Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 21 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Evaluation of dimensional stability, surface roughness, colour, flexural properties and decay resistance of thermally modified <em>Acacia auriculiformis</em>]]> Abstract: This paper presents the effect of thermal modification of 14-15 year-old plantation grown Acacia auriculiformis wood in the 150-240ºC temperature range under vacuum condition. Important techno-mechanical parameters of thermally modified wood such as density, dimensional stability, colour, surface roughness, decay resistance against brown and white rot fungi and flexural properties were evaluated and compared with control. Depending on severity of heat treatment, colour of modified sapwood was turned from light to dark brownish. Moreover, the change in colour was found to be uniform throughout the thickness of wood blocks. Amount of shrinkage of Acacia auriculiformis wood was observed to be decreased with increasing treatment temperatures. Maximum dimensional stability of wood thermally modified at 240ºC was in the range of 60-65%. The surface roughness parameters (Ra and Rz) were reduced significantly after the treatment. The flexural strength (modulus of rupture-MOR) was observed to be reduced with increasing treatment temperatures. However, flexural stiffness (modulus of elasticity-MOE) was not found to be affected significantly up to 210ºC temperature. The lower amount of weight loss of thermally modified wood compared to untreated control showed improved decay resistance against white and brown rot fungi. With desirable improvements in various esthetic and technologically important quality parameters such as enhanced dimensional stability, biological durability against fungi and certain other properties, thermally modified wood from short-rotation Acacia auriculiformis may be considered as viable alternative to scarcely available timber resource for different value-added applications. <![CDATA[Crystallinity of cellulose microfibers derived from <em>Cistus ladanifer</em> and <em>Erica arborea</em> shrubs]]> Resumen: La efectividad del uso de las fibras de celulosa como reforzantes en materiales particulados/compuestos requiere el estudio de la cristalinidad de dichas fibras. El objetivo del presente trabajo es proporcionar información sobre el grado de cristalinidad de las microfibras de celulosa obtenidas de los tallos de dos especies arbustivas, Cistus ladanifer y Erica arborea, a través de diversos métodos y en concreto, mediante tratamiento alcalino y uso de disolventes eutécticos profundos (DES) conjuntamente con la aplicación de microondas. Los índices de cristalinidad (CrI) obtenidos a partir de los patrones de difracción de rayos X en polvo indican que el CrI es más alto para la celulosa obtenida mediante el tratamiento con DES. También se aporta información complementaria sobre el grado de cristalinidad a partir de otras metodologías: espectro vibracional de espectroscopía infrarroja con transformada de Fourier por reflexión total atenuada (ATR-FTIR), micrografías obtenidas mediante microscopía electrónica de barrido (SEM) y medidas de accesibilidad para la celulosa obtenida por tratamiento con DES para ambas especies. Los resultados de cristalinidad para las fibras de estas dos especies arbustivas mediterráneas se encuentran dentro del rango de los resultados obtenidos para la pulpa de papel, por lo que es factible su valorización para aplicaciones de empaquetado o para su uso como reforzantes de materiales compuestos junto con otros biopolímeros.<hr/>Abstract: The effectiveness of the use of cellulose fibers as particulates/composite reinforcers involves the assessment of the crystallinity of such fibers. The aim of the present work is to provide information on the degree of crystallinity of the cellulose microfibers obtained from the stems of Cistus ladanifer and Erica arborea shrubs through two different methods, namely an alkaline treatment and a microwave-assisted deep eutectic solvent (DES) method. The crystallinity indexes (CrI) obtained from X-ray powder diffraction patterns indicated that higher CrI were attained for cellulose obtained from the DES treatment. Complementary information on the degree of crystallinity was also retrieved from attenuated total reflection- Fourier transform infrared spectroscopy (ATR-FTIR) vibrational spectra, scanning electron microscopy (SEM) micrographs, and accessibility data for the DES-treated celluloses from the two species. The crystallinity results for the fibers derived from these two Mediterranean shrubs were within the range of the results for those derived from wood pulp, opening the door to their valorization for cellulose-derived packing applications or for their use as reinforcers in composite materials in combination with other biopolymers. <![CDATA[Resistance improvement of rubberwood treated with zinc oxide nanoparticles and phenolic resin against white-rot fungi, <em>Pycnoporus sanguineus</em>]]> Abstract: Phenolic resin or phenol formaldehyde (PF) resin containing different percentage of zinc oxide (ZnO) nanoparticles was prepared and used to treat rubberwood. Three types of treatment solutions were prepared, namely (1) low molecular weight phenol formaldehyde resin (LMwPF), (2) 1,5 wt % nano ZnO dissolved in water (ZnO/H2O), and (3) combination of both LMwPF and 1,5 wt % nano ZnO (LMwPF/ZnO). The rubberwood samples were submerged into the treatment solutions for 60, 90, and 120 min, before vacuum impregnation. The untreated rubberwood samples served as the controlled samples. The thermal stability behaviour and resistance against white-rot fungi (Pycnoporus sanguineus) of the treated rubberwood samples were evaluated. The results reveal that the treated rubberwood had slightly better thermal stability compared to the untreated samples. In terms of decay resistance, the rubberwood treated with LMwPF and LMwPF/ZnO possess very high resistance against white-rot fungi. On the other hand, the rubberwood treated with ZnO/H2O did not attain similar effectiveness as the other two treatments, except for the samples that were submerged in ZnO/H2O for 120 min. The results indicate that 1,5 wt % nano ZnO could be sufficient in imparting superior durability to rubberwood provided that longer submersion time is adopted. <![CDATA[Evaluation of wood surface coating performance using water based, solvent based and powder coating]]> Abstract: The objective of this study was to evaluate the surface coating performance using water base, solvent base and powder coating on medium density fiberboard. Samples were coated using water-base, solvent-base and powder coating. Coating performance was performed by using adhesion strength, surface coating hardness, layer thickness and rapid deformation test. The results were analyzed with two different statistical methods. Adhesion strength, layer thickness and surface hardness were determined by using ANOVA analysis, while results of rapid deformation test were analyzed by using Kruskal-Wallis method. According to these results, coating type was effective factor on the adhesion strength, surface coating hardness, layer thickness and rapid deformation test. Water-based painting application for adhesion strength and impact deformation resistance were higher than solvent-based coating. In the powder coating application, although surface coating hardness was higher than solvent and water base coating application, rapid deformation results were lower than solvent and water base coating applications. Adequacy of models was performed R-square (R²) and Adjusted R-square (Adj-R 2 ) values. R 2 values of adhesion strength, layer hardness and film layer thickness were 93,60 %; 95,33 % and 73,90 %, respectively. Adj-R 2 values of adhesion strength, layer hardness and film layer thickness were 93,45 %; 95,23 % and 73,30 %, respectively. <![CDATA[Influence of combined heat treatment and densification on mechanical properties of poplar wood]]> Abstract: In this study, influence of combined heat treatment and densification on mechanical properties of poplar wood (Populus usbekistanica) such as density, EMC, compression strength, modulus of elasticy, modulus of rupture and static bending strength were investigated. Poplar samples were subjected to a temperature of 120oC, 160oC and 200oC for 1 and 3h. After the heat treatment, the heat treated samples were compressed in a hot press at a temperature of 120oC, press pressure of 5 MPa and press time of 30 minutes for densification. The results showed that the heat treatment affected the densification with increasing density. Additionally, the heat treatment decreased modulus of rupture (MOR), modulus of elasticity (MOE) and impact bending strength (IBS) with increasing temperature for undensified poplar wood. In conclusion, densification process has improved all the mechanical tested properties. <![CDATA[Optimization of wood machining parameters in CNC routers: Taguchi orthogonal array based simulated angling algorithm]]> Abstract: In the present study, two mathematical models were developed to optimize the surface roughness for machining condition of Cedar of Lebanon pine (Cedrus libani). Taguchi approach was applied to examine the effect of CNC processing variables. Quality characteristics parameters were selected as arithmetic average roughness (R a) and average maximum height of the profile (R z ) for wood material. Analysis of variance (ANOVA) was used to determine effective machining parameters. Developed mathematical models using response surface methodology (RSM) were optimized by a combined approach of the Taguchi’s L 27 orthogonal array based simulated angling algorithm (SA). Optimum machining levels for determining the minimum surface roughness values were carried out three stages. Firstly, the desirability function was used to optimize the mathematical models. Secondly, the results obtained from the desirability function were selected as the initial point for the simulated angling algorithm. Finally, the optimum parameter values were obtained by using simulated angling algorithm. Minimum R a value was obtained spindle speed of 17377 rpm, feed rate of 2,012 m/min, tool radius of 8 mm and depth of cut of 2,009 mm by using desirability function based simulated angling algorithm. For R z these results were found as 16980 rpm, 2,004 m/min, 8,001 mm and 2,003 mm. The R-square values of the R a and R z were 95,91 % and 96,12 %, respectively. The proposed models obtained the minimum surface roughness values and provided better results than the observed values. <![CDATA[The quality comparison of particleboards produced from heartwood and sapwood of European larch]]> Abstract: In this paper, the impacts of heartwood and sapwood usage on the physical, mechanical, and surface properties and formaldehyde emission of particleboard are investigated. European Larch (Larix decidua) trees are chosen as a raw material. The logs are divided into three segments: sapwood, heartwood and total wood. The highest amounts of cellulose (51,54%), and hemicelluloses (22,24%) in the sapwood, followed by total wood, and the heartwood, respectively. However, the highest amount of lignin (30,54%) was found in the heartwood. The highest extractives values are obtained from heartwood, followed by total wood, and the sapwood, respectively. While the lowest pH value (3,03) is found in heartwood, the sapwood samples provide the highest values (4,95). The highest ash (0,49%) content and amount of condensed tannin (13,89%) are extracted from heartwood, followed by total wood, and sapwood, respectively. The test panels manufactured from sapwood have the smoothest surface (7,49 µm (Ra), 48,86 µm (Ry), and 35,12 µm (Rz)) and the lowest contact angles (67,8°), while the roughest surface (14,20 µm (Ra), 68,05 µm (Ry), and 50,02 µm (Rz)) and highest contact angle (96,9°) are obtained from the panels of heartwood. The thickness swelling (19,88%) and formaldehyde emission (7,28%) values of the panels manufactured from heartwood are significantly lower than the panels manufactured from the total wood and sapwood. The highest modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) values are observed on sapwood, respectively, 15,60 MPa (MOR), 2201 MPa (MOE), and 0,523 MPa (IB). These mechanical strength values (MOR, MOE, and IB) are followed by total wood, and the heartwood, respectively. Surface smoothness and wettability of the particleboards manufactured from sapwood are better than those of total wood and heartwood. <![CDATA[Physical properties of <em>Guazuma crinita</em> by conventional methods and near infrared spectroscopy]]> Abstract: The aim of the present study was to determine the physical properties of the Guazuma crinita wood by conventional methods, as well as to estimate these properties by near infrared spectroscopy (NIR) through the development of multivariate calibration models. The samples were obtained from five trees and from three levels longitudinally for 5 and 8 years of age randomly selected from a plantation in Puerto Inca, Department of Huánuco (Perú). Basic density, volumetric, tangential and radial contraction were determined by the conventional methods. Models were developed by regression of partial least squares (PLS) through mathematical transformations. For the validation of the models, a new group of samples -which did not participate in the development of the model were used. Statistical significance was found F 5años = 191,5; F 8 años =84,9) between the different heights in the stem. Basic density and volumetric contraction show values of (0,88 and 0,83) and RPDp (1,55 and 3,27) acceptable for prediction.<hr/>Resumen: El objetivo del presente estudio fue determinar las propiedades físicas de la madera de Guazuma crinita por el método convencional, así como estimar estas propiedades por espectroscopia infrarroja cercana (NIR) a través del desarrollo de modelos de calibración multivariada. Las muestras fueron obtenidas de tres niveles del eje longitudinal en 5 árboles para 5 y 8 años de edad seleccionados al azar de una plantación en la zona de Puerto Inca, departamento de Huánuco (Perú). Se determinó la densidad básica, contracción total volumétrica, tangencial y radial por el método destructivo o convencional. Los modelos fueron desarrollados por regresión de mínimos cuadrados parciales (PLS) mediante transformaciones matemáticas. Para la validación de los modelos se empleó un grupo de muestras que no participo en el desarrollo del modelo. Se encontró diferencias estadísticas significativas (F 5años = 191,5; F 8años =84,9) entre las tres alturas en el fuste. Para densidad básica y contracción volumétrica se encontró valores de (0,88 y 0,83) y RPDp (1,55 y 3,27) aceptables para la predicción. <![CDATA[Physicochemical properties of <em>Pinus massoniana</em> wood subjected to silicone oil heat treatment]]> Abstract: In this Study, Pinus massoniana wood was heat treated with silicone oil to modify the chemical composition relative to the unmodified wood. Specifically, polysaccharide, lignin, extractives and ash contents were the properties investigated. The wood samples were first of all pre-heated in a micro-wave oven to ease heat transfer within the wood. Silicone oil heat treatment was carried out at 150, 180 and 210°C for 2, 4, 8 h. The silicone oil heat treated wood was characterized by Fourier transformed infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and contact angle. Results showed that silicone oil heat treatment caused significant decrease in the polysaccharide (P ˂ 0,0001) and ash contents (P ˂ 0,0001) and significant increase in the lignin (P ˂ 0,0001) and extractives contents (P ˂ 0,0001) as the treatment time increased. FTIR results showed that the chemical constituents of the wood were affected by the treatment, while TGA showed that the treated wood resulted in higher thermal stability with increase in the crystallinity index. Silicone oil heat treatment proved to be effective in increasing the contact angle of the wood. <![CDATA[Energy efficiency performance enhancement of industrial conventional wood drying kiln by adding forced ventilation and waste heat recovery system: A comparative study]]> Abstract: Conventional kilns dominate the wood drying industry. However, energy consumption during the process of ventilation remains a significant challenge. In this study, we designed a device to recover waste heat from exhausted wet air during kiln drying. To determine energy conservation, the device was installed in a 50 m3 kiln used for drying sawn timber in two different Chinese cities, and a traditional kiln with identical size was chosen to enable comparison. Two kinds of hardwood (Betula costata Trautv and Quercus mongolica) swan timbers were dried using conventional technology to investigate the energy saving effect of rainy seasons as well as seasonally different temperature. The results revealed that drying time and energy consumption decreased with the use of this energy-conserving device. Electrical and energy consumption were reduced by 18,9% and 38,5%, respectively. Waste heat recovery efficiencies ranged from 20,32% to 28,15%. Energy-conservation efficiency can be predicted to range from 12,23% to 22,74% annually. Equipment costs can be recovered within 3,5 years. <![CDATA[Investigation of an alternative testing protocol to determine the shear strength of bamboo parallel to the grain]]> Abstract: The common testing protocol to determine the shear strength of bamboo parallel to grain is ISO 22157 (2004). However, widely documented limitations of this test procedure calls for an alternative testing protocol. This study compared ISO 22157 (2004) (TP1) and 2 alternative testing protocols proposed by Base Bahay (TP2a and 2b) in determining shear strength of bamboo parallel to grain. The study used a local bamboo known as “kawayang tinik” (Bambusa blumeana). Results showed that TP1 produced more pure shear failures at 65% compared to TP2a and TP2b at 55% each. Shear strength values between the three methods were not significantly different, although, TP2b resulted in the lowest coefficient of variation at 18%. Also, TP2b was found to be the most effective in terms of specimen preparation, ease of assembly of testing equipment, and low variability in data. <![CDATA[Recommendation of non-destructive sampling method for density estimation of the <em>Eucalyptus</em> wood]]> Abstract: This study aimed to determine the wood density using destructive and non-destructive sampling methods in a eucalypt hybrid clonal and determine the best point for the non-destructive sampling of the tree. A 5,6-year-oldEucalyptus urophylla x Eucalyptus grandis hybrid clone, from an energetic forest, was used, planted in the municipal district of Martinho Campos, MG, Brazil. The trees were sampled by three methods of destructive sampling. The traditional method (0%, 25%, 50%,75% and 100% of the commercial height Hc); alternative method (2%, 10%, 30% and 70% Hc) and via a meter by meter method starting from a height of 1,30 m from the soil (DBH). Three non-destructive sampling methods were also appraised: Resistograph®, Pilodyn® and 22 mm diameter cores at a DBH. The use of the Resistograph® at the 1,10 m or 1,50 m points and the Pilodyn® at 1,50m of height from the soil results the best correlations with the basic density determined by the three destructive sampling methods considered. <![CDATA[Mechanical characteristics of impregnated white Jabon wood ( <em>Anthocephalus cadamba</em> ) using merbau extractives and selected polymerised merbau extractives]]> Abstract: This paper presents results of a study on the mechanical characteristics of impregnated Jabon wood (Anthocephalus cadamba) using Merbau extractives (ME) and two types of polymerised Merbau extractives (PME), i.e PME22 and PME33. A set of tests on hardness, shear, modulus of elasticity (MOE) and modulus of rupture (MOR) was conducted according to the relevant standards. Two types qualitative analysis by means of FTIR spectra and XRD analysis were carried out to explore relationship between the mechanical characteristics alteration with physico-chemical characteristics. The results indicated that a positive improvement in mechanical characteristics was obtained for Jabon wood impregnated with PME22 and PME33. Surface hardness of modified wood samples exhibited higher values compared to the non-impregnated samples for end and side hardness, by 20,04 and 30,54 % (PME22), and 32,73 and 39,89 (PME33),respectively. Shear strength increased by 41,87 and 49,58 % (PME22) and 74,02 and 79,10 %(PME) for radial (T) and tangential (T) sections, respectively. MOE increased by 23,52%(PME22) and by 40,12% (PME33), MOR values also increased by 28,50 and 41,19 % after impregnation with PME22 and PME33, respectively. The increment of mechanical properties of treated Jabon wood after impregnation treatment using polymerised Merbau extractives were confirmed by FTIR spectra and crystallinity (XRD) analysis. <![CDATA[Fractionation of <em>Pinus radiata</em> wood by combination of steam explosion and organosolv delignification]]> Abstract: This work proposes a sequential combination of steam explosion and organosolv delignification for Pinus radiata fractionation. An efficient pretreatment to fully optimize the use of lignocellulosic materials is the key to make a biorefinery profitable, especially for softwoods, known to be more recalcitrant than other lignocellulosic raw materials. Steam explosion has a dual effect on biomass as morphological and chemical changes are introduced. A delignifying stage has been stated to be necessary in order to ease hydrolytic enzymes accessibility to cellulose while avoiding non-productive bonds with the lignin present. Three steam explosion conditions were tested (170°C, 5 min; 180°C, 10 min; 170°C, 5+5 min) followed by an organosolv delignification stage, carried out at two different conditions (170°C, 60 min; 170°C, 90 min). All treatment yields, delignification extent, and hydrolysis yields were determined to evaluate each stage. The steam explosion treatment did not produce high delignification extent. Maximum global delignification (50,4%) was achieved when combining the two-cycle steam explosion with the most severe post-treatment condition tested. Enzymatic hydrolysis of the cellulosic residue improved after organosolv delignification; however, hydrolysis yields did not exceed 35%. The chemical changes undergone by softwood lignins are presumably responsible for the low digestibility. <![CDATA[Assessment of physical, mechanical, and biological properties of bamboo plastic composite made with polylactic acid]]> Abstract: The effects of different mixing, bamboo mesh size and heat treatment on the physical and mechanical properties and biodegradability of a polylactic acid (PLA) composite were determined. The results indicated that this composite exhibited high strength in all mechanical properties examined, except hardness using the pure polymer (PLA). The mesh size of the bamboo flour and heat treatment had considerable effects on all tests expect the decay resistance. The water absorbance and thickness swelling of the PLA composite was reduced to nearly zero after 3000 hours immersion in water. Moreover, the fungal decay test results demonstrated that PLA was highly resistant to both Basidiomycetes and Ascomycetes fungi. The brown rot fungi, however, produced an extensive mass loss in the composite composed of different levels of bamboo flour. <![CDATA[Effects of wood flour on the mechanical, thermal and morphological properties of poly (L-lactic acid)-chitosan biopolymer composites]]> Abstract: The aim of this paper was to investigate the effects of wood flour on the mechanical, morphological and thermal properties of poly (L-lactic acid) (PLA)-chitosan biopolymer composites produced by compression molding. The composites were characterized by a combination of mechanical properties, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The addition of chitosan to PLA matrix reduced the tensile strength from 57,1 MPa for pure PLA to 34,3 MPa for 5% chitosan and 11,5 MPa for 10% chitosan, and the flexure strength from 72,3 MPa for pure PLLA to 30,4 MPa for 5% chitosan and 24,6 MPa for 10% chitosan. The change trend in the young’s modulus was found to be similar as compare with the tensile strength. However, the flexure modulus generally increased with the addition of the chitosan as comparison with pure PLA. The mechanical properties of the PLA-chitosan blends with wood flour were found to be lower than theirs of the pure PLA. According to SEM images, some holes and small voids at various diameters on the fractured section of the all composites were seen. Tonset, T10%, T50%, T85% of the pure PLA decreased with the addition of both chitosan and wood flour. Thermal stability of the PLA-chitosan blends was determined to be better than the PLA-chitosan composites with wood flour. <![CDATA[Selection of superior clones of <em>Corymbia</em> hybrids based on wood and charcoal properties]]> Abstract: The use of fast-growing trees is a good economic strategy for charcoal production. Wood with adequate chemical and physical properties generally is positively correlated with charcoal quality. The objective of this research was to evaluate wood quality from fast-growing hybrids for charcoal production. Three Corymbia citriodora x Corymbia torelliana and four Corymba torelliana x Corymba citriodora hybrid clones were evaluated. Parameters used to evaluate wood quality were wood basic density, elemental and structural chemical composition, energy efficiency and thermogravimetric analysis and the parameters evaluated for charcoal quality were apparent relative density, gravimetric yield, high heating value, proximate analysis and energy efficiency. All clones had wood basic density superior than 0,5 g cm-3 and ash inferior than 1%, which are desirable for a good quality of charcoal. Lignin content did not differ among clones with an average less than the 28% recommended for energetic use. Although clones differed in wood parameters, as dry matter, high heating value, energy density, total extractives, holocellulose content, it did not reflect in charcoal quality differences. Wood from all clones had equal and satisfying high heating value of charcoal and energy efficiency quality for charcoal production and differed in apparent relative density and ash content.