| The surface of wood/polyethylene (PE) composites was treated by coupling agent coating treatment to improve its adhesion properties. The change on the surface characteristics and the durability of bonding joint of the treated composites in different environments of soaking, heating, and natural aging were studied by using the analysis of contact angle, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS) and bonding strength test.The concentration of coupling agent, processing temperature and processing time showed a great influence on the processing effect of coupling agent on the surface for composites. The optimum processing technics of silicane coupling agent coating treatment for wood/PE composites were the coating process of silicane coupling agent concentration of5%, processing temperature of120℃and processing time of20min. The optimum processing technics of phosphate ester coupling agent coating treatment for wood/PE composites were the coating process of phosphate ester coupling agent concentration of1%, processing temperature of120℃and processing time of20min. After surface treatment of roughing and then KH560, KH550and phosphate ester coupling agent coating, there occurred chemical bond between coupling agent and the surface of the composites, and the epoxy groups, amido groups and C=C were introduced on the surface of the composites, which would be of great benefit to the adhesion between epoxy adhesive or acrylic ester adhesive and wood/PE composites. In the condition of water soaking, the roughness for the surface of the composites increased and the contact angle decreased, the water absorption for the bonding joint increased, the new groups were not formed on the surface of the composites, but the relative content of carbon element and oxygen element within the surface of composites changed. The swelling of wood fiber within the KH560coating treated PE/wood composite caused by absorbing water could result in the residual stress within the adhesion interface, which reduced the bonding strength for the joint. In the condition of heating, the roughness for the surface of the composites decreased firstly and then increased, the contact angle increased firstly and then decreased, the new groups were not formed on the surface of the composites, but the relative content of carbon element and oxygen element within the surface of composites changed. The changes for the surface properties of the KH560coating treated wood/PE composites reduced the bonding strength for the joint. The test results for natural aging experiment showed that when the bonding joints suffered by light, temperature and humidity together, the bonding performance of the bonding joints declined.The test results for the samples indicated that the environment shows a great influence on the surface properties of the treated wood/PE composites, and the greatest extent is soaking. |
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