A MOF-reinforced carbon fiber composite material and its preparation method

Abstract

This invention provides a MOF-reinforced carbon fiber composite material and its preparation method. The preparation method includes carbon fiber pretreatment, preparation of UIO-66 nanocrystals, preparation of UIO-66 seed solution, preparation of secondary growth solution, and carbon fiber surface modification steps to obtain a carbon fiber composite material loaded with UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals. The preparation method of this invention ensures that the UIO-66-NH2-encapsulated DOPO flame retardant structure is uniformly dispersed on the carbon fiber surface, improving the surface energy and flame retardant properties of the carbon fiber, and providing a good functional reinforcement for the preparation of resin-based composite materials.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, and more specifically, to a MOF-reinforced carbon fiber composite material and its preparation method. Background Technology

[0002] Carbon fiber (CF) reinforced resin composites possess advantages such as lightweight, high strength, corrosion resistance, and excellent thermal stability, and have been widely used in aerospace, automotive, and construction industries. However, due to the low number of active carbon atoms at the surface edges and the low surface energy, carbon fibers exhibit inertness and poor wettability with the resin matrix. Furthermore, internal pores generated during the production of carbon fiber composites can lead to interfacial discontinuities between the fiber and the matrix. This has been a long-standing technical challenge, limiting the widespread application of carbon fiber composites to some extent.

[0003] Modifying the surface of carbon fibers can effectively improve the interfacial properties between the fiber and the matrix. There are various modification mechanisms, such as carbon fiber surface etching, which increases the surface area of ​​the fiber by increasing its roughness, thereby achieving mechanical interlocking between the fiber and the matrix; carbon fiber surface oxidation, which forms acidic functional groups, promoting the formation of chemical bonds with the polymer matrix and improving the surface activity and wettability of the fiber; and removing the weak interfacial layer on the fiber surface, reducing defects in the carbon fiber material. However, these methods require sophisticated equipment, are difficult to operate, and can easily damage the inherent strength of the fiber.

[0004] Hydrothermal treatment of carbon fibers has gained widespread application due to its advantages such as ease of operation, simple equipment, and no damage to the carbon fibers. For example, patent document CN105133317A discloses a method for modifying the surface of carbon fibers with a metal framework. This method involves depositing or attaching MOF (Metal-Oxide-Foil) nanoparticles to the carbon fiber surface, which can improve the surface activity of the fibers, enhance the wettability of the matrix to the fibers, and endow the composite material with functions such as self-healing, wave absorption, and electromagnetic shielding. Improving the flame retardant properties of carbon fiber reinforced resin composites is also a current research focus. For instance, patent document CN116641227A discloses a method for modifying the surface of carbon fibers, using a hydrothermal method to grow manganese dioxide nanosheets on the carbon fiber surface, followed by in-situ growth of MOF onto the CF / MnO2 surface. However, existing processes make it difficult for MOF to adhere and disperse on the carbon fiber surface, reducing the wetting effect of the resin matrix on the carbon fibers, thus affecting interfacial properties and flame retardant properties. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to make MOF and flame retardant uniformly dispersed on the carbon fiber surface and improve the adhesion effect, thereby improving the surface energy and flame retardant performance of carbon fiber.

[0006] To address the above problems, this invention provides a method for preparing MOF-reinforced carbon fiber composite materials, characterized by comprising the following steps:

[0007] S1. Carbon fiber pretreatment: Clean the carbon fiber surface, perform plasma surface etching treatment, oxidize the carbon fiber surface with acid, then treat the carbon fiber surface with silane coupling agent, and obtain functionalized carbon fiber after cleaning and drying.

[0008] S2. Preparation of UIO-66 nanocrystals: Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N dimethylformamide, dispersed evenly, and then subjected to a hydrothermal reaction. The product was separated, washed, dried, and ground to obtain UIO-66-NH2 nanocrystals.

[0009] S3. Preparation of UIO-66 seed solution: Disperse UIO-66-NH2 nanocrystals in a mixed solution of ethanol and polyethyleneimine to obtain UIO-66-NH2 seed solution;

[0010] S4. Preparation of secondary growth solution: Zirconium tetrachloride and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide solution, DOPO flame retardant and surfactant are added and uniformly dispersed to obtain secondary growth solution;

[0011] S5. Surface modification of carbon fiber: The functionalized carbon fiber obtained in step S1 is immersed in the UIO-66-NH2 seed solution obtained in step S3, dried and then immersed in the secondary growth solution obtained in step S4 for hydrothermal reaction. After the reaction is completed, it is dried to obtain a carbon fiber composite material loaded with UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

[0012] This invention first attaches UIO-66-NH2 nanocrystals to the surface of carbon fiber to form a seed layer, and then uses a hydrothermal method to grow UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals in situ on the seed layer, so that MOF generates a hierarchical reinforcing structure on the carbon fiber surface. This preparation method makes the UIO-66-NH2-encapsulated DOPO flame retardant structure uniformly dispersed on the carbon fiber surface, improving the surface energy and flame retardant properties of carbon fiber, and can provide a good functional reinforcement for the preparation of resin-based composite materials.

[0013] Furthermore, in step S5, the hydrothermal reaction temperature is 70–160°C, and the time is 8–24 hours.

[0014] Furthermore, in step S2, the hydrothermal reaction temperature is 80–120°C, and the time is 5–24 hours.

[0015] Further, in step S4, the mass ratio of zirconium tetrachloride, 2-aminoterephthalic acid, and DOPO flame retardant is 5-20:4-20:1-5.

[0016] Furthermore, in step S4, the zirconium tetrachloride content in the secondary growth solution is 5–40 g / L.

[0017] Furthermore, in step S4, a regulator is added to the secondary growth solution. The regulator is acetic acid and / or benzoic acid, and the content of the regulator is 2-20 g / L.

[0018] Further, in step S4, the surfactant is selected from one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, and polyvinylpyrrolidone, and the concentration of the surfactant in the secondary growth solution is 0.1 to 0.6 mol / L.

[0019] Further, in step S2, the concentration of zirconium tetrachloride in the uniformly dispersed mixed solution is 0.1–1.0 mol / L, and the concentration of 2-aminoterephthalic acid is 0.1–0.5 mol / L.

[0020] Furthermore, in step S3, the content of UIO-66-NH2 nanocrystals in the UIO-66-NH2 seed solution is 1.0–5.0 wt%.

[0021] Furthermore, in step S3, the volume ratio of ethanol to polyethyleneimine in the mixed solution is 1:1 to 7.

[0022] The present invention also provides a MOF-reinforced carbon fiber composite material, which is prepared by the above-described preparation method. The MOF-reinforced carbon fiber composite material includes a carbon fiber body and UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals coated on the surface of the carbon fiber body.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) In this invention, UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals are uniformly coated on the carbon fiber body. The nanocrystals have a hierarchical reinforcement structure, which improves the surface roughness of the carbon fiber and enhances the wettability of the carbon fiber and the resin matrix, thereby improving the interface effect.

[0025] (2) The present invention introduces a large number of active functional groups and DOPO flame retardant on the surface of inert fibers, which improves the interfacial bonding strength and ultimately improves the fire resistance of the composite material.

[0026] (3) The present invention uses a hydrothermal method to modify the surface of carbon fiber, avoiding the damage to carbon fiber caused by traditional processing technology. The operation is simple and the raw materials required are inexpensive, making it suitable for large-scale industrial production. Attached Figure Description

[0027] Figure 1 This is a SEM image of the carbon fiber composite material prepared in Example 1 of the present invention.

[0028] Figure 2 This is a SEM image of the UIO-66-NH2-encapsulated DOPO nanocrystals prepared in Example 1 of this invention.

[0029] Figure 3 This is the XRD pattern of the carbon fiber composite material prepared in Example 1 of the present invention. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0031] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] This invention provides a MOF-reinforced carbon fiber composite material and its preparation method. The MOF-reinforced carbon fiber composite material includes a carbon fiber matrix with its surface uniformly coated with UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals, exhibiting excellent surface energy and flame retardant properties. The preparation method of the MOF-reinforced carbon fiber composite material includes the following steps:

[0033] S1, Carbon fiber pretreatment

[0034] The carbon fiber surface is cleaned to remove sizing agents and other impurities. In this specific embodiment, ultrasonic cleaning with acetone or ethanol is used. After cleaning, the carbon fiber undergoes plasma surface etching to increase its surface roughness. Then, the carbon fiber surface is oxidized with acid to introduce oxygen-containing active groups. Subsequently, the carbon fiber surface is treated with a silane coupling agent to increase surface activity, which is beneficial for improving the subsequent MOF grafting strength. After cleaning and drying, functionalized carbon fibers are obtained.

[0035] S2. Preparation of UIO-66 nanocrystals

[0036] Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide (DMF), uniformly dispersed, and then subjected to a hydrothermal reaction. In a specific embodiment, the concentration of zirconium tetrachloride was 0.1–1.0 mol / L, the concentration of 2-aminoterephthalic acid was 0.1–0.5 mol / L, the hydrothermal reaction temperature was 80–120 °C, and the reaction time was 5–24 h. After the reaction was completed, the product was separated by centrifugation, and the product was washed, dried, and ground to obtain UIO-66-NH2 nanocrystals.

[0037] S3. Prepare UIO-66 seed solution

[0038] UIO-66-NH2 nanocrystals were dispersed in a mixed solution of ethanol and polyethyleneimine (PEI) to obtain a UIO-66-NH2 seed solution. In a specific embodiment, the volume ratio of ethanol to polyethyleneimine in the mixed solution was 1:1 to 7, and the content of UIO-66-NH2 nanocrystals in the seed solution was 1.0 to 5.0 wt%.

[0039] S4. Preparation of secondary growth solution

[0040] Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in an N,N-dimethylformamide solution, and DOPO flame retardant and surfactant were added and uniformly dispersed to obtain a secondary growth solution. In a specific embodiment, the mass ratio of zirconium tetrachloride, 2-aminoterephthalic acid, and DOPO flame retardant was 5–20:4–20:1–5, and the content of zirconium tetrachloride in the secondary growth solution was 5–40 g / L. The surfactant was used to improve the stability of the solution, and could be hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, etc., with a surfactant concentration of 0.1–0.6 mol / L.

[0041] Preferably, a regulator is also added to the secondary growth solution to adjust the coordination ability between zirconium tetrachloride and 2-aminoterephthalic acid, thereby reducing the size of the formed MOF and improving the surface energy. In specific embodiments, the regulator can be acetic acid or benzoic acid, and the content of the regulator in the secondary growth solution is 2-20 g / L.

[0042] S5, carbon fiber surface modification

[0043] The functionalized carbon fibers obtained in step S1 are immersed in the UIO-66-NH2 seed solution obtained in step S3, dried, and then removed. In a specific embodiment, the drying temperature is 60–100°C and the drying time is 3–10 h. They are then immersed in the secondary growth solution obtained in step S4 for a hydrothermal reaction. In a specific embodiment, the hydrothermal reaction temperature is 70–160°C and the time is 8–24 h. After the reaction is complete, the carbon fiber composite material is removed and dried to obtain carbon fiber composite material with UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals.

[0044] The above preparation method first grows a uniform seed layer on the surface of carbon fiber, and then performs secondary growth on the seed layer to grow UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals on the carbon fiber surface. These nanocrystals have a hierarchical reinforcement structure, which improves the surface energy and flame retardant properties of carbon fiber and can provide a good functional reinforcement for the preparation of resin-based composite materials.

[0045] The technical solution and effects of the present invention will be described below through specific embodiments.

[0046] Example 1

[0047] In this embodiment, MOF-reinforced carbon fiber composite material was prepared. The preparation process is as follows:

[0048] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities from the surface; plasma etching is used to improve the surface roughness of carbon fiber; acid oxidation is used to chemically treat the surface of carbon fiber; then plasma etching is used for 10 min; then KH-550 is used to treat the surface of carbon fiber, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0049] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.1 mol / L. The mixture was hydrothermally reacted at 100 °C for 5 hours. The resulting mixed solution was centrifuged and washed with methanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0050] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 1 wt%.

[0051] (4) Dissolve 0.5g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.1g DOPO flame retardant, 0.2g acetic acid and 0.1g PVP in 50mL DMF to obtain a secondary growth solution.

[0052] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 80°C for 6 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 100°C for 12 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain a composite material of carbon fiber surface modified UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

[0053] The MOF-reinforced carbon fiber composite material prepared in this embodiment was observed using scanning electron microscopy, and the results are as follows: Figure 1 and Figure 2 As shown, UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals are uniformly loaded onto the surface of the carbon fiber fabric. These nanocrystals have an octahedral structure. XRD tests were performed on the reinforced carbon fiber composite, and the results are as follows: Figure 3 As shown, this indicates that the composite material contains carbon fibers and UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals.

[0054] The properties of MOF-reinforced carbon fiber composites were tested, and the results showed that the surface energy was 50 mN / m and the interfacial shear strength was 65 MPa.

[0055] Adding 10% of the MOF-reinforced carbon fiber composite material prepared in this example to polyamide (PA) increases the limiting oxygen index by about 5%, and significantly improves the flame retardant and smoke-suppressing performance.

[0056] Example 2

[0057] In this embodiment, MOF-reinforced carbon fiber composite material was prepared. The preparation process is as follows:

[0058] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities on the surface; plasma etching is used for 10 min; acid oxidation is used to chemically treat the carbon fiber surface; then plasma etching is used; then KH-550 is used to treat the carbon fiber surface, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0059] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.1 mol / L. The mixture was hydrothermally reacted at 80 °C for 2 hours. The resulting mixed solution was centrifuged and washed with methanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0060] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 2 wt%.

[0061] (4) Dissolve 0.5g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.2g DOPO flame retardant, 0.2g acetic acid, and 0.1g hexadecyltrimethylammonium bromide in 50mL DMF to obtain a secondary growth solution.

[0062] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 80°C for 6 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 80°C for 10 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain a composite material of carbon fiber surface modified UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

[0063] The properties of the MOF-reinforced carbon fiber composite material prepared in this embodiment were tested, and the results showed that its surface energy was 45 mN / m and its interfacial shear strength was 55 MPa.

[0064] Adding 10% of the MOF-reinforced carbon fiber composite material prepared in this example to polyamide (PA) increases the limiting oxygen index by about 4%, and significantly improves the flame retardant and smoke-suppressing performance.

[0065] Example 3

[0066] In this embodiment, MOF-reinforced carbon fiber composite material was prepared. The preparation process is as follows:

[0067] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities on the surface; plasma etching is used for 5 minutes; acid oxidation is used to chemically treat the carbon fiber surface; then plasma etching is used; then KH-550 is used to treat the carbon fiber surface, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0068] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.2 mol / L. The mixture was hydrothermally reacted at 80 °C for 12 hours. The resulting mixed solution was centrifuged and washed with ethanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0069] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 1.5 wt%.

[0070] (4) Dissolve 1.0g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.3g DOPO flame retardant, 0.5g acetic acid and 0.1g sodium dodecyl sulfonate in 50mL DMF to obtain a secondary growth solution.

[0071] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 80°C for 3 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 130°C for 24 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain a composite material of carbon fiber surface modified UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

[0072] The properties of the MOF-reinforced carbon fiber composite material prepared in this embodiment were tested, and the results showed that its surface energy was 40 mN / m and its interfacial shear strength was 55 MPa.

[0073] Adding 5% of the MOF-reinforced carbon fiber composite material prepared in this embodiment to epoxy resin fiber increases the limiting oxygen index by about 3%.

[0074] Example 4

[0075] In this embodiment, MOF-reinforced carbon fiber composite material was prepared. The preparation process is as follows:

[0076] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities on the surface; plasma etching is used for 3 minutes; acid oxidation is used to chemically treat the carbon fiber surface; then plasma etching is used; then KH-550 is used to treat the carbon fiber surface, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0077] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.5 mol / L. The mixture was hydrothermally reacted at 80 °C for 8 hours. The resulting mixed solution was centrifuged and washed with ethanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0078] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 3 wt%.

[0079] (4) Dissolve 2.0g ZrCl4, 1.5g 2-aminoterephthalic acid, 0.5g DOPO flame retardant, 1.0g acetic acid, and 0.1g sodium dodecylbenzenesulfonate in 50mL DMF to obtain a secondary growth solution.

[0080] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 60°C for 3 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 90°C for 24 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain a composite material of carbon fiber surface modified UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

[0081] The properties of the MOF-reinforced carbon fiber composite material prepared in this embodiment were tested, and the results showed that its surface energy was 40 mN / m and its interfacial shear strength was 50 MPa.

[0082] Adding 5% of the MOF-reinforced carbon fiber composite material prepared in this embodiment to epoxy resin fiber increases the limiting oxygen index by about 3%.

[0083] Comparative Example 1

[0084] This comparative example demonstrates the preparation of surface-modified carbon fiber composite materials. The preparation process is as follows:

[0085] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities from the surface; plasma etching is used to improve the surface roughness of carbon fiber; acid oxidation is used to chemically treat the surface of carbon fiber; then plasma etching is used for 10 min; then KH-550 is used to treat the surface of carbon fiber, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0086] (2) Dissolve 0.5g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.1g DOPO flame retardant, 0.2g acetic acid and 0.1g PVP in 50mL DMF to obtain a growth solution.

[0087] (3) The pretreated functionalized carbon fiber is immersed in the growth solution and subjected to a hydrothermal reaction at 100°C for 12 hours. After the reaction is completed, the carbon fiber is taken out, washed and dried to obtain the surface modified carbon fiber composite material.

[0088] The properties of the surface-modified carbon fiber composite material in this comparative example were tested, and the results showed that its surface energy was 15 mN / m and its interfacial shear strength was 60 MPa.

[0089] Adding 10% of the MOF-reinforced carbon fiber composite material prepared in this example to polyamide (PA) increases the limiting oxygen index by about 1%.

[0090] Comparative Example 2

[0091] This comparative example demonstrates the preparation of surface-modified carbon fiber composite materials. The preparation process is as follows:

[0092] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove sizing agent and other impurities from its surface.

[0093] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.1 mol / L. The mixture was hydrothermally reacted at 100 °C for 5 hours. The resulting mixed solution was centrifuged and washed with methanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0094] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 1 wt%.

[0095] (4) Dissolve 0.5g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.1g DOPO flame retardant, 0.2g acetic acid and 0.1g PVP in 50mL DMF to obtain a secondary growth solution.

[0096] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 80°C for 6 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 100°C for 12 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain surface modified carbon fiber composite material.

[0097] The properties of the surface-modified carbon fiber composite material in this comparative example were tested, and the results showed that its surface energy was 20 mN / m and its interfacial shear strength was 62 MPa.

[0098] Adding 10% of the MOF-reinforced carbon fiber composite material prepared in this example to polyamide (PA) increases the limiting oxygen index by about 1%.

[0099] Comparative Example 3

[0100] This comparative example demonstrates the preparation of surface-modified carbon fiber composite materials. The preparation process is as follows:

[0101] (1) Carbon fiber is cleaned with acetone and ultrasonically treated to remove slurry and other impurities from the surface; plasma etching is used to improve the surface roughness of carbon fiber; acid oxidation is used to chemically treat the surface of carbon fiber; then plasma etching is used for 10 min; then KH-550 is used to treat the surface of carbon fiber, and finally it is cleaned and dried to obtain functionalized carbon fiber.

[0102] (2) Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in 50 mL of DMF and ultrasonically dispersed evenly. The molar concentrations of both zirconium tetrachloride and 2-aminoterephthalic acid were 0.1 mol / L. The mixture was hydrothermally reacted at 100 °C for 5 hours. The resulting mixed solution was centrifuged and washed with methanol, dried and ground to obtain UIO-66-NH2 nanocrystals.

[0103] (3) Add UIO-66-NH2 nanocrystal seeds to an ethanol / polyethyleneimine (1:1) mixed solution, stir for 1 h, and ultrasonically disperse for 1 h to obtain a UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 1 wt%.

[0104] (4) Dissolve 0.5g ZrCl4, 0.5g 2-aminoterephthalic acid, 0.2g acetic acid and 0.1g PVP in 50mL DMF to obtain a secondary growth solution.

[0105] (5) The pretreated functionalized carbon fiber was immersed in UIO-66-NH2 seed solution, placed in an oven, dried at 80°C for 6 hours, and then taken out and immersed in secondary growth solution. The hydrothermal reaction was carried out at 100°C for 12 hours. After the reaction was completed, the carbon fiber was taken out, washed and dried to obtain surface modified carbon fiber composite material.

[0106] The properties of the surface-modified carbon fiber composite material in this comparative example were tested, and the results showed that its surface energy was 50 mN / m and its interfacial shear strength was 66 MPa.

[0107] Adding 10% of the MOF-reinforced carbon fiber composite material prepared in this example to polyamide (PA) increases the limiting oxygen index by about 1.5%.

[0108] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing MOF-reinforced carbon fiber composite material, characterized in that, Includes the following steps: S1. Carbon fiber pretreatment: Clean the carbon fiber surface, perform plasma surface etching treatment, oxidize the carbon fiber surface with acid, then treat the carbon fiber surface with silane coupling agent, and obtain functionalized carbon fiber after cleaning and drying. S2. Preparation of UIO-66 nanocrystals: Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N dimethylformamide, dispersed evenly, and then subjected to a hydrothermal reaction. The product was separated, washed, dried, and ground to obtain UIO-66-NH2 nanocrystals. S3. Preparation of UIO-66 seed solution: Disperse UIO-66-NH2 nanocrystals in a mixed solution of ethanol and polyethyleneimine to obtain UIO-66-NH2 seed solution, wherein the content of UIO-66-NH2 nanocrystals is 1.0-5.0 wt%. S4. Preparation of secondary growth solution: Zirconium tetrachloride and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide solution, DOPO flame retardant and surfactant are added and uniformly dispersed to obtain secondary growth solution. The mass ratio of zirconium tetrachloride, 2-aminoterephthalic acid and DOPO flame retardant is 5-20:4-20:1-5. The content of zirconium tetrachloride in the secondary growth solution is 5-40 g / L. A regulator is added to the secondary growth solution. The regulator is acetic acid and / or benzoic acid, and the content of the regulator is 2-20 g / L. S5. The functionalized carbon fiber obtained in step S1 is immersed in the UIO-66-NH2 seed solution obtained in step S3, dried and then immersed in the secondary growth solution obtained in step S4 for hydrothermal reaction. After the reaction is completed, it is removed and dried to obtain a carbon fiber composite material loaded with UIO-66-NH2 encapsulated DOPO flame retardant nanocrystals.

2. The method for preparing MOF-reinforced carbon fiber composite material according to claim 1, characterized in that, In step S5, the hydrothermal reaction temperature is 70–160°C, and the time is 8–24 hours.

3. The method for preparing MOF-reinforced carbon fiber composite material according to claim 1, characterized in that, In step S2, the hydrothermal reaction temperature is 80–120°C, and the time is 5–24 hours.

4. The method for preparing MOF-reinforced carbon fiber composite material according to claim 1, characterized in that, In step S4, the surfactant is selected from one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, and polyvinylpyrrolidone, and the concentration of the surfactant in the secondary growth solution is 0.1 to 0.6 mol / L.

5. The method for preparing MOF-reinforced carbon fiber composite material according to claim 1, characterized in that, In step S2, the concentration of zirconium tetrachloride in the uniformly dispersed mixed solution is 0.1–1.0 mol / L, and the concentration of 2-aminoterephthalic acid is 0.1–0.5 mol / L.

6. The method for preparing MOF-reinforced carbon fiber composite material according to claim 1, characterized in that, In step S3, the volume ratio of ethanol to polyethyleneimine in the mixed solution is 1:1 to 7.

7. A MOF-reinforced carbon fiber composite material, characterized in that, The MOF-reinforced carbon fiber composite material, prepared by any one of the preparation methods of claims 1-6, comprises a carbon fiber body and UIO-66-NH2-encapsulated DOPO flame retardant nanocrystals coated on the surface of the carbon fiber body.

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