Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> http://www.scielo.cl/rss.php?pid=0718-221X20210001&lang=pt vol. 23 num. lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[Chemical variation of five natural extracts by non-polar solvent]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100401&lng=pt&nrm=iso&tlng=pt Abstract: Chemical compounds of wood preservation from plants vary and are not known specific to the species. Chemical analysis of plants is responsible to ensure active compound in natural extracts wood treatment. There are many sources of natural extracts found in Indonesia that were explored for wood preservatives chemicals. They are bark of acacia and alstonia, leaves of orthosiphon and azardirachta and Dioscorea tubers. The present study was aimed at investigating the variation of the chemical constituent of natural extracts material of wood preservative through GC-MS analysis. Five natural extract sources were acacia bark (Acacia spp.), pulai bark (Alstonia scholaris), kumis kucing leaves (Orthosiphon spp.), mimba leaves (Azardirachta indica), and gadung tubers (Dioscorea spp.). Two non-polar solvents, i.e., n-hexane and petroleum ether were used for five natural source extractions following ASTM soxhlet extraction. The research showed that triterpene and fatty acid derivatives were the major compounds present in five natural extracts. They were lupeol; 7,22-Ergostadienone; Lup-20(29)-en-3-one; Lup-20(29)-en-3-ol, acetate, (3.beta.)-; urs-12-en-3-one; ethanol,2,2-diethoxy-; stigmasta-5,22-dien-3-ol, acetate,(3.beta.)-; 5H-3,5a-Epoxynaphth(2,1-c)oxepin, dodecahydro-3,8,8,11a-tetramethyl-; linoleic acid; naphthalene, 1-methyl-. These compounds have been assigned as the possibly responsible to against termites or fungi. <![CDATA[Thermal properties of <em>Acacia mangium</em> Cross Laminated Timber and its gluelines bonded with two structural adhesives]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100402&lng=pt&nrm=iso&tlng=pt Abstract: The properties of CLT can be affected by the type of adhesives used. The thermal properties of the adhesive that join the timber together is essential to determine the thermal endurance of the CLT product. In this study, two types of adhesives were used to join the cross laminated timber (CLT) manufactured from Acacia mangium namely phenol resorcinol formaldehyde (PRF) and one component polyurethane (PUR). The thermal properties of the adhesives, A. mangium wood and the glue lines were determined via Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA) tests. The TGA test showed that PRF adhesive had higher degradation temperature at 530 ºC compared to PUR adhesive at 430 ºC. Meanwhile, the PRF adhesive as a glue line in CLT also showed better thermal resistance where a higher amount of residue of 20,94 % was recorded at temperature up to 900 ºC compared to PUR glue line with 18,26 % residue. The integrity of the CLT over temperature was determined via DMA test and the results showed that PRF adhesive as glue line had superior properties, indicating better interfacial bonding with the woods. <![CDATA[Energy gains of <em>Eucalyptus</em> by torrefaction process]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100403&lng=pt&nrm=iso&tlng=pt Abstract: The aim of this study was to evaluate the changes in the characteristics of Eucalyptus spp. from Paraíba Valley region, Sao Paulo - Brazil after torrification process. Torrification is a thermochemical process that occurs at temperatures lower than the pyrolysis process as a pretreatment to improve biomass characteristics for use as biofuel energy in power generation. An experimental study was carried out in a batch reactor at three temperatures (240 °C, 260 °C and 280 °C) with residence time of 30 and 60 minutes. At the indicated operating conditions by elemental analysis, higher heating value and thermogravimetric analysis were evaluated. Result showed that there was a reduction in the oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, causing an increase in the thermal energy quality of torrified wood, about of 28 % and 47 % at temperatures of 260 °C with residence time of 60 minutes and 280 °C with 30 minutes, respectively. A thermogravimetric analysis showed that at 260 °C the hemicellulose was almost completely degraded leaving the fuel in better conditions for combustion or gasification processes. <![CDATA[Viability of wood decaying fungal mycelium after microwave radiation of bamboo culm]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100404&lng=pt&nrm=iso&tlng=pt Abstract: The present study was carried out to evaluate the effects of microwave (MW) radiation on viability of wood decaying fungi. The white rot (Trametes versicolor) and brown rot (Rhodonia placenta) fungi were grown on bamboo culm-samples. The mycelium growths were observed in controlled as well as microwave treated samples. The results showed that the viability of fungi decreased according to the applied MW time. This study proved the ability of the microwaves and exposure time MW3 (180 seconds) to kill the fungal colonies and do not allow for the growth of fungal spores, means the rate of growth of fungal colonies is inversely proportional to time of microwave exposure. <![CDATA[Nanocellulose-reinforced phenol-formaldehyde resin for plywood panel production]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100405&lng=pt&nrm=iso&tlng=pt Abstract: The search for new technologies to improve adhesives and the properties of reconstituted wood panels is constant, and nanotechnology is a tool for this purpose. The aim of this study is investigating the effect of adding nanocellulose in the formulation of the adhesive phenol-formaldehyde on the physico-mechanical properties of Pinus taeda plywood panels. Three ratios of nanofibrillated cellulose (NFC) were added to the adhesive formulation used to produce plywood panels: 0,026 %; 0,038 % or 0,064 %. The panels were tested according to the European standards; apparent density, resistance to parallel and perpendicular flexure and glue line shear strength were determined after 6 hours of boiling and after the boiling cycle for the 1st glue line (face) and 2nd glue line (core). The use of NFC in the adhesive caused an increase of viscosity and reduction of the gel time of the adhesive. The apparent density of the panels was not influenced by the addition of NFC, but the properties of parallel bending, perpendicular flexing and glue line shear were sensitive to the addition of NFC. The NR2 treatment (0,038 % NFC) presented the best results in the mechanical tests. <![CDATA[A new method for determining air permeabilities of wood-based panels]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100406&lng=pt&nrm=iso&tlng=pt Abstract: In this study, a new apparatus for measuring the air permeability of wood-based panel specimens without using water displacement was developed with the aim of decreasing the influence of variation in atmospheric pressure on permeability measurement. Validation experiments were conducted using plywood, oriented strand board (OSB), particleboard, and medium-density fiberboard (MDF) panels and a control specimen sealed with an epoxy resin. The background (leakage) flow of the apparatus was evaluated based on the experimental results of the control specimen. A methodology for the determination of air permeability based on Darcy’s law for gases and the evaluated background flow rate was proposed. The results of the current study were compared with those obtained in a previous study, indicating that the new method provides valid measurements for wood-based panels with high and low air permeability. No significant influence of variation in atmospheric pressure on the experimental results was observed, suggesting that the proposed method is suitable for a long-term continuous experiment for evaluating a specimen with extremely low permeability. <![CDATA[Radial variation in cell morphology of <em>Melia azedarach</em> planted in northern Vietnam]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100407&lng=pt&nrm=iso&tlng=pt Abstract: The radial variation in cell morphology of ten-year-old Melia azedarach trees planted in northern Vietnam was experimentally investigated. The earlywood fiber lumen diameter and latewood fiber lumen diameter were almost unchanged from pith to 6th ring before significantly decreasing and remaining constant from 7th ring outwards. In contrast, fiber cell wall thickness in both earlywood and latewood increased from pith to 7th ring before becoming stable towards the bark. The maturation age of earlywood vessel lumen diameter estimated by segmented regression analysis indicated that wood of the Melia azedarach could be classified into core wood and outer wood, and the boundary between core and outer wood may be located at 7th ring from pith. This should be taken into account in wood processing using M. azedarach grown in northern Vietnam. <![CDATA[Colorimetry of bamboo stems (<em>Guadua angustifolia</em>) in three maturity stages]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100408&lng=pt&nrm=iso&tlng=pt Resumen: El objetivo de este trabajo fue describir el color del tallo, también conocido como culmo, de Guadua angustifolia con el sistema colorimétrico CIE-L*a*b* y analizar la variabilidad entre los tres estados de madurez (joven, maduro y sobremaduro). El material de estudio se recolectó desde una plantación ubicada en Reforma, Chiapas, México. Se trabajó con 12 culmos de dos, cuatro y seis años, y se midió el color utilizando los parámetros del sistema CIE-L*a*b* con ayuda de un colorímetro digital. Posteriormente, se utilizó la metodología propuesta por la Commission Internationale de L’Eclairage (CIE) para obtener la variación total de color (∆E*) y medir la magnitud de la diferencia del color entre los tres estados de madurez. Como consecuencia de la madurez se observó un cambio secuencial de coloración en la parte externa del culmo, desde un verde claro, verde grisáceo, gris, hasta un tono café. Los valores de ∆E* fueron mayores de 20, lo que de acuerdo a los criterios de percepción de diferencia de color, indica que la variación del color entre un estado de madurez y otro puede clasificarse como “Muy grande”. Asimismo, al realizar un análisis de Kruskal Wallis en las coordenadas CIE-L*a*b* se encontró que la diferencia del color por edad es estadísticamente significativa (p&lt;0,05).<hr/>Abstract: The aim of this study was to describe the Guadua angustifolia stelm (culm) color with the CIE-L*a*b* color system and to analyze the color variation among the three stages of maturity (young, mature and overripe). The study material was collected from the plantation, located in Reforma, Chiapas in Mexico. Bamboo culms were categorized into three ages according to their maturity. Twelve culms of two, four and six years., and the color was measured using the CIE-L * a * b * system parameters by using a digital colorimeter. Then, with the methodology proposed by the The International Commission on Illumination (CIE), the total color variation (ΔE*) andthe magnitude of the color difference between the three maturity stages were obtained. As a consequence of maturity, a sequential change in coloration was observed in the outer part of the culm, going from light green, greyish green, grey to brown. The ΔE* values were greater than 20, which according to the perception of color difference criteria, indicates that the color variation between one stage of maturity and another can be classified as “Very large”. Also, when performing an analysis of variance in the CIE-L*a*b* coordinates, it was found that the difference in color by age is statistically significant (p &lt;0,05). <![CDATA[Shear strength in friction welded joint of poplar wood impregnated with copper-based wood preservative]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100409&lng=pt&nrm=iso&tlng=pt Abstract: Environmentally friendly processes are of great interest and considerably needed due to the worldwide problem of pollution. Linear vibration welding of timber structural elements provides new opportunities to potentially achieve structural joints. Mechanically induced vibrational wood fusion welding is shown to be due mostly to the melting and flowing of some amorphous, cells-interconnecting polymer material in the structure of wood, mainly lignin, but also hemicelluloses. In this study, poplar (Populus euramericana) samples were impregnated with alkaline copper quat (ACQ) in order to enhance welding performance. Chemical changes of the impregnated and welded specimens were characterized by FT-IR techniques. A decrease in the proportion of unoxidized phenolic groups in the lignin was observed by FT-IR and the decreased joint strength observed is impregnated wood. After impregnation, shear strength decreased by 37 % to 54%. The X-ray CT-scanning results revealed that the average density of the poplar wood (368 kg/m3) increased to 710 kg/m3 by welding. <![CDATA[Properties of thermally modified teakwood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100410&lng=pt&nrm=iso&tlng=pt Abstract: Thermal modification is a treatment that seeks to improve the properties of wood and reduce the heterogeneity in its color. The objective of this work was to evaluate the effect of thermal treatment on the anatomical, chemical, physical, mechanical, colorimetric, and thermal stability properties of teakwood. For this, teakwood samples were treated by an industrial autoclave at final cycle temperature of 160 ºC. The reduction of cell wall thickness, the formation of cross-fissures and the crystallization of the wax inside the pores were observed in the anatomical structure. Chemically, the extractives evaporated and the polysaccharides ruptured, of which hemicellulose was the most affected. The heat treatment promoted lower equilibrium moisture, reducing the hygroscopicity and improving the dimensional stability of the wood. Considering the mechanical properties, the rupture modulus and the longitudinal and tangential hardness decreased after the heat treatment. The color of the wood changed significantly, from pink to dark brown. The treated wood had higher thermal stability, with greater weight loss at higher temperatures than the untreated wood. <![CDATA[Physical and mechanical properties of wood from invasive tree species]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100411&lng=pt&nrm=iso&tlng=pt Abstract: Because invasive tree species are being suppressed all over the world, there is a lack of basic information needed for their use in the processing industry. One piece of important information for woodworking applications is the air-dry density, which is 653 kg/m3 in the case of tree of heaven (Ailanthus altissima), 536 kg/m3 for box elder (Acer negundo), and 702 kg/m3 for green ash (Fraxinus pennsylvanica). The order of the 3 species is the same for oven-dry and basic density. In terms of compression and bending, tree of heaven has higher values than green ash. Because the strength of the tree of heaven and the green ash are largely the same as the common ash (Fraxinus excelsior), it can be replaced by these tree species. The properties of box elder wood are significantly different from those of sycamore (Acer pseudoplatanus), so this tree species is not suitable for replacement. <![CDATA[Evaluation of wood-based coating performance for ultraviolet roller and conventional air-atomization processes]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100412&lng=pt&nrm=iso&tlng=pt Abstract: In this study, the effects of two different coating processes on the surface coating performance of wood-based panels were investigated. The samples were prepared using an ultraviolet roller coater and conventional air-atomized systems. Adhesion strength, surface coating hardness, and layer thickness were selected as the coating performance parameters. These coating performance parameters were analyzed using an analysis of variance, Grubb’s test, and probability plot. Adhesion strength, surface coating hardness, and layer thickness were measured using the pull-off test, pendulum hardness, and ultrasonic layer thickness, respectively. According to the ANOVA results, the coating process type was the most significant factor on adhesion strength, layer thickness, and surface coating hardness. <![CDATA[Status of production, distribution and determinants of biomass briquette acceptability in Kampala City, Uganda]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100413&lng=pt&nrm=iso&tlng=pt Abstract: Biomass briquettes have been identified as a plausible and close alternative to commonly used energy fuels such as charcoal and firewood whose prices are escalating due to the dwindling natural resource base. However, briquettes do not seem to be as popular as would be expected. This study assessed the production, distribution and acceptability of the briquettes in Kampala district. A total of 60 respondents, 50 of whom were briquette users and 10 briquette producers were sampled from five divisions of Kampala district to evaluate consumer acceptability, preference for briquette type and shape. Households and institutions were identified to be the major consumers of briquettes while community-based organizations were the major distributors of briquettes. The Chi square test of independence showed significant association between briquette acceptability and briquette attributes of substitutability and low cost (p&lt;0,05). The Kruskal Wallis test showed that low income class people preferred non-carbonized briquettes. Gender, marital status and income level also cause variation in preference for spherical, stick and honey comb briquettes (p&lt;0,05). The major challenges faced by briquette users in Kampala were; production of a lot of ash, frequent crushing and limited access of briquettes. The producers of briquettes were mainly challenged by regular machine breakdown, raw material scarcity and poor carbonizing units. It was concluded that briquettes have market and are generally accepted in Kampala. However, user preferences need to be taken into account by briquette produces, suitable cook stoves should be availed to users and there is need for standards to ensure quality of briquettes. <![CDATA[Properties of biomass obtained from short-rotation Inger willow clone grown on a contaminated and non-contaminated land]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100414&lng=pt&nrm=iso&tlng=pt Abstract: The paper aims to analyze the biomass at one year growth, resulting from the cultivation of the INGER energy willow clone as a short rotation crop (SRC), in order to use it as a renewable fuel. The paper completes the data in the field of renewable energies in the context of decreasing fossil energy reserves worldwide and emphasizing the impact on renewable energies. The effect of a contaminated land on the survival rate of the planted seedlings and the effect of the energy willow culture on the composition of the contaminated soil are analyzed. The obtained results show that the biomass characteristics, such as the calorific power of about 18,21 kJ/g to18,90 kJ/g, and the ash content of about 2,25%, are comparable with the ones of other lignocellulosic energy materials. The results found in this study showed that the woody biomass in the first vegetation year of energy willow can be used directly as a renewable fuel without the need for compaction in the form of briquettes or pellets. <![CDATA[Energy efficiency evaluation of a continuous treatment of agroforestry waste biomass by hydrothermal carbonization]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100415&lng=pt&nrm=iso&tlng=pt Resumen: Dentro de los procesos disponibles para tratar biomasas residuales, se destaca la conversión térmica en medio acuoso a condiciones subcríticas, conocida como carbonización hidrotérmica, que permite obtener un sólido con mayor poder calorífico que la biomasa original y con propiedades hidrofóbicas. Este trabajo presenta el modelado y simulación de un proceso continuo de tratamiento de 2 biomasas residuales, el aserrín de Pinus radiata proveniente de la industria maderera y el afrecho de raps (Brassica napus) del sector industrial mediante carbonización hidrotérmica. Se considera desde la mezcla de las materias primas con agua antes del ingreso al reactor hasta la obtención del pellet final. Todas las operaciones unitarias fueron modeladas con ecuaciones fenomenológicas, excepto el poder calorífico y el rendimiento másico de la reacción que se estimaron mediante Regresión Lineal Múltiple, utilizando como variables explicativas el índice de polaridad, el índice de reactividad, el factor de severidad y la razón biomasa/agua. El mejor modelo tuvo un coeficiente de determinación ajustado (R2 a) de 0,90. Finalmente, el proceso presentó un rendimiento energético superior al 72 % para el aserrín y al 77 % para raps, de lo cual se puede concluir que la carbonización hidrotérmica debe ser considerada como una alternativa para valorizar biomasa del sector agroforestal a gran escala.<hr/>Abstract: Among the processes available to treat waste biomass, the thermal conversion with water in subcritical conditions, called Hydrothermal Carbonization, is being studied in deep the last years. Hydrothermal Carbonization needs lower temperatures than other thermal processes, and a solid with high energy density and hydrophobic properties are obtained. This work presents the modeling and simulation of continuous operation of the Hydrothermal Carbonization process for two residual biomasses: Pinus radiata sawdust from the wood industry and rapeseeds (Brassica napus) as industrial waste. The analysis was performed evaluating the whole process, from mixing the raw biomass with water and the reaction until obtaining the final pellet. All unit operations were modeled with phenomenological equations. The Higher Heating Value and the Mass Yield of the reaction were estimated by Multiple Linear Regression equations, using as an explanatory variable the Polarity Index, the Reactivity Index, the Severity Factor, and the Biomass: Water Ratio. The best model had an adjusted determination coefficient (R2 a) of 0,90. Finally, the process presented an energy efficiency greater than 72% for sawdust and 77 % for rapeseed. Therefore, Hydrothermal Carbonization must be considered as an alternative to valorize agroforestry waste biomass to an industrial scale. <![CDATA[Flooring characteristics of thermo-mechanical densified wood from three hardwood tropical species in Costa Rica]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100416&lng=pt&nrm=iso&tlng=pt Abstract: Densification is one method used to modify low-density woods to make them achieve the hardness required for flooring application. The purpose of this study was to investigate the effect of thermo-mechanical densification with pre-heating in wood of Alnus acuminata, Vochysia ferruginea and Vochysia guatemalensis from, seeking to stabilize and reduce spring-back of the densified wood and evaluate its performance in flooring applications. The results showed that the wood of the three species turned dark. This is because brightness diminished and yellowness and redness increased. Weight loss due to pre-heating was statistically higher in V. ferruginea and V. guatemalensis. The final density and spring-back were statistically similar in the three species. The percentage of densification of A. acuminata and V. guatemalensis were statistically higher than for V. ferruginea and the degree of compression was statistically higher in V. guatemalensis. As for flooring evaluation, the percentage of densification, temperature and time of pre-heating affected the behavior of densified wood flooring. The low percentage of densification and high weight loss in the pre-heating stage caused greater values of wear, wear index, residual deformation, residual indentation for the falling ball indentation test, and more damages in the surface indentation test in wood of V. ferruginea. <![CDATA[Steam sterilization time of stacked radiata pine packaging material]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100417&lng=pt&nrm=iso&tlng=pt Resumen: La madera de pino radiata destinada a la fabricación de embalajes para exportación requiere ser esterilizada de acuerdo a las normas fitosanitarias internacionales NIMF 15. En el presente trabajo se estudió en secaderos industriales el tiempo de esterilización con vapor que es necesario emplear con madera aserrada verde de pino radiata apilada sin separadores y destinada a la fabricación de embalajes, considerando como factores variables la temperatura del vapor (80 ºC, 90 ºC y 100 °C), el espesor de las piezas de madera (16 mm, 38 mm y 53 mm) y la altura del subpaquete de madera (150 mm, 200 mm y 400 mm). Un experimento piloto fue realizado en un horno industrial de 40 m3. Posteriormente se escaló el experimento a hornos industriales de 100 m3. Los resultados mostraron que el tiempo necesario para la esterilización con vapor en el rango de temperaturas analizado aumenta significativamente con el espesor de las tablas y con la altura del subpaquete. El tiempo mínimo para obtener las condiciones de esterilización con vapor en la madera apilada de pino radiata varió de 123 min hasta un máximo de 2275 min.<hr/>Abstract: Radiata pine wood packaging needs to be sterilized according to international phytosanitary standards. In this work the heat sterilization time of green radiata pine packaging material stacked without separators was studied on an industrial scale, considering as variable factors the steam temperature (80, 90 and 100) °C, the thickness of the wood (16, 38 and 53) mm and the height of the wood pile (150, 200 and 400) mm. The pilot experiment was conducted in a 40 m3 industrial oven. Subsequently the experiment was scaled to 100 m3 ovens. The results showed that the heat sterilization time in the analyzed temperature range depends significantly on the thickness and height of the stack. The minimum time to obtain heat sterilization conditions of radiata pine packaging material varied from 123 min to a maximum of 2275 min. <![CDATA[Estimation of density, moisture content and strength properties of <em>Tectona grandis</em> wood using Near Infrared Spectroscopy]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100418&lng=pt&nrm=iso&tlng=pt Abstract: Near infrared spectroscopy is non-invasive and may be applied as a rapid and cost effective technique for assessment of quality parameters of timber. Near infrared spectra of Tectona grandis (teak) wood samples were collected before measuring physical (density, equilibrium moisture content) and strength (flexural and compressive) properties using conventional methods. Partial least squares regression was used to develop calibration models between measured wood properties and near infrared data. The best near infrared spectra pre-processing methods differed by property. Linear calibration models with high R², low error and high ratio of performance to deviation values were observed from partial least squares analysis for different wood properties. These linear models may be applied for rapid and precise estimation of the properties examined in testing and evaluation procedures for commercially valuable teak wood. <![CDATA[Structural analyses of wooden chairs by finite element method (FEM) and assessment of the cyclic loading performance in comparison with allowable design loads]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100419&lng=pt&nrm=iso&tlng=pt Abstract: Tests were carried out to investigate the cyclic loading performance of chairs constructed of Scotch pine (Pinus sylvestris) and Oriental beech (Fagus orientalis). Totally, 30 real size chairs were constructed and assembled with polyvinyl acetate adhesive. Chairs were tested under 3 cyclic loading directions; namely, front to back, back to front, and backrest according to American Library Association (ALA) specifications, and obtained loading performances of chairs were crosschecked with allowable design load levels. Additionally, specimens were analyzed as structures by using the finite element method in order to obtain axial, shear, and bending stresses acting on each member under loadings and compare these values with design stresses. As a result, it was concluded that finite element method analyses achieve reasonable estimates for strength performances and failure behaviors of chairs. Depending on allowable design loads by American Library Association; chairs constructed of beech could meet the medium service for front to back and back to front loading, while heavy service for backrest loading. In the case of pine chairs; they could meet the medium service for front to back and back to front loading, while light service for backrest loading. <![CDATA[Changes in wood properties of chestnut wood structural elements with natural aging]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100420&lng=pt&nrm=iso&tlng=pt Abstract: Knowing the effects of natural aging on wood properties is important both for the conservation of historical wooden material and for reuse of aged wood. The aim of this study was to investigate the wood properties of old wooden elements not impregnated with any protective chemicals and taken from different parts of Zeytinlik houses in Giresun, Turkey. Test samples were prepared from old wooden elements and freshly cut chestnut timber. The anatomical, chemical, physical and mechanical properties were determined according to standard procedure, and the results were compared with those of recent wood specimen. As a result of the anatomical identification, it was determined that the wooden elements used in traditional Zeytinlik houses belong to species of Anatolian chestnut (Castanea sativa), and after an average service life of 88, 113 and 120 years, there was no change in the anatomical structure of the old wooden elements. Fourier transform infrared band characterization of old wood specimens revealed that hemicelluloses degraded and lignin structure changed on the surface of almost all specimens. Especially, the wood density values of the facade elements were smaller than that of recent wood specimen. Except for the modulus of rupture of window sill and rafter, all mechanical properties were significantly greater compared with those of recent wood specimen. The results of this research showed that old wood not damaged by fungi and insects could be evaluated for reuse. <![CDATA[Juvenile-mature wood evaluation along the bole considering the influence of silvicultural treatments]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100421&lng=pt&nrm=iso&tlng=pt Abstract: Wood used for structural purposes has increased in the last decade in Spain. However, as raw material, wood needs to comply with requirements that are not always present. Knowledge about the wood quality from the trees on the stand is essential for providing feedback to forest managers and for taking the required actions to obtain suitable silviculture treatments. Two of the main wood species used in construction in Spain, Pinus nigra and Pinus sylvestris, have been studied in order to determine the amount of juvenile wood, which has been identified as a harmful characteristic for its decrease in quality of the physical-mechanical properties of these species. Being relevant for the best quality of timber in the part along the bole where the logs are obtained, the distribution of juvenile wood at different heights and the effect of several silvicultural treatments have had on juvenile wood formation has been considered. The juvenile-mature wood boundary (transition year) was calculated through segmented linear mixed models employing as variables annual latewood density, obtained through micro X-ray densitometry, silvicultural practices, and a drought index. The results show how juvenile and mature wood is distributed along the bole and the proportion of juvenile wood. Its reduction according to the different thinning and pruning silvicultural practices is presented. <![CDATA[The use of borax pentahydrate of inorganic filler in medium density fiberboard production]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100422&lng=pt&nrm=iso&tlng=pt Abstract: The aim of the study was the use of the inorganic borax pentahydrate mineral in medium density fiberboard production instead of biomass fiber and to specify the performance which physical, mechanical, combustion of produced boards. Chips used in manufacture were subjected to cooking for 4,5 minutes in Asplund defibrator at the vapor pressure of 7,6 kg/cm2 pressure and 190 ºC temperature. 1,6 % paraffin based on oven-dried wood fibers was added to cooked chips before the fiber processing in segments of defibrillator section. 1 % ammonium sulfate based on oven-dried wood fibers were added to fiber in the bowline. Borax pentahydrate was prepared in a separate tank in order to use the production of medium density fiberboard. Borax pentahydrate inorganic mineral was mixed with urea-formaldehyde resin. Urea-formaldehyde glue was prepared as three different solutions including the borax pentahydrate as 3 % (20 kg), 6 % (40 kg) and 9 % (60 kg) respectively. Borax pentahydrate mixed fibers were dried to 12 % moisture. Mat was formed before prepress. Daily multi-press was manufactured at 188 °C temperature and 32 kg/cm² pressure and, 270 second pressing time. Manufactured boards size were 2100 x 4900 x 18 (mm). According to this work result, 3 % and 6 % rate borax pentahydrate added medium density fiberboard boards were measured more good physical and mechanical test results compare to control boards. 9 % borax pentahydrate added medium density fiberboard boards were shown incredibly superior performance at fire resistance. <![CDATA[Evaluation of the properties of hybrid yellow poplar (<em>Liriodendron sino-americanum</em>): A comparison study with yellow poplar (<em>Liriodendron tulipifera</em>)]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100423&lng=pt&nrm=iso&tlng=pt Abstract: As one of the fast-growth wood species, hybrid yellow poplar (YP-h, Liriodendron sino-americanum) has been extensively planted throughout China, however, little is known about its properties and applicability in structural and nonstructural applications such as construction and furniture. The aim of this study was to evaluate the properties of YP-h and examine its differences with yellow poplar (YP, Liriodendron tulipifera). The average vessel diameter of YP-h (55 μm) was 19 % lower than YP (68 μm), but, the density of YP-h was 37 % higher than YP and the dimensional change in YP-h was higher than YP. Comparable tensile strength and flexural modulus were found in YP-h and YP, however, the flexural, shear, and impact strength of YP-h was 35 %, 40 %, and 55 % higher than those of YP, respectively. The drilling, mortising, and turning processability of YP-h were superior to those of YP. Compared to the gluing and coating performance of YP, YP-h had inferior gluing properties and equivalent coating performance. Therefore, hybrid yellow poplar can be an ideal candidate for yellow poplar to be utilized in construction and furniture. <![CDATA[Natural weathering performance of thermally treated poplar and black pine wood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100424&lng=pt&nrm=iso&tlng=pt Abstract: The wood of poplar (Populus sp.) and black pine (Pinus nigra) species was subjected to thermal treatment under variant conditions of temperature, 180 ºC and 200 ºC, and duration of 3 h, 5 h, 7 h, and its resistance to natural weathering was investigated through the determination of crucial properties, such as the colour and surface roughness, while the appearance of the boards was assessed both visually and through a microscope, prior to and after their exposure outdoors. Prior to the outdoors exposure, it was observed that, as the intensity of heat treatment increases, wood tends to darken, with the parallel decrease of L* index, referring to the tangential, radial and cross-sectional surface of both species specimens. The surface roughness of both wood species was found to decrease only in the boards of the mildest treatment, while as the treatment intensity increases, the roughness degree demonstrated a strong increase compared to unmodified wood. After the 100-day exposure of poplar and pine boards to external conditions, they acquired a wilder look and new checks and cracks emerged in the boards surface, while fungi infestation signs appeared, most apparent in control and boards treated at milder treatments, with modified poplar boards to demonstrate more dense defects patterns on their surfaces, compared to modified black pine boards. A similar degree of discoloration recorded on unmodified boards was observed also on the thermally modified boards, which was except for the visual assessment, confirmed by the recorded progress of L*, a* and b* colour indexes of poplar and pine surfaces and is probably attributed to leaching of the water soluble extractives. The roughness of all of the exposed boards surfaces was found higher than the respective values recorded prior to the exposure and among the treated boards only those of the milder treatments presented lower roughness values than the unmodified ones. Thermal treatment enhanced the biological durability and dimensional stability of both species, but it did not adequately protect the wood from the weathering effect when it was exposed outdoors. Nevertheless, wood modified at short-term heat treatments exhibited enhanced properties compared to unmodified wood and taking into account that the milder treatments did not cause mechanical strength loss, these materials could be utilized in applications where structures are not continually and directly exposed to aging factors, such as under shelter applications, or after the application of a thermal and surface modification with protective preservatives combination. <![CDATA[Quantitative evaluation of microwave irradiation on short-rotation plantation wood species]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100425&lng=pt&nrm=iso&tlng=pt Abstract: The durability of imported timber is a matter of growing concern in the tropical Indian climate, with their refractory nature further adding to the woes with respect to further processing. In the present study, the effect of microwave pre-treatment, exposure time and initial wood moisture content on retention, treatability and cross-sectional anatomical properties of Tectona grandis and Southern yellow pine imported from Ghana and South America were evaluated. Water based preservative copper chrome borate (CCB) of 2 % concentration was used for the study. The experimental study in combination with dip-diffusion method returned with significant improvement in retention of about 5-6 folds more than the control sets in Southern yellow pine and Tectona grandis. Another set of Southern yellow pine and Tectona grandis samples were further treated using a full cell pressure method after microwave, without initial vacuum, which showed similar trends with a 3-4 folds increase in retention over controls. Both experiments returned with significant improvement in the treatability class of Tectona grandis and Southern yellow pine. The anatomical analysis was performed using a light microscope with 5 and 10x magnifications on treated and untreated samples of both Tectona grandis and Southern yellow pine. The outcome of the anatomical study exhibited improvement in vessel diameters in the treated samples of Tectona grandis with a reduction in the degree of occlusion by the presence of tyloses. For Southern yellow pine, checks on micro level and cracks on macro level appeared along with the ray cells and the diameter of the resin canals was substantially expanded which ascertains that microwave pre-treatment ameliorated the flow of fluids in the wood microstructure which improved permeability and resulted in better uptake and penetration. <![CDATA[Effects of microcrystalline cellulose on some performance properties of chitosan aerogels]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100426&lng=pt&nrm=iso&tlng=pt Abstract: The aim of this research was to investigate the effect of the microcrystalline cellulose reinforcement on some physical, mechanical, thermal, and morphological properties of the chitosan aerogels. The bio-based chitosan aerogels were produced using chitosan as a matrix and the microcrystalline cellulose as a reinforce material through the freeze-drying method. The aerogel suspensions were prepared in five different ratios to investigate the effect of microcrystalline cellulose content. The density, porosity, thermogravimetric analysis, and compressive resistance tests were conducted according to relevant standards. Morphological properties were investigated using a scanning electron microscope. The introduction of microcrystalline cellulose significantly improved the compressive resistance, thermal properties (Tonset and T%50) of the chitosan aerogels. The optimum performance properties determined as 0,12 MPa for compressive resistance, 0,27 MPa for compressive modulus, 292,45 °C for Tonset and 365 °C for T%50. According to scanning electron microscope images, aerogels showed microporous structure as expected. As a result, the bio-based chitosan aerogels reinforced with microcrystalline cellulose were successfully manufactured. The mechanical and thermal properties including compressive resistance, compressive modulus, Tonset and T%50 of chitosan- microcrystalline cellulose aerogels found promising. <![CDATA[Elastic constants of Chilean <em>Pinus radiata</em> using ultrasound]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100427&lng=pt&nrm=iso&tlng=pt Abstract: In general, data regarding the mechanical properties of wood is still incomplete, mainly owing to the difficulties involved in preparing well-made standard testing samples, as well as the time-consuming evaluation tests. Therefore, the elastic constants for Pinus radiata in this paper were determined using ultrasound technology. In parallel, typical compression mechanical testing was carried out to compare the effectiveness of the nondestructive test using the ultrasound. The longitudinal elastic constant values were similar to the mechanical testing (ultrasound was 12,8 % higher than mechanical testing), showing that ultrasound technique is a reliable and valid tool. The values for radial and tangential moduli obtained by the ultrasound versus mechanical testing showed statistically significant differences. This may be due to the difficulty in obtaining adequate samples for mechanical testing. The symmetry of the shear modulus was revealed by the ultrasound technique (Gij = Gji). Poisson’s ratios were not comparable using either method; however, values obtained were more consistent with the existing literature for Pinus species. Additionally, the elastic anisotropy of the analyzed wood samples was demonstrated through the ultrasound velocity propagation in the material. It was thus possible to obtain the twelve engineering constants that characterize the mechanical behavior of wood employing of the proposed ultrasound technique. The results proved that this technique could be a useful tool for such characterization. <![CDATA[Phenolics content and antioxidant activity of wood extractives from three clones of <em>Acacia</em> hybrid (<em>Acacia mangium</em> × <em>Acacia auriculiformis)</em>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100428&lng=pt&nrm=iso&tlng=pt Abstract: Breeding strategy of Acacia hybrid is being developed by Center for Forest Biotechnology and Tree Improvement Indonesia and has produced three superior clones in growth (Clone 16, 25, and 44). Understanding the extractives of the new clones might determine future development steps to improve its resistance to diseases especially heartrot. The objective of this study was to investigate the extractive content in three radial directions (SW = sapwood; OHW = outer heartwood; IHW = inner heartwood); total phenolic, flavonoid, flavanol contents (colorimetric assay); and antioxidant activity (1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay). Extractions were done with three different solvents in successive (n-hexane = H; methanol = M; hot water = W), yielded 0,69 % - 1,70 %; 1,51 % - 10,86 %; and 0,51 % - 1,16 % of extractive contents, respectively. The total phenolic content (TPC) from TPC-H, TPC-M, and TPC-W ranged between 3,68 mg of gallic acid equivalent (GAE)/g - 10,41 mg GAE/g; 76,83 mg GAE/g - 448,35 mg GAE/g; and 43,28 mg GAE/g - 198,92 mg GAE/g, respectively; the total flavonoid content (TFC) from TFC-H, TFC-M, and TFC-W between 4,23 mg of quercetin equivalent (QE)/g - 41,51 mg QE/g; 29,55 mg QE/g - 133,71 mg QE/g; and 7,70 mg QE/g - 29,37 mg QE/g, respectively; total flavanol content (TVC) from TVC-H, TVC-M, and TVC-W ranged between 28,74 mg of catechin equivalent (CE)/g - 66,90 mg CE/g; 83,39 mg CE/g - 247,18 mg CE/g; and 7,08 mg CE/g - 29,21 mg CE/g, respectively. Furthermore, the antioxidant activity was found to be significantly affected by the radial factor with the strongest activity exhibited by inner heartwood extract with an IC50 value of 255,77 μg/ml (gallic acid IC50 showed a value of 39,00 μg/ml). Among clones, clone 16 was determined to have the highest extractive, total flavonoid as well as flavanol contents. Thus, clone 16 was hypothesized to be more resistance against heart rot disease. <![CDATA[Evaluation of <em>Eucalyptus</em> woodchip utilization as fuel for thermal power plants]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100429&lng=pt&nrm=iso&tlng=pt Abstract: This paper aims to evaluate the implications of Eucalyptus woodchip utilization as an alternative solid fuel for thermal power plants, highlighting its energy properties, power generation expenses and unit variable costs. Woodchip samples were collected from different sources and a proximate analysis was carried out in order to determine their moisture content, basic and bulk densities, ash content and higher heating value. Then, with these properties, empirical indices of a 10-megawatt thermal power plant were used to simulate the potential woodchip consumption, the forest area needed and the unit variable cost (US$·MWh−1) for each sample. The results indicate that woodchip samples with lower moisture content and improved higher heating value presented: reduced woodchip consumption for the same power generation, decreased generation expenses, reduced unit variable costs and smaller Eucalyptus plantations area needed to supply the woodchip consumption. Greater energy density may result in lower transportation and storage expenses, however, does not indicate better generation performance, since it is influenced by biomass field conditions. All samples obtained satisfactory levels of ash content, which may result in lower emissions of pollutants and superior operational efficiency. Finally, all samples presented unit variable costs below the limit established by the government for participation in the regulated energy market, which might be an economic attraction for this kind of project. Therefore, Eucalyptus woodchip moisture content, higher heating value and energy density are key issues in sustainable thermal power generation and should be managed by Eucalyptus power plants in order to reach better generation performance and reduced expenses. <![CDATA[Evaluation of wetting, structural and thermal properties of electrospun nanofibers at different pineapple leaf fiber / polyethylene terephthalate ratios]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100430&lng=pt&nrm=iso&tlng=pt Abstract: In this study, pineapple leaf fiber and polyethylene terephthalate electrospun nanofibers were produced via electrospinning process. Six ratios of pineapple leaf fiber/polyethylene terephthalate, namely 1/10; 1/7,5; 1/5; 1/1 and 1,3/1 were prepared and their wetting, structural and thermal properties were characterised. Wetting properties of this sample were studied using contact angle measurement. X-Ray Diffraction, differential scanning calorimetry and thermogravimetric analysis were conducted to get better understanding on the structural and its thermal properties, respectively. The results revealed that increasing the pineapple leaf fiber content simultaneously increased the ability of nanofibers to adsorb water as shown by lower contact angle degree with 81,6° and adsorption time of 15 seconds. An increase in pineapple leaf fiber ratio did not change the peak position in X-Ray Diffraction and no new peaks observed for any sample. However, the peak at 23° for samples with ratio 1/1 and ratio 1,3/1 exhibited higher intensity compared to that of pure polyethylene terephthalate. Thermal properties obtained from thermogravimetric analysis results suggested that thermal properties were not influenced by the pineapple leaf fiber ratio. Overall, pineapple leaf fiber/polyethylene terephthalate electrospun nanofibers produced at the ratio of 1/1 displayed the optimum performance. <![CDATA[Weathering characteristics of impregnated and coated Calabrian pine wood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100431&lng=pt&nrm=iso&tlng=pt Abstract: This study was designed to investigate the weathering characteristics of Calabrian pine (Pinus brutia) wood. The wood specimens were impregnated with some copper-based chemicals and then varnish coated. As copper-based chemicals, Celcure C4, Korasit KS, and Tanalith E 8000 were used for impregnation. Polyurethane varnish (PV) and water-based varnish (WBV) were used as coating materials. Firstly, Calabrian pine wood was impregnated with 2,5 % and 5 % aqueous solutions of chemicals then coated with PV and WBV. Impregnated and coated Calabrian pine wood specimens were subjected to 6 months of natural weathering in Muğla, Turkey. After weathering, surface hardness, surface roughness, and adhesion strength changes of Calabrian pine wood specimens were determined. Impregnation caused to increase in surface hardness values of Calabrian pine. Surface hardness increases of WBV coated Calabrian pine specimens were higher than that of PV coated Calabrian pine specimens. Impregnation resulted in higher surface roughness values of Calabrian pine specimens. PV coated Calabrian pine specimens gave higher surface roughness than that of WBV coated Calabrian pine specimens. The adhesion strength values of all treatment groups were decreased after weathering. In general, adhesion strength decreases of WBV coated Calabrian pine specimens were higher than that of PV coated Calabrian pine specimens. The concentration levels of chemicals did not have a significant effect on surface roughness and adhesion strength of Calabrian pine wood after weathering.