Summary of problems related to plywood

Summary of problems related to plywood

Advantages of plywood

1、 Plywood not only has all the advantages of natural wood, such as light bulk density, high strength, beautiful texture, insulation and so on, but also can make up for some natural defects of natural wood, such as knots, small width, deformation, large mechanical difference between vertical and horizontal.

2、 Plywood production can make rational use of logs. Because it has no sawdust, every 2.2-2.5 cubic meters of logs can produce 1 cubic meter of plywood, which can replace about 5 cubic meters of logs to be sawn into boards. And every 1 cubic meter of plywood products, it can also produce 1.2-1.5 cubic meters of residue, which is a better raw material for the production of MDF and particleboard.

Defects of plywood

1. Low bonding strength: mainly due to the poor quality of the glue. If the hot pressing conditions are not well controlled, such as low hot pressing temperature, insufficient pressure and too short pressing time, this kind of defect will also appear. If the moisture content of veneer is too high, the gluing amount is insufficient, the veneer quality is poor, and the aging time is too long or too short, the bonding strength will also be reduced.

2. Blistering and local debonding: the reasons are that the pressure drop speed is too fast, the glue pressing time is insufficient, the moisture content of veneer is too high, there are blank spots in gluing, there are inclusions and dirt on the veneer, or the temperature of pine veneer is too high.

3. Plywood warpage: it is caused by the internal stress of plywood. The reason is that the moisture content of the surface and back board is not consistent, the veneer of different tree species is not reasonable, the veneer has twist lines, the temperature of individual hot pressing plate is not enough, and the stacking of boards is not equal.

4. Corner debonding: this defect is caused by insufficient pressure caused by the wear of the pressing plate edges and corners, the edges and corners of the slab in each interval are not aligned, the slab is placed askew during loading, the pressure is uneven, the pressing degree of veneer Edge rotary cutting is insufficient, the glue relay is weak, the corner is short of glue, the glue is dried up prematurely, and the local temperature of pressing plate is low.

5. Penetration: the reasons are too thin glue, too much glue, too deep crack on the back of veneer, too high moisture content of veneer, and too large aging time and pressure.

6. Lamination and seam separation of core plate: the reasons are that the reserved gap is too large or too small when arranging the core manually, the core plate is misplaced or overlapped when installing the plate, and the edge of the zero piece is not even.

Classification of plywood

The first type of plywood is weather resistant and boiling water resistant, which has the advantages of durability, high temperature resistance and steam treatment from one to the other; the second type is water-resistant plywood, which can be dipped in cold water and hot water for a short time; the third type 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 is used for furniture and general construction purposes; four types of plywood are moisture resistant plywood, which are used in normal indoor conditions. The general plywood materials include beech, basswood, Fraxinus mandshurica, birch, elm, poplar, etc.

Main specifications of plywood

The specification of plywood is mainly 2.0-30mm thick, 1220×2440 conventional size. The price depends on your quantity and material (core, glue, surface) requirements.

Characteristics of flame retardant plywood

Flame retardant plywood is a kind of three-layer or multi-layer board like material, which is made by cutting wood segments into veneers or square planks, and then glued with adhesives after fire-retardant treatment. It is usually made of odd number of veneers, and the fiber direction of adjacent veneers is perpendicular to each other. The flame retardant plywood is made of wood as the main raw material. Because of its reasonable structure and fine processing in the production process, it can generally overcome the defects of wood, greatly improve and improve the physical and mechanical properties of wood. At the same time, the fire-retardant plywood overcomes the shortcomings of ordinary plywood which is easy to burn, and effectively improves the fire-retardant performance of plywood It is an important method to make rational use of wood and improve its properties.

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