Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion

Nonbiocidal techniques for wood protection have become more and more important in the last few years. One of the possible treatments to enhance wood durability is use of water repellents. In this research, the influence of one of the possible water repellents, the montan wax emulsion, on the moisturizing and the sorption characteristics of impregnated wood was investigated. To achieve a better protection against wood decay fungi, wood was impregnated with montan wax emulsion enriched with boric acid. The equilibrium moisture content (MC) was monitored during the adsorption and the desorption processes at five levels of relative air humidity (RH₁ = 20%, RH₂ = 33%, RH₃ = 65%, RH₄ = 88%, and RH₅ = 98%). Water repellence efficiency was monitored in the chamber with high RH (87%) and during dipping in the water. Impregnated samples were also exposed outdoors in a covered position for 5 months to determine MC changes according to changes in outdoor humidity and temperature. The results showed that the sorption properties of the impregnated wood are strongly related to retention of preservative solutions after impregnation and its composition. Montan wax reduced equilibrium MC of the impregnated wood up to 25% (relatively), whereas specimens impregnated with combination of montan wax and boric acid resulted in decreased MC in some cases and in increased MC in some cases. The Guggenheim–Andersen–deBoer model of sorption isotherms was fitted to experimental data to explain the sorption mechanisms. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Method for Studying Dynamic Sorption Behavior of Small Wood Samples

A method for determining mass changes (～ 0.0001 g) in small (～ 4-mm cubes) wood samples using the resonance of small mechanical springs mounted on piezoelectric sensors is presented. The size of the sample allows individual heartwood or sapwood, earlywood, latewood, and compression wood samples to be measured in an oscillating relative humidity environment and compared in terms of time constant and moisture gain. Since the apparatus is cost effective, many replicates can be achieved in one experiment. The use of small wood samples such that all tracheids are exposed removes the effect of structure on bound water transport. This, in combination with the ability to measure the response to small perturbations in relative humidity, presents the possibility to determine gaseous diffusion coefficients as a function of moisture content for individual wood types.

Preliminary, representative results of a study comparing the effect of drying temperature on sorption behavior of wood dried at 20, 90, and 150°C are presented.     

Effect of high-pressure processing on moisture sorption properties of brown rice

The effect of high-pressure treatment (0.1 to 500 MPa for 10 min) on the moisture sorption properties of brown rice (Feng Liang You Xiang No. 1) was investigated. Air was maintained at selected conditions (temperature between 20°C and 40°C, equilibrium relative humidity between 11% and 75%) and equilibrium moisture content was measured. The control attained a higher equilibrium moisture content than treated samples, while the 300 MPa treated sample had the lowest. The area of hysteresis of the 300 MPa test sample was the largest and the BET model was applied to determine the monolayer moisture content.     

Effects of Wood Drying Schedules on Fluid Flow in Paulownia Wood

Effects of three drying schedules on fluid flow were studied in the sapwood and heartwood of Paulownia wood (Paulownia fortunei). Boards with a commercial thickness of 5 cm were randomly dried to a final moisture content of 8 ± 2% using a mild (T₆E₃), a moderate (T₆E₄), and a severe (T₇E₄) drying schedule. Permeability measurement was carried out when specimens reached the final moisture content. Results showed a significant difference in the specific gas permeability as well as liquid permeability of the boards dried under the three drying schedules. Furthermore, a significant difference was observed in the gas permeability of sapwood and heartwood, dried under the different schedules, but not much significant difference was seen in the liquid permeability between sapwood and heartwood. T₆E₃ had the highest liquid permeability; furthermore, it was reported to have resulted in the lowest warping and most homogeneous moisture profile. This mild schedule is therefore recommended for commercial drying of Paulownia wood when further preservation and impregnation processes are planned for the dried boards. In the meantime, it is concluded that the age and drying schedule have significant effects on the formation of tyloses, significantly affecting gas and liquid permeability in Paulownia wood.     

Moisture sorption/desorption behavior of various manmade cellulosic fibers

The kinetics of dynamic water vapor sorption and desorption on viscose, modal, cotton, wool, down, and polyester fibers and lyocell knit fabrics were investigated according to the parallel exponential kinetics (PEK) model. The total equilibrium moisture regain (M_inf(total)) in all the materials decreased with increasing temperature. However, the partial equilibrium fast sorption, determined by PEK simulation at 60% relative humidity (RH) and 36°C, was larger than that at 20°C, whereas the partial equilibrium slow sorption was smaller. The characteristic times in fast sorption (τ₁) and in slow sorption (τ₂) for lyocell were reduced when the conditions were changed from 60% RH and 20°C to 36°C, whereas those for the other fibers increased. Lyocell exhibited the highest M_inf(total) value and the lowest τ₁ and τ₂ values, and this suggested high equilibrium moisture content and fast moisture uptake/release, that is, high moisture accessibility for lyocell. The relationships between the moisture regain, hysteresis, water retention capacity, and Brunauer–Emmett–Teller surface volume in the materials were also examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1621–1625, 2005     

Effects of superheated steam treatment on moisture adsorption and mechanical properties of pre-dried rubberwood

Abstract

Rubberwood (Hevea brasiliensis) was treated with superheated steam (140–160?°C) for 1–3?h and then its adsorption ability, mechanical properties, and color changes were investigated. The results of adsorption show decreased equilibrium moisture content (EMC) for all heat-treated cases throughout the hygroscopic range. The Hailwood–Horrobin model was used to analyze the sorption isotherms and determine the monolayer and polylayer moisture contents for untreated and heat-treated rubberwood. The monolayer moisture content clearly decreased with treatment temperature and duration, whereas the reduction in polylayer moisture was relatively smaller. Moreover, the least density of water adsorption sites was found in wood after treatment at 160?°C for 3?h, indicating this as the cause for reduced equilibrium adsorption. All treatment conditions had improved mechanical properties, including compression parallel-to-grain, hardness, and tensile strength. The total color difference of the wood surface increased with increasing temperature and treatment duration.     

Non-destructive Measurement of Moisture Distribution in Wood during Drying Using Digital X-ray Microscopy

The objective of this study was to develop a nondestructive method by which moisture distribution in wood during drying could be predicted. A newly developed digital X-ray microscope was used to measure the moisture content of wood and its accuracy and resolution was evaluated compared to the classic oven-dry method.

Small green wood specimens of Sugi (Cryptomeria japonica D. Don) were cut and dried under constant temperature and humidity. As the weight was decreasing during drying, X-ray microscope images of cross section were obtained. From these digital images and specimen weight, the moisture content during drying was measured by the two methods. After the shrinkage of the specimen was canceled, the standard error achieved finally was about 1% moisture content within the experimental range. As the image was divided into small subimages, the clear moisture distribution can be seen. It was found that the image divided into 32 × 32 subimages in each size of 0.625 × 0.625 mm might be valid to determine the moisture distribution, and that the drying rate in early wood is larger than in late wood.     

Letter to the Editor

Abstract

The water sorption isotherms of the Erythrina fusca Lour bark at 30 and 40°C were determined over relative humidity ranging from 55 to 85%. The equilibrium moisture content was determined gravimetrically. The moisture sorption isotherms showed that the equilibrium moisture decreases with increase of temperature. Six models were used for to fit the experimental curves of equilibrium humidity. Parameters of each equation were determined by nonlinear regression analysis. The isosteric heat of moisture sorption was calculated using the Claussius-Clapeyron equation.     

Analysis and Evaluation of Power Formulations for Wood and Hardboard Using Radio Frequency and Microwave Energy

This article analyzes the influence of frequency, temperature, moisture content, and structural orientation on the applicability of the Beer-Lambert law for various wood species using radio frequency and microwave radiation. To achieve this objective, the study compares the power dissipation computed from Maxwell's equation and Lambert's power law. The wood species considered are white oak (Quercus alba), Douglas fir (Pseudotsuga menziesii), trembling aspen (Populus tremuloides), white birch (Betula paperyfera), yellow birch (Betula alleghaniensis), sugar maple (Acer saccharum), and four commercial hardboards. The dielectric constant and dielectric loss factor are examined as a function of moisture conditions, temperature, frequencies, and the three principal structural orientations. The study involved 3,000 complex dielectric constants. It was found that the radial critical thickness is somewhat smaller than the tangential critical thickness (0.95 times smaller) and the longitudinal critical thickness is significantly smaller than the radial (0.52 times). It was demonstrated that the critical thickness L _crit above which the Beer-Lambert law is valid for all of the wood species studied under various conditions obeys the following conditions: log₁₀(L _crt) = 0.999 log₁₀(β^?1) + 0.4122, where β^?1 is the penetration depth (cm). In the case of microwave radiation, the critical thickness can be estimated from L _crt = 2.615 β^?1 ? 0.0626. Finally, a model is proposed to take into consideration the effect of moisture content with frequency (or with attenuation constant).     

Moisture transport in coated wood

Moisture accumulation inside wood causes favorable conditions for decay. Application of a coating alters the moisture sorption of wood and prevents accumulation of moisture. This paper presents the results of a nuclear magnetic resonance (NMR) study on the influence of a coating on the moisture absorption of wood.NMR allows to determine both local wood moisture content and rate of water absorption during water absorption and desorption of coated and uncoated wood. In contrast to weighing, both quantities are measured dynamically and non destructively with high spatial and temporal resolution in relatively short experiments. In addition, NMR relaxometry distinguishes between moisture in lumina and moisture in cell walls, which allows to accurately characterize sorption processes in wood. In the present study, samples with a diameter of 20 mm and a height of 10 mm, are studied in a 4.7 T NMR scanner with a spatial resolution of 33 ± 3 μm.Several commonly used wood–coating combinations are studied. Water is placed on the tangential side of samples equilibrated at 22% relative humidity while the wood moisture content (MC) is monitored for 24 h. This research shows that the sorption behavior of coated wood depends on the specific combination of wood and coating. Additionally, the amount of water that is absorbed in a coating may have a strong influence on the moisture content of the coated wood.We found that the water absorption of a hardwood dark red meranti sample is diffusion dominated. Application of a waterborne acrylic coating has no influence on this absorption process, which is attributed to the large water uptake of the coating. A solvent borne alkyd coating that absorbs very little water is found to strongly reduce the water uptake of the meranti studied. The waterborne coating reduces the water uptake of pine by preventing capillary water uptake of rays present in this softwood. The solvent borne alkyd coating further reduces uptake. Uncoated spruce also absorbs water by capillary suction. On this wood, the acrylic coating strongly reduces the water uptake; comparable to alkyd coated spruce. This is a result of the pits of spruce which became aspirated during drying. Application of a coating might fixate the aspirated pits, resulting in a structure with low permeability.     

Effect of Adsorption Conditions on Effective Diffusivity and Textural Property of Dry Banana Foam Mat

Foamed banana product, a crispy snack, can quickly adsorb the moisture from the moist air, leading to loss of textural property. The main purpose of this research was therefore to study moisture adsorption kinetics of dry banana foam mat and its texture quality change. The adsorption isotherm experiments were carried out with a standard static method using saturated salt solutions over a wide range of relative humidities from 32 to 82% and temperatures of 35, 40, and 45°C. Three dry banana foam densities of 0.21, 0.26, and 0.30 g/cm³ adsorbed water vapor under controlled conditions. Fick's second law coupled with an optimization technique was used to estimate the effective moisture diffusivity at sorption conditions. Empirical equations with two and three constant parameters for describing the dependence of the effective moisture diffusivity on moisture content were tested. The two constant parameters could suitably describe the variation of the effective moisture diffusivity with moisture content. The initial foam density, relative humidity, and temperature significantly affected the effective moisture diffusivity. The banana foam mats for all densities lost their crispy texture at moisture content of 0.078 kg/kg db.     

Effects of material parameters on the diffusion and sorption properties of wood‐flour/polypropylene composites

Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. Knowledge of moisture uptake and transport properties would be useful in estimating moisture‐related effects such as fungal attack and loss of mechanical strength. Our objectives were to determine how material parameters and their interactions affect the moisture uptake and transport properties of injection‐molded composites of wood‐flour and polypropylene and to compare two different methods of measuring moisture uptake and transport. A two‐level, full‐factorial design was used to investigate the effects and interactions of wood‐flour content, wood‐flour particle size, coupling agent, and surface removal on moisture uptake and transport of the composites. Sorption and diffusion experiments were performed at 20°C and 65 or 85% relative humidity as well as in water, and diffusion coefficients were determined. The wood‐flour content had the largest influence of all parameters on moisture uptake and transport properties. Many significant interactions between the variables were also found. The interaction between wood‐flour content and surface treatment was often the largest. The diffusion coefficients derived from the diffusion experiments were different from those derived from the sorption experiments, suggesting that different mechanisms occur. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 752–763, 2007     

THE MOISTURE SORPTION ISOTHERMS OF CEFOTAXIME SODIUM SALT

ABSTRACT

The water sorption isotherms of the cefotaxime sodium salt were determined at 30 and 40° C. Cefotaxime sodium salt was maintained at equilibrium relative humidities ranging from 40 to 80 %. Equilibrium moisture content was determined by the Karl Fischer method. The moisture sorption isotherms showed that the equilibrium moisture decrease while the temperature increase. The experimental curves of equilibrium humidity were fitted by different models (Bradley, Halsey, Henderson, Kuhn, Smith and Iglesias and Chirife and GAB). Parameters of each equations were determined by non-linear regression analysis. The best fit was obtained by Iglesias and Chirife model. The isosteric heat of moisture sorption calculated by Claussius Clapeyron equation varied from 64·45 to 48·03 kJ/mol when moisture content changed from 7 to 9·5 %.     

Effect of Relative Humidity on the Antioxidant Activity of Spray-Dried Banana Passion Fruit (Passiflora Mollisima Baley)-Coated Pulp: Measurement of the Thermodynamic Properties of Sorption

The antioxidant activity of the spray-dried banana passion fruit-coated pulp with maltodextrin10 DE was evaluated throughout 30 days of storage at a temperature of 25°C for different relative humidity values It was influenced by the relative humidity throughout the 30 days of storage. In addition, the sorption equilibria of water for spray-dried banana passion fruit-coated pulp with maltodextrin 10 DE at 25, 35, 45, and 55°C, over a range of relative humidity levels from 0.113 to 0.843, was determined using a gravimetric static method. The isosteric heat and Gibbs free energy were calculated from the sorption equilibrium. The Guggenheim-Anderson-Boer (GAB) and Brunauer-Emmett-Teller (BET) models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves, exhibiting an error smaller than 10% and an r greater than 0.99. The monolayer moisture content values for the sorption at different temperatures that were calculated using the GAB model ranged between 0.05315 to 0.05716 g water/g dry matter. The sorption curves exhibited a Type III behavior. The isosteric heat decreased with increasing moisture content while the Gibbs free energy increased.     

Relative humidity versus moisture content relationship for several commercial wood species and its potential effect on flame spread

Recently, measured flame spread indices on commercial wood species tested per ASTM E84 were found to be lower than previously published data. One reason for this may be that the hygrothermal conditioning of the red oak calibrant required by the test standards for measuring flame spread was changed between 1973 and 1981. This paper examines how much variability there is in the moisture content of commercially important wood species at 50% relative humidity by collecting water vapor sorption isotherms. Additionally, the effect of moisture content on the flame spread was evaluated after conducting 14 tests with eastern white pine in accordance with CAN/ULC‐S102 and four in accordance with ASTM E84 at four commercial test laboratories. For the sorption isotherms, it was found that the moisture contents at 50% relative humidity ranged from 6.8% to 11.4% moisture content and depended on the species and whether the specimens had been conditioned in absorption or desorption. The flame spread indices, as measured as different laboratories, also varied from 37% at 10.4% reported moisture content to 200% at 6.5% reported moisture content. The findings suggest that the wood moisture content and conditioning requirements of the standards are important test variables that affect the flame spread results.     

Intelligent Computation of Moisture Content in Shrinkable Biomaterials

A technique of intelligent computation of moisture content in shrinkable biomaterials from multiple predictors was developed. All measurable predictors were structured in three sets: biomaterial properties (volume, density, porosity, diffusivity); drying conditions (time, air temperature, humidity, velocity, pressure); and drying technologies. Two typical drying models were considered: time-dependent (thermodynamical) and time-independent (relational). The relationship between predictors and moisture content was established on the basis of multi-factorial linear regression (MLR) and neural networks (NN). Accuracy of statistical approximation was strongly dependent on drying model and chosen set of predictors. Time-independent models demonstrated better accuracy (MSE = 0.214) than time-dependent models (MSE = 0.254). Redundant predictors did not affect the accuracy and generalization ability of statistical models.

Results of NN training and testing showed superior accuracy with respect to statistical models. NN worked perfectly well for any combination of non-correlated predictors, improving accuracy to MSE = 0.01. Elimination of redundant predictors further improved accuracy and generalization ability of NN models.

The performance of both models was tested for drying of ginseng roots in the range of temperatures from 38 to 50°C, sizes from 10 to 32 mm, and relative humidity from 12 to 40%. Due to the high accuracy and computational efficiency, NN can be used as online estimator of moisture content in drying process.     

Study on properties of simul wood (Bombax ceiba L.) impregnated with styrene acrylonitrile copolymer, TiO2, and nanoclay

Dimensional stability, thermal, and water repellency are very important properties of wood. In this research, wood polymer nanocomposite (WPNC) has been prepared by impregnation of styrene acrylonitrile copolymer (SAN), ??-trimethoxy silyl propyl methacrylate-modified TiO₂ nanoparticles, nanoclay into simul (Bombex ceiba L.) wood. The characterization of the composites was done by using Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetry. The resultant WPNC exhibited an improvement in water repellency, moisture resistance, dimensional stability, chemical resistance, hardness, and thermal stability. The maximum improvement in all the properties has been observed for the wood sample treated with SAN/TiO₂ (0.5?%)/nanoclay (0.5?%).     

Effect of porous properties on self-cooling of fired clay plate by evaporation of absorbed water

Porous ceramic plates were prepared from clay and wood charcoal powder at 900 and 1100?°C and their porous properties, water absorption and the cooling effect of porous plates were investigated to produce eco-friendly porous ceramics for cooling by the evaporation of absorbed water. Porous properties were dependent on the firing temperature, and total pore volume, average pore size and porosity, which were 0.38–0.39 cm³/g, 0.15–0.17 μm and 49–50%, respectively at 900?°C and 0.31–0.33 cm³/g, 2.47–2.59 μm and 43–44%, respectively at 1100?°C. By the addition of wood charcoal powder, the cooling rate of porous plate fired at 1100?°C was 1.7 times faster than that of the plate fired at 900?°C and the cooling temperature difference (?T) was around 2.3?°C at 22.5?°C and 52–54% of relative humidity and around 3.2?°C at 29?°C and 77–80% of relative humidity. The porous ceramic plates developed here are potential materials for cooling buildings.     

Moisture transport in coated wood

Moisture accumulation inside wood causes favorable conditions for decay. Application of a coating alters the moisture sorption of wood and prevents accumulation of moisture. This paper presents the results of a nuclear magnetic resonance (NMR) study on the influence of a coating on the moisture absorption of wood.NMR allows to determine both local wood moisture content and rate of water absorption during water absorption and desorption of coated and uncoated wood. In contrast to weighing, both quantities are measured dynamically and non destructively with high spatial and temporal resolution in relatively short experiments. In addition, NMR relaxometry distinguishes between moisture in lumina and moisture in cell walls, which allows to accurately characterize sorption processes in wood. In the present study, samples with a diameter of 20 mm and a height of 10 mm, are studied in a 4.7 T NMR scanner with a spatial resolution of 33 ± 3 μm.Several commonly used wood–coating combinations are studied. Water is placed on the tangential side of samples equilibrated at 22% relative humidity while the wood moisture content (MC) is monitored for 24 h. This research shows that the sorption behavior of coated wood depends on the specific combination of wood and coating. Additionally, the amount of water that is absorbed in a coating may have a strong influence on the moisture content of the coated wood.We found that the water absorption of a hardwood dark red meranti sample is diffusion dominated. Application of a waterborne acrylic coating has no influence on this absorption process, which is attributed to the large water uptake of the coating. A solvent borne alkyd coating that absorbs very little water is found to strongly reduce the water uptake of the meranti studied. The waterborne coating reduces the water uptake of pine by preventing capillary water uptake of rays present in this softwood. The solvent borne alkyd coating further reduces uptake. Uncoated spruce also absorbs water by capillary suction. On this wood, the acrylic coating strongly reduces the water uptake; comparable to alkyd coated spruce. This is a result of the pits of spruce which became aspirated during drying. Application of a coating might fixate the aspirated pits, resulting in a structure with low permeability.     

The Effect of Wood Drying on Crystallinity and Microfibril Angle in Black Spruce (Picea mariana)

Abstract

The effect of drying on wood cellulose crystallinity, crystallite size, and microfibril angle was investigated using wide angle X-ray diffraction. Forty replicated specimens of black spruce (Picea mariana) wood were dried at constant temperatures of 40°C and 80°C and relative humidities of 34% and 47% in attempts to attain samples possessing final moisture content of 15% and 8% at each temperature. X-ray evaluation of wood specimens, comparing individual samples pre- and post-drying, revealed that both the mass fraction of crystalline cellulose and crystallite width increased with drying. In contrast, mean microfibril angle of the wood was not significantly affected by drying. It was also apparent that the changes in wood ultrastructure resulting from drying were not influenced by the drying conditions, including temperature, relative humidity, and final moisture contents.