Large-scale preparation method of carbon fiber with surface embedded carbon nanotube structure

Abstract

The invention relates to the technical field of carbon fiber preparation, and discloses a large-scale preparation method of a carbon fiber with a surface embedded carbon nanotube structure, which comprises the following steps: uniformly mixing a carbon nanotube dispersion liquid with a solution which is simultaneously dissolved in the carbon nanotube dispersion liquid and soluble polyacrylonitrile; coating the surface of the polyacrylonitrile fiber multifilament with the mixed solution in a spraying manner, and sequentially putting the polyacrylonitrile fiber multifilament in an environment capable of accelerating volatilization of a carbon nanotube dispersion solution solvent to be separated from a solid phase system and facilitating removal of a solution simultaneously dissolved in the carbon nanotube dispersion solution and a solution capable of dissolving polyacrylonitrile; after treatment, the non-soluble polyacrylonitrile component in the polyacrylonitrile fiber multifilament can be removed, and the polyacrylonitrile fiber multifilament and the mixed solution can be partially softened and infiltrated into the carbon nano tube, and finally, the carbon nano tube is implanted into the surface of the formed polyacrylonitrile fiber. The carbonized carbon fiber has an interface topological structure under the condition that the original preparation process of the polyacrylonitrile fiber and the internal structure of the polyacrylonitrile fiber are not influenced.

Description

Technical Field

[0001] The invention relates to a large-scale preparation method of carbon fibers with surface-embedded carbon nanotube structures, and belongs to the technical field of carbon fiber preparation. Background Art

[0002] Carbon fiber is a high-performance fiber material widely used in aerospace, automotive manufacturing, and other fields. Currently, polyacrylonitrile-based carbon fiber has the most mature and widely used production process, accounting for over 90% of the global carbon fiber production.

[0003] National invention patent CN201910586775.4 discloses a process for preparing carbon fiber with carbon nanotubes embedded on the surface. The carbon fiber precursor is charged with static electricity when it exits the spinneret, and adsorbs carbon nanotubes dispersed in the gas phase before solidification. It is then stretched, solidified, and carbonized to obtain carbon fiber with part of the carbon nanotubes embedded inside and part exposed to the outside structure. This process can effectively enhance the mechanical, electrical and chemical properties of carbon fiber composites and has stable performance.

[0004] However, according to publicly available technology, during the vapor-phase dispersion of carbon nanotubes, the dispersant dimethyl sulfoxide (DMSO) decomposes under the high temperatures of the electric spark, producing impurities that adhere to the polyacrylonitrile precursor. Furthermore, the carbon nanotubes, originally intended to be evenly dispersed and adhered to the polyacrylonitrile precursor, actually exhibit undesirable clumping. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a large-scale preparation method of carbon fibers with surface-embedded carbon nanotube structures:

[0006] 1. Evenly mix the carbon nanotube dispersion and substance A to obtain a mixed solution;

[0007] 2. Applying the mixed solution in step 1 to the surface of the polyacrylonitrile fiber multifilament;

[0008] 3. placing the polyacrylonitrile fiber multifilament obtained in step 2 in an environment at temperature T1 for a period of time t1;

[0009] 4. The polyacrylonitrile fiber multifilament obtained in step 3 is placed in a temperature T2 environment for a time period of t2:

[0010] 5. Carbonizing the polyacrylonitrile fiber multifilament obtained in step 4 according to a carbon fiber carbonization process to obtain modified carbon fiber;

[0011] 6. Substance A can be a pure substance or a mixture and should be soluble in both the carbon nanotube dispersion and polyacrylonitrile described in step 1. To achieve this, the preferred carbon nanotube dispersion is an aqueous dispersion and substance A is dimethyl sulfoxide, but the combination of aqueous dispersion and dimethyl sulfoxide is not limited thereto.

[0012] 7. The temperature T1 is 10-300% of the boiling point of the carbon nanotube dispersion solvent, but does not exceed the lowest boiling point of substance A. Its function is to accelerate the volatilization of the carbon nanotube dispersion solvent from the solid phase system;

[0013] 8. The time t1 is long enough to ensure that the carbon nanotube dispersion solvent contained in the polyacrylonitrile fiber multifilament obtained in step 3 is less than 3% after coating, and its function is to remove the non-polyacrylonitrile solvent components in the polyacrylonitrile fiber multifilament;

[0014] 9. The temperature T2 is 20-300% of the lowest boiling point of substance A, but does not exceed any lowest temperature at which the polyacrylonitrile decomposes or melts, and its function is to remove substance A and make the polyacrylonitrile fiber reach a fully solid state;

[0015] 10. The duration of t2 allows the polyacrylonitrile fiber multifilament finally obtained in step 4 to partially soften and infiltrate the carbon nanotubes after reacting with the mixed solution described in step 1. As time passes, the molecules of substance A diffuse toward the center of the polyacrylonitrile fiber, affecting the arrangement and bonding of the polyacrylonitrile molecules. Therefore, it is necessary to limit this process. This process is affected by temperature, action time, and the material itself. Therefore, it is centrally adjusted through t2. t2 should ensure that the surface of the polyacrylonitrile fiber reaches a viscous flow state in the region of 100-600% of the carbon nanotube diameter thickness. At the same time, with the surface as a reference, the molecular weight content of substance A at 1000% of the carbon nanotube diameter thickness in the center is not higher than 60%.

[0016] The beneficial effect of the present invention is that carbon nanotubes are implanted on the surface of the formed polyacrylonitrile fiber without affecting the original preparation process of the polyacrylonitrile fiber and the internal structure of the polyacrylonitrile fiber, so that the carbonized carbon fiber has an interface topological structure, and the carbon nanotubes and the carbon fiber body have a strong connection structure. Under the shear trend, the shear force between the carbon nanotubes and the carbon fiber can be relied on to break through the weak mechanical properties of the existing technology that relies on the chemical bonding of the carbon nanotubes and the carbon fiber, thereby greatly improving the interface performance of the carbon fiber composite material; after the polyacrylonitrile fiber is modified, no fiber adhesion occurs, ensuring the consistency of the fiber before and after treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the operation process of the large-scale preparation method of carbon fiber with surface-embedded carbon nanotube structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the carbon nanotubes of the present invention embedded in the surface of polyacrylonitrile precursor. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be described clearly and completely below with reference to the accompanying drawings, and the following is one of the examples:

[0020] 1. Mix the carbon nanotube dispersion, DMSO, and deionized water in a mass ratio of 1:1:4 to obtain a mixed solution;

[0021] 2. Method 1: Spray the mixture obtained in step 1 onto the surface of the polyacrylonitrile multifilament fiber, wherein the atomization method is ultrasonic atomization, and the average particle size of the spray is 110% of the diameter of a single fiber of the polyacrylonitrile multifilament fiber;

[0022] Method 2: applying the mixed solution obtained in step 1 to the surface of the polyacrylonitrile fiber multifilament by dipping;

[0023] 3. Drying the polyacrylonitrile fiber multifilament obtained in step 2 in an environment at a temperature of 100° C. for 4 minutes. The temperature of 100° C. is 90% of the boiling point of the carbon nanotube dispersion solvent and does not exceed the lowest boiling point of DMSO. The purpose is to accelerate the volatilization of the carbon nanotube dispersion solvent from the solid phase system. The carbon nanotube dispersion solvent contained in the polyacrylonitrile fiber multifilament obtained after 4 minutes is 3% of the coating content. The purpose is to remove the non-DMSO solvent components in the polyacrylonitrile fiber multifilament.

[0024] 4. The polyacrylonitrile fiber multifilament finally obtained in step 3 is placed in an environment with a temperature of 180° C. and dried for 3 minutes to obtain a polyacrylonitrile fiber multifilament with a surface-embedded carbon nanotube structure. The temperature of 180° C. is 95% of the lowest boiling point of the substance DMSO, which is used to remove DMSO and make the polyacrylonitrile fiber reach a fully solid state. The 3-minute drying time allows the polyacrylonitrile fiber multifilament finally obtained to react with the mixed solution in step 1 to partially soften and infiltrate the carbon nanotubes, so that the DMSO molecules diffuse toward the center of the polyacrylonitrile fiber over time and affect the arrangement and bonding of the polyacrylonitrile molecules. This process is affected by temperature, reaction time, and the material itself. Therefore, the reaction time is centrally adjusted to ensure that the surface of the polyacrylonitrile fiber reaches a viscous flow state at a thickness of 300% of the carbon nanotube diameter. At the same time, from the surface as a reference, the DMSO molecular weight content at a thickness of 1000% of the carbon nanotube diameter in the center is 40%;

[0025] 5. Carbonizing the polyacrylonitrile fiber multifilament with a surface-embedded carbon nanotube structure obtained in step 4 according to a carbon fiber carbonization process to obtain a carbon fiber with a surface-embedded carbon nanotube structure.

Claims

1. A method for large-scale preparation of carbon fibers with surface-embedded carbon nanotube structures, characterized in that: (1) mixing a carbon nanotube dispersion and a substance A to obtain a mixed solution; (2) applying the mixed solution obtained in step (1) to the surface of a polyacrylonitrile fiber multifilament; (3) placing the polyacrylonitrile fiber multifilament obtained in step (2) in an environment at a temperature of T1 for a time period of t1; (4) placing the polyacrylonitrile fiber multifilament obtained in step (3) in an environment at a temperature of T2 for a time period of t2; (5) carbonizing the polyacrylonitrile fiber multifilament obtained in step (4) according to a carbon fiber carbonization process to obtain a modified carbon fiber; Substance A can be a pure substance or a mixture, and should have the property of being soluble in the carbon nanotube dispersion and polyacrylonitrile in step (1); temperature T1 is 10-300% of the boiling point of the carbon nanotube dispersion solvent, but does not exceed the lowest boiling point of substance A, and its function is to accelerate the volatilization of the carbon nanotube dispersion solvent from the solid phase system; time t1 is such that the carbon nanotube dispersion solvent contained in the polyacrylonitrile fiber multifilament finally obtained in step (3) is less than 3% after coating, and its function is to remove the non-polyacrylonitrile solvent components in the polyacrylonitrile fiber multifilament; temperature T2 is 20-300% of the lowest boiling point of substance A, but does not exceed any lowest temperature at which the polyacrylonitrile decomposes or melts, and its function is to remove substance A so that the polyacrylonitrile fiber reaches a fully solid state; The duration of t2 allows the polyacrylonitrile fiber multifilament finally obtained in step (4) to partially soften and infiltrate the carbon nanotubes after reacting with the mixed solution in step (1). As time passes, the molecules of substance A diffuse toward the center of the polyacrylonitrile fiber, affecting the arrangement and bonding of the polyacrylonitrile molecules. Therefore, it is necessary to limit the process. This process is affected by temperature, action time, and the material itself. Therefore, it is centrally adjusted through t2. t2 should allow the surface layer of the polyacrylonitrile fiber to reach a viscous flow state in the region of 100-600% of the carbon nanotube diameter thickness. At the same time, with the surface layer as a reference, the molecular weight content of substance A at the center of 1000% of the carbon nanotube diameter thickness is not higher than 60%.

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