Insulated pull rod vacuum pressure impregnation device and method

Abstract

The application discloses an insulating pull rod vacuum pressure impregnation forming device and method, which comprises an outer mold module and an inner mold module coaxially nested; a pull rod impregnation forming cavity is formed between the inner wall of the outer mold module and the outer wall of the inner mold module; an upper pressing plate is arranged at the top of the forming cavity, and the upper pressing plate is provided with a pressure structure for adjusting the pressure of the upper pressing plate; the upper pressing plate is uniformly distributed with a plurality of controllable open-close overflow ports communicated with the forming cavity; the bottom of the outer mold module and the inner mold module is provided with a bottom mold module, and the bottom mold module is uniformly provided with a plurality of controllable open-close feeding ports communicated with the forming cavity; the opposite two sides of the forming cavity are respectively provided with grounding modules and high-voltage modules, and the grounding modules and the high-voltage modules are used for forming an electric field in the forming cavity to generate an electric field effect on the impregnation liquid in the forming cavity. The tensile strength, shear strength and fracture toughness of the insulating pull rod processed by the application are greatly improved, and the curing temperature of the epoxy resin is also significantly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrical component forming device and method, in particular to an insulation pull rod vacuum pressure impregnation forming device and method. BACKGROUND

[0002] The insulation pull rod is generally prepared by using a vacuum pressure impregnation process to prepare a composite material insulation tube, and then machining and matching metal joints to prepare the insulation pull rod.

[0003] Vacuum pressure impregnation (VPI) refers to placing a product to be processed in a closed container (mold) for vacuum treatment, injecting impregnation liquid, and applying a certain pressure to allow the impregnation liquid to enter the product being processed, and then solidifying and forming. VPI technology is currently the best insulation treatment technology. The VPI forming process of the insulation pull rod includes: winding fiber fabric on a mandrel and then placing it in a corresponding metal mold, closing the mold, heating, and vacuumizing to remove moisture and air in the mold cavity; performing defoaming treatment on the prepared epoxy resin system, injecting and filling the resin into the mold cavity through the valve pipe under suitable vacuum pressure and temperature, and then solidifying and forming under certain pressure and temperature; machining the completely solidified composite material tube to prepare the insulation pull rod by bonding metal joints.

[0004] In recent years, during the operation of high-voltage grade GIS, breakdown and flashover failures of the insulation pull rod occur from time to time, which brings great challenges to the safe and stable operation of the power grid, and it is urgent to improve the mechanical properties and electrical properties of the insulation pull rod. The performance reliability of the insulation pull rod mainly depends on the quality of the composite material insulation tube. The composite material insulation tube is prepared by using the VPI forming process, and the common defects of the VPI forming process are incomplete impregnation of the epoxy resin and the reinforcing material, which specifically manifests as dry spots and micropores in the product body, which seriously affect the electrical properties of the insulation pull rod and easily cause breakdown and flashover failures.

[0005] The most common method to reduce the number of dry spots and micropores is to chemically modify the surface of the fiber. Oxygen-containing functional groups are added or coupling agent treatment is performed, but these methods are complex, difficult to accurately control, and unevenly affect the fiber fabric from the outside to the inside (gradually decreasing). Moreover, this scheme has potential chemical pollution hazards and is not conducive to large-scale production. Improving the curing process to enhance the flowability of the resin is also a common technical means, for example, using vacuum-assisted resin transfer molding to reduce the porosity of the composite material. However, the process involved is complex, high in cost and difficult to control, and on the other hand, it may lead to poor interlaminar fracture toughness. In order to make up for this, nano particles are usually added to the resin matrix to enhance the interlaminar toughness, but the nano particles are dispersed in the matrix and embedded between the layers, hindering the crosslinking of the matrix, reducing the strength of the matrix, and reducing the overall performance of the composite material.

[0006] The long curing time and high temperature of the epoxy resin result in high energy consumption, large carbon emission and low molding efficiency, and the molding is a high energy consumption and high carbon emission process. There is a strong practical demand to reduce the energy consumption and carbon emission of the production process of epoxy products.

[0007] Therefore, there is an urgent application need to explore a simple, controllable process, scalable production, no chemical pollution and low energy consumption alternative technology to control the defects of the insulation pull rod VPI molding process and improve the process stability. SUMMARY

[0008] The purpose of the present application is to provide an insulation pull rod vacuum pressure impregnation molding device capable of improving the mechanical and electrical properties of the insulation pull rod.

[0009] The second purpose of the present application is to provide a method for impregnation molding insulation pull rod which reduces energy consumption, cost and carbon emission under the premise of ensuring mechanical and electrical properties.

[0010] Technical scheme: the insulation pull rod vacuum pressure impregnation molding device comprises an outer mold module and an inner mold module arranged in a concentric nested manner; the inner wall of the outer mold module and the outer wall of the inner mold module form a pull rod impregnation molding cavity; the top of the molding cavity is provided with an upper pressing plate, the upper pressing plate is provided with a pressure structure for adjusting the pressure of the upper pressing plate; the upper pressing plate is uniformly provided with a plurality of controllable opening and closing overflow ports communicated with the molding cavity; the bottom of the outer mold module and the inner mold module is provided with a bottom mold module, the bottom mold module is uniformly provided with a plurality of controllable opening and closing feeding ports communicated with the molding cavity; the opposite two sides of the molding cavity are respectively provided with a grounding module and a high-voltage module, the grounding module and the high-voltage module are used to form an electric field in the molding cavity so as to produce an electric field effect on the impregnation liquid in the molding cavity.

[0011] Among them, the direction of the electric field formed between the high-voltage module and the grounding module is perpendicular to the flow direction of the impregnation liquid flowing into the molding cavity.

[0012] Among them, the high-voltage module is arranged in the outer mold module and located on the side of the molding cavity away from the inner mold module; the grounding module is arranged in the inner mold module and located on the side of the molding cavity close to the inner mold module.

[0013] Among them, the molding device of the present application further comprises a first insulation structure and a second insulation structure; the outer mold module is provided with a receiving groove penetrating the wall surface of the outer mold module and corresponding to the molding cavity; the high-voltage module is received in the receiving groove, the first insulation structure is arranged between the high-voltage module and the inner wall of the receiving groove to insulate the high-voltage module from the outer mold module; the second insulation structure is arranged in the inner mold module to insulate the peripheral wall of the molding cavity from the inner mold module.

[0014] The method for impregnation forming the insulating pull rod by using the insulating pull rod vacuum pressure impregnation forming device comprises the following steps:

[0015] (A) fixing the insulating core rod on the inner mold module and winding the fiber fabric outside the core rod, and fixing the outer mold module and the inner mold module on the bottom mold module;

[0016] (B) controlling the feeding system to reach the feeding condition, and feeding the impregnation liquid from the feeding unit to the forming cavity through the feeding port to perform impregnation;

[0017] (C) opening the high-voltage module to form an electric field on both sides of the forming cavity;

[0018] (D) after impregnation, performing solidification forming.

[0019] The electrolyte has a structural formula as follows:

[0020]

[0021] R1 and R2 are alkyl groups with 1-3 carbon atoms.

[0022] Preferably, the electrolyte is at least one of N,N-dimethyl morpholine tetrafluoroborate, N,N-diethyl morpholine tetrafluoroborate or N-methyl-N-ethyl morpholine tetrafluoroborate; and the concentration of the electrolyte is 1-5 mmol / L.

[0023] The electric field strength applied to the high-voltage module (40) is 2-5 kV / cm. The high-voltage module uses a direct current, alternating current or pulse voltage source, or a superimposed source formed by any two of the three voltage sources.

[0024] The impregnation liquid is a bisphenol A epoxy system with a viscosity range of 200-500 mPa·s.

[0025] Invention principle:

[0026] The liquid epoxy resin flows in the inter-fiber voids, so the dynamic evolution process of the liquid epoxy resin wetting the fiber bundle can be described by the Navier-Stokes equation. Under a uniform external electric field, the molecular dipoles in the epoxy resin align along the direction of the electric field, forming a net macroscopic dipole moment. Therefore, an electric field force f (Maxwell stress) is generated at the gas-liquid resin interface as the driving force for the flow of the liquid resin, which can be expressed as:

[0027]

[0028] where p is the spatial density of free charges in the dielectric liquid, Vε is the dielectric gradient, and E is the electric field. The first and second terms on the right side of the equation represent the Coulomb force and the dielectric force, respectively. Since the epoxy resin contains very few or no conductive ions, only the dielectric force is present in the epoxy resin when only an electric field is applied.

[0029] Maxwell stress is related not only to the electric field strength, but also to the electrical properties of the epoxy resin. The application of an electric field results in a rapid wetting state transition of the epoxy resin droplets due to the dielectric alignment of the polar epoxy molecules and the migration of the dissociated ions. The epoxy resin with electrolyte exhibits a significantly higher wetting rate under the action of an applied electric field. In addition, the wetting rate increases with increasing ion concentration. This enhancement is attributed to the introduction of conductive ions in the epoxy resin, which, under the action of an electric field, changes the driving force from the dielectric force to the sum of the dielectric force and the Coulomb force.

[0030] Specifically, when the fiber filler is well mixed with the epoxy resin under the action of an electric field compared to the conventional impregnation process, a portion of the heat is additionally released. On the other hand, because the thermal conductivity of the fiber filler is superior to that of the epoxy material, heat transfer is facilitated, which is beneficial to the progress of the curing reaction. These two reasons can make the well-impregnated epoxy material be cured at a lower temperature. Due to the aforementioned principle, the additional Maxwell stress caused by the addition of electrolyte further increases the compatibility of the fiber filler and the epoxy resin, optimizes the curing temperature and curing effect. A small amount of electrolyte is dispersed at the molecular level in the epoxy resin without forming obvious agglomerates or particles, and at the same time, due to the promotion of the compatibility of the epoxy resin and the glass fiber, the microstructure of the cured resin is more dense and uniform, so the finished product has little effect on the electrical properties.

[0031] However, further increasing the electrolyte content, as the curing temperature decreases, the viscosity of the liquid resin gradually increases, resulting in an increase in surface tension and viscous resistance, leading to an increase in the resistance of the resin to penetrate the gap between the fibers, and the effectiveness of the electric field in driving the resin to flow is also reduced. On the other hand, the formation of a small amount of conductive paths after curing and molding also reduces the overall insulation performance and dielectric constant of the material. After a small amount of ionic electrolyte is added to the epoxy, the ionic electrolyte in the epoxy resin may form ion pairs or ion clusters. These ions will move directionally under the action of an electric field, forming an ionic current. The presence of ionic current increases the electrical conductivity of the material, reducing its insulation performance and dielectric constant.

[0032] Beneficial effects: compared with the prior art, the present application has the following remarkable effects: (1) the tensile strength, shear strength and fracture toughness of the shaped epoxy resin prepared by the molding device of the present application under the action of an electric field are greatly improved, and the curing temperature of the impregnating liquid, i.e. bisphenol A epoxy resin, is reduced by about 10℃; (2) the electrolyte of the present application can significantly improve the effect of the electric field on the impregnating liquid, and the mechanical properties of the insulating pull rod can be further improved by adding an organic macromolecular electrolyte; (3) the high-voltage insulating pull rod molding method of the present application is simple and effective, which overcomes the deficiency of the resin flowability between the fibers of the fabric, improves the wettability of the resin, and reduces the pore content in the fiber reinforced composite material; (4) the present application can significantly reduce the cost of the production process, the curing temperature is reduced by 10℃, and the overall carbon emission can be reduced by more than 10%, thereby expanding the use range of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a longitudinal sectional view of the molding device of embodiment 1 of the present application;

[0034] Figure 2 is a cross-sectional view of the molding device of embodiment 1 of the present application. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below.

[0036] Embodiment 1

[0037] As shown in Figure 1 , 2 , the vacuum pressure impregnation molding device 100 provided by the first scheme of the present application. The vacuum pressure impregnation molding device 100 is used to receive the impregnating liquid to be cured with the core rod and the wound fiber fabric 201 into an insulating pull rod 1000. The vacuum pressure impregnation molding device 100 comprises an outer mold module 10, an inner mold module 20, a bottom mold module 30, a high-pressure module 40 and a grounding module 50.

[0038] The bottom mold module 30 is formed with a feeding port 301 and a first transmission flow channel 302 communicating with the feeding port 301. The feeding port 301 is used to connect the injection device (not shown in the figure) to receive the impregnating liquid injected by the injection device. When the injection device injects the impregnating liquid into the feeding port 301, the impregnating liquid will flow into the first transmission flow channel 302. Figure 1

[0039] The outer mold module 10 comprises an outer mold module 101 and an upper pressing plate 102. The upper pressing plate 102 is located at the top of the outer mold module 101, which is used to control the length of the insulating pull rod 1000. The outer mold module is formed with an overflow port 103 and a second transmission flow channel 104 communicating with the overflow port 103.

[0040] ​The outer mold module 10 and the inner mold module 20 can be fixed with the bottom mold module 30 through buckling, screws, etc., and the outer mold module 10 is used to cooperate with the inner mold module 20 to form the insulating pull rod 1000.

[0041] The outer mold module 10 and the inner mold module 20 form a forming cavity 60 and are in communication with the second transmission flow channel 104 and the first transmission flow channel 302. The forming cavity 60 includes oppositely arranged first and second sides.

[0042] The high-voltage module 40 is located in the outer mold module 10, i.e., the first side of the forming cavity 60; the first side of the forming cavity is the side away from the inner mold module 20 in the direction from the inner mold module 20 to the outer mold module 10, and the grounding module 50 is arranged in the inner mold module 20; the second side of the forming cavity is the side close to the inner mold module 20 in the direction from the inner mold module 20 to the outer mold module 10, so that the electric field direction formed between the first side and the second side of the forming cavity is perpendicular to the direction of the impregnating liquid flowing into the forming cavity.

[0043] Alternatively, the high-voltage module is located in the inner mold module and is located on the side close to the inner mold module 20 in the direction from the inner mold module 20 to the outer mold module 10 in the forming cavity, and the grounding module 50 is arranged in the outer mold module 10 and is located on the side away from the inner mold module 20 in the direction from the inner mold module 20 to the outer mold module 10 in the forming cavity, so that the electric field direction formed between the first side and the second side of the forming cavity is perpendicular to the direction of the impregnating liquid flowing into the forming cavity.

[0044] Embodiment 2

[0045] The application provides a high-voltage insulating pull rod forming method, which uses the insulating pull rod vacuum pressure impregnation forming device of embodiment 1 to realize impregnation forming of the insulating pull rod, and comprises the following steps:

[0046] (1) fixing the insulating core rod 201 on the inner mold module 20 and winding the fiber fabric 202 outside the core rod 201, and fixing the outer mold module 10 on the bottom module 30;

[0047] (2) controlling the feeding system to reach the feeding condition, conveying the impregnating liquid from the feeding unit to the forming cavity through the feeding port 301 and the first transmission flow channel 302 to perform impregnation operation;

[0048] (3) starting the high-voltage module 40 and the grounding module 50 to form an electric field on both sides of the forming cavity 60;

[0049] (4) after the impregnation operation is completed, performing solidification forming operation.

[0050] The electric field intensity is 5 kV / cm, and the high voltage module is a direct current voltage source. The fiber fabric is glass fiber, which is woven into a three-dimensional mixed fiber fabric of a certain size by a three-dimensional mixing method. The impregnating liquid is a bisphenol A epoxy system with a viscosity range of 300 mPa-s. The curing temperature is 85°C. The impregnation time is 30 minutes. N,N-dimethylmorpholine tetrafluoroborate is added to the impregnating liquid, and the concentration is 5 mmol / L.

[0051] The specific steps of Examples 3-11 and Comparative Example 1-11 are the same as those of Example 1, and the parameter values are shown in Table 1 below. The electric field intensity in the molding method, the curing temperature, the concentration and type of added electrolyte, and the impregnation time are changed, and otherwise the same operations as in Example 2 are performed to make the pull rods shown in Table 1, respectively.

[0052] Table 1: Pull rod molding process parameters of each example and comparative example

[0053]

[0054] Each example and comparative example embodies a combination of different parameters and methods, including applying an electric field, adding an electrolyte, and changing the curing temperature. By comparing and analyzing these examples and comparative examples, the effects of the electric field and the electrolyte on the mechanical properties of the pull rod and the curing temperature can be obtained. Details are described as follows.

[0055] Test method:

[0056] Porosity: The porosity of the cured product is estimated by the cross-sectional gray scale statistics of the SEM image.

[0057] Interlaminar shear strength: The interlaminar shear strength formula is:

[0058]

[0059] In the formula, P b The maximum load observed during the test is also measured by the universal mechanical testing machine, and each test is performed at least 5 times, and the final result is the average of the results obtained in each test. The relevant test results are shown in Table 2.

[0060] Table 2: Effect of molding process on impregnation quality

[0061]

[0062] Comparing the test results of Example 2, Example 8, Comparative Example 9, and Comparative Example 1, after applying an electric field during the impregnation process, the porosity of the pull rod is significantly reduced, and decreases with the increase of the electric field intensity. At the same time, the interlaminar shear strength of the pull rod is significantly improved, and increases with the increase of the electric field intensity.

[0063] Comparing the test results of Comparative Example 2, Example 9, Comparative Example 9, Comparative Example 1 and Comparative Example 8, after adding electrolyte, the porosity is further reduced with the increase of electrolyte content, and the interlaminar shear strength is increased.

[0064] Comparing Comparative Example 2 and Comparative Example 10, it can be seen that if the electric field strength is too low, the forming quality of the pull rod will not be significantly improved.

[0065] Tensile strength, modulus, and bending strength, modulus:

[0066] According to the national standard, the tensile strength and bending strength of the composite material are measured by a universal mechanical testing machine. The tensile modulus of the composite material is measured by a tensile meter. Each test is carried out at least 5 times, and the final result is the average value of the results obtained in each test.

[0067] Comparing Comparative Example 1 and Comparative Example 8, it can be seen that the mechanical strength of the pull rod is significantly improved before and after applying an electric field during the impregnation process; comparing the test results of Examples 2, 3, 9 and Comparative Example 8, it can be seen that under the same electric field, increasing the electrolyte concentration can significantly improve the mechanical strength of the pull rod.

[0068] Table 3 Effect of forming process on mechanical strength

[0069]

[0070] Effect of forming method on curing temperature:

[0071] By comparing the test results of Comparative Example 2, 4-7 and Comparative Examples 1-5, it can be seen that compared with Comparative Example 1, under the premise of achieving similar mechanical properties, the curing temperature of the composite material can be reduced by more than 10℃ by applying an electric field and adding an electrolyte.

[0072] Table 4 Effect of forming process on temperature

[0073]

[0074] Surface flashover voltage:

[0075] The insulation flashover voltage and axial electrical strength of the finished pull rod were tested by a flashover voltage breakdown tester.

[0076] Comparing the test results of Examples 2, 3 and Comparative Examples 1, 6, 11, after adding ionic liquid electrolyte, the flashover voltage and axial electrical strength slightly decrease, but when the electrolyte concentration is too high or replaced by ionic electrolyte, the electrical properties decrease significantly.

[0077] Table 5 Effect of forming process on electrical strength

[0078] Name Flashover voltage (kV) Axial electrical strength (kV / mm) Comparative Example 1 185 17 Comparative Example 6 155 13 Comparative Example 11 165 13 Example 2 175 15 Example 3 177 16

[0079] In summary, by using the forming device and forming method of the application, the porosity of the pull rod is significantly reduced after the electric field is applied in the impregnation process, and the impregnation quality is obviously improved; in the case of applying the same electric field, as the electrolyte concentration increases, the impregnation quality increases accordingly. Under the premise of achieving the same mechanical properties, the method of applying an electric field and adding an electrolyte can reduce the curing temperature required for the forming of the composite material. When the electrolyte concentration is too high or replaced by an ionic electrolyte, the electrical strength of the pull rod decreases significantly; and without adding electrolyte and with too short impregnation time, the mechanical strength of the pull rod decreases significantly.

Claims

1. A method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device, characterized in that, The aforementioned vacuum pressure impregnation molding device for insulating tie rods includes an outer mold module (10) and an inner mold module (20) coaxially nested together; the inner wall of the outer mold module (10) and the outer wall of the inner mold module (20) form a tie rod impregnation molding cavity (60); an upper pressure plate (102) is provided at the top of the molding cavity (60), and the upper pressure plate (102) is provided with a pressure structure for adjusting the pressure of the upper pressure plate (102); the upper pressure plate (102) is evenly distributed with a plurality of controllable overflow ports communicating with the molding cavity (60). (103); The bottom of the outer mold module (10) and the inner mold module (20) is provided with a bottom mold module (30), and the bottom mold module (30) is evenly distributed with a number of controllable feed ports (301) communicating with the molding cavity (60); The two opposite sides of the molding cavity (60) are respectively provided with a grounding module (50) and a high voltage module (40), and the grounding module (50) and the high voltage module (40) are used to generate an electric field in the molding cavity (60) so as to generate an electric field effect on the impregnation liquid in the molding cavity (60); The method includes the following steps: (A) Fix an insulating core rod (201) on the inner mold module (20) and wrap a fiber fabric (202) around the outside of the core rod, and fix the outer mold module (10) and the inner mold module (20) on the bottom mold module (30); (B) Control the feeding system to reach the feeding conditions, and transport the impregnation liquid from the feeding unit through the feed port (301) into the molding cavity (60) for impregnation; the impregnation liquid contains an electrolyte; the electrolyte has the following structural formula: ; Among them, R1 and R2 are alkyl groups with 1 to 3 carbon atoms; (C) Turn on the high voltage module (40) to form an electric field on both sides of the molding cavity (60); (D) After impregnation, the mixture is cured and molded.

2. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, The electrolyte is at least one of N,N-dimethylmorpholine tetrafluoroborate, N,N-diethylmorpholine tetrafluoroborate, or N-methyl-N-ethylmorpholine tetrafluoroborate.

3. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, The concentration of the electrolyte is 1~5 mmol / L.

4. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, In step (C), the electric field strength applied to the high-voltage module (40) is 2~5 kV / cm.

5. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, The direction of the electric field formed between the high-voltage module (40) and the grounding module (50) is perpendicular to the flow direction of the impregnation liquid flowing into the molding cavity (60).

6. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, The high-voltage module (40) is located inside the outer mold module (10) and on the side of the molding cavity (60) away from the inner mold module (20); the grounding module (50) is located inside the inner mold module (20) and on the side of the molding cavity (60) close to the inner mold module (20).

7. The method for impregnating and molding an insulating tie rod using a vacuum pressure impregnation molding device according to claim 1, characterized in that, It also includes a first insulating structure and a second insulating structure; the outer mold module (10) has a receiving groove that penetrates the wall of the outer mold module (10) and corresponds to the molding cavity (60); the high voltage module (40) is received in the receiving groove, the first insulating structure is disposed between the high voltage module (40) and the inner wall of the receiving groove to insulate the high voltage module (40) from the outer mold module (10); the second insulating structure is disposed in the inner mold module (20) to insulate the peripheral wall of the molding cavity (60) from the inner mold module (20).

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