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This article focuses on the plane milling of thermally modified birch wood while taking into account technological parameters that have substantial effects on the processed wood surface's arithmetic mean deviation of the waviness profile (Wa). The milling process was affected by the cutting speed, which varied from 20 to 60 m/s, with a feed rate of 4, 8, and 11 m/min. The results obtained on the set of thermally modified test specimens, were compared with the results obtained on test specimens without heat treatment. The surface finish was measured using various milling parameters. The material removal was 1 mm per pass. The results indicate that the thermal modification of wood did not significantly influence the arithmetic mean deviation of the waviness profile (Wa). Cutting speed and feed rate had the most significant effects among the monitored factors. The lowest arithmetic mean deviation of the waviness profile (Wa) was determined at a feed rate of 4 m/min and cutting speed of 40 m/s. An increase in cutting speed led to a decrease in the average roughness, while increased feed rate had the opposite effect. [ABSTRACT FROM AUTHOR]

Wood-based materials are used to manufacture various types of panels, including particleboard, fiberboard, and plywood, and they can also be used to manufacture furniture as well as interior and exterior building materials. However, wood-based materials exhibit a number of problems, including the emission of indoor air pollutants from adhesives used during production and their inherent fire risk. To date, a number of studies have investigated the emission of indoor air pollutants, and in recent years, there has been an increasing amount of interest in the flame-retardant performance of wood-based materials. In this study, the use of carbon materials was studied to improve the flame-retardant performance of wood-based materials. A comparison was made with various methods that are currently in use. The thermal conductivity was measured by the TCi method developed by C-Therm Technologies Ltd to evaluate the energy characteristics of wood-based materials that are used as interior materials. [ABSTRACT FROM AUTHOR]

Thermally-modified wood (TMW) has enhanced properties and its production does not involve the use of chemicals. However, the adoption of TMW in the marketplace has been limited in the U.S. for reasons that have not yet been clearly established. In this study, the marketing practices of U.S. producers and distributors of TMW were investigated, by conducting semi-structured interviews. Topics included major products and species, markets, distribution channels, promotional strategies, perceived barriers to adoption, and the outlook for TMW markets. Results show that TMW producers in general export a significant percent of their production; that TMW is considered a high-end product; and that customers are not as sensitive to prices as in other mainstream markets. Common products sold include siding, decking, flooring, millwork, and components for musical instruments. Respondents believe that the low awareness of TMW among the American public is a major barrier to wider adoption of TMW. However, companies envision a bright future for TMW as sales and inquiries have increased at a fast rate during the last few years. [ABSTRACT FROM AUTHOR]

Quercus pubescens Willd. is a common oak species in the Mediterranean area, where it is currently exploited mainly for purposes such as firewood. To improve the technological properties of its wood, various steaming and/or heat treatments were applied to 160 wood samples from a southern Italian stand, cut from either sapwood or heartwood, while 20 samples served as controls. Steaming was carried out in an autoclave at 120 °C, whereas heat treatments were performed in an oven at 150 or 200 °C for 3 or 6 h. The equilibrium moisture content, swelling, mass loss, wood density, compression strength, color variation, and lignin content of the samples were measured and compared among treatments. The swelling and water adsorption of wood samples decreased due to the hydrothermal treatments. The mass loss was strictly related to the temperature and duration of the heat treatments, whereas it was not influenced by the steaming treatment. The average axial compression strength value was positively influenced by the combination of steaming and heat treatments. A significant and general darkening of color was also observed for the harshest treatments, while an increase of lignin content was detected mainly in the sapwood. Thus, pubescent oak wood subjected to steaming and heat treatments may acquire useful characteristics suitable for its industrial use. [ABSTRACT FROM AUTHOR]

To upgrade the utilization of kraft lignin (KL) for high-performance lignin-based materials (e.g., carbon fiber), the purity, molecular mass distribution (MMD), and thermal properties need to be improved and adjusted to target values. Therefore, different methods, such as ultrasonic extraction (UE), solvent extraction, dialysis, and hot water treatment (HWT), were applied for the purification of KL. The chemical and thermal properties of purified lignin have been characterized by nuclear magnetic resonance, Fourier transform infrared, gel permeation chromatography, elemental analysis, differential scanning calorimetry, and thermogravimetric analysis. The lignin fractions obtained by UE with ethanol/acetone (E/A) mixture (9:1) revealed a very narrow MMD and were nearly free of inorganic compounds and carbohydrates. Further, the E/A-extracted lignin showed a lower glass transition temperature ( Tg) and a clearly detectable melting temperature ( Tm). Dialysis followed by HWT at 220°C is an efficient method for the removal of inorganics and carbohydrates; however, lignin was partly forming condensed structures during the treatment. [ABSTRACT FROM AUTHOR]

Casuarina equisetifolia wood is extensively used as fire wood and is also being used extensively in gassifiers. Drying is an important procedure which has to be carried out before the wood is burnt. Experiments on Casuarina wood chips of dimension 5.08 cm × 5.08 cm with 2.54 cm thickness were carried out between 80°C to 100°C in a tray drier using air flow velocity of 0.5m/s. Initial moisture content was found to be 48% on dry basis. The experimental drying curves showed only the falling rate period. Eleven thin-layer drying kinetic models were fitted with the experimental drying kinetics values and individual model constants were found. These models were compared using statistical measures like correlation coefficient, root mean square error, mean bias error and reduced chi-square to estimate the best model that would fit for the experiment. The drying rate and effective diffusion coefficient (Deff) were found to increase with temperature. [ABSTRACT FROM AUTHOR]

For reducing the environmental impact of the building sector, novel sustainable composites have recently been developed, by bonding hemp hurds with a new hybrid organic–inorganic binder. These composites, designed as substitutes for traditional insulating materials or as substitutes for formaldehyde-bonded wood particle boards, exhibit very promising properties. To ensure that the panel performance is maintained during the building operation phase, durability needs to be specifically evaluated as well. Therefore, in this study three composite types with low, medium and high density (LD, MD and HD, respectively) were subjected to accelerated ageing and the alterations in their physical–mechanical properties were evaluated. Composite resistance to accelerated ageing is strongly correlated with bulk density. HD composites, the only ones actually designed to be directly exposed to rainfall, exhibited almost negligible decreases in mechanical properties and hence a substantially satisfactory behavior. MD and LD composites, designed to provide thermal insulation and hence to be sheltered by HD panels, were affected to a larger extent by accelerated ageing, which however was definitely more severe than the real exposure conditions of the composites during their service life. Further studies are currently in progress to optimize the composites formulation and physical–mechanical durability. [ABSTRACT FROM AUTHOR]

This article reports a study of flame retardancy and thermal and mechanical properties of wood-plastic composites (WPCs) based on high-density polyethylene and pine flour. The study shows that sample composition plays an important role in WPCs' properties. The influence of additives like fillers (SiO2or CaCO3) and flame retardants ammonium polyphosphate (APP) and pentaerythritol (PER) on WPCs' properties has been considered. The best properties are shown in samples using SiO2as filler and treated with the intumescent fire retardant APP/PER. Such samples have excellent fire retardancy with V-0 rating (UL-94 test) and imply that APP/PER fire retardant ensures effective fire retardancy for WPCs. [ABSTRACT FROM AUTHOR]

In this study, the effect of two-step freeze–heat treatments on the thermochemical and physical properties of two Eucalyptus wood were investigated. Five treatments were performed and compared to untreated control: freezing (WF), freezing followed by heat treatment at 180 and 200 °C (WFT180 and WFT200) and heat treatment at 180 and 200 °C (WT180 and WT200). The freeze step was performed at −22 °C for 72 h and the heat step was performed at 180–200 °C for 3.5 h. Thermochemical (wet chemical analysis, FTIR and TGA), physical (water absorption and ASE) and surface properties (wettability) were measured. The two-step freeze–heat treatments changed the holocellulose and extractives contents, and stabilized the 1% NaOH solubility. Dimensional stability increased and hygroscopicity of thermally treated eucalypt wood decreased. The two-step treatments resulted in lower chemical changes than the application of a heat treatment only. The apparent contact angle of thermally treated wood increased, confirming the improvement of wood hydrophobicity. [ABSTRACT FROM AUTHOR]

Thermally modified wood has high dimensional stability and biological durability. But if the process parameters of thermal modification are not appropriate, then there will be a decline in the physical properties of wood.A neural network algorithm was employed in this study to establish the relationship between the process parameters of high-temperature and high-pressure thermal modification and the mechanical properties of the wood. Three important parameters: temperature, relative humidity, and treatment time, were considered as the inputs to the neural network. Back propagation (BP) neural network and radial basis function (RBF) neural network models for prediction were built and compared. The comparison showed that the RBF neural network model had advantages in network structure, convergence speed, and generalization capacity. On this basis, the inverse model, reflecting the relationship between the process parameters and the mechanical properties of wood, was established. Given the desired mechanical properties of the wood, the thermal modification process parameters could be inversely optimized and predicted. The results indicated that the model has good learning ability and generalization capacity. This is of great importance for the theoretical and applicational studies of the thermal modification of wood. [ABSTRACT FROM AUTHOR]

This paper deals with the determination of the surface quality of both thermally treated and thermally untreated wood after the plane milling process. The milled surface quality was evaluated on the basis of the arithmetical mean deviation of the assessed profile, Ra. Surface quality measurements were carried out for various milling process parameters, such as tool clearance angles of 15°, 20°, and 25°, cutting speeds of 20, 30, and 40 m/s, and feed speeds of 4, 8, and 11 m/min. A splinter with a uniform thickness of 1 mm was removed from the wood through milling. Based on the results, it can be stated that thermal treatment of wood has no statistically significant impact on roughness. The most significant impact of the monitored factors were associated with feed speed, clearance angle, and cutting speed. The lowest average roughness values were found at 20° clearance angles, a feed speed of 4 m/min, and a cutting speed of 40 m/s. Increases in cutting speed led to a decrease in average roughness, while an increase in feed speed had the opposite effect. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the influence of varying temperature on the strength characteristics of joints bonded using three types of one-component PVAc adhesives (i.e., Rakoll Express D3, Titebond II Premium, and Rhenocoll 3W, 4B Plus) that belong to the group of thermoplastic wood adhesives intended for non-construction bonding applications. The measuring procedure was a transverse tensile test for estimation of joint strength. As documented by the test results, a higher joint strength achieved at a higher temperature was achieved again after a gradual increase in the joint temperature from 20 °C to 140 °C and subsequent cooling to the starting temperature. After cooling the joint to the starting temperature, all tested adhesives complied with the minimum strength, namely 10 MPa. The results obtained in this study indicated that the resistance and thus the strength of joints bonded using contemporary PVAc adhesives increases with time. [ABSTRACT FROM AUTHOR]

In the Great East Japan Earthquake on March 11, 2011, large amounts of disaster waste were generated by the earthquake and subsequent tsunami. Much of the mixed wood waste was stored in a temporary storage facility for an extended period of time, and fire broke out due to spontaneous ignition. Consequently, it is now the practice that when a metropolitan epicentral earthquake occurs, disaster waste will be generated and stored locally. Fire caused by the same type of spontaneous ignition is a grave cause for concern. Thus, in order to prevent such fires, we evaluated the thermal behavior of the oxidation heat of the wood that was believed to be the cause of the heat generation in disaster waste. As a result of studies using TG-DTA and TAM, it was revealed that the thermal danger of wood increases due to increases in the temperature and in the concentration of unsaturated fatty acids in the wood. It is thought that the oxidation heat of the unsaturated fatty acids contained in the waste wood contributed to heat generation near 70 °C after heat generation by fermentative bacteria. [ABSTRACT FROM AUTHOR]

The aim of this study was to enhance the water repellency and dimensional stability of thermally modified wood by combining the preimpregnation of paraffin wax emulsion. To achieve this, Southern pine (SP; Pinus spp.) samples were first impregnated with paraffin wax emulsion (with 2.0% solid content) and then subjected to thermal modification (TM) in an oven at 180°C and 220°C for 4 and 8 h. The contact angle (CA), surface free energy, water absorption rate (WAR), anti-swelling efficiency (ASE), and bending properties of the control and modified samples were investigated. Moreover, the chemical and morphological alterations were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Both the wax impregnation and TM decreased the surface wettability, water absorption, and tangential swelling, while the combination of wax and thermal treatment exhibited the best water repellency and dimensional stability, indicating the synergism between the two procedures. However, the wax preimpregnation did not affect the mechanical properties of thermally modified wood. The FTIR, SEM, and XPS analyses confirmed that the synergistic effect is mainly due to the redistribution of the paraffin wax during TM rather than its impact on the chemical changes caused by thermal degradation. [ABSTRACT FROM AUTHOR]

Composites have been prepared with polypropylene (PP) as a matrix and pine flours, either thermally treated (Wtr) or not (W), as fillers resulting in wood plastic composites (WPCs). The treatment by retification at 280° mainly elevates the hydrophobicity of wood. The WPCs were fabricated with a co-rotating twin-screw extruder with the screw speeds of 500 and 1200 rpm and specimens were prepared by injection molding. Viscoelastic behavior, tensile test and Charpy impact test of Wtr PC were compared with PP and WPC. Wtr PC has a better dispersion and highest tensile modulus. As expected, a decrease in elongation at break and impact strength was observed for all composites. Processing at 1200 rpm improved by 60% the Young modulus of the WPC compared to 500 rpm, whereas 500 rpm was enough to obtain the highest modulus for Wtr PC. [ABSTRACT FROM AUTHOR]

Numerical analysis of temperature profiles during thermal modification of wood was carried out. The numerical solution - based on finite element analysis, FEA - of the 3D problem of transient nonlinear heat transfer model is presented for wood as a typical anisotropic material. The numerical model was enhanced for describing chemical reactions of cellulose, hemicelluloses and lignin (pyrolysis model), which takes into account the exothermic reactions as an internal source of heat energy. Experimental as well as theoretical process schedules were applied and the influence of sample dimensions (sample geometry) and wood species was studied. The influence of wood species was negligible on heating time to reach the highest temperature, i.e., the temperature differences were about 2°C during the drying phase. A expected, the sample size played an important role in the heating duration and in terms of the exothermic reactions of wood. The experimental and numerical data are generally in good agreement. The numerical error increased in the range of higher temperatures. The results can be improved by consideration of wood species (mass of wood compounds) and boundary conditions in the pyrolysis model, thus, better insight into details of thermal modification of wood could be reached. [ABSTRACT FROM AUTHOR]

We analyzed the effects of heat treatment on the chemical structure of wood from narrow-leafed Ash (Fraxinus angustifolia), a fast-growing and economically valuable species. We also analyzed the effects of heat treatment on the wood's resistance to four decay fungi. Narrow-leafed Ash wood samples were heated with saturated steam to 140, 180, 200, and 220°C for 2, 4, and 6 h. The relative contents of extractable components were analyzed, as well as the levels of holocellulose, cellulose, and lignin. In addition, the density, equilibrium moisture content, and pH of the samples were measured. To determine the effects of heat treatment on resistance to decay fungi, the samples were exposed to the white rot fungus Trametes versicolor, dry rot fungus Serpula lacrymans, and the brown rot fungi Coniophoraputearía and Gloeophyllum trabeum. Changes in the chemical composition of the wood due to heat treatment were correlated with increased resistance to fungal decay. While the hemicellulose content was dramatically reduced with increasing temperature and treatment duration, the lignin content increased proportionately. Thus, heat treatment is an environmentally friendly method of preserving narrow-leafed Ash wood against various decay fungi. [ABSTRACT FROM AUTHOR]

Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. However, this improvement of durability is realized at the expense of the mechanical resistance. Decay resistance and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. However, the introduction of a fast and accurate system for measuring this mass loss on an industrial scale is very difficult. Nowadays, many studies are conducted on the determination of control parameters which could be correlated with the treatment conditions and final heat treated wood quality such as decay resistance. The aim of this study is to investigate the relations between kinetics of temperature used during thermal treatment process representing heat treatment intensity, mass losses due to thermal degradation and conferred properties to heat treated wood. It might appear that relative area of treatment temperature curves is a good indicator of treatment intensity. Heat treatment with different treatment conditions (temperature-time) have been performed under vacuum, on four wood species (one hardwood and three softwoods) in order to obtain thermal degradation mass loses of 8, 10 and 12%. For each experiment, relative areas corresponding to temperature kinetics, mass loss, decay resistance and mechanical properties have been determined. Results highlight the statement that the temperature curves' area constitutes a good indicator in the prediction of needed treatment intensity, to obtain required wood durability and mechanical properties such as bending resistance and Brinell hardness. [ABSTRACT FROM AUTHOR]

Information about several papers discussed at the 10th annual Wood Science & Engineering (WSE) network meeting held in Edinburgh, Scotland on October 13-14, 2014 is presented. Topics include timber engineering, wood technology, and thermal and chemical modification of wood. The meeting featured several speakers including Peter Wilson, Callum Hill, and Peter Wilson.

Adhesives based on renewable resources have inferior efficiency compared to the synthetic ones. To improve the adhesive properties of soy protein isolate (SPI) adhesives, a new method of thermally modifying SPI was developed. The commercial SPI powder was thermally modified in a vacuum chamber at different temperatures (50, 100, 150, and 200 °C). Thermally modified and unmodified SPI powders were dispersed in distilled water and stirred at 24, 50 or 90 °C. Dispersions were prepared without and with pH adjustment to 10.0. The viscosity of the resulting adhesives was measured. Effective penetration and bond strength in longitudinal tensile shear were tested with bonded beech specimens. Regardless of the pH value and dispersion preparation temperature, SPI thermally modified at 150 and 200 °C exhibited no adhesive properties, while adhesive bonding was achieved with SPI modified at 50 and 100 °C. Adhesives without pH adjustment had viscosity below 28 mPas and exhibited no adhesive penetration. pH adjustment increased the viscosity and adhesive penetration, which improved the adhesive bond strength. Thermal modification at 50 °C resulted in improved wet shear strength, while the temperature of 100 °C deteriorated it. Increased dispersion preparation temperature to 50 °C increased wet shear strength, while temperature of 90 °C decreased it. The combination of thermal modification at 50 °C, dispersion preparation at 50 °C, and pH increase resulted in an adhesive with the highest shear strength. [ABSTRACT FROM AUTHOR]

This paper addresses the thawing of frozen wood by microwave. The effect of thermal and dielectric anisotropy on thawing wood is considered. The nonlinear heat conduction problem involving phase changes such as wood freezing is solved using three-dimensional volumetric specific enthalpy based on finite-element analysis. The dielectric and thermophysical properties are a function of temperature, moisture content and structural orientation. The specific volumetric enthalpy approach is validated by analytical, numerical and experimental testing. Finally, we studied the thermal effect and dielectric anisotropy on thawing frozen sugar maple wood ( Acer saccharum) at 2466 MHz. [ABSTRACT FROM AUTHOR]

This paper presents the European initiatives, strategies, and directives that must be considered in future development of thermally modified timber and when optimising the existing, commercialised processes and discusses the next steps in developing thermally modified timber needed to meet the requirements of the European low carbon economy. The standards for assessment of environmental impacts of processes and products with the focus on Environmental Product Declarations (EPDs) for materials used in the built environment are presented and followed by discussion about the need to consider the environmental impacts on sustainably aspects of thermally modified timber. This includes: determination of environmental impacts of processing and resulting products; design of processes and products towards minimal environmental impacts; and acquisition of EPDs and of Product Category Rules (PCR) for products of thermally modified timber. [ABSTRACT FROM AUTHOR]

Oligomers of lactic and glycolic acid (OLA, OGA) and poly(butylene succinate/adipate) (OBS, OBA) were impregnated and heated into wood for dimensional stabilisation. These bio-polyesters variously provide bulking and lumen filling treatments. Solvent extraction of treated wood showed that ca. 50% of the polymer remains in wood with in situ polymerisation evidenced by GPC. OGA readily penetrates the wood cell wall, which occurred only on heating OLA, whereas OBS/OBA was lumen filling with any cell wall penetration only evident after water soaking. Stability of OLA/OGA treated wood was improved, but did not withstand extended leaching, whereas OBS/OBA treated wood presented higher stability once leached. Bending resistance was influenced by OLA/OGA treatments, but original MOE values were recovered after leaching. Overall, the results show the bio-polyester treatment can confer specific properties of the modified wood to suit selected end use applications. [ABSTRACT FROM AUTHOR]

A large number of different heating technologies has been put into use for industrial scale thermal modification of wood. A useful classification of these processes is by the level of water vapour pressure, which ranges from vacuum to high saturated steam pressures. Only high water vapour pressure systems can maintain a finite moisture content during the heat treatment, but little is known about the water vapour pressure dependence of the thermal modification chemistry and the resulting modified wood properties. It is concluded from our analysis that the thermal wood reaction chemistry at the molecular functional group level is quite independent of the process and wood species. Wood properties that are strongly determined by wood chemical composition, such as the fungal durability and the equilibrium moisture content (EMC), can hence be equally achieved by all processes and for all wood species. This finding cannot be transferred to every other thermally modified wood property. [ABSTRACT FROM AUTHOR]

This paper examined the effect of temperature of pressing on the strength of width glued elements during the process of production of solid wood panels. It has been used the polyvinylacetate D3 adhesive and solid beech wood ( Fagus silvatica ). Time of pressing has been determinate separately for each level of temperature of bonding, which amounted to (30 o , 40°, 50°, 60°, 70 o C). For each level has been formed 20 samples in order to determinate the value of the shear strength of bonded joint. The results were processed using the Student's t -test. This research showed that with increasing the temperature and pressing time increases the shear strength of the bonded joint, but non-linear. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of thermal treatment on the resistance of Corymbia citriodora and Pinus taeda woods to the xylophagous termite Nasutitermes corniger, in a food preference test. We used temperatures of 100 °C (control), 160 °C, 180 °C, 200 °C, 220 °C, 240 °C for both wood species, and 260 °C only for Pinus taeda. Three wood planks measuring 6 cm x 16 cm x 56 cm (thickness x width x length) were thermally treated and manufactured in specimens of 10.0 cm x 2.54 cm x 0.64 cm (longitudinal x radial x tangential). Specimens were distributed in randomized blocks, with six treatments (Corymbia citriodora) and seven treatments (Pinus taeda) with 10 repetitions in a 250 liters box with 10 cm of sand; specimens were inserted in the sand, up to 1/3 of their height. The test was maintained for 45 days under laboratory conditions (25 °C ± 2 °C and 65% ± 5% relative humidity). Temperatures of 220 °C and 240 °C slightly improved the resistance of Corymbia citriodora wood to the termite. Improvements on Pinus taeda wood happened at temperatures of 240 °C and 260 °C. The temperatures of 160 °C for the eucalyptus wood and 200 °C for pinus decreased their resistance to the tested termite. [ABSTRACT FROM AUTHOR]

Le traitement thermique superficiel du bois permet de rehausser ses propriétés hydrophobe, antifongique et anti-gonflement contribuant à le mettre à l'abri des aléas naturels. Nous avons étudié la pertinence d'un traitement solvothermique d'éprouvettes de bois d'épinette noire imprégnées de liquides ioniques hydrophile ([EMIM][OTf]) et hydrophobe ([HMIM][TF2N]) comparativement à un traitement thermique simple sous balayage à l'azote. Les éprouvettes ont été soumises à des tests d'adsorption d'humidité, d'absorption d'eau, de gonflement, et de propriétés mécaniques après des traitements réalisés dans les gammes de température et de temps suivantes: [180 °C-260 °C] et [30 min-4 h]. Les tests ont montré une diminution notable de la teneur ultime en humidité et de prise d'eau liquide lorsque les échantillons de bois sont préalablement imprégnés de liquide ionique hydrophobe et que la température de traitement reste inférieure à 200 °C. Cependant, les tests de propriétés mécaniques ont montré que les modules d'élasticité et de rupture des éprouvettes affichaient une tendance à la baisse avec l'augmentation de la température et du temps de traitement. L'imprégnation de liquide ionique ne changeait rien à ce comportement même si en général une fragilisation accrue des éprouvettes pouvait être notée à cause de la solubilisation partielle des principaux composants de bois. Surface heat treatment of wood improves its hydrophobic, antifungal, and anti-swelling properties, and strengthens its resistance to the vagaries of natural exposure. We investigated the relevance of a superficial solvothermal treatment of wood specimens impregnated with hydrophilic ([EMIM][OTf]) and hydrophobic ([EMIM][OTf]) ionic liquids which we compared to a conventional heat treatment under nitrogen atmosphere over the following treatment temperature and time ranges: [180 °C - 260 °C] and [30 min - 4 h]. The treated specimens were subjected to moisture adsorption, water absorption, swelling, and mechanical properties testing. The results revealed a notable decrease in ultimate moisture content and water uptake of the samples, provided they were impregnated with a hydrophobic ionic liquid before heat treatment at temperatures less than 200 °C. However, the mechanical properties testing showed that the elastic and rupture moduli of specimens decreased with increasing treatment temperature and time irrespective of using ionic liquids. However, the impregnated samples suffered in general increased breakability which was ascribed to partial solubilization of wood components in the ionic liquid. [ABSTRACT FROM AUTHOR]

Dry thermal treatments of wood samples were carried out at 160 and 200 °C. After each treatment, the samples were irradiated using a strong UV emitter mercury lamp, and the colour change was then evaluated. For control, untreated samples were also irradiated using the same mercury lamp. Results showed that the extractive content of the wood played an important role in the colour change not only during thermal treatment but also during light irradiation. It was found that, compared to the thermally untreated samples, the thermal treatment at 200 °C reduced the red colour change due to photodegradation. The yellow colour change of photodegradation was hardly affected by the applied thermal treatments, showing that thermal treatments were not able to reduce the light degradation of lignin. The applied treatments slightly stabilized the wood against the degrading effect of light. The wood treated at lower temperature (160 °C) had less colour change induced by the light source. [ABSTRACT FROM AUTHOR]

This paper deals with nail withdrawal strength of spruce (Picea abies L.) with a focus on its dependence on thermal modification. Nail withdrawal strength is a feature of wood that is very important in the construction of wooden buildings. There are many studies dealing with the nail withdrawal strength of natural wood; however, this feature is much less explored with respect to thermally modified wood. Spruce wood was thermally modified at three different temperatures (140, 180, and 240 °C), and the nail withdrawal strength was evaluated for three types of nails driven into three anatomical directions. Values of nail withdrawal strength of thermally modified wood were compared with values of control spruce wood. The effect of thermal modification was clear: with increasing temperature, gradually decreasing values of nail withdrawal strength were obtained. The highest values were found in the tangential direction, and the lowest occurred in the axial direction. Annularly threaded nails had the highest values of nail withdrawal strength, while helically threaded nails had the lowest results. [ABSTRACT FROM AUTHOR]

A study was undertaken with the aim to determine thermal properties of balsa wood grown in plantations in Papua New Guinea. Thermal conductivity values were measured using the needle probe procedure according to ASTM D5334 (2008). The mean thermal conductivity results of balsa were in the range of 0.0381 W/mK to 0.0665 W/mK, similar to other materials currently used as insulators in the construction industry. A balsa sample with a density of 113 kg m³ had the lowest thermal conductivity value, 0.0339 W/mK, across the tangential and radial wood grain directions. Balsa is exported from Papua New Guinea mostly as endgrain panels to international markets to optimise its strength properties in the axial direction for applications that are exposed to compressive forces. This study revealed that there is the opportunity for Papua New Guinea balsa processors to consider producing perpendicular-grain panels for insulation markets, as the mean thermal conductivity values in this direction can be as low as 0.0381 W/mK, which is much lower than the thermal conductivity of the current end-grain panels at 0.0665 W/mK. The finding creates a potential design opportunity for balsa processors to consider entering new commercial markets to promote Papua New Guinea-grown balsa. [ABSTRACT FROM AUTHOR]

The self-heating propensity of biomass fuels is a major challenge to the large scale handling of e.g. wood pellets. The insulating properties in combination with exothermal processes sometimes lead to fires when larger volumes of wood pellets are stored. Recently, the thermal conductivity and specific heat of wood pellets have been investigated (Gou et al., 2013) through back-calculations of transient temperatures in wood bulk storage. Such properties are important in order to make simulations and predictions about safe storage and use. However, little information is available about the temperature dependence of these properties as well as the bulk properties of broken pellets, which is abundant in critical parts of a storage facility. In this study we show that the specific heat and thermal conductivity of wood pellets can be directly measured using the Transient Plane Source technique. We present data between 22 and 120 °C for bulk wood pellets and investigate the change in conductivity for fine particle bulk material. In addition, we investigate the possibility of measuring on individual pellets while studying the moisture content dependence. [ABSTRACT FROM AUTHOR]

ABSTRACT Many wooden objects from cultural heritage consist in wooden panels, painted on one face. Some of these panels show permanent cupping, micro-cracks of the painted layer, and cracks of the painted support itself. Different physical and mechanical phenomena are at the origin of these damages: wood is a hygroscopic material (its dimensions vary with humidity), it is highly anisotropic, the paint layer on one face has properties of permeability different from those of raw wood of the back face, and a rigid frame possibly restrained the deformation of the panel. Experimentations on our mock-up panels combined with numerical simulations of these panels in real situations of hygrothermal fluctuations will allow us to test specific situations and eventually to make suggestions to conservators and restorers and guide them in their interventions. Hygrothermal treatments are often used to improve wood durability thanks a reduction of its hygroscopicity. They have been considered as means to reproduce the physical properties of ancient wood. We intend to model the mechanisms involved in mechanical and chemical effects of wooden painted panels exposed to climatic variations. To develop such conservation tool, we need to work on mock-up, which replicate panel painting. So we will investigate the process of hygroscopic ageing and compression set generation of the back of painted panels to explain their permanent cupping and replicate their ageing state. For this purpose, digital image correlation is used to evaluate the strain field of the section of a wood piece submitted to variations of relative humidity. [ABSTRACT FROM AUTHOR]

Effects of heat-treatment on longitudinal permeability of circular and square wood specimens were studied here. Specimens were heated to 50, 75, 100, 125, 150, and 185 °C. Results showed that permeability increased at the lowest temperature due to shrinkage; then, it decreased due to irreversible hydrogen bonding and stiffness. The highest temperature increased permeability due to micro-cracks. The higher perimeter in the square specimens aggravated the effects of heat treatment. [ABSTRACT FROM AUTHOR]

The thermal expansion behavior of dry solid wood was investigated by dynamic dilatometry and thermal mechanical analysis. Anomalous thermal expansion behavior was observed concerning the displacement change under a constant compression pressure, which was not previously reported. Wood submitted to temperatures below 0°C under dry conditions exhibited a large increment in the linear thermal expansion coefficient (CLTE) and a sudden drop in the CLTE around 50°C as well as above 130°C during heating. In subsequent cooling/heating processes, these anomalous behaviors remained at temperatures below 100°C, although less pronounced, and disappeared at temperatures above 100°C. These behaviors were clearly perceptible in the radial and tangential directions but not in the longitudinal direction. The CLTE depended strongly on the heat and moisture history of the samples and the effects are species-specific. [ABSTRACT FROM AUTHOR]

Effects of zinc-oxide nanoparticles on physical and mechanical properties, as well as biological resistance of untreated and heat-treated beech wood were investigated in this study. Test specimens were prepared from sapwood and impregnated with a 5,000-ppm nano-zinc-oxide (NZ) suspension with a size ranging from 10 to 80 nm at 2.5 bars of pressure and using the Rueping process for 20 min. Control (C) and nano-zinc-oxide-impregnated specimens after (NZA) and before (NZB) heat treatment were divided into four subgroups of unheated (C and CNZ), heated at 50, 145 and 185 °C. Heat treatment resulted in a significant decrease in mechanical strength at temperatures of 145 and 185 °C. Heat-treated specimens showed less dimensional instability and fungal degradation. Impregnation with nano-zinc resulted in a slight and significant increase in weight loss and biological resistance against Trametes versicolor. The results showed that the impregnation significantly decreased the water absorption of the specimens. Impregnation before heat treatment showed considerable effect on the properties of wood compared to that of untreated ones. [ABSTRACT FROM AUTHOR]

This research work aimed at studying the effects of oleothermal modification of fir wood by using combined soybean oil with maleic anhydride (OHT-MA) to achieve lower treatment temperatures and enhance physico-mechanical properties. Wood blocks were oleothermally treated with soybean oil and OHT-MA at five different treatment temperatures (100, 120, 140, 160 and 180 °C) for three different holding times (30, 60 and 180 min). Afterward, physical and mechanical properties of the treated samples were determined, i.e., density, water absorption and volumetric swelling as the physical properties and bending strength, compression parallel to grain and impact load resistance as the mechanical properties. Results revealed increases in densities and reduction in water absorption as well as volumetric swelling of all treated samples. The mechanical properties were affected by OHT-MA treatment at different temperatures. Bending modulus of elasticity as well as compression parallel to grain was increased due to OHT-MA treatment. In addition, there was less reduction in impact load resistance of the treated samples. It was revealed that the OHT-MA enhanced wood properties at low treatment temperatures as well as shorter holding times. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate the effect of thermal change in the physical properties of wood Corymbia citriodora and Eucalyptus saligna, compared with the control (untreated wood). For that were sampled three trees of each species, with approximately 40 years of age, which were taken the first two logs 3 feet long. The thermal modification of wood was conducted by employing final temperature of 140°C, 160°C and 180°C for 2.5 hours, over the control (no treatment) using an oven with forced air circulation. Tests of physical properties were performed according to established procedures in ASTM and adaptations (ASTM 143-94, 2000), and consisted in evaluating the equilibrium moisture content, weight loss, swelling coefficient of total (linear and volumetric) and coefficient anisotropy. Overall, the results showed that the thermal modification was effective in reducing the moisture balance, weight loss, decrease in swelling and total anisotropy coefficient of both species, with the higher values observed in the treatments of higher temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effects of heat treatment temperature and duration on MOR and MOE were studied. [•] The MOR and MOE values were predicted by artificial neural network (ANN). [•] MOR and MOE decreased with increasing heat treatment temperature and duration. [•] ANN was quite successful in the prediction of MOR and MOE values. [•] It was shown that ANN can be used successfully for predicting MOR and MOE values. [Copyright &y& Elsevier]

This study aimed to evaluate physical and mechanical properties and colour changes of fast-growing Gympie messmate wood subjected to two-step steam-heat treatments. To achieve this, Gympie messmate wood was thermally treated under different conditions. Combined steam (127°C and ∼0,1471 MPa) and heat treatments in an oven (180–240°C for 4 hours) were performed. Physical and mechanical properties were evaluated by weight loss, equilibrium moisture content, specific gravity, volumetric and linear swelling and static bending tests, while colour changes were studied using CIEL*a*b*technique. The main findings showed that the steam pre-treatment in autoclave influenced most of the technological properties evaluated, mainly for heat treatments performed in low temperatures (180–200°C). The most significant changes after thermal treatments were observed for dimensional stability, which increased as a function of temperature of treatment. On the other hand, mechanical strength of thermally modified wood was significantly affected, while stiffness did not change. Colour modifications due to the application of two-step steam-heat treatments confirm the possibility to using these samples for aesthetic purposes. [ABSTRACT FROM PUBLISHER]

Chemically or physically modified wood materials have enhanced resistance to wood decay fungi. In contrast to treatments with traditional wood preservatives, where the resistance is caused mainly by the toxicity of the chemicals added, little is known about the mode of action of nontoxic wood modification methods. This study reviews established theories related to resistance in acetylated, furfurylated, dimethylol dihydroxyethyleneurea-treated, and thermally modified wood. The main conclusion is that only one theory provides a consistent explanation for the initial inhibition of brown rot degradation in modified wood, that is, moisture exclusion via the reduction of cell wall voids. Other proposed mechanisms, such as enzyme nonrecognition, micropore blocking, and reducing the number of free hydroxyl groups, may reduce the degradation rate when cell wall water uptake is no longer impeded. [ABSTRACT FROM AUTHOR]

Melamine formaldehyde-furfuryl alcohol copolymer was impregnated into softwood in combination with 1,3-dimethylol-4,5-dihydroxy ethyleneurea, a crosslinking agent, nanoclay, and a renewable polymer, collected as gum from a local plant ( Moringa oleifera) under vacuum condition and polymerized by catalyst heat treatment. Fourier-transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy were used to characterize the nanocomposites. Transmission electron microscopy showed uniform distribution of nanoclay in the composites. The mechanical properties were improved after the addition of plant polymer. The plant polymer had a marked influence on the flammability and thermal stability of the prepared composites. The apparent activation energy was determined by Ozawa-Flynn-Wall's and Vyazovkin methods. The activation energy of the composites decreased up to a certain decomposed fraction thereafter it remained constant. Higher the plant polymer content higher was the activation energy of the prepared composites which indicated a better interfacial adhesion and thermal stability. [ABSTRACT FROM AUTHOR]

The effect of the thermo-hydro-mechanical (THM) densification in a closed system on the set recovery and thermal stability of lime ( Tilia cordata) wood was evaluated. The THM densification process consists of four steps: plastification, densification, post-treatment and cooling. The THM-densified wood samples were subjected to three different post-treatment temperatures, and for each one, three different periods were used. Comparison between THM-densified wood sample without and with post-treatment at different temperatures and times was made. The set recovery tests showed that the post-treatment at higher temperatures and times improves the dimensional stability of the samples suggesting a permanent fixation of the transversal compression, but also reduces their thermal stability, by having lower temperatures corresponding to the maximum decomposition rate, lower values for the mass loss at the end of decomposition stage and lower values for the kinetic parameters. The samples with post-treatments at lower temperatures showed high set recovery values and exhibited higher values for the temperatures corresponding to the maximum decomposition rate, lower values for the mass loss at the end of the stage and higher activation energies and reaction orders. [ABSTRACT FROM AUTHOR]

Thermal conductivity values for heat-treated wild cherry (Cerasus avium (L.) Monench) were measured for radial and tangential directions and compared with those for untreated cherry wood. The wild cherry was heat-treated at a temperature of 212°C for two periods of time: 1.5-2.5 hours, respectively. The thermal conductivity test was performed with a quick thermal conductivity meter based on the ASTM C1113-99 (2004) hot-wire method, and measurements were carried out at the room temperature of 20°C. The results show that the heat treatment caused an important decrease on thermal conductivity of wood compared to untreated wood and the thermal conductivity decreased with increasing heat treatment duration. The highest decrease in thermal conductivity was recorded for a treatment duration of 2.5h. Compared with untreated cherry wood, the thermal conductivity on tangential direction, and radial direction of 1.5h and 2.5h heat-treated cherry wood decreased with 22.21%, 19.76% and 29.43%, 29.67% respectively. Radial thermal conductivity was similar to the tangential thermal conductivity. The data are useful when calculating the energy required to kiln-dry lumber and predicting the thermal insulating qualities of log homes made from the species. [ABSTRACT FROM AUTHOR]

In this study the effects of thermal modification of beech wood (Fagus sylvatica) on color changes after heat treatment were determined. The heat treatment of beech wood was conducted in a temperature of 180°C and 200°C for five different durations ranging from 2 to 10h. It was observed a gradual color change of treated samples whereas after 4h treatment no significant changes were recorded, measured with a colorimeter. The greatest reduction of lightness indicator L* was observed between 2 and 4 hours whereas the most intense color differences compare to untreated samples were occurred in 8h and 10h treatments. Comparing the two treatment conditions there is an obvious colour difference. Moreover, at 4h treatments time the differences were approximately 27.92 units more. Finally, radial direction gave higher values regarding lightness and longitudinal the lowest. [ABSTRACT FROM AUTHOR]

Physical, chemical, biological and microscopic properties change in unprotected wooden material that is exposed to weathering conditions and so its structural and some characteristic properties such as colour, gloss and hardness are ruined. The aim of this study is to determine changing of colour, gloss and hardness values of heat treated wood exposed to weathering. For this purpose, Anatolian black pine, calabrian pine, sessile oak and chestnut woods have been used. The experimental samples were subjected to heat under atmospheric pressure at three different temperatures (130, 180 and 230°C) and two different time levels (2 and 8 h). Then, heat treated samples have been exposed to accelerated weathering conditions to two different time levels (120 and 240 h) according to related standards. After the accelerated weathering procedure, changes in the colour, gloss and hardness of the samples have been determined according to related standards. The hardness values of heat-treated wood increased at low heating temperature and time. Aged wood hardness and gloss decreased, compared to the control specimens. Also, results have been compared with values of control samples belonging to each group. [ABSTRACT FROM AUTHOR]

Boards of poplar wood were subjected to thermal treatment at 180°C and 200°C, for durations of 2, 4, 6, 8 and 10 hours, in order to investigate the effect of heat treatment on the hygroscopic properties. Specifically, the change of equilibrium moisture content, density, swelling and absorption of wood were examined, in order to determine the significance of treatment temperature and duration in the enhancement of wood hygroscopicity. Generally, swelling in tangential direction proved to be quite higher than swelling in radial direction, while thermal treatment enhanced in great extent swelling in tangential and radial direction and the absorption of the specimens as well. Swelling in tangential direction decreased within the range of 8.17% and 33.3% for specimens treated at 180°C and the range of 43.85% and 65.09% for specimens treated at 200°C for 2-10 hours, referring to the final measurement after 72 hours of water immersion. In radial direction, the swelling decrease ranged between 2.47% and 28.45% for specimens treated at 180°C and between 19.62% and 60.87% for specimens treated at 200°C for 2-10 hours, respectively, after 72 hours immersion. Most of the heat treatments resulted also in absorption decrease, attesting the improvement of the poplar wood hygroscopic behavior. Finally, as it was proved, the higher the treatment temperature that is applied, the shorter is the duration, needed for the same swelling and absorption decrease level to be achieved. [ABSTRACT FROM AUTHOR]

OSB (oriented strandboards) made from Scots pine (Pinus sylvestris) were thermally post-treated at three different maximum treatment temperatures in the laboratory thermal treatment chamber of the Institute for Wood Technology Dresden (IHD). The OSB were supplied by a European manufacturer of OSB and bonded with methylene diphenyl diisocyanate (MDI). Post-treatment means that rather than thermally treating wood or strands before panel production, cut industry panels, i. e. 650mmx1200mm, were modified in IHD's lab kiln. The main goals of the thermal post-treatment of full-sized OSB were to improve the hygroscopic properties, i. e. to reduce the thickness swell (TS) and the equilibrium moisture content (EMC), as well as to improve the long-term properties creep behaviour and dimensional stability, without significantly reducing further mechanical properties like e. g. internal bond (IB) or bending properties, however. It was observed that the thermal post-treatment of the aforementioned OSB had a very positive effect on the moisture-related properties TS and EMC. The modified OSB showed far better values for said properties than the respective untreated ones. In can be concluded, that the thermal modification of OSB panels is possible and leads to very positive effects regarding their hygroscopic properties. [ABSTRACT FROM AUTHOR]

The vibrational properties of Japanese cedar wood at high temperature were measured. The specimen, its support system, a magnetic driver, and a deflection sensor were placed in an electric drying oven, where vibration tests were conducted. The heating temperatures ranged from 25 ºC to 200 ºC in 25 ºC increments. The resonance frequency decreased with higher heating temperature and decreased most dramatically in the temperature range of 150 ºC to 200 ºC. The loss tangent had a minimum value at 100 ºC and changed more in the temperature range from 150 ºC to 200 ºC than in the range from 25 ºC to 150 ºC. The changes in the resonance frequency and loss tangent of the specimens with larger distance from the pith (d) were smaller than those around the pith. These tendencies are believed to have occurred because the portion with a larger d had a smaller number of intercellular layers than the portion around the pith. [ABSTRACT FROM AUTHOR]

Abstract: The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood such as the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: The thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique and planing off the nutrient enriched evaporation surfaces. [Copyright &y& Elsevier]