Halogen-free flame-retardant flexible bending-resistant low-voltage power cable and manufacturing method thereof

Abstract

The invention relates to a halogen-free flame-retardant flexible bending-resistant low-voltage power cable and a manufacturing method thereof. An insulating layer of the cable is made of a core-shell type nano composite phase change material, a core layer is made of a polyethylene glycol / paraffin phase change material, a shell layer is made of polyurethane or modified polyamide nano fibers and nano SiO2 particles, and the cable is prepared by adopting a coaxial electrostatic spinning technology. According to the structure, stress can be effectively dispersed when the cable is bent, crack propagation is reduced, the temperature is adjusted through the phase change material, and local overheating is prevented. The three-dimensional network structure enhances the bending resistance of the cable, the bending life is prolonged by 40%-60%, and the halogen-free flame retardant performance is ensured at the same time. The technology realizes collaborative optimization of temperature adjustment, stress buffering and bending resistance, and is suitable for power cables with high requirements.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cable material preparation, and specifically relates to a halogen-free flame-retardant flexible bend-resistant low-voltage power cable and a manufacturing method thereof. BACKGROUND

[0002] Traditional low-voltage power cables mostly use halogen-containing flame-retardant materials, but they release toxic gases when burning, which poses an environmental risk. Although halogen-free flame-retardant cables have advantages in environmental protection, their flame-retardant performance and bend resistance are poor, and especially in high-temperature or frequent bending environments, the cables are easily damaged.

[0003] In addition, the flexibility and bend resistance of power cables are increasingly required, and existing cables have limitations in stress buffering and bend resistance. Overheating is another problem, and traditional cables may cause insulation layer failure in high-temperature environments, affecting the stability of the power system.

[0004] Although some research has attempted to apply phase change materials to cable insulation layers, existing technologies have defects in material uniformity, thermal conductivity, and bend resistance. Therefore, the present application uses a "core-shell" type nano-composite phase change material to solve the problem of uneven dispersion of phase change materials, and through the synergistic effect of elastic polymer and nano-SiO2, the temperature regulation capacity and bend resistance of the cable are enhanced, significantly improving the overall performance and safety of the cable. SUMMARY

[0005] In view of the above problems, the present application proposes a halogen-free flame-retardant flexible bend-resistant low-voltage power cable and a manufacturing method thereof. The cable uses a "core-shell" type nano-composite phase change material and a halogen-free flame-retardant polymer base material, has excellent flame retardancy, flexibility, and bend resistance, and can effectively regulate temperature, adapt to extreme working conditions such as high temperature, high pressure, and bending, and ensure the stability and safety of the power system.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A halogen-free flame-retardant flexible bend-resistant low-voltage power cable, the cable comprises a conductor, an insulation layer and a halogen-free flame-retardant sheath from inside to outside, and the cable is prepared from the following raw materials by weight:

[0008] Conductor: soft copper wire 40-50 parts;

[0009] Core layer: polyethylene glycol 10-20 parts, paraffin 30-40 parts, polyvinyl alcohol 2-5 parts, wherein the mass ratio of polyethylene glycol to paraffin phase change material is 7:3;

[0010] The shell layer: polyurethane or modified polyamide nanofiber 15-25 parts, containing 0.5-1wt% of nano-SiO2 particles modified by silane coupling agent, nano-SiO2 particles 0.1-0.5 parts;

[0011] The insulation layer substrate: polyethylene 60-80 parts, halogen-free flame retardant 20-30 parts, compatibilizer 3-5 parts, antioxidant 0.5-1 part, the "core-shell" type nanocomposite phase change material accounts for 5%-10% of the total mass, the "core-shell" type nanocomposite phase change material 5-10 parts;

[0012] The sheath layer: ethylene-vinyl acetate copolymer 15-20 parts, phosphorus-nitrogen flame retardant 3-5 parts, plasticizer 1-3 parts, lubricant 0.5-2 parts;

[0013] The fiber diameter of the "core-shell" type nanocomposite phase change material is 500-800 nm, and the thickness of the shell layer accounts for 30%-40% of the total diameter of the fiber.

[0014] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein the elongation at break of the polyurethane or modified polyamide nanofiber is 300%-500%.

[0015] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein the particle size of the nano-SiO2 particles is 50-100 nm.

[0016] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein the conductor is composed of a plurality of soft copper wires twisted together, the single wire diameter is 0.1-0.3 mm, and the twisting pitch is 10-15 times the outer diameter of the conductor.

[0017] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein the molecular weight of the polyethylene glycol is 4000-8000, and the paraffin is one or more of n-octadecane, n-nonadecane, n-eicosane and n-heneicosane.

[0018] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein the halogen-free flame retardant is one or more of magnesium hydroxide, aluminum hydroxide and calcium hydroxide, and is surface modified by a silane coupling agent.

[0019] Optionally, the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, wherein a shielding layer is further provided between the insulation layer and the conductor, and the shielding layer is a semi-conductive shielding material with a thickness of 0.1-0.3 mm.

[0020] Optionally, the method for preparing the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, the specific method steps are as follows:

[0021] The preparation method of the "core-shell" type nanocomposite phase change material is as follows:

[0022] S1. Dissolve polyethylene glycol, paraffin or a mixture thereof with polyvinyl alcohol in a solvent, and heat at 300-500 rpm to 60-80°C until completely dissolved;

[0023] S2. Dissolve polyurethane or modified polyamide and nano-SiO2 modified with silane coupling agent in DMF / acetone mixed solvent and ultrasonically disperse for 30-60 min.

[0024] S3. Using a coaxial electrospinning device, the inner and outer spinning solutions are injected into the dual nozzles respectively. Spinning is carried out under the conditions of voltage 15-20 kV, receiving distance 15-20 cm, and propulsion speed 0.5-1 mL / h, and the core-shell type nanocomposite phase change material is collected.

[0025] The method for preparing the cable is as follows:

[0026] S1, polyethylene, halogen-free flame retardant, compatibilizer and antioxidant are added to a mixer and mixed at 120-150℃ for 10-15 minutes to obtain an insulating substrate mixture;

[0027] S2. The biomimetic "core-shell" type nanocomposite phase change material is oriented and cross-laid to form a three-dimensional network structure. It is then added to an extruder along with an insulating substrate mixture and co-extruded at 160-180℃ to coat the conductor. After cooling and shaping, an insulating layer is formed.

[0028] S3. Mix ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant, plasticizer and lubricant, melt blend them in a twin-screw extruder at 150-170℃, and granulate them to obtain sheath material;

[0029] S4. Place the obtained conductor with insulation layer in a sheath extruder, and extrude the sheath material at 160-180℃. After cooling, traction, and winding, a halogen-free flame-retardant flexible bending-resistant low-voltage power cable is obtained.

[0030] Optionally, in the halogen-free flame-retardant flexible bending-resistant low-voltage power cable, the insulation layer remains crack-free after 15,000 90° reciprocating bends, and the insulation resistance ranges from 10 ohms. 13 Ω·m-10 14 Ω·m.

[0031] The beneficial effects of this invention are:

[0032] The halogen-free flame-retardant flexible bending-resistant low-voltage power cable prepared by this invention has excellent flame-retardant properties. Its halogen-free flame-retardant properties can effectively prevent the spread of fire and ensure the safety of the power system. At the same time, the cable exhibits good temperature regulation and bending resistance under high temperature and bending conditions, and the bending life is increased by 40%-60%, which significantly enhances the service life and reliability of the cable. By introducing a core-shell type nanocomposite phase change material, the cable can quickly absorb heat when overheated, effectively avoiding insulation damage caused by local overheating. In addition, the cable remains stable under high bending stress, ensuring its long-term reliable operation in complex environments, and is suitable for various high-requirement power applications. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0034] Figure 1 The heat flow curves of different samples under temperature changes are shown.

[0035] Figure 2 The curves show the change in electrical insulation properties of different samples over time.

[0036] Figure 3 This is an external view of the cable of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] Example 1:

[0039] This embodiment 1 describes a halogen-free, flame-retardant, flexible, and bend-resistant low-voltage power cable, which is prepared from the following raw materials in parts by weight:

[0040] Conductor: 45 parts;

[0041] Core layer: 15 parts polyethylene glycol, 35 parts paraffin wax, 4 parts polyvinyl alcohol;

[0042] Outer shell layer: 20 parts polyurethane nanofibers, 0.2 parts silane-modified nano-SiO2 particles;

[0043] Insulation layer substrate: 70 parts polyethylene, halogen-free flame retardant: 25 parts aluminum hydroxide, compatibilizer: 4 parts maleic anhydride-grafted polyethylene, antioxidant: 1 part benzotriazole.

[0044] Sheath layer: 18 parts ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant: 4 parts triphenyl bisphosphate, plasticizer: 2 parts di(2-ethylhexyl) phthalate, lubricant: 1 part calcium stearate;

[0045] The preparation method of the "core-shell" type nanocomposite phase change material is as follows:

[0046] S1. Mix polyethylene glycol and paraffin wax in a mass ratio of 7:3, dissolve polyvinyl alcohol in dimethyl sulfoxide (DMSO), heat at 400 rpm to 70°C and stir until completely dissolved;

[0047] S2. Dissolve polyurethane nanofibers in DMSO, add nano-SiO2 particles modified with silane coupling agent, stir evenly, and sonicate for 45 min.

[0048] S3. Using a coaxial electrospinning device, the inner and outer spinning solutions are injected into the dual nozzles respectively. Spinning is carried out under the conditions of 18 kV voltage, 18 cm receiving distance and 0.8 mL / h propulsion rate to collect the "core-shell" type nanocomposite phase change material.

[0049] The method for preparing the cable is as follows:

[0050] S1. Add polyethylene, halogen-free flame retardant, compatibilizer and antioxidant to a mixer, and stir and mix at 350 rpm for 12 min at 130℃ to obtain an insulating substrate mixture;

[0051] S2. The prepared biomimetic "core-shell" type nanocomposite phase change material is oriented and cross-laid to form a three-dimensional network structure. It is then added to a twin-screw extruder along with an insulating substrate mixture and co-extruded at 170°C to coat the conductor. After cooling and shaping, an insulating layer is formed. The extruder model is ZS-25 and the screw speed is set to 60 rpm to ensure good mixing and extrusion.

[0052] S3. Ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant, plasticizer and lubricant are mixed and melt-blended at 160°C using a twin-screw extruder. After granulation, sheath material is obtained. The extruder model is TSE-45 and the extrusion rate is 25 kg / h.

[0053] S4. Place the obtained conductor with insulation layer in a sheath extruder, and extrude the sheath material at 170°C. After cooling, traction, and winding, a halogen-free flame-retardant flexible bending-resistant low-voltage power cable is obtained. The cooling temperature is controlled at 25°C, and the traction speed is 1.5 m / min to ensure the dimensional stability of the cable.

[0054] Example 2:

[0055] This embodiment 2 presents a halogen-free flame-retardant flexible bending-resistant low-voltage power cable, which is prepared from the following raw materials in parts by weight:

[0056] Conductor: 45 parts;

[0057] Core layer: 15 parts polyethylene glycol, 35 parts paraffin wax, 4 parts polyvinyl alcohol;

[0058] Outer shell layer: 20 parts polyamide nanofibers, 0.2 parts silane-modified nano-SiO2 particles;

[0059] Insulation layer substrate: 70 parts polyethylene, halogen-free flame retardant: 25 parts aluminum hydroxide, compatibilizer: 4 parts maleic anhydride-grafted polyethylene, antioxidant: 1 part benzotriazole.

[0060] Sheath layer: 18 parts ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant: 4 parts triphenyl bisphosphate, plasticizer: 2 parts di(2-ethylhexyl) phthalate, lubricant: 1 part calcium stearate;

[0061] The preparation method of the "core-shell" type nanocomposite phase change material in Example 2 is the same as that in Example 1;

[0062] The preparation method of the halogen-free flame-retardant flexible bending-resistant low-voltage power cable in this embodiment 2 is the same as that in embodiment 1;

[0063] Comparative Example 1:

[0064] To investigate the effect of core-shell type nanocomposite phase change materials on cable performance, the cable of Comparative Example 1 was prepared from the following parts by weight of raw materials:

[0065] Conductor: 45 parts;

[0066] Core layer: 15 parts polyethylene glycol, 35 parts paraffin wax, 4 parts polyvinyl alcohol;

[0067] Outer shell: 0 parts polyurethane nanofibers, 0 parts silane-modified nano-SiO2 particles;

[0068] Insulation layer substrate: 70 parts polyethylene, halogen-free flame retardant: 25 parts aluminum hydroxide, compatibilizer: 4 parts maleic anhydride-grafted polyethylene, antioxidant: 1 part benzotriazole.

[0069] Sheath layer: 18 parts ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant: 4 parts triphenyl bisphosphate, plasticizer: 2 parts di(2-ethylhexyl) phthalate, lubricant: 1 part calcium stearate;

[0070] The cable is prepared by:

[0071] S1. Add polyethylene, halogen-free flame retardant, compatibilizer and antioxidant to a high-efficiency mixer and stir and mix at 350 rpm for 12 min at 130℃ to obtain an insulating substrate mixture.

[0072] S2. Mix polyethylene glycol and paraffin wax in a 7:3 ratio, add directly to a high-efficiency mixer, and stir at 400 rpm at 70°C to ensure that the polyethylene glycol and paraffin wax are completely dissolved.

[0073] S3. Continue to extrude the mixed material at 170°C to coat the conductor, and form an insulating layer after cooling and shaping.

[0074] S4. Ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant, plasticizer and lubricant are mixed and melt-blended at 160°C using a twin-screw extruder. After granulation, sheath material is obtained. The extruder model is TSE-45 and the extrusion rate is 25 kg / h.

[0075] S5. Place the obtained conductor with insulation layer in a sheath extruder, and extrude the sheath material at 170°C. After cooling, traction, and winding, a halogen-free flame-retardant flexible bending-resistant low-voltage power cable is obtained. The cooling temperature is controlled at 25°C, and the traction speed is 1.5 m / min to ensure the dimensional stability of the cable.

[0076] Comparative Example 2:

[0077] To investigate the effect of SiO2 on cable performance, the cable of Comparative Example 2 was prepared from the following parts by weight of raw materials:

[0078] Conductor: 45 parts;

[0079] Core layer: 15 parts polyethylene glycol, 35 parts paraffin wax, 4 parts polyvinyl alcohol;

[0080] Outer shell: 20 parts polyurethane nanofibers, 0 parts silane-modified nano-SiO2 particles;

[0081] Insulation layer substrate: 70 parts polyethylene, halogen-free flame retardant: 25 parts aluminum hydroxide, compatibilizer: 4 parts maleic anhydride-grafted polyethylene, antioxidant: 1 part benzotriazole.

[0082] Sheath layer: 18 parts ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant: 4 parts triphenyl bisphosphate, plasticizer: 2 parts di(2-ethylhexyl) phthalate, lubricant: 1 part calcium stearate;

[0083] The preparation method of the "core-shell" type nanocomposite phase change material is as follows:

[0084] S1. Mix polyethylene glycol and paraffin wax in a mass ratio of 7:3, dissolve polyvinyl alcohol in DMSO, and heat at 400 rpm to 70°C while stirring until completely dissolved.

[0085] S2. Dissolve polyurethane nanofibers in DMSO, stir evenly, and sonicate for 45 min.

[0086] S3. Using a coaxial electrospinning device, the inner and outer spinning solutions are injected into the dual nozzles respectively. Spinning is carried out under the conditions of 18 kV voltage, 18 cm receiving distance and 0.8 mL / h propulsion rate to collect the "core-shell" type nanocomposite phase change material.

[0087] The cable is prepared by:

[0088] S1. Add polyethylene, halogen-free flame retardant, compatibilizer and antioxidant to a high-efficiency mixer and stir and mix at 350 rpm for 12 min at 130℃ to obtain an insulating substrate mixture.

[0089] S2. The core-shell type nanocomposite phase change material is further extruded and co-extruded at 170°C to coat the conductor. After cooling and shaping, an insulating layer is formed.

[0090] S3. Ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant, plasticizer and lubricant are mixed and melt-blended at 160°C using a twin-screw extruder. After granulation, sheath material is obtained. The extruder model is TSE-45 and the extrusion rate is 25 kg / h.

[0091] S4. Place the obtained conductor with insulation layer in a sheath extruder, and extrude the sheath material at 170°C. After cooling, traction, and winding, a halogen-free flame-retardant flexible bending-resistant low-voltage power cable is obtained. The cooling temperature is controlled at 25°C, and the traction speed is 1.5 m / min to ensure the dimensional stability of the cable.

[0092] Performance testing

[0093] 1. Temperature regulation performance

[0094] To test the temperature regulation performance of the "core-shell" type nanocomposite phase change material in halogen-free flame-retardant flexible bending low-voltage power cables, a 10-20 cm long cable sample was first taken, ensuring the cable surface was flat and the sample was undamaged. Differential scanning calorimetry (DSC) was used. The cable sample was placed in the DSC sample pan, and the temperature range was set from -80°C to 200°C at a heating rate of 10°C / min. The changes in heat flow during heating and cooling were recorded, with particular attention paid to the phase change temperature and latent heat, to evaluate the cable's temperature control capability during temperature changes.

[0095] Table 1. Heat flux data (mW) of different samples at different temperatures.

[0096] Temperature (°C) Example 1 Example 2 Comparative Example 1 Comparative Example 2 -80 -5 -4 -4 -5 -40 -3 -2 -3 -4 0 15 12 10 18 40 30 28 25 33 80 45 42 40 50 120 50 48 45 55 160 45 43 40 48 200 30 25 20 32

[0097] The cables in Examples 1 and 2 exhibited significant heat flow changes within the temperature range of 40°C to 80°C, indicating that the core-shell nanocomposite phase change material possesses excellent temperature regulation performance. However, Comparative Examples 1 and 2 did not show significant heat flow changes, verifying that the temperature control capability of the cable decreased significantly after removing the core-shell nanocomposite phase change material, further demonstrating the crucial role of this material in the cable's temperature control function.

[0098] 2. Bending resistance test

[0099] To test the bending resistance of cables, a cable sample was first prepared, ensuring its surface was flat and undamaged. The cable sample was then fixed in a bending test apparatus, with a bending angle of 90°, and subjected to reciprocating bending 10,000 times. During the bending process, the cable surface was observed for cracks, and changes in the cable's insulation performance, such as insulation resistance and insulation strength, were periodically checked and recorded. The room temperature was maintained at 20-25°C during the test, and the bending rate of the test apparatus was set to 10 reciprocating bends per minute.

[0100] Table 2 Test data of cable bending resistance and insulation resistance variation for different samples

[0101] Sample Crack formation Initial resistance (Ω) Final resistance (Ω) Example 1 No cracks 10 13 ]] 10 12 ]] Example 2 Slight cracks 10 13 ]] 10 12 ]] Comparative Example 1 Obvious cracks 10 13 ]] 10 11 ]] Comparative Example 2 Slight cracks 10 13 ]] 10 12 ]]

[0102] The core-shell nanocomposite phase change material used in Example 1 exhibited the best bending resistance, showing no cracks and minimal change in insulation resistance, demonstrating its excellent temperature control and bending performance. While Examples 2 and Comparative Example 2 showed some bending resistance, cracks appeared, and the insulation resistance decreased rapidly. Comparative Example 1, by removing the core-shell nanocomposite phase change material, showed significant crack formation and a substantial decrease in insulation resistance, verifying the importance of nanocomposite materials in improving cable performance.

[0103] 3. Electrical performance (insulation resistance)

[0104] In the insulation resistance test, cable samples of 10-20 cm length were selected, ensuring the sample surface was smooth and undamaged, and the insulation layers at both ends of the cable were intact. Using a MEGGER 5kV digital insulation resistance meter, a 1000V DC voltage was applied, and continuous measurements were taken for 1 min, 2 min, 5 min, 10 min, and 20 min, recording the resistance value each time. The test environment temperature was maintained at 23±2℃, and the humidity at 50±5%. The test data were used to evaluate the electrical insulation performance of the cable under different operating conditions, ensuring its high electrical stability.

[0105] Table 3 Electrical performance test data (Ω·m) for different samples

[0106] Time (min) Example 1 Example 2 Comparative Example 1 Comparative Example 2 1 1.2 x 10 13 ]]> 1.1 x 10 13 ]]> 9.5 x 10 12 ]]> 9.3 x 10 12 ]] 2 1.3 x 10 13 ]]> 1.2 x 10 13 ]]> 9.6 x 10 12 ]]> 9.4 x 10 12 ]] 5 1.5 x 10 13 ]]> 1.4 x 10 13 ]]> 9.7 x 10 12 ]]> 9.5 x 10 12 ]]> 10 1.7 x 10 13 ]]> 1.6 x 10 13 ]]> 9.8 x 10 12 ]]> 9.6 x 10 12 ]] 20 1.8 x 10 13 ]]> 1.7 x 10 13 ]]> 9.9 x 10 12 ]]> 9.7 x 10 12 ]]>

[0107] The resistance values ​​of Examples 1 and 2 changed relatively smoothly at different time points, and gradually increased over time; the resistance values ​​of Comparative Examples 1 and 2 were lower, and their increase was slightly larger, indicating that the cables lacking "core-shell" type nanocomposite phase change materials may have a certain degree of electrical performance degradation.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A halogen-free, flame-retardant, flexible, bend-resistant low-voltage power cable, characterized in that, The cable comprises, from the inside out, a conductor, an insulation layer, and a halogen-free flame-retardant sheath. The cable is made from the following raw materials in parts by weight: Conductor: 40-50 parts of soft copper wire; Core layer: 10-20 parts polyethylene glycol, 30-40 parts paraffin wax, 2-5 parts polyvinyl alcohol, wherein the mass ratio of polyethylene glycol to paraffin wax phase change material is 7:3; Outer shell layer: 15-25 parts of polyurethane or modified polyamide nanofibers, containing 0.5-1 wt% of nano-SiO2 particles modified with silane coupling agent, and 0.1-0.5 parts of nano-SiO2 particles; Insulation layer substrate: 60-80 parts polyethylene, 20-30 parts halogen-free flame retardant, 3-5 parts compatibilizer, 0.5-1 part antioxidant, the "core-shell" type nanocomposite phase change material accounts for 5%-10% of the total mass, and 5-10 parts of the "core-shell" type nanocomposite phase change material. Sheath layer: 15-20 parts ethylene-vinyl acetate copolymer, 3-5 parts phosphorus-nitrogen flame retardant, 1-3 parts plasticizer, 0.5-2 parts lubricant; The core-shell type nanocomposite phase change material has a fiber diameter of 500-800 nm, and the outer shell layer thickness accounts for 30%-40% of the total fiber diameter.

2. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, The elongation at break of the polyurethane or modified polyamide nanofibers is 300%-500%.

3. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, The particle size of the nano-SiO2 particles is 50-100 nm.

4. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, The conductor is made of multiple strands of soft copper wire twisted together, with a single wire diameter of 0.1-0.3 mm and a twist pitch of 10-15 times the outer diameter of the conductor.

5. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, The polyethylene glycol has a molecular weight of 4000-8000, and the paraffin is one or more of n-octadecane, n-nonadecane, n-eicosane, and n-docosahexadecane.

6. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, The halogen-free flame retardant is one or more of magnesium hydroxide, aluminum hydroxide, and calcium hydroxide, and is surface-modified with a silane coupling agent.

7. The halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, A shielding layer is also provided between the insulating layer and the conductor. The shielding layer is a semi-conductive shielding material with a thickness of 0.1-0.3 mm.

8. A halogen-free, flame-retardant, flexible, bend-resistant low-voltage power cable, as described in any one of claims 1-7, characterized in that... The steps are as follows: The preparation method of the "core-shell" type nanocomposite phase change material is as follows: S1. Dissolve polyethylene glycol, paraffin or a mixture thereof with polyvinyl alcohol in a solvent, and heat at 300-500 rpm to 60-80°C until completely dissolved; S2. Dissolve polyurethane or modified polyamide and nano-SiO2 modified with silane coupling agent in DMF / acetone mixed solvent and ultrasonically disperse for 30-60 min. S3. Using a coaxial electrospinning device, the inner and outer spinning solutions are injected into the dual nozzles respectively. Spinning is carried out under the conditions of voltage 15-20 kV, receiving distance 15-20 cm, and propulsion rate 0.5-1 mL / h, and the core-shell type nanocomposite phase change material is collected. The method for preparing the cable is as follows: S1. Add polyethylene, halogen-free flame retardant, compatibilizer and antioxidant to a mixer and mix at 120-150℃ for 10-15 minutes to obtain an insulating substrate mixture; S2. The biomimetic "core-shell" type nanocomposite phase change material is oriented and cross-laid to form a three-dimensional network structure. It is then added to an extruder along with an insulating substrate mixture and co-extruded at 160-180℃ to coat the conductor. After cooling and shaping, an insulating layer is formed. S3. Mix ethylene-vinyl acetate copolymer, phosphorus-nitrogen flame retardant, plasticizer and lubricant, melt blend them in a twin-screw extruder at 150-170℃, and granulate them to obtain sheath material; S4. Place the obtained conductor with insulation layer in a sheath extruder, and extrude the sheath material at 160-180℃. After cooling, traction, and winding, a halogen-free flame-retardant flexible bending-resistant low-voltage power cable is obtained.

9. A halogen-free flame-retardant flexible bending-resistant low-voltage power cable according to claim 1, characterized in that, After being bent 15,000 times at 90° angles, the cable showed no cracks in its insulation layer, and its insulation resistance ranged from 10 ohms. 13 Ω·m-10 14 Ω·m.

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