Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 20 num. 4 lang. <![CDATA[SciELO Logo]]> <![CDATA[Veinte años después: Enfocados en las Ciencias de la Madera]]> <![CDATA[Using artificial neural networks in estimating wood resistance]]> Abstract: The purpose of this research was to evaluate the potential of Artificial Neural Networks in estimating the properties of wood resistance. In order to do so, a hybrid of eucalyptus (Eucalyptus urograndis) planted in the Northern Region of the State of Mato Grosso was selected and ten trees were collected. Then, four samples of each tree were removed, totaling 40 samples, which were later subjected to non-destructive testing of apparent density, ultrasonic wave propagation velocity, dynamic modulus of elasticity obtained by ultrasound, and Janka hardness. These properties were used as estimators of resistance and compressive strength parallel to fibers, and hardness. Multilayer Perceptron networks were also employed, training 100 of them for each of the evaluated parameters. The obtained results indicated that the use of Artificial Neural Networks is an efficient tool for predicting wood resistance. <![CDATA[Radio frequency heating for sterilization of wood packaging material of radiata pine. Part 1: Total treatment time]]> Resumen: En este trabajo se estudió el tiempo total de calentamiento utilizando radiofrecuencia para esterilizar madera apilada de Pinus radiata, mediante las condiciones 56 °C y 60 °C por 30 y 1 minutos respectivamente, según normas fitosanitarias internacionales. Los ensayos fueron realizados en un equipo de radiofrecuencia de laboratorio de 3 m3 de capacidad. Se determinó el tiempo de calentamiento y se desarrollaron modelos de predicción, en función del espesor, separación de placa y el volumen de carga de madera, con unos niveles de confianza superiores al 90%. Los resultados mostraron que el tiempo total de esterilización por radiofrecuencia es mayor en la superficie de la pila y fueron estadísticamente similares bajo ambas condiciones de tratamiento.<hr/>Abstract: In this work the total heating time was studied using radio frequency to sterilize wood packaging material of Pinus radiata, through the conditions 56 ° C and 60 ° C for 30 and 1 minutes respectively, according to international phytosanitary norms. The experimental tests were carried out in a laboratory radiofrequency equipment of 3 m3 capacity. The heating time was determined and prediction models were developed, depending on the thickness, plaque separation and wood loading volume, with confidence levels above 90%. The results showed that the total time of radiofrequency sterilization was greater in the surface of the pile and were statistically similar under both treatment conditions. <![CDATA[Prediction of microfibril angle for <em>Eucalyptus microcorys</em> wood by fiber length and basic density]]> Abstract: Aim of the study was to estimate the influence of the fiber length and basic density on microfibril angle of Eucalyptus microcorys wood. The study area was in an experimental planting at the Universidade Federal de Lavras, Minas Gerais State, Brazil. Three 37 year-old Eucalyptus microcorys trees were used, from whose stems six centimeter-thick discs were removed, cut at a high of three meters. The disks were sanded and planed to highlight the growth rings. Specimens were taken every 1,5 cm across the radius from pith to bark for determining microfibril angle, fiber length and wood basic density. The microfibril angles were determined by use of polarized light microscopy, while the fiber morphology and basic density were determined by usual methods. The averages found for microfibril angle (12,6°), fiber length (968 µm) and basic density (480 kg.m-3) are, in general, within the range of values reported for these characteristics of wood. The microfibril angle showed accentuated reduction of the average values in the pith-bark direction. The fiber length and basic density showed the opposite behavior. We observed that the density and fiber length may be used as a microfibril angle predictor, accounting for 96% and 79% of its variation, respectively. <![CDATA[Influence of coupling agents on rheological, thermal expansion and morphological properties of recycled poypropylene wood flour composites]]> Abstract: In this work, thermal expansion and morphological properties of recycled polypropylene wood flour composites were evaluated in order to verify the effect caused by the usage of a natural oil as coupling agent. The natural oil used as coupling agent was octanoic acid (C8), maleic anhydride grafted polypropylene (MAPP), widely used in industry but from non-renewable source, was also used for comparison. Composites were obtained by twin screw extrusion and injection molded. The results showed that the addition of octanoic acid and maleic anhydride grafted polypropylene reduced the coefficient of thermal expansion of the composites. The dependence of melt viscosity obeyed the Arrhenius-Eyring expression, and the activation energy values for composite viscous flow were higher than matrix. The composite morphology revels that octanoic acid promotes strong interfacial adhesion between filler and matrix, similar to that observed when maleic anhydride grafted polypropylene were used. Octanoic acid showed similar results when compared with maleic anhydride grafted polypropylene in all properties evaluated, indicating that can be used as an alternative instead of use coupling agent from non-renewable sources. <![CDATA[Influence of relative humidity and temperature on cultivation of <em>Pleurotus</em> species]]> Abstract: Fungi exhibit different behavior under different conditions and react to light, temperature, moisture content etc. The objective of this study was to evaluate the degradation capability of three common white rot fungi, namely: Pleurotus ostreatus, P. pulmonarius, and Lentinus sajor-caju. The respective fungi were cultivated on rice straw under three different environmental conditions for 90 days. The fungi were collected, pure cultured, DNA extracted, and sequenced by ITS regions. The highest consumption of substrate occurred under the Cellar (dark) exposure condition with P. pulmonarius producing the least mass loss. The least amount of degradation occurred under the Air (daylight) condition for all of the fungi with the exception of P. pulmonarius. Exposure to light promoted the formation of fruiting bodies. <![CDATA[Evaluation of palm fiber components an alternative biomass wastes for medium density fiberboard manufacturing]]> Abstract: This work deals with assessing the date Palm component wastes as alternative lignocellulosic material for production of Medium density fiberboards, in order to establish economic and balance between production/consumer ratio at different provinces rather than Upper Egypt. Palm leafs and Palm frond was used as Medium density fiberboards precursors. Different urea formaldehyde levels (10-14%/fiber) and pressing pressure (2,5-3,5 MPa) were applied in this evaluation. The acceptable interaction of Palm fibers component with urea formaldehyde was optimized by characterizing its differential scanning calorimetry and thermogravimetric analysis, in comparison with commercial used sugarcane bagasse fibers. The promising Medium density fiberboards Panel is obtained from Palm frond fibers and its mechanical and water resistance properties fulfill the ANSI standard for high grade Medium density fiberboards wood products, especially on applying urea formaldehyde level 12-14%, and pressing pressure 3,5 MPa. It is interesting to note that, applying higher pressing pressure together with 12% urea formaldehyde level provided Palm frond-based Medium density fiberboards with static bending properties, higher than commercial bagasse-based Medium density fiberboards. The insignificant effect of pressing pressure was noticed on water swelling property and free-HCHO of Medium density fiberboards panels. Where, both type of fibers have the same water swelling property (reached ~ 10%), and free-HCHO (~ 27 mg/100g board). <![CDATA[Inverse determination of thermal conductivity in wood of <em>Pinus radiata</em>]]> Resumen: Se realizan experimentos a escala de laboratorio para caracterizar el secado artificial de madera de pino radiata a temperaturas convencionales y aceleradas, con el propósito de obtener datos que permitan determinar la conductividad térmica de la madera mediante metodología inversa. El análisis comparativo muestra que la implementación de la metodología inversa desarrollada entrega información consistente con datos disponibles en la literatura especializada: conductividades térmicas crecientes con el aumento de la humedad y la temperatura, cuyos valores fluctúan entre 0,34 y 0,56 (W/m K) para variaciones de humedad entre 22% y 64%; y temperaturas entre 70°C a 90°C, respectivamente.<hr/>Abstract: Laboratory scale experiments are performed in order to characterize the artificial wood drying of Pinus radiata at conventional temperatures and accelerated temperatures. The experimental data allow determining the wood thermal conductivity through inverse methodology. The comparative analysis shows that the implementation of the developed inverse methodology is consistent with information available in the specialized literature; which means increased thermal conductivities with increased humidity and temperature, whose values oscillate between 0,34 and 0,56 (W/m K) to moisture variations between 22% and 64%; and temperatures between 70°C and 90°C, respectively. <![CDATA[Microwave-assisted solvothermal: An efficient and new method to obtain hydrophobic wood surfaces]]> Abstract: The objective of this work was to form a hydrophobic surface in a highly porous wood by coating and incorporating TiO2 micro/nano structures through the microwave-assisted solvotermal method, without need any pre- or post-modification of the wood substrate, using low temperatures and short times. The behavior and morphology of the TiO2-treated surfaces was characterized using scanning electron microscopy (SEM), while the elemental composition was determined via energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. The results indicated that the crystallization of the TiO2 anatase phase was efficient and fully coated the wood surface during the solvothermal process. The treated wood contained TiO2 particles agglomerate with an average diameter of 200 nm that also allowed to coat an abundant fraction of tracheids cell walls. When investigated through X-ray spectroscopy-mapping, the element titanium appeared abundantly throughout the wood. After TiO2 growth in wood through the microwave-assisted solvotermal method, a roughness at the micro/nano scales structures was created on the wood surface, originating an increase in the contact angle up to 137°, which characterizes the appearance of a hydrophobic surface. The TiO2-treated wood demonstrated 85% of water absorption after 400 h of immersion, while untreated wood reached 160%, suggesting that the microwave-assisted solvotermal process promotes a delay in the progression of water absorption. This feature can improve the dimensional stability of wood, contributing to the increase of its durability and applications. <![CDATA[Risk assessment of mould growth on spruce wood during transport in an intermodal container]]> Abstract: Microclimatic conditions (relative humidity and temperature) were monitored in a shipment of Norway spruce (Picea abies) wood inside an intermodal container on its 66-day transport from Slovenia to Japan. In parallel, the susceptibility of Norway spruce wood to moulding fungi was determined and a dynamic vapour sorption analysis was performed. Considerable moulding developed on specimens that were exposed to a climate with relative humidity above 93%. The results of the laboratory assessment correlated with the observations of mould development in the container. The relative humidity in the container was below 93%, so there was no mould growth on the transported Norway spruce wood. <![CDATA[Potential use of NIR and visible spectroscopy to analyze chemical properties of thermally treated wood]]> Abstract: The modification of wood by thermal treatments produces characteristic changes in its chemical composition and surface color and can improve the structural and esthetic quality. The objective of this paper is to evaluate the potential of near infrared and visible spectroscopy to predict the modifications in chemical composition of Eucalyptys grandis and Pinus taeda after thermal treatment. Near infrared and visible spectra were collected directly on the longitudinal surface of wood samples. The thermally modified wood of both species showed higher content of lignin and extractives than the untreated wood. There was darkening of thermally modified wood, as a result of chemical modification caused by heat. The Near infrared/visible technique identified the groups that were modified by treatment. NIR and visible spectroscopy can be used to predict chemical composition of natural or thermally treated Eucalyptus grandis and Pinus taeda. <![CDATA[Determinants of job satisfaction in wood and paper industry: study in spain and findings in other countries]]> Resumen: Esta investigación se desarrolla en el colectivo de trabajadores ocupados pertenecientes a la cosecha forestal, industria de la madera y papel, y su comparación con el total nacional. El ámbito es el mercado laboral español. Se escogen 14 variables cuantitativas, extraídas de la Encuesta de calidad de vida en el trabajo (Ministerio Empleo y Seguridad Social). El objetivo primero es averiguar qué variables y agrupaciones de variables (o factores) afectan a la satisfacción laboral en el sector forestal, madera y papel, comparando estos resultados con el conjunto nacional al que pertenece. Las metodologías son análisis de componentes principales, análisis de conglomerados y regresión múltiple stepwise. El segundo objetivo es recopilar estudios parecidos en otros países y ver si se puede establecer algún patrón común. El análisis en ambos colectivos (forestal, madera y papel por un lado, y conjunto nacional español por otro) permite averiguar si los determinantes coinciden o difieren en función de los epígrafes de actividad; en ambos casos, el salario es una de las últimas variables en la explicación de la satisfacción laboral, siendo la motivación y el desarrollo personal las variables que ocupan los primeros puestos en esta explicación. A partir de estudios en otros países no es posible construir una teoría general y válida en todos los ámbitos, de forma que si el contexto es diferente, los determinantes que afectan a la satisfacción laboral son también distintos.<hr/>Abstract: This paper is carried out in a workers group of logging, wood and paper industry, which is compared with the whole of the labor market. We select 14 quantitative variables of job-related features. For this purpose, we use data Quality of Labor Life Survey (ECVT) by the Spanish Ministry of Employment and Social Security. The first objective is to find out which variables and groups of variables (or factors) affect job satisfaction in logging, wood and paper industry, comparing these results with the national set. Our methodologies are principal component analysis, cluster analysis, and stepwise multiple regression. The second objective is to review similar studies in other countries in order to find some common pattern. The analysis in both groups (logging, wood, and paper on the one hand, and the Spanish national set on the other) allows us to find whether determinants are the same or different according to activity. So, in both cases, a wage is one of the last factors that explain labor satisfaction, whereas motivation and personal development are in the top position. It is not possible to propose a general and valid theory in all areas from studies in other countries so that if the context is different, the determinants that affect job satisfaction are also different. <![CDATA[Colour responses of <em>Eucalyptus grandis</em> wood to the Brazilian process of thermal modification]]> Abstract: A study of colour assessment, using the CIEL*a*b* system, was conducted with samples of Eucalyptus grandis wood thermally treated by the Brazilian industrial process of thermal modification, VAP HolzSysteme®, at three different temperatures, i.e. 140, 160 and 180 °C. Previous to the treatment, the samples were classified into three groups according to their distance to the wood pith, on the radial direction. All thermally modified samples presented a noticeable colour change, confirmed by high values of ΔE*. As the intensity of the treatment increased, the eucalypt samples presented an increase of red colour tone (a*) (up to 160 ºC) and a decrease of colour lightness (L*). Significant colour differences were found among the classified groups, for both untreated and thermally modified samples. The eucalypt samples groups showed different colour responses when thermally treated at 140 and 160 ºC. At 180 ºC the groups didn’t show a significant colour response variation. <![CDATA[Ultrasound measurement of exterior wood coating thickness]]> Abstract: The present paper deals with the measurement of coat thickness on wood using an ultrasonic measurement method. Exterior wood coatings (waterborne acrylate dispersions) with coating film thickness between 80 - 115 µm were examined. The non-destructive film thickness measurement used a Sursonic ultrasound measuring device, enabling measurement of the thickness of thin films on non-ferromagnetic and simultaneously non-conductive materials. The device also enables measurement of very thin layers of coating films, where the transit time of an ultrasound pulse through the film is shorter than the time width of the pulse. The accuracy of measurement using this measuring device was determined; destructive measurement using a light microscope was chosen as a reference measurement method. Differences in the results measured using the destructive and non-destructive methods were recorded; nevertheless, in most cases, these differences are smaller than the uncertainty of measurement using the light microscope. It can be concluded, therefore, that the results of the two compared methods match over the entire range of thickness of 80 - 115 µm. The largest differences in the measurement readings from the destructive and non-destructive methods were identified in the range of 97 - 103 µm. <![CDATA[Recycling wood waste from construction and demolition to produce particleboards]]> Abstract: The objective of this study was to evaluate the feasibility of construction and demolition (C&amp;D) waste wood to produce of particleboard. The raw material was obtained from a waste recycling company and it was divided into four types of materials: MDF (medium density fiberboard), MDP (medium density particleboard), plywood and timber. After reduction of these wood product residues to particles, particleboards were produced, in the UFPR Laboratory, with urea-formaldehyde resin and a target density of 0,75 g / cm³ and their physical and mechanical properties were determined. Particleboards made from industrial Pinus spp. particles were also produced as control samples. C&amp;D wood waste showed potential for use as raw material for particleboard. The properties of particleboard made of recycled timber, MDP, plywood and the mixture of the four sources of material indicated that particleboard industries could use these waste resources for the production of the inner layer of MDP products. <![CDATA[A modeling study to evaluate the quality of wood surface]]> Abstract: The goal of this study was to develop a model to predict sanding conditions of different type of materials such as Lebnon cedar (Cedrus libani) and European Black pine (Pinus nigra). Specimens were prepared using different values of grit size, cutting speed, feed rate, and sanding direction. Surface quality values of specimens were measured employing a laser- based robotic measurement system and stylus type measurement equipment. Full factorial design based Analysis of Variance was applied to determine the effective factors. These factors were used to develop the Artificial Neural Networks models for two different measurement systems. The MATLAB Neural Network Toolbox was used to predict the Artificial Neural Networks models. According to the results, the Artificial Neural Networks models were performed using Mean Absolute Percentage Error and R-square values. Mean Absolute Percentage Error values for laser and stylus equipment were found as 2,405 % and 3,766 %, respectively. R-square values were determined as 96,2% and 92,7 % for laser and stylus measurement equipment, respectively. These results showed that the proposed models can be successfully used to predict the surface roughness values. <![CDATA[Encapsulation of precipitated calcium carbonate fillers using carboxymethyl cellulose /polyaluminium chloride: preparation and its influence on mechanical and optical properties of paper]]> Abstract: Inorganic fillers are usually used in papermaking industry to reduce production costs and enhance paper optical properties. As an attempt to improve fillers application in papermaking, carboxymethyl cellulose (CMC) and poly aluminum chloride (PAC) were used to encapsulate precipitated calcium carbonate (PCC) filler and modify its surfaces. In the first step, the optimum conditions for filler treatment (i.e. pH, CMC and PAC contents) were obtained. Through the second step, different amounts of CMC-encapsulated PCC were added to fiber suspension and some hand-sheets were made. Then, the effect of modified filler addition in different levels of 20, 25, and 35% on mechanical and optical properties of paper was investigated. The PAC dosage was found to be a critical factor for effective encapsulation of PCC fillers by carboxymethyl cellulose. When the dosages of CMC and PAC were 4% and 0.8% (based on the dry weight of PCC), respectively, filler modification caused to improve significantly the retention by more than twice. Strength properties of the hand-sheets fabricated with the CMC/PAC-modified PCC were also found to be significantly better than those obtained with the unmodified PCC at similar levels of filler content. In addition, the brightness and opacity of the filled papers at 30% addition of CMC-modified fillers were strikingly enhanced to 88,45 and 77%, respectively. SEM observations of the filled papers also demonstrated that CMC-encapsulated filler particles were clustered and retained efficiently onto the fiber network. The present method for modification of PCC may provide an alternative approach to increase the filler amount in the paper structure by alleviating filler drawbacks. <![CDATA[Effect of the Brazilian process of thermal modification on the physical properties of <em>Eucalyptus grandis</em> juvenile wood]]> Abstract: This study is a continuation of a previous study published in this journal, with the aim of evaluating the effect of the Brazilian industrial thermal modification process on some physical properties of Eucalyptus grandis juvenile wood. Flatsawn boards of juvenile wood were tested for four treatment levels: untreated and thermally modified wood at final cycle temperatures of 140 °C, 160 °C and 180 °C. Physical properties were assessed according to a standard of the Comisión Panamericana de Normas Técnicas and a method proposed by the specialized literature encompassing equilibrium moisture content (a measure of wood’s hygroscopicity), density (oven-dried and air-dried) and radial, tangential and volumetric swelling (from oven-dried to green moisture content). Thermally modified Eucalyptus grandis wood became less hygroscopic, more dimensionally stable (tangential and volumetric swelling) and less dense, even at the lowest temperature tested (140 °C), except for radial swelling, which did not differ from untreated wood. <![CDATA[Analysis of biological pretreatment of rapeseed straw with white rot fungi for enzymatic hydrolysis]]> Abstract: The effect of biological pretreatment on the rapeseed straw was evaluated by solid-state cultivation of white rot fungi Phanerochaete chrysosporium. P.chrysosporium degraded the lignin during the pretreatment, with enzymatic hydrolysis ratios increasing in the pretreated straw (3-fold after a 15 day pretreatment). The samples were identified by XRD, FTIR and SEM. X-ray analysis showed that pretreated samples had higher crystallinity than untreated samples (39,47% for a pretreated sample compared to 33,17% for untreated samples) and FTIR spectroscopy demonstrated that the content of lignocellulose also decreased during the biological pretreatment process. The surface characterization study showed morphological changes in pretreated samples. Moreover, the biological pretreatment slowed a plunge in hydrolysis rate during enzymatic hydrolysis. <![CDATA[Infrared spectroscopy of the surface of thermally-modified teak juvenile wood]]> Abstract: During the thermal modification of the wood there is a decreasing gradient of temperature from the surface to its interior, therefore, the most severe chemical modifications occur on the surface. These chemical modifications directly affect the quality and durability of adhesives and coating. Therefore, this study investigated the chemical modification of the surface of thermally-modified teak juvenile wood. Heartwood and sapwood samples were treated at 180 and 200ºC. Chemical analyses were performed by Fourier transform infrared spectroscopy (FTIR) in reflectance mode with a microscope. Spectra showed an increase in cellulose crystallinity and a decrease in relative contents of hydroxyl groups, lignin and extractives - especially quinones, waxes and oils - following thermal modification. Extractive content of the heartwood was relatively higher than that of sapwood. Heartwood was more susceptible to thermal degradation than sapwood. <![CDATA[Asbestos-free autoclaved wood fiber-cement sheets from recycled old corrugated containers and kraft pulp of Douglas fir: properties and scanning electron microscopy]]> Abstract: This study was conducted in cooperation with a United States pulp and paper company targeting part of the pulp production as raw material for fiber-reinforced cement sheets manufacturing. Virgin kraft pulp of Douglas fir (Pseudotsuga menziesii) and recycled fiber of old corrugated containers were used in making wood fiber-cement flat sheets. The physical and mechanical properties of the sheets were compared with an available commercial product. Results showed that Douglas fir fiber is a potential choice as reinforcement for wood fiber-cement sheets, as this fiber type outperformed the commercial ones for most of the properties studied. The difference in kappa number from 25 to 35 did not have any effect on the properties of Douglas fir sheets. Even recycled old corrugated containers fiber provided sheets with some properties comparable to the commercial product. Scanning electron microscopy analysis showed that a dual mechanism of fiber breakage and pull out occurred at rupture.