Equilibrium Moisture Content Of Wood Research Articles

Surface Wettability Of Boron And Oil-Treated Wood

Background: Nowadays, demands for more environmentally friendly and cost-effective preservatives are increasing, and new non-traditional procedures are being explored in wood protection field. Plant oils improve the dimensional stability, water repellency and equilibrium moisture content of wood, and protect wood against decay fungi by means of its hydrophobic properties. The aim of this study is to investigate the influence of heat treatment and oil impregnation with or without prior treatment with boron compounds on wetting characteristic of Scots pine ( Pinus sylvestris L.) and beech ( Fagus orientalis L.) wood. Wood specimens were impregnated with boric acid, borax and agricultural boron at concentrations of 1%, 2% and 5% followed by oil heat treated with waste and sunflower oil at 160ºC. Wettability was measured by contact angle with the sessile drop technique using water. Results: Water contact angles on oil treated specimens increased while wetting tension decreased, and the wood more poorly wetted by water compared to the controls. A change in the drop volume on the surface of double treated specimens was around 5% based on the initial drop volume. Waste oil treatment resulted in having the greatest water repellent efficiency. High loadings of boron compounds decreased the contact angle and therefore the quantity of water absorbed by the wood increased. Conclusion: Wettability was decreased in specimens pretreated with boron and this confirmed that the hydrophobic surface was created by oil. Wettability is a prerequisite for good adhesion, coating and painting and this feature may be reduced by the less hydrophilic surfaces created after oil heat treatment.

Effect of Microstructure on the Permeability and Sorption of Wood of Sterculia rhinopetala and Albizia ferruginea

This paper sets to find out the effect of the microstructure of wood on the permeability and sorption of the wood of Sterculia rhinopetala and Albizia ferruginea. Permeability, the way of ingress of water into wood mass, is one of the most variable properties of timber and it further influences nearly all the physical properties of wood. Wood exposed to high humidity conditions or to liquid water during use may be subjected to biological deterioration which makes equilibrium moisture content of wood very important. Equilibrium moisture content is the moisture level where the wood neither gains nor loses moisture since it is at equilibrium with the relative humidity and temperature of the surrounding environment. Sixteen randomly sampled specimens of each of the wood of Sterculia rhinopetala and Albizia ferruginea species (heartwood and sapwood) with dimensions 3 cm x 3 cm x 3 cm were exposed at various relative humidity conditions of 30 %, 45 %, 60 %, 75 % and 90 % in a temperature and humidity-controlled climate chamber. The order of water uptake in terms of percentage volume is arranged from the lowest to the highest. Sterculia rhinopetala heartwood had the lowest uptake per volume with a value of 0.31 %. On the uptake per weight Sterculia rhinopetala heartwood again had the lowest uptake whilst Albizia ferruginea had the highest with a value of 6.77 %. The sapwood of Sterculia rhinopetala had a relatively higher uptake per volume value of 0.53 % and a value of uptake per weight of 0.72 % compared to the heartwood. The equilibrium moisture content values of Sterculia rhinopetala suggests that it can have minimal dimensional changes when used in both the Southern and the Northern parts of Ghana.

Physical properties of Tectona grandis (Lamiaceae) juvenile wood thermally modified in a closed system

This paper reports the first results of the effect of an industrial closed-system thermal modification process on the physical properties of fast-growth teak wood (Tectona grandis L.f.). The wood (juvenile) came from thinning a 15–18-year-old plantation located in Mato Grosso state, Midwest Brazil, broken down into plainsawn battens measuring 25 × 70 × 1 070 mm (radial × tangential × longitudinal). The battens were from material close to the pith which was combined heartwood (≈75%) and sapwood. We sampled untreated and thermally modified battens, which were transformed into specimens for testing. The thermal modification was carried out at 160 °C in an industrial scale reactor, according to the parameters of the TanWood process, which is classified as a closed hygrothermal system. Twelve specimens by treatment (25 × 60 × 50 mm3 — radial × tangential × longitudinal) were conditioned in a climatic chamber set up at 35 °C and the relative humidity (RH) was raised stepwise (31%, 49%, 69% and 81%). Apparent density and equilibrium moisture content of the specimens were measured at every step. The latter was used as an index of wood hygroscopicity. For the statistical analysis, only the results of apparent density and moisture content at 35 °C and 69% RH were compared. At the end of the conditioning, the specimens were saturated in water, followed by oven-drying and then the total swelling (from saturated to oven-dried) was calculated. Thermally modified wood became less dense, less hygroscopic and more dimensionally stable than untreated wood. The apparent density and the equilibrium moisture content of wood were reduced by 20% and 18% respectively. With the continuous increase of RH from 31% to 81%, the thermally modified wood proportionally adsorbed less water than the untreated wood. The radial, tangential and volumetric total swelling were reduced by 25%, 5% and 15% respectively.

Dimensional stability and hygroscopic properties of waterlogged archaeological wood treated with alkoxysilanes

Archaeological waterlogged elm wood was treated with methyltrimethoxysilane (MTMS) and (3-mercaptopropyl)trimethoxysilane (MPTES), respectively, and anti-shrink efficiency and sorption properties of the impregnated wood samples were determined. The applied impregnants stabilized wood dimensions efficiently enough, i.e. the obtained anti-shrink efficiency was 81 and 98% for MTMS- and MPTES-treated wood, respectively. Both alkoxysilanes can be considered as potential new consolidants. Hygroscopic properties of untreated and impregnated wood were investigated with the DVS experiments. The application of MTMS and MPTES reduced wood equilibrium moisture content (EMC) and sorption hysteresis e.g. hysteresis relative change was −83.7 and −73.7% for MTMS- and MPTES-treated wood, respectively. The EMC reduction was observed in the whole hygroscopic range and it was primary due to the monolayer capacity decrease to 50 and 30% of the value for untreated wood and observed for adsorption and desorption modes, respectively. The DVS experiments revealed chemical instability of the MTMS-wood system which was neutralized after the cyclic sorption. The possible scenarios of the interaction of both alkoxysilanes with wood structure were discussed.

Calculating the Equilibrium Moisture Content for Wood Based on Humidity Measurements

If given enough time, the moisture content of wood will reach an equilibrium with its surrounding environment. The temperature and relative humidity (RH) of the surrounding air will establish equilibrium moisture content (EMC) conditions, and the moisture content of the wood in that environment will approach a value determined by the RH. This article introduces an Excel spreadsheet that will calculate an estimate of the EMC based on any one of the following three pairs of data: RH and dry-bulb temperature, wet-bulb temperature and dry-bulb temperature, or dew-point temperature and dry-bulb temperature.

Кинетика сушки и увлажнения древесины

The article presents the results of experimental and computational studies of the kinetics of drying of different types of wood in a helium environment. Wood is considered as a multi-component composite, one component of which is free and bound moisture. A model describing the removal of bound moisture, as a set of direct (desorption) and reverse (sorption) processes is described. The experimental-computational method for determining the kinetic parameters of sorption is suggested. They are determined from the condition that the rate of sorption and desorption is equal with equilibrium moisture content of wood.

Changes of chemical properties and the water vapour sorption of Eucalyptus pellita wood thermally modified in vacuum

The aim of this study was to evaluate the chemical composition and the dynamic water vapour sorption properties of Eucalyptus pellita wood thermally modified in vacuum. For this purpose, wood samples were thermally modified in a vacuum oven at 160–240 °C for 4 h. Chemical composition were investigated by wet chemical analysis, elemental analysis, as well as Fourier transform infrared (FTIR) analysis, and dynamic water vapour sorption properties were evaluated by dynamic vapour sorption apparatus. The results showed that holocellulose and alpha-cellulose contents decreased and lignin and extractives contents relatively increased during the heat process. Elemental analysis showed a reduction in hydrogen content and an increase in carbon content. FTIR analysis indicated that the degradation of hemicellulose and condensation reactions of lignin occurred. In addition, the thermo-vacuum resulted in a reduction in the equilibrium moisture content of wood during the adsorption or desorption process. And the sorption hysteresis had a decreasing trend with increasing treatment temperature. The development of the hygroscopicity was related to the increase in the relative content of lignin, the degradation of the carbonyl groups in xylan and the loss of carbonyl group linked to the aromatic skeleton in lignin after heat treatment.

Sazonalidade da umidade de equilíbrio da madeira para o Estado de Mato Grosso

Por ser um material orgânico, heterogêneo e higroscópico, a madeira pode apresentar variações dimensionais e deformações decorrentes da interação com o ambiente. Em uso ou nos processos de secagem, quando são atingidos os equilíbrios entre a madeira e o ar atmosférico, têm-se a obtenção da umidade de equilíbrio da madeira (UEM). Em função da elevada importância dessa matéria-prima para o Estado de Mato Grosso, torna-se fundamental conhecer a sazonalidade de UEM. O presente trabalho objetivou estimar a UEM da madeira, pelo modelo de Simpson, para 30 municípios do Estado de Mato Grosso, distribuídos nas diferentes regiões de planejamento do Zoneamento Sócio-Econômico Ecológico do Estado. Os dados meteorológicos foram obtidos da Rede de Estações Meteorológicas Automáticas do Instituto Nacional de Meteorologia, entre 2006 e 2012. A UEM foi estimada diariamente, com posterior obtenção das médias mensais. Na estação seca ocorreram variações da UEM entre 5,08 e 9,57% e no período chuvoso entre 8,58 e 13,49%. Nos meses de janeiro, fevereiro e março ocorrem os maiores valores de UEM no estado. As condições ambientais durante o período seco (julho a setembro) favorecem a secagem natural da madeira serrada, por condicionarem uma secagem mais rápida.

Complex Modelling Drying Plant in the Composition of the Cogeneration System

The paper presents the architecture of a cogeneration system, the foundation of which is the dynamic subsystem. It includes a co-generation plant, drying plant, air heating heat exchanger, an air fan. Other units are units of discharge, charge, assessment of functional efficiency, which are consistent with the dynamic interaction subsystem. It is proposed a n analytical evaluation of changes in the moisture content of the air in the drying chamber at an air temperature measured at the outlet of the drying chamber. The structural scheme of an complex modeling dryer is developed. Using the cyclic structure set functioning levels of dryer air temperature change at the inlet of the heat exchanger and heating the air leaving the heat exchanger which corresponds to a change of the equilibrium moisture content of wood in the drying chamber. The air flow entering the air-heating heat exchanger which corresponds to the level functioning the dryer is defined. The valid values change in the moisture content of the air in the drying chamber obtained They allow to change the flow rate of air supplied to the air preheating heat exchanger when the air temperature measured at the outlet of the drying chamber. Changing the air blower motor speed for changes in air flow provides thermal drying treatment in the drying chamber. Coordination of temperature and aerodynamic regimes of drying wood allows, for example, the production of 5.8 thousand t ons of wood pellets per year to provide 860 apartments measuring 120 m 2 pellet fuel that given the frequency regulation on electric air fan drying materials, provides gain saving money using pellet fuel for heating and hot water to 40% and reduce the cost of power generation and heat within 20%-30% in in the conditions of the cogeneration system // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o

Control working ability of the drying plant in the composition of the cogeneration system

The paper presents the architecture of a cogeneration system, the foundation of which is the dynamic subsystem. It includes a co-generation plant, drying plant, air heating heat exchanger, an air fan. Other units are units of discharge, charge, assessment of functional efficiency, which are consistent with the dynamic interaction subsystem. It is proposed an analytical evaluation of changes in the moisture content of the air in the drying chamber at an air temperature measured at the outlet of the drying chamber. Set functioning levels of dryer air temperature change at the inlet of the heat exchanger and heating the air leaving the heat exchanger which corresponds to a change of the equilibrium moisture content of wood in the drying chamber. The air flow entering the air-heating heat exchanger which corresponds to the level functioning the dryer is defined. The valid values change in the moisture content of the air in the drying chamber obtained. The block diagram of logical modeling dryer developed, The functional information is obtained. It allows to change the air flow entering the heat exchanger preheating the air in measuring air temperature at the outlet of the drying chamber. Changing the air blower motor speed for changes in air flow provides thermal drying treatment in the drying chamber. Coordination of temperature and aerodynamic regimes of drying wood allows, for example, the production of 5.8 thousand tons of wood pellets per year to provide 860 apartments measuring 120 m2 pellet fuel that given the frequency regulation on electric air fan drying materials, provides gain saving money using pellet fuel for heating and hot water to 40% and reduce the cost of power generation and heat within 20%-30% in in the conditions of the cogeneration system

Mechanical parameters of thermally modified ash wood determined by compression in radial direction

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.

Effect of heat treatment on wettability and MOE of pine and spruce wood

This research was performed in order to determine how the heating process affects the wettability and mechanical properties of spruce ( Picea abies ) and pine ( Pinus silvestris ) wood. Studies were carried out using wood heated in laboratory. The measurements of specimens were 315x20x20mm. Specimens were divided into the following four groups: specimens of one group were not exposed to heating, whereas specimens of three other groups were subjected to heating at the temperature of 190 ○ C for 1 to 3 hours respectively, in the air under atmospheric pressure. Both heated and unheated specimens were moistened and dried in a climatic chamber. Before and after treatment the mechanical properties of specimens were assessed using the original method of transverse vibrations and contact angle measurements were carried out using the water drop method. The results showed a significant increase in wood hydrophobicity after treatment. Spruce contact angle after treatment increased from 1.3 to 1.45, pine from 1.4 to 2 times. MOE of pine wood decreased, while MOE of spruce slighty increased after heat treatment. Wood equilibrium moisture content after treatment is redused and it is known, that the drier the wood - the better its mechanical properties. This factor may have the biggest influence to such result. DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7304

Umidade de Equilíbrio em Madeira Termorretificada de Cupiúba da Região Amazônica

The heat treatment promotes low equilibrium moisture content of wood, bringing improvements in its physical and technological properties, as well as reducing the hygroscopicity and improving the dimensional stability. The objective of this study was to analyze the gain curve of moisture and hygroscopic equilibrium content after thermal rectification of samples Goupia glabra Aubl. (cupiuba). Were applied temperatures of 140 °C , 160 °C and 180 °, for time three hours, in body-of-proves dimensions 2x3x5cm, settled 15 body-of-proves for each treatment. Before the thermal rectification the samples were calibrated temperature-controlled room at 12% moisture of hygroscopic equilibrium after thermal rectification samples returned to the room again and calibration with a 18% hygroscopic equilibrium moisture for the purpose of moisture gain. There was growing moisture gain curve provided of 18 % hygroscopic equilibrium moisture after the thermal rectification, the witnesses absorbed less moisture that the samples underwent thermal rectification, but the samples subjected to 180 ° C absorbed less moisture of which 160 and 140 °C, as a consequence of loss of hydrophilic components. In the same condition it was observed that the equilibrium moisture content of the body-of-proves was larger in witnesses, followed by temperatures of 140, 160 and 180 °C respectively. However, the experiment evidence that the equilibrium moisture content and gain curve moisture influenced the reduction of hygroscopicity of wood material analyzed. Keywords: heat treatment; hygroscopicity; desorption; adsorption.

Capillary pore-size distribution and equilibrium moisture content of wood determined by means of pressure plate technique

Abstract This paper deals with the determination of the capillary pore-size distribution (CPSD) and equilibrium moisture content (EMC) of untreated and thermally modified (TM) Norway spruce [Picea abies (L.) Karst.] by means of the pressure plate technique (PPT). Desorption experiments were conducted at very high values of relative humidity (RH) in the range between 99.2% and 100%. The thermal modification of spruce results in an alteration of the CPSD, owing to the formation of intercellular cracks in the middle lamella, as a result of cell-wall compression. The desorption curves for both untreated and TM spruce show an extremely upward bend at 99.97% RH. This step reflects an EMC of 38.1% for untreated spruce and 33.8% for TM spruce. None of the samples shrunk during the PPT measurements. Following desorption experiments at 97.4% RH, all samples shrunk. This step reflects an EMC of 27.9% for untreated spruce and 21.7% for TM spruce.

Dimensional variation of three softwood due to hygroscopic behavior

With the aim of monitor the hygroscopic behavior of three softwood species in situations of changes in its moisture content, an experimental program based on dimensional measurements, hygrometer readings and weightings procedure, was carried out. Maritime Pine (Pinus pinaster), Spruce (Picea abies) and Scots Pine (Pinus sylvestris) specimens were evaluated and compared. For each wood species, half of specimens were previously dried while the other half was previously saturated. Three main variables studied during the period of specimen’s adjustment to an external environment of 20°C and 57.5% relative humidity (RH) were: mass, dimensional and moisture content variations. Based on the obtained experimental results, the equilibrium moisture content, as well as coefficients of linear shrinkage and expansion, were determined. Experimental results confirmed that besides RH and temperature, the equilibrium moisture content of wood depends on its moisture history. Moreover, using the obtained values it was possible to identify differences between the hygroscopic behavior of the softwood species studied.

Cork oak (Quercus suber L.) wood hygroscopic properties and dimensional stability

Cork oak (Quercus suber L.) wood has a potential for high value uses because of its strength and aesthetic properties but one obstacle is the lack of knowledge of the wood-water relations. Variations in wood equilibrium moisture content, density and dimensions were studied at air temperatures of 22°C and 27°C (representing acclimatized homes and summer non-acclimatized homes, respectively) varying from 80% to 30% of relative humidity. For indoor uses (22-27°C, 50-65% of relative humidity), the wood equilibrium moisture content ranged 12-17% and these values are recommended for the final commercial drying of cork oak wood. The fibre saturation point averaged 27%. Total volumetric shrinkage at 22°C-27°C averaged 12%, the linear shrinkage 8.1-8.5% and 3.6-3.6%, respectively in tangential and radial directions. Anisotropy averaged 2.3. Wood density at 12% moisture content ranged 0.63 to 0.67 g/cm3. The higroscopicity obtained was 0.003. The average tangential differential shrinkage was 0.32 for both temperatures and the average radial differential shrinkage was 0.14 and 0.15, at 22°C and 27°C respectively. The shrinkage factor was 0.90 cm3/g and 0.82 cm3/g, at 22°C and 27°C respectively. Differences between temperatures were only statistically significant at 80-70% of relative humidity.

Variation of Equilibrium Moisture Content of Heat-treated Couratari oblongifolia, Fraxinus excelsior, and Quercus rubra Wood

Heat treatment may result in variation of wood equilibrium moisture content (EMC). During this study, tauari (Couratari oblongifolia), ash (Fraxinus excelsior), and oak (Quercus rubra) woods were heat-treated at 190, 200, and 210ºC for 3 hours and then put into a conditioning chamber with a temperature from 30 to 75ºC and a relative humidity from 50 to 90%. The isothermal moisture adsorption curve was subsequently analyzed. Results indicated that the EMC of heat-treated wood was reduced by 23.4 to 37.4% compared to non-treated wood, but the EMC difference at different heat-treated temperatures for three hardwoods was quite small and the EMC of heat-treated wood was inversely proportional to their dry density.

Equation of Equilibrium Moisture Content of Wood under Vacuum by Regression Analysis

Relationship among equilibrium moisture content (EMC), temperature and pressure was established under vacuum condition, and EMC regression equation was constructed based on experimental data, with Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) as Experimental material, and MC was measured by oven-drying method. The experimental temperature range was from 40 to 90°C at the interval of 10°C, and pressure range was from 0.02 to 0.08 MPa at the interval of 0.02 MPa. EMC Comparison of Chinese fir and paper wafer sensor showed: EMC of paper wafer sensor changed in the same trend of solid wood. A regression equation was presented and the calculated EMC value was highly correlated with experimental data. This regression equation can be used to predict EMC under vacuum, especially for automatic control system of wood drying under vacuum.

A Handheld Programmable-Logic-Device-Based Temperature and Relative-Humidity Sensor, Processor, and Display System Platform for Automation and Control of Industry Processes

The development, testing, and validation of a small versatile battery-powered handheld programmable-logic-device (PLD)-based temperature and relative-humidity (RH) sensor, processor, and display system platform is addressed in this paper. An initial and illustrative application of the platform, which is used for its validation-temperature and RH sensing, calculation, and display of equilibrium moisture content of wood, is described. The platform may be utilized for computation and display of a range of temperature- and RH-sensitive metrics/parameters of importance to other process industries. The cost of the platform is important but not the highest priority. As illustrated in the wood-process-industry application of the platform, a higher priority is an ability to efficiently explore, implement, and compare, in a timely manner, different processor microarchitectures and display system formats which may be used in the calculation and display of any process-industry temperature- and/or RH-dependent process metric(s). This could include simultaneous calculation and display of multiple metrics which are a function of temperature and RH. After comparison, a best processor microarchitecture and display system can then be chosen and implemented based on specific industry process application performance/cost and other requirements. A PLD-based sensor, processor, and display system platform offers this opportunity.

Dynamic water vapour sorption properties of wood treated with glutaraldehyde

The dynamic water vapour sorption properties of Scots pine (Pinus sylvestris L.) wood samples were studied to investigate the modifying effects of glutaraldehyde. Pine sapwood was treated with solutions of glutaraldehyde and a catalyst (magnesium chloride) to obtain weight per cent gains of 0.5, 8.6, 15.5, and 21.0%, respectively. The sorption behaviour of untreated and treated wood was measured using a Dynamic Vapour Sorption apparatus. The results showed considerable reduction in equilibrium moisture content of wood and the corresponding equilibrium time at each target relative humidity (RH) due to glutaraldehyde treatment. The moisture adsorption and desorption rates of modified and unmodified wood were generally faster in the low RH range (up to approximate 20%) than in the high range. Modification primarily reduced the adsorption and desorption rates over the high RH range of 20–95%. Glutaraldehyde modification resulted in a reduction in sorption hysteresis due to the loss of elasticity of cell walls.