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This paper presents the interfacial optimisation of wood plastic composites (WPC) based on recycled wood flour and polyethylene by employing maleated and silane coupling agents. The effect of the incorporation of the coupling agents on the variation of chemical structure of the composites were investigated by Attenuated total reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Solid state 13C Nuclear Magnetic Resonance spectroscopy (NMR) analyses. The results revealed the chemical reactions that occurred between the coupling agents and raw materials, which thus contributed to the enhancement of compatibility and interfacial adhesion between the constituents of WPC. NMR results also indicated that there existed the transformation of crystalline cellulose to an amorphous state during the coupling agent treatments, reflecting the inferior resonance of crystalline carbohydrates. Fluorescence Microscope (FM) and Scanning Electron Microscope (SEM) analyses showed the improvements of wood particle dispersion and wettability, compatibility of the constituents, and resin penetration, and impregnation of the composites after the coupling agent treatments. The optimised interface of the composites was attributed to interdiffusion, electrostatic adhesion, chemical reactions, and mechanical interlocking bonding mechanisms.

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In this paper, we discuss the effects of a nanometer silicon dioxide (nano-SiO 2 ) coupling agent, dispersal methods and the amount of nano-SiO 2 /urea formaldehyde resin. The results of our study indicate that when nano-SiO 2 , using KH-550 silane as a coupling agent, was added to UF resin by discontinuous ultrasonic vibration, its properties improved effectively. When the content of nano-SiO 2 was below 1.5%, the amount of free formaldehyde decreased, and the viscosity and bonding strength of resin increased with an increase in the added nano-SiO 2 , which did not prolong the curing time. The performance indices of plywood, particleboard and medium density fiberboard (MDF), hot-pressed by nano-SiO2 (1%)/UF resin (F/U molar ratio=1.2), exceeded the requirements of the National Standard. Their free formaldehyde emission reached E1 grade. Finally, we analyzed the mechanism of the strengthening effects of nano-SiO 2 on UF resin by means of infrared spectrum analysis and X-ray photoelectronic spectrum (XPS).Keywords nanometer silicon dioxide, urea formaldehyde (UF) resin, bonding strength, free formaldehyde, X-ray photoelectronic spectrum (XPS) 2 Materials and methods Experimental materialBoth urea and formaldehyde are commercial products. The content of nano-SiO 2 was 99%, the average diameter of particles 20 nm and the specific surface area 440 m 2 /g. There are four kinds of nano-SiO 2 : 1) NMSi-0, non-surfacing; 2) NMSi-A, using a 1% KH-550 silane coupling agent for treatment (molecular formula RESEARCH ARTICLE

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