A fire-retardant extruded insulation low voltage power cable

Abstract

This invention relates to the field of cables and discloses a flame-retardant extruded insulated low-voltage power cable, comprising a conductor core, an insulation layer, a filling layer, an inner sheath layer, an armor layer, and an outer sheath layer. The sheath layer materials include: low-density polyethylene, EPDM rubber, ethylene-tetrafluoroethylene copolymer, modified halloysite nanotubes, modified ammonium polyphosphate, and additives. The modified halloysite nanotubes are prepared by grafting octaaminopropyl cage-like polysilsesquioxane onto the surface of halloysite nanotubes using a sol-gel method after loading titanium dioxide onto the surface of the halloysite nanotubes. The modified ammonium polyphosphate is prepared by grafting a functionalized silane coupling agent prepared by reacting a cyclotriphosphazene derivative with 3-chloropropyltrimethoxysilane with polysiloxane-coated ammonium polyphosphate. The cyclotriphosphazene derivative is prepared by reacting 3-amino-1,2,4-triazole with hexachlorocyclotriphosphazene and then coordinating with cobalt ions using a hydrothermal method, thereby endowing the material with good mechanical properties, UV resistance, heat and wear resistance, flame retardancy, and antibacterial properties.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically relating to a flame-retardant extruded insulated low-voltage power cable. Background Technology

[0002] As a crucial component of power transmission and distribution systems, low-voltage power cables play a vital role in the reliability and safety of power supply. Traditional low-voltage power cables often lack sufficient flame-retardant properties, which can lead to power outages and even secondary disasters in extreme environments such as fires, seriously threatening life and property. Especially in low-voltage power systems, the flame-retardant performance of cables directly affects the continuous power supply to critical facilities such as emergency lighting and fire-fighting equipment. Therefore, low-voltage power cables need to possess excellent flame-retardant properties to ensure that they can slow the spread of fire and reduce the losses caused by fire.

[0003] The sheath material, as a crucial component of cables, plays a vital role in electrical insulation and protection. Its performance directly impacts the cable's lifespan and the system's operational stability. Existing sheath materials are typically based on polyolefins, which, while possessing good electrical properties, are prone to decomposition under high temperatures or fire conditions, releasing large amounts of smoke and toxic gases, thus exacerbating fire hazards. Current technologies incorporate flame retardants into the sheath material to enhance its flame-retardant performance. However, excessive amounts of conventional flame retardants can negatively affect the material's mechanical properties and processing techniques, while insufficient amounts fail to achieve the desired flame-retardant effect, failing to provide continuous protection for the cable. Furthermore, the molecular structure of polyolefins is sensitive to high temperatures and ultraviolet radiation. Prolonged exposure to high temperatures or ultraviolet radiation can lead to oxidative degradation, causing molecular chain breakage and cross-linking, resulting in a significant decline in mechanical properties. Moreover, warm and humid environments make the protective layer material susceptible to bacterial growth, corroding the cable core material and severely limiting the cable's lifespan. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a flame-retardant extruded insulated low-voltage power cable, which, through the addition of modified halloysite nanotubes and modified ammonium polyphosphate, endows the material with excellent mechanical properties, UV resistance, heat and wear resistance, flame retardancy, and antibacterial properties.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A flame-retardant extruded insulated low-voltage power cable includes, from the inside out, a conductor core, an insulation layer, a filling layer, an inner sheath layer, an armor layer, and an outer sheath layer. Both the inner and outer sheath layers are prepared by extruding sheath layer material outside the filling layer and the armor layer, respectively, using an extrusion device. The sheath layer material comprises the following components by weight: 55-80 parts low-density polyethylene, 10-20 parts ethylene propylene diene monomer (EPDM) rubber, 5-15 parts ethylene-tetrafluoroethylene copolymer, 4-10 parts modified halloysite nanotubes, 2-5 parts modified ammonium polyphosphate, 3.5-6 parts dicumyl peroxide, 2-6 parts triallyl isocyanurate, 1-3 parts plasticizer, and 0.1-1 parts lubricant.

[0007] The modified halloysite nanotubes were prepared by loading titanium dioxide onto the surface of halloysite nanotubes using the sol-gel method, then treating the prepared loaded halloysite nanotubes with sodium hydroxide solution and grafting octaaminopropyl cage-like polysilsesquioxane onto epichlorohydrin.

[0008] The modified ammonium polyphosphate is prepared by grafting a functionalized silane coupling agent, prepared by a substitution reaction between a cyclotriphosphazene derivative and 3-chloropropyltrimethoxysilane, onto the surface of the coated ammonium polyphosphate. The cyclotriphosphazene derivative is prepared by a substitution reaction between 3-amino-1,2,4-triazole and hexachlorocyclotriphosphazene to prepare a cyclotriphosphazene substitute, which is then coordinated with the cyclotriphosphazene substitute using a hydrothermal method. The coated ammonium polyphosphate is prepared by using dimethyldiethoxysilane and tetraethyl orthosilicate as precursors and modifying the ammonium polyphosphate with polysiloxane using a sol-gel method.

[0009] Preferably, the method for preparing the modified halloysite nanotubes includes the following steps:

[0010] A. Take tetrabutyl titanate and anhydrous ethanol and mix them evenly. Add acetic acid and halloysite nanotubes and stir for 10-12 hours. Then, place the resulting gel in an oven to dry. Then, calcine the dry gel in a muffle furnace at 480-520℃ for 3-5 hours with a heating rate of 5℃ / min to prepare supported halloysite nanotubes.

[0011] B. Take deionized water, methanol and tetraethylammonium hydroxide aqueous solution into a reactor and stir evenly at 45~55℃. Then add 3-aminopropyltriethoxysilane dropwise while stirring continuously. After the addition is complete, place the reactor at 70~75℃ and stir for 20~24h. After the reaction is completed, add the reaction solution into petroleum ether. Filter and dry the precipitate to prepare octaaminopropyl cage-like polysilsesquioxane.

[0012] C. The supported halloysite nanotubes were placed in a 0.5 mol / L sodium hydroxide solution and stirred for 1.5-2 h. Then, they were placed in N,N-dimethylformamide and ultrasonically dispersed evenly. Epichlorohydrin was added and stirred for 1-1.5 h. Subsequently, octaaminopropyl cage-like polysilsesquioxane was added and stirred for 1-1.5 h. After the reaction was completed, the modified halloysite nanotubes were prepared by centrifugation, washing and drying.

[0013] Preferably, in step A, the addition ratio of tetrabutyl titanate, anhydrous ethanol, acetic acid, and halloysite nanotubes is 3.5~4.5mL: 30~40mL: 2.5~3mL: 1g.

[0014] Preferably, in step C, the mass ratio of supported halloysite nanotubes to octaaminopropyl cage-like polysilsesquioxane is 1:1~2.

[0015] Preferably, the preparation method of the modified ammonium polyphosphate includes the following steps:

[0016] I. Disperse ammonium polyphosphate in a mixed solution of anhydrous ethanol and deionized water, add ammonia dropwise to adjust the pH of the system to 9.5-10, add dimethyldiethoxysilane and tetraethyl orthosilicate and stir evenly, place at 40-45℃ for 2.5-3 hours, filter and wash after the reaction, then extract the powder with anhydrous ethanol and dry to prepare coated ammonium polyphosphate;

[0017] II. Hexachlorocyclotriphosphazene and acetonitrile were placed in a reactor, stirred and dissolved, and then heated to 45-50°C. A mixed solution of 3-amino-1,2,4-triazole and deionized water was added, stirred evenly, and then sodium hydroxide solid was added. The mixture was refluxed for 6-7 hours. After the reaction was completed, the product was evaporated and dried. The solid product was fully dissolved in methanol, filtered to obtain the filtrate, and then evaporated and dried to prepare the substituted cyclotriphosphazene.

[0018] III. Take the cyclic triphosphazene substituted product and cobalt nitrate hexahydrate into a high-pressure reactor, add deionized water and stir to mix evenly, then add sodium hydroxide solid and stir thoroughly. Purge the reaction with nitrogen gas and place it at 180~185℃ for 10~12h. After the reaction is completed, centrifuge, wash and dry to prepare the cyclic triphosphazene derivative.

[0019] IV. Take a cyclotriphosphazene derivative and N,N-dimethylformamide in a reactor, add 3-chloropropyltrimethoxysilane dropwise over 1 hour using a dropping funnel, then add triethylamine acid binder, purge the reaction with nitrogen, and continue the reaction at 75-85°C for 6-8 hours. After the reaction is completed, filter, rotary evaporate, and dry to prepare a functionalized silane coupling agent.

[0020] V. Take coated ammonium polyphosphate and ultrasonically disperse it in anhydrous ethanol and deionized water, then add functionalized silane coupling agent, and stir the reaction at 55~70℃ for 4~6h. After the reaction is completed, filter, wash and dry to prepare modified ammonium polyphosphate.

[0021] Preferably, in step I, the mass ratio of ammonium polyphosphate, dimethyldiethoxysilane, and tetraethyl orthosilicate is 4.5~6:1:1.

[0022] Preferably, in step II, the molar ratio of hexachlorocyclotriphosphazene and 3-amino-1,2,4-triazole is 1:6.

[0023] Preferably, in step III, the molar ratio of the cyclotriphosphazene substituent to cobalt nitrate hexahydrate is 1:2.

[0024] Preferably, the preparation method of the sheath layer material includes the following steps: weighing each component according to the weight parts, mixing low-density polyethylene, ethylene propylene diene monomer (EPDM) rubber, ethylene-tetrafluoroethylene copolymer, modified halloysite nanotubes, modified ammonium polyphosphate, dicumyl peroxide, triallyl isocyanurate, plasticizer and lubricant evenly, and then extruding them in a twin-screw extruder to obtain the sheath layer material;

[0025] The plasticizer is one or more of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate; the lubricant is polyethylene wax or oxidized polyethylene wax.

[0026] Preferably, the method for preparing the flame-retardant extruded insulated low-voltage power cable includes the following steps:

[0027] S1. A copper rod is drawn using a wire drawing machine to obtain copper wire, which is then annealed to obtain a conductor. Then, at least two of the conductors are twisted together to obtain a conductor core.

[0028] S2. Use an extruder to extrude a cross-linked polyethylene insulation layer onto the outside of the conductor core;

[0029] S3. PP filler rope is used to fill the outside of the insulation layer to form a filler layer;

[0030] S4. Extruding sheath material onto the outside of the filler layer to form an inner sheath layer;

[0031] S5. Tin-plated copper wire is used to braid the outer side of the inner sheath layer, with a braiding density of ≥90%, to form an armor layer.

[0032] S6. An outer sheath layer is formed by extruding sheath material on the outside of the armor layer to prepare a flame-retardant extruded insulated low-voltage power cable.

[0033] The beneficial effects of this invention are:

[0034] This invention utilizes a sol-gel method to load titanium dioxide onto the surface of halloysite nanotubes, followed by treatment of the loaded halloysite nanotubes with sodium hydroxide solution to enrich their surface with hydroxyl groups. Modified halloysite nanotubes are then prepared by grafting octaaminopropyl cage-like polysilsesquioxane onto epichlorohydrin. The octaaminopropyl cage-like polysilsesquioxane is produced using 3-aminopropyltriethoxysilane as a starting material via a polycondensation reaction, exhibiting high heat resistance. The halloysite nanotubes possess a unique one-dimensional tubular rod structure and exhibit certain mechanical strength and UV shielding capabilities. Titanium dioxide effectively absorbs and shields long- and medium-wave ultraviolet rays, providing excellent UV protection. The shielding performance and weather resistance were improved by loading titanium dioxide onto halloysite surfaces using the sol-gel method. This solved the problem of agglomeration caused by the high surface energy of nano-sized titanium dioxide. Furthermore, grafting octaaminopropyl cage-like polysilsesquioxane improved the compatibility between the supported halloysite nanotubes and the matrix material. In addition, the cage-like polysilsesquioxane structure introduced into the modified halloysite nanotubes and the matrix material formed a denser Si-O-Si cross-linked network structure through hydrogen bonding, reducing the transmittance of ultraviolet light and effectively improving the ultraviolet shielding efficiency of the material. As a result, the prepared modified halloysite nanotubes endowed the material with excellent mechanical properties, ultraviolet resistance, and heat and wear resistance.

[0035] This invention utilizes dimethyldiethoxysilane and tetraethyl orthosilicate as precursors to modify ammonium polyphosphate with polysiloxane coating via a sol-gel method, thereby improving the hydrophobicity, thermal stability, and compatibility with the matrix of ammonium polyphosphate. Simultaneously, this invention utilizes the substitution reaction between the -NH group in 3-amino-1,2,4-triazole and the six chlorine atoms in hexachlorocyclotriphosphazene to prepare cyclotriphosphazene substituted products. Then, using a hydrothermal method, under high temperature and pressure, the cobalt element in cobalt nitrate hexahydrate coordinates with two adjacent -NH2 groups in the cyclotriphosphazene substituted products to prepare cobalt-doped cyclotriphosphazene derivatives. The remaining two uncoordinated ammonia atoms... A functionalized silane coupling agent is prepared by reacting the functionalized group with 3-chloropropyltrimethoxysilane. This functionalized silane coupling agent is then grafted onto the surface of coated ammonium polyphosphate, promoting relatively uniform dispersion of the modified ammonium polyphosphate in the matrix material. This facilitates the full utilization of the modified polyphosphate's properties. Furthermore, the organopolysiloxane coating on the surface of the ammonium polyphosphate provides excellent wear resistance and heat resistance. Additionally, the functionalized silane coupling agent bonded to the surface of the modified ammonium polyphosphate introduces flame-retardant nitrogen-phosphorus-silicon elements, which synergistically contribute to excellent flame retardancy with the coated ammonium polyphosphate. The introduced triazole ring and cobalt ions also provide synergistic antibacterial effects, endowing the material with good antibacterial properties. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] A method for preparing modified halloysite nanotubes includes the following steps:

[0039] A. Take 24 mL of tetrabutyl titanate and 200 mL of anhydrous ethanol and mix them evenly. Add 16 mL of acetic acid and 6 g of halloysite nanotubes and stir for 10 h. Then place the resulting gel in an oven to dry. Then calcine the dry gel in a muffle furnace at 500 °C for 4 h at a heating rate of 5 °C / min to prepare supported halloysite nanotubes.

[0040] B. Take 54 mL of deionized water, 24 mL of methanol and 3 mL of 25% tetraethylammonium hydroxide aqueous solution into a reactor and stir evenly at 50 °C. Then, add 120 mL of 3-aminopropyltriethoxysilane dropwise while stirring continuously. After the addition is complete, place the reactor at 70 °C and stir for 24 h. After the reaction is complete, add the reaction solution into 800 mL of petroleum ether. Filter and dry the precipitate to prepare octaaminopropyl cage-like polysilsesquioxane.

[0041] C. Take 5g of supported halloysite nanotubes and place them in 0.5mol / L sodium hydroxide solution and stir for 2h. Then, put them into 230mL of N,N-dimethylformamide and disperse them evenly by ultrasonication. Add 20mL of epichlorohydrin and stir for 1h. Then, add 5g of octaaminopropyl cage-like polysilsesquioxane and stir for 1h. After the reaction is completed, centrifuge, wash and dry to prepare modified halloysite nanotubes.

[0042] Example 2

[0043] A method for preparing modified ammonium polyphosphate includes the following steps:

[0044] I. Disperse 100g of ammonium polyphosphate in a mixed solution of 290mL anhydrous ethanol and 110mL deionized water, add ammonia water dropwise to adjust the pH of the system to 10, add 20g of dimethyldiethoxysilane and 20g of tetraethyl orthosilicate and stir evenly, place at 45℃ for 2.5h. After the reaction is completed, filter and wash, then extract the powder with anhydrous ethanol and dry to prepare coated ammonium polyphosphate.

[0045] II. Take 8.7g of hexachlorocyclotriphosphazene and 150mL of acetonitrile in a reactor, stir to dissolve, heat to 50℃, add a mixed solution of 12.6g of 3-amino-1,2,4-triazole and 50mL of deionized water, stir evenly, add 6g of sodium hydroxide solid, reflux for 6h, after the reaction is completed, rotary evaporate and dry, dissolve the solid product in methanol, filter to obtain filtrate, rotary evaporate and dry the filtrate to prepare the substituted cyclotriphosphazene;

[0046] III. Take 6.3g of cyclotriphosphazene substituted product and 5.8g of cobalt nitrate hexahydrate into a high-pressure reactor, add 80mL of deionized water and stir to mix evenly, then add 1.6g of sodium hydroxide solid and stir thoroughly. Purge the reaction with nitrogen gas and place it at 180℃ for 12h. After the reaction is completed, centrifuge, wash and dry to prepare cyclotriphosphazene derivative.

[0047] IV. Take 7.4 g of cyclotriphosphazene derivative and 100 mL of N,N-dimethylformamide in a reactor, add 4.1 g of 3-chloropropyltrimethoxysilane dropwise over 1 h using a dropping funnel, then add 2 g of triethylamine acid binder, purge the reaction with nitrogen gas, and continue the reaction at 80 °C for 7 h. After the reaction is completed, filter, rotary evaporate, and dry to prepare the functionalized silane coupling agent.

[0048] V. Take 5g of coated ammonium polyphosphate and ultrasonically disperse it in 90mL of anhydrous ethanol and 20mL of deionized water. Then add 3.7g of functionalized silane coupling agent and stir the mixture at 65℃ for 5h. After the reaction is completed, filter, wash and dry to prepare modified ammonium polyphosphate.

[0049] Example 3

[0050] A sheathing material comprises the following components in parts by weight: 58 parts low-density polyethylene, 12 parts ethylene propylene diene monomer (EPDM) rubber, 5.5 parts ethylene-tetrafluoroethylene copolymer, 4.2 parts modified halloysite nanotubes prepared in Example 1, 2.3 parts modified ammonium polyphosphate prepared in Example 2, 3.7 parts dicumyl peroxide, 2.4 parts triallyl isocyanurate, 1.1 parts plasticizer dioctyl adipate, and 0.2 parts lubricant polyethylene wax.

[0051] The preparation method of the above-mentioned sheath layer material includes the following steps: weigh each component according to the weight parts, mix low-density polyethylene, ethylene propylene diene monomer (EPDM) rubber, ethylene-tetrafluoroethylene copolymer, modified halloysite nanotubes, modified ammonium polyphosphate, dicumyl peroxide, triallyl isocyanurate, plasticizer and lubricant evenly, and then put them into a twin-screw extruder for extrusion molding to prepare the sheath layer material.

[0052] A method for preparing a flame-retardant extruded insulated low-voltage power cable includes the following steps:

[0053] S1. A copper rod is drawn using a wire drawing machine to obtain copper wire, which is then annealed to obtain a conductor. Then, at least two of the conductors are twisted together to obtain a conductor core.

[0054] S2. Use an extruder to extrude a cross-linked polyethylene insulation layer onto the outside of the conductor core;

[0055] S3. Fill the outside of the insulation layer with 0.04mm non-woven PP filler rope to form a filler layer;

[0056] S4. Extruding sheath material onto the outside of the filler layer to form an inner sheath layer;

[0057] S5. Tin-plated copper wire is used to braid the outer side of the inner sheath layer with a braiding density of 92% to form an armor layer.

[0058] S6. An outer sheath layer is formed by extruding sheath material on the outside of the armor layer to prepare a flame-retardant extruded insulated low-voltage power cable.

[0059] Example 4

[0060] A sheathing material comprises the following components in parts by weight: 67 parts low-density polyethylene, 15 parts EPDM rubber, 7.7 parts ethylene-tetrafluoroethylene copolymer, 7.3 parts modified halloysite nanotubes prepared in Example 1, 3.8 parts modified ammonium polyphosphate prepared in Example 2, 4.5 parts dicumyl peroxide, 4.2 parts triallyl isocyanurate, 1.7 parts plasticizer dimethyl phthalate, and 0.5 parts lubricant oxidized polyethylene wax.

[0061] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0062] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0063] Example 5

[0064] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts ethylene propylene diene monomer (EPDM) rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts modified halloysite nanotubes prepared in Example 1, 4.8 parts modified ammonium polyphosphate prepared in Example 2, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts plasticizer dioctyl phthalate, and 0.8 parts lubricant oxidized polyethylene wax.

[0065] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0066] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0067] Comparative Example 1

[0068] A method for preparing modified ammonium polyphosphate includes the following steps:

[0069] I. Disperse 100g of ammonium polyphosphate in a mixed solution of 290mL anhydrous ethanol and 110mL deionized water, add ammonia water dropwise to adjust the pH of the system to 10, add 20g of dimethyldiethoxysilane and 20g of tetraethyl orthosilicate and stir evenly, place at 45℃ for 2.5h. After the reaction is completed, filter and wash, then extract the powder with anhydrous ethanol and dry to prepare coated ammonium polyphosphate.

[0070] II. Take 8.7g of hexachlorocyclotriphosphazene and 150mL of acetonitrile in a reactor, stir to dissolve, heat to 50℃, add a mixed solution of 12.6g of 3-amino-1,2,4-triazole and 50mL of deionized water, stir evenly, add 6g of sodium hydroxide solid, reflux for 6h, after the reaction is completed, rotary evaporate and dry, dissolve the solid product in methanol, filter to obtain filtrate, rotary evaporate and dry the filtrate to prepare the substituted cyclotriphosphazene;

[0071] III. Take 6.3g of cyclotriphosphazene substituted product and 100mL of N,N-dimethylformamide in a reactor. Add 4.1g of 3-chloropropyltrimethoxysilane dropwise over 1h using a dropping funnel, and then add 2g of triethylamine acid binder. Purge the reaction with nitrogen gas and continue the reaction at 80℃ for 7h. After the reaction is completed, filter, rotary evaporate, and dry to prepare the functionalized silane coupling agent.

[0072] IV. Take 5g of coated ammonium polyphosphate and ultrasonically disperse it in 90mL of anhydrous ethanol and 20mL of deionized water. Then add 3.7g of functionalized silane coupling agent and stir at 65℃ for 5h. After the reaction is completed, filter, wash and dry to prepare modified ammonium polyphosphate.

[0073] Comparative Example 2

[0074] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts ethylene propylene diene monomer (EPDM) rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts supported halloysite nanotubes prepared in Example 1, 4.8 parts modified ammonium polyphosphate prepared in Example 2, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts plasticizer dioctyl phthalate, and 0.8 parts lubricant oxidized polyethylene wax.

[0075] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0076] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0077] Comparative Example 3

[0078] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts ethylene propylene diene monomer (EPDM) rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts halloysite nanotubes, 4.8 parts modified ammonium polyphosphate prepared in Example 2, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts dioctyl phthalate plasticizer, and 0.8 parts oxidized polyethylene wax lubricant.

[0079] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0080] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0081] Comparative Example 4

[0082] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts EPDM rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts modified halloysite nanotubes prepared in Example 1, 4.8 parts modified ammonium polyphosphate prepared in Comparative Example 1, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts plasticizer dioctyl phthalate, and 0.8 parts lubricant oxidized polyethylene wax.

[0083] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0084] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0085] Comparative Example 5

[0086] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts ethylene propylene diene monomer (EPDM) rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts modified halloysite nanotubes prepared in Example 1, 4.8 parts coated ammonium polyphosphate prepared in Example 2, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts plasticizer dioctyl phthalate, and 0.8 parts lubricant oxidized polyethylene wax.

[0087] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0088] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0089] Comparative Example 6

[0090] A sheathing material comprises the following components in parts by weight: 77 parts low-density polyethylene, 18 parts ethylene propylene diene monomer (EPDM) rubber, 12.6 parts ethylene-tetrafluoroethylene copolymer, 9.5 parts modified halloysite nanotubes prepared in Example 1, 4.8 parts ammonium polyphosphate, 5.6 parts dicumyl peroxide, 5.3 parts triallyl isocyanurate, 2.6 parts plasticizer dioctyl phthalate, and 0.8 parts lubricant oxidized polyethylene wax.

[0091] The preparation method of the above-mentioned sheath layer material is the same as that in Example 3.

[0092] The preparation method of a flame-retardant extruded insulated low-voltage power cable is the same as in Example 3.

[0093] Performance testing

[0094] The performance of the sheathing materials prepared in Examples 3-5 and Comparative Examples 2-6 was tested:

[0095] a. Tensile properties were tested using a universal testing machine according to GB / T 1040.2-2022. The sample dimensions were 100mm × 5mm × 3.5mm. The sample was placed under a 20W ultraviolet lamp emitting short-wave ultraviolet light with a characteristic wavelength of 253.7nm. The ultraviolet irradiance at 20cm vertically from the center of the lamp was 1400μw / cm². 2 The sample was placed parallel to the light source in a fixed position and subjected to ultraviolet irradiation for 200h and 400h to determine its tensile properties, thereby evaluating its UV resistance. The impact strength test was carried out according to GB / T1843-2008, with the sample size being 80mm×10mm×4mm. The data results are shown in Table 1.

[0096] b. Place the sample in a TGA-103 thermogravimetric analyzer and, under nitrogen protection, raise the temperature from room temperature to 800℃ at a rate of 5℃ / min. Record the initial decomposition temperature of the material and evaluate its heat resistance. Generally speaking, the higher the initial decomposition temperature, the stronger the heat resistance, and vice versa. The data results are shown in Table 1.

[0097] c. Using a CSM ball-and-disc friction and wear tester, the amplitude was set to 2.5 cm, the load to 5 N, and the speed to 10 cm / s. A 6 mm steel ball was used as the mating material to conduct friction tests on the samples and evaluate their wear resistance. The data results are shown in Table 1.

[0098] d. The limiting oxygen index of the samples was tested according to GB / T 2406.2-2009 to evaluate the flame retardant performance of the samples. The sample size was 100mm×7mm×4mm. The data results are shown in Table 1.

[0099] e. The antibacterial performance was tested according to QB / T 2591-2003, and the test strain was Staphylococcus aureus. The data results are shown in Table 1.

[0100] Table 1 Sample performance test results

[0101]

[0102] As shown in Table 1, the sheathing materials prepared in Examples 3-5 of this invention possess good mechanical properties and maintain high tensile strength even after UV aging for 200h and 400h, exhibiting excellent UV resistance. They also possess good heat resistance, wear resistance, flame retardancy, and antibacterial properties. In Comparative Example 2, modified halloysite nanotubes were replaced with supported halloysite nanotubes in equal amounts. In Comparative Example 3, no modification treatment was applied to the halloysite nanotubes. The mechanical properties, tensile strength after UV aging, and initial thermal decomposition temperature of Comparative Examples 2-3 were found to be lower than those of Examples 3-5, indicating that grafting with octaaminopropyl cage-like polysilsesquioxane is beneficial for improving the mechanical properties, UV resistance, and heat resistance of the materials. Furthermore, the decrease in mechanical properties and tensile strength after UV aging in Comparative Example 3 was more significant than that in Comparative Example 2, indicating that the loading of titanium dioxide nanoparticles further improved the mechanical properties and UV resistance of the materials to a certain extent. The modified ammonium polyphosphate component added in Comparative Example 4 was not... In Comparative Example 5, cobalt nitrate hexahydrate was introduced. In Comparative Example 6, modified ammonium polyphosphate was replaced with coated ammonium polyphosphate in equal amounts. In Comparative Example 6, no modification treatment was performed on the ammonium polyphosphate. The limiting oxygen index and antibacterial rate of Comparative Examples 4-6 were found to be lower than those of Examples 3-5, indicating that the introduction of cobalt element is beneficial to improving the flame retardant and antibacterial properties of the material. The flame retardant and antibacterial properties of Comparative Examples 5-6 were found to be more significantly lower than those of Comparative Example 4. This is because flame retardant nitrogen-phosphorus-silicon elements, antibacterial triazole rings, and cobalt ions were not introduced. In addition, the wear resistance and heat resistance of Comparative Example 6 were found to be significantly lower than those of Examples 3-5, indicating that the coating of organopolysiloxane can provide good wear resistance and heat resistance of the material.

[0103] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0104] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A flame-retardant extruded insulated low-voltage power cable, characterized in that, The material comprises, from the inside out, a conductor core, an insulating layer, a filling layer, an inner sheath layer, an armor layer, and an outer sheath layer. Both the inner and outer sheath layers are prepared by extruding sheath layer material outside the filling layer and the armor layer, respectively, using an extrusion device. The sheath layer material comprises the following components by weight: 55-80 parts low-density polyethylene, 10-20 parts EPDM rubber, 5-15 parts ethylene-tetrafluoroethylene copolymer, 4-10 parts modified halloysite nanotubes, 2-5 parts modified ammonium polyphosphate, 3.5-6 parts dicumyl peroxide, 2-6 parts triallyl isocyanurate, 1-3 parts plasticizer, and 0.1-1 parts lubricant. The method for preparing the modified halloysite nanotubes includes the following steps: A. Take tetrabutyl titanate and anhydrous ethanol and mix them evenly. Add acetic acid and halloysite nanotubes and stir for 10-12 hours. Then, place the resulting gel in an oven to dry. Then, calcine the dry gel in a muffle furnace at 480-520℃ for 3-5 hours with a heating rate of 5℃ / min to prepare supported halloysite nanotubes. B. Take deionized water, methanol and tetraethylammonium hydroxide aqueous solution into a reactor and stir evenly at 45~55℃. Then add 3-aminopropyltriethoxysilane dropwise while stirring continuously. After the addition is complete, place the reactor at 70~75℃ and stir for 20~24h. After the reaction is completed, add the reaction solution into petroleum ether. Filter and dry the precipitate to prepare octaaminopropyl cage-like polysilsesquioxane. C. The supported halloysite nanotubes were placed in a 0.5 mol / L sodium hydroxide solution and stirred for 1.5-2 h. Then, they were placed in N,N-dimethylformamide and ultrasonically dispersed evenly. Epichlorohydrin was added and stirred for 1-1.5 h. Subsequently, octaaminopropyl cage-like polysilsesquioxane was added and stirred for 1-1.5 h. After the reaction was completed, the modified halloysite nanotubes were prepared by centrifugation, washing and drying. The modified ammonium polyphosphate is prepared by grafting a functionalized silane coupling agent, prepared by a substitution reaction between a cyclotriphosphazene derivative and 3-chloropropyltrimethoxysilane, onto the surface of the coated ammonium polyphosphate. The cyclotriphosphazene derivative is prepared by a substitution reaction between 3-amino-1,2,4-triazole and hexachlorocyclotriphosphazene to prepare a cyclotriphosphazene substitute, which is then coordinated with the cyclotriphosphazene substitute using a hydrothermal method. The coated ammonium polyphosphate is prepared by using dimethyldiethoxysilane and tetraethyl orthosilicate as precursors and modifying the ammonium polyphosphate with polysiloxane using a sol-gel method.

2. The flame-retardant extruded insulated low-voltage power cable according to claim 1, characterized in that, In step A, the addition ratio of tetrabutyl titanate, anhydrous ethanol, acetic acid, and halloysite nanotubes is 3.5~4.5mL: 30~40mL: 2.5~3mL: 1g.

3. The flame-retardant extruded insulated low-voltage power cable according to claim 1, characterized in that, In step C, the mass ratio of supported halloysite nanotubes to octaaminopropyl cage-like polysilsesquioxane is 1:1~2.

4. The flame-retardant extruded insulated low-voltage power cable according to claim 1, characterized in that, The preparation method of the modified ammonium polyphosphate includes the following steps: I. Disperse ammonium polyphosphate in a mixed solution of anhydrous ethanol and deionized water, add ammonia dropwise to adjust the pH of the system to 9.5-10, add dimethyldiethoxysilane and tetraethyl orthosilicate and stir evenly, place at 40-45℃ for 2.5-3 hours, filter and wash after the reaction, then extract the powder with anhydrous ethanol and dry to prepare coated ammonium polyphosphate; II. Hexachlorocyclotriphosphazene and acetonitrile were placed in a reactor, stirred and dissolved, and then heated to 45-50°C. A mixed solution of 3-amino-1,2,4-triazole and deionized water was added, stirred evenly, and then sodium hydroxide solid was added. The mixture was refluxed for 6-7 hours. After the reaction was completed, the product was evaporated and dried. The solid product was fully dissolved in methanol, filtered to obtain the filtrate, and then evaporated and dried to prepare the substituted cyclotriphosphazene. III. Take the cyclic triphosphazene substituted product and cobalt nitrate hexahydrate into a high-pressure reactor, add deionized water and stir to mix evenly, then add sodium hydroxide solid and stir thoroughly. Purge the reaction with nitrogen gas and place it at 180~185℃ for 10~12h. After the reaction is completed, centrifuge, wash and dry to prepare the cyclic triphosphazene derivative. IV. Take a cyclotriphosphazene derivative and N,N-dimethylformamide in a reactor, add 3-chloropropyltrimethoxysilane dropwise over 1 hour using a dropping funnel, then add triethylamine acid binder, purge the reaction with nitrogen, and continue the reaction at 75-85°C for 6-8 hours. After the reaction is completed, filter, rotary evaporate, and dry to prepare a functionalized silane coupling agent. V. Take coated ammonium polyphosphate and ultrasonically disperse it in anhydrous ethanol and deionized water, then add functionalized silane coupling agent, and stir the reaction at 55~70℃ for 4~6h. After the reaction is completed, filter, wash and dry to prepare modified ammonium polyphosphate.

5. The flame-retardant extruded insulated low-voltage power cable according to claim 4, characterized in that, In step I, the mass ratio of ammonium polyphosphate, dimethyldiethoxysilane, and tetraethyl orthosilicate is 4.5~6:1:

1.

6. The flame-retardant extruded insulated low-voltage power cable according to claim 4, characterized in that, In step II, the molar ratio of hexachlorocyclotriphosphazene and 3-amino-1,2,4-triazole is 1:

6.

7. The flame-retardant extruded insulated low-voltage power cable according to claim 4, characterized in that, In step III, the molar ratio of the cyclotriphosphazene substituent to cobalt nitrate hexahydrate is 1:

2.

8. The flame-retardant extruded insulated low-voltage power cable according to claim 1, characterized in that, The preparation method of the sheath layer material includes the following steps: weigh each component according to the weight parts, mix low-density polyethylene, ethylene propylene diene monomer (EPDM) rubber, ethylene-tetrafluoroethylene copolymer, modified halloysite nanotubes, modified ammonium polyphosphate, dicumyl peroxide, triallyl isocyanurate, plasticizer and lubricant evenly, and then put them into a twin-screw extruder for extrusion molding to prepare the sheath layer material. The plasticizer is one or more of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate; the lubricant is polyethylene wax or oxidized polyethylene wax.

9. The flame-retardant extruded insulated low-voltage power cable according to claim 8, characterized in that, The method for preparing the flame-retardant extruded insulated low-voltage power cable includes the following steps: S1. A copper rod is drawn using a wire drawing machine to obtain copper wire, which is then annealed to obtain a conductor. Then, at least two of the conductors are twisted together to obtain a conductor core. S2. Use an extruder to extrude a cross-linked polyethylene insulation layer onto the outside of the conductor core; S3. PP filler rope is used to fill the outside of the insulation layer to form a filler layer; S4. Extruding sheath material onto the outside of the filler layer to form an inner sheath layer; S5. Tin-plated copper wire is used to braid the outer side of the inner sheath layer, with a braiding density of ≥90%, to form an armor layer. S6. An outer sheath layer is formed by extruding sheath material on the outside of the armor layer to prepare a flame-retardant extruded insulated low-voltage power cable.

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