Self-monitoring, shock absorption, and self-healing integrated protective coating and its preparation method

Abstract

This invention discloses an integrated protective coating for self-monitoring, shock absorption, and self-repair, and also discloses a method for preparing the coating, comprising: in-situ interface modification of a piezoelectric phase to obtain a piezoelectric functional phase; adding a conductive phase to water to obtain a conductive pre-dispersion liquid; adding a resin matrix containing dynamic covalent bonds to the conductive pre-dispersion liquid, and then adding the piezoelectric functional phase to obtain a protective coating; coating the coating onto the surface of a substrate, and subjecting it to low-temperature pre-curing and deep curing under a DC electric field to achieve piezoelectric phase domain polarization orientation, thereby obtaining an integrated protective coating. The coating of this invention achieves real-time and accurate self-monitoring of impact damage and load through the piezoelectric effect of the piezoelectric phase; adaptive adjustment of coating stiffness and damping is achieved by relying on the inverse piezoelectric effect combined with an external controllable DC electric field; and active on-demand repair of microcracks is achieved by utilizing the electrothermal effect of the conductive network to trigger dynamic covalent bond recombination. It possesses the core advantages of integrating self-monitoring, adaptive shock absorption, and active repair.

Description

Technical Field

[0001] This invention belongs to the field of emergency rescue protective materials technology, specifically relating to an integrated protective coating that integrates self-monitoring, shock absorption, energy absorption, and self-repair. This invention also relates to a method for preparing the protective coating. Background Technology

[0002] Emergency rescue is a crucial operation in response to sudden events such as natural disasters, accidents, and public health emergencies. Rescue operations often face complex risks including falls from heights, object impacts, explosions, aftershocks, and sharp object punctures. The protective equipment worn by rescue personnel, the rescue gear used, and the temporary protective facilities on-site directly determine the safety of rescuers and the success or failure of the rescue mission. Protective coatings, as the core protective barrier of emergency rescue equipment, must simultaneously achieve an integrated closed-loop function encompassing damage self-monitoring, dynamic adjustment of impact intensity, efficient shock absorption and energy dissipation, and active damage repair to continuously and stably provide protection in complex, extreme, and highly dynamic rescue scenarios.

[0003] Currently, most protective coatings used in emergency rescue are single-function or simply layered, often exhibiting functional fragmentation and a lack of synergistic action. Existing shock-absorbing coatings primarily utilize elastomers, foam materials, damping composites, polyurea, and aramid fiber reinforcement systems, relying mainly on the material's viscoelastic deformation, interfacial debonding, and cell collapse to dissipate impact energy. Related research largely focuses on matrix modification, filler reinforcement, and multilayer structure design. While these coatings can improve static buffering performance to some extent, they lack real-time in-situ self-monitoring capabilities. Under repeated impacts, alternating loads, or extreme environments, the coating is prone to developing hidden damage such as microcracks, interlayer delamination, and matrix aging. This damage is difficult to identify visually and accumulates, eventually causing a sharp decline in shock-absorbing performance and even leading to sudden failure of protective equipment. Some protective coatings with monitoring capabilities employ embedded or surface-mounted piezoelectric sensors, fiber optic sensors, strain gauges, and other external devices to monitor damage and stress by collecting signals such as strain, voltage, and acoustic waves. These methods typically require supporting signal acquisition, power supply, and data processing systems, resulting in complex structures, low integration, and high costs. Furthermore, the external sensors and the coating body have large differences in modulus and low interfacial bonding strength, making them prone to detachment, breakage, and signal interruption under strong dynamic loads such as high-speed impacts, explosive impacts, and sharp object punctures. This makes it difficult to achieve stable, continuous, and in-situ damage monitoring, and even more difficult to achieve adaptive dynamic adjustment of protection strength based on real-time sensing signals.

[0004] Furthermore, existing protective coatings generally lack active damage repair capabilities. Traditional repair methods rely on post-processing techniques such as manual recoating and hot-pressing, which are slow to respond, complex to operate, and difficult to complete real-time repair of micro-damage at the rescue site. While a few coatings incorporating microcapsules or phase-change repair systems possess some self-healing effects, they generally suffer from drawbacks such as stringent repair triggering conditions, limited repair cycles, and poor compatibility with shock absorption and energy dissipation functions. Microcracks are difficult to heal completely on their own, leading to a continuous decline in the coating's mechanical properties and protective reliability. On the other hand, the shock absorption and energy dissipation performance of traditional protective coatings is mostly fixed in design and cannot be adjusted online. Damping characteristics, buffer stiffness, and energy absorption thresholds are essentially fixed after preparation, making it impossible to adaptively and dynamically adjust the impact intensity based on the impact size, impact rate, and load type. In weak impact and low-frequency vibration scenarios, the coating's rigidity is too high and its flexibility is insufficient, affecting the comfort of equipment use. In strong impact and high-speed collision scenarios, the coating's energy absorption is insufficient and its buffering capacity is limited, making it difficult to effectively attenuate impact energy and failing to meet the protection requirements of complex and variable emergency rescue scenarios with multiple load couplings.

[0005] The piezoelectric effect, a physical effect that converts mechanical energy into electrical energy, can be used to sense mechanical deformation caused by external impacts and convert it into electrical signals for damage self-monitoring. Simultaneously, the inverse piezoelectric effect and damping synergistically utilize the piezoelectric material to achieve dynamic adjustment of impact intensity and efficient shock absorption. Therefore, developing an intelligent protective coating based on the piezoelectric effect, integrating self-monitoring, dynamic adjustment of impact intensity, shock absorption, and active repair, overcomes the technical bottlenecks of existing protective coatings' single function and inability to achieve closed-loop coordination. This is of great significance and application value for significantly improving the intelligence level and protective reliability of emergency rescue equipment, ensuring the safety of rescue personnel, and improving emergency response efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated protective coating that integrates self-monitoring, shock absorption, energy absorption, and self-repair, enabling integrated closed-loop control of the electric field for self-monitoring, dynamic adjustment of impact strength, shock absorption, energy absorption, and active repair.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned protective coating.

[0008] The technical solution adopted in this invention is: The preparation method of the integrated protective coating that integrates self-monitoring, shock absorption, energy absorption, and self-healing is carried out according to the following steps: Step 1: Use a silane coupling agent to perform in-situ interface modification on the piezoelectric phase to obtain a surface-modified piezoelectric functional phase; Step 2: Add the conductive phase to deionized water and disperse to obtain a conductive pre-dispersion. Step 3: Add the resin matrix containing dynamic covalent bonds to the conductive pre-dispersion liquid, mix well, and then add the surface-modified piezoelectric functional phase. After uniform dispersion, an integrated protective coating is obtained. Step 4: Apply the protective coating to the surface of the substrate, perform low-temperature pre-curing, and then perform deep curing and piezoelectric domain polarization orientation under the action of a DC electric field to obtain an integrated protective coating.

[0009] The invention is further characterized by: Step 1 is as follows: The silane coupling agent is added to a mixed solvent of ethanol and deionized water and hydrolyzed for 10–30 min. Then, the piezoelectric phase is added and stirred at 400–1500 rpm for 15–60 min to form a uniform monolayer of silane coupling agent on the surface of the piezoelectric phase. Finally, the mixture is centrifuged, washed with water, and vacuum dried to obtain the surface-modified piezoelectric functional phase.

[0010] The piezoelectric phase is barium titanate, zinc oxide, or lead zirconate titanate nanoparticles; the silane coupling agent is one or a mixture of several of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane. The volume ratio of ethanol to deionized water in the mixed solvent is 5–10:1; the mass ratio of the piezoelectric phase to the silane coupling agent is 100:0.5–2.

[0011] Step 2 is as follows: The conductive phase is added to deionized water and sonicated for 15–60 min to allow it to peel and disperse. Then, a dispersant is added to obtain a conductive pre-dispersion.

[0012] The conductive phase is carbon nanotubes or graphene; the dispersant is polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, or hexadecyltrimethylammonium bromide; the mass ratio of the conductive phase to the dispersant is 30–60:1, and the mass ratio of the sum of the conductive phase and the dispersant to deionized water is 1:20–40.

[0013] Step 3 specifically involves: The resin matrix containing dynamic covalent bonds is preheated to 40-50°C and then added to the conductive pre-dispersion liquid obtained in step 2. The mixture is stirred at 400-1000 rpm for 3-10 hours. Then, the piezoelectric functional phase obtained in step 1 is added and stirred for 6-24 hours to ensure uniform dispersion. Finally, the mixture is vacuum degassed for 10-30 minutes to obtain an integrated protective coating.

[0014] The resin matrix containing dynamic covalent bonds is a polyurethane containing disulfide bonds, an epoxy resin matrix containing dynamic hydrazone bonds, or an epoxy resin matrix containing dynamic Schiff base bonds; the mass ratio of the surface-modified piezoelectric functional phase, the conductive phase, and the resin matrix is ​​15-45:0.5-5:100.

[0015] Step 4 specifically involves: The composite coating obtained in step 3 is applied to the surface of the substrate, and the wet film thickness is controlled to be 100-300 μm. It is pre-cured at room temperature for 12-24 h to allow the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes are prepared on the upper and lower surfaces of the coating to form a sandwich capacitor structure. The sandwich capacitor structure is placed in a silicone oil bath, and a DC electric field with an intensity of 2-6 kV / mm is applied. The oil bath temperature is raised to 60-120°C. After holding at this temperature and electric field for 15-60 min, the deep curing of the resin and the polarization orientation of the piezoelectric domains are completed simultaneously. Finally, the electric field is kept constant and removed after natural cooling to room temperature to obtain an integrated protective coating.

[0016] Another technical solution adopted in this invention is an integrated protective coating that integrates self-monitoring, shock absorption, energy absorption, and self-repair, which is prepared by the above method.

[0017] The beneficial effects of this invention are: (1) The method of the present invention first constructs a resin matrix containing dynamic covalent bonds, then disperses the piezoelectric functional phase and ensures orientation, and finally selectively introduces conductive fillers to construct a continuous network, avoiding mutual interference between the piezoelectric phase and the conductive phase, realizing structural hierarchy and functional synergy. The prepared intelligent protective coating has the core advantages of self-monitoring, adaptive shock absorption and energy absorption and active repair. (2) Through the piezoelectric effect of the built-in piezoelectric functional phase, when the coating is subjected to external impact, the piezoelectric functional phase undergoes mechanical deformation and is converted into an electrical signal, realizing real-time and accurate self-monitoring of the impact intensity, impact location and coating structure damage. It can quickly capture key information such as microcrack initiation and impact load changes, providing accurate triggering signals for subsequent regulation and repair. (3) In addition, relying on the inverse piezoelectric effect of the piezoelectric functional phase and combined with the coordinated control of the external controllable DC electric field, the electric field parameters are dynamically adjusted according to the monitored impact intensity signal, so that the coating undergoes controllable expansion or contraction deformation, thereby realizing the adaptive adjustment of the coating stiffness and damping coefficient. In weak impact scenarios, it maintains low stiffness and high damping, effectively buffering and absorbing shock and dissipating impact energy; in strong impact scenarios, it improves stiffness and toughness, enhances the ability to resist impact damage, realizes adaptive dissipation of impact energy and precise shock absorption, and avoids damage to the substrate due to impact load; (4) At the same time, by utilizing the electrothermal effect of the conductive network (such as CNT, graphene) inside the coating, after the damage signal is detected, the conductive phase is triggered by the electric field to generate Joule heating, which in turn induces the dynamic covalent bonds (such as disulfide bonds, dynamic urea bonds) in the coating matrix to undergo reversible breakage and recombination, thereby realizing the active on-demand repair of microcracks without the need for additional repair agents or artificial intervention. The repair process precisely matches the location and extent of damage. (5) The entire system uses an electric field as a unified stimulus-response switch, organically linking impact monitoring, damping adjustment, and damage repair to form a closed-loop intelligent response mechanism of "impact sensing - parameter adjustment - damage repair". The same electric field simultaneously drives the piezoelectric positive effect (sensing), the inverse piezoelectric effect (stiffness adjustment), and conductive Joule heating (repair). The three are linked in sequence, coupled in parameters, and respond on demand, rather than simply superimposing materials. This significantly improves the adaptive control capability, structural reliability, and long-term service performance of protective materials, effectively extends the service life of the substrate, reduces maintenance costs, and adapts to the protection needs of various complex impact environments. It provides stable and reliable technical support for emergency rescue work, promotes the development of emergency rescue protection technology towards intelligence, integration, and long-term effectiveness, and has important engineering application value and social significance. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments.

[0019] The preparation method of the integrated protective coating with self-monitoring, shock absorption, energy absorption, and self-healing functions of this invention is specifically implemented according to the following steps: Step 1, in-situ interface modification treatment of the piezoelectric phase: A silane coupling agent is added to a mixed solvent of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 5–10:1. After hydrolysis for 10–30 min, a piezoelectric phase is added, with a mass ratio of piezoelectric phase to silane coupling agent of 100:0.5–2. The mixture is then stirred at 400–1500 rpm for 15–60 min at room temperature to allow the silane coupling agent to form a uniform monolayer on the surface of the piezoelectric phase. Subsequently, after centrifugation and washing with deionized water, the mixture is vacuum dried to obtain the surface-modified piezoelectric functional phase.

[0020] The piezoelectric phase is barium titanate (BaTiO3), zinc oxide (ZnO), or lead zirconate titanate (PZT) nanoparticles; the silane coupling agent is one or a mixture of several of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), or γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0021] Step 2, Pre-dispersion of the conductive phase and construction of the three-dimensional conductive network: The conductive phase is added to deionized water and sonicated for 15–60 min to allow it to separate and disperse. Then, a small amount of dispersant is added to prevent the conductive phase from agglomerating again, so as to form a three-dimensional conductive network structure and obtain a conductive pre-dispersion.

[0022] The conductive phase is either carbon nanotubes or graphene; the dispersant is either polyvinylpyrrolidone (PVP), sodium dodecylbenzenesulfonate (SDBS), or hexadecyltrimethylammonium bromide (CTAB); the mass ratio of the conductive phase to the dispersant is 30–60:1, and the mass ratio of the sum of the conductive phase and the dispersant to deionized water is 1:20–40.

[0023] Step 3, Synergistic composite preparation of piezoelectric / conductive phase and dynamically covalently bonded resin: The resin matrix containing dynamic covalent bonds is preheated to 40-50°C to reduce its viscosity, and then added to the conductive pre-dispersion liquid obtained in step 2. The mixture is stirred at a low speed of 400-1000 rpm for 3-10 hours. The surface-modified piezoelectric functional phase obtained in step 1 is then added, and the mixture is stirred at room temperature for 6-24 hours to ensure uniform dispersion. Subsequently, vacuum degassing is performed for 10-30 minutes to eliminate air bubbles, thereby achieving a uniform composite of piezoelectric, conductive, and self-healing functions at the molecular scale. This results in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair.

[0024] The resin matrix containing dynamic covalent bonds is either a polyurethane matrix containing disulfide bonds or an epoxy resin matrix containing dynamic acylhydrazone / Schiff base bonds; the mass ratio of the surface-modified piezoelectric functional phase, the conductive phase and the resin matrix is ​​15-45:0.5-5:100.

[0025] Step 4: Prepare an integrated intelligent protective coating that combines self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair using a low-temperature curing method combined with electric field polarization activation. The composite coating obtained in step 3 is applied to the substrate surface, with the wet film thickness controlled at 100–300 μm. Pre-curing at room temperature for 12–24 hours allows the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes are fabricated on the upper and lower surfaces of the coating, forming a sandwich capacitor structure. The sandwich capacitor structure is then placed in a silicone oil bath, and a DC electric field of 2–6 kV / mm is applied. The oil bath temperature is increased to 60–120°C. After holding at this temperature and under the combined action of the electric field for 15–60 minutes, the resin deep curing and piezoelectric domain polarization orientation are simultaneously completed. Finally, the electric field is kept constant, and the coating is removed after natural cooling to room temperature, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0026] Example 1: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-aminopropyltriethoxysilane (KH-550) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 5:1. After hydrolysis for 10 min, barium titanate (BaTiO3) at a mass ratio of 100:1 to KH-550 was added, and the mixture was magnetically stirred at 600 rpm for 15 min at room temperature to form a uniform monolayer of KH-550 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Carbon nanotubes were added to deionized water and ultrasonically treated for 20 minutes to allow them to peel off and disperse. Then, polyvinylpyrrolidone (PVP) with a mass ratio of 50:1 to carbon nanotubes was added to prevent the conductive phase from agglomerating again, thus forming a three-dimensional conductive network structure. The mass of deionized water was 30 times the total mass of carbon nanotubes and PVP.

[0027] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The polyurethane matrix containing disulfide bonds is preheated to 40°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 600 rpm for 5 hours, the surface-modified barium titanate obtained in step 1 is added. The mass ratio of surface-modified barium titanate, carbon nanotubes and polyurethane containing disulfide bonds is controlled at 15:2:100. The mixture is stirred at room temperature for 12 hours to ensure uniform dispersion. Then, vacuum degassing is performed for 20 minutes to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 150 μm. Pre-curing at room temperature for 12 hours allowed the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating, forming a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 3 kV / mm DC electric field was applied. The oil bath temperature was raised to 60°C, and the sample was held at this temperature and electric field for 15 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. Maintaining the electric field, the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0028] Example 2: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 7:1. After hydrolysis for 20 min, zinc oxide nanoparticles at a mass ratio of 100:2 to KH-560 were added, and the mixture was magnetically stirred at 1000 rpm for 30 min at room temperature to form a uniform monolayer of KH-560 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Graphene was added to deionized water and ultrasonically treated for 40 minutes to exfoliate and disperse it. Then, sodium dodecylbenzenesulfonate (SDBS) with a mass ratio of 60:1 to graphene was added to prevent the conductive phase from agglomerating again, so as to form a three-dimensional conductive network structure. The mass of deionized water was 40 times the total mass of graphene and SDBS.

[0029] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The epoxy resin matrix containing dynamic hydrazone bonds is preheated to 50°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 800 rpm for 10 h, the surface-modified zinc oxide obtained in step 1 is added. The mass ratio of surface-modified zinc oxide, graphene and epoxy resin containing dynamic hydrazone bonds is controlled at 25:2:100. The mixture is stirred at room temperature for 24 h to ensure uniform dispersion. Then, vacuum degassing is performed for 30 min to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 300 μm. Pre-curing at room temperature for 20 hours allowed the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating, forming a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 6 kV / mm DC electric field was applied. The oil bath temperature was raised to 100°C, and the sample was held at this temperature and electric field for 30 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. Maintaining the electric field, the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0030] Example 3: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-Methacryloxypropyltrimethoxysilane (KH-570) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 9:1. After hydrolysis for 20 min, lead zirconate titanate nanoparticles with a mass ratio of 100:0.5 to KH-570 were added, and the mixture was magnetically stirred at 800 rpm for 40 min at room temperature to form a uniform monolayer of KH-570 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Carbon nanotubes were added to deionized water and ultrasonically treated for 30 minutes to allow them to peel off and disperse. Then, hexadecyltrimethylammonium bromide (CTAB) with a mass ratio of 35:1 to carbon nanotubes was added to prevent the conductive phase from agglomerating again, thus forming a three-dimensional conductive network structure. The mass of deionized water was 20 times the total mass of carbon nanotubes and CTAB.

[0031] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The epoxy resin matrix containing dynamic Schiff base bonds is preheated to 45°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 800 rpm for 6 hours, the surface-modified lead zirconate titanate obtained in step 1 is added. The mass ratio of surface-modified lead zirconate titanate, carbon nanotubes and epoxy resin containing dynamic Schiff base bonds is controlled at 40:1:100. The mixture is stirred at room temperature for 12 hours to ensure uniform dispersion. Then, vacuum degassing is performed for 20 minutes to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 150 μm. Pre-curing at room temperature for 20 hours allowed the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating, forming a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 2 kV / mm DC electric field was applied. The oil bath temperature was raised to 80°C, and the sample was held at this temperature and electric field for 30 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. Maintaining the electric field, the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0032] Example 4: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-aminopropyltriethoxysilane (KH-550) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 8:1. After hydrolysis for 15 min, barium titanate nanoparticles at a mass ratio of 100:1 to KH-550 were added, and the mixture was magnetically stirred at 1000 rpm for 50 min at room temperature to form a uniform monolayer of KH-550 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Carbon nanotubes were added to deionized water and ultrasonically treated for 30 minutes to allow them to peel off and disperse. Then, polyvinylpyrrolidone (PVP) with a mass ratio of 40:1 to carbon nanotubes was added to prevent the conductive phase from agglomerating again, thus forming a three-dimensional conductive network structure. The mass of deionized water was 35 times the total mass of carbon nanotubes and PVP.

[0033] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The polyurethane matrix containing disulfide bonds is preheated to 45°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 800 rpm for 8 hours, the surface-modified barium titanate obtained in step 1 is added. The mass ratio of surface-modified barium titanate, carbon nanotubes and polyurethane containing disulfide bonds is controlled at 45:3:100. The mixture is stirred at room temperature for 12 hours to ensure uniform dispersion. Then, vacuum degassing is performed for 15 minutes to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 200 μm. It was pre-cured at room temperature for 24 hours to allow the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating to form a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 4 kV / mm DC electric field was applied. The oil bath temperature was raised to 90°C, and the sample was held at this temperature and electric field for 30 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. The electric field was kept constant, and the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0034] Example 5: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-aminopropyltriethoxysilane (KH-550) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 8:1. After hydrolysis for 20 min, barium titanate at a mass ratio of 100:1.5 to KH-550 was added, and the mixture was magnetically stirred at 1000 rpm for 40 min at room temperature to form a uniform monolayer of KH-550 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Graphene was added to deionized water and ultrasonically treated for 30 minutes to exfoliate and disperse it. Then, sodium dodecylbenzenesulfonate (SDBS) with a mass ratio of 55:1 to graphene was added to prevent the conductive phase from agglomerating again, so as to form a three-dimensional conductive network structure. The mass of deionized water was 25 times the total mass of graphene and SDBS.

[0035] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The polyurethane matrix containing disulfide bonds is preheated to 45°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 800 rpm for 8 hours, the surface-modified barium titanate obtained in step 1 is added. The mass ratio of surface-modified barium titanate, graphene and polyurethane containing disulfide bonds is controlled at 45:4:100. The mixture is stirred at room temperature for 24 hours to ensure uniform dispersion. Then, vacuum degassing is performed for 20 minutes to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 150 μm. Pre-curing at room temperature for 20 hours allowed the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating, forming a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 4 kV / mm DC electric field was applied. The oil bath temperature was raised to 100°C, and the sample was held at this temperature and electric field for 40 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. Maintaining the electric field, the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0036] Example 6: Step 1, in-situ interface modification treatment of the piezoelectric phase: γ-aminopropyltriethoxysilane (KH-550) was added to a mixed solvent of ethanol and deionized water at a volume ratio of 8:1. After hydrolysis for 25 min, lead zirconate titanate nanoparticles at a mass ratio of 100:0.75 to KH-550 were added, and the mixture was magnetically stirred at 1000 rpm for 45 min at room temperature to form a uniform monolayer of KH-550 on the piezoelectric phase surface. Subsequently, after centrifugation and washing with deionized water, the surface-modified piezoelectric functional phase was obtained by vacuum drying. Step 2: Pre-dispersion of the conductive phase and construction of a three-dimensional conductive network; Carbon nanotubes were added to deionized water and ultrasonically treated for 45 minutes to allow them to peel off and disperse. Then, sodium dodecylbenzenesulfonate (SDBS) with a mass ratio of 45:1 to carbon nanotubes was added to prevent the conductive phase from agglomerating again, thus forming a three-dimensional conductive network structure. The mass of deionized water was 30 times the total mass of carbon nanotubes and SDBS.

[0037] Step 3: Synergistic composite preparation of piezoelectric / conductive phase and dynamic covalent bond resin; The epoxy resin matrix containing dynamic hydrazone bonds is preheated to 45°C to reduce the viscosity of the system and added to the conductive pre-dispersion liquid in step 2. After stirring at 600 rpm for 8 hours, the surface-modified lead zirconate titanate obtained in step 1 is added. The mass ratio of surface-modified lead zirconate titanate, carbon nanotubes and epoxy resin containing dynamic hydrazone bonds is controlled at 45:4:100. The mixture is stirred at room temperature for 12 hours to ensure uniform dispersion. Then, vacuum degassing is performed for 20 minutes to eliminate bubbles. This achieves uniform composite of piezoelectric, conductive and self-healing functions at the molecular scale, resulting in an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption and active repair. Step 4: Low-temperature curing combined with electric field polarization activation to prepare an integrated intelligent protective coating that integrates self-monitoring, dynamic adjustment of impact strength, shock absorption, and active repair. The composite coating obtained in step 3 was applied to the substrate surface, with the wet film thickness controlled at 200 μm. It was pre-cured at room temperature for 24 hours to allow the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes were fabricated on the upper and lower surfaces of the coating to form a sandwich capacitor structure. The sample was then placed in a silicone oil bath, and a 5 kV / mm DC electric field was applied. The oil bath temperature was raised to 80°C, and the sample was held at this temperature and electric field for 30 minutes to simultaneously achieve deep resin curing and piezoelectric domain polarization orientation. The electric field was kept constant, and the sample was allowed to cool naturally to room temperature before the electric field was removed, resulting in an integrated protective coating with self-monitoring, shock absorption, and self-healing properties.

[0038] The impact strength, piezoelectric response voltage and self-healing rate of the integrated protective coatings with self-monitoring, shock absorption and energy absorption and self-healing prepared in Examples 1-6 were tested and compared with those of traditional commercial polyurethane coatings. The results are shown in Table 1.

[0039] Table 1 Comparison of performance test results of coatings in various embodiments

[0040] Test data shows that, compared with commercially available ordinary protective polyurethane coatings, this invention effectively solves the technical shortcomings of traditional protective materials, such as single function, poor impact adaptability, lack of damage monitoring, and inability to self-repair, through a collaborative design strategy of dynamic covalent bond construction of the matrix, directional dispersion of piezoelectric functional phases, and controllable construction of a continuous network of conductive fillers.

[0041] Commercial polyurethane has an impact strength of only 2.3±0.7MPa, no piezoelectric response, an output voltage close to 0mV, and a self-healing rate of only 5.6±1.5%. The coating of this invention increases the impact strength to 18.6±1.5MPa, improving the overall impact resistance by approximately 8.1 times, and can effectively resist extreme loads such as high-altitude impacts, falling objects, and explosive impacts. The piezoelectric response voltage can reach 512.7±1.5mV, realizing a wide range of gradient electrical signal output, and possessing all-weather impact level identification and real-time micro-damage monitoring capabilities, completely making up for the lack of intelligent sensing in traditional materials. In addition, relying on the reversible recombination of dynamic covalent bonds and the Joule thermal synergy of conductive networks, the material's self-healing rate is increased to 99.9±0.6%, and the self-healing performance is improved by approximately 17.8 times, enabling rapid in-situ crack closure and long-term recovery of mechanical properties.

[0042] This invention integrates impact self-monitoring, dynamic stiffness and damping adjustment, vibration reduction and energy absorption, and electric field-triggered active repair. While significantly improving adaptability to extreme environments and service life, it also reduces the cost of equipment maintenance. It provides high-performance intelligent protective materials for high-risk scenarios such as emergency rescue, high-altitude protection, and disaster response, promoting the upgrade of protective materials from passive protection to intelligent adaptive protection. It has outstanding engineering application value and industrialization prospects.

Claims

1. A method for preparing an integrated protective coating that combines self-monitoring, shock absorption, energy absorption, and self-healing, characterized in that, The specific steps are as follows: Step 1: Use a silane coupling agent to perform in-situ interface modification on the piezoelectric phase to obtain a surface-modified piezoelectric functional phase; Step 2: Add the conductive phase to deionized water and disperse to obtain a conductive pre-dispersion. Step 3: Add the resin matrix containing dynamic covalent bonds to the conductive pre-dispersion liquid, mix well, and then add the surface-modified piezoelectric functional phase. After uniform dispersion, an integrated protective coating is obtained. Step 4: Apply the protective coating to the surface of the substrate, perform low-temperature pre-curing, and then perform deep curing and piezoelectric domain polarization orientation under the action of a DC electric field to obtain an integrated protective coating.

2. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 1, characterized in that, Step 1 is as follows: The silane coupling agent is added to a mixed solvent of ethanol and deionized water and hydrolyzed for 10–30 min. Then, the piezoelectric phase is added and stirred at 400–1500 rpm for 15–60 min to form a uniform monolayer of silane coupling agent on the surface of the piezoelectric phase. Finally, the mixture is centrifuged, washed with water, and vacuum dried to obtain the surface-modified piezoelectric functional phase.

3. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 2, characterized in that, The piezoelectric phase is barium titanate, zinc oxide, or lead zirconate titanate nanoparticles; the silane coupling agent is one or a mixture of several of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane. The volume ratio of ethanol to deionized water in the mixed solvent is 5 to 10:1; the mass ratio of the piezoelectric phase to the silane coupling agent is 100:0.5 to 2.

4. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 1, characterized in that, Step 2 is as follows: The conductive phase is added to deionized water and sonicated for 15–60 min to allow it to peel and disperse. Then, a dispersant is added to obtain a conductive pre-dispersion.

5. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 4, characterized in that, The conductive phase is carbon nanotubes or graphene; the dispersant is polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, or hexadecyltrimethylammonium bromide; the mass ratio of the conductive phase to the dispersant is 30-60:1, and the mass ratio of the sum of the conductive phase and the dispersant to deionized water is 1:20-40.

6. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 1, characterized in that, Step 3 specifically involves: The resin matrix containing dynamic covalent bonds is preheated to 40-50°C and then added to the conductive pre-dispersion liquid obtained in step 2. The mixture is stirred at 400-1000 rpm for 3-10 hours. Then, the piezoelectric functional phase obtained in step 1 is added and stirred for 6-24 hours to ensure uniform dispersion. Finally, the mixture is vacuum degassed for 10-30 minutes to obtain an integrated protective coating.

7. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 6, characterized in that, The resin matrix containing dynamic covalent bonds is a polyurethane containing disulfide bonds, an epoxy resin matrix containing dynamic hydrazone bonds, or an epoxy resin matrix containing dynamic Schiff base bonds; the mass ratio of the surface-modified piezoelectric functional phase, the conductive phase, and the resin matrix is ​​15-45:0.5-5:

100.

8. The method for preparing the integrated protective coating with self-monitoring, shock absorption, and self-healing properties according to claim 1, characterized in that, Step 4 specifically involves: The composite coating obtained in step 3 is applied to the surface of the substrate, and the wet film thickness is controlled to be 100-300 μm. It is pre-cured at room temperature for 12-24 h to allow the coating to initially set and become non-flowing. Subsequently, flexible conductive electrodes are prepared on the upper and lower surfaces of the coating to form a sandwich capacitor structure. The sandwich capacitor structure is placed in a silicone oil bath, and a DC electric field with an intensity of 2-6 kV / mm is applied. The oil bath temperature is raised to 60-120°C. After holding at this temperature and electric field for 15-60 min, the deep curing of the resin and the polarization orientation of the piezoelectric domains are completed simultaneously. Finally, the electric field is kept constant and removed after natural cooling to room temperature to obtain an integrated protective coating.

9. An integrated protective coating for self-monitoring, shock absorption, energy absorption, and self-repair, characterized in that: It is prepared by the method described in any one of claims 1-8.

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