1.PEX Cross-Link System
In this system, the incoming heat to the radiator is 90° C and the outcoming heat is 70° C. PEX (PE-Xb and Pe-Xc) pipes are used in this system.
‘PE’ stands for the raw material and ‘X’ indicates the cross linkage. PEX means cross-linked polyethylene. In this manner, a three dimensional molecuar formation is achieved. The main priciple in cross-linking is to connect the Carbon atoms at the two polyethylene chains which normally stands individually. Cross-link system maintains high temperature and pressure resistancy for the pipes.
| 2. PEX Types | ||||||
| Types regarding the cross-linkage and the density of the cross-links. | ||||||
| Standard | PEX Type | Definition | Cross link density | |||
| DIN16892 | PE-Xa | Pipes cross-linked with peroxide | 75% | |||
| DIN16892 | PE-Xb | Pipes cross-linked with hyrdosilicon | 65% | |||
| DIN16892 | PE-Xc | Pipes cross-linked with radiation (electron bombing) | 60% | |||
| DIN16892 | PE-Xd | Pipes cross-linked with azo | 60% | |||
2.1. PE-Xa PIPEs
Formed with the peroxide that is mixed into the raw material during the extrusion. Peroxide is the chemical that is activated by heat and forms free radicals for the cross-link. These kind of pipes are called PE-Xa cross-link pipes.
2.2. PE-Xb PIPEs
Pipes are connected crossly to the polyethylene Xylan with hydrosilicon during and after the process. These kind of pipes are called PE-Xb cross link pipes.
2.3. PE-Xc PIPEs
Radiation (electron bombarding) is applied to the polyethylene to maintain cross-linked chains. These kind of pipes are called PE-Xc cross-link pipes.
2.4. PE-Xd PIPEs
The pipes that are maintained by cross linking the chains at the Azo (nitro-amine) environment are called PE-Xd cross-link pipes.
As being defined by the same standarts, all PEX pipes are proper functionally regardless of the production style. However depending on the cross-link method some differences are observed.
DIN 16892, DIN 16893 standarts defined the required cross-link density increases the material`s strength. That helps it to be resistant to higher perssure and temperatures.
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