Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 19 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<strong>Recovery of phenolic compounds from Eucalyptus wood wastes using ethanol-salt-based aqueous two-phase systems</strong>]]> In this work the partition behavior of phenols using ethanol-salt-based aqueous two phase systems (ATPS) was evaluated. The aim was the recovery of phenolic compounds with antioxidant capacity from eucalyptus wood industrial wastes. Experiments were planned to study the influence of several parameters on phenols partition, including type of inorganic salt (ammonium sulphate, a mixture of monopotassium phosphate and potassium diphosphate and potassium diphosphate), tie-lie lenght (TLL), volume ratio (Vr), settlement time and temperature. Phenols could be recovered preferently from the top or bottom phases depending on the salt used. It was demostrated that tie-lie lenght, volume ratio and temperature had influence on phenols partition. The highest total phenols yield 5,36 mg gallic acid equivalent (100 mg oven dried wood)-1 and FRAP antioxidant activity, 20 mmol AAE (100 g oven dried wood)-1, was obtained using ATPS formed by 40,6% (w/w) ethanol and 12% (w/w) of ammonium sulphate at 65°C. Analysis of the extract by RP-HPLC-ESI-TOF confirmed the presence of the phenolic compounds with potential antioxidant activity, namely, ellagic acid, myricetin 3-O-rhamnoside and quercetin 3-glucoside. <![CDATA[<strong>Dimensional stabilization of wood by chemical modification using isopropenyl acetate</strong>]]> Chemical modification of wood with isopropenyl acetate (IPA) using iodine (I2) as catalyst has been carried out. Rubber wood (Hevea brasiliensis) specimens were reacted with IPA using iodine (I2) catalyst at 95°C up to 10 h under solvent free conditions. The effect of catalyst concentration and reaction time was studied. The extent of acetylation was measured by determining weight percent gain and the modified wood was characterized by FTIR-ATR and 13C NMR spectroscopy. It was found that IPA in the presence of iodine is an excellent acylating reagent for wood. Modified wood exhibited high dimensional stability. <![CDATA[<strong>Color and gloss evaluation in decorative stain applied to cases of</strong><em><b> Pinus radiata </b></em><strong>wood treated with copper azole micronized Type C</strong>]]> Six treatments (one control and five decoration coatings) were applied to radiata pine wood treated with micronized copper azole for outdoor use at a rate of 3,08 kg/m³ retention. One decoration coating was applied prior to impregnation, prestain and two decoration coatings were applied in a mixture with the micronized copper azole preservative Black Cylinder and Red Cylinder. The following two varnishes were tested: a water-based varnish and a solvent- based varnish. Additionally, untreated radiata pine specimens were tested as a reference. The changes in the gloss and color of these five decorative coatings were evaluated after undergoing natural aging tests for three months and accelerated aging trials during exposure to ultra-violet radiation of 340 nm for 500 hours. In the accelerated aging trials treatments, changes in gloss and color showed the lowest variations in treatment trials prestain and Black Cylinder and the highest variations in treatment trial Red Cylinder. In the aging tests trials, changes in gloss and color showed the lowest variations in treatment trials prestain and Black Cylinder. The costs of each decorative coating were assessed in terms of performance according to timber volume coated. The lowest cost of the three decoration treatments was prestain, with a value of US$ 16/ m³, followed by Black Cylinder with a value of US$ 24/m³. Compared with the alternative siding products available in the market, such as fiber cement and vinyl siding, colored wood treated with prestain is competitive with vinyl siding, with 58% lower costs than fiber-cement. <![CDATA[<strong>Effect of torrefaction temperature on properties of Patula pine</strong>]]> The objective of this work was to study the effect of torrefaction temperature on properties of patula pine (Pinus patula) wood that could be of interest for further thermochemical processing. Torrefaction temperature was varied from 200 to 300 °C for 30 minutes using a batch spoon type reactor. Raw and torrefied materials were characterized for proximate and ultimate analyses, thermogravimetry, and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Results showed that torrefied pine has greater higher heating value and chemical exergy due to the reduction of O/C and H/C ratios. Compared with raw biomass, the material torrefied at 200 and 250 °C did not present significant changes in chemical composition and thermal behavior. Conversely, material torrefied at 300 °C did show important changes in both chemical composition and thermal behavior. Py-GC/MS results suggested that the main constituents of biomass, i.e., hemicellulose, cellulose and lignin, suffer a progressive thermal degradation with increase in torrefaction temperature. <![CDATA[<strong>The bending and tension strength of furniture joints bonded with polyvinyl acetate nanocomposites</strong>]]> Furniture is the general name given for the portable equipment used in various human activities such as seating, working and relaxing. They can be a product of design and is considered a form of decorative art. They can widely be manufactured with different adhesives. Biodegradable and bio-based adhesives which have no toxic compounds and non-dangerous elements have been selected since the furniture is generally benefited in interior locations. Meanwhile, polyvinyl acetate (PVAc) is a thermoplastic polymer which is widely used in the furniture industry. In this study, tension and bending strength of the furniture joints bonded with polyvinyl acetate adhesives filled with nano-TiO2 and nano-SiO2 were investigated. Three materials; oak (Quercus robur) wood, beech (Fagus orientalis) wood and plywood made with beech veneers were selected, and the joints were prepared by mortise and tenon joints. The results showed that the maximum value for the tension strength and bending strength were obtained to beech wood and oak wood in 2% addition of nano-SiO2 fillers. The minimum values for the tension and bending strength nano-SiO2 were found to plywood and 4% loading. <![CDATA[<strong>Assessment of the thermal behavior of lignins from softwood and hardwood species</strong>]]> The thermal behavior of lignins from softwood and hardwood species has been investigated using thermogravimetry and differential scanning calorimetry. Klason Lignin from Pinus taeda and Klason lignin from Eucalyptus grandis were studied. The differential scanning calorimetry results showed that both Klason lignins studied presented similar glass transition temperature. Thermogravimetric results showed that the lignin degradation occurs in three stages. The Klason lignin of Pinus taeda is more thermally stable than Eucalyptus grandis, probably because of the higher thermal stability of the guaiacyl units in softwood lignin. The degradation of both lignins initiate by a diffusion process. However when the conversion values are higher than 0,1 the lignin degradation mechanism is a complex procedure and involves the degradation of a highly condensed aromatic structure formed at the previous degradation stages. <![CDATA[<strong>Insect damaged wood as a source of reinforcing filler for thermoplastic composites</strong>]]> In this study, wood polymer composites were manufactured using insect damaged Eastern Black Sea Fir (A. Nordmanniana) wood as filler. The effects of wood type (sound vs insect damaged) and presence of coupling agent (0% vs 3%) on the flexural, tensile, impact, thermal and morphological properties of the wood polymer composites were investigated. The mechanical property values of the wood polymer composites specimens decreased when insect damaged wood was used as filler than sound wood, except for the impact strength values. Flexural, tensile and impact strength values, insect damaged wood filled with coupling agent composites provided higher values compared to sound wood filled without coupling agent composites. However, addition of maleic anhydride-grafted-polyethylene coupling agent into polymeric matrix improved both sound and insect damaged filled composite properties. Thermogravimetric analysis analysis showed two main decomposition peaks for polymer composites. Compared to unfilled high-density polyethylene, addition of both sound and insect damaged wood reduced decomposition peak but increased the residue due to the charring of the wood. The results of differential scanning calorimeter analysis showed that addition of sound or insect damaged wood in polymer matrix increase the crystallinity compared the unfilled high-density polyethylene due to the nucleating effect of the filler. Among the composite maleic anhydride-grafted-polyethylene modified composites provided higher crystallinity than unmodified ones. <![CDATA[<strong>Bondability of Black locust (</strong><em><b>Robinia pseudoacacia</b></em><strong>) and Beech wood (</strong><em><b>Fagus sylvatica</b></em><strong>) with polyvinyl acetate and polyurethane adhesives</strong>]]> In the previous years, black locust wood (Robinia pseudoacacia) has been participating in the European subsidizing programme of tree species cultivation, aiming in the establishing of new plantations in many European countries, therefore large quantities of this species is going to be harvested in the forthcoming years and the examination of its properties would be very crucial for future utilization. In the present research, the bondability of black locust wood is examined using two different adhesives, Polyvinyl acetate and Polyurethane and two different pressure levels. Beech wood is also included in the research for comparative reasons. According to the results, the shear bond strength of black locust wood was found to be satisfying, especially in the presence of Polyvinyl acetate adhesive and the less intensive pressure used during the specimens' construction, although it was found lower compared to beech wood, referring both to Polyvinyl acetate and Polyurethane adhesive. <![CDATA[<strong>Modeling and simulation of an industrial indirect solar dryer for Iroko wood (</strong><em><b>Chlorophora excelsa</b></em><strong>) in a tropical environment</strong>]]> This paper presents a modeling of an instrumental indirect solar wood dryer less expensive functioning in a Cameroonian climate applied to the climate of Yaoundé. The dryer is easy to build and electric energy is only used for the fan. Applications are done on Iroko wood (Chlorophora excelsa), a tropical wood 50mm thick most utilized in Africa. A satisfactory agreement between experimental and numerical results was found. Influences of thickness, wood initial water content and airflow rate were studied. <![CDATA[<strong>Effects of adhesive and loading directions on the load-carrying capacity of V-nails</strong>]]> Effects of tensile and compression loading on the overall strength of two miter frame corner joints, namely V-nail and dovetail joints, with and without adhesive were studied for medium-density fiberboard and particleboard. Two sizes of V-nails were chosen, sizes 7 and 10. Tensile and compression load-carrying capacity values were measured on the internal and external corners of the joints. Results showed that both wood-composites had greater load-carrying capacities for compression stress in comparison to tensile stress. Medium-density fiberboard demonstrated higher strength compared to particleboard specimens because of its higher compactness of fibers and more integrity in the composite matrix. Application of adhesive resulted in a significant increase in the strength of all joints and both composites. The increase in medium-density fiberboard was significantly higher in comparison to particleboard because lower permeability in medium-density fiberboard did not let adhesive to be uselessly penetrated into the texture. In particleboard specimens, however, adhesive penetrated into the voids and spaces in the composite, and the adhesive line was weakened between the surfaces of the composite bodies. It was concluded that V-nails are recommended for craftsmen in case adhesive is used. However, dovetail joints provide higher strength if the production process necessitates not to use adhesive in joints.