General Information on Cross Linked Polyethylene The applications of plastic pipes are so common in our daily life that these types of pipes have come to replace conventional pipes on a large scale. One of the most important breakthroughs is their use in hot water networks. The raw materials used are polypropylene (PP) and cross-linked polyethylene (PE-X) produced from a special composition of high density polyethylene (HDPE). In HDPE, a reaction is induced in the double bonds, so that many of them get connected and by the help of silane molecules, a three-dimensional homogenous network is created of high molecular weight. The final product (crosslinked polyethylene) has excellent performance at high temperatures combined with high pressures, has improved resistance to impact and to chemicals and has a longer lifespan. Today, 50 years after their first applications and based on their successful history, Pex pipes are constantly growing in demand gaining a significant market share.
All aforementioned methods achieve the same results in PE-X pipes and meet the DIN 16892/16893 and the recent European EN ISO 15875-1/2 standards. Additionally Como-pex pipes meet the ASTM F876, NSF-ANSI 14/61 and CSA B137.5. Their only difference lies in the cross-linking degree specified in the US and EN standards. 70% for method –a, 65% for method –b, and -60% for method –c. For example, a pipe with a cross-linking degree of 68% that has been produced using method –a does not meet the specifications, while a pipe with the same cross-linking degree produced by method –b does. The Como-pex pipes of Interplast are produced using the –b method. It is a method that has managed to improve the characteristics of Pex pipes since the fact that cross-linking degree continues over time, which is considered as a huge advantage, leading as such to exceptional properties of the product during its use. Furthermore, -b method pipes, in varying degrees of cross-linking, are more homogenous in their behavior. Characteristic is the ever increasing demand of method –b in the markets, with ever increasing trends in the recent years compared to cross-linked manufactured products of the other alternatives.
GLOBAL CONSUMPTION IN TONS PEX
AREA PE-Xa PE-Xb PE-Xc
PE-X OVERALL
Europe
24.000 38.000 20.000
82.000
Middle East & Africa
1.300
8.000 1.800
11.100
Russia
200
4.000
4.200
North America South America Asia (Pacific)
9.000 14.000
23.000
Cross-linking methods The most common cross-linking methods used in industrial production are:
5.000
5.000
3.000 20.000
23.000 148.300
Total:
37.500 89.000 21.800
Consumption 2007, Source: Pex Association
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