Surface-modified polymeric insulators and methods of making the same

Abstract

The application provides a surface-modified polymer insulator and a preparation method thereof, and can solve the problem that the existing surface chemical modification method cannot prepare a chemical component with a high vacuum surface flashover voltage on the surface of the polymer insulator, and the voltage resistance is not obviously improved and is unstable. The insulator comprises a polymer insulator body and a high-voltage-resistant characteristic molecular group grafted on the surface of the polymer insulator body. The material of the polymer insulator body can undergo a hydrolysis or aminolysis reaction. The high-voltage-resistant characteristic molecular group forms a flexible two-dimensional molecular film structure on the surface of the polymer insulator body, and is used for reducing the secondary electron emission coefficient and gas adsorption amount of the surface of the polymer insulator body. The preparation method comprises the following steps: preparing a polymer insulator body; placing the polymer insulator body into a hydrolysis or aminolysis system for reaction; cleaning and drying the obtained polymer insulator after the reaction; reacting with an acylation reagent; and finally performing cleaning and drying treatment.

Description

Technical Field

[0001] This invention relates to an insulator and its preparation method, specifically to a surface-modified polymer insulator and its preparation method. Background Technology

[0002] Vacuum surface flashover is a common surface discharge phenomenon in vacuum high-voltage devices such as pulsed power supplies, high-power microwave (HPM) transmission windows, klystrons, and accelerators. This discharge phenomenon significantly reduces the withstand voltage of the dielectric surface, making it the most vulnerable area in the device. Furthermore, this discharge phenomenon is a bottleneck problem faced by vacuum high-voltage devices. Currently, it is generally believed that secondary electron emission and multiplication on the insulator surface are important processes in the formation of surface flashover, and reducing secondary electron emission can effectively improve the surface flashover voltage. The secondary electron emission coefficient (SEY), as a surface physical property, is determined by the surface state of the insulator. Therefore, in order to reduce the secondary electron emission coefficient and increase the vacuum surface flashover voltage, researchers usually modify the surface of insulators. Among them, the modification of the chemical composition of the insulator surface, as a method that can change the inherent secondary electron emission coefficient of the surface, plays an important role in improving the vacuum surface withstand voltage level of insulators (see: H. Craig Miller, "Flashover of insulators in vacuum: the last twenty years," IEEE Transactions on Dielectrics & Electrical Insulation 22(6), 3641-3657 (2016). Shengtao Li, Yongjie Nie and Daomin Min et al., "Research Progress on Vacuum Surface Flashover of Solid Dielectrics," Transactions of China Electrotechnical Society 32(8), 1-9 (2017).).

[0003] Commonly used chemical modification methods for vacuum insulator surfaces include fluorination (including direct gas fluorination, plasma-assisted fluorination, and fluorination of fluorinated organic molecules), coating preparation, plasma treatment, and ion implantation (see: Tao Shao, Wenjin Yang and Cheng Zhang et al., "Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge," ApplPhysLett 105(7), 71607(2014). Chao Wang, JiaGuo and Wen-Dong Li et al., "Enhancing Electrical Strength of AcrylatePolymer by Using Fluorinated Monomer as Surface Modifier," Mater Lett 249(15), 17-20(2019).). Through these methods, various chemical components are modified onto the surface of vacuum insulators. However, since the relationship between surface molecular structure and vacuum surface withstand voltage characteristics of insulators has not yet been established, it is unknown which surface chemical components can effectively improve the vacuum surface flashover voltage of insulators. Therefore, existing surface chemical modification methods cannot prepare chemical components with high vacuum surface flashover voltage on the surface of polymer insulators, and the withstand voltage improvement is not significant and unstable. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem that existing surface chemical modification methods cannot prepare chemical compositions with high vacuum surface flashover voltage on the surface of polymer insulators, and the withstand voltage improvement is not significant and unstable. The invention provides a surface-modified polymer insulator and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A surface-modified polymer insulator, characterized by:

[0007] It includes the polymer insulator body and high-voltage-resistant molecular groups grafted onto the surface of the polymer insulator body;

[0008] The material of the polymer insulator body can undergo hydrolysis or aminolysis reaction;

[0009] The high-voltage-resistant molecular groups are those that can be grafted onto the surface of the polymer insulator body according to the chemical reaction characteristics of the polymer insulator body material; the high-voltage-resistant molecular groups form a flexible two-dimensional molecular film structure on the surface of the polymer insulator body, which is used to reduce the secondary electron emission coefficient and gas adsorption amount on the surface of the polymer insulator body.

[0010] Furthermore, the polymer insulator body is made of polyamide, polyimide, polyetherimide, polyester, or epoxy resin;

[0011] The high-pressure-resistant molecular groups are long-chain alkyl, fluorocarbon, or delocalized electron groups.

[0012] Meanwhile, the present invention also provides a method for preparing the above-mentioned surface-modified polymer insulator, which is characterized by including the following steps:

[0013] Step 1: Prepare the polymer insulator body;

[0014] Step 2: Place the polymer insulator body into a 0.5 mol / L to 2 mol / L hydrolysis system and stir the reaction at 50℃ to 80℃ for 4h to 8h to obtain the hydrolyzed polymer insulator.

[0015] Alternatively, the polymer insulator body can be placed in an aminolysis system of 10 mg / ml to 50 mg / ml and stirred at 50°C to 60°C for 3 to 6 hours to obtain the aminolysis polymer insulator.

[0016] Step 3: Clean and dry the polymer insulator obtained in Step 2;

[0017] Step 4: Place the dried polymer insulator from Step 3 into a non-polar organic solvent. Add the acylation reagent according to the mass-volume ratio of acylation reagent to non-polar organic solvent of 1g:100mL to 2g:100mL. Stir the reaction at room temperature for at least 2 hours to obtain a polymer insulator with high voltage-resistant molecular groups grafted onto its surface.

[0018] Step 5: Clean and dry the polymer insulator obtained in step 4 to complete the preparation of the surface-modified polymer insulator.

[0019] Furthermore, in step 2, the hydrolysis system is an acidic solution or an alkaline solution; the aminolysis system is an aqueous solution of diamine or an ethanolic solution of diamine.

[0020] In step 4, the reaction is stirred for at least 2 hours and then allowed to stand for at least 12 hours.

[0021] The nonpolar organic solvent is n-octane, toluene, or chloroform; the acylation reagent is octadecyl acyl chloride, perfluoroundecyl acyl chloride, perfluorooctyl acyl chloride, or phenethyl acyl chloride.

[0022] Further, in step 2, the acidic solution is a hydrochloric acid solution or a sulfuric acid solution; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the aqueous solution of the diamine is an aqueous solution of ethylenediamine or an aqueous solution of hexamethylenediamine; and the ethanolic solution of the diamine is an ethanolic solution of ethylenediamine or an ethanolic solution of hexamethylenediamine.

[0023] Step 3 specifically involves placing the polymer insulator obtained in step 2 into deionized water, ultrasonically washing it for at least 30 minutes, and then drying it at 50℃~80℃ for at least 12 hours.

[0024] Further, step 5 specifically involves washing the polymer insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for at least 30 minutes, and then drying it at 50℃~80℃ for at least 12 hours to complete the preparation of the surface-modified polymer insulator.

[0025] Step 1 specifically involves machining the polymer insulating material into a polymer insulator body with a predetermined geometric structure and size.

[0026] Further, step 1 specifically involves machining the epoxy resin insulating material into an epoxy resin insulator body with a predetermined geometric structure and size.

[0027] Step 2 specifically involves placing the epoxy resin insulator body into a 2 mol / L sodium hydroxide solution and stirring the mixture at 80°C for 4 hours to obtain the hydrolyzed epoxy resin insulator.

[0028] Step 3 specifically involves placing the epoxy resin insulator obtained in step 2 into deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours.

[0029] Further, step 4 specifically involves placing the dried epoxy resin insulator from step 3 into n-octane, adding perfluoroundecyl chloride at a mass-to-volume ratio of 1g:100mL, stirring and reacting at room temperature for 2 hours, and then allowing it to stand for 12 hours to obtain an epoxy resin insulator with perfluoroundecyl chloride grafted onto its surface.

[0030] Step 5 specifically involves washing the epoxy resin insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours to complete the preparation of the surface-modified epoxy resin insulator.

[0031] Further, step 1 specifically involves machining the polyamide insulating material into a polyamide insulator body with a predetermined geometric structure and dimensions.

[0032] Step 2 specifically involves placing the polyamide insulator body into a 50 mg / ml hexamethylenediamine solution and stirring the mixture at 60°C for 3 hours to obtain the amino-hydrolyzed polyamide insulator.

[0033] Step 3 specifically involves placing the polyamide insulator obtained in step 2 into deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours.

[0034] Further, step 4 specifically involves placing the dried polyamide insulator from step 3 into n-octane, adding octadecyl chloride at a mass-to-volume ratio of 1 g to 100 mL, stirring and reacting at room temperature for 2 hours, and then allowing it to stand for 12 hours to obtain a polyamide insulator with octadecyl chloride grafted onto its surface.

[0035] Step 5 specifically involves washing the polyamide insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours to complete the preparation of the surface-modified polyamide insulator.

[0036] The beneficial effects of this invention are:

[0037] 1. This invention provides a surface-modified polymer insulator and its preparation method. In this invention, high withstand voltage molecular groups are grafted onto the surface of the polymer insulator body, which can reduce the secondary electron emission coefficient and gas adsorption amount on the surface of the polymer insulator body, thereby achieving a significant improvement in the vacuum surface withstand voltage performance of the insulator. Moreover, the withstand voltage improvement is relatively stable.

[0038] 2. Compared with the traditional method of preparing a modified layer by using intermolecular interaction forces and mechanical bonding to the surface of the insulator body, the high voltage withstand molecular groups in this invention are chemically linked to the insulator body. The molecular modified layer will not change over time and has high bonding strength and stability.

[0039] 3. In this invention, liquid phase reaction conditions are adopted, and a uniform chemical reaction can occur at the location where the insulator body contacts the liquid phase. The grafted high withstand voltage molecular groups are evenly distributed, and the flashover voltage is improved and stabilized. In addition, liquid phase reaction conditions can be used for insulators of various shapes, and have a wide range of applications.

[0040] 4. In this invention, the grafting of high voltage-resistant molecular groups onto the surface of the insulator body will not damage the bulk structure of the insulator and can ensure the mechanical strength of the insulator; it can play a role as soon as the grafting is completed, without changing any structural parameters of the original insulation system. Attached Figure Description

[0041] Figure 1 This is a reaction route diagram of the preparation method of surface-modified epoxy resin insulator in Embodiment 1 of the present invention (R is perfluoroundecyl); in the diagram, Polymer-OH represents the hydroxyl-containing epoxy resin after hydrolysis;

[0042] Figure 2 This is a reaction route diagram of the preparation method of surface-modified epoxy resin insulators in other embodiments of the present invention (R is a high voltage withstand molecular group such as long-chain alkyl, fluorocarbon or delocalized electron group); in the figure, HO-Polymer-NH2 represents epoxy resin containing amino and hydroxyl groups after aminolysis;

[0043] Figure 3 This is a reaction route diagram of the preparation method of surface-modified nylon insulator in Embodiment 2 of the present invention (R is octadecyl); in the diagram, Polymer-NH2 represents amino-containing nylon after aminolysis;

[0044] Figure 4 This is a reaction route diagram of the preparation method of surface-modified polyimide insulator in Example 3 of the present invention (R is phenylethyl); in the diagram, Polymer-NH2 represents amino-containing polyimide after aminolysis;

[0045] Figure 5 This is a reaction route diagram of the preparation method of surface-modified nylon insulator in Embodiment 5 of the present invention (R is octadecyl); in the diagram, Polymer-NH2 represents amino-containing nylon after hydrolysis;

[0046] Figure 6 This is a reaction route diagram of the preparation method of surface-modified polyimide insulator in Example 6 of the present invention (R is phenylethyl); in the diagram, Polymer-NH2 represents amino-containing polyimide after hydrolysis. Detailed Implementation

[0047] Example 1

[0048] A surface-modified polymer insulator includes a polymer insulator body and high-voltage-resistance molecular groups grafted onto the surface of the polymer insulator body. The polymer insulator body is capable of hydrolysis or aminolysis. The high-voltage-resistance molecular groups are those that can be grafted onto the surface of the polymer insulator body based on the chemical reactivity of the polymer insulator body material. These high-voltage-resistance molecular groups are regularly arranged on the surface of the polymer insulator body, forming a flexible two-dimensional molecular film structure to reduce the secondary electron emission coefficient and gas adsorption amount on the surface of the polymer insulator body. In this embodiment, the polymer insulator body is made of epoxy resin, and the high-voltage-resistance molecular group is perfluoroundecyl. Driven by intermolecular forces, the perfluoroundecyl groups grafted onto the surface of the epoxy resin insulator body are regularly arranged on the surface of the epoxy resin insulator body, forming a flexible two-dimensional molecular film structure. Because the molecular groups of this structure can swing and adjust spontaneously within a certain range, it has a certain degree of flexibility. This flexible two-dimensional molecular film structure can give the insulator surface higher stability and reduce the adsorption of gas molecules. That is, it can reduce the secondary electron emission coefficient and gas adsorption amount on the surface of the epoxy resin insulator, thereby inhibiting the development of vacuum surface flashover on the insulator surface and improving the vacuum surface withstand voltage performance of the epoxy resin insulator.

[0049] This embodiment also provides a method for preparing the above-mentioned surface-modified epoxy resin insulator, including the following steps:

[0050] Step 1: The epoxy resin insulating material is processed into an epoxy resin insulator body with a thickness of 5mm and a diameter of 30mm by mechanical processing.

[0051] Step 2: Place the epoxy resin insulator body into a 2 mol / L sodium hydroxide solution and stir for 4 hours at 80°C to hydrolyze it, thereby obtaining the hydrolyzed epoxy resin insulator.

[0052] Step 3: Place the epoxy resin insulator obtained in Step 2 into deionized water, ultrasonically wash for 30 minutes, and then dry it in an oven at 80°C for 12 hours.

[0053] Step 4: Place the dried epoxy resin insulator from Step 3 into 50 mL of n-octane, add 0.5 g of perfluoroundecyl chloride according to the mass-volume ratio of perfluoroundecyl chloride to n-octane of 1 g: 100 mL, stir and react for 2 h at room temperature, then let stand for 12 h to carry out amidation, and obtain epoxy resin insulator with perfluoroundecyl chloride grafted on the surface.

[0054] Step 5: After washing the epoxy resin insulator obtained in step 4 with a large amount of tap water, place it in deionized water and ultrasonically wash for 30 minutes. Then, use an oven to dry it at 80°C for 12 hours to complete the preparation of the surface-modified epoxy resin insulator, which is designated as "perfluoroundecyl grafted insulator 1".

[0055] Figure 1 This is a reaction route diagram of the preparation method of the surface-modified epoxy resin insulator in this embodiment, which is composed of... Figure 1 It is known that, based on the chemical reaction characteristics of epoxy resin, hydroxyl groups are grafted onto the epoxy resin molecular chain by hydrolysis, and then an acyl chloride with a perfluoroundecyl (i.e., fluorocarbon) end group is grafted onto the surface of the epoxy resin insulator body through the esterification reaction of the hydroxyl group and the acyl chloride. This reduces the secondary electron emission coefficient and surface gas adsorption of the insulator body surface, thereby improving the vacuum surface withstand voltage performance of the epoxy resin insulator.

[0056] Figure 2 This is a reaction route diagram for the preparation method of surface-modified epoxy resin insulators in other embodiments. Based on the chemical reaction characteristics of epoxy resin, amino and hydroxyl groups can also be grafted onto the epoxy resin molecular chain by aminolysis. Then, acyl chlorides with high voltage withstand properties, such as long-chain alkyl, fluorocarbon, or delocalized electron groups, are grafted onto the surface of the epoxy resin insulator body through amidation reaction of amino groups and esterification reaction of hydroxyl groups. This reduces the secondary electron emission coefficient and surface gas adsorption of the insulator body surface, thereby improving the vacuum surface withstand voltage performance of the epoxy resin insulator.

[0057] Example 2

[0058] The difference between the polymer insulator in this embodiment and the polymer insulator in Embodiment 1 is as follows:

[0059] The polymer insulator body is made of polyamide, specifically nylon, and the molecular group with high voltage resistance is octadecyl.

[0060] This embodiment also provides a method for preparing surface-modified nylon insulators, including the following steps:

[0061] Step 1: Through mechanical processing, the nylon insulating material is made into a nylon insulator body with a thickness of 5mm and a diameter of 30mm.

[0062] Step 2: Place the nylon insulator body into a 50 mg / ml hexamethylenediamine aqueous solution and stir for 3 hours at 60°C to carry out aminolysis, thereby obtaining the aminolyzed nylon insulator.

[0063] Step 3: Place the nylon insulator obtained in step 2 into deionized water, ultrasonically wash for 30 minutes, and then dry it in an oven at 80°C for 12 hours.

[0064] Step 4: Place the dried nylon insulator from Step 3 into 50 mL of n-octane. Add 0.5 g of octadecanyl chloride at a mass-to-volume ratio of 1 g to 100 mL of octadecanyl chloride. Stir and react for 2 h at room temperature, then let stand for 12 h to perform amidation, and obtain a nylon insulator with octadecanyl chloride grafted onto its surface.

[0065] Step 5: After washing the nylon insulator obtained in step 4 with a large amount of tap water, place it in deionized water and ultrasonically wash for 30 minutes. Then, use an oven to dry it at 80°C for 12 hours to complete the preparation of the surface-modified nylon insulator, which is referred to as "octadecyl grafted insulator 2".

[0066] Figure 3 This is a reaction route diagram of the preparation method of the surface-modified nylon insulator in this embodiment. According to the chemical reaction characteristics of nylon, amino groups are grafted onto the nylon molecular chain by amino hydrolysis. Then, octadecyl groups are grafted onto the nylon molecular chain by the amidation reaction of amino groups and octadecyl chloride.

[0067] Example 3

[0068] The difference between the polymer insulator in this embodiment and the polymer insulator in Embodiment 1 is as follows:

[0069] The polymer insulator body is made of polyimide, and the high voltage withstand characteristic molecular group is phenylethyl (i.e., delocalized electron group). In other embodiments, the polyimide material can be replaced with polyetherimide.

[0070] This embodiment also provides a method for preparing surface-modified polyimide insulators, including the following steps:

[0071] Step 1: Through mechanical processing, the polyimide insulating material is made into a polyimide insulator body with a thickness of 5mm and a diameter of 30mm.

[0072] Step 2: The polyimide insulator body is placed in a 30 mg / ml aqueous solution of ethylenediamine and stirred at 55°C for 4 hours to undergo aminolysis, obtaining the aminolyzed polyimide insulator. In other embodiments, the aqueous solution of ethylenediamine in this step can be replaced with an aqueous solution of hexamethylenediamine.

[0073] Step 3: Place the polyimide insulator obtained in step 2 into deionized water, ultrasonically wash for 35 minutes, and then dry it in an oven at 65°C for 12.5 hours.

[0074] Step 4: Place the dried polyimide insulator from Step 3 into 50 mL of toluene. Add 0.75 g of phenylethyl chloride according to the mass-volume ratio of phenylethyl chloride to toluene of 1.5 g: 100 mL. Stir and react for 2 h at room temperature, then let stand for 13 h to carry out amidation, and obtain a polyimide insulator with phenylethyl chloride grafted on the surface.

[0075] Step 5: After washing the polyimide insulator obtained in step 4 with a large amount of tap water, place it in deionized water and ultrasonically wash for 35 minutes. Then, use an oven to dry it at 65°C for 12.5 hours to complete the preparation of the surface-modified polyimide insulator, which is designated as "Phenylethyl grafted insulator 3".

[0076] Figure 4 This is a reaction route diagram for the preparation method of the surface-modified polyimide insulator in this embodiment. The reaction principle explained in this diagram is the same as that in Example 2. Figure 3 The reaction principle is explained similarly.

[0077] Example 4

[0078] The difference between the polymer insulator in this embodiment and the polymer insulator in Embodiment 1 is as follows:

[0079] The polymer insulator body is made of polyester, and the high voltage withstand characteristic molecular group is perfluorooctyl.

[0080] This embodiment also provides a method for preparing surface-modified polyester insulators, including the following steps:

[0081] Step 1: The polyester insulation material is processed into a polyester insulator body with a thickness of 5mm and a diameter of 30mm by mechanical processing.

[0082] Step 2: Place the polyester insulator body into an ethanol solution of 10 mg / ml ethylenediamine and stir for 6 hours at 50°C to perform aminolysis, obtaining the aminolyzed polyester insulator. In other embodiments, the ethanol solution of ethylenediamine in this step can be replaced with an ethanol solution of hexamethylenediamine.

[0083] Step 3: Place the polyester insulator obtained in Step 2 into deionized water, ultrasonically wash for 40 minutes, and then dry it in an oven at 50°C for 13 hours.

[0084] Step 4: Place the dried polyester insulator from Step 3 into 50 mL of chloroform. Add 1 g of perfluorooctyl chloride according to the mass-volume ratio of perfluorooctyl chloride to chloroform of 2 g: 100 mL. Stir and react for 2.5 h at room temperature, then let stand for 12 h to carry out amidation, and obtain a polyester insulator with perfluorooctyl chloride grafted on the surface.

[0085] Step 5: After washing the polyester insulator obtained in step 4 with a large amount of tap water, place it in deionized water and ultrasonically wash for 40 minutes. Then, use an oven to dry it at 50°C for 13 hours to complete the preparation of the surface-modified polyester insulator, which is designated as "perfluorooctyl grafted insulator 4".

[0086] The reaction principle explanation in this embodiment is the same as in Embodiment Two. Figure 3 The reaction principle is explained similarly. In other embodiments, polyester insulators with perfluorooctyl groups grafted onto their surface can also be obtained via a hydrolysis-esterification route, and the reaction principle is explained as in Example 1. Figure 1 The reaction principle is explained in the same way.

[0087] Example 5

[0088] The polymer insulator in this embodiment is the same as the polymer insulator in Embodiment 2.

[0089] The difference between the preparation method in this embodiment and the preparation method in Example 2 is as follows:

[0090] Step 2 specifically involves placing the nylon insulator body into a 1 mol / L potassium hydroxide solution and stirring the reaction at 65°C for 6 hours to hydrolyze the nylon insulator, thereby obtaining the hydrolyzed nylon insulator.

[0091] In step 3, the ultrasonic washing time is 40 minutes, the drying temperature is 50°C, and the drying time is 13 hours.

[0092] Step 4 is as follows: Place the dried nylon insulator from step 3 into 50 mL of toluene, add 1 g of octadecyl chloride according to the mass-volume ratio of 2 g to 100 mL of octadecyl chloride, stir and react for 2.5 h at room temperature, then let stand for 12 h to carry out amidation, and obtain nylon insulators with octadecyl chloride grafted on the surface.

[0093] In step 5, the ultrasonic washing time is 40 min, the drying temperature is 50℃, and the drying time is 13 h. The prepared surface-modified nylon insulator is designated as "octadecyl grafted insulator 5".

[0094] Figure 5 This is a reaction route diagram of the preparation method of the surface-modified nylon insulator in this embodiment. According to the chemical reaction characteristics of nylon, the amino group is grafted onto the nylon molecular chain by hydrolysis. Then, the octadecyl group is grafted onto the nylon molecular chain by the amidation reaction of the amino group and octadecyl chloride.

[0095] Example 6

[0096] The polymer insulator in this embodiment is the same as the polymer insulator in Embodiment 3.

[0097] The difference between the preparation method in this embodiment and the preparation method in Example 3 is as follows:

[0098] Step 2 specifically involves placing the polyimide insulator body into a 0.5 mol / L hydrochloric acid solution and stirring at 50°C for 8 hours to hydrolyze the mixture, obtaining the hydrolyzed polyimide insulator. In other embodiments, the hydrochloric acid solution can be replaced with a sulfuric acid solution.

[0099] Step 4 is as follows: Place the dried polyimide insulator from step 3 into 50 mL of chloroform, add 0.75 g of phenylethyl chloride according to the mass-volume ratio of phenylethyl chloride to chloroform of 1.5 g: 100 mL, stir and react for 2 h at room temperature, then let stand for 13 h to carry out amidation, and obtain a polyimide insulator with phenylethyl chloride grafted on the surface.

[0100] In step 5, the surface-modified polyimide insulator prepared is designated as "phenylethyl grafted insulator 6".

[0101] Figure 6 This is a reaction route diagram for the preparation method of the surface-modified polyimide insulator in this embodiment. The reaction principle explained in this diagram is the same as that in Example 5. Figure 5 The reaction principle is explained in the same way.

[0102] The surface-modified polymer insulators prepared in Examples 1 to 6 above, along with the corresponding polymer insulator bodies, were subjected to vacuum surface flashover voltage tests on a vacuum surface flashover voltage test bench with a pulse width of 500 ns. The flashover voltage test results are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] As shown in Table 1, the flashover voltage of the insulator with high voltage-resistant molecular groups grafted onto its surface according to the present invention is increased by 30% to 40% compared with that of the polymer insulator body, indicating that the surface-modified polymer insulator prepared by the present invention can effectively improve the flashover voltage of the insulator.

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a surface-modified polymer insulator, wherein the surface-modified polymer insulator comprises a polymer insulator body and high-voltage-resistance molecular groups grafted onto the surface of the polymer insulator body; the polymer insulator body is capable of hydrolysis or aminolysis; the high-voltage-resistance molecular groups are high-voltage-resistance molecular groups that can be grafted onto the surface of the polymer insulator body according to the chemical reaction characteristics of the polymer insulator body material; the high-voltage-resistance molecular groups form a flexible two-dimensional molecular film structure on the surface of the polymer insulator body to reduce the secondary electron emission coefficient and gas adsorption amount on the surface of the polymer insulator body; the polymer insulator body is made of polyamide, polyimide, polyetherimide, polyester, or epoxy resin; the high-voltage-resistance molecular groups are long-chain alkyl, fluorocarbon, or delocalized electron groups; characterized in that... Includes the following steps: Step 1: Prepare the polymer insulator body; Step 2: Place the polymer insulator body into a 0.5 mol / L to 2 mol / L hydrolysis system and stir the reaction at 50℃ to 80℃ for 4h to 8h to obtain the hydrolyzed polymer insulator. Alternatively, the polymer insulator body can be placed in an aminolysis system of 10 mg / ml to 50 mg / ml and stirred for 3 to 6 hours at 50°C to obtain an aminolysis polymer insulator. Step 3: Clean and dry the polymer insulator obtained in Step 2; Step 4: Place the dried polymer insulator from Step 3 into a non-polar organic solvent. Add the acylation reagent at a mass-to-volume ratio of 1g:100mL to 2g:100mL. Stir and react at room temperature for at least 2 hours to obtain a polymer insulator with high voltage-resistant molecular groups grafted onto its surface. The acylation reagent is octadecyl acyl chloride, perfluoroundecyl acyl chloride, perfluorooctyl acyl chloride, or phenylethyl acyl chloride. Step 5: Clean and dry the polymer insulator obtained in step 4 to complete the preparation of the surface-modified polymer insulator.

2. The method for preparing the surface-modified polymer insulator according to claim 1, characterized in that: In step 2, the hydrolysis system is an acidic solution or an alkaline solution; the aminolysis system is an aqueous solution of diamine or an ethanolic solution of diamine. In step 4, the reaction is stirred for at least 2 hours and then allowed to stand for at least 12 hours. The nonpolar organic solvent is n-octane, toluene, or chloroform.

3. The method for preparing the surface-modified polymer insulator according to claim 2, characterized in that: In step 2, the acidic solution is a hydrochloric acid solution or a sulfuric acid solution; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the aqueous solution of the diamine is an aqueous solution of ethylenediamine or an aqueous solution of hexamethylenediamine; and the ethanolic solution of the diamine is an ethanolic solution of ethylenediamine or an ethanolic solution of hexamethylenediamine. Step 3 specifically involves immersing the polymer insulator obtained in step 2 in deionized water, ultrasonically washing it for at least 30 minutes, and then drying it at 50℃~80℃ for at least 12 hours.

4. The method for preparing the surface-modified polymer insulator according to claim 3, characterized in that: Step 5 specifically involves washing the polymer insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for at least 30 minutes, and then drying it at 50℃~80℃ for at least 12 hours to complete the preparation of the surface-modified polymer insulator. Step 1 specifically involves machining the polymer insulating material into a polymer insulator body with a predetermined geometric structure and size.

5. The method for preparing the surface-modified polymer insulator according to claim 4, characterized in that: Step 1 specifically involves machining epoxy resin insulating material into an epoxy resin insulator body with a predetermined geometric structure and dimensions. Step 2 specifically involves placing the epoxy resin insulator body into a 2 mol / L sodium hydroxide solution and stirring the mixture at 80°C for 4 hours to obtain the hydrolyzed epoxy resin insulator. Step 3 specifically involves placing the epoxy resin insulator obtained in step 2 into deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours.

6. The method for preparing the surface-modified polymer insulator according to claim 5, characterized in that: Step 4 specifically involves placing the dried epoxy resin insulator from step 3 into n-octane, adding perfluoroundecyl chloride at a mass-to-volume ratio of 1g:100mL, stirring and reacting at room temperature for 2 hours, and then allowing it to stand for 12 hours to obtain an epoxy resin insulator with perfluoroundecyl chloride grafted onto its surface. Step 5 specifically involves washing the epoxy resin insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours to complete the preparation of the surface-modified epoxy resin insulator.

7. The method for preparing the surface-modified polymer insulator according to claim 4, characterized in that: Step 1 specifically involves machining the polyamide insulating material into a polyamide insulator body with a predetermined geometric structure and dimensions. Step 2 specifically involves placing the polyamide insulator body into a 50 mg / ml hexamethylenediamine solution and stirring the mixture at 60°C for 3 hours to obtain the amino-hydrolyzed polyamide insulator. Step 3 specifically involves placing the polyamide insulator obtained in step 2 into deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours.

8. The method for preparing the surface-modified polymer insulator according to claim 7, characterized in that: Step 4 specifically involves placing the dried polyamide insulator from step 3 into n-octane, adding octadecyl chloride at a mass-to-volume ratio of 1 g to 100 mL, stirring and reacting at room temperature for 2 hours, and then allowing it to stand for 12 hours to obtain a polyamide insulator with octadecyl chloride grafted onto its surface. Step 5 specifically involves washing the polyamide insulator obtained in step 4 with tap water, immersing it in deionized water, ultrasonically washing it for 30 minutes, and then drying it at 80°C for 12 hours to complete the preparation of the surface-modified polyamide insulator.

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