Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> https://scielo.conicyt.cl/rss.php?pid=0718-221X20130001&lang=pt vol. 15 num. 1 lang. pt <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>MORPHOLOGICAL AND MECHANICAL CARACTERIZATION OF RECYCLED THERMOPLASTIC FOAMS REINFORCED WITH WOOD SUB-PRODUCTS</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100001&lng=pt&nrm=iso&tlng=pt El objetivo del presente estudio fue observar la morfología y caracterizar las propiedades mecánicas de materiales compuestos de madera y plásticos reciclados espumados. Se mezcló polietileno de alta densidad reciclado con fibra de madera de Pinus radiata D.Don (pino radiata) de 60 mesh. Las concentraciones de fibra fueron de 15 y 25% en peso, el polímero se espumó con un agente químico ACA (azodicarbonamida) y se utilizó anhídrido maleico MAPE (Epolene E-20) como agente de acoplamiento. Los compuestos se obtuvieron usando un proceso de extrusión en un equipo doble tornillo. Los resultados demostraron que el agente acoplamiento tiene un efecto positivo sobre la adherencia del polímero reciclado y la fibra de madera. La densidad de los compuestos disminuyó con el agente espumante y las propiedades mecánicas de dureza, impacto, módulo de elasticidad en flexión y tracción fueron superiores para los compuestos no espumados. Se Se concluyó que al aumentar la concentración de fibra aumentan las propiedades mecánicas de los compuestos a excepción de la tenacidad que al incorporar el agente espumante disminuyeron ligeramente.<hr/>The objective of the present study was to observe the morphology and characterize the mechanical properties of wood plastic composite foams. Recycled high density polyethylene was mixed with Pinus radiata D. Don (radiata pine) wood fiber of 60 mesh. The fiber concentrations were 15 and 25% by weight. The compounds were foamed with a chemical agent ACA (azodicabonamide) and MAPE (Epolene E-20) was used as a coupling agent. The composites were obtained by twin-screw extrusion. The results showed that the coupling agent has a positive effect on the adhesion of the recycled polymer and wood fiber. The density of the compounds decreases with blowing agent and the mechanical properties of hardness, impact, modulus of elasticity in bending and tension were higher for unfoamed composites. It was concluded that increasing the concentration of fiber increases the mechanical properties with the exception of impact resistance of the compounds and incorporating the blowing agent slightly. <![CDATA[<b>VARIABILITY OF PHYSICAL, MORPHOLOGICAL AND THERMAL PROPERTIES OF <i>Eucalyptus</i></b> <b><i>nitens </i>BARK FIBER</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100002&lng=pt&nrm=iso&tlng=pt Se estudió la variabilidad en las propiedades morfológicas, físicas y térmicas de la fibra de corteza de Eucalyptus nitens (Deane & Maiden) en veinticuatro árboles procedentes de dos sitios y seis familias; mediante técnicas de microscopía óptica convencional, microscopía electrónica (SEM) y análisis termo-gravimétrico (TGA). Dichas propiedades son determinantes para que una fibra lignocelulósica alcance una posible aplicación industrial como material de refuerzo en una matriz termoplástica. Se detectaron diferencias estadísticas significativas en las propiedades de la fibra al analizar el sitio de procedencia de las muestras, la familia y la altura de fuste. Destacan en los resultados de propiedades físicas el espesor promedio de la capa de corteza (4.4 mm), su peso específico (0.757), sus propiedades morfológicas tales como razón longitud/diámetro de fibra (l f/d f= 69.14) y presencia de fibra (45%) en este material. La estabilidad térmica de esta fibra natural hasta los 200ºC y la baja temperatura de fusión de termoplásticos como el polietileno de alta densidad (HDPE); indican que las fibras de corteza de esta especie son una buena opción para aplicarla como material de refuerzo en matrices termoplásticas.<hr/>It was studied the variability in morphological, physical and thermal properties of fiber bark of Eucalyptus nitens (Deane & Maiden) coming from twenty four trees, two sites and six families; using techniques such as conventional light microscopy, electron microscopy (SEM) and thermo-gravimetric analysis (TGA). Such properties are relevant for a lignocellulosic fiber to have a possible industrial application as reinforcement material in a thermoplastic matrix. Significant statistical differences were detected in the fiber properties by analyzing the site of origin of the samples, family and stem height. Standing out in the results of physical properties, the average thickness of the bark layer (4.4 mm), its Specific Gravity (0.757), its morphological properties such as length/diameter of fiber (l f/d f= 69.14) and fiber presence (45%) in this material. The thermal stability of this natural fiber to 200ºC and low melting temperature of thermoplastics such as High Density Polyethylene (HDPE); indicate that the bark fibers of this species are a good option to apply as a reinforcement material in thermoplastics matrices. <![CDATA[<b>EFFECT OF THE BENCH SCALE EXTRACTION CONDITIONS ON <i>Pinus radiata</i> BARK EXTRACT YIELD, ANTIOXIDANT PROPERTIES AND COMPOSITION</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100003&lng=pt&nrm=iso&tlng=pt Many pine bark extracts have antioxidant properties. This work examined bench scale extraction on the yield, the composition and antioxidant properties of Pinus radiata. Acetone solvent (98.7% w/w at 120 °C) yielded maximum phenols concentration, tannins concentration, anti-radical activity (DPPH) and reducing activity (FRAP), although its extraction yield was the lowest. When the organic solvent in the mixture decreased, the chelating activity increased (ICA) and antiradical and reducing activities decreased. The extract largest yield was obtained with water at 120ºC, but the antioxidant properties were relatively poor. Taxifolin (dihydroquercetin) and catechin were the main extract components detected by RP-HPLC. The best extraction conditions for high extractive yield and antioxidant properties was achieved with ethanol/water at 120 °C. <![CDATA[<b>ULTRAVIOLET RAY AGING EFFECT ON LATHE CHECK SURFACE PROPAGATION IN <i>Eucalyptus nitens</i> Plywood</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100004&lng=pt&nrm=iso&tlng=pt El objetivo de este estudio fue evaluar el efecto de un envejecimiento acelerado mediante rayos ultravioleta y condiciones ambientales controladas sobre la propagación de grietas de debobinado y agrietamiento superficial, al simular las condiciones de servicio en exterior de tableros contrachapados fabricados con chapas provenientes de tres alturas de trozas de familias segregadas de Eucalyptus nitens y bajo condiciones de debobinado controladas. Para realizar el ensayo se uso una cámara de envejecimiento acelerado UV (rayos ultravioleta) capaz de reproducir el espectro de radiación emitido por el sol bajo condiciones climáticas controladas de humedad relativa, condensación y temperatura, de acuerdo a la norma ASTM G154-06. Mediante análisis de imágenes se evaluó el nivel de agrietamiento superficial porcentual en el área envejecida de las probetas, además del ancho de grietas en la superficie de los tableros. El análisis de imágenes del área envejecida de las probetas mostró que el ancho de grietas y área de agrietamiento disminuye con respecto a la altura de la troza, existiendo diferencias significativas en agrietamiento, entre familias segregadas de Eucalyptus nitens. Además las grietas de debobinado en las chapas se propagan hacia la superficie, siendo éstas responsables del agrietamiento en las caras de tableros contrachapados. Basado en los resultados del estudio, el envejecimiento acelerado mediante UV es un buen indicador para evaluar la propagación de grietas de debobinado y el agrietamiento superficial en muestras de tableros contrachapados expuestos al exterior.<hr/>The objective of this study was to evaluate the effect of accelerated aging with UV rays and controlled environmental conditions in lathe check propagation and surface cracking, simulating the conditions of outside service of plywood made with veneers from three heights of logs families segregated of Eucalyptus nitens and under conditions of controlled peeling process. To perform the test using an accelerated aging chamber UV (ultraviolet rays) can reproduce the spectrum of radiation emitted by the sun under controlled climatic conditions of relative humidity, condensation and temperature according to ASTM G154-06. By image analysis assessed the level of surface cracking in the area percentage of the specimens aged in addition to the width of cracks on the plywood surface. Image analysis of the aging of the specimen area showed that the crack width and crack area decreases with respect to the height of the log, showing significant differences in cracking between segregated families of Eucalyptus nitens. Besides lathe checks in the veneers spread to the surface, these being responsible for the cracking in the plywood surface. Based on the results of the study, UV-accelerated aging is a good indicator for evaluating the late check propagation and surface cracking in samples exposed to the exterior plywood. <![CDATA[<b>THERMAL MODIFICATION OF <i>Eucalyptus grandis</i> WOOD</b>: <b>VARIATION OF COLORIMETRIC PARAMETERS</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100005&lng=pt&nrm=iso&tlng=pt The color modifications in Eucalyptus grandis thermally modified wood were investigated. One hundred eighty specimens (10 x 10 x 200 mm) were prepared and thermally modified in an electric kiln for 4 and 8 h at 180-240ºC. The color parameters (L*, a*, b*, C*, h* and ΔE) were determined by the CIE-L*a*b* method on radial and tangential sections of untreated and treated wood. The results indicated the darkening of specimens in the radial and tangential sections. Both sections showed variation of L* between 73 and 30, a* between 9 and 5 and b* between 20 and 8. The thermally modified wood at 180 and 200ºC showed similar patterns, equally at 220 and 240ºC. The time of exposure indicated significance just in treatment at 200ºC. <![CDATA[<b>THE EFFECT OF WOOD SPECIES ON THE ANTI-SKID RESISTANCE OF COATINGS</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100006&lng=pt&nrm=iso&tlng=pt The anti-skid resistance of six coatings (Alfa, Beta, Gamma, Lambda, Mu and Theta) designed for outdoor wood flooring were tested in chestnut (Castanea sativa Mill.) and pine (Pinus pinasterAit.) using a Portable Skid Resistance Tester according to standard ENV 12633. Film thickness, coating retention level, and presence of mineral particles were determined for each coating. Furthermore, the liquid water absorption coefficient of chestnut was determined in accordance with standard UNE-EN 1609, to relate all parameters. The highest value of skid resistance in both chestnut and pine was obtained with coating Mu (49.75) and coating Gamma (53.16), respectively. Film thickness and coating retention level were consistently higher for pine than for chestnut. Gamma presented the highest presence of minerals. For chestnut the absorption coefficient of liquid water in the tangential direction was 0.0056 ± 0.0010 kg·m-2·s-0.5, considerably lower than the value found for pine: 0.011 kg·m-2·s-0.5. The different performance of the system wood-coating, and consequently the anti-skid resistance, was attributed to the absorption properties of the different species. <![CDATA[RADIATA PINE pH AND BUFFERING CAPACITY: EFFECT OF AGE AND LOCATION IN THE STEM]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100007&lng=pt&nrm=iso&tlng=pt In this work the effect of age and location within the stem on pH and buffering capacity of radiata pine sapwood was investigated. Mature and juvenile wood samples from three different heights in the trunk were obtained from 20, 25, and 30 year-old trees. Aqueous wood extracts from the samples were used to determine the pH and buffering capacity of wood. Results show a significant effect of age and location in the tree, although a strong interaction among all factors was also detected. In general sapwood tended to be more acidic in the lower part of trees, but juvenile wood showed to be more acidic than mature wood. From both type of wood tested, juvenile wood was more sensitive to change its pH and buffering capacity with the height and age. The effect of wood pH and buffering capacity in the manufacture of wood composites is discussed and further research is recommended to determine whether the variations detected in this study can affect the curing of resins and quality of wood base composite manufactured with radiata pine wood. <![CDATA[<strong>BONDING BEHAVIOR OF <i>Eucalyptus benthamii</i> WOOD TO MANUFACTURE EDGE GLUED PANELS</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100008&lng=pt&nrm=iso&tlng=pt The main objective of this study was to evaluate the performance of Eucalyptus benthamii Maiden et Cambage wood for the production of edge glued panels. Wood pieces with planed and sanded surfaces were bonded using cross-linking polyvinyl acetate (PVAc) and polyurethane (PUR) based adhesives, at pressures of 0.7 MPa and 1.0 MPa. The same adhesives were used for finger jointing at a pressure of 1.5 MPa. The bonding strength was determined through glue-line shear strength and bending test for finger jointing. According to the results, the pressure and surface preparation variables did not influence the glue-line shear strength of the adhesive PVAc, whereas for the PUR adhesive strength was influenced by the pressures and machining used. All treatments met the minimum values required by the standard; however, the highest bonding strength was found in the sample glued with PUR adhesive at a pressure of 1.0 MPa and sanded surface. The highest modulus of rupture was obtained in the samples glued using PVAc, while the modulus of elasticity was not affected by the type of adhesive used. These results enabled concluding that with regard to its technological properties assessed in the present study, E. benthamii wood is suitable for the production of edge glued panel. <![CDATA[<b>ANATOMICAL ELEMENTS FORMATION IN HARDWOODS</b>: <b>A REVIEW FROM A GENOMIC PERSPECTIVE</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100009&lng=pt&nrm=iso&tlng=pt La madera es un recurso natural renovable que proporciona materia prima para la construcción, generación de energía, fibras para la producción de pulpa y papel, paneles y tableros, y más recientemente para biocombustibles y biomateriales, lo que la hace el quinto producto comercial más importante del mundo. Diferencias en las propiedades físicas, químicas y anatómicas de la madera la hacen un material altamente variable y complejo. Estas propiedades influyen de forma directa en su valor comercial y derivan del tamaño, forma y arreglo de los diferentes tipos de células, y de la estructura y composición química de la pared celular de las distintas células del xilema. Éstas a su vez, están controladas por distintos factores ambientales y genéticos que regulan los procesos de biosíntesis de los diferentes componentes de la madera. Para aplicar herramientas moleculares y genéticas que permitan optimizar los procesos de selección de especies forestales con características superiores, es necesario entender los mecanismos que regulan estas propiedades, lo cual incluye comprender la dinámica de la estructura de la pared celular desde la formación de la célula cambial inicial hasta la formación de las células diferenciadas finales que conforman el xilema. La presente revisión explora las principales características anatómicas y el proceso de xilogénesis, enfocado particularmente en angiospermas, discutiendo los aspectos genéticos involucrados en la determinación de las características anatómicas de la madera, como dimensiones de los elementos celulares y características de la fibra, basándose en diferentes estudios realizados con especies de los géneros Populus y Eucalyptus, además de la planta modelo Arabidopsis thaliana.<hr/>Wood is a renewable natural resource that provides raw material for construction, power generation, fibers for pulp and paper production, panels and boards, and more recently, biofuels and biomaterials, making it the fifth most important commercial product in the world. The wood is a highly variable and complex material that has different chemical, physical and anatomical properties that are influencing their commercial value. These properties depend on the size, shape and arrangement of the different cell types, and of the structure and chemical composition of the xylem cell wall. At the same time, these properties are controlled by different environmental and genetic factors that regulate the biosynthesis processes of the different wood components. To apply molecular and genetic tools to optimize the selection processes of forest species with superior traits, it is necessary to understand the mechanisms that regulate these properties, as the dynamics of cell wall structure from the initial cambial cell formation to the final differentiated cells formation that compose the xylem. This review explores the main anatomical traits and the xylogenesis processes, particularly focused in angiosperms, discussing the genetic aspects involved in the determination of wood anatomical characteristics, as cellular elements and fiber characteristics, based on different studies with species of the Populus and Eucalyptus genus, besides the model plant Arabidopsis thaliana. <![CDATA[<b>INFLUENCE OF LIQUEFIED AND CCB CONTAINING LIQUEFIED WOOD ON GROWTH OF WOOD DECAY FUNGI</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0718-221X2013000100010&lng=pt&nrm=iso&tlng=pt There are high amounts of post-consumed protected waste wood removed from service every year. The residual biocides, including copper, chromium and boron from CCB (Cu, Cr, B) in post-consumed wood that was protected with biocides may cause environmental problems during waste management, for example during land filling. Therefore, the aim of this study was to find out if Cu and Cr in the processed waste wood, previously treated with CCB, can be re-used as a wood preservative or in coatings made of liquefied wood. Liquefaction of CCB containing waste wood could be as well the first step in the elimination process of metals. So, the optimal conditions for liquefaction of CCB (Cu, Cr and B) containing black poplar (Populus nigra L.) wood were established and compared with liquefaction of uncontaminated black poplar wood. The reactants for liquefaction of black poplar wood sawdust were ethylene glycol (EG) and sulphuric acid. It was observed that in the last stages of the liquefaction process, the presence of Cu, Cr and B did not have any influence on liquefaction yield (LY), while their influence was observed in first stages of the solvolytic reaction. Investigations of fungicidal properties of uncontaminated and CCB containing liquefied wood showed higher antifungal efficacy of liquefied wood without Cu, Cr and B than of liquefied wood that contained CCB. In the tested concentration range, the presence of Cu even promoted the growth of selected wood decay fungi. One of the reasons for higher toxicity of liquefied black poplar sawdust without Cu, Cr and B, was its very low pH value.