XLPE-SiO2 nano composite insulating material and preparation method thereof

Abstract

The invention belongs to the technical field of XLPE-based insulating materials, and relates to an XLPE-SiO2 nano composite insulating material and a preparation method thereof, the XLPE-SiO2 nano composite insulating material comprises the following components by mass fraction: 97-99 wt% of crosslinked polyethylene particles, 0.5-2.5 wt% of surface modified nano SiO2 particles, and 0.5% of an antioxidant. The method comprises the following steps: firstly, carrying out surface modification on nano SiO2 through wet modification, and then carrying out melt blending on the nano SiO2 and crosslinked polyethylene particles to ensure uniform dispersion of the nano SiO2. And finally, carrying out hot pressing treatment to prepare the XLPE-SiO2 nano composite insulating material. The material has excellent high-temperature insulation performance and thermal aging resistance, and is suitable for the field of cable insulation.

Description

Technical Field

[0001] The invention belongs to the technical field of XLPE-based insulating materials and relates to an XLPE-SiO 2 Nanocomposite insulating material and preparation method thereof. Background Art

[0002] Cross-linked polyethylene (XLPE) is the main material for the insulation layer of medium and high voltage cables and is widely used in underground power distribution and transmission systems. However, long-term exposure to thermal, electrical and mechanical stresses will cause changes in its chemical structure and morphology, which will in turn cause performance degradation. As a cable insulation material, although cross-linked polyethylene (XLPE) has significant advantages in electrical properties, mechanical properties and processing properties, it still has some obvious disadvantages and deficiencies in practical applications. First, XLPE is prone to electrical tree aging during long-term operation. Especially under high electric field strength, the initiation and expansion of electrical tree will significantly reduce the insulation performance of the material, leading to increased local discharge, which may eventually cause insulation breakdown and affect the reliability of the cable. XLPE has limited heat resistance and is prone to thermal oxidation aging when exposed to high temperature for a long time, resulting in a decrease in the mechanical strength of the material and deterioration of the insulation performance, which limits its application in high temperature occasions. In addition, XLPE is prone to water tree aging in a humid environment, which further accelerates the degradation of insulation performance. These shortcomings limit the application of XLPE in high voltage, high temperature and complex environments, and it is urgent to improve its comprehensive performance through material modification. Summary of the invention

[0003] In order to solve the above problems, the present invention proposes a XLPE-SiO 2 Nanocomposite insulating material and preparation method thereof. In order to improve the insulation performance of XLPE, the present invention adds nano-SiO 2 Filler, Nano-SiO 2 The addition of not only improves the insulation properties of the material, effectively inhibits the growth of electrical trees, enhances the dielectric strength and partial discharge tolerance, but also significantly improves the heat resistance of the material. Nanoparticles can also enhance the thermal stability of the material, delay the thermal aging process, and enable the composite material to maintain excellent mechanical and electrical properties in high temperature environments, thereby extending the service life of the cable and improving operational reliability. By adjusting its content, its effect on the volume resistivity and AC breakdown strength of XLPE was explored.

[0004] This method firstly modifies nano-SiO by wet method. 2 After surface modification, it was then melt-blended with cross-linked polyethylene particles to ensure that the nano-SiO 2 Finally, XLPE-SiO 2Nanocomposite insulation material. This material has excellent high temperature insulation performance and heat aging resistance, and is suitable for the field of cable insulation.

[0005] The present invention is achieved through the following technical solutions:

[0006] A kind of XLPE-SiO 2 The nanocomposite insulating material has the following composition ratios by mass fraction: 97-99wt% cross-linked polyethylene particles, surface-modified nano-SiO 2 Particles 0.5-2.5wt%, antioxidant 0.5%.

[0007] The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

[0008] The surface modified nano-SiO 2 It is obtained by the following method: First, add KH-570 silane coupling agent to acetone aqueous solution and stir it thoroughly to make it evenly dispersed. Then, adjust the pH value of the solution to the acidic range (usually pH = 4-6) with hydrochloric acid to promote the hydrolysis reaction of the silane coupling agent to obtain solution A; during the hydrolysis process, the alkoxy group in the KH-570 molecule reacts with water to form a silanol group, thereby enhancing its ability to bind to the surface of the nanoparticles. Then, add nano-SiO 2 The powder was slowly added into solution A, wherein nano-SiO 2 The mass ratio of the nano-SiO2 to KH-570 silane coupling agent is 100:1, and the temperature is kept in a constant temperature water bath within the range of 50-70°C, and stirred continuously for 30-60 minutes to ensure that the nano-SiO2 2 The surface is fully modified and evenly dispersed in the solution. After the reaction is completed, the solid product is separated by vacuum filtration and repeatedly washed with deionized water until no chloride ions are detected in the filtrate (which can be detected by silver nitrate solution). Finally, the washed product is dried at 60-80°C for 3-5h to remove residual moisture, and activated at 140-160°C for 8-9h to further enhance the nano-SiO 2 Chemical bonding between the silane coupling agent and the surface modified nano-SiO 2 .

[0009] The above XLPE-SiO 2 The method for preparing a nanocomposite insulating material comprises the following steps:

[0010] Step (1) Preparation of nano-SiO2 surface modified by wet method 2

[0011] First, KH-570 silane coupling agent was added to the acetone aqueous solution and stirred thoroughly to make it uniformly dispersed. Then, the pH value of the solution was adjusted to the acidic range with hydrochloric acid to obtain solution A. Then, nano-SiO 2 The powder was slowly added into solution A, wherein nano-SiO 2 The mass ratio of the nano-SiO2 to KH-570 silane coupling agent is 100:1, and the temperature is kept in a constant temperature water bath within the range of 50-70°C, and stirred continuously for 30-60 minutes to ensure that the nano-SiO2 2 The surface is fully modified and evenly dispersed in the solution. After the reaction is completed, the solid product is separated by vacuum filtration and repeatedly washed with deionized water until no chloride ions are detected in the filtrate. Finally, the washed product is dried at 60-80°C for 3-5h to remove residual moisture, and activated at 140-160°C for 8-9h to finally obtain surface-modified nano-SiO 2 .

[0012] Step (2) Premix

[0013] Cross-linked polyethylene particles, surface modified with nano-SiO 2 The particles and antioxidants are dried separately, and then the cross-linked polyethylene particles are 97-99wt%, and the surface is modified with nano-SiO 2 The particles 0.5-2.5wt% and the antioxidant 0.5wt% are mixed uniformly in a mass ratio to obtain a premix.

[0014] Step (3) Melt Blending

[0015] The premix was added into a twin-screw extruder for melt blending to obtain XLPE-SiO 2 Nanocomposite insulating material; then subsequent hot pressing molding is performed as needed.

[0016] In the step (2), the drying condition is to dry in a vacuum drying oven at 60-70° C. for 12-14 hours.

[0017] In the step (3), the twin-screw extruder is set to melt blending at a speed of 25 to 30 rpm, a temperature of 125 to 130° C., and a blending time of 10 to 15 min. After blending is completed, the sample is taken out and cooled at a constant temperature at room temperature.

[0018] Beneficial effects of the present invention:

[0019] The present invention uses nano-SiO2 modified by KH-570 silane coupling agent. 2 The doped modified XLPE matrix has good compatibility with the polymer matrix, is evenly dispersed, and has no obvious agglomeration. 2The hydroxyl groups on its surface form chemical bonds with the XLPE matrix, and the surface adsorption and hydrogen bonding of the nanoparticles work together to make the nano-SiO 2 A strong interface is formed between the XLPE matrix. On the one hand, deep traps are introduced to significantly improve the insulation performance. On the other hand, the XLPE-SiO 2 The nanocomposite material forms a small spherulite structure, which improves the crystallinity, hinders the penetration of oxygen molecules, and significantly improves the heat aging resistance. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is further described below in conjunction with the technical solution.

[0021] Table 1 Mass fraction ratio of each embodiment

[0022] Components Example 1 Example 2 Example 3 Comparative Example Cross-linked polyethylene particles 99％ 98％ 97％ 99.5％ <![CDATA[Nano SiO 2 > 0.5％ 1.5％ 2.5％ 0％ Antioxidants 0.5％ 0.5％ 0.5％ 0.5％

[0023] Example 1

[0024] Step (1) Preparation of nano-SiO2 surface modified by wet method 2

[0025] First, KH-570 silane coupling agent was added to the acetone aqueous solution and stirred thoroughly to make it uniformly dispersed. Then, the pH value of the solution was adjusted to 4 with hydrochloric acid to obtain solution A. Then, nano-SiO 2 The powder was slowly added into solution A, wherein nano-SiO 2 The mass ratio of 1:1 to KH-570 silane coupling agent was 100:1, and the temperature was kept within 50°C in a constant temperature water bath and stirred for 60 minutes. After the reaction was completed, the solid product was separated by vacuum filtration and repeatedly washed with deionized water until no chloride ions were detected in the filtrate. Finally, the washed product was dried at 60°C for 5h to remove residual moisture, and activated at 140°C for 9h to obtain surface-modified nano-SiO 2 .

[0026] Step (2) Premix

[0027] Cross-linked polyethylene particles, surface modified with nano-SiO 2 The particles and antioxidants were dried in a vacuum oven at 60 °C for 14 h, and then the surface of the cross-linked polyethylene particles was modified with nano-SiO 2 The particles 0.5 wt % and the antioxidant 0.5 wt % are mixed uniformly in a mass ratio to obtain a premix.

[0028] Step (3) Melt Blending

[0029] The premix was added into a twin-screw extruder for melt blending. The speed of the twin-screw extruder was set at 25 rpm, the temperature was 130 °C, and the blending time was 15 min. After the blending was completed, the sample was taken out and cooled at room temperature to obtain XLPE-SiO 2 Nanocomposite insulating materials.

[0030] Step (4) Hot Pressing

[0031] The sample was placed in the mold and hot-pressed using a flat vulcanizer, with the temperature set to 180°C, preheated for 5 minutes, and the pressure set to 30t for 10 minutes. After hot pressing, the sample was taken out and naturally cooled to room temperature to obtain a circular sample with a thickness of 0.1mm and a diameter of 10cm.

[0032] Example 2

[0033] Step (1) Preparation of nano-SiO2 surface modified by wet method 2

[0034] First, KH-570 silane coupling agent was added to the acetone aqueous solution and stirred thoroughly to make it uniformly dispersed. Then, the pH value of the solution was adjusted to 6 with hydrochloric acid to obtain solution A. Then, nano-SiO 2 The powder was slowly added into solution A, wherein nano-SiO 2 The mass ratio of 1:1 to KH-570 silane coupling agent was 100:1, and the temperature was kept within 70°C in a constant temperature water bath and stirred for 30 minutes. After the reaction was completed, the solid product was separated by vacuum filtration and repeatedly washed with deionized water until no chloride ions were detected in the filtrate. Finally, the washed product was dried at 80°C for 3h to remove residual moisture, and activated at 160°C for 8h to obtain surface-modified nano-SiO 2 .

[0035] Step (2) Premix

[0036] Cross-linked polyethylene particles, surface modified with nano-SiO 2 The particles and antioxidants were dried in a vacuum oven at 70 °C for 12 h, and then the surface of the cross-linked polyethylene particles was modified with nano-SiO 2 The particles 1.5wt% and the antioxidant 0.5wt% are mixed uniformly in a mass ratio to obtain a premix.

[0037] Step (3) Melt Blending

[0038] The premix was added into a twin-screw extruder for melt blending. The speed of the twin-screw extruder was set at 30 rpm, the temperature was 125 °C, and the blending time was 10 min. After the blending was completed, the sample was taken out and cooled at room temperature to obtain XLPE-SiO 2 Nanocomposite insulating materials.

[0039] Step (4) Hot Pressing

[0040] The sample was placed in the mold and hot-pressed using a flat vulcanizer, with the temperature set to 180°C, preheated for 5 minutes, and the pressure set to 30t for 10 minutes. After hot pressing, the sample was taken out and naturally cooled to room temperature to obtain a circular sample with a thickness of 0.1mm and a diameter of 10cm.

[0041] Example 3

[0042] Step (1) Preparation of nano-SiO2 surface modified by wet method 2

[0043] First, KH-570 silane coupling agent was added to the acetone aqueous solution and stirred thoroughly to make it uniformly dispersed. Then, the pH value of the solution was adjusted to 5 with hydrochloric acid to obtain solution A. Then, nano-SiO 2 The powder was slowly added into solution A, wherein nano-SiO 2 The mass ratio of 1:1 to KH-570 silane coupling agent was 100:1, and the temperature was kept within 60°C in a constant temperature water bath and stirred for 50 minutes. After the reaction was completed, the solid product was separated by vacuum filtration and repeatedly washed with deionized water until no chloride ions were detected in the filtrate. Finally, the washed product was dried at 70°C for 4h to remove residual moisture, and activated at 145°C for 8.5 hours to obtain surface-modified nano-SiO 2 .

[0044] Step (2) Premix

[0045] Cross-linked polyethylene particles, surface modified with nano-SiO 2 The particles and antioxidants were dried in a vacuum oven at 65°C for 13 h, and then the surface of the cross-linked polyethylene particles was modified with nano-SiO 2 The particles 2.5wt% and the antioxidant 0.5wt% are mixed uniformly in a mass ratio to obtain a premix.

[0046] Step (3) Melt Blending

[0047] The premix was added into a twin-screw extruder for melt blending. The speed of the twin-screw extruder was set at 30 rpm, the temperature was 125 °C, and the blending time was 10 min. After the blending was completed, the sample was taken out and cooled at room temperature to obtain XLPE-SiO 2 Nanocomposite insulating materials.

[0048] Step (4) Hot Pressing

[0049] The sample was placed in the mold and hot-pressed using a flat vulcanizer, with the temperature set to 180°C, preheated for 5 minutes, and the pressure set to 30t for 10 minutes. After hot pressing, the sample was taken out and naturally cooled to room temperature to obtain a circular sample with a thickness of 0.1mm and a diameter of 10cm.

[0050] Comparative Example

[0051] The steps for preparing XLPE insulation material are as follows:

[0052] (1) The cross-linked polyethylene particles and antioxidant were vacuum dried at 60°C for 3 hours.

[0053] (2) Premix the dried components and stir them evenly to obtain a premix.

[0054] (3) Add the premixed mixture into a twin-screw extruder, set the speed to 30 rpm, the temperature to 130° C., and the blending time to 10 min. After the blending is completed, take out the sample and cool it to room temperature.

[0055] (4) Place the sample in the mold and use a flat vulcanizer for hot pressing. Set the temperature to 180°C, preheat for 5 minutes, and press at 30t for 10 minutes. After hot pressing, take out the sample and cool it naturally to room temperature to obtain a circular sample with a thickness of 0.1 mm and a diameter of 10 cm.

[0056] Performance Analysis:

[0057] The samples obtained in Examples 1-3 and the comparative example were subjected to a volume resistivity test at 30-120°C. The AC breakdown field strength test at 30-120°C was statistically performed using Weibull distribution, with each group of samples tested 12 times. The changes in insulation performance were statistically analyzed, and the results are shown in the following table.

[0058] Table 2 Volume resistivity measurement results at different temperatures

[0059]

[0060] Table 3 AC breakdown test results at different temperatures

[0061]

[0062] According to Table 2 and Table 3, the XLPE-SiO 2 Nanocomposite insulation materials have significant advantages over ordinary XLPE in terms of insulation performance and temperature resistance. 2 Nanoparticles, the material shows higher breakdown field strength and volume resistivity, improving electrical performance and reliability. In terms of temperature resistance, SiO 2Nanoparticles enhance the thermal stability and thermal conductivity of the material, enabling it to maintain good electrical properties in high temperature environments and have excellent resistance to thermal aging. These properties make XLPE-SiO 2 Nanocomposite insulation materials are suitable for high-voltage cables, high-temperature working conditions, and areas with high requirements for long life.

Claims

1. A XLPE-SiO2 nanocomposite insulating material, characterized in that: The composition ratio of the XLPE-SiO2 nano composite insulating material is measured by mass fraction as follows: 97-99wt% of cross-linked polyethylene particles, 0.5-2.5wt% of surface modified nano SiO2 particles, and 0.5% of antioxidant.

2. The XLPE-SiO2 nanocomposite insulating material according to claim 1, characterized in that: The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate].

3. A XLPE-SiO2 nanocomposite insulating material according to claim 1 or 2, characterized in that: The surface modified nano-SiO2 is obtained in the following manner: first, KH-570 silane coupling agent is added to an acetone aqueous solution, and the solution is stirred sufficiently to be uniformly dispersed; subsequently, the pH value of the solution is adjusted to an acidic range with hydrochloric acid to promote the hydrolysis reaction of the silane coupling agent, thereby obtaining solution A; then, nano-SiO2 powder is slowly added to solution A, wherein the mass ratio of nano-SiO2 to KH-570 silane coupling agent is 100:1, and the temperature is maintained in a constant temperature water bath within a range of 50 to 70° C., and stirring is continued for 30 to 60 minutes; after the reaction is completed, the solid product is separated by reduced pressure filtration, and is repeatedly washed with deionized water until no chloride ions are detected in the filtrate; finally, the washed product is dried at 60 to 80° C. for 3 to 5 hours to remove residual moisture, and is activated at 140 to 160° C. for 8 to 9 hours, thereby finally obtaining the surface modified nano-SiO2.

4. The method for preparing the XLPE-SiO2 nanocomposite insulating material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step (1) Preparation of nano-SiO2 surface modified by wet method First, KH-570 silane coupling agent is added to an acetone aqueous solution and stirred to make it uniformly dispersed; then, hydrochloric acid is used to adjust the pH value of the solution to an acidic range to obtain solution A; then, nano-SiO2 powder is slowly added to solution A, wherein the mass ratio of nano-SiO2 to KH-570 silane coupling agent is 100:1, and the temperature is maintained in a constant temperature water bath within a range of 50 to 70° C., and stirring is continued for 30 to 60 minutes to ensure that the surface of nano-SiO2 is fully modified and uniformly dispersed in the solution; after the reaction is completed, the solid product is separated by reduced pressure filtration, and repeatedly washed with deionized water until no chloride ions are detected in the filtrate; finally, the washed product is dried at 60 to 80° C. for 3 to 5 hours to remove residual moisture, and activated at 140 to 160° C. for 8 to 9 hours to finally obtain surface-modified nano-SiO2; Step (2) Premix The cross-linked polyethylene particles, the surface-modified nano-SiO2 particles, and the antioxidant are dried separately, and then mixed evenly in a mass ratio of 97-99wt% of the cross-linked polyethylene particles, 0.5-2.5wt% of the surface-modified nano-SiO2 particles, and 0.5wt% of the antioxidant to obtain a premix; Step (3) Melt Blending The premix is ​​added into a twin-screw extruder for melt blending to obtain an XLPE-SiO2 nanocomposite insulating material; and then subsequent hot pressing molding is performed as required.

5. The method for preparing a XLPE-SiO2 nanocomposite insulating material according to claim 4, characterized in that: In the step (2), the drying condition is to dry in a vacuum drying oven at 60-70° C. for 12-14 hours.

6. The method for preparing a XLPE-SiO2 nanocomposite insulating material according to claim 4 or 5, characterized in that: In the step (3), the twin-screw extruder is set to melt blending at a speed of 25 to 30 rpm, a temperature of 125 to 130° C., and a blending time of 10 to 15 min. After blending is completed, the sample is taken out and cooled at a constant temperature at room temperature.

Images