Preparation method and application of modified graphene / polyurethane anti-erosion composite coating

Abstract

This invention provides a method for preparing a modified graphene / polyurethane anti-erosion composite coating, comprising the following steps: dry ball milling of graphene raw materials to obtain graphene powder; wet ball milling of the graphene powder with polyether polyol to obtain a modified graphene dispersion; adding the modified graphene dispersion to the polyether polyol and stirring evenly; further adding glycerol and a silane coupling agent and stirring evenly; then adding isophorone diisocyanate, a polyurethane defoamer, and dibutyltin dilaurate, stirring, and allowing to stand to obtain the modified graphene / polyurethane anti-erosion composite coating. This invention uses the polyether polyol in the base material for wet ball milling of graphene, improving the interfacial properties of graphene and enhancing its dispersion performance in the polyurethane coating matrix; it can balance the coating's water resistance, UV resistance, salt spray resistance, erosion resistance, and electrochemical properties, improving the coating's anti-erosion protection effect in hydraulic steel components.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coating technology, specifically to a method for preparing and applying a modified graphene / polyurethane anti-erosion composite coating. Background Technology

[0002] Due to the complex working conditions of the Yangtze River, the demand for high-performance erosion-resistant coatings in the steel structure building corrosion protection industry is increasing. Polyurethane, as a superior coating matrix, is highly favored for its excellent weather resistance, UV resistance, and elasticity. However, relying solely on pure polyurethane coatings for protection is insufficient to withstand the impact and abrasion from water and sand under extreme environments and harsh working conditions.

[0003] Therefore, there is an urgent need for a new type of polyurethane coating that can be applied to the working conditions of the Yangtze River to improve the water resistance, chemical corrosion resistance, and protection against external impacts and abrasion of steel structure buildings in the Yangtze River water conditions. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method for preparing and applying a modified graphene / polyurethane anti-erosion composite coating, thereby solving the technical problem that existing technologies, such as steel structure buildings relying on pure polyurethane coatings in the Yangtze River basin, cannot cope with the impact and wear of water and sand under extreme environments and harsh working conditions.

[0005] The technical solution adopted in this invention is as follows:

[0006] In a first aspect, a method for preparing a modified graphene / polyurethane erosion-resistant composite coating is provided, comprising the following steps:

[0007] Modified graphene dispersions were prepared by dry ball milling and wet ball milling with polyether polyols.

[0008] The modified graphene dispersion was added to the polyether polyol and stirred until homogeneous.

[0009] Continue adding glycerol and silane coupling agent, and stir until homogeneous;

[0010] Then, isophorone diisocyanate, polyurethane defoamer, and dibutyltin dilaurate are added, stirred, and allowed to stand to obtain a modified graphene / polyurethane anti-erosion composite coating.

[0011] Furthermore, a modified graphene dispersion was prepared by dry ball milling and wet ball milling with polyether polyol, including: dry ball milling of graphene raw materials to obtain graphene powder; adding polyether polyol to the graphene powder and wet ball milling to obtain the modified graphene dispersion.

[0012] Furthermore, polyether polyol is added to the graphene powder and wet ball milling is performed, wherein the mass ratio of polyether polyol to graphene powder is 40:1.

[0013] Furthermore, the dry ball milling time is 1 hour, and the wet ball milling time is 3 hours.

[0014] Furthermore, the mass parts of each component are as follows: graphene 0.12-1.08 parts, polyether polyol 72 parts, glycerol 1.2 parts, silane coupling agent 1.8 parts, isophorone diisocyanate 48 parts, polyurethane defoamer 0.36 parts, and dibutyltin dilaurate 0.24 parts.

[0015] Furthermore, the graphene particles account for 0.5 wt% of the polyurethane matrix.

[0016] In a second aspect, a modified graphene / polyurethane anti-erosion composite coating is provided, which is prepared using the preparation method described in the first aspect.

[0017] Thirdly, it provides applications of modified graphene / polyurethane anti-erosion composite coatings in steel corrosion protection.

[0018] Fourthly, it provides the application of modified graphene / polyurethane anti-erosion composite coatings in steel structure buildings to resist water and sand impact and abrasion.

[0019] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows:

[0020] 1. Combining ball milling and chemical modification methods, and utilizing the synergistic effect of mechanical dispersion and chemical grafting, a new, effective, and simple method for dispersing and modifying graphene is proposed. Graphene is wet-milled using polyether polyols in the base material, which improves the interfacial properties of graphene and enhances its dispersion performance in polyurethane coating matrices.

[0021] 2. The preparation method and component formulation ratio of the modified graphene / polyurethane anti-erosion composite coating were optimized. The graphene content of the prepared modified graphene / polyurethane composite coating was determined to be 0.5wt%, which can balance the coating's water resistance, UV resistance, salt spray resistance, erosion resistance, and electrochemical properties, improve the coating's protective ability, and enhance the coating's anti-erosion protection effect in hydraulic steel components. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0023] Figure 1 This is a flowchart illustrating the preparation method of the modified graphene / polyurethane erosion-resistant composite coating according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram illustrating the preparation process of the modified graphene / polyurethane anti-erosion composite coating according to an embodiment of the present invention.

[0025] Figure 3 This is a graph showing the differential distribution of graphene under different dry and wet grinding times in an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram showing the particle size of graphene samples under different conditions in the embodiments of the present invention;

[0027] Figure 5 These are optical microscopic images of different graphene dispersions in the embodiments of the present invention;

[0028] Figure 6 This is a graph showing the changes of different coatings under salt spray test in an embodiment of the present invention;

[0029] Figure 7 This is a diagram showing the changes in different coatings after being scratched in a salt spray test in an embodiment of the present invention;

[0030] Figure 8 The Nyquist plots show different coatings immersed in a 3.5 wt% sodium chloride solution for different times in embodiments of the present invention. Detailed Implementation

[0031] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0032] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0033] Example

[0034] For steel structures in the Yangtze River basin, the main causes of corrosion and coating peeling are water and sand erosion, electrochemical corrosion, and ultraviolet radiation damage. To enhance the protective ability of polyurethane coatings against these effects, this embodiment provides a modified graphene / polyurethane anti-erosion composite coating, such as... Figure 1 , Figure 2 As shown, it is prepared using the following method:

[0035] S1. Modified graphene dispersion was prepared by dry ball milling and wet ball milling with polyether polyol.

[0036] Graphene sheets exhibit strong interlayer forces, making them prone to interlayer stacking and aggregation. Furthermore, the surface of graphene typically contains oxides or other functional groups, which can affect the compatibility between graphene and the coating matrix, leading to dispersion difficulties. The properties of the coating and its compatibility with graphene also influence dispersion stability. Therefore, the preparation of composite coatings must first address the dispersion problem of graphene in polyurethane, requiring a comprehensive consideration of both the inherent properties of graphene and the properties of the polyurethane matrix to select an appropriate dispersion method.

[0037] In this embodiment, a novel, effective, and simple method for dispersing and modifying graphene is provided by combining ball milling and chemical modification, utilizing the synergistic effect of mechanical dispersion and chemical grafting. This method subjects graphene particles to the impact and friction of steel balls in a ball mill jar, causing shear forces between the sheet-like particles. This leads to deformation and breakage of the graphene particles, reducing the interaction forces between particles and improving their compatibility with the polyurethane matrix in subsequent processing steps, thus promoting uniform dispersion. The chemical modification method, by modifying the graphene surface with functional groups, enhances its affinity with the polyurethane matrix in subsequent processing steps, thereby strengthening its compatibility with the polyurethane matrix and promoting the dispersion stability of graphene.

[0038] Specifically as follows:

[0039] S11. Dry ball milling of graphene raw materials to obtain graphene powder.

[0040] First, prepare the graphene raw materials, grinding jar, and grinding balls. Calculate the grinding ball ratio based on the Hosfield theory. Dry the graphene raw materials, grinding jar, and grinding balls in a 60℃ oven until ready for use.

[0041] Dry graphene raw materials and ball milling media are placed into a ball mill jar, and the ball mill is started to dry-mill for a certain period of time using the rolling and impact action of the ball milling media to obtain graphene powder.

[0042] In some embodiments, small-sized few-layer graphene powder can be obtained by filtering with a clean sieve, which facilitates further wet ball milling dispersion of graphene in polyether polyols during subsequent processing steps.

[0043] S12. Add polyether polyol to graphene powder and perform wet ball milling.

[0044] After dry ball milling, a modified graphene dispersion was prepared by wet ball milling of graphene powder with polyether polyol, combining ball milling and chemical modification methods. Upon starting the ball mill, the size of the graphene particles gradually decreases due to shearing, increasing the contact area between the particles and the polyether polyol molecules. This allows the polyether polyol to better encapsulate the graphene particles, improving the dispersion effect and achieving both physical dispersion and chemical modification of the graphene.

[0045] Experiments revealed that during the wet ball milling of graphene powder and polyether polyol compositions, insufficient graphene powder content leads to inadequate shear force, hindering wet ball milling, affecting dispersion, and impeding subsequent dilution for dispersion preparation. Conversely, excessive graphene powder content results in overly viscous mixed solutions, making wet ball milling difficult, wasting raw materials, and hindering direct sampling after wet ball milling. In some embodiments, the mass ratio of polyether polyol to few-layer graphene powder was set to 20:1, 30:1, 40:1, and 50:1, and flowability and viscosity were observed to analyze the ball milling phenomenon. The preferred technical solution was determined to be a mass ratio of 40:1 for the wet ball milled graphene powder and polyether polyol composition.

[0046] For the ball milling process described above, controlling the rotation speed and time of the ball mill is crucial to achieving the desired dispersion effect. Experiments revealed that if the ball mill speed is too low or the time is too short, it may fail to provide sufficient mechanical shearing and impact forces, leading to aggregation and accumulation of graphene particles, resulting in poor dispersion. Conversely, if the ball mill speed is too high or the time is too long, it may cause excessive mechanical shearing and impact, potentially damaging and thermally injuring the graphene particles, thus compromising their structure and properties. Through continuous parameter adjustments, the optimal technical solution was determined to be: a ball mill speed of 600 r / min, dry ball milling for 1 hour, and wet ball milling for 3 hours. The specific experimental process is as follows:

[0047] The graphene raw material was directly dry-ball-milled for 1 hour, and the resulting powder was then subjected to particle size testing. The testing equipment was a laser particle size analyzer, which is an instrument used to measure particle size distribution. It can quickly and accurately measure parameters such as the average particle size and particle size distribution curve to determine the particle size distribution. Figure 3 As shown in Figure a, it can be clearly observed that the differential particle distribution curve of graphene raw materials after 1 hour of dry grinding exhibits two peaks. The average particle sizes corresponding to these two peaks, calculated using the peak method, are 60 nm and 17 μm, respectively. The figure shows that after direct dry ball milling, the size of the small graphene particles is mainly concentrated around 60 μm, while a small number of larger particles are concentrated around 17 μm, indicating uneven particle size distribution and some particle agglomeration. Figure 4As shown, the D10 particle size of the graphene raw material after dry milling for 1 hour is 41 nm, the D50 particle size is 78 nm, and the D90 is 18.13 μm. The purchased graphene raw material has a D50 of about 7-12 μm, indicating that the particle size of the graphene raw material is significantly reduced under the action of dry ball milling.

[0048] The graphene powder obtained after dry grinding for 1 hour was mixed with a certain proportion of polyether polyol and ball-milled for 1 hour, followed by particle size testing. Figure 3 As shown in Figure b, the particle differential distribution curve exhibits multiple peaks with asymmetrical shapes, indicating variations in particle size and uneven distribution. This is because the addition of the polyol, the short ball milling time, insufficient shearing and exfoliation, incomplete chemical modification, and particle aggregation interact, increasing the complexity of the particle size distribution and resulting in different peak patterns. Figure 4 As shown, the D10, D50, and D90 particle sizes all increased after wet milling for 1 hour, especially the D90 particle size, which reached 631.2 μm, indicating that the particles were encapsulated and aggregated after the addition of polyether polyol.

[0049] Extending the wet milling time, graphene powder was mixed with a certain proportion of polyether polyol and ball-milled for 3 hours, followed by particle size testing. As shown in Figure 3c, the particle size distribution curve exhibits a single peak with a relatively symmetrical shape and a narrow curve, with a peak value of 21.741 μm. This indicates that the particle size distribution is relatively uniform, mainly distributed around 21.741 μm, demonstrating good particle dispersion, with particle sizes generally smaller than those produced after 1 hour of wet milling. This is because the mechanical force during wet milling causes the graphene sheets to gradually peel off. In the initial stage, these peeled particles may exist in different size distributions due to various reasons, resulting in multiple peak values. As the wet milling time increases, the peeling and dispersion process of the polyether polyol-modified graphene gradually completes, contributing to the particle size distribution curve gradually approaching a single peak. Figure 4 As shown, the particle sizes of D10 (1.769 μm), D50 (11.58 μm), and D90 (36.27 μm) after wet milling for 3 hours are relatively similar and all larger than the particle sizes of particles after dry milling for 1 hour.

[0050] Graphene powder was mixed with a certain proportion of polyether polyol and ball-milled for 4 hours, followed by particle size testing. Figure 3 As shown in the figure, the particle size distribution curve is relatively narrow, with the highest peak at 21.741 μm, exhibiting a bimodal phenomenon. This may be because excessive ball milling time leads to mechanical damage and structural reorganization of the particle surface, affecting the particle size distribution. Figure 4As shown, the particle sizes of D10 after 4 hours of wet milling are 1.883 μm, D50 after 4 hours of wet milling are 15.07 μm, and D90 after 4 hours of wet milling are 31.39 μm. The particle sizes are also relatively similar. However, the particle sizes of D10 and D50 are larger than those of particles after 3 hours of wet milling. This indicates that excessively long wet milling time will affect the particle size distribution.

[0051] Analysis of the above experimental results revealed that mixing dry-milled graphene powder with a certain proportion of polyether polyol and ball-milling for 3 hours resulted in a relatively symmetrical single-peak particle size distribution curve, indicating the most uniform particle size distribution. Insufficient wet ball milling time may lead to large differences in particle size and poor dispersibility; excessive wet ball milling time may cause structural remodeling and wear on the particle surface, affecting the uniformity of particle size distribution.

[0052] The properties of the graphene dispersion prepared in this step are analyzed below:

[0053] Two samples were prepared for comparative testing. Modified graphene dispersions, obtained by dry grinding and wet grinding assisted by polyether polyol, were added to the polyether polyol and stirred for a certain time to prepare modified graphene dispersion sample 1. Untreated graphene was directly added to the polyether polyol and stirred for a certain time to prepare the original graphene dispersion sample 2 with the same amount of added graphene.

[0054] Images of the two dispersions were observed using an optical microscope, such as... Figure 5 As shown. Figure 5 The three images on the left (a, b, and c) are modified graphene dispersion sample 1, and the three images on the right (d, e, and f) are original graphene dispersion sample 2. From... Figure 5 It can be seen that, at different magnifications, the directly prepared original graphene dispersion sample 2 has a larger and more varied particle size, with large and uneven spacing between graphene particles, and numerous agglomeration and aggregation phenomena, especially compared to... Figure 5 The graphene particles in the c-wave and f-wave configurations were compared. The graphene particles in the f-wave configuration, after agglomeration, were tens of times larger than those in the c-wave configuration, indicating a significantly poor dispersion effect from the original graphene. The modified graphene dispersion sample 1 showed significantly smaller particle sizes, ranging from several micrometers to tens of nanometers. Furthermore, at different agglomeration levels, the spacing between graphene particles was appropriate, the particle distribution was relatively uniform, agglomeration was significantly reduced, and the dispersion effect was significantly improved. This demonstrates that the size and structure of the graphene particles changed under the new ball milling modification method, the utilization rate of graphene in the polyether polyol liquid phase system was improved, and the compatibility between graphene and polyether polyol was enhanced. The graphene dispersion method provided in this embodiment can effectively enhance the dispersion effect.

[0055] The stability of the graphene dispersion was evaluated: Modified graphene dispersion sample 1 and original graphene dispersion sample 2, with equal amounts added, were placed in two separate glass vials for dispersion stability observation. Environmental conditions were ensured to be identical for both samples. Photos were taken at regular time intervals over time to allow for a direct comparison and analysis of the dispersion effects. Figure 6 As shown, graphs a, b, c, and d correspond to the stratification after 2 hours, 24 hours, 120 hours, and 400 hours of precipitation, respectively. From... Figure 6 As can be seen, after 2 hours of precipitation, particles began to settle to the bottom in Sample 2, and the distribution of suspended particles was uneven; Sample 1 was uniformly dispersed, with no precipitation or agglomeration. After 24 hours of precipitation, the number of suspended particles in Sample 2 decreased and obvious stratification began to appear; Sample 1 remained unchanged. After 120 hours of precipitation, the number of suspended particles in Sample 2 decreased further, the particle settling rate was fast, and most of the graphene particles settled to the bottom of the bottle; Sample 1 remained uniformly dispersed without stratification or settling. After 400 hours of precipitation, almost all the graphene particles in Sample 2 settled to the bottom, and the graphene and polyether polyol were completely stratified; Sample 1 still maintained good dispersion, without obvious stratification, suspension, or precipitation.

[0056] Through the above analysis and comparison, the modified graphene dispersion prepared in this step can be used to wet-modify ball-milled graphene with polyether polyol, one of the raw materials for preparing polyurethane coatings. This can effectively enhance the compatibility between graphene and polyurethane coatings, improve the dispersion effect of graphene in coatings, and help improve the uniformity and stability of polyurethane composite coatings.

[0057] S2. Add a certain mass of modified graphene dispersion to a certain mass of polyether polyol and stir evenly; then add an appropriate amount of glycerol (GI) and silane coupling agent (KH-560) and stir evenly; continue to add a certain mass of isophorone diisocyanate (IPDI), polyurethane defoamer (B-454), and dibutyltin dilaurate (DBTDL), stir and let stand. Preferably, stir for 5 minutes with an electric mixer and let stand for 10 minutes to make the graphene evenly dispersed in the coating to obtain the modified graphene / polyurethane anti-erosion composite coating.

[0058] In a specific embodiment, preferably, the mass parts of each component are as follows: 0.12-1.08 parts of graphene, 72 parts of polyether polyol, 1.2 parts of glycerol, 1.8 parts of silane coupling agent, 48 parts of isophorone diisocyanate, 0.36 parts of polyurethane defoamer, and 0.24 parts of dibutyltin dilaurate.

[0059] In use, the modified graphene / polyurethane anti-erosion composite coating prepared above is coated on a steel substrate of a certain size, the film thickness is controlled, and it is cured at room temperature for 24 hours to obtain the modified graphene / polyurethane anti-erosion composite coating (MGOPU).

[0060] The modified graphene / polyurethane anti-erosion composite coating can be prepared with various different graphene content ratios. In order to screen out the optimal amount of modified graphene and optimize the composite coating formulation, five modified graphene / polyurethane anti-erosion composite coatings with different graphene contents were prepared, with the mass fraction of graphene particles in the polyurethane matrix being 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, and 0.9wt%, respectively.

[0061] Water resistance and erosion resistance tests were conducted on the five composite coatings with different graphene content ratios. The coating characteristics were compared and analyzed, as follows:

[0062] Water resistance test: Referring to the "Determination of Water Resistance of Coating Films" (GB / T 1733-1993), the water resistance of the coatings was tested using the immersion test method. Five composite coatings with different graphene contents were subjected to a 360-hour water resistance test. As shown in Table 1, with the increase of graphene content, the mass change of the modified graphene / polyurethane anti-erosion composite coating was initially large, then decreased, and subsequently increased again. The appearance morphology of the coating also showed a corresponding trend. The composite coating did not exhibit serious peeling, blistering, or corrosion. The MGOPU (0.5wt%) coating showed the smallest mass change, at 0.0047g, indicating that it did not show significant changes and thus had good water resistance.

[0063] Table 1 Results of 360h water resistance test

[0064]

[0065] Erosion resistance test: An accelerated erosion wear test device was used for the erosion resistance test, with the stone and sand particle size set to be less than 1.18 mm and the sand content to be 30 kg / m³. 3 The stirrer was set at 300 r / min, and five composite coatings with different graphene contents were subjected to a 36-hour erosion resistance test. Changes in coating thickness and gloss were observed. As shown in Table 2, the thickness change of all coatings was less than 30 μm, indicating that the addition of graphene improved the wear resistance of the coatings with minimal thickness damage. The gloss of the coatings varied with different graphene contents. The MGOPU (0.1 wt%), MGOPU (0.3 wt%), and MGOPU (0.9 wt%) coatings showed significant gloss changes, while the MGOPU (0.5 wt%) coating exhibited the smallest changes in both thickness and gloss. This indicates that the erosion test has a significant impact on the coating gloss, and different graphene contents lead to differences in erosion resistance.

[0066] Table 2 Results of 36h erosion resistance test

[0067]

[0068] UV resistance test: Referring to the standard "Artificial Climate Aging Exposure of Paint and Varnish Coatings to Fluorescent Ultraviolet Light and Water" (GB / T 23987-2009), a UV aging test was conducted. The irradiance was set at 0.76 W / m² at 340 nm, and the temperature was set at 63℃. Five composite coatings with different graphene contents were subjected to a 36-hour UV resistance test, and the changes in coating thickness and gloss were observed. As shown in Table 3, the thickness changes of MGOPU (0.1 wt%), MGOPU (0.5 wt%), and MGOPU (0.9 wt%) were relatively small, while the thickness changes of MGOPU (0.3 wt%) and MGOPU (0.7 wt%) were relatively larger. However, the coating thickness changes did not exceed 30 μm, which is attributed to the combined effect of the coating's inherent UV resistance and the sheet-like structure of graphene. The gloss of the coating initially decreased and then increased with increasing graphene content, with MGOPU showing the largest increase.

[0069] The gloss change was minimal at 0.5 wt%, indicating that the graphene content should not be too high. Excessive graphene content may lead to accumulation and agglomeration, resulting in a rough coating surface and significantly affecting optical properties. It is evident that appropriately and uniformly filling the coating with graphene particles can improve the smoothness and gloss of the coating surface, and also provides a certain degree of UV resistance.

[0070] Table 3 Results of 36h UV resistance test

[0071]

[0072]

[0073] The above experiments show that appropriately controlling the graphene content is crucial for the protective performance of the coating. A reasonable graphene content can balance the mechanical and optical properties of the coating, thereby improving its protective efficacy. Combining preparation research and performance analysis, the MGOPU (0.5wt%) coating was found to have the best relative performance, thus determining it as the optimal formulation for graphene / polyurethane anti-erosion composite coatings.

[0074] To analyze the characteristics of the MGOPU (0.5wt%) coating, five coating samples were prepared: a polyurethane coating (PU), a thick-film epoxy glass flake coating (TSEGSC), a carbon black / polyurethane composite coating (CBPU) prepared by adding 0.5wt% carbon black to a polyurethane coating, a raw graphene / polyurethane composite coating (PGOPU) prepared by adding 0.5wt% raw graphene to a polyurethane coating, and a modified graphene / polyurethane composite coating (MGOPU) prepared by adding 0.5wt% modified graphene to a polyurethane coating. The above five coatings were subjected to the following performance tests: water resistance, erosion resistance, UV resistance, salt spray resistance, and electrochemical impedance spectroscopy analysis to evaluate the comprehensive protective performance of MGOPU.

[0075] Water resistance test: Referring to the "Determination of Water Resistance of Coating Films" (GB / T 1733-1993), the immersion test method was used to test the water resistance of the coatings, and the test time was 360 hours. The test results are shown in Table 4. The TSEGSC coating showed the largest change in quality and exhibited discoloration and cracking, indicating that its water resistance was generally poor. The CBPU, PGOPU, and MGOPU coatings with added carbon black, virgin graphene, and modified graphene, respectively, all showed smaller changes in quality than the PU coating, indicating that the addition of inorganic fillers such as carbon black, virgin graphene, and modified graphene can improve the water resistance of PU to a certain extent. Observation of the surface appearance of the coatings after water resistance testing revealed that the PU coating exhibited whitening, minor blistering, and slight corrosion. The PGOPU coating with added raw graphene showed discoloration, minor blistering, and more significant corrosion, indicating that water molecules had reached the steel structure surface. Ironically, the coating's water resistance was even worse. This is related to the uneven aggregation and dispersion of graphene in the coating; the aggregated graphene particles could not completely fill the coating, resulting in a rough surface and affecting its water resistance. The MGOPU coating, however, showed no significant changes in quality or appearance, maintaining good water resistance.

[0076] Table 4 Results of 360h Water Resistance Test

[0077]

[0078]

[0079] Erosion resistance test: An accelerated erosion wear test device was used for the erosion resistance test, with the stone and sand particle size set to be less than 1.18 mm and the sand content to be 30 kg / m³. 3The stirrer speed was 300 r / min, and the test time was 108 h. The changes in coating thickness and gloss were observed. The test results are shown in Table 6. After 108 h of erosion aging test, the TSEGSC coating showed the largest change in thickness. This coating has high hardness, high brittleness, and low adhesion, resulting in weak resistance to water and sand erosion. The thickness changes of CBPU and PGOPU were greater than those of the PU coating. This is related to the low carbon black content and uneven dispersion of the original graphene, which led to a decrease in the coating's resistance to water and sand erosion. The MGOPU coating showed the smallest change in thickness, indicating its strong resistance to water and sand abrasion. As for the gloss of the coating, the gloss loss rate of PU, TSEGSC, and PGOPU were all higher than 50%, while MGOPU still had the lowest gloss loss rate at 15.43%, indicating that uniformly dispersed modified graphene can resist erosion and maintain good gloss, and has good erosion resistance.

[0080] Table 6 Results of 108h erosion resistance test

[0081]

[0082] Then, an accelerated erosion aging test was conducted using an accelerated erosion wear test device for 3 minutes. The appearance of the coating was observed and analyzed. Based on the test data, the thickness change and quality damage of the coating were analyzed to further evaluate the coating's erosion resistance. The test results are shown in Table 7. Under the 3-minute accelerated erosion aging test, the TSEGSC coating showed the largest thickness change, far exceeding the other four coatings, indicating severe erosion wear. The thickness changes of the other four coatings were very small, not exceeding 20 μm.

[0083] Table 7. Changes in mass and thickness during accelerated erosion resistance testing.

[0084]

[0085] Overall, MGOPU coating has good erosion resistance, followed by CBPU coating, TSEGSC coating has very poor erosion resistance, and PGOPU has reduced erosion resistance due to graphene agglomeration and dispersion issues.

[0086] UV Resistance Test: Five coatings were subjected to a 120-hour accelerated UV aging test. The thickness change and gloss loss rate of the coatings were observed. The results are shown in Table 8. The TSEGSC coating showed the largest thickness change, far exceeding the other four coatings, indicating extremely poor light stability. This is related to the epoxy groups contained in the coating. Aromatic ether bonds are easily broken under UV light irradiation, which may cause surface chalking and lead to significant thickness changes. The CBPU, PGOPU, and MGOPU coatings showed relatively small thickness changes, all around 20 μm. Regarding gloss, PGOPU had the largest gloss loss rate, followed by MGOPU, while CBPU had the smallest. This indicates that uniformly dispersed modified graphene and carbon black can improve UV resistance. However, the PGOPU coating, like the PU coating, exhibited significant gloss loss, which is related to the agglomeration and uneven dispersion of graphene. The MGOPU coating showed the smallest thickness change and gloss loss rate after UV aging, verifying its superior UV resistance and good light stability.

[0087] Table 8 Results of 120h UV resistance test

[0088]

[0089] Salt spray resistance test: The salt spray resistance test is an environmental test that uses artificially simulated salt spray conditions to assess the corrosion resistance of metallic materials. It is an important aspect of evaluating the comprehensive protective capability of coatings. Referring to the standard "Determination of Neutral Salt Spray Resistance of Paints and Varnishes" (GB / T1771-2007), five coatings were first subjected to a neutral salt spray test for 24-384 hours. Further tests were then conducted, and the salt spray resistance of the coatings was observed.

[0090] Figure 6 From left to right, images a, b, c, d, and e correspond to PU, TSEGSC, CBPU, PGOPU, and MGOPU coatings, respectively. Figure 6 As shown in Table 9, the steel substrate exhibited severe corrosion after salt spray testing, which worsened over time, indicating that salt spray testing accelerates the corrosion rate of the steel substrate. Specifically, the PU coating showed slight blistering and a few rust spots after 48 hours, and moderate rust spots after 384 hours, with numerous blisters surrounding the rust spots. The TSEGSC coating had an uneven surface, showing several rust spots after 96 hours and a few more after 384 hours, but scraping off the coating revealed small areas of localized corrosion. The CBPU coating showed slight contamination and a few rust spots after 96 hours, with only slight deterioration between 96 and 384 hours. The PGOPU coating showed slight blistering and numerous rust spots after 24 hours, reaching dense rust spots by 384 hours, exhibiting the worst salt spray resistance; the unevenly dispersed graphene accelerated corrosion. The MGOPU coating showed very slight contamination, with no significant change during the 384-hour salt spray test, exhibiting the longest salt spray resistance.

[0091] Table 9 Results of Neutral Salt Spray Test

[0092]

[0093] Figure 7 From left to right, images a, b, c, d, and e correspond to PU, TSEGSC, CBPU, PGOPU, and MGOPU coatings, respectively. (Refer to Table 10 and...) Figure 7 Further analysis of the salt spray corrosion after the coatings were scored revealed the following grades: corrosion propagation along the score line greater than 2mm was grade A, less than 2mm was grade B, greater than 1mm was grade C, and less than 1mm was grade D. The PU coating began to show corrosion propagation along the score line less than 2mm after 96 hours, with moderate rust spots appearing nearby. The TSEGSC coating showed corrosion propagation along the score line greater than 1mm after 192 hours, with several rust spots, but localized corrosion appeared within the coating itself; a comprehensive analysis of corrosion resistance is needed in conjunction with electrochemical testing. The CBPU coating showed corrosion propagation along the score line less than 1mm after 96 hours, with a few rust spots. The PGOPU coating showed corrosion propagation along the score line greater than 2mm, with many rust spots. The MGOPU coating showed corrosion propagation along the score line less than 1mm after 384 hours, with no obvious rust spots, indicating good resistance to transverse corrosion.

[0094] Neutral salt spray test results showed that, based on the apparent appearance, the salt spray resistance generally followed the order MGOPU > CBPU > TSEGSC > PU > PGOPU. This indicates that the MGOPU coating exhibits better salt spray resistance, suggesting that uniformly dispersed modified graphene helps improve the salt spray performance of the polyurethane coating. The poor salt spray resistance of the PGOPU coating is attributed to graphene agglomeration and dispersion issues. While the TSEGSC coating showed less obvious changes in appearance, scraping it revealed internal corrosion. Therefore, further analysis using electrochemical impedance spectroscopy is needed to comprehensively assess the coating's corrosion resistance.

[0095] Table 10 Results of Cross-Marking of Coatings in Neutral Salt Spray Test

[0096]

[0097] Electrochemical impedance spectroscopy (EIS) analysis: EIS is an effective means of evaluating the corrosion resistance of materials and is of great significance in assessing the corrosion performance of coatings. It is usually analyzed in the form of Bode plots and Nyquist plots, both of which can provide important information about the electrochemical performance of coatings.

[0098] like Figure 8As shown, five different coatings were immersed in a 3.5 wt% sodium chloride solution for 0.5 h and 384 h, respectively. During the test, the Nyquist plot capacitive arc radius showed a pattern of MGOPU > CBPU > TSEGSC > PU > PGOPU. Simultaneously, with time, the impedance point location and capacitive radius of all coatings decreased, indicating a certain degree of decrease in the protective ability of the coatings. The MGOPU coating maintained the best performance, while PGOPU showed the greatest change.

[0099] Electrochemical impedance spectroscopy (EIS) analysis revealed the following Nyquist plot capacitive arc radius: MGOPU > CBPU > TSEGSC > PU > PGOPU. The PGOPU coating exhibited the worst salt spray resistance and electrochemical performance, indicating that the dispersibility of graphene significantly impacts the coating's protective effect; agglomeration and uneven dispersion may accelerate corrosion. The MGOPU coating, with its high impedance point, large capacitive arc radius, and minimal variation, demonstrates excellent electronic isolation, effectively preventing the transport of electrons and ions between the metal surface and the surrounding environment, thus slowing down or preventing metal corrosion. The results of the electrochemical impedance spectroscopy test are consistent with those of the salt spray test, indicating that the MGOPU coating possesses good anti-corrosion performance.

[0100] By comparing the above experimental data, it can be concluded that the polyurethane composite coating MGOPU with modified graphene has the best overall protective ability, but the polyurethane composite coating PGOPU with original graphene does not perform well in terms of overall protective ability, and it is the worst in salt spray resistance and electrochemical impedance spectroscopy tests. This indicates that the dispersibility of graphene has a great influence on the protective effect of the coating. Agglomeration and uneven dispersion will accelerate the corrosion of the coating. Therefore, the addition of graphene to polyurethane requires high graphene dispersibility. The modified graphene dispersion preparation method described above in this embodiment can solve this technical problem.

[0101] This embodiment also provides a modified graphene / polyurethane anti-erosion composite coating, which is prepared using the preparation method of the modified graphene / polyurethane anti-erosion composite coating described above.

[0102] This embodiment also provides the application of modified graphene / polyurethane anti-erosion composite coatings in steel corrosion protection, especially in the application of hydraulic steel components in anti-erosion protection.

[0103] This embodiment also provides the application of modified graphene / polyurethane anti-erosion composite coatings in steel structure buildings to resist water and sand impact and abrasion.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a modified graphene / polyurethane erosion-resistant composite coating, characterized in that, The method comprises the following steps: Preparation of modified graphene dispersion liquid by dry ball milling and polyether polyol wet modification ball milling; Add the modified graphene dispersion liquid into the polyether polyol and stir uniformly; Continue to add glycerol and silane coupling agent and stir uniformly; Then add isophorone diisocyanate, polyurethane defoaming agent and dibutyl tin dilaurate, stir and stand to obtain the modified graphene / polyurethane anti-erosion composite coating.

2. The production method according to claim 1, characterized by, Preparation of modified graphene dispersion liquid by dry ball milling and polyether polyol wet modification ball milling, comprising: Dry ball milling of graphene raw material to obtain graphene powder; Wet ball milling of graphene powder by adding polyether polyol to obtain modified graphene dispersion liquid.

3. The preparation method according to claim 2, characterized in that, Wet ball milling of graphene powder by adding polyether polyol, and the mass ratio of polyether polyol to graphene powder is 40:

1.

4. The production method according to claim 2, characterized by, The dry ball milling time is 1h and the wet ball milling time is 3h.

5. The method of claim 1, wherein, The mass parts of each component are as follows: graphene 0.12-1.08 parts, polyether polyol 72 parts, glycerol 1.2 parts, silane coupling agent 1.8 parts, isophorone diisocyanate 48 parts, polyurethane defoaming agent 0.36 parts and dibutyl tin dilaurate 0.24 parts.

6. The preparation method according to claim 5, characterized in that, The mass fraction of graphene particles in the polyurethane base material is 0.5wt%.

7. A modified graphene / polyurethane erosion resistant composite coating characterized in that, The preparation method is prepared by any one of claims 1-6.

8. Application of the modified graphene / polyurethane anti-erosion composite coating of claim 7 in steel corrosion prevention.

9. Application of the modified graphene / polyurethane anti-erosion composite coating of claim 7 in resisting water and sand impact and wear of steel structure building.

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