KR101802074B1 - Method for carbon nano tube fiber having specific strength and carbon nano tube fiber therefrom - Google Patents

Abstract

A method for manufacturing carbon nanotube fiber according to the present invention comprises the steps of: arranging unbound carbon nanotube fiber; generating a functional group in the unbound carbon nanotube fiber while removing impurities from the unbound carbon nanotube fiber; and acquiring the carbon nanotube fiber having specific strength increased by cross-linking the functional group. In addition, a method for manufacturing carbon nanotube fiber according to the present invention comprises the steps of: performing acid treatment for unbound carbon nanotube fiber synthesized and manufactured by an aerogel method; inputting a cross-linking agent into the acid treated carbon nanotube fiber; acquiring cross-linked carbon nanotube fiber; and performing heat treatment for the cross-linked carbon nanotube fiber. The present invention provides the carbon nanotube fiber having the specific strength greater than 0.8 N/tex, wherein carbon nanotube forming the carbon nanotube fiber has a mutually cross-linked form of at least one portion, and the cross-linked form is at least one between an ester bond and an amide bond of the carbon nanotubes. The present invention enhances the specific strength of the carbon nanotube fiber by using the functional group generated via the acid treatment.

Description

METHOD FOR CARBON NANO TUBE FIBER HAVING SPECIFIC STRENGTH AND CARBON NANO TUBE FIBER THEREFOROM BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method for increasing the specific strength of carbon nanotube fibers through cross-linking between carbon nanotube fibers, and to carbon nanotubes therefrom.

Carbon nanotubes are attracting much attention as next generation material because they have excellent properties such as tensile strength stronger than iron and electric conductivity superior to copper. However, carbon nanotubes are too short in length to have practical application limitations.

We can overcome these drawbacks by making carbon nanotube fibers that are made by twisting carbon nanotubes. However, the tensile strength of carbon nanotube fibers is still far below the tensile strength of individual carbon nanotubes. Therefore, it is necessary to develop a technique for increasing the tensile strength of carbon nanotube fibers.

Korean Patent Publication No. 1531023

Accordingly, an object of the present invention is to provide a method for enhancing the specific strength of carbon nanotube fibers by utilizing functional groups generated through acid treatment.

It is an object of the present invention to provide a method of manufacturing carbon nanotubes, comprising the steps of: preparing unbound carbon nanotube fibers; removing impurities present in the unbound carbon nanotube fibers to form functional groups in the unbound carbon nanotube fibers; And cross-linking the functional groups to obtain carbon nanotube fibers having increased specific strength.

The preparation of unbonded carbon nanotube fibers can be performed by any one of an aerosol method, a forest method and a solution method.

Removal of impurities can be carried out by acid treatment.

The acid treatment may be carried out with a solution of at least one of sulfuric acid and nitric acid.

Carboxyl groups can be produced through acid treatment.

The cross-linking is carried out using an esterification reaction, and the cross-linking step comprises adding an alcohol, wherein the alcohol may be provided from a linker comprising an alcohol.

The linker may comprise at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol.

The cross-linking is carried out using an amide reaction, and the amide reaction further comprises the step of adding an amine, wherein the amine can be provided from a linker comprising an amine.

The linker may include at least one of ethylene diamine and 1,3-diaminopropane.

The carbon nanotubes may further include a heat treatment step of applying heat after cross-linking the unbound carbon nanotubes, and the heat treatment may be performed within a range of 120 to 240 degrees Celsius.

It is another object of the present invention to provide a method for producing carbon nanotube fibers, which comprises performing acid treatment on unbound carbon nanotube fibers synthesized by an airgel method, adding a crosslinking agent to the acid- To obtain cross-linked carbon nanotube fibers; and heat-treating the cross-linked carbon nanotube fibers.

Through the acid treatment, a carboxylic acid functional group can be generated in the carbon nanotube fiber.

The crosslinking agent comprises an alcohol, the alcohol is provided from a linker comprising an alcohol, and the linker comprising an alcohol is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, And 1,6-hexanediol. ≪ / RTI >

The cross-linking agent comprises an amine, the amine is provided from a linker comprising an amine, and the linker comprising an amine may comprise at least one of ethylenediamine and 1,3-diaminopropane.

The heat treatment can be performed within a range of 120 to 240 degrees Celsius.

It is another object of the present invention to provide a carbon nanotube fiber having a specific strength of more than 0.8 N / tex, wherein carbon nanotubes constituting carbon nanotube fibers are at least partially crosslinked with each other, An ester bond between carbon nanotubes and an amide bond.

According to the present invention, there is provided a method for improving the specific strength of carbon nanotube fibers by utilizing functional groups generated through acid treatment.

FIG. 1 shows a state in which the synthesized unbound carbon nanotube fibers are placed on a quartz boat, inverted and impregnated with a mixed solution of sulfuric acid and nitric acid.
FIG. 2 is a schematic view showing a process of producing a carboxylic acid by acid treatment of the synthesized unbound carbon nanotube fiber and a process of esterification reaction, which is a reaction between a carboxylic acid and an alcohol.
FIG. 3 is a transmission electron microscopy (SEM) image showing that iron particles and amorphous carbon on the surface of unbound carbon nanotube fibers after acid treatment have been removed.
FIG. 4 is a Raman spectroscopic result showing the chemical bonding state of carbon present in acid-treated unbound carbon nanotube fibers and cross-linked carbon nanotube fibers after the esterification reaction.
FIG. 5 shows the results of specific strength and Young's modulus of crosslinked carbon nanotube fibers after the acid treatment and the esterification reaction.

In order to increase the usability of carbon nanotubes having short application due to their short length, a carbon nanotube fiber is synthesized by twisting carbon nanotubes in the prior art.

However, since the twisted carbon nanotube fibers are connected by the van der Waals attractive force, they are not significantly different from the specific strength and tensile strength of the individual carbon nanotubes.

Therefore, if the weak van der Waals attractive force can be replaced by a covalent bond by introducing crosslinking, improvement of the specific strength and tensile strength of the carbon nanotube fiber can be expected.

Methods for synthesizing carbon nanotube fibers include forest spinning, in which carbon nanotube fibers are extracted, spinning solutions, in which only carbon nanotubes are aggregated from a solution in which carbon nanotubes are dispersed Direct spinning, which produces carbon nanotube fibers by synthesizing carbon nanotubes in airgel state, is often used because of its excellent productivity.

However, in the direct spinning method, a process of removing iron and sulfur components used as catalysts or activators from impurities is required. This process is carried out by reducing the amount of catalyst or by acid treatment. The process of reducing the amount of catalyst to reduce the impurities deteriorates the productivity of the carbon nanotube fibers. Therefore, most of the impurities are removed through acid treatment. At this time, functional groups are generated in the carbon nanotube fibers.

However, the acid treatment for impurity removal reduces the strength and tensile strength of the carbon nanotube fibers, thereby deteriorating the usability of the carbon nanotube fibers. Accordingly, there is a need for a method capable of improving the non-strength and tensile strength while removing impurities from the synthesized carbon nanotube fibers.

The present invention relates to a carbon nanotube fiber improved in non-strength and tensile strength by cross-linking functional groups of carbon nanotubes produced by acid treatment.

In the present invention, all carbon nanotube fibers before introducing crosslinking are defined as 'unbound carbon nanotube fibers', and they are all not limited to any physical or chemical bonds between unbridged carbon nanotube fibers .

The method for manufacturing carbon nanotube fibers according to the present invention includes the steps of generating functional groups on carbon nanotubes while removing impurities present in unbound carbon nanotube fibers and crosslinking functional groups to form carbon nanotube fibers having increased non- ≪ / RTI >

The unbonded carbon nanotube fibers used in the present invention may be uncoated carbon nanotube fibers synthesized by airgel method, but the present invention is not limited thereto. There may be various embodiments such as using unbonded carbon nanotube fibers synthesized by forest spinning or solution spinning.

A method of removing impurities present in unbound carbon nanotube fibers proceeds through an acid treatment, and a functional group is generated in unbound carbon nanotubes through such an acid treatment.

The acid used herein may be treated with a solution of sulfuric acid, nitric acid, or a mixture thereof, but the present invention is not limited thereto, and various kinds of acids are possible as long as the functional groups can be generated in unbound carbon nanotubes. Preferably, all known acid treatment methods capable of introducing a carboxyl group into unbound carbon nanotubes are included in the scope of the present invention. Also, the sulfuric acid, nitric acid, or mixture thereof solution may contain minor amounts of other components.

Various functional groups are generated in unbound carbon nanotubes from which an impurity is removed by an acid treatment. In the present invention, crosslinking is formed by at least one of esterification and amide reactions using the most reactive carboxyl group.

The crosslinking step using the esterification reaction according to the present invention comprises the step of adding an alcohol, wherein the alcohol is provided from a linker containing an alcohol.

The linker containing an alcohol used in the esterification reaction may be any one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6- But it is not limited thereto, and various embodiments are possible as long as crosslinking can be formed on the carbon nanotube fibers.

The esterification reaction according to the present invention may use a catalyst containing sulfuric acid, but is not limited thereto, and various embodiments are possible as long as crosslinking can be well formed in unbound carbon nanotube fibers.

The esterification reaction according to the present invention may further include a heat treatment, wherein the temperature range is from 120 deg. C to 240 deg. C, preferably from 150 deg. C to 230 deg. C, more preferably from 190 deg. C to 210 deg. But is not limited to, it can be carried out at different temperatures if cross-linking can be well formed in unbonded carbon nanotube fibers. However, if the reaction temperature is lower than 120 deg. C, the esterification reaction is not performed well and crosslinking can not be formed well. If the reaction temperature is more than 240 deg. C, synthesized unbound carbon nanotube fibers may be scattered due to high temperature .

Another cross-linking step of the invention using an amide reaction comprises adding an amine, wherein the amine is provided from a linker comprising an amine.

The linker including an amine used for the amide reaction may include any one or more of ethylene diamine and 1,3-diaminopropane, but is not limited thereto, and may be a crosslinked carbon nanotube fiber Other linkers are available if you can.

The amide reaction according to the present invention can be carried out using a catalyst containing acetic anhydride, but not limited thereto, and other catalysts capable of forming crosslinked bonds in unbound carbon nanotube fibers are also possible.

The amide reaction according to the present invention may further include a heat treatment, wherein the temperature range is from 120 deg. C to 240 deg. C, preferably from 140 deg. C to 220 deg. C, more preferably from 160 deg. C to 210 deg. It is not limited. When the reaction temperature is less than 120 degrees Celsius, crosslinking of the unbound carbon nanotube fibers can not be formed well. If the reaction temperature is more than 240 degrees Celsius, the carbon nanotube fibers may be scattered due to the high temperature.

Hereinafter, embodiments using the esterification reaction according to the present invention will be described in detail. However, the following examples are intended to illustrate the present invention and the scope of the present invention is not limited by the following examples.

≪ Example 1 >

1) Experimental method

① Synthesis of Unbound Carbon Nanotube Fibers

The carbon source of methane was injected into the electric furnace at 1135 ℃ at a rate of 3.3 × 10 ^-3 mol min ^-1 . At this time, the catalyst, ferrocene, thiophene, hydrogen, and hydrogen were activated at 5.4 × 10 -4 mol min ^-1 , 3.5 × 10 -4 mol min ^-1 , 1.8 × 10 ^-2 mol min ^-1 , Speed to synthesize unbonded carbon nanotube fibers.

② Acid treatment

For the acid treatment, a mixture of 15 ml and 5 ml of 98% sulfuric acid and 70% nitric acid, respectively, was used.

The synthesized unbound carbon nanotube fibers were placed on a quartz boat as shown in Fig. 1 and impregnated in a mixed solution of sulfuric acid and nitric acid prepared in advance. After one hour, the unbound carbon nanotube fibers were taken out and rinsed with acetone to remove the acid solution on the surface.

③ Esterification reaction

10 mL of 1,5-pentanediol was used as a linker containing an alcohol to be used in the esterification reaction, and 100 μL of 98% sulfuric acid as a catalyst was mixed to prepare an alcohol solution.

The acid-treated unbound carbon nanotube fibers were impregnated in an alcohol solution for 10 minutes and taken out.

④ Heat treatment

The unesterified carbon nanotube fibers that had undergone the esterification reaction were heat-treated while being flowed into a heating furnace at 200 ° C in an argon gas atmosphere. After 1 hour, the cross-linked carbon nanotube fibers were rinsed with acetone and 1,5-pentanediol was removed.

2) Analysis of results

Transmission Electron Microscopy Analysis

FIG. 2 (a) is a process of forming a carboxyl group by subjecting the unbound carbon nanotube fibers according to the present invention to an acid treatment, and FIG. 2 (b) is a schematic diagram of a process in which an esterification reaction as a reaction between a carboxyl group and an alcohol is performed .

FIG. 3 is a photograph of the untreated carbon nanotube observed with a transmission electron microscope in order to confirm whether the impurity was removed through acid treatment as shown in FIG. 2 (a).

FIG. 3 (a) is an unbonded carbon nanotube fiber before the acid treatment, and FIG. 3 (b) shows unbound carbon nanotube fibers after the acid treatment.

3 (a) and 3 (b), it can be seen that the iron particles that were present in FIG. 3 (a) disappeared in FIG. 3 (b), and the amorphous carbon surrounding the unbound carbon nanotubes It can also be confirmed that it is removed. Thus, it can be confirmed that the acid treatment effectively removes the impurities present in the unbound carbon nanotube fibers.

② Raman spectroscopy analysis

FIG. 4 is a graph showing the results of experiments conducted in accordance with the present embodiment, showing that unbound carbon nanotube fibers (labeled 'Pristine'), unbound carbon nanotube fibers after acid treatment (labeled 'Acid treated'), Raman spectroscopy confirms the structural change of carbon in bonded carbon nanotube fibers ('cross-linked').

The most characteristic Raman peak of a carbon material is may be referred to as D-band (1350 cm-1 ) observed at the sp ³ carbon and G-band (1580 cm-1 ) observed in a sp ² carbon, the strength of these two bands The larger the ratio (intensity ratio, IG / ID), the more sp ² carbon in carbon nanotubes is said to be relatively larger than sp ³ carbon.

As shown in FIG. 4, it can be seen that the IG / ID of the unbound carbon nanotube fibers decreased from 6.44 to 4.35 when subjected to an acid treatment. This can be attributed to the conversion of sp ² carbon to sp ³ carbon because a functional group such as a carboxyl group was formed in the unbound carbon nanotube fiber due to the acid treatment.

③ Measurement of nasal cavity strength

In order to confirm the effect of increasing the specific strength of the carbon nanotube fibers formed through the acid treatment and crosslinking, it is preferable that each unbound carbon nanotube fiber, acid-treated unconjugated carbon nanotube fiber and crosslinked carbon nanotube fiber elongation (N / tex) and modulus (N / tex) were measured.

Through a Textechno Favimat instrument, the specific strength was measured at a load cell of 0.2 N, a resolution of 10 ^-6 N, a gauge length of 10 mm and an elongation rate of 2 mm / min.

Table 1 shows the results of four measurements of respective values of the carbon nanotube fibers at each step.

Untreated carbon nanotube fibers (labeled 'pristine'), acid-treated unbound carbon nanotube fibers (labeled 'acid-treated'), and cross-linked carbon nanotube fibers Elongation (%), Force (cN), Linear Density (tex), Specific Strength (N / tex) and Modulus (N / Elongation
 (%) Force
(cN) Linear Density
(tex) Specific Strength
(N / tex) Modulus
(N / tex) pristine-1 3.09 1.72 0.04 0.4076 31.382 pristine-2 3.24 1.73 0.05 0.3687 28.212 pristine-3 4.3 1.94 0.04 0.4326 29.416 pristine-4 3.42 1.94 0.06 0.3005 22.018 acid-treated-1 1.9 1.31 0.15 0.0849 8.541 acid-treated-2 4.67 1.78 0.12 0.1544 9.458 acid-treated-3 3.2 1.3 0.08 0.1693 11.632 acid-treated-4 1.54 1.47 0.15 0.097 13.5 cross-linked-1 4.56 5.75 0.06 1.0227 47.574 cross-linked-2 3.71 5.18 0.05 1.0029 49.224 cross-linked-3 4.69 5.59 0.05 1.1225 47.57 cross-linked-4 2.93 4.49 0.05 0.8323 46.071

As shown in Table 1, when the numerical values of Specific Strength (N / tex) and Young's Modulus (N / tex) of each step are checked, unbound carbon nanotube fibers are treated with acid to remove impurities When removed, the nasal cavity strength decreases sharply on average. However, the carbon nanotube fibers formed through the cross-linking formed by the esterification reaction according to the present invention showed a significantly higher specific strength than that of unconjugated carbon nanotube fibers before the acid treatment, and the average Young's modulus also increased significantly.

That is, the unbonded carbon nanotube fibers marked with 'pristine' formed by twisting carbon nanotubes have significantly lowered their specific strength after impurity treatment, but the carbon nanotube fibers formed through cross-linking according to the present invention are acid treated It was found that the specific strength of the unbonded carbon nanotube fiber was improved as compared with the unbonded carbon nanotube fiber produced by twisting. As a result, it was confirmed that the utilization of the carbon nanotube fibers can be greatly improved as compared with the prior art in which the non-rigidity is small and the usability is low.

Untreated carbon nanotube fibers (labeled 'pristine'), acid-treated unbound carbon nanotube fibers (labeled 'acid-treated'), and cross-linked carbon nanotube fibers Specific Strength (N / tex) according to strain (%) strain (%) pristine acid-treated cross-linked 0 0.006649 0.004816 0.005433 0.2 0.048483 0.025814 0.059605 0.4 0.104012 0.041693 0.153071 0.6 0.153442 0.052639 0.235751 0.8 0.191921 0.06233 0.310215 One 0.220575 0.071688 0.37789 1.219999 0.245101 0.081901 0.447557 1.419999 0.26335 0.091166 0.507068 1.619999 0.27923 0.100239 0.563403 1.819999 0.29328 0.10956 0.617324 2.019999 0.305809 0.118731 0.667622 2.219999 0.317279 0.125022 0.715294 2.419998 0.327914 0.133259 0.760612 2.619998 0.338013 0.141337 0.803982 2.819998 0.347614 0.149354 0.844902 2.999998 0.355851 0.156503 0.879729 3.239998 0.366281 0.92288 3.339998 0.370502 0.939789 3.619997 0.985053 3.799997 1.011963 4.199997 1.06521 4.399997 1.088355 4.619997 1.111451

5 (a) shows the specific strength (N / tex) value measured in Table 1, FIG. 5 (b) shows the Young's modulus (N / tex) (c) shows the correlation between strain (%) and Specific Strength (N / tex) values using the respective Specific Strength (N / tex) values measured in Table 1.

As shown in Table 1 and FIGS. 5 (a) to 5 (c), the unbonded carbon nanotube fibers show a sharp decrease in the specific strength due to partial destruction of the carbon nanotube fibers by the acid treatment, As a result of the cross-linking using the functional groups, the intrinsic strength and Young's modulus increase. From these results, it can be confirmed that the experiment through this example was successfully conducted, and that the strong covalent bond formed by the crosslinking of the carboxyl group increases the specific strength of the carbon nanotube fiber. These results indicate that the weight of each carbon nanotube fiber is similar and that the tensile strength also increases because the specific strength of the carbon nanotube fiber covalently bonded by the esterification reaction is increased.

The method for improving the specific strength of the carbon nanotube fibers according to the present invention is a method for improving the specific strength of the carbon nanotube fibers by using the carbon nanotube fibers from which the impurities have been removed, . In addition, the cross-linking formed according to the present invention is not only simple because it uses the functional groups generated through the acid treatment of the carbon nanotube fibers, but also enhances the specific strength and tensile strength of the carbon nanotube fibers Therefore, it can be expected to have a wider utility.

The above-described embodiments are illustrative of the present invention, and the present invention is not limited thereto. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (17)

Providing unbonded carbon nanotube fibers;
Forming functional groups on the unbound carbon nanotube fibers while removing impurities present in the unbound carbon nanotube fibers;
And cross-linking the functional groups to obtain carbon nanotube fibers having increased specific strength,
The crosslinking is carried out using either an esterification reaction or an amide reaction,
The crosslinking, which is carried out using the esterification reaction,
Adding an alcohol,
Wherein the alcohol is provided from a linker comprising an alcohol,
The crosslinking, which is carried out using the amide reaction,
Adding an amine,
Wherein the amine is provided from a linker comprising an amine. The method according to claim 1,
Wherein the unconjugated carbon nanotube fibers are prepared by any one of an airgel method, a forest method, and a solution method. The method according to claim 1,
Wherein the impurity removal is performed by an acid treatment. The method of claim 3,
Wherein the acid treatment is performed in a solution of at least one of sulfuric acid and nitric acid. The method of claim 3,
Wherein the carboxyl group is formed through the acid treatment. delete delete The method according to claim 1,
Wherein the linker comprises at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol. Fiber. delete The method according to claim 1,
Wherein the linker comprises at least one of ethylene diamine and 1,3-diaminopropane. The method according to claim 1,
A heat treatment step of applying heat after cross-linking the unbound carbon nanotubes;
Further comprising:
Wherein the heat treatment is performed at a temperature in the range of 120 to 240 degrees Celsius. Performing acid treatment on unbonded carbon nanotube fibers synthesized by an airgel method;
Introducing a cross-linking agent into the acid-treated carbon nanotube fibers; And injecting to obtain cross-linked carbon nanotube fibers; and
Heat treating the cross-linked carbon nanotube fibers;
Lt; / RTI >
Wherein the cross-linking agent comprises any one of an alcohol and an amine,
Wherein the alcohol is provided from a linker comprising the alcohol,
The linker containing the alcohol includes at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol,
Wherein said amine is provided from a linker comprising said amine,
Wherein the amine-containing linker comprises at least one of ethylene diamine and 1,3-diaminopropane. 13. The method of claim 12,
Wherein a carboxylic acid functional group is formed in the carbon nanotube fiber through the acid treatment. delete delete 13. The method of claim 12,
Wherein the heat treatment is performed at a temperature in the range of 120 to 240 degrees Celsius. delete

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