A method for preparing a super-high voltage electric line foam-filled fiber reinforced epoxy resin insulating rod

Abstract

The application relates to the field of high-voltage electric line equipment and discloses a preparation method of an ultrahigh-voltage electric line foam-filled fiber-reinforced epoxy resin insulating rod, which comprises the following steps: (1) activating aramid fibers to prepare activated aramid fibers, and treating the activated aramid fibers with a waterproof agent to prepare hydrophobic aramid fibers; (2) treating the hydrophobic aramid fibers through three-dimensional weaving to prepare a preformed body, wherein the three-dimensional weaving mode comprises the following steps: two-dimensional weaving of the fibers with a mold surface as a base, and pultrusion winding of the fibers on the mold surface with a mold central axis as an axis; and (3) immersing the preformed body in an epoxy resin curing system, and curing after complete immersion to prepare the ultrahigh-voltage electric line foam-filled fiber-reinforced epoxy resin insulating rod; the raw materials of the method are aramid fibers and epoxy resin, the process comprises fiber surface modification, three-dimensional weaving and vacuum impregnation curing, the method has simple process and low cost, and the prepared product is light in weight and has significantly improved mechanical performance.

Description

Technical Field

[0001] This invention relates to the field of high-voltage power line equipment, and in particular to a method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high-voltage power lines. Background Technology

[0002] Insulating operating rods are essential operating equipment in the maintenance of ultra-high voltage transmission lines. They consist of a working head, an insulating rod, and a handle. The insulating rod connects the working head and the handle. The raw materials of the insulating rod are mainly resin systems or fiber-filled resin systems. The resin system provides electrical insulation properties for the insulating rod, and reinforcing fibers are added to the resin system to increase the mechanical properties of the insulating rod.

[0003] Currently, domestic insulating rod products commonly use glass fiber epoxy resin systems, which generally suffer from large rod thickness and heavy weight. Furthermore, the fiber layup structure has not been designed or explored; to meet performance requirements, the number of fiber layers is usually increased, resulting in a significant weight. Since insulating rods are typically used in high-altitude environments, the heavy weight of these rods reduces user convenience during prolonged operation, severely impacting work efficiency. Internationally, insulating rods are often manufactured using in-line weaving or vacuum impregnation methods, such as the insulating rods from Hastings in the United States. These rods feature a pull-out triangular shape, preventing twisting at the joints when extended and offering good stability. The fibers are laid up using various methods, including radial, circumferential, and cross-winding. However, the manufacturing process for these insulating rods is currently more complex and costly.

[0004] Currently, the transmission voltage of high-voltage power lines has increased to 500KV, and the performance of existing insulating rod products can no longer meet the needs of operation. Therefore, there is an urgent need to provide a lightweight, high-strength, foam-filled, fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines that is simple to manufacture, low in cost, and has low cost. Summary of the Invention

[0005] To overcome the problems of complex manufacturing processes, high costs, heavy weight, and low mechanical strength in existing ultra-high voltage power line insulation rods, this application provides a method for preparing foam-filled fiber-reinforced epoxy resin insulation rods for ultra-high voltage power lines. This method includes fiber waterproofing modification treatment, three-dimensional fiber weaving treatment, and vacuum curing process. The method uses aramid fiber and epoxy resin curing system as raw materials, and prepares foam-filled fiber-reinforced epoxy resin insulation rods for ultra-high voltage power lines through three-dimensional weaving and vacuum curing processes. This process is simple and low-cost, and the resulting product is lightweight and has strong mechanical properties.

[0006] The specific technical solution of this invention is as follows:

[0007] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0008] (1) Activated aramid fiber is produced by activating aramid fiber, and water-repellent aramid fiber is produced by treating activated aramid fiber with a waterproofing agent.

[0009] (2) The hydrophobic aramid fiber is three-dimensionally woven to form a preform. The three-dimensional weaving method includes: the fiber is woven in two dimensions with the mold surface as the base, and the fiber is pultruded and wound around the mold surface with the central axis of the mold as the axis.

[0010] (3) The preform is impregnated in an epoxy resin curing system and cured after complete impregnation to form an ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod.

[0011] This application provides a method for preparing foam-filled fiber-reinforced epoxy resin insulating rods for ultra-high voltage power lines. The method uses aramid fiber and epoxy resin curing system as raw materials, and prepares the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rods through a three-step process of aramid fiber surface modification, aramid fiber three-dimensional weaving, and preform vacuum impregnation and curing. The process is simple, low-cost, and the resulting product is lightweight and has significantly improved mechanical properties. Compared with other similar fibers, the aramid fiber used in this application has the characteristics of high heat resistance, high elastic modulus (95-125GPa), light weight, and strong structure. When used as a fiber reinforcement, it significantly reduces the overall weight of the product. This application also modifies the surface of the aramid fiber. During the production process, the surface of the aramid fiber contains a lot of coupling agent silane polar groups, which are easy to absorb water and moisture. After being combined with the resin system, it will significantly reduce the insulation and mechanical properties of the product. Therefore, this application first activates the aramid fiber to destroy the surface layer of the aramid fiber, and then chemically grafts the surface layer of the aramid fiber with a waterproofing agent to produce hydrophobic aramid fiber, so that the aramid fiber can have waterproof properties and prevent it from absorbing water and reducing the insulation of the product.

[0012] The fiber weaving in this application employs a special three-dimensional weaving technology. This technology involves two-dimensional weaving on the mold surface while simultaneously winding and pultruding the fibers. This method can complete the weaving-winding-pultrusion process simultaneously, simplifying the process. The fibers formed by three-dimensional weaving can provide structural support in the three-dimensional direction of the insulating rod, significantly improving its mechanical properties. Furthermore, this application has designed the weaving method, pultrusion speed, weaving angle, and winding angle in the weaving process. Aramid fibers have a high elastic modulus and will deform during three-dimensional weaving. Therefore, the weaving angle, winding angle, and pultrusion speed after weaving all have a significant impact on the structure of the final preform. After molding, the fibers exert axial pressure on the preform. If the pressure is too high, the final preform will be deformed; if the pressure is insufficient, the fibers will not be able to exert their reinforcing effect after the preform is formed into an insulating rod.

[0013] The vacuum impregnation and curing process described in this application involves placing a preform in an impregnation mold. One end of the mold is connected to a container filled with epoxy resin, and the other end is connected to a negative pressure device. During vacuum impregnation, the negative pressure device is activated, extracting air from the mold. Under the negative pressure, the mold encapsulates the preform, while simultaneously, the epoxy resin cured body at the other end of the mold enters the mold and immerses the preform under the negative pressure. Under the vacuum negative pressure, the epoxy resin penetrates into the fiber gaps of the preform, resulting in a dense overall structure of the preform fibers and epoxy resin, preventing defects such as bubbles. After impregnation, the impregnated preform is cured. This application optimizes different epoxy resin curing systems and curing conditions to ensure that the insulation performance of the epoxy resin system meets the requirements for ultra-high voltage transmission lines.

[0014] Preferably, the waterproofing agent mentioned in step (1) is selected from one or more of PEG, MSE100, IC701, PRTV, DS-02, and CSS; the waterproofing agent used in this application is an organosilicon waterproofing agent. This type of product can form a -Si-O hydrophobic film on the surface of aramid fibers, which significantly improves the waterproof performance of the aramid fiber surface. At the same time, it also improves the interfacial compatibility between aramid fibers and epoxy resin curing system, which can significantly improve the bonding degree between aramid fibers and epoxy resin, and significantly improve the mechanical properties of the product; in addition, organosilicon waterproofing agents are environmentally friendly, non-toxic, and harmless.

[0015] Preferably, the activation treatment step is as follows: immersing the aramid fiber in methanesulfonic acid, and then rinsing it with distilled water after immersion. The methanesulfonic acid content is 60%, and the immersion time is 30 hours. In this application, the activation treatment of the aramid fiber uses methanesulfonic acid. Aramid fibers can be activated in acid solutions, but strong oxidizing acid solutions can damage the internal core layer of the aramid fiber, which will significantly reduce the mechanical properties of the aramid fiber. Therefore, this application uses methanesulfonic acid, a strong protic acid with low oxidizing power, to treat the aramid fiber. After treatment with methanesulfonic acid, the surface layer of the aramid fiber is activated, while the internal core layer structure is not damaged. At the same time, the mechanical properties of the aramid fiber are not significantly reduced.

[0016] Preferably, the two-dimensional weaving in step (1) is selected from three-dimensional four-way weaving and three-dimensional five-way weaving.

[0017] Preferably, the weaving mold in step (1) has a diameter of 30 mm and a length of 500 mm, and the weaving mold is provided with a release agent.

[0018] Preferably, the pultrusion speed in step (1) is 200-400 mm / min.

[0019] Preferably, the weaving angle of the three-dimensional weaving in step (1) is 40-60°, and the winding angle of the winding is 40-50°.

[0020] Preferably, the epoxy resin curing system comprises, by weight, 100 parts epoxy resin, 80-90 parts curing agent, and 0.5 parts accelerator.

[0021] Preferably, the immersion conditions in step (3) are: temperature 60°C, vacuum.

[0022] Preferably, the curing conditions in step (3) are: curing temperature 90-130℃, curing time 1-4h, and vacuum.

[0023] Compared with the prior art, this application has the following technical effects:

[0024] (1) The method provided in this application uses aramid fiber and epoxy resin curing system as raw materials, including three-step process of aramid fiber surface modification, aramid fiber three-dimensional weaving and preform vacuum impregnation curing. The method is simple, low-cost, and the resulting product is lightweight and has significantly improved mechanical properties.

[0025] (2) The fiber weaving of this application adopts a special three-dimensional weaving technology. This technology performs two-dimensional weaving on the surface of the mold while winding and pultruding the fiber. This method can complete the weaving-winding-pultrusion process at the same time, and the process is simple. Attached Figure Description

[0026] Figure 1 These are SEM images of the aramid fibers before and after the activation treatment of the present invention.

[0027] Figure 2 This is a schematic diagram of the three-dimensional weaving operation of the present invention.

[0028] Figure 3 This is a cross-sectional schematic diagram of the braided layer of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod of the present invention.

[0029] Figure 4 This is a SEM image of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod of the present invention.

[0030] Figure 5 This is a microstructure diagram of the tensile cross-section of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments.

[0032] All raw materials used in the following examples were commercially available.

[0033] The basic parameters of aramid fiber are: two-dimensional weaving, fiber filament length of 800-1200d, and areal density of 140-200g / m². 2 Warp and weft density (radial: 6-10 threads / 10cm, weft: 6-10 threads / 10cm), mass per unit area: 160-200g / m² 2 Tensile strength (radial: 2863 N / 5 cm, weft: 1204 N / 5 cm), elongation at break (radial: 2.3%, weft: 13.1%);

[0034] The epoxy resin is bisphenol A type epoxy resin, the curing agent is phenolic resin, and the accelerator is methyl diethanolamine.

[0035] Example 1:

[0036] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0037] (1) Immerse aramid fibers in methanesulfonic acid (mass fraction of 60%) for 36 hours. After immersion, wash with distilled water to produce activated aramid fibers. Treat the activated aramid fibers with a waterproofing agent (PEG) to produce hydrophobic aramid fibers.

[0038] (2) A preform is made by three-dimensionally weaving hydrophobic aramid fibers. The three-dimensional weaving method includes: two-dimensional weaving of the fibers with the mold surface as the base, and pultrusion winding of the fibers around the mold surface with the central axis of the mold as the axis. The two-dimensional weaving is selected from three-dimensional four-way weaving, the pultrusion speed is 300 mm / min, the weaving angle is 40°, and the winding angle is 50°.

[0039] (3) Cut a suitable size of sealing bag, place the vacuum bag on a flat glass plate, then place the preform on the vacuum bag, fold the vacuum bag in half, fix the conduits on both sides of the preform as inlet and outlet ports, and finally apply sealant around the vacuum bag to form a sealed bag; use a vacuum pump to evacuate the sealed bag to remove air from the sample and the bag, plug the conduit openings, and check the airtightness of the sealed bag; mix 100 parts of epoxy resin, 80 parts of curing agent, and 0.5 parts of accelerator evenly and place them in a vacuum dryer at 60°C. The solution is degassed in a chamber until no air bubbles remain inside. After checking the airtightness, the sealed bag and the prepared resin solution are placed in an oven at 60°C. One end of the conduit in the sealed bag is placed into the resin solution, and the other end is connected to a vacuum pump. The resin solution will enter the sealed bag under the pressure difference between the inside and outside, wetting the entire surface and interior of the preform. After the preform is completely wetting, the conduits at both ends are plugged, and the resin is cured at 90°C for 2 hours to produce a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines.

[0040] Example 2:

[0041] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0042] (1) Immerse aramid fibers in methanesulfonic acid (mass fraction of 60%) for 36 hours. After immersion, wash with distilled water to produce activated aramid fibers. Treat the activated aramid fibers with a waterproofing agent (MSE100) to produce hydrophobic aramid fibers.

[0043] (2) A preform is made by three-dimensionally weaving hydrophobic aramid fibers. The three-dimensional weaving method includes: two-dimensional weaving of the fibers with the mold surface as the base, and pultrusion winding of the fibers around the mold centerline. The two-dimensional weaving is selected from three-dimensional four-way weaving, the pultrusion speed is 200 mm / min, the weaving angle is 40°, and the winding angle is 40°.

[0044] (3) Cut a suitable size of sealing bag, place the vacuum bag on a flat glass plate, then place the preform on the vacuum bag, fold the vacuum bag in half, fix the conduits on both sides of the preform as inlet and outlet ports, and finally apply sealant around the vacuum bag to form a sealed bag; use a vacuum pump to evacuate the sealed bag to remove air from the sample and the bag, plug the conduit openings, and check the airtightness of the sealed bag; mix 100 parts of epoxy resin, 85 parts of curing agent, and 0.5 parts of accelerator evenly and place them in a vacuum dry place at a temperature of 60℃. The solution is degassed in a drying oven until no air bubbles remain. After checking the airtightness, the sealed bag and the prepared resin solution are placed in an oven at 60°C. One end of the conduit in the sealed bag is placed in the resin solution, and the other end is connected to a vacuum pump. The resin solution will enter the sealed bag under the pressure difference between the inside and outside, wetting the entire surface and interior of the preform. After the preform is completely wetting, the conduits at both ends are plugged, and the resin is cured at 110°C for 1 hour to produce a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines.

[0045] Example 3:

[0046] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0047] (1) Immerse aramid fibers in methanesulfonic acid (mass fraction of 60%) for 36 hours. After immersion, wash with distilled water to produce activated aramid fibers. Treat the activated aramid fibers with a waterproofing agent (DS-02) to produce hydrophobic aramid fibers.

[0048] (2) A preform is made by three-dimensionally weaving hydrophobic aramid fibers. The three-dimensional weaving method includes: two-dimensional weaving of the fibers with the mold surface as the base, and pultrusion winding of the fibers around the mold surface with the central axis of the mold as the axis. The two-dimensional weaving is selected from three-dimensional four-way weaving, the pultrusion speed is 400 mm / min, the weaving angle is 60°, and the winding angle is 50°.

[0049] (3) Cut a suitable size of sealing bag, place the vacuum bag on a flat glass plate, then place the preform on the vacuum bag, fold the vacuum bag in half, fix the conduits on both sides of the preform as inlet and outlet ports, and finally apply sealant around the vacuum bag to form a sealed bag; use a vacuum pump to evacuate the sealed bag to remove air from the sample and the bag, plug the conduit openings, and check the airtightness of the sealed bag; mix 100 parts of epoxy resin, 90 parts of curing agent, and 0.5 parts of accelerator evenly and place them in a vacuum dryer at 60°C. The solution is degassed in a chamber until no air bubbles remain inside. After checking the airtightness, the sealed bag and the prepared resin solution are placed in an oven at 60°C. One end of the conduit in the sealed bag is placed into the resin solution, and the other end is connected to a vacuum pump. The resin solution will enter the sealed bag under the pressure difference between the inside and outside, wetting the entire surface and interior of the preform. After the preform is completely wetting, the conduits at both ends are plugged, and the resin is cured at 130°C for 4 hours to produce a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines.

[0050] Example 4:

[0051] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0052] (1) Immerse aramid fibers in methanesulfonic acid (mass fraction of 60%) for 36 hours. After immersion, wash with distilled water to produce activated aramid fibers. Treat the activated aramid fibers with a water-repellent agent (CSS) to produce hydrophobic aramid fibers.

[0053] (2) A preform is made by three-dimensionally weaving hydrophobic aramid fibers. The three-dimensional weaving method includes: two-dimensional weaving of the fibers with the mold surface as the base, and pultrusion winding of the fibers around the mold centerline. The two-dimensional weaving is selected from three-dimensional five-directional weaving, the pultrusion speed is 300 mm / min, the weaving angle is 60°, and the winding angle is 50°.

[0054] (3) Cut a suitable size sealing bag, place the vacuum bag on a flat glass plate, then place the preform on the vacuum bag, fold the vacuum bag in half, fix the conduits on both sides of the preform as inlet and outlet ports, and finally apply sealant around the vacuum bag to form a sealed bag; use a vacuum pump to evacuate the sealed bag to remove air from the sample and the bag, plug the conduit openings, and check the airtightness of the sealed bag; mix 100 parts epoxy resin, 80 parts curing agent, and 0.5 parts accelerator evenly and place them in a vacuum drying oven at 60℃. Perform degassing treatment until the solution is free of air bubbles; after checking the airtightness, place the sealed bag and the prepared resin solution into an oven, set the oven temperature to 60℃, put one end of the conduit in the resin solution, and connect the other end to a vacuum pump. At the same time, the resin solution will enter the sealed bag under the action of the internal and external pressure difference, wetting the entire surface and interior of the preform. After the preform is completely wetted, plug the conduits at both ends and heat at 130℃ for 4 hours, and let the resin cure at 110℃ for 1 hour to produce the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod.

[0055] Example 5:

[0056] A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines includes the following steps:

[0057] (1) Immerse aramid fibers in methanesulfonic acid (mass fraction of 60%) for 36 hours. After immersion, wash with distilled water to produce activated aramid fibers. Treat the activated aramid fibers with a waterproofing agent (PRTV) to produce hydrophobic aramid fibers.

[0058] (2) A preform is made by three-dimensionally weaving hydrophobic aramid fibers. The three-dimensional weaving method includes: two-dimensional weaving of the fibers with the mold surface as the base, and pultrusion winding of the fibers around the mold surface with the central axis of the mold as the axis. The two-dimensional weaving is selected from three-dimensional five-directional weaving, the pultrusion speed is 400 mm / min, the weaving angle is 40°, and the winding angle is 50°.

[0059] (3) Cut a suitable size of sealing bag, place the vacuum bag on a flat glass plate, then place the preform on the vacuum bag, fold the vacuum bag in half, fix the conduits on both sides of the preform as inlet and outlet ports, and finally apply sealant around the vacuum bag to form a sealed bag; use a vacuum pump to evacuate the sealed bag to remove air from the sample and the bag, plug the conduit openings, and check the airtightness of the sealed bag; mix 100 parts of epoxy resin, 85 parts of curing agent, and 0.5 parts of accelerator evenly and place them in a vacuum dryer at 60°C. The solution is degassed in a chamber until no air bubbles remain inside. After checking the airtightness, the sealed bag and the prepared resin solution are placed in an oven at 60°C. One end of the conduit in the sealed bag is placed into the resin solution, and the other end is connected to a vacuum pump. The resin solution will enter the sealed bag under the pressure difference between the inside and outside, wetting the entire surface and interior of the preform. After the preform is completely wetting, the conduits at both ends are plugged, and the resin is cured at 110°C for 1 hour to produce a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines.

[0060] Example 6: (Influence of pultrusion speed, braiding angle, and winding angle)

[0061] Using the method in Example 1, the pultrusion speeds in step 2 were 200 mm / min, 300 mm / min, and 400 mm / min, the braiding angles were 45° and 60°, and the winding angles were 40° and 50°, respectively; all other conditions were the same as in Example 1. The effects of different pultrusion speeds, different braiding angles, and different winding angles on the sand line angle of the preform were investigated, and the results are shown in Table 1.

[0062] Table 1. Yarn angles at different pultrusion speeds, different weaving angles, and different winding angles.

[0063]

[0064] As shown in Table 1, the error between the theoretical and experimental values ​​of the yarn angles of each layer of the fitting decreases with the increase of the fitting diameter. The theoretical values ​​of the yarn angles of each layer of the fitting are all greater than the experimental values, and the angle errors are all less than 2°. The error of the yarn angle in the braided layer of the fitting is smaller than the error of the yarn angle in the winding layer. Since the yarn angle error rate of the fitting is controlled below 5%, the mechanical properties of the fitting are guaranteed to meet the process design requirements. Under the same fitting diameter, the faster the pultrusion speed, the smaller the error between the theoretical and experimental values ​​of the braiding angle and the winding angle; the yarn angle error decreases with the increase of the pultrusion speed, and the braiding angle error is smaller. The theoretical values ​​of the yarn angles of the fitting are all greater than the measured values, with a difference range of 3.0°, and the difference in the winding angle is greater than the difference in the braiding angle. The faster the pultrusion speed, the smaller the impact on the fiber angle error of the composite tube. However, a faster pultrusion speed is not conducive to the complete curing of the tube. How to select a pultrusion speed that can ensure that the fiber angle error is within a small range and that the tube is completely cured is particularly important for the braiding-winding-pultrusion process.

[0065] like Figure 1 As shown in the figure, the device for the three-dimensional weaving process includes a weaving mold made of silicone, which is 500mm long and 30mm in diameter. To facilitate the demolding of the preform, a release cloth is also provided on the weaving mold. The three-dimensional weaving method is three-dimensional four-way weaving and three-dimensional five-way weaving. The weaving device is a rotary rectangular weaving machine. The rotary rectangular weaving machine weaves by changing the number of rows and columns of the weaving yarn and cooperating with different weaving molds. The pattern formed on the preform is a four-step 1×1 square weaving pattern.

[0066] like Figure 2As shown in the figure, the cross-sectional structure of the braided layer of the pipe fitting after axial compression is illustrated. The figure reveals that the failure process of the three-dimensional braided composite pipe fitting under overload is highly complex, exhibiting multiple phenomena and failure modes, often coexisting and interacting. During the bending process, as the pressure plate on the pressure testing machine decreases, the chamfer at the top of the composite pipe fitting fails first, triggering a stable failure of the entire pipe fitting under the pressure plate. Initially, cracks appear in the pipe wall, leading to failure. Subsequently, with increasing axial compression, the fiber bundles inside the pipe break, and the resin on the surface begins to detach. Therefore, the breakage and buckling deformation of the fiber bundles in the composite pipe fitting are crucial for energy absorption. The folding failure mode refers to the stable, progressive failure of the entire composite pipe fitting after the top of the pipe fails under axial compressive load. During axial compression, the surface of the composite pipe fitting exhibits a layered, downward folding failure. As axial compression progresses, the pipe wall undergoes a significant folding state, and the pipe fitting's appearance shows an S-shaped deformation. After axial compression, numerous fiber bundle cracks and some fiber breaks appeared in the upper part of the sample. The fiber bundles inside the sample were arranged relatively neatly, and the three-dimensional braided structure was basically undamaged.

[0067] Comparative Example 1 (without activator treatment)

[0068] Compared with Example 1, the fibers in step (1) are not treated with an activator, and all other conditions are the same as in Example 1.

[0069] The hydrophobic properties of the fiber surfaces of Examples 1-5 and Comparative Example 1 were tested using an optical contact angle tester. The mechanical properties of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rods prepared in Examples 1-5 were tested using a mechanical property testing machine. The test results are shown in Table 2.

[0070] Table 2 Mechanical properties of foam-filled fiber-reinforced epoxy resin insulated rods for ultra-high voltage power lines

[0071]

[0072] As shown in Table 2, the bending strength can reach over 200 MPa, and the bending strength data is relatively stable, meeting the requirement of a bending performance greater than 180 MPa for high-performance insulating rods. This is achieved through the composition and layup design of the fiber fabric in the fiber-reinforced insulating operating rod tube, and through the design of the fiber fabric's areal density and fiber axial direction weaving. This increases the bending strength of the fiber-reinforced insulating operating rod tube. This is because aramid fiber has excellent mechanical properties. By selecting the weaving method and fiber monofilament diameter of the PBO fiber fabric, it achieves good wettability with epoxy resin. The PBO fiber fabric provides sufficient strength and toughness for the composite material in the radial fiber direction. The shear strength reaches over 20 MPa, indicating that the fiber-reinforced insulating operating rod has excellent shear performance. Shear strength is a key parameter for the performance of fiber-reinforced insulating operating rods, and in the actual engineering application of insulating operating rods, the shear strength of the material will affect the service life of the fiber-reinforced insulating operating rod. It possesses excellent electrical insulation properties, with axial and radial electrical strengths comparable to those of fiber-reinforced insulated operating rods from abroad. This also reflects the good density of the composite material, fewer defects, and good interfacial bonding between the epoxy resin and aramid fiber fabric, meeting the insulation requirements for live-line work. The dielectric constant of the fiber-reinforced insulated operating rod is between 3 and 4, and its dielectric loss is relatively low. Dielectric loss can also characterize the electrical insulation properties of insulating materials to some extent.

[0073] Example of detection:

[0074] The aging performance of the foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines prepared in Example 1 was tested. The test method adopted was GB 11026.2-2000. The aging temperatures were 80℃, 110℃, and 140℃, and the aging time was 30 days. The mechanical and electrical properties of the test samples at different aging temperatures were tested. The test results are shown in Table 3.

[0075] Table 3 Aging performance of foam-filled fiber-reinforced epoxy resin insulating rods for ultra-high voltage power lines

[0076]

[0077] As shown in Table 3, the electrical insulation performance parameters of the fiber-reinforced insulated operating rod show very little change compared to before aging at 80℃ and 110℃. This indicates that the polymer main chain breakage caused by the chemical reaction has little impact on the aging process of the fiber-reinforced insulated operating rod, suggesting that no significant chemical aging occurs below 110℃. The breakdown strength, dielectric constant, and dielectric loss of the fiber-reinforced insulated operating rod do not change significantly compared to before aging, meeting the operating temperature requirements of the insulated rod. When the aging temperature reaches 140℃, the data in the table shows that the breakdown strength of the fiber-reinforced insulated operating rod decreases significantly, the dielectric constant increases, and the dielectric loss increases significantly compared to before aging. This indicates that under long-term aging conditions at 140℃, the epoxy resin may undergo partial chemical reaction, causing the breakage of the epoxy resin molecular main chain structure and an increase in molecular polarization. The thermo-oxidative aging process of thermosetting resin-based composite insulation materials generally includes dehumidification, curing, and decomposition processes, involving a series of complex physicochemical reaction processes such as moisture removal, physical and chemical aging. During the chemical reaction, the polymer structure inside the material undergoes breakage and branching in a high-temperature, thermo-oxidative environment, increasing the number of polarized groups. This leads to an increased contribution of orientation polarization to the dielectric constant, macroscopically manifested as an increase in the dielectric constant. Mechanical property results show that after aging at 80℃ and 110℃ for 30 days, the flexural and tensile strengths of the fiber-reinforced insulating operating rod remain almost unchanged compared to before aging, indicating that the fiber-reinforced insulating operating rod can meet long-term operation requirements at 110℃. When the aging temperature reaches 140℃, the flexural and tensile strengths of the fiber-reinforced insulating operating rod decrease by nearly 10% compared to before aging, indicating a significant decrease in the mechanical properties of the composite material at the current temperature. The aramid fiber fabric exhibits good stability at the current temperature, suggesting that the molecular structure within the epoxy resin system undergoes breakage of the polymer backbone or changes in internal molecular groups at higher temperatures, leading to a decrease in the mechanical properties of the composite material.

[0078] The tensile fracture surfaces of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rods prepared in Examples 1-5 were scanned using a scanning electron microscope. The results are shown in the figure. Figure 4 ;like Figure 4 As shown, by controlling the adjustment of the vacuum impregnation molding process parameters, the resin system can be fully impregnated into the fiber bundle, thereby ensuring the density of the composite material and giving the composite material excellent electrical insulation properties and mechanical properties.

[0079] The cross-sectional microstructure of the ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rods prepared in Examples 1-5 was scanned using a microscope. The results are shown in the figure. Figure 5 ;like Figure 5As shown, the light-colored, discontinuous strands represent fiber bundles, while the dark-colored, continuous strands represent resin. The resin between the fiber bundles is uniform and continuous. The load-bearing warp threads are relatively neat and straight, providing high bending strength, while the weft threads are fully impregnated with resin, providing support and fixation, thus ensuring the structural integrity. The unique design of the aramid fabric ensures good wetting between the fiber fabric and the resin. Introducing new fiber fabric in the weft direction improves the wetting between the fiber fabric and the epoxy resin, effectively solving the wetting problem between the fiber fabric and the epoxy resin.

Claims

1. A method for preparing a foam-filled fiber-reinforced epoxy resin insulating rod for ultra-high voltage power lines, characterized in that, Includes the following steps: (1) Activated aramid fiber is produced by activating aramid fiber, and water-repellent aramid fiber is produced by treating activated aramid fiber with a waterproofing agent. (2) The hydrophobic aramid fiber is three-dimensionally woven to form a preform. The three-dimensional weaving method includes: the fiber is woven in two dimensions with the mold surface as the base, and the fiber is pultruded and wound around the mold surface with the central axis of the mold as the axis. (3) The preform is impregnated in the epoxy resin curing system and cured after complete impregnation to form an ultra-high voltage power line foam-filled fiber-reinforced epoxy resin insulating rod.

2. The preparation method according to claim 1, characterized in that, The waterproofing agent mentioned in step (1) is selected from one or more of PEG, MSE100, IC701, PRTV, DS-02, and CSS.

3. The preparation method according to claim 1, characterized in that, The activation treatment step is as follows: aramid fibers are immersed in methanesulfonic acid, and then washed with distilled water after immersion. The methanesulfonic acid content is 60%, and the immersion time is 36 hours.

4. The preparation method according to claim 1, characterized in that, The two-dimensional weaving described in step (2) is selected from either three-dimensional four-way weaving or three-dimensional five-way weaving.

5. The preparation method according to claim 1, characterized in that, The mold in step (2) has a diameter of 30 mm and a length of 500 mm, and a release agent is provided on the mold.

6. The preparation method according to claim 1, characterized in that, The pultrusion speed in step (2) is 200~400mm / min.

7. The preparation method according to claim 1, characterized in that, The weaving angle of the three-dimensional weaving in step (2) is 40~60°, and the winding angle is 40~50°.

8. The preparation method according to claim 1, characterized in that, The epoxy resin curing system comprises, by weight, 100 parts epoxy resin, 80-90 parts curing agent, and 0.5 parts accelerator.

9. The preparation method according to claim 1, characterized in that, The immersion conditions described in step (3) are: temperature 60°C, vacuum.

10. The preparation method according to claim 1, characterized in that, The curing conditions described in step (3) are: curing temperature 90~130℃, curing time 1~4h, and vacuum.

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