Epoxy resin / silicone composite insulation material resistant to tracking and preparation thereof

Abstract

The present application relates to the field of electrical insulation materials, and provides an epoxy resin / silicone composite insulation material resistant to tracking and its preparation method, which comprises the following steps: S1, adopting coating treatment to obtain microcapsules; S2, adopting a first surface modifier to perform surface modification treatment on the microcapsules to obtain modified microcapsules; S3, fully wetting and uniformly dispersing the modified microcapsules in polydimethylsiloxane, then adding a polydimethylsiloxane crosslinking agent and a crosslinking catalyst to form an organic silicone premix system; S4, mixing the organic silicone premix system with an alicyclic epoxy resin, a curing agent and an accelerator, and then adding inorganic fillers to uniformly disperse to obtain a composite mixed system; and S5, pouring the composite mixed system into a mold and then performing heat curing treatment to obtain the composite insulation material; the composite insulation material has excellent interface bonding, durable surface hydrophobicity and migration, and high tracking resistance.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials technology, and more specifically, to an epoxy resin / silicone composite insulation material resistant to tracking and its preparation. Background Technology

[0002] As power systems develop towards higher voltage, larger capacity, and longer-distance transmission, the performance requirements for external insulation materials in complex environments such as humidity, heat, and pollution are increasingly stringent. As a crucial component ensuring the reliability of power grid operation, organic insulation materials not only need excellent electrical insulation properties and mechanical strength, but also must maintain long-term stable hydrophobicity and anti-flashover capabilities under complex and variable environmental conditions. In recent years, alicyclic epoxy resins have attracted widespread attention in the field of external insulation due to their outstanding mechanical strength, excellent weather resistance and moisture barrier properties, and reliable aging resistance at the sheath / core rod interface. They are considered a potential solution to compensate for the shortcomings of traditional silicone rubber external insulation materials in high humidity and heat environments and to improve the reliability of transmission lines in extreme environments.

[0003] However, as a polar polymer, alicyclic epoxy resins lack intrinsic hydrophobicity and hydrophobic migration. Furthermore, under harsh environments such as high heat, high salt spray, and severe pollution, their surfaces easily absorb water, adsorb salt and dirt, leading to increased surface conductivity of the sheds. Localized electric field concentration along the insulator surface easily occurs, resulting in surface discharge, carbonization, and ablation, accelerating the deterioration of the outer insulation material. Therefore, existing technologies have further modified alicyclic epoxy resins as follows:

[0004] Firstly, coating the epoxy resin surface with a millimeter-thick layer of silicone rubber material can achieve excellent hydrophobic properties. However, there is a macroscopic interface between the silicone rubber coating layer and the epoxy resin matrix, which is prone to aging and failure in high humidity and heat environments, resulting in interface debonding, coating damage and peeling.

[0005] Secondly, in order to improve the tracking resistance of alicyclic epoxy resins, existing technologies mainly involve doping the epoxy resin with a large amount of inorganic fillers. While this can effectively improve the tracking resistance of epoxy resins, the addition of a large amount of inorganic fillers not only sacrifices the resin's water resistance but also severely reduces the mechanical properties of the external insulation material.

[0006] Therefore, there is an urgent need for an external insulation material that can simultaneously achieve excellent interfacial adhesion, durable surface hydrophobicity and migration, and high resistance to tracking. Summary of the Invention

[0007] In view of the above-mentioned shortcomings in the prior art, the core objective of this invention is to solve the technical problem that existing external insulation materials are difficult to simultaneously possess excellent interfacial adhesion, durable surface hydrophobicity and migration properties, and high resistance to tracking.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing an epoxy resin / silicone composite insulating material resistant to tracking includes the following steps:

[0010] S1. A single-layer capsule wall material is formed on the surface of a perfluorinated inert phase change medium using a coating process to obtain microcapsules with a perfluorinated inert phase change medium as the core material.

[0011] S2. The microcapsules are surface-modified using a first surface modifier to obtain modified microcapsules; the first surface modifier includes: a silane coupling agent and / or oligodimethylsiloxane; the number average molecular weight of the oligodimethylsiloxane is 300-1500 g / mol.

[0012] S3. The modified microcapsules are fully wetted and uniformly dispersed in polydimethylsiloxane, and then polydimethylsiloxane crosslinking agent and crosslinking catalyst are added to form an organosilicon premixed system. The number average molecular weight of the polydimethylsiloxane is 800-20000 g / mol.

[0013] S4. The organosilicon premix system is mixed with alicyclic epoxy resin, curing agent and accelerator to obtain a composite mixture system;

[0014] S5. The composite mixture system is poured into a mold and then subjected to thermosetting treatment to obtain an epoxy resin / organic silicon composite insulation material.

[0015] Furthermore, in step S1, the capsule wall material used in the coating process includes one or more of urea-formaldehyde resin, acrylic photocurable resin, polyurea, polyurethane, and silica inorganic shell.

[0016] Further, in step S1, the core material used in the coating treatment is a perfluorinated inert phase change medium; the perfluorinated inert phase change medium includes one or more of perfluoroethers, perfluoropolyethers, or perfluorinated electronic fluids. More preferably, the perfluorinated inert phase change medium is one or more of perfluorohexanone, perfluoroethers, perfluoropolyethers, and perfluorinated electronic fluids; even more preferably, the atmospheric boiling point range of the perfluorinated inert phase change medium is 50–200 °C; even more preferably, the atmospheric boiling point range of the perfluorinated inert phase change medium is 140–180 °C.

[0017] Further, in step S1, the coating treatment is any one of photocuring, interfacial polymerization, or sol-gel methods.

[0018] Those skilled in the art can prepare microcapsules using one or more of the above-described encapsulation methods based on the selection of capsule wall material.

[0019] Furthermore, the photocuring method uses an acrylate photocurable resin as the capsule wall material, and the acrylate photocurable resin is preferably one or more of acrylate, (meth)acrylate or epoxy acrylate resin containing double bonds or epoxy groups.

[0020] The specific preparation method for microcapsules using this capsule wall material includes the following steps:

[0021] S11. Using a perfluorinated inert phase change medium as the inner phase, an acrylate photocurable resin precursor as the intermediate phase, and a stable aqueous phase as the outer phase, a coaxial three-phase microfluidic process is adopted to form core-shell droplets.

[0022] S12. The core-shell droplets are subjected to online photocuring treatment to solidify the acrylate photocurable resin precursor into a shell layer, thereby obtaining a functional microcapsule suspension.

[0023] S13. The functional microcapsule suspension is sequentially separated, washed and dried to obtain the microcapsules with a single-layer capsule wall material.

[0024] Preferably, in step S11, the stable aqueous phase is a polyvinyl alcohol aqueous solution; the mass fraction of the polyvinyl alcohol aqueous solution is 3-8 wt%.

[0025] More preferably, the acrylate photocurable resin precursor further includes a photoinitiator.

[0026] Preferably, in step S12, the online photocuring process uses ultraviolet or visible light as the light source; the wavelength of the light source is 320–420 nm, and the irradiation intensity is 50–200 mW / cm². 2 The irradiation time is 10–120 s.

[0027] Preferably, in step S13, the separation is any one of static sedimentation, centrifugal separation, or sieving; the washing uses deionized water; and the drying is carried out at 20–40 °C or in a vacuum low-temperature environment.

[0028] Furthermore, the interfacial polymerization method uses urea-formaldehyde resin, polyurea, or polyurethane as the shell material to form a core material droplet containing a first reactive component through emulsification or microfluidic technology, and makes the droplet contact with the second reactive component in the dispersed phase, and a polymerization reaction occurs at the droplet interface to form a shell layer.

[0029] Furthermore, the sol-gel method uses a silica inorganic shell as the capsule wall material to form core droplets through emulsification or microfluidic technology, and causes silane or silicate precursors to undergo hydrolysis and condensation reactions on the droplet surface to form a silica shell.

[0030] Further, in step S2, the surface modification treatment is as follows: the microcapsules are dispersed in an organic solvent containing a first surface modifier, and the mixture is stirred to react, thereby obtaining the modified microcapsules.

[0031] Furthermore, the silane coupling agent in the first surface modifier is one or more of aminopropyltriethoxysilane, epoxysilane, or vinylsilane; the organic solvent is anhydrous ethanol or a mixture of ethanol and water.

[0032] Further, in step S3, the polydimethylsiloxane is one or more of terminal epoxy polydimethylsiloxane, terminal hydroxyl polydimethylsiloxane, terminal amino polydimethylsiloxane, and vinyl polydimethylsiloxane.

[0033] Further, in step S3, the polydimethylsiloxane crosslinking agent is one or more of a de-alcoholized crosslinking agent, a dehydrating crosslinking agent, an addition-type crosslinking agent, or a condensation-type crosslinking agent. More preferably, the polydimethylsiloxane crosslinking agent is one or more of tetraethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, hydrogen-containing polysiloxane, methylhydrosilicone oil, hydrogen-containing polysiloxane, and methylhydrosilicone oil.

[0034] Further, in step S3, the crosslinking catalyst is one or more of tin-based catalysts, platinum-based catalysts, titanium-based catalysts, and aluminum-based catalysts.

[0035] Further, in step S3, the alicyclic epoxy resin is one or more selected from 3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexylcarboxylate, bis((3,4-epoxycyclohexyl)methyl)adipic acid ester, tetrahydroindene diepoxide, 3,4-epoxycyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexyl methacrylate, and vinyl cyclohexene dioxide.

[0036] Furthermore, the curing agent is one or more of methylhexahydrophthalic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0037] Further, the accelerator is N,N-dimethylbenzylamine or 2,4,6-tris(dimethylaminomethyl)phenol.

[0038] Further, in step S4, after mixing the organosilicon premixed system with alicyclic epoxy resin, curing agent and accelerator, a modified inorganic filler is added to obtain the composite mixed system; the modified inorganic filler is prepared by dispersing the inorganic filler in a second surface modifier and performing a surface grafting reaction under stirring conditions; wherein, the second surface modifier is a silane coupling agent and / or oligomeric dimethylsiloxane.

[0039] Furthermore, the inorganic filler is one or more of aluminum hydroxide, magnesium hydroxide, and silicon dioxide.

[0040] Preferably, the silane coupling agent in the second surface modifier is one or more of aminopropylsilane, vinylsilane, or epoxysilane.

[0041] Furthermore, in step S5, the temperature of the thermosetting treatment is 100–120 °C, and the curing time is 2–6 h.

[0042] The second objective of this invention is to provide an epoxy resin / silicone composite insulating material resistant to tracking, prepared by the above-described method, comprising the following raw materials in parts by weight:

[0043] The mixture contains 80-120 parts of alicyclic epoxy resin, 70-100 parts of curing agent, 0.5-3 parts of accelerator, 5-30 parts of polydimethylsiloxane, 1-10 parts of polydimethylsiloxane crosslinking agent, 0.1-2 parts of crosslinking catalyst, and 5-30 parts of modified microcapsules.

[0044] Alternatively, 80-120 parts of alicyclic epoxy resin, 70-100 parts of curing agent, 0.5-3 parts of accelerator, 5-30 parts of polydimethylsiloxane, 1-10 parts of polydimethylsiloxane crosslinking agent, 0.1-2 parts of crosslinking catalyst, 5-30 parts of modified microcapsules; and 50-300 parts of surface-modified aluminum hydroxide filler.

[0045] The overall inventive concept of this invention is as follows:

[0046] First, this invention does not rely on external energy fields such as magnetic fields or electric fields for induction. Instead, it utilizes the inherent thermodynamic incompatibility between alicyclic epoxy resin and organosilicon systems to achieve spontaneous phase separation during the curing process, thereby constructing a component gradient structure with a continuous transition from the bottom epoxy-rich region to the surface organosilicon-rich region. This gradient structure ensures excellent interfacial adhesion between the epoxy layer and the mandrel while forming a functional layer rich in organosilicon components on the surface, endowing the material with excellent hydrophobicity and hydrophobic migration ability. Unlike traditional layered structures, this method forms a continuous transition interface during the spontaneous layering process, avoiding the introduction of macroscopic interfacial defects. More importantly, the spontaneous layering process provides a basis for the synergistic migration of microcapsule components during the layering process.

[0047] Furthermore, to address the problem of random distribution of microcapsules and fillers in epoxy / organosilicon systems and the difficulty in achieving directional enrichment, the surface of the outer wall of the microcapsules and the surface of the inorganic fillers are modified to introduce siloxane functional groups and / or organosilicon segments that can interact with organosilicon molecular chains through chain entanglement or flexible interaction.

[0048] Furthermore, during the material curing and self-stratification process, the microcapsules and inorganic fillers, relying on the close molecular interactions with the organosilicon layer, are synergistically dragged by the organosilicon layer and preferentially enriched in the organosilicon-rich regions of the material surface, achieving autonomous selective distribution of microcapsules and inorganic fillers. This method can achieve a high density of microcapsules and aluminum hydroxide on the material surface without significantly increasing the overall amount added, providing conditions for suppressing surface creepage.

[0049] Furthermore, when localized creepage or tracking discharge occurs on the material surface, the micro-arc generated in the discharge area and its localized high temperature act on the microcapsules enriched in the surface organosilicon phase, triggering the microcapsules to rupture. After the microcapsules rupture, the internal perfluorinated inert phase change medium undergoes an instantaneous vaporization phase change under the synergistic effect of electro-thermal interaction. This process converts the energy originally generated by surface discharge into a triggering source that suppresses surface discharge. On the one hand, the perfluorinated inert phase change medium has a large latent heat of vaporization during the phase change process, which can absorb the localized heat generated by the discharge and reduce the transient temperature rise in the discharge area, thereby providing thermal protection for the matrix material. On the other hand, the localized volume release and gas generation accompanying the phase change will disturb the micro-arc discharge process, weaken the arc maintenance conditions, and shorten its duration. At the same time, the above-mentioned phase change process can disturb and destroy the continuity and stable adhesion state of the carbonized residual structure in the ablation area, inhibit the formation of surface conductive channels, increase the local surface resistivity, and thus increase the difficulty of subsequent surface discharge, reduce the probability of surface arcs repeating along the original path, thereby improving the tracking resistance of the outer insulation material. Meanwhile, inorganic fillers enriched in the organosilicon layer, such as aluminum hydroxide, undergo endothermic dehydration reactions under the localized high temperatures generated by surface creep or tracking discharge, absorbing discharge heat and inhibiting surface ablation. Their synergistic effect with the perfluorinated inert phase change medium released by the functional microcapsules further weakens the conditions for maintaining the discharge channel and improves the material's resistance to tracking.

[0050] This invention relates to the modification mechanism of microcapsules: based on the self-stratifying epoxy / organosilicon system of microcapsules and inorganic fillers, a surface modification method is further provided that enables autonomous selective distribution, which is particularly applicable to microcapsules, inorganic fillers, or their combined systems. This surface modification method modifies the surface chemical properties of functional components to form stronger interfacial interactions with the organosilicon phase, thereby achieving synergistic migration and directional enrichment with the organosilicon phase during material curing. Specifically, microcapsules are dispersed in an organic solvent system containing a silane coupling agent, and then, under stirring conditions, the silane coupling agent is hydrolyzed to generate silanol groups. These silanol groups further undergo condensation or grafting reactions with hydroxyl, amino, or other active groups on the surface of the microcapsules, thereby introducing siloxane functional structures onto the surface of the microcapsules. Furthermore, during the surface modification process, low molecular weight or low viscosity polydimethylsiloxane prepolymers can be introduced to fix them onto the surface of the functional components through chain entanglement, physical adsorption, and / or local polycondensation, forming a surface coating layer rich in flexible siloxane segments on their exterior. Thus, through this interface regulation treatment, the surface polarity and surface energy of the functional components are transformed from the original high polarity or medium polarity state to a low surface energy characteristic with high thermodynamic affinity for the organosilicon phase.

[0051] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0052] (1) This invention utilizes the thermodynamic incompatibility of the system to achieve spontaneous phase separation and constructs a gradient structure that continuously transitions from an epoxy-enriched bottom layer to an organosilicon-enriched surface layer in one step. The process is simple and efficient.

[0053] (2) The present invention achieves high bonding strength of the matrix layer and high hydrophobicity of the surface layer simultaneously through the continuous gradient structure formed by the spontaneous phase separation of material components, without the need for external field assistance.

[0054] (3) By modifying the surface, the present invention enables microcapsules and inorganic fillers to accumulate on the material surface at a lower addition amount, and can simultaneously trigger gas phase fire extinguishing and solid phase heat absorption during discharge, forming synergistic protection, thereby significantly improving the resistance to leakage current tracking performance without affecting the mechanical properties of the matrix. Detailed Implementation

[0055] Example 1

[0056] This embodiment provides a method for preparing an epoxy resin / silicone composite insulating material resistant to tracking, including the following steps:

[0057] S1. Preparation of microcapsules

[0058] (1) Coating treatment: A coaxial three-phase microfluidic chip device is used, which has coaxial nested inner, middle and outer capillary channels, respectively:

[0059] Inner phase: perfluorohexanone, injected into the inner capillary at a flow rate of 5 μL / min.

[0060] Intermediate phase: a homogeneous mixture of bisphenol A type epoxy acrylate resin and 2-hydroxy-2-methyl-1-phenyl-1-propanone, injected into the intermediate layer capillary at a flow rate controlled at 15 μL / min; the amount of 2-hydroxy-2-methyl-1-phenyl-1-propanone added is 2 wt% of the mass of bisphenol A type epoxy acrylate resin.

[0061] External phase: A 5 wt% aqueous solution of polyvinyl alcohol 1788 is injected into the outer capillary at a flow rate controlled at 150 μL / min. In a constant temperature environment of 20-25 °C, by precisely controlling the flow rates of the three phases, the fluid shear force completely encapsulates the inner core material with the intermediate shell precursor, forming well-dispersed, uniformly sized O / O / W core-shell droplets at the outlet under the shear of the external phase. The degree of alcoholysis of the polyvinyl alcohol 1788 aqueous solution is 87-89%, and the viscosity of a 4% aqueous solution is 20-30 mPa·s.

[0062] (2) In-line photocuring: The continuous phase containing core-shell droplets from step (1) is guided into a transparent polytetrafluoroethylene tube with an inner diameter of 1 mm. This section of the tube is placed in an adjustable UV curing zone. A 365 nm UV LED light source is used, with a wavelength of 100 mW / cm² at a distance of 5 cm from the tube. 2 The flowing droplets were irradiated with an intensity of [unspecified] for 60 seconds. During this process, the epoxy acrylate resin in the shell rapidly underwent free radical polymerization under the action of a photoinitiator, solidifying into a continuous and dense polymer capsule wall, thereby forming a structurally stable perfluorohexanone microcapsule suspension.

[0063] (3) Separation, washing and drying: The microcapsule suspension obtained in step (2) was transferred to a centrifuge tube and centrifuged at 3000 rpm for 5 min. The supernatant was removed. Deionized water was added to the precipitated microcapsules, and the mixture was redispersed by vortexing. The mixture was centrifuged again, and this washing process was repeated three times to thoroughly remove residual PVA and unreacted small molecules. The washed microcapsule wet material was transferred to a petri dish and placed in a vacuum drying oven at 30 ℃. It was dried for 12 h under a vacuum of -0.1 MPa to obtain dry, free-flowing, uniformly distributed monolayer capsule wall material perfluorohexanone microcapsule powder.

[0064] S2. Preparation of modified microcapsules:

[0065] Five parts by weight of the perfluorohexanone microcapsule powder prepared in step (3) were weighed and dispersed in 100 parts of anhydrous ethanol. The mixture was placed in a flask equipped with a mechanical stirrer and a reflux condenser. 0.3 parts of γ-aminopropyltriethoxysilane were added to the system, and the mixture was pre-reacted at 300 rpm for 1 h under a water bath temperature of 40 ℃. Then, 0.2 parts of terminal epoxy oligomeric siloxane with a number average molecular weight of 600 g / mol were added, and the reaction was continued under the same conditions for 4 h. After the reaction was completed, the mixture was filtered, the solid product was collected and washed three times with anhydrous ethanol, and finally the product was dried to constant weight in a vacuum drying oven at 40 ℃ to obtain the modified microcapsules.

[0066] Preparation of S3 and Organosilicon Premixed System

[0067] Weigh 15 parts by weight of hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 800 g / mol into a dry beaker; mechanically stir at a low speed of 200 rpm to mix evenly; then slowly add 10 parts of the modified microcapsules prepared in step S2 to the mixture and continue stirring for 30 min to ensure that the microcapsules are fully wetted and evenly dispersed in the system to form a premixed slurry.

[0068] Add 0.3 parts of γ-aminopropyltriethoxysilane, 3 parts of methyltriethoxysilane and 0.5 parts of stannous octoate to the above premixed slurry in sequence, and continue stirring at the same speed for 15 min until the whole system presents a uniform and viscous paste state to obtain the organosilicon premixed system.

[0069] S4, Preparation of Composite Mixture System

[0070] Add the components to the above silicone premix system in the following order by weight, and stir thoroughly at 500 rpm for 10 min after each addition to ensure homogeneity:

[0071] First, add 100 parts of 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexylcarboxylate; then add 85 parts of methylhexahydrophthalic anhydride and 1 part of N,N-dimethylbenzylamine.

[0072] Then, 50 parts of surface-modified aluminum hydroxide filler were added. The preparation method of the surface-modified aluminum hydroxide filler was as follows: 50 parts of aluminum hydroxide powder with an average particle size of 5 μm were dispersed in a second surface modifier solution composed of 2 parts of γ-aminopropyltriethoxysilane, 3 parts of hydroxyl-terminated oligomeric dimethylsiloxane with a number average molecular weight of 1000 g / mol, and 200 parts of anhydrous ethanol. Specifically, γ-aminopropyltriethoxysilane was added first at 60 °C, and the reaction was carried out at a stirring speed of 300 rpm for 1 h. Then, hydroxyl-terminated oligomeric dimethylsiloxane was added, and the reaction was continued for 1 h. After the reaction was completed, the mixture was filtered, the solid product was washed three times with anhydrous ethanol, and dried to constant weight in a vacuum drying oven at 80 °C to obtain the surface-modified aluminum hydroxide filler.

[0073] The entire mixture was placed under a high-speed disperser and dispersed at 1000 rpm for 15 min until a viscous, uncured composite mixture with a uniform appearance and no obvious particles or agglomerates was obtained.

[0074] S5, Casting and Thermosetting Treatment

[0075] The composite mixture obtained in step S3 is transferred to a vacuum degassing chamber and degassed under a vacuum of -0.1 MPa for approximately 10 minutes. Then, the degassed mixture is poured into a preheated (80 °C) flat silicone rubber mold, which can be 100 mm × 100 mm × 4 mm in size. The poured mold is then transferred to a forced-air drying oven for thermosetting according to the following procedure:

[0076] First stage: Pre-gelation was carried out by incubating at 80 ℃ for 1 h.

[0077] Second stage: Heat to 110 ℃ and hold at this temperature for 4 h to complete the curing of epoxy resin and the crosslinking reaction of polydimethylsiloxane.

[0078] After the curing process is completed, turn off the oven power and allow the material to cool naturally to below room temperature. Demold the material to obtain the epoxy resin / silicone composite insulating material board resistant to tracking as described in this embodiment.

[0079] Example 2

[0080] The difference between this embodiment and Embodiment 1 is that the surface modification treatment of both the microcapsules and the inorganic fillers uses only γ-aminopropyltriethoxysilane as a single surface modifier.

[0081] Example 3

[0082] The difference between this embodiment and Embodiment 1 is that, in step S4, aluminum hydroxide filler without surface modification is directly used to prepare the composite mixture system.

[0083] Example 4

[0084] The difference between this embodiment and Embodiment 1 is that the proportions of the core raw materials are changed. The specific steps are as follows:

[0085] S2. Preparation of modified microcapsules:

[0086] Weigh 30 parts by weight of the perfluorohexanone microcapsule powder obtained in step (3), disperse it in 300 parts by weight of anhydrous ethanol, and place it in a flask equipped with a mechanical stirrer and a reflux condenser; add 1.5 parts by weight of γ-aminopropyltriethoxysilane to the system. React at 40 °C with stirring at 300 rpm for 4 h. After the reaction is complete, filter the mixture, collect the solid product and wash it three times with anhydrous ethanol. Finally, dry the product in a vacuum drying oven at 40 °C to constant weight to obtain the modified microcapsules.

[0087] Preparation of S3 and Organosilicon Premixed System

[0088] By weight, 6 parts of hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 800 g / mol were weighed into a dry beaker; the mixture was mechanically stirred at a low speed of 200 rpm to ensure uniform mixing; then, 30 parts of the modified microcapsules prepared in step S2 were slowly added to the mixture, and stirring was continued for 30 min to ensure that the microcapsules were fully wetted and uniformly dispersed in the system to form a premixed slurry.

[0089] Add 0.3 parts of γ-aminopropyltriethoxysilane, 1 part of methyltriethoxysilane and 0.2 parts of stannous octoate to the above premixed slurry in sequence, and continue stirring at the same speed for 15 min until the whole system presents a uniform and viscous paste state to obtain the organosilicon premixed system.

[0090] S4, Preparation of Composite Mixture System

[0091] Add the components to the above silicone premix system in the following order by weight, and stir thoroughly at 500 rpm for 10 min after each addition to ensure homogeneity:

[0092] First, add 80 parts of 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexylcarboxylate; then add 100 parts of methylhexahydrophthalic anhydride and 0.8 parts of N,N-dimethylbenzylamine.

[0093] Then, 220 parts of surface-modified aluminum hydroxide filler were added. The preparation method of the surface-modified aluminum hydroxide filler was as follows: 100 parts of aluminum hydroxide powder with an average particle size of 5 μm were dispersed in a second surface modifier solution composed of 2 parts of γ-aminopropyltriethoxysilane, 3 parts of oligomeric dimethylsiloxane with a number average molecular weight of 600 g / mol and 200 parts of anhydrous ethanol. The mixture was reacted at 60 °C with a stirring speed of 300 rpm for 2 h. After the reaction was completed, the mixture was filtered, the solid product was washed three times with anhydrous ethanol, and dried to constant weight in a vacuum drying oven at 80 °C to obtain the surface-modified aluminum hydroxide filler.

[0094] The entire mixture was placed under a high-speed disperser and dispersed at 1000 rpm for 15 min until a viscous, uncured composite mixture with a uniform appearance and no obvious particles or agglomerates was obtained.

[0095] Example 5

[0096] The difference between this embodiment and Embodiment 1 is that the internal phase is replaced, specifically with a perfluorinated electronic fluid, the commercial model of which is Fluorinert™ FC-40.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that it does not include the preparation and introduction of microcapsules, does not construct a self-layered structure of organosilicon / epoxy resin, and uses a pure alicyclic epoxy resin matrix and unmodified aluminum hydroxide filler for composite formation. The specific differences in steps are as follows:

[0099] By weight, 100 parts of 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexylcarboxylate, 85 parts of methylhexahydrophthalic anhydride, and 1 part of N,N-dimethylbenzylamine were stirred and mixed at 500 rpm for 10 min to obtain an epoxy resin mixture. Subsequently, 50 parts of untreated aluminum hydroxide powder were directly added to the epoxy resin mixture, and the entire mixture was dispersed at 1000 rpm for 15 min in a high-speed disperser to obtain an uncured composite mixture.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 1 is that it does not include the preparation and introduction of microcapsules, but retains the self-layered structure of organosilicon / epoxy resin, and uses surface-modified aluminum hydroxide filler. The specific differences are as follows:

[0102] By weight, 15 parts of hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 800 g / mol were weighed into a dry beaker and stirred at 200 rpm. Then, 0.3 parts of γ-aminopropyltriethoxysilane, 3 parts of methyltriethoxysilane and 0.5 parts of stannous octoate were added sequentially and stirred for 15 min to obtain a microcapsule-free organosilicon premixed system.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 3 is that, after the microcapsules are prepared, no surface siloxane modification treatment is performed on them. The specific difference is as follows:

[0105] After obtaining perfluorohexanone microcapsule powder by sub-step (3) in step S1, weigh out 5 portions of the unmodified microcapsule powder for use in subsequent steps.

[0106] Experimental Example 1

[0107] This test example is based on the samples prepared in Examples 1-6 and Comparative Examples 1-3. Further static contact angle and tracking resistance tests were conducted with reference to GB / T19519-2014 "Definition, Test Methods and Acceptance Criteria for Suspension and Tension Composite Insulators for AC Systems with Nominal Voltage Higher than 1000V for Overhead Lines". The specific test results are as follows:

[0108] Table 1. Static contact angle and tracking resistance test results

[0109]

[0110] Based on the data analysis in Table 1, we can conclude that:

[0111] First, in Examples 1-5, which construct epoxy / organosilicon self-layered structures, the static contact angle of the surface is greater than 102°, exhibiting good hydrophobicity. This directly confirms the effectiveness of spontaneously forming an organosilicon-rich surface layer through thermodynamic incompatibility, solving the fundamental problem of surface hydrophilicity in traditional epoxy materials, i.e., Comparative Example 1.

[0112] Furthermore, the surface modification process has a decisive impact on the final performance. Example 1, which adopted a stepwise modification scheme of first adding a silane coupling agent and then adding oligomeric dimethylsiloxane, achieved the best results, with the highest surface contact angle and the shallowest ablation depth after tracking resistance test. This indicates that this stepwise modification most effectively enhances the affinity between the functional component and the organosilicon phase, achieving efficient synergistic enrichment of microcapsules and aluminum hydroxide on the surface. In contrast, Example 2, which only used silane coupling agent modification, had an increased ablation depth, thus proving that stepwise modification is more critical for improving enrichment efficiency and protective effect. Example 3, which failed in the test without modification of the filler, strongly confirms from the opposite perspective that if the inorganic filler cannot migrate to the surface with the organosilicon phase, it will destroy the gas-solid phase synergistic protection mechanism, leading to protection failure.

[0113] Furthermore, although the ablation depth of Comparative Example 2 (without microcapsules) and Comparative Example 3 (with unmodified microcapsules) was better than that of the pure epoxy system (i.e., better than Comparative Example 1), it was significantly lower than that of Example 1. This further highlights that the gas phase fire extinguishing and disturbance mechanism provided by the surface-modified and enriched microcapsules is an indispensable core component.

[0114] In summary, the data in Table 1 fully validates that the present invention, through its multi-layered design of constructing a gradient structure through self-layering, achieving directional enrichment of functional components through stepwise surface modification, and synergistic protection of the gas and solid phases, can simultaneously impart excellent surface hydrophobicity and outstanding resistance to leakage current tracking to the material without affecting the matrix performance.

Claims

1. A method for preparing an epoxy resin / silicone composite insulating material resistant to tracking, characterized in that, Includes the following steps: S1. A single-layer capsule wall material is formed on the surface of a perfluorinated inert phase change medium using a coating treatment method to obtain microcapsules with a perfluorinated inert phase change medium as the core material; wherein, the capsule wall material used in the coating treatment is selected from acrylate photocurable resins, and the acrylate photocurable resins are selected from one or more of (meth)acrylate or epoxy acrylate resins. S2. The microcapsules are surface-modified using a first surface modifier to obtain modified microcapsules; the first surface modifier includes: a silane coupling agent or a silane coupling agent and an oligomeric dimethylsiloxane; the number-average molecular weight of the oligomeric dimethylsiloxane is 300-1500 g / mol. S3. The modified microcapsules are thoroughly wetted and uniformly dispersed in polydimethylsiloxane, followed by the addition of a polydimethylsiloxane crosslinking agent and a crosslinking catalyst to form an organosilicon premixed system. The number-average molecular weight of the polydimethylsiloxane is 800–20000 g / mol. The polydimethylsiloxane is one or more of terminal epoxy polydimethylsiloxane, terminal hydroxyl polydimethylsiloxane, terminal amino polydimethylsiloxane, and vinyl polydimethylsiloxane. S4. The organosilicon premix system is mixed with alicyclic epoxy resin, curing agent and accelerator, and then modified inorganic filler is added to obtain a composite mixture system; the modified inorganic filler is prepared by dispersing the inorganic filler in a second surface modifier and performing a surface grafting reaction under stirring conditions; wherein, the second surface modifier includes: silane coupling agent or silane coupling agent and oligomeric dimethylsiloxane; S5. The composite mixture system is poured into a mold and then subjected to thermosetting treatment to obtain an epoxy resin / organic silicon composite insulation material.

2. The method for preparing the tracking-resistant epoxy resin / organic silicon composite insulating material according to claim 1, characterized in that, In step S1, the perfluorinated inert phase change medium includes one or more of perfluorinated ethers, perfluorinated polyethers, or perfluorinated electronic liquids.

3. The method for preparing the tracking-resistant epoxy resin / organic silicon composite insulating material according to claim 1, characterized in that, In step S5, the temperature of the thermosetting treatment is 100-120 °C, and the curing time is 2-6 h.

4. The method for preparing the tracking-resistant epoxy resin / organic silicone composite insulating material according to claim 3, characterized in that, The inorganic filler is one or more of aluminum hydroxide, magnesium hydroxide, and silicon dioxide.

5. A tracking-resistant epoxy resin / silicone composite insulating material prepared by the method described in claim 4, characterized in that, The raw materials comprise the following parts by weight: 80-120 parts alicyclic epoxy resin, 70-100 parts curing agent, 0.5-3 parts accelerator, 5-30 parts polydimethylsiloxane, 1-10 parts polydimethylsiloxane crosslinking agent, 0.1-2 parts crosslinking catalyst, 5-30 parts modified microcapsules, and 50-100 parts modified inorganic filler.

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