 °C, indicating the wood’s optimal toughness and plasticity. Poisson’s ratio and K/G values were largest at 210 °C, indicating the optimal toughness and plasticity of wood. The thermal modification of wood under different conditions can not only retain its natural advantages, but also improve its own performance, expand the application range of wood, and increase the utilization rate of wood. Therefore, the appropriate temperature and other conditions can be selected according to the actual needs of the wood heat treatment, which has significant practical significance for the study of wood heat treatment.

Analysis of chemical properties of thermally treated Pinus roxburghii Sargent wood

Effects of thermal modification were determined relative to chemical parameters of Pinus roxburghii. Thermal modification of wood was carried out at 80, 120, 160, and 200 °C for 2, 4, and 6 h. The chemical properties were different for different temperatures and different heating time. All parameters were similar except for cold water soluble extractives. Among the chemical properties studied, the maximum mean value of cold water extractives (8.20%), hot water soluble extractives (12.7%), holocellulose content (71.8%), and ash content (1.46%) were recorded at 120 °C, whereas the maximum mean values of alcohol benzene soluble extractives (13.9%) and lignin content (33.7%) were observed at 200 °C. The minimum mean value of cold water soluble extractives (5.82%), hot water soluble extractives (9.27%), holocellulose content (65.8%), and ash content (1.03%) were found to be at 200 °C, while the highest value of alcohol benzene soluble extractives 12.2% (control) and lignin content (28.0%) were found to be at 80 °C.

Degradation of Chemical Components of Thermally Modified Robinia pseudoacacia L. Wood and Its Effect on the Change in Mechanical Properties

Currently, emphasis is placed on using environmentally friendly materials both from a structural point of view and the application of protective means. For this reason, it is advisable to deal with the thermal modification of wood, which does not require the application of protective substances, to increase its service life. The main reason for the thermal modification of black locust is that although black locust grows abundantly in our country, it has no industrial use. It is mainly used outdoors, where thermal modification could increase its resistance. This article deals with the thermal modification of black locust wood (Robinia pseudoacacia L.) and the impact of this modification on the chemical components of the wood with an overlap in the change in mechanical properties compared to untreated wood. Static (LOP, MOR, and MOE) and dynamic (IBS) bending properties were evaluated as representative mechanical properties. At the same time, the impact of thermal modification on the representation of chemical components of wood (cellulose, lignin, hemicellulose) was also tested. As a result of the heat treatment, the mechanical properties gradually decreased as the temperature increased. The highest decrease in mechanical values found at 210 °C was 43.7% for LOP and 45.1% for MOR. Thermal modification caused a decrease in the content of wood polysaccharides (the decrease in hemicelluloses content was 33.2% and the drop in cellulose was about 29.9% in samples treated at 210 °C), but the relative amount of lignin in the wood subjected to increased temperature was higher due to autocondensation, and mainly because of polysaccharide loss. Based on the correlations between chemical and mechanical changes caused by thermal modification, it is possible to observe the effects of reducing the proportions of chemical components and changes in their characteristic properties (DP, TCI) on the reduction in mechanical properties. The results of this research serve to better understand the behavior of black locust wood during thermal modification, which can primarily be used to increase its application use.

Influence of Thermal Modification in Nitrogen Atmosphere on the Selected Mechanical Properties of Black Poplar Wood (Populus nigra L.).

The thermal modification of wood in a nitrogen atmosphere shapes the functional properties of wood. The aim of this research was to determine the influence of different levels of temperature and the duration of thermal modification on the mechanical properties of the black poplar (Populus nigra L.). Black poplar was thermally modified in nitrogen atmosphere in the temperature range from 160 °C to 220 °C (6 levels) for 2 h to 8 h (4 levels), resulting in a total of 24 treatments. The effect of these treatments on compressive strength parallel to the grain (CS), modulus of rupture (MOR), and modulus of elasticity during bending (MOE) were analyzed. Thermal modification influenced the mechanical properties of black poplar wood. After thermal modification occurred in a nitrogen atmosphere, an increase in compressive strength was noticeable for all variants of black poplar wood modification. The highest 16% increase in CS was obtained for the modification carried out at the temperature of 160 °C and for 2 h. An increase was also found for MOE when modified under mild conditions, while a decrease occurred for variants at higher temperatures, i.e., for 200 °C and 220 °C. The study showed that for all modification variants, there was a decrease in MOR alongside the increase in modification temperature and time.

Color as an Indicator of Properties in Thermally Modified Scots Pine Sapwood.

The aim of this study was to determine the dependencies between mechanical properties of modified wood and its color. Within its scope, quantitative changes in color and chemical composition (mass loss, total carbon content, content of extractives and main components of wood), as well as mechanical properties (compressive strength along the grain, strength and modulus of elasticity in longitudinal tension tests, compression across the grain and impact resistance) of the modified Scots pine sapwood, were determined. Modifications were conducted in the atmosphere of superheated steam (time—4 h, temperature of 130, 160, 190, 220 °C). Thermal modification of wood results in an increase in the modulus of elasticity, a reduction of elasticity, longitudinal tensile strength and compressive strength perpendicular to grain. It was found that color parameters ∆E, ∆L and ∆a are linear functions of the modification temperature. The existence of functional dependencies between mass loss, longitudinal tensile strength, radial modulus of elasticity and parameters of ∆E and ∆L makes it possible to determine these properties of modified wood based on color. In turn, chemical analysis indicated that an increase in the temperature of wood modification caused a decrease of holocellulose and hemicelluloses contents, especially in wood samples modified at 220 °C.

Effect of Thermal Treatment on Chemical, Biological and Mechanical Properties of African Whitewood (Triplochiton scleroxylon K. SCHUM)

The thermal modification of wood is a potential alternative method for improving wood properties. This paper evaluates the effect of thermal treatment on the chemical, biological and mechanical properties of African Whitewood (Triplochiton scleroxylon K. Schum) by subjecting the wood to three temperature (200, 170, 140 ℃) at three different time (3, 6, 12 h). Fourier Transformed infrared (FT-IR) spectrometer was used to ascertain the effect of heat treatment on the chemical constituent of the wood while mechanical properties were determined by Modulus of Elasticity (MOE) and Modulus of Rupture (MOR). Durability of heat-treated wood against subterranean termites using field test was also investigated. FTIR results provided information on the chemical constituents after heat treatment revealing the cellulose and hemicelluloses of Triplochiton scleroxylon wood samples. The decreasing intensity of hydroxyl groups stretching at 3341 cm-1 indicated that heat-treated samples have lost some of their hydroxyl groups. The results showed that the MOR of heated-treated wood at 200 ℃ was significantly higher than the untreated samples. There was also a 26% increase in the MOE of the 170 ℃ heat-treated wood relative to untreated samples. Wood samples thermally treated at 170 ℃ and 200 ℃ as well as untreated wood samples were strongly degraded in term of weight loss (WL) by termite though the degree of degradation varied based on temperature and time in which the wood was modified. However, heat-treated wood at 140 ℃ gave the lowest WL of 20.41% compared to other treated and untreated wood samples. Therefore, strength properties and termites’ resistance of African whitewood also known as Obeche wood in Nigeria could be improved when thermally modified at 170 ℃ and 140 ℃ respectively.

Evaluation of the Effect of a Combined Chemical and Thermal Modification of Wood though the Use of Bicine and Tricine

The effects of thermal modification of wood have been well established, particularly in terms of reductions in mechanical performance. In recent years, there has been an increase in studies related to the Maillard reaction. More commonly associated with food chemistry, it involves the reaction of amines and reducing sugars during cooking procedures. This study has attempted to combine the use of amines and thermal modification, with subsequent properties investigated for the treatment of spruce (Picea abies (L.) H. Karst) and beech (Fagus sylvatica L.). In this initial study, the combined effects of chemical treatments by tricine and bicine were investigated with thermal modification. Along with some preliminary data on mechanical properties, the modifications which appeared in the wood structure were evaluated by infrared spectroscopy and biological studies according to EN113 and EN117 methodologies. The hierarchal study interpretation of FTIR suggested interactions between the bicine or tricine and the wood, which was partly supported by the analysis of volatile organic compounds (VOC), though other tests were not as conclusive. The potential of the method warrants further consideration, which will be described.

Influences of extractives and thermal modification on the UV resistance of Albizia lebbeck wood

ABSTRACT Thermal modification is a chemical-free process for improving hydrophobicity, dimensional stability, and biological durability of wood. There are inconsistent reports on the UV resistance of thermally modified wood with the majority of studies indicating its vulnerability to UV degradation. This may be due to the natural variability of chemical constituents, particularly extractives, in different wood species. In this study, the UV resistance of sapwood and heartwood of Albizia lebbeck was evaluated to elucidate the role of extractives on photo-stabilisation. A comparison between the extractive rich untreated and heat-treated sapwood and heartwood was carried out. UV resistance was evaluated by exposing modified wood to UV light in an accelerated weathering tester. Untreated sapwood attained dark colour (photoyellowing) upon UV light exposure, whereas thermally modified sapwood showed contrasting behaviour (lightening). Untreated heartwood showed more resistance to photodegradation. Thermally modified heartwood retained its colour for a considerable extent and exhibited good UV resistance than the untreated samples. Results indicate that extractives present in the heartwood of A. lebbeck act as UV absorber to impart substantial UV stability to wood. Furthermore, the enhanced UV resistance of heat-treated heartwood could be due to the accumulation of photostable compounds evolved during the thermal modification of wood.

Temperature, Time, and Interactions between Them in Relation to Colour Parameters of Black Poplar (Populus nigra L.) Thermally Modified in Nitrogen Atmosphere.

Thermal modification of wood in nitrogen atmosphere permits its usability value to be improved. The aim of the research was to determine the impact of technological modification parameters at different levels on the colour of black poplar (Populus nigra L.). Black poplar was thermally modified in nitrogen atmosphere at a range of temperatures from 160 °C to 220 °C, at times between 2 h and 8 h. The parameters of wood colour were measured according to the CIE L*a*b* colour space model. The changes in a* and b* had a non-linear profile. The maximum value of a* for black poplar wood was achieved after a modification at the temperature of 200 °C, while the maximum value of the b* parameter was achieved after modification at 190 °C. Colour changes in the ΔE of black poplar after modification at 160 °C and 170 °C were similar, and the dynamics of changes increased after modification at the temperature of 180 °C. The highest value of ΔE, around 40, was observed after modification at the temperature of 220 °C and time of 8 h. There were no statistically significant differences between the ΔE for radial and tangential sections. Statistical analysis showed that modification temperature was responsible for the variability of the L* value in 90%, and in ca. 70% for the changes in parameters a* and b*. The influence of the modification time on the colour parameters was minor—below 4%. The influence of the interaction between modification temperature and time on the colour parameters was below 10%. As a consequence, in the case of ΔE of black poplar wood, the influence of temperature was at a level of ca. 80%. On the other hand, the influence of time and the interaction between temperature and time of modification was low—below 3%.

Exploring volatile organic compound emission from thermally modified wood by PTR-ToF-MS.

Thermal modification of wood is a well-known industrial process performed to increase the durability and dimensional stability or to change the colour of natural wood. The treatment influences many other properties of wood including the emission of volatile organic compounds (VOCs). VOC release ultimately affects the quality of indoor air and the capability of having low VOC emission is often included as a key parameter for the attribution of quality labels. In the present work, wood from six tree species was subjected to different types of treatment and VOC profiling was carried out on both treated and untreated samples by means of PTR-ToF-MS. Different types of thermal treatment were tested, involving either overpressure or vacuum and the effect of different temperature profiles was evaluated. Hardwood and softwood showed different release profiles under all tested conditions: the headspace of softwood was richer in several VOCs, such as terpenes, phenols and C6-C9 aldehydes and carboxylic acids. Upon thermal treatment, terpene emissions decreased, whereas several other VOCs, such as formic acid, formaldehyde, furfural and acetic acid, were released in higher amounts. With its high sensitivity and throughput, PTR-ToF-MS appears to be a very powerful analytical tool, useful in supporting the selection of wood materials for different end uses.

Beech wood thermally modified in the melt of polyethylene glycol

Various techniques of wood thermal modification in air, liquids, or melts at temperatures above 160 °C improve its resistance to biological damage and water. In this experiment, the European beech (Fagus sylvatica L.) wood was held for 1 to 4 hours in the melt of polyethylene glycol 6000 (PEG 6000) and during a given time either heated at 100 °C or thermally modified at 190 or 210 °C. Its decay resistance improved – maximally at using the more intense modification mode 210 °C/4h – to Poria placenta by 60.3% and to Trametes versicolor by 62.8%. The soaking and volume swelling in water of the PEG-thermally treated beech wood usually was significantly reduced, after 336 h maximally by 60% and 34.6%, respectively. The presence of PEG during the thermal modification processes caused darkening of beech wood – a decoratively interesting and more pronounced effect than what occurs in traditional air-thermal modifications – at which the Eab* was also great from 13.1 to 52.6. However, since the mechanical properties of the PEG-thermally modified beech wood worsened – impact bending strength maximally by 34% and Brinell hardness maximally by 43.3% – its application for structural elements would be limited.

Life Cycle Assessment of Coated and Thermally Modified Wood Façades

Façades—their design, aesthetics, performance, type of cladding material, and understructure—determine architectural expression and form unique appearances of individual buildings. In connection to the sustainable development idea, wood façades provide one of the alternatives of a contemporary building exterior look. Façade cladding made of coated and thermally modified wood can be successfully used for these buildings. In addition, thermally modified wood allows the use of local European wood species, while keeping cladding elements relatively thin. On the other hand, wood has certain structural limitations and disadvantages due to the properties of wood. The main weakness is caused by the surface durability of wood and its related need for maintenance over time. The scope of the study was a comprehensive assessment of coated non-heat-treated and thermally modified wood façades, performed in terms of life cycle assessment. The aim was to identify which type of wooden façade had the lowest environmental impact. According to the EN 15804 + A2 standard, the principle of evaluation of environmental parameters “cradle-to-gate-with options” was used to evaluate wooden façades and coatings and surface preservation methods. Simulations with the SimaPro program showed that the thermal modification of wood has a significant impact on the environment at the product stage. Nonetheless the thermally modified façade without any surface coating showed the lowest environmental impact in a 30 year time-horizon of the “use stage”. It was showed that surface maintenance methods applied, the coatings used, and the frequency of their application play an important role in the environmental impact of the investigated wooden façades.

Effect of thermal modification on wood properties of 38-year-old Cariniana legalis cultivated at different spacing

Planting spacing influences wood production. However, for tropical species we have scarce information about the effect of spacing on production and wood quality. In general, wood from native species produced in reforestation does not have the same quality compared to that from natural forests. Then, wood thermal modification can help improve the potential for using wood. In this context, our goal was to evaluate the influence of thermal modification on properties of 38-year-old Cariniana legalis wood cultivated at different spacing (3 x 1.5m, 3 x 2m and 3 x 2.5m) at the Luiz Antônio Experimental Station, Luiz Antônio City, São Paulo. We felled 15 trees, five of each spacing, and from each tree, a log, 1 meter in length, a central plank was cut, and from these planks, we cut specimens for anatomical and wood properties investigations according to standard techniques. In the specimens, a thermal modification at a temperature of 200ºC was carried out for one hour and after the specimens were compared with the control specimens. According to the results presented, we found that spacing did not influence vessel diameter, apparent density and volumetric shrinkage significantly. Thermal modification reduced apparent density and volumetric shrinkage. The reduction in vessel diameter can be estimated as a function of the wood thermal modification.

Correlation of Studies between Colour, Structure and Mechanical Properties of Commercially Produced ThermoWood® Treated Norway Spruce and Scots Pine

The thermal modification of wood has become the most-commonly commercialised wood modification process globally, with the ThermoWood® process currently being the most dominant. As with all commercial processes, there is a need to have a robust quality control system, with several small–scale studies undertaken to date investigating quality control using a range of analytical methods, culminating in a multi-year assessment of colour as a means of quality control. This study, as an extension to this multi-year assessment, further explores the colour of Norway spruce and Scots pine commercially modified by the ThermoWood® S and D processes, respectively, along with the mechanical properties and structural characterisation by Fourier transform infrared (FT–IR) spectroscopy and principal component analysis (PCA) to ascertain further correlations between colour and other measurable properties. Infrared spectroscopy indicated modifications in the amorphous carbohydrates and lignin, whereas the use of PCA allowed for the differentiation between untreated and modified wood. Colour measurements indicated reduced brightness, and shifting toward red and yellow colours after thermal modification, hardness values decreased, whereas MOE and MOR values were similar for modified wood compared to unmodified ones. However, by combining the colour measurements and PC scores, it was possible to differentiate between the two modification processes (Thermo–S and Thermo–D). By combining the mechanical properties and PC scores, it was possible to differentiate the untreated wood from the modified ones, whereas by combining the mechanical properties and colour parameters, it was possible to differentiate between the three groups of studied samples. This demonstrates there is a degree of correlation between the test methods, adding further confidence to the postulation of using colour to ensure quality control of ThermoWood®.

Experimental Studies of the Physical and Mechanical Properties of Glued Building Materials Based on Modified Veneer

Today, glued timber products occupy a significant place in the volume of finished products of modern construction and woodworking enterprises. Plywood is one such product. The durability and structural characteristics of plywood depend on the quality of binder, the type of wood and the quality of veneer. The paper explores the technology of ultraviolet treatment of thermally modified birch veneer with subsequent production of waterproof plywood. The results of a study on the influence of the operating parameters of veneer modification on the complex of sorption and strength characteristics of plywood materials are presented. It is established that the combination of thermal modification of wood throughout the entire volume with surface treatment with ultraviolet radiation allows creating glued wood material with increased water resistance and high-quality adhesive interaction.

Enhancing Weathering Resistance of Wood—A Review

Wood is a truly sustainable and aesthetically pleasant material used in indoor and outdoor applications. Every material, including wood, is expected to have long-term durability and to retain its original appearance over time. One of the major disadvantages of wood is the deterioration of its surface when exposed outdoors, known as weathering. Although weathering is primarily a surface phenomenon, it is an important issue for wood products as it affects their appearance, service life, and wood-coating performance. To encourage the use of wood as a material for joinery and other building components, the results of research into increasing the weathering resistance of wood are extremely significant. The development of weathering protection methods is of great importance to reduce the maintenance requirements for wood exposed outdoors and can have a major environmental impact. There are various methods of protecting wood surfaces against weathering. This paper provides a literature survey on the recent research results in protecting wood from weathering. The topics covered include surface treatments of wood with photostabilizers; protection with coatings; the deposition of thin film onto wood surfaces; treatments of wood with inorganic metal compounds and bio-based water repellents; the chemical modification of wood; the modification of wood and wood surfaces with thermosetting resins, furfuryl alcohol, and DMDHEU; and the thermal modification of wood.