PROCESS FOR PREPARING A COMPOSITE PART THAT IS ELECTRICALLY CONDUCTIVE AT THE SURFACE, AND APPLICATIONS

Abstract

A process is provided for preparing a high-performance composite part that is electrically conductive at the surface. The process is used for improving the resistance of an electrically insulating part to rubbing, wear, and harsh atmospheric and/or chemical conditions, and to ensure the protection of an electrically insulating part against electromagnetic radiation (electromagnetic shielding) and/or against electrostatic discharges. The process improves the surface electrical conductivity of a material.

Claims

1. A process for preparing a high-performance composite part that is electrically conductive at the surface having an electrically insulating solid substrate, a conductive film deposited on at least one portion of the surface of the substrate, and a metal layer deposited on at least one portion of the free surface of the conductive film, the electrically insulating solid substrate having at least one polymer material, and the metal layer having at least one metal, said process comprising the following steps: 1) a step of preparing a liquid composition having at least one polymer material and at least one metal in the form of filiform nanoparticles, said liquid composition comprising from 0.2% to 10% by volume of said metal relative to the total volume of the liquid composition, 2) a step of applying the liquid composition from step 1) to at least one portion of the surface of said electrically insulating substrate, 3) a step of drying, and optionally of heat treatment, of the liquid composition in order to obtain an intermediate composite part having the electrically insulating solid substrate and the conductive film deposited on at least one portion of the surface of the substrate, said conductive film comprising said polymer material and from 1% to 10% by volume of said metal in the form of filiform nanoparticles relative to the total volume of the conductive film, 4) a step of electrodeposition of at least one metal on at least one portion of the free surface of the conductive film, in order to obtain said composite part.

2. The process as claimed in claim 1, wherein the electrically insulating solid substrate additionally has a reinforcing agent and/or conductive particles.

3. The process as claimed in claim 2, wherein the substrate has at most 10% by volume of conductive particles and/or reinforcing agent.

4. The process as claimed in claim 1, wherein the polymer material is a thermosetting polymer.

5. The process as claimed in claim 1, wherein the liquid composition from step 1) additionally has a metal identical to the metal but not being in the form of filiform nanoparticles.

6. The process as claimed in claim 1, wherein step 1) further comprises the following sub-steps: 1.sub.a) a step of preparing a dispersion of at least one metal in the form of filiform nanoparticles in a solvent, 1.sub.b) a step of mixing the dispersion from the preceding step 1.sub.a) with at least one polymer material, 1.sub.c) a step of homogenizing the mixture from the preceding step 1.sub.b) in order to form a liquid composition comprising at least one polymer material and at least one metal in the form of filiform nanoparticles, said liquid composition comprising from 0.2% to 10% by volume of said metal relative to the total volume of the liquid composition.

7. The process as claimed in claim 6, wherein the solvent from step 1.sub.a) is selected from the group consisting of hydrocarbon solvents, oxygenated solvents, chlorinated solvents, water and mixtures thereof.

8. The process as claimed in claim 1, wherein step 2) is carried out by spraying the liquid composition from step 1) onto at least one portion of the surface of said electrically insulating solid substrate, or with the aid of a brush, or else by immersing at least one portion of the surface of said electrically insulating solid substrate in the liquid composition from step 1).

9. The process as claimed in claim 1, wherein said process further comprises a step i), prior to step 2), of degreasing the substrate.

10. The process as claimed in claim 1, wherein the conductive film from step 3) comprises from 1% to 5% by volume of metal relative to the total volume of said conductive film.

11. The process as claimed in claim 5, wherein the conductive film obtained in step 3) is from 0.5% to 10% by volume of metal relative to the total volume of the conductive film.

12. The process as claimed in claim 1, wherein said process further comprises, between steps 3) and 4), a step ii) of sanding at least one portion of the free surface of the conductive film in order to adapt the surface finish before step 4).

13. The process as claimed in claim 1, wherein the metal is selected from the group consisting of Cu, Sn, Co, Fe, Pb, Ni, Cr, Au, Pd, Pt, Ag, Bi, Sb, Al, Li and mixtures thereof.

14. The process as claimed in claim 1, wherein said metal is a stainless metal.

15. A high-performance composite part that is electrically conductive at the surface having an electrically insulating solid substrate, a conductive film deposited on at least one portion of the surface of the electrically insulating substrate, and a metal layer deposited on at least one portion of the free surface of the conductive film, said part (CP.sub.1) wherein: the electrically insulating solid substrate has at least one polymer material, the conductive film has at least one polymer material and at least one metal in the form of filiform nanoparticles, said conductive film having from 1% to 10% by volume of said metal relative to the total volume of the conductive film, the metal layer has at least one metal, and the substrate, the conductive film, the metal layer, the metal, the metal, the polymer material and the polymer material are as defined in claim 1.

16. A housing for an electrical and/or electronic component comprising: a high-performance composite part that is electrically conductive at the surface as prepared as claimed in the process defined in claim 1.

17. An electrically insulating part having abrasion resistance, wear resistance and resistance to harsh atmospheric and/or chemical conditions, said electrically insulating part comprising: a high-performance composite part that is electrically conductive at the surface as defined in claim 1.

18. An electrically insulating part that is resistant against electromagnetic radiation (electromagnetic shielding) and/or against electrostatic discharges, said electrically insulating part comprising: a high-performance composite part that is electrically conductive at the surface as defined in claim 1.

19. A material having and improved surface electrical conductivity, said material comprising: a high-performance composite part that is electrically conductive at the surface as defined in claim 1.

Description

EXAMPLES

[0129] The raw materials used in the examples are listed below: [0130] 10 cm10 cm substrate produced by stacking sheets of a composite material based on polyetheretherketone (PEEK) reinforced with carbon fibers (in a proportion of 65% by volume of carbon fibers relative to the total volume of the material), said sheets being sold under the trade name APC-2 by Cytec Industries, (hereinafter referred to as Substrate S1); [0131] 10 cm10 cm substrate produced by stacking sheets of a composite material based on polyepoxide resin reinforced with carbon fibers (T700, Toray), in a proportion of 66% by volume of carbon fibers relative to the total volume of the material, said sheets being sold under the trade name HexPly M21 by the company Hexcel (hereinafter referred to as Substrate S2); [0132] 10 cm10 cm substrate produced from a composite material comprising a matrix made of polyphenylene sulfide (PPS) reinforced with carbon fibers in a proportion of 45% by volume, said material being sold under the trade name Cetex TC1100 by the company TenCate (hereinafter referred to as Substrate S3); [0133] 10 cm10 cm substrate made of polyetheretherketone (PEEK) sold under the trade name Victrex 450G (hereinafter referred to as Substrate S4); [0134] aqueous dispersion of a hydroxy-functional acrylic resin made of polyurethane (PU) sold under the trade name Macrynal VSM 6299W/42WA by the company Allnex, [0135] liquid polyepoxide resin comprising an amine-type crosslinking agent, sold under the trade name HexFlow RTM 6 by the company Hexcel, [0136] nickel, Good Fellow, [0137] ethanol, Sigma Aldrich, [0138] silver particles in the form of flakes having a size<20 m, 90% purity, Alfa Aesar, [0139] multiwall carbon nanotubes sold under the trade name Graphistrength by the company Arkema, [0140] aliphatic polyisocyanate (crosslinking agent), sold under the trade name Easaqua X D401 by the company Vencorex.

[0141] Unless otherwise indicated, all these raw materials were used as received from the manufacturers.

Example 1

Preparation of a Composite Part CP.SUB.1-A .in Accordance with the Invention and Prepared According to the Process in Accordance with the Invention

[0142] A dispersion comprising 3.21 g of silver nanowires and 100 ml of ethanol was prepared. The silver nanowires were prepared beforehand according to a growth process in solution from silver nitrate (AgNO.sub.3) and polyvinylpyrrolidone (PVP) as described by Sun Y. G. et al., Crystalline silver nanowires by soft solution processing, Nano Letters, 2002. 2(2): p. 165-168, with a PVP/AgNO.sub.3 ratio of 1.53.

[0143] The dispersion of silver nanowires was mixed with 9.29 g of an aqueous dispersion of Macrynal VSM 6299W/42WA acrylic resin and 1.61 g of Easaqua X D401 polyisocyanate so as to obtain a mixture which was then homogenized in an ultrasonic bath, at a frequency of 50 kHz and a power of 25 W per 5 second pulse. A liquid composition comprising ethanol, the PU acrylic resin, the polyisocyanate and the silver nanowires was thus obtained.

[0144] The liquid composition was then deposited on a portion of the surface (one of the faces) of the substrate S1 by spraying with the aid of a compressed air spray gun.

[0145] After drying in air then heat treatment at 80 C. for 30 minutes in an oven, a conductive film (CF) with a thickness of 30 m, deposited on a portion of the surface of the substrate S1, was obtained, said conductive film (CF) comprising 4.5% by volume of silver nanowires relative to the total volume of the conductive film (CF). At the end of this step, an intermediate composite part CP.sub.2-A was thus obtained.

[0146] Next, nickel was deposited on the conductive film (CF) (i.e. on the free surface of the conductive film) by electrodeposition with the aid of an electrochemical cell comprising: [0147] an anode formed of a nickel plate (Goodfellow, 99.99%), and electrically connected to a current source, [0148] the conductive film, as cathode, placed parallel to the anode at a distance of 2 cm approximately and electrically connected to said current source, and [0149] a Watts solution comprising nickel sulfate at a concentration of 330 g/l, nickel chloride at a concentration of 45 g/l, and boric acid at a concentration of 37 g/l.

[0150] The deposition was carried out at 25 C., with a voltage set at 3 V approximately and an intensity of 15 mA approximately for 15 minutes approximately. A nickel layer (ML) of approximately 2 m deposited on the conductive film (CF) was thus obtained.

[0151] A composite part CP.sub.1-A was thus obtained comprising a first material formed by the substrate S1, a second material formed by the conductive film (CF) comprising a PU resin and silver nanowires, and finally a third material formed by a nickel layer (ML).

[0152] FIG. 1 is a schematic representation of the composite part (CP.sub.1-A) of the invention.

Example 2

Preparation of a Composite Part CP.SUB.1-B .in Accordance with the Invention and Prepared According to the Process in Accordance with the Invention

[0153] A dispersion comprising 4.34 g of silver nanowires and 100 ml of acetone was prepared.

[0154] The dispersion was mixed with 10 g of HexFlow RTM 6 liquid polyepoxide resin so as to obtain a mixture which was then homogenized in an ultrasonic bath under the conditions as described in example 1. The acetone was evaporated at 80 C. for 10 minutes using a Buchi rotary evaporator of vertical R3 type.

[0155] The mixture obtained was heated at 80 C. so as to obtain a liquid composition comprising the polyepoxide resin and the silver nanowires. This mixture may remain fluid at 80 C. for 10 hours before the solidification thereof.

[0156] The liquid composition was then deposited on at least one portion of the surface (one of the faces) of the substrate S2, by spraying with the aid of the compressed air spray gun from example 1. This spray gun was able to keep the HexFlow RTM 6 polyepoxide resin at a temperature of 80 C. in order to prevent it from solidifying.

[0157] After drying in air then heat treatment in an oven at 180 C. for 1 hour, a conductive film (CF) with a thickness of 30 m, deposited on at least one portion of the surface of the substrate S2, was obtained, said conductive film comprising 4.5% by volume of silver nanowires relative to the total volume of the conductive film. At the end of this step, an intermediate composite part CP.sub.2-B was thus obtained.

[0158] Next, nickel was deposited under the same electrodeposition conditions as those described in example 1.

[0159] A nickel layer (ML) of approximately 2 m deposited on the conductive film (CF) was thus obtained.

[0160] A composite part CP.sub.1-B was thus obtained comprising a first material formed by the composite substrate made of polyepoxide composite resin (S2), a second material formed by the conductive film (CF) comprising a polyepoxide resin and silver nanowires, and finally a third material formed by a nickel layer (ML).

Example 3

Preparation of a Composite Part CP.SUB.1-C .in Accordance with the Invention and Prepared According to the Process in Accordance with the Invention

[0161] A dispersion comprising 3.21 g of silver nanowires and 100 ml of ethanol was prepared.

[0162] The dispersion of silver nanowires was mixed with 9.29 g of Macrynal VSM 6299W/42WA and 1.61 g of Easaqua X D401 polyisocyanate so as to obtain a mixture which was then homogenized in an ultrasonic bath under the conditions as described in example 1. A liquid composition comprising ethanol, the PU acrylic resin, the polyisocyanate and the silver nanowires was thus obtained.

[0163] The liquid composition was then deposited on at least one portion of the surface of the substrate S2 by spraying with the aid of the compressed air spray gun from example 1.

[0164] After drying in air then heat treatment at 80 C. for 30 minutes in an oven, a conductive film (CF) with a thickness of 30 m, deposited on at least one portion of the surface of the substrate S2, was obtained, said conductive film comprising 4.5% by volume of silver nanowires relative to the total volume of the conductive film. At the end of this step, an intermediate composite part CP.sub.2-C was thus obtained.

[0165] Next, nickel was deposited under the same electrodeposition conditions as those described in example 1.

[0166] A nickel layer (ML) of approximately 2 m deposited on the conductive film (CF) was thus obtained.

[0167] A composite part CP.sub.1-C was thus obtained comprising a first material formed by the composite substrate made of polyepoxide resin (S2), a second material formed by the conductive film (CF) comprising a PU resin and silver nanowires, and finally a third material formed by a nickel layer (ML).

Example 4

Preparation of a Composite Part CP.SUB.1-D .in Accordance with the Invention and Prepared According to the Process in Accordance with the Invention

[0168] A dispersion comprising 3.21 g of silver nanowires and 100 ml of ethanol was prepared.

[0169] The dispersion was mixed with 9.29 g of Macrynal VSM 6299W/42WA and 1.61 g of Easaqua X D401 polyisocyanate so as to obtain a mixture which was then homogenized in an ultrasonic bath under the conditions as described in example 1. A liquid composition comprising ethanol, the PU acrylic resin, the polyisocyanate and the silver nanowires was thus obtained.

[0170] The liquid composition was then deposited on at least one portion of the surface of the substrate S3 by spraying with the aid of the compressed air spray gun from example 1.

[0171] After drying in air then heat treatment at 80 C. for 30 minutes in an oven, a conductive film (CF) with a thickness of 30 m, deposited on at least one portion of the surface of the substrate S3, was obtained, said conductive film (CF) comprising 4.5% by volume of silver nanowires relative to the total volume of the conductive film. At the end of this step, an intermediate composite part CP.sub.2-D was thus obtained.

[0172] Next, nickel was deposited under the same electrodeposition conditions as those described in example 1.

[0173] A nickel layer (ML) of approximately 2 m deposited on the conductive film (CF) was thus obtained.

[0174] A composite part CP.sub.1-D was thus obtained comprising a first material formed by the composite substrate made of PPS resin, a second material formed by the conductive film (CF) comprising a PU resin and silver nanowires, and finally a third material formed by a nickel layer (ML).

Example 5

Preparation of a Composite Part CP.SUB.1-E .in Accordance with the Invention and Prepared According to the Process in Accordance with the Invention

[0175] A dispersion comprising 3.21 g of silver nanowires and 100 ml of ethanol was prepared.

[0176] The dispersion was mixed with 9.29 g of Macrynal VSM 6299W/42WA and 1.61 g of Easaqua X D401 polyisocyanate so as to obtain a mixture which was then homogenized in an ultrasonic bath under the conditions as described in example 1. A liquid composition comprising ethanol, the PU acrylic resin, the polyisocyanate and the silver nanowires was thus obtained.

[0177] The liquid composition was then deposited on at least one portion of the surface of the substrate S4 by spraying with the aid of the compressed air spray gun from example 1.

[0178] After drying in air then heat treatment at 80 C. for 30 minutes in an oven, a conductive film (CF) with a thickness of 30 m, deposited on at least one portion of the surface of the substrate S4, was obtained, said conductive film (CF) comprising 4.5% by volume of silver nanowires relative to the total volume of the conductive film. At the end of this step, an intermediate composite part CP.sub.2-E was thus obtained.

[0179] Next, nickel was deposited under the same electrodeposition conditions as those described in example 1.

[0180] A nickel layer (ML) of approximately 2 m deposited on the conductive film (CF) was thus obtained.

[0181] A composite part CP.sub.1-E was thus obtained comprising a first material formed by the substrate made of non-reinforced PEEK resin (S4), a second material formed by the conductive film (CF) comprising a PU resin and silver nanowires, and finally a third material formed by a nickel layer (ML).

Comparative Example 6

Comparison of the Intermediate Composite Part CP.SUB.2-C .in Accordance with the Invention with Intermediate Composite Parts CP.SUB.2-A., CP.SUB.2-B and CP.SUB.2-C not in Accordance with the Invention

[0182] The intermediate composite part CP.sub.2-C in accordance with the invention and as prepared in example 3 above was compared with three intermediate composite parts CP.sub.2-A, CP.sub.2-B and CP.sub.2-C not in accordance with the invention.

[0183] The intermediate composite part CP.sub.2-A that is not part of the invention was prepared using the same process as that described in example 3 but in which the silver nanowires were replaced by silver particles in the form of flakes having a size of strictly less than 20 m.

[0184] The intermediate composite part CP.sub.2-B that is not part of the invention was prepared using the same process as that described in example 3 but in which the silver nanowires were replaced by multiwall carbon nanotubes.

[0185] The intermediate composite part CP.sub.2-C that is not part of the invention was prepared using the same process as that described in example 3 but in which the silver nanowires were replaced by silver particles in the form of flakes having a size of strictly less than 20 m and the conductive film (CF) obtained comprised 25% by volume of said silver particles relative to the total volume of the conductive film.

[0186] The surface resistivities of the intermediate composite parts CP.sub.2-C, CP.sub.2-A, CP.sub.2-B and CP.sub.2-C were measured with the aid of an apparatus sold under the trade name Keithley 2420 SourceMeter in 4-wire mode and a concentric ring probe according to ASTM Standard D257-99.

[0187] Step 4) of electrodeposition in accordance with the invention onto these intermediate composite parts was then carried out when this was technically possible.

[0188] Finally, the mechanical resistances of the intermediate composite parts CP.sub.2-C, CP.sub.2-A, CP.sub.2-B and CP.sub.2-C were evaluated with the aid of the adhesive tape (A-Tape) test which consists in applying a piece of adhesive tape to a coating and in pulling it off in order to see if the coating has a good adhesion to said coating.

[0189] Table 1 below shows the results of the resistivity, electrodeposition test, mechanical resistance via the A-Tape test, and also the references for the corresponding images of each of the intermediate composite parts CP.sub.2-C, CP.sub.2-A, CP.sub.2-B and CP.sub.2-C prepared above.

TABLE-US-00001 TABLE 1 Observation of Composite Electro- the surface of part Resistivity deposition A-Tape the composite CP.sub.2 (/square) step 4) test test part CP.sub.2 CP.sub.2-C ~1 OK OK FIG. 2a CP.sub.2-A (*) >1000000 Failure FIG. 2b CP.sub.2-B (*) ~1000 Failure FIG. 2c CP.sub.2-C (*) ~1 OK Failure FIG. 3 (*) not in accordance with the invention

[0190] Thus, the results from table 1 show that the size, the shape, the content and the nature of the compound introduced into the conductive film are determining factors for enabling, on the one hand, the electrodeposition of the metal M.sub.1 according to step 4) and, on the other hand, a good mechanical resistance of the composite part of the invention.

[0191] Owing to the use of filiform nanoparticles at 4.5% by volume, the mechanical properties of the conductive film (CF) are maintained, which is not the case when 25% by volume of particles in the form of flakes are used.