A method for preparing a modified carbon fiber reinforced polyimide composite

Abstract

The application discloses a preparation method of a modified carbon fiber reinforced polyimide composite material, and comprises the following steps: (1) washing a carbon fiber cloth; (2) oxidizing the carbon fiber cloth: adding the washed carbon fiber cloth into a strong oxidant solution to modify the carbon fiber cloth; (3) preparing a modified coating: immersing the carbon fiber cloth in a silane coupling agent solution, and drying to obtain a modified carbon fiber cloth; and (4) preparing the composite material: sequentially layering polyimide films and the modified carbon fiber cloth in an ABAB...A order, with the polyimide films being A and the carbon fiber cloth being B, and placing the polyimide films and the modified carbon fiber cloth into a hot press to obtain the carbon fiber reinforced polyimide composite material. Through the oxidation treatment of the carbon fiber cloth by the strong oxidant, the surface roughness of the carbon fiber is increased, and the interfacial strength between the carbon fiber cloth and the matrix is improved by adding the silane coupling agent, so that the interlaminar shear performance and the impact performance of the material are greatly improved.

Description

Technical Field

[0001] This invention relates to a method for preparing modified carbon fiber composite materials, and more particularly to a method for preparing modified carbon fiber reinforced polyimide composite materials. Background Technology

[0002] Fiber-reinforced composites are composite materials formed by laminating reinforcing fibers with a matrix material through molding processes such as lamination, filament winding, or pultrusion. Fiber-reinforced composites have gained applications due to their excellent properties, and the crucial role of reinforcing fibers in composite materials is self-evident. Since the advent of composite materials, reinforcing fibers have evolved from natural fibers to synthetic fibers. Currently, common reinforcing fibers include glass fibers, aramid fibers, and carbon fibers, among which carbon fibers exhibit particularly excellent comprehensive properties. Carbon fiber fabric, typically woven from carbon fibers, possesses many superior properties, such as heat resistance, tensile and compressive strength, and can be applied in numerous fields. Carbon fiber fabric can significantly improve the mechanical properties of composite materials; moreover, the symmetrical distribution of carbon fiber fabric within the composite material ensures the symmetry of its mechanical properties. However, a major problem in the application of carbon fiber fabric in various fields is its poor compatibility with other materials, which easily leads to delamination of the resulting composite material. Therefore, improving the interlayer bonding strength of composite materials has become a key issue.

[0003] To address the aforementioned issues, patent application CN110872428A introduces epoxy resin through an RTM process, impregnating the surface of the carbon fiber cloth with epoxy resin. This method of adding resin to bond the matrix and carbon fiber cloth only strengthens the bond from a physical perspective, resulting in low interfacial strength and an impact performance improvement of only 27%. Patent application CN109411721B discloses a method of anodizing the carbon cloth to increase its surface roughness, thereby increasing the contact area between the matrix and the carbon fiber. However, this is still a physical-level connection, with limited improvement in interlaminar shear performance. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing modified carbon fiber reinforced polyimide composite materials with improved interlaminar shear properties.

[0005] Technical solution: The preparation method of the modified carbon fiber reinforced polyimide composite material of the present invention includes the following steps:

[0006] (1) Cleaning carbon fiber cloth: Use a mixture of anhydrous ethanol and acetone to remove impurities from the surface of the carbon fiber cloth and wash the carbon fiber cloth until it is neutral;

[0007] (2) Oxidation treatment of carbon fiber cloth: The cleaned carbon fiber cloth is added to a strong oxidant solution to modify the carbon fiber cloth;

[0008] (3) Preparation of modified coating: Mix silane coupling agent, anhydrous ethanol and water to prepare a modified solution, wherein the concentration of silane coupling agent is 5% to 10%, and adjust the pH value of the solution to 4-5 with acid. Place the carbon fiber cloth in the solution, soak it, wash it until neutral, and dry it after the solution evaporates to obtain the modified carbon fiber cloth.

[0009] (4) Preparation of composite material: Polyimide film and modified carbon fiber cloth are laid in the order of ABAB…A, with polyimide film as A and carbon fiber cloth as B. They are then placed in a hot press to obtain carbon fiber reinforced polyimide composite material.

[0010] Furthermore, the volume ratio of anhydrous ethanol and acetone in step (1) is 2:3 to 1:1, preferably 1:1.

[0011] Furthermore, the strong oxidant mentioned in step (2) is either sodium hydroxide or hydrogen peroxide.

[0012] Further, the concentration of sodium hydroxide in step (2) is 2% to 5%, and the concentration of hydrogen peroxide is 2% to 5%.

[0013] Furthermore, in step (2), the strong oxidant is sodium hydroxide with a concentration of 5%.

[0014] Further, the silane coupling agent mentioned in step (3) is one of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and 3-aminopropyltrimethoxysilane.

[0015] Further, the volume ratio of the silane coupling agent, anhydrous ethanol and water in step (3) is 1:8:1 to 2:6:2.

[0016] Further, the method for preparing the polyimide film in step (4) is as follows: dissolve dialdehyde in anhydrous ethanol solution, then dissolve amine curing agent in anhydrous ethanol solvent and stir evenly to prepare a mixed solution, pour it into a mold and dry and cure to obtain polyimide film.

[0017] Furthermore, the dialdehyde is a para-dialdehyde, including an aliphatic dialdehyde or an aromatic dialdehyde containing a benzene ring.

[0018] Furthermore, the amine curing agent includes diamine and triamine; the diamine is specifically one or more of diethylenetriamine, N,N-bis(2-aminoethyl)-1,3-propanediamine, and diethylenetriamine; the triamine is specifically one or more of triethylenetetramine, tri(2-aminoethyl)amine, and triethylenetetramine.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0020] (1) The carbon fiber cloth is oxidized by a strong oxidant to increase the surface roughness of the carbon fiber, which increases the bonding area with the matrix and improves the interlayer bonding force between the carbon fiber and the polyimide film.

[0021] (2) The addition of silane coupling agent improves the interfacial strength between carbon fiber cloth and matrix. In addition to physical connection, chemical bond connection is also formed between modified carbon fiber cloth and polyimide film. The hydrolyzed silane coupling agent O-Si is connected to the surface of modified carbon fiber at one end and connected to C=N in polyimide at the other end, forming a stable connection relationship, improving interlayer bonding force, and greatly improving the interlayer shear performance and impact performance of the material. Attached Figure Description

[0022] Figure 1 These are the infrared spectra of Example 1 and Comparative Example 1. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0024] Example 1:

[0025] (1) Cleaning carbon fiber cloth: Cut the carbon fiber cloth into 650mm*650mm sizes, a total of 8 pieces, put them into a 1:1 mixture of anhydrous ethanol and acetone, and soak for 2 hours; then wash with deionized water until neutral.

[0026] (2) Oxidation treatment of carbon fiber cloth: The cleaned carbon fiber cloth is placed in a 5% NaOH solution and ultrasonically treated for 30 minutes. After that, it is taken out and washed with deionized water until neutral. The washed carbon fiber is placed in a room temperature blower until the moisture is completely evaporated. The blower drying oven is heated to 80°C to dry the carbon fiber cloth and the preliminarily modified carbon fiber cloth is obtained.

[0027] (3) Preparation of modified coating: 3-aminopropyltrimethoxysilane, anhydrous ethanol and deionized water are mixed to form a solution. The pH value of the solution is adjusted to neutral with hydrochloric acid and stirred evenly. The carbon fiber cloth is immersed in the mixed solution for 2 hours, then washed with deionized water until neutral, and placed in a room temperature blower until the water evaporates completely. The blower drying oven is heated to 80°C to dry the cloth and the treated carbon fiber cloth is obtained.

[0028] (4) Preparation of composite materials:

[0029] Weigh 0.8g of terephthalaldehyde containing a benzene ring and dissolve it in 36ml of anhydrous ethanol solution; use a pipette to measure 189μl of diethylenetriamine and 410μl of tris(2-aminoethyl)amine and dissolve them in 42ml of anhydrous ethanol solvent, then stir well to prepare a mixed solution; add the solution to a silicone paper box with a pre-folded bottom size of 650mm*650mm; add the terephthalaldehyde solution to the same silicone paper box; place the solvent in a room temperature blower to evaporate completely; gradually cure in a drying oven, curing at 75℃, 85℃ and 105℃ for 30 minutes successively; obtain a defect-free polyimide film;

[0030] The aforementioned polyimide film and carbon fiber were stacked in the order of layer A / layer B / layer A…layer B / layer A, where layer A is the polyimide film and layer B is the carbon fiber cloth. The stacked layers were then laid flat between two hot presses. The hot press was heated to 150°C and simultaneously pressurized to 6.5 MPa, holding the pressure for 30 minutes. After cooling, the carbon fiber reinforced polyimide composite material was obtained. The resulting composite material underwent infrared testing, as shown in the figure. Figure 1 The prepared composite material was subjected to mechanical property tests. The impact properties are shown in Table 1, and the interlaminar shear properties are shown in Table 2.

[0031] Example 2, the specific preparation method is basically the same as that of Example 1, the difference is that hydrogen peroxide is used in step (2), the concentration of which is 5%; the mechanical properties of the prepared composite material are tested, the impact properties are shown in Table 1, and the interlaminar shear properties are shown in Table 2.

[0032] Comparative Example 1: The specific preparation method is as shown in Example 1, except that step (3) is omitted. The obtained composite material is subjected to infrared testing, see... Figure 1 The prepared composite material was subjected to mechanical property tests. The impact properties are shown in Table 1, and the interlaminar shear properties are shown in Table 2.

[0033] Comparative Example 2 uses the same preparation method as in Example 1, except that steps (2) and (3) are omitted. The prepared composite material was subjected to mechanical property tests. The impact properties are shown in Table 1, and the interlaminar shear properties are shown in Table 2.

[0034] By comparing the spectra of Example 1 and Comparative Example 1 ( Figure 1 As can be seen from the curves in the figure, there are obvious Si-O bonds in Example 1, and Si-O bonds have high bond energy and excellent mechanical properties. Combining Tables 1 and 2, by comparing the impact strength and interlaminar shear strength of Comparative Example 1, Comparative Example 2, and Example 1, the impact performance and interlaminar shear strength of Example 1 are significantly improved. The modification method of first oxidizing the carbon fiber and then coating it creates chemical bonds between the carbon fiber and the polyimide film, resulting in a significant improvement in the interfacial strength of the final composite material.

[0035] The difference between Example 1 and Example 2 lies in the choice of oxidant. As can be seen from the impact strength in Table 1 and the interlaminar shear strength in Table 2, the impact strength and interlaminar shear strength of Example 1 are significantly higher than those of Example 2. Therefore, using NaOH to oxidize carbon fiber cloth is more effective, which shows that the preparation method of this patent does indeed greatly enhance the interfacial bonding ability of composite materials.

[0036] Table 1

[0037]

[0038] Table 2

[0039]

Claims

1. A method for producing a modified carbon fiber-reinforced polyimide composite material, characterized by, The method comprises the following steps: (1) washing the carbon fiber cloth: using a mixture of anhydrous ethanol and acetone to remove impurities on the surface of the carbon fiber cloth, and washing the carbon fiber cloth to neutral; (2) oxidizing the carbon fiber cloth: adding the washed carbon fiber cloth into a strong oxidizing agent solution to modify the carbon fiber cloth; The strong oxidizing agent is sodium hydroxide or hydrogen peroxide; the concentration of sodium hydroxide is 2%-5%, and the concentration of hydrogen peroxide is 2%-5%; (3) preparing a modified coating: mixing silane coupling agent, anhydrous ethanol and water to prepare a modified solution, wherein the concentration of silane coupling agent is 5%-10%, and the pH value of the solution is adjusted to 4-5 with acid, and the carbon fiber cloth obtained in step (2) is placed in the solution, soaked and washed to neutral, and then dried to obtain a modified carbon fiber cloth; the silane coupling agent is one of 3-[2-(2-aminoethylamino) ethylamino] propyl-trimethoxysilane and 3-aminopropyltrimethoxysilane; (4) preparing a composite material: sequentially laying polyimide film and the modified carbon fiber cloth obtained in step (3) in the order of ABAB…A, polyimide film is A, and the modified carbon fiber cloth obtained in step (3) is B, and then placing them into a hot press to obtain a carbon fiber reinforced polyimide composite material.

2. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 1, characterized by, The volume ratio of the mixture of anhydrous ethanol and acetone in step (1) is 2:3-1:

1.

3. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 1, characterized by, The strong oxidizing agent is sodium hydroxide with a concentration of 5%.

4. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 1, characterized by, The volume ratio of the silane coupling agent, anhydrous ethanol and water in step (3) is 1:8:1-2:6:

2.

5. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 1, characterized by, In step (4), the method for preparing polyimide film is as follows: dissolving dialdehyde in anhydrous ethanol solution, then stirring uniformly after dissolving amine curing agent in anhydrous ethanol solvent to prepare a mixed solution, pouring into a mold and drying to obtain polyimide film.

6. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 5, characterized by, The dialdehyde is p-dialdehyde, including one of aliphatic dialdehyde or aromatic dialdehyde containing benzene ring.

7. The method for producing a modified carbon fiber-reinforced polyimide composite material according to claim 5, characterized by, The amine curing agent includes diamine and triamine; the diamine is one or more of diethylene triamine, N,N-bis(2-aminoethyl)-1,3-propanediamine, and diethylene triamine; the triamine is one or more of triethylene tetramine, tri(2-aminoethyl)amine, and triethylene tetramine.

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