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.
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.
