The investigation of physico-mechanical characteristics of poplar wood impregnated with melamine formaldehyde resin

There are several methods for improving wood properties; one of them is the impregnation of wood with a variety of monomers, and converting them into a polymer inside the wood. This leads to the production of a new product called wood polymer. One of the monomers used for wood impregnation is amino resins such as urea formaldehyde as well as melamine formaldehyde (MF). In this research, MF resin was used for the impregnation of poplar wood in order to improve the dimensional stability and mechanical properties. MF was synthesized experimentally with a molar ratio of 1.5:1 (F: M) which had lower free F and viscosity than industrial resin. The samples were impregnated using vacuum/pressure method with different concentrations (7, 15, 27 and 35%) of experimental MF as well as industrial ones with concentration of 27%. The results showed that the percentage of weight gain (WPG) of samples significantly increased by increasing the amount of resin concentration. The volumetric swelling and the water absorption of samples significantly decreased even after long-term immersion in water according to the WPG values. The mechanical resistances including modulus of rupture, modulus of elasticity, hardness and pressure parallel to the grain increased by an increase in WPG values compared to the that of controls. However, the impact bending in the treated samples were lower than the controls, this seems to be due to the high toughness of the melamine crystals formed inside the wood. The experimental MF resin produced in this study with low formaldehyde content showed high potential for improving the physico-mechanical properties of poplar wood.