METHOD OF PREPARING CARBON COMPOSITE FIBER AND CARBON COMPOSITE FIBER

Abstract

The present invention relates to a method for manufacturing carbon composite fibers and carbon nanofibers, and more particularly, to a method for manufacturing carbon composite fiber with greatly improved specific tensile strength, specific modulus, electrical conductivity, and thermal conductivity.

Claims

1. A method for manufacturing carbon composite fiber, comprising: preparing a spinning dope by dispersing carbon nanomaterials and polyamic acid in super acid; obtaining preliminary fibers by spinning the spinning dope; and imidizing the preliminary fiber to obtain polyimide composite fibers; wherein the spinning dope comprises the carbon nanomaterial and the polyimide precursor in a mass ratio of 90:10 to 20:80.

2. The method of claim 1, wherein: the carbon nanomaterial comprises at least one selected from the group consisting of carbon nanotubes (CNT), graphene, graphene nanoribbons, and combinations thereof.

3. The method of claim 1, wherein: the polyamic acid is manufactured by reacting a diamine and a dianhydride compound, wherein the diamine is an aromatic ring compound and comprises at least one selected from the group consisting of p-phenyl diamine(PDA), 4,4′-oxydianiline(ODA), p-methylenedianiline(MDA), 3,3′-dihydroxy-4,4′-diaminobiphenyl(HAB) and combinations thereof, wherein the dianhydride compound is characterized in that it is an aromatic ring compound and comprises at least one selected from the group consisting of pyromellitic dianhydride(PMDA), biphenyltertracarboxylic dianhydride(BPDA), and combinations thereof.

4. The method of claim 1, wherein: the super acid comprises at least one selected from the group consisting of chlorosulfonic acid, sulfuric acid, fuming sulfuric acid, fluorosulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, fluoroantimonic acid, carboranic acid, and combinations thereof.

5. The method of claim 1, comprising: spinning the spinning dope in a coagulation solvent to obtain a preliminary fiber, wherein the coagulation solvent comprises at least one selected from the group consisting of acetone, diethyl ether, dichloromethane, dimethyl sulfoxide, and combinations thereof.

6. The method of claim 1, wherein: the carbon nanomaterial is oxidized by heat treatment at 400° C. to 700° C. in an oxygen atmosphere.

7. The method of claim 1, wherein: the preliminary fiber is imidized by heat treatment at 200° C. to 450° C.

8. The method of claim 1, further comprising: the step of carbonizing the polyimide composite fiber by heat treatment at 500° C. to 1700° C. in an inert gas atmosphere.

9. The method of claim 1, further comprising: the step of graphitizing the polyimide fibers by heat treatment at 1700° C. to 3300° C. in an inert gas atmosphere.

10. The method of claim 1, wherein: the carbon composite fiber has a density of 1.0 g/cm.sup.3 to 2.2 g/cm.sup.3, a specific tensile strength is 0.5N/Tex to 5N/Tex, a specific tensile modulus is 100N/Tex to 600N/Tex, and a thermal conductivity of 100 W/mk to 1,000 W/mk.

11. A method for manufacturing carbon composite fiber, comprising: preparing a spinning dope by dispersing the carbon nanomaterial and the base substrate in super acid; obtaining preliminary fibers by spinning the spinning dope; and carbonizing the preliminary fiber by heat treatment; wherein the base substrate is a polymer-based substrate; ora petroleum-based or coal-based base material.

12. The method of claim 11, wherein: in the polymer-based substrate, the polymer is polyamic acid, thermoplastic polyimide, polyetherimide(PEI), polyacrylonitrile(PAN), polyphenylene sulfide(PPS), or a combination thereof.

13. The method of claim 11, wherein: the petroleum-based or coal-derived base material is, pitch, coal tar, carbon black, or a combination thereof.

14. The method of claim 11, wherein: the elastic modulus of the manufactured carbon composite fiber is 100 GPa or more, and the tensile strength is 1.5 GPa or more.

15. The method of claim 11, wherein: the manufactured carbon composite fiber satisfies Equation 1 below.
280≤a≤600  [Equation 1]
a={Specific Tensile Modulus(N/tex)*Specific Tensile Strength(N/tex)}/Density(g/cm.sup.3)

16. The method of claim 11, wherein: the polymer-based substrate is polyetherimide (PEI), wherein the content of polyetherimide is 10 to 40% by weight based on 100% by weight of the total spinning dope.

17. The method of claim 11, wherein: the polymer-based substrate is polyimide, wherein the content of polyimide is 10 to 30% by weight based on 100% by weight of the total spinning dope.

18. The method of claim 11, wherein: the polymer-based substrate is polyphenylene sulfide (PPS), wherein the content of polyphenylene sulfide (PPS) is 10 to 30% by weight based on 100% by weight of the total spinning dope.

19. The method of claim 11, wherein: the polymer-based substrate is polyacrylonitrile(PAN), wherein the content of polyacrylonitrile(PAN) is 5 to 20% by weight based on 100% by weight of the total spinning dope.

20. The method of claim 11, wherein: the petroleum-based or coal-derived substrate is pitch, wherein the pitch content is 5 to 30% by weight based on 100% by weight of the total spinning dope.

21. A carbon composite fiber that satisfies Equation 1 below.
280≤a≤600  [Equation 1]
a={Specific Tensile Modulus(N/tex)*Specific Tensile Strength(N/tex)}/Density(g/cm.sup.3)

22. A carbon composite fiber of claim 21, wherein: The a value is a carbon composite fiber that satisfies 300≤a≤550.

23. A carbon composite fiber of claim 21, wherein: the carbon composite fiber is a form in which carbon nanomaterials are dispersed in a base substrate, and in a final fiber state, the base substrate is in a carbonized form, wherein the base substrate is a polymer-based substrate; or petroleum- or coal-based bases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0094] FIG. 1 shows a method for manufacturing a carbon composite fiber according to the present invention.

[0095] FIG. 2 is a graph of strength elongation change of fiber according to Comparative Examples 1 to 4.

[0096] FIG. 3 is a graph showing changes in strength and elongation of polyimide composite fiber according to Examples 1 to 4.

[0097] FIG. 4 is a graph of strength elongation change of carbon fibers according to Examples 5 to 8.

[0098] FIG. 5 is a graph of strength elongation change of graphite fiber according to Examples 9 to 12.

[0099] FIG. 6 is a graph showing the specific tensile strength according to the content of carbon nanofiber according to an embodiment of the present invention.

[0100] FIG. 7 is a graph showing the Specific Tensile modulus according to the content of carbon nanofiber according to an embodiment of the present invention.

[0101] FIG. 8 is a graph showing the specific tensile strength according to the content of carbon nanofiber according to an embodiment of the present invention.

[0102] FIG. 9 is a graph showing the Specific Tensile modulus according to the content of carbon nanofiber according to an embodiment of the present invention.

[0103] FIG. 10 is a graph showing the specific tensile strength according to the content of carbon nanofiber according to an embodiment of the present invention.

[0104] FIG. 11 is a graph showing the Specific Tensile modulus according to the content of carbon nanofiber according to an embodiment of the present invention.

[0105] FIG. 12 is a graph showing the specific tensile strength according to the content of carbon nanofiber according to an embodiment of the present invention.

[0106] FIG. 13 is a graph showing the Specific Tensile modulus according to the content of carbon nanofiber according to an embodiment of the present invention.

[0107] FIG. 14 is a graph showing the specific tensile strength according to the content of carbon nanofiber according to an embodiment of the present invention.

[0108] FIG. 15 is a graph showing the Specific Tensile modulus according to the content of carbon nanofiber according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0109] The following examples illustrate the present invention in more detail. However, the following example is only a preferred embodiment of the present invention, but the present invention is not limited to the following example.

Comparative Example 1: Polyimide Fiber

[0110] Polyimide varnish of Korea PI Advanced Materials was melted in NMP (N-Methyl-2-pyrrolidone) and spun using a syringe. Spinning was performed using a needle having a diameter of 0.18 mm, and fiber was spun with a stretch ratio of about 10.0 or more. The coagulation bath was used by mixing acetone and water at a ratio of 1:1, and the water washing bath was used while heating water at 80° C., and fibers were obtained through winding. Finally, in order to dry the water, the polyamic acid fibers were obtained by drying in a vacuum oven at 80° C. for more than one day. The polyamic acid fiber refer to non-imidized fiber.

[0111] The polyamic acid fibers were additionally imidized using a furnace. Since air present inside the heating furnace is oxidized during heat treatment, the vacuum was pulled to 10.sup.−3 torr before heat treatment, and nitrogen or argon gas was filled inside. Nitrogen was flowed into the furnace at a rate of 20 sccm. Heat treatment was performed by raising the temperature to about 450° C. at a heating rate of 3° C./min to 10° C./min. Specifically, after maintaining the temperature at a temperature of about 80° C. for 1 hour, at 140° C. for 1 hour, at 220° C. for 1 hour, and at 300° C. for 1 hour, the temperature was raised to about 450° C., and then the imidation was terminated. During all imidization processes, polyimide fibers were manufactured by naturally cooling in a state where nitrogen or argon gas was flowing.

Comparative Example 2: Carbon Fiber

[0112] The polyimide fibers of Comparative Example 1 were carbonized using a heating furnace. Since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before carbonization and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. The polyimide fibers were carbonized by raising the temperature to about 1200° C. at a heating rate of 3° C./min to 10° C./min. After carbonization was completed, carbon fibers were manufactured by naturally cooling in a state where nitrogen or argon gas was flowing.

Comparative Example 3: Graphite Fiber

[0113] Graphite fibers were manufactured by heat-treating the polyimide fibers of Comparative Example 1 in the same manner as in Comparative Example 3, except that the temperature was changed to 2700° C.

Example 1: Polyimide Composite Fiber

[0114] A spinning dope was prepared by mixing carbon nanotubes and polyamic acid(PAA) manufactured by Meijo, Japan at a mass ratio of 90:10, and adding chlorosulfonic acid (CSA) at a concentration of 8 mg/mL. The carbon nanotubes are a mixture of single wall carbon nanotubes (SWCNT) and double wall carbon nanotubes (DWCNT) in a mass ratio of 55:45. In order to increase the dispersibility of the carbon nanotubes, they were oxidized by heat treatment at about 400° C. for 6 hours. After stirring the spinning dope for more than one day, it was spun using a syringe. Specifically, a preliminary fiber was obtained by spinning at a stretch ratio of about 2.0 or more using a needle having a diameter of 0.26 mm. Both the coagulation bath and the washing bath used acetone. Washing was carried out for 2 hours and finally dried in a vacuum oven at 170° C. for more than one day to evaporate chlorosulfonic acid (CSA) inside.

[0115] The preliminary fiber was heat-treated by raising the temperature to about 450° C. at a heating rate of 3° C./min to 10° C./min. Specifically, after maintaining the temperature at a temperature of about 80° C. for 1 hour, at 140° C. for 1 hour, at 220° C. for 1 hour, and at 300° C. for 1 hour, the temperature was raised to about 450° C., and then imidized to obtain polyimide composite fibers.

Example 2: Polyimide Composite Fiber

[0116] Polyimide composite fibers were obtained in the same manner as in Example 1, except that the mass ratio of carbon nanotubes and polyamic acid was adjusted to 70:30.

Example 3: Polyimide Composite Fiber

[0117] Polyimide composite fibers were obtained in the same manner as in Example 1, except that the mass ratio of carbon nanotubes and polyamic acid was adjusted to 50:50.

Example 4: Polyimide Composite Fiber

[0118] Polyimide composite fibers were obtained in the same manner as in Example 1, except that the mass ratio of carbon nanotubes and polyamic acid was adjusted to 40:60.

Example 5 to Example 8: Carbon Fiber

[0119] Each of the polyimide composite fibers according to Examples 1 to 4 was carbonized in the same manner as in Comparative Example 3 to obtain carbon fibers. Specifically, since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before carbonization and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. Each of the polyimide composite fibers according to Examples 1 to 4 were carbonized by raising the temperature to about 1200° C. at a heating rate of 3° C./min to 10° C./min. After carbonization was completed, carbon fibers were manufactured by naturally cooling in a state where nitrogen or argon gas was flowing.

Example 9 to Example 12: Graphite Fiber

[0120] Graphite fibers were obtained by graphitizing each of the polyimide composite fibers according to Examples 1 to 4 in the same manner as in Comparative Example 4. Specifically, since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before carbonization and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. Each polyimide composite fiber according to Examples 1 to 4 was graphitized by raising the temperature to about 2700° C. at a heating rate of 3° C./min to 10° C./min. After completion of graphitization, graphite fibers were manufactured by naturally cooling in a state where nitrogen or argon gas was flowing.

Evaluation Example

[0121] The specific tensile strength, linear density, specific tensile modulus, electrical conductivity, and thermal conductivity of the carbon composite fibers of Comparative Examples 1 to 3 and Examples 1 to 12 were measured.

[0122] The above-described physical property measurement was performed using FAVIMAT+ (short fiber property measuring instrument). This equipment measures tensile strength (N) and linear density (tex) and calculates specific tensile strength (N/tex).

[0123] FAVIMAT may calculate the linear density (μ) using the formula of

[00001]$f=\frac{1}{2L}\sqrt{\frac{T}{\mu }}$

using the natural frequency of the fiber. where f is the natural frequency [Hz], T is the tension [N], and L is the length of the fiber [km]. After measuring the linear density in this way, the tensile strength is measured through a tensile test. It is a device that can know the specific tensile strength by calculating the measured tensile strength and linear density.

[0124] Specific tensile strength (N/tex) is a value calculated using the linear density calculated in FAVIMAT and the tensile strength (Force, N) measured in a tensile test.

[0125] Specific tensile modulus (N/tex) shows the slope in the graph of the elongation and the tensile strength. The elongation refers to the maximum elongation until the fiber breaks through the tensile test of the fiber in FAVIMAT. The elongation is expressed in %. Usually, it represents the initial slope value and calculates and displays the section in which the strength constantly increases according to the elongation.

[0126] Electrical conductivity (S/cm) was calculated according to a formula by measuring resistance. The resistance was measured after applying silver paste to the composite fibers at 1 cm intervals. And the linear density measured by FAVIMAT was calculated according to cm/(4 Fiber Area).

[0127] The density was obtained by mixing two solvents having different densities and using a density gradient tube, which is a method of measuring the degree to which fibers are located by the difference in density in the solvent. The density gradient tube is a device that creates an environment with different densities within one solvent by mixing benzene and tetrabromomethane solvents in appropriate ratios. For the density, the difference in density was distinguished using beads for reference whose density was already known. After putting the composite fibers in the prepared solvent, the fibers were left for at least 6 hours so that they could be accurately positioned at the corresponding density, and then the location of the composite fibers was observed to measure the density.

[0128] Thermal conductivity was measured using the DC thermal bridge method and was performed in high vacuum (˜10.sup.−6 Torr). For the one-dimensional thermal conductivity equation, the thermal conductivity (k) may be obtained using

[00002]$\frac{d^{2}T\left(x\right)}{{\mathrm{dx}}^2}+\frac{Q}{\mathrm{kA}}=0$

equation. where x is the position of the sample at 0 [m], T(x) is the temperature at position x [K], Q is the heat generated by Joule heating [W], A is the cross-sectional area of the sample [m.sup.2], k is the thermal conductivity of the sample [W m.sup.−1 K.sup.−1]. Using this equation, the average temperature rise of the sample may be rewritten as an equation

[00003]$\Delta T=\frac{\mathrm{QL}}{12\mathrm{kA}}.$

where L is the length of the sample [m]. The thermal conductivity was measured in this way, and the current was measured using a Source-meter (source measuring device) and the voltage was measured using a Nanovoltmeter (nano-voltmeter) to measure the amount of heat generated. The length of the sample was measured with an optical microscope and a scanning electron microscope (SEM).

[0129] FIG. 2 is a graph of strength elongation change of fiber according to Comparative Examples 1 to 4. FIG. 3 is a graph showing changes in strength and elongation of polyimide composite fiber according to Examples 1 to 4. FIG. 4 is a graph of strength elongation change of carbon fibers according to Examples 5 to 8. FIG. 5 is a graph of strength elongation change of graphite fiber according to Examples 9 to 12.

[0130] The specific tensile strength, linear density, specific tensile modulus, electrical conductivity and thermal conductivity of the fibers according to Comparative Examples 1 to 3 and the carbon composite fibers according to Examples 1 to 12 are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Specific Specific carbonization- Tensile Tensile Electrical Thermal temperature Strength modulus Density Conductivity Conductivity classified component [° C.] [N/tex] [N/tex] [g/cm.sup.3] [S/cm] [W/mk] Comparative Example1 PI fiber — 0.44 6.60 1.7 — — Comparative Example2 carbonfiber 1200 1.40 68.9 1.81 431  10 Comparative Example3 graphitefiber 2700 0.49 126 1.97 1,481 142 Example1 PI compositefiber — 2.51 173 1.80 53,200 — Example2 PI compositefiber — 2.70 223 1.78 57,500 — Example3 PI compositefiber — 2.44 190 1.75 47,800 — Example4 PI compositefiber — 1.99 169 1.75 37,900 — Example5 carbonfiber 1200 2.76 240 1.80 24,000 — Example6 carbonfiber 1200 3.07 245 1.81 24,400 — Example7 carbonfiber 1200 2.73 240 1.78 20,900 — Example8 carbonfiber 1200 1.84 194 1.78 17,000 — Example9 graphitefiber 2700 2.28 418 1.85 3,300 438 Example10 graphitefiber 2700 2.26 375 1.87 3,400 441 Example11 graphitefiber 2700 1.18 333 1.84 2,100 390 Example12 graphitefiber 2700 0.91 226 1.80 1,600 335

[0131] Referring to Table 1, it may be confirmed that Examples 1 to 4 have much higher specific tensile strength, specific tensile modulus, and electrical conductivity than Comparative Examples 1 and 2.

[0132] Meanwhile, it may be confirmed that Examples 5 to 8 and Examples 9 to 12 also have improved specific tensile strength, specific tensile modulus, electrical conductivity, and thermal conductivity compared to Comparative Examples 3 and 4, respectively.

[0133] Through this, in implementing the polyimide-based carbon composite fiber as in the present invention, it may be confirmed that the application of high-capacity carbon nanomaterials such as carbon nanotubes may significantly increase the properties of the carbon composite fibers, such as specific tensile strength, specific tensile modulus, electrical conductivity, and thermal conductivity. As a method for manufacturing the above carbon composite fibers, the present invention has technical significance in presenting a specific method, such as using super acid as a solvent for spinning dope and using carbon nanomaterials oxidized under specific conditions.

Example: Carbon Composite Fiber

[0134] Carbon nanotubes from Meijo, Japan, and polymers or pitch were mixed in the mass ratio shown in the table below, and were added to chlorosulfonic acid (CSA) at a concentration of 8 mg/mL to prepare a spinning dope.

[0135] The carbon nanotubes are a mixture of single wall carbon nanotubes (SWCNTs) and double wall carbon nanotubes (DWCNTs) in a mass ratio of 55:45. In order to increase the dispersibility of the carbon nanotubes, they were oxidized by heat treatment at about 400° C. for 6 hours. After stirring the spinning dope for more than one day, it was spun using a syringe. Specifically, a preliminary fiber was obtained by spinning at a stretch ratio of about 2.0 or more using a needle having a diameter of 0.26 mm. Both the coagulation bath and the washing bath used acetone. Washing was carried out for 2 hours and finally dried in a vacuum oven at 170° C. for more than one day to evaporate chlorosulfonic acid (CSA) inside.

[0136] Carbon fibers were obtained by carbonizing each of the carbon composite fibers under the conditions shown in the table below. Specifically, since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before carbonization and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. Each carbon composite fiber was carbonized by raising the temperature to about 1,200-1,800° C. at a heating rate of 3° C./min to 10° C./min.

[0137] After carbonization was completed, carbon fibers were produced by naturally cooling in a state where nitrogen or argon gas was flowing.

[0138] The following Chemical formulas are structural formulas of repeating units and compounds of polymers used in Examples.

##STR00001##

Comparative Example: Polyimide Carbonization Fiber

[0139] Polyimide varnish from Korea PI Advanced Materials was melted in NMP (N-Methyl-2-pyrrolidone) and spun using a syringe. Spinning was performed using a needle having a diameter of 0.18 mm, and fibers were spun with a stretch ratio of about 10.0 or more. The coagulation bath was used by mixing acetone and water at a ratio of 1:1, and the washing bath was used while heating water at 80° C., and fibers were obtained through winding. Finally, in order to dry the water, the polyamic acid fibers were obtained by drying in a vacuum oven at 80° C. for more than one day. The polyamic acid fibers refer to non-imidized fibers.

[0140] The polyamic acid fibers were additionally imidized using a heating furnace. Since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before heat treatment and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. Heat treatment was performed by raising the temperature to about 450° C. at a heating rate of 3° C./min to 10° C./min. Specifically, after maintaining the temperature at a temperature of about 80° C. for 1 hour, at 140° C. for 1 hour, at 220° C. for 1 hour, and at 300° C. for 1 hour, the temperature was raised to about 450° C., and then the imidation was terminated. During all imidization processes, polyimide fibers were prepared by naturally cooling in a state where nitrogen or argon gas was flowing.

[0141] The polyimide fibers were carbonized using a heating furnace. Since air present inside the heating furnace oxidization occurs during heat treatment, the vacuum was pulled up to 10.sup.−3 torr before carbonization and nitrogen or argon gas was filled inside. Nitrogen was flowed into the heating furnace at a rate of 20 sccm. The polyimide fibers were carbonized by raising the temperature to about 1200° C. at a heating rate of 3° C./min to 10° C./min. After carbonization was completed, carbon fibers were produced by naturally cooling in a state where nitrogen or argon gas was flowing.

Evaluation Example

[0142] The properties of the carbon composite fibers of Examples and Comparative Examples were measured.

[0143] The above-described physical property measurement was performed using FAVIMAT+(short fiber property measuring instrument). This equipment measures tensile strength (N) and linear density (tex) and calculates specific tensile strength (N/tex).

[0144] FAVIMAT may calculate the linear density (μ) using the formula of

[00004]$f=\frac{1}{2L}\sqrt{\frac{T}{\mu }}$

using the natural frequency of the fiber. where f is the natural frequency [Hz], T is the tension [N], and L is the length of the fiber [km]. After measuring the linear density in this way, the tensile strength is measured through a tensile test. It is a device that can know the specific tensile strength by calculating the measured tensile strength and linear density.

[0145] Specific tensile strength (N/tex) is a value calculated using the linear density calculated in FAVIMAT and the tensile strength (Force, N) measured in a tensile test.

[0146] Specific tensile modulus (N/tex) shows the slope in the graph of the elongation and the tensile strength. The elongation refers to the maximum elongation until the fiber breaks through the tensile test of the fiber in FAVIMAT. The elongation is expressed in %. Usually, it represents the initial slope value and calculates and displays the section in which the strength constantly increases according to the elongation.

[0147] The density was obtained by mixing two solvents having different densities and using a density gradient tube, which is a method of measuring the degree to which fibers are located by the difference in density in the solvent. The density gradient tube is a device that creates an environment with different densities within one solvent by mixing benzene and tetrabromomethane solvents in appropriate ratios. For the density, the difference in density was distinguished using beads for reference whose density was already known. After putting the composite fibers in the prepared solvent, the fibers were left for at least 6 hours so that they could be accurately positioned at the corresponding density, and then the location of the composite fibers was observed to measure the density.

[0148] The length of the sample was measured with an optical microscope and a scanning electron microscope (SEM).

TABLE-US-00002 TABLE 2 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density 10 2.61 4.78 196 358 1.83 512 280 20 3.22 5.76 247 443 1.79 795 444 30 2.77 4.82 199 346 1.74 551 317 40 2.54 4.33 160 272 1.71 406 238 60 2.05 3.51 161 275 1.71 330 193 * 1,400° C. carbonization CNT-UItem composite fiber

TABLE-US-00003 TABLE 3 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density 10 2.99 5.53 221 362 1.85 661 357 20 3.01 5.47 234 377 1.82 704 387 30 2.86 5.09 221 353 1.78 632 355 40 1.55 2.69 157 272 1.73 243 141 60 1.32 2.21 113 190 1.68 149 89 * 1,400° C. carbonization CNT-P84 composite fiber

TABLE-US-00004 TABLE 4 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density 10 2.97 5.05 244 415 1.7 725 426 20 2.97 4.78 286 460 1.61 849 528 30 2.52 5.07 249 408 1.64 627 383 40 1.98 3.19 157 253 1.61 311 193 60 0.95 1.52 113 181 1.6 107 67 * 1,400° C. carbonization CNT-PPS composite fiber

TABLE-US-00005 TABLE 5 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density 2 2.42 4.6 242 377 1.56 586 375 5 2.6 4.87 260 429 1.65 676 410 10 2.86 5.76 286 501 1.75 818 467 15 2.7 4.29 270 446 1.65 729 442 20 2.59 3.08 259 409 1.58 671 425 30 2.13 2.65 213 332 1.56 454 291 40 2.03 1.75 203 315 1.55 412 266 * 1,800° C. carbonization CNT-PAN composite fiber

TABLE-US-00006 TABLE 6 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density 5 2.01 3.48 244 422 1.73 490 283 10 2.03 3.55 291 509 1.75 591 338 15 2.05 3.55 308 533 1.73 631 365 30 1.66 2.65 316 506 1.6 525 328 * 1,800° C. carbonization CNT-pitch composite fiber

TABLE-US-00007 TABLE 7 Specific Specific Specific Tensile (Specific Tensile Tensile Tensile Tensile Elastic Modulus * Modulus * Specific Strength strength Modulus modulus Density Specific Tensile Tensile Strength)/ wt % (N/tex) (Gpa) (N/tex) (Gpa) (g/cm.sup.3) Strength Density N/A 1.4 — 6.6 — 1.7 9 5 * 1,200° C. polyimide carbonization fiber

[0149] FIG. 6 to FIG. 15 are arranged data for the above-described embodiment of the present application.

[0150] Referring to Table 2 and the drawings, it may be confirmed that in the case of Ultem polymer, which is polyetherimide (PEI), the density decreases according to the content of the polymer, but the strength and the specific tensile strength are improved.

[0151] At this time, it may be confirmed that a certain content range (for example, 10-30% by weight) shows the best effect.

[0152] Referring to Table 3 and the drawings, it may be confirmed that the P84 polymer, which is a thermoplastic polyimide, exhibits the best properties in the range of 10-30% by weight.

[0153] Referring to Table 4 and the drawings, in the case of the PPS polymer, it may be confirmed that the range of 10-30% by weight shows the best properties.

[0154] Referring to Table 5 and the drawings, in the case of the PAN polymer, most of the generally excellent properties were shown, but up to 30% by weight showed particularly excellent properties.

[0155] Referring to Table 6 and the drawings, in the case of pitch, most of the generally excellent properties were shown. However, in the case of the 30% by weight condition, it may be confirmed that the specific tensile strength tended to be somewhat lowered.

[0156] As a comparative example, in the case of a fiber spun with a polymer other than a composite fiber, it showed a very low value in terms of specific tensile strength and a very low elastic modulus.

[0157] In order to select the appropriate specifications of these carbon composite fibers, the following Equation 1 was derived.

280≤a≤600  [Equation 1]

a={Specific Tensile Modulus(N/tex)*Specific Tensile Strength(N/tex)}/Density(g/cm.sup.3)

[0158] This is a value that may be compared with the degree of superiority of the specific tensile modulus and specific tensile strength for the density of the target product. The specific tensile modulus and the specific tensile strength may be improved simultaneously, but they did not show a tendency to be improved simultaneously at a predetermined ratio.

[0159] Based on the evaluated examples, carbon composite fibers satisfying the range of a value of 280 to 600 may be defined as having comprehensively improved characteristics.

[0160] More preferably, a value in the range of 300 to 550 may be required.

[0161] In the above, preferred implementations according to the present invention have been described with reference to drawings and embodiments, but this is only exemplary, those skilled in the art will understand that various modifications and equivalent other implementations are possible therefrom. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0162] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.