Production and application of plywood
For the production of this material, a veneer is needed. Produce it as follows: the heat treated and peeled logs begin to rotate around their axis and remove the "wide shavings" with the help of a grinding knife. This is veneer. Further it is dried, cut, sorted. Then the cloths are laid out in such a way that their fibers are perpendicular to each other and bled on both sides with glue. At the final stage, plywood can be laminated and ground, but not always.
Areas of application of plywood are extremely diverse. It is used in construction, in industrial shipbuilding and machine building, for packing cargo and materials, for furniture production, etc. For example, in construction it is well suited for both interior and exterior decoration of any kind of premises. In particular, it is widely used as a floor covering, because it has high moisture resistance, durability and reliability.
When using plywood in shipbuilding and mechanical engineering, its advantage is high corrosion resistance and lightness. That's why the material is simply laid and transported. And when creating furniture( countertops, shelving, kitchen furniture and bathroom items), aesthetically pleasing appearance and low cost of plywood are of particular importance.
Classification of plywood
Plywood can be classified according to the material from which it is made, impregnation, the number of layers. If we talk about the material, then most often apply two types of wood: coniferous species( spruce, fir, larch) and birch. The first are more suitable for decorative purposes. The second( plywood birch) is used in all areas of construction. By the number of layers the plywood is divided into: 3, 5 and multi-layer.
If we talk about impregnation, then it is necessary to increase the resistance to moisture. In this regard, plywood sheets are divided into: FBA, FSF, FC, FB, BS, BW. The first( FBA) are glued with albuminocasein natural glue. The second( PSF) are connected by phenol-formaldehyde glue. The third( FC) is made using a carbamide compound. The fourth( FB) is processed first lacquer, and then glued together. Fifth( BS) impregnated with alcohol-soluble bakelite composition. Well, the sixth( BV) - a water-soluble bakelite mixture.
By the way, it has plywood dimensions: 1525x1525, 1270x1525 and 1220x1525 mm( FC sheets).A PSF canvases usually have other parameters: 1500x3000, 1220x2440, 1525x3050, 1250x2500 mm.
In this case, the plywood, the thickness of which can vary between 1.5 and 40 mm, is also classified according to the type of surface treatment: NS, Ш1 and Ш2, which means, accordingly: unpolished, grinding on one side and on both sides.
Sorts of plywood, or how to find quality material?
In accordance with GOST, there are 5 varieties of this material. Grade E is considered elite. There are practically no defects in it. Further on the quality is the first grade, in which cracks and fractures can not be more than 20 mm. The second grade may have defects up to 200 mm in size. In general, they should be no more than 2% of the total area.
The third grade allows the presence of wormholes, up to 10 pieces per 1 square meter. Fourth - the lowest quality grade. In it there can be knots, defects of edges, a wormhole up to 40 mm in diameter and other. Therefore, when buying this material, be sure to consider the grade. It is also important to know what kind of work it needs. For example, the plywood that is suitable for laying a laminate will not always be suitable for formwork.
