Self-lubricating polyimide resin, preparation method and application thereof

Abstract

The application belongs to the technical field of polymer composites, and particularly relates to a self-lubricating polyimide resin as well as a preparation method and application thereof. The self-lubricating polyimide resin is prepared by the following steps: preparing carbon dot-based ionic liquid by using organic acid and amino-containing ionic liquid precursor; mixing the carbon dot-based ionic liquid, fluorine-containing aromatic diamine monomer, polar solvent and fluorine-containing aromatic dianhydride monomer to perform reaction, obtaining a side chain functionalized pre-grafting linear polyamide acid solution, mixing the pre-grafting linear polyamide acid solution with a phenylethynyl group-containing capping agent to perform reaction, obtaining a polyamide acid solution with a three-dimensional network structure, and solidifying the polyamide acid solution to obtain the self-lubricating polyimide resin. The self-lubricating polyimide resin can chemically stabilize and solidly load ionic liquid in a polyimide system, has the characteristics of structural stability, high-temperature self-lubrication and high bearing capacity, and is of great significance for promoting the application of high-performance tribological materials in extreme environments.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a self-lubricating polyimide resin, its preparation method, and its application. Background Technology

[0002] As aerospace, high-end equipment manufacturing, and other fields develop towards high speed, heavy load, and high temperature, more stringent requirements are being placed on the comprehensive performance of key friction pair materials under extreme operating conditions. Although traditional polyimide resins have excellent thermal stability and mechanical strength, their inherent molecular structure makes it difficult to form an effective lubricating film at the friction interface at high temperatures (such as above 300 °C), resulting in a significant increase in the coefficient of friction and a sharp increase in wear, which cannot meet the requirements for long-term, high-reliability operation.

[0003] To improve the high-temperature lubrication performance of polyimide, existing technologies often employ the addition of ionic liquids as high-temperature lubricants. Ionic liquids possess high thermal stability, low volatility, and excellent extreme-pressure lubrication characteristics, theoretically capable of significantly reducing interfacial wear. However, when introduced into the polyimide matrix through physical blending, two major problems arise: first, the interfacial bonding between the ionic liquid and the polymer matrix is ​​weak, making it prone to migration and seepage under high temperatures or shear stress, leading to rapid lubrication failure; second, dispersion uniformity is difficult to control, easily resulting in agglomeration and defects, which weakens the overall mechanical properties and durability of the material. For example, an ionic liquid-modified polyimide composite material prepared by blending exhibited a friction coefficient fluctuation exceeding 30% during long-term operation at 300 °C, and its wear rate increased by approximately 20% compared to pure resin, indicating that simple blending is insufficient to achieve long-term stable lubrication. Summary of the Invention

[0004] The purpose of this invention is to provide a self-lubricating polyimide resin, its preparation method, and its application. The self-lubricating polyimide resin provided by this invention can chemically stabilize and immobilize ionic liquids in a polyimide system, achieving continuous and controllable high-temperature lubrication while maintaining the high strength of the matrix. The self-lubricating polyimide resin provided by this invention combines structural stability, high-temperature self-lubrication, and high load-bearing capacity, which is of great significance for promoting the application of high-performance tribological materials in extreme environments.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a self-lubricating polyimide resin, comprising the following steps: (1) Mix organic acid and amino-containing ionic liquid precursor, and then perform melt polymerization and plasma treatment in sequence to obtain carbon dot-based ionic liquid; (2) The carbon dot-based ionic liquid, fluorinated aromatic diamine monomer, polar solvent and fluorinated aromatic dianhydride monomer are mixed and reacted to obtain a side-chain functionalized pre-grafted linear polyamic acid solution. (3) The pre-grafted linear polyamic acid solution with side chain functionalization is mixed with a phenylacetylene-containing end-capping agent and reacted to obtain a polyamic acid solution with a three-dimensional network structure. (4) The polyamic acid solution with a three-dimensional network structure is cured to obtain the self-lubricating polyimide resin; the curing includes a first stage of curing, a second stage of curing and a third stage of curing in sequence. The temperature of the first stage of curing is ≤120 ℃. The second stage of curing is carried out in a cycle of 1 to 3 times: "first heat preservation at the first temperature, cooling down from the first temperature to the second temperature, second heat preservation at the second temperature, and heating up from the second temperature to the first temperature" under a pressure ≥0.1 MPa. The first temperature is 220~250 ℃, the second temperature is 20~40 ℃ lower than the first temperature, the first heat preservation time is 30~90 min, and the second heat preservation time is 30~90 min. The temperature of the third stage of curing is ≥300 ℃.

[0006] Preferably, in step (1), the organic acid is citric acid, and the amino-containing ionic liquid precursor is 3-(3-aminopropyl)-1-methyl-1H-imidazol-3-onium bromide; the molar ratio of the organic acid to the amino-containing ionic liquid precursor is 1:2 to 1:3; the melt polymerization is carried out under microwave-assisted heating, the microwave power is 300 to 800 W, the melt polymerization temperature is 180 to 220 °C, the time is 10 to 20 min, the melt polymerization is carried out in a protective gas atmosphere, and the plasma treatment conditions include: plasma discharge power of 50 to 150 W, working gas is argon and / or nitrogen, and the plasma treatment time is 5 to 30 min; the particle size of the carbon dot-based ionic liquid is 2 to 5 nm, and the surface amino functionalization degree is not less than 0.25 mmol / g.

[0007] Preferably, the mass of the carbon dot-based ionic liquid accounts for 0.5-2% of the total mass of the fluorinated aromatic diamine monomer, the fluorinated aromatic dianhydride monomer, and the phenylacetylene-containing end-capping agent; in step (2), the reaction is carried out in a protective gas atmosphere; the reaction includes the following steps: premixing the carbon dot-based ionic liquid, the fluorinated aromatic diamine monomer, and a polar solvent to obtain a pre-assembled solution; performing a polycondensation reaction between the pre-assembled solution and the fluorinated aromatic dianhydride monomer to obtain a side-chain functionalized pre-grafted linear polyamic acid solution; the premixing temperature is 40-60 °C and the time is 1-3 h; the polycondensation reaction temperature is 60-80 °C and the time is 5-12 h.

[0008] Preferably, in step (3), the reaction temperature is 70~90 ℃ and the time is 6~12 h.

[0009] Preferably, in step (3), after the reaction is completed, an initial reaction system is obtained; the process further includes adjusting the solid content of the initial reaction system with a polar solvent to obtain the polyamic acid solution with a three-dimensional network structure; the solid content of the polyamic acid solution with a three-dimensional network structure is 40~50 wt.%.

[0010] Preferably, the fluorinated aromatic dianhydride monomer is selected from at least one of aromatic tetracarboxylic dianhydrides whose structure contains a hexafluoroisopropylalkyl or trifluoromethyl-substituted benzene ring as a linking group; the fluorinated aromatic diamine monomer is selected from at least one of aromatic diamines whose structure contains a diphenyl ether unit and whose benzene ring is substituted by trifluoromethyl; and the end-capping agent containing a phenylacetylene group is selected from at least one of aromatic acid anhydride compounds having a phenylacetylene substituent.

[0011] Preferably, the fluorinated aromatic dianhydride monomer is 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA); the fluorinated aromatic diamine monomer is 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA); and the phenylacetylene-containing end-capping agent is 4-phenylacetylphenyl anhydride (4-PEPA).

[0012] Preferably, the curing temperature of the first stage is 80~120 ℃, and the holding time is 1~3 h; the heating rate from the curing temperature of the first stage to the first temperature is ≤5 ℃ / min; the cooling rate from the first temperature to the second temperature is ≤2 ℃ / min; the heating rate from the second temperature to the first temperature is ≤5 ℃ / min; the curing temperature of the third stage is 300~400 ℃, the pressure is ≥0.1 MPa, and the holding time is 1~3 h.

[0013] The present invention provides a self-lubricating polyimide resin prepared by the preparation method described in the above technical solution.

[0014] This invention provides the application of the self-lubricating polyimide resin described above in sliding bearings, sealing rings, electrical contact parts, or moving parts.

[0015] This invention provides a method for preparing a self-lubricating polyimide resin, comprising the following steps: (1) mixing an organic acid and an amino-containing ionic liquid precursor, and sequentially performing melt polymerization and plasma treatment to obtain a carbon dot-based ionic liquid (CDs-ILs); (2) mixing the carbon dot-based ionic liquid, a fluorinated aromatic diamine monomer, a polar solvent, and a fluorinated aromatic dianhydride monomer to react and obtain a side-chain functionalized pre-grafted linear polyamic acid solution; (3) mixing the side-chain functionalized pre-grafted linear polyamic acid solution with a phenylacetylene-containing end-capping agent to react and obtain a polyamic acid solution with a three-dimensional network structure; (4) curing the polyamic acid solution with a three-dimensional network structure to obtain the self-lubricating polyimide resin; the curing includes sequentially performing a first-stage curing, a second-stage curing, and a third-stage curing, wherein the temperature of the first-stage curing is ≤120 ℃, and the pressure of the second-stage curing is ≥0.1 ℃. Under MPa conditions, the temperature is increased from the first stage curing temperature to the first temperature, followed by 1-3 cycles of "first holding at the first temperature, cooling down to the second temperature, second holding at the second temperature, and then increasing back to the first temperature." The first temperature is 220-250 °C, the second temperature is 20-40 °C lower than the first temperature, the first holding time is 30-90 min, and the second holding time is 30-90 min. The third stage curing temperature is ≥300 °C. The self-lubricating polyimide resin prepared by this invention has a "bead chain suspended" node reinforcement structure. This invention uses fluorinated polyimide with ether bonds as the flexible main chain, and covalently grafts carbon dot-based ionic liquid as multifunctional reinforcing nodes onto the side chains through chemical bonds, forming a "bead chain-suspended ball" reinforcement structure. This invention employs a "stepwise synthesis-directional grafting-programmed curing" preparation method, achieving uniform node distribution and structural stabilization through stepwise temperature increases during the curing stage. Under extreme conditions of 350 °C and 20 N, the self-lubricating polyimide resin obtained by this invention has a coefficient of friction of 0.005 and a wear rate of 1.2 × 10⁻⁶. -14 m 3 The self-lubricating polyimide resin prepared in this invention exhibits excellent high-temperature self-lubricating properties, with a load-bearing capacity 100% higher than that of pure ether-bonded fluorinated polyimide resin. This self-lubricating polyimide resin is suitable for applications such as high-temperature sliding bearings in aerospace, high-load sealing rings, and electrical contact components under extreme operating conditions. Compared with existing technologies, this invention has the following advantages: This invention pioneered the "bead chain suspension" structural model, which uses chemical grafting to stably immobilize CDs-ILs onto the polyimide backbone, solving the problems of easy migration and uneven dispersion of lubricating components, and achieving a balance between structural stability and long-lasting function.

[0016] The self-lubricating polyimide resin prepared by this invention exhibits a synergistic reinforcing effect: rigid carbon dots strengthen the nodes and improve the matrix's load-bearing capacity; side-chain ionic liquid anions provide a continuous high-temperature lubrication source, significantly reducing friction and wear. Experiments of this invention show that when the mass percentage of the carbon dot-based ionic liquid in the total mass of the fluorinated aromatic diamine monomer, the fluorinated aromatic dianhydride monomer, and the phenylacetylene-based end-capping agent (i.e., the CDs-ILs addition amount) is 1.0 wt.%, the composite material achieves a load-bearing capacity of 20 N at 350 °C.

[0017] The self-lubricating polyimide resin prepared by this invention can still maintain an ultra-low coefficient of friction (0.005) and excellent anti-wear properties under extreme working conditions (350 °C, 20 N, 0.05 m / s).

[0018] The self-lubricating polyimide resin prepared by this invention contains CDs-ILs that combine the characteristics of carbon dots and the functions of ionic liquids, introducing new performance dimensions such as conductivity to polyimide resins and expanding their application prospects in the field of multifunctional composite materials.

[0019] This invention provides a self-lubricating polyimide resin prepared by the preparation method described in the above technical solution. The self-lubricating polyimide resin provided by this invention is a high-temperature self-lubricating polyimide resin with a "bead chain suspension" structure. This invention covalently grafts carbon dot-based ionic liquids (CDs-ILs) onto the side chains of the ether-bonded fluorinated polyimide main chain via chemical bonds, constructing a unique "bead chain-suspended ball" reinforced structure, thereby achieving a synergistic improvement in low friction, high wear resistance, and high load-bearing capacity under extreme high-temperature and high-load conditions. Attached Figure Description

[0020] Figure 1 The 1H NMR spectra of the FOPI resin prepared in Comparative Example 1 and the CDs-ILs@FOPI resin prepared in Example 1 are shown. Figure 2 The high-temperature load-bearing friction resistance of CDs-ILs@FOPI prepared in Example 1. Detailed Implementation

[0021] This invention provides a method for preparing a self-lubricating polyimide resin, comprising the following steps: (1) Mix organic acid and amino-containing ionic liquid precursor, and then perform melt polymerization and plasma treatment in sequence to obtain carbon dot-based ionic liquid; (2) The carbon dot-based ionic liquid, fluorinated aromatic diamine monomer, polar solvent and fluorinated aromatic dianhydride monomer are mixed and reacted to obtain a side-chain functionalized pre-grafted linear polyamic acid solution. (3) The pre-grafted linear polyamic acid solution with side chain functionalization is mixed with a phenylacetylene-containing end-capping agent and reacted to obtain a polyamic acid solution with a three-dimensional network structure. (4) The polyamic acid solution with a three-dimensional network structure is cured to obtain the self-lubricating polyimide resin; the curing includes a first stage of curing, a second stage of curing and a third stage of curing in sequence. The temperature of the first stage of curing is ≤120 ℃. The second stage of curing is carried out in a cycle of 1 to 3 times: "first heat preservation at the first temperature, cooling down from the first temperature to the second temperature, second heat preservation at the second temperature, and heating up from the second temperature to the first temperature" under a pressure ≥0.1 MPa. The first temperature is 220~250 ℃, the second temperature is 20~40 ℃ lower than the first temperature, the first heat preservation time is 30~90 min, and the second heat preservation time is 30~90 min. The temperature of the third stage of curing is ≥300 ℃.

[0022] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0023] Step (1): In this invention, an organic acid and an amino-containing ionic liquid precursor are mixed and sequentially subjected to melt polymerization and plasma treatment to obtain a carbon dot-based ionic liquid. This invention uses a one-step method to prepare the carbon dot-based ionic liquid. This invention uses a microwave-plasma time-coupled method to prepare the carbon dot-based ionic liquid. In this invention, the melt polymerization and plasma treatment can be carried out in a reactor equipped with a microwave-plasma coupling reaction chamber. In this invention, the organic acid is preferably citric acid. The amino-containing ionic liquid precursor is preferably 3-(3-aminopropyl)-1-methyl-1H-imidazolium-3-onium bromide. The molar ratio of the organic acid to the amino-containing ionic liquid precursor is preferably 1:2 to 1:3, and in the examples, it can be 1:2.5. The melt polymerization is carried out under microwave-assisted heating conditions, and the microwave power is preferably 300 to 800 W, more preferably 500 to 600 W. The temperature of the melt polymerization is preferably 180 to 220 °C, and in the examples, it can be 200 °C. The time of the melt polymerization is preferably 10 to 20 min, and in the examples, it can be 15 min. The melt polymerization is carried out in a protective gas atmosphere, which can be nitrogen. The plasma treatment conditions preferably include: a temperature of 50-70 °C, more preferably 60 °C in the examples; a plasma discharge power of 50-150 W, more preferably 100 W in the examples; a working gas of argon and / or nitrogen; and a plasma treatment time of 5-30 min, more preferably 5-10 min. This invention enables the in-situ grafting of ionic liquid structures onto the surface of generated carbon dots through plasma treatment. After the plasma treatment, a reactant is obtained; preferably, the reactant is purified by supercritical CO2 extraction to obtain the carbon dot-based ionic liquid.

[0024] In this invention, the particle size of the carbon dot-based ionic liquid is preferably 2-5 nm, and in the examples it can be 2.7 nm or 3 nm. The degree of surface amino functionalization of the carbon dot-based ionic liquid is preferably not less than 0.25 mmol / g, preferably 0.25-0.4 mmol / g, and in the examples it can be 0.27 mmol / g or 0.35 mmol / g.

[0025] Step (2): After obtaining the carbon dot-based ionic liquid, the present invention mixes the carbon dot-based ionic liquid, a fluorinated aromatic diamine monomer, a polar solvent, and a fluorinated aromatic dianhydride monomer to react and obtain a side-chain functionalized pre-grafted linear polyamic acid solution.

[0026] In this invention, the mass of the carbon dot-based ionic liquid preferably accounts for 0.5 to 2% of the total mass of the fluorinated aromatic diamine monomer, the fluorinated aromatic dianhydride monomer, and the phenylacetylene-containing end-capping agent; in the examples, it can be 0.5%, 1%, 1.5%, or 2%.

[0027] In this invention, the preferred molar ratio of the phenylacetylene-containing end-capping agent, the fluorinated aromatic dianhydride monomer, and the fluorinated aromatic diamine monomer is 2:n:n+1, where n is a natural number, and in this invention, n=2.

[0028] In this invention, the reaction is carried out in a protective gas atmosphere, which may be nitrogen. The reaction preferably includes the following steps: premixing the carbon-dot-based ionic liquid, a fluorinated aromatic diamine monomer, and a polar solvent to obtain a pre-assembled solution; and subjecting the pre-assembled solution to a polycondensation reaction with a fluorinated aromatic dianhydride monomer to obtain a side-chain functionalized pre-grafted linear polyamic acid solution. In this invention, the fluorinated aromatic dianhydride monomer is preferably selected from at least one of aromatic tetracarboxylic dianhydrides containing a hexafluoroisopropylyl or trifluoromethyl-substituted benzene ring as a linking group; in the examples, it may be 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA). The fluorinated aromatic diamine monomer is preferably selected from at least one of aromatic diamines containing a diphenyl ether unit and a benzene ring substituted with a trifluoromethyl group; in the examples, it may be 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA). The polar solvent may be N,N-dimethylacetamide (DMAc).

[0029] In this invention, the premixing temperature is preferably 40-60 °C, and in some examples it can be 50 °C; the premixing time is preferably 1-3 h, and in some examples it can be 2 h. The premixing is carried out under stirring conditions. This invention uses premixing to allow the amino groups on the surface of CDs-ILs to form a homogeneous pre-assembled solution with the amino groups of a fluorinated aromatic diamine monomer (e.g., 6FODA) through hydrogen bonding and possible interactions. In this invention, the fluorinated aromatic dianhydride monomer is preferably added to the pre-assembled solution in batches for the polycondensation reaction. The polycondensation reaction temperature is preferably 60-80 °C, and in some examples it can be 70 °C. The polycondensation reaction time after the addition of the fluorinated aromatic dianhydride monomer is preferably 5-12 h, more preferably 6-10 h. The polycondensation reaction allows polyamic acid segments to grow directly on the surface of carbon dots under the initiation of amino groups, forming a pre-grafted linear polyamic acid solution with side-chain functionalization. Specifically, during the polycondensation reaction, the polycondensation reaction of the polyamic acid (PAA) chain segments is directly initiated and grown by the amino groups on the surface of CDs-ILs and on the fluorinated aromatic diamine monomer (e.g., 6FODA), thereby achieving the pre-grafting of CDs-ILs on the side chains of polyamic acid in the early stage of polymerization, resulting in a pre-grafted linear polyamic acid solution with side chain functionalization.

[0030] Step (3): After obtaining the side-chain functionalized pre-grafted linear polyamic acid solution, the present invention mixes the side-chain functionalized pre-grafted linear polyamic acid solution with a phenylacetylene-containing end-capping agent to react and obtain a polyamic acid solution with a three-dimensional network structure. In the present invention, the phenylacetylene-containing end-capping agent is preferably selected from at least one of aromatic acid anhydrides with phenylacetylene substituents, and in the examples, it can be 4-phenylacetylene phthalic anhydride (4-PEPA). In the present invention, the reaction is end-capping and chain extension. The reaction temperature is preferably 70~90 °C, and in the examples, it can be 80 °C. The reaction time is preferably 6~12 h, and in the examples, it can be 10 h. The present invention controls the molecular weight and introduces crosslinkable end groups through the reaction.

[0031] In this invention, an initial reaction system is obtained after the reaction is completed. The invention also includes adjusting the solid content of the initial reaction system using a polar solvent to obtain the polyamic acid solution with a three-dimensional network structure. The polar solvent can be N,N-dimethylacetamide (DMAc). The solid content of the polyamic acid solution with a three-dimensional network structure is 40-50 wt%, and in the examples it can be 45 wt%.

[0032] Step (4): After obtaining the polyamic acid solution with a three-dimensional network structure, the present invention cures the polyamic acid solution with a three-dimensional network structure to obtain the self-lubricating polyimide resin; the curing includes sequentially performing a first stage curing, a second stage curing and a third stage curing. The temperature of the first stage curing is ≤120 ℃. The second stage curing is performed under a pressure ≥0.1 MPa, where the temperature is raised from the temperature of the first stage curing to the first temperature and then subjected to 1 to 3 cycles of "first heat preservation at the first temperature, cooling down from the first temperature to the second temperature, second heat preservation at the second temperature, and raising the temperature from the second temperature to the first temperature". The first temperature is 220~250 ℃, the second temperature is 20~40 ℃ lower than the first temperature, the first heat preservation time is 30~90 min, and the second heat preservation time is 30~90 min. The temperature of the third stage curing is ≥300 ℃.

[0033] In this invention, prior to curing, the polyamic acid solution with a three-dimensional network structure is preferably molded. The molding process is preferably performed by casting the polyamic acid solution with a three-dimensional network structure into a film.

[0034] In this invention, the curing is carried out in a pressurized curing oven. The curing is performed in a protective gas atmosphere, which may be nitrogen. In this invention, the first stage of curing is carried out under normal pressure. The temperature of the first stage of curing is preferably 80~120℃, and in the embodiment, it can be 100℃. The holding time is preferably 1~3 h, and in the embodiment, it can be 2 h. The heating rate from room temperature to the first stage curing temperature is preferably ≤5℃ / min, and in the embodiment, it can be 3~5℃ / min. The pressure of the second stage of curing is preferably 0.1~1 MPa, more preferably 0.5~1 MPa. The heating rate from the first stage curing temperature to the first temperature is preferably ≤5℃ / min, and in the embodiment, it can be 3~5℃ / min. The cycle unit of "first holding at the first temperature, cooling from the first temperature to the second temperature, second holding at the second temperature, and heating from the second temperature to the first temperature" is preferably performed twice. The first temperature is preferably 220℃. The first holding time is preferably 60~80 min. The second temperature is preferably 190℃. The cooling rate from the first temperature to the second temperature is ≤2 °C / min, preferably 1~2 °C / min, and in the embodiment, it can be 2 °C / min. The second holding time is preferably 60~80 min. The heating rate from the second temperature to the first temperature is ≤5 °C / min, and in the embodiment, it can be 3~5 °C / min. The curing temperature in the third stage is preferably 300~400 °C, more preferably 350~370 °C. The curing pressure in the third stage is preferably 0.1~1 MPa, more preferably 0.5~1 MPa. The holding time in the third stage is preferably 1~3 h, and in the embodiment, it can be 2 h. The heating rate from the first temperature to the third stage curing is preferably ≤5 °C / min, and in the embodiment, it can be 3~5 °C / min. The pressure condition during the heating process from the first temperature to the third stage curing is preferably 0.1~1 MPa, more preferably 0.5~1 MPa.

[0035] In this invention, the first stage of curing involves pre-crosslinking and solvent removal. The second stage of curing is a "thermo-mechanical coupled programmed curing" process, which achieves structural rearrangement and internal stress release. The third stage of curing achieves complete imidization and node strengthening, completing the imidization reaction and thermal crosslinking of the end-capping agent to obtain the final self-lubricating polyimide resin.

[0036] The present invention provides a self-lubricating polyimide resin prepared by the preparation method described in the above technical solution.

[0037] The self-lubricating polyimide resin provided by the present invention is a high-temperature self-lubricating polyimide resin with a "bead chain suspension" type. The self-lubricating polyimide resin is composed of a flexible linear main chain skeleton of ether bond fluorinated polyimide, and carbon dot-based ionic liquid is covalently grafted as a multifunctional node to the side chain position of the main chain through chemical bonds to form a "bead chain-suspended ball" composite reinforcement structure.

[0038] In this invention, the self-lubricating polyimide resin has a friction coefficient of no more than 0.01 and a wear rate of no more than 6.0 × 10⁻⁶ under a load of 20 N and a temperature of 350 °C. -14 m 3 / (N·m), the load-bearing capacity is increased by no less than 15% compared with the unmodified ether-bonded fluorinated polyimide resin.

[0039] This invention provides the application of the self-lubricating polyimide resin described above in sliding bearings (high-temperature sliding bearings), sealing rings (high-load sealing rings), electrical contact components, or moving components (moving components that require both lubrication and load-bearing functions under extreme conditions). In this invention, the extreme conditions include: temperature ≥ 300 °C and / or pressure of 15~20 N.

[0040] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1 1) Preparation of carbon dot-based ionic liquids (CDs-ILs): 1.0 g of citric acid and 2.67 g of 3-(3-aminopropyl)-1-methyl-1H-imidazol-3-onium bromide (molar ratio approximately 1:2.5) were mixed and placed in a reactor equipped with a microwave-plasma-coupled reaction chamber. Under nitrogen protection, the mixture was first heated to 200 °C with a microwave power of 500 W for 15 minutes to induce melt polymerization. Subsequently, a low-temperature plasma treatment (temperature 60 °C, power 100 W, argon atmosphere) was initiated for 10 minutes to allow the ionic liquid structure to be grafted in situ onto the surface of the generated carbon dots. The reaction product was purified by supercritical CO2 extraction to obtain carbon dot-based ionic liquid (CDs-ILs) powder with a surface amino functionalization degree of 0.35 mmol / g and a particle size of approximately 3 nm.

[0042] 2) Preparation of pre-grafted linear polyamic acid solution: Under nitrogen protection, 0.12 g (1.0 wt.% of the total mass of 6FODA, 6FDA, and 4-PEPA) of the CDs-ILs powder prepared in step 1) was added to 20 mL of N,N-dimethylacetamide (DMAc) along with 5.04 g (0.01 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA). The mixture was mechanically stirred at 50 °C for 2 hours to allow the amino groups on the surface of the CDs-ILs to form a homogeneous pre-assembled solution with the amino groups of 6FODA through hydrogen bonding and possible interactions. Subsequently, under continuous stirring, 4.44 g (0.01 mol) of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) was added in batches to the pre-assembled solution. After the addition was complete, the reaction system temperature was raised to 70 °C, and the reaction was continued to be stirred for 6 hours. During this process, the polycondensation reaction of the polyamic acid (PAA) segments was directly initiated and grown by the amino groups on the surface of CDs-ILs and 6FODA, thereby achieving pre-grafting of CDs-ILs on the side chains of polyamic acid in the early stage of polymerization, resulting in a pre-grafted linear polyamic acid solution with side chain functionalization.

[0043] 3) End sealing and chain extension: 2.48 g (0.005 mol) of 4-phenylethynylphthalic anhydride (4-PEPA) was added as a capping agent to the pre-grafted linear polyamic acid solution with side chain functionalization obtained in step 2). The reaction temperature was raised to 80 °C, and the reaction was stirred for 10 hours to control the polymer molecular weight and introduce thermally crosslinkable phenylethynyl end groups. After the reaction was completed, an appropriate amount of DMAc solvent was added to precisely adjust the total solid content of the system to 45 wt.%, resulting in a homogeneous, viscous polyamic acid solution with a three-dimensional network structure, CDs-ILs@FOPI.

[0044] 4) Curing and molding: This curing process adopts a "thermal-mechanical coupled programmed curing" process. The polyamic acid solution with a three-dimensional network structure obtained in step 3) was cast into a film and placed in a pressure curing oven (N2 protection). The procedure is as follows: First stage: Increase the temperature to 100 ℃ at 3℃ / min and hold for 2 h; The second stage involves applying an external pressure of 0.5 MPa and raising the temperature from 100℃ to 220℃ at a rate of 3℃ / min. Two cycles of "holding-slow cooling-holding-heating" are then performed at this temperature: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. This process is repeated: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. Third stage: Apply an external pressure of 0.5 MPa, raise the temperature from 220℃ to 370℃ at a rate of 3℃ / min, and hold for 2 hours; After cooling, the film is demolded to obtain CDs-ILs@FOPI resin film.

[0045] 5) Performance Testing: Referring to "Reciprocating Friction and Wear Tests Part 2: High Temperature Test Methods" (No.: T / GMES 033—2025), such as... Figure 2 As shown, Figure 2 The high-temperature load-bearing friction resistance of CDs-ILs@FOPI prepared in Example 1 was assessed. Under conditions of 350 °C, 0.05 m / s, and 20 N load, the coefficient of friction of the CDs-ILs@FOPI resin prepared in Example 1 was 0.005, and the wear rate was 1.2 × 10⁻⁶. -14 m 3 / N·m. Compared with the pure ether-containing fluorinated polyimide (FOPI) resin prepared in Comparative Example 1, its load-bearing capacity is increased by approximately 100%, achieving a super-lubricated state. Meanwhile, the CDs-ILs@FOPI resin prepared in Example 1 maintains excellent dimensional stability and mechanical strength at high temperatures, making it suitable for high-temperature friction components in aerospace applications.

[0046] Example 2 1) Preparation of carbon dot-based ionic liquids (CDs-ILs): CDs-ILs were prepared using the same steps as in Example 1. 2) Preparation of polyamic acid solution: Under nitrogen protection, 0.18 g (1.5 wt.% of the total mass of 6FODA, 6FDA, and 4-PEPA) of the CDs-ILs powder prepared in step 1) was added to 20 mL of N,N-dimethylacetamide (DMAc) along with 5.04 g (0.01 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA). The mixture was mechanically stirred at 60 °C for 2 hours to allow the amino groups on the surface of the CDs-ILs to form a uniform pre-assembly with the amino groups of 6FODA through hydrogen bonding and possible interactions.

[0047] Subsequently, under continuous stirring, 4.44 g (0.01 mol) of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) was added in batches to the pre-assembled solution. After the addition was complete, the reaction system temperature was raised to 80 °C, and the reaction was continued to be stirred for 6 hours. During this process, the polycondensation reaction of the polyamic acid (PAA) segments was directly initiated and grown by the amino groups on the surface of CDs-ILs and 6FODA, thereby achieving pre-grafting of CDs-ILs on the side chains of polyamic acid in the early stage of polymerization, resulting in a pre-grafted linear polyamic acid solution with side chain functionalization.

[0048] 3) End sealing and chain extension: 2.48 g (0.005 mol) of 4-phenylethynylphthalic anhydride (4-PEPA) was added as a capping agent to the pre-grafted linear polyamic acid solution with side chain functionalization obtained in step 2). The reaction temperature was raised to 80 °C, and the reaction was stirred for 10 hours to control the polymer molecular weight and introduce thermally crosslinkable phenylethynyl end groups. After the reaction was completed, an appropriate amount of DMAc solvent was added to precisely adjust the total solid content of the system to 45 wt.%, resulting in a homogeneous, viscous polyamic acid solution with a three-dimensional network structure, CDs-ILs@FOPI.

[0049] 4) Curing and molding: This curing process adopts a "thermal-mechanical coupled programmed curing" process. The polyamic acid solution with a three-dimensional network structure obtained in step 3) was cast into a film and placed in a pressure curing oven (N2 protection). The procedure is as follows: First stage: Increase the temperature to 100 ℃ at 3℃ / min and hold for 2 h; The second stage involves applying an external pressure of 0.5 MPa and raising the temperature from 100℃ to 220℃ at a rate of 3℃ / min. Two cycles of "holding-slow cooling-holding-heating" are then performed at this temperature: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. This process is repeated: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. Third stage: Apply an external pressure of 0.5 MPa, raise the temperature from 220℃ to 370℃, and keep it at that temperature for 2 hours; After cooling, the film is demolded to obtain CDs-ILs@FOPI resin film.

[0050] 5) Performance Testing: Referring to "Reciprocating Friction and Wear Tests Part 2: High Temperature Test Methods" (No.: T / GMES 033—2025), under the conditions of 350 ℃, 0.05 m / s, and 18 N load, the coefficient of friction is 0.0045, and the wear rate is 1.4 × 10⁻⁶. -14 m 3 / N·m. The performance is better than that of the pure FOPI prepared in Comparative Example 1, but slightly lower than that of the sample with an addition of 1.0 wt.% in Example 1.

[0051] Example 3 1) Preparation of carbon dot-based ionic liquids (CDs-ILs): 1.0 g of citric acid and 2.67 g of 3-(3-aminopropyl)-1-methyl-1H-imidazol-3-onium bromide (molar ratio approximately 1:2.5) were mixed and placed in a reactor equipped with a microwave-coupled plasma reaction chamber. Under nitrogen protection, the mixture was first heated to 200 °C with a microwave power of 500 W for 15 minutes to induce melt polymerization. Subsequently, a low-temperature plasma treatment (temperature 60 °C, power 100 W, argon atmosphere) was initiated for 5 minutes to allow the ionic liquid structure to be grafted in situ onto the surface of the generated carbon dots. The reaction product was purified by supercritical CO2 extraction to obtain carbon dot-based ionic liquid (CDs-ILs) powder with a surface amino functionalization degree of 0.27 mmol / g and a particle size of approximately 2.7 nm.

[0052] 2) Preparation of polyamic acid solution: Under nitrogen protection, 0.06 g (0.5 wt.% of the total mass of 6FODA, 6FDA, and 4-PEPA) of the CDs-ILs powder prepared in step 1) was added to 20 mL of N,N-dimethylacetamide (DMAc) along with 5.04 g (0.01 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA). The mixture was mechanically stirred at 60 °C for 2 hours to allow the amino groups on the surface of the CDs-ILs to form a uniform pre-assembly with the amino groups of 6FODA through hydrogen bonding and possible interactions. Subsequently, under continuous stirring, 4.44 g (0.01 mol) of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) was added in batches to the pre-assembled solution. After the addition was complete, the reaction system temperature was raised to 80 °C, and the reaction was continued to be stirred for 6 hours. During this process, the polycondensation reaction of the polyamic acid (PAA) segments was directly initiated and grown by the amino groups on the surface of CDs-ILs and 6FODA, thereby achieving pre-grafting of CDs-ILs on the side chains of polyamic acid in the early stage of polymerization, resulting in a pre-grafted linear polyamic acid solution with side chain functionalization.

[0053] 3) End sealing and chain extension: 2.48 g (0.005 mol) of 4-phenylethynylphthalic anhydride (4-PEPA) was added as a capping agent to the pre-grafted linear polyamic acid solution with side chain functionalization obtained in step 2). The reaction temperature was raised to 80 °C, and the reaction was stirred for 10 hours to control the polymer molecular weight and introduce thermally crosslinkable phenylethynyl end groups. After the reaction was completed, an appropriate amount of DMAc solvent was added to precisely adjust the total solid content of the system to 45 wt.%, resulting in a homogeneous, viscous polyamic acid solution with a three-dimensional network structure, CDs-ILs@FOPI.

[0054] 4) Curing and molding: This curing process adopts a "thermal-mechanical coupled programmed curing" process. The polyamic acid solution with a three-dimensional network structure obtained in step 3) was cast into a film and placed in a pressure curing oven (N2 protection). The procedure is as follows: First stage: Increase the temperature to 100 ℃ at 3℃ / min and hold for 2 h; The second stage involves applying an external pressure of 1.0 MPa and raising the temperature from 100℃ to 220℃ at a rate of 3℃ / min. Two cycles of "holding-slow cooling-holding-heating" are then performed at this temperature: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. This process is repeated: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. Third stage: Apply an external pressure of 0.5 MPa, raise the temperature from 220℃ to 370℃, and keep it at that temperature for 2 hours; After cooling, the film is demolded to obtain CDs-ILs@FOPI resin film.

[0055] 5) Performance Testing: According to the standard "Reciprocating Friction and Wear Tests Part 2: High Temperature Test Methods" (No.: T / GMES 033—2025), the test was conducted at 350 ℃, 0.05 m / s, and a load of 15 N. The measured coefficient of friction was 0.015, and the wear rate was 5.24 × 10⁻⁶. -14 m 3 / N·m, with a load-bearing capacity of 15 N. The results show that a lower addition amount can still effectively improve performance, but the optimal load-bearing capacity did not reach the higher addition level of Example 1.

[0056] Example 4 1) Preparation of carbon dot-based ionic liquids (CDs-ILs): The same steps as in Example 1 are used for CDs-ILs.

[0057] 2) Preparation of pre-grafted linear polyamic acid solution: Under nitrogen protection, 0.24 g (2.0 wt.% of the total mass of 6FODA, 6FDA, and 4-PEPA) of the CDs-ILs powder prepared in step 1) was added to 20 mL of N,N-dimethylacetamide (DMAc) along with 5.04 g (0.01 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA). The mixture was mechanically stirred at 60 °C for 2 hours to allow the amino groups on the surface of the CDs-ILs to form a uniform pre-assembly with the amino groups of 6FODA through hydrogen bonding and possible interactions. Subsequently, under continuous stirring, 4.44 g (0.01 mol) of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) was added in batches to the pre-assembled solution. After the addition was complete, the reaction system temperature was raised to 80 °C, and the reaction was continued to be stirred for 6 hours. During this process, the polycondensation reaction of the polyamic acid (PAA) segments was directly initiated and grown by the amino groups on the surface of CDs-ILs and 6FODA, thereby achieving pre-grafting of CDs-ILs on the side chains of polyamic acid in the early stage of polymerization, resulting in a pre-grafted linear polyamic acid solution with side chain functionalization.

[0058] 3) End sealing and chain extension: 2.48 g (0.005 mol) of 4-phenylethynylphthalic anhydride (4-PEPA) was added as a capping agent to the pre-grafted linear polyamic acid solution with side chain functionalization obtained in step 2). The reaction temperature was raised to 80 °C, and the reaction was stirred for 10 hours to control the polymer molecular weight and introduce thermally crosslinkable phenylethynyl end groups. After the reaction was completed, an appropriate amount of DMAc solvent was added to precisely adjust the total solid content of the system to 45 wt.%, resulting in a homogeneous, viscous polyamic acid solution with a three-dimensional network structure, CDs-ILs@FOPI.

[0059] 4) Curing and molding: This curing process adopts a "thermal-mechanical coupled programmed curing" process. The polyamic acid solution with a three-dimensional network structure obtained in step 3) was cast into a film and placed in a pressure curing oven (N2 protection). The procedure is as follows: First stage: Increase the temperature to 100 ℃ at 3℃ / min and hold for 2 h; The second stage involves applying an external pressure of 0.5 MPa and raising the temperature from 100℃ to 220℃ at a rate of 3℃ / min. Two cycles of "holding-slow cooling-holding-heating" are then performed at this temperature: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. This process is repeated: holding at 220℃ for 60 min, slowly cooling to 190℃ at a rate of 2℃ / min, holding at 190℃ for 60 min, and then raising the temperature back to 220℃ at a rate of 3℃ / min. Third stage: Apply an external pressure of 0.5 MPa, raise the temperature from 220℃ to 370℃, and keep it at that temperature for 2 hours; After cooling, the film is demolded to obtain CDs-ILs@FOPI resin film.

[0060] 5) Performance Testing: According to the standard "Reciprocating Friction and Wear Tests Part 2: High Temperature Test Methods" (No.: T / GMES 033—2025), the test was conducted at 350 ℃, 0.05 m / s, and a load of 17 N. The measured coefficient of friction was 0.009, and the wear rate was 1.47 × 10⁻⁶. -14 m 3 / N·m. The high wear rate indicates that excessive CDs-ILs addition may lead to decreased interfacial compatibility or agglomeration, affecting wear resistance. Overall, 1.0 wt.% is the optimal addition ratio.

[0061] Comparative Example 1 Comparison benchmark: Pure FOPI resin with zero added CDs-ILs 1) Preparation of polyamic acid solution: Under nitrogen protection, 4.44 g of 6FDA was dissolved in 5.9 mL of DMAc. After complete dissolution, 5.04 g of 6FODA and 4.7 mL of DMAc were added, and the mixture was stirred at 80 °C for 6 h to obtain a polyamic acid solution with a three-dimensional network structure.

[0062] 2) End-capping and curing: 2.48 g of 4-PEPA and 4 mL of DMAc were directly added to the polyamic acid solution with a three-dimensional network structure prepared in step 1). After reacting for 18 h, the solution was coated and cured without adding carbon dots. The solution was uniformly coated onto a clean glass plate and pretreated with a stepped heating program (heating rate of 3 ℃ / min, 80 ℃ / 2 h, 150 ℃ / 2 h, 250 ℃ / 2 h, 320 ℃ / 2 h). Finally, it was cured at 370 ℃ for 2 h, cooled, and then demolded to obtain a pure FOPI resin film.

[0063] 3) Performance testing: Referring to "Reciprocating Friction and Wear Tests Part 2: High Temperature Test Methods" (No.: T / GMES 033—2025), under the conditions of 350 ℃, 0.05 m / s, and 10 N load, the coefficient of friction of FOPI resin is 0.024, and the wear rate is 1.0×10⁻⁶. -13 m 3 / (N·m). The ultimate load-bearing capacity is only 10 N. Its performance is significantly lower than all carbon dot modified examples, highlighting the necessity of carbon dot end-capping modification.

[0064] Figure 1 The 1H NMR spectra of the FOPI resin prepared in Comparative Example 1 and the CDs-ILs@FOPI resin prepared in Example 1 are shown. Figure 1It can be seen that, compared with the FOPI resin provided in Comparative Example 1, the product prepared in Example 1 showed a new peak at 8.33 ppm. This peak is attributed to the imide characteristic peak of the CDs-ILs@FOPI resin prepared in Example 1, indicating that the carboxyl groups on the surface of CDs-ILs react with the amino groups of 6FODA to form imide bonds, which shows that the ionic liquid is chemically stabilized and immobilized in the polyimide system.

[0065] The performance test results are shown in Table 1: Table 1 Performance test results of the products prepared in the examples and comparative examples

[0066] Comparative Example 2 The preparation method is basically the same as that in Example 1, except that: 4) Curing and molding: This curing process adopts a "thermal-mechanical coupled programmed curing" process. The polyamic acid solution with a three-dimensional network structure obtained in step 3) was cast into a film and placed in a pressure curing oven (N2 protection). The procedure is as follows: First stage: Increase the temperature to 100 ℃ at 3℃ / min and hold for 2 h; Second stage: Apply an external pressure of 0.5 MPa, and raise the temperature from 100℃ to 220℃ at a rate of 3℃ / min. Slowly lower the temperature from 220℃ to 190℃ at a rate of 2℃ / min, hold at 190℃ for 60 min, and then raise the temperature back to 220℃ at a rate of 3℃ / min. Then, slowly lower the temperature from 220℃ to 190℃ at a rate of 2℃ / min, hold at 190℃ for 60 min, and then raise the temperature back to 220℃ at a rate of 3℃ / min.

[0067] Third stage: Apply an external pressure of 0.5 MPa, raise the temperature from 220℃ to 370℃, and keep it at that temperature for 2 hours.

[0068] The sample broke upon demolding after cooling, and CDs-ILs@FOPI resin film could not be obtained.

[0069] As can be seen from the above embodiments, the polyimide resin with a "bead chain suspension" structure provided by the present invention. In this resin, carbon dot-based ionic liquid acts as a multifunctional "suspended ball" connected to the "bead chain" of ether-bonded fluorinated polyimide main chain via chemical bonds. The carbon dot component enhances the rigidity and stability of local connection points; the ionic liquid component can form an effective lubricating film at the interface during high-temperature friction and participate in the generation of a tribochemical reaction film containing iron fluoride, iron oxide, etc. The present invention provides the application of the above-mentioned polyimide resin in the preparation of high-temperature sliding bearings, sealing rings, or electrical contact components that require high load-bearing capacity, low wear, and certain conductivity.

[0070] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a self-lubricating polyimide resin, characterized in that, Includes the following steps: (1) Mix organic acid and amino-containing ionic liquid precursor, and then perform melt polymerization and plasma treatment in sequence to obtain carbon dot-based ionic liquid; (2) The carbon dot-based ionic liquid, fluorinated aromatic diamine monomer, polar solvent and fluorinated aromatic dianhydride monomer are mixed and reacted to obtain a side-chain functionalized pre-grafted linear polyamic acid solution. (3) The pre-grafted linear polyamic acid solution with side chain functionalization is mixed with a phenylacetylene-containing end-capping agent and reacted to obtain a polyamic acid solution with a three-dimensional network structure. (4) The polyamic acid solution with a three-dimensional network structure is cured to obtain the self-lubricating polyimide resin; the curing includes a first stage of curing, a second stage of curing and a third stage of curing in sequence. The temperature of the first stage of curing is ≤120 ℃. The second stage of curing is carried out in a cycle unit of "first heat preservation at the first temperature, cooling down from the first temperature to the second temperature, second heat preservation at the second temperature and heating up from the second temperature to the first temperature" 1 to 3 times under the condition of pressure ≥0.1 MPa. The first temperature is 220~250 ℃, the second temperature is 20~40 ℃ lower than the first temperature, the first heat preservation time is 30~90 min, and the second heat preservation time is 30~90 min. The temperature of the third stage of curing is ≥300 ℃.

2. The preparation method according to claim 1, characterized in that, In step (1), the organic acid is citric acid, and the amino-containing ionic liquid precursor is 3-(3-aminopropyl)-1-methyl-1H-imidazol-3-onium bromide; the molar ratio of the organic acid to the amino-containing ionic liquid precursor is 1:2 to 1:3; the melt polymerization is carried out under microwave-assisted heating, the microwave power is 300 to 800 W, the melt polymerization temperature is 180 to 220 °C, the time is 10 to 20 min, the melt polymerization is carried out in a protective gas atmosphere, and the plasma treatment conditions include: plasma discharge power of 50 to 150 W, working gas is argon and / or nitrogen, and the plasma treatment time is 5 to 30 min; the particle size of the carbon dot-based ionic liquid is 2 to 5 nm, and the surface amino functionalization degree is not less than 0.25 mmol / g.

3. The preparation method according to claim 1, characterized in that, The mass of the carbon dot-based ionic liquid accounts for 0.5-2% of the total mass of the fluorinated aromatic diamine monomer, the fluorinated aromatic dianhydride monomer, and the phenylacetylene-containing end-capping agent; in step (2), the reaction is carried out in a protective gas atmosphere; the reaction includes the following steps: The carbon dot-based ionic liquid, fluorinated aromatic diamine monomer, and polar solvent are premixed to obtain a pre-assembled solution; the pre-assembled solution is then subjected to a polycondensation reaction with a fluorinated aromatic dianhydride monomer to obtain a side-chain functionalized pre-grafted linear polyamic acid solution; the premixing temperature is 40~60℃ and the time is 1~3 h; the polycondensation reaction temperature is 60~80℃ and the time is 5~12 h.

4. The preparation method according to claim 1, characterized in that, In step (3), the reaction temperature is 70~90℃ and the time is 6~12 h.

5. The preparation method according to claim 1, characterized in that, In step (3), after the reaction is completed, an initial reaction system is obtained; the step also includes adjusting the solid content of the initial reaction system with a polar solvent to obtain the polyamic acid solution with a three-dimensional network structure; the solid content of the polyamic acid solution with a three-dimensional network structure is 40~50 wt.%.

6. The preparation method according to claim 1, 3, or 4, characterized in that, The fluorinated aromatic dianhydride monomer is selected from at least one of aromatic tetracarboxylic dianhydrides whose structure contains a hexafluoroisopropylalkyl or trifluoromethyl substituted benzene ring as a linking group; the fluorinated aromatic diamine monomer is selected from at least one of aromatic diamines whose structure contains a diphenyl ether unit and whose benzene ring is substituted by trifluoromethyl; the end-capping agent containing a phenylacetylene group is selected from at least one of aromatic acid anhydride compounds having a phenylacetylene substituent.

7. The preparation method according to claim 6, characterized in that, The fluorinated aromatic dianhydride monomer is 4,4'-(hexafluoroisopropene) phthalic anhydride; the fluorinated aromatic diamine monomer is 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether; and the phenylacetylene-containing end-capping agent is 4-phenylacetylene phthalic anhydride.

8. The preparation method according to claim 1, characterized in that, The first stage of curing is performed at a temperature of 80~120℃ and a holding time of 1~3 h; the heating rate from the first stage curing temperature to the first temperature is ≤5 ℃ / min; the cooling rate from the first temperature to the second temperature is ≤2 ℃ / min; the heating rate from the second temperature to the first temperature is ≤5 ℃ / min; the third stage of curing is performed at a temperature of 300~400℃, a pressure ≥0.1 MPa, and a holding time of 1~3 h.

9. The self-lubricating polyimide resin prepared by the preparation method according to any one of claims 1 to 8.

10. The use of the self-lubricating polyimide resin of claim 9 in sliding bearings, sealing rings, electrical contact parts or moving parts.

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