Strong interface bonding carbon fiber / epoxy electromagnetic shielding composite material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, and particularly discloses a strong interface bonding carbon fiber / epoxy electromagnetic shielding composite material and a preparation method thereof.The preparation method comprises the steps that oxidized carbon fibers O-CF, organic ligands and an iron source are subjected to a hydrothermal reaction together in a solvent, and MIL-loaded carbon fibers are obtained after the fibers are washed and dried; carrying out carbonization treatment to obtain iron-based oxide loaded carbon fiber dF (at) CF; epoxy resin is introduced into the multi-layer carbon fiber dF (at) CF through a vacuum auxiliary method, and the carbon fiber / epoxy electromagnetic shielding composite material is obtained through curing. An organic ligand and ferric ions are synthesized on active sites on the surface of the carbon fiber to generate a large amount of rhombic MIL, and the rhombic MIL is carbonized and reduced into iron-based oxide nanoparticles which are tightly loaded on the surface of the carbon fiber, so that the electromagnetic shielding effectiveness is improved while the interface bonding performance is improved, and the electromagnetic shielding effect is improved. The carbon fiber / epoxy composite material with both interface and electromagnetic shielding effectiveness is realized.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding and a preparation method thereof. Background Art

[0002] Carbon fiber reinforced resin matrix composites have the characteristics of light weight, high specific strength and specific modulus, and have been widely used in aerospace, transportation, electronics and other fields. The poor interface performance between carbon fiber and resin matrix is ​​still one of the key problems that need to be solved in carbon fiber reinforced resin matrix composites. In addition, the shielding of electromagnetic waves by carbon fiber / epoxy composites is mainly through reflection loss, which will cause secondary pollution to the environment. Therefore, it is of great significance to expand its application field by surface modification of carbon fiber to improve its interface bonding strength with the resin matrix and increase the absorption loss of electromagnetic shielding.

[0003] At present, traditional carbon fiber / epoxy composite materials still have problems with poor electromagnetic shielding performance and interface performance, and research is needed on modifications that take both properties into account.

[0004] For example, CN115710824A discloses a method for preparing a water-soluble epoxy resin emulsion for carbon fiber surface treatment, in which the carbon fiber is sized with a water-soluble epoxy resin emulsion prepared from polyethylene glycol, epoxy resin and a catalyst as raw materials to increase the roughness and wettability of the carbon fiber surface, thereby improving the interface performance between the carbon fiber and the thermosetting matrix.

[0005] For example, CN117698176A discloses a method for preparing a graphene-carbon fiber / epoxy composite material, in which a homemade graphene oxide dispersion is coated on a carbon fiber fabric, hydrogen is introduced into a vacuum chamber, annealing is performed, a carbon source and hydrogen are introduced after the temperature is increased, and finally a prepreg is obtained by resin impregnation, and an electromagnetic shielding composite material is obtained by hot pressing.

[0006] The above inventions only study the single interface or electromagnetic shielding performance of the carbon fiber / epoxy composite material. Therefore, the carbon fiber / epoxy resin composite material with both interface performance and electromagnetic shielding performance still needs further research.

[0007] In-situ growth is one of the carbon fiber surface modification methods to improve the interface and electromagnetic shielding performance of carbon fiber / epoxy composites. Researchers are also committed to growing conductive nanoparticles on the surface of carbon fiber to improve the interface and electromagnetic shielding effectiveness of epoxy composites. However, conductive particles will increase the proportion of reflection loss of carbon fiber / epoxy composites in electromagnetic shielding, causing secondary pollution of electromagnetic waves. There are few studies on in-situ growth of magnetic particles on the surface of carbon fiber to form electromagnetic synergy with carbon fiber to improve the interface performance and electromagnetic shielding of carbon fiber / epoxy composites, while increasing the proportion of absorption loss. Summary of the invention

[0008] In view of the poor interface bonding performance and poor electromagnetic shielding effectiveness of existing epoxy resin-based carbon fiber composite materials, the present invention provides a carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding. By surface modification of the carbon fiber, its interface bonding performance is improved while the electromagnetic shielding effectiveness is increased, thereby achieving a carbon fiber / epoxy composite material with both interface and electromagnetic shielding effectiveness.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing a carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding comprises the following steps:

[0011] Step 1, oxidizing the desized carbon fiber with nitric acid to obtain oxidized carbon fiber O-CF;

[0012] Step 2, hydrothermally reacting the O-CF, the organic ligand and the iron source in a solvent, washing and drying the fiber to obtain the carbon fiber loaded with MIL;

[0013] Step 3, carbonizing the carbon fiber loaded with MIL under an inert gas environment to obtain the iron-based oxide loaded carbon fiber dF@CF;

[0014] Step 4: introducing epoxy resin into the multilayer carbon fiber dF@CF by a vacuum-assisted method, and obtaining the carbon fiber / epoxy electromagnetic shielding composite material through curing.

[0015] In the present invention, micron-scale carbon fiber is used, and under certain conditions, organic ligands and trivalent iron ions are used to synthesize at the active sites on the surface of the carbon fiber to generate a large number of rhombic MILs, and the carbon fiber modified by the rhombic MILs is subjected to high-temperature carbonization treatment under the protection of an inert gas, and the rhombic MI is reduced to iron-based oxide nanoparticles tightly loaded on the surface of the carbon fiber, and its epoxy resin-based composite material is prepared under vacuum assistance, thereby obtaining a carbon fiber / epoxy electromagnetic shielding composite material modified by iron-based oxides derived from MIL. The iron-based oxides derived from MIL are loaded on the surface of the carbon fiber, which increases the surface roughness of the carbon fiber, enhances the mechanical meshing of the epoxy resin, and improves its interfacial bonding performance. At the same time, the iron-based oxides form an electromagnetic synergistic effect with the carbon fiber, increases the electromagnetic shielding effectiveness, and improves the proportion of absorption loss, thereby achieving a carbon fiber / epoxy composite material that has both interface and electromagnetic shielding effectiveness.

[0016] The organic ligand includes at least one of terephthalic acid, fumaric acid and trimesic acid; the iron source includes at least one of ferric nitrate nonahydrate, ferric chloride hexahydrate and ferric nitrate nonahydrate.

[0017] The molar ratio of the organic ligand to the iron source is 1:0.1 to 1:5, preferably 1:1.

[0018] In step 2, the total molar concentration of the organic ligand and the iron source in the solvent is 20% to 30%.

[0019] In the hydrothermal reaction of step 2, the mass volume ratio of O-CF carbon fiber to solvent is 40g-70g:300-500ml.

[0020] In step 1, the desizing is performed by an organic solvent extraction method, the extraction temperature is 60° C. to 100° C., and the time is 50 to 100 hours; the organic solvent includes at least one of methanol, ethanol, and acetone.

[0021] The desizing is carried out by an organic solvent extraction method, and the mass volume ratio of carbon fiber to solvent is 40g-70g:500ml-700ml.

[0022] The temperature of the oxidation treatment in step 1 is 20-120° C., the reaction time is 1-48 hours, and the concentration of nitric acid is 90-98%.

[0023] In step 2, the solvent includes one or more of water, ethanol, ether, acetone, acetonitrile, tetrahydrofuran, and N,N-dimethylformamide;

[0024] The temperature of the hydrothermal reaction is 60-100° C., and the reaction time is 2-10 hours.

[0025] The temperature of the carbonization treatment in step 3 is 300-600°C, and the treatment time is 1-10 hours. The carbonization temperature is preferably 300-500°C, more preferably 350-450°C, and more preferably 400°C.

[0026] The curing agent used in step 4 includes one or more combinations of diethylenetriamine, triethylenetetramine, metaphenylenediamine, and polyamide; the mass ratio of epoxy resin to curing agent is 1:0.05 to 1:0.25.

[0027] In step 4, the curing process is 0.5 to 2 hours at 70 to 90° C., 1 to 3 hours at 100 to 130° C., and 1 to 3 hours at 140 to 160° C.

[0028] The present invention also provides a carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding obtained according to the preparation method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the present invention, diamond-shaped MIL is loaded on the surface of carbon fiber. After carbonization, the diamond-shaped MIL on the surface is structurally cracked and reduced to iron-based oxide at high temperature, which can improve the roughness of the carbon fiber surface and serve as a mechanical anchor point for bonding with the resin to increase the interfacial bonding strength between the carbon fiber and the resin. The iron-based oxide introduced on the surface of the carbon fiber in the carbon fiber / epoxy composite material increases the magnetic loss, multiple reflection loss and interfacial polarization loss, thereby effectively improving the electromagnetic shielding effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of the in-situ growth of diamond-shaped MIL on the carbon fiber surface in Example 1.

[0032] Figure 2 This is a scanning electron microscope image of the in-situ growth of diamond-shaped MIL-derived iron-based oxide on the surface of the carbon fiber in Example 1.

[0033] Figure 3 This is a scanning electron microscope image of the in-situ growth of diamond-shaped MIL-derived iron-based oxide on the surface of the carbon fiber in Example 2.

[0034] Figure 4 This is a scanning electron microscope image of the in-situ growth of diamond-shaped MIL-derived iron-based oxide on the surface of the carbon fiber in Example 3. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0036] The raw materials used in the following specific embodiments are all purchased from the market, and the carbon fiber plain weave fabric is provided by Toray Industries, Ltd. of Japan, model 12k-T700.

[0037] The interface performance evaluation device evaluated the interface shear strength of carbon fiber and epoxy resin through a droplet debonding test. First, a single carbon fiber was fixed on a concave metal frame (26mm×58mm) with a high temperature resistant glue. Secondly, the epoxy resin (E-51) and the curing agent (TETA) were fully mixed at a mass ratio of 100:12, degassed under vacuum conditions, and finally micro-coated on the carbon fiber surface with a steel needle. Due to the surface tension effect, the liquid resin on the fiber surface will spontaneously shrink into an ellipsoid. Then it was cured at 120°C for 6 hours. The IFSS value can be calculated by formula (1):

[0038]

[0039] Where Fmax is the maximum load recorded, d is the average diameter of CF, and l is the embedding length of epoxy droplet. The IFSS data of each sample is the average of at least 30 valid data.

[0040] The interlaminar shear strength (ILSS) of the composite material was tested using an Instron 5985 universal testing machine, and the test standard was ASTM D2344.

[0041] The electromagnetic interference shielding effectiveness (EMI SE) of the composite material was tested using an E506A vector network analyzer. The test frequency was 8.2-12.4 GHz (X-band). The length × width × thickness of the test rectangular spline was 10.16 mm × 22.86 mm × 2 mm.

[0042] Comparative Example 1

[0043] The carbon fiber was placed in a Soxhlet extractor and desized with acetone at 80°C for 72 hours. After desizing, it was rinsed with deionized water three times and dried in an oven at 80°C for 12 hours to obtain desized carbon fiber, which was recorded as d-CF. The epoxy resin and triethylenetetramine were mixed in a mass ratio of 1:0.12, and the bubbles were removed at room temperature. The resin was injected into d-CF with 5 layers of the same size through a vacuum-assisted injection molding process, and kept at 80°C for 2 hours. After natural cooling, the desized carbon fiber / epoxy composite material was obtained. The test results are shown in Table 1.

[0044] Comparative Example 2

[0045] The d-CF prepared in Comparative Example 1 was acidified with concentrated nitric acid at 100°C for 2h, a large number of hydroxyl and carboxyl active groups were introduced on the surface of the carbon fiber, and after washing to neutrality, it was kept in an oven at 80°C for 12h to obtain oxidized carbon fiber, which was recorded as O-CF. Five layers of oxidized carbon fiber / epoxy composite materials were prepared using the same preparation method and curing process as Comparative Example 1, and the test results are shown in Table 1.

[0046] Example 1

[0047] Take 10.82g of ferric chloride and 4.64g of fumaric acid and add them to 300ml of N,N-dimethylformamide in sequence, and stir them magnetically to dissolve. Pour the reaction solution into a hydrothermal kettle, add 60g of O-CF prepared in Comparative Example 2, tighten the hydrothermal kettle and put it into a 100℃ oven for 4h, cool it naturally, take it out for washing, and dry it in a vacuum oven at 60℃ for 12h to obtain a carbon fiber with diamond-shaped MIL on the surface, and its microscopic morphology is as follows: Figure 1 shown.

[0048] The in-situ grown carbon fiber was placed in a high-temperature tube furnace and maintained at 400 °C for 4 h in a nitrogen atmosphere with a heating rate of 5 °C / min. After natural cooling, carbon fiber loaded with ferroferric oxide nanoparticles was obtained, which was denoted as dF-400@CF. Its microscopic morphology is shown in Figure 2 As shown, it can be seen that the diamond-shaped MIL is oxidized to form iron oxide attached to the fiber surface. Five layers of modified carbon fiber / epoxy composite material were prepared using the same preparation method and curing process as in Comparative Example 1, and were recorded as dF-400@CF / EP composite material. The test results are shown in Table 1.

[0049] Example 2

[0050] The carbon fiber loaded with diamond-shaped MIL in Example 1 was placed in a high-temperature tube furnace and maintained at 300°C for 4 hours at a heating rate of 5°C / min under a nitrogen atmosphere. After natural cooling, carbon fiber loaded with ferroferric oxide nanoparticles was obtained, which was recorded as dF-300@CF. Its microscopic morphology is shown in FIG. Figure 3A five-layer modified carbon fiber / epoxy composite material was prepared by the same preparation method and curing process as in Comparative Example 1, which was recorded as dF-300@CF / EP composite material. The test results are shown in Table 1.

[0051] Example 3

[0052] The carbon fiber loaded with diamond-shaped MIL in Example 1 was placed in a high-temperature tube furnace and maintained at 500°C for 4 h at a heating rate of 5°C / min under a nitrogen atmosphere. After natural cooling, carbon fiber loaded with ferroferric oxide nanoparticles was obtained, which was recorded as dF-500@CF. Its microscopic morphology is shown in FIG. Figure 4 A five-layer modified carbon fiber / epoxy composite material was prepared by the same preparation method and curing process as in Comparative Example 1, which was recorded as dF-500@CF / EP composite material. The test results are shown in Table 1.

[0053] Comparative Example 3

[0054] The same preparation method and curing process as in Comparative Example 1 were adopted, and Japanese Toray T700 12k plain weave was used as carbon fiber to prepare a 5-layer carbon fiber cloth / epoxy composite material. The test results are shown in Table 1.

[0055] Table 1 Properties of carbon fiber cloth / epoxy composites prepared in Examples and Comparative Examples

[0056]

[0057] Among them, the large amount of iron-based oxides on the surface of the carbon fiber in Example 1 can provide more mechanical anchor points, enhance the mechanical engagement with the resin, and have higher interface performance. In addition, the more iron-based oxides in Example 1 can improve the magnetic loss, multiple reflection loss and interface polarization loss of the carbon fiber / epoxy composite material, thereby effectively improving the electromagnetic shielding effectiveness and the proportion of absorption loss. The loaded iron-based oxides generated after the cracking of MIL at 400°C carbonization in Example 1 are more uniform and dense than those in Example 2 and Example 3, and the epoxy composite material prepared therefrom has stronger interface bonding and electromagnetic shielding effectiveness. In Example 2, the carbonization temperature at 300°C is too low, and the MIL loaded on the surface of the carbon fiber cannot be completely converted into iron-based oxides, so that the composite material prepared therefrom has lower electromagnetic shielding effectiveness than the composite material in Example 1. In Example 3, the carbonization temperature at 500°C is too high, resulting in the cracking and shedding of the MIL loaded on the surface of the carbon fiber, so that the composite material prepared therefrom has lower interface performance and electromagnetic shielding effectiveness than the composite material in Example 1, but the overall performance is better than the comparative example.

Claims

1. A method for preparing a carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding, characterized in that: Includes steps: Step 1, oxidizing the desized carbon fiber with nitric acid to obtain oxidized carbon fiber O-CF; Step 2, hydrothermally reacting the O-CF, the organic ligand and the iron source in a solvent, washing and drying the fiber to obtain the carbon fiber loaded with MIL; Step 3, carbonizing the carbon fiber loaded with MIL under an inert gas environment to obtain the iron-based oxide loaded carbon fiber dF@CF; Step 4: introducing epoxy resin into the multilayer carbon fiber dF@CF by a vacuum-assisted method, and obtaining the carbon fiber electromagnetic shielding epoxy composite material through curing.

2. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: The organic ligand includes at least one of terephthalic acid, fumaric acid and trimesic acid; the iron source includes at least one of ferric nitrate nonahydrate, ferric chloride hexahydrate and ferric nitrate nonahydrate.

3. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: The molar ratio of the organic ligand to the iron source is 1:0.1 to 1:5; In step 2, the total molar concentration of the organic ligand and the iron source in the solvent is 20% to 30%.

4. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: In step 1, the desizing is performed by an organic solvent extraction method, the extraction temperature is 60° C. to 100° C., and the time is 50 to 100 hours; the organic solvent includes at least one of methanol, ethanol, and acetone.

5. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: The temperature of the oxidation treatment in step 1 is 20-120° C., the reaction time is 1-48 hours, and the concentration of nitric acid is 90-98%.

6. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: In step 2, the solvent includes one or more combinations of water, ethanol, ether, acetone, acetonitrile, tetrahydrofuran, and N,N-dimethylformamide; The temperature of the hydrothermal reaction is 60-100° C., and the reaction time is 2-10 hours.

7. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: The temperature of the carbonization treatment in step 3 is 300-600° C., and the treatment time is 1-10 h.

8. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: The curing agent used in step 4 includes one or more combinations of diethylenetriamine, triethylenetetramine, metaphenylenediamine, and polyamide; the mass ratio of epoxy resin to curing agent is 1:0.05 to 1:0.

25.

9. The method for preparing the carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding according to claim 1, characterized in that: In step 4, the curing process is 0.5 to 2 hours at 70 to 90° C., 1 to 3 hours at 100 to 130° C., and 1 to 3 hours at 140 to 160° C.

10. A carbon fiber / epoxy electromagnetic shielding composite material with strong interface bonding obtained according to the preparation method according to any one of claims 1 to 9.

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