Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 14 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<strong>Influence of uron resins on the performance of UF resins as adhesives for plywood</strong>]]> Uron resin, a kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared. Several modified UF resins were obtained from mixing uron resins with normal UF resins as well as synthesizing UF resin with uron resin as raw material. This work demonstrated that the introducing of the uron structure reduced free formaldehyde content of UF resin and formaldehyde emission levels in bonded plywood panels significantly, the former were reduced by 76% and 84% in the latter. The synthesis time of uron resin can be shortened to 8 hours. The test result of free formaldehyde content, formaldehyde emission levels and bond strength indicated that specimen of 20 parts uron resin synthesized in 8 hours mixed with 100 parts UF resins (F/U molar ratio of 1.3) had a potential advantage to industrial application. The beneficial effect of uron resin on the performance of UF resin can be attributed to the opening of uron cycle structure and the following reaction with free formaldehyde and its oligomeric glycol forms. <![CDATA[<b>Physical and mechanical properties of bark flour or wood flour of <i>Pinus radiata</i> recycled polyethylene composites</b>]]> Se ensayaron compuestos de polietileno de baja densidad reciclado y harina de madera y de corteza de Pinus radiata D. Don, para evaluar el efecto del contenido de harina y la densidad del compuesto sobre la absorción de agua e hinchamiento, dureza Rockwell, resistencia a la tracción y módulo de elasticidad en tracción. Estos compuestos fueron fabricados mediante moldeo por inyección y sin aditivos, en proporciones harina/polietileno de 20/80, 40/60 y 60/40 peso/peso. Se determinaron varias propiedades físicas y mecanicas de los compuestos. Los resultados fueron sometidos a pruebas de comparación de medias y Análisis de Regresión Lineal Múltiple (ARLM), seguido por el método paso a paso o Stepwise (SWM). Los resultados indican que las propiedades físicas aumentaron con el incremento harina, al igual que la rigidez de los compuestos, mientras que la resistencia a la tracción y a la penetración tendieron a disminuir. Los compuestos con harina de corteza fueron más rígidos, absorbieron menos agua y se hincharon menos que los compuestos con harina de madera, en cambio, no se observaron diferencias estadísticas en la dureza, y sólo el compuesto con 20% de harina de corteza presentó mayor resistencia a la tracción que el resto de los compuestos. El contenido de harina fue la variable que más afecta las propiedades evaluadas, excepto para el E y la dureza de los compuestos con harina de madera, las que fueron mayormente afectadas por su densidad.<hr/>Composites made of recycled low density polyethylene and wood or bark flour of Pinus radiata D. Don were tested, the effect of the flour content and density of the composites on physical and mechanical properties were determinated. These both types of composites were prepared by injection moulding and without chemical additives at 20/80, 40/60 and 60/40 of flour/polyethylene (w/w). Several physical and mechanical properties were measured. The results were tested for comparison of means and Multiple Linear Regression Analysis (ARLM), followed by the method stepwise (SWM). The results indicate that the physical properties and the E increased with increasing flour content, while the tensile strength and the hardness tended to decline. The composites made with bark flour had higher stiffness, absorbed less water and swelled less, and show similar hardness than the composite made with wood flour, but only the composite with 20% (w/w) of bark flour showed greater tensile strength than the others composites. The content of flour was the variable that most affects the properties evaluated, except to the E and the hardness of the wood flour composites, they were most affected by their density. <![CDATA[La-modified SBA-15/H<sub>2</sub>O<sub>2</sub> systems for the microwave assisted oxidation of organosolv beech wood lignin]]> In this manuscript, the influence of organosolv beech wood lignin (LOB) on its oxidative conversion to high added-value phenolic aldehydes is discussed. Environmental friendly and low-cost H2O2 was used as the oxygen atom donor. The catalyst was prepared by immobilizing Lanthanum compounds onto the periodic mesoporous channels of siliceous SBA-15. The activity of the La/SBA-15 was investigated towards oxidation of LOB in the presence of hydrogen peroxide as oxidant with microwave irradiation. Considering the characteristics of LOB, an unexpected low syringaldehyde concentration at 10min of reaction time (1.47 g/L, corresponding to 15.66% yield) was obtained; the other major product was vanillin at 25min (0.78 g/L, i.e., 9.94% yield). The high reactivity of syringyl nuclei may be pointed out as the main reason for the faster production and degradation of syringaldehyde in oxidation. Other low molecular weight phenolic products were found: vanillic acid, syringic acid and minor quantities of aceto-derivatives. The profile of products concentration with the reaction time of catalytic oxidation with microwave irradiation are shown and discussed with reference to the investigated lignin features. The mechanism of the microwave catalytic oxidation for LOB under alkaline conditions was proposed. <![CDATA[<b>The potential use of organosilane water soluble nanomaterials as water vapor diffusion retarders for wood</b>]]> The retarding effect of organosilane water soluble nanomaterials (nano-zycosil and nano-zycofil) on water vapor diffusion through poplar wood (P.nigra) was evaluated in comparison with that of clear coatings (sealer and nitrocellulose lacquer and polyester lacquer) using cup and sorption methods. Two drying methods were applied to dry the nanomaterials -coated substrates: oven drying at temperature of 103 ± 2 °C for 24 hrs, and climatically drying at temperature of 25 °C and relative humidity of 65% for 20 minutes. The results showed that both coating materials decreased the water vapor diffusion rate through the wood. The sealer and nitrocellulose lacquer coating represented a stronger effect on the diffusion coefficient of wood compared to the other coatings. In this case, the nano-zycosil represented a better performance compared to the nano-zycofil. Furthermore, the drying method of the nanomaterials -coated substrates can impact the nanomaterials performance. The water vapor diffusion through the oven-dried substrates was faster than that through the climatically dried ones. <![CDATA[<strong>Heartwood and sapwood content in <i>Eucalyptus globulus</i> and <i>Acacia melanoxylon </i>growing in Argentina</strong>]]> Los objetivos del trabajo fueron determinar la proporción de duramen y el ancho de la albura en Eucalyptus globulus y Acacia melanoxylon, estudiar su variación axial en el fuste y establecer relaciones entre duramen y el diámetro y volumen del fuste. Se muestrearon 10 árboles de E. globulus de 9 años y 10 árboles de A. melanoxylon de 19 a 32 años, en dos sitios de Buenos Aires, Argentina. En cuatro rodajas por árbol (base, 1.3 m, 30 % y 50 % de la altura total), se determinaron el área, volumen y porcentaje de duramen y el ancho de albura. En E. globulus el porcentaje de duramen disminuyó significativamente hacia el ápice (46 % en la base y 30 % en la última altura muestreada); en A. melanoxylon no hubo diferencias significativas (48 % a 31 %). El ancho de albura fue relativamente constante a lo largo del fuste, siendo en promedio de 26 mm para ambas especies. El volumen de duramen con respecto al volumen del fuste fue de 37 % para E. globulus y de 43 % para A. melanoxylon. Se hallaron regresiones lineales significativas entre el volumen del duramen y dos variables de interés comercial e inventarial: volumen del fuste y diámetro a la altura de pecho.<hr/>The aims of the work were to determine heartwood and sapwood content in Eucalyptus globulus and Acacia melanoxylon trees, to study their variation and to establish relationships between heartwood and log volume and diameter. Ten trees of 9-years old E. globulus and ten trees of A. melanoxylon between 19 and 32 years old were sampled in Buenos Aires, Argentina. Heartwood area, volumes and percentage, and sapwood width were measured and calculated at four discs by tree (base, 1.3 m, 30% and 50% of total height). E. globulus heartwood percentage decreased significantly from the base upwards (46% at the base and 30% at the last sample height); in A. melanoxylon axial differences were not significant (48% to 31%). Sapwood width was relatively constant with sample height and its means were 26 mm for both species. Average heartwood volume represented 37 % of the log volume for E. globulus and 43 % for A. melanoxylon. For both species, linear regression models show positives relationships between heartwood volume and two variables of commercial and inventorial importance: log volume and diameter at breast height. <![CDATA[<strong>Identification of knotty core in <i>Pinus radiata</i> logs from CT images: Comparative Study</strong>]]> El objetivo de este estudio fue comparar la precisión de los algoritmos de máxima verosimilitud (MV) y otro basado en redes neuronales artificiales (RNA), en la identificación del cilindro nudoso a partir de imágenes TC (Tomografía Computarizada) de trozas podadas de pino radiata (Pinus radiata D.Don). Para este fin, treinta trozas podadas fueron seleccionadas y luego escaneadas en un escáner médico multi-slice de rayos X (Tomografía Computarizada). Del total de imágenes TC obtenidas del escáner, 270 fueron seleccionadas para este estudio. Estas imágenes TC fueron clasificadas utilizando ambos algoritmos y los mapas temáticos obtenidos de este proceso, fueron posteriormente filtrados utilizando un filtro median de 7 x 7. Los resultados de la evaluación cuantitativa indicaron que el cilindro nudoso puede ser identificado con una precisión de 98.5 % y 96.3 % utilizando el clasificador MV y RNA, respectivamente. Aunque ambos algoritmos presentaron elevados valores de precisión para identificar el cilindro nudoso, el análisis estadístico de estos resultados arrojo diferencias significativas entre ambos valores de precisión; por lo tanto se concluye que el algoritmo de máxima verosimilitud presenta un mejor desempeño que el algoritmo basado en redes neuronales artificiales, en la identificación del cilindro nudoso en imágenes TC de trozas de pino radiata (Pinus radiata D.Don).<hr/>The aim of this study was to compare the accuracy of both the maximum likelihood classifier (ML) algorithm and another one based on an artificial neural networks classifier (ANN) algorithm for knotty core identification in CT images of pruned radiata pine (Pinus radiate D. Don) logs. For this purpose, thirty pruned radiata pine logs were chosen and then scanned in an X-ray multi-slice medical scanner (Computed Tomography (CT)). From the total CT images obtained, a sample of 270 CT images was selected for this study. This CT images were classified using both methods and the thematic map obtained afterwards, were filtered by a 7 x 7 median filter. Quantitative assessment results showed that knotty core can be identified with 98.5 % and 96.3 % accuracy by using the ML and ANN classifiers respectively. Although both algorithms showed a high capacity level to detect knotty core statistical analysis showed significant differences among those accuracy values; this is an indication that the maximum likelihood classifier algorithm shows a better performance compared to the algorithms based on artificial neural networks for knotty core identification in CT images of radiata pine logs. <![CDATA[<b>Evaluation of wooden materials deteriorated by marine-wood boring organisms in the Black Sea</b>]]> Marine borers can destroy wooden structures exposed to the marine environment and cause great monetary loss. In the region of Amasra of the Black Sea in Turkey, ships continue to be built from wood, mainly Castanea sativa (sweet chestnut) and Quercus petraea (sessile oak) and therefore are subject to destruction by marine borers. Copper-chromium-arsenic (CCA), used to be one of the most common wood preservatives used in Turkey. However, in this area its efficacy against marine borers is unknown. The resistance of untreated and CCA-treated samples of chestnut, oak and Scots pine (Pinus sylvestris) was examined and after twelve months evaluated in two ways, EN 275, and a non-destructive measurement for dynamic modulus of elasticity (MOE). Untreated samples, particularly Scots pine were severely attacked by Teredo navalis. Treated samples of oak and chestnut were moderately attacked while treated samples of Scots pine sapwood and heartwood were sound. Severity of wood boring attack determined using MOE showed a very good correlation with that determined by visual assessment in untreated wood, and a good correlation for treated wood. Dynamic MOE allows rapid on-site evaluation rather than measurements within a laboratory and also without causing damage to the structures being evaluated. <![CDATA[<b>Effect of growing conditions on fungal yeast-mycelium dimorphism of <i>Ophiostoma piceae</i> albino strain PcF2A29</b>]]> Los hongos del género Ophiostoma promueven la ocurrencia de la mancha azul en madera de coníferas, afectando significativamente la calidad en los productos de apariencia. Para la prevención de la mancha azul se han empleado productos químicos de diferente naturaleza. El control biológico de la mancha azul con cepas albinas del género Ophiostoma aparece como una alternativa de promisorio potencial. Algunos de estos hongos cuando cultivados en medio líquido presentan un crecimiento dimórfico, con alta proporción de micelio, que dificulta su utilización. El dimorfismo, transformación reversible de las morfologías levadura y micelio, es controlado por factores químicos y del entorno. En esta investigación mediante la aplicación de un diseño factorial completo de dos niveles, se estudió el efecto de cuatro variables operacionales sobre el crecimiento levaduriforme de la cepa albina PcF2A29 de la especie Ophiostoma piceae (Münch) H. & P. Syd., creciendo en medio de cultivo líquido complejo. Los resultados mostraron que el tamaño del inóculo, la temperatura y la interacción tamaño del inóculo-temperatura tuvieron un efecto estadístico significativo sobre el crecimiento levaduriforme de la cepa albina PcF2A29de la especie O. piceae. De éstas variables, el tamaño del inóculo resultó ser el efecto más importante y explicó el 53% de la variabilidad observada. Estos resultados sugieren por primera vez, en la especie O. piceae, la existencia de un mecanismo de detección del quórum asociado a la variable tamaño del inóculo.<hr/>Ophiostoma fungi promote the occurrence of blue stain in coniferous wood, affecting the appearance wood products quality. Thus, different chemical products have been attempted to control them. Biological control of these sapstaining fungi, using albino strains of Ophiostoma looks like a successfully alternative to be applied. However, some Ophiostoma strains present a dimorphic behavior in liquid culture, which make them difficult to work with. Fungal dimorphism is defined as an environmentally and chemically controlled, reversible transformation of the yeast and mycelia morphologies. In this research, a two level factorial design was applied for evaluating the effect of four operative variables on albino strain PcF2A29 (Ophiostoma piceae (Münch) H. & P. Syd.) yeast-like growth a complex liquid medium. The results showed that inoculum size, temperature and their interaction had a statistically significant effect on yeast-like growth of albino strain PcF2A29. The most important effect was inoculum size. This factor explained 53% of the observed variability. The effect of inoculum size on yeast-like growth, phenomenon that is described in the O. piceae species by the first time with this paper, would be associated to quorum sensing activity. <![CDATA[<b>Chemical acetylation treatment in radiata pine wood</b>]]> Al saturar la pared celular de la madera con anhídrido acético, se reemplazan los grupos hidroxilos libres de las macromoléculas celulosa y hemicelulosa. Con ello se logra rellenar los espacios moleculares con grupos acetilo y así evitar que éstos reaccionen con las moléculas de agua o con los complejos enzimáticos de los hongos de pudrición. Así, se produce la muerte de los hongos por falta de alimento. Con esta modificación química de la madera también se ha mejorado la estabilidad dimensional y la resistencia a agentes xilófagos. Bajo esta premisa, se evaluó el tratamiento químico de acetilación para la protección de madera de Pinus radiata D. Don. Se empleó una metodología en condiciones de laboratorio que permitió determinar el efecto de la acetilación sobre las propiedades de: contenido de humedad; densidad; absorción de agua; estabilidad dimensional y biodegradación por hongos en madera de Pinus radiata D. Don. Se trabajó con dos tiempos de inmersión en anhídrido acético y dos tiempos en autoclave logrando ganancias en peso que fueron desde 6 a 20%. Se mejoraron algunas propiedades de la madera del Pinus radiata D. Don, tales como: a) la resistencia a la degradación producto de la acción de hongos de pudrición café, dado que las pérdidas de peso en las maderas acetiladas fueron desde 1.38% a 17.43% en comparación con la madera control que alcanzó un 64.94%, con el mismo hongo; b) Con un hongo de pudrición blanca se obtuvieron valores de pérdida de peso en madera acetilada que fueron entre 2.96% y 9.12% en comparación con madera no acetilada que exhibió sólo 17.9%, tras cuatro meses de exposición. Además, se mejoraron las propiedades de estabilidad dimensional y absorción de agua.<hr/>When woody cell wall is saturated with acetic anhydride, the free hydroxyl groups present on cellulosic structures are replaced. Thus, the capillary spaces are filled with acetyl groups and this replacement avoids further reactions with water or enzymatic degradation provoked by rot fungi. So, the death of different fungi is produced by the lack of food. It has been observed too that this chemical modification has improved the dimensional stability and the resistance to xylophages agents. Under this premise, we conducted a research in order to test acetylation of Pinus radiata D. Don wood as a strategy for their protection. An experimental methodology was used under laboratory conditions to determine the effect of the acetylation on some properties such as: water content; density, water uptake; dimensional stability and biodegradation provoked by rot fungi in Pinus radiata D. Don. Two immersion times of pine wood on acetic anhydride and two times in autoclave were tested (30 and 60 minutes). Thus, observed weight gains ranged between 6 and 20%. We also noted the improvement of other properties such as: a) the resistance to the degradation provoked by brown rot fungi, because in treated wood the weight losses ranged between 1.38% and 17.43% in comparison to control samples which reached 64.94% when the same fungi strain was used; b) when a white rot fungi strain was tested, weight losses ranged between 2.96% and 9.12% for acetylated samples in comparison to untreated pieces which showed 17.9% after 4 months of incubation. Furthermore, the dimensional stability and water absorption capacity improved. <![CDATA[<strong>Influence of blue stain on density and dimensional stability of <i>Pinus sylvestris</i> timber</strong>]]> La madera de Pinus sylvestris tiene interés comercial aunque su valor se reduce considerablemente cuando presenta hongos de azulado. En el presente estudio se apearon siete pinos procedentes de plantaciones españolas, y de los fustes se muestrearon 14 rodajas a diferentes alturas. Cuando éstas estaban parcialmente azuladas se labraron para obtener probetas pequeñas sin defectos anatómicos, sobre las que se determinó la densidad y además la estabilidad dimensional en volumen y en las tres dimensiones principales de la madera. En cada rodaja se compararon las propiedades físicas de las probetas completamente azuladas y las no azuladas, mediante el análisis de la varianza con un factor. El método permitió analizar la influencia específica del azulado eliminando otras fuentes de variación: factor árbol, altura en el fuste, anchura de anillos, presencia de albura y edad cambial. Solo en algunas rodajas la madera azulada de pino silvestre resultó significativamente diferente en densidad y contracción axial (madera azulada un 1% más densa y con la contracción axial un 13% mayor).<hr/>Pinus sylvestris timber is commercially important, but its value is considerably decreased by the effects of blue stain fungi. Seven pine trees from Spanish plantations were felled for the study, and 14 discs were sampled from different heights in their stems. When the discs showed partial discolouration due to fungal infection, they were cut to produce small defect-free specimens for determining density and dimensional stability (in volume and in the three main dimensions of wood). The physical properties of fully stained and stain free specimens were compared, in each disc, by one-factor analysis of variance. This method enabled analysis of the specific influence of the blue stain fungi while avoiding other sources of variation: tree factor, height in the stem, ring width, presence of sapwood and cambial age. However, the only significant differences between discoloured and unstained wood were in the density and axial shrinkage, in some discs (the density of the blue-stained wood was 1% higher and the axial shrinkage 13% higher than in the unstained wood).