Modification of Paulownia Wood with methylolated dimethyloldihydroxyethylenurea (mDMDHEU) and the investigation of its effect on Some of Strength Properties

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.