Low-smoke halogen-free flame-retardant cable for charging pile

Abstract

The invention discloses a low-smoke halogen-free flame-retardant cable for a charging pile, and belongs to the technical field of cables. The cable sequentially comprises a conductor, an insulating layer and an outer sheath layer from inside to outside, the conductor is formed by mutually twisting copper-tin alloy wires; the insulating layer is made of butadiene styrene rubber; the outer sheath layer is prepared from the following components in parts by weight: 40 to 60 parts of high-density polyethylene, 15 to 20 parts of acrylate rubber, 10 to 15 parts of ethylene-vinyl acetate copolymer, 8 to 10 parts of modified silicon dioxide, 3 to 8 parts of compatilizer, 1 to 2 parts of antioxidant and 1 to 2 parts of lubricant. The prepared modified silicon dioxide is used as a flame-retardant reinforcing component in the outer sheath layer, and the comprehensive performance of the low-smoke halogen-free flame-retardant cable for the charging pile can be remarkably improved.

Description

A low-smoke halogen-free flame-retardant cable for charging piles Technical Field

[0001] This invention belongs to the field of cable technology, specifically, it relates to a low-smoke halogen-free flame-retardant cable for charging piles. Background Technology

[0002] With the rapid development of new energy vehicles, charging piles, as a key supporting facility, face increasingly stringent safety requirements. Charging pile cables must operate stably in complex outdoor environments for extended periods and possess excellent flame-retardant, low-smoke, and halogen-free properties to minimize fire risks and the generation of toxic and harmful gases, thereby ensuring personal and property safety.

[0003] Currently, halogen-free flame-retardant solutions for charging pile cables mostly employ metal hydroxides (such as aluminum hydroxide and magnesium hydroxide) or phosphorus-nitrogen intumescent flame-retardant systems. Metal hydroxides require high filler content to achieve the desired flame-retardant effect, but this significantly deteriorates the mechanical properties and processing fluidity of the cable. Phosphorus-nitrogen flame retardants can promote char formation during combustion, but the resulting char layer is often loose and lacks strength, easily cracking and peeling under heat flow or flame impact, making it difficult to maintain the flame-retardant barrier effect for long.

[0004] Silica, a common inorganic filler, possesses advantages such as good thermal stability and wide availability, and is often used to enhance the flame retardancy and mechanical properties of polymer materials. However, unmodified silica has a hydrophilic surface, resulting in poor compatibility with hydrophobic polymer matrices (such as high-density polyethylene and ethylene-vinyl acetate copolymers), leading to easy agglomeration and uneven dispersion within the matrix. This not only affects the mechanical and processing properties of cable materials but also makes it difficult for silica to fully exert its reinforcing and stabilizing effect on the char layer during combustion. Furthermore, ordinary silica itself has limited catalytic char formation ability, making its effect on improving the flame retardancy rating of materials rather indirect.

[0005] Therefore, developing a novel flame-retardant reinforcing material that is both compatible with the cable sheath matrix material and can efficiently catalyze the formation of a dense, high-strength residual char layer during combustion is of great practical significance for improving the overall safety performance of charging pile cables. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-smoke halogen-free flame-retardant cable for charging piles.

[0007] The objective of this invention can be achieved through the following technical solution: a low-smoke halogen-free flame-retardant cable for charging piles, comprising, from the inside out: a conductor, an insulation layer, and an outer sheath layer; the conductor is made of copper-tin alloy wires twisted together; the insulation layer is made of styrene-butadiene rubber; the raw materials for preparing the outer sheath layer include the following components: by weight, 40-60 parts high-density polyethylene, 15-20 parts acrylic rubber, 10-15 parts ethylene-vinyl acetate copolymer, 8-10 parts modified silica, 3-8 parts compatibilizer, 1-2 parts antioxidant, and 1-2 parts lubricant.

[0008] Further, the preparation process of the modified silica is as follows: S1: 4-hydroxyphenylboronic acid is added to tetrahydrofuran and stirred at 0°C until dissolved. Triethylamine is slowly added dropwise, and after the addition is complete, the mixture is stirred for 10-12 minutes. Then, diphenyl chlorophosphate is dissolved in tetrahydrofuran and slowly poured into the above system. The mixture is reacted at 0°C for 2-3 hours, then the temperature is raised to room temperature and the reaction continues for 2-3 hours. After the reaction is complete, the mixture is filtered, and the filtrate is slowly poured into deionized water. The precipitated white precipitate is washed and dried to obtain... Intermediate A; S2: Intermediate A, 3-amino-1,2-propanediol, and N,N-dimethylformamide are mixed and stirred at room temperature for 24 h. After the reaction is complete, the mixture is filtered, washed, and dried under vacuum at 80 °C for 24 h to obtain the modifier; S3: Epoxidized silica and the modifier are added to anhydrous N,N-dimethylformamide and stirred at 60-65 °C for 10-12 h. After the reaction is complete, the mixture is filtered, washed 2-3 times with anhydrous ethanol, and dried under vacuum at 80 °C for 12 h to obtain modified silica.

[0009] First, the key modifier is synthesized through a two-step reaction: Under low temperature and triethylamine catalysis, 4-hydroxyphenylboronic acid undergoes esterification with diphenyl chlorophosphate to generate intermediate A, which contains phenylboronic acid groups and phosphorus-oxygen bonds. Subsequently, this intermediate undergoes dehydration condensation with 3-amino-1,2-propanediol in DMF (N,N-dimethylformamide), where its boronic acid groups further form stable boron ester rings with adjacent diol structures, thus yielding a composite modifier possessing a boron ester ring, phosphorus-oxygen bonds, and a terminal active amino group. Finally, under heating conditions, this modifier undergoes a ring-opening reaction between its terminal active amino group and the epoxy groups on the surface of epoxidized silica to obtain modified silica.

[0010] The structure of the modifier is shown below: Furthermore, the raw materials for preparing intermediate A include the following components: by weight, 10-12 parts of 4-hydroxyphenylboronic acid, 200-300 parts of tetrahydrofuran, 6-8 parts of triethylamine, and 15-16 parts of diphenyl chlorophosphate.

[0011] Furthermore, the raw materials for preparing the modifier include the following components: by weight, 10-12 parts of intermediate A, 5-8 parts of 3-amino-1,2-propanediol, and 80-100 parts of N,N-dimethylformamide.

[0012] Furthermore, the raw materials for preparing the modified silica include the following components: by weight, 10-12 parts of epoxidized silica, 2-4 parts of modifier, and 80-100 parts of anhydrous N,N-dimethylformamide.

[0013] Furthermore, the antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2.

[0014] Furthermore, the lubricant is calcium stearate and ethylene bis-stearamide in a mass ratio of 3:1.

[0015] Furthermore, the compatibility is POE-g-GMA.

[0016] The beneficial effects of this invention are as follows: The low-smoke halogen-free flame-retardant cable for charging piles provided by this invention introduces modified silica with a specific structural design into the outer sheath layer. Under high temperature or combustion conditions, modified silica can decompose to produce acidic substances such as phosphoric acid and boric acid. These acidic products effectively catalyze the dehydration and cross-linking of polymer matrices such as high-density polyethylene and ethylene-vinyl acetate copolymer, promoting the rapid formation of a dense and highly graphitized composite carbon layer on the material surface. This carbon layer not only isolates heat and oxygen, inhibiting flame spread and smoke generation, but also, the uniformly distributed silica particles further enhance the mechanical strength and thermal stability of the carbon layer, effectively preventing cracking or detachment under thermal shock, thus maintaining a continuous barrier protection effect. Furthermore, through surface modification treatment of silica, its dispersion and interfacial compatibility in the polymer matrix are significantly improved, allowing for more uniform distribution in the sheath material and effectively improving the overall mechanical strength. Detailed Implementation

[0017] 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.

[0018] Pre-preparation: The preparation process of epoxy silica is as follows: First, γ-glycidoxypropyltrimethoxysilane is dissolved in an ethanol aqueous solution (volume fraction 50%) and stirred on a magnetic stirrer at room temperature for 20 min. Then, nano-silica is added to the mixed solution, the temperature is raised to 80℃, and the mixture is stirred at high speed for 60 min. After centrifugation, washing, drying, and grinding, epoxy silica is obtained. The ratio of γ-glycidoxypropyltrimethoxysilane, ethanol aqueous solution, and nano-silica is 22.8 g: 300 mL: 1 g.

[0019] Example 1: A method for preparing a low-smoke halogen-free flame-retardant cable for charging piles is as follows: Copper-tin alloy wires are twisted together to form a conductor, and styrene-butadiene rubber is extruded over the conductor to form an insulation layer. Then, a sheathing material is extruded and coated onto the surface of the insulation layer to form a sheathing layer. The raw materials for preparing the outer sheathing layer include the following components: by weight, 40 parts high-density polyethylene, 15 parts acrylic rubber, 10 parts ethylene-vinyl acetate copolymer, 8 parts modified silica, 3 parts compatibilizer (POE-g-GMA), 1 part antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2), and 1 part lubricant (calcium stearate and ethylene bis-stearamide in a mass ratio of 3:1). The modified silica is prepared... The preparation process is as follows: S1: Add 10 parts of 4-hydroxyphenylboronic acid to 80 parts of tetrahydrofuran, stir at 0℃ until dissolved, slowly add 6 parts of triethylamine, stir for 10 min after the addition is complete, then dissolve 15 parts of diphenyl chlorophosphate in 120 parts of tetrahydrofuran, slowly pour into the above system, react at 0℃ for 2 h, then raise to room temperature and continue the reaction for 2 h. After the reaction is complete, filter, slowly pour the filtrate into deionized water, wash and dry the precipitated white precipitate to obtain intermediate A; S2: Mix 10 parts of intermediate A, 5 parts of 3-amino-1,2-propanediol and 80 parts of N,N-dimethylformamide, stir and react at room temperature for 24 h, filter, wash, and vacuum dry at 80℃ for 24 hours after the reaction is complete. h, to obtain the modifier; S3: Add 10 parts of epoxidized silica and 2 parts of the modifier to 80 parts of anhydrous N,N-dimethylformamide, stir at 60℃ for 10h, filter after the reaction, wash twice with anhydrous ethanol, and vacuum dry at 80℃ for 12h to obtain modified silica.

[0020] Example 2: A method for preparing a low-smoke halogen-free flame-retardant cable for charging piles is as follows: Copper-tin alloy wires are twisted together to form a conductor, and styrene-butadiene rubber is extruded over the conductor to form an insulation layer. Then, a sheathing material is extruded and coated onto the surface of the insulation layer to form a sheathing layer. The raw materials for preparing the outer sheathing layer include the following components: by weight, 60 parts high-density polyethylene, 20 parts acrylic rubber, 15 parts ethylene-vinyl acetate copolymer, 10 parts modified silica, 8 parts compatibilizer (POE-g-GMA), 2 parts antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2), and 2 parts lubricant (calcium stearate and ethylene bis-stearamide in a mass ratio of 3:1). The modified silica is prepared... The preparation process is as follows: S1: 12 parts of 4-hydroxyphenylboronic acid are added to 100 parts of tetrahydrofuran and stirred at 0°C until dissolved. 8 parts of triethylamine are slowly added dropwise. After the addition is complete, the mixture is stirred for 12 minutes. Then, 16 parts of diphenyl chlorophosphate are dissolved in 200 parts of tetrahydrofuran and slowly poured into the above system. The mixture is reacted at 0°C for 3 hours, then raised to room temperature and reacted for another 3 hours. After the reaction is complete, the mixture is filtered, and the filtrate is slowly poured into deionized water. The precipitated white precipitate is washed and dried to obtain intermediate A; S2: 12 parts of intermediate A, 8 parts of 3-amino-1,2-propanediol, and 100 parts of N,N-dimethylformamide are mixed and stirred at room temperature for 24 hours. After the reaction is complete, the mixture is filtered, washed, and dried under vacuum at 80°C for 24 hours. h, to obtain the modifier; S3: Add 12 parts of epoxidized silica and 4 parts of the modifier to 100 parts of anhydrous N,N-dimethylformamide, stir and react at 65℃ for 12h, filter after the reaction, wash 3 times with anhydrous ethanol, and vacuum dry at 80℃ for 12h to obtain modified silica.

[0021] Example 3: A method for preparing a low-smoke halogen-free flame-retardant cable for charging piles is as follows: Copper-tin alloy wires are twisted together to form a conductor, and styrene-butadiene rubber is extruded over the conductor to form an insulation layer. Then, a sheathing material is extruded and coated on the surface of the insulation layer to form a sheathing layer. The raw materials for preparing the outer sheathing layer include the following components: by weight, 50 parts high-density polyethylene, 17.5 parts acrylic rubber, 12.5 parts ethylene-vinyl acetate copolymer, 9 parts modified silica, 5.5 parts compatibilizer (POE-g-GMA), 1.5 parts antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2), and 1.5 parts lubricant (calcium stearate and ethylene bis-stearamide in a mass ratio of 3:1). The preparation process of the modified silica is as follows: S1: 11 parts of 4-hydroxyphenylboronic acid are added to 90 parts of tetrahydrofuran and stirred at 0°C until dissolved. 7 parts of triethylamine are slowly added dropwise. Amine was added dropwise and stirred for 11 min. Then, 15.5 parts of diphenyl chlorophosphate were dissolved in 160 parts of tetrahydrofuran and slowly poured into the above system. The reaction was carried out at 0℃ for 2.5 h, then raised to room temperature and continued to react for 2.5 h. After the reaction was completed, the mixture was filtered, and the filtrate was slowly poured into deionized water. The precipitated white precipitate was washed and dried to obtain intermediate A. S2: 11 parts of intermediate A, 6.5 parts of 3-amino-1,2-propanediol, and 90 parts of N,N-dimethylformamide were mixed and stirred at room temperature for 24 h. After the reaction was completed, the mixture was filtered, washed, and dried under vacuum at 80℃ for 24 h to obtain the modifier. S3: 11 parts of epoxidized silica and 3 parts of the modifier were added to 90 parts of anhydrous N,N-dimethylformamide and stirred at 62.5℃ for 11 h. After the reaction was completed, the mixture was filtered, washed 2.5 times with anhydrous ethanol, and dried under vacuum at 80℃ for 12 h to obtain modified silica.

[0022] Comparative Example 1: No modification of the epoxy silica is performed. Specifically, the following is a method for preparing a low-smoke halogen-free flame-retardant cable for charging piles: Copper-tin alloy wires are twisted together to form a conductor, and styrene-butadiene rubber is extruded over the conductor to form an insulation layer. Then, a sheathing material is extruded and coated on the surface of the insulation layer to form a sheathing layer. The raw materials for preparing the outer sheathing layer include the following components: by weight, 50 parts high-density polyethylene, 17.5 parts acrylic rubber, 12.5 parts ethylene-vinyl acetate copolymer, 9 parts epoxy silica, 5.5 parts compatibilizer (POE-g-GMA), 1.5 parts antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2), and 1.5 parts lubricant (calcium stearate and ethylene bis-stearamide in a mass ratio of 3:1).

[0023] Testing experiments: The sheath layers of the examples and comparative examples were subjected to the following tests: (1) The tensile strength of the specimens was tested according to standard ASTM D412; (2) The oxygen index of the specimens was tested according to standard GB / T2406.1-2008 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 1: Guidelines"; (3) The smoke density of the specimens was measured according to standard GB / T8323.2-2018; The data obtained are shown in the table below: Conclusion: Experimental data show that using the modified silica prepared in this invention as a flame-retardant reinforcing component in the outer sheath layer can significantly improve the overall performance of low-smoke halogen-free flame-retardant cables for charging piles. Compared with unmodified epoxy silica, the modified silica has better dispersion and interfacial compatibility in the polymer matrix. It not only effectively enhances the mechanical strength of the sheath material, increasing its tensile strength to about 22 MPa, but also exhibits outstanding effects in flame retardancy and smoke suppression: the oxygen index reaches over 33%, indicating that the material has excellent flame-retardant self-extinguishing properties; at the same time, the smoke density is significantly reduced to below 115, indicating that the amount of smoke generated during cable combustion is significantly reduced, meeting the low-smoke safety requirements. This modified silica, through its special structure, catalyzes the formation of a dense, high-strength composite carbon layer at high temperatures, effectively isolating heat and oxygen, inhibiting flame spread and smoke generation, thereby comprehensively improving the safety and reliability of the cable in fire scenarios, especially suitable for charging pile applications with stringent requirements for flame retardancy, low smoke, and halogen-free performance.

[0024] In the description of this specification, the 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 present invention. In this specification, the 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.

[0025] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A low-smoke halogen-free flame-retardant cable for charging piles, characterized in that, From the inside out, it comprises: a conductor, an insulation layer, and an outer sheath layer; the conductor is made of copper-tin alloy wire twisted together; the insulation layer is made of styrene-butadiene rubber; the raw materials for preparing the outer sheath layer include the following components: by weight, 40-60 parts high-density polyethylene, 15-20 parts acrylate rubber, 10-15 parts ethylene-vinyl acetate copolymer, 8-10 parts modified silica, 3-8 parts compatibilizer, 1-2 parts antioxidant, and 1-2 parts lubricant.

2. The low-smoke halogen-free flame-retardant cable for charging piles according to claim 1, characterized in that, The preparation process of the modified silica is as follows: S1: 4-hydroxyphenylboronic acid is added to tetrahydrofuran and stirred at 0°C until dissolved. Triethylamine is slowly added dropwise, and after the addition is complete, the mixture is stirred for 10-12 minutes. Then, diphenyl chlorophosphate is dissolved in tetrahydrofuran and slowly poured into the above system. The mixture is reacted at 0°C for 2-3 hours, then the temperature is raised to room temperature and the reaction continues for 2-3 hours. After the reaction is complete, the mixture is filtered, and the filtrate is slowly poured into deionized water. The precipitated white precipitate is washed and dried to obtain intermediate A; S2: Intermediate A, 3-amino-1,2-propanediol, and N,N-dimethylformamide are mixed and stirred at room temperature for 24 hours. After the reaction is complete, the mixture is filtered, washed, and vacuum dried at 80°C for 24 hours. h, to obtain the modifier; S3: Add epoxidized silica and the modifier to anhydrous N,N-dimethylformamide, stir and react at 60-65℃ for 10-12h, filter after the reaction, wash with anhydrous ethanol 2-3 times, and vacuum dry at 80℃ for 12h to obtain modified silica.

3. The low-smoke halogen-free flame-retardant cable for charging piles according to claim 2, characterized in that, The raw materials for preparing intermediate A include the following components: by weight, 10-12 parts of 4-hydroxyphenylboronic acid, 200-300 parts of tetrahydrofuran, 6-8 parts of triethylamine, and 15-16 parts of diphenyl chlorophosphate.

4. A low-smoke halogen-free flame-retardant cable for charging piles according to claim 2, characterized in that, The raw materials for preparing the modifier include the following components: by weight, 10-12 parts of intermediate A, 5-8 parts of 3-amino-1,2-propanediol, and 80-100 parts of N,N-dimethylformamide.

5. A low-smoke halogen-free flame-retardant cable for charging piles according to claim 2, characterized in that, The raw materials for preparing the modified silica include the following components: by weight, 10-12 parts of epoxidized silica, 2-4 parts of modifier, and 80-100 parts of anhydrous N,N-dimethylformamide.

6. A low-smoke halogen-free flame-retardant cable for charging piles according to claim 1, characterized in that, The antioxidants are antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

2.

7. A low-smoke halogen-free flame-retardant cable for charging piles according to claim 1, characterized in that, The lubricant is calcium stearate and ethylene bis-stearamide in a mass ratio of 3:

1.

8. A low-smoke halogen-free flame-retardant cable for charging piles according to claim 1, characterized in that, The compatibility is POE-g-GMA.

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