Polypropylene: 100 Years of Service Life
Polyethylene pipes fully meet the high requirements for supply and disposal networks as well as telecommunications. The key advantage lies in the homogeneous, material-bonded connection of the pipes by means of welding. The low weight and high flexibility allow for easy and environmentally friendly installation. Throughout the entire service life, there is no corrosion, deposits, or encrustation. The material possesses excellent mechanical properties, so that no damage to the polyethylene pipes is to be expected when properly installed. And last but not least, the resistance to almost all polar solvents as well as acids, alkalis, water, and alcohols makes polyethylene an ideal material for pipe production.
Standardized Service Life
The polyethylene types for pipes manufactured today by the leading raw material producers meet the requirements of DIN 8074/75 for a scientifically and normatively validated service life of more than 100 years. How is this possible, given that polyethylene is a raw material that has only been produced for approximately 50 years? With the help of short-term tests at a temperature of 80°C, the service life of PE pipes can be extrapolated using the Arrhenius approach.
Development of New Catalysts
Polyethylene pipe materials are classified according to their behavior in the long-term internal pressure test. The first grades were classified as PE 63: The long-term strength of pipes manufactured from them is at least 6.3 MPa at 20°C (water) after 50 years. Through the development of new catalysts, it has been possible to produce polymer blends of long-chain and short-chain polyethylene molecules, which equally increased toughness and stiffness. Such modern bimodal polyethylenes achieve a long-term strength of over 10.0 MPa at 20°C (water) after 50 years and are thus classified as PE 100.
Two Advancements
The higher strength of the pipe material enables two advancements in PE 100 pipes compared to pipes made of PE 80 – to increase the operating pressure with the same wall thickness or to reduce the wall thickness while maintaining the same operating pressure. Alternatively, an increase in the safety factor is also possible.
PE 100-RC
The further development of the proven PE 100 materials with regard to stress crack resistance makes it possible to meet the special requirements of alternative installation techniques. These special materials are characterized by a service life in the FNCT (Full Notch Creep Test) or in the point load test at 80°C; Sigma 4 N/mm²; 2% Arkopal N-100 of at least 8,760 hours. Only PE 100 materials that meet this requirement may be designated as PE 100-RC in the future. For comparison: the minimum requirement for the approval of PE 100 at the German Institute for Building Technology is only 300 hours under the same test conditions.
PE-RT
PE-RT (Polyethylene of Raised Temperature Resistance) represents a further development aimed at enabling the use of polyethylene even at elevated operating temperatures. In contrast to the cross-linked polyethylene types (PEX), this was achieved by modifying the structural composition of the PE macromolecules, without impairing the advantageous properties such as the good stress crack resistance or toughness of unmodified polyethylene.
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Advantageous Properties at a Glance