Hydrophilic covalent organic framework modified PEEK composite material and preparation method thereof

Abstract

The invention discloses a hydrophilic covalent organic framework modified PEEK composite material and a preparation method thereof, and relates to the technical field of high polymer materials, the composite material is prepared from the following raw materials: COF-COOH and polyether-ether-ketone in a weight fraction ratio of (1-10): 100; the molecular structural formula of the COF-COOH is # imgabs0 #. COF-COOH is blended and doped into a polyether-ether-ketone base material, and the hydration effect of the composite material can be greatly improved by using carboxyl contained in COF-COOH molecules and a porous structure of the COF-COOH molecules, so that the composite material can quickly adsorb hydrated cations in a solution in a water lubricating medium to form a hydration layer, and the friction coefficient can be remarkably reduced in a friction test; the wear resistance is enhanced, but the mechanical strength of the base material is not changed.

Description

Technical Field

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

[0002] Generally, various friction pairs in mechanical transmission systems are often composed of metal components and use oil as a lubricant medium, such as various bearings and sealing device parts of industrial equipment such as ships, water pumps, and water turbines. However, oil is not an ideal lubricant medium. Oil lubrication not only consumes a large amount of oil and precious metals but also has problems such as friction wear, impact vibration, and noise generated by various friction pairs during movement. Among them, the most fatal one is the leakage problem of oil-lubricated bearings. Since the oil resource crisis in the 1970s and the increasing attention to environmental protection in recent years, the oil pressure transmission technology has faced serious challenges, and water-lubricated bearings have gradually been promoted and used. Among them, polyetheretherketone (PEEK), as a high-performance water-lubricated bearing material, not only combines rigidity and toughness but also has the advantage of light weight compared with metals, which conforms to the lightweight trend in multiple downstream fields and is a potential candidate expected to replace steel with plastic. However, a water-lubricated bearing is a bearing with water as a lubricant medium, but water is a low-viscosity liquid, and the load-bearing capacity of the water film is much lower than that of the oil film, making it difficult to form hydrodynamic lubrication. Using pure PEEK directly as the matrix of a water-lubricated bearing has problems such as poor hydrophilicity, large friction coefficient, difficulty in forming a water film, and unstable friction performance, which will further cause problems such as high wear, high heat, and high noise, affecting the service life of the water-lubricated bearing. Therefore, it is necessary to modify PEEK to enhance its water-lubrication performance.

[0003] In the prior art, in order to improve the friction performance of polyetheretherketone (PEEK), polyetheretherketone (PEEK) is usually modified. For example, the Chinese invention patent with the application number 202311618740.7 discloses that by sulfonating and modifying polyetheretherketone and introducing pores, the friction pairs can be reduced and the service life of the water-lubricated bearing can be improved. However, this modification has the following defects: First, it is difficult to accurately control the degree of sulfonation, which directly affects the hydrophilicity and friction coefficient of the material; second, sulfonation will change the integrity of the chemical structure of the polyetheretherketone substrate, resulting in a change in its mechanical properties and affecting its service life; and third, the pore-forming technology in this method has uncontrollability, and the size and quantity of pores cannot be controlled.

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

[0005] In view of the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a hydrophilic covalent organic framework modified PEEK composite material and its preparation method, aiming to solve the defects in the prior art that it is difficult to control the sulfonation degree and the mechanical properties of the substrate are changed during the sulfonation modification of polyether ether ketone.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions: A hydrophilic covalent organic framework modified PEEK composite material, wherein the raw materials for preparing the composite material include COF-COOH and polyether ether ketone with a weight fraction ratio of (1-10):100; the molecular structural formula of the COF-COOH is .

[0007] In the hydrophilic covalent organic framework modified PEEK composite material, the raw materials for preparing the composite material include COF-COOH and polyether ether ketone with a weight fraction ratio of 5:100.

[0008] In the hydrophilic covalent organic framework modified PEEK composite material, the method for preparing the COF-COOH includes the following steps: Step S01: Dissolve 2,3,6,7,10,11-hexahydroxy triphenylene, tetrafluoro terephthalonitrile and anhydrous potassium carbonate in a mixed solvent of 1,3,5-trimethylbenzene and N-methylpyrrolidone to obtain a mixed solution; Step S02: Perform vacuum treatment on the mixed solution obtained in step S01, evacuate the internal oxygen, and then perform vacuum sealing; heat up to 100-130 °C and keep warm for 48-96 h; after the heat preservation is completed, let it stand and cool to room temperature; Step S03: Perform vacuum filtration on the mixed solution obtained in step S02, and wash and filter it multiple times with N,N-dimethylformamide and pure water respectively, and dry the solid product to obtain COF-CN; Step S04: Disperse COF-CN in a 20% sodium hydroxide solution, stir and heat, and reflux at 120-130 °C for 48-72 h; after the reaction is completed, cool to room temperature; Step S05: Adjust the pH value of the solution obtained in step S04 to 6-6.5; after vacuum filtration treatment, washing, filtration and drying, obtain COF-COOH.

[0009] In the hydrophilic covalent organic framework modified PEEK composite material, in step S01, the molar ratio of 2,3,6,7,10,11-hexahydroxy triphenylene:tetrafluoro terephthalonitrile: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 2,3,6,7,10,11-hexahydroxytriphenylene to the mixed solvent is 1 mmol of 2,3,6,7,10,11-hexahydroxytriphenylene: (1 - 2) mL of the mixed solvent.

[0010] In the hydrophilic covalent organic framework modified PEEK composite material, in the step S04, the ratio of COF-CN to the sodium hydroxide solution is 100 mg: (20 - 30) mL of the sodium hydroxide solution.

[0011] A preparation method of a hydrophilic covalent organic framework modified PEEK composite material, wherein the method includes the steps of: taking COF-COOH and polyether ether ketone powder, mixing them evenly, and firing at 390 - 410 °C and a pressure of 20 - 40 MPa for 2 - 4 h to prepare the hydrophilic covalent organic framework modified PEEK composite material as described above.

[0012] Beneficial effects: The present invention provides a hydrophilic covalent organic framework modified PEEK composite material. By blending COF-COOH in the polyether ether ketone substrate and utilizing the carboxyl groups contained in the COF-COOH molecules and the porous structure of the COF-COOH molecules, the hydration effect of the composite material can be greatly improved, enabling the composite material to rapidly adsorb hydrated cations in the solution to form a hydration layer in the water lubricating medium, significantly reducing the friction coefficient and enhancing the wear resistance during the friction test without changing the mechanical properties of the substrate.

[0013] The second aspect of the present invention also provides a preparation method of the hydrophilic covalent organic framework modified PEEK composite material. Through physical blending and firing steps, the hydrophilic covalent organic framework modified PEEK composite material can be obtained. The preparation method has simple steps, easy control of the doping ratio of COF-COOH, enables the hydration effect of the composite material to be controllable, and physical blending does not change the mechanical properties of the substrate, making the composite material have better performance. Description of the drawings

[0014] Figure 1 It is a schematic diagram of the synthesis route of the hydrophilic covalent organic framework COF-COOH.

[0015] Figure 2 It is the chemical structure characterization, crystalline form characterization, and porosity characterization of COF-COOH. Detailed implementation manners

[0016] The present invention provides a hydrophilic covalent organic framework modified PEEK composite material and a preparation method thereof. To make the objectives, technical solutions and effects of the present invention clearer and more definite, the following examples are given to further elaborate the present invention in detail. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] In the prior art, the method of modifying polyetheretherketone (PEEK) by sulfonation has defects such as uncontrollable sulfonation degree and change of the mechanical properties of the polyetheretherketone substrate itself.

[0018] To solve this technical problem, the present invention provides a hydrophilic covalent organic framework modified PEEK composite material. This material is prepared by incorporating COF-COOH with a hydrophilic covalent organic framework into the polyetheretherketone substrate. The molecular structural formula of COF-COOH is , which is rich in carboxyl groups and has a porous structure. Therefore, by utilizing the carboxyl groups and porous structure characteristics on the surface of COF-COOH, 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 at the same time enhancing the wear resistance of the composite material.

[0019] Specifically, the COF-COOH is an organic compound with a hydrophilic covalent organic framework. It is prepared by polycondensation reaction of 2,3,6,7,10,11-hexahydroxytriphenylene (HTP) and tetrafluoroterephthalonitrile (TTP), and then carboxylation reaction. Its synthesis route is specifically as Figure 1 shown. The specific preparation steps are as follows: Step S01: Dissolve 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; wherein, the molar ratio of 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 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.

[0020] Step S02: Subject the mixed solution obtained in Step S01 to vacuum treatment to remove the internal oxygen, and then perform vacuum sealing; then heat up to 100-130 °C and keep the temperature for reaction for 48-96 h; after the heat preservation ends, let it stand and cool to room temperature; Step S03: The mixture obtained in Step S02 is subjected to vacuum filtration. The obtained solid is washed and filtered multiple times with N,N-dimethylformamide and pure water respectively. Through repeated washing, the solid product is purified. The specific number of washing times can be determined according to actual needs, and can be three or more times to remove impurities. After washing, the solid product is dried to obtain COF-CN; Step S04: Take COF-CN and disperse it in a 20 wt% sodium hydroxide solution, where the ratio of COF-CN to the sodium hydroxide solution is 100 mg COF-CN: (20 - 30) mL sodium hydroxide solution; then stir and heat, and reflux at 120 - 130 °C for 48 - 72 h; after the reaction, cool to room temperature.

[0021] Step S05: The solution obtained in Step S04 is adjusted to a pH value of 6 - 6.5 with 1 M dilute hydrochloric acid; then, after vacuum filtration, the solid is washed with water, filtered, and dried to obtain COF-COOH.

[0022] The prepared COF-COOH and the intermediate COF-CN were characterized, and their infrared spectra are as shown in Figure 2 Figure a in. As can be seen from Figure a, in the spectrum of COF-CN, there are signal peaks at 1266 cm -1 and 1022 cm -1 , indicating the formation of polyether bonds, and the signal at 2244 cm -1 proves the retention of cyanide groups in COF-CN. However, in the spectrum of COF-COOH, the signal at 2244 cm -1 disappears, indicating the conversion of cyanide groups to carboxyl groups, thus proving that COF-COOH is obtained. At the same time, powder X-ray characterization was carried out on the COF-COOH powder, as shown in Figure b specifically. As can be seen from Figure b, COF-COOH has high crystallinity, its crystal structure is regular and has periodicity. Combining with the molecular structural formula of COF-COOH, it can be determined that it can form a porous structure similar to a honeycomb structure. In addition, nitrogen adsorption and desorption tests were also carried out on COF-COOH, 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 595 m 2 g -1 ， It has porous characteristics and can help enhance the hydration effect of the composite material.

[0023] The prepared COF-COOH obtained in the previous step is doped into polyether ether ketone in a specific ratio, and the resulting composite material has a low coefficient of friction. Among them, due to the carboxyl groups rich in the molecular structure of COF-COOH, it can quickly adsorb hydrated cations in the solution, and the porous property of the covalent organic framework of COF-COOH can further enrich the hydration layer and enhance the hydration property, which can significantly reduce the coefficient of friction and enhance the wear resistance during the friction test. Moreover, the water contact angle of the composite material will gradually decrease with the increase of the doping ratio of COF-COOH. For example, when the doping ratio of COF-COOH is 1:100, the water contact angle of the composite material is 85°. When the doping ratio of COF-COOH is 5:100, the water contact angle of the composite material is 74°. When the doping ratio of COF-COOH is 10:100, the water contact angle of the composite material is 68°.

[0024] Since the doping ratio of COF-COOH will affect the water contact angle of the composite material, but too small a contact angle will cause the water film formed on the surface of the composite material to be too thin and be easily extruded under the action of high pressure or high shear force, leading to boundary wetting and even dry friction, resulting in an increase in the coefficient of friction of the composite material and an increase in the wear rate. Therefore, as a preferred embodiment, in the raw materials for preparing the composite material, the weight part ratio of COF-COOH to polyether ether ketone is (1-10):100, and a composite material with a smaller water contact angle, a smaller coefficient of friction and a smaller wear rate can be obtained.

[0025] More preferably, in the raw materials for preparing the composite material, the weight part ratio of COF-COOH to polyether ether ketone is 5:100, and the obtained composite material has a smaller water contact angle, a better coefficient of friction and a lower wear rate. Its coefficient of friction can be as low as 0.04, and the wear rate is as low as 3.6×10 -7 mm 3 / Nm.

[0026] The second aspect of the present invention also discloses a preparation method of the hydrophilic covalent organic framework modified PEEK composite material. The method includes the steps of: taking COF-COOH and polyether ether ketone powder in proportion, mixing them evenly, and firing at 390-410°C and a pressure of 20-40 MPa for 2-4 h, and after cooling, preparing a hydrophilic covalent organic framework enhanced and modified PEEK composite material.

[0027] This preparation method realizes the hydrophilic modification and enhancement of polyetheretherketone (PEEK) by physically blending the hydrophilic covalent organic framework organic matter COF-COOH and PEEK, and through simple firing. By changing the blending content of COF-COOH, the hydrophilic degree of the composite material can be controlled. Therefore, compared with the modification of PEEK by chemical sulfonation, its hydrophilic degree is easier to control and the mechanical properties of the PEEK substrate will not be changed. Moreover, the COF-COOH crystal has a porous property by itself, eliminating the need for pore formation during the preparation of the material, making the preparation method simpler. The pore size and structure of the COF-COOH crystal are regular and uniformly distributed, which has a better enhancing effect on the hydration characteristics of the composite material.

[0028] To further elaborate on a hydrophilic covalent organic framework modified PEEK composite material and its preparation method provided by the present invention, the following examples are provided.

[0029] Example 1 A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: By weight, take COF-COOH and PEEK powder in a ratio of 1:100. After mixing evenly, sinter at 390 °C and a pressure of 20 MPa for 4 h. After cooling, a hydrophilic covalent organic framework enhanced and modified PEEK composite material is prepared.

[0030] Example 2 A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: By weight, take COF-COOH and PEEK powder in a ratio of 2:100. After mixing evenly, sinter at 400 °C and a pressure of 30 MPa for 3 h. After cooling, a hydrophilic covalent organic framework enhanced and modified PEEK composite material is prepared.

[0031] Example 3 A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: By weight, take COF-COOH and PEEK powder in a ratio of 5:100. After mixing evenly, sinter at 400 °C and a pressure of 30 MPa for 3 h. After cooling, a hydrophilic covalent organic framework enhanced and modified PEEK composite material is prepared.

[0032] Example 4 A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: By weight, take COF-COOH and PEEK powder in a ratio of 7:100. After mixing evenly, sinter at 400 °C and a pressure of 30 MPa for 3 h. After cooling, a hydrophilic covalent organic framework enhanced and modified PEEK composite material is prepared.

[0033] Example 5 A hydrophilic covalent organic framework modified PEEK composite material is prepared by the following steps: By weight, take COF-COOH and polyetheretherketone powder in a ratio of 10:100, mix them evenly, and then sinter at 410 °C and a pressure of 40 MPa for 2 h. After cooling, a hydrophilic covalent organic framework reinforced and modified PEEK composite material is prepared.

[0034] The performance tests were carried out on the composite materials prepared in Examples 1-5. At the same time, unmodified polyetheretherketone was used as Comparative Example 1. The specific test results are shown in Table 1. Among them, the water contact angle was measured by a contact angle measuring instrument; the friction coefficient was measured by a UMT-5 instrument, and the test conditions were: rotation speed 100 rpm, load 15 N, rotation radius 5 mm, and the test environment was 3% sodium chloride solution; the wear rate was calculated by a white light interferometer; the tensile strength was measured by a mechanical testing machine according to the ISO527 standard.

[0035]

[0036] As can be seen from Table 1, the water contact angle, friction coefficient and wear rate of Examples 1-5 are all smaller than those of Comparative Example 1. This shows that COF-COOH can improve the hydration performance of polyetheretherketone, greatly improve its hydrophilicity, and then reduce the friction coefficient and wear rate; and at the same time of improving the hydration performance, COF-COOH also improves the mechanical strength of polyetheretherketone to a certain extent. Especially in Example 3, when the ratio of COF-COOH to PEEK is 5:100, its friction coefficient can be as low as 0.040, and the wear rate is only 3.6×10 -7 mm 3 / Nm.

[0037] In summary, the present invention discloses a hydrophilic covalent organic framework modified PEEK composite material and its preparation method. Among them, in the hydrophilic covalent organic framework modified PEEK composite material, the incorporated COF-COOH has a porous property with carboxylic acid groups rich on the surface and a high specific surface area. It can enhance and modify the PEEK material. Its carboxylic acid groups can quickly adsorb hydrated cations in the solution to form a hydration layer in the water lubricating medium, forming a hydration effect. The porous property of COF-COOH can further enrich the hydration layer and enhance the hydration characteristics, and can significantly reduce the friction coefficient and enhance the wear resistance in the friction test. By enhancing and modifying PEEK in this aspect, the disadvantages of PEEK such as poor hydrophilicity, high friction coefficient and unstable friction performance in water lubricated friction are overcome, which has important value for realizing the long-term and efficient operation of water lubricated bearing equipment underwater.

[0038] It will be understood that those of ordinary skill in the art can make equivalent substitutions or changes based on the technical solutions of the present invention and its inventive concept, and all such changes or substitutions shall fall within the protection scope of the appended claims of 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 polyether ether ketone with a weight fraction ratio of (1-10):100; the molecular structural formula of the COF-COOH is 。 2. The hydrophilic covalent organic framework modified PEEK composite material according to claim 1, wherein The raw materials for preparing the composite material include COF-COOH and polyether ether ketone with a weight fraction ratio of 5:

100.

3. The hydrophilic covalent organic framework modified PEEK composite material according to claim 1, wherein, The method for preparing the COF-COOH includes the following steps: Step S01: Dissolve 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: Perform a vacuum treatment on the mixed solution obtained in Step S01, evacuate the internal oxygen, and then perform vacuum sealing; heat up to 100-130 °C and keep warm for 48-96 h; after the heat preservation ends, let it stand and cool to room temperature; Step S03: Perform vacuum filtration on the mixed solution obtained in Step S02, and wash and filter it multiple times with N,N-dimethylformamide and pure water respectively, and dry the solid product to obtain COF-CN; Step S04: Take COF-CN and disperse it in a 20% sodium hydroxide solution, stir and heat, and reflux at 120-130 °C for 48-72 h; after the reaction ends, cool to room temperature; Step S05: Adjust the pH value of the solution obtained in Step S04 to 6-6.5; after vacuum filtration, washing, filtration and drying, obtain COF-COOH.

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

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

6. A preparation method of a hydrophilic covalent organic framework modified PEEK composite material, characterized in that, The said method includes the steps: Take COF-COOH and polyether ether ketone powder, mix them evenly, and then sinter at 390-410 °C and a pressure of 20-40 MPa for 2-4 h to prepare the hydrophilic covalent organic framework modified PEEK composite material as described in any one of Claims 1-5.

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