Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 18 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<strong>Cutting distance as factor to evaluate the quality of wood machined surfaces</strong>: <strong>A preliminary study</strong>]]> Surface quality of solid wood products is an important subject of study since it influences further manufacturing processes, such as finishing or strength of adhesive joint. In this study, the surface quality of the machined surfaces was evaluated through the cutting distance, which is defined as the accumulated linear meters of wood processed by a cutting tool. The roughness (Rz) and wetting (contact angle) behaviour on wood machined surfaces have been assessed each 2000 meters respectively, from 0 to 10000 meters. In Pinus radiata samples, machined using a three hydro centred mounting cutter-heads of 6 knives HSS (High Speed Steel) 6 % W (Wolfram) and a rake angle of 15° each, similar contact angles were found associated to different values of Rz through the cutting distance. This study verifies that a wide spectrum of cutting distance allows an accurate evaluation of roughness and wettability behaviour surface characteristics. <![CDATA[<strong>Evaluation of the mechanical and physical properties of particleboard manufactured from Canola (</strong><em><b>Brassica napus</b></em><strong>) straws</strong>]]> This study examined possible feasibility of canola (Brassica napus) straws in the production of particleboard. Three-layer experimental particleboards with density 0,7 g/cm³ were manufactured using different canola straws particle ratios (0%, 25%, 50%, 75% and 100%) and urea formaldehyde (UF) adhesive. Modulus of elasticity (MOE), modulus of rupture (MOR), internal bond strength (IB), water absorption (WA) and thickness swelling (TS) properties of the boards were evaluated and a statistical analysis was performed in order to examine possible feasibility of these straws in commercial particleboard manufacturing. The results indicated that, the addition of canola straws particle significantly improved modulus of rupture and modulus of elasticity of the panels and greatly reduced their internal bonding. Overall findings showed that most panels made from above-mentioned materials exceed the EN Standards for MOR, MOE and IB. Also, the water absorption and thickness swelling increased with increasing canola straws content in the panels. The experimental results have shown that production of general purpose and furniture grade particleboard used in dry conditions using canola straws is technically viable. The results of the study demonstrate that canola straws can be an alternative raw material source for particleboard industry. <![CDATA[<strong>Mechanical, morphological and thermal properties of nano-boron nitride treated wood materials</strong>]]> Thermal instability is the one of the most important disadvantages of wood since it begins to decompose at a low temperature (>110 °C). Many scientists, past and present, have conducted studies aimed at improving the thermal stability of wood. The aim of this study was to impregnate wood with nano-sized boron nitride (NBN) to improve its thermal stability and to investigate the changes in the properties of Scots pine (Pinus sylvestrist), Ash (Fraxinus exelsior), and Iroco (Chlorophora excelsa) woods after the impregnation. The effects of the impregnation with NBN also were investigated on the heat-treated woods. The impregnation was conducted with using full-cell method in a chamber under a pressure of 0,6 MPa for 1 h. Densities at 0% and 12% moisture content (MC), mechanical properties, color changes, thermal stability, and scanning electron microscopy (SEM/EDAX) analysis were determined. The test results showed that the impregnation of wood with NBN increased generally the flexural strength and elasticity of modulus at bending, but the NBN impregnation decreased generally the compression strength except for ACI, ATWI, IC, and ICI. It was also determined that the changes in density and color were statistically different after the impregnation. According to the SEM/EDAX results, deposits of nano-sized boron nitride were found inside the cell wall and on the pits. But the deposits were also determined in inside structure of the wood with EDAX analysis. Thermal stability in T10% and T50% of wood was found to improve after the impregnation with NBN. TG/DTG and DTA values for some samples were found to fluctuate due to the heterogeneous dispersion of the NBN in the wood. <![CDATA[<strong>Decay resistance of four fast-growing Eucalypts wood exposed to three types of fields</strong>]]> The evaluation of wood durability enables the definition of reliable parameters to predict the service-life of wood-based products. This study aimed to evaluate the wood deterioration of four fast-growing eucalypts species (Eucalyptus botryoides, Corymbia citriodora, Eucalyptus paniculata e Eucalyptus tereticornis) exposed to three field tests (outdoor, flooded site and forest canopy) during 540 days. The physical properties measured were: mass loss, density and moisture content. Furthermore, we determined changes in wood color by CIEL*a*b* method and performed a visual analysis by CEN grades. Among the four wood eucalypts, Eucalyptus tereticornis presented the highest decay resistance. The flooded site presented the best conditions for the proliferation of xylophagous agents. Mature wood was least susceptible to deterioration than juvenile wood. <![CDATA[<strong>Analysis of the mechanical properties of wood-plastic composites based on agriculture Chili pepper waste</strong>]]> In this study, a new composite material conception based on polypropylene (PP) and wood particles obtained from agricultural waste was investigated. Specifically, stalks and leafs of chili plants of the region of New Mexico, Texas, USA were used as a plant-based reinforcing material. For this, a design of experiments (DOE) is proposed considering different percentages of PP, wood, fire retardant, coupling agent and UV stabilizer, different mesh sizes are also considered. Samples were obtained using an extrusion molding machine. A statistical analysis is proposed to obtain the optimal percentages of the components considered in the fabrication of the samples in order to enhance the mechanical and morphologic properties of this new composite. Results show that the yield stress, breaking stress and ultimate tensile stress can be maximized with a proportion of 3 to 1 (63,75% PP and 21,25% wood fiber) of PP and wood fiber. <![CDATA[<strong>Effect of microwave treatment on the impregnability and mechanical properties of </strong><em><b>Eucalyptus globulus</b></em><strong> wood</strong>]]> Application of microwave energy to wood can increase permeability in order to improve the impregnation of treatments, particularly important in refractory species such as eucalyptus. However, microwave treatment can also affect the physical and mechanical properties of wood. This paper discusses the application of microwave treatments of different intensities to improve impregnability (uptake and retention) and examines the effects on the mechanical properties of eucalyptus wood (Eucalyptus globulus). Microwave treatments significantly improve uptake and retention of the protective agent, especially in the most severe treatment. In contrast, there was a clear decrease in mechanical properties (modulus of elasticity and bending, compression, tension and shear strength) as a function on the energy applied. The effect of microwaves on the properties of wood varies depending on moisture content at the time of treatment. <![CDATA[<strong>A preliminary investigation of nigerian</strong><em><b> Gmelina arborea</b></em><strong> and </strong><em><b>Bambusa vulgaris</b></em><strong> for pulp and paper production</strong>]]> Two common Nigerian-grown biomasses, gmelina (Gmelina arborea) and bamboo (Bambusaa vulgaris) have been pulped and their fibre characteristics and paper properties examined. The results of their chemical compositions showed some fair similarities. The amount of glucose in the pulps of both biomasses indicated their suitability as lignocellulosic materials for pulping. Their pulp yield ranged between 48,0-54,1%, which fell within the acceptable range for good pulpwoods. The analysis of their fibre dimensions revealed that bamboo fibre has a wider fibre length distribution and higher fine length content. Gmelina and bamboo had weighted mean fibre lengths of 0,93 and 2,07 mm and mean fibre widths of 24,1 and 16,9 µm, respectively. The Runkel ratios of the samples were 0,4 (gmelina) and 0,9 (bamboo): this is indicative of their suitability for paper making. Mechanical properties of handsheets obtained from gmelina compared fairly well with South African pulpwoods (Eucalyptus grandis and Pinus paluta). Bamboo exhibited better tear index values than these woods but with lower sheet density and tensile index. These properties were significantly improved in handsheets obtained from blends of gmelina and bamboo, raising the prospect of producing paper from blends of both raw materials in Nigeria. <![CDATA[<strong>The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers</strong>]]> The study investigated the effects of short-term thermo-mechanical (STTM) densification temperature and pressure on changes in surface wettability of alder (Alnus glutinosa), beech (Fagus sylvatica), birch (Betula verrucosa) and pine (Pinus sylvestris) wood veneer. Veneer sheets were densified using pressure levels of 4 MPa, 8 MPa and 12 MPa at three temperatures: 100°C, 150°C and 200°C for a short time of 4 min. Wettability was determined by measuring contact angles with distilled water. The results were compared with those of non-densified veneers. The results showed that in a relatively short process time wettability can be changed significantly. The wettability analysis showed that STTM-densified veneer surfaces became more hydrophobic, which indicates poor wettability. However, it was found that even STTM densification of veneers provides stable properties; in particular, contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. The effect of temperature on the contact angle was more evident than that of pressure. Linear correlations were found between contact angle and both mass loss and compression ratio for all investigated wood species. These findings may be used to provide initial data for adhesive/coating application processes in woodworking industry. <![CDATA[<strong>Plasticity increase of beech veneer by steaming and gaseous ammonia treatment</strong>]]> Ammonia treatment was used in order to change the colour of wood and also to plasticize the wood before bending or compressing. The mechanism and the process of gaseous ammonia treatment impact on wood are not very well known. The goal of this study was to quantify the effect of gaseous ammonia on mechanical properties, i.e., modulus of elasticity (MOE), modulus of rupture (MOR) and deflection at maximal loading force (yFmax). When wood was treated by water and ammonia vapour together, significant changes in plasticity of wood were observed. The samples which were firstly exposed to water vapour and then to ammonia vapour exhibit the lowest values of MOE and MOR and an enhanced flexibility of the material. The results show that ammonia treatment increases wood plasticity. This process can be used for manufacturing of bent furniture. <![CDATA[<strong>Ultrasonic phytosanitation of pinewood nematode infected wood</strong>]]> Pinewood nematode (Bursaphelenchus xylophilus) mortality was investigated after ultrasonic treatment at 20 and 40 kHz frequency. Experiments were conducted with infected small wood specimens that were ultrasonically treated for 1, 3, 5 and 7 hours and two variable temperature conditions, namely, a gradually increasing from ambient to a maximum of 70°C and a decreasing from ambient to a minimum of 5°C. The results revealed that the ultrasonic treatment itself had no significant effect on the nematode mortality at the 5°C level, while at the 70°C level, considerable nematode mortality was observed in short time periods and at 7 hours of sonic exposure it reached 100%. Therefore, certain combinations of timing and frequency of ultrasonic waves and produced heat can be effective in killing pinewood nematodes thus resulting in phytosanitized wood. <![CDATA[<strong>Timber wastes torrefaction for energy use</strong>]]> The experiment consists in the realization of timber wastes torrefaction at a final temperature of 280ºC, with heating rates of 0,5ºC.min-1, with 1 hour permanence in the final temperature. Three different types of wastes were analyzed by composition. Moisture content, bulk density, torrefied mass yield, gross calorific value, particle size, and physical and mechanical resistance were determined. Except the moisture content, the remaining variables were evaluated before and after torrefaction. The results indicated that torrefaction increased the wastes energy density. The torrefied material yield was influenced by the particle size. Bulk density was reduced; however, the mass reduction was higher than the volume reduction. The calorific value was increased for all types of torrefied wastes. Torrefied wastes friability was higher compared to in natura wastes. <![CDATA[<strong>Color changes of wood from </strong><em><b>Pinus taeda</b></em><strong> and </strong><em><b>Schizolobium parahybum</b></em><strong> treated by </strong><em><b>in situ</b></em><strong> polymerization of methyl methacrylate using cross-linkers</strong>]]> The aim of this study was to evaluate the colorimetric properties of Pinus taeda and Schizolobium parahybum woods treated by in situ polymerization. The wood samples were impregnated in a vacuum/pressure system and polymerized in an oven at 90°C for 10h, using benzoyl peroxide at 1,5wt% as the catalyst. The treatments were characterized using attenuated total reflectance infrared (ATR-IR) spectroscopy and weight percentage gain (WPG). The color evaluation was performed using CIEL*a*b* concepts, specular gloss, and UV-Visible spectrophotometry. Treated woods showed increases in band intensity related to polymers (1730, 1460 and 1145 cm-1), and WPG ranged from 39 to 164%, depending of the wood species and treatments. Lightness decreased, while the Chroma, gloss and the color coordinates increased. A darkening of the all treated samples was observed, and confirmed by the decrease in the reflectance intensity between 400 and 700 nm. <![CDATA[<strong>Effect of Microwave treatment on longitudinal air permeability and preservative uptake characteristics of chir pine wood</strong>]]> Low permeability of many wood species due to their anatomical properties causes problems during timber drying as well as impregnating with preservatives and resins. Microwave (MW) treatment influences heartwood permeability and improves preservative uptake and distribution. In the present study, microwave treatment of chir pine (Pinus roxburghii) wood was done at 2,45 GHz frequency at different level of intensity and radiation time. The gas permeability of chir pine wood was measured in an in-house built apparatus. Preservative uptake was tested using acid copper chromate (ACC) preservative by a dipping process. The effect of radiation intensity and time on preservative uptake and air permeability were studied. The results revealed remarkable increase in longitudinal wood air permeability and preservative uptake with the increase of intensity and time of treatment. The results indicate that this technology can be tested and applied on pilot scale for application in wood preservation industry. <![CDATA[<strong>Color de la madera de dos eucaliptos expuestas al intemperismo natural en tres entornos ambientales diferentes</strong>]]> La degradación superficial en madera de exteriores se debe a una combinación de factores meteorológicos inherentes al entorno de exposición y a la colonización de organismos xilófagos. Desde un punto de vista técnico y económico se trata de uno de los principales problemas para la industria de productos y materiales hechos a partir de la madera. El objetivo del presente trabajo es el de monitorizar la degradación superficial de las maderas de Corymbia citriodora y Eucalyptus tereticornis originarias de plantaciones de rápido crecimiento de Brasil, las cuales han sido expuestas a ensayos de intemperismo natural en tres entornos ambientales distintos. La monitorización de los cambios en el material fue realizada mediante estimaciones del color (método CIEL*a*b*), en ciclos de 45 días, hasta completar un periodo de 360 días de exposición. Los resultados mostraron que el material expuesto al entorno forestal fue menos afectado por los factores ambientales, lo que ha sido probablemente debido al aislamiento térmico y solar que proporciona este tipo de ecosistema. A su vez, se observó que las probetas de madera de Corymbia citriodora presentaron mayor resistencia al deterioro que las probetas de madera de Eucalyptus tereticornis, posiblemente debido a ciertas diferencias en su constitución química.<hr/>Surface degradation in outdoor wood and products is due to a combination of inherent climate factors together with colonization of decay organisms. From a technical and economic standpoint it is one of the main problems for the industry of products and materials made from wood. The aim of this work is to track the surface degradation of Corymbia citriodora and Eucalyptus tereticornis timbers originating from fast-growing plantations in Brazil, which have been exposed to outdoor weathering tests in three different environmental conditions. Changes in the material were monitoring using color measurement (CIEL*a*b* method), in cycles of 45 days up to a period of 360 days of exposure. The results showed that timber exposed to a forest ecosystem was less affected by environmental factors; this is probably due to climate insulation provided by these ecosystems. Besides, it was observed that samples of Corymbia citriodora had higher resistance to degradation compared with samples of Eucalyptus tereticornis, possibly due to differences in its chemical constitution. <![CDATA[<strong>Physical and mechanical properties of heat treated wood from </strong><em><b>Aspidosperma populifolium</b></em><strong>, </strong><em><b>dipteryx odorata</b></em><strong> and</strong><em><b> mimosa scabrella</b></em>]]> Heat treatment improves some wood properties namely: equilibrium moisture, dimensional stability and durability and mechanical properties. In this study, the heat treatment was applied to woods of three natural species from Brazil: Aspidosperma populifolium (peroba mica), Dipteryx odorata (cumaru) and Mimosa scabrella (bracatinga). The woods were heated in an oven under vacuum and under nitrogen, at 180, 200, and 220°C for one hour. The untreated and heat-treated woods were characterized in relation to equilibrium moisture content, basic density, shrinkage, Janka hardness, and bending MOR and MOE according to NBR 7190 standards. All the thermal rectified woods showed a reduction in the hygroscopic equilibrium content, especially when the heating was under vacuum from 13-15% in the untreated woods to 1-3% for vacuum treatment at 220°C. The dimensional stability was improved to only a small extent e.g. volumetric shrinkage tended to decrease with increasing temperature. The mechanical properties were affected differently for the three wood species. Heat- treated cumaru showed increased Janka hardness, MOR and MOE; and peroba mica increased MOR and MOE but not Janka hardness; while bracatinga was less influenced by the heat treatment. <![CDATA[<strong>Effects of wollastonite on the properties of medium-density fiberboard (MDF) made from wood fibers and camel-thorn</strong>]]> The effects of wollastonite fibers on the physical and mechanical properties of medium-density fiberboards composed of wood fibers with up to 10 % camel-thorn chips were studied. Approximately 30 % of the wollastonite fibers were less than 100 nm while the remainder were less than 1 μm. Wollastonite fibers significantly improved most of the physical and mechanical properties while addition of camel-thorn produced more variable effects on panel properties. Up to 10 % camel-thorn could be added to panels without negative effects. A combination of 10% camel-thorn and 5% wollastonite fibers produced panels with the best properties. <![CDATA[<strong>The effect of some technological production variables on mechanical and physical properties of particleboard manufactured from cotton (</strong><em><b>Gossypium hirsutum</b></em><strong>) stalks</strong>]]> The current study aims to improve properties of particleboard manufactured from cotton (Gossium hirsutum) stalks glued with urea formaldehyde. To this aim, panel density (at three levels: 0,5; 0,65 and 0,8 g/cm³), press temperature (at two levels: 150 and 180°C) and press closing speed (at two levels: 4 and 8 mm/s) were selected as independent variables. The mechanical properties consist of modulus of rupture, modulus of elasticity and internal bonding and physical behaviors such as water absorption and thickness swelling of panels were determined. Results showed that with increasing the density of panels and press temperature modulus of rupture, modulus of elasticity and internal bonding of panels increased, while bending strengths of panels were differently affected by press closing speed compared to the internal bonding, so that with increasing the press closing speed modulus of rupture increased, but internal bonding decreased. Moreover, increasing panel density and press temperature, water absorption and thickness swelling of panels decreased. The press closing speed affected the water absorption and thickness swelling, insignificantly. <![CDATA[<strong>Wood chile peppers stalks-plastic composite production</strong>]]> Nowadays, most common wood fibers used to produce wood plastic composites are from Oak and pine trees, rice hull, recycled paper, pallets and post-industrial oak fiber, furniture waste, or cedar wood chips. This paper is focused on a new wood plastic composites based on pre-dried New Mexico red chile stems and leafs with high-density polyethylene. The specimens were manufactured following ASTM 638-9 standard using injection molding. A series of experiments were designed to investigate how wood fiber length, geometry, and water absorption affects the microcellular structure of the new sustainable material. The effects of proportions and particle size on the strength of the resulting blend were analyzed. It was found that larger particle sizes of wood fiber showed higher mechanical properties. The blending of additives in the new sustainable material has shown to increase proper fiber dispersion improving the strength of the material. <![CDATA[<strong>Optimization of termite in-ground monitoring stations</strong>: <strong>An evaluation trial</strong>]]> Subterranean termites are serious pests of wood in service in much of the world. One of the most popular techniques for monitoring and controlling termites is the use of in-ground monitoring stations. Different cellulosic matrices were evaluated in terms of mass loss, moisture content variation and termite presence, accounting for spatial coordinates and monitoring station conditional variables, including: type of cellulosic matrix, matrix treatment and meteorological conditions, during one year in field conditions, both in Portugal and in the USA. A multivariate redundancy analysis was performed resulting in 60,4% of data variability being explained by the variables considered in this analysis. Spatial variables were responsible for the highest amount of variance observed in the response variables monitored for the termite monitoring stations, followed by the type of cellulosic matrix, from which cellulose and Hevea brasiliensis were the most influential variables. The optimization of termite in-ground monitoring stations should be performed through correct evaluation of termite feeding preferences and decay resistance, in order to choose an adequate bait matrix and a proper bait design. The termite species biology and the geographical location where control programs will be applied should also be taken into account. <![CDATA[<strong>Characterization of sorption behavior and mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa</strong>]]> This study provides the sorption isotherm, its hysteresis and their mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia superba), lotofa (Sterculia rhinopetala), sapele (Entandrophragma cylindricum) and ayous (Triplochiton scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40°C with air relative humidity ranged from 0% to 90%. Mass diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and mass transfer properties were determined in the tangential direction with a "false" quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model´s explains plausibly the experimental sorption isotherms data. Results on characterization of mass transfer properties showed that, in the steady state, mass diffusivity decreases exponentially when basal density increases. Mass diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and mass diffusivity.