Carbon fiber composite material for linerless liquid hydrogen container and its preparation method

Abstract

This invention relates to a linerless liquid hydrogen container carbon fiber composite material and its preparation method. The preparation method includes the following steps: reacting a hydroxyl-terminated polymer with a sulfonyl chloride group to generate a first solution; the hydroxyl-terminated polymer includes a hydroxyl-terminated hyperbranched polymer, a hydroxyl-terminated polyether polyol, or a hydroxyl-terminated liquid rubber; the sulfonyl chloride group organic compound includes dodecylbenzenesulfonyl chloride or ethylsulfonyl chloride; reacting the first solution with 1-methylimidazole, washing the product with a solvent, and vacuum drying to evaporate the solvent to obtain an ionic liquid; mixing the ionic liquid uniformly with graphene or hexagonal boron nitride nanosheets, adding a curing agent, mixing uniformly, then adding epoxy resin, mixing uniformly, and repeatedly vacuuming to obtain a modified epoxy resin mixed solution; and using the modified epoxy resin mixed solution to wind and mold carbon fiber composite material parts. This invention enhances the low-temperature toughness and gas barrier properties of carbon fiber composite materials.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage cylinder materials technology, and in particular to a carbon fiber composite material for a linerless liquid hydrogen container and its preparation method. Background Technology

[0002] Hydrogen production involves four core steps: extraction, storage, transportation, and application. Among these four stages, the storage of liquid hydrogen directly affects the safety and efficiency of hydrogen energy systems. Currently, new hydrogen storage equipment includes Type V linerless (also known as lined) hydrogen cylinders, which typically utilize a carbon fiber epoxy resin composite material system.

[0003] Currently, the design and manufacture of linerless, all-composite cryogenic containers using all-carbon fiber composites face two key challenges. First, conventional carbon fiber reinforced resin matrix composite systems exhibit extremely poor hydrogen barrier performance. After removing the inner liner, the carbon fiber composite needs to function as both a gas barrier and a structural pressure-bearing structure. However, during the winding and curing process, carbon fiber composites often exhibit micropores or microcracks, allowing hydrogen molecules to easily penetrate the composite layer and cause leakage. Second, cryogenic conditions weaken the mechanical properties of carbon fiber composites. During liquid hydrogen refueling, cryogenic strain increases the internal stress of the container wall. Traditional metal containers have high toughness and strong resistance to cryogenic deformation. However, the mechanical properties of carbon fiber composites are greatly affected by temperature, especially the poor toughness of the resin matrix, which easily generates microcracks at low temperatures. This reduces the composite's ability to transmit shear loads, affecting the overall cryogenic mechanical properties of the composite. Existing technologies lack feasible solutions to enhance the cryogenic toughness and gas barrier properties of carbon fiber composites. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a carbon fiber composite material for a linerless liquid hydrogen container and its preparation method, with the aim of enhancing the low-temperature toughness and gas barrier properties of the carbon fiber composite material.

[0005] The technical solution adopted in this invention is as follows:

[0006] This invention provides a method for preparing carbon fiber composite materials, comprising the following steps:

[0007] S1. A first solution is generated by reacting a hydroxyl-terminated polymer with a sulfonyl chloride group organic compound;

[0008] The hydroxyl-terminated polymer includes hydroxyl-terminated hyperbranched polymers, hydroxyl-terminated polyether polyols, or hydroxyl-terminated liquid rubbers.

[0009] The sulfonyl chloride group organic compound includes dodecylbenzenesulfonyl chloride or ethylsulfonyl chloride;

[0010] S2. React the first solution with 1-methylimidazole, wash the product with solvent, and vacuum dry to evaporate the solvent to obtain an ionic liquid;

[0011] S3. Mix the ionic liquid with graphene or hexagonal boron nitride nanosheets evenly, add a curing agent, mix evenly, then add epoxy resin, mix evenly, and repeatedly vacuum to obtain a modified epoxy resin mixed solution.

[0012] S4. The modified epoxy resin mixture is used to wind and mold carbon fiber composite parts.

[0013] The further technical solution is as follows:

[0014] The hydroxyl-terminated polymer is hydroxyl-terminated polybutadiene.

[0015] S1 specifically includes:

[0016] Hydroxyl-terminated polybutadiene and dodecylbenzenesulfonyl chloride are added to an inert organic solvent. An organic alkaline catalyst is added dropwise to neutralize the byproduct hydrogen chloride. The pH value is monitored to ensure that the reaction fully utilizes the hydroxyl-terminated polybutadiene to generate dodecylbenzenesulfonate-based polybutadiene, which is the first solution.

[0017] In S2, the ionic liquid is polybutadiene-1-methylimidazolium dodecylbenzenesulfonate, wherein the cation is polybutadiene-1-methylimidazolium and the anion is dodecylbenzenesulfonate.

[0018] In S1, the molar ratio of the hydroxyl-terminated polybutadiene to dodecylbenzenesulfonyl chloride ranges from 0.5:1 to 2:1.

[0019] In S2, the reaction conditions between the first solution and 1-methylimidazole are: 8-12 h under a water bath at 65℃-85℃.

[0020] The vacuum drying conditions are: temperature 60℃-80℃, time 6-10h.

[0021] In S2, the molar ratio of the terminal dodecylbenzene sulfonate polybutadiene to 1-methylimidazole ranges from 0.5:1 to 2:1.

[0022] The inert organic solvent includes dichloromethane or N,N-dimethylformamide; the organic basic catalyst includes triethylamine.

[0023] In step S3, the mass ratio of the ionic liquid to graphene is 2:1 to 10:1.

[0024] In the modified epoxy resin mixed solution, the mass fraction of the mixture of ionic liquid and graphene or hexagonal boron nitride nanosheets is 0.1%-3%.

[0025] The mass ratio of epoxy resin to curing agent is 2:1 to 4:1.

[0026] S3 specifically includes:

[0027] The ionic liquid was mixed with graphene or hexagonal boron nitride nanosheets and sonicated at 60-90°C for 0.5-2 hours, then cooled to room temperature.

[0028] Then add the curing agent, stir for 0.5-2 hours, and sonicate for 0.5-2 hours;

[0029] Add epoxy resin and stir for 0.25-1 hour, then repeatedly vacuum to remove air bubbles.

[0030] The present invention also provides a carbon fiber composite material, which is prepared by the aforementioned preparation method.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention first prepares ionic liquids existing in both anionic and cation forms. It then utilizes cations to modify graphene materials with a π-π conjugated structure but no functional groups on the surface, improving toughness while increasing interlayer spacing. Simultaneously, anions are used as surfactants, physically adsorbed and anchored onto the graphene surface, enhancing the dispersibility and stability of graphene through electric layer repulsion and steric hindrance. Furthermore, by modifying an epoxy resin composite material system with graphene-ionic liquid, not only is the dispersibility and stability of graphene in epoxy resin improved, preventing agglomeration, but the composite material also exhibits a synergistic improvement in gas barrier properties and toughness, making it more suitable for use in liquid hydrogen containers. Graphene can be replaced by hexagonal boron nitride nanosheets or other materials with π-π conjugated structures, or materials that form π-π interactions with conjugated polymers through non-covalent functionalization.

[0033] Other features and advantages of the invention will be set forth in the following description or may be learned by practicing the invention. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart of the preparation method in Example 1 of the present invention.

[0035] Figure 2 This is a schematic diagram of the test results of the modified epoxy resin obtained in Example 1 of the present invention. Detailed Implementation

[0036] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0037] Example 1

[0038] See Figure 1This embodiment provides a method for preparing carbon fiber composite materials, including the following steps:

[0039] S1. A first solution is generated by reacting a hydroxyl-terminated polymer with a sulfonyl chloride group organic compound;

[0040] S2. React the first solution with 1-methylimidazole, wash the product with solvent, and vacuum dry to evaporate the solvent to obtain an ionic liquid;

[0041] S3. Mix the ionic liquid with graphene or hexagonal boron nitride nanosheets evenly, add a curing agent, mix evenly, then add epoxy resin, mix evenly, and repeatedly vacuum to obtain a modified epoxy resin mixed solution.

[0042] S4. The modified epoxy resin mixture is used to wind and mold carbon fiber composite parts.

[0043] The hydroxyl-terminated polymer is a hydroxyl-terminated hyperbranched polymer, a hydroxyl-terminated polyether polyol, or a hydroxyl-terminated liquid rubber. Preferably, it is hydroxyl-terminated polybutadiene.

[0044] The sulfonyl chloride group organic compound includes dodecylbenzenesulfonyl chloride or ethylsulfonyl chloride, preferably dodecylbenzenesulfonyl chloride.

[0045] The graphene is preferably graphene nanosheets.

[0046] As a specific implementation method, the preparation method specifically includes the following steps:

[0047] S1. Add hydroxyl-terminated polybutadiene and dodecylbenzenesulfonyl chloride to an inert organic solvent, add an organic alkaline catalyst dropwise to neutralize the byproduct hydrogen chloride, monitor the pH value, and ensure that the reaction fully utilizes the hydroxyl-terminated polybutadiene to generate dodecylbenzenesulfonate-based polybutadiene, i.e., the first solution.

[0048] The molar ratio of the hydroxyl-terminated polybutadiene to dodecylbenzenesulfonyl chloride ranges from 0.5:1 to 2:1.

[0049] The inert organic solvent includes dichloromethane or N,N-dimethylformamide; the organic basic catalyst includes triethylamine.

[0050] S2. The terminal dodecylbenzenesulfonate-based polybutadiene is reacted with 1-methylimidazole in a water bath at 65℃-85℃ for 8-12 hours. The product is washed with solvent, and then vacuum dried at 60℃-80℃ for 6-10 hours to allow the solvent to evaporate, yielding an ionic liquid. The resulting ionic liquid is polybutadiene-1-methylimidazole dodecylbenzenesulfonate, wherein the cation is polybutadiene-1-methylimidazole and the anion is dodecylbenzenesulfonate.

[0051] The molar ratio of the terminal dodecylbenzene sulfonate-based polybutadiene to 1-methylimidazole ranges from 0.5:1 to 2:1.

[0052] S3. Mix the ionic liquid and graphene nanosheets at 60-90℃ and sonicate for 0.5-2h, then cool to room temperature; add curing agent, stir for 0.5-2h, and sonicate for 0.5-2h; then add epoxy resin, stir for 0.25-1h, and repeatedly vacuum until there are no obvious bubbles to obtain a modified epoxy resin mixed solution.

[0053] The mass ratio of the ionic liquid to the graphene nanosheets is 2:1 to 10:1.

[0054] In the modified epoxy resin mixed solution, the mass fraction of the ionic liquid and graphene mixture is 0.1%-3%.

[0055] The mass ratio of epoxy resin to curing agent is 2:1 to 4:1.

[0056] Specifically, the curing agent may be an amine-based curing agent such as polyetheramine.

[0057] S4. Carbon fiber composite parts, including carbon fiber plates, pipes, etc., are formed by wet winding process using the modified epoxy resin mixture solution.

[0058] In a preferred embodiment, the preparation method specifically includes the following steps:

[0059] S1. Add 250 g (0.5 mol) of hydroxyl-terminated polybutadiene, 344.5 g (1 mol) of dodecylbenzenesulfonyl chloride, and 500 mL of dichloromethane to a four-necked flask. Connect the flask to a mechanical stirrer, a reflux condenser, and a separatory funnel. Simultaneously, slowly add triethylamine (101.2 g, 1 mol). Measure the pH value every 10 min until the pH value stabilizes and is not less than 7. Stop the reaction, let it stand for 5 h, and wash the product 2-3 times with hot ethanol to generate hydroxyl-terminated dodecylbenzenesulfonate-based polybutadiene.

[0060] S2. Dissolve 108.4 g, 0.1 mol of terminal dodecylbenzenesulfonate polybutadiene in 200 mL of 1-methylimidazole, stir at 80 °C for 10 h, wash the precipitate with dichloromethane, and then dry under vacuum for 6 h to obtain the ionic liquid generated by the reaction. The cation is polybutadiene-1-methylimidazole cation, and the anion is dodecylbenzenesulfonate.

[0061] S3. Mix the ionic liquid (2.4g) and graphene nanosheets (0.48g) in a 60℃ water bath and sonicate for 2h. Add 20g of curing agent, stir for 0.5h, sonicate for 0.5h, add 60g of epoxy resin, stir for 0.25h, and repeatedly evacuate the vacuum until no obvious bubbles are observed in the mixed solution to obtain a graphene-ionic liquid modified epoxy resin mixed solution.

[0062] S4. Pour the mixed solution obtained in S3 into the resin tank of the winding machine, and set the parameters: winding angle 0-5°, winding speed 5-20r / min, fiber pretension 5-20N; by changing different mandrels, wind carbon fiber plates and pipes; after winding, let stand for 0.5-2h, and vacuum cure at 100-130℃ for 1.5-3h.

[0063] To verify the effectiveness of this embodiment, the performance of the graphene-ionic liquid modified epoxy resin mixed solution obtained in S3 under different graphene contents was tested, with an ionic liquid to graphene mass ratio of 2:1 and an epoxy resin to curing agent mass ratio of 3:1. The gas permeability coefficient test results are as follows: Figure 1 As shown in Table 1, the impact strength at room temperature and under 77K conditions is as follows.

[0064] Table 1 Impact strength of graphene-ionic liquid modified epoxy resin mixture at room temperature and 77K.

[0065]

[0066] The test results show that the material obtained by this method has low gas permeability and high impact strength. Specifically, the ionic liquid obtained in step S2 exists in both anionic and cationic forms. In step S3, graphene (nanoflakes) are encapsulated within it. The polybutadiene-1-methylimidazolium cation interacts with the graphene through π-π conjugated stacking and non-covalent bonding, improving toughness while increasing interlayer spacing and preventing aggregation. The dodecylbenzenesulfonate anion acts as a graphene surfactant, physically adsorbing and anchoring to the graphene surface, enhancing the dispersibility and stability of the graphene through electric layer repulsion and steric hindrance.

[0067] Example 2

[0068] This embodiment provides a carbon fiber composite material, which is prepared using the preparation method described in Example 1.

[0069] The linerless hydrogen storage cylinder prepared using the carbon fiber composite material in this embodiment can serve both the functions of gas barrier and structural pressure bearing.

[0070] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing carbon fiber composite material, characterized in that, Includes the following steps: S1. A first solution is generated by reacting a hydroxyl-terminated polymer with a sulfonyl chloride group organic compound. The hydroxyl-terminated polymer is hydroxyl-terminated polybutadiene; The sulfonyl chloride group organic compound includes dodecylbenzenesulfonyl chloride or ethylsulfonyl chloride; S2. React the first solution with 1-methylimidazole, wash the product with solvent, and vacuum dry to evaporate the solvent to obtain an ionic liquid; S3. Mix the ionic liquid with graphene or hexagonal boron nitride nanosheets evenly, add a curing agent, mix evenly, then add epoxy resin, mix evenly, and repeatedly vacuum to obtain a modified epoxy resin mixed solution. S4. The modified epoxy resin mixture is used to wind and mold carbon fiber composite parts.

2. The preparation method according to claim 1, characterized in that, S1 specifically includes: Hydroxyl-terminated polybutadiene and dodecylbenzenesulfonyl chloride are added to an inert organic solvent. An organic alkaline catalyst is added dropwise to neutralize the byproduct hydrogen chloride. The pH value is monitored to ensure that the reaction fully utilizes the hydroxyl-terminated polybutadiene to generate dodecylbenzenesulfonate-based polybutadiene, which is the first solution. In S2, the ionic liquid is polybutadiene-1-methylimidazolium dodecylbenzenesulfonate, wherein the cation is polybutadiene-1-methylimidazolium and the anion is dodecylbenzenesulfonate.

3. The preparation method according to claim 2, characterized in that, In S1, the molar ratio of the hydroxyl-terminated polybutadiene to dodecylbenzenesulfonyl chloride ranges from 0.5:1 to 2:

1.

4. The preparation method according to claim 2, characterized in that, In S2, the reaction conditions between the first solution and 1-methylimidazole are: 8-12 h under a water bath at 65℃-85℃. The vacuum drying conditions are: temperature 60℃-80℃, time 6-10h.

5. The preparation method according to claim 2, characterized in that, In S2, the molar ratio of the terminal dodecylbenzene sulfonate polybutadiene to 1-methylimidazole ranges from 0.5:1 to 2:

1.

6. The preparation method according to claim 2, characterized in that, The inert organic solvent includes dichloromethane or N,N-dimethylformamide; the organic basic catalyst includes triethylamine.

7. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of the ionic liquid to graphene is 2:1 to 10:

1. In the modified epoxy resin mixture solution, the mass fraction of the mixture of ionic liquid and graphene or hexagonal boron nitride nanosheets is 0.1%-3%. The mass ratio of epoxy resin to curing agent is 2:1 to 4:

1.

8. The preparation method according to claim 1, characterized in that, S3 specifically includes: The ionic liquid was mixed with graphene or hexagonal boron nitride nanosheets and sonicated at 60-90°C for 0.5-2 hours, then cooled to room temperature. Then add the curing agent, stir for 0.5-2 hours, and sonicate for 0.5-2 hours; Add epoxy resin and stir for 0.25-1 hour, then repeatedly vacuum to remove air bubbles.

9. A carbon fiber composite material, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

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