Polyurethane urea-based composite insulating material and preparation method and application thereof

Abstract

The application belongs to the technical field of high-voltage power transmission insulation protection, and discloses a polyurethane-urea-based composite insulation material and a preparation method and application thereof.The polyurethane-urea-based composite insulation material comprises a polyurethane-urea matrix and modified fillers dispersed in the polyurethane-urea matrix; the polyurethane-urea matrix is polymerized from isocyanate, polyether polyol and a chain extender containing a disulfide bond; the modified fillers are halloysite nanotubes modified by a silane coupling agent; and the silane coupling agent comprises an amino functional group.The polyurethane-urea-based composite insulation material improves the engineering performance of traditional polyurea-based materials and significantly improves the reliability and durability of the polyurethane-urea-based composite insulation material under humid, high-temperature and long-term service conditions, thereby providing a new material and a technical solution with great potential for the field of high-voltage power equipment insulation protection, outdoor electrical component packaging and flexible electronic device protection.

Description

Technical Field

[0001] This invention relates to the field of high-voltage power transmission insulation and protection technology, specifically to a polyurethane urea-based composite insulation material, its preparation method, and its application. Background Technology

[0002] With the continuous expansion of my country's power grid, the climatic and geographical conditions faced by high-voltage and ultra-high-voltage transmission lines are becoming increasingly complex. Ecological restoration has led to lush vegetation along the lines, increasing bird habitats and activities. Outdoor towers have become primary nesting sites for birds, and discharge faults caused by bird droppings and short circuits have been rising year by year, posing a significant threat to the safe operation of these lines. Simultaneously, global climate change has resulted in frequent severe storms. Extreme wind deflection (instantaneous wind speeds exceeding 30 m / s) significantly compresses the air gap between the conductor and the tower material. When the gap shrinks to less than 1 meter, breakdown can occur even at operating voltage. Especially in 220kV and above lines, the combined effects of bird damage and wind deflection, along with conductor vibration and insufficient insulation margin, further reduce the insulation withstand capability of the air gap, leading to frequent discharge breakdown accidents and posing a serious threat to the safe operation of transmission lines.

[0003] Currently, the commonly used protective measures in engineering are to coat the tower material with insulating material or install insulating sleeves on the ground potential side, in order to improve the overall air gap discharge withstand voltage by enhancing the insulation strength of the tower surface. However, actual operation results show that this protective method has many insurmountable technical limitations and cannot effectively curb gap discharge accidents caused by bird damage and wind deflection, especially for transmission lines with voltage levels of 110kV and above. Specifically, firstly, molded insulating sleeves are difficult to adapt to the complex and irregular structures of towers, and cannot achieve full coverage of the ground potential side, resulting in poor adaptability to high-voltage scenarios; secondly, traditional coating systems are prone to interface seal failure during long-term field service, with moisture penetrating along defects, causing dielectric properties to decrease by more than 30%, and inducing electrochemical corrosion of steel, accelerating coating cracking and peeling; thirdly, due to the constraints of the tower structure, existing molded insulating components and conventional coating materials can only achieve coverage of the high-voltage side of the conductor. There are a large number of metal sharp points at key ground potential discharge points such as crossarm connection nodes and tower material cross splicing points. The electric field distortion rate in this area is significantly higher, and conventional insulation methods are difficult to form a continuous and complete insulating shielding layer. The phenomenon of partial discharge at the sharp points occurs frequently, and gap breakdown faults are difficult to fundamentally curb.

[0004] To adapt to the complex and irregular structures of towers and achieve continuous insulation protection across the entire ground potential side, the industry is gradually shifting towards fast-curing spray-applied composite insulation materials. Polyurea materials have attracted much attention due to their advantages such as instantaneous gelation, convenient construction, and seamless coating. However, existing polyurea modifications mostly use inorganic nanoparticles (such as nano-silica, nano-alumina, etc.) for physical blending or simple doping, lacking a systematic design of the surface chemistry and interface structure of the filler. This results in uneven filler dispersion, easy agglomeration, and the introduction of a large number of micropores and defects, which in turn reduces the dielectric properties by 15%-20% compared to pure polyurea matrix.

[0005] Meanwhile, the key performance indicators of traditional polyurea insulation materials are also insufficient to meet the operational requirements of ultra-high voltage and extra-high voltage transmission lines under extreme environments. Firstly, regarding dielectric strength, the breakdown field strength of existing materials is typically only 15kV / mm-16kV / mm, and the dielectric constant is approximately 3.5. When extreme wind deflection causes the air gap between the conductor and the tower to shorten to 0.25m, the breakdown voltage of the air gap is only about 162kV, lower than the minimum insulation margin required for 220kV transmission lines. Secondly, regarding thermal stability, the glass transition temperature (Tg) of conventional polyurea materials is only about 45℃, while the temperature of transmission towers under high summer temperatures, especially the surface temperature of unshaded metal towers under direct sunlight, can reach over 60℃. At this temperature, the molecular chain segment movement intensifies, the polarization response decreases, and the dielectric properties... With an attenuation exceeding 25%, the insulation reliability at high temperatures is significantly reduced. Furthermore, the arc resistance of this type of material is also significantly insufficient. When a local arc or surface discharge occurs, the material surface is prone to ablation cracks under the high temperature of the arc. After the cracks expand, they lead to coating peeling and irreversible loss of insulation performance. In addition, in terms of moisture and water resistance, the static water contact angle of existing materials is usually only 60°-65°, and the water absorption rate is close to 4%. In long-term humid environments or rainy and foggy weather, moisture can gradually penetrate to the coating / metal interface through the micropores and interface defects inside the coating, resulting in a significant decrease in dielectric properties and inducing corrosion of metal tower materials, thus shortening the service life of the tower structure.

[0006] It is evident that existing polyurea-based spray coating materials have significant shortcomings in terms of interfacial compatibility, dielectric strength, thermal stability, moisture resistance, and adaptability to complex structures, making it difficult to meet the protection requirements of high-voltage transmission lines in areas with high electric field distortion at ground potential. Therefore, there is an urgent need to develop a novel polyurea-based composite insulation material that combines excellent interfacial compatibility, high breakdown field strength, good thermal stability, and moisture resistance. This material would significantly improve insulation protection capabilities while maintaining adaptability to on-site construction, and would have significant engineering value and socio-economic benefits for ensuring the long-term safe operation of transmission lines under conditions of frequent bird damage and extreme weather. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyurethane urea-based composite insulating material, its preparation method, and its application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a polyurethane urea-based composite insulating material, comprising a polyurethane urea matrix and a modified filler dispersed in the polyurethane urea matrix; The polyurethane urea matrix is ​​polymerized from isocyanate, polyether polyol and chain extender containing disulfide bonds; The modified filler is halloysite nanotube modified with a silane coupling agent; the silane coupling agent includes amino functional groups; The mass ratio of the modified filler to the polyurethane urea matrix is ​​(0.2-1):100.

[0009] This invention modifies halloysite nanotubes with a silane coupling agent containing amino functional groups, and then combines them with a polyurethane urea matrix containing disulfide bonds, which is polymerized from isocyanate, polyether polyol and chain extender containing disulfide bonds. This achieves a multi-level synergistic reinforcement effect and successfully constructs a polyurethane urea-based composite insulation material with excellent hydrophobic and water-resistant properties, high insulation strength, efficient self-healing function and excellent resistance to thermal and damp heat aging. It effectively improves the common technical problems of existing polyurea insulation materials, such as poor interfacial compatibility, easy agglomeration of nanofillers, limited improvement of dielectric properties, insufficient high temperature stability and irreversible performance degradation after service damage.

[0010] Specifically, in this invention, the amino functional groups of the silane coupling agent can form strong hydrogen bonds with the urea groups in the polyurethane urea matrix, constructing an organic modified layer on the surface of halloysite nanotubes. This effectively reduces the surface polarity of the filler and improves its interfacial compatibility with the polyurethane urea matrix. Furthermore, the unique hollow tubular structure of halloysite nanotubes can form physical crosslinking points and topological constraint effects in the matrix, effectively restricting the thermal motion of polyurethane urea molecular chains at high temperatures and improving the thermal stability and glass transition temperature of the material. On the other hand, it can enhance the interfacial polarization effect under the action of an electric field, achieving a good balance between dielectric constant and breakdown field strength. Simultaneously, the chain extender containing disulfide bonds introduces dynamic covalent bonds in the hard segments of polyurethane urea, endowing the material with a self-healing function that achieves scratch closure and insulation performance recovery through disulfide bond exchange reactions after mechanical damage.

[0011] Through research, the inventors discovered that by controlling the mass of the modified filler in the polyurethane urea matrix within the aforementioned range in the polyurethane urea-based composite insulating material of this invention, the nano-reinforcement effect and interfacial polarization contribution of halloysite nanotubes can be more fully utilized, while avoiding agglomeration and network structure damage caused by excessive filler. If there is too little modified filler, the nano-reinforcement phase cannot form an effective three-dimensional topological constraint network and interfacial polarization contribution, resulting in limited improvement in the material's thermal stability, dielectric strength, and hydrophobic properties, failing to achieve the expected comprehensive protective effect. If there is too much modified filler, on the one hand, the filler will inevitably agglomerate in the matrix, forming stress concentration points and structural defects, which become sources of partial discharge and charge accumulation under an applied electric field, leading to a decrease in breakdown strength instead of an increase. On the other hand, it will restrict the mobility of polyurethane urea molecular chains, reduce the exchange efficiency and self-healing performance of dynamic disulfide bonds, and increase the viscosity of the system, deteriorating the coating film-forming performance.

[0012] In a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the mass ratio of the modified filler to the polyurethane urea matrix is ​​(0.5-0.75):100.

[0013] Preferably, the mass ratio of the modified filler to the polyurethane urea matrix is ​​one or a combination of 0.5:100, 0.55:100, 0.6:100, 0.65:100, 0.7:100, and 0.75:100.

[0014] As a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the isocyanate includes at least one of 4,4′-diphenylmethane diisocyanate, toluene-2,4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and naphthalene diisocyanate.

[0015] This invention utilizes isocyanates containing aromatic ring structures, such as 4,4′-diphenylmethane diisocyanate and toluene-2,4-diisocyanate, which are beneficial for increasing the content of hard segments and molecular chain rigidity in polyurethane urea, thereby improving the dielectric properties and thermal stability of the material. When it is necessary to improve the flexibility and weather resistance of the material, a compound system of isophorone diisocyanate or hexamethylene diisocyanate and toluene-2,4-diisocyanate can be used. By introducing flexible segments through alicyclic or aliphatic isocyanates, the glass transition temperature of the system is reduced and the elongation at break is increased.

[0016] Preferably, the isocyanate comprises 4,4′-diphenylmethane diisocyanate and toluene-2,4-diisocyanate.

[0017] More preferably, the mass ratio of the 4,4′-diphenylmethane diisocyanate to the toluene-2,4-diisocyanate is 1:(0.8-1.5).

[0018] More preferably, the mass ratio of the 4,4′-diphenylmethane diisocyanate to the toluene-2,4-diisocyanate is 1:1.

[0019] As a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the polyether polyol includes a first polyether polyol with a number average molecular weight of 1500-3000 and a second polyether polyol with a number average molecular weight of 300-600.

[0020] The number-average molecular weight of the polyether polyols of this invention is calculated based on the hydroxyl value. The hydroxyl value is determined according to the method specified in GB / T 12008.3-2009. Each sample is measured in parallel three times and the arithmetic mean is taken.

[0021] Preferably, the molar ratio of the first polyether polyol to the second polyether polyol is (0.5-2):1.

[0022] In the polyurethane urea-based composite insulation material of the present invention, the first polyether polyol is used to introduce flexible soft segments, providing the mobility of molecular chains and the toughness of the material, improving the flexibility and coating adaptability of the polyurethane urea-based material, and ensuring good adhesion and mechanical impact resistance of the coating on complex curved surfaces and irregular structures of towers; the second polyether polyol is used to improve the regularity of chain segments and the proportion of hard segments, increase the density of urea bonds and the number of intermolecular hydrogen bond crosslinking points, and improve the mechanical strength and dielectric properties of the material.

[0023] The inventors discovered through research that when the amounts of the first and second polyether polyols are within the aforementioned range, optimal microphase separation equilibrium can be achieved between the flexible soft segments and the rigid hard segments. If the proportion of the first polyether polyol is too high, the material's flexibility increases, but the content of hard segments is relatively insufficient, resulting in a decrease in physical crosslinking density and a significant reduction in thermal stability and dielectric strength. Conversely, if the proportion of the second polyether polyol is too high, the system's hard segment ratio is too high, viscosity increases sharply, the material becomes more brittle, and the molecular chain mobility is restricted, which is detrimental to the self-healing function of dynamic disulfide bonds. At the same time, excessively high urea bond density leads to an increase in the material's water absorption rate, worsening its moisture resistance.

[0024] More preferably, the molar ratio of the first polyether polyol to the second polyether polyol is 1:1.

[0025] Preferably, the number average molecular weight of the first polyether polyol is 2000.

[0026] Preferably, the number average molecular weight of the second polyether polyol is 400.

[0027] As a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the chain extender containing disulfide bonds includes at least one of 2,2′-diaminodiphenyl disulfide, 4,4′-diaminodiphenyl disulfide, cystamine, and di(2-hydroxyethyl) sulfide.

[0028] This invention utilizes the aforementioned chain extenders containing disulfide bonds to introduce dynamic disulfide bond structures into the hard segments of polyurethane urea, while simultaneously enhancing intermolecular chain forces. This is beneficial for scratch closure and insulation recovery after mechanical damage. Specifically, disulfide chain extenders containing aromatic rings (e.g., 2,2′-diaminodiphenyl disulfide, 4,4′-diaminodiphenyl disulfide) exhibit higher bond energy stability and rigidity contribution than aliphatic disulfides, thus better maintaining the material's mechanical strength while achieving dynamic exchange.

[0029] Preferably, the chain extender containing disulfide bonds includes 2,2′-diaminodiphenyl disulfide.

[0030] In a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the halloysite nanotubes have an average length of 2μm-3μm.

[0031] In a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the silane coupling agent includes (3-aminopropyl)triethoxysilane.

[0032] In a preferred embodiment of the polyurethane urea-based composite insulating material of the present invention, the volume ratio of the silane coupling agent to the mass ratio of the halloysite nanotube is (2-6) mL:1 g.

[0033] This invention uses the aforementioned amount of silane coupling agent to modify the surface of halloysite nanotubes, which facilitates the formation of a uniform and dense organosilane modified layer on the nanotube surface. If the amount of silane coupling agent is too low, the grafting density on the halloysite nanotube surface is insufficient, some surface polar hydroxyl groups are not effectively shielded, and the improvement in interfacial compatibility between the filler and the polyurethane urea matrix is ​​limited. When the amount of silane coupling agent is too high, the excess silane coupling agent will undergo a self-condensation reaction on the halloysite nanotube surface, forming a loose polysilane physically adsorbed layer rather than a chemically grafted layer. Moreover, this physically adsorbed layer is prone to detachment during composite material processing, thus introducing interfacial defects.

[0034] Preferably, the volume ratio of the silane coupling agent to the mass ratio of the halloysite nanotube is 4 mL: 1 g.

[0035] Secondly, the present invention provides a method for preparing the polyurethane urea-based composite insulating material, comprising the following steps: S1. The isocyanate is reacted with the polyether polyol to obtain the isocyanate-terminated prepolymer. S2. The isocyanate-terminated prepolymer is subjected to a chain extension reaction with a chain extender containing disulfide bonds to obtain a polyurethane urea matrix; S3. Halloysite nanotubes are modified with silane coupling agents to obtain modified fillers; S4. The modified filler is mixed with the polyurethane urea matrix, and the mixture is then molded to obtain the polyurethane urea-based composite insulating material.

[0036] In a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S1, the temperature of the prepolymerization reaction is 20℃-40℃ and the time is 12h-36h.

[0037] Preferably, in step S1, the temperature of the prepolymerization reaction is 25°C and the time is 24 hours.

[0038] In a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S1, the molar ratio of the isocyanate and the polyether polyol is (0.8-3):1.

[0039] In a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S2, the temperature of the chain extension reaction is 60℃-80℃ and the reaction time is 12h-36h.

[0040] Preferably, in step S2, the chain extension reaction is carried out at a temperature of 70°C for 24 hours.

[0041] In a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S2, the molar ratio of active hydrogen in the chain extender containing disulfide bonds to the residual isocyanate groups in the isocyanate-terminated prepolymer is (0.8-1.2):1.

[0042] Through research, the inventors discovered that when the amount of active hydrogen functional groups added to the chain extender containing disulfide bonds is lower than the above range, the isocyanate groups in the system do not react sufficiently. The residual isocyanate groups are prone to react with moisture in the air to generate urea bonds and carbon dioxide, resulting in bubbles and micro-defects inside the material. At the same time, the dynamic disulfide bond density is insufficient, and the scratch repair ability of the material decreases. When the amount of active hydrogen functional groups added is higher than the above range, the proportion of hard segments and the crosslinking density in the system are too high, which can easily lead to increased brittleness of the material, restricted molecular chain mobility, and affect coating film formation performance and self-repair efficiency.

[0043] Preferably, in step S2, the molar ratio of active hydrogen in the disulfide-bonded chain extender to the residual isocyanate groups in the isocyanate-terminated prepolymer is (0.9-1.1):1.

[0044] More preferably, the molar ratio of active hydrogen in the disulfide-bonded chain extender to the residual isocyanate groups in the isocyanate-terminated prepolymer is 1:1.

[0045] In a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S3, the temperature of the modification reaction is 20℃-30℃ and the time is 18h-30h.

[0046] As a preferred embodiment of the preparation method of the polyurethane urea-based composite insulating material of the present invention, in step S3, the modification reaction includes the following steps: dispersing the halloysite nanotubes in a solvent, adding the silane coupling agent and water, adding a pH adjuster to adjust the pH value of the reaction system to 8-11, and carrying out a hydrolysis-condensation reaction under ultrasonic assistance.

[0047] Preferably, the solvent includes anhydrous ethanol.

[0048] Preferably, the mass ratio of the halloysite nanotubes to the volume ratio of the solvent is 1 g:(45-60) mL.

[0049] More preferably, the mass ratio of the halloysite nanotubes to the volume ratio of the solvent is 1 g: 50 mL.

[0050] Preferably, the volume of the water is 1-3 times the volume of the silane coupling agent.

[0051] Preferably, the pH adjuster comprises an aqueous ammonia solution.

[0052] Preferably, the temperature of the ultrasound is ≤40℃.

[0053] Preferably, the power of the ultrasound is 300W-600W and the duration is 15min-60min.

[0054] More preferably, the power of the ultrasound is 500W and the duration is 30min.

[0055] Thirdly, the present invention provides the application of the polyurethane urea-based composite insulating material in the insulation protection of power equipment or the encapsulation of electrical components.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The polyurethane urea-based composite insulating material of the present invention uses a silane coupling agent containing amino functional groups to chemically modify the surface of halloysite nanotubes, which effectively improves the common technical problem of poor interfacial compatibility and easy agglomeration between traditional inorganic nanofillers and polyurethane urea matrix; (2) The polyurethane urea-based composite insulating material of the present invention forms physical crosslinking points and topological constraint effects in the polyurethane urea matrix through the unique hollow tubular structure of halloysite nanotubes, and forms a dual network structure of static physical crosslinking + dynamic covalent crosslinking with the dynamic covalent network introduced by the disulfide bond chain extender, thereby achieving the unity of material thermal stability and self-healing function; (3) The present invention The polyurethane urea-based composite insulation material invented uses silane coupling agent to modify the strong hydrogen bonding between the amino functional groups on the surface of halloysite nanotubes and the polyurethane urea matrix, and the effective shielding of the natural hydrophilic surface of halloysite nanotubes to construct a low surface energy hydrophobic interface layer on the surface of the composite material. This ensures the stability of the dielectric properties of the material in long-term humid environments or rainy and foggy weather, and effectively avoids the dielectric property decay and metal tower corrosion caused by water vapor penetrating along the micropores and interface defects inside the coating. (4) The preparation method of the present invention is simple in process and mild in conditions, and is easy to scale up for production and on-site construction application. It is suitable for promotion and application in various transmission tower external insulation protection and high voltage power equipment insulation transformation scenarios. Attached Figure Description

[0057] Figure 1 The images show the FT-IR spectra of the HNTs / DPU composite insulating material of Example 1, the DPU composite insulating material of Comparative Example 1, and the UHNTs / DPU composite insulating material of Comparative Example 2 of the present invention. Figure 2 The images show the SEM images of the unmodified HNTs of this invention, the APTES-modified HNTs of Example 1, the HNTs / DPU composite insulation material of Example 1, the DPU composite insulation material of Comparative Example 1, and the UHNTs / DPU composite insulation material of Comparative Example 2. in, Figure 2 (a) and Figure 2 (b) represents unmodified HNTs; Figure 2 (c) APTES-modified HNTs of Example 1; Figure 2 (d) is the DPU composite insulation material of Comparative Example 1; Figure 2 (e) is the UHNTs / DPU composite insulation material of Comparative Example 2; Figure 2 (f) is the HNTs / DPU composite insulation material of Example 1; Figure 3The images show the DSC curves of the HNTs / DPU composite insulating material of Example 1, the DPU composite insulating material of Comparative Example 1, the UHNTs / DPU composite insulating material of Comparative Example 2, the CPU material of Comparative Example 9, and the CIS material of Comparative Example 10. Detailed Implementation

[0058] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0059] The following description, in conjunction with specific embodiments, illustrates the practical effects of the present invention.

[0060] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials, reagents, equipment, etc. used are all commercially available unless otherwise specified.

[0061] The raw materials used in the following embodiments and comparative examples are described below, but are not limited to these materials: Toluene-2,4-diisocyanate (TDI), 98% pure, purchased from Aladdin; 4,4′-Diphenylmethane diisocyanate (MDI), 98% pure, purchased from Aladdin; Hexamethylene diisocyanate (HDI), 98% pure, purchased from Aladdin; Isophorone diisocyanate (IPDI), 98% pure, purchased from Aladdin; Dicyclohexylmethane diisocyanate (HMDI), 98% pure, purchased from Aladdin; Naphthalene diisocyanate (NDI), 98% pure, purchased from Aladdin; Polypropylene glycol 2000 (PPG-2000), with a number average molecular weight of 2000 and a purity of 99%, was purchased from Sigma-Aldrich. Polypropylene glycol 1500 (PPG-1500), with a number average molecular weight of 1500 and a purity of 99%, was purchased from Sigma-Aldrich. Polypropylene glycol 400 (PPG-400), with a number average molecular weight of 400 and a purity of 99%, was purchased from Sigma-Aldrich. Polypropylene glycol 300 (PPG-300), with a number average molecular weight of 300 and a purity of 99%, was purchased from Sigma-Aldrich. 2,2′-Diaminodiphenyl disulfide, 98% pure, purchased from Aladdin; 4,4′-Diaminodiphenyl disulfide, 98% pure, purchased from Aladdin; Di(2-hydroxyethyl) sulfide, 98% pure, purchased from Aladdin; N,N-Dimethylacetamide (DMAC), 99% pure, purchased from Aladdin; Halloysite nanotubes (HNTs), with a purity of 97%, are available in 2μm-3μm size and have an average length of 2.5μm. They were purchased from Xinlei Minerals Co., Ltd. Nano-silica (SiO2), with a purity of 99.5% and an average particle size of 20nm-30nm, was purchased from Aladdin. (3-Aminopropyl)triethoxysilane (APTES), 99% pure, purchased from Aladdin; Anhydrous ethanol, 99% pure, purchased from Aladdin; Ammonia solution, analytical grade, purchased from Aladdin; CPU, a commercially available two-component spray-coated polyurea material, is a spray-coated polyurea elastomer purchased from Shijiazhuang Weishiqi New Material Co., Ltd. CIS, a commercially available prefabricated insulating sleeve for power equipment, is a product specification for electrical insulation protective sleeve, purchased from Langfang Changao Power Technology Co., Ltd.

[0062] Example 1: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The preparation method includes the following steps: (1) Preparation of polyurethane urea matrix (DPU) containing disulfide bonds (I) 4,4′-diphenylmethane diisocyanate (MDI) was briefly melted at 40°C under dry nitrogen protection until it formed a homogeneous liquid for later use; toluene-2,4-diisocyanate (TDI) was sealed and stored under dry nitrogen protection at room temperature for later use; polypropylene glycol 2000 (PPG-2000) and polypropylene glycol 400 (PPG-400) were vacuum dehydrated at 80°C for 3 hours for later use. Under nitrogen protection, add 20 mL of N,N-dimethylacetamide (DMAC) to a 500 mL three-necked flask, and accurately weigh 5.25 g of MDI and 5.25 g of TDI (i.e., the mass ratio of MDI to TDI is 1:1) and add them to the flask. Stir magnetically at 300 rpm until completely dissolved. Then, weigh 16.67g of PPG-2000 and 3.33g of PPG-400 (i.e., the molar ratio of PPG-2000 to PPG-400 is 1:1), mix them evenly, and then add them dropwise to a three-necked flask through a constant pressure dropping funnel at a rate of 1mL / min, while controlling the solution temperature at 25℃ during the dropping process; After titration, the reaction was carried out under a nitrogen atmosphere (nitrogen flow rate of 50 mL / min) at room temperature with stirring. Samples were taken every 2 hours during the reaction, and the content of NCO groups in the isocyanate-terminated prepolymer solution was determined according to HG / T 2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). This method allows the NCO groups in the sample to react fully with excess di-n-butylamine, and then the remaining di-n-butylamine is titrated with hydrochloric acid standard titration solution. The reaction was corrected by a blank test. When the content of NCO groups decreased to 2.5% ± 0.1%, the reaction was stopped, and the isocyanate-terminated prepolymer solution was obtained.

[0063] After the prepolymerization reaction is completed, weigh the actual total mass of the obtained isocyanate-terminated prepolymer solution, and calculate the molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution according to the measured mass fraction of NCO groups using the following formula: n NCO =( m p × w NCO ) / 42.02; In the formula, n NCO The molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution, expressed in mol. m p The total actual mass of the isocyanate-terminated prepolymer solution is expressed in grams. w NCO The mass fraction of NCO groups is the measured value, substituted as a decimal; 42.02 is the molar mass of the NCO groups, in g / mol.

[0064] In this embodiment, the actual total mass of the obtained isocyanate-terminated prepolymer solution was 49.3 g, the measured mass fraction of NCO groups was 2.5%, and the molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution was calculated to be 0.0293 mol.

[0065] (II) In this embodiment, 2,2′-diaminodiphenyl disulfide is used as a chain extender containing disulfide bonds. Its dosage is determined based on the equimolar reaction stoichiometry between the active hydrogen in 2,2′-diaminodiphenyl disulfide and the residual NCO groups in the isocyanate-terminated prepolymer solution (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to the residual NCO groups in the isocyanate-terminated prepolymer solution is 1:1). The specific calculation process is as follows: The molar mass of 2,2′-diaminodiphenyl disulfide is 248.37 g / mol. Each mole of 2,2′-diaminodiphenyl disulfide contains 2 mol of amino active hydrogen that can react with NCO groups. The added mass is calculated according to the following formula: m 扩链剂 =( m p × w NCO ) / 42.02=3.64g; Therefore, 3.64 g of 2,2′-diaminodiphenyl disulfide was weighed and dissolved in 10 mL of N,N-dimethylacetamide (DMAC). The solution was ultrasonically dispersed at 300 W for 10 min until completely dissolved to obtain a chain extender solution. The chain extender solution was slowly added dropwise to the isocyanate-terminated prepolymer solution over 30 minutes using a constant-pressure dropping funnel. After the addition is complete, the temperature is raised to 70℃ (oil bath temperature control), and the reaction continues under nitrogen protection. Every 4 hours, samples are taken to detect the content of NCO groups according to HG / T2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). When the NCO content is ≤0.1%, the reaction is stopped, and a dynamic polyurethane urea matrix (DPU) solution containing disulfide bonds is obtained, with a solid content of 35%.

[0066] (2) Preparation of (3-aminopropyl)triethoxysilane-modified halloysite nanotubes (APTES-modified HNTs) 2g of halloysite nanotubes (HNTs) were added to 100mL of anhydrous ethanol, magnetically stirred at 500rpm for 1h at room temperature, and ultrasonically dispersed at 500W for 30min to obtain a uniform HNTs ethanol dispersion.

[0067] 8 mL of (3-aminopropyl)triethoxysilane (APTES) and 10 mL of distilled water were added sequentially to the obtained HNTs ethanol dispersion. The pH of the system was then adjusted to 9±0.2 using 5 mL of ammonia solution, and the system was sonicated at 500 W for 30 min to promote the hydrolysis of APTES and the reaction on the surface of HNTs. During this period, the system temperature was controlled to not exceed 40 °C using an ice-water bath. After sonication, the reaction was carried out at room temperature with magnetic stirring at 400 rpm for 24 h. The reaction solution was then transferred to a centrifuge tube and centrifuged at 6800 rpm for 10 min. The supernatant (containing unreacted APTES) was removed. The precipitate was washed three times with 50 mL of anhydrous ethanol (centrifuged at 6800 rpm for 10 min each time) and twice with 50 mL of distilled water until the pH of the washing solution was 7 ± 0.2. The washed precipitate was placed in a vacuum oven and dried at 60°C for 12 hours to obtain APTES-modified HNTs powder with a yield of 92.3%.

[0068] (3) Preparation of polyurethane urea-based composite insulating materials containing dynamic disulfide bonds Take 0.5g of APTES modified HNTs powder prepared in step (2) and add it to the DPU solution in step (1) (wherein, the mass ratio of APTES modified HNTs to DPU is 0.5:100). Stir magnetically at 600rpm for 2h at room temperature, and ultrasonically disperse at 400W for 15min every 30min during the process to obtain APTES modified HNTs / DPU mixed solution. SEM observation showed that APTES-modified HNTs maintained a typical hollow tubular structure with an outer diameter of approximately 50 nm-100 nm and an average length of approximately 2 μm-3 μm. After ultrasonic dispersion, APTES-modified HNTs were dispersed relatively uniformly in DPU solution, and no obvious micron-sized aggregates were observed.

[0069] Then, the obtained APTES-modified HNTs / DPU mixed solution was poured into a polytetrafluoroethylene mold (50mm×50mm×2mm) and placed in a vacuum oven at 50℃ and -0.09MPa for 3 hours. During this period, the gas was released every 30 minutes to remove residual solvent. After drying, the material was cooled to room temperature and demolded to obtain a polyurethane urea-based composite insulating material containing dynamic disulfide bonds, denoted as HNTs / DPU composite insulating material. It appears as a light yellow sheet with no obvious agglomerates, and the product yield is 90.1%.

[0070] Example 2: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), 4,4′-diphenylmethane diisocyanate is replaced with an equal mass of hexamethylene diisocyanate; 2,2′-diaminodiphenyl disulfide is replaced with an equal molar amount of 4,4′-diaminodiphenyl disulfide; The remaining steps and parameters are exactly the same as in Example 1.

[0071] Example 3: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), 4,4′-diphenylmethane diisocyanate is replaced with an equal mass of isophorone diisocyanate; 2,2′-diaminodiphenyl disulfide is replaced with an equal molar amount of di(2-hydroxyethyl) sulfide; The remaining steps and parameters are exactly the same as in Example 1.

[0072] Example 4: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), 4,4′-diphenylmethane diisocyanate is replaced with an equal mass of dicyclohexylmethane diisocyanate; The remaining steps and parameters are exactly the same as in Example 1.

[0073] Example 5: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), toluene-2,4-diisocyanate is replaced with an equal mass of naphthalene diisocyanate; The remaining steps and parameters are exactly the same as in Example 1.

[0074] Example 6: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass ratio of 4,4′-diphenylmethane diisocyanate to toluene-2,4-diisocyanate is 0.8:1; The remaining steps and parameters are exactly the same as in Example 1.

[0075] Example 7: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass ratio of 4,4′-diphenylmethane diisocyanate to toluene-2,4-diisocyanate is 1.5:1; The remaining steps and parameters are exactly the same as in Example 1.

[0076] Example 8: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), PPG-2000 is replaced with an equimolar amount of PPG-1500, and PPG-400 is replaced with an equimolar amount of PPG-300; The remaining steps and parameters are exactly the same as in Example 1.

[0077] Example 9: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), PPG-2000 is replaced with an equimolar amount of PPG-3000, and PPG-400 is replaced with an equimolar amount of PPG-600; The remaining steps and parameters are exactly the same as in Example 1.

[0078] Example 10: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), PPG-2000 is replaced with an equimolar amount of PPG-400; The remaining steps and parameters are exactly the same as in Example 1.

[0079] Example 11: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), PPG-400 is replaced with an equimolar amount of PPG-2000; The remaining steps and parameters are exactly the same as in Example 1.

[0080] Example 12: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass of PPG-2000 is 17.65g and the mass of PPG-400 is 2.35g (i.e., the molar ratio of PPG-2000 to PPG-400 is 1.5:1). The remaining steps and parameters are exactly the same as in Example 1.

[0081] Example 13: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass of PPG-2000 is 16g and the mass of PPG-400 is 4g (i.e., the molar ratio of PPG-2000 to PPG-400 is 0.8:1). The remaining steps and parameters are exactly the same as in Example 1.

[0082] Example 14: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass of 2,2′-diaminodiphenyl disulfide is 2.91 g (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to residual NCO groups in the isocyanate-terminated prepolymer solution is 0.8:1). The remaining steps and parameters are exactly the same as in Example 1.

[0083] Example 15: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), the mass of 2,2′-diaminodiphenyl disulfide is 4.37 g (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to residual NCO groups in the isocyanate-terminated prepolymer solution is 1.2:1). The remaining steps and parameters are exactly the same as in Example 1.

[0084] Example 16: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (2), the amount of (3-aminopropyl)triethoxysilane (APTES) used is 4 mL; The remaining steps and parameters are exactly the same as in Example 1.

[0085] Example 17: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (2), the amount of (3-aminopropyl)triethoxysilane (APTES) used is 12 mL; The remaining steps and parameters are exactly the same as in Example 1.

[0086] Example 18: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (3), the mass of APTES modified HNTs powder is 0.2g (wherein, the mass ratio of APTES modified HNTs to DPU is 0.2:100). The remaining steps and parameters are exactly the same as in Example 1.

[0087] Example 19: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (3), the mass of APTES modified HNTs powder is 0.75 g (wherein, the mass ratio of APTES modified HNTs to DPU is 0.75:100). The remaining steps and parameters are exactly the same as in Example 1.

[0088] Example 20: This embodiment prepares a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (3), the mass of APTES modified HNTs powder is 1g (wherein, the mass ratio of APTES modified HNTs to DPU is 1:100). The remaining steps and parameters are exactly the same as in Example 1.

[0089] Comparative Example 1: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The preparation method includes the following steps: (1) Preparation of polyurethane urea matrix (DPU) containing disulfide bonds (I) 4,4′-diphenylmethane diisocyanate (MDI) was briefly melted at 40°C under dry nitrogen protection until it formed a homogeneous liquid for later use; toluene-2,4-diisocyanate (TDI) was sealed and stored under dry nitrogen protection at room temperature for later use; polypropylene glycol 2000 (PPG-2000) and polypropylene glycol 400 (PPG-400) were vacuum dehydrated at 80°C for 3 hours for later use. Under nitrogen protection, add 20 mL of N,N-dimethylacetamide (DMAC) to a 500 mL three-necked flask, and accurately weigh 5.25 g of MDI and 5.25 g of TDI (i.e., the mass ratio of MDI to TDI is 1:1) and add them to the flask. Stir magnetically at 300 rpm until completely dissolved. Then, weigh 16.67g of PPG-2000 and 3.33g of PPG-400 (i.e., the molar ratio of PPG-2000 to PPG-400 is 1:1), mix them evenly, and then add them dropwise to a three-necked flask through a constant pressure dropping funnel at a rate of 1mL / min, while controlling the solution temperature at 25℃ during the dropping process; After titration, the reaction was carried out under a nitrogen atmosphere (nitrogen flow rate of 50 mL / min) at room temperature with stirring. Samples were taken every 2 hours during the reaction, and the content of NCO groups in the isocyanate-terminated prepolymer solution was determined according to HG / T 2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). This method allows the NCO groups in the sample to react fully with excess di-n-butylamine, and then the remaining di-n-butylamine is titrated with hydrochloric acid standard titration solution. The reaction was corrected by a blank test. When the content of NCO groups decreased to 2.5% ± 0.1%, the reaction was stopped, and the isocyanate-terminated prepolymer solution was obtained.

[0090] After the prepolymerization reaction is completed, weigh the actual total mass of the obtained isocyanate-terminated prepolymer solution, and calculate the molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution according to the measured mass fraction of NCO groups using the following formula: n NCO =( m p × wNCO ) / 42.02; In the formula, n NCO The molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution, expressed in mol. m p The total actual mass of the isocyanate-terminated prepolymer solution is expressed in grams. w NCO The mass fraction of NCO groups is the measured value, substituted as a decimal; 42.02 is the molar mass of the NCO groups, in g / mol.

[0091] In this comparative example, the actual total mass of the obtained isocyanate-terminated prepolymer solution was 49.3 g, the measured mass fraction of NCO groups was 2.5%, and the calculated molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution was 0.0293 mol.

[0092] (II) In this comparative example, 2,2′-diaminodiphenyl disulfide was used as a chain extender containing disulfide bonds. Its dosage was determined based on the equimolar reaction stoichiometry between the active hydrogen in 2,2′-diaminodiphenyl disulfide and the residual NCO groups in the isocyanate-terminated prepolymer solution (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to the residual NCO groups in the isocyanate-terminated prepolymer solution was 1:1). The specific calculation process is as follows: The molar mass of 2,2′-diaminodiphenyl disulfide is 248.37 g / mol. Each mole of 2,2′-diaminodiphenyl disulfide contains 2 mol of amino active hydrogen that can react with NCO groups. The added mass is calculated according to the following formula: m 扩链剂 =( m p × w NCO ) / 42.02=3.64g; Therefore, 3.64 g of 2,2′-diaminodiphenyl disulfide was weighed and dissolved in 10 mL of N,N-dimethylacetamide (DMAC). The solution was ultrasonically dispersed at 300 W for 10 min until completely dissolved to obtain a chain extender solution. The chain extender solution was slowly added dropwise to the isocyanate-terminated prepolymer solution over 30 minutes using a constant-pressure dropping funnel. After the addition is complete, the temperature is raised to 70℃ (oil bath temperature control), and the reaction continues under nitrogen protection. Every 4 hours, samples are taken to detect the content of NCO groups according to HG / T2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). When the NCO content is ≤0.1%, the reaction is stopped, and a dynamic polyurethane urea matrix (DPU) solution containing disulfide bonds is obtained, with a solid content of 35%.

[0093] (2) Preparation of polyurethane urea-based composite insulating materials containing disulfide bonds The disulfide-bonded dynamic polyurethane urea matrix (DPU) solution prepared in step (1) was poured into a polytetrafluoroethylene mold (50mm×50mm×2mm) and placed in a vacuum oven at 50℃ and -0.09MPa for 3h. During this period, the gas was released once every 30min to remove residual solvent. After drying, the material was cooled to room temperature and demolded to obtain a polyurethane urea-based composite insulating material containing dynamic disulfide bonds, denoted as DPU composite insulating material. The material has a light yellow, uniform sheet appearance with a smooth surface and no bubbles.

[0094] Comparative Example 2: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The preparation method includes the following steps: (1) Preparation of polyurethane urea matrix (DPU) containing disulfide bonds (I) 4,4′-diphenylmethane diisocyanate (MDI) was briefly melted at 40°C under dry nitrogen protection until it formed a homogeneous liquid for later use; toluene-2,4-diisocyanate (TDI) was sealed and stored under dry nitrogen protection at room temperature for later use; polypropylene glycol 2000 (PPG-2000) and polypropylene glycol 400 (PPG-400) were vacuum dehydrated at 80°C for 3 hours for later use. Under nitrogen protection, add 20 mL of N,N-dimethylacetamide (DMAC) to a 500 mL three-necked flask, and accurately weigh 5.25 g of MDI and 5.25 g of TDI (i.e., the mass ratio of MDI to TDI is 1:1) and add them to the flask. Stir magnetically at 300 rpm until completely dissolved. Then, weigh 16.67g of PPG-2000 and 3.33g of PPG-400 (i.e., the molar ratio of PPG-2000 to PPG-400 is 1:1), mix them evenly, and then add them dropwise to a three-necked flask through a constant pressure dropping funnel at a rate of 1mL / min, while controlling the solution temperature at 25℃ during the dropping process; After titration, the reaction was carried out under a nitrogen atmosphere (nitrogen flow rate of 50 mL / min) at room temperature with stirring. Samples were taken every 2 hours during the reaction, and the content of NCO groups in the isocyanate-terminated prepolymer solution was determined according to HG / T 2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). This method allows the NCO groups in the sample to react fully with excess di-n-butylamine, and then the remaining di-n-butylamine is titrated with hydrochloric acid standard titration solution. The reaction was corrected by a blank test. When the content of NCO groups decreased to 2.5% ± 0.1%, the reaction was stopped, and the isocyanate-terminated prepolymer solution was obtained.

[0095] After the prepolymerization reaction is completed, weigh the actual total mass of the obtained isocyanate-terminated prepolymer solution, and calculate the molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution according to the measured mass fraction of NCO groups using the following formula: n NCO =( m p × w NCO ) / 42.02; In the formula, n NCO The molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution, expressed in mol. m p The total actual mass of the isocyanate-terminated prepolymer solution is expressed in grams. w NCO The mass fraction of NCO groups is the measured value, substituted as a decimal; 42.02 is the molar mass of the NCO groups, in g / mol.

[0096] In this comparative example, the actual total mass of the obtained isocyanate-terminated prepolymer solution was 49.3 g, the measured mass fraction of NCO groups was 2.5%, and the calculated molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution was 0.0293 mol.

[0097] (II) In this comparative example, 2,2′-diaminodiphenyl disulfide was used as a chain extender containing disulfide bonds. Its dosage was determined based on the equimolar reaction stoichiometry between the active hydrogen in 2,2′-diaminodiphenyl disulfide and the residual NCO groups in the isocyanate-terminated prepolymer solution (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to the residual NCO groups in the isocyanate-terminated prepolymer solution was 1:1). The specific calculation process is as follows: The molar mass of 2,2′-diaminodiphenyl disulfide is 248.37 g / mol. Each mole of 2,2′-diaminodiphenyl disulfide contains 2 mol of amino active hydrogen that can react with NCO groups. The added mass is calculated according to the following formula: m 扩链剂 =( m p × w NCO ) / 42.02=3.64g; Therefore, 3.64 g of 2,2′-diaminodiphenyl disulfide was weighed and dissolved in 10 mL of N,N-dimethylacetamide (DMAC). The solution was ultrasonically dispersed at 300 W for 10 min until completely dissolved to obtain a chain extender solution. The chain extender solution was slowly added dropwise to the isocyanate-terminated prepolymer solution over 30 minutes using a constant-pressure dropping funnel. After the addition is complete, the temperature is raised to 70℃ (oil bath temperature control), and the reaction continues under nitrogen protection. Every 4 hours, samples are taken to detect the content of NCO groups according to HG / T2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). When the NCO content is ≤0.1%, the reaction is stopped, and a dynamic polyurethane urea matrix (DPU) solution containing disulfide bonds is obtained, with a solid content of 35%.

[0098] (2) Preparation of polyurethane urea-based composite insulating materials containing dynamic disulfide bonds Take 0.5g of unmodified HNTs powder and add it to the DPU solution in step (1). Stir magnetically at 600rpm for 2h at room temperature, and ultrasonically disperse at 400W for 15min every 30min during the period to obtain unmodified HNTs / DPU mixed solution. The average aggregate particle size of HNTs in the system was measured by a laser particle size analyzer to be 300nm-500nm. Then, the obtained unmodified HNTs / DPU mixed solution was poured into a polytetrafluoroethylene mold (50mm×50mm×2mm) and placed in a vacuum oven at 50℃ and -0.09MPa for 3h. During the drying process, the gas was released every 30min to remove residual solvent. After drying, the material was cooled to room temperature and demolded to obtain a polyurethane urea-based composite insulating material containing dynamic disulfide bonds, denoted as UHNTs / DPU composite insulating material. It appears as a light yellow sheet with a small number of tiny particles (aggregates) visible on the surface.

[0099] Comparative Example 3: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The preparation method includes the following steps: (1) Preparation of polyurethane urea matrix (DPU) containing disulfide bonds (I) 4,4′-diphenylmethane diisocyanate (MDI) was briefly melted at 40°C under dry nitrogen protection until it formed a homogeneous liquid for later use; toluene-2,4-diisocyanate (TDI) was sealed and stored under dry nitrogen protection at room temperature for later use; polypropylene glycol 2000 (PPG-2000) and polypropylene glycol 400 (PPG-400) were vacuum dehydrated at 80°C for 3 hours for later use. Under nitrogen protection, add 20 mL of N,N-dimethylacetamide (DMAC) to a 500 mL three-necked flask, and accurately weigh 5.25 g of MDI and 5.25 g of TDI (i.e., the mass ratio of MDI to TDI is 1:1) and add them to the flask. Stir magnetically at 300 rpm until completely dissolved. Then, weigh 16.67g of PPG-2000 and 3.33g of PPG-400 (i.e., the molar ratio of PPG-2000 to PPG-400 is 1:1), mix them evenly, and then add them dropwise to a three-necked flask through a constant pressure dropping funnel at a rate of 1mL / min, while controlling the solution temperature at 25℃ during the dropping process; After titration, the reaction was carried out under a nitrogen atmosphere (nitrogen flow rate of 50 mL / min) at room temperature with stirring. Samples were taken every 2 hours during the reaction, and the content of NCO groups in the isocyanate-terminated prepolymer solution was determined according to HG / T 2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). This method allows the NCO groups in the sample to react fully with excess di-n-butylamine, and then the remaining di-n-butylamine is titrated with hydrochloric acid standard titration solution. The reaction was corrected by a blank test. When the content of NCO groups decreased to 2.5% ± 0.1%, the reaction was stopped, and the isocyanate-terminated prepolymer solution was obtained.

[0100] After the prepolymerization reaction is completed, weigh the actual total mass of the obtained isocyanate-terminated prepolymer solution, and calculate the molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution according to the measured mass fraction of NCO groups using the following formula: n NCO =( m p × w NCO ) / 42.02; In the formula, n NCO The molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution, expressed in mol. m p The total actual mass of the isocyanate-terminated prepolymer solution is expressed in grams. w NCO The mass fraction of NCO groups is the measured value, substituted as a decimal; 42.02 is the molar mass of the NCO groups, in g / mol.

[0101] In this comparative example, the actual total mass of the obtained isocyanate-terminated prepolymer solution was 49.3 g, the measured mass fraction of NCO groups was 2.5%, and the calculated molar amount of residual NCO groups in the isocyanate-terminated prepolymer solution was 0.0293 mol.

[0102] (II) In this comparative example, 2,2′-diaminodiphenyl disulfide was used as a chain extender containing disulfide bonds. Its dosage was determined based on the equimolar reaction stoichiometry between the active hydrogen in 2,2′-diaminodiphenyl disulfide and the residual NCO groups in the isocyanate-terminated prepolymer solution (i.e., the molar ratio of active hydrogen in 2,2′-diaminodiphenyl disulfide to the residual NCO groups in the isocyanate-terminated prepolymer solution was 1:1). The specific calculation process is as follows: The molar mass of 2,2′-diaminodiphenyl disulfide is 248.37 g / mol. Each mole of 2,2′-diaminodiphenyl disulfide contains 2 mol of amino active hydrogen that can react with NCO groups. The added mass is calculated according to the following formula: m 扩链剂 =( m p × w NCO ) / 42.02=3.64g; Therefore, 3.64 g of 2,2′-diaminodiphenyl disulfide was weighed and dissolved in 10 mL of N,N-dimethylacetamide (DMAC). The solution was ultrasonically dispersed at 300 W for 10 min until completely dissolved to obtain a chain extender solution. The chain extender solution was slowly added dropwise to the isocyanate-terminated prepolymer solution over 30 minutes using a constant-pressure dropping funnel. After the addition is complete, the temperature is raised to 70℃ (oil bath temperature control), and the reaction continues under nitrogen protection. Every 4 hours, samples are taken to detect the content of NCO groups according to HG / T2409-2023 Method A (di-n-butylamine-anhydrous toluene / hydrochloric acid standard titration solution method). When the NCO content is ≤0.1%, the reaction is stopped, and a dynamic polyurethane urea matrix (DPU) solution containing disulfide bonds is obtained, with a solid content of 35%.

[0103] (2) Preparation of polyurethane urea-based composite insulating materials containing dynamic disulfide bonds 0.5g of unmodified HNTs powder and 8mL of APTES were directly added to the DPU solution in step (1), and the mixture was magnetically stirred at 600rpm for 2h at room temperature. During this period, ultrasonic dispersion at 400W was performed for 15min every 30min to obtain a physically blended APTES modified HNTs / DPU mixed solution. Then, the obtained physically blended APTES modified HNTs / DPU mixed solution was poured into a polytetrafluoroethylene mold (50mm×50mm×2mm) and placed in a vacuum oven to dry at 50℃ and -0.09MPa for 3 hours. During this period, the gas was released once every 30 minutes to remove residual solvent. After drying, the mixture was cooled to room temperature and demolded to obtain a polyurethane urea-based composite insulating material containing dynamic disulfide bonds, which is denoted as physically blended APTES modified HNTs / DPU composite insulating material.

[0104] Comparative Example 4: This comparative example prepared a polyurethane urea-based composite insulating material without dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (1), 2,2′-diaminodiphenyl disulfide is replaced with an equimolar amount of 4,4′-diaminodiphenylmethane (MDA). The remaining steps and parameters are exactly the same as in Example 1.

[0105] Comparative Example 5: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (2), (3-aminopropyl)triethoxysilane (APTES) is replaced with an equal volume of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560). The remaining steps and parameters are exactly the same as in Example 1.

[0106] Comparative Example 6: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (2), halloysite nanotubes are replaced with an equal mass of nano-silica (SiO2). The remaining steps and parameters are exactly the same as in Example 1.

[0107] Comparative Example 7: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (3), the mass of APTES modified HNTs powder is 0.05 g (wherein, the mass ratio of APTES modified HNTs to DPU is 0.05:100). The remaining steps and parameters are exactly the same as in Example 1.

[0108] Comparative Example 8: This comparative example prepared a polyurethane urea-based composite insulating material containing dynamic disulfide bonds. The only difference between its preparation method and that of Example 1 is: In step (3), the mass of APTES modified HNTs powder is 5g (wherein, the mass ratio of APTES modified HNTs to DPU is 5:100). The remaining steps and parameters are exactly the same as in Example 1.

[0109] Comparative Example 9: This comparative example uses commercially available two-component sprayed polyurea material (CPU), which is cut into test samples of 50mm×50mm×2mm. The surface is smoothed with 1000-grit sandpaper, wiped clean with anhydrous ethanol, and then dried in a vacuum oven at 50℃ for 1 hour for later use.

[0110] Comparative Example 10: This comparative example uses commercially available prefabricated insulating sleeves (CIS) for electrical equipment. The CIS is cut into 50mm×50mm×2mm test samples, the surface is smoothed with 1000-grit sandpaper, wiped clean with anhydrous ethanol, and then dried in a vacuum oven at 50℃ for 1 hour for later use.

[0111] Test Example 1: This test example used a Thermo Fisher Nicolet Summit (USA) infrared spectrometer to characterize and analyze the chemical structures of the HNTs / DPU composite insulation material in Example 1, the DPU composite insulation material in Comparative Example 1, and the UHNTs / DPU composite insulation material in Comparative Example 2. The number of scans was 32, and the resolution was 4 cm⁻¹. -1 .

[0112] like Figure 1 As shown, at 2240cm -1 -2280cm -1 Within the band, no characteristic absorption peaks belonging to isocyanate groups (-NCO) were detected, indicating that the -NCO groups have fully reacted with the -NH groups to form urea bonds. This suggests that the DPU network structure in the HNTs / DPU composite insulation material, DPU composite insulation material, and UHNTs / DPU composite insulation material of this invention has been successfully cured; and in the spectrum, the peak at approximately 3413 cm⁻¹ is... -1 The absorption peak at 2854 cm⁻¹ is attributed to the stretching vibration of NH₃; -1 and 2932cm -1 The absorption peaks at approximately 1104 cm⁻¹ correspond to symmetric and asymmetric CH stretching vibrations, respectively. -1 The absorption peak at approximately 520 cm⁻¹ is attributed to the stretching vibration of COC; while the peak at approximately 520 cm⁻¹ is attributed to the stretching vibration of COC. -1 The absorption peak at that point corresponds to the stretching vibration of the disulfide bond (SS).

[0113] Further analysis revealed that, in Comparative Example 2, the UHNTs / DPU composite insulation material still retained a small amount of -NCO groups after the introduction of unmodified natural HNTs. This indicates that the direct addition of HNTs has a certain inhibitory effect on the condensation curing reaction of DPU. The possible reason is that the surface of unmodified HNTs is rich in polar hydroxyl groups, which can form competitive hydrogen bonds with isocyanate groups or undergo irreversible adsorption, thereby reducing the effective collision probability between -NCO and -NH and delaying the chain extension reaction. In contrast, in Example 1 of this invention, the -NCO characteristic peak of the HNTs / DPU composite insulation material completely disappeared after the introduction of APTES-modified HNTs, and its curing behavior was consistent with the pure DPU system. This demonstrates that the APTES modification of this invention can effectively eliminate the negative impact of HNTs on the DPU synthesis reaction, thereby endowing the composite material with higher chemical structural stability.

[0114] Furthermore, compared to the DPU composite insulation material of Comparative Example 1, the HNTs / DPU composite insulation material of Example 1 and the UHNTs / DPU composite insulation material of Comparative Example 2 show better insulation performance at 3750 cm⁻¹. -1 -4000cm -1 and approximately 910cm -1 A significant change in absorption peak intensity was observed, which can be attributed to the superimposed contribution of the characteristic functional groups of HNTs (such as surface hydroxyl groups and Si-O-Si framework vibrations). Therefore, the APTES-modified HNTs of this invention help to construct structurally complete and stable polyurethane urea-based composite insulating materials, providing a reliable microstructural basis for subsequent performance optimization and widespread application in fields such as high-voltage power equipment insulation protection, weather-resistant coatings, and flexible electronic packaging.

[0115] Test Example 2: This test example uses a FEI Nova NanoSEM 450 (USA) field emission scanning electron microscope to characterize and analyze the morphological changes of unmodified HNTs and APTES-modified HNTs of Example 1, as well as the microstructure of HNTs / DPU composite insulation material of Example 1, DPU composite insulation material of Comparative Example 1, and UHNTs / DPU composite insulation material of Comparative Example 2.

[0116] like Figure 2 As shown, Figure 2 (a) and Figure 2 (b) is a SEM image of unmodified HNTs; Figure 2 (c) is a SEM image of the APTES-modified HNTs of Example 1; Figure 2 (d) is a SEM image of the DPU composite insulation material of Comparative Example 1; Figure 2 (e) is a SEM image of the UHNTs / DPU composite insulation material of Comparative Example 2; Figure 2(f) is a SEM image of the HNTs / DPU composite insulation material of Example 1; Specifically, such as Figure 2 (a) and Figure 2 As shown in (b), unmodified HNTs exhibit typical tubular or short rod-like structures, with a certain degree of overlap and aggregation between nanotubes. This indicates that unmodified HNTs are prone to aggregation due to surface hydroxyl groups, while... Figure 2 As shown in (c), the HNTs in the APTES-modified HNTs of Example 1 of the present invention still retain the original nanotube framework, indicating that the APTES modification process did not destroy the basic structure of HNTs; at the same time, certain roughening features or local deposition phenomena can be observed on its surface, which is speculated to be related to the formation of an organosilane modified layer on the surface of HNTs after the hydrolysis and condensation of APTES.

[0117] like Figure 2 As shown in (d), although the overall structure of the DPU composite insulation material in Comparative Example 1 is relatively continuous, it lacks the interfacial regulation and dielectric enhancement effects of HNTs on the polyurethane urea matrix due to the absence of inorganic nanofillers; Figure 2 As shown in (e), localized filler agglomeration and interface defects can be observed in the UHNTs / DPU composite insulation material of Comparative Example 2, indicating insufficient compatibility between unmodified HNTs and the DPU matrix, which easily leads to the formation of micropores, phase separation, or filler aggregation regions within the composite material; in contrast, as Figure 2 As shown in (f), the HNTs / DPU composite insulating material of Example 1 of the present invention has a more continuous and dense structure. The dispersion state of HNTs in the DPU matrix is ​​improved, and no obvious large-sized agglomerates are observed. This indicates that the APTES modification of the present invention can improve the interfacial bonding between HNTs and the DPU matrix, which is beneficial to reducing internal defects of the composite material.

[0118] Test Example 3: In this test example, a NETZSCH 3500 Sirius (Germany) differential scanning calorimeter was used to test the glass transition temperature (Tg) and thermal stability of the HNTs / DPU composite insulation material of Example 1, the DPU composite insulation material of Comparative Example 1, the UHNTs / DPU composite insulation material of Comparative Example 2, the CPU material of Comparative Example 9, and the CIS material of Comparative Example 10. The heating rate was 20℃ / min.

[0119] like Figure 3As shown, the Tg of the DPU composite insulation material in Comparative Example 1 is 45.1℃. Since it lacks an inorganic nano-reinforcing phase, the thermal confinement effect of the polyurea molecular chain segments is limited. In Comparative Example 2, the Tg of the UHNTs / DPU composite insulation material drops to 41.9℃ after the addition of unmodified HNTs. This is presumably because the polar hydroxyl groups on the surface of the unmodified HNTs form competitive hydrogen bonds with the urea bonds in the DPU hard segments, partially disrupting the intermolecular forces between the hard segments and weakening the physical cross-linking network. In contrast, in the HNTs / DPU composite insulation material of Example 1 of this invention, the APTES-modified HNTs and DPU... A stronger interfacial bond was formed between the matrices, effectively suppressing the destruction of the hard-segment hydrogen bond network. The hollow tubular structure also provided topological constraint on the polyurea molecular chains, resulting in a significant increase in the glass transition temperature (Tg) of the composite material, reaching 47.8℃. Meanwhile, the glass transition temperatures of the CPU material in Comparative Example 9 and the CIS material in Comparative Example 10 were both lower than those in Example 1 of this invention, at only 29.4℃ and 26.1℃, respectively. This indicates that the present invention effectively enhances the thermal stability of the material through the synergistic composite of APTES-modified HNTs and a disulfide-bonded dynamic polyurethane urea matrix, providing strong support for its long-term stable operation under high-temperature conditions.

[0120] Test Example 4: This test case examines the surface hydrophobicity and water resistance of the polyurethane urea-based composite insulation materials of the examples and comparative examples. The test results are summarized in Table 1.

[0121] Test Method: Following ISO 15989:2004 standard, an SZ-CAMD33 contact angle meter was used. Deionized water was used as the test liquid to perform static contact angle tests on each sample. Samples were cut into 4cm × 4cm pieces and immersed in deionized water for 72 hours. The mass of the samples before and after immersion was measured, and the water absorption rate was calculated using the following formula: Water absorption rate (%) = (m1 - m0) / m0; Where m0 is the sample mass (g) before soaking, and m1 is the sample mass (g) after soaking.

[0122] Test Example 5: This test example demonstrates the dielectric properties of the polyurethane urea-based composite insulating materials used in the embodiments and comparative examples. The test results are summarized in Table 1.

[0123] Test method: According to IEC 60243-1:2013 standard, the power frequency breakdown strength of each sample was tested using ball electrodes at a voltage rise rate of 1kV / s. The breakdown data was analyzed by Weibull distribution function. Each group of samples was tested 10 times. Then, the dielectric constant of each sample was determined using a WY2858-2 dielectric constant tester at a test frequency of 50Hz.

[0124] Test Example 6: This test case examines the self-healing performance of the polyurethane urea-based composite insulation materials of the examples and comparative examples. The test results are summarized in Table 1.

[0125] Test Method: Using a knife tip or scratch tester, a surface scratch approximately 10 mm long and 25% of the sample thickness was made along the same direction at the center of each sample surface. The samples were then placed in a 70℃ oven for 2 hours to trigger the dynamic exchange of the disulfide-bonded polyurea network and the scratch self-healing process. After treatment, the samples were removed and allowed to stand at room temperature for 12 hours. The scratch morphology was observed using an optical microscope, and the scratch width before and after repair was measured. The scratch closure rate was calculated using the following formula: Scratch closure rate (%) = (w0-w1) / w0; Where w0 is the width of the scratch before repair, and w1 is the width of the scratch after repair.

[0126] Table 1. Test results of surface hydrophobicity and water resistance, dielectric properties, and self-healing properties of the polyurethane urea-based composite insulating materials of the embodiments and comparative examples of the present invention. As can be seen from the results in Table 1, the polyurethane urea-based composite insulation material containing dynamic disulfide bonds in the embodiments of the present invention exhibits excellent and balanced comprehensive performance in terms of surface hydrophobicity, water resistance, dielectric properties, and self-healing properties. Specifically, the static contact angle of each embodiment is stable in the highly hydrophobic range of 91.38°-94.58°, all reaching above 90° (exhibiting good surface hydrophobicity), while the water absorption rate is controlled at a relatively low level of 3.63%-4.08%, and the breakdown strength is maintained at 22.68 kV·mm. -1 -25.33kV·mm -1 The material exhibits high insulation performance, with a dielectric constant ranging from 3.8 to 4.20 and a scratch closure rate as high as 80.3% to 88.9%. This indicates that the present invention, through the synergistic design of APTES-modified HNTs and a disulfide-bonded dynamic polyurethane urea matrix, successfully constructs a composite material system that combines excellent hydrophobic surface, tight interfacial structure, efficient dynamic cross-linking network, and good dielectric matching characteristics. This ensures the material's resistance to hydrolysis and long-term insulation reliability in humid environments, while also endowing it with efficient self-healing capabilities through the dynamic exchange of disulfide bonds, thus laying a solid foundation for the engineering application of high-performance insulating and protective materials.

[0127] In contrast, all comparative examples deviated from the key formulations or process conditions of this invention, resulting in significant deterioration in core performance indicators. Specific analyses are as follows: Comparative Example 1, without the introduction of nanofillers, exhibited insufficient surface hydrophobicity, water resistance, and insulation strength, and its self-healing efficiency was relatively limited, making it difficult to meet the comprehensive requirements of high-performance insulating materials; Comparative Example 2, with its unmodified HNTs exhibiting strong surface hydrophilicity and poor compatibility with the matrix, not only failed to effectively improve hydrophobicity and water resistance but also suffered from suppressed self-healing efficiency due to agglomeration defects; Comparative Example 3, employing simple physical blending, could not achieve effective grafting of the APTES of this invention onto the HNTs surface, nor could it form stable interfacial interactions; Comparative Example 4, without... The polyurethane urea matrix with disulfide bonds not only lost its dynamic repair capability, but also suffered a significant decrease in overall hydrophobicity and insulation performance due to changes in the hard segment structure. KH-560 used in Comparative Example 5 lacked amino functional groups, resulting in poor interface modification. Ordinary nano-silica filler used in Comparative Example 6 had poor interfacial compatibility with the polyurethane urea matrix and lacked hollow structure and interfacial polarization enhancement, resulting in limited reinforcement. The filler content in Comparative Example 7 was insufficient, failing to form effective nano-reinforcement and hydrophobic surface coverage, leading to a significant deterioration in the overall material performance. The excessive filler content in Comparative Example 8 disrupted the continuity of the polyurea network, resulting in a decrease in dielectric constant but severely impaired insulation strength and self-repair capability.

[0128] Therefore, this invention effectively improves the interfacial compatibility of inorganic nanofillers in a polyurethane urea matrix by precisely controlling the surface chemical properties of HNTs, APTES modification process parameters, and filler dosage, and by selecting a chain extender containing dynamic disulfide bonds and a polyurea formulation with an appropriate ratio of soft and hard segments. This significantly inhibits the large-scale aggregation of fillers, fully leveraging the nano-reinforcement and interfacial polarization effects of HNTs while ensuring the self-healing ability and structural integrity of the polyurea network. The resulting product exhibits excellent comprehensive performance and can meet the application requirements of high-voltage power equipment insulation protection, outdoor electrical component encapsulation, and flexible electronic device protection. It demonstrates highly competitive application prospects and industrialization value in the fields of electrical insulation materials, functional coatings, and advanced composite materials.

[0129] Test Example 7: This test example demonstrates the thermal aging performance of the polyurethane urea-based composite insulation materials of the embodiments and comparative examples. The test results are summarized in Table 2.

[0130] Test method: Each sample was prepared as a sheet with a thickness of 0.5mm±0.05mm, cut into the same size and placed in a forced-air drying oven. It was aged continuously at 80℃ for 168h. After aging, the sample was taken out and left to stand at room temperature for 24h to eliminate the influence of thermal history. Then the breakdown strength, static contact angle and 72h water absorption rate before and after aging were tested.

[0131] Table 2. Thermal aging performance test results of polyurethane urea-based composite insulation materials of the present invention and comparative examples. As can be seen from the results in Table 2, the polyurethane urea-based composite insulation material containing dynamic disulfide bonds in the embodiments of the present invention exhibits excellent and balanced comprehensive performance in terms of thermal aging. After thermal aging at 80℃ for 168 hours, the contact angle remains stable at 82.42°-90.42°, and the contact angle retention rate is above 85% (indicating excellent thermal stability of surface hydrophobicity). At the same time, the water absorption rate only slightly increases to a low level of 3.96%-4.78% after aging, and the breakdown strength retention rate is as high as 86.5%-93.5%. This indicates that the present invention has successfully constructed a composite material system with excellent thermal stability through the synergistic design of APTES-modified HNTs and disulfide-bonded dynamic polyurethane urea matrix. This system not only ensures the stability of the surface chemical structure and microstructure of the material during high-temperature aging, but also effectively inhibits the damage to insulation performance caused by thermo-oxidative degradation through tight interfacial bonding, thus laying a good foundation for the long-term reliable service of the material under high-temperature conditions.

[0132] Test Example 8: This test example demonstrates the damp heat aging performance of the polyurethane urea-based composite insulation materials of the embodiments and comparative examples. The test results are summarized in Table 3.

[0133] Test method: Each sample was prepared as a sheet with a thickness of 0.5 mm ± 0.05 mm and placed in a constant temperature and humidity test chamber. It was treated for 168 h at a temperature of 60 °C and a relative humidity of 95%. After treatment, the sample was taken out and left to stand at room temperature for 24 h. Then the static contact angle, water absorption rate and breakdown strength before and after damp heat aging were tested.

[0134] Table 3. Test results of damp heat aging performance of polyurethane urea-based composite insulation materials of the present invention and comparative examples. As can be seen from the results in Table 3, the polyurethane urea-based composite insulation material containing dynamic disulfide bonds in the embodiments of the present invention also exhibits excellent performance in terms of damp heat aging. After 168 hours of damp heat aging at 60℃ / 95%RH, the contact angle remains stable at 77.18°-87.76°, with a contact angle retention rate of over 80%. Meanwhile, the water absorption rate only increases to 4.22%-5.18% after aging, and the breakdown strength retention rate is as high as 80.8%-90.7%. This further demonstrates that the polyurethane urea-based composite insulation material containing dynamic disulfide bonds of the present invention effectively inhibits the wetting and penetration of moisture on the material surface under high temperature and high humidity conditions, and maintains the long-term stability of insulation performance through stable interfacial bonding and the hydrolysis resistance of the polyurea network. This provides a reliable guarantee for the long-term application of the material under harsh climatic conditions such as outdoor humidity and rain.

[0135] In summary, this invention successfully constructs a polyurethane urea-based composite insulation material by surface modification of halloysite nanotubes with APTES and subsequent composite with a polyurethane urea matrix containing dynamic disulfide bonds. This material possesses excellent hydrophobic and water-resistant properties, high insulation strength, efficient self-healing function, and outstanding resistance to thermal and humid aging. Furthermore, while moderately improving the engineering performance of traditional polyurea materials, this material significantly enhances their reliability and durability under humid, high-temperature, and long-term service conditions. It provides a highly promising new material and technical solution for fields such as insulation protection of high-voltage power equipment, packaging of outdoor electrical components, and protection of flexible electronic devices.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyurethane urea-based composite insulating material, characterized in that, It includes a polyurethane urea matrix and a modified filler dispersed in the polyurethane urea matrix; The polyurethane urea matrix is ​​polymerized from isocyanate, polyether polyol and chain extender containing disulfide bonds; The modified filler is halloysite nanotube modified with a silane coupling agent; the silane coupling agent includes amino functional groups; The mass ratio of the modified filler to the polyurethane urea matrix is ​​(0.2-1):

100.

2. The polyurethane urea-based composite insulating material as described in claim 1, characterized in that, The isocyanate includes at least one of 4,4′-diphenylmethane diisocyanate, toluene-2,4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and naphthalene diisocyanate. And / or, the polyether polyol comprises a first polyether polyol with a number average molecular weight of 1500-3000 and a second polyether polyol with a number average molecular weight of 300-600; And / or, the chain extender containing disulfide bonds includes at least one of 2,2′-diaminodiphenyl disulfide, 4,4′-diaminodiphenyl disulfide, cystamine, and di(2-hydroxyethyl) sulfide.

3. The polyurethane urea-based composite insulating material as described in claim 1, characterized in that, The halloysite nanotubes have an average length of 2μm-3μm.

4. The polyurethane urea-based composite insulating material as described in claim 1, characterized in that, The silane coupling agent includes (3-aminopropyl)triethoxysilane.

5. The polyurethane urea-based composite insulating material as described in claim 1, characterized in that, The volume ratio of the silane coupling agent to the mass of the halloysite nanotube is (2-6) mL:1 g.

6. A method for preparing the polyurethane urea-based composite insulating material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. The isocyanate is reacted with the polyether polyol to obtain the isocyanate-terminated prepolymer. S2. The isocyanate-terminated prepolymer is subjected to a chain extension reaction with a chain extender containing disulfide bonds to obtain a polyurethane urea matrix; S3. Halloysite nanotubes are modified with silane coupling agents to obtain modified fillers; S4. The modified filler is mixed with the polyurethane urea matrix, and the mixture is then molded to obtain the polyurethane urea-based composite insulating material.

7. The method for preparing the polyurethane urea-based composite insulating material as described in claim 6, characterized in that, In step S1, the temperature of the prepolymerization reaction is 20℃-40℃, and the time is 12h-36h; And / or, in step S1, the molar ratio of the isocyanate to the polyether polyol is (0.8-3):

1.

8. The method for preparing the polyurethane urea-based composite insulating material as described in claim 6, characterized in that, In step S2, the chain extension reaction is carried out at a temperature of 60℃-80℃ for a time of 12h-36h. And / or, in step S2, the molar ratio of active hydrogen in the disulfide-bonded chain extender to the residual isocyanate groups in the isocyanate-terminated prepolymer is (0.8-1.2):

1.

9. The method for preparing the polyurethane urea-based composite insulating material as described in claim 6, characterized in that, In step S3, the modification reaction includes the following steps: dispersing the halloysite nanotubes in a solvent, adding the silane coupling agent and water, adding a pH adjuster to adjust the pH of the reaction system to 8-11, and carrying out a hydrolysis-condensation reaction under ultrasonic assistance.

10. The application of the polyurethane urea-based composite insulating material according to any one of claims 1-5 in the insulation protection of power equipment or the encapsulation of electrical components.

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