Plywood is a building material consisting of pressed and glued layers of wood veneer. In this case, the wood fibers in alternating layers are arranged perpendicular to each other. This gives the plywood strength in both directions, while in ordinary wood it is only across the grain. An odd number of layers are used to keep the top and bottom wood grains in the same direction.
Application
Plywood has strength, durability, lightness and rigidity. It also has increased resistance to deformation, bending and splitting. In almost every hardware store it can be purchased at a fairly affordable price. Plywood, given its environmental friendliness, is used not only in traditional construction projects, but also in shipbuilding, creating aquariums and tanks.
The use of this material to create furniture and partitions is widespread. Its high strength allows it to be used in combination with regular wood or other framing materials. This versatility and sustainability of interior plywood has led tobecause it has become a favorite with designers and interior decorators.
When buying this material, please note that there are different grades. The usual grading system uses numbers from 1 to 4, as well as the letter E - an elite variety that does not allow any defects. Grade 1 - the best quality, practically without defects, very well polished. Grade 4 - extremely low quality, usually contains the maximum allowable number of defects. Double marking. The first number or letter refers to the outside, and the second to the inside. Each variety has its own area of application.
Pros of plywood:
- Sufficiently resistant to adverse climatic conditions.
- Less warp or crack than hardwood.
- Good looking and high strength at a lower price.
Cons of plywood:
- Veneer may chip, exposing less expensive wood underneath.
- Damage is difficult to repair.
- Some types of plywood use glue and formaldehyde.
Production
In the plywood production process, individual layers of veneer are first obtained by rotary cutting of the wood. To do this, the logs are rotated around the longitudinal axis, and the cutter cleans it (the thickness of each layer is usually less than 2.5 mm). Next, the adhesive is applied to the layers using a special machine. It helps in achieving an even distribution of the adhesive. The layers are superimposed on each otherfriend and pressed tightly with a hot press machine.
The high temperature and pressure generated by this technique ensures that the layers adhere strongly. Their number in each sheet of plywood can vary from 3 to 13. The thickness of sheets from different manufacturers is in the range of 3 mm - 30 mm. Standard sheet sizes are 1220 by 2440 mm. There are other, more convenient sizes to use. It all depends on the manufacturer. The user can cut or grind these sheets according to the required specifications. There are several basic types of glue used for manufacturing. Plywood type, composition, environmental friendliness should be considered before buying.
FSF
Phenol-formaldehyde adhesive is a type of synthetic or artificial polymer that is made by chemical reactions between phenol and formaldehyde.
Phenolic resins provide a stronger bond than urea-based compounds. Hence, they are used in the manufacture of stronger and higher quality plywood. The moisture resistance of this material is very high. Marking is: FSF. The main and very significant drawback of formaldehyde resins is the harmful substances that make up their composition. Their use is unacceptable for furniture production and residential premises.
FKM
Melamine glue contains less harmful substances, but the level of moisture resistance of such plywood is much lower. Such material is used where there are no requirements for moisture resistance and an increased level of safety. Plywood is marked like this: FKM.
FC and FBA
There are no harmful substances in the composition of carbamide and albumin-casein glue. As a result, plywood, in the production of which they are used, can be used in the decoration of any buildings, even kindergartens. It is also used in furniture. The main disadvantage is that this material is not waterproof. In FK plywood, environmental friendliness is ensured by the safe carbamide glue used in its production. FBA plywood contains albcminocasein glue.
FB
Sometimes moisture resistance is a priority requirement. In these cases, ship plywood is used. In the production of this material, the best brands of moisture-resistant bakelite glue are used. Such plywood is most often marked as follows: FB. She has two top quality surfaces, but a limited selection of hardwoods that are suitable for marine use. As a rule, birch is used. Marine plywood is much more difficult to find. It costs more than other varieties of this material. Depending on the method of gluing, plywood subspecies are distinguished:
- FBS - impregnated with alcohol-soluble glue and has increased moisture resistance.
- FBV - impregnated with water-soluble glue and has increased strength.
Plywood environmental friendliness and harm to he alth
Materials in which formaldehyde resins are present, according to European standards, are divided into 3 categories (E0, E1, E3). The figure shows the level of harmful substances. The safest plywood is E0.
The use of veneer expands the possibilities of using natural wood species. Veneer is an absolutely natural material. However, the production of plywood requires a significantly smaller amount of wood compared to solid wood products. This reduces the number of trees cut down. Veneer is an environmentally friendly alternative to hardwoods.
He alth concerns are caused by the glue used in wood production, as it contains harmful substances. This is especially true for phenol and formaldehyde. Not so long ago they were considered safe for he alth, but now the opinion of experts has changed dramatically. Studies show that these substances adversely affect people's he alth.
Allergic reactions, headaches, respiratory problems and all kinds of inflammation are some of the possible problems caused by these substances. Carcinogenic properties are also attributed to phenol-formaldehyde compounds. The proportion of harmful substances in modern plywood is small, but they are present. This fact should not be ignored.
Reduce Harm
Modern science does not stand still. Methods are being developed to help increase the environmental friendliness of plywood. One solution is to create a modified adhesive based on phenol-formaldehyde resin. Wheat flour and chalk were introduced into its composition, which increase the elasticity and viscosity of the adhesive joint. However, they are natural products. This improves the toxicity andcontributes to energy saving in production.
There are also concerted attempts by manufacturers from around the world to develop a completely environmentally friendly adhesive to make plywood a completely safe material for people and the environment. An alternative would be adhesives such as soy-based amino acids. They do not contain contaminants that cause gas formation. Safe plywood is also produced with an agro fiber or wheat straw core, further making it environmentally compliant.
Russia is a country with a fairly developed woodworking industry. Our plywood production has a long tradition and a high level of accumulated knowledge. Rich forest resources and competitive production provide good opportunities to invest in new technologies, resulting in more environmentally friendly plywood.
