Electric cable with improved temperature ageing resistance
An electric cable has at least one semi-conductive layer obtained from a polymer composition having at least one polypropylene-based thermoplastic polymer material, at least one first antioxidant and at least one metal deactivator.
1. Electric cable comprising:
at least one elongated electrically conductive element; and
at least one semi-conductive layer surrounding said elongated electrically conductive element,
wherein the semi-conductive layer is obtained from a polymer composition comprising at least one polypropylene-based thermoplastic polymer material, at least one first antioxidant,
and at least one metal deactivator,
wherein the semi-conductive layer is a non-crosslinked layer,
wherein the polymer composition further comprises a dielectric liquid
wherein the polypropylene-based thermoplastic polymer material comprises an amount of less than 10% by weight of polar polymer(s), with respect to the total weight of the polypropylene-based thermoplastic polymer material.
2. Electric cable according to claim 1 , wherein the first antioxidant is selected from hindered phenols, aromatic amines, and nitrogen-containing aromatic heterocyclics.
3. Electric cable according to claim 1 , wherein the polymer composition comprises at least 0.3% by weight of the first antioxidant, based on the total weight of the polymer composition.
4. Electric cable according to claim 1 , wherein the metal deactivator is selected from nitrogen-containing aromatic heterocycles, and aromatic compounds comprising at least one function —NH—C(═O)—.
5. Electric cable according to claim 1 , wherein the polymer composition comprises at least 0.2% by weight of the metal deactivator, based on the total weight of the polymer composition.
6. Electric cable according to claim 1 , wherein the polymer composition comprises at least 6% by weight of conductive filler, based on the total weight of the polymer composition.
7. Electric cable according to claim 1 , wherein the polypropylene-based thermoplastic polymer material comprises a propylene copolymer P 1 .
8. Electric cable according to claim 7 , wherein the polypropylene-based thermoplastic polymer material comprises a random propylene copolymer or a heterophasic propylene copolymer, as propylene copolymer P 1 .
9. Electric cable according to claim 1 , wherein the polypropylene-based thermoplastic polymer material comprises a random propylene copolymer and a heterophasic propylene copolymer, or two different heterophasic propylene copolymers.
10. Electric cable according to claim 1 , wherein the polypropylene-based thermoplastic polymer material can further comprise an olefin homopolymer or copolymer P 2 .
11. Electric cable according to claim 1 , wherein the polypropylene-based thermoplastic polymer material comprises at least 50% by weight of propylene polymer(s), based on the total weight of the polypropylene-based thermoplastic polymer material.
12. Electric cable according to claim 1 , wherein the polymer composition further comprises a second antioxidant different from the first antioxidant.
13. Electric cable according to claim 12 , wherein the polymer composition comprises at least 0.2% by weight of the second antioxidant, based on the total weight of the polymer composition.
14. Electric cable according to claim 1 , wherein the semi-conductive layer has a reduction in tensile strength after temperature ageing of at most 40%.
15. Electric cable according to claim 1 , wherein the semi-conductive layer has a reduction in elongation at break after temperature ageing of at most 50%.
16. Electric cable according to claim 1 , wherein said electric cable further comprises an electrically insulating layer.
17. Electric cable according to claim 1 , wherein the dielectric liquid includes a mineral oil.