WO2024042353A1

WO2024042353A1 - Electrically conductive composite, a process of preparation and the use

Info

Publication number: WO2024042353A1
Application number: PCT/IB2022/057962
Authority: WO
Inventors: Carolina BRANCO; Américo José LUVIZOTTO; Guainumbi Medeiros
Original assignee: Rhodia Brasil S.A.
Priority date: 2022-08-25
Filing date: 2022-08-25
Publication date: 2024-02-29

Abstract

The present invention is relative to an electrically conductive composite containing at least one polyamide functionalized with a functionalizing agent comprising graphene, and at least one intrinsically conductive polymer. The polyamide is PA X.Y, X and Y being independently from one another selected from monomers containing from 4 to 16 carbon atoms.

Description

Electrically Conductive Composite, a process of preparation and the use

The present invention relates to an electrically conductive composite containing at least one polyamide functionalized with a functionalizing agent comprising graphene, and at least one intrinsically conductive polymer. The polyamide is PA X.Y, X and Y being independently from one another selected from monomers containing from 4 to 16 carbon atoms. The present invention also discloses a method for obtaining such composite and articles made therefrom. The composite is obtained by functionalizing a polyamide using graphene following addition of intrinsically conductive polymer. The present invention also relates to the use of the electrically conductive composite in smart materials.

Polymers with electrically conductive properties can be used in an intelligent way and present a challenge in terms of exploiting their electronic properties for a wide range of applications such as health, sport, automotive and aerospace.

Polymers such as polyamides are versatile compounds but when used isolated are insulating, which limits their application in some sectors for example for producing smart materials. Smart materials have been investigated for diverse applications in fabrics, electronics, medical and structural engineering devices.

There is a need to develop a composite with electrically conductive properties and versatile to produce fibers and engineering and structural devices with the advantage of having suitable mechanical and comfort properties.

Polyamide fiber is the most suitable fiber for improving comfort among the synthetic fibers available in the market with high durability, good physical and chemical properties and easy-care properties.

Polyamide, also known as nylon, is a linear condensation polymer composed of repeated primary bonds of amide group. The amide group -(-CO-NH-)- provides hydrogen bonding between polyamide intermolecular chains. A polyamide fiber is generally produced by melt-spinning extrusion.

Graphene is well known to increase the electrical conductive and mechanical properties of polymers. However, it is commonly used in high amounts since when it is applied in very low amounts it is difficult to achieve electrical percolation.

Particularly, a direct addition of graphene into the fiber can be made or graphene can be added as a coating to the textile's surface. The coating technique is cost- effective, simple, and is ideally suitable for various textiles and associated high- value materials. However, coating technique implicates in the use of graphene in high amounts.

Intrinsically conductive polymers (ICPs) are organic polymers able to conduct electricity. Among the uses of ICPs, it is possible to apply them with polymers onto textile surfaces. The used substrates are natural or synthetic fibers like polyamide. Although such textiles exhibit good electrical conductivity there is a drawback of reducing textile mechanical properties. Therefore, there is a challenging target on the manufacturing of intelligent materials, which consist of electrical conductive yams and ICPs.

United States Patent Application Publication No. US2017/018326 discloses the incorporation of graphene and intrinsically conductive polymer in fibrous substrate made by infusion processes. In this process, graphene is trapping into the fibers followed by the coating of such fibrous substrate with intrinsically conductive polymer. However, this process makes necessary to have a fibrous substrate structure before submitting this final structure to the two steps according to described above to produce a textile with electrically conductive properties.

There is, thus, a need for development of electrically conductive composites able to be applied in diverse fields of smart materials, from engineering to textiles and to be produced using a simple and cost-effective method.

Pursuing research in this field, the Applicant has now discovered a novel and original approach, which makes possible to effectively produce electrically conductive composites able of being used in diverse applications with the additional advantage of maintenance of mechanical and comfort properties, in particular for textiles.

The subject of the present invention is therefore an electrically conductive composite comprising:

An electrically conductive composite comprising:

-at least one polyamide PA X.Y, X and Y being independently from one another selected from monomers containing from 4 to 16 carbon atoms, wherein the polyamide is a functionalized polyamide with a functionalizing agent comprising graphene, and;

-at least one intrinsically conductive polymer.

It has been surprisingly found that electrically conductive composite containing functionalized polyamide and intrinsically conductive polymer can be industrially prepared using simple, scalable and usual process with achievement not only of excellent percolation with very small amounts of functionalizing agent and intrinsically conductive polymer, but also maintaining of mechanical and comfort properties, essential for applications in devices and textiles.

The present invention also aims at a method for obtaining said electrically conductive composite with improved percolation, wherein the composite is obtained by addition of the intrinsically conductive polymer to the functionalized polyamide by melt extrusion. Also, the present invention proposes an electrically conductive article comprising the composite with improved electrical conductivity as defined above and below in the following paragraphs; and a method for obtaining such a electrically conductive article, wherein the electrically conductive composite of the invention is transformed in a fiber, a staple fiber, a flock, a woven or non-woven fabric or a textile.

Then, another object of the present invention is the use of said electrically conductive composite with improved electrical conductivity as defined above and below in smart materials selected from sensors, engineer plastics, automobilistic parts, gps, flexible fabric keyboards, airplanes parts, electromagnetic shielding, protective clothing, touch screen displays and medical textiles.

Other subjects, characteristics, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples that follow.

The advantages described above are clearer to those skilled in the art from the figures:

FIG. 1 (a) and (b) shows two examples of the distribution of graphene in the polyamide: PA 66 + 0.5w.t.% Graphene and PA 66 + 1.0w.t.% Graphene, respectively.

FIG. 2 shows the Specific heat (J/g.K) curves for the composite samples 1 (PA66), 2 (PA66 + lwt% Graphene) and 3 (PA66 + 0.5wt% Graphene + lwt% PAni) produced according to the invention.

Throughout the description, including the claims, the term "comprising one" or “comprising a" should be understood as being synonymous with the term "comprising at least one", unless otherwise specified, "between" and “from... to. ..” should be understood as being inclusive of the limits.

As used herein, “weight percent,” “wt%,” “percent by weight,” “% by weight,” and variations thereof refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100.

Terms “a” and “an” should be considered as a singular or a generic plural all along the present specification, except otherwise specified.

By “composite”, it should be understood as a solid material which is composed of two or more substances having different physical characteristics and in which each substance retains its identity while contributing to desirable properties for the whole.

As used herein, the term “percolation” is understood as a critical concentration at which a conductive material is added to an insulating material, above which a continuous path is established in the matrix of the insulating material that becomes electrically conductive. The percolation can be measured using the resistivity value so that when the resistivity decreases, the percolation increases, showing that the material usualy insulating is becoming electricaly conductive.

The expression “functionalized polyamide” in the sense of the present invention is understood as a polyamide containing functionalizing agent molecules intercalated in the polyamide chain by chemical bond and obtained during the polyamide polymerization reaction to produce the polymer.

As used herein, a “fiber” in the sense of the present invention is the generic term including the following spun articles: a fiber, a monofilament, a multifilament and a yarn. An “electrically conductive article” according to the invention is a transformed or treated electrically conductive composite and includes staple fibers, any flock or any textile composition made of the composite, especially fabrics.

Throughout the description, including the claims, all method terms should be understood as being synonymous with the term process.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The present invention provides a composite containing a functionalized polyamide with a functionalizing agent comprising graphene.

Functionalization of polyamides by admixing a wide variety of additives, such as functionalizing agents, with polyamides with the aim of improving impact strength of polyamides is commonly known by prior art.

Advantageously, functionalizing agents such as graphene may allow an insulating polyamide to become electrically conductive.

In general, graphene is a two dimensional sheet of carbon atoms, sp2-bonded into a hexagonal arrangement. Graphene has properties of conducting heat and electricity very efficiently.

Advantageously, there is a family of graphene-related materials, which differ from pure graphene in that they may contain multiple stacked layers (such as graphene nanoplaques and nanoparticles), or different chemical structures (such as graphene oxide).

In a particular embodiment of the invention, the graphene is chosen from nanoparticles and nanoplaques and mixtures thereof. According to a preferred embodiment, the graphene is chosen from nanoplaques of graphene.

The nanoplaques of the present invention can be characterized by their size distribution D90 (in short "D90"), according to which 90% of the nanoplaques in the sample are smaller and 10% of the particles in the sample are larger. Particle Size Analysis can for example take place in a Laser Diffraction Analyzers (Malvern Mastersize 3000).

According to one embodiment, the nanoplaques of the present invention present the particle size D90 ranging from 0.1 pm to 30 pm, preferably from 0.5 to 20 pm, more preferably from 1 to 15 pm, even more preferably from 5 to 7 pm and most preferably from 1 to 5 pm.

Functionalized

According to a first embodiment of the invention, the electrically conductive composite contains polyamide functionalized with a functionalizing agent comprising graphene.

Specifically, the functionalized polyamide comprises graphene chemically bonded into the polyamide chain according to transmission electron microscopy (TEM), i.e. the bond between polyamide chain and graphene molecules are evidenced by image formed from the interaction of the electrons with the sample (functionalized polyamide) as a beam of electrons is transmitted through the sample.

Advantageously, the composite of the invention contains very low amounts of graphene.

According to one embodiment of the invention, the functionalized polyamide of the composite contains from 0.3 to 3% by weight of graphene based on the total weight of the functionalized polyamide.

According to one preferred embodiment of the invention, the functionalized polyamide of the composite contains preferably from 0.5 to 2 % by weight of graphene based on the total weight of the functionalized polyamide.

In another preferred embodiment, the functionalized polyamide of the composite contains preferably from 0.5 to 1.5% by weight of graphene based on the total weight of the functionalized polyamide.

The functionalized polyamide is an aliphatic polyamide composed of at least one polyamide X.Y, X and Y being independently from one another selected from monomers containing from 4 to 16 carbon atoms.

The polyamide may be prepared by a polycondensation from a combination of monomers diamine and dicarboxylic acid. In principle, any polyamide may be suitable for the composite according to the present invention. Examples include, polyamides obtained using diamines such as tetramethylenediamine (1,4- diaminobutane or putrescine), pentamethylenediamine and hexamethylenediamine (1,6-hexanediamine) and the following dicarboxylic acids :butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), octanedioic acid (suberic acid), nonanedioic acid (azelaic acid), decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid. All those diamines and diacids are commercially available. The preparation of the polyamides is conventionally known.

According to one preferred embodiment, the polyamide of the composite according to the present invention is chosen from PA 6.6.

The main advantage of the present invention is that the electrically conductive composite is prepared using very low amounts of electrically conductive ingredients between graphene and intrinsically conductive polymers.

The addition of the intrinsically conductive polymers (ICP) in the composite are evidenced by the specific heat capacity (Cp), i.e. the amount of heat needed to increase the temperature of the material or a sample. By the propose of the present invention, the Cp can be used to evaluate the successful addition of the ICP in the composite showing a different profile on the temperature curve. Specific heat capacity can take place, for example, in a Shimadzu, model DSC-60.

Intrinsically conductive polymers are polymers characterized by having electrical conductivity and electrical properties from semi-conductors to conductive. Electrical conductivity requires freely moving charge carriers and electrically selfconducting polymers have an extensive 7t-electron system in the form of conjugated double bonds with holes serving as charge carriers. Aromatic or heteroaromatic rings as well as triple bonds also belong to the group of poly conjugated bond systems.

In an embodiment, exemplary of intrinsically conductive polymer that can be used in the composite of the present invention is selected from polyaniline, a substituted polyaniline, poly(3,4-ethylenedi oxythiophene) polystyrene sulfonate (PEDOT:PSS), a poly(3, 4-ethylenedioxythiophene), a substituted poly(3, 4- ethylenedioxythiophene), poly(thiophene), a substituted poly(thiophene), poly(pyrrole), a substituted poly(pyrrole), poly(acetylene), poly(p- phenylenevinylene) (PPV), a poly(indole), a substituted poly(indole), a poly(carbazole), a substituted poly (carbazole), a poly(azepine), a (poly)thieno P,4-b]thiophene, a substituted poly(thienoP, 4-b]thiophene), a poly (dithienoP, 4- b:3',4'-d]thiophene), a poly(thienoP, 4-b] furan), a substituted poly(thienoP, 4- b] furan), a derivative thereof, or a combination of two or more thereof. In a preferred embodiment, intrinsically conductive polymer is selected from poly aniline (PAni).

Advantageously, by the use of very small amounts of intrinsically conductive polymer it is possible to achieve excellent electrical conductivity of the composite of the present invention.

The total amount of intrinsically conductive polymer in the composite can be from 0.5 to 3% by weight, based on the total weight of the composite.

Preferably, the amount of intrinsically conductive polymer in the composite can be from 1 to 2% by weight, based on the total weight of the composite.

Process for

of the electrically conductive

The invention also provides a method for obtaining an electrically conductive composite as described above.

Advantageously, the method for obtaining the electrically conductive composite comprises the following steps: a. functionalization of the polyamide, and; b. addition of the intrinsically conductive polymer to the functionalized polyamide.

In step a, the functionalization of the polyamide may be carried out by the use of graphene. Particularly, the functionalization of the polyamide is performed during the polymerization step for preparing a polyamide. The “polymerization” is understood as a production of a polymer from monomers by polycondensation reaction. The functionalized polyamide is prepared by polymerization between graphene and nylon salt containing a diamine and a dicarboxylic acid. The method includes a conventional polymerization method to prepare polyamide, this means being well known by a person skilled in the art. The diamine and dicarboxylic acid may be used in liquid or solid form in the reaction and the graphene may be used in nanoplaques, nanoparticles, reduced graphene oxide or graphene oxide form.

In step b, the addition of the intrinsically conductive polymer to the functionalized polyamide may be by the use of extrusion method. The intrinsically conductive polymer and the functionalized polyamide may be fed to the melt extrusion device in granules or pellets form. The method includes any conventional extrusion means suitable for melt extrusion of polyamides or its derivatives, these means being well known by a person skilled in the art, such as single-screw extruder, double-screw extruder, bi-component extruder and grid spinning head.

By the method of the functionalization of the polyamide of the present invention, it is obtained a polyamide chain containing graphene chemically bonded into the polymer chain. Particularly, the polyamide X.Y is made of from nylon X.Y salt containing a diamine and a dicarboxylic acid.

In a particular embodiment, the polyamide is polyamide 6.6 and is prepared from the polymerization of a nylon 6.6 salt containing mainly hexamethylenediamine and adipic acid.

The functionalization of the polyamide advantageously comprises the following steps: al. Feeding a batch reactor with the nylon X.Y salt; a2. Heating, agitating and pressurizing the batch reactor for at least 60 min; a3. Injecting a suspension of the graphene to obtain a reactor medium; a4. Depressing the batch reactor under heating for at least 60 min; a5. Extruding the reactor medium to produce the functionalized polyamide.

In step al the nylon X.Y salt is continuously introduced in a batch reactor at a temperature about 60°C. In step a2, the batch reactor is preferably heated at a temperature from 140 to 270°C, at a pressure from 1 to 20 bar and under stirring during at least 60 minutes.

Then, in step a3 the graphene in nanoplaques or nanoparticles is injected in the reactor, preferably in form of a suspension at a concentration from 2 to 6 wt% in water obtaining a reaction medium. In step a4, the batch reactor is preferably depressurized while the temperature is kept from 250 to 280°C for at least 60 minutes. The reaction medium is maintained preferably for at least more 15 minutes to ensure complete polymerization.

Then, in step a5, the reactor medium is extruded preferably in the form of granules or pellets to produce functionalized polyamide.

Advantageously, the intrinsically conductive polymer is added to the functionalized polyamide by melt extrusion of the functionalized polyamide with the intrinsically conductive polymer.

In a preferred embodiment of the invention, the melt extrusion comprises the following steps: bl. Feeding into the inlet of a screw extruder the functionalized polyamide in the form of a melt, pellets, granules or powder and at least one intrinsically conductive polymer to obtain a composition; b2. Extruding the composition to form a composite; b3. Cooling down the composite and granulating it into pellets or granules. In step bl the functionalized polyamide preferably previously dried under vacuum at temperatura from 50 to 80°C and the at least one intrinsically conductive polymer may be continuously introduced as a melt, pellets, granules or powder form into the inlet of a extruder device obtaining a composition.

Then, according to step b2 the composition containing molten functionalized polyamide and intrinsically conductive polymer is extruded in a screw-extruder preferably at a temperature from 210 to 270°C, and using a screw rotation of 250 rpm.

Step b3 is the step of cooling down the extruded composite until the solidified form and submit it to granulating process into pellets or granules.

Electrically conductive article

Advantageously, the method of the present invention allows to produce composites which can be used to prepare various final structures from textiles to engineering devices and, therefore, be used in a wide range of applications.

By “engineering devices” it should be understood any devices using plastics raw material that can be used after transformation by processing, such as but not limited to automotive parts, electronic components, home appliances parts and construction devices.

The composite of the present invention can be transformed into an electrically conductive article notably a textile fabric or garment. An electrically conductive article is preferably a fiber, a staple fiber, a flock, a woven or non-woven fabric or a textile article made from the composite as defined above or obtained from the process according to the invention.

Typically, the electrically conductive textiles produced according to the present invention may present durability, launderability, reusability and fibrous performances similar to performances of the textiles produced using polyamide without electrical conductivity property.

Advantageously, the composite of the present invention can be used in smart materials able to sense external conditions or stimuli, to respond and adapt behaviour to them in an intelligent way and may be present in several fields such as but not limited to health, sport, automotive and aerospace.

According to a particular preferred embodiment, the composite of the present invention can be used in smart materials selected from sensors, engineer plastics, automobilistic parts, gps, flexible fabric keyboards, radio frequency circuits, airplanes parts, electromagnetic shielding, protective clothing, touch screen displays and medical textiles.

Other details or advantages of the invention will become more clearly apparent in the light of the examples given below. EXAMPLES:

Graphene was obtained from CODEMGE/CDTN/UFMG/MGGRAFENO as a sludge, with approximately 10 to 20% by weight in a suspension of water and surfactant.

Polyaniline (PAni) was obtained as emeraldine salt from Sigma- Aldrich.

Nylon 6.6 salt was obtained from Solvay using conventional process of preparation by mixing adipic acid and hexamethylenediamine.

Example 1 : Functionalization of polyamide (PA) with graphene

Step 1. Preparation of graphene was made by diluting 2wt% or 4wt% of graphene nanoplaques in water to make a suspension.

Step 2. Polymerization: In step al, at a batch reactor under 60°C, it was added a mixture of 4kg of nylon 6.6 salt, 0.6 g of antifoam, 3.55g of HMD (hexamethylenediamine), 500 g of water under stirring and N2 atmosphere. In step a2 the temperature and pressure were increased up to 145.8°C and 1.31 bar, respectively for salt concentration. Then, the temperature and pressure were increased up to 225°C and 17.27 bar, respectively. While the temperature was increasing to 265.5°C, the pressure was kept constant for 60 min. In step a3 500g of graphene suspension (2wt% or 4wt% of concentration) was injected. An extra injection of 500g of water was executed to wash out any remaining graphene suspension from the injector. Then, in step a4 the pressure was reduced during 55 min until ambient pressure, and the temperature was increased up to 275°C. To finish the polymerization reaction, the reactor medium was kept for 15 min in the reactor. In step a5 the reactor medium was extruded and granulated to produce functionalized polyamide.

Example 2 : Raman Spectroscopy Analysis

Raman Spectroscopy analysis was performed in a Witec Alpha 300RA equipment with polyamide 6.6 fimctionilized with graphene to evaluate the graphene distribution in the polymeric matrix. Samples of 2x2 cm were submitted to 25 spectras collected each one using laser 532 nm, potencial 0.8 mW and objective lens (zoom) 50x.

As shown by the samples (a) and (b) in Figure 1, gray squares represented areas without graphene signal and black squares represented the areas with graphene signal. The results showed that the samples obtained by the process of example 1 demonstrated a concentration from 0.5 wt% and lwt% of graphene, having homogenous distribution throughout the sample.

Example 3 : Addition of intrinsically conductive polymer A number of composite trial samples were prepared including different amounts of polyamide (PA6.6) with graphene or polyamide (PA6.6) with graphene and PAni according the Table 1. PA6.6 was used as control sample.

The functionalized polyamide 6.6 was dried for 24h, under 80°C in a vacuum oven. The electrically conductive composite was made by melt extrusion using an equipment screw extruder Coperion Cte 35 plus. In step bl, the previously dried functionalized polyamide 6.6 was fed into the inlet of the screw extruder in the form of dried pellets. Then, the polyaniline (Pani) powder was fed into the inlet of the screw extruder in the form of powder at a temperature around 220°C. The mixture composition was melted, homogenized and pressurized inside the screw extruder at a temperature of around 260°C and at screw rotation speed of 250rpm. Then, according to step b2, the molten composition of functionalized polyamide 6.6 and polyaniline was extruded “in a noodle” form. In step b3, the extruded composition was granulated into pellets. The pellets were the composite of functionalized polyamide 6.6 and polyaniline (composite PA66 + Graphene + PAni), which were submitted to eletrical properties evaluation.

TABLE 1. Composite trial samples

Example 4 : Differential Scanning Calorimetry - DSC

Specific heat capacity (Cp) of samples 1, 2 and 3 were measured in a DSC in a Shimadzu, model DSC-60, with N2 and heating rate of 10°C/min. As shown in Figure 2, different profiles of curves, mainly comparing sample 2 and 3 demonstrated the successful addition of the PAni in the composite sample 3. The Cp curve is higher for sample 3 at temperatures above 200°C and the thermal event is slightly shifted for lower temperature, showing the influence on PAni addition.

Example 5 : Electrical Properties Bulk resistivity evaluation was measured according to a method described in ASTM D 257:2014(2021) ed.l, using a resistance meter and a resistivity cell, both from HP, and samples of lOOxlOOmm and thickness from 1.3 to 2.8 mm.

The electrical conductivity of the samples were calculated by the inverse of bulk resistivity (c =1/ p). The results for the trial samples 1 to 6 prepared according to examples 1 and 3 can be seen in Table 2 below.

TABLE 2. Electrical conductivity (a) and Bulk Resistivity (p) for the composite samples

As demonstrated by the results of Table 2 the lower the bulk resistivity the higher the level of electrical conductivity.

Composite samples 5 and 6 showed highest electrical conductivity, with even better results showed by sample 6.

Example 6 : Mechanical Properties

Mechanical evaluation of the composite samples were measured according to tensile, impact and flexural properties.

Tensile tests were performed following ASTM D638:2014 “Standard Test Method for Tensile Properties of Plastics” in an equipment Instron EMIC, model 23-30. Impact test were performed following ASTM D256: 10(2018) - “Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics” in an equipment NZ Philpolymer, model XRL - 400.

TABLE 3. Mechanical properties for the composite samples

As demonstrated in Table, all mechanical properties showed the same magnitude and similar values compared to the control sample 1 (PA66).

Therefore, surprisingly, it has been found a composite containing very small amounts of functionalized polyamide and intrinsically conductive polymer with unexpected enhanced results on electrical conductivity and maintenance of mechanical and contort properties.

It should be understood that the invention is not limited by the above description but rather by the claims appended hereto.

Claims

C L A I M S

1. An electrically conductive composite comprising:

- at least one polyamide PA X.Y, X and Y being independently from one another selected from monomers containing from 4 to 16 carbon atoms, wherein the polyamide is a functionalized polyamide with a functionalizing agent comprising graphene, and;

- at least one intrinsically conductive polymer.

2. The composite according to claim 1, wherein the graphene is chosen from nanoparticles, nanoplaques and mixtures thereof, preferably the graphene is nanoplaques of graphene.

3. The composite according to claim 2, wherein the D90 size of the nanoplaques of graphene ranges from 0.1 to 30 pm, preferably from 0.5 to 20 pm, more preferably from 1 to 15 pm, even more preferably from 5 to 7 pm and most preferably from 1 to 5 pm.

4. The composite according to anyone of the preceding claims, wherein the functionalized polyamide comprises graphene chemically bonded into the polyamide chain.

5. The composite according to anyone of the preceding claims, wherein the functionalized polyamide comprises from 0.3 to 3% by weight of graphene, preferably from 0.5 to 2 % by weight, more preferably from 0.5 to 1.5 % by weight, based on the total weight of the functionalized polyamide.

6. The composite according to anyone of the preceding claims, wherein the polyamide is chosen from PA 6.6.

7. The composite according to to anyone of the preceding claims, wherein the at least one intrinsically conductive polymer is selected from polyaniline, a substituted polyaniline, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), a poly(3, 4-ethylenedioxythiophene), a substituted poly(3, 4- ethylenedioxythiophene), poly(thiophene), a substituted poly(thiophene), poly(pyrrole), a substituted poly(pyrrole), poly(acetylene), poly(p- phenylenevinylene) (PPV), a poly(indole), a substituted poly(indole), a poly(carbazole), a substituted poly (carbazole), a poly(azepine), a (poly)thieno P,4-b]thiophene, a substituted poly(thienoP, 4-b]thiophene), a poly (dithienoP, 4- b:3',4'-d]thiophene), a poly(thienoP, 4-b] furan), a substituted poly(thienoP, 4- b] furan), a derivative thereof, or a combination of two or more thereof, preferably the intrinsically conductive polymer is polyaniline.

8. The composite according to anyone of the preceding claims comprising from 0.5 to 3% by weight of the intrinsically conductive polymer, preferably from 1 to 2% by weight, based on the total weight of the composite.

9. Method for obtaining an electrically conductive composite as defined in anyone of claims 1 to 8, wherein the composite is obtained by: a. functionalization of the polyamide, and; b. addition of the intrinsically conductive polymer to the functionalized polyamide.

10. Method according to claim 9, wherein the polyamide is made of from nylon X.Y salt and, wherein the functionalization of the polyamide comprises the following steps: al. Feeding a batch reactor with the nylon X.Y salt; a2. Heating, agitating and pressurizing the batch reactor for at least 60 min; a3. Injecting a suspension of the graphene to obtain a reactor medium; a4. Depressing the batch reactor under heating for at least 60 min; a5. Extruding the reactor medium to produce the functionalized polyamide.

11. Method according to claims 9 or 10, wherein the intrinsically conductive polymer is added to the functionalized polyamide by melt extrusion of the functionalized polyamide with the intrinsically conductive polymer.

12. Method according to the claim 11, wherein the melt extrusion comprises the following steps: bl. Feeding into the inlet of a screw extruder the functionalized polyamide in the form of a melt, pellets, granules or powder and at least one intrinsically conductive polymer to obtain a composition, b2. Extruding the composition to form a composite; b3. Cooling down the composite and granulating it into pellets or granules.

13. Electrically conductive article comprising a composite as defined in anyone of claims 1 to 8 or obtained from the method as defined in anyone of claims 9 to 12.

14. Electrically conductive article according to claim 13, wherein the electrically conductive article is a fiber, a staple fiber, a flock, a woven or non-woven fabric or a textile article.

15. Use of a composite as defined in anyone of claims 1 to 8 or obtained from the process as defined in anyone of claims 9 to 12 in smart materials selected from sensors, engineer plastics, automobilistic parts, gps, flexible fabric keyboards, radio frequency circuits, airplanes parts, electromagnetic shielding, protective clothing, touch screen displays and medical textiles.