Near-infrared response self-repairing coating and preparation method thereof

Abstract

The invention discloses a near-infrared response self-repairing coating and a preparation method thereof, and relates to the technical field of functional coatings. The invention relates to a near-infrared response self-repairing coating which is prepared from the following components in parts by mass: 100 parts of matrix resin, 1-3 parts of a near-infrared absorbent, 10-20 parts of a self-repairing agent, 8-15 parts of a curing agent, 1-3 parts of a dispersing agent, 0.5-2 parts of a defoaming agent and 20-30 parts of a solvent. The organic molecule near-infrared absorbent with a specific structure is adopted, the compatibility with matrix resin is good, molecular-level uniform dispersion can be achieved, the problem that a traditional inorganic photo-thermal material is prone to agglomeration is solved, meanwhile, the photo-thermal conversion efficiency is remarkably improved, and the defect that a conventional organic dye is insufficient in photo-thermal conversion capacity is overcome.

Description

Technical Field

[0001] This invention relates to the field of functional coating technology, specifically to a near-infrared responsive self-healing coating and its preparation method. Background Technology

[0002] With the continuous advancement of materials science, self-healing smart coatings have shown great application potential in coatings used in fields such as shipbuilding, aircraft, high-speed rail, and marine engineering due to their ability to autonomously repair microcracks, extend the service life of substrates, and reduce maintenance costs. Among the many self-healing triggering mechanisms, near-infrared photoresponsive self-healing coatings are based on the principle of photothermal conversion. They utilize non-contact remote control to convert light energy into heat energy, thereby driving polymer chain segment movement or triggering dynamic chemical bond recombination, thus achieving rapid repair of coating damage. They have significant advantages such as convenient operation and strong spatiotemporal controllability.

[0003] In existing technologies, the mainstream strategy for constructing near-infrared responsive self-healing coatings is to physically dope photothermal conversion materials into the resin matrix. Commonly used photothermal conversion materials mainly include inorganic nanomaterials, such as carbon nanotubes, graphene, gold nanorods, and indium tin oxide, as well as some conventional organic dyes, such as anthocyanins and phthalocyanine compounds. Although the above-mentioned existing technical solutions endow the coating with photothermal response characteristics to a certain extent, they still face many technical bottlenecks in practical engineering applications.

[0004] On the one hand, inorganic nanomaterials, due to their high surface energy and poor interfacial compatibility with organic polymer matrices, are prone to agglomeration during coating preparation and film formation. This uneven dispersion not only leads to uneven distribution of hot spots within the coating, severely affecting the consistency of self-healing effects, but also damages the original mechanical properties and optical transparency of the coating, limiting its application in fields with high requirements for appearance and light transmittance. Furthermore, improving dispersibility usually requires the addition of large amounts of dispersants, which further increases the complexity of the system and may introduce impurities and defects. On the other hand, conventional organic dye photothermal agents, although having relatively good compatibility with resin matrices, typically suffer from low photothermal conversion efficiency and poor photostability. Under near-infrared irradiation, these materials exhibit slow heat generation rates, insufficient to rapidly drive the rearrangement of the polymer network, resulting in excessively long self-healing response times and low repair efficiency. Simultaneously, some organic dyes are prone to photobleaching or decomposition under prolonged light exposure, causing the coating to fail after multiple repair cycles, making it difficult to meet the requirements for long-term service.

[0005] Therefore, developing a near-infrared responsive self-healing coating that combines excellent resin compatibility and efficient photothermal conversion capability, especially designing and introducing an organic photothermal agent with a specific structure that can significantly improve the response speed and is molecularly dispersed in the resin, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to address the technical problems in existing technologies, such as poor dispersion of inorganic photothermal fillers in resin matrices and low photothermal conversion efficiency of conventional organic dyes leading to slow coating repair response speeds. This invention provides a near-infrared responsive self-healing coating and its preparation method. By introducing organic molecules with specific structures as near-infrared absorbers, molecular-level uniform dispersion and efficient photothermal conversion of photothermal materials are achieved in the coating, thereby endowing the coating with rapid and excellent crack self-healing properties while maintaining good appearance and mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A near-infrared responsive self-healing coating, by weight, is composed of the following components: 100 parts of matrix resin, 1-3 parts of near-infrared absorber, 10-20 parts of self-healing agent, 8-15 parts of curing agent, 1-3 parts of dispersant, 0.5-2 parts of defoamer, and 20-30 parts of solvent. The near-infrared absorber is a compound represented by Formula 1: Formula 1: .

[0008] Furthermore, the matrix resin is at least one of polyurethane resin and epoxy resin.

[0009] Furthermore, the self-healing agent is at least one of dithiodicaprolactam and dithiodibenzothiazole.

[0010] Furthermore, the curing agent is matched with the matrix resin. When the matrix resin is a polyurethane resin, the curing agent is selected from at least one of isophorone diisocyanate and toluene diisocyanate; when the matrix resin is an epoxy resin, the curing agent is selected from at least one of 4,4'-diaminodicyclohexylmethane and 4,4'-diaminodiphenyl sulfone.

[0011] Furthermore, the dispersant is at least one of BYK-161 and BYK-163.

[0012] Furthermore, the defoamer is at least one of BYK-066N and BYK-141.

[0013] Furthermore, the solvent is at least one of xylene, butyl acetate, and propylene glycol methyl ether acetate.

[0014] A method for preparing a near-infrared responsive self-healing coating includes the following steps: S1: Place the matrix resin and solvent in a stirring device and stir for 15-30 minutes at 25-35℃ and 300-500r / min to obtain a resin solution; S2: Add the dispersant and near-infrared absorber to the resin solution, adjust the stirring speed to 800-1200 r / min, stir for 40-60 min, and then disperse using ultrasound to obtain a uniformly dispersed mixture A; S3: Add the self-healing agent and defoamer to the mixture A, adjust the stirring speed to 500-700 r / min, stir for 20-30 min, and obtain the mixture B; S4: Add the curing agent to the mixture B, and stir for 10-20 minutes at 25-35℃ and 400-600r / min to obtain the coating slurry; S5: Apply the coating slurry to the substrate surface by spraying, scraping or brushing, let it stand at room temperature for 1-2 hours, then place it in an oven at 50-80℃ for 2-4 hours to cure, and after cooling to room temperature, a near-infrared responsive self-healing coating is obtained.

[0015] Furthermore, in S2, the ultrasonic dispersion power is 80-120W, the ultrasonic dispersion time is 20-30min, and the system temperature is controlled not to exceed 40℃ during the dispersion process.

[0016] Application of a near-infrared responsive self-healing coating, the coating being used for surface protection and self-healing of metal components, electronic device housings, and automotive parts.

[0017] This invention addresses the technical problems of poor dispersibility, easy agglomeration, low photothermal conversion efficiency, and slow repair response of existing near-infrared responsive self-healing coatings by precisely matching and synergistically combining the various formulation components. First, the core component, the near-infrared absorber, utilizes a structurally specific organic molecule with good compatibility with matrix resins such as polyurethane. This allows for uniform molecular-level dispersion within the resin system, avoiding the agglomeration problem caused by the high surface energy of inorganic nanomaterials. Simultaneously, this absorber possesses excellent photothermal conversion efficiency, overcoming the shortcomings of conventional organic dyes in terms of weak photothermal conversion stability. Second, the matrix resin provides a well-suited dispersion carrier for the absorber, self-healing agent, and other components, ensuring the coating's basic mechanical properties while creating a stable environment for photothermal conduction and the self-healing reaction. The self-healing agent and the near-infrared absorber form a highly efficient responsive combination. After the absorber rapidly converts near-infrared light energy into heat energy, it can immediately drive dynamic chemical bond recombination or polymer chain segment movement in the self-healing agent, significantly shortening the repair response time. Dispersants further assist in the uniform dispersion of near-infrared absorbers and various functional components in the resin, avoiding localized high or low concentrations that could affect repair consistency. Defoamers eliminate bubbles generated during the preparation process, ensuring the density of the coating structure. Solvents regulate the system viscosity, promoting full integration of components. Curing agents ensure stable coating film formation and meet mechanical property standards. Combined with a stepwise stirring and ultrasonic dispersion process, the synergistic effect of each component is fully realized, ultimately achieving a coating that possesses excellent dispersion uniformity, efficient photothermal conversion capability, and rapid self-healing performance, while maintaining good appearance and mechanical properties to meet practical application requirements.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. Superior photothermal conversion and dispersion performance: The use of organic near-infrared absorbers with specific structures has good compatibility with the matrix resin, enabling uniform dispersion at the molecular level. This avoids the problem of easy agglomeration of traditional inorganic photothermal materials, while significantly improving photothermal conversion efficiency and solving the defect of insufficient photothermal conversion capacity of conventional organic dyes.

[0019] 2. More efficient self-healing response: The photothermal absorber and the self-healing agent work synergistically, and the light energy can be quickly converted into heat energy to drive the self-healing reaction. Compared with the existing technology, the coating responds to damage faster and has a more ideal repair effect, and can better achieve autonomous crack repair.

[0020] 3. More stable overall performance: While improving photothermal response and self-healing performance, the basic mechanical properties and structural density of the coating are well maintained, avoiding performance imbalance caused by the addition of functional components, and better meeting the needs of protection and long-term service in practical applications. Attached Figure Description

[0021] Figure 1This is the NMR spectrum of the near-infrared absorber of the present invention.

[0022] Figure 2 This is the near-infrared absorption spectrum of the near-infrared absorber of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Preparation example: Preparation of near-infrared absorbers: first step: ; Under nitrogen protection, 5.00 g of raw material 1, 4.30 g of raw material 2, and 2.60 g of sodium tert-butoxide were added sequentially to the reaction flask, followed by 0.25 g of tris(dibenzylacetone)palladium and 0.30 g of 1,1'-bis(diphenylphosphine)ferrocene. The reaction flask was purged with nitrogen three times, and then 80 mL of anhydrous toluene was added. The mixture was stirred and placed in a reflux atmosphere at 100°C for 12 hours with stirring. After the reaction was complete, the reaction solution was cooled to room temperature and filtered through diatomaceous earth to remove insoluble salts and palladium black. The filter cake was washed with ethyl acetate, and the filtrate was transferred to a separatory funnel and washed sequentially with deionized water and saturated brine. The organic phase was separated, dried with anhydrous sodium sulfate, filtered to remove the desiccant, and the filtrate was concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography using a mixed solution of petroleum ether and dichloromethane as the eluent. The fraction containing the target product was collected, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain 5.57 g of intermediate 1. The mass spectra of intermediate 1 were [M+H]. + m / z: 530.

[0025] Step Two: ; Under nitrogen protection, 5.57 g of intermediate 1 was added to the reaction flask, followed by 80 mL of anhydrous tetrahydrofuran. Stirring was initiated to form a homogeneous solution. The system was cooled to -78°C and held at this temperature for 15 minutes. At -78°C, 5.0 mL of 2.5 mol / L n-butyllithium was slowly added dropwise over 10 minutes. After the addition was complete, the temperature was maintained at -78°C and stirring continued for 4 hours. 3.14 g of trimethyltin chloride was dissolved in 20 mL of anhydrous tetrahydrofuran to prepare a trimethyltin chloride solution. One hour later, the trimethyltin chloride solution was slowly added dropwise to the reaction system at -78°C. After the addition was complete, the dry ice bath was removed, and the mixture was allowed to warm naturally to room temperature. The reaction was then stirred and continued at room temperature for 2 hours. After the reaction was complete, a saturated ammonium chloride aqueous solution was added to the reaction flask to quench the reaction. The mixture was transferred to a separatory funnel, and deionized water and dichloromethane were added for extraction to separate the organic phase. The aqueous phase was then extracted with dichloromethane again. The organic phases were combined and washed successively with deionized water and saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered to remove the drying agent, and the filtrate was concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography using a mixed solution of n-hexane and dichloromethane as the eluent. The fraction containing the target product was collected, the solvent was removed by rotary evaporation, and the fraction was dried under vacuum to obtain 5.24 g of intermediate 2. The mass spectra of intermediate 2 were [M+H]. + m / z: 616.

[0026] Step 3: ; Under nitrogen protection, 5.24 g of intermediate 2 and 1.36 g of starting material 3 were added to the reaction flask, followed by 60 mL of anhydrous toluene. The reaction flask was purged with nitrogen three times. Then, 0.22 g of tetrakis(triphenylphosphine)palladium was added under a nitrogen flow, and the mixture was purged with nitrogen three more times. The reaction flask was placed at 115°C and refluxed under light-protected conditions for 24 hours. After the reaction was complete, the reaction solution was cooled to room temperature. A saturated potassium fluoride aqueous solution was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours. The solution was filtered through diatomaceous earth to remove the precipitate and palladium black. The filter cake was washed with dichloromethane. The filtrate was transferred to a separatory funnel, and the organic phase was collected. The aqueous phase was extracted with dichloromethane. The organic phases were combined and washed successively with deionized water and saturated brine. The mixture was dried over anhydrous sodium sulfate, filtered to remove the drying agent, and the filtrate was concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography. Elution was performed using a mixed solution of petroleum ether and dichloromethane as the eluent. The fraction containing the target product was collected, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain 2.81 g of near-infrared absorber. The mass spectra of the near-infrared absorber were [M+H]. + m / z: 1093, NMR spectrum of the near-infrared absorber as follows Figure 1 As shown.

[0027] Example 1 Preparation of a near-infrared responsive self-healing coating: 1. Raw material components: Matrix resin 100: is a hydroxyl-terminated polyurethane resin; Two parts of near-infrared absorber: the near-infrared absorber prepared in the preparation example; 15 parts of self-healing agent: dithiodicaprolactam; 12 parts of curing agent: isophorone diisocyanate; Two parts of dispersant: BYK-161; One part of defoamer: BYK-066N; Solvent 25 parts: propylene glycol methyl ether acetate.

[0028] 2. Preparation method: S1: Place 100 parts of matrix resin and 25 parts of solvent in a high-speed stirring tank, control the system temperature at 28℃, adjust the stirring speed to 400r / min, and continue stirring for 20min to obtain a homogeneous resin solution. S2: Add 2 parts of dispersant and 2 parts of near-infrared absorber to the above resin solution, increase the stirring speed to 1000 r / min, stir at high speed for 50 min, then transfer to an ultrasonic dispersion device, set the ultrasonic power to 100 W, the dispersion time to 25 min, and control the system temperature to 30℃ through circulating cooling water during the dispersion process to obtain a uniformly dispersed mixture A. S3: Transfer the above mixture A back into the mixing tank, add 15 parts of self-healing agent and 1 part of defoamer, adjust the stirring speed to 600 r / min, stir for 25 min, fully eliminate the bubbles in the system and make the self-healing agent evenly dispersed to obtain mixture B; S4: Add 12 parts of curing agent to the above mixture B, keep the system temperature at 30℃, adjust the stirring speed to 500r / min, stir at constant temperature for 15min, and obtain a stable dispersion coating slurry; S5: The above coating slurry is uniformly coated onto the surface of the substrate using an air spraying device, and the wet film thickness of the coating is controlled to be 80μm. After standing at room temperature for 1.5h, the substrate is placed in a 65℃ oven for constant temperature curing for 3h. After curing, it is taken out and cooled to room temperature to obtain a near-infrared responsive self-healing coating.

[0029] Example 2 The preparation of a near-infrared responsive self-healing coating is carried out according to the preparation method in Example 1, except that the matrix resin in the raw materials is replaced with bisphenol A type epoxy resin, the curing agent is replaced with 4,4'-diaminodicyclohexylmethane, and other operations are the same as in Example 1.

[0030] Example 3 The preparation of a near-infrared responsive self-healing coating is carried out by referring to the preparation method in Example 1, except that the mass fraction of the self-healing agent in the raw materials is replaced with 20 parts, and other operations are kept the same as in Example 1.

[0031] Comparative Example 1 The preparation of a near-infrared responsive self-healing coating is carried out by referring to the preparation method in Example 1, except that the near-infrared absorber in the raw materials is replaced with reduced graphene oxide, and other operations are the same as in Example 1.

[0032] Comparative Example 2 The preparation of a near-infrared responsive self-healing coating is carried out by referring to the preparation method in Example 1, except that the near-infrared absorber in the raw materials is replaced with carbon nanotubes, and other operations are the same as in Example 1.

[0033] Comparative Example 3 The preparation of a near-infrared responsive self-healing coating is carried out according to the preparation method in Example 1, without adding the near-infrared absorber in the raw materials, and the other operations are the same as in Example 1.

[0034] Comparative Example 4 The preparation of a near-infrared responsive self-healing coating is carried out according to the preparation method in Example 1, without adding the dispersant in the raw materials, and the other operations are the same as in Example 1.

[0035] Comparative Example 5 The preparation of a near-infrared responsive self-healing coating is carried out according to the preparation method in Example 1, without adding the self-healing agent in the raw materials, and the other operations are the same as in Example 1.

[0036] Blank control group The preparation of a near-infrared responsive self-healing coating is carried out according to the preparation method in Example 1, without adding the near-infrared absorber and self-healing agent in the raw materials, and the other operations are the same as in Example 1.

[0037] Performance testing: 1. Self-healing performance test: The coatings prepared in the examples and comparative examples were applied to Q235 steel with a dry film thickness of 80 μm. After curing, a through-crack was created on the sample surface using a falling ball impact tester. The initial crack width W0 and length L0 were recorded. A near-infrared laser was used to irradiate the crack area for 30 min, and the ambient temperature was controlled to be ≤40℃. After repair, the sample was left to stand in a standard environment for 1 h, and the crack width W1 and length L1 were observed. The repair rate R was calculated as R=[(W0-W1) / W0+(L0-L1) / L0] / 2×100%, and the results are shown in Table 1.

[0038] 2. Photothermal conversion efficiency test: The coatings prepared in the examples and comparative examples were applied to Q235 steel with a dry film thickness of 80 μm. After curing, the samples were placed in a room temperature environment for 2 hours to equilibrate. The near-infrared light source was turned on and the sample surface was vertically irradiated for 10 minutes. At the same time, the surface temperature of the sample was recorded using an infrared thermal imager. The surface temperature of the coating and the heating rate after irradiation were recorded. The results are shown in Table 1.

[0039] 3. Adhesion test: The coatings prepared in the examples and comparative examples were applied to Q235 steel with a dry film thickness of 80 μm. After curing, the adhesion of the samples was tested according to GB / T 9286-2021 standard. The results are shown in Table 1.

[0040] 4. Surface hardness test: The coatings prepared in the examples and comparative examples were applied to Q235 steel with a dry film thickness of 80 μm. After curing, the surface hardness of the samples was tested according to GB / T 6739-2022 standard. The results are shown in Table 1.

[0041] 5. Dispersion Test: The coatings prepared in the examples and comparative examples were applied to Q235 steel. Five test areas of equal area were selected, ensuring that each area was free of scratches and impurities. A UV-Vis-NIR spectrophotometer was used, with the test wavelength range set to 400-1200 nm. Using a blank substrate (Q235 steel) as a reference, the diffuse reflectance spectrum of the test areas was recorded. The absorbance values ​​of each area at the characteristic absorption wavelength of the near-infrared absorber were recorded, and the relative standard deviation (RSD) of the absorbance of the test areas was calculated. If RSD ≤ 5%, it indicates that the near-infrared absorber is uniformly dispersed in the coating and has good compatibility; if RSD > 5%, it indicates uneven dispersion.

[0042] Table 1. Performance Test Results

[0043] As can be seen from the data trends in Table 1, the examples using near-infrared absorbers with specific structures significantly outperformed the comparative examples in all aspects, exhibiting extremely high repair efficiency and excellent photothermal conversion capabilities, enabling faster heating rates and higher surface temperatures. In contrast, the comparative examples using inorganic nanomaterials or without any absorbers showed a significant decrease in photothermal response and crack repair effects, and mechanical properties such as adhesion and surface hardness were also negatively affected to varying degrees. Furthermore, the absence of components also leads to a decline in the overall performance of the coating, further demonstrating the necessity of the synergistic effect of the components in the formulation of this invention, that is, achieving efficient and rapid near-infrared response self-repair function while ensuring the physical strength and adhesion of the coating.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A near-infrared responsive self-healing coating, characterized in that, By weight, it consists of the following components: 100 parts matrix resin, 1-3 parts near-infrared absorber, 10-20 parts self-healing agent, 8-15 parts curing agent, 1-3 parts dispersant, 0.5-2 parts defoamer, and 20-30 parts solvent. The near-infrared absorber is a compound represented by Formula 1: Formula 1: .

2. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The matrix resin is at least one of polyurethane resin and epoxy resin.

3. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The self-healing agent is at least one of dithiodicaprolactam and dithiodibenzothiazole.

4. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The curing agent is matched with the matrix resin. When the matrix resin is polyurethane resin, the curing agent is selected from at least one of isophorone diisocyanate and toluene diisocyanate. When the matrix resin is epoxy resin, the curing agent is selected from at least one of 4,4'-diaminodicyclohexylmethane and 4,4'-diaminodiphenyl sulfone.

5. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The dispersant is at least one of BYK-161 and BYK-163.

6. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The defoamer is at least one of BYK-066N and BYK-141.

7. The near-infrared responsive self-healing coating according to claim 1, characterized in that, The solvent is at least one of xylene, butyl acetate, and propylene glycol methyl ether acetate.

8. A method for preparing a near-infrared responsive self-healing coating according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Place the matrix resin and solvent in a stirring device and stir for 15-30 minutes at 25-35℃ and 300-500r / min to obtain a resin solution; S2: Add the dispersant and near-infrared absorber to the resin solution, adjust the stirring speed to 800-1200 r / min, stir for 40-60 min, and then disperse using ultrasound to obtain a uniformly dispersed mixture A; S3: Add the self-healing agent and defoamer to the mixture A, adjust the stirring speed to 500-700 r / min, stir for 20-30 min, and obtain the mixture B; S4: Add the curing agent to the mixture B, and stir for 10-20 minutes at 25-35℃ and 400-600r / min to obtain the coating slurry; S5: Apply the coating slurry to the substrate surface by spraying, scraping or brushing, let it stand at room temperature for 1-2 hours, then place it in an oven at 50-80℃ for 2-4 hours to cure, and after cooling to room temperature, a near-infrared responsive self-healing coating is obtained.

9. The method for preparing a near-infrared responsive self-healing coating according to claim 8, characterized in that, The ultrasonic dispersion power in S2 is 80-120W, the ultrasonic dispersion time is 20-30min, and the system temperature is controlled not to exceed 40℃ during the dispersion process.

10. The application of a near-infrared responsive self-healing coating according to any one of claims 1-7, characterized in that, The coating is used for surface protection and self-healing of metal components, electronic device housings, and automotive parts.

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