Sizing agent based on highly dispersed composite filler, its modified carbon fiber reinforced polyetheretherketone composite material and preparation method thereof

Abstract

Sizing agent based on highly dispersed composite filler, its modified carbon fiber reinforced polyetheretherketone composite material and preparation method thereof. The present invention belongs to the field of carbon fiber sizing agents and their composite materials. The purpose of the present invention is to solve the technical problem that the sizing agent for existing carbon fiber reinforced polyetheretherketone composite materials cannot further improve the interfacial bonding strength between carbon fibers and resin matrix and the mechanical properties of the composite materials. The present invention uses hydroxylated boron nitride and carboxylated carbon nanotubes as raw materials, and forms an organic unified whole by esterification reaction between the two. Using it as a filler to compound with polyetherimide to prepare a sizing agent, significantly improving the mechanical properties of the composite material and the bonding strength at the interface.

Description

Technical Field

[0001] The present invention belongs to the field of carbon fiber sizing agents and their composite materials, and particularly relates to a sizing agent based on highly dispersed composite fillers, a carbon fiber reinforced polyetheretherketone composite material modified thereby, and a preparation method thereof. Background Art

[0002] Carbon fiber reinforced resin matrix composites are widely used in the fields of aviation, aerospace, defense equipment, mechanical equipment, etc. due to their excellent properties such as light weight, high strength, corrosion resistance, electrical and thermal conductivity. And carbon fiber reinforced resin matrix composites can solve problems such as energy resource consumption and environmental pollution by reducing weight, improving fuel efficiency, and reducing carbon emissions. However, due to the poor wettability between carbon fiber and resin matrix and weak interfacial bonding, it affects the effective transfer and dispersion of load between resin and fiber. Therefore, the mechanical properties of the composite material have always been unable to be greatly improved. Thus, the problems of tensile and impact damage delamination of carbon fiber are the difficult problems faced currently.

[0003] In the prior art, in order to improve the interlaminar bonding force of carbon fiber, methods of modifying carbon fiber or epoxy resin matrix are often adopted. Modifying the epoxy resin matrix can improve the mechanical properties of the matrix and also improve the interfacial bonding performance between carbon fiber and resin matrix to a certain extent, but the chemical bond binding between the modified matrix and carbon fiber is weak. Modifying carbon fiber is easier to control. Currently, existing modification methods include various processes such as chemical infiltration, electroplating, chemical vapor deposition, plasma deposition, etc. Although these methods can improve the interfacial bonding performance of carbon fiber reinforced resin matrix composites, at the same time, they are often accompanied by problems such as complex process treatment procedures and long time, and are not suitable for industrial production.

[0004] Sizing agent treatment has the characteristics of simplicity and easy large-scale production, which makes it widely concerned. A good sizing agent can further improve the bonding force between fiber and resin. For existing carbon fiber sizing agents, there are still the following technical problems: 1) The enhancement effect of the sizing agent is not ideal, and it cannot enhance the interfacial performance and mechanical properties of the composite material simultaneously; 2) Common sizing agents have problems such as poor dispersibility and cannot uniformly cover the carbon fiber surface, and thus cannot achieve the effect of uniformly sizing carbon fiber. Therefore, seeking a modification and optimization method based on sizing agents to improve the comprehensive performance of carbon fiber resin matrix composites has important practical significance and application value. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the improvement of the interfacial bonding strength between carbon fiber and resin matrix and the mechanical properties of the composite material by the sizing agent used in existing carbon fiber reinforced polyetheretherketone composites cannot be further improved, and to provide a sizing agent based on highly dispersed composite fillers, a carbon fiber reinforced polyetheretherketone composite material modified thereby, and a preparation method thereof.

[0006] One of the objectives of the present invention is to provide a highly dispersible composite filler, which is esterified from hydroxylated boron nitride (BNO) and carboxylated carbon nanotubes (CNT-COOH).

[0007] Another objective of the present invention is to provide a method for preparing a highly dispersible composite filler. The preparation method of the composite filler is carried out according to the following steps:

[0008] S1: Dissolve hydroxylated boron nitride (BNO) and carboxylated carbon nanotubes (CNT-COOH) in dimethylformamide (DMF) respectively. After ultrasonic treatment, mix the solutions to obtain a mixed solution.

[0009] S2: Add N,N'-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) to the mixed solution, then stir magnetically for a certain period of time, wash and filter by suction to obtain the BNO-CNT composite filler, that is, the highly dispersible composite filler.

[0010] Further defined, the hydroxylated boron nitride (BNO) in S1 is prepared from boron nitride (BN) and sodium cholate (SC).

[0011] More specifically defined, the mass ratio of boron nitride (BN) to sodium cholate (SC) is (80-120):1.

[0012] Further defined, the mass ratio of hydroxylated boron nitride (BNO) to carboxylated carbon nanotubes (CNT-COOH) in S1 is (0.8-1.2):1.

[0013] Further defined, the ultrasonic treatment in S1 is carried out for 1-3 h.

[0014] Further defined, the mass ratio of hydroxylated boron nitride (BNO) to N,N'-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) in S2 is (0.1-1.0):(5-8):(0.5-1).

[0015] Further defined, the magnetic stirring in S2 is carried out for 60-80 h.

[0016] Another objective of the present invention is to provide a high-performance sizing agent, which comprises the above-mentioned highly dispersible composite filler and polyetherimide (PEI).

[0017] Another objective of the present invention is to provide a method for preparing the above-mentioned high-performance sizing agent. The preparation method comprises the following steps:

[0018] Dissolve the above-mentioned highly dispersible composite filler and polyetherimide (PEI) in dimethylformamide (DMF), and carry out ultrasonic treatment to obtain the high-performance sizing agent.

[0019] Further defined, the mass ratio of the highly dispersed composite filler to polyetherimide (PEI) is (0.1 - 1):(1 - 1.5).

[0020] Further defined, the mass of polyetherimide (PEI) to the volume of dimethylformamide (DMF) is (1 - 1.5) g:100 mL.

[0021] Further defined, ultrasonic treatment is carried out for 2 - 4 h.

[0022] The fifth object of the present invention is to provide a high-strength carbon fiber reinforced polyetheretherketone composite material, and the carbon fiber in the composite material is modified with the above high-performance sizing agent.

[0023] The sixth object of the present invention is to provide a preparation method of a high-strength carbon fiber reinforced polyetheretherketone composite material, and the preparation method is carried out according to the following steps:

[0024] First, the carbon fiber cloth is desized and oxidized, then immersed in the above high-performance sizing agent, dried, and then alternately laminated with polyetheretherketone powder, and then subjected to three-stage hot pressing to obtain a high-strength carbon fiber reinforced polyetheretherketone composite material.

[0025] Further defined, the three-stage hot pressing is specifically as follows: the first stage: heating from room temperature to 190 - 210 °C, holding for 20 - 35 min, and simultaneously maintaining a pressure of 2.5 - 5.5 MPa; the second stage: heating to 360 - 380 °C, holding for 20 - 35 min, and maintaining a pressure of 2.5 - 5.5 MPa; the third stage: cooling to 290 - 310 °C, holding for 20 - 35 min, and maintaining a pressure of 2.5 - 5.5 MPa.

[0026] The remarkable effects of the present invention compared with the prior art:

[0027] The present invention uses hydroxylated boron nitride and carboxylated carbon nanotubes as raw materials, and forms an organic unified whole through an esterification reaction between the two. On the one hand, the interface influence between the fillers is eliminated after the reaction, avoiding the aggregation phenomenon of the fillers themselves, improving the surface energy of the fillers, and thus significantly improving the dispersibility of reinforcing phases such as boron nitride and carbon nanotubes in the fiber matrix, enabling the load to be evenly transferred and dispersed between the resin and the fiber. Among them, the two components in the composite filler can give full play to their own functions. Two-dimensional BNO plays roles such as uniformly enhancing the surface roughness of carbon fibers and increasing the surface energy of carbon fibers, and carbon nanotubes play a role in inhibiting crack propagation and enhancing mechanical meshing at the interface. The two fillers, as a whole, each exert their own performance advantages and synergistically enhance the interface performance, avoiding stress concentration to the greatest extent, and thus significantly improving the mechanical properties of the composite material. On the other hand, due to its own ring structure, boron nitride is more likely to generate π-π conjugation with polyetherimide and polyetheretherketone that also have ring structures. Therefore, polyetherimide with good compatibility with polyetheretherketone is used as the polymer carrier to prepare a sizing agent with the composite filler, thereby establishing a connection between the sizing agent and the resin matrix. The sizing layer is designed as a bridge between the resin matrix and carbon fibers, tightly connecting the matrix and the reinforcement, and significantly enhancing the interface performance and mechanical properties of the composite material. Description of the Drawings

[0028] Figure 1 FIG. is the infrared spectrum of BNO, CNT-COOH, and BNO-CNT composite fillers in Example 1;

[0029] Figure 2 FIG. is the thermogravimetric curve of the sizing agent and PEI prepared in Example 1;

[0030] Figure 3 FIG. is the surface morphology diagram of the desized carbon fiber (DCF) in Example 1 before and after being modified by the sizing agent, where a - DCF, b - after being modified by the sizing agent;

[0031] Figure 4 FIG. is the contact angle comparison diagram of the desized carbon fiber (DCF) in Example 1 before and after being modified by the sizing agent;

[0032] Figure 5 FIG. is the surface energy comparison diagram of the desized carbon fiber (DCF) in Example 1 before and after being modified by the sizing agent;

[0033] Figure 6 FIG. is the bar chart of the flexural strength / flexural modulus of the composite material obtained in Example 1;

[0034] Figure 7 FIG. is the bar chart of the interlaminar shear strength of the composite material obtained in Example 1. Detailed Embodiments

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art and can be obtained by those skilled in the art through commercial channels without special instructions.

[0037] The terms "comprising", "including", "having", "containing" or any other variation thereof used in the following embodiments are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or device containing the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or device.

[0038] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, it should be understood that all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value are specifically disclosed, regardless of whether the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the specification and claims of the present application, range limitations can be combined and / or interchanged, and if not otherwise stated, these ranges include all sub-ranges contained therein.

[0039] The indefinite articles "a" and "an" before the elements or components of the present invention have no restrictive requirements on the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the singular form of the element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0040] Example 1:

[0041] The preparation method of the high-strength carbon fiber-reinforced polyetheretherketone composite material in this embodiment is carried out according to the following steps:

[0042] The first step is to prepare a highly dispersed composite filler:

[0043] First, 3 g of boron nitride (BN) and 0.03 g of sodium cholate (SC) were added to 120 mL of deionized water, ultrasonically dispersed at 600 W for 6 h, centrifuged, and dried at 60 °C to obtain hydroxylated boron nitride (BNO).

[0044] Then, 0.5 g of BNO and 0.5 g of carboxylated carbon nanotubes (CNT-COOH) were separately dissolved in 100 mL of DMF, ultrasonically treated for 1 h, and the above two solutions were mixed to obtain a mixed solution.

[0045] Next, 6.93 g of N,N'-dicyclohexylcarbodiimide (DCC) and 0.51 g of 4-dimethylaminopyridine (DMAP) were added to the mixed solution, followed by magnetic stirring for 68 h. After filtration, it was rinsed with absolute ethanol and dried to obtain the BNO-CNT composite filler, namely the highly dispersed composite filler.

[0046] Second step: Preparation of sizing agent

[0047] 0.5 g of BNO-CNT and 1 g of polyetherimide (PEI) were dissolved in 100 mL of dimethylformamide (DMF) and ultrasonically treated for 2 h to obtain a sizing agent with high interfacial bonding.

[0048] Third step: Preparation of composite material

[0049] First, the carbon fiber cloth was immersed in acetone and then refluxed at 80 °C for 24 h to complete the desizing of the carbon fiber cloth. The desized carbon fiber cloth was immersed in an anhydrous ethanol solution of mesoxalic acid with a concentration of 10 g / mL for oxidation treatment for 1.5 h and dried to obtain oxidized carbon fiber cloth.

[0050] Then, the oxidized carbon fiber cloth was immersed in the sizing agent prepared in the second step for 2 h and dried to obtain modified carbon fiber cloth. The content of the sizing agent in the modified carbon fiber cloth was 0.5 wt.%.

[0051] Next, polyetheretherketone powder and modified carbon fiber cloth were alternately laminated. There were 8 layers of modified carbon fiber cloth and 9 layers of polyetheretherketone powder in total. The volume ratio of polyetheretherketone powder to modified carbon fiber cloth was preset to 3:2 to obtain a green body.

[0052] Finally, three-stage hot pressing was carried out. The first stage: heating from room temperature to 190 °C, holding for 25 min, and simultaneously maintaining a pressure of 3.5 MPa; the second stage: heating to 360 °C, holding for 25 min, and maintaining a pressure of 3.5 MPa; the third stage: cooling to 300 °C, holding for 25 min, and maintaining a pressure of 3.5 MPa. After that, it was naturally cooled to room temperature and the pressure was released to obtain a high-strength carbon fiber-reinforced polyetheretherketone composite material.

[0053] Detection test

[0054] (1) Infrared spectrum analysis was carried out on the BNO, CNT-COOH, and BNO-CNT composite fillers in Example 1, and the results are as Figure 1 shown. It was found that in the infrared spectrum, there was an obvious absorption peak at around 1700 cm -1 , which proved the successful progress of the esterification reaction.

[0055] (2) Under nitrogen protection, the temperature was raised from 25 °C to 800 °C at a heating rate of 10 °C / min, and thermogravimetric analysis was carried out on the PEI and the prepared sizing agent in Example 1. The curve was drawn according to the mass of the substance before and after heating as Figure 2 shown. The results showed that the weight loss of the two sizing components was less than 5% near the molding temperature of 360 °C, which proved that it could be used for the preparation of carbon fiber polyether ether ketone composites.

[0056] (3) The surface morphology of the desized carbon fiber (DCF) in Example 1 before and after being modified by the sizing agent was analyzed, and its SEM image is as Figure 3 shown. The results showed that the sizing layer was evenly covered on the surface of the carbon fiber. Compared with the desized carbon fiber, the surface roughness was significantly improved after modification.

[0057] (4) The contact angle and surface energy of the composites of the desized carbon fiber (DCF) in Example 1 before and after being modified by the sizing agent were tested, and the results are as Figure 4 and Figure 5 shown. The results showed that after the introduction of the sizing layer, the contact angle of the carbon fiber surface decreased, and the surface energy increased significantly, which proved that the composite sizing agent enhanced the surface energy of the carbon fiber and improved the surface activity degree of the carbon fiber.

[0058] (5) According to the ASTM D7264 and ASTM D2344 standards, the composites obtained in Example 1 were sampled and tested. The bar chart of the flexural strength / flexural modulus of the composites measured is as Figure 6 shown, and the bar chart of the interlaminar shear strength of the composites is as Figure 7 shown. The results showed that compared with the desized carbon fiber (DCF), the flexural strength, flexural modulus, and interlaminar shear strength of the modified composites increased by 77.71%, 59.39%, and 68.93% respectively. The composite sizing agent improved the surface roughness and active strength of the carbon fiber, and then improved the interfacial bonding strength, thus achieving the effect of improving the mechanical properties of the composites.

[0059] The above are only the preferred specific embodiments of the present invention. These specific embodiments are all different implementation manners based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A high-performance sizing agent, characterized in that, It comprises a highly-dispersed composite filler and polyetherimide, and the highly-dispersed composite filler is esterified from hydroxylated boron nitride and carboxylated carbon nanotubes.

2. The high-performance sizing agent according to claim 1, characterized in that The preparation method of the highly-dispersed composite filler is carried out according to the following steps: S1: Dissolve hydroxylated boron nitride and carboxylated carbon nanotubes in dimethylformamide respectively. After ultrasonic treatment, mix the solutions to obtain a mixed solution. S2: Add N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine to the mixed solution, then stir magnetically for a certain time, wash and filter by suction to obtain a BNO-CNT composite filler, namely the highly-dispersed composite filler.

3. The high-performance sizing agent according to claim 2, wherein In S1, the hydroxylated boron nitride is prepared from boron nitride and sodium cholate. The mass ratio of hydroxylated boron nitride to carboxylated carbon nanotubes is (0.8-1.2):1, and ultrasonic treatment is carried out for 1-3 h.

4. The high-performance sizing agent according to claim 2, characterized in that, In S2, the mass ratio of hydroxylated boron nitride to N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is (0.1-1.0):(5-8):(0.5-1), and magnetic stirring is carried out for 60-80 h.

5. The preparation method of the high-performance sizing agent according to claim 1, characterized in that, It includes the following steps: Dissolve the highly-dispersed composite filler and polyetherimide in dimethylformamide, and carry out ultrasonic treatment to obtain a high-performance sizing agent.

6. The method according to claim 5, wherein The mass ratio of the highly-dispersed composite filler to polyetherimide is (0.1-1):(1-1.5), and the mass ratio of polyetherimide to the volume of dimethylformamide is (1-1.5) g:100 mL, and ultrasonic treatment is carried out for 2-4 h.

7. A high-strength carbon fiber-reinforced polyetheretherketone composite material, characterized in that, In the composite material, the carbon fiber is modified by using the high-performance sizing agent described in Claim 1.

8. The preparation method of the high-strength carbon fiber-reinforced polyetheretherketone composite material according to claim 7, characterized in that, It is carried out according to the following steps: First, desize and oxidize the carbon fiber cloth, then immerse it in the high-performance sizing agent described in Claim 1, dry it, lay it alternately with polyether ether ketone powder in layers, and then carry out three-stage hot pressing to obtain a high-strength carbon fiber reinforced polyether ether ketone composite material.

9. The method according to claim 8, characterized in that The three-stage hot pressing is specifically as follows: The first stage: Heat up from room temperature to 190-210 °C, keep warm for 20-35 min, and keep the pressure at 2.5-5.5 MPa at the same time. The second stage: Heat up to 360-380 °C, keep warm for 20-35 min, and keep the pressure at 2.5-5.5 MPa; The third stage: Cool down to 290-310 °C, keep warm for 20-35 min, and keep the pressure at 2.5-5.5 MPa.

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