Processing technology of high-temperature-resistant super-flexible motor lead wire

Abstract

This invention relates to the field of cable technology, specifically to a processing technology for high-temperature resistant, ultra-flexible motor lead wires. The process involves preparing two types of hexagonal boron nitride fillers with different surface properties through hydroxylation and silane modification, and applying them in separate layers of a three-layer insulating compound. Combined with a polysiloxane alkyl body with increasing phenyl content from the inside out, flexible single-end segments on the inner side, and a differentiated crosslinking agent / inhibitor system, the lead wire is obtained through three-layer co-extrusion and multi-stage temperature-increasing vulcanization. This process solves the problems of decreased flexibility, poor bending reliability, and easy failure of interlayer interfaces caused by high phenyl / high filler content in traditional methods, achieving a balance between high-temperature resistance, ultra-flexibility, and stable electrical performance.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a processing technology for high-temperature resistant ultra-flexible motor lead wires. Background Technology

[0002] Currently, motors, especially those with high power density or operating in high-temperature environments (such as drive motors for new energy vehicles and servo motors), face more stringent requirements for the performance of their lead wires. Lead wires not only need excellent electrical insulation, but also must withstand the high temperatures generated inside the motor and the mechanical stresses under complex external operating conditions, especially the challenges posed by frequent bending.

[0003] Traditional solutions often focus on improving a single property of the material. For example, heat-resistant silicone rubber (such as methyl vinyl silicone rubber) is used as an insulating material, and its high-temperature resistance is improved by introducing phenyl side groups (such as methyl phenyl silicone rubber). However, increasing the phenyl content in silicone rubber often sacrifices the material's flexibility, leading to increased insulation layer hardness and a larger minimum bending radius. Under installation, wiring, or long-term vibration and bending conditions, this can easily cause problems such as insulation layer cracking and conductor fatigue breakage, affecting connection reliability.

[0004] Another common technical approach involves adding thermally conductive insulating fillers, such as hexagonal boron nitride (h-BN), to silicone rubber insulators to improve heat dissipation and enhance corona or partial discharge resistance. However, the introduction of fillers, especially when their content is high or unevenly dispersed, can significantly worsen the processing flowability and mechanical properties of the compound after curing, making the cable stiff and hindering flexible applications. More importantly, homogeneous filler systems form numerous inorganic-organic interfaces within the compound. These interfaces can become the origin of defects during thermo-oxidative aging, leading to decreased insulation resistance and deteriorated dielectric properties.

[0005] Furthermore, existing heat-resistant flexible leads mostly employ single-layer insulation structures or simple inner and outer double-layer structures. Single-layer homogeneous structures struggle to simultaneously optimize inner flexibility, stress buffering in the middle layer, and heat resistance protection in the outer layer. Meanwhile, simple double-layer structures, if poorly designed with appropriate interlayer formulations and performance gradients, are prone to interlayer stress concentration under thermal and mechanical coupling due to modulus or thermal expansion coefficient mismatches. This can lead to delamination after long-term use, becoming a weak point in insulation breakdown. Therefore, systematically addressing the reduced flexibility, decreased bending reliability, and interlayer interface failure after long-term thermal aging caused by high-filler or high-phenyl systems, while ensuring the heat resistance and insulation performance of the motor lead wire foundation, has become a critical technical challenge requiring breakthroughs in this field. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a processing technology for high-temperature resistant ultra-flexible motor leads, so as to solve the technical problems of decreased flexibility and poor bending reliability of existing high-temperature resistant motor leads caused by simply increasing the phenyl content or uniformly adding fillers, as well as the increase of interface defects and degradation of insulation performance after high-temperature aging caused by interlayer performance mismatch.

[0007] To achieve the above objectives, the present invention provides a processing technology for high-temperature resistant ultra-flexible motor lead wires, comprising the following steps:

[0008] (1) First, hydroxylated hexagonal boron nitride is prepared, and then vinylsilane-modified hexagonal boron nitride and phenyl-vinylbissilane-modified hexagonal boron nitride are prepared respectively;

[0009] (2) The nickel-plated fine stranded copper conductor is cleaned and dried to obtain a pretreated conductor;

[0010] (3) Prepare inner methyl-enriched rubber compound, transition rubber compound and outer phenyl-enriched rubber compound respectively;

[0011] (4) The inner methyl enriched rubber, the transition rubber and the outer phenyl enriched rubber are sequentially coated on the outer surface of the pretreated conductor by three-layer co-extrusion to form a wire blank containing an inner methyl enriched layer, a transition layer and an outer phenyl enriched layer.

[0012] (5) The wire blank is subjected to multi-stage heating vulcanization and post-vulcanization treatment to obtain high-temperature resistant ultra-flexible motor lead wire;

[0013] The inner methyl-enriched adhesive is prepared from the following raw materials in parts by weight:

[0014] 630-670 parts vinyl-terminated polydimethylsiloxane, 75-105 parts vinyl-terminated methylphenyl polysiloxane, 110-130 parts monovinyl-terminated polydimethylsiloxane, 85-95 parts hydrophobic fumed silica, 23-27 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 0.25-0.35 parts 1-ethynyl-1-cyclohexanol and 0.45-0.55 parts platinum-divinyltetramethyldisiloxane complex;

[0015] The transition compound is prepared from the following raw materials in parts by weight:

[0016] 410-450 parts vinyl-terminated polydimethylsiloxane, 300-340 parts vinyl-terminated methylphenyl polysiloxane, 105-115 parts hydrophobic fumed silica, 18-22 parts vinylsilane-modified hexagonal boron nitride, 40-46 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 0.52-0.68 parts 1-ethynyl-1-cyclohexanol and 0.50-0.60 parts platinum-divinyltetramethyldisiloxane complex;

[0017] The outer phenyl-enriched adhesive, by weight parts, is prepared from the following raw materials:

[0018] 160-200 parts vinyl-terminated polydimethylsiloxane, 590-650 parts vinyl-terminated methylphenyl polysiloxane, 85-95 parts hydrophobic fumed silica, 45-55 parts phenyl-vinylbissilane modified hexagonal boron nitride, 72-84 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 1.08-1.32 parts 1-ethynyl-1-cyclohexanol and 0.65-0.75 parts platinum-divinyltetramethyldisiloxane complex.

[0019] Preferably, the vinylsilane-modified hexagonal boron nitride is obtained by reacting hydroxylated hexagonal boron nitride with vinyltriethoxysilane; the phenyl-vinylbissilane-modified hexagonal boron nitride is obtained by reacting hydroxylated hexagonal boron nitride first with phenyltriethoxysilane, and then with vinyltriethoxysilane.

[0020] Preferably, the hydroxylated hexagonal boron nitride is obtained by treating hexagonal boron nitride with a 10% (w / w) aqueous solution of hydrogen peroxide; the mass ratio of the hexagonal boron nitride, the 10% (w / w) aqueous solution of hydrogen peroxide, and the deionized water is 45-55:380-460:900-1100.

[0021] Preferably, the mass ratio of hydroxylated hexagonal boron nitride to vinyltriethoxysilane in the raw materials for preparing vinylsilane-modified hexagonal boron nitride is 8-12:0.8-1.2; and the mass ratio of hydroxylated hexagonal boron nitride, phenyltriethoxysilane, and vinyltriethoxysilane in the raw materials for preparing phenyl-vinylbissilane-modified hexagonal boron nitride is 28-34:3.4-4.5:0.8-1.2.

[0022] Preferably, the thickness of the inner methyl enrichment layer is 240-280 μm, the thickness of the transition layer is 160-200 μm, and the thickness of the outer phenyl enrichment layer is 240-280 μm.

[0023] Preferably, the vinyl-terminated polydimethylsiloxane has a viscosity of 5150 cSt at 25°C and a vinyl content of 0.12%; the vinyl-terminated methylphenyl polysiloxane has a viscosity of 5000 cSt at 25°C and a vinyl content of 0.5%; the monovinyl-terminated polydimethylsiloxane has a viscosity of 1000 cSt at 25°C and a vinyl content of 0.21%; and the silane-hydrogen bond content of the methylhydrosiloxane-dimethylsiloxane copolymer is 1.8 mmol / g.

[0024] Preferably, the hydrophobic fumed silica has a BET specific surface area of ​​110 m². 2 / g; the average particle size of the hexagonal boron nitride used to prepare the hydroxylated hexagonal boron nitride is 1 μm.

[0025] Preferably, the multi-stage heating vulcanization process is as follows: passing through a 78-82℃ hot air section for 2-2.5 minutes; then sequentially passing through an 88-92℃ hot air section for 3.5-4.5 minutes, a 125-135℃ hot air section for 5.5-6.5 minutes, a 160-170℃ hot air section for 7.5-8.5 minutes, and a 195-205℃ hot air section for 11-13 minutes.

[0026] Preferably, the post-vulcanization is performed by placing the vulcanizer in an oven at 215-225℃ for 1.8-2.2 hours.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention achieves a gradient distribution and synergistic effect in performance by designing a three-layer composite insulation structure with progressively increasing phenyl side groups from the inside out and differentiated modification of hexagonal boron nitride filler in different zones. The inner methyl-rich adhesive ensures ultra-flexibility and low modulus in the contact layer with the conductor, with a minimum bending radius as low as 6 mm, effectively absorbing bending stress; the outer phenyl-rich adhesive combined with phenyl-vinylbissilane-modified BN provides excellent high-temperature resistance and thermal conductivity; the intermediate transition adhesive and the corresponding BN modification method play a good role in connecting the flexible and rigid layers and providing stress buffering. This structural design enables the product to achieve a conductor resistance change rate as low as 0.22% after harsh bending tests, significantly improving the reliability of long-term use.

[0029] (2) This invention introduces monovinyl-terminated polydimethylsiloxane as a flexible segment into the inner compound and employs differentiated ratios of hydrogen-containing silicone oil and inhibitors in the three-layer compound to construct a crosslinking sequence and gradient crosslinking density adapted from the inside out. The moderately delayed crosslinking on the inner side ensures sufficient flow and coating of the compound on the conductor surface, forming a dense interface; the earlier and higher degree of crosslinking on the outer side rapidly constructs a heat-resistant skeleton. Combined with a specific multi-stage heating and vulcanization process, this design significantly reduces interlayer stress caused by differences in curing shrinkage. Test results show that this synergistic effect can effectively inhibit the hardening and embrittlement of the insulation layer after high-temperature aging. The elongation at break after aging can reach up to 86.4%, and the insulation resistance can reach up to 15465 MΩ·km, far exceeding the comparative example, thus solving the contradiction of flexibility and thermal stability that is common in high heat-resistant material systems. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] The raw materials used are as follows: the nickel-plated fine stranded copper conductor is from Zhejiang Meitong Conductor Technology Co., Ltd., with a specification of 2mm. 2 Fine stranded wire; vinyl-terminated polydimethylsiloxane is SiSiBVF6030-5000 from Nanjing SiSiB Silicones, with a viscosity of 5150 cSt at 25℃ and a vinyl content of 0.12%; vinyl-terminated methylphenyl polysiloxane is SiSiB VF6805 from Nanjing SiSiB Silicones, with a viscosity of 5000 cSt at 25℃ and a vinyl content of 0.5%; monovinyl-terminated polydimethylsiloxane is SiSiB VF6031 from Nanjing SiSiB Silicones, with a viscosity of 1000 cSt at 25℃ and a vinyl content of 0.21%; methyl hydrogen siloxane-dimethylsiloxane copolymer is SiSiB HF2050-H18 from Nanjing SiSiB Silicones, with a silane-hydrogen bond content of 1.8 mmol / g; hydrophobic fumed silica is Evonik AEROSIL R972, with a BET specific surface area of ​​110 m². 2 / g; hexagonal boron nitride was produced using Sigma-Aldrich 255475 with a particle size of approximately 1 μm; platinum-divinyltetramethyldisiloxane complex was produced using Sigma-Aldrich 479535 with a concentration of 0.05 mol / L, and the solvent was vinyl-terminated polydimethylsiloxane.

[0032] Example 1:

[0033] Step 1: Weigh 50g of hexagonal boron nitride, 420g of 10% hydrogen peroxide aqueous solution and 1000g of deionized water and add them to a corrosion-resistant reaction vessel. Heat the mixture to 85℃ with a stirring speed of 500rpm and keep it at that temperature for 6h. After the reaction is complete, filter the mixture and wash the filter cake five times with 1000g of deionized water. Control the pH of the filtrate from the fifth wash to be 6.8. Place the filter cake in a 100℃ oven and dry it for 4h. Then, sieve it through a 200-mesh sieve to obtain hydroxylated hexagonal boron nitride.

[0034] Step 2: Weigh 30g of the hydroxylated hexagonal boron nitride obtained in Step 1, 260g of anhydrous ethanol, 40g of deionized water and 1g of glacial acetic acid, and disperse them at 1000rpm for 20min; add 4g of phenyltriethoxysilane and react at 70℃ for 2h; then add 1g of vinyltriethoxysilane and continue the reaction at 70℃ for 3h; after the reaction, filter, wash the filter cake three times with 300g of anhydrous ethanol, and then dry at 120℃ for 3h to obtain hexagonal boron nitride modified with phenyl-vinylbissilane on the outside;

[0035] Step 3: Weigh 10g of the hydroxylated hexagonal boron nitride obtained in Step 1, 100g of anhydrous ethanol, 20g of deionized water and 1g of glacial acetic acid, and disperse them at 1000rpm for 20min; add 1g of vinyltriethoxysilane and react at 70℃ for 3h; after the reaction, filter, wash the filter cake three times with 150g of anhydrous ethanol, and then dry at 120℃ for 3h to obtain the hexagonal boron nitride modified with vinylsilane in the transition zone;

[0036] Step 4: Weigh 1 kg of nickel-plated fine stranded copper conductor, continuously wipe the outer surface of the conductor with 300 g of anhydrous ethanol, dry it in 80℃ hot air for 30 min, and then place it in an environment of 25℃ and 50% relative humidity for 20 min before proceeding to the coating process.

[0037] Step 5: Weigh 650g of vinyl-terminated polydimethylsiloxane, 90g of vinyl-terminated methylphenyl polysiloxane, 120g of monovinyl-terminated polydimethylsiloxane, and 90g of hydrophobic fumed silica, and mix them at 35°C and 60rpm for 20min; then add 25g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 300mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10min; after cooling to 25°C, add 500mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5min, and degas under -90kPa vacuum for 10min to obtain an inner methyl-enriched rubber compound;

[0038] Step 6: Weigh 430g of vinyl-terminated polydimethylsiloxane, 320g of vinyl-terminated methylphenyl polysiloxane, 110g of hydrophobic fumed silica, and 20g of vinylsilane-modified hexagonal boron nitride obtained in Step 3. Mix at 35°C and 60 rpm for 25 min. Then add 43g of methylhydrosiloxane-dimethylsiloxane copolymer and 600mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 550mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -90kPa vacuum for 10 min to obtain the transition compound.

[0039] Step 7: Weigh 180g of vinyl-terminated polydimethylsiloxane, 620g of vinyl-terminated methylphenyl polysiloxane, 90g of hydrophobic fumed silica, and 50g of the phenyl-vinylbissilane-modified hexagonal boron nitride obtained in Step 2. Mix at 35°C and 60 rpm for 30 min. Then add 78g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 1200mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 700mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -90kPa vacuum for 10 min to obtain the phenyl-enriched rubber compound.

[0040] Step 8: Take 850g of the inner methyl-enriched rubber material obtained in Step 5, 850g of the transition rubber material obtained in Step 6, and 850g of the outer phenyl-enriched rubber material obtained in Step 7, and add them to the corresponding barrels of the three-layer co-extrusion equipment respectively; preheat the nickel-plated fine stranded copper conductor obtained in Step 4 to 70℃, control the die head temperature to 55℃, and the linear speed to 4m / min, so that the coating thickness of the inner methyl-enriched rubber material is 260μm, the coating thickness of the transition rubber material is 180μm, and the coating thickness of the outer phenyl-enriched rubber material is 260μm; after extrusion, first pass through the 80℃ hot air section for 2min; then pass through the 90℃ hot air section for 4min, the 130℃ hot air section for 6min, the 165℃ hot air section for 8min, and the 200℃ hot air section for 12min in sequence; then place the wire blank in a 220℃ oven for post-curing for 2h to obtain the high-temperature resistant ultra-flexible motor lead wire.

[0041] Example 2:

[0042] Step 1: Weigh 45g of hexagonal boron nitride, 380g of 10% hydrogen peroxide aqueous solution and 900g of deionized water and add them to a corrosion-resistant reaction vessel. Heat the mixture to 80℃ with a stirring speed of 450rpm and keep it at that temperature for 5h. After the reaction is complete, filter the mixture and wash the filter cake five times with 900g of deionized water. Control the pH of the filtrate from the fifth wash to be 6.6. Place the filter cake in a 95℃ oven and dry it for 3.5h. Then, sieve it through a 200-mesh sieve to obtain hydroxylated hexagonal boron nitride.

[0043] Step 2: Weigh 28g of the hydroxylated hexagonal boron nitride obtained in Step 1, 240g of anhydrous ethanol, 35g of deionized water and 0.8g of glacial acetic acid, and disperse them at a stirring speed of 950rpm for 18min; add 3.5g of phenyltriethoxysilane and react at 68℃ for 1.8h; then add 0.8g of vinyltriethoxysilane and continue to react at 68℃ for 2.8h; after the reaction, filter, wash the filter cake three times with 270g of anhydrous ethanol, and then dry at 115℃ for 2.8h to obtain hexagonal boron nitride modified with phenyl-vinylbissilane on the outside;

[0044] Step 3: Weigh 8g of the hydroxylated hexagonal boron nitride obtained in Step 1, 90g of anhydrous ethanol, 18g of deionized water and 0.8g of glacial acetic acid, and disperse them at a stirring speed of 950rpm for 18min; add 0.8g of vinyltriethoxysilane, and react at 68℃ for 2.8h; after the reaction, filter, wash the filter cake three times with 140g of anhydrous ethanol, and then dry at 115℃ for 2.8h to obtain the vinylsilane-modified hexagonal boron nitride in the transition zone;

[0045] Step 4: Weigh 1 kg of nickel-plated fine stranded copper conductor, continuously wipe the outer surface of the conductor with 250 g of anhydrous ethanol, dry it in 75℃ hot air for 25 min, and then place it in an environment of 24℃ and 48% relative humidity for 18 min before proceeding to the coating process.

[0046] Step 5: Weigh 670g of vinyl-terminated polydimethylsiloxane, 75g of vinyl-terminated methylphenyl polysiloxane, 130g of monovinyl-terminated polydimethylsiloxane, and 85g of hydrophobic fumed silica, and mix them at 33°C and 55 rpm for 18 min; then add 23g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 250mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 9 min; after cooling to 24°C, add 450mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -88kPa vacuum for 9 min to obtain an inner methyl-enriched rubber compound;

[0047] Step 6: Weigh 450g of vinyl-terminated polydimethylsiloxane, 300g of vinyl-terminated methylphenyl polysiloxane, 105g of hydrophobic fumed silica, and 18g of vinylsilane-modified hexagonal boron nitride obtained in Step 3. Mix at 33°C and 55 rpm for 23 min. Then add 40g of methylhydrosiloxane-dimethylsiloxane copolymer and 520mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 9 min. After cooling to 24°C, add 500mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -88kPa vacuum for 9 min to obtain the transition compound.

[0048] Step 7: Weigh 200g of vinyl-terminated polydimethylsiloxane, 590g of vinyl-terminated methylphenyl polysiloxane, 85g of hydrophobic fumed silica, and 45g of the phenyl-vinylbissilane-modified hexagonal boron nitride obtained in Step 2. Mix at 33°C and 55 rpm for 28 min. Then add 72g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 1080mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 9 min. After cooling to 24°C, add 650mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -88kPa vacuum for 9 min to obtain the phenyl-enriched rubber compound on the outside.

[0049] Step 8: Take 830g of the inner methyl-enriched rubber material obtained in Step 5, 830g of the transition rubber material obtained in Step 6, and 830g of the outer phenyl-enriched rubber material obtained in Step 7, and add them to the corresponding barrels of the three-layer co-extrusion equipment respectively; preheat the nickel-plated fine stranded copper conductor obtained in Step 4 to 65℃, control the die head temperature to 52℃, and the linear speed to 3.5m / min, so that the coating thickness of the inner methyl-enriched rubber material is 240μm, the coating thickness of the transition rubber material is 160μm, and the coating thickness of the outer phenyl-enriched rubber material is 240μm; after extrusion, first pass through a 78℃ hot air section for 2min; then pass through an 88℃ hot air section for 3.5min, a 125℃ hot air section for 5.5min, a 160℃ hot air section for 7.5min, and a 195℃ hot air section for 11min in sequence; then place the wire blank in a 215℃ oven for post-curing for 1.8h to obtain a high-temperature resistant ultra-flexible motor lead wire.

[0050] Example 3:

[0051] Step 1: Weigh 55g of hexagonal boron nitride, 460g of 10% hydrogen peroxide aqueous solution and 1100g of deionized water and add them to a corrosion-resistant reaction vessel. Heat the mixture to 90℃ with a stirring speed of 550rpm and keep it at that temperature for 7h. After the reaction is complete, filter the mixture and wash the filter cake five times with 1100g of deionized water. Control the pH of the filtrate from the fifth wash to 7.0. Place the filter cake in an oven at 105℃ and dry it for 4.5h. Then, sieve it through a 200-mesh sieve to obtain hydroxylated hexagonal boron nitride.

[0052] Step 2: Weigh 34g of the hydroxylated hexagonal boron nitride obtained in Step 1, 290g of anhydrous ethanol, 45g of deionized water and 1.2g of glacial acetic acid, and disperse them at 1050rpm for 22min; add 4.5g of phenyltriethoxysilane and react at 72℃ for 2.2h; then add 1.2g of vinyltriethoxysilane and continue the reaction at 72℃ for 3.2h; after the reaction, filter, wash the filter cake three times with 330g of anhydrous ethanol, and then dry at 125℃ for 3.2h to obtain hexagonal boron nitride modified with phenyl-vinylbissilane on the outside;

[0053] Step 3: Weigh 12g of the hydroxylated hexagonal boron nitride obtained in Step 1, 110g of anhydrous ethanol, 22g of deionized water and 1.2g of glacial acetic acid, and disperse them at 1050rpm for 22min; add 1.2g of vinyltriethoxysilane and react at 72℃ for 3.2h; after the reaction, filter, wash the filter cake three times with 160g of anhydrous ethanol, and then dry at 125℃ for 3.2h to obtain the vinylsilane-modified hexagonal boron nitride in the transition zone;

[0054] Step 4: Weigh 1 kg of nickel-plated fine stranded copper conductor, continuously wipe the outer surface of the conductor with 350 g of anhydrous ethanol, dry it in 85℃ hot air for 35 min, and then place it in an environment of 26℃ and 52% relative humidity for 22 min before proceeding to the coating process.

[0055] Step 5: Weigh 630g of vinyl-terminated polydimethylsiloxane, 105g of vinyl-terminated methylphenyl polysiloxane, 110g of monovinyl-terminated polydimethylsiloxane, and 95g of hydrophobic fumed silica, and mix them at 37°C and 65 rpm for 22 min; then add 27g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 350mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 11 min; after cooling to 26°C, add 550mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -92kPa vacuum for 11 min to obtain an inner methyl-enriched rubber compound;

[0056] Step 6: Weigh 410g of vinyl-terminated polydimethylsiloxane, 340g of vinyl-terminated methylphenyl polysiloxane, 115g of hydrophobic fumed silica, and 22g of vinylsilane-modified hexagonal boron nitride obtained in Step 3. Mix at 37°C and 65 rpm for 27 min. Then add 46g of methylhydrosiloxane-dimethylsiloxane copolymer and 680mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 11 min. After cooling to 26°C, add 600mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -92kPa vacuum for 11 min to obtain the transition compound.

[0057] Step 7: Weigh 160g of vinyl-terminated polydimethylsiloxane, 650g of vinyl-terminated methylphenyl polysiloxane, 95g of hydrophobic fumed silica, and 55g of the phenyl-vinylbissilane-modified hexagonal boron nitride obtained in Step 2. Mix them at 37°C and 65 rpm for 32 min. Then add 84g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 1320mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 11 min. After cooling to 26°C, add 750mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -92kPa vacuum for 11 min to obtain the phenyl-enriched rubber compound.

[0058] Step 8: Take 870g of the inner methyl-enriched rubber material obtained in Step 5, 870g of the transition rubber material obtained in Step 6, and 870g of the outer phenyl-enriched rubber material obtained in Step 7, and add them to the corresponding barrels of the three-layer co-extrusion equipment respectively; preheat the nickel-plated fine stranded copper conductor obtained in Step 4 to 75℃, control the die head temperature to 58℃, and the linear speed to 4.5m / min, so that the coating thickness of the inner methyl-enriched rubber material is 280μm, the coating thickness of the transition rubber material is 200μm, and the coating thickness of the outer phenyl-enriched rubber material is 280μm; after extrusion, first pass through the 82℃ hot air section for 2.5min; then pass through the 92℃ hot air section for 4.5min, the 135℃ hot air section for 6.5min, the 170℃ hot air section for 8.5min, and the 205℃ hot air section for 13min in sequence; then place the wire blank in a 225℃ oven for post-curing for 2.2h to obtain the high-temperature resistant ultra-flexible motor lead wire.

[0059] Example 4:

[0060] Step 1: Weigh 48g of hexagonal boron nitride, 400g of 10% hydrogen peroxide aqueous solution and 960g of deionized water and add them to a corrosion-resistant reaction vessel. Heat the mixture to 83℃ at a stirring speed of 480rpm and keep it at that temperature for 5.5h. After the reaction is complete, filter the mixture and wash the filter cake five times with 960g of deionized water. Control the pH of the filtrate from the fifth wash to 6.7. Place the filter cake in a 98℃ oven and dry it for 3.8h. Then, sieve it through a 200-mesh sieve to obtain hydroxylated hexagonal boron nitride.

[0061] Step 2: Weigh 29g of the hydroxylated hexagonal boron nitride obtained in Step 1, 250g of anhydrous ethanol, 38g of deionized water and 0.9g of glacial acetic acid, and disperse them at a stirring speed of 980rpm for 19min; add 3.8g of phenyltriethoxysilane and react at 69℃ for 1.9h; then add 0.9g of vinyltriethoxysilane and continue to react at 69℃ for 2.9h; after the reaction, filter, wash the filter cake three times with 290g of anhydrous ethanol, and then dry at 118℃ for 2.9h to obtain hexagonal boron nitride modified with phenyl-vinylbissilane on the outside;

[0062] Step 3: Weigh 9g of the hydroxylated hexagonal boron nitride obtained in Step 1, 95g of anhydrous ethanol, 19g of deionized water and 0.9g of glacial acetic acid, and disperse them at a stirring speed of 980rpm for 19min; add 0.9g of vinyltriethoxysilane, and react at 69℃ for 2.9h; after the reaction, filter, wash the filter cake three times with 145g of anhydrous ethanol, and then dry at 118℃ for 2.9h to obtain the vinylsilane-modified hexagonal boron nitride in the transition zone;

[0063] Step 4: Weigh 1 kg of nickel-plated fine stranded copper conductor, continuously wipe the outer surface of the conductor with 280 g of anhydrous ethanol, dry it in 78℃ hot air for 28 min, and then place it in an environment of 25℃ and 49% relative humidity for 19 min before proceeding to the coating process.

[0064] Step 5: Weigh 660g of vinyl-terminated polydimethylsiloxane, 85g of vinyl-terminated methylphenyl polysiloxane, 125g of monovinyl-terminated polydimethylsiloxane, and 88g of hydrophobic fumed silica, and mix them at 34°C and 58 rpm for 19 min; then add 24g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 280mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min; after cooling to 25°C, add 480mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -89kPa vacuum for 10 min to obtain an inner methyl-enriched rubber compound;

[0065] Step 6: Weigh 440g of vinyl-terminated polydimethylsiloxane, 310g of vinyl-terminated methylphenyl polysiloxane, 108g of hydrophobic fumed silica, and 19g of vinylsilane-modified hexagonal boron nitride obtained in Step 3. Mix at 34°C and 58 rpm for 24 min. Then add 42g of methylhydrosiloxane-dimethylsiloxane copolymer and 560mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 530mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -89kPa vacuum for 10 min to obtain the transition compound.

[0066] Step 7: Weigh 190g of vinyl-terminated polydimethylsiloxane, 610g of vinyl-terminated methylphenyl polysiloxane, 88g of hydrophobic fumed silica, and 48g of the phenyl-vinylbissilane-modified hexagonal boron nitride obtained in Step 2. Mix them at 34°C and 58 rpm for 29 min. Then add 76g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 1150mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 680mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -89kPa vacuum for 10 min to obtain the phenyl-enriched rubber compound.

[0067] Step 8: Take 840g of the inner methyl-enriched rubber material obtained in Step 5, 840g of the transition rubber material obtained in Step 6, and 840g of the outer phenyl-enriched rubber material obtained in Step 7, and add them to the corresponding barrels of the three-layer co-extrusion equipment respectively; preheat the nickel-plated fine stranded copper conductor obtained in Step 4 to 68℃, control the die head temperature to 54℃, and the linear speed to 3.8m / min, so that the coating thickness of the inner methyl-enriched rubber material is 250μm, the coating thickness of the transition rubber material is 170μm, and the coating thickness of the outer phenyl-enriched rubber material is 250μm; after extrusion, first pass through the 79℃ hot air section for 2min; then pass through the 89℃ hot air section for 3.8min, the 128℃ hot air section for 5.8min, the 162℃ hot air section for 7.8min, and the 198℃ hot air section for 11.5min in sequence; then place the wire blank in a 218℃ oven for post-curing for 1.9h to obtain the high-temperature resistant ultra-flexible motor lead wire.

[0068] Example 5:

[0069] Step 1: Weigh 52g of hexagonal boron nitride, 440g of 10% hydrogen peroxide aqueous solution and 1040g of deionized water and add them to a corrosion-resistant reaction vessel. Heat the mixture to 87℃ with a stirring speed of 520rpm and keep it at that temperature for 6.5h. After the reaction is complete, filter the mixture and wash the filter cake five times with 1040g of deionized water. Control the pH of the filtrate from the fifth wash to be 6.9. Place the filter cake in an oven at 102℃ and dry it for 4.2h. Then, sieve it through a 200-mesh sieve to obtain hydroxylated hexagonal boron nitride.

[0070] Step 2: Weigh 32g of the hydroxylated hexagonal boron nitride obtained in Step 1, 275g of anhydrous ethanol, 42g of deionized water and 1.1g of glacial acetic acid, and disperse them at 1020rpm for 21min; add 4.2g of phenyltriethoxysilane and react at 71℃ for 2.1h; then add 1.1g of vinyltriethoxysilane and continue the reaction at 71℃ for 3.1h; after the reaction, filter, wash the filter cake three times with 315g of anhydrous ethanol, and then dry at 122℃ for 3.1h to obtain hexagonal boron nitride modified with phenyl-vinylbissilane on the outside;

[0071] Step 3: Weigh 11g of the hydroxylated hexagonal boron nitride obtained in Step 1, 105g of anhydrous ethanol, 21g of deionized water and 1.1g of glacial acetic acid, and disperse them at a stirring speed of 1020rpm for 21min; add 1.1g of vinyltriethoxysilane, and react at 71℃ for 3.1h; after the reaction, filter, wash the filter cake three times with 155g of anhydrous ethanol, and then dry at 122℃ for 3.1h to obtain the vinylsilane-modified hexagonal boron nitride in the transition zone;

[0072] Step 4: Weigh 1 kg of nickel-plated fine stranded copper conductor, continuously wipe the outer surface of the conductor with 320 g of anhydrous ethanol, dry it in 82℃ hot air for 32 min, and then place it in an environment of 25℃ and 51% relative humidity for 21 min before proceeding to the coating process.

[0073] Step 5: Weigh 640g of vinyl-terminated polydimethylsiloxane, 100g of vinyl-terminated methylphenyl polysiloxane, 115g of monovinyl-terminated polydimethylsiloxane, and 92g of hydrophobic fumed silica, and mix them at 36°C and 62rpm for 21min; then add 26g of methyl hydrogen siloxane-dimethylsiloxane copolymer and 330mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10min; after cooling to 25°C, add 520mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5min, and degas under -91kPa vacuum for 10min to obtain an inner methyl-enriched rubber compound;

[0074] Step 6: Weigh 420g of vinyl-terminated polydimethylsiloxane, 330g of vinyl-terminated methylphenyl polysiloxane, 112g of hydrophobic fumed silica, and 21g of vinylsilane-modified hexagonal boron nitride obtained in Step 3. Mix at 36°C and 62 rpm for 26 min. Then add 45g of methylhydrosiloxane-dimethylsiloxane copolymer and 640mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 570mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -91kPa vacuum for 10 min to obtain the transition compound.

[0075] Step 7: Weigh 170g of vinyl-terminated polydimethylsiloxane, 640g of vinyl-terminated methylphenyl polysiloxane, 92g of hydrophobic fumed silica, and 52g of the phenyl-vinylbissilane-modified hexagonal boron nitride obtained in Step 2. Mix them at 36°C and 62 rpm for 31 min. Then add 82g of methylhydrosiloxane-dimethylsiloxane copolymer and 1260mg of 1-ethynyl-1-cyclohexanol, and continue mixing for 10 min. After cooling to 25°C, add 730mg of platinum-divinyltetramethyldisiloxane complex, mix for another 5 min, and degas under -91kPa vacuum for 10 min to obtain the phenyl-enriched rubber compound.

[0076] Step 8: Take 860g of the inner methyl-enriched rubber material obtained in Step 5, 860g of the transition rubber material obtained in Step 6, and 860g of the outer phenyl-enriched rubber material obtained in Step 7, and add them to the corresponding barrels of the three-layer co-extrusion equipment respectively; preheat the nickel-plated fine stranded copper conductor obtained in Step 4 to 72℃, control the die head temperature to 56℃, and the linear speed to 4.2m / min, so that the coating thickness of the inner methyl-enriched rubber material is 270μm, the coating thickness of the transition rubber material is 190μm, and the coating thickness of the outer phenyl-enriched rubber material is 270μm; after extrusion, first pass through the 81℃ hot air section for 2.5min; then pass through the 91℃ hot air section for 4.2min, the 132℃ hot air section for 6.2min, the 168℃ hot air section for 8.2min, and the 202℃ hot air section for 12.5min in sequence; then place the wire blank in a 222℃ oven for post-curing for 2.1h to obtain the high-temperature resistant ultra-flexible motor lead wire.

[0077] Comparative Example 1:

[0078] The difference from Example 1 is that the amounts of vinyl-terminated polydimethylsiloxane and vinyl-terminated methylphenyl polysiloxane in steps 5, 6, and 7 are adjusted to be the same for all three layers, i.e., 420g of vinyl-terminated polydimethylsiloxane and 343g of vinyl-terminated methylphenyl polysiloxane are used in each step. Specifically, step 5 still includes 120g of monovinyl-terminated polydimethylsiloxane and 90g of hydrophobic fumed silica; step 6 still includes 110g of hydrophobic fumed silica and 20g of vinylsilane-modified hexagonal boron nitride in the transition zone obtained in step 3; and step 7 still includes 90g of hydrophobic fumed silica and 50g of phenyl-vinylbissilane-modified hexagonal boron nitride on the outer side obtained in step 2. All other conditions are the same as in Example 1.

[0079] Comparative Example 2:

[0080] The difference from Example 1 is that the addition positions of hexagonal boron nitride in steps 5, 6, and 7 are adjusted to be uniformly distributed. Specifically, in step 5, 23.3g of vinylsilane-modified hexagonal boron nitride is added to the transition zone obtained in step 3; in step 6, 23.3g of vinylsilane-modified hexagonal boron nitride is added to the transition zone obtained in step 3; and in step 7, 23.4g of phenyl-vinylbissilane-modified hexagonal boron nitride is added to the outer layer obtained in step 2. Simultaneously, the amount of hydrophobic fumed silica in step 5 is adjusted from 90g to 66.7g, in step 6 from 110g to 106.7g, and in step 7 from 90g to 116.6g, so that the total mass of hydrophobic fumed silica and modified hexagonal boron nitride in the three-layer adhesive is consistent with that in Example 1. All other conditions are the same as in Example 1.

[0081] Comparative Example 3:

[0082] The difference from Example 1 is that in step 7, 50g of the outer layer obtained in step 2, modified with phenyl-vinylbissilane, is replaced with 50g of the transition zone obtained in step 3, modified with vinylsilane, to replace it with hexagonal boron nitride. All other conditions are the same as in Example 1.

[0083] Comparative Example 4:

[0084] The difference from Example 1 is that in step 6, 20g of the transition zone obtained in step 3 is replaced with 20g of the outer layer obtained in step 2, which is modified with phenyl-vinylbissilane. All other conditions are the same as in Example 1.

[0085] Comparative Example 5:

[0086] The difference from Example 1 is that 120g of monovinyl-terminated polydimethylsiloxane is not added in step 5, and the amount of vinyl-terminated polydimethylsiloxane in step 5 is adjusted from 650g to 770g to maintain the total mass of polysiloxane added in the inner methyl-rich adhesive consistent with that in Example 1. All other conditions are the same as in Example 1.

[0087] Comparative Example 6:

[0088] The difference from Example 1 is that the amount of methylhydrosiloxane-dimethylsiloxane copolymer used in steps 5, 6, and 7 is adjusted to 48.7 g, and the amount of 1-ethynyl-1-cyclohexanol used is adjusted to 700 mg. The order of addition of the remaining raw materials, the amount of platinum-divinyltetramethyldisiloxane complex, the mixing conditions, and the degassing conditions in steps 5, 6, and 7 remain unchanged. All other conditions are the same as in Example 1.

[0089] Comparative Example 7:

[0090] The difference from Example 1 is that in step 8, after extrusion, instead of sequentially passing through a 90°C hot air section for 4 minutes, a 130°C hot air section for 6 minutes, a 165°C hot air section for 8 minutes, and a 200°C hot air section for 12 minutes, the wire rod is directly passed through a 200°C hot air section for 30 minutes; subsequently, the wire rod is still placed in a 220°C oven for vulcanization for 2 hours. The remaining conditions are the same as in Example 1.

[0091] Performance testing:

[0092] The samples used for performance testing were all derived from the high-temperature resistant ultra-flexible motor leads prepared in Examples 1-5 and Comparative Examples 1-7. For each example or comparative example, a 50m long motor lead was continuously prepared. After discarding the first and last 5m, test samples were taken from the middle 40m segment. For samples used in infrared spectroscopy, thermogravimetric analysis, thermal conductivity, Shore hardness, and tensile testing, the insulator was first cut along the conductor axis, and the nickel-plated fine stranded copper conductor was peeled off. Samples were then taken from the inner, middle, and outer positions. Samples used for finished product electrical performance and bending performance testing were directly cut from the finished motor lead. All samples were conditioned for 24 hours at 23°C and 50% relative humidity before testing. To ensure fair comparison, the examples and comparative examples used the same conductor specifications, the same raw material batch, the same three-layer co-extrusion equipment, the same traction equipment, the same post-vulcanization oven, and the same testing instruments.

[0093] Thermal conductivity test: The thermal conductivity was tested according to GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials - hot wire method". The outer phenyl-enriched rubber materials obtained in step 7 of Examples 1-5 and Comparative Examples 1-7 were used to prepare flat plate samples with a thickness of 2.0 mm, a length of 100 mm, and a width of 100 mm under the same hot air segmented vulcanization and post-vulcanization conditions as the corresponding examples or comparative examples. Before testing, the flat plate samples were conditioned for 24 hours at 23°C and 50% relative humidity. The test temperature was 25°C. Three flat plates were selected for each sample, and three locations were tested on each plate. The average of the nine test values ​​was taken as the thermal conductivity of the sample.

[0094] Mechanical properties after high-temperature hot air aging: The mechanical properties before and after hot air aging were tested according to GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods - Thickness and Dimensional Measurement - Mechanical Properties Test" and GB / T2951.12-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 12: General Test Methods - Thermal Aging Test Method". 5m of motor leads from Examples 1-5 and Comparative Examples 1-7 were taken, and the insulation was peeled off and strips were cut axially. The sample width was 4.0mm, the gauge length was 20mm, and the tensile speed was 250mm / min. The aging conditions were 220℃ hot air aging for 168h, followed by a 16h recovery period at 23℃ and 50% relative humidity before testing. Record the tensile strength before aging, tensile strength after aging, elongation at break before aging, and elongation at break after aging, and calculate the retention rate of tensile strength and elongation at break after aging. Five samples were tested for each sample, and the average value was taken.

[0095] Shore hardness change: The Shore A hardness was tested according to GB / T 39693.4-2025 "Determination of hardness of vulcanized rubber or thermoplastic rubber - Part 4: Determination of indentation hardness by Shore hardness tester (Shore hardness)". The inner methyl-rich rubber compounds obtained in step 5 of Examples 1-5 and Comparative Examples 1-7 were used, and 6.0 mm thick flat plate samples were prepared according to the vulcanization conditions of the corresponding examples or comparative examples; three plates were prepared for each sample. Before testing, the samples were conditioned in an environment of 23℃ and 50% relative humidity for 24 hours. The Shore A hardness was measured using a Shore A hardness tester, with five measuring points on each plate, the distance between the measuring points not less than 6 mm, and the hardness before aging was recorded. Subsequently, the same batch of plates were placed in hot air at 220℃ for 168 hours, and after a 16-hour recovery period, the hardness after aging was tested using the same method, and the difference between the hardness after aging and the hardness before aging was calculated.

[0096] Minimum bending radius: Based on the bending test concept in GB / T 5013.2-2008 "Rubber insulated cables with rated voltage of 450 / 750V and below - Part 2: Test methods", the minimum bending radius of the finished motor lead wire was tested. Five motor lead wires from Examples 1-5 and Comparative Examples 1-7 were used, each with a length of 500mm. After conditioning the samples in an environment of 23℃ and 50% relative humidity for 24 hours, they were successively wound around stainless steel cylindrical mandrels with radii of 15mm, 12mm, 10mm, 8mm, and 6mm, holding each radius for 60 seconds. After each bend, the insulation surface was observed under a 10x magnifying glass for cracks, whitening, bulging, or conductor exposure. The bent samples were then subjected to an AC withstand voltage pre-test according to GB / T 3048.8-2007. The minimum mandrel radius that showed no cracks, whitening, bulging, conductor exposure, and passed the AC withstand voltage pre-test was recorded as the minimum bending radius. Five samples were tested for each sample, and the median value was taken as the result.

[0097] The rate of change of conductor resistance after repeated bending: Based on the flexural test method in GB / T 5013.2-2008, and according to GB / T 3048.4-2025 "Test Methods for Electrical Properties of Wires and Cables Part 4: DC Resistance Test of Conductors", the DC resistance of the conductor before and after bending was determined. Three motor leads from Examples 1-5 and Comparative Examples 1-7 were used, each with a length of 1000 mm. Before testing, the samples were conditioned for 24 hours at 23℃ and 50% relative humidity. The DC resistance of each sample was measured at 20℃ as the resistance before bending. Then, the samples were installed on a reciprocating bending device with a bending radius of 10 mm, a bending angle of 90° to the left and right, a frequency of 30 times / min, and continuous bending for 5000 times. After bending, the DC resistance of the conductor at 20℃ was measured again, and the rate of change of conductor DC resistance was calculated. The average value of three samples was taken for each sample.

[0098] Insulation resistance: The insulation resistance was tested according to GB / T 3048.5-2007 "Test Methods for Electrical Properties of Wires and Cables - Part 5: Insulation Resistance Test". Three motor leads from Examples 1-5 and Comparative Examples 1-7 were used, each 5m long. 20mm of insulation was stripped from both ends, and the ends were ensured to be dry before connecting the conductors to the water bath electrodes. The samples were immersed in a 20℃ water bath for 2 hours before testing. The test voltage was 500V DC. After applying the voltage for 1 minute, the stable resistance value was read and converted to MΩ·km according to the sample length. Three leads were tested for each sample, and the average value was taken.

[0099] AC withstand voltage: The AC withstand voltage test was conducted according to GB / T 3048.8-2007 "Test Methods for Electrical Performance of Wires and Cables - Part 8: AC Voltage Test". Three motor leads from Examples 1-5 and Comparative Examples 1-7 were used, each 5m in length. Before the AC withstand voltage test, the samples were immersed in a 20℃ water bath for 2 hours. The conductor was connected to the high-voltage end, the water bath electrodes were grounded, and a 3000V power frequency AC voltage was applied and maintained for 5 minutes. The results of breakdown, flashover, or no breakdown were recorded.

[0100] Table 1 Performance Test Results

[0101] sample Thermal conductivity / W / (m·K) Tensile strength / MPa Elongation at break / % Tensile strength retention rate after aging / % Elongation at break retention rate after aging / % Shore A hardness change after aging / HA Minimum bending radius / mm Change rate of conductor DC resistance after 5000 bends / % Insulation resistance / MΩ·km AC withstand voltage result / 3000V × 5min Example 1 0.364 9.4 472.6 90.4 83.6 3.2 8 0.22 12382 pass Example 2 0.336 8.7 515.4 86.2 78.4 4.1 6 0.25 10722 pass Example 3 0.391 10.1 421.7 93.2 86.4 2.5 10 0.36 15465 pass Example 4 0.351 8.9 498.8 87.8 80.2 3.7 6 0.27 11384 pass Example 5 0.377 9.8 445.2 92.0 85.1 2.8 8 0.30 14021 pass Comparative Example 1 0.326 8.4 397.6 81.5 70.6 6.9 12 0.86 9862 pass Comparative Example 2 0.278 8.2 382.4 84.3 72.9 6.2 12 1.08 8428 pass Comparative Example 3 0.303 7.9 401.3 80.1 69.4 3.3 10 0.64 8764 pass Comparative Example 4 0.363 8.6 428.9 86.1 77.3 3.1 10 0.56 10156 pass Comparative Example 5 0.365 9.0 336.7 88.5 66.8 8.7 15 1.40 11285 pass Comparative Example 6 0.348 8.2 351.9 78.4 64.5 9.4 15 1.55 7344 pass Comparative Example 7 0.333 7.5 360.2 75.2 61.7 10.2 15 1.78 6021 pass

[0102] As shown in Table 1, the motor leads obtained in Examples 1-5 achieved a good overall balance between thermal conductivity, heat aging resistance, flexibility, and insulation performance. In Comparative Example 1, after adjusting the methyl / phenyl polysiloxane ratio in the three-layer compound to be the same, although the modified hexagonal boron nitride on the outer side and the monovinyl segment on the inner side were still retained, the structure of the phenyl side groups increasing from the inside to the outside was weakened, the thermal conductivity decreased to 0.326 W / (m·K), and the retention rates of tensile strength and elongation at break after aging decreased to 81.5% and 70.6%, respectively. The minimum bending radius increased to 12 mm, indicating that simply using a uniform phenyl content is insufficient to simultaneously achieve both external heat resistance and internal flexibility.

[0103] In Comparative Example 2, after hexagonal boron nitride was evenly distributed in the three-layer compound, the thermally conductive filler and the lamellae barrier effect on the outer side were insufficient. At the same time, the introduction of lamellae filler into the inner compound increased the bending stress, and its thermal conductivity was only 0.278 W / (m·K). After 5000 bends, the change rate of DC resistance of the conductor increased to 1.08%, indicating that the more uniform the addition of hexagonal boron nitride, the more beneficial it is.

[0104] In Comparative Example 3, after replacing the outer phenyl-vinylbissilane modified hexagonal boron nitride with vinylsilane modified hexagonal boron nitride, the thermal conductivity, tensile strength, and insulation resistance were all lower than those in Example 1. This indicates that using bissilane modified fillers that are compatible with the phenyl chain segments in the outer phenyl-rich adhesive is beneficial for reducing outer interface defects and improving thermal conductivity continuity.

[0105] The thermal conductivity of Comparative Example 4 is close to that of Example 1, but its elongation at break retention rate, resistance change rate after bending, and insulation resistance are all lower than those of Example 1, indicating that the modification method of the filler in the transition zone has an important impact on the stress transfer and interface continuity between the three layers.

[0106] In Comparative Example 5, after removing the inner monovinyl end-capped polydimethylsiloxane, the tensile strength could still be maintained at 9.0 MPa, but the elongation at break decreased to 336.7%, the minimum bending radius increased to 15 mm, and the change rate of DC resistance of the conductor increased to 1.40% after 5000 bends. This indicates that the inner single-end access segment has a significant effect on maintaining ultra-flexibility and reducing bending damage.

[0107] After the gradient combination of crosslinking agent / inhibitor and the segmented temperature rise vulcanization procedure were cancelled in Comparative Examples 6 and 7, respectively, the elongation retention rate after aging decreased to 64.5% and 61.7%, respectively, and the insulation resistance decreased to 7344 MΩ·km and 6021 MΩ·km, respectively. This indicates that the crosslinking sequence and vulcanization procedure have an important impact on reducing interlayer stress concentration and insulation defects.

[0108] Compared with the comparative examples above, Examples 1-5, through the combination of inner methyl-enriched adhesive, transition adhesive, and outer phenyl-enriched adhesive, maintain the flexibility of the inner side, with the transition zone serving as a connector and buffer, and the outer side serving as a heat-resistant, thermally conductive, and barrier. Among them, the DC resistance change rate of the conductor after 5000 bends in Example 1 was only 0.22%, the thermal conductivity and insulation resistance of Example 3 reached 0.391 W / (m·K) and 15465 MΩ·km, respectively, and the elongation at break after aging in Example 5 reached 85.1%. This shows that the present invention is not simply achieved by increasing the phenyl content, adding hexagonal boron nitride alone, or simply increasing the crosslinking density, but by the synergistic combination of phenyl gradient, filler partition modification, and crosslinking time gradient, to achieve a comprehensive improvement in high temperature resistance, ultra-flexibility, and stable electrical properties.

[0109] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A process for processing high temperature resistant super flexible motor lead, characterized in that, Includes the following steps: (1) First, hydroxylated hexagonal boron nitride is prepared, and then vinylsilane-modified hexagonal boron nitride and phenyl-vinylbissilane-modified hexagonal boron nitride are prepared respectively; (2) The nickel-plated fine stranded copper conductor is cleaned and dried to obtain a pretreated conductor; (3) Prepare inner methyl-enriched rubber compound, transition rubber compound and outer phenyl-enriched rubber compound respectively; (4) The inner methyl enriched rubber, the transition rubber and the outer phenyl enriched rubber are sequentially coated on the outer surface of the pretreated conductor by three-layer co-extrusion to form a wire blank containing an inner methyl enriched layer, a transition layer and an outer phenyl enriched layer. (5) The wire blank is subjected to multi-stage heating vulcanization and post-vulcanization treatment to obtain high-temperature resistant ultra-flexible motor lead wire; The inner methyl-enriched adhesive is prepared from the following raw materials in parts by weight: 630-670 parts vinyl-terminated polydimethylsiloxane, 75-105 parts vinyl-terminated methylphenyl polysiloxane, 110-130 parts monovinyl-terminated polydimethylsiloxane, 85-95 parts hydrophobic fumed silica, 23-27 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 0.25-0.35 parts 1-ethynyl-1-cyclohexanol and 0.45-0.55 parts platinum-divinyltetramethyldisiloxane complex; The transition compound is prepared from the following raw materials in parts by weight: 410-450 parts vinyl-terminated polydimethylsiloxane, 300-340 parts vinyl-terminated methylphenyl polysiloxane, 105-115 parts hydrophobic fumed silica, 18-22 parts vinylsilane-modified hexagonal boron nitride, 40-46 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 0.52-0.68 parts 1-ethynyl-1-cyclohexanol and 0.50-0.60 parts platinum-divinyltetramethyldisiloxane complex; The outer phenyl-enriched adhesive, by weight parts, is prepared from the following raw materials: 160-200 parts vinyl-terminated polydimethylsiloxane, 590-650 parts vinyl-terminated methylphenyl polysiloxane, 85-95 parts hydrophobic fumed silica, 45-55 parts phenyl-vinylbissilane modified hexagonal boron nitride, 72-84 parts methyl hydrogen siloxane-dimethylsiloxane copolymer, 1.08-1.32 parts 1-ethynyl-1-cyclohexanol and 0.65-0.75 parts platinum-divinyltetramethyldisiloxane complex.

2. The process for processing high temperature resistant super flexible motor lead according to claim 1, wherein, The vinylsilane-modified hexagonal boron nitride is obtained by reacting hydroxylated hexagonal boron nitride with vinyltriethoxysilane; the phenyl-vinylbissilane-modified hexagonal boron nitride is obtained by reacting hydroxylated hexagonal boron nitride first with phenyltriethoxysilane, and then with vinyltriethoxysilane.

3. The process for processing high temperature resistant super flexible motor lead according to claim 1, wherein, The hydroxylated hexagonal boron nitride is obtained by treating hexagonal boron nitride with a 10% (w / w) aqueous solution of hydrogen peroxide; the mass ratio of the hexagonal boron nitride, the 10% (w / w) aqueous solution of hydrogen peroxide, and deionized water is 45-55:380-460:900-1100.

4. The process for processing high temperature resistant super flexible motor lead according to claim 2, wherein, The mass ratio of hydroxylated hexagonal boron nitride to vinyltriethoxysilane in the raw materials for preparing vinylsilane-modified hexagonal boron nitride is 8-12:0.8-1.2; the mass ratio of hydroxylated hexagonal boron nitride, phenyltriethoxysilane, and vinyltriethoxysilane in the raw materials for preparing phenyl-vinylbissilane-modified hexagonal boron nitride is 28-34:3.4-4.5:0.8-1.

2.

5. The process for processing high temperature resistant super flexible motor lead according to claim 1, wherein, The thickness of the inner methyl enrichment layer is 240-280 μm, the thickness of the transition layer is 160-200 μm, and the thickness of the outer phenyl enrichment layer is 240-280 μm.

6. The process for processing high temperature resistant super flexible motor lead according to claim 1, wherein, The vinyl-terminated polydimethylsiloxane has a viscosity of 5150 cSt at 25°C and a vinyl content of 0.12%; the vinyl-terminated methylphenyl polysiloxane has a viscosity of 5000 cSt at 25°C and a vinyl content of 0.5%; the monovinyl-terminated polydimethylsiloxane has a viscosity of 1000 cSt at 25°C and a vinyl content of 0.21%; and the silane-hydrogen bond content of the methylhydrosiloxane-dimethylsiloxane copolymer is 1.8 mmol / g.

7. The processing technology of the high-temperature resistant ultra-flexible motor lead wire according to claim 1, characterized in that, The hydrophobic fumed silica has a BET specific surface area of 110 m 2 / g; the average particle size of the hexagonal boron nitride used to produce the hydroxylated hexagonal boron nitride is 1 μm.

8. The processing technology of the high-temperature resistant ultra-flexible motor lead wire according to claim 1, characterized in that, The multi-stage heating vulcanization process consists of: passing through a 78-82℃ hot air section for 2-2.5 minutes; then sequentially passing through an 88-92℃ hot air section for 3.5-4.5 minutes, a 125-135℃ hot air section for 5.5-6.5 minutes, a 160-170℃ hot air section for 7.5-8.5 minutes, and a 195-205℃ hot air section for 11-13 minutes.

9. The processing technology for the high-temperature resistant ultra-flexible motor lead wire according to claim 1, characterized in that, The post-vulcanization process involves placing the container in an oven at 215-225℃ for 1.8-2.2 hours for post-vulcanization.