Arc-resistant flame-retardant epoxy composite material for distribution box and preparation process thereof

Abstract

The application relates to the technical field of high polymer insulation composite materials, and discloses an arc-resistant flame-retardant epoxy composite material for a distribution box and a preparation process thereof. The composite material takes bisphenol A type epoxy resin as a matrix, and is compounded with self-made phosphorus-based flame retardant, modified white carbon black, modified hexagonal boron nitride nanosheet and diethylenetriamine curing agent. The phosphorus-based flame retardant constructs a boron-silicon-phosphorus synergistic flame-retardant system, and the interface compatibility of the hexagonal boron nitride is improved through modification of a coupling agent. The preparation process is simple, and the composite material can be formed through only normal-temperature mixing and curing without the need of complex equipment. The obtained composite material is halogen-free and environmentally-friendly, has excellent arc resistance, flame retardancy and mechanical stability, can effectively resist arc burning, carbonization and cracking, is suitable for the harsh service environment of the distribution box with high pressure and high temperature, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of polymer insulating composite materials technology, specifically to an arc-resistant and flame-retardant epoxy composite material for distribution boxes and its preparation process. Background Technology

[0002] As the core terminal equipment of power distribution systems, distribution boxes require their core components, such as shells and insulating supports, to operate under high voltage, electric arc, and high temperature environments for extended periods. This places stringent requirements on the insulation, arc resistance, flame retardancy, and mechanical stability of the materials used. Epoxy resin is widely used in the insulating components of distribution boxes due to its excellent adhesion, insulation, and processability. However, pure bisphenol A epoxy resin has inherent defects: poor flame retardancy (limiting oxygen index of only 19-20%, no UL94 flame retardancy rating), weak arc breakdown resistance, and significant degradation of mechanical properties at high temperatures. It is also prone to carbonization and cracking during arc burning, potentially causing short-circuit fires, and thus cannot meet the high safety requirements of distribution boxes.

[0003] Existing technologies often improve flame retardancy by adding halogenated flame retardants. However, halogenated materials release toxic and corrosive gases when burning, failing to meet environmental standards for electrical materials. Excessive addition of inorganic flame retardants severely reduces the mechanical strength and processing fluidity of composite materials. Single arc-resistant fillers have poor dispersibility, making it difficult to form a continuous arc-resistant insulation barrier, thus failing to achieve a synergistic improvement in flame retardancy, arc resistance, and mechanical properties. Therefore, developing a halogen-free, environmentally friendly epoxy composite material for distribution boxes that exhibits excellent arc resistance, high flame retardancy, and stable mechanical properties has become a pressing technical challenge for the industry. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an arc-resistant and flame-retardant epoxy composite material for distribution boxes and its preparation process, which has good flame retardancy, arc resistance and mechanical properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an arc-resistant and flame-retardant epoxy composite material for distribution boxes, comprising the following weight components: 75-85 parts by weight of bisphenol A type epoxy resin, 2-4 parts by weight of phosphorus-based flame retardant, 3-4 parts by weight of modified silica, 1-2 parts by weight of modified hexagonal boron nitride nanosheets, and 10-12 parts by weight of diethylenetriamine curing agent.

[0006] Furthermore, the preparation method of the phosphorus-based flame retardant is as follows: S1. Add hydroxyl-terminated polydimethylsiloxane and 4-aminophenylboronic acid to anhydrous ethanol in a reaction flask, stir at room temperature for 8-12 min, and then react at 65-70℃ for 4-6 h. After the reaction is completed, distill under reduced pressure to obtain boron-containing amino-terminated silane. S2. Add DOPO and dihydroxybenzophenone to a reaction flask, purge with nitrogen for protection, heat to 120-130℃ and react for 1-2 hours, then continue heating to 165-170℃ until the system becomes viscous, stop heating and allow to cool naturally. After the reaction is complete, wash the product with ethanol, filter, and dry to obtain dihydroxylated DOPO. S3. Add DOPO modified with bisphenol hydroxyl group and phenylphosphodichloro to a reaction flask, purge with nitrogen for protection, and melt-react at 145-150℃ for 1-2 hours. Then raise the temperature to 175-180℃ and react for 1-2 hours. After the reaction is completed, lower the temperature to 45-50℃ and continue to add acetone solution containing boron-containing amino-terminated silane to the reaction flask. Reflux at 65-70℃ for 1-2 hours. After the reaction is completed, filter and rotary evaporate to obtain phosphorus-based flame retardant.

[0007] Furthermore, in S1, the ratio of hydroxyl-terminated polydimethylsiloxane to 4-aminophenylboronic acid is 2-4 mmol: 1-2 mmol.

[0008] Furthermore, in S2, the ratio of DOPO to benzophenone is 2-3 mmol: 1-1.5 mmol.

[0009] Furthermore, in S3, the ratio of bisphenol hydroxyl-modified DOPO, phenylphosphodichloro, and boron-containing amino-terminated silane is 0.6-1 mmol: 0.6-1 mmol: 0.1-0.2 mmol.

[0010] Furthermore, the modified hexagonal boron nitride nanosheets are prepared by adding 4-5g of hexagonal boron nitride powder to 120-140mL of ethanol, dispersing it under ultrasonic conditions of 300W for 0.8-1h, then adding 0.12-0.15g of KH-550 coupling agent and refluxing at 50-60℃ for 1-1.5h to obtain modified hexagonal boron nitride nanosheets.

[0011] Further, the method includes the following steps: adding bisphenol A type epoxy resin, phosphorus-based flame retardant, modified silica, modified hexagonal boron nitride nanosheets, and diethylenetriamine curing agent to a stirrer, stirring and mixing, and curing at room temperature to obtain an arc-resistant and flame-retardant epoxy composite material for distribution boxes.

[0012] Furthermore, the curing time is 12-15 hours.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: The phosphorus-based flame retardant of the present invention contains three flame retardant elements: phosphorus, boron, and silicon. The phosphorus element catalyzes the carbonization of the resin matrix in the condensed phase, forming a dense insulating layer that blocks oxygen and heat transfer. The boron and silicon elements work together to enhance the integrity of the carbon layer structure, suppress the generation of molten droplets and toxic fumes during combustion, and overcome the environmental defects of traditional halogen-based flame retardants, achieving halogen-free and environmentally friendly flame retardancy.

[0014] Modified hexagonal boron nitride nanosheets possess high insulation and high thermal conductivity. After modification with coupling agents, they can be uniformly dispersed in the resin matrix to form a continuous and dense arc-resistant insulation barrier. Combined with the physical barrier effect of modified silica, they effectively disperse arc energy, preventing matrix carbonization, cracking, and insulation breakdown caused by concentrated arc burning. This significantly improves the long-term arc resistance of the material and ensures the safe operation of electrical equipment.

[0015] Modified hexagonal boron nitride nanosheets and modified silica undergo surface modification treatment to reduce interfacial compatibility defects with the organic epoxy resin matrix, reduce the risk of filler agglomeration, and enable the filler to be uniformly embedded in the resin cross-linking network, forming chemical bonds and physical entanglements with the epoxy resin matrix. When the material is subjected to external impact or microcracks are generated, the modified nanofiller can dissipate a large amount of impact energy through crack deflection, prevent the propagation of microcracks, and achieve better mechanical effects. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] DOPO: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0018] KH550: γ-aminopropyltriethoxysilane.

[0019] Hydroxyl-terminated polydimethylsiloxane: ≥99.5%, 40cst Maclean Chemical Reagent Co., Ltd.

[0020] The preparation of modified silica is referenced in "Preparation and Properties of Silica Modified with 1,2-Dithiocyclopentane-Terminated Silane Coupling Agent and its Rubber Composites" from *Polymer Materials Science and Engineering*, Vol. 41, No. 01. To prepare the modified silica, add 25 mL of ethanol and 2.5 mL of deionized water to a 500 mL round-bottom flask, then add 0.4 g of LATES. Adjust the pH to 7–8 with 1 mol / L HCl and hydrolyze at room temperature for 1 h. Next, add 200 mL of ethanol, adjust the pH to 7–8 with 1 mol / L HCl, and then add 8 g of silica A200. React at 70 °C for 9 h. Wash the obtained product with ethanol, centrifuge at least three times, and dry at 60 °C for 16 h to obtain the final modified silica.

[0021] Example 1 An arc-resistant and flame-retardant epoxy composite material for distribution boxes is composed of the following weight components: 75 parts by weight of bisphenol A type epoxy resin, 2 parts by weight of phosphorus-based flame retardant, 3 parts by weight of modified silica, 1 part by weight of modified hexagonal boron nitride nanosheets, and 10 parts by weight of diethylenetriamine curing agent.

[0022] Preparation of phosphorus-based flame retardants S1. Add 2 mmol of hydroxyl-terminated polydimethylsiloxane, 1 mmol of 4-aminophenylboronic acid and 25 mL of anhydrous ethanol to the reaction flask, stir at room temperature for 8 min, react at 65 °C for 4 h, and distill under reduced pressure to obtain boron-containing amino-terminated silane. S2. Add 2 mmol of DOPO and 1 mmol of dihydroxybenzophenone to the reaction flask, heat to 120°C under nitrogen protection and react for 1 h, continue to heat to 165°C and react until the system becomes viscous, cool naturally, wash with ethanol, filter and dry to obtain dihydroxy modified DOPO. S3. Add 0.6 mmol of bisphenol hydroxyl-modified DOPO and 0.6 mmol of phenylphosphodichloro to the reaction flask, melt and react at 145 °C for 1 h under nitrogen protection, raise the temperature to 175 °C and react for 1 h, cool to 45 °C, add 30 mL of acetone solution containing 0.1 mmol of boron-containing amino-terminated silane, reflux at 65 °C for 1 h, filter and rotary evaporate to obtain phosphorus-based flame retardant.

[0023] Preparation of modified hexagonal boron nitride nanosheets 4g of hexagonal boron nitride powder was added to 120mL of ethanol and ultrasonically dispersed at 300W for 0.8h. Then, 0.12g of KH550 coupling agent was added and refluxed at 50℃ for 1h to obtain modified hexagonal boron nitride nanosheets.

[0024] Preparation method of arc-resistant and flame-retardant epoxy composite material for distribution boxes: Bisphenol A type epoxy resin, phosphorus-based flame retardant, modified silica, modified hexagonal boron nitride nanosheets, and diethylenetriamine curing agent were added to a stirrer, mixed, and cured at room temperature for 12 hours to obtain an arc-resistant and flame-retardant epoxy composite material for distribution boxes.

[0025] Example 2 An arc-resistant and flame-retardant epoxy composite material for distribution boxes is composed of the following weight components: 80 parts by weight of bisphenol A type epoxy resin, 3 parts by weight of phosphorus-based flame retardant, 3.5 parts by weight of modified silica, 1.5 parts by weight of modified hexagonal boron nitride nanosheets, and 11 parts by weight of diethylenetriamine curing agent.

[0026] Preparation of phosphorus-based flame retardants S1. Add 3 mmol of hydroxyl-terminated polydimethylsiloxane, 1.5 mmol of 4-aminophenylboronic acid and 30 mL of anhydrous ethanol to a reaction flask, stir at room temperature for 10 min, react at 68 °C for 5 h, and distill under reduced pressure to obtain boron-containing amino-terminated silane. S2. Add 2.5 mmol of DOPO and 1.2 mmol of dihydroxybenzophenone to the reaction flask, heat to 125 °C under nitrogen protection and react for 1.5 h, continue to heat to 168 °C and react until the system becomes viscous, cool naturally, wash with ethanol, filter and dry to obtain DOPO modified with dihydroxyl groups. S3. Add 0.8 mmol of bisphenol hydroxyl-modified DOPO and 0.8 mmol of phenylphosphodichloro to the reaction flask, melt and react at 148 °C for 1.5 h under nitrogen protection, raise the temperature to 178 °C and react for 1.5 h, cool to 48 °C, add 35 mL of acetone solution containing 0.15 mmol of boron-containing amino-terminated silane, reflux at 68 °C for 1.5 h, filter and rotary evaporate to obtain phosphorus-based flame retardant.

[0027] Preparation of modified hexagonal boron nitride nanosheets 4.5g of hexagonal boron nitride powder was added to 130mL of ethanol, ultrasonically dispersed at 300W for 0.9h, 0.13g of KH550 coupling agent was added, and refluxed at 55℃ for 1.2h to obtain modified hexagonal boron nitride nanosheets.

[0028] Preparation method of arc-resistant and flame-retardant epoxy composite material for distribution boxes: Bisphenol A type epoxy resin, phosphorus-based flame retardant, modified silica, modified hexagonal boron nitride nanosheets, and diethylenetriamine curing agent were added to a stirrer, mixed, and cured at room temperature for 13 hours to obtain an arc-resistant and flame-retardant epoxy composite material for distribution boxes.

[0029] Example 3 An arc-resistant and flame-retardant epoxy composite material for distribution boxes is composed of the following weight components: 85 parts by weight of bisphenol A type epoxy resin, 4 parts by weight of phosphorus-based flame retardant, 4 parts by weight of modified silica, 2 parts by weight of modified hexagonal boron nitride nanosheets, and 12 parts by weight of diethylenetriamine curing agent.

[0030] Preparation of phosphorus-based flame retardants S1. Add 4 mmol of hydroxyl-terminated polydimethylsiloxane, 2 mmol of 4-aminophenylboronic acid and 35 mL of anhydrous ethanol to the reaction flask, stir at room temperature for 12 min, react at 70 °C for 6 h, and distill under reduced pressure to obtain boron-containing amino-terminated silane. S2. Add 3 mmol of DOPO and 1.5 mmol of dihydroxybenzophenone to the reaction flask, heat to 130℃ under nitrogen protection and react for 2 h, continue to heat to 170℃ and react until the system becomes viscous, cool naturally, wash with ethanol, filter and dry to obtain dihydroxy modified DOPO. S3. Add 1 mmol of bisphenol hydroxyl-modified DOPO and 1 mmol of phenylphosphine dichloride to the reaction flask, melt and react at 150°C for 2 h under nitrogen protection, raise the temperature to 180°C and react for 2 h, cool to 50°C, add 40 mL of acetone solution containing 0.2 mmol of boron-containing amino-terminated silane, reflux at 70°C for 2 h, filter and rotary evaporate to obtain phosphorus-based flame retardant.

[0031] Modified hexagonal boron nitride nanosheets were prepared by adding 5g of hexagonal boron nitride powder to 140mL of ethanol, ultrasonically dispersing at 300W for 1h, adding 0.15g of KH550 coupling agent, and refluxing at 60℃ for 1.5h.

[0032] Preparation method of arc-resistant and flame-retardant epoxy composite material for distribution boxes: Bisphenol A type epoxy resin, phosphorus-based flame retardant, modified silica, modified hexagonal boron nitride nanosheets, and diethylenetriamine curing agent were added to a stirrer, mixed, and cured at room temperature for 15 hours to obtain an arc-resistant and flame-retardant epoxy composite material for distribution boxes.

[0033] Comparative Example 1 The difference between this comparative example and Example 3 is that hydroxyl-terminated polydimethylsiloxane was used instead of phosphorus-based flame retardant. The other raw material components, preparation process and reaction parameters were completely consistent with Example 3, and a control epoxy composite material was obtained.

[0034] Comparative Example 2 The difference between this comparative example and Example 3 is that no modified hexagonal boron nitride nanosheets were added, while the other raw material components, preparation process, and reaction parameters were completely consistent with Example 3, resulting in a control epoxy composite material.

[0035] Comparative Example 3 The difference between this comparative example and Example 3 is that an equal amount of unmodified silica was used to replace the modified silica, while the other raw material components, preparation process, and reaction parameters were completely consistent with Example 3, resulting in a control epoxy composite material.

[0036] Flame retardant performance testing, including limiting oxygen index (LOI), was conducted according to GB / T2406.2-2009; vertical flammability rating was tested according to UL94-2024 standard. Arc resistance performance was tested in accordance with GB / T1411-2021 "Test for dry solid insulating materials to withstand high voltage and low current arc discharge". The arc resistance time of the material was recorded, and the material's resistance to breakdown and carbonization was evaluated.

[0037] Tensile strength was tested according to GB / T2567-2021 "Test Methods for Properties of Resin Castings"; Impact resistance test: conducted in accordance with GB / T1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test".

[0038] Table 1: Performance Tests

[0039] As shown in Table 1, Comparative Example 1, which replaced the phosphorus-based flame retardant with hydroxyl-terminated polydimethylsiloxane, experienced a decrease in limiting oxygen index, resulting in a flame retardancy rating of only V-1. Comparative Examples 2 and 3, lacking modified hexagonal boron nitride nanosheets or using unmodified silica, had lower limiting oxygen indices than the examples, indicating a weakened synergistic flame retardant effect. This data fully demonstrates that the phosphorus-boron-silicon synergistic flame retardant is the core for achieving high flame retardancy. Comparative Example 1 exhibited a significantly shortened arc resistance time, containing only a single hydroxyl-terminated polydimethylsiloxane and lacking phosphorus and boron char-forming catalysts. This prevented the formation of a continuous and dense insulating carbon layer, causing the resin matrix to directly undergo thermal decomposition, carbonization, and cracking under the influence of an electric arc, resulting in a loss of insulation protection and a significant decrease in arc resistance. Comparative Example 2, lacking modified hexagonal boron nitride nanosheets, could not construct a continuous arc-resistant insulating barrier, resulting in the largest decrease in arc resistance performance. Comparative Example 3, using unmodified silica, suffered from filler agglomeration, leading to a decrease in barrier effect and a similar deterioration in arc resistance. This indicates that the synergistic construction of an insulating barrier structure by modified hexagonal boron nitride nanosheets and modified silica is key to improving the material's arc resistance and effectively preventing carbonization cracking and insulation failure caused by arc burning.

[0040] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An arc-resistant and flame-retardant epoxy composite material for distribution boxes, characterized in that, It includes the following components by weight: 75-85 parts by weight of bisphenol A type epoxy resin, 2-4 parts by weight of phosphorus-based flame retardant, 3-4 parts by weight of modified silica, 1-2 parts by weight of modified hexagonal boron nitride nanosheets, and 10-12 parts by weight of diethylenetriamine curing agent.

2. The arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 1, characterized in that, The preparation method of the phosphorus-based flame retardant is as follows: S1. Add hydroxyl-terminated polydimethylsiloxane and 4-aminophenylboronic acid to anhydrous ethanol in a reaction flask, stir at room temperature for 8-12 min, and then react at 65-70℃ for 4-6 h. After the reaction is completed, distill under reduced pressure to obtain boron-containing amino-terminated silane. S2. Add DOPO and dihydroxybenzophenone to a reaction flask, purge with nitrogen for protection, heat to 120-130℃ and react for 1-2 hours, then continue heating to 165-170℃ until the system becomes viscous, stop heating and allow to cool naturally. After the reaction is complete, wash the product with ethanol, filter, and dry to obtain dihydroxylated DOPO. S3. Add DOPO modified with bisphenol hydroxyl group and phenylphosphodichloro to a reaction flask, purge with nitrogen for protection, and melt-react at 145-150℃ for 1-2 hours. Then raise the temperature to 175-180℃ and react for 1-2 hours. After the reaction is completed, lower the temperature to 45-50℃ and continue to add acetone solution containing boron-containing amino-terminated silane to the reaction flask. Reflux at 65-70℃ for 1-2 hours. After the reaction is completed, filter and rotary evaporate to obtain phosphorus-based flame retardant.

3. The arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 2, characterized in that, In S1, the ratio of hydroxyl-terminated polydimethylsiloxane to 4-aminophenylboronic acid is 2-4 mmol: 1-2 mmol.

4. The arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 2, characterized in that, In S2, the ratio of DOPO to benzophenone is 2-3 mmol: 1-1.5 mmol.

5. The arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 2, characterized in that, In S3, the ratio of bisphenol hydroxyl-modified DOPO, phenylphosphodichloro, and boron-containing amino-terminated silane is 0.6-1 mmol: 0.6-1 mmol: 0.1-0.2 mmol.

6. The arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 2, characterized in that, The modified hexagonal boron nitride nanosheets are prepared by adding 4-5g of hexagonal boron nitride powder to 120-140mL of ethanol, dispersing it under ultrasonic conditions of 300W for 0.8-1h, then adding 0.12-0.15g of KH-550 coupling agent and refluxing at 50-60℃ for 1-1.5h to obtain modified hexagonal boron nitride nanosheets.

7. A method for preparing an arc-resistant and flame-retardant epoxy composite material for a distribution box as described in any one of claims 1-6, characterized in that, Includes the following steps: Bisphenol A type epoxy resin, phosphorus-based flame retardant, modified silica, modified hexagonal boron nitride nanosheets, and diethylenetriamine curing agent were added to a stirrer, mixed, and cured at room temperature to obtain an arc-resistant and flame-retardant epoxy composite material for distribution boxes.

8. The method for preparing the arc-resistant and flame-retardant epoxy composite material for distribution boxes according to claim 7, characterized in that, The curing time is 12-15 hours.

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