The Effect Factors On The Thickness Swelling Rate Of Water Absorption Of The Eucalyptus Particle Board And The Manufacturing Technique Research

This study investigated the manufacture and properties of particleboard made fromEucalyptus grandis×urophglla. The factors affecting the performance of thickness swellingafter24-hours water soaking were also examined. The factors considered included theproportion of surface-to-core materials, resin content, wax content, board density, and hotpressing parameters. Orthogonal experiments design was applied to determine the optimalmanufacture process and parameters. The results indicated that particleboard had the optimalperformances when manufactured under a combination of the following conditions: a hotpressing pressure of2.5MPa, a pressing temperature of160℃, a pressing time of8minwith a particle moisture content of12%and8%a resin content of12%and8%for surfaceand core, respectively, and a bark content of5%. Tested in accordance with GB/T17657-1999"Test methods for evaluating the properties of wood-based panels and surfacedecorated wood-based panels", the manufactured particleboard had a modulus of rapture of14.2MPa, a modulus of elasticity of2265MPa, an internal bonding strength of0.44MPa,and a thickness swelling after2-hours water soaking of less than8%, which meet the designvalues required in GB/T4897-2003"Particleboard". The results also suggested thatparticleboard can have acceptable performances if manufactured under the followingparameters: a surface-to-core ratio of55to45, a UF resin content of10%, a wax content of1%, a board density ranging from600to650kg/m3, and a pressing time ranging from5to6s/mm. The four temperature zones in the continuous press can be set at230℃,215℃,190℃, and135℃.The proportion of surface-to-core has an important impact on the mechanicalproperties of particleboard manufactured. It is positively correlated to bending stiffness andstrength, and negatively correlated to thickness swelling. While it has a sophisticatedrelationship with internal bonding strength, it has no significant effect on the vertical densityprofile. Board density has a positive correlation with mechanical properties, however, it hasno significant impact on vertical density profile. Board density controls the rate of waterabsorption and thickness swelling at the beginning of water soaking.X-ray densitometric analysis showed that the particleboard had an average density of637.26kg/m3After-sanding vertical density profile showed a clear three-layer structure,with the density distribution being symmetric along the center line of the board thickness.Formaldehyde emission level determined with perforator method met the requirement ofEuropean grade E0.