Mar. 04, 2021
Panel furniture is increasingly popular with consumers due to its cost-effectiveness, rich appearance and ease of dismantling and assembly. Man-made panels are the main material for panel furniture, which includes fibreboard, particleboard and plywood. Unlike solid wood materials, man-made panels can make full use of wood such as small-diameter timber, saving forest resources, while also having the texture and colour of natural solid wood.
Of the many man-made panels, plywood has the longest history of development. Plywood is relatively easy to process, has a low weight capacity, high specific strength, low energy consumption for processing and greenhouse gas emissions, and can have the texture and feel of natural wood. However, plywood can still slowly release free formaldehyde in the process of use, polluting the indoor environment and, more seriously, affecting people's health. So how can plywood be produced to be 'aldehyde free?
Formaldehyde-free plywood is produced using wood or wood components as raw materials and formaldehyde-free materials like adhesives, such as plant and animal proteins, starch, plastics, isocyanates, etc., or by modifying aldehyde-containing adhesives to reduce the formaldehyde produced when the resin is cured. This is followed by gluing using the traditional man-made board gluing process and veneering to make man-made boards.
The formaldehyde released from plywood is influenced by three main factors: the manufacture of the panels, the secondary processing and the external environment. The main factors in the manufacture of plywood are the choice of adhesives and the hot pressing process. The external environment also has an impact on the amount of formaldehyde released, when the relative humidity or temperature increases it will promote the release of formaldehyde in plywood.
(1) Modification of aldehyde-containing adhesives. Adding formaldehyde absorbers in the process of modifying aldehyde-containing adhesives can effectively reduce the free formaldehyde content. If UF resin is used, urea can be added in batches to reduce the amount of formaldehyde released.
(2) Formaldehyde-free adhesives. The different materials can be divided into biomass adhesives, isocyanate adhesives, thermoplastic resin adhesives.
(3) Other treatments. Impregnation of the veneer with borax prior to plywood preparation can weaken the hydrolysis of the UF resin and thus reduce the amount of formaldehyde released.
Due to its small deformation, large width, ease of construction and good tensile properties, plywood is used in a great variety of applications, not only in the furniture industry but also in the construction, car and boat industries. The production of aldehyde-free plywood is not only a requirement of national policy but also improves the indoor environment in which people live.
The use of natural polymer and biomass materials as plywood adhesives is a promising new approach, and the modification of these materials to improve their water resistance and mechanical strength is the focus of research and manufacture of aldehyde-free plywood.
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