Rubber insulating material and sheath material for wind power generation

Abstract

The invention relates to the technical field of wind power generation materials, in particular to a rubber insulating material and a sheath material for wind power generation. The rubber insulating material for wind power generation comprises an insulating inner layer, an interface transition layer and a sheath outer layer, in the rubber insulating material for wind power generation and the sheath material, through double mechanisms of chemical coupling of a plant-based diluent and nano-cellulose and physical adsorption of expanded graphite, the insulating inner layer has excellent heat resistance and mechanical strength on the basis of keeping the heat resistance and mechanical strength of the material; the processing viscosity of the epoxy resin system is reduced; the outer layer of the sheath improves the mechanical property and salt mist erosion resistance of the material through the chemical anchoring of plant fibers and resin and the barrier effect of the nanosheet layer; meanwhile, the natural latex-cellulose nanocrystalline composite network of the interface transition layer strengthens the interface compatibility of the insulating layer and the sheath layer, and avoids the interlayer separation risk, thereby improving the reliability and service life of the material in an extreme environment of offshore wind power equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation materials, in particular to a rubber insulating material and a sheath material for wind power generation. Background Art

[0002] In the field of wind power generation, especially offshore wind power, equipment must withstand long-term extreme environments such as high salt spray, strong ultraviolet rays, high humidity and high pressure, placing stringent demands on the comprehensive performance of insulation and sheath materials. Epoxy resin-based composites, due to their excellent electrical insulation, chemical corrosion resistance, and structural strength, are ideal for protecting offshore wind power cables and precision components. However, their inherent high viscosity leads to problems such as uneven mixing, high extrusion resistance, and low molding efficiency during processing, affecting the molding quality and overall performance of the composites, and increasing processing difficulty and cost.

[0003] In the existing technology, the problem of high viscosity of epoxy resin processing is mainly solved through chemical modification, physical compounding and traditional process optimization. Chemical modification, such as the introduction of low molecular weight resin or active diluent, can reduce viscosity, but it will lead to a decrease in heat resistance or an increase in internal stress of the material, affecting long-term performance; physical compounding relies on the addition of some additives such as leveling agents and release agents, which can easily cause additive migration and deterioration of interfacial adhesion, and may accelerate material failure in complex offshore environments; traditional process optimization, such as upgrading planetary screw equipment or using vacuum degassing, can improve processing results, but the equipment investment cost is high and the production cycle is long, and high-temperature treatment may cause resin oxidation and yellowing, which not only reduces the insulation performance and appearance quality of the material, but may also cause a decrease in the mechanical properties of the material, thereby reducing the long-term stable operation of offshore wind power equipment.

[0004] In view of this, there is an urgent need for a rubber insulating material and a sheath material for wind power generation. Summary of the Invention

[0005] The object of the present invention is to provide a rubber insulating material and a sheath material for wind power generation to solve the problems raised in the above background technology.

[0006] To achieve the above objectives, firstly, according to Figure 1 As shown, the present invention provides a rubber insulation material and sheath material for wind power generation, comprising an insulating inner layer, an interface transition layer and a sheath outer layer, wherein:

[0007] The insulating inner layer adopts a low-viscosity and high-efficiency insulating layer with a high dielectric strength of ≥25kV / mm and a mixed viscosity of ≤3000mPa·s. The insulating inner layer includes 100-120 parts of epoxy resin (E-51), 15-20 parts of plant-based diluent, 5-8 parts of nanocellulose (CNF), 1-2 parts of natural silane coupling agent and 10-15 parts of expanded graphite (EG);

[0008] The interface transition layer comprises 25-35 parts of natural latex (NR latex), 10-18 parts of cellulose nanocrystals (CNC), 8-12 parts of castor oil-based epoxy acrylate and 3-5 parts of rosmarinic acid (RA);

[0009] The interface transition layer also includes the following preparation steps:

[0010] The natural latex was placed in a 30°C constant temperature water bath and stirred (speed 300r / min), and cellulose nanocrystals (CNC, diameter 50-100nm), castor oil-based epoxy acrylate and rosmarinic acid (RA) were added in sequence and stirred for 2 hours. During this period, the hydroxyl groups on the surface of the cellulose nanocrystals and the amino groups of the latex protein were hydrogen bonded, the epoxy groups of the castor oil-based epoxy acrylate and the residual carboxyl groups of the NR latex were slightly cross-linked, and the phenolic hydroxyl groups of the rosmarinic acid and the thiol groups of the latex were reacted by Michael addition to form a stable network. Finally, a milky white interface transition layer coating liquid with a solid content of 45%-50% and a viscosity of 800mPa·s-1200mPa·s was formed. The coating liquid was evenly applied to the surface of the inner layer of the insulation by a roller coating process with a thickness of 50μm-80μm. After drying at room temperature for 24 hours, an interface layer with both adhesiveness and antioxidant properties was formed.

[0011] The outer layer of the sheath comprises 70-90 parts of epoxy castor oil modified epoxy resin (CO-EP), 20-25 parts of sisal fiber (SF), 12-18 parts of glycerol trioleate (GTO) and 6-10 parts of montmorillonite-sodium alginate intercalation compound;

[0012] The plant-based diluent uses a turpentine-based epoxy diluent (such as terpene glycidyl ether), which is biodegradable (degradation rate ≥ 60%) and undergoes a secondary cross-linking reaction with the epoxy resin through epoxy groups to form an interpenetrating network structure, thereby preventing small molecule migration. The natural silane coupling agent uses γ-aminopropyltriethoxysilane (KH-550), one end of which reacts with the epoxy resin hydroxyl group, and the other end of which condenses with the nanocellulose hydroxyl group to form an organic-inorganic covalent bond bridge, further improving the integrity of the composite material. The expanded graphite has an expansion ratio of 200 to 300 times and presents a worm-like porous structure, which reduces viscosity while improving thermal conductivity.

[0013] The hydroxyl groups on the surface of the cellulose nanocrystals are hydrogen-bonded to the amino groups of the natural latex protein and simultaneously condensed with the hydroxyl groups of the epoxy castor oil-modified epoxy resin in the sheath layer to construct an organic-inorganic covalent bridge, thereby enhancing the compatibility of the interface layer with the inner insulating layer and the outer sheath layer. The epoxy groups at both ends of the castor oil-based epoxy acrylate molecular chain and the epoxy resin in the insulating layer initiate a secondary cross-linking reaction via a curing agent to form a covalent bond network. The phenolic hydroxyl groups in the rosmarinic acid molecules undergo a Michael addition reaction with the thiol groups of the natural latex protein to form a stable cross-linked structure, which is used to enhance the antioxidant properties of the interface transition layer. At the same time, its aromatic ring structure and the hydroxyl groups on the surface of the cellulose nanocrystals consolidate the network structure of the interface layer through a π-π stacking effect.

[0014] The epoxy castor oil modified epoxy resin is prepared by the ring-opening addition reaction of castor oil hydroxyl groups and bisphenol A epoxy resin epoxy groups. Flexible fatty acid chain segments of castor oil are introduced into its molecular chain and bonded to the cellulose hydroxyl groups of sisal fiber in the outer layer of the sheath through ester bonds. At the same time, its remaining epoxy groups undergo cross-linking reaction with the hydroxyl groups of triolein to form an interpenetrating network structure of "rigid epoxy skeleton + flexible fatty acid chain + plant fiber reinforcement".

[0015] Secondly, the present invention provides a rubber insulation material for wind power generation, comprising the following steps for preparing an insulating inner layer:

[0016] S1.1. Place turpentine-based epoxy diluent into a reactor, heat to 60°C, and stir at 200 r / min. Simultaneously, add γ-aminopropyltriethoxysilane and continue stirring for 30 min to allow the amino groups of the silane coupling agent to undergo a preliminary addition reaction with the epoxy groups of the diluent, forming a pre-crosslinked intermediate with active silyl groups, which improves the subsequent dispersion compatibility of the nanocellulose.

[0017] S1.2. Add nanocellulose (CNF, diameter 20-50 nm) to the reactor, maintain 60°C, increase the stirring rate to 500 rpm, and disperse for 1 hour. During this time, the hydroxyl groups on the nanocellulose surface react with the siloxy groups of the silane coupling agent through condensation reaction to form covalent bonds, producing a uniformly dispersed nanocellulose-silane-diluent composite solution.

[0018] S1.3. Add epoxy resin to a dual planetary mixer, raise the temperature to 80°C, and evacuate to -0.09 MPa. Add the nanocellulose-silane-diluent composite solution and stir at 300 rpm for 20-30 minutes. Then add expanded graphite (expansion factor 200-300 times) and continue vacuum mixing for 30-40 minutes. The worm-like porous structure of the expanded graphite absorbs the resin and diluent, reducing the system viscosity to ≤3000 mPa·s.

[0019] S1.4. Mix methyltetrahydrophthalic anhydride and accelerator DMP-30 in a mass ratio of 9:1, heat to 60°C, melt, and add to a mixer. Maintain the mixture at 80°C and a vacuum of -0.09 MPa. Stir at 100 rpm for 15-20 minutes to uniformly disperse the curing agent. Maintain the vacuum state for 30 minutes to remove air bubbles from the system and ensure that there are no pore defects after curing, thereby obtaining an epoxy resin-based insulating material.

[0020] S1.5. Coat the surface of the conductive core wire with epoxy resin-based insulating material through a single-screw extruder, set the temperature: feeding section 60℃ → compression section 80℃ → metering section 100℃, screw speed 15r / min, coating thickness 3±0.2mm; after coating, enter the stepped curing furnace, first cure at 100℃ for 2h, then heat to 130℃ for 4h, and detect the curing degree by differential scanning calorimetry (DSC) to be ≥95%, forming a high-insulation inner layer with an interpenetrating network structure.

[0021] In the invention, a "diluent-silane-nanocellulose" chemical connection system is first constructed through the pre-crosslinking reaction of a plant-based diluent and a natural silane coupling agent and the covalent grafting of nanocellulose; the epoxy group of the turpentine-based epoxy diluent undergoes a ring-opening addition reaction with the amino group of KH-550 to generate a siloxy-containing intermediate, which then condenses with the hydroxyl group on the surface of the nanocellulose to form an organic-inorganic covalent network, which not only solves the problem of high processing viscosity, but also achieves a high specific surface area of ​​nanocellulose (≥200m 2 / g) and expanded graphite, forming a synergistic structure of "nano-reinforced skeleton + resin flexible matrix"; for example, the worm-like pores of expanded graphite (pore diameter 50-100nm) can physically adsorb resin molecules, reducing intermolecular entanglement. At the same time, its high thermal conductivity improves the thermal conductivity of the insulation layer, effectively improving heat dissipation efficiency and delaying thermal aging of the material.

[0022] Thirdly, the present invention provides a sheath material for wind power generation, comprising the following steps of preparing the outer layer of the sheath:

[0023] S2.1. After cleaning and removing impurities and dust from the sisal fiber, soak it in a 5%-10% sodium hydroxide solution for 2-3 hours to remove wax and pectin impurities on the surface of the sisal fiber and improve the interfacial bonding between the fiber and the resin; after soaking, rinse the sisal fiber with deionized water until it is neutral, and then dry it in an oven at 80°C-100°C to constant weight (weigh it every 2 hours, and the difference between two consecutive weights is ≤0.1% as constant weight). Finally, cut the dried sisal fiber into short fibers with a length of 2 cm-5 cm;

[0024] S2.2. Add the epoxy resin modified with castor oil (CO-EP) into a high-speed mixer, raise the temperature to 50-60°C, and stir at a speed of 150-200 r / min for 15-20 minutes to fully soften it; then add the treated sisal fiber (SF) and continue stirring for 30-40 minutes to allow the sisal fiber to be evenly dispersed in the epoxy resin. During this period, the cellulose hydroxyl groups of the sisal fiber and the hydroxyl groups of the epoxy resin modified with castor oil are ester-bonded; then add glycerol trioleate (GTO) and montmorillonite-sodium alginate intercalation complex, increase the stirring speed to 300-400 r / min, and stir for 1-1.5 hours to fully mix the components to form a mixture with good fluidity and uniformity;

[0025] S2.3. Transfer the mixed material to a twin-screw extruder. Set the extruder temperature to 60-70°C in the feeding section, 80-90°C in the compression section, and 100-110°C in the metering section. Extrusion is performed at a screw speed of 20-30 r / min. The extruded profile is directly and tightly connected to the insulating inner layer pre-coated with the interface transition layer. Through the bonding effect of the interface transition layer, the outer layer of the sheath and the inner layer of the insulation are firmly bonded to form an integral structure.

[0026] S2.4. Transfer the outer layer profile of the sheath connected to the inner insulating layer to a curing oven for curing and molding. First, maintain a pre-curing temperature of 40℃-60℃ for 2h-3h. At this stage, the material is initially cross-linked and shaped, and the molecular chains begin to initially combine. After the pre-curing is completed, gradually increase the temperature to 70℃-90℃ for post-curing for 6h-8h. After the material is fully cured, take the product out of the curing oven and cool it naturally to room temperature to obtain a sheath material for wind power generation with the required performance and shape.

[0027] In the invention, first, sodium hydroxide solution is used to remove impurities on the surface of sisal fiber and activate hydroxyl groups, so that it forms a chemical anchor with the hydroxyl groups of epoxy resin modified with castor oil through ester bonds, which not only enhances the interfacial bonding between the fiber and the resin, but also, triolein is inserted into the epoxy network as a flexible plasticizer to relieve the internal stress of the rigid skeleton, and the montmorillonite-sodium alginate intercalation complex forms a physical barrier through nanosheet peeling; for example, the cellulose chain of sisal fiber and the fatty acid chain segment of epoxy resin modified with castor oil are entangled through intermolecular forces to form a "rigid-flexible interlocking" structure, which can also effectively improve the impact resistance and salt spray aging resistance of the sheath material.

[0028] Secondly, according to Figure 1 As shown, the wrapping process of the present invention is: conductive core wire → insulating inner layer → interface transition layer → sheath outer layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the rubber insulation material and sheath material for wind power generation, the inner insulation layer uses the dual mechanisms of chemical coupling of plant-based diluents and nanocellulose and physical adsorption of expanded graphite to reduce the processing viscosity of the epoxy resin system while maintaining the heat resistance and mechanical strength of the material, solving the contradiction between performance, cost and stability in traditional chemical modification, physical compounding and process optimization; the outer layer of the sheath introduces a sisal fiber reinforcement system and montmorillonite-sodium alginate nano-intercalation technology, which improves the mechanical properties and salt spray erosion resistance of the material through the chemical anchoring of plant fibers and resins and the barrier effect of nanosheets; at the same time, the natural latex-cellulose nanocrystal composite network of the interface transition layer strengthens the interface compatibility between the insulation layer and the sheath layer, avoids the risk of interlayer separation, and thus improves the reliability and service life of the material in offshore wind power equipment under extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a flowchart of the process of wrapping rubber insulation material and sheath material for wind power generation. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1

[0034] Formula (parts by mass):

[0035] Insulation inner layer: E-51 epoxy resin 100 parts, turpentine-based epoxy diluent 15 parts, nanocellulose (CNF) 5 parts, KH-550 silane coupling agent 1 part, expanded graphite (EG) 10 parts, methyltetrahydrophthalic anhydride curing agent 80 parts, DMP-30 accelerator 8 parts;

[0036] Interface transition layer: natural latex (NR latex) 25 parts, cellulose nanocrystals (CNC) 10 parts, castor oil-based epoxy acrylate 8 parts, rosmarinic acid (RA) 3 parts;

[0037] Sheath outer layer: 70 parts of epoxy castor oil modified epoxy resin (CO-EP), 20 parts of sisal fiber (SF), 12 parts of glycerol trioleate (GTO), 6 parts of montmorillonite-sodium alginate intercalation complex, and 2 parts of 2-ethyl-4-methylimidazole curing agent.

[0038] Preparation steps:

[0039] Preparation steps for the inner insulating layer: Pour turpentine-based epoxy diluent into a reactor, heat to 60°C and stir at 200 r / min, add KH-550 silane coupling agent and stir for 30 minutes to form a pre-crosslinked intermediate; add nanocellulose (diameter 20-50nm) and disperse at 500 r / min for 1 hour to prepare a composite liquid. Add epoxy resin to a double planetary mixer, evacuate to -0.09MPa at 80°C, add the composite liquid and stir for 30 minutes, then add expanded graphite and mix under vacuum for 40 minutes to reduce the viscosity to 2800mPa·s; then add a mixture of methyltetrahydrophthalic anhydride and DMP-30, vacuum stir for 20 minutes and degas for 30 minutes, and apply it to the core wire through a single-screw extruder (temperature 60-100°C, speed 15r / min), and step-curing (100°C / 2h→130°C / 4h) to form an insulating layer;

[0040] Preparation steps of the interface transition layer: natural latex is placed in a 30°C water bath, CNC (diameter 50-100 nm), castor oil-based epoxy acrylate, and rosmarinic acid are added in sequence at 300 r / min, and stirred for 2 hours to form a coating solution with a solid content of 45%. The solution is then roller-coated on the surface of the insulation layer (thickness 50 μm) and dried at room temperature for 24 hours.

[0041] Preparation steps of the outer layer of the sheath: soak the sisal fiber in a 5% NaOH solution for 2 hours, wash and dry it, and then cut it into 2cm short fibers; epoxy castor oil modified epoxy resin is softened by stirring at 50°C, added to the sisal fiber and mixed for 40 minutes, and then triolein and montmorillonite-sodium alginate intercalation complex are added and stirred at 400r / min for 1 hour; the material is transferred to a twin-screw extruder (temperature 60-110°C, speed 20r / min) to extrude the coating interface layer, and is molded by pre-curing (50°C / 2h) and post-curing (80°C / 6h).

[0042] Example 2

[0043] Formula (parts by mass):

[0044] Insulation inner layer: E-51 epoxy resin 110 parts, turpentine-based epoxy diluent 18 parts, nanocellulose (CNF) 6 parts, KH-550 silane coupling agent 1.5 parts, expanded graphite (EG) 13 parts, methyltetrahydrophthalic anhydride curing agent 85 parts, DMP-30 accelerator 9 parts;

[0045] Interface transition layer: 30 parts of natural latex (NR latex), 15 parts of cellulose nanocrystals (CNC), 10 parts of castor oil-based epoxy acrylate, and 4 parts of rosmarinic acid (RA);

[0046] Sheath outer layer: 80 parts of epoxy castor oil modified epoxy resin (CO-EP), 23 parts of sisal fiber (SF), 15 parts of glycerol trioleate (GTO), 8 parts of montmorillonite-sodium alginate intercalation complex, and 2.5 parts of 2-ethyl-4-methylimidazole curing agent.

[0047] Preparation steps:

[0048] Preparation steps of the insulating inner layer: heating the turpentine-based epoxy diluent to 60°C, adding KH-550 silane coupling agent and stirring for 35 minutes to form an intermediate containing active silyl groups; adding nanocellulose with a diameter of 30nm and dispersing at a high speed of 550r / min for 1.5 hours to obtain a uniform composite liquid; adding epoxy resin into a double planetary mixer, adding the composite liquid and stirring for 25 minutes under a vacuum environment at 80°C, then adding expanded graphite with an expansion ratio of 250 times, and vacuum mixing for 35 minutes until the viscosity drops to 2500mPa·s; then adding a mixture of methyltetrahydrophthalic anhydride and DMP-30 in a molten state, vacuum stirring for 18 minutes and degassing for 25 minutes, and coating it on the core wire through a single-screw extruder with a temperature gradient of 65°C in the feeding section, 85°C in the compression section, and 105°C in the metering section (speed 18r / min), curing at 105°C for 2.5 hours, and then heating to 135°C for curing for 3.5 hours to form an insulating layer;

[0049] Preparation of the interface transition layer: natural latex was placed in a 30°C water bath and stirred at 350 rpm. Cellulose nanocrystals with a diameter of 80 nm, castor oil-based epoxy acrylate, and rosmarinic acid were added in sequence and stirred for 2.5 hours until a coating solution with a solid content of 48% was formed. The coating solution was then evenly applied to the surface of the insulating layer (70 μm thick) using a roller coating process and dried at room temperature for 20 hours to form an interface layer.

[0050] Preparation steps of the outer layer of the sheath: soak the sisal fiber in 8% sodium hydroxide solution for 2.5 hours, wash and dry it, and then cut it into 3.5 cm short fibers; heat the epoxy castor oil modified epoxy resin to 55°C to soften it, add the sisal fiber and stir for 35 minutes, then add triolein and montmorillonite-sodium alginate intercalation complex, and stir at 350r / min for 1.2 hours; transfer the material into a twin-screw extruder (feeding section 65°C, compression section 88°C, metering section 108°C, speed 25r / min) to extrude the coating interface layer, first pre-curing at 55°C for 2.5 hours, then heating to 85°C and curing for 7 hours to form the sheath layer.

[0051] Example 3

[0052] Formula (parts by mass):

[0053] Insulation inner layer: E-51 epoxy resin 120 parts, turpentine-based epoxy diluent 20 parts, nanocellulose (CNF) 8 parts, KH-550 silane coupling agent 2 parts, expanded graphite (EG) 15 parts, methyltetrahydrophthalic anhydride curing agent 90 parts, DMP-30 accelerator 10 parts;

[0054] Interface transition layer: natural latex (NR latex) 35 parts, cellulose nanocrystals (CNC) 18 parts, castor oil-based epoxy acrylate 12 parts, rosmarinic acid (RA) 5 parts;

[0055] Sheath outer layer: 90 parts of epoxy castor oil modified epoxy resin (CO-EP), 25 parts of sisal fiber (SF), 18 parts of glycerol trioleate (GTO), 10 parts of montmorillonite-sodium alginate intercalation compound, and 3 parts of 2-ethyl-4-methylimidazole curing agent.

[0056] Preparation steps:

[0057] Preparation steps for the inner insulation layer: Heat the turpentine-based epoxy diluent to 60°C, add KH-550 silane coupling agent and stir for 40 minutes to form a pre-crosslinked intermediate; add nanocellulose with a diameter of 50nm and disperse at 600r / min for 2 hours to prepare a composite liquid. Epoxy resin is placed in a double planetary mixer and the composite liquid is added and stirred for 30 minutes under a vacuum environment at 80°C. Then, expanded graphite with a 300-fold expansion ratio is added and vacuum mixed for 40 minutes until the viscosity drops to 2200mPa·s. Then, a mixture of methyltetrahydrophthalic anhydride and DMP-30 is added, vacuum stirred for 20 minutes and degassed for 30 minutes. The mixture is then applied to the core wire through a single-screw extruder (rotating at 20r / min) with a temperature gradient of 70°C in the feeding section, 90°C in the compression section, and 110°C in the metering section. After curing at 110°C for 3 hours, the temperature is raised to 140°C and cured for 4 hours to form the insulation layer.

[0058] Preparation of the interface transition layer: natural latex was placed in a 30°C water bath and stirred at 400 rpm. Cellulose nanocrystals with a diameter of 100 nm, castor oil-based epoxy acrylate, and rosmarinic acid were added sequentially and stirred for 3 hours until a coating solution with a solid content of 50% was formed. The coating solution was then evenly applied to the surface of the insulating layer (80 μm thick) using a roller coating process and dried at room temperature for 24 hours to form an interface layer.

[0059] Preparation steps of the outer layer of the sheath: soak the sisal fiber in a 10% sodium hydroxide solution for 3 hours, wash and dry it, and then cut it into 5cm short fibers; heat the epoxy castor oil modified epoxy resin to 60°C to soften it, add the sisal fiber and stir for 40 minutes, then add triolein and montmorillonite-sodium alginate intercalation complex, and stir at 400r / min for 1.5 hours; transfer the material into a twin-screw extruder (feeding section 70°C, compression section 90°C, metering section 110°C, speed 30r / min) to extrude the coating interface layer, first pre-curing at 60°C for 3 hours, then heating to 90°C and curing for 8 hours to form the sheath layer.

[0060] Table 1 Amounts of raw materials used in Examples 1-4

[0061]

[0062] In order to verify that the rubber insulation material and sheath material for wind power generation prepared in the embodiment of the present invention have good insulation reliability and composite structure stability, the rubber insulation material and sheath material for wind power generation provided in the embodiment of the present invention are described through the following test examples.

[0063] Test example

[0064] The purpose of this test group is to explore the influence of different component ratios on rubber insulation materials and sheath materials for wind power generation, and to detect the insulation properties, mechanical properties, weather resistance and interface bonding properties of the rubber insulation materials and sheath materials for wind power generation of the present invention.

[0065] Test objectives: Test groups A, B, and C respectively use the composition ratios of the rubber insulation material and sheath material for wind power generation provided in Examples 1-3; the control examples use control groups A, B, C, D, E, and F, wherein:

[0066] Control group A

[0067] formula:

[0068] Insulation inner layer: 80 parts of E-51 epoxy resin, 20 parts of low molecular weight E-12 epoxy resin, 15 parts of reactive diluent (styrene-based ethylene oxide), 20 parts of nano-alumina, 80 parts of curing agent (methyltetrahydrophthalic anhydride);

[0069] Sheath outer layer: 100 parts of pure E-44 epoxy resin, 30 parts of silicon carbide filler, 1 part of leveling agent, and 15 parts of curing agent (isophorone diamine).

[0070] Control group B

[0071] formula:

[0072] Insulation inner layer: 100 parts of E-51 epoxy resin, 15 parts of turpentine-based epoxy diluent, 2 parts of leveling agent (polydimethylsiloxane), 10 parts of expanded graphite, and 80 parts of curing agent;

[0073] Sheath outer layer: epoxy resin (E-44) 70 parts, sisal fiber 20 parts, paraffin release agent 3 parts, montmorillonite 10 parts, curing agent 15 parts.

[0074] Control group C

[0075] formula:

[0076] Insulation inner layer: 100 parts of E-51 epoxy resin, 15 parts of turpentine-based epoxy diluent, 5 parts of nanocellulose, 10 parts of expanded graphite, and 80 parts of curing agent;

[0077] Outer layer of the sheath: 70 parts of epoxy castor oil modified epoxy resin, 20 parts of sisal fiber, 12 parts of glycerol trioleate, 6 parts of montmorillonite-sodium alginate intercalation compound, and 2 parts of curing agent.

[0078] Control group D

[0079] formula:

[0080] Insulation inner layer: E-51 epoxy resin 100 parts, traditional reactive diluent (acrylate epoxy monomer) 15 parts, nanocellulose 5 parts, expanded graphite 10 parts, curing agent 80 parts;

[0081] Interface transition layer / sheath outer layer: same as in Example 1.

[0082] Control group E

[0083] formula:

[0084] Insulation inner layer: 100 parts of E-51 epoxy resin, 15 parts of turpentine-based epoxy diluent, 1 part of silane coupling agent, 10 parts of expanded graphite, and 80 parts of curing agent;

[0085] Interface transition layer / sheath outer layer: same as in Example 1.

[0086] Control group F

[0087] Formula: Same as Example 1, but the curing process is constant temperature 120°C for 4 hours.

[0088] Test method: According to the present invention, the insulation properties, mechanical properties, weather resistance and interface bonding properties of the rubber insulation material and sheath material for wind power generation are tested respectively. The specific test methods are as follows:

[0089] Insulation performance test method: According to GB / T1410-2006 "Test method for volume resistivity and surface resistivity of solid insulating materials", the inner layer of the insulation is processed into For the disc sample, under the environment of 23±2℃ and relative humidity of 50±5%, a 500V DC voltage is applied using a three-electrode system and the insulation resistance value is measured after 1 minute. The volume resistivity is calculated by the formula: Calculate (where R v is the volume resistance, A is the electrode area, and d is the sample thickness); the dielectric strength test is carried out according to IEC60243-1:2013. The sample is immersed in transformer oil and the voltage is increased at a rate of 2kV / s until breakdown. The ratio of the breakdown voltage to the sample thickness is the dielectric strength (unit: kV / mm);

[0090] Table 2 shows the insulation performance test indicators

[0091] Volume resistivity (Ω·cm) Dielectric strength (kV / mm) Experimental group A <![CDATA[1.2×10 14 ]]> 26 Experimental group B <![CDATA[1.3×10 14 ]]> 27 Experimental Group C <![CDATA[1.1×10 14 ]]> 25 Control group A <![CDATA[8.0×10 14 ]]> 22 Control group B <![CDATA[9.5×10 14 ]]> 23 Control group C <![CDATA[1.0×10 14 ]]> 24 Control group D <![CDATA[7.5×10 14 ]]> 21 Control group E <![CDATA[9.0×10 14 ]]> 23 Control group F <![CDATA[1.1×10 14 ]]> 25

[0092] Test method for mechanical properties: Tensile performance test follows GB / T528-2009 "Determination of tensile stress and strain properties of vulcanized rubber or thermoplastic rubber", prepare dumbbell-shaped specimens (gauge length 50mm), stretch at a speed of 500mm / min, record the maximum stress at break (tensile strength, unit: MPa) and gauge section elongation (elongation at break, %); impact resistance is based on GB / T1843-2008 "Determination of cantilever beam impact strength of plastics", process the outer layer of the sheath into 80mm×10mm×4mm specimens, use 5J pendulum impact energy test, calculate the energy absorbed per unit area when the specimen is broken (impact strength, unit: kJ / m 2 );

[0093] Table 3 shows the mechanical properties test indicators

[0094]

[0095]

[0096] Weathering resistance test method: The salt spray aging test is performed according to ISO9227:2017. The composite sample is placed in a 35°C, 5% NaCl solution spray box for 1000 hours. The surface corrosion is observed and the tensile strength retention is tested. The calculation formula is: The UV aging test was conducted in accordance with GB / T16422.3-2014 using a UVB-313 light source (irradiance 1.0 W / m 2 ), 500 h of cumulative exposure under the cycle conditions of 60 ° C UV irradiation for 8 h and 50 ° C condensation for 4 h, and measure the color difference (ΔE) and surface resistivity retention of the samples;

[0097] Table 4 shows the weather resistance performance test indicators

[0098]

[0099] Test method for interface bonding performance: The interlayer peel strength is tested using the modified ASTM D3359-2017 method. A three-layer composite specimen of 100 mm × 25 mm × (3 + 0.05) mm is prepared. The peel force (unit: N / mm) between the insulation layer and the sheath layer is tested using the 90° peeling method. The peeling speed is 100 mm / min, and the average value of 5 tests is taken. The interface shear strength is tested according to the ASTM D2344-2016 short beam shear method. The composite specimen is processed into 40 mm × 10 mm × 5 mm, the span is set to 20 mm, and the loading speed is 1 mm / min. The formula is: Calculate the shear strength (where F is the failure load, b is the specimen width, and h is the specimen thickness).

[0100] Table 5 is the interface bonding performance test index

[0101] Interlayer peel strength (N / mm) Interface shear strength (MPa) Experimental group A 8.5 12.0 Experimental group B 9.2 13.5 Experimental Group C 9.8 15.0 Control group A 3.2 5.5 Control group B 4.0 6.8 Control group C 7.0 10.0 Control group D 6.5 9.2 Control group E 8.0 11.0 Control group F 7.5 10.5

[0102] According to Table 2-5, the above comparative data are summarized as follows:

[0103] Insulation performance: The volume resistivity of the insulation inner layer of the test group AC of the present invention is ≥1.1×10 14 Ω·cm, with a dielectric strength ≥25kV / mm, outperforming control groups A (traditional low molecular weight resin + reactive diluent, dielectric strength 22kV / mm) and D (acrylate diluent, dielectric strength 21kV / mm). The core reason is that the turpentine-based epoxy diluent forms an interpenetrating network through secondary crosslinking, avoiding insulation degradation caused by small molecule migration; the covalent bonding of nanocellulose and silane coupling agent (control group E does not introduce nanocellulose and has a dielectric strength 2kV / mm lower) effectively reduces interfacial defects, and the physical adsorption of expanded graphite further improves system uniformity, stabilizing insulation performance at a high level.

[0104] Mechanical properties: The test group's sheath layer has tensile strength (43-48MPa), elongation at break (240%-260%) and impact strength (28-32kJ / m 2 ) are better than the control group A (pure epoxy resin sheath, impact strength 18kJ / m 2 ) and control group B (containing paraffin release agent, tensile strength 30MPa); the key differences are: the flexible fatty acid chain segments of epoxy resin modified by epoxidized castor oil form ester bonds with the hydroxyl groups of sisal fiber (control group C is unmodified epoxy resin, tensile strength is 5MPa lower), constructing a "rigid epoxy skeleton + flexible chain segment" interlocking structure; the nanosheets of montmorillonite-sodium alginate intercalation composite are peeled off (control group E does not introduce intercalation technology, impact strength is 5kJ / m 2 ) Forming a physical reinforcement barrier to improve mechanical properties by 40%-70%;

[0105] Weathering performance: After 1000 hours of salt spray aging, the test group achieved a tensile strength retention rate of ≥92%, and a color difference ΔE of ≤1.2 after 500 hours of UV aging, significantly outperforming control group A (salt spray retention of 75%, color difference of 3.5) and control group D (UV surface resistivity retention of 80%). The core technological advantage lies in: the rosmarinic acid in the interfacial transition layer cross-links with natural latex via a Michael addition reaction, and its aromatic ring structure provides antioxidant capacity (control group F, which did not use rosmarinic acid, had a color difference 0.5 higher). The ion exchange function of the montmorillonite-sodium alginate complex captures chloride ions in seawater (control group C, which used ordinary montmorillonite, had a salt spray retention rate 7% lower), and the hydrogen bond network of the cellulose nanocrystals slows the aging process.

[0106] Interface bonding performance: The interlayer peel strength (8.5-9.8 N / mm) and interfacial shear strength (12.0-15.0 MPa) of the test group were higher than those of control group A (peel strength 3.2 N / mm) and control group F (shear strength 10.5 MPa without step-curing). The key technological breakthrough lies in: the cellulose nanocrystals in the interface transition layer form covalent bridges with the nanocellulose in the insulating layer and the hydroxyl groups of the epoxy castor oil in the sheath layer through hydrogen bonds (control group E did not use an interface layer and had a peel strength 0.5 N / mm lower). The stepped curing process (control group F constant temperature curing) reduces internal stress through gradient crosslinking, forming a chemical melt bond between the interface layer and the inner and outer layers, and increasing the interlayer force by 2-3 times.

[0107] In summary, the present invention solves the contradictions in processing viscosity, environmental adaptability and interlayer compatibility of traditional epoxy resin-based materials through chemical functionalization of plant-based components (cross-linking with turpentine diluent and modification with castor oil), cross-scale reinforcement of nanomaterials (cellulose nanocrystals / montmorillonite sheets) and multiple bonding design of the interface layer (hydrogen bond-covalent bond-π-π stacking). Compared with the control group, while maintaining high insulation performance, the processing viscosity is reduced by 40%-60% (mixed viscosity ≤3000mPa·s), the salt spray aging life is increased by more than 20%, and the interface bonding strength is increased by 150%-200%, thereby improving the processing efficiency, environmental reliability and service life of insulation and sheath materials for offshore wind power equipment.

[0108] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A rubber insulating material and sheath material for wind power generation, characterized in that: It includes an inner insulating layer, an interface transition layer and an outer sheath layer, wherein: The insulating inner layer comprises epoxy resin, plant-based diluent, nanocellulose, natural silane coupling agent and expanded graphite; the interface transition layer comprises natural latex, cellulose nanocrystals, castor oil-based epoxy acrylate and rosmarinic acid; the sheath outer layer comprises epoxy castor oil-modified epoxy resin, sisal fiber, glycerol trioleate and montmorillonite-sodium alginate intercalation composite; The plant-based diluent and the epoxy resin undergo a secondary cross-linking reaction through the epoxy group to form an interpenetrating network structure; the amino group at one end of the natural silane coupling agent reacts with the hydroxyl group of the epoxy resin, and the siloxy group at the other end condenses with the hydroxyl group of the nanocellulose to form an organic-inorganic covalent bond bridge; The hydroxyl groups on the surface of the cellulose nanocrystals bind to the amino groups of the natural latex protein through hydrogen bonds, and simultaneously condense with the hydroxyl groups of the epoxy resin modified with castor oil in the sheath layer to form an organic-inorganic covalent bridge. The epoxy groups at both ends of the castor oil-based epoxy acrylate molecular chain and the epoxy resin in the insulating layer initiate a secondary cross-linking reaction through a curing agent to form a covalent bond network. The epoxy castor oil modified epoxy resin is prepared by the ring-opening addition of castor oil and bisphenol A epoxy resin. The molecular chain contains flexible fatty acid segments that can react with sisal fiber hydroxyl groups and triolein hydroxyl groups to form an interpenetrating network structure.

2. The rubber insulating material and sheathing material for wind power generation according to claim 1, characterized in that: The insulating inner layer adopts a low-viscosity and high-efficiency insulating layer with a high insulation strength of ≥25kV / mm and a mixed viscosity of ≤3000mPa·s.

3. The rubber insulating material and sheathing material for wind power generation according to claim 1, characterized in that: The amounts of the insulating inner layer, interface transition layer and outer sheath layer are as follows: Insulation inner layer: 100-120 parts epoxy resin, 15-20 parts plant-based diluent, 5-8 parts nanocellulose, 1-2 parts natural silane coupling agent, 10-15 parts expanded graphite; Interface transition layer: 25-35 parts natural latex, 10-18 parts cellulose nanocrystals, 8-12 parts castor oil-based epoxy acrylate, 3-5 parts rosmarinic acid; Outer layer of the sheath: 70-90 parts of epoxy resin modified by epoxy castor oil, 20-25 parts of sisal fiber, 12-18 parts of glycerol trioleate, and 6-10 parts of montmorillonite-sodium alginate intercalation compound.

4. The rubber insulating material and sheathing material for wind power generation according to claim 1, characterized in that: The interface transition layer further comprises the following preparation steps: The natural latex was placed in a constant temperature water bath at 30°C and stirred, and cellulose nanocrystals, castor oil-based epoxy acrylate and rosmarinic acid were added in sequence and stirred for 2 hours. During this period, the hydroxyl groups on the surface of the cellulose nanocrystals were hydrogen-bonded with the amino groups of the latex protein, the epoxy groups of the castor oil-based epoxy acrylate were slightly cross-linked with the residual carboxyl groups of the natural latex, and the phenolic hydroxyl groups of the rosmarinic acid were reacted with the thiol groups of the latex through Michael addition reaction to form a stable network. Finally, a milky white interface transition layer coating liquid with a solid content of 45%-50% and a viscosity of 800mPa·s-1200mPa·s was formed. The coating liquid was evenly applied to the surface of the inner layer of the insulation through a roller coating process with a thickness of 50μm-80μm. After drying at room temperature for 24 hours, an interface layer with both adhesiveness and antioxidant properties was formed.

5. The rubber insulating material and sheathing material for wind power generation according to claim 1, characterized in that: The plant-based diluent adopts turpentine-based epoxy diluent, which is biodegradable and has a degradation rate of ≥60%; the natural silane coupling agent adopts gamma-aminopropyltriethoxysilane.

6. The rubber insulating material and sheathing material for wind power generation according to claim 1, characterized in that: The expanded graphite has an expansion ratio of 200 to 300 times and presents a worm-like porous structure.

7. A rubber insulating material for wind power generation obtained by using the rubber insulating material for wind power generation and the sheath material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps of preparing the inner insulating layer: S1.

1. Place turpentine-based epoxy diluent into a reactor, heat to 60°C, and stir at 200 rpm. Simultaneously, add γ-aminopropyltriethoxysilane and continue stirring for 30 minutes to form a pre-crosslinked intermediate. S1.

2. Add nanocellulose to the reactor, maintain the temperature at 60°C, increase the stirring rate to 500 rpm, and disperse for 1 hour to obtain a nanocellulose-silane-diluent composite solution. S1.

3. Add epoxy resin to a dual planetary mixer, heat to 80°C, and evacuate to -0.09 MPa. Add the nanocellulose-silane-diluent composite solution and stir at 300 rpm for 20-30 minutes. Then add expanded graphite and continue vacuum mixing for 30-40 minutes until the system viscosity is reduced to ≤3000 mPa·s. S1.

4. Mix methyltetrahydrophthalic anhydride and accelerator DMP-30 in a mass ratio of 9:1, heat to 60°C and melt, then add to the mixer. Maintain 80°C and -0.09 MPa vacuum conditions, and stir at 100 rpm for 15-20 minutes to evenly disperse the curing agent. Then, the vacuum state was maintained for 30 minutes to remove bubbles in the system, thereby obtaining an epoxy resin-based insulating material; S1.

5. Use a single-screw extruder to coat the epoxy resin-based insulating material on the surface of the conductive core wire. After coating, enter the stepped curing furnace and cure at 100°C for 2 hours. Then heat it to 130°C and cure it for 4 hours. The degree of curing is detected by differential scanning calorimetry to be ≥95%, forming a high-insulation inner layer with an interpenetrating network structure.

8. The rubber insulating material for wind power generation according to claim 7, characterized in that: In the S1.5, the temperature setting of the single-screw extruder is: feeding section 60°C → compression section 80°C → metering section 100°C, the screw speed is 15 r / min, and the coating thickness is 3±0.2 mm.

9. A sheath material for wind power generation obtained by using the rubber insulating material for wind power generation and the sheath material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps of preparing the outer layer of the sheath: S2.

1. After cleaning and removing impurities and dust from the sisal fibers, soak them in a 5%-10% sodium hydroxide solution for 2-3 hours. Rinse the fibers with deionized water until neutral, dry them in an oven at 80-100°C to constant weight, and cut them into short fibers of 2-5 cm in length. S2.

2. Add the epoxy castor oil-modified epoxy resin to a high-speed mixer, raise the temperature to 50-60°C, and stir at 150-200 r / min for 15-20 minutes to fully soften it; then add the short fibers and continue stirring for 30-40 minutes to evenly disperse the sisal fibers in the epoxy resin; then add glycerol trioleate and montmorillonite-sodium alginate intercalation complex, increase the stirring speed to 300-400 r / min, and stir for 1-1.5 hours to fully mix the components to form a mixed material; S2.

3. Transfer the mixed material to a twin-screw extruder for extrusion; the extruded profile is directly and tightly bonded to the insulating inner layer pre-coated with the interface transition layer, forming an integral structure through the bonding effect of the interface transition layer; S2.

4. Transfer the outer layer profile of the sheath connected to the inner insulating layer to a curing furnace for curing and molding. First, maintain the temperature at 40℃-60℃ for 2h-3h for pre-curing, then gradually increase the temperature to 70℃-90℃ for post-curing for 6h-8h. After the material is fully cured, take it out and cool it naturally to room temperature to obtain the sheath material for wind power generation.

10. The sheath material for wind power generation according to claim 9, characterized in that: In S2.3, the twin-screw extruder is set to the following temperatures: 60°C-70°C in the feeding section, 80°C-90°C in the compression section, 100°C-110°C in the metering section, and a screw speed of 20r / min-30r / min for extrusion.

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