High-conductivity high-strength carbon paper and preparation method thereof

Abstract

The invention provides high-conductivity and high-strength carbon paper and a preparation method thereof, and relates to the technical field of carbon paper. The preparation method comprises the following steps: pretreating chopped carbon fibers, mixing the pretreated chopped carbon fibers with a dispersing agent, a binder and conductive carbon powder to prepare slurry, and performing papermaking to prepare a carbon paper precursor; carrying out impregnation treatment on the carbon paper precursor in an impregnation liquid formed by thermosetting resin and conductive carbon powder, and then carrying out resin curing to prepare cured carbon paper; performing carbonization treatment on the cured carbon paper, and then performing graphitization treatment. The carbon paper is prepared by the preparation method. By adding the conductive carbon powder into the carbon paper precursor, the conductive carbon powder on the surface of the carbon fiber can enhance the surface roughness of the carbon fiber and improve the strength of a carbon fiber junction point in the carbon paper precursor, so that the prepared carbon paper precursor has better mechanical properties and electrical properties.

Description

Technical Field

[0001] The present application relates to the technical field of carbon paper, and in particular to a high-conductivity and high-strength carbon paper and a preparation method thereof. Background Art

[0002] As an important C / C composite material, high-performance carbon paper has a wide range of applications in hydrogen energy devices, battery manufacturing, aerospace materials and other fields. However, the traditional carbon paper preparation process often has problems such as uneven resin distribution and low impregnation efficiency, which directly affect the physical properties and service life of carbon paper. The uneven resin distribution in the carbon paper manufacturing process leads to the inconsistency of the internal structure of the carbon paper, which in turn affects its mechanical and electrical properties.

[0003] In order to overcome the above problems, existing technical means mainly improve the selection of raw materials, such as using multi-layer carbon paper base paper impregnation and hot pressing curing, or using resin to add adhesive to improve mechanical strength, but these methods usually lead to the loss of comprehensive performance of carbon paper. Multi-layer lamination increases the interface of carbon paper and reduces the mechanical properties of carbon paper; adding resin to adhesive will reduce its uniform distribution in carbon paper. Summary of the invention

[0004] In order to improve the problem of poor comprehensive performance of current carbon paper, the present application provides a high-conductivity and high-strength carbon paper and a preparation method thereof.

[0005] In a first aspect, the present application provides a method for preparing high-conductivity and high-strength carbon paper, using the following technical solution: A method for preparing high-conductivity and high-strength carbon paper comprises the following steps: Step S1: pre-treating the chopped carbon fibers, mixing them with a dispersant, a binder and a conductive carbon powder to obtain a slurry, and then making paper to obtain a carbon paper precursor; Step S2: impregnating the carbon paper precursor in an impregnation solution formed by a thermosetting resin and conductive carbon powder, and then curing the resin to obtain a cured carbon paper; Step S3, the solidified carbon paper is first subjected to a carbonization treatment, and then subjected to a graphitization treatment to obtain carbon paper.

[0006] The present application adds conductive carbon powder to the carbon paper precursor. The conductive carbon powder on the carbon fiber surface can enhance the surface roughness of the carbon fiber, improve the strength of the carbon fiber intersection in the carbon paper precursor, and make the carbon paper precursor have better mechanical and electrical properties. Moreover, adding dispersed conductive carbon powder during the dissociation and dispersion of carbon fiber can make the conductive carbon powder better dispersed in the carbon paper precursor. The interface adsorption performance of the uniformly distributed conductive carbon powder improves the bonding ability between the carbon fiber and the resin in the later resin impregnation process, thereby improving the mechanical properties of the carbon paper.

[0007] Optionally, the conductive carbon fiber has a length of 2-10 mm and a diameter of 5-10 μm.

[0008] Optionally, the conductive carbon powder is selected from one or more of carbon black, acetylene black, activated carbon, graphite powder, carbon nanotubes, graphene oxide, and graphene.

[0009] Optionally, the conductive carbon powder is selected from one or more of Vulcan carbon black, Ketjen carbon black, acetylene black, activated carbon, graphite powder, carbon nanotubes, graphene oxide, and graphene.

[0010] Optionally, the particle size of the conductive carbon powder is larger than the pore size of a forming mesh used in a papermaking machine during the process of forming a carbon paper precursor.

[0011] The conductive carbon powder used in the present application can significantly improve the conductive properties of carbon paper. These conductive carbon powders have good electronic conductivity and can form a conductive network in the carbon paper to reduce the resistivity.

[0012] Optionally, in step S1, the dispersant is selected from one or more of Tween 80, hydroxyethyl cellulose, sodium lignin sulfate, N-methylpyrrolidone, and N,N-dimethylformamide Triton; the binder is selected from one or more of sodium carboxymethyl cellulose, sodium dodecylbenzene sulfonate, and polyacrylamide.

[0013] The dispersant used in the present application can change the liquid-solid surface of the carbon fiber dispersion system, adsorb on the interface of the carbon fiber and the conductive carbon powder, make the surface of the condensed carbon fiber and the conductive carbon powder easy to wet, enhance the interaction between carbon fiber and carbon fiber, carbon fiber and conductive carbon powder, and conductive carbon powder and conductive carbon powder, and achieve a dispersion effect.

[0014] The binder used in the present application can enhance the bonding force between carbon fiber and conductive carbon powder, and improve the mechanical strength of carbon paper. At the same time, they can also work synergistically with the dispersant to improve the fluidity of the slurry and the paper-forming properties.

[0015] Optionally, in step S2, the mass concentration of the thermosetting resin in the impregnation solution is 5%-20%, and the mass concentration of the conductive carbon powder is 0.01%-3%.

[0016] Adding an appropriate amount of conductive carbon powder to the impregnation solution can improve the mechanical properties and conductive properties of carbon paper.

[0017] Optionally, in step S1, the slurry preparation process is specifically as follows: The dispersant and the binder are mixed to form a dispersion having a concentration of 0.1‰-5‰, wherein the mass ratio of the dispersant to the binder is 1:1-5; The conductive carbon powder is mixed with the dispersion to form a slurry A, and the carbon fiber is mixed with the dispersion to form a slurry B; The A slurry and the B slurry are mixed in a volume ratio of 1:1; Wherein, the mass of the conductive carbon powder is 0.5%-3% of the mass of the carbon fiber.

[0018] By adopting the above technical solution, the uniform distribution of conductive carbon powder and carbon fiber in the slurry can be ensured. At the same time, the mass ratio of the conductive carbon powder can be controlled to further optimize the conductive performance and strength of the carbon paper.

[0019] Optionally, in step S1, the pretreatment process of the chopped carbon fibers is specifically as follows: the chopped carbon fibers are immersed in a heated organic solvent, and then dried and then oxidatively calcined.

[0020] Optionally, the organic solvent is selected from one or both of ethanol and acetone, the soaking temperature is 30° C.-50° C., the soaking solid-liquid ratio is 1:5-50, and the soaking time is 1 h-10 h.

[0021] Optionally, the calcination temperature is 300° C.-450° C., and the calcination time is 0.5 h-5 h.

[0022] The present application uses a heated organic solvent to soak the carbon fiber, which can remove dust on the surface of the carbon fiber and the slurry on the surface of the fiber; since the surface of the carbon fiber is relatively smooth and inert, its dispersion performance in aqueous solvents is poor and its interfacial bonding ability with the resin is low. Therefore, the present application performs an oxidative calcination treatment on the carbon fiber after soaking and drying. The roughness and active functional groups on the surface of the carbon fiber after oxidative calcination are increased, thereby improving the dispersion degree of the carbon fiber in the aqueous solvent and enhancing the bonding ability between the fiber and the resin, and having better high temperature resistance and chemical stability.

[0023] Optionally, in step S2, the resin curing is performed in three stages of hot pressing, specifically including: The first stage of hot pressing has a temperature of 100-120°C, a pressure of 0.1-0.4 MPa, and a time of 1-20 min. The second stage of hot pressing is performed at a temperature of 120°C-150°C, a pressure of 0.4-0.7MPa, and a time of 1min-20min; The third stage hot pressing temperature is 150°C-200°C, the pressure is 0.8-1.5MPa, and the time is 1min-20min.

[0024] The present application adopts a segmented hot pressing curing process for resin cross-linking, which can reduce the violent flow of the resin after heating, reduce the displacement or aggregation of the resin during the cross-linking reaction, improve the uniformity of the distribution of the resin between the carbon fibers, reduce local stress concentration, and extend the service life of the carbon paper.

[0025] Optionally, the thermosetting resin is selected from one or both of epoxy resin and phenolic resin.

[0026] In a second aspect, the present application provides a highly conductive and high-strength carbon paper, which adopts the following technical solution: A high-conductivity and high-strength carbon paper is prepared by the method for preparing the high-conductivity and high-strength carbon paper.

[0027] The uniformity, mechanical strength and electrochemical performance of the carbon paper material prepared by the preparation method provided in this application are comprehensively improved, effectively solving the defects of traditional carbon paper.

[0028] In summary, the present application includes at least one of the following beneficial effects: 1. The present application adds conductive carbon powder to the carbon paper precursor. The conductive carbon powder on the carbon fiber surface can enhance the surface roughness of the carbon fiber, improve the strength of the carbon fiber intersection in the carbon paper precursor, and make the carbon paper precursor have better mechanical and electrical properties. Moreover, adding dispersed conductive carbon powder during the dissociation and dispersion of carbon fiber can make the conductive carbon powder better dispersed in the carbon paper precursor. The interface adsorption performance of the uniformly distributed conductive carbon powder improves the bonding ability between the carbon fiber and the resin in the later resin impregnation process, thereby improving the mechanical properties of the carbon paper.

[0029] 2. The present application uses a heated organic solvent to soak the carbon fiber, thereby removing dust on the surface of the carbon fiber and the slurry on the surface of the fiber; since the surface of the carbon fiber is relatively smooth and inert, its dispersion performance in aqueous solvents is poor and its interfacial bonding ability with the resin is low. Therefore, the present application performs an oxidative calcination treatment on the carbon fiber after soaking and drying. The roughness and active functional groups on the surface of the carbon fiber after oxidative calcination are increased, thereby improving the dispersion degree of the carbon fiber in the aqueous solvent and enhancing the bonding ability between the fiber and the resin, and having better high temperature resistance and chemical stability.

[0030] 3. The present application adopts a segmented hot pressing curing process for resin cross-linking, which can reduce the violent flow of the resin after heating, reduce the displacement or aggregation of the resin during the cross-linking reaction, improve the uniformity of the resin distribution between carbon fibers, reduce local stress concentration, and extend the service life of carbon paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a SEM image of the carbon fiber pretreated in step S1 of Example 1 of the present application; Figure 2 This is a SEM image of the carbon paper prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0032] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0033] It should be noted that the particle size of the conductive carbon powder used in the following examples and comparative examples of the present application is larger than the pore size of the forming mesh used in the papermaking machine in the process of forming the carbon paper precursor.

[0034] Example 1 Example 1 provides a high-conductivity and high-strength carbon paper, and the preparation method thereof is as follows: Step S1: Chopped carbon fibers with a length range of 2-10 mm and a diameter of 5-10 μm are selected as raw materials, and the chopped carbon fibers are soaked in 50° C. acetone for 10 hours, with a mass ratio of the chopped carbon fibers to the acetone of 1:50; after soaking, the chopped carbon fibers are taken out and placed in an 80° C. oven for drying for 2 hours, and after drying, the chopped carbon fibers are placed in a calcining furnace for oxidative calcination to obtain pretreated chopped carbon fibers, with a calcination temperature of 400° C. and a calcination time of 5 hours; Hydroxyethyl cellulose is used as a dispersant and sodium carboxymethyl cellulose is used as a binder. The two are mixed in a mass ratio of 1:4 to form a solute, and water is used as a solvent to form a dispersion with a mass concentration of 5‰; conductive carbon powder acetylene black is mixed with the dispersion to form a slurry A, and the short-cut carbon fiber is preliminarily dispersed in a fiber disintegrator and then mixed with the dispersion to form a slurry B, wherein the mass of the conductive carbon powder is 1% of the mass of the short-cut carbon fiber; the A slurry and the B slurry are mixed in a volume ratio of 1:1 to obtain a slurry, and then papermaking is carried out on a paper sample sheeter to obtain a carbon fiber wet paper web, which is pressed and dried at 120°C to obtain a carbon paper precursor; Among them, the pre-treated short-cut carbon fiber is 35g / m 2 Add the weight of Step S2: Phenolic resin (solid content of 60%, viscosity (25°C) of 200 mPa·s) and conductive carbon powder acetylene black are mixed to form an impregnation solution, wherein the impregnation solution uses ethanol as a solvent, the mass concentration of the phenolic resin is 10%, and the mass concentration of the conductive carbon powder acetylene black is 1%, and the carbon paper precursor prepared in step S1 is immersed in the impregnation solution for 20 minutes, and the impregnation solution is sufficient to cover the carbon paper precursor; Then, a flat vulcanizing machine is used to perform resin curing on the impregnated carbon paper precursor to obtain a cured carbon paper with a thickness of 0.2 mm. The resin curing is a three-stage hot pressing step, which specifically includes: the first stage hot pressing temperature is 120° C., the pressure is 0.4 MPa, and the time is 10 min; the second stage hot pressing temperature is 150° C., the pressure is 0.7 MPa, and the time is 10 min; the third stage hot pressing temperature is 200° C., the pressure is 1.5 MPa, and the time is 10 min; Step S3: First, the cured carbon paper obtained in step S2 is carbonized under the protection of a high-purity nitrogen atmosphere. The specific operation is as follows: first, the temperature is raised to 1000°C at a heating rate of 5°C / min, and a carbonization treatment is performed at the treatment temperature for 60 minutes, and then the temperature is continued to be raised to 2100°C for graphitization treatment. After keeping the temperature for 1.5 hours, the carbon paper is cooled with the furnace to obtain a graphite paper. During the graphitization treatment, a graphite mold is used to pressurize the carbon paper at a pressure of 30Kpa.

[0035] Figure 1 is a SEM image of the pretreated carbon fiber in step S1 of Example 1 of the present application. Figure 1 The surface of the pretreated carbon fiber is rough and not smooth. Figure 2 is a SEM image of the carbon paper prepared in Example 1 of the present application. Figure 2 , carbon fibers are evenly distributed.

[0036] Example 2 Example 2 is substantially the same as Example 1, except that the conductive carbon powder in Example 2 is all Ketjen carbon black.

[0037] Example 3 Example 3 is basically the same as Example 1, except that all the conductive carbon powder in Example 3 is graphene.

[0038] Example 4 Example 4 is substantially the same as Example 1, except that Tween 80 is used as the dispersant in Example 4.

[0039] Example 5 Example 5 is substantially the same as Example 1, except that the binder in Example 5 is sodium dodecylbenzene sulfonate.

[0040] Comparative Example 1 Comparative Example 1 is substantially the same as Example 1, except that the chopped carbon fibers in step S1 of Comparative Example 1 are not subjected to oxidative calcination treatment.

[0041] Comparative Example 2 Comparative Example 2 is substantially the same as Example 1, except that no conductive carbon powder acetylene black is added to the slurry for papermaking in step S1 of Comparative Example 2 and to the impregnation liquid in step S2.

[0042] Comparative Example 3 Comparative Example 3 is substantially the same as Example 1, except that in step S1 of Comparative Example 3, no conductive carbon powder acetylene black is added to the slurry used for papermaking.

[0043] Comparative Example 4 Comparative Example 4 is substantially the same as Example 1, except that the resin curing in step S2 of Comparative Example 4 is a constant temperature and constant pressure process, with a hot pressing temperature of 150° C., a pressure of 0.7 MPa, and a time of 30 min.

[0044] Performance Testing The carbon paper performance test was performed on the above embodiments and comparative examples according to GB / T 20042.7-2014 Proton Exchange Membrane Fuel Cell Part 7: Carbon Paper Performance Test Method. The test items included: resistivity (in plane direction), tensile strength, and porosity. The test results are shown in Table 1 below.

[0045] Table 1 Carbon paper performance test results of the embodiments and comparative examples Test items Resistivity (Ω·mm) Tensile strength(MPa) Porosity (%) Example 1 0.097 37.5 75.2 Example 2 0.091 36.9 74.7 Example 3 0.102 37.0 75.0 Example 4 0.095 36.8 75.1 Example 5 0.098 36.4 74.8 Comparative Example 1 0.127 30.7 73.9 Comparative Example 2 0.158 28.1 72.4 Comparative Example 3 0.135 30.5 73.0 Comparative Example 4 0.113 35.4 74.3 Combining Example 1 and Comparative Example 1 and Table 1, it can be seen that in Comparative Example 1, the chopped carbon fibers were not subjected to oxidative calcination treatment, and the resistivity of the carbon paper was relatively high and the tensile strength was low, indicating that the oxidative calcination treatment can increase the roughness and active functional groups on the surface of the chopped carbon fibers, thereby improving the conductive properties and mechanical properties of the carbon paper.

[0046] From Example 1 and Comparative Examples 2-3 and Table 1, it can be seen that in Comparative Example 2, no conductive carbon powder was added to the slurry and impregnation liquid for preparing the carbon paper precursor, and the obtained carbon paper had a higher resistivity and a lower tensile strength, indicating that the addition of conductive carbon powder is beneficial to improving the conductive properties and mechanical properties of the carbon paper; Comparative Example 3 adds conductive carbon powder to the impregnation liquid on the basis of Comparative Example 2, and the resistivity of the obtained carbon paper is significantly reduced, and the tensile strength is also increased, but there is still a large gap compared with Example 1, indicating that adding conductive carbon powder in the slurry for preparing the carbon paper precursor can greatly improve the conductive properties and mechanical properties of the carbon paper.

[0047] Combining Example 1 and Comparative Example 4 with Table 1, it can be seen that Comparative Example 4 adopts a constant temperature and constant pressure curing mode, and the resistivity of the obtained carbon paper increases and the tensile strength decreases slightly, indicating that the segmented hot pressing curing process is more conducive to the uniform curing of the resin and the close bonding between the carbon fiber and the resin, thereby improving the conductivity.

[0048] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing high-conductivity and high-strength carbon paper, characterized in that: The steps include: Step S1: pre-treating the chopped carbon fibers, mixing them with a dispersant, a binder and a conductive carbon powder to obtain a slurry, and then making paper to obtain a carbon paper precursor; Step S2: impregnating the carbon paper precursor in an impregnation solution formed by a thermosetting resin and conductive carbon powder, and then curing the resin to obtain a cured carbon paper; Step S3, the solidified carbon paper is first subjected to a carbonization treatment, and then subjected to a graphitization treatment to obtain carbon paper.

2. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: The conductive carbon powder is selected from one or more of carbon black, acetylene black, activated carbon, graphite powder, carbon nanotubes, graphene oxide, and graphene.

3. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: In the step S1, the dispersant is selected from one or more of Tween 80, hydroxyethyl cellulose, sodium lignin sulfate, N-methylpyrrolidone, and N,N-dimethylformamide Triton; the binder is selected from one or more of sodium carboxymethyl cellulose, sodium dodecylbenzene sulfonate, and polyacrylamide.

4. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: In the step S2, the mass concentration of the thermosetting resin in the impregnation solution is 5%-20%, and the mass concentration of the conductive carbon powder is 0.01%-3%.

5. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: In step S1, the slurry preparation process is specifically as follows: The dispersant and the binder are mixed to form a dispersion having a concentration of 0.1‰-5‰, wherein the mass ratio of the dispersant to the binder is 1:1-5; The conductive carbon powder is mixed with the dispersion to form a slurry A, and the carbon fiber is mixed with the dispersion to form a slurry B; The A slurry and the B slurry are mixed in a volume ratio of 1:1; Wherein, the mass of the conductive carbon powder is 0.5%-3% of the mass of the carbon fiber.

6. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: In the step S1, the pretreatment process of the chopped carbon fibers is specifically as follows: the chopped carbon fibers are immersed in a heated organic solvent, and then dried and then oxidatively calcined.

7. The method for preparing high-conductivity and high-strength carbon paper according to claim 6, characterized in that: The organic solvent is selected from one or both of ethanol and acetone, the soaking temperature is 30° C.-50° C., the soaking solid-liquid ratio is 1:5-50, and the soaking time is 1 h-10 h.

8. The method for preparing high-conductivity and high-strength carbon paper according to claim 6, characterized in that: The calcination temperature is 300°C-450°C, and the calcination time is 0.5h-5h.

9. The method for preparing high-conductivity and high-strength carbon paper according to claim 1, characterized in that: In step S2, the resin curing is a three-stage hot pressing step performed in stages, specifically comprising: The first stage of hot pressing has a temperature of 100-120°C, a pressure of 0.1-0.4 MPa, and a time of 1-20 min. The second stage of hot pressing is performed at a temperature of 120°C-150°C, a pressure of 0.4-0.7MPa, and a time of 1min-20min; The third stage hot pressing temperature is 150°C-200°C, the pressure is 0.8-1.5MPa, and the time is 1min-20min.

10. Carbon paper prepared by the method for preparing high-conductivity and high-strength carbon paper according to any one of claims 1 to 9.

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