Recent advances in PE-RT developments: unleashing the potential of metallocene technology for pressure pipes [PERT]

« Single site catalyst » or « metallocene » technology is successfully used since many years for the production of linear low density film grades thanks to a unique combination of processability, mechanical and optical properties. The huge potential of this catalyst platform to produce PE grades for hot and cold water pipes is demonstrated in this paper. In the first stage of this study, small scale tests have been developed to assess the influence of the crystalline and molecular structure of PE on the long term hydrostatic strength at high temperature. In a second step, the small scale tests have been used to compare - with respect to high temperature performance - the single site catalyst technology to different conventional catalyst technologies like Chromium and Ziegler-Natta. It has been demonstrated that the single site catalyst technology improves significantly the mechanical properties at high temperature and is by far the best candidate for the development of an optimized PE-RT grade with well balanced properties. The outstanding properties can be explained by the unique microstructure created by our proprietary single site catalyst. Indeed, this catalyst leads to a specific comonomer distribution along the polymer chains by forcing the incorporation of comonomer on the longest chains. This property is well known to enhance the stress crack resistance and long term performance at high temperature. Beyond the superior mechanical strength at high temperature – as evidenced by the regression curve according to ISO 9080 – and the very easy processing, this new generation of highly flexible pipes also exhibits excellent oxidative, chlorine, chemical and impact resistance. The use of these novel PE-RT type materials is no longer limited to domestic hot & cold water pipes  : their outstanding characteristics open the door to new industrial applications. Keywords : PE-RT, single-site, ESCR, chlorine resistance