A corona-resistant composite sheet for new energy vehicle motors and its preparation method

Abstract

This application discloses a corona-resistant composite sheet for use in new energy vehicle motors and its preparation method. The composite sheet is prepared from the following raw materials in weight percentages: a first hot-melt film layer of 10-40%, a mica paper layer of 20-80%, and a second hot-melt film layer of 10-40%. This application uses a hot-melt film to reinforce the mica paper layer, resulting in a corona-resistant composite sheet with high density, excellent corona resistance, electrical strength, heat resistance, mechanical properties, high partial discharge initiation voltage, and good application process performance.

Description

Technical Field

[0001] This application relates to a corona-resistant composite sheet for use in new energy vehicle motors and its preparation method, belonging to the technical field of corona-resistant composite materials for new energy motors. Background Technology

[0002] Existing high-temperature resistant slot and phase insulation paper for new energy vehicle motors, classified as H or higher, is mostly made of aramid fiber pure paper, or aramid fiber paper combined with polyimide film using high-temperature resistant adhesives. A typical composite paper structure is Nomex fiber paper / PI film / Nomex fiber paper (NHN), and the composite adhesives are mostly epoxy, polyurethane, or polyacrylate adhesives. Aramid fiber pure paper or NHN composite paper has high heat resistance, making it excellent for insulation structures in 400V voltage platform motors of new energy vehicles. However, for 800V voltage platform motors, due to the higher voltage level, pulse width modulation peak voltage, and environmental factors, the maximum safe voltage may reach 2300V or even higher. This far exceeds the partial discharge initiation voltage (PDIV) of existing conventional low-voltage motor insulation materials, resulting in a very high probability of partial discharge during motor operation. Therefore, the corona resistance of the insulation material must be considered for 800V voltage platform automotive motors.

[0003] Existing technologies improve the corona resistance life of composite papers by adding mica to organic aramid fiber paper or by using epoxy, polyurethane, or polyacrylate adhesives to bond aramid fiber paper and mica paper. However, mica-containing composite papers prepared by these two methods suffer from problems such as easy powdering, easy delamination, and brittleness. Their corona resistance and high-temperature resistance are generally poor, and their partial discharge initiation voltage (PDIV) is low, which cannot meet the process requirements for large-scale application in new energy vehicle motors. Summary of the Invention

[0004] To address the aforementioned issues, a corona-resistant composite sheet for new energy vehicle motors and its preparation method are provided. A hot-melt film is used to reinforce the mica paper layer, resulting in a corona-resistant composite sheet with high density, excellent corona resistance, electrical strength, heat resistance, mechanical properties, high partial discharge initiation voltage, and good application process performance.

[0005] According to one aspect of this application, a corona-resistant composite sheet for a new energy vehicle motor is provided, which is prepared from the following raw materials in weight percentages: 10-40% of a first hot melt film layer, 20-80% of a mica paper layer, and 10-40% of a second hot melt film layer.

[0006] Optionally, no adhesive is used between the first hot melt film layer, the mica paper layer, and the second hot melt film layer.

[0007] Optionally, the thickness of the first hot melt film layer is 0.02-0.15 mm, the thickness of the mica paper layer is 0.05-0.20 mm, and the thickness of the second hot melt film layer is 0.02-0.15 mm.

[0008] Preferably, the thickness ratio of the first hot melt film layer, the mica paper layer, and the second hot melt film layer is 1:2:1.

[0009] Optionally, the first hot melt film layer is selected from one or more of polyphenylene sulfide, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone and polyether imide.

[0010] Optionally, the second hot melt film layer is selected from one or more of polyphenylene sulfide, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone and polyether imide.

[0011] The materials of the first and second hot melt film layers may not be exactly the same. Both are thermoplastic plastics that are resistant to high temperatures above 180°C and oil, giving the composite sheet oil resistance and enabling it to adapt to complex environments such as oil inside the equipment, making it highly adaptable.

[0012] Preferably, the first and second hot melt film layers are thermoplastics that are resistant to high temperatures above 180°C and oil, with a dielectric constant of less than 4. Selecting a plastic with a lower dielectric constant can improve the partial discharge initiation voltage (PDIV).

[0013] Optionally, the first hot melt film layer and / or the second hot melt film layer may further include inorganic nanoparticles.

[0014] Optionally, the inorganic nanoparticles are one or more of silicon dioxide, aluminum oxide, boron nitride, aluminum nitride, and titanium dioxide, and the particle size of the inorganic nanoparticles is 10nm-800nm.

[0015] By adding inorganic nanoparticles and limiting their particle size, the corona resistance of the material is improved, and the inorganic nanoparticles exhibit good dispersion uniformity.

[0016] Preferably, the amount of inorganic nanoparticles added is 2.5%-15% of the weight of the first or second hot melt film layer.

[0017] Optionally, the mica paper layer includes mica flakes and reinforcing material, wherein the mica flakes have a particle size of 30-800 mesh.

[0018] Optionally, the reinforcing material includes one or both of aramid fiber and glass fiber. Adding glass fiber or aramid fiber improves the mechanical properties and processability of the material.

[0019] Preferably, the glass fiber is chopped glass fiber, the aramid fiber is precipitated meta-aramid fiber, and the amount of glass fiber and / or aramid fiber added is 5-30% of the weight of the mica paper layer.

[0020] According to another aspect of this application, a method for preparing a corona-resistant composite sheet for a new energy vehicle motor as described above is also provided, comprising the following steps:

[0021] (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers.

[0022] (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 290-390℃ and a pressure of 5-20MPa.

[0023] (3) After hot pressing, the corona-resistant composite sheet for new energy vehicle motors is obtained.

[0024] The beneficial effects of this application include, but are not limited to:

[0025] 1. According to the corona-resistant composite sheet for new energy vehicle motors of this application, a hot melt film is used to reinforce the mica paper layer, so that the final corona-resistant composite sheet has high density and excellent corona resistance, electrical strength, heat resistance, mechanical properties, high partial discharge initiation voltage and good application process performance.

[0026] 2. The corona-resistant composite sheet for new energy vehicle motors according to this application uses a hot-melt film layer that is resistant to high temperature and oil and has a low dielectric constant, and then reinforced with inorganic nanoparticles. It is then hot-pressed with a mica paper layer. Compared with mica in other states, the mica flakes in the mica paper layer have better corona resistance. The dual corona resistance characteristics of the mica flake structure and nanoparticles can significantly improve the corona resistance life of the composite material, thus giving the composite sheet excellent corona resistance and high PDIV.

[0027] 3. The corona-resistant composite sheet for new energy vehicle motors according to this application uses glass fiber and aramid fiber to form a mica paper layer with mica flakes. The precipitated aramid fiber is a light film. The aramid fiber adheres to the rod-shaped short chopped fiber, which helps to form a fiber support. When subjected to external force, it can play a role in transmitting stress. The network structure formed by the interweaving of fibers and other materials makes the composite sheet dense, with excellent corona resistance and long service life.

[0028] 4. The corona-resistant composite sheet for new energy vehicle motors according to this application uses high-temperature resistant plastic as a hot-melt film layer to fuse mica flakes, without using any other adhesives. This reduces the impact of adhesives on the mechanical, electrical, heat resistance, and oil resistance of the composite sheet. Simultaneously, during hot pressing, the plastic can penetrate more evenly and fully into the mica paper layer, resulting in a composite sheet with a denser microstructure and superior electrical and mechanical properties. The hot-melt film layer used has a low dielectric constant, which can significantly increase the partial discharge initiation voltage of the mica paper composite sheet, meeting the performance requirements of 800V high-voltage motors for new energy vehicles.

[0029] 5. According to the preparation method of the corona-resistant composite sheet for new energy vehicle motors of this application, by setting matching hot-pressing temperature and pressure according to the different thicknesses and compositions of the first hot-melt film layer, the second hot-melt film layer and the mica paper layer, the three layers of the first hot-melt film layer, the second hot-melt film layer and the mica paper layer can achieve a complete fusion state, avoiding partial interface fusion between adjacent layers, which would affect the performance of the composite sheet. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a schematic diagram of the material composition of the corona-resistant composite sheet for new energy vehicle motors involved in the embodiments of this application;

[0032] Figure 2 This is a schematic cross-sectional view of the corona-resistant composite sheet used in new energy vehicle motors according to an embodiment of this application.

[0033] Reference numerals: 1. First hot melt film layer; 2. Mica paper layer; 21. Mica flakes; 22. Reinforcing material; 3. Second hot melt film layer. Detailed Implementation

[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0036] In this embodiment, the first hot melt film layer, the second hot melt film layer, and the mica paper layer are all prepared by conventional hot pressing or other processes such as papermaking.

[0037] Example 1 Composite Sheet 1#

[0038] Composite sheet 1# is made from the following raw materials by weight percentage: 10% of the first hot melt film layer, 80% of the mica paper layer, and 10% of the second hot melt film layer; the first hot melt film layer, the mica paper layer, and the second hot melt film layer are completely fused in the thickness direction.

[0039] The first hot-melt film layer has a thickness of 0.02 mm, the mica paper layer has a thickness of 0.20 mm, and the second hot-melt film layer has a thickness of 0.02 mm. Both the first and second hot-melt film layers are tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymers with a dielectric constant of 2.03. Both the first and second hot-melt film layers also include inorganic nanoparticles, specifically boron nitride with a particle size of 20 nm, added at 5% of the weight of the first hot-melt film layer. The mica paper layer includes mica flakes with a particle size of 30 mesh. The mica paper layer also includes precipitated meta-aramid fibers, added at 5% of the weight of the mica paper layer.

[0040] The preparation method of composite sheet #1 includes the following steps:

[0041] (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers.

[0042] (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 380°C and a pressure of 20MPa.

[0043] (3) After hot pressing, corona-resistant composite sheet 1# for use in new energy vehicle motors is obtained.

[0044] Example 2 Composite Sheet 2#

[0045] Composite sheet #2 is made from the following raw materials by weight percentage: 30% first hot melt film layer, 40% mica paper layer, and 30% second hot melt film layer; the first hot melt film layer, mica paper layer, and second hot melt film layer are completely fused in the thickness direction.

[0046] The first hot-melt film layer has a thickness of 0.08 mm, the mica paper layer has a thickness of 0.10 mm, and the second hot-melt film layer has a thickness of 0.08 mm. Both the first and second hot-melt film layers are polyetheretherketone (PEEK) with a dielectric constant of 3.2. Both the first and second hot-melt film layers also include inorganic nanoparticles, specifically aluminum oxide (ANO) with a particle size of 400 nm, added at 10% of the weight of the first hot-melt film layer. The mica paper layer includes mica flakes with a particle size of 400 mesh. The mica paper layer also includes chopped glass fibers, added at 15% of the weight of the mica paper layer.

[0047] The preparation method of composite sheet #2 includes the following steps:

[0048] (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers.

[0049] (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 390°C and a pressure of 15MPa.

[0050] (3) After hot pressing, corona-resistant composite sheet 2# for use in new energy vehicle motors is obtained.

[0051] Example 3 Composite Sheet 3#

[0052] Composite sheet #3 is made from the following raw materials by weight percentage: 20% first hot melt film layer, 60% mica paper layer, and 20% second hot melt film layer; the first hot melt film layer, mica paper layer, and second hot melt film layer are completely fused in the thickness direction.

[0053] The first hot-melt film layer has a thickness of 0.10 mm, the mica paper layer has a thickness of 0.20 mm, and the second hot-melt film layer has a thickness of 0.10 mm. Both the first and second hot-melt film layers are made of polyphenylene sulfide with a dielectric constant of 3.1. Both the first and second hot-melt film layers also include inorganic nanoparticles, specifically titanium dioxide with a particle size of 800 nm, added at 10% of the weight of the first hot-melt film layer. The mica paper layer includes mica flakes with a particle size of 800 mesh. The mica paper layer also includes precipitated meta-aramid fibers, added at 20% of the weight of the mica paper layer.

[0054] The preparation method of composite sheet #3 includes the following steps:

[0055] (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers.

[0056] (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 300°C and a pressure of 15MPa.

[0057] (3) After hot pressing, corona-resistant composite sheet 3# for use in new energy vehicle motors is obtained.

[0058] Example 4 Composite Sheet 4#

[0059] Composite sheet #4 is made from the following raw materials by weight percentage: 20% first hot melt film layer, 60% mica paper layer, and 20% second hot melt film layer; the first hot melt film layer, mica paper layer, and second hot melt film layer are completely fused in the thickness direction.

[0060] The first hot-melt film layer has a thickness of 0.10 mm, the mica paper layer has a thickness of 0.20 mm, and the second hot-melt film layer has a thickness of 0.10 mm. Both the first and second hot-melt film layers are made of polyphenylene sulfide with a dielectric constant of 3.1. The mica paper layer consists of mica flakes with a particle size of 600 mesh.

[0061] The preparation method of composite sheet #4 includes the following steps:

[0062] (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers.

[0063] (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 295°C and a pressure of 10MPa.

[0064] (3) After hot pressing, corona-resistant composite sheet 4# for use in new energy vehicle motors is obtained.

[0065] Comparative Example 1 vs. Composite Sheet #1

[0066] The difference between composite sheet 1# and composite sheet 3# is that composite sheet 1# does not have a second hot melt film layer, but only a first hot melt film layer, which consists of 20% hot melt film layer and 80% mica paper layer. The preparation method is the same as in Example 3.

[0067] Comparative Example 2 vs. Composite Sheet 2#

[0068] The difference between composite sheet 2# and composite sheet 3# is that the first hot melt film layer is 5%, the mica paper layer is 90%, and the second hot melt film layer is 5%, and the preparation method is the same as in Example 3.

[0069] Comparative Example 3 vs. Composite Sheet 3#

[0070] The difference between composite sheet #3 and composite sheet #3 is that the first and second hot melt film layers of composite sheet #3 use polyphthalamide plastic with a dielectric constant of 4.3, while the rest are the same.

[0071] Comparative Example 4 vs. Composite Sheet #4

[0072] The difference between composite sheet #4 and composite sheet #3 is that the hot pressing temperature in step (2) of the preparation method is 200℃ and the pressure is 5MPa.

[0073] Experimental Example

[0074] 1. Electrical performance

[0075] PDIV (Partial Discharge Initiation Voltage): The test was conducted in accordance with the national standard GB / T 7354-2018. AC voltage frequency: 50 Hz; voltage rise rate: 50 V / s; partial discharge quantity of 10 PC was used as the initiation voltage point; experimental temperature: 21-25℃, humidity: 45-55%.

[0076] 2. Temperature resistance test

[0077] Experimental method: The test was conducted in accordance with the national standard GB / T 4074.7-2009, and the heat resistance grade of the material was evaluated using the three-point method.

[0078] 3. Tensile strength

[0079] Experimental methods: Determined according to national standards GB / T 20629.2-2013 and GB / T 5591.2-2017.

[0080] 4. Square wave corona resistance life

[0081] Experimental method: The test was conducted in accordance with the T / CEEIA 415-2019 standard. Test conditions: peak-to-peak voltage Vp-p = 3000V, temperature 155±3℃, frequency = 20KHz, rise time 100±10ns, duty cycle 50%.

[0082] The composite sheets 1#-4# and the control composite sheets 1#-4# were sampled and tested for the above four experiments. The experimental results are shown in Table 1.

[0083] Table 1 Experimental data for various composite sheets

[0084]

[0085] Figure 1 This is a schematic diagram of the material composition of the corona-resistant composite sheet for new energy vehicle motors prepared in Examples 1-4 of this application; Figure 2 This is a schematic diagram of the cross-section of the corona-resistant composite sheet for new energy vehicle motors prepared in Examples 1-4 of this application.

[0086] The experimental data above show that the composite sheets 1#-4# prepared by the raw materials and methods specified in this application have higher PDIV, longer square wave corona resistance life, excellent high temperature resistance, and excellent mechanical properties.

[0087] Compared with composite material 1#, which uses a single hot melt film layer, the final result is that the electrical performance and high temperature resistance are average. Compared with composite material 2#, which uses the proportion of the first and second hot melt film layers below the range specified in this application, the final result is that the electrical performance and high temperature resistance are average.

[0088] Compared with composite material #3, which uses a plastic with a larger dielectric constant, the final result is that the electrical performance is average and the PDIV is low. Compared with composite material #4, which is used at a temperature lower than the range specified in this application, the final result is that the fusion effect between the first and second hot melt film layers and the mica paper layer is poor, resulting in partial interface fusion. As a result, the electrical performance is average, the square wave corona resistance life is short, and the mechanical properties are average.

[0089] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A corona-resistant composite sheet for use in electric motors of new energy vehicles, characterized in that, It is made from the following raw materials in weight percentage: 10-40% first hot melt film layer, 20-80% mica paper layer and 10-40% second hot melt film layer; the corona-resistant composite sheet for new energy vehicle motors after hot pressing, wherein the first hot melt film layer, the mica paper layer and the second hot melt film layer are completely fused in the thickness direction. The first hot melt film layer is selected from one or more of polyphenylene sulfide, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone and polyether imide; The second hot melt film layer is selected from one or more of polyphenylene sulfide, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone and polyether imide.

2. The corona-resistant composite sheet for new energy vehicle motors according to claim 1, characterized in that, No adhesive is used between the first hot melt film layer, the mica paper layer and the second hot melt film layer.

3. The corona-resistant composite sheet for new energy vehicle motors according to claim 1, characterized in that, The thickness of the first hot melt film layer is 0.02-0.15 mm, the thickness of the mica paper layer is 0.05-0.20 mm, and the thickness of the second hot melt film layer is 0.02-0.15 mm. The thickness ratio of the first hot melt film layer, the mica paper layer, and the second hot melt film layer is 1:2:

1.

4. The corona-resistant composite sheet for new energy vehicle motors according to claim 1, characterized in that, The first hot melt film layer and / or the second hot melt film layer further include inorganic nanoparticles.

5. The corona-resistant composite sheet for new energy vehicle motors according to claim 4, characterized in that, The inorganic nanoparticles are one or more of silicon dioxide, aluminum oxide, boron nitride, aluminum nitride, and titanium dioxide, and the particle size of the inorganic nanoparticles is 10nm-800nm.

6. The corona-resistant composite sheet for new energy vehicle motors according to claim 1, characterized in that, The mica paper layer includes mica flakes and reinforcing materials, wherein the mica flakes have a particle size of 30-800 mesh.

7. The corona-resistant composite sheet for new energy vehicle motors according to claim 6, characterized in that, The reinforcing material includes one or both of aramid fiber and glass fiber.

8. A method for preparing a corona-resistant composite sheet for a new energy vehicle motor as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Unwind the first hot melt film layer, the mica paper layer and the second hot melt film layer and stack them together in sequence. No adhesive is needed between the layers. (2) The stacked multi-layered materials are hot-pressed by hot rollers at a temperature of 290-390℃ and a pressure of 5-20MPa; (3) After hot pressing, the corona-resistant composite sheet for new energy vehicle motors is obtained.

Images