DVP - what is it? Where is the material used? plate properties. Wood fiber boards. Production of wood fiber boards. Plate color. Plate sizes. Absorption of water due to adsorption. hygroscopicity of the plates. Swelling. Plates with low density. Teplopro

(often also called fiber cement) are composed of cement (80-90%), reinforcing fiber and mineral aggregates. Asbestos fiber-reinforced concrete appeared as early as 1901. Austrian Ludwig Hachek registered his discovery a year earlier as a patent for "Method of producing artificial stone slabs from fibrous substances and binders hardening in them."

Today, in addition to asbestos, synthetic fibers are also used as fibers, and even special alkali-resistant glass fibers. Research in the field of creating non-asbestos reinforcing fibers was associated with the struggle to ban the use of asbestos-containing products in Western Europe in the late 70s and early 80s.

In Russia, the use and use of asbestos is not prohibited, asbestos-containing products are subject to examination and have the necessary hygienic certificates. Chrysolite asbestos has been used by man for more than a hundred years in many areas of life, and Russian doctors and scientists find no reason to refuse to use it. That's why fiber cement boards, produced in Russia, are mainly asbestos-containing, and the products of Western mills are based on synthetic fibers.

Due to its composition, the plates are practically non-flammable and environmentally friendly. They are frost-resistant, not afraid of corrosion, decay, UV radiation and acid rain. The boards are moisture-proof, sound-isolating and shock-resistant. facade panels based on cement combine the strength of concrete and the versatility of panels.

The slabs can be sanded (either on one or both sides), through impregnated, painted with acrylic water-based paint or be painted and clad in place. Also widely used fiber cement boards with a surface layer covered with natural stone chips, and not only the color (due to the type of stone), but also the crumb fraction can vary. The epoxy binds the crushed stone to the base. A polyurethane coating can also be applied to the fiber cement board, which gives high protection against UV radiation and weathering.

Plates with different coatings can be used separately or combined with each other, achieving the desired effect.

Fiber cement boards are resistant to weathering, and from a technical point of view do not require any protective coatings. However, the color of the usual fiber cement board- natural gray, so the panels are most often painted for aesthetic reasons. Paints and staining methods intended for concrete surfaces are usually suitable for fiber cement boards.

New fiber cement boards can be painted both before installation - the boards are fully primed and painted at the factory, and after it - the primed board can be left in its original color, but it is recommended to paint within 2 years after installation.

The most important criterion when choosing a concrete surface paint is the alkali resistance of the paint. Most paints meet this requirement. For example, all latex paints are resistant to alkalis, and therefore suitable for painting fiber cement boards. Alkyd paints cannot be used to work with concrete surfaces. Also, the paint must "breathe", pass water vapor.

To ensure good adhesion to previously unpainted surfaces, it is recommended to coat them with solvent-based acrylic paints. They penetrate the substrate better than waterborne acrylate paint. The degree of gloss of acrylic paints can be from semi-gloss to matte.

Silicate paints based on inorganic potassium silicate are generally well suited for concrete surfaces, which are themselves composed of silicate compounds. Silicate paint perfectly passes air, and besides it is resistant to weathering. Silicate paints are always matt and water-thinnable. Painting too wet and alkaline surface fiber cement board silicate paint will not work. Therefore, it is recommended to paint the plates approximately six months after installation.

Application area fiber cement boards- new buildings and structures, as well as reconstructed facilities. They can be used not only for wall cladding, but also for balconies and plinths.

The panels can be equipped with special mounting elements and accessories: strips for external and internal corners (painted in the color of aluminum and galvanized steel plates), drainage sheets with a special coating, window drains and slopes, as well as gasket tapes fixed between the slab and the crate ( black EPDM rubber, white TPE rubber), edge protection paint, etc.

When choosing slabs, static and dynamic loads and internal stresses arising in the slabs should be taken into account. It is necessary to pay attention to the fact that the painted slab absorbs from the air about half of the moisture that the uncoated slab receives in the same period of time. In practice, this means that the moisture expansion of a painted board is half that of an unpainted board. For this reason, the maximum allowed size of a painted board is larger than the size of an unfinished board.

Plate fixing produced on acid-resistant nails or screws to wood or metal frame. The seams are sealed with rubber tape (black or natural white EPDM rubber) or aluminum strips of various profiles. The pitch of the frame, the type of fastening and the consumption of fasteners must be calculated. Plate manufacturers usually have developed special tables that facilitate the calculation.

In order to avoid the penetration of moisture into the structures, a horizontal seam bar (weir) is always used in horizontal seams. When installing horizontal planks, it is necessary to leave a gap between the plank and the underlying slab for free air circulation.

Panels are usually cut at the factory, but can also be cut on site. To do this, use conventional woodworking tools with a carbide disc. Since cement dust is released during the processing of the boards, it is recommended to use dust collection systems and respirators.

Produce fiber cement boards V different countries, the most famous in our country are the products of the firms "OY Minerit AB" (Finland) and "Eternit AG" (Germany). In CemStone, CemColour, Cynop panels widely known in Russia (production of LTM-Company OY, Finland), the Minerit fiber cement board is the base on which various coatings are applied.

Russian manufacturers of asbestos-cement panels: OJSC "Volna", Plant "FASST" and others. Panels reinforced with alkali-resistant fiber (glass fiber reinforced concrete) are manufactured by ORTOST-FASAD.

At the end of April, Kazan hosted the annual VolgaStroyExpo exhibition. At present, the construction complex of the Republic of Tatarstan is developing dynamically in Russian Federation. In the republic, in particular in Kazan, housing construction is gaining momentum, as well as the construction of new high-tech industries and social and cultural facilities, overhaul housing stock, historical and architectural monuments are being restored.

At the exhibition "VolgaStroyExpo", dedicated to the development of the construction industry, Albert Galautdinov, an assistant at the Department of Construction Technology of KSUAE, proposed organizing the production of cement-fiber boards (fiber-cement panels) in Tatarstan. He stressed that even today in Kazan and the republic there is a problem with the restoration of the housing stock, many buildings do not meet modern aesthetic and thermal requirements.

According to him, using the problem can be solved quickly. The use of ventilated facades allows you to insulate old buildings, give them a modern look. appearance. At present, facing material is used in Kazan, which has to be imported into the republic, which increases its cost. Albert Galautdinov also noted a number of other shortcomings. For example, a very popular material for facades - porcelain stoneware, he called heavy and fragile, aluminum panels - expensive and fragile, and asbestos-cement slabs - short-lived. All these materials are not produced in Tatarstan, but purchased in other regions or imported from abroad. To solve the problem, KSUAE proposes to organize in Tatarstan the production of a new facing material for the republic - cement-fiber boards. The raw materials for it are cement, gypsum, ground quartz sand, cellulose fibers and a number of active mineral and chemical additives.

In the production of CVP (cement panels, fiber boards), asbestos, glass and synthetic materials are used as reinforcing additives. Fiber cement, formed in the form of a panel, has good resistance to temperature changes, decomposition, external influences.

Fiber cement board (fiber cement panels) is successfully used in the following types of outdoor work:

* wall cladding of new buildings;
* wall insulation;
* repair of walls on objects of reconstruction;
* insulation of balconies and basement floors.

The calculation and volume of investments will be 10.7 million euros, and the payback period is 5 years. Research and development funding has already been received. Now we need investors.

Fibreboard (MDF) is a sheet material obtained by pressing a mixture of wood fibers and special additives at high temperatures. industrial production was launched in 1922 in the USA. At present, the production of products from fiberboard is widespread in many countries of the world. But, despite this, not everyone will be able to answer the question: “Fiberboard - what is it?” Let's see what this material is and where it is used.

Raw materials for the production of fibreboard

For the manufacture of fiberboard, woodworking and sawmilling waste, wood chips, plant fires, etc. are used. Wood raw materials are processed into fiber in defibrators by steaming and grinding.

Synthetic resins are added as a binder to the pressed mass. Their number depends on the ratio of softwood and hardwood fibers and varies, as a rule, in the range of 4-7%. In the case of the production of soft boards, the binder may not be introduced, since the wood fibers contain lignin, which has adhesive properties when high temperatures.

To increase moisture resistance, ceresin, paraffin or rosin are introduced into the mass. In addition, other special additives, in particular antiseptics, are used in the manufacture of plates.

Methods for the production of fiberboard boards

As a rule, fibreboards are produced by wet and dry processes.

In the process of making fiberboard with a wet method, a carpet of a board consisting of wood fiber pulp is formed in water and pressed under heat. After that, the resulting sheet is cut into sheets. The moisture content of such material is in the range from 60 to 70%.

With the dry method, the formation of the carpet occurs in air at higher temperatures and lower pressures compared to the wet method. The result of such production is the production of low-pressure boards, characterized by a looser and more porous structure and relatively low humidity (from 6 to 8%).

There are also intermediate manufacturing methods - wet-dry and semi-dry. In the first case, the carpet of the slab is formed in water, after which it is dried and only after that it is pressed. In the second, the manufacture of fiberboards is carried out according to the dry method, but the moisture content of the material changes (from 16 to 18%).

Types of fibreboard

Fiberboards, depending on the properties and purpose, are divided into several types. Let's look at their characteristics and applications.

Soft fiberboard - what is it?

The material is characterized by low strength, high porosity and low thermal conductivity. The thickness of the plate can be from 8 to 25 mm. Material densities range from 150 to 350 kg per cubic meter. meter. Depending on the density, the following brands of soft fiberboards are distinguished: M-1, M-2, M-3.

Due to their low strength, soft boards are not used as the base material. Most often they are used in construction as a sound and heat insulating material in the construction of walls, floors, roofs, etc.

Semi-hard fibreboards

This type of slab has a much higher strength and density compared to soft slabs. The average density of semi-solid fiberboard sheets is at least 850 kg per cubic meter. meter. The thickness of the fiberboard sheet is 6-12 mm. The material is widely used in the production of such furniture structures as drawers, back walls, shelves, etc.

Solid fiberboard options

Hardboard density values ​​range from 800 to 1000 kg per cubic meter. meter (high rates for fiberboard). The dimensions of the carpet thickness are on average from 2.5 to 6 mm. These fiberboard sheets are used to produce the back walls of furniture, panel doors and a number of other products.

Solid fiberboard sheets depending on the indicators of density, strength and type of the front side, they are divided into the following grades:

• T - plate, the front surface of which is not ennobled;
• T-C - has a front layer made of finely dispersed wood pulp;
• T-V - has an unfinished front surface and is characterized by increased water resistance;
• T-SV - the front layer of the material is made of a finely dispersed mass, the material is characterized by increased water resistance;
• T-P - the front layer of the plate is tinted;
• T-SP - has a tinted front layer of finely dispersed mass;
• NT is a material characterized by a reduced density.

Super hard plates

This material is characterized high quality performance, ease of processing and ease of installation. It has an increased density, the values ​​\u200b\u200bof which are at least 950 kg per cubic meter. meter. The material acquires high hardness due to impregnation of fiberboard sheet with pectol. What it is? Pectol is a by-product from the processing of tall oil. Superhard plates are used for construction purposes for the manufacture of doors, arches, partitions, for the production of various types of containers from fiberboard. On the floor are used for the manufacture of floor coverings.

Refined wood fiber boards (DVPO)

The distinctive advantages of ennobled fibreboard are beautiful appearance, high resistance to abrasion and moisture. In the production of this type of plates, a technology is used that provides for the application of a multilayer coating on the front side. After careful processing, a primer layer that creates the background part is applied to the surface. Then a pattern is printed that mimics the wood structure.

Ennobled slabs are used for the manufacture of doors, as a material for finishing ceilings and walls, etc. They are also used to make various internal furniture parts (lower and rear walls of cabinets, drawers, etc.).

Laminated fibreboard (HDF)

To date, fiberboard laminated is also produced. This is a material that is sheets on which a special composition of synthetic resins is applied. Thanks to this coating, laminated fiberboard is characterized by increased strength and moisture resistance. This makes it possible to use it for various purposes.

Fiberboard: sheet dimensions

Despite the small thickness, fiberboard sheets are quite impressive in size. So, the length of the carpet can be from 1.22 to 3 m, and the width - from 1.22 to 1.7 m. Fiberboard is also produced, the sheet dimensions of which are 6.1 × 2.14 m. This is the maximum area of ​​manufactured fiberboard . Sheet dimensions allow the use of such material for industrial purposes.

Conclusion

Now we know the answer to the question: "Fibreboard - what is it?" Awareness is an important point when choosing certain building materials. After all, the quality and financial cost of the construction or facing work performed will depend on the correct choice.

When conducting construction works a wide range of modern building materials are used, which, due to their quality indicators, serve for many years without requiring the cost of repairs and reconstruction.

One of these materials is fiber cement board, which is successfully used in the following types of outdoor work:

• wall cladding of new buildings;
• wall insulation;
• repair of walls at reconstruction sites;
• insulation of balconies and basement floors.

Slabs are produced, which can also be used for finishing inside buildings.

The composition of the CVP

Fiber-cement (or fiber cement) panels are boards based on cement (up to 90%), and the remaining 10% are filled with reinforcing fiber and additives. The name fiber cement just reflects the essence of the product: the word fiber means “fiber”. In the production of CVP, asbestos, glass and synthetic materials are used as reinforcing additives. Fiber cement, formed in the form of a panel, has good resistance to temperature changes, decomposition, external influences.

Benefits of finishing CVP walls

Years of use has shown that fiber cement board for outdoor use is a good insulating material. Its advantages are:

• easy installation;
• low susceptibility to mechanical damage;
• soundproofing;
• water resistance;
• fire resistance;
• resistance to temperature changes;
• resistance to decay and corrosion.

Cement-Fiber Hardboard is a type of board obtained by combining cement, water and wood wool impregnated with liquid glass or calcium chloride. The second name is fibrolite. Wood wool in this case is a reinforcing frame. The appearance of this type of plates is caused by disputes about the dangers of asbestos on the human body. Although scientists have not found evidence of the danger posed by CVP, and they are being used further, fibreboard has been proposed as a reasonable alternative, which definitely does not pose a threat to people.

Fiberboard density marking: F300, F400 and F500. F300 panels are used as thermal insulation internal walls premises, and denser grades - as thermal insulation of walls, ceilings and other surfaces separating the inner and outer parts of buildings. Low density expands the range of premises in which the use of fibrolite is acceptable. These plates can be laid as a base under floor tiles or sheathe them with special refrigerating chambers.

Varieties of fiber boards

Industrial enterprises produce several types of CVP. First of all, the classification can be carried out according to the reinforcing component:

• asbestos-cement sheet;
• fiber cement;
• cement-wood fiber.

According to the manufacturing method, the plates are divided into:

• pressed;
• unpressed.

By the presence of coloring and coatings:

• unpainted;
• with through impregnation;
• with the application of a protective layer for painting and cladding;
• painted;
• covered with crumbs.

According to the type of surface of the plate are:

• polished on both sides;
• polished on one side.

Plates on which a layer of finely crushed stone chips is applied with the help of epoxy resins are widely popular. Depending on the type of stone and the degree of its grinding, dozens of types of various coatings can be obtained.

Often, the fiber cement sheet is coated with a special polyurethane composition that protects the panel from exposure to ultraviolet radiation and harmful atmospheric phenomena.

CVP installation

For fixing the panels, mounting accessories are made:

• strips for corners made of galvanized steel or aluminum;
• window drains, slopes;
• drainage sheets;
• rubber bands-gaskets in black and white;
• protective paint for edges.

Screws or acid-resistant nails are used to fasten the boards to the frame. The seams are sealed with black (EPDM) and white (TPE) rubber tape. All calculations for fastener consumption are available from plate manufacturers in the form of special tables.

Panel dimensions

At the moment, you can buy CVP with a thickness of 6, 8, 10 and 20 mm.

Size standardization (width x length, mm):

• 800×1200;
• 1200x2800 and 1200x3000;
• 1500×1200; 1500x1500 and 1500x1800;
• 1500×2400; 1500×2800; 1500x3600 and 1500x3000;

Rates

The price of a cement board depends on the type of reinforcing components used in it and the method of production.

The prices for the material on average look something like this:

Plate type, manufacturer	Size, mm	Price, rubles
LATONIT	3000x1500x8	660
LATONIT-NP	3000x1500x8	220
LATONIT-P	3000x1500x8/10	330/420
Fiber cement structural board LATONIT, pressed, unpainted for outdoor use	3000x1500x8	355
painted for outdoor use	3000x1500x8	680
Asbestos-cement sheet NP	1500x1000x10	400
Asbestos-cement sheet NP	3000x1500x10	980
Asbestos-cement sheet P	3000x1500x20	4100
Facade sheet "PROFIST - Color Premium"	1570/1500x1200x8	555
Facade sheet "PROFIST - Stone"	1570/1500x1200x8	595
Facade sheet "PROFIST - Flock"	1500/1570×1200	535

TO Category:

Fibreboard production

Properties and scope of fiber boards

Properties of fibreboard

Fibreboard refers to organic materials made from wood, wood chips and wood waste by grinding followed by shaping and drying the product, which is obtained mainly in the form of flat boards.

By volumetric weight, the following main types of fiberboards are distinguished: solid with a bulk density of 800-1100 kg / m3, semi-solid finishing - 500-700 kg / m3, insulating and finishing - 300-400 kg / m3, porous - 180-300 kg /m3 and ultraporous - 60-150 kg/m3. Between the indicated types, there are several transitional types of plates, more or less different from those listed in terms of physical properties, having different areas of application. With the development of the production of fibreboard, the number of their varieties is growing and the classification is changing in accordance with the needs of consumers.

Physical properties wood fiber boards, which are guided in their classification and application: a) dimensions, i.e. length, width and thickness, b) mechanical strength for static bending, hardness and stretching, c) thermal conductivity, d) sound-absorbing and sound-insulating ability, e) water resistance: hygroscopicity, water absorption and associated form changeability, f) fire resistance, g) biostability, h) ability to be machined, glued and finished.

The dimensions of the plates must be in accordance with GOST. Typically, the longest length of boards produced by machines is 5400 mm. The width of the slabs is determined by the need to make the most complete use of the working width of the existing casting equipment and is usually 1200 mm for solid and semi-solid slabs, and 2400 mm for porous slabs. Sometimes there are machines with a working width of 1600 and 2000 mm. The thickness of solid boards is 3-5 mm, semi-solid 6-12 mm, insulating and finishing 6-12.5 mm, insulating 6-25 mm and ultraporous 25-40 mm and more.

Of the physical and mechanical properties of fiberboards, the most interesting are: temporary resistance to static and dynamic bending, hardness and temporary tensile strength.

The resistance to static bending of boards produced by the domestic industry is: for insulating boards 8 kg/cm2, for semi-solid finishing boards 40 kg/m2 and for hard boards over 150 kg/cm2. These indicators are the minimum allowable and can be increased by rational choice of raw materials, the method of grinding and sorting the mass, as well as the conditions for the formation of plates.

Thermal conductivity is important for all types of fibreboard, but especially for insulating and ultraporous boards, which are primarily used as thermal insulation boards.

When testing plates, it is necessary to take into account their humidity, since water, having a large heat capacity compared to fiber and air, greatly increases the coefficient of thermal conductivity of the plates. Similarly, any mineral additives that increase the volumetric weight of the plates have a negative effect. The coefficient of thermal conductivity of ultraporous boards with a bulk density of 70 kg/m3 is 0.035.

The coefficient of thermal conductivity of wood-fiber boards in comparison with other building materials is given in Table. 15. As can be seen from her data, the coefficient of thermal conductivity-St” for insulating and ultraporous boards, which are heat-insulating, is the most favorable in comparison with other building materials, including heat-insulating materials. Cork boards, which have a more favorable coefficient of thermal conductivity, cannot compare with fibreboards for economic reasons, because cork is a very scarce and expensive material that is not of serious importance in construction. The table also shows that 1 cm of porous fibreboard replaces 15-17 cm of thickness brickwork in terms of thermal conductivity.

For wood-fiber boards, as for a building material, the value of the vapor permeability coefficient is important, showing the amount of water vapor in grams passing by diffusion through 1 m2 of a 1 m thick wall with a difference in water vapor elasticity on both sides of 1 mm Hg. Art. The value of the coefficient of vapor permeability of porous wood fiber boards in comparison with other building materials is given in Table. 16. According to her, porous fibreboard has a high vapor permeability approaching foam concrete with a bulk density of 400 kg/m3.

Fibreboard, like any building material, must have sufficient air resistance to prevent excessive cooling of the enclosure. They show that fibreboard has a relatively high air resistance, but this value can easily be increased by laying building paper between the skin and fibreboard when using the latter in the outer layers of the fence. Of course, all the properties of fibreboard as thermal insulation material will change with changes in the volumetric weight and moisture content of the plates.

The sound absorption capacity of fibreboards is a consequence of their porous structure. According to available data, there are about 30 million microscopic air layers - capillary pores - per 1 m2 of a porous slab 13 mm thick. When the air vibrates inside these pores, a very

For a sound having, for example, 400 vibrations per second, the value of h is only 0.64 mm. If sound waves travel through a tube, they experience significant friction, especially when the tube diameter is close to h. Therefore, porous materials absorb sound well. At various sizes In pores, larger diameter channels give sound access to deeper layers, which increases the effective surface of the pore walls and improves absorption in a wide frequency range. This is the basis for the technology of special types of sound-absorbing plates - with small-diameter holes artificially drilled into them.

The mechanism of sound absorption by porous materials is characterized by the scheme shown in fig. 8. According to this scheme, the sound beam falls on the front face of the sound-absorbing plate

Periodically changing sound pressure at the surface of the material sets in oscillatory motion the air enclosed in its pores, as well as individual fibers or particles of the material. Due to the presence of viscosity, friction of air particles occurs in the pores and relaxation losses occur due to the non-ideal elasticity of the medium, which leads to a partial conversion of sound energy into thermal energy. The rest of the sound is reflected from the back surface of the wall AB, and part of the sound passes through the thickness of the fence into the adjacent room. The ray reflected from the back face and passed a double path through the material is indicated by the number III. The sound energy of beams II and III in total is characterized by the reflection coefficient.

Rice. 1. Mechanism of sound absorption by porous materials

The sound absorption coefficient a characterizes the lost part of the energy. It represents the ratio of the part of the sound energy absorbed by the surface to the incident one, and the absorbed part means the part of the sound energy that has turned into heat, as well as the energy, . passed through the fence.

Thus, the absorption coefficient will be characteristic mainly for those cases when the sound-absorbing plate will be installed not for sound insulation, but for dampening the noise in the room where it is placed (typing bureau, industrial noise). On fig. 8 it can be seen that in order to increase sound absorption, one should strive to obtain as little reflection as possible (beam III ) from the front face of the CD material and at the same time create losses inside the material that ensure the minimum amount of energy reflection (beam III ).

Rice. 2. Dependence of the sound absorption coefficient on the frequency

In many cases, it is necessary to know the sound absorption coefficient not only at a frequency of 512 Hz, for which the sound absorption table has been compiled various materials, but also for other frequencies: low and high.

From the data it contains, it can be seen that porous wood fiber boards can be used as a sound absorbing material for various frequencies, but especially for high frequencies. The dependence of the sound absorption coefficient on the oscillation frequency (expressed in hertz) for porous fiberboards with a volumetric weight of 250-300 kg/m3 and a thickness of 15 and 6 mm is shown in fig. 2.

When using wood fiber boards as a soundproofing material, i.e. to protect against noise penetrating into a given room from an adjacent one, the degree of soundproofing, or soundproofing capacity TZ, is important.

If the level difference is taken in relation to the threshold of audibility (the minimum value of effective sound pressure that gives listeners a barely perceptible sensation of tone), then the measured value is expressed in phons.

The semi-rigid fiberboards of the Moscow Dry Plaster Plant have a soundproofing capacity at various frequencies from 37 to 43 dB (average 39 dB) with four xu each 10-11 mm thick, as can be seen from the following data:

From the data in this table, we can conclude that the soundproofing ability of materials increases with an increase in the thickness and weight of 1 m2 of the surface of the material or the wall that is made of it. Therefore, light (porous) boards are less suitable for sound insulation than semi-rigid boards. This is due to the ability of sound waves to cause mechanical vibrations of walls (partitions).

The water resistance of fibreboards is characterized by their hygroscopicity, water absorption and linear and volumetric deformations. The presence of moisture in the plates determines their ability to be infected with fungal spores, for the germination of which it is necessary to have about 25% water in the material. From the hygroscopicity of the plates, and partly from the ability to absorb water, their tendency to linear deformations depends - an extremely unpleasant property that manifests itself during their operation. In rooms where the air humidity changes dramatically, the plates are periodically deformed - they bulge from the walls and ceilings, and then warp. With strong moisture, the plates significantly lose their mechanical strength and may even fall away from the walls. The change in the dimensions of the boards in length due to their hygroscopicity can be about 1.2 mm for boards 3.5 m long, when the board absorbs only 1% of moisture from the air. In width, this value can be about 0.4 mm in the same conditions. From this it is clear that the plates installed in an over-dried or under-dried form will cause certain inconveniences during their operation, and when installed in place, they will require additional manual trimming and extension. Air dry boards contain 6-8% moisture, depending on the equilibrium relative humidity air. The hygroscopicity and water absorption of the plates increases the coefficient of their thermal conductivity.

Moisture adsorption isotherms for fiberboards made from pine and spruce wood are shown in fig. 3. Isotherms obtained at 20° and in both cases have S-shape for adsorption and desorption curves. These data can only be accepted with a certain degree of approximation, since the hygroscopicity of wood-fiber boards varies during their manufacture depending on the degree of grinding and drying conditions (temperature and duration). This can be seen in the example of the water vapor adsorption isotherm at t = 20° on a porous, fibreboard made of spruce wood obtained by us for various degrees of grinding and shown in Fig. 4. As can be seen from the diagram, with an increase in the degree of grinding, the hygroscopicity of the plates increases, especially at high relative humidity; the latter circumstance indicates that the degree of grinding of wood pulp has little effect on the adsorption part of hygroscopic moisture. A significantly greater influence of the degree of grinding is felt in the region of capillary-condensed moisture, i.e., in the region above 50% relative air humidity.

Rice. 3. Moisture adsorption isotherms: a - spruce wood; b - pine wood

Rice. 4. Dependence of water vapor absorption on the degree of grinding: 1 - grinding to 75° SR; 2 - the same up to 55° SR; 3 - the same up to 35° SR; 4 - the same up to 13° SR

These results are 6-7 times different from Merat's data. In our opinion, the difference is due to different ways of dewatering the plates. During dehydration according to a typical scheme, i.e., with the use of presses, the deformations of the fibrous plate are partially highly elastic, which manifests itself during the subsequent wetting of the plates in the form of their increased swelling in thickness. In our case, dehydration was carried out by free flow, so there were no indicated deformations during dehydration. The construction industry makes demands both on the hygroscopicity of the boards and on their water absorption.

To achieve these properties, special refinement of the plates is required, which will be discussed in detail below.

Fire resistance is a common requirement for building materials, including wood fiber boards. However, all materials are divided into several categories according to fire resistance: a) fire-resistant (cement, crushed stone, gravel), b) semi-fire-resistant (iron, granite), c) semi-combustible (felt in clay, reeds with mineral filler), d) combustible (felt, timber). Wood-fiber boards belong to the category of combustible materials. fire resistance is determined by exposing the material to a flame (TsNIIPO method) according to the “fire pipe” method for minutes, followed by determining the degree of burnout of the material over time (ignition, flame extinction, burn through, charring), either by weight loss, or by ignition temperature .

For wood-fiber boards, the requirement for resistance to wood-destroying fungi (for example, the house fungus merulius lakrymans, etc.) is imposed, since the boards are often used to insulate damp walls; this creates conditions conducive to the development of fungal spores, for which fiberboards are an excellent nutrient substrate. Fungal hyphae germinate most easily on porous and ultraporous slabs. Semi-rigid and extra-rigid

due to their dense structure, you have a significant co-heating to the germinating fungal hyphae. “^ Solid fibreboards of a rigid type have approximately the same ability as natural wood to all types of machining and finishing: sawing, planing, drilling, grinding; the ability to stick together, treated with mordants, dyes, polishes and varnishes.

Porous thin slabs are easily cut with a knife. Thicker slabs are sawn with round saws with fine teeth.

The elastic properties of the plates are characterized by static and dynamic moduli of elasticity, as well as a "factor of merit", reflecting internal losses during elastic deformations of the material under the influence of a variable load.

Considering that the last two tables were obtained by completely different fundamental methods, it can be recognized that the values ​​of the static and dynamic modules are quite close to each other.

From the above data, certain conclusions can be drawn when choosing the initial semi-finished product, the degree of its grinding and the required molding density for cases where fiberboards and cardboards are used, when high elastic properties are required.

The addition of 10% synthetic resin C-1 to the wood fiber suspension by weight of the fiber increases the static and dynamic modulus of elasticity of the boards.

Our study of the relationship between the fine structure of the fibers and the elastic properties characterized by the Q index allows us to conclude that this index depends on the degree of cellulose polymerization. Therefore, natural fibers are the most elastic; technical cellulose in the process of its release loses its elasticity the more, the more stringent conditions are used for its release.

It can be seen from the table that plates with a volumetric weight of about 1 resonate as much as possible; plates with a bulk density of 0.375 (insulating), as well as with a bulk weight of 1.117, resonate worse; the former, obviously, due to increased sound absorption, and the latter due to a very high volumetric weight (it is more difficult to swing). These properties are important when using boards for sound insulation.

Application of fibreboard

The main area of ​​​​application of plates is housing and industrial engineering; they are used as heat and sound insulating materials (insulating, semi-solid boards), for insulating roofs, floors, walls. In addition, insulating boards are used in car, ship and auto construction for refrigerator cars and passenger cars. Rigid and semi-rigid boards are mainly used for interior decoration walls, floors and ceilings in stone and wooden buildings, for the construction of partitions, for the manufacture of furniture and formwork for concrete work. Wood-spring-fiber boards are especially widely used in low-rise, settlement, rural and summer cottage construction, in standard housing construction, as well as for light, temporary buildings and storage facilities.

Slabs can be fastened to wooden walls either directly with nails, or along beacon rails (with air punches between the wall and the slabs), as illustrated in Fig. 5 and 6. On the middle part of fig. 12 shows the mounting method

Rice. 5. Methods for fixing plates and sealing joints between them

Rice. 6. Partition light type: 1 - fibreboard; 2 - frame racks; 3 - backfill

Fibreboard to stone walls with gypsum plaster. Instead, it is possible to glue the plates to the state walls using bitumen in hot and cold ways, as well as on a wooden slatted frame, which itself is attached to the stone wall with nails driven into wooden plugs pre-embedded in the wall. This method is shown on the right side of the figure. Fixing wood fiber boards to brick walls may be provided in advance. In this case, when laying the outer walls, rows of nailed bricks or wooden planks are laid to which the plates are sewn.

When fixing the plates with nails, seams between the plates are 2-3 mm. Between nails (galvanized) gaps of 125 mm are established; nails are driven in at a distance of 15 mm from the edges of the plates. Dimensions of nails for semi-rigid boards: thickness 2-3 mm and length 25-30 mm. With an increase in the thickness of the plates, the length of the nails also increases. Gluing plates on walls can be done using gypsum, liquid glass, magnesite, petroleum bitumen, generator and peat pitch. The bonding strength of rigid boards with various surfaces is given in Table. 32. The best results, as can be seen from the data in the table, are obtained when gluing with liquid glass. Gluing the plates makes it possible to avoid an unpleasant phenomenon: moisture condensation that appears on the nails during finishing inner surface outer walls.

The seams between the plates can be specially sealed to become invisible, or covered with profiled overlays. In the first case, the edges of the slabs are covered with drying oil, and the seams between the slabs are filled with putty with a seal. In some cases, the plates are produced with oblique edges (cut "on a mustache"). After puttying, the seams are ground with pumice or sealed with strips of fabric or paper and sanded.

When sealing seams with overlays, wooden, plastic or metal layouts are used, which are nailed or fastened with screws.

On fig. 7 shows the use of insulating boards in a permanent floor.

In the furniture industry, solid boards are used to make cabinet walls, drawer bottoms, tables, table tops, chair seats and backs, etc. When finishing these surfaces with the dry method described below, any color and texture can be obtained, including imitation of the texture of valuable tree species.

Rice. 7. Insulation of interfloor floors: 1 - layers of roofing felt on clebemass; 2 - wood-fiber board, under it a layer of glassine on klebemass

Fiberboards are successfully used in the construction of stationary refrigerators, thermostats, greenhouses, warehouses for storing fruits, meat and fish.

Fibreboards are also widely used in other areas: for soundproofing telephone booths, screens in cinemas and film factory equipment, for walls and garage insulation, for sound insulation of auditoriums, concert halls, for thermal insulation of air pipelines, as containers for food products ( boxes with cells for milk bottles, eggs, etc.), for the construction of showcases in shops, as screens, for thermal insulation of tanks, for theatrical props, for the production of doors and many other purposes. The wide area of ​​application of fiberboards is explained by their cheapness and the possibility of manufacturing from affordable, low-value plant raw materials, including wood waste from various industries.

It is not surprising, therefore, that a number of countries last years greatly expands the production of fiberboards, the use of which in these areas is technically and economically more justified compared to plywood and solid wood.

The use of fibreboard in low-rise and prefabricated housing construction

The law on the fourth five-year plan provided for the creation of a new industry - factory housing construction. Its advantages over conventional construction lies in a more economical consumption of wood: 0.4-0.5 m3 of wood per 1 m2 of area ( frame houses) instead of 0.9-1 for log houses; in a sharp reduction in labor consumption for the construction of houses: the cost of labor for the manufacture and construction of 1 m2 of living space for a log house is 8 man-days, and for a small-panel standard house - 2.5 man-days. Finally, with standard housing construction, construction time is significantly reduced. Fibreboard in standard frame and panel housing construction is used as a heat insulator, finishing material for interior walls, ceilings and floors. Behind Lately in the Soviet Union, experiments began on the use of slabs as exterior finishes.

Wood fiber boards are widely used in the construction of prefabricated houses in foreign countries. Thus, in Finland, which in 1945 produced over 600,000 m2 of prefabricated houses, 5 m2 of "insulite" (16.6 kg) was spent per 1 m2 of area; ultraporous slabs (“Rauma” slabs) are also used for thermal insulation (“TAL” houses of panel construction). In Sweden, wood-fiber boards are used as heaters in typical designs of boards of the "Swedish house", as well as in the houses of the "Gareboda" system. In Germany, which produces prefabricated wooden frame and panel houses, and in England, which produces prefabricated houses made of concrete and aluminum, fibreboard is used for interior wall cladding.

In the USA, 75 firms are engaged in the production of standard wooden houses, the production capacity of which ranges from 1.5 to 30 thousand houses per year; 62% of all manufactured prefabricated houses have fiberboard interior cladding and 7% double-sided fiberboard cladding; the remaining 31% of houses have double-sided plywood cladding. A feature of the United States is the production of prefabricated houses of frame-slab structures, where lined heat-insulating plates 45 mm thick, 1.2X3.6 m in size, weighing 100 kg are used as a wall-forming material.