Bio-based high-frequency transformer shell material and preparation method thereof

Abstract

The invention relates to the technical field of bio-based materials, in particular to a preparation method of a bio-based high-frequency transformer shell material, which is prepared from the following raw materials in parts by weight: 50 to 55 parts of bio-based polyamide, 42 to 45 parts of heat-conducting filler, 8 to 10 parts of main flame retardant, 5 to 7 parts of auxiliary flame retardant, 10 to 12 parts of glass fiber and 1 to 2 parts of lubricant. According to the invention, the overall heat dissipation efficiency of the material is improved through the porous structure of the composite oyster shell powder and the diatomite, the composite oyster shell powder forms nanoscale pits and secondary micropores through etching of organic acid secreted by bacillus pasteurii and freezing-unfreezing circulation treatment, and the nanoscale pits and secondary micropores are filled with fine particles of the red mud extract or the diatomite; meanwhile, the esterified starch uniformly wraps the surface of the calcined oyster shell powder, gaps among particles are filled, air barrier in a heat conduction path is reduced, heat can be continuously transmitted along a filler interface, and temperature rise during operation of the transformer is reduced.

Description

Technical Field

[0001] This invention relates to the field of bio-based materials technology, specifically a method for preparing a bio-based high-frequency transformer shell material. Background Technology

[0002] The shell material of a high-frequency transformer is a key structural component of the transformer. Its function is not only physical protection, but also crucial to ensuring the high efficiency and stable operation of the transformer. Bio-based shell materials are mainly made from bio-based polymers such as polyamide and polylactic acid, as well as renewable resources such as plant starch and microbial fermentation products. However, in the existing technology, bio-based materials generally have problems such as low mechanical strength and poor thermal conductivity, which make it difficult to directly meet the high heat dissipation requirements of high-frequency transformers. Based on this, the present invention provides a bio-based high-frequency transformer shell material and its preparation method. Summary of the Invention

[0003] The purpose of this invention is to provide a bio-based high-frequency transformer shell material and its preparation method. The bio-based high-frequency transformer shell material prepared by this invention not only optimizes thermal conductivity and reduces transformer operating temperature rise, but also enhances its impact resistance and toughness.

[0004] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a bio-based high-frequency transformer housing material, comprising the following raw materials in parts by weight: 50-55 parts bio-based polyamide, 42-45 parts thermally conductive filler, 8-10 parts primary flame retardant, 5-7 parts secondary flame retardant, 10-12 parts glass fiber, and 1-2 parts lubricant.

[0005] Furthermore, the thermally conductive filler is prepared by mixing modified additives, activated diatomaceous earth, and alumina.

[0006] Furthermore, the modified additive is obtained by co-culturing compound oyster shell powder and red mud extract with microorganisms, followed by repeated freeze-thaw cycles.

[0007] Further, the preparation method of the thermally conductive filler is as follows: the modified additive, activated diatomaceous earth and alumina powder are mixed in a mass ratio of (20-30):(20-30):(50-60), ball-milled for 2 hours, dried at 120℃ and passed through a 200-mesh sieve to obtain the thermally conductive filler, wherein the alumina powder has a particle size of 50-100μm.

[0008] Furthermore, the preparation method of the modified additive is as follows: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of (0.8-1.2)×10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:(8-12), adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 1-3%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:(4-6), freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

[0009] Furthermore, the preparation method of the composite oyster shell powder is as follows: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 8-9, calcine them at 500℃ for 2-4 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder.

[0010] B. Mix acetate starch and calcined oyster shell powder at a mass ratio of 1:(3-5), add deionized water at a solid-liquid ratio of 1:5, stir at 50-70℃ for 30 min, set to 200W, ultrasonically disperse at 40kHz for 15 min, dry at 60℃ and pass through a 300-mesh sieve to obtain composite oyster shell powder.

[0011] Further, the preparation method of the red mud extract is as follows: crush the red mud ore to a particle size of less than 10 mm to obtain red mud powder, mix the red mud powder with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:(2-4), stir at 80°C for 1 h, centrifuge to remove the supernatant, wash the precipitate to neutral and then dry to obtain the red mud extract.

[0012] Further, the preparation method of the oxalic acid treatment solution is as follows: oxalic acid crystals and deionized water are mixed at a mass ratio of 1:(4-6) to obtain an oxalic acid solution. Activated carbon powder is added to the oxalic acid solution, and the mixture is stirred at 300 r / min for 20 min and then filtered to obtain the oxalic acid treatment solution. The mass of the activated carbon powder is 1-2% of the mass of the oxalic acid.

[0013] Further, the preparation method of the activated diatomaceous earth is as follows: the raw diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:(2-4), ultrasonically treated for 20 minutes, the supernatant is discarded after standing, the precipitate is washed with water until neutral, dried at 105℃ and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

[0014] Furthermore, the main flame retardant is zinc borate, and the auxiliary flame retardant is aluminum hydroxide, wherein the particle size of zinc borate is 20 μm and the particle size of aluminum hydroxide is 10 μm.

[0015] Furthermore, the bio-based polyamide is nylon 1010, and the lubricant is paraffin wax.

[0016] Secondly, this invention provides a method for preparing a bio-based high-frequency transformer casing material, comprising the following steps: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feed zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 200-300rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to: front section 235℃, middle section 240℃, rear section 245℃, mold temperature 70-80℃, injection pressure 80-90MPa, holding time 15s, and obtain the bio-based high-frequency transformer shell material.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, the porous structure of composite oyster shell powder and diatomaceous earth improves the overall heat dissipation efficiency of the material. The organic acid etching secreted by Bacillus pasteurellium and the freeze-thaw cycle treatment cause the composite oyster shell powder to form nanoscale pits and secondary micropores, which are filled by fine particles of red mud extract or diatomaceous earth. At the same time, esterified starch is uniformly coated on the surface of calcined oyster shell powder, filling the gaps between particles, reducing air blockage in the heat conduction path, and enabling heat to be continuously transferred along the filler interface, reducing the temperature rise of the transformer during operation.

[0018] 2. In this invention, micropores are created by co-culturing red mud extract and composite oyster shell powder with microorganisms and by freezing-thawing cycle treatment. This makes the bonding between filler particles more uniform and the interface bonding stronger. At the same time, the flexible segments of acetate starch form an elastic buffer layer between calcined oyster shell powder particles. When the material is impacted, the starch segments absorb the impact energy through stretching and sliding, reduce stress concentration, and reduce interface debonding and crack propagation caused by impact. This makes the transformer shell more impact-resistant and less prone to breakage. Attached Figure Description

[0019] Figure 1 The flowchart illustrates a bio-based high-frequency transformer housing material and its preparation method. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0022] A bio-based high-frequency transformer housing material comprises the following raw materials in parts by weight: 50-55 parts bio-based polyamide, 42-45 parts thermally conductive filler, 8-10 parts primary flame retardant, 5-7 parts secondary flame retardant, 10-12 parts glass fiber, and 1-2 parts lubricant.

[0023] In this embodiment, the thermally conductive filler is prepared by mixing modified additives, activated diatomaceous earth, and alumina.

[0024] In this embodiment, the modified additive was obtained by co-culturing composite oyster shell powder and red mud extract with microorganisms and then subjecting them to repeated freeze-thaw cycles.

[0025] In this embodiment, the preparation method of the thermally conductive filler is as follows: the modified additive, activated diatomaceous earth and alumina powder are mixed in a mass ratio of (20-30):(20-30):(50-60), ball-milled for 2 hours, dried at 120°C and passed through a 200-mesh sieve to obtain the thermally conductive filler, wherein the alumina powder has a particle size of 50-100μm.

[0026] In this embodiment, the preparation method of the modified additive is as follows: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of (0.8-1.2)×10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:(8-12), adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 1-3%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:(4-6), freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

[0027] In this embodiment, the preparation method of the composite oyster shell powder is as follows: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 8-9, calcine them at 500℃ for 2-4 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder.

[0028] B. Mix acetate starch and calcined oyster shell powder at a mass ratio of 1:(3-5), add deionized water at a solid-liquid ratio of 1:5, stir at 50-70℃ for 30 min, set to 200W, ultrasonically disperse at 40kHz for 15 min, dry at 60℃ and pass through a 300-mesh sieve to obtain composite oyster shell powder.

[0029] In this embodiment, the preparation method of red mud extract is as follows: the red mud ore is crushed to a particle size of less than 10 mm to obtain red mud powder. The red mud powder is mixed with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:(2-4), stirred at 80°C for 1 h, the supernatant is removed by centrifugation, the precipitate is washed to neutral and then dried to obtain red mud extract.

[0030] In this embodiment, the preparation method of oxalic acid treatment solution is as follows: oxalic acid crystals and deionized water are mixed at a mass ratio of 1:(4-6) to obtain oxalic acid solution. Activated carbon powder is added to the oxalic acid solution, and the mixture is stirred at 300 r / min for 20 min and then filtered to obtain oxalic acid treatment solution. The mass of activated carbon powder is 1-2% of the mass of oxalic acid.

[0031] In this embodiment, the method for preparing activated diatomaceous earth is as follows: diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:(2-4), ultrasonically treated for 20 minutes, allowed to stand and the supernatant is discarded, the precipitate is washed with water until neutral, dried at 105°C and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

[0032] In this embodiment, the main flame retardant is zinc borate, and the auxiliary flame retardant is aluminum hydroxide, wherein the particle size of zinc borate is 20 μm and the particle size of aluminum hydroxide is 10 μm.

[0033] In this embodiment, the bio-based polyamide is nylon 1010, and the lubricant is paraffin wax.

[0034] In this embodiment, a method for preparing a bio-based high-frequency transformer casing material includes the following steps: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feed zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 200-300rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to: front section 235℃, middle section 240℃, rear section 245℃, mold temperature 70-80℃, injection pressure 80-90MPa, holding time 15s, and obtain the bio-based high-frequency transformer shell material.

[0035] Based on the foregoing embodiments, the inventors also conducted the following sets of experiments: It should be noted that all raw materials used in the following experiments are commercially available.

[0036] Experiment 1: Prepare the following raw materials by weight: 50 parts bio-based polyamide, 42 parts thermally conductive filler, 8 parts primary flame retardant, 5 parts secondary flame retardant, 10 parts glass fiber, and 1 part lubricant.

[0037] Preparation of composite oyster shell powder: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 8, calcine them at 500℃ for 2 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder.

[0038] B. Mix starch acetate and calcined oyster shell powder at a mass ratio of 1:3, add deionized water at a solid-liquid ratio of 1:5, stir at 50°C for 30 min, ultrasonically disperse at 200W and 40kHz for 15 min, dry at 60°C and pass through a 300-mesh sieve to obtain composite oyster shell powder.

[0039] Preparation of oxalic acid treatment solution: Oxalic acid crystals and deionized water were mixed at a mass ratio of 1:4 to obtain an oxalic acid solution. Activated carbon powder was added to the oxalic acid solution, and the mixture was stirred at 300 r / min for 20 min and then filtered to obtain the oxalic acid treatment solution. The mass of activated carbon powder was 1% of the mass of oxalic acid.

[0040] Preparation of red mud extract: The raw red mud ore was crushed to a particle size of less than 10 mm to obtain red mud powder. The red mud powder was mixed with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:2, stirred at 80°C for 1 h, the supernatant was removed by centrifugation, the precipitate was washed until neutral and then dried to obtain red mud extract.

[0041] Preparation of modified additives: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of 0.8 × 10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:8, adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72 h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 1%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:4, freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

[0042] Preparation of activated diatomaceous earth: The raw diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:2, ultrasonically treated for 20 minutes, the supernatant is discarded after standing, the precipitate is washed with water until neutral, dried at 105℃ and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

[0043] Preparation of thermally conductive filler: Modified additives, activated diatomaceous earth and alumina powder are mixed at a mass ratio of 20:20:50, ball-milled for 2 hours, dried at 120℃ and passed through a 200-mesh sieve to obtain thermally conductive filler, wherein the alumina powder has a particle size of 50μm.

[0044] Preparation of bio-based high-frequency transformer housing materials: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feeding zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 200rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to 235℃ for the front section, 240℃ for the middle section, and 245℃ for the rear section, the mold temperature to 70℃, the injection pressure to 80MPa, and the holding time to 15s to obtain the bio-based high-frequency transformer shell material.

[0045] Experiment 2: Prepare the following raw materials by weight: 52 parts bio-based polyamide, 44 parts thermally conductive filler, 9 parts primary flame retardant, 6 parts secondary flame retardant, 11 parts glass fiber, and 1.5 parts lubricant.

[0046] Preparation of composite oyster shell powder: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 8.5, calcine them at 500℃ for 3 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder.

[0047] B. Mix starch acetate and calcined oyster shell powder at a mass ratio of 1:4, add deionized water at a solid-liquid ratio of 1:5, stir at 60°C for 30 min, ultrasonically disperse at 200W and 40kHz for 15 min, dry at 60°C and pass through a 300-mesh sieve to obtain composite oyster shell powder.

[0048] Preparation of oxalic acid treatment solution: Oxalic acid crystals and deionized water were mixed at a mass ratio of 1:5 to obtain an oxalic acid solution. Activated carbon powder was added to the oxalic acid solution, and the mixture was stirred at 300 r / min for 20 min and then filtered to obtain the oxalic acid treatment solution. The mass of activated carbon powder was 1.5% of the mass of oxalic acid.

[0049] Preparation of red mud extract: The raw red mud ore was crushed to a particle size of less than 10 mm to obtain red mud powder. The red mud powder was mixed with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:3, stirred at 80°C for 1 h, the supernatant was removed by centrifugation, the precipitate was washed until neutral and then dried to obtain red mud extract.

[0050] Preparation of modified additives: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of 1.0 × 10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:10, adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72 h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 2%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:5, freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

[0051] Preparation of activated diatomaceous earth: The raw diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:3, ultrasonically treated for 20 minutes, allowed to stand and the supernatant is discarded, the precipitate is washed with water until neutral, dried at 105℃ and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

[0052] Preparation of thermally conductive filler: Modified additives, activated diatomaceous earth and alumina powder are mixed in a mass ratio of 25:25:55, dried at 120℃ and passed through a 200-mesh sieve to obtain thermally conductive filler, wherein the alumina powder has a particle size of 75μm.

[0053] Preparation of bio-based high-frequency transformer housing materials: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feed zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 250rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to: front section 235℃, middle section 240℃, rear section 245℃, mold temperature 75℃, injection pressure 85MPa, holding time 15s, and obtain the bio-based high-frequency transformer shell material.

[0054] Experiment 3: Prepare the following raw materials by weight: 55 parts bio-based polyamide, 45 parts thermally conductive filler, 10 parts primary flame retardant, 7 parts secondary flame retardant, 12 parts glass fiber, and 2 parts lubricant.

[0055] Preparation of composite oyster shell powder: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 9, calcine them at 500℃ for 4 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder.

[0056] B. Mix starch acetate and calcined oyster shell powder at a mass ratio of 1:5, add deionized water at a solid-liquid ratio of 1:5, stir at 70℃ for 30 min, ultrasonically disperse at 200W and 40kHz for 15 min, dry at 60℃ and pass through a 300-mesh sieve to obtain composite oyster shell powder.

[0057] Preparation of oxalic acid treatment solution: Oxalic acid crystals and deionized water were mixed at a mass ratio of 1:6 to obtain an oxalic acid solution. Activated carbon powder was added to the oxalic acid solution, and the mixture was stirred at 300 r / min for 20 min and then filtered to obtain the oxalic acid treatment solution. The mass of activated carbon powder was 2% of the mass of oxalic acid.

[0058] Preparation of red mud extract: The raw red mud ore was crushed to a particle size of less than 10 mm to obtain red mud powder. The red mud powder was mixed with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:4, stirred at 80°C for 1 h, the supernatant was removed by centrifugation, the precipitate was washed until neutral and then dried to obtain red mud extract.

[0059] Preparation of modified additives: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of 1.2 × 10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:12, adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72 h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 3%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:6, freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

[0060] Preparation of activated diatomaceous earth: The raw diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:4, ultrasonically treated for 20 minutes, allowed to stand and the supernatant is discarded, the precipitate is washed with water until neutral, dried at 105℃ and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

[0061] Preparation of thermally conductive filler: Modified additives, activated diatomaceous earth and alumina powder are mixed in a mass ratio of 30:30:60, ball-milled for 2 hours, dried at 120℃ and passed through a 200-mesh sieve to obtain thermally conductive filler, wherein the alumina powder has a particle size of 100μm.

[0062] Preparation of bio-based high-frequency transformer housing materials: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feed zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 300rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to 235℃ for the front section, 240℃ for the middle section, and 245℃ for the rear section, the mold temperature to 80℃, the injection pressure to 90MPa, and the holding time to 15s, to obtain the bio-based high-frequency transformer shell material.

[0063] Comparative Example 1: The difference between this comparative example and Experiment 1 is as follows: In this comparative example, alumina powder is used instead of thermally conductive filler.

[0064] Comparative Example 2: The difference between this comparative example and Experiment 1 is as follows: This comparative example does not contain any modified additives.

[0065] Comparative Example 3: The difference between this comparative example and Experiment 1 is that: In this comparative example, the modified additives removed the microbial co-culture and freeze-thaw cycle steps.

[0066] Comparative Example 4: The difference between this comparative example and Experiment 1 is as follows: In this comparative example, calcined oyster shell powder was used instead of composite oyster shell powder.

[0067] Performance testing: The performance of the bio-based high-frequency transformer shell materials prepared in Experiments 1, 2, 3, Comparative Examples 1, 2, 3, and 4 was tested, and the test data are recorded in the table below:

[0068] In the performance testing, the thermal conductivity test was conducted in accordance with GB / T 42919.1-2023, and the impact toughness test was conducted in accordance with GB / T1043.1-2008.

[0069] The thermal conductivity test results of the bio-based high-frequency transformer shell materials prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 0.88 W / (m·K), 0.95 W / (m·K), 1.01 W / (m·K), 0.42 W / (m·K), 0.58 W / (m·K), 0.66 W / (m·K) and 0.73 W / (m·K), respectively.

[0070] The impact toughness test results of the bio-based high-frequency transformer shell materials prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 5.7 kJ / m², 5.9 kJ / m², 6.2 kJ / m², 3.1 kJ / m², 3.7 kJ / m², 4.4 kJ / m² and 4.8 kJ / m², respectively.

[0071] It is evident that the thermal conductivity and impact toughness of the bio-based high-frequency transformer shell materials prepared in Comparative Examples 1, 2, 3, and 4 are all lower than those in Experiments 1, 2, and 3. This indicates that the modified additive, prepared from composite oyster shell powder and red mud extract through microbial co-cultivation and freeze-thaw cycles, allows the calcium element in the composite oyster shell powder and the metal oxides in the red mud extract to form a stable porous composite under the action of microorganisms. This composite effectively transfers heat and disperses impact stress. During the microbial co-cultivation process, Bacillus pasteurellii etches nanoscale pits on the material surface under a strong acid environment, providing more pathways for heat conduction and allowing energy absorption through the deformation of the pores upon impact, thus reducing material breakage due to impact. The freezing-thawing cycle causes the composite oyster shell powder within the material to form secondary micropores. The fine particles of red mud extract or diatomaceous earth fill these micropores, reducing air barriers in the heat conduction path. Heat can be continuously transferred along the filler interface, promoting thermal conductivity. At the same time, the particles are more evenly bonded, the interface is more firmly bonded, stress concentration points are reduced, and the material's impact resistance and toughness are enhanced. In the preparation of the composite oyster shell powder, acetate starch can evenly coat the calcined oyster shell powder particles, reducing gaps between particles and making the heat conduction path more continuous. The polar groups of acetate starch can also form hydrogen bonds with the molecular chains of bio-based polyamide, enhancing the interfacial bonding between the calcined oyster shell powder and the matrix material, and improving heat conduction and stress transfer efficiency.

[0072] By comparing and analyzing the relevant data in the table, it can be seen that the bio-based high-frequency transformer shell material prepared by this invention not only has good thermal conductivity but also good impact toughness. This indicates that the bio-based high-frequency transformer shell material and its preparation method provided by this invention have broader market prospects and are more suitable for widespread application.

[0073] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A bio-based high-frequency transformer housing material, characterized in that, The raw materials include the following parts by weight: 50-55 parts bio-based polyamide, 42-45 parts thermally conductive filler, 8-10 parts main flame retardant, 5-7 parts auxiliary flame retardant, 10-12 parts glass fiber, and 1-2 parts lubricant. The thermally conductive filler is prepared by mixing modified additives, activated diatomaceous earth and alumina; The modified additive is obtained by co-culturing compound oyster shell powder and red mud extract with microorganisms, followed by repeated freeze-thaw cycles.

2. The bio-based high-frequency transformer housing material according to claim 1, characterized in that, The preparation method of the thermally conductive filler is as follows: the modified additive, activated diatomaceous earth and alumina powder are mixed in a mass ratio of (20-30):(20-30):(50-60), ball-milled for 2 hours, dried at 120℃ and passed through a 200-mesh sieve to obtain the thermally conductive filler, wherein the alumina powder has a particle size of 50-100μm.

3. The bio-based high-frequency transformer housing material according to claim 2, characterized in that, The preparation method of the modified additive is as follows: (1) Culture Bacillus pasteurellii to the logarithmic phase, collect the cells by centrifugation, and resuspend in sterile water to a concentration of (0.8-1.2)×10⁻⁶. 8 CFU / mL, to obtain a microbial suspension; (2) Mix the compound oyster shell powder and red mud extract at a mass ratio of 1:1, add microbial suspension at a solid-liquid ratio of 1:(8-12), adjust the pH to 2.5 with dilute sulfuric acid solution, and culture at 28℃ with shaking for 72h to obtain a co-culture mixture, wherein the mass fraction of dilute sulfuric acid solution is 1-3%; (3) Mix the co-culture mixture with a 10% sodium chloride solution at a solid-liquid ratio of 1:(4-6), freeze at -20℃ for 2 hours and thaw at room temperature. Repeat the cycle 5 times. After centrifugation, wash the filter residue with deionized water until neutral, dry at 105℃ and pass through a 300-mesh sieve to obtain the modified additive.

4. The bio-based high-frequency transformer housing material according to claim 3, characterized in that, The preparation method of the composite oyster shell powder is as follows: A. Crush oyster shells to a particle size of less than 5 mm, spray them with 5% acetic acid solution to pH 8-9, calcine them at 500℃ for 2-4 hours, pulverize them and pass them through a 300-mesh sieve to obtain calcined oyster shell powder; B. Mix acetate starch and calcined oyster shell powder at a mass ratio of 1:(3-5), add deionized water at a solid-liquid ratio of 1:5, stir at 50-70℃ for 30 min, set to 200W, ultrasonically disperse at 40kHz for 15 min, dry at 60℃ and pass through a 300-mesh sieve to obtain composite oyster shell powder.

5. The bio-based high-frequency transformer housing material according to claim 3, characterized in that, The preparation method of the red mud extract is as follows: crush the red mud ore to a particle size of less than 10 mm to obtain red mud powder, mix the red mud powder with 5% oxalic acid treatment solution at a solid-liquid ratio of 1:(2-4), stir at 80°C for 1 h, centrifuge to remove the supernatant, wash the precipitate to neutral and then dry to obtain the red mud extract.

6. The bio-based high-frequency transformer housing material according to claim 5, characterized in that, The preparation method of the oxalic acid treatment solution is as follows: oxalic acid crystals and deionized water are mixed at a mass ratio of 1:(4-6) to obtain an oxalic acid solution. Activated carbon powder is added to the oxalic acid solution, and the mixture is stirred at 300 r / min for 20 min and then filtered to obtain the oxalic acid treatment solution. The mass of the activated carbon powder is 1-2% of the mass of the oxalic acid.

7. The bio-based high-frequency transformer housing material according to claim 1, characterized in that, The method for preparing the activated diatomaceous earth is as follows: diatomaceous earth ore is mixed with a 10% sodium chloride solution at a solid-liquid ratio of 1:(2-4), ultrasonically treated for 20 minutes, allowed to stand and the supernatant is discarded, the precipitate is washed with water until neutral, dried at 105℃ and passed through a 300-mesh sieve to obtain activated diatomaceous earth.

8. The bio-based high-frequency transformer housing material according to claim 1, characterized in that, The main flame retardant is zinc borate, and the auxiliary flame retardant is aluminum hydroxide, wherein the particle size of zinc borate is 20 μm and the particle size of aluminum hydroxide is 10 μm.

9. The bio-based high-frequency transformer housing material according to claim 1, characterized in that, The bio-based polyamide is nylon 1010, and the lubricant is paraffin wax.

10. The method for preparing the bio-based high-frequency transformer housing material according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Add bio-based polyamide, thermally conductive filler, main flame retardant and auxiliary flame retardant to a high-speed mixer and premix at 500 rpm for 10 min; S2: Add glass fiber and lubricant to the product obtained in S1, and continue mixing for 5 minutes to obtain a mixture; S3: Feed the mixture into a twin-screw extruder, set the zone temperature control: feed zone 190℃, melting zone 230℃, homogenization zone 240℃, main machine speed 200-300rpm, extrude and granulate, dry at 80℃ for 2h to obtain granules; S4: Feed the granules into the injection molding machine, set the barrel temperature to: front section 235℃, middle section 240℃, rear section 245℃, mold temperature 70-80℃, injection pressure 80-90MPa, holding time 15s, and obtain the bio-based high-frequency transformer shell material.

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