Powder metallurgical friction material and method for its production

Abstract

The application belongs to the technical field of friction materials, and relates to a powder metallurgy friction material and a preparation method thereof. Raw materials for preparing the powder metallurgy friction material include 10wt%-15wt% silicon carbide nanoparticles, 5wt%-15wt% aluminum oxide nanoparticles, 5wt%-10wt% molybdenum disulfide, 5wt%-10wt% hexagonal boron nitride, 5wt%-10wt% microencapsulated self-repairing agent, and the rest nano-copper powder. The application improves the wear resistance and mechanical properties of the powder metallurgy friction material through the synergistic use of the silicon carbide nanoparticles, nano-copper powder and microencapsulated self-repairing agent, and the preparation method is simple and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of friction material technology, and relates to a silicon carbide-containing friction material, and more particularly to a powder metallurgy friction material and its preparation method. Background Technology

[0002] Powder metallurgy is an industrial technology that produces metal powders or uses metal powders as raw materials, through molding and sintering, to create metallic materials, composite materials, and various types of products. Powder metallurgy possesses unique chemical compositions and mechanical and physical properties that cannot be obtained using traditional casting methods.

[0003] Copper-based powder metallurgy friction materials are composite materials prepared using copper and its alloys as the matrix, with the addition of friction and lubrication components. Compared to organic friction materials, these materials offer advantages such as better heat resistance, higher mechanical strength, and more stable friction and wear performance, making them widely used in the automotive industry. However, with the development of automobiles towards high speeds and heavy loads, traditional copper-based powder metallurgy friction materials experience severe wear during use and can no longer meet the comprehensive performance requirements of automotive braking materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a powder metallurgy friction material and its preparation method. The present invention improves the wear resistance and mechanical properties of the powder metallurgy friction material by synergistic use of silicon carbide nanoparticles, nano copper powder, and microencapsulated self-healing agents. Moreover, the preparation method is simple and suitable for large-scale industrial production.

[0005] To achieve this objective, the present invention employs the following technical solution:

[0006] In a first aspect, the present invention provides a powder metallurgy friction material, wherein, by mass percentage, the raw materials for preparing the powder metallurgy friction material include: 10wt%-15wt% silicon carbide nanoparticles, 5wt%-15wt% alumina nanoparticles, 5wt%-10wt% molybdenum disulfide, 5wt%-10wt% hexagonal boron nitride, 5wt%-10wt% microencapsulated self-healing agent, and the balance being nano copper powder.

[0007] In the powder metallurgy friction material provided by the present invention, nano copper powder is used as the matrix material, which can form a copper film on the surface of the powder metallurgy friction material, increase the friction coefficient, improve the braking effect, and at the same time reduce wear and increase service life.

[0008] Silicon carbide nanoparticles are a type of reinforcing material, possessing high hardness and wear resistance. They can effectively improve overall hardness, enhance wear resistance, reduce material loss during friction, and improve the consistency of friction performance of powder metallurgy friction materials under different working conditions. A suitable mass percentage helps to maximize the reinforcing effect of silicon carbide nanoparticles. In this invention, the mass percentage of silicon carbide nanoparticles is 10wt%-15wt%, for example, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or 15wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0009] Alumina nanoparticles, as a reinforcing material, possess high strength and stiffness, significantly improving the mechanical properties of powder metallurgy friction materials. Appropriate content can also enable powder metallurgy friction materials to achieve an ideal coefficient of friction. A suitable mass percentage helps to maximize the reinforcing effect of alumina nanoparticles. In this invention, the mass percentage of alumina nanoparticles is 5wt%-15wt%, for example, 5wt%, 8wt%, 10wt%, 12wt%, or 15wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0010] Molybdenum disulfide, as a lubricating material, can effectively reduce the coefficient of friction and decrease frictional heat generation, thus improving the thermal stability and reliability of powder metallurgy friction materials and extending their service life. A suitable mass percentage helps to maximize the lubricating effect of molybdenum disulfide. In this invention, the mass percentage of molybdenum disulfide is 5wt%-10wt%, for example, 5wt%, 6wt%, 8wt%, 9wt%, or 10wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0011] Hexagonal boron nitride, as a lubricating material, possesses a layered structure similar to graphite, maintaining good lubrication performance under high-temperature conditions and improving the high-temperature stability and reliability of powder metallurgy friction materials. A suitable mass percentage helps to maximize the lubricating effect of hexagonal boron nitride. In this invention, the mass percentage of hexagonal boron nitride is 5wt%-10wt%, for example, it can be 5wt%, 6wt%, 8wt%, 9wt%, or 10wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0012] Microencapsulated self-healing agents, as repair and reinforcement materials, can rupture and release their internal repair agents when cracks or damage occur in powder metallurgy friction materials during use. This repairs the cracks, restores the material's integrity, and improves its service life and reliability. It can also reduce the coefficient of friction and decrease frictional losses. A suitable mass percentage helps to maximize the repair and reinforcement effects of the microencapsulated self-healing agent. In this invention, the mass percentage of the microencapsulated self-healing agent is 5wt%-10wt%, for example, 5wt%, 6wt%, 8wt%, 9wt%, or 10wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0013] Furthermore, in the powder metallurgy friction material provided by this invention, there is a synergistic effect between nano-copper powder, silicon carbide nanoparticles, and microencapsulated self-healing agent. During the friction process, silicon carbide nanoparticles and nano-copper powder can accelerate the rupture of the microencapsulated self-healing agent and the release of the repair agent, making the repair process faster and more effective. Moreover, silicon carbide nanoparticles can fill cracks and pores, improving density, while nano-copper powder can enhance the bonding force through interaction with other components, giving the powder metallurgy friction material good mechanical properties. The synergistic effect of the three can also enable the powder metallurgy friction material to have a friction coefficient that meets the process requirements.

[0014] Preferably, the average particle size of the silicon carbide nanoparticles is 50nm-200nm, for example, it can be 50nm, 80nm, 100nm, 120nm, 150nm, 160nm, 180nm or 200nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the average particle size of the alumina nanoparticles is 20nm-100nm, for example, it can be 20nm, 40nm, 50nm, 60nm, 80nm or 100nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the average particle size of the molybdenum disulfide is 50nm-500nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the average particle size of the hexagonal boron nitride is 0.5μm-5μm, for example, it can be 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the average particle size of the microencapsulated self-healing agent is 1μm-20μm, for example, it can be 1μm, 3μm, 5μm, 8μm, 10μm, 15μm, 18μm or 20μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the average particle size of the nano-copper powder is 20nm-100nm, for example, it can be 20nm, 40nm, 50nm, 60nm, 80nm or 100nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the nano-copper powder is nano-copper powder that has undergone surface treatment with a silane coupling agent. The silane coupling agent surface treatment includes: the copper powder is successively washed, dried and acid-washed, then immersed in a silane coupling agent solution, and after immersion, it is dried to obtain the nano-copper powder.

[0021] As a preferred technical solution of the present invention, the surface treatment of copper powder with silane coupling agent can improve the dispersibility of nano copper powder, enabling it to be uniformly dispersed in powder metallurgy friction material and improving the service life of the material; at the same time, copper powder treated with silane coupling agent can better combine with microencapsulated self-healing agent, improve the interfacial bonding force between microencapsulated self-healing agent and metal powder, and improve the mechanical properties of powder metallurgy friction material.

[0022] The surface treatment technology for silane coupling agents provided by this invention does not specifically limit the average particle size of the copper powder used, as long as the average particle size of the obtained nano copper powder meets the process requirements.

[0023] Optionally, when cleaning the copper powder, an organic solvent is used to remove surface oil and impurities. Preferably, the organic solvent used for cleaning the copper powder includes acetone and / or ethanol.

[0024] Optionally, the acid used when pickling the copper powder includes hydrochloric acid and / or sulfuric acid.

[0025] When copper powder is exposed to air, its surface oxidizes into copper oxide. Pickling can increase the surface roughness of the copper powder, thereby improving the adhesion of the silane coupling agent.

[0026] Preferably, the volume ratio of acid used in the pickling is 5%-15%, for example, it can be 5%, 8%, 10%, 12% or 15%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] The "volume ratio of acid" mentioned in this invention refers to the percentage of the volume of acid in the acid solution used for pickling, relative to the total volume of the acid solution.

[0028] Preferably, the pickling time is 1 min to 30 min, for example, it can be 1 min, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, when treating the surface with a silane coupling agent, the mass concentration of the silane coupling agent solution is 0.5wt%-2wt%, for example, it can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, when treating the surface of the silane coupling agent, the soaking time is 10 min to 30 min, for example, 10 min, 15 min, 20 min, 25 min or 30 min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the silane coupling agent includes any one or a combination of at least two of KH-540, KH-550, KH-560, KH-580, A-151, A-171, or KH-590. Typical but non-limiting combinations include combinations of KH-540 and KH-550, KH-550 and KH-560, KH-580 and KH-590, A-151 and A-171, KH-550, KH-580 and KH-590, KH-550, KH-560, KH-580 and KH-590, or KH-540, KH-550, KH-560, KH-580, A-151, A-171 and KH-590.

[0032] Preferably, the silicon carbide nanoparticles are silicon carbide nanoparticles that have undergone surface treatment with a copper-aminosilane composite. The surface treatment with the copper-aminosilane composite includes: after the silicon carbide nanoparticles are cleaned, dried and surface hydroxylated, they are immersed in a copper salt-aminosilane composite solution. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0033] As a preferred technical solution of the present invention, the surface treatment of silicon carbide nanoparticles with copper-aminosilane composite can improve the dispersibility of silicon carbide nanoparticles; the presence of copper ions strengthens the bonding force between silicon carbide nanoparticles and nano copper powder, further enhances the strength of powder metallurgy friction materials, solves the problem of unstable bonding due to large material density differences in the physical interface mixing and connection of silicon carbide and copper, and improves the stability of product quality.

[0034] Preferably, the surface hydroxylation treatment is performed using hydrochloric acid, nitric acid, or sodium hydroxide solution.

[0035] This invention does not limit the specific method of surface hydroxylation treatment; any treatment of silicon carbide nanoparticles with hydrochloric acid, nitric acid, or sodium hydroxide solution will suffice.

[0036] Preferably, the method for preparing the copper salt-aminosilane complex solution includes:

[0037] The copper salt-aminosilane complex solution is obtained by mixing a copper salt solution with a mass concentration of 0.1wt%-1wt% and an aminosilane solution with a mass concentration of 1wt%-5wt% in a volume ratio of 1:2-1:4.

[0038] The volume ratio of the copper salt solution to the aminosilane solution is 1:2 to 1:4, for example, it can be 1:2, 1:3 or 1:4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] The mass concentration of the copper salt solution is 0.1wt%-1wt%, for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.6wt%, 0.8wt% or 1wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] The mass concentration of the aminosilane solution is 1wt%-5wt%, for example, it can be 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the molten salt solution is prepared by dissolving copper salt in deionized water; the copper salt includes copper nitrate and / or copper sulfate.

[0042] Preferably, the aminosilane solution is prepared by dissolving aminosilane in ethanol and / or deionized water.

[0043] Preferably, the aminosilane in the aminosilane solution includes any one or a combination of at least two of KH-550, KH-602, KH-792 or KH540. Typical but non-limiting combinations include combinations of KH-550 and KH-602, KH-792 and KH540, KH-550, KH-602 and KH540, or KH-550, KH-602, KH-792 and KH540.

[0044] Preferably, the microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1-100:0.5, for example, 100:0.1, 100:0.2, 100:0.3, 100:0.4 or 100:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] This invention utilizes a microencapsulated self-healing agent. The polymer in the microencapsulated self-healing agent contains reversible chemical bonds, and the catalyst microcapsule contains a catalyst. When the friction material is damaged, the microcapsule ruptures, releasing the internal polymer and catalyst, which causes the reversible chemical bonds to break and recombine. The polymer flows to the damaged area and undergoes a polymerization reaction with the surrounding material to form a new polymer, filling the damaged area and achieving self-repair, thereby improving the wear resistance of the friction material.

[0046] Preferably, the preparation method of the self-healing polymer microcapsules includes: dissolving the self-healing polymer in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1μm-20μm; adding an aqueous diamine solution, followed by dropwise addition of isocyanate to form an interfacial polycondensation reaction, with a reaction temperature of 20℃-60℃ and a reaction time of 30min-120min, to obtain the self-healing polymer microcapsules.

[0047] Preferably, the hydrophobic solvent includes toluene and / or cyclohexane.

[0048] Preferably, the emulsifier includes any one or a combination of at least two of Tween 80, Span 20, Span 40, or Span 80. Typical but non-limiting combinations include combinations of Tween 80 and Span 20, combinations of Span 20 and Span 40, combinations of Span 20, Span 40, and Span 80, or combinations of Tween 80, Span 20, Span 40, and Span 80.

[0049] Preferably, the volume ratio of the oil phase to the water phase is 1:5 to 1:10, for example, it can be 1:5, 1:6, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the molar ratio of the diamine to the isocyanate in the diamine aqueous solution is 1:(0.8-1.2), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Optionally, the diamine in the aqueous diamine solution includes ethylenediamine and / or hexamethylenediamine.

[0052] Optionally, the isocyanate includes any one or a combination of at least two of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (PAPI), hexamethylene diisocyanate (HDI), isoflurone diisocyanate (IPDI), or dicyclohexylmethane diisocyanate (HMDI). Typical but non-limiting combinations include combinations of TDI and MDI, PAPI and HDI, IPDI and HMDI, combinations of TDI, MDI, PAPI, and HDI, combinations of PAPI, HDI, IPDI, and HMDI, or combinations of TDI, MDI, PAPI, HDI, IPDI, and HMDI.

[0053] Preferably, the total mass of the diamine and the isocyanate in the diamine aqueous solution is 5%-20% of the mass of the self-healing polymer, for example, it can be 5%, 8%, 10%, 12%, 15%, 18% or 20%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Preferably, the self-healing polymer of the self-healing polymer microcapsules comprises: hydroxyvinyl silicone resin and a compound containing disulfide bonds dissolved in a solvent; a first catalyst is added and stirred until homogeneous; the mixture is heated to react at 50°C-100°C; after the reaction is completed, the self-healing polymer is obtained by filtration, washing and drying.

[0055] Optionally, the hydroxyvinyl silicone resin includes any one or a combination of at least two of methyl hydroxyvinyl silicone resin, phenyl hydroxyvinyl silicone resin, or fluorohydroxyvinyl silicone resin.

[0056] Optionally, the disulfide-containing compound includes dithiobenzoic acid (DTSA), sodium polydithiopropane sulfonate (PSS), or 4,4-dithiobenzoic acid (DTSA). ` - Any one or at least two of the dithiodimorpholine (DTDM), typical but non-limiting combinations include combinations of DTSA and PSS, PSS and DTDM, DTSA and DTDM, or DTSA, PSS and DTDM.

[0057] Preferably, the first catalyst comprises an acidic catalyst and / or a basic catalyst.

[0058] Preferably, the acidic catalyst comprises sulfuric acid and / or hydrochloric acid.

[0059] Preferably, the alkaline catalyst comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, or triethylamine.

[0060] Preferably, the preparation method of the catalyst microcapsules includes: dissolving a second catalyst in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1μm-20μm; adding an aqueous diamine solution, followed by dropwise addition of isocyanate to form an interfacial polycondensation reaction, with a reaction temperature of 20℃-60℃ and a reaction time of 30min-120min, to obtain catalyst microcapsules.

[0061] Preferably, the second catalyst comprises any one or a combination of at least two of organotin compounds, organotitanium compounds, or thiols.

[0062] Optionally, the organotin compound includes any one or a combination of at least two of dibutyltin dilaurate, stannous octoate, or di(dodecyl sulfide)dibutyltin.

[0063] Optionally, the organotitanium compound includes any one or a combination of at least two of tetraisopropyl titanate, tetrabutyl titanate, or tetraethyl titanate.

[0064] Optionally, the thiol compound includes any one or a combination of at least two of tert-dodecyl mercaptosan, 3-mercaptopropionic acid, or ethanethiol.

[0065] Preferably, the hydrophobic solvent includes toluene and / or cyclohexane.

[0066] Preferably, the emulsifier includes any one or a combination of at least two of Tween 80, Span 20, Span 40, or Span 80. Typical but non-limiting combinations include combinations of Tween 80 and Span 20, combinations of Span 20 and Span 40, combinations of Span 20, Span 40, and Span 80, or combinations of Tween 80, Span 20, Span 40, and Span 80.

[0067] Preferably, the volume ratio of the oil phase to the water phase is 1:5 to 1:10, for example, it can be 1:5, 1:6, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] Preferably, the molar ratio of the diamine to the isocyanate in the diamine aqueous solution is 1:(0.8-1.2), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] Optionally, the diamine in the aqueous diamine solution includes ethylenediamine and / or hexamethylenediamine.

[0070] Optionally, the isocyanate includes any one or a combination of at least two of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (PAPI), hexamethylene diisocyanate (HDI), isoflurone diisocyanate (IPDI), or dicyclohexylmethane diisocyanate (HMDI). Typical but non-limiting combinations include combinations of TDI and MDI, PAPI and HDI, IPDI and HMDI, combinations of TDI, MDI, PAPI, and HDI, combinations of PAPI, HDI, IPDI, and HMDI, or combinations of TDI, MDI, PAPI, HDI, IPDI, and HMDI.

[0071] Preferably, the total mass of the diamine and the isocyanate in the diamine aqueous solution is 5%-20% of the mass of the second catalyst, for example, it can be 5%, 8%, 10%, 12%, 15%, 18% or 20%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0072] In a second aspect, the present invention provides a method for preparing a powder metallurgy friction material, the method comprising: mixing nano-copper powder, silicon carbide nanoparticles, alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to a formula amount to obtain a mixed powder; the mixed powder is then subjected to cold pressing and sintering in sequence to obtain the powder metallurgy friction material described in the first aspect.

[0073] Preferably, the cold pressing pressure is 550MPa-650MPa, for example, it can be 550MPa, 580MPa, 600MPa, 620MPa or 650MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] Preferably, the sintering is carried out in a protective atmosphere, the gas used in the protective atmosphere including nitrogen and / or an inert gas.

[0075] Preferably, the inert gas includes helium and / or argon.

[0076] Preferably, the sintering temperature is 800℃-1300℃, for example, it can be 800℃, 900℃, 1000℃, 1200℃ or 1300℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0077] Preferably, the sintering time is 30 min to 120 min, for example, it can be 30 min, 50 min, 60 min, 80 min, 100 min or 120 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] In the powder metallurgy friction material provided by this invention, there is a synergistic effect between nano-copper powder, silicon carbide nanoparticles, and microencapsulated self-healing agent. During the friction process, silicon carbide nanoparticles and nano-copper powder can accelerate the rupture of the microencapsulated self-healing agent and the release of the repair agent, making the repair process faster and more effective. Moreover, silicon carbide nanoparticles can fill cracks and pores, improving density, while nano-copper powder can enhance the bonding force through interaction with other components, giving the powder metallurgy friction material good mechanical properties. The synergistic effect of the three can also enable the powder metallurgy friction material to have a friction coefficient that meets the process requirements. Detailed Implementation

[0081] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0082] Example 1

[0083] This embodiment provides a powder metallurgy friction material. By mass percentage, the raw materials for preparing the powder metallurgy friction material include: 12 wt% silicon carbide nanoparticles, 12 wt% alumina nanoparticles, 9 wt% molybdenum disulfide, 8 wt% hexagonal boron nitride, 8 wt% microencapsulated self-healing agent, and the balance being nano copper powder.

[0084] The silicon carbide nanoparticles have an average particle size of 100 nm; the alumina nanoparticles have an average particle size of 50 nm; the molybdenum disulfide has an average particle size of 300 nm; the hexagonal boron nitride has an average particle size of 3 μm; the microencapsulated self-healing agent has an average particle size of 10 μm; and the copper nanoparticles have an average particle size of 50 nm.

[0085] The microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.2;

[0086] The method for preparing the self-healing polymer microcapsules includes:

[0087] (1) Preparation of self-healing polymer: Hydroxyvinyl silicone resin (Sihai Chemical, SH5202) and disulfide-containing compound (dithiodibenzoic acid) are dissolved in a solvent; sulfuric acid as the first catalyst is added and stirred evenly; the reaction is heated at 80°C; after the reaction is completed, the self-healing polymer is obtained by filtration, washing and drying.

[0088] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer was dissolved in a hydrophobic solvent (toluene) to form an oil phase; the emulsifier (Tween 80) was dissolved in water to form an aqueous phase; the oil phase was dispersed in the aqueous phase to form an O / W emulsion with a particle size of 10 μm; an aqueous solution of diamine (ethylenediamine) was added, followed by the dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction. The reaction temperature was 30 °C and the reaction time was 60 min to obtain self-healing polymer microcapsules; the volume ratio of the oil phase to the aqueous phase was 1:6; the molar ratio of diamine to isocyanate was 1:1; and the total mass of diamine and isocyanate accounted for 10% of the mass of the self-healing polymer.

[0089] The method for preparing the catalyst microcapsules includes: dissolving the second catalyst, an organotin compound (dibutyltin dilaurate), in a hydrophobic solvent (cyclohexane) to form an oil phase; dissolving an emulsifier (Span 80) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 5 μm; adding an aqueous solution of diamine (ethylenediamine), followed by dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction at a reaction temperature of 40°C and a reaction time of 60 min to obtain catalyst microcapsules; the volume ratio of the oil phase to the aqueous phase is 1:8; the molar ratio of diamine to isocyanate is 1:1; and the total mass of diamine and isocyanate accounts for 15% of the mass of the second catalyst.

[0090] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano-copper powder, silicon carbide nanoparticles, alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 600 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 800℃ and a sintering time of 120 min to obtain the powder metallurgy friction material.

[0091] Example 2

[0092] This embodiment provides a powder metallurgy friction material. By mass percentage, the raw materials for preparing the powder metallurgy friction material include: 10 wt% silicon carbide nanoparticles, 15 wt% alumina nanoparticles, 10 wt% molybdenum disulfide, 5 wt% hexagonal boron nitride, 5 wt% microencapsulated self-healing agent, and the balance being nano copper powder.

[0093] The silicon carbide nanoparticles have an average particle size of 50 nm; the alumina nanoparticles have an average particle size of 20 nm; the molybdenum disulfide has an average particle size of 50 nm; the hexagonal boron nitride has an average particle size of 0.5 μm; the microencapsulated self-healing agent has an average particle size of 1 μm; and the copper nanoparticles have an average particle size of 20 nm.

[0094] The microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1;

[0095] The method for preparing the self-healing polymer microcapsules includes:

[0096] (1) Preparation of self-healing polymer: Hydroxyvinyl silicone resin (Sihai Chemical, SH5202) and disulfide-containing compound (dithiodibenzoic acid) are dissolved in solvent; sodium hydroxide as the first catalyst is added and stirred evenly; the reaction is heated at 50°C; after the reaction is completed, the self-healing polymer is obtained by filtration, washing and drying.

[0097] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer was dissolved in a hydrophobic solvent (cyclohexane) to form an oil phase; the emulsifier (Span 40) was dissolved in water to form an aqueous phase; the oil phase was dispersed in the aqueous phase to form an O / W emulsion with a particle size of 1 μm; an aqueous solution of diamine (ethylenediamine) was added, followed by the dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction. The reaction temperature was 20 °C and the reaction time was 120 min to obtain self-healing polymer microcapsules; the volume ratio of the oil phase to the aqueous phase was 1:5; the molar ratio of diamine to isocyanate was 1:1; and the total mass of diamine and isocyanate accounted for 5% of the mass of the self-healing polymer.

[0098] The method for preparing the catalyst microcapsules includes: dissolving a second catalyst (tetraisopropyl titanate) in a hydrophobic solvent toluene to form an oil phase; dissolving an emulsifier (Span 20) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm; adding an aqueous solution of diamine (ethylenediamine), followed by dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction at a reaction temperature of 20°C and a reaction time of 120 min to obtain catalyst microcapsules; the volume ratio of the oil phase to the aqueous phase is 1:5; the molar ratio of diamine to isocyanate is 1:1; and the total mass of diamine and isocyanate accounts for 5% of the mass of the second catalyst.

[0099] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano-copper powder, silicon carbide nanoparticles, alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 550 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 1300℃ and a sintering time of 30 min to obtain the powder metallurgy friction material.

[0100] Example 3

[0101] This embodiment provides a powder metallurgy friction material. By mass percentage, the raw materials for preparing the powder metallurgy friction material include: 15 wt% silicon carbide nanoparticles, 5 wt% alumina nanoparticles, 5 wt% molybdenum disulfide, 5 wt% hexagonal boron nitride, 5 wt% microencapsulated self-healing agent, and the balance being nano copper powder.

[0102] The silicon carbide nanoparticles have an average particle size of 200 nm; the alumina nanoparticles have an average particle size of 100 nm; the molybdenum disulfide has an average particle size of 500 nm; the hexagonal boron nitride has an average particle size of 5 μm; the microencapsulated self-healing agent has an average particle size of 20 μm; and the copper nanoparticles have an average particle size of 100 nm.

[0103] The microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.5;

[0104] The method for preparing the self-healing polymer microcapsules includes:

[0105] (1) Preparation of self-healing polymer: Hydroxyvinyl silicone resin (Sihai Chemical, SH5202) and disulfide-containing compound (dithiodibenzoic acid) are dissolved in a solvent; triethylamine, the first catalyst, is added and stirred evenly; the reaction is heated at 100°C; after the reaction is completed, the self-healing polymer is obtained by filtration, washing and drying.

[0106] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer was dissolved in a hydrophobic solvent (cyclohexane) to form an oil phase; the emulsifier (Span 80) was dissolved in water to form an aqueous phase; the oil phase was dispersed in the aqueous phase to form an O / W emulsion with a particle size of 20 μm; an aqueous solution of diamine (ethylenediamine) was added, followed by the dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction. The reaction temperature was 60 °C and the reaction time was 30 min to obtain self-healing polymer microcapsules; the volume ratio of the oil phase to the aqueous phase was 1:10; the molar ratio of diamine to isocyanate was 1:1; and the total mass of diamine and isocyanate accounted for 20% of the mass of the self-healing polymer.

[0107] The method for preparing the catalyst microcapsules includes: dissolving a second catalyst (tert-dodecyl mercaptan) in a hydrophobic solvent (cyclohexane) to form an oil phase; dissolving an emulsifier (Span 80) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 20 μm; adding an aqueous solution of diamine (ethylenediamine), followed by dropwise addition of isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction at a reaction temperature of 60°C for 30 min to obtain catalyst microcapsules; the volume ratio of the oil phase to the aqueous phase is 1:10; the molar ratio of diamine to isocyanate is 1:1; and the total mass of diamine and isocyanate accounts for 20% of the mass of the second catalyst.

[0108] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano-copper powder, silicon carbide nanoparticles, alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride, and microencapsulated self-healing agent according to the formula to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 650 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 1000℃ for 60 min to obtain the powder metallurgy friction material.

[0109] Example 4

[0110] This embodiment provides a powder metallurgy friction material, except that the nano copper powder therein is nano copper powder that has been surface-treated with a silane coupling agent, and all other aspects are the same as in Example 1.

[0111] The surface treatment of the silane coupling agent includes: cleaning copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol; etching the surface of the copper powder with hydrochloric acid (10% by volume) for 15 minutes to increase roughness; then immersing the copper powder in a 1 wt% silane coupling agent (KH-550) solution for 15 minutes, and drying after immersion to obtain the nano copper powder.

[0112] Example 5

[0113] This embodiment provides a powder metallurgy friction material, except that the nano copper powder therein is nano copper powder that has been surface-treated with a silane coupling agent, and all other aspects are the same as in Example 1.

[0114] The surface treatment of the silane coupling agent includes: cleaning copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol; etching the surface of the copper powder with hydrochloric acid (5% by volume) for 30 minutes to increase roughness; then immersing the copper powder in a 0.5 wt% silane coupling agent (KH-550) solution for 30 minutes, and drying after immersion to obtain the nano copper powder.

[0115] Example 6

[0116] This embodiment provides a powder metallurgy friction material, except that the nano copper powder therein is nano copper powder that has been surface-treated with a silane coupling agent, and all other aspects are the same as in Example 1.

[0117] The surface treatment of the silane coupling agent includes: cleaning copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol; etching the surface of the copper powder with hydrochloric acid (15% by volume) for 1 minute to increase roughness; then immersing the copper powder in a 2wt% silane coupling agent (KH-550) solution for 10 minutes, and drying after immersion to obtain the nano copper powder.

[0118] Example 7

[0119] This embodiment provides a powder metallurgy friction material, which is the same as that in Example 1, except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles that have been surface-treated with a copper-aminosilane composite.

[0120] The surface treatment of the copper-aminosilane composite includes: after cleaning and drying, silicon carbide nanoparticles are treated with sodium hydroxide for surface hydroxyl groups, then immersed in a copper salt-aminosilane composite solution for 20 minutes. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0121] The preparation method of the copper salt-aminosilane complex solution includes: mixing a copper nitrate solution with a mass concentration of 0.5 wt% and an aminosilane solution with a mass concentration of 3 wt% (KH-550 dissolved in deionized water) at a volume ratio of 1:3 to obtain the copper salt-aminosilane complex solution.

[0122] Example 8

[0123] This embodiment provides a powder metallurgy friction material, which is the same as that in Example 1, except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles that have been surface-treated with a copper-aminosilane composite.

[0124] The surface treatment of the copper-aminosilane composite includes: after cleaning and drying, silicon carbide nanoparticles are treated with sodium hydroxide for surface hydroxyl groups, then immersed in a copper salt-aminosilane composite solution for 10 minutes. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0125] The preparation method of the copper salt-aminosilane complex solution includes: mixing a copper nitrate solution with a mass concentration of 0.1 wt% and an aminosilane solution with a mass concentration of 1 wt% (KH-550 dissolved in deionized water) at a volume ratio of 1:2 to obtain the copper salt-aminosilane complex solution.

[0126] Example 9

[0127] This embodiment provides a powder metallurgy friction material, which is the same as that in Example 1, except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles that have been surface-treated with a copper-aminosilane composite.

[0128] The surface treatment of the copper-aminosilane composite includes: after cleaning and drying, silicon carbide nanoparticles are treated with sodium hydroxide for surface hydroxyl groups, then immersed in a copper salt-aminosilane composite solution for 30 minutes. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0129] The preparation method of the copper salt-aminosilane complex solution includes: mixing a 1 wt% copper nitrate solution and a 5 wt% aminosilane (KH-550 dissolved in deionized water) solution at a volume ratio of 1:4 to obtain the copper-aminosilane complex solution.

[0130] Example 10

[0131] This embodiment provides a powder metallurgy friction material, except that the nano-copper powder is nano-copper powder surface-treated with a silane coupling agent and the silicon carbide nanoparticles are silicon carbide nanoparticles surface-treated with a copper-aminosilane composite, the rest are the same as in Example 1.

[0132] The surface treatment of the silane coupling agent includes: cleaning copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol; etching the surface of the copper powder with hydrochloric acid for 15 minutes to increase roughness; then immersing the copper powder in a 1 wt% silane coupling agent (KH-550) solution for 15 minutes, and drying after immersion to obtain the nano copper powder.

[0133] The surface treatment of the copper-aminosilane composite includes: after cleaning and drying, silicon carbide nanoparticles are treated with sodium hydroxide for surface hydroxyl groups, then immersed in a copper salt-aminosilane composite solution for 20 minutes. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0134] The preparation method of the copper salt-aminosilane complex solution includes: mixing a copper nitrate solution with a mass concentration of 0.5 wt% and an aminosilane solution with a mass concentration of 3 wt% (KH-550 dissolved in deionized water) at a volume ratio of 1:3 to obtain the copper salt-aminosilane complex solution.

[0135] Comparative Example 1

[0136] This comparative example provides a powder metallurgy friction material that is identical to Example 1 except that it does not contain silicon carbide nanoparticles, and the proportions of alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride, microencapsulated self-healing agent, and nano copper powder are the same as in Example 1.

[0137] Comparative Example 2

[0138] This comparative example provides a powder metallurgy friction material that is identical to Example 1 except that it does not contain microencapsulated self-healing agents and the proportions of alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride, silicon carbide nanoparticles, and nano-copper powder are the same as in Example 1.

[0139] Performance Characterization

[0140] Friction tests under simulated real-world conditions are used to measure the coefficient of friction of materials under specific loads and speeds; the wear rate is calculated by measuring the system losses of the material during the friction process.

[0141] Table 1

[0142]

[0143]

[0144] In summary, the powder metallurgy friction material provided by this invention exhibits a synergistic effect among nano-copper powder, silicon carbide nanoparticles, and microencapsulated self-healing agent. During friction, silicon carbide nanoparticles and nano-copper powder accelerate the rupture and release of the microencapsulated self-healing agent, making the repair process faster and more effective. Furthermore, silicon carbide nanoparticles can fill cracks and pores, improving density, while nano-copper powder can enhance bonding through interaction with other components, giving the powder metallurgy friction material excellent mechanical properties. The synergistic effect of these three components also enables the powder metallurgy friction material to achieve a friction coefficient that meets process requirements.

[0145] The polymer in the microcapsule self-healing agent contains reversible chemical bonds, and the catalyst microcapsule contains a catalyst. When the friction material is damaged, the microcapsule ruptures, releasing the internal polymer and catalyst, which causes the reversible chemical bonds to break and recombine. The polymer flows to the damaged area and undergoes a polymerization reaction with the surrounding material to form a new polymer, filling the damaged area and achieving self-repair, thereby improving the wear resistance of the friction material.

[0146] As a further preferred technical solution, treating the surface of copper powder with a silane coupling agent can improve the dispersibility of the nano-copper powder, enabling it to be uniformly dispersed in the powder metallurgy friction material and improving the service life of the material. At the same time, the copper powder treated with the silane coupling agent can better combine with the microencapsulated self-healing agent, improve the interfacial bonding force between the microencapsulated self-healing agent and the metal powder, and improve the mechanical properties of the powder metallurgy friction material.

[0147] As a further preferred technical solution, surface treatment of silicon carbide nanoparticles with copper-aminosilane composite can improve the dispersibility of silicon carbide nanoparticles; the presence of copper ions strengthens the bonding force between silicon carbide nanoparticles and nano copper powder, further enhancing the strength of powder metallurgy friction materials, solving the problem of unstable bonding due to large material density differences in the physical interface mixing and connection of silicon carbide and copper, and improving the stability of product quality.

[0148] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A powder metallurgy friction material, characterized in that, The raw materials for preparing the powder metallurgy friction material, by weight percentage, include: 10wt%-15wt% silicon carbide nanoparticles, 5wt%-15wt% alumina nanoparticles, 5wt%-10wt% molybdenum disulfide, 5wt%-10wt% hexagonal boron nitride, 5wt%-10wt% microencapsulated self-healing agent, and the balance being nano copper powder. The microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1-100:0.5; The method for preparing the self-healing polymer microcapsules includes: dissolving the self-healing polymer in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1μm-20μm; adding a diamine aqueous solution, followed by dropwise addition of isocyanate to form an interfacial polycondensation reaction, with a reaction temperature of 20℃-60℃ and a reaction time of 30min-120min, to obtain the self-healing polymer microcapsules; The preparation method of the self-healing polymer includes: dissolving hydroxyvinyl silicone resin and a compound containing disulfide bonds in a solvent; adding a first catalyst and stirring until homogeneous; heating the reaction at 50°C-100°C; after the reaction is completed, obtaining the self-healing polymer by filtration, washing and drying. The method for preparing the catalyst microcapsules includes: dissolving a second catalyst in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1μm-20μm; adding an aqueous diamine solution, followed by dropwise addition of isocyanate to form an interfacial polycondensation reaction, with a reaction temperature of 20℃-60℃ and a reaction time of 30min-120min, to obtain catalyst microcapsules; The second catalyst comprises any one or a combination of at least two of organotin compounds, organotitanium compounds, or thiols.

2. The powder metallurgy friction material according to claim 1, characterized in that, The average particle size of the silicon carbide nanoparticles is 50nm-200nm. And / or, the average particle size of the alumina nanoparticles is 20nm-100nm; And / or, the average particle size of the molybdenum disulfide is 50 nm to 500 nm; And / or, the average particle size of the hexagonal boron nitride is 0.5 μm-5 μm; And / or, the average particle size of the microencapsulated self-healing agent is 1 μm-20 μm; And / or, the average particle size of the nano-copper powder is 20nm-100nm.

3. The powder metallurgy friction material according to claim 1, characterized in that, The nano-copper powder is nano-copper powder that has undergone surface treatment with a silane coupling agent. The silane coupling agent surface treatment includes: Copper powder is sequentially cleaned, dried, and acid-washed, then immersed in a silane coupling agent solution. After immersion, it is dried to obtain the nano-copper powder.

4. The powder metallurgy friction material according to claim 3, characterized in that, The silane coupling agent includes any one or a combination of at least two of KH-540, KH-560, KH-550, KH-580, KH-590, A-151 or A-171.

5. The powder metallurgy friction material according to claim 1, characterized in that, The silicon carbide nanoparticles are silicon carbide nanoparticles that have undergone surface treatment with a copper-aminosilane composite, and the copper-aminosilane composite surface treatment includes: After being cleaned, dried, and surface-hydroxylated, silicon carbide nanoparticles are immersed in a copper salt-aminosilane complex solution. After immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

6. The powder metallurgy friction material according to claim 5, characterized in that, The preparation method of the copper salt-aminosilane complex solution includes: The copper salt-aminosilane complex solution is obtained by mixing a copper salt solution with a mass concentration of 0.1wt%-1wt% and an aminosilane solution with a mass concentration of 1wt%-5wt% in a volume ratio of 1:2-1:

4. And / or, the aminosilane in the aminosilane solution includes any one or a combination of at least two of KH-550, KH-602, KH-792 or KH-540.

7. A method for preparing a powder metallurgy friction material as described in any one of claims 1-6, characterized in that, The preparation method includes: mixing nano-copper powder, silicon carbide nanoparticles, alumina nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula to obtain a mixed powder; the mixed powder is then subjected to cold pressing and sintering to obtain the powder metallurgy friction material.

8. The preparation method according to claim 7, characterized in that, The pressure for cold pressing is 550MPa-650MPa; And / or, the sintering temperature is 800℃-1300℃; And / or, the sintering time is 30 min to 120 min.

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