Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> http://www.scielo.cl/rss.php?pid=0718-221X20210001&lang=es vol. 23 num. lang. es <![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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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[Colorimetría de los tallos del bambú (<em>Guadua angustifolia</em>) en tres estados de madurez]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100408&lng=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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[Evaluación de la eficiencia energética de un proceso continuo de tratamiento de residuos agroforestales mediante carbonización hidrotérmica]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100415&lng=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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[Tiempo de esterilización mediante vapor de la madera aserrada de Pino radiata]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100417&lng=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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=es&nrm=iso&tlng=es 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. <![CDATA[Shear and adhesion strength of open and closed system heat-treated wood samples]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100432&lng=es&nrm=iso&tlng=es Abstract: This paper investigated the effects of heat treatment in open (atmospheric pressure) and a closed (under pressure) system on the shear and adhesion strength of Scots pine (Pinus sylvestris) wood. In addition, pull-off adherence testing was carried out of the coatings with water-based, polyurethane-based and oil/wax-based varnishes. Shear strength decreased significantly after heat treatment in Scots pine (31 % to 39 %) in the open system, while it decreased between 2 % and 38% in the closed system without glue. The shear strength of the wood samples glued with glue was higher than the samples without glue at the laboratory scale. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of the brittle modified wood substrate. With increasing, heat treatment temperature adherence decreased. Maximum pull-off adhesion (4,80 MPa) was observed in the control samples coated with polyurethane-based varnish. <![CDATA[Characterizations of tree-decay fungi by molecular and morphological investigationsin aniranian alamdardeh forest]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100433&lng=es&nrm=iso&tlng=es Abstract: Forest trees are considered important in ameliorating climate change through removing carbon dioxide from the atmosphere, stabilizing water catchments and for timber production. Wood decay fungi are among the most important biotic factors in ecosystems, infecting valuable landscaping trees causing an economic loss or the preeminent recyclers of the wood. In a survey of forest trees in the Alamdardeh forest, northern Iran, fungal fruit bodies were collected and isolations made. Based on a combination of macro-morphological characteristics and molecular analyses, using the sequence data of ITS-rDNA, isolates were identified to the species level. A total of 22 species in nine families and 15 genera were identified. Most isolates were the white-rot fungi. Additionally, the brown-rot fungus Laetiporus sulphureus and the soft-rot species Xylaria longipes were identified. <![CDATA[Influence of initial wood moisture on decay process by two brown-rot fungi]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100434&lng=es&nrm=iso&tlng=es Abstract: The biological decomposition of lignocellulosic materials caused by basidiomycetes plays an essential role in the carbon cycle. Brown rot fungi represent important agents in the biodegradation of wood products and standing coniferous trees in natural ecosystems. The initial moisture content of the wood is an important factor in the degradation process. In this work, the effects of initial moisture content of Eucalyptus grandis sapwood on decay by two brown rot fungi Gloeophyllum trabeum and Laetiporus sulphureus were studied over a 10-month period. The fungal activity was evaluated, through wood weight loss, moisture content, anatomical changes (scan electronic and fluorescence microscopy) and Fourier-transform infrared spectroscopy. Weight loss increased through the 10-month test for both fungi, Laetiporus sulphureus producing higher mass losses. Colonization of the wood by both fungi started below the fiber saturation range. It was observed that the initial moisture content of the wood influenced the rate of deterioration: the wet samples showed higher weight loss compared to the dry samples. Changes in the chemical composition and structure of cell walls were detected. The initial moisture content of the substrate affected the development of the fungi, slowing their growth. <![CDATA[Combined effects of neem (<em>Azadirachta indica</em>) and sesame <em>(Sesamum indicum)</em> oil as a wood preservative on subterranean termites in the field]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100435&lng=es&nrm=iso&tlng=es Abstract: The current study was aimed to evaluate the effect of neem and sesame oils on the improvement of poplar (Populus spp.) wood resistance to subterranean termite in the field. Concentrations of 10 %, 20 %, and 30 % of both oils alone in toluene and their different combinations along with heat treatment were bio-assayed against termites. Results showed that both oils protected woods against termites differently; however, neem oil was more protectant than sesame oil. Moreover, neem oil, when combined with sesame oil, significantly improved the wood resistance compared to separate oils treatment. Heat treatment alone was not enough to enhance resistance against subterranean termites. The treatment at 200 ºC for 6 h combined with 75 % neem and 25 % sesame (3:1) appears to be the best treatment condition in this investigation. It is concluded that neem oil can be useful as a wood preservative against subterranean termites combined with sesame oil and heat treatment. <![CDATA[Crystallinity and impact strength improvement of wood-polylactic acid biocomposites produced by rotational and compression molding]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100436&lng=es&nrm=iso&tlng=es Abstract: Polylactic acid is one of the most used biopolymers due to its overall properties and biodegradability. Nevertheless, polylactic acid has important drawbacks such as brittleness, low thermal stability, and higher cost than most commodity polymers. In order to overcome those disadvantages without compromising biodegradability, the addition of wood particles and thermal annealing on the crystallinity and impact strength of wood-polylactic acid biocomposites were studied. The samples were prepared by compression and rotational molding using two different wood particles: white ash and tzalam. The results showed that thermal annealing at 100 °C, 40 minutes, increased the crystallinity up to 60 % and also improved the thermal stability of polylactic acid and its biocomposites as determined via dynamic mechanical analysis. The specimens not exposed to thermal annealing exhibited important storage modulus loss above 60 °C, which mostly disappeared with the thermal treatment. Furthermore, the impact strength was substantially increased by the thermal treatment. Additionally, accelerated weathering tests showed that the thermally annealed samples had better dimensional stability growing their potential applications over a wider range of conditions. <![CDATA[Synergistic influence of flame retardant additives and citric acid on the functional properties of rice husk/wood blended particleboards]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100437&lng=es&nrm=iso&tlng=es Abstract: The selected functional properties of rice husk/wood blended particleboards which include thermal analysis, limiting oxygen index, morphological analysis, and mechanical properties have been investigated. Rice husk/wood particleboards were produced with one step hot press casting technique using citric acid to improve the compatibility in the particleboards with calcium oxide and aluminum oxide as flame retardants. The results showed improvement in the mechanical properties, flame retardancy, and thermal stability with the addition of flame retardants to the particleboards. The aluminum oxide synergy with citric acid in rice husk/wood particleboards gave the best flame retardancy. <![CDATA[Tio<sub>2</sub>-modified <em>Pinus elliottii</em>: A pine wood presenting increased resistance to water and ultraviolet radiation]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100438&lng=es&nrm=iso&tlng=es Abstract: The aim of the present study is to subject Pinus elliottii wood specimens to TiO2-based modification in order to make them resistant to water and UV radiation. The microwave-assisted solvothermal method, which is little reported in the literature, was here in use for this purpose. The adopted methodology led to a 1 % mass gain; although it was a low value, it was enough to fully coat the surface of the wood with nanoparticles to the extent of changing its characteristics and turning it into a functional material. The nanoparticle distribution on the surface of the wood changed your natural topography by increasing the surface area and, consequently, increasing the contact angle of the modified wood (approximately 130°). The leaching test showed that the wood remained coated after it was immersed in water, as well as that it did not lose its water-repelling ability. This result demonstrates the stable interaction between the two materials, due to hydroxyl radicals found in them. The coating also protected the wood against UV radiation for 500 hours of intense exposure, besides preserving its initial color. The properties achieved through this simple and fast modification process provide an alternative to help to improve the performance of the herein investigated wood species, mainly for applications in environments subjected to high solar incidence and humidity. <![CDATA[Use of <em>Eucalyptus grandis</em> clones treated with a water repellent to improve the dimensional stability of utility poles]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100439&lng=es&nrm=iso&tlng=es Abstract: Wood is a common construction material used in most environments. However, its sensibility to abiotic agents, in particular those that affect the dimensional stability, limits the durability of the material and decreases its properties. In this work, the efficiency of a paraffin-emulsion-based product as a water repellent, combined with the selection of Eucalyptus grandis clones with a low cracking index, was tested for its use in utility poles in order to improve the woods dimensional stability. Four selected Eucalyptus grandis clones were treated with the product mixed with Chromated Copper Arsenate - the most commonly used wood protector - in a single stage by the Bethell method at two retention levels. The dimensional stability of the treated samples was studied through the determination of anti-shrink efficiency. Test samples were also exposed to accelerated weathering processes for 200 h, and later analyzed by SEM microscopy. Results showed a significant improvement in the dimensional stability of treated wood when compared to samples without the water repellent, with variable efficacy depending on the clone used. Despite the weathering process slightly affected the appearance of the wood surface, the product is suitable for exterior use. <![CDATA[Influence of harvest region on properties of Cambará wood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100440&lng=es&nrm=iso&tlng=es Abstract: This research intends to evaluate the relation, aided by the Brazilian Standard and statistical analysis (Kruskal-Wallis ANOVA and bootstrap technique), between physical and mechanical properties of Cambará-Rosa wood harvested from three different regions: Vera, Mucajaí and South Rondonia. In addition, the possibility to estimate (regression models) physical and mechanical properties in function of apparent density was analyzed. Different climate and soil conditions which tree thrives may influence its growth and, consequently, its properties values. The results of ANOVA indicated an elevated equivalence index for all three regions. The bootstrap technique led to similar results for Vera and Mucajai regions, and for South Rondonia region, equivalence index equals to 89 %. The ANOVA results to estimate physical and mechanical properties in function of apparent density indicated that it is not possible to perform such estimates for Cambará-Rosa wood species. <![CDATA[Bonding quality of two lesser-used wood species <em>Brachystegia spiciformis</em> and <em>Julbernardia globiflora</em> from Mozambique]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100441&lng=es&nrm=iso&tlng=es Abstract: The objective of this study was to evaluate the density, chemical properties and bonding quality of two lesser-used Mozambican wood species known as messassas (Brachystegia spiciformis and Julbernardia globiflora) aiming at edge-glued panel production. The bonding was performed using structural adhesive polyvinyl acetate D4, semi-structural adhesive emulsion polymer isocyanate and non-structural polyvinyl acetate D3 applied at 120·m-2 and 180·m-2 weights. Density, chemistry, edge shear bonding, wood failure percentage and the finger-joint tests were performed in accordance with standards. The results showed that both species have medium density, high extractives and lignin contents typical of tropical wood. The emulsion polymer isocyanate adhesive was approved with better performance compared to polyvinyl acetate D3 and D4 adhesives. It can also be affirmed that Brachystegia spiciformis and Julbernardia globiflora have similar bonding behaviour and the potential for producing edge glued panel panels, especially for indoor use. <![CDATA[Effects of hot-cold oil treatment on biological resistance and physical properties of Brutia pine sapwood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100442&lng=es&nrm=iso&tlng=es Abstract: This study investigated the physical properties of hot-cold oil-treated Brutia pine sapwood (Pinus brutia) and its biological resistance against wood-decay fungi. Weight percent gain, density, water absorption, and volumetric shrinking were chosen as the physical properties of the wood. White rot (Trametes versicolor) and brown rot (Neolentinus lepideus) were selected as the wood-decay fungi. Two different temperatures and two different time intervals were determined for the hot-cold oil treatment. Castor oil (Ricinus communis), flaxseed oil (Oleum linii), and a mixture of the two were used as the treatment oils (the medium of the hot-cold treatment). The results showed that the physical properties of the hot-cold oil-treated samples improved significantly compared to those of the control samples. In addition, after exposure to the decay fungi, the mass loss of the hot-cold flaxseed oil-treated samples decreased significantly more than in either the untreated samples or those treated with the other oils. There was a significant increase in the water repellent effectiveness and dimensional stability of the Brutia pine sapwood with all hot-cold oil treatments, but the hot-cold castor oil treatment appeared to have had no effect on decay resistance. A hot-cold oil treatment using flaxseed oil or a mixture including it could be a suitable method for improvement of the water repellent effectiveness, dimensional stability, and decay resistance of Brutia pine sapwood, as they both reduced the water uptake and the mass loss against the wood-decay fungi compared to the results of the control samples. <![CDATA[Relationship between vessel parameters and cleavage associated with checking in <em>Eucalyptus grandis</em> wood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100443&lng=es&nrm=iso&tlng=es Abstract: In this work, the relationship between vessels parameters and the wood cleavage strength were studied to clarify the process of formation of this type of check, very common in Eucalyptus wood. The objective was to identify the relationship between the wood cleavage strength, the average area of the vessel, and the percentage area of vessels on the wood transverse surface. For this, two Eucalyptus grandis trees at 22 years old were felled and specimens for the cleavage test were produced to determine the wood cleavage strength. From these specimens, samples were taken to determine the average area of the vessel and the percentage area of vessels, aiming at adjusting mathematical models that explain the variation in the cleavage strength. The results showed that the higher the average area of the vessel and the percentage of area occupied by vessels in the wood, the lower its cleavage strength. The multiple linear regression model can estimate the cleavage strength as a function of the average area of the vessel, and the percentage area of the vessels. <![CDATA[Bending moment resistance of t-type joints reinforced with basalt and glass woven fabric materials]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100444&lng=es&nrm=iso&tlng=es Abstract: This study investigated the bending moment resistance of T-type, two-pin dowel joints connected with Scotch pine dowel (Pinus slyvestris), beech dowel (Fagus orientalis), chestnut dowel (Castanea sativa) and oak dowel (Quercus petraea) and reinforced with basalt and glass woven fabric. The tests was carried out to determine the bending moment resistance of dowel joints. As a result of bending test, it was determined that one layer and two surfaces the reinforce with fiber woven fabrics increases the mechanical performance of furniture fasteners according to obtained data from tests conducted on the T-type, two pin dowel joints. The test samples prepared from the oak wooden give the higher moment values than the beech wooden. This study showed that the joining with the oak dowel was 13 % higher than the beech dowel, 32 % the chestnut dowel, and 43 % higher than the Scotch pine dowel (for the bending moment resistance), respectively. According to the bending moment resistance of the samples reinforced by fiber woven fabrics. The highest bending moment resistance value was obtained in the test specimens of reinforced with the basalt woven fabric, the lowest bending moment resistance value was obtained in the test specimens not reinforced (Control). In general, it was determined that the wood species by 3 %, wooden dowel species by 43 %, and fiber woven fabric types by 72 % have been effects on the results of the bending tests. <![CDATA[Comparative analysis of the physical and mechanical properties of kraft paper and watercolor paper]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100445&lng=es&nrm=iso&tlng=es Abstract: In order to study the feasibility of kraft paper as watercolor paper, the wetting properties, mechanical properties and friction properties of kraft paper and watercolor paper were compared before and after aging. The aging test was carried out on kraft paper and the watercolor paper by aging chamber, the wetting properties of distilled water and three watercolor solutions before and after aging of kraft paper and watercolor paper were compared, tensile tear test of paper on the tensile testing machine, the fracture changes of paper were analyzed by scanning electron microscope, the friction tester performs the paper friction test. The results show that both kinds of paper are amorphous, watercolor paper was showed hydrophobicity before and after the aging, the contact angle was maintained at about 119,09° ± 5° in four different solutions, unaged kraft paper exhibited hydrophilicity, the aged kraft paper showed hydrophobicity with a contact angle of 92,52° ± 1°,the aged kraft paper shows better performance in both tensile and tearing aspects and tensile strength is 20 MPa higher than watercolor paper, the surface roughness of kraft paper is higher than watercolor paper. The experiment is helpful for the market to consider whether the cheaper kraft paper replaces the more expensive watercolor paper in some aspects and provides some scientific reference value for future research. <![CDATA[Kinetic analysis of thermal degradation of <em>Cedrela odorata</em>, <em>Marmaroxylon racemosum</em> and <em>Tectona grandis</em> from timber industry]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100446&lng=es&nrm=iso&tlng=es Abstract: Thermal analysis is a powerful tool to predict the composition and thermal stability of different materials. In this work, thermogravimetric analysis of Cedrela odorata, Marmaroxylon racemosum and Tectona grandis was carried out at four different heating rates (5°C·min-1, 10°C·min-1, 20°C·min-1 and 40°C·min-1) in a non-isothermal condition. The degradation kinetics was evaluated based on Flynn-Wall-Ozawa and Criado methods. The half-life time of wood degradation reaction was also studied. The wood thermal degradation process in an oxidizing atmosphere can be divided in dehydration, devolatilization, and combustion. The kinetic results revels apparent activation energy values of 130-240 kJ·mol-1 for Tectona grandis, 150-191 kJ·mol-1 for Marmaroxylon racemosum and 188-205 kJ·mol-1 for Cedrela odorata, when conversion values ranged from 0,1-0,5. The most probable degradation mechanism for wood species studied is a diffusion model based on a three-dimensional diffusion. Cedrela odorata presented the lowest reaction half-life time while Marmaroxylon racemosum showed the highest. On the basis of these results, it can be concluded that Flynn-Wall-Ozawa and Criado methods associated with half-life time of reaction may contribute to better understand the wood degradation before use it in polymer composites. <![CDATA[Biologically synthesised copper oxide and zinc oxide nanoparticle formulation as an environmentally friendly wood protectant for the management of wood borer, <em>Lyctus africanus</em>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100447&lng=es&nrm=iso&tlng=es Abstract: The management of Lyctus africanus, one of the major dry wood pests in the tropical region is difficult due to its secluded habits and long lifecycle and therefore, its control measures are limited to the usage of insecticides. The insecticides particularly the metal salts are effective, but in some cases their leaching leads to concerns about environmental pollution. Nanometal particles are found to be more effective than metal salts. Presently available metal nanoparticles are synthesized using physical or chemical methods and their production results in toxic by-products and are costly. The current investigation deals with synthesis and use of metal nanoparticle for wood protection in an environmentally friendly and cost-effective way. The plant extracts that are reported to have wood preservative properties were used for the synthesis of metal nanoparticles. Copper oxide and zinc oxide nanoparticles were synthesized using leaf extracts of Lantana camara. The efficacy of the synthesized Lantana camara leaf extract and copper oxide or zinc oxide nanoparticle formulation as a wood protectant was tested against Lyctus africanus according to standard BIS. The formulation of copper oxide nanoparticle and Lantana camara leaf extract effectively protected the treated rubberwood blocks from Lyctus africanus attack, when compared to zinc oxide nanoparticle Lantana camara leaf extract formulation and can be developed into a stable, ecofriendly wood preservative. <![CDATA[Preparation and performance of tannin-glyoxal-urea resin-bonded grinding wheel loaded with SiO<sub>2</sub> reinforcing particles]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100448&lng=es&nrm=iso&tlng=es Abstract: In this study, an easily prepared bio-based abrasive grinding wheel based on tannin-glyoxal-urea (TGU)thermosetting matrix is presented.The synthesised resin was prepared via co-polycondensation reaction of glyoxal and ureawith condensed tannin, which is a forest-derived product. Fourier transform infrared spectroscopy and electrospray ionisation mass spectrometry results confirmed that urea and glyoxal react well under acidic conditions and that -(OH)CH-NH-group is primarily involved in TGU cross-linking. Differential scanning calorimetry, thermomechanical analysis and thermogravimetric analysis investigations showed that the preparation of TGU resin is easier compared to commercial phenol-formaldehyde (PF) resin; moreover, TGU resin has a more robust chemical network structure, which contributes efficiently to heat resistance and improved mechanical properties. This observation is supported by Brinell hardness, compression resistance and grinding testing; these showed that the new grinding wheel acquired higher hardness, superior resistance against compression and stronger abrasion resistance compared with a PF-based grinding wheel prepared in the laboratory. Moreover, few holes and no cracks were found in the new grinding wheel. <![CDATA[Efficient utilization of corn stalk and poplar planer shavings in manufacturing particleboard]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100449&lng=es&nrm=iso&tlng=es Abstract: In this study, particleboards were manufactured using a mixture of corn stalks and poplar wood particles at different ratios utilizing 10 % urea-formaldehyde adhesive. Panels with a density of 0,70 g/cm3 were manufactured using various amount of corn stalks and poplar wood from 100 to 25 %. Manufactured panels were tested the mechanical properties including modulus of rupture, modulus of elasticity and internal bond and the water absorption and thickness swelling. In addition, the chemical properties and fiber dimensions of poplar wood and corn stalks were also evaluated. Some properties of the manufactured panels increased with the content of poplar particles. The addition of wood poplar particles resulted in a significant increase of some properties of particleboards. From this study, it can be concluded that the combination of poplar particles and corn stalks resulted in particleboards acceptable for interior applications due to low water absorption and thickness swelling. The internal bond strength, the most serious deficiency of stalks, was upgraded sufficiently by increasing the content of wood poplar particles. This study demonstrate that corn stalks may be considered as a charger for wood poplar particleboards manufacturer in region where wood is not abundant. unusual to wood material in the production of particleboards. <![CDATA[Influence of silicone oil thermal modification on mechanical properties of Masson pine wood]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100450&lng=es&nrm=iso&tlng=es Abstract: In this study, the effect of silicone oil thermal modification at different treatment temperatures (150 ºC, 180 ºC and 210 ºC for 2 h and 4 h.) on the mechanical properties of Masson pine (Pinus Massoniana Lamb.) wood was investigated. The density, modulus of elasticity (MOE), modulus of rupture (MOR), impact bending, compressive strength, and hardness of silicone oil thermal treated samples were evaluated and compared with those of untreated samples. Results showed the mechanical properties of Masson pine wood reduces after silicone oil thermal modification. The higher the modification temperature, the lower the mechanical properties of Mason pine wood. At 210 ºC for 4 h, mechanical properties of the modified samples were two times lower than the mechanical properties of the untreated. Higher modification temperature and longer treatment time contributed to lower mechanical properties. <![CDATA[Theoretical model for further development of intumescent substances to remediate smoldering in wood fiber insulation panels]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100451&lng=es&nrm=iso&tlng=es Abstract: Wood fiber insulation boards, as many other wooden materials, are susceptible to smolder. This type of slow and flameless thermal degradation has three upmost important drawbacks. First, smoldering can develop unseen until damages are noticed; second, it does not need any external heat to keep progressing, thus behaving as a self-sustaining process; third, it may shift into flaming combustion. Although wooden insulation materials are very competitive as insulators, its use is not permitted in several countries beyond mid-rise buildings due to smoldering hazard. As measuring of physical parameters is difficult and expensive at high temperatures, the objective of this investigation was to develop a theoretical model that comprises most relevant physical phenomena in order to serve as a supportive tool for further development of fire-retardant substances. The constructed model presents the novelty that it can simulate the self-sustaining smoldering without needing any external radiation heat, but only the self-heating generated by its own exothermic reactions. The model was built based on a program of experimental testing that included thermo-gravimetric analyses and differential-scanning calorimetry, being able to predict particle degradation at different heating rates and oxygen concentrations with errors of about 7,5 %. The adequacy of the model was also compared at the structural scale against a non-standard cone calorimeter test with terminal switching off heat radiation to emulate self-sustaining smoldering, which was used as model validation showing fits of about 23 % in consideration of mass loss, mass-loss rate and temperature profile. A comprehensive sensitivity analysis comprising 60 distinct parameters permitted to thoroughly assess the influence of each model input parameter, which is being presented as a ranking from the most to the less influencing parameters that prevent or foster self-sustaining smoldering. Several unexpected conclusions raised, positioning species’ densities, capacities and reaction activation energies as the most important parameters. To the best knowledge of the authors, this is the first model that can simulate the self-sustaining smoldering of wooden insulation materials, so it is expected to contribute on further development of fire retardant compounds for wooden products. <![CDATA[Influences of different drying climates on <em>Eucalyptus camaldulensis</em> wood properties]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100452&lng=es&nrm=iso&tlng=es Abstract: One of the most important disadvantages of the wood material, whose usage is becoming more and more widespread, is the dimensional instability that occurs in its interaction with water. Therefore, studies to improve these drawbacks of wood, remain always up to date. For the mentioned purpose in this study, some chemical, morphological, physical and mechanical properties of Eucalyptus camaldulensis woods, which were naturally dried in outdoor and indoor climate in Eastern Mediterranean (Kahramanmaraş province) atmosphere conditions of Turkey, were investigated. According to the results of the study, chemical properties of Eucalyptus woods dried indoor were measured as merely 0,23 % higher than dried ones outdoor. The results of morphological measurements indicated that the fiber dimensions of eucalypt wood dried in indoor were average 1,48 % lower than the ones dried out outdoor. Also, as a result of statistical analysis, it was found that there were significant differences (ρ &lt; 0,000) between the physical properties of Eucalyptus wood samples indoor and outdoor according to the t-test. At the same time, as a result of the t-test applied to determine the effect of drying conditions on mechanical properties of Eucalyptus wood, modulus of elasticity, compression, tensile, dynamic bending and shear strength did not cause any significant difference between indoor and outdoor, while bending and Janka hardness strengths showed significant differences at ρ &lt; 0,000 level. Finally, when the data obtained as a whole is considered, it can be said that testing of Eucalyptus wood which requires a very sensitive drying in different climates has important contributions on the subject. Regarding eucalypts, which has a high distribution area (20 million hectares) in the world, it is recommended to relevant institutions and organizations to expand and maintain such study in the future. Lastly, according to obtained data from this study, it can be said that the experiments of Eucalyptus woods which require a very delicate drying in different environments provide important contributions on the subject. <![CDATA[Using of versine and sagitta calculations for log sawing optimization, part 1: Circular cross-section]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100453&lng=es&nrm=iso&tlng=es Abstract: Log sawing can be defined as a problem with obtaining squares from a cylindrical shaped raw material, log. There are traditional sawing methods such as live, cant, quarter, etc. for sawmills. However, they cant generally obtain maximum yield due to log and lumber variables for each log. Therefore, many mathematical approaches and computer programs were improved for log sawing. In this study, suitability of two geometrical calculations, versine and sagitta, were tried for log sawing process. Logs were assumed having cylindrical shape and circular cross section. The estimation accuracy of calculations was tested for live and can’t sawing methods with in a drawing software. The results showed that one of versine equations works almost as well as the real dimensions. It is suggested that the equation can be used inside of algorithms for log sawing optimization. However, the real log defects such as taper, irregular cross-section, curvature, etc. should be considered for more realistic yield and accuracy. <![CDATA[Glulam connections assembled with screws in different installation angles]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100454&lng=es&nrm=iso&tlng=es Abstract: Self-tapping screws are the recognized state-of-the-art in fastener technology for timber structures. Combining fasteners of different stiffness, such as self-tapping screws with different installation angles, can be advantageous to simultaneously achieve high connection stiffness and ductility. In this paper, experimental investigations on a total of 65 glued-laminated timber joints assembled with a variety of installation angles including several combinations of self-tapping screws acting axially in withdrawal with self-tapping screws acting laterally are presented. The connection performance was analyzed in terms of the load-carrying capacity, the deformation capacity, the stiffness, and the ductility. The findings demonstrated that joint assemblies with self-tapping screws loaded primarily laterally exhibit low stiffness but high ductility, whereas joint assemblies with self-tapping screws loaded primarily in withdrawal are very stiff but exhibit low ductility. Combining screws in different installation angles created glued-laminated timber connections that combine high stiffness with high ductility. Existing analytical expressions were deemed suitable to estimate load-carrying capacity through simple summation of the different screws’ individual resistances. <![CDATA[Vigas de pino resinoso del noreste de Argentina bajo cargas de larga duración: Deformaciones, recuperación y criterios de diseño]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100455&lng=es&nrm=iso&tlng=es Resumen: En este artículo se presentan y discuten los resultados de un proyecto orientado a investigar las deformaciones bajo carga de larga duración, y la recuperación luego de la descarga, en vigas de pino resinoso de rápido crecimiento (Pinus taeda y Pinus elliottii) cultivado en el noreste de Argentina. La investigación empírica se llevó a cabo en un local sin climatización con el propósito de incorporar fluctuaciones de la temperatura y la humedad relativa ambiente durante el período de carga, utilizando una muestra integrada por 14 vigas de muy variada calidad. Las deformaciones se registraron bajo carga constante durante 392 días y luego libres de carga durante un período de recuperación de 28 días. No obstante, las variaciones climáticas producidas, se encontró una destacada similitud entre el valor de la deformación inicial instantánea de cada viga y el de su recuperación instantánea luego de la descarga. Los resultados también probaron que, independientemente de la calidad de la madera, el desarrollo de las deformaciones diferidas se mantiene estable y las reglas de diseño resultan eficaces para calcular su valor si el nivel de tensión en la viga es inferior al 35 % de su resistencia instantánea.<hr/>Abstract: This paper presents and discusses the results of a project aimed at investigating the deformations under long-term loading, and recovery after unloading, in beams of fast-growing resinous pine (Pinus taeda and Pinus elliottii) cultivated in the northeast of Argentina. A sample containing 14 beams exhibiting great variations in quality was tested in a room without air conditioning with the purpose of incorporating the fluctuations in temperature and relative humidity during the loading period. Deformations were recorded under constant loading through 392 days and then free of load during a recovery period of 28 days. Notwithstanding the climate variations, a remarkable similarity was found between the value of the initial instantaneous deformation of each beam and that of its instantaneous recovery after unloading. Results also proved that, regardless of the wood quality, creep remains stable and design rules are effective to calculate its value if the stress level in the beam is less than 35 % of its instantaneous strength. <![CDATA[Compressive strength parallel to grain of earlywood and latewood of yellow pine]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100457&lng=es&nrm=iso&tlng=es Abstract: The compressive strength parallel to grain of earlywood and latewood from the yellow pine sapwood and heartwood areas was examined in the study. The structure of the basic anatomical elements of wood - tracheids, which conduct water and/or perform the mechanical function - was also characterized. The compressive strength parallel to grain of latewood in the sapwood area was found to be twice as high as the compressive strength parallel to grain of earlywood. The compressive strength parallel to grain of latewood in the heartwood area, on the other hand, was found to be 2,5 times higher than the compressive strength parallel to grain of earlywood. This was due to the density of particular areas of wood and the dimensions of structural elements - tracheids. In the sapwood area, the density of latewood was ca. twice as high as the density of earlywood. Similar relationships were found for heartwood. The thickness of latewood tracheids was found to be 1,5 times greater than the thickness of earlywood tracheids. These relationships were observed in sapwood and heartwood. The diameter of earlywood tracheids in radial direction was twice as large as the diameter of latewood tracheids. These relationships were observed in yellow pine sapwood and heartwood. <![CDATA[Biochemical features of organic extractives from <em>Eucalyptus</em> and <em>Corymbia</em> woods using ethanol as a solvent]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100458&lng=es&nrm=iso&tlng=es Abstract: This study aims to evaluate chemical characteristics, antioxidant and antibacterial activities of organic compounds extracted from three Eucalyptus wood and Corymbia maculate wood using ethanol as a solvent. To obtain the ethanolic extracts, 15 g of a powdered wood sample was mixed with 150 mL of ethyl alcohol 99 % PA by constant mechanical stirring, which was further magnetically mixed at 60 ºC for 24 h. The extractives were analyzed utilizing percent yield, Fourier-transform infrared spectrum, inhibitory index (measured after antimicrobial tests), antioxidant activity, and condensed tannins content. The Eucalyptus dunnii extract showed the highest percent yield. The infrared spectra of all the extractives presented similar profiles, with remarkable bands ascribed to the presence of lipophilic extracts, sterols, fatty acids, and other hydroxylated substances, such as carbohydrates and phenolic compounds. In all cases, the higher the concentration of the extractive was, the higher the antioxidant activity was. The antioxidant activity of Eucalyptus saligna extract stood out since overcame that of the positive control (ascorbic acid). Regarding the condensed tannins content, that extract from Eucalyptus grandis excelled. <![CDATA[Decay capabilities of basidiomycetes colonizing air-seasoning red oak and blackgum railroad ties]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100459&lng=es&nrm=iso&tlng=es Abstract: Fungi cultured from air-seasoning blackgum and red oak timbers were assessed for their ability to cause wood decay using two hardwoods and one softwood species in an AWPA E10 soil block test. Weight losses were greatest for bigleaf maple and tended to be much lower on southern pine. Almost a quarter of the 35 taxa tested caused less than 5 % weight loss, suggesting they posed a relatively low decay risk, even under ideal laboratory conditions; despite all fungi tested having the ability to depolymerize wood. Three of the four fungi causing the largest weight losses were brown-rot fungi, although brown-rot fungi represented an only small proportion of the total isolates from the original hardwood timbers. These results illustrate the wide array of decay capabilities of fungi colonizing air-seasoning red oak and blackgum timbers, and the potential of many isolates to negatively affect wood properties through biodeterioration. <![CDATA[Comparative performance of Polymeric Xylenol Tetrasulfide versus creosote in an AWPA E7 field stake test]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100460&lng=es&nrm=iso&tlng=es Abstract: A need exists to develop new organic, environmentally benign wood preservatives for industrial applications to replace the older creosote and pentachlorophenol systems. In this study the performance of creosote at three retentions was compared to a new wood preservative candidate formulated with Polymeric Xylenol Tetrasulfide (PXTS) in an E7 AWPA field study using two sets of southern pine and yellow poplar field stakes treated with three creosote retentions or five retentions of PXTS. The stakes were installed at two test sites and evaluated after 3,5 years, 6 years, and 14 years exposure. After six years of exposure at both sites, which is double the minimum recommended exposure period of three years’ field data for AWPA submission of a proposed new preservative system, the average decay ratings data for southern pine stakes after three years exposure was not sufficient to definitively determine which system provides superior protection against decay and termite attack (Creosote at the AWPA UC4B pole retentions versus pine stakes treated with much lower PXTS levels). However, after a longer exposure time of 14 years the data conclusively shows that pine stakes treated to the utility pole AWPA UC4B creosote retention performed poorer at both sites against decay and termite degradation than pine stakes treated with 26 Kg/m3 PXTS. Similar results were obtained with the yellow poplar stakes. We conclude that: 1) much longer E7 exposure times are necessary then the minimum recommended three years in the AWPA GDA Standard for submission of new systems to definitively determine the efficacy of a proposed oil borne system compared to the efficacy of a traditional organic preservative for commercial applications, and 2) long term field PXTS performance against decay and termite deterioration is equal or greater than that obtained with creosote at about four times the PXTS retention. <![CDATA[Determination of the strength performance of table frames]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100461&lng=es&nrm=iso&tlng=es Abstract: The objective of this study was to investigate the relation of diameter of pilot hole and screw, and machining accuracy on withdrawal strengths of the screws and durability of the dining tables. For this purpose, fasteners and material types on the failure loads of dining table corner joints have been analyzed experimentally and statistically. Double ended thread bolts with different drilling regimes have been used as fastener types. A parallel investigation of rigidity and durability of tables, and withdrawal capacities in accordance with the according to current norms, was performed. According to the results, it is concluded that the diameter of the drilled hole significantly influences the value of the withdrawal strengths of the screws. By analyzing the effect of drilling diameter on the rigidity of tables, a statistically significant difference was determined. As the drilling diameter increases, the rigidity of the examined dining tables decreases. <![CDATA[Experimental and numerical study on a novel bamboo joint for furniture considering effect of loading type on mechanical parameters used in finite element method]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100462&lng=es&nrm=iso&tlng=es Abstract: The effect of loading type (tension, compression and bolt-bearing) on mechanical properties (elastic modulus, Poisson’s ratio and ultimate strength) of Moso bamboo (Phyllostachys heterocycla var. pubescens) in longitudinal direction was evaluated in this study. In addition, experimental and numerical tests were conducted to evaluate withdrawal force capacity and bending moment resistances of a novel demountable bamboo-bolt joint considering effect of loading type on mechanical parameters used in finite element method. The results showed that loading type had significant effect on mechanical properties of Moso bamboo, especially, for ultimate strength; the values of mechanical properties evaluated in this study measured in tension were all much higher than those measured in bolt-bearing state and followed by compression accordingly; in tension, the tensile elastic modulus and Poisson’s ratio measured at outer surface were bigger than those at inner surface, respectively; finite element method got more accurate results using the mechanical parameters measured in compression than those in tension and bolt-bearing states; the bamboo-bolt joint proposed in this study can be used in lightweight bamboo structures through improving the embedding strength of beech wood in bamboo culm. In conclusion, one should consider the loading type used to obtain the mechanical parameters inputted in finite element method. In addition, further studies will focus on effect of size and geometry of samples used to determine mechanical properties used in finite element method, and the method of improving embedding strength of beech wood in bamboo culm to increase withdrawal force capacity and bending moment resistances of the demountable bamboo-bolt joint proposed in this study. <![CDATA[Particle image velocimetry technique for analysis of retractibility in woods of <em>Pinus elliottii</em>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100463&lng=es&nrm=iso&tlng=es Abstract: The aim of this work was to verify the ability to use the Particle Image Velocimetry technique for measurements of dimensional variations resulting from wood retractability of Pinus elliottii wood, initially saturated and with the surface marked with multiple dots of ink randomly distributed, was used in this work to apply the Particle Image Velocimetry technique. The specimens were dried and images were captured during the process. The images obtained were processed by the Particle Image Velocimetry algorithm and the deformations that occurred were calculated. For comparison, a conventional method (pachymeter) was used to measure the dimensions of the specimen during drying. The variation in dimensions obtained on the surface of the specimens from the Particle Image Velocimetry technique was 2,28 % for the radial direction and 0,20 % for the longitudinal direction of the fibers. With the standardized method, these values were 2,18 % for the radial direction and 0,21 % for longitudinal. The reduction in the average area of the specimens was 3,85 % by the Particle Image Velocimetry technique and 3,77 % by the conventional methodology. It was concluded that the Particle Image Velocimetry technique was able to accurately measure the displacements on the surface of the Pinus elliottii specimens, resulting in values statistically similar to those reached through the use of the conventional measurement method, demonstrating its reliability. <![CDATA[Efecto en las propiedades mecánicas de una resina pinífera modificada biodegradable, al utilizarla como compatibilizante o acoplante en formulaciones elastoméricas sin o con fibra de agave y hule de poli(estireno-butadieno). Un paso hacia la formulación de elastómeros verdes]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100464&lng=es&nrm=iso&tlng=es Resumen: En este trabajo se valora la eficiencia de una resina de pino modificada biodegradable (A-30), al utilizarla como compatibilizante o acoplante para sustituir al resorcinol (que es tóxico y no es biodegradable), comparando las propiedades mecánicas (contra formulaciones preparadas usando el sistema resorcinol-hexametilentetramina (R-HMT) en: a) polímeros elastoméricos reticulados de estireno-butadieno (SBR), y: b) compósitos de SBR reforzados con fibra de agave de desecho. Para la comparación como compatibilizante, aquí se preparan formulaciones equivalentes con A-30 o R-HMT. Para la comparación de los compósitos equivalentes, se varía el agente de acoplamiento (R-HMT o A-30) y la cantidad de azufre como agente de entrecruzamiento (2,5 partes por cien de elastómero (phr), 7,5 phr o 15 phr). En las pruebas de tracción a temperatura ambiente, y el análisis mecanodinámico con barridos de temperatura (de - 70 °C a 40 °C) y frecuencia (de 0,4 Hz a 40 Hz), se obtuvieron incrementos en módulos (hasta un 74 % en módulo de Young) y en capacidad de deformación (hasta 260 %), para los materiales conteniendo el agente A-30, por encima de las formulaciones en las que se usó el resorcinol. El mejor desempeño como compatibilizante o acoplante del A-30, se reflejó también con claridad morfológicamente mediante microscopía electrónica de barrido, al mostrar mayor compacidad en la matriz formulada y mayor cercanía entre fibra y matriz en muestras fracturadas criogénicamente. Se ha demostrado aquí, que el A-30 puede sustituir al par R-HMT con éxito, ya que funciona mejor como agente compatibilizante o acoplante y es biodegradable. Este tipo de agentes tiene un gran potencial para contribuir al desarrollo de elastómeros y compósitos flexibles amigables con el medio ambiente.<hr/>Abstract: In this work, the effectiveness of a biodegradable modified pine rosin (Amberyl MP-30 (A-30)), is evaluated as compatibilizer or coupling agent to substitute resorcinol (which is toxic and non-biodegradable) in elastomeric formulations. Their mechanical properties are compared vs formulations containing resorcinol-hexamethylenetetramine (R-HMT) in: a) styrene-butadiene elastomers (SBRs), and: b) SBR composites reinforced with discarded agave fibers. For the comparison as compatibilizer, equivalent formulations containing resorcinol or A-30 are prepared. Likewise, for the equivalent composites comparison, the coupling agent (R-HMT or A-30) and sulfur amount as crosslinking agent (2,5 parts per 100 rubber (phr), 7,5 phr or 15 parts per 100 phr) are varied. The Tensile tests at room temperature, and the mechanodynamic analysis using sweeps of temperature (from - 70 °C to 40 °C) and frequency (from 0,4 Hz to 40 Hz), allowed the observation of moduli improvements (up to 74 % in Young modulus) and deformation capacity (up to 260 %) for the materials with A-30 over the materials where resorcinol was used. The better performance as compatibilizer or coupling agent of the A-30 was also shown with clarity in the morphological characterization, showing higher compacity in the formulated polymer matrix, and higher closeness between matrix and fibers, comparing with fractured samples using R-HMT. It has been shown here, that formulating rubbers or elastomeric composites with A-30 and HMT, can successfully substitute the R-HMT pair, because it works better as compatibilizer or coupling agent and is biodegradable. Agents of natural origin like this one, have a great potential to contribute to the development of elastomers and flexible composites that are environmentally friendly. <![CDATA[Automatic identification of charcoal origin based on deep learning]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100465&lng=es&nrm=iso&tlng=es Abstract: The differentiation between the charcoal produced from (Eucalyptus) plantations and native forests is essential to control, commercialization, and supervision of its production in Brazil. The main contribution of this study is to identify the charcoal origin using macroscopic images and Deep Learning Algorithm. We applied a Convolutional Neural Network (CNN) using VGG-16 architecture, with preprocessing based on contrast enhancement and data augmentation with rotation over the training set images. on the performance of the CNN with fine-tuning using 360 macroscopic charcoal images from the plantation and native forests. The results pointed out that our method provides new perspectives to identify the charcoal origin, achieving results upper 95 % of mean accuracy to classify charcoal from native forests for all compared preprocessing strategies. <![CDATA[Comparison of some wood properties of juvenile black pines of different origin planted in the same habitat]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2021000100466&lng=es&nrm=iso&tlng=es Abstract: Black pine (Pinus nigra) is a significant raw material source for the forest products industry in Turkey. The purpose of this research was to study some chemical, anatomical, physical, and mechanical properties of wood obtained from juvenile black pines planted in Kavaklıdere - Muğla, originating from five different locations: Muğla, Balıkesir, Denizli, Bursa, and Kütahya. Although pines originating from Muğla and Balıkesir were good in terms of wood properties, those from Denizli, Bursa, and Kütahya exhibited no remarkable features. Black pine of Muğla origin was recommended for planting in Kavaklıdere and similar habitats, whereas pines of Denizli, Bursa, and Kütahya origins were not recommended. However, pine of Balıkesir origin may be an alternative to that of Muğla origin for black pine plantations at Kavaklıdere and similar sites.