Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> http://www.scielo.cl/rss.php?pid=0718-221X20100002&lang=es vol. 12 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>EL MAÑANA ES LA EDAD DE LA MADERA</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200001&lng=es&nrm=iso&tlng=es <![CDATA[<b>INVESTIGATION OF CHEMICAL CHANGES IN THE STRUCTURE OF THERMALLY MODIFIED WOOD</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200002&lng=es&nrm=iso&tlng=es Thermal modification beneficially alters several technological parameters of wood. The changes in the physical parameters are due to the significant alterations of the structure and the chemical composition of wood, which take place during the modification process. These changes are complex and some aspects are still far from being completely understood. Various industrially important hardwoods and softwoods have been treated in an autoclave in N2 atmosphere. The physical (density, L-value, moisture content, bending strength, MOE) and chemical (pH, hemicellulose-, total phenol- and soluble carbohydrate content) parameters have been measured and evaluated. By establishing linear correlations between physical and chemical parameters the chemical changes affecting the physical properties could be investigated and tracked. Very good correlations have been found for hardwood samples, whereas for softwoods only poor correlations have been established. Results could contribute to a better understanding of the reactions of thermal modification, and could furthermore provide a basis for wood species dependent technology optimization in the future. <![CDATA[NEW METHODOLOGY TO OPTIMIZE SORTING IN WOOD DRYING]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200003&lng=es&nrm=iso&tlng=es One important problem in lumber drying is to maintain the lumber moisture content distribution within certain minimum and maximum values. Over-drying and under-drying are common causes for lower grade recovery and dimensional stability problems. It is known that both over-drying and under-drying can be reduced by sorting green lumber into different moisture content groups and sorting also offers the opportunity to redesign drying schedules. In this study, a new methodology was designed and tested to optimize kiln drying of lumber by implementing green sorting coupled with modified drying schedules. The methodology was applied to optimize the drying of 114 by 114mm² hem-fir lumber sorted with an NMI capacitance type meter at a local sawmill. It was found that in comparison to unsorted lumber, sorting into three groups can reduce the drying time by 7% approximately and recover around 3/4 of the under-dried lumber. The experimental data on lumber degrade and moisture gradients measured after drying were also reported in this paper. <![CDATA[<strong>MEASUREMENT OF DYNAMIC SORPTION BEHAVIOUR OF SMALL SPECIMENS OF PINUS RADIATA - INFLUENCE OF WOOD TYPE AND MOISTURE CONTENT ON DIFFUSION RATE</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200004&lng=es&nrm=iso&tlng=es Sorption behaviour of radiata pine has been investigated by weighing small specimens continuously during isothermal step changes in relative humidity. The use of wood specimens shorter in the longitudinal direction than the average tracheid length of radiata pine ensures that all tracheids in a specimen are exposed, reducing the effect of wood structure on bound water transport. The small size also allows the specimens to be prepared from a single band of earlywood or latewood. Using the dynamic sorption platform developed at Scion, a number of sorption experiments were undertaken comparing dynamic sorption behaviour of individual bands of earlywood and latewood, which had been heat treated to mimic the chemical changes that occur during high temperature drying. Diffusion coefficients and surface emission coefficients have been calculated from the sorption data, and are presented here. Earlywood and latewood had different sorption behaviour, but no measurable changes in sorption behaviour were seen with the different heat treatments. Diffusion coefficients were strongly dependent on moisture content. <![CDATA[<strong>INFLUENCE OF AGE AND HEIGHT POSITION ON COLOMBIAN <i>GUADUA ANGUSTIFOLIA</i> BAMBOO MECHANICAL PROPERTIES</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200005&lng=es&nrm=iso&tlng=es The age of bamboo is a key factor that affects its mechanical properties. Bamboo Guadua angustifolia kunt (Guadua a.k.) has been used as a construction material in America, but the influence of the age and height position of the culm on the mechanical properties has not been studied in detail. In this study, selected mechanical properties of Guadua a.k from 2 to 5 year old culms, located at different heights, were investigated using international standard test procedures (ISO 22157). Based on the experimental results, it was found that the top portion (sobrebasa) showed the maximum strength and modulus of elasticity compared to the other portions, since this portion of bamboo has higher density. More over, density of Guadua a.k. culm has more influence in modulus of rupture in bending, than in any of the other studied mechanical properties. Regardless of the culm height, it seems that the mature age of Guadua angustifolia kunt is reached between 3 and 4 years old, because the mechanical properties at those ages were the highest and remained almost constant, whereas the mechanical properties of the culms at the age of 5 were the lowest. <![CDATA[<strong>OF TRANSIENT MASS TRANSFER OF A GASEOUS COMPONENT IN AN ISOTHERMAL POROUS ADSORBENT</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200006&lng=es&nrm=iso&tlng=es The present study is avoided to a better understanding of the complexity of the adsorption process of a gaseous constituent on a porous solid (wood) with the purpose to improve the modeling. During the sorption on the porous solid, the diffusion mass transfer of the gaseous substance A occurs simultaneously in gaseous and adsorbed phases. The mass balance equations are written for the simultaneous diffusion transfers. The thermodynamic equilibrium between the phases is also represented. Four different models have been compared. Numerical results have been compared with experimental data and show that the hypothesis of equilibrium conditions between the gaseous and the adsorbed phases is not always verified. <![CDATA[<strong>ACTIVITY OF COMMERCIAL STILL WATERS FROM VOLATILE OILS PRODUCTION AGAINST WOOD DECAY FUNGI</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200007&lng=es&nrm=iso&tlng=es The antifungal properties of some commercial plant waters obtained as side products in producing distilled oils were investigated. Paper disc samples were impregnated with various plant waters and exposed to wood decay fungi for 3 months in Petri dishes. Ten types of plant water (Laurus nobilis, Calluna vulgaris, Lavandula stoechas, Thymus vulgaris, Myrtus communis, Eucalyptus globulus, Mentha pulegium, Urtica dioica, Melissa officinalis, and Matricaria chamomilla were examined. Seven fungi were used (Phanerochaete chrysosporium, Ceriporiopsis subvermisphora, Gloeophyllum trabeum, Trametes versicolor, Oligoporus placenta, Pleurotus ostreatus, and Coniophora puteana). The antifungal activities of the plant waters obtained from thyme and lavender were particularly high. <![CDATA[<strong>ESTUDIO EXPLORATORIO DE LA VARIABILIDAD RADIAL Y APICAL DEL TAMAÑO Y FRECUENCIA DE LOS CANALES RESINÍFEROS EN PINO RADIATA</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200008&lng=es&nrm=iso&tlng=es En este trabajo se cuantifica la variabilidad radial y apical de los canales resiníferos de pino radiata (Pinus radiata) de 14 años. Se determinó la frecuencia y el tamaño de los canales resiníferos en muestras microtomadas usando un software comercial. Las muestras fueron extraídas de árboles en pie presentando tres niveles diferentes de resinación externa, es decir, moderada/leve, e intensa. Se evaluó la variabilidad de los canales resiníferos según la posición radial a tres diferentes alturas: base, DAP, y al comienzo de la copa del árbol. Los resultados muestran que la variación radial y apical del tamaño y la frecuencia de canales resiníferos aparece débilmente correlacionada con el nivel de intensidad de resinación observada en árboles en pie de pino radiata.<hr/>Radial and apical variation in resin canals of radiata pine were studied. The frequency and size of resin canals were examined, using microscopic techniques from a commercial software. Wood samples from standing trees were taken, showing three different levels of external resin-bleeding intensity : moderate, light and intense. The variability of the resin canals were examined according to the radial position at three different heights ; bottom, breast height diameter and at the beginning of the tree top. The results show that the apical and radial variation of the size and frequency of resin canals appeared weakly correlated with the intensity level of the tree resin-bleeding of the standing radiata pine trees. <![CDATA[<strong>INFLUENCE OF THE SURFACE ROUGHNESS OF PARTICLEBOARDS AND THEIR PERFORMANCE TOWARDS COATING</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200009&lng=es&nrm=iso&tlng=es The effect of surface properties on the quality of the adhesion was evaluated for coated particleboards. Uncoated UF- and TF-bonded particleboards made using different raw materials were conditioned under 20°C and 65 % relative humidity and coated with a nitrocellulose lacquer primer by a conventional process. The interaction between the primer and surface seems to be a very important factor determining the strength of adherence.<hr/>Las propiedades de la superficie y su efecto en la calidad de la adhesion fueron evaluadas en tableros pintados. Tableros de partículas sin recubrir encolados con resinas UF y TF hechos utilizando diferentes materias primas fueron acondicionados a clima 20°C and 65 % de humedad relativa fueron pintados con un aparejo nitrocelulósico mediante un proceso convencional. La interacción entre el aparejo y la superficie parece ser un importante factor que determina la fuerza de la adherencia. <![CDATA[<b>STUDY OF PEDESTRIAN-INDUCED VIBRATIONS ON TIMBER FOOTBRIDGESC</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2010000200010&lng=es&nrm=iso&tlng=es The effect of surface properties on the quality of the adhesion was evaluated for coated particleboards. Uncoated UF- and TF-bonded particleboards made using different raw materials were conditioned under 20°C and 65 % relative humidity and coated with a nitrocellulose lacquer primer by a conventional process. The interaction between the primer and surface seems to be a very important factor determining the strength of adherence.<hr/>Las propiedades de la superficie y su efecto en la calidad de la adhesion fueron evaluadas en tableros pintados. Tableros de partículas sin recubrir encolados con resinas UF y TF hechos utilizando diferentes materias primas fueron acondicionados a clima 20°C and 65 % de humedad relativa fueron pintados con un aparejo nitrocelulósico mediante un proceso convencional. La interacción entre el aparejo y la superficie parece ser un importante factor que determina la fuerza de la adherencia.