Basalt fiber / weather-resistant polyurethane resin-based composite material as well as preparation method and application thereof

Abstract

The invention relates to the field of high-performance composite materials, and discloses a basalt fiber / weather-resistant polyurethane resin-based composite material as well as a preparation method and application thereof. Comprising the following steps: mixing polyether polyol, polyester polyol, a blocked isocyanate prepolymer and a DA monomer to react to obtain a polyurethane prepolymer; mixing a polyurethane prepolymer, a nano silicon dioxide modifier, a hindered amine light stabilizer, a microencapsulated latent curing agent and a phosphorus-nitrogen synergistic flame retardant to obtain a polyurethane resin mixture; the preparation method comprises the following steps: coating the surface of basalt fiber with a silane coupling agent to obtain modified basalt fiber, forming an epoxy nano-alumina coating and a polyurethane resin mixture layer on the surface of the modified basalt fiber, soaking in a polyurethane resin mixture, and curing to obtain the basalt fiber / weather-resistant polyurethane resin-based composite material. According to the scheme, the basalt fibers are coated in a gradient manner to form a chemical-physical synergistic enhancement structure, so that the interfacial force between the polyurethane resin and the basalt fibers is enhanced.

Description

Technical Field

[0001] This invention relates to the field of high-performance composite materials, specifically to basalt fiber / weather-resistant polyurethane resin-based composite materials, their preparation methods, and applications. Background Technology

[0002] Continuous basalt fiber (CBF) is a type of continuous fiber made from pure natural volcanic rock (mainly basalt). The rock is crushed and added to a melting furnace, where it is melted at a high temperature of 1450–1500℃. The resulting fiber is then drawn into continuous fibers using a platinum-rhodium alloy spinneret. Because the production process of continuous basalt fiber is short and produces very little waste, it is an environmentally friendly material that is non-toxic, harmless, resource- and energy-efficient, and recyclable.

[0003] Compared to steel, basalt fiber offers several performance advantages: high specific strength and modulus, resistance to high and low temperatures (-269~700℃), good resistance to water damage, resistance to acid, alkali, and salt corrosion, resistance to ultraviolet light, electrical insulation, polar fiber surface, all-natural and environmentally friendly properties, fire retardancy, strong UV resistance, low moisture absorption, high-temperature filtration performance, radiation resistance, and wave transmission. Compared to other fibers, basalt fiber boasts outstanding comprehensive performance, offering high cost-effectiveness. For example, most of its mechanical properties exceed those of glass fiber, exhibiting good durability and suitability for structural materials. Its strength, stiffness, and various durability properties also reach or exceed those of high-tech aramid fiber, particularly its high tensile strength and yield strength, with continuous fiber filaments achieving tensile strengths of 3000-4840 MPa. Taking composite material poles in the power industry as an example, basalt fiber materials offer higher tensile and yield strengths, resistance to high and low temperatures (-269~700℃), good resistance to water damage, and are also inexpensive and easy to process. Currently, there is considerable research and application of basalt fiber materials in concrete materials in the construction field in China. However, power grid companies have not yet applied basalt materials to transmission and distribution equipment materials (pole, insulator, composite insulated crossarm). Only a few manufacturers and research institutions have trial-produced basalt fiber composite insulated crossarms. Related research shows that utilizing the high mechanical strength and stability characteristics of basalt fiber composite materials can extend the service life of composite poles in high-temperature, high-humidity, and high-salt-alkali areas. Under the condition of line mechanical properties, it can reduce the size of the composite core profile of the pole and the deflection of the composite pole under standard test loads, and improve the bending moment strength. In terms of "lightweight reinforcement modification", it has a significant competitive advantage over existing glass fiber composite poles.

[0004] Existing power composite materials generally use epoxy or vinyl ester resin matrices, which suffer from problems such as high brittleness, poor weather resistance, and complex curing processes. While basalt fiber offers advantages such as high strength and corrosion resistance, its interfacial compatibility with polyurethane resin is insufficient, resulting in composite materials with flexural strength generally below 800 MPa and tensile strength below 900 MPa. Furthermore, traditional polyurethane resins also suffer from moisture absorption and foaming, leading to significant performance degradation in humid and hot environments (as shown in schemes CN103483801A and CN102993398B). Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of insufficient interfacial compatibility between basalt fiber and polyurethane resin in the prior art, and to provide basalt fiber / weather-resistant polyurethane resin-based composite materials, their preparation methods and applications. In this scheme, basalt fiber is sequentially coated with a silane coupling agent layer, an epoxy nano-alumina sol coating, and a polyurethane prepolymer gradient coating to achieve a gradient interface design on the fiber surface, forming a chemical-physical synergistic reinforcement structure, thereby enhancing the interfacial force between polyurethane resin and basalt fiber.

[0006] To achieve the above objectives, the present invention provides a method for preparing a basalt fiber / weather-resistant polyurethane resin-based composite material, comprising: A first reaction is carried out by mixing polyether polyol, polyester polyol and blocked isocyanate prepolymer to obtain terminal-NCO prepolymer. The terminal-NCO prepolymer is then mixed with DA monomer to carry out a second reaction to obtain polyurethane prepolymer. Aminosilane-modified nano-SiO2 was mixed with polyurethane prepolymer to carry out a third reaction to obtain nano-silica modifier. Then, polyurethane prepolymer, nano-silica modifier, hindered amine light stabilizer, microencapsulated latent curing agent and phosphorus-nitrogen synergistic flame retardant were mixed to obtain polyurethane resin mixture. A silane coupling agent is coated on the surface of basalt fiber and dried to obtain modified basalt fiber. Then, an epoxy nano-alumina coating is formed on the surface of the modified basalt fiber to obtain epoxy alumina basalt fiber. Then, a polyurethane resin mixture layer is formed on the surface of the epoxy alumina basalt fiber to obtain surface-modified basalt fiber. Surface-modified basalt fibers are impregnated in a polyurethane resin mixture to obtain impregnated surface-modified basalt fibers. The impregnated surface-modified basalt fibers are then cured to obtain a basalt fiber / weather-resistant polyurethane resin-based composite material.

[0007] Preferably, the molar ratio of the polyether polyol to the polyester polyol is (1.5-4):1; More preferably, the weight ratio of the blocked isocyanate prepolymer to the total weight of the polyether polyol and the polyester polyol is (60-65):30.

[0008] Preferably, the blocked isocyanate prepolymer is a hexamethylene diisocyanate trimer or a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; More preferably, when the blocked isocyanate prepolymer is a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer, the molar ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate trimer is ≥3:1.

[0009] Preferably, the conditions for the first reaction include: a temperature of 85-95°C and a time of 2-4 hours.

[0010] Preferably, the molar ratio of DA monomer to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer is (5-8):100; More preferably, the conditions for the second reaction include: a temperature of 75-80°C and a time of 1.5-2.5 h.

[0011] Preferably, the preparation method of the aminosilane-modified nano-SiO2 includes: mixing aminosilane, ethanol and water, stirring at room temperature for 30-40 min to obtain a silane solution, mixing nano-SiO2 with an organic solvent to obtain a dispersion, mixing the silane solution and the dispersion, stirring and reacting at 60-120℃ for 2-8 h, then filtering, washing and drying the filtered solid to obtain aminosilane-modified nano-SiO2; More preferably, the weight ratio of the aminosilane to nano-SiO2 is (2-5):100.

[0012] Preferably, the aminosilane-modified nano-SiO2 is mixed with polyurethane prepolymer to carry out the third reaction, wherein the weight ratio of aminosilane-modified nano-SiO2 to polyurethane prepolymer is (5-10):100. More preferably, the conditions for the third reaction include: a temperature of 40-60°C and a time of 30-60 min.

[0013] Preferably, the process of mixing polyurethane prepolymer, nano-silica modifier, microencapsulated latent curing agent and phosphorus-nitrogen synergistic flame retardant to obtain polyurethane resin mixture includes: mixing polyurethane prepolymer, nano-silica modifier and microencapsulated latent curing agent and then shearing and dispersing to obtain resin matrix, and mixing resin matrix with phosphorus-nitrogen synergistic flame retardant to obtain polyurethane resin mixture; More preferably, the microencapsulated latent curing agent is a polyacrylic acid-encapsulated dibutyltin dilaurate capsule; More preferably, the polyacrylic acid-encapsulated dibutyltin dilaurate capsules have a particle size of 1-3 μm.

[0014] Preferably, in the polyurethane resin mixture, the content of microencapsulated latent curing agent is 0.2-0.6 wt%, the content of nano silica modifier is 2-5 wt%, the content of phosphorus-nitrogen synergistic flame retardant is 5-10 wt%, and the content of hindered amine light stabilizer is 0.5-1.2 wt%.

[0015] Preferably, the operation of forming an epoxy nano-alumina coating on the surface of modified basalt fibers includes: coating the surface of modified basalt fibers with an epoxy nano-alumina mixture, and then drying it; More preferably, the preparation method of the epoxy nano-alumina mixture includes: dissolving epoxy resin and coupling agent in a mixed solvent to obtain an epoxy resin mixed solution, and uniformly dispersing nano-Al2O3 into the epoxy resin mixed solution to obtain the epoxy nano-alumina mixture.

[0016] Preferably, the surface-modified basalt fiber content in the impregnated surface-modified basalt fiber is 65-82 wt%.

[0017] Preferably, the impregnated surface-modified basalt fibers are cured using pultrusion, winding, or molding processes.

[0018] A second aspect of the present invention provides a basalt fiber / weather-resistant polyurethane resin-based composite material prepared by the above-described preparation method.

[0019] The third aspect of this invention provides an application of the above-mentioned basalt fiber / weather-resistant polyurethane resin-based composite material in transmission towers, insulating crossarms, offshore wind power structures, photovoltaic supports, and marine engineering equipment.

[0020] Compared with existing technologies, the advantages of this invention are fully demonstrated in the following ways: 1. The method for synthesizing polyurethane resin according to the present invention is simple and the route is clear. Furthermore, the performance, strength, and toughness of the synthesized polyurethane resin can be controlled by selecting and adjusting the addition ratio of active HDI and IPDI trimers.

[0021] 2. Using a closed-type isocyanate prepolymer, the resin viscosity is low, which can reduce or avoid the use of solvents, making the product with high solids content. This helps to reduce pollution and is not easy to deteriorate. The viscosity does not change much after storage, the curing agent has a long service life, which is beneficial to construction operations. It also has excellent weather resistance and the resin is not easy to yellow.

[0022] 3. Nano-SiO2 is treated with aminosilane (KH550) and reacts with the -NCO groups of polyurethane prepolymer to form an interpenetrating network with fixed chemical bonds, which significantly reduces the water absorption rate of the resin material.

[0023] 4. By using the gradient of silane coupling agent and epoxy nano-alumina sol, and the three-dimensional interface design of polyurethane resin, the chemical bonding, physical hydrogen bonding, and electrostatic anchoring of basalt fiber, nano-alumina particles and polyurethane resin are achieved, thereby improving the interfacial bonding strength and solving the technical problem of poor interfacial bonding between basalt and polyurethane resin.

[0024] 5. The introduced Diels-Alder (DA) bond can be thermally triggered at 80-100℃ to achieve a dynamic reversible reaction, enabling self-repair of microcracks and reducing the damage rate of composite material products.

[0025] 6. The addition of a phosphorus-nitrogen synergistic flame retardant (polytetrabromobisphenol A phosphononitrile) works synergistically with flame-retardant basalt to improve the flame retardancy of basalt composite materials to UL94 V0 level, solving the limitations of the application scenarios and expanding the multi-functional application scenarios. Attached Figure Description

[0026] Figure 1 This is a technical roadmap for the preparation of surface-modified basalt fibers according to the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions provided in the various embodiments of this invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0030] This invention provides a method for preparing a basalt fiber / weather-resistant polyurethane resin-based composite material, comprising: A first reaction is carried out by mixing polyether polyol, polyester polyol and blocked isocyanate prepolymer to obtain terminal-NCO prepolymer. The terminal-NCO prepolymer is then mixed with DA monomer to carry out a second reaction to obtain polyurethane prepolymer. Aminosilane-modified nano-SiO2 was mixed with polyurethane prepolymer to carry out a third reaction to obtain nano-silica modifier. Then, polyurethane prepolymer, nano-silica modifier, hindered amine light stabilizer, microencapsulated latent curing agent and phosphorus-nitrogen synergistic flame retardant were mixed to obtain polyurethane resin mixture. A silane coupling agent is coated on the surface of basalt fiber and dried to obtain modified basalt fiber. Then, an epoxy nano-alumina coating is formed on the surface of the modified basalt fiber to obtain epoxy alumina basalt fiber. Then, a polyurethane resin mixture layer is formed on the surface of the epoxy alumina basalt fiber to obtain surface-modified basalt fiber. Surface-modified basalt fibers are impregnated in a polyurethane resin mixture to obtain impregnated surface-modified basalt fibers. The impregnated surface-modified basalt fibers are then cured to obtain a basalt fiber / weather-resistant polyurethane resin-based composite material.

[0031] In this invention, the molar ratio of polyether polyol to polyester polyol is (1.5~4):1. During the subsequent reaction, polyether polyol and polyester polyol will form a polyether-polyester block copolymer. By changing the content of polyether and polyester, the strength and toughness of polyurethane resin can be designed. The higher the polyester content, the greater the strength of the resin, but the lower the toughness. Therefore, it is more appropriate to control the ratio of polyether polyol to polyester polyol within the above range.

[0032] In one specific embodiment, the polyether polyol has an average molecular weight of 2000; the polyester polyol is mainly composed of adipic acid and neopentyl glycol copolymer, with an average molecular weight of 1800.

[0033] The weight ratio of the blocked isocyanate prepolymer to the total weight of the polyether polyol and polyester polyol is (60-65): 30.

[0034] In this invention, the blocked isocyanate prepolymer is a hexamethylene diisocyanate (HDI) trimer or a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate (IPDI) trimer.

[0035] When the blocked isocyanate prepolymer is a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer, the molar ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate trimer is ≥3:1. At this time, the crosslinking degree of the polymer can be controlled by the content ratio of HDI and IPDI trimers, thereby controlling the strength and toughness of the resin. A high HDI trimer content results in high resin toughness but low strength, while a high IPDI trimer content results in high resin strength but low toughness.

[0036] In the preferred case, the polyether polyol and polyester polyol need to be vacuum dehydrated before they can be mixed with the blocked isocyanate prepolymer for the first reaction. This is because the blocked isocyanate prepolymer has a higher reactivity with water than with the polyether polyol and polyester polyol. If water is present, the blocked isocyanate prepolymer will react preferentially with water, affecting the product performance. Therefore, the polyether polyol and polyester polyol need to be vacuum dehydrated beforehand to remove moisture.

[0037] The vacuum dehydration temperature is generally 40-50℃ to avoid the volatilization of vacuum polyols due to excessive temperature, and the vacuum dehydration time is generally 0.5-1h.

[0038] Preferably, the conditions for the first reaction include: a temperature of 85-95°C and a time of 2-4 hours.

[0039] The terminal-NCO prepolymer in this invention contains -CNO groups, which can react with hydroxyl and amino groups generated on the surface of nano-SiO2 after modification with aminosilane.

[0040] The DA monomer in this invention is a furan-maleimide system, containing furan-maleimide segments, and is commercially available.

[0041] The molar ratio of DA monomer to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer is (5-8):100. By adding DA monomer to introduce Diels-Alder (DA) bonds, a dynamic reversible reaction can be thermally triggered at 80-100℃, enabling the product to achieve self-repair of microcracks and avoid microcracks due to thermal stress concentration during the later heat release process of the produced product, thus achieving functional self-repair.

[0042] Specifically, the conditions for the second reaction include: a temperature of 75-80°C and a time of 1.5-2.5 hours.

[0043] In a preferred embodiment, the aminosilane-modified nano-SiO2 of the present invention is prepared in-house. The preparation method of the aminosilane-modified nano-SiO2 includes: mixing aminosilane, ethanol and water, stirring at room temperature for 30-40 min to obtain a silane solution, mixing nano-SiO2 with an organic solvent to obtain a dispersion, mixing the silane solution and the dispersion, stirring and reacting at 60-120°C for 2-8 h, then filtering, washing and drying the filtered solid to obtain aminosilane-modified nano-SiO2.

[0044] In one specific embodiment, the aminosilane is KH550.

[0045] In the preparation method of aminosilane modified nano-SiO2, the weight ratio of ethanol to water is 4:1.

[0046] In this invention, aminosilane, ethanol and water are mixed and stirred to hydrolyze the ethoxy group (-C2H5O) to generate silanol group (-Si-OH) to obtain a silane solution; wherein the weight ratio of the amount of aminosilane to the total amount of aminosilane, ethanol and water is (2-5):100.

[0047] Preferably, the weight ratio of the aminosilane to nano-SiO2 is (2-5):100.

[0048] In the above-mentioned method for preparing aminosilane-modified nano-SiO2, the organic solvent used is a high-boiling-point solvent (such as n-butanol and / or toluene). After mixing nano-SiO2 with the organic solvent, the mixture is ultrasonically treated for 15 minutes to improve dispersibility and ensure that the nano-SiO2 is fully and uniformly dispersed to obtain a dispersion. The amount of organic solvent used is only sufficient to fully and uniformly disperse the nano-SiO2.

[0049] Furthermore, to avoid agglomeration, in actual operation, the silane solution is added dropwise to the dispersion and mixed, and then stirred at 60-120℃ for 2-8 hours. During the reaction, the silanol groups of KH550 condense with the hydroxyl groups on the surface of SiO2 to form Si-O-Si bonds, grafting amino (-NH2) and alkyl (-CH2-) groups. After the reaction is completed, the mixture is filtered, and the solid obtained by filtration is washed three times with ethanol to remove unreacted reagents. After drying, it is ground to obtain aminosilane modified nano-SiO2.

[0050] Further, aminosilane-modified nano-SiO2 is mixed with polyurethane prepolymer for a third reaction, wherein the weight ratio of aminosilane-modified nano-SiO2 to polyurethane prepolymer is (5-10):100.

[0051] Preferably, the conditions for the third reaction include: a temperature of 40-60°C and a time of 30-60 min.

[0052] In the third reaction described above, the outermost layer of aminosilane-modified nano-SiO2, after being treated with polyurethane prepolymer, can form an interpenetrating network of organic-inorganic oligomers with fixed chemical bonds. This network can serve as a rigid crosslinking point in the polyurethane resin, enhancing the resin's strength and modulus.

[0053] In a specific embodiment of the present invention, the process of mixing polyurethane prepolymer, nano-silica modifier, microencapsulated latent curing agent and phosphorus-nitrogen synergistic flame retardant to obtain a polyurethane resin mixture includes: mixing polyurethane prepolymer, nano-silica modifier, hindered amine light stabilizer (HALS) and microencapsulated latent curing agent and then shearing and dispersing the mixture to obtain a resin matrix; and mixing the resin matrix with the phosphorus-nitrogen synergistic flame retardant to obtain a polyurethane resin mixture.

[0054] Specifically, the microencapsulated latent curing agent is a polyacrylic acid-encapsulated dibutyltin dilaurate capsule, which is commercially available.

[0055] Furthermore, the polyacrylic acid-encapsulated dibutyltin dilaurate capsules have a particle size of 1-3 μm; the microencapsulated latent curing agent can be released in a controlled manner above 90°C, ensuring the stability of polyurethane resin at room temperature and rapid curing at high temperature, and the resin gel time at 130°C is <10 min, while being compatible with pultrusion and winding process requirements.

[0056] Preferably, in the polyurethane resin mixture, the content of microencapsulated latent curing agent is 0.2-0.6 wt%, the content of nano silica modifier is 2-5 wt%, the content of phosphorus-nitrogen synergistic flame retardant is 5-10 wt%, and the content of hindered amine light stabilizer is 0.5-1.2 wt%.

[0057] In one specific embodiment, the material is sheared and dispersed at 2500 rpm for 40 min.

[0058] Specifically, the phosphorus-nitrogen synergistic flame retardant used in this invention is polytetrabromobisphenol A phosphononitrile.

[0059] The basalt fiber in this invention can be common fiber materials such as chopped basalt fiber, continuous basalt fiber, and basalt fiber cloth. The diameter of the basalt fiber is generally 6mm.

[0060] The silane coupling agent in this invention is γ-glycidoxypropyltrimethoxysilane.

[0061] In this invention, after coating the surface of basalt fiber with a silane coupling agent, the fiber is dried at 70°C to form a silane coupling agent layer on the surface of the basalt fiber, thereby obtaining modified basalt fiber. The amount of silane coupling agent used is only required to ensure that the thickness of the final silane coupling agent layer is 200-800 nm, and in order to ensure uniform coating, 1-2 coats are sufficient.

[0062] In specific embodiments, a silane coupling agent can be directly coated onto the surface of basalt fibers, and after drying, a silane coupling agent layer can be formed on the surface of the basalt fibers; alternatively, a silane coupling agent solution can be obtained by mixing the silane coupling agent with an ethanol aqueous solution (obtained by mixing ethanol and water at a weight ratio of 4:1) (the solid-liquid ratio of the silane coupling agent to the ethanol aqueous solution is 30-50g:100mL), and then coating the surface of the basalt fibers with the silane coupling agent solution. After drying, the solvent evaporates, and finally a silane coupling agent layer is formed on the surface of the basalt fibers.

[0063] Furthermore, the operation of forming an epoxy nano-alumina coating on the surface of modified basalt fibers includes: coating the surface of modified basalt fibers with an epoxy nano-alumina mixture and then drying it.

[0064] In this invention, the preparation method of the epoxy nano-alumina mixture includes: dissolving epoxy resin and coupling agent in a mixed solvent to obtain an epoxy resin mixed solution, and uniformly dispersing nano-Al2O3 into the epoxy resin mixed solution (ultrasonic treatment for 30-60 min can be used to ensure uniform dispersion) to obtain the epoxy nano-alumina mixture.

[0065] The weight ratio of coupling agent to epoxy resin is 0.5-2:100; the weight ratio of nano Al2O3 to epoxy resin is 5-7.5:100.

[0066] The coupling agent mentioned above is an aminosilane and / or a fluorosiloxane (such as heptadecafluorodecyltriethoxysilane (PFDTES)); the amount of mixed solvent used is only required to ensure that the epoxy resin and the coupling agent are completely dissolved.

[0067] In this invention, the preparation method of nano-Al2O3 can be a conventional preparation process. Specifically, the preparation method of nano-Al2O3 is as follows: aluminum salt is used as a precursor and dissolved in a solvent to obtain a homogeneous solution. Then, it is hydrolyzed for 2-4 hours under the action of a catalyst to obtain aluminum hydroxide sol. The viscosity and stability of the sol are adjusted by controlling the pH value (usually 3-5) and the hydrolysis temperature (25-60℃). Then, it is aged at room temperature for 12-48 hours to form a gel with a three-dimensional network structure. The gel is dried (particle agglomeration can be reduced by freeze drying or supercritical drying) to obtain nano-Al2O3 with a particle size of 20-50 nm.

[0068] The aluminum salt may be one or more of aluminum nitrate and / or aluminum alkoxide (such as aluminum isopropoxide).

[0069] The solvent can be ethanol and / or isopropanol, and the amount of solvent is only enough to fully dissolve the aluminum salt.

[0070] The catalyst described in this invention can be an acidic catalyst (such as nitric acid) or an alkaline catalyst (such as ammonia), and the weight ratio of the catalyst to the aluminum salt is (0.2-0.3):100.

[0071] Specifically, to avoid excessive viscosity of epoxy resin leading to agglomeration, the epoxy resin can be diluted with acetone or xylene to a suitable viscosity before being mixed and dissolved with coupling agent and mixed solvent (xylene and ethyl acetate prepared at a weight ratio of 3:1). The purpose of using coupling agent is to introduce active groups (-NH2 or -Si-O-) into epoxy resin to enhance the interfacial bonding with nano-alumina.

[0072] The epoxy resin used in this invention can be bisphenol A type epoxy resin E-51.

[0073] The room temperature in this invention refers to 25-30°C.

[0074] Specifically, the epoxy nano-alumina mixture can be coated onto the surface of the modified basalt fiber by coating the surface with an epoxy nano-alumina mixture or by depositing the modified basalt fiber in the epoxy nano-alumina mixture. The amount of epoxy nano-alumina mixture on the surface only needs to make the thickness of the formed epoxy nano-alumina coating 10-40 μm.

[0075] Specifically, epoxy alumina basalt fibers can be immersed in a polyurethane resin mixture, removed and dried to form a polyurethane resin mixture layer on the surface of the epoxy alumina basalt fibers, thus obtaining surface-modified basalt fibers. These surface-modified basalt fibers have a gradient coating layer, in which a silane coupling agent layer, an epoxy nano-alumina coating, and a polyurethane resin mixture layer are sequentially coated on the surface of the basalt fibers.

[0076] The thickness of the polyurethane resin mixture layer is 20-60 μm.

[0077] The technical roadmap for preparing surface-modified basalt fibers of this invention is shown in the figure below. Figure 1 As shown.

[0078] Preferably, the surface-modified basalt fiber is impregnated in a polyurethane resin mixture to obtain impregnated surface-modified basalt fiber, wherein the content of the surface-modified basalt fiber in the impregnated surface-modified basalt fiber is 65-82 wt%, and the content of the polyurethane resin mixture is 18-35 wt%.

[0079] In this invention, the surface-modified basalt fibers after impregnation can be cured by pultrusion, winding, or molding processes.

[0080] When using pultrusion to cure impregnated surface-modified basalt fibers, the specific operation is as follows: the impregnated surface-modified basalt fibers are fed into the pultrusion equipment, and the inlet temperature of the pultrusion equipment is set to 75-80℃, the middle temperature to 125-135℃, the rear middle temperature to 165-170℃, and the outlet temperature to 125-130℃, with a traction speed of 0.8-2.0 m / min. Furthermore, when using the pultrusion process, it is necessary to control the volume content of the impregnated surface-modified basalt fibers to an accuracy of ±1.5% (the pultrusion process has fiber precision control; the fiber content cannot vary too much or too little, as this will lead to incomplete pultruded profiles and even the risk of cracking), with a surface-modified basalt fiber content of 78-82 wt%.

[0081] Preferably, when using the pultrusion process, in order to ensure smooth molding and curing, the polyurethane resin mixture needs to be preheated to 45°C before the surface-modified basalt fiber is placed in it for impregnation.

[0082] When using a winding process to cure the impregnated surface-modified basalt fiber, the specific operation is as follows: the impregnated surface-modified basalt fiber is wet-wound with a tension of 12-18 N (to ensure that each fiber is taut and laid taut on the mold surface, ensuring that each fiber can bear the force well), then kept at 85-90℃ for 1.5-2 h, followed by kept at 125-130℃ for 1-1.5 h; and during the winding process, the content of surface-modified basalt fiber in the impregnated surface-modified basalt fiber is controlled to be 65-78 wt%.

[0083] When using the winding process, the viscosity of the polyurethane resin mixture needs to be controlled at 400-600 mPa•s before it is used to impregnate the surface-modified basalt fibers. The viscosity of the polyurethane resin mixture can be controlled by adjusting the amount of nano-silica. As the amount of nano-silica increases, the concentration of the polyurethane resin mixture will increase accordingly.

[0084] When using a molding process to cure the impregnated surface-modified basalt fibers, the specific operation is as follows: In the molding equipment, the impregnated surface-modified basalt fibers are stacked neatly layer by layer until the designed thickness is reached. Then, the upper mold is closed, and the upper and lower molds maintain a pressure of 10-12 MPa. Next, the temperature is maintained at 85-90℃ for 1.5-2 hours, and then at 130-140℃ for 1-1.5 hours.

[0085] When the basalt fiber used is in the form of basalt fiber cloth, it is preferable to use a molding process for curing.

[0086] A second aspect of the present invention provides a basalt fiber / weather-resistant polyurethane resin-based composite material prepared by the above-described preparation method.

[0087] The third aspect of this invention provides an application of the above-mentioned basalt fiber / weather-resistant polyurethane resin-based composite material in transmission towers, insulating crossarms, offshore wind power structures, photovoltaic supports, and marine engineering equipment.

[0088] This invention utilizes a gradient interface design between a silane coupling agent and an epoxy nano-alumina sol to achieve a synergistic effect of chemical bonding and physical anchoring between basalt fibers and polyurethane resin, thereby enhancing the interfacial bonding strength. It employs an interpenetrating network formed by a nano-silica modifier and a blocked isocyanate prepolymer to block water molecule penetration pathways, and combines this with the hydrophobic properties of the polyether-polyester block copolymer to reduce the resin's water absorption rate. Furthermore, by introducing Diels-Alder dynamic covalent bonds into the polyurethane molecular chain, its unique structure enables self-repair capabilities for small cracks generated during processing. Finally, the controlled release of a microcapsule catalyst above 90°C ensures the resin's stability during room temperature storage and rapid, uniform curing at high temperatures.

[0089] The present invention will be described in detail below through examples. Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. The DA monomer (furan-maleimide system) used in the following examples was purchased from Aladdin Reagent; the hindered amine light stabilizer was purchased from Beijing Tiangang Additives Co., Ltd.; the microencapsulated latent curing agent was purchased from Jiangsu Ausjia Materials Technology Co., Ltd.; and the phosphorus-nitrogen synergistic flame retardant was purchased from Nanjing Dongze Chemical Materials Co., Ltd.

[0090] In the following examples, room temperature refers to 25°C.

[0091] Example 1 (1) In a 75000ml esterification dehydration reactor, 1200g of polyether polyol (average molecular weight of 2000) and 270g of polyester polyol (average molecular weight of 1800) (molar ratio of polyether polyol to polyester polyol of 4:1) were vacuum dehydrated at 45°C for 1h, and then mixed with 3185g of blocked isocyanate prepolymer (hexamethylene diisocyanate trimer) (the molecular weight of the blocked isocyanate prepolymer is about 2500, and the weight ratio of the blocked isocyanate prepolymer to the total weight of polyether polyol and polyester polyol is 65:30) for the first reaction. The conditions of the first reaction included: temperature of 90°C and time of 2h, to obtain end-NCO prepolymer. The end-NCO prepolymer was then mixed with 18g of A second reaction was carried out by mixing DA monomers (average molecular weight 177) (the molar ratio of DA monomers to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer was 5:100). The conditions for the second reaction included a temperature of 75°C and a time of 2 hours to obtain a polyurethane prepolymer. (2) Mix aminosilane (KH550), ethanol and water (the weight ratio of ethanol to water is 4:1), stir at room temperature for 30 min to obtain a silane solution (the weight ratio of aminosilane to the total amount of aminosilane, ethanol and water is 3:100). Mix 90 g of nano-SiO2 with an organic solvent (n-butanol), sonicate for 15 min to obtain a dispersion. Add 200 ml of silane solution dropwise to the dispersion and mix, controlling the weight ratio of aminosilane to nano-SiO2 to be 2:100. Stir the reaction at 60 °C for 8 h, then filter. Wash the filtered solid with ethanol 3 times. Then, after drying at 80℃, it was ground to obtain aminosilane-modified nano-SiO2. The aminosilane-modified nano-SiO2 was mixed with a polyurethane prepolymer (weight ratio of aminosilane-modified nano-SiO2 to polyurethane prepolymer was 5:100) for a third reaction. The conditions for the third reaction included a temperature of 50℃ and a time of 60 min, yielding a nano-silica modifier. Then, the polyurethane prepolymer, nano-silica modifier, hindered amine light stabilizer, and microencapsulated latent curing agent (dibutyltin dilaurate capsules encapsulated in polyacrylic acid, with a particle size of 1-3 μm) were mixed and heated at 2500 °C. The resin matrix was obtained by shear dispersion at rpm for 40 min. The resin matrix was then mixed with a phosphorus-nitrogen synergistic flame retardant (polytetrabromobisphenol A phosphononitrile) to obtain a polyurethane resin mixture. The polyurethane resin mixture contained 0.5 wt% microencapsulated latent curing agent, 5 wt% nano-silica modifier, 7 wt% phosphorus-nitrogen synergistic flame retardant, and 1 wt% hindered amine light stabilizer. (3) Using aluminum salt (aluminum isopropoxide) as a precursor, dissolve it in a solvent (ethanol) to obtain a homogeneous solution. Then, hydrolyze it for 3 hours under the action of a catalyst (nitric acid). The weight ratio of catalyst to aluminum salt is 0.2:100 to obtain aluminum hydroxide sol. The viscosity and stability of the sol are adjusted by controlling the pH value (usually 4) and hydrolysis temperature (30℃). Then, age it at room temperature for 40 hours to form a gel with a three-dimensional network structure. Dry the gel (freeze-dry or supercritical drying) to obtain nano-Al2O3 with a particle size of 20-50 μm. nm; Epoxy resin (bisphenol A type epoxy resin E-51) is first diluted with acetone to a suitable viscosity, and then mixed and dissolved with aminosilane and a mixed solvent (xylene and ethyl acetate at a weight ratio of 3:1) to obtain an epoxy resin mixed solution (the weight ratio of aminosilane to epoxy resin is 1:100). Nano Al2O3 is uniformly dispersed into the epoxy resin mixed solution (ultrasonic treatment for 30 min to ensure uniform dispersion) to obtain an epoxy nano alumina mixture (the weight ratio of nano Al2O3 to epoxy resin is 5:100); 1-2 coats of silane coupling agent solution are uniformly sprayed onto the surface of basalt fiber (unidirectional basalt fiber cloth, the diameter of basalt fiber is 6 mm). A silane coupling agent solution was obtained by mixing glycidyl etheroxypropyltrimethoxysilane with an aqueous ethanol solution (obtained by mixing ethanol and water at a weight ratio of 4:1, with a solid-liquid ratio of 40g:100mL). After standing and surface drying, the solution was dried at 70℃ to form a silane coupling agent layer on the surface of basalt fibers, resulting in modified basalt fibers with a silane coupling agent layer thickness of 500nm. Then, 1-2 coats of an epoxy nano-alumina mixture were sprayed onto the surface of the modified basalt fibers, and the mixture was dried to form an epoxy nano-alumina coating with a thickness of 30nm. μm, to obtain epoxy alumina basalt fiber, then place the epoxy alumina basalt fiber in the polyurethane resin mixture in step (2) for immersion, take it out and dry it at 80°C, and form a polyurethane resin mixture layer on the surface of the epoxy alumina basalt fiber with a thickness of 60 μm, to obtain surface-modified basalt fiber. (4) The surface-modified basalt fiber is impregnated in the polyurethane resin mixture in step (2) to obtain the impregnated surface-modified basalt fiber. The content of the surface-modified basalt fiber in the impregnated surface-modified basalt fiber is 80wt%. In the molding equipment, the impregnated surface-modified basalt fiber is stacked neatly layer by layer until the designed thickness of 5mm is reached. Then the upper mold is closed and the upper and lower molds are kept under a pressure of 10MPa. Then the temperature is kept at 85℃ for 1.5 h and then at 130℃ for 1 h to obtain the basalt fiber / weather-resistant polyurethane resin-based composite material.

[0092] Example 2 The method was implemented according to Example 1, except that in step (1), 600g of polyether polyol (average molecular weight of 2000) and 270g of polyester polyol (average molecular weight of 1800) (molar ratio of polyether polyol to polyester polyol of 2:1) were vacuum dehydrated at 45°C for 1 hour in a 5000ml esterification dehydration reactor. Then, they were mixed with 1740g of blocked isocyanate prepolymer (hexamethylene diisocyanate trimer) (the molecular weight of the blocked isocyanate prepolymer is about 2500, and the weight ratio of the blocked isocyanate prepolymer to the total weight of polyether polyol and polyester polyol is 60:30) for a first reaction. The conditions for the first reaction included a temperature of 85°C and a time of 2 hours to obtain an end-NCO prepolymer. The end-NCO prepolymer was then mixed with 10.2g of... A second reaction was carried out by mixing DA monomers (average molecular weight 177) (the molar ratio of DA monomers to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer was 5:100). The conditions for the second reaction included a temperature of 80°C and a time of 2 hours to obtain a polyurethane prepolymer. In step (2), the polyurethane resin mixture contains 0.6 wt% microencapsulated latent curing agent, 2 wt% nano-silica modifier, 8 wt% phosphorus-nitrogen synergistic flame retardant, and 0.5 wt% hindered amine light stabilizer. In step (4), the surface-modified basalt fiber after impregnation has a content of 70 wt% and a designed thickness of 6 mm; thus, a basalt fiber / weather-resistant polyurethane resin-based composite material is obtained.

[0093] Example 3 The method was implemented according to Example 1, except that in step (1), 900g of polyether polyol (average molecular weight of 2000) and 270g of polyester polyol (average molecular weight of 1800) (molar ratio of polyether polyol to polyester polyol of 3:1) were vacuum dehydrated at 45°C for 1 hour in a 5000ml esterification dehydration reactor. Then, they were mixed with 2535g of blocked isocyanate prepolymer (hexamethylene diisocyanate trimer) (the molecular weight of the blocked isocyanate prepolymer is about 2500, and the weight ratio of the blocked isocyanate prepolymer to the total weight of polyether polyol and polyester polyol is 65:30) for a first reaction. The conditions for the first reaction included a temperature of 95°C and a time of 2 hours to obtain an end-NCO prepolymer. The end-NCO prepolymer was then mixed with 22.6g of... A second reaction was carried out by mixing DA monomers (average molecular weight 177) (the molar ratio of DA monomers to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer was 8:100). The conditions for the second reaction included a temperature of 80°C and a time of 2 hours to obtain a polyurethane prepolymer. In step (2), the polyurethane resin mixture contains 0.3 wt% microencapsulated latent curing agent, 3 wt% nano-silica modifier, 10 wt% phosphorus-nitrogen synergistic flame retardant, and 1.2 wt% hindered amine light stabilizer. The basalt fiber used in step (3) is short-cut basalt fiber; in step (4), the polyurethane resin mixture in step (2) is preheated to 45°C, and then the surface-modified basalt fiber is placed in it for impregnation. The volume content of the surface-modified basalt fiber in the impregnated surface-modified basalt fiber is controlled to be ±1.5%; the impregnated surface-modified basalt fiber is fed into the pultrusion equipment, and the inlet temperature of the pultrusion equipment is set to 75°C, the middle temperature to 130°C, the middle and rear temperature to 170°C, the outlet temperature to 125°C, and the traction speed to 1 m / min; a basalt fiber / weather-resistant polyurethane resin-based composite material is obtained.

[0094] Example 4 A basalt fiber / weather-resistant polyurethane resin matrix composite material is prepared by the method of Example 1.

[0095] Example 5 A basalt fiber / weather-resistant polyurethane resin matrix composite material is prepared by the method of Example 2.

[0096] Example 6 A basalt fiber / weather-resistant polyurethane resin matrix composite material is prepared by the method of Example 3.

[0097] Example 7 The basalt fiber / weather-resistant polyurethane resin-based composite materials in Examples 4-6 have high strength and excellent weather resistance, and can be applied to transmission towers, insulating crossarms, offshore wind power structures, photovoltaic supports, and marine engineering equipment.

[0098] Test Example 1 The bending properties, tensile properties, notched impact properties, and UV accelerated aging properties of the basalt fiber / weather-resistant polyurethane resin-based composite materials in Examples 4-6 were tested.

[0099] Test methods: The bending performance of the specimens was tested according to ASTM D7264 / D7264M-21, "Standard Test Method for Bending Properties of Polymer-Based Composites"; the tensile performance was tested according to ASTM D3039 / D3039M, "Standard Test Method for Tensile Properties of Polymer-Based Composites"; the notched impact test method was based on ASTM D6110, "Standard Test Method for Impact Resistance of Notched Specimens of Plastics"; and the accelerated UV aging performance was tested according to ASTM G154, "Standard Procedure for Fluorescent UV Lamp Irradiation of Nonmetallic Materials". The test results are as follows: Mechanical properties: Flexural strength 1050-1250 MPa, flexural modulus 58-65 GPa; tensile strength 1150-1350 MPa, tensile modulus 55-62 GPa; impact toughness ≥150 kJ / m 2 (Charpy gap impact).

[0100] UV accelerated aging resistance: After 1500 hours of QUV accelerated aging (UVA-340 lamp, 60℃ / 8 h light exposure + 50℃ / 4 h condensation), the flexural strength retention rate is ≥97%, and the surface is free from cracking and powdering.

[0101] The results above show that the polyurethane basalt fiber composite material prepared by this invention has excellent mechanical properties and maintains good UV aging resistance. After 1500h accelerated aging, its modulus retention rate is still above 97%.

[0102] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0103] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a basalt fiber / weather-resistant polyurethane resin-based composite material, characterized in that, include: A first reaction is carried out by mixing polyether polyol, polyester polyol and blocked isocyanate prepolymer to obtain terminal-NCO prepolymer. The terminal-NCO prepolymer is then mixed with DA monomer to carry out a second reaction to obtain polyurethane prepolymer. Aminosilane-modified nano-SiO2 was mixed with polyurethane prepolymer to carry out a third reaction to obtain nano-silica modifier. Then, polyurethane prepolymer, nano-silica modifier, hindered amine light stabilizer, microencapsulated latent curing agent and phosphorus-nitrogen synergistic flame retardant were mixed to obtain polyurethane resin mixture. A silane coupling agent is coated on the surface of basalt fiber and dried to obtain modified basalt fiber. Then, an epoxy nano-alumina coating is formed on the surface of the modified basalt fiber to obtain epoxy alumina basalt fiber. Then, a polyurethane resin mixture layer is formed on the surface of the epoxy alumina basalt fiber to obtain surface-modified basalt fiber. Surface-modified basalt fibers are impregnated in a polyurethane resin mixture to obtain impregnated surface-modified basalt fibers. The impregnated surface-modified basalt fibers are then cured to obtain a basalt fiber / weather-resistant polyurethane resin-based composite material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the polyether polyol to the polyester polyol is (1.5-4):1; and / or The weight ratio of the blocked isocyanate prepolymer to the total weight of the polyether polyol and polyester polyol is (60-65):

30.

3. The preparation method according to claim 1 or 2, characterized in that, The blocked isocyanate prepolymer is a hexamethylene diisocyanate trimer or a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; and / or When the blocked isocyanate prepolymer is a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer, the molar ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate trimer is ≥3:

1.

4. The preparation method according to claim 1, characterized in that, The conditions for the first reaction include: a temperature of 85-95℃ and a time of 2-4 hours.

5. The preparation method according to claim 1 or 4, characterized in that, The molar ratio of DA monomer to the total molar ratio of polyether polyol, polyester polyol and blocked isocyanate prepolymer is (5-8):100; and / or The conditions for the second reaction include a temperature of 75-80℃ and a time of 1.5-2.5h.

6. The preparation method according to claim 1, characterized in that, The preparation method of the aminosilane-modified nano-SiO2 includes: mixing aminosilane, ethanol, and water, stirring at room temperature for 30-40 min to obtain a silane solution; mixing nano-SiO2 with an organic solvent to obtain a dispersion; mixing the silane solution with the dispersion; stirring and reacting at 60-120℃ for 2-8 h; then filtering; washing and drying the filtered solid to obtain aminosilane-modified nano-SiO2; and / or The weight ratio of aminosilane to nano-SiO2 is (2-5):

100.

7. The preparation method according to claim 1 or 6, characterized in that, A third reaction is carried out by mixing aminosilane-modified nano-SiO2 with polyurethane prepolymer, wherein the weight ratio of aminosilane-modified nano-SiO2 to polyurethane prepolymer is (5-10):

100. and / or The conditions for the third reaction include: a temperature of 40-60℃ and a time of 30-60 min.

8. The preparation method according to claim 1, characterized in that, The process of mixing polyurethane prepolymer, nano-silica modifier, microencapsulated latent curing agent, and phosphorus-nitrogen synergistic flame retardant to obtain a polyurethane resin mixture includes: mixing the polyurethane prepolymer, nano-silica modifier, and microencapsulated latent curing agent, followed by shear dispersion to obtain a resin matrix; mixing the resin matrix with the phosphorus-nitrogen synergistic flame retardant to obtain the polyurethane resin mixture; and / or The microencapsulated latent curing agent is a dibutyltin dilaurate capsule encapsulated in polyacrylic acid; and / or The polyacrylic acid-encapsulated dibutyltin dilaurate capsules have a particle size of 1-3 μm.

9. The preparation method according to claim 8, characterized in that, In the polyurethane resin mixture, the content of microencapsulated latent curing agent is 0.2-0.6 wt%, the content of nano silica modifier is 2-5 wt%, the content of phosphorus-nitrogen synergistic flame retardant is 5-10 wt%, and the content of hindered amine light stabilizer is 0.5-1.2 wt%.

10. The preparation method according to claim 1, characterized in that, The process of forming an epoxy nano-alumina coating on the surface of modified basalt fibers includes: coating the surface of the modified basalt fibers with an epoxy nano-alumina mixture, followed by drying; and / or The preparation method of the epoxy nano-alumina mixture includes: dissolving epoxy resin and coupling agent in a mixed solvent to obtain an epoxy resin mixed solution, and uniformly dispersing nano-Al2O3 into the epoxy resin mixed solution to obtain an epoxy nano-alumina mixture.

11. The preparation method according to claim 1, characterized in that, The surface-modified basalt fiber after impregnation contains 65-82 wt% surface-modified basalt fiber.

12. The preparation method according to claim 1, characterized in that, The impregnated surface-modified basalt fibers are cured using pultrusion, winding, or molding processes.

13. The basalt fiber / weather-resistant polyurethane resin-based composite material prepared by the preparation method according to any one of claims 1-12.

14. The application of the basalt fiber / weather-resistant polyurethane resin matrix composite material according to claim 13 in transmission towers, insulating crossarms, offshore wind power structures, photovoltaic supports and marine engineering equipment.

Images