Plastic Pipes Conference Association # 2001 Munich
Berthold, Boehm, Enderle, Lackner, Lilge, Schulte
The new generation pipe materials PE 100 are now well positioned in the market because of their unusual combination of mechanical properties. Major advantages are high resistance versus slow crack growth combined with superior stiffness. These new PE 100 resins show very high long term hydrostatic strength for pressurized pipes used for drinking water systems and sewage lines as well.1 They further have a much higher resistance versus rapid crack propagation and can therefore be used for gas distribution systems at higher pressures.2 PE 100 resins are polymer alloys having a bimodal molecular mass distribution and an inverse comonomer composition distribution controlled by the polymerization process. A highly active 3rd generation Ziegler-catalyst system is used in a cascade slurry process to produce in a 1st reactor a low molecular mass homopolymer and in a 2nd reactor a high molecular mass copolymer. A further improvement was recently achieved using Basell´s new Advanced Cascade Process (ACP). The new pipe resins show better processibility and a significant higher melt strength to avoid sagging of the polymer melt during pipe extrusion. It is therefore qualified to produce large pipes with high wall thickness. This resin further enjoys a better stiffness environmental stress crack resistance (ESCR) correlation. This new material has successfully been tested in the market.
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