Double-walled self-lubricating microcapsule, preparation method and application thereof

Abstract

The present disclosure relates to a double-walled self-lubricating microcapsule, a preparation method and application thereof. The double-walled self-lubricating microcapsule is composed of a lubricant and a carbon layer and a polydopamine layer which are sequentially wrapped outside the lubricant. The double-walled self-lubricating microcapsule provided by the present disclosure has excellent thermal stability, compactness and good compatibility with polymers, and the release rate of the lubricant is stable and controllable. The present disclosure utilizes hollow carbon spheres and lubricants to obtain single-walled microcapsules by impregnation, and then utilizes polydopamine to coat the surface of the single-walled microcapsules to form a double-walled structure. The preparation method is simple and easy to operate, has strong operability, low cost, is suitable for industrial application, and has good economic benefits.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of lubricating materials, in particular to a double-wall self-lubricating microcapsule and a preparation method and application thereof. BACKGROUND

[0002] Friction and wear are the main reasons for mechanical component failure and energy loss. Polymer-based self-lubricating materials are widely used in tribology due to their good self-lubricating properties, light weight, and excellent environmental adaptability, and are widely used in mechanical lubricating parts such as aerospace and oil field chemical industry.

[0003] Microcapsule type self-lubricating polymer material is a new type of self-lubricating material, which fills microcapsules into a polymer matrix. The microcapsule has a "core-shell" structure, the capsule core contains a lubricant, and the capsule wall is generally made of a material with a high melting point, mainly including polysulfone (PSF), polydopamine (PDA), melamine urea formaldehyde resin (MUF), polymethyl methacrylate (PMMA), graphite, SiO2, CaCO3, etc. However, the organic capsule wall generally has the disadvantages of poor compactness, poor high-temperature resistance, and brittleness and fragility. As for the inorganic capsule wall such as graphite, SiO2, and CaCO3, the synthesis process is relatively complex, which leads to the problems of brittleness and fragility of the capsule wall, poor temperature resistance, poor compatibility with the polymer matrix, and poor compactness leading to oil leakage, thereby limiting its further processing and application, and it is difficult to meet the requirements of modern high-performance resin matrix under high temperature, high pressure, high speed, and other conditions.

[0004] Therefore, it is of great significance to develop a microcapsule with high temperature resistance, good compactness, and good compatibility with the polymer matrix. SUMMARY

[0005] In order to solve the above technical problems, the present disclosure provides a double-wall self-lubricating microcapsule and a preparation method and application thereof. The double-wall self-lubricating microcapsule provided by the present disclosure has excellent thermal stability, compactness, and good compatibility with polymers, and has a stable and controllable lubricant release rate.

[0006] In a first aspect, the present disclosure provides a double-wall self-lubricating microcapsule, which is composed of a lubricant and a carbon layer and a polydopamine layer wrapped outside the lubricant in sequence.

[0007] The double-wall self-lubricating microcapsule provided by the present disclosure has excellent thermal stability, compactness, and good compatibility with polymers, and has a stable and controllable lubricant release rate. Specifically,

[0008] The double-wall self-lubricating microcapsule provided by the present disclosure has a core-shell structure, and the carbon material and the polydopamine in the capsule wall can effectively protect the lubricant in the capsule core, thereby improving the stability of the capsule core, having a stable and controllable lubricant release rate and high temperature resistance. Meanwhile, the present disclosure uses polydopamine as the outer wall material of the capsule wall structure, which has good compatibility with polymers, can effectively improve the hydrophilicity of the microcapsule, the compatibility with polymers and the thermal stability, and thereby ensures the mechanical properties of the microcapsule.

[0009] As a preferred technical solution of the present disclosure, the mass ratio of the lubricant to the carbon layer is (1-200):1, for example, 2:1, 5:1, 10:1, 20:1, 50:1, 100:1, 150:1, 180:1, etc.

[0010] As a preferred technical solution of the present disclosure, the mass ratio of the carbon layer to the polydopamine layer is (1-100):1, for example, 2:1, 5:1, 10:1, 20:1, 50:1, 80:1, 90:1, etc.

[0011] As a preferred technical solution of the present disclosure, the particle size of the double-wall self-lubricating microcapsule is 0.1-60 μm, for example, 0.2 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, etc.

[0012] As a preferred technical solution of the present disclosure, the thickness of the carbon layer is 0.01-10 μm, for example, 0.02 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm, etc.

[0013] As a preferred technical solution of the present disclosure, the thickness of the polydopamine layer is 0.01-1 μm, for example, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, etc.

[0014] As a preferred technical solution of the present disclosure, the lubricant is selected from oil-soluble lubricating oil and / or ionic liquid.

[0015] As a preferred technical solution of the present disclosure, the oil-soluble lubricating oil is selected from any one or a combination of at least two of perfluoropolyether (PFPE) lubricating oil, polyalkylene glycol (PAG) lubricating oil, polyalphaolefin (PAO) lubricating oil, alkylbenzene lubricating oil, saturated polyol ester lubricating oil, silicone oil lubricating oil, polyester lubricating oil or phosphate ester lubricating oil.

[0016] As a preferred technical solution of the present disclosure, the ionic liquid is selected from any one or a combination of at least two of trifluoroacetate ionic liquid, triflate ionic liquid, tetrafluoroborate ionic liquid, or hexafluorophosphate ionic liquid.

[0017] As a preferred technical solution of the present disclosure, the ionic liquid is selected from any one or a combination of at least two of 1-hexyl imidazole trifluoroacetate, 1-octyl imidazole triflate, 1-ethyl-3-methyl imidazole tetrafluoroborate, 1-octyl imidazole tetrafluoroborate, 2-fluoro-1,3-dimethyl imidazole hexafluorophosphate, or 1-allyl-3-methyl imidazole hexafluorophosphate.

[0018] In a second aspect, the present disclosure provides a preparation method of the double-wall self-lubricating microcapsule of the first aspect, and the preparation method comprises the following steps:

[0019] (1) The hollow carbon sphere is immersed in a lubricant, so that the hollow structure of the hollow carbon sphere is filled with the lubricant, to obtain a single-wall microcapsule coated with a carbon layer and a lubricant;

[0020] (2) The single-wall microcapsule is coated with polydopamine to obtain the double-wall self-lubricating microcapsule.

[0021] The present disclosure uses a hollow carbon sphere and a lubricant to obtain a single-wall microcapsule by immersion, and then uses polydopamine to coat the surface of the single-wall to form a double-wall structure, thereby solving the problems of easy breakage, poor compactness, and poor temperature resistance of the single-wall microcapsule. Moreover, polydopamine has good compatibility with polymers, which greatly enhances the compatibility of the microcapsule with the polymer matrix and avoids the risk of oil leakage.

[0022] The preparation method provided by the present disclosure is simple and easy to operate, has strong operability, low cost, and is suitable for industrial application, and has good economic benefits.

[0023] As a preferred technical solution of the present disclosure, the particle size of the hollow carbon sphere is 0.1-50 μm, for example, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, etc. The particle size of the hollow carbon sphere in the present disclosure is the average particle size of the hollow carbon sphere (±0.5 μm).

[0024] As a preferred technical solution of the present disclosure, the wall thickness of the hollow carbon sphere is 0.01-10 μm, for example, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, etc.

[0025] As a preferred technical solution of the present disclosure, step (1) is performed in a negative pressure environment.

[0026] As a preferred technical solution of the present disclosure, the impregnation time in step (1) is 12-168 h, such as 15 h, 20 h, 50 h, 80 h, 100 h, 120 h, 150 h, etc.

[0027] As a preferred technical solution of the present disclosure, stirring is required during the impregnation in step (1), and the stirring rate is 200-1000 rpm, such as 400 rpm, 600 rpm, 800 rpm, etc.

[0028] As a preferred technical solution of the present disclosure, the mass ratio of the hollow carbon spheres to the lubricant in step (1) is 1:(1-200), such as 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:150, 1:180, etc.

[0029] As a preferred technical solution of the present disclosure, step (1) further comprises drying after impregnation, which can be room temperature natural drying, oven drying, freeze drying, etc.

[0030] As a preferred technical solution of the present disclosure, step (2) is: dispersing the single-walled microcapsules in a buffer containing dopamine hydrochloride, and performing a polymerization reaction on the dopamine hydrochloride to form a polydopamine coating layer on the surface of the single-walled microcapsules.

[0031] As a preferred technical solution of the present disclosure, the polymerization reaction time in step (2) is 6-48 h, such as 8 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, etc.

[0032] In the present disclosure, stirring is required during the polymerization reaction in step (2), and the polymerization reaction is performed in an oxygen-containing atmosphere.

[0033] As a preferred technical solution of the present disclosure, step (2) further comprises drying after coating.

[0034] As a preferred technical solution of the present disclosure, the drying can be room temperature natural drying, oven drying, freeze drying, etc.

[0035] As a preferred technical solution of the present disclosure, in the buffer, the concentration of the dopamine hydrochloride is 0.1-20 mg / mL, such as 0.5 mg / mL, 1 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, etc.

[0036] As a preferred technical solution of the present disclosure, the mass ratio of the single-walled microcapsules to the dopamine hydrochloride is 1:(0.1-10), such as 1:0.2, 1:0.5, 1:1, 1:2, 1:5, 1:8, etc.

[0037] The present disclosure does not excessively limit the source of the hollow carbon spheres, which can be commercially available or self-made, and any hollow carbon spheres that can be applied to the present disclosure can be used.

[0038] The present disclosure also provides a preparation method of the hollow carbon spheres, comprising the following steps:

[0039] (1) mixing tetrapropoxysilane with an ethanol / water solution, adding ammonia water, stirring uniformly, adding resorcinol and formaldehyde to fully react, to obtain a turbid solution;

[0040] (2) centrifuging the turbid solution, washing, drying, carbonizing, reacting in a sodium hydroxide solution, washing, and drying to obtain the hollow carbon spheres.

[0041] As a specific embodiment of the present disclosure, the preparation method of the hollow carbon spheres comprises the following steps:

[0042] (1) adding 1-100 mL of tetrapropoxysilane to 0.1-2 L of an ethanol / water mixed solution, adding 1-50 mL of ammonia water, stirring uniformly, then adding 0.1-50 g of resorcinol and 1-50 mL of formaldehyde, and fully reacting for 8-48 h to obtain a turbid solution;

[0043] (2) centrifuging the obtained turbid solution, washing, drying, carbonizing, and other processes, reacting the sample in a 1-5 M sodium hydroxide solution for 8-48 h, and washing and drying to obtain the hollow carbon spheres.

[0044] In a third aspect, the present disclosure provides an application of the double-walled self-lubricating microcapsule of the first aspect in aerospace lubricants, mechanical lubricants, or building lubricants.

[0045] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0046] 1. The double-walled self-lubricating microcapsule provided by the present disclosure has excellent thermal stability, compactness, and good compatibility with polymers, and the lubricant release rate is stable and controllable.

[0047] 2. The present disclosure uses hollow carbon spheres and lubricants to obtain single-walled microcapsules by impregnation, and then uses polydopamine to coat the surface of the single-walled structure to form a double-walled structure. The preparation method is simple and easy to operate, has strong operability, is low in cost, is suitable for industrial application, and has good economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0048] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present disclosure and, together with the specification, serve to explain the principles of the present disclosure.

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0050] Figure 1 SEM image of the double-wall microcapsules according to Example 1 of the present disclosure;

[0051] Figure 2 SEM image of the single-wall microcapsules according to Comparative Example 1 of the present disclosure;

[0052] Figure 3 Thermogravimetric curve of the microcapsules obtained according to Example 1 and Comparative Example 1 of the present disclosure and PFPE lubricating oil;

[0053] Figure 4 Thermogravimetric curve of the microcapsules obtained according to Example 2 and Comparative Example 2 of the present disclosure and PAO6 lubricating oil;

[0054] Figure 5 Thermogravimetric curve of the microcapsules obtained according to Comparative Example 4 of the present disclosure;

[0055] Figure 6 Friction performance diagram of the microcapsule composite polyimide material prepared according to Example 1 and Comparative Example 1 of the present disclosure and pure polyimide. DETAILED DESCRIPTION

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0057] In the following description, many specific details are set forth in order to provide a thorough understanding of the present disclosure. However, the present disclosure can be practiced without the specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the present disclosure.

[0058] Preparation Example 1

[0059] The present preparation example provides a preparation method of hollow carbon spheres, comprising the following steps:

[0060] (1) 50 mL of tetrapropoxysilane is added to 1 L of ethanol / water mixed solution, 25 mL of ammonia water is added, and after stirring uniformly, 25 g of resorcinol and 25 mL of formaldehyde are added, and the reaction is carried out for 24 h to obtain a turbid solution;

[0061] (2) The obtained turbid solution is centrifuged, washed, dried, carbonized, and the like, and the sample is placed in a 3M sodium hydroxide solution for reaction for 24h, and then washed and dried to obtain the hollow carbon sphere.

[0062] Example 1

[0063] The embodiment provides a double-wall self-lubricating microcapsule and a preparation method thereof, the double-wall self-lubricating microcapsule is composed of a lubricant and a carbon layer and a polydopamine layer wrapped outside the lubricant in sequence, and the double-wall self-lubricating microcapsule comprises the following components in percentage by mass:

[0064] The mass ratio of the lubricant and the carbon layer is 4:1, the mass ratio of the carbon layer and the polydopamine layer is 1:1, the thickness of the carbon layer is 0.05μm, and the thickness of the polydopamine layer is 0.05μm;

[0065] The preparation method of the double-wall self-lubricating microcapsule comprises the following steps:

[0066] (1) 5g of hollow carbon spheres and 20g of PFPE lubricating oil are placed in a sealed three-necked flask, impregnated under vacuum at 500rpm for 48h, filtered and dried to obtain single-wall microcapsules PFPE@HMC, and the average particle size of the hollow carbon spheres is 0.5μm;

[0067] (2) 10g of PFPE@HMC single-wall microcapsules and 2g of dopamine hydrochloride are dissolved in 1L of Tris HCl buffer solution, magnetically stirred for 24h, and then vacuum filtration, washing and drying are performed on the reacted solution to obtain PFPE@HMC / PDA double-wall microcapsules.

[0068] Example 2

[0069] The embodiment provides a double-wall self-lubricating microcapsule and a preparation method thereof, the double-wall self-lubricating microcapsule is composed of a lubricant and a carbon layer and a polydopamine layer wrapped outside the lubricant in sequence, and the double-wall self-lubricating microcapsule comprises the following components in percentage by mass:

[0070] The mass ratio of the lubricant and the carbon layer is 200:1, the mass ratio of the carbon layer and the polydopamine layer is 50:1, the thickness of the carbon layer is 5μm, and the thickness of the polydopamine layer is 0.5μm;

[0071] The preparation method of the double-wall self-lubricating microcapsule comprises the following steps:

[0072] (1) 5g of hollow carbon spheres and 1000g of PAO6 lubricating oil are placed in a sealed three-necked flask, impregnated under vacuum at 1000rpm for 12h, filtered and dried to obtain PAO6@HMC single-wall microcapsules, and the average particle size of the hollow carbon spheres is 50μm;

[0073] (2) Take 1010g [Emim]BF4@HMC single-walled microcapsules and 0.1g dopamine hydrochloride into 1L Tris HCl buffer solution, magnetic stirring for 6h, vacuum filtration and washing after the reaction solution is dried, to obtain [Emim]BF4@HMC / PDA double-walled microcapsules.

[0074] Example 3

[0075] The embodiment provides a double-walled self-lubricating microcapsule and a preparation method thereof.

[0076] The mass ratio of the lubricant and the carbon layer is 100:1, the mass ratio of the carbon layer and the polydopamine layer is 100:1, the thickness of the carbon layer is 10μm, and the thickness of the polydopamine layer is 0.8μm.

[0077] The preparation method of the double-walled self-lubricating microcapsule comprises the following steps.

[0078] (1) Take 10g hollow carbon spheres and 1000g 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4) ionic liquid into a sealed three-necked flask, immerse in a vacuum state under 200rpm stirring for 168h, filter and dry to obtain [Emim]BF4@HMC single-walled microcapsules, and the average particle size of the hollow carbon spheres is 25μm.

[0079] (2) Take 1010g [Emim]BF4@HMC single-walled microcapsules and 0.1g dopamine hydrochloride into 1L Tris HCl buffer solution, magnetic stirring for 6h, vacuum filtration and washing after the reaction solution is dried, to obtain [Emim]BF4@HMC / PDA double-walled microcapsules.

[0080] Examples 4-5

[0081] The embodiment provides a double-walled self-lubricating microcapsule and a preparation method thereof.

[0082] The difference from the embodiment 1 is that in the embodiment, the PFPE lubricating oil is replaced by AB-6 lubricating oil (Example 4) and 1-hexyl imidazole trifluoroacetate (Example 5) respectively in the step (1) of the preparation method of the double-walled self-lubricating microcapsule.

[0083] Comparative Example 1

[0084] The comparative example provides a single-walled self-lubricating microcapsule and a preparation method thereof, and the difference from the embodiment 1 is that in the comparative example, the single-walled microcapsule is prepared in the step (1) of the preparation method, and then the coating of the second outer wall is not performed.

[0085] Comparative Example 2

[0086] The present comparative example provides a single-wall self-lubricating microcapsule and a preparation method thereof, which is different from Example 2 in that, in the present comparative example, after the single-wall microcapsule is prepared in step (1) of the preparation method, no coating of the second outer wall is performed.

[0087] Comparative Example 3

[0088] The present comparative example provides a single-wall self-lubricating microcapsule and a preparation method thereof, which is different from Example 3 in that, in the present comparative example, after the single-wall microcapsule is prepared in step (1) of the preparation method, no coating of the second outer wall is performed.

[0089] Comparative Example 4

[0090] The present comparative example provides a double-wall self-lubricating microcapsule and a preparation method thereof, which is different from Example 1 in that, in the present comparative example, dopamine hydrochloride is replaced by silane coupling agent KH550 in step (2) of the preparation method.

[0091] Comparative Example 5

[0092] The present comparative example provides a double-wall self-lubricating microcapsule and a preparation method thereof, which is different from Example 1 in that, in the present comparative example, hollow carbon spheres are replaced by hollow silica spheres in step (1) of the preparation method.

[0093] Performance Test 1

[0094] The microcapsules obtained in Example 1 and Comparative Example 1 were subjected to scanning electron microscope (SEM) tests, Figure 1 is an SEM image of the double-wall microcapsule obtained in Example 1, Figure 2 is an SEM image of the single-wall microcapsule obtained in Comparative Example 1.

[0095] From the comparison between Figure 1 and Figure 2 , it can be seen that dopamine hydrochloride self-polymerizes on the surface of the single-wall microcapsule in the Tris HCl buffer solution, and the double-wall microcapsule prepared has a clear PDA coating layer on the surface, while the surface of the single-wall microcapsule is relatively smooth.

[0096] Performance Test 2

[0097] The microcapsules obtained in Examples 1-5 and Comparative Examples 1-5 as well as PFPE lubricating oil were subjected to thermogravimetric analysis to investigate the oil content of the microcapsules. The test method was as follows: 5 mg of sample was placed in a crucible, heated to above 500℃ at a rate of 10℃ / min, and cooled to room temperature to obtain the thermogravimetric curve data, as shown in Table 1 and Figures 3-5 . Figure 3 is the thermogravimetric curve of the microcapsules obtained in Example 1, Comparative Example 1 and PFPE lubricating oil, Figure 4Thermogravimetric curve of the microcapsules obtained in Example 2, Comparative Example 2 and PAO6 lubricating oil, Figure 5 Thermogravimetric curve of the microcapsules obtained in Comparative Example 4.

[0098] Table 1

[0099] Sample Maximum service temperature / °C Oil content Example 1 309.75 90 wt% Example 2 257.88 82 wt% Example 3 435.95 75 wt% Example 4 356.58 81 wt% Example 5 206.91 67 wt% Comparative Example 1 253.31 73 wt% Comparative Example 2 194.71 68 wt% Comparative Example 3 400.95 57 wt% Comparative Example 4 68.57 11 wt% Comparative Example 5 299.80 44 wt%

[0100] As can be seen from Table 1, single-wall and double-wall affect the oil content of the microcapsules. Compared with single-wall microcapsules, the oil content of double-wall microcapsules is significantly improved. The single-wall microcapsules coated by polydopamine in the present disclosure can effectively protect the core, prevent the leakage of lubricant, improve the stability of the core, and have a stable and controllable release rate.

[0101] In addition, the use temperature of the double-wall microcapsules prepared in the present disclosure is much higher than that of single-wall microcapsules. The maximum use temperature of the microcapsules is affected by the thermal volatilization temperature of the selected core lubricant. Combined with Table 1 and Figures 3-5 It can be seen that PFPE lubricating oil, PAO6 lubricating oil and [Emim]BF4 ionic liquid are decomposed at 285.67℃, 233.37℃ and 400.95℃, respectively. The maximum use temperature of the double-wall microcapsules is higher than the thermal volatilization temperature of the lubricant, and the maximum use temperature of the single-wall microcapsules is lower than the thermal volatilization temperature of the lubricant. Therefore, the coating of single-wall microcapsules with polydopamine improves the thermal stability of the microcapsules, indicating that the double-wall microcapsules have significantly improved high temperature resistance compared with single-wall microcapsules.

[0102] And from the comparison of Example 1 and Comparative Example 4, it can be seen that polydopamine as the outer wall of the double-wall microcapsule has better effect than silane coupling agent. From the comparison of Example 1 and Comparative Example 5, it can be seen that hollow carbon spheres as the inner wall of the double-wall microcapsule have better effect than hollow silica spheres.

[0103] Application Example

[0104] The microcapsules prepared in Examples 1-5 and Comparative Examples 1-5 are added as additives to polyimide (PI) film (the addition amount is 5wt%), and the microcapsule composite polyimide material is obtained by curing at high temperature.

[0105] Performance Test 3

[0106] The microcapsule composite polyimide material obtained in the application example and pure polyimide (blank example) are subjected to reciprocating friction and wear test: the test sample is fixed on a horizontal sample table, and the support and the moving platform are relatively moved by changing the speed and load conditions, so that the measured sample is subjected to plane reciprocating friction and wear. The friction coefficient generated during the friction process is the ratio of the friction force between the two surfaces to the vertical force acting on one surface. The test results are shown in Table 2 andFigure 6 As shown, Figure 6 The friction performance chart of the microcapsule composite polyimide material prepared for Example 1, Comparative Example 1, and pure polyimide.

[0107] Table 2

[0108]

[0109]

[0110] From Table 2 and Figure 6 It can be found that the friction coefficient of the double-wall microcapsule composite polyimide prepared by the present disclosure is low, wherein the friction coefficient of pure polyimide is about 0.4-0.5, the friction coefficient of PFPE@HMC single-wall microcapsule is 0.2, and the friction coefficient of PFPE@HMC / PDA double-wall microcapsule is 0.1, which proves that the coating of polydopamine on the single-wall microcapsule improves the compatibility between the microcapsule and the polymer and greatly improves the lubricating performance of the composite material.

[0111] It should be noted that, in this document, relational terms such as“first” and“second”, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms“comprises”,“comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element preceded by“comprises... a” does not, without more limitations, foreclose the existence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0112] The above description is merely that of specific embodiments of the present disclosure to enable a person skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A double-walled self-lubricating microcapsule, characterized in that, The double-walled self-lubricating microcapsule is composed of a lubricant and a carbon layer and a polydopamine layer sequentially wrapped around the outside of the lubricant. The carbon layer is a hollow carbon sphere, and the lubricant fills the hollow structure of the hollow carbon sphere.

2. The double-walled self-lubricating microcapsule according to claim 1, characterized in that, The mass ratio of the lubricant to the carbon layer is (1-200):1; And / or, the mass ratio of the carbon layer to the polydopamine layer is (1-100):

1.

3. The double-walled self-lubricating microcapsule according to claim 1 or 2, characterized in that, The particle size of the double-walled self-lubricating microcapsules is 0.1-60 μm; And / or, the thickness of the carbon layer is 0.01-10 μm; And / or, the thickness of the polydopamine layer is 0.01-1 μm.

4. The double-walled self-lubricating microcapsule according to claim 1 or 2, characterized in that, The lubricant is selected from oil-soluble lubricating oils and / or ionic liquids.

5. The double-walled self-lubricating microcapsule according to claim 4, characterized in that, The oil-soluble lubricating oil is selected from any one or a combination of at least two of the following: perfluoropolyether lubricating oil, polyalkylene glycol lubricating oil, polyalphaolefin lubricating oil, alkylbenzene lubricating oil, saturated polyol ester lubricating oil, silicone oil lubricating oil, polyester lubricating oil, or phosphate ester lubricating oil.

6. The double-walled self-lubricating microcapsule according to claim 4, characterized in that, The ionic liquid is selected from any one or a combination of at least two of the following: trifluoroacetate ionic liquids, trifluoromethanesulfonate ionic liquids, tetrafluoroborate ionic liquids, or hexafluorophosphate ionic liquids.

7. The double-walled self-lubricating microcapsule according to claim 6, characterized in that, The ionic liquid is selected from any one or a combination of at least two of the following: 1-hexylimidazolium trifluoroacetate, 1-octylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-octylimidazolium tetrafluoroborate, 2-fluoro-1,3-dimethylimidazolium hexafluorophosphate, or 1-allyl-3-methylimidazolium hexafluorophosphate.

8. The method for preparing the double-walled self-lubricating microcapsules according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Hollow carbon spheres are impregnated in lubricant so that the lubricant fills the hollow structure of the hollow carbon spheres, thereby obtaining single-walled microcapsules of lubricant coated with carbon layer; (2) The single-walled microcapsules were coated with polydopamine to obtain the double-walled self-lubricating microcapsules.

9. The preparation method according to claim 8, characterized in that, The hollow carbon spheres have a particle size of 0.1-50 μm; And / or, the wall thickness of the hollow carbon sphere is 0.01-10 μm.

10. The preparation method according to claim 8 or 9, characterized in that, Step (1) is carried out under negative pressure, and the immersion time is 12-168 h; And / or, the mass ratio of the hollow carbon ball to the lubricant in step (1) is 1:(1-200).

11. The preparation method according to claim 10, characterized in that, Step (2) is as follows: the single-walled microcapsules are dispersed in a buffer solution containing dopamine hydrochloride, and the dopamine hydrochloride undergoes a polymerization reaction to form a polydopamine coating layer on the surface of the single-walled microcapsules; And / or, step (2) may also include drying after coating.

12. The preparation method according to claim 11, characterized in that, In the buffer solution, the concentration of dopamine hydrochloride is 0.1-20 mg / mL; And / or, the mass ratio of the single-walled microcapsule to the dopamine hydrochloride is 1:(0.1-10).

13. The use of the double-walled self-lubricating microcapsules according to any one of claims 1-7 in aerospace lubricants, machinery lubricants or building lubricants.

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