| Urea-formaldehyde (UF) resin has been widely used because of its good bonding properties and low price in wood based panel industry. The aging resistance of wood based panel bonded with urea-formaldehyde resin directly affects the products lifetime and formaldehyde emission. It is of great theoretical significance and practical value to study on the aging resistant factors to enhance panel’s durability and to reduce formaldehyde emission of wood based panel.In this thesis, artificial accelerated aging tests, such as British standard BS5669, French standard V100, V63aging method and cyclic soak-day aging test, were used to process the plywood bonded with UF resin and/or modified UF resin. The formaldehyde emission and bonding strength after various artificial aging tests were determined, so as to research the aging resistance of wood based panel.The main conclusions are as follows:(1) Various accelerated aging tests can be used to investigate the aging resistance of wood based panel bonded with UF resin. Treated by British standard BS5669three cycle aging test, mechanical strength of plywood decreased by30%or so. Applying French standard V100, bonding strength badly dropped about75%. Compared with BS5669, five cycles of V63aging method caused the equivalent aging effect, and V63method was easier and more quickly. Cyclic soak-day accelerated aging test is simple, quick and effective. The aging degree of wood based panel could be well indicated after three cycle soak-day aging treatment.(2) High temperature, high humidity, and acid conditions obviously accelerate the aging degree of plywood bonded with UF resin and/or modified UF resin.(3) Melamine modified urea-formaldehyde resin could improve the plywood performance of aging resistance. As more melamine added (Melamine/Urea=1%-20%), the aging resistance of plywood enhances. The influence of process conditions on mechanical properties and formaldehyde emission of plywood can be minimized by adding little melamine (M/U=5%) to UF resin. |
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