A high flame-retardant cable sheathing material and its preparation method

Abstract

This application provides a highly flame-retardant cable sheathing material and its preparation method. The highly flame-retardant cable sheathing material comprises the following raw materials in parts by weight: 100 parts polyethylene resin, 20-30 parts ethylene-vinyl acetate copolymer, 3-15 parts flame retardant, 5-15 parts functional agent, 20-30 parts plasticizer, 3-5 parts heat stabilizer, and 1-2 parts lubricant; the flame retardant is PN-rGO@LDH material; the functional agent is a zinc carbonate and zinc phytate composite. Through the addition of the above flame retardant and functional agent, the cable sheathing material obtained in this application exhibits excellent flame-retardant properties, meeting the application requirements of cables under high safety requirements.

Description

Technical Field

[0001] This disclosure relates to the field of cable sheathing materials, specifically to a highly flame-retardant cable sheathing material and its preparation method. Background Technology

[0002] The flame retardancy of cable sheathing materials directly affects the safety and stability of cables. With increasing demands for flame retardancy and safety in fields such as new energy and rail transportation, traditional halogenated flame retardant materials face severe challenges. Traditional cable sheathing materials mostly rely on high-filler flame retardants, but high filler rates can affect the material's mechanical properties, failing to meet the demands of high-performance cable materials. To improve the flame retardancy of cable materials, researchers have recently begun exploring composite materials and functional modification technologies.

[0003] For example, the introduction of graphene materials has improved the flame retardancy and thermal stability of cable sheathing materials, becoming a research hotspot for new flame-retardant cable materials. Patent CN120554734A proposes a cross-linked polyethylene insulated flame-retardant power cable. The power cable sheathing material, made from raw materials such as low-density polyethylene, high-density polyethylene, phosphate-modified yttrium-graphene nanoporous particles, hydroxyapatite porous nanorods, cross-linking agents, co-cross-linking agents, and antioxidants, exhibits excellent insulation and flame retardancy.

[0004] However, the problem with the aforementioned patent is that the phosphate-modified yttrium-graphene nanoporous particles in the application may rely more on gas-phase flame retardancy than solid-phase flame retardancy. Although this gas-phase flame retardancy can slow down the spread of flames to some extent, it does not effectively isolate oxygen through the physical barrier of the carbon layer like traditional carbonized materials. At high temperatures, the flame retardancy may decrease due to thermal decomposition.

[0005] Therefore, there is a need to provide a cable sheathing material with high flame retardancy that has a gas-solid synergistic flame retardant system. Summary of the Invention

[0006] This application provides a highly flame-retardant cable sheathing material and its preparation method.

[0007] In a first aspect, this application provides a highly flame-retardant cable sheathing material, comprising the following raw materials in parts by weight: 100 parts of polyethylene resin, 20-30 parts of ethylene-vinyl acetate copolymer, 3-15 parts of flame retardant, 5-15 parts of functional agent, 20-30 parts of plasticizer, 3-5 parts of heat stabilizer, and 1-2 parts of lubricant; the flame retardant is PN-rGO@LDH material, which is obtained by phosphorus and nitrogen co-doping modification of graphene oxide and composite layered bimetallic hydroxide, and the surface of the PN-rGO@LDH material is grafted with polydimethylsiloxane segments; the functional agent includes a zinc carbonate and zinc phytate composite, wherein the zinc phytate is coated on the surface of zinc carbonate.

[0008] According to this application, polyethylene resin, as the main matrix, has excellent electrical insulation, chemical corrosion resistance, and certain mechanical strength. Ethylene-vinyl acetate copolymer can be used as a flexible adjustment phase, which can improve the flexibility of the material after introduction, while optimizing the compatibility and dispersibility of the filler. The flame retardant is a modified graphene composite material, which retains the excellent thermal conductivity and barrier properties of graphene. The functional agent is selected from zinc compounds, which can promote the formation of char layer and inhibit smoke release under combustion conditions. Furthermore, when the flame retardant in the raw materials is 5-10 parts and the functional agent is 8-12 parts, the flame retardant performance of the cable sheathing material is better.

[0009] Specifically, the flame retardant PN-rGO@LDH composite material in the cable sheathing material is obtained by modifying graphene oxide with phosphorus and nitrogen co-doping and then composite with layered double metal hydroxide (LDH). The two-dimensional layered structure and high specific surface area of ​​graphene can act as a physical barrier in the material, and can also promote the formation of a denser and continuous char layer during combustion. The doped phosphorus element in PN-rGO usually exists in the form of phosphate or phosphate ions. At high temperatures, phosphate or phosphate ions can dehydrate and promote the carbonization reaction, which helps to form a phosphorus-rich char layer and improve thermal stability. The doped nitrogen element in PN-rGO usually exists in the form of CN. Under high-temperature conditions, the CN bond decomposes and releases nitrogen-containing gases. These gases can dilute the concentration of combustible gases and inhibit the combustion chain reaction; while L When DH decomposes under heat, it releases interlayer water and carbon dioxide, which can play a role in heat absorption and cooling. Furthermore, the siloxane film generated by the decomposition of PDMS at high temperature can cover the surface of the carbon layer, blocking the micropores of the carbon layer formed by PN-rGO and LDH. At the same time, the metal oxides of siloxane and LDH decomposition can form a relatively stable high-temperature resistant barrier layer. In addition, the sheet-like covering layer formed by LDH on the surface of PN-rGO and the combination of PN-rGO form a double barrier structure, which can prolong the heat diffusion path. Under combustion conditions, LDH releases CO2 gas in the early stage, and PN-rGO releases nitrogen-containing gas in the middle stage, which can form gas phase flame retardancy. In the later stage, the phosphorus element in PN-rGO can promote the graphitization of the carbon layer to form condensed phase flame retardancy. Together, they constitute a multi-flame retardant mechanism coupling system, which can significantly improve the flame retardancy of the material.

[0010] On the other hand, the functional agents in the cable sheathing material include a zinc carbonate and zinc phytate composite. The zinc phytate is coated on the surface of the zinc carbonate. At high temperatures, when the temperature reaches the decomposition temperature of zinc carbonate, the CO2 released from the core cannot escape rapidly under the constraint of the shell layer. This dilutes the combustible gas and promotes the moderate expansion of the carbon layer. At the same time, the ZnO generated by decomposition is trapped by the shell carbon layer and catalyzes the cross-linking and densification of the carbon layer in situ, forming a solid barrier of polyphosphate carbon layer and ZnO reinforcement, realizing a continuous connection from gas phase dilution to solid phase barrier. In addition, two-dimensional sheet materials generally have a tendency to accumulate on the surface in polymer matrices. The phosphate released by the decomposition of zinc phytate can supplement the phosphorus catalytic blind zone of PN-rGO@LDH inside the matrix. This creates a gradient charring system where surface charring (dominated by PN-rGO) and internal charring (dominated by zinc phytate) work synergistically. The ZnO from the decomposition of zinc carbonate can also synergistically reinforce the char layer with the Al2O3 from the decomposition of PN-rGO@LDH. The slow-released CO2 from the core and shell, along with the H2O and nitrogen-containing gases released by PN-rGO@LDH, form a stable triple inert gas atmosphere. The polyphosphate in the zinc phytate shell and the PDMS segments grafted onto PN-rGO@LDH can also jointly increase the melt viscosity and suppress dripping. Furthermore, the ZnO-catalyzed crosslinking of the char layer synergistically with the two-dimensional sheet framework of PN-rGO@LDH forms a composite barrier of graphene, polyphosphate, and metal oxides, further enhancing the flame retardant properties of the material.

[0011] Therefore, the cable sheathing material in this application achieves a synergistic effect of multiple flame retardant mechanisms through flame retardants and functional agents, resulting in a better flame retardant effect and meeting the high flame retardancy requirements of cable sheathing layers.

[0012] In some embodiments, the preparation method of the PN-rGO@LDH material includes the following steps:

[0013] S1: Graphene oxide is dispersed in water to obtain a GO dispersion;

[0014] S2: Add nitrogen-containing precursor and phosphorus-containing precursor to GO dispersion and mix to react the nitrogen-containing precursor and phosphorus-containing precursor with GO to obtain PN-rGO;

[0015] S3: Dissolve divalent and trivalent metal salts in water to obtain a mixed solution of metal salts;

[0016] S4: Disperse PN-rGO in water, add a mixed solution of metal salts, and adjust the pH to allow the divalent and trivalent metal salts to form a layered double metal hydroxide that is deposited on PN-rGO, thus obtaining PN-rGO@LDH material;

[0017] S5: React PN-rGO@LDH with an epoxy coupling agent to obtain epoxy-modified PN-rGO@LDH;

[0018] S6: React epoxy-modified PN-rGO@LDH with monohydroxy-terminated polydimethylsiloxane to react the hydroxyl groups with the epoxy groups on PN-rGO@LDH, thereby obtaining PN-rGO@LDH with polydimethylsiloxane segments grafted on the surface, which is used as PN-rGO@LDH material.

[0019] In some of the above embodiments, a method for preparing PN-rGO@LDH material is described. Specifically, graphene oxide is reacted with a nitrogen-containing precursor and a phosphorus-containing precursor to obtain PN-rGO material. A layered double metal hydroxide is then deposited on the surface of PN-rGO to form PN-rGO@LDH material. In the material prepared by the above method, the interface between LDH and PN-rGO is coordinated through metal ion-oxygen-containing groups, which may form an interface confinement effect and enhance the barrier effect. The two-dimensional sheets of rGO and the metal oxides formed by the thermal decomposition of LDH may further construct a "carbon-oxide" dual physical composite barrier. The high thermal conductivity of PN-rGO and the endothermic decomposition characteristics of LDH work synergistically to suppress local overheating and delay flame spread, thereby effectively improving the flame retardancy of cable sheathing materials.

[0020] Furthermore, the surface of the PN-rGO@LDH is grafted with polydimethylsiloxane segments. A method for grafting polydimethylsiloxane segments onto the surface of PN-rGO@LDH is described: PN-rGO@LDH is reacted with an epoxy coupling agent, causing active sites such as hydroxyl groups on the material surface to chemically bond with the epoxy coupling agent. The resulting epoxy-modified PN-rGO@LDH is then reacted with a monohydroxyl-terminated polydimethylsiloxane, causing the hydroxyl groups to react with the epoxy groups on the PN-rGO@LDH, resulting in PN-rGO@LDH with polydimethylsiloxane segments grafted onto its surface. Polydimethylsiloxane segments possess good flexibility and hydrophobicity. After grafting, they can reduce the surface energy of the material, inhibit filler agglomeration, improve the dispersibility and compatibility of flame retardants in the resin matrix, and may decompose at high temperatures to produce a low-molecular-weight siloxane coating layer, thereby improving thermal insulation performance. The number-average molecular weight of the monohydroxy-terminated polydimethylsiloxane is 4000-6000. Using monohydroxy-terminated polydimethylsiloxanes within this range for the reaction results in higher grafting efficiency and helps to form a denser char layer under high-temperature combustion conditions, thereby improving the flame retardancy of the material.

[0021] In some embodiments, the highly flame-retardant cable sheathing material satisfies at least one of the following conditions:

[0022] 1) The nitrogen-containing precursor includes at least one of urea and ammonium salt;

[0023] 2) The phosphorus-containing precursor includes at least one of dihydrogen phosphate, hydrogen phosphate, and ammonium phosphate;

[0024] 3) The divalent metal salt includes at least one of zinc salt, magnesium salt, nickel salt, and cobalt salt;

[0025] 4) The trivalent metal salt includes at least one of aluminum salt, iron salt, and chromium salt.

[0026] In some of the above embodiments, selecting at least one of the nitrogen- and phosphorus-containing precursors for doping allows for easy decomposition to generate active substances during heat treatment, resulting in high doping efficiency. Selecting divalent metal ions can regulate the charge density of the layers, while trivalent metal ions can enhance structural stability, contributing to the formation of a more stable layered bimetallic hydroxide structure and potentially improving the fixation and exchange capacity of anions. Therefore, these preferred conditions help to construct a multi-mechanism flame-retardant system and improve the flame-retardant performance of the material.

[0027] In some embodiments, the preparation method of the PN-rGO@LDH material includes the following steps:

[0028] S1: Disperse 10 parts of graphene oxide in 90-190 parts of water to obtain a GO dispersion;

[0029] S2: Add 10-25 parts of urea and 5-10 parts of NH4H2PO4 to the GO dispersion to obtain a mixture. React the mixture at 140-180℃ for 6-12 hours to obtain PN-rGO.

[0030] S3: Take 5-15 parts of Zn 2+ Metal salt, 2-8 parts Al 3+ Metal salts are dissolved in water to obtain a mixed solution of metal salts;

[0031] S4: Disperse 5 parts of PN-rGO in water, add a mixed solution of metal salts, continue to add Na2CO3 solution, adjust the pH to 9-11, react for 4-8 hours to obtain PN-rGO@ZnAl-LDH;

[0032] S5: Disperse 5 parts of PN-rGO@ZnAl-LDH in 50~150 parts of propylene glycol methyl ether-water solution, add 2~4 parts of γ-glycidoxypropyltrimethoxysilane, adjust the pH to 4.5~5.5, and react at 60~70℃ for 2~4h to obtain a solution of PN-rGO@ZnAl-LDH containing epoxy groups;

[0033] S6: Add 1-2 parts of monohydroxyl-terminated polydimethylsiloxane to a solution containing epoxy-modified PN-rGO@ZnAl-LDH, adjust the pH to 7.5-8.5, and react at 50-100℃ for 6-12 h to obtain PN-rGO@ZnAl-LDH with polydimethylsiloxane segments grafted on the surface, which is used as PN-rGO@LDH material.

[0034] In some of the above embodiments, the preparation method of PN-rGO@LDH material involves dispersing graphene oxide in water to obtain a relatively uniform GO dispersion.

[0035] In step S2, P and N double-doped PN-rGO is obtained in one step to optimize the flame retardant properties of graphene.

[0036] In step S3, Zn is selected. 2+ Metal salts and Al 3+ The better flame-retardant effect of ZnAl-LDH prepared by metal salts may be due to the fact that Zn... 2+ At high temperatures, ZnO can be generated, which can act as a Lewis acid catalyst to promote polymer dehydration and crosslinking, forming a relatively stable carbon layer. Al 3+ A higher charge density can enhance the charge balance and structural stability of LDH layers. Al 3+ OH between LDH layers - When combined, Al2O3 may be formed during thermal decomposition, which can improve the thermal stability of the material, delay thermal decomposition, and at the same time absorb heat and release water vapor.

[0037] In step S4, Na2CO3 solution is added dropwise to adjust the pH. Na2CO3 provides an alkaline environment for Zn. 2+ Al 3+ The precipitation forms hydroxides and may also provide interlayer anions (CO3). 2- Embedded structure, CO3 2- The high charge density helps to form a more stable laminate structure through electrostatic interaction, and the carbonate-type ZnAl-LDH releases CO2 gas at high temperatures, which helps to block the combustion chain reaction.

[0038] In step S5, γ-glycidoxypropyltrimethoxysilane (GPTMS) segments are grafted first. After the Si-(OR)3 in GPTMS is hydrolyzed to generate Si-OH, it can condense with M-OH on the surface of PN-rGO@ZnAl-LDH material to form Si-OM bonds, which are anchored to the surface relatively stably. The Si-O-Zn / Al bond energy is high, which can improve the thermal stability of LDH and help promote the formation of carbon layer at high temperature. The steric hindrance effect of silane segments may also make the filler more uniformly dispersed.

[0039] In step S6, polydimethylsiloxane (PDMS) segments are further grafted onto the surface of the epoxy-modified material. The -OH at the end of PDMS can undergo a ring-opening reaction with the epoxy groups in GPTMS to generate hydroxyl ether bonds, thereby achieving a more stable PDMS graft. PDMS may provide Si-O groups during pyrolysis, which can promote the deposition of inorganic phases in the char layer and make the char layer structure more robust. The decomposition products of PDMS may also form a barrier film on the burning surface, partially blocking oxygen diffusion. In addition, the low surface energy of the long PDMS chain can inhibit the moisture absorption of LDH, and the flexible PDMS segments can also improve the dispersibility of flame retardants, thereby improving the flame retardant efficiency of the material.

[0040] In some embodiments, the method for preparing the functional agent includes:

[0041] M1: A precipitation reaction is carried out between sodium carbonate solution and zinc salt solution to obtain zinc carbonate particles;

[0042] M2: Dissolve phytic acid in water to obtain a phytic acid solution;

[0043] M3: Add zinc salt solution dropwise to phytic acid solution, stir and age to obtain zinc phytate composite solution;

[0044] M4: Add zinc carbonate particles to the zinc phytate composite solution to coat the zinc carbonate surface with zinc phytate, thus obtaining zinc carbonate@zinc phytate particles.

[0045] In some of the above embodiments, a method for preparing zinc carbonate@zinc phytate granular materials as functional agents is described. Specifically, zinc carbonate granules are first obtained through a precipitation reaction, and then the zinc carbonate granules are placed in a zinc phytate composite solution formed by the complexation of phytic acid and zinc salt, so that zinc phytate forms a core-shell structure on the surface of the zinc carbonate granules, thereby obtaining zinc carbonate@zinc phytate granules. The zinc carbonate@zinc phytate granules obtained by this method can improve the flame retardancy of cable sheathing layers. This may be because the zinc carbonate in the zinc carbonate@zinc phytate granules undergoes endothermic decomposition under heating conditions, releasing gas, which weakens the free radical chain reaction through a gas-phase flame retardant mechanism. The decomposition of zinc phytate can generate polyphosphoric acid, which can catalyze the dehydration and cross-linking of polymer molecular chains, forming a three-dimensional network cross-linked carbon layer, thereby increasing melt viscosity. Furthermore, the core-shell structure can inhibit the rapid escape of CO2, prolonging the gas-phase barrier time. Through steric hindrance effects, it may also enhance the performance of the functional agents. Dispersibility; In addition, under heating conditions, the zinc carbonate@zinc phytate functional agent with a core-shell structure first decomposes the zinc phytate shell to generate polyphosphate and PO· free radicals, which play an early char-forming flame retardant role. Subsequently, the zinc carbonate core decomposes again, and the released CO2 gas promotes the melting and foaming of the generated polyphosphate, which can fill the interlayer gaps of PN-rGO@LDH, assist the early char layer expansion, and form a relatively dense graphite layer-porous expansion layer composite barrier structure, realizing the integration of acid source, gas source and carbon source, and improving the flame retardancy and safety of cable sheathing under fire conditions.

[0046] In some embodiments, the method for preparing the functional agent further includes the following steps:

[0047] M5: Disperse zinc carbonate@zinc phytate particles and organosilane in an ethanol-water solution to covalently bond the silane functional groups to the material surface, thereby obtaining silane-modified zinc carbonate@zinc phytate particles; wherein, the organosilane includes γ-aminopropyltriethoxysilane.

[0048] In some of the above embodiments, the surface of the functional agent is modified with an organosilane, and a specific modification method is described. Organosilane modification introduces organic segments and active functional groups onto the surface of zinc carbonate@zinc phytate particles, thereby improving the dispersibility and interfacial compatibility of the material in the organic polymer matrix and reducing agglomeration. The organosilane chosen is γ-aminopropyltriethoxysilane, possibly because it can form Si-O-Si or Si-O-Zn covalent bonds with zinc carbonate@zinc phytate, constructing a denser siloxane layer that acts as a hydrophobic modifier, inhibiting moisture absorption and migration, and improving the stability of the functional agent. At high temperatures, this siloxane layer can also form a more continuous carbon layer, reducing oxygen permeation. Furthermore, γ-aminopropyltriethoxysilane can improve the interfacial bonding between zinc carbonate@zinc phytate and the polymer matrix.

[0049] In some embodiments, the preparation method of the functional agent includes the following steps:

[0050] M1: Dissolve 10 parts of zinc salt in 20-50 parts of water to obtain a zinc salt solution, dissolve 1-5 parts of sodium carbonate in 30-60 parts of water to obtain a sodium carbonate solution, add the sodium carbonate solution to the zinc salt solution, adjust the pH to 9-10, react for 1-3 hours to obtain zinc carbonate granules.

[0051] M2: Dissolve 10-20 parts of phytic acid in 30-50 parts of water, adjust the pH to 4-6, and obtain a phytic acid solution;

[0052] M3: Dissolve 15 parts of zinc salt in 40-80 parts of water to obtain zinc nitrate solution. Add zinc nitrate solution to phytic acid solution and age at pH 4-6 for 2-8 hours to obtain zinc phytate composite solution.

[0053] M4: Add 1-10 parts of zinc carbonate particles to the zinc phytate composite solution and react for 2-6 hours at pH 4-6 and 60-80℃ to obtain zinc carbonate@zinc phytate particles;

[0054] M5: Dissolve 5 parts of zinc carbonate@zinc phytate granules and 0.5~2 parts of γ-aminopropyltriethoxysilane in 40~60 parts of ethanol-water solution, adjust the pH to 4~6, and react at 30~50℃ for 6~10h to obtain silane-modified zinc carbonate@zinc phytate granules.

[0055] In some of the above embodiments, a method for preparing zinc carbonate@zinc phytate granular material as a functional agent is specifically described. The functional agent prepared by the above process conditions can form a good synergistic effect with the flame retardant, thereby improving the flame retardancy of the cable sheathing material.

[0056] In some embodiments, the plasticizer is at least one of polyester plasticizers, phosphate plasticizers, and epoxy plasticizers; the heat stabilizer is at least one of calcium-zinc stabilizers and organosilicon stabilizers; and the lubricant is at least one of stearic acid and its derivatives. Based on the above embodiments, the use of the above additives can give the cable sheathing material better processing fluidity, flexibility, and thermal stability, thereby improving the overall performance of the cable sheathing material.

[0057] Secondly, this application provides a method for preparing a highly flame-retardant cable sheathing material, comprising:

[0058] Raw materials are provided for the highly flame-retardant cable sheathing material according to any embodiment of the first aspect;

[0059] The raw materials are fed into a mixer in proportion, mixed evenly, and then fed into a twin-screw extruder for melt extrusion. After cooling, pelletizing, and drying, a highly flame-retardant cable sheathing material is obtained.

[0060] According to this application, the method can prepare the cable sheathing material of the first aspect, and thus has the beneficial effects of the first aspect, and the obtained cable sheathing material has good flame retardancy.

[0061] Thirdly, this application provides an application of the high flame-retardant cable sheathing material according to any embodiment of the second aspect in the field of flame-retardant cables.

[0062] According to this application, the cable sheathing material prepared by the method according to any embodiment of the second aspect, when applied to the outer sheath or covering layer of a cable, can improve the flame retardant performance of the cable under heated or burning conditions, and exhibits a good effect of delaying the spread of flames. At the same time, the cable sheathing material also has good mechanical properties, which can improve the overall safety and reliability of the cable while meeting the performance requirements of the cable.

[0063] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0064] This application introduces PN-rGO@LDH material as a flame retardant into cable sheathing materials. This leverages the layered barrier properties and high thermal conductivity of graphene. P and N doping enables gas-phase dilution and catalytic char formation. Simultaneously, LDH decomposes endothermally at high temperatures, releasing inert gases. The generated metal oxides promote the densification of the char layer, constructing a multi-layered flame-retardant system with synergistic gas-phase and condensed-phase flame retardancy. Zinc carbonate@zinc phytate is introduced as a functional agent. Zinc carbonate decomposes at high temperatures, endothermally releasing CO2 to dilute combustible gases. The generated ZnO promotes char layer densification. Zinc phytate forms a phosphorus-rich char layer during combustion, further suppressing dripping. The core-shell structure of zinc carbonate@zinc phytate extends the flame-retardant duration through the slow release of active ingredients. Furthermore, zinc carbonate@zinc phytate synergizes with PN-rGO@LDH, constructing an intumescent flame-retardant system and a double-layer barrier, enhancing the overall flame-retardant performance of the material. Detailed Implementation

[0065] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. 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.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0069] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0070] Polyethylene resin: Model is INEOS HDPE 4804;

[0071] Ethylene-vinyl acetate copolymer: ExxonMobil EVA UL00328;

[0072] Single-hydroxyl-terminated polydimethylsiloxane: CAS number 102782-86-5, number average molecular weight approximately 4670;

[0073] γ-glycidyl etheroxypropyltrimethoxysilane: model number KH-560;

[0074] γ-aminopropyltriethoxysilane: Model number KH-550;

[0075] Epoxidized soybean oil: Model number E-10;

[0076] Calcium-zinc heat stabilizer: Model CZ-108;

[0077] Oxidized polyethylene wax: model number OPE WAX 6825.

[0078] Preparation Example 1

[0079] Preparation of PN-rGO@LDH materials:

[0080] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0081] S2: Add 20 parts of urea and 8 parts of NH4H2PO4 to 160 parts of GO dispersion and mix. Transfer the mixture to a high-pressure reactor and react at 160°C for 10 hours. After the reaction is completed, centrifuge, wash 3 times with deionized water, and dry at 80°C for 6 hours to obtain PN-rGO.

[0082] S3: Dissolve 10 parts Zn(NO3)2·6H2O and 5 parts Al(NO3)3·9H2O in 100 parts deionized water to obtain a mixed solution of metal salts;

[0083] S4: Disperse 5 parts of PN-rGO in 75 parts of deionized water, add 100 parts of the metal salt mixed solution described in S3, stir and mix, add Na2CO3 solution dropwise to the mixed solution with a molar concentration of 0.3 mol / L, adjust the pH value to 10, stir and react for 6 h, centrifuge after the reaction is completed, wash 3 times with deionized water, and dry at 80℃ for 6 h to obtain PN-rGO@ZnAl-LDH material;

[0084] S5: Disperse 5 parts of PN-rGO@ZnAl-LDH in 100 parts of propylene glycol methyl ether-water solution (mass ratio of propylene glycol methyl ether to deionized water is 95:5), sonicate (frequency 40kHz, power 200W) for 15min, add 3 parts of γ-glycidoxypropyltrimethoxysilane to the dispersion, adjust the pH to 5 by adding acetic acid dropwise, and react at 65℃ for 3h to obtain a solution containing epoxy-modified PN-rGO@ZnAl-LDH;

[0085] S6: Add 1.5 parts of monohydroxy-terminated polydimethylsiloxane to the above solution, slowly add triethylamine to adjust the pH to 8, raise the temperature to 80℃, react for 8 hours, centrifuge after the reaction, wash three times with deionized water and anhydrous ethanol, and vacuum dry at 70℃ for 12 hours to obtain PN-rGO@ZnAl-LDH material with polydimethylsiloxane segments grafted on the surface, as flame retardant A.

[0086] Preparation Example 2

[0087] Preparation of PN-rGO@LDH materials:

[0088] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0089] S2: Add 20 parts of urea and 8 parts of NH4H2PO4 to 160 parts of GO dispersion and mix. Transfer the mixture to a high-pressure reactor and react at 160°C for 10 hours. After the reaction is completed, centrifuge, wash 3 times with deionized water, and dry at 80°C for 6 hours to obtain PN-rGO.

[0090] S3: Dissolve 10 parts Zn(NO3)2·6H2O and 5 parts Al(NO3)3·9H2O in 100 parts deionized water to obtain a mixed solution of metal salts;

[0091] S4: Disperse 5 parts of PN-rGO in 75 parts of deionized water, add 100 parts of the metal salt mixed solution described in S3, stir and mix, add Na2CO3 solution dropwise to the mixed solution with a molar concentration of 0.3 mol / L, adjust the pH value to 10, stir and react for 6 h, centrifuge after the reaction is completed, wash 3 times with deionized water, and dry at 80℃ for 6 h to obtain PN-rGO@ZnAl-LDH material;

[0092] S5: Disperse 5 parts of PN-rGO@ZnAl-LDH in 100 parts of propylene glycol methyl ether-water solution (mass ratio of propylene glycol methyl ether to deionized water is 95:5), sonicate (frequency 40kHz, power 200W) for 15min, add 4.5 parts of monohydroxy-terminated polydimethylsiloxane to the dispersion, slowly add triethylamine to adjust the pH to 8, raise the temperature to 80℃, react for 8h, centrifuge after the reaction, wash 3 times with deionized water and anhydrous ethanol, and vacuum dry at 70℃ for 12h to obtain PN-rGO@ZnAl-LDH material with polydimethylsiloxane segments grafted on the surface, as flame retardant B.

[0093] Preparation Example 3

[0094] Preparation of PN-rGO@LDH materials:

[0095] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0096] S2: Add 20 parts of urea and 8 parts of NH4H2PO4 to 160 parts of GO dispersion and mix. Transfer the mixture to a high-pressure reactor and react at 160°C for 10 hours. After the reaction is completed, centrifuge, wash 3 times with deionized water, and dry at 80°C for 6 hours to obtain PN-rGO.

[0097] S3: Dissolve 10 parts Zn(NO3)2·6H2O and 5 parts Al(NO3)3·9H2O in 100 parts deionized water to obtain a mixed solution of metal salts;

[0098] S4: Disperse 5 parts of PN-rGO in 75 parts of deionized water, add 100 parts of the metal salt mixed solution described in S3, stir and mix, add Na2CO3 solution dropwise to the mixed solution with a molar concentration of 0.3 mol / L, adjust the pH value to 10, stir and react for 6 h, centrifuge after the reaction is completed, wash 3 times with deionized water, and dry at 80℃ for 6 h to obtain PN-rGO@ZnAl-LDH material;

[0099] S5: Disperse 5 parts of PN-rGO@ZnAl-LDH in 100 parts of propylene glycol methyl ether-water solution (mass ratio of propylene glycol methyl ether to deionized water is 95:5), sonicate (frequency 40kHz, power 200W) for 15min, add 4.5 parts of γ-glycidyl etheroxypropyltrimethoxysilane to the dispersion, adjust the pH to 5 by adding acetic acid dropwise, react at 65℃ for 3h, centrifuge after reaction, wash 3 times with deionized water and anhydrous ethanol, and vacuum dry at 70℃ for 12h to obtain epoxy-modified PN-rGO@ZnAl-LDH material, which is used as flame retardant C.

[0100] Preparation Example 4

[0101] Preparation of PN-rGO@LDH materials:

[0102] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0103] S2: Add 20 parts of urea and 8 parts of NH4H2PO4 to 160 parts of GO dispersion and mix. Transfer the mixture to a high-pressure reactor and react at 160°C for 10 hours. After the reaction is completed, centrifuge, wash 3 times with deionized water, and dry at 80°C for 6 hours to obtain PN-rGO.

[0104] S3: Dissolve 10 parts Zn(NO3)2·6H2O and 5 parts Al(NO3)3·9H2O in 100 parts deionized water to obtain a mixed solution of metal salts;

[0105] S4: Disperse 5 parts of PN-rGO in 75 parts of deionized water, add 100 parts of the metal salt mixed solution described in S3, stir and mix, add Na2CO3 solution dropwise to the mixed solution with a molar concentration of 0.3 mol / L, adjust the pH value to 10, stir and react for 6 h, centrifuge after the reaction is completed, wash 3 times with deionized water, and dry at 80℃ for 6 h to obtain PN-rGO@ZnAl-LDH material, which is used as flame retardant D.

[0106] Preparation Example 5

[0107] Preparation of zinc carbonate@zinc phytate:

[0108] M1: Dissolve 10 parts of Zn(NO3)2·6H2O in 30 parts of deionized water to obtain a zinc nitrate solution. Dissolve 3.5 parts of Na2CO3 in 40 parts of deionized water to obtain a sodium carbonate solution. Slowly add the sodium carbonate solution dropwise to the zinc nitrate solution, adjust the pH to 9.5, stir the reaction for 2 hours, centrifuge after the reaction is complete, wash 3 times with anhydrous ethanol, and vacuum dry at 50℃ for 10 hours to obtain zinc carbonate particles.

[0109] M2: Dissolve 15 parts of phytic acid in 40 parts of deionized water, adjust the pH to 5, and form a phytic acid solution.

[0110] M3: Dissolve 20 parts of zinc nitrate in 60 parts of deionized water to obtain a zinc nitrate solution. Slowly add the zinc nitrate solution dropwise to the phytic acid solution, stir for 2 hours, and then age for 4 hours while maintaining the pH value at 5 to obtain a zinc phytate composite solution.

[0111] M4: Add 5 parts of zinc carbonate granules to 55 parts of the zinc phytate composite solution described in S3, adjust the temperature to 70℃, stir the reaction for 4 hours, keep the pH value at 5, centrifuge after the reaction is completed, wash 3 times with deionized water, and vacuum dry at 50℃ for 10 hours to obtain zinc carbonate@zinc phytate granules.

[0112] M5: Dissolve 5 parts of zinc carbonate@zinc phytate granules and 1 part of γ-aminopropyltriethoxysilane in 50 parts of ethanol-water solution (48 parts of anhydrous ethanol and 2 parts of deionized water), adjust the pH to 5, react at 40℃ for 8 h, centrifuge after reaction, wash 3 times with anhydrous ethanol, and vacuum dry at 50℃ for 10 h to obtain silane-modified zinc carbonate@zinc phytate granules, as functional agent A.

[0113] Preparation Example 6

[0114] Preparation of zinc carbonate@zinc phytate:

[0115] M1: Dissolve 10 parts of Zn(NO3)2·6H2O in 30 parts of deionized water to obtain a zinc nitrate solution. Dissolve 3.5 parts of Na2CO3 in 40 parts of deionized water to obtain a sodium carbonate solution. Slowly add the sodium carbonate solution dropwise to the zinc nitrate solution, adjust the pH to 9.5, stir the reaction for 2 hours, centrifuge after the reaction is complete, wash 3 times with anhydrous ethanol, and vacuum dry at 50℃ for 10 hours to obtain zinc carbonate particles.

[0116] M2: Dissolve 15 parts of phytic acid in 40 parts of deionized water, adjust the pH to 5, and form a phytic acid solution.

[0117] M3: Dissolve 20 parts of zinc nitrate in 60 parts of deionized water to obtain a zinc nitrate solution. Slowly add the zinc nitrate solution dropwise to the phytic acid solution, stir for 2 hours, and then age for 4 hours while maintaining the pH value at 5 to obtain a zinc phytate composite solution.

[0118] M4: Add 5 parts of zinc carbonate granules to 55 parts of the zinc phytate composite solution described in S3, adjust the temperature to 70℃, stir and react for 4 hours, keep the pH value at 5, centrifuge after the reaction is completed, wash 3 times with deionized water, and vacuum dry at 50℃ for 10 hours to obtain zinc carbonate@zinc phytate granules, which are used as functional agent B.

[0119] Comparative Preparation Example 1

[0120] Preparation of PN-rGO:

[0121] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0122] S2: Add 20 parts of urea and 8 parts of NH4H2PO4 to 160 parts of GO dispersion and mix. Transfer the mixture to a high-pressure reactor and react at 160°C for 10 hours. After the reaction is complete, centrifuge, wash three times with deionized water, and dry at 80°C for 6 hours to obtain PN-rGO, which is used as flame retardant E.

[0123] Comparative Preparation Example 2

[0124] Preparation of rGO@LDH:

[0125] S1: Disperse 10 parts of graphene oxide in 150 parts of deionized water and sonicate (frequency 40kHz, power 200W) for 30min to obtain GO dispersion;

[0126] S2: The dispersion was transferred to a high-pressure reactor and treated at 160°C for 10 hours. After treatment, it was centrifuged, washed three times with deionized water, and dried at 80°C for 6 hours to obtain rGO.

[0127] S3: Dissolve 10 parts Zn(NO3)2·6H2O and 5 parts Al(NO3)3·9H2O in 100 parts deionized water to obtain a mixed solution of metal salts;

[0128] S4: Disperse 5 parts of rGO in 75 parts of deionized water, add 100 parts of the metal salt mixed solution described in S3, stir and mix, add Na2CO3 solution dropwise to the mixed solution with a molar concentration of 0.3 mol / L, adjust the pH value to 10, stir and react for 6 h, centrifuge after the reaction is completed, wash 3 times with deionized water, and dry at 80℃ for 6 h to obtain rGO@ZnAl-LDH material, which is used as flame retardant F.

[0129] Comparative preparation example 3

[0130] Preparation of zinc carbonate:

[0131] M1: Dissolve 10 parts of Zn(NO3)2·6H2O in 30 parts of deionized water to obtain a zinc nitrate solution. Dissolve 3.5 parts of Na2CO3 in 40 parts of deionized water to obtain a sodium carbonate solution. Slowly add the sodium carbonate solution to the zinc nitrate solution, adjust the pH to 9.5, stir the reaction for 2 hours, centrifuge after the reaction is complete, wash three times with anhydrous ethanol, and vacuum dry at 50℃ for 10 hours to obtain zinc carbonate particles, which are used as functional agent C.

[0132] Comparative preparation example 4

[0133] Preparation of zinc phytate:

[0134] M1: Dissolve 15 parts of phytic acid in 40 parts of deionized water, adjust the pH to 5, and form a phytic acid solution.

[0135] M2: Dissolve 20 parts of zinc nitrate in 60 parts of deionized water to obtain a zinc nitrate solution. Slowly add the zinc nitrate solution dropwise to a phytic acid solution, stir for 2 hours, and then age for 4 hours while maintaining the pH at 5 to obtain a zinc phytate complex solution. Centrifuge the solution, wash it three times with deionized water, and vacuum dry it at 50°C for 10 hours to obtain zinc phytate particles, which are used as functional agent D.

[0136] Example 1

[0137] Preparation of high flame-retardant cable sheathing materials:

[0138] N1: Dry polyethylene resin and ethylene-vinyl acetate copolymer at 80°C for 3 hours;

[0139] N2: Add 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 8 parts of flame retardant A, 10 parts of functional agent A, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax to a mixer and mix at 800 rpm for 15 minutes to obtain a mixture.

[0140] N3: The mixture is fed into a twin-screw extruder for melt extrusion. The feeding temperature is set to 135℃, the compression section temperature to 155℃, the melting section temperature to 160℃, the homogenization section temperature to 165℃, and the extrusion section temperature to 160℃. After extrusion, the mixture is cooled, pelletized, and dried to obtain a highly flame-retardant cable sheathing material.

[0141] Example 2

[0142] Preparation of high flame-retardant cable sheathing materials:

[0143] Similar to Example 1, the only difference is the mass fraction of flame retardant and functional agent in N2. Specifically, 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 4 parts of flame retardant A, 14 parts of functional agent A, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax are added to a mixer and mixed at 800 rpm for 15 minutes to obtain a mixture.

[0144] Example 3

[0145] Preparation of high flame-retardant cable sheathing materials:

[0146] Similar to Example 1, the only difference is the mass fraction of flame retardant and functional agent in N2. Specifically, 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 12 parts of flame retardant A, 6 parts of functional agent A, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax are added to a mixer and mixed at 800 rpm for 15 minutes to obtain a mixture.

[0147] Example 4

[0148] Preparation of high flame-retardant cable sheathing materials:

[0149] It is largely the same as Example 1, except that flame retardant A in N2 is replaced with flame retardant B.

[0150] Example 5

[0151] Preparation of high flame-retardant cable sheathing materials:

[0152] It is largely the same as Example 1, except that flame retardant A in N2 is replaced with flame retardant C.

[0153] Example 6

[0154] Preparation of high flame-retardant cable sheathing materials:

[0155] It is largely the same as Example 1, except that flame retardant A in N2 is replaced with flame retardant D.

[0156] Example 7

[0157] Preparation of high flame-retardant cable sheathing materials:

[0158] It is largely the same as Example 1, except that functional agent A in N2 is replaced with functional agent B.

[0159] Comparative Example 1

[0160] Preparation of high flame-retardant cable sheathing materials:

[0161] It is largely the same as Example 1, except that flame retardant A in N2 is replaced with flame retardant E.

[0162] Comparative Example 2

[0163] Preparation of high flame-retardant cable sheathing materials:

[0164] It is largely the same as Example 1, except that flame retardant A in N2 is replaced with flame retardant F.

[0165] Comparative Example 3

[0166] Preparation of high flame-retardant cable sheathing materials:

[0167] Similar to Example 1, except that the functional agent used in N2 is different. It consists of zinc carbonate particles obtained from Comparative Preparation Example 3 and zinc phytate particles obtained from Comparative Preparation Example 4. Specifically, 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 8 parts of flame retardant A, 5 parts of functional agent C, 5 parts of functional agent D, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax are added to a mixer and mixed at 800 rpm for 15 minutes to obtain a mixture.

[0168] Comparative Example 4

[0169] Preparation of high flame-retardant cable sheathing materials:

[0170] Similar to Example 1, the only difference is that no functional agent was added to N2. Specifically, 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 18 parts of flame retardant A, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax were added to a mixer and mixed at 800 rpm for 15 minutes to obtain a mixture.

[0171] Comparative Example 5

[0172] Preparation of high flame-retardant cable sheathing materials:

[0173] Similar to Example 1, except that no flame retardant was added to N2. Specifically, 100 parts of polyethylene resin, 25 parts of ethylene-vinyl acetate copolymer, 18 parts of triphenyl phosphate, 7 parts of epoxidized soybean oil, 18 parts of functional agent A, 4 parts of calcium-zinc heat stabilizer, 1 part of calcium stearate, and 0.5 parts of oxidized polyethylene wax were added to a mixer and mixed at 800 rpm for 15 minutes to obtain a mixture.

[0174] Test section

[0175] The cable materials prepared in Examples 1-7 and Comparative Examples 1-5 were subjected to performance tests. The limiting oxygen index (LOI) was tested using an oxygen index tester in accordance with the standard method ASTM D2863. The UL-94 flame retardancy rating was tested using a horizontal-vertical burning test apparatus in accordance with the vertical burning test. The tensile strength was tested using an electronic universal testing machine in accordance with the national standard GB / T1040.1-2018. The test results are shown in Table 1.

[0176] Table 1

[0177]

[0178] As can be seen from Examples 1-7 and Comparative Examples 1-5 in Table 1, the cable sheathing material provided in this application has good flame retardancy and improved mechanical properties, exhibiting good tensile strength. The reasons may be as follows: In Comparative Example 1, the flame retardant is PN-rGO, lacking an LDH layer, thus failing to form a composite barrier and lacking the heat absorption and gas dilution flame retardant effect provided by LDH, resulting in reduced flame retardant performance. Furthermore, the LDH layered structure can physically isolate the PN-rGO sheets, preventing stacking and improving dispersion uniformity. Without LDH, PN-rGO may agglomerate due to van der Waals forces, forming stress concentration points and reducing tensile strength. In Comparative Example 2, the flame retardant is rGO@LDH, which lacks P and N doping, leading to decreased flame retardancy. The reduced interfacial bonding force between the undoped flame retardant and the matrix may also reduce tensile strength. In Comparative Example 3, the functional agent is a blend of zinc carbonate particles and zinc phytate particles. Due to surface energy differences, zinc carbonate and zinc phytate may separate in the resin matrix, forming localized agglomerates. This results in poor mechanical properties, and the lack of a core-shell structure may prevent the effective formation of the ZnO / polyphosphate composite layer, leading to a decrease in flame retardant efficiency. In Comparative Example 4, only flame retardants were added without functional agents. The PN-rGO@LDH material can play a role in gas-phase flame retardancy and condensed-phase flame retardancy, but the lack of functional agents to assist in the expansion and foaming of the carbon layer and the inhibition of dripping by zinc phytate may result in poor flame retardant performance. Furthermore, the lack of functional agents as matrix reinforcement units may reduce the tensile strength of the material. In Comparative Example 5, only functional agents were added without flame retardants. The flame retardant effect brought about by the endothermic decomposition of zinc carbonate and the catalytic carbonization of zinc phytate by the functional agents is very limited, resulting in a significant decrease in flame retardant performance. However, due to the addition of functional agents, the modified interface of the functional agents may improve the interfacial bonding force, thus reducing the decrease in mechanical properties.

[0179] As shown in Examples 1, 2, and 3, the mass ratio of flame retardant and functional agent in the raw materials has a certain influence on the flame retardancy and mechanical properties of the cable sheathing material. When mixed at a certain mass ratio, the flame retardant and functional agent have good dispersibility. The flame retardant can provide a sufficient char skeleton, and the functional agent provides sufficient gas-phase dilution and phosphate catalysis, which can make the generated char layer structure more compact, thereby improving the flame retardancy of the material. In addition, the mechanical properties of the material are also improved. This may be because the core-shell-silane layer structure of the functional agent can form a continuous stress transfer interface in the composite material, reducing interface defects. At the same time, the flexible PDMS segments of the flame retardant can suppress stress concentration and optimize filler dispersibility, thereby improving tensile strength.

[0180] As shown in Examples 1, 4-6, changes in the preparation process of PN-rGO@LDH material have a certain impact on the flame retardancy and mechanical properties of cable sheathing materials. When only PDMS is added during the surface modification process, PDMS can only be combined with the hydroxyl groups on the LDH surface through condensation of terminal hydroxyl groups. The sheathing layer is relatively loose and may migrate or form agglomerates during the melt co-extrusion stage, resulting in a small improvement in flame retardancy and mechanical properties. When only epoxy groups are modified on the PN-rGO@LDH material, the epoxy layer can improve the compatibility and dispersibility of the particle-matrix interface to a certain extent, which is beneficial to improving the flame retardancy efficiency. However, under combustion conditions, epoxy groups may decompose to produce combustible small molecules or discontinuous coking products, thereby weakening the thermal barrier effect and limiting the flame retardancy improvement effect. However, epoxy groups can improve the interfacial rigidity, which is beneficial to maintaining mechanical strength. Modifying the surface of PN-rGO@LDH material with epoxy groups before grafting PDMS segments can improve the grafting density and coverage uniformity of PDMS, making it less likely to migrate or peel off during processing or at high temperatures, thereby improving flame retardancy and tensile strength.

[0181] As shown in Examples 1 and 7, silane modification of the surface of zinc carbonate@zinc phytate has a certain impact on the flame retardancy and mechanical properties of cable sheathing materials. γ-aminopropyltriethoxysilane can enhance interfacial bonding and promote uniform dispersion. At the same time, the silane layer decomposes at high temperature to generate silicon-oxygen precursors, which can synergistically form a composite barrier layer with the phosphorus-catalyzed carbonization of zinc phytate. Modifying the functional agent with γ-aminopropyltriethoxysilane can improve the flame retardancy and tensile strength of the material.

[0182] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A highly flame retardant cable covering material, characterized by, The following raw materials are included by mass parts: polyethylene resin 100 parts, ethylene-vinyl acetate copolymer 20-30 parts, flame retardant 3-15 parts, functional agent 5-15 parts, plasticizer 20-30 parts, heat stabilizer 3-5 parts, lubricant 1-2 parts; The flame retardant is a PN-rGO@LDH material, which is obtained by phosphorus and nitrogen co-doping modification of graphene oxide and compounding with layered double hydroxide, and the surface of the PN-rGO@LDH material is grafted with polydimethylsiloxane segments; the functional agent includes a zinc carbonate and zinc phytate composite, and the zinc phytate is coated on the surface of the zinc carbonate.

2. The high flame retardant cable covering material according to claim 1, characterized in that, The preparation method of the PN-rGO@LDH material includes the following steps: S1: dispersing graphene oxide in water to obtain a GO dispersion; S2: adding a nitrogen-containing precursor and a phosphorus-containing precursor into the GO dispersion to mix, so that the nitrogen-containing precursor and the phosphorus-containing precursor react with the GO to obtain PN-rGO; S3: dissolving divalent metal salt and trivalent metal salt in water to obtain a metal salt mixed solution; S4: dispersing the PN-rGO in water, adding the metal salt mixed solution, adjusting the pH to make the divalent metal salt and the trivalent metal salt form layered double hydroxide and deposit on the PN-rGO to obtain PN-rGO@LDH; S5: reacting the PN-rGO@LDH with an epoxy-based coupling agent to obtain epoxy-modified PN-rGO@LDH; S6: reacting the epoxy-modified PN-rGO@LDH with monohydroxyl-terminated polydimethylsiloxane to make the hydroxyl react with the epoxy on the PN-rGO@LDH to obtain PN-rGO@LDH grafted with polydimethylsiloxane segments, as the PN-rGO@LDH material.

3. The high flame retardant cable covering material according to claim 2, characterized in that, At least one of the following conditions is met: 1) the nitrogen-containing precursor includes at least one of urea and ammonium salt; 2) the phosphorus-containing precursor includes at least one of dihydrogen phosphate, hydrogen phosphate, and ammonium phosphate; 3) the divalent metal salt includes at least one of zinc salt, magnesium salt, nickel salt, and cobalt salt; 4) the trivalent metal salt includes at least one of aluminum salt, iron salt, and chromium salt.

4. The high flame retardant cable covering material according to any one of claims 1 to 3, characterized in that, The preparation method of the PN-rGO@LDH material includes the following steps: S1: dispersing 10 parts of graphene oxide in 90-190 parts of water to obtain a GO dispersion; S2: adding 10-25 parts of urea and 5-10 parts of NH4H2PO4 into the GO dispersion to obtain a mixed solution, and reacting the mixed solution at 140-180℃ for 6-12h to obtain PN-rGO; S3: 5-15 parts of Zn 2+ metal salt, 2-8 parts of Al 3+ metal salt, dissolved in water to obtain a mixed solution of metal salts; S4: dispersing 5 parts of PN-rGO in water, then adding the metal salt mixed solution, continuously adding Na2CO3 solution to adjust the pH value to 9-11, and reacting for 4-8h to obtain PN-rGO@ZnAl-LDH; S5: 5 parts of PN-rGO@ZnAl-LDH are dispersed in 50-150 parts of propylene glycol methyl ether-water solution, 2-4 parts of γ-glycidoxypropyltrimethoxysilane are continuously added, the pH value is adjusted to 4.5-5.5, and the reaction is carried out at 60-70°C for 2-4 hours to obtain a solution containing PN-rGO@ZnAl-LDH modified with epoxy groups; S6: 1-2 parts of monohydroxyl-terminated polydimethylsiloxane are added to the solution containing PN-rGO@ZnAl-LDH modified with epoxy groups, the pH value is adjusted to 7.5-8.5, and the reaction is carried out at 50-100°C for 6-12 hours to obtain PN-rGO@ZnAl-LDH grafted with polydimethylsiloxane segments as a PN-rGO@LDH material.

5. The high flame retardant cable covering material of claim 1, wherein, The preparation method of the functional agent comprises the following steps: M1: A sodium carbonate solution and a zinc salt solution are subjected to a precipitation reaction to obtain zinc carbonate particles; M2: Phytic acid is dissolved in water to obtain a phytic acid solution; M3: The zinc salt solution is added dropwise to the phytic acid solution, and stirring and aging are carried out to obtain a zinc phytate composite solution; M4: The zinc carbonate particles are added to the zinc phytate composite solution, so that the zinc phytate is coated on the surface of the zinc carbonate to obtain zinc carbonate@zinc phytate particles.

6. The high flame retardant cable covering material according to claim 5, characterized in that, The preparation method of the functional agent further comprises the following steps: M5: The zinc carbonate@zinc phytate particles and organosilane are dispersed in an ethanol-water solution, so that the silane functional groups are covalently bonded to the surface of the material to obtain silane-modified zinc carbonate@zinc phytate particles; wherein the organosilane comprises γ-aminopropyltriethoxysilane.

7. The high flame retardant cable covering material of claim 1, wherein, The plasticizer is at least one of a polyester plasticizer, a phosphate plasticizer, and an epoxy plasticizer; the thermal stabilizer is at least one of a calcium-zinc stabilizer and an organic silicon stabilizer; and the lubricant is calcium stearate.

8. A process for the preparation of a high flame retardant cable covering material, characterized in that, Comprise: Providing raw materials for the high-flame-retardant cable coating material according to any one of claims 1-7; The raw materials are proportionally fed into a mixer, uniformly mixed, and then fed into a twin-screw extruder for melt extrusion, cooling, granulation, and drying to obtain the high-flame-retardant cable coating material.

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