When choosing a material for construction, most often the owners of suburban real estate pay attention to wood. Wood has been the most demanded product from time immemorial. It has many positive properties, both operational and decorative.

However, it also has its drawbacks - in particular, a strong dependence on environmental factors, especially when used in street structures. Currently, for the installation of floor coverings, the dpk decking board is very popular, which is devoid of the disadvantages inherent in natural wood.

Produced today the following types terrace boards:

• Solid wood boards... This material is made from wood species with a high resin content, resistant to moisture and mechanical damage. After laying, such boards are treated with special protective and decorative compounds (see).
• Heat-treated wood boards... This material is processed in special chambers at a temperature of 120-190 degrees, thereby increasing its strength, water resistance and durability.
• WPC boards.

WPC decking production

The first production for the production of WPC boards was opened in Switzerland, back in the seventies of the last century - however, the product did not immediately gain popularity. A new round of development of this direction and the popularization of the KDP began in the nineties in America. In Russia, the WPC market is still in its infancy, but the trend suggests that in a few years it will become one of the largest.

Currently, factories for the production of decking made of wood-polymer composite operate everywhere. The quality of the manufactured products directly depends on the equipment and technology used.

Decking made of wood-polymer composite is produced by extrusion. As raw materials, it is allowed to use waste of polymer production, as well as recyclable materials and woodworking waste. This is extremely important with today's environmental and deforestation problems.

Stages of making a WPC decking.

Wood shredding

In a crushing machine, wood is crushed and turned into chips. Fraction of wood powder required for the production of decking: 0.4-1.5 mm. The smaller the particle size, the better the finished product is.

Drying of wood fraction

Drying of wood flour is necessary if its moisture content is more than 15%. Different methods are used for this. The most common is chamber heat treatment.

Dosing and mixing of ingredients

Different manufacturers use their own, individual manufacturing recipes. So, the content of wood flour can be 55-80%, polymer (PVC, high and low pressure polyethylene, polypropylene are used for production) ̶ 20-40%.

Some manufacturers add chopped straw and rice husks to the mass. Additionally, modifiers and dyes are added to the product. All components are mixed as directed by the instructions. Then they are granulated.

Extrusion

At this stage, melting occurs under pressure and at a high temperature of the resulting mixture. The molten mass is squeezed out through the dies from the extruder, pulled, cooled and the boards are faced ( standard length boards: 3.4 or 6 meters).

The extrusion process ensures a high density of the material and a minimum amount of scrap. Production waste is subject to recycling.

The production equipment can be one-stage, two-stage or three-stage lines:

• One-step production. In this case, all ingredients are immediately sent to the extruder, where granulation, drying, mixing and extrusion takes place. This equipment provides the most convenient and fastest technological process, takes up little space, is the least energy and labor intensive, but it is very expensive.
• Two-stage production... Granulation and extrusion are carried out on separate lines.
• Three-stage line. Granulation, mixing and extrusion are divided into stages and are performed on separate equipment. This is the most a budget option production, however, the equipment takes up a lot of space.

As a result, perfectly flat boards are obtained, which are packed and sent to the warehouse.

Description of material, types, characteristics, areas of application

Materials made from WPC have found their application in various fields: in furniture production, in the automotive industry, in the production of garden structures and building materials. In the segment of building materials, WPC is represented by facade boards or siding, boards for the manufacture of fences and fences, window sills, steps for stairs. Half of the total volume of WPC produced is occupied by.

Where is the wood-polymer composite decking used:

• during the construction of berths and piers;
• in the arrangement of tourist and resort recreation areas;
• when arranging the territory around the pools;
• as floor covering terraces, verandas and gazebos;
• when finishing balconies and loggias;
• on the operated roofs of buildings;
• in premises for keeping livestock;
• as a base for sports and playgrounds;
• for the device of paths and platforms for cars.

Standard decking dimensions: width 135… 165 mm, thickness 18… 28 mm.

WPC decking can vary in structure and be:

• corpulent;

Such boards are very resistant to shock and point loads. They are used in high traffic areas such as embankments, sports grounds, dance floors. A solid deck is stronger, heavier and more expensive. Withstands a load of 1000 kg / m2.

• hollow.

Such structures are distinguished by the presence of voids inside. They can withstand loads of 100-600 kg / m2.

According to the method of surface treatment, the board is:

• polished
• grooved

According to the sectional shape, the composite decking is divided into:

• Boards without ribs.
• Boards with closed edges.
• Boards with open edges.

The first two types are laid on logs, the second on a rigid base (if the ribs are wide, it can also fit on logs).

Advantages and disadvantages of WPC boards

The deck made of wood-polymer composite is endowed with numerous advantages:

• The material is highly durable.
• Durability. The service life of the products exceeds 30 years.
• Excellent moisture resistant qualities. Water absorption does not exceed 5%.
• UV resistant.
• The composite is not subject to decay and corrosion.
• Resistance to temperature extremes. Boards can be operated in the range of -45 ... + 90 degrees. Polyethylene becomes soft at high temperatures, and polypropylene becomes brittle at low temperatures. To improve these indicators, special modifiers are used.
• High resistance to abrasion and mechanical damage. Scratches and chips practically do not appear on a high-quality coating.
• Resistance to aggressive environments. The coating is not afraid of the effects of salts, acids, alkalis, and can be treated with detergents.
• Environmental friendliness. In the production of products containing PVC, it is possible for unscrupulous manufacturers to add additives containing lead, which adversely affects human health when it is released. When used in the production of polyethylene and polypropylene, such modifiers are not added.
• Non-slip surface.
• Ease of maintenance.
• The material is easily processed (drilled, sawn).
• Attractive appearance, imitating the structure of wood, a large selection of shades and textures.

• There are many products on the market that are produced either on low-quality equipment or in violation of technology. As a result, boards can have durability problems, poor heat and UV resistance.

Important! The low price of decking can mean the use of low-grade raw materials and additives in its release. Please read product specifications carefully before purchasing. Otherwise, you can purchase a material that in a couple of years will lose its wonderful properties.

• The presence of polymers in the decking assumes the possibility of linear expansion of the material with a change in the ambient temperature. However, the installation of the board using special fasteners provides the necessary mobility of the material, and hides a possible change in dimensions.

Installation of WPC decking

The deck is laid using a suture or seamless method.

In the first case, the board is attached to the terminals, which provide an even seam between the boards. In the second, the boards are stacked closely using secret clips.

Important! Due to the linear expansion of the material, it is not recommended to use this installation method on areas larger than 10 m2.

To carry out the work, it is necessary to purchase materials.

So, in addition to the board itself, to build a terrace you will need:

• Support or bearing logs:

1. The choice of this or that option depends on the structure of the terrace. If your site already has a reliable level foundation: dense rocky soil, or a concreted area, adjustable supports and support beams are used to install the frame part.
2. On weak soil, a foundation has to be erected under the terrace. In this case, it is advisable to give preference screw piles and bearing lags.

• Clamps or mounting clips:

1. Clamps are metal fasteners with which the decking is fixed to the substructure. They provide a small gap between the boards - no more than 3 mm.
2. Plastic mounting clips are also used to attach the board to the log, but it allows you to make a gap already up to 6 mm. Average consumption fasteners for 1m / 2 of flooring is 20-23 pcs.

• End fittings: accessories in the form of plugs, side strips and corners are used to decorate the end part of the flooring and steps - they give the terrace a finished look. They are also made of wood composite, and are selected in accordance with the color of the board used.

In a set for decking, manufacturers also offer piles and adjustable supports. When buying materials, you should first of all pay attention to the quality of the composite.

It should be uniform, without any inclusions and voids on the front side and sections. Too low price of material should certainly alert you - the price of 1m2 of WPC board can in no way cost less than 1600 rubles.

Tools that you will need when laying the board with your own hands:

Decking composite decking board is attached as follows:

Illustration	Description
	Before starting work, you should already have a ready-made base. There can be many options here: Aerated concrete blocks; Strip-type concrete foundation; Columnar concrete foundation; Brick supports; Wooden beam; Adjustable feet. There is not much difference, the main thing is that the base is solid.
	Logs are laid across the supports. They should be located in increments of no more than 40 cm.If high loads will be exerted on the surface, then the spacing of the elements should be 20 cm. If the decking will fit diagonally, then the logs must also be placed every 20 cm.
	The lags are set so that from the center to the center of the elements is no more than 40 cm. At this stage, they do not need to be additionally fixed.
	To fix the elements, you need to drill holes like this: In the upper part, you need to use a drill 2-3 mm larger than the diameter of the used dowel-nail; The inner partition is drilled with the same drill as the dowel diameter. You just need to insert a thinner drill into a wide hole and drill the log and base underneath. The depth should be about 20 mm less than the length of the dowel.
	The dowel is inserted into the hole flush with the upper partition. Just stick the fasteners in all places, fixing will be done later.
	This is how the dowel is located at the intermediate stage. It is important to get into the bottom hole so that the fasteners are level and not fall off.
	To finally fix the lags, you need to finish off the fasteners to the end using any spacer. In our case, this is a broken drill from a hammer drill. Since the hole is 20 mm smaller, the dowel will not enter completely. It turns out a floating mount, which does not allow the elements to move, but at the same time does not interfere with them during deformations that can occur during temperature and humidity changes. Important! Never push the dowels to the end, the minimum power reserve for the lags should be at least 5 mm.
	From the side of the beginning of laying the decking, you need to put start clips. They should stand on each log, yellow self-tapping screws 3x30 mm will be used for fastening.
	The clip must be positioned correctly. So that the lags are not visible from under the decking, the edges of the retainer should extend beyond the end by 1-2 mm. Do not forget about this nuance when you screw the elements.
	The board is cut to size if necessary, then it is placed along the edge and snapped into place on the clips. To fix the element, you should press it in with force so that the bracket enters the groove and is firmly held in it.
	Plastic cleats are installed so that one protrusion goes into the groove of the decking, and the lower part rested against the lag. Just press the element against the edge of the board and hold with one finger. A 3x30 mm self-tapping screw is inserted into the hole, which will be used to fix it.
	The kleimer is not screwed in completely with a screwdriver. The screw head should protrude 1-2 mm above the surface of the plastic retainer. This will give a little free play to the connection and allow for better docking of the next elements to be stacked.
	Fasteners are placed on each lag. This is very important for the strength of the structure, you should not save money and put the kleimers through one - the surface will subsequently walk.
	The second board is placed like this: the element is pressed tightly along the entire length, after which you need to additionally knock out all the joints with a rubber mallet. This will provide the best fit and the gap will be the same everywhere.
	There should be a gap of 4-5 mm between the elements. It is necessary for the smooth removal of moisture and good ventilation of the structure. Thanks to the cleamers, the gap will always be as it should be. You just have to tightly join the boards and fasten them.
	After laying the four boards, you need to tighten the fasteners between the first and second boards. A long bit is taken, put on the slot of the self-tapping screw and screwed in until it stops. This is how the final attachment of the deck is made. The next rows are drawn in the same way. But there is no need to rush, only the joints can be tightened, starting from the second from the edge of the board, this process should not be carried out immediately.
	The work continues in the same way until you cover the entire surface. The boards are laid, knocked out with a rubber hammer and fastened. After connection, they reach through the slots to securely fix the KDP.
	The last floorboard is secured with metal clips. Only now they are first tightly inserted into the groove, and then screwed on with a self-tapping screw. It is important to fix the edge well so that the outer board does not wobble and stands securely.
	When the work is over, you can start installing the plugs. First, take a close look at them to figure out how to properly arrange the elements. In the lower part there are always holes for moisture drainage, and on the upper part, a rounding of the corner is made so as not to cling to your feet.
	Plastic elements must be placed very carefully as they can be easily damaged. First, the protrusions are placed in the grooves of the decking, then, holding the element with one hand, it is gently knocked out with a rubber mallet, as shown in the photo. Try to drive the plug evenly, knocking it in from different sides.
	This is what the result of the work looks like. It turns out very neatly, while the ends are securely closed.
	An end plate made of aluminum is placed on the edge. First, measurements are taken, and the element is cut off with a hacksaw or jigsaw. After that, you need to firmly attach it to the surface to make sure that the corner fits well along its entire length.
	The corner is fastened. Everything is simple here: there are grooves for self-tapping screws on the surface, so you place the fasteners with the required pitch, no instructions are needed here.
	This is what a fixed bar looks like. After that, the terrace can be used, the work is over.

As you can see, it will not be difficult to lay the composite coating on your own. The assembly of the composite decking is clearly demonstrated in the video in this article:

If you decide to make a floor covering that will have excellent performance characteristics and serve as an exterior decoration, you will certainly be interested in a decking made of dpc. By purchasing quality material, and having laid it in accordance with the technology, you will not regret your choice for many years.

Wood-polymer composite (WPC) is a mixture that contains a polymer (chemical or natural), as well as a wood filler, most often modified by chemical agents. This material is called "liquid wood", and wood-plastic composite, and wood plastic, and polywood. The main feature of such a material is that the final product is obtained, in fact, from production and consumption waste, such as sawdust, shavings, wood flour, agricultural waste and different types consumption waste. Today, methods are being created that make it possible to use not primary, but secondary polymers in the production process.

What it is?

Externally, a wood-polymer composite with a high wood content is very similar to MDF or hard fiberboard, and with a small amount of it - to plastic. Such material lends itself well to sawing, planing with a plane. Nails are easily driven into it. It can also be painted with ordinary paints and enamels, or finished with synthetic films, natural veneer.

Wood-polymer composite is an ultra-modern material. WPC possesses all the best natural properties of wood, but at the same time it is devoid of such disadvantages as a tendency to rot and mold, flammability, surface flaws, susceptibility to moisture.

The KDP contains:

• wood flour (or shredded chips), size from 0.5 to 2 mm
• polymer, which can be PVC, polyethylene or polypropylene
• additives.

Manufacturing of extrusion wood-polymer composites can be called one of the most promising areas in the field rational use residues of sawmills, furniture and woodworking industries, the use of low-grade timber, plant waste, which contains a lot of cellulose, recycled plastics to create high-quality profile parts.

Advantages of wood-polymer composite

The main advantages of such material include:

• WPC board does not need to be painted every year
• terrace board does not slip in the rain, because it has a corrugated surface
• the material can withstand colossal differences temperature regime(from -50 ° С to + 50 ° С)
• high strength. Products made from this material can withstand heavy loads, which makes it possible to use them as flooring even in car parks.

The most popular KDP in such areas of activity:

• construction. In this industry, it is used for exterior cladding of houses, for creating door and window profiles, panels, as well as for finishing openings, gable boards
• landscape design. Floorings (decking), sidewalks, fences, fences, garden architecture (benches, gazebos), outbuildings, playgrounds are made of polymer-wood composite. They are also used for swimming pools and flooring.
• interior decoration. In this industry, handrails, stairs, shutters, decorative profiles, finishing panels, kitchen built-in wardrobes, parquet, office furniture, shelves, baseboards, soundproof panels are created from WPC.
• industry. Bridges, transport pallets, containers, piers, sea piles and bulkheads, railway parts (sleepers), garbage containers, plates, signboards are made from "liquid wood".

Decking, or in other words, decking made of wood-polymer composite is the most modern material among outdoor floor coverings. Wood flour and polymer endow this material with unique properties. The service life of such a board reaches 40 years. This material requires annual antiseptic treatment and painting.

Basic properties:

• no slipping even when wet
• high strength and wear resistance
• temperature regime from -50 to +80 0С
• not susceptible to moisture, can be used outdoors
• not afraid of ultraviolet rays, does not fade, does not rot, does not grow moldy.

Today the following types of decking are produced:

• suture, have a seam from 2 to 6 mm. They are used on large areas, over 300 m2, where it is necessary to guarantee a large outflow of water
• seamless. Such boards are ideal for outdoor cafes where you need to make a monolithic floor.
• full-bodied are used on piers and ship decks
• hollow. This board is lighter and therefore less expensive
• with PVC polymer. Have better wear resistance, greater UV resistance, strength
• with polyethylene. Differs in low cost
• sanded boards
• brushed, brushed, i.e. aged
• embossed with a textured pattern
• embossing, with a natural wood texture.

WPC boards are easier to install than wood boards.

Wood-polymer composite production

WPC is an innovative material, the manufacturing technology of which is based on mixing flour, PE, PP, PVC and other components using special equipment in accordance with established standards.

In order to create a wood-polymer composite, it is necessary, first of all, to grind wood raw materials. After shredding, the wood must be thoroughly dried. This is followed by the stage of precise weighing and measuring of the components. After mixing all the ingredients, the material is extruded. The final stage of production is trimming to length as well as cutting to width.

The WPC production scheme is very similar to the creation of chipboard boards. However, the implementation of the process takes place on chemical equipment, i.e. plastics industry. Such installations are quite compact, that is, they do not need a large room. Enterprises producing WPC are effective even with small production volumes, therefore, they are incomparable with the scale of particle board or MDF factories.

Wood-polymer composite market

Today, the world market for DPKT is in the growth stage, and every year it is growing by about 18-20%. According to the latest data, even the American market does not have a saturation point. In the coming years, a boom in the consumption and production of wood-polymer composites is expected.

Taking into account the periods of the market life cycle, the dynamics of consumption and production growth in Russia and other countries, the potential of the Russian wood-filled composites market is enormous.

The scope of this material is very wide. In Russia, the main area of ​​use is construction. Also, according to analysts, in the coming years, wood composites will be actively used in the automotive industry and in the production of furniture.

This material is highly resistant to the influence of the external environment, temperature extremes, it is more durable in comparison with wood and wood-based panels. Such properties are extremely important in the harsh climate of most of our state. Manufacturing of outdoor furniture from DPKT (benches, railings, flooring) is of higher quality. Due to the ability of wood polymers to take any shape during production, furniture makers have the possibility of wider use of design elements and creative ideas while designing furniture.

Construction on a suburban area is not limited exclusively to the construction of a residential building. Also, accompanying buildings for recreation, storage and ancillary work are being constructed, for which the appropriate building materials with the necessary characteristics are selected.

Materials that are used outdoors require solid strength, durability and resistance to environmental influences. Therefore, for the construction of buildings such as terraces, gazebos and open areas, the highest quality material is chosen. And first of all, this applies to the floor covering, which is experiencing a greater load in comparison with the rest of the building elements.

Decking

For outdoor flooring, the reliability of the material is extremely important. Therefore, for the manufacture of the floor, as a rule, solid wood boards are used. However, more recently, a new construction material having the best characteristics.

This is a WPC decking board that has all the advantages of a natural material in the absence of its disadvantages. High performance characteristics are successfully combined with ease of installation and lack of costs in the process of use. WPC production volumes are growing annually, for example, one of the leaders in WPC production in Russia, Smart Decking, produced only 10,000 m2 per year in 2008, and in 2016 it was already about 60,000 m2.

WPC production involves the use of two types of raw materials - wood (mainly shavings) and polymer. This combination made it possible to achieve unique strength and durability of the material.

What to choose: natural wood decking or WPC?

To understand which is better - wood-polymer composites or solid wood, it is necessary to consider and compare the characteristics of both materials.

The durability of WPC boards is about 40-50 years, while those of solid wood are about 15-20 years. But only if the wooden board is properly impregnated with all protective equipment. At the same time, the tree requires not only initial treatment with varnish or paint, but also periodic renewal of the coating. WPC decking in this regard is not only more convenient, but also profitable in operation, since it does not require additional maintenance during use.

The main advantages of wood-polymer composite

In addition to durability, WPC has a number of additional advantages that determine its use as a floor covering for buildings located in the open air:

How much does a WPC board cost?

It makes sense to separately mention the cost of WPC. Facade board made of wood-polymer composite at first glance seems prohibitively expensive. However, if you consider the fact that a significant part of the cost of additional consumables is simply not required, in the end it turns out that WPC decking is quite profitable.

In addition, the installation of the flooring is so simple that it can be done independently without the involvement of a specialist. The board fits on almost any substrate, with the exception of swampy ground. However, after carrying out a high-quality drainage system, this problem is also solved.

Is it really expensive?

WPC board, the price of which is slightly higher in comparison with the solid wood, perfectly compensates for this disadvantage with its resistance to environmental influences. This material does not swell from high humidity, does not fade in sunlight and does not dry out from high temperatures.

The estimated cost for wood-polymer composites varies within 300-470 rubles. per running meter depending on the manufacturer and brand of the product. Another factor affecting the cost of a board is the type of wood used in its manufacture. The more valuable the wood, the more the amount that will have to be paid for the material for construction.

Operating conditions for WPC boards

Even so unpretentious to the conditions of use, the material has its own limitations in operation:

• WPC decking is not used in places with permanent high humidity without access to wind and sunlight. The deck must be ventilated periodically. Otherwise, even this building material can become moldy.
• It is absolutely unacceptable to operate a composite decking while constantly being in water.
• And the last limitation. Do not use the material in rooms with frequent and large temperature fluctuations, such as a steam room. This can deform the board.

I must say that although wood-polymer composites decking practically does not fade in the sun, slight discoloration is still possible.

From all of the above, we can conclude that the rather high cost of decking made of wood-polymer composites will pay off later due to the durability of the material. While solid wood flooring will become unusable much earlier. Therefore, we can say with confidence that the future belongs to the KDP.

Wood-polymer composite materials (WPC) intended for processing by extrusion consist of three main components:

• shredded wood particles
• synthetic or organic thermoplastic polymers or mixtures thereof,
• a complex of special chemical additives (modifiers) that improve the technological and other properties of the composition and the resulting products, often also called additives.

Composite materials differ from traditional wood-filled plastics (DVP) by a high (more than 50 percent) wood content by weight in the overall composition and its corresponding influence on the properties of the finished product. There is not a lot of wood filler in DNP and the properties of such plastic are mainly determined by the properties of the polymer. And when there is more wood, the properties of the composite are already determined:

• properties of the matrix,
• properties of wood particles,
• the nature of the bonds between wood particles and the matrix,
• the structure of the resulting composite.

The figures below show three schematic structures of a filled material:

Weak-filled plastic, medium-filled composite, and high-filled composite.

The wood content in the wood-polymer composite based on thermoplastic resins can vary within wide limits. Most American manufacturers are still working with compositions containing 50 - 70% wood. European developers of DPKT extrusion technologies strive to obtain compositions containing a higher wood filling - up to 80% or more.

The wood is crushed in special mills of various types and converted into wood flour or wood fiber. Currently, wood flour is most widely used for the manufacture of WPC. The production of wood flour has long been mastered by the domestic industry. It is used as a filler for plastics, raw materials for explosives, for microbioprom, etc.). Along with specially crushed wood, small sawdust and grinding dust can be included in the DPKT.

It is promising to use wood fibers in DPKT, by the type used in the production of fiberboard, MDF and paper. Wood fibers are produced by the deflection method, i.e. splitting wood into fibers. In some cases, ready-made fiber from cardboard and paper waste (waste paper) is used. For example, a Chinese company has experience in industrial recycling in WPC production T paper milk bags containing polyethylene, paper and even aluminum foil at the same time.

Fig. 1. Fuel pellets

Finnish specialists have tested the possibility of using standard wood pellets (on a Conex-type extruder) as a raw material for compounding.

Granules are easier to transport and store than flour

The appearance of fuel pellets, see Fig. 1.

Wood flour (English wood flour, wood meal, it is holzmehl)- is made mainly of soft, non-resinous, wood species, such as pine. The use of hard hardwoods is not at all excluded, only they are somewhat more difficult to grind. In our country, flour is produced in accordance with GOST 16361-87 "Wood flour. Technical conditions".

Abroad, wood flour is successfully produced for use in thermoplastic WPCs from the shells of plant grains (rice husks, nutshells). The American company Heartland BioComposites LLC has recently mastered the use of wheat straw as a raw material.

In most cases, the size of the wood particles in the composite is in the range from 500 to 50 microns. Wood flour particles can take on a wide variety of shapes. The ratio of the lengths of flour particles to their widths ranges from 1: 1 to 4: 1.

In mills, during grinding, the selection of the desired fraction of flour is carried out using a sieve system or centrifugal methods. Abroad, it is customary to designate the flour fraction using the Mesh number. According to the Russian standard, the division of wood flour is carried out according to several brands.

Wood fiber (wood fiber) the length depends on the type of wood: for hardwoods 1 - 1.5 mm, for conifers 3 - 3.5 mm. The length to thickness ratio of the wood fiber is 1: 10 to 1: 20.

Wood is traditionally used in the mechanical processing of metals as a grinding and polishing material, as it has noticeable abrasive properties. These properties are retained in wood flour as well. However, the abrasiveness of wood is lower than that of fiberglass and some other mineral fillers used in the production of filled plastics and composites. Therefore, it is considered a relatively "soft" filler.

The rate of abrasive wear of equipment is proportional to the pressure in the extruder barrel (and die), the temperature and speed of the working mixture relative to the surface of the working bodies and naturally depends on the composition of the working mixture (the ratio of the amount of flour and resin, the type of resin, types and amounts of lubricants, and other factors ). Depending on the durability, the working cylinders and screws of the extruders can be operated for 1-2 years before being replaced or repaired.

The bulk density of wood flour and fiber can range from 100 to 300 kg / m3. It is desirable to have no more than 8% moisture content of flour in the delivery. In the finished composite, the moisture content of the wood particles should generally be less than 1%. The less moisture in the structure of the material, the more resistant it is to external influences.

There are different and sometimes conflicting opinions regarding the use of different types of wood and particle sizes.

Let's note the obvious things:

• studies have studied the effect of particle size on the mechanical properties of composites, but it is not very large;
• too small (dust) and too large particles deteriorate the strength of the composite, but this is not always critical for the finished product;
• large particles reduce the productivity of the preparatory equipment due to their low bulk density;
• at a composite density approaching 1.4 g / cc, i.e. to the true density of wood, the type of wood is no longer of fundamental importance.

A composite made from coarse particles will have a grainier surface similar to that of a chipboard and this may require sanding, thickening and / or surface finishing. For example, from the experience of the furniture industry, the graininess of profiles made by milling from chipboard is not always possible to hide when veneering with expensive decorative films based on resin-impregnated papers with a total weight of up to 130 g per 1 square meter. And for veneering MDF profiles with a fine uniform structure, cheaper decorative films weighing less than 80 g per 1 sq. M can be successfully used. In addition, large wood particles, especially those located near the surface of the product, are more susceptible to moisture and damage under the influence of adverse environmental factors.

Very fine dust particles (less than 50 microns) have a large specific surface area and therefore require the use of a larger amount of resin to form a complete polymer matrix.

Note. Currently, research is underway on the use of microcellulose in composite materials. But it will rather be a different class of materials, the so-called. nanocomposites.

The final transformation of the working mixture into a composite material occurs gradually along the zones of the extruder and in the die. The polymer must cover the entire surface of the particle of the wood particle, penetrate into its pores and thereby ensure a tight molecular interaction between wood and polymer. This significantly distinguishes the process of extrusion of WPC from the process of extrusion of conventional plastics, because wood is poorly wetted by polymer melt. It is difficult to intensify the wetting process by increasing the temperature in the extruder due to the danger of thermal destruction of wood, polymer and ignition of the mixture (at a temperature of more than 200 degrees C).

Therefore, from the point of view of the quality of the products obtained and the productivity of the process, the technological level of the equipment used and the composition of the mixture formulation (the quality of the base resin, the type and amount of additives - modifiers introduced into the formulation) are very important.

Notes:

1. Technological and physical-mechanical properties close to wood-polymer composites are composite materials obtained on the basis of other plant fibers, for example: hemp (Hemp), flax (Flax), sisal (Sisal), Kenaf (Kenaf), etc. fibrous plants.

Plant fibers can be added to the WPC and simultaneously with wood fibers. The use of non-wood fibers of plant origin is especially actively developed now in the countries of Southeast Asia, in particular in China. For more information on fibers, see the dedicated application and the Biocomposites library.

2. With the outward simplicity of the idea of ​​WPC production, the very structure of the wood-polymer composite material has a very complex structure. Chemical, physical and mechanical processes of extrusion WPC production technology are no less difficult to describe. These difficulties are determined by the complexity and heterogeneity of the wood itself.

With more or less success, any thermoplastic polymers can be used in the production of WPC, but in practice there are mainly four types of thermoplastic resins in use: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and, to a lesser extent, polystyrene. (PS). The diagram (Fig. 4.2.) Reflects the existing ratios of the use of various resins and fillers and the forecast for the coming years.

Fig. 2. Status and forecast of the applicability of base resins and fillers in the production of composites

Thus, in the first place in terms of applicability is polyethylene (high and low density), followed by PVC and polypropylene. However, in Europe, polypropylene is considered the most promising. In particular, the German company Advanced Extruder Technologies AG (a manufacturer of equipment for extrusion of WPC) indicates the following optimal ratios of filling the composite with wood for various types of base resins:

• based on PVC - 60%
• based on polyethylene - 70%
• based on polypropylene - 80% or more.

Significant growth is expected for all types of composites, but since 2003, the use of other (non-wood) plant fibers as a basis for a composite is growing especially rapidly.

Along with prefabricated resins supplied in the form of a suspension or granules, a number of American companies use plastic industrial and household waste (packaging film, bottles, etc.) in the production of WPC, which is washed, dried and shredded.

Experiments are also being conducted on the use of other industrial thermoplastics in thermoplastic WPC - ABS plastic, polyamides (nylon, nylon), polycarbonates, polyethylene terephthalate, etc. in primary forms and waste.

Approximate ratios of world prices for raw materials (in British pounds per ton, March 2003) used in the production of WPC are given in table. 4.1

This table illustrates well the economic essence of interest in the problems of the production of wood-polymer composites and objective trends in the development and improvement of their production technology. It should be borne in mind that the current prices for base resins on the world market are highly dependent on oil prices and are subject to significant fluctuations.

In the production of wood-polymer composites, the following types of additives - modifiers are used: binding agents, lubricants, antimicrobial additives, antioxidants, foaming agents, pigments, fire retardants, shockproof modifiers, light stabilizers, temperature stabilizers, etc.

These additives are used in the extrusion and casting of conventional filled and unfilled plastic profiles and for approximately the same purposes, but their ratio in combination with wood varies slightly. This primarily applies to binding agents, lubricants, and, if necessary, to impact modifiers. Supplements are supplied individually or as complexes (like multivitamins, all in one granule).

Wood, in contrast to mineral fillers for plastics, does not have very high adhesion to base resins, especially to polyolefin resins. This can be explained by the very complex shape of the surfaces of its particles, which complicates the process of wetting it with a molten polymer, as well as its chemical composition... This circumstance places increased demands on the selection of additives and on the design of the extruder. The photos below show 2 PCB samples (electron microscope, 200x magnification, 60% polypropylene ratio, 40% wood flour).

The left photograph clearly shows numerous voids not filled with polymer. On the right sample, the structure of the material is solid. This is what makes the material - a composite in which both a polymer matrix and wood work. Improvement of the structure is provided by the inclusion in the composition of the material of a special binding agent, which provides a good bond between the particles of wood and resin.

Typical structural defects of the composite are shown schematically in two figures below.

In the diagram on the left, individual voids that are not filled with resin are highlighted in blue. The diagram on the right shows the formation of agglomerates made up of several wood particles that are not glued together. The presence of such defects, especially on the surface of products, leads to a decrease in the strength and durability of the material.

Specific formulations of wood-polymer composites are developed in relation to the specified products, used base resins and technological processes. They are often trade secrets of the manufacturer of specific products or licensed by the supplier of technology or equipment.

An important direction in the development of modern formulations of extrusion WPC is the search for the use of natural, i.e. biological polymers. A successful achievement in this area was the use of starchy substances, for example, corn flour (materials such as Fasal - Fasalex). Research is being actively carried out on the use of lignin (waste from cellulose production), waste from the leather and meat and dairy industries, etc. There is information about the research of Russian specialists on the possibility of using coniferous resin - oleoresin as one of the components of extrusion WPC.

The appearance of wood-polymer composites.

In its natural form, WPC with a high wood content is most reminiscent of MDF and or hard fiberboard, see Fig. 3. It can be dyed in mass or varnished with ordinary paints and enamels, or veneered with synthetic films or natural veneer. The composite is warm to the touch, sometimes slightly oily.

Fig. 3. Sections of WPC profiles

There is a technology of covering WPC with a thin facing layer of plastic, or even several plastics directly in the process of extrusion in the extruder. This technology, which is widely used in the plastic industry, is called co-extrusion or co-extrusion.

However, if wood particles of coarse fractions were used in the manufacture of the compound, then the surface of the product will be closer in appearance to the surface particle board... Such profiles are produced, for example, by the Dutch company Tech-Wood.

Thermoplastic WPCs have a faint smell of wood (sawdust).

Physical and mechanical properties of composites

The density of extrusion composites can be in the range of 1000 - 1400 kg / m3. The density of products can be reduced by using special foaming agents to 700-900 kg / m3, but only the polymer matrix can be foamed.

Notes:

1. The density of the composite depends on the density of the base resin used and the additives used and their amount and density of wood particles. During compounding and extrusion, under the influence of high pressure and temperature, wood particles are compacted, up to a value of 1400 kg / m3, i.e. achieving the true density of wood, free from pores and other voids.
2. The true density of wood is practically independent of its species.
3. The issues of using hollow microfillers (plastic and glass microspheres) in WPC are being studied.

The strength properties of WPC largely depend on the type of base resin, see table. 2.

However, by controlling the composition of the composite and technological process it is possible to significantly improve its strength and other properties.

Let us consider the properties of WPC using the example of three specific modifications produced under the brand name "Fasal" developed using polypropylene as a base resin by the Austrian company "Austel research and development" Gmbh and sold by the company "Fasalex", Austria, see table. 3.

Table 3. Properties of WPC.

Properties	Dimension	Fasal F134	Fasal F 386	Fasal F 465
Density	kg / dm 3	1,4	1,35	1,2
Tensile strength (tensile strength)	MPa	25	17	23
Tensile modulus (Young's mod)	GPa	8	4	5,1
Bending resistance	MPa	41	30	52
Flexural modulus	GPa	5,8	3,8	5
Tensile elongation	%	0,5	0,6	1
Charpy impact strength	KJ / m2	3,2	3,3	4
Biodegradation time	weeks	months	non-degradable
Reduction of resistance to bending in water at 23 degrees C:
- after 30 min. excerpts	%	65	14	0
- after 120 min. excerpts	%	90	35	0

In the composition offered by Strandex, USA, polyethylene and its waste are used as the base resin. Hardwoods and softwoods are considered acceptable, as well as other cellulosic fibers such as straw, flax, rice hulls, peanut hulls, bamboo, kenaf, etc. Particle size 425 microns (40 mesh) or less. A large content of finer particles (200 mesh and finer) is acceptable, including grinding dust. The density of the composite is 0.98 - 1.2 kg / dm3. The composite and technology are patented and sold under license together with dies. The cost of one die is more than 20,000 US dollars, the cost of a license (according to some sources) is more than 1 million US dollars.

However, there is a serious problem in the use of particle board and MDF waste. It is associated with the sublimation of formaldehyde vapors from phenolic resins contained in these slabs.

Note. Although the strength of thermoplastic WPC during testing is at the level of natural wood materials, their real operational strength in many cases is significantly higher, because products made of WPC do not have natural defects inherent in wood (knots, cracks, curliness, etc.), do not change their strength with increasing humidity and are not affected by fungi and bacteria.

At the beginning of mastering the production of WPC, technologists tried to ensure the maximum biostability of products. And this task was solved. In particular, a number of WPC manufacturers provide guarantees for 10, 25 and 50 years of operation of finished products on the street, i.e. the highest resistance to moisture, light, fungi and insects without special protection. Most of the manufactured WPCs can take a small amount (0.1 - 4%) of moisture without losing their shape and strength and restore their previous properties when dried.

A new direction in the production of WPC is the creation of formulations for easily utilized biodegradable WPC with reduced biostability. They are offered, for example, by Fasalex - as environmentally friendly throughout life cycle(the above compositions Fasal F 134 and F 386).

It should be noted that despite the already solid production experience and numerous studies already carried out, there is still a huge number of unexplored areas in the field of wood-polymer composites. On the one hand, this is due to the endless possibilities of polymer chemistry, and on the other hand, it is explained by the youth of this new industry itself.

Processing ability

WPC products are processed with the same tools as wood. WPC is easily sawn, planed, drilled, sanded, etc. Holds nails, staples, screws very well, see fig. 4.

Many composite formulations are adhesive. Some formulations can be welded like plastic. The practice of bending shaped products after heating, like plastic profiles, etc., has already been mastered.

Fig. 4 Processing of wood-polymer composites

WPC are not very easily flammable, especially if they are made on the basis of polyvinyl chloride resin.

An interesting direction in the use of extrusion WPC is the combined use of WPC profile and rolled metal. In this case, a steel pipe, strip, etc. is inserted into the profile cavity. The metal takes on all or part of the power load, and the profile performs decorative, protective and other functions.

There is no accepted standardized classification for thermoplastic WPCs yet.

Wood is perhaps the most demanded building and finishing material. Wood is versatile in processing, has high thermal insulation and aesthetic qualities, is indispensable for the creation of unusual architectural buildings, exquisite furniture, interior decoration and decoration of personal plots. The only drawback of the tree is its susceptibility to adverse external factors and the ability to rot.

In an effort to preserve all the advantages of wood and nullify all its disadvantages, manufacturers have created an innovative building material - wood-polymer composite. Let's consider what "polywood" is, what properties, characteristics are inherent in modern material, and what is the scope of its application.

The main types of wood composites

Wood composites are materials obtained by combining different raw materials. The main component of the wood composite is wood. The amount of wood waste, as well as the type of binder component, determine the main characteristics of the composite material.

The most common wood composites are:

Wood-polymer composite: photo of a base for a patio from a decking board

​

Let us dwell in more detail on the composition of the innovative material, its production technology and technical and operational characteristics.

Wood-polymer composite: production and composition of the material

The structure of the WPC includes three main components:

1. Particles of crushed wood (some manufacturers add particles of rice husk or oil cake to reduce the cost of production).
2. Thermoplastic polymer (polyvinyl chloride, polyethylene, polypropylene).
3. A complex of modifiers - chemical additives (up to 5% in the composition of the material).

The production of wood-polymer composite is carried out according to the scheme.

Shredding wood. The wood is processed on hammer and knife crushers to obtain particles with a size of 0.7-1.5 mm. After crushing, the wood is sieved and fractionated.

From the smallest fractions, a profile is made without surface finishing, from medium components - a profile for finishing with veneer, paint or film, and coarse wood fractions are used to create technical profiles

Drying wood carried out if the moisture content of raw materials exceeds 15%.

Dosing and mixing of components... All components of the WPC are combined in the right proportions and mixed with each other. The most commonly used ratios of wood flour / polymer components are:

• 70/30 - the composite contains such a property of wood fibers as moisture expansion; WPC is considered more fragile and has a service life of about 5-7 years;
• 50/50 - the optimal ratio of wood and polymer, which preserves the decorative properties of wood and the strength of the polymer;
• 40/60 - the aesthetic qualities of wood are weakened, the material feels and looks like plastic.

Pressing and formatting the product. The final stage, at which the technical properties of the WPC are formed and the material acquires a presentation.

Technical and operational characteristics of wood-polymer composite

The properties of the composite are determined by the amount of wood in the material, the type of wood and polymer used. Let's note the general mechanical and physical indicators of the WPC:

1. The density of the material. The indicator depends on the base resin used, the amount of additives used and the density of wood particles. The maximum density of WPC is 1.4 kg / dm3 (true wood density).
2. Tensile elongation - 0.5-1%;
3. Bending resistance - 25-60 MPa;
4. Charpy impact strength - 3-4 KJ / m2.

The woody part of the WPC gives the material the following properties:

The polymer qualities of WPC are manifested as follows:

Comparative characteristics of wood and WPC

In order to more clearly characterize the wood-polymer composite, we will conduct a comparative analysis of the main qualitative and economic indicators of wood and WPC.

Scope of WPC

Due to its merits, wood composite has won wide popularity in the industrial sector, construction and in everyday life:

More than 50% of wood-polymer composite is used as "decking" - wooden boards and tiles for decoration of coastal and backyard architecture

Product overview of the main manufacturers of WPC boards

WPC decking boards are presented on the construction market by many manufacturers. When choosing a material, it is better to give preference to well-known companies - their product has already passed the test of time for quality and has won a positive reputation around the world.

Terrace board Bruggan(Belgium) is made from high quality raw materials, the products are focused on the international market. In terms of textile feel, the board is as close as possible to wood.

The Bruggan board has the following composition:

• wood - 60%;
• polymers - 30%;
• additives - 10%.

The company produces hollow and full-bodied decking, which is used for arranging areas around swimming pools, creating terraces, summer areas for hotels, bars, restaurants, and building stairs.

Bruggan Multicolor solid decking board has a full-thickness wood texture, suitable for sanding and radius trimming

The approximate price of the Bruggan board is 1000-1200 rubles for one profile

Terrace board Mirradex(Malaysia) is made from tropical tree fibers, which increases the moisture resistance of the material. The board does not require additional processing. The structure of the board is double-sided - this allows the material to be used to create vertical structures (fences, barriers).

Mirradex board composition:

• wood - 50%;
• polymer (polypropylene) - 40%;
• additives and various additives - 10%.

Mirradex terrace board belongs to the category of premium materials, but at the same time it has a relatively affordable cost (about 750 rubles per profile).

Terrace board Legro(Hungary) has a special protective layer that increases the wear resistance of the material. Legro board is suitable for arranging terraces and areas in public places with high traffic.

Advantages of the Legro board:

• does not fade;
• no stains remain on the surface;
• resistance to damage (scratches, dents);
• double-sided indelible texture.

Composition of WPC Legro:

• shredded wood - 50%;
• polypropylene - 45%;
• additives - 5%.

You can buy Legro wood-polymer composite at a price of 3500 rubles for one profile measuring 150 * 25 * 5800 mm.

"Liquid tree": do it yourself and use in everyday life

At home, you can create an analogue of a wood-polymer composite with your own hands. As a result of the work, a "liquid tree" will be obtained, which is suitable for the restoration of furniture from chipboard, repair of parquet boards and laminate.

The whole process of making a homemade "liquid wood" can be broken down into the following steps:

• Grind the sawdust with an ordinary coffee grinder.
• Combine the resulting flour with PVA glue. The ratio of the components: 70% wood, 30% glue. " Liquid tree»Must have a thick consistency.

The resulting paste is applied to the damaged area of ​​furniture or flooring, and left to harden completely (about 4-5 hours). After that, the excess "liquid wood" must be cleaned with sandpaper.

To give the "liquid wood" the desired shade, you can add a dye intended for water-based paint to the mixture.

The advent of wood-polymer composites made it possible to combine the most significant advantages of wood and plastic in one material. Structures and structures made of WPC are easy to install, have excellent performance characteristics and have an aesthetically noble appearance inherent in natural wood products.