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In musical instrument making, there is a strong need to find alternatives to the traditional endangered and expensive tropical wood species used today. The present study examined whether different commercial and experimental modified wood materials have the necessary acoustic qualities under different humid conditions (dry, standard and wet) to contribute to the use of raw materials for wooden musical instruments. The materials were thermally-modified wood (ash, aspen and birch), acetylated wood (beech, maple and radiata pine), melamine- and phenol formaldehyde-treated beech and furfurylated Scots pine (Kebony Scots pine). Investigations involved physical (density ρ , Equilibrium moisture content EMC , volumetric shrinkage) and dynamic elastic testing by a free-free flexural vibration method to determine various acoustic characteristics: specific dynamic modulus ( MOE dyn / ρ ), damping coefficient ( tanδ ), speed of sound ( c ), specific acoustic impedance ( z ), sound radiation coefficient ( R ) and acoustic conversion efficiency ( ACE ). The modified materials and especially acetylated wood showed low EMC values and high dimensional stability at each humidity level, which are considered important factors for making quality musical instruments. Based on the obtained value ranges of all acoustical properties, the different modified wood materials could find uses in musical instruments where specific characteristics of sound are required. Furthermore, most of the modified materials showed an excellent acoustic performance in the three humid conditions based on a high ACE and low tanδ . Furfurylated Scots pine and phenol formaldehyde-treated beech showed an inferior acoustic quality with the lowest ACE and the highest tanδ , which is a less favourable combination for most of the musical instruments. [ABSTRACT FROM AUTHOR]

Weathering period and exposure conditions can affect the degradation rate of wood surfaces. Longer weathering exposure periods are more reliable for end-use performance evaluations, and therefore it is desirable to investigate the role of long exposure periods on wood properties. This study aimed to investigate the effect of thermal modification on surface composition, roughness and color of ash, iroko, Scots pine and spruce wood species during natural weathering in East Black Sea Region of Turkey for 48 months. All measurements were performed at 6 month intervals. Regarding the results, surface roughness increased as the weathering period increased. Surface quality and color stability of the samples were enhanced with the thermal modification for all wood species, and those properties were much better for hardwoods than softwoods. FTIR data showed that changes in surface composition of thermally modified and unmodified wood were so high even at the first weathering exposure period. Thus, thermal modification may not be an effective protection method in long term outdoor conditions if the surface appearance and color stability is required. [ABSTRACT FROM AUTHOR]

Wood is an ideal building material as it is renewable and green. However, low dimensional stability and durability might restrict its usage in structural application. Therefore, modification is needed to improve the aforementioned issues. As an environmentally friendly wood modification method, heat treatment of wood using oil as a heating medium has brought to researcher’s attention to the fact that it might serve as an excellent treatment procedure in treating wood. This paper presents a review about the effects of oil heat treatment on the properties of wood such as colour stability, dimensional stability, mechanical strength and durability against termites and fungi as well as its potential to be used as construction and building materials. The pros and cons of using oil as a heating medium in wood treatment are discussed. This review shows discrepancies between the treatment methods or procedures and its resultant findings. Moreover, the effectiveness of the treatment is governed by several factors such as the type of oils used and wood species. The objective of the present paper is to conduct a review of the published literatures regarding the properties of wood modified by oil heat treatment and the results obtained were compared systematically. [ABSTRACT FROM AUTHOR]

In this work, chemical properties and structure of patula pine wood chips torrefied under air atmosphere are studied. Oxidative conditions instead of inert environment are an interesting way to reduce torrefaction operating costs. In this way, the torrefaction process was carried out in a batch rotary kiln by varying temperature (180, 210, and 240 °C) and residence time (30, 75 and 120 min). Sample amount (∼50 g), heating rate (10 °C/min), airflow (1 slpm), and particle size (between 10 and 20 mm) were fixed. Proximate, ultimate, and heating value analyses, as well as the contents of hemicellulose, cellulose and lignin of raw and torrefied biomasses were determined. Similarly, changes in thermal behavior by DTG, chemical structure by FTIR, surface area by BET, and cell-wall structure by SEM were analyzed. A severe degradation of both hemicellulose and cellulose was found at 240 °C, and a char-like material rich in lignin with high LHV is obtained. At this temperature, oxidation reactions are favored leading to highest specific surface area (174.95 m 2 /g) at 75 min. In addition, the reactivity of torrefied biomasses were higher than the raw material; particularly, those produced at 180 and 210 °C. Likewise, their structure exhibited a higher aromaticity with torrefaction severity. Therefore, torrefaction under air conditions upgrades the quality of patula pine wood as a solid biofuel for further thermochemical processing such as combustion or gasification. [ABSTRACT FROM AUTHOR]

The mechanical and thermal performance of wood flour composites (WFCs) containing thermoset resin is known to be strongly dependent on the curing reaction. In the present work, WFCs were prepared based on either unsaturated polyester, vinylester or epoxy reinforced by oil palm shell (OPS) flour with a major focus being the preferential reaction of the curing initiator with the natural fiber cells instead of the thermoset resin. Increasing the loading of OPS was found to delay the curing reaction of all thermoset resins by decreasing the peak exothermic temperature and increasing the time to peak. Selecting a suitable surface treatment for the OPS was observed to play a significant effect on the rate of curing reaction. Thermal degradation (in an inert atmosphere) and linear shrinkage of the WFCs was found to decrease with an increase in filler load. In terms of the mechanical performance, the flexural modulus increased steadily with filler load whereas the tensile modulus reached its maximum value of 2.74 GPa (30% improvement) at a filler content of 23 wt% for the hot alkali treated OPS reinforced polyester composite. Increasing the filler load was found to decrease the tensile strength whilst the flexural strength experienced an optimal value of 70.6 MPa (28% improvement) for a filler load of 9 wt%. Furthermore, the OPS filler exhibited improved interfacial bonding with the polyester matrix when compared to vinylester and epoxy. [ABSTRACT FROM AUTHOR]

Wood plastic composites (WPCs) were produced from thermally treated beech ( Fagus orientalis L.) wood and polypropylene (PP) polymer with coupling agent, by using injection molding. The wood chips were thermally treated for 30 or 120 min at three different temperatures (120 °C, 150 °C, or 180 °C) under saturated steam in a digester and then grounded (40-mesh size) by wood mill. Long-term water absorption kinetics of the composites were investigated with water immersion test. It was found that the water absorption decreased with increasing severity of the thermal-treatment and water immersion time as compared to the control composites. Furthermore, the composites produced with wood treated at 180 °C for 120 min exhibited the least water absorption. Microstructures of the composites were examined by SEM analysis to understand the mechanisms for the wood–plastic interaction which affected the water absorption. Further studies were conducted to model the water diffusion of the composites. Diffusion coefficient parameter in the models was obtained by fitting the model predictions with the experimental data. Water absorption of the studied composites was proved to follow the kinetics of a Fickian diffusion process. [ABSTRACT FROM AUTHOR]

Many studies have utilized a small-scale experimental apparatus such as the cone calorimeter to investigate the piloted ignition of wood exposed to constant levels of incident heat flux; however, there is a deficiency of similar studies related to the non-piloted ignition of wood exposed to time-varying heat fluxes which might represent more realistic fire exposures. In this study, a method was established for producing well-controlled, time-varying exposures using the conical radiant heater of a cone calorimeter. Experiments were conducted in which the incident flux, time to non-piloted ignition, and back-surface temperature of spruce wood were measured. Measured data were used in combination with a numerical heat transfer model to compute the time-dependent temperature distribution through each specimen, and thereby deduce the surface temperature at ignition. From the 30 specimens tested, the average surface temperature for non-piloted ignition of wood was determined to be 521±10 °C. From this surface temperature range, the heat transfer model was used to predict the range of time over which non-piloted ignition was likely to occur for a given time-varying exposure. This procedure was found to produce excellent predictions of ignition time for the time-varying exposures considered in this study. In addition, several existing ignition models were considered, and their suitability for predicting the non-piloted ignition of wood was assessed. [ABSTRACT FROM AUTHOR]

The modelling of the pyrolysis of wet wood provides more realistic fire scenarios for structural fire design by taking into account variable thermal properties of wood which are beyond the scope of conventional structural fire design codes. The proposed numerical methodology has been written in MATLAB environment. A 2D nonlinear finite element analysis (FEA) is performed to model the pyrolysis of wet wood subjected to high temperature. The varying of thermal proprieties of wood are discussed from the point of view of changes of structure and chemical composition under fire condition. The validity of the model is established by comparing the predicted results with results from fire resistance tests presented in literature. Qualitatively, the model provides good agreement with the experimental data. It is shown that the model can handle layers of a wooden composite structure. Temperature profiles at different points in the wood sample and the two-dimensional charring depth of Laminated Veneer Lumber (LVL) panels are calculated and compared with experimental data. [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]

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]

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 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 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]

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]

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]

Highlights: [•] Used X-ray to visualize, quantify thermo-physical behaviour of wood for first time. [•] Visualization of intra-particle conversion during devolatilization for first time. [•] Visualization of propagation of char front and anisotropic effect for first time. [•] Determined “char formation time” and “shrinkage” during devolatilization. [•] 3-D model used to predict the intra-particle propagation of conversion fronts. [Copyright &y& Elsevier]

Abstract: This study aims to investigate the change in chemical composition, surface characteristic and mechanical properties of heat treated four wood species (ash, iroko, Scots pine and spruce) during artificial weathering from 400 h to 1600 h in relation to their color changes, surface roughness, compression strength, modulus of elasticity, modulus of rupture and surface composition. Original color of wood species was significantly changed by heat treatment and artificial weathering. Artificial weathering decreased color change of heat treated wood samples except for iroko. Color change significantly increased with longer weathering exposure for heat treated wood samples however similar trend was not observed for control samples exposed to weathering factors. In general, heat treatment alone did not have a considerable effect on surface roughness of wood. Heat treatment seemed to protect wood surface to become rougher after weathering for softwoods. Compression strength and MOR of samples decreased while MOE increased during heat treatment. Compression strength, MOR and MOE of samples decreased considerably with longer weathering exposure both for heat treated and control samples. Softwood species seemed to be more affected by heat and weathering than hardwood species did with respect of loss on the strength properties. Severe delignification and hemicellulose degradation occurred in heat treated and control samples for all wood species during weathering from 400 h to 1600 h evident from rapid decrease at 1504/1508 cm−1 and 1730 cm−1, respectively. Heat treatment did not fully protect hemicellulose degradation and delignification occurred by weathering with longer exposure periods. [Copyright &y& Elsevier]

The influence of wood components and cellulose crystallinity on the kinetic degradation of different wood species has been investigated using thermogravimetry. Four wood species were studied: Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP). Thermogravimetric results showed that higher extractive contents in the wood accelerate the degradation process and promote an increase in the conversion values at low temperatures. Alternatively, the results indicated that the cellulose crystallinity inhibits wood degradation; organized cellulose regions slow the degradation process because the well-packed cellulose chains impede heat diffusion, which improves the wood’s thermal stability. The wood degradation mechanism occurs by diffusion processes when the conversion values are below 0.4. When the conversion values are above 0.5, the degradation is a result of random nucleation with one nucleus in each particle. [ABSTRACT FROM AUTHOR]

Abstract: Natural wood, being biological material, undergoes rapid degradation by ultraviolet (UV) radiations and other environmental factors under outdoor exposure. In order to protect wood from such degradation, the chemical structure of wood is altered by chemical modification or heat treatment. In the present study, heat treated specimens of rubberwood (Hevea brasiliensis) were exposed to xenon light source in a weather-o-meter for different periods up to 300h. Photostability of modified and unmodified wood was evaluated in terms of colour and chemical changes. Light coloured untreated wood became dark upon UV irradiation whereas, dark colour of heat treated wood lightened on UV exposure. CIE lightness parameter (L *) decreased for untreated wood whereas its value increased for heat treated wood upon irradiation. Other colour coordinates a * and b * increased with exposure duration for both untreated and heat treated wood. The overall colour change (ΔE *) increased for both untreated and heat treated wood. The Fourier Transform Infrared (FTIR) spectroscopic studies revealed severe lignin degradation of heat treated wood due to UV light exposure. Colour changes and FTIR measurements indicate that thermal modification of wood was ineffective in restricting light induced colour changes and photodegradation of wood polymers. [Copyright &y& Elsevier]

Abstract: Eucalyptus globulus Labill. is managed in commercial plantations for the pulp and paper industry as a coppice system. For stand reforestation the stumps are uprooted and at present used as biofuel. In this study, the biomass of stumps collected in six eucalypt stands in Portugal was evaluated in terms of physical, chemical and fuel properties. Stumps had basic density between 0.55gcm−3 and 0.71gcm−3, and the chemical composition showed 15.1% total extractives (mainly ethanol soluble extractives, 10.5%), 24.8% lignin and 67.0% holocellulose. In terms of thermal properties the stumps presented 18.9MJkg−1 for higher heating value (HHV) and 0.6%, 81.1% and 18.3% respectively for ash, volatile matter and fixed carbon. The elemental composition (C=51.0%; H=5.8%; O=45.3%; Cl=0.04%) has adequate values for use as woodfuel. [Copyright &y& Elsevier]

Abstract: In order to promote the use of Pinus pinea L. wood within the Migliarino-San Rossore Nature Reserve (Pisa, central Italy), three low-environmental-impact wood treatments, supposed to enhance natural durability, were compared. Impregnations with an oil-based preservative and natural waxes and a wood thermal treatment were tested in the field in accordance with standards ENV 12037 and EN 252. The above-ground test revealed that: P. pinea sapwood is more durable than Pinus sylvestris sapwood; all the alternative treatments showed a low mean decay level; wax and oil treatments performed as well as the traditional copper-based preservative; the natural durability class of P. pinea will only be calculated upon the complete failure of all reference lap-joints. The main outcomes from the in-ground test were: All the tested treatments increased the durability of wood, and the protective effectiveness of alternative treatments was comparable to traditional copper-based ones, or even superior in the case of heated oil. Taking certain mechanical and aesthetic limitations into account, all the treatments were suitable for the promotion of the P. pinea wood commodity in use classes 3 and 4. [Copyright &y& Elsevier]

Abstract: The purpose of this study is to investigate the torrefaction behavior of woody biomass (Lauan) blocks and its influence on the properties of the wood. Three different torrefaction temperatures of 220, 250 and 280 °C, corresponding to light, mild and severe torrefactions, and four torrefaction times of 0.5, 1, 1.5 and 2 h were considered. After analyzing the torrefied woods, it was found that the torrefaction temperature of 280 °C was able to increase the calorific value of the wood up to 40%. However, over 50% of weight was lost from the wood. The grindability of the torrefied wood could be improved in a significant way if the torrefaction temperature was as high as 250 °C and the torrefaction time longer than 1 h. Therefore, the torrefaction temperature of 250 °C along with the torrefaction time longer than 1 h was the recommended operation to intensify the heating value and grindability as well as to avoid too much mass loss of the wood. This study also suggested that over 50% of the reacted wood was converted into condensed liquid. The main components in the liquid were monoaromatics; little amount of heterocyclic hydrocarbons were also obtained from the torrefactions, especially at the torrefaction temperature of 280 °C. [Copyright &y& Elsevier]

Abstract: The Higher Heating Value (HHV) of 17 wood fuels was correlated with their Klason lignin (L) and extractive contents (Ext). There was a highly significant correlation between higher heating value, Klason lignin and extractive contents. The HHV (MJ/kg) of wood fuels as a function of lignin and extractive contents can be calculated using the following equation: qv,gr,d = 14.3377 + 0.1228 (L) + 0.1353 (Ext). The correlation coefficient (r) was 0.915. The standard error for Klason lignin was 0.017 and to extractive contents of 0.024. The proportion explained by Klason lignin was 56.4% and explained by extractive contents was 43.6%. [Copyright &y& Elsevier]

Abstract: This research aims at developing a new approach able to simulate 3-D heat and moisture transfer coupled with the mechanical behaviour of a wood during drying process. From the moisture content and temperature profiles, a 3-D formulation and a relevant constitutive model are used to calculate the stress/strain evolution within the board due to shrinkage and external mechanical loading. This allows a fast, comprehensive and realistic model to be implemented. The mechanical model takes into account the hydrous, thermal, mechano-sorptive and elastic deformations, as well as the changes of wood properties, caused by these processes, e.g. porosity, permeability, stress–strain relation, etc. The mathematical model describing simultaneous unsteady heat and moisture transfer between a gas phase and a solid phase during heat treatment has been developed. The conservation equations for the wood sample are obtained using diffusion equation and the 3-D incompressible Navier–Stokes equations have been solved for the flow field. The constitutive equations are discussed in some detail. ANSYS-CFX10 commercial code was used to solve the hygro-thermal problem and FESh++ for the mechanical behaviour. Experimental results obtained regarding temperature, moisture content and deformation profiles during industrial drying of black spruce wood are compared with the numerical results. Satisfactory agreement is obtained over a range of drying air temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The present study is devoted to a numerical study with experimental validation of the high-temperature thermal treatment of three-dimensional wood pole. During the heat treatment process, the heat and mass transfer takes place between the solid and the drying medium, and the moisture evaporation occurs within the solid due to the capillarity action and diffusion. The development of the model equations, taking into account both bulk phases and interfaces of the multiphase system is described, starting from the microscopic scale. Fundamental to this model is the ability to quantify the effects of key material and geometric properties of the pole. The three-dimensional and unsteady-state mathematical model equations are solved numerically by the commercial package FEMLAB for the temperature and moisture content histories under different treatment conditions. A detailed discussion of the computational model and the solution algorithm is given. Heat treatment was applied on the test samples in an oven for three final temperatures (180, 200 and 220°C). A series of experimental tests aimed at determination of heat treatment schedules kinetics curves and the temperature and moisture profiles and there time evolution were carried out. A very good agreement between the experimental and predicted results was obtained, implying that the proposed numerical algorithm can be used as a useful tool in designing high-temperature wood pole treatment processes. [Copyright &y& Elsevier]

Abstract: In order to shed light on the thermal carbohydrate transformation chemistry, the non-volatile composition of natural and toasted oak wood samples of different origins were studied. GC–MS analysis revealed the presence of monosaccharide anhydrides (MAs) only in toasted oak wood samples. They were formed by the cellulose and hemicelluloses thermal degradation produced during the toasting process, and the content was dependent on the degree of toasting. The principal MAs formed in the oak wood toasting process were 1,6-anhydro-β-d-glucopyranose (levoglucosan), 1,6-anhydro-β-d-galactosane (galactosan) and 1,6-anhydro-β-d-mannopyranose (mannosan), with levoglucosan being the dominant MAs detected. Monosaccharide anhydrides can be considered specific products formed during the thermal treatment of wood; therefore they are proposed as markers of toasted wood and could be used to monitor and determine the intensity of toasting process. [Copyright &y& Elsevier]

Abstract: A comprehensive heat and mass transfer computational model is used to analyse the intricate two-way coupling arising from the activated chemical reactions involved in the heat treatment of wood. The 2D version of a drying code known as TransPore is used to simulate the coupled heat and mass transfer phenomena. This code accounts for the internal pressure in the porous medium. The pyrolysis model describing the chemical reactions occurring in the main constituents within the cell walls of wood (cellulose, hemicelluloses and lignins) is derived using data taken from the literature. Refined computational strategies were required to address the two-way coupling between the heat and mass transfer and chemical mechanisms, including the thermal activation of the chemical reactions, together with the treatment of heat sources (or sinks) and the production of volatiles. The experimental set-up allows the overall weight loss, and the internal temperature and pressure at specific locations within the board to be determined during processing. The reported simulations highlight that the model is able to capture two particular phenomena observed during the heat treatment of wood: the double pressure peak due to water evaporation and volatiles production; and the temperature overshoot during the heat treatment phase. [Copyright &y& Elsevier]

Abstract: Surface densification technique can be used to enhance mechanical properties of low-density wood at a relative low temperature such as 145°C. However, the final dimensions of densified wood products are not stable when exposed to cyclic weathering. Post-high-temperature heat-treatment could assist in solving this problem through the modification of chemical components in wood. This study examined the interactive effect of surface densification and post-heat-treatment on aspen (Populus tremuloides). Thickness swelling and other selected properties of heat-treated surface densified aspen were compared to untreated aspen. As expected, the heat-treatment significantly improved the dimensional stability of surface densified aspen and reduced the mechanical properties to some degree. However, the mechanical properties of heat-treated densified specimens were still greater than those unheat-treated undensified ones. [Copyright &y& Elsevier]

Abstract: Heat treatment of wood at relatively high temperatures (in the range of 180–240°C) is an effective method to improve the dimensional stability and increase biological durability of wood. In this article, a coupling method is presented for high thermal treatment of a wood based on ThermoWood technology. A three-dimensional mathematical model describing simultaneous unsteady heat and moisture transfer between a gas phase and a solid phase during heat treatment has been developed. The conservation equations for the wood sample are obtained using diffusion equation with variable diffusion coefficients and the 3-dimensional incompressible Reynolds averaged Navier–Stokes equations have been solved for the flow field. The experimental results and model predictions were found to be in good agreement. [Copyright &y& Elsevier]

Abstract: Experimental techniques such as the cone calorimeter, representing realistic fire conditions, and the thermogravimetric analyser (TGA) combined with evolved gas analysis (EGA) can be used to determine flammability and degradation properties of materials. The desire is to correlate the flammability properties measured in the cone calorimeter for samples of size 100mm×100mm with those measured or deduced from TGA combined with EGA for milligram samples. Such an achievement will allow the design of fire-safe materials by quickly assessing (a) the fire safety of materials in their earliest milligram formulation and (b) the dependence of their flammability properties on the molecular structure of the material. In the present study, a cone calorimeter and TGA investigation is conducted for commercial Nordic Spruce wood impregnated by mono-ammonium phosphate (fire retardant, FR) through a vacuum pressure method. Experiments in the cone calorimeter with increasing FR concentrations indicated that (a) the char yields increased, (b) the apparent ignition temperature increased, (c) time to piloted ignition increased, (d) the total amount of heat released was reduced, (e) the peak heat release rate was reduced and (f) the carbon monoxide and smoke yields increased especially before ignition occurred. By comparison, char yields also increased with FR content in the TGA degradation experiments in nitrogen. The increase in the char yield with FR content explains quantitatively the decrease in the heat release in the cone calorimeter. By contrast, the onset temperatures measured in TGA decreased, whereas the ignition temperature deduced in the cone calorimeter increased with FR content. This difference is attributed to reduced yield of levoglucosan (reported in recent literature using TGA/EGA) with increased char yield as well as to the presence of phosphorous containing moieties in the volatiles, which both can quench piloted ignition. Finally, the TGA measurements showed that the FR concentrations decreased for milligram samples at different distances from the surface of the wood used in the cone calorimeter measurements. The variation of FR retardant with depth needs to be considered when using TGA data to interpret cone calorimeter measurements and the fire performance of the FR wood in approval tests such as the single burning item (SBI). [Copyright &y& Elsevier]

Abstract: The different methods of wood biomass thermal liquefaction at atmospheric and elevated pressures were investigated in order to select the more effective one. Wood biomass liquefaction by melted formate/alkali mixtures and with the use of metallic iron/Na2CO3 system is carried out at low pressures. But these methods give only moderate yield of bio-liquids. The highest yield of bio-liquid was obtained in the process of biomass dissolvation in methanol media in the presence of Zn–Cr–Fe catalyst at 20MPa. Co-pyrolysis and co-hydropyrolysis of biomass/polyolefine mixtures makes it possible to obtain the rather high yield of bio-liquid at the moderate pressures (3MPa). [Copyright &y& Elsevier]