Chemical crosslinking modified carbon nanotube fiber and preparation method thereof
By diazotization modification and chemical cross-linking treatment of carbon nanotubes, covalent bonds are constructed between carbon nanotubes, which solves the problem of low modification degree in existing modification methods, improves the mechanical properties and production efficiency of carbon nanotube fibers, and realizes high-quality continuous preparation.
Patent Information
- Application Number
- CN202410448018.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-12
- Publication Date
- 2025-10-21
AI Technical Summary
Existing methods for modifying carbon nanotube fibers are limited by the degree of wetting of the chemical modification solution, resulting in a low degree of modification and limited improvement in the mechanical properties of the fibers.
After diazotizing carbon nanotubes, modified carbon nanotube fiber precursors are prepared by wet spinning, and cross-linking reaction is carried out in a chemical cross-linking solution with a cross-linking agent to build covalent bonds between carbon nanotubes, thereby improving the stress transfer of the fiber.
It significantly improves the mechanical properties and production efficiency of modified carbon nanotube fibers, and realizes high-quality continuous preparation, which has significant economic and technological advantages.
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Figure CN120818918A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of carbon nanotube fiber preparation, and in particular relates to a chemically cross-linked modified carbon nanotube fiber and a preparation method thereof. Background Art
[0002] Since their discovery in 1991 by Japanese scientist Iijima Sumio, carbon nanotubes have become a research hotspot in materials science and nanotechnology due to their exceptional physical, chemical, and mechanical properties. Carbon nanotubes possess extremely high strength and modulus, electrical and thermal conductivity, as well as unique optical and chemical properties, which give them a wide range of potential applications in multiple fields. The preparation of carbon nanotube fibers involves aggregating carbon nanotubes into macroscopic continuous fibers, which retains the unique properties of carbon nanotubes while making them more readily adaptable for practical applications. Carbon nanotube fibers exhibit superior mechanical, electrical, and thermal properties compared to traditional materials, and therefore have enormous potential for application in high-performance composite materials, conductive materials, and heat-resistant materials.
[0003] Wet spinning is an effective method for producing carbon nanotube (CNT) fibers, particularly suitable for producing continuous, high-performance CNT fibers. This method decouples the current fiber preparation process (CNT raw material, spinning solution dispersion, and coagulation bath), is simple to operate, and readily industrializable, enabling the production of high-performance CNT fibers with excellent mechanical, electrical, and thermal properties. Summary of the Invention
[0004] To solve the above problems, the present invention provides a method for preparing chemically cross-linked modified carbon nanotube fibers, which specifically comprises the following steps:
[0005] (1) providing diazotized modified carbon nanotubes, wherein the diazotized modified carbon nanotubes are carbon nanotubes onto which benzene ring groups containing functional groups are grafted, and wet spinning the diazotized modified carbon nanotubes to prepare modified carbon nanotube fiber precursors;
[0006] (2) Immersing the modified carbon nanotube fiber precursor in a chemical crosslinking solution containing a crosslinking agent, causing the crosslinking agent to react with the functional group to produce a crosslinking reaction, thereby preparing the chemically crosslinked modified carbon nanotube fiber.
[0007] According to a specific embodiment of the present invention, the functional group is one or both of -OH and -COOH.
[0008] According to a specific embodiment of the present invention, the preparation method of the diazotized modified carbon nanotubes is specifically as follows: carbon nanotubes are placed in a diazonium salt solution composed of a mixture of aniline derivatives with functional groups, nitrite, and strong acid to carry out a grafting reaction, and benzene ring groups with the functional groups are grafted onto the carbon nanotubes to prepare diazotized modified carbon nanotubes.
[0009] According to a specific embodiment of the present invention, the aniline derivative is one or more of 4-aminophenol (p-aminophenol), 4-aminobenzoic acid, 4-amino-2-fluorobenzoic acid, 4-amino-3-fluorobenzoic acid, and 4-amino-2,3,5,6-tetrafluorobenzoic acid.
[0010] According to a specific embodiment of the present invention, the molar ratio of the aniline derivative molecules to the carbon atoms in the carbon nanotubes is 1:(20-100).
[0011] According to a specific embodiment of the present invention, step (1) specifically includes:
[0012] S1, dissolving the diazotized modified carbon nanotubes in chlorosulfonic acid to obtain a modified carbon nanotube spinning solution;
[0013] S2. Injecting the spinning solution into a spinning device through a syringe, extruding the solution into a coagulation bath through the spinning device, forming fibers through double diffusion, and then winding the fibers after washing to prepare the modified carbon nanotube fiber precursor.
[0014] According to a specific embodiment of the present invention, the concentration of the diazotized modified carbon nanotubes in the spinning solution is 0.5 wt % to 2.0 wt %.
[0015] According to a specific embodiment of the present invention, the ratio of the winding rate to the extrusion rate is 1-10.
[0016] According to a specific embodiment of the present invention, the cross-linking agent is one or more of a vulcanizing agent, boric acid, a silane cross-linking agent, and an isocyanate cross-linking agent.
[0017] Another object of the present invention is to provide the chemically cross-linked modified carbon nanotube fiber prepared by the above method.
[0018] Beneficial effects:
[0019] In existing technologies, modified carbon nanotube fibers are prepared by post-treating pure carbon nanotube fibers to achieve the desired properties. This modification method is limited by the degree of wetting of the carbon nanotube fibers by the chemical modification solution, resulting in a low degree of modification. The present invention provides a method for preparing modified carbon nanotube fibers with excellent stress transfer properties by constructing a cross-linked structure between the carbon nanotubes, thereby enhancing the interactions between the carbon nanotubes and improving the mechanical properties of the carbon nanotube fibers. This method not only improves the production efficiency and quality of the modified carbon nanotube fibers, but also, due to its continuous production capability, offers significant economic and technical advantages for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 The Raman spectra of the diazotized carbon nanotubes and the raw carbon nanotubes prepared in Example 1 are shown;
[0021] Figure 2 XPS characterization of the diazotized modified carbon nanotubes and raw material carbon nanotubes prepared in Example 1;
[0022] Figure 3 The SEM morphology of the modified carbon nanotube fiber precursor obtained in Examples 1-4;
[0023] Figure 4 The bar graph of the drafting multiple-tensile strength of the modified carbon nanotube fiber precursors obtained in Examples 1-5 is shown;
[0024] Figure 5 The SEM images of the chemically cross-linked modified carbon nanotube fibers prepared in Comparative Example 1 and Example 1 are shown;
[0025] Figure 6 This is a bar graph showing the immersion time-tensile strength of the chemically cross-linked modified carbon nanotube fibers obtained in Example 1 and Comparative Examples 1-2; DETAILED DESCRIPTION
[0026] The present invention will be described in detail below with reference to specific embodiments.
[0027] The present invention provides a method for preparing chemically cross-linked modified carbon nanotube fibers, which specifically comprises the following steps:
[0028] (1) providing diazotized modified carbon nanotubes (CNT@N), wherein the diazotized modified carbon nanotubes are carbon nanotubes onto which benzene ring groups containing functional groups are grafted, and wet spinning the diazotized modified carbon nanotubes to prepare modified carbon nanotube fiber precursors;
[0029] (2) Immersing the modified carbon nanotube fiber precursor in a chemical crosslinking solution containing a crosslinking agent, causing the crosslinking agent to react with the functional group to produce a crosslinking reaction, thereby preparing the chemically crosslinked modified carbon nanotube fiber.
[0030] First, the present invention chemically crosslinks the modified carbon nanotube fibers and connects the modified carbon nanotubes through chemical covalent bonds, which helps to improve the stress transfer of the carbon nanotube fibers and enhance the mechanical properties of the final product carbon nanotube fibers.
[0031] Secondly, compared with the method of post-modification of carbon nanotube fibers in the corresponding technology, the present invention first adopts diazotization modification of the raw carbon nanotubes, which provides more sites for subsequent chemical cross-linking modification, thereby helping to improve the stress transfer and mechanical properties of carbon nanotube fibers.
[0032] In addition, the present invention adopts the method of diazotization modification of carbon nanotubes, and the carbon atoms on the carbon nanotubes are modified from SP to 2 hybrid transformation to SP 3 Compared with other modification methods, hybridization can provide more sites for subsequent chemical cross-linking modification while ensuring that the geometric structure of carbon nanotubes is not excessively destroyed.
[0033] In an optional embodiment, the preparation method of the diazotized modified carbon nanotubes is specifically as follows: placing the carbon nanotubes in a diazonium salt solution composed of a mixture of aniline derivatives with functional groups, nitrite, and strong acid to carry out a grafting reaction, and grafting the benzene ring group with the functional group onto the carbon nanotubes to prepare the diazotized modified carbon nanotubes.
[0034] Specifically, the diazotization modification steps of carbon nanotubes are as follows: placing carbon nanotubes in a diazonium salt solution composed of a mixture of aniline derivatives with functional groups, nitrite, and strong acid to undergo a grafting reaction, thereby grafting the benzene ring groups containing functional groups onto the surface of the carbon nanotubes. The specific grafting process can be that NaNO2 is added to the strong acid solution, and the amino groups of the aniline derivatives are converted to -N2 + After obtaining electrons, N2 is removed, leaving a carbon radical of the benzene ring to attack the side wall of the carbon nanotube to achieve the grafting of the benzene ring group containing functional groups. The strong acid can be chlorosulfonic acid, sulfuric acid, hydrochloric acid, etc. The carbon atoms on the carbon tube are removed from sp by the diazotization process. 2 Hybrid transformation to sp 3 Hybridization, therefore, the geometric structure of the carbon nanotubes is protected as much as possible during the chemical modification process, avoiding the introduction of geometric defects of the carbon nanotubes, and thus the mechanical properties of the composite fiber will not be reduced due to the modification of the carbon nanotubes.
[0035] The functional groups of the aniline derivatives may be one or both of -OH and -COOH.
[0036] In an optional embodiment, the molar ratio of the aniline derivative molecules to the carbon atoms in the carbon nanotubes is 1:(20-100).
[0037] By controlling the molar ratio of aniline derivative molecules to carbon atoms in carbon nanotubes, the degree of modification of carbon nanotubes can be controlled, keeping the structural defects of carbon nanotubes at a low level before and after modification and meeting the requirements of carbon nanotube modification. The G / D ratio in the Raman spectrum can be used as a basis for judging the structural defect density of carbon nanotubes (i.e., the G peak in the Raman spectrum is between 1600 cm -1 and D peak ~1350cm -1 The results show that the higher the G / D value, the fewer structural defects of the carbon nanotubes. When the G / D of carbon nanotubes is below 20, it will seriously affect the mechanical properties of the fiber after fiberization. When the G / D is above 50, the modification effect of carbon nanotubes is not obvious. Therefore, the molar ratio of aniline derivative molecules to carbon atoms of carbon nanotubes is 1: (20-100) to modify carbon nanotubes, and obtain diazotized modified carbon nanotubes with a G / D ratio of 20-50, which are then used for wet spinning. Preferably, the molar ratio of aniline derivative molecules to carbon atoms of carbon nanotubes is selected to be 1:60, and modified carbon nanotubes with a G / D ratio of 30 are obtained for wet spinning.
[0038] In an optional embodiment, the carbon nanotubes are common carbon nanotubes in the art, such as one or more of single-walled carbon nanotubes and few-walled carbon nanotubes.
[0039] In an optional embodiment, the nitrite is a nitrite commonly used in the art, such as NaNO2, KNO2.
[0040] The aniline derivative may be one commonly used in the art, preferably one or more of 4-aminophenol (p-aminophenol), 4-aminobenzoic acid, 4-amino-2-fluorobenzoic acid, 4-amino-3-fluorobenzoic acid, and 4-amino-2,3,5,6-tetrafluorobenzoic acid.
[0041] Compared with other nitrogen-containing reagents, aniline derivatives can better achieve grafting on the surface of carbon nanotubes, thereby providing more sites for subsequent chemical cross-linking modification.
[0042] In an optional embodiment, the strong acid in the diazonium salt solution is one or more of chlorosulfonic acid, sulfuric acid, and hydrochloric acid.
[0043] In an optional embodiment, step (1) specifically includes the following steps: mixing the carbon nanotubes and the aniline derivative, dissolving the mixture in a solvent of the diazonium salt solution, and cooling the mixture at -25°C to -20°C. After cooling, adding the diazotizing agent, stirring, slowly adding the mixture dropwise to the ice-water mixture, and filtering the mixture to obtain the diazotized carbon nanotubes.
[0044] In an optional embodiment, the step (2) specifically includes:
[0045] S1, dissolving the diazotized modified carbon nanotubes in chlorosulfonic acid to obtain a modified carbon nanotube spinning solution;
[0046] S2. Injecting the spinning solution into a spinning device through a syringe, extruding the solution into a coagulation bath through the spinning device, forming fibers through double diffusion, and then winding the fibers after washing to prepare the modified carbon nanotube fiber precursor.
[0047] Among them, the role of cleaning is to remove the coagulation bath solvent.
[0048] In an optional embodiment, the concentration of the diazotized modified carbon nanotubes in the spinning solution is 0.5 wt% to 2.0 wt%, for example, 0.5 wt%, 0.75 wt%, 1.0 wt%, 1.25 wt%, 1.5 wt%, 1.75 wt%, or 2.0 wt%.
[0049] In an optional embodiment, the coagulation bath is one or more of acetone, dichloromethane, and N-methylpyrrolidone, preferably acetone.
[0050] The function of the coagulation bath is as follows: when the spinning solution enters the coagulation bath, the dispersion solvent and the coagulation bath solution undergo two-phase diffusion. During this process, chlorosulfonic acid gradually diffuses into the coagulation bath, the protonation effect of the spinning solution is weakened, and the carbon tubes flocculate into fibers, which are then washed in a water bath and wound up.
[0051] In an optional embodiment, the extrusion rate is 5 to 15 μL / min; the aperture of the spinneret is 80 to 150 μm, preferably 100 to 120 μm; and the ratio of the winding rate to the extrusion rate is 1 to 10.
[0052] Due to the significant reduction in the viscosity of the modified carbon nanotube spinning solution, the normal wet spinning process cannot produce modified carbon nanotube precursors with stable spinning process and good performance; therefore, in the wet spinning process, it is necessary to control the spinneret aperture and extrusion rate.
[0053] In the technical solution of the present invention, the draft ratio can be controlled by controlling the ratio of the winding rate to the extrusion rate, thereby further improving the mechanical properties of the chemically cross-linked modified carbon nanotube fiber product.
[0054] In an optional embodiment, the step S2 further comprises: drying the fibers in an air atmosphere at room temperature after winding to obtain the modified carbon nanotube fiber precursor.
[0055] In an optional embodiment, the cross-linking agent of the present invention can be selected from cross-linking agents in the art having corresponding grafting functional groups; for example, if the aniline derivative is selected as p-aminophenol (whose functional group is -OH), it is necessary to select a cross-linking agent that can correspond to the functional group -OH; for example, the isocyanate group (-NCO) in diphenylmethane diisocyanate (MDI) can react with the hydroxyl group to form an urethane group (-NHCOO-); if the aniline derivative is selected as 4-aminobenzoic acid (whose functional group is -COOH), the cross-linking agent needs to be selected to be a cross-linking agent that can cross-link with the functional group -COOH, and so on.
[0056] The crosslinking agent can be one or more of boric acid, a silane crosslinking agent, and an isocyanate crosslinking agent, and can be selected and used according to the above method. For example, when the aniline derivative is p-aminophenol, the crosslinking agent can be MDI. The isocyanate group (-NCO) in MDI can react with the hydroxyl group in p-aminophenol to form a urethane group (-NHCOO-).
[0057] In an optional embodiment, the temperature of the cross-linking reaction is 60°C to 90°C, for example, 60°C, 70°C, 80°C, or 90°C.
[0058] In an optional embodiment, in the cross-linking reaction, the modified carbon nanotube fiber precursor is immersed for a time of ≥12 h.
[0059] Another object of the present invention is to provide chemically cross-linked modified carbon nanotube fibers prepared by the above method.
[0060] Example 1
[0061] (1) 0.1 g of CNT (single-walled carbon nanotube) was mixed with 0.015 g of p-aminophenol (the molar ratio of p-aminophenol molecules to carbon atoms in carbon nanotubes was 1:60), dissolved in 20 g of chlorosulfonic acid solution, stirred for 20 minutes, and cooled at -20 ° C for 30 minutes. After cooling, 0.01 g of NaNO2 was added to the solution, stirred for 20 minutes, and then slowly added dropwise to the ice-water mixture. The diazotized carbon nanotubes (CNT@N) were collected by filtration; the Raman spectra and XPS characterizations of the prepared CNT@N and the raw material CNT are shown in Figure 2. Figure 1 and Figure 2 shown. Figure 1 In the Raman spectrum of CNT@N, the G / D ratio (G peak ~1600cm -1 and D peak ~1350cm-1 The area ratio is 30.
[0062] (2) The diazotized modified carbon nanotubes prepared in step (1) are dissolved in chlorosulfonic acid, wherein the concentration of CNT@N is 1 wt%, and stirred at 3000 rpm for 1 hour by a high-speed stirrer to prepare a modified carbon nanotube spinning solution; the spinning solution is transferred to a syringe and extruded into a spinneret, wherein the number of holes at the outlet of the spinneret is 1 and the pore size is 100 μm; the spinning solution is extruded into a pure acetone coagulation bath through the spinneret at an extrusion speed of 10 μL / min, and flocculated into fibers; the fibers are then washed in a water bath and rolled up; the rolling rate is 9 times the extrusion rate, and the modified carbon nanotube spinning solution can achieve in-situ spinning at a high rolling rate. The fiber precursor is dried in air for 1 day and then tested to obtain the modified carbon nanotube fiber precursor. The SEM morphology of the obtained modified carbon nanotube fiber precursor is shown as follows: Figure 3 shown.
[0063] (3) The modified carbon nanotube fiber precursor obtained in step (2) is immersed in a chemical crosslinking solution at 70°C, wherein the chemical crosslinking solution is prepared by mixing acetonitrile, methyl acetate, and MDI in a ratio of 7:2:1. After immersing for 12 hours, the fiber is taken out and immersed in acetone again to wash away the excess organic components in the fiber to obtain a chemically crosslinked modified carbon nanotube fiber having a morphology as shown in FIG. Figure 5 shown.
[0064] Examples 2-5
[0065] The other conditions are the same as those in Example 1, except that the winding rates in Examples 2-5 are 1, 3, 5, and 7 times the extrusion rates, respectively. The SEM morphologies of the modified carbon nanotube fiber precursors obtained in Examples 1-3 and 5 are shown in FIG. Figure 3 shown.
[0066] The tensile properties of the modified carbon nanotube fiber precursors prepared in Examples 1-5 were tested, and the results were as follows: Figure 4 shown.
[0067] Comparative Example 1-2
[0068] The other conditions are the same as those in Example 1, except that the soaking time in step (3) of Comparative Examples 1-2 is 4 hours and 8 hours respectively. The SEM images of the chemically cross-linked modified carbon nanotube fibers prepared in Comparative Example 1 and Example 1 are shown in FIG. Figure 5 As shown, the tensile strength is Figure 6 As shown. Figure 5 and Figure 6It can be seen that after cross-linking, there will be a certain amount of polymer surface coating and the fiber diameter will become thicker. However, when the time is short, the degree of cross-linking between the polymer and the fiber is low, the surface polymer does not bear the axial stress transfer of the fiber, and the tensile strength is lower than before cross-linking.
[0069] The tensile strengths of the modified carbon nanotube fiber precursors prepared in Examples 1, 4-5 and the tensile strengths of the chemically cross-linked modified carbon nanotube fibers prepared in Example 1 and Comparative Examples 1-2 are summarized in Table 1.
[0070] Table 1
[0071]
[0072] The tensile strength test method of the present invention is as follows: a Shimadzu single-column electronic universal testing machine EZ-LX is used to perform a tensile strength test, with a fiber sample length of 30 mm, a test distance of 20 mm, and a tensile speed of 2 mm / min.
[0073] Unless otherwise defined, the terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.
[0074] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, but is only limited by the claims.
Claims
1. A method for preparing chemically cross-linked modified carbon nanotube fibers, characterized in that: The specific steps include: (1) providing diazotized modified carbon nanotubes, wherein the diazotized modified carbon nanotubes are carbon nanotubes onto which benzene ring groups containing functional groups are grafted, and wet spinning the diazotized modified carbon nanotubes to prepare modified carbon nanotube fiber precursors; (2) Immersing the modified carbon nanotube fiber precursor in a chemical crosslinking solution containing a crosslinking agent, causing the crosslinking agent to react with the functional group to produce a crosslinking reaction, thereby preparing the chemically crosslinked modified carbon nanotube fiber.
2. The preparation method according to claim 1, characterized in that The functional group is one or both of -OH and -COOH.
3. The preparation method according to claim 1, characterized in that The preparation method of the diazotized carbon nanotubes is specifically as follows: placing the carbon nanotubes in a diazonium salt solution composed of a mixture of aniline derivatives with functional groups, nitrite, and strong acid to carry out a grafting reaction, grafting the benzene ring groups with the functional groups onto the carbon nanotubes, and preparing the diazotized carbon nanotubes.
4. The preparation method according to claim 3, characterized in that The aniline derivative is one or more of 4-aminophenol, 4-aminobenzoic acid, 4-amino-3-fluorobenzoic acid, and 4-amino-2,3,5,6-tetrafluorobenzoic acid.
5. The preparation method according to claim 3, characterized in that The molar ratio of the aniline derivative molecules to the carbon atoms in the carbon nanotubes is 1:(20-100).
6. The preparation method according to claim 1, characterized in that The step (1) specifically includes: S1, dissolving the diazotized modified carbon nanotubes in chlorosulfonic acid to obtain a modified carbon nanotube spinning solution; S2. Injecting the spinning solution into a spinning device through a syringe, extruding the solution into a coagulation bath through the spinning device, forming fibers through double diffusion, and then winding the fibers after washing to prepare the modified carbon nanotube fiber precursor.
7. The preparation method according to claim 6, characterized in that The concentration of the diazotized modified carbon nanotubes in the spinning solution is 0.5 wt % to 2.0 wt %.
8. The preparation method according to claim 6, characterized in that The ratio of the winding rate to the extrusion rate is 1 to 10.
9. The preparation method according to claim 1, characterized in that The crosslinking agent is one or more of a vulcanizing agent, boric acid, a silane crosslinking agent, and an isocyanate crosslinking agent.
10. The chemically cross-linked modified carbon nanotube fiber prepared by the method according to any one of claims 1 to 9.