阅读说明：本技术 一种电缆绝缘失效修复材料的制备方法 (Preparation method of cable insulation failure repair material ) 是由 邝少毅 于 2019-11-01 设计创作，主要内容包括：本发明涉及一种电缆绝缘失效修复材料的制备方法,属于修复材料技术领域。本发明将聚乙烯接枝马来酸酐作为原料,与EVA乳液进行共混改性,以纳米氧化锌插层有机蒙脱土作为填料,制备出的复合材料作为第一层和第三层,以聚乙烯接枝马来酸酐作为原料,结合填料制备的材料为中间材料,通过热压制备出一种具有三明治结构的电缆绝缘失效修复材料；蒙脱土可从抑制聚乙烯复合介质中空间电荷的注入,但是这种抑制作用随着蒙脱土含量的增加而递减；纳米氧化铝插层有机蒙脱土的引入,减少材料内部的空间电荷积累量,直流条件下,提高极性反转时材料的绝缘性能；一定程度降低掺杂材料的绝缘电阻,但能显著地提高其对温度的依赖性。(The invention relates to a preparation method of a cable insulation failure repair material, and belongs to the technical field of repair materials. According to the invention, polyethylene grafted maleic anhydride is used as a raw material, the polyethylene grafted maleic anhydride is blended and modified with EVA emulsion, nano zinc oxide intercalated organic montmorillonite is used as a filler, the prepared composite material is used as a first layer and a third layer, the polyethylene grafted maleic anhydride is used as a raw material, the material prepared by combining the filler is used as an intermediate material, and the cable insulation failure repair material with a sandwich structure is prepared by hot pressing; the montmorillonite can inhibit the injection of space charge in the polyethylene composite medium, but the inhibition effect is reduced along with the increase of the content of the montmorillonite; the introduction of the nano aluminum oxide intercalated organic montmorillonite reduces the space charge accumulation amount in the material, and improves the insulating property of the material when the polarity is reversed under the direct current condition; the insulation resistance of the doped material is reduced to some extent, but the temperature dependence thereof can be significantly increased.)

1. A preparation method of a cable insulation failure repair material is characterized by comprising the following specific preparation steps:

(1) mixing polyethylene, maleic anhydride, benzoyl peroxide, an inhibitor CALA, xylene and acetone, heating, stirring and reacting to obtain a reaction solution, adding the maleic anhydride, the benzoyl peroxide and the inhibitor CALA into the reaction solution, continuously stirring and reacting for 2-3 hours to obtain a mixed solution, adding acetone into the mixed solution, stirring, filtering to obtain filter residue, washing the filter residue with acetone for 3-5 times, drying in an oven at the temperature of 40-60 ℃ to constant weight, and cooling to room temperature to obtain modified polyethylene;

(2) mixing the modified polyethylene and the EVA emulsion according to the mass ratio of 1: 4, and blending for 30-40 min at the temperature of 150-160 ℃ to obtain a blend;

(3) taking organic montmorillonite, nano zinc oxide and deionized water, mixing the organic montmorillonite and the deionized water, performing ultrasonic dispersion to obtain a suspension, adding the nano zinc oxide into the suspension, placing the suspension into a ball mill, and performing ball milling treatment to obtain mixed slurry; filtering the mixed slurry to obtain a precipitate, washing the precipitate for 3-5 times by using deionized water, placing the precipitate at the temperature of 80-90 ℃ and drying the precipitate at normal pressure to constant weight, cooling the precipitate to room temperature, grinding the precipitate and sieving the precipitate by using a 200-300-mesh sieve to obtain a filler;

(4) mixing the filler and the modified polyethylene, carrying out melting and stirring treatment to obtain a melt, placing the melt in a flat vulcanizing machine, and carrying out hot pressing treatment to obtain an intermediate material;

(5) mixing the filler and the blend according to a mass ratio of 1: 10, melting and stirring at a temperature of 140-150 ℃ and a stirring speed of 500-600 r/min for 20-30 min to obtain a melt, placing the melt in a flat vulcanizing machine, and hot-pressing at a temperature of 140-150 ℃ for 1-2 min to obtain a first layer material and a third layer material;

(6) and (3) placing the intermediate material between the first layer material and the third layer material, and carrying out hot-pressing treatment to obtain the cable insulation failure repair material.

2. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the proportions of the polyethylene, the maleic anhydride, the benzoyl peroxide, the inhibitor CALA, the xylene and the acetone in the step (1) are respectively as follows: respectively weighing 30-50 parts of polyethylene, 1-10 parts of maleic anhydride, 0.5-0.7 part of benzoyl peroxide, 0.3-0.5 part of inhibitor CALA, 50-60 parts of dimethylbenzene and 5-15 parts of acetone according to parts by weight.

3. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the heating and stirring treatment step in the step (1) is as follows: mixing polyethylene and dimethylbenzene, and heating and stirring for 20-30 min at the temperature of 90-110 ℃ and the stirring speed of 300-400 r/min.

4. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the stirring treatment step in the step (1) is as follows: cooling the mixed solution to 60-70 ℃, adding acetone, and stirring for 10-15 min at the stirring speed of 1000-1500 r/min.

5. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the proportions of the organic montmorillonite, the nano zinc oxide and the deionized water in the step (3) are respectively as follows: respectively weighing 20-30 parts of organic montmorillonite, 10-20 parts of nano zinc oxide and 60-80 parts of deionized water according to parts by weight.

6. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the ultrasonic dispersion step in the step (3) is as follows: mixing organic montmorillonite and deionized water, and ultrasonically dispersing for 5-10 min under the power of 300-350W.

7. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the ball milling treatment step in the step (3) is as follows: adding nano zinc oxide into the suspension, placing the suspension into a ball mill, and carrying out ball milling for 30-40 min at the rotating speed of 400-500 r/min.

8. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the melting stirring treatment step in the step (4) is as follows: mixing the filler and the modified polyethylene according to the mass ratio of 1: 10, and melting and stirring for 20-30 min at the temperature of 140-150 ℃ and the stirring speed of 500-600 r/min.

9. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the hot pressing treatment step in the step (4) is as follows: and putting the melt into a flat vulcanizing machine, and carrying out hot pressing for 1-2 min at the temperature of 140-150 ℃.

10. The preparation method of the cable insulation failure repair material according to claim 1, wherein the preparation method comprises the following steps: the hot pressing treatment step in the step (6) is as follows: and (3) placing the intermediate material between the first layer material and the third layer material, and carrying out hot pressing for 1-2 min at the temperature of 130-140 ℃ and the pressure of 13-15 MPa.

Technical Field

The invention relates to a preparation method of a cable insulation failure repair material, and belongs to the technical field of repair materials.

Background

The cable is mainly used for power transmission among power production departments, transmission departments, use departments and equipment, and is used for meeting the power consumption requirements of cities, important projects and important equipment. However, under the combined action of electrical stress, thermal stress, mechanical stress and environmental stress (water, oxygen, corrosive acidic and alkaline substances, salts, microorganisms and the like in the environment), the insulation of the cable is gradually aged, so that the insulation naturally fails. The cable insulation failure is characterized in that the cable insulation fails in an unconventional manner under accidental mechanical external force and special conditions, and once the cable insulation failure occurs, if the cable insulation failure cannot be repaired in time, the cable insulation failure can cause early cable scrap and unnecessary economic loss; the failure problem can be avoided and effectively and quickly repaired, and the method has important scientific and economic significance.

The accidental and special failures of cable insulation mainly include water tree defect failure, electrical tree defect failure and mechanical defect failure. The water tree defects are divided into three categories according to different generation positions and development directions: the water guide structure comprises an inner water guide tree which develops from a conducting layer close to the inside to the outside, an outer water guide tree which develops from the conducting layer close to the outside to the inside, and a butterfly water guide tree which develops from impurities or gap defect positions in the insulating layer to the inside and the outside in two opposite directions.

The change process of the water tree growth in the epoxy resin is observed through an optical microscope, which shows that the water tree growth mainly goes through three stages:

(1) water molecules penetrate into the non-standard pores of the insulating layer. No matter whether any insulating material has insulation failure or not, a little small pores always exist among molecular chains, under the action of an electric field force, water molecules in the environment diffuse into non-standard pores in an amorphous region which is easy to absorb water in the insulating material, and the small pores gradually gather and grow under the action of the electric field.

Water-filled cavities are gradually formed. The amorphous area is easy to absorb moisture in the environment, more and more water molecules are gathered in the material with more amorphous areas, the water-filling holes are gradually enlarged, and the distance between large holes is also gradually shortened.

The water filling holes are communicated with each other to form water branches. After the above steps, the water drops in the large holes break the molecular chains of the insulating material between the holes under the action of the electric field, the distance between the large holes is shortened, and finally, a connecting channel appears, so that gathered water branches are formed.

At local defects (pores, impurities, etc.) of the insulating material, electric field concentrations are easily induced, and local high electric fields cause breakdown of the insulation voltage, thereby forming discharge channels in the insulating layer, which are called electrical dendrites. Unlike water tree which grows slowly, the time from generation to insulation breakdown of the electrical tree is short, and the development process is an electroerosion process including local high pressure and high temperature, local discharge, physicochemical change and the like. The formation and development of electrical dendrites is a random process that is susceptible to the type of insulation, the microstructure, and the state of aging.

In the initial stage of electrical dendrite formation, dendritic cracks with a channel diameter of about 0.1 μm typically occur in the region about a few micrometers in front of the needle-tip electrode. When the diameter of the electric branch channel gradually develops to about 10 mu m, the partial discharge pulse can be detected and identified, and the partial discharge phenomenon occurs. Many factors can influence the complex growth process of the electrical tree branch. The internal factors are defects in the material, fillers, crystallization, etc., and the main external factors are voltage, frequency, ambient temperature, etc.

During the production, transportation, installation and operation of the cable, air gaps, impurities, cracks, deformation, mechanical damage and other defects in insulation can be caused, and the defects become the starting points of insulation failure. In the cable manufacturing stage, if the raw materials are not pure enough, impurities such as metal, fiber, dust and the like are mixed, and a local air gap is generated in the insulating layer. In the cable transportation stage, if collision, extrusion and the like occur, the outer sheath and the insulating layer of the cable can be damaged, so that the cable insulation generates cracks and deformation. During the cable installation stage, the cable may be subjected to mechanical vibration, external force extrusion and impact, resulting in the damage of the insulation layer. In the working stage of the cable, insulation damage of the cable can be caused by various roads or building construction projects. If the mechanical defects in the above form are not found and processed in time, the defects develop irreversibly towards the fault direction under the influence of factors such as local electric field force, and the insulation resistance value of the cable gradually decreases along with the increase of the working time of the cable, so that the cable fault buried undervoltage pen is obtained.

The current repair techniques for cable insulation failure fall into two broad categories. Aiming at the failure of 'water tree defects' and 'electric tree defects', expert scholars develop a kind of injection chemical comprehensive repair method, repair liquid is injected into the defect position between a cable insulating layer and a conductor, the repair liquid reacts with water molecules to generate a substance with dielectric parameters similar to those of a cable insulating material to fill a water tree channel, so that water in the channel is removed, the electric field distribution of the original defect position tends to be uniform, and the effect of prolonging the service life of a cable is achieved. Aiming at the failure of local mechanical defects, people develop a material filling and repairing technology, and apply a self-adhesive insulating material or a hot-melting repairing sheet to wind or fill the damaged part to repair the damaged insulating layer of the cable.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: aiming at the problem that the repair effect is influenced by the side effect generated by the maintenance of the existing cable repair material, the preparation method of the cable insulation failure repair material is provided.

In order to solve the technical problems, the invention adopts the technical scheme that:

(1) mixing polyethylene, maleic anhydride, benzoyl peroxide, an inhibitor CALA, xylene and acetone, heating, stirring and reacting to obtain a reaction solution, adding the maleic anhydride, the benzoyl peroxide and the inhibitor CALA into the reaction solution, continuously stirring and reacting for 2-3 hours to obtain a mixed solution, adding acetone into the mixed solution, stirring, filtering to obtain filter residue, washing the filter residue with acetone for 3-5 times, drying in an oven at the temperature of 40-60 ℃ to constant weight, and cooling to room temperature to obtain modified polyethylene;

(2) mixing the modified polyethylene and the EVA emulsion according to the mass ratio of 1: 4, and blending for 30-40 min at the temperature of 150-160 ℃ to obtain a blend;

(3) taking organic montmorillonite, nano zinc oxide and deionized water, mixing the organic montmorillonite and the deionized water, performing ultrasonic dispersion to obtain a suspension, adding the nano zinc oxide into the suspension, placing the suspension into a ball mill, and performing ball milling treatment to obtain mixed slurry; filtering the mixed slurry to obtain a precipitate, washing the precipitate for 3-5 times by using deionized water, placing the precipitate at the temperature of 80-90 ℃ and drying the precipitate at normal pressure to constant weight, cooling the precipitate to room temperature, grinding the precipitate and sieving the precipitate by using a 200-300-mesh sieve to obtain a filler;

(4) mixing the filler and the modified polyethylene, carrying out melting and stirring treatment to obtain a melt, placing the melt in a flat vulcanizing machine, and carrying out hot pressing treatment to obtain an intermediate material;

(5) mixing the filler and the blend according to a mass ratio of 1: 10, melting and stirring at a temperature of 140-150 ℃ and a stirring speed of 500-600 r/min for 20-30 min to obtain a melt, placing the melt in a flat vulcanizing machine, and hot-pressing at a temperature of 140-150 ℃ for 1-2 min to obtain a first layer material and a third layer material;

(6) and (3) placing the intermediate material between the first layer material and the third layer material, and carrying out hot-pressing treatment to obtain the cable insulation failure repair material.

The proportions of the polyethylene, the maleic anhydride, the benzoyl peroxide, the inhibitor CALA, the xylene and the acetone in the step (1) are respectively as follows: respectively weighing 30-50 parts of polyethylene, 1-10 parts of maleic anhydride, 0.5-0.7 part of benzoyl peroxide, 0.3-0.5 part of inhibitor CALA, 50-60 parts of dimethylbenzene and 5-15 parts of acetone according to parts by weight.

The heating and stirring treatment step in the step (1) is as follows: mixing polyethylene and dimethylbenzene, and heating and stirring for 20-30 min at the temperature of 90-110 ℃ and the stirring speed of 300-400 r/min.

The stirring treatment step in the step (1) is as follows: cooling the mixed solution to 60-70 ℃, adding acetone, and stirring for 10-15 min at the stirring speed of 1000-1500 r/min.

The proportions of the organic montmorillonite, the nano zinc oxide and the deionized water in the step (3) are respectively as follows: respectively weighing 20-30 parts of organic montmorillonite, 10-20 parts of nano zinc oxide and 60-80 parts of deionized water according to parts by weight.

The ultrasonic dispersion step in the step (3) is as follows: mixing organic montmorillonite and deionized water, and ultrasonically dispersing for 5-10 min under the power of 300-350W.

The ball milling treatment step in the step (3) is as follows: adding nano zinc oxide into the suspension, placing the suspension into a ball mill, and carrying out ball milling for 30-40 min at the rotating speed of 400-500 r/min.

The melting stirring treatment step in the step (4) is as follows: mixing the filler and the modified polyethylene according to the mass ratio of 1: 10, and melting and stirring for 20-30 min at the temperature of 140-150 ℃ and the stirring speed of 500-600 r/min.

The hot pressing treatment step in the step (4) is as follows: and putting the melt into a flat vulcanizing machine, and carrying out hot pressing for 1-2 min at the temperature of 140-150 ℃.

The hot pressing treatment step in the step (6) is as follows: and (3) placing the intermediate material between the first layer material and the third layer material, and carrying out hot pressing for 1-2 min at the temperature of 130-140 ℃ and the pressure of 13-15 MPa.

Compared with other methods, the method has the beneficial technical effects that:

(1) according to the invention, polyethylene grafted maleic anhydride is used as a raw material, the polyethylene grafted maleic anhydride is blended and modified with EVA emulsion, nano zinc oxide intercalated organic montmorillonite is used as a filler, the prepared composite material is used as a first layer and a third layer, the polyethylene grafted maleic anhydride is used as a raw material, the material prepared by combining the filler is used as an intermediate material, and the cable insulation failure repair material with a sandwich structure is prepared by hot pressing; the montmorillonite can inhibit the injection of space charge in the polyethylene composite medium, but the inhibition effect is reduced along with the increase of the content of the montmorillonite; when the content of the nano montmorillonite is low, free carriers are captured by traps introduced by the nano particles, so that the carrier concentration and the mobility are reduced, the number of space charges is reduced, and the accumulation of the charges is inhibited; maleic anhydride is grafted on polyethylene and introduced into a charge trap, so that space charge can be well inhibited; the introduction of the nano aluminum oxide intercalated organic montmorillonite reduces the space charge accumulation amount in the material, and improves the insulating property of the material when the polarity is reversed under the direct current condition; improving the stress reversal characteristics of the composite material; changing the morphology of the composite material; the insulation resistance of the doped material is reduced to a certain degree, but the temperature dependence of the doped material can be obviously improved;

(2) according to the invention, the EVA emulsion and the polyethylene are blended and modified, so that injected charges can be obviously reduced, the frictional electrification phenomenon is eliminated, and deep traps in the polyethylene are reduced; the nano zinc oxide intercalated organic montmorillonite is used as a filler, the nano particles can reduce trap energy, the probability of thermal trap removal and the carrier mobility are increased, and space charges can reduce the accumulation in the heat-sensitive material due to the fact that the migration speed of electrons in the heat-sensitive material is higher; the conductivity of the interaction zone between the nanoparticles and the polymer matrix is much higher than the conductivity of the nanoparticles and the polymer matrix used, and therefore the carriers have a greater tendency to pass through the interaction zone of the nanoparticles and the polymer matrix, resulting in suppression of space charge; a trap center located near the interface between the material and the electrode can trap charge injected into the nanocomposite, which will reduce the electric field distorted near charge injection; therefore, space charge injection will be suppressed; the contact potential barrier may be reduced by the influence of the interaction region, thereby suppressing space charge injection;

(3) the trap in the prepared cable insulation failure repair material has certain influence on electrical property, so that the charge accumulation in the material can be inhibited, the distortion of a material electric field can be reduced, and the repair effect cannot be influenced by side effects generated in the post-repair process.

Detailed Description

Respectively weighing 30-50 parts by weight of polyethylene, 1-10 parts by weight of maleic anhydride, 0.5-0.7 part by weight of benzoyl peroxide, 0.3-0.5 part by weight of inhibitor CALA, 50-60 parts by weight of xylene and 5-15 parts by weight of acetone, mixing the polyethylene and the xylene, heating and stirring at the temperature of 90-110 ℃ and the stirring speed of 300-400 r/min for 20-30 min to obtain a reaction solution, adding the maleic anhydride, the benzoyl peroxide and the inhibitor CALA into the reaction solution, continuously stirring for reaction for 2-3 h to obtain a mixed solution, cooling the mixed solution to the temperature of 60-70 ℃, adding the acetone, stirring at the stirring speed of 1000-1500 r/min for 10-15 min, filtering to obtain filter residues, washing the filter residues with the acetone for 3-5 times, placing the filter residues into an oven at the temperature of 40-60 ℃, drying to the constant weight, and cooling to the room temperature to obtain the modified polyethylene; mixing the modified polyethylene and the EVA emulsion according to the mass ratio of 1: 4, and blending for 30-40 min at the temperature of 150-160 ℃ to obtain a blend; respectively weighing 20-30 parts of organic montmorillonite, 10-20 parts of nano zinc oxide and 60-80 parts of deionized water according to parts by weight, mixing the organic montmorillonite and the deionized water, carrying out ultrasonic dispersion for 5-10 min under the power of 300-350W to obtain a suspension, adding the nano zinc oxide into the suspension, placing the suspension into a ball mill, and carrying out ball milling for 30-40 min under the rotating speed of 400-500 r/min to obtain mixed slurry; filtering the mixed slurry to obtain a precipitate, washing the precipitate for 3-5 times by using deionized water, placing the precipitate at the temperature of 80-90 ℃ and drying the precipitate at normal pressure to constant weight, cooling the precipitate to room temperature, grinding the precipitate and sieving the precipitate by using a 200-300-mesh sieve to obtain a filler; mixing the filler and the modified polyethylene according to the mass ratio of 1: 10, melting and stirring at the temperature of 140-150 ℃ and the stirring speed of 500-600 r/min for 20-30 min to obtain a melt, putting the melt into a flat vulcanizing machine, and hot-pressing at the temperature of 140-150 ℃ for 1-2 min to obtain an intermediate material; mixing the filler and the blend according to a mass ratio of 1: 10, melting and stirring at a temperature of 140-150 ℃ and a stirring speed of 500-600 r/min for 20-30 min to obtain a melt, placing the melt in a flat vulcanizing machine, and hot-pressing at a temperature of 140-150 ℃ for 1-2 min to obtain a first layer material and a third layer material; and (3) placing the intermediate material between the first layer material and the third layer material, and carrying out hot pressing for 1-2 min at the temperature of 130-140 ℃ and the pressure of 13-15 MPa to obtain the cable insulation failure repair material.