Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 17 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Phytosanitation of mountain pine beetle infected lodgepole pine using dielectric fields at radio frequencies]]> As an environmentally friendly alternative to chemical treatment, this research aimed to establish whether dielectric heating at high frequency of infested lodgepole pine (Pinus contorta) boards and logs, obtained from the mountain pine beetle devastated forests of British Columbia, can result in wood free of living fungi, nematodes and insects. The sample set contained 230 boards, 50x150 and 50x100 mm² in cross-section and 20 logs, 200-300 mm in diameter; all tested specimens were roughly one meter long. The intention was to test the efficiency of two temperature/time combinations: 56ºC for 30min and 60ºC for 15min that were identified in past works as effective phytosanitary combinations. Data showed that both permutations eradicated all infestation levels and types. The electric field power density per treatment cycle ranged from 23 to 50 kW/m³ and the total heating cycle varied from 42 to 116 minutes for all pest and wood type combinations tested. <![CDATA[<strong>Influence of specimen orientation on determination of elesticity in static bending</strong>]]> Wood is a natural material and so many factors interfere in estimation of its physical and mechanical properties. Consequently variability in properties should be taken into account to rationalize its application. Longitudinal modulus of elasticity is one of the main mechanical properties of the material, and its value can be obtained via standardized tests. The aim of this study is to evaluate the influence of test conditions compatible with ABNT NBR 7190:1997 Code requirements to determine modulus of elasticity in static bending. For each of eight species, eight specimens were tested, all of them four times, with the sample oriented on each of its four faces related to load application. Data analysis was performed independently of species and their respective strength class, using hypothesis testing to evaluate influence of specimens’ orientations to determination. It was concluded that specimen orientation is significant in determining modulus of elasticity in static bending according to ABNT NBR 7190:1997. This aspect can lead to a future normative review by the National Committee responsible by redaction of this Code. To represent natural variability of wood in specimens’ volume by only one bending test, values of the modulus of elasticity should be lessened in 8%. <![CDATA[<strong>Prediction of mechanical properties - modulus of rupture and modulus of elasticity - of five tropical species by nondestructive methods</strong>]]> This paper analyzes the usability of different dynamic moduli of elasticity and wood density for the prediction of mechanical properties - static modulus of elasticity and modulus of rupture - in samples with grain deflection from the longitudinal direction. Five tropical hardwoods (Afzelia bipindensis, Intsia bijuga, Millettia laurentii, Astronium graveolens and Microberlinia brazzavillensis) with different grain characteristics were used for this purpose. The fiber deflection was caused by the presence of interlocked grain or the working process. The three nondestructive techniques used in this study - longitudinal and flexural resonance method and ultrasound method - provided higher values of modulus of elasticity than the static bending test, but close correlation was observed between these variables. The weakest correlation was found for the ultrasound method which is probably caused by its measuring mechanism. The prediction of the modulus of rupture is less accurate when the dynamic modulus of elasticity is compared with the static modulus of elasticity; on the other hand, it was still good in comparison with the density model, which is inapplicable when grain deflection occurs in wood. In the wood of Zebrano where the interlocked grain was strongly developed, almost all of the correlation coefficients showed the lowest values and the prediction of modulus of rupture by nondestructive techniques was unsatisfactory. <![CDATA[<strong>Utilization of temperature kinetics as a method to predict treatment intensity and corresponding treated wood quality</strong>: <strong>Durability and mechanical properties of thermally modified wood</strong>]]> Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. However, this improvement of durability is realized at the expense of the mechanical resistance. Decay resistance and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. However, the introduction of a fast and accurate system for measuring this mass loss on an industrial scale is very difficult. Nowadays, many studies are conducted on the determination of control parameters which could be correlated with the treatment conditions and final heat treated wood quality such as decay resistance. The aim of this study is to investigate the relations between kinetics of temperature used during thermal treatment process representing heat treatment intensity, mass losses due to thermal degradation and conferred properties to heat treated wood. It might appear that relative area of treatment temperature curves is a good indicator of treatment intensity. Heat treatment with different treatment conditions (temperature-time) have been performed under vacuum, on four wood species (one hardwood and three softwoods) in order to obtain thermal degradation mass loses of 8, 10 and 12%. For each experiment, relative areas corresponding to temperature kinetics, mass loss, decay resistance and mechanical properties have been determined. Results highlight the statement that the temperature curves’ area constitutes a good indicator in the prediction of needed treatment intensity, to obtain required wood durability and mechanical properties such as bending resistance and Brinell hardness. <![CDATA[<strong>Analytical and experimental studies on stress capacity with modified wood members under combined stresses</strong>]]> The stress capacity of joints made of modified wood members under loading can be affected by design of joints and type of adhesive. Hence, these factors were addressed in this study by assessment of stress capacity variations in corner joints under diagonal applied compressive load induced combined stresses. The joints with mitered and butted design were constructed by application of epoxy and polyvinyl acetate (PVAc) adhesives from furfurylated wood samples with two weight percentage gains (WPGs), i.e., 20% as low level and 60% as high level. Results indicated that stress capacity in both corner joints was not significantly decreased with increasing polymerization of furfuryl alcohol (FA) in wood. Despite the high compression strength in mitered joint, the induced compression stresses were low in comparison with butted joint. The stress capacity in mitered joint bonded with epoxy adhesive enhanced with increasing the level of furfurylation. This was true for shear stress parallel to grain as well. Generally, it could be concluded that mitered joint made of furfurylated members and bonded with epoxy adhesive would be stronger than other corner joints. <![CDATA[<strong>Liquefied wood as a partial substitute of melamine-urea-formaldehyde and urea-formaldehyde resins</strong>]]> Maritime pine (Pinus pinaster) sawdust was used to produce liquefied wood by the polyhydric method with acid catalysis. The process was optimized to produce the highest amount of liquefied wood. Wood liquefied at 160ºC for 90 min was used in the adhesion tests. The bond strength of veneer glued with urea-formaldehyde and melamine-urea-formaldehyde resins and several mixtures of liquefied wood with urea- formaldehyde and melamine-urea-formaldehyde wasevaluated by automated bonding evaluation system. With the increase in liquefied wood content the bond strength decreased. Nevertheless for 20% liquefied wood the reduction of internal bond strength is relatively small and still within the minimum standards required. When 70% of liquefied wood is employed there is a significant decrease in bond strength. In conclusion it is possible to use a small amount of maritime pine sawdust liquefied wood as a partial substitute of urea-formaldehyde and melamine-urea-formaldehyde resins in the particleboard production, thus decreasing the formaldehyde content. <![CDATA[<strong>Evaluation of wood surface roughness depending on species characteristics </strong>]]> This study is focused on the impacts of species characteristics on the surface roughness of five species with different wood density namely white fir, Aleppo pine, European beech, walnut and white oak. The sample specimens tested were 300x300x30 mm in size and their surface quality was evaluated by the "the direct contact method" based on a mechanical system of measurement, giving the possibility of reproducing the surface measured and analyzing its profile. The surface roughness measurements were performed with a contact stylus profilometer, holding the moisture content of the specimens constant at 10%. The evaluation of the surface characteristics of the wood samples considered the roughness parameters: arithmetic mean deviation of the profile, maximum two point height of the profile, mean roughness depth and root-mean-square deviation of the profile. From the study result showed different average values of surface roughness parameters for broadleaved and conifers species. The differences can be explain by the influence on the roughness of the wood surface of the wood texture and the texture uniformity. <![CDATA[<strong>Addition of nanofibrillated cellulose to the stone groundwood suspensions and on surface</strong>: <strong>a good alternative to classic beating process</strong>]]> Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF ), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper - Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.<hr/>The effect of different application amounts of nanofibrilated cellulose (CNF), from 0 to 6%, on the physico-mechanical properties of the paper obtained from stone ground wood pulp fiber has been studied. The results have been compared with the conventional beating process at different degrees (from 0 to 2500 rpm). Afterwards the effect of the application of CNF on the surface, in papers with and without CNF in bulk, has been studied. The results showed that the paper stiffness and breaking length increased with freeness; however the Schopper-Riegler grade (ºSR) increased significantly hindering drainage. The contribution of CNF in bulk also increased °SR and breaking length, therefore the °SR beaten at 1500 rev was equivalent to a content of CNF between 4,5 and 6%, but its breaking length was found to be substantially greater. It can be concluded that the CNF in bulk can be viewed as an alternative to mechanical beating and that the application of CNF at the paper surface allows increasing strength properties without affecting the drainage capacity. <![CDATA[<strong>Characterization of the </strong><em><b>rhizophora</b></em><strong> particleboard as a tissue-equivalent phantom material bonded with bio-based adhesive</strong>]]> In this study, some characteristics of Rhizophora spp. particleboards bonded with Serishoom (traditional animal-based adhesive) as a phantom material was investigated. The Rhizophora spp. particleboards were fabricated in two Serishoom adhesive treatment levels (6% and 12%) with three Rhizophora spp. particle sizes (≤ 149 µm, 149 µm - 500 µm, and 500 µm - 1000 µm) at 1 of the target density. The internal bond strength and the dimensional stability of the Serishoom-bonded Rhizophora spp. particleboards were improved by using the smaller Rhizophora spp. particle size and the higher Serishoom adhesive treatment level. The effective atomic numbers of the Serishoom-bonded Rhizophora spp. particleboards were determineted to be 7,56 to 7,58 by an energy dispersive X-ray, which is in good agreement with those of water and breast tissue. In addition, the density distribution profiles of the fabricated Serishoom-bonded Rhizophora spp. particleboards were determined by the Kriging method with the use Surfer8 computer software, which indicated that there was good density homogeneity throughout the Serishoom-bonded Rhizophora spp. particleboards. The results showed a potential of the Serishoom-bonded Rhizophora spp. particleboard bonded with Serishoom to be used as a phantom material. <![CDATA[<strong>Physical and mechanical properties of nanoreinforced particleboard composites</strong>]]> Novel composite materials having desired performance properties can be developed by nanotechnology. The major objective of this research was to produce nanomaterial- reinforced particleboard composites with enhanced physical and mechanical performance. Urea formaldehyde adhesive used to produce particleboard composites was reinforced with nanoSiO2, nanoAl2O3, and nanoZnO at loading level of 0%, 1%, and 3%. To evaluate physical properties density, thickness swelling, water absorption, and equilibrium moisture content were determined while modulus of rupture, modulus of elasticity, bonding strength, and screw withdrawal strength tests were carried out to evaluate mechanical properties of the particleboard composites. The results acquired in this work revealed that nanomaterial reinforcement technique significantly affected the physical and mechanical performance properties of the particleboard composites. The findings showed that the modulus of rupture, modulus of elasticity, bonding strength, and screw withdrawal resistance of the composites improved by all the nanomaterials used in this study, except 3% nanoZnO. It was also determined that using 1% nanoSiO2 or 1% nanoAl2O3 in the composites had the best results in the bonding strength and screw withdrawal resistance. The findings indicate that it is possible to produce novel wood composites by using proper nanomaterial type and loading level. <![CDATA[<strong>Predicting moisture content from basic density and diameter during air drying of</strong> <em><b>Eucalyptus </b></em><strong>and </strong><em><b>corymbia </b></em><strong>logs</strong>]]> In air drying of Eucalyptus urophylla and Corymbia citriodora logs for the production of charcoal it is necessary to be able to predict when logs have reached the required moisture content of ≤ 35%.This study is aimed to produce models using basic density and diameter to predict the moisture content of Eucalyptus urophylla and Corymbia citriodora logs after 30, 60 and 90 days drying. 1,2 m long logs were taken at three different heights from three C. citriodora trees and three trees each from two E. urophylla clones (VM4 and Mn463). The 27 debarked, end sealed logs were air dried under cover for 90 days during which the change in moisture content was monitored. The relationship between density and drying was analyzed by Pearson’s correlation coefficient and the models for predicting the moisture content based on the basic density and diameter were produced. The density and the drying showed a high correlation coefficient. The coefficient of determination of the models was above 0,89 with a standard error lower than 6%. The use of the density and diameter to estimate the wood moisture content simplifies the production of the models, which can be used for Eucalyptus and Corymbia genetic materials. <![CDATA[<strong>Application of aqueous two phase systems based on polyethylene glycol and sodium citrate for the recovery of phenolic compounds from <i>E</i></strong><em><b>ucalyptus</b></em><strong> wood</strong>]]> This paper proposes an alternative way to intensify the exploitation of Eucalyptus wood wastes before valorisation for energy production. An aqueous two-phase system (ATPS) based on PEG 2000 and sodium citrate was investigated for the recovery of phenolic compounds that could act as natural antioxidants for applications including cosmetics, pharmaceuticals, food additives and other industrial applications. The influence of the tie line length (TLL) (26,1-46,1%), extraction temperature (25-65ºC), extraction time (90-390 min) and phase settlement time (1-8 h) were studied. Phenolic compounds were concentrated preferentially in the PEG-rich phase. A partition coefficient of 38 and a total phenols yield of 1,29 mg gallic acid equivalent/100 mg wood dry basis were obtained under the operational conditions selected: TLL, 46,1%, temperature 65ºC, extraction time 90 min and settlement time 1 h. Analysis of the extracts by RP-HPLC-ESI-TOF confirmed the presence of various phenolic compounds with demonstrated antioxidant activity: monogalloyl glucose, (-)-gallic acid, ellagic acid and quercetin 3-O-rhamnoside. <![CDATA[Design and efficiency of a small-scale woodchip furnace]]> Although advances have been made in combustion efficiency in large-scale woodchip furnaces, less experimental results are available at the <20 kW range. Compact feed systems, as well as optimized grates and combustor chambers, continue to represent a challenge for the wider use of low-cost wood chips. This study describes the design and testing of a small-scale woodchip furnace that operates at a range of 9-18 kW. The efficiency test takes account of the feedstock Eucalyptus nitens, with three moisture contents and the combination of different air excess (?) and primary/secondary air ratios. The results reveal a maximum of combustion efficiency of 85% for the low moisture content sample (16%) at ?=1,5 and 82% for samples with 29% and 40% moisture content, at ?= 2,0 and 2,1 respectively. The integrated heat exchanger proved to be highly efficient by reducing gas temperature by up to 69% prior to its exit. <![CDATA[<strong>Effects of thinning on diameter, heartwood, density and drying defects of </strong><em><b>Gmelina arborea</b></em>]]> The effect of three levels thinning intensity in Gmelina arborea plantation on tree diameter, heartwood (diameter and percentage), wood density and drying defects (twist, crook, bow and check) was studied. Wood used for this study was obtained from eight-year-old plantations with thinning intensity of 60, 70 and 80% of initial density. Nine trees were selected from each trial. Results showed that tree diameter and wood density were similar in thinning intensity of 70 and 80%, but tree diameter from the plantation with 60% of thinning intensity was lower than plantation of 70 and 80%. Wood density of trees from 60% thinning intensity plantation was higher than 70 and 80%. Heartwood diameter and its percentage were the highest in 80% of thinning intensity. But not difference was found between 60 and 70% in heartwood (diameter and percentage). Finally, drying defects were not affected significantly by thinning intensity. <![CDATA[<strong>Treatability of </strong><em><b>Melia composita </b></em><strong>using vacuum pressure impregnation</strong>]]> The performance of treated wood in the field is ultimately affected by retention and penetration of preservative in wood. In the present study, a new preservative system ZiBOC and a commercially used preservative copper-chrome-arsenate (CCA) were used for evaluation of treatability of Melia composita by the vacuum pressure method at different pressure levels in unsealed and end sealed specimens. The retention and penetration levels of both the preservatives were significantly different at (P< 0,05) in sapwood, heartwood and pith zones. Melia composita exhibited treatability class ‘C’ (21 - 42% penetration). The results revealed that longitudinal penetration in Melia composita was the dominant flow as examined by spot test for copper in unsealed and end sealed specimens. <![CDATA[<strong>The effect of moisture content on the retention and distribution of nano-titanium dioxide in the wood</strong>]]> When chemically treating wood products is used to enhance the properties, the distribution of chemicals in the wood can be more important than the amount of chemical uptake. In this research, two moisture contents (MC) (0 and 25%) were used to study the effect of MC on the nanomaterial retention and distribution in cottonwood (Populus deltoides) sapwood treated with nano-titanium dioxide. The wood samples were impregnated by a full-cell process at three levels of nano‐TiO2 concentration: 0,5; 1 and 1,5%. The nanomaterial retention was calculated and SEM images were used to investigate the distribution of nanoparticles in the wood. The results showed that increasing the nano-TiO2 concentration caused more retention and the MC difference caused almost identical retention at 0,5 and 1% concentrations. Although the retention in the 0% MC samples was slightly more than those of 25% MC, this retention was significantly more in these samples (0% MC) at 1,5% concentration. SEM images indicated that the nanoparticles had more uniform distribution in the 0% MC samples than the 25% MC ones and the difference was clearly visible at 1,5% concentration. Low MC ranges (about 0%) are better than high MC’s to impregnate cottonwood samples with nano-TiO2 by using the full-cell process. <![CDATA[<strong>Effect of thinning on the anatomical properties of </strong><em><b>Pinus taeda</b></em><strong> wood</strong>]]> El raleo tiene implicancias económicas y técnicas para producción forestal y para la actividad industrial. El objetivo del estudio fue determinar la influencia de la intensidad de raleo sobre las propiedades anatómicas de la madera. Se trabajó con muestras tomadas a 1,30 m de altura, de 24 árboles proveniente de un ensayo de raleo en Pinus taeda de 20 años de edad, intervenido a los 3 años, con remoción del 0%, 50%, 75% y 87,5% de las plantas de la densidad inicial de plantación (1960 árboles/ ha). Se midieron diámetro a la altura de pecho, altura total, diámetro en la base de la copa viva y altura a la base de la copa viva, longitud de traqueidas, espesor de pared celular y ángulo microfibrilar. La longitud de traqueidas fue mayor en el tratamiento con 87,5% de raleo. Los tratamientos con 0% y 50% de raleo favorecieron la obtención de mayores valores de espesor de pared y menores valores de ángulo microfibrilar. Se concluyó que esta práctica silvícola altera a las propiedades anatómicas de la madera de Pinus taeda y que la longitud de traqueidas está fuertemente relacionada con el tamaño del árbol y con la longitud de la copa verde.<hr/>Thinning has technical and economic implications for both, forest production and industrial activity. The aim of this study was to determine the effect of thinning intensity on the anatomical properties of pine wood. Samples were taken at 1,30 m height, from 24 Pinus taeda trees of 20 years old, coming from a thinning treatment. The plantation was intervened at 3 years, with removal of 0%, 50%, 75% and 87,5% of the trees from the initial density (1960 trees/ha). The evaluated variables were: diameter at breast height, total height, diameter on the base of the live crown, height at base of live crown, tracheid length, cell wall thickness and microfibril angle. The tracheid length was higher in 87,5% thinning treatment. Treatments with 0 % and 50% thinning have favored the obtaining of higher values of cell wall thickness and lower values of microfibril angle. Results suggest that this silvicultural practice alters the anatomical properties of Pinus taeda wood and that tracheid length is strongly related to tree size and length of live crown. <![CDATA[<strong>Influence of moisture content on the wave velocity to estimate the mechanical properties of large cross-section pieces for structural use of </strong><em><b>Scots pine</b></em><strong> from Spain</strong>]]> The aim of this research is to evaluate the influence of the moisture content of wood on stress wave velocity, as a nondestructive technique for estimating the mechanical properties of gross cross-section Spanish Scots pine (Pinus sylvestris L.) lumber for structural use. 26 100 x 150 x 3000 mm pieces from Segovia, Spain, were tested with different moisture content values, from 35,5 to 9%. Measurements of longitudinal stress wave velocity were carried out during the natural drying process by using three commercial portable devices based on ultrasonic, acoustic and vibrational techniques. The results can be summarized as three percentage points of decreasing velocity per percentage point of increased wood moisture content in the range from 11,8 to 21,4%: 0,48% for ultrasonic, 0,50% for acoustic wave and 0,65% for longitudinal vibration. <![CDATA[<strong>3D optimization of cutting patterns for logs of radiata pine with cylindrical defective core</strong>]]> El objetivo de este estudio fue encontrar un método eficiente en tiempo y rendimiento que permita aumentar el aprovechamiento volumétrico y utilidad de los aserraderos que procesan trozas podadas de Pinus radiata, compenetrando la información externa entregada por un escáner de producción industrial y la simulación del Cilindro Central Defectuoso (CCD) en la constitución de una troza tridimensional, donde se estableció un patrón de corte optimo por medio de un algoritmo de programación dinámica. Se simuló el aserrado con una muestra de 30 trozas obtenidas aleatoriamente de un proceso de escaneo industrial. Los resultados fueron comparados con los obtenidos por una heurística, desarrollada por una empresa, basada en la práctica. El algoritmo de programación dinámica alcanzó un aprovechamiento de la materia prima del 64% y en términos relativos se obtuvo una utilidad neta promedio de 11 US$/troza.<hr/>The objective of this study was to find an efficient method that allows time and yield increase volume use and utility of the sawmills that process logs pruned Pinus radiata, linking external information provided by a scanner industry and simulation of Cylindrical Defective Core (CDC) in the constitution of a three-dimensional log, where the optimal cutting pattern was established by means of a dynamic programming algorithm. Sawing was simulated on a sample of 30 logs obtained randomly industrial process of scanning. The results were compared with those obtained by a heuristic developed by a company. Dynamic programming algorithm achieved a yield of the raw material of 64% and an average relative net utility of 11 US$/log was obtained. <![CDATA[<strong>Changes in the</strong> <strong>chemical structure and decay resistance of heat-treated</strong> <strong>narrow-leaved ash wood</strong>]]> We analyzed the effects of heat treatment on the chemical structure of wood from narrow-leafed Ash (Fraxinus angustifolia), a fast-growing and economically valuable species. We also analyzed the effects of heat treatment on the wood’s resistance to four decay fungi. Narrow-leafed Ash wood samples were heated with saturated steam to 140, 180, 200, and 220°C for 2, 4, and 6 h. The relative contents of extractable components were analyzed, as well as the levels of holocellulose, cellulose, and lignin. In addition, the density, equilibrium moisture content, and pH of the samples were measured. To determine the effects of heat treatment on resistance to decay fungi, the samples were exposed to the white rot fungus Trametes versicolor, dry rot fungus Serpula lacrymans, and the brown rot fungi Coniophora puteana and Gloeophyllum trabeum. Changes in the chemical composition of the wood due to heat treatment were correlated with increased resistance to fungal decay. While the hemicellulose content was dramatically reduced with increasing temperature and treatment duration, the lignin content increased proportionately. Thus, heat treatment is an environmentally friendly method of preserving narrow-leafed Ash wood against various decay fungi.