Plywood is a building material consisting of pressed and glued layers of wood veneer. In this case, wood fibers in alternating layers are perpendicular to each other. This ensures the strength of plywood in both directions, and in ordinary wood, it is only across the fibers. An odd number of layers is used so that the wood fibers of the upper and lower lay in the same direction.
Application
Plywood has the 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, the creation of 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 ordinary wood or other framing materials. This versatility and environmental friendliness of plywood for interior work has led to the fact that it has become a favorite among designers and interior decorators.
When buying this material, please note that there are various varieties. The usual grading system uses numbers from 1 to 4, and also 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 number of defects. The marking is double. The first number or letter refers to the outside, and the second to the inside. Each grade has its own field of application.
Pros of plywood:
- It is rather steady against adverse climatic conditions.
- Less deformed or cracked than solid wood.
- It has a good appearance and high strength at a lower price.
Cons of plywood:
- The veneer can chip, exposing the less expensive wood beneath it.
- Damage is difficult to repair.
- Some types of plywood use glue and formaldehyde.
Production
During the production of plywood, individual veneer layers are first obtained by rotary cutting of 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 glue. In this case, the layers are superimposed on each other and are tightly pressed using the hot pressing apparatus.
The high temperature and pressure created by this technique provide strong adhesion of the layers. 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 to use sizes. It all depends on the manufacturer. The user can cut or grind these sheets in accordance with the required technical specifications. There are several basic types of glue used for manufacturing. The type of plywood, composition, environmental friendliness should be studied before purchase.
FSF
Phenol-formaldehyde adhesive is a type of synthetic or artificial polymer that is obtained by chemical reactions of phenol and formaldehyde.
Phenolic resins provide a stronger bond than urea based substances. Therefore, they are used in the manufacture of more durable and high-quality plywood. The moisture resistance of such a material is very high. The 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 in residential premises.
FCM
Less harmful substances are contained in melamine glue, 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 as follows: FKM.
FC and FBA
There are no harmful substances in the composition of the urea and albuminocasein glue. As a result, the 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 drawback is that this material is not waterproof. In FC plywood, environmental friendliness is ensured by the safe urea adhesive used in its production. FBA plywood contains albumin-casein glue.
Fb
Moisture resistance is sometimes a priority. 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 often labeled as follows: FB. It has two surfaces of the highest quality, but there is a limited selection of hardwoods that are suitable for use in marine conditions. As a rule, birch is used. Ship plywood is much more difficult to find. It costs more than other grades of this material. Depending on the method of sizing, there are subtypes of plywood:
- FBS - is impregnated with alcohol-soluble glue and has increased moisture resistance.
- FBV - is impregnated with water-soluble glue and has increased strength.
Eco-friendly plywood and harm to health
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 E0 plywood.
The use of veneer expands the possibilities of using natural wood species. Veneer is an absolutely natural natural material. However, the production of plywood requires significantly less wood compared to solid wood products. This reduces the number of trees felled. Veneer is an environmentally friendly alternative to hardwoods.
Health concerns are caused by the glue used in the production of wood, as it contains harmful substances. This is especially true for phenol and formaldehyde. Not so long ago, they were considered safe for health, but now the opinion of experts has changed dramatically. Studies show that these substances negatively affect people's health.
Allergic reactions, headaches, respiratory problems and all kinds of inflammations are some of the possible problems caused by these substances. Carcinogenic properties of phenol-formaldehyde compounds are also attributed. The proportion of harmful substances in modern plywood is small, but they are present. This fact should not be ignored.
Reduction of harmful effects
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. It included wheat flour and chalk, which increase the elasticity and viscosity of the adhesive. Moreover, they are natural products. This improves toxicity and contributes to energy savings in the workplace.
Currently, concerted efforts are also being made by manufacturers from different countries to develop a completely environmentally friendly adhesive to make plywood completely safe for people and the environment. An alternative would be adhesives, for example, soy-based amino acids. They do not contain gas pollutants. Safe plywood is also produced with a core of agrofibre or wheat straw, which additionally makes it consistent with environmental standards.
Russia is a country with a sufficiently 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 for investing in new technologies, which leads to increased environmental friendliness of plywood.