Low-smoke halogen-free insulating material and preparation method and application thereof
By combining modified flame retardants with polydopamine-coated ceramic oxides, an oxygen-barrier and heat-insulating protective layer is formed, which solves the problem of decreased material flexibility and mechanical properties caused by high addition of flame retardants in existing technologies, and achieves efficient flame retardancy and smoke suppression as well as improved mechanical properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN HONGYAN WIRE IND CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-05
AI Technical Summary
The high addition amount of existing flame retardants in the polymer matrix leads to a decrease in the flexibility and mechanical properties of the material, as well as poor interfacial compatibility, which affects the molding quality and electrical insulation of the insulation material.
A modified flame retardant with low filler content is combined with polydopamine-coated ceramic oxide to form an oxygen-barrier and heat-insulating protective layer with a dense outer layer and a sparse inner layer. The flame retardant and smoke-suppressing performance is synergistically improved through the endothermic decomposition of the modified flame retardant and the formation of the char layer of the polydopamine-coated oxide, and the stability of the char layer is enhanced through the P–O–C bond cross-linking network.
It improves the flame retardant properties and mechanical strength of the insulation material, enhances the material's processing and mechanical properties, and reduces the amount of flame retardant required, thus preventing cracking and degradation of mechanical properties.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This application relates to the field of cable materials, and in particular to a low-smoke halogen-free insulating material, its preparation method, and its application. Background Technology
[0002] Currently, the mainstream technical route for preparing flame-retardant electrical insulation materials in the industry is to add various flame retardants to the polymer matrix to achieve flame-retardant modification. Among them, halogen-free inorganic flame retardants and phosphorus-nitrogen composite flame retardants are the most widely used categories. In particular, halogen-free flame retardant systems have become the preferred solution for insulation materials of medium and high voltage cables, rail transit cables, and indoor dense power distribution equipment because they release low smoke, non-toxic and non-corrosive gases during combustion, which meets the requirements of environmental protection and fire escape safety.
[0003] However, existing conventional flame retardants generally suffer from core shortcomings such as low flame retardant efficiency and a single flame retardant mechanism. Relying solely on conventional flame retardants requires a significant increase in their proportion in the insulation matrix. In most scenarios, the amount of flame retardant added needs to reach more than 60% of the matrix resin mass, and in some high-flame-retardant scenarios, the amount added even exceeds 150 parts (based on 100 parts of the matrix resin), forming a highly filled flame-retardant system to meet the UL94 V-0 flame retardant standard. This high-addition method of flame retardancy directly leads to a significant deterioration of many key mechanical properties of the insulation material, severely restricting the practical application and service life of the material.
[0004] On the one hand, the addition of large amounts of inorganic or organic flame-retardant fillers will significantly dilute the continuous phase structure of the polymer matrix, destroying the continuity of the molecular chains and the density of the cross-linked network of the matrix material itself, leading to hardening and brittleness of the material and a significant reduction in flexibility. Under cable laying, bending, dragging, and long-term mechanical stress, problems such as cracking, damage, and peeling of the insulation layer are very likely to occur, resulting in a loss of insulation protection. On the other hand, the poor interfacial compatibility between high-volume flame retardants and the polymer matrix makes it easy for filler agglomeration and uneven dispersion to occur. This not only further exacerbates the decline in mechanical properties but also leads to poor flowability, surface roughness, and material accumulation in the die during material extrusion processing, affecting the molding quality of the insulation layer and the uniformity of electrical insulation. Summary of the Invention
[0005] This application provides a low-smoke halogen-free insulating material, its preparation method, and its application. By using a modified flame retardant with a low filler content and polydopamine to coat ceramic oxide to construct an oxygen-barrier and heat-insulating protective layer with a dense outer layer and a sparse inner layer, the flame retardant and smoke-suppressing properties of the insulating material are synergistically improved, and the mechanical strength of the material is improved simultaneously.
[0006] To address the aforementioned technical problems, one objective of this application is to provide a low-smoke halogen-free insulating material comprising the following components by mass fraction: Ethylene-vinyl acetate copolymer: 20-45%; Polyethylene: 4-18%; Modified flame retardant: 40%-50%; Polydopamine-coated ceramic oxide: 5%-10%; Antioxidant: 1%-3%; Crosslinking agent: 1%-3%; Processing aids: 1%-3%; The mass ratio of polydopamine to ceramic oxide in the polydopamine-coated ceramic oxide is (0.02-0.08):1; the modified flame retardant is a flame retardant surface-treated with bis(dioctyloxypyrophosphate) ethylene titanate.
[0007] This application utilizes a low-filling-content modified flame retardant in conjunction with polydopamine-coated ceramic oxide to synergistically improve the flame retardant and smoke-suppressing properties of insulation materials. The modified flame retardant undergoes endothermic decomposition to lower the polymer's decomposition temperature. The resulting oxides form a dense physical barrier on the material surface. Simultaneously, this barrier, combined with the heat-insulating char layer formed by the heated polydopamine-coated oxide, creates a dense outer and sparse inner barrier layer that effectively blocks oxygen and heat. Furthermore, the ceramic phase formed by the ceramic oxide at high temperatures supports the expanded char layer structure, enhancing its stability and synergistically improving the flame retardant and smoke-suppressing capabilities of the insulation material. In addition, the modified flame retardant undergoes a bis(dioctyloxypyrophosphate) ethylene titanate surface treatment. The introduced pyrophosphate groups crosslink with the polydopamine-coated oxide at high temperatures, forming stable P–O–C bonds. This multi-crosslinked network further enhances the stability of the char layer, forming a continuous and robust char skeleton with a synergistic flame-retardant effect. Moreover, the modified flame retardant introduces long-chain organic functional groups, which can reduce the polarity of the filler, improve the compatibility with the EVA and PE matrix of the system, and improve the material processing performance and mechanical properties.
[0008] In some embodiments, the mass ratio of polydopamine to ceramic oxide in the polydopamine-coated ceramic oxide is (0.04-0.06):1.
[0009] This application controls the ratio of polydopamine to ceramic oxide in the polydopamine-coated ceramic oxide within the aforementioned range, which avoids the polydopamine coating layer being too thin or the ceramic oxide content being too low, thus comprehensively improving the flame retardant and smoke-suppressing effect of the insulation material. If the polydopamine coating thickness is too thin, it will not provide sufficient flame retardancy, and excessive carbonization of the matrix will result in a loose carbon layer structure, which is prone to cracking and pulverization, thereby failing to provide effective protection and shielding, affecting the flame retardant performance. If the ceramic oxide content is too low, there will be insufficient ceramic phase in the carbon layer to provide support, reducing the stability of the carbon layer and also leading to a decrease in the flame retardant effect.
[0010] In some embodiments, the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide is (4-10):1.
[0011] In some embodiments, the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide is (5-6):1.
[0012] This application controls the ratio of modified flame retardant and polydopamine-coated ceramic oxide within the above-mentioned range, which can ensure sufficient endothermic decomposition of modified flame retardant to increase the decomposition temperature of the matrix. Furthermore, the content of modified flame retardant allows the oxide formed by its decomposition to form a dense physical barrier on the surface, isolating oxygen and promoting the formation of a tough ceramic-carbon composite layer inside using polydopamine-coated ceramic oxide to isolate heat transmission and synergistically improve the flame retardant effect.
[0013] In some embodiments, the preparation method of the modified flame retardant includes the following steps: adding the flame retardant to an organic solution, simultaneously adding bis(dioctyloxypyrophosphate) ethylene titanate, stirring and reacting at 60-90 °C for 3-8 h, filtering, and drying to obtain the modified flame retardant.
[0014] In some embodiments, the mass ratio of the flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate is 1:(1-3).
[0015] In some embodiments, the organic solution comprises 10%-30% isopropanol by volume and the balance being water.
[0016] In some embodiments, the flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, melamine, and ammonium tripolyphosphate.
[0017] In some embodiments, the flame retardant comprises aluminum hydroxide and magnesium hydroxide in a mass ratio of (1-2):(1-2).
[0018] The flame retardant in this modified flame retardant uses a combination of aluminum hydroxide and magnesium hydroxide. The two complement each other through their decomposition temperatures to achieve continuous heat absorption and cooling throughout the entire temperature range, releasing water vapor stepwise to dilute combustible gases and oxygen, and forming a continuous and dense oxide barrier layer on the material surface. This synergistically enhances heat and oxygen insulation, smoke suppression and anti-dripping, and the stability of the char layer structure, significantly improving the flame retardant efficiency of the material.
[0019] In some embodiments, the preparation method of the polydopamine-coated ceramic oxide includes the following steps: adding ceramic oxide particles to an organic solution, adjusting the pH of the system to 8-10 to obtain a mixture; then adding an aqueous solution of dopamine hydrochloride with a concentration of 1-3 mg / mL, stirring the reaction, filtering, washing, and drying to prepare the polydopamine-coated ceramic oxide.
[0020] In some embodiments, the stirring reaction time in the preparation method of the polydopamine-coated ceramic oxide is 8-16 h.
[0021] In some embodiments, in the method for preparing the polydopamine-coated ceramic oxide, the organic solution comprises 20%-40% ethanol by volume and the balance being water.
[0022] In some embodiments, the ceramic oxide in the polydopamine-coated ceramic oxide includes at least one of zirconium oxide, magnesium oxide, and aluminum oxide.
[0023] In some embodiments, the ceramic oxide in the polydopamine-coated ceramic oxide includes zirconium oxide.
[0024] The preferred ceramic oxide in this application is zirconium oxide, which can further improve the flame retardant properties of the matrix. This is because zirconium oxide has a low thermal radiation coefficient at high temperatures, effectively blocking the transmission of infrared thermal radiation to the substrate. In addition, the high interfacial coating strength between zirconium oxide and polydopamine improves the stability of the char layer, thereby improving the flame retardant properties of the material.
[0025] In some embodiments, the average particle size of the ceramic oxide in the polydopamine-coated ceramic oxide is 100-300 nm.
[0026] In some embodiments, the ethylene-vinyl acetate copolymer has a VA content of 10-30% and a melt index of 2-3 g / 10 min at 190 °C and 2.16 kg.
[0027] In some embodiments, the polyethylene has a melt index of 5-12 g / 10 min at 190 °C and 21.6 kg.
[0028] In some embodiments, the antioxidant includes at least one selected from 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tri-tert-butylphenol, and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane.
[0029] In some embodiments, the crosslinking agent includes at least one selected from triallyl isocyanurate, triallyl cyanurate, 1,4-butanediol dimethacrylate, trimethylolpropane trimethacrylate, and triethylene glycol dimethacrylate.
[0030] In some embodiments, the processing aid includes at least one of plasticizers, lubricants, and stabilizers.
[0031] To address the aforementioned technical problems, a second objective of this application is to provide a method for preparing a low-smoke halogen-free insulating material, comprising the following steps: (1) After the ethylene-vinyl acetate copolymer, polyethylene, antioxidant, modified flame retardant, polydopamine-coated ceramic oxide, crosslinking agent, and processing aid are mixed evenly, the mixture is subjected to intensive mixing to obtain intensively mixed material; (2) The mortar is added to a twin-screw extruder and extruded and granulated to prepare an insulating material.
[0032] In some implementations, in step (1), the mixing temperature is 110-125 °C and the time is 20-60 min.
[0033] In some embodiments, in step (2), the extrusion granulation temperature is 130-150 °C.
[0034] To address the aforementioned technical problems, a third objective of this application is to provide an application of a low-smoke halogen-free insulating material in the field of power equipment or cable materials.
[0035] Compared with the prior art, this application has the following beneficial effects: 1. The oxides produced by the thermal decomposition of the modified flame retardant in this application can form a dense physical barrier on the material surface. At the same time, the oxides coated with polydopamine form a tough and stable heat-insulating ceramic-carbon composite layer after heating, forming a barrier layer with a dense outer layer and a sparse inner layer to jointly block oxygen and heat, thereby synergistically improving the flame retardant and smoke-suppressing ability of the insulation material.
[0036] 2. In this application, the modified flame retardant is surface-treated with bis(dioctyloxypyrophosphate) ethylene titanate. The pyrophosphate groups introduced therein decompose upon heating to produce phosphoric acid, which can react with polydopamine-coated oxides to form stable P–O–C bonds, forming a multi-physical cross-linked network, further enhancing the char layer strength and synergistically improving the flame retardant performance.
[0037] 3. The modified flame retardant of this application is surface-treated with bis(dioctyloxypyrophosphate) ethylene titanate, which introduces long-chain organic functional groups. This can reduce the polarity of the filler, improve the compatibility with the EVA and PE matrix of the system, and improve the processing performance and mechanical properties of the material. At the same time, in combination with the synergistic flame retardant effect of polydopamine-coated ceramic oxide, the required filling amount of the modified flame retardant can be reduced, and the overall processing performance and mechanical strength of the material can be improved. Detailed Implementation
[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0039] Ethylene-vinyl acetate copolymer (EVA): Dow's Elvax® 3170, with 18% VA content, a melt index (190 °C / 2.16 kg) of 2.5 g / 10 min, and a density of 0.940 g / cm³. 3 ; Polyethylene (PE): Shanghai SECCO HD5401AA model, melt index (190 ℃ / 21.6 kg) is 9.5 g / 10min.
[0040] Preparation Example 1 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 2 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 12 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.05:1.
[0041] Preparation Example 2 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 100 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia to obtain a mixed solution; (2) Add a 1 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 16 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.02:1.
[0042] Preparation Example 3 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 300 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia to obtain a mixed solution; (2) Add a 3 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 8 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.07:1.
[0043] Preparation Example 4 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of alumina particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 2 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 12 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to alumina is 0.05:1.
[0044] Preparation Example 5 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of magnesium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 2 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 12 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to magnesium oxide is 0.05:1.
[0045] Preparation Example 6 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 1 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 12 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.02:1.
[0046] Preparation Example 7 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 3 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 12 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.07:1.
[0047] Comparative Preparation Example 1 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 0.5 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 8 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.01:1.
[0048] Comparative Preparation Example 2 A method for preparing polydopamine-coated ceramic oxide includes the following steps: (1) Add 1 g of zirconium oxide particles with an average particle size of 200 nm to 300 mL of ethanol aqueous solution with a volume fraction of 30 wt%, and adjust the pH of the system to 9 with ammonia water to obtain a mixed solution; (2) Add a 5 mg / mL solution of dopamine hydrochloride to the mixture. The volume ratio of the mixture to the dopamine hydrochloride solution is 10:1. Stir the reaction at room temperature for 16 h. After filtration, wash with deionized water and dry at 60 °C for 30 min to prepare polydopamine-coated ceramic oxide. At this time, the mass ratio of polydopamine to zirconium oxide is 0.12:1.
[0049] Example 1 A low-smoke halogen-free insulating material comprises the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 30%; polyethylene (PE): 10%; modified flame retardant: 45%; antioxidant: 2%; plasticizer: 2%; crosslinking agent: 3%; polydopamine-coated ceramic oxide of Preparation Example 1: 8%; the antioxidant is 2,6-di-tert-butyl-p-cresol, the plasticizer is phthalate, the crosslinking agent is triallyl isocyanurate, the modified flame retardant is a flame retardant surface-modified with bis(dioctyloxypyrophosphate) ethylene titanate, the flame retardant comprising aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1; the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide of Preparation Example 1 is 5.63:1.
[0050] The preparation method of the above-mentioned low-smoke halogen-free insulating material includes the following steps: (1) 1 g of flame retardant was added to 20 mL of 15 wt% isopropanol aqueous solution. The flame retardant included aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1. At the same time, bis(dioctyloxypyrophosphate) ethylene titanate was added. The mass ratio of flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate was 1:2. The mixture was stirred and reacted at 80 °C for 5 h. After filtration, the mixture was dried at 60 °C for 30 min to prepare the modified flame retardant. (2) Ethylene-vinyl acetate copolymer, polyethylene, antioxidant, modified flame retardant, polydopamine-coated ceramic oxide, crosslinking agent, and plasticizer are added to a high-speed mixer and mixed evenly. Then, the mixture is kneaded at 120 °C for 30 min to obtain the kneaded material. (3) Add the mortar into a twin-screw extruder and extrude and granulate it at a temperature of 130 ℃-150 ℃ to prepare the insulating material.
[0051] Example 2 A low-smoke halogen-free insulating material comprises the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 45%; polyethylene (PE): 4%; modified flame retardant: 40%; antioxidant: 1%; plasticizer: 1%; crosslinking agent: 2%; polydopamine-coated ceramic oxide of Preparation Example 2: 7%; the antioxidant is 2,2'-methylenebis(4-methyl-6-tert-butylphenol), the plasticizer is phthalate, the crosslinking agent is triallyl isocyanurate, the modified flame retardant is a flame retardant surface-modified with bis(dioctyloxypyrophosphate) ethylene titanate, the flame retardant comprising aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1; the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide of Preparation Example 1 is 5.71:1.
[0052] The preparation method of the above-mentioned low-smoke halogen-free insulating material includes the following steps: (1) 1 g of flame retardant was added to 20 mL of 15 wt% isopropanol aqueous solution. The flame retardant included aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1. At the same time, bis(dioctyloxypyrophosphate) ethylene titanate was added. The mass ratio of flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate was 1:2. The mixture was stirred and reacted at 80 °C for 5 h. After filtration, the mixture was dried at 60 °C for 30 min to prepare the modified flame retardant. (2) Ethylene-vinyl acetate copolymer, polyethylene, antioxidant, modified flame retardant, polydopamine-coated ceramic oxide, crosslinking agent, and plasticizer are added to a high-speed mixer and mixed evenly. Then, the mixture is kneaded at 120 °C for 30 min to obtain the kneaded material. (3) Add the mortar into a twin-screw extruder and extrude and granulate it at a temperature of 130 ℃-150 ℃ to prepare the insulating material.
[0053] Example 3 A low-smoke halogen-free insulating material comprises the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 20%; polyethylene (PE): 18%; modified flame retardant: 50%; antioxidant: 3%; plasticizer: 3%; crosslinking agent: 1%; polydopamine-coated ceramic oxide of Preparation Example 3: 5%; the antioxidant is 2,4,6-tri-tert-butylphenol, the plasticizer is phthalate, the crosslinking agent is triallyl isocyanurate, the modified flame retardant is a flame retardant surface-modified with bis(dioctyloxypyrophosphate) ethylene titanate, the flame retardant comprising aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1; the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide of Preparation Example 1 is 10:1.
[0054] The preparation method of the above-mentioned low-smoke halogen-free insulating material includes the following steps: (1) 1 g of flame retardant was added to 20 mL of 15 wt% isopropanol aqueous solution. The flame retardant included aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1. At the same time, bis(dioctyloxypyrophosphate) ethylene titanate was added. The mass ratio of flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate was 1:2. The mixture was stirred and reacted at 80 °C for 5 h. After filtration, the mixture was dried at 60 °C for 30 min to prepare the modified flame retardant. (2) Ethylene-vinyl acetate copolymer, polyethylene, antioxidant, modified flame retardant, polydopamine-coated ceramic oxide, crosslinking agent, and plasticizer are added to a high-speed mixer and mixed evenly. Then, the mixture is kneaded at 120 °C for 30 min to obtain the kneaded material. (3) Add the mortar into a twin-screw extruder and extrude and granulate it at a temperature of 130 ℃-150 ℃ to prepare the insulating material.
[0055] Example 4 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Preparation Example 4.
[0056] Example 5 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Preparation Example 5.
[0057] Example 6 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Preparation Example 6.
[0058] Example 7 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Preparation Example 7.
[0059] Example 8 A low-smoke halogen-free insulating material differs from Example 1 in that the modified flame retardant is a flame retardant modified with bis(dioctyloxypyrophosphate) ethylene titanate, and the flame retardant is aluminum hydroxide. In step (1) of the preparation method, 1 g of aluminum hydroxide is added to 20 mL of isopropanol aqueous solution with a volume fraction of 15 wt%, and bis(dioctyloxypyrophosphate) ethylene titanate is added at the same time. The mass ratio of the flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate is 1:2. The mixture is stirred and reacted at 80 °C for 5 h, filtered, and dried at 60 °C for 30 min to obtain the modified flame retardant.
[0060] Example 9 A low-smoke halogen-free insulating material differs from Example 1 in that the modified flame retardant is a flame retardant modified with bis(dioctyloxypyrophosphate) ethylene titanate, and the flame retardant is magnesium hydroxide. In step (1) of the preparation method, 1 g of magnesium hydroxide is added to 20 mL of isopropanol aqueous solution with a volume fraction of 15 wt%, and bis(dioctyloxypyrophosphate) ethylene titanate is added at the same time. The mass ratio of the flame retardant to bis(dioctyloxypyrophosphate) ethylene titanate is 1:2. The mixture is stirred and reacted at 80 °C for 5 h, filtered, and dried at 60 °C for 30 min to obtain the modified flame retardant.
[0061] Example 10 A low-smoke halogen-free insulating material differs from Example 1 in that the content of the modified flame retardant and the polydopamine-coated ceramic oxide of Preparation Example 1 are different. Specifically, it includes the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 30%; polyethylene (PE): 10%; modified flame retardant: 43%; antioxidant: 2%; plasticizer: 2%; crosslinking agent: 3%; and polydopamine-coated ceramic oxide of Preparation Example 1: 10%. In this case, the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide of Preparation Example 1 is 4.3:1.
[0062] Example 11 A low-smoke halogen-free insulating material differs from Example 1 in that the content of the modified flame retardant and the polydopamine-coated ceramic oxide of Preparation Example 1 are different. Specifically, it includes the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 30%; polyethylene (PE): 10%; modified flame retardant: 48%; antioxidant: 2%; plasticizer: 2%; crosslinking agent: 3%; and polydopamine-coated ceramic oxide of Preparation Example 1: 5%. In this case, the mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide of Preparation Example 1 is 9.6:1.
[0063] Comparative Example 1 A low-smoke halogen-free insulating material differs from Example 1 in that the modified flame retardant and the polydopamine-coated ceramic oxide of Preparation Example 1 are both replaced by an equal amount of flame retardant, which includes aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1.
[0064] Comparative Example 2 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Example 1 is replaced with a modified flame retardant, specifically comprising the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 30%; polyethylene (PE): 10%; modified flame retardant: 53%; antioxidant: 2%; plasticizer: 2%; crosslinking agent: 3%.
[0065] Comparative Example 3 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Example 1 is replaced with polydopamine and zirconium oxide, specifically comprising the following components by mass fraction: ethylene-vinyl acetate copolymer (EVA): 30%; polyethylene (PE): 10%; modified flame retardant: 45%; antioxidant: 2%; plasticizer: 2%; crosslinking agent: 3%; polydopamine: 3wt%; zirconium oxide: 5wt%.
[0066] Comparative Example 4 A low-smoke halogen-free insulating material differs from Example 1 in that the modified flame retardant is replaced by an equal amount of flame retardant, which includes aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1.
[0067] Comparative Example 5 A low-smoke halogen-free insulating material differs from Example 1 in that the modified flame retardant is a flame retardant surface-modified with 3-methacryloxypropyltrimethoxysilane. In step (1) of the preparation method, 1 g of flame retardant is added to 20 mL of isopropanol aqueous solution with a volume fraction of 15 wt%. The flame retardant includes aluminum hydroxide and magnesium hydroxide in a mass ratio of 1:1. At the same time, 3-methacryloxypropyltrimethoxysilane is added, and the mass ratio of flame retardant to 3-methacryloxypropyltrimethoxysilane is 1:2. The mixture is stirred and reacted at 80 °C for 5 h, filtered, and dried at 60 °C for 30 min to obtain the modified flame retardant.
[0068] Comparative Example 6 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Comparative Preparation Example 1.
[0069] Comparative Example 7 A low-smoke halogen-free insulating material differs from Example 1 in that the polydopamine-coated ceramic oxide of Preparation Example 1 is replaced by an equal amount of the polydopamine-coated ceramic oxide of Comparative Preparation Example 2.
[0070] Performance testing 1. Limiting Oxygen Index: The limiting oxygen index of the insulating materials prepared in the examples and comparative examples was tested according to the GB / T 2406.2-2009 test standard. The test results are shown in Table 1 below.
[0071] 2. Flame retardancy rating: The flame retardancy rating of the insulating materials prepared in the examples and comparative examples was tested according to the GB / T 2408-2021 test standard. The vertical burning ratings were divided into V-0, V-1 and V-2. The test results are shown in Table 1 below.
[0072] 3. Tensile strength and elongation at break: The tensile strength and elongation at break of the insulating materials prepared in the examples and comparative examples were tested according to the test standard GB / T 1040.1-2025. The test results are shown in Table 1 below.
[0073] Table 1 - Performance test results of embodiments and comparative examples of this application A comparison of the schemes in Example 1 and Comparative Examples 1-2 in Table 1 shows that Example 1 of this application uses oxides generated by the thermal decomposition of modified flame retardants to form a dense oxygen-barrier physical barrier on the material surface. Simultaneously, the polydopamine-coated oxide forms a tough and stable heat-insulating ceramic-carbon composite layer upon heating, creating a barrier layer with a dense outer layer and a sparse inner layer to jointly block oxygen and heat, thus synergistically improving the flame-retardant performance of the insulation material. In contrast, Comparative Examples 1-2 did not add polydopamine-coated ceramic oxides; they only used flame retardants or modified flame retardants to provide flame retardancy. They could not utilize the polydopamine-coated oxides to form a tough ceramic-carbon composite layer to insulate heat, resulting in a reduced flame-retardant effect. Furthermore, the higher content of flame retardants affected processing performance, reducing the tensile strength and elongation at break of the insulation material, leading to poor mechanical strength.
[0074] Comparing the solutions of Example 1 and Comparative Example 3 in Table 1, it can be seen that after the insulating material of Example 1 is heated, polydopamine promotes the formation of a tough char layer in the matrix, while the coated ceramic oxide forms a ceramic phase at high temperature, providing skeletal support to improve the stability of the char layer, thereby improving the flame retardant effect. In contrast, in Comparative Example 3, the polydopamine-coated ceramic oxide is replaced by a physically mixed polydopamine and zirconium oxide. The zirconium oxide has a small particle size, and when directly added to a polar matrix, it is easy for them to agglomerate. This results in an uneven distribution of the ceramic phase in the char layer formed after heating, which cannot provide a balanced skeletal support. The weak points of the char layer are prone to cracking and pulverization, affecting the flame retardant performance of the material. Furthermore, the agglomeration of filler particles leads to a simultaneous decrease in the mechanical strength of the material matrix.
[0075] Comparing the schemes of Example 1 and Comparative Example 4 in Table 1, it can be seen that the flame retardant in Example 1 of this application uses bis(dioctyloxypyrophosphate) ethylene titanate surface treatment. The introduced pyrophosphate groups crosslink with polydopamine-coated oxide at high temperature to form stable P–O–C bonds. This multi-crosslinked network can further improve the stability of the char layer, forming a continuous and tough char skeleton, further improving the flame retardant effect. Moreover, the modified flame retardant introduces long-chain organic functional groups, which can reduce the polarity of the filler, improve the compatibility with the EVA and PE matrix of the system, and improve the material processing performance and mechanical properties. In contrast, Comparative Example 4 uses an unmodified flame retardant, which does not introduce pyrophosphate groups to form a stable multi-crosslinked network. The stability of the char layer is reduced, and it cannot decompose to produce phosphoric acid to catalyze the char formation of polydopamine, thus reducing the final flame retardant performance. Furthermore, the flame retardant has poor compatibility with the matrix, affecting the mechanical properties of the material.
[0076] Comparing the solutions of Example 1 and Comparative Example 5 in Table 1, it can be seen that the flame retardant of Comparative Example 5 uses 3-methacryloyloxypropyltrimethoxysilane for surface modification. Although it can effectively improve the compatibility between the filler and the polymer matrix, the flame retardant cannot produce phosphoric acid after heating. Therefore, it cannot form a multi-crosslinked network with polydopamine-coated ceramic oxide, nor can it catalyze polydopamine to char. As a result, the toughness and strength of the char layer formed after heating are poor, and it is easy to crack and pulverize. The flame retardant performance is not as good as that of Example 1.
[0077] Comparing the solutions of Example 1 and Comparative Examples 6-7 in Table 1, it can be seen that the polydopamine coating layer in Comparative Example 6 is too thin, resulting in insufficient flame retardancy. Excessive carbonization of the matrix will form a loosely structured char layer, which is prone to cracking and pulverization, thus failing to provide effective oxygen and heat insulation protection and shielding, affecting the flame retardant performance. In Comparative Example 7, the polydopamine coating layer is relatively thick, resulting in insufficient overall content of ceramic oxides. Consequently, there is insufficient ceramic phase in the char layer to provide support, reducing the stability of the char layer and also leading to a decrease in flame retardant effect.
[0078] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.
Claims
1. A low smoke, halogen-free insulation compound, characterized in that, Components including the following mass fractions: Ethylene-vinyl acetate copolymer: 20-45%; Polyethylene: 4-18%; Modified flame retardant: 40%-50%; Polydopamine-coated ceramic oxide: 5%-10%; Antioxidant: 1%-3%; Crosslinking agent: 1%-3%; Processing aids: 1%-3%; The mass ratio of polydopamine to ceramic oxide in the polydopamine-coated ceramic oxide is (0.02-0.08):1; the modified flame retardant is a flame retardant surface-treated with bis(dioctyloxypyrophosphate) ethylene titanate.
2. The low-smoke halogen-free insulating material as described in claim 1, characterized in that, The mass ratio of the modified flame retardant to the polydopamine-coated ceramic oxide is (4-10):
1.
3. The low-smoke halogen-free insulating material as described in claim 1, characterized in that, The preparation method of the modified flame retardant includes the following steps: adding the flame retardant to an organic solution, simultaneously adding bis(dioctyloxypyrophosphate) ethylene titanate, stirring and reacting at 60-90 °C for 3-8 h, filtering and drying to obtain the modified flame retardant.
4. The low-smoke halogen-free insulating material as described in claim 1 or 3, characterized in that, The flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, melamine, and ammonium tripolyphosphate.
5. The low-smoke halogen-free insulating material as described in claim 1, characterized in that, The preparation method of the polydopamine-coated ceramic oxide includes the following steps: adding ceramic oxide particles to an organic solution, adjusting the pH of the system to 8-10 to obtain a mixed solution; then adding an aqueous solution of dopamine hydrochloride with a concentration of 1-3 mg / mL, stirring the reaction, filtering, washing, and drying to prepare the polydopamine-coated ceramic oxide.
6. The low-smoke halogen-free insulating material as described in claim 1 or 5, characterized in that, The ceramic oxide in the polydopamine-coated ceramic oxide includes at least one of zirconium oxide, magnesium oxide, and aluminum oxide.
7. The low-smoke halogen-free insulating material as described in claim 1 or 5, characterized in that, The average particle size of the ceramic oxide in the polydopamine-coated ceramic oxide is 100-300 nm.
8. The low-smoke halogen-free insulating material as described in claim 1, characterized in that, The antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tri-tert-butylphenol, and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane; And / or, the crosslinking agent includes at least one of triallyl isocyanurate, triallyl cyanurate, 1,4-butanediol dimethacrylate, trimethylolpropane trimethacrylate, and triethylene glycol dimethacrylate; And / or, the processing aids include at least one of plasticizers, lubricants, and stabilizers.
9. A method for preparing a low-smoke halogen-free insulating material as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) After the ethylene-vinyl acetate copolymer, polyethylene, antioxidant, modified flame retardant, polydopamine-coated ceramic oxide, crosslinking agent, and processing aid are mixed evenly, the mixture is subjected to intensive mixing to obtain intensively mixed material; (2) The mortar is added to a twin-screw extruder and extruded and granulated to prepare an insulating material.
10. The application of a low-smoke halogen-free insulating material as described in any one of claims 1-8 in the field of power equipment or cable materials.