Graphene aluminum-based alloy enameled wire and preparation method thereof

Abstract

The invention relates to the technical field of wires, and particularly discloses a graphene aluminum-based alloy enameled wire and a preparation method thereof. The graphene content of the conductive wire core is optimized, the components of the insulating paint layer are limited, and the heat conduction performance and the heat resistance of the enameled wire are improved. By means of the good heat conductivity, the aluminum alloy enameled wire can enable heat to be distributed more evenly inside, on one hand, rapid heat dissipation is facilitated, on the other hand, in cooperation with the good heat stability, the aluminum alloy enameled wire can effectively reduce damage to the insulating paint layer under the high-temperature condition, and the service life of the aluminum alloy enameled wire is prolonged. Therefore, the effectiveness of insulation protection can be maintained for a long time, and the reliability and stability of the electronic equipment can be improved.

Description

Technical Field

[0001] This application relates to the technical field of wires. More specifically, it relates to a graphene aluminum-based alloy enameled wire and a preparation method thereof. Background Art

[0002] Enameled wire is a main type of winding wire, consisting of two parts: a conductor and an insulating layer. Usually, the bare wire is annealed and softened, then painted on the surface and baked to form the enameled wire. Currently, various motors and electrical appliances are developing towards miniaturization, lightweight, and high performance. Therefore, enameled wire is required to be made thinner and thinner. Due to the shortage of copper raw materials, aluminum is used instead of copper for the conductor of enameled wire in some electrical appliances.

[0003] In the related art, there is a rare earth aluminum alloy enameled wire, which includes a conductive wire core and an insulating paint layer. The conductive wire core is made of rare earth aluminum alloy, and the insulating paint layer is composed of a first paint layer, a second paint layer, and a third paint layer sequentially coated on the conductive wire core from the inside out; among them, the first paint, the second paint, and the third paint are all mainly composed of polyamic acid, and are respectively added with fluorinated graphite powder, titanium dioxide, and silica sol. After the above-mentioned paint is coated and thermally imidized, an insulating layer mainly composed of polyimide can be formed.

[0004] Regarding the above-mentioned related technology, the inventor believes that although the rare earth aluminum alloy conductive wire core in the related technology has good electrical and mechanical properties, compared with the copper-based conductor, the application of the aluminum-based composite material will lead to an increase in the thermal load of the enameled wire, and the current insulating material has limited heat resistance and cannot ensure the effectiveness of insulation protection for a long time. Summary of the Invention

[0005] In the related technology, the application of the aluminum-based composite material will lead to an increase in the thermal load of the enameled wire, and the current insulating material has limited heat resistance and cannot ensure the effectiveness of insulation protection for a long time. To improve this defect, this application provides a graphene aluminum-based alloy enameled wire and a preparation method thereof.

[0006] In the first aspect, this application provides a graphene aluminum-based alloy enameled wire, adopting the following technical solution: A graphene aluminum-based alloy enameled wire, including a conductive wire core and an insulating paint layer. The conductive wire core is made of a graphene aluminum-based alloy with a graphene content of 0.32 - 0.44 wt%. The insulating paint layer includes the following components in parts by weight: 100 parts of polyimide, 8.6 - 9.8 parts of heat-resistant additive, 0.44 - 0.48 parts of hexagonal boron nitride nanosheets, and 0.36 - 0.40 parts of fluorinated graphene; the polyimide is the imidized product of polyamic acid, the heat-resistant additive includes nanocellulose and hydroxyapatite nanowires, and the polyimide contains an o-carborane unit and a benzimidazole group.

[0007] By adopting the above technical solutions, the present application optimizes the graphene content of the conductive wire core and defines the components of the insulating paint layer. Graphene fluoride and hexagonal boron nitride nanosheets in the insulating paint layer can conduct heat synergistically, which is conducive to the uniform dispersion of heat, can effectively prevent local heat accumulation, and the addition of graphene fluoride can also effectively reduce the dielectric constant of the insulating paint layer, making up for the deficiency of polyimide in electrical properties. The polyimide in the present application contains an o-carborane unit, and the o-carborane unit has a cage-like rigid structure; the benzimidazole group in the polyimide can associate with nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network, and the rigid structure and the hydrogen bond network can synergistically improve the thermal stability of the insulating paint layer. In addition, in the polyimide molecule of the insulating paint layer, the o-carborane unit can form a boron oxide passivation layer on the surface of the insulating paint layer, thereby isolating oxygen and reducing the high-temperature oxidation of the insulating paint layer. With good thermal conductivity, the aluminum alloy enameled wire of the present application can make the heat distribute more evenly inside. On the one hand, it is conducive to rapid heat dissipation, and on the other hand, combined with good thermal stability, it can effectively reduce the damage suffered by the insulating paint layer under high-temperature conditions, so as to maintain the effectiveness of insulation protection for a long time, which helps to improve the reliability and stability of electronic devices.

[0008] Preferably, the weight ratio of the nanocellulose to the hydroxyapatite nanowires is 1:(8 - 10).

[0009] By adopting the above technical solutions, the present application optimizes the weight ratio of the nanocellulose to the hydroxyapatite nanowires, which helps to improve the high-temperature resistance performance of the enameled wire.

[0010] Preferably, the hydroxyapatite nanowires are prepared according to the following method: Mix sodium oleate and deionized water, stir and dissolve to obtain a sodium oleate solution. Sequentially add an aqueous calcium chloride solution and an aqueous sodium dihydrogen phosphate solution to the sodium oleate solution, continue to stir to obtain a suspension, transfer the suspension to a hydrothermal reaction kettle for reaction, filter the product to obtain a filter cake, wash and dry the filter cake to obtain hydroxyapatite nanowires.

[0011] By adopting the above technical solutions, the present application uses sodium oleate and calcium chloride to react to produce calcium oleate, and carries out a hydrothermal reaction with calcium oleate as the precursor. Calcium oleate serves as both a precursor and a calcium source, and can slowly release calcium ions. The calcium ions combine with hydroxide ions and phosphate ions during the hydrothermal reaction to obtain hydroxyapatite nanowires.

[0012] Preferably, the heat-resistant additive further includes halloysite nanotubes.

[0013] By adopting the above technical solution, there are a large number of silanol groups and aluminol groups on the wall of halloysite nanotubes, which can associate with benzimidazole groups, nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network, increasing the complexity of the hydrogen bond network and improving the high-temperature resistance of the enameled wire.

[0014] Preferably, the weight ratio of the nanocellulose to the halloysite nanotubes is 1:(2.6 - 2.8).

[0015] By adopting the above technical solution, the present application optimizes the weight ratio of the nanocellulose to the halloysite nanotubes, which helps to improve the high-temperature resistance of the enameled wire.

[0016] Preferably, the polyamic acid is made from a diamine monomer and a dianhydride monomer, and the diamine monomer includes an o-carborane diamine monomer.

[0017] By adopting the above technical solution, the present application optimizes the type of the diamine monomer. By using a diamine monomer containing an o-carborane unit to prepare the polyamic acid, a polyimide molecule containing an o-carborane unit can be obtained after the imidization reaction.

[0018] Preferably, the o-carborane diamine monomer is prepared according to the following method: (1) Under the condition of an ice-water bath, add nitrosulfuric acid mixture and DCM to DPCB, stir and react, then pour the mixture into ice water for quenching, extract with DCM, wash and dry the organic phase, and then perform rotary evaporation and concentration to obtain a dinitro intermediate; (2) Use stannous chloride as a reducing agent to reduce the dinitro intermediate to obtain the o-carborane diamine monomer.

[0019] By adopting the above technical solution, the present application first sulfonates DPCB with nitrosulfuric acid mixture to obtain a dinitro intermediate, and then uses stannous chloride to reduce the nitro group to an amino group, thereby obtaining the o-carborane diamine monomer.

[0020] Preferably, the diamine monomer further includes at least one of 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0021] By adopting the above technical solution, the present application optimizes the type of the diamine monomer. The above two diamine monomers can introduce benzimidazole groups and phenyl groups into the polyamic acid, which can effectively improve the heat resistance of the aluminum alloy enameled wire.

[0022] Preferably, the polyamic acid is prepared according to the following method: Mix the diamine monomer and DMAC, stir under nitrogen protection to obtain a diamine solution, and add the dianhydride monomer and DMAC to the diamine solution under an ice-water bath condition, and continue to stir in a nitrogen atmosphere to obtain polyamic acid.

[0023] By adopting the above technical solution, the present application optimizes the preparation method of polyamic acid. Through the above method, polyamic acid with good fluidity can be synthesized, which is convenient for coating on the surface of the conductive wire core.

[0024] In a second aspect, the present application provides a preparation method of a graphene aluminum-based alloy enameled wire, adopting the following technical solution.

[0025] A preparation method of a graphene aluminum-based alloy enameled wire includes the following steps: (1) Mix polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and a heat-resistant additive to obtain an insulating paint for standby; wash the conductive wire core and send it into an annealing furnace for annealing, and then wash and dry it for standby; (2) Coat the insulating paint on the surface of the conductive wire core, and cure the insulating paint into an insulating paint layer by baking, and then wait for the conductive wire core to cool; (3) Coat lubricating oil on the surface of the insulating paint layer, dry it and wind up the wire to obtain a graphene aluminum-based alloy enameled wire.

[0026] By adopting the above technical solution, the present application first prepares an insulating paint, anneals the conductive wire core, then coats the insulating paint on the surface of the conductive wire core, cures the conductive wire core into a film after thermal imidization, and then coats lubricating oil to obtain a graphene aluminum-based alloy enameled wire with high heat resistance.

[0027] In summary, the present application has the following beneficial effects: 1. The present application optimizes the graphene content of the conductive wire core and limits the components of the insulating paint layer, improving the thermal conductivity and heat resistance of the enameled wire. With good thermal conductivity, the aluminum alloy enameled wire of the present application can make the heat distribute more evenly inside, which is beneficial to rapid heat dissipation on the one hand, and on the other hand, combined with good thermal stability, the aluminum alloy enameled wire of the present application can effectively reduce the damage suffered by the insulating paint layer under high temperature conditions, so as to maintain the effectiveness of insulation protection for a long time, which helps to improve the reliability and stability of electronic devices.

[0028] 2. The present application preferably uses halloysite nanotubes as the third component of the heat-resistant additive. There are a large number of silicon hydroxyl groups and aluminum hydroxyl groups on the wall of the halloysite nanotubes, which can associate with benzimidazole groups, nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network, increasing the complexity of the hydrogen bond network and improving the high-temperature resistance of the enameled wire.

[0029] 3. In the polyimide molecules of the insulating paint layer, the o-carborane units can form a boron oxide passivation layer on the surface of the insulating paint layer, thereby isolating oxygen and reducing the high-temperature oxidation of the insulating paint layer. Detailed implementation manners

[0030] The present application will be further described in detail below with reference to examples, preparation examples and comparative examples. The raw materials involved in the present application are all commercially available.

[0031] Preparation example of hydroxyapatite nanowires The following takes Preparation Example 1 as an example for illustration.

[0032] Preparation Example 1 In this preparation example, the hydroxyapatite nanowires are prepared according to the following method: 2.44 g of sodium oleate and 25 g of deionized water are mixed and stirred until dissolved to obtain a sodium oleate solution. 25 mL of an aqueous calcium chloride solution (containing 0.22 g of anhydrous calcium chloride) and 25 mL of an aqueous sodium dihydrogen phosphate solution (containing 0.28 g of sodium dihydrogen phosphate dihydrate) are successively added to the sodium oleate solution, and stirring is continued for 35 min to obtain a suspension. The suspension is transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene inner liner and reacted at 200 °C for 36 h. The product is filtered to obtain a filter cake, and the filter cake is washed and dried to obtain hydroxyapatite nanowires.

[0033] Preparation example of polyamic acid The following takes Preparation Example 2 as an example for illustration.

[0034] Preparation Example 2 In this preparation example, the molar ratio of the diamine monomer to the dianhydride monomer is 1:1.02. The diamine monomer is composed of an o-carborane diamine monomer and a benzimidazole monomer mixed in a weight ratio of 1:3. The benzimidazole monomer is 2-(3,5-diaminophenyl)-benzimidazole; the dianhydride monomer is BTDA.

[0035] The o-carborane diamine monomer is prepared according to the following method: (1) Under ice-water bath conditions, 6.77 mmol of diphenyl o-carborane (DPCB) is added with a nitrosulfuric acid mixture (10 mL of 65 wt% nitric acid and 30 mL of 98 wt% sulfuric acid) and 30 mL of dichloromethane (DCM), and the mixture is stirred and reacted for 3 h. Then the mixture is poured into 250 mL of ice water for quenching, extracted with DCM, the organic phase is washed successively with saturated sodium bicarbonate solution and saturated sodium chloride solution, and anhydrous sodium sulfate is added for drying for 6 h. Then the dried product is concentrated by rotary evaporation to obtain a dinitro intermediate; (2) Under a nitrogen atmosphere, 4.82 mmol of the dinitro intermediate, 48.77 mmol of stannous chloride, 40 mL of absolute ethanol, 40 mL of ethyl acetate, and 4 mL of hydrochloric acid with a concentration of 36.5 wt% were mixed, heated under reflux at 80 °C for 6 h. After the reaction, the pH of the product solution was adjusted to 8 with sodium bicarbonate, extracted with ethyl acetate, and the organic phase was washed with saturated sodium chloride solution. The obtained solution was dried with anhydrous sodium sulfate for 6 h and concentrated by rotary evaporation to obtain the o-carborane diamine monomer.

[0036] This preparation example provides a polyamic acid, which is prepared according to the following method: The diamine monomer and DMAC were mixed in a ratio of 1 g:2.5 mL, stirred under nitrogen protection to obtain a diamine solution. Under ice-water bath conditions, the dianhydride monomer and DMAC (with the same amount of DMAC used for preparing the diamine solution) were added to the diamine solution, and stirring was continued in a nitrogen atmosphere for 24 h to obtain the polyamic acid.

[0037] Preparation Example 3 The difference between this preparation example and Preparation Example 1 is that the benzimidazole monomer is composed of 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole mixed in a weight ratio of 1:1.5.

[0038] Preparation Example of Fluorinated Graphene The following takes Preparation Example 4 as an example for illustration.

[0039] Preparation Example 4 This preparation example provides a fluorinated graphene, which is prepared according to the following method: Graphite fluoride and NMP were mixed to obtain a graphite fluoride solution with a concentration of 5 mg / mL. The solution was heated under reflux at 55 °C for 2.5 h, and then ultrasonic exfoliation was carried out under the condition of 300 W for 4 h. After removing the solvent NMP, fluorinated graphene was obtained.

[0040] Preparation Example of Conductive Wire Core The following takes Preparation Example 5 as an example for illustration.

[0041] Preparation Example 5 In this preparation example, the conductive wire core is made of a graphene aluminum-based alloy. The elemental weight composition of the graphene aluminum-based alloy is as follows: silicon 0.14%, iron 0.9%, copper 0.4%, vanadium 0.08%, graphene 0.32%, zirconium 0.06%, boron 0.08%, lanthanum 0.02%, scandium 0.01%, and the balance is aluminum and impurities that have no effect on performance.

[0042] This preparation example provides a conductive wire core, which is prepared according to the following method: (1) Melting: Weigh the raw materials corresponding to the composition of the aluminum matrix composite conductor, put the aluminum raw material into a crucible, heat it up to 730 °C, add the remaining raw materials and continuously stir to form a uniform melt; (2) Refining: Maintain the temperature at 730 °C, under an inert protective atmosphere of Ar, add a refining agent for refining. During the refining process, permanent magnetic stirring is carried out every 10 minutes, and each stirring time is 3 minutes. After the refining is completed, slag skimming operation is carried out; (3) Degassing in the holding furnace: Under the holding state, introduce a mixed gas into the melt for degassing treatment. The mixed gas is 60 vol% Ar and 40 vol% Cl2; (4) Casting and continuous casting: Cast and continuously cast the melt to obtain an aluminum matrix alloy rod. The total cooling rate during the casting process is controlled at 10 °C / s; (5) Tempering treatment: Place the aluminum matrix alloy rod in a tempering furnace for treatment. The tempering temperature is 340 °C and the tempering time is 4 h; (6) Drawing and aging treatment: Carry out drawing treatment on the aluminum matrix alloy rod after tempering treatment, and then enter the aging furnace for aging treatment; In this step, the drawing diameter is φ0.2 mm, the aging treatment temperature is 165 °C, and the aging treatment time is 4 h; (7) Stranding and bunch stranding: Strand and bunch strand the aluminum matrix alloy wires to finally obtain a conductor core. Example

[0043] Examples 1 - 3 The following takes Example 1 as an example for illustration.

[0044] Example 1 This example provides a graphene aluminum matrix alloy enameled wire, including a conductor core and an insulating paint layer with a thickness of 40 μm. The conductor core is prepared according to the method of Preparation Example 5. The insulating paint layer includes the following components in parts by weight: 100 parts of polyimide, 8.6 parts of heat-resistant additive, 0.44 parts of hexagonal boron nitride nanosheets, and 0.36 parts of fluorinated graphene; The polyimide is made from the polyamic acid of Preparation Example 2. The heat-resistant additive includes nanocellulose and hydroxyapatite nanowires, and the weight ratio of nanocellulose to hydroxyapatite nanowires is 1:12. The specific surface area of the hexagonal boron nitride nanosheets is 82 m 2 / g, and the fluorinated graphene is prepared according to the method of Preparation Example 4.

[0045] This example provides a preparation method of a graphene aluminum matrix alloy enameled wire, including the following steps: (1) Mix the polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and heat-resistant additive to obtain an insulating paint for standby; Wash the conductor core and send it into an annealing furnace for annealing, and then wash and dry it for standby; (2) Coat the surface of the conductive wire core with insulating paint, and cure the insulating paint into an insulating paint layer by baking, and then wait for the conductive wire core to cool down; in this step, the coating amount is 12 passes, and each pass is baked once after coating. The baking procedure for each time is as follows: starting from 25°C, raise the temperature to 130°C in 1 hour, keep the temperature for 1 hour, then raise the temperature to 300°C in 2 hours, keep the temperature for 1 hour, and then raise the temperature to 350°C in 50 minutes, keep the temperature for 2 hours, and then cool down naturally; (3) Coat lubricating oil on the surface of the insulating paint layer, dry it and wind up the wire to obtain the graphene aluminum-based alloy enameled wire.

[0046] As shown in Table 1, the main differences between Examples 1-3 are the composition of the insulating paint layer and the graphene content in the conductive wire core.

[0047] Table 1 Composition of the insulating paint layer (by weight) and graphene content in the conductive wire core Sample Example 1 Example 2 Example 3 Polyimide / parts 100 100 100 Heat-resistant additive / parts 8.6 9.2 9.8 Hexagonal boron nitride nanosheet / parts 0.44 0.46 0.48 Fluorinated graphene / parts 0.36 0.38 0.40 Graphene content in the conductive wire core / % 0.32 0.38 0.44 Example 4 The difference between this example and Example 3 is that the weight ratio of nanocellulose to hydroxyapatite nanowires is 1:10.

[0048] Example 5 The difference between this example and Example 3 is that the weight ratio of nanocellulose to hydroxyapatite nanowires is 1:9.

[0049] Example 6 The difference between this example and Example 3 is that the weight ratio of nanocellulose to hydroxyapatite nanowires is 1:8.

[0050] Example 7 The difference between this example and Example 6 is that the heat-resistant additive also includes halloysite nanotubes, and the weight ratio of nanocellulose to halloysite nanotubes is 1:2.1.

[0051] Example 8 The difference between this example and Example 7 is that the weight ratio of nanocellulose to halloysite nanotubes is 1:2.6.

[0052] Example 9 The difference between this example and Example 7 is that the weight ratio of nanocellulose to halloysite nanotubes is 1:2.7.

[0053] Example 10 The difference between this example and Example 7 is that the weight ratio of nanocellulose to halloysite nanotubes is 1:2.8.

[0054] Example 11 The difference between this example and Example 10 is that the polyamic acid is prepared according to the method of Preparation Example 3.

[0055] Comparative Example Comparative Example 1 This comparative example provides a rare earth aluminum alloy enameled wire, which includes a conductive wire core and an insulating paint layer with a thickness of 40 μm. The conductive wire core is made of rare earth aluminum alloy, and its size specification is the same as that of Example 1. The raw material components in the conductive wire core are by weight: 0.245% of copper, 0.1% of zinc, 0.005% of cerium, and the balance is aluminum and impurities that have no effect on the performance. The insulating paint layer is composed of a first paint layer, a second paint layer, and a third paint layer that are sequentially coated on the conductive wire core from the inside out.

[0056] In this comparative example, the first paint layer, the second paint layer, and the third paint layer are all made of a polyamic acid precursor as the raw material. The polyamic acid precursor is prepared according to the following method: Take 3,3,4,4-benzophenone tetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether in a molar ratio of 1.02:1, and dissolve them together in N, N-dimethylacetamide, and continuously stir until the solution wraps around the shaft to obtain the polyamic acid precursor.

[0057] The first paint is prepared according to the following method: Take graphite fluoride powder and add it to an N-methylpyrrolidone solvent to prepare a solution with a concentration of 4 mg / mL. Heat it to 55 °C and reflux for 60 minutes. After cooling, centrifuge and collect the supernatant. Mix the supernatant with the polyamic acid precursor solution in a volume ratio of 1:10 and mechanically stir for 4 hours to obtain the first paint.

[0058] The second paint is prepared according to the following method: Bake titanium dioxide at 100 °C for 120 minutes and then add it to the polyamic acid precursor solution at a mass fraction of 5%. After ultrasonic oscillation for 30 minutes, mechanically stir for 60 minutes to obtain the second paint; where the titanium dioxide is mixed-crystalline gas-phase nano-titanium dioxide particles with an average particle size of 22 nm and a specific surface area of 56 m 2 / g, where the mass ratio of anatase to rutile is 7:2.

[0059] The third paint is prepared according to the following method: Add a 0.1 mol / L sodium hydroxide solution to the polyamic acid precursor solution until the pH is 8.5, and then add 10% of the silica sol by the mass of the solution. Stir at 40 °C for 2 hours to obtain the third paint.

[0060] The preparation method of the rare earth aluminum alloy enameled wire is: (1) Wash the conductive wire core and send it into an annealing furnace for annealing. Cool the wire core with 50°C purified water and then quickly dry it. (2) Send the annealed wire core into the painting area of the drying oven. Use painting molds to sequentially coat the first paint, the second paint, and the third paint on the surface of the conductive wire core to form a first paint layer, a second paint layer, and a third paint layer. During the painting process, the coating amount of the first paint is 6 coats, the coating amount of the second paint is 2 coats, and the coating amount of the third paint is 4 coats. After each coat is completed, a baking process is carried out. The baking procedure each time is as follows: starting from 25°C, raise the temperature to 130°C in 1 hour, keep the temperature for 1 hour, then raise the temperature to 300°C in 2 hours, keep the temperature for 1 hour, and then raise the temperature to 350°C in 50 minutes. After keeping the temperature for 2 hours, cool it naturally. (3) After cooling the painted conductive wire core, coat a layer of lubricating oil on its surface, dry it, and then wind up the wire to obtain a rare earth aluminum alloy enameled wire.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the insulating paint layer does not contain nanocellulose.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that the insulating paint layer does not contain hydroxyapatite nanowires.

[0063] Comparative Example 4 The difference between this comparative example and Example 1 is that the insulating paint layer does not contain fluorinated graphene.

[0064] Comparative Example 5 The difference between this comparative example and Example 1 is that the insulating paint layer does not contain hexagonal boron nitride nanosheets.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is that the diamine monomer for synthesizing polyamic acid does not include o-carborane diamine monomer.

[0066] Comparative Example 7 The difference between this comparative example and Example 1 is that the diamine monomer for synthesizing polyamic acid does not include benzimidazole monomer.

[0067] Performance detection test method I. Heat resistance of insulating paint According to the methods described in each example and comparative example, coat the insulating paint on the surface of a glass plate. The glass plate is pre-cleaned with deionized water, acetone, dichloromethane, and isopropanol, and ultrasonically treated in deionized water for 15 minutes. After completing the film coating, place the glass plate with the paint in a laminar flow bench. After 24 hours, perform thermal imidization to obtain a sample film.

[0068] In a nitrogen atmosphere, the temperature was raised at a rate of 10 °C / min in the temperature range of 25 °C to 800 °C. The temperature at which the film lost 5% of its weight was recorded as the 5% weight loss temperature. The results are shown in Table 2.

[0069] II. Creep strain The test was carried out in accordance with "Aluminum alloy wire for cable conductors GB / T 30552 Appendix B". The test objects were the conductor cores of Examples 1-3 and Comparative Example 1. The test conditions were: creep temperature of 200 °C, stress of 60 MPa, and 100 h. The results are shown in Table 2.

[0070] Table 2 Relative weight loss temperature Sample 5% weight loss temperature / °C Sample 5% weight loss temperature / °C Example 1 565.2 Example 10 574.5 Example 2 565.7 Example 11 577.3 Example 3 566.4 Comparative Example 1 518.4 Example 4 567.1 Comparative Example 2 539.8 Example 5 568.5 Comparative Example 3 542.5 Example 6 570.3 Comparative Example 4 553.2 Example 7 571.0 Comparative Example 5 548.4 Example 8 572.4 Comparative Example 6 546.4 Example 9 572.8 Comparative Example 7 541.9 Table 3 Creep strain Sample Creep variable / % Example 1 0.18 Example 2 0.17 Example 3 0.16 Comparative Example 1 0.23 Combining Examples 1-3 and Comparative Example 1 and referring to Table 2 and Table 3, it can be seen that the 5% weight loss temperature measured in Examples 1-3 is relatively high. This is because the graphene content of the conductor core is optimized in this application, and the components of the insulating paint layer are limited, thereby improving the thermal conductivity and heat resistance of the enameled wire. The creep strain measured in Examples 1-3 is relatively small, indicating that the conductor core also has good stability. With good thermal conductivity, the aluminum alloy enameled wire of this application can make the heat distribute more evenly inside. This characteristic is beneficial for rapid heat dissipation on the one hand, and on the other hand, combined with good thermal stability, it can effectively reduce the damage to the insulating paint layer under high temperature conditions, thereby being able to maintain the effectiveness of insulation protection for a long time and contributing to improving the reliability and stability of electronic devices.

[0071] Combining Example 1 and Comparative Examples 2-3 and referring to Table 2 and Table 3, it can be seen that when nanocellulose and apatite nanowires are not used in combination, they cannot form an association through hydrogen bonds. The lack of hydrogen bonds results in a poor heat resistance effect of the insulating paint layer, so the insulating paint layer will reach a 5% mass loss at a relatively low temperature.

[0072] Combining Example 1 and Comparative Examples 4-5 and referring to Table 2 and Table 3, it can be seen that when fluorinated graphene and hexagonal boron nitride nanosheets are not used in combination, due to poor heat conduction in the insulating paint layer, local temperature accumulation is likely to occur, resulting in reaching a 5% mass loss prematurely. Combining Example 1 and Comparative Examples 6-7 and referring to Table 2 and Table 3, it can be seen that when either the carbon borane unit or the benzimidazole group is missing in the polyimide, due to the influence on the synergistic effect, the heat resistance performance of the insulating paint layer has decreased, and a 5% mass loss is reached at a relatively low temperature.

[0073] Combined with Example 3 and Examples 4 - 6 and in combination with Table 2 and Table 3, it can be seen that when the weight ratio of nanocellulose to hydroxyapatite nanowires is 1:(8 - 10), the heat resistance of the insulating paint layer is relatively good, so the enameled wire can resist high temperatures more persistently.

[0074] Combined with Example 6 and Examples 7 - 10 and in combination with Table 2 and Table 3, it can be seen that when the weight ratio of nanocellulose to halloysite nanotubes is 1:(2.6 - 2.8), the hydrogen bonds associated with the heat-resistant filler are more perfect, so the heat resistance of the insulating paint layer is relatively good, and the enameled wire can resist high temperatures more persistently.

[0075] Combined with Example 10 and Example 11 and in combination with Table 2 and Table 3, it can be seen that when the diamine monomer includes both 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole, the heat resistance of the insulating paint layer is good and it has a strong resistance to high temperatures.

[0076] The above embodiments are only explanations of the present application and not limitations thereof. Those skilled in the art can make modifications to the embodiments of the present application without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A graphene aluminum-based alloy enameled wire, characterized in that, It includes a conductive wire core and an insulating paint layer. The conductive wire core is made of a graphene-aluminum alloy with a graphene content of 0.32 - 0.44 wt%. The insulating paint layer comprises the following components in parts by weight: 100 parts of polyimide, 8.6 - 9.8 parts of heat-resistant additive, 0.44 - 0.48 parts of hexagonal boron nitride nanosheets, and 0.36 - 0.40 parts of fluorinated graphene; the polyimide is the imidization product of polyamic acid, the heat-resistant additive includes nanocellulose and hydroxyapatite nanowires, and the polyimide contains o-carborane units and benzimidazole groups.

2. The enameled wire made of graphene aluminum-based alloy according to claim 1, wherein, The weight ratio of the nanocellulose to the hydroxyapatite nanowires is 1:(8 - 10).

3. The enameled wire made of graphene-aluminum-based alloy according to claim 1, wherein, The hydroxyapatite nanowires are prepared according to the following method: Mix sodium oleate and deionized water, stir and dissolve to obtain a sodium oleate solution. Sequentially add an aqueous calcium chloride solution and an aqueous sodium dihydrogen phosphate solution to the sodium oleate solution, continue stirring to obtain a suspension, transfer the suspension to a hydrothermal reaction kettle for reaction, filter the product to obtain a filter cake, wash and dry the filter cake to obtain hydroxyapatite nanowires.

4. The enameled wire made of graphene aluminum-based alloy according to claim 3, characterized in that, The heat-resistant additive further includes halloysite nanotubes.

5. The enameled wire made of graphene aluminum-based alloy according to claim 4, characterized in that The weight ratio of the nanocellulose to the halloysite nanotubes is 1:(2.6 - 2.8).

6. The enameled wire made of graphene aluminum-based alloy according to claim 1, characterized in that The polyamic acid is made from a diamine monomer and a dianhydride monomer. The diamine monomer includes an o-carborane diamine monomer.

7. The enameled wire made of graphene aluminum-based alloy according to claim 6, wherein The o-carborane diamine monomer is prepared according to the following method: (1) Add nitrosulfuric acid mixture and DCM to DPCB under an ice-water bath condition, stir and react, then pour the mixture into ice water for quenching, extract with DCM, wash and dry the organic phase, and then perform rotary evaporation and concentration to obtain a dinitro intermediate; (2) Use stannous chloride as a reducing agent to reduce the dinitro intermediate to obtain the o-carborane diamine monomer.

8. The enameled wire made of graphene aluminum-based alloy according to claim 6, characterized in that, The diamine monomer further includes at least one of 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole.

9. The enameled wire made of graphene aluminum-based alloy according to claim 6, characterized in that, The polyamic acid is prepared according to the following method: Mix the diamine monomer and DMAC, stir under nitrogen protection to obtain a diamine solution, add the dianhydride monomer and DMAC to the diamine solution under an ice-water bath condition, and continue stirring in a nitrogen atmosphere to obtain polyamic acid.

10. The preparation method of the graphene aluminum-based alloy enameled wire according to any one of claims 1-9, characterized in that, It includes the following steps: (1) Mix polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and heat-resistant additive to obtain an insulating paint, and set aside; wash the conductive wire core and send it into an annealing furnace for annealing, then wash and dry it for standby; (2) Coat the insulating paint on the surface of the conductive wire core, and cure the insulating paint into an insulating paint layer by baking, then wait for the conductive wire core to cool; (3) Coat lubricating oil on the surface of the insulating paint layer, dry it and wind up the wire to obtain a graphene-aluminum alloy enameled wire.