Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 16 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<strong>Wood thermodegradation</strong>: <strong>experimental analysis and modeling of mass loss kinetics</strong>]]> Wood heat treatment is an attractive alternative to improve decay resistance of low natural durability of wood species. Decay resistance is strongly correlated to thermal degradation of wood cell wall components. Some recent studies proposed the use of wood mass loss during the heat treatment as a valuable marker to predict final properties of the material (Hakkou et al. 2006, Welzbacher et al. 2007). In this study, heat treatment was carried out in a relatively low temperature (230˚C). Mass loss kinetics was studied using equipment, specially conceived to measure sample’s mass during the thermal treatment. Laboratory experiments were performed for heating rates of 1˚C min-1. Mathematical model for kinetics of pyrolysis process was used and validated. During the pyrolysis of dry wood samples under inert atmosphere, measurements of temperature distribution and dynamic weight loss were performed. Five different wood species Fagus sylvatica (Beech), Populus nigra (Poplar), Fraxinus excelsior (Ash), Pinus sylvestris (Pine) and Abies pectinata (Silver Fir) were investigated. The unsteady-state mathematical model equations were solved numerically using the commercial package Femlab 2.0. A detailed discussion of the computational model and the solution algorithm is given. The validity of different model assumptions was analyzed. Experimental results were compared with those calculated by the model. Acceptable agreement was achieved. <![CDATA[<strong>Oak wood inhabiting fungi and their effect on lignin studied by UV microspectrophotometry</strong>]]> Decayed-wood samples were collected from a naturally-infected bridge made of Quercus robur. Fruiting bodies of the white-rot basidiomycetes Hymenochaete rubiginosa and Stereum hirsutum were sampled. The white-rot fungus Fuscoporia ferrea and the secondary saprobiont Mycena galericulata were identified from the rotten wood by means of rDNA-ITS sequencing. The topochemistry of lignin degradation within individual cell-wall layers was determined by cellular UV-microspectrophotometry (UMSP) at 278 nm wavelength. Increased delignification occurred in compound middle lamella regions (CML), secondary wall layers of fibres (S2), longitudinal and ray parenchyma cells as well in vessels. The highest lignin content at initial and medium decay was recorded in the CML, whereas in advanced decay secondary wall layers of the vessels exhibited the highest content of residual lignin. In all stages of degradation, the S2 layers of fibres had the lowest lignin amount. <![CDATA[<strong>Study on preparation and properties of phenol-formaldehyde-chinese fir liquefaction copolymer resin</strong>]]> A new zero-waste and zero-pollution composite adhesive labeled Chinese fir-based adhesive for exterior plywood was synthesized by blending alkaline Chinese fir (Cunninghamia lanceolata) liquid with a small amount of phenol-formaldehyde (PF). The free phenol and free formaldehyde content of the Chinese fir-based adhesive were sharply decreased compared to normal PF resin by more than 50%. The synthetic adhesive show with excellent water resistance and environmental friendliness, which had a 28h boil-dry-boil wet bonding strength of 1,73MPa according to standard JIS K6806-2003 and a formaldehyde emission of 0,045mg/L according to standard JIS A1460-2003. The structural properties and their thermal properties of cured adhesives were evaluated using Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC). The FT-IR analysis confirmed the expected chemical structure as the Chinese fir liquid reacted with formaldehyde and phenol which occurred at the wavenumbers of 1733, 1698, 1652cm-1 and 1077, 1048 cm-1. Although the DSC results indicated that the Chinese fir-based adhesive's curing need higher temperature than the control PF resin, the higher curing temperature hardly cripple the availability of Chinese fir-based resin in the plywood production. <![CDATA[<strong>W</strong><b>ood-based panels industry in Turkey</b>: <b>future raw material challenges and suggestions</b>]]> World production of wood based panel has grown from 63,1 million cubic meters in 2005 to 75,5 million m³ in 2009, a 12 million m³ rise in production. China is the world's largest wood based panel’s manufacturer. The Turkish wood based panels industry has shown a tendency of fluctuating during this time. Turkey, as the world’s 4th largest producer of wood based panels, is an important contributor to the industry. Turkey has made great strides in the last 20 years in the forest products industry. Both the development of new materials and techniques of domestic and international market demand have played a decisive role. Turkey's wood panel production has gone from 100000 m³ in the early 2000s, to 5,5 million m³ of production in 2010. The sector's total production capacity is approximately 9 million m³. The results obtained thus far indicate that the Turkish wood based panel industry demand for raw material is not being met by the GDF's chip wood fiber production. Where the raw material supply problem in the industry, as well as the problems encountered in the forest and on the basis of the villagers living adjacent to, not to the time of product problems related to storage and transportation of raw materials and other related problems are bottlenecks. We examine problems related to the provision of raw materials and raw materials research, the need for future estimates of the level at which the world and close to the periphery countries will be examined, wood composite panel production and trade policy recommendations will be developed. <![CDATA[<b>Free shrinkage of wood determined at the cellular level using an environmental scanning electron microscopE</b>]]> The shrinkage at the cellular level was determined in the transverse plane of wood using an environmental scanning electron microscope (ESEM). The whole procedure is based on pairs of images grabbed with the same imaging conditions (magnification, working distance, voltage) without removing the sample from the chamber: one image collected at saturated conditions (1067 Pa, 1°C) and the other at air-dry state (533 Pa, 16°C). A closed chain of the same reference points chosen from the anatomical markers was defined on both images at the external part of the zone of interest. A custom software program, called MeshPore, allowed the shrinkage coefficients to be extracted from the slight difference of shape between these two chains. Measurements of transverse shrinkage were performed on earlywood and latewood zones from Norway spruce (Picea abies), only normal wood was studied. The interested zones were isolated from the rest of the annual ring with the aid of a microtome blade, insuring the observations to be done under free shrinkage. As additional features, the changes of the cellular morphology and the cell wall thickness were also evaluated thanks to the resolution provided by the ESEM. <![CDATA[<strong>Cutting forces by Oak and Douglas fir machining</strong>]]> In this work the multi-factor, non-linear dependencies between main (tangential) F C and normal (radial) F N cutting forces upon two machining parameters by up-routing and down-routing wood of Douglas fir (Pseudotsuga Menziesii) and Oak (Quercus petraea) were evaluated. The relationships are graphically illustrated and discussed. The obtained data were compared with cutting forces evolution models according to grain orientation from the literature in order to verify if literature statements or models comply with measured data. Evidence of several contradictions was found relative to results from available literature. <![CDATA[<strong>Analysis of rigidity loss and deterioration from exposure in a decay test field of thermorectificated<i> Eucalyptus grandis</i> wood</strong>]]> The objective was to evaluate the elasticity dynamic modulus reduction (MOEd) and deterioration of E. grandis thermorectificated wood by exposure to environmental weathering. Six trees were used to obtain 14 logs of 2,4m, with seven from external (sapwood) and the others from internal (heartwood) part of the trunk. A total of 84 wood samples of 2,5x 5x 50cm were made, with half from the inner and the other from the external trunk portion. 14 treatments were evaluated with six replicates composed of thermorectificated wood submitted two differents times (2 and 4 hours) and three temperatures (200, 215 and 230˚C). An ultrasound Stress Wave Timer device was used to evaluate MOEd and the mass measured by weighing. Samples remained in the decay test field for ten months, and monthly inspected and recorded to xylophogous organism’s occurrence. At the end of this period MOEd and mass were revaluated. The central portion of wood samples were more deteriorated, with mass losses and stiffness losses ranging from (8-56%) and (18-91%), respectively. Lower values ​​were observed in the wood coming from the external portion, with mass losses and stiffness ranging from (3-10%) and (8-20%), respectively. The thermorectificated wood samples were more damaged by action the termites and less by the action of fungi, compared to controls. <![CDATA[<strong>Toxicity potential in the extraneous compounds of white mulberry wood (<i>Morus alba</i>)</strong>]]> The health problems amongst musical instrument makers working on the White mulberry (Morus alba), lead to investigate the toxicity potential of wood extractives. Five solvents of different polarity and two methods of extractions were used to ensure a thorough, clear and classified compound removal. The compounds were identified using qualitative GC-mass and the toxicity were determined by studying their effect on termite survival (Reticulitermes flavipes). The results indicated the presence of different compound categories like phenols, higher hydrocarbons, fatty acids, sterols and aromatic components in the extractives. These compounds were not removable by just one solvent and the order of removal was polarity related. The extractives were found toxic towards termites. Resorcinol, which corresponded to the highest proportion of peaks in the GC-mass spectra, has been assigned as the possible compound responsible for the allergic reactions by the artisans. <![CDATA[<strong>Antitermitic effects of three wood stain treatments</strong>]]> Potential antitermitic properties of some common wood stains were tested against Coptotermes formosanus. Four different wood species treated with 3 different stain chemicals at the 0,1 kg/m2 retention level were exposed to no-choice termite feeding test in laboratory conditions. Mean mass loses, mortality rates and consumption rates were calculated based on weight changes before and after the test. While the hardwood species (beech (Fagus orientalis) and chestnut (Castanea sativa) tested were unaffected by the treatments, the softwood species tested showed drastically reduced mass losses with some stain treatments. Scots pine (Pinus sylvestris) and spruce (Picea orientalis) sapwood exhibited significant reductions in mass losses when treated with the chemical stain. <![CDATA[<strong>A methodology to select a group of species among 131 tropical (colombian) species for bowed timber applications</strong>]]> We present a methodology of selecting wood species for architectural purposes, especially when a curved shape is required. First, a mechanical criterion is associated with a morphology, more specifically a characteristic value of stress-strain relation is associated with the attitude of wood for bowing. Second, a filtering is done using data of wood in the green state and in the dry state, and then the wood selection is refined by using relevant criteria related to environment and economic considerations. The following four species are the result of the selection: Sande or Guaimaro (Brosimum utile), Ceiba (Ceiba pentandra), Tamarindo (Dialum guianense), and Roble flor morado (Tabebuia rosea). Information given in the literature is complemented with results of bending experiments when information is lacking. The result emphasizes that tropical species are fitter than temperate species for bowed wood applications.