A low-air-gap, high-compatibility stress-relieving adhesive for power cables

Abstract

This invention provides a low-gap, high-compatibility stress-relieving adhesive for power cables, relating to the field of functional materials for power cable accessories. It comprises the following components by weight ratio: 80-120 parts of a chlorinated polymer, 25-60 parts of a compound plasticizing system, 20-40 parts of C5 petroleum resin, 40-80 parts of a high-dielectric filler, 3-8 parts of a special compatibilizer, 1-4 parts of an antioxidant, and 1-4 parts of a processing aid. This invention introduces MAH-g-EVA as a special compatibilizer. The maleic anhydride groups in its molecular chain can chemically bond with the polar groups of the chlorinated polymer. The EVA segment can achieve molecular-level compatibility with the compound plasticizing system, forming a stable matrix-compatible-plasticizer molecular structure. This completely solves the core problem of poor compatibility and easy phase separation between the matrix and plasticizer in existing technologies. The adhesive contains no micro-gap, significantly improving the reliability of insulation protection. High-magnification electron microscopy reveals no obvious interfaces or voids.

Description

Technical Field

[0001] This invention relates to the field of functional materials for power cable accessories, and in particular to a low-air-gap, high-compatibility stress-relieving adhesive for power cables. Background Technology

[0002] Stress relief adhesive is a core functional material for medium and high voltage cable accessories. Its main function is to alleviate the problem of electric field concentration at the cut-off point of the cable shield layer, and to prevent cable accessory failure caused by partial discharge and insulation aging. It is a key material to ensure the safe and stable operation of the power system and is currently widely used in medium and high voltage cable projects in power, municipal, rail transit, and new energy fields. Existing stress relief adhesives are mostly made from chlorinated polymers as the matrix, combined with plasticizers, high-dielectric fillers, tackifying resins, and other components, prepared through a mixing process. This is currently the mainstream technical solution in the industry.

[0003] Existing stress-relief adhesives suffer from poor compatibility between the matrix and plasticizers, weak intermolecular interfacial bonding, and a tendency for phase separation during mixing and long-term operation. This leads to the formation of tiny air gaps within the adhesive, exacerbating electric field concentration. Current technologies can only mitigate externally introduced air gaps, failing to address the inherent phase separation problem within the material itself. Furthermore, plasticizers are often of a single type, resulting in hardening and embrittlement of the adhesive at low temperatures and poor adhesion, while at high temperatures, plasticizers tend to migrate and separate into oils. These defects are even more pronounced under alternating high and low temperature conditions, making them unsuitable for diverse climates and harsh operating environments. Simultaneously, high-dielectric fillers exhibit insufficient dispersibility and agglomeration, affecting not only the stability and adjustability of dielectric properties but also indirectly creating air gaps. Moreover, their narrow dielectric constant control range makes them unsuitable for various applications. Different voltage levels require different performance levels; furthermore, the lack of a targeted compatibility system design, with performance improvement achieved only through simple component compounding, fails to enhance the bonding force between the matrix and plasticizer at the molecular level. Consequently, the adhesive degrades rapidly under long-term operation and harsh conditions, resulting in a service life far shorter than the designed lifespan of the cable itself. The preparation process is a conventional one-step mixing process, without considering the component characteristics to design the feeding sequence and temperature parameters, leading to uneven filler dispersion, insufficient component bonding, and poor batch stability. Moreover, most industry-standard improvement solutions focus on single-performance optimizations, failing to achieve a comprehensive and synergistic performance improvement. Therefore, this invention proposes a low-air-gap, high-compatibility stress-relieving adhesive for power cables to address the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a low-gap, high-compatibility stress-relieving adhesive for power cables. This adhesive incorporates MAH-g-EVA as a dedicated compatibilizer. The maleic anhydride groups in its molecular chain can chemically bond with the polar groups of chlorine-containing polymers. The EVA segment can achieve molecular-level compatibility with the compounded plasticizer system, forming a stable matrix-compatible-plasticizer molecular structure. This completely solves the core problem of poor compatibility and easy phase separation between the matrix and plasticizer in existing technologies. The adhesive contains no micro-gaps, significantly improving the reliability of insulation protection. High-magnification electron microscopy reveals no obvious interfaces or voids, solving the core difficulty of internal gaps that cannot be addressed by existing technologies.

[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a low-air-gap, high-compatibility stress-relieving adhesive for power cables, comprising the following components by weight ratio: 80-120 parts of chlorinated polymer, 25-60 parts of compound plasticizing system, 20-40 parts of C5 petroleum resin, 40-80 parts of high-dielectric filler, 3-8 parts of special compatibilizer, 1-4 parts of antioxidant, and 1-4 parts of processing aid;

[0006] The chlorinated polymer is a compound of chlorinated polyethylene and chlorohydrin rubber as the rubber matrix. The compounded plasticizing system is a compound of liquid nitrile rubber and TP-95 plasticizer. The high dielectric filler is barium titanate. The special compatibilizer is MAH-g-EVA. The processing aid is a compound of stearic acid and polyethylene glycol dispersant. The antioxidant is antioxidant 1010. Its preparation method includes plasticizing, initial mixing, filler mixing, plasticizing and thickening, and molding, using a step-by-step feeding and gradient temperature mixing process.

[0007] A further improvement is that the mass ratio of chlorinated polyethylene to chlorohydrin rubber in the chlorinated polymer is 1:1 to 3:1. Within this ratio range, optimal synergy between insulation and processability is achieved, avoiding poor processing flowability or decreased insulation performance.

[0008] A further improvement is that in the compound plasticizing system, the weight ratio of liquid nitrile rubber to TP-95 plasticizer is 15:10 to 35:25. The two work synergistically to exert a plasticizing effect, avoid hardening at low temperatures and oil separation at high temperatures, and at the same time improve the interfacial adhesion between the rubber compound and the cable insulation layer.

[0009] A further improvement is that the high dielectric filler barium titanate has a particle size of 1 to 5 μm. This particle size range is used to achieve uniform dispersion of the filler in the adhesive matrix without agglomeration, avoid air gaps, and at the same time improve the stability of dielectric properties.

[0010] A further improvement is that the grafting rate of the special compatibilizer MAH-g-EVA is 1-3%, which is used to balance the compatibility between the matrix and the plasticizer as well as the softness and conformability of the rubber compound.

[0011] A further improvement is that the density of the chlorinated polyethylene in the chlorinated polymer is 1.20–1.25 g / cm³. 3 Chlorohydrin rubber has an epoxy value of 0.3 to 0.5 mol / 100g. The two are compounded to improve the insulation stability and processing efficiency of the rubber compound.

[0012] A further improvement is that the weight ratio of stearic acid to polyethylene glycol dispersant in the processing aid is 0.5:0.5 to 2:2. The two work synergistically, with stearic acid used to adjust the processing fluidity of the rubber compound and polyethylene glycol dispersant used to prevent the agglomeration of high dielectric fillers.

[0013] Further improvements include the following preparation steps:

[0014] Plasticizing: Heat the internal mixer to 70-90°C, add the rubber matrix, and plasticize for 3-5 minutes until the rubber is uniform, soft, and free of obvious particles;

[0015] Initial mixing: Add the special compatibilizer, antioxidant and processing aid to the internal mixer and mix for 2-3 minutes until the additives are evenly dispersed in the rubber matrix;

[0016] Filler mixing: Add the high dielectric filler into the internal mixer in 2 to 3 batches, mixing for 2 to 3 minutes after each addition to ensure that the filler does not agglomerate;

[0017] Plasticizing and thickening: Add the compound plasticizing system and C5 petroleum resin, heat the internal mixer to 110-135°C, and continue mixing for 5-8 minutes until all components are fully integrated;

[0018] Molding: The uniformly mixed rubber compound is discharged, filtered to remove impurities, calendered or extruded into sheets, and cut into the required specifications to obtain the finished product.

[0019] A further improvement is made in that: during the plasticizing process, the speed of the internal mixer is controlled at 40-60 r / min, and during the plasticizing and thickening processes, the speed of the internal mixer is controlled at 60-80 r / min.

[0020] A further improvement is made in that: during the molding process, an 80-120 mesh filter is used to remove impurities and undispersed particles from the rubber compound, ensuring that the rubber compound has uniform and consistent properties.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention introduces MAH-g-EVA as a dedicated compatibilizer. The maleic anhydride groups in its molecular chain can chemically bond with the polar groups of chlorine-containing polymers. The EVA segment can achieve molecular-level compatibility with the compound plasticizing system, forming a stable matrix-compatibility-plasticizer molecular structure. This completely solves the core problem of poor compatibility and easy phase separation between the matrix and plasticizer in the prior art. There are no micro-gaps in the colloid, which greatly improves the reliability of insulation protection. High-magnification electron microscopy shows no obvious interfaces and voids, solving the core difficulty of internal gaps that the prior art cannot solve.

[0023] 2. This invention uses liquid nitrile rubber and TP-95 plasticizer. Liquid nitrile rubber is a reactive plasticizer that can be lightly crosslinked with the matrix without the risk of migration and oil separation. TP-95 plasticizer is a polar ether ester plasticizer that combines high compatibility, low-temperature flexibility, and thermal stability. The two work together to avoid the shortcomings of single plasticizers, such as hardening at low temperatures and oil separation at high temperatures. At the same time, combined with the tackifying effect of C5 petroleum resin, it improves the interfacial adhesion between the rubber compound and the cable insulation layer, making it suitable for different climates and harsh working conditions such as high and low temperature alternation, high humidity, and coastal salt spray, thus solving the problem of poor compatibility of existing rubber compounds.

[0024] 3. This invention selects barium titanate with a particle size of 1-5μm as a high dielectric filler. This particle size range ensures that the filler is uniformly dispersed in the matrix without agglomeration. Combined with the auxiliary effect of polyethylene glycol dispersants, it effectively avoids the air gap problem caused by filler agglomeration. At the same time, the dielectric constant of the adhesive can be precisely controlled between 15 and 25, which is suitable for the electric field dissipation requirements of cable accessories of different voltage levels such as 10kV, 35kV, and 110kV. The dielectric performance fluctuation is ≤5% during long-term operation, and the stability is significantly better than existing products, which solves the defects of unstable dielectric performance and narrow control range of existing adhesives.

[0025] 4. This invention employs a step-by-step feeding process of "initial mixing of compatibilizer followed by step-by-step addition of fillers and plasticizers" and a gradient temperature process of "low-temperature plasticizing - medium-high temperature plasticizing," which is fundamentally different from the existing conventional one-step mixing process. This ensures that all components are fully dispersed and reacted, avoiding thermal aging of components. At the same time, no special equipment is required; conventional internal mixers and calenders can be used for production. The batch performance fluctuation of the product is ≤5%, the production efficiency is high, and it is suitable for large-scale industrial production. Moreover, the service life of the rubber compound can reach more than 10 years, which matches the design service life of the cable body. This solves the problems of complex processing, poor batch stability, and short service life of existing rubber compounds.

[0026] 5. The compatibility, dielectric properties, workability, aging resistance, and interfacial adhesion of the adhesive of this invention form a synergistic effect, solving the problem of single-performance optimization and overall performance imbalance of existing products. It greatly enhances the overall application value of stress relief adhesive and can be widely used in 10kV and above medium and high voltage cable joints and terminal accessories in fields such as power, municipal, rail transit, and new energy. It is especially suitable for cable engineering under harsh working conditions and has broad market application prospects, filling the technical gap of existing products in terms of compatibility and air gap control. Attached Figure Description

[0027] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0028] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] Example 1

[0030] according to Figure 1 As shown in the figure, this embodiment proposes a low-air-gap, high-compatibility stress-relieving adhesive for power cables:

[0031] Composition (by weight): 60 parts chlorinated polyethylene, 40 parts chlorohydrin rubber (mass ratio of the two is 3:2, within the range of 1:1 to 3:1, which can achieve synergistic optimization of insulation and processability), 25 parts liquid nitrile rubber, 15 parts TP-95 plasticizer (total number of the compounded plasticizer system is 40 parts, within the range of 25 to 60 parts, which synergistically avoids the shortcomings of a single plasticizer), 30 parts C5 petroleum resin (to improve the self-adhesion and interfacial adhesion of the rubber compound), 60 parts barium titanate (particle size 3μm, within the range of 1 to 5μm, with excellent dispersibility), 5 parts MAH-g-EVA (grafting rate 2%, within the range of 1 to 3%, which achieves effective compatibilization), 2 parts antioxidant 1010 (to inhibit the aging of the rubber compound), 1 part stearic acid, 1 part polyethylene glycol dispersant (total number of processing aids is 2 parts, within the range of 1 to 4 parts, which improves processing performance and prevents filler agglomeration).

[0032] Preparation process: Specific parameters are as follows: plasticizing temperature 80℃ (within the range of 70~90℃ to avoid thermal aging of the matrix and ensure sufficient plasticizing), time 4min (within the range of 3~5min); initial mixing time 2.5min (within the range of 2~3min to ensure uniform dispersion of additives); barium titanate is added in two batches, each time mixing for 2.5min (each mixing time within the range of 2~3min to avoid filler agglomeration); plasticizing and thickening temperature 120℃ (within the range of 110~135℃ to promote component fusion and avoid resin decomposition), time 6min (within the range of 5~8min); the product is calendered into a 2mm thick stress-relief tape, filtered through a 100-mesh filter to remove impurities, ensuring product purity and uniformity.

[0033] Testing and Effects: The prepared stress-relieving adhesive underwent professional testing, and its performance indicators are as follows: dielectric constant 20 (adjustable within the range of 15-25, suitable for 10kV voltage level), dielectric loss tangent 0.015 (≤0.02, excellent dielectric properties), Shore A hardness 18 (within the range of 10-25, good flexibility and conformability), volume resistivity ≥5×10¹³Ω・cm (excellent insulation performance), and adhesion strength with the cross-linked polyethylene insulation layer of the cable 0.9MPa (≥0.8MPa, tight adhesion); high-magnification electron microscopy. Microscopic observation revealed no phase separation air gaps within the adhesive, completely solving the air gap problem of existing technologies. It exhibits no hardening at -20℃ and excellent adhesion to the cable interface; at 135℃, it shows no oil separation or flow, making it suitable for the low-temperature climate of northern regions. After aging at 135℃ for 168 hours, the hardness change is +2 Shore A (≤±3 Shore A), with a performance retention rate of 90% (≥85%). It exhibits strong self-adhesion, no springback during construction and winding, and can be stably applied to 10kV power cable terminal accessories. It is particularly suitable for cable projects in low-temperature northern regions, demonstrating significantly better performance than existing conventional adhesives.

[0034] Example 2

[0035] according to Figure 1 As shown in the figure, this embodiment proposes a low-air-gap, high-compatibility stress-relieving adhesive for power cables:

[0036] Composition (by weight): 75 parts chlorinated polyethylene, 25 parts chlorohydrin rubber (mass ratio of the two is 3:1, within the range of 1:1 to 3:1, with excellent processing fluidity), 30 parts liquid nitrile rubber, 20 parts TP-95 plasticizer (total number of the compound plasticizer system is 50 parts, within the range of 25 to 60 parts, with excellent high and low temperature performance), 35 parts C5 petroleum resin, 70 parts barium titanate (particle size 5μm, within the range of 1 to 5μm), 6 parts MAH-g-EVA (grafting rate 3%, within the range of 1 to 3%), 3 parts antioxidant 1010, 1.5 parts stearic acid, 1.5 parts polyethylene glycol dispersant (total number of processing aids is 3 parts, within the range of 1 to 4 parts).

[0037] Preparation process: Specific parameters are as follows: plasticizing temperature 90℃ (within the range of 70~90℃), time 5min (within the range of 3~5min); initial mixing time 3min (within the range of 2~3min); barium titanate is added in 3 parts, each mixing for 2min (each mixing time within the range of 2~3min); plasticizing and thickening temperature 130℃ (within the range of 110~135℃), time 7min (within the range of 5~8min); the product is extruded into stress-relieving blocks with a specification of 50×50mm, and filtered through a 120-mesh filter to remove impurities, ensuring product uniformity and purity.

[0038] Testing and Performance: The stress-relieving adhesive was professionally tested, and its performance indicators are as follows: dielectric constant 23 (adjustable within the range of 15-25, suitable for 35kV voltage level), dielectric loss tangent 0.018 (≤0.02), Shore A hardness 20 (within the range of 10-25), volume resistivity ≥3×10¹³Ω・cm, and bonding strength with the cross-linked polyethylene insulation layer of the cable 1.0MPa (≥0.8MPa); high-magnification electron microscopy revealed no phase separation air gaps within the adhesive, completely solving the phase separation problem; it exhibits good adhesion and no cracking at -30℃, and no oil separation or deformation at 135℃, making it suitable for high and low temperature alternating operating conditions; after aging at 135℃ for 168h, the performance retention rate is 88% (≥85%), and the dielectric properties are stable, making it stable for use in 35kV power cable joint accessories, especially suitable for cable projects in high-altitude areas with alternating high and low temperatures, with comprehensive performance superior to existing technology products.

[0039] Example 3

[0040] according to Figure 1 As shown in the figure, this embodiment proposes a low-air-gap, high-compatibility stress-relieving adhesive for power cables:

[0041] Composition (by weight): 50 parts chlorinated polyethylene, 50 parts chlorohydrin rubber (mass ratio of the two is 1:1, within the range of 1:1 to 3:1, with excellent insulation properties), 20 parts liquid nitrile rubber, 12 parts TP-95 plasticizer (total number of parts in the compound plasticizing system is 32, within the range of 25 to 60 parts), 25 parts C5 petroleum resin, 50 parts barium titanate (particle size 1μm, within the range of 1 to 5μm, with excellent dispersibility), 4 parts MAH-g-EVA (grafting rate 1%, within the range of 1 to 3%), 2 parts antioxidant 1010, 0.8 parts stearic acid, 0.8 parts polyethylene glycol dispersant (total number of processing aids is 1.6 parts, within the range of 1 to 4 parts).

[0042] Preparation process: Specific parameters are as follows: plasticizing temperature 70℃ (within the range of 70~90℃), time 3min (within the range of 3~5min); initial mixing time 2min (within the range of 2~3min); barium titanate is added in two batches, each time mixing for 3min (each mixing time within the range of 2~3min); plasticizing and thickening temperature 115℃ (within the range of 110~135℃), time 5min (within the range of 5~8min); stress relief tape with a thickness of 1.5mm is produced by calendering and sheeting, and impurities are removed by filtration through an 80-mesh filter to meet the requirements of industrial production.

[0043] Testing and Performance: The prepared stress-relieving adhesive underwent professional testing, and its performance indicators are as follows: dielectric constant 18 (adjustable within the range of 15 to 25, suitable for 10kV voltage level), dielectric loss tangent 0.012 (≤0.02), Shore A hardness 15 (within the range of 10 to 25), volume resistivity ≥6×10¹³Ω・cm, and bonding strength with the cross-linked polyethylene insulation layer of the cable 0.85MPa (≥0.8MPa); high-magnification electron microscopy revealed no phase separation air gaps within the adhesive, indicating stable performance; no hardening at -25℃ and no flow at 135℃, making it suitable for high-humidity environments; after aging at 135℃ for 168h, the performance retention rate is 92% (≥85%), exhibiting tight adhesion during construction and excellent self-adhesion. It can be stably applied to 10kV power cable joint accessories, and is particularly suitable for cable projects in the high-humidity southern coastal areas, demonstrating strong practicality.

[0044] Comparative example (existing conventional stress-relieving adhesive)

[0045] Composition (by weight): 100 parts chlorohydrin rubber, 30 parts naphthenic oil (single plasticizer), 60 parts TiO2 filler (no specific particle size, prone to agglomeration), 25 parts rosin ester, 2 parts antioxidant 264, 1 part stearic acid (no special compatibilizer, no compound plasticizing system, no barium titanate with specific particle size, which is in stark contrast to the present invention).

[0046] Preparation process: The existing conventional one-step mixing process is adopted, in which all components are added to the internal mixer at the same time, mixed at 120°C for 10 minutes, and then calendered into sheets (without step feeding and gradient temperature design, which is fundamentally different from the process of this invention).

[0047] Test results: The colloid contains minute phase separation air gaps, has a dielectric constant of 16 (narrow control range), a Shore A hardness of 35 (higher than the range of this invention, poor flexibility), hardens and becomes brittle at -20℃, exhibits slight oil separation at 135℃, retains 65% of its performance after aging at 135℃ for 168h (lower than the range of this invention), has a bonding strength with cable insulation layer of 0.4MPa (lower than the range of this invention), and exhibits batch-to-batch performance fluctuation of 12% (higher than the range of this invention). All core performance characteristics are significantly inferior to those of the products in Examples 1-3 of this invention, fully highlighting the technical advantages of this invention.

[0048] The stress-relieving adhesive prepared in the embodiments of the present invention, through the synergistic effect of a dedicated compatible system, a compound plasticizing system, specific particle size fillers, and a stepwise gradient preparation process, exhibits significantly superior core properties compared to existing conventional adhesives. It solves the core pain points of the prior art, such as internal air gaps, poor compatibility, unstable dielectric properties, and poor high and low temperature performance. The product has high batch stability, a simple preparation process, and does not require special equipment, making it suitable for large-scale industrial production. Each embodiment is adapted to different climate and voltage level operating conditions.

[0049] Internal air gap none There are tiny phase separation air gaps Dielectric constant range 15-25 (precisely adjustable) 10-20 (narrow range of regulation) Shore A hardness 10～25 25～40 -30℃ low temperature performance It doesn't harden and has good adhesion. Hardening, brittleness, and poor adhesion 135℃ high temperature performance No oil separation, no dripping Slight oil separation, prone to dripping 135℃×168h aging performance retention rate ≥85% ≤70% Bond strength with cable insulation layer ≥0.8MPa ≤0.5MPa Product batch performance fluctuations ≤5% ≥10%

[0050] This low-gap, high-compatibility stress-relieving adhesive for power cables incorporates MAH-g-EVA as a dedicated compatibilizer. The maleic anhydride groups in its molecular chain can chemically bond with the polar groups of chlorine-containing polymers. The EVA segment can achieve molecular-level compatibility with the compounded plasticizer system, forming a stable matrix-compatible-plasticizer molecular structure. This completely solves the core problem of poor compatibility and easy phase separation between the matrix and plasticizer in existing technologies. There are no micro-gapes in the adhesive, which greatly improves the reliability of insulation protection. High-magnification electron microscopy shows no obvious interfaces or voids, solving the core difficulty of internal air gaps that existing technologies cannot address. This invention uses liquid nitrile rubber and TP-95 plasticizer. Liquid nitrile rubber is a reactive plasticizer that can be lightly crosslinked with the matrix without the risk of migration and oil separation. TP-95 plasticizer is a polar ether ester plasticizer that combines high compatibility, low-temperature flexibility, and thermal stability. The two work together to avoid the shortcomings of single plasticizers, such as hardening at low temperatures and oil separation at high temperatures. At the same time, combined with the tackifying effect of C5 petroleum resin, it improves the interfacial adhesion between the rubber compound and the cable insulation layer, making it suitable for different climates and harsh working conditions such as high and low temperature alternation, high humidity, and coastal salt spray, thus solving the problem of poor compatibility of existing rubber compounds. This invention selects barium titanate with a particle size of 1-5 μm as a high dielectric filler. This particle size range ensures that the filler is uniformly dispersed in the matrix without agglomeration. Combined with the auxiliary effect of polyethylene glycol dispersants, it effectively avoids air gap problems caused by filler agglomeration. At the same time, the dielectric constant of the adhesive can be precisely controlled between 15 and 25, which is suitable for the electric field dissipation requirements of cable accessories of different voltage levels such as 10kV, 35kV, and 110kV. The dielectric performance fluctuation is ≤5% during long-term operation, and the stability is significantly better than existing products, solving the defects of unstable dielectric performance and narrow control range of existing adhesives. This invention employs a step-by-step feeding process of "initial mixing of compatibilizer followed by step-by-step addition of fillers and plasticizers" and a gradient temperature process of "low-temperature plasticizing - medium-high-temperature plasticizing," which is fundamentally different from the existing conventional one-step mixing process. This ensures sufficient dispersion and reaction of each component, avoids thermal aging, and requires no special equipment; it can be produced using conventional internal mixers and calenders. Product batch performance fluctuations are ≤5%, resulting in high production efficiency suitable for large-scale industrial production. Furthermore, the rubber compound has a service life of over 10 years, matching the designed service life of the cable body, thus solving the problems of complex processing, poor batch stability, and short service life of existing rubber compounds. The compatibility, dielectric properties, workability, aging resistance, and interfacial adhesion of the rubber compound of this invention create a synergistic effect, solving the problem of single-performance optimization and overall performance imbalance in existing products. This significantly enhances the overall application value of stress-relieving adhesives and can be widely used in 10kV and above medium- and high-voltage cable joints and terminal accessories in power, municipal, rail transit, and new energy fields. It is particularly suitable for cable engineering under harsh working conditions, with broad market application prospects, filling the technological gap in compatibility and air gap control of existing products.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-air-gap, high-compatibility stress-relieving adhesive for power cables, characterized in that, It includes the following components by weight ratio: 80-120 parts of chlorinated polymer, 25-60 parts of compound plasticizing system, 20-40 parts of C5 petroleum resin, 40-80 parts of high dielectric filler, 3-8 parts of special compatibilizer, 1-4 parts of antioxidant, and 1-4 parts of processing aid. The chlorinated polymer is a compound of chlorinated polyethylene and chlorohydrin rubber as the rubber matrix. The compounded plasticizing system is a compound of liquid nitrile rubber and TP-95 plasticizer. The high dielectric filler is barium titanate. The special compatibilizer is MAH-g-EVA. The processing aid is a compound of stearic acid and polyethylene glycol dispersant. The antioxidant is antioxidant 1010. Its preparation method includes plasticizing, initial mixing, filler mixing, plasticizing and thickening, and molding, using a step-by-step feeding and gradient temperature mixing process.

2. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: In the chlorinated polymer, the mass ratio of chlorinated polyethylene to chlorohydrin rubber is 1:1 to 3:

1. Within this range, the optimal synergy between insulation and processability is achieved, avoiding poor processing flow or decreased insulation performance.

3. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: In the compound plasticizing system, the weight ratio of liquid nitrile rubber to TP-95 plasticizer is 15:10 to 35:

25. The two work synergistically to exert a plasticizing effect, avoid hardening at low temperatures and oil separation at high temperatures, and at the same time improve the interfacial adhesion between the rubber compound and the cable insulation layer.

4. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: The high dielectric filler barium titanate has a particle size of 1 to 5 μm. This particle size range is used to achieve uniform dispersion of the filler in the adhesive matrix without agglomeration, avoid air gaps, and improve the stability of dielectric properties.

5. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: The grafting rate of the special compatibilizer MAH-g-EVA is 1-3%, which is used to balance the compatibility between the matrix and the plasticizer, as well as the softness and conformability of the rubber compound.

6. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: In the chlorinated polymer, the density of chlorinated polyethylene is 1.20–1.25 g / cm³. 3 Chlorohydrin rubber has an epoxy value of 0.3 to 0.5 mol / 100g. The two are compounded to improve the insulation stability and processing efficiency of the rubber compound.

7. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: In the processing aid, the weight ratio of stearic acid to polyethylene glycol dispersant is 0.5:0.5 to 2:

2. The two work synergistically, with stearic acid used to adjust the processing fluidity of the rubber compound and polyethylene glycol dispersant used to prevent the agglomeration of high dielectric fillers.

8. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 1, characterized in that: The preparation steps include the following: Plasticizing: Heat the internal mixer to 70-90°C, add the rubber matrix, and plasticize for 3-5 minutes until the rubber is uniform, soft, and free of obvious particles; Initial mixing: Add the special compatibilizer, antioxidant and processing aid to the internal mixer and mix for 2-3 minutes until the additives are evenly dispersed in the rubber matrix; Filler mixing: Add the high dielectric filler into the internal mixer in 2 to 3 batches, mixing for 2 to 3 minutes after each addition to ensure that the filler does not agglomerate; Plasticizing and thickening: Add the compound plasticizing system and C5 petroleum resin, heat the internal mixer to 110-135°C, and continue mixing for 5-8 minutes until all components are fully integrated; Molding: The uniformly mixed rubber compound is discharged, filtered to remove impurities, calendered or extruded into sheets, and cut into the required specifications to obtain the finished product.

9. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 8, characterized in that: In the plasticizing process, the speed of the internal mixer is controlled at 40-60 r / min, and in the plasticizing and thickening processes, the speed of the internal mixer is controlled at 60-80 r / min.

10. The low-air-gap, high-compatibility stress-relieving adhesive for power cables according to claim 8, characterized in that: During the molding process, an 80-120 mesh filter is used to remove impurities and undispersed particles from the rubber compound, ensuring that the rubber compound has uniform properties.

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