Polyrotaxane functionalized basalt composite coating and application

Abstract

This invention discloses a polyrotaxane-functionalized basalt composite coating and its application, belonging to the field of high-performance composite material interface engineering and anti-corrosion coating technology. The composite coating comprises an epoxy resin matrix and polyrotaxane-functionalized basalt flakes dispersed therein. The functionalized basalt flakes consist of a basalt flake substrate and polyrotaxane molecules covalently grafted onto its surface via amide bonds. These polyrotaxane molecules are formed by a host-guest inclusion reaction between end-carboxyl-terminated polyethylene glycol and cyclodextrin, and the cyclic molecules can slide along the polymer axis. In preparation, the basalt flakes are first pretreated with acid and activated with a quaternary ammonium base, then grafted with amino groups. The synthesized end-carboxyl-terminated polyrotaxane is then grafted onto the flake surface via amide bonds, and finally dispersed in the epoxy resin. This invention constructs an interface buffer layer with mechanical interlocking and dynamic sliding characteristics between the filler and the resin, effectively alleviating stress concentration and delaying crack propagation. It possesses both high barrier properties and high toughness, making it suitable for metal protection in marine engineering, deep-sea equipment, and bridge steel structures.

Description

Technical Field

[0001] This invention relates to the field of high-performance composite material interface engineering and anti-corrosion coating technology, and in particular to a polyrotaxane functionalized basalt composite coating and its application. Background Technology

[0002] Anti-corrosion composite coatings often incorporate lamellar or layered inorganic fillers (such as basalt flakes) into organic matrices like epoxy resins. The "maze effect" created by these fillers extends the diffusion path of corrosive media, thereby improving the coating's shielding performance and corrosion resistance lifespan. Due to its abundant resources, high chemical stability, and the physical barrier effect of its lamellar structure, basalt flakes have become one of the most sought-after functional fillers in epoxy anti-corrosion coating systems.

[0003] To improve the interfacial compatibility and bonding strength between basalt flakes and epoxy resin, existing technologies generally adopt the technical route of "inorganic strong base etching and activation combined with silane coupling agent modification". By forming a chemical bonding interface on the flake surface, the uniformity of filler dispersion in resin, coating adhesion and initial anti-corrosion performance are improved to a certain extent.

[0004] However, the aforementioned existing technologies share the following shortcomings:

[0005] (1) The interface structure is statically rigid and lacks dynamic stress buffering capacity. The interface layer in the existing scheme is mainly characterized by "fixed connection points" such as covalent bonds, ionic bonds or hydrogen bonds, which are static, rigid or quasi-rigid interface structures. In the actual service process of the coating, dynamic mechanical loads such as impact, vibration, shear or fluid disturbance are unavoidable. Under such loads, the fixed connection points are prone to modulus abrupt change and stress concentration at the filler-resin interface, which in turn induces microcrack initiation, interface peeling and accelerates the penetration of corrosive media, forming a structural contradiction of "high interface bonding strength but increased brittleness and insufficient resistance to dynamic damage".

[0006] (2) Barrier performance and interfacial toughness are difficult to coordinate and unify. Although existing technologies can improve the initial barrier performance of coatings through the labyrinth effect of lamellar fillers, once microcracks are generated at the interface under dynamic loads, the continuity of the barrier structure is destroyed, and corrosive media penetrate rapidly along the damage channels, leading to premature coating failure. In other words, existing solutions have not yet achieved a coordinated design of "high barrier" and "high interfacial damage tolerance".

[0007] (3) Lack of molecular-scale interfacial buffer layer design. Most existing modification methods focus on improving the chemical activity of the filler surface, failing to construct a continuous, deformable, and energy-dissipating interfacial intermediate phase between the filler and the resin. Therefore, under extreme service environments such as deep-sea high pressure, flow field erosion, and cyclic loading, the stability of the coating interface is difficult to maintain, and the long-term protective performance is significantly reduced.

[0008] In summary, there is an urgent need to provide a new basalt interface modification technology that can not only firmly anchor to the basalt surface, but also form a continuous intermediate layer with a buffering effect at the filler / resin interface, thereby taking into account interface strength, mechanical toughness and long-term corrosion resistance. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the purpose of this invention is to provide a production line device for packaging various dried fruits in kraft paper food bags. The specific technical solution is as follows:

[0010] A polyrotaxane-functionalized basalt composite coating, the composite coating comprising an epoxy resin matrix and polyrotaxane-functionalized basalt flakes dispersed in the epoxy resin matrix;

[0011] The polyrotaxane-functionalized basalt flakes include a basalt flake substrate and polyrotaxane molecules grafted onto the surface of the basalt flake substrate via covalent bonds;

[0012] The polyrotaxane molecule comprises a linear polymer axis and a cyclic molecule sleeved on the linear polymer axis and capable of sliding along it;

[0013] The end functional groups of the polyrotaxane molecule and the functional groups on the surface of the basalt flake substrate form covalent bonds through a covalent reaction;

[0014] The composite coating forms an interface buffer layer with mechanical interlocking and dynamic slip characteristics between the basalt flakes and the epoxy resin matrix.

[0015] The linear polymer axis is a linear polymer capable of forming a host-guest inclusion-coating structure with cyclodextrin. The linear polymer axis is selected from one or two of polyethylene glycol, combinations of polyethylene glycols with different number-average molecular weights, and polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymers. The number-average molecular weight of the linear polymer axis is 200 to 4000.

[0016] The terminal functional group of the polyrotaxane molecule is a carboxyl group, the reactive functional group on the surface of the basalt flakes is an amino group, and the covalent bond is an amide bond.

[0017] A preferred embodiment of the polyrotaxane-functionalized basalt composite coating is a method for preparing the polyrotaxane-functionalized basalt flakes, comprising the following steps:

[0018] Step S1: Basalt flake pretreatment and surface functionalization;

[0019] Basalt flakes are first subjected to acidic pretreatment and quaternary ammonium alkaline activation treatment to remove surface impurities, increase surface hydroxyl groups and form a rough structure that is conducive to subsequent grafting. Then, the activated basalt flakes are reacted with a diaminosilane coupling agent to introduce amino functional groups on its surface, thus obtaining surface-functionalized basalt flakes.

[0020] Step S2: Preparation of polyrotaxane by cyclodextrin synthesis;

[0021] Polyethylene glycol is subjected to end-group oxidation to obtain carboxyl-terminated polyethylene glycol; then, the carboxyl-terminated polyethylene glycol is reacted with cyclodextrin in an aqueous system to form a polyrotaxane precursor structure; subsequently, after separation, washing and drying, polyrotaxane with carboxyl-terminated groups is obtained.

[0022] Step S3: Polyrotaxane grafting reaction;

[0023] The carboxylated polyrotaxane obtained in step S2 and the surface-functionalized basalt flakes prepared in step S1 are covalently grafted in a coupling system, so that the carboxyl groups of the polyrotaxane end group are connected to the amino groups on the surface of the basalt flakes through amide bonds. After washing and drying, polyrotaxane-functionalized basalt flakes are obtained.

[0024] The preferred embodiment of the polyrotaxane-functionalized basalt composite coating is as follows: the acidic pretreatment solution in step S1 is an aqueous hydrochloric acid solution with a concentration of 0.1~0.5 mol / L, and the treatment time is 0.5~2 h; the quaternary ammonium base is an aqueous tetramethylammonium hydroxide solution with a concentration of 0.5wt%~5wt%; the treatment temperature is 50~90℃; the treatment time is 0.5~3 h; and the bisaminosilane coupling agent is KH792, with a mass ratio of KH792 to activated basalt flakes of 1:20~1:5.

[0025] The preferred embodiment of the polyrotaxane-functionalized basalt composite coating is as follows: In step S2, the cyclodextrin is α-cyclodextrin, or a combination mainly composed of α-cyclodextrin and containing β-cyclodextrin; when the cyclodextrin is composed of α-cyclodextrin and β-cyclodextrin, the molar fraction of β-cyclodextrin in the total cyclodextrin is 0~20%; the coverage of cyclodextrin on the linear polymer axis is 20%~90%; the number average molecular weight of the polyethylene glycol is 400~1000; the mass ratio of cyclodextrin to polyethylene glycol is 2:1~10:1; and the host-guest encapsulation reaction is carried out at a temperature of 0~10℃ for 8~24h.

[0026] The preferred embodiment of the polyrotaxane functionalized basalt composite coating is as follows: the covalent grafting in step S3 uses a HATU or EDC / NHS activation system, the reaction solvent is DMF, DMSO or a mixture thereof, the reaction temperature is 20~40℃, and the reaction time is 4~24h.

[0027] The preferred embodiment of the polyrotaxane functionalized basalt composite coating is that the epoxy resin matrix is ​​a compound system of bisphenol A type epoxy resin and bisphenol F type epoxy resin, with a mass ratio of 3:1 to 1:1; the amount of functionalized basalt flakes added to the composite coating is 0.1% to 10% of the resin mass.

[0028] The preferred embodiment of the polyrotaxane-functionalized basalt composite coating is that the composite coating is prepared by a phase-separated premixing and then compounding method; the specific preparation method is as follows:

[0029] First, polyrotaxane-functionalized basalt flakes were added to bisphenol A type epoxy resin and pre-dispersed with an organic mixed solvent. After mechanical stirring, high-speed dispersion and ultrasonic treatment, component A was obtained.

[0030] Next, a silane coupling agent is added to bisphenol F type epoxy resin for premixing to obtain component B. The silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and its addition amount is 0.1% to 5% of the mass of bisphenol F type epoxy resin.

[0031] Component B is slowly added to component A and mixed evenly. Then, curing agent and additives are added, and vacuum degassing is performed. Finally, the resulting system is coated onto the surface of the substrate and cured by a program to obtain a composite protective coating.

[0032] The organic mixed solvent is one or more of xylene, n-butanol and isopropanol; the thickness of the composite protective coating is 100-300 μm.

[0033] The amount of polyrotaxane grafted onto the basalt flake surface is 1 wt% to 15 wt%.

[0034] The basalt flakes have a grain size of 1~500 μm, a thickness of 0.1~10 μm, and an aspect ratio of 10~1000.

[0035] This invention provides applications of the composite coating, wherein the applications include at least one of the following:

[0036] 1) Application as a coating for marine engineering and deep-sea equipment;

[0037] 2) Applications as coatings for ships and offshore wind power facilities;

[0038] 3) As a coating for cross-sea bridges and port facilities.

[0039] Beneficial effects

[0040] 1) The polyrotaxane slip ring structure of the present invention achieves the migration of connection points by sliding along the axis of the ring molecules when under stress, avoiding stress localization at the fixed nodes of the interface, thereby homogenizing the external load and realizing staged energy dissipation, effectively suppressing interface stress concentration and crack propagation, improving crack resistance and alleviating the problem of high brittleness of strong interfaces.

[0041] 2) This invention fixes polyrotaxane to the surface of basalt by end-group covalent grafting, constructing a stable and gentle interface structure, avoiding the risk of interface migration and debonding that may occur in physical adsorption or blending systems, thereby improving interface stability and long-term service reliability.

[0042] 3) This invention preferably uses a compound system of bisphenol A type epoxy resin and bisphenol F type epoxy resin, and prepares the composite protective coating through the following process: First, polyrotaxane-functionalized basalt flakes are added to bisphenol A type epoxy resin to prepare a pre-dispersion mother liquor of component A. Then, KH560 is added to bisphenol F type epoxy resin to prepare component B. Subsequently, component B is slowly added to component A for compound mixing, and a curing agent is further added. After vacuum degassing, moisture-controlled coating, and programmed temperature curing, the composite protective coating is obtained. Compared with the conventional method of directly dispersing and forming a film with a single epoxy resin, the above process is more conducive to improving the dispersion uniformity and interfacial wetting and coating effect of polyrotaxane-functionalized basalt flakes in the resin system, reducing internal bubbles and film-forming defects, thereby obtaining a composite coating with good interfacial bonding, fewer internal defects, and better overall performance.

[0043] This invention employs a combined acid pretreatment and quaternary ammonium alkali activation process, which, compared to single alkali activation, is gentler and more effective in increasing the hydroxyl density on the basalt flake surface and forming a micro-rough structure conducive to grafting. Simultaneously, the use of the diaminosilane coupling agent KH792 introduces high-density amino groups, improving the grafting density and interfacial continuity of the polyrotaxane. Attached Figure Description

[0044] Figure 1 The image shows a comparison of scanning electron microscopy images of polyrotaxane-functionalized basalt flakes (PEB) prepared in Example 1 and activated basalt flakes (EB) in Comparative Example 1.

[0045] Wherein, (a) is the tensile stress-strain curve; (b) is the calculated toughness value; (c) is the surface morphology of the EP–PEB coating after impact; and (d) is the surface morphology of the EP–EB coating after impact.

[0046] Figure 2 The image shows a comparison of the Fourier transform infrared (FT-IR) spectra of the polyrotaxane-functionalized basalt flakes (PEB) prepared in Example 1 and the activated basalt flakes (EB) in Comparative Example 1.

[0047] Among them, (a) is the sedimentation behavior of EB dispersion in epoxy resin over time; (b) is the sedimentation behavior of PEB dispersion over time.

[0048] Figure 3 This is a comparison diagram of the tensile stress-strain curves of the composite coating (EP-PEB) obtained in Example 1 and the composite coating (EP-EB) in Comparative Example 1.

[0049] Where a1 and a2 are the scanning electron microscope characterizations of EB material; c1 and c2 are the scanning electron microscope characterizations of PEB filler.

[0050] Figure 4 This is a comparison of the low-frequency modulus values ​​of the electrochemical impedance spectroscopy of the composite coating (EP-PEB) obtained in Example 1 and the composite coating (EP-EB) in Comparative Example 1 under a simulated deep-sea environment. Detailed Implementation

[0051] In this invention, the basalt flake substrate is preferably pretreated basalt flakes. The basalt flakes have a grain size of 1-500 μm, a thickness of 0.1-10 μm, and an aspect ratio of 10-1000. The pretreatment includes acidic pretreatment and quaternary ammonium alkaline activation treatment to increase the hydroxyl density on the flake surface; the acidic pretreatment solution is an aqueous hydrochloric acid solution with a concentration of 0.1-0.5 mol / L, and the treatment time is 0.5-2 h; subsequently, quaternary ammonium alkaline activation treatment is performed, wherein the quaternary ammonium alkaline activation solution is an aqueous tetramethylammonium hydroxide solution with a concentration of 0.5 wt%-5 wt%; the treatment temperature is 50-90 °C; and the treatment time is 0.5-3 h.

[0052] The polyrotaxane molecule comprises a linear polymer axis and cyclic molecules. The linear polymer axis is a linear polymer capable of forming a host-guest encapsulation structure with cyclodextrin, preferably polyethylene glycol or a linear polymer containing polyethylene glycol segments. The linear polymer axis is selected from polyethylene glycol, combinations of polyethylene glycols with different number-average molecular weights, and one or two of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymers, with polyethylene glycol being the most preferred. The number-average molecular weight of the linear polymer axis is 200-4000. The ends of the linear polymer axis are one or more of hydroxyl, carboxyl, amino, isocyanate, or epoxy groups, preferably carboxyl groups. The linear polymer axis can be pre-treated by introducing carboxyl groups through an end-group oxidation reaction to obtain a carboxyl-terminated polymer axis chain, facilitating subsequent coupling reactions with functional groups on the basalt surface.

[0053] The cyclic molecule is a cyclodextrin compound, selected from one or both of α-cyclodextrin and β-cyclodextrin. The cyclic molecule is α-cyclodextrin, or a combination primarily composed of α-cyclodextrin and containing a small amount of β-cyclodextrin; when the cyclic molecule is composed of α-cyclodextrin and β-cyclodextrin, the molar fraction of β-cyclodextrin in the total cyclodextrin is preferably 0-20%. The cyclic molecule is mainly composed of α-cyclodextrin, and the internal size of α-cyclodextrin is more compatible with polyethylene glycol segments, which is more conducive to forming a stable through-cell structure and a regular polyrotaxane configuration. The through-cell rate of the cyclic molecule is 20%-95%.

[0054] The cyclic molecules are fitted onto the straight-chain polymer axis and can slide along the axial direction to form a slip ring structure. The slip ring structure is a mechanically interlocked but not rigidly fixed topology. Under the action of external forces, thermal stress, pressure fluctuations, fluid scouring, or cyclic mechanical loads, the cyclic molecules can migrate along the straight-chain polymer axis, thereby redistributing the stress originally concentrated at local interface nodes, and achieving staged energy dissipation through continuous slip and hydrogen bond recombination.

[0055] The polyrotaxane is covalently bonded to the functional groups on the basalt flake surface via terminal functional groups. The terminal functional groups are preferably one or more of carboxyl, hydroxyl, amino, isocyanate, and epoxy groups, with a preference for carboxyl. The functional groups on the basalt flake surface are preferably one or more of amino, hydroxyl, and epoxy groups introduced through activation or surface modification, with a preference for amino. The terminal carboxyl groups of the polyrotaxane molecule form amide bonds with the amino groups on the basalt surface through a condensation reaction; or, the terminal hydroxyl or carboxyl groups of the polyrotaxane form ester bonds with the hydroxyl groups on the basalt surface through an esterification reaction; or, the terminal isocyanate groups of the polyrotaxane form urethane or urea bonds with the hydroxyl or amino groups on the basalt surface. All of the above connection methods can achieve a firm anchorage of the polyrotaxane to the basalt surface, with amide bond connection being more preferred because its reaction conditions are milder, the connection stability is higher, and it is more suitable for maintaining interfacial integrity in the subsequent resin system over a long period.

[0056] To introduce suitable reaction sites for covalent bonding with polyrotaxanes onto the surface of basalt flakes, it is preferable to first perform a surface diaminoation treatment on the pretreated basalt flakes. This surface functionalization treatment uses a diaminosilane coupling agent, KH792, to introduce amino functional groups onto the basalt flake surface. The mass ratio of KH792 to activated basalt flakes is 1:20 to 1:5. The activated basalt flakes are dispersed in an ethanol / water mixture, and the diaminosilane coupling agent is added. The mixture is stirred and reacted at 50–80°C for 2–6 hours. After washing and drying, basalt flakes with a high amino density on the surface are obtained. Using a diaminosilane coupling agent provides more reactive amino sites on the basalt surface, which is beneficial for improving the grafting density of subsequent carboxylated polyrotaxanes and the continuity of the interface layer construction. The grafting reaction between the diamined basalt flakes and the carboxylated polyrotaxane is carried out in a polar organic solvent, wherein the solvent is DMF, DMSO or a mixture thereof; the coupling system is HATU or EDC / NHS activation system; the reaction temperature is preferably 20~40℃, and the reaction time is preferably 4~24h.

[0057] The preferred method for preparing the polyrotaxane includes the following steps: First, polyethylene glycol is subjected to end-group oxidative modification, changing its hydroxyl-terminated structure to a carboxyl-terminated structure, resulting in carboxyl-terminated polyethylene glycol (PEG-COOH). Then, the PEG-COOH is reacted with cyclodextrin in an aqueous system to undergo a self-assembly reaction, allowing the cyclodextrin to attach to the PEG-COOH segments, forming a polyrotaxane structure. The mass ratio of cyclodextrin to polyethylene glycol is 2:1 to 10:1. The end-group oxidation reaction can be carried out using a TEMPO-mediated oxidation system, preferably comprising TEMPO, NaBr, and NaClO. The reaction pH is 10-11, the reaction temperature is room temperature, and the reaction time is 5-60 min. After oxidation, the carboxyl-terminated polyethylene glycol is obtained through acidification, extraction, recrystallization, and vacuum drying. The obtained PEG-COOH and cyclodextrin are added to deionized water to form a slurry. The mixture is then allowed to stand or be stirred at low temperature to allow the cyclodextrin to gradually coat the PEG-COOH, and the α-cyclodextrin to gradually coat the PEG-COOH. The reaction temperature is 0–10°C; the preferred reaction time is 8–24 h. After the reaction is complete, the mixture is centrifuged, washed with water, and freeze-dried to obtain a grayish-white or off-white powdered polyrotaxane.

[0058] The grafting reaction between polyrotaxane and basalt flakes is carried out on the surface of basalt flakes that have undergone pretreatment and diamine treatment. Amino functional groups are introduced into the surface of the basalt flakes using a diamine silane coupling agent, KH792. The grafting reaction is preferably carried out in a polar organic solvent, preferably DMF, DMSO, or a mixture thereof. The diamine-treated basalt flakes are first dispersed in the polar organic solvent and then ultrasonically dispersed. The system is then protected with an inert gas or deoxygenated. A condensation coupling agent and an organic base, preferably triethylamine, are then added. After activation for a certain period, a polyrotaxane solution dissolved in the organic solvent is added, and the mixture is stirred and ultrasonically assisted to improve grafting uniformity and the continuity of the interface layer construction. The grafting reaction temperature is 20–40°C; the reaction time is 4–24 h. After the reaction was completed, the product was collected by centrifugation and washed several times with organic solvent, alcohol solvent and deionized water in sequence to remove unreacted polyrotaxane and small molecule byproducts. Finally, it was dried under vacuum at 40~80℃ for 6~24h to obtain polyrotaxane-functionalized basalt flakes.

[0059] In this invention, the organic layer formed on the surface of the polyrotaxane-functionalized basalt flakes not only serves as an anchoring and connecting layer, but also interacts with the resin matrix at multiple points during subsequent resin curing. The α-cyclodextrin macrocycle is rich in hydroxyl sites, which can form multiple hydrogen bonds with hydroxyl and amine groups in the epoxy resin, curing agent, and their cured products, thereby constructing a continuous polymer intermediate phase between the basalt flakes and the epoxy matrix. The thickness of the intermediate phase is 5-500 nm, more preferably 10-200 nm. Through the construction of this intermediate phase, a "soft-hard gradient transition interface" can be formed between the hard inorganic phase and the organic resin phase, reducing abrupt changes in interfacial modulus and improving interfacial stability, load transfer capacity, and damage tolerance.

[0060] In this invention, the polyrotaxane-functionalized basalt flakes are used in an epoxy resin composite coating system. Bisphenol A type epoxy resin provides high film strength and adhesion, while bisphenol F type epoxy resin has low viscosity and good interfacial wetting ability. The combination of these two resins is more conducive to the uniform dispersion and interfacial wetting and coating of the polyrotaxane-functionalized basalt flakes in the resin system. The epoxy resin matrix is ​​a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, with a preferred mass ratio of 3:1 to 1:1. The preferred amount of functionalized basalt flakes added is 0.1% to 10% of the resin mass.

[0061] The composite coating is prepared by premixing phase separation before compounding. Specifically, component A containing polyrotaxane-functionalized basalt flakes is prepared first, followed by component B containing a silane coupling agent. Component A and component B are then compounded and mixed, and a curing agent and additives are further added. After degassing, coating, and programmed curing, a composite protective coating is obtained. The preparation method of component A is as follows: polyrotaxane-functionalized basalt flakes are first added to bisphenol A type epoxy resin and pre-dispersed with an appropriate amount of organic mixed solvent to form a filler pre-dispersion mother liquor. Subsequently, the pre-dispersion mother liquor is subjected to mechanical stirring, high-speed dispersion, and ultrasonic synergistic treatment to improve the dispersion uniformity of functionalized basalt flakes in bisphenol A type epoxy resin and reduce sheet aggregation. The preparation method of component B is as follows: a silane coupling agent is first added to bisphenol F type epoxy resin and premixed under stirring conditions to uniformly disperse the silane coupling agent in the bisphenol F type epoxy resin, forming an interface-controlled resin phase. The silane coupling agent is KH560, and its addition amount in the bisphenol F epoxy resin is 0.1% to 5% of the mass of the bisphenol F epoxy resin. After the preparation of components A and B, component B is slowly added to component A, and the mixture is compounded under medium-low speed stirring conditions to avoid local viscosity abrupt changes and secondary agglomeration of fillers caused by rapid one-time mixing. If necessary, appropriate amounts of leveling agents, defoamers, or diluents can be added, and stirring continues until the system is homogeneous. Subsequently, a curing agent is added to the obtained composite resin system, and stirring continues to mix evenly. Afterward, the obtained system is subjected to vacuum degassing treatment to reduce film-forming defects and internal bubbles. The organic mixed solvent is one or more of xylene, n-butanol, and isopropanol; the mass ratio of the bisphenol A epoxy resin to the bisphenol F epoxy resin is 3:1 to 1:1; the humidity-controlled environment is an environment with a relative humidity not exceeding 45%. The coating thickness is 100 to 300 μm. The programmed temperature curing method includes room temperature pre-curing, low temperature curing, medium temperature curing, and post-curing steps if necessary. Specifically, room temperature pre-curing is performed for 12–24 hours, curing at 50°C for 1–3 hours, curing at 80°C for 2–6 hours, and post-curing at 100°C for 0.5–2 hours as needed.

[0062] The mechanism of action of the polyrotaxane-functionalized basalt flakes is as follows: Firstly, the lamellar structure of the basalt flakes themselves can form tortuous diffusion paths in the coating, extending the penetration paths of water molecules, oxygen, and corrosive ions, thus improving barrier performance. Secondly, the polyrotaxane layer grafted onto the basalt surface provides dynamic interface buffering capacity through a mechanically interlocking slip ring structure. This slip ring structure can migrate along the polymer axis under external force, thereby alleviating local stress concentration and reducing the tendency for interfacial brittle fracture. Thirdly, the abundant hydroxyl groups on the cyclodextrin macrocycle can form a multi-point hydrogen bond network with the epoxy group, ensuring interfacial bonding while forming a continuous interfacial intermediate phase, thus balancing interfacial strength and stress dissipation capacity. These three effects combined enable the modified basalt flakes to exhibit superior dispersion stability, interfacial compatibility, mechanical reinforcement effect, and corrosion resistance compared to ordinary basalt fillers in epoxy resin.

[0063] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] The chemical reagents used in the embodiments and comparative examples of this invention are all common commercially available products.

[0065] Example 1

[0066] I. Preparation of polyrotaxane-functionalized basalt flakes;

[0067] Weighing of raw materials (by mass)

[0068] Basalt flakes: 30g;

[0069] Hydrochloric acid solution (0.2 mol / L): appropriate amount;

[0070] Tetramethylammonium hydroxide aqueous solution (2wt%): 900 mL;

[0071] Polyethylene glycol (PEG, average number-average molecular weight Mn=600): 10g;

[0072] 2,2,6,6-Tetramethylpiperidine-1-oxy (TEMPO): 10 mg;

[0073] Sodium bromide (NaBr): 100 mg;

[0074] Sodium hypochlorite aqueous solution (NaClO, available chlorine content ≥5.0%): 10 mL;

[0075] α-Cyclodextrin (α-CD): 12g;

[0076] Dichloromethane (CH2Cl2): 100mL;

[0077] N,N-Dimethylformamide (DMF): 60 mL;

[0078] 2-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethylureonium hexafluorophosphate (HATU): 20 mg;

[0079] Triethylamine: 16 mg;

[0080] Diaminosilane coupling agent KH792: 3.0g;

[0081] Bisphenol A type epoxy resin E44: 10g;

[0082] Bisphenol F type epoxy resin: 5g;

[0083] KH560: 0.05g;

[0084] Polyamide curing agent TY650: 8g;

[0085] Polyrotaxane-functionalized basalt flakes (PEB): 0.2g;

[0086] Xylene: 1.4g;

[0087] n-Butanol: 0.6g;

[0088] Isopropanol: 0.4g.

[0089] S1: Basalt flake pretreatment and surface functionalization treatment;

[0090] First, 30g of basalt flakes were added to a 0.2mol / L hydrochloric acid solution and stirred at room temperature for 1 hour. After filtration, the flakes were washed with deionized water until neutral. Then, the pretreated basalt flakes were added to 900mL of tetramethylammonium hydroxide aqueous solution and stirred continuously at 70℃ for 1.5 hours. After the reaction, the solid was collected by vacuum filtration and washed thoroughly with deionized water until the filtrate was neutral. The solid was then vacuum dried at 80℃ for 12 hours to obtain activated basalt flakes. The activated basalt flakes were then added to an ethanol / water mixed solution, and bis(aminosilane) coupling agent KH792 was added at a mass ratio of 1:10 (KH792 to activated basalt flakes). The mixture was stirred at 60℃ for 4 hours. After the reaction, the flakes were filtered and washed successively with ethanol and deionized water. The flakes were then vacuum dried at 60℃ to obtain surface-functionalized basalt flakes.

[0091] S2: Preparation of polyrotaxanes with carboxyl groups at the ends;

[0092] Raw material mixing: Add 10g of polyethylene glycol to 100mL of deionized water and stir at room temperature until completely dissolved. Then add 10mg of TEMPO, 100mg of NaBr and 10mL of NaClO aqueous solution with an effective chlorine content of not less than 5.0% in sequence, and continue stirring to mix to obtain a homogeneous reaction solution.

[0093] Oxidation reaction: Adjust the pH of the reaction solution to 10-11 and react at room temperature for 15 minutes to induce oxidation of the end groups of polyethylene glycol.

[0094] Post-processing: After the reaction was completed, the system was acidified with hydrochloric acid to pH < 2, 100 mL of dichloromethane was added for extraction, the organic phase was collected, the solvent was removed under reduced pressure, and then recrystallized with ethanol. Finally, it was dried under vacuum at 40 °C to obtain a yellow liquid carboxyl-terminated polyethylene glycol (PEG-COOH).

[0095] Preparation of polyrotaxane:

[0096] Raw material mixing: Add 3.0g of PEG-COOH and 12g of α-cyclodextrin to 100mL of deionized water to form a homogeneous slurry;

[0097] Coiling reaction: The reaction was carried out overnight at 4°C, allowing α-cyclodextrin to gradually coat the PEG-COOH molecular chain to form a polyrotaxane structure;

[0098] Post-processing: After the reaction was completed, the product was collected by centrifugation and washed four times with 200 mL of deionized water each time to remove unreacted free α-cyclodextrin and small molecule impurities. Finally, it was freeze-dried for 24 h to obtain a grayish-white powder with carboxyl-terminated polyrotaxane.

[0099] S3: Covalent grafting reaction;

[0100] Grafting reaction: 1 g of surface-functionalized basalt flakes was weighed and added to 50 mL of DMF, and ultrasonically dispersed in a three-necked flask for 10 min. After purging with nitrogen, 20 mg of HATU and 16 mg of triethylamine were added, and the mixture was stirred for 10 min. Then, 2.83 g of polyrotaxane dissolved in 10 mL of DMF was added, and the mixture was stirred for another 10 min and ultrasonicated again for 5 min. The reaction was carried out at room temperature for 6 h under nitrogen protection. After the reaction was completed, the product was collected by centrifugation, washed three times with DMF, three times with ethanol, and twice with deionized water. Finally, the product was vacuum dried at 60 °C for 12 h to obtain polyrotaxane-functionalized basalt flakes (PEB).

[0101] The obtained polyrotaxane-functionalized basalt flakes include a basalt flake substrate and polyrotaxane molecules grafted onto the surface of the basalt flake substrate via amide bonds; the polyrotaxane molecules include a polyethylene glycol linear polymer axis and an α-cyclodextrin cyclic molecule sleeved on the polyethylene glycol linear polymer axis and capable of sliding along it.

[0102] II. Preparation of polyrotaxane functionalized basalt composite coating;

[0103] S1: Preparation of component A;

[0104] Weigh 5g of 10g of bisphenol A type epoxy resin E44, 0.2g of polyrotaxane-functionalized basalt flakes PEB, 1.4g of xylene, 0.6g of n-butanol, and 0.4g of isopropanol, add them to a container, and magnetically stir for 20min at room temperature to obtain a pre-dispersion mother liquor of component A; then, the component A is dispersed at high speed for 15min and ultrasonically treated for 15min to further improve the dispersion uniformity of PEB in bisphenol A type epoxy resin and reduce the agglomeration of flakes;

[0105] S2: Preparation of component B;

[0106] Weigh 5g of bisphenol F type epoxy resin, add 0.05g of KH560, and stir at room temperature for 20min to uniformly disperse KH560 in the bisphenol F type epoxy resin to obtain component B;

[0107] S3: Composite and curing;

[0108] Component B is slowly added to component A and mixed for 20 minutes under medium-low speed stirring conditions; then 5 g of the remaining bisphenol A type epoxy resin E44 and 8 g of polyamide curing agent TY650 are added and stirred for 20 minutes, followed by vacuum degassing for 15 minutes to obtain a uniform coating slurry.

[0109] The obtained slurry was coated onto the surfaces of a transparent silicone sheet and a Q235 steel plate under an environment with a relative humidity not exceeding 45%, forming a free membrane sample and a protective coating sample, with the coating thickness controlled at 180~220μm. The coated samples were then subjected to programmed temperature curing: pre-curing at room temperature for 18h, curing at 50℃ for 2h, curing at 80℃ for 4h, followed by post-curing at 100℃ for 1h, to obtain the EP-PEB composite coating.

[0110] The resulting composite coating comprises an epoxy resin matrix (a mixture of bisphenol A and bisphenol F epoxy resins in a 1:1 mass ratio) and polyrotaxane-functionalized basalt flakes dispersed within the epoxy resin matrix (added at 1.33% of the epoxy resin mass). This composite coating forms an interfacial buffer layer with mechanical interlocking and dynamic slippage characteristics between the basalt flakes and the epoxy resin matrix.

[0111] Comparative Example 1

[0112] I. Preparation of activated basalt flakes;

[0113] Weighing of raw materials (by mass)

[0114] Basalt flakes: 30g;

[0115] Hydrochloric acid solution (0.2 mol / L): appropriate amount;

[0116] Tetramethylammonium hydroxide aqueous solution (2wt%): 900 mL;

[0117] Bisphenol A type epoxy resin E44: 10g;

[0118] Bisphenol F type epoxy resin: 5g;

[0119] KH560: 0.05g;

[0120] Polyamide curing agent TY650: 8g;

[0121] Activated basalt flakes (EB): 0.2g;

[0122] Xylene: 1.4g;

[0123] n-Butanol: 0.6g;

[0124] Isopropanol: 0.4g.

[0125] The preparation steps for activated basalt (EB) are as follows:

[0126] First, 30g of basalt flakes were added to a 0.2mol / L hydrochloric acid solution and stirred at room temperature for 1 hour. After filtration, the flakes were washed with deionized water until neutral. Then, the pretreated basalt flakes were added to 900mL of a 2wt% tetramethylammonium hydroxide aqueous solution and stirred continuously at 70℃ for 1.5 hours. After the reaction, the solid product was collected by vacuum filtration and repeatedly washed with deionized water until neutral. Finally, the product was vacuum dried at 80℃ for 12 hours to obtain activated basalt flakes (EB).

[0127] II. The preparation steps of the composite coating are as follows:

[0128] S1: Preparation of component A;

[0129] Weigh 5g of 10g of bisphenol A type epoxy resin E44, 0.2g of activated basalt flakes EB, 1.4g of xylene, 0.6g of n-butanol, and 0.4g of isopropanol, add them to a container, and magnetically stir for 20min at room temperature to obtain a pre-dispersion mother liquor of component A; then, the component A is dispersed at high speed for 15min and ultrasonically treated for 15min to improve the dispersion uniformity of EB in bisphenol A type epoxy resin and reduce the agglomeration of flakes;

[0130] S2: Preparation of component B;

[0131] Weigh 5g of bisphenol F type epoxy resin, add 0.05g of KH560, and stir at room temperature for 20min to uniformly disperse KH560 in the bisphenol F type epoxy resin to obtain component B;

[0132] S3: Composite and curing;

[0133] Component B is slowly added to component A and mixed for 20 minutes under medium-low speed stirring conditions; then 5 g of the remaining bisphenol A type epoxy resin E44 and 8 g of polyamide curing agent TY650 are added and stirred for 20 minutes, followed by vacuum degassing for 15 minutes to obtain a uniform coating slurry.

[0134] The obtained slurry was coated onto the surface of a transparent silicone sheet and a Q235 steel plate under an environment with a relative humidity not exceeding 45% to obtain a free film and a coated sample, respectively, with the coating thickness controlled at 180~220μm; then, a programmed temperature curing was performed, specifically: pre-curing at room temperature for 18h, curing at 50℃ for 2h, curing at 80℃ for 4h, and then post-curing at 100℃ for 1h to obtain the EP-EB composite coating.

[0135] Comparative Example 1 is a control experiment of Example 1, as shown in Table 1:

[0136] Table 1. Summary of Control Experiments in Comparative Example 1

[0137]

[0138] Performance testing

[0139] 1. Testing Standards

[0140] Component characterization: filler structure (Fourier transform infrared spectroscopy (FT-IR)); polyrotaxane molecular structure (1H-NMR); surface elemental composition and chemical state (X-ray photoelectron spectroscopy (XPS)); surface charge and interfacial electrostatic properties (Zeta potentiometer); dispersion stability (sedimentation experiment).

[0141] Morphological characterization: Scanning electron microscopy (SEM) was used to observe the morphology of the coating surface, substrate surface, and cross-section;

[0142] Mechanical properties: Tensile strength (GB / T1040-2023, universal testing machine, tensile rate 2mm / min, specimen thickness 200±10μm, gauge length 25mm×4mm); Dynamic mechanical analysis (DMA) (test temperature range 20~200℃, heating rate 10℃ / min); Impact resistance (GB / T 1732-2020, falling ball impact test).

[0143] Corrosion resistance: Electrochemical impedance spectroscopy (EIS) test (GB / T 40299-2021, test frequency range is 10). 5 ~10 - 2 The test system used a three-electrode system with a perturbation voltage of 20mV and a corrosive medium of 3.5wt.% NaCl aqueous solution. The service environment was a pseudo-deep-sea condition (fluid velocity 3m / s, hydrostatic pressure 6MPa, test time 240h).

[0144] 2. Test Results

[0145] The results of Example 1 and Comparative Example 1 are summarized in Table 2, the DMA test results are summarized in Table 3, and the electrochemical fitting parameters are shown in Table 4.

[0146] Table 2. Summary of test results for Example 1 and Comparative Example 1

[0147]

[0148] Table 3. Summary of DMA test results for Example 1 and Comparative Example 1

[0149]

[0150] Table 4. Electrochemical fitting parameters of Example 1 and Comparative Example 1

[0151]

[0152] 3. Conclusion

[0153] 1) Test results show that, in this embodiment, polyrotaxane-functionalized basalt flakes (PEB) were successfully prepared by covalently grafting polyrotaxane synthesized from cyclodextrin onto the basalt surface. Combined with FT-IR, Zeta potential, and SEM characterization results, it is evident that PEB exhibits different surface chemical structures and interfacial properties compared to EB, indicating that polyrotaxane has been successfully introduced into the basalt surface. Simultaneously, sedimentation experiments show that the dispersion stability of PEB in epoxy resin is significantly better than that of EB, indicating that the constructed polyrotaxane interfacial layer is beneficial for improving the uniformity of filler dispersion and interfacial compatibility in the resin matrix.

[0154] 2) Mechanical properties and impact results show that the EP-PEB composite coating obtained in this invention has a superior strengthening and toughening effect compared to the control system EP-EB. Compared with EP-EB, the maximum tensile stress of EP-PEB increased from about 33 MPa to about 41 MPa, the fracture strain increased from about 7% to about 11%, and the toughness increased from about 213 MJ·m. -3 Increased to approximately 316 MJ·m -3 Meanwhile, no obvious cracks were observed on the surface of EP-PEB after impact, while obvious cracks appeared on EP-EB, indicating that the polyrotaxane interface layer can effectively alleviate interfacial stress concentration and improve the material's crack resistance and impact damage resistance.

[0155] 3) Corrosion resistance and service results show that after 240 hours of service under simulated deep-sea conditions (6MPa, 3m / s), the low-frequency impedance modulus of EP–PEB remains at 3.20×10⁻⁶. 10 Ω·cm 2 The magnitude is significantly higher than EP–EB's 6.80 × 10⁻⁶. 9 Ω·cm 2 Meanwhile, its Rct still reached 3.71 × 10⁻⁶ at 240 h. 10 Ω·cm 2 The EP–EB is only 0.69 × 10⁻⁶. 10 Ω·cm 2 .

[0156] 4) Combining the surface and cross-sectional morphology after service, it can be seen that the EP-PEB coating surface did not show obvious cracking, and the interface maintained good integrity, while the EP-EB system showed cracks, enrichment of corrosion products, and interface deterioration. This indicates that the polyrotaxane functionalized basalt technology with α-cyclodextrin as the preferred cyclic molecule can achieve a unity of strong interfacial bonding, dynamic buffering, and long-term barrier, and has good engineering application prospects.

[0157] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A polyrotaxane functionalized basalt composite coating, characterized in that, The composite coating comprises an epoxy resin matrix and polyrotaxane-functionalized basalt flakes dispersed in the epoxy resin matrix; The polyrotaxane-functionalized basalt flakes include a basalt flake substrate and polyrotaxane molecules grafted onto the surface of the basalt flake substrate via covalent bonds; The polyrotaxane molecule comprises a linear polymer axis and a cyclic molecule sleeved on the linear polymer axis and capable of sliding along it; The end functional groups of the polyrotaxane molecule and the functional groups on the surface of the basalt flake substrate form covalent bonds through a covalent reaction; The composite coating forms an interface buffer layer with mechanical interlocking and dynamic slip characteristics between the basalt flakes and the epoxy resin matrix. The linear polymer axis is a linear polymer capable of forming a host-guest encapsulation structure with cyclodextrin, and is selected from one or two of polyethylene glycol and linear polymers containing polyethylene glycol segments; The terminal functional group of the polyrotaxane molecule is a carboxyl group, the reactive functional group on the surface of the basalt flakes is an amino group, and the covalent bond is an amide bond.

2. A polyrotaxane functionalized basalt composite coating according to claim 1, characterized in that, The polyrotaxane-functionalized basalt flakes are prepared by the following steps: S1: Basalt flake pretreatment and surface functionalization treatment; Basalt flakes are first subjected to acidic pretreatment and quaternary ammonium base activation treatment to remove surface impurities, increase surface hydroxyl groups and form a rough structure that is conducive to subsequent grafting; then the activated basalt flakes are reacted with a diaminosilane coupling agent to introduce amino functional groups on its surface, thus obtaining surface-functionalized basalt flakes. S2: Preparation of polyrotaxane by cyclodextrin synthesis; Polyethylene glycol with carboxyl groups at the ends was subjected to a host-guest inclusion-coating reaction with cyclodextrin to obtain polyrotaxane with carboxyl groups at the ends. S3: Polyrotaxane grafting reaction; The polyrotaxane obtained in step S2 is covalently grafted with the surface-functionalized basalt flakes obtained in step S1, so that the carboxyl groups of the polyrotaxane end group are connected to the amino groups on the surface of the basalt flakes through amide bonds, thereby obtaining polyrotaxane-functionalized basalt flakes.

3. A polyrotaxane functionalized basalt composite coating according to claim 2, characterized in that, In step S1, the quaternary ammonium base is an aqueous solution of tetramethylammonium hydroxide; the bisaminosilane coupling agent is KH792, and the mass ratio of KH792 to activated basalt flakes is 1:20 to 1:

5.

4. The polyrotaxane-functionalized basalt composite coating according to claim 2, characterized in that, In step S2, the cyclodextrin is α-cyclodextrin, or a combination mainly composed of α-cyclodextrin and containing β-cyclodextrin; when the cyclic molecule is composed of α-cyclodextrin and β-cyclodextrin, the molar fraction of β-cyclodextrin in the total cyclodextrin is 0~20%.

5. A polyrotaxane functionalized basalt composite coating according to claim 2, characterized in that, In step S2, the number average molecular weight of the polyethylene glycol is 400-1000; the mass ratio of the cyclodextrin to the polyethylene glycol is 2:1-10:1; and the host-guest encapsulation reaction is carried out at 0-10°C for 8-24 hours.

6. A polyrotaxane functionalized basalt composite coating according to claim 2, characterized in that, In step S3, the covalent grafting uses a HATU or EDC / NHS activation system, the reaction solvent is DMF, DMSO or a mixture thereof, the reaction temperature is 20~40℃, and the reaction time is 4~24h.

7. A polyhedral oligomeric functionalized basalt composite coating according to claim 1, characterized in that, The epoxy resin matrix is ​​a compound system of bisphenol A type epoxy resin and bisphenol F type epoxy resin, with a mass ratio of 3:1 to 1:

1. The amount of functionalized basalt flakes added to the composite coating is 0.1% to 10% of the resin mass.

8. A polyhedral oligomeric functionalized basalt composite coating according to claim 7, characterized in that, The composite coating is prepared by a method comprising the following steps: The polyrotaxane-functionalized basalt flakes were dispersed in bisphenol A type epoxy resin to obtain component A. Silane coupling agent was dispersed in bisphenol F type epoxy resin to obtain component B; The B component is added to the A component and mixed, then a curing agent is added, and the mixture is subjected to vacuum degassing, coating, and programmed temperature curing to obtain the composite coating.

9. A polyrotaxane functionalized basalt composite coating according to claim 8, characterized in that, The silane coupling agent in component B is γ-glycidoxypropyltrimethoxysilane, and its addition amount is 0.1% to 5% of the mass of bisphenol F epoxy resin.

10. Use of a polyrotaxane functionalized basalt composite coating according to any of claims 1-9, characterized in that, The application is selected from at least one of the following: 1) Corrosion protection of metal surfaces in marine engineering equipment; 2) Corrosion protection of metal surfaces in deep-sea equipment; 3) Corrosion protection on the metal surface of bridge steel structures.

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