CN112210122B - Preparation method of self-repairing insulating material - Google Patents

Preparation method of self-repairing insulating material Download PDF

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CN112210122B
CN112210122B CN202011091264.4A CN202011091264A CN112210122B CN 112210122 B CN112210122 B CN 112210122B CN 202011091264 A CN202011091264 A CN 202011091264A CN 112210122 B CN112210122 B CN 112210122B
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repairing
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insulating material
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CN112210122A (en
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何金良
谢佳烨
李琦
胡军
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Tsinghua University
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Abstract

The existing photo-induced self-repairing material has the requirement on the transparency of a matrix, cannot be applied to a non-transparent matrix, and the repairing liquid mixed with a photosensitizer contained in the photo-induced self-repairing material is easy to lose efficacy in long-term operation. The application provides a preparation method of a self-repairing insulating material, which comprises the following steps: uniformly mixing acrylate resin and polyfunctional group active diluent according to a proportion, and adding dimethylaniline into the mixture to prepare a repair liquid; preparing an aqueous solution containing sodium dodecyl benzene sulfonate and polyvinyl alcohol, slowly adding a repair solution into the aqueous solution, and stirring to form uniformly dispersed oil-in-water core material emulsion; preparing urea and formaldehyde into a solution according to a proportion, stirring to form a water-soluble prepolymer solution of mono-and dimethylol ureas, and treating; and adding the prepolymer solution into the oil-in-water core material emulsion, and processing to obtain the self-repairing microcapsule. The problem of the stability of the repair liquid of the microcapsule-based self-repairing insulating material in long-term operation is solved.

Description

Preparation method of self-repairing insulating material
Technical Field
The application belongs to the technical field of electrical materials, and particularly relates to a preparation method of a self-repairing insulating material.
Background
Organic matters such as polyethylene, silicon rubber, epoxy resin and the like and composite materials thereof are widely applied to electrical insulation, and in the using process, micro-discharge defects represented by electric trees and water trees are inevitably generated in the organic matters along with long-term aging, and the micro-defects further develop to cause the insulation damage of materials, so that the insulation failure and the equipment failure are caused. Therefore, if the high polymer material can have a self-repairing function, the defects can be repaired at the early stage of defect development, so that the problems can be solved, the service life of the insulating medium is remarkably prolonged, and the safety of the product is improved. Aiming at micro-discharge defects in the cable, particularly water tree defects, the early repair technology mainly adopts three materials of dry N2, hydrophobic compounds and siloxane as repair media to artificially repair the cable with reduced insulation strength so as to prolong the service life of the cable. The method is not widely applied due to the reasons of large manual intervention, large resource consumption, poor effect, unobvious effect on the defects of the electric tree and the like.
In 2001, the concept of self-repairing a resin-based composite material by using microcapsules is firstly proposed, the microcapsules filled with repairing liquid are embedded in the composite material, when micro defects are generated in the material, the defects expand to cause the microcapsules to break and release the repairing liquid to contact with a catalyst embedded in a matrix to generate a cross-linking polymerization reaction to repair the defect surface, and therefore the purpose of preventing and repairing the defects is achieved. In principle, self-healing materials can be divided into two categories: (1) intrinsic self-repairing, namely, after the local material is damaged, the aim of repairing is achieved through thermal diffusion and chemical reaction; (2) the purpose of self-repairing is achieved through transportation and chemical reaction of external materials after the local materials are damaged. As the micro-discharge defects are damaged along with the chemical properties of the material, the original self-repairing performance of the local material is also damaged, and the intrinsic self-repairing is difficult to be applied to the self-repairing of the micro-discharge defects. The purpose of self-repairing is achieved through transportation of external materials by extrinsic self-repairing, the problems are effectively solved, and the method is more suitable for self-repairing of micro-discharge defects.
However, most of the existing extrinsic self-repairing systems are two-component microcapsule systems, the systems are complex in structure, the repairing agent and the catalyst need to be stored and dispersed in the polymer respectively, and when micro-discharge defects occur, it is difficult to ensure that the repairing agent can contact with the catalyst before the repairing agent fails and complete self-repairing. More importantly, the catalyst dispersed in the polymer matrix also severely affects the insulating properties of the material. Therefore, the development of a one-component microcapsule self-repairing system is vital, the existing one-component method such as a photo-induced self-repairing material has the requirement on the transparency of a matrix, the existing one-component method cannot be applied to a non-transparent matrix, and a repairing liquid mixed with a photosensitizer contained in the one-component microcapsule self-repairing system is easy to lose efficacy in long-term operation. Therefore, the development of the single-component self-repairing material with wide application range and excellent stability is still difficult.
Disclosure of Invention
1. Technical problem to be solved
The existing single-component method such as the photo-induced self-repairing material has the requirement on the transparency of the matrix, cannot be applied to the non-transparent matrix, and the repairing liquid mixed with the photosensitizer is easy to lose efficacy in long-term operation. Therefore, the development of the single-component self-repairing material with wide application range and excellent stability is still a difficult problem, and the application provides a preparation method of the self-repairing insulating material.
2. Technical scheme
In order to achieve the above object, the present application provides a method for preparing a self-repairing insulating material, comprising the steps of:
step 1: uniformly mixing acrylate resin and polyfunctional group active diluent according to a proportion, and adding dimethylaniline into the mixture to prepare a repair liquid;
step 2: preparing an aqueous solution containing sodium dodecyl benzene sulfonate and polyvinyl alcohol, slowly adding the repair liquid into the aqueous solution, and stirring to form uniformly dispersed oil-in-water core material emulsion;
and step 3: preparing urea and formaldehyde into a solution according to a proportion, stirring to form a water-soluble prepolymer solution of mono-methylol urea and dihydroxy-methylol urea, adding a proper amount of deionized water into the prepolymer solution, cooling to room temperature, and adding diluted hydrochloric acid to adjust the pH value to 7;
and 4, step 4: adding the prepolymer solution into the oil-in-water core material emulsion, adding a catalyst and a pH value regulator, regulating the pH value of the solution to 3-4, heating to 50-60 ℃, reacting for 3-5 hours, removing unreacted core materials and wall materials, cooling, washing, sieving, and naturally drying to obtain the self-repairing microcapsule.
Another embodiment provided by the present application is: the acrylate resin in the step 1 is bisphenol A epoxy acrylate, bisphenol A ethoxy diacrylate, novolac epoxy acrylate, epoxidized oil acrylate or modified epoxy acrylate.
Another embodiment provided by the present application is: in the step 1, the polyfunctional active diluent is trimethylolpropane triacrylate or ethoxylated trimethylolpropane triacrylate.
Another embodiment provided by the present application is: in the step 1, the mass ratio of the acrylate resin in the mixture is 25-50%, and the mass ratio of the dimethylaniline is 0.5-2 wt% of the mixture.
Another embodiment provided by the present application is: preparing an aqueous solution containing 1 wt.% of sodium dodecyl benzene sulfonate and 0.2 wt.% of polyvinyl alcohol in the step 2, slowly adding 10 wt.% to 20 wt.% of the repair liquid into the aqueous solution, and mechanically stirring at a rotating speed of 1000 to 1500r/min for 20min to 30min to completely emulsify the repair liquid to form a uniformly dispersed oil-in-water core emulsion.
Another embodiment provided by the present application is: in the step 3, a solution is prepared by mixing urea and formaldehyde in a molar ratio of 1:2, the solution is magnetically stirred and reacts for 1 hour under the alkaline conditions of 70 ℃ and a pH value of 8-9 to form a water-soluble prepolymer of the monohydroxymethylurea and the dimethylol urea, a proper amount of deionized water is added into the prepolymer solution, the prepolymer solution is cooled to room temperature, and diluted hydrochloric acid is added to adjust the pH value to 7.
Another embodiment provided by the present application is: and 4, adding the prepolymer solution into the oil-in-water core material emulsion, adding a catalyst of resorcinol and a pH value regulator of ammonium chloride, regulating the pH value of the solution to 3-4 by using 1-2% by mass of dilute hydrochloric acid, heating to 50-60 ℃ at the speed of 1 ℃/min, reacting for 3-5 hours, removing unreacted core materials and wall materials, cooling, washing, sieving, and naturally drying to obtain the microcapsule.
Another embodiment provided by the present application is: the mass ratio of the prepolymer to the repairing liquid in the step 4 is 1 (2-1), the addition amount of the catalyst is 3% -6% of the prepolymer solution, and the addition amount of the pH value regulator is 5% -6% of the prepolymer.
The application also provides a preparation method of the self-repairing insulating material, and the self-repairing microcapsule is applied to the insulating material to obtain the self-repairing insulating material with the electric damage self-repairing capability.
Another embodiment provided by the present application is: the volume percentage of the microcapsule in the composite matrix is 3-10%;
the insulating material is epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, or a composite insulating material obtained by mixing the insulating material with glass fiber and nano/micron filler.
3. Advantageous effects
Compared with the prior art, the preparation method of the self-repairing insulating material has the beneficial effects that:
the preparation method of the self-repairing insulating material provided by the application is an electrical damage self-repairing material caused by free radicals.
The preparation method of the self-repairing insulating material provided by the application is a pan-matrix microcapsule-based self-repairing insulating material initiated by free radicals.
The preparation method of the self-repairing insulating material solves the problem of stability of the repairing liquid of the microcapsule-based self-repairing insulating material in long-term operation, has no requirement on the type of the base material, can be widely applied to common high-molecular insulating materials including epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate and the like, and can also be a composite insulating material formed by the high-molecular materials and inorganic oxide filler or glass fiber and the like, thereby widening the actual application scene.
The preparation method of the self-repairing insulating material provided by the application widens the application range and the long-term reliability of the microcapsule-based self-repairing insulating material.
According to the preparation method of the self-repairing insulating material, the free radicals generated in the electrical tree aging process are used as trigger sources to trigger curing of the repairing liquid, and self-repairing capability is given to the material.
According to the preparation method of the self-repairing insulating material, the generation and development mechanism of free radicals in the electrical tree aging process of the insulating material and the mechanism of generating hydroperoxide by the free radicals and oxygen are researched, and the free radicals and the hydroperoxide can be maintained for a long time on the whole, so that the free radical polymerization reaction can be triggered.
According to the preparation method of the self-repairing insulating material, the repairing liquid obtained by mixing the acrylate resin and the polyfunctional group reactive diluent in a certain proportion is synthesized. The repairing liquid can rapidly generate polymerization reaction under the triggering of free radicals, and a product with excellent insulating property is obtained.
According to the preparation method of the self-repairing insulating material, the mass ratio of the acrylate resin in the mixture is 25% -50%, so that the obtained repairing liquid is guaranteed to have low viscosity, high reaction speed and high product strength after curing.
According to the preparation method of the self-repairing insulating material, the content of the added dimethylaniline is 0.5-2 wt% of the repairing liquid, so that the obtained repairing liquid can be cured more quickly in the presence of a free radical donor, and sufficient stability is maintained.
According to the preparation method of the self-repairing insulating material, the self-repairing mechanism is irrelevant to the type of the used insulating material, so that the self-repairing insulating material can form a self-repairing composite insulating material with most insulating materials, the used insulating material can comprise epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate and the like, and can also be a composite insulating material which is obtained by mixing glass fiber and nano/micron filler and has wider application. The volume percentage of the microcapsule in the composite matrix is 3-10% so as to maintain reliable repairing effect and enough insulation strength.
According to the preparation method of the self-repairing insulating material, free radicals, hydroperoxides and the like generated in the process of aging the electrical tree are used as factors for triggering curing of the repairing liquid, and the free radicals and the hydroperoxides are the largest adverse factors of chain reaction caused in the process of aging the material.
According to the preparation method of the self-repairing insulating material, adverse factors are changed into beneficial factors, the free radicals are used for triggering the curing of the repairing liquid, the content and the harm of the free radicals are reduced, existing electric damage can be repaired, and the performance of the material can be recovered.
According to the preparation method of the self-repairing insulating material, the obtained self-repairing material does not depend on any trigger or a specific base material, so that the self-repairing insulating material can be suitable for different insulating materials and different operating conditions.
According to the preparation method of the self-repairing insulating material, dimethylaniline reacts with hydroperoxide to generate more free radicals, so that the curing process of the repairing liquid is accelerated.
Drawings
FIG. 1 is a schematic diagram of a free radical chain reaction process involving oxygen in the insulation material of the present application;
FIG. 2 is a schematic diagram of the mechanism of electrical dendron aging of the present application and the free radical processes therein.
Detailed Description
Hereinafter, specific embodiments of the present application will be described in detail with reference to the accompanying drawings, and it will be apparent to those skilled in the art from this detailed description that the present application can be practiced. Features from different embodiments may be combined to yield new embodiments, or certain features may be substituted for certain embodiments to yield yet further preferred embodiments, without departing from the principles of the present application.
Referring to fig. 1-2, the application provides a preparation method of a self-repairing insulating material, which comprises the following steps:
step 1: uniformly mixing acrylate resin and polyfunctional group active diluent according to a proportion, and adding dimethylaniline into the mixture to prepare a repair liquid;
step 2: preparing an aqueous solution containing sodium dodecyl benzene sulfonate and polyvinyl alcohol, slowly adding the repair liquid into the aqueous solution, and stirring to form uniformly dispersed oil-in-water core material emulsion;
and step 3: preparing urea and formaldehyde into a solution according to a proportion, stirring to form a water-soluble prepolymer solution of mono-methylol urea and dihydroxy-methylol urea, adding a proper amount of deionized water into the prepolymer solution, cooling to room temperature, and adding diluted hydrochloric acid to adjust the pH value to 7;
and 4, step 4: adding the prepolymer solution into the oil-in-water core material emulsion, adding a catalyst and a pH value regulator, regulating the pH value of the solution to 3-4, heating to 50-60 ℃, reacting for 3-5 hours, removing unreacted core materials and wall materials, cooling, washing, sieving, and naturally drying to obtain the self-repairing microcapsule.
The repair liquid in step 1 is a repair liquid capable of reacting with a radical donor such as hydroperoxide.
Further, the acrylate resin in step 1 is bisphenol a epoxy acrylate, bisphenol a ethoxy diacrylate, novolac epoxy acrylate, epoxidized oil acrylate, or modified epoxy acrylate.
Further, in the step 1, the multifunctional reactive diluent is trimethylolpropane triacrylate or ethoxylated trimethylolpropane triacrylate.
Further, the mass ratio of the acrylate resin in the mixture in the step 1 is 25% -50% so as to ensure that the repair liquid has proper viscosity and sufficient insulation performance after curing. The dimethylaniline is 0.5 wt.% to 2 wt.% of the mixture.
Further, in the step 2, an aqueous solution containing 1 wt.% of sodium dodecyl benzene sulfonate and 0.2 wt.% of polyvinyl alcohol is prepared, then 10 wt.% to 20 wt.% of the repair liquid is slowly added into the aqueous solution, and the repair liquid is mechanically stirred at a rotating speed of 1000 to 1500r/min for 20min to 30min, so that the repair liquid is completely emulsified to form the uniformly dispersed oil-in-water core emulsion.
Further, in the step 3, a solution is prepared by mixing urea and formaldehyde in a molar ratio of 1:2, the solution is magnetically stirred and reacts for 1 hour under the alkaline conditions of 70 ℃ and pH 8-9 to form a water-soluble prepolymer of the monomethylol urea and the dimethylol urea, a proper amount of deionized water is added into the prepolymer solution, the prepolymer solution is cooled to room temperature, and diluted hydrochloric acid is added to adjust the pH value to 7.
Further, in the step 4, the prepolymer solution is added into the oil-in-water core material emulsion, a catalyst of resorcinol and a pH value regulator of ammonium chloride are added, the pH value of the solution is regulated to 3-4 by using 1-2% by mass of dilute hydrochloric acid, the temperature is raised to 50-60 ℃ at the speed of 1 ℃/min, after reaction is carried out for 3-5 hours, unreacted core materials and wall materials are removed, and the microcapsule is obtained by cooling, washing, sieving and naturally drying.
Furthermore, the mass ratio of the prepolymer to the repair liquid in the step 4 is 1 (2-1), the addition amount of the catalyst is 3% -6% of the prepolymer solution, and the addition amount of the pH value regulator is 5% -6% of the prepolymer.
The application also provides a preparation method of the self-repairing insulating material, and the self-repairing microcapsule is applied to the insulating material to obtain the self-repairing insulating material with the electric damage self-repairing capability.
Further, the volume percentage of the microcapsule in the composite matrix is 3-10%;
the insulating material is epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, or a composite insulating material obtained by mixing the insulating material with glass fiber and nano/micron filler.
Taking epoxy resin as an example, when normal epoxy resin is prepared, the self-repairing microcapsule is added, the mixture is uniformly stirred and vacuumized to remove bubbles, the mixture is poured into a mold for molding, and the self-repairing insulating material is obtained after curing under proper curing conditions.
When the obtained self-repairing insulating material runs under the working condition, if electric dendritic aging occurs in the material, the molecular chain of the material is broken due to partial discharge caused by aging, and radical donors such as alkyl radicals, hydroperoxides and the like are generated. When the electric tree continuously develops until the microcapsule is broken, the repair liquid flows into the electric tree channel, dimethylaniline contained in the electric tree channel can react with radical donors such as hydroperoxide and the like to generate a large amount of free radicals, and the free radicals and the original alkyl free radicals trigger the crosslinking reaction of the repair liquid, so that the repair liquid is gradually cured, and the damage is repaired. The repairing liquid in the microcapsule can be used for many times due to the protection of the microcapsule wall, and the service life of the material is prolonged.
The application firstly synthesizes microcapsules containing a repairing liquid capable of being polymerized by free radicals, and the microcapsules are introduced into different insulating matrixes to endow insulating materials with the capability of repairing micro-discharge defects. When the electric tree caused by the micro-discharge defect develops into the microcapsule, the microcapsule is broken and the repairing liquid is filled in the electric tree channel, and then the repairing liquid is solidified under the catalysis of free radicals generated by partial discharge in the tree channel, so that the electric tree defect is repaired, and the electric performance is recovered. The self-repairing mechanism designed by the application can realize complete self-repairing after the injury is generated without any additional human intervention. Because the composite insulating material only depends on the initiation of free radicals generated in the electrical damage process, the composite insulating material can be applied to a wide range of insulating materials, including epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate and the like, and can also be mixed with glass fiber and nano/micron filler to obtain a composite insulating material with wider application. These high molecular weight polymers all generate free radicals during electrical dendron aging. Meanwhile, the microcapsule isolates the contact between the repair liquid and potential free radicals, so that the repair liquid maintains high stability before flowing out of the microcapsule, the reliability of long-term operation is enhanced, and the service life and the reliability of the insulating material can be effectively improved.
The application has verified the self-repairing performance and the insulating performance through experiments, and the influence of each parameter on the self-repairing performance and the insulating performance is verified, so that a good result is obtained.
A potential alternative of the present application may be to perform nano-modification of the used stable repair liquid, such as adding nano boron nitride, silicon dioxide, etc., to improve the insulation performance after curing.
Although the present application has been described above with reference to specific embodiments, those skilled in the art will recognize that many changes may be made in the configuration and details of the present application within the principles and scope of the present application. The scope of protection of the application is determined by the appended claims, and all changes that come within the meaning and range of equivalency of the technical features are intended to be embraced therein.

Claims (7)

1. A preparation method of a self-repairing insulating material is characterized by comprising the following steps: the method comprises the following steps:
step 1: uniformly mixing acrylate resin and a polyfunctional group active diluent according to a proportion, and adding dimethylaniline into the mixture, wherein the dimethylaniline is used for repairing electrical damage to prepare a repairing liquid for free radical initiated polymerization;
step 2: preparing an aqueous solution containing sodium dodecyl benzene sulfonate and polyvinyl alcohol, slowly adding the repair liquid into the aqueous solution, and stirring to form uniformly dispersed oil-in-water core material emulsion;
and step 3: preparing urea and formaldehyde into a solution according to a proportion, stirring to form a water-soluble prepolymer solution of mono-methylol urea and dihydroxy-methylol urea, adding a proper amount of deionized water into the prepolymer solution, cooling to room temperature, and adding diluted hydrochloric acid to adjust the pH value to 7;
and 4, step 4: adding the prepolymer solution into the oil-in-water core material emulsion, adding a catalyst and a pH value regulator, regulating the pH value of the solution to 3-4, heating to 50-60 ℃, reacting for 3-5 hours, removing unreacted core materials and wall materials, cooling, washing, sieving, and naturally drying to obtain the self-repairing microcapsule; the self-repairing microcapsule is applied to an insulating material to obtain a self-repairing insulating material with electric damage self-repairing capability;
the acrylate resin in the step 1 is bisphenol A epoxy acrylate, bisphenol A ethoxy diacrylate, novolac epoxy acrylate or epoxidized oil acrylate;
in the step 1, the polyfunctional active diluent is trimethylolpropane triacrylate or ethoxylated trimethylolpropane triacrylate.
2. The method for preparing a self-healing insulating material according to claim 1, wherein: in the step 1, the mass ratio of the acrylate resin in the mixture is 25-50%, and the mass ratio of the dimethylaniline is 0.5-2 wt% of the mixture.
3. The method for preparing a self-healing insulating material according to claim 1, wherein: preparing an aqueous solution containing 1 wt.% of sodium dodecyl benzene sulfonate and 0.2 wt.% of polyvinyl alcohol in the step 2, slowly adding 10 wt.% to 20 wt.% of the repair liquid into the aqueous solution, and mechanically stirring at a rotating speed of 1000 to 1500r/min for 20min to 30min to completely emulsify the repair liquid to form a uniformly dispersed oil-in-water core emulsion.
4. The method for preparing a self-healing insulating material according to claim 1, wherein: in the step 3, a solution is prepared from urea and formaldehyde in a molar ratio of 1:2, the solution is magnetically stirred and reacts for 1 hour under the alkaline conditions of 70 ℃ and a pH value of 8-9 to form a water-soluble prepolymer of the monomethylol urea and the dimethylol urea, a proper amount of deionized water is added into the prepolymer solution, the prepolymer solution is cooled to room temperature, and diluted hydrochloric acid is added to adjust the pH value to 7.
5. The method for preparing a self-healing insulating material according to claim 1, wherein: and 4, adding the prepolymer solution into the oil-in-water core material emulsion, adding a catalyst of resorcinol and a pH value regulator of ammonium chloride, regulating the pH value of the solution to 3-4 by using 1-2% by mass of dilute hydrochloric acid, heating to 50-60 ℃ at the speed of 1 ℃/min, reacting for 3-5 hours, removing unreacted core materials and wall materials, cooling, washing, sieving, and naturally drying to obtain the microcapsule.
6. The method for preparing a self-healing insulating material according to claim 1, wherein: the mass ratio of the prepolymer to the repairing liquid in the step 4 is 1 (2-1), the addition amount of the catalyst is 3% -6% of the prepolymer solution, and the addition amount of the pH value regulator is 5% -6% of the prepolymer.
7. The method for preparing a self-healing insulating material according to claim 1, wherein: the volume percentage of the microcapsule in the composite matrix is 3-10%;
the insulating material is epoxy resin, silicon rubber, polyimide, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, or a composite insulating material obtained by mixing the insulating material with glass fiber and nano/micron filler.
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