Novel copolymers are described comprising ethylene and alpha-olefins having (a) a density (D) in the range 930 - 960 kg/m3 (b) a melt index (MI2) in the range 0.1 - 3.5 g/10 min (c) a melt elastic modulus G' (G"= 500 Pa) in the range 40 to 150 Pa, and (d) a ratio of complex dynamic shear viscosities ?*(0.1)/?*(100) in the range 1.5 to 5.5. The novel copolymers are particularly suitable for use as Polyethylenes of Raised Temperature Resistance (PE-RT) for use in hot water piping systems. The novel copolymers may be prepared by use of metallocene catalyst systems. Pipes having a time to failure of = 500 hrs measured according to ISO 1167 at 110oC and 2.6 MPa prepared in a single reactor are also disclosed.
