Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 19 num. 4 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Optimization of sanding parameters using response surface methodology]]> Abstract: The main objective of this work is to develop a mathematical model to evaluate optimum sanding conditions of Europen black pine (Pinus nigra). Samples were sanded using different of grit size, feed rate, cutting speed and depth of cut. Average surface roughness ( Ra ) values of each type of specimens were measured employing a stylus type of equipment. Interaction between sanding parameters and surface roughness of the species were analyzed using Minitab software and response surface methodology. Based on the findings in the work feed rate, cutting speed, grit size and depth of cut values of 5,39 m/min, 19,75 m/sec, 220 P and 9 mm were determined as optimum sanding conditions. <![CDATA[Toxic effects of three selected Malaysian timbers plant extracts against subterranean termites]]> Abstract: The toxic effects of selected Malaysian timbers (Madhuca utilis, Anisoptera laevis and Endospermum malaccense) heartwood extracts were studied with the aim to determine and understanding the function of wood extracts as a natural protection against termite. The results show that no-choice experiments revealed toxic properties of all investigated extracts by the contact against Coptotermes gestroi and Coptotermes curvignathus. However, high termite mortality was only achieved with Madhuca utilis extracts and methanol solvents. <![CDATA[Mechanical, dynamic mechanical and morphological properties of composites based on recycled polystyrene filled with wood flour wastes]]> Abstract: In this work, the potential for usage recycled polystyrene and wood flour wastes as materials for development wood plastic composites was evaluated. The effects of wood flour loading and coupling agent addition on the mechanical, dynamic mechanical and morphological properties of polystyrene wood flour composites were examined. The results showed that the mechanical properties decreased with the wood flour loading. However, an improvement in composite compatibility was observed when the coupling agent was used resulting in the increase of mechanical and dynamic mechanical properties. A morphological study demonstrates the positive effect in the interfacial adhesion between filler and matrix caused by the coupling agent addition. Based on the findings of this work, both waste materials can be used for development composites with higher performance. <![CDATA[Valorization of <em>Cistus ladanifer</em> and <em>Erica arborea</em> shrubs for fuel: Wood and bark thermal characterization]]> Abstract: As a form of upgraded biomass characterized by its high energy density, low production costs, and low process energy requirements, wood pellets are an environmentally friendly fuel allowing for carbon neutral heating with high energy efficiency. In this work, the suitability of a valorization of the woods from the two most representative shrub species from the Iberian Peninsula (namely Cistus ladanifer and Erica arborea) for heating has been assessed. Whereas Erica arborea met the requirements of ISO 17225-2:2014 for ENplus-B class (the calorific content for both wood and bark was high and not significantly different, and the ash content was permissible for specimens with branch diameter ≥2,8 cm), Cistus ladanifer was in the limit of the normative and only met the requirements in terms of acceptable ash percentage (1,9%) and heating value (19 kJ·g-1) for old specimens with branch diameters &gt;3,4 cm. Consequently, while the harvest of E. arborea for its use as fuel does not need to be selective, that of C. ladanifer should be limited to the most robust specimens and foliage should be avoided. <![CDATA[Influence of test method on biodegradation of bamboo-plastic composites by fungi]]> The effects of differing ratios of bamboo/plastic polymers on resistance to fungal attack was assessed using two different decay test methods. Weight losses for non-treated southern pine and Carpinus betulus sapwood blocks indicated that the test conditions were suitable for aggressive decay by Gloeophyllum trabeum and Trametes versicolor. Mass losses on the bamboo/composites tended to be very low, regardless of the method employed. In general, moisture levels in the composites were extremely low although they were close to the point where fungal attack could occur when only the bamboo components were considered. The standard decay tests indicated that bamboo can be considered a suitable substitute for wood flour in wood-plastic composites. <![CDATA[Using a parametric study to analyse the performance of wood solar dryers with glazed walls]]> Abstract: Parameters characterizing wood and air were studied in order to analyze the performance of a wood solar dryer functioning under Moroccan climate. A mathematical model based on the climate data of Rabat city was used to investigate theoretically the wood drying process. Two wood species-thuya (Tetraclinis articulate) and pine (Pinus pinaster)-were examined in the present study. The results obtained by computer simulations are in good agreement with the experimental values. Furthermore, our findings indicate that the use of a global mass transfer coefficient for low temperature convective and homogenous drying conditions allows the influence of the principal operating parameters (wood thickness, wood density, air temperature, air velocity and ventilation mode) on the drying time to be estimated with great accuracy. Analyses pertaining to the two studied wood species revealed that(1) pine dries more quickly than thuya, (2) the drying process is faster in the summer relative to other seasons, (3) increasing the air velocity by 100% results in a 20% reduction in the drying time, and (4)continued ventilation reduces the drying time by 43%. <![CDATA[The effect of Nano-MgO on the mechanical and flammability properties of hybrid nano composites from wood flour-polyethylene]]> Abstract: This study considered the effect of nanomagnesium oxide on the mechanical and flammability features of composites made of wood flour and high-density polyethylene. A sample of wood flour was made from the mixture of hardwoods and high density polyethylene with the weight ratio of 50%. Maleic anhydride was added as a compatibilizer (2 phc), and nanomagnesium oxide was applied at 6 levels (0, 1, 2, 3, 4, 5 phc). These materials were mixed, and samples were prepared with determined sizes by injection molding machine. The samples were subjected to flexural tests to examine the mechanical features, and to study flammability strength, various tests were conducted with a cone calorimeter, including the amount of char residue, total smoke production, time to ignition, and heat release rate, according to ASTM E1354-92 (1992). The addition of up to 3 phc nanomagnesium oxide increased flexural strength and modulus, but further additions decreased these values. The addition of 5 phc nanomagnesium oxide increased the char residue and ignition time, and it decreased the heat release rate, total smoke production, and burning rate. Scanning electron microscopy and energy dispersive X-ray (EDX) analysis indicated the improper transmittance of nanomagnesium oxide and accumulations in the samples. <![CDATA[Micro-mechanical properties of Oak wood and comparison with standard-sized samples]]> Abstract: The aim of this study was to investigate micro-mechanical properties of Oak (Quercus petraea) wood and to compare with standard-size test specimens values. Bending strength, modulus of elasticity in bending, compression strength and tensile strength were determined using micro- and standard-size mechanical test samples. In the micro- and standard size samples, bending strengths were evaluated as 71,2 MPa and 99,4 MPa, modulus of elasticity in bending as 2741,3 MPa and 11394,1 MPa tensile strengths as 98,7 MPa and 93,8 MPa and compression strengths as 45,4 MPa and 46,6 MPa respectively. The results showed that the bending strength, modulus of elasticity and compression strength of the micro-size samples were lower compared to the standard-size samples, while the tensile strength was higher in the micro-size samples. The compression strength values of micro- and standard-size samples were not significantly different. The regression analyses indicated a positive linear regression between the mechanical properties of micro- and standard-size samples. Micro-size specimens can be used to estimate the mechanical properties of Oak wood when obtaining standard-size specimens is not possible. <![CDATA[The effect of titanium dioxide nanoparticles obtained by microwave-assisted hydrothermal method on the color and decay resistance of pinewood]]> Abstract: This study aimed to synthesize titanium dioxide nanoparticles by microwave-assisted hydrothermal method to incorporate them to the structure of Pinus elliottii wood. The color changes and the decay resistance of impregnated wood was investigated. The titanium dioxide nanoparticles were impregnated into Pinus elliottii wood by vacuum-pressure and simple immersion methods. Furthermore, Pinus elliottii wood was treated with chromated copper borate solution tocompare their effectiveness to the titanium dioxide treated wood. The titanium dioxide nanoparticles impregnated by vacuum-pressure were presented especially on the wood surface, forming a homogeneous coating. The titanium dioxide nanoparticles did not change the natural color of wood and, at the same time, decreased the degree of the white rot fungus (Ganoderma applanatum) colonization in the wood structure and the wood decay, compared to the untreated one. The titanium dioxide treated wood samples provided similar protection against decay in comparison to wood treated with chromated copper borate. The impegnation with titanium dioxide nanoparticles can be a good alternative to decrease/avoid the fungi proliferation, providing to Pinus elliottii wood a self-cleaning mechanism. <![CDATA[Decay resistance of wood impregnated with monoethanolamine and sodium bisulfite pulping black liquors]]> Abstract: The efficacy of monoethanolamine and sodium bisulfite pulping black liquors at three concentrations of 1; 1,5 and 2% on the preservation of poplar wood from white rot (Trametes versicolor) was investigated. The wood specimens were impregnated with the black liquors using a full-cell method. The black liquors enhanced the decay resistance without any reduction in mechanical strength, and a remarkable increase was observed at higher concentrations and weight gain percentage. The performance of monoethanolamine black liquor was more pronounced, probably due to lower kappa number and higher pH. The durability class of specimens impregnated with 2% monoethanolamine and sodium bisulfite black liquors improved from 5 (not durable) to 1 (very durable), and from 5 to 3 (moderately durable), respectively. Chemical analysis showed that the presence of additional lignin in wood alters the white rot. Results of anatomical studies showed that the fibers of the control and impregnated wood specimens were collapsed after 16 weeks of incubation. Leaching tests confirmed that the fixation of black liquors in wood should be examined for further studies. <![CDATA[Evaluation of plastic composites made with <em>Laccosperma secundiflorum</em> and <em>Eremospatha macrocarpa</em> canes]]> Abstract: The feasibility of using rattan canes (Laccosperma secundiflorum and Eremospatha macrocarpa) as reinforced fillers for high density polyethylene based plastic composite production was investigated. Extruded composites were tested for water sorption, tensile and thermal properties. The results obtained indicated that the rattan composites were dimensionally (water absorption: 2,2-21,4% thickness swell: 0,9-5,3%) and thermally stable (Tc: 116,8-118,2°C) and possessed adequate tensile properties (7,3-21,7 MPa). Composites made from L. secundiflorum had higher strength and thermal properties but lower sorption values compared to those of E. macrocarpa. Differences in the densities of the composites and the anatomical structures of the rattans seemed to influence properties of the composites. <![CDATA[Efecto de la presión de prensado y la adición de lignina kraft en la producción de tableros aglomerados autoenlazados a partir de <em>Gynerium sagittatum</em> pretratada con vapor]]> Resumen: El Gynerium sagittatum es una gramínea que presenta gran adaptabilidad ecológica lo cual la hace una fuente lignocelulósica ideal para la fabricación de tableros aglomerados sin aditivos sintéticos. Se evalúa el efecto de la presión de prensado y de la adición de lignina kraft purificada sobre las propiedades fisicomecánicas de tableros de fibras de Gynerium sagittatum de alta densidad. La materia prima es pretratada en un reactor de steam explosion a severidad 4,1 y la temperatura de prensado se fija en 217°C. Se varia la presión de prensado entre 2 y 15 MPa. Se determina que la presión de prensado más apropiada para obtener tableros de buena calidad es 2 MPa obteniendo valores para el módulo de elasticidad de 6000 MPa, módulo de ruptura de 47 MPa, enlace interno de 1,50 MPa, absorción de agua durante 24 horas de 25% e hinchamiento en espesor durante 24 horas del 15%. Partiendo de estas condiciones de operación, se evalúa la inclusión de lignina entre 0 y 30%. Se determina que el aumento de lignina no afecta significativamente el desempeño mecánico de los tableros, pero sí su estabilidad dimensional, dando como resultado una absorción de agua durante 24 horas de 19% e hinchamiento en espesor durante 24 horas del 8,5%, a un valor óptimo de 20% de inclusión de lignina.<hr/>Abstract: Gynerium sagittatum is a grass that has great ecological adaptability, which makes it an ideal lignocellulosic source for the manufacture of fiberboards. The effects of pressing pressure and the addition of kraft lignin on the physicomechanical properties of high density fiberboards of Gynerium sagittatum are evaluated. The raw material is pretreated in a steam explosion reactor at severity 4,1. The pressing temperature is set at 217°C. The pressing pressure is varied between 2 and 15 MPa. The most appropriate pressing pressure to obtain a good quality boards is 2 MPa. The values of properties at optimal conditions are: modulus of elasticity 6000 MPa, modulus of rupture 47 MPa, internal bond 1,50 MPa 24 h water absorption 25% and 24 h thickness swelling 15%. Based on these operating conditions, the inclusion of lignin between 0 and 30% is evaluated. The addition of lignin does not significantly affect the mechanical performance of the fiberboards but improve its dimensional stability. The obtained values for 24 h water absorption and 24 h thickness swelling are 19% and 8,5% respectively, at a 20% of lignin addition.