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The present work studied the numerical modelling of heat transfer in a pile of Pinus radiata samples of a square cross-section by using radio frequency heating. More precisely, the study focused on the effects of the energy transferred to a dielectric material (wood) from an electromagnetic field, which required the calculation of the dielectric loss factor and its correlation with conservative equations. In this way, the temperature distribution across Pinus radiata samples was obtained through the integration of the energy equation using the finite volume method. The numerical results were compared to experimental data obtained from three experiments of radio-frequency heating of wood samples of a crosssectional area of 4 in × 4 in, 3.1-m-long, and 20 cm of separation between plates. According to the observed linear behavior of the heat transfer process, the numerical results of the transient variation of temperature were in agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Five types of alternative sandwich composite structures designed for building walls were investigated in this study using various core materials such as wood shavings, recycled acrylonitrile butadiene styrene panels, and rock wool. The sandwich structures were designed for exterior walls with a thickness of 175 mm. The experiment simulated the conditions for inside and outside temperatures during winter and summer seasons. The thermal conductivity coefficient associated with winter was lower by about 55% than those registered for summer. Wood shavings and one ABS panel as core components led to the most thermally stable structure. The best insulation solutions were the rock wool core structures with a mean thermal conductivity coefficient between 0.0564 W/mK and 0.0605 W/mK for the entire testing cycle. The two ABS panels from the core configurations had a negative impact on the thermal performance. The lowest thermal performance was recorded by the pure wood shavings core structure, with a maximum value of thermal conductivity coefficient of 0.150 W/mK. Compressed wood shaving core structures can compete with rock wool as thermal insulation solution. [ABSTRACT FROM AUTHOR]

Wood modification is an efficient method to improve wood performance and expand the applications of wood material. In this study, a combination modification method of aluminum sol-gel and furfurylation was developed to improve the performance of poplar wood. Wood samples were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The properties of the treated wood, including thermal stability, water uptake, dimensional stability, and dynamic wettability were also evaluated. The thermogravimetric analysis results indicated that the incorporation of an aluminum-based gel could prevent furfurylated wood from thermal degradation by converting the gel into nano-Al2O3. The aluminum-based sol-gel apparently hindered furfuryl alcohol polymerization and reduced the weight percent gain of the samples; the anti-swelling efficiency of the treated wood was over 57% (with little decrease) due to crosslinking between the wood and aluminum-based gel. The water uptake and hydrophobicity of the modified samples were improved significantly in comparison to the control samples. [ABSTRACT FROM AUTHOR]

To improve the thermal properties of softwood soda lignin, we studied a method of lignin modification using black liquor powder and polyethylene glycol (PEG). In this process, the black liquor powder was directly treated with PEG under alkaline conditions to produce a thermal melting material (alkaline PEG treatment). A model experiment was performed to determine the reaction of the lignin. The lignin in the black liquor powder consisted of 62.16% acid-insoluble lignin (purified lignin) and 37.84% acid-soluble lignin. After alkaline PEG treatment using purified lignin, the samples exhibited weak thermal melting during softening point analysis but did not exhibit appropriate thermal melting during thermal mechanical analysis (TMA). Nuclear magnetic resonance (NMR) data suggest that there was no linkage between lignin and PEG in the alkaline PEG-treated lignin prepared from the purified lignin. On the other hand, when using acidsoluble lignin, NMR data suggest that PEG was introduced to the lignin at its a-carbon position. Acid-soluble lignin PEG derivatives could work as plasticizers to induce the thermal melting of the alkaline PEG-treated lignin prepared from black liquor powder. [ABSTRACT FROM AUTHOR]

The influence of the burning temperature was evaluated for the nonvolatile combustible content of wood and bark of plantation-grown trees, at temperature intervals ranging from 500 °C to 1000 °C relative to ash production and the concentration of Ca, Mg, K, Mn, Zn, and Fe in ash, thermal properties, and ash fusibility. Production of ash from combustion of juvenile wood at t = 500 °C was Ad = 0.74% and juvenile bark Ad = 6.88%. Ash production decreased with increasing burning temperature. This was attributed to the chemical diversity of minerals contained in the wood and bark and their slow decomposition. Analyses of the presence of inorganic substances in ash from wood and bark revealed the highest presence of Ca. The concentration of calcium in ash from wood was Ca = 189 ± 46 g.kg-1 and in bark Ca = 278 ± 25g.kg-1. The ratio of processed calcium, potassium, magnesium, zinc, manganese, and iron in ash from wood at a burning temperature of t = 500 °C was Ca:K:Mg:Zn:Mn:Fe = 1:0.58:0.13:0.04:0.03:0.02 and from bark Ca:K:Mg:Zn:Mn:Fe = 1:0.41:0.07:0.01:0.01:0.003, respectively. The influence of the burning temperature non-volatile combustible was reflected in the concentration of each elements in ash and was contradictory. While concentration of Ca, Mg, Mn, and Fe in ash from wood and bark increased, concentration K and Zn in ash decreased. The decrease in concentration K, had a positive influence upon the thermal characteristics of the ash and the creation of ash in the form of loose matter. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the color and chemical changes of thermo-vacuum treated larch wood. Specimens were heat treated in a vacuum at various temperatures for 4 h. The color parameters of untreated and heat-treated samples were measured using the CIELab color system. Changes in the chemistry of larch wood were investigated using X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis spectroscopy. The results showed that the color of larch wood became darker at higher treatment temperatures. The O/C ratio decreased with an increase in treatment temperature. The C1 peaks showed that there was an elevated content of lignin and extractives on the wood surface after heat treatment. There were more free radicals for thermally treated wood samples, as demonstrated by the increase in the intensities of the ESR signals. Some groups of lignin that contribute to the darkness of the wood increased after thermo-vacuum treatment. Changes in surface chemistry may be the cause of discolorations that occurred during thermo-vacuum treatment. [ABSTRACT FROM AUTHOR]

Thermally modified wood is widely used in cladding, decking, and other construction projects that are meant for outdoor exposure. The purpose of this study was to investigate changes in the color, microstructure, and chemical composition of heat-treated, Larix spp. wood that was exposed to artificial weathering. In this study, accelerated weathering tests (UV and moisture) were conducted over a period of 3000 h. Photodegradation of both heat-treated and untreated wood was evaluated in terms of color, microstructure, and chemical changes that were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Ultra-violet radiation caused the degradation of lignin and extractives of wood, resulting in an immediate color change of the wood. The SEM observation of the heat-treated wood showed deformations and cracks in both treated and untreated samples. Irradiation resulted in a pronounced reduction in the absorption intensity and broadening of the FTIR spectra. It was found that the industrial heattreatment of wood products resulted in more color stability than untreated wood during the early stages of weathering. Thermal modification was found, however, was ineffective in improving the UV resistance wood over long-term photodegradation conditions. [ABSTRACT FROM AUTHOR]

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]

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]

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 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]

The thermal and dielectric properties of medium density fiberboard (MDF) with different moisture contents were measured by light flash and the parallel-plane capacitor method, respectively. The results show that increasing moisture content has a positive effect on both thermal properties and dielectric properties. The higher the moisture content, the higher the thermal conductivity and dielectric properties were. The thermal conductivity of MDF with different moisture contents varies in the temperature range of 25 to 150 ºC in a double-hump pattern rather than a proportional pattern. The dielectric constant decreases with increasing frequency up to 1000 MHz. The dielectric loss factor undulates within the frequency range of 1 to 100 MHz, and the peak value occurs at around 10 MHz. The results presented in this study can be used for radio frequency heating, wood building energy, material design, and radio frequency evaluation. [ABSTRACT FROM AUTHOR]

The effect of zinc borate (ZB) treatment on the mechanical and morphological properties of wood flour/polypropylene composites was investigated. Wood flour was first treated with ZB solution (1% w/w in ethanol-distilled water), followed by 24 hours of soaking on an unheated magnetic stirrer hot plate until relatively complete saturation was reached. Then, composites based on ZB-pretreated, ZB-treated-during-manufacturing, and untreated wood flour, polypropylene and coupling agent were made by melt compounding and then injection molding. The ZB treatment had no significant influence on mechanical properties of the composite with the exception of tensile strength. The composite made with ZB-pretreated wood flour exhibited the same mechanical properties as the composites made with ZB-in-process-treated wood flour; however there were statistically significant differences between flexural modulus and tensile strength of ZB-pretreated composites and ZB-in-process treated ones. Specimens containing the ZB showed lower flexural, tensile, and impact strength compared with the untreated specimens. However, the zinc borate treatments produced modest improvements in hardness performance. The SEM micrographs revealed that the outer surface of the wood fibers was coated by some crystalline deposits of zinc borate. [ABSTRACT FROM AUTHOR]

The longitudinal compressive and multi-directional bending properties after hydrothermal treatment of juvenile and mature elm wood were analyzed. Wood chemical composition and X-ray diffraction analyses were conducted in order to investigate the different properties of the juvenile and mature wood. Scanning electron microscopy was used to observe the wood's microstructure during longitudinal compression. The results indicated that both juvenile and mature wood could bend multi- directionally and that their relative cellulose crystallinities increased after hydrothermal treatment. The hydrothermal-treated juvenile wood contained more hemicellulose with unstable net-linked polysaccharide and condensed lignin, higher relative crystallinities degree than did mature wood, and more spaces formed by the extractive separation of mature wood. The longitudinal compressive and bending performances of the juvenile wood were worse than those of mature wood. The relationship between variations of stress and strain was separated into two stages, both of which displayed linear increases. However, the stage after the proportional ultimate stress increased slowly and smoothly, confirming the formation of some folds in the wood cells. [ABSTRACT FROM AUTHOR]

The effect of hydrothermal treatment at various temperatures (100 to 160 °C) and treatment times (30 to 720 minutes) on color changes (ΔE*), equilibrium moisture content (EMC), tensile strength (TS), shear strength (SS), brown-rot fungal decay mass loss (FML), and termite attack score (TAS) of rubberwood was examined. Response surface methodology (RSM) with a two-factor, four level (42 ) full factorial was employed. The mathematical models describing those properties as functions of treatment temperature and logarithm of treatment time were obtained. Hydrothermal treatment adversely and positively influenced mechanical properties (TS and SS) and durability (FML and TAS), respectively, of rubberwood. Strong correlations between ΔE*, TS, SS, and FML of hydrothermally treated rubberwood, proposed to be a consequence of degradation of hemicelluloses, were observed. Finally, ΔE* proved to be a good indicator of TS, SS, and FML but not that of EMC and TAS of hydrothermally treated rubberwood. [ABSTRACT FROM AUTHOR]

With thermal modification, changes in properties of wood, such as the presence of VOC and water-soluble carbohydrates, may occur. Thermal modifications under saturated steam conditions (160°C or 170°C) and superheated steam conditions (170, 185, and 212°C) were investigated by analysing the presence of water-soluble 5-(hydroxymethyl)furfural (HMF), furfural, and carbohydrates in heat-treated wood. The influence of thermal modifications on Scots pine, Norway spruce, and silver birch was also studied. Furfurals were analysed using HPLC at 280 nm, while monosaccharides and water-soluble carbohydrates were determined by GC-FID as their acetylated alditiols and, after methanolysis, as their trimethylsilylated methyl-glycosides, respectively. The amount of furfurals was larger in boards thermally modified under saturated steam conditions than those treated under superheated steam conditions. Generally, more of HMF than furfural was found in the thermally modified boards. In process water, in which saturated steam conditions had been used, furfural and only traces of HMF were found. Higher content of water-soluble carbohydrates was found in boards treated in saturated steam rather than in superheated steam. After modification in saturated steam, substantial parts of the water-soluble carbohydrates were due to monosaccharides, but only traces of monosaccharides were found in boards treated under superheated steam conditions. [ABSTRACT FROM AUTHOR]

Changes in color (CIE L*a*b*) and properties (density, mass loss, density loss, and bending properties) of heat-treated beechwood were researched, as well as the possibilities of predicting these properties based on color. Considering the different market values of sapwood and red heartwood, the aim of this study was to establish whether these parts of beechwood differ after a heat treatment. Samples were exposed to temperatures of 170°C, 190°C, and 210°C, respectively, for 4 hours. In order to predict the properties, a linear regression with color change (ΔE) and ΔL predictors was used, as well as the partial least squares (PLS) regression with 12 color variables. It has been shown that heat treatment reduces the properties of sapwood and red heartwood in the same manner, and equalizes the colors. The PLS-R showed the best results of prediction and presented the very high coefficients of determination for the mass loss, density loss, and modulus of rupture (MOR) in both sapwood and red heartwood. The equalized colors of heat-treated red heartwood and sapwood can significantly increase the use of products made out of red heartwood. Color can be an important indicator of the quality of such beechwood. [ABSTRACT FROM AUTHOR]

Wood-TiO2 (titania) composites were prepared by a sol-gel process, in which wood was impregnated with the precursor solutions prepared from tetrabutyl titanate (TBT), followed by a curing step. The surface morphology and moisture absorption behavior of the wood composites, as well as their thermal and mechanical performances, were examined. Environmental scanning electron microscopy (ESEM) analysis revealed that TiO2 gels were deposited principally in the cell lumens and partly in the cell walls, as confirmed by the energy dispersive X-ray (EDX) analysis. By this inorganic modification, the hygroscopicity of wood was significantly reduced and its dimensional stability was improved consequently. Greater amounts of TiO2 gel deposited in the cell lumens were not helpful in enhancing the hygroscopicity of wood. Thermal analysis (TG-DTA) showed that the incorporation of TiO2 gel retarded the thermal decomposition of wood matrix and improved the thermal stability of wood. The incorporated inorganic gel seemed to stiffen the wood cell walls, as indicated by the increased resistance of the wood composites to deformation and collapse in compression. [ABSTRACT FROM AUTHOR]

In this study the thermal conductivity of different wood materials was determined. For this purpose, Scots pine (Pinus sylvestris L.), Uludag fir (Abies Bornmülleriana Matff), Oriental beech (Fagus orientalis L), Oak (Quercus robur L.), and Chestnut of Anatolia (Castanea sativa Mill.) woods were used. In the test, the thermal conductivity of the woods was measured according to procedure of ASTM C 1113-99 standards. The lowest thermal conductivity was obtained in the perpendicular direction of Scots pine samples as 0.156 Kcal/mh°C. The highest thermal conductivity was obtained from perpendicular direction of samples in Oriental beech as 0.331 Kcal/mh°C. [ABSTRACT FROM AUTHOR]

In this paper, the thermal conductivity and dielectric parameters for pine [Pinus sylvesttfs (L.)] woods were d~ermined in transverse directions for moisture conditions from oven-dry to 22 percent at a room temperature of 22 to 24 °C. Results indicate that the behaviors of thermal conductivity and dielectric parameters with moisture content and structural directions were similar. In general, the properties increased within the range studied with increasing moisture content. The radial values were similar to tangential values for both thermal conductivity and dielectric properties. The data presented here should be useful in most design problems where pine wood is subjected to microwave electric fields and heat changes. [ABSTRACT FROM AUTHOR]

Chemical modification of hardwood sawdust from ash-tree species was carried out with a solution of maleic anhydride in acetone. Wood polymers, lignin, and cellulose were isolated from the wood sawdust and modified by the same method. Samples were characterized by Fourier transform infrared spectroscopy (FTIR), providing evidence that maleic anhydride esterifies the free hydroxyl groups of the wood polymer components. Composites comprising chemically modified wood sawdust and wood polymers (cellulose, lignin)-as variable weight percentages-, and poly (vinyl chloride) were obtained and further characterized by using FTIR spectroscopy and scanning electron microscopy (SEM). The thermal behavior of composites was investigated by using the thermogravimetric analysis (TGA). In all cases, thermal properties were affected by fillers addition. [ABSTRACT FROM AUTHOR]