A high-strength, high-insulation aramid insulating paper for electrical equipment, its preparation method and application

Abstract

This invention discloses a high-strength, high-insulation aramid insulating paper for electrical equipment, its preparation method, and its application, comprising the following steps: Step 1: Aramid fibers are modified by plasma treatment to obtain modified aramid fibers, which are then impregnated in ZnO quantum dot seed solution and annealed to obtain aramid fiber A with ZnO nanowires on its surface; Step 2: Aramid nanofiber spinning solution and polyvinyl alcohol solution are mixed and electrospun to obtain composite nanofiber B; Step 3: A fiber pulp suspension solution of aramid fiber A and a fiber pulp suspension solution of composite nanofiber B are mixed, dehydrated, and then cured at high temperature to obtain the desired insulating paper; The insulating paper obtained by this invention has high interfacial bonding strength, stable structure, and significantly improved mechanical properties and insulation.

Description

Technical Field

[0001] This invention relates to the field of insulating materials technology, specifically to a high-strength, high-insulation aramid insulating paper for electrical equipment, its preparation method, and its application. Background Technology

[0002] As power systems develop towards ultra-high voltage, large capacity, and intelligentization, key power equipment such as gas-insulated switchgear (GIS) and oil-immersed transformers place more stringent requirements on the comprehensive performance of insulation materials. Core components such as insulating rods, insulating cylinders, and the oil-paper insulation system of transformers need to withstand the combined effects of high electric fields, large mechanical stresses, and complex operating conditions over long periods of time during operation, and their reliability is directly related to the safe and stable operation of the power grid.

[0003] Currently, aramid fiber composite materials are widely used as insulating materials due to their excellent specific strength, heat resistance, and insulation properties. However, the highly crystalline and chemically inert surface of aramid fibers, along with poor uniformity, weak bonding, and easy detachment, make it difficult to meet the multiple requirements of electrical equipment for insulating materials with high strength, high insulation, and resistance to electrical aging. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a high-strength, high-insulation aramid insulating paper for electrical equipment, its preparation method, and its application.

[0005] The technical solution adopted in this invention is: a method for preparing high-strength, high-insulation aramid insulating paper for electrical equipment, comprising the following steps: Step 1: Aramid fibers are modified by plasma treatment. The modified aramid fibers are then impregnated in ZnO quantum dot seed solution and annealed to obtain aramid fiber A with ZnO nanowires on the surface. Step 2: Mix the aramid nanofiber spinning solution and the polyvinyl alcohol solution, and obtain composite nanofiber B by electrospinning; Step 3: Mix the fiber pulp suspension solution of aramid fiber A obtained in Step 1 and the fiber pulp suspension solution of composite nanofiber B obtained in Step 2, dehydrate and then cure at high temperature to obtain the desired insulating paper. The mass ratio of aramid fiber A to composite nanofiber B is 2 to 1:1.

[0006] Furthermore, in step 1, during the plasma treatment process, the voltage is 4–8 kV, the frequency is 20–40 kHz, and the treatment time is 1–5 min.

[0007] Furthermore, the ZnO quantum dot seed solution preparation process in step 1 is as follows: Equal volumes of NaOH ethanol solution and Zn(CH3COO)2·2H2O ethanol solution are mixed and stirred at 400–600 rpm for 30–45 min at 45–60℃ to obtain ZnO quantum dot seed solution. The molar ratio of NaOH to Zn(CH3COO)2·2H2O is 8:5.

[0008] Furthermore, in step 1, the modified aramid fiber is impregnated in ZnO quantum dot seed solution N times, where N≥2; Each soaking time is 15 to 30 minutes.

[0009] Furthermore, in step 1, the annealing and curing temperature is 120–150 °C, and the curing time is 15–20 min.

[0010] Furthermore, in step 2, the electrospinning voltage is 15–20 kV, the collection distance is 10–15 cm, and the receiving speed is 30–45 rpm.

[0011] Furthermore, the fiber pulp preparation process for aramid fiber A in step 3 is as follows: Aramid fiber A was immersed in an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 2-3×10 mol / L and a temperature of 45℃ for 2-3 h. After washing, it was vacuum dried. The slurry was homogenized and opened at a speed of 12000-15000 rpm for 20-30 min to obtain the fiber slurry of aramid fiber A. The preparation process of the fiber pulp of composite nanofiber B is as follows: Composite nanofiber B was vacuum dried for 2 h at a pressure of 0.2–0.5 MPa and a temperature of 45–60 °C; then homogenized and loosened at a speed of 12,000–15,000 rpm for 20–30 min to obtain the fiber pulp of composite nanofiber B.

[0012] Furthermore, in step 3, the dehydration pressure is 0.1–0.2 MPa and the temperature is 60–80 ℃; the high-temperature curing temperature is 100–120 ℃ and the pressure is 6–8 MPa.

[0013] A high-strength, high-insulation aramid insulating paper for use in electrical equipment.

[0014] An application of a high-strength, high-insulation aramid insulating paper for electrical equipment, wherein the insulating paper is used in the preparation of heat dissipation devices in electronic devices and electrical equipment.

[0015] The beneficial effects of this invention are: This invention modifies the surface of aramid fibers through plasma treatment, improving the surface morphology and chemical composition of the aramid fibers and enhancing interfacial interactions. Furthermore, an inorganic nanowire array is grown on the fiber surface, significantly improving interfacial strength and enhancing the insulation and mechanical properties of the polymer composite material. The mixing of micron-sized aramid fibers and aramid nanofibers can achieve self-reinforcement, improving the interfacial bonding strength and structural stability of the composite insulating paper. Attached Figure Description

[0016] Figure 1 This is a SEM image of the aramid fiber used in Example 1 of the present invention.

[0017] Figure 2 This is a cross-sectional SEM image of the composite insulating paper obtained in Example 1 of the present invention.

[0018] Figure 3 This is a tensile strength distribution diagram for embodiments and comparative examples of the present invention.

[0019] Figure 4 This is a breakdown strength distribution diagram for embodiments and comparative examples of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] A method for preparing high-strength, high-insulation aramid insulating paper for electrical equipment includes the following steps: Step 1: Aramid fibers are modified by plasma treatment. The modified aramid fibers are then impregnated in ZnO quantum dot seed solution and annealed to obtain aramid fiber A with ZnO nanowires on the surface. First, the aramid fibers were ultrasonically cleaned in acetone at a power of 400–500 W for 2–3 hours. Following ultrasonic cleaning, plasma treatment was performed under an argon atmosphere (99.99% purity) using a DBD (Digital Dioxide) device. The DBD device used 100 mm circular metal electrodes for both the high-voltage and grounding electrodes. The voltage was 4–8 kV, the frequency was 20–40 kHz, the argon flow rate was 1–5 L / min, and the DBD treatment time was 1–5 min. This plasma treatment introduced -COOH groups onto the surface of the aramid fibers, resulting in modified aramid fibers, namely AF-COOH.

[0022] ZnO quantum dot seed solution was synthesized using the sol-gel method. Modified aramid fibers were immersed in the ZnO quantum dot seed solution N times (N≥2), successfully growing ZnO nanowires onto the surface of the modified aramid fibers. Aramid fiber A, namely AF-COOH@ZnONW composite fiber, was then successfully grown. The specific process is as follows: A 20 mM NaOH ethanol solution and a 12.5 mM Zn(CH3COO)2·2H2O ethanol solution were mixed and stirred at 45–60 °C and 400–600 rpm for 30–45 min to obtain a ZnO quantum dot seed solution (the mass ratio of NaOH to Zn(CH3COO)2·2H2O was 1:2). Modified aramid fibers were impregnated in the ZnO quantum dot seed solution N times; each impregnation time was 15–30 min, followed by annealing and curing at 120–150 °C for 15–20 min.

[0023] Step 2: Mix the aramid nanofiber spinning solution and the polyvinyl alcohol solution, and obtain composite nanofibers (ANF / PVA)B by electrospinning; The preparation process of aramid nanofiber spinning solution is as follows: Aramid fibers were cut into small pieces less than 0.5 cm, and ultrasonically treated with acetone at a temperature of 20–30 °C for 14–28 days. The mixture was then mixed with KOH, DMSO and deionized water and stirred in the dark to obtain a dark red ANF / DMSO spinning solution.

[0024] A DMSO solution of polyvinyl alcohol was mixed with an ANF / DMSO spinning solution (the concentration of the spinning solution and the ratio of the two spinning solutions were adjusted according to the actual situation), and composite nanofibers B were obtained by electrospinning. The voltage during electrospinning was 15-20 kV, the distance of the syringe short collector was 10-15 cm, and the receiving speed was 30-45 rpm.

[0025] Step 3: Mix the fiber pulp suspension solution of aramid fiber A obtained in Step 1 and the fiber pulp suspension solution of composite nanofiber B obtained in Step 2, dehydrate and then cure at high temperature to obtain the desired insulating paper. The preparation process of aramid fiber A's fiber pulp is as follows: Aramid fiber A was immersed in an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 2-3×10 mol / L and a temperature of 45 ℃ for 2-3 h. After washing, it was vacuum dried. The slurry was homogenized and opened at a speed of 12000-15000 rpm for 20-30 min to obtain aramid fiber slurry A. The preparation process of the fiber pulp of composite nanofiber B is as follows: Composite nanofiber B was vacuum dried for 2 h at a pressure of 0.2–0.5 MPa and a temperature of 45–60 °C; then homogenized and loosened at a speed of 12,000–15,000 rpm for 20–30 min to obtain the fiber pulp of composite nanofiber B.

[0026] The concentrations of both the aramid fiber A and composite nanofiber B fiber pulp suspensions were 0.1 wt.%, with a mass ratio of aramid fiber A to composite nanofiber B of 2–1:1. After mixing the two fiber suspensions, dehydration was performed at a pressure of 0.1–0.2 MPa and a temperature of 60–80 °C. Then, hot-pressing curing was carried out at a temperature of 100–120 °C and a pressure of 6–8 MPa for 3 minutes to obtain the desired insulating paper.

[0027] Example 1 A method for preparing high-strength, high-insulation aramid insulating paper for electrical equipment includes the following steps: Step 1: Place the aramid fiber AF in acetone and ultrasonically clean it at 500 W for 3 h. After removal, rinse repeatedly with anhydrous ethanol and deionized water, and dry for later use. Place the cleaned aramid fiber in a quartz reactor and perform plasma treatment in an argon atmosphere (purity 99.99%). The high-voltage electrode and ground electrode of the DBD device are both circular metal electrodes with a diameter of 100 mm, the voltage is 4 kV, the frequency is 30 kHz, the internal height of the reactor is 8 mm, and the diameter is 120 mm. Treat at an argon flow rate of 1 L / min for 2 min to introduce a new oxygen-containing group (-COOH) to obtain AF-COOH.

[0028] Figure 1 This is a SEM image of the aramid fiber used in this invention.

[0029] A 20 mM NaOH / ethanol solution was prepared by dissolving 1 g of sodium hydroxide (NaOH) in 1000 ml of anhydrous ethanol. The solution was stirred vigorously at 500 rpm for 10 min at 50 °C and then cooled to obtain an alkaline solution. A 12.5 mM zinc acetate dihydrate (Zn(CH3COO)2·2H2O) / ethanol solution was prepared by dissolving 2 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) in 600 ml of anhydrous ethanol. The solution was stirred vigorously at 500 rpm for 10 min at 50 °C and then cooled to obtain a zinc salt solution.

[0030] Take 40 mL of 20 mM NaOH / ethanol solution and add it to 400 mL of ethanol. Take 40 mL of 12.5 mM zinc acetate / ethanol solution and add it to 100 mL of ethanol. Preheat both diluted solutions to 65 °C. Mix the two preheated solutions and stir vigorously at 500 rpm for 30 min at 65 °C. During this process, OH... - With Zn 2+ The reaction produces Zn(OH)2, which is immediately dehydrated to form ZnO crystal nuclei. By controlling the reaction conditions (concentration, temperature), a fine and uniform ZnO quantum dot colloidal suspension (i.e., seed solution) can be generated.

[0031] The cleaned AF-COOH was immersed in the ZnO seed solution for 15 min, and this step was repeated 3 times. After removal, it was annealed (cured) at 120 °C for 15 min. After removal, it was immersed in the ZnO seed solution again for 15 min, and then annealed (cured) at 150 °C for 15 min. The resulting composite fiber AF-COOH@ZnONW (i.e., aramid fiber A) with zinc oxide nanowires grown on the surface of aramid fiber was obtained.

[0032] Step 2: After cleaning, the aramid fibers were cut into small pieces less than 0.5 cm in size. Acetone was poured in until it covered the fiber surface, and the fibers were ultrasonically treated at 500 W for 24 h. After filtering the acetone, the fibers were dried in a vacuum oven at 45 ℃ and stored in a sealed container. The treated aramid fibers (3.2 g) and KOH (5 g) were weighed and added to a mixed solution of DMSO (600 mL) and deionized water (20 mL). The solution was stirred at 25 ℃ in the dark for 28 days to obtain a dark red ANF / DMSO spinning solution (1 wt%).

[0033] Weigh 2 g of PVA powder and add it to 50 ml of dimethyl sulfoxide (DMSO). Heat and stir at 60 ℃ and 500 rpm for 12 h to prepare a PVA / DMSO solution.

[0034] 30 g of ANF / DMSO spinning solution was mixed thoroughly with 5 g of PVA / DMSO solution and placed on an electrospinning syringe. The voltage during electrospinning was 20 kV. The short collector distance of the syringe was 12 cm, and the receiving speed was 40 rpm. Under the conditions of 25 ℃ and 25% humidity, ANF / PVA composite nanofibers (i.e., composite nanofiber B) were obtained.

[0035] Step 3: Pulp, filter and dry AF-COOH@ZnONW and ANF / PVA composite nanofibers respectively to obtain two types of fiber pulp; The pretreatment process for aramid staple fibers is as follows: AF-COOH@ZnONW is immersed in a solution with a concentration of 2×10⁻⁶. - The solution was immersed in an aqueous solution of sodium dodecylbenzenesulfonate at 3 mol / L and 45 °C for 3 h. After that, it was washed twice with deionized water and then dried in a vacuum drying oven at 90 °C for 3 h.

[0036] The pretreatment of ANF / PVA composite nanofibers was carried out in a vacuum drying oven under the conditions of 0.5 MPa pressure and 45 ℃ for 2 hours, followed by heating to 60 ℃ for another 2 hours.

[0037] After undergoing the aforementioned pretreatment, the two types of fibers were placed separately in homogenizers, deionized water was added, and homogenization and loosening were carried out at 15,000 rpm for 20 minutes. Subsequently, the homogenizers were further homogenized for 1 hour using water as the dispersion medium to obtain a homogeneous slurry. After filtration and drying, the slurries were used to prepare the corresponding fiber pulps.

[0038] AF-COOH@ZnONW was mixed with dispersant PEO and water, and dispersed under high-speed shear at 10,000 rpm for 3 min to form an AF-COOH@ZnONW fiber suspension with a solid content of 1 wt%.

[0039] ANF / PVA composite nanofibers were processed into a 0.1 wt% suspension by a refining machine at 1000 rpm until homogeneous.

[0040] Subsequently, the two suspensions were mixed and stirred to homogenize them at a mass ratio of 2:1 for AF-COOH@ZnONW and ANF / PVA composite nanofibers. After vacuum filtration and molding, the mixture was initially dehydrated and compacted under a pressure of 0.2 MPa and a temperature of 80 °C. Finally, it was hot-pressed at 120 °C and a pressure of 8 MPa for 3 minutes to solidify and obtain insulating paper.

[0041] Figure 2 This is a cross-sectional SEM image of the insulating paper obtained in this embodiment.

[0042] Example 2 The other steps in this embodiment are the same as in Embodiment 1, except that the argon flow rate is 2 L / min.

[0043] Example 3 The other steps in this embodiment are the same as in Embodiment 1, except that the argon flow rate is 3 L / min.

[0044] Example 4 The other steps in this embodiment are the same as in Embodiment 1, except that the argon flow rate is 4 L / min.

[0045] Example 5 The other steps in this embodiment are the same as in embodiment 2, except that the AF-COOH is immersed in the ZnO seed solution for 20 min.

[0046] Example 6 The other steps in this embodiment are the same as in embodiment 2, except that the AF-COOH is immersed in the ZnO seed solution for 25 minutes.

[0047] Example 7 The other steps in this embodiment are the same as in embodiment 2, except that the AF-COOH is immersed in the ZnO seed solution for 30 min.

[0048] Example 8 The other steps in this embodiment are the same as in Embodiment 5, except that the mass ratio of AF-COOH@ZnONW and ANF / PVA is 3:2. Example 9 The other steps in this embodiment are the same as in embodiment 5, except that the mass ratio of AF-COOH@ZnONW and ANF / PVA is 1:1.

[0049] Comparative Example 1 The other steps in this comparative example are the same as in Example 1, except that step 1 does not include the plasma treatment of aramid fiber AF.

[0050] Comparative Example 2 The other steps in this comparative example are the same as those in Comparative Example 1, except that the mass ratio of AF-COOH@ZnONW and ANF / PVA is 3:2.

[0051] Comparative Example 3 The other steps in this comparative example are the same as those in Comparative Example 1, except that the mass ratio of AF-COOH@ZnONW and ANF / PVA is 2:1.

[0052] Comparative Example 4 The other steps in this comparative example are the same as in Example 1, except that step 1 does not include the annealing and curing process after impregnating the modified aramid fibers in ZnO quantum dot seed solution.

[0053] Comparative Example 5 The other steps in this comparative example are the same as those in Comparative Example 4, except that the mass ratio of AF-COOH and ANF / PVA is 3:2.

[0054] Comparative Example 6 The other steps in this comparative example are the same as those in Comparative Example 4, except that the mass ratio of AF-COOH and ANF / PVA is 1:1.

[0055] Comparative Example 7 The other steps in this comparative example are the same as in Example 1, except that in step 2, aramid nanofiber spinning solution is used to obtain aramid nanofibers by electrospinning.

[0056] Comparative Example 8 The other steps in this comparative example are the same as those in Comparative Example 7, except that the mass ratio of AF-COOH@ZnONW to ANF is 3:2.

[0057] Comparative Example 9 The other steps in this comparative example are the same as those in Comparative Example 7, except that the mass ratio of AF-COOH@ZnONW and ANF is 1:1.

[0058] The performance of the insulating paper obtained in the embodiments and comparative examples of the present invention was tested, and the results are shown in Table 1.

[0059] Figure 3 This is a tensile strength distribution diagram of the embodiments and comparative examples of the present invention. Figure 4 This is a breakdown strength distribution diagram for embodiments and comparative examples of the present invention.

[0060] Table 1. Performance test results of insulating paper obtained in comparative examples and embodiments.

[0061] As can be seen from Table 1, the insulating paper obtained in the examples has significantly higher overall performance in terms of tensile strength and breakdown strength than the results obtained in the comparative examples.

[0062] The insulating paper obtained in the examples exhibits a tensile strength of up to 259.6 MPa, demonstrating excellent mechanical strength and fully meeting the long-term operational requirements of electrical equipment insulation components under high mechanical stress. In Comparative Examples 1-3, the AF, which was not treated with DBD plasma, showed significantly lower tensile strength and breakdown field strength compared to Example 9.

[0063] This is because the high-energy particles in DBD plasma etch the fiber surface, making it rougher and forming nanoscale grooves and protrusions, thereby significantly improving the mechanical interlocking and friction between the fiber and the ANF filler. Simultaneously, the ANF obtained through deprotonation exfoliation contains abundant active groups on its surface. As a self-reinforcing filler, its addition to the AF matrix significantly improves the interfacial bonding of the composite insulation paper, resulting in a tightly bonded composite insulation paper layer by layer and reduced internal defects. Plasma treatment can introduce active oxygen-containing polar groups (-COOH) onto the inert surface of aramid fibers, forming strong hydrogen bonds between the AF and ANF / PVA fillers, further enhancing the interfacial interaction improvement effect.

[0064] In Comparative Examples 4-6, the AF-COOH surface was not coated with zinc oxide nanowires (ZnONW). The tensile strength showed little change compared to the present invention, but the breakdown field strength was significantly reduced. This is because the nanowires effectively fill the micron / nanoscale gaps between fibers, making the overall structure of the composite material more compact and reducing air gaps or weak areas that can lead to partial discharge. Furthermore, the ZnO nanowires introduce numerous dangling bonds and defect energy levels at the fiber interface, creating deep traps and reducing carrier mobility, thereby improving the breakdown strength of the composite insulating paper.

Claims

1. A method for preparing high-strength, high-insulation aramid insulating paper for electrical equipment, characterized in that, Includes the following steps: Step 1: Aramid fibers are modified by plasma treatment. The modified aramid fibers are then impregnated in ZnO quantum dot seed solution and annealed to obtain aramid fiber A with ZnO nanowires on the surface. Step 2: Mix the aramid nanofiber spinning solution and the polyvinyl alcohol solution, and obtain composite nanofiber B by electrospinning; Step 3: Mix the fiber pulp suspension solution of aramid fiber A obtained in Step 1 and the fiber pulp suspension solution of composite nanofiber B obtained in Step 2, dehydrate and then cure at high temperature to obtain the desired insulating paper. The mass ratio of aramid fiber A to composite nanofiber B is 2 to 1:

1.

2. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, In step 1, during the plasma treatment process, the voltage is 4–8 kV, the frequency is 20–40 kHz, and the treatment time is 1–5 min.

3. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, The ZnO quantum dot seed solution preparation process in step 1 is as follows: Equal volumes of NaOH ethanol solution and Zn(CH3COO)2·2H2O ethanol solution are mixed and stirred at 400–600 rpm for 30–45 min at 45–60℃ to obtain ZnO quantum dot seed solution. The molar ratio of NaOH to Zn(CH3COO)2·2H2O is 8:

5.

4. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, In step 1, the modified aramid fiber is impregnated in ZnO quantum dot seed solution N times, where N≥2; Each soaking time is 15 to 30 minutes.

5. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, In step 1, the annealing and curing temperature is 120–150 °C, and the curing time is 15–20 min.

6. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, In step 2, the electrospinning voltage is 15–20 kV, the collection distance is 10–15 cm, and the receiving speed is 30–45 rpm.

7. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, The preparation process of aramid fiber A fiber pulp in step 3 is as follows: Aramid fiber A was immersed in an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 2-3×10 mol / L and a temperature of 45℃ for 2-3 h. After washing, it was vacuum dried. The slurry was homogenized and opened at a speed of 12000-15000 rpm for 20-30 min to obtain the fiber slurry of aramid fiber A. The preparation process of the fiber pulp of composite nanofiber B is as follows: Composite nanofiber B was vacuum dried for 2 h at a pressure of 0.2–0.5 MPa and a temperature of 45–60 °C; then homogenized and loosened at a speed of 12,000–15,000 rpm for 20–30 min to obtain the fiber pulp of composite nanofiber B.

8. The method for preparing a high-strength, high-insulation aramid insulating paper for electrical equipment according to claim 1, characterized in that, In step 3, the dehydration pressure is 0.1–0.2 MPa and the temperature is 60–80 ℃; the high-temperature curing temperature is 100–120 ℃ and the pressure is 6–8 MPa.

9. High-strength, high-insulation aramid insulating paper for electrical equipment obtained by any of the preparation methods described in claims 1 to 8.

10. The application of the high-strength, high-insulation aramid insulating paper for electrical equipment as described in claim 9, characterized in that, The insulating paper is used in the preparation of heat dissipation devices in electronic components and electrical equipment.

Images