Polyethylene composition having high swell ratio, fnct and impact resistance

A polyethylene composition having the following features:

• 1) a density from 0.945 to 0.958 g/cm3 determined according to ISO 1183 at 23° C.;
• 2) a ratio MIF/MI10 from 2 to 10, where MIF is the melt flow index at 190° C. with a load of 21.60 kg, and MI10 is the melt flow index at 190° C. with a load of 10 kg, both determined according to ISO 1133;
• 3) a η0.02 from 200,000 to 800,000 Pa·s, wherein η0.02 is the complex shear viscosity at an angular frequency of 0.02 rad/s, measured with dynamic oscillatory shear in a plate-plate rotational rheometer at a temperature of 190° C.;
• 4) a long-chain branching index, LCBI equal to or lower than 0.80, wherein LCBI is the ratio of the measured mean-square radius of gyration Rg, measured by GPC-MALLS, to the mean-square radius of gyration for a linear PE having the same molecular weight, at a molecular weight of 1,000,000 g/mol;
• and
• 5) a ratio η0.02/1000)/LCBI, which is between η0.02 divided by 1000 and LCBI, equal to or greater than 350.