Construction-grade plywood is a board formed by cutting logs into large veneers in the direction of annual rings, and after drying and gluing, they are assembled and glued according to the principle that the wood grain directions of adjacent veneer layers are perpendicular to each other. The number of veneer layers is an odd number, usually three to thirteen layers. The common ones are three plywood, five plywood, nine plywood, and thirteen plywood (commonly known in the market as three plywood, five plywood, nine plywood, and 13 plywood. board). The front single board of the outermost layer is called the front panel, the back side is called the back panel, and the inner board is called the core board. Plywood can improve the utilization rate of wood and is a major way to save wood.
Construction-grade plywood is one of the commonly used materials for construction and furniture. It is one of the three major panels of wood-based panels. It can also be used as a material for aircraft, ships, trains, automobiles, buildings, and packaging boxes. A group of veneers is usually glued according to the adjacent layers of wood grain directions perpendicular to each other. The surface board and the inner board are usually arranged symmetrically on both sides of the central layer or the core. The glued veneer is criss-crossed in the wood grain direction to form a slab, and then further heated or not heated, and finally pressed into a plywood. The physical and mechanical properties of plywood in the vertical and horizontal directions are relatively small.
The usual length and width specifications of construction-grade plywood are: 1220×2440mm, and the thickness specifications are generally: 3, 5, 9, 12, 15, 18mm, etc. The main tree species are: camphor, willow, poplar, eucalyptus, etc.
Construction-grade plywood can be divided into five categories:Ⅰ plywood is weather-resistant and boiling water-resistant plywood, which has the advantages of high temperature resistance and steam treatment; Ⅱ plywood is water-resistant plywood, which can be immersed in cold water or in hot water for a short time; Ⅲ plywood is moisture-resistant plywood, which can be dipped in cold water for a short time, and is suitable for indoor use at room temperature. It can be used for furniture and general construction purposes; the Ⅳ plywood are non-moisture-resistant plywood, which is used under normal indoor conditions. The plywood materials suitable for general purposes include beech, basswood, ash, birch, elm and poplar.
Construction-grade plywood is mainly used in outdoor conditions, such as exterior decoration and concrete formwork. In decoration works, it is mainly used in ceilings, wall skirts, floor liners, cabinets, tables, etc.