Electrical insulating material of photovoltaic power distribution cabinet and preparation method of electrical insulating material

Abstract

The invention belongs to the technical field of photovoltaic power distribution cabinets, and particularly relates to an electrical insulating material for a photovoltaic power distribution cabinet and a preparation method thereof.The electrical insulating material is prepared from, by weight, 40-60 parts of epoxy resin, 20-30 parts of silicone rubber, 10-15 parts of glass fiber, 5-10 parts of nanometer aluminum oxide, 3-8 parts of flame retardant, 2-5 parts of flexibilizer, 1-3 parts of antioxidant and 1-3 parts of mica powder. The nano aluminum oxide particles are uniformly dispersed to enhance the interface bonding force, the glass fibers form a three-dimensional network to provide mechanical support, and the epoxy resin and the silicone rubber form an interpenetrating network toughening agent to form an elastic micro-area. In addition, the flame retardant aluminum hydroxide, the magnesium hydroxide and the microencapsulated flame retardant further improve the flame retardant property, the thermal stability and the electrical insulation property of the insulating material, so that the insulating material can be kept stable at the temperature of-40 DEG C to 150 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic distribution cabinets, and particularly relates to an electrical insulating material for a photovoltaic distribution cabinet and a preparation method thereof. Background Art

[0002] During the operation of a photovoltaic power station, the photovoltaic distribution cabinet plays a crucial role. It distributes, controls, and protects the electric energy generated by the photovoltaic system. However, the environment where the photovoltaic power station is located is complex and diverse. In some areas, the temperature difference between day and night is extremely large. For example, in desert areas, the temperature of the photovoltaic distribution cabinet can reach above 50°C under high-temperature exposure during the day, and drop below -10°C at night. Such frequent and large-scale temperature changes will cause the insulating material inside the distribution cabinet to expand and contract thermally. After long-term exposure to such temperature cycles, the internal structure of the insulating material is easily damaged, cracks and other problems occur, which will lead to a decline in insulation performance, seriously affecting the normal operation of the photovoltaic distribution cabinet, and even possibly causing safety accidents.

[0003] In addition, during the operation of the photovoltaic distribution cabinet, the internal electrical components will generate heat, causing the temperature inside the cabinet to rise. When the equipment stops operating or the load changes, the temperature will drop again. This temperature fluctuation caused by operation will also affect the insulating material. Some existing insulating materials are difficult to maintain good structural stability and electrical insulation performance under long-term temperature fluctuations, which limits the reliable operation of the photovoltaic distribution cabinet in a complex temperature environment. Chinese Patent CN202211177889.1 provides a high-temperature resistant cable insulating material and a preparation method thereof, including the following components A and B in parts by weight. Component A: 60 - 90 parts of low-density polyethylene, 10 - 20 parts of ethylene-vinyl acetate copolymer, 10 - 20 parts of phenylene silicone rubber, 2 - 8 parts of carbon nanotubes, 3 - 10 parts of potassium titanate whiskers, 5 - 10 parts of silica microspheres, 1 - 2 parts of compatibilizer, 140 - 160 parts of flame retardant, 1.5 - 2.5 parts of antioxidant. Component B: 20 - 30 parts of low-density polyethylene, 0.2 - 0.4 parts of vulcanizing agent. However, this insulating material cannot adapt to large temperature changes and maintain stable performance.

[0004] Therefore, it is of great practical significance to develop an electrical insulating material for a photovoltaic distribution cabinet and a preparation method thereof that can adapt to large temperature changes and maintain stable performance under different temperature conditions. Summary of the Invention

[0005] In view of the deficiencies existing in the prior art, the present invention provides an electrical insulating material for a photovoltaic power distribution cabinet and a preparation method thereof. This insulating material has excellent temperature change resistance performance and can maintain a stable structure and good electrical insulation performance in an environment of frequent large-scale temperature changes, solving the problem that insulating materials cannot operate stably for a long time under extreme temperature difference conditions, and is applicable to the long-term stable operation of photovoltaic power distribution cabinets under extreme temperature difference conditions.

[0006] To solve the above technical problems, a technical solution provided by the present invention is: an electrical insulating material for a photovoltaic power distribution cabinet, comprising the following components in parts by weight: 40 - 60 parts of epoxy resin, 20 - 30 parts of silicone rubber, 10 - 15 parts of glass fiber, 5 - 10 parts of nano-aluminum oxide, 3 - 8 parts of flame retardant, 2 - 5 parts of toughening agent, 1 - 3 parts of antioxidant, and 1 - 3 parts of mica powder.

[0007] Further, the antioxidant is a hindered phenol antioxidant, and the toughening agent is a polyurethane elastomer.

[0008] Further, the particle size of the nano-aluminum oxide is 20 - 50 nm, and the length of the glass fiber is 1 - 3 μm.

[0009] Further, the flame retardant includes aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant, and the mass ratio of aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant is 3 - 4:3 - 4:5 - 6.

[0010] Epoxy resin has excellent mechanical strength and electrical insulation performance, but it is brittle and prone to cracking at low temperatures. Silicone rubber has good flexibility and high and low temperature resistance and can maintain elasticity at extreme temperatures. Therefore, the present invention uses epoxy resin and silicone rubber as the matrix, and forms an interpenetrating network structure through the blending of epoxy resin and silicone rubber, forming a "rigid-flexible combination" composite system microscopically. Epoxy resin provides rigid support, while silicone rubber fills between the molecular chains of epoxy resin, playing a buffering role. This structure can resist thermal expansion at high temperatures and relieve shrinkage stress at low temperatures, thus avoiding material cracking.

[0011] Nano-aluminum oxide has high thermal conductivity, high hardness, and good thermal stability. Nano-aluminum oxide particles are evenly dispersed in the matrix material, forming a "nano-reinforcement effect", which can effectively inhibit the propagation of internal cracks in the material, improve the thermal conductivity of the material at the same time, make the heat distribution more uniform, and reduce local thermal stress. In addition, nano-aluminum oxide particles can also form a strong interfacial bond with the matrix material, enhancing the overall mechanical properties of the material.

[0012] Glass fiber has high strength and heat resistance, forms a three-dimensional network structure in the material, and plays a "skeleton" role. At high temperatures, glass fiber can inhibit the thermal expansion of the matrix material; at low temperatures, glass fiber can resist shrinkage stress and prevent the material from cracking. At the same time, the interfacial bonding force between the glass fiber and the matrix material is strong, which can effectively transfer stress and avoid stress concentration.

[0013] The toughening agent has high elasticity and flexibility, forms elastic micro-regions in the material, and can absorb energy when the material is subjected to thermal expansion and contraction stress, preventing the generation and propagation of cracks. These "elastic micro-regions" can maintain flexibility at low temperatures to avoid the material becoming brittle; and maintain stability at high temperatures to prevent the material from softening. The antioxidant can inhibit the oxidative degradation of the material at high temperatures. Aluminum hydroxide or magnesium hydroxide in the inorganic filler can improve the flame retardancy of the material, and at the same time decompose endothermically at high temperatures to reduce the material temperature. The antioxidant prevents the molecular chains of the material from breaking at high temperatures by capturing free radicals. The flame retardant significantly improves the flame retardancy, thermal stability, and electrical insulation performance of the insulating material through mechanisms such as endothermic cooling, generating water vapor, and forming a protective layer. The improvement of these properties enables the material to operate stably in complex environments for a long time and meet the requirements of high-performance applications such as photovoltaic distribution cabinets. In the present invention, the hindered phenol antioxidant protects the stability of the material at high temperatures and extends its service life by inhibiting the oxidation reaction. The polyurethane elastomer further improves the performance of the material by enhancing its flexibility and impact resistance, preventing the material from cracking under low temperature or stress, enabling the material to maintain stable electrical insulation performance and mechanical performance in extreme temperature environments, and meeting the complex working conditions requirements of photovoltaic distribution cabinets.

[0014] Mica powder has excellent electrical insulation performance, can significantly improve the dielectric strength and resistivity of the insulating material, reduce the dielectric loss of the material, and can also enhance the high-temperature resistance of the insulating material, enabling it to maintain good insulation performance and mechanical performance in high-temperature environments. In addition, mica powder can also play a barrier role in the insulating material, preventing the penetration of gases and liquids, and improving the corrosion resistance and sealing performance of the material.

[0015] Aluminum hydroxide and magnesium hydroxide are efficient flame retardants that can decompose to generate water vapor at high temperatures. The generation of water vapor can absorb a large amount of heat, reduce the surface temperature of the material, and at the same time dilute the concentration of combustible gases. In addition, the decomposition residues (aluminum oxide and magnesium oxide) will form a dense protective layer on the surface of the material, further isolating the transfer of heat and oxygen, thereby significantly improving the flame retardant performance of the material. However, the consumption of aluminum hydroxide and magnesium hydroxide is an irreversible process. Once consumed, the flame retardant performance of the material will decline. Adding too much aluminum hydroxide and magnesium hydroxide flame retardants is prone to agglomeration, resulting in uneven dispersion and poor compatibility with organic matrix materials, which will further reduce the mechanical properties and electrical insulation properties of the material, with low flame retardant efficiency and the material becoming brittle and prone to cracking under stress. Therefore, in the present invention, aluminum hydroxide and magnesium hydroxide are encapsulated in microcapsules. When the material is subjected to high temperature, the microcapsules rupture to release the flame retardant, thereby restoring the flame retardant performance of the material. The present invention uses aluminum hydroxide and magnesium hydroxide as core materials, and polylactic acid, polycaprolactone, polycarbonate and nano-silica as shell materials, and prepares the microencapsulated flame retardant by interfacial polymerization.

[0016] The preparation method of the microencapsulated flame retardant is as follows: (1) Add aluminum hydroxide, magnesium hydroxide and a dispersant to deionized water, and stir for 10 - 15 min to form a stable suspension; (2) Dissolve polylactic acid, polycaprolactone and polycarbonate in dichloromethane to form an oil phase, and then disperse nano-silica in the oil phase; (3) Mix the suspension with an emulsifier, stir evenly, slowly add the oil phase, and emulsify for 5 - 10 min under high-speed stirring to form an oil-in-water (O / W) emulsion. Then add a stabilizer to the emulsion, continue stirring, and react at room temperature for 4 - 6 h to form a dense microcapsule shell layer of the shell material on the surfaces of aluminum hydroxide and magnesium hydroxide; (4) Filter the reacted suspension, collect the microcapsules, wash them 3 - 5 times with deionized water, vacuum dry them at 40 - 50 °C for 4 - 6 h, and then coat a layer of polytetrafluoroethylene on the surface of the microcapsules to obtain the dried microencapsulated flame retardant.

[0017] Furthermore, in step (1), the mass ratio of the core materials aluminum hydroxide and magnesium hydroxide is 3 - 4:3 - 4, the dispersant is polyvinylpyrrolidone, the addition amount of the dispersant is 2% - 4% of the mass of the core materials, and the mass of deionized water is 3 - 6 times the mass of the core materials.

[0018] Further, in step (2), the mass ratio of the shell materials polylactic acid, polycaprolactone, polycarbonate and nano-silica is 14:3:3:2, and the total mass of the shell materials is 45% - 55% of the total mass of the core materials in step (1), and the mass of dichloromethane is 5 - 10 times the total mass of the shell materials.

[0019] Further, in step (3), the emulsifier is sodium dodecyl sulfate, and the addition amount is 2% - 4% of the mass of the core materials, and the stabilizer is polyvinyl alcohol, and the addition amount is 2% - 3% of the mass of polylactic acid.

[0020] Further, in step (1), the stirring speed is 1000 - 1500 rpm, and in step (3), the stirring speeds are all 1500 - 2000 rpm.

[0021] Further, the specific operation method for coating a layer of polytetrafluoroethylene on the surface of the microcapsules in step (4) is as follows: disperse polytetrafluoroethylene powder in deionized water to a concentration of 1 - 2 wt%, add a sodium dodecyl sulfate dispersant of 0.05% - 0.1% of the mass of polytetrafluoroethylene to form a stable suspension, immerse the microcapsules in the suspension, stir at 50 - 100 rpm for 5 - 10 min, take out the microcapsules, and vacuum dry at 40 - 50 °C for 2 - 4 h to cure the polytetrafluoroethylene coating.

[0022] The shell materials adopt a blend system of polylactic acid, polycaprolactone and polycarbonate. Among them, the melting point of polylactic acid is about 150 - 160 °C, the glass transition temperature (Tg) of polycarbonate is about 150 °C, and the addition of polycaprolactone improves the low-temperature toughness of the shell. The synergistic effect of the three makes the shell stable at high temperatures. Nano-silica (SiO2) is added as a heat-resistant filler to further improve the thermal stability and mechanical strength of the shell; in addition, the shell thickness is adjusted to about 200 - 300 nm by controlling the mass ratio of the core materials and the shell materials and the emulsification time; finally, a polytetrafluoroethylene (PTFE) coating is applied on the surface of the microcapsules to further enhance the heat resistance and hydrophobicity of the shell, so that the microcapsules can stably rupture and release the flame retardant in the range of 150 - 180 °C, which matches the decomposition temperature of aluminum hydroxide and magnesium hydroxide, thereby realizing the effective release of the flame retardant.

[0023] To solve the above technical problems, another technical solution provided by the present invention is: a preparation method of an electrical insulating material for a photovoltaic power distribution cabinet, and the specific steps are as follows: S1: Prepare a composite polymer masterbatch: add mica powder, nano-aluminum oxide and a toughening agent to a high-speed mixer according to the formula, mix for 10 - 15 min, and then extrude and pelletize with a twin-screw extruder. S2: Kneading: Turn on the cooling water, adjust the roller speeds of the front and rear rollers of the two-roll kneader to 1:1.2. According to the formula, pass the masterbatch, epoxy resin, and silicone rubber prepared in step S1 through the rollers for plastic refining for 2 - 5 min. Adjust the roller gap to 2 - 3 mm. After the masterbatch wraps around the rollers, add glass fiber and antioxidant in sequence. Control the roller temperature at 100 - 120 °C and knead for 10 - 15 min to make it disperse evenly. Pack and thin-pass 5 times each, and adjust the roller distance to slice at a thickness of 2 mm to obtain a kneaded rubber sheet; S3: Vulcanization and molding: After the kneaded rubber sheet prepared in step S2 is parked at room temperature for 18 - 24 h, place it in a flat vulcanizing machine at 15 - 20 MPa for high-temperature vulcanization and molding to obtain the insulating material.

[0024] Furthermore, the high-temperature vulcanization in step S3 is divided into primary vulcanization and secondary vulcanization. The primary vulcanization reaction temperature is 120 - 140 °C, and the reaction time is 30 - 40 min; the secondary vulcanization reaction temperature is 200 - 220 °C, and the reaction time is 50 - 60 min.

[0025] The beneficial effects of the present invention are as follows: The present invention provides an electrical insulating material for a photovoltaic power distribution cabinet. Through the synergistic effect of each component, a "multi-scale composite structure" is formed microscopically: nano-aluminum oxide particles are evenly dispersed to enhance the interfacial bonding force, glass fibers form a three-dimensional network to provide mechanical support, epoxy resin and silicone rubber form an interpenetrating network toughener to form elastic micro-regions. This multi-scale composite structure can effectively disperse stress at extreme temperatures, avoid local stress concentration, and thus maintain the overall stability of the material. In addition, flame retardants aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardants further improve the flame retardancy, thermal stability, and electrical insulation performance of the insulating material. Therefore, the present invention improves the comprehensive performance of the material from the perspectives of chemical stability and mechanical properties, enabling it to remain stable in the temperature range of -40 °C to 150 °C. At the same time, the preparation method of the present invention has a reasonable process and feasible operation, is suitable for industrial production, and can prepare a high-performance electrical insulating material that meets the use requirements of photovoltaic power distribution cabinets under complex working conditions. Specific embodiments

[0026] The following further illustrates the present invention with reference to embodiments, but the present invention is not limited thereto. The experimental methods in the following embodiments are all conventional methods unless otherwise specified.

[0027] Example 1 An electrical insulating material for a photovoltaic power distribution cabinet includes the following components by weight: 40 parts of epoxy resin, 20 parts of silicone rubber, 10 parts of glass fiber, 5 parts of nano-aluminum oxide, 3 parts of flame retardant, 2 parts of polyurethane elastomer, 1 part of hindered phenol antioxidant, and 1 part of mica powder.

[0028] Further, the flame retardant includes aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant, and the mass ratio of aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant is 3:3:5.

[0029] The present invention uses aluminum hydroxide and magnesium hydroxide as core materials, and polylactic acid, polycarbonate, and nano-silica as shell materials, and prepares the microencapsulated flame retardant by the interfacial polymerization method. The specific preparation method is as follows: (1) Add aluminum hydroxide, magnesium hydroxide with a mass ratio of 1:1 and polyvinylpyrrolidone with a mass of 2% of the total mass of aluminum hydroxide and magnesium hydroxide to deionized water, where the mass of deionized water is 3 times the total mass of aluminum hydroxide and magnesium hydroxide, and stir at 1000 rpm for 10 min to form a stable suspension; (2) Dissolve polylactic acid, polycaprolactone, and polycarbonate in dichloromethane to form an oil phase, and then disperse nano-silica in the oil phase. The mass ratio of the shell materials polylactic acid, polycaprolactone, polycarbonate, and nano-silica is 14:3:3:2, and the total mass of the shell materials is 45% of the total mass of the core materials in step (1). The mass of dichloromethane is 5 times the total mass of the shell materials; (3) Mix the suspension with sodium dodecyl sulfate with a mass of 2% of the mass of aluminum hydroxide and magnesium hydroxide, stir evenly, slowly add the oil phase, emulsify at 1500 rpm for 5 min to form an oil-in-water (O / W) emulsion, then add polyvinyl alcohol to the emulsion, continue to stir, and react at room temperature for 4 h to form a dense microcapsule shell layer on the surface of aluminum hydroxide and magnesium hydroxide; (4) Filter the reacted suspension, collect the microcapsules, wash them 3 to 5 times with deionized water, and vacuum dry them at 40 to 50 °C for 4 to 6 h to obtain dry microcapsules; (5) Disperse polytetrafluoroethylene powder in deionized water to a concentration of 1 wt%, add a sodium dodecyl sulfate dispersant with a mass of 0.05% of the mass of polytetrafluoroethylene to form a stable suspension, immerse the microcapsules obtained in step (4) in the suspension, stir at 50 rpm for 5 min, take out the microcapsules, and vacuum dry them at 40 °C for 2 h to obtain dry microencapsulated flame retardant coated with a layer of polytetrafluoroethylene.

[0030] A preparation method of an electrical insulation material for a photovoltaic power distribution cabinet, the specific steps are as follows: S1: Prepare a composite polymer masterbatch: Add mica powder, nano-aluminum oxide, and toughening agent to a high-speed mixer according to the formula, mix for 10 to 15 min, and then extrude and pelletize with a twin-screw extruder; S2: Kneading: Turn on the cooling water, adjust the roller speeds of the front and rear rollers of the two-roll kneader to 1:1.2. According to the formula, pass the masterbatch, epoxy resin, and silicone rubber prepared in step S1 through the rollers for plasticizing for 2 - 5 min. Adjust the roller gap to 2 - 3 mm. After the masterbatch wraps around the rollers, sequentially add glass fiber and antioxidant, control the roller temperature at 100 - 120 °C, knead for 10 - 15 min to make it disperse evenly, bale and thin pass 5 times each, adjust the roller distance to sheet at a thickness of 2 mm to obtain a kneaded rubber sheet; S3: Vulcanization and molding: After the kneaded rubber sheet prepared in step S2 is parked at room temperature for 18 - 24 h, place it in a flat vulcanizing machine at 15 - 20 MPa for high-temperature vulcanization. The first vulcanization reaction temperature is 120 - 140 °C, and the reaction time is 30 - 40 min; the second vulcanization reaction temperature is 200 - 220 °C, and the reaction time is 50 - 60 min. After vulcanization and molding, the insulating material can be obtained.

[0031] Example 2 An electrical insulating material for a photovoltaic power distribution cabinet, comprising the following components by weight: 60 parts of epoxy resin, 30 parts of silicone rubber, 15 parts of glass fiber, 10 parts of nano-aluminum oxide, 8 parts of flame retardant, 5 parts of polyurethane elastomer, 3 parts of hindered phenol antioxidant, and 3 parts of mica powder.

[0032] Further, the flame retardant includes aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant, and the mass ratio of aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant is 4:4:5.

[0033] The present invention uses aluminum hydroxide and magnesium hydroxide as the core materials, and polylactic acid, polycarbonate, and nano-silica as the shell materials, and prepares the microencapsulated flame retardant by the interfacial polymerization method. The specific preparation method is as follows: (1) Add aluminum hydroxide and magnesium hydroxide with a mass ratio of 3:4 and polyvinylpyrrolidone with a mass of 4% of the total mass of aluminum hydroxide and magnesium hydroxide to deionized water, where the mass of deionized water is 6 times the total mass of aluminum hydroxide and magnesium hydroxide, and stir at 1500 rpm for 15 min to form a stable suspension; (2) Dissolve polylactic acid, polycaprolactone, and polycarbonate in dichloromethane to form an oil phase, and then disperse nano-silica in the oil phase. The mass ratio of the shell materials polylactic acid, polycaprolactone, polycarbonate, and nano-silica is 14:3:3:2, and the total mass of the shell materials is 55% of the total mass of the core materials in step (1). The mass of dichloromethane is 10 times the total mass of the shell materials; (3) Mix the suspension with sodium dodecyl sulfate which is 4% of the mass of aluminum hydroxide and magnesium hydroxide, stir evenly, slowly add the oil phase, emulsify for 10 min under high-speed stirring at 2000 rpm to form an oil-in-water (O / W) emulsion, then add polyvinyl alcohol to the emulsion, continue stirring, and react at room temperature for 6 h to form a dense microcapsule shell layer on the surface of aluminum hydroxide and magnesium hydroxide; (4) Filter the reacted suspension, collect the microcapsules, wash them 5 times with deionized water, and vacuum dry them at 50 °C for 6 h to obtain dry microcapsules; (5) Disperse polytetrafluoroethylene powder in deionized water to a concentration of 2 wt%, add a sodium dodecyl sulfate dispersant which is 0.1% of the mass of polytetrafluoroethylene to form a stable suspension, immerse the microcapsules obtained in step (4) in the suspension, stir at 100 rpm for 10 min, take out the microcapsules, and vacuum dry them at 50 °C for 4 h to obtain dry microencapsulated flame retardants coated with a layer of polytetrafluoroethylene.

[0034] A preparation method of an electrical insulating material for a photovoltaic power distribution cabinet, the specific steps are as follows: S1: Prepare a composite polymer masterbatch: Add mica powder, nano-aluminum oxide and a toughening agent to a high-speed mixer according to the formulation, mix for 15 min, and then extrude and pelletize with a twin-screw extruder; S2: Kneading: Turn on the cooling water, adjust the roller speeds of the front and rear rollers of the two-roll kneader to 1:1.2, plastify the masterbatch, epoxy resin and silicone rubber prepared in step S1 through the rollers according to the formulation for 5 min, adjust the roller spacing to 3 mm, and after the masterbatch wraps around the roller, add glass fiber and antioxidant in sequence, control the roller temperature at 120 °C, knead for 15 min to make them disperse evenly, pack and thin-pass 5 times each, adjust the roller distance to sheet at a thickness of 2 mm to obtain a kneaded rubber sheet; S3: Vulcanization and molding: After standing the kneaded rubber sheet prepared in step S2 at room temperature for 24 h, place it in a flat vulcanizer at 20 MPa for high-temperature vulcanization. The first vulcanization reaction temperature is 140 °C and the reaction time is 40 min; the second vulcanization reaction temperature is 220 °C and the reaction time is 60 min. After vulcanization and molding, the insulating material can be obtained.

[0035] Example 3 An electrical insulating material for a photovoltaic power distribution cabinet, comprising the following components by weight: 50 parts of epoxy resin, 25 parts of silicone rubber, 12 parts of glass fiber, 8 parts of nano-aluminum oxide, 5 parts of flame retardant, 3 parts of polyurethane elastomer, 2 parts of hindered phenol antioxidant, and 2 parts of mica powder.

[0036] Further, the flame retardant includes aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant, and the mass ratio of aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant is 1:1:2.

[0037] The present invention uses aluminum hydroxide and magnesium hydroxide as core materials, and polylactic acid, polycarbonate and nano-silica as shell materials, and prepares a microencapsulated flame retardant by an interfacial polymerization method. The specific preparation method is as follows: (1) Add aluminum hydroxide, magnesium hydroxide with a mass ratio of 4:3 and polyvinylpyrrolidone with a mass of 3% of the total mass of aluminum hydroxide and magnesium hydroxide to deionized water, where the mass of deionized water is 5 times the total mass of aluminum hydroxide and magnesium hydroxide, and stir at 1250 rpm for 12 min to form a stable suspension; (2) Dissolve polylactic acid, polycaprolactone and polycarbonate in dichloromethane to form an oil phase, and then disperse nano-silica in the oil phase. The mass ratio of the shell materials polylactic acid, polycaprolactone, polycarbonate and nano-silica is 14:3:3:2, and the total mass of the shell materials is 50% of the total mass of the core materials in step (1). The mass of dichloromethane is 8 times the total mass of the shell materials; (3) Mix the suspension with sodium dodecyl sulfate with a mass of 3% of the mass of aluminum hydroxide and magnesium hydroxide, stir evenly, slowly add the oil phase, and emulsify at 1750 rpm for 7 min to form an oil-in-water (O / W) emulsion. Then add polyvinyl alcohol to the emulsion and continue stirring. React at room temperature for 5 h to form a dense microcapsule shell layer on the surface of aluminum hydroxide and magnesium hydroxide; (4) Filter the reacted suspension, collect the microcapsules, wash them 4 times with deionized water, and vacuum dry them at 45 °C for 5 h to obtain dry microcapsules; (5) Disperse polytetrafluoroethylene powder in deionized water to a concentration of 1.5 wt%, add a sodium dodecyl sulfate dispersant with a mass of 0.07% of the mass of polytetrafluoroethylene to form a stable suspension, immerse the microcapsules obtained in step (4) in the suspension, stir at 75 rpm for 7 min, take out the microcapsules, and vacuum dry them at 45 °C for 3 h to obtain a dry microencapsulated flame retardant coated with a layer of polytetrafluoroethylene.

[0038] A preparation method of an electrical insulating material for a photovoltaic power distribution cabinet, the specific steps are as follows: S1: Prepare a composite polymer masterbatch: Add mica powder, nano-aluminum oxide and a toughening agent to a high-speed mixer according to the formulation, mix for 12 min, and then extrude and pelletize with a twin-screw extruder; S2: Kneading: Turn on the cooling water, adjust the roller speeds of the front and rear rollers of the two-roll kneader to 1:1.2. According to the formula, pass the masterbatch, epoxy resin, and silicone rubber prepared in step S1 through the rollers for plasticizing for 3 min. Adjust the roller gap to 2.5 mm. After the masterbatch wraps around the rollers, add glass fiber and antioxidant in sequence. Control the roller temperature at 110 °C and knead for 12 min to make it disperse evenly. Pack and thin-pass 5 times each, adjust the roller gap to sheet at a thickness of 2 mm to obtain a kneaded rubber sheet; S3: Vulcanization and molding: After the kneaded rubber sheet prepared in step S2 is parked at room temperature for 21 h, place it in a flat vulcanizing machine at 18 MPa for high-temperature vulcanization. The first vulcanization reaction temperature is 130 °C and the reaction time is 35 min; the second vulcanization reaction temperature is 210 °C and the reaction time is 55 min. After vulcanization and molding, the insulating material can be obtained.

[0039] Comparative example 1: This comparative example 1 is basically the same as Example 3, except that there is no microencapsulated flame retardant in the flame retardant.

[0040] Comparative example 2: This comparative example 2 is basically the same as Example 3, except that step (5) is not included in the preparation steps of the microencapsulated flame retardant.

[0041] Testing experiment: Take the 5 insulating materials of Examples 1 to 3 and Comparative examples 1 to 2 as test samples for testing, and the test results are shown in Tables 1 and 2 below.

[0042] 1. Performance test results Table 1 Performance test results Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Heat distortion temperature (°C) 150 145 160 80 90 Limiting oxygen index (%) 32 30 31 26 28 Vertical burning test (grade) V-0 V-1 V-0 Failed V-2 2. Temperature cycle resistance test Refer to the international standard IEC 60068-2-14 (Environmental testing - Part 2-14: Tests - N: Change of temperature) or GB / T 2423.22 (Environmental testing for electric and electronic products - Test methods for change of temperature).

[0043] Testing equipment: High and low temperature alternating test chamber, programmable control temperature range (-70 °C to +200 °C), adjustable heating and cooling rate.

[0044] Testing steps: (1) Sample preparation Prepare standard test square samples from the products of Examples 1 to 3 and Comparative examples 1 to 2, with dimensions conforming to relevant test standards (such as ISO 527, ASTM D149). There are at least 5 groups of each sample to ensure data reliability.

[0045] (2) Pretreatment Place the sample in a standard laboratory environment (23°C ± 2°C, 50% ± 5% RH) for 24 hours to eliminate processing stress.

[0046] (3) Temperature cycle program setting High temperature setting: 150°C; Low temperature setting: -40°C; Number of cycles: 50 - 100 times (adjust according to actual working conditions); Single cycle process: Heating stage: Rise from room temperature to 150°C, heating rate ≤ 5°C / min; High temperature holding: Hold at 150°C for 2 hours; Cooling stage: Drop from 150°C to -40°C, cooling rate ≤ 5°C / min; Low temperature holding: Hold at -40°C for 2 hours; Rewarming stage: Rise from -40°C to room temperature, heating rate ≤ 5°C / min.

[0047] (4) Test execution Place the sample in a high and low temperature chamber, ensuring there is a gap between samples (to avoid heat conduction interference); Start the temperature cycle program, record the temperature, humidity inside the chamber and the surface temperature of the sample throughout the process; After every 10 cycles, take out some samples for intermediate performance testing.

[0048] Table 2 Temperature cycle resistance test results As shown in Table 1 and Table 2, the limiting oxygen index of Examples 1 - 3: 30% - 32%, significantly better than the comparative examples (26% - 28%); Vertical burning test: Examples 1 and 3 reach V - 0 level, Example 2 is V - 1 level, while Comparative Example 1 fails and Comparative Example 2 is only V - 2 level. Therefore, the examples containing microencapsulated flame retardants can significantly improve the flame retardancy efficiency, and the polytetrafluoroethylene coating can further optimize the performance.

[0049] The heat distortion temperature of Examples 1 - 3 (145 - 160°C) is much higher than that of Comparative Examples 1 - 2 (80 - 90°C), and they are resistant to temperature cycling (50 times). For the examples: the tensile strength retention rate ≥ 90%, the dielectric strength retention rate ≥ 85%; while the performance of the comparative examples drops significantly (tensile strength retention rate ≤ 76%, dielectric strength retention rate ≤ 55%). Therefore, the microencapsulated flame retardant and the PTFE coating act synergistically to effectively resist the performance degradation caused by extreme temperature differences.

[0050] Through the design of microencapsulated flame retardants and PTFE coatings, the present invention significantly improves the flame retardancy, temperature resistance stability and reliability under extreme environments of the material.

[0051] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. An electrical insulation material for a photovoltaic distribution cabinet, characterized in that: The invention comprises the following components in parts by weight: 40-60 parts of epoxy resin, 20-30 parts of silicone rubber, 10-15 parts of glass fiber, 5-10 parts of nano-alumina, 3-8 parts of flame retardant, 2-5 parts of toughening agent, 1-3 parts of antioxidant and 1-3 parts of mica powder.

2. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant, the toughening agent is a polyurethane elastomer, the particle size of nano alumina is 20-50nm, the length of the glass fiber is 1-3um, the flame retardant includes aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant, and the mass ratio of aluminum hydroxide, magnesium hydroxide, and microencapsulated flame retardant is 3-4:3-4:5-6.

3. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 2, characterized in that: The microencapsulated flame retardant uses aluminum hydroxide and magnesium hydroxide as core materials, polylactic acid, polycaprolactone, polycarbonate and nano-silicon dioxide as shell materials, and is prepared by interfacial polymerization. The specific steps are as follows: (1) Add aluminum hydroxide, magnesium hydroxide and dispersant into deionized water and stir for 10 to 15 minutes to form a stable suspension; (2) dissolving polylactic acid, polycaprolactone and polycarbonate in dichloromethane to form an oil phase, and then dispersing nano-silicon dioxide in the oil phase; (3) Mix the suspension with the emulsifier, stir evenly, slowly add the oil phase, and emulsify for 5 to 10 minutes under high-speed stirring to form an oil-in-water (O / W) emulsion. Then add the stabilizer to the emulsion, continue stirring, and react at room temperature for 4 to 6 hours to allow the shell material to form a dense microcapsule shell on the surface of aluminum hydroxide and magnesium hydroxide; (4) Filter the suspension after the reaction, collect the microcapsules, wash them with deionized water for 3 to 5 times, and vacuum dry them at 40 to 50° C. for 4 to 6 hours. Then, coat a layer of polytetrafluoroethylene on the surface of the microcapsules to obtain a dry microencapsulated flame retardant.

4. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 3, characterized in that: In step (1), the mass ratio of the core materials aluminum hydroxide and magnesium hydroxide is 3-4:3-4, the dispersant is polyvinyl pyrrolidone, the amount of the dispersant added is 2%-4% of the mass of the core material, and the mass of deionized water is 3-6 times the mass of the core material.

5. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 3, characterized in that: In step (2), the mass ratio of the shell materials polylactic acid, polycaprolactone, polycarbonate and nano-silicon dioxide is 14:3:3:2, and the total mass of the shell materials is 45% to 55% of the total mass of the core materials in step (1), and the mass of dichloromethane is 5 to 10 times the total mass of the shell materials.

6. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 3, characterized in that: In step (3), the emulsifier is sodium dodecyl sulfate, and the amount added is 2% to 4% of the mass of the core material; the stabilizer is polyvinyl alcohol, and the amount added is 2% to 3% of the mass of the polylactic acid.

7. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 3, characterized in that: The stirring speed in step (1) is 1000-1500 rpm, and the stirring speed in step (3) is 1500-2000 rpm.

8. The electrical insulating material for a photovoltaic power distribution cabinet according to claim 3, characterized in that: The specific operation method of coating a layer of polytetrafluoroethylene on the surface of the microcapsule in step (4) is as follows: polytetrafluoroethylene powder is dispersed in deionized water to a concentration of 1 to 2 wt%, and a sodium dodecyl sulfate dispersant of 0.05% to 0.1% by weight of polytetrafluoroethylene is added to form a stable suspension, and the microcapsules are immersed in the suspension, stirred at 50 to 100 rpm for 5 to 10 minutes, and the microcapsules are taken out and vacuum dried at 40 to 50° C. for 2 to 4 hours to solidify the polytetrafluoroethylene coating.

9. The method for preparing an electrical insulating material for a photovoltaic power distribution cabinet according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: Preparation of composite polymer masterbatch: mica powder, nano-alumina and toughening agent are added into a high-speed mixer according to the formula, mixed for 10 to 15 minutes, and then extruded into granules using a twin-screw extruder; S2: Mixing: Turn on the cooling water, adjust the roller speed of the front and rear rollers of the double-roll mill to 1:1.2, and roll the masterbatch, epoxy resin and silicone rubber prepared in step S1 for 2-5 min according to the formula, adjust the roller spacing to 2-3 mm, and after the masterbatch is rolled, add glass fiber and antioxidant in sequence, control the roller temperature to 100-120 ° C, mix for 10-15 min to make it evenly dispersed, pack and thin pass 5 times each, adjust the roller spacing to roll out a sheet with a thickness of 2 mm, and obtain a mixed film; S3: Vulcanization molding: After the mixed rubber sheet prepared in step S2 is left at room temperature for 18 to 24 hours, it is placed in a 15 to 20 MPa flat plate vulcanizer for high temperature vulcanization molding to obtain an insulating material.

10. The preparation method according to claim 9, characterized in that: In step S3, the high temperature vulcanization is divided into primary vulcanization and secondary vulcanization. The primary vulcanization reaction temperature is 120-140°C and the reaction time is 30-40 minutes; the secondary vulcanization reaction temperature is 200-220°C and the reaction time is 50-60 minutes.

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