Electric cable comprising a metal layer

Abstract

An electric cable has at least one elongated electrical conductor (1), at least one electrically insulating layer (2) surrounding the elongated electrical conductor (1), and at least one metal layer (3) surrounding electrically insulating layer (2). The metal layer (3) has metal nanowires.

Claims

1. An electric cable comprising: at least one elongated electrical conductor, at least one electrically insulating layer surrounding said elongated electrical conductor, at least one metal layer surrounding said electrically insulating layer, wherein the metal layer is obtained from a composition comprising metal nanowires and a hydroxylated solvent, and wherein the aspect ratio of the metal nanowires making up the metal layer is of at least 50.

2. The electric cable according to claim 1, wherein at least one of the metal nanowires has one of its dimensions of at most 400 nm.

3. The electric cable according to claim 1, wherein at least one of the metal nanowires comprises at least one metal chosen from silver, gold, copper, nickel and one of their mixtures.

4. The electric cable according to claim 1, wherein at least one of the metal nanowires comprises at least 10% by weight of metal, with respect to the total weight of said nanowire.

5. The electric cable according to claim 1, wherein the metal layer comprises at least 5% by weight of metal nanowires and preferably at least 10% by weight of metal nanowires, with respect to the total weight of the metal layer.

6. The electric cable according to claim 1, wherein the metal layer is obtained from a composition comprising metal nanowires, and at least one polymer and/or at least one polymer precursor.

7. The electric cable according to claim 1, wherein the metal layer is directly in physical contact with the electrically insulating layer.

8. The electric cable according to claim 1, wherein the thickness of the metal layer ranges from 20 nm to 1.0 mm.

9. The electric cable according to claim 1, wherein the electrically insulating layer is a polymeric layer comprising at least one olefin polymer, preferably at least one ethylene polymer and particularly preferably at least one fluoroethylene polymer (FEP).

10. The electric cable according to claim 1, wherein the electrically insulating layer is a hydrophilic layer.

11. The electric cable according to claim 1, wherein said cable is additionally comprises an exterior protective sheath surrounding the metal layer.

12. A process for the manufacture of a cable according to claim 1, wherein said process comprises the following stage: iii. forming the metal layer around the electrically insulating layer.

13. The process according to claim 12, wherein said manufacturing process additionally comprises the following stage ii, prior to stage iii: ii. treating the exterior surface of the electrically insulating layer.

14. The process according to claim 13, wherein stage ii consists in oxidizing the exterior surface of the electrically insulating layer.

15. The electric cable according to claim 1, wherein the aspect ratio of the metal nanowires making up the metal layer is of at least 100.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the present invention will become apparent in the light of the description of non-limiting examples of an electric cable according to the invention, given with reference to the single figure.

(2) FIG. 1 represents a diagrammatic view in lateral section of an electric cable in accordance with the invention.

DETAILED DESCRIPTION

(3) For reasons of clarity, only the elements essential to the understanding of the invention have been presented, diagrammatically, without observing a scale.

(4) The electric cable, illustrated in FIG. 1, is a “coaxial” cable, comprising a central elongated electrically conducting element 1, in particular made of copper or of aluminium, comprising a plurality of metal wires, the electrically conducting element having a nominal cross section of 0.0020 mm.sup.2 (diameter of 0.05 mm).

(5) The electric cable additionally comprises several layers positioned successively and coaxially around this conducting element 1, namely: an electrically insulating layer 2 of a fluoroethylene polymer (FEP) sold by Chemours under the reference FEP 106, a metal layer 3 comprising metal nanowires according to the invention, a protective sheath 4 of a fluoroethylene polymer (FEP) sold by Chemours under the reference FEP 106.

(6) The layers 2 and 4 are conventional polymeric layers, extruded by techniques well known to a person skilled in the art.

(7) The metal layer 3 of the electric cable of FIG. 1 can be produced according to the examples which will follow.

Exemplary Embodiments of an Electric Cable According to the Invention

(8) 1. Starting from a Composition Comprising Metal Nanowires and a Solvent

(9) An electric cable comprising a central elongated electrical conductor made of copper surrounded by an electrically insulating layer of a fluoroethylene polymer (FEP) sold by Chemours under the reference FEP 106 is treated by oxygen plasma under the following conditions: 100 millilitres of oxygen per minute; 120 watts; for 90 seconds.

(10) The electric cable thus treated is then passed under a system for spray coating with a liquid composition comprising a solvent of the isopropanol type and silver nanowires at 0.5 gram per litre in the liquid composition, said silver nanowires having an aspect ratio equal to 125 (cylindrically shaped nanowires having the following dimensions: length of 10 μm and diameter of 80 nm) and being manufactured according to the process described in the paper Nanotechnology, 24 (2013), 215501 (6 pp). The liquid composition is nebulized under air.

(11) Prior to the nebulization of the liquid composition, the electric cable is preheated to 90° C., the solvent thus evaporating during the deposition.

(12) The metal layer is thus formed around the electrically insulating layer and has a thickness of 200 nm.

(13) The metal layer comprises 100% by weight of metal nanowires, with respect to the total weight of the metal layer.

(14) It makes possible efficient shielding with a sheet resistance of less than 10 ohms/square.

(15) 2. Starting from a Composition Comprising Metal Nanowires and an Organic Polymer Precursor

(16) An electric cable comprising a central elongated electrical conductor made of copper surrounded by an electrically insulating layer of a fluoroethylene polymer (FEP) sold by Chemours under the reference FEP 106 is treated by passing into a liquid medium based on nitric acid (mixture of 40% by weight of nitric acid and of 60% by weight of sulfuric acid) for 30 seconds and is then dried with hot air.

(17) The electric cable thus treated is then dipped in a liquid composition comprising: epoxy resin precursors, such as, for example, the compounds referenced Araldite CY 179CH (epoxy resin) and Aradur 917 (hardener of the epoxy resin), which are sold by Huntsman; and copper nanowires at 1 gram per litre in the liquid composition, said copper nanowires having an aspect ratio equal to 500 (cylindrically shaped nanowires having the following dimensions: length of 50 μm and diameter of 100 nm) and being manufactured according to the process described in the paper Nano Research, 2014, 7(3), 315-324.

(18) At the dipping outlet, the electric cable thus dipped is heated at a temperature of 150° C. for 2 minutes in order to obtain the cured resin containing the copper nanowires around the electrically insulating layer.

(19) The metal layer is thus formed around the electrically insulating layer and has a thickness of 300 nm.

(20) The metal layer comprises 50% by weight of metal nanowires, with respect to the total weight of the metal layer.

(21) It makes possible efficient shielding with a sheet resistance of less than 10 ohms/square.

(22) 3. Starting from a Composition Comprising Metal Nanowires and at Least One Organic Polymer

(23) An electric cable comprising a central elongated electrical conductor made of copper surrounded by an electrically insulating layer of a fluoroethylene polymer (FEP) sold by Chemours under the reference FEP 106 is treated by physical oxidation of the argon plasma type for 120 to 180 seconds, with a power of 300 watts.

(24) The electric cable thus treated is then dipped in a liquid composition comprising: 1.8% by weight of silver nanowires having an aspect ratio equal to 125 (cylindrically shaped nanowires having the following dimensions: length of 10 μm and diameter of 80 nm), said silver nanowires being manufactured according to the process described in the paper Nanotechnology, 24 (2013), 215501 (6 pp), 1.2% by weight of a polysaccharide polymer of the carboxymethyl cellulose (CMC) type, sold by Sigma-Aldrich under the reference sodium carboxymethyl cellulose, 40% by weight of methanol as solvent, and 57% by weight of water as solvent.

(25) The amounts expressed in the above liquid composition are expressed as percentages by weight, with respect to the total weight of the liquid composition.

(26) At the dipping outlet, the electric cable thus dipped is dried until the solvent has evaporated. The cable can subsequently be heated at a temperature of 230° C. for 2 minutes in order to improve its mechanical strength and the electrical resistance.

(27) The metal layer is thus formed around the electrically insulating layer and has a thickness of 800 nm.

(28) The metal layer comprises 60% by weight of metal nanowires, with respect to the total weight of the metal layer.

(29) It makes possible efficient shielding with a sheet resistance of less than 10 ohms/square and an attenuation of at least 20 decibels (dB) according to Standard IEC 62153-4-10 (2015).