Polyethylene is a material that is used in various industries. Products from it are also used in everyday life. Conventional polyethylene retains its strength up to a temperature of 130 degrees. However, often there is a need to use this material in more severe conditions, at a higher temperature and pressure conditions, for example, in heating and hot water supply systems.
This need has led to the search for ways to obtain more durable material. The technology found 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 to mean a process in which the links of molecules, due to the formation of cross-links, are connected into a three-dimensional wide-mesh network.
Depending on the applied effect, chemical and physical crosslinking is distinguished. In the latter case, pipes (cross-linked polyethylene is used to create these products) are irradiated with hard x-rays. This technology is very productive, and in a minute you can get up to 80 meters of material.
The disadvantage of this method is that cross-linked polyethylene has unevenness in the thickness of the pipe. The inner side produces the lowest percentage of the combination of molecules, while the outer side, on the contrary, has the highest.
Accordingly, the properties of the product in volume differ. The result is a crosslinked polyethylene of category C (PEX).
When using the chemical method, a special substance silane is used to replace the hydrogen atoms in the molecules. Accordingly, a silane crosslinked polyethylene is obtained. Pipes during production pass through a special bath filled with a substance. That allows you to make the process of cross-linking from the inner and outer surfaces deeper into the walls of the pipe. This technology makes it possible to obtain pipes with a high percentage of processing, and the material is designated PEX-B.
There is a technique for treating polyethylene with nitrogen radicals; the resulting material is designated PEX-D. However, this technology is not used due to low efficiency.
Crosslinking with peroxides is also carried out. In this case, the production process involves mixing peroxide and polyethylene, after which cross-linked polyethylene of the PEX-A group is obtained in the molten state and under the influence of high temperature.
Pipes from materials (groups B, C) are used for water supply and heating, however, they have a number of limitations that are associated with the strength and ductility of products.
The most successful are pipes made of group A polyethylene, they have high fatigue strength, crack resistance, shape stability, flexibility, and impact resistance.
Cross -linked polyethylene heating pipes are widely used for individual, civil and industrial construction. With their help, they carry out floor radiator wiring and create floor heating systems.