Characteristics and use of laminated moisture resistant plywood

Introduction

Plywood is a multi-layer material that is made from veneer. The number of veneer layers is always odd, that is, there are three-layer, five-layer and multi-layer. There is plywood that can have 23 layers

To maximize strength, the layers are always arranged perpendicularly, although, of course, there may be options with a parallel arrangement, but this is a very rare case and should not be taken into account. Plywood differs in its durability from other wood-based panels, such as chipboard

Plywood is processed and sawn without the use of any special industrial tools, you can even use an ordinary household jigsaw and simple wood saws.

Plywood selection criteria for formwork

What is the best plywood to use for formwork? The building materials market offers a huge selection of different types of plywood, differing in composition and processing options. In addition, the product line is presented from numerous manufacturers.

And if you still doubt which formwork material fits better, pay attention to certain criteria:

plywood thickness for foundation formwork. The final price of plywood depends on this indicator, and it is quite understandable that the desire to save money immediately appears. But one should act wisely. If the plywood turns out to be too thin, you will not achieve a good result - the formwork panels will bend from the pressure created by the concrete solution, and their destruction may occur. The optimal solution is considered to be a plywood thickness of 1 - 1.2 cm, and if concrete is to be poured with a thick layer, experts recommend using a more reliable 18 - 20 mm film faced plywood;
grade. Plywood material is of different classes, the most expensive of which is considered "extra". Samples of I - IV classes are considered cheaper. The material should be selected taking into account its intended use, and most often it is plywood of I and II classes, which has a good margin of safety;
feedstock

When purchasing plywood, you need to pay attention not only to the glue used in the production, but also to the veneer material. Preference is most often given to coniferous woods or birch

Each of these varieties is affordable. More expensive materials include fir, larch and teak plywood sheets. If difficult operating conditions are expected, it is recommended to buy a reliable and expensive material that can withstand a large number of work cycles.

GOST defines several options:

• the standard is square sheets, the length of the sides is 122 and 152.5 cm. There are rectangular sheets, the length and width of which is 152.5 and 122 cm, respectively. The main advantage of such material is its acceptable cost;
• large format. On sale you will find film faced plywood, the parameters of which are 3000 x 1500 x 18 mm. It is more convenient to use such sheets of material in the construction of plywood formwork for walls. Their cost is slightly higher than the standard ones, but the shields are made without joining seams. In addition, for pouring 2 meter walls, the formwork panels will turn out to be solid;
• non-standard. It is possible to manufacture plywood material according to individual customer requests. This creates certain advantages, but the cost of such an order increases significantly.

An important criterion that you should pay attention to when choosing plywood is the quality with which the surface of the material is processed.The ideal solution would be flat and smooth sheets.

Their application will allow:

• speed up the dismantling work, because plywood sheets separate from the hardened concrete much easier;
• the monolithic surface is smooth, plywood lends itself better to subsequent processing.

An important feature of the choice of film faced plywood for formwork is the country in which the product was produced. Today, material from domestic and Chinese manufacturers is in demand, while plywood from China is less expensive.

It is used as an economy option when a low-rise facility or structure with small architectural forms is being built. As a rule, such black plywood used for formwork can withstand a limited number of cycles, but is well worth the cost.

With large working volumes, it is recommended to purchase domestic material and, for the reliability of its use, install plywood formwork on metal racks. To increase the turnover rate of laminated plywood for formwork, experienced specialists advise using special lubricants - barrier or chemically active. In the first case, you create additional protection, and in the second, you increase the plywood's resistance to moisture.

Plywood moisture resistant: material features

This wood-based panel material consists of sheets of deciduous (most often birch) or coniferous veneer, peeled according to a certain technology. Initially, the raw materials have natural resins, which determine the level of moisture resistance. Hardwoods are better protected from getting wet than conifers, so the former are used for exterior decoration, and the latter for indoor work.

The use of synthetic binders increases the moisture resistance and makes it possible to obtain an already water-resistant plywood. The following types of glue are used for impregnation:

1. Urea compounds - the limit of resistance to water is 5–12%. Materials based on them do not withstand prolonged exposure to moisture, therefore, the use of such waterproof plywood is limited to interior decoration of rooms with medium humidity. Plywood sheets are produced under the FC brand.
2. Phenol-formaldehyde compounds - resistance of impregnation to moisture 12–17% due to the use of synthetic resins. The substance has good astringent and waterproof properties. It is used more often for exterior decoration, but has also found application in interior decoration, arrangement of moisture-resistant structures. Such material is produced under the FSF brand.
3. Film faced plywood - the strength characteristics and moisture resistance of this material largely depend on the type of protective coating. The lamination technology gives the product parameters that are not typical for wood, but at the same time preserves the natural structure of the wood. This material is widely used in monolithic construction, used in the furniture industry and design. Produced under the FOF brand.

Let's take a closer look at the types of laminated moisture-resistant plywood. The material is made on the basis of FSF boards, in which the veneer is glued with phenol-formaldehyde resins. Thus, even without lamination, it is classified as a durable product. Further, the characteristics and properties of laminated moisture-resistant plywood depend on the type of protective film used:

• phenol-formaldehyde coating - the film is impregnated with phenol and formaldehyde resins, waterproof substances. The scope of application of the slabs is limited to external work, the manufacture of formwork, facade cladding, etc.;
• melamine coating is a fairly waterproof substance. Types of moisture-resistant melamine-faced plywood are used for interior decoration of rooms with high humidity.

In addition, the characteristics and properties of moisture-resistant film faced plywood depend on the type of texture of the protective coating: SP - for painting, F - smooth, W - mesh or embossed.The ends of the products are treated with waterproof acrylic paint.

Difference of film faced plywood from ordinary

Some of the characteristics that have been defined by GOST 2010 are described below:

• For the production of laminated plywood boards, plywood of the 1st and 2nd grade of the phenol emission class of the E1 level is used, and at the same time everything meets the strict requirements for the presence of defects on the veneer, the method of gluing and the final density of the material.
• The plywood sheathing can be made from thermosetting plastic or high tenacity plastic film. According to the test conditions, the coating should be unchanged even after 6 hours of boiling, as well as in contact with liquid concrete and an alkaline environment.

A sheet of film faced plywood, in contrast to the bakelite variety, is impregnated with a hot method, and it contains less phenol. As a result, we obtain an elastic and at the same time sufficiently strong material, which has a lacquered protective polymer layer. Film faced plywood with water resistant effect is more ductile than bakelite plate, which is better than a laminated sample in terms of water resistance characteristics, but has an increased sensitivity to abrasion and shock.

To create the coating of the laminated fork, in addition to textured paper and phenol-formaldehyde resin, PVC films and melamine varnishes are used. Although the technical characteristics of melamine and PVC coatings are slightly worse than FFS, they are indispensable when creating a plywood sheet in color. If standard samples have a phenol emission class E1 according to GOST, then a colored PVC sample emit several times less toxic substances.

According to the technical characteristics of film faced plywood and the method of using GOST, the laminated board is used for exterior decoration and in the manufacture of concrete casting molds. If the same plywood sheet is painted, then it can be used for interior work during finishing, as well as for wall cladding in a frame house and as a sublayer for leveling the floor.

It is easy to distinguish standard film faced plywood from painted plywood - it all comes down to color, since the standard version is dark brown, and colored boards are tinted in shades that are lighter than the original.

Moisture-resistant laminated plywood

It can be made, alternating, birch and coniferous veneer. Moisture resistance is the ability not to be exposed to moisture from the environment. The brands of such products are different depending on the brand of glue used:

1. Elements are glued with urea formaldehyde, marked with FC, it can be used even inside apartments;
2. The veneer is glued with phenol-formaldehyde resin, marked with FSF, it is better to keep it in the fresh air;
3. Using bakelite adhesive, it is marked with FBS. The most waterproof, such a building material is allowed to be used even in shipbuilding, aircraft and automobile construction.

Strength characteristics of laminated sheet

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Veneer for plywood production

Veneer is the main element of plywood, which is thin sheets of wood with a thickness of 0.1 mm to 8 mm. To understand the peculiarities of plywood, you need to tell in more detail about the veneer from which it is made.

Normative base

Veneer production is regulated by the following regulations:

• GOST 99-96 "Peeled veneer"
• GOST 2977-82. "Sliced ​​veneer"
• GOST 99-89. "Rotary cut veneer" (obsolete)

There are three main ways to produce veneer:

• Peeling;
• Planing;
• Sawing.

Rotary cut veneer

For the peeling operation, special peeling machines are used.The principle is as follows - a churak (a sawn tree trunk, cleared of bark) rotates around its own axis, and a special knife of a peeling machine, located parallel to the log, cuts off a thin layer of wood of a given thickness from it. As the block rotates, the knife moves to its center, thereby providing a uniform veneer thickness. For peeling, both coniferous and deciduous wood species can be used:

• Pine;
• Birch;
• Linden;
• beech;
• oak;
• maple;
• ash;
• fir;
• cedar;
• alder;
• aspen;
• spruce

etc.

Sliced ​​veneer

To obtain sliced ​​veneer, cutting (planing) is performed wood surface on special machines. In this case, the width of the veneer obtained does not exceed the width of the planed bar.

By varying the different angles of the knife relative to the longitudinal axis of the bar, a different pattern and texture can be obtained. Both coniferous and deciduous wood species can be used for planing:

• Pine;
• Birch
• beech;
• oak;
• pear;
• elm;
• chestnut;
• Red tree;
• Linden;
• ash;
• alder;
• maple;
• velvet tree;
• nut

etc.

Sawn veneer

This is the simplest and oldest method, in which a plate with a thickness of 0.5 - 5 mm is simply sawed off from the workpiece. For the manufacture of sawn veneer, both coniferous and deciduous woods are mainly used:

• Pine;
• Birch
• beech;
• oak;
• Linden

etc.

Fine-line veneer

If the above types of veneer production result in a thin sheet of wood, then fine-line veneer is an artificial veneer. It is based on wood, but there is also glue and dyes (about 8%). For its manufacture is taken natural veneer from soft wood, soaked in special solutions and dye, after which they are glued and pressed under high pressure into special packs. Subsequently, these pressed bundles are cut into ultra-thin sheets, which are called fine-line veneers.

The resulting veneer has a number of advantages:

• as well as natural veneer it is environmentally friendly;
• has no defects on the surface, unlike traditional 100% veneer;
• any pattern, texture, or just a solid color can be applied on it;
• high - elasticity and flexibility;
• inexpensive types of wood are used for its manufacture, which makes it less expensive compared to traditional 100% veneer;
• moisture resistant, that is, it can be used in rooms with high humidity.

However, there are also disadvantages, namely:

• Low strength (fragility). Due to the use of soft wood species, it is subject to deformation under mechanical stress;
• Possible cracking. To increase the strength, the material is coated with varnish, which, under certain influences, can form cracks.
• The presence of artificial components (8% glue and dyes) in the composition does not allow this material to be classified as 100% ecological.

Fine-line veneer has a wide range of applications. For example, it is widely used in the production of furniture, doors, floor coverings, as well as various decorative materials for creating design solutions in rooms.

Marking, designation

As a rule, the outer layers of plywood sheets are made from solid birch, beech, maple, linden, alder, poplar, birch. For internal veneer layers, the following are used: pine, larch, spruce, fir and Siberian cedar. The number of layers, their combination and arrangement are regulated by GOST 30427. If plywood is made from different types of wood, then it is classified as combined.

Table 2. Thickness and number of plywood layers.

The material is produced in 5 grades (E, I, II, III, IV) and various grades. FSB is a moisture-resistant plywood designed for active use in high humidity conditions, and FC is an ordinary water-resistant plywood exclusively for indoor use. The layers of FBA plywood are glued with an albuminocasein compound.FSF is a plywood made using phenol-formaldehyde glue. The advantage of this plywood is its high mechanical strength, extreme water resistance and wear resistance. BS and BV plywood is impregnated with a bakelite composition and has an ultra-high mechanical strength. It is resistant to aggressive environments.

The nominal thickness and dimensions of plywood can be found in tables 1, 2.

Plywood sheets are cut at an angle of 90. The deviation from perpendicularity should not exceed 2 mm per 1 running meter. m edge. The symbol of the sheet must indicate:

1. Product name.
2. Brand.
3. The type of wood that was used to form the outer layers of the product.
4. Product emission.
5. Dimensions.
6. Type of mechanical processing of the outer surface.
7. GOST.

Ply thickness of plywood from different types of wood, general purpose.

An example of the correct designation of a plywood sheet with outer layers of beech veneer, FSB grade, outer layers I / III, emission E2, sanded on one side only, length 3600 mm, width 1800 mm, thickness 6.5 mm: plywood, beech FSB, I / III, E2, Sh1, 3600x1800x6.5 GOST 3916.1-96. Typically, the thickness of the veneer is 3.5-4 mm.

Plywood inventory can be kept in m2 and m3. The correct marking of each sheet is made with paint, which is applied strictly to the reverse side with the obligatory indication of the grade and brand. The marking must contain the following data:

1. Country of origin.
2. The plant where the product was made.
3. Trademark and mark of conformity.
4. Product designation.
5. Number of pieces in a package.
6. Transport markings.

Packaging is made in packages of 1.5 tons, taking into account the size, grade and characteristics of the product.

Characteristics of moisture resistant plywood produced by the Sveza holding.

Hardness with low weight.
The products manufactured by the Sveza holding have excellent strength characteristics and are lightweight. Furniture made from it
will undoubtedly be strong, light, comfortable and will last a very long time. Moisture resistant plywood board possesses
an indisputable advantage over a simple tree in terms of the stability of geometric dimensions, since knots on natural wood can lead to deformation of the finished product.
At the same time, thin sheets are successfully used for the production of bent-glued figures. Environmental friendliness
The fact that birch veneer sheets are glued with urea glue makes the material absolutely environmentally friendly. Such plywood can be safely used even for manufacturing
children's furniture.Resistant to temperature changes.
Wood heats up the more, the higher its moisture content.
Plywood fk, manufactured at the factories of the Sveza holding, is moisture resistant and, due to this, resistant to temperature changes. Nice appearance.
The slab veneer is cut from northern birch, which has a uniform density and beautiful texture. High, so-called furniture grades, are distinguished by the ideal surface of the veneer without knots and defects, perfectly sanded. The use of transparent colored films in combination with the beautiful texture of wood allows many design ideas to be realized. Good sound absorption.
Plywood sheets have good acoustic properties. With a sheet thickness of 21 mm, the sound absorption coefficient is about 27 dB. Acoustic performance can be improved with special soundproofing layers. Water resistance.
According to GOST 3916.96, according to the degree of water resistance of the glue joint, FC plywood is water resistant. Thus, when exposed to moisture,
it does not swell, deform and does not crack when dry. Resistance to aggressive environments.
Natural wood itself has anti-corrosion resistance, and in combination with the use of moisture-resistant urea glue, this characteristic reaches high values.

Additional points

FSF plywood, made from softwood, is much more suitable for construction than the same birch plywood. It is used as a frame in the construction of buildings, it is an alternative to OSB. Basically FSF plywood is coniferous, it is considered a direct competitor to OSB. Builders, when it is necessary to lay sub-floors, mainly use FSF coniferous plywood. Fasteners can be easily screwed into this material. It has high elasticity, does not undergo deformation. The properties listed above are the main advantages of softwood plywood over birch grade.

Another positive property of softwood plywood is its excellent wear resistance and tremendous strength when chipping occurs.

When such softwood plywood is made, due to the high porosity of the needles, the glue sinks much deeper into the veneer layers, as a result, flexibility increases, and the strength of the material increases. This type of plywood is endowed with excellent thermal insulation properties. Coniferous slabs are used by builders for particularly critical structures.

Properties and characteristics of film faced plywood

A sheet of film faced plywood, unlike ordinary plywood, does not absorb moisture. Its penetration into the pores of wood fibers is prevented by a polyvinyl chloride film.

In principle, veneer can be made resistant to decay, but it is not profitable for industrialists to engage in this. Let's recall the technology of building houses in the old days. The forest was cut in early spring, when the trunks are filled with resin. Then, the trees were heated for 2-3 years. The water pushed air particles out of the rock.

Moisture could not take a full-fledged place in the trunks. The density of the resin is less. The sap of the tree spread evenly over it. So the resin grabbed the entire trunk. Having taken it out after a couple of years, they chopped it off with sparks. The wood became so dense. As if you are sawing a stone.

In the conditions of industrialization and a century of consumption, no one will engage in long-term soaking of wood, and it is problematic to cut veneer from "stone" trunks.

In general, plywood is a common raw material with a mass of hollow chambers with gas that easily displaces water. Most of the trees are cut in the summer. There are few spring resins.

Without them, plywood absorbs moisture, begins to rot, swell, become covered with fungi and mold, and smell musty. Lamination solves problems for a penny.

Moisture resistant film faced plywood

An additional plus of the film coating is aesthetics. Polyvinyl chloride is easy to paint, imitates different materials. Instead of unsightly pine veneer, the look is the surfaces of oak, ash, mahogany.

Film on film faced plywood can also be made of paper. It would seem the same cellulose. However, to cover plywood, it is impregnated with formaldehyde or melamine-formaldehyde resins.

It is they who turn the paper into a waterproof film. It inhibits bacteria that don't like formaldehyde. It turns out that the surface of the laminated plywood is antiseptic.

Filling microcracks in the upper layers of plywood, resins seem to reinforce it. The sheets are stronger than usual, more dense. Cracking of wood-based panels is a thing of the past.

Colored Film Faced Plywood

This cracking is partly caused by the gradual drying of the plywood. It evaporates water just as easily as it absorbs it. Without internal moisture, the material becomes brittle. The film, on the other hand, blocks the evaporation of internal moisture and does not allow vapors to come from outside. So the flexibility and resilience of plywood is preserved.

The polymer film over the sheets of the heroine of the article is more chemically inert than wood. The resistance of the coating to fuels and lubricants is especially important. The tree, as we remember, is highly flammable. Laminate boards are not easy to set on fire.

However, the “smoke” from laminated boards is different. These are the same formaldehydes used in paper impregnation, and polyvinyl chloride also contains them.Substances are volatile and toxic.

Under normal conditions, formaldehyde is considered safe, which, however, is controversial. The safety argument is the lack of the ability to evaporate at room temperature. But when heated, formaldehydes rush from the film into the atmosphere. So, from the point of view of environmental friendliness, ordinary plywood is considered to be advanced.

Film faced plywood with glossy finish

However, it is difficult to protect oneself from formaldehydes in the current century. You won't buy plywood, you will find toxins in laminate, wall panels, ceiling tiles, even synthetic curtains and trousers.

The ends of the laminated boards are protected with acrylic paint. It also forms a surface, waterproof film. Such additions to conventional plywood increase its price. However, we will talk about this in a separate chapter. In the meantime, consider the types of the heroine of the article.

Peculiarities

There are many options for such a material, they all differ in their width, coating and manufacturing features.

In order to choose the optimal product, you need to pay close attention to the study of the characteristics. Plywood is a regular sheet that is created using wood

In turn, it goes through several stages of processing, which gives the product its unique properties.

The process of gluing the layers is due to the use of special compounds, which are usually obtained on the basis of resins. The result is a lightweight material that can also boast of its resistance to temperature extremes.

Among the main advantages of such a product are the following.

• Resistant to moisture, so the material can even be used to decorate a bathroom. This can be achieved due to the fact that upon contact with water, the plywood sheets do not delaminate and do not lose their shape.
• Ease of processing and installation. This material is famous for its durability, so you can use any tools for processing without fear. Plywood is easily cut, sawn or drilled, which favorably distinguishes it from other materials.
• The ability to combine with other materials. It should be noted that film faced plywood is very often used as an additional material, therefore it is perfect for finishing the ceiling, floor or roof. Most experts use this plywood in combination with natural wood.
• Huge scope of application. Film faced plywood can boast of its unique performance characteristics, which makes it possible to use it in the process of finishing works, in the production of furniture and decorations.

A distinctive feature of moisture-resistant film faced plywood is that it takes much longer to process during the manufacturing process, and is also covered with thicker paper. This paper is impregnated with a special composition, which makes the finished product durable and allows it not to lose its properties for a long time. In addition, it provides water resistance.

Film faced plywood differs from other materials in that it is almost not susceptible to temperature changes, therefore it can be used even in a bath. The special layer also protects against the effects of cleaning agents, including aggressive abrasives. Another feature of such plywood is that it contains a minimum amount of phenol. As a result, a more elastic and durable material is obtained, which also has a varnished protective polymer layer.

Varieties and labeling

FSF plywood is made from soft or hard tree species, they can be both deciduous and coniferous. It can be longitudinal or transverse, have 3, 5 or more layers (three, five and multi-layer, respectively). These gradations can be combined by manufacturers in various proportions.

Building material can have different grades:

• grade I is characterized by the greatest damage - the total length of defects on 1 sheet should not exceed 20 cm;
• Grade II - the length of the cracks is up to 15 cm, the presence of an adhesive composition is permissible on the surface of the products (no more than 2% of the plank area);
• III grade - openings from knots, falling out knots, wormholes are permissible for it;
• Grade IV implies the presence of various manufacturing defects (an unlimited number of wormholes up to 4 cm in diameter, intergrown and non-intergrown knots), such products are considered to be of the lowest quality.

They are characterized by minimal deviations in the structure of wood. Wormholes, knots and holes from them, streaks and other defects are not allowed.

To determine the main parameters of a plywood board, manufacturers attach markings to the building material. Let's give an example "pine plywood FSF 2/2 Е2 Ш2 1500х3000 х 10 GOST 3916.2-96". The marking says that the presented plywood sheet is made of pine veneer using the FSF technology, with a front and back surface of grade 2, grade 2 of phenolic emission, double-sided grinding, 10 mm thick and 1500x3000 mm in size, manufactured in accordance with the standards of GOST 3916.2-96.