Aisona Talaei; Vahid Heydari
Abstract
In the present study, the functional properties of medium-density fiber board made with formaldehyde urea resin as a control with MDF made with chitosan and carboxylic acids were investigated and compared. Various compounds including chitosan acetate solution, chitosan acetate –butane tetra carboxylic ...
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In the present study, the functional properties of medium-density fiber board made with formaldehyde urea resin as a control with MDF made with chitosan and carboxylic acids were investigated and compared. Various compounds including chitosan acetate solution, chitosan acetate –butane tetra carboxylic acid solution, chitosan acetate -citric acid solution and citric acid solution were investigated. The chemical structure of specimens was investigated by infrared spectroscopy (FTIR). The results of spectroscopy clearly showed the difference in the use of different compounds. The formation of cross-links between cellulose chains and carboxylic acids was confirmed, as well as the formation of hydrogen bonds between chitosan and lignin. Specimens made with the combination of acetate chitosan-BTCA showed better dimensional stability. Also, the internal bonding of MDF specimens made with chitosan acetate solution was higher than controls. Boards made of Chitosan acetate -BTCA compound can be considered as a successful substitute for urea-formaldehyde adhesive due to its better dimensional stability and good internal bonding.
Aisona Talaei; Mohammad Hadi Rezvani; Hosseinali Rajabi Cham Heidari
Abstract
The widespread use of chemically/thermally modified wood in outdoor applications and in environments with high relative humidity and high temperature has doubled the importance of using hydrophobic monomers. To evaluate the effect of fluorocarbon modification as a binder on the physical properties and ...
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The widespread use of chemically/thermally modified wood in outdoor applications and in environments with high relative humidity and high temperature has doubled the importance of using hydrophobic monomers. To evaluate the effect of fluorocarbon modification as a binder on the physical properties and chemical structure of paulownia wood, thermal modification was performed at two temperature levels of 150 and 160°C and chemical modification with fluorocarbon at two levels of 15 and 25%. Chemical/thermal modification causes the fluorocarbon monomer and heat to be uniformly transferred into the wood and to reduce its hydrophilicity by causing chemical changes in the wood structure. Specimens were divided into control, thermal and thermal fluorocarbon treatment groups. The thermal fluorocarbon treatment caused modification of the hydroxyl groups and hydrophobicity in specimens. Infrared spectroscopy confirmed the presence of fluorocarbons and bonding with wood polymers. The fluorocarbon reaction resulted in chemical changes, weight gain and bulking of the specimens. The water uptake and volumetric swelling of the heat-treated fluorocarbon specimens were lower than the control and heat-treated ones. Improvement of water repellency efficiency and anti-swelling efficiency of thermal fluorocarbon specimens increased the dimensional stability compared to the thermal control and created a super hydrophobic and leak-resistant coating on the cell walls and inside the lumens. It was attributed to the greater penetration of fluorocarbons and the reduction of wood porosity.
Mohammad mahdi Mehrandish; Aisona Talaei; Mohammad Hadi Rezvani
Abstract
Flammability is one of the most important parameters that limits the range of wood use. Therefore, it is important to improve the fire retardancy properties of wood. The aim of this study was to evaluate the effect of modification with citric acid and its comparison with borax and ammonium chloride on ...
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Flammability is one of the most important parameters that limits the range of wood use. Therefore, it is important to improve the fire retardancy properties of wood. The aim of this study was to evaluate the effect of modification with citric acid and its comparison with borax and ammonium chloride on the flammability of paulownia wood. Test specimens were prepared and in vitro cylinders were saturated with chemical solutions at 10% depletion. Based on pre-treatment conditions, the modification was performed by heating with oven at different temperature and time levels. The fire performance of the samples was evaluated by measuring different parameters. The effect of different fire retardants on water absorption and short-term swelling of the specimens was also studied. The fire test showed that by treating the samples with citric acid and fire retardant materials, less mass reduction, flame retardation time and longer ignition time were obtained. These findings were attributed to the formation of a protective carbon layer by citric acid and fire retardant materials. The flame retardant properties of borax treatment yielded better results than those using citric acid and ammonium chloride. In addition, water absorption and dimensional stability were improved by the presence of citric acid and fire retardant agents. The results of FTIR spectra showed that the carboxylic acid groups reacted with the hydroxyl groups of the wood and increased the weight of the samples. Changes in the crystallinity indices of cellulose, carbonyl and hydroxyl were also obtained from FTIR spectra.
Management and Economics wood
Aisona Talaei
Abstract
The present study was carried out with the aim of thermal analysis of furfurylated wood produced from beech (Fagus orientalis) and fir (Abies alba). In this regard, the specimens were saturated with two different levels of furfurylation in the form of low levels (14% fir and 20% beech) and high levels ...
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The present study was carried out with the aim of thermal analysis of furfurylated wood produced from beech (Fagus orientalis) and fir (Abies alba). In this regard, the specimens were saturated with two different levels of furfurylation in the form of low levels (14% fir and 20% beech) and high levels (38% fir and 65% beech), and compared with control samples. The results showed that changes in the TGA and DTA thermograms occur with an increase in the furfurylation level. In the first section of TGA graphs, thermal stability of the wood increased with furfurylation and its level change due to decreased water absorption and evaporation of gases during the process of furfurylation. But in the second and third regions, because of the replacement of furfuryl alcohol with lower thermal stability and flammability in the structure of wood and changes in the chemical structure of the wood, the thermal stability of wood polymers in both species decreased. The results of the analysis of DTA thermograms, in addition to confirming the findings from the TGA analysis, made clear the results of the impact of wood species on the thermal stability of wood polymers. Due to the difference in cellulose and hemicellulose and lignin in the structure of softwoods and hardwoods, the hemi-cellulose type in two species and the thermal stability difference of different implementation, wood polymers from two beech and fir are different in the variation of the surface under the curve of the DTA thermograms, the initial temperatures and peak temperatures.
Management and Economics wood
Mohammad Hadi Rezvani; Aisona Talaei; Hosseinali Rajabi Cham Heidari
Abstract
One of the main strategies to develop the extent of wood modification is using active functional groups in wood structure or the so-called impregnation with modified N-methylol compound. The aim of this study was to evaluate the physical properties of paulownia wood after modify with Polycrease ECR Cell ...
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One of the main strategies to develop the extent of wood modification is using active functional groups in wood structure or the so-called impregnation with modified N-methylol compound. The aim of this study was to evaluate the physical properties of paulownia wood after modify with Polycrease ECR Cell wall resin, to name modified dimethylol-dihydroxyethyleneurea (mDMDHEU). Physical test samples were prepared according to ASTM and EN standard and treated with pressure vessel method at two concentration levels; 15 and 25 percent of soluble resin. For polymerization, treated samples were heated in oven for 24-hour periods at 145 and 155 ºC respectively. Weight percent gain (WPG), bulking, water soaking, swelling, anti-swelling efficiency (ASE), leaching and contact angle were determined. High mDMDHEU concentration increased the weight gain and cell wall bulking. Highest weight percent gain (10.70%) and bulking efficiency (6.85%) in to levels of 25% were determined at 155 ˚C. In comparison with the unmodified wood, the mDMDHEU modified wood due to absorbed polymer enhancement exhibited improved dimensional stability and reduced water uptake, and maximum dimensional stability were determined in samples modified using to level 25% mDMDHEU containing solutions and curing temperature 155 ºC. Moreover, mDMDHEU treatment was resistant to leaching. Contact angle measurement further confirmed the improved hydrophobicity of wood after modification. Modification with mDMDHEU improved significantly the physical properties. The improve of the resistance of chemically modified wood exposed to can be attributed to the reduction of wood moisture, bulking of cell walls and cell cavities blocking affect to dominant reactivity mDMDHEU with cell wall wood polymer.
Management and Economics wood
Aisona Talaei; Mohammad Hadi Rezvani
Abstract
In this research the effect of chemical modification with Polycrease ECR on the functional performance of poplar wood to use as wood polymer were investigated. Polycrease ECR the modified dimethyloldihydroxy-ethyleneurea (DMDHEU) was used for chemical modification of wood by impregnation method. Specimens ...
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In this research the effect of chemical modification with Polycrease ECR on the functional performance of poplar wood to use as wood polymer were investigated. Polycrease ECR the modified dimethyloldihydroxy-ethyleneurea (DMDHEU) was used for chemical modification of wood by impregnation method. Specimens prepared according to the ASTM standard and treated in two levels of 30 and 50%. Modification process of specimens were performed at 24 hours in temperature of 120°C. Functional performance including Weight percent gain (WPG), bulking, long term water absorption and volumetric swelling in 8 weeks, bending strength (MOR) and modulus of elasticity (MOE), compression strength parallel to the grain, shear strength and withdrawal resistance of screw parallel to the grain was measured. Two-way analysis of variance (ANOVA) was used for statistical analysis. Obtained results of modified specimens were compared with untreated control. Results showed that modification with Polycrease ECR had significant effects on physical and mechanical properties in treated specimens. Chemical modification in 30% level, lead to reduce long term water absorption and volumetric swelling. Reduction in mechanical properties were not considerable. Chemical modification with Polycrease ECR in 30 % level compared to 50 % level, showed better physical and mechanical properties. Generally, influence of chemical modification on the physical properties (long term water absorption and volumetric swelling) were dominant.
Physics and Mechanical Wood
Aysoda Talaei; Mohammad saleh Zare; Hamideh Abdolzadeh
Abstract
The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high ...
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The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high (fir 38% and beech 65%) levels were prepared and evaluated in comparison with untreated specimens. The furfurylation was performed after impregnating the specimens by furfuryl alcohol under vacuum condition followed by heating duration to complete polymerization and crosslinking. Specimens were prepared according to standard ASTM D 905 in order to assess shear strength of bond line formed with three different types of adhesives, single-component polyurethane, polyvinyl acetate as well as urea-formaldehyde. Also screw withdrawal resistance of wood polymer specimens was measured perpendicular to grain and parallel to grain. The results indicated that the shear strength of the bond line decreased and screw withdrawal resistance increased by furfurylation level. Examination of adhesion mechanism demonstrated that formation of an appropriate interface between water-soluble adhesives and wood-polymer involves effective penetration of adhesive into cell wall. Hence, the interface of adhesives and material would be the determining factor in developing strength of adhesive joints. Since the wood-furfuryl alcohol is a cell-wall wood-polymer, the possibility of creating an appropriate interface by increasing of furfurylation level was impaired. On the other hand, the adhesion mechanism of polyurethane glue compared to water-soluble adhesives such as polyvinyl acetate and urea-formaldehyde is significantly different, therefore exhibited more strength. The withdrawal screw resistance of furfurylated wood was increased by furfurylation level due to changing nature of wood and increasing shear strength of wood-polymer. This gain was also more evident in fir than beech. The results showed that screw withdrawal resistance perpendicular to grain was higher than parallel to grain.
