Self-repairing coating, repairing device, preparation method and application

Abstract

The invention discloses a self-repairing coating, a repairing device, a manufacturing method and application, and belongs to the technical field of metal anti-corrosion coatings. The invention relates to a self-repairing coating, which realizes an automatic repairing function of a metal surface through combination of a microcapsule technology and a polyurethane coating matrix. According to the coating, the repairing agent is coated with the microcapsule technology, the repairing agent can be effectively protected, and the repairing efficiency is improved. After the coating is damaged, the microcapsule is broken to release the repairing agent, and the heating effect of the electrified coil promotes the repairing agent to be quickly released and cured, so that the self-repairing of the coating is realized. The coating has good corrosion resistance, and the service life of the metal material is prolonged. According to the repairing system, the flat coil is used for heating the metal coating, the flat coil is far away from the metal coating through the thermal expansion effect of kerosene in the telescopic rod, and the eddy current heating effect is reduced; the repairing system can adaptively control the heating temperature, and the temperature of a repairing area is controllable.

Description

Technical Field

[0001] This invention relates to a self-healing coating, a repair device, a manufacturing method, and an application, belonging to the field of metal anti-corrosion coating technology. Background Technology

[0002] Metals are widely used in aerospace, bridges, automobiles, electronics, and other fields due to their high mechanical properties and electrical conductivity. However, corrosion of metals in service environments not only imposes a huge economic burden but can also lead to serious safety problems and environmental hazards. Currently, using protective coatings with anti-corrosion properties is considered the most effective, economical, and convenient strategy for metal corrosion protection. However, during transportation and service, the shielding performance of coatings may be lost due to environmental factors and mechanical damage, creating channels for corrosive media and causing metal corrosion. For example, scratches are inevitable on automotive coatings. If repairs are not timely, corrosive media such as rainwater can penetrate and cause rust on automotive metal parts, leading to depreciation and a shortened lifespan of the vehicle. Most damaged coatings require manual repair or replacement, which is both expensive and time-consuming.

[0003] While self-healing coating technology has shown promise in the automotive industry, existing heat-triggered solutions suffer from fundamental flaws, resulting in repair effects far from meeting practical requirements. The core issue lies in the uncontrollability of the repair process, particularly the inadequacy of temperature management: general heating methods struggle to precisely control temperature, easily leading to uneven heating of the repaired area. If the temperature is too low, the microcapsules cannot effectively rupture, resulting in insufficient release of the repair agent, incomplete repair, and the visible scratches. If the temperature is too high, it can cause the repair agent or components in the substrate to vaporize, resulting in bulging, or cause the substrate to overheat, age, crack, and yellow, causing secondary damage. Furthermore, existing methods lack standardized control over the repair process, relying excessively on operator experience, leading to significant fluctuations in repair quality. Therefore, developing a technology and device capable of precise, automatic temperature control to ensure a smooth, flat coating free of secondary defects after repair has become a key bottleneck in propelling automotive self-healing coatings from the laboratory to practical application.

[0004] In recent years, self-healing materials have become a research hotspot, especially self-healing coatings achieved through microencapsulation technology. However, existing self-healing coatings still have shortcomings in terms of repair efficiency, durability, and applicability, requiring further improvement. This invention combines eddy current heating coils and microencapsulation technology to provide a self-healing coating, repair device, and its applications. Compared to traditional repair methods, it offers lower costs, more significant repair performance, and more precise and controllable temperature management, making it suitable for applications such as automotive coating repair. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention aims to provide a self-healing coating.

[0006] Meanwhile, the present invention provides a repair device adapted to a self-healing coating.

[0007] Meanwhile, the present invention provides a method for preparing a self-healing coating.

[0008] Meanwhile, this invention provides an application of a self-healing coating and repair device in automotive coating repair.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A self-healing coating, through the combination of microencapsulation technology and a polyurethane coating matrix, enables automatic repair of metal surfaces. This self-healing coating exhibits excellent repair performance and corrosion resistance, and is suitable for metal materials such as magnesium alloys, aluminum alloys, and steel.

[0010] A self-healing coating and repair device and their application are disclosed, wherein the self-healing coating components include microcapsules, epoxy resin, and polyurethane; the repair device includes a flat copper metal coil and a surface insulation layer.

[0011] The polyurethane resin matrix is ​​a hydroxyl-terminated hyperbranched polyurethane with a hydroxyl value of 80-150 mg KOH / g. This hyperbranched polyurethane can be prepared using the A2+B3 polycondensation method known in the art [see: Research Progress on Synthesis Methods and Applications of Hyperbranched Polymers, Xiao Wenqing, Hu Jianqing, Tu Weiping, 2007 (School of Chemical Engineering and Energy, South China University of Technology)]. For example, using isophorone diisocyanate (IPDI) and trimethylolpropane (TMP) as raw materials, by controlling the molar ratio (R value) of -NCO to -OH between 0.85 and 0.95, hyperbranched polyurethane with a hydroxyl value in the range of 80-150 mg KOH / g can be obtained. Its hydroxyl value is determined according to the ASTM D4274 standard method. This specific functional group density and type ensures that, under the hot-pressing conditions provided by the repair device, it can undergo a sufficient cross-linking and curing reaction with the epoxy resin released from the microcapsules, forming a dense interpenetrating network, which is key to achieving consistent mechanical properties and a smooth appearance between the repaired surface and the original coating.

[0012] Microencapsulation technology for preparing self-healing coatings is a technique that enables automatic repair of coating damage by encapsulating repair agents in microcapsules and dispersing them in the coating matrix.

[0013] The core of microencapsulated self-healing coatings lies in the use of microcapsules to encapsulate repair agents. When damage or cracks occur on the coating surface, the microcapsules rupture, releasing the repair agent. The agent diffuses at the damaged site and undergoes a chemical reaction (such as polymerization or cross-linking), thereby filling the cracks and restoring the integrity of the coating. This technology can significantly improve the durability and service life of coatings, and is especially suitable for anti-corrosion coatings.

[0014] Microencapsulation technology is used to encapsulate the core material, epoxy resin E-51, and the wall material, urea-formaldehyde resin, and then uniformly mix them into the coating. The wall material urea-formaldehyde resin protects the epoxy resin; when damaged, it ruptures to release the core epoxy resin, which then flows out as a repair agent, thereby repairing the damage.

[0015] (a) A method for preparing microcapsules, comprising the following steps: The epoxy resin microcapsules were prepared using an in-situ polymerization method to create dual-wall microcapsules. A1. Core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 8:1 to 10:1 to obtain a mixture. Then, 0.5-1% of fumed silica nanoparticles are added to the mixture and ultrasonically dispersed for 30-60 minutes to form a homogeneous and stable core material phase.

[0016] A2. Preparation of the first layer of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:1 to 1:2, the pH is adjusted to 8 to 9 with triethanolamine, and the mixture is reacted in a water bath at 65-70℃ for 1.5 to 2 hours to obtain a transparent and viscous urea-formaldehyde prepolymer.

[0017] A3. Preparation of the second layer wall material prepolymer: Melamine and formaldehyde are mixed in a three-necked flask at a molar ratio of 1:2 to 1:4. The pH is adjusted to 8 to 9, and the mixture is stirred at 70-80°C until it becomes clear, thus obtaining the melamine-formaldehyde prepolymer for later use.

[0018] A4. Preparation of Multiphase Emulsion: The core phase obtained in step 1 is slowly added to an aqueous phase containing 1-2% sodium dodecyl sulfate emulsifier under high-speed shearing at 10000-12000 rpm. The oil-to-water mass ratio (core phase: aqueous phase) is 1:4-1:6. Emulsification is carried out for 15-30 minutes to form a stable O / W type primary emulsion. Subsequently, under slow stirring, the urea-formaldehyde prepolymer obtained in step 2 is slowly added dropwise to the primary emulsion. The amount of urea-formaldehyde prepolymer added is 30%-60% of the mass of the core phase, initially coating the core material to obtain emulsion one.

[0019] A5. First layer curing: Slowly adjust the pH of the emulsion obtained in step A4 to 4.0-5.0 with 10-15% citric acid solution, and react at 45-50℃ for 2-3 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material, forming the inner wall material.

[0020] A6. Second layer coating and curing: Maintain the pH and temperature of the emulsion system, and slowly add the melamine-formaldehyde prepolymer prepared in step A3 to the above system. The amount of melamine-formaldehyde prepolymer added is 20%-50% of the mass of the core material phase. Under the same conditions (pH 4.0-5.0, 45-50℃), continue the reaction for 2-3 hours to allow the melamine-formaldehyde resin to further cross-link and deposit on the outer layer, forming a dense and tough outer wall material.

[0021] A7. Post-treatment and activation: After the reaction is complete, neutralize to neutral with NaOH solution, filter, and wash. Finally, vacuum dry the obtained microcapsules at 50-55℃ for 24-36 hours, and then heat-treat at 105-110℃ for 15-30 minutes to completely cross-link the wall material and enhance its thermal response sensitivity.

[0022] The fumed silica nanoparticles are fumed silica with a specific surface area of ​​150-300 m². 2 / g, preferably 200 m 2 / g. The amount of fumed silica nanoparticles added is 0.5%-1% of the total mass of the core material. Their function is to stabilize the core material emulsion and impart the required thixotropic properties to the repair agent, so as to achieve a smooth and flat repair effect.

[0023] Preparation of polyurethane emulsion: Hydroxyl-terminated hyperbranched polyurethane resin, an appropriate amount of deionized water, and an emulsifier (one or a combination of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether (such as OP-10)) are mixed and emulsified at high-speed shearing at 5000-8000 rpm for 10-20 minutes to form a stable aqueous emulsion with a solid content of 30%-50%. By weight percentage, the total emulsion includes 30%-50% hydroxyl-terminated hyperbranched polyurethane resin, 1%-3% emulsifier, and the balance deionized water.

[0024] (ii) The mixing of microcapsules and polyurethane coating includes the following steps: B1. Weighing: Weigh appropriate amounts of polyurethane emulsion and microcapsules according to the required coating thickness and repair performance. Preferably, the self-healing coating (by total coating mass) comprises 5-15% microcapsules and 85-95% polyurethane emulsion. Preferably, the polyurethane resin matrix is ​​waterborne polyurethane (WPU) or hyperbranched polyurethane (i.e., hydroxyl-terminated hyperbranched polyurethane resin with a hydroxyl value of 80-150 mg KOH / g), and the active functional groups of its molecular chain are hydroxyl (-OH) or amino (-NH2).

[0025] B2. Mixing: Add the microcapsules to the polyurethane emulsion and treat with an ultrasonic dispersion device for 30-60 minutes to ensure uniform dispersion of the microcapsules.

[0026] B3. Stirring: Continue stirring for 12-18 hours to ensure that the microcapsules are fully mixed with the polyurethane emulsion.

[0027] B4. Adding curing agent: Add the trimer curing agent based on hexamethylene diisocyanate (HDI) (i.e., HDI trimer curing agent, CAS No. 3779-63-3) at a mass ratio of 5:1 for polyurethane emulsion to polyisocyanate curing agent, and stir evenly at a low speed of 300-500 rpm.

[0028] B5. Defoaming treatment: Add 0.1%-0.5% of the total mass of the paint to an organosilicon or mineral oil-based water-based defoamer, and then ultrasonically treat it for 10-20 minutes at a power of 200-400W to remove the air bubbles mixed in the system.

[0029] B6. Coating: Apply the mixed coating to the surface of the metal substrate using methods such as spraying, brushing, or dipping (the metal substrate should be pre-treated beforehand: degreasing, rust removal, and sanding are performed on the surface of the metal substrate). The coating thickness is 120±10μm, forming a paint film. Select heat curing, curing at 80-85℃ for 2-3 hours to form a self-healing coating.

[0030] (III) Repair steps for self-healing coatings: Electrical Repair: The repair device is placed on the scratched area of ​​a metal plate coated with a self-healing coating. When the coating is damaged, the metal plate is placed on a heated metal coil plate. Voltage is applied to the metal coil, causing it to heat up and in turn heats the microcapsule repair agent, causing the microcapsules to rupture and release the repair agent to repair the damage. The output power range is 50~500W, powered by 50Hz industrial frequency. As the temperature rises, due to the thermal expansion effect of kerosene, the flat coil moves away from the metal coating via a telescopic rod (i.e., a piston rod). o Stop heating at C, hold the temperature for 10-30 minutes to complete the coating repair.

[0031] The energized repair device includes: a flat coil comprising a copper coil and a high-temperature resistant polyimide insulating varnish covering the outer surface of the copper coil; a telescopic rod (i.e., piston rod) whose top end is fixedly connected to the flat coil, and whose bottom end is located inside a sealed kerosene pipe; the copper coil is made of copper wire wound into a flat spiral structure with a coil spacing of 0.5~2mm, which heats up when energized, heating the coating above (such as the automotive coating to be repaired); the telescopic rod (i.e., piston rod) whose top end is fixedly connected to the flat coil; and a sealed kerosene pipe, the interior of which is filled with thermosensitive kerosene, connected to the bottom end of the telescopic rod (i.e., piston rod). The flat coil, telescopic rod (i.e., piston rod), and kerosene pipe are connected sequentially from top to bottom, forming a temperature-controlled actuator. The output power range is 50~500W, powered by a 50Hz industrial frequency. When the flat coil heats up, causing the kerosene to expand and push the telescopic rod (i.e., piston rod) upward, it moves the flat coil away from the coating, increasing the heat transfer distance and achieving cooling. When the temperature drops, the kerosene contracts, and the telescopic rod (i.e., piston rod) moves downward. Through this dynamic adjustment, the temperature of the repair area is automatically stabilized at a preset 60°C. The self-healing device can heat the metal and surface coating to trigger the melting of the microcapsule shell, releasing a repair agent to fill coating defects. This invention addresses the industry pain points of high energy consumption, difficulty in precise temperature control, and complex procedures in repairing damaged protective coatings, and is widely applicable to the corrosion and protection of metal materials.

[0032] The self-healing coating and its matching repair device of the present invention can achieve a repair efficiency of 84.1% to 95.1% after the coating scratches are repaired by electricity.

[0033] Method and structure for fabricating temperature control actuator: This is a structural framework diagram of the core component of the temperature-controlled repair device described in this invention—the temperature-controlled actuator.

[0034] 1. Overall structure and connection relationship: The mechanism consists of a flat coil, a heat-conducting connecting seat, a piston rod (i.e., a telescopic rod), a return spring, a sealing end cap, a thermal expansion cavity (i.e., a kerosene pipe), and a working medium, forming a closed mechanical feedback system from top to bottom.

[0035] 2. Detailed description of each component

[0036] (1) Flat coil: Serves as both a heat source and the actuator. It is made of copper wire wound into a flat spiral structure with a coil spacing of approximately 0.5~2mm. The copper wire is coated with a high-temperature resistant polyimide insulating varnish layer. The total resistance of the copper coil is designed to be 161Ω, and the output power is approximately 300W under a 220V, 50Hz power supply. The entire flat coil is embedded or encapsulated in an aluminum alloy thermally conductive connector using thermally conductive silicone grease.

[0037] (2) Thermally conductive connecting seat and piston rod: The lower center of the thermally conductive connecting seat is provided with a threaded hole, which is fastened to the top of the piston rod by threads. The piston rod is a stainless steel optical shaft with an annular shoulder in its middle.

[0038] (3) Return spring and sealing end cap: The return spring is sleeved on the piston rod, with its upper and lower ends abutting against the piston rod shoulder and the inner plane of the sealing end cap, respectively. The sealing end cap has a precision guide hole in the center, with an embedded dynamic sealing ring to ensure that the piston rod can slide axially and has a good seal. The outer edge of the sealing end cap is fastened to the thermal expansion cavity by threads.

[0039] (4) Thermal expansion cavity and working medium: The thermal expansion cavity is a cylindrical copper container closed at one end, with an oil injection hole on its side wall, which is sealed by a sealing screw. Aviation kerosene is filled into the cavity as the working medium, and its filling volume accounts for 70%±5% of the net internal volume of the cavity.

[0040] 3. Key Design Parameters and Calibration Methods

[0041] By coordinating the design of the following parameters, the temperature of the repaired area can be automatically stabilized at (60±2)℃: Kerosene filling rate: 70% ± 5%. This is the basis for generating the required expansion driving force.

[0042] Piston rod diameter (Ø8mm): The output thrust is determined together with the kerosene expansion pressure.

[0043] Return spring stiffness coefficient (k): This is the core adjustable calibration parameter. By selecting a spring with a suitable k value through experiments, when the surface temperature of the flat coil reaches 58-62℃, the thrust generated by the expansion of kerosene can just balance the spring's return force, and the piston rod begins to move significantly.

[0044] 4. Work Process

[0045] Initially, the preload of the return spring positions the flat coil at its lowest point (closest to the coating). Upon energization, the flat coil heats up, and the heat is transferred to the cavity via the heat-conducting connector and piston rod. The kerosene expands due to the heat, pushing the piston rod upwards against the spring force, moving the flat coil away from the coating. This reduces heat transfer efficiency, achieving negative feedback regulation, and ultimately achieving dynamic temperature equilibrium at the preset value. Upon de-energization, the temperature drops, the kerosene contracts, and the spring pushes the system back to its original position.

[0046] The beneficial effects of this invention are: ① The coating of this invention uses microencapsulation technology to encapsulate the repair agent, which effectively protects the repair agent and improves repair efficiency. After damage, the microcapsules rupture and release the repair agent. The heating effect of the energized coil promotes the rapid release and curing of the repair agent, achieving self-repair of the coating. The coating of this invention has good anti-corrosion properties and extends the service life of metal materials.

[0047] ② The repair system uses a flat coil to heat the metal coating, and utilizes the thermal expansion effect of kerosene in the telescopic rod to move the flat coil away from the metal coating, thereby reducing the eddy current heating effect; the repair system can adaptively control the heating temperature to achieve controllable temperature in the repair area.

[0048] ③ The preparation method of this invention is simple and easy to implement, and suitable for large-scale production. The self-healing coating of this invention has excellent adhesion, wear resistance, corrosion resistance and other properties, and can provide good protection for metal substrates. Attached Figure Description

[0049] Figure 1 This is a SEM image of the surface morphology of the microcapsules prepared in this invention; Figure 2 This is a frame diagram of the self-made temperature control device prepared in this invention; Figure 3 This is an engineering drawing of the specific structure of the self-made temperature control device prepared in this invention; Figure 4 These are comparison images of the coating scratches before and after electrical repair in this invention. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0051] A method for preparing a self-healing metal coating includes the following steps: A1. Core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 8:1. Then, 0.5% of fumed silica nanoparticles are added according to the total mass of the core material. The mixture is ultrasonically dispersed for 30 minutes to form a homogeneous and stable core material phase.

[0052] A2. Preparation of the first layer of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:1, the pH is adjusted to 8 with triethanolamine, and the mixture is reacted in a water bath at 65°C for 1.5 hours to obtain a transparent and viscous urea-formaldehyde prepolymer.

[0053] A3. Preparation of the second layer wall material prepolymer: Melamine and formaldehyde are mixed in a three-necked flask at a molar ratio of 1:2. The pH is adjusted to 8, and the mixture is stirred at 70°C until it becomes clear, thus obtaining the melamine-formaldehyde prepolymer for later use.

[0054] A4. Preparation of Multiphase Emulsion: The core material phase obtained in step 1 is slowly added to an aqueous phase containing 1% sodium dodecyl sulfate emulsifier under high-speed shearing at 10,000 rpm, and emulsified for 15 minutes to form a stable O / W type primary emulsion. Subsequently, the urea-formaldehyde prepolymer obtained in step 2 is slowly added dropwise to the emulsion under slow stirring to initially coat the core material.

[0055] A5. First layer curing: Slowly adjust the pH of the emulsion obtained in step 4 to 4.0 with 10% citric acid solution, and react at 45°C for 2 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material, forming the inner wall material.

[0056] A6. Second layer coating and curing: While maintaining the pH and temperature of the system, slowly add the melamine-formaldehyde prepolymer prepared in step 3 to the above system and continue the reaction for 2 hours under the same conditions to allow the melamine-formaldehyde resin to further cross-link and deposit on the outer layer, forming a dense and tough outer wall material.

[0057] A7. Post-treatment and activation: After the reaction is complete, neutralize to neutral with NaOH solution, filter, and wash. Finally, the obtained product is as follows: Figure 1 The microcapsules shown were vacuum dried at 50°C for 24 hours and then heat-treated at 105°C for 15 minutes to completely cross-link the wall material and enhance its thermal response sensitivity.

[0058] The coating preparation method and coating repair method of the self-healing coating and repair device of the present invention are as follows: B1. Surface pretreatment: The surface of the metal substrate is treated with degreasing, rust removal, grinding, etc. The self-healing coating (by total coating mass) comprises 10% microcapsules and 90% polyurethane emulsion. The microcapsules are added to the polyurethane emulsion and treated with an ultrasonic disperser for 40 minutes to ensure uniform dispersion. Stirring continues for 15 hours to ensure thorough mixing of the microcapsules and polyurethane emulsion. A curing agent (based on hexamethylene diisocyanate (HDI) trimer) is added at a mass ratio of 5:1 and stirred until homogeneous. Then, 0.3% of a silicone-based or mineral oil-based water-based defoamer, preferably water-based mineral oil defoamer ZH-7009, is added. The mixture is then ultrasonically treated at 300W for 15 minutes to remove air bubbles, yielding the self-healing paint.

[0059] B2. Coating: Apply self-healing paint to the surface of the metal substrate by spraying, brushing or dipping, with a coating thickness of 120±10μm to form a paint film. B3. Curing and molding: The coated metal substrate is cured at 80°C for 2 hours to form a self-healing coating; B4. Electrical Repair: When the coating is damaged, the metal is placed on a heated metal coil plate. Voltage is applied to the metal coil, causing it to heat up. This heats the microcapsule repair agent, causing the microcapsules to rupture and release the repair agent, thus repairing the damage. The output power range is 300W, powered by 50Hz mains frequency. As the temperature rises, due to the thermal expansion effect of kerosene, the flat coil moves away from the metal coating via a telescopic rod. o Stop heating at C, maintain the temperature for 20 minutes, and the coating repair is complete.

[0060] like Figure 2 and Figure 3 As shown, the repair device includes: a flat coil 1, which comprises a copper coil and a high-temperature resistant polyimide insulating varnish covering the outer surface of the copper coil; the top end of a telescopic rod is fixedly connected to the flat coil 1, and the bottom end of the telescopic rod is located inside a sealed kerosene pipe; the copper coil is made of copper wire wound into a flat spiral structure with a coil spacing of 1mm. The kerosene pipe is filled with thermosensitive kerosene. The flat coil, telescopic rod, and kerosene pipe are connected sequentially from top to bottom to form a temperature control actuator. The resistance of the flat coil is designed to be approximately 161Ω, and the output power is approximately 300W under a 220V, 50Hz power supply.

[0061] Overall structure and connection relationship: The temperature control actuator consists of a flat coil 1, a heat-conducting connecting seat 2, a piston rod 3 (i.e., telescopic rod), a return spring 4, a sealing end cover 5, a thermal expansion cavity 6 (i.e., kerosene pipe), and a working medium 7 from top to bottom, forming a closed mechanical feedback system.

[0062] Detailed description of each component:

[0063] (1) Flat coil 1: Serves as a heat source and actuator. It is made of copper wire wound into a flat spiral structure with a coil spacing of approximately 0.5~2mm. The copper wire is coated with a high-temperature resistant polyimide insulating varnish layer. The total resistance of the copper coil is designed to be 161Ω, and the output power is approximately 300W under a 220V, 50Hz power supply. The flat coil 1 is embedded or encapsulated in an aluminum alloy thermally conductive connector 2 using thermally conductive silicone grease.

[0064] (2) Thermally conductive connecting seat 2 and piston rod 3: The lower center of the thermally conductive connecting seat 2 is provided with a threaded hole, which is fastened to the top of the piston rod 3 by threads. The piston rod 3 is a stainless steel optical shaft with an annular shoulder in its middle.

[0065] (3) Return spring 4 and sealing end cap 5: The return spring 5 is sleeved on the piston rod 3, and its upper and lower ends abut against the shoulder of the piston rod 3 and the inner plane of the sealing end cap, respectively. The sealing end cap 5 has a precision guide hole in the center, with a dynamic sealing ring embedded inside, to ensure that the piston rod 3 can slide axially and is well sealed. The outer edge of the sealing end cap 5 is fastened to the thermal expansion cavity 6 by threads.

[0066] (4) Thermal expansion cavity 6 and working medium 7: The thermal expansion cavity 6 is a cylindrical copper container closed at one end, with an oil injection hole on its side wall, which is sealed by a sealing screw. Aviation kerosene is filled into the cavity as the working medium 7, and its filling volume accounts for 70% ± 5% of the net internal volume of the cavity.

[0067] The thermal expansion cavity 6 is connected to the bottom end of the piston rod 3.

[0068] The self-healing coating obtained in this embodiment has a thickness of 120±10μm and includes 10wt% microcapsules and 90wt% polyurethane resin.

[0069] The self-healing coating in this embodiment is used in conjunction with the repair device to achieve adaptive control of the heating temperature of the coating being repaired, thus ensuring that the temperature of the repaired area is controllable. This avoids the problem that the microcapsules of the coating cannot be effectively broken due to the repair temperature being too low, resulting in insufficient release of the repair agent and incomplete repair with scratches still visible. At the same time, it avoids the problem that the repair agent or components in the matrix will vaporize and cause bulging due to the repair temperature being too high, or that the matrix will overheat and age, causing cracking and yellowing, which will result in secondary damage.

[0070] like Figure 4 As shown, Figure 4 The three images, from left to right, show the original layer, the layer after being scratched, and the layer after being repaired by electro-hydraulic treatment. Original coating: The coating surface is smooth, flat, and continuous, without any defects. The coating is tightly bonded to the metal substrate, exhibiting a uniform material and gloss. After scratching: A clear, sharp artificial scratch exists on the coating surface. The scratch is uniform in width and penetrates the entire coating to expose the bare metal substrate. After electro-hydraulic repair: The scratched area has been effectively filled with new repair material. Compared to the original scratch, the surface of the repaired area has been essentially restored to flatness, with minimal height difference from the surrounding original coating. The interface between the repaired area and the original coating is blurred and tightly bonded, without obvious cracks or gaps. No obvious bubbles, pores, or shrinkage cracks are observed within the repaired area. The surface morphology and gloss of the repaired area are highly similar to the original coating area.

[0071] Conclusion: The self-healing coating system of this invention, under the action of a dedicated repair device, can achieve efficient and high-quality repair of penetrating scratches. The repaired coating surface is smooth and flat, the repaired body is dense and well-bonded with the original coating, with no obvious interface defects. This directly demonstrates that the synergistic effect of the "dual-wall microcapsules prepared by a specific complex process" and the "intelligent temperature-controlled hot-pressing repair device" successfully solves common problems in traditional heat repair such as incomplete repair, bulging, and cracking, thereby achieving and supporting a repair efficiency as high as 84.1%~95.1%. This repair effect far exceeds that of ordinary self-healing coatings, reflecting the significant progress and inventiveness of this invention.

[0072] The self-healing coating and its matching repair device in this embodiment can achieve a repair efficiency of 84.1% after the coating scratches are repaired by electricity. Example 2

[0073] A method for preparing a self-healing metal coating includes the following steps: A1. Core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 9:1. Then, 0.5% of fumed silica nanoparticles are added according to the total mass of the core material. The mixture is then ultrasonically dispersed for 30 minutes to form a homogeneous and stable core material phase.

[0074] A2. Preparation of the first layer of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:1.5, the pH is adjusted to 9 with triethanolamine, and the mixture is reacted in a water bath at 65°C for 2 hours to obtain a transparent and viscous urea-formaldehyde prepolymer.

[0075] A3. Preparation of the second layer wall material prepolymer: Melamine and formaldehyde are mixed in a three-necked flask at a molar ratio of 1:3. The pH is adjusted to 9, and the mixture is stirred at 70°C until it becomes clear, thus obtaining the melamine-formaldehyde prepolymer for later use.

[0076] A4. Preparation of Multiphase Emulsion: The core material phase obtained in step 1 is slowly added to an aqueous phase containing 1% sodium dodecyl sulfate emulsifier under high-speed shearing at 10,000 rpm, and emulsified for 15 minutes to form a stable O / W type primary emulsion. Subsequently, the urea-formaldehyde prepolymer obtained in step 2 is slowly added dropwise to the emulsion under slow stirring to initially coat the core material.

[0077] A5. First layer curing: Slowly adjust the pH of the emulsion obtained in step 4 to 4.0 with 10% citric acid solution, and react at 45°C for 2 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material, forming the inner wall material.

[0078] A6. Second layer coating and curing: While maintaining the pH and temperature of the system, slowly add the melamine-formaldehyde prepolymer prepared in step 3 to the above system and continue the reaction for 2 hours under the same conditions to allow the melamine-formaldehyde resin to further cross-link and deposit on the outer layer, forming a dense and tough outer wall material.

[0079] A7. Post-treatment and activation: After the reaction, the microcapsules were neutralized to neutral with NaOH solution, filtered, and washed. Finally, the obtained microcapsules were vacuum dried at 50°C for 24 hours, followed by heat treatment at 105°C for 15 minutes to completely cross-link the wall material and enhance its thermal response sensitivity.

[0080] B1. Surface pretreatment: The surface of the metal substrate is treated with degreasing, rust removal, grinding, etc. The self-healing coating (by total coating mass) comprises 5% microcapsules and 95% polyurethane emulsion. The microcapsules are added to the polyurethane emulsion and treated with an ultrasonic disperser for 30 minutes to ensure uniform dispersion. Stirring continues for 12 hours to ensure thorough mixing of the microcapsules and polyurethane emulsion. A curing agent (based on hexamethylene diisocyanate (HDI) trimer) is added at a mass ratio of 5:1 and stirred until homogeneous. Then, 0.1% of a silicone or mineral oil-based water-based defoamer is added, followed by ultrasonic treatment at 200W for 10 minutes to remove air bubbles, resulting in the self-healing paint.

[0081] B2. Coating: Apply self-healing paint to the surface of the metal substrate by spraying, brushing or dipping, with a coating thickness of 120±10μm to form a paint film. B3. Curing and molding: The coated metal substrate is cured at 80°C for 2 hours to form a self-healing coating; B4. Electrical Repair: When the coating is damaged, the metal is placed on a heated metal coil plate. Voltage is applied to the metal coil, causing it to heat up. This heats the microcapsule repair agent, causing the microcapsules to rupture and release the repair agent, thus repairing the damage. The output power range is 50W, 50Hz mains frequency power supply. As the temperature rises, due to the thermal expansion effect of kerosene, the flat coil moves away from the metal coating via a telescopic rod. o Stop heating at C, hold the temperature for 10 minutes, and the coating repair is complete.

[0082] The self-healing coating obtained in this embodiment has a thickness of 120±10μm and includes 5wt% microcapsules and 95wt% polyurethane resin.

[0083] The self-healing coating in this embodiment is used in conjunction with the repair device to achieve adaptive control of the heating temperature of the coating being repaired, thus ensuring that the temperature of the repaired area is controllable. This avoids the problem that the microcapsules of the coating cannot be effectively broken due to the repair temperature being too low, resulting in insufficient release of the repair agent and incomplete repair with scratches still visible. At the same time, it avoids the problem that the repair agent or components in the matrix will vaporize and cause bulging due to the repair temperature being too high, or that the matrix will overheat and age, causing cracking and yellowing, which will result in secondary damage.

[0084] The self-healing coating and its matching repair device in this embodiment can achieve a repair efficiency of 95.1% after the coating scratches are repaired by electricity. Example 3

[0085] A method for preparing a self-healing metal coating includes the following steps: A1. Core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 10:1. Then, 0.5% of fumed silica nanoparticles are added, and the mixture is ultrasonically dispersed for 30 minutes to form a homogeneous and stable core material phase.

[0086] A2. Preparation of the first layer of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:2, the pH is adjusted to 8.5 with triethanolamine, and the mixture is reacted in a water bath at 65°C for 2 hours to obtain a transparent and viscous urea-formaldehyde prepolymer.

[0087] A3. Preparation of the second layer wall material prepolymer: Melamine and formaldehyde are mixed in a three-necked flask at a molar ratio of 1:4. The pH is adjusted to 8.5, and the mixture is stirred at 70°C until it becomes clear, thus obtaining the melamine-formaldehyde prepolymer for later use.

[0088] A4. Preparation of Multiphase Emulsion: The core material phase obtained in step 1 is slowly added to an aqueous phase containing 1% sodium dodecyl sulfate emulsifier under high-speed shearing at 10,000 rpm, and emulsified for 15 minutes to form a stable O / W type primary emulsion. Subsequently, the urea-formaldehyde prepolymer obtained in step 2 is slowly added dropwise to the emulsion under slow stirring to initially coat the core material.

[0089] A5. First layer curing: Slowly adjust the pH of the emulsion obtained in step 4 to 4.0 with 10% citric acid solution, and react at 45°C for 2 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material, forming the inner wall material.

[0090] A6. Second layer coating and curing: While maintaining the pH and temperature of the system, slowly add the melamine-formaldehyde prepolymer prepared in step 3 to the above system and continue the reaction for 2 hours under the same conditions to allow the melamine-formaldehyde resin to further cross-link and deposit on the outer layer, forming a dense and tough outer wall material.

[0091] A7. Post-treatment and activation: After the reaction, the microcapsules were neutralized to neutral with NaOH solution, filtered, and washed. Finally, the obtained microcapsules were vacuum dried at 50°C for 24 hours, followed by heat treatment at 105°C for 15 minutes to completely cross-link the wall material and enhance its thermal response sensitivity.

[0092] B1. Surface pretreatment: The surface of the metal substrate is treated with degreasing, rust removal, grinding, etc. The self-healing coating (by total coating mass) comprises 15% microcapsules and 85% polyurethane emulsion. The microcapsules are added to the polyurethane emulsion and treated with an ultrasonic disperser for 60 minutes to ensure uniform dispersion. Stirring continues for 18 hours to ensure thorough mixing of the microcapsules and polyurethane emulsion. A curing agent (a trimer based on hexamethylene diisocyanate (HDI)) is added at a polyurethane emulsion to curing agent mass ratio of 5:1, and stirred until homogeneous. Then, 0.5% of a silicone or mineral oil-based water-based defoamer is added, followed by ultrasonic treatment at 400W for 20 minutes to remove air bubbles, resulting in the self-healing paint.

[0093] B2. Coating: Apply self-healing paint to the surface of the metal substrate by spraying, brushing or dipping, with a coating thickness of 120±10μm to form a paint film. B3. Curing and molding: The coated metal substrate is cured at 80°C for 2 hours to form a self-healing coating; B4. Electrical Repair: When the coating is damaged, the metal is placed on a heated metal coil plate. Voltage is applied to the metal coil, causing it to heat up. This heats the microcapsule repair agent, causing the microcapsules to rupture and release the repair agent, thus repairing the damage. The output power range is 500W, powered by 50Hz mains frequency. As the temperature rises, due to the thermal expansion effect of kerosene, the flat coil moves away from the metal coating via a telescopic rod. o Stop heating at C, maintain the temperature for 30 minutes, and the coating repair is complete.

[0094] The self-healing coating obtained in this embodiment has a thickness of 120±10μm and includes 15wt% microcapsules and 85wt% polyurethane resin.

[0095] The self-healing coating in this embodiment is used in conjunction with the repair device to achieve adaptive control of the heating temperature of the coating being repaired, thus ensuring that the temperature of the repaired area is controllable. This avoids the problem that the microcapsules of the coating cannot be effectively broken due to the repair temperature being too low, resulting in insufficient release of the repair agent and incomplete repair with scratches still visible. At the same time, it avoids the problem that the repair agent or components in the matrix will vaporize and cause bulging due to the repair temperature being too high, or that the matrix will overheat and age, causing cracking and yellowing, which will result in secondary damage.

[0096] The self-healing coating and its matching repair device in this embodiment can achieve a repair efficiency of 87.8% after the coating scratches are repaired by electricity.

[0097] Comparative Example 1

[0098] The only difference between this comparative example and Example 1 is that: A method for preparing a self-healing metal coating includes the following steps: Prepare conventional single-layer urea-formaldehyde resin wall material microcapsules.

[0099] Specifically, A1, core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 8:1, and then 0.5% of fumed silica nanoparticles are added according to the total mass of the core material. After ultrasonic dispersion for 30 minutes, a homogeneous and stable core material phase is formed.

[0100] A2. Preparation of urea-formaldehyde prepolymer for wall materials: Urea and formaldehyde are mixed in a molar ratio of 1:1, the pH is adjusted to 8 with triethanolamine, and the mixture is reacted in a water bath at 65°C for 1.5 hours to obtain a transparent and viscous urea-formaldehyde prepolymer.

[0101] A3. Preparation of Multiphase Emulsion: The core material phase obtained in step 1 was slowly added to an aqueous phase containing 1% sodium dodecyl sulfate emulsifier under high-speed shearing at 10,000 rpm, and emulsified for 15 minutes to form a stable O / W type primary emulsion. Subsequently, the urea-formaldehyde prepolymer obtained in step 2 was slowly added dropwise to the emulsion under slow stirring to initially coat the core material.

[0102] A4. Curing: Slowly adjust the pH of the emulsion obtained in step 4 to 4.0 with 10% citric acid solution, and react at 45°C for 2 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material, forming a urea-formaldehyde resin wall material.

[0103] A5. Post-treatment and activation: After the reaction, the microcapsules were neutralized to neutral with NaOH solution, filtered, and washed. Finally, the obtained microcapsules were vacuum dried at 50°C for 24 hours, followed by heat treatment at 105°C for 15 minutes to completely cross-link the wall material and enhance its thermal response sensitivity.

[0104] Comparative Example 2

[0105] The only difference between this comparative example and Example 1 is that: A method for preparing a self-healing metal coating includes the following steps: A1. Preparation of core material solution: Mix epoxy resin E-51 and diluent acetone at a mass ratio of 5:1 and stir for 45 minutes to form a homogeneous solution.

[0106] A2. Preparation of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:1.5, and triethanolamine is added to adjust the pH to 8-9; the mixture is reacted at -60℃ for 1.8h until the solution is transparent and viscous to obtain urea-formaldehyde prepolymer; A3. Emulsion preparation: Emulsification and dispersion: The prepolymer is mixed with the emulsifier Tween-80 to form an aqueous phase. The epoxy resin-acetone solution obtained in step A1 is mixed with ethyl acetate at a ratio of 1:1 to form an oil phase. The oil phase is slowly added to the aqueous phase at a volume ratio of 1:4. The mixture is sheared and emulsified at 8000 rpm for 10-20 min to form an emulsion. A4. Acidification and curing: Add 10wt% dilute sulfuric acid to the emulsion obtained in step A3, adjust the pH to 2.5~3.0, add resorcinol (5% of the prepolymer mass) as curing agent, and react at 60℃ for 2~3h to crosslink and cure the wall material on the surface of the core material. A5. Post-treatment: Neutralize to pH=7 with 5wt% sodium carbonate solution, filter and wash; vacuum dry at 40℃ for 24h to evaporate acetone and residual solvent, and obtain single-layer wall material microcapsules.

[0107] Comparative Example 3

[0108] The only difference between this comparative example and Example 1 is that: B4. Electrical Repair: When the coating is damaged, the metal is placed on a heated metal coil plate. A common constant power heating non-lifting repair device is used to heat the microcapsule repair agent. The repair temperature is set to 60℃, which causes the microcapsules to rupture, release the repair agent, and repair the damage.

[0109] Comparative Example 3 uses a constant power heating device without automatic distance adjustment. This device can consist of a resistance heating plate with a fixed power, or it can be a commercially available constant temperature heating device with a fixed heating plate. For example, the furnace bottom plate of the KSL series high temperature furnace produced by MTI can be used as a fixed heating platform. The difference between this device and the present invention is that it does not have an automatic lifting function that changes with temperature through thermal expansion medium.

[0110] Characterization results

[0111] The self-healing metal coatings prepared in Examples 1-3 were tested for their self-healing performance, corrosion resistance, and salt spray resistance. Electrochemical impedance spectroscopy (EIS) was used to test the corrosion resistance of the coatings; the impedance value was 8.2 × 10⁻⁶. 7 The results showed that the repair efficiency reached 85%-95%, indicating that the coating has excellent corrosion resistance. Salt spray test: The coating samples were placed in a 500-hour salt spray test (5% NaCl) to verify the corrosion resistance of the coating. As shown in Table 1 below.

[0112] Table 1 Performance of Self-Healing Coatings

[0113] The automatic repair performance test results showed that Example 2 performed best, with a repair rate of 95.1% and a repair time of only 10 minutes. The combination of a dilution ratio of 9:1 and a urea:formaldehyde ratio of 1:1.5 optimized the release characteristics of the microcapsules. Example 3 may have experienced a slight decrease in repair efficiency due to an excessively high dilution ratio. The corrosion resistance test results, using electrochemical impedance spectroscopy, showed that Example 2 had the highest impedance in the low-frequency region, indicating its optimal protective performance. The order of low-frequency impedance was: Example 2 > Example 3 > Example 1 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1, demonstrating that high impedance in this invention signifies a better corrosion protection barrier. The salt spray corrosion resistance test results showed that after 480 hours of salt spray testing in NaCl solution, the order of corrosion area was: Example 2 < Example 3 < Example 1 < Comparative Example 3 < Comparative Example 2 < Comparative Example 1.

[0114] The causes of bulging and bubbling in Comparative Examples 1 and 2 are as follows: Even when using the temperature-controlled repair device of this invention, the temperature of the single-layer urea-formaldehyde resin wall microcapsules (or single-layer wall material microcapsules) may momentarily exceed the tolerance limit of the repair agent or the substrate due to the single-layer wall material. This causes the residual solvent to rapidly vaporize or the repair agent to partially decompose, generating gas and forming bulges and bubbles inside the coating. The causes of cracking and incomplete repair in Comparative Example 3 are as follows: The constant power heating device that cannot be raised or lowered cannot provide a stable and uniform thermal field. Temperature fluctuations may lead to uneven curing stress or insufficient cross-linking of the repair agent. The repair agent of complex microcapsules needs to be at a constant optimal temperature of 60°C and pressure provided by the device of this invention to achieve sufficient leveling and perfect cross-linking. Without stable hot-pressing conditions, defects are easily generated inside the repair body, leading to cracking; at the same time, insufficient heat may also prevent some microcapsules from effectively rupturing, resulting in incomplete repair.

[0115] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0116] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0117] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing epoxy resin microcapsules, characterized in that, Includes the following steps: A1. Core material emulsification and dispersion: Epoxy resin E-51 and reactive diluent benzyl glycidyl ether are mixed at a mass ratio of 8:1 to 10:1 to obtain a mixture. Then, 0.5-1% of fumed silica nanoparticles are added to the mixture and ultrasonically dispersed for 30-60 minutes to form a homogeneous and stable core material phase. A2. Preparation of the first layer of wall material prepolymer: Urea and formaldehyde are mixed in a molar ratio of 1:1 to 1:2, the pH is adjusted to 8 to 9 with triethanolamine, and the mixture is reacted in a water bath at 65-70℃ for 1.5 to 2 hours to obtain a transparent and viscous urea-formaldehyde prepolymer. A3. Preparation of the second layer wall material prepolymer: Melamine and formaldehyde are mixed in a three-necked flask at a molar ratio of 1:2 to 1:

4. The pH is adjusted to 8 to 9. The mixture is stirred at 70-80℃ until it becomes clear, and the melamine-formaldehyde prepolymer is obtained for later use. A4. Preparation of Multiphase Emulsion: The core phase obtained in step A1 is slowly added to an aqueous phase containing 1-2 wt% sodium dodecyl sulfate emulsifier under high-speed shearing at 10000-12000 rpm. The ratio of core phase to aqueous phase is 1:4-1:

6. Emulsification is carried out for 15-30 minutes to form a stable O / W type primary emulsion. Subsequently, under slow stirring, the urea-formaldehyde prepolymer obtained in step A2 is slowly added dropwise to the primary emulsion. The amount of urea-formaldehyde prepolymer added is 30%-60% of the mass of the core phase, which initially coats the core material to obtain emulsion one. A5. First layer curing: Slowly adjust the pH of the emulsion obtained in step A4 to 4.0-5.0 with 10-15% citric acid solution, and react at 45-50℃ for 2-3 hours to allow the urea-formaldehyde resin to crosslink and cure on the surface of the core material to form the inner wall material. A6. Second layer coating and curing: Maintain the pH and temperature of the emulsion system, and slowly add the melamine-formaldehyde prepolymer prepared in step A3 to the above system. The amount of melamine-formaldehyde prepolymer added is 20%-50% of the mass of the core material phase. Continue the reaction for 2-3 hours at pH 4.0-5.0 and 45-50℃ to allow the melamine-formaldehyde resin to further cross-link and deposit on the outer layer, forming a dense and tough outer wall material. A7. Post-treatment and activation: After the reaction is complete, neutralize to neutral with NaOH solution, filter and wash; finally, vacuum dry the obtained microcapsules at 50-55℃ for 24-36 hours, and then heat treat at 105-110℃ for 15-30 minutes.

2. The method for preparing epoxy resin microcapsules according to claim 1, characterized in that, The specific surface area of ​​the fumed silica nanoparticles is 150-300 m². 2 / g.

3. A self-healing coating, characterized in that, The mixture includes 5-15 wt% epoxy resin microcapsules and 85-95 wt% polyurethane emulsion obtained by the method for preparing epoxy resin microcapsules according to claim 1 or 2.

4. The self-healing coating according to claim 3, characterized in that, The polyurethane resin matrix in the polyurethane emulsion is waterborne polyurethane (WPU) or hydroxyl-terminated hyperbranched polyurethane resin; the hydroxyl value of the hydroxyl-terminated hyperbranched polyurethane resin is 80-150 mg KOH / g.

5. The method for preparing a self-healing coating according to claim 4, characterized in that, Includes the following steps: B1. Weighing: Weigh the polyurethane emulsion and epoxy resin microcapsules to obtain the paint; B2. Mixing: Add epoxy resin microcapsules to polyurethane emulsion and treat with ultrasonic dispersion equipment for 30-60 minutes to ensure uniform dispersion of microcapsules; B3. Stirring: Continue stirring for 12-18 hours to ensure that the epoxy resin microcapsules and polyurethane emulsion are fully mixed. B4. Adding the curing agent: Add the curing agent at a mass ratio of 5:1 for polyurethane emulsion to polyisocyanate curing agent, and stir evenly at 300-500 rpm. B5. Defoaming treatment: Add 0.1%-0.5% of an organosilicon or mineral oil-based water-based defoamer by weight of the paint, and then ultrasonically treat it for 10-20 minutes at a power of 200-400W to obtain the mixed paint. B6. Coating: Apply the mixed paint to the surface of the metal substrate by spraying, brushing or dipping; the coating thickness is 120±10μm to form a paint film; heat to cure, cure at 80-85℃ for 2-3 hours to form a self-healing coating.

6. A repair device used in conjunction with the self-healing coating as described in claim 3, characterized in that, include: Flat coil: used as a heat source and actuator; the flat coil is made of copper wire wound into a flat spiral structure, with a coil spacing of 0.5~2mm; The copper wire is coated with a high-temperature resistant polyimide insulating varnish layer; the entire flat coil is embedded or cast into an aluminum alloy thermally conductive connector using thermally conductive silicone grease. Piston rod: The lower part of the heat-conducting connector is provided with a threaded hole, and the top of the piston rod is fastened to the threaded hole of the heat-conducting connector through a thread; the piston rod is a stainless steel smooth shaft, and the middle part of the piston rod is provided with an annular shoulder; Return spring: The return spring is sleeved on the piston rod, and the upper and lower ends of the return spring abut against the annular shoulder of the piston rod and the inner plane of the sealing end cover, respectively; the sealing end cover has a guide hole in the center for penetrating the piston rod, and a dynamic sealing ring is embedded in the guide hole. After the bottom end of the piston rod passes through the sealing end cover and the dynamic sealing ring, it moves within the thermal expansion cavity. Thermal expansion cavity: The thermal expansion cavity is a cylindrical copper container closed at one end, with an oil injection hole on its side wall, which is sealed by a sealing screw; the cavity is filled with aviation kerosene as the working medium, and the filling volume of aviation kerosene accounts for 70%±5% of the net internal volume of the cavity.

7. A self-healing coating repair method using the repair device according to claim 6, characterized in that, The process includes the following steps: Electrical Repair: Place the repair device on the scratched area of ​​a metal plate coated with a self-healing coating, and apply electrical repair. When the metal plate with the self-healing coating is damaged, place it on the repair device and apply voltage to the flat coil. This heats the coil, causing the epoxy resin microcapsules to rupture and release the repair agent, thus repairing the damage. The flat coil's output power range is 50~500W, powered by 50Hz industrial frequency. As the temperature rises, due to the thermal expansion effect of aviation kerosene, the flat coil moves away from the metal plate with the self-healing coating via the piston rod. o Stop heating at C, hold the temperature for 10-30 minutes to complete the coating repair.

8. A metal plate covered with the self-healing coating of claim 3, characterized in that, Metal sheets include magnesium alloy sheets, aluminum alloy sheets, or steel sheets.

9. The application of the metal plate according to claim 8 in self-healing coated plates in the fields of aviation, bridges, automobiles, and electronics.

10. The application of the repair device according to claim 6 in automotive coating repair, characterized in that, The repair efficiency can reach 84.1%~95.1%.

Images