FR3068504A1 - CABLE COMPRISING AN ELECTRICALLY CONDUCTIVE ELEMENT COMPRISING METALLIC CARBON FIBERS - Google Patents

Abstract

The present invention relates to an electrical cable (1) comprising at least one elongated electrically conductive element (2) surrounded by at least one polymeric layer (4), said elongated electrically conductive element (2) comprising a metallized carbon fiber or at least one set of metallized carbon fibers (3), characterized in that the metallized carbon fiber or said set (3) of metallized carbon fibers has a specific conductivity of at least 8%.

Description

CABLE COMPRISING AN ELECTRICALLY CONDUCTIVE ELEMENT COMPRISING METALLIZED CARBON FIBERS

The invention relates to an electric cable comprising at least one elongated electrically conductive element comprising a metallized carbon fiber or at least one set of metallized carbon fibers.

Electric cables are widely used for the transport of electrical energy as well as for data transmission. Electric cables must have different properties depending on their use and in particular, good electrical conductivity, good mechanical resistance, while being as light as possible.

An electric cable conventionally comprises an electrically conductive single-strand or multi-strand element, most often surrounded by an insulating material. The electrically conductive element is generally made of metallic materials such as, for example, copper or aluminum. However, the use of these metallic materials in electric cables has several drawbacks. Indeed, these metals can have mechanical properties not always adapted to the needs, a low availability and a high price. Furthermore, metals are materials of high density which poses a problem for the manufacture and installation of electric cables, in particular very long (more than 2 km), and in applications where the minimization of the mass of the systems is sought, such as for example in aeronautical systems.

The object of the present invention is to overcome the drawbacks of the prior art by providing a light and inexpensive electrically conductive element while having very good electrical conductivity and improved mechanical properties.

The present invention thus relates to an electric cable comprising at least one elongated electrically conductive element surrounded by at least one polymeric layer, preferably an electrically insulating polymeric layer, said elongated electrically conductive element comprising a metallized carbon fiber or at least one assembly of metallized carbon fibers, characterized in that the metallized carbon fiber or said set of metallized carbon fibers has a specific conductivity of at least 8%, and preferably at least 10%.

Thanks to the electric cable of the invention, the use of solid metal conductors is limited, or even avoided. The electric cable of the invention has good specific conductivity while having mechanical properties, such as tensile strength, thermal resistance, and / or flexibility (eg necessary for its winding and its installation), improved (s ) significantly. In addition, another advantage is that the electric cable of the invention has in particular very good physicochemical properties, such as a low thermal expansion of the electrically conductive element. Furthermore, the electric cable of the invention advantageously takes advantage of the low density of carbon fibers in comparison with the densities of metals. In addition, it has a lower linear mass than an electric cable comprising one or more metallic conductor (s) as the sole conductive element (s), and has a comparable manufacturing cost.

Elongated electrically conductive element

A carbon fiber is mainly composed of crystalline carbon atoms aligned more or less parallel to the axis of the carbon fiber. The carbon element content of a carbon fiber is generally between 90% and 99%, and essentially depends on the stages of the manufacturing process.

The metallized carbon fiber used in the present invention may include a carbon fiber surrounded by one or more metallic layer (s).

The set of metallized carbon fibers used in the present invention comprises several metallized carbon fibers, each of said metallized carbon fibers comprising a carbon fiber surrounded by one or more metallic layer (s).

The carbon fiber of the metallized carbon fiber or the carbon fibers of the set of metallized carbon fibers can (respectively) be one or more fibers (s) called (s) carbon-based. The term “carbon-based” means a fiber which may be composed of carbon, and more particularly of carbon nanofibers, carbon nanotubes and / or graphene.

A set of carbon fibers according to the invention comprises several carbon fibers which can be conventionally organized into carbon threads commonly known as "wicks". A carbon wire can comprise several thousand carbon fibers designated by the letter K, for example a wire of 12000 carbon fibers is called "12K".

The specific conductivity of at least 8% of the metallized carbon fiber or of the set of metallized carbon fibers advantageously allows said metallized carbon fiber or said set of metallized carbon fibers to be used as an element. electrically conductive elongated in an electric cable according to the invention.

The elongated electrically conductive element may preferably have a specific conductivity of at least 15%, preferably of at least 25%, and more preferably of at least 35%.

The specific conductivity of a material is expressed in S.ir ^ -kg ' ¹ , and corresponds to the ratio of its electrical conductivity expressed in Siemens per meter (S / m) divided by its density expressed in kg / m ³ .

The specific conductivity of a material, expressed in%, is determined relative to the specific conductivity at 20 ° C of pure annealed copper which is 6524.71 Sm ² .kg ' ¹ . The density at 20 ° C of pure annealed copper is 8890 kg.m ' ^3. The electrical conductivity (S / m) characterizes the ability of a material to let the electrons it contains move freely under the effect of an electric field and therefore allow the passage of an electric current.

In the invention, a set of metallized carbon fibers is defined as several metallized carbon fibers organized, for example, in parallel to one another. According to a possible variant, the carbon fibers of an assembly can be twisted or braided.

In the electric cable of the invention, the set of metallized carbon fibers can comprise at least 2 metallized carbon fibers, preferably at least 1000 metallized carbon fibers, preferably at least 3000 metallized carbon fibers, preferably at minus 6000 metallized carbon fibers, and more preferably at least 12000 metallized carbon fibers.

In the electric cable of the invention, the set of metallized carbon fibers can comprise at most 48,000 metallized carbon fibers, or even the set of metallized carbon fibers can comprise more than 48,000 metallized carbon fibers.

In the present invention, the elongated electrically conductive element can comprise:

- only metallized carbon fiber, and / or

- a single set or several sets of metallized carbon fibers, in particular at most 10 sets of metallized carbon fibers.

In a particular embodiment, the elongated electrically conductive element of the invention can also comprise at least one metallic conductor.

When the elongated electrically conductive element comprises several sets of metallized carbon fibers, each set may comprise a different number of metallized carbon fibers and / or a different metal constituting the metallic layer surrounding the carbon fibers.

The elongated electrically conductive element may also comprise additional elements such as for example one or more non-metallized carbon fibers.

In the present invention, the metal layer (s) of metallized carbon fiber (s) can (s) comprise at least one metal chosen from copper, zinc, tin, silver, aluminum, and their alloys. By “alloy” is meant the combination or mixture of at least two metals, in particular chosen from those listed above.

Preferably, the metal layer can comprise only copper or only a copper alloy.

When the metallized carbon fiber or metallized carbon fibers of a set of metallized carbon fibers are surrounded by several metallic layers, at least one of the metallic layers may comprise copper or a copper alloy, the other metallic layers which may comprise a different metal, in particular chosen from zinc, nickel, tin, silver, aluminum, and one of their mixtures.

The metal layer may be in direct physical contact with the carbon fiber of the metallized carbon fiber or with each carbon fiber of said set of metallized carbon fibers.

The metal layer can be linked by physical and / or chemical interactions, preferably by covalent bonding, to the carbon fiber to allow good adhesion of the metal layer to the carbon fiber.

An intermediate layer called "adhesion" can be placed between the carbon fiber and the metal layer of the metallized carbon fiber, in order to improve the adhesion of the metal layer around the carbon fiber. The intermediate layer may be a metallic layer, which may include one or more metals chosen from tin, nickel, copper, aluminum, silver, and one of their mixtures.

In the invention, the metal layer may have an average thickness of at least 100 nm, preferably at least 500 nm, and more preferably at least 1 µm.

Preferably, the metal layer may have a constant thickness over the entire length of the carbon fiber or carbon fibers of a set of metallized carbon fibers. A constant thickness means that the thickness of the metallic layer can vary by at most ± 30% compared to the average thickness of the metallic layer, preferably by at most ± 20% compared to the average thickness of the metal layer, and more preferably at most ± 10% relative to the average thickness of the metal layer.

In the invention, the thickness of the metal layer can be adapted according to the nature of the metal or metals which it comprises and according to the desired conductivity. In particular, a metal layer comprising a metal having a low conductivity may be thicker than a metal layer comprising a metal having a higher conductivity.

The metallization of the carbon fiber or carbon fibers of a set of carbon fibers can be carried out by a process chosen from electroplating, electroplating (known as "electroplating"), l electroplating without electric current (known as “electroless plating”), thermal evaporation under vacuum (“heated evaporation”), evaporation by electron beam (“electron beam evaporation”), sputtering ( "Sputtering"), ion-assisted deposition ("ion assisted deposition"). According to a preferred embodiment, the metallization of the carbon fiber (s) can be carried out by the process by electrodeposition.

In the invention, the metallized carbon fiber (s) can have a length ranging from 100 m to 200 km, preferably ranging from 100 m to 10 km, and more preferably ranging from 100 m at 3 km. Thanks to the use of a metallized carbon fiber or a set of metallized carbon fibers, good specific conductivity and good mechanical properties are maintained over the entire length of the electric cable.

The carbon fiber (non-metallized) of a metallized carbon fiber or the carbon fibers (non-metallized) constituting the set of metallized carbon fibers can (have) a diameter ranging from 0.5 μm to 100 pm, preferably ranging from 1 pm to 50 pm, and more preferably ranging from 5 pm to 10 pm. These values are given for carbon fiber without taking into account the possible metallic layer (s) covering it.

The metallized carbon fiber or the set of metallized carbon fibers may have a cross section ranging from 0.2 pm ² to 1000 pm ² , preferably ranging from 1 pm ² to 500 pm ² , and more preferably ranging from 10 pm ² at 100 pm ² .

According to the invention, the elongated electrically conductive element may have an electrical conductivity in direct current of at least 3% IACS, preferably at least 5% IACS, and more preferably at least 10% IACS. According to the invention, the elongated electrically conductive element can have a DC electrical conductivity of at most 50% IACS

The electrical conductivity of a material is expressed in Siemens per meter (S / m).

The electrical conductivity of a material, expressed in% IACS (IACS corresponding to Anglicism "International Annealed Copper Standard"), is determined relative to the electrical conductivity at 20 ° C of pure annealed copper which is 5.8001xl0 ⁷ S / m.

Polymeric layer

In the invention, the elongated electrically conductive element is surrounded by at least one polymeric layer. Preferably, the polymeric layer is an electrically insulating layer. The term "electrically insulating layer" means a layer whose electrical conductivity can be at most 1.10 ' ⁹ S / m (siemens per meter) (at 25 ° C).

According to a first possible variant, the elongated electrically conductive element may comprise a single metallized carbon fiber surrounded by at least one polymeric layer.

According to a second possible variant, the elongated electrically conductive element may comprise several metallized carbon fibers, all of said metallized fibers being surrounded by at least one polymeric layer.

By polymeric layer is meant a layer comprising at least one polymer, the term “polymer” as such meaning generally homopolymer or copolymer (e.g. block copolymer, random copolymer, terpolymer, etc.).

In the invention, the polymer can advantageously be an olefin polymer (polyolefin) or, in other words, an olefin homo- or co-polymer, and can in particular be a thermoplastic or crosslinked polymer.

Preferably, the olefin polymer is a polymer of ethylene or propylene.

The polymeric layer of the invention may comprise at least one polymer chosen from a linear low density polyethylene (LLDPE), a very low density polyethylene (VLDPE), a low density polyethylene (LDPE), a medium density polyethylene (MDPE), a high density polyethylene (HDPE), a copolymer of ethylene and vinyl acetate (EVA), a copolymer of ethylene and butyl acrylate (EBA), methyl acrylate (EMA), 2-hexylethyl acrylate (2HEA), a copolymer of ethylene and alpha-olefins, a copolymer of ethylene and propylene (EPR.), a polyurethane, a fluorinated polymer, a chlorinated polymer such as a polyvinyl chloride (PVC), a polyphenylene oxide (PPO), a technical polymer, and a mixture thereof.

As an example of a copolymer of ethylene and of alpha-olefin, mention may, for example, be made of polyethylene octene (PEO).

As an example of copolymers of ethylene and propylene (EPR), mention may be made of terpolymers of ethylene propylene diene (EPDM).

The term “technical polymer” means a polymer having improved properties, which can in particular be chosen from a polyphenylethylene ether, a polyamide, polyetheretherketone (PEEK), a polyimide, a fluorinated ethylene copolymer (FEP), a polyethylene furanoate (PEF ), and one of their mixtures.

The polymeric layer may also comprise at least one additive chosen from antioxidants, stabilizers, crosslinking agents, toasting retarders, crosslinking co-agents, processing-promoting agents such as lubricants or waxes , compatibilizers, coupling agents, charge stabilizers, and a mixture thereof.

Preferably, the polymeric layer is a so-called “HFFR” layer for Anglicism “Hatogen-Free Ftame Retardant” according to standard IEC 60754 Parts 1 and 2 (2011).

The polymeric layer can also comprise at least one filler. The filler of the invention can be a mineral or organic filler. It can be chosen from a flame retardant filler, an inert filler and one of their mixtures.

By way of example, the flame-retardant filler can be a hydrated filler, chosen in particular from metal hydroxides such as for example magnesium dihydroxide (MDH) or aluminum trihydroxide (ATH). These flame retardant charges act mainly by physical means, decomposing in an endothermic manner (e.g. release of water), which has the consequence of lowering the temperature of the polymeric layer and limiting the propagation of flames along the electrical device. We speak in particular of flame retardant properties, well known under Anglicism "flame retardant".

The inert filler can be chalk, talc, clay (e.g. kaolin), carbon black, or carbon nanotubes.

The polymeric layer can preferably be extruded.

The polymeric layer can be crosslinked or uncrosslinked. Crosslinking can be carried out by conventional crosslinking techniques well known to those skilled in the art such as, for example, peroxide crosslinking and / or hydrosilylation under the action of heat; silane crosslinking in the presence of a crosslinking agent; crosslinking by electron beams, gamma rays, X-rays, or microwaves; crosslinking by photochemical means such as irradiation under beta radiation, or irradiation under ultraviolet radiation in the presence of a photoinitiator. The crosslinking is preferably carried out according to the silane crosslinking technique.

The polymeric layer can have a thickness ranging from 10 μm to 2 mm, preferably from 100 μm to 1 mm, and more preferably from 100 μm to 700 μm.

Sheath

The electric cable of the invention may further comprise a sheath, in particular a protective sheath, surrounding the polymer layer (s).

Preferably, the sheath can be the outermost layer of the electric cable of the invention.

The sheath is in particular a continuous and uniform layer around at least said polymeric layer. It makes it possible to ensure the protection of the electrically conductive elongated element or elements, in particular against humidity, deterioration of mechanical origin and / or deterioration of chemical origin. It can also protect against mechanical damage. This sheath can be produced conventionally from suitable thermoplastic materials such as HDPE (high density polyethylene), MDPE (medium density polyethylene) or LLDPE (linear low density polyethylene); or materials retarding the propagation of the flame or resistant to the propagation of the flame.

The polymers mentioned for the polymeric layer of the invention can also be used.

Preferably, the outer protective sheath is an electrically insulating sheath.

The sheath can have a thickness ranging from 100 μm to 2 mm, preferably from 100 μm to 1.5 mm, and more preferably ranging from 100 μm to 1 mm.

Electric cable

The electric cable of the invention can typically, but not exclusively, be applied to the fields of low voltage power cables (especially less than 6kV), medium voltage (especially from 6 to 45-60 kV) or high voltage (especially above 60 kV, and up to 800 kV), whether direct or alternating current.

Other characteristics and advantages of the present invention will appear in the light of the description of nonlimiting examples of electric cables according to the invention, made with reference to FIG. 1.

FIG. 1 represents a cross-sectional view of an electric cable according to an embodiment of the invention.

For reasons of clarity, only the essential elements for the understanding of the invention have been represented schematically, and this without respecting the scale.

Figure 1 shows a cross-sectional view of an electric cable 1 according to a particular embodiment of the invention.

The electric cable 1 comprises an elongated electrically conductive element 2 central comprising a set of 12,000 metallized carbon fibers 3, each carbon fiber of said set being surrounded by a metallic layer of copper.

The elongated electrically conductive element 2 is surrounded by a polymeric layer 4.

An electrically insulating sheath 5 is placed around the polymeric layer 4.

In this particular example, the polymeric layer 4 is directly in physical contact with the elongated electrically conductive element 2 and the electrically insulating sheath 5 is directly in physical contact with the polymeric layer 4.

Examples

In order to show the technical effects of the present invention, tests were carried out using metallized carbon fibers according to the invention and so-called “comparative” carbon fibers.

Formation of the elongated electrically conductive element

Example 1 (comparative example)

Example 1 consists in preparing an elongated electrically conductive element comprising 12,000 non-metallized carbon fibers sold by the company Toray under the reference TORAYCA T300. The diameter of each carbon fiber is 7 µm. Their length is 200 meters or more.

The density of the elongated electrically conductive element is determined by densimetric measurement according to standard ASTM D792-08, and is 1.76 g / cm ³ .

Example 2 (comparative example)

Example 2 consists in preparing an elongated electrically conductive element comprising 12,000 nickel-plated carbon fibers sold by the company Teijin under the reference TOHO TENAX HTS40. The diameter of each carbon fiber alone (without the nickel layer) is 7 µm, and the nickel layer has a thickness of 1 µm around each carbon fiber. The length of the nickel-plated carbon fibers is 200 meters or more.

The density of the elongated electrically conductive element is determined by densimetric measurement according to standard ASTM D792-08, and is 2.7 g / cm ³ .

Example 3 / example according to the invention)

Example 3 consists in preparing an elongated electrically conductive element comprising 12,000 copper-plated carbon fibers.

The metallization of carbon fibers with copper is carried out by electrodeposition, with metallic copper (Cu ⁽⁰⁾ ) sold by the company SIFCO under the reference CUIVRE ALCALIN DEPOT THAIS CODE 5280, around respectively 12,000 non-metallized carbon fibers marketed by Toray under the reference TORAYCA T300. The diameter of each unmetallized carbon fiber is 7 µm and their length is 200 meters or more.

The electrodeposition is carried out with a device of the current generator type of the brand TTI under the reference QPX600DP, for approximately 5 min, to obtain a copper-colored layer approximately 1 μm thick around the carbon fibers.

An elongated electrically conductive member is formed from carbon fibers coppery with 12,000 of said fibers.

The density of the elongated electrically conductive element is determined by densimetric measurement according to standard ASTM D792-08, and is 4.4 g / cm ³ .

Measurement of the specific conductivity of the elongated electrically conductive elements of examples 1 to 3

The measurement of the specific conductivity (%) of the elongated electrically conductive elements of Examples 1, 2 and 3 is carried out by measuring 4 points according to standard ASTM B193 and ISO 3915.

The calculation of the specific conductivity is then determined from the value of the electrical conductivity and the density of the elongated electrically conductive element.

The results are collated in the table below:

Specific conductivity (%) Example 1: 12,000 fibers of non-metallic carbon 0.6 Example 2: 12,000 fibers of carbon nickel plated 7.4 Example 3: 12,000 fibers of carbon copper 39.9

Thus, the electrically conductive element of the invention, as exemplified in Example 3, has a specific conductivity much higher than that of Example 1 and of Example 2.

The electrically conductive element of the invention in an electric cable makes it possible to significantly limit, or even avoid, the use of solid metallic conductors, while having very good mechanical and physico-chemical properties.

Claims (11)

1. Electric cable (1) comprising at least one elongated electrically conductive element (2) surrounded by at least one polymeric layer (4), said elongated electrically conductive element (2) comprising a metallized carbon fiber or at least one set of fibers of metallized carbon (3), characterized in that the metallized carbon fiber or said set (3) of metallized carbon fibers has a specific conductivity of at least 8%. 2. Electric cable (1) according to claim 1, characterized in that said elongated electrically conductive element (2) has a specific conductivity of at least 15%, preferably at least 25%, and more preferably at least minus 35%. 3. Electric cable (1) according to any one of the preceding claims, characterized in that said set of metallized carbon fibers (3) comprises at least 1000 metallized carbon fibers, preferably at least 6000 metallized carbon fibers, and more preferably at least 12,000 metallized carbon fibers. 4. Electric cable (1) according to any one of the preceding claims, characterized in that the metallized carbon fiber or the set of metallized carbon fibers respectively comprises one or more carbon fibers surrounded by at least one metallic layer. 5. Electric cable (1) according to claim 4, characterized in that said metal layer comprises copper or a copper alloy. 6. Electric cable (1) according to claim 4 or 5, characterized in that the metal layer is directly in physical contact with the carbon fiber of said metallized carbon fiber or with each carbon fiber of said set of metallized carbon fibers . 7. Electric cable (1) according to any one of claims 4 to 6, characterized in that the metal layer may have an average thickness of at least 100 nm, preferably at least 500 nm, and more preferably d '' at least 1 pm. 8. Electric cable (1) according to any one of the preceding claims, characterized in that it further comprises a sheath (5) surrounding the polymeric layer (4). 9. Electric cable (1) according to any one of the preceding claims, characterized in that the metallized carbon fiber (s) have a length ranging from 100 m to 200 km, preferably ranging from 100 m to 10 km , and more preferably ranging from 100 m to 3 km. 10. Electric cable (1) according to any one of the preceding claims, characterized in that the carbon fiber of the metallized carbon fiber or the constituent carbon fibers of the set of metallized carbon fibers has / have a diameter ranging from 0.5 pm to 100 pm, preferably ranging from 1 pm to 50 pm, and more preferably ranging from 5 pm to 10 pm. 11. Electric cable (1) according to any one of the preceding claims, characterized in that said elongated electrically conductive element (2) has a DC electrical conductivity of at least 3% IACS, preferably at least 5 % IACS, and more preferably at least 10% IACS.