Polyethylene is a material that is used in various sectors of the economy. Products from it are also used in everyday life. Ordinary polyethylene retains its strength up to a temperature of 130 degrees. However, it often becomes necessary to use this material in more severe conditions, at higher temperatures and pressures, for example, in heating and hot water systems.
This need led to the search for ways to obtain a more durable material. The found technology made it possible to obtain cross-linked polyethylene, which has a higher molecular weight compared to conventional material and has improved characteristics. Cross-linking is understood as a process in which the links of molecules are connected into a three-dimensional wide-mesh network due to the formation of cross-links.
Depending on the impact applied, chemical and physical crosslinking is distinguished. In the latter case, pipes (cross-linked polyethylene is used to create these products) are irradiated with x-ray hardrays. This technology is very productive, and up to 80 meters of material can be obtained in a minute.
The disadvantage of this method is that the cross-linked polyethylene is uneven in the thickness of the pipe. The inner side has the lowest percentage of molecular bonding, while the outer side, on the contrary, has the highest.
Accordingly, the properties of the product in volume also differ. The result is cross-linked polyethylene of category C (PEX).
When using the chemical method, a special substance silane is used to replace hydrogen atoms in molecules. Accordingly, a silane crosslinked polyethylene is obtained. Pipes during production pass through a special bath filled with a substance. This makes it possible to make the stitching process uniform from the inner and outer surfaces deep into the pipe walls. This technology makes it possible to obtain pipes with a high percentage of processing, and the material is designated PEX-B.
There is a method of processing polyethylene with nitrogen radicals, the resulting material is designated PEX-D. However, this technology is not used due to low efficiency.
Cross-linking with peroxides is also performed. In this case, the production process includes mixing peroxide and polyethylene, after which, in the molten state and under the influence of high temperature, cross-linked polyethylene of the PEX-A group is obtained.
Pipes made of materials (groups B, C) are used for water supply and heating, however, they have a number of limitations thatassociated with the strength and ductility of products.
The most successful are the pipes made of group A polyethylene, they have high fatigue strength, crack resistance, shape stability, flexibility, impact resistance.
XLPE heating pipes are widely used for individual, civil and industrial construction. With their help, floor-by-floor radiator wiring is carried out and floor heating systems are created.
