Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> http://www.scielo.cl/rss.php?pid=0718-221X20170003&lang=en vol. 19 num. 3 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<strong>Machine strength grading of boards of resinous pines cultivated in the northeast of Argentina</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300001&lng=en&nrm=iso&tlng=en En este artículo se presentan y discuten los resultados de una investigación orientada al análisis de modelos mecánicos para clasificar por resistencia tablas de pino resinoso cultivado en el nordeste de Argentina. El programa experimental se llevó a cabo según los lineamientos de las normas europeas EN sobre una muestra de 233 tablas de tamaño estructural ensayadas a flexión y sobre otra conteniendo 100 tablas ensayadas en tracción paralela a las fibras. Se diseñaron dos modelos, uno empleando el módulo de elasticidad global como parámetro simple y otro basado en un parámetro combinado que incluyó al módulo de elasticidad junto a la densidad y la nudosidad. Los resultados mostraron una mayor eficiencia en los modelos desarrollados que en el método visual adoptado por la norma IRAM. Esa mayor eficiencia se puso de manifiesto en i) el alcance de los valores característicos adoptados para las propiedades principales en la normativa vigente; ii) un aumento del rendimiento en los grados estructurales y, iii) una disminución de la dispersión en los valores del módulo de elasticidad dentro de cada clase resistente, lo cual permite estar en línea con la variabilidad adoptada por las reglas de diseño estructural del país.<hr/>The present paper reports the results of an investigation regarding the analysis of models for machine strength grading boards of resinous pine cultivated in the northeast of Argentina. An empirical research project with one sample containing 233 boards in structural sizes subjected to static bending and one sample enclosing 100 boards subjected to tension was carried out according to the European standards. One model based on a single parameter (modulus of elasticity) and another one based on a combined parameter (modulus of elasticity + density + knot ratio) were designed. Results showed that the efficiency of both models was higher than that of the visual method adopted by the standard IRAM. The high efficiency of both models was made evident by: i) the achievement of the characteristic values adopted by standards for the main properties; ii) an increase of the yield in the structural grades and, iii) a decrease of the spread results for modulus of elasticity within each strength class, which makes it possible to satisfy the variability requirements adopted by the national design rules. <![CDATA[<strong>Polypropylene-based wood-plastic composites</strong>: <strong>Effect of using a coupling agent derived from a renewable resource</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300002&lng=en&nrm=iso&tlng=en In this work, post-consumer polypropylene and wood flour from Pinus elliottii were used to produce wood plastic composites. The effect of polypropylene grafted with itaconic acid used as a coupling agent on mechanical properties, thermal stability and morphology of the composites was investigated and compared with the composite developed with polypropylene grafted with maleic anhydride, commonly used as coupling agent in wood plastic composites. Composites with 30 wt% of wood flour and 2 wt% of coupling agent were produced in a co-rotating twin-screw extruder and after were injection molded. The mechanical properties showed that flexural strength improved on 29% and 35% with addition of polypropylene grafted with itaconic acid and polypropylene grafted with maleic anhydride respectively, when compared with the wood plastic composites without coupling agent. On the other hand, the incorporation of polypropylene grafted with itaconic acid does not change the impact strength values significantly. Additionally, the temperature corresponding to 3 wt% of weight loss determined by thermogravimetry for composites with polypropylene grafted with itaconic acid increased by 14°C when compared with wood plastic composites without coupling agent, while addition of polypropylene grafted with maleic anhydride increased approximately 6°C the composite thermal stability. A morphological study revealed the positive effect of the polypropylene grafted with itaconic acid on the interfacial bonding of recycled polypropylene and wood flour. <![CDATA[<strong>Larvicidal activities of some bark and wood extracts against wood-damaging insects</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300003&lng=en&nrm=iso&tlng=en This study investigates the larvicidal activities of plant extracts and tannins against wood-damaging insects. Scots pine (Pinus sylvestris), beech (Fagus orientalis), and poplar wood (Populus tremula) were subjected to larvae of Spondylis buprestoides (Coleoptera: Cerambycidae) by impregnating them with mimosa (Acacia mollissima), quebracho (Schinopsis lorentzii) and redpine bark (Pinus brutia) extracts. At the end of the 6-month experiment, the numbers of dead and live larvae as well as the mean mass losses of woods were determined. In terms of wood species, the lowest larva resistance was observed in Scots pine wood, while the highest larva resistance was achieved by beech wood. The lowest mass losses and the highest dead termite rates in all tree species were observed when the concentration of mimosa and quebracho extracts was 12%. On the other hand, the pine bark extract showed a lower larvicide effect than the other two extracts. <![CDATA[<strong>Effect of silvicultural management on wood density from short rotation forest systems</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300004&lng=en&nrm=iso&tlng=en Los sistemas forestales de rotación corta (SFRC) son establecidos en condiciones que difieren del manejo convencional, con una alta densidad de especies arbóreas en el plantío y mayores dosis de fertilización; así como periodos de cosecha más cortos. Aún hoy, son pocos los estudios sobre la calidad de biomasa producida en estos sistemas. Este trabajo tuvo por objetivo analizar el efecto del espaciamiento del plantío y fertilización sobre la densidad básica del fuste de Eucalyptus urophylla × Eucalyptus grandis (clone C219) en un sistema de rotación corta a los dos años de edad. Los resultados muestran que el espaciamiento del plantío y la fertilización produjeron un efecto significativo sobre la densidad de madera. La densidad básica fue mayor en los plantíos con espaciamientos menos densos (2380 árboles ha-1) próximo de 375 kg m-3, y en el de mayores dosis de fertilizantes (140 g planta-1) de 379 kg m-3. Los valores encontrados fueron próximos al de otras especies forestales manejadas en sistemas de rotación corta para bioenergía en el mundo.<hr/>The short rotation forest systems are managed under conditions that differ from conventional management with greater density planting and fertilizer levels, also shorter harvesting cycles. Even today, there are few studies about the quality of the biomass produced on these systems. This work aimed to analyze the effect planting spacement and fertilizing levels in the stem basic density of Eucalyptus urophylla × Eucalyptus grandis (clone C219) from short rotation system at two years of age. The results showed that the density was affected significantly by planting spacement and fertilization. It was higher for the lower planting spacement (2380 trees ha-1) about 375 kg m-3 and greater fertilizer level (140 g plant-1) to 379 kg m-3. The values found were close to other forest species managed in short rotation systems for bioenergy in the world. <![CDATA[<strong>Xilotecnia of the wood of </strong><em><b>Acacia schaffneri</b></em><strong> from the State of Hidalgo, Mexico</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300005&lng=en&nrm=iso&tlng=en The genus Acacia spp belongs to the family Leguminosae, with more than 1300 species distributed naturally in all continents except Europe. In Mexico there are 85 species, of which 46 are endemic, most located in arid and semiarid regions, being Acacia coulteri and Acacia farnesiana the most widely distributed. The aim of this study was to determine the technological characteristics of the wood of Acacia schaffneri. To determine the anatomical characteristics, the methodology of Autonomous Chapingo University's wood anatomy laboratory was used; for the physical properties, standards NOM EE-117-1981 and NMX-EE-167-1983 were used, and in calculating the mechanical properties the mathematical formulas were employed. The wood is reddish brown and has interlocked grain with diffuse porosity, aliform confluent parenchyma and in confluent bands, and crystals and gums. The proportion of cells was 11,87% vessel elements, 50,65% fibers 27,76% axial parenchyma and 9,81% ray parenchyma. Basic density was 880 kg/m³, tangential, radial, axial and volumetric shrinkage values were 10,57%; 4,97%; 0,10% and 15,82 % respectively, and fiber saturation point was 19,97%. The mechanical properties were very high, so it can be used in the manufacture of floors and in building constructions. <![CDATA[<strong>Determination of decay resistance against </strong><em><b>Pleurotus ostreatus</b></em><strong> and </strong><em><b>Coniophora puteana</b></em><strong> fungus of heat-treated scotch pine, oak and beech wood species</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300006&lng=en&nrm=iso&tlng=en The objective of this study, to investigate decay resistance against Pleurotus ostreatus and Coniophora puteana fungus of heat-treated (ThermoWood method) Scotch pine, oak and beech wood species. Scotch pine (Pinus sylvestris), oak (Quercus petreae) and beech (Fagus orientalis) wood species were heat treated at 190°C for 2 h, 212°C for 1 h and 2 h by the ThermoWood® method. Untreated and heat-treated specimens were exposed to white-rot fungus (Pleurotus ostreatus) and brown-rot fungus (Coniophora puteana) for 12 weeks according to procedures defined in JIS K 1571 standard. After weight losses of all specimens were calculated. According to the results, least weight loss was determined on heat treated at 212°C for 2 h. Heat treatment can be used effectively against fungal attack for Scotch pine, oak and beech wood species. <![CDATA[<strong>Improvement of the durability of heat-treated wood against termites</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300007&lng=en&nrm=iso&tlng=en Thermal modification is an attractive alternative to improve the decay durability and dimensional stability of wood. However, thermally modified wood is generally not resistant to termite attacks, limiting the field of application of such materials. One way to overcome this drawback is to combine thermal modification treatment with an additional treatment. One such treatment is the impregnation of a boron derivative associated with appropriate vinylic monomers, which takes advantage of the thermal treatment to polymerise these monomers for boron fixation. Using this strategy, we recently showed that an impregnation of borax (2 or 4% boric acid equivalent) dissolved in a 10% aqueous solution of polyglycerolmethacrylate followed by thermal treatment under nitrogen at 220°C protects wood from both termite and decay degradations, even after leaching. Additionally, wood samples treated with a 10% polyglycerolmethacrylate aqueous solution and subjected to thermal treatment at 220°C presented improved resistance to termites while avoiding boron utilization. Based on these results, we investigate the effect of impregnation with two types of vinylic monomers, which are already used in the presence of boron, followed by thermal treatments at different temperatures. We evaluate termite and decay durability of wood to evaluate if thermal modification associated with light chemical modification could be a solution for utilization of thermally modified materials in termite-infested areas. <![CDATA[<strong>Thermal analysis of oriental beech sawdust treated with some commercial wood preservatives</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300008&lng=en&nrm=iso&tlng=en In this study, investigation of the thermal properties of Oriental beech (Fagus orientalis) sawdust treated with 0,25; 1 and 4,70% aqueous solutions of Adolit KD-5, Wolmanit CX-8 and Tanalit-E were performed by using thermogravimetric analysis, differential-thermal analysis, and differential-thermal analysis under argon atmosphere. Results were compared with the untreated wood (control). It was found that the treatment with Adolit KD-5, Wolmanit CX-8 and Tanalit-E decreased the Tmax (maximum degradation temperature) and increased residual char amount with respect to the control sample. Increases in the concentration of applied preservatives promote the char formation. It was found that the char content after pyrolysis experiment had good agreement with the boric acid amount in wood preservatives. <![CDATA[<strong>Physical, mechanical and thermal properties of wood/zeolite/plastic hybrid composites</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300009&lng=en&nrm=iso&tlng=en Effect of zeolite content on the physical, mechanical and thermal properties of wood plastic composites was investigated in this study. To meet this objective, pine wood flour (0, 10, 20, 30, 40, 50 wt%) with compatibilizing agent, zeolite (0, 10, 20, 30, 40, 50 wt%), and polypropylene were compounded in a twin screw co-rotating extruder. The mass ratio of the wood flour to polypropylene was 50/50 (w/w) in all compounds. Test specimens were produced using injection molding machine from the pellets. Physical and mechanical, and thermal (Thermogravimetry Analysis/Differential Scanning Calorimetry) properties of the wood plastic composites were determined. The water absorption and thickness swelling properties of wood plastic composites improved with increasing zeolite content. The flexural and tensile properties of the wood plastic composites decreased with increasing zeolite content. All the wood plastic composites provided the values of flexural strength (58,4-72,9 MPa) and flexural modulus (2718-5024 MPa) that were well over the requirement by the standard specified in ASTM D 6662. The mass loss rates values of wood plastic composites increased with increasing zeolite contents. The Differential Scanning Calorimetry analysis showed that the melt crystallization enthalpies and degree of crystallization of wood plastic composites decreased with increasing zeolite content. The decrease in the Tc and Xc indicated that zeolite was the poor nucleating agent for the wood plastic composites. <![CDATA[<strong>Using resistography method for prediction of wood basic density in standing trees of </strong><em><b>Pinus radiata</b></em>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300010&lng=en&nrm=iso&tlng=en El objetivo de esta investigación fue desarrollar modelos de estimación de la densidad básica de la madera a nivel de árbol completo y a diferentes alturas de árboles de Pinus radiata, a partir de la resistencia de la madera medida con el resistógrafo, a la altura del pecho a 1,3 m sobre el nivel suelo (DAP). Se utilizó una muestra de 29 árboles de 15 años de edad, obtenidos al azar, en un ensayo clonal establecido en la Región del Bío-Bío, Chile. Para cada árbol, en seis diferentes alturas relativas del fuste, se determinó la resistencia de la madera y la densidad básica, a partir de 174 mediciones realizadas con el resistógrafo y en muestras de rodelas. Los resultados obtenidos indicaron que tanto la densidad básica como la resistencia de la madera disminuyeron significativamente en función de la altura del árbol, en la dirección base y altura comercial, en un 16,8% y 38,5%, respectivamente. Los valores de resistencia media determinados al DAP, presentaron una variación entre árboles de 11% y 19%. Se generó un modelo que estima la densidad básica a nivel de árbol completo utilizando como única variable predictora la resistencia media de la madera medida al DAP, con un error de estimación de 11,9 kg/m³, el cual no disminuye al incorporar variables de estado de árbol (DAP y HT). A partir de este modelo se generó un método para estimar la densidad básica en diferentes secciones del árbol.<hr/>The objective of this research was to develop models for estimation of the basic density of wood at full tree level and at different heights of Pinus radiata standing trees, measured from the wood resistance using the resistography at DBH level. A sample of 29 trees of 15 years old was used for the experiment. The trees were selected in a clonal field test established in the Bío-Bío Region, Chile. For each tree, 174 measurements were made with the resistograph and wood disks were obtained to determine the wood resistance and the basic density at six different relative heights of the stem. As a result, a significant decrease of the basic density and resistance of the wood was observed, from the base to the apex of the trees, with values of 16,8% and 38,5% of decrease, respectively for each variable. The average for the resistance values determined at DBH varied between 11% and 19% among the measured trees. A prediction model was generated to estimate the basic density at the tree level using the average resistance of the wood measured to the DBH. The adjustment parameters of the model was a root mean square error value of 11,9 kg/m³, which did not decrease when other variables of tree (DBH or total height) were incorporated. As a main conclusion, a new method to estimate the wood basic density at different sections of the tree was generated using the adjusted model. <![CDATA[<strong>The influence of raw material growth region, anatomical structure and chemical composition of wood on the quality properties of particleboards</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300011&lng=en&nrm=iso&tlng=en In the present study, the impact of raw material grown region on the physical, mechanical, surface properties and formaldehyde emission of the particleboard was investigated. Ailanthus altissima wood grown in Trabzon had longer fiber length and thicker fiber and trachea cell wall than those of the wood grown in Artvin. The highest amounts of lignin, ash, condensed tannin and solubility values were found in wood grown in Artvin. Ailanthus altissima wood grown in Trabzon had higher amounts of cellulose and hemicellulose than those of the wood grown in Artvin. Particleboards made from wood grown in Artvin had worse surface quality and mechanical strength properties than those of panels made from wood grown in Trabzon. On the other hand, the results showed that particleboards produced from wood grown in Artvin had lower thickness swelling and formaldehyde emision values than those of the panels produced from wood grown in Trabzon. <![CDATA[<strong>Properties particleboards manufactured with </strong><em><b>Eucalyptus urophylla</b></em><strong>  wood</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300012&lng=en&nrm=iso&tlng=en Este es un estudio exploratorio para dar uso a la madera de Eucalyptus urophylla en la elaboración de tableros aglomerados de partículas. Por lo tanto, los objetivos fueron determinar sus propiedades físico-mecánicas y evaluar los resultados bajo norma Alemana Instituto Alemán de Normalización (DIN) y Venezolana Comisión Venezolana de Normas Industriales (CONEVIN). Para los tableros de densidad real de 731 kg/m³, la absorción de agua promedio a 2 y 24 horas no cumple de acuerdo a las normas, para el caso de los tableros de densidad real 831 kg/m³ cumple con la norma. La variación del espesor (hinchamiento) promedio por inmersión en agua a 2 horas para los tableros con densidad de 731 kg/m³ no cumple con lo exigido en ambas normas, pero si cumple con los requerimientos para 24 horas. Para el caso de los tableros con densidad de 838 kg/m³ la variación de espesor a 2 y 24 horas cumplió con las normas. Respecto de las propiedades mecánicas, tanto el módulo de ruptura en flexión estática como la tensión perpendicular (adhesión interna) para ambos niveles de densidad superaron el valor mínimo aceptado en las normas, demostrando que las partículas de madera de Eucalyptus urophylla presentan características tecnológicas adecuadas para la fabricación de tableros de partículas de densidad media.<hr/>This is an exploratory study on the feasibility of using Eucalyptus urophylla wood for the production of particleboards. Therefore, the aims were to determine their physical and mechanical properties and to evaluate the results with German Standards Institute (DIN) and Industrial Standards Commission Venezuelan (COVENIN). For boards with a real density of 731 kg/m³, the average water absorption at 2 and 24 hours does not meet the standards, in the case of real density boards 831 kg/m³ that fulfilled with both standards. The average water absorption at 2 and 24 hours of boards for the actual density of 731 kg/m³ did not comply with the requirements for both standards, unlike the particleboards with density equal 831 kg/m³ that fulfilled with them. The average thickness variation (swelling) by immersion in water for 2 hours for boards with a density of 731 kg/m³ did not meet the requirements of both standards, but meet the requirements for 24 hours. In the case of boards with a density of 838 kg /m³, thickness variation at 2 and 24 hours meet with the standards. Regarding mechanical properties both, the modulus of rupture in static bending and perpendicular tension (internal bond) for both real density levels exceed the minimum accepted by standards, demonstrating that E. urophylla wood exhibit suitable technological characteristics for particleboards medium density manufacture. <![CDATA[<strong>Enhancing dimensional stability of oriented strand composites within biorefinery</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2017000300013&lng=en&nrm=iso&tlng=en The objective of this study was to investigate the effects of hot water extraction process on the dimensional stability of oriented strand composites. Aspen wood strands were extracted using various severity factor levels. Phenol formaldehyde and polymethylene diphenyl diisocyanate resins were used for production of the oriented strandboard panels. Six panel groups were produced from the extracted or unextracted aspen wood strands. The dimensional stability of the material was evaluated by measures of equilibrium moisture content and thickness swell and water absorption after soaking in water for 2 hours and 24 hours. Results obtained in this study showed that thickness swell and water absorption values significantly decreased with the hot water extraction process, with the thickness swell of phenol formaldehyde bonded panels decreasing 70% after 2 hours soaking. The panels with polymethylene diphenyl diisocyanate resin exhibited lower thickness swell and water absorption relative to the panels prepared with phenol formaldehyde resin. Equilibrium moisture content values of the panels bonded with both phenol formaldehyde and polymethylene diphenyl diisocyanate resin decreased with the extraction process. The findings of this work indicate that hot water extraction process could be effectively used to produce oriented strand composites having an enhanced dimensional stability property.