High lubrication composite material, preparation method and composite gear

Abstract

The application belongs to the technical field of nylon composite materials, and particularly relates to a high-lubrication composite material, a preparation method and a composite gear. A high-lubrication composite material is prepared by in-situ polymerization of carbon nanotubes uniformly dispersed in modified PA6, wherein the carbon nanotubes are double-coated by polyethylene glycol-polypropylene glycol copolymer and polyacrylate, polyethylene glycol is used as a promoter, and caprolactam is used as a monomer, and the modified PA6 is blended with polyphenylene sulfide, SEBS-g-MAH, a heat stabilizer and an antioxidant in proportion to obtain the high-lubrication composite material. The prepared high-lubrication composite material has the characteristics of excellent mechanical properties, strong impact resistance and good friction resistance, and is suitable for preparing a composite gear.

Description

Technical Field

[0001] This invention belongs to the field of nylon composite material technology, and in particular relates to a high-lubricity composite material, its preparation method, and a composite gear. Background Technology

[0002] Nylon, or polyamide, is a high-performance polymer material with excellent mechanical properties, heat resistance, wear resistance, chemical resistance, and self-lubricating properties. It also has a low coefficient of friction and some flame retardancy. These characteristics make nylon an ideal material to replace metal in gear manufacturing.

[0003] The trend towards lightweighting in the automotive industry necessitates the use of more lightweight materials to replace metal components. Nylon gears, with their unique combination of properties, are gradually replacing traditional metal gears, especially in areas such as lightweighting, noise reduction, and corrosion resistance, where they are irreplaceable.

[0004] Despite the significant advantages of nylon gears, they also have some drawbacks, such as: the flexible structure of nylon molecular chains limits their ability to resist instantaneous impacts and continuous loads; under long-term alternating loads, microcracks are prone to appear on the tooth surface and gradually expand, eventually leading to fatigue fracture; they have poor high-temperature resistance and thermal conductivity; and in high-load environments, the self-lubricating layer wears down, exposing the substrate and causing direct friction between the metal mating parts and the nylon, resulting in abrasive wear.

[0005] Carbon nanotubes, as a nanoscale reinforcing filler, possess extremely high axial strength and elastic modulus. When applied to nylon gears, they can significantly compensate for the performance deficiencies of traditional nylon materials, such as mechanical strength, thermal conductivity, self-lubrication, and antistatic properties. The high flexibility of carbon nanotubes can absorb stress concentration caused by alternating loads, delaying the initiation and propagation of microcracks on the tooth surface. Their axial thermal conductivity reaches as high as 3000 W / (m·K), forming a "thermal conduction pathway" within the nylon matrix, accelerating frictional heat transfer. Their interaction with nylon molecular chains restricts chain segment movement, enhancing their resistance to thermal deformation. The smooth surface reduces adhesive wear during tooth surface contact, creating an effect similar to a solid lubricant. The rigid framework resists the penetration of abrasive particles such as dust and silt, protecting the nylon matrix and improving resistance to abrasive wear.

[0006] However, if carbon nanotubes are directly added to a nylon matrix, their surface inertness, high aspect ratio, and strong van der Waals forces can lead to severe agglomeration problems, resulting in a series of performance defects, such as poor dispersibility (the lack of polar groups like hydroxyl and carboxyl groups on the surface of carbon nanotubes leads to poor interfacial compatibility with the nylon matrix, and their high aspect ratio causes them to become tightly entangled with each other through van der Waals forces, forming agglomerates with diameters of tens to hundreds of micrometers); deteriorated processing fluidity; weak interfacial bonding, resulting in deteriorated mechanical and fatigue properties; and deteriorated self-lubricating properties. These defects may cause the composite material to have lower performance than pure nylon. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a high-lubricity composite material, a preparation method, and a composite gear, which effectively solves the defects of carbon nanotubes in nylon composite substrates.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, this application provides a high-lubricity composite material comprising the following raw materials in parts by weight: 80-100 parts modified PA6, 20-40 parts polyphenylene sulfide, 5-12 parts SEBS-g-MAH (styrene-(ethylene-butene)-styrene block copolymer grafted with maleic anhydride), 2-5 parts heat stabilizer, and 10-12 parts antioxidant; wherein the modified PA6 is obtained by in-situ polymerization of caprolactam, double-coated carbon nanotubes, and polyethylene glycol; wherein the surface of the double-coated carbon nanotubes is coated with polyethylene glycol-polypropylene glycol copolymer and polyacrylate.

[0010] Furthermore, the modified PA6 is obtained through the following steps: S1, caprolactam is heated and melted, then double-coated carbon nanotubes and polyethylene glycol are added and ultrasonically dispersed evenly to obtain a mixed melt; S2, sodium hydroxide and diphenylmethane diisocyanate are added to the mixed melt in sequence under vigorous stirring and stirred evenly to obtain a catalytic melt; S3, the catalytic melt is heated to initiate an anionic ring-opening polymerization reaction to obtain modified PA6.

[0011] Furthermore, in S1, the amount of double-coated carbon nanotubes added is 0.8-1.2 wt% of caprolactam; the amount of polyethylene glycol added is 10-15 wt% of caprolactam; and the heating and melting temperature is 78-85℃.

[0012] The ether bonds in the polyethylene glycol molecule form hydrogen bond induction sites with the amide groups of PA6, promoting the formation of fine and uniform γ crystals in PA6. Compared with the traditional α crystal form, the impact toughness of γ crystal PA6 is improved while maintaining tensile strength.

[0013] Furthermore, in S2, the molar amount of sodium hydroxide is 10-12% of the molar amount of caprolactam; the molar amount of diphenylmethane diisocyanate is the same as that of sodium hydroxide.

[0014] Furthermore, the S3 heating temperature is 150-170℃, and the polymerization reaction time is 60-80 min.

[0015] Further, the preparation steps of the double-coated carbon nanotubes are as follows: (1) Immerse the carbon nanotubes in a concentrated acid solution and sonicate them to oxidize the surface of the carbon nanotubes to obtain oxidized carbon nanotubes; (2) Add the oxidized carbon nanotubes to an ethanol solution containing polyethylene glycol-polypropylene glycol copolymer, sonicate them for 2-3 hours, centrifuge and dry them to obtain modified carbon nanotubes; (3) Sonicate the modified carbon nanotubes to toluene, then add acrylate monomers and initiators, heat them under a nitrogen atmosphere to initiate the polymerization of acrylate monomers, after the reaction is completed, pour them into methanol to precipitate, centrifuge and dry them to obtain double-coated carbon nanotubes.

[0016] Furthermore, the heat stabilizer is calcium carbonate.

[0017] Furthermore, the antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants.

[0018] Secondly, this application provides a method for preparing the above-mentioned high-lubricity composite material, comprising the following steps: vacuum drying each raw material to remove moisture; then adding it to a high-speed mixer in proportion and mixing it evenly; then transferring it to a twin-screw extruder for melt blending, extrusion granulation; wherein the processing temperature of the twin-screw extruder is: feeding zone 265-270℃; pre-compression zone 275-280℃; compression zone 285-295℃.

[0019] Thirdly, this application provides a composite gear, which consists of a two-layer structure, with an inner layer being a metal insert and an outer layer being a highly lubricated composite material.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention utilizes double-coated carbon nanotubes generated by modifying polyethylene glycol-polypropylene glycol copolymer and polyacrylate, and prepares modified PA6 with uniformly dispersed carbon nanotubes through in-situ polymerization using polyethylene glycol as a promoter. The modified PA6 is then blended with polyphenylene sulfide, SEBS-g-MAH, heat stabilizer, and antioxidant to prepare a highly lubricated composite material with excellent mechanical properties, strong impact resistance, and good friction resistance.

[0022] This invention achieves double coating of carbon nanotubes using polyethylene glycol-polypropylene glycol copolymer and polyacrylate. The hydrophilic segment of polyethylene glycol in the molecular chain forms hydrogen bonds with the amide groups of nylon, while the oleophilic segment of polypropylene glycol encapsulates the carbon nanotubes through hydrophobic interaction, which can reduce surface energy and inhibit aggregation. The polyacrylate segments are covalently grafted onto the surface of the carbon nanotubes, forming a steric hindrance effect that further prevents the stacking of carbon nanotubes. The ester groups of the polyacrylate chain further enhance the interfacial adhesion between the polyacrylate chain and the nylon matrix through van der Waals forces, which is beneficial to the uniform dispersion of carbon nanotubes in the nylon substrate.

[0023] This application improves the heat resistance, dimensional stability, mechanical strength and rigidity of nylon material PA6 by blending it with polyphenylene sulfide in a specific ratio, and uses SEBS-g-MAH as a compatibilizer to regulate the compatibility between modified PA6 and polyphenylene sulfide, thereby promoting the dispersion of carbon nanotubes in the overall matrix. Attached Figure Description

[0024] Figure 1 The images show SEM images of carbon nanotubes and double-coated carbon nanotubes, with carbon nanotubes on the left and double-coated carbon nanotubes on the right.

[0025] Figure 2 The images show SEM images of modified PA6, with the left side representing Comparative Example 1 and the right side representing Example 2.

[0026] Figure 3 The images show cross-sectional SEM images of the high-lubricity composite material, with Example 2 at the top and Comparative Example 3 at the bottom.

[0027] Figure 4 This is a wear SEM image of a highly lubricated composite material, where the upper part shows the worn surface and the lower part shows the morphology of the transfer film. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A highly lubricating composite material comprises the following raw materials by weight: 80 kg modified PA6, 20 kg polyphenylene sulfide, 5 kg SEBS-g-MAH, 2 kg heat stabilizer, and 10 kg antioxidant.

[0031] In this embodiment, the modified PA6 is obtained through the following steps:

[0032] S1. 4 kg of caprolactam was heated to 78°C to melt, then double-coated carbon nanotubes and polyethylene glycol were added. After stirring for 10 min, the mixture was ultrasonically treated for 1 h to obtain a mixed melt. The amount of double-coated carbon nanotubes added was 0.8 wt% of caprolactam; the amount of polyethylene glycol added was 10 wt% of caprolactam. The molecular weight of polyethylene glycol was 20,000.

[0033] S2, the mixed melt is refluxed under vacuum for 30 min to remove moisture from the system; sodium hydroxide is added to the mixed melt under vigorous stirring, and refluxed under vacuum again to ensure that there is no moisture in the reaction environment, then diphenylmethane diisocyanate is added and stirred evenly to obtain a catalytic melt; the molar amount of sodium hydroxide is 10% of the molar amount of caprolactam; the molar amount of diphenylmethane diisocyanate is the same as that of sodium hydroxide.

[0034] S3, the catalytic melt is heated to 150°C to initiate anionic ring-opening polymerization. The polymerization reaction takes 60 minutes. After cooling to room temperature, modified PA6 is obtained.

[0035] In this embodiment, the double-coated carbon nanotubes are prepared through the following steps:

[0036] (1) Immerse 10g of carbon nanotubes in 100mL of concentrated acid solution (the volume ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 3:1) and sonicate for 1h to oxidize the surface of carbon nanotubes to obtain oxidized carbon nanotubes.

[0037] (2) 10 g of carbon nanotubes were added to 50 mL of an ethanol solution containing polyethylene glycol-polypropylene glycol copolymer, sonicated for 2 h, centrifuged at 10000 r / min for 15 min, the precipitate was washed with anhydrous ethanol, and dried at 50 °C to obtain modified carbon nanotubes. The average molecular weight of the polyethylene glycol-polypropylene glycol copolymer was 5800, the content of polyethylene glycol was 30 wt%, and the concentration of the ethanol solution of polyethylene glycol-polypropylene glycol copolymer was 0.05 g / mL.

[0038] (3) 10g of modified carbon nanotubes were ultrasonically dispersed in 100mL of toluene, and then 5g of acrylate monomer and azobisisobutyronitrile (AIBN) initiator were added. Under a nitrogen atmosphere, the mixture was heated to 80℃ to initiate the polymerization of the acrylate monomer. The mixture was stirred for 6h. After the reaction was completed, the precipitate was poured into methanol, centrifuged at 8000r / min for 15min, washed with methanol, and dried at 50℃ to obtain double-coated carbon nanotubes. The acrylate monomer was composed of methyl acrylate and ethyl acrylate in a mass ratio of 1:1; the molar amount of the initiator was 0.5% of the acrylate monomer.

[0039] The grafting rate of SEBS-g-MAH in this embodiment is 1.2%.

[0040] The heat stabilizer in this embodiment is calcium carbonate.

[0041] The antioxidant in this embodiment is composed of hindered phenolic antioxidant Irganox 1010 and phosphite antioxidant Irgafos 168 in a mass ratio of 1:1.

[0042] Example 2

[0043] A highly lubricating composite material comprises the following raw materials by weight: 90 kg modified PA6, 30 kg polyphenylene sulfide, 8 kg SEBS-g-MAH, 4 kg heat stabilizer, and 11 kg antioxidant.

[0044] In this embodiment, the modified PA6 is obtained through the following steps:

[0045] S1. Caprolactam was heated to 80°C to melt, then double-coated carbon nanotubes and polyethylene glycol were added. After stirring for 12 minutes, the mixture was ultrasonically treated for 1.2 hours to obtain a mixed melt. The amount of double-coated carbon nanotubes added was 1.0 wt% of caprolactam, and the amount of polyethylene glycol added was 12 wt% of caprolactam. The molecular weight of polyethylene glycol was 20,000.

[0046] S2, the mixed melt was refluxed under vacuum for 40 min to remove moisture from the system; sodium hydroxide was added to the mixed melt under vigorous stirring, and refluxed under vacuum again to ensure that there was no moisture in the reaction environment, then diphenylmethane diisocyanate was added and stirred evenly to obtain the catalytic melt; the molar amount of sodium hydroxide was 11% of the molar amount of caprolactam; the molar amount of diphenylmethane diisocyanate was the same as that of sodium hydroxide.

[0047] S3, the catalytic melt is heated to 160℃ to initiate anionic ring-opening polymerization. The polymerization reaction time is 70 min. After cooling to room temperature, modified PA6 is obtained.

[0048] In this embodiment, the double-coated carbon nanotubes are prepared through the following steps:

[0049] (1) Immerse 11g of carbon nanotubes in 110mL of concentrated acid solution (the volume ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 3:1) and sonicate for 1.2h to oxidize the surface of carbon nanotubes to obtain oxidized carbon nanotubes.

[0050] (2) 11 g of carbon nanotubes were added to 65 mL of an ethanol solution containing polyethylene glycol-polypropylene glycol copolymer, sonicated for 2.5 h, centrifuged at 12000 r / min for 18 min, the precipitate was washed with anhydrous ethanol, and dried at 50 °C to obtain modified carbon nanotubes. The average molecular weight of the polyethylene glycol-polypropylene glycol copolymer was 5800, the content of polyethylene glycol was 30 wt%, and the concentration of the ethanol solution of polyethylene glycol-polypropylene glycol copolymer was 0.06 g / mL.

[0051] (3) 11g of modified carbon nanotubes were ultrasonically dispersed in 150mL of toluene, and then 7g of acrylate monomer and azobisisobutyronitrile (AIBN) initiator were added. Under a nitrogen atmosphere, the mixture was heated to 80℃ to initiate the polymerization of the acrylate monomer. The mixture was stirred for 7h. After the reaction was completed, the precipitate was poured into methanol, centrifuged at 90000r / min for 18min, washed with methanol, and dried at 50℃ to obtain double-coated carbon nanotubes. The acrylate monomer was composed of methyl acrylate and ethyl acrylate in a mass ratio of 1:1; the molar amount of the initiator was 0.8% of the acrylate monomer.

[0052] The grafting rate of SEBS-g-MAH in this embodiment is 1.2%.

[0053] The heat stabilizer in this embodiment is calcium carbonate.

[0054] The antioxidant in this embodiment is composed of hindered phenolic antioxidant Irganox 1010 and phosphite antioxidant Irgafos 168 in a mass ratio of 1:1.

[0055] Example 3

[0056] A highly lubricating composite material comprises the following raw materials by weight: 100 kg modified PA6, 40 kg polyphenylene sulfide, 12 kg SEBS-g-MAH, 5 kg heat stabilizer, and 12 kg antioxidant.

[0057] In this embodiment, the modified PA6 is obtained through the following steps:

[0058] S1. Caprolactam is heated to 85°C to melt, double-coated carbon nanotubes and polyethylene glycol are added, stirred for 15 min, and then ultrasonically treated for 1.5 h to obtain a mixed melt; the amount of double-coated carbon nanotubes added is 1.2 wt% of caprolactam; the amount of polyethylene glycol added is 15 wt% of caprolactam, and the molecular weight of polyethylene glycol is 20000.

[0059] S2, the mixed melt was refluxed under vacuum for 50 min to remove moisture from the system; sodium hydroxide was added to the mixed melt under vigorous stirring, and refluxed under vacuum again to ensure that there was no moisture in the reaction environment, then diphenylmethane diisocyanate was added and stirred evenly to obtain the catalytic melt; the molar amount of sodium hydroxide was 12% of the molar amount of caprolactam; the molar amount of diphenylmethane diisocyanate was the same as that of sodium hydroxide.

[0060] S3, the catalytic melt is heated to 170°C to initiate anionic ring-opening polymerization. The polymerization reaction takes 80 minutes. After cooling to room temperature, modified PA6 is obtained.

[0061] In this embodiment, the double-coated carbon nanotubes are prepared through the following steps:

[0062] (1) Immerse 12g of carbon nanotubes in 120mL of concentrated acid solution (the volume ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 3:1) and sonicate for 1.5h to oxidize the surface of carbon nanotubes to obtain oxidized carbon nanotubes.

[0063] (2) 12g of carbon nanotubes were added to 80mL of an ethanol solution containing polyethylene glycol-polypropylene glycol copolymer, sonicated for 3h, centrifuged at 15000r / min for 20min, the precipitate was washed with anhydrous ethanol and dried at 50℃ to obtain modified carbon nanotubes. The average molecular weight of the polyethylene glycol-polypropylene glycol copolymer was 5800, the content of polyethylene glycol was 30wt%, and the concentration of the ethanol solution of polyethylene glycol-polypropylene glycol copolymer was 0.08g / mL.

[0064] (3) 12g of modified carbon nanotubes were ultrasonically dispersed in 200mL of toluene, and then 8g of acrylate monomer and azobisisobutyronitrile (AIBN) initiator were added. Under a nitrogen atmosphere, the mixture was heated to 80℃ to initiate the polymerization of the acrylate monomer. The mixture was stirred for 8h. After the reaction was completed, the precipitate was poured into methanol, centrifuged at 10000r / min for 20min, washed with methanol, and dried at 50℃ to obtain double-coated carbon nanotubes. The acrylate monomer was composed of methyl acrylate and ethyl acrylate in a mass ratio of 1:1; the molar amount of the initiator was 1% of the acrylate monomer.

[0065] The grafting rate of SEBS-g-MAH in this embodiment is 1.2%.

[0066] The heat stabilizer in this embodiment is calcium carbonate.

[0067] The antioxidant in this embodiment is composed of hindered phenolic antioxidant Irganox 1010 and phosphite antioxidant Irgafos 168 in a mass ratio of 1:1.

[0068] Comparative Example 1

[0069] Similar to Example 2, except that carbon nanotubes of equal mass were used instead of double-coated carbon nanotubes to prepare modified PA6.

[0070] Comparative Example 2

[0071] Similar to Example 2, except that polyethylene glycol is not added during the preparation of modified PA6.

[0072] Comparative Example 3

[0073] Same as Example 2, except that ethylene-methyl acrylate-glycidyl methacrylate is used instead of SEBS-g-MAH.

[0074] The preparation method of the above-mentioned high lubricity composite material includes the following steps: vacuum drying each raw material to remove moisture; then adding it to a high-speed mixer in proportion and mixing it evenly; then transferring it to a twin-screw extruder for melt blending, extrusion and granulation; the processing temperature of the twin-screw extruder is: feeding zone 265-270℃; pre-compression zone 275-280℃; compression zone 285-295℃.

[0075] Performance testing:

[0076] The high-lubricity composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were dried in a forced-air drying oven at 120°C for 6 hours, and then injection molded into standard test specimens. Tensile strength was tested according to GB / T1040.1-2025, flexural strength according to GB / T9341-2008, cantilever beam notched impact strength according to GB / T1843-2008, and friction performance according to GB / T3960-2016. The results are shown in Table 1.

[0077] Table 1. Performance Test Results

[0078]

[0079] As can be seen from Table 1, compared with Comparative Examples 1-3, the high-lubricity composite materials prepared in Examples 1-3 of this application have the highest tensile strength and flexural strength, strong impact resistance, and excellent friction performance.

[0080] The carbon nanotubes and double-coated carbon nanotubes in Example 2 were observed and analyzed by SEM. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, both carbon nanotubes and double-coated carbon nanotubes exhibit a coiled and entangled appearance, but their stacking morphologies differ, with carbon nanotubes showing a more compact stacking. This is due to the strong hydrogen bonding between carbon nanotubes, which brings them closer together, resulting in a locally ordered arrangement and providing conditions for tight stacking. The double-coated carbon nanotubes modified with polyethylene glycol-polypropylene glycol copolymer and polyacrylate show a reduced degree of packing density. This means that the double coating weakens the hydrogen bonding interactions between carbon nanotubes, leading to a looser stacking morphology. This looser stacking morphology is more conducive to their dispersion in a nylon matrix.

[0081] The modified PA6 prepared in Example 2 and Comparative Example 1 were subjected to SEM morphology observation and analysis, and the results are as follows: Figure 2 As shown. From Figure 2As can be seen from the example, compared with Comparative Example 1, in the preparation of modified PA6 in Example 2, the carbon nanotubes double-coated by polyethylene glycol-polypropylene glycol copolymer and polyacrylate have stronger dispersion in the nylon matrix and significantly enhanced interfacial bonding with the nylon matrix.

[0082] The cross-sectional morphology of the high-lubricity composite materials prepared in Example 2 and Comparative Example 3 was observed and analyzed by SEM. The results are as follows: Figure 3 As shown. From Figure 3 As can be seen from the data, compared with Comparative Example 3, the carbon nanotubes in Example 2 have stronger dispersion in the overall matrix. This indicates that the addition of SEBS-g-MAH is more beneficial than ethylene-methyl acrylate-glycidyl methacrylate in improving the compatibility of modified PA6 and polyphenylene sulfide, thereby improving the dispersion of carbon nanotubes in the overall matrix.

[0083] The highly lubricating composite material prepared in Example 2 was subjected to ring-block wear testing on an M-200 sliding wear testing machine with a load of 200 N, a speed of 0.5 m / s, and a time of 120 min. Then, SEM morphology testing was performed on the worn surface sample and the steel ring surface to observe the morphology of the worn surface and the transfer film. The results are as follows: Figure 4 As shown. From Figure 4 As can be seen, the surface of the high-lubricity composite material lacks obvious deep grooves, instead exhibiting uniformly distributed exposed areas of carbon nanotubes. This indicates that the wear mechanism is a "cooperative interaction between carbon nanotubes and the matrix" rather than a "matrix-dominated" one. The carbon nanotubes are oriented along the sliding direction, with some tips protruding from the matrix surface, forming "load-bearing peaks" that reduce the area of ​​direct contact between the matrix and the metal. Furthermore, the matrix surface of the high-lubricity composite material shows visible plastic deformation traces with a wrinkled texture, but no melting marks, indicating that the thermal conductivity and load-bearing capacity of the carbon nanotubes effectively suppresses frictional heat accumulation. The transfer film is a uniform and continuous thin film that completely covers the metal surface. The transfer film contains short carbon nanotube fragments, oriented along the sliding direction, forming a "carbon nanotube-polymer" composite film layer, which enhances the film's strength and stability.

[0084] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly lubricating composite material, characterized in that: The raw materials include the following parts by weight: 80-100 parts modified PA6, 20-40 parts polyphenylene sulfide, 5-12 parts SEBS-g-MAH, 2-5 parts heat stabilizer, and 10-12 parts antioxidant; the modified PA6 is obtained by in-situ polymerization of caprolactam, double-coated carbon nanotubes, and polyethylene glycol; the surface of the double-coated carbon nanotubes is coated with polyethylene glycol-polypropylene glycol copolymer and polyacrylate; The modified PA6 is obtained through the following steps: S1, caprolactam is heated and melted, then double-coated carbon nanotubes and polyethylene glycol are added and ultrasonically dispersed to obtain a mixed melt; S2, sodium hydroxide and diphenylmethane diisocyanate are added to the mixed melt in sequence under vigorous stirring and stirred evenly to obtain a catalytic melt; S3, the catalytic melt is heated to initiate an anionic ring-opening polymerization reaction to obtain modified PA6; The amount of double-coated carbon nanotubes added in S1 is 0.8-1.2 wt% of caprolactam; the amount of polyethylene glycol added is 10-15 wt% of caprolactam; and the heating and melting temperature is 78-85℃. The preparation steps of the double-coated carbon nanotubes are as follows: (1) Immerse the carbon nanotubes in a concentrated acid solution and sonicate them to oxidize the surface of the carbon nanotubes to obtain oxidized carbon nanotubes; (2) Add the oxidized carbon nanotubes to an ethanol solution containing polyethylene glycol-polypropylene glycol copolymer, sonicate them for 2-3 hours, centrifuge and dry them to obtain modified carbon nanotubes; (3) Sonicate the modified carbon nanotubes to toluene, then add acrylate monomers and initiators, heat them under a nitrogen atmosphere to initiate the polymerization of acrylate monomers, after the reaction is completed, pour them into methanol to precipitate, centrifuge and dry them to obtain double-coated carbon nanotubes.

2. The high-lubricity composite material according to claim 1, characterized in that: In S2, the molar amount of sodium hydroxide is 10-12% of the molar amount of caprolactam; the molar amount of diphenylmethane diisocyanate is the same as that of sodium hydroxide.

3. The high-lubricity composite material according to claim 1, characterized in that: The S3 heating temperature is 150-170℃, and the polymerization reaction time is 60-80min.

4. The high-lubricity composite material according to claim 1, characterized in that: The heat stabilizer is calcium carbonate.

5. The high-lubricity composite material according to claim 1, characterized in that: The antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants.

6. A method for preparing a highly lubricating composite material as described in any one of claims 1-5, characterized in that: The process includes the following steps: vacuum drying each raw material to remove moisture; then adding it to a high-speed mixer in proportion and mixing evenly; then transferring it to a twin-screw extruder for melt blending, extrusion, and granulation; the processing temperature of the twin-screw extruder is: 265-270℃ in the feeding zone; 275-280℃ in the pre-compression zone; and 285-295℃ in the compression zone.

7. A composite gear, characterized in that: The composite gear consists of a two-layer structure, with an inner layer being a metal insert and an outer layer being a high-lubricity composite material as described in any one of claims 1-5.

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