Abstract
In cured urea-formaldehyde (UF) resin with low molar ratio of formaldehyde/urea (F/U), existent crystalline regions are believed to affect the properties of wood-based composites bonded with UF resins. The effects of crystalline regions on physicomechanical properties and formaldehyde emission of the plywood bonded with UF resin modified by nano Manganese dioxide (MnO2) were studied in this work. Results show that the modified UF resins with 0.9% MnO2 has a higher ratio of crystalline regions than those of neat resins. They resulted in a 79% improvement in the wet shear strength and a 70% reduction in the formaldehyde emission. The X-ray diffraction (XRD) results show that the crystallinity in the cured UF increases with the amount of MnO2 added. No change in the structure of the cured UF was found in the Fourier transforms infrared spectroscopy (FT-IR) with the addition of MnO2.
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