Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 17 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<strong>Heat treatment of Tunisian soft wood species</strong>: <strong>Effect on the durability, chemical modifications and mechanical properties</strong>]]> <![CDATA[<strong>Natural coloration of wood material by red beetroot (</strong><em><b>Beta vulgaris</b></em><strong>) and determination color stability under UV exposure</strong>]]> This study is aimed to develop an eco-friendly wood stained extracted from beetroot (Beta vulgaris) and determine the color stability of this stain to UV light irradiation. Natural dyestuff were extracted from beetroot by ultrasonic-assisted method and prepared from aqueous solution with ferrous sulphate, aluminum sulphate, copper sulphate and vinegar mordant mixes. Scots pine (Pinus sylvestris), oriental beech (Fagus orientalis), oak (Quercus petraea) and walnut (Juglans regia) wood specimens were used for the study. After treatment with stain, wood specimens were exposed to UV irradiation for periods of 50, 100 and 150 hours. Results showed that the color change values for all wood specimens colored with beetroot extract had better performance compared to synthetic dye. Beetroot extracts may be used as an upper surface dyestuff for indoor application and toys. Therefore, alternative to synthetic dyes more economical and eco-friendly, wood paints may be developed. <![CDATA[<strong>The percentiles ratio 20<sup>th</sup> to 5<sup>th</sup> of bending strength and stiffness distribution in the case of spanish softwoods</strong>]]> A group of databases making a total of approximately 9300 sawn timber pieces from Spanish coniferous species, tested according to European standards and visually graded mainly according Spanish standards were analyzed. The percentiles ratio 20th/5th of bending strength, modulus of elasticity and density distribution were obtained for different combinations of species and visual stress grade. The Eurocode 5 proposes this percentile ratio by a coefficient k fi which is used to determine the design values of mechanical properties in fire situation. The percentile ratios obtained were compared with the specified value in Eurocode 5 for solid timber (k fi = 1,25). In lower grades of Spanish coniferous timber, this value was overly conservative. A value of k fi of 1,4 seems to be more adequate for the case of the bending modulus of elasticity and 1,4 to 1,5 for the bending strength. It is noted that, in the case of the upper grades, this value should be of 1,3; close to the Eurocode proposal. Furthermore, in the case of density, the value should be of 1,1; hence lower than suggested in the code. <![CDATA[<strong>Segmentation of anatomical elements in wood microscopic images using artificial vision techniques</strong>]]> Las características de los elementos que componen las imágenes microscópicas de madera son claves para la identificación de la especie de la cual proviene una muestra. En este artículo se presentó un método novedoso de segmentación de poros, radios y fibras. La metodología propuesta utilizó un conjunto de algoritmos de visión artificial acordes a las características de cada elemento. Para los poros se usó un descriptor de texturas, un algoritmo de agrupamiento y contornos activos; para los radios se utilizaron morfología matemática y filtros de Gabor para destacarlos y para segmentar se procedió en tres pasos: agrupamiento mean-shift, un muestrador de Gibbs y apertura de área; la fibra fue tomada como el excedente de los procesos de segmentación anteriores. Resultados experimentales con 18 muestras segmentadas manualmente de la especie Gaiadendron punctatum demostraron la eficiencia del método propuesto, usando estadísticas de desempeño tales como la precisión a nivel global y la sensibilidad y especificidad por cada elemento.<hr/>The characteristics of the elements of wood microscopic images are keys to identify the species of which comes a sample. This paper presented a novel segmentation method for pores, rays and fiber. The proposed methodology uses a set of algorithms from digital image processing consistent with the characteristics of each element. For pores, a texture descriptor, a clustering algorithm and active contours were used; for radios, mathematical morphology and Gabor filters were used for emphasis and to segment proceeds in three steps: mean-shift clustering, a Gibbs sampler and area opening; the fiber was taken as the surplus of previous segmentation processes. Experimental results with 18 manually segmented samples of Gaiadendron punctatum species demonstrate the efficiency of the proposed method, using performance statistics such as the overall success rate and the specificity and sensibility by element. <![CDATA[<strong>The effect of extractives on acoustical properties of persian silk wood (</strong><em><b>Albizia julibrissin)</b></em>]]> It was previously reported that extractives from Pernambuco wood (a species from Leguminosae family, native to South America) are positive for acoustical performance of wood. Thus the present study set to investigate the effect of extraction in hot water and ethanol/acetone mixture on acoustical properties of Persian silk wood (Albizia julibrissin, a species from Leguminosae family, native to Iran). Contactless forced flexural vibration on both free-ends of beams was performed on thin small specimens before and after extraction. Results showed that the extractive components soluble in hot water were positively useful to acoustical properties because removing these extractives reduced the acoustic property of the wood. Raw wood from Persian silk tree based on a combination of studied acoustical characteristics has theoretically the potential to be applied in violin backs and ribs. <![CDATA[<strong>Moisture sorption isotherms and heat of sorption of Algerian bay leaves (</strong><em><b>Laurus nobilis</b></em><strong>)</strong>]]> The moisture sorption isotherms of Algerian bay leaves (Laurus nobilis) were determined experimentally in this work. The equilibrium moisture contents of the leaves were measured at 40, 50, and 60 °C using static gravimetric method. Six mathematical models were tested to fit the experimental data of sorption isotherms and predict the hygroscopic behavior during storage or drying. Peleg model was found to be the best fitting model for describing the sorption curves. The net isosteric heat of sorption was computed from the equilibrium data at different temperatures by applying the integrated form of the Clausius-Clapeyron equation. The net isosteric heat of sorption is inversely proportional to the equilibrium moisture content and is found to be an exponential function of moisture content. <![CDATA[<strong>Effect of spacing on some mechanical properties of narrow leaved ash (</strong><em><b>Fraxinus angustifolia</b></em><strong>) wood</strong>]]> In this study, conducted to test the effect of spacing on wood quality; the effect of four different spacing types, applied in Adapazari Süleymaniye plantation (Region 1; 3x2 m; Region 2; 3x2,5 m; Region 3; 3,75x3,75 m; Region 4; 4x4 m), on some mechanical properties of narrow leaved ash (Fraxinus angustifolia) have been studied. In the present study, some mechanical properties such as the compression strength parallel to grain, tensile stress perpendicular to grain, bending strength, impact bending strength and modulus of elasticity were determined. As a result, the ash wood, grown in region 4 with a wide range of planting, has high mechanical properties. However, when analyzed in terms of wood quality characteristics, it has been found that spacing in region 1 (2x3 m) is more suitable for applications of ash plantations. <![CDATA[<strong>Physical properties of beech wood thermally modified in hot oil and in hot air at various temperatures</strong>]]> In this study, beech wood was treated in hot oil and in hot air to determine the differences in the effects of the two processes on the physical properties of the wood. Heat treatment was conducted at temperatures of 160, 190, and 220 °C for 2 h at atmospheric pressure. After the heat treatment, various properties of the wood, including mass increase in hot oil treatment (wt% gain), mass loss in hot air treatment (wt% loss), oven-dried density, swelling, equilibrium moisture content, fiber saturation point, and moisture content were determined. Regression analyses were conducted to assess the differences in mass change and volumetric swelling, and the findings were analyzed statistically. The results showed that heat treatment in hot oil influenced the physical properties of beech wood more than treatment in hot air. However, the extensive uptake of oil by the wood samples, resulting in mass increases, was a negative issue associated with the hot oil treatment. <![CDATA[<strong>Natural weathering performance of three fast-growing </strong><em><b>Eucalypt</b></em><strong> woods</strong>]]> We investigated the effect of outdoor exposure on the wood surface from three fast - growing Brazilian eucalypts through color, wetting and thermal analyzes. Gympie messmate (Eucalyptus cloeziana), rose gum (Eucalyptus grandis) and blue gum (Eucalyptus saligna) woods were exposed outdoors in a subtropical region for 360 days. We performed three collections every 120 days. We investigated color changes of untreated and weathered woods through a spectrophotometer (CIEL*a*b* system) and changes in macro compounds of wood through thermogravimetric analysis. In addition, the apparent contact angle and work of adhesion were evaluated using a goniometer. Outdoor exposure for 120 days provided significant increment in grayish of wood surface. Thermogravimetric curves of wood changed after the weathering, especially in the regions related to hemicelluloses and lignin thermal degradation. Outdoor exposure for 360 days converted hydrophilic wood surface into a very hydrophilic one, wherein occurrence of microcracks contributed to fully spreading of water droplets. <![CDATA[<strong>Density and mechanical properties of Argentinean </strong><em><b>Acacia melanoxylon</b></em>]]> El trabajo se enfocó en la determinación de la densidad normal y las propiedades mecánicas de la madera de Acacia melanoxylon implantada en Argentina, y en analizar la relación entre estas variables. El material se seleccionó al azar del obtenido del aserrado de 20 árboles provenientes de cuatro sitios del sudeste de la provincia de Buenos Aires. Se determinó la densidad aparente conforme a la norma IRAM 9544 y los ensayos mecánicos se ejecutaron sobre cuerpos de prueba pequeños y libres de defectos según los lineamientos de la norma ASTM D 143. El valor medio de la densidad fue 564 kg.m-3 y la tensión de rotura mostró los siguientes valores medios: 89,9 en flexión; 49,5 en compresión paralela a las fibras; 11,7 en compresión perpendicular y 11,6 en corte paralelo. La dureza promedio alcanzó 45,3 y el módulo de elasticidad en flexión exhibió un valor medio de 10926 Los resultados de las propiedades mecánicas son los esperados para una madera de densidad media y pueden considerarse adecuados para el uso de la especie en la industria de la construcción y del mueble. Los modelos de regresión entre la densidad y las propiedades mecánicas exhibieron valores del coeficiente de determinación (R²) comprendidos entre 0,70 y 0,87. El modelo de regresión entre el módulo de elasticidad y la resistencia en flexión mostró un valor de R² igual a 0,72.<hr/>The aim of this paper was to determine the density (at 12 % m. c.) and the mechanical properties of sawn wood of Argentinean Acacia melanoxylon, and to study the relationship between these properties. Test samples were randomly selected from the material obtained by sawing 20 trees harvested in four different plantations grown in the southeast of Buenos Aires province. Density was determined according to IRAM 9544 and mechanical tests were carried out by following the procedures of ASTM D 143. The mean value obtained for density reached 564 kg.m-3. Strength exhibited the following mean values: 89,9 in bending, 49,5 in compression parallel to the grain, 11,7 in compression perpendicular and 11,6 in shear parallel. The average hardness reached 45,3 and the modulus of elasticity in bending exhibited a mean value of 10926 These results are congruent with those expected for a medium-density wood and they can be considered suitable for uses related to the construction and furniture industries. Coefficients of determination (R²) ranging from 0,73 to 0,87 were found between density and mechanical properties. R² reached 0,72 between modulus of elasticity and bending strength. <![CDATA[<strong>The effect of traditional hygro-thermal pretreatments on the acoustical characteristics of white mulberry wood (</strong><em><b>Morus alba</b></em><strong>)</strong>]]> The wood used in making musical instruments usually undergoes pre-treatments or conditioning. Some processes have resulted from laboratory research, while many treatments are applied by craftsmen using traditional methods that have not yet been scientifically assessed. This paper is based on laboratory methods which simulate hydrothermal pre- treatments traditionally applied by Iranian lute makers to mulberry (Morus alba), an important wood for lutes from the Middle East to Japan. By applying a cyclic process, drying (60°C) and ambient re-conditioning, which mimics wood seasoning and short-term aging, the damping coefficient (tanδ) was decreased down to 10% without negatively affecting specific modulus of elasticity (E’/ρ). Long-term (up to 4 months) soaking in cold water removed extractives, and decreased density as well as E’/ρ, but did not affect tanδ. Short-term hot water treatment removed as many extractives, but caused a smaller decrease in E’/ρ than cold water, and significantly increased tanδ. This paper helps to clarify some traditional processes used by instrument makers, and can provide a basis for necessary cross-cultural scientific studies in the future. <![CDATA[<strong>Effects of nano-wollastonite on physical and mechanical properties of medium-density fiberboard</strong>]]> Effects of nano-wollastonite (NW) on physical and mechanical properties of medium density fiberboard (MDF) were studied. NW was applied at 5, 10, 15, and 20 g/kg dry weight basis of wood fibers; the results were then compared with control specimens. Two application methods of NW were used: surface and internal applications. Density was kept constant at 0,67 g/cm³ for all treatments and tests were carried out in accordance with ASTM D-1037. Addition of NW contributed in improving the physical and mechanical properties of the panels, both when applied internally or as surface treatment. It was concluded that NW contents of 10% and 15% were the optimal levels for industrial purposes for internal and surface applications, respectively. <![CDATA[<strong>Properties of OSB panels with veneer inclusion</strong>]]> This work aimed to evaluate the effect of veneer inclusion with different wood species, and also different levels of pressing pressure applied in the moment of the veneer inclusion over physical- mechanical properties of already consolidated OSB (Oriented Strand Board) panels. Treatments were arranged in factorial scheme 4 x 2 (four wood types for veneer inclusion - Pinus oocarpa, Eucalyptus urophylla, Parkia gigantocarpa, Brosimum parinarioides; and two pressing pressures - 1 and 2 MPa) and also a control (without veneer inclusion). Veneer inclusion was made with 180 phenol formaldehyde adhesive, in a simple glue line, perpendicular to the external layer of panels. The pressing cycle used was 150ºC for 4 minutes under pressure 1 or 2 MPa pressure depending on the pre- established treatment. It was possible to conclude that: 1) Veneer inclusion with pines, eucalypt and amapá promoted significant improvements for physical-mechanical properties of OSB panels, highlighting eucalypt and amapá; 2) There was not a significant effect of the level of pressing pressure over mechanical properties of OSB with veneer inclusion; and 3) Regarding physical properties, the highest pressure level (2 MPa) promoted a negative effect in some properties, while veneer inclusion the pressure of 1 MPa generally promoted significant improvement of all physical properties. <![CDATA[<strong>Effect of extractives on wood color of heat treated </strong><em><b>Pinus radiata</b></em><strong> and </strong><em><b>Eucalyptus pellita</b></em>]]> Heat treatment can change wood color without any use of environmentally harmful chemicals, and the efficiency of this process depends on the raw material to be treated. The objective of this study was to evaluate the influence of extractives on the color change of Eucalyptus pellita and Pinus radiata wood during heat treatment. The extractives were extracted in cold water and in dichloromethane as well as totally removed and the wood was treated at 170°C and 200°C for three hours under atmospheric pressure and in presence of air for evaluating the lightness (L*), green-red coordinate (a*), blue-yellow coordinate (b*), color saturation (C) and tonality angle (H) values. Pinus radiata wood was more resistant to discoloration by heat treatment. The removal of total and cold water-soluble extractives before heat treatment changed the L* value of Pinus radiata, a* value of Eucalyptus pellita, and b*, C, and H values of both species. Removal of extractives soluble in dichloromethane did not affect the color of heat treated wood. Thus, understanding the influence of extractives on heat treated wood can allow adapting the raw material to the process for enhancing the applicability of heat treatment for changing wood color. <![CDATA[<strong>Mechanical, thermal, morpological properties and decay resistance of filled hazelnut husk polymer composites</strong>]]> Four different formulations of natural fiber-polymer composites were fabricated from mixtures of hazelnut (Corylus avellana) husk flour (HHF), polypropylene (PP) and high density polyethylene (HDPE). Variables examined included polymer and coupling agent types. All formulations were compression molded in a hot press for 3 minutes at 175 0C. The resulted specimens were tested for mechanical properties according to ASTM D-790 and ASTM D-638. In addition, scanning electron microscopy (SEM), thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) analysis were performed to characterize rheological properties of the fabricated composite. Furthermore, decay tests were performed to determine degradation of hazelnut husk polymer matrices. Hazelnut husk polymer composites had high mechanical properties for the tested formulations. The thermal studies showed that incorporation of hazelnut husk into the polymer matrices used did not adversely affect the composite. The HDPE+50% wood + 3% MAPE (HHF2) formulation showed the highest natural durability with only 3,47% and 4,60% mass losses against Trametes versicolor and Postia plecenta, respectively, while Scots pine solid controls experienced around 32% mass loss under the same exposure condition. <![CDATA[<strong>Kraft pulping properties of European black pine cone</strong>]]> In this study, different mixtures of cones and wood chips of European black pine (Pinus nigra) were kraft cooked, and the resulting pulp and paper properties were investigated. Also, the chemical compositions and fiber dimensions of the cones and wood were examined. Cone chips were mixed in different ratios (5%, 10%, 15%, and 20%) with wood chips prior to pulping. Also, kraft pulping of 100% cone chips and 100% wood chips were conducted so the results could be compared. The kraft pulp of 100% cone chips had lower pulp yield, lower pulp strength, and higher kappa number than that of 100% wood chips. As the ratio of cone chips was increased in the mixture of cone chips and wood chips, higher kappa numbers and lower total screened yield were obtained. Additionally, the strength properties and brightness of the resulting kraft pulp were decreased gradually. However, the opacity of the pulp was increased slightly. Consequently, cone fibers of European black pine can be used as a raw material in the paper industry by mixing with wood fibers. <![CDATA[<strong>Evaluation of axial impregnation as an alternative to classical wood vacuum pressure impregnation method</strong>]]> The evolution of laws on the use of biocide products has led to important changes in the field of wood preservation leading to an increasing interest for non "biocidal treatments" like thermal or chemical modifications. While thermal modifications become more and more common on industrial scale, development of chemical modifications progresses slowly. One reason for the challenges encountered is probably the difficulty to use actual vacuum pressure plant to impregnate wood with solutions of reactive chemicals aimed to react with or within the wood. In this context, the presented research focuses on a new alternative called axial impregnation, derived from Boucherie process, for impregnation of treatable non durable hardwood species. This process consists of low-pressure impregnation of green wood logs through its lower extremity with treatment solution transiting via natural pathways of vessels. In order to evaluate the feasibility of the method, logs of different hardwood species were impregnated with a copper based preservative solution and the distribution of copper within the wood was determined. Results indicated that treatable wood species like beech, hornbeam and birch can be easily and homogeneously treated using axial impregnation method, while ash known for its weak impregnability remained untreated. <![CDATA[<strong>Dimensional and morphological analysis of the detritus from six European wood boring insects</strong>]]> Detailed morphological and dimensional analysis of the detritus deposited in the galleries of wood-boring insects was performed for some of the most common xylophagous insect larvae in timber construction in Spain. The samples studied belong to six species of four common families of borers: Cerambycidae, Anobiidae, Curculionidae and Lyctidae. The samples were provided by Spanish and German companies and laboratories. The detritus was assessed for size, shape, and colour and, for different species, was found to show morphological and dimensional differences, enabling better and faster identification of these destructive agents. Frass shape and colour assessment together with statistical dimensional data of the six species are presented. A predictive function based on length and width variables of the detritus is proposed, using multivariate discriminant analysis methodology. This function has been proven to be more than 78% effective in tests of the model. <![CDATA[<strong>Effects of oleothermal treatment and polydimethylsiloxane (PDMS) coating on natural weathering of beech and fir woods</strong>]]> Effects of natural weathering on oleothermally treated wood and coated with an organic silicone compound were studied. Slats of beech and fir woods were cut in sizes of 20×10×1 cm. The slats were treated by soybean oil at 230°C for 1 h. Then, the half of the untreated and oleothermally treated slats were coated with polydimethylsiloxane (PDMS) and the rest of them were considered as control. All slats were hanged in 45° angle at the southwest (SW) direction for 90 days. They were analyzed for color changes, roughness, and contact angle properties at 30-day intervals. Results showed that the oleothermal treatment of wood reduced discoloration of fir samples against natural weathering; however, the reducing effect was lower in the Beech samples. This treatment also reduced the surface roughness of the fir samples during weathering while it increased the surface roughness of beech. Wettability of the samples in both species, before and after weathering, was reduced by the oleothermal treatment. Results also revealed that coating of the wood surface with PDMS does not prevent the discoloration and surface roughness against weathering. Nevertheless, the coating could considerably decrease the hydrophilicity of the woods even after weathering. <![CDATA[<strong>Empirical statistical model for predicting wood properties of </strong><em><b>Paulownia fortunie</b></em>: <strong>Part 1: Physical and biometrical properties</strong>]]> This paper describes the development of model to predict the within-tree variation of wood density, shrinkage, fiber length, fiber diameter and cell wall thickness from pith-to-bark and bottom-to-top, using data collected from a 13-year-old paulownia (Paulownia fortunie) stand where trees were planted in an experimental plantation in Iran. The sample disks were taken from each tree to examine the wood density, shrinkage, fiber length, fiber diameter and cell wall thickness variation from pith to bark at 5, 25, 50 and 75% of the total tree height. The study was laid out in a randomized complete block design. Linear prediction model were developed using longitudinal direction (bottom-to-top) and radial direction (pith-to-bark) indices as explanatory variables. The results indicated that, the wood density, shrinkage, fiber length, fiber diameter and cell wall thickness, considerably changes from pith to bark and from the base upwards. Based on the final model, it was found that the physical and biometrical properties were significantly influenced by longitudinal and radial directions. The model equation were based on the model used to describe the within-tree variation in the wood density, shrinkage, fiber length, fiber diameter and cell wall thickness of Paulownia, and is functions of radial and longitudinal directions.