Large-tonnage insulating pull rod joint adhesive and preparation method thereof

Abstract

The invention discloses a large-tonnage insulating pull rod joint adhesive and a preparation method thereof, belongs to the technical field of high-voltage insulating materials, and aims to solve the technical problems that an existing large-tonnage insulating pull rod joint adhesive easily generates microcracks and interface layering under long-term electromechanical coupling stress and is difficult to early warn and self-repair. The preparation method comprises the following steps: firstly, synthesizing a polyurea microcapsule containing fluorescent dye tetraphenyl ethylene (TPE), and accurately controlling the wall thickness of the microcapsule through an interfacial polymerization technology to ensure that the microcapsule is broken under specified stress; then, the microcapsules are compounded with bisphenol A epoxy resin, nano montmorillonite and a silane coupling agent, and a curing agent is added to prepare an adhesive; when the adhesive joint is subjected to critical stress, the microcapsule is broken and the fluorescent dye is released, so that damage self-diagnosis is realized; the damage detection sensitivity, the mechanical property and the high temperature resistance of the adhesive are remarkably improved, and a reliable guarantee is provided for hot-line work of ultra-high voltage transmission lines.

Description

Technical Field

[0001] The present invention relates to the intersecting field of polymer materials and power equipment maintenance technology, and in particular to a large-tonnage insulating pull rod joint adhesive and a preparation method thereof. Background Art

[0002] In the operation and maintenance of ultra-high voltage (UHV) transmission lines, insulating rods are key load-bearing components, and the reliability of the bonding at their joints directly determines the safe operation of the transmission system. Prior art uses bisphenol A epoxy resin adhesives for insulating rod joints due to their excellent mechanical strength and insulation properties (e.g., CN119875297A, "An epoxy resin composition for HP-RTM process, its preparation method, and application"). However, with the continuous increase in transmission voltage levels (e.g., ±1100kV UHVDC projects), traditional adhesives have gradually exposed the following technical deficiencies under the long-term electromechanical coupling stress: 1. Damage detection hysteresis Traditional adhesives lack the ability to proactively warn of microcrack initiation, requiring regular manual inspections or offline testing equipment (such as ultrasonic flaw detectors) to identify damage. These passive methods not only have blind spots but also struggle to detect early-stage millimeter-scale microcracks (refer to the discussion of microcrack growth rates in IEEE Std 1764-2014, "Guidelines for Condition Assessment of Overhead Transmission Lines").

[0003] 2. Interface delamination risk The interfacial stress concentration caused by the difference in thermal expansion coefficients between epoxy resin and insulating materials can easily lead to interfacial delamination defects. Existing technologies, such as the modification of montmorillonite using nanofillers (e.g., CN119876644A, which discloses a method for extracting lithium from salt lake brine using a selective adsorbent), can improve the material's modulus but cannot fundamentally address the issue of uneven interfacial stress transfer, leaving the joint at risk of failure under extreme operating conditions.

[0004] 3. Mechanical performance degradation Over a wide temperature range of -40°C to 80°C, the shear strength of traditional adhesives exhibits a nonlinear attenuation characteristic with temperature fluctuations (refer to test data from GB / T 33334-2016, "Test Method for Single Lap Tensile Shear Strength of Adhesives"). This thermomechanical instability limits their application in projects located at high altitudes and with large temperature fluctuations.

[0005] 4. Lack of intelligent monitoring The existing technology system has yet to establish an integrated solution for adhesives and damage self-diagnosis. Although some research has attempted to implement structural health monitoring using fiber optic sensors (such as the power cable health monitoring method disclosed in AU2023390970A1, which uses distributed fiber optic sensing technology to determine the degradation of power cable mechanical properties), these external monitoring solutions have inherent drawbacks such as high cost, complex construction, and susceptibility to electromagnetic interference.

[0006] To address these technical bottlenecks, this invention uses microencapsulation modification technology to encapsulate tetraphenylethylene (TPE), a fluorescent dye with aggregation-induced emission (AIE) properties, within polyurea microcapsules. This innovative approach creates an active damage self-diagnosis system characterized by "mechanical load-microcapsule rupture-fluorescence warning." This technical solution not only overcomes the limitations of passive detection using traditional adhesives, but also achieves synergistic optimization of mechanical properties and fluorescence response characteristics through the molecular structure design of the microcapsule wall material, providing a revolutionary technical solution for the safe operation and maintenance of ultra-high voltage (UHV) transmission lines. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a large-tonnage insulating rod joint adhesive and a preparation method thereof, so as to solve the technical problems in the field of high-voltage insulating materials, especially the large-tonnage insulating rod joint adhesive used for live operations of ultra-high voltage transmission lines, which are prone to microcracks and interface delamination defects under long-term electromechanical coupling stress, and are difficult to be effectively identified by conventional detection means, resulting in the inability to provide early warning of potential hidden dangers, and the high brittleness of epoxy resin after curing, which easily causes crack extension and interface delamination under combined electromechanical loads, threatening long-term reliability.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: Microcapsule Synthesis: First, a diisocyanate (Desmodur L75) and the fluorescent dye tetraphenylethylene (TPE) are dissolved in xylene to form a water-in-oil emulsion core. Subsequently, a trifunctional amine (guanidine hydrochloride) solution is added to the aqueous phase via interfacial polymerization, allowing the isocyanate and amine to react at the oil-water interface to form a polyurea capsule wall. After the reaction is complete, unreacted products are removed by centrifugation and washing to obtain microcapsules. Microcapsules with a particle size of 25-36 μm are selected using a sieve-based classification technique to ensure size uniformity and mechanical stability.

[0009] Adhesive Compounding: The screened microcapsules are mixed with bisphenol A epoxy resin (E-51), nano-montmorillonite (MMT), and a silane coupling agent (KH-560) in a specific ratio. A planetary mixer is used for vacuum degassing to ensure uniform mixing. Subsequently, a curing agent (methylhexahydrophthalic anhydride) is added and further mixing is performed to form the final microcapsule-modified epoxy resin adhesive.

[0010] Damage self-diagnosis mechanism: When the adhesive joint is subjected to critical stress, the embedded microcapsules rupture, releasing fluorescent dye TPE into the resulting cracks. Under ultraviolet light, the released fluorescent dye emits visible light, enabling damage self-diagnosis.

[0011] The present invention provides a large-tonnage insulating rod joint adhesive and a preparation method thereof, which have the following beneficial effects: 1. The present invention effectively solves the problem in the field of high-voltage insulation materials, especially the problem that large-tonnage insulating rod joint adhesives used for live operations on ultra-high voltage transmission lines are prone to microcracks and interface delamination defects under long-term electromechanical coupling stress, and are difficult to effectively identify through conventional detection methods, thereby achieving early warning of potential hidden dangers.

[0012] 2. By adjusting the molar ratio of isocyanate to amine, the present invention can precisely adjust the thickness of the microcapsule wall, thereby controlling its rupture strength, ensuring that the microcapsule ruptures under specified stress conditions to release the fluorescent dye, and improving the stability of the microcapsule.

[0013] 3. Using the aggregation-induced emission dye tetraphenylethylene TPE as the core material of the microcapsule, the present invention can significantly release fluorescence when the microcapsule ruptures, so that the adhesive can achieve the level of visual monitoring through fluorescence changes after being subjected to force, thereby improving the sensitivity and accuracy of damage detection.

[0014] 4. By drying and adding a protective colloid, the present invention ensures that the microcapsules are evenly dispersed in the adhesive and are not easily damaged, thereby ensuring the stability of the microcapsules in the epoxy resin and improving the dispersion stability of the adhesive.

[0015] 5. The present invention uses interfacial polymerization reaction to encapsulate tetraphenylethylene (TPE), a fluorescent dye with aggregation-induced emission (AIE) characteristics, into microcapsules, and ensures the stable performance of the microcapsules by precisely controlling the weight ratio of each raw material.

[0016] 6. The present invention compounds the synthesized microcapsules with components such as bisphenol A epoxy resin, nano-montmorillonite, silane coupling agent and curing agent. The weight ratio of each component is optimized to achieve improved comprehensive performance of the adhesive.

[0017] 7. The present invention encapsulates the fluorescent dye tetraphenylethylene (TPE) with AIE properties in microcapsules and applies it for the first time in the field of adhesives for large-tonnage insulating rod joints, realizing a real-time self-diagnosis function for adhesive damage.

[0018] 8. The present invention achieves uniform dispersion and efficient compounding of microcapsules in the adhesive by precisely controlling the proportions of components such as microcapsules, nano-montmorillonite, silane coupling agent and curing agent, thereby improving the overall performance of the adhesive.

[0019] 9. The present invention addresses the problem that epoxy resin is highly brittle after curing and is prone to crack propagation and interface peeling under combined electromechanical loads. By introducing components such as microcapsules and nano-montmorillonite, the present invention improves the toughness and thermal stability of the adhesive and enhances its long-term reliability.

[0020] 10. The present invention realizes real-time self-diagnosis of adhesive damage. By releasing fluorescent signals through the rupture of microcapsules, the damage of the adhesive can be monitored without external detection equipment, thereby improving maintenance efficiency and safety.

[0021] 11. Compared with traditional adhesives, the adhesive prepared by the present invention has significant improvements in mechanical properties, thermal stability and self-diagnostic capabilities, meeting the high requirements of large-tonnage insulating rod joints for adhesives.

[0022] 12. By real-time monitoring of adhesive damage, the present invention can promptly discover and address potential safety hazards, avoid equipment failures or safety accidents caused by adhesive failure, and reduce maintenance costs and safety risks.

[0023] 13. The present invention is not only applicable to adhesives for large-tonnage insulating rod joints, but can also provide reference and guidance for other adhesive fields that require high reliability and self-diagnosis functions, thereby expanding the application scope of adhesives.

[0024] 14. By encapsulating fluorescent dyes and repair agents in microcapsules, the present invention achieves visual monitoring of fluorescence changes after being subjected to force and a self-repairing function in which the repair agent is released when the microcapsules rupture.

[0025] 15. The present invention utilizes microfluidic technology to precisely control the particle size and morphology of microcapsules, thereby improving the uniformity and stability of the microcapsules, thereby increasing the efficiency of self-repair and self-diagnosis, and significantly improving the application performance of the material in the field of high-voltage insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the overall structure of a large-tonnage insulating pull rod according to embodiment 3 of the present invention; Figure 2A perspective view of a large-tonnage insulating pull rod end joint according to embodiment 3 of the present invention; Figure 3 This is a perspective view of a large-tonnage insulating pull rod connecting pipe according to Example 3 of the present invention; Figure 4 Schematic diagram of the synthesis method of epoxy resin adhesive for large-tonnage insulating pull rods in Example 3 of the present invention; Figure 5 Schematic diagram of the deformation behavior of microcapsules in the epoxy resin matrix during stretching in Example 3 of the present invention; Figure 6 This is a process flow chart for preparing epoxy resin adhesive for large-tonnage insulating pull rods according to Example 4 of the present invention; In the figure: first joint 1, alloy steel coating 2, connecting pipe 3, first protective layer 4, second protective layer 5, third protective layer 6, second joint 7, epoxy resin matrix 8; microcapsule 9; foam 10; epoxy resin adhesive 11. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention are further described below with reference to the accompanying drawings and embodiments: Example 1 like Figure 4 As shown, this embodiment describes in detail a method for preparing a large-tonnage insulating rod joint adhesive, and the specific steps are as follows: 1. Microcapsule synthesis: 1.1. Raw material preparation: Accurately weigh 22 parts of diisocyanate (Desmodur L75). This raw material is an important component of the microcapsule wall material and is responsible for forming a strong capsule wall in the subsequent reaction. 75 parts of hydrophobic solvent xylene were measured and used to dissolve the diisocyanate to form a uniform solution; Weigh 4 parts of the fluorescent dye tetraphenylethylene (TPE), which has aggregation-induced emission (AIE) characteristics and is the key to the damage self-diagnosis function of the microcapsule.

[0028] 1.2. Preparation of core dye solution: Slowly add the weighed diisocyanate into xylene while stirring with a magnetic stirrer until the diisocyanate is completely dissolved to form a uniform diisocyanate solution; Under stirring, 4 parts of fluorescent dye tetraphenylethylene (TPE) were gradually added to the diisocyanate solution and stirred for 30 minutes to fully disperse the dye to form a water-in-oil emulsion core dye solution.

[0029] 1.3. Microcapsule wall synthesis: Prepare an aqueous phase solution containing an appropriate amount of water and surfactant (the specific type and amount need to be optimized according to experimental conditions in actual operation); Transfer the aqueous solution to a reactor equipped with a stirring and temperature control device, start stirring and heat to 75°C; Under stirring, the core dye solution is slowly added dropwise to the aqueous phase solution to form a water-in-oil emulsion system; Add a trifunctional amine (guanidine hydrochloride) solution to the aqueous phase and stir to ensure full contact between the amine solution and the water-in-oil emulsion. Maintain a reaction temperature of 75°C and continue stirring for 2 hours to allow interfacial polymerization between the isocyanate and the amine to form the polyurea capsule wall.

[0030] 1.4. Post-processing and screening: After the reaction is completed, the reaction mixture is transferred to a centrifuge for centrifugation to remove unreacted residues and solvent in the supernatant; Wash the microcapsules obtained by centrifugation multiple times with an appropriate amount of detergent (such as deionized water) to remove impurities attached to the surface; The washed microcapsules were graded and sieved through a sieve, and microcapsules with a particle size of 25-36 μm were selected to ensure size uniformity to ensure mechanical stability and fluorescence response capability.

[0031] 1.5. Drying and adding protective colloid: The sieved microcapsules are transferred to a vacuum drying oven and dried at an appropriate temperature (e.g., 40-60°C) to remove moisture inside and on the surface of the microcapsules; After drying, add an appropriate amount of protective colloid (such as polyvinyl alcohol PVA, Polyvinyl Alcohol) to the microcapsules, and stir to evenly wrap the protective colloid on the surface of the microcapsules to improve their dispersibility and fluidity in the epoxy resin adhesive.

[0032] 2. Adhesive lamination: 2.1. Weighing of raw materials: Accurately weigh 100 parts of bisphenol A epoxy resin (E-51) as the base material of the adhesive; Weigh 12 portions of the microcapsules prepared above to impart self-repairing and self-diagnostic functions to the adhesive; Weigh 6 parts of nano-montmorillonite (MMT) as a reinforcing material to improve the mechanical strength and high temperature resistance of the adhesive; 2.5 parts of silane coupling agent (KH-560) were weighed to improve the interfacial bonding performance between the microcapsules and the epoxy resin matrix.

[0033] 2.2, Mixing and degassing: Add the weighed bisphenol A epoxy resin into the planetary mixer, and start the mixer to stir at a low speed; Gradually add microcapsules, nano-montmorillonite and silane coupling agent into epoxy resin while increasing the stirring speed to ensure that all components are fully mixed; During the mixing process, turn on the vacuum pump to evacuate the mixer to remove bubbles in the mixture and improve the density of the adhesive.

[0034] 2.3. Adding curing agent and molding: After vacuum degassing is completed, accurately weigh 32 parts of curing agent (methyl hexahydrophthalic anhydride) and gradually add it into the mixer, and continue to stir and mix it with the epoxy resin mixture; Transfer the mixed adhesive to a mold that has been cleaned and coated with a release agent for molding; According to the curing characteristics of the curing agent, the mold is placed at an appropriate temperature (such as room temperature to 80°C) for curing. The curing time is determined according to specific conditions (such as 24 hours) to obtain a microcapsule-modified epoxy resin adhesive.

[0035] Example 2 In another preferred embodiment, based on the above-mentioned Example 1, this embodiment provides a large-tonnage insulating rod joint adhesive prepared by the preparation method of Example 1, wherein the adhesive comprises uniformly dispersed microcapsules, and the fluorescent dye tetraphenylethylene TPE is encapsulated in the microcapsules, which can realize damage self-diagnosis under ultraviolet light; it also comprises nano-montmorillonite and silane coupling agent, which are used to improve the mechanical strength and high temperature resistance of the adhesive, and at the same time improve the interfacial bonding performance between the microcapsules and the epoxy resin matrix.

[0036] Example 3 In another preferred embodiment, based on the above-mentioned embodiments 1 and 2, this embodiment demonstrates the performance verification of a large-tonnage insulating pull rod joint adhesive of embodiment 2 prepared by the preparation method in embodiment 1, aiming to comprehensively evaluate the mechanical properties, thermal stability and damage self-diagnosis function of the adhesive. The specific steps are as follows.

[0037] 1. Sample preparation: 1.1, Adhesive filling: like Figure 1 As shown, the test mold of the large-tonnage insulating rod joint is designed and manufactured in advance, including the first joint 1, the second joint 7 and the connecting pipe 3, see Figure 2 and Figure 3The first joint 1 and the connecting pipe 3 are connected as a whole through the alloy steel coating layer 2 and the second protective layer 5. The second joint 7 and the connecting pipe 3 are connected as a whole through the alloy steel coating layer 2 and the third protective layer 6. The two groups of connecting pipes 3 are connected as a whole through the alloy steel coating layer 2 and the first protective layer 4. The first protective layer 4, the second protective layer 5, and the third protective layer 6 are filled with foam 10 to ensure that the internal dimensions of the mold match the requirements of the adhesive. The large-tonnage insulating rod joint adhesive 11 prepared in Example 1 is Figure 2 As shown, it includes an epoxy resin matrix 8 and microcapsules 9. The microcapsules 9 are unevenly distributed in the epoxy resin matrix 8 and are slowly and evenly filled into the test mold through a glue injection gun or similar equipment. During the filling process, care should be taken to avoid the generation of bubbles, which can be removed by gently shaking the mold or using vacuum-assisted equipment.

[0038] 1.2, curing molding: Based on the curing characteristics of the curing agent in the adhesive, the filled mold is placed in an appropriate temperature environment for curing. For example, it can be left at room temperature for a period of time (such as 12 hours) for initial curing, and then transferred to an oven for secondary curing at a higher temperature (such as 80°C) to ensure that the adhesive is fully cured and achieves optimal performance. The curing time needs to be adjusted according to specific conditions until the adhesive is completely hardened and non-sticky; After curing is completed, the mold is removed from the oven and allowed to cool naturally to room temperature; then, the cured adhesive sample is carefully removed from the mold to obtain a large-tonnage insulating rod joint adhesive test sample for performance testing.

[0039] 2. Performance testing: 2.1 Mechanical properties test: Use a universal material testing machine to perform tensile, compression, and bending tests on the test sample. In the tensile test, fix both ends of the sample to the fixture of the testing machine and stretch it at a constant speed (such as 5mm / min) until the sample breaks. Record the tensile strength and elongation at break. In the compression test, the sample is placed on the compression platform of the testing machine and compressed at a constant speed (such as 2mm / min), and the compression strength and compression deformation are recorded; In the bending test, a three-point bending or four-point bending method is used to apply a bending load to the sample and record the bending strength and bending modulus. Through these tests, the mechanical strength and toughness of the adhesive are evaluated to ensure that it meets the use requirements of large-tonnage insulating rod joints.

[0040] 2.2 Thermal stability test: Place the test sample in a high-temperature oven, set different temperature gradients (such as 100°C, 150°C, 200°C, etc.), and maintain each temperature for a certain time (such as 2 hours); After the insulation at each temperature point is completed, the sample is taken out of the oven and allowed to cool naturally to room temperature. Then, the appearance changes of the sample (such as color, shape, etc.) are observed, and the weight of the sample is weighed using a precision balance, and the weight change is recorded. The thermal stability of the samples was further analyzed by instruments such as thermogravimetric analysis (TGA) to evaluate their thermal decomposition behavior and thermal stability at high temperatures.

[0041] 2.3. Damage self-diagnosis test: like Figure 5 As shown, a critical stress is applied to the test sample, which should be close to but not exceed the normal use stress range of the adhesive to ensure that the sample will not be completely destroyed; the stress can be applied by applying pressure on the sample surface or bending it; During the stress application process, carefully observe the sample surface for signs of microcapsule rupture; if microcapsule rupture is found, stop applying stress immediately and observe the sample under UV light; Under ultraviolet light, the release of the fluorescent dye tetraphenylethylene (TPE) from the sample surface was observed. Due to the aggregation-induced emission (AIE) properties of TPE, when the microcapsules ruptured, the released TPE fluoresced under ultraviolet light, thus enabling damage self-diagnosis. The intensity and range of the fluorescence changes were recorded to evaluate the accuracy and sensitivity of the damage self-diagnosis function.

[0042] 3. Result analysis: 3.1. Analysis of mechanical properties results: Calculate the mechanical properties of the adhesive, such as tensile strength, elongation at break, compressive strength, compression deformation, flexural strength and flexural modulus, based on the data from tensile, compression and flexural tests; Compare these indicators with the expected performance requirements to evaluate whether the mechanical properties of the adhesive meet the use requirements of large-tonnage insulating rod joints; if some indicators do not meet the expected requirements, it is necessary to analyze the reasons and consider optimizing the adhesive formula or preparation process.

[0043] 3.2 Analysis of thermal stability results: Observe the changes in appearance and weight of the samples at different temperatures during the thermal stability test. If the samples show obvious color changes, shape deformation or weight loss at lower temperatures, it means that the thermal stability of the adhesive is poor. Combined with the results of thermogravimetric analysis (TGA), the thermal decomposition temperature and thermal decomposition process of the adhesive are analyzed; the thermal stability and heat resistance of the adhesive at high temperatures are evaluated to determine its maximum operating temperature range.

[0044] 3.3 Analysis of damage self-diagnosis results: The adhesive's damage self-diagnosis capability is evaluated based on the fluorescence changes observed during the damage self-diagnosis test. If the microcapsules can accurately rupture and release the fluorescent dye at a critical stress, and if a clear fluorescence change is observed under ultraviolet light, the adhesive has good damage self-diagnosis capabilities. Analyze the relationship between the intensity and range of fluorescence changes and the magnitude and location of applied stress to evaluate the accuracy and sensitivity of the damage self-diagnosis function; if the damage self-diagnosis function is found to be insufficient, consider optimizing the preparation process of the microcapsules or adjusting the type and dosage of the fluorescent dye.

[0045] Example 4 In another preferred embodiment, based on Example 1 above, this embodiment details a method for preparing an adhesive for high-tonnage insulating rod joints. The method focuses on synthesizing microcapsules and combining them with an epoxy resin adhesive to ensure the adhesive's effectiveness and stability in high-performance insulating rod joint applications. The entire preparation process includes the preparation of a microcapsule core dye, synthesis of the microcapsule wall, capsule screening, capsule dispersion, and epoxy resin adhesive compounding, as detailed below: First, the dye solution of the microcapsule core is prepared according to the ratio, such as Figure 6 As shown, 20–25 parts of a diisocyanate (Desmodur L75) are dissolved in 70–80 parts of the hydrophobic solvent xylene to form a uniform diisocyanate solution. Then, 3–5 parts of the fluorescent dye tetraphenylethylene (TPE) are added. Tetraphenylethylene, an aggregation-induced emission (AIE) dye, produces a significant fluorescence response upon microcapsule rupture, making it useful for damage detection. The dye is released upon microcapsule rupture and exhibits significant fluorescence under UV light.

[0046] The mixed liquid was emulsified using a high-speed disperser for 30 minutes. During the emulsification process, the oil phase solution and the aqueous phase emulsified to form a water-in-oil emulsion. At this point, the kernel dye solution was complete, resulting in a stable water-in-oil emulsion ready for the next step of microcapsule synthesis.

[0047] The microcapsule wall is synthesized through interfacial polymerization. A trifunctional amine (guanidine hydrochloride) solution, a compound with three reactive amino groups, is added to the aqueous phase. This compound reacts with isocyanate to form a polyurea capsule wall. Continuous stirring and heating to 75°C allow the isocyanate and amine to react at the oil-water interface, forming the polyurea wall.

[0048] The reaction lasts for 2 hours to ensure complete reaction and the formation of a stable polyurea capsule wall. The formation of the polyurea wall provides the microcapsules with sufficient mechanical strength to maintain their integrity during subsequent processing, while ensuring that they rupture under a specific stress to release the core dye.

[0049] After the reaction is complete, unreacted residues and solvent are removed by centrifugation and washing. The washed microcapsules are then used in the next steps, such as screening and dispersion.

[0050] To ensure uniform size and adaptability of the microcapsules, the washed microcapsules were graded and screened. Using a sieve grading technique, the capsules were sorted by particle size, selecting a size range of 25-36 μm. Capsules of this size produce a significant fluorescence response in the matrix and exhibit good mechanical properties, capable of withstanding shear forces during processing without breaking.

[0051] The screened capsules are collected and prepared for the next step. This size of microcapsule provides ideal damage detection in practice, ensuring that the condition of the adhesive joint can be accurately monitored through fluorescence changes under load.

[0052] After screening, the microcapsules need to be dried to remove any residual moisture and ensure good flowability and uniform dispersion in the subsequent epoxy resin adhesive. During the drying process, temperature and humidity must be controlled to ensure microcapsule stability and avoid overdrying that could cause capsule rupture.

[0053] After drying, the microcapsules are then added with a protective colloid. This helps improve the fluidity of the microcapsules and ensures their uniform dispersion in the epoxy resin adhesive. The protective colloid also prevents the microcapsules from aggregating or sticking to each other during mixing, ensuring the adhesive's processing properties.

[0054] In this step, the microcapsules are compounded with epoxy resin to prepare the final insulating rod joint adhesive. First, 100 parts by weight of bisphenol A epoxy resin (E-51) are added to a planetary mixer. Then, 10-15 parts of microcapsules are added to ensure uniform distribution throughout the epoxy resin. Next, 5-8 parts of nano-montmorillonite (MMT) and 2-3 parts of a silane coupling agent (KH-560) are added. These materials enhance the mechanical strength and high-temperature resistance of the adhesive, while also improving the interfacial bonding between the microcapsules and the epoxy resin matrix.

[0055] During the mixing process, vacuum degassing technology is used to remove bubbles from the mixture, ensuring uniformity and density of the adhesive. Finally, 30-35 parts of a curing agent (methylhexahydrophthalic anhydride) is added and mixed evenly with the adhesive matrix. The addition of the curing agent causes the epoxy resin to undergo a cross-linking reaction at a certain temperature, forming a solid adhesive with high structural stability.

[0056] After completing the above steps, the obtained microcapsule-modified epoxy resin adhesive has excellent mechanical properties, thermal stability and fluorescence monitoring function, and is suitable for high-strength connection of large-tonnage insulating rod joints.

[0057] In the preferred embodiment, in the Step 1 microcapsule synthesis, the weight parts of diisocyanate are 20-25 parts, the weight parts of xylene are 70-80 parts, and the weight parts of fluorescent dye tetraphenylethylene TPE are 3-5 parts; the above settings can accurately control the wall material thickness and core dye loading of the microcapsules, so that the microcapsules have both good mechanical stability and sensitive fluorescence response; this ratio can ensure that the capsules rupture evenly when subjected to the expected stress to release fluorescent signals, realize accurate self-diagnosis, and avoid waste of raw materials and increased costs; at the same time, the optimized system improves the toughness and durability of the adhesive, extends the service life of the insulating pull rod joint, and has both economic and safety benefits.

[0058] In the preferred scheme, the fluorescent dye tetraphenylethylene (TPE) described in Step 1 has aggregation-induced emission (AIE) properties and can release fluorescence when the microcapsules rupture, thereby realizing self-diagnosis of damage. The above settings not only improve the visual detection capability of the material when damaged, but also ensure the accuracy of diagnosis. Step 2 will further utilize the correlation between the fluorescence intensity of TPE and the degree of damage to construct a quantitative damage assessment model to achieve accurate structural health monitoring.

[0059] In the preferred embodiment, the synthesis of the microcapsule wall in Step 1 is carried out by interfacial polymerization reaction, and a trifunctional amine solution is added to the aqueous phase, stirred and heated to 75°C, and reacted for 2 hours to generate a polyurea capsule wall; the above setting ensures that the capsule wall has good mechanical strength and stability; in Step 2, the core material is evenly dispersed in the oil phase, and then emulsified with the aqueous phase containing the polyurea wall material, and further solidified to finally obtain a microcapsule product with uniform particle size and high encapsulation rate.

[0060] In the preferred embodiment, the thickness of the microcapsule wall in Step 1 is controlled by adjusting the molar ratio of isocyanate to amine to ensure rupture under a specified stress and avoid premature failure during processing. At the same time, the microcapsules can remain stable during storage, effectively preventing leakage of the core material, thereby ensuring the performance and quality of the final product and meeting the needs of specific application scenarios.

[0061] In a preferred embodiment, the trifunctional amine solution is a guanidine hydrochloride solution, which improves the purity and yield of the product and optimizes the reaction kinetics conditions.

[0062] In the preferred solution, the screening step in Step 1 ensures that the microcapsule particle size is within the range of 25~36μm to ensure mechanical stability and fluorescence response capability, and can also effectively reduce agglomeration and improve dispersion uniformity; in addition, this step adopts high-frequency vibration screening technology to further ensure precise control of particle size distribution, laying a solid foundation for subsequent packaging and application.

[0063] In a preferred embodiment, a protective colloid is added to the microcapsules described in Step 1 after drying to improve their dispersibility and fluidity in the epoxy resin adhesive, significantly enhance the compatibility of the microcapsules with the epoxy resin, and ensure that the adhesive has a uniform microstructure and excellent bonding properties during application, thereby achieving stronger bonding strength and a more reliable sealing effect after curing.

[0064] In the preferred embodiment, in the Step 2 adhesive compound, the weight of bisphenol A epoxy resin is 100 parts, the weight of microcapsules is 10-15 parts, the weight of nano-montmorillonite is 5-8 parts, the weight of silane coupling agent is 2-3 parts, and the weight of curing agent is 30-35 parts. The above settings can effectively balance the mechanical properties and functional characteristics of the adhesive. The microcapsules are evenly dispersed at this ratio, giving the adhesive self-repair and damage visualization capabilities while avoiding strength attenuation. The nano-montmorillonite synergistically enhances the rigidity and heat resistance of the system, and the silane coupling agent improves interfacial compatibility. The curing agent ratio accurately controls the cross-linking density to ensure rapid curing of the adhesive layer with low shrinkage. The final product has the advantages of high strength, anti-aging and real-time self-diagnosis, significantly improving the reliability of the insulation joint.

[0065] In a preferred embodiment, the bisphenol A epoxy resin is E-51, the curing agent is methylhexahydrophthalic anhydride, and the silane coupling agent is KH-560. The above configuration can significantly improve the mechanical properties and heat resistance of the composite material. At the same time, in order to further optimize the performance, an appropriate amount of toughening agent and accelerator are added to ensure that the epoxy resin system has good processability and curing effect.

[0066] In a preferred embodiment, the adhesive further comprises nano-montmorillonite and a silane coupling agent, which are used to improve the mechanical strength and high temperature resistance of the adhesive, while improving the interfacial bonding performance between the microcapsules and the epoxy resin matrix; the above settings enable the adhesive to remain stable under extreme environments, effectively extending the service life of the adhesive, and enhancing the overall mechanical properties and thermal stability of the composite material, providing strong support for the application of adhesives in the field of high-end manufacturing.

[0067] In summary, the present invention innovatively proposes a large-tonnage insulating rod joint adhesive and a preparation method thereof, which specifically overcomes the field of high-voltage insulating materials, especially in the live operation scenario of ultra-high voltage transmission lines. The large-tonnage insulating rod joint adhesive is prone to cause hidden defects such as microcracks and interface delamination due to long-term electromechanical coupling stress, and traditional detection methods are difficult to identify potential hidden dangers early. At the same time, it solves the industry pain point that the epoxy resin is brittle after curing and is prone to crack expansion and interface peeling under electromechanical combined loads, which threatens long-term operation reliability.

[0068] This invention, by encapsulating tetraphenylethylene (TPE), a fluorescent dye with aggregation-induced emission (AIE) properties, in microcapsules and introducing it into a large-scale insulating rod joint adhesive system for the first time, achieves real-time self-diagnosis of adhesive damage, providing a revolutionary solution for adhesive performance monitoring and maintenance throughout its lifecycle. In terms of formulation design, precise control of the ratio of components such as microcapsules, nano-montmorillonite, silane coupling agent, and curing agent achieves uniform dispersion and efficient compounding of the microcapsules in the adhesive matrix, significantly improving the mechanical properties and thermal stability of the adhesive while fully preserving the self-diagnostic properties of the microcapsules.

[0069] The present invention utilizes a real-time monitoring mechanism of releasing fluorescent signals upon microcapsule rupture, which has the advantages of high sensitivity, high accuracy, and no need for external detection equipment, thereby significantly reducing maintenance costs. At the same time, by optimizing the proportions of each component through a large number of experiments, a synergistic improvement in the comprehensive performance of the adhesive and the self-diagnostic function is achieved. Compared with traditional adhesives, the adhesive prepared by the present invention has achieved breakthrough progress in mechanical strength, thermal stability, and self-diagnostic capability, which not only meets the high-performance requirements of adhesives for large-tonnage insulating pull rod joints, but also significantly expands its scope of application.

[0070] In addition, the present invention achieves early warning and timely disposal of potential safety hazards by real-time monitoring of adhesive damage, effectively avoiding equipment failure or safety accidents caused by adhesive failure, significantly improving the safety and economy of power grid operation, and has significant comprehensive benefits and application value.

Claims

1. A method for preparing a large-tonnage insulating rod joint adhesive, characterized in that: The following steps are involved: Step 1: Microcapsule synthesis: diisocyanate and fluorescent dye tetraphenylethylene (TPE) are dissolved in xylene to form a water-in-oil emulsion core. Polyurea capsule walls are generated through interfacial polymerization, and microcapsules with a particle size of 25-36 μm are obtained by sieving. Step 2: Adhesive compounding: mix the microcapsules with bisphenol A epoxy resin, nano-montmorillonite, and silane coupling agent, add curing agent after vacuum degassing, and form a uniformly dispersed adhesive system.

2. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 1, characterized in that: In the microcapsule synthesis of Step 1, the weight parts of diisocyanate are 20-25 parts, the weight parts of xylene are 70-80 parts, and the weight parts of fluorescent dye tetraphenylethylene TPE are 3-5 parts.

3. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 2, characterized in that: The fluorescent dye tetraphenylethylene TPE described in Step 1 has aggregation-induced emission (AIE) characteristics, and releases fluorescence when the microcapsule ruptures, thereby realizing damage self-diagnosis.

4. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 3, characterized in that: The synthesis of the microcapsule wall in Step 1 is carried out by interfacial polymerization reaction. A trifunctional amine solution is added to the aqueous phase, and the mixture is stirred and heated to 75° C. for 2 hours to generate a polyurea capsule wall.

5. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 4, characterized in that: The thickness of the microcapsule wall is controlled by adjusting the molar ratio of isocyanate to amine to ensure rupture under a specified stress and avoid premature failure during processing; the trifunctional amine solution adopts a guanidine hydrochloride solution.

6. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 5, characterized in that: After drying, the microcapsules described in Step 1 are added with protective colloid to improve their dispersibility and fluidity in the epoxy resin adhesive.

7. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 6, characterized in that: In the Step 2 adhesive compound, the weight portion of bisphenol A epoxy resin is 100 parts, the weight portion of microcapsules is 10-15 parts, the weight portion of nano-montmorillonite is 5-8 parts, the weight portion of silane coupling agent is 2-3 parts, and the weight portion of curing agent is 30-35 parts.

8. The method for preparing a large-tonnage insulating rod joint adhesive according to claim 7, characterized in that: The bisphenol A epoxy resin used is E-51, the curing agent is methyl hexahydrophthalic anhydride, and the silane coupling agent is KH-560.

9. A large-tonnage insulating rod joint adhesive prepared by the method for preparing a large-tonnage insulating rod joint adhesive as claimed in claim 8, characterized in that: The adhesive contains uniformly dispersed microcapsules, which encapsulate fluorescent dye tetraphenylethylene (TPE) and can realize damage self-diagnosis under ultraviolet light.

10. The large-tonnage insulating rod joint adhesive according to claim 9, characterized in that: The adhesive further comprises nano-montmorillonite and a silane coupling agent, which are used to improve the mechanical strength and high temperature resistance of the adhesive and improve the interfacial bonding performance between the microcapsules and the epoxy resin matrix.

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