Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

It is known that there is a correlation between hydration heat and physico-mechanical properties of wood based cement panels.  Cement hydration is affected by many variables, such as chemical composition, water/cement ratio, wood/cement ratio, wood chemical properties, mineral additions and producing conditions. This study mainly aimed to investigate the effects of press temperature on some properties of three-layer cement bonded particleboard made from the particles of spruce (Picea orientalis) and poplar (Populus tremula). For this purpose, a total of 16 experimental board groups with 1200 kg/m3 target density and 1/3 wood-cement ratio were produced at the press temperatures of (20, 30, 40, 50, 60, 70 and 80) °C. As cement curing accelerator, CaCl2 was used at a rate of 5 % (cement weight basis). The physical, mechanical and thermal properties of the boards were determined. The results indicated that the press temperature substantially affected the properties of cement-bonded particleboard depending on the wood species. In the light of this study, the optimum temperatures in producing of cement-bonded particleboard were found as 40 °C for poplar wood and 60 °C for spruce wood.

In this study, a new apparatus for measuring the air permeability of wood-based panel specimens without using water displacement was developed with the aim of decreasing the influence of variation in atmospheric pressure on permeability measurement. Validation experiments were conducted using plywood, oriented strand board (OSB), particleboard, and medium-density fiberboard (MDF) panels and a control specimen sealed with an epoxy resin. The background (leakage) flow of the apparatus was evaluated based on the experimental results of the control specimen. A methodology for the determination of air permeability based on Darcy’s law for gases and the evaluated background flow rate was proposed. The results of the current study were compared with those obtained in a previous study, indicating that the new method provides valid measurements for wood-based panels with high and low air permeability. No significant influence of variation in atmospheric pressure on the experimental results was observed, suggesting that the proposed method is suitable for a long-term continuous experiment for evaluating a specimen with extremely low permeability.

Because invasive tree species are being suppressed all over the world, there is a lack of basic information needed for their use in the processing industry. One piece of important information for woodworking applications is the air-dry density, which is 653 kg/m3 in the case of tree of heaven (Ailanthus altissima), 536 kg/m3 for box elder (Acer negundo), and 702 kg/m3 for green ash (Fraxinus pennsylvanica). The order of the 3 species is the same for oven-dry and basic density. In terms of compression and bending, tree of heaven has higher values than green ash. Because the strength of the tree of heaven and the green ash are largely the same as the common ash (Fraxinus excelsior), it can be replaced by these tree species. The properties of box elder wood are significantly different from those of

The aim of the study was the use of the inorganic borax pentahydrate mineral in medium density fiberboard production instead of biomass fiber and to specify the performance which physical, mechanical, combustion of produced boards.  Chips used in manufacture were subjected to cooking for 4,5 minutes in Asplund defibrator at the vapor pressure of 7,6 kg/cm2 pressure and 190 ºC temperature. 1,6 % paraffin according to based on oven-dried wood fibers was added to cooked chips before the fiber processing in segments of defibrillator section. 1 % ammonium sulphate according to based on oven-dried wood fibers were added to fiber in the bowline. Borax pentahydrate was prepared in a separate tank in order to use the production of medium density fiberboard medium density fiberboard. Borax pentahydrate inorganic mineral was mixed with urea-formaldehyde resin. Urea-formaldehyde glue was prepared as three different solutions including the borax pentahydrate as 3 % (20 kg), 6 % (40 kg) and 9 % (60 kg) respectively. Borax pentahydrate mixed fibers were dried to 12 % moisture. Mat was formed before prepress. Daily multi-press was manufactured 188 °C temperature and 32 kg/cm² pressure and 270 second pressing time. Manufactured boards size were 2100x4900x18 (mm). According to this work result, 3 % and 6 % rate borax pentahydrate added medium density fiberboard boards were measured more good physical and mechanical test results compare to control boards. 9 % borax pentahydrate added medium density fiberboard boards were shown incredibly superior performance at fire resistance.

Cedrelinga cateniformis (tornillo) is a timber species of the South American Amazon Basin. In its natural distribution area, the wood has various local uses, such as furniture, art work, door and window frames, and light construction. In order to promote this lesser known species for high valued applications on the international market, wood anatomical, topochemical and physical/mechanical studies were carried out to characterize the wood properties. The topochemical distribution of the lignin and phenolic extractives in the tissue were studied by means of cellular UV microspectrophotometry (UMSP). The results of the structural and topochemical analyses were compared with the interrelation of certain anatomical and subcellular structures as well as the chemical composition with regard to the physical and mechanical properties. The natural durability of the mature heartwood was analyzed according to the European Standards and is resulting in a durability class 1 against basidiomycetes. Based on the findings of the comprehensive investigations concerning physical and biological features, e.g. the dimensional stability and durability, Cedrelinga cateniformis is ideally suited as a substitute for overexploited tropical woods currently used in Europe for wooden window frames and other above ground outdoor applications and thus can contribute to increase the value-added production in Peruvian forests.

The effect of applying cetol and varnish finishing products and sanding on the surface roughness and colour of marupa (Simarouba amara) wood was evaluated. Three coats of each product were applied and two sandpaper grits were used, 280 and 320). The analyzes were performed on untreated samples and between each coat of products in order to analyze the effect of sanding, the products and the number of coats. According to colorimetry, the L* value for the control treatment was 82.83 and the treatments reduced the L* to 61.70 on average for the cetol treatment and 77.09 for the varnish treatment, showing that the cetol darkened the wood more than the varnish. The yellowish and reddish pigmentations became more intense according to the positive values of Δa* and Δb*, especially after applying the cetol. The total colour variation ΔE average was 40.79 for the cetol treatment and 9.83 for the varnish treatment, confirming a much more significant colour change in the cetol treatment. Sanding with different grits did not significantly alter the surface colour. The product application made the wood surface smoother, and was noticeable from the second coat. Sanding reduced roughness on the wood surface, but the finishing product was the largest source of variation.

This study investigated the morphological characteristics and chemical properties of the wood and the chemical properties of the bark of the oleaster (Elaeagnus angustifolia) tree, which grows in a variety of climatic conditions in different regions of Turkey. The study materials were taken from three different regions of Turkey having different climatic conditions and elevations with the aim to determine the chemical properties of the bark and wood and the fiber properties of the wood. According to chemical analyses, no significant differences in the core components of the cell wall were observed between the heartwood and the sapwood. The samples collected from the Çankırı region had the highest holocellulose content (84.9%), while the proportions of alpha cellulose (52.3%) and lignin (24.0%) in samples taken from the Balikesir region were found to be higher than in samples from the other regions. According to the sugar analysis, glucose and xylose were found to be higher in the heartwood than in the sapwood. When the sugar ratios were evaluated by region, the glucose and xylose ratios were the highest in the Çankırı region (43.7% and 22.8%) and the lowest in the Konya region (38.3% and 20.5%). When looking at the inner bark (phloem) and outer bark (rhylidome) rates, the amounts of holocellulose and alpha cellulose were higher in the inner bark and the lignin rates were higher in the outer bark. The wood solubility values for cold and hot water, ethyl alcohol and the 1% NaOH were highest in samples from the Çankırı region and lowest in those from the Konya region, whereas bark solubility rates were highest in the samples taken from the Balıkesir region. When morphological characteristics were examined, no obvious differences were seen among the regions in terms of the fiber length, fiber width, lumen diameter or double wall thickness. Upon further investigation, it was determined that the oleaster tree wood was suitable for papermaking, but that the produced paper would exhibit a low resistance value because the average felting rate among the three growing regions was low (39.87%).

A comprehensive testing program has been developed to assess different physical and mechanical properties of 26 commercial and lesser-known PNG species from secondary and plantation forests. The impact of log position in a tree on the mechanical properties has also been assessed to optimize the utilization of timbers along the value chain. The results showed that stiffness and bending strength tend to decrease or remain unchanged along the stem. Shear strength and Janka hardness displayed a similar trend to a lesser extent where the position in the tree had a limited impact on compression strength properties. Thus, segregating based on log position can be of interest where desired mechanical properties and costs associated with segregating justify optimum mechanical properties for the intended end use. The properties of selected species from plantations and regrowth forests were generally lower than those found in the literature for timbers from old-growth forests. The size of specimens tested, the amount and provenance of tested material, and some adaptive traits for tropical tree species are some factors potentially explaining observed differences. However, a comparison with recent studies tends to confirm the overall reduction of physical and mechanical properties when compared with old-growth forests timbers.

To ensure the safety of wooden structures, estimation of wood strength is based on the characteristicstrength values. The Brazilian standard (NBR, in Portuguese Norma Brasileira Regulamentadora) 7190 proposesequations to estimate the strength properties with a simplified procedure, which allows obtaining thecharacteristic values through relations that correlate different mechanical properties. Using these equations,the values of tensile (ft0,k) and shear (fv0,k) strength can be calculated in a simplified way from the compressivestrength (fc0,k) values. In the present work, 36 tropical hardwood species were evaluated for tensile, shear andcompressive strength in the direction parallel to the grain, with a total of 1296 experimental measurements,and the precision of the relations defined by the Brazilian standard was assessed using the analysis of variance(ANOVA) method. Two-parameter regression models, based on linear, exponential, logarithmic and geometricfunctions, were used as an alternative proposal for the estimation of the strength properties. The statisticalanalysis validated the proposed relations, with the linear (ft0,k) and geometric (fv0,k) regression models beingthe models of best fit, with the coefficients of determination (R2) equal to 63,02 % and 70,15 %, respectively.In addition, new simplified equations were suggested. The least squares method was used to determine theoptimal coefficient (α) for validation of the Brazilian standard equations. The obtained coefficients validatedthe tensile strength relationship (ft0,k = fc0,k / 0,77), but failed to validate the shear strength relationship (fv0,k =0,12∙ fc0,k). In the latter case, the obtained values were significantly higher (up to 91 % higher) when comparedto those estimated by the Standard

El objetivo de este trabajo fue describir el color del tallo, también conocido como culmo, de Guadua angustifolia con el sistema colorimétrico CIE-L*a*b* y analizar la variabilidad entre los tres estados de madurez (joven, maduro y sobremaduro). El material de estudio se recolectó en la plantación de la empresa AGROMOD, ubicada en Reforma, Chiapas, México. Se tomaron 12 culmos de dos, cuatro y seis años, 36 en total, y se midió el color utilizando los parámetros del sistema CIE-L*a*b* con ayuda de un colorímetro digital. Posteriormente, se utilizó la metodología propuesta por CIE 2004 para obtener la variación total de color (∆E*) y medir la magnitud de la diferencia del color entre los tres estados de madurez.  Como consecuencia de la madurez se observó un cambio secuencial de coloración en la parte externa del culmo, desde un verde claro, verde grisáceo, gris, hasta un tono café. Los valores de ∆E* fueron mayores de 20, lo que de acuerdo a los criterios de percepción de diferencia de color ∆E* indica que la variación del color entre un estado de madurez y otro puede clasificarse como “Muy grande”. Asimismo, al realizar un análisis de Kruskal Wallis en las coordenadas CIE-L*a*b* se encontró que la diferencia del color por edad es estadísticamente significativa (p < 0,05).