Search

The problem of using natural building materials in low-rise construction lies in ensuring their durability during operation in conditions of atmospheric fluctuations, as well as in ensuring their thermal insulation properties. The purpose of this study is to find the thermal insulation properties of materials, namely thermally modified common hornbeam wood (the outer surface of the building), common pine wood (the inner surface of the building) and a thermal insulation layer of reeds, which allow justifying the effectiveness of their use in construction. The study uses a comprehensive research method, which included figuring out the thermal insulation properties of materials and justifying their feasibility in construction. The thermal insulation properties of wood and reed materials were calculated based on thermophysical dependences. The coefficient of thermal conductivity for wood reaches 0.0082 W/(m∙K), and for reed – 0.0022 W/(m∙K). Therewith, the thermal conductivity is no more than 0.19·10-6 m²/s, the heat capacity of wood is within 70÷90 kJ/(kg·K), and the heat capacity of a reed product is 337.2 kJ/(kg·K) respectively, which refers them to thermal-insulating materials. The practical value of this study lies in the substantiation of the method of establishing thermal insulation characteristics of building materials by finding their physical and thermophysical properties. The obtained results also expand the scope of application of products and building structures made of wood and reed. [ABSTRACT FROM AUTHOR]

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]

Aging resistance is an important index to evaluate the performance of thermochromic wood materials. In this paper, UV absorber was added to modify the organic thermochromic thin wood, with UV accelerated aging method, and the addition of UV light absorbers was investigated for thermochromic properties, thermal stability, weatherability, and surface wettability of the thermochromic wood. The results showed that the addition of UV-326 and UV-531 did not alter the thermal discoloration interval and surface wettability of the thermochromic wood. The addition of UV-326 with low addition amount had no obvious effect on the thermal stability of the material, but the thermochromic wood treated with UV-531 showed poor stability in the cold-heat cycle test. In the ultraviolet accelerated aging text, the addition of UV-326 improved the aging resistance of the material in 8h, the addition of UV-531 showed better anti-aging performance for materials above 12h, the total chromatic aberration of UV-531 thermochromic wood surface could be reduced by 23.76%, after adding 0.4% of the aging treatment after 36h. [ABSTRACT FROM AUTHOR]

The article offers information on a study which examined anisotropic thermal management capabilities of cellulose nanofibrils fabricated nanowood. It mentions that a simple approach is developed for preparation of thermally insulating bulk material through direct chemical treatment of nanowood. It shows that the thermal management, low mass density, and high mechanical strength of the nanowood make the material attractive for thermal insulation applications.

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]

This paper deals with the results of a study of the thermodestruction of the earlywood and latewood in the 1988-1998 growth rings of Gmelin larch ( Larix gmelinii (Rupr.) Rupr.) trees growing along the polar tree line (7052′53″N, 102°58′26″E, Taimyr Peninsula). The study used methods of thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Thermogravimetric data obtained were analyzed by Ozawa-Flynn-Wall kinetic model. We determined macrokinetic parameters of thermodestruction. Earlywood and latewood showed no significant difference in cellulose/hemicellulose/lignin ratio, whereas they differed significantly in destruction average value of activation energy (197.55 and 55.90 kJ mol, respectively). Our analysis of the correlation of thermodestruction values with mean monthly air temperature and precipitation revealed that component composition of both earlywood and latewood was influenced more by the weather conditions at the beginning of the growing season (April-June). Air temperature had markable influence on the wood component composition during cell wall synthesis only in latewood, whereas precipitation influenced the composition in both latewood and earlywood. TG/DTG and DSC methods were found to be promising for developing information on biochemical composition of early and latewood tracheids in stems and for identifying the extent of the influence of climatic changes on cell wall synthesis. [ABSTRACT FROM AUTHOR]

The wood of poplar (Populous sp.) species seem to be of low quality, mechanical resistance and is susceptible to microorganisms attacks, therefore, the application of thermal treatment is necessary, in order to improve some of its properties and increase its duration. Thermal modification of poplar (Populous sp.) wood was implemented at 180oC and 200oC, for 3, 5 and 7 hours in the presence of air and some of the most crucial mechanical properties were investigated. As the intensity of heat treatment increases, the mass loss of poplar boards is increased, attributed to moisture loss and the degradation and loss of chemical wood components. The bending strength decreased (2.05%-44.65%) compared to control, due to the treatments, while the elasticity decreased in all the treatment categories (5.66%-24.86%). The tangential hardness of poplar modified at 180oC for 3 and 5 hours, decreased by 10.24% and 14.59%, respectively and at 7 hours it grew by 2.35%, while at 200oC a decrease of 17.04-26.05% was recorded. The radial hardness decreased (2.81%-11.06%) at 180oC (3 and 5 hours) and when the duration reached 7h, it increased (9.28%), while at the treatments of 200oC radial hardness decreased (2.68%-18.86%). All the treatments reduced the impact bending strength of poplar specimens (24.27%-62.02%), even though they raised the resistance levels to compressive forces. Only the milder treatment achieved to decrease the roughness of poplar wood surface, while increasing further the treatment intensity, the degree of roughness showed a strong increase. [ABSTRACT FROM AUTHOR]

The effective specific heat of wood briquettes was determined by using a mathematical model developed for bulk pellets/briquettes and by measurements made in parallel and perpendicularly to the briquettes axis in the range of moisture contents below and above equilibrium moisture content. The mathematical model was based on the assumption that bulk pellets/briquettes are a porous system, consisting of solid particles and gas, with effective thermal properties. The model applied to the briquettes with the moisture content above the equilibrium moisture content is different to that applied to the briquettes with the moisture content below equilibrium moisture content, since alongside with wood fiber swelling, the magnitude and the number in the voids between chips increases. That is why, the briquettes density decreased in this moisture content range. New equations are proposed for this moisture content range considering a larger wood cell lumen that includes the chips interspaces. Experiments were performed at the temperature of briquettes ranging from 19 to 24°C and the average moisture content from 0 to 22.7%, dry basis. When increasing the moisture content above equilibrium moisture content, the briquettes expanded due to fiber swelling, but also due to the increase in the magnitude and number of chips interspaces. Both swelling and increase in briquettes voids influenced the effective specific heat. [ABSTRACT FROM AUTHOR]

Thermal modification of wood does not only change the color of the wood, it also changes wood properties that are closely related to its reaction to water (changes in dimensions, weight, density,...). These properties of thermally modified wood play an important role, limiting the use of thermally modified wood itself. These changes may be positive or negative depending on the wood species, thermal modification mode, the temperature used during the modification and other factors. The aim of this article is to broaden and collect knowledge about the effect of different thermal modification temperatures (160°C, 180°C and 210°C) on selected physical characteristics of spruce wood. The results of the study show that thermal modification at a temperature range of 160°C - 210°C has a statistically significant effect on the absorbability of thermally modified wood, as well as on tangential and volumetric swelling. Conversely, the effect of thermal modification on longitudinal swelling and a change in density during absorption was not proven. [ABSTRACT FROM AUTHOR]

The effect of thermo-hydro treatment (THT) on the durability of birch wood veneers and two plywood products - A and B was studied. THT was carried out in a multi-functional pilot scale wood modification device under elevated water vapour pressure at the following temperatures and treatment times (°C/min): 150/10; 150/50; 160/10 and 160/50. After THT, durability was examined according to the standards ENV 12038, EN 84 and EN 73. The durability class (DC) according to the CEN/TS 15083-1 was assigned to each treatment after fungal exposure. Water soluble extractives from THT samples were analysed with a UV-Vis Spectrometer in a range of 200 - 400nm, potentiometric titration and the Malaprade reaction. The best DC (2 - 3) for aged veneers was reached with the THT 160°C against the white rot fungus. The THT of industrial plywood A at 160°C enabled producing a material with improved durability (DC 1 - 3) after ageing. Plywood B with glued THT veneers showed lower decay resistance than plywood A. After ageing, better performance of plywood B was achieved at the THT 160°C assigning to DC 2 - 4. At the THT regimes under study, water soluble products (acids, sugars, aromatic compounds) were formed from both polysaccharides and lignin. [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]

The feasibility of using rattan canes (Laccosperma secundiflorum and Eremospatha macrocarpa) as reinforced fillers for high density polyethylene based plastic composite production was investigated. Extruded composites were tested for water sorption, tensile and thermal properties. The results obtained indicated that the rattan composites were dimensionally (water absorption: 2,2-21,4% thickness swell: 0,9-5,3%) and thermally stable (Tc: 116,8-118,2°C) and possessed adequate tensile properties (7,3-21,7 MPa). Composites made from L. secundiflorum had higher strength and thermal properties but lower sorption values compared to those of E. macrocarpa. Differences in the densities of the composites and the anatomical structures of the rattans seemed to influence properties of the composites. [ABSTRACT FROM AUTHOR]

The cross-section design of wood/polyvinyl chloride composite log-wall panels was studied for effects on compressive load, thermal and acoustic properties. Variation in the slenderness ratio (2, 4, 8, 10 and 12) on compressive load was also included. Two parameters of log-wall cross sections consisting of web thickness (3.5, 7.0 and 10.0 mm) and flange spacing (45, 60 and 90 mm) were also investigated. Experimental results indicated that higher web thickness and lower flange spacing of wood/polyvinyl chloride composite log-wall cross sections increased the ultimate compressive load and noise reduction. However, lateral deflection and thermal resistance decreased. Increasing the slenderness ratio of the log-wall panels resulted in lower ultimate compressive load and higher lateral deflection. Empirical equations for predicting the ultimate compressive load of wood/polyvinyl chloride composite log-wall panels in practical uses were proposed regarding web thickness, flange spacing and slenderness ratio. [ABSTRACT FROM AUTHOR]

The aim of this paper was to determine the moisture desorption isotherms and essentials thermodynamic properties of two Oak wood varieties. Desorption isotherms were measured using a static gravimetric method at 50, 60, 70 and 80 °C within the range of 5-90 % relative humidity. The equilibrium moisture content decreased with increasing temperature and decreased with decreasing relative humidity at a constant temperature. The 'Thermodynamic' sorption equation was found to be the best for describing the experimental moisture sorption isotherms of woods within the range of temperature and water activity investigated. The Fiber saturation point, deduced from the 'Thermodynamic' model parameters, depends on the temperature and varying from 22.6 to 54.4 (% kg water/kg dry matter). Isosteric heat of desorption and differential entropy were calculated by applying Clausius-Clapeyron equation to the desorption data fitted by the 'Thermodynamic' model. The isosteric heat of desorption and the differential entropy decreased with increasing moisture content according to an exponential law equation and varying from 2.03 to 31.14 kJ/mol and from 73.98 to 4.34 J/(mol K), respectively. The linear relationship between differential enthalpy and entropy satisfied the enthalpy-entropy compensation theory. The sign of Gibbs free energy was found to be positive (+283 J/mol) and (+97 J/mol) for Quercus robur and Quercus canariensis, respectively. The isokinetic temperature was found to be greater than the harmonic temperature. Based on the enthalpy-entropy compensation theory, it could be concluded that the moisture desorption isotherm of Oak wood is a non-spontaneous and enthalpy-controlled process. [ABSTRACT FROM AUTHOR]

In this study, silica sol (SiO sol) and KCO were used as flame retardants for wood. The synergistic effect of SiO sol and KCO on the flame retardancy, leaching resistance, and thermal properties of wood was investigated. The limiting oxygen index results revealed a significant improvement in the flame retardancy and leaching resistance of the wood sample treated with KCO and SiO sol using the double bath technique. The thermal analysis results showed that the synergistic effect of KCO and the SiO sol effectively prolonged the degradation of the wood sample during the charring stage and improved the stability of the char residue. The thermogravimetry-mass spectrometry analysis and scanning electron microscopy results showed that KCO catalyzed the degradation reaction of the wood sample at lower temperatures resulting in an increase in the water and carbon dioxide output, and the SiO sol formed a compact and melted barrier on the surface of the char residue, which hindered the transfer of heat and combustible gases in the condensed phase. Thus, the combination of KCO and SiO sol proves to be a promising flame-retardant system for wood. [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]

This study examines the dynamic compression and thermo-physical properties of some wood particles obtained from Akure, south local government area, Ondo State, South Western Nigeria. These wood particles are of the species of Celtis zenkeri and Celtis philippensis of the Ulmaceae family. The samples were possessed into different particle sizes (300, 600 and 850 μm) and subjected to varied compacting pressures (2.60-3.0 MPa). The density and specific heat capacity of the wood samples were determined using weighing displacement methods and temperature dependent model while the thermal diffusivity was estimated from other thermal properties. The results revealed significant variation in the values of the specific heat capacity as a result of change in pressure for all the wood samples considered. The density of wood samples lies between 4.51×102 -7.32×102 kg/m3 and the specific heat capacity values obtained for the samples fall within the range of 1.28×103-1.33×103 J/kg/K. It was also noted that the thermal diffusivity obtained falls within the range of 1.37×10-7-2.10×10-7 m2/s for the wood materials considered. However, the values of the densities, specific heat capacities and thermal diffusivities of the samples were found to change as the compacting pressure increased due to decreased in porosity. The implication of the study is that the materials have potential for use in polymer applications and the fabrication of film based photographic devices. [ABSTRACT FROM AUTHOR]

Aims Analyse the controversial relationship existing between wood density, precipitation, temperature and aridity, and its importance in shaping forest communities facing drought. Location New Caledonia (SW Pacific). Methods We sampled wood density in 1580 trees belonging to 175 species across nine sites (eight 1-ha plots) located in dry, mesic and humid forests. We tested whether wood density varied across species, communities and habitats, and depended on mean annual precipitation (MAP), mean annual temperature (MAT) and an aridity index (AI). We also tested whether the variations observed in community mean wood density (WDmean) and in wood density standard deviation differed from those obtained by a randomized species distribution across communities. We constructed a phylogenetic supertree at genus level and tested for the non-random distribution of WDmean. Results We found that WDmean tended to increase with increasing aridity (i.e. decreasing MAP and increasing MAT) and was significantly higher than expected under randomized species distribution at the dry forest site only. However, some species with low wood density grew well at these dry sites. At genus level, wood density was not random within the phylogenetic supertree. Some lineages exhibiting higher wood density than expected by randomization were also the most represented at the dry sites. Conclusions Although we did not observe an environmental filter sensu stricto, aridity associated with a low MAP and a high MAT at the dry and mesic forest sites was likely to favour species with a high wood density. Our phylogenetic results suggested that species belonging to a few lineages exhibiting high wood density were likely to be adapted to drought, hence favoured by increasing drought. [ABSTRACT FROM AUTHOR]

Thermal modification is the most important commercial modification procedure. Thermally modified (TM) wood has improved durability, but its performance does not meet expectations predominately under moist conditions. To reduce water uptake of TM wood, Norway spruce specimens were treated with suspensions of a natural wax by dipping impregnation (DipI) or by vacuum-pressure impregnation (VPI). Wax-treated specimens were subsequently TM at 185, 200, 215, and 230°C. Control specimens were heated up to 100°C only. Contact angle (CA), short-term and long-term water uptake, bending strength, and performance against wood decay fungi of the resulting material were determined. The results show that a combination of wax treatment and thermal modification have a synergistic effect that considerably improves hydrophobicity, reduces liquid water uptake, slows down water vapor uptake, and improves the resistance against fungal decay of the treated material. [ABSTRACT FROM AUTHOR]

Thermally modified (TM) wood production has significantly increased in the last decade. The trend for TM wood residues should be similar – rapidly increasing, which has prompted this research on the possible efficient uses of these residues, such as sawdust. One of the possibilities could be the production of wood plastic composites (WPCs). In this work, three different hydrothermal modification regimes were used to modify birch boards. Modified and unmodified birch boards were milled to obtain sawdust. WPCs were made with a two-roll mill, and they consisted of 50 wt-% wood fibres + 50 wt-% polypropylene. Melt flow index (MFI), flexural properties, impact strength, microhardness water absorption and dimensional stability were tested. WPCs with TM wood showed improvement in flexural properties, MFI and other properties, however there was a decrease in impact strength. Scanning electron microscopy pictures of impact strength samples fracture surfaces were taken. [ABSTRACT FROM AUTHOR]

Sisal-carbon hybrid composites were produced from mixtures having different weight ratios of sisal, carbon fibers and recycled polypropylene. All formulations were tested and evaluated for tensile and flexural properties. In addition, the thermal stability of the sisal-carbon hybrid composites were examined via thermogravimetric analysis and decay tests were conducted to determine the degradation of the hybrid composites. Results showed that the biological durability and mechanical and thermal properties improved with the increasing weight ratios of carbon fiber in the hybrid composites. According to the mechanical tests, the optimum hybrid composite formulation was found to be 12% sisal fiber + 28% carbon fiber + 60% rPP. [ABSTRACT FROM AUTHOR]

Mechanical parameters of ash wood (Fraxinus excelsior) subjected to compression in radial direction, before and after its thermal modification and measured at moisture content close to the equilibrium moisture content of wood exposed in and outside (4 and 12%) were compared. Thermal modification of wood was performed at 190°C or 200°C for 2 h in industrial conditions. During the measurements, the moisture content of the modified and control samples was identical. The parameters compared included: modulus of elasticity, stress at proportionality limit, relative linear strain at proportionality limit and accumulated elastic energy. Changes in the mechanical parameters of wood induced by its thermal modification were found to depend on the modification temperature and wood moisture content. [ABSTRACT FROM AUTHOR]

High-temperature heat treatment (HTHT) is an effective method for improving the wood dimensional stability and biological durability at present. However, the quantitative control of the wood color during the HTHT has been a more difficult problem for a long time. To solve the problem of quantitative control of wood color under the thermo-vacuum treatment (TVT) process, the mathematical model of heat and moisture transfer in alder birch wood (Betula alnoides) during the TVT process was built, and its application in the quantitative control of the wood color was also studied. (1) The experimental values and the model values of heat and moisture transfer in wood were found to be in good agreement. (2) The changes of wood temperature and moisture content (MC) were influenced obviously by the heat treatment temperature, the initial MC, and the thickness of specimen as well. The higher the heat treatment temperature was, the more rapid was the rise in the wood temperature and the drop in MC. The higher the initial MC of the wood was and the thicker the wood got, the slower the rise in wood temperature and the drop in MC. (3) Based on the mathematical model of heat and moisture transfer during the TVT process and the wood color index difference regression equations in the function of the temperature and time, the quantitative control of alder birch wood color during the TVT process was achieved. Therefore, it is feasible that heat and mass transfer principle applied during the TVT process guided the wood color quantitative control. [ABSTRACT FROM PUBLISHER]

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]

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]

Ensuring reliability of data on thermal properties of wood-based panels is important for manufacturing processes, especially when it is recommended to shorten the cooling phase and stack the panels in hot conditions. Prediction of the heat transfer during cooling phase and normal or hot stacking based on accurate data is essentially important for attaining panels of required properties. The thermal properties are also required when designing houses, especially low-energy or passive ones. Therefore, a water calorimeter was adequately designed and constructed to ensure improvement in the accuracy of the specific heat measurements. The calorimeter was used to determine the specific heat. The attained accuracy estimated by the relative error was significantly increased, and the error values were less than 2 % for all types of the investigated particleboard and OSB. In case of low-density fiberboard (LDF), the maximum value of the relative error did not exceed 4 %. It was also shown that high accuracy required for the specific heat measurements was achieved for experiments in which high-mass samples were used, in contrast to measurements for such samples in traditional DSC systems. The results for the specific heat were within the range from 1420 to 1450 J/kg K for LDF and all types of particleboard. The effect of the investigated material density on the specific heat was not found. The only exception was in case of OSB for which the specific heat was ca. 1550 J/kg K, and it was approximately 100 J/kg K higher when compared to other panels. [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]

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]

An asymmetrical two-layer laminated densified wood product is prone to cupping when it is placed in a fluctuating moisture environment. This study was aimed at developing a 2D finite element (FE) model to simulate this situation. Two types of specimens with two thickness ratios of 0.18 (type I) and 0.58 (type II) were prepared. A 6-week moisture and temperature treatment was conducted. The cupping value of deformed specimens was measured for verification. The major results were: (1) The cupping value of type I specimens experimentally measured and predicted was 0.307 and 0.327 mm, respectively, while that of type II specimens was 0.440 and 0.396 mm, respectively; (2) FE and experimental results were in good agreement since the FE results lied in the 95 % confidence interval of the experimental results. The developed FE model can be used to predict the moisture-induced cupping of a two-layer laminated wood product. [ABSTRACT FROM AUTHOR]

Cupping is a critical issue that affects the performance of a two-layer laminated densified wood product in service. Many parameters including material properties and product geometry can influence the cupping. It is more efficient to study the influence of these parameters on cupping using a model than by testing. A model sensitivity analysis is helpful in identifying key parameters so that product design can be optimized. This paper expanded the discussion on the finite element model developed and its application. It was found that (1) swelling/shrinkage coefficient and modulus of elasticity in the tangential direction and equilibrium moisture content were three key material parameters; (2) increasing the modulus of elasticity could offset part of cupping; (3) thickness ratio of two wood layers, as a key geometry parameter, was independent of three key material parameters; and (4) the optimal thickness ratio of two wood layers was 0.12. [ABSTRACT FROM AUTHOR]

To clarify the decay resistance effects of wood treated with different preservatives, the thermal behavior of treated samples was investigated. A thermal dynamic model was established using a mathematical method. The results showed that untreated Pinus massoniana had maximum mass loss, and the decay resistance effects of this species treated with different preservatives improved with an increase in the largest mass loss of pyrolysis. The pyrolysis can be divided into primary pyrolysis and secondary pyrolysis reactions in the lower and higher temperature regions, respectively. The activation energy represents a different degree of reduction from the primary pyrolysis reaction to the secondary pyrolysis reaction. The higher the retained cellulose content, the higher the activation energy. The sample's activation energy in the primary pyrolysis reaction can represent the decay resistance effects of wood treated with different preservatives. [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]

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]