Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 16 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Surface roughness of heat treated Eucalyptus grandis wood]]> This study aimed to evaluate surface roughness of heat treated Eucalyptus grandis wood after peripheral planning and sanding performed in directions to the grain and against the grain. For machining tests, workpieces were collected from two different regions in the radial direction, as follows: internal, nearby the pit; external, nearby the bark. Heat treatment was carried out by heating samples at a maximum temperature of 190ºC, with total treatment duration of 390 minutes. Heat treated and control samples underwent peripheral planning and sanding tests. The quality of machined surfaces was assessed by means of roughness average (Ra) measurements across and along the grain orientation. Results indicated significant differences in surface roughness as a function of machining feed direction, sandpaper grit size, and heat treatment. Surface roughness has not shown any difference in the radial direction. <![CDATA[Density, Calorific Value and Cleavage Strength of Selected Hybrid Eucalypts Grown in Uganda]]> This study was done to ascertain the suitability of Uganda’s clonal eucalypts for fuelwood. The objectives were to determine: (i) basic density (BD); (ii) calorific value (CV); and (iii) cleavage resistance (CLR) parallel to the grain of widely adopted clones i.e. GU7, GU8, GC540, GC550 and GC796 and to compare these properties with those of their parent materials; i.e. Eucalyptus grandis, Eucalyptus cammaldulensis, and Eucalyptus urophylla. Tests were done according to BS373(1957) and ASTM:E870-82(2006) procedures. Clone GC540 showed the highest BD (664kg/m³), GU7 had the highest CV (17800kJ/kg), GU7 and GC540 had higher values for CLR (20N/mm). BD and CLR means were in-between parent material means for GC clones. All clones had lower values of CV compared to parent materials. It was concluded that clonal wood at 6-7 years remains a viable alternative for fuelwood due to high volume increment per unit time and moderate CLR values to allow ease of splitting. <![CDATA[Efecto de la temperatura de termotratamiento en el comportamiento eléctrico de la madera de pino radiata]]> En el presente trabajo se analiza el efecto de la temperatura del termotratamiento sobre la conductividad eléctrica de la madera de pino radiata. Sobre probetas de madera de pino radiata de procedencia País Vasco (España), termotratada a 190ºC y 210ºC por el método Thermowood así como sobre piezas testigo de la misma especie, procedencia y dimensiones, acondicionadas todas ellas hasta masa constante a 20ºC/40%HR, 20ºC/65%HR y 20ºC/90%HR se evaluó la resistencia eléctrica (longitudinal y transversal) y, posteriormente, se ajustó el modelo Samuelsson para modelizar en cada tipo de material la relación humedad de la madera-resistencia eléctrica. Se concluye que la temperatura empleada en el tratamiento térmico de la madera afecta no sólo a la humedad de equilibrio sino, también, a su conductividad eléctrica, siendo máximo este efecto en el tratamiento efectuado a 210ºC.<hr/>This paper analyzes the effect of heat treatment temperature on the electrical conductivity of radiata pine wood. On specimens of radiata pine of the Basque Country provenance (Spain), heat treated at 190°C and 210°C by the method Thermowood as well as not treated matched samples, conditioned up to constant mass at the standard conditions of 20°C/40%; 20°C/65% and 20°C/90% RH the electrical resistance (longitudinal and transverse) was measured and a Samuelsson model fitted to describe the relationship between the electrical resistance and moisture content of each material. From the data is concluded that the temperature employed in the thermal treatment timber not only affects equilibrium moisture content of wood but also to its electrical conductivity, being this effect maximum in the processing performed at 210°C. <![CDATA[Efectos del contenido de harina de corteza y madera de <em>Pinus radiata</em> sobre la biodegradación acelerada de compuestos madera-plástico]]> Se evaluaron distintas formulaciones de compuestos fabricados en base a polietileno de baja densidad reciclado (PEr) y harinas tanto de corteza como de madera de Pinus radiata, mediante ensayos estandarizados de biodegradación acelerada. Los compuestos tipo Wood Plastic Composites (WPCs) fueron obtenidos mediante moldeo por inyección sin aditivos químicos, a partir de las siguientes mezclas entre PEr-harina en distintas proporciones: 100-0%, 80-20%; 60-40% y 40-60 %. Los ensayos de biodegradación acelerada fueron realizados de acuerdo a la norma ASTM D-2017, bajo condiciones controladas durante 3 meses, usando dos tipos de hongos degradadores, un hongo de pudrición café (Gloeophyllum trabeum) y por un hongo de pudrición blanca (Pleurotus ostreatus). Al término del período de biodegradación se determinó el porcentaje de pérdida de peso de cada tipo de compuesto. Los resultados indicaron que la pérdida de peso de los compuestos aumenta conforme aumenta la proporción de harina en la mezcla, siendo significativamente mayor con el hongo de pudrición café (Gt), más que con el hongo de pudrición blanca (Po). Independientemente del tipo de hongo utilizado, la harina de corteza presentó mayor susceptibilidad a la degradación en comparación con la harina de madera.<hr/>Composites of wood and bark of Pinus radiata-recycled low polyethylene (RLPE) were submitted to accelerated decay using white and brown rot fungi. These WPCs were obtained by injection molding without chemical additives at proportions: 100-0%, 80-20%, 60-40% and 40-60%. Accelerated decay tests were conducted according to ASTM D-2017-05, using a brown rot fungus (Gloeophyllum trabeum) and a white rot fungus (Pleurotus ostreatus), during 3 months, under controlled conditions. After that, percentage of weight loss of each type of composite was determined. The results shown that the biodegradation of composites increased with increasing of flour in the mixture being higher in brown rot fungus (Gt) than in white rot fungus (Po) treatment. Bark flour had higher susceptibility to biodegradation in comparison with the wood flour. <![CDATA[Effects of nanosilver-impregnation and alfalfa-intercropping on fluid transfer in downy black poplar wood]]> Effects of alfalfa-intercropping and nanosilver-impregnation were studied here on the specific gas permeability of 10-year old Populus nigra var. betulifolia. Specimens were impregnated with a 200 ppm aqueous dispersion of silver nanoparticles under 250 kPa pressure; the results were then compared with the un-impregnated specimens. The size range of silver nanoparticles was 10 to 80 nm. After the initial measurement, specimens were kept in vaporized chamber for six months (43±2°C, and 80±3% relative humidity); permeability was measured every month. Results showed that maximum specific longitudinal gas permeability was observed in the nanosilver-impregnated inner-wood specimens of the treatment with alfalfa (1614,4 × 10-13 m³ m-1), and minimum permeability was found in the un-impregnated outer-wood specimens of the treatment without alfalfa (491,7 × 10-13 m³ m-1) before the vaporization. Vaporized chamber made permeability decrease permeability at the first phases because of the absorption of water vapors and the consequent swelling; however, due to the proliferation of pits and perforation plates by fungi and molds, permeability was eventually increased. Antibacterial property of silver did not significantly decrease the growth of molds and fungi in the nanosilver-impregnated specimens. <![CDATA[Leaching and decay resistance of alder and pine wood treated with copper based wood preservatives]]> The objective of this study was to determine the leaching and decay resistance of Alder (Alnus glutinosa) and Scots pine (Pinus sylvestris) wood samples treated with copper based preservatives. Samples were treated with CCA, ACQ, Tanalith E and Wolmanit with different concentrations. Scots pine samples were exposed the mini-block test against brown rot fungi (Poria placenta (Fries) Cook sensu J. Eriksson (FPRL 280)) and Coniophora puteana Karsten (BAM Ebw. 15) while alder wood samples were tested against brown rot fungi (Coniophora puteana) Karsten (BAM Ebw. 15) and white rot fungi (Coriolus versicolor )(CTB 863A). Regarding to leaching test, treated samples were impregnated with 300 ml of distilled water and after 6, 24, 48 and thereafter at 48-hour intervals, the leachate was removed and replaced with fresh distilled water according to AWPA E11. Samples of each leachate were collected and retained for copper analysis. Amount of copper released from treated wood during the leaching test was chemically analyzed with Atomic Absorption spectroscopy. Perchloric acid procedure for the digestion of wood was used according to AWPA A7-97. The amount of copper component (Qd), the cumulative quantities leached (Qc) and the average daily fluxes (FLUX) were calculated. Results shows that CCA treated samples release less copper compared to other copper based preservatives used in this study. Highest mass losses were obtained from the leached samples treated with 1% of ACQ-2200 against decay fungi. <![CDATA[Determinación experimental de valores característicos de resistencia para Guadua angustifolia]]> Para el diseño de estructuras que utilizan como material estructural principal el bambú Guadua angustifolia, es necesario conocer los valores característicos de sus propiedades mecánicas y módulos elásticos. En este artículo se presenta la metodología experimental utilizada para la determinación de los valores característicos de resistencia mecánica a flexión longitudinal, compresión, corte y tracción paralela a la fibra, torsión, y comprensión perpendicular a la fibra y módulos elásticos de la Guadua angustifolia. Se realizaron ensayos en probetas tomadas de la parte inferior, media y superior de culmos de guaduas provenientes de tres departamentos diferentes de Colombia. Se encontraron los valores característicos de la resistencia a compresión, tensión y corte paralelos a la fibra, flexión longitudinal, torsión y compresión perpendicular así como valores de módulo de elasticidad longitudinal y circunferencial.<hr/>For the design of structures built with bamboo Guadua angustifolia as structural material it is necessary to know the characteristics values of its mechanical properties and elastics modulus. This article shows the experimental methodology used in the determination of characteristics values for bending, compression, shear and tensile parallel to fiber, torsion, compression perpendicular to fiber and elastics modulus for Guadua angustifolia. Tests were performed in samples taken from the bottom, middle and upper parts of culms of bamboos from three different areas of Colombia. Characteristic values of compression, tension and shear parallel to the fiber, bending, torsion and perpendicular compression strengths were found. Also the elastic longitudinal modulus and the circumferential modulus were determined. <![CDATA[Prediction of bending properties for beech lumber using stress wave method]]> In this study; bending properties of beech wood (Fagus orientalis) were predicted using stress - wave method and compared with static bending tests. First, lumbers which were different in length and cross section were weighed and dimensions were measured. Then, moisture contents were obtained via moisture meter. By using the density, moisture, and dimensions of the samples in MTG Timber Grader device, dynamic modulus of elasticity values were determined. And then, samples were subjected to 3 point bending test. Modulus of elasticity and bending strengths were calculated using load - deformation curves. Regression models were developed to interpret relationships between dynamic modulus elasticity and bending properties. Results showed that there is a high regression coefficient (0,86) between dynamic modulus of elasticity and static modulus of elasticity. Regression coefficient between dynamic modulus of elasticity and static bending strength was measured as (0,72) and regression coefficient between static modulus of elasticity and static bending strength was measured as (0,74). Results indicate that bending properties of beech wood lumber can be predicted using stress wave method. <![CDATA[Some mechanical properties of plywood produced from eucalyptus, beech, and poplar veneer]]> In this study, we determined the flexural properties and tensile shear strength of five-ply plywood panels produced with eucalyptus (Eucalyptus grandis), beech (Fagus orientalis.), and hybrid poplar (Populus x euramericana) using urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Flexural properties were tested on both parallel and perpendicular to grain samples. Tensile shear-strength tests were conducted on four glue lines of the plywood panels, and the effects of species of trees, type of adhesives, and direction of load were determined. The results of variance analyses showed that the effects of species of trees, direction of load, and type of adhesive on flexural properties were significant, but it was determined by specific flexural properties that the effect of the type of adhesive was based on the density of the plywood. In addition, as a result of findings, it can be said that specific mechanical properties may be a good predictor for comparative studies. <![CDATA[Marine borers resistance of chemically modified portuguese wood]]> This study deals with the role of hardness and chemical toxicity in the resistance of pinewood to marine borers. Portuguese wood Maritime pine (Pinus pinaster Ait.) was modified with 1,3-dimethylol 4,5-dihydroxy ethylene urea (DMDHEU), methylated methylol melamine (MMF), tetraethoxysilane (TEOS) and two types of wax. In addition, for comparative purposes, different control species, Ipê, Beech and Blue Gum and CCA treated pine were included. All specimens were exposed over 2 years in sea (Porto, north of Portugal). Three inspections were performed after exposure (6, 12 and 24 months). The influence of type and level of modification as well as hardness was evaluated. As results: Specimens modified with resin have shown slight or trace attack by Teredinids in DMDHEU with low level of modification (10% of weight percent gain, WPG); MMF resin with high and low level of modification (25% and 10% of WPG) have shown trace to moderate attack, respectively. With the TEOS and wax impregnated wood which fill the cell lumens no significant difference in marine borers attack was found as compared to unmodified control specimens, despite the increased hardness.