Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 20 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Surface roughness of thin wood veneers sliced from laminated green wood lumber]]> Abstract: Freshly-felled Chinese fir (Cunninghamia lanceolate), Masson Pine (Pinus massoniana) and Camphor Tree (Cinnamomum camphora) logs were reconstituted to form laminated lumber with moisture content above fiber saturation point by slicing, finger-jointing, gluing, and cold-pressing processes. The laminated lumber was then sliced into wood veneers, which were air-dried to about 15% moisture content. The surface roughness of the veneer was tested in comparison with two commercial engineered wood veneers using a stylus tracing method. The influence of the wood surface roughness was relatively small for the wood species chosen due to their similar densities. All roughness parameter values were consistently larger along the transverse direction compared with these along longitudinal direction. The values of surface roughness at the finger-joint region were higher than these that at the non-finger-joint region along both longitudinal direction and transverse direction. The two engineered wood veneers had surface roughness values noticeably smaller in the longitudinal direction, but their values in transverse direction were comparable and even larger compared with these of the prepared wood veneers including both non-finger-joint and finger-joint regions. Overall, the process of laminating finger-jointed green wood planks and subsequently slicing can be used to yield acceptable wood veneers with sufficient surface quality. <![CDATA[Effect of nanoclay-treated UF resin on the physical and mechanical properties of plywood manufactured with wood from tropical fast growth plantations]]> Abstract: Physical and mechanical properties were evaluated on cross-laminated panels (plywood) fabricated with three plantation species (Cordia alliodora, Gmelina arborea and Vochysia ferruginea) from tropical climates in Costa Rica. The panels were glued with urea-formaldehyde resin modified with nanoclay at four concentrations (0,75; 1,00; 1,50 and 2,00 %) and unmodified resin. It was determined that addition of nanoclay to urea-formaldehyde adhesive positively decreased moisture absorption and swelling of the plywood panel with statistical significance. However, nano-modification did not have a significant effect on the density and specific weight of plywood. Nano-modification of urea-formaldehyde resin with nanoclay at 0,75 % improved the Module of rupture and Modulus of elasticity in flexure parallel to surface in the three species, also increasing mechanical resistance to strains in parallel tension, shear and compression. By means of electronic microscopy, it was evidenced that the nano-modified adhesive became diffused at the inside of the cellular structure of wood in a better way, allowing for the generation of a transition zone that increased the mechanical properties at the macro level. According to the properties evaluated, it was determined that 0,75 % is the optimal percentage to use of nanoclay on urea-formaldehyde resin. <![CDATA[Impact of feed rate, milling depth and tool rake angle in peripheral milling of oak wood on the cutting force]]> Abstract: The paper presents the results of investigations performed in the peripheral milling of oak wood (Quercus robur), where the impact of cutting regime elements and tool geometry on the cutting force is analyzed. A large-scale experiment was conducted to implement the obtained results in developing a reliable analytical and simulation model for analyzing and predicting the cutting forces, depending on the feed rate, the milling depth and the tool rake angle. The generated mathematical model is adequate and describes accurately enough the dependence of the cutting forces upon the selected impact factors in the adopted test conditions. The evaluation of the model parameters significance indicates a significant impact of feed rate and milling depth, whereas tool rake angle does not show any significant impact in this case. The developed mathematical model can be employed in manufacturing conditions as an indicator of wood and wood-based materials machinability. <![CDATA[Monitoring the cell wall characteristics of degraded beech wood by white-rot fungi: Anatomical, chemical, and photochemical study]]> Abstract: Meticulous chemical analysis of decaying xylem and linking it to corresponding anatomical modification at the cellular level can improve our understanding of the decay process. The aim of this study was to monitor the histological, chemical, photochemical, and progression of wood degradation by two white-rot fungi at different intervals. Oriental beech wood (Fagus orientalis) blocks were exposed to Pleurotus ostreatus and Trametes versicolor to investigate the degradation capabilities of these two fungi. Light microscopy was used to study the decay patterns in wood. Decayed wood samples were also analyzed to determine lignin, cellulose and sugar contents and also evaluated at two week intervals by FT-IR spectroscopy to study chemical alterations. According to chemical analyses lignin is the most degraded polymer followed by cellulose and hemicelluloses for both white rot fungi. However, both test fungi tended to consume lignin more than cellulose. FT-IR spectra changes for lignin and carbohydrates in beech wood supported chemical alteration and indicated that both fungi decay wood in a simultaneous pattern. <![CDATA[Strength grading of turkish black pine structural timber by visual evaluation and nondestructive testing]]> Abstract: We examined the compatibility between the visual strength grading and the mechanical properties determined by using nondestructive and destructive test methods in Turkish Black Pine structural timbers. Fifty three structural timber were graded with three different visual strength grading standards. Dynamic modulus of elasticity was determined by longitudinal vibration (MOEdv) and stress wave (MOEds) test methods. The static modulus of elasticity (MOEs) and the modulus of rupture (MOR) of the timbers were determined in structural size. The average dynamic and static modulus of elasticity and modulus of rupture values of the timber sorted into best class of all standards were considerably higher than the lower classes. The differences in the modulus of elasticity values between the strength classes were found significant for British and German standards but insignificant for Turkish standard. However the decrease in modulus of rupture values with decreasing grading class was found significant for all standards. Best compliance between the visual grading class and the dynamic or static modulus of elasticity and modulus of rupture was observed. Strong correlations were found between the dynamic modulus of elasticity and static modulus of elasticity and modulus of rupture. Longitudinal vibration method showed better correlation with the static modulus of elasticity and modulus of rupture than stress wave method. <![CDATA[Examining the efficiency of mechanic/enzymatic pretreatments in micro/nanofibrillated cellulose production]]> Abstract: There is still a need to improve the production sequences of micro fibrillated and nano fibrillated celluloses to obtain more economic and better quality products. The aim of this study was to improve the production efficiency and quality of micro fibrillated and nano fibrillated celluloses by examining the enzyme (xylanase endo-1,4-) employed in pretreatment sequences. Fairly homogeneous nano fibrillated cellulose with a width of 35 ± 12 nm was produced in this study. Sequences employed to produce micro fibrillated and nano fibrillated celluloses decreased the cellulose crystallinity of bleached kraft pulp and lower total crystalline index and lateral order index values were observed for micro fibrillated and nano fibrillated celluloses in FTIR examinations. Lower crystallinities were also defined by 13C-NMR (46,2 ppm) which was substantiated with C6 peaks in the amorphous domain. Sequences to produce micro fibrillated and nano fibrillated celluloses resulted in shorter fiber dimensions with less ordered cellulose structure leading lower thermal degradation that reveal main polymer chain source from cellulose units. Dynamic mechanical thermal analysis results showed that the initial and maximum storage modulus of the nano fibrillated and micro fibrillated celluloses films were improved by 114% and 101%, respectively. The storage modulus of micro fibrillated and nano fibrillated celluloses films were 4,96 GPa and 2,66 GPa at temperature of 235°C, respectively. <![CDATA[Effect of pole size on preservative penetration and retention in air-dried ugandan grown eucalypt utility poles]]> Abstract: Treated wooden utility poles, from trees such as eucalypts, are the most commonly used for telephone and electricity transmission lines in Uganda. In the last decade, however, frequent failure of wooden poles in service has been reported, likely due to the preservative chemical, wood used or the treatment process. The objective of this study was to assess the creosote preservative penetration and retention in eucalypt wood. A total of 126 Eucalyptus grandis poles i.e. 42 poles for each size category, with an average moisture content of below fibre saturation point (28%) were treated in different charges depending on their size. In length, poles used were 9, 11 and 14m. Every charge consisted of poles within the same size category. The Full Cell pressure method was used to treat the different charges with creosote preservative. For all the charges the same treatment schedule was maintained. Creosote penetration was highest in 14m poles (20,5mm) and lowest in 9m poles (18,4mm), Creosote retention was also highest in 14m poles (193kgm-3), but lowest in 11m poles (162kgm-3). Irrespective of differences in level of penetration and retention among the various pole sizes, all the poles acquired more than the required standard minimum level of penetration and retention i.e. 15mm and 115kgm-3 respectively. However, for all the pole sizes, creosote penetration was less than the sapwood depth. The current treatment schedule seems better suited for the larger poles of 14m than the 9 and 11m. For better treatment, it is recommended that smaller poles i.e. 9m and 11m should be treated for a longer period than 14m poles since they tend to have lager sapwood. The minimum basis of 15mm penetration should be increased to at least cover the entire pole sapwood depth. <![CDATA[Colour changes and morphological performance of impregnated jabon wood using polymerised merbau extractives]]> Abstract: Colour can be one of the preferencial factors prior to making a decision when people want to make a purchase of a wood product. Impregnation treatment can alter the wood colour. This study investigated the colour change of young plantation Jabon wood due to impregnation using Polymerised Merbau Extractives. Colour evaluation was done using the CIEL*a*b* system. Investigations also included morphological appearance by Scanning Electron Microscopic and chemical change by Fourier Transform Infrared analysis. The results demonstrated that impregnation treatment using selected Polymerised Merbau Extractives i.e. PME22 and PME33, resulted in the colour change of the wood. Appearance of the impregnated wood was different from the original wood; it was like a 'new wood'. The colour was changed permanently. PME33 caused Jabon wood samples to be darker. The SEM results of untreated and treated Jabon wood showed apparent difference due to deposited cured polymerised Merbau extractives (PME) in wood vessels. Obviously, a certain amount of cured PME precipitated on the surface of wood vessels and filled in the cell wall illustrated by the cross section of treated wood. FTIR spectra revealed that impregnating treatment using polymerised Merbau extractives made chemical changes in the wood of new functional groups bonded to Jabon wood. <![CDATA[<em>Eucalyptus globulus</em> and <em>Quercus robur</em> engineered wood flooring. impact resistance for several compositions]]> Resumen: Utilizando el test de impacto, basado en la norma ASTM D1037-99, se compara la resistencia de diversas composiciones de fabricación de parquet multicapa de Eucalyptus globulus y Quercus robur, con distintos espesores de capa noble y utilizando para cada uno de ellos tres tipos diferentes de soporte base con el propósito de evaluar la aptitud de Eucalyptus globulus como parte destacada (capa noble) en la elaboración de un parquet multicapa. El resultado del ensayo de impacto resultó ser estadísticamente independiente de la especie utilizada (eucalipto o roble) como capa noble, habiéndose analizado con niveles de significación superiores al 95%, siendo, sin embargo, dependiente del tipo de elemento de soporte utilizado y del espesor de la capa noble. Un modelo lineal, que utiliza la densidad media en los 4 primeros milímetros de profundidad de cada pieza, permitió explicar hasta un 82% de la variación del diámetro de huella en el ensayo de impacto, lo que permite utilizar con suficiente garantía esta densidad como predictor del diámetro de huella del ensayo de impacto<hr/>Abstract: The resistance of several Eucalyptus globulus and Quercus robur engineered wood flooring compositions has been tested using the impact test, according to the ASTM D1037-99 standard. The test samples were made up of different top layer, top layer thicknesses and different inner lays. The result not showing significant differences between the two wood species. The impact test result was statistically independent of the species tested (eucalyptus or oak) as top layer, being analyzed with significance levels above 95%; however, statistically significant results were obtained for support material and top layer thickness. A linear model, using the average density on the first 4 mm depth, explained 82% of the impact results obtained by the tests that allow to use, with sufficient guarantee, this average density as a good predictor of the results (diameter of impress mark) of the impact test. <![CDATA[Influence of combined hygro-thermo-mechanical treatment on technical characteristics of poplar wood]]> Abstract: Combined hygro-thermo-mechanical technique was adopted and used for densification of poplar wood instead of sole treatment. This technique is combination of two techniques of hygrothermal treatment and densification of wood. For treatment, poplar wood blocks were initially treated hygrothermally at temperatures of 130, 150 and 170°C for holding time of 20, 40 minutes. Afterwards, the densification process was carried out under a hot press (temperature 160°C for 20 minutes). For densification compression set was adjusted for 40 and 60 % based on the initial thickness (radial direction) of the blocks. The densified and non-densified wood blocks were tested for physical and mechanical properties as density, water absorption, thickness swelling, springback, bending strength, modulus of elasticity as well as shear strength parallel to grain. Results revealed that wood properties were enhanced due to the combined hygro-thermo-mechanical -treatment. According to the results, wood density was increased due to the combined hygro-thermo-mechanical -treatment significantly. The treatment improved the dimensional stability of the densified samples. It was also found that the combined hygro-thermo-mechanical -treatment could significantly improve mechanical properties and also reduce the springback in the densified poplar wood. <![CDATA[Comparison of two kiln-drying schedules for turkish hazel ( <em>Corylus colurna</em> ) lumber of 5-cm thickness]]> Abstract: Turkish hazel (Corylus colurna) lumber with a nominal thickness of 5 cm from the Kastamonu region, Turkey, was dried through conventional kiln drying using two different programs, a non-protective drying schedule and a protective drying schedule. The goal of the study was to obtain a kiln schedule that would maintain wood quality and also save drying time until a final moisture content of 8 ± 2% was reached. The intensity of warping (twisting, bowing, cupping, crooking), superficial, internal, and end checks, residual stresses, drying rate, and moisture gradient of the dried woods were measured, and the results were evaluated according to the classification of the European Drying Group. The results showed a more homogeneous moisture profile, fewer occurrences of superficial checks, and an absence of internal checks when using the protective drying schedule due to low warping values compared with those for the non-protective drying schedule. From the point of view of energy efficiency, by saving 60 h of drying time, the non-protective schedule reduced electricity by 960 KWh and was therefore more profitable by $105,60 in this trial. Therefore, it seems that the protective drying schedule should be recommended as the optimum program for drying Turkish hazel lumber from the Kastamonu region at the commercial scale. <![CDATA[Particularities of hollow-core briquettes obtained out of spruce and oak wooden waste]]> Abstract: Wooden hollow-core briquettes made of wooden waste represent an important category of wood-based combustible materials used in heating chambers. This paper aims to determine some of the characteristics of these briquettes made of spruce and oak waste. The comparison to the classic types of briquettes is made in order to identify the advantages and disadvantages of such briquettes. The main characteristics of these briquettes are presented, starting from size, density, abrasion, compression and ending with the inferior and superior calorific values, calorific density and ash content. The obtained results show that there are few differences between their characteristics and those of the classic ones. These differences depend on the pressing method and equipment, in comparison to other briquettes without a hollow core. Apart from the characteristics and the nature of the material being used, the hollow-core briquettes remain renewable combustible materials increasingly used in combustion (for heating purposes or in order to cook food or for heating in rural households or as substitutes for charcoal or cogenerate in various industrial fields). Given their economical character, there is complete suitability of these briquettes for cooking and heating.