DESC:FIELD OF THE INVENTION:
The present invention relates to high thermal and electrical conductive carbon-polymer composite. Moreover, this invention relates to preparation of high thermal and electrical conductive carbon-polymer composite and composition of the same. The present invention also relates to application of the high thermal and electrical conductive carbon-polymer composite.
BACKGROUND OF THE INVENTION:
Thermoplastic polymer composites have low thermal and electrical conductivity properties. As such polymer composites are not directly employed, there is a need for high thermal and electrical conductivity applications. In general, to improve the thermal and electrical conductivity, conductive fillers are added. Addition of conductive fillers may lead to reduced mechanical properties. Further, there is a challenge in dispersion of conductive fillers over the thermoplastic polymers. So, there is a need for selection of conductive fillers, compatible thermo plastic polymers, dispersion of conductive fillers as well as maintain the mechanical as well as thermo, electrical properties depending on applications.
CN114133665 discloses a method of high conductive carbon black and Carbon nanotube. Further it discloses the dispersion liquid contains ethanol, vinyltriethoxysilane, and 3-(phenylamino) propyltrimethoxysilane and its electrical conductivity. However, in the method of preparation of a high-conductivity composite includes preparation of a master batch of dispersed carbon nanotubes and carbon black in a high amount of dispersion medium, wherein the preparation of the master batch comprises taking carbon black and carbon nano tubes as raw materials, dispersing the raw materials in a high amount of a dispersion liquid, followed by then adding a dispersing agent and a high polymer material for melt blending. Moreover, the high-conductivity composite of the reference is not a cost effective composite due to employing higher amount of the constituents i.e. carbon black and carbon nanotube etc.
US 2016/0297952 discloses a method of carbon nanotube based high electrical conductive polymer composite with its functionalization of carbon nanotube. However, in the preparation of the high electrical conductive polymer composite of the reference includes functionalization of carbon nanotubes for dispersion of the conductive materials in the polymer matrix.
US006048919A discloses the high thermal conductive polymer composite with filler having carbon fiber and boron nitride.
CN104844795 A discloses a high thermal conductive nylon 6 preparation method, and it involves dispersion grapheme in aqueous titanate by in-situ polymerization with caprolactam. However, disclosed preparation method of the high-strength heat conduction nylon 6 includes a very high content of costly graphene viz. in an amount 30- 70 wt. %, along with little amount of the aqueous titanic acid ester to modify the graphene surface, even than the graphene surface modification could not achieved in a required quantity, as addition of a higher amount of the aqueous titanic acid ester is associated with declination of material property of the graphene.
CN104341592A discloses a process for preparing high strength high toughness polyamide nylon material wherein the process involves pre-polymerizing of functionalized CNT, Calcium carbonate and Polyamide.
US20160297952A1 & US 8,299,159 B2 discloses a thermal conductive moldable thermo plastic compositions. However, in the preparation of the thermal conductive moldable polymer composite of the reference includes employment of higher amount of a plurality of metal-coated filler particles; a plurality of secondary filler particles; and a polymer matrix in admixture with the metal-coated filler particles and the secondary filler particles.
Wen-Yan Wang et al. in the paper titled “Flexible, multifunctional, and thermally conductive nylon/graphene nanoplatelet composite papers with excellent EMI shielding performance, improved hydrophobicity and flame resistance” J. Mater. Chem. A, 2021,9, 5033-5044 discloses a thermally conductive nylon/graphene nanoplatelet composite papers and a method of preparation thereof, wherein the method of preparation of the composite paper comprises employment of a higher amount of the graphene nanoplatelet (GNP) of a specific thickness viz. 180 µm.
Moreover, the available methods and the composites of the prior arts involve functionalization of carbon nanotube for dispersion along the carbon matrix as well as polymer matrix. However, functionalization led to the destruction of the carbon nanotube properties. Further, prior art uses complex procedure for dispersion of carbon nanotubes. Functionalization requires additional process requirement as well as scalability is a matter of concern.
In view of the above shortcomings, there is an urgent need for an improved thermal and electrically conductive composite and a process of preparation thereof.
Accordingly, the present disclosure provides an improved thermal and electrically conductive carbon-polymer composite and an advanced, cost-effective and less energy intensive process of preparation thereof.
OBJECTIVE OF THE INVENTION:
The primary objective of the invention is to provide a high thermal and electrical conductive carbon-polymer composite.
Another objective of the invention is to provide a process of preparation of a high thermal and electrical conductive carbon-polymer composite.
Yet another objective of the invention is to provide a stepwise process preparation of carbon composite in a dispersible form along with a polymer matrix.
Further objective of the invention is to provide carbon composite comprising pristine multiwalled carbon nanotubes (MWCNTs) with a purity of 90 % to 95 %.
Another objection of the invention is to provide an application of a high thermal and electrical conductive carbon-polymer composite for high thermal conductive product development pertaining to the field of aerospace, mobility, LED etc.
SUMMARY OF THE INVENTION:
In general dispersion of multiwalled carbon nanotube (MWCNT) along the base polymer matrix is a major challenge. The present invention deals with preparation of dispersion which is compatible to polymer matrix with pristine MWCNT having purity in a range of 90 to 95 %. Further present invention deals with dispersion of carbon composite which is compatible to polymer matrix by using water based surfactant solution and organic oil (linseed oil) as anchoring agent mainly forming the emulsion which enhances the dispersibility of MWCNT based carbon composite. Furthermore, the present invention relates to a high thermal and a high electrically conductive carbon-polymer composite and a process of preparation thereof. In addition, the present invention also relates to applications of the high thermal and electrically conductive carbon-polymer composite.
In an aspect of the present invention, a carbon-polymer composite comprising: a) a carbon component in an amount of 40 to 80 weight % of the carbon-polymer composite; and b) a polymer matrix component in an amount of 20 to 60 weight % of the carbon-polymer composite; wherein the carbon component comprises constituents selected from: i) a carbon source selected from multiwalled carbon nano tubes (MWCNTs), an expanded graphite, a carbon black, a graphite powder and a combination thereof; ii) an alkali salt; iii) an oil; and iv) a hydrocarbon resin, wherein the polymer matrix component comprises constituents selected from: a polymer, glass fibres, and carbon fibres.
In another aspect of the present disclosure, there is provided a process for preparing a carbon-polymer composite, said process comprising: a). preparing a carbon component; b). dispersing the carbon component in a polymer matrix component to obtain a carbon-polymer composite mixture; and c). extruding the carbon-polymer composite mixture to obtain the carbon-polymer composite.
DESCRIPTION OF THE PRESENT INVENTION
The following description includes the preferred best mode of one embodiment of the present invention. It will be clear from this description of the invention that the invention is not limited to these illustrated embodiments but that the invention also includes a variety of modifications and embodiments thereto. Therefore, the present description should be seen as illustrative and not limited. While the invention is susceptible to various modifications and alternative constructions, it should be understood that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims.
In an aspect of the present invention, there is provided a high thermal and electrical conductive carbon-polymer composite.
In another aspect of the present invention, there is provided a process for preparing a high thermal and electrical conductive carbon-polymer composite.
In a preferred aspect of the present invention, a carbon-polymer composite comprising: a) a carbon component in an amount of 40 to 80 weight % of the carbon-polymer composite; and b) a polymer matrix component in an amount of 20 to 60 weight % of the carbon-polymer composite; wherein the carbon component comprises constituents selected from: i) a carbon source selected from multiwalled carbon nano tubes (MWCNTs), an expanded graphite, a carbon black, a graphite powder and a combination thereof; ii) an alkali salt; iii) an oil; and iv) a hydrocarbon resin, wherein the polymer matrix component comprises constituents selected from: a polymer, glass fibres, and carbon fibres.
In another aspect of the present invention, the carbon source is selected from a three-dimensional carbon, a two-dimensional carbon, a one-dimensional carbon and a combination thereof, wherein preferably the three-dimensional carbon is an expanded graphite, one-dimensional carbon is a multiwalled carbon nanotube (MWCNT), and the two-dimensional carbon is graphite.
In an aspect of the present invention, the carbon component comprises constituents selected from: i) a carbon source selected from multiwalled carbon nano tubes (MWCNTs), an expanded graphite, a carbon black, a graphite powder and a combination thereof; ii) an alkali salt; iii) an oil; and iv) a hydrocarbon resin, wherein the multiwalled carbon nano tubes (MWCNTs) is in an amount of 2 to 20 weight % of the carbon component, wherein the expanded graphite is in an amount of 50 to 90 weight % of the carbon component, wherein the carbon black is in an amount 1 to 4 weight % of the carbon component, wherein the graphite powder is in an amount 10 to 20 weight % of the carbon component, wherein the alkali salt is in an amount of 0.5 to 20 weight % of the carbon component, the oil is in an amount of 5 to 15 weight % of the carbon component, and wherein the hydrocarbon resin is in an amount ranging from 0.5 to 2 weight % of the carbon component.
In a preferred aspect of the present invention, the carbon component comprises the multiwalled carbon nano tubes (MWCNTs) in an amount of 2 to 20 weight % of the carbon component; the expanded graphite in an amount of 50 to 90 weight % of the carbon component; the alkali salt is sodium silicate in an amount of 0.5 to 20 weight % of the carbon component; the oil in an amount of 5 to 15 weight % of the carbon component; and the hydrocarbon resin in an amount ranging from 0.5 to 2 weight % of the carbon component.
In another aspect of the present invention, the polymer matrix component comprises constituents selected from: a polymer, glass fibres, and carbon fibres, wherein the polymer is a thermoplastic polymer in an amount of 25 to 60 weight % of the carbon-polymer composite and is selected from Nylon-6, Polyethylene, Polypropylene, Polystyrene and a combination thereof.
In still another aspect of the present invention, the glass fibre is in an amount of 0.5 to 20 weight % of the carbon-polymer composite, wherein the carbon fibre is in an amount of 1 to 8 weight % of the carbon-polymer composite, and wherein the glass fibre and the carbon fibre have a particle size in a range of 1 to 8 mm, preferably 4 mm.
In yet another aspect of the present invention, the carbon-polymer composite has a thermal conductivity in a range of 10 to 30 W/mK at 298 K; a tensile strength in a range of 4.0 x 107 to 7.0 x 107 Pascal; a flexural modulus in a range of 3.5 x 109 to 1.25 x 1010 Pascal; a flexural strength in a range of 3.5 x 107 to 7.0 x 107 Pascal; an izod impact in a range of 10 to 25 Joule/metre; a heat deflection temperature (at 0.455 x 106 Pascal) in a range of 180 to 220 °C; and a surface resistivity in a range of 20 to 100 O/ cm square.
In a preferred aspect of the present invention, a process for preparing a carbon-polymer composite, said process comprising: a). preparing a carbon component; b). dispersing the carbon component in a polymer matrix component to obtain a carbon-polymer composite mixture; and c). extruding the carbon-polymer composite mixture to obtain the carbon-polymer composite.
In another aspect of the present invention, the preparation of the carbon component comprises: i). mixing 2 to 20 weight % of multiwalled carbon nano tubes (MWCNTs), 50 to 90 weight % of an expanded graphite, optionally 1 to 4 weight % of carbon black or 10 to 20 weight % of graphite powder; and 0.5 to 20 weight % of an alkali salt solution to obtain a carbon pre-mix; ii). adding 5 to 15 weight % of an oil into the carbon pre-mix followed by a grinding for a time period of 150 to 200 minutes in an organic solvent as grinding medium, to obtain an oil dispersed carbon pre-mix; iii). adding 0.5 to 2 weight % of a hydrocarbon resin solution into the oil dispersed carbon pre-mix followed by grinding for a time period of 20 to 50 minutes to obtain a carbon mixture solution; and iv). drying the carbon mixture solution at a temperature ranging from 100 to 150 °C to obtain the carbon component.
In yet another aspect of the present invention, the hydrocarbon resin solution comprises C9+ hydrocarbon resin dispersed in toluene, wherein preferably the oil is linseed oil, and wherein and wherein the alkali salt is sodium silicate.
In still another aspect of the present invention, the polymer matrix component comprises a polymer, glass fibres, and carbon fibres; wherein the polymer is in an amount of 20 to 60 weight % of the carbon-polymer composite; the glass fibres is in an amount of 0.5 to 20 weight % of the carbon-polymer composite; and the carbon fibres is in an amount of 1 to 8 weight % of the carbon-polymer composite; wherein the glass fibres and the carbon fibres have a particle size ranging from 1 to 8 mm, preferably 4mm; and wherein the polymer is a thermoplastic polymer preferably selected from Nylon-6, Polyethylene, Polypropylene, Polystyrene and a combination thereof.
In an aspect of the present invention, the carbon-polymer composite comprises a carbon component dispersed polymer matrix component.
In still another aspect of the present invention, the expanded graphite is selected for a higher specific heat and a high thermal conductivity.
In yet another aspect of the present invention, the expanded graphite is derived from a natural or a synthetic graphite, wherein the natural or the synthetic graphite is subjected for an acid treatment followed by a thermal expansion at 700°C to 1000°C, wherein the acid treatment is used for functional groups attached to the graphite, and wherein the acid is selected from the group of sulphuric acid, nitric acid, hydrochloric acid or a mixture thereof.
In still another aspect of the present invention, the carbon-polymer composite comprises pristine multiwalled carbon nanotubes (MWCNTs) with high purity of 90 % to 95 %, wherein the multiwalled carbon nanotubes (MWCNTs) have a particle size in a range of 5 to 30 nm, and wherein the pristine multiwalled carbon is selected to maintain mechanical, thermal and electrical properties of the carbon-polymer composite.
In another aspect of the present invention, dispersing of the carbon source selected from multiwalled carbon nano tubes (MWCNTs), an expanded graphite, a carbon black, a graphite powder and a combination thereof, in a dispersant and an anchoring agent is achieved in a wet grinding in an aromatic solvent as grinding medium for a time period of 150 to 200 minutes to obtained an oil dispersed carbon pre-mix, wherein the dispersant is a water-based surfactant solution preferably water-based sodium silicate solution, and the anchoring agent is an organic oil (linseed oil), wherein the aromatic solvent is added in a mass ratio 0.8 to 1.5 times of the carbon pre-mix, and wherein the dispersant and the anchoring agent form an emulsion and enhance dispersibility of the MWCNT. Moreover, mixing both the dispersant and the anchoring agent forms the emulsion which facilitates dispersion of the MWCNT along with the solvent. The solvent is also used as the wet grinding medium, wherein the solvent is compatible with thermoplastic polymers selected from Nylon-6, Polyethylene, Polypropylene, Polystyrene and a combination thereof. Further to enhance the dispersion, wet mixing or grinding is used.
In an aspect of the present invention, the carbon component comprises a curing agent, wherein the curing agent is added after sufficient time of grinding of an oil dispersed carbon pre-mix, wherein the curing agent is a hydrocarbon resin solution.
In still another aspect of the present invention, the hydrocarbon resin solution is prepared by dissolving a hydrocarbon resin (C9+) in a solvent.
In yet another aspect of the present invention, the carbon mixture solution is dried at a temperature ranging from 100 °C to 150 °C to obtain the carbon component, wherein the drying removes solvent and water from the carbon component.
In an aspect of the present invention, a process for preparing a carbon-polymer composite, said process comprises:
a) mixing of an expanded graphite, multiwalled carbon nano tubes (MWCNT) (5 to 30 nm) with a purity of 90-95 % to obtain a carbon source mixture;
b) adding a dispersant and an anchoring agent along with the carbon source mixture in a wet milling, followed by wet grinding of said mixture in an aromatic solvent as grinding medium in a mass ratio 0.8 to 1.5 of the mixture, for a time period of 150 to 200 minutes, wherein the dispersant is a water-based surfactant solution preferably water-based sodium silicate solution, and the anchoring agent is an organic oil (linseed oil), wherein the dispersant and the anchoring agent form an emulsion and enhance dispersibility of the MWCNT;
c) adding a hydrocarbon resin solution to the oil dispersed carbon pre-mix followed by grinding for a time period of 20 to 50 minutes to obtain a carbon mixture solution; and
d) drying the carbon mixture solution at 120 °C for suitable time to obtain the carbon component.
In an aspect of the present invention, the carbon component comprises:
the expanded graphite in a range of 60 wt.% to 90 wt.% of the carbon component;
the MWCNT in a range of 2 wt. % to 20 wt. % of the carbon component;
Sodium silicate solution in a range of 0.5 wt. % 3 wt. % of the carbon component;
Linseed oil in a range of 3 wt.% to 10 wt. % of the carbon component; and
Hydrocarbon resin in a range of 0.5 wt.% to 2 wt.% of the carbon component.
In another aspect of the present invention, a process of preparation of a high thermal and electrical conductive carbon-polymer composite comprising,
a. preparing a carbon component;
b. mixing of the carbon component with carbon fibre, glass fibre and a thermo plastic polymer selected from Nylon, Polyethylene, Polypropylene, Polystyrene, to obtain a carbon-polymer composite mixture; and
c. extruding the carbon-polymer composite mixture in an extruder to obtain the high thermal and electrical conductive carbon polymer composite.
In another aspect of the present invention, the carbon-polymer composite comprising:
1. a thermo plastic polymer in the range of 25 wt. % to 60 wt. % of the carbon polymer composite;
2. carbon fibres in a range of 1 wt.% to 8 wt.% of the carbon-polymer composite; and
3. glass fibres in a range of 0.5 wt.% to 3 wt.% of the carbon-polymer composite;
In an aspect of the present invention, the high thermal and electrical conductive carbon-polymer composite / MWCNT-Carbon-Polymer composite having properties:

Thermal conductivity in a range of 12 W/mK to 28 W/mK,
Surface resistivity in a range of 20 Ohm/cm2 to 100 Ohm/cm2.
Density in a range of 1300 kg /cubic metre to 1500 kg/cubic metre.
Flexural modulus in the range of 5000 to 12000 MPa.
Heat deflection temperature in the range of 180 °C to 220 °C.
Examples
A. Preparation of Carbon Component:
Example: 1
Pristine multiwalled carbon nano tube (MWCNT, Purity 90-95%) in an amount of 81 grams, expanded graphite in an amount of 396 grams were taken and mixed with 10 grams of 25 wt.% of sodium silicate water solution to obtain a carbon pre-mix. In the carbon pre-mix 50 grams of linseed oil was also added. The obtained mixture was further subjected to a wet grinding for 180 minutes, wherein 720 grams of toluene solvent was used as a wet grinding medium to obtain an oil dispersed carbon pre-mix. After 180 minutes, a hydrocarbon resin (C9+) solution was mixed, wherein the hydrocarbon resin (C9+) solution was prepared by dispersing 6 grams of the hydrocarbon resin (C9+) in 25 grams of toluene and fed into the oil dispersed carbon pre-mix followed by grinding for 30 minutes to obtain a carbon mixture solution. After grinding, the carbon mixture solution was dried for 12 hours at 120 °C to obtain the carbon component.
Example: 2
Pristine Multiwalled carbon nano tube (MWCNT, Purity 90-95 %) in an amount of 25 grams, carbon black in an amount of 12.5 grams, expanded graphite in an amount 439.5 grams were taken and mixed with 10 grams of 25 wt.% of sodium silicate water solution to obtain the carbon pre-mix. In the carbon pre-mix 50 grams of linseed oil was fed and said mix was subjected for the wet grinding for 180 minutes to obtain an oil dispersed carbon pre-mix, wherein 720 grams of toluene solvent was used as wet grinding medium. After 180 minutes, 6 grams of hydrocarbon resin (C9+) was mixed in 25 grams of toluene and fed into the oil dispersed carbon pre-mix and obtained mixture was further grinded for 30 minutes to obtain the carbon mixture solution. After grinding, the carbon mixture solution was dried for 12 hours at 120 °C.
Example: 3
Multiwalled carbon nano tube (MWCNT, Purity 90-95 %) in a amount of 25 grams, graphite powder in an amount of 90.4 grams, expanded graphite in an amount of 361.6 grams were taken and mixed with 4 grams of 25 wt.% of sodium silicate water solution to obtain a carbon pre-mix. In the carbon pre-mix 25 grams of linseed oil was fed and the mixture was further subjected to the wet grinding for 180 minutes to obtain the oil dispersed carbon pre-mix, wherein 670 grams of toluene solvent was used as wet grinding medium. After 180 minutes, 1 gram of hydrocarbon resin (C9+) was mixed with 25 grams of toluene and fed into the oil dispersed carbon pre-mix and said mixture was further grinded for 30 minutes to the carbon mixture solution. After grinding, the mixture solution was dried for 12 hours at 120 °C.
Example: 4
Multiwalled carbon nano tube (MWCNT) in an amount of 37.5 grams and expanded graphite in an amount of 439.5 grams were taken and mixed with 10 grams of 25 wt.% of sodium silicate solution to obtain a carbon pre-mix. In the carbon pre-mix 50 grams of linseed oil was fed. The said mixture was further subjected to a wet grinding for 180 minutes to obtain the oil dispersed carbon pre-mix, wherein 720 grams of toluene solvent was used as wet grinding medium. After 180 minutes, 6 grams of hydrocarbon resin (C9+) was mixed in 25 grams of toluene and fed into the mixture. The mixture was further grinded for 30 minutes. After grinding, the carbon mixture solution was dried for 12 hours at 120 °C to obtain to obtain the carbon component.

B. Preparation of Carbon-Polymer Composite:
Example: 5
The dried carbon component. of Example: 1 was blended with 30 wt.% Nylon-6 polymer and extruded with a twin screw extruder and obtained a MWCNT-Nylon composite. Thermal conductivity of the obtained MWCNT-Carbon-Nylon composite was 27.65 W/mK at 298° Kelvin as per ISO standard 22007-2.
Example: 6
The dried carbon component of Example: 1 was blended with 40 wt.% Nylon-6 polymer and obtained mixture was extruded with the twin screw extruder to obtain a MWCNT-Nylon composite. Thermal conductivity of the obtained MWCNT-Carbon-Nylon composite (the carbon-polymer composite) was 18.15 W/mK at 298° Kelvin as per ISO standard 22007-2. The mechanical properties of the said MWCNT-Carbon-Polymer composite are given in Table: 1
Table:1
S.No Properties Test method Units Value
1 Density ISO 1183 Kg/m^3 1360
2 Tensile strength at
Yield ASTM D 638 Pascal 41.6*106
3 Flexural modulus ASTM D 790 Pascal 7760*106
4 Flexural strength ASTM D 790 Pascal 65*106
5 Izod impact (N) ASTM D 256 Joules/metre 14.1
6 Heat Deflection Temperature @ 0.455*106 Pascal ASTM D 648 Degree Celsius 190
7 Surface resistivity ASTM D 257 Ohm/square 25

Example: 7.
The dried carbon component as prepared in Example: 3 was blended with 40 wt. % Nylon-6 polymer and obtained mixture was extruded with a twin-screw extruder to obtain a MWCNT-Nylon composite. Thermal conductivity of the obtained MWCNT-Carbon-Nylon composite was 17.6 W/mK as per ISO standard 22007-2. The mechanical properties of MWCNT-Carbon-Polymer composite are given in Table: 2.
Table :2
S.No Properties Test method Units Value
1 Density ISO 1183 Kg/m^3 1380
2 Tensile strength at
Yield ASTM D 638 Pascal 44*106
3 Flexural modulus ASTM D 790 Pascal 3970*106
4 Flexural strength ASTM D 790 Pascal 43*106
5 Izod impact (N) ASTM D 256 Joules/metre 11.5
6 Heat Deflection Temperature @ 0.455*106 Pascal ASTM D 648 Degree Celsius 193
7 Surface resistivity ASTM D 257 Ohm/square 32

Example: 8
The dried carbon component from Example: 4 was blended with 40 wt.% Nylon-6 polymer,4 wt.% of carbon fibre of size 4 mm, and 1wt.% of glass fibre of size 4 mm to obtain the carbon-polymer composite mixture. Said carbon-polymer composite mixture was extruded with a twin screw extruder to obtain the MWCNT-Nylon composite. Thermal conductivity of the obtained MWCNT-Carbon-Nylon composite was 14.7 W/mK at 298° Kelvin as per ISO standard 22007-2. The mechanical properties of MWCNT-Carbon-Polymer composite are given in Table: 3
Table:3
S.No Properties Test method Units Value
1 Density ISO 1183 Kg/m^3 1450
2 Tensile strength ASTM D 638 Pascal 48*106
3 Flexural modulus ASTM D 790 Pascal 8100*106
4 Flexural strength ASTM D 790 Pascal 43.5*106
5 Izod impact (N) ASTM D 256 Joules/metre 21.9
6 Heat Deflection Temperature @ 0.455*106 Pascal ASTM D 648 Degree Celsius 206
7 Surface resistivity ASTM D 257 Ohm/square 55

Example: 9
The dried carbon component from Example: 4 was blended with 40 wt.% of Nylon-6 polymer, 5 wt.% of carbon fibres having a particle size of 4 mm and 2 wt.% of glass fibres having a particle size of 4mm to obtain the carbon-polymer composite mixture. Said carbon-polymer composite mixture was extruded with twin screw extruder to obtain MWCNT-Nylon composite. Thermal conductivity of the obtained MWCNT-Carbon-Nylon composite was 13.76 W/mK at 298° Kelvin as per ISO standard 22007-2. The mechanical properties of said MWCNT-Carbon-Polymer composite are given in Table: 4
Table:4
S.No Properties Test method Units Value
1 Density ISO 1183 Kg/m^3 1476
2 Tensile strength ASTM D 638 Pascal 54*106
3 Flexural modulus ASTM D 790 Pascal 8340*106
4 Flexural strength ASTM D 790 Pascal 48.2*106
5 Izod impact (N) ASTM D 256 Joules/metre 22.5
6 Heat Deflection Temperature @ 0.455*106 Pascal ASTM D 648 Degree Celsius 212
7 Surface resistivity ASTM D 257 Ohm/square 64

Example: 10
The dried carbon component from Example: 4 was blended with 45 wt.% of Nylon-6 polymer, 5 wt.% of carbon fibres having a particle size of 4mm and 3 wt. % of glass fibre having a particle size of 4mm extruded with twin screw extruder and obtained MWCNT-Nylon composite. Thus obtained MWCNT-Carbon-Nylon composite thermal conductivity was 12.2 W/mK at 298° Kelvin as per ISO standard 22007-2. The mechanical properties of MWCNT-Carbon-Polymer composite are given in Table: 5
Table:5
S.No Properties Test method Units Value
1. Density ISO 1183 Kg/m^3 1454
2. Tensile strength at Yield ASTM D 638 Pascal 65*106
3. Flexural modulus ASTM D 790 Pascal 12100*106
4. Izod impact (N) ASTM D 256 Joules/metre 23.1
5. Heat Deflection Temperature @ 0.455*106 Pascal ASTM D 648 Degree Celsius 218
6. Surface resistivity ASTM D 257 Ohm/square 86

Example: 11
A compositional comparison of the carbon component of the carbon-polymer composite of the present invention is given in Table 6.
Table 6:
Example
Components
1 2 3 4
MWCNT(g) 81 25 25 37.5
Expanded graphite (g) 365 439.5 361.6 439.5
Carbon black Nil 12.5 Nil Nil
Graphite powder (g) Nil Nil 90.4 Nil
Sodium silicate (25 wt.%) g 10 10 4 10
Linseed oil (g) 50 50 25 50
Hydrocarbon resin (g) 6 6 1 6

A compositional comparison along with their mechanical properties of the exemplified carbon-polymer composites of the present invention is given in Table 7.
Table 7:
Example
Components
5 6 7 8 9 10
Carbon component Example 1 Example 1 Example 3 Example 4 Example 4 Example 4
Nylon-6 (wt. %) 30 40 40 40 40 45
Carbon fibre (wt. %) Nil Nil Nil 4 5 5
Glass fibre (wt. %) Nil Nil Nil 1 2 3
Properties
T.C.(W/mK) 27.65 18.15 17.6 14.7 13.76 12.2
H.D. (°C) 190 193 206 212 218
S.R. (O/ sq.) 25 32 55 64 86
T.S.(P) 4.16 x 107 4.4 x 107 4.8 x 107 5.4 x 107 6.5 x 107
F.M. (P) 7.76 x 109 3.97 x 109 8.10 x 109 8.34 x 109 1.21 x 1010
F.S. (P) 6.5 x 107 4.3 x 107 4.35 x 107 4.82 x 107
Izod impact (N) 14.1 11.5 21.9 22.5 23.1
T.C.= Tensile strength; H.D. = Heat Deflection; T.S. = Tensile strength; F.M. = Flexural modulus; F.S. = Flexural strength.
From Table 7, it has been observed that on increasing the amount of the polymer Nylon-6 or on increasing the amount of the carbon and glass fibres, thermal conductivity of the carbon-polymer composite decreases, while tensile strength, heat deflection and surface resistivity increases.
The carbon-polymer composites prepared by using the carbon component of Example 4 shows a trend of decreasing thermal conductivity and increasing surface resistivity. Also, a trend of increasing heat deflection with higher amount of glass fibres in the carbon-polymer composite. Experiments show that an increase in the amount of glass fibres from 1 wt.% to 3 wt.%, the thermal conductivity decreases from 14.7 to 12.2 W/mK, while the surface resistivity and heat deflection increases from 55 to 86 O/ cm sq. and 206 to 218°C, respectively. The tensile strength of the carbon-polymer composite prepared with the carbon component of Example 4, having MWCNT in an amount of 37.5g (6.9 wt. %), is the highest among all the exemplified carbon-polymer composites. The observed trend of the tensile strength is in agreement with the flexural modulus results. Therefore, the tensile strength of carbon-polymer composite congruently improves along with the improvement in the flexural modulus that is tensile strength increases by 58 % (from 41.6 MPa to 65 MPa) with simultaneous increase in the flexural modulus by 57 % (from 7.76 GPa to 12.1 GPa). Trends of the properties show that in the optimized carbon-polymer composite composition the carbon components and the polymer matrix components are in synergy and facilitate dispersion of the MWCNT to provide desirable properties to the carbon-polymer composite. The obtained carbon-polymer composite was employed for producing LEDs. ,CLAIMS:We Claim
1. A carbon-polymer composite comprising:
a) a carbon component in an amount of 40 to 80 weight % of the carbon-polymer composite; and
b) a polymer matrix component in an amount of 20 to 60 weight % of the carbon-polymer composite;
wherein the carbon component comprises constituents selected from:
i) a carbon source selected from multiwalled carbon nano tubes (MWCNTs), an expanded graphite, a carbon black, a graphite powder and a combination thereof;
ii) an alkali salt;
iii) an oil; and
iv) a hydrocarbon resin,
wherein the polymer matrix component comprises constituents selected from: a polymer, glass fibres, and carbon fibres.

2. The carbon-polymer composite as claimed in claim 1, wherein the multiwalled carbon nano tubes (MWCNTs) is in an amount of 2 to 20 weight % of the carbon component, wherein the expanded graphite is in an amount of 50 to 90 weight % of the carbon component, wherein the carbon black is in an amount 1 to 4 weight % of the carbon component, wherein the graphite powder is in an amount 10 to 20 weight % of the carbon component, wherein the alkali salt is in an amount of 0.5 to 20 weight % of the carbon component, wherein the oil is in an amount of 5 to 15 weight % of the carbon component, and wherein the hydrocarbon resin is in an amount ranging from 0.5 to 2 weight % of the carbon component.

3. The carbon-polymer composite as claimed in claim 1, wherein the carbon component preferably comprises the multiwalled carbon nano tubes (MWCNTs) in an amount of 2 to 20 weight % of the carbon component; the expanded graphite in an amount of 50 to 90 weight % of the carbon component; the alkali salt is sodium silicate in an amount of 0.5 to 20 weight % of the carbon component; the oil in an amount of 5 to 15 weight % of the carbon component; and the hydrocarbon resin in an amount ranging from 0.5 to 2 weight % of the carbon component.

4. The carbon-polymer composite as claimed in claim 1, wherein the polymer is a thermoplastic polymer in an amount of 25 to 60 weight % of the carbon-polymer composite and is selected from Nylon-6, Polyethylene, Polypropylene, Polystyrene and a combination thereof.
5. The carbon-polymer composite as claimed in claim 1, wherein the glass fibre is in an amount of 0.5 to 20 weight % of the carbon-polymer composite, wherein the carbon fibre is in an amount of 1 to 8 weight % of the carbon-polymer composite, and wherein the glass fibre and the carbon fibre have a particle size in a range of 1 to 8 mm, preferably 4 mm.

6. The carbon-polymer composite as claimed in claim 1, wherein the carbon-polymer composite has a thermal conductivity in a range of 10 to 30 W/mK at 298 K; a tensile strength in a range of 4.0 x 107 to 7.0 x 107 Pascal; a flexural modulus in a range of 3.5 x 109 to 1.25 x 1010 Pascal; a flexural strength in a range of 3.5 x 107 to 7.0 x 107 Pascal; an izod impact in a range of 10 to 25 Joule/metre; a heat deflection temperature (at 0.455 x 106 Pascal) in a range of 180 to 220 °C; and a surface resistivity in a range of 20 to 100 O/ cm square.

7. A process for preparing a carbon-polymer composite, said process comprising:
a. preparing a carbon component;
b. dispersing the carbon component in a polymer matrix component to obtain a carbon-polymer composite mixture; and
c. extruding the carbon-polymer composite mixture to obtain the carbon-polymer composite.

8. The process as claimed in claim 7, wherein the preparation of the carbon component comprises:
i. mixing 2 to 20 weight % of multiwalled carbon nano tubes (MWCNTs), 50 to 90 weight % of an expanded graphite, optionally 1 to 4 weight % of carbon black or 10 to 20 weight % of graphite powder; and 0.5 to 20 weight % of an alkali salt solution to obtain a carbon pre-mix;
ii. adding 5 to 15 weight % of an oil into the carbon pre-mix followed by a grinding for a time period of 150 to 200 minutes in an organic solvent as grinding medium, to obtain an oil dispersed carbon pre-mix;
iii. adding 0.5 to 2 weight % of a hydrocarbon resin solution into the oil dispersed carbon pre-mix followed by grinding for a time period of 20 to 50 minutes to obtain a carbon mixture solution; and
iv. drying the carbon mixture solution at a temperature ranging from 100 to 150 °C to obtain the carbon component.

9. The process as claimed in claim 8, wherein the hydrocarbon resin solution comprises C9+ hydrocarbon resin dispersed in toluene, wherein preferably the oil is linseed oil; and wherein the alkali salt is sodium silicate.

10. The process as claimed in claim 7, wherein the polymer matrix component comprises a polymer, glass fibres, and carbon fibres; wherein the polymer is in an amount of 20 to 60 weight % of the carbon-polymer composite; the glass fibres is in an amount of 0.5 to 20 weight % of the carbon-polymer composite; and the carbon fibres is in an amount of 1 to 8 weight % of the carbon-polymer composite; wherein the glass fibres and the carbon fibres have a particle size ranging from 1 to 8 mm, preferably 4 mm; and wherein the polymer is a thermoplastic polymer preferably selected from Nylon-6, Polyethylene, Polypropylene, Polystyrene and a combination thereof.