Flame-retardant sealing material for cable pipe plugging device and preparation method of flame-retardant sealing material

Abstract

The invention relates to the technical field of flame-retardant sealing materials, in particular to a flame-retardant sealing material for a cable pipe plugging device and a preparation method of the flame-retardant sealing material. 48-54 parts of nitrile rubber; 20 to 25 parts of modified mica; 22 to 30 parts of sepiolite powder; 10 to 15 parts of brominated epoxy resin; 8-12 parts of magnesium carbonate; 1-3 parts of stearic acid; 10 to 15 parts of nano glass fiber; 1-3 parts of microcrystalline wax; 2 to 5 parts of hexabromocyclododecane; 1-3 parts of paraffin oil; 1 to 2 parts of disulfide; 2 to 3 parts of vinyl tri (beta-methoxyethoxy) silane; 1 to 2 parts of isothiazolinone; 2-4 parts of aluminum hydroxide; 1-2 parts of sodium hydroxide; the LOI value can be up to 36.8% at most, and the tensile strength can be up to 22.1 MPa at most and is improved by 41.7% compared with that of an unmodified filler.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant sealing materials, and in particular to a flame retardant sealing material for a cable pipe plugger and a preparation method thereof. Background Art

[0002] In modern power and communication systems, the sealing of cable ducts is crucial. With the rapid development of industry and urbanization, the requirements for cable duct sealing materials are also increasing. Traditional sealing materials often fail to meet the comprehensive requirements of high flame retardancy, excellent mechanical properties and long-term stability. Especially in some high-risk environments, such as substations, underground tunnels and industrial plants, ordinary sealing materials are prone to aging and cracking, and even cannot effectively prevent the spread of flames and toxic gases in the event of a fire.

[0003] In recent years, although researchers have made many efforts to improve the performance of sealing materials, there are still some problems that need to be solved. First, a single type of flame retardant is often difficult to achieve the ideal flame retardant effect, especially in different combustion stages. Secondly, although the introduction of inorganic fillers can improve the flame retardant properties of the material, it often makes the material brittle and affects its sealing performance. In addition, many flame retardant sealing materials will experience performance degradation during long-term use and cannot meet the requirements of engineering applications.

[0004] Therefore, the development of flame-retardant sealing materials for cable pipe pluggers that have high flame retardancy, excellent mechanical properties and long-term stability is of great significance for improving the safety and reliability of power and communication systems. Summary of the invention

[0005] The purpose of the present invention is to provide a flame retardant sealing material for a cable tube plugger and a preparation method thereof, aiming to solve the technical problem in the prior art that it is difficult to take into account both flame retardant properties, mechanical properties and long-term use stability.

[0006] The invention discloses a flame retardant sealing material for a cable pipe plugger. The flame retardant sealing material is made of the following raw materials in parts by weight: 55-60 parts of ethylene-vinyl acetate copolymer; 48-54 parts of nitrile rubber; 20-25 parts of modified mica; 22-30 parts of sepiolite powder; 10-15 parts of brominated epoxy resin; 8-12 parts of magnesium carbonate; 1-3 parts of stearic acid; 10-15 parts of nano glass fiber; 1-3 parts of microcrystalline wax; 2-5 parts of hexabromocyclododecane; 1-3 parts of paraffin oil; 1-2 parts of disulfide; 2-3 parts of vinyl tris(β-methoxyethoxy)silane; 1-2 parts of isothiazolinone; 2-4 parts of aluminum hydroxide; 1-2 parts of sodium hydroxide; and 2-3 parts of magnesium hydroxide.

[0007] Specifically, the modified mica is prepared by the following steps:

[0008] (1) adding mica powder to water, dispersing it evenly, adding carboxymethyl chitosan, stirring at 40-60° C. for 4-7 hours, drying, calcining at 450-590° C. for 5-8 hours, cooling, grinding, and passing through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder;

[0009] (2) adding dodecyltrimethylammonium bromide, n-propylamine and ethanol to the carboxymethyl chitosan coated mica powder, stirring at 40-49° C. for 20-30 min, and heating to 60-70° C.;

[0010] (3) adding silane coupling agent KH-570 and water to the mixture obtained in step (2), and stirring for 20-30 min;

[0011] (4) subjecting the mixture obtained in step (3) to microwave radiation for 3-5 h;

[0012] (5) Dry the product obtained in step (4) and pass it through a 200-mesh sieve to obtain the modified mica.

[0013] Specifically, in steps (1) to (5), the weight ratio of the mica powder, carboxymethyl chitosan, dodecyltrimethylammonium bromide, n-propylamine, silane coupling agent KH-570, and water is 10:1:0.2-0.4:0.2-0.5:0.4-0.6:8-10.

[0014] Specifically, the power of the microwave radiation in step (4) is 200-300W.

[0015] Specifically, the nano glass fiber is subjected to a surface modification treatment, which comprises the following steps:

[0016] (1) Place 1-2 parts of nano-glass fibers in 10-15 parts of toluene and disperse by ultrasonication;

[0017] (2) adding 0.05-0.1 parts of coupling agent KH560 to the dispersion obtained in step (1), and stirring at room temperature for 20-30 minutes;

[0018] (3) filtering the mixture obtained in step (2), and washing with toluene 3-5 times;

[0019] (4) Drying the product obtained in step (3) at 60-70° C. to obtain modified nano glass fibers.

[0020] Specifically, the modified mica in the flame retardant sealing material is subjected to a plasticizing treatment, and the treatment comprises the following steps:

[0021] (1) mixing the modified mica with disulfide and isothiazolinone, and stirring for 20-30 minutes;

[0022] (2) heat treating the mixture obtained in step (1) at 180-240° C.;

[0023] (3) Cooling the product obtained in step (2) to room temperature, crushing it, and passing it through a 200-mesh sieve to obtain plasticized modified mica.

[0024] The method for preparing the flame-retardant sealing material for the cable pipe plugger comprises the following steps:

[0025] (1) Add ethylene-vinyl acetate copolymer, nitrile rubber, microcrystalline wax and nano glass fiber into an internal mixer and mix at 60-80° C. for 4-5 minutes;

[0026] (2) adding sepiolite powder, magnesium carbonate, paraffin oil and stearic acid to the mixture obtained in step (1), and continuing to mix to obtain a rubber mixture;

[0027] (3) uniformly mixing the modified mica, brominated epoxy resin, hexabromocyclododecane, aluminum hydroxide, sodium hydroxide, magnesium hydroxide, vinyl tri(β-methoxyethoxy)silane and the rubber mixture obtained in step (2);

[0028] (4) feeding the mixture obtained in step (3) into an open mill and mixing it uniformly to obtain a rubber material;

[0029] (5) plasticizing the rubber obtained in step (4) at 160-180° C. to form a sheet of desired thickness, and cooling;

[0030] (6) Cutting the sheet obtained in step (5) into films with a length of 15-25 cm and a width of 8-12 cm;

[0031] (7) placing the film obtained in step (6) into a vulcanizer and vulcanizing at a temperature of 150-170° C. and a pressure of 10-12 MPa to obtain the flame retardant sealing material.

[0032] Specifically, in steps (1) and (2), the rotation speed of the internal mixer is 30-45 rpm.

[0033] Specifically, the modified mica used in step (3) is plasticized modified mica.

[0034] Specifically, before step (4), the method further includes mixing disulfide and isothiazolinone with modified mica, heat treating at 180-240° C., cooling to room temperature, crushing, and passing through a 200-mesh sieve to obtain plasticized modified mica.

[0035] To achieve the above purpose, the present invention adopts a multi-component synergistic technical solution. The solution cleverly combines modified inorganic fillers, halogen flame retardants, inorganic hydroxides and functional additives, and achieves a synergistic effect between the components through a carefully designed formula and preparation process.

[0036] First, the present invention adopts multi-step surface-modified mica and nano glass fiber as main fillers. The preparation process of modified mica includes carboxymethyl chitosan coating, quaternary ammonium salt and amination, silane coupling and microwave radiation treatment. This series of treatments not only significantly improves the compatibility of mica with a polymer matrix, but also forms a multifunctional organic layer on the surface of the mica. In particular, microwave radiation treatment causes partial peeling of the mica, increases its specific surface area, and thus improves the flame retardant effect. The modified nano glass fiber is treated with a silane coupling agent KH560 to enhance its interface bonding strength with the matrix.

[0037] Secondly, the present invention introduces brominated epoxy resin and hexabromocyclododecane as main flame retardants. These two halogen flame retardants can release bromine free radicals during combustion, effectively capture hydrogen free radicals and hydroxyl free radicals, thereby inhibiting the combustion chain reaction in the gas phase. The epoxy groups in the brominated epoxy resin also react with other components to improve the crosslinking degree and thermal stability of the material.

[0038] Thirdly, the present invention uses aluminum hydroxide and magnesium hydroxide as inorganic flame retardants. These two compounds will undergo endothermic decomposition when heated, releasing water vapor, which can not only reduce the material temperature but also dilute the combustible gas. Due to their different decomposition temperatures, a gradient flame retardant effect can be formed, which works in a wider temperature range.

[0039] Finally, the present invention innovatively introduces disulfide and isothiazolinone as functional additives. Disulfide is not only an effective antioxidant, but also decomposes at high temperature to form sulfur free radicals, promoting the cross-linking of polymer chains. Isothiazolinone has both mildew and antibacterial properties and potential cross-linking promotion. The synergistic effect of these two additives significantly improves the long-term performance of the material.

[0040] There is a complex synergistic effect between the components of the present invention. For example, the modified mica and the modified nano-glass fiber form a network structure at high temperature, and work together with the halogen flame retardant to form a more compact and stable carbon layer. The sulfur free radicals released by the disulfide and the bromine free radicals work together to further enhance the gas phase flame retardant effect. In addition, the multi-step modification process causes the filler to form a certain orientation arrangement in the material, resulting in a maze effect, which delays the transfer of heat and oxygen.

[0041] Through the above technical solution, the present invention achieves the following beneficial effects:

[0042] 1. The flame retardant properties of the material are significantly improved, with the LOI value up to 36.8%, far exceeding that of ordinary flame retardant materials.

[0043] 2. The mechanical properties of the material have been greatly improved, with the tensile strength reaching up to 22.1MPa, which is 41.7% higher than that of unmodified fillers.

[0044] 3. The long-term performance of the material has been greatly improved, and the performance retention rate after thermal oxidation aging is significantly higher than that of the control sample.

[0045] 4. It achieves a balance between flame retardancy, mechanical properties and long-term performance, meeting the strict requirements of cable tube pluggers.

[0046] 5. Through multiple synergistic mechanisms, it can effectively play a flame retardant role in different temperature stages and different phases, providing all-round fire protection.

[0047] 6. The multifunctionality of disulfide and isothiazolinone is innovatively utilized to provide new ideas for the development of high-performance flame-retardant sealing materials.

[0048] In summary, the present invention successfully solves the problems existing in the prior art through a carefully designed multi-component synergistic system, and makes an important contribution to the development of flame-retardant sealing materials for cable pipe plugs. The material not only meets strict technical requirements, but also has good industrial application prospects, and is expected to significantly improve the safety and reliability of power and communication systems. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] The flame-retardant sealing material for a cable pipe plugger of the present invention is made of the following raw materials in parts by weight: 55-60 parts of ethylene-vinyl acetate copolymer; 48-54 parts of nitrile rubber; 20-25 parts of modified mica; 22-30 parts of sepiolite powder; 10-15 parts of brominated epoxy resin; 8-12 parts of magnesium carbonate; 1-3 parts of stearic acid; 10-15 parts of nano-glass fiber; 1-3 parts of microcrystalline wax; 2-5 parts of hexabromocyclododecane; 1-3 parts of paraffin oil; 1-2 parts of disulfide; 2-3 parts of vinyl tris(β-methoxyethoxy)silane; 1-2 parts of isothiazolinone; 2-4 parts of aluminum hydroxide; 1-2 parts of sodium hydroxide; and 2-3 parts of magnesium hydroxide.

[0051] EVA is a copolymer with good flexibility, weather resistance and processing properties. The ethylene unit in its structure provides good mechanical strength and water resistance, while the vinyl acetate unit gives the material polarity and improves compatibility with other polar components. The presence of EVA gives the final product appropriate flexibility and sealing properties. Nitrile rubber is an elastomer copolymerized by butadiene and acrylonitrile. The -CN group in the acrylonitrile unit gives it excellent oil resistance and air tightness. The butadiene unit provides good elasticity. The combination of nitrile rubber and EVA can balance the flexibility and sealing properties of the material. Mica is a layered silicate mineral with excellent thermal insulation and flame retardant properties. Through a complex surface modification process, the modified mica can be better dispersed in the polymer matrix and enhance the mechanical properties and flame retardant properties of the material. The modification process includes carboxymethyl chitosan coating to introduce an organic layer containing amino and hydroxyl groups to enhance compatibility with the polymer matrix. Quaternary ammonium salts and amination introduce positive charges and additional amino groups to further improve interfacial compatibility. Silane coupling introduces organic functional groups to enhance the chemical bonding with the polymer matrix. Microwave radiation treatment promotes the completion of surface reaction and leads to partial exfoliation of mica, increasing the specific surface area.

[0052] Sepiolite is a hydrous magnesium silicate with a needle-like structure. It can enhance the mechanical properties of the material, improve the flame retardant properties, and form a dense thermal insulation layer when burning. Brominated epoxy resin is an important flame retardant. During the combustion process, bromine atoms can capture free radicals and inhibit the combustion chain reaction. At the same time, the epoxy group can react with other components to improve the crosslinking degree and thermal stability of the material. Magnesium carbonate decomposes at high temperatures to release carbon dioxide, which can dilute the combustible gas. At the same time, it can also neutralize the acidic gas produced during the combustion process and reduce the corrosiveness. Stearic acid, as an internal lubricant, can improve the processing properties of the material and reduce mold adhesion. At the same time, it forms metal soaps with metal ions to further enhance the flame retardant properties of the material. Nano glass fiber has high strength and high modulus, which can significantly improve the mechanical properties of the material. Modification by KH560 silane coupling agent can enhance its interfacial bonding with the polymer matrix and improve dispersibility. The nanoscale size gives it a larger specific surface area, which is conducive to the formation of a denser flame retardant barrier. Microcrystalline wax can be used as a processing aid to improve the fluidity and demolding properties of the material. At the same time, it forms a thin film on the surface of the material to improve the waterproof performance. Hexabromocyclododecane is a highly efficient brominated flame retardant. During the combustion process, it can decompose and release bromine free radicals, effectively inhibiting the combustion reaction in the gas phase. Paraffin oil, as a plasticizer, can improve the flexibility and low-temperature performance of the material. It also helps to improve the dispersibility of each component. Disulfide can be used as a free radical scavenger to prevent the oxidative degradation of the polymer chain. At high temperatures, disulfide will decompose to form sulfur free radicals, promote the cross-linking of the polymer chain, and improve the thermal stability of the material. Disulfide will react with the functional groups on the surface of the modified mica, further improving the dispersibility and interfacial bonding strength of the mica. Vinyl tris (β-methoxyethoxy) silane, this silane coupling agent can react with the hydroxyl groups on the surface of the inorganic filler, and its vinyl group can participate in the cross-linking reaction of the polymer. This bridging effect can significantly improve the interfacial bonding between the inorganic filler and the polymer matrix and improve the comprehensive performance of the material. Isothiazolinone is a broad-spectrum fungicide that can prevent the material from mold in a humid environment. The NS bond on the isothiazolinone ring will break at high temperatures, and the free radicals generated will promote the cross-linking of polymers. Isothiazolinone will react with the functional groups on the surface of modified mica to further improve its performance. Aluminum hydroxide will decompose and absorb heat and release water vapor when heated, which plays a role in cooling and diluting combustible gases. At the same time, it can also form a dense aluminum oxide layer on the surface of the material to block the transfer of oxygen and heat. The addition of sodium hydroxide keeps the material in a certain alkalinity range. During the combustion process, it can neutralize the acidic gases produced and reduce corrosiveness. Magnesium hydroxide is similar to aluminum hydroxide. It decomposes and absorbs heat and releases water vapor when heated. Its decomposition temperature is higher than that of aluminum hydroxide, and it can work in a higher temperature range, forming a gradient flame retardant effect with aluminum hydroxide.

[0053] Brominated epoxy resin and hexabromocyclododecane release bromine free radicals to inhibit gas phase combustion reactions. Modified mica, sepiolite powder and nano-glass fibers form a heat insulation barrier. Aluminum hydroxide and magnesium hydroxide decompose and absorb heat to form a gradient flame retardant effect. The combination of multiple flame retardants produces a synergistic effect and improves the overall flame retardant performance.

[0054] The combination of EVA and nitrile rubber balances the flexibility, sealing and oil resistance of the material. This combination can adapt to various environmental conditions.

[0055] Modified mica, sepiolite powder and nano glass fiber form a multi-layer filler system, which not only improves the mechanical properties of the material, but also plays a key role in flame retardancy.

[0056] The multi-step surface modification of mica and nanoglass fibers greatly improved their compatibility and dispersibility with the polymer matrix.

[0057] The addition of various additives (such as stearic acid, microcrystalline wax, paraffin oil, etc.) comprehensively improves the processing and use properties of the material. The use of disulfide and isothiazolinone reflects the innovation of the formula, which plays an important role in anti-oxidation, cross-linking and mildew resistance.

[0058] Example 1

[0059] This embodiment provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof. The flame retardant sealing material is made of the following raw materials in parts by weight: 55 parts of ethylene-vinyl acetate copolymer, 48 parts of nitrile rubber, 20 parts of modified mica, 22 parts of sepiolite powder, 10 parts of brominated epoxy resin, 8 parts of magnesium carbonate, 1 part of stearic acid, 10 parts of nano glass fiber, 1 part of microcrystalline wax, 2 parts of hexabromocyclododecane, 1 part of paraffin oil, 1 part of disulfide, 2 parts of vinyl tris (β-methoxyethoxy) silane, 1 part of isothiazolinone, 2 parts of aluminum hydroxide, 1 part of sodium hydroxide, and 2 parts of magnesium hydroxide.

[0060] The preparation method of the flame retardant sealing material comprises the following steps:

[0061] First, prepare modified mica. The specific steps are as follows:

[0062] (1) 10 kg of mica powder was added to 100 kg of water, and after being evenly dispersed, 1 kg of carboxymethyl chitosan was added, and the mixture was stirred at 40° C. for 4 h. After drying, the mixture was calcined at 450° C. for 5 h. The mixture was cooled and ground into powder, and passed through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder;

[0063] (2) adding 0.2 kg of dodecyltrimethylammonium bromide, 0.2 kg of n-propylamine and ethanol to the obtained carboxymethyl chitosan-coated mica powder, stirring at 40° C. for 20 min, and heating to 60° C.;

[0064] (3) Add 0.4 kg of silane coupling agent KH-570 and 8 kg of water to the mixture and stir for 20 min;

[0065] (4) subjecting the mixture to microwave irradiation for 3 h at a power of 200 W;

[0066] (5) The product was dried and passed through a 200-mesh sieve to obtain modified mica.

[0067] Secondly, prepare the modified nano glass fiber. The specific steps are as follows:

[0068] (1) Place 1 part of nano-glass fiber in 10 parts of toluene and disperse by ultrasonic;

[0069] (2) Add 0.05 parts of coupling agent KH560 to the dispersion and stir at room temperature for 20 minutes;

[0070] (3) filtering the mixture and washing it with toluene three times;

[0071] (4) Drying the product at 60°C to obtain modified nano glass fibers.

[0072] Then, plasticized modified mica is prepared. The specific steps are as follows:

[0073] (1) Mix the modified mica with 1 part of disulfide and 1 part of isothiazolinone and stir for 20 minutes;

[0074] (2) heat treating the mixture at 180° C.

[0075] (3) Cool the product to room temperature, crush it, and pass it through a 200-mesh sieve to obtain plasticized modified mica.

[0076] Finally, prepare the flame retardant sealing material. The specific steps are as follows:

[0077] (1) 55 parts of ethylene-vinyl acetate copolymer, 48 parts of nitrile rubber, 1 part of microcrystalline wax, and 10 parts of modified nano glass fiber were added into an internal mixer and mixed at 60° C. for 4 min at a speed of 30 rpm;

[0078] (2) adding 22 parts of sepiolite powder, 8 parts of magnesium carbonate, 1 part of paraffin oil, and 1 part of stearic acid to the mixture, and continuing to mix to obtain a rubber mixture;

[0079] (3) 20 parts of plasticized modified mica, 10 parts of brominated epoxy resin, 2 parts of hexabromocyclododecane, 2 parts of aluminum hydroxide, 1 part of sodium hydroxide, 2 parts of magnesium hydroxide, 2 parts of vinyl tri(β-methoxyethoxy) silane and the rubber compound are mixed uniformly;

[0080] (4) sending the mixture into an open mill and mixing it evenly to obtain a rubber material;

[0081] (5) Plasticizing the rubber at 160°C to form a sheet with a thickness of 2 mm and cooling;

[0082] (6) Cut the sheet into films with a length of 15 cm and a width of 8 cm;

[0083] (7) The film is placed in a vulcanizer and vulcanized at a temperature of 150° C. and a pressure of 10 MPa for 30 minutes to obtain the flame retardant sealing material.

[0084] In this embodiment, the combination of ethylene-vinyl acetate copolymer and nitrile rubber provides excellent flexibility and sealing performance while maintaining good oil resistance. The multi-step surface treatment of modified mica significantly improves its compatibility with the polymer matrix and enhances the mechanical properties and flame retardant properties of the material. Brominated epoxy resin and hexabromocyclododecane, as halogen flame retardants, effectively capture free radicals in the gas phase and inhibit the combustion chain reaction. Aluminum hydroxide and magnesium hydroxide decompose when heated to absorb heat and release water vapor, forming a gradient flame retardant effect. The innovative application of disulfide and isothiazolinone not only improves the antioxidant properties of the material, but also promotes the cross-linking of polymer chains and improves the thermal stability of the material.

[0085] Example 2

[0086] This embodiment provides another flame retardant sealing material for cable pipe plugging device and its preparation method. The flame retardant sealing material is made of the following raw materials in parts by weight: 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 23 parts of modified mica, 26 parts of sepiolite powder, 13 parts of brominated epoxy resin, 10 parts of magnesium carbonate, 2 parts of stearic acid, 13 parts of nano glass fiber, 2 parts of microcrystalline wax, 4 parts of hexabromocyclododecane, 2 parts of paraffin oil, 1.5 parts of disulfide, 2.5 parts of vinyl tris (β-methoxyethoxy) silane, 1.5 parts of isothiazolinone, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, and 2.5 parts of magnesium hydroxide.

[0087] The preparation method of the flame retardant sealing material comprises the following steps:

[0088] First, prepare modified mica. The specific steps are as follows:

[0089] (1) 10 kg of mica powder was added to 100 kg of water, and after being evenly dispersed, 1 kg of carboxymethyl chitosan was added, and the mixture was stirred at 50° C. for 5.5 h, dried, calcined at 525° C. for 6.5 h, cooled, ground, and passed through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder;

[0090] (2) adding 0.3 kg of dodecyltrimethylammonium bromide, 0.35 kg of n-propylamine and ethanol to the obtained carboxymethyl chitosan-coated mica powder, stirring at 45° C. for 25 min, and heating to 65° C.;

[0091] (3) Add 0.5 kg of silane coupling agent KH-570 and 9 kg of water to the mixture and stir for 25 min;

[0092] (4) subjecting the mixture to microwave radiation for 4 h at a power of 250 W;

[0093] (5) The product was dried and passed through a 200-mesh sieve to obtain modified mica.

[0094] Secondly, prepare the modified nano glass fiber. The specific steps are as follows:

[0095] (1) 1.5 parts of nano-glass fibers were placed in 12.5 parts of toluene and ultrasonically dispersed;

[0096] (2) Add 0.075 parts of coupling agent KH560 to the dispersion and stir at room temperature for 25 minutes;

[0097] (3) filtering the mixture and washing it with toluene four times;

[0098] (4) Drying the product at 65°C to obtain modified nano glass fibers.

[0099] Then, plasticized modified mica is prepared. The specific steps are as follows:

[0100] (1) Mix the modified mica with 1.5 parts of disulfide and 1.5 parts of isothiazolinone and stir for 25 minutes;

[0101] (2) heat treating the mixture at 210° C.

[0102] (3) Cool the product to room temperature, crush it, and pass it through a 200-mesh sieve to obtain plasticized modified mica.

[0103] Finally, prepare the flame retardant sealing material. The specific steps are as follows:

[0104] (1) 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 2 parts of microcrystalline wax, and 13 parts of modified nano glass fiber were added into an internal mixer and mixed at 70° C. for 4.5 min at a speed of 37 rpm;

[0105] (2) adding 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of paraffin oil, and 2 parts of stearic acid to the mixture, and continuing to mix to obtain a rubber mixture;

[0106] (3) 23 parts of plasticized modified mica, 13 parts of brominated epoxy resin, 4 parts of hexabromocyclododecane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, 2.5 parts of magnesium hydroxide, and 2.5 parts of vinyl tri(β-methoxyethoxy) silane are mixed uniformly with the rubber compound;

[0107] (4) sending the mixture into an open mill and mixing it evenly to obtain a rubber material;

[0108] (5) Plasticizing the rubber at 170°C to form a sheet with a thickness of 2.5 mm and cooling;

[0109] (6) Cut the sheet into films with a length of 20 cm and a width of 10 cm;

[0110] (7) The film is placed in a vulcanizer and vulcanized at a temperature of 160° C. and a pressure of 11 MPa for 35 minutes to obtain the flame retardant sealing material.

[0111] In the present embodiment, the amount of ethylene-vinyl acetate copolymer and nitrile rubber is increased, and the flexibility and sealing performance of the material are further improved. In the preparation process of modified mica, the processing time and temperature are increased, and the surface modification effect is further improved. The amount of brominated epoxy resin and hexabromocyclododecane is also increased, and it is expected that the flame retardant properties of the material will be improved. In addition, the amount of disulfide and isothiazolinone is slightly increased, which will further enhance the antioxidant properties and crosslinking degree of the material.

[0112] Example 3

[0113] This embodiment provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof. The flame retardant sealing material is made of the following raw materials in parts by weight: 60 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 25 parts of modified mica, 30 parts of sepiolite powder, 15 parts of brominated epoxy resin, 12 parts of magnesium carbonate, 3 parts of stearic acid, 15 parts of nano glass fiber, 3 parts of microcrystalline wax, 5 parts of hexabromocyclododecane, 3 parts of paraffin oil, 2 parts of disulfide, 3 parts of vinyl tris (β-methoxyethoxy) silane, 2 parts of isothiazolinone, 4 parts of aluminum hydroxide, 2 parts of sodium hydroxide, and 3 parts of magnesium hydroxide.

[0114] The preparation method of the flame retardant sealing material comprises the following steps:

[0115] First, prepare modified mica. The specific steps are as follows:

[0116] (1) 10 kg of mica powder was added to 100 kg of water, and after being evenly dispersed, 1 kg of carboxymethyl chitosan was added, and the mixture was stirred at 60° C. for 7 h, dried, calcined at 590° C. for 8 h, cooled, ground, and passed through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder;

[0117] (2) adding 0.4 kg of dodecyltrimethylammonium bromide, 0.5 kg of n-propylamine and ethanol to the obtained carboxymethyl chitosan-coated mica powder, stirring at 49° C. for 30 min, and heating to 70° C.;

[0118] (3) Add 0.6 kg of silane coupling agent KH-570 and 10 kg of water to the mixture and stir for 30 min;

[0119] (4) subjecting the mixture to microwave irradiation for 5 h at a power of 300 W;

[0120] (5) The product was dried and passed through a 200-mesh sieve to obtain modified mica.

[0121] Secondly, prepare the modified nano glass fiber. The specific steps are as follows:

[0122] (1) Put 2 parts of nano glass fibers into 15 parts of toluene and disperse them by ultrasonic;

[0123] (2) Add 0.1 parts of coupling agent KH560 to the dispersion and stir at room temperature for 30 minutes;

[0124] (3) filtering the mixture and washing it with toluene five times;

[0125] (4) Drying the product at 70°C to obtain modified nano glass fibers.

[0126] Then, plasticized modified mica is prepared. The specific steps are as follows:

[0127] (1) Mix the modified mica with 2 parts of disulfide and 2 parts of isothiazolinone and stir for 30 minutes;

[0128] (2) heat treating the mixture at 240° C.

[0129] (3) Cool the product to room temperature, crush it, and pass it through a 200-mesh sieve to obtain plasticized modified mica.

[0130] Finally, prepare the flame retardant sealing material. The specific steps are as follows:

[0131] (1) 60 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 3 parts of microcrystalline wax, and 15 parts of modified nano glass fiber were added into an internal mixer and mixed at 80° C. for 5 min at a speed of 45 rpm;

[0132] (2) adding 30 parts of sepiolite powder, 12 parts of magnesium carbonate, 3 parts of paraffin oil, and 3 parts of stearic acid to the mixture, and continuing to mix to obtain a rubber mixture;

[0133] (3) 25 parts of plasticized modified mica, 15 parts of brominated epoxy resin, 5 parts of hexabromocyclododecane, 4 parts of aluminum hydroxide, 2 parts of sodium hydroxide, 3 parts of magnesium hydroxide, and 3 parts of vinyl tri(β-methoxyethoxy)silane are mixed uniformly with the rubber compound;

[0134] (4) sending the mixture into an open mill and mixing it evenly to obtain a rubber material;

[0135] (5) Plasticizing the rubber at 180°C to form a sheet with a thickness of 3 mm and cooling;

[0136] (6) Cut the sheet into films with a length of 25 cm and a width of 12 cm;

[0137] (7) The film is placed in a vulcanizer and vulcanized at a temperature of 170° C. and a pressure of 12 MPa for 40 minutes to obtain the flame retardant sealing material.

[0138] In the present embodiment, the consumption of each component is further increased, particularly the content of ethylene-vinyl acetate copolymer and acrylonitrile-butadiene rubber has reached the upper limit, which can make the material have higher flexibility and sealing performance. The preparation process of modified mica has adopted the highest temperature and the longest processing time, and it is expected that the best surface modification effect can be obtained. The consumption of brominated epoxy resin and hexabromocyclododecane has also reached the upper limit, which can significantly improve the flame retardant properties of the material.

[0139] It is noteworthy that the amount of disulfide and isothiazolinone in this embodiment reaches the maximum value. As an antioxidant, disulfide can effectively capture free radicals to prevent oxidative degradation of polymer chains. At the same time, at high temperatures, disulfide will decompose to form sulfur free radicals, promote the cross-linking of polymer chains, and further improve the thermal stability of the material. Isothiazolinone not only has excellent mildew and antibacterial properties, but also the NS bond on its ring will break at high temperatures, and the free radicals generated promote the cross-linking of polymers, thereby improving the heat resistance and mechanical strength of the material.

[0140] In addition, the amount of sepiolite powder and nano glass fiber in this embodiment also reached the highest value. The needle-like structure of sepiolite can form a three-dimensional network in the material, reinforcing the mechanical properties of the material. Nano glass fiber can significantly improve the mechanical properties and flame retardant properties of the material. The synergistic effect of these two fillers is expected to make the material have more excellent comprehensive properties.

[0141] Example 4

[0142] This embodiment provides a flame retardant sealing material for cable pipe plugging device with an intermediate ratio and a preparation method thereof. The flame retardant sealing material is made of the following raw materials in parts by weight: 57 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 22 parts of modified mica, 26 parts of sepiolite powder, 12 parts of brominated epoxy resin, 10 parts of magnesium carbonate, 2 parts of stearic acid, 12 parts of nano glass fiber, 2 parts of microcrystalline wax, 3 parts of hexabromocyclododecane, 2 parts of paraffin oil, 1.5 parts of disulfide, 2.5 parts of vinyl tris (β-methoxyethoxy) silane, 1.5 parts of isothiazolinone, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, and 2.5 parts of magnesium hydroxide.

[0143] The preparation method of the flame retardant sealing material comprises the following steps:

[0144] First, prepare modified mica. The specific steps are as follows:

[0145] (1) 10 kg of mica powder was added to 100 kg of water, and after being evenly dispersed, 1 kg of carboxymethyl chitosan was added, and the mixture was stirred at 50° C. for 5.5 h, dried, calcined at 525° C. for 6.5 h, cooled, ground, and passed through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder;

[0146] (2) adding 0.3 kg of dodecyltrimethylammonium bromide, 0.35 kg of n-propylamine and ethanol to the obtained carboxymethyl chitosan-coated mica powder, stirring at 44.5° C. for 25 min, and heating to 65° C.;

[0147] (3) Add 0.5 kg of silane coupling agent KH-570 and 9 kg of water to the mixture and stir for 25 min;

[0148] (4) subjecting the mixture to microwave radiation for 4 h at a power of 250 W;

[0149] (5) The product was dried and passed through a 200-mesh sieve to obtain modified mica.

[0150] Secondly, prepare the modified nano glass fiber. The specific steps are as follows:

[0151] (1) 1.5 parts of nano-glass fibers were placed in 12.5 parts of toluene and ultrasonically dispersed;

[0152] (2) Add 0.075 parts of coupling agent KH560 to the dispersion and stir at room temperature for 25 minutes;

[0153] (3) filtering the mixture and washing it with toluene four times;

[0154] (4) Drying the product at 65°C to obtain modified nano glass fibers.

[0155] Then, plasticized modified mica is prepared. The specific steps are as follows:

[0156] (1) Mix the modified mica with 1.5 parts of disulfide and 1.5 parts of isothiazolinone and stir for 25 minutes;

[0157] (2) heat treating the mixture at 210° C.

[0158] (3) Cool the product to room temperature, crush it, and pass it through a 200-mesh sieve to obtain plasticized modified mica.

[0159] Finally, prepare the flame retardant sealing material. The specific steps are as follows:

[0160] (1) 57 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 2 parts of microcrystalline wax, and 12 parts of modified nano glass fiber were added to an internal mixer and mixed at 70° C. for 4.5 min at a speed of 37 rpm;

[0161] (2) adding 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of paraffin oil, and 2 parts of stearic acid to the mixture, and continuing to mix to obtain a rubber mixture;

[0162] (3) 22 parts of plasticized modified mica, 12 parts of brominated epoxy resin, 3 parts of hexabromocyclododecane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, 2.5 parts of magnesium hydroxide, and 2.5 parts of vinyl tri(β-methoxyethoxy) silane are mixed uniformly with the rubber compound;

[0163] (4) sending the mixture into an open mill and mixing it evenly to obtain a rubber material;

[0164] (5) Plasticizing the rubber at 170°C to form a sheet with a thickness of 2.5 mm and cooling;

[0165] (6) Cut the sheet into films with a length of 20 cm and a width of 10 cm;

[0166] (7) The film is placed in a vulcanizer and vulcanized at a temperature of 160° C. and a pressure of 11 MPa for 35 minutes to obtain the flame retardant sealing material.

[0167] In this embodiment, the dosage of each component is selected as an intermediate value, aiming to obtain a balance of various properties. The dosage of ethylene-vinyl acetate copolymer and nitrile rubber is moderate, and it is expected to achieve a good balance between flexibility and sealing performance. The preparation process of modified mica adopts a moderate temperature and processing time, which will obtain a good surface modification effect while maintaining a high production efficiency.

[0168] It is worth noting that the dosage of disulfide and isothiazolinone in this embodiment is moderate. This ratio will strike a balance between antioxidant performance, crosslinking degree and mildew and antibacterial properties. Disulfide as an antioxidant and potential crosslinking accelerator, and isothiazolinone as a mildew inhibitor and crosslinking aid, their synergistic effect is expected to provide comprehensive performance improvement for the material.

[0169] In addition, the dosage of brominated epoxy resin and hexabromocyclododecane in this embodiment is also selected to be an intermediate value. This ratio will strike a balance between flame retardancy and other material properties (such as mechanical properties). At the same time, the dosage of aluminum hydroxide and magnesium hydroxide is also moderate, which is expected to provide a moderate heat absorption and cooling effect without affecting other properties of the material too much.

[0170] Comparative Example 1

[0171] This comparative example provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof, for comparison with Example 1. The flame retardant sealing material is made of the following raw materials in parts by weight: 55 parts of ethylene-vinyl acetate copolymer, 48 parts of nitrile rubber, 20 parts of unmodified mica, 22 parts of sepiolite powder, 10 parts of brominated epoxy resin, 8 parts of magnesium carbonate, 1 part of stearic acid, 10 parts of unmodified nano glass fiber, 1 part of microcrystalline wax, 2 parts of hexabromocyclododecane, 1 part of paraffin oil, 2 parts of vinyl tris (β-methoxyethoxy) silane, 2 parts of aluminum hydroxide, 1 part of sodium hydroxide, and 2 parts of magnesium hydroxide.

[0172] The preparation method of this comparative example is basically the same as that of Example 1, but does not include the modification steps of mica and nano-glass fibers, and does not use disulfide and isothiazolinone. The specific preparation steps are as follows:

[0173] First, 55 parts of ethylene-vinyl acetate copolymer, 48 parts of nitrile rubber, 1 part of microcrystalline wax, and 10 parts of unmodified nano glass fibers were added to an internal mixer and mixed at 60° C. for 4 min at a speed of 30 rpm. Secondly, 22 parts of sepiolite powder, 8 parts of magnesium carbonate, 1 part of paraffin oil, and 1 part of stearic acid were added to the mixture, and mixing was continued to obtain a rubber compound. Then, 20 parts of unmodified mica, 10 parts of brominated epoxy resin, 2 parts of hexabromocyclododecane, 2 parts of aluminum hydroxide, 1 part of sodium hydroxide, 2 parts of magnesium hydroxide, and 2 parts of vinyl tris(β-methoxyethoxy) silane were mixed with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 1.

[0174] This comparative example is intended to verify the effects of surface modification of mica and nano-glass fibers and the addition of disulfide and isothiazolinone on material properties. It is expected that the material of this comparative example will exhibit poor dispersibility and interfacial bonding strength, resulting in a decrease in mechanical properties and flame retardant properties. In addition, due to the lack of disulfide and isothiazolinone, the material will exhibit poor oxidation resistance and heat resistance.

[0175] Comparative Example 2

[0176] This comparative example provides another flame retardant sealing material for cable pipe plugging device and its preparation method, which is used for comparison with Example 2. The flame retardant sealing material is made of the following raw materials in parts by weight: 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 23 parts of modified mica, 26 parts of sepiolite powder, 13 parts of brominated epoxy resin, 10 parts of magnesium carbonate, 2 parts of stearic acid, 13 parts of modified nano glass fiber, 2 parts of microcrystalline wax, 4 parts of hexabromocyclododecane, 2 parts of paraffin oil, 2.5 parts of vinyl tris (β-methoxyethoxy) silane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, and 2.5 parts of magnesium hydroxide.

[0177] The preparation method of this comparative example is basically the same as that of Example 2, but does not include the preparation step of plasticized modified mica, that is, disulfide and isothiazolinone are not used. The specific preparation steps are as follows:

[0178] First, modified mica and modified nano glass fiber were prepared according to the method of Example 2. Then, 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 2 parts of microcrystalline wax, and 13 parts of modified nano glass fiber were added to an internal mixer and mixed at 70°C for 4.5 minutes at a speed of 37 rpm. Next, 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of paraffin oil, and 2 parts of stearic acid were added to the mixture, and mixing was continued to obtain a rubber compound. Subsequently, 23 parts of modified mica (non-plasticized), 13 parts of brominated epoxy resin, 4 parts of hexabromocyclododecane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, 2.5 parts of magnesium hydroxide, and 2.5 parts of vinyl tris(β-methoxyethoxy)silane were mixed uniformly with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 2.

[0179] This comparative example is intended to verify the effect of plasticized modified mica on material properties. It is expected that the material in this comparative example will show poor mica dispersibility and interface bonding strength with the polymer matrix, resulting in a decrease in mechanical properties and flame retardant properties. In addition, due to the lack of disulfide and isothiazolinone, the material will show poor antioxidant, heat resistance and antibacterial properties.

[0180] Comparative Example 3

[0181] This comparative example provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof, which is used for comparison with Example 3. The flame retardant sealing material is made of the following raw materials in parts by weight: 60 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 25 parts of modified mica, 30 parts of sepiolite powder, 15 parts of brominated epoxy resin, 12 parts of magnesium carbonate, 3 parts of stearic acid, 15 parts of modified nano-glass fiber, 3 parts of microcrystalline wax, 5 parts of hexabromocyclododecane, 3 parts of paraffin oil, 2 parts of disulfide, 2 parts of isothiazolinone, and 3 parts of vinyl tris (β-methoxyethoxy) silane.

[0182] The preparation method of this comparative example is basically the same as that of Example 3, but aluminum hydroxide, sodium hydroxide and magnesium hydroxide are not used. The specific preparation steps are as follows:

[0183] First, modified mica, modified nano glass fiber and plasticized modified mica were prepared according to the method of Example 3. Then, 60 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 3 parts of microcrystalline wax and 15 parts of modified nano glass fiber were added to an internal mixer and mixed at 80° C. for 5 min at a speed of 45 rpm. Then, 30 parts of sepiolite powder, 12 parts of magnesium carbonate, 3 parts of paraffin oil and 3 parts of stearic acid were added to the mixture and the mixture was continued to be mixed to obtain a rubber compound. Subsequently, 25 parts of plasticized modified mica, 15 parts of brominated epoxy resin, 5 parts of hexabromocyclododecane, 2 parts of disulfide, 2 parts of isothiazolinone and 3 parts of vinyl tri(β-methoxyethoxy)silane were mixed uniformly with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 3.

[0184] This comparative example is intended to verify the effects of aluminum hydroxide, sodium hydroxide and magnesium hydroxide on the flame retardant properties of the material. It is expected that the material in this comparative example will exhibit poor flame retardant properties, especially at high temperatures. Due to the lack of these inorganic hydroxides, the material cannot effectively absorb heat and release water vapor during combustion, resulting in a significant reduction in the flame retardant effect.

[0185] Comparative Example 4

[0186] This comparative example provides another flame retardant sealing material for cable pipe plugging device and its preparation method, which is used for comparison with Example 4. The flame retardant sealing material is made of the following raw materials in parts by weight: 57 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 22 parts of modified mica, 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of stearic acid, 12 parts of modified nano glass fiber, 2 parts of microcrystalline wax, 2 parts of paraffin oil, 1.5 parts of disulfide, 2.5 parts of vinyl tris (β-methoxyethoxy) silane, 1.5 parts of isothiazolinone, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, and 2.5 parts of magnesium hydroxide.

[0187] The preparation method of this comparative example is basically the same as that of Example 4, but brominated epoxy resin and hexabromocyclododecane are not used. The specific preparation steps are as follows:

[0188] First, modified mica, modified nano glass fiber and plasticized modified mica were prepared according to the method of Example 4. Then, 57 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 2 parts of microcrystalline wax, and 12 parts of modified nano glass fiber were added to an internal mixer and mixed at 70°C for 4.5 minutes at a speed of 37 rpm. Next, 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of paraffin oil, and 2 parts of stearic acid were added to the mixture, and mixing was continued to obtain a rubber compound. Subsequently, 22 parts of plasticized modified mica, 1.5 parts of disulfide, 1.5 parts of isothiazolinone, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, 2.5 parts of magnesium hydroxide, and 2.5 parts of vinyl tris(β-methoxyethoxy) silane were mixed uniformly with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 4.

[0189] This comparative example is intended to verify the effects of brominated epoxy resin and hexabromocyclododecane on the flame retardancy of the material. It is expected that the material in this comparative example will show significantly reduced flame retardancy, especially in gas phase flame retardancy. Due to the lack of these halogen flame retardants, the material cannot effectively capture free radicals during the combustion process, making it difficult to suppress the combustion chain reaction.

[0190] Comparative Example 5

[0191] This comparative example provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof, which is used for comparison with Example 1 and Example 3. The flame retardant sealing material is made of the following raw materials in parts by weight: 55 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 25 parts of modified mica, 22 parts of sepiolite powder, 15 parts of brominated epoxy resin, 8 parts of magnesium carbonate, 3 parts of stearic acid, 15 parts of modified nano glass fiber, 1 part of microcrystalline wax, 5 parts of hexabromocyclododecane, 1 part of paraffin oil, 2 parts of disulfide, 2 parts of vinyl tris (β-methoxyethoxy) silane, 2 parts of isothiazolinone, 4 parts of aluminum hydroxide, 1 part of sodium hydroxide, and 3 parts of magnesium hydroxide.

[0192] The preparation method of this comparative example combines the methods of Example 1 and Example 3. The specific preparation steps are as follows:

[0193] First, modified mica, modified nano glass fiber and plasticized modified mica were prepared according to the method of Example 3. Then, 55 parts of ethylene-vinyl acetate copolymer, 54 parts of nitrile rubber, 1 part of microcrystalline wax and 15 parts of modified nano glass fiber were added to an internal mixer and mixed at 60° C. for 4 min at a speed of 30 rpm. Next, 22 parts of sepiolite powder, 8 parts of magnesium carbonate, 1 part of paraffin oil and 3 parts of stearic acid were added to the mixture and the mixture was continued to be mixed to obtain a rubber compound. Subsequently, 25 parts of plasticized modified mica, 15 parts of brominated epoxy resin, 5 parts of hexabromocyclododecane, 2 parts of disulfide, 2 parts of isothiazolinone, 4 parts of aluminum hydroxide, 1 part of sodium hydroxide, 3 parts of magnesium hydroxide and 2 parts of vinyl tris(β-methoxyethoxy)silane were mixed uniformly with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 1.

[0194] This comparative example is intended to verify the synergistic effect of the dosage of each component. By combining the characteristics of Example 1 and Example 3, it can be observed that when the dosage of certain components (such as modified mica, modified nano glass fiber, brominated epoxy resin, etc.) is increased, while the dosage of other components (such as ethylene-vinyl acetate copolymer, sepiolite powder, etc.) remains unchanged, the change in material properties. It is expected that this combination will lead to improved certain properties of the material (such as flame retardancy), but will affect other properties (such as flexibility and processability).

[0195] Comparative Example 6

[0196] This comparative example provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof, which is used for comparison with Example 2 and Example 4. The flame retardant sealing material is made of the following raw materials in parts by weight: 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, and 6 parts of

[0197] This comparative example provides a flame retardant sealing material for a cable pipe plug and a preparation method thereof, which is used for comparison with Example 2 and Example 4. The flame retardant sealing material is made of the following raw materials in parts by weight: 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 23 parts of unmodified mica, 26 parts of sepiolite powder, 13 parts of brominated epoxy resin, 10 parts of magnesium carbonate, 2 parts of stearic acid, 13 parts of unmodified nano glass fiber, 2 parts of microcrystalline wax, 4 parts of hexabromocyclododecane, 2 parts of paraffin oil, 2.5 parts of vinyl tris (β-methoxyethoxy) silane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, and 2.5 parts of magnesium hydroxide.

[0198] The preparation method of this comparative example combines the methods of Example 2 and Example 4, but does not include the modification steps of mica and nano-glass fibers, and does not use disulfide and isothiazolinone. The specific preparation steps are as follows:

[0199] First, 58 parts of ethylene-vinyl acetate copolymer, 51 parts of nitrile rubber, 2 parts of microcrystalline wax, and 13 parts of unmodified nano glass fibers were added to an internal mixer and mixed at 70°C for 4.5 min at a speed of 37 rpm. Secondly, 26 parts of sepiolite powder, 10 parts of magnesium carbonate, 2 parts of paraffin oil, and 2 parts of stearic acid were added to the mixture, and mixing was continued to obtain a rubber compound. Then, 23 parts of unmodified mica, 13 parts of brominated epoxy resin, 4 parts of hexabromocyclododecane, 3 parts of aluminum hydroxide, 1.5 parts of sodium hydroxide, 2.5 parts of magnesium hydroxide, and 2.5 parts of vinyl tris(β-methoxyethoxy) silane were mixed uniformly with the rubber compound. Finally, the preparation was completed according to steps (4)-(7) of Example 2.

[0200] This comparative example is intended to verify the comprehensive effects of the surface modification of mica and nano-glass fibers and the addition of disulfide and isothiazolinone on material properties. By comparing with Example 2 and Example 4, the contribution of these key innovations to material properties can be observed.

[0201] The materials of this comparative example are expected to exhibit the following characteristics:

[0202] 1. Dispersibility and interface bonding strength: Due to the use of unmodified mica and nano-glass fibers, the material will have the problem of uneven filler dispersion, resulting in local stress concentration, thus affecting the mechanical properties of the material. At the same time, the interface bonding strength between the unmodified filler and the polymer matrix is ​​weak, which will cause the material to easily detach from the interface when subjected to force, thereby reducing the overall strength and toughness of the material.

[0203] 2. Flame retardant performance: Although this comparative example contains halogen flame retardants such as brominated epoxy resin and hexabromocyclododecane, the overall flame retardant performance of the material will be affected due to the lack of effective thermal insulation barrier formed by modified mica and modified nano-glass fiber. Especially at high temperatures, the unmodified filler cannot form a dense carbon layer structure, thereby reducing the flame retardant effect of the material.

[0204] 3. Antioxidation and heat resistance: Due to the lack of disulfide, an important antioxidant, the material will undergo oxidative degradation under high temperature or long-term use conditions, resulting in decreased performance. At the same time, the cross-linking effect formed by disulfide at high temperature cannot be achieved, which will affect the heat resistance of the material.

[0205] 4. Antibacterial properties: Since isothiazolinone is not added, the material lacks effective anti-mildew and antibacterial properties, and mold growth may occur when used in a humid environment.

[0206] 5. Processing performance: Although this comparative example retains processing aids such as microcrystalline wax and stearic acid, the processing performance of the material will be slightly reduced due to the lack of plasticizing effect brought by disulfide and isothiazolinone.

[0207] 6. Long-term performance: Due to the lack of synergistic effects of disulfide and isothiazolinone, the material will experience performance degradation during long-term use, especially in high temperature, humid or chemical environments.

[0208] Through these six comparative examples, the innovative points and technical effects of the present invention can be fully verified. These comparative examples cover all endpoint values ​​and some intermediate values ​​in the formula, including components and detailed preparation methods of the components. By comparison with the examples, it can be clearly seen that the addition of modified mica, modified nano-glass fiber, disulfide and isothiazolinone, and the synergistic effect between the components have a significant effect on the material properties. These results strongly support the creativity of the present invention and highlight its important contribution in the field of flame-retardant sealing materials for cable tube plugs.

[0209] In order to comprehensively evaluate the effectiveness and innovation of the flame-retardant sealing material for cable pipe plugging device and the preparation method thereof of the present invention, a series of test experiments were designed to verify key indicators such as the flame-retardant performance, mechanical properties, interface bonding strength, anti-oxidation performance and long-term use performance of the material.

[0210] First, a limiting oxygen index (LOI) test was conducted to evaluate the flame retardant properties of the material. The test method followed the GB / T2406.2-2009 standard and used a JF-3 oxygen index tester. The sample size was 80mm×10mm×4mm, the test temperature was 23±2℃, and the relative humidity was 50±5%.

[0211] Secondly, the tensile strength and elongation at break were tested using a universal testing machine to evaluate the mechanical properties of the material. The test method followed the GB / T 1040.2-2006 standard and used a CMT5105 universal testing machine. The sample was dumbbell-shaped, the test speed was 50 mm / min, the test temperature was 23 ± 2 °C, and the relative humidity was 50 ± 5%.

[0212] Then, the cross-sectional morphology of the material was observed using a scanning electron microscope (SEM) to evaluate the dispersion of the filler and the interfacial bonding strength. The equipment used was a JSM-7500F field emission scanning electron microscope with an accelerating voltage of 5 kV. The sample was treated with gold spraying after liquid nitrogen brittle fracture.

[0213] Again, a thermogravimetric analysis (TGA) test was conducted to evaluate the thermal stability and flame retardancy of the material. The equipment used was a TGA / DSC 3+ thermogravimetric analyzer with a heating rate of 10°C / min, a temperature range of room temperature to 800°C, and a nitrogen atmosphere.

[0214] Finally, a thermal oxidative aging test was conducted to evaluate the long-term performance of the material. The test method follows the GB / T3512-2014 standard, aging at 150°C for 7 days, and then testing the retention of tensile strength and elongation at break.

[0215] Based on the above tests, the following results were obtained:

[0216] Table 1. Performance test results of examples and comparative examples

[0217]

[0218] It can be seen from the results in Table 1 that Example 3 exhibits the best comprehensive performance and is the best embodiment of the present invention. All embodiments are significantly better than the comparative examples, which fully proves the innovation and technical effects of the present invention.

[0219] After in-depth analysis of the test results, it is found that the present invention has the following unexpected technical effects:

[0220] 1. Super synergistic flame retardant effect: The LOI value of Example 3 reaches 36.8%, which is much higher than that of each comparative example. This shows that there is a significant synergistic effect between the modified mica, modified nano-glass fiber, bromine-based flame retardant and inorganic hydroxide in the present invention. The modified filler not only improves the flame retardant properties of the material, but also improves the carbon layer structure, and forms a gas-solid dual-phase flame retardant system with the bromine-based flame retardant. The degree of this synergistic effect is far beyond expectations, providing a new idea for the development of high-efficiency flame retardant materials.

[0221] 2. Interface enhancement effect: The tensile strength of Example 3 reached 22.1 MPa, which is 41.7% higher than that of Comparative Example 1. This result shows that a strong interface interaction is formed between the filler and the polymer matrix through the multi-step surface modification process. In particular, the addition of disulfide and isothiazolinone forms chemical bonds at the interface, further enhancing the interface bonding strength. This interface enhancement effect not only improves the mechanical properties of the material, but also improves its flame retardant properties and long-term performance.

[0222] 3. Mechanism of improving thermal stability: The TGA carbon residue of Example 3 reached 32.7%, which was 42.8% higher than that of Comparative Example 4. This result reveals a new mechanism for improving thermal stability. The modified mica and modified nano-glass fibers form a network structure at high temperatures, while the disulfide promotes the cross-linking of polymer chains when heated. This multiple effect enables the material to form a denser and more stable carbon layer structure at high temperatures, thereby significantly improving the thermal stability and flame retardant properties of the material.

[0223] 4. Long-term performance maintenance mechanism: The tensile strength retention rate and elongation at break retention rate of Example 3 after thermal oxidative aging reached 95.8% and 92.5%, respectively, which are much higher than those of the comparative examples. This shows that the disulfide and isothiazolinone in the present invention not only play an antioxidant and mildew-proof role, but also continuously promote the dynamic crosslinking of the material during long-term use. This dynamic crosslinking process can repair the microscopic damage generated by the material during use, thereby maintaining the long-term performance of the material.

[0224] 5. Filler orientation effect: Through SEM observation, it was found that the modified mica and modified nano-glass fibers in the examples showed a certain orientation in the material. This orientation effect is caused by the specific functional groups introduced during the multi-step modification process. The oriented fillers not only improve the mechanical properties of the material, but also form a maze effect, effectively delaying the transfer of heat and oxygen, and further improving the flame retardant properties of the material.

[0225] In summary, the present invention achieves comprehensive improvement in flame retardancy, mechanical properties and long-term performance through a carefully designed multi-component synergistic system. These unexpected technical effects not only verify the innovation and advancement of the present invention, but also provide a new research direction for the development of high-performance flame retardant sealing materials.

[0226] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. Flame retardant sealing materials for cable pipe pluggers, It is characterized in that The flame retardant sealing material is made of the following raw materials in parts by weight: 55-60 parts of ethylene-vinyl acetate copolymer; 48-54 parts of nitrile rubber; 20-25 parts of modified mica; 22-30 parts of sepiolite powder; 10-15 parts of brominated epoxy resin; 8-12 parts of magnesium carbonate; 1-3 parts of stearic acid; 10-15 parts of nano glass fiber; 1-3 parts of microcrystalline wax; 2-5 parts of hexabromocyclododecane; 1-3 parts of paraffin oil; 1-2 parts of disulfide; 2-3 parts of vinyl tris(β-methoxyethoxy)silane; 1-2 parts of isothiazolinone; 2-4 parts of aluminum hydroxide; 1-2 parts of sodium hydroxide; and 2-3 parts of magnesium hydroxide.

2. The flame retardant sealing material for cable pipe plugging device according to claim 1, It is characterized in that The modified mica is prepared by the following steps: (1) adding mica powder to water, dispersing it evenly, adding carboxymethyl chitosan, stirring at 40-60° C. for 4-7 hours, drying, calcining at 450-590° C. for 5-8 hours, cooling, grinding, and passing through a 200-mesh sieve to obtain carboxymethyl chitosan-coated mica powder; (2) adding dodecyltrimethylammonium bromide, n-propylamine and ethanol to the carboxymethyl chitosan coated mica powder, stirring at 40-49° C. for 20-30 min, and heating to 60-70° C.; (3) adding silane coupling agent KH-570 and water to the mixture obtained in step (2), and stirring for 20-30 minutes; (4) subjecting the mixture obtained in step (3) to microwave radiation for 3-5 h; (5) Dry the product obtained in step (4) and pass it through a 200-mesh sieve to obtain the modified mica.

3. The flame retardant sealing material for cable pipe plugging device according to claim 2, It is characterized in that In steps (1) to (5), the weight ratio of the mica powder, carboxymethyl chitosan, dodecyltrimethylammonium bromide, n-propylamine, silane coupling agent KH-570, and water is 10:1:0.2-0.4:0.2-0.5:0.4-0.6:8-10.

4. The flame retardant sealing material for cable pipe plugging device according to claim 2, It is characterized in that The power of the microwave radiation in step (4) is 200-300W.

5. The flame retardant sealing material for cable pipe plugging device according to claim 1, It is characterized in that The nano glass fiber is subjected to a surface modification treatment, which comprises the following steps: (1) Place 1-2 parts of nano-glass fibers in 10-15 parts of toluene and disperse by ultrasonication; (2) adding 0.05-0.1 parts of coupling agent KH560 to the dispersion obtained in step (1), and stirring at room temperature for 20-30 minutes; (3) filtering the mixture obtained in step (2), and washing with toluene 3-5 times; (4) Drying the product obtained in step (3) at 60-70° C. to obtain modified nano glass fibers.

6. The flame retardant sealing material for cable pipe plugging device according to claim 1, It is characterized in that The modified mica in the flame retardant sealing material is subjected to plasticization treatment, and the treatment comprises the following steps: (1) mixing the modified mica with disulfide and isothiazolinone, and stirring for 20-30 minutes; (2) heat treating the mixture obtained in step (1) at 180-240° C.; (3) Cooling the product obtained in step (2) to room temperature, crushing it, and passing it through a 200-mesh sieve to obtain plasticized modified mica.

7. A method for preparing a flame retardant sealing material for a cable pipe plug according to any one of claims 1 to 6, It is characterized in that The following steps are involved: (1) Add ethylene-vinyl acetate copolymer, nitrile rubber, microcrystalline wax and nano glass fiber into an internal mixer and mix at 60-80° C. for 4-5 minutes; (2) adding sepiolite powder, magnesium carbonate, paraffin oil and stearic acid to the mixture obtained in step (1), and continuing to mix to obtain a rubber mixture; (3) uniformly mixing the modified mica, brominated epoxy resin, hexabromocyclododecane, aluminum hydroxide, sodium hydroxide, magnesium hydroxide, vinyl tri(β-methoxyethoxy)silane and the rubber mixture obtained in step (2); (4) feeding the mixture obtained in step (3) into an open mill and mixing it uniformly to obtain a rubber material; (5) plasticizing the rubber obtained in step (4) at 160-180° C. to form a sheet of desired thickness, and cooling; (6) Cutting the sheet obtained in step (5) into films with a length of 15-25 cm and a width of 8-12 cm; (7) placing the film obtained in step (6) into a vulcanizer and vulcanizing at a temperature of 150-170° C. and a pressure of 10-12 MPa to obtain the flame retardant sealing material.

8. The preparation method according to claim 7, It is characterized in that In steps (1) and (2), the rotation speed of the internal mixer is 30-45 rpm.

9. The preparation method according to claim 7, It is characterized in that The modified mica used in step (3) is plasticized modified mica.

10. The preparation method according to claim 7, It is characterized in that Before step (4), the method further includes mixing disulfide and isothiazolinone with modified mica, heat treating at 180-240° C., cooling to room temperature, crushing, and passing through a 200-mesh sieve to obtain plasticized modified mica.

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