Copolymer of ethylene and an alpha-olefin, having a density>0.930 g/cm 3 ,melt index (g/10 min)>4, molecular weight distribution (MWD)>3.0, and FNCT>250 hours. The copolymer is suitable for use in rotomolding applications. The copolymer possesses improved impact strength, improved permeation resistance and improved environmental stress crack resistance and may suitably be prepared by use of metallocene catalysts.
1. A rotomoulded article comprising a copolymer of ethylene and an alpha-olefin, said copolymer having a
(a) density>0.930 g/cm 3 ,
(b) melt index >4, measured at 2.16kg and 190° C.,
(c) molecular weight distribution (MWD)>3.0,
(d) full notch creep test (FNCT)>250 hours, measured at 23.0° C. and 6.00 MPa, and
(e) a Composition Distribution Branch Index (CDBI) in the range 55 to 75%.
2. A rotomoulded article comprising a copolymer of ethylene and an alpha-olefin, said copolymer having a
(a) density>0.930 g/cm 3 ,
(b) melt index >4, measured at 2.16kg and 190° C.,
(c) molecular weight distribution (MWD)>3.5,
(d) full notch creep test (FNCT)>500 hours, measured at 23.0° C. and 6.00 MPa, and
(e) a Composition Distribution Branch Index (CDBI) in the range 55 to 75%.
3. The rotomoulded article according to claim 1 having a melt index >6.
4. The rotomoulded article according to claim 1 having a molecular weight distribution >3.5.
5. The rotomoulded article according to claim 1 having a FNCT of >450 hours.
6. The rotomoulded article according to claim 1 having a FNCT of >500 hours.
7. The rotomoulded article according to claim 1 having a whiteness index (WI) >40.
8. The rotomoulded article according to claim 2 having a whiteness index (WI) >60.
9. The rotomoulded article according to claim 2 , wherein the alpha-olefin has C4-C12 carbon atoms.
10. The rotomoulded article according to claim 9 wherein the alpha-olefin is 1-hexene.