Fluorescent self-warning anticorrosive coating, preparation method and application thereof

Abstract

The application discloses a fluorescent self-warning anticorrosive coating and a preparation method and application thereof, and the coating comprises a coupling probe molecule and epoxy resin. The fluorescent emission wavelength of the probe molecule is located in a near-infrared region, and the fluorescent intensity is enhanced under an acidic condition, thereby improving the detection reliability and early warning signal detection depth of the self-warning anticorrosive coating. The acidic pH response type fluorescent self-warning anticorrosive coating can accurately detect coating cracks of different shapes. The acidic pH response type fluorescent self-warning anticorrosive coating has good stability, can perform long-time early warning on the anticorrosive coating, and provides long-term protection for a ship.

Description

TECHNICAL FIELD

[0001] The present application relates to a fluorescent self-warning anticorrosive coating, a preparation method and application thereof, and belongs to the technical field of high polymer materials. BACKGROUND

[0002] Anticorrosive coating is a main means to prevent metal corrosion and prolong the service life of metal structure. The main function of traditional anticorrosive coatings such as polyurethane, epoxy and silicone resin is to play a physical isolation role between the metal substrate and the corrosive medium. However, the coating protection has an important defect, that is, when the coating is damaged, the corrosive medium can directly contact the metal substrate at the damaged coating, thereby causing corrosion. If not repaired in time, the corrosion will continue to spread, which will seriously reduce the protective performance of the coating and cause adverse effects on the metal material. Rapid and accurate positioning of local defect damage of anticorrosive coating is of great significance for timely repair of damaged coating and improvement of the anticorrosive ability of the coating.

[0003] Anticorrosive coating is mainly composed of high polymer materials. The current developed nondestructive testing technology of materials includes ultrasonic testing, infrared testing, electronic speckle pattern interferometry, alternating magnetic field measurement method, X-ray detection technology, etc. Although these traditional material testing methods can detect defects in material devices, these testing equipment is complex and expensive, and has high professional technical requirements for the operator. It is difficult to detect inaccessible areas, and some detection technologies are complex and time-consuming. The sensitivity and resolution of the detection are limited, and the drift phenomenon is easy to occur in part of the measurement results. The applicability of part of the detection means is narrow, such as alternating magnetic field detection which can only be applied to materials containing metal iron. Therefore, it is necessary to design and prepare an intelligent material capable of self-warning of high polymer material damage, which can be conveniently, quickly and effectively prepared for self-monitoring of damage. The warning agent of the damaged high polymer material makes the damaged area and the undamaged area of the high polymer material have obvious color difference, which facilitates the monitoring personnel to quickly and accurately capture the small cracks in the polymer material, and thus the damage of the material is obvious at a glance.

[0004] In order to visually observe the defects existing in the material, dye molecules and fluorescence means are introduced into the material damage detection, and various methods for visually observing material damage are developed, such as adding pH indicator and small molecule probe into anticorrosive coating. Although certain progress has been made in the self-warning anticorrosive coating at present, there are still some problems: 1) the curing agent of the epoxy resin coating is a molecule containing an amino active group, and in the process of mixing and curing with the probe molecule, the basic microenvironment will activate the fluorescence of the probe molecule, causing the self-warning function to fail, therefore, the basic pH response probe is not suitable for application in the epoxy resin-based anticorrosive coating; 2) the self-warning anticorrosive coating based on nano microspheres has two steps to realize self-warning, first, the nano microspheres are broken to release the probe molecules, and then the probe molecules respond at the damage and defect site to emit characteristic fluorescence, the response rate of the two steps is slow, and the breaking of the nano microspheres is related to the trend of the crack, therefore, the self-warning anticorrosive coating based on nano microspheres has the possibility of not being able to warn and slow warning; 3) according to the electrochemical principle of metal corrosion, after corrosion occurs, the cathode region receives electrons, and under the reaction of oxygen and water, hydroxyl ions are generated, causing the pH of the cathode region to rise, while the anode metal corrosion loses electrons and becomes metal ions at the same time, which reduces the pH value of the anode region, the basic pH response self-warning material currently studied is mainly used for detecting the cathode region, while the real corrosion region is in the anode, and the self-warning anticorrosive coating based on acidic pH response probe is less studied; 4) the emission wavelength of the currently studied responsive probe is concentrated in the ultraviolet visible region, which not only has limited penetration depth and cannot realize deep detection, but also is easy to be confused with the color of the coating, and it is difficult to realize the warning function; 5) the pH response probe is mainly designed as a small molecule, which is directly or encapsulated in nano microspheres and mixed with the anticorrosive coating, and is easy to leak, not resistant to seawater immersion and washing, the warning signal is weak, and the visualization degree is low. Therefore, it is necessary to develop an acidic pH response fluorescent self-warning anticorrosive coating to improve the sensitivity and accuracy of coating defect detection. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a fluorescent self-warning anticorrosive coating with acidic pH responsiveness, its preparation method and application, which contains fluorescent probe molecules, the fluorescent probe molecules have the function of rapidly and sensitively indicating fluorescence to acidic pH, when the anticorrosive coating is damaged and the metal substrate is exposed, the metal substrate corrodes, the anode metal corrosion loses electrons and becomes metal ions, at the same time, the pH value of the anode region is reduced, at this time, the fluorescence intensity of the fluorescent probe molecules with acidic pH responsiveness in the fluorescent self-warning anticorrosive coating of the present application is enhanced, realizing the function of detecting and warning the early corrosion of the metal substrate under the coating.

[0006] In order to achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] The fluorescent self-warning anticorrosive coating comprises a coupling probe molecule and an epoxy resin.

[0008] The structure of the probe molecule is shown in Formula I.

[0009]

[0010] R is

[0011] n is an integer greater than or equal to 2, preferably an integer from 3 to 10; m is an integer greater than or equal to 45, preferably an integer from 45 to 230.

[0012] The amino group in R is covalently connected after ring opening of the epoxy group in the epoxy resin.

[0013] The probe molecule has acidic pH responsiveness, has a structure of a fluoran dye type, and contains an amino functional group; under acidic conditions, butyrolactam in the structure of the probe molecule undergoes a hydrolysis reaction, so that the five-membered ring is opened, and the fluorescence intensity of the probe molecule is enhanced.

[0014] The epoxy resin is a bisphenol A type epoxy resin, a glycidyl ester type epoxy resin, a linear aliphatic type epoxy resin, or an alicyclic type epoxy resin.

[0015] The preparation method of the fluorescent self-warning anticorrosive coating comprises the following steps:

[0016] (1) cyclohexanone and 2-(4-diethylamine-2-hydroxybenzoyl) benzoic acid are added to concentrated sulfuric acid to perform a first reaction to obtain product 1, and the product 1 and Fisher's aldehyde are dissolved in acetic anhydride to perform a second reaction to obtain product 2;

[0017] The product 2, a BOP reagent, and a compound terminated by two amino groups are dissolved in a first solvent to perform a third reaction to obtain the small molecule probe; or the product 2, a BOP reagent, and a double-end amino polyethylene glycol are dissolved in a second solvent to perform a fourth reaction to obtain the large molecule probe.

[0018] The structure of the compound terminated by two amino groups and the double-end amino polyethylene glycol is shown in Formula II and III, respectively.

[0019]

[0020] n is an integer greater than or equal to 2; m is an integer greater than or equal to 45.

[0021] (2) the small molecule probe or the macromolecule probe prepared in step (1) is dissolved in a third solvent to react with the epoxy resin to obtain a crude product;

[0022] (3) the crude product prepared in step (2) is washed and dried to obtain the epoxy resin of the coupling probe molecule;

[0023] (4) the epoxy resin of the coupling probe molecule prepared in step (3) is dissolved in a fourth solvent with a curing agent to obtain the fluorescent self-prewarning anticorrosive coating.

[0024] In step (1), the first solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran and N,N-dimethylformamide, and is preferably dichloromethane; and the second solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran, methanol and N,N-dimethylformamide, and is preferably dichloromethane.

[0025] In step (1), the first reaction is carried out at a temperature of 40-150°C for 0.5-24h, and is preferably carried out at 90°C for 2h; the second reaction is carried out at a temperature of 25-150°C for 0.5-24h by stirring, and is preferably carried out at 50°C for 1.5h by stirring; the third reaction is carried out at room temperature for 0.5-48h by stirring; and the fourth reaction is carried out at room temperature for 0.5-48h by avoiding light.

[0026] Step (1) is a method for preparing the probe molecule (including a small molecule probe and a macromolecule probe), and the specific preparation method is referred to the synthesis method of the near-infrared fluorescent probe (CyR) in the literature Xie Jun-Ying, Li Chun-Yan, Li Yong-Fei, et al. Near-Infrared Fluorescent Probe with High Quantum Yield and Its Application in the Selective Detection of Glutathione in Living Cells and Tissues. Anal Chem. 2016; 88 (19): 9746-9752. doi: 10.1021 / acs.analchem.6b02646.

[0027] In step (2), the mass ratio of the small molecule probe to the epoxy resin is 3-40:100; and the mass ratio of the macromolecule probe to the epoxy resin is 3-50:100.

[0028] In step (2), the third solvent is any one or a combination of several of tetrahydrofuran, toluene, ethyl acetate, ethanol, cyclohexanone and N,N-dimethylformamide, preferably tetrahydrofuran; and the third solvent is used in an amount sufficient to dissolve the probe molecule and the epoxy resin.

[0029] In step (2), the reaction is carried out at a temperature of 50-120°C for 2-48 hours.

[0030] In step (3), the washing is carried out by washing the crude product several times with a mixture of methanol and water in a volume ratio of 1:20; and the drying is carried out by mixing sodium sulfate with the washed crude product.

[0031] In step (4), the mass ratio of the epoxy resin of the coupled probe molecule to the curing agent is 100:10-200; the curing agent is any one of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent or a resin oligomer containing a group of the above curing agents; the fourth solvent is any one or a combination of several of xylene, toluene, cyclohexanone, ethyl acetate and ethanol, preferably xylene; and the fourth solvent is used in an amount of 10%-50% of the mass of the epoxy resin.

[0032] In step (4), after the epoxy resin of the coupled probe molecule and the curing agent are dissolved in the fourth solvent, an additive in the prior art can be added as needed, including a dispersing agent, a defoaming agent and a leveling agent.

[0033] The application further relates to the application of the fluorescent self-warning anticorrosive coating in visual monitoring and detection of corrosion of a metal substrate.

[0034] Specifically, the fluorescent self-warning anticorrosive coating is coated on the surface of a metal substrate, dried and cured at room temperature to form a coating; when the metal substrate corrodes, the fluorescence intensity of the probe molecule in the coating is enhanced, thereby achieving convenient tracking of early corrosion of the metal substrate under the coating.

[0035] In the application, the fluorescent self-warning anticorrosive coating is coated on the surface of a metal substrate by brushing, dipping, spraying or pouring; the metal substrate is steel, aluminum or copper; and the thickness of the coating is 50 microns to 5 millimeters.

[0036] Beneficial effects:

[0037] (1) When the epoxy resin material of the coupled probe molecule is used as an anticorrosive coating, the anticorrosive coating has a self-warning capability. The epoxy resin material of the coupled probe molecule has an acidic pH responsiveness, and its fluorescence intensity is enhanced in an acidic environment. The coating defect and crack can be detected with high sensitivity and precision by fluorescence, and the coating crack can be detected and positioned for a long time due to the good stability.

[0038] (2) The current self-warning anticorrosive coating mostly uses basic pH-responsive probe molecules, which is difficult to apply in the epoxy resin anticorrosive coating cured by using an amino curing agent, and the acid pH-responsive probe molecules used in the present application solve this problem well.

[0039] (3) The fluorescence wavelength of the probe molecules used in the current self-warning anticorrosive coating is mostly in the visible region, and the penetration depth is limited, and the fluorescence emission wavelength of the fluorescent probe molecules of the present application is expanded from the ultraviolet-visible region to the near-infrared region, which improves the detection reliability and early warning signal detection depth of the self-warning anticorrosive coating.

[0040] (4) The fluorescent probe molecules are coupled with the epoxy resin to prepare the fluorescent self-warning anticorrosive coating, and compared with the existing fluorescent indicator type corrosion self-warning coating prepared by directly adding the fluorescent probe molecules into the coating, the fluorescent self-warning anticorrosive coating has better stability, and the fluorescence emission performance is more stable and is not easily disturbed by other components in the coating.

[0041] (5) The present application uses a macromolecular probe instead of a traditional small molecule probe and a nano microsphere encapsulating the probe, and couples it with the epoxy resin, and the probe molecules are uniformly distributed in the epoxy resin, which improves the detection speed and detection width on the one hand, and increases the stability of the material on the other hand, and can extend the detection capacity to 30 days, avoiding the problems of slow early warning efficiency and inability to early warn different cracks of the existing nano microsphere-based self-warning coating. BRIEF DESCRIPTION OF DRAWINGS

[0042] The above and / or other aspects of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0043] Figure 1 It is the nuclear magnetic resonance spectrum of the small molecule probe in Example 1.

[0044] Figure 2 It is the mass spectrum of the small molecule probe in Example 1.

[0045] Figure 3 It is the nuclear magnetic resonance spectrum of the macromolecular probe in Example 2.

[0046] Figure 4 It is the mass spectrum of the macromolecular probe in Example 2.

[0047] Figure 5 It is the ultraviolet absorption spectrum of the small molecule probe in Example 3 in different pH solutions.

[0048] Figure 6 It is the fluorescence emission spectrum of the small molecule probe in Example 3 in different pH solutions.

[0049] Figure 7 NMR spectrum of the epoxy resin material coupled with the small molecule probe in Example 4.

[0050] Figure 8 NMR spectrum of the epoxy resin material coupled with the macromolecule probe in Example 4.

[0051] Figure 9 Acidic pH response performance of the acidic pH responsive fluorescent self-warning anticorrosive coating based on the small molecule probe in Example 5.

[0052] Figure 10 Acidic pH response performance of the acidic pH responsive fluorescent self-warning anticorrosive coating based on the macromolecule probe in Example 6.

[0053] Figure 11 Warning and detection performance of the acidic pH responsive fluorescent self-warning anticorrosive coating based on the small molecule probe in Example 7 for different shapes of coating cracks.

[0054] Figure 12 Warning and detection performance of the acidic pH responsive fluorescent self-warning anticorrosive coating based on the macromolecule probe in Example 8 for different shapes of coating cracks. DETAILED DESCRIPTION

[0055] The present application is further illustrated below according to the following examples, and it should be understood that the following examples are only used to illustrate the present application, but not to limit the present application.

[0056] The specific techniques or conditions not mentioned in the examples are carried out according to the techniques or conditions described in the literature in the art, or according to the product instructions. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased through regular channels.

[0057] Synthesis of the small molecule probe in Example 1

[0058] In this example, the structural formula of the small molecule probe is shown as Formula IV.

[0059]

[0060] The preparation method is as follows:

[0061] Cyclohexanone (12.74 mmol, 1.32 mL) was added dropwise into concentrated sulfuric acid (14 mL) and cooled to 0 °C using an ice bath, then the reactant 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (6.4 mmol, 2 g) was added gradually and stirred. The reaction mixture was reacted at 90 °C for 2 h, then poured into ice water (100 g) after cooling, and perchloric acid (mass fraction 70%, 1.4 mL) was added to filter out the precipitate, which was washed with cold water (50 mL) to obtain the product 1 as a red solid.

[0062] The product 1 (4.2 mmol, 1.58 g) was dissolved in acetic anhydride (25 mL) with Fisher aldehyde (4.4 mmol, 0.88 g) and stirred at 50 °C for 1.5 h, then water (25 mL) was added to quench the reaction. The solvent was removed by rotary evaporation, and the crude product was separated and purified by silica gel column chromatography with dichloromethane: ethanol = 20: 1 as the developing agent to obtain the product 2 as a green solid.

[0063] The product 2 (100 mg, 0.18 mmol) was dissolved in 5 mL of ultra-dry dichloromethane with ethylenediamine (0.25 mL, 3.7 mmol) and BOP reagent (1.6 g, 3.7 mol), and stirred at room temperature for 2 h. The solvent was removed by rotary evaporation, and the crude product was separated and purified by silica gel column chromatography with dichloromethane: ethanol = 100: 1 ~ 10 as the developing agent. The nuclear magnetic resonance and mass spectrometry results of the product as the small molecule probe are shown in Figure 1 and Figure 2 .

[0064] Synthesis of the small molecule probe

[0065] In this embodiment, the structure of the small molecule probe is shown in formula V.

[0066]

[0067] The preparation method is as follows:

[0068] The product 2 (40 mg, 0.07 mmol) prepared in Example 1 was dissolved in 5 mL of dichloromethane with BOP reagent (100 mg, 0.23 mmol) to obtain solution A, and polyethylene glycol with an amino group at both ends and a polymerization degree of 45 (500 mg) was dissolved in 1 mL of dichloromethane to obtain solution B. Solution B was added dropwise to solution A, and the reaction was carried out at room temperature overnight in the dark. The reaction solution was separated and purified by silica gel column chromatography, and the structure of the product was confirmed as the target product, the macromolecular probe, by nuclear magnetic resonance spectroscopy and mass spectrometry. The nuclear magnetic resonance and mass spectrometry results of the macromolecular probe are shown in Figure 3 and Figure 4 .

[0069] pH-responsive detection of the probe molecule of Example 3

[0070] Prepare buffer solutions with pH values of 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5, respectively. The pH = 3.0 buffer solution is prepared using a citric acid-sodium citrate buffer solution, the pH = 3.5-5.5 buffer solutions are prepared using an acetic acid-sodium acetate buffer solution, and the pH = 6.0-7.5 buffer solutions are prepared using a phosphoric acid buffer solution. Dissolve the small-molecule probe in the above buffer solutions at the same concentration (10 μM). Use a UV spectrophotometer and a fluorescence spectrometer to test the UV absorption intensity and the fluorescence emission intensity of the solution, respectively. Set the excitation wavelength to 709 nm and the emission wavelength range to 720-800 nm.

[0071] The UV absorption spectrum and the fluorescence emission spectrum of the small-molecule probe in different pH solutions in this example are shown in Figure 5 and Figure 6 respectively. The results show that the prepared small-molecule probe has good pH response ability. With the increase of the acidity of the solution, the UV absorption intensity gradually increases, and the fluorescence intensity also gradually increases. The fluorescence response is more sensitive, and the response starts when the pH is less than 7.5.

[0072] Preparation of an acidic pH-responsive anticorrosion coating

[0073] Dissolve the small-molecule probe (20 mg) and the epoxy resin (200 mg) in tetrahydrofuran (30 mL) and react overnight at 70°C. Wash the crude product with a methanol-water (1:20, v / v) solution three times, and dry by adding sodium sulfate to obtain product 3, which is an epoxy resin material modified with the probe molecule (small-molecule probe). The structure is confirmed by nuclear magnetic resonance spectroscopy, and the nuclear magnetic resonance spectroscopy results are shown in Figure 7 .

[0074] Dissolve the macromolecular probe (18 mg) and the epoxy resin (200 mg) in tetrahydrofuran (30 mL) and react overnight at 70°C. Wash the crude product with a methanol-water (1:20, v / v) solution three times, and dry by adding sodium sulfate to obtain product 4, which is an epoxy resin material modified with the probe molecule (macromolecular probe). The structure is confirmed by nuclear magnetic resonance spectroscopy, and the nuclear magnetic resonance spectroscopy results are shown in Figure 8 .

[0075] Take 100 mg of product 3 and product 4, respectively, and dissolve them in xylene (10 mg) with a curing agent (Macklin, CAS: NONE 6720, 50 mg) to obtain the fluorescent self-warning anticorrosion coating material according to the present application. Apply it to a steel plate, and cure overnight at room temperature to obtain an acidic pH-responsive fluorescent self-warning anticorrosion coating.

[0076] Example 5 pH-responsive detection of epoxy resin-based anticorrosive coating based on small molecule probe

[0077] 0.1M citric acid-sodium citrate buffer solution with pH of 3.0, acetic acid-sodium acetate buffer solution with pH of 5.0 and phosphate buffer solution with pH of 7.0 were respectively configured, and different pH buffer solutions were added to different areas on the surface of the same piece of acidic pH-responsive fluorescent self-warning anticorrosive coating (small molecule probe coupled epoxy resin-based anticorrosive coating prepared in Example 4), and the buffer solution added areas were kept covered by the buffer solution during the test. A near-infrared imager was used to perform fluorescent imaging on the coating at different time points, and the excitation wavelength was set to 704 nm, and the fluorescent signals in the range of 740-950 nm were collected.

[0078] Figure 9 For the acidic pH-responsive performance of the acidic pH-responsive fluorescent self-warning anticorrosive coating in this example, it can be seen from Figure 9 It can be seen that the prepared fluorescent self-warning anticorrosive coating has good pH responsiveness, and the fluorescent intensity of the coating in the region with pH of 3.0 is obviously stronger than that in the regions with pH of 5.0 and 7.0. Meanwhile, the pH-responsive performance of the prepared fluorescent self-warning anticorrosive coating has good stability, and still has good pH-responsive performance and can still emit strong fluorescence after 1 month, which further illustrates the advancement of the present application in coupling probe molecules with epoxy resin to prepare fluorescent self-warning anticorrosive coating, which has good pH-responsive performance and good stability.

[0079] Example 6 pH-responsive detection of epoxy resin-based anticorrosive coating based on macromolecule probe

[0080] 0.1M citric acid-sodium citrate buffer solution with pH of 3.0, acetic acid-sodium acetate buffer solution with pH of 5.0 and phosphate buffer solution with pH of 7.0 were respectively configured, and different pH buffer solutions were added to different areas on the surface of the same piece of acidic pH-responsive fluorescent self-warning anticorrosive coating (small molecule probe coupled epoxy resin-based anticorrosive coating prepared in Example 4), and the buffer solution added areas were kept covered by the buffer solution during the test. A near-infrared imager was used to perform fluorescent imaging on the coating at different time points, and the excitation wavelength was set to 704 nm, and the fluorescent signals in the range of 740-950 nm were collected.

[0081] Figure 10 For the acidic pH-responsive performance of the acidic pH-responsive fluorescent self-warning anticorrosive coating in this example, it can be seen from Figure 9 It can be seen that the prepared acidic pH-responsive fluorescent self-warning anticorrosive coating based on macromolecule probe has good pH responsiveness, and the stronger the acidity of the solution, the brighter the fluorescence of the coating and the greater the fluorescent intensity. And compared with the epoxy resin-based anticorrosive coating based on small molecule probe Figure 9Compared with the small molecule probe, the macromolecular probe can obviously distinguish the regions of pH = 5.0 and pH = 7.0, and has strong fluorescence in the region of pH = 5.0, indicating that the pH responsiveness of the macromolecular probe-based anticorrosive coating is better than that of the small molecule probe-based anticorrosive coating.

[0082] Example 7 Detection of the fluorescence self-warning ability of the epoxy resin-based anticorrosive coating based on a small molecule probe

[0083] Cracks in the form of crosses and circles were constructed on the surface of the acidic pH-responsive fluorescent self-warning anticorrosive coating based on a small molecule probe, the coating was covered with 3.5% sodium chloride aqueous solution to simulate seawater (the coating was kept covered with 3.5% sodium chloride aqueous solution during the test), and the fluorescence imaging of the coating was performed at different time points using a near-infrared imaging instrument, the excitation wavelength was set to 704 nm, and the fluorescence signals in the range of 740-950 nm were collected. The ability of the acidic pH-responsive fluorescent self-warning anticorrosive coating to detect coating cracks in a seawater environment was tested.

[0084] Figure 11 The warning and detection performance of the acidic pH-responsive fluorescent self-warning anticorrosive coating in this example for different shapes of coating cracks were determined by Figure 11 It can be seen that the fluorescence intensity of the crack region is significantly higher than that of the intact coating region, and the enhanced fluorescence intensity image is consistent with the shape of the crack, indicating that the acidic pH-responsive fluorescent self-warning anticorrosive coating has good self-warning ability and can accurately locate the crack region and shape.

[0085] Example 8 Detection of the fluorescence self-warning ability of the epoxy resin-based anticorrosive coating based on a macromolecular probe

[0086] Cracks in the form of crosses and circles were constructed on the surface of the acidic pH-responsive fluorescent self-warning anticorrosive coating based on a macromolecular probe prepared from polyethylene glycol, the coating was covered with 3.5% sodium chloride aqueous solution to simulate seawater (the coating was kept covered with 3.5% sodium chloride aqueous solution during the test), and the fluorescence imaging of the coating was performed at different time points using a near-infrared imaging instrument, the excitation wavelength was set to 704 nm, and the fluorescence signals in the range of 740-950 nm were collected. The ability of the acidic pH-responsive fluorescent self-warning anticorrosive coating to detect coating cracks in a seawater environment was tested.

[0087] Figure 12 The warning and detection performance of the acidic pH-responsive fluorescent self-warning anticorrosive coating in this example for different shapes of coating cracks were determined by Figure 12It can be seen that the fluorescence intensity of the crack area is significantly higher than that of the area with intact coating, and the enhanced image of fluorescence intensity is consistent with the shape of the crack, indicating that the acid pH-responsive fluorescent self-warning anticorrosive coating has good self-warning ability and can accurately locate the area and shape of the crack. Moreover, after 15 days, the acid pH-responsive fluorescent self-warning anticorrosive coating was subjected to near-infrared imaging, and the results are shown in Figure 12 It can be seen that the fluorescence intensity of the crack area is significantly higher than that of the area with intact coating, and the enhanced image of fluorescence intensity is consistent with the shape of the crack, indicating that the acid pH-responsive fluorescent self-warning anticorrosive coating has good self-warning ability and can accurately locate the area and shape of the crack. Moreover, after 15 days, the acid pH-responsive fluorescent self-warning anticorrosive coating was subjected to near-infrared imaging, and the results are shown in

[0088] The present application provides a preparation method of a fluorescent self-warning anticorrosive coating, and there are many methods and approaches to realize the technical solution. The above description is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the present application, several improvements and refinements can be made, which should be considered as the protection scope of the present application. The components not explicitly described in the embodiment can be realized by the existing technology.

Claims

1. A fluorescent self-warning anti-corrosion coating, characterized in that: The fluorescent self-warning anti-corrosion coating comprises an epoxy resin coupled with a probe molecule; Wherein, the structural formula of the probe molecule is shown in Formula I; Where R is n is an integer greater than or equal to 2; m is an integer greater than or equal to 45; The amino group in R opens the ring of the epoxy group in the epoxy resin and then covalently links to it.

2. The fluorescent self-warning anti-corrosion coating according to claim 1 is characterized in that: The epoxy resin is bisphenol A epoxy resin, glycidyl ester epoxy resin, linear aliphatic epoxy resin or alicyclic epoxy resin.

3. The method for preparing the fluorescent self-warning anti-corrosion coating according to claim 1 or 2, characterized in that: The steps include: (1) adding cyclohexanone and 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid to concentrated sulfuric acid for a first reaction to obtain product 1, and dissolving the product 1 and Fischer's aldehyde in acetic anhydride for a second reaction to obtain product 2; Dissolving the product 2, the BOP reagent, and the compound terminated with amino groups at both ends in a first solvent to carry out a third reaction to obtain a small molecule probe; or dissolving the product 2, the BOP reagent, and double-terminated amino polyethylene glycol in a second solvent to carry out a fourth reaction to obtain a macromolecular probe; Wherein, the structural formulas of the compound terminated with amino groups at both ends and the double-terminated amino polyethylene glycol are shown in Formula II and Formula III respectively; Wherein, n is an integer greater than or equal to 2; m is an integer greater than or equal to 45; (2) dissolving the small molecule probe or macromolecular probe prepared in step (1) and epoxy resin in a third solvent to react to obtain a crude product; (3) washing and drying the crude product obtained in step (2) to obtain an epoxy resin coupled with a probe molecule; (4) dissolving the epoxy resin coupled with the probe molecule obtained in step (3) and the curing agent in a fourth solvent to obtain a fluorescent self-warning anti-corrosion coating.

4. The preparation method according to claim 3, characterized in that In step (1), the first solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran and N,N-dimethylformamide; the second solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran, methanol and N,N-dimethylformamide.

5. The preparation method according to claim 3, characterized in that In step (2), the mass ratio of the small molecule probe to the epoxy resin is 3 to 40:100; the mass ratio of the macromolecular probe to the epoxy resin is 3 to 50:

100.

6. The preparation method according to claim 3, characterized in that In step (2), the third solvent is any one or a combination of tetrahydrofuran, toluene, ethyl acetate, ethanol, cyclohexanone and N,N-dimethylformamide.

7. The preparation method according to claim 3, characterized in that In step (2), the reaction temperature is 50-120° C. and the reaction time is 2-48 h.

8. The preparation method according to claim 3, characterized in that In step (3), the washing step comprises washing the crude product with a mixture of methanol and water in a volume ratio of 1:20; and the drying step comprises mixing sodium sulfate with the washed crude product and drying the mixture.

9. The preparation method according to claim 3, characterized in that In step (4), the mass ratio of the epoxy resin of the coupled probe molecule to the curing agent is 100:10~200; the curing agent is any one of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent, or a resin oligomer containing the above curing agent groups; the fourth solvent is any one of xylene, toluene, cyclohexanone, ethyl acetate and ethanol, or a combination of several thereof.

10. Use of the fluorescent self-warning anti-corrosion coating according to claim 1 or 2 in visual monitoring and detection of corrosion of metal substrates.

11. The use according to claim 10, characterized in that The fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate and dried and cured at room temperature to form a coating; when corrosion occurs on the metal substrate, the fluorescence intensity of the probe molecules in the coating is enhanced, thereby enabling convenient tracking of early corrosion of the metal substrate under the coating.

12. The use according to claim 11, characterized in that The fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate by brushing, dipping, spraying or pouring; the metal substrate is steel, aluminum or copper; and the coating thickness is 50 microns to 5 mm.

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