Self-lubricating composite material based on high-temperature-resistant lubricating oil microcapsules and preparation method thereof

Abstract

This invention discloses a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules and its preparation method, comprising: preparing lubricating oil-containing polyimide microcapsules using soluble polyimide; dispersing the lubricating oil-containing polyimide microcapsules in an aqueous solution containing a polyelectrolyte; surface-modifying the lubricating oil-containing polyimide microcapsules; subsequently loading carbon nanomaterials with functionalized surfaces to obtain high-temperature resistant, interface-reinforced polyimide microcapsules; mixing and dispersing the high-temperature resistant, interface-reinforced polyimide microcapsules with high-performance thermoplastic engineering plastics; and molding to prepare the self-lubricating composite material. This invention introduces surface-modified and nano-reinforced high-temperature resistant lubricating oil microcapsules into a high-performance thermoplastic engineering plastic matrix, constructing a stable self-lubricating composite system under high-temperature molding conditions, thereby significantly improving its tribological properties while maintaining the material's mechanical and heat resistance properties.

Description

Technical Field

[0001] This invention belongs to the field of self-lubricating materials technology. More specifically, this invention relates to a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules and its preparation method. Background Technology

[0002] High-performance thermoplastic engineering plastics are widely used in aerospace, rail transportation, and precision machinery due to their excellent heat resistance, mechanical properties, and chemical stability. However, these materials typically suffer from high friction coefficients and high wear rates under friction and wear conditions, limiting their further application in self-lubricating components. To improve the tribological properties of engineering plastics, existing technologies usually employ the introduction of solid lubricating fillers or lubricating oils into the matrix to achieve friction reduction. However, solid lubricating fillers at high concentrations can easily weaken the mechanical properties of the material; while lubricating oils are prone to volatilization, migration, or loss during high-temperature processing or service, making it difficult to maintain stable lubrication over a long period. In recent years, lubricating oil microencapsulation technology has been proposed for the encapsulation and sustained release of lubricating oils. However, existing microcapsules mostly use polymers with limited heat resistance as wall materials, which are prone to structural damage under high-temperature molding conditions, making them difficult to match with the high-temperature processing technology of high-performance engineering plastics. Furthermore, the insufficient dispersibility and interfacial compatibility of microcapsules in the engineering plastic matrix also limit their practical application effectiveness. Therefore, how to introduce functional fillers that can withstand high-temperature molding processes and stably play a lubricating role while ensuring the heat resistance and mechanical properties of engineering plastics remains a technical problem that urgently needs to be solved in this field.

[0003] The following methods are mainly used in existing technologies to improve the lubrication properties of thermoplastic engineering plastics: Direct filling with solid lubricants: This method involves introducing solid lubricants such as polytetrafluoroethylene (PTFE), graphite, and molybdenum disulfide into an engineering plastic matrix to reduce the coefficient of friction and improve wear resistance. This approach is simple to implement and has found some application in low- and medium-temperature friction conditions. However, solid lubricants typically require a high filling amount to significantly reduce the coefficient of friction. High filling amounts can lead to a significant decrease in the material's toughness, strength, and other mechanical properties, limiting its application under high-load conditions.

[0004] Direct lubricant addition: This method involves externally adding lubricant or oily additives, relying on the lubricating effect of the lubricant to reduce friction and wear after molding or during service. However, lubricants are prone to volatilization, migration, or seepage during the high-temperature molding or service of engineering plastics, making it difficult to maintain the lubrication effect and even causing material performance degradation.

[0005] Conventional polymer wall material microencapsulation lubrication solutions employ conventional polymer materials such as urea-formaldehyde resin, polyurethane, and polymethyl methacrylate as wall materials to microencapsulate lubricating oil. These microcapsules are then introduced as fillers into an engineering plastic matrix to achieve a slow-release effect. However, conventional microcapsules often use polymer materials with limited heat resistance as wall materials, which are prone to softening, cracking, or degradation during the high-temperature processing of engineering plastics, making them difficult to integrate with the high-temperature molding processes of high-performance engineering plastics.

[0006] High-performance engineering plastic matrix modification schemes: These schemes aim to improve the overall tribological properties of engineering plastics by modifying their molecular structure or blending them with other engineering plastics. However, existing schemes typically only offer a trade-off between reducing frictional performance and maintaining mechanical properties, making it difficult to simultaneously achieve stable self-lubricating properties and excellent structural performance under high-temperature conditions. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0008] To achieve these and other advantages according to the present invention, the present invention provides a method for preparing a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules, comprising the following steps: Step 1: Prepare lubricating oil-containing polyimide microcapsules using soluble polyimide; Step 2: Disperse the lubricating oil-containing polyimide microcapsules in an aqueous solution containing polyelectrolytes to modify the surface of the lubricating oil-containing polyimide microcapsules, forming a charged modified layer on the surface of the lubricating oil-containing polyimide microcapsules. Then, load nanomaterials with functionalized surfaces to obtain high-temperature resistant, interface-enhanced polyimide microcapsules. Step 3: Mix and disperse high-temperature resistant, interface-reinforced polyimide microcapsules with high-performance thermoplastic engineering plastics, and then mold them to prepare a self-lubricating composite material.

[0009] Preferably, the soluble polyimide is a polyimide containing hexafluoroisopropyl structural units.

[0010] Preferably, in step one, the specific method for preparing lubricating oil-containing polyimide microcapsules using soluble polyimide includes: An aqueous / oil phase emulsion system was used to mix soluble polyimide, lubricating oil, and halogenated hydrocarbon solvent to form an oil phase, while a water-soluble polymeric stabilizer was dissolved in water to form an aqueous phase. Under high shear conditions, the oil phase was dispersed in the aqueous phase to form a stable emulsion, and the solvent was gradually evaporated under temperature-controlled stirring conditions, thereby forming a polyimide coating layer on the surface of the lubricating oil, resulting in lubricating oil-containing polyimide microcapsules.

[0011] Preferably, the lubricating oil includes one or a combination of two of benzyl silicone oil and polyalphaolefin lubricating oil; The halogenated hydrocarbon solvent includes one of dichloromethane and trichloromethane; The mass ratio of soluble polyimide, lubricating oil and halogenated hydrocarbon solvent is 1~5:1~8:110~150; The water-soluble polymeric stabilizer includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, gelatin, sodium dodecylbenzene sulfonate, and polyethylene glycol octylphenyl ether; the mass ratio of the water-soluble polymeric stabilizer to water is 1:100 to 5:100. The volume ratio of the oil phase to the water phase is 1:1 to 1:5.

[0012] Preferably, in step two, the polyelectrolyte solution includes one or more of sodium polystyrene sulfonate solution, polyethylene sulfonic acid solution, and poly(2-acrylamide-2-methylpropanesulfonic acid) solution, and the concentration of the polyelectrolyte solution is 1~20 mg / mL; the ratio of the soluble polyimide to the polyelectrolyte solution is 1~5 g:100 mL.

[0013] Preferably, in step two, the nanomaterial with a functionalized surface includes one or more of the following: aminated carbon nanotubes, aminated graphene, aminated graphene quantum dots, surface oxygen ionized MXene, aminated boron nitride, aminated MoS2, and aminated g-C3N4; the mass ratio of the nanomaterial with a functionalized surface to the lubricating oil-containing polyimide microcapsules is 1:20 to 1:5.

[0014] Preferably, in step three, the high-temperature resistant, interface-reinforced polyimide microcapsules account for 5% to 20% of the mass of the self-lubricating composite material.

[0015] Preferably, the high-performance thermoplastic engineering plastic includes one or a mixture of two or more of polyetherimide, polyetheretherketone, polyphenylene sulfide, and polysulfone.

[0016] Preferably, the molding method includes hot pressing, injection molding, or extrusion molding; wherein the hot pressing temperature is 320~350℃ and the hot pressing time is 30~120min.

[0017] A self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules, wherein the self-lubricating composite material is prepared by the above-mentioned preparation method of the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules.

[0018] The present invention has at least the following beneficial effects: 1. This invention uses polyimide polymers as the wall material of lubricating oil microcapsules, enabling the microcapsules to withstand high-temperature molding processes above 300°C and maintain structural integrity under high-performance engineering plastic processing conditions. This effectively avoids the problem of lubricating oil loss during processing and significantly improves the high-temperature stability of high-performance engineering plastics.

[0019] 2. This invention introduces lubricating oil into the engineering plastic matrix in the form of microcapsules, achieving slow release of lubricating oil during the material's service life. Compared with the method of directly adding lubricating oil, it can stably reduce the coefficient of friction of the material and reduce wear in the long term, achieving stable and long-lasting self-lubricating performance.

[0020] 3. The high-temperature resistant lubricating oil microcapsules described in this invention are introduced into the engineering plastic matrix as functional fillers. While improving tribological properties, they do not require a large amount of solid lubricant, thus effectively avoiding adverse effects on the mechanical properties of the material, that is, taking into account both tribological and mechanical properties.

[0021] 4. This invention significantly improves the dispersibility and interfacial bonding performance of microcapsules in engineering plastic matrices by surface modification of microcapsules and reinforcement with carbon-based nanomaterials, thereby enhancing the overall stability of the composite material and exhibiting excellent interfacial compatibility and dispersibility.

[0022] 5. The self-lubricating composite material of the present invention is applicable to a variety of high-performance thermoplastic engineering plastic systems and can be prepared by conventional processing methods such as hot pressing, injection molding or extrusion, and has good prospects for engineering applications.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0024] Figure 1 This is a microscopic morphology image of the lubricating oil-containing polyimide microcapsules in Example 1; Figure 2 Microscopic images of the polyimide microcapsules assembled from aminated carbon nanotubes in Example 1; Figure 3 The decomposition temperature of the lubricating oil before and after polyimide microcapsule encapsulation; Figure 4 The friction coefficients of the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules prepared in Example 1 are compared with those of the polyetherimide material prepared in Comparative Example 1. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0026] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof. The polyimide used in each embodiment is 6FDA-based polyimide, and its preparation method includes: 10 mmol of 4,4′-(hexafluoroisopropene)phthalic anhydride (6FDA) and 10 mmol of 2,2′-di(trifluoromethyl)diaminobiphenyl were weighed separately and added to a three-necked flask. 76 g of N-methylpyrrolidone was also added, and the reaction was allowed to proceed for 24 h. Subsequently, an acetic anhydride-pyridine solution (1 g of acetic anhydride and 0.48 g of pyridine) was prepared at a molar ratio of 1:0.6 and added to the reaction system. The mixture was stirred for another 24 h. Finally, the entire reaction system was slowly poured into water or ethanol to form a soluble 6FDA-based polyimide powder.

[0027] Example 1 A method for preparing a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules includes the following steps: Step 1: Dissolve 10g of polyvinylpyrrolidone in 500mL of deionized water to form an aqueous phase; Dissolve 2g of 6FDA-based polyimide in a mixed solvent of 80mL dichloromethane and 20mL trichloromethane, and add 2g of benzyl silicone oil to form an oil phase; The oil phase was added to the aqueous phase and emulsified at 15,000 rpm for 8 min. Then, the mixture was stirred at 37 °C for 5 h to allow the solvent to evaporate and form a polyimide coating layer on the surface of the lubricating oil, thus obtaining lubricating oil-containing polyimide microcapsules. Step 2: Disperse the lubricating oil-containing polyimide microcapsules prepared in Step 1 in 100 mL of sodium polystyrene sulfonate solution with a concentration of 10 mg / mL, sonicate for 60 min, and then centrifuge and wash to obtain the microcapsule dispersion system. Add 0.2g of aminated carbon nanotube dispersion to the above microcapsule dispersion system, sonicate for 120min to load carbon nanotubes onto the surface of microcapsules, centrifuge to remove excess carbon nanotubes, repeat the above operation 3 times to obtain high temperature resistant, interface-reinforced polyimide microcapsules.

[0028] Step 3: Mix 1g of the high-temperature resistant, interface-reinforced polyimide microcapsules obtained in Step 2 with 9g of polyetherimide resin, and disperse in 100mL of ethanol and stir for 15min. After the solvent is evaporated by heating, the mixture is placed in a mold and hot-pressed at 320°C for 1.5 hours to obtain a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules.

[0029] The microstructure of the lubricating oil-containing polyimide microcapsules prepared in step one of this embodiment is shown in the figure below. Figure 1 As shown; the surface morphology of the aminated carbon nanotube-coated polyimide microcapsules in step two of this embodiment is as follows. Figure 2 As shown.

[0030] like Figure 3 As shown, the heat resistance of the microcapsules before and after the assembly of aminated carbon nanotubes is compared. After assembly, the initial decomposition temperature of the lubricating oil increases to 406℃.

[0031] Example 2 The difference between this embodiment and embodiment 1 is that in step three of this embodiment, the mass ratio of high-temperature resistant, interface-reinforced polyimide microcapsules to polyetherimide resin is 15:85. The methods and parameters of the remaining steps in this embodiment are the same as those in embodiment 1.

[0032] Example 3 The difference between this embodiment and Embodiment 1 is that the polyetherimide resin in step three is replaced with an equal mass of polyetheretherketone resin. The methods and parameters of the remaining steps in this embodiment are the same as those in Embodiment 1.

[0033] Comparative Example 1 This comparative example uses the same molding process as Example 1, but only uses pure polyetherimide resin for hot pressing to obtain the comparative sample.

[0034] like Figure 4 The test results show that the polyetherimide material prepared in this comparative example has a high coefficient of friction, significant wear, and does not exhibit self-lubricating properties. The test conditions were: the composite material was rubbed against a steel ball, the test load was 5 N, the rotation speed was 1 cm / s, the running time was 1.0 h, and the wear rate was the average of 3 to 5 tests.

[0035] Comparative Example 2 In this comparative example, the self-lubricating composite material was directly mixed with benzyl silicone oil and polyetherimide resin at a mass ratio of 1:9 and then hot-pressed. During the molding process, lubricating oil volatilization or migration occurred, resulting in unstable frictional properties and a significant decrease in mechanical properties.

[0036] Comparative Example 3 A method for preparing a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules includes the following steps: Step 1: Dissolve 10g of soluble polyvinylpyrrolidone in 500mL of deionized water to form an aqueous phase; Dissolve 2g of 6FDA-based polyimide in a mixed solvent of 80mL dichloromethane and 20mL trichloromethane, and add 2g of benzyl silicone oil to form an oil phase; The oil phase was added to the aqueous phase and emulsified at 15,000 rpm for 8 min. Then, the mixture was stirred at 37 °C for 5 h to allow the solvent to evaporate and form a polyimide coating layer on the surface of the lubricating oil, thus obtaining lubricating oil-containing polyimide microcapsules. Step 2: Mix 1g of the lubricating oil-containing polyimide microcapsules obtained in Step 1 with 9g of polyetherimide resin, and disperse them in 100mL of ethanol and stir for 15min. After the solvent is evaporated by heating, the mixture is placed in a mold and hot-pressed at 320°C for 1.5 hours to obtain a self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules.

[0037] The friction coefficients of the samples obtained in Examples 1-3 and Comparative Examples 1-3 were measured respectively, and the results are shown in the table below: Table 1. Comparison of friction coefficients of samples from Examples 1-3 and Comparative Examples 1-3. The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0038] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a self-lubricating composite material based on high-temperature-resistant lubricating oil microcapsules, characterized in that, Includes the following steps: Step 1: Prepare lubricating oil-containing polyimide microcapsules using soluble polyimide; Step 2: Disperse the lubricating oil-containing polyimide microcapsules in an aqueous solution containing polyelectrolytes to modify the surface of the lubricating oil-containing polyimide microcapsules, forming a charged modified layer on the surface of the lubricating oil-containing polyimide microcapsules. Then, load nanomaterials with functionalized surfaces to obtain high-temperature resistant, interface-enhanced polyimide microcapsules. Step 3: Mix and disperse high-temperature resistant, interface-reinforced polyimide microcapsules with high-performance thermoplastic engineering plastics, and then mold them to prepare a self-lubricating composite material.

2. The method for producing a high-temperature-resistant lubricating oil microcapsule-based self-lubricating composite material according to claim 1, characterized by, The soluble polyimide is a polyimide containing hexafluoroisopropyl structural units.

3. The method for preparing a high-temperature-resistant lubricating oil microcapsule-based self-lubricating composite material according to claim 1, characterized in that, In step one, the specific method for preparing lubricating oil-containing polyimide microcapsules using soluble polyimide includes: An aqueous / oil phase emulsion system was used to mix soluble polyimide, lubricating oil, and halogenated hydrocarbon solvent to form an oil phase, while a water-soluble polymeric stabilizer was dissolved in water to form an aqueous phase. Under high shear conditions, the oil phase was dispersed in the aqueous phase to form a stable emulsion, and the solvent was gradually evaporated under temperature-controlled stirring conditions, thereby forming a polyimide coating layer on the surface of the lubricating oil, resulting in lubricating oil-containing polyimide microcapsules.

4. The method for producing a high-temperature-resistant lubricating oil microcapsule-based self-lubricating composite material according to claim 3, characterized by, The lubricating oil includes one or a combination of two of benzyl silicone oil and polyalphaolefin lubricating oil. The halogenated hydrocarbon solvent includes one of dichloromethane and trichloromethane; The mass ratio of soluble polyimide, lubricating oil and halogenated hydrocarbon solvent is 1~5:1~8:110~150; The water-soluble polymeric stabilizer includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, gelatin, sodium dodecylbenzene sulfonate, and polyethylene glycol octylphenyl ether; the mass ratio of the water-soluble polymeric stabilizer to water is 1:100 to 5:

100. The volume ratio of the oil phase to the water phase is 1:1 to 1:

5.

5. The method for preparing a high-temperature-resistant lubricating oil microcapsule-based self-lubricating composite material according to claim 1, characterized by, In step two, the polyelectrolyte solution includes one or more of sodium polystyrene sulfonate solution, polyethylene sulfonic acid solution, and poly(2-acrylamide-2-methylpropanesulfonic acid) solution, and the concentration of the polyelectrolyte solution is 1~20 mg / mL; the ratio of the soluble polyimide to the polyelectrolyte solution is 1~5 g:100 mL.

6. The method for preparing a high-temperature-resistant lubricating oil microcapsule-based self-lubricating composite material according to claim 1, characterized by, In step two, the nanomaterial with functionalized surface includes one or more of the following: aminated carbon nanotubes, aminated graphene, aminated graphene quantum dots, surface oxygen ionized MXene, aminated boron nitride, aminated MoS2, and aminated g-C3N4; the mass ratio of the nanomaterial with functionalized surface to the lubricating oil-containing polyimide microcapsules is 1:20 to 1:

5.

7. The method for preparing the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules as described in claim 1, characterized in that, In step three, the high-temperature resistant, interface-reinforced polyimide microcapsules account for 5% to 20% of the mass of the self-lubricating composite material.

8. The method for preparing the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules as described in claim 1, characterized in that, The high-performance thermoplastic engineering plastic includes one or a mixture of two or more of polyetherimide, polyetheretherketone, polyphenylene sulfide, and polysulfone.

9. The method for preparing the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules as described in claim 1, characterized in that, The molding method includes hot pressing, injection molding or extrusion molding; wherein the hot pressing temperature is 320~350℃ and the hot pressing time is 30~120min.

10. A self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules, characterized in that, The self-lubricating composite material is prepared by the preparation method of the self-lubricating composite material based on high-temperature resistant lubricating oil microcapsules as described in any one of claims 1-9.

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