MDF panels

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In this Article: A History of MDF manufacturing technology; decorative finishing methods; specifications; pros and cons of MDF; application area; domestic producers of MDF.

MDF panels

What material, equally popular among builders and furniture makers, belongs to the palm? Without a doubt, wood – in ancient times, this material protected us from cold weather, giving shelter and warmth of the hearth, and all household utensils were created from wood. Centuries passed, wood invariably remained in demand and popular – huge areas of forests were used for sawn timber, while a significant part of the trunks was waste, non-business. The situation changed about a century ago, when the lumber industry started thinking – is it possible to somehow use wood chips and shavings, in many cases remaining after sawing tree trunks. This is how fiberboard and chipboard were created, the experience of which made it possible to obtain MDF boards, whose characteristics were practically equal, and in some ways even exceeded the capabilities of industrial wood..

The history of the creation of MDF

The first board, consisting not of shredded shavings, but of wood fibers, was accidentally created in 1924 by the American William Mason. This inventor tried to find a use for the heaps of waste chips, shavings and sawdust, which rose like hills around every timber processing plant, to get from them a slab, at least closely resembling plywood. However, initially he hoped to make paper from wood fibers …

Mason built the device, which later received the nickname “Mason’s gun”: a steel pipe welded on one side and equipped with a removable lid that can be opened from a distance on the other. Sawmill waste was poured into the pipe and a certain amount of water was poured, then the inventor installed a gas burner under it – under its heating the pressure in the pipe increased, the lid was removed and the wood fibers obtained under pressure were thrown from the barrel of the “cannon” into the bunker of the trap. gun “wood particles mostly disintegrated into fibers.

Inventor William Mason
Inventor William Mason

But, to Mason’s disappointment, the wood fibers were too coarse for paper, he decided to try to collect them and put them in a steam press, hoping to get a board for construction purposes. And here the inventor was lucky twice – the technical malfunction of the old steam press and the feeling of hunger turned out to be very appropriate! Having put the fibers obtained in the morning into a steam press, Mason did not notice that his valve was leaking, letting steam directly into the carpet of wood fibers laid between the press plates. One mistake was not enough – in the afternoon, the inventor rushed to lunch, forgetting to turn off the press.

So, the wood fibers were under pressure and, at the same time, under the influence of hot steam for several hours. Returning to the shop, William Mason feverishly turned off the steam press and was determined that all morning work was lost – but after lifting the slider, he saw a homogeneous, surprisingly tough fiberboard underneath. He called the fiberboard he created “Masonite” – in terms of its characteristics it was significantly inferior to modern hardboard, but the foundation for fiberboard was laid.

Fiberboard “masonite”

Medium density fiberboard, better known to us from the letter combination MDF, derived from the English name for this material – medium density fiberboard – was mass-produced around 1966 in the United States. The development of this slab was carried out simultaneously by many manufacturers, so it is impossible to accurately name the inventor who created the first MDF slab.

In the USSR, MDF boards were not produced, the first line for the production of this material appeared only in 1997 in the Vologda region, the village of Sheksna. Today, China is the world’s largest producer of MDF boards and products from them..

Production of MDF – technology

In the middle of the last century, fibreboards were produced using the “wet method” – this method is in many ways similar to the technology of cardboard production. Currently, MDF boards are produced by the “dry method”. The technological process of the “dry method” includes several stages: preparation of raw materials; obtaining wood fibers; the formation of a carpet from wood fibers, its pressing and sawing of finished MDF; grinding of the resulting slabs.

Raw materials – preparation. In the production of MDF, the raw material is round timber of any kind of wood. Tree trunks are placed in drum machines, completely removing bark from them, then they are loaded into chippers-disintegrators, processing round timber into chips. Machine felling of tree trunks also makes it possible to soften and weaken the bonds formed by lignin, a natural polymer that connects wood fibers to each other. The resulting technological chips are laid out on a belt conveyor, above which a powerful electromagnet is installed, which removes any metal inclusions from the chips. Further – sorting into three fractions in vibrating screens with meshes of different diameters, from coarse to finer.

MDF production

Excessively coarse chips are sent to re-cutting in a disintegrator, too small – to a waste bunker for subsequent incineration in a boiler room. Chips of optimal size enter vertical cyclones, where mineral impurities are washed out from it and debris is removed. At the end of the washing cycle, the chips enter the hopper for steam treatment – the task of this operation is to uniformly heat the chips to 100 ° C, with a moisture content of more than 80% throughout its mass.

Receiving wood fibers. Chips, moistened and heated to the required temperature, enter a special machine – a defibrator or, as it is also called, a refinator. The chips loaded into the defibrator, entrained by the auger feeder, pass between the conical and disc blades, as a result of which they are separated into fibers.

Receiving wood fibers

If necessary, the chip processing operation in the defibrator is repeated two or three times – in this case, the defibrators are installed in a cascade. During the processing of chips in a defibrator, paraffin, resins, hardeners and binders are introduced into its mass.

Reference:The procedure for obtaining wood fibers is completely different from the milling technology. In the production of wood flour, tree trunks are abraded into particles of a certain fraction and inhomogeneous shape, but for the production of fiberboard it is required to separate wood fiber of a natural structure and size, and the length of the fibers depends on the species of this wood.

The finished wood fibers, heated by steam, are fed into a tube-shaped dryer – in which each batch of fibers is treated with hot air (temperature 170-240 ° C) for 5 seconds. The dry mass of fiber is sent to a cyclone, where excess air is removed from it, then transported to a storage hopper, from there – to forming.

Carpet shaping and pressing. A carpet of prepared wood fibers is created on a conveyor – molding is performed with rollers, during this operation, the wood fiber carpet undergoes weighing and initial pressing, during which air chambers remaining after processing in a cyclone are eliminated in it. The formed carpet goes to the main press, which completes the formation of the plates. The finished MDF sheet is cut into plates of a given size, then they are cooled by air flows.

MDF boards

Grinding MDF boards. At the exit from the main press, the plates often have different thicknesses, insufficiently smooth surfaces and small defects on them, therefore they are subjected to grinding. Fully finished slabs are marked and stored or sent for decorative surface finishing.

Lamination and other ways of finishing MDF

The most popular are three types of decorative finishes: lamination, painting and veneering..

Pasting the outer surfaces of the MDF panel with PVC film is called lamination. The color of the film applied to the panels can be glossy or matte, monochromatic in color and patterned on natural stone or wood. The pvc film is glued under pressure, the adhesive layer is made with formaldehyde resin. The surfaces of the laminated MDF panels are resistant to mechanical wear, do not accumulate static charge, do not fade or collapse under the influence of sunlight.

Lamination and other ways of finishing MDF

To obtain veneered MDF, a veneer of wood, as a rule, of its valuable species, is glued to the surface of the panel. The MDF panels obtained by veneering do not outwardly differ from real wood, while possessing better characteristics – they do not dry out or warp, are more durable and moisture resistant.

MDF painting is performed with enamels and paints with good fluidity and elasticity. As a result of painting, MDF panel acquires not only an aesthetically pleasing appearance, but also reliable protection against various physical and mechanical influences. Before applying a layer of paintwork materials, the surfaces of MDF panels are putty and primed.

MDF characteristics

There is no Gosstandard of Russia for medium-density fiberboard, MDF manufacturers either develop their own specifications or produce boards according to the European standard ANSI A208.2.

MDF characteristics

We produce MDF boards of the first and second grade, with a thickness of 6 to 24 mm, gluing wood fibers using urea-formaldehyde resins and wood lignin. Many manufacturers declare only lignin as a binder: they say, no environmentally harmful components are present – this statement is not true.

Standard sizes of MDF panels: 1650 by 1650 mm, 2800 by 1650 mm, 2750 by 1650 mm, 2250 by 1650 mm and 2440 by 1650 mm. We also produce panels of “additional” sizes – 3660 by 1650 mm, 3050 by 1650 mm, 2100 by 1650 mm and 1850 by 1650 mm.

The surfaces of grade I MDF panels have absolutely no defects – they are perfectly flat, without chips, scratches or any stains.

Plates II grade may have scratches no more than 0.3 mm deep and no more than 20 mm long, small chips on the edges, small grinding defects.

Class III MDF is suitable only for construction needs, because has multiple chips and surface defects.

The density of the produced MDF boards ranges from 600 to 1200 kg / m3. The emission class (release of free formaldehyde from 100 g of mass) for any type of MDF is E1, i.e. does not exceed 10 mg.

Any MDF panel has a high moisture resistance and the thicker the panel is, the higher its moisture resistance – the maximum swelling for 6-8 mm thick plates will not exceed 17% of the initial volume of MDF.

During the production process, MDF boards can be given higher quality properties in terms of water resistance, fire resistance and biostability than those of serial boards.

Pros and cons of MDF

Positive properties:

  • moisture resistance. The high density and homogeneity of the structure of the boards, which are provided by wood fibers, together with the external decorative coating, significantly increase the moisture resistance, allowing, for example, periodic wet cleaning. However, MDF panels are not recommended for installation in rooms with a constantly high level of air humidity, except for their waterproof modifications;
  • strength. MDF panels have a strength that is almost equal to wood and much higher than chipboard, therefore they are used in the creation of structures for functional and decorative purposes;
  • low price. The cost of a laminated MDF panel with a thickness of 16 mm is about 300 rubles. per m2, what is cheaper than natural wood;
  • long service life. The surfaces of the panels retain their shape during temperature extremes; special impregnations protect them from fungus, insects and mold. A durable coating does not require periodic painting or varnishing and, subject to the instructions for use, will last for several decades;
  • decorative finishing. Existing methods of finishing MDF panels, the possibility of combining several methods (painting and veneering), create great opportunities in the construction of interiors;
  • simple installation. MDF panels are easy to install – no special training or tools are required. In case of damage to a fragment of MDF finishing with panels, simply replace it with a new one, because factory sizes are standard;
  • easy handling. The high density of MDF boards allows milling, with the creation of a variety of relief.

Negative properties:

  • more weight. Unlike wood of a similar width, MDF boards are more weighty;
  • dusting. During the processing and milling of the plates, a lot of dust is generated – the use of a respirator is mandatory;
  • the need to drill holes. It will be almost impossible to drive in a nail or screw a screw into MDF; preliminary drilling of a hole for fastening is required;
  • insufficient load-bearing strength. If for vertical racks MDF plates are quite suitable, then for vertical ones they are not very – long bookshelves, for example, it is better not to arrange from such plates;
  • the content of formaldehyde resins. Despite the environmental friendliness claimed by some manufacturers, this is not entirely true. Yes, the emission class of MDF is low and almost equal to natural wood, but the emission of formaldehyde is still present.

MDF application

Panels made of this material are widely used in interior decoration – in finishing ceilings and building air ducts, in the production of interior doors. A denser modification of MDF, called HDF, is used as a basis for laminate flooring, to create decorative perforated plates used in the construction of office partitions and to hide heating batteries. Window sills are created from MDF panels.

MDF application

In construction, T-beams made of MDF are popular, used as the core of interfloor beams in monolithic construction. Waterproof MDF for roof lathing – elements of such lathing are painted with oil paint for a longer service life.

This material is especially popular with furniture makers. The existing technique of bending MDF elements allows them to be used in the creation of chairs and armchairs. Laminated and veneered MDF is used to produce cabinet furniture intended for living quarters and kitchens.

In addition, MDF and HDF are produced: legs of musical instruments; railings, steps and balusters of stairs inside buildings; speaker enclosures; interior decoration of public transport, trucks, etc..

MDF manufacturers in Russia

Contrary to popular belief that there are no domestic producers of MDF boards, this is not the case. This material is produced by ZAO Plitspichprom, OAO Lesplitinvest, ZAO Russian Laminat, OOO Kronostar and, one of the first domestic producers of MDF boards, OOO Sheksninsky KDP.

When choosing MDF of domestic production, pay attention to the formaldehyde emission class declared by the manufacturer on the packaging and in the accompanying documents – it is often equal to E2, i.e. higher than that of Western products. However, the emission class should be checked regardless of the country of origin of MDF products …

Read more  Methods and methods of joining wooden parts
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