Preparation method and application of composite insulation material based on recycling of waste dry type bushing

Abstract

This invention discloses a method for preparing composite insulation materials based on the reuse of waste dry bushings. The method includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushing to prepare micron-sized EP / crepe paper filler. The EP / crepe paper filler is then mixed with an epoxy resin matrix, wherein the mass percentage of the EP / crepe paper filler is 5-10%. The mixture is stirred in a constant-temperature oil bath at 100-110°C using a combination of mechanical and ultrasonic vibration to ensure uniform dispersion of the EP / crepe paper filler in the epoxy resin matrix. The mixture is then degassed under vacuum, poured into a mold, and cured using a stepped heating method to obtain the epoxy resin-based composite insulation material. This invention also discloses the application method of this epoxy resin-based composite insulation material, including its use in preparing basin-type insulators, giving new life to waste dry bushings and promoting the development of dry bushing insulation system recycling towards a more reliable and sustainable direction.

Description

Technical Field

[0001] This invention belongs to the field of waste insulation material recycling technology, and relates to the preparation method and application of composite insulation materials based on the recycling of waste dry bushings. Background Technology

[0002] Dry bushings are insulating bushings made of solid insulating materials (such as epoxy resin). Their main insulation is typically an epoxy resin-impregnated crepe paper capacitor core, and the outer insulation is usually a silicone rubber composite jacket, exhibiting excellent insulation performance. The application of epoxy-impregnated crepe paper in dry bushings is an important technological direction in the field of power equipment insulation. Due to its unique microporous and wrinkled structure, crepe paper provides ideal penetration space for epoxy resin impregnation. In the vacuum impregnation process, low-viscosity epoxy resin fully fills the pores of the crepe paper, forming a dense three-dimensional interpenetrating network structure after curing. This composite system not only significantly improves the dielectric strength and partial discharge suppression capability of the material but also endows the insulation layer with excellent mechanical toughness, enabling it to withstand mechanical vibration and thermal stress impact during equipment operation. Furthermore, the high cross-linking properties of epoxy resin enhance the heat resistance and anti-aging properties of the composite material, making it suitable for complex environments such as high altitudes and humidity. The excellent performance and widespread use have also led to an increase in dry bushing waste, making reasonable, green, and economical recycling a major problem that urgently needs to be solved.

[0003] Currently, the main methods for dealing with waste dry bushings are landfilling and incineration, which not only cause environmental pollution but also waste resources. Summary of the Invention

[0004] One objective of this invention is to provide a method for preparing composite insulation materials based on the reuse of waste dry bushings, which solves the problem that existing waste dry bushings can only be landfilled or incinerated and cannot be effectively reused.

[0005] Another object of the present invention is to provide a method for applying composite insulation materials based on the reuse of waste dry bushings.

[0006] One technical solution adopted in this invention is a method for preparing composite insulation materials based on the reuse of waste dry bushings. This method includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushing to prepare micron-sized EP / crepe paper filler. The EP / crepe paper filler is then mixed with an epoxy resin matrix, wherein the mass percentage of the EP / crepe paper filler is 5-10%. The mixture is stirred in a constant-temperature oil bath at 100-110℃ using a combination of mechanical and ultrasonic vibration to ensure uniform dispersion of the EP / crepe paper filler in the epoxy resin matrix. The mixture is then degassed under vacuum, poured into a mold, and cured using a stepped heating method to obtain the epoxy resin-based composite insulation material.

[0007] The epoxy-impregnated crepe paper insulation in waste dry bushings is peeled off and ground. This includes peeling and cutting the epoxy-impregnated crepe paper insulation in the waste dry bushings using a lathe, then mechanically crushing the waste material into particles with a diameter of 0.8 mm to 1.5 mm using a pulverizer. The prepared waste particles are placed in a ball mill, sealed under an argon atmosphere, ground, and then sieved to obtain micron-sized EP / crepe paper filler. The micron-sized EP / crepe paper filler is then dried at 100°C for 8 to 15 hours and then sealed and stored.

[0008] The prepared waste particles are placed in a ball mill. During the grinding process, the ball-to-material ratio is 50:1, the grinding beads are stainless steel grinding beads, the ball mill speed is 300-500 rpm, and the grinding time is 50-60 h. The particles are then sieved with a 150 mesh screen. The powder that does not pass through the screen is then put back into the ball mill for grinding.

[0009] The mixing process employs a combination of mechanical and ultrasonic vibration, with a mixer speed of 400–500 r / min and a mixing time of 1–1.5 h.

[0010] Vacuum degassing is performed using a vacuum pump for 0.4h to 0.6h. Before pouring into the mold, a release agent is applied to the inner cavity of the mold. After pouring into the mold, vacuum degassing is performed for 0.5h to 1.5h.

[0011] The drying oven is heated in stages, including first raising the temperature to 50-70℃ and holding it for 1.5-2.5 hours, then raising it to 80-100℃ and holding it for 0.5-1.5 hours, then raising it to 110-130℃ and holding it for 2-4 hours, then lowering it to 80-100℃ and holding it for 2-4 hours, and finally slowly cooling it to room temperature.

[0012] The epoxy resin matrix is ​​CT5531Cl bisphenol A type epoxy resin particles.

[0013] Another technical solution adopted in this invention is a method for using composite insulating materials based on the reuse of waste dry bushings. The composite insulating material prepared by the above preparation method is used to prepare basin insulators. The method includes crushing the composite insulating material and mixing it evenly with alumina powder, then adding an accelerator and a curing agent in sequence, stirring continuously for 20 to 40 minutes with a mechanical stirrer, finally degassing under vacuum, pouring it into a mold for casting basin insulators, heating and curing to form the shape, and obtaining the basin insulator after demolding.

[0014] The curing agent is HT903Cl carboxylic acid anhydride type curing agent. The mass ratio of the curing agent to the epoxy resin matrix in the composite insulation material is 0.85:1. The mass ratio of alumina powder to the epoxy resin matrix in the composite insulation material is 2.5:1. The amount of accelerator accounts for 5% of the mass of the epoxy resin matrix in the composite insulation material.

[0015] The beneficial effects of this invention are that by peeling and grinding the epoxy-impregnated crepe paper insulation portion of waste dry bushings, it is transformed into micron-sized EP / crepe paper filler, which is then combined with an epoxy resin matrix to form a composite insulation material. This composite insulation material exhibits a significant cross-sectional stress dissipation mechanism, effectively inhibiting crack propagation, and its tensile strength can reach 58 MPa. The orientation and arrangement of the crepe paper fibers, in synergy with the epoxy matrix, reduce the risk of localized field concentration. Furthermore, the secondary cross-linking reaction between the pre-cured epoxy particles and the matrix forms a dense interfacial network, which inhibits cracking through chemical bonding. The accumulation of interfacial charge delays the propagation of the breakdown path, resulting in a significantly higher breakdown field strength for this composite insulation material compared to pure epoxy resin. When this composite insulation material is used to prepare pot-type insulators, the mechanical and electrical properties of the prepared pot-type insulators are not significantly different from existing pot-type insulators, showing no deterioration. This method gives new life to discarded dry bushings, achieving a cascaded amplification of the wrinkle paper reinforcement effect and opening a new path for the high-performance development of epoxy resin composite materials. It has significant engineering value in promoting the recycling of dry bushing insulation systems towards a more reliable and sustainable direction. Attached Figure Description

[0016] Figure 1 This is a cross-sectional morphology diagram of pure epoxy resin. Figure 2 The cross-sectional morphology of the composite insulating material prepared in Comparative Example 1 is shown. Figure 3 The cross-sectional morphology of the composite insulating material prepared in Example 4 is shown. Figure 4 The cross-sectional morphology of the composite insulating material prepared in Example 5 is shown in the figure. Figure 5 The cross-sectional morphology of the composite insulating material prepared in Comparative Example 2 is shown. Figure 6 The cross-sectional morphology of the composite insulating material prepared in Comparative Example 3 is shown. Figure 7 Volume resistivity diagrams for composite insulation materials with different EP / crepe paper filler contents; Figure 8 Non-isothermal exothermic curves of composite insulation materials with different EP / crepe paper filler contents in DSC test; Figure 9 Glass transition temperature curves of composite insulation materials with different EP / crepe paper filler contents in DSC test; Figure 10A comparison chart of the dielectric constants of composite insulating materials with different EP / crepe paper filler contents; Figure 11 A comparison chart of dielectric losses for composite insulation materials with different EP / crepe paper filler contents; Figure 12 A comparison chart of the breakdown strength of composite insulation materials with different EP / crepe paper filler contents; Figure 13 Weibull probability distribution diagram for composite insulation materials with different EP / crepe paper filler contents; Figure 14 Figures showing the tensile strength and elongation at break of composite insulation materials with different EP / crepe paper filler contents. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushing; peeling and cutting the epoxy-impregnated crepe paper insulation portion of the waste dry bushing using a lathe; mechanically crushing the waste material into particles with a particle size of 0.8 mm to 1.5 mm using a pulverizer; placing the prepared waste material particles into a ball mill; sealing and grinding them under an argon atmosphere; and then sieving them to obtain micron-sized EP / crepe paper filler; drying the micron-sized EP / crepe paper filler at 100°C for 8 to 15 hours; and then sealing and storing it. Weigh out EP / crepe paper filler and epoxy resin matrix separately, and mix them together. The mass percentage of EP / crepe paper filler is 5-10%, and the epoxy resin matrix is ​​CT5531Cl bisphenol A type epoxy resin particles. Stir the mixture in a constant temperature oil bath at 100-110℃ using a combination of mechanical and ultrasonic vibration to ensure that the EP / crepe paper filler is uniformly dispersed in the epoxy resin matrix. Then, degas the mixture under vacuum, pour it into a mold, and cure it using a stepped heating method. Demolding the mixture yields the epoxy resin-based composite insulation material.

[0019] Example 2 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings; peeling and cutting the epoxy-impregnated crepe paper insulation portion of the waste dry bushings using a lathe; mechanically crushing the waste material into particles with a particle size of 0.8 mm to 1.5 mm using a pulverizer; placing the prepared waste material particles into a ball mill; sealing them under an argon atmosphere and then grinding them; the ball-to-material ratio during grinding is 50:1; the grinding balls are stainless steel grinding balls; the ball mill speed is 300 to 500 rpm; the grinding time is 50 to 60 hours; then the material is sieved to obtain micron-sized EP / crepe paper filler; the micron-sized EP / crepe paper filler is dried at 100°C for 8 to 15 hours; and then sealed and stored. Weigh out EP / crepe paper filler and epoxy resin matrix separately, and mix them together. The mass percentage of EP / crepe paper filler is 5-10%, and the epoxy resin matrix is ​​CT5531Cl bisphenol A type epoxy resin particles. Stir in a constant temperature oil bath at 100-110℃ using a combination of mechanical and ultrasonic vibration. The stirrer speed is 400-500 r / min, and the stirring time is 1-1.5h to ensure that the EP / crepe paper filler is uniformly dispersed in the epoxy resin matrix. Then, vacuum degassing is performed, and the mixture is poured into a mold and cured by step heating. Demolding yields the epoxy resin-based composite insulation material.

[0020] Example 3 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings; peeling and cutting the epoxy-impregnated crepe paper insulation portion of the waste dry bushings using a lathe; mechanically crushing the waste material into particles with a particle size of 0.8 mm to 1.5 mm using a pulverizer; placing the prepared waste material particles into a ball mill; sealing them under an argon atmosphere and then grinding them; the ball-to-material ratio during grinding is 50:1; the grinding balls are stainless steel grinding balls; the ball mill speed is 300 to 500 rpm; the grinding time is 50 to 60 hours; then the material is sieved to obtain micron-sized EP / crepe paper filler; the micron-sized EP / crepe paper filler is dried at 100°C for 8 to 15 hours; and then sealed and stored. Weigh out EP / crepe paper filler and epoxy resin matrix separately, and mix the EP / crepe paper filler with epoxy resin matrix, wherein the mass percentage of EP / crepe paper filler is 5-10%, and the epoxy resin matrix is ​​CT5531Cl bisphenol A type epoxy resin particles; stir in a constant temperature oil bath at 100-110℃ using a combination of mechanical and ultrasonic vibration, with a stirrer speed of 400-500 r / min and a stirring time of 1-1.5h, so that the EP / crepe paper filler is uniformly dispersed in the epoxy resin matrix. Then, vacuum degassing is performed using a vacuum pump for 0.4-0.6h. Pour into a mold coated with release agent and perform vacuum degassing treatment for 0.5-1.5h. The product is cured and molded using a stepped heating method. The temperature is raised in a drying oven, which includes first raising the temperature to 50-70°C and holding it for 1.5-2.5 hours, then raising it to 80-100°C and holding it for 0.5-1.5 hours, then raising it to 110-130°C and holding it for 2-4 hours, then lowering it to 80-100°C and holding it for 2-4 hours, and finally slowly cooling it to room temperature.

[0021] Example 4 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings. The epoxy-impregnated crepe paper insulation portion of the waste dry bushings is peeled and cut using a lathe. Then, the waste material is mechanically shredded into particles with a diameter of approximately 1 mm using a pulverizer. The prepared waste particles and stainless steel grinding balls are placed in a vacuum stainless steel ball mill jar and ground using a QM-3SP2 planetary ball mill at a ball-to-material ratio of 50:1. After sealing under an argon atmosphere, grinding is performed at a ball mill speed of 400 rpm, with the rotation direction reversed every half hour for 50 hours. The material is then sieved using a 150-mesh screen to obtain micron-sized EP / crepe paper filler. Waste material that does not pass through the screen is returned to the ball mill and ground together with the unground waste material until it reaches the micron level. The obtained micron-sized EP / crepe paper filler is dried at 100°C for 10 hours and then sealed for storage. EP / crepe paper filler and epoxy resin matrix were weighed separately and mixed together. The mass percentage of EP / crepe paper filler was 5%, and the epoxy resin matrix was CT5531Cl bisphenol A type epoxy resin particles. The mixture was stirred in a 100℃ constant temperature oil bath using a combination of mechanical and ultrasonic vibration at a speed of 400 r / min for 1 hour to ensure uniform dispersion of EP / crepe paper filler in the epoxy resin matrix. Then, vacuum degassing was performed using a vacuum pump for 0.6 hours. The mixture was then poured into a mold coated with a release agent for vacuum degassing treatment for 1 hour. The epoxy resin-based composite insulating material is cured and molded by step heating. The temperature is raised to 60°C and held for 2 hours in a drying oven. Then, the temperature is raised to 80°C and held for 1 hour. The temperature is raised to 120°C and held for 3 hours. Then, the temperature is lowered to 90°C and held for 3 hours. Finally, the temperature is slowly cooled to room temperature and demolded to obtain the epoxy resin-based composite insulating material.

[0022] Example 5 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings. The epoxy-impregnated crepe paper insulation portion of the waste dry bushings is peeled and cut using a lathe. Then, the waste material is mechanically shredded into particles with a diameter of approximately 0.8 mm using a pulverizer. The prepared waste particles and stainless steel grinding balls are placed in a vacuum stainless steel ball mill jar and ground using a QM-3SP2 planetary ball mill at a ball-to-material ratio of 50:1. After sealing under an argon atmosphere, grinding is performed at a ball mill speed of 350 rpm, with the rotation direction reversed every half hour for a total grinding time of 55 hours. The material is then sieved using a 150-mesh screen to obtain micron-sized EP / crepe paper filler. Larger particles on the screen can be ground again until they reach the micron level. The obtained micron-sized EP / crepe paper filler is dried at 100°C for 12 hours and then sealed for storage. EP / crepe paper filler and epoxy resin matrix were weighed separately and mixed together. The mass percentage of EP / crepe paper filler was 10%, and the epoxy resin matrix was CT5531Cl bisphenol A type epoxy resin particles. The mixture was stirred in a constant temperature oil bath at 110℃ using a combination of mechanical and ultrasonic vibration at a speed of 500 r / min for 1.5 h to ensure uniform dispersion of EP / crepe paper filler in epoxy resin matrix. Then, vacuum degassing was performed using a vacuum pump for 0.5 h. The mixture was then poured into a mold coated with release agent for vacuum degassing treatment for 1 h. The epoxy resin-based composite insulation material is cured and molded by step heating. The temperature is first raised to 50°C and held for 1.5 hours in a drying oven, then raised to 80°C and held for 1.5 hours, then raised to 110°C and held for 2 hours, then lowered to 80°C and held for 2 hours, and finally slowly cooled to room temperature. After demolding, the epoxy resin-based composite insulation material is obtained.

[0023] Example 6 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings. The epoxy-impregnated crepe paper insulation portion of the waste dry bushings is peeled and cut using a lathe. Then, the waste material is mechanically shredded into particles with a particle size of approximately 1.2 mm using a pulverizer. The prepared waste particles and stainless steel grinding balls are placed in a vacuum stainless steel ball mill jar and ground using a QM-3SP2 planetary ball mill at a ball-to-material ratio of 50:1. After sealing under an argon atmosphere, grinding is performed at a ball mill speed of 450 rpm, with the rotation direction reversed every half hour for 6 hours. The material is then sieved using a 150-mesh screen to obtain micron-sized EP / crepe paper filler. Larger particles on the screen can be ground again until they reach the micron level. The obtained micron-sized EP / crepe paper filler is dried at 100°C for 12 hours and then sealed for storage. EP / crepe paper filler and epoxy resin matrix were weighed separately and mixed together. The mass percentage of EP / crepe paper filler was 8%, and the epoxy resin matrix was CT5531Cl bisphenol A type epoxy resin particles. The mixture was stirred in a constant temperature oil bath at 110℃ using a combination of mechanical and ultrasonic vibration at a speed of 1100 r / min for 3 hours to ensure uniform dispersion of EP / crepe paper filler in epoxy resin matrix. Then, vacuum degassing was performed using a vacuum pump for 0.5 hours. The mixture was then poured into a mold coated with release agent for vacuum degassing treatment for 1 hour. The epoxy resin-based composite insulation material is cured and molded by step heating. The temperature is raised to 70°C and held for 2.5 hours in a drying oven. Then, the temperature is raised to 100°C and held for 0.5 hours. The temperature is raised to 130°C and held for 4 hours. Then, the temperature is lowered to 100°C and held for 4 hours. Finally, the temperature is slowly cooled to room temperature and demolded to obtain the epoxy resin-based composite insulation material.

[0024] Example 7 The composite insulating material prepared in Example 5 was used to prepare the basin insulator. The process included crushing the composite insulating material and mixing it evenly with alumina powder, then adding an accelerator and a curing agent in sequence, stirring continuously for 20 to 40 minutes with a mechanical stirrer, and finally degassing under vacuum. The mixture was then poured into a mold for casting basin insulators, heated and cured, and the basin insulator was obtained after demolding.

[0025] The curing agent is HT903Cl carboxylic acid anhydride type curing agent. The mass ratio of the curing agent to the epoxy resin matrix in the composite insulation material is 0.85:1. The mass ratio of alumina powder to the epoxy resin matrix in the composite insulation material is 2.5:1. The amount of accelerator accounts for 5% of the mass of the epoxy resin matrix in the composite insulation material.

[0026] Comparative Example 1 A method for preparing composite insulation material based on the reuse of waste dry bushings includes peeling and grinding the epoxy-impregnated crepe paper insulation portion of the waste dry bushings. The epoxy-impregnated crepe paper insulation portion of the waste dry bushings is peeled and cut using a lathe. Then, the waste material is mechanically shredded into particles with a diameter of approximately 1 mm using a pulverizer. The prepared waste particles and stainless steel grinding balls are placed in a vacuum stainless steel ball mill jar and ground using a QM-3SP2 planetary ball mill at a ball-to-material ratio of 50:1. After sealing under an argon atmosphere, grinding is performed at a ball mill speed of 400 rpm, with the rotation direction reversed every half hour for 5 hours. The material is then sieved using a 150-mesh screen to obtain micron-sized EP / crepe paper filler. Larger particles on the screen can be ground again until they reach the micron level. The obtained micron-sized EP / crepe paper filler is dried at 100°C for 10 hours and then sealed for storage. EP / crepe paper filler and epoxy resin matrix were weighed separately and mixed together. The mass percentage of EP / crepe paper filler was 1%, and the epoxy resin matrix was CT5531Cl bisphenol A type epoxy resin particles. The mixture was stirred in a 100℃ constant temperature oil bath using a combination of mechanical and ultrasonic vibration at a speed of 1200 r / min for 1 hour to ensure uniform dispersion of EP / crepe paper filler in epoxy resin matrix. Then, vacuum degassing was performed using a vacuum pump for 0.6 hours. The mixture was then poured into a mold coated with release agent for vacuum degassing treatment for 1 hour. The epoxy resin-based composite insulating material is cured and molded by step heating. The temperature is raised to 60°C and held for 2 hours in a drying oven. Then, the temperature is raised to 80°C and held for 1 hour. The temperature is raised to 120°C and held for 3 hours. Then, the temperature is raised to 140°C and held for 3 hours. Finally, it is slowly cooled to room temperature and demolded to obtain the epoxy resin-based composite insulating material.

[0027] Comparative Example 2 A method for preparing composite insulation material based on the reuse of waste dry bushings, except that the mass percentage of EP / cream paper filler in the composite insulation material is 15%, the other processes are the same as those in Comparative Example 1.

[0028] Comparative Example 3 A method for preparing composite insulation material based on the reuse of waste dry bushings, except that the mass percentage of EP / cream paper filler in the composite insulation material is 20%, the other processes are the same as those in Comparative Example 1.

[0029] The morphology of epoxy resin-based composite insulating materials prepared by pure epoxy resin, Comparative Example 1 (EP / crepe paper filler content 1%), Comparative Example 2 (EP / crepe paper filler content 15%), Comparative Example 3 (EP / crepe paper filler content 20%), Example 4 (EP / crepe paper filler content 5%), and Example 5 (EP / crepe paper filler content 10%) was observed using a Hitachi Regulus SU8230 scanning electron microscope (SEM). The cross-sectional morphology is shown in the figure. Figure 1-6 As shown, Figure 1 This is a cross-sectional morphology diagram of pure epoxy resin. Figure 2 This is a cross-sectional morphology diagram of the epoxy resin-based composite insulating material prepared in Comparative Example 1. Figure 3 This is a cross-sectional morphology diagram of the epoxy resin-based composite insulating material prepared in Example 4. Figure 4 This is a cross-sectional morphology diagram of the epoxy resin-based composite insulating material prepared in Example 5. Figure 5 This is a cross-sectional morphology diagram of the epoxy resin-based composite insulating material prepared in Comparative Example 2. Figure 6 The image shows the cross-sectional morphology of the epoxy resin-based composite insulating material prepared in Comparative Example 3. Figures 1-6 It can be seen that with low doping of EP / crepe paper filler, the filler is uniformly dispersed in the epoxy resin matrix, forming limited stress concentration points. The crack propagation path is relatively straight, exhibiting typical brittle fracture characteristics. Notably, with the increase of crepe paper / epoxy composite particle doping, the cross-sectional morphology of the material changes further when the EP / crepe paper filler content reaches 5%, exhibiting a morphology containing multiple characteristic regions interspersed. Affected by the change in doping amount, the material's cross-sectional morphology gradually changes from typical brittle fracture to quasi-cleavage fracture, exhibiting typical cleavage facets, dimples, and tear ridges. This is because the increased filler density promotes cross-linking between the filler and the matrix, forming multi-scale interfaces. These interfaces become preferential sites for crack initiation and deflection, promoting energy dissipation and manifesting as a quasi-cleavage fracture morphology. Crepe paper itself has micron-scale wrinkles and nano-scale fiber networks. The crepe paper / epoxy particles form a multi-level reinforcing structure in the matrix. During fracture, the synergistic failure of structures at different scales leads to morphological diversity. Further increases in doping concentration lead to filler agglomeration, which is more pronounced in the cross-sectional morphology of the material when the EP / crepe paper filler content reaches 20%. This morphological characteristic is detrimental to the improvement of the composite material's mechanical properties and may negatively impact its overall performance. Therefore, controlling the EP / crepe paper filler content to 5–10% results in a more pronounced stress dissipation mechanism in the prepared epoxy resin-based composite insulation material, which inhibits or alters crack development, thus better optimizing mechanical properties.

[0030] The volume resistivity of epoxy resin-based composite insulating materials prepared with pure epoxy resin, Comparative Example 1 (EP / crepe paper filler content 1%), Comparative Example 2 (EP / crepe paper filler content 15%), Comparative Example 3 (EP / crepe paper filler content 20%), and Examples 4 (EP / crepe paper filler content 5%) and 5 (EP / crepe paper filler content 10%) was tested at a voltage level of 500V using a Keithley 6517B electrometer / high resistance meter. The test results are as follows: Figure 7 As shown in the figure, the volume resistivity of the composite insulation material decreases with increasing EP / crepe paper filler doping content. However, at low doping levels, its DC volume resistivity is significantly higher than that of pure epoxy resin. The decrease in volume resistivity due to gradually increasing doping content is attributed to two main factors. Firstly, the hygroscopicity of the filler leads to deterioration of insulation performance. Since crepe paper is mainly composed of fiber, it has natural hydrophilicity and easily absorbs moisture from the environment. As the filler content increases, the moisture absorption of the composite material increases significantly. Ions in the moisture form conductive channels, causing the volume resistivity to decrease from 3.21 × 10⁻⁶. 16 Ω·cm decreased to 0.88×10 16 On the other hand, due to the influence of filler doping content, when the filler is highly doped, the interface between the ground crepe paper particles and the epoxy resin matrix is ​​not sufficiently bonded, forming micron-sized gaps or pores. These defects become areas of concentrated electric field, inducing local leakage current and reducing overall insulation performance. The crepe paper also forms a continuous network through physical contact. Although the fibers themselves are not conductive, impurity ions or moisture adsorbed on their surface can establish conductive paths between the fibers, significantly reducing the volume resistivity.

[0031] The epoxy resin-based composite insulation materials prepared in Example 4 (EP / crepe paper filler content 5%), Example 5 (EP / crepe paper filler content 10%), Comparative Example 1 (EP / crepe paper filler content 1%), Comparative Example 2 (EP / crepe paper filler content 15%), and Comparative Example 3 (EP / crepe paper filler content 20%) were tested using a DZ-DSC300 differential scanning calorimeter manufactured by Nanjing Dazhan Testing Instruments Co., Ltd. The test results are as follows: Figure 8 and Figure 9As shown in the figure, Z represents the EP / crepe paper filler content. It can be seen from the figure that as the EP / crepe paper filler content in the composite insulation material increases, the Tg value (glass transition temperature) of the material first decreases and then increases. Since the cured epoxy resin is crystalline while the insulating paper is amorphous, the insulating paper does not have a significant impact on the glass transition temperature. Therefore, the cured epoxy resin powder in the EP / crepe paper filler is the main reason affecting the change in the Tg value of the composite material. The addition of cured epoxy resin powder, through the competition mechanism between the free volume effect and the secondary cross-linking at the interface, leads to a non-monotonic change in the Tg value of the prepared composite insulation material, which first decreases and then increases.

[0032] The dielectric spectra of the epoxy resin-based composite insulating materials prepared in Examples 4 (EP / cream paper filler content 5%), 5 (EP / cream paper filler content 10%), and Comparative Examples 1 (EP / cream paper filler content 1%), 2 (EP / cream paper filler content 15%), and 3 (EP / cream paper filler content 20%) were measured using a Concept 80 broadband dielectric spectrometer from Novocontrol, Germany. The measurement results are as follows: Figures 10-11 As shown in the figures, Z represents the EP / crepe paper filler content. These two figures demonstrate that as the EP / crepe paper filler doping content increases, the dielectric constant first increases and then decreases. This is because at low doping levels, the filler is uniformly dispersed in the matrix, forming numerous crepe paper-epoxy interfaces. Under low-frequency electric fields, interfacial polarization dominates, significantly enhancing charge accumulation at the interfaces, leading to an increase in dielectric constant with increasing content. With increasing filler doping content, the filler dispersion reaches its optimal state at 10% EP / crepe paper filler content, maximizing the interfacial polarization effect and achieving a peak dielectric constant. However, with excessive filler, insufficient contact between a large number of fibers and the resin matrix reduces the contribution of interfacial polarization. Furthermore, as the frequency increases, the overall dielectric constant of the material decreases. This is because at high frequencies, the rate of change of the electric field exceeds the interfacial polarization relaxation time, preventing the interfacial charge from following the electric field change and suppressing the polarization contribution. At this point, only dipole polarization and electronic polarization remain effective, contributing relatively little and resulting in an overall decrease in dielectric constant. Figure 11 It can be observed that at high frequencies, the dielectric loss curves of composite insulating materials with different EP / crepe paper filler doping contents coincide, indicating that the dielectric loss is independent of the doping amount. This is because at high frequencies, interfacial polarization is suppressed, and the loss is mainly contributed by the movement of resin molecular chain segments. Due to the low dipole activity of crepe paper itself, its content variation has a limited impact on high-frequency loss. Compared with pure epoxy resin, the increase in dielectric constant and loss tangent observed in epoxy resin / crepe paper composites is a result of interfacial polarization. Therefore, at low frequencies, the interfacial polarization intensity is the highest in the Z-10% content system, and the reciprocating migration of charges at the interface induces Joule heating, leading to an increase in dielectric loss.

[0033] AC breakdown tests were conducted on epoxy resin-based composite insulating materials prepared from pure epoxy resin, Comparative Example 1 (EP / crepe paper filler content 1%), Comparative Example 2 (EP / crepe paper filler content 15%), Comparative Example 3 (EP / crepe paper filler content 20%), Example 4 (EP / crepe paper filler content 5%), and Example 5 (EP / crepe paper filler content 10%). The temperature was room temperature, the upper limit of voltage was 40kV, the upper limit of current was 40mA, and the voltage rise rate was 0.5 kV / s. The test results are as follows: Figure 12 and 13 As shown in the figure, Z represents the EP / crepe paper filler content. It is evident from the figure that the breakdown field strength of all composite insulation materials containing EP / crepe paper filler is significantly higher than that of pure epoxy resin. When the EP / crepe paper filler content further increases, the composite insulation material with an EP / crepe paper filler content of 20% reaches its peak breakdown strength, increasing from 41.10 kV / mm at 1% EP / crepe paper filler content to 43.08 kV / mm. This phenomenon can be attributed to the synergistic effect of the crepe paper fiber orientation and epoxy matrix, which further reduces the risk of local field strength concentration. Furthermore, the secondary cross-linking reaction between the pre-cured epoxy particles and the matrix forms a dense interfacial network, which inhibits interfacial charge accumulation through chemical bonding, thus delaying the propagation of the breakdown path.

[0034] Tensile strength tests were conducted on epoxy resin-based composite insulating materials prepared from pure epoxy resin, Comparative Example 1 (EP / crepe paper filler content 1%), Comparative Example 2 (EP / crepe paper filler content 15%), Comparative Example 3 (EP / crepe paper filler content 20%), Example 4 (EP / crepe paper filler content 5%), and Example 5 (EP / crepe paper filler content 10%). The test results are as follows: Figure 14As shown in the figure, the tensile strength of the material initially increases and then decreases with increasing EP / crepe paper filler content. At a filler content of 5%, the tensile strength reaches its maximum value of 58 MPa, a 16% improvement compared to pure epoxy resin. A small amount of filler, evenly dispersed in the matrix, effectively transfers stress through mechanical interlocking or chemical bonding, inhibiting matrix deformation and thus improving strength. When the filler content increases to 15%, the tensile strength deteriorates, but remains superior to pure EP, maintaining a high strength. At this point, filler dispersion may decrease, and local agglomeration leads to stress concentration, weakening the reinforcing effect. This is consistent with the results shown by SEM, where the morphology changes from brittle to quasi-cleavage and then to interface-dominated failure with increasing filler content. The bonded layer formed by the filler and matrix has mechanical properties intermediate between those of the filler and matrix, further regulating the crack propagation mode. When the filler content further increases to 20%, the tensile strength may decrease significantly. Excessive filler leads to the disruption of matrix continuity, an increase in interface defects, and cracks that are prone to propagate in the filler agglomeration zone.

[0035] Mechanical and electrical performance tests were conducted on the basin-type insulator prepared in Example 7. Compared with existing basin-type insulators, there was no deterioration, indicating that the method for preparing composite insulation materials based on the reuse of waste dry bushings and its application method proposed in this invention are feasible.

[0036] my country requires the field of solid waste resource utilization in the power industry to maintain an average annual growth rate of 15% to 20%. As a core component of GIS, the annual demand for basin insulators is about 500,000 to 800,000 units, corresponding to a market size of 800 million to 1.2 billion yuan. This invention uses the epoxy-impregnated corrugated paper insulation part of waste dry bushings to prepare basin insulators, which has significant implications for the recycling and reuse of waste dry bushings.

Claims

1. A method for preparing composite insulating materials based on the reuse of waste dry bushings, characterized in that, The process involves peeling and grinding the epoxy-impregnated crepe paper insulation from waste dry bushings to prepare micron-sized EP / crepe paper filler. The EP / crepe paper filler is then mixed with an epoxy resin matrix, with the EP / crepe paper filler accounting for 5-10% of the total mass. The mixture is stirred in a constant-temperature oil bath at 100-110℃ using a combination of mechanical and ultrasonic vibration to ensure uniform dispersion of the EP / crepe paper filler in the epoxy resin matrix. After vacuum degassing, the mixture is poured into a mold and cured using a stepped heating method to obtain an epoxy resin-based composite insulation material.

2. The method for preparing composite insulating material based on the reuse of waste dry bushings according to claim 1, characterized in that, The epoxy-impregnated crepe paper insulation portion of the waste dry bushing is peeled off and ground. This includes peeling and cutting the epoxy-impregnated crepe paper insulation portion of the waste dry bushing using a lathe, then mechanically crushing the waste material into particles with a particle size of 0.8mm to 1.5mm using a pulverizer. The prepared waste particles are placed in a ball mill, sealed under an argon atmosphere, ground, and then sieved to obtain micron-sized EP / crepe paper filler. The micron-sized EP / crepe paper filler is then dried at 100°C for 8 to 15 hours and then sealed and stored.

3. The method for preparing composite insulation material based on the reuse of waste dry bushings according to claim 2, characterized in that, The prepared waste particles are placed in a ball mill. During the grinding process, the ball-to-material ratio is 50:1, the grinding beads are stainless steel grinding beads, the ball mill speed is 300-500 rpm, and the grinding time is 50-60 h. The particles are then sieved with a 150 mesh screen. The powder that does not pass through the screen is then put back into the ball mill for grinding.

4. The method for preparing composite insulating material based on the reuse of waste dry bushings according to claim 1, characterized in that, The mixing process employs a combination of mechanical and ultrasonic vibration, with a mixer speed of 400–500 r / min and a mixing time of 1–1.5 h.

5. The method for preparing composite insulation material based on the reuse of waste dry bushings according to claim 1, characterized in that, Vacuum degassing is performed using a vacuum pump for 0.4h to 0.6h. Before pouring into the mold, a release agent is applied to the inner cavity of the mold. After pouring into the mold, vacuum degassing is performed for 0.5h to 1.5h.

6. The method for preparing composite insulating material based on the reuse of waste dry bushings according to claim 1, characterized in that, The drying oven is heated in stages, including first raising the temperature to 50-70℃ and holding it for 1.5-2.5 hours, then raising it to 80-100℃ and holding it for 0.5-1.5 hours, then raising it to 110-130℃ and holding it for 2-4 hours, then lowering it to 80-100℃ and holding it for 2-4 hours, and finally slowly cooling it to room temperature.

7. The method for preparing composite insulating material based on the reuse of waste dry bushings according to claim 1, characterized in that, The epoxy resin matrix is ​​CT5531Cl bisphenol A type epoxy resin particles.

8. A method for applying composite insulation materials based on the reuse of waste dry bushings, characterized in that, The composite insulating material prepared by any of the preparation methods described in claims 1-7 is used to prepare a basin-type insulator, which includes crushing the composite insulating material and mixing it evenly with alumina powder, then adding an accelerator and a curing agent in sequence, continuing to stir with a mechanical stirrer for 20 min to 40 min, finally degassing under vacuum, pouring it into a mold for casting basin-type insulators, heating and curing to form the shape, and obtaining the basin-type insulator after demolding.

9. The application method of composite insulation material based on the reuse of waste dry bushings according to claim 8, characterized in that, The curing agent is HT903Cl carboxylic acid anhydride type curing agent. The mass ratio of the curing agent to the epoxy resin matrix in the composite insulation material is 0.85:

1. The mass ratio of alumina powder to the epoxy resin matrix in the composite insulation material is 2.5:

1. The amount of accelerator accounts for 5% of the mass of the epoxy resin matrix in the composite insulation material.

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