Method for preparing carbon paper by collaborative resin impregnation of modified carbon fiber and aramid fiber

Abstract

The present invention discloses a method for preparing carbon paper by collaborative resin impregnation of modified carbon fiber and aramid fiber, which includes placing aramid fiber water in a deflaker for deflaking, adding carbon fiber and polyvinyl alcohol fiber and fully mixing to obtain a slurry suspension, and then hot pressing the slurry suspension after wet forming to obtain a carbon paper base paper; preparing a phenolic resin ethanol solution, adding MXene to the phenolic resin ethanol solution, ultrasonic stirring and dispersing to obtain a resin impregnation liquid, impregnating the carbon paper base paper in the resin impregnation liquid and performing ultrasonic treatment to obtain a preform; the preform is hot pressed after drying, and then carbonized in a high-temperature tube furnace, and taken out after cooling to obtain a finished product. The present invention can improve the mechanical properties and electrical conductivity of carbon paper, thereby improving the practicality of carbon paper in fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon paper, and in particular to a method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with a resin. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) is considered the most likely hydrogen fuel cell to achieve industrial application in the near term. The membrane electrode of a PEMFC consists of a gas diffusion layer (GDL), a catalyst layer, and a proton exchange membrane. Carbon paper (CP) is the most important base material in the GDL. Research shows that CP plays five important roles in PEMFCs: gas transmission and distribution, electron conduction, improved water management, catalyst layer support, and heat removal. It requires excellent electrical and thermal conductivity, good strength and surface smoothness, high permeability, and a uniform pore size distribution.

[0003] Carbon paper (CP) is made of chopped carbon fibers as the main raw material through wet papermaking, resin impregnation, hot pressing, carbonization, graphitization and other methods. The resin impregnation method refers to the use of polymer binders such as phenolic resin to improve its mechanical strength and water resistance. Carbonization can significantly improve the electrical conductivity and structural stability of CP. However, the membrane expansion of phenolic resin between carbon fibers during hot pressing will lead to uneven pore size and distribution of carbon paper, as well as low porosity, which has a negative impact on the conductive properties and strength of carbon paper.

[0004] After a long period of research, it was found that the use of aramid fiber in the raw materials of carbon paper can improve the tensile strength of carbon paper, but it will increase the resistivity of carbon paper and have an adverse effect on its electrochemical performance. x MXene nanoparticles are a new type of two-dimensional material with excellent electrical conductivity. Therefore, how to effectively improve the performance of carbon paper by using MXene as a conductive filler in combination with modified carbon fibers and aramid fibers has become a pressing technical challenge for applicants. Summary of the Invention

[0005] The present invention aims to provide a method for preparing carbon paper by impregnating modified carbon fibers with aramid fibers in a resin. The present invention can improve the mechanical and electrical properties of the carbon paper, thereby enhancing its practicality in fuel cells.

[0006] The technical solution provided by the present invention is as follows: a method for preparing carbon paper by impregnating modified carbon fibers and aramid fibers with a resin, comprising the following steps:

[0007] The steps include:

[0008] Step 1: Add 5-10 g of carbon fiber to 0.8-1.2 L of a dopamine hydrochloride solution containing 2-3 g of dopamine hydrochloride, stir at room temperature, and react for 20-26 hours. Then, filter the carbon fiber and dry it to obtain dopamine hydrochloride-modified carbon fiber;

[0009] Step 2: Prepare 30-80 parts by mass of dopamine hydrochloride-modified carbon fiber, 5-15 parts by mass of polyvinyl alcohol fiber, 1500-2500 parts by mass of water, and 100-200 parts by mass of aramid fiber; first, place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and then hot-press to obtain a carbon paper base paper;

[0010] Step 3: Prepare an 8-15 wt% phenolic resin-ethanol solution, add 5%-15% of MXene by weight to the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution;

[0011] Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 15-25 minutes. Take out the carbon paper base and lay it flat to ensure uniform resin penetration, and use it as a preform;

[0012] Step 5: Dry the preform and then hot press it for 50-70 minutes at a temperature of 140-160°C and a pressure of 2-4 MPa.

[0013] Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 5-10°C / min, a sintering temperature of 1000-1200°C, and a holding time of 0.5-1.5 hours. After cooling, take out the finished product.

[0014] In the above-mentioned method for preparing carbon paper by cooperatively impregnating modified carbon fiber and aramid fiber with resin, in step 1, 8 g of carbon fiber is added by mass to 1 L of a solution containing 2.5 g of dopamine hydrochloride, stirred at room temperature, and reacted for 24 hours.

[0015] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fiber and aramid fiber with resin, before step 1, carbon fiber with a length of 4 mm is selected and dispersed in a 1.00 mol / L NaOH solution, stirred and allowed to stand for 30 minutes to remove grease impurities on the surface of the carbon fiber.

[0016] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fibers and aramid fibers with resin, in step 1, the dopamine hydrochloride solution is prepared by first preparing 1 L of 0.01 mol / L Tis-HCl solution, then adding a few drops of NaOH solution to adjust the pH to 8.5, and then adding the weighed dopamine hydrochloride to prepare the solution.

[0017] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fiber and aramid fiber with resin, in step 2, 50 parts of dopamine hydrochloride modified carbon fiber, 10 parts of polyvinyl alcohol fiber, 2000 parts of water and 140 parts of aramid fiber are prepared by mass.

[0018] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fibers and aramid fibers with resin, in step 3, a 12 wt% phenolic resin-ethanol solution is prepared, and MXene is added in an amount accounting for 10% by mass of the phenolic resin-ethanol solution.

[0019] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fibers and aramid fibers with resin, in step 5, hot pressing is performed for 60 minutes at a hot pressing temperature of 150° C. and a hot pressing pressure of 3 MPa.

[0020] In the aforementioned method for preparing carbon paper by cooperatively impregnating modified carbon fiber and aramid fiber with resin, in step 6, the heating rate is 8°C / min, the sintering temperature is 1100°C, and the holding time is 1 hour.

[0021] Compared with the prior art, the present invention uses high-strength and low-thermal expansion aramid fibers and dopamine hydrochloride-modified carbon fibers to prepare carbon paper base paper. This can reduce the residual thermal stress generated during the hot pressing and curing process after phenolic resin impregnation, thereby enhancing the interfacial bonding strength between the fibers. The present invention adds MXene to the phenolic resin, allowing the phenolic resin to fully solidify and crosslink the bonding material before carbonization. At the same time, it utilizes the properties of MXene to improve the electrical conductivity of the carbon paper. The resulting carbon paper product has good mechanical properties and conductor properties, making it have good application prospects in fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the SEM surface morphology of carbon fibers before and after DPH modification;

[0023] Figure 2 The tensile strength (left) and flexural strength (right) of the carbon paper prepared in Examples 1-4 and Comparative Example 1 are shown;

[0024] Figure 3 The resistivity of the carbon paper base papers prepared in Examples 1-4 and Comparative Example 1 is shown;

[0025] Figure 4 The density of the carbon paper base prepared in Examples 1-4 and Comparative Example 1 is shown. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the embodiments and drawings, but they are not intended to limit the present invention.

[0027] Example 1: A method for preparing carbon paper by collaborative resin impregnation of modified carbon fiber and aramid fiber, the raw materials are as follows: carbon fiber, length 4 mm (Zhongfu Shenying Carbon Fiber Co., Ltd.), polyvinyl alcohol fiber, length 6 mm (Shanghai Chenqi Chemical Technology Co., Ltd.), dopamine hydrochloride (DPH, 189.64 MW, Aladdin Holding Group Co., Ltd.), sodium hydroxide (AR, Shanghai Lingfeng Chemical Reagent Co., Ltd.), anhydrous ethanol (AR, Chengdu Kelong Chemical Co., Ltd.), phenolic resin (BR, Shanghai Maclean Biochemical Technology Co., Ltd.), Tris-HCl (1.0 M, pH: 6.8, Shanghai Maclean Biochemical Technology Co., Ltd.), aramid fiber (length 6 mm, Hubei Tengdi New Materials Co., Ltd.);

[0028] Proceed as follows:

[0029] Step 1: Select carbon fibers with a length of 4 mm and disperse them into a 1.00 mol / L NaOH solution. Stir and let it stand for 30 minutes to remove grease impurities on the surface of the carbon fibers. Prepare 1L of 0.01mol / L Tis-HCl solution, add a few drops of NaOH solution to adjust the pH to 8.5, add weighed dopamine hydrochloride to make a 2.5g / L reaction solution, add 5g of carbon fibers to 1L of dopamine hydrochloride solution by mass, stir at room temperature, react for 24 hours, then filter the carbon fibers and dry them to obtain dopamine hydrochloride-modified carbon fibers.

[0030] Step 2: Prepare 40 g of dopamine hydrochloride-modified carbon fiber, 15 parts of polyvinyl alcohol fiber, 2000 g of water, and 100 g of aramid fiber in parts by mass; first, place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and hot-press to obtain a carbon paper base;

[0031] Step 3: Prepare an 8 wt% phenolic resin-ethanol solution, add MXene accounting for 10% of the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution;

[0032] Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 25 minutes. Take out the carbon paper base and lay it flat to ensure uniform resin penetration, and use it as a preform;

[0033] Step 5: Dry the preform and then hot press it for 55 minutes at a temperature of 145°C and a pressure of 2 MPa.

[0034] Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 8°C / min, a sintering temperature of 1100°C, and a holding time of 1 hour. After cooling, take out the finished product.

[0035] Example 2: Method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin. The raw materials are the same as those in Example 1, and the steps are as follows:

[0036] Step 1: Select carbon fibers with a length of 4 mm and disperse them in a 1.00 mol / L NaOH solution. Stir and let stand for 30 minutes to remove grease impurities on the surface of the carbon fibers. Prepare 1L of 0.01mol / L Tis-HCl solution, add a few drops of NaOH solution to adjust the pH to 8.5, add weighed DPH to make a 2.5g / L reaction solution, add 8g of carbon fibers to 1L of dopamine hydrochloride solution by mass, stir at room temperature, react for 24 hours, then filter the carbon fibers and dry them to obtain dopamine hydrochloride-modified carbon fibers.

[0037] Step 2: Prepare 50 g of dopamine hydrochloride-modified carbon fiber, 10 parts of polyvinyl alcohol fiber, 2000 g of water, and 140 g of aramid fiber in parts by mass; first, place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and hot-press to obtain a carbon paper base;

[0038] Step 3: Prepare a 12 wt% phenolic resin-ethanol solution, add MXene accounting for 10% of the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution;

[0039] Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 20 minutes. Take out the carbon paper base and lay it flat to ensure uniform resin penetration, and use it as a preform;

[0040] Step 5: Dry the preform and then hot press it for 60 minutes at a temperature of 150°C and a pressure of 3 MPa.

[0041] Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 8°C / min, a sintering temperature of 1100°C, and a holding time of 1 hour. After cooling, take out the finished product.

[0042] Example 3: Method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin. The raw materials are the same as those in Example 1, and the steps are as follows:

[0043] Step 1: Select carbon fibers with a length of 4 mm and disperse them into a 1.00 mol / L NaOH solution. Stir and let stand for 30 minutes to remove grease impurities on the surface of the carbon fibers. Prepare 1L of 0.01mol / L Tis-HCl solution, add a few drops of NaOH solution to adjust the pH to 8.5, add weighed DPH to make a 3g / L reaction solution, add 5g of carbon fibers to 1L of dopamine hydrochloride solution by mass, stir at room temperature, react for 24 hours, then filter the carbon fibers and dry them to obtain dopamine hydrochloride-modified carbon fibers.

[0044] Step 2: Prepare 60 g of dopamine hydrochloride-modified carbon fiber, 8 parts of polyvinyl alcohol fiber, 1500 g of water, and 160 g of aramid fiber in parts by mass; first place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and hot-press to obtain a carbon paper base;

[0045] Step 3: Prepare a 10 wt% phenolic resin-ethanol solution, add MXene at a mass ratio of 5% of the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution;

[0046] Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 25 minutes. Take out the carbon paper base and lay it flat to ensure uniform resin penetration, and use it as a preform;

[0047] Step 5: Dry the preform and then hot press it for 65 minutes at a temperature of 150°C and a pressure of 3 MPa.

[0048] Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 10°C / min, a sintering temperature of 1050°C, and a holding time of 1 hour. After cooling, take out the finished product.

[0049] Example 4: Method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin. The raw materials are the same as those in Example 1, and the steps are as follows:

[0050] Step 1: Select carbon fibers with a length of 4 mm and disperse them into a 1.00 mol / L NaOH solution. Stir and let stand for 30 minutes to remove grease impurities on the surface of the carbon fibers. Prepare 1L of 0.01mol / L Tis-HCl solution, add a few drops of NaOH solution to adjust the pH to 8.5, add weighed DPH to make a 2g / L reaction solution, add 10g of carbon fibers to 1L of dopamine hydrochloride solution by mass, stir at room temperature, react for 24 hours, then filter the carbon fibers and dry them to obtain dopamine hydrochloride-modified carbon fibers.

[0051] Step 2: Prepare 80 g of dopamine hydrochloride-modified carbon fiber, 15 parts of polyvinyl alcohol fiber, 2500 g of water, and 200 g of aramid fiber in parts by mass; first, place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and hot-press to obtain a carbon paper base paper;

[0052] Step 3: Prepare a 15 wt% phenolic resin-ethanol solution, add MXene accounting for 8% of the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution;

[0053] Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 15 minutes. Take out the carbon paper base and lay it flat to ensure the uniformity of resin penetration, and use it as a preform;

[0054] Step 5: Dry the preform and then hot press it for 65 minutes at a temperature of 160°C and a pressure of 4 MPa.

[0055] Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 6°C / min, a sintering temperature of 1200°C, and a holding time of 1 hour. After cooling, take out the finished product.

[0056] Comparative Example 1: A conventional carbon paper preparation method, wherein carbon fibers are used as the raw material of a slurry suspension, and the slurry suspension is wet-formed and then hot-pressed to obtain a carbon paper base paper; then, a 10wt% phenolic resin-ethanol solution is used for impregnation, and after impregnation, the paper is hot-pressed and solidified, and then carbonized in a high-temperature tube furnace with a heating rate of 10°C / min, a sintering temperature of 1100°C, a holding time of 1 hour, and taken out after cooling to obtain the carbon paper.

[0057] To further illustrate the improvements of the present invention, the SEM morphology changes of dopamine hydrochloride modified carbon fibers were first investigated. Figure 1 The following are SEM surface morphologies of carbon fibers before and after DPH modification. (a) shows the unmodified carbon fibers, which have a relatively smooth surface. After 24 hours of DPH modification, (b) shows a thin layer of particles on the carbon fiber surface. Comparing the contact angle values ​​of the carbon fibers in the smaller figure, it can be found that the contact angle of the carbon fibers before and after DPH modification changes from 129° to 92°. This phenomenon is caused by the formation of PDA deposition on the carbon fiber surface due to the autotrophic polymerization of DPH, which introduces polar groups such as -NH2 and -OH on the carbon fiber surface, thereby improving the wettability and dispersibility of the carbon fibers.

[0058] Secondly, the applicant investigated the mechanical properties, resistivity and air permeability of the carbon paper base papers prepared in Examples 1-4 of the present invention and Comparative Example 1. Figure 2The tensile strength (left) and flexural strength (right) of the carbon paper prepared in Examples 1-4 and Comparative Example 1 are shown. Figure 3 The resistivity of the carbon paper prepared in Examples 1-4 and Comparative Example 1 is shown. Figure 4 The density of the carbon paper base prepared in Examples 1-4 and Comparative Example 1 is shown. Figures 2 to 4 As can be seen, the carbon paper prepared in the examples of this application exhibits excellent mechanical properties and a significantly improved resistivity compared to the comparative example, indicating enhanced conductivity. In terms of bulk density, the increased density of the hot-pressed carbon paper leads to uniform and tight bonding between fibers, which increases the ability for electrons to pass through, thereby reducing the resistivity of the hot-pressed carbon paper.

[0059] In summary, the present invention uses high-strength and low-thermal expansion coefficient aramid fibers and dopamine hydrochloride-modified carbon fibers to prepare carbon paper base paper, which can reduce the residual thermal stress generated during the hot pressing and curing process after phenolic resin impregnation, thereby enhancing the interfacial bonding strength between the fibers. The present invention adds MXene to the phenolic resin, so that the phenolic resin is fully cured and cross-linked before carbonization. The properties of MXene are also utilized to improve the electrical conductivity of the carbon paper. The carbon paper finished product prepared by the present invention has good mechanical properties and conductor properties, so that it has good application prospects in the use of fuel cells.

Claims

1. A method for preparing carbon paper by impregnating modified carbon fibers and aramid fibers with a resin, characterized in that: The steps include: Step 1: Add 5-10 g of carbon fiber to 0.8-1.2 L of a dopamine hydrochloride solution containing 2-3 g of dopamine hydrochloride, stir at room temperature, and react for 20-26 hours. Then, filter the carbon fiber and dry it to obtain dopamine hydrochloride-modified carbon fiber; Step 2: Prepare 30-80 parts by mass of dopamine hydrochloride-modified carbon fiber, 5-15 parts by mass of polyvinyl alcohol fiber, 1500-2500 parts by mass of water, and 100-200 parts by mass of aramid fiber; first, place the aramid fiber water in a deflaker for deflaking, then add the carbon fiber and polyvinyl alcohol fiber and mix thoroughly to obtain a slurry suspension, and then wet-form the slurry suspension and then hot-press to obtain a carbon paper base paper; Step 3: Prepare an 8-15 wt% phenolic resin-ethanol solution, add 5%-15% of MXene by weight to the phenolic resin-ethanol solution, and disperse by ultrasonic stirring to obtain a resin impregnation solution; Step 4: Immerse the carbon paper base in the resin impregnation solution and perform ultrasonic treatment for 15-25 minutes. Take out the carbon paper base and lay it flat to ensure uniform resin penetration, and use it as a preform; Step 5: Dry the preform and then hot press it for 50-70 minutes at a temperature of 140-160°C and a pressure of 2-4 MPa. Step 6: Carbonize the hot-pressed solidified carbon paper in a high-temperature tube furnace at a heating rate of 5-10°C / min, a sintering temperature of 1000-1200°C, and a holding time of 0.5-1.5 hours. After cooling, take out the finished product.

2. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 1, 8 g of carbon fiber was added to 1 L of a dopamine hydrochloride solution containing 2.5 g by mass, stirred at room temperature, and reacted for 24 h.

3. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: Before step 1, select carbon fibers with a length of 4 mm and disperse them in a 1.00 mol / L NaOH solution. Stir and let stand for 30 minutes to remove grease and impurities on the surface of the carbon fibers.

4. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 1, the dopamine hydrochloride solution is prepared by first preparing 1 L of 0.01 mol / L Tis-HCl solution, then adding a few drops of NaOH solution to adjust the pH to 8.5, and then adding the weighed dopamine hydrochloride.

5. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 2, 50 parts of dopamine hydrochloride modified carbon fiber, 10 parts of polyvinyl alcohol fiber, 2000 parts of water and 140 parts of aramid fiber were prepared by mass.

6. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 3, a 12 wt% phenolic resin-ethanol solution is prepared, and MXene is added in an amount accounting for 10% of the mass of the phenolic resin-ethanol solution.

7. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 5, hot pressing is performed for 60 minutes, the hot pressing temperature is 150° C., and the hot pressing pressure is 3 MPa.

8. The method for preparing carbon paper by impregnating modified carbon fiber and aramid fiber with resin according to claim 1, characterized in that: In step 6, the heating rate is 8°C / min, the sintering temperature is 1100°C, and the holding time is 1 hour.

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