Polyethylene compositions and their use in the manufacture of pipes

摘要

The invention relates to a polyethylene composition with a bimodal molecular weight distribution comprising at least a low molecular weight (LMW) component and a high molecular weight (HMW) ethylene copolymer component, wherein the polyethylene composition has a ductile-brittle transition temperature of less than -20°C, a total impact Charpy energy of more than 200 J/m at 23°C according to ASTM D6110-2004e1, and a PENT test value of more than 750 hours according to ASTM F1473: 2001, and the LMW component has a comonomer content of less than 0.1 branches per 1000 carbon atoms as determined by 13 C NMR spectroscopy and a double bond final chain content between 0.2 to 10 double bonds per 1000 carbon atoms, as determined by 13 C NMR spectroscopy. The invention also relates to a process for preparing said composition and its use in the manufactures of pipes.