Self-repairing graphene-based wind driven generator blade protective film and preparation method thereof

Abstract

The invention discloses a self-repairing graphene-based wind driven generator blade protection film and a preparation method thereof, and relates to the technical field of wind power generation equipment protection. The protection film adopts a gradient structure of a bonding buffer layer, a self-repairing functional layer and a multifunctional protection layer; the self-repairing functional layer comprises a hybrid network formed by hydroxylated functionalized graphene and elastomer particles and bionic packaging microcapsules, inner layer capsules containing graphene quantum dot reinforced resin and a latent catalyst curing agent are packaged in the microcapsules, multiple times of repairing of the same damaged area can be achieved, and the repairing strength is high; the multifunctional protective layer endows the coating with super-hydrophobic, anti-icing and ultraviolet-resistant functions through fluorinated graphene and nano TiO2 (at) ZnO composite particles; the preparation process is mature, the comprehensive protection performance is excellent, and the coating is suitable for wind driven generator blade protection in the severe environment.

Description

Technical Field

[0001] This invention relates to the field of wind power equipment protection technology, specifically a self-healing graphene-based wind turbine blade protective film and its preparation method. Background Technology

[0002] Wind turbine blades are exposed to harsh outdoor environments for extended periods, enduring ultraviolet radiation, rain erosion, sand and dust abrasion, hail impact, and salt spray corrosion in marine environments. This makes the surface coating prone to microcracks and peeling. These damages not only affect aerodynamic performance but also allow moisture to penetrate the composite material layers, leading to more severe structural failure. Currently, blade maintenance relies primarily on manual inspections and downtime repairs, which are costly and inefficient.

[0003] Self-healing materials offer a new approach to solving the aforementioned problems. Currently, in the field of coating materials, self-healing methods based on microcapsule technology have been studied. The typical mechanism involves encapsulating a repair agent or curing agent within microcapsules and dispersing them within the coating matrix; when the coating is damaged and cracks occur, the microcapsules rupture, releasing their contents, and repair is achieved through a chemical reaction or physical process. However, existing technologies in this field generally have the following shortcomings: (1) Most existing designs use single-layer microcapsules. Once they rupture and release, the contents are exhausted at once, making it impossible to repair the same damaged area again. The self-repair function has the limitation of being "one-time".

[0004] (2) The repair reaction often occurs on the surface of the crack. The interfacial bonding force between the newly generated repair body and the original substrate coating is weak, resulting in a low recovery rate of mechanical properties in the repaired area, which is difficult to meet the high requirements of wind turbine blades for coating load-bearing capacity and durability.

[0005] (3) Commonly used repair chemical reactions (such as some epoxy-amine curing systems) are sensitive to environmental conditions such as temperature and humidity. In low temperature or high humidity environments, the fluidity, reaction rate and curing degree of the repair agent may decrease significantly, resulting in low repair efficiency or even complete failure, which limits its application in harsh environments such as cold regions or offshore wind fields.

[0006] Therefore, developing a blade protective film that can achieve multiple efficient self-repairs, has high repair strength, and strong environmental adaptability is of urgent need and great significance for reducing wind power operation and maintenance costs, extending blade service life, and improving wind farm operation efficiency. Summary of the Invention

[0007] This invention provides a self-healing graphene-based protective film for wind turbine blades and its preparation method to solve the above-mentioned problems.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A self-healing graphene-based wind turbine blade protective film includes an adhesive buffer layer, a self-healing functional layer, and a multi-functional protective layer arranged sequentially from the surface of the blade substrate outwards. The adhesive buffer layer comprises an epoxy resin matrix, elastomer particles dispersed therein (such as polyurethane elastomer particles with a particle size of about 1 μm and a Shore hardness of A60-A80), and a silane coupling agent (such as a compound of KH-560 and KH-550). Its main function is to provide excellent interfacial adhesion, impact buffering, and stress transition. The self-healing functional layer comprises an epoxy resin matrix, hydroxylated functionalized graphene dispersed therein, elastomer particles (such as polyurethane elastomer particles with a particle size of 50-100 nm and a Shore hardness of A40-A60), and biomimetic encapsulation microcapsules; the hydroxylated functionalized graphene and elastomer particles form hydrogen bonds in the matrix through surface hydroxyl groups, constructing a "rigid island-flexible sea" hybrid network. This network not only improves the mechanical properties of the coating body but also guides the directional diffusion of the repair agent and enhances the repair interface; The biomimetic encapsulation microcapsule has a two-level nested structure, a biomimetic "pine cone-pine nut" type two-component microcapsule encapsulation structure, including an outer protective capsule (pine cone) and multiple inner repair capsules (pine nuts) encapsulated inside it; the inner repair capsules include type A capsules and type B capsules, the wall material of type A capsules is urea-formaldehyde resin, and the core material is a repair resin containing epoxy resin and graphene quantum dots; the wall material of type B capsules is gelatin-gum arabic composite, and the core material is a curing system containing modified amine curing agents and latent catalysts. The burst strength of the outer protective capsule is lower than that of the inner type A capsules and type B capsules.

[0009] When microcracks appear in the coating, the stress at the crack tip first causes the weaker outer protective capsule to rupture, releasing a large number of A and B type inner capsules. Under the pressure and friction of the crack, some A and B capsules are simultaneously ruptured. The resin and curing agent mix and cure rapidly under the action of a latent catalyst, achieving the first repair. The remaining unruptured inner capsules are embedded in the repaired "scar". When damage occurs again near this location, the stress can directly act on these residual capsules, triggering their rupture and achieving a second or even third repair.

[0010] The graphene quantum dots (GQDs) in the A-type capsule core material act as "nanorodivers," migrating to the crack interface during repair. Through their surface functional groups, they form strong forces with the matrix, greatly enhancing the repair strength. Meanwhile, the hybrid network formed by the hydroxylated functionalized graphene and elastomer particles interpenetrating in the epoxy resin matrix in the self-healing functional layer matrix provides additional toughness and strength to the coating and improves the dispersibility of the microcapsules.

[0011] The multifunctional protective layer comprises fluorosilicone modified resin, fluorinated graphene, and nano-TiO2@ZnO composite particles. Fluorinated graphene provides a superhydrophobic surface, while nano-TiO2@ZnO provides UV resistance and photocatalytic self-cleaning function. The nano-TiO2@ZnO composite particles have a core-shell structure, with TiO2 as the core and ZnO as the shell, and a particle size of 20-50 nm. The mass ratio of TiO2 to ZnO is 7:3.

[0012] The dynamic modulus of the adhesive buffer layer is 0.5-1.0 GPa, the dynamic modulus of the self-healing functional layer is 1.5-2.5 GPa, and the dynamic modulus of the multifunctional protective layer is 3.0-4.0 GPa. The dynamic modulus is measured by dynamic mechanical analysis (DMA) under the conditions of 25°C and 1Hz.

[0013] The three-layer structure forms a modulus gradient from flexible to rigid, working together to achieve strong adhesion, intelligent repair, and comprehensive protection.

[0014] Preferably, the preparation method of the hydroxylated functionalized graphene is as follows: graphene powder is added to a hydrogen peroxide aqueous solution with a concentration of 30-50 wt%, and refluxed at 80-100℃ for 4-6 hours. After filtration, it is washed with deionized water until neutral, and then vacuum dried to obtain hydroxylated functionalized graphene with a hydroxyl content of 4-6 wt% and a sheet size of 1-5 μm.

[0015] Preferably, the bursting strength of the outer protective capsule is 0.5-1.0 MPa, the bursting strength of the type A capsule is 2.5-3.5 MPa, and the bursting strength of the type B capsule is 3.5-4.5 MPa. The bursting strength test method is as follows: a miniature pressure testing machine is used, equipped with a spherical indenter with a diameter of 1 mm, and the loading speed is 0.01 mm / s. The maximum pressure when a single capsule bursts is tested, and the average value of 30 capsules is taken.

[0016] Preferably, the outer protective capsule has a particle size of 50-100 μm, and the inner repair capsule has a particle size of 5-15 μm; the dry weight ratio of the type A capsule to the type B capsule is 1:0.8-1.2; in the core material of the type A capsule, the content of graphene quantum dots is 3-9 wt% of the epoxy resin mass; in the core material of the type B capsule, the latent catalyst is 2-ethyl-4-methylimidazole, and its content is 1-3 wt% of the total mass of the curing system.

[0017] Preferably, the wall material of the type A capsule and / or type B capsule further contains 1-2 wt% nano-silica particles based on the solid mass of the wall material.

[0018] The present invention also provides a method for preparing the above-mentioned self-healing graphene-based wind turbine blade protective film, comprising the following steps: S1. Preparation of Type A Capsule Suspension: Epoxy resin and graphene quantum dot dispersion are mixed as the oil phase; urea, formaldehyde, and sodium lignosulfonate are dissolved in water, wherein the molar ratio of urea to formaldehyde is 1:1.5-2.5, and the amount of dispersant is 0.5-1.5% of the total mass of the aqueous phase. The pH is adjusted to 8.0-9.0 to form the aqueous phase; the oil phase is added to the aqueous phase under emulsification conditions (stirring speed 8000-12000 rpm, emulsification time 10-20 minutes), and the ratio of the total mass of the oil phase to the volume of the aqueous phase (g:mL) is controlled at 1:2-4. Then the pH is lowered to 2.5-3.5, and in-situ polymerization is carried out at 55-65℃ for 2-4 hours. After the reaction, the mixture is washed with water and an organic solvent (such as ethanol), and vacuum dried at 30-50℃ to obtain Type A Capsule Powder. S2. Preparation of Type B Capsule Suspension: A modified amine curing agent and a latent catalyst are mixed as the core material; gelatin and gum arabic are dissolved in water, the pH is adjusted to 6.0-7.0, the temperature is maintained at 45-55℃, the core material is emulsified and dispersed in the gelatin solution under stirring, and then the gum arabic solution is added. A wall material is formed on the surface of the core material droplets by the complex coagulation method. After cross-linking and curing with a cross-linking agent (such as 0.5-2wt% of glutaraldehyde by weight of the core material, concentration 20-30wt%) (at 5-15℃, 1-3 hours), and washing, the Type B Capsule Suspension is obtained. S3. Preparation of biomimetic encapsulation microcapsules: The type A capsule powder obtained in step S1 and the type B capsule suspension obtained in step S2 are mixed at a dry weight ratio of 1:1-1.2. A dispersant is added, and the mixture is ultrasonically treated to obtain a uniform mixed capsule slurry. This slurry is used as a new core material and dispersed in an aqueous phase containing a surfactant. The polyurethane prepolymer is dissolved in an organic solvent as an oil phase. The oil phase is added to the aqueous phase under stirring to emulsify. Then, an aqueous solution of ethylenediamine is added to carry out interfacial polymerization to form an outer protective capsule. After washing and drying, biomimetic encapsulation microcapsules are obtained. The biomimetic encapsulated microcapsules exhibit good storage stability in the coating: after 6 months of sealed storage at 25℃, the microcapsule sedimentation rate is ≤3% and the rupture rate is ≤1%; the coating storage temperature is controlled at 5-30℃, and direct sunlight is avoided; under accelerated aging conditions of 40℃ / 75% RH, the microcapsule encapsulation rate decreases by ≤6% and the rupture rate is ≤4% after 6 months.

[0019] S4. Preparation and application of coatings: a) Preparation of adhesive buffer coating: Using epoxy resin as the matrix, add 20-50% by weight of elastomer particles, 1-3% by weight of silane coupling agent and appropriate amount of rheology modifier, and adjust the viscosity of the system to 150-250 mPa·s. b) Formulating self-healing functional layer coating: First, use epoxy resin as the matrix, add 2-6% by weight of hydroxylated functionalized graphene, 3-8% by weight of elastomer particles and dispersant, and form a hybrid network matrix through high-speed shearing; then add 10-20% by weight of biomimetic encapsulation microcapsules under low-speed stirring, and adjust the viscosity of the system to 200-350 mPa·s. c) Formulate a multifunctional protective coating: Use fluorosilicone modified resin as the matrix, add 3-8% of its solids by weight of fluorinated graphene, 2-5% of nano TiO2@ZnO composite particles and leveling agent, grind to fineness ≤20μm, and adjust viscosity to 150-250 mPa·s. d) On the pretreated blade substrate surface, the above three coatings are sprayed sequentially using a wet-on-wet process (spraying pressure 0.3-0.5MPa, spraying distance 15-25cm, spraying speed 5-10cm / s), controlling the thickness of each wet film to be 60-100 μm and the interlayer flash-off time to be 15-30 minutes; finally, it is cured at 60-80℃ for 6-10 hours to form a complete self-healing protective film.

[0020] Preferably, in step S1, the graphene quantum dot dispersion is prepared by the following method: graphene oxide is refluxed in concentrated acid at 120-140°C for 8-12 hours, and then purified by dialysis to obtain an aqueous dispersion of graphene quantum dots with carboxyl groups on the surface; the epoxy resin is bisphenol A type epoxy resin E-51.

[0021] Preferably, in step S3, the dispersant is polyethylene glycol-6000, and its addition amount is 0.5 wt% of the total mass of the mixed capsule slurry; the ultrasonic treatment conditions are: power 500W, frequency 20kHz, and time 30 minutes.

[0022] Preferably, in step S4, during the wet-on-wet spraying process, the ambient temperature is controlled at 15-30℃ and the relative humidity is ≤75%.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By designing a "two-level nested" biomimetic encapsulation microcapsule structure, the same damaged area can be effectively repaired 2-3 times, greatly extending the service life of the protective film.

[0024] 2. By introducing GQDs and latent catalysts, the repaired material is firmly bonded to the original substrate interface, and the mechanical properties of the repaired coating recover well.

[0025] 3. By modifying the capsule wall material and repair agent, the protective film can still maintain a repair efficiency of more than 80% under low temperature of -20℃ and high humidity of 95%, adapting to harsh environments such as the sea and the north.

[0026] 4. The gradient coating structure provides multiple protections in one go, including self-healing, strong adhesion, superhydrophobicity, anti-icing, and UV resistance, resulting in excellent overall performance.

[0027] 5. The preparation method is based on mature technology, and the construction adopts conventional wet-on-wet spraying. The raw material cost is controllable and it is suitable for large-scale blade coating. Attached Figure Description

[0028] Figure 1 The flowchart illustrates a method for preparing a self-healing graphene-based protective film for wind turbine blades, as provided by this invention.

[0029] Figure 2 These are microscope images of the scratches before and after coating repair in Example 4. Detailed Implementation

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] Example 1 Preparation of type A capsules: Core material: 100g of bisphenol A epoxy resin E-51, mixed with 60g of graphene quantum dot aqueous dispersion (10% solid content, rich in carboxyl groups on the surface) and dehydrated; Aqueous phase: Dissolve 15g urea, 40g 37% formaldehyde aqueous solution, and 1.5g sodium lignosulfonate in 200g deionized water, and adjust the pH to 8.5 with 10% NaOH solution; The core material was added to the aqueous phase under high-speed stirring (10,000 rpm) and emulsified for 15 minutes. Adjust the pH to 3.0 with 10% HCl solution and react at 60°C for 3 hours; After the reaction was completed, the mixture was filtered, washed with water and ethanol, and dried under vacuum at 40°C to obtain type A capsule powder.

[0033] Preparation of type B capsules: Core material: 80g modified polyamide curing agent (V-140) mixed with 2g 2-ethyl-4-methylimidazolium (latent catalyst); Aqueous phase: Prepare 200g each of 3% gelatin solution and 3% gum arabic solution, maintain the temperature at 50℃, and adjust the pH to 6.5; Add the core material to the gelatin solution and homogenize and emulsify (8000 rpm) for 10 minutes; Slowly add gum arabic solution, stir and allow to cool naturally to 10°C, then add 2 mL of 25% glutaraldehyde for crosslinking for 2 hours; Filter and wash with water to obtain type B capsule wet cake.

[0034] Preparation of biomimetic encapsulated microcapsules: Mix type A capsule powder with type B capsule wet cake (at a dry weight ratio of 1:1), add 0.5% of PEG-6000 and 100g of water by total mass, and disperse evenly by ultrasonication (500W, 20kHz, 30min); The above-mentioned mixed slurry was used as a new core material and added to 500g of aqueous phase containing 2g of OP-10 emulsifier, and dispersed evenly. Oil phase: Dissolve 50g of polyurethane prepolymer (6% NCO content) in 50g of xylene; The oil phase was slowly added dropwise to the aqueous phase, and emulsified at high speed (12000 rpm) for 20 minutes. Add dropwise 50g of aqueous solution containing 5g of ethylenediamine, and react at 40℃ for 4 hours; Filter, wash, and dry to obtain biomimetic encapsulated microcapsules (outer layer particle size approximately 80 μm).

[0035] Coating preparation and coating: Adhesive buffer coating: 70g epoxy resin E-20, 30g polyurethane elastomer particles (particle size about 1μm), 2g complex coupling agent (KH-560:KH-550=1:1), 1g nano montmorillonite, appropriate amount of fumed silica rheology modifier and mixed solvent (xylene:n-butanol=4:1), adjust viscosity to 180 mPa·s; Self-healing functional layer coating: a) Preparation of premixed base material: Mix 100g epoxy resin E-51, 3g hydroxylated functionalized graphene, 5g polyurethane elastomer particles and 0.5g dispersant (BYK-163), and perform high-speed shear dispersion at 1500-2500 rpm for 30 minutes to form a uniform resin base material containing a hybrid reinforcing network.

[0036] b) Microcapsule incorporation: Under low-speed stirring (e.g., 300-500 rpm), slowly add 15g of biomimetic encapsulated microcapsules to the above premixed base material and continue stirring until the microcapsules are evenly dispersed.

[0037] c) Adjusting viscosity: Add an appropriate amount of solvent to adjust the viscosity of the entire coating system to about 280 mPa·s; Multifunctional protective coating: 100g fluorosilicone modified acrylic resin, 5g fluorinated graphene (prepared into a 20% pre-dispersed slurry), 3g nano TiO2@ZnO composite particles (TiO2 to ZnO mass ratio of 7:3, average particle size of 30-50nm), 0.3g leveling agent (BYK-333), mixed solvent (ethyl acetate: propylene glycol methyl ether acetate = 3:1), sand milled to a fineness ≤20μm, viscosity adjusted to 200 mPa·s; The preparation method of the nano-TiO2@ZnO composite particles adopts the sol-gel method, and the specific steps are as follows: Preparation of TiO2 core layer sol: Tetrabutyl titanate (titanium source) and anhydrous ethanol were mixed at a volume ratio of 1:4 and stirred for 30 min. Then, 0.1 mol / L nitric acid was added dropwise (to adjust the pH to 2.0-3.0). The mixture was stirred in a constant temperature water bath at 60℃ for 2 h to form a transparent TiO2 sol. Core drying and calcination: TiO2 sol was dried in an oven at 80℃ for 12h to obtain TiO2 gel; then calcined in a muffle furnace at 500℃ for 2h, cooled and ground, and passed through a 200-mesh sieve to obtain TiO2 core particles with a particle size of 20-30nm. ZnO shell coating: The above TiO2 core particles were dispersed in deionized water and sonicated (500W, 20kHz) for 30min to form a suspension; zinc nitrate (zinc source) was added at a TiO2 to ZnO mass ratio of 7:3, stirred and dissolved, and ammonia was added dropwise to adjust the pH to 8.0-9.0. The mixture was reacted at 50℃ for 3h to form TiO2@ZnO composite particle precursor; Post-processing: The precursor was centrifuged (8000 rpm, 10 min), washed three times alternately with deionized water and ethanol, dried at 100℃ for 6 h, and finally calcined at 400℃ for 1 h to obtain core-shell structured nano-TiO2@ZnO composite particles with a particle size of 30-50 nm and a TiO2:ZnO ratio of 7:3.

[0038] On a sandblasted (Sa 2.5) epoxy fiberglass plate (simulating blade substrate), three layers of coating were sequentially wet-on-wet sprayed using a spray gun (pressure 0.4MPa, distance 20cm). Each wet film was approximately 80μm thick, with a flash-drying time of 25 minutes. Finally, the coating was cured in a 70℃ oven for 7 hours to form a protective film with a total dry film thickness of approximately 150μm.

[0039] Example 2 The preparation of the type A capsules was basically the same as in Example 1, except that the amount of graphene quantum dots added (based on the mass of epoxy resin) was changed: 3 wt% in Example 2-1 and 9 wt% in Example 2-2.

[0040] Example 3 The following adjustments were made based on Example 1: During the preparation of the wall material for both type A and type B capsules, a nano-silica dispersion equivalent to 1.5% of the solid mass of the wall material was added during the polymerization / re-coagulation stage.

[0041] The epoxy resin in the core material of type A capsules was replaced with a mixture of 90g E-51 and 10g methylphenylsiloxane modified epoxy resin.

[0042] The testing environment was changed to a low temperature environment of -20℃.

[0043] Example 4 The difference from Example 1 is that: the amount of GQDs added is 6 wt%, 1.5% nano SiO2 is added to the wall material of both type A and type B capsules, the epoxy resin in the core material is a mixture of 90 wt% bisphenol A type epoxy resin E-51 and 10 wt% methylphenylsiloxane modified epoxy resin, the content of hydroxylated functionalized graphene in the self-healing functional layer is 5 wt%, and the protective layer contains 8% fluorinated graphene and 5% nano TiO2@ZnO.

[0044] Example 5 The difference from Example 1 is that in the multifunctional protective coating, the amount of nano-TiO2@ZnO composite particles added is 2 wt% of the solid content of the fluorosilicone modified resin, and the rest is the same as in Example 1.

[0045] Example 6 The difference from Example 1 is that in the multifunctional protective coating, the amount of nano-TiO2@ZnO composite particles added is 5 wt% of the solid content of the fluorosilicone modified resin, and the rest is the same as in Example 1.

[0046] Comparative Example 1: Ordinary blade coating without self-healing function Use commercially available high-performance polyurethane topcoat for wind turbine blades, and apply it according to the product instructions to the same dry film thickness.

[0047] Comparative Example 2 To simulate common self-healing coating technologies in this field, a control coating was prepared using the following method: Preparation of epoxy resin monolayer microcapsules: Using bisphenol A epoxy resin E-51 as the core material and urea-formaldehyde resin as the wall material, microcapsules (denoted as mA) with a particle size distribution of 30-80 μm were prepared by interfacial polymerization method similar to that of type A capsules in Example 1 of the original application (but without adding graphene quantum dots).

[0048] Preparation of single-layer microcapsules of curing agent: Using modified polyamide curing agent (V-140) as core material and gelatin-gum arabic as wall material, microcapsules (denoted as mB) with similar particle size distribution were prepared by a complex coagulation method similar to that of type B capsules in Example 1 of the original application (but without adding latent catalyst).

[0049] Coating preparation: The above mA and mB microcapsules were physically mixed at a dry weight ratio of 1:1, with a total addition amount of 15 wt% of the epoxy resin matrix (E-51). The mixture was dispersed in the epoxy resin matrix, and an equal amount of curing agent as in Example 1 was added (directly added to the coating, not encapsulated). After stirring evenly, the mixture was coated onto the substrate and cured under the same conditions (70℃ / 7h) to form a film, resulting in a single-layer self-healing control coating.

[0050] Comparative Example 3: Biomimetic Microcapsule Coating Without Graphene Quantum Dot Reinforcement The method is basically the same as in Example 1, except that graphene quantum dots are not added when preparing type A capsules.

[0051] Comparative Example 4: A single coating with no gradient structure The three-layer coating formulation components in Example 1 were simply mixed to form a single coating, which was then sprayed onto the same total thickness in one go and cured at 70°C for 7 hours.

[0052] Comparative Example 5: Self-healing coating without hybrid network The difference from Example 1 is that no 5g of polyurethane elastomer particles are added to the self-healing functional layer coating.

[0053] Performance testing Repair efficiency test: Standard scratches (50±5μm wide, depth to the substrate) were made on the cured coating using a blade. The initial width W0 was measured. Using a 5mm diameter spherical stainless steel indenter, a pressure of 0.8 MPa was applied uniformly and repeatedly to the scratched area three times (holding the pressure for 5 seconds each time) to simulate damage stress and trigger repair. After resting for 24 hours, the scratch widths W1, W2, and W3 were measured after the first, second, and third damage repairs. The repair efficiency η was then measured. n =(1-W n / W0)×100%(n=1,2,3).

[0054] Mechanical property recovery rate: Dumbbell-shaped coated specimens were prepared, and their original tensile strength σ0 was tested using a universal testing machine; the specimens were stretched until microcracks (strain of about 5%) were generated, and then unloaded. They were placed under standard conditions (25℃, 50%RH) for 48 hours to allow them to self-heal, and the tensile strength σ1 was tested again; tensile strength recovery rate = σ1 / σ0 × 100%.

[0055] Low-temperature environment repair efficiency: After placing the scratched sample in a -20℃ environment for 2 hours to equilibrate, the repair was triggered according to the above method, and the sample was left to stand at -20℃ for 24 hours to test the first repair efficiency.

[0056] Adhesion test: The pull-off test shall be conducted in accordance with GB / T 5210-2006.

[0057] Dynamic modulus test: The storage modulus of the coating was tested using a dynamic thermomechanical analyzer (DMA) at a temperature of 25°C and a frequency of 1Hz.

[0058] Contact angle and freezing delay: The static contact angle (23°C) of 5 μL of deionized water was measured using a contact angle meter; the coated sample was placed in an environment of -10°C and 85%RH, and 10 μL of water was added, and the time required for complete freezing was recorded.

[0059] Salt spray resistance: Conduct a 500-hour neutral salt spray test according to GB / T 1771-2007, and observe and record the width of the scratch spread on one side.

[0060] UV resistance: Artificial UV aging test (UVA-340 lamp, 1000h) was conducted according to GB / T 1865-2009 to evaluate the changes in the surface condition of the coating. The performance test results are shown in Table 1 below: Table 1 Performance Test Data Dynamic modulus: The dynamic modulus of the three layers of the protective film in Example 4 is gradient distributed. The moduli of the adhesive buffer layer, the self-healing functional layer and the multifunctional protective layer are approximately 0.9 GPa, 2.2 GPa and 3.8 GPa (DMA, 25℃, 1Hz), respectively.

[0061] Anti-icing and weather resistance: In Example 4, the coating surface showed a water droplet freezing delay time of up to 70 minutes. After 500 hours of salt spray testing, the scratch erosion width was less than 0.5 mm. After 1000 hours of UV aging, there was no powdering or cracking.

[0062] Performance test results show that: All embodiments exhibited significant second (>86%) and third (>78%) repair efficiencies. In contrast, Comparative Example 2 (simulating monolayer microcapsule technology) showed a second repair efficiency of 0% after the first repair.

[0063] The tensile strength recovery rate of Comparative Example 3 (without GQDs) (78.4%) was significantly lower than that of Example 1 (90.5%), demonstrating the interface reinforcement effect of GQDs; the strength recovery rate of Comparative Example 5 (without hybrid network) further decreased to 75.3%, and its functional layer modulus was too large, resulting in increased brittleness.

[0064] Example 3 improved the repair efficiency at -20℃ from 65.3% (Example 1) to 81.6% through wall material and resin modification, and Example 4 even reached 83.5%, which fully verified the reliable performance of the present invention at extreme low temperatures and solved the problem of poor environmental adaptability of the prior art.

[0065] Example 4, as a representative of comprehensive optimization, has the best performance in all core performance data. Its high adhesion (8.5 MPa), high contact angle (159°), excellent anti-icing and weather resistance performance prove the synergistic effect of each functional layer under the gradient structure design. Comparative Example 4 (without gradient structure) is significantly inferior in all repair performance and adhesion.

[0066] The core self-healing functional layer composition of Examples 5 and 6 is the same as that of Example 1. Therefore, its self-healing efficiency, mechanical property recovery rate and adhesion data are basically the same as those of Example 1. The main difference is the difference in contact angle caused by the change in the filler content of the protective layer.

[0067] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A self-repairing graphene-based wind turbine blade protection film, characterized in that, The adhesive buffer layer, the self-repairing functional layer and the multi-functional protective layer are sequentially arranged from the surface of the blade substrate outward; The adhesive buffer layer comprises an epoxy resin matrix, elastomer particles dispersed therein and a silane coupling agent; The self-repairing functional layer comprises an epoxy resin matrix, hydroxylated functionalized graphene dispersed therein, elastomer particles and biomimetic encapsulated microcapsules; The biomimetic encapsulated microcapsules have a two-level nested structure, comprising an outer protective capsule and a plurality of inner repair capsules encapsulated in the outer protective capsule; The inner repair capsules comprise A-type capsules and B-type capsules, the wall material of the A-type capsules is urea-formaldehyde resin, and the core material is a repair resin containing epoxy resin and graphene quantum dots; The wall material of the B-type capsules is a gelatin-arabic gum compound, and the core material is a curing system containing a modified amine curing agent and a latent catalyst, and the breaking strength of the outer protective capsule is lower than that of the inner A-type capsules and B-type capsules.

2. The self-healing graphene-based wind turbine blade protection film according to claim 1, wherein, The breaking strength of the outer protective capsule is 0.5-1.0 MPa, the breaking strength of the A-type capsules is 2.5-3.5 MPa, and the breaking strength of the B-type capsules is 3.5-4.5 MPa.

3. The self-healing graphene-based wind turbine blade protection film according to claim 1, wherein, The particle size of the outer protective capsule is 50-100 μm, and the particle size of the inner repair capsules is 5-15 μm; The dry mass ratio of the A-type capsules to the B-type capsules is 1:0.8-1.2; in the core material of the A-type capsules, the content of the graphene quantum dots is 3-9 wt% of the mass of the epoxy resin; in the core material of the B-type capsules, the latent catalyst is 2-ethyl-4-methyl imidazole, and the content is 1-3 wt% of the total mass of the curing system.

4. The self-healing graphene-based wind turbine blade protection film according to claim 1, wherein, The wall material of the A-type capsules and / or B-type capsules further contains 1-2 wt% of nano-silicon dioxide particles based on the solid mass of the wall material. 5.The self-repairing graphene-based wind turbine blade protection film according to claim 1, wherein, The multi-functional protective layer comprises a fluorosilicon modified resin, fluorinated graphene and nano TiO2@ZnO composite particles, wherein the content of the fluorinated graphene is 3-8 wt% of the mass of the fluorosilicon modified resin, and the content of the nano TiO2@ZnO composite particles is 2-5 wt% of the mass of the fluorosilicon modified resin.

6. The self-healing graphene-based wind turbine blade protection film according to claim 1, wherein, The dynamic modulus of the adhesive buffer layer is 0.5-1.0 GPa, the dynamic modulus of the self-repairing functional layer is 1.5-2.5 GPa, and the dynamic modulus of the multi-functional protective layer is 3.0-4.0 GPa, and the dynamic modulus is tested by dynamic mechanical analysis, and the test conditions are temperature 25℃ and frequency 1Hz.

7. A method of preparing a self-repairing protective film according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. Preparing an A-type capsule suspension: mixing an epoxy resin and a graphene quantum dot dispersion as an oil phase; dissolving urea, a formaldehyde aqueous solution and sodium lignosulfonate in water, adjusting the pH to 8.0-9.0 as an aqueous phase; adding the oil phase to the aqueous phase under emulsification conditions, then reducing the pH to 2.5-3.5, and performing in-situ polymerization reaction; after the reaction is completed, washing and drying to obtain A-type capsule powder; S2. Preparation of B-type capsule suspension: the modified amine curing agent and latent catalyst are mixed as the core material; the gelatin and gum arabic are dissolved in water respectively, the pH is adjusted to 6.0-7.0, the temperature is kept at 45-55℃, the core material is emulsified and dispersed in the gelatin solution under stirring, then the gum arabic solution is added, the wall material is formed on the surface of the core material droplets by complex coacervation, and after cross-linking, curing and washing, the B-type capsule suspension is obtained; S3. Preparation of biomimetic encapsulated microcapsules: the A-type capsule powder obtained in step S1 and the B-type capsule suspension obtained in step S2 are mixed in a dry weight mass ratio of 1:1-1.2, a dispersing agent is added, and a uniform mixed capsule slurry is obtained by ultrasonic treatment; the slurry is used as a new core material and dispersed in an aqueous phase containing a surfactant; a polyurethane prepolymer is dissolved in an organic solvent as an oil phase, which is emulsified in the aqueous phase under stirring, and then an ethylenediamine aqueous solution is added for interfacial polymerization to form an outer protective capsule, and after washing and drying, the biomimetic encapsulated microcapsules are obtained; S4. Preparation of coatings and coating: adhesive buffer layer coating, self-repairing functional layer coating and multifunctional protective layer coating are prepared respectively; On the clean blade surface, the adhesive buffer layer coating, the self-repairing functional layer coating and the multifunctional protective layer coating are sprayed in sequence in a wet-on-wet manner, the flash drying time between each layer is controlled to be 20-30 minutes, and finally the self-repairing protective film is formed by curing at 60-80℃ for 6-8 hours.

8. The method of claim 7, wherein the graphene-based wind turbine blade protection film is prepared by the steps of: (a) preparing a graphene-based film; (b) coating the graphene-based film with a self-healing agent; and (c) curing the graphene-based film. In step S1, the graphene quantum dot dispersion is prepared by the following method: graphene oxide is refluxed in concentrated acid at 120-140℃ for 8-12 hours, and then dialyzed and purified to obtain a graphene quantum dot water dispersion with a surface rich in carboxyl groups; the epoxy resin is bisphenol A type epoxy resin E-51.

9. The method of claim 7, wherein the self-repairing graphene-based wind turbine blade protective film is prepared by the steps of: (a) preparing a graphene-based film; (b) coating the graphene-based film with a self-repairing material; and (c) coating the graphene-based film with a protective material. In step S3, the dispersing agent is polyethylene glycol-6000, and the addition amount is 0.5wt% of the total mass of the mixed capsule slurry; the ultrasonic treatment conditions are: power 500W, frequency 20kHz, time 30 minutes.

10. The method of claim 7, wherein the self-repairing graphene-based wind turbine blade protective film is prepared by the steps of: (a) preparing a graphene-based film; (b) coating the graphene-based film with a self-repairing material; and (c) coating the graphene-based film with a protective material. In step S4, the multifunctional protective layer coating is prepared by the following method: a fluorosilicon modified resin, fluorinated graphene, nano TiO2@ZnO composite particles, a leveling agent and a solvent are mixed and ground to a fineness of ≤20μm by a sand mill; wherein the addition amount of the fluorinated graphene is 5wt% of the mass of the fluorosilicon modified resin, and the mass ratio of TiO2 to ZnO in the nano TiO2@ZnO composite particles is 7:3, and the addition amount is 3wt% of the mass of the fluorosilicon modified resin.

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