Plywood boards are a type of wooden panel formed by the union of several sheets of natural wood with excellent qualities in terms of stability and resistance. It is known in different ways depending on the geographical area: multilaminate, plywood, plywood, etc., and in English-speaking countries, such as plywood.
Always use a odd number of veneers, which are joined by alternating grain directions. That is, each sheet is perpendicular to the next and / or previous one. This definition is very important, as it gives it many advantages over other types of panels. It is normal to use 1.5-1.8-2-3 mm thick sheets, although this is not always the case.
Glues are added to this sheet joint and pressure is applied. The manufacturing process for these plates is not new, it has been known since the beginning of the last century, although it has not failed to incorporate improvements: innovations in adhesives, selection and production of plates, cutting …
This type of board is well known and its use is very widespread, but not everyone knows that there are different types of plywood. Each of these types, despite having many characteristics in common, may have differences that make them suitable for some specific uses.
FEATURES OF PLYWOOD BOARDS
Resistance. Wood naturally offers greater resistance in the direction of the grain. In the case of this type of plate, as the directions alternate in successive sheets, greater uniformity and resistance in all directions is achieved, which becomes more and more equal as the number of sheets increases.
Lightness. To a large extent, this characteristic is defined by the wood species used. Light or semi-light wood (400-700 kg / m3), although there are exceptions. This feature facilitates transportation, handling and many other tasks.
Stability. It is very stable, which is a fundamental characteristic. It is due to its manufacturing process, since the tendency of movement of each leaf is counteracted by the adjacent leaves.
Easy to work. The shape of the board makes work much easier, and because it does not use excessively dense wood also in machining.
Interesting properties like sound insulation and conditioner.
it is Fire resistance It is determined by the wood used and the treatment that may have been applied to it.
Can be used outdoors and / or humid. This characteristic is conditioned to the use of adhesives and suitable wood.
Easy to fold. There are limitations on the wood used, the thickness of the board and the availability of the necessary machinery. However, it will always be easier than folding a solid board.
Unlike other cards it is generally not sharp. In this case, the exposed edge, with a very characteristic aspect, is highly decorative.
DISADVANTAGES OF PLYWOOD PANELS
● Possibility of weak and / or empty points. Wood has natural defects, like us. At these points, the metal sheet is weaker and, if several nodes also coincide, the resistance of the whole can be impaired. Another common problem, especially with cheap or cheap plywood, is that there may be small internal voids, that is, pieces of a sheet are missing or not well bonded.
● Comparatively higher price than other types of boards: OSB, MDF or chipboard.
USUAL MEASURES OF PLYWOOD BOARDS
The most common measurement is the panel industry standard: 244 × 122 centimeters. Although the 244 × 210 are also frequent, mainly for construction.
As for thickness or thickness, it can vary between 5 and 50 millimeters. Although, again, the most common thicknesses are the same as the rest of the plates: 10, 12, 15, 16, 18 and 19 millimeters.
SHEET SELECTION
Unrolling sheets are used which generally exceed 7 millimeters in thickness. Once obtained, they go through a selection process that classifies them according to their appearance and / or the number of defects they may present (mainly us).
Blades that do not fit aesthetically will be used to make structural panels. Those that are most attractive by design and grain will have a decorative purpose.
TYPES OF PLYWOOD BOARDS
The parameters vary from one type to another:
● Wood species used.
● Veneer quality. The quality of the internal veneers is not always specified. However, mention is made of the quality of the outer or expensive leaves.
● Thickness of the leaves and the whole.
● Bonding type.
According to their use or usage environment. This classification was established in UNE-EN 335-1 and UNE-EN 314-2 for bonding quality.
● Interior (collage 1). Made with urea-formaldehyde glues and resins.
● Exterior Covered or semi-exterior (Glued 2). Melamine urea formaldehyde resins are used.
● Exterior (collage 3). In this type of environment it is necessary to combine wood with good natural resistance to moisture and rot, together with phenolic glues.
According to the wood used. Many woods can be used for the manufacture of plywood, giving their technical properties to the result. Therefore, a birch plywood is not the same as an okume plywood.
But it is not just the wood in question, but also the quality with which it was selected. It is customary, in the corresponding technical sheets, to mention the quality of the facial, rear and interior plates. It is that the same thing is not sought when using a construction board, as when it is used to make furniture.
Main woods used in plywood boards: Birch, okume, sapelly, poplar, calabó, walnut, cherry, pine or eucalyptus. A common characteristic among woods is that they perform well against unwinding, the main technique for obtaining veneers in logs.
On some occasions, wood is used that a priori is not the most suitable for different reasons. For example, pine or spruce can be used to make a board for industrial or structural use due to its low price, or more decorative woods like oak looking for just that.
Combinations of wood or mixed plywood are also common. Species with better appearance or aesthetics for the faces are used mainly, and cheaper species for the interior veneers.
Triplay. This concept was initially used to talk about plywood made up of three sheets. However, today the concept has spread and is used to talk about plywood in general.
Phenolic plywood. Adhesives based on phenolic resins are used to manufacture this type of cardboard. This type of adhesive allows the plate to be used in damp and outdoor environments.
If we also use wood with excellent properties for external use (or treated), we obtain what is called marine plywood. Previously they were called WBP (Water boiled proof), but the new European regulations catalog them in this way.
Bodyboard or Finnish plywood. It is a class of plywood with a proper name due to its success or demand. Birch wood is used and then the panel is covered with a phenolic film that improves its resistance to abrasion, shock and moisture. This outer layer also adds non-slip properties, so it is used as a floor, deck for boats and as a cargo surface in vans or trailers.
Melamine plywood. They are melamine-coated plywood with a clearly decorative purpose. Although it is common to find them mainly in plain colors, such as white or gray, they can also be found imitating other woods.
The idea is to reduce the costs associated with applying finishes and increase their resistance to abrasion or friction.
USES OF PLYWOOD BOARDS
● Structural use. It presents an ideal binomial within a building: lightness and resistance. Roofs, floors, formwork, fences, mixed beams … In this use, OSB boards have become a common substitute, mainly due to their lower price.
● Manufacture of furniture: chairs, tables, shelves
● Wall covering. Decorative, where noble woods are usually used, or not decorative or hidden, where lower quality plywood is used.
● Naval and aeronautical carpentry: Manufacture of ships, airplanes …
● Transport sector: railway wagons, trailers and more recently the camping of vans.
● Packing
● Curved surfaces. It is an ideal type of board to fold, especially those of less thickness.
● Construction: concrete molds, screeds, scaffolding …
WHEN AND WHY TO USE ONE PLYWOOD BOARD INSTEAD OF ANY OTHER?
The answer is relatively simple, in uses that require anything else, and other cards cannot be used. And, of course, also wherever a card is needed, since it is probably the most versatile of all.
For external use, practically the only option we have is the laminated phenolic plywood. Other options can be compact HPL (composed mainly of resins) or slatted boards made of wood that naturally have extra moisture resistance. The first, if it could be a substitute, the second, besides being unusual, has comparatively much higher prices.
Despite its lightness, the plywood offers much greater resistance to flexing than solid wood (in similar weights and densities). Therefore, they are used in applications where large loads must be supported.
Post time: Dec-21-2022