A fracture induction type intelligent coating material for automobile brake leaf springs and a preparation method thereof

Abstract

The application relates to the functional coating technical field, and particularly discloses a fracture induction type intelligent coating material for automobile brake spring pieces and a preparation method thereof. The fracture induction type intelligent coating material comprises a piezoelectric sensing layer and a heat dissipation layer; the piezoelectric sensing layer is mainly made of the following raw materials: piezoelectric ceramic, carbon nanotubes, silver nanowires, aluminum oxide, liquid phenolic epoxy resin, a curing agent, polyvinylpyrrolidone, a silane coupling agent and an organic silicon surfactant; and the heat dissipation layer is mainly made of the following raw materials: graphene, silicon carbide, liquid phenolic epoxy resin, a curing agent, polyvinylpyrrolidone and a silane coupling agent. The fracture induction type intelligent coating material can realize timely sensing and early warning before the brake spring piece is fractured through the mutual cooperation between the piezoelectric sensing layer and the heat dissipation layer, and has the advantages of high coating adhesion, high sensitivity and good durability, thereby improving the safety and reliability of the brake spring piece and meeting the market demand.

Description

Technical Field

[0001] This application relates to the field of functional coating technology, and more specifically, it relates to a fracture-sensing smart coating material for automotive brake pads and its preparation method. Background Technology

[0002] As a core system ensuring vehicle safety, the reliability of an automotive braking system directly affects the lives of passengers and the stable operation of the vehicle. Brake pads play a crucial role in transmitting and regulating braking force, and are one of the core components ensuring the normal operation of the braking system. During braking, the brake pads, through their elastic deformation and recovery, precisely transmit braking pressure between the brake pads and the brake disc, achieving close contact and separation between them. This effectively controls the vehicle's speed, ensuring timely and stable stopping under various road conditions. If the brake pads break, the transmission of braking force will be affected, leading to brake failure or uneven braking force. This can cause the vehicle to lose effective braking ability during driving, easily resulting in traffic accidents and posing a safety hazard to occupants.

[0003] With the development of the automotive industry and the increasing emphasis on driving safety, higher demands are being placed on the reliability and safety of brake springs. Traditional brake spring coating materials primarily focus on protecting brake springs from corrosion and wear. These coatings can, to a certain extent, isolate external corrosion and improve wear resistance, extending service life. However, they are insufficient in detecting brake spring fractures. When brake springs develop cracks due to fatigue, overload, or other reasons and gradually propagate to fracture, traditional coating materials cannot detect and issue warning signals in a timely manner. This makes it difficult for drivers to notice the abnormal condition of the brake springs immediately, thus hindering timely and effective countermeasures. Therefore, researching a fracture-sensing intelligent coating material for automotive brake springs is of great significance for improving the performance of automotive brake springs and ensuring the reliability and safety of vehicle operation. Summary of the Invention

[0004] In order to detect and issue an early warning in a timely manner when cracks appear on the brake spring before it breaks, this application provides a fracture-sensing smart coating material for automotive brake springs and its preparation method.

[0005] In a first aspect, this application provides a fracture-sensing smart coating material for automotive brake pads, employing the following technical solution: A fracture-sensing smart coating material for automotive brake pads, comprising a piezoelectric sensing layer and a heat dissipation layer. The piezoelectric sensing layer is mainly made of the following raw materials in parts by weight: 30-40 parts piezoelectric ceramic, 5-10 parts carbon nanotubes, 8-12 parts silver nanowires, 10-15 parts alumina, 20-30 parts liquid phenolic epoxy resin, 1-3 parts curing agent, 1-3 parts polyvinylpyrrolidone, 2-4 parts silane coupling agent, and 1-3 parts organosilicon surfactant. The heat dissipation layer is mainly made of the following raw materials in parts by weight: 40-50 parts graphene, 5-15 parts silicon carbide, 33-43 parts liquid phenolic epoxy resin, 1-3 parts curing agent, 1-3 parts polyvinylpyrrolidone, and 2-4 parts silane coupling agent.

[0006] The fracture-sensing smart coating material of this application includes a piezoelectric sensing layer and a heat dissipation layer sequentially disposed on the surface of a brake spring. The piezoelectric sensing layer contains piezoelectric ceramics, which generate electrical charges under stress; the greater the stress, the greater the charge generation. When a crack develops in the brake spring, it causes significant changes in the electrical parameters of the piezoelectric sensing layer, such as resistance and charge. By detecting these electrical parameters, such as voltage, the stress state of the brake spring and the presence of cracks can be accurately predicted, enabling sensing and early warning of impending brake spring fracture. When a crack appears in the brake spring, measures such as reducing vehicle speed and activating the backup braking system can be taken to ensure driving safety. The heat dissipation layer contains graphene and silicon carbide; their interaction forms a heat dissipation network, which can quickly dissipate frictional heat, reducing the impact of thermal stress on the performance of the piezoelectric sensing layer and improving durability. The fracture-sensing intelligent coating material of this application has a coating adhesion >7MPa, sensitivity >110mV / mm, and sensitivity >100mV / mm after 50,000 braking cycles. It has the advantages of high coating adhesion, high sensitivity, good durability, and good stability, which meets market demand.

[0007] In the raw materials of the piezoelectric sensing layer, silver nanowires are added in addition to piezoelectric ceramics. These nanowires form a conductive network, facilitating signal transmission. Liquid phenolic epoxy resin and a curing agent are added, which integrate the piezoelectric ceramics, carbon nanotubes, and silver nanowires into a continuous and stable coating structure, reducing the likelihood of piezoelectric ceramics detachment. A silane coupling agent is also added, which increases the compatibility between raw materials, improves dispersion uniformity, reduces agglomeration, and increases interfacial bonding, reducing gaps between the piezoelectric ceramic layer and the braking spring, facilitating efficient strain transfer and improving coating adhesion and sensitivity. An organosilicon surfactant is also added, which reduces interfacial tension, increases uniformity, improves microstructure, reduces defects such as bubbles, and enhances the overall microstructure, contributing to improved coating adhesion and sensitivity.

[0008] Optionally, the piezoelectric ceramic is selected from one or more of barium titanate, lead zirconate titanate, lithium niobate, and potassium sodium niobate.

[0009] By employing the above technical solutions, the piezoelectric ceramics are specified, facilitating their selection. Furthermore, barium titanate, lead zirconate titanate, lithium niobate, and potassium sodium niobate can all convert the mechanical strain of the braking spring into an electrical signal, enabling timely sensing and early warning before fracture.

[0010] Optionally, the piezoelectric ceramic has an average particle size of 1-10 μm, a piezoelectric constant of 200-500 pC / N, and a dielectric constant of 1500-3500.

[0011] In several implementations, the piezoelectric ceramic has an average particle size of 3 μm, a piezoelectric constant of 450 pC / N, and a dielectric constant of 2500. The average particle size can also be set to 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., as needed. The piezoelectric constant can also be set to 200 pC / N, 250 pC / N, 300 pC / N, 350 pC / N, 400 pC / N, 450 pC / N, 500 pC / N, etc., as needed. The dielectric constant can also be set to 1500, 1800, 2000, 2300, 2800, 3000, 3300, 3500, etc., as needed. However, it is not limited to the values ​​listed, and other unlisted values ​​within this range are also applicable.

[0012] Optionally, the carbon nanotubes have an average diameter of 1-50 nm and an average length of 1-50 μm.

[0013] Optionally, the silver nanowires have an average diameter of 10-100 nm and an average length of 1-50 μm.

[0014] In several implementations, the carbon nanotubes have an average diameter of 10 nm and an average length of 10 μm. The average diameter can also be set to 1 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc., as needed, and the average length can also be set to 1 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc., as needed. However, they are not limited to the values ​​listed, and other unlisted values ​​within this range are also applicable.

[0015] In several implementations, the silver nanowires have an average diameter of 50 nm and an average length of 10 μm. The average diameter can also be set to 10 nm, 20 nm, 30 nm, 40 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., as needed, and the average length can also be set to 1 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc., as needed, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Optionally, the alumina has an average particle size of 1-50 μm; the graphene has an average particle size of 1-20 μm; and the silicon carbide has an average particle size of 1-20 μm.

[0017] In several embodiments, the average particle size of alumina is 10 μm. However, the average particle size can also be set to 1 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. In several embodiments, the average particle size of graphene is 2 μm. However, the average particle size can also be set to 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. In several embodiments, the average particle size of silicon carbide is 5 μm. However, the average particle size can also be set to 1 μm, 2 μm, 10 μm, 15 μm, 20 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] Optionally, the liquid phenolic epoxy resin is selected from one or more of phenolic epoxy resins DH546654, DEN439, DEN431, and DEN425.

[0019] By employing the above technical solution, the liquid phenolic epoxy resin is limited, facilitating its selection. Furthermore, the liquid phenolic epoxy resin possesses excellent adhesion, enabling the integration of piezoelectric ceramics, carbon nanotubes, and silver nanowires into a continuous and stable coating structure. It can also integrate graphene and silicon carbide into a continuous and stable coating structure, ensuring the performance and quality of the fracture-sensitive smart coating material.

[0020] Optionally, the curing agent is selected from one or more of hexamethylenetetramine, isophorone diamine, 4,4'-diaminodiphenylmethane, and benzoguanidine.

[0021] By employing the above technical solution, the curing agent is limited, facilitating its selection. The curing agent enables the liquid phenolic epoxy resin to be effectively cured, forming a three-dimensional network structure and ensuring the formation of the piezoelectric sensing layer and heat dissipation layer.

[0022] Optionally, the polyvinylpyrrolidone is selected from one or more of polyvinylpyrrolidone PVP K30, polyvinylpyrrolidone PVPPK25, polyvinylpyrrolidone PVP K17, and polyvinylpyrrolidone PVP K15.

[0023] By employing the above technical solution, polyvinylpyrrolidone (PVP) is specified, facilitating its selection. Furthermore, PPVP can increase the dispersion uniformity of piezoelectric ceramics, carbon nanotubes, and silver nanowires, ensuring efficient strain transfer and contributing to improved performance of the piezoelectric sensing layer.

[0024] Optionally, the silane coupling agent is selected from one or more of 3-aminopropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, and octyltriethoxysilane.

[0025] By employing the above technical solution, the selection of silane coupling agents is facilitated. Furthermore, silane coupling agents can increase compatibility and interfacial bonding, enabling efficient strain transfer and contributing to improved coating adhesion and sensitivity.

[0026] Optionally, the silicone surfactant is selected from one or more of silicone surfactants BYK-3420, BYK-3450, BYK-3455, and BYK-3480.

[0027] By employing the above technical solution, the selection of silicone surfactants is facilitated. Furthermore, silicone surfactants can reduce interfacial tension, improve microstructure, and reduce defects, thus contributing to the enhancement of the overall performance of fracture-sensitive smart coating materials.

[0028] Optionally, the thickness of the piezoelectric sensing layer is 10-100 μm and the thickness of the heat dissipation layer is 50-200 μm.

[0029] By adopting the above technical solution, the thickness of the piezoelectric sensing layer and the heat dissipation layer is limited, which facilitates the preparation of the piezoelectric sensing layer and the heat dissipation layer. Through the mutual cooperation between the piezoelectric sensing layer and the heat dissipation layer, not only is the fracture-sensing smart coating material guaranteed to have good coating adhesion and sensitivity, but it also maintains good heat dissipation performance, which helps to improve the overall performance and stability of the fracture-sensing smart coating material.

[0030] In several embodiments, the thickness of the piezoelectric sensing layer is 50 μm, but it can also be set to 10 μm, 20 μm, 30 μm, 40 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. In several embodiments, the thickness of the heat dissipation layer is 100 μm, but it can also be set to 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] Secondly, this application provides a method for preparing the fracture-sensitive smart coating material for automotive brake pads, which adopts the following technical solution: A method for preparing the fracture-sensitive smart coating material for automotive brake pads includes the following steps: S1. Mix liquid phenolic epoxy resin, curing agent, polyvinylpyrrolidone, silane coupling agent, and organosilicon surfactant, then add piezoelectric ceramics, carbon nanotubes, silver nanowires, and alumina to obtain a piezoelectric sensing mixture. S2. Mix liquid phenolic epoxy resin, curing agent, polyvinylpyrrolidone, and silane coupling agent, then add graphene and silicon carbide to obtain a heat dissipation mixture. S3. Clean, dry, sandblast, and blow away residual sand on the surface of the brake spring pad substrate to obtain the pretreated substrate. S4. Coat the surface of the pretreated substrate with piezoelectric sensing mixture, heat to 80-100℃, and keep it at that temperature for 30-60 minutes to obtain a semi-finished product. S5. Apply heat dissipation mixture to the surface of the semi-finished product, heat to 110-120℃ and keep it at that temperature for 1-3 hours, then heat to 130-160℃ and keep it at that temperature for 4-6 hours. At this time, the piezoelectric sensing mixture solidifies to form a piezoelectric sensing layer and the heat dissipation mixture solidifies to form a heat dissipation layer, thus obtaining the product.

[0032] By adopting the above technical solution, the piezoelectric sensing mixture is easily cured to form a piezoelectric sensing layer, and the heat dissipation mixture is cured to form a heat dissipation layer, thus obtaining a fracture-sensitive smart coating material. In step S4, a heat treatment at 80-100℃ for 30-60 minutes allows the liquid phenolic epoxy resin in the piezoelectric sensing mixture to initially solidify. Then, the heat dissipation mixture is applied, and step-curing is used to completely cure the liquid phenolic epoxy resin in both the piezoelectric sensing mixture and the heat dissipation mixture. Using the above preparation method, the bonding strength between the piezoelectric sensing layer and the heat dissipation layer can be significantly increased, improving the stability and lifespan of the fracture-sensitive smart coating material.

[0033] Optionally, in step S3, the surface roughness Ra of the pretreated substrate is 1-5 μm.

[0034] By employing the above technical solution and using sandblasting, the surface roughness Ra of the pretreated substrate is reduced to 1-5 μm. This creates "micro-pits" on the surface, which, through mechanical interlocking, improves the bonding force between the piezoelectric sensing layer and the brake spring, enhancing coating adhesion. This improves the performance and reliability of the fracture-sensing smart coating material on the brake spring. In several embodiments, the surface roughness Ra of the pretreated substrate is 3 μm. However, the surface roughness Ra can also be set to 1 μm, 2 μm, 4 μm, 5 μm, etc., as needed, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In summary, this application has at least the following beneficial effects: 1. The fracture-sensing intelligent coating material of this application comprises a piezoelectric sensing layer and a heat dissipation layer. The piezoelectric ceramic in the piezoelectric sensing layer converts crack changes occurring before brake spring breakage into electrical signals, enabling timely sensing and early warning of brake spring breakage. The graphene and silicon carbide in the heat dissipation layer form a heat dissipation network, dissipating heat, reducing the impact of thermal stress on the performance of the piezoelectric sensing layer, and improving durability. The fracture-sensing intelligent coating material of this application, through the synergy between the piezoelectric sensing layer and the heat dissipation layer, exhibits coating adhesion >7MPa, sensitivity >110mV / mm, and sensitivity >100mV / mm after 50,000 braking cycles. It possesses advantages such as high coating adhesion, high sensitivity, and good durability, improving the safety and reliability of brake springs and meeting market demands.

[0036] 2. The piezoelectric sensing layer of this application incorporates a silane coupling agent and an organosilicon surfactant in its raw materials. The silane coupling agent enhances compatibility, dispersion uniformity, and interfacial bonding, facilitating efficient strain transfer and improving coating adhesion and sensitivity. The organosilicon surfactant reduces interfacial tension, improves microstructure, reduces defects such as bubbles, and enhances the overall microstructure, also contributing to improved coating adhesion and sensitivity. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments. Example

[0038] Table 1. Amount of each raw material used in the piezoelectric sensing layer (unit: ×10g)

[0039] Table 2. Amount of each raw material used in the heat dissipation layer (unit: ×10g)

[0040] Example 1 A fracture-sensing smart coating material for automotive brake springs comprises a piezoelectric sensing layer and a heat dissipation layer sequentially disposed on the surface of the brake spring. The thickness of the piezoelectric sensing layer is 50 μm, and the thickness of the heat dissipation layer is 100 μm. The raw materials and their proportions for the piezoelectric sensing layer are shown in Table 1. The raw materials and their proportions for the heat dissipation layer are shown in Table 2.

[0041] Among them, the piezoelectric ceramic is lead zirconate titanate, with an average particle size of 3 μm, a piezoelectric constant of 450 pC / N, and a dielectric constant of 2500; the carbon nanotubes have an average diameter of 10 nm and an average length of 10 μm; the silver nanowires have an average diameter of 50 nm and an average length of 10 μm; the alumina has an average particle size of 10 μm; the liquid phenolic epoxy resin is selected from phenolic epoxy resin DH546654, with a solid content of 60%, and is selected from Donghao Chemical (Shandong) Co., Ltd.; the curing agent is selected from hexamethylenetetramine; the polyvinylpyrrolidone is selected from polyvinylpyrrolidone PVP K25; the silane coupling agent is selected from 3-(2,3-epoxypropoxy)propyltrimethoxysilane; the organosilicon surfactant is selected from organosilicon surfactant BYK-3450; the graphene has an average particle size of 2 μm; and the silicon carbide has an average particle size of 5 μm.

[0042] A method for preparing a fracture-sensitive smart coating material for automotive brake pads includes the following steps: S1. At a temperature of 13℃, add curing agent, polyvinylpyrrolidone, silane coupling agent, and organosilicon surfactant to liquid phenolic epoxy resin and stir for 5 min. Then add piezoelectric ceramics, carbon nanotubes, silver nanowires, and alumina, and stir for 30 min to obtain piezoelectric sensing mixture.

[0043] S2. At a temperature of 13℃, add curing agent, polyvinylpyrrolidone, and silane coupling agent to liquid phenolic epoxy resin and stir for 5 minutes. Then add graphene and silicon carbide and stir for 30 minutes to obtain a heat-dissipating mixture.

[0044] S3. Clean and dry the surface of the brake spring pad substrate. Then, sandblast it with brown fused alumina until the surface roughness Ra is 3μm. Blow away the residual sand to obtain the pretreated substrate. At this time, the surface roughness Ra of the pretreated substrate is 3μm.

[0045] S4. Coat the surface of the pretreated substrate with piezoelectric sensing mixture, heat to 90°C, and keep warm for 50 minutes to obtain a semi-finished product.

[0046] S5. Apply a heat dissipation mixture to the surface of the semi-finished product, heat to 120℃, and hold for 2 hours. Then heat to 150℃ and hold for 5 hours. At this point, the piezoelectric sensing mixture solidifies to form a piezoelectric sensing layer, and the heat dissipation mixture solidifies to form a heat dissipation layer. The piezoelectric sensing layer and the heat dissipation layer together form a fracture-sensitive smart coating material, thus obtaining the product.

[0047] Example 2 A fracture-sensing smart coating material for automotive brake pads differs from Example 1 in that the raw material ratios of the piezoelectric sensing layer and the heat dissipation layer are different. The raw material ratios of the piezoelectric sensing layer are shown in Table 1, and the raw material ratios of the heat dissipation layer are shown in Table 2.

[0048] Example 3 A fracture-sensing smart coating material for automotive brake pads differs from Example 1 in that the raw material ratios of the piezoelectric sensing layer and the heat dissipation layer are different. The raw material ratios of the piezoelectric sensing layer are shown in Table 1, and the raw material ratios of the heat dissipation layer are shown in Table 2.

[0049] Example 4 A fracture-sensing smart coating material for automotive brake pads differs from Example 1 in that the raw material ratios of the piezoelectric sensing layer and the heat dissipation layer are different. The raw material ratios of the piezoelectric sensing layer are shown in Table 1, and the raw material ratios of the heat dissipation layer are shown in Table 2.

[0050] Example 5 A fracture-sensing smart coating material for automotive brake pads differs from Example 1 in that the raw material ratios of the piezoelectric sensing layer and the heat dissipation layer are different. The raw material ratios of the piezoelectric sensing layer are shown in Table 1, and the raw material ratios of the heat dissipation layer are shown in Table 2.

[0051] Comparative Example Comparative Example 1 A fracture-sensing smart coating material for automotive brake pads differs from Example 3 in that no silane coupling agent is added to the raw materials of the piezoelectric sensing layer.

[0052] Comparative Example 2 A fracture-sensing smart coating material for automotive brake pads differs from Example 3 in that no organosilicon surfactant is added to the raw materials of the piezoelectric sensing layer.

[0053] Performance testing The products obtained in Examples 1-5 and Comparative Examples 1-2 were used as samples, and the fracture-sensitive smart coating material of the products was subjected to the following performance tests. The test results are shown in Table 3.

[0054] In particular, the adhesion of the fracture-sensitive smart coating material was tested according to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test".

[0055] Sensitivity was assessed using the following method: an artificial crack was pre-created on the product's brake spring. The product was then subjected to a bending load at a rate of 10 N / s. The load was stopped after the crack had propagated to 0.2 mm. Electrical signals during crack propagation were collected, and the sensitivity was calculated. Higher sensitivity indicates the smaller the crack that can be detected, and a sensitivity ≥ 100 mV / mm is required.

[0056] Durability was tested using the following method: the product was installed on a braking system test bench, and the fracture-sensitive smart coating material was subjected to 50,000 braking cycles, and the sensitivity of the 50,000 braking cycles was tested.

[0057] Table 3 Test Results

[0058] As shown in Table 3, the fracture-sensing intelligent coating material of this application exhibits high coating adhesion, ranging from 7.62 to 7.97 MPa, demonstrating excellent adhesion. It also exhibits high sensitivity, ranging from 119 to 135 mV / mm, showcasing high sensitivity. However, the sensitivity decreases slightly after 50,000 braking cycles. This may be due to aging of the piezoelectric sensing layer caused by long-term braking cycles, and the appearance of tiny gaps at the interface between the piezoelectric sensing layer and the brake spring, affecting strain transmission. Furthermore, the fracture-sensing intelligent coating material of this application maintains high sensitivity after 50,000 braking cycles, ranging from 108 to 122 mV / mm, demonstrating high durability. Through the interaction between the piezoelectric sensing layer and the heat dissipation layer, the fracture-sensing intelligent coating material of this application achieves the advantages of high coating adhesion, high sensitivity, and good durability, improving the safety and reliability of the brake spring and meeting market demands.

[0059] Comparative Example 1 and Example 3 were compared. In Example 3, a silane coupling agent was added to the raw material of the piezoelectric sensing layer compared to Comparative Example 1. It can be seen that adding the silane coupling agent improves the coating adhesion and sensitivity. This is likely because the silane coupling agent increases the compatibility between the piezoelectric ceramic and the resin matrix, reduces the agglomeration of the piezoelectric ceramic, increases dispersion uniformity, and also increases the bonding force between the piezoelectric sensing layer and the braking spring, reducing gaps between them, thus enabling efficient strain transmission and improving coating adhesion and sensitivity.

[0060] Comparative Example 2 and Example 3 were compared. In Example 3, compared to Comparative Example 1, an organosilicone surfactant was added to the raw material of the piezoelectric sensing layer. It can be seen that adding an organosilicone surfactant can also improve the coating adhesion and sensitivity. This may be because the organosilicone surfactant can reduce interfacial tension, increase the uniformity of the piezoelectric sensing layer, improve the microstructure of the piezoelectric sensing layer, reduce defects such as bubbles, and improve the overall structural integrity, thus contributing to the improvement of the comprehensive performance of the fracture-sensitive smart coating material.

[0061] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A fracture-sensing smart coating material for automotive brake pads, characterized in that: It includes a piezoelectric sensing layer and a heat dissipation layer; The piezoelectric sensing layer is mainly made of the following raw materials in parts by weight: 30-40 parts piezoelectric ceramic, 5-10 parts carbon nanotubes, 8-12 parts silver nanowires, 10-15 parts alumina, 20-30 parts liquid phenolic epoxy resin, 1-3 parts curing agent, 1-3 parts polyvinylpyrrolidone, 2-4 parts silane coupling agent, and 1-3 parts organosilicon surfactant. The heat dissipation layer is mainly made of the following raw materials in parts by weight: 40-50 parts graphene, 5-15 parts silicon carbide, 33-43 parts liquid phenolic epoxy resin, 1-3 parts curing agent, 1-3 parts polyvinylpyrrolidone, and 2-4 parts silane coupling agent.

2. The fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The piezoelectric ceramic is selected from one or more of barium titanate, lead zirconate titanate, lithium niobate, and potassium sodium niobate.

3. The fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The liquid phenolic epoxy resin is selected from one or more of phenolic epoxy resins DH546654, DEN 439, DEN 431, and DEN 425.

4. A fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The curing agent is selected from one or more of hexamethylenetetramine, isophorone diamine, 4,4'-diaminodiphenylmethane, and benzoguanidine.

5. A fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The polyvinylpyrrolidone is selected from one or more of polyvinylpyrrolidone PVP K30, polyvinylpyrrolidone PVP K25, polyvinylpyrrolidone PVP K17, and polyvinylpyrrolidone PVP K15.

6. The fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The silane coupling agent is selected from one or more of 3-aminopropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, and octyltriethoxysilane.

7. The fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The organosilicon surfactant is selected from one or more of organosilicon surfactants BYK-3420, BYK-3450, BYK-3455, and BYK-3480.

8. The fracture-sensing smart coating material for automotive brake pads according to claim 1, characterized in that: The thickness of the piezoelectric sensing layer is 10-100 μm, and the thickness of the heat dissipation layer is 50-200 μm.

9. A method for preparing a fracture-sensing smart coating material for automotive brake pads as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. Mix liquid phenolic epoxy resin, curing agent, polyvinylpyrrolidone, silane coupling agent, and organosilicon surfactant, then add piezoelectric ceramics, carbon nanotubes, silver nanowires, and alumina to obtain a piezoelectric sensing mixture. S2. Mix liquid phenolic epoxy resin, curing agent, polyvinylpyrrolidone, and silane coupling agent, then add graphene and silicon carbide to obtain a heat dissipation mixture. S3. Clean, dry, sandblast, and blow away residual sand on the surface of the brake spring pad substrate to obtain the pretreated substrate. S4. Coat the surface of the pretreated substrate with piezoelectric sensing mixture, heat to 80-100℃, and keep it at that temperature for 30-60 minutes to obtain a semi-finished product. S5. Apply heat dissipation mixture to the surface of the semi-finished product, heat to 110-120℃ and keep it at that temperature for 1-3 hours, then heat to 130-160℃ and keep it at that temperature for 4-6 hours. At this time, the piezoelectric sensing mixture solidifies to form a piezoelectric sensing layer and the heat dissipation mixture solidifies to form a heat dissipation layer, thus obtaining the product.

10. A method for preparing a fracture-sensing smart coating material for automotive brake pads according to claim 9, characterized in that: In step S3, the surface roughness Ra of the pretreated substrate is 1-5 μm.

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