Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 14 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Surface properties of MDF coated with calcite/clay and effects of fire retardants on these properties</b>]]> The coating of wood and wood panel surfaces basically serves for surface protection and its surface can be improved at various user areas. Different application methods are used for the coating of MDF surface. These are methods such as curtain coating, spraying, rolling, knife, etc. In this study, suitability of pigment coating method instead of the traditional surface coating methods used for coating MDF panels and the effects of fire retardants on surface properties of MDF coated by the best appropriate coating mixture was investigated. Calcite and clay were used as coating pigment and latex, urea formaldehyde, and melamine formaldehyde were used as adhesive. Coating/adhesive mixture obtained was applied to MDF panels with knives. Before the analysis, test samples were put to condition room and they were kept in there for 1 week. According to the results obtained, the best appropriate coating material was found as calcite. 22% concentrated melamine formaldehyde as adhesive and 0.25 mm as coating thickness was determined better than other combinations. Borax, boric acid and zinc borate as fire retardant were added to calcite /melamine formaldehyde with 22% mixture. So, the effects of fire retardant on surface characterization were determined. Surface properties of coated MDF panels tested were found lower than standard requirements except for abrasion resistance. <![CDATA[<b>Why Simulate a Sample of Recycled Wood?</b>]]> Wood products follow the same cycle as other materials: manufacture, use and disposal. For certain applications, chemical additives are added to wood to increase its durability against biological and physical attack. At the end of life, waste wood is chipped or crushed before being recovered as raw material for new products or as fuel for energy. In recycled wood, there is the potential that some wood particles are contaminated by hazardous substances, such as organic or heavy metal preservatives. Therefore there is a need for a quality control method of assessing recovered wood that is on the one hand sufficiently precise and on the other not too expensive to preclude the use of recycling wood in to new products. This paper covers some preliminary research that is part of a large study that aims to develop a robust analytical method for recovered wood. However the extreme variability of recovered wood makes it difficult to develop such protocols on real recovered wood samples. Consequently, model chip piles with known contamination levels were created to simulate real world recovered wood samples. <![CDATA[<b>Efficiency of natural wood extractives as wood preservatives against termite attack</b>]]> Wood extractives play a major role in the protection of wood against termite and fungal attack. Wood extractives from three hard wood species of Milicia excelsa, Albizia coriaria and Markhamia lutea that are known to be very resistant against termite attack and fungal decay were studied to assess their role as wood preservatives in Uganda. Acetone, hexane and distilled water were used in the extraction of these compounds from the outer heartwood of the selected durable species. Extraction was done using a soxhlet extractor. The extractives obtained were used to treat Pinus caribaea and Antiaris toxicaria species known to be susceptible to termites and fungal attack. Treated blocks were then exposed to Macrotermes bellicosus termites in the field. It was observed that wood extracts used as preservatives improved the resistance of less durable samples to termite attack by 50% compared to the controls. It was also observed that removal of extractives decreased resistance of the durable samples. It can be concluded that wood extractives contribute greatly to the protection of less durable wood species against termite attack. <![CDATA[<b>Wood treated with Zn and Mn and effectiveness of treatment with borax to prevent leaching</b>]]> Continuando con el estudio del uso de una solución obtenida en un proceso de reciclado de baterías domésticas como preservante para madera, se estableció un primer cementerio de estacas basado en la norma EN 252, que evalúa la durabilidad adquirida por probetas de Pinus taeda L. Dicha solución es ácida, contiene 32 g l-1 de Zn y 15 g l-1 de Mn como sulfatos, libre de metales pesados; en ensayos de laboratorio ha demostrado propiedades funguicidas e insecticidas específicos, a concentraciones menores a 3% en Zn (máxima concentración obtenida del reciclado). A las probetas tratadas con la mencionada solución por el método de célula llena, se les realizó un tratamiento posterior antilixiviante con bórax al 2%, por pincelado y por célula. Se comparó la durabilidad natural y la adquirida, con dicha solución (con o sin bórax), con arseniato de cobre cromatado (CCA) a dos retenciones. A 32 meses del inicio del ensayo, las concentraciones de Zn de 3% y mayores con el bórax aplicado por el método de célula llena son las más efectivas. Se analizaron además los agentes de deterioro de madera (insectos, hongos y bacterias) presentes en las probetas.<hr/>As part of the study of the application of a solution obtained from a domestic batteries recycling process as a wood preservative, a field stakes test was established to assess the acquired durability in loblolly pine (Pinus taeda L.) specimens following the internationally accepted standard EN 252. This solution is acidic, containing 32 g l-1 Zn and 15 g l-1 of Mn as sulfates and free of heavy metals; in laboratory tests the solution proved to have specific fungicidal and insecticidal properties against organisms that degrade wood, at concentrations lower than 3% Zn (the highest concentration obtained from the recycling process). The specimens treated by the full cell method with the mentioned solution were afterwards treated with 2% in borax by the full cell method and by brushing in order to prevent leaching. Natural and acquired durability are compared using different concentrations of the studied solution as well as chromated copper arsenate (CCA) at two different retention levels. At 32 months, 3 % and higher concentrations of Zn and borax applied by full cell method showed to be the most effective. Main degrading agents (insects, fungi and bacteria) found in the specimens are also described. <![CDATA[<strong>Jointing knives and tool wear effect in the surface quality of radiata pine moldings</strong>]]> Se estudia el efecto que ejerce el talón de rectificado de cuchillos en acero rápido sobre la calidad superficial de molduras sólidas de pino radiata. Se analizan los defectos fibra encontrada (grano velloso o fuzzy grain) y fibra astillada (grano arrancado o torn grain) en molduras de perfil plano que se generan en el proceso de moldurado. Se evaluó la relación talón de rectificado - calidad superficial, a través de dos procedimientos, en el primero se realiza el rectificado en forma sistemática, y en el segundo sólo una vez, al inicio del proceso, para en ambos casos cuantificar los defectos generados en las piezas. Los resultados indican que la aparición de fibra encontrada y fibra astillada se pueden relacionar con la distancia de corte y con el estado del talón de rectificado, asimismo, la calidad del material de corte y las condiciones de operación deben tenerse en cuenta ya que de estos factores depende el rendimiento del proceso.<hr/>The effect exerted by the land of jointing of high speed steel knives is studied on the surface quality of radiata pine solid moldings. Fuzzy grain and torn grain are analyzed on flat molding profile. To evaluate these defects, the relationship land of jointing - surface quality was assessed through two procedures, on the first the jointing was done systematically, and on the second only once, early in the process. The results indicate that fuzzy grain and torn grain are related to cutting distance and jointing process, the quality of the cutting material and operating conditions must be taken into account because of these factors depends the process performance as well. <![CDATA[<b>Wettability and surface roughness characteristics of medium density fiberboard panels from rhododendron (<i>Rhododendron ponticum</i>) biomass</b>]]> Wettability and surface roughness properties of medium density fiberboard (MDF) panels made from Rhododendron biomass were examined in this study. Rhododendron dominates the understory layer of the forests throughout the Black Sea Region in Turkey with substantial biomass potential. This study was conducted to evaluate suitability of Rhododendron fiber for MDF production. For the experiments, rhododendron and commercially-manufactured-chip (Pinus sylvestris L. and Quercus robur L.) with 11% moisture content were used. The mixing ratios of rhododendron with commercially-manufactured-chip were 100:0, 75:25, 50:50, 25:75 and 0:100 %, respectively. Commercial urea formaldehyde (UF) adhesive was used as a binder. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements by the stylus method were taken perpendicularly to the fiber. There was a significant difference (p=0.05) between surface roughness parameters (Ra, Rz, Rq, and Ry). The results obtained in this study revealed that all the panels have met the general purpose-use requirements of European Norm (EN). It was found that panels made with a 25/75 ratio of rhododendron to commercially-manufactured-chip had a significantly lower contact angle (88.14º) than panels made with a 100/0 ratio (117.91º). Surface roughness measurements are based on four roughness parameters, average roughness (Ra), mean peak-to-valley height (Rz), root mean square roughness (Rq), and maximum peak-to-valley height (Ry) were considered to evaluate the surface characteristics of the panels and supported the above findings as the panels made with a 25/75 ratio had a slightly rougher surface with average values of 2.929 ìm (Ra). From the tests performed, we conclude that increasing the rhododendron mixing portion increased surface roughness and decreased wettability. Based on these results, rhododendron biomass could be an alternative raw material for MDF manufacturing. <![CDATA[<b>Effect of bark stripping on the electrical impedance of<i> Quercus suber</i> leaves</b>]]> This study examined the effect of bark stripping on the electrical impedance parameters of cork oak young leaves between 40Hz and 100 kHz. This was a new application of the electrical impedances spectroscopy (EIS) in plant science. Various stripping coefficients (CD) were applied on the trees. Bark stripping is expected to affect water metabolism of leaves and therefore changes in the EIS parameters are expected as well. Single-DCE (ZARC) model was used as equivalent circuit for leaves. Several electrophysiological parameters of this model were compared with moisture content (MC) of the leaves. Intracellular resistance (Ri), extracellular resistance (Re) and relaxation time (τ) of the leaves increased during 14 days after stripping while the distributed coefficient (Ψ) and MC decreased. Significant correlation between EIS parameters, MC and trees treatments were found. <![CDATA[<b>Effect of initial planting density in dynamic modulus of elasticity in standing trees and logs of 28 years old radiata pine plantation in sandy soil, Chile</b>]]> En un ensayo de densidad de plantación inicial (DPI), se evaluó el efecto de cuatro tratamientos (2500, 1667, 833 y 625 árb·ha-1) en el módulo de elasticidad dinámico (MOEd) de Pinus radiata D. Don, de 28 años, creciendo sobre un suelo de la serie Arenales, en la Región del Biobío, Chile. El MOEd se determinó con tecnología acústica utilizando el método de tiempo de vuelo (Tv) para árboles en pie y posterior a su volteo se usó el método de resonancia (Res) para dos trozas de 5 m de longitud (primera y segunda troza), extraídas desde la base y a lo largo del fuste de cada árbol. La DPI no afectó significativamente el MOEd de los tratamientos más densos (2500, 1667 y 833 árb·ha-1), tanto para árboles en pie, como para las dos trozas. En cambio, el tratamiento menos denso (625 árb·ha-1) presentó el mayor MOEd, significativamente diferente en árboles en pie y la primera troza, y similar entre la primera y segunda troza.<hr/>The influence of initial planting density (DPI) on the dynamic modulus of elasticity (MOEd) was examinated at a 28 years old Pinus radiata D. Don spacing experiment with four treatments (2500, 1667, 833 and 625 stem·ha-1) growing on sandy soil, in the Biobío Region, Chile. The MOEd acoustic technology was determined using the method of time of flying (Tv) for standing trees and the resonance method (Res) for two logs of 5 m long, extracted from the tree base to the top of each tree. MOEd was not significantly influenced by DPI in high initial stocking treatments (2500, 1667 and 833 stem·ha-1), both standing trees and logs level. In contrast, the lowest initial stocking treatment (625 stem·ha-1) had the highest MOEd, significantly different in standing trees and the first the log, and similar between the first and second log. <![CDATA[<strong>Fracture in <i>Eucalyptus nitens</i> wood</strong>: <strong>effect of nanomechanical properties, ultrastructure and anatomical level</strong><strong> </strong>]]> Se realizó un estudio para indagar en las causas y posibles factores que originan la fractura en la estructura de la madera de Eucalyptus nitens. Para esto se examinó el comportamiento nanomecánico de la lamela media (LM), de las capas S1 y S2 de la pared celular. También se determinaron el número, área y diámetro de los vasos que están asociados a niveles de agrietamiento extremos (alto y bajo). Se estudiaron dos familias de Eucalyptus nitens procedentes de dos sitios de la 8va Región de Chile. Mediante el cálculo y análisis de la razón de ductilidad (E/H), se determinó que la LM es más quebradiza que la capa S1, y ésta a su vez más quebradiza que la capa S2; existiendo diferencias significativas en la ductilidad de estas capas. La LM y capa S1 se comportan como materiales resilientes, no así la capa S2. La diferencia en el módulo de resiliencia se relacionó con las mayores tensiones de corte que se presentaron en las interfaces LM/S2 y S1/S2. La caracterización de los vasos mostró que la familia con nivel de agrietamiento mayor, tiene mayor frecuencia, área y diámetro de vasos, los cuales contribuyen a la concentración de esfuerzos en la estructura celular de la madera. Los resultados evidenciaron que la capa S1 fue más débil que la capa S2 y LM dada la diferencia en resistencia entre ellas y que complementado con las tensiones internas que se generan en el proceso de crecimiento del árbol se producen las microgrietas.<hr/>This study was conducted to investigate the causes and posibles factors related to fractures in the cellular structure in Eucalyptus nitens. Nanomechanical cell wall properties at the middle lamella level (ML), S1 and S2 layers were evaluated. In addition, the area, and diameter of vessels were measured. These parameters were associated with extreme levels of cracking (high and low) in two Eucalyptus nitens families. The samples were taked from two sites of the 8th Region of Chile. The analysis of the ductility ratio (E/H) demonstrated that the ML is more brittle than the S1 layer; and the S1 is more brittle than S2 layer. The ML and S1 layer behave like resilient materials, but not the S2 layer. The difference in the modulus of resilience was related to higher shear stresses at the ML/S2 and at S1/S2 interfaces. The characterization of the vessels showed that the families with greater level of cracking have also lower frequency and greater area and diameter of vessels The S1 layer was weaker tan S2 layer and LM due to their difference in resistance between them and combined with the internal stresses might propagate the microcracks. <![CDATA[<b>Effect of thermal rectification on colors of <i>Eucalyptus Saligna </i>and <i>Pinus caribaea</i> Woods</b>]]> Eucalyptus saligna and Pinus caribaea var. hondurensis woods underwent a variety of thermal rectification treatments (from 120ºC to 180ºC) to evaluate the effect of heating on their colorimetric properties. The following color parameters were measured: lightness (L), a* coordinate (green-red coordinate), b* coordinate (blue-yellow coordinate), saturation (C), and tonality angle (H). This study demonstrates that thermal rectification can be regarded as a tool for adding value to wood through color modification by heating. Results also suggest that thermal rectification might be a tool for homogenizing wood tonality and reddish color between species. Both tested species have shown very distinct colorimetric behaviors as a function of thermal treatments. The conifer was more resistant to thermal darkening than the hardwood while exposed to temperatures below 160ºC. The green-red coordinate (a*) and the tonality angle (H) tended to be homogenized for both species, as they decreased in eucalyptus, and increased in pinus, as a function of heating. The effect of wood heating on the blue-yellow coordinate (b*), saturation (C), and tonality angle (H) was likely to be opposite between both tested species.