Plastic Pipes Conference Association # 2006 Washington DC
Polyethylene, especially PE100 Resin has been steadily increasing its use in pressure pipes for water and gas based on its superior property balance. Of all the properties required for PE100, when we consider the defects on the pipe surface and the stress concentrations on the fitting of complicated shape, the most important for the lifetime of pipe should be the resistance to Slow Crack Growth (SCG). Recent requirements for cost reduction by no-dig or no-sand installation have been enhancing the need for the improvement of SCG resistance. Requirements to Rapid Crack Propagation (RCP) for higher operating pressure and no sag for large diameter - thick wall pipe are also increasing. To meet these requirements, we investigated the relationship between molecular architecture and resin properties in detail, and we optimized the molecular weight, molecular weight distribution, co-monomer, co-monomer distribution using our advanced multi-modal polymerization process and high activity catalyst. Our new PE100 resin has the Notch Pipe Test result of more than 17,000 h. This value is far above the typical values of PE100 resins so far on the market and more than 3 times greater than the requirement for PEX pipe. It has the RCP-S4 value of more than 25 bar, and its designed high shear sensitivity also gives a good no sag property without sacrificing extrusion/injection processing properties. We believe that continuous improvements of resin performance will help PE pipe to continue to expand, meeting more demanding new installation methods and contributing to enhance the safety margin of the PE pipe system.
Author(s) : Tomomi Hiramoto, Tetsuya Yoshikiyo
Polyethylene has been used for various pipe applications. In particular the use of PE100 material has been expanding in pressure pipes for gas and water service. In general, PE100 materials have very high molecular weight component in order to improve the performance of durability, so they have high viscosity and...