A composite material based on MOFs and a self-lubricating fabric composite material as well as preparation method and application thereof

Abstract

The present invention belongs to the technical field of lubricating materials, and provides a MOFs-based composite material and a self-lubricating fabric composite material, as well as a preparation method and application thereof. In the MOFs-based composite material provided by the present invention, the phase change material can continuously release friction stress to achieve self-lubrication; titanium dioxide with high thermal conductivity helps to improve the thermal stability of the self-lubricating fabric composite material. Cu-MOFs not only exhibits excellent lubrication properties, but also reduces the impact of large-sized microcapsules on the self-lubricating fabric composite material. The MOFs-based composite material of the present invention is used as a reinforcing material to modify the self-lubricating fabric composite material, and nano-scale flexible Cu-MOFs and large-sized microcapsules are combined to form micro-nanostructured capsules. The tribological properties of the self-lubricating fabric composite material are significantly enhanced by their complementary reinforcing effect, thereby extending the service life of the self-lubricating fabric composite material as a component of the lubricating layer.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating materials, and in particular to a MOFs-based composite material and a self-lubricating fabric composite material, as well as a preparation method and application thereof. Background Art

[0002] Friction is a fundamental phenomenon in human life, and the resulting wear and tear seriously impacts the operational reliability and lifespan of large-scale industrial equipment. The development of self-lubricating materials has become an effective solution to this problem, as they provide continuous lubrication without the need for external lubricants. Self-lubricating fabric composites, with their high modulus, high strength, and wear resistance, play a vital role in many fields, including aerospace, water conservancy vessels, and weaponry. Although self-lubricating fabric composites are already widely used, their improvement continues to flourish due to increasingly demanding service environments and the increasing demands on equipment performance.

[0003] Research has shown that there are three main approaches to improving self-lubricating textile composites: manipulating the fabric's microstructure, enhancing the fiber-resin interface, and adding functional reinforcements. Adding functional reinforcements is currently the most popular modification method. Metal-organic frameworks (MOFs) are a class of porous crystalline materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination. MOFs have advantages such as adjustable shape, large specific surface area, good thermal stability, and ease of shearing, and have been successfully used to enhance the tribological properties of composites. However, the effect of adding MOFs on improving the tribological properties of self-lubricating textile composites is limited. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a composite material and a self-lubricating fabric composite material based on MOFs, as well as a preparation method and application thereof. The MOFs-based composite material provided by the present invention can significantly improve the tribological properties of the self-lubricating fabric composite material.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a composite material based on MOFs, comprising microcapsules, and MOFs bound to the microcapsules;

[0007] The microcapsule comprises a capsule core and a capsule wall surrounding the capsule core;

[0008] The capsule core is a phase change material, the capsule wall is titanium dioxide, and the MOFs are Cu-MOFs.

[0009] Preferably, the phase change material includes one or more of n-docosane, eicosane, octadecane and hexadecane, and the thickness of the capsule wall is 50 to 200 nm.

[0010] Preferably, the Cu-MOFs have a two-dimensional layered structure.

[0011] Preferably, the Cu-MOFs are bound to the microcapsules through electrostatic interactions, the microcapsules are positively charged, and the Cu-MOFs are negatively charged.

[0012] The present invention also provides a method for preparing the MOFs-based composite material described in the above technical solution, comprising the following steps:

[0013] mixing a phase change material, an emulsifier and an organic solvent, and emulsifying the mixture to obtain an oil-in-water emulsion;

[0014] The oil-in-water emulsion and the titanium dioxide precursor are mixed to perform a pre-reaction. After the pre-reaction is completed, acetic acid and a mixed solvent are sequentially added to the obtained reaction system to perform hydrolysis to obtain microcapsules;

[0015] After the microcapsules and cationic electrolytes are mixed, Cu-MOFs are added to the obtained mixed system to perform self-assembly to obtain the MOFs-based composite material.

[0016] Preferably, the preparation method of Cu-MOFs comprises the following steps:

[0017] dissolving a soluble copper salt to obtain a copper salt solution;

[0018] Mixing the copper salt solution and the organic ligand, and performing a hydrothermal reaction to obtain the Cu-MOFs;

[0019] The organic ligand includes terephthalic acid.

[0020] The present invention also provides a self-lubricating fabric composite material, comprising the MOFs-based composite material described in the above technical solution or the MOFs-based composite material prepared by the preparation method described in the above technical solution.

[0021] The present invention also provides a method for preparing the self-lubricating fabric composite material described in the above technical solution, comprising the following steps:

[0022] dispersing the MOFs-based composite material in a resin solution to obtain an impregnation solution;

[0023] The fabric is immersed in the impregnation liquid, taken out, and then hot-pressed and cured in sequence to obtain the self-lubricating fabric composite material.

[0024] Preferably, the mass of the MOFs-based composite material is 0.8-10% of the mass of the resin in the resin solution.

[0025] The present invention also provides the use of the MOFs-based composite material described in the above technical solution or the self-lubricating fabric composite material described in the above technical solution in a lubrication system.

[0026] The present invention provides a composite material based on MOFs, comprising microcapsules and MOFs bound to the microcapsules; the microcapsules comprise a capsule core and a capsule wall wrapping the capsule core; the capsule core is a phase change material, the capsule wall is titanium dioxide, and the MOFs are Cu-MOFs.

[0027] The MOFs-based composite material provided by the present invention has a phase change material that can continuously release frictional stress to achieve self-lubrication; titanium dioxide with high thermal conductivity helps to improve the thermal stability of the self-lubricating fabric composite material. Cu-MOFs not only exhibit excellent lubrication properties, but also reduce the impact of large-sized microcapsules on the self-lubricating fabric composite material. The MOFs-based composite material of the present invention is used as a reinforcing material to modify the self-lubricating fabric composite material. Nano-scale flexible Cu-MOFs and large-sized microcapsules are combined to form micro-nanostructured capsules. Their complementary reinforcement effect significantly enhances the tribological properties of the self-lubricating fabric composite material, thereby extending the service life of the self-lubricating fabric composite material as a component of the lubricating layer.

[0028] The present invention also provides a method for preparing the MOFs-based composite material described in the above technical solution. This method comprises synthesizing phase-change microcapsules comprising a phase-change material core and titanium dioxide walls through interfacial polycondensation. After the microcapsules are formed, a layer of Cu-MOFs is fixed to the surface of the phase-change microcapsules through electrostatic self-assembly to obtain the MOFs-based composite material. The preparation method provided by the present invention is simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM images of Cu-MOFs (a) obtained in Comparative Example 2, TiO2-MePCM (b) obtained in Comparative Example 3, and Cu-MOFs@TiO2-MePCM (c) obtained in Example 1;

[0030] Figure 2 XRD patterns of Cu-MOFs obtained in Comparative Example 2, TiO2-MePCM obtained in Comparative Example 3, Cu-MOFs@TiO2-MePCM obtained in Example 1, and n-docosane;

[0031] Figure 3Graphs showing the wear rate (a) and average friction coefficient (b) of the self-lubricating fabric composite materials obtained in Example 1 and Comparative Examples 1 to 3;

[0032] Figure 4 These are SEM photos of the worn surfaces of the self-lubricating textile composite material (a) obtained in Comparative Example 1 and the self-lubricating textile composite material (b) obtained in Example 1. DETAILED DESCRIPTION

[0033] The present invention provides a composite material based on MOFs, comprising microcapsules, and MOFs bound to the microcapsules;

[0034] The microcapsule comprises a capsule core and a capsule wall surrounding the capsule core;

[0035] The capsule core is a phase change material, the capsule wall is titanium dioxide, and the MOFs are Cu-MOFs.

[0036] The MOFs-based composite material provided herein includes microcapsules, each comprising a core and a wall surrounding the core. In the present invention, the phase change material preferably comprises one or more of n-docosane, eicosane, octadecane, and hexadecane, with n-docosane being more preferred. In the present invention, the wall is titanium dioxide, and the wall thickness is preferably 50 to 200 nm. In the present invention, the microcapsules preferably have a particle size of 1.4 to 3 μm.

[0037] The MOFs-based composite material provided by the present invention includes MOFs bound to the microcapsules, wherein the MOFs are Cu-MOFs, which refer to MOFs whose inorganic metal center is Cu. In the present invention, copper is a relatively soft metal compared to other metals, has good thermal conductivity and ductility, and the use of Cu-MOFs can improve the lubricity of the material. In the present invention, the Cu-MOFs preferably have a two-dimensional layered structure. In the present invention, Cu-MOFs with a two-dimensional layered structure are more conducive to improving lubrication performance. Cu-MOFs not only exhibit excellent lubrication performance, but also reduce the impact of large-sized microcapsules on the performance of the composite material.

[0038] In the present invention, the Cu-MOFs are preferably bound to the microcapsules through electrostatic interactions, the microcapsules are preferably positively charged, and the Cu-MOFs are preferably negatively charged.

[0039] The present invention also provides a method for preparing the MOFs-based composite material described in the above technical solution, comprising the following steps:

[0040] mixing a phase change material, an emulsifier and an organic solvent, and emulsifying the mixture to obtain an oil-in-water emulsion;

[0041] The oil-in-water emulsion and the titanium dioxide precursor are mixed to perform a pre-reaction. After the pre-reaction is completed, acetic acid and a mixed solvent are sequentially added to the obtained reaction system to perform hydrolysis to obtain microcapsules;

[0042] After the microcapsules and cationic electrolytes are mixed, Cu-MOFs are added to the obtained mixed system to perform self-assembly to obtain the MOFs-based composite material.

[0043] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0044] The present invention mixes a phase change material, an emulsifier and an organic solvent, and emulsifies the mixture to obtain an oil-in-water emulsion.

[0045] In the present invention, the emulsifier preferably includes one or more of sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate, polyethylene glycol ether, and Tween 80, and is more preferably sodium dodecyl sulfate. In the present invention, the organic solvent is preferably an amide, and the amide is preferably one or more of formamide, acetamide, and N,N-dimethylformamide, and is more preferably formamide.

[0046] In the present invention, the mass ratio of the phase change material to the emulsifier is preferably 2-12:2-12, more preferably 2-12:2-5, and specifically preferably 5:3.3. In the present invention, the amount ratio of the phase change material to the organic solvent is preferably 2-12g:40-120mL, more preferably 2-12g:50-100mL, and specifically preferably 5g:70mL.

[0047] In the present invention, the emulsification temperature is preferably 30-60°C, specifically preferably 30°C, 40°C, 50°C, 55°C or 60°C; the emulsification is preferably carried out under stirring (referred to as the first stirring), and the rotation speed of the first stirring is preferably 200-800rpm, specifically preferably 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 750rpm or 800rpm; the emulsification time is preferably 1-6h, specifically preferably 1h, 2h, 3h, 4h, 5h or 6h.

[0048] In the present invention, the emulsification can form a stable oil-in-water (O / W) emulsion.

[0049] After the emulsification, the oil-in-water emulsion is preferably obtained directly without any treatment.

[0050] After obtaining the oil-in-water emulsion, the present invention mixes the oil-in-water emulsion with a titanium dioxide precursor for a pre-reaction. After the pre-reaction is completed, acetic acid and a mixed solvent are sequentially added to the obtained reaction system for hydrolysis to obtain microcapsules.

[0051] In the present invention, the titanium dioxide precursor preferably includes one or more of tetrabutyl titanate (TBT), isopropyl titanate, titanium tetrachloride, and titanium trichloride, and is more preferably TBT. In the present invention, the ratio of the phase change material to the titanium dioxide precursor is preferably 2-12 g:2-12 mL, more preferably 5-10 g:5-10 mL, and more preferably 5 g:5 mL.

[0052] In the present invention, the mixing of the oil-in-water emulsion and the titanium dioxide precursor preferably comprises the following steps: adding the titanium dioxide precursor to the oil-in-water emulsion.

[0053] In the present invention, the temperature of the pre-reaction is preferably 30-60°C, specifically preferably 30°C, 40°C, 50°C, 55°C or 60°C; the pre-reaction is preferably carried out under stirring (denoted as second stirring), and the speed of the second stirring is preferably 200-800rpm, specifically preferably 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 750rpm or 800rpm; the time of the pre-reaction is preferably 0.2-4h, specifically preferably 0.2h, 0.5h, 50min, 1h, 2h, 3h or 4h.

[0054] In the present invention, during the pre-reaction process, the titanium dioxide precursor forms a stable shell layer on the surface of the droplet through electrostatic interaction.

[0055] In the present invention, the ratio of acetic acid to titanium dioxide precursor is preferably 0.04-0.4 g: 2-12 mL, more preferably 0.04-0.4 g: 5-10 mL, and more preferably 0.1 g: 5 mL. After the addition of acetic acid, the present invention preferably performs stirring (referred to as the third stirring), and the time of the third stirring is preferably 4-20 min, more preferably 4 min, 5 min, 10 min, 15 min or 20 min; the acetic acid is used to prevent the hydrolysis rate of the titanium dioxide precursor from being too fast.

[0056] In the present invention, the mixed solvent preferably includes water and formamide, the water is preferably deionized water, and the amount ratio of water to formamide in the mixed solvent is preferably 2-8g:20-80mL, more preferably 4-6g:20-50mL, and specifically preferably 5g:30mL; the amount ratio of water in the titanium dioxide precursor and the mixed solvent is preferably 2-12mL:2-8g, more preferably 5-10mL:4-6g, and specifically preferably 5mL:5g. In the present invention, the mixed solvent is preferably added dropwise.

[0057] In the present invention, the hydrolysis temperature is preferably 30-60°C, specifically preferably 30°C, 40°C, 50°C or 60°C; the hydrolysis is preferably carried out under stirring (denoted as the fourth stirring), and the rotation speed of the fourth stirring is preferably 200-800rpm, specifically preferably 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm or 800rpm; the hydrolysis time is preferably 1-6h, specifically preferably 1h, 2h, 3h, 4h, 5h or 6h.

[0058] After the hydrolysis is completed, the present invention preferably further comprises: filtering the obtained hydrolyzed liquid to obtain a filter residue; and vacuum drying the filter residue to obtain the microcapsules. In the present invention, washing is preferably performed during the filtration process, and the washing reagents preferably include water and anhydrous ethanol, and the water is preferably deionized water. In the present invention, the vacuum drying temperature is preferably 40°C and the drying time is preferably 20 hours. In the present invention, the hydrolysis can hydrolyze the titanium dioxide precursor to form titanium dioxide, even if the titanium dioxide encapsulates the phase change material to form microcapsules.

[0059] After obtaining the microcapsules, the present invention mixes the microcapsules with cationic electrolytes, and then adds Cu-MOFs to the obtained mixed system for self-assembly to obtain the MOFs-based composite material.

[0060] In the present invention, the cationic electrolyte preferably includes one or more of polydiallyldimethylammonium chloride (PDDA), polyethyleneimine, and polyvinylamide, and is more preferably PDDA. In the present invention, the cationic electrolyte is preferably present in the form of a cationic electrolyte solution, and the concentration of the cationic electrolyte solution is preferably 0.2-2 wt%, more preferably 0.5-1.5 wt%, and particularly preferably 1 wt%. The solvent of the cationic electrolyte solution is preferably a water-N,N-dimethylformamide system, and the volume ratio of water to N,N-dimethylformamide in the water-N,N-dimethylformamide system is preferably 20-100:20-100, more preferably 40-80:40-80, and more preferably 60:60.

[0061] In the present invention, the mass ratio of the microcapsules to the cationic electrolyte is preferably 0.2-2 g:0.8-4 g, and specifically preferably 0.5 g:1.2 g.

[0062] In the present invention, the microcapsules and cationic electrolytes are preferably mixed under ultrasonic conditions, and the ultrasonic time is preferably 2 to 10 minutes, specifically preferably 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes. In the present invention, the cationic electrolytes impart a positive charge to the microcapsules.

[0063] In the present invention, the mass ratio of the microcapsules to the Cu-MOFs is preferably 0.2-2:0.08-2, more preferably 0.5-1:0.1-1, and particularly preferably 0.5:0.2.

[0064] In the present invention, the preparation method of the Cu-MOFs comprises the following steps:

[0065] dissolving a soluble copper salt to obtain a copper salt solution;

[0066] Mixing the copper salt solution and the organic ligand, and performing a hydrothermal reaction to obtain the Cu-MOFs;

[0067] The organic ligand includes terephthalic acid.

[0068] In the present invention, the soluble copper salt preferably includes one or more of copper nitrate, copper sulfate, and copper chloride, more preferably copper nitrate. In a specific embodiment of the present invention, the soluble copper salt is preferably Cu(NO3)2·3H2O. In the present invention, the dissolving solvent is preferably an organic solvent, more preferably N,N-dimethylformamide (DMF).

[0069] In the present invention, the usage ratio of the soluble copper salt to the dissolved solvent is preferably 0.001-0.01 mol:40-100 mL, more preferably 0.0015-0.005:50-80 mL, and particularly preferably 0.0018 mol:60 mL.

[0070] In the present invention, the dissolution temperature is preferably 24-50°C, specifically preferably 24°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C; the time is preferably 2-8h, specifically preferably 2h, 3h, 4h, 5h, 6h, 7h or 8h; and the dissolution is preferably carried out under stirring conditions.

[0071] In the present invention, the concentration of the copper salt solution is preferably 0.01 to 0.1 mol / L, specifically preferably 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L.

[0072] After obtaining the copper salt solution, the present invention mixes the copper salt solution with an organic ligand and performs a hydrothermal reaction to obtain the Cu-MOFs.

[0073] In the present invention, the organic ligand comprises terephthalic acid (H2BDC). In the present invention, the molar ratio of the organic ligand to the soluble copper salt is preferably 1:1.

[0074] In the present invention, the copper salt solution and the organic ligand are preferably mixed under ultrasonic treatment, and the ultrasonic treatment time is preferably 0.6 to 4 hours, specifically preferably 0.6 hours, 1 hour, 2 hours, 3 hours or 4 hours.

[0075] In the present invention, the temperature of the hydrothermal reaction is preferably 80-200°C, specifically preferably 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C; the time of the hydrothermal reaction is preferably 16-30 hours, specifically preferably 16 hours, 18 hours, 20 hours, 21 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours. In the present invention, the hydrothermal reaction is preferably carried out in a hydrothermal kettle.

[0076] After the hydrothermal reaction is completed, the present invention preferably further comprises: cooling the resulting hydrothermal reaction solution to room temperature, filtering to obtain a filter residue; and sequentially washing and drying the filter residue to obtain the Cu-MOFs. In the present invention, the washing agent is preferably N,N-dimethylformamide (DMF). In the present invention, the drying temperature is preferably 60°C, the drying time is preferably 12 hours, and the drying is preferably performed in a vacuum oven.

[0077] In this invention, the concentration of the copper salt solution is controlled to 0.01 to 0.1 mol / L; the molar ratio of the organic ligand to the soluble copper salt is also controlled to 1:1, resulting in two-dimensional layered Cu-MOFs, which are more suitable for tribomechanical applications. In this invention, terephthalic acid is used as the organic ligand, resulting in negatively charged Cu-MOFs.

[0078] In the present invention, the temperature of the self-assembly is preferably 24-50°C, specifically preferably 24°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C; the time is preferably 1-8h, specifically preferably 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h; the self-assembly is preferably carried out under stirring conditions.

[0079] After the self-assembly, the present invention preferably further comprises: centrifuging the obtained self-assembly liquid to collect the solid; and sequentially washing and drying the solid to obtain the MOFs-based composite material. In the present invention, the centrifugal speed is preferably 4000-8000 rpm, specifically preferably 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm or 8000 rpm. In the present invention, the washing reagent preferably comprises ethanol and deionized water. In the present invention, the drying is preferably vacuum drying, and the vacuum drying temperature is preferably 30-60°C, specifically preferably 30°C, 40°C, 50°C or 60°C.

[0080] The present invention also provides a self-lubricating fabric composite material, comprising the MOFs-based composite material described in the above technical solution or the MOFs-based composite material prepared by the preparation method described in the above technical solution.

[0081] In the present invention, a composite material based on MOFs is used as a functional material to improve the tribological properties of the self-lubricating fabric composite material, thereby extending the service life of the component in which the self-lubricating fabric composite material serves as a lubricating layer.

[0082] The present invention also provides a method for preparing the self-lubricating fabric composite material described in the above technical solution, comprising the following steps:

[0083] dispersing the MOFs-based composite material in a resin solution to obtain an impregnation solution;

[0084] The fabric is immersed in the impregnation liquid, taken out, and then hot-pressed and cured in sequence to obtain the self-lubricating fabric composite material.

[0085] In the present invention, the MOFs-based composite material is dispersed in a resin solution to obtain an impregnation solution.

[0086] In the present invention, the mass content of the resin in the resin solution is preferably 4-20%, specifically preferably 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%. In the present invention, the resin in the resin solution is preferably one or more of phenolic resin, polyimide resin, epoxy resin and polyamide-imide.

[0087] In the present invention, the mass of the MOFs-based composite material is 0.8-10% of the mass of the resin in the resin solution, and specifically preferably 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0088] After obtaining the impregnation liquid, the present invention immerses the fabric in the impregnation liquid, takes it out, and then performs hot pressing molding and curing in sequence to obtain the self-lubricating fabric composite material.

[0089] In the present invention, the fabric is preferably a PPS / PTFE self-lubricating fabric. The weft yarns of the PPS / PTFE self-lubricating fabric are PPS fibers, and the warp yarns are PTFE fibers. The reinforcing fibers of the PPS / PTFE self-lubricating fabric are PPS fibers, and the lubricating fibers are PTFE fibers. The weave of the PPS / PTFE self-lubricating fabric is preferably plain, twill, or satin, or a derivative of these three basic weaves. In the present invention, the warp density of the PPS / PTFE self-lubricating fabric is preferably 240 to 400 roots / cm, specifically 240 roots / cm, 250 roots / cm, 260 roots / cm, 270 roots / cm, 280 roots / cm, 290 roots / cm, 300 roots / cm, 310 roots / cm, 320 roots / cm, 330 roots / cm, 340 roots / cm, 350 roots / cm, 360 roots / cm, 370 roots / cm, 380 roots / cm / cm, 390 roots / cm or 400 roots / cm; the weft density is preferably 220-360 roots / cm, specifically 220 roots / cm, 230 roots / cm, 240 roots / cm, 250 roots / cm, 260 roots / cm, 270 roots / cm, 280 roots / cm, 290 roots / cm, 300 roots / cm, 310 roots / cm, 320 roots / cm, 330 roots / cm, 340 roots / cm, 350 roots / cm or 360 roots / cm.

[0090] In the present invention, the fabric is preferably pretreated before use, and the pretreatment preferably includes: desizing, washing and drying in sequence. The present invention does not impose any specific restrictions on the washing, as long as the oil agent on the fiber surface can be washed away.

[0091] In the present invention, the impregnation is preferably repeated. After each impregnation, the impregnated fabric is preferably removed and dried. The drying temperature is preferably 30 to 80°C, specifically preferably 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C. The drying is preferably carried out in an oven. Each drying step preferably includes weighing and calculating the weight gain of the resin in the fabric. The present invention does not specifically limit the number of repeated impregnations; the fabric is impregnated until the mass fraction of the fabric in the fabric and resin composite reaches 40 to 85%.

[0092] The present invention does not specifically limit the operation of the hot pressing forming, and those skilled in the art can configure it according to actual needs.

[0093] In the present invention, the curing temperature is preferably 100-240°C, specifically preferably 100°C, 120°C, 140°C, 150°C, 160°C, 180°C, 184°C, 200°C, 220°C or 240°C; the curing pressure is preferably 0.2-2 MPa, specifically preferably 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 1.5 MPa or 2 MPa; the curing time is preferably 80-260 min, specifically preferably 80 min, 100 min, 120 min, 140 min, 150 min, 160 min, 180 min, 200 min, 210 min, 220 min, 240 min or 260 min. In the present invention, the heating rate to the curing temperature is preferably 6 to 20°C / min, specifically preferably 6°C / min, 8°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min or 20°C / min.

[0094] The present invention also provides the use of the MOFs-based composite material described in the above technical solution or the self-lubricating fabric composite material described in the above technical solution in a lubrication system.

[0095] The present invention does not specifically limit the application of the MOFs-based composite material or the self-lubricating fabric composite material described in the above technical solution, and those skilled in the art can configure it according to actual needs.

[0096] The MOFs-based composite material and self-lubricating fabric composite material provided by the present invention, as well as their preparation methods and applications, are described in detail below with reference to the examples. However, these examples should not be construed as limiting the scope of protection of the present invention.

[0097] Comparative Example 1

[0098] (1) PPS fiber and PTFE fiber were used to weave PPS / PTFE self-lubricating fabric (twill structure, warp density of 320 strands / cm, weft density of 290 strands / cm), which was then desized and cleaned with fiber surface oil and then dried for use.

[0099] (2) The PPS / PTFE self-lubricating fabric was repeatedly immersed in a phenolic resin solution (the mass content of phenolic resin was 15%) until the mass fraction of the fabric in the fabric and resin composite material reached 75±5wt%, thereby obtaining an uncured self-lubricating fabric composite material. The uncured self-lubricating fabric composite material was bonded to the surface of a metal substrate using a phenolic resin adhesive and cured at 0.8 MPa and 184°C for 2 h to obtain a nationally produced self-lubricating fabric composite material test piece, which was recorded as Pure FC.

[0100] The friction and wear properties of the self-lubricating fabric composite material were evaluated using a Xuanwu No. 3 friction and wear tester. The contact mode was pin-disc. At room temperature, the dynamic load was 45 MPa, the rotation speed was 0.3 m / s, and the friction test was carried out for 2 h. The results showed that the average friction coefficient and wear rate of the self-lubricating fabric composite material were 0.053 and 5.94×10 -14 m 3 / N·m.

[0101] Comparative Example 2

[0102] (1) PPS fiber and PTFE fiber were used to weave PPS / PTFE self-lubricating fabric (twill structure, warp density of 320 strands / cm, weft density of 290 strands / cm), which was then desized and cleaned with fiber surface oil and then dried for use.

[0103] (2) When the organic ligand and soluble copper salt are adjusted to appropriate concentrations in the solvent, two-dimensional layered MOFs can be synthesized by a one-step hydrothermal method. Cu(NO3)2·3H2O (0.0018 mol) was added to DMF (60 mL) and stirred at 30°C for 4 h to obtain a uniform blue copper salt solution. Then, terephthalic acid H2BDC was added to the copper salt solution in the same molar amount as copper nitrate and ultrasonicated for 1 h. The resulting mixture was then placed in a hydrothermal reactor and hydrothermally reacted at 120°C for 24 h. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered, and the filter residue was washed with DMF four times and dried in a vacuum oven at 60°C for 12 h to obtain Cu-MOFs.

[0104] (3) The PPS / PTFE self-lubricating fabric was repeatedly immersed in a phenolic resin solution containing Cu-MOFs (the mass fraction of Cu-MOFs relative to phenolic resin was 2 wt%, and the mass content of phenolic resin in the phenolic resin solution was 15%) until the mass fraction of the fabric in the fabric and resin composite material reached 75±5 wt%, thereby obtaining an uncured self-lubricating fabric composite material. The uncured self-lubricating fabric composite material was bonded to the surface of a metal substrate using a phenolic resin adhesive and cured at 0.8 MPa and 184°C for 2 h to obtain a nationally produced self-lubricating fabric composite material test piece, which was designated as FC-1.

[0105] The friction and wear properties of the self-lubricating fabric composite material were evaluated using a Xuanwu No. 3 friction and wear tester. The contact mode was pin-disc. At room temperature, the dynamic load was 45 MPa, the rotation speed was 0.3 m / s, and the friction test was carried out for 2 h. The results showed that the average friction coefficient and wear rate of the self-lubricating fabric composite material were 0.05 and 4.71×10 -14 m 3 / N·m.

[0106] Comparative Example 3

[0107] (1) PPS fiber and PTFE fiber were used to weave PPS / PTFE self-lubricating fabric (twill structure, warp density of 320 strands / cm, weft density of 290 strands / cm), which was then desized and cleaned with fiber surface oil and then dried for use.

[0108] (2) Phase change microcapsules based on n-docosane core and titanium dioxide wall were synthesized by interfacial condensation. 5.0 g of docosane, 70.0 mL of formamide and 3.3 g of SDS were mixed in a closed beaker and stirred at 750 rpm at 55 °C for 2 h to form a stable oil-in-water (O / W) emulsion. Then, 5.0 mL of titanium dioxide precursor TBT was added to the beaker and stirred at 750 rpm at 55 °C for 50 min to form a stable shell on the droplet surface through electrostatic interaction. Subsequently, 0.1 g of acetic acid was added to the emulsion and stirred for 10 min to prevent the hydrolysis rate of TBT from being too fast. Finally, 5.0 g of deionized water and 30.0 mL of formamide mixed solvent was added dropwise to the above reaction system and stirred at 500 rpm for 4 h. After the reaction was completed, the mixture was repeatedly washed with deionized water and anhydrous ethanol during filtration and vacuum dried at 40 °C for 20 h to obtain microcapsules, which were recorded as TiO2-MePCM.

[0109] (3) The PPS / PTFE self-lubricating fabric was repeatedly immersed in a phenolic resin solution of TiO2-MePCM (the mass fraction of TiO2-MePCM relative to phenolic resin was 2 wt%, and the mass fraction of phenolic resin in the phenolic resin solution was 15%) until the mass fraction of the fabric in the fabric and resin composite material reached 75±5 wt%, thereby obtaining an uncured self-lubricating fabric composite material. The uncured self-lubricating fabric composite material was bonded to the surface of a metal substrate using a phenolic resin adhesive and cured at 0.8 MPa and 184°C for 2 h to obtain a nationally produced self-lubricating fabric composite material test piece, which was designated as FC-2.

[0110] The friction and wear properties of the self-lubricating fabric composite material were evaluated using a Xuanwu No. 3 friction and wear tester. The contact mode was pin-disc. At room temperature, the dynamic load was 45 MPa, the rotation speed was 0.3 m / s, and the friction test was carried out for 2 h. The results showed that the average friction coefficient and wear rate of the self-lubricating fabric composite material were 0.0491 and 4.12×10 -14 m 3 / N·m.

[0111] Example 1

[0112] (1) PPS fiber and PTFE fiber were used to weave PPS / PTFE self-lubricating fabric (twill structure, warp density of 320 strands / cm, weft density of 290 strands / cm), which was then desized and cleaned with fiber surface oil and then dried for use.

[0113] (2) Cu-MOFs modified TiO2-MePCM was prepared by electrostatic self-assembly. First, 0.5 g of TiO2-MePCM (obtained in Comparative Example 3) was added to a 1 wt% PDDA solution (60 mL of deionized water and 60 mL of DMF, including 1.2 g of PDDA) and ultrasonicated for 5 minutes. Then, 0.2 g of Cu-MOFs (obtained in Comparative Example 2) was added to the above solution and stirred at 30°C for 3 hours. After the reaction was completed, centrifugation was carried out at 6000 r / min, and the excess reactants were removed by washing with ethanol and deionized water. The MOFs-based composite material was vacuum dried at 40°C to obtain Cu-MOFs@TiO2-MePCM.

[0114] (3) The PPS / PTFE self-lubricating fabric was repeatedly immersed in the phenolic resin solution of Cu-MOFs@TiO2-MePCM (the mass fraction of Cu-MOFs@TiO2-MePCM relative to the phenolic resin was 2 wt%, and the mass content of the phenolic resin in the phenolic resin solution was 15%) until the mass fraction of the fabric in the fabric and resin composite material reached 75±5 wt%, and an uncured self-lubricating fabric composite material was obtained. The uncured self-lubricating fabric composite material was bonded to the surface of the metal substrate using a phenolic resin adhesive and cured at 0.8 MPa and 184 °C for 2 h to obtain a nationally produced self-lubricating fabric composite material test piece, which was recorded as FC-3.

[0115] The friction and wear properties of the self-lubricating fabric composite material were evaluated using a Xuanwu No. 3 friction and wear tester. The contact mode was pin-disc. At room temperature, the dynamic load was 45 MPa, the rotation speed was 0.3 m / s, and the friction test was carried out for 2 h. The results showed that the average friction coefficient and wear rate of the self-lubricating fabric composite material were 0.047 and 2.76×10 -14 m 3 / N·m.

[0116] Figure 1 TEM images of Cu-MOFs (a) obtained in Comparative Example 2, TiO2-MePCM (b) obtained in Comparative Example 3, and Cu-MOFs@TiO2-MePCM (c) obtained in Example 1; Figure 1 It can be seen that the Cu-MOFs have a stacked sheet structure with a very smooth surface, while the TiO2-MePCM has a regular spherical morphology without any surface defects. In contrast, the surface of the Cu-MOFs@TiO2-MePCM becomes rough and exhibits wrinkled crystalline layers, clearly showing the two-dimensional layered structure of the Cu-MOFs.

[0117] Figure 2 The XRD patterns of Cu-MOFs obtained in Comparative Example 2, TiO2-MePCM obtained in Comparative Example 3, Cu-MOFs@TiO2-MePCM obtained in Example 1, and n-docosane are shown; Figure 2It can be seen that the characteristic peaks of 10.2°, 12.1°, 17.2°, 20.4° and 24.8° appearing in the spectrum of Cu-MOFs belong to the (110), (001), (-201), (220) and (131) crystal planes, indicating that it has a high degree of crystallinity and a face-centered cubic structure. The spectra of Cu-MOFs@TiO2-MePCM and n-docosane have similar diffraction peaks, which indicates that n-docosane still has a stable crystal structure after layer-by-layer encapsulation and can achieve the absorption and release of frictional heat. It is worth noting that the diffraction peak of TiO2 cannot be observed in the spectrum because it is in an amorphous state. The above characterization analysis proves that the core-shell structured Cu-MOFs-based composite material has been successfully prepared.

[0118] The friction and wear performance of the self-lubricating fabric composite material was evaluated using a Xuanwu No. 3 friction and wear tester. The contact mode was pin-disc, the dynamic load was 45 MPa, the rotation speed was 0.3 m / s, and the friction test was 2 h. The results are as follows Figure 3 As shown, Figure 3 The wear rate (a) and average friction coefficient (b) of the self-lubricating fabric composite materials obtained in Example 1 and Comparative Examples 1 to 3 are shown in FIG. Figure 3 As shown in the figure, the wear rate of the pure self-lubricating fabric composite is large, and the direct and dual contact of PTFE fibers reduces the friction coefficient. After adding MePCM, the wear rate of the self-lubricating fabric composite is significantly reduced, and FC-3 with the addition of Cu-MOFs@TiO2-MePCM shows the smallest average wear rate and friction coefficient.

[0119] Figure 4 The SEM photos of the wear surfaces of the self-lubricating fabric composite material (a) obtained in Comparative Example 1 and the self-lubricating fabric composite material (b) obtained in Example 1 are shown in FIG. Figure 4 As can be seen, for the pure self-lubricating fabric composite, a large number of fibers were pulled out and broken due to severe wear, and the phenolic resin on the worn surface was peeled off. For FC-3 with the addition of Cu-MOFs@TiO2-MePCM, the reinforcing fibers were tightly integrated with the resin matrix, and the worn surface was quite smooth, with only a small amount of phenolic resin falling off.

[0120] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite material based on MOFs, characterized in that: comprising microcapsules, and MOFs bound to the microcapsules; The microcapsule comprises a capsule core and a capsule wall surrounding the capsule core; The capsule core is a phase change material, the capsule wall is titanium dioxide, and the MOFs are Cu-MOFs; The Cu-MOFs have a two-dimensional layered structure; The Cu-MOFs are bound to the microcapsules through electrostatic interactions, the microcapsules are positively charged, and the Cu-MOFs are negatively charged.

2. The MOFs-based composite material according to claim 1, characterized in that The phase change material includes one or more of n-docosane, eicosane, octadecane and hexadecane, and the thickness of the capsule wall is 50-200 nm.

3. The method for preparing a MOFs-based composite material according to any one of claims 1 to 2, characterized in that: The following steps are involved: mixing a phase change material, an emulsifier and an organic solvent, and emulsifying the mixture to obtain an oil-in-water emulsion; The oil-in-water emulsion and the titanium dioxide precursor are mixed to perform a pre-reaction. After the pre-reaction is completed, acetic acid and a mixed solvent are sequentially added to the obtained reaction system to perform hydrolysis to obtain microcapsules; After mixing the microcapsules and cationic electrolytes, Cu-MOFs are added to the obtained mixed system to perform self-assembly to obtain the MOFs-based composite material; The preparation method of the Cu-MOFs comprises the following steps: dissolving a soluble copper salt to obtain a copper salt solution; Mixing the copper salt solution and the organic ligand, and performing a hydrothermal reaction to obtain the Cu-MOFs; The organic ligand includes terephthalic acid.

4. A self-lubricating fabric composite material, characterized in that: The MOFs-based composite material comprises the MOFs-based composite material according to any one of claims 1 to 2 or the MOFs-based composite material prepared by the preparation method according to claim 3.

5. The method for preparing the self-lubricating fabric composite material according to claim 4, characterized in that: The following steps are involved: dispersing the MOFs-based composite material in a resin solution to obtain an impregnation solution; The fabric is immersed in the impregnation liquid, taken out, and then hot-pressed and cured in sequence to obtain the self-lubricating fabric composite material.

6. The preparation method according to claim 5, characterized in that The mass of the MOFs-based composite material is 0.8-10% of the mass of the resin in the resin solution.

7. Use of the MOFs-based composite material according to any one of claims 1 to 2 or the self-lubricating fabric composite material according to claim 4 in a lubrication system.

Images