Flame-retardant wear-resistant bus cable and preparation method thereof

Abstract

The application discloses a kind of flame-retardant wear-resistant bus cable and its preparation method, it is related to the technical field of cable, preparation method includes: providing conductor core coated with insulating layer;The surface of aramid fiber is activated and treated, the aramid fiber after activation is immersed in flame-retardant dispersion liquid and is impregnated, then the aramid fiber after impregnation is heat treated, to obtain composite aramid fiber, composite aramid fiber is woven on the insulating layer to form composite fiber filling layer;Flame-retardant wear-resistant protective layer precursor is coated on the surface of composite fiber filling layer after melting to form flame-retardant wear-resistant protective layer.In the application, by sequentially setting insulating layer, composite fiber filling layer and flame-retardant wear-resistant protective layer on the conductor core, the insulation of cable is guaranteed and the flame-retardant wear resistance of cable is improved.

Description

Technical Field

[0001] This application relates to the technical field of cables, specifically to a flame-retardant and wear-resistant bus cable and its preparation method. Background Technology

[0002] Currently, higher demands are being placed on the safety, durability, and environmental adaptability of cables, a critical component in power transmission systems. Cables must not only possess excellent electrical insulation and mechanical strength, but also outstanding flame retardancy and abrasion resistance. However, existing cables still suffer from insufficient flame retardancy in practical applications, making it difficult to meet increasingly stringent fire safety requirements. Summary of the Invention

[0003] The first aspect of this application provides a method for preparing a flame-retardant and wear-resistant bus cable, the method comprising: Provide conductor cores covered with an insulating layer; The surface of aramid fiber is activated, and the activated aramid fiber is immersed in a flame retardant dispersion for impregnation. Then, the impregnated aramid fiber is heat-treated to obtain composite aramid fiber. The composite aramid fiber is woven on the insulation layer to form a composite fiber filling layer. The flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer.

[0004] In some optional embodiments of the first aspect of this application, the activation treatment of the aramid fiber surface includes: Aramid fibers were sequentially subjected to ultrasonic cleaning, alkali treatment, and acid treatment to obtain treated aramid fibers. The treated aramid fibers were washed with water until neutral, and then vacuum dried at 55℃~65℃ for 10h~14h to obtain activated aramid fibers. And / or, ultrasonic cleaning includes: ultrasonically cleaning the aramid fibers sequentially with acetone, anhydrous ethanol and deionized water for 10 min to 20 min each; And / or, alkaline treatment includes: placing the ultrasonically cleaned aramid fibers in a 0.2 mol / L to 0.5 mol / L sodium hydroxide solution and treating them at a temperature of 50°C to 65°C for 20 min to 40 min; And / or, acid treatment includes: soaking the alkali-treated aramid fibers in 0.05mol / L~0.1mol / L dilute hydrochloric acid for 5min~10min.

[0005] In some optional embodiments of the first aspect of this application, the impregnated aramid fibers are then subjected to heat treatment, including: The impregnated aramid fibers were dried at 55℃~65℃ for 1.5h~2.5h, and then heat-treated at 120℃~140℃ in an inert gas atmosphere for 50min~80min. And / or, the impregnation treatment includes: immersing activated aramid fibers in a flame-retardant dispersion at room temperature for 1.0 h to 2.0 h.

[0006] In some optional embodiments of the first aspect of this application, the flame-retardant and wear-resistant protective layer precursor includes: a matrix resin, an elastomer toughening agent, modified graphene oxide, modified nano-magnesium hydroxide, an anti-dripping agent, a compatibilizer, and an antioxidant. Based on the total mass of the flame-retardant and wear-resistant protective layer precursor, the mass fraction of the matrix resin is 50%~62%, the mass fraction of the elastomer toughening agent is 3%~8%, the mass fraction of the modified graphene oxide is 1%~2%, the mass fraction of the modified nano magnesium hydroxide is 25%~32%, the mass fraction of the anti-dripping agent is 0.8%~2.0%, the mass fraction of the compatibilizer is 2%~4%, and the mass fraction of the antioxidant is 0.3%~0.8%.

[0007] In some optional embodiments of the first aspect of this application, the flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer, comprising: The flame-retardant and wear-resistant protective layer precursor is mixed for 10-20 minutes, melted and granulated at 155-175℃ to obtain granules; The granules are continuously extruded and coated onto the composite fiber filling layer under controlled traction tension to form a flame-retardant and wear-resistant protective layer; wherein the thickness of the flame-retardant and wear-resistant protective layer is 0.6mm~1.2mm.

[0008] In some optional embodiments of the first aspect of this application, the preparation method further includes preparing a flame-retardant dispersion, wherein preparing the flame-retardant dispersion includes: Anhydrous ethanol and deionized water are mixed to obtain a first mixture, and the pH value of the first mixture is adjusted to 4.0~4.5; wherein the volume ratio of anhydrous ethanol to deionized water is (1.5~4.0):1. Add the silane coupling agent mixture to the first mixture to obtain the second mixture, and stir the second mixture at 50℃~65℃ for 45min~75min; Modified nano-magnesium hydroxide was added to the second mixture to obtain the third mixture, and the third mixture was ultrasonically dispersed for 20 min to 40 min. Add 1.5 mg / mL to 2.5 mg / mL of modified graphene oxide aqueous dispersion to the third mixture while stirring, and then sonicate for 30 min to 50 min to obtain a flame retardant dispersion.

[0009] In some optional embodiments of the first aspect of this application, the mass of the modified nano-magnesium hydroxide is 20% to 60% of the mass of the modified graphene oxide; And / or, the mass of the silane coupling agent mixture is 4% to 15% of the total mass of the modified graphene oxide and the modified nano magnesium hydroxide; And / or, the silane coupling agent mixture includes γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, wherein the mass ratio of γ-aminopropyltriethoxysilane to γ-glycidoxypropyltrimethoxysilane is (1~5):1.

[0010] In some optional embodiments of the first aspect of this application, the modified nano-magnesium hydroxide is obtained by modifying nano-magnesium hydroxide with a silane coupling agent, and the D50 of the nano-magnesium hydroxide is 50nm~100nm.

[0011] In some optional embodiments of the first aspect of this application, the modified graphene oxide surface is grafted with amino and / or phosphorus-containing functional groups, and the total content of nitrogen and / or phosphorus in the modified graphene oxide is not less than 2 wt%.

[0012] The second aspect of this application provides a flame-retardant and wear-resistant bus cable, which is prepared by the above-described method for preparing flame-retardant and wear-resistant bus cables.

[0013] Beneficial effects:

[0014] The method for preparing a flame-retardant and wear-resistant busbar cable provided in the first aspect of this application involves covering the conductor core with an insulation layer, weaving composite aramid fibers on the insulation layer to form a composite fiber filling layer, and covering the composite fiber filling layer with a flame-retardant and wear-resistant protective layer precursor to form a flame-retardant and wear-resistant protective layer. By sequentially setting the insulation layer, the composite fiber filling layer, and the flame-retardant and wear-resistant protective layer on the conductor core, the insulation of the cable is ensured and the flame-retardant and wear-resistant properties of the cable are improved.

[0015] The flame-retardant and wear-resistant bus cable provided in the second aspect of this application has excellent flame-retardant properties, produces little smoke during combustion, and self-extinguishes rapidly, effectively suppressing the spread of flames. It also possesses outstanding fire resistance, maintaining line integrity even under prolonged exposure to high-temperature flames. Furthermore, while maintaining high flame retardancy, the cable also exhibits good mechanical properties, demonstrating an excellent balance between strength and flexibility, making it suitable for power transmission scenarios with stringent requirements for safety, reliability, and environmental adaptability. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation process of a flame-retardant and wear-resistant bus cable in one embodiment of this application; Figure 2 This is a flowchart illustrating the preparation of composite aramid fibers in one embodiment of this application. Detailed Implementation

[0017] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the present application.

[0018] The first aspect of this application provides a method for preparing a flame-retardant and wear-resistant bus cable, the method comprising: Provide conductor cores covered with an insulating layer; The surface of aramid fiber is activated, and the activated aramid fiber is immersed in a flame retardant dispersion for impregnation. Then, the impregnated aramid fiber is heat-treated to obtain composite aramid fiber. The composite aramid fiber is woven on the insulation layer to form a composite fiber filling layer. The flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer.

[0019] In the above scheme, the conductor core is made of annealed soft copper or aluminum, and is tightly wrapped with fire-resistant mica tape using an overlapping wrapping method to form an insulation layer. Composite aramid fibers are then woven onto the insulation layer to form a composite fiber filling layer. Finally, a flame-retardant and wear-resistant protective layer precursor is wrapped onto the composite fiber filling layer to form the flame-retardant and wear-resistant protective layer. Specifically, the aramid fibers are first activated to improve their surface energy and reactivity. Then, the activated aramid fibers are immersed in a flame-retardant dispersion and heat-treated to load a flame-retardant coating onto the surface of the aramid fibers, improving the overall flame-retardant properties of the cable. By sequentially setting the insulation layer, composite fiber filling layer, and flame-retardant and wear-resistant protective layer on the conductor core, the cable's insulation performance and flame-retardant and wear-resistant properties are ensured.

[0020] In some optional embodiments of this application, the activation treatment of the aramid fiber surface includes: Aramid fibers were sequentially subjected to ultrasonic cleaning, alkali treatment, and acid treatment to obtain treated aramid fibers. The treated aramid fibers were washed with water until neutral, and then vacuum dried at 55℃~65℃ for 10h~14h to obtain activated aramid fibers.

[0021] In some optional embodiments of this application, ultrasonic cleaning includes: ultrasonically cleaning the aramid fibers sequentially with acetone, anhydrous ethanol, and deionized water for 10 to 20 minutes each. This setup removes oil and impurities from the surface of the aramid fibers through ultrasonic cleaning, improving the adhesion of the subsequent flame-retardant coating.

[0022] In some optional embodiments of this application, the alkaline treatment includes: placing the ultrasonically cleaned aramid fibers in a 0.2 mol / L to 0.5 mol / L sodium hydroxide solution and treating them at a temperature of 50°C to 65°C for 20 to 40 minutes. This setup uses NaOH to slightly etch the aramid fibers to introduce polar groups such as -COOH / -OH, significantly improving the fiber surface energy and reactivity.

[0023] In some optional embodiments of this application, the acid treatment includes immersing the alkali-treated aramid fibers in 0.05 mol / L to 0.1 mol / L dilute hydrochloric acid for 5 to 10 minutes. This setting ensures acid neutralization and prevents residual alkali from damaging the subsequent flame-retardant dispersion system.

[0024] In some optional embodiments of this application, the preparation method further includes preparing a flame-retardant dispersion, wherein preparing the flame-retardant dispersion includes: Anhydrous ethanol and deionized water are mixed to obtain a first mixture, and the pH value of the first mixture is adjusted to 4.0~4.5; wherein the volume ratio of anhydrous ethanol to deionized water is (1.5~4.0):1. Add the silane coupling agent mixture to the first mixture to obtain the second mixture, and stir the second mixture at 50℃~65℃ for 45min~75min; Modified nano-magnesium hydroxide was added to the second mixture to obtain the third mixture, and the third mixture was ultrasonically dispersed for 20 min to 40 min. Add 1.5 mg / mL to 2.5 mg / mL of modified graphene oxide aqueous dispersion to the third mixture while stirring, and then sonicate for 30 min to 50 min to obtain a flame retardant dispersion.

[0025] In some optional embodiments of this application, the modified graphene oxide surface is grafted with amino and / or phosphorus-containing functional groups, and the total content of nitrogen and / or phosphorus in the modified graphene oxide is not less than 2 wt%. In this embodiment, the modified graphene oxide surface is grafted with amino and / or phosphorus-containing functional groups, which can be prepared by the following method: First, the graphene oxide is dispersed in a polar solvent (such as N,N-dimethylformamide or water) and ultrasonically treated to fully exfoliate it; then, a modifier containing amino and / or phosphorus-containing functional groups (such as 3-aminopropyltriethoxysilane, aminopropylphosphonic acid, or diethylphosphoethylamine, etc.) is added, and the mixture is heated to 60℃~120℃ under an inert atmosphere and stirred for 6h~24h, so that the modifier is grafted onto the carboxyl, hydroxyl, or epoxy groups on the surface of the graphene oxide through condensation, nucleophilic substitution, or esterification reactions; after the reaction, the product is centrifuged, washed, and vacuum dried to obtain modified graphene oxide with amino and / or phosphorus-containing functional groups grafted on its surface; by controlling the amount of modifier and reaction conditions, the total content of nitrogen and / or phosphorus in the obtained material can be ensured to be not less than 2wt%.

[0026] In some optional embodiments of this application, the silane coupling agent mixture includes γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560).

[0027] In some optional embodiments of this application, the modified nano-magnesium hydroxide is obtained by modifying nano-magnesium hydroxide with a silane coupling agent, and the D50 of the nano-magnesium hydroxide is 50nm~100nm.

[0028] In this embodiment, the modified nano-magnesium hydroxide can be prepared by the following method: nano-magnesium hydroxide, silane coupling agent and ethanol are mixed to obtain a mixture. The mixture is stirred at 50℃~65℃ for 25min~35min to allow the KH550 silane coupling agent to be fully hydrolyzed and undergo a condensation reaction with the hydroxyl groups on the surface of the nano-magnesium hydroxide. The reaction system is then cooled to room temperature, and the solid product is collected by centrifugation or filtration. The solid product is washed several times with anhydrous ethanol and deionized water alternately to remove unreacted coupling agent and byproducts. Finally, the obtained solid is vacuum dried at 60℃~80℃ for 6h~12h to obtain the modified nano-magnesium hydroxide.

[0029] In the above scheme, an organic-inorganic interpenetrating network with both flexibility and thermal stability is constructed through the co-hydrolysis of KH550 and KH560 silanes in an ethanol / water system. Specifically, the amino groups of KH550 chemically bond with the carboxyl groups on the surface of modified graphene oxide (GO), effectively functionalizing GO; while the epoxy groups of KH560 can crosslink with the hydroxyl groups on the surface of aramid fibers or the active groups in the subsequent curing system, enhancing the interfacial adhesion between the coating and the substrate. After KH550 silanization treatment, nano-magnesium hydroxide significantly improves its dispersion stability in organic media, effectively inhibiting agglomeration and ensuring uniform distribution of the flame retardant in the coating. Upon heating, nano-magnesium hydroxide decomposes endothermically and releases water vapor, diluting flammable gases and achieving highly efficient halogen-free flame retardancy. Simultaneously, the GO surface is grafted with amino and phosphorus-containing groups (N / P ≥ 2wt%), endowing it with intrinsic flame retardant properties. Its two-dimensional layered structure can also form a "maze effect," effectively delaying the transfer of heat and flammable volatiles. GO and Mg(OH)2 work synergistically to construct a highly efficient intumescent flame retardant system of "GO forming a char skeleton + Mg(OH)2 cooling and diluting", which improves flame retardant efficiency while taking into account mechanical properties.

[0030] In some optional embodiments of this application, the mass of the modified nano-magnesium hydroxide is 20% to 60% of the mass of the modified graphene oxide.

[0031] In some optional embodiments of this application, the mass of the silane coupling agent mixture is 4% to 15% of the total mass of the modified graphene oxide and the modified nano magnesium hydroxide.

[0032] By precisely controlling the mass ratio of modified nano-magnesium hydroxide to modified graphene oxide to be (0.2~0.6):1 and the silane coupling agent mixture to be 4%~15% of the total mass of modified graphene oxide and modified nano-magnesium hydroxide, excellent flame retardant performance is ensured while taking into account the mechanical properties of the coating, avoiding embrittlement caused by excessive coupling agent.

[0033] In some optional embodiments of this application, the mass ratio between γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane is (1~5):1.

[0034] γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) are compounded at a mass ratio of (1~5):1 to synergistically construct an organic / inorganic hybrid network with both reactivity and flexibility: the amino groups of KH550 efficiently bond to the carboxyl groups of graphene oxide, improving filler dispersibility and interfacial bonding; the epoxy groups of KH560 crosslink with the aramid hydroxyl groups or amino groups in the system, enhancing coating adhesion and toughness. This ratio ensures sufficient coupling while avoiding excessive crosslinking and embrittlement, optimizes the distribution of flame-retardant components, and provides a structural basis for the GO / Mg(OH)2 synergistic flame-retardant system. In some optional embodiments of this application, the impregnated aramid fibers are then heat-treated, including: The impregnated aramid fibers were dried at 55℃~65℃ for 1.5h~2.5h, and then heat-treated at 120℃~140℃ in an inert gas atmosphere for 50min~80min.

[0035] In some optional embodiments of this application, the impregnation treatment includes immersing activated aramid fibers in a flame-retardant dispersion at room temperature for 1.0 h to 2.0 h. In this embodiment, room temperature refers to (23±2) °C.

[0036] In the above scheme, the activated aramid is allowed to fully absorb the flame-retardant dispersion and penetrate into the fiber gaps by static impregnation. Then, a gradient curing strategy is adopted: first, it is dried at a low temperature of 55℃~65℃ for 1.5h~2.5h to steadily remove the solvent and avoid boiling. Then, it is heat-treated in an inert gas atmosphere such as nitrogen at 120℃~140℃ for 50min~80min to promote silane condensation crosslinking and form a strong and flexible GO / Mg(OH)2@silane composite coating. The nitrogen protection throughout the process effectively prevents the aramid from oxidizing and degrading at high temperature, thereby maintaining its mechanical strength.

[0037] In some optional embodiments of this application, the flame-retardant and wear-resistant protective layer precursor includes: a matrix resin, an elastomer toughening agent, modified graphene oxide, modified nano magnesium hydroxide, an anti-dripping agent, a compatibilizer, and an antioxidant. Based on the total mass of the flame-retardant and wear-resistant protective layer precursor, the mass fraction of the matrix resin is 50%~62%, the mass fraction of the elastomer toughening agent is 3%~8%, the mass fraction of the modified graphene oxide is 1%~2%, the mass fraction of the modified nano magnesium hydroxide is 25%~32%, the mass fraction of the anti-dripping agent is 0.8%~2.0%, the mass fraction of the compatibilizer is 2%~4%, and the mass fraction of the antioxidant is 0.3%~0.8%.

[0038] In this embodiment, the modified graphene oxide and modified nano magnesium hydroxide used in the flame-retardant and wear-resistant protective layer precursor are the same as those used in the preparation of the flame-retardant dispersion.

[0039] In the above scheme, the matrix resin includes ethylene-vinyl acetate copolymer and / or thermoplastic polyurethane, and the flame-retardant and wear-resistant protective layer precursor uses ethylene-vinyl acetate copolymer and / or thermoplastic polyurethane as the composite matrix. 25%–32% modified nano-magnesium hydroxide is used as the main flame retardant, while 1%–2% modified graphene oxide is introduced to synergistically promote the formation of a dense, high-strength char layer, significantly improving thermal insulation performance and char stability. To address the embrittlement problem caused by high filler content, 3%–8% elastomer toughening agent is added to effectively improve toughness, and 2%–4% compatibilizer strengthens the interfacial bonding between the inorganic filler and the polymer matrix, thus achieving excellent tensile and tear strength. Furthermore, 0.8%–2.0% anti-dripping agent PTFE micropowder not only reduces the surface friction coefficient and enhances wear resistance but also effectively inhibits dripping during combustion, preventing flame spread.

[0040] In some optional embodiments of this application, the flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer, including: The flame-retardant and wear-resistant protective layer precursor is mixed for 10-20 minutes, melted and granulated at 155-175℃ to obtain granules; The granules are continuously extruded and coated onto the composite fiber filling layer under controlled traction tension to form a flame-retardant and wear-resistant protective layer; wherein the thickness of the flame-retardant and wear-resistant protective layer is 0.6mm~1.2mm.

[0041] The second aspect of this application provides a flame-retardant and wear-resistant bus cable, which is prepared by the above-described method for preparing a flame-retardant and wear-resistant bus cable.

[0042] The present application is further illustrated below with reference to embodiments and comparative examples. Unless otherwise specified, the raw materials, reagents, materials and equipment used in this application are all commercially available products conventionally used in the art.

[0043]

Example 1

[0044] S2. Preparation of composite fiber filling layer (1) Take meta-aramid filaments (PMIA) with a linear density of 1.5D and clean them sequentially in acetone, anhydrous ethanol and deionized water at 40kHz for 15min. Then immerse them in 0.3mol / L NaOH aqueous solution and treat them in a constant temperature water bath at 60℃ for 30min. After taking them out, quickly transfer them to 0.1mol / L dilute hydrochloric acid for 8min to neutralize and slightly etch them. Then rinse them repeatedly with deionized water until neutral (pH=7) and dry them in a vacuum drying oven at 60℃ for 12h to obtain activated aramid fibers.

[0045] (2) Preparation of flame retardant dispersion: Anhydrous ethanol and deionized water were mixed at a volume ratio of 2.5:1 to obtain a first mixture. The pH of the first mixture was adjusted to 4.2 with glacial acetic acid. A mixture of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) (KH550 to KH560 mass ratio of 3:1) was added to the first mixture to obtain a second mixture. The total mass of KH550 and KH560 was 9% of the mass of the modified graphene oxide used subsequently. The mixture was stirred and hydrolyzed at 60°C for 60 min. Modified nano-hydrogen ions were then taken. Magnesium hydroxide (surface modified with KH550) was used. The mass of the modified nano-magnesium hydroxide was 40% of the mass of the modified graphene oxide. The modified magnesium hydroxide was added to the second mixture to obtain the third mixture. The third mixture was ultrasonically dispersed for 30 min. A modified graphene oxide aqueous dispersion with a concentration of 2.0 mg / mL (graphene oxide was co-modified with KH550 and phosphate ester, and the total content of N and P elements was 2.3 wt%) was slowly added dropwise to the third mixture while mechanically stirring. After the addition was completed, ultrasonication was continued for 40 min to obtain a uniform and stable flame-retardant dispersion.

[0046] (3) The activated aramid fiber was completely immersed in the flame retardant dispersion and left to stand at room temperature (25°C) for 1.5 hours. After being taken out, it was dried in a 60°C oven for 2.0 hours and then transferred to a nitrogen-protected tube furnace for heat treatment at 130°C for 60 minutes to allow the silane to fully crosslink and solidify, thereby obtaining a composite aramid fiber with a surface-loaded graphene oxide / magnesium hydroxide@silane flame retardant coating.

[0047] (4) After the composite aramid fibers are bundled together, they are twisted on a twisting machine with a constant tension of 1.2cN / dtex to produce a composite yarn with a linear density of 600D and a twist of 60 twists / meter.

[0048] (5) On the outside of the insulation layer obtained in S1, a 24-spindle high-speed braiding machine is used to cover it with a braiding angle of 45° and a single-layer high-density braiding method, and the coverage rate is controlled to be ≥88%. After the braiding is completed, it is heat-set at 130°C for 10 minutes to form a dense, continuous and well-adhered composite fiber filling layer.

[0049] S3. Preparation of Flame-Retardant and Wear-Resistant Protective Layer The flame-retardant and wear-resistant protective layer precursor is composed of the following components by mass percentage: 58% matrix resin ethylene-vinyl acetate copolymer, 5% POE elastomer toughening agent, 1.5% modified graphene oxide, 30% modified nano magnesium hydroxide, 1.2% anti-dripping agent polytetrafluoroethylene (PTFE) micro powder, 3% maleic anhydride-grafted EVA compatibilizer, and 0.5% antioxidant AN1010 / AN168 compound (1:1). The flame-retardant and wear-resistant protective layer precursor is mixed in a high-speed mixer for 15 minutes and then melt-granulated at 165℃ using a twin-screw extruder (maximum temperature zone ≤180℃). The granules are continuously extruded and coated onto the braided layer through a concentric extruder head under traction speed control to form a sheath layer with a thickness of 0.9mm. After extrusion, the material is cooled in a 25℃ water bath, dried with compressed air, and wound into a coil.

[0050] S4. Sheath Surface Pretreatment After cooling, the cable is subjected to brush dust removal and corona treatment in sequence, and the corona power is adjusted to stabilize the surface tension of the sheath at 44mN / m.

[0051] S5. Application of Intumescent Fire-Retardant Coating In a cleanroom with an ambient temperature of 28℃ and a relative humidity of 50%, intumescent fire-retardant coating is applied to the cable surface in two coats using an automatic spraying device, with a 30-minute interval between each coat, controlling the total dry film thickness to be 200μm. After spraying, the cable is first left to stand at room temperature for 1.5 hours, then dried in a 45℃ hot air circulating oven for 8 hours, and finally aged at room temperature for 24 hours to obtain the finished flame-retardant and wear-resistant bus cable.

[0052]

Example 2

[0053] S2. Preparation of composite fiber filling layer (1) Take meta-aramid filaments (PMIA) with a linear density of 1.5D and clean them sequentially in acetone, anhydrous ethanol and deionized water at 40kHz for 15min. Then immerse them in 0.3mol / L NaOH aqueous solution and treat them in a constant temperature water bath at 60℃ for 30min. After taking them out, quickly transfer them to 0.1mol / L dilute hydrochloric acid for 8min to neutralize and slightly etch them. Then rinse them repeatedly with deionized water until neutral (pH=7) and dry them in a vacuum drying oven at 60℃ for 12h to obtain activated aramid fibers.

[0054] (2) Preparation of flame retardant dispersion: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4.0:1 to obtain a first mixture. The pH of the first mixture was adjusted to 4.5 with glacial acetic acid. A mixture of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) (KH550 to KH560 mass ratio of 5:1) was added to the first mixture to obtain a second mixture. The total mass of KH550 and KH560 was 15% of the mass of the modified graphene oxide used subsequently. The mixture was stirred and hydrolyzed at 60°C for 60 min. The modified nano-hydrogen... Magnesium oxide (surface modified with KH550) was used. The mass of the modified nano-magnesium hydroxide was 60% of the mass of the modified graphene oxide. The modified magnesium hydroxide was added to the second mixture to obtain the third mixture. The third mixture was ultrasonically dispersed for 30 min. A modified graphene oxide aqueous dispersion with a concentration of 2.5 mg / mL (graphene oxide was co-modified with KH550 and phosphate ester, and the total content of N and P elements was 2.3 wt%) was slowly added dropwise to the third mixture while mechanically stirring. After the addition was completed, the mixture was ultrasonically dispersed for another 40 min to obtain a uniform and stable flame-retardant dispersion.

[0055] (3) The activated aramid fiber was completely immersed in the flame retardant dispersion and left to stand at room temperature (25°C) for 1.5 hours. After being taken out, it was dried in a 60°C oven for 2.0 hours and then transferred to a nitrogen-protected tube furnace for heat treatment at 130°C for 60 minutes to allow the silane to fully crosslink and solidify, thereby obtaining a composite aramid fiber with a surface-loaded graphene oxide / magnesium hydroxide@silane flame retardant coating.

[0056] (4) After the composite aramid fibers are bundled together, they are twisted on a twisting machine with a constant tension of 1.2cN / dtex to produce a composite yarn with a linear density of 600D and a twist of 60 twists / meter.

[0057] (5) On the outside of the insulation layer obtained in S1, a 24-spindle high-speed braiding machine is used to cover it with a braiding angle of 45° and a single-layer high-density braiding method, and the coverage rate is controlled to be ≥88%. After the braiding is completed, it is heat-set at 130°C for 10 minutes to form a dense, continuous and well-adhered composite fiber filling layer.

[0058] S3. Preparation of Flame-Retardant and Wear-Resistant Protective Layer The flame-retardant and wear-resistant protective layer precursor is composed of the following components by mass percentage: 62% thermoplastic polyurethane matrix resin, 5% POE elastomer toughening agent, 2% modified graphene oxide, 32% modified nano magnesium hydroxide, 2.0% anti-dripping agent polytetrafluoroethylene (PTFE) micro powder, 4% maleic anhydride-grafted POE compatibilizer, and 0.8% antioxidant AN1010 / AN168 compound (1:1). The flame-retardant and wear-resistant protective layer precursor is mixed in a high-speed mixer for 20 minutes and then melt-granulated at 165℃ using a twin-screw extruder (maximum temperature zone ≤180℃). The resulting granules are continuously extruded and coated onto the braided layer through a concentric extruder head under closed-loop traction tension control to form an integrated flame-retardant and wear-resistant sheath with a thickness of 1.2mm. After extrusion, the sheath is cooled in a 20℃ water bath, dried with compressed air, and automatically wound into a coil.

[0059] S4 and S5 are the same as in Example 1.

[0060]

Example 3

[0061] S2. Preparation of composite fiber filling layer (1) Take meta-aramid filaments (PMIA) with a linear density of 1.5D and clean them sequentially in acetone, anhydrous ethanol and deionized water at 40kHz for 15min. Then immerse them in 0.3mol / L NaOH aqueous solution and treat them in a constant temperature water bath at 60℃ for 30min. After taking them out, quickly transfer them to 0.1mol / L dilute hydrochloric acid for 8min to neutralize and slightly etch them. Then rinse them repeatedly with deionized water until neutral (pH=7) and dry them in a vacuum drying oven at 60℃ for 12h to obtain activated aramid fibers.

[0062] (2) Preparation of flame retardant dispersion: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4.0:1 to obtain a first mixture. The pH of the first mixture was adjusted to 4.5 with glacial acetic acid. A mixture of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) (KH550 to KH560 mass ratio of 1:1) was added to the first mixture to obtain a second mixture. The total mass of KH550 and KH560 was 4% of the mass of the modified graphene oxide used subsequently. The mixture was stirred and hydrolyzed at 60°C for 60 min. Modified nano-hydrogen ions were then taken. Magnesium hydroxide (surface modified with KH550) was used. The mass of the modified nano-magnesium hydroxide was 20% of the mass of the modified graphene oxide. The modified magnesium hydroxide was added to the second mixture to obtain the third mixture. The third mixture was ultrasonically dispersed for 30 min. A modified graphene oxide aqueous dispersion with a concentration of 1.5 mg / mL (graphene oxide was co-modified with KH550 and phosphate ester, and the total content of N and P elements was 2.0 wt%) was slowly added dropwise to the third mixture while mechanically stirring. After the addition was completed, ultrasonication was continued for 40 min to obtain a uniform and stable flame-retardant dispersion.

[0063] (3) The activated aramid fiber was completely immersed in the flame retardant dispersion and left to stand at room temperature (25°C) for 1.5 hours. After being taken out, it was dried in a 60°C oven for 2.0 hours and then transferred to a nitrogen-protected tube furnace for heat treatment at 130°C for 60 minutes to allow the silane to fully crosslink and solidify, thereby obtaining a composite aramid fiber with a surface-loaded graphene oxide / magnesium hydroxide@silane flame retardant coating.

[0064] (4) After the composite aramid fibers are bundled together, they are twisted on a twisting machine with a constant tension of 1.2cN / dtex to produce a composite yarn with a linear density of 600D and a twist of 60 twists / meter.

[0065] (5) On the outside of the insulation layer obtained in S1, a 24-spindle high-speed braiding machine is used to cover it with a braiding angle of 45° and a single-layer high-density braiding method, and the coverage rate is controlled to be ≥88%. After the braiding is completed, it is heat-set at 130°C for 10 minutes to form a dense, continuous and well-adhered composite fiber filling layer.

[0066] S3. Preparation of Flame-Retardant and Wear-Resistant Protective Layer The flame-retardant and wear-resistant protective layer precursor is composed of the following components by mass percentage: 50% matrix resin ethylene-vinyl acetate copolymer, 3% POE elastomer toughening agent, 1% modified graphene oxide, 25% modified nano magnesium hydroxide, 0.8% anti-dripping agent polytetrafluoroethylene (PTFE) micro powder, 2% maleic anhydride-grafted EVA compatibilizer, and 0.3% antioxidant AN1010 / AN168 compound (1:1). The above materials are mixed in a high-speed mixer for 20 minutes and then melt-granulated at 165℃ (maximum temperature zone ≤180℃) using a twin-screw extruder. The resulting granules are continuously extruded and coated onto the outside of the braided layer through a concentric extruder head under closed-loop traction tension control to form an integrated flame-retardant and wear-resistant sheath with a thickness of 1.2mm. After extrusion, the sheath is cooled in a 20℃ water bath, dried with compressed air, and automatically wound into a coil.

[0067] S4 and S5 are the same as in Example 1.

[0068] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in step S2 (1), while all other steps and parameters are the same, as detailed below: S2. (1) Aramid fiber treatment Meta-aramid filaments (PMIA) with a linear density of 1.5D are used directly for subsequent impregnation and coating without any cleaning or chemical treatment.

[0069] The remaining S1, S2(2)~(5), S3, S5, and S6 are the same as in Example 1.

[0070] Comparative Example 2 Comparative Example 2 differs from Example 1 in that unmodified nano-magnesium hydroxide is used in step S2 (2), while all other steps and parameters are the same, as follows: S2. (2) Preparation of flame-retardant dispersion: Anhydrous ethanol and deionized water were mixed at a volume ratio of 2.5:1 to obtain the first mixture. The pH of the first mixture was adjusted to 4.2 with glacial acetic acid. A mixture of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) (KH550 to KH560 mass ratio of 3:1) was added to the first mixture to obtain the second mixture. The total mass of KH550 and KH560 was 9% of the mass of the modified graphene oxide used subsequently. Hydrolyze the mixture at 60℃ for 60 min; separately, take unmodified nano-magnesium hydroxide, whose mass is 40% of the modified graphene oxide mass, and add it to the second mixture to obtain the third mixture, which is then ultrasonically dispersed for 30 min; slowly add a 2.0 mg / mL modified graphene oxide aqueous dispersion (graphene oxide co-modified with KH550 and phosphate ester, with a total N and P element content of 2.3 wt%) to the third mixture while mechanically stirring, and continue ultrasonication for 40 min after the addition is complete to obtain a uniform and stable flame-retardant dispersion.

[0071] The remaining S1, S2(1), S2(3)~(5), S3, S5, and S6 are the same as in Example 1.

[0072] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that unmodified graphene oxide was used in step S2 (2), while all other steps and parameters are the same, as follows: S2. (2) Preparation of flame retardant dispersion: Anhydrous ethanol and deionized water were mixed at a volume ratio of 2.5:1 to obtain the first mixture. The pH of the first mixture was adjusted to 4.2 with glacial acetic acid. A mixture of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560) (KH550 to KH560 mass ratio of 3:1) was added to the first mixture to obtain the second mixture. The total mass of KH550 and KH560 was 9% of the mass of graphene oxide used subsequently. Hydrolyze the mixture at 60℃ for 60 min; take modified nano magnesium hydroxide (surface modified with KH550), the mass of modified nano magnesium hydroxide is 40% of the mass of graphene oxide, add the modified magnesium hydroxide to the second mixture to obtain the third mixture, and ultrasonically disperse the third mixture for 30 min; slowly add a 2.0 mg / mL aqueous dispersion of graphene oxide (graphene oxide was not modified) to the third mixture while mechanically stirring, and continue ultrasonication for 40 min after the addition is complete to obtain a uniform and stable flame-retardant dispersion.

[0073] The remaining S1, S2(1), S2(3)~(5), S3, S5, and S6 are the same as in Example 1.

[0074] Comparative Example 4 Comparative Example 3 differs from Example 1 in that modified graphene oxide and modified magnesium hydroxide are not used in step S3. All other steps and parameters are the same, as detailed below: S3. Preparation of Flame-Retardant and Wear-Resistant Protective Layer The flame-retardant and wear-resistant protective layer precursor is composed of the following components by mass percentage: 89.7% matrix resin ethylene-vinyl acetate copolymer, 5% POE elastomer toughening agent, 1.2% anti-dripping agent polytetrafluoroethylene (PTFE) micro powder, 3% maleic anhydride grafted EVA compatibilizer, and 0.5% antioxidant AN1010 / AN168 compound (1:1). The flame-retardant and wear-resistant protective layer precursor is mixed in a high-speed mixer for 15 minutes and then melt-granulated at 165℃ using a twin-screw extruder (maximum temperature zone ≤180℃). The granules are then continuously extruded and coated onto the braided layer through a concentric extruder head under traction speed control to form a sheath layer with a thickness of 0.9mm. After extrusion, the material is cooled in a 25℃ water bath, dried with compressed air, and wound into a coil.

[0075] All steps S1, S2, S5, and S6 are completely identical to those in Example 1. [Performance Testing] The finished flame-retardant and wear-resistant bus cables obtained from each embodiment and comparative example were subjected to performance tests. The test methods are as follows: (1) Tensile strength and elongation at break: The sheath layer (the sheath layer is all the layers in the cable except the conductor core) is peeled off from the finished cable. Dumbbell-shaped specimens are prepared according to IEC60811-501 and tested at a tensile rate of 250 mm / min at room temperature (23±2℃). The maximum tensile force (MPa) and the percentage of elongation at break (%) are recorded. ≥5 valid specimens are tested in each group of samples, and the average value is taken.

[0076] (2) Oxygen Index (LOI): Cut a strip with dimensions of 80×10×4mm from the sheath layer of the finished cable, adjust the oxygen / nitrogen mixture ratio according to the standard, ignite the top, and record the minimum oxygen concentration (%) required to maintain combustion for just 3 minutes or a combustion length ≥50mm. Each test group should have ≥3 strips.

[0077] (3) Smoke density (Dsmax): at 3m 3 A 1m cable sample was subjected to a 750℃ heat source in a smoke chamber, and the transmittance was monitored in real time using a photometer. The maximum smoke density Dsmax was calculated from the transmittance: Dsmax = (1-T) / (1-T) min ) × 100. T min It has the lowest light transmittance.

[0078] (4) Vertical Burning Performance (VW-1): A 610mm long cable is suspended vertically and burned twice with a Bunsen burner (125mm inner flame), each time for 15 seconds, with a 15-second interval. Judgment criteria: flame self-extinguishing time ≤ 60s (total of two times ≤ 120s); dripping material must not ignite the cotton pad below; charred length ≤ 2.5m. Meeting these criteria constitutes "pass".

[0079] (5) Fire resistance performance: A 1.2m cable sample was horizontally placed in a refractory furnace, and the rated voltage and 3A current were applied. The furnace temperature was raised to 950℃ according to the standard temperature rise curve and maintained for 180min. During this period, the line was continuously monitored for short circuits or open circuits. If the line remained energized for 180min, it was judged as "pass (line intact)"; the failure time (min) was recorded.

[0080] The test results of each embodiment and comparative example are shown in Table 1.

[0081] Table 1. Comparison of test results for each embodiment and comparative example.

[0082] Compared with Example 1, Comparative Example 1 (aramid fiber unactivated) showed a decrease in tensile strength from 18.2 MPa to 12.3 MPa, an increase in elongation at break from 285% to 240%, a decrease in oxygen index (LOI) from 52.5% to 28.5%, an increase in smoke density from 28 to 55, and although it passed vertical burning, it exhibited dripping ignition. The fire resistance performance decreased from 180 min with the line intact to 80 min with failure. This indicates that the lack of surface activation treatment of aramid fiber resulted in insufficient interfacial bonding between the fiber and the flame-retardant coating. The coating was prone to peeling off at high temperatures and could not effectively protect the inner structure, thus significantly weakening the overall mechanical properties, flame-retardant efficiency, and fire resistance stability.

[0083] Compared to Example 1, Comparative Example 2 (unmodified nano-magnesium hydroxide) showed a decrease in tensile strength to 10.5 MPa, an elongation at break to 190%, an oxygen index (LOI) to 26.0%, an increase in smoke density to 62, failed vertical combustion and continued burning, and had a fire resistance time of only 65 min. This is because the unmodified nano-magnesium hydroxide agglomerates in the coating solution, which not only disrupts the continuity of the matrix and reduces mechanical properties, but also reduces the effective flame-retardant surface area, resulting in a decrease in endothermic decomposition efficiency, uneven char formation, and deterioration of flame retardant and smoke-suppressing capabilities.

[0084] Comparative Example 3 (unmodified graphene oxide) showed that although the tensile strength and elongation at break were close to those of Example 1, the oxygen index (LOI) decreased to 25.0%, the smoke density increased to 70, vertical combustion failed due to droplet ignition, and the fire resistance was only maintained for 50 minutes. This indicates that unmodified ordinary graphene oxide lacks the ability to catalyze char formation and capture gaseous free radicals, and cannot form a dense and stable heat-insulating carbon layer. At high temperatures, the material rapidly pyrolyzes, releasing a large amount of smoke and generating combustible droplets, and the synergistic flame-retardant mechanism fails.

[0085] In Comparative Example 4 (without modified magnesium hydroxide and modified graphene oxide in the flame-retardant and wear-resistant protective layer precursor), the tensile strength dropped to 9.8 MPa, the oxygen index (LOI) was only 21.0%, the smoke density reached 80, it failed the rapid burn-through test during vertical combustion, and the fire resistance time was only 40 minutes. Although its elongation at break was relatively high, the flame-retardant and wear-resistant protective layer completely lacked modified graphene oxide and modified magnesium hydroxide, resulting in neither a condensed phase carbon skeleton nor heat absorption and smoke suppression. The outer flame-retardant and wear-resistant protective layer melted and burned rapidly in the flame. Even though the internal composite fiber filling layer existed briefly, the overall structure still failed prematurely due to the collapse of the outer layer. This fully demonstrates that the flame-retardant function of the flame-retardant and wear-resistant protective layer itself is indispensable to the overall fire resistance performance of the cable.

[0086] It should be noted that, in this document, "comprising," "including," or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0087] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0088] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a flame-retardant and wear-resistant bus cable, characterized in that, The preparation method includes: Provide conductor cores covered with an insulating layer; The surface of the aramid fiber is activated, and the activated aramid fiber is immersed in a flame retardant dispersion for impregnation. Then, the impregnated aramid fiber is heat-treated to obtain composite aramid fiber. The composite aramid fiber is woven on the insulating layer to form a composite fiber filling layer. The flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer. The activation treatment of the aramid fiber surface includes: Aramid fibers were sequentially subjected to ultrasonic cleaning, alkali treatment, and acid treatment to obtain treated aramid fibers. The treated aramid fiber was washed with water until neutral, and then vacuum dried at 55℃~65℃ for 10h~14h to obtain the activated aramid fiber. The preparation method further includes preparing a flame-retardant dispersion, wherein preparing the flame-retardant dispersion comprises: Anhydrous ethanol and deionized water are mixed to obtain a first mixture, and the pH value of the first mixture is adjusted to 4.0~4.5; wherein the volume ratio of anhydrous ethanol to deionized water is (1.5~4.0):

1. Add a silane coupling agent mixture to the first mixture to obtain a second mixture, and stir the second mixture at 50℃~65℃ for 45min~75min; Modified nano-magnesium hydroxide was added to the second mixture to obtain a third mixture, which was then ultrasonically dispersed for 20 to 40 minutes. Add 1.5 mg / mL to 2.5 mg / mL of modified graphene oxide aqueous dispersion to the third mixture while stirring, and then sonicate for 30 min to 50 min to obtain the flame retardant dispersion. The modified nano magnesium hydroxide is obtained by modifying nano magnesium hydroxide with a silane coupling agent, and the D50 of the nano magnesium hydroxide is 50nm~100nm. The modified graphene oxide has amino and / or phosphorus-containing functional groups grafted onto its surface, and the total content of nitrogen and / or phosphorus in the modified graphene oxide is not less than 2 wt%. The mass of the modified nano-magnesium hydroxide is 20% to 60% of the mass of the modified graphene oxide; The mass of the silane coupling agent mixture is 4% to 15% of the total mass of the modified graphene oxide and the modified nano magnesium hydroxide; The silane coupling agent mixture includes γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, with a mass ratio of (1~5):1 between γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

2. The method for preparing a flame-retardant and wear-resistant busbar cable according to claim 1, characterized in that, The ultrasonic cleaning process includes: ultrasonically cleaning the aramid fiber sequentially with acetone, anhydrous ethanol and deionized water for 10 min to 20 min each; And / or, the alkaline treatment includes: placing the ultrasonically cleaned aramid fibers in a 0.2 mol / L to 0.5 mol / L sodium hydroxide solution and treating them at a temperature of 50°C to 65°C for 20 min to 40 min; And / or, the acid treatment includes: soaking the alkali-treated aramid fibers in 0.05mol / L to 0.1mol / L dilute hydrochloric acid for 5 min to 10 min.

3. The method for preparing a flame-retardant and wear-resistant busbar according to claim 1, characterized in that, The impregnated aramid fibers are then subjected to heat treatment, including: The impregnated aramid fibers were dried at 55℃~65℃ for 1.5h~2.5h, and then heat-treated at 120℃~140℃ in an inert gas atmosphere for 50min~80min. And / or, the impregnation treatment includes: immersing the activated aramid fibers in the flame-retardant dispersion at room temperature for 1.0h to 2.0h.

4. The method for preparing a flame-retardant and wear-resistant bus cable according to claim 1, characterized in that, The flame-retardant and wear-resistant protective layer precursor includes: a matrix resin, an elastomer toughening agent, modified graphene oxide, modified nano magnesium hydroxide, an anti-dripping agent, a compatibilizer, and an antioxidant. Based on the total mass of the flame-retardant and wear-resistant protective layer precursor, the mass fraction of the matrix resin is 50%~62%, the mass fraction of the elastomer toughening agent is 3%~8%, the mass fraction of the modified graphene oxide is 1%~2%, the mass fraction of the modified nano magnesium hydroxide is 25%~32%, the mass fraction of the anti-dripping agent is 0.8%~2.0%, the mass fraction of the compatibilizer is 2%~4%, and the mass fraction of the antioxidant is 0.3%~0.8%.

5. The method for preparing a flame-retardant and wear-resistant bus cable according to claim 1, characterized in that, The flame-retardant and wear-resistant protective layer precursor is melted and coated onto the surface of the composite fiber filling layer to form a flame-retardant and wear-resistant protective layer, comprising: The flame-retardant and wear-resistant protective layer precursor is mixed for 10 min to 20 min, melted and granulated at 155℃ to 175℃ to obtain granules. The granules are continuously extruded and coated onto the composite fiber filling layer under controlled traction tension to form a flame-retardant and wear-resistant protective layer; wherein the thickness of the flame-retardant and wear-resistant protective layer is 0.6mm~1.2mm.

6. A flame-retardant and wear-resistant bus cable, characterized in that, It is prepared by the method for preparing the flame-retardant and wear-resistant bus cable according to any one of claims 1 to 5.

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