Preparation method of modified aramid fiber and aramid fiber insulation pull rod

Abstract

The invention relates to a preparation method of modified aramid fibers and an aramid fiber insulation pull rod, and belongs to the technical field of high-voltage equipment materials. The preparation method of the modified aramid fiber comprises the following steps: soaking the aramid fiber in a dopamine self-polymerization reaction solution for modification treatment to obtain the modified aramid fiber, the dopamine self-polymerization reaction solution is prepared from acetate, periodate, dopamine salt and water. According to the invention, the dopamine self-polymerization reaction liquid is utilized to carry out rapid surface modification treatment on the aramid fiber, and polydopamine is deposited on the aramid fiber, so that the roughness of the fiber surface is improved on one hand, the activity of the fiber surface is improved on the other hand, and the combination strength between the fiber and the epoxy resin is increased through the synergistic effect of the two components; and the mechanical performance of the insulating pull rod is improved.

Description

Technical Field

[0001] The invention relates to a preparation method of modified aramid fiber and an aramid fiber insulating pull rod, belonging to the technical field of high-voltage equipment materials. Background Art

[0002] The insulating rod is a key component in the high-voltage DC circuit breaker, playing an important role in insulation and power transmission. On the one hand, it is used between the high potential and low potential of the high-voltage DC circuit breaker, and needs to have excellent insulation performance to withstand the long-term effect of the electric field; on the other hand, it is used to connect the contacts and operating mechanism of the high-voltage DC circuit breaker to transmit mechanical power. The circuit breaker has a short opening and closing action time, high speed, and large impact load, which puts high requirements on the mechanical properties of the insulating rod. In the early stage of the development of high-voltage DC circuit breaker equipment, the reinforcing material of the insulating rod is generally glass fiber. With the increase of the voltage level of the equipment, the insulating rod has to complete the more demanding breaking task, and the insulating rod for DC circuit breakers needs to withstand higher and higher field strengths and greater mechanical stress. In this form, the insulating rod using aramid fiber as the reinforcing material came into being, and gradually formed two products: aramid fiber insulating rod and glass fiber insulating rod.

[0003] Since aramid fiber has excellent properties such as low density, high tensile strength and tensile modulus, insulating rods with aramid fiber reinforced epoxy resin composite materials as the main body have become a new application trend. However, aramid fiber has an inert surface and high crystallinity, and its interface bonding with epoxy resin is poor, which will cause defects such as dry spots and air gaps inside the insulating rod. When the insulating rod is put into operation, the internal defects are prone to cause partial discharge or even breakdown under the action of a strong electric field. Therefore, how to improve the interface compatibility between aramid fiber and epoxy resin as well as the electrical insulation and mechanical properties is an urgent problem that needs to be solved.

[0004] Chinese patent document CN116515141A discloses a method for modifying aramid fiber for insulating pull rod based on dopamine secondary treatment. The modification method disclosed in the patent document includes the following steps: washing and drying the aramid fiber for insulating pull rod; placing the aramid fiber in a dielectric barrier discharge plasma device for plasma modification; soaking the aramid fiber in a dopamine solution (the dopamine solution is prepared by dissolving dopamine hydrochloride in Tris buffer) for dopamine modification; washing and drying the modified aramid fiber; vacuum pressure impregnating the aramid fiber with epoxy resin; high temperature curing the aramid fiber insulating pull rod after vacuum pressure impregnation to obtain the finished aramid fiber insulating pull rod. However, when the patent document uses dopamine solution to modify the aramid fiber, since it uses oxygen as an oxidant to complete the oxidation deposition of dopamine, but the oxidizability of oxygen is low, the uniformity of the deposited polydopamine is poor, resulting in poor interface compatibility between the aramid fiber and the epoxy resin. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing modified aramid fiber, which can solve the problem of poor interface compatibility between aramid fiber and epoxy resin when aramid fiber is currently used to prepare insulating pull rods.

[0006] Another object of the present invention is to provide an aramid fiber insulating pull rod, which can solve the problem that the insulating pull rod currently made of aramid fiber has poor electrical insulation and mechanical properties.

[0007] In order to achieve the above objectives, the technical solution adopted by the method for preparing the modified aramid fiber of the present invention is:

[0008] A method for preparing modified aramid fiber comprises the following steps: in a light-proof condition, immersing the aramid fiber in a dopamine self-polymerization reaction liquid for modification treatment to obtain the modified aramid fiber; the dopamine self-polymerization reaction liquid consists of acetate, periodate, dopamine salt and water, the concentration of acetate is 40-60 mmol / L, the concentration of periodate is 1-4 g / L, and the concentration of dopamine salt is 1-4 g / L.

[0009] The preparation method of the modified aramid fiber of the present invention is based on the characteristic that dopamine undergoes an oxidative self-polymerization reaction after being oxidized by a strong oxidant under weakly acidic conditions, and uses a dopamine self-polymerization reaction liquid to perform rapid surface modification treatment on the aramid fiber, and deposits polydopamine on the aramid fiber, which improves the roughness of the fiber surface on the one hand, and improves the activity of the fiber surface on the other hand. The two play a synergistic role, increase the bonding strength between the fiber and the epoxy resin, and improve the mechanical properties of the insulating rod. In addition, the probability of the generation of tiny interface defects in the fiber-reinforced insulating rod prepared by the modified aramid fiber prepared by the present invention is reduced, which can reduce the probability of surface flashover, and improve the electrical insulation performance of the insulating rod.

[0010] Preferably, the soaking time is 10 to 60 minutes.

[0011] Preferably, the immersion is carried out on a shaker at a rotation speed of 60 to 180 rpm.

[0012] Preferably, the modification treatment is followed by water washing and drying, the drying temperature being 50 to 70° C. and the drying time being 2 to 6 hours.

[0013] Preferably, the preparation method of the dopamine self-polymerization reaction liquid is as follows: under light-proof conditions, acetate is added to water to obtain an acetate solution, then periodate is added to the acetate solution and fully dissolved, and finally dopamine salt is added to obtain the dopamine self-polymerization reaction liquid after it is fully dissolved.

[0014] Preferably, the acetate is sodium acetate.

[0015] Preferably, the periodate is sodium periodate.

[0016] Preferably, the dopamine salt is dopamine hydrochloride.

[0017] The technical solution adopted by the aramid fiber insulation pull rod of the present invention is:

[0018] An aramid fiber insulating pull rod made of modified aramid fiber prepared by the modified aramid fiber preparation method as described above.

[0019] In the aramid fiber insulating pull rod of the present invention, the interface bonding strength between the modified aramid fiber and the epoxy resin matrix is ​​large, the probability of generating tiny interface defects in the material is low, the probability of surface flashover can be reduced, and the electrical insulation performance of the material is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the preparation process of dopamine self-polymerization reaction solution in Example 1;

[0021] Figure 2 Schematic diagram of the modification process of the modified aramid fiber in Example 1;

[0022] Figure 3 This is a schematic diagram of a process for preparing an aramid fiber insulating pull rod according to Example 4;

[0023] Figure 4 is the SEM image of the aramid fiber to be treated;

[0024] Figure 5 is a SEM image of the modified aramid fiber prepared in Comparative Example 1;

[0025] Figure 6 This is the SEM image of the modified aramid fiber prepared in Example 1. DETAILED DESCRIPTION

[0026] The preparation method of the modified aramid fiber of the present invention is a pioneering invention. The present invention uses the characteristic of dopamine that it can be rapidly oxidized and polymerized under the action of a strong oxidant to achieve rapid modification of the aramid fiber for insulating pull rods, which can significantly shorten the modification time of the aramid fiber. Compared with the conventional dopamine polymerization modification treatment method in an air environment using oxygen in the air as an oxidant, under the same deposition time, the polydopamine deposited on the surface of the aramid fiber treated by the present invention is more uniform, and the roughness of the fiber surface is significantly improved. In addition, the treatment method does not affect the strength of the fiber itself. The uniformly deposited polydopamine further increases the surface activity of the fiber, thereby increasing the bonding strength with the epoxy resin and improving the electrical insulation performance of the insulating pull rod.

[0027] The preparation method of the aramid fiber insulating pull rod of the present invention comprises the following steps: rolling the modified aramid fiber into a shape, then impregnating it with epoxy resin to obtain a prepreg, and finally heating and curing it to obtain the aramid fiber insulating pull rod; the heating and curing is to first heat the prepreg to 80-100°C, keep it warm for 2-4 hours, then heat it to 120-140°C, and keep it warm for 4-8 hours.

[0028] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0029] 1. The specific embodiment of the method for preparing the modified aramid fiber of the present invention is as follows:

[0030] Example 1

[0031] The preparation method of the modified aramid fiber of this embodiment specifically comprises the following steps:

[0032] (1) The aramid fiber to be treated was immersed in an acetone solution for 1 hour, then ultrasonically cleaned in deionized water for 1 hour, and finally dried in a 50°C vacuum oven for 4 hours to obtain the pretreated aramid fiber.

[0033] (2) Under light-proof conditions, sodium acetate is added to water to prepare a sodium acetate solution (pH=5), sodium periodate is then added to the sodium acetate solution to fully dissolve, and finally dopamine hydrochloride is added to obtain a dopamine self-polymerization reaction liquid after full dissolution; in the dopamine self-polymerization reaction liquid, the concentration of sodium acetate is 50 mmol / L, the concentration of sodium periodate is 2 g / L, and the concentration of dopamine hydrochloride is 2 g / L. The schematic diagram of the preparation process of the dopamine self-polymerization reaction liquid is as follows Figure 1 As shown. Since dopamine hydrochloride will undergo oxidative self-polymerization under the action of sodium periodate, the dopamine self-polymerization reaction solution needs to be prepared and used immediately.

[0034] (3) Under light-proof conditions, place the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turn on the shaker and rotate it at a speed of 120 rpm, then soak the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 30 minutes. After the soaking, take out the aramid fiber, rinse it with deionized water, and then put the rinsed aramid fiber into a 50°C oven for 2 hours to obtain modified aramid fiber. The modification process of modified aramid fiber is shown in the following figure. Figure 2 As shown. In this embodiment, periodate is used as a strong oxidant to quickly oxidize dopamine under acidic conditions to form a coating. Under alkaline conditions, dopamine will be oxidized by oxygen in the air. Acetate solution, as a buffer solution, can provide a relatively stable weakly acidic environment for the oxidation of dopamine, ensuring that the oxidative deposition of dopamine is dominated by periodate. Dopamine will oxidize after being irradiated by ultraviolet rays, which will affect the oxidative effect of the strong oxidant in the solution on dopamine and reduce the modification quality of the fiber surface. Therefore, the preparation of the dopamine self-polymerization reaction solution and the modification of the aramid fiber need to be carried out in the dark.

[0035] Example 2

[0036] The preparation method of the modified aramid fiber of this embodiment specifically comprises the following steps:

[0037] (1) The aramid fiber to be treated was immersed in an acetone solution for 2 h, then ultrasonically cleaned in deionized water for 2 h, and finally dried in a vacuum oven at 70 °C for 8 h to obtain the pretreated aramid fiber.

[0038] (2) Under light-proof conditions, sodium acetate is added to water to prepare a sodium acetate solution (pH=5), sodium periodate is then added to the sodium acetate solution to fully dissolve, and finally dopamine hydrochloride is added to obtain a dopamine self-polymerization reaction liquid after full dissolution; in the dopamine self-polymerization reaction liquid, the concentration of sodium acetate is 50 mmol / L, the concentration of sodium periodate is 4 g / L, and the concentration of dopamine hydrochloride is 4 g / L.

[0039] (3) Under light-proof conditions, placing the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turning on the shaker to rotate at a speed of 180 rpm, and then immersing the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 60 min. After the immersion is completed, taking out the aramid fiber, rinsing it with deionized water, and then placing the rinsed aramid fiber in a 70°C oven and drying it for 6 h to obtain a modified aramid fiber.

[0040] Example 3

[0041] The preparation method of the modified aramid fiber of this embodiment specifically comprises the following steps:

[0042] (1) The aramid fiber to be treated was immersed in an acetone solution for 1.5 h, then ultrasonically cleaned in deionized water for 1.5 h, and finally dried in a 60° C. vacuum oven for 6 h to obtain the pretreated aramid fiber.

[0043] (2) Under light-proof conditions, sodium acetate is added to water to prepare a sodium acetate solution (pH=5), sodium periodate is then added to the sodium acetate solution to fully dissolve, and finally dopamine hydrochloride is added to obtain a dopamine self-polymerization reaction liquid after full dissolution; in the dopamine self-polymerization reaction liquid, the concentration of sodium acetate is 50 mmol / L, the concentration of sodium periodate is 1 g / L, and the concentration of dopamine hydrochloride is 1 g / L.

[0044] (3) Under light-proof conditions, placing the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turning on the shaker to rotate at a speed of 60 rpm, and then immersing the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 10 min. After the immersion is completed, taking out the aramid fiber, rinsing it with deionized water, and then placing the rinsed aramid fiber in a 60° C. oven and drying it for 4 h to obtain a modified aramid fiber.

[0045] 2. The specific embodiments of the aramid fiber insulation pull rod of the present invention are as follows:

[0046] Example 4

[0047] The aramid fiber insulating pull rod of this embodiment is prepared by using the modified aramid fiber obtained in Example 1. The preparation process is as follows: Figure 3 As shown, the preparation method specifically comprises the following steps:

[0048] (1) The modified aramid fiber obtained in Example 1 is wound on a core rod, then placed in a tubular mold, and then subjected to epoxy resin vacuum assisted resin transfer molding to obtain a prepreg; the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg is 2:5, the epoxy resin is composed of bisphenol A type epoxy resin E51, a curing agent and a curing accelerator, the curing agent model is HY918, the curing accelerator is a benzylamine accelerator, the model is DY602, and the mass ratio of the bisphenol A type epoxy resin E51, the curing agent and the curing accelerator is 100:85:0.5.

[0049] (2) The prepreg obtained in step (1) is first heated to 80° C., kept warm for 2 h, then heated to 120° C., kept warm for 4 h, and cooled to room temperature to obtain an aramid fiber insulating pull rod.

[0050] Example 5

[0051] The aramid fiber insulating pull rod of this embodiment is prepared by using the modified aramid fiber obtained in Example 2, and the preparation method is the same as that of Example 4.

[0052] Example 6

[0053] The aramid fiber insulating pull rod of this embodiment is prepared by using the modified aramid fiber obtained in embodiment 3, and the preparation method is the same as that in embodiment 4.

[0054] Comparative Example 1

[0055] The preparation method of the aramid fiber insulating pull rod of this comparative example specifically comprises the following steps:

[0056] (1) The aramid fiber to be treated was immersed in an acetone solution for 1 hour, then ultrasonically cleaned in deionized water for 1 hour, and finally dried in a 50°C oven for 4 hours to obtain the pretreated aramid fiber.

[0057] (2) Under light-proof conditions, sodium acetate is added into water to fully dissolve, and finally dopamine hydrochloride is added to obtain a dopamine self-polymerization reaction liquid after full dissolution; in the dopamine self-polymerization reaction liquid, the concentration of sodium acetate is 50 mmol / L, and the concentration of dopamine hydrochloride is 2 g / L.

[0058] (3) Under light-proof conditions, placing the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turning on the oscillation at a frequency of 120 rpm, and then immersing the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 30 min. After the immersion, taking out the aramid fiber, rinsing it with deionized water, and then drying the rinsed aramid fiber in a 50° C. oven for 2 h to obtain a modified aramid fiber.

[0059] (4) Winding the modified aramid fiber obtained in step (3) on a tubular mold and subjecting it to vacuum impregnation with epoxy resin to obtain a prepreg; the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg is the same as the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg of Example 1.

[0060] (5) The prepreg obtained in step (4) is first heated to 80° C., kept warm for 2 h, then heated to 120° C., kept warm for 4 h, and cooled to room temperature to obtain an aramid fiber insulating pull rod.

[0061] Comparative Example 2

[0062] The preparation method of the aramid fiber insulating pull rod of this comparative example specifically comprises the following steps:

[0063] (1) The aramid fiber to be treated was immersed in an acetone solution for 1 hour, then ultrasonically cleaned in deionized water for 1 hour, and finally dried in a 50°C oven for 4 hours to obtain the pretreated aramid fiber.

[0064] (2) In a light-proof condition, dopamine hydrochloride powder is added to deionized water to dissolve to obtain a 1 g / L dopamine hydrochloride solution, Tris buffer is slowly added to the dopamine hydrochloride solution multiple times, the pH value is gradually measured, and the pH is adjusted to 8.5 to obtain a dopamine self-polymerization reaction solution.

[0065] (3) Under light-proof conditions, place the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turn on the oscillation, and the oscillation frequency is 60 rpm. Then, immerse the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 10 minutes. After the immersion, take out the aramid fiber, rinse it with deionized water, and then put the rinsed aramid fiber into a 50°C oven and dry it for 2 hours to obtain a modified aramid fiber.

[0066] (4) Winding the modified aramid fiber obtained in step (3) on a tubular mold and subjecting it to vacuum impregnation with epoxy resin to obtain a prepreg; the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg is the same as the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg of Example 1.

[0067] (5) The prepreg obtained in step (4) is first heated to 80° C., kept warm for 2 h, then heated to 120° C., kept warm for 4 h, and cooled to room temperature to obtain an aramid fiber insulating pull rod.

[0068] Comparative Example 3

[0069] The difference between the preparation method of the aramid fiber insulating rod of this comparative example and the preparation method of the aramid fiber insulating rod of Example 4 is that in the preparation method of the aramid fiber insulating rod of this comparative example, the modified aramid fiber obtained in Example 1 is replaced by the pretreated aramid fiber obtained in step (1) of Example 1.

[0070] Comparative Example 4

[0071] The preparation method of the aramid fiber insulating pull rod of this comparative example specifically comprises the following steps:

[0072] (1) The aramid fiber to be treated was immersed in an acetone solution for 1 hour, then ultrasonically cleaned in deionized water for 1 hour, and finally dried in a 50°C vacuum oven for 4 hours to obtain the pretreated aramid fiber.

[0073] (2) Under natural light, sodium acetate is added to water to prepare a sodium acetate solution (pH=5), sodium periodate is then added to the sodium acetate solution to fully dissolve, and finally dopamine hydrochloride is added to obtain a dopamine self-polymerization reaction liquid after full dissolution; in the dopamine self-polymerization reaction liquid, the concentration of sodium acetate is 50 mmol / L, the concentration of sodium periodate is 2 g / L, and the concentration of dopamine hydrochloride is 2 g / L.

[0074] (3) Under natural light, placing the container containing the dopamine self-polymerization reaction liquid obtained in step (2) on a shaker, turning on the shaker to rotate at a speed of 120 rpm, and then immersing the pretreated aramid fiber obtained in step (1) in the dopamine self-polymerization reaction liquid for 30 minutes. After the immersion is completed, taking out the aramid fiber, rinsing it with deionized water, and then placing the rinsed aramid fiber in a 50°C oven and drying it for 2 hours to obtain a modified aramid fiber.

[0075] (4) The modified aramid fiber is wound on a core rod, and then placed in a tubular mold, and then epoxy resin vacuum-assisted resin transfer molding is performed to obtain a prepreg; the mass ratio of the modified aramid fiber to the epoxy resin in the prepreg is 2:5, the epoxy resin is composed of bisphenol A type epoxy resin E51, a curing agent and a curing accelerator, the curing agent model is HY918, the curing accelerator is a benzylamine accelerator, the model is DY602, and the mass ratio of the bisphenol A type epoxy resin E51, the curing agent and the curing accelerator is 100:85:0.5.

[0076] (5) The prepreg is first heated to 80°C, kept at this temperature for 2 hours, then heated to 120°C, kept at this temperature for 4 hours, and cooled to room temperature to obtain an aramid fiber insulating rod.

[0077] Experimental Example 1

[0078] In this experimental example, a scanning electron microscope was used to characterize the appearance of the modified aramid fiber prepared in Example 1 and Comparative Example 1 and the aramid fiber to be treated. The results are as follows: Figure 4-6 shown. Figure 4 is the SEM image of the aramid fiber to be treated. Figure 5 is the SEM image of the modified aramid fiber prepared in Comparative Example 1, Figure 6 This is a SEM image of the modified aramid fiber prepared in Example 1. Figure 4-6 It can be seen that the surface morphology of the modified aramid fiber prepared in Comparative Example 1 is relatively close to the aramid fiber to be treated, the polydopamine deposition is uneven, there are small fragments, most of the aramid fiber surface is still exposed, and the modification effect is not obvious. The surface roughness of the modified aramid fiber prepared in Example 1 is higher, and the polydopamine deposition is more uniform, which is beneficial to improve the interface bonding performance between the fiber and the epoxy resin.

[0079] Experimental Example 2

[0080] In this experimental example, the mechanical properties and electrical insulation properties of the aramid fiber insulating pull rods prepared in various embodiments and comparative examples were tested, and the results are shown in Table 1. The tensile strength was tested according to the provisions of the standard GB / T 3354-2014, and the breakdown strength was tested according to the provisions of the standard GB / T1408.1-2006.

[0081] Table 1 Mechanical properties and electrical insulation properties of aramid fiber insulation rods prepared in various embodiments and comparative examples

[0082] Aramid fiber insulation pull rod Tensile strength(MPa) Breakdown strength (kV / mm) Example 4 638 51.23 Example 5 593 44.68 Example 6 580 47.37 Comparative Example 1 486 38.7 Comparative Example 2 557 40.41 Comparative Example 3 465 37.85 Comparative Example 4 524 38.74

[0083] As shown in Table 1, the performance of the modified aramid fiber composite material prepared in Comparative Example 1 is not significantly different from that of Comparative Example 3. This is because dopamine cannot be oxidized under acidic conditions, so there is no obvious improvement effect on the performance of the material. In Comparative Example 2, since oxygen can promote the oxidation deposition of dopamine under alkaline conditions, the performance of the composite material is significantly improved compared with Comparative Examples 1 and 3. However, due to the low oxidation efficiency of oxygen, the mechanical properties and insulation properties of the composite material are still quite different from those of Examples 4, 5, and 6. Due to the combined effect of light conditions and strong oxidants, the oxidation rate of dopamine is too fast, and the amount of deposition on the surface of the aramid fiber is reduced. Therefore, the performance of Comparative Example 4 is lower than that of the examples. By comparing all the examples and comparative examples, it can be seen that the use of strong oxidants can significantly promote the oxidation deposition of dopamine on aramid fibers and improve the mechanical properties and insulation properties of the fiber composite material.

Claims

1. A method for preparing modified aramid fiber, characterized in that: The following steps are involved: Under light-proof conditions, the aramid fiber is immersed in a dopamine self-polymerization reaction liquid for modification treatment to obtain a modified aramid fiber; the dopamine self-polymerization reaction liquid consists of acetate, periodate, dopamine salt and water, the concentration of acetate is 40-60 mmol / L, the concentration of periodate is 1-4 g / L, and the concentration of dopamine salt is 1-4 g / L.

2. The method for preparing modified aramid fiber according to claim 1, characterized in that: The soaking time is 10 to 60 minutes.

3. The method for preparing modified aramid fiber according to claim 1 or 2, characterized in that: The soaking is carried out on a shaking table with a rotation speed of 60 to 180 rpm.

4. The method for preparing modified aramid fiber according to claim 1, characterized in that: After the modification treatment, the modified product is washed with water and dried at a temperature of 50 to 70° C. for 2 to 6 hours.

5. The method for preparing modified aramid fiber according to claim 1, characterized in that: The preparation method of the dopamine self-polymerization reaction liquid is as follows: under light-proof conditions, acetate is added into water to obtain an acetate solution, then periodate is added into the acetate solution to fully dissolve, and finally dopamine salt is added to obtain the dopamine self-polymerization reaction liquid after it is fully dissolved.

6. The method for preparing modified aramid fiber according to claim 1 or 5, characterized in that: The acetate is sodium acetate.

7. The method for preparing modified aramid fiber according to claim 1 or 5, characterized in that: The periodate is sodium periodate.

8. The method for preparing modified aramid fiber according to claim 1 or 5, characterized in that: The dopamine salt is dopamine hydrochloride.

9. An aramid fiber insulating pull rod of modified aramid fiber prepared by the method for preparing modified aramid fiber according to any one of claims 1 to 8.

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