Polyurea reinforced epoxy resin anticorrosive and wear-resistant coating for high-speed train

Abstract

The present application relates to anticorrosive wear-resistant coating, and in particular to polyurea reinforced epoxy resin anticorrosive wear-resistant coating for high-speed train. The epoxy resin anticorrosive wear-resistant coating contains polyurea nanofiber, which is obtained by addition polymerization with diisocyanate and diamine as raw materials. The polyurea nanofiber has continuous reinforcing interface and high dispersibility, and can significantly enhance the corrosion resistance and wear resistance of traditional epoxy resin within a certain mass ratio range.

Description

Technical Field

[0001] This invention relates to anti-corrosion and wear-resistant coatings, specifically to polyurea-reinforced epoxy resin anti-corrosion and wear-resistant coatings for high-speed trains. Background Technology

[0002] Aluminum alloys, due to their light weight and high strength, find diverse applications in various engineering and non-engineering fields such as automotive, aerospace, and shipbuilding. However, with the further expansion and deepening of their applications, the service conditions of equipment are becoming increasingly harsh. Consequently, the wear and corrosion behavior of aluminum alloys during use is further exacerbated. Under various harsh conditions, aluminum alloys are prone to physical defects such as porosity, cracks, and melting during use. The most economical and effective method to address these application problems is to select a suitable coating as a protective layer for the metal. However, traditional surface coatings have little long-term protection effect on the aluminum alloy substrate. For example, conventional coatings on high-speed trains are severely affected by sand or other hard particles during high-speed travel, resulting in wear and corrosion. Once the aluminum alloy body loses its protection, surface defects will appear in a short period, jeopardizing equipment safety. Therefore, developing a high-performance anti-corrosion and wear-resistant coating is crucial. Summary of the Invention

[0003] This invention proposes the synthesis and application of a polyurea nanofiber-reinforced epoxy resin composite coating. Highly dispersed nanofibers with continuously reinforced interfaces can significantly enhance the corrosion resistance and wear resistance of traditional epoxy resins within a certain mass ratio range. This invention relates to the research of the corrosion and wear resistance properties of coatings, and is suitable for applications involving wear and corrosion of aluminum alloy materials. It shows great promise for corrosion and wear resistance on the outer surfaces of high-speed trains.

[0004] A type of polyurea nanofiber is obtained by addition polymerization of diisocyanate and diamine as raw materials.

[0005] The method for preparing the polyurea nanofibers includes: providing a diamine solution in anhydrous ethanol; providing a diisocyanate in ethyl acetate; reacting the diamine solution and diisocyanate at 40-60°C for 1-2 hours; then reacting at 70-80°C for 80-100 minutes with stirring; after the reaction is complete, washing with water to remove excess diisocyanate; drying to form or prepare polyurea nanofibers.

[0006] The application of the polyurea nanofibers in the preparation of polyurea epoxy resin composite coatings. Optionally, the content of the polyurea nanofibers in the polyurea epoxy resin composite coating is 0.1wt%-0.5wt%.

[0007] A polyurea-epoxy resin composite coating includes polyurea nanofibers and an epoxy resin matrix; wherein the weight ratio of the polyurea nanofibers to the epoxy resin matrix is ​​(0.1-0.5):(80-120).

[0008] The method for preparing the polyurea epoxy resin composite coating includes mixing the polyurea nanofibers and the epoxy resin matrix; stirring; then coating the mixture onto a substrate and curing it.

[0009] The excellent dispersibility of the polyurea nanofibers in this invention can effectively repair micro-defects, achieving optimal barrier performance and thus extending or even inhibiting the corrosion diffusion path of the electrolyte. The polyurea nanofibers prepared in this invention have a small contact angle with the epoxy resin coating, exhibiting good wettability, allowing an appropriate amount of polyurea nanofibers to be uniformly distributed in the epoxy resin during coating preparation. The wear resistance of the composite coating stems from the ability of the entangled polyurea nanofibers to transmit the forces and interfacial resistance at the contact surface, thereby preventing coating displacement. Attached Figure Description

[0010] Figure 1 This is the Fourier transform infrared absorption spectrum of the polyurea nanofibers synthesized in Example 1 of this invention.

[0011] Figure 2 The contact angles of the polyurea nanofiber sheet obtained by compaction in Example 1 of this invention with epoxy resin (top) and 3.5wt% sodium chloride solution (bottom) are shown.

[0012] Figure 3 The Nyquist spectrum of Example 2 of the present invention is obtained by immersing a 0.25 wt% polyurea fiber composite coating in a 3.5 wt% sodium chloride solution for 28 days.

[0013] Figure 4 The image shown is a Byrd pattern of a 0.25 wt% polyurea fiber composite coating that has been immersed in a 3.5 wt% sodium chloride solution for 28 days, according to Example 2 of this invention.

[0014] Figure 5 This is the dynamic mechanical-thermal analysis curve of the energy storage modulus of the 0.25wt% polyurea fiber composite coating in Example 2 of the present invention.

[0015] Figure 6 The two-dimensional morphology of the indentation of the epoxy resin composite coating (PU-0.25%) prepared in Example 2 of this invention is shown in the figure.

[0016] Figure 7 The Nyquist spectrum of Example 3 of the present invention is obtained by immersing a 0.1 wt% polyurea fiber composite coating in a 3.5 wt% sodium chloride solution for 28 days.

[0017] Figure 8The image shown is a Byrd pattern of a 0.1 wt% polyurea fiber composite coating that has been immersed in a 3.5 wt% sodium chloride solution for 28 days, according to Example 3 of this invention.

[0018] Figure 9 This is the dynamic mechanical-thermal analysis curve of the energy storage modulus of the polyurea fiber composite coating containing 0.1 wt% in Example 3 of the present invention.

[0019] Figure 10 The Nyquist plot of Comparative Example 2 of this invention is obtained by immersing a 0.6 wt% polyurea fiber composite coating in a 3.5 wt% sodium chloride solution for 28 days.

[0020] Figure 11 The image shown is the Byrd pattern of Comparative Example 2 of this invention, which contains a 0.6 wt% polyurea fiber composite coating and is immersed in a 3.5 wt% sodium chloride solution for 28 days.

[0021] Figure 12 This is the dynamic mechanical-thermal analysis curve of the energy storage modulus of the composite coating containing 0.6 wt% polyurea fiber in Comparative Example 2 of this invention. Detailed Implementation

[0022] Epoxy coatings and composites possess advantages such as strong adhesion to substrates, good chemical resistance, simple processing, economy, and environmental friendliness, leading to their widespread application in municipal engineering, transportation, and defense industry construction. However, defects such as microcracks, blistering, and micropores often occur during their curing process. These phenomena reduce the physical protection of the coating on the substrate, allowing external corrosive media to enter and cause severe corrosion damage. Therefore, internal defects can cause the coating to lose its protective performance under extreme external conditions (friction, high salt, ultraviolet radiation, etc.). To address this issue, researchers have employed various methods to enhance the protective performance of coatings and extend their service life, including but not limited to adding pigments, reinforcing agents, and corrosion inhibitors in different forms. A series of studies have shown that adding appropriate fillers can significantly improve the protective performance of coatings. Therefore, it is necessary to find a suitable filler to compensate for this deficiency of traditional epoxy resins.

[0023] Among various filler selections, choosing the right filler and balancing the affinity between the fiber filler and the resin remains a hot topic. Although researchers have applied various fiber fillers to impart better performance and more applications to coatings, two problems still exist in the application of fiber fillers. First, non-nanofiber fillers have poor self-dispersibility in resins and are prone to agglomeration during stirring; second, the network distribution of fiber fillers mostly does not significantly improve coating performance.

[0024] To address at least one of the above technical problems, this invention introduces polyurea nanofibers as a filler, and explores and confirms their strengthening effect on the coating.

[0025] Although fibrous polyurea has been extensively studied for its mechanical properties, hydrolytic stability, and chemical resistance, its application as a filler in epoxy coatings is rarely investigated. Polyurea nanofibers were prepared via an addition polymerization reaction of diamine and diisocyanate. The resulting polyurea powder exhibited a near-two-dimensional ultrafine fiber morphology. As a filler, the nanofibers, with their excellent dispersibility, could be uniformly distributed and cross-linked in the coating, significantly reducing its porosity and enhancing its barrier properties. Results showed that the prepared polyurea nanofibers possessed good solubility, dispersibility, and hydrophobicity in common organic solvents, resulting in excellent long-term corrosion resistance in the composite coating.

[0026] This invention first provides a polyurea nanofiber, which is obtained by addition polymerization of diisocyanate and diamine as raw materials. The polyurea nanofiber has good dispersibility and a continuously reinforced interface, which can enhance the corrosion resistance and wear resistance of traditional epoxy resins.

[0027] In some specific instances, the diisocyanate is in excess relative to the diamine to allow the diamine to react completely.

[0028] In some specific examples, the mass ratio of diisocyanate to diamine is (3.0-5.0):(3.5-4.0). To ensure maximum synthesis of urea groups while maintaining the molecular chain length of polyurea fibers, the amount of diisocyanate used should be slightly more than that of diamine. However, an excessively high or low mass ratio can lead to overly vigorous reactions or significantly prolonged reaction times. Generally, when the mass ratio of diisocyanate to diamine is greater than 3:2, the rapid formation of urea groups can prevent monomers from forming long molecular chains, reducing the success rate of polyurea fiber synthesis. Conversely, a lower mass ratio will reduce reaction time efficiency and polyurea synthesis efficiency.

[0029] In some specific examples, the preparation method of the polyurea nanofibers includes:

[0030] Provide a diamine solution, with anhydrous ethanol as the solvent;

[0031] Provide diisocyanate, with ethyl acetate as solvent;

[0032] The diamine solution and diisocyanate were first reacted at 40-60℃ for 1-2 hours; then, under stirring, the reaction was carried out at 70-80℃ for 80-100 minutes.

[0033] After the reaction is complete, wash with water (deionized water) to remove excess diisocyanate; dry to form or produce polyurea nanofibers.

[0034] In some specific examples, the preparation method of the polyurea nanofibers includes:

[0035] 1) Dissolve an appropriate amount of diamine in anhydrous ethanol (the ratio of diamine to anhydrous ethanol is 1:10 by mass) and sonicate; prepare or prepare a diamine solution;

[0036] 2) Dissolve diisocyanate in ethyl acetate (the ratio of diisocyanate to ethyl acetate is 1:10 by mass), and then add it to the diamine solution;

[0037] In some cases, the diisocyanate is used in excess relative to the diamine to allow the diamine to react completely;

[0038] In some cases, the mass ratio of diisocyanate to diamine is (3.0-5.0):(3.5-4.0);

[0039] 3) Keep the flask in an oil bath at 40-60℃ for 1-2 hours; then heat the oil bath to 70-80℃ and stir at 300-600 rpm for 80-100 minutes.

[0040] 4) Then add 10-50 mL of deionized water to the flask and stir for 10-30 minutes to remove excess diisocyanate. Finally, vacuum dry the reaction product at 50-60°C for 20-30 hours and grind it into powder for use.

[0041] In some specific examples, the diisocyanate may be selected from one of diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and dicyclohexylmethane diisocyanate (HMDI).

[0042] In some specific instances, the diamine may be selected from one of hexamethylenediamine, ethylenediamine, diaminodiphenylmethane, o-phenylenediamine, or diethanolamine.

[0043] The present invention also provides the application of the above-mentioned polyurea nanofibers in the preparation of polyurea epoxy resin composite coatings.

[0044] In some specific examples, the content of the polyurea nanofibers in the polyurea epoxy resin composite coating is 0.1wt%-0.5wt%, preferably 0.25wt%. If the content of polyurea nanofibers is too high, it will affect the porosity of the coating and reduce its anti-corrosion performance; if it is too low, it will not show any performance. The illustration uses 0.25% as a comparison, and the effect is the best.

[0045] The present invention also provides a polyurea epoxy resin composite coating, comprising the above-mentioned polyurea nanofibers and epoxy resin matrix; wherein the weight ratio of polyurea nanofibers to epoxy resin matrix is ​​(0.1-0.5):(80-120).

[0046] In some specific examples, the mass ratio of polyurea nanofibers to epoxy resin matrix is ​​(0.1-0.5):100.

[0047] Studies have found that the mass ratio of polyurea nanofibers to epoxy resin matrix can be freely distributed within the above range, and a wear-resistant and corrosion-resistant coating with similar properties can be obtained. If the content is lower than 0.1:100, the polyurea fibers in the epoxy resin matrix are too loosely dispersed, which is insufficient to provide the resin matrix with sufficient wear-resistant and corrosion-resistant properties. If the content is higher than 0.5:100, the dispersion of fibers cannot be guaranteed, and too many nanofibers will hinder the cross-linking and film formation of epoxy resin molecules, making it difficult for the coating to cure and form, which is not conducive to its use as a coating.

[0048] In some specific examples, the epoxy resin matrix is ​​made of uncured epoxy resin, curing agent, diluent, catalyst and dispersant in a mass ratio of (4-6):(8-12):(5-10):(1-5:(1-1.5).

[0049] In some specific examples, the preparation method of the epoxy resin matrix includes: the epoxy resin matrix is ​​mainly composed of uncured epoxy resin, curing agent, diluent, catalyst and dispersant mixed in proportion, and then stirred (for example, stirred at a speed of 2000-5000 rpm for 10-30 minutes) to obtain the epoxy resin matrix.

[0050] The polyurea epoxy resin composite coating described in this invention can be applied to various aluminum alloy material wear and corrosion scenarios, such as the outer surface of high-speed trains.

[0051] The present invention also provides a method for preparing the above-mentioned polyurea epoxy resin composite coating, comprising mixing the above-mentioned polyurea nanofibers and epoxy resin matrix; stirring, then coating on a substrate and curing.

[0052] In some specific instances, the stirring speed is 3000-4000 rpm.

[0053] In some specific instances, the substrate is an aluminum alloy, particularly aluminum alloys used in high-speed train bodies.

[0054] In some specific instances, the substrate (aluminum alloy) is polished (with sandpaper) and cleaned (with acetone ultrasonic cleaning) before coating.

[0055] In some specific instances, curing was performed at room temperature under vacuum conditions for 20-30 hours.

[0056] In some specific examples, the uncured epoxy resin may be one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, cyanuric acid epoxy resin, and alicyclic epoxy resin.

[0057] In some specific examples, the curing agent may be selected from one or more of tetramethylethylenediamine, diethylenetriamine, dibenzylamine ether, benzoyl peroxide, and dicyandiamine.

[0058] In some specific instances, the diluent may be one or more of alkylene glycidyl ether, n-butanol, benzyl alcohol, xylene, acetone, and dimethylformamide.

[0059] In some specific examples, the catalyst may be selected from one or more of dibutyltin, tetrabutyltin, dibutyltin dilaurate, and tributyltin chloride.

[0060] In some specific examples, the dispersant may be one or more of dodecyl dimethyl benzyl ammonium bromide, sodium dodecylbenzene sulfonate, polyvinyl alcohol, and hydroxypropyl methylcellulose.

[0061] For pure epoxy coatings, the evaporation of the thinner during the curing process leaves numerous micropores within the coating. In harsh external corrosive environments, these defects provide diffusion paths for corrosive media. The dense oxide film on the aluminum alloy surface is destroyed by chloride ions in the corrosive media. Simultaneously, oxygen dissolved in the salt solution induces depolarization on the metal surface, thereby accelerating the dissolution of the anolyte metal.

[0062] The polyurea nanofiber reinforced composite coating of this invention improves corrosion resistance in three main ways: (a) the interlaced arrangement of polyurea nanofibers provides an excellent barrier against corrosive solutions, making the diffusion path of the corrosive solutions serrated, and the physical barrier effect of the filler is fully utilized in the coating; (b) the reduction of coating defects leads to a reduction in the penetration of corrosive media; (c) the polyurea nanofibers can uniformly distribute the internal stress caused by the expansion of corrosion products, reducing blistering of the coating.

[0063] The wear resistance of polyurea nanofiber reinforced composite coatings is mainly due to the blending and strengthening effect caused by the dispersion of polyurea nanofibers in the coating, which greatly improves the storage modulus of the composite coating and thus effectively prevents the coating from deforming under external forces.

[0064] Example 1

[0065] This embodiment provides a polyurea nanofiber-reinforced epoxy resin composite coating, which is synthesized from hexamethylenediamine, diphenylmethane diisocyanate and bisphenol A type epoxy resin matrix.

[0066] Specifically as follows:

[0067] 1) Preparation of polyurea nanofibers:

[0068] Dissolve 1.2 g of hexamethylenediamine in 12 g of anhydrous ethanol (about 15 mL) and disperse by sonication. Weigh 1.6 g of diphenylmethane diisocyanate, dissolve it in 16 g (about 18 mL) of ethyl acetate, mix the solutions, and add them to the hexamethylenediamine solution.

[0069] Place the flask containing the mixed solution in an oil bath at 50°C for 1.5 hours. Then, heat the oil bath to 80°C and add a magnetic rotor. Stir thoroughly at 600 rpm for 90 minutes.

[0070] 25 mL of deionized water was added to the flask and stirred for 10 minutes to remove excess diisocyanate. The reaction product was then vacuum-dried at 60°C for 30 hours and ground into powder for use. In this example, 2.4 g of polyurea nanofibers were obtained.

[0071] 2) Preparation of epoxy resin matrix:

[0072] Weigh 20g of bisphenol A epoxy resin, 10g of dibutyltin, and 5g of dodecyl dimethyl benzyl ammonium bromide into a flask equipped with a magnetic stir bar. Then, add 40g of tetramethylethylenediamine and 30g of xylene to the flask, and stir at 4000 rpm for 30 minutes at room temperature to obtain the epoxy resin matrix.

[0073] 3) Preparation of epoxy resin composite coating:

[0074] A fixed-size aluminum alloy block (15mm×15mm×5mm) was polished with sandpaper and then ultrasonically cleaned three times with acetone to remove surface contaminants. Polyurea nanofibers and epoxy resin matrix were mixed at a mass ratio of 0.5:100 and stirred at 3000 rpm for 20 minutes. The mixture was then uniformly sprayed onto the aluminum alloy block and cured at room temperature under vacuum for 30 hours.

[0075] The epoxy resin composite coating prepared in this embodiment is marked as PU-0.5%.

[0076] The polyurea-reinforced epoxy resin coating prepared by this method can reduce the wear rate by 3 / 4 and significantly improve the wear resistance of the coating.

[0077] Fourier transform infrared spectroscopy analysis was performed on the polyurea nanofibers synthesized in this embodiment, and the results are shown in the figure. Figure 1 The peak of the tensile vibration of the NH bond occurs at 3325 cm⁻¹. -1 The asymmetric and symmetric stretching vibrations of the CH bond at 2855 cm⁻¹ -1 and 2922cm -1 The characteristics of the C=O functional group in the urea group were observed at 1635 cm⁻¹. -1 1561cm -1The peak at that position is attributed to the bending vibration of the NH single bond in the amide bond. Based on the Fourier transform infrared spectroscopy analysis, it is inferred that the isocyanate group (-NCO) of diphenylmethane diisocyanate interacts with the amino group (-NH) in the diamine. 2 The formation of urea groups (N-CO-N) demonstrates the successful preparation of polyurea based on the addition polymerization scheme.

[0078] The polyurea nanofibers of this embodiment were compressed into tablets using a powder tableting machine. Then, a high-speed camera was used to photograph the contact angles of the same volume of epoxy resin and 3.5 wt% sodium chloride solution on the compressed powder tablets. The results are shown in [Figure Number]. Figure 2 The results showed that the contact angle between the powder tablet and the epoxy resin was 45°, and the contact angle with the 3.5 wt% sodium chloride solution was 90°. The smaller the contact angle, the lower the interfacial tension at the interface between the polyurea nanofibers and the epoxy resin. After mechanical stirring, the filler and coating were fully emulsified, allowing an appropriate amount of polyurea nanofibers to be uniformly distributed in the epoxy resin during coating preparation. Conversely, the relatively large contact angle with the 3.5 wt% sodium chloride solution indirectly indicates that the polyurea nanofibers possess excellent barrier properties within the coating during the penetration of corrosive media.

[0079] Example 2

[0080] This embodiment provides a polyurea nanofiber reinforced epoxy resin composite coating, which is synthesized from diethanolamine, isoflurane diisocyanate and bisphenol A type epoxy resin matrix.

[0081] Specifically as follows:

[0082] 1) Preparation of polyurea nanofibers:

[0083] Dissolve 0.8 g of diethanolamine in 8 g of anhydrous ethanol (about 10 mL) and disperse by sonication. Weigh 1.0 g of isophorone diisocyanate, dissolve it in 10 g (about 11 mL) of ethyl acetate, mix the solutions, and add them to the diethanolamine solution.

[0084] Place the flask containing the mixed solution in an oil bath at 60°C for 2 hours. Then, heat the oil bath to 70°C and add a magnetic rotor. Stir thoroughly at 600 rpm for 90 minutes.

[0085] 20 mL of deionized water was added to the flask and stirred for 10 minutes to remove excess diisocyanate. The reaction product was then vacuum-dried at 50°C for 25 hours and ground into powder for use. In this example, 1.6 g of polyurea nanofibers were obtained.

[0086] 2) Preparation of epoxy resin matrix:

[0087] Weigh 16g of bisphenol A epoxy resin, 16g of dibutyltin dilaurate, and 4g of polyvinyl alcohol into a flask equipped with a magnetic stir bar. Then, add 40g of diethylenetriamine and 20g of alkylene glycidyl ether to the flask and stir at 3000 rpm for 20 minutes at room temperature to obtain the epoxy resin matrix.

[0088] 3) Preparation of epoxy resin composite coating:

[0089] A fixed-size aluminum alloy block (15mm×15mm×5mm) was polished with sandpaper and then ultrasonically cleaned three times with acetone to remove surface contaminants. Polyurea and epoxy resin matrix were mixed at a mass ratio of 0.25:100 and stirred at 3500 rpm for 15 minutes. The mixture was then evenly sprayed onto the aluminum alloy block and cured at room temperature under vacuum for 20 hours.

[0090] The epoxy resin composite coating prepared in this embodiment is marked as PU-0.25%.

[0091] The Nyquist plot of the epoxy resin composite coating after immersion in a 3.5 wt% sodium chloride solution for 28 days is shown below. Figure 3 . Figure 3 In comparison with PU-0% (i.e., Comparative Example 1), the epoxy resin composite coating containing 0.25% polyurea nanofibers showed a significant increase in capacitive arc diameter after immersion for 28 days. The change in resistance value is attributed to the formation of a physical barrier network by the polyurea nanofibers within the coating.

[0092] The Bode plot of the epoxy resin composite coating after immersion in a 3.5 wt% sodium chloride solution for 28 days is shown below. Figure 4 . Figure 4 It can be intuitively observed that the impedance value (|Z|) of PU-0.25% at low frequencies is... f＝0.01Hz The value of |Z| is very high and remains stable within a certain frequency range, then decreases rapidly with increasing frequency, indicating that the coating changes from resistive to capacitive characteristics across the entire frequency range. The coating exhibits resistive characteristics at low frequencies. f＝0.01Hz The larger the capacitance, the more difficult it is for electrons to transfer in the electrolyte, thus increasing the coating's corrosion resistance. As corrosive media penetrate, the coating capacitance increases and the resistance decreases, causing the Bode curve plateau to lengthen and weakening the coating's capacitive characteristics.

[0093] The dynamic mechanical-thermal analysis curve of the energy storage modulus of the epoxy resin composite coating is shown below. Figure 5 . Figure 5Storage modulus refers to the energy stored during elastic deformation of a viscoelastic material. It is the contribution of the elastic portion of the viscoelastic material and reflects the material's resistance to deformation. The storage modulus of the samples shows a decreasing trend with increasing temperature, because the increase in temperature leads to sufficient movement of bonds in the polymer. As the molecular chain motion becomes more active, the coating gradually transitions from a highly elastic state to a viscoelastic state. Based on this, the addition of polyurea nanofibers in the glassy and rubbery states significantly improves the storage modulus. The storage modulus of PU-0.25% is 1170 MPa higher than that of PU-0% (i.e., Comparative Example 1 below), indicating that the addition of polyurea nanofibers has an excellent reinforcing effect on epoxy coatings. The dispersion of polyurea nanofibers in the PU-0.25% coating has a blending strengthening effect, which can effectively prevent the coating from deforming under external force. Therefore, PU-0.25% has better wear resistance under applied load. However, with the increase of the addition amount, polyurea nanofibers will agglomerate, and the decrease in storage modulus is caused by the weak interfacial bonding between the filler and the resin due to filler agglomeration.

[0094] In addition, material stiffness and hardness tests were conducted on PU-0.25%, and its indentation two-dimensional morphology is shown in [the figure]. Figure 6 .Depend on Figure 6 As can be seen, under applied load, the Brinell hardness tester pressed deep pits into the surface of the resin block. The pit diameter of PU-0% (i.e., Comparative Example 1 below) was 1.7 mm and the depth was 60 mm, while the diameter and depth of PU-0.25% were 1.5 mm and 35 mm, respectively. The difference in pit depth clearly shows that the hardness of the coating was significantly improved due to the addition of polyurea nanofibers.

[0095] Example 3

[0096] The only difference from Example 2 is that in the preparation of the epoxy resin composite coating, polyurea nanofibers and epoxy resin matrix are mixed at a mass ratio of 0.1:100.

[0097] The epoxy resin composite coating prepared in this embodiment is marked as PU-0.1%.

[0098] Figure 7 , Figure 8 , Figure 9 The Nyquist plot and Bode plot of the PU-0.1% composite coating after immersion in 3.5wt% sodium chloride solution for 28 days are shown, along with the dynamic mechanical-thermal analysis curve of the storage modulus. When the nanofiber filler content is 0.1%, the coating's anti-corrosion performance is still significantly improved. However, in practical applications, using less filler may lead to excessive dispersion of the filler in the coating, making it difficult to exert a positive anti-corrosion effect. Furthermore, the storage modulus of the coating is still significantly improved (compared to Comparative Example 1), ensuring that the composite coating with this ratio still possesses a certain degree of wear resistance.

[0099] Comparative Example 1

[0100] The epoxy resin coating differs from that in Example 2 only in that polyurea nanofibers are not added during the preparation of the epoxy resin coating.

[0101] The epoxy resin coating prepared in this comparative example is labeled as PU-0.

[0102] The Nyquist plot of the epoxy resin coating in this comparative example after immersion in a 3.5 wt% sodium chloride solution for 28 days is shown below. Figure 3 The Byrd plot of the epoxy resin composite coating after immersion in a 3.5 wt% sodium chloride solution for 28 days is shown below. Figure 4 The dynamic mechanical-thermal analysis curves of the energy storage modulus of the epoxy resin composite coating are shown below. Figure 5 It can be seen that epoxy resin coatings without polyurea nanofiber fillers do not have sufficient anti-corrosion and wear-resistant properties, and a certain amount of polyurea nanofibers needs to be added to adjust them.

[0103] Comparative Example 2

[0104] The only difference from Example 2 is that in the preparation of the epoxy resin composite coating, polyurea nanofibers and epoxy resin matrix are mixed at a mass ratio of 0.6:100.

[0105] The epoxy resin composite coating prepared in this comparative example is labeled as PU-0.6%.

[0106] Figure 10 , Figure 11 , Figure 12 The Nyquist plot and Bode plot of the PU-0.6% composite coating after immersion in 3.5wt% sodium chloride solution for 28 days are shown, along with the dynamic mechanical-thermal analysis curve of the storage modulus. The increased amount of nanofiber filler leads to numerous defects in the epoxy resin matrix, making it easier for corrosive media to penetrate and thus affecting the anti-corrosion performance. Simultaneously, excessive filler causes slow or insufficient curing of the coating, resulting in a significant decrease in the storage modulus. Therefore, excessive filler has a considerable negative impact on the anti-corrosion and wear-resistant properties of the coating (compared to Example 2 and Comparative Example 1).

[0107] This invention prepares a dimensionally stable and high-performance two-dimensional nanofiber material through a simple addition polymerization method. Polyurea nanofibers are then introduced into an epoxy resin coating at a specific mass ratio. Results show that even a small amount of polyurea nanofibers not only improves the corrosion resistance of the coating but also enhances its wear resistance. At the optimal addition amount, polyurea nanofibers significantly reduce microscopic defects in the coating. They also prevent corrosive media from penetrating into the metal substrate, resulting in a nearly fourfold increase in the impedance of the prepared composite coating, providing durable protection even in harsh environments. Furthermore, polyurea nanofibers can significantly improve the wear resistance of the coating by reducing the wear rate by 3 / 4.

[0108] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A polyurea epoxy resin composite coating, characterized in that, It includes polyurea nanofibers and an epoxy resin matrix; wherein the weight ratio of the polyurea nanofibers to the epoxy resin matrix is ​​(0.1-0.5):(80-120); the polyurea nanofibers are obtained by addition polymerization using diisocyanate and diamine as raw materials.

2. The polyurea epoxy resin composite coating according to claim 1, characterized in that, The mass ratio of polyurea nanofibers to epoxy resin matrix is ​​(0.1-0.5):

100.

3. The polyurea epoxy resin composite coating according to claim 1, characterized in that, The epoxy resin matrix is ​​made from uncured epoxy resin, curing agent, diluent, catalyst and dispersant in a mass ratio of (4-6):(8-12):(5-10):(1-5):(1-1.5).

4. The polyurea epoxy resin composite coating according to claim 3, characterized in that, The uncured epoxy resin may be selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, cyanuric acid epoxy resin, and alicyclic epoxy resin; and / or The curing agent may be selected from one or more of tetramethylethylenediamine, diethylenetriamine, dibenzylamino ether, benzoyl peroxide, and dicyandiamine; and / or, The diluent may be selected from one or more of alkylene glycidyl ether, n-butanol, benzyl alcohol, xylene, acetone, and dimethylformamide; and / or, The catalyst may be selected from one or more of dibutyltin, tetrabutyltin, dibutyltin dilaurate, and tributyltin chloride; and / or, The dispersant may be selected from one or more of dodecyl dimethyl benzyl ammonium bromide, sodium dodecylbenzene sulfonate, polyvinyl alcohol, and hydroxypropyl methylcellulose.

5. The polyurea epoxy resin composite coating according to any one of claims 1-4, characterized in that, The preparation method of the epoxy resin matrix includes: the epoxy resin matrix is ​​mainly composed of uncured epoxy resin, curing agent, diluent, catalyst and dispersant mixed in proportion, and the epoxy resin matrix is ​​obtained after stirring.

6. The polyurea epoxy resin composite coating according to claim 1, characterized in that, The mass ratio of diisocyanate to diamine is (3.0-5.0):(3.5-4.0); and / or, The diisocyanate is selected from one of diphenylmethane diisocyanate, isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; and / or, The diamine is selected from one of diamine, ethylenediamine, diaminodiphenylmethane, o-phenylenediamine, and diethanolamine.

7. The polyurea epoxy resin composite coating according to claim 1 or 6, characterized in that, include: Provide a diamine solution, with anhydrous ethanol as the solvent; Provide diisocyanate, with ethyl acetate as solvent; The diamine solution and diisocyanate were first reacted at 40-60℃ for 1-2 hours; then, under stirring, the reaction was carried out at 70-80℃ for 80-100 minutes. After the reaction is complete, excess diisocyanate is removed by washing with water; then dried to produce polyurea nanofibers.

8. The method for preparing the polyurea epoxy resin composite coating according to any one of claims 1-7, characterized in that, The process includes mixing the polyurea nanofibers and the epoxy resin matrix; stirring; then coating the mixture onto a substrate and curing it.

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