What is XLPE and what is it like?

Cross-linked polyethylene - what is it, how is it used, is it better than polypropylene and metal-plastic, what is its service life and other characteristics that distinguish this type of polymer? These and other questions arise for those who are planning to replace pipes. In search of the optimal material for laying communications in the house or in the country, sewn polyethylene should definitely not be discounted.

For a long time, polymer materials have been trying to get rid of their main drawback - increased thermoplasticity. Crosslinked polyethylene is an example of the victory of chemical technology over previous shortcomings. The material has a modified mesh structure that forms additional bonds in the horizontal and vertical planes. In the process of cross-linking, the material acquires a high density, does not deform when exposed to heat. It belongs to thermoplastics, products are manufactured in accordance with GOST 52134-2003 and TU.

The main technical characteristics of the material include the following parameters:

• weight - about 5.75-6.25 g per 1 mm of product thickness;
• tensile strength - 22-27 MPa;
• nominal pressure of the medium - up to 10 bar;
• density - 0.94 g / m3;
• thermal conductivity coefficient - 0.35-0.41 W / m ° С;
• operating temperature - from -100 to +100 degrees;
• toxicity class of products evaporated during combustion - T3;
• flammability index - G4.

Standard sizes range from 10, 12, 16, 20, 25 mm to a maximum of 250 mm. Such pipes are suitable for both water supply and sewer networks. The wall thickness is 1.3-27.9 mm.

The marking of the material in the international classification looks like this: PE-X. In Russian, the designation is most often used PE-S... It is produced in straight-type lengths, as well as rolled into coils or on spools. The service life of cross-linked polyethylene and products made from it reaches 50 years.

The production of pipes and casings from this material is carried out by processing in an extruder. Polyethylene passes through the forming hole, is fed into the calibrator, passing through cooling using water streams. After the final shaping, the workpieces are cut according to the specified size. PE-X pipes can be manufactured using several methods.

1. PE-Xa... Peroxide stitched material. It has a uniform structure containing a significant proportion of crosslinked particles. Such a polymer is safe for human health and the environment, and has high strength.
2. PE-Xb. Pipes with this marking use the silane crosslinking method. This is a tougher version of the material, but just as durable as the peroxide counterpart. When it comes to pipes, it is worth checking the hygienic certificate of the product - not all types of PE-Xb are recommended for use in domestic networks. Most often, the sheath of cable products is made from it.
3. PE-Xc... A material made from radiation cross-linked polyethylene. With this method of production, the products are quite tough, but the least durable.

The use of cross-linked polyethylene is limited to only a few areas of activity. The material is used to produce pipes for radiator heating, underfloor heating or water supply. Long distance routing requires a solid foundation. That's why the main distribution of the material was obtained when working as part of systems with a hidden installation method.

In addition, in addition to the pressure supply of the medium, such pipes are well suited for the technical transportation of gaseous substances. Cross-linked polyethylene is one of the main materials used in laying underground gas pipelines. Also, polymer parts of devices, some types of building materials are made from it.

Crosslinking of polyethylene has become necessary due to its features, which are directly related to the high level of thermal deformations. The new material received a fundamentally different structure, providing higher strength and reliability to products made from it. Stitched polyethylene has additional molecular bonds and has a memory effect. After a slight thermal deformation, it regains its previous characteristics.

For a long time, the oxygen permeability of cross-linked polyethylene has also been a serious problem. When this gaseous substance enters the coolant, persistent corrosive compounds are formed in the pipes, which is very dangerous when using metal fittings or other elements of ferrous metals that connect the system during installation. Modern materials are devoid of this drawback, since they contain an inner oxygen-impermeable layer of aluminum foil or EVON.

In the manufacture of cross-linked polyethylene, up to 15 different methods can be used, affecting the final result. The main difference in them lies in the way of influencing the material. It affects the degree of crosslinking and some other characteristics. The most commonly used are only 3 technologies.

• Physical or based on exposure to radiation on the molecular structure of polyethylene... The degree of crosslinking reaches 70%, which is above the average level, but here the thickness of the polymer walls has a significant influence. Such products are labeled as PEX-C. Their main difference is uneven connection. The production technology is not used in the EU countries.

• Silanol-crosslinked polyethylene obtained by chemical combination of a silane with a base. In the modern B-Monosil technology, a compound with peroxide, PE, is created for this, and then fed to the extruder. This ensures uniformity of stitching, significantly increases its intensity. Instead of dangerous silanes, organosilanide substances with a safer structure are used in modern production.

• Peroxide crosslinking method for polyethylene also provides for the chemical combination of components. Several substances are involved in the process. These are hydroperoxides and organic peroxides added to polyethylene during its melting prior to extrusion, which makes it possible to obtain crosslinking up to 85% and ensure its complete uniformity.

Choosing which is better - cross-linked polyethylene, polypropylene or metal-plastic, the consumer must take into account all the pros and cons of each material. Changing your home water or heating system to PE-X is not always advisable. The material does not have a reinforcing layer, which is in metal-plastic, but it easily withstands repeated freezing and heating, while its analogue under such operating conditions will become unusable, cracking along the walls. The advantage is also the high reliability of the welded seam.Metalloplast often exfoliates during operation; at a medium pressure above 40 bar, it simply breaks.

Polypropylene - a material that has long been considered as a non-alternative replacement for metal in private housing construction. But this material is very capricious in installation, with a decrease in atmospheric temperatures, it is quite difficult to assemble a line qualitatively. In case of errors in the assembly, the permeability of the pipes will inevitably deteriorate, and leaks will appear. PP-products are not suitable for laying in floor screeds, hidden wiring in walls.

XLPE is devoid of all these disadvantages.... The material is supplied in coils of 50-240 m, which allows to significantly reduce the number of fittings during installation. The pipe has a memory effect, restoring its original shape after its distortion.

If we consider all 3 types of plastic pipes in comparison, we can say that it all depends on the operating conditions. In urban housing with a main supply of water and heat, it is better to install metal-plastic, well adapted to a wide range of operating pressures and constant temperature conditions. In suburban housing construction, the leadership in the laying of communal systems today is firmly held by cross-linked polyethylene.

Among the brands on the market, you can find many well-known companies that produce PE-X pipes using different technologies. The most famous of them deserve special attention.

• Rehau... The manufacturer uses peroxide technology for crosslinking polyethylene, produces pipes with a diameter of 16.2-40 mm, as well as the necessary components for their installation. The Stabil series has an oxygen barrier in the form of aluminum foil, it also has the lowest coefficient of thermal expansion. The Flex series has pipes of non-standard diameters up to 63 mm.

• Valtec... Another recognized market leader. In production, the silane method of cross-linking is used, the available pipe diameters are 16 and 20 mm, the installation is carried out by the crimping method. Products are considered reliable, focused on laying internal hidden communications.

• Uponor... The manufacturer manufactures products with a polymer-based diffusion barrier. For heat supply systems, Radi Pipe products with a diameter of up to 63 mm and an increased wall thickness are intended, as well as the Comfort Pipe Plus line with an operating pressure of up to 6 bar.

These are the main manufacturers known far beyond the borders of the Russian Federation. The products of international companies have a lot of advantages: they are certified according to stricter standards and comply with hygiene standards. But the cost of such products is significantly higher than the offers of little-known Chinese brands or Russian companies.

The choice of products made of cross-linked polyethylene is most often carried out before laying internal and external communications. When it comes to pipes, it is recommended to pay attention to the following parameters.

1. Visual properties... The presence of roughness on the surface, thickenings, distorting or violating the established wall thickness is not allowed. Defects do not include minimal waviness, longitudinal stripes.
2. Uniformity of material staining... It should have a uniform color, a surface free of bubbles, cracks, and foreign particles.
3. Mode of production... The best properties are possessed by cross-linked polyethylene made by the peroxide method. For silane products, it is imperative to check the hygiene certificate - it must comply with the standards of drinking or technological pipelines.
4. Specifications... They are indicated in the marking of the material and products from it.It is important to figure out from the very beginning which diameter and thickness of the pipe walls will be optimal. The presence of an oxygen barrier is required if the pipe is used in the same system with metal counterparts.
5. Temperature regime in the system. Cross-linked polyethylene, although it has a calculated heat resistance of up to 100 degrees Celsius, is still not intended for systems with an ambient temperature of more than +90 degrees. With an increase in this indicator by only 5 points, the service life of products decreases tenfold.
6. Manufacturer's choice. Since XLPE is a relatively new, high-tech material, it is better to choose it from well-known brands. Among the leaders are Rehau, Unidelta, Valtec.
7. Production cost. It is lower than that of polypropylene, but still quite high. The price varies depending on the stitching method used.

Considering all these points, it is possible to choose products made of cross-linked polyethylene with the desired characteristics without unnecessary trouble.

The following video describes the installation of XLPE products.