A hydrophilic covalent organic framework modified PEEK composite material and preparation method thereof

Abstract

Disclosed are a hydrophilic covalent organic framework-modified PEEK composite material and a preparation method thereof, relating to the technical field of polymer materials. The raw materials for preparing the composite material include COF-COOH and polyetheretherketone (PEEK) in a weight fraction ratio of (1-10):100; the molecular structure of the COF-COOH is #imgabs0#. By blending COF-COOH into a polyetheretherketone (PEEK) matrix, the carboxyl groups and porous structure of the COF-COOH molecules are utilized to significantly enhance the hydration effect of the composite material. In aqueous lubrication, the composite material can rapidly absorb hydrated cations in the solution to form a hydrated layer. This significantly reduces the friction coefficient and enhances wear resistance in friction tests, without changing the mechanical strength of the matrix.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a hydrophilic covalent organic framework modified PEEK composite material and a preparation method thereof. Background Art

[0002] Typically, friction pairs in mechanical transmission systems are composed of metal components and lubricated with oil. This applies to bearings and seals in industrial equipment like ships, pumps, and turbines. However, oil is not an ideal lubricant. Oil lubrication not only consumes large amounts of oil and precious metals, but is also associated with friction, wear, impact, vibration, and noise caused by the movement of the various friction pairs. The most significant issue is leakage in oil-lubricated bearings. Since the oil crisis of the 1970s and the increasing emphasis on environmental protection in recent years, hydraulic transmission technology has faced significant challenges, leading to the gradual adoption of water-lubricated bearings. Polyetheretherketone (PEEK), a high-performance water-lubricated bearing material, combines both rigidity and toughness with the advantages of lightness compared to metal. This material aligns with the lightweighting trend in various downstream industries and holds great potential for replacing steel with plastic. However, water-lubricated bearings use water as their lubricant, but water is a low-viscosity liquid, and the load-bearing capacity of a water film is much lower than that of an oil film, making it difficult to achieve hydrodynamic lubrication. Using pure PEEK directly as the substrate for water-lubricated bearings can lead to poor hydrophilicity, a high coefficient of friction, difficulty forming a water film, and unstable friction performance. This can lead to high wear, high heat, and high noise, shortening the service life of water-lubricated bearings. Therefore, PEEK needs to be modified to enhance its water lubrication properties.

[0003] To improve the friction properties of polyetheretherketone (PEEK), existing technologies typically modify PEEK. For example, Chinese invention patent application number 202311618740.7 discloses that sulfonating PEEK and introducing pores can reduce friction and increase the service life of water-lubricated bearings. However, this modification has the following drawbacks: First, it is difficult to precisely control the degree of sulfonation, which directly affects the material's hydrophilicity and friction coefficient. Second, sulfonation alters the chemical integrity of the PEEK substrate, altering its mechanical properties and affecting its service life. Furthermore, the pore-forming technology employed in this method is uncontrollable, making it impossible to control the size and volume of the pores.

[0004] It can be seen that the existing technology still needs to be improved and enhanced. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a hydrophilic covalent organic framework modified PEEK composite material and a preparation method thereof, aiming to solve the defects in the prior art of sulfonation modification of polyetheretherketone, such as the difficulty in controlling the sulfonation degree and the change in the mechanical properties of the substrate.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A hydrophilic covalent organic framework modified PEEK composite material, wherein the raw materials for preparing the composite material include COF-COOH and polyetheretherketone in a weight fraction ratio of (1-10):100; the molecular structure of the COF-COOH is

[0008] .

[0009] In the hydrophilic covalent organic framework modified PEEK composite material, the raw materials for preparing the composite material include COF-COOH and polyetheretherketone in a weight fraction ratio of 5:100.

[0010] In the hydrophilic covalent organic framework modified PEEK composite material, the method for preparing the COF-COOH comprises the following steps:

[0011] Step S01: dissolving 2,3,6,7,10,11-hexahydroxytriphenylene, tetrafluoroterephthalonitrile and anhydrous potassium carbonate in a mixed solvent of 1,3,5-trimethylbenzene and N-methylpyrrolidone to obtain a mixed solution;

[0012] Step S02: vacuuming the mixed solution obtained in step S01 to remove the oxygen inside, and then vacuum-sealing it; heating it to 100-130° C. and keeping it warm for 48-96 hours; and then cooling it to room temperature after the end of the heat preservation;

[0013] Step S03: vacuum filtration is performed on the mixed solution obtained in step S02, and the mixture is washed with N,N-dimethylformamide and purified water, and filtered multiple times, and the solid product is dried to obtain COF-CN;

[0014] Step S04: Disperse COF-CN in a 20% sodium hydroxide solution, stir, heat, and reflux at 120-130° C. for 48-72 hours; and cool to room temperature after the reaction is complete.

[0015] Step S05: adjusting the pH value of the solution obtained in step S04 to a pH value of 6 to 6.5; and obtaining COF-COOH after vacuum filtration, washing, filtration, and drying.

[0016] In the hydrophilic covalent organic framework modified PEEK composite material, in step S01, the molar ratio of 2,3,6,7,10,11-hexahydroxytriphenylene:tetrafluoroterephthalonitrile:anhydrous potassium carbonate is 1:(1.2-1.8):10;

[0017] In the mixed solvent, the volume ratio of 1,3,5-trimethylbenzene to N-methylpyrrolidone is 3:1 to 1:3:

[0018] The ratio of the 2,3,6,7,10,11-hexahydroxytriphenylene to the mixed solvent is 1 mmol 2,3,6,7,10,11-hexahydroxytriphenylene: (1-2) mL mixed solvent.

[0019] In the hydrophilic covalent organic framework modified PEEK composite material, in step S04, the ratio of the COF-CN to the sodium hydroxide solution is 100 mg: (20-30) mL of the sodium hydroxide solution.

[0020] A method for preparing a hydrophilic covalent organic framework modified PEEK composite material, wherein the method comprises the steps of taking COF-COOH and polyetheretherketone powder, mixing them evenly, and sintering them at 390-410° C. and a pressure of 20-40 MPa for 2-4 hours to prepare the hydrophilic covalent organic framework modified PEEK composite material as described above.

[0021] Beneficial effects:

[0022] The present invention provides a hydrophilic covalent organic framework modified PEEK composite material. By blending COF-COOH into a polyetheretherketone (PEEK) base material, the carboxyl groups contained in the COF-COOH molecules and the porous structure of the COF-COOH molecules are utilized to greatly improve the hydration effect of the composite material. The composite material can quickly absorb hydrated cations in the solution to form a hydration layer in a water lubricating medium. In a friction test, the friction coefficient can be significantly reduced and the wear resistance can be enhanced without changing the mechanical properties of the base material.

[0023] The second aspect of the present invention also provides a method for preparing a hydrophilic covalent organic framework modified PEEK composite material. The preparation method can obtain a hydrophilic covalent organic framework modified PEEK composite material through physical blending and firing steps. The preparation method has simple steps, the doping ratio of COF-COOH is easy to control, the hydration effect of the composite material can be controlled, and physical blending will not change the mechanical properties of the substrate, so that the composite material has better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the synthesis route of the hydrophilic covalent organic framework COF-COOH.

[0025] Figure 2 It is the chemical structure characterization, crystal type characterization and porosity characterization of COF-COOH. DETAILED DESCRIPTION

[0026] The present invention provides a hydrophilic covalent organic framework-modified PEEK composite material and a method for preparing the same. To further clarify the objectives, technical solutions, and effects of the present invention, the following examples further illustrate the present invention. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0027] In the prior art, polyetheretherketone (PEEK) is modified by sulfonation, but there are defects such as uncontrollable sulfonation degree and changes in the mechanical properties of the polyetheretherketone substrate itself.

[0028] In order to solve this technical problem, the present invention provides a hydrophilic covalent organic framework modified PEEK composite material, which is prepared by adding COF-COOH with a hydrophilic covalent organic framework into a polyetheretherketone substrate. The molecular structure of the COF-COOH is , which is rich in carboxyl groups and has a porous structure. Therefore, by utilizing the rich carboxyl groups and porous structure characteristics on the COF-COOH surface, the composite material can quickly adsorb hydrated cations in the solution to form a hydration layer, thereby greatly enhancing the hydration characteristics of the composite material, reducing the friction coefficient of the composite material, and enhancing the wear resistance of the composite material.

[0029] Specifically, the COF-COOH is an organic compound with a hydrophilic covalent organic framework, which is prepared by polycondensation of 2,3,6,7,10,11-hexahydroxytriphenylene (HTP) and tetrafluoroterephthalonitrile (TTP), followed by carboxylation. The specific synthesis route is as follows: Figure 1 As shown, the specific preparation steps are as follows:

[0030] Step S01: 2,3,6,7,10,11-hexahydroxytriphenylene, tetrafluoroterephthalonitrile, and anhydrous potassium carbonate are dissolved in a mixed solvent of 1,3,5-trimethylbenzene and N-methylpyrrolidone to obtain a mixed solution; wherein the molar ratio of the 2,3,6,7,10,11-hexahydroxytriphenylene:tetrafluoroterephthalonitrile:anhydrous potassium carbonate is 1:(1.2-1.8):10; in the mixed solvent, the volume ratio of 1,3,5-trimethylbenzene to N-methylpyrrolidone is 3:1-1:3; in the mixed solution, the ratio of the 2,3,6,7,10,11-hexahydroxytriphenylene to the mixed solvent is 1 mmol 2,3,6,7,10,11-hexahydroxytriphenylene:(1-2) mL mixed solvent.

[0031] Step S02: vacuuming the mixed solution obtained in step S01 to remove oxygen from the interior and then vacuum-sealing the solution; heating the solution to 100-130° C. and maintaining the temperature for 48-96 hours; and allowing the solution to stand and cool to room temperature after the temperature is maintained.

[0032] Step S03: The mixed solution obtained in step S02 is subjected to vacuum filtration, and the obtained solid is washed with N,N-dimethylformamide and pure water, and filtered multiple times. The solid product is purified by repeated washing. The specific number of washing times can be determined according to actual needs and can be three or more to remove impurities. After the washing is completed, the solid product is dried to obtain COF-CN;

[0033] Step S04: Disperse COF-CN in a 20 wt % sodium hydroxide solution at a ratio of 100 mg COF-CN to (20-30) mL sodium hydroxide solution. Stir and heat the mixture under reflux at 120-130° C. for 48-72 hours. Cool the mixture to room temperature after the reaction is complete.

[0034] Step S05: The solution obtained in step S04 is adjusted to a pH of 6 to 6.5 using 1M dilute hydrochloric acid; the solution is then vacuum filtered, and the solid is washed with water, filtered, and dried to obtain COF-COOH.

[0035] The prepared COF-COOH and intermediate product COF-CN were characterized, and their infrared spectra were as follows: Figure 2 As shown in Figure a. As can be seen from Figure a, in the spectrum of COF-CN, at 1266cm -1 and 1022cm -1 There is a signal peak, indicating the formation of polymerized ether bonds, and 2244cm -1 The signal at the position proves the retention of cyano group in COF-CN. However, in the spectrum of COF-COOH, 2244 cm -1 The signal at the position disappears, indicating the conversion of cyano group to carboxyl group, thus proving that COF-COOH is obtained. At the same time, the powder X-ray characterization of COF-COOH powder is carried out, as shown in Figure b. As can be seen from Figure b, COF-COOH has high crystallinity, and its crystal structure is regular and periodic. Combined with the molecular structure of COF-COOH, it can be determined that it can form a porous structure similar to a honeycomb structure. In addition, COF-COOH is also subjected to nitrogen adsorption and desorption test, and the test results are shown in Figure c. As can be seen from Figure c, the specific surface area of ​​COF-COOH is as high as 595m 2 g -1 ， Porous properties can help enhance the hydration effect of composite materials.

[0036] The COF-COOH prepared in the above steps is doped into polyetheretherketone in a specific ratio, and the resulting composite material has a low friction coefficient. Among them, due to the rich carboxyl groups in the molecular structure of COF-COOH, it can quickly adsorb hydrated cations in the solution, and the porous properties of the covalent organic framework possessed by COF-COOH can further enrich the hydration layer and enhance the hydration properties. In the friction test, it can significantly reduce the friction coefficient and enhance the wear resistance. In addition, the water contact angle of the composite material will gradually decrease with the increase of the COF-COOH doping ratio. For example, when the COF-COOH doping ratio is 1:100, the water contact angle of the composite material is 85°, when the COF-COOH doping ratio is 5:100, the water contact angle of the composite material is 74°, and when the COF-COOH doping ratio is 10:100, the water contact angle of the composite material is 68°.

[0037] The COF-COOH doping ratio affects the composite's water contact angle. However, a too-small contact angle results in an excessively thin water film on the composite's surface, which is easily squeezed out under high pressure or shear forces, causing boundary wetting or even dry friction. This can actually increase the composite's friction coefficient and wear rate. Therefore, as a preferred embodiment, the raw materials for preparing the composite include a weight ratio of COF-COOH to polyetheretherketone of (1-10):100, resulting in a composite with a low water contact angle, friction coefficient, and wear rate.

[0038] More preferably, in the raw materials for preparing the composite material, the weight ratio of COF-COOH and polyetheretherketone is 5:100, and the obtained composite material has a smaller water contact angle, a better friction coefficient, and a lower wear rate. The friction coefficient can be as low as 0.04, and the wear rate can be as low as 3.6×10 -7 mm 3 / Nm.

[0039] The second aspect of the present invention also discloses a method for preparing the hydrophilic covalent organic framework modified PEEK composite material, which includes the steps of taking COF-COOH and polyetheretherketone powder in proportion, mixing them evenly, firing them at 390-410°C and a pressure of 20-40 MPa for 2-4 hours, and cooling them to prepare a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0040] The preparation method physically blends the hydrophilic covalent organic framework organic matter COF-COOH and polyetheretherketone (PEEK), and after simple firing, the hydrophilicity of the PEEK can be modified and enhanced. The hydrophilicity of the composite material can be controlled by changing the COF-COOH blending content. Therefore, compared with the modification of PEEK by chemical sulfonation, the hydrophilicity is easier to control and the mechanical properties of the PEEK substrate are not changed. In addition, the COF-COOH crystals have inherent porous properties, and there is no need to form pores in the material during preparation, which makes the preparation method simpler. The pore size, structure and uniform distribution of the COF-COOH crystals themselves have a better enhancing effect on the hydration properties of the composite material.

[0041] To further illustrate the hydrophilic covalent organic framework modified PEEK composite material and its preparation method provided by the present invention, the following examples are provided.

[0042] Example 1

[0043] A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: taking COF-COOH and polyetheretherketone powder in a ratio of 1:100 by weight, mixing them evenly, sintering them at 390°C and a pressure of 20 MPa for 4 hours, and cooling them to obtain a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0044] Example 2

[0045] A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: taking COF-COOH and polyetheretherketone powder in a ratio of 2:100 by weight, mixing them evenly, firing them at 400°C and a pressure of 30 MPa for 3 hours, and cooling them to prepare a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0046] Example 3

[0047] A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: taking COF-COOH and polyetheretherketone powder in a ratio of 5:100 by weight, mixing them evenly, sintering them at 400°C and a pressure of 30 MPa for 3 hours, and cooling them to obtain a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0048] Example 4

[0049] A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: taking COF-COOH and polyetheretherketone powder in a ratio of 7:100 by weight, mixing them evenly, sintering them at 400°C and a pressure of 30 MPa for 3 hours, and cooling them to obtain a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0050] Example 5

[0051] A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: taking COF-COOH and polyetheretherketone powder in a ratio of 10:100 by weight, mixing them evenly, sintering them at 410°C and a pressure of 40 MPa for 2 hours, and cooling them to prepare a hydrophilic covalent organic framework reinforced modified PEEK composite material.

[0052] Performance tests were conducted on the composite materials prepared in Examples 1-5, with unmodified polyetheretherketone used as Comparative Example 1. The specific test results are shown in Table 1. The water contact angle was measured using a contact angle meter; the friction coefficient was measured using a UMT-5 instrument under the following test conditions: a rotation speed of 100 rpm, a load of 15 N, a rotation radius of 5 mm, and a 3% sodium chloride solution. The wear rate was calculated using a white light interferometer; and the tensile strength was measured using a mechanical testing machine according to ISO 527.

[0053]

[0054] As shown in Table 1, the water contact angles, friction coefficients, and wear rates of Examples 1-5 are all lower than those of Comparative Example 1. This indicates that COF-COOH can improve the hydration properties of PEEK, greatly increasing its hydrophilicity and thereby reducing the friction coefficient and wear rate. Furthermore, while improving the hydration properties, COF-COOH also improves the mechanical strength of PEEK to a certain extent. In particular, in Example 3, when the ratio of COF-COOH to PEEK is 5:100, the friction coefficient can be reduced to 0.040, and the wear rate is only 3.6×10 -7 mm 3 / Nm.

[0055] In summary, the present invention discloses a hydrophilic covalent organic framework modified PEEK composite material and a preparation method thereof, wherein the surface of the incorporated COF-COOH in the hydrophilic covalent organic framework modified PEEK composite material is rich in carboxylic acid groups and has a porous property of high specific surface area, which can enhance the modification of the PEEK material, and its carboxylic acid group can quickly adsorb hydrated cations in the solution in the water lubrication medium to form a hydration layer, forming a hydration effect, and the porous property of COF-COOH can further enrich the hydration layer and enhance the hydration property, which can significantly reduce the friction coefficient and enhance the wear resistance in the friction test. This aspect overcomes the shortcomings of PEEK in water lubrication friction, such as poor hydrophilicity, high friction coefficient, and unstable friction performance, by enhancing the modification of PEEK, and is of great value for realizing long-term and efficient operation of water-lubricated bearing equipment underwater.

[0056] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A hydrophilic covalent organic framework modified PEEK composite material, characterized in that: The raw materials for preparing the composite material include COF-COOH and polyetheretherketone in a weight fraction ratio of (1-10):100; the molecular structure of the COF-COOH is 。 2. The hydrophilic covalent organic framework modified PEEK composite material according to claim 1, characterized in that: The raw materials for preparing the composite material include COF-COOH and polyetheretherketone in a weight fraction ratio of 5:

100.

3. The hydrophilic covalent organic framework modified PEEK composite material according to claim 1, characterized in that: The method for preparing the COF-COOH comprises the following steps: Step S01: dissolving 2,3,6,7,10,11-hexahydroxytriphenylene, tetrafluoroterephthalonitrile and anhydrous potassium carbonate in a mixed solvent of 1,3,5-trimethylbenzene and N-methylpyrrolidone to obtain a mixed solution; Step S02: vacuuming the mixed solution obtained in step S01 to remove the oxygen inside, and then vacuum-sealing it; heating it to 100-130° C. and keeping it warm for 48-96 hours; and then cooling it to room temperature after the end of the heat preservation; Step S03: vacuum filtration is performed on the mixed solution obtained in step S02, and the mixture is washed with N,N-dimethylformamide and purified water, and filtered multiple times, and the solid product is dried to obtain COF-CN; Step S04: Disperse COF-CN in 20% sodium hydroxide solution, stir, heat, and reflux at 120-130° C. for 48-72 hours; cool to room temperature after the reaction is complete; Step S05: adjusting the pH value of the solution obtained in step S04 to a pH value of 6 to 6.5; and obtaining COF-COOH after vacuum filtration, washing, filtration, and drying.

4. The hydrophilic covalent organic framework modified PEEK composite material according to claim 3, characterized in that: In the step S01, the molar ratio of the 2,3,6,7,10,11-hexahydroxytriphenylene:tetrafluoroterephthalonitrile:anhydrous potassium carbonate is 1:(1.2-1.8):10; In the mixed solvent, the volume ratio of 1,3,5-trimethylbenzene to N-methylpyrrolidone is 3:1 to 1:3: The ratio of the 2,3,6,7,10,11-hexahydroxytriphenylene to the mixed solvent is 1 mmol 2,3,6,7,10,11-hexahydroxytriphenylene: (1-2) mL mixed solvent.

5. The hydrophilic covalent organic framework modified PEEK composite material according to claim 3, characterized in that: In step S04 , the ratio of the COF-CN to the sodium hydroxide solution is 100 mg: (20-30) mL of the sodium hydroxide solution.

6. A method for preparing a hydrophilic covalent organic framework modified PEEK composite material, characterized in that: The method comprises the steps of taking COF-COOH and polyetheretherketone powder, mixing them evenly, and calcining them at 390-410° C. and 20-40 MPa pressure for 2-4 hours to prepare the hydrophilic covalent organic framework modified PEEK composite material according to any one of claims 1-5.

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