Fireproofing and flame-retardant plastic and method for producing the same

Abstract

This invention discloses a fire-retardant plastic and its preparation method, relating to the field of plastics. In preparing the fire-retardant plastic, modified reduced graphene oxide nanosheets are obtained by reacting reduced graphene oxide nanosheets, allylphosphine dichloride, phosphorus oxychloride, and 4,4-diaminodiphenylmethane; modified polyvinyl chloride is obtained by reacting allyl hydrazine and polyvinyl chloride powder; and the modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate, and benzoyl peroxide are mixed and reacted to obtain the fire-retardant plastic. The fire-retardant plastic prepared by this invention exhibits excellent flame-retardant properties, corrosion resistance, aging resistance, and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of plastics, specifically to a fire-retardant plastic and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is an important polymer with high toughness, wear resistance, corrosion resistance, and good chemical stability. It plays a vital role in our daily lives, widely used in building materials and everyday consumer goods, such as pipes, defense cables, packaging bags, and medical supplies. PVC contains a large amount of chlorine, which, when burned, produces large amounts of black smoke, heat, and toxic or corrosive gases (such as HCl and CO), posing a threat to human life and property. Therefore, flame retardants are often introduced to enhance the flame-retardant properties of polymer materials. Based on the different properties of the flame retardants, the flame-retardant types of polymer materials can be mainly divided into two categories: inorganic flame-retardant systems and organic flame-retardant systems.

[0003] Inorganic flame retardants, characterized by convenient processing and low smoke and toxicity, mainly include three types: metal hydroxides, expandable graphite, and nanocomposites. Aluminum hydroxide and magnesium hydroxide, currently the most widely used inorganic flame retardants, are typical metal hydroxide flame retardants. Their flame-retardant mechanism focuses on endothermic decomposition reactions, releasing water of crystallization to dilute the concentration of combustible gases around the flame and generating a metal oxide-reinforced char layer to achieve thermal barrier and thus quench the flame. However, their high addition levels often lead to a decrease in the material's mechanical properties as flame retardancy improves. Nanofillers, such as montmorillonite and carbon nanotubes, can improve flame retardancy by physically blocking the release of pyrolysis products, but they still face the same problem of severely degraded mechanical and other properties.

[0004] Compared to inorganic flame retardants, organic flame retardants prevent the chain reaction of combustion through chemical reactions. These mainly include halogen-based, phosphorus-based, nitrogen-based, and silicon-based flame retardants. Halogen-based flame retardants primarily exert their flame-retardant effect through a gas-phase free radical capture mechanism, reacting with highly reactive ·OH and ·H free radicals during combustion to quench the flame. Phosphorus-based flame retardants mainly function through a dual effect of condensation-assisted char formation and gas-phase dilution. In recent years, phosphorus-nitrogen synergistic systems have become a research hotspot due to their highly efficient synergistic effect. Therefore, this invention provides a flame-retardant fire-resistant plastic and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a fire-retardant plastic and its preparation method to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A fire-retardant plastic is prepared by mixing and reacting modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide.

[0007] As an optimization, the rare earth composite stabilizer is model WWP-C, sourced from Guangdong Weilinna Functional Materials Co., Ltd.

[0008] As an optimization, the modified polyvinyl chloride is prepared by reacting allyl hydrazine with polyvinyl chloride powder.

[0009] As an optimization, the polyvinyl chloride powder is model DG-700, sourced from Dongguan Zhangmutou Hengtai Plastic Raw Material Business Department.

[0010] As an optimization, the modified reduced graphene oxide nanosheets are prepared by reacting reduced graphene oxide nanosheets, allylphosphine dichloride, and 4,4-diaminodiphenylmethane.

[0011] As an optimization, the reduced graphene oxide nanosheets are model SY-rGO-L and are from Beijing Meiston Technology Development Co., Ltd.

[0012] A fire-retardant plastic and its preparation method, comprising the following preparation steps: (1) Mix reduced graphene oxide nanosheets and acetonitrile at a mass ratio of 1:(290~310), and ultrasonically disperse for 1~3h. At 1~3℃, add 6~7 times the mass of the reduced graphene oxide nanosheets of triethylamine and 1~3 times the mass of the reduced graphene oxide nanosheets of 4,4-diaminodiphenylmethane. Under a nitrogen atmosphere, add 0.2~0.4 times the mass of the reduced graphene oxide nanosheets of allylphosphine dichloride and 1.1~1.2 times the mass of the reduced graphene oxide nanosheets of phosphorus oxychloride at a uniform rate over 20~40min. Continue ultrasonication for 55~65min, raise the temperature to 45~55℃ and reflux for 23~25h. After cooling, filter, wash with deionized water 3~5 times, and dry at 55~65℃ for 11~13h to obtain modified reduced graphene oxide nanosheets. (2) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide are mixed in a mass ratio of 1:(0.3~0.4):(40~50):(260~280), stirred at 75~85℃ and 200~400rpm for 1~3h, cooled to 20~30℃, methanol is added until the mass of the precipitate remains unchanged, then filtered, dissolved in tetrahydrofuran, methanol is precipitated and filtered, the dissolution and precipitation are repeated 2~4 times, and dried at 55~65℃ for 23~25h to obtain modified polyvinyl chloride; (3) Modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide are mixed in a mass ratio of 1:(0.03~0.05):(0.04~0.06):(0.04~0.06):(0.005~0.015). The mixture is then mixed and plasticized for 7~9 minutes using a two-roll mill at a mixing temperature of 170~180℃ and a roller speed ratio of 1:(1~2). Samples are prepared using a 25t hydraulic flatbed press at 170~180℃. After cooling, the samples are cut using a universal sample preparation machine and left to stand at 20~30℃ for 23~25 hours to obtain fire-retardant plastic.

[0013] As an optimization, the reaction equation for the modified polyvinyl chloride in step (2) is as follows: .

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing fire-retardant plastics, this invention involves reacting reduced graphene oxide nanosheets, allylphosphine dichloride, phosphorus oxychloride, and 4,4-diaminodiphenylmethane to obtain modified reduced graphene oxide nanosheets; reacting allyl hydrazine and polyvinyl chloride to obtain modified polyvinyl chloride; and then mixing and reacting the modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate, and benzoyl peroxide to obtain fire-retardant plastics.

[0015] First, modified reduced graphene oxide nanosheets were prepared by reacting reduced graphene oxide nanosheets, allylphosphine dichloride, phosphorus oxychloride, and 4,4-diaminodiphenylmethane. Reduced graphene oxide has fewer surface functional groups, resulting in better UV absorption and gas barrier capabilities, forming a dense physical barrier that enhances the material's anti-aging and corrosion resistance. Simultaneously, reduced graphene oxide can also serve as a char-forming framework, catalyzing the formation of a continuous, dense, and robust carbonaceous protective layer during combustion. This layer provides heat insulation, oxygen barrier, prevents the continued combustion of lower layers, and suppresses smoke release, thus improving the material's fire resistance. Long-chain organic compounds grafted onto the surface can hinder aggregation between sheets, improve compatibility with the matrix, and enhance the dispersibility of reduced graphene oxide in the matrix, further strengthening the material's anti-aging and corrosion resistance. The introduction of P and N flame-retardant elements and a rigid benzene ring structure into the long-chain organic compounds allows the PN system to release non-flammable gases during combustion, diluting the oxygen concentration and generating strong dehydrating substances that promote char formation, further improving the material's fire resistance.

[0016] Secondly, modified polyvinyl chloride (PVC) is prepared by reacting allyl hydrazine with PVC. Then, fire-retardant plastic is prepared by mixing and reacting modified PVC, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate, and benzoyl peroxide. The hydrazine group can capture free radicals generated during combustion, reduce the content of combustible free radicals, reduce the degree of gas phase combustion, and improve the flame retardant performance of the material. At the same time, the hydrazine group can also capture and remove R·, RO·, and ROO· generated during aging, inhibit the attack of free radicals on chain segments, slow down chain segment breakage, and synergize with the ultraviolet light shielding ability of reduced graphene oxide to delay the aging process of the material. The double bonds on the side chains of PVC can form crosslinks with the double bonds on the modified reduced graphene oxide nanosheets, enhancing the mechanical properties of the material. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] The raw materials used in the following examples and comparative examples are all commercially available: The rare earth composite stabilizer is model WWP-C and comes from Guangdong Weilinna Functional Materials Co., Ltd. The polyvinyl chloride powder is model DG-700 and comes from Dongguan Zhangmutou Hengtai Plastic Raw Materials Business Department. The reduced graphene oxide nanosheets are model number SY-rGO-L and are from Beijing Meiston Technology Development Co., Ltd. The graphene oxide nanosheets are model number MG-NGO-01 and are from Shanghai Maoguo Nanotechnology Co., Ltd. Example 1:

[0019] A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Reduced graphene oxide nanosheets and acetonitrile were mixed at a mass ratio of 1:290 and ultrasonically dispersed for 1 h. At 1 °C, 6 times the mass of the reduced graphene oxide nanosheets of triethylamine and 1 times the mass of the reduced graphene oxide nanosheets of 4,4-diaminodiphenylmethane were added. Under a nitrogen atmosphere, 0.2 times the mass of the reduced graphene oxide nanosheets of allylphosphine dichloride and 1.1 times the mass of the reduced graphene oxide nanosheets of phosphorus oxychloride were uniformly reduced within 20 min. Ultrasonic treatment was continued for 65 min. The temperature was raised to 45 °C and refluxed for 25 h. After cooling, the mixture was filtered, washed 3 times with deionized water, and dried at 55 °C for 13 h to obtain modified reduced graphene oxide nanosheets. (2) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide were mixed in a mass ratio of 1:0.3:40:260 and stirred at 75°C and 200 rpm for 3 h. The mixture was cooled to 20°C and methanol was added until the mass of the precipitate remained unchanged. The mixture was then filtered. The precipitate was dissolved in tetrahydrofuran and filtered again after methanol precipitation. The dissolution and precipitation were repeated twice. The mixture was dried at 55°C for 25 h to obtain modified polyvinyl chloride. (3) Modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.03:0.04:0.04:0.005. The mixture was then mixed and plasticized for 9 minutes using a two-roll mill at a mixing temperature of 170℃ and a roller speed ratio of 1:1. Samples were prepared at 170℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and allowed to stand at 20℃ for 25 hours to obtain fire-retardant plastic. Example 2:

[0020] A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Reduced graphene oxide nanosheets and acetonitrile were mixed at a mass ratio of 1:300 and ultrasonically dispersed for 2 h. At 2 °C, 6.5 times the mass of the reduced graphene oxide nanosheets of triethylamine and 2 times the mass of the reduced graphene oxide nanosheets of 4,4-diaminodiphenylmethane were added. Under a nitrogen atmosphere, 0.3 times the mass of the reduced graphene oxide nanosheets of allylphosphine dichloride and 1.15 times the mass of the reduced graphene oxide nanosheets of phosphorus oxychloride were added at a uniform rate over 30 min. The mixture was ultrasonicated for 60 min, heated to 50 °C and refluxed for 24 h. After cooling, the mixture was filtered, washed 4 times with deionized water, and dried at 60 °C for 12 h to obtain modified reduced graphene oxide nanosheets. (2) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide were mixed in a mass ratio of 1:0.35:45:270 and stirred at 80℃ and 300rpm for 2h. The mixture was cooled to 25℃ and methanol was added until the mass of the precipitate remained unchanged. The mixture was then filtered. The precipitate was dissolved in tetrahydrofuran and filtered again after methanol precipitation. The dissolution and precipitation were repeated 3 times. The mixture was dried at 60℃ for 24h to obtain modified polyvinyl chloride. (3) Modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.04:0.05:0.05:0.01. The mixture was then mixed and plasticized for 8 minutes using a two-roll mill at a mixing temperature of 175℃ and a roller speed ratio of 1:1.5. Samples were prepared at 175℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and left to stand at 25℃ for 24 hours to obtain fire-retardant plastic. Example 3:

[0021] A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Reduced graphene oxide nanosheets and acetonitrile were mixed at a mass ratio of 1:310 and ultrasonically dispersed for 3 h. At 3 °C, triethylamine (7 times the mass of the reduced graphene oxide nanosheets) and 4,4-diaminodiphenylmethane (3 times the mass of the reduced graphene oxide nanosheets) were added. Under a nitrogen atmosphere, allylphosphine dichloride (0.4 times the mass of the reduced graphene oxide nanosheets) and phosphorus oxychloride (1.2 times the mass of the reduced graphene oxide nanosheets) were added at a uniform rate over 40 min. The mixture was ultrasonicated for 55 min, heated to 55 °C and refluxed for 23 h. After cooling, the mixture was filtered, washed 5 times with deionized water, and dried at 65 °C for 11 h to obtain modified reduced graphene oxide nanosheets. (2) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide were mixed in a mass ratio of 1:0.4:50:280 and stirred at 85℃ and 400rpm for 1h. The mixture was cooled to 30℃ and methanol was added until the mass of the precipitate remained unchanged. The mixture was then filtered. The precipitate was dissolved in tetrahydrofuran and filtered again after methanol precipitation. The dissolution and precipitation were repeated 4 times. The mixture was dried at 65℃ for 23h to obtain modified polyvinyl chloride. (3) Modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.05:0.06:0.06:0.015. The mixture was then mixed and plasticized for 7 minutes using a two-roll mill at a mixing temperature of 180℃ and a roller speed ratio of 1:2. Samples were prepared at 180℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and allowed to stand at 30℃ for 23 hours to obtain fire-retardant plastic.

[0022] Comparative Example 1: A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide were mixed in a mass ratio of 1:0.35:45:270 and stirred at 80℃ and 300rpm for 2h. The mixture was cooled to 25℃ and methanol was added until the mass of the precipitate remained unchanged. The mixture was then filtered, dissolved in tetrahydrofuran, and precipitated with methanol. The precipitate was then filtered again. The dissolution and precipitation were repeated 3 times. The mixture was dried at 60℃ for 24h to obtain modified polyvinyl chloride. (2) Modified polyvinyl chloride, reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.04:0.05:0.05:0.01. The mixture was then mixed and plasticized for 8 minutes using a two-roll mill at a mixing temperature of 175℃ and a roller speed ratio of 1:1.5. Samples were prepared at 175℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and allowed to stand at 25℃ for 24 hours to obtain fire-retardant plastic.

[0023] Comparative Example 2: A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Reduced graphene oxide nanosheets and acetonitrile were mixed at a mass ratio of 1:300 and ultrasonically dispersed for 2 h. At 2 °C, 6.5 times the mass of the reduced graphene oxide nanosheets of triethylamine and 2 times the mass of the reduced graphene oxide nanosheets of 4,4-diaminodiphenylmethane were added. Under a nitrogen atmosphere, 0.3 times the mass of the reduced graphene oxide nanosheets of allylphosphine dichloride and 1.15 times the mass of the reduced graphene oxide nanosheets of phosphorus oxychloride were added at a uniform rate over 30 min. The mixture was ultrasonicated for 60 min, heated to 50 °C and refluxed for 24 h. After cooling, the mixture was filtered, washed 4 times with deionized water, and dried at 60 °C for 12 h to obtain modified reduced graphene oxide nanosheets. (2) Polyvinyl chloride powder, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.04:0.05:0.05:0.01. The mixture was then mixed and plasticized for 8 minutes using a two-roll mill at a mixing temperature of 175℃ and a roller speed ratio of 1:1.5. Samples were prepared at 175℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and left to stand at 25℃ for 24 hours to obtain fire-retardant plastic.

[0024] Comparative Example 3: A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Polyvinyl chloride powder, reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.04:0.05:0.05:0.01. The mixture was then mixed and plasticized for 8 minutes using a two-roll mill at a mixing temperature of 175℃ and a roller speed ratio of 1:1.5. Samples were prepared at 175℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and left to stand at 25℃ for 24 hours to obtain fire-retardant plastic.

[0025] Comparative Example 4: A fire-retardant plastic and its preparation method are disclosed, the fire-retardant plastic and its preparation method comprising the following preparation steps: (1) Mix graphene oxide nanosheets and acetonitrile at a mass ratio of 1:300, and ultrasonically disperse for 2 hours. At 2°C, add triethylamine (6.5 times the mass of graphene oxide nanosheets) and 4,4-diaminodiphenylmethane (2 times the mass of graphene oxide nanosheets). In a nitrogen atmosphere, add allylphosphine dichloride (0.3 times the mass of graphene oxide nanosheets) and phosphorus oxychloride (1.15 times the mass of graphene oxide nanosheets) at a uniform rate over 30 minutes. Continue ultrasonication for 60 minutes, raise the temperature to 50°C and reflux for 24 hours. After cooling, filter, wash with deionized water 4 times, and dry at 60°C for 12 hours to obtain modified graphene oxide nanosheets. (2) Allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide were mixed in a mass ratio of 1:0.35:45:270 and stirred at 80℃ and 300rpm for 2h. The mixture was cooled to 25℃ and methanol was added until the mass of the precipitate remained unchanged. The mixture was then filtered. The precipitate was dissolved in tetrahydrofuran and filtered again after methanol precipitation. The dissolution and precipitation were repeated 3 times. The mixture was dried at 60℃ for 24h to obtain modified polyvinyl chloride. (3) Modified polyvinyl chloride, modified graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide were mixed in a mass ratio of 1:0.04:0.05:0.05:0.01. The mixture was then mixed and plasticized for 8 minutes using a two-roll mill at a mixing temperature of 175℃ and a roller speed ratio of 1:1.5. Samples were prepared at 175℃ using a 25t hydraulic flatbed press. After cooling, the samples were cut using a universal sample preparation machine and left to stand at 25℃ for 24 hours to obtain fire-retardant plastic.

[0026] Test example: Flame retardancy test method: The fire-retardant plastics obtained from each example and comparative example are tested for limiting oxygen index according to GB / T2406.

[0027] Mechanical property testing method: The fire-retardant plastics obtained from each embodiment and comparative example are tested for tensile strength N0 according to GB / T1040.

[0028] Anti-aging test method: The fire-retardant plastics obtained from each example and comparative example were aged in an aging chamber at 120°C and 50 air changes / h for 24 hours in a hot and oxygen environment. The tensile strength N1 was tested according to GB / T1040, and the aging rate was calculated as (N0-N1) / N0*100%.

[0029] Corrosion resistance test method: Take a 50mm long and 50mm wide sample of the fire-retardant plastic obtained from each example and comparative example according to ISO / 175, suspend it in an 80% sulfuric acid solution for 7 days, take it out and wipe it dry, and test the tensile strength N2 according to GB / T1040. Calculate the corrosion rate = (N0-N2) / N0*100%.

[0030] Table 1 A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1 reveals that the fire-retardant plastic prepared by the present invention has good flame-retardant properties, corrosion resistance, aging resistance and mechanical properties.

[0031] By comparison, Examples 1, 2, and 3 showed higher limiting oxygen index and tensile strength, and lower aging rate and corrosion resistance compared to Comparative Example 1. This indicates that the long-chain organic compounds grafted onto the surface of the reduced graphene oxide sheets can hinder the aggregation between sheets, improve compatibility with the matrix, enhance the dispersibility of reduced graphene oxide in the matrix, and strengthen the material's anti-aging and corrosion resistance. The introduction of P and N flame-retardant elements and the rigid structure of benzene rings into the long-chain organic compounds allows the PN system to release non-flammable gases to dilute the oxygen concentration during combustion, generating strong dehydrating substances that promote char formation, further improving the material's fire resistance and flame retardancy. The double bonds on the modified reduced graphene oxide nanosheets can cross-link with the double bonds on the polyvinyl chloride side chains, enhancing the material's mechanical properties.

[0032] By comparison, Examples 1, 2, and 3 showed higher limiting oxygen index and tensile strength, and lower aging rate than Comparative Example 2. This indicates that hydrazine groups can capture free radicals generated during combustion, reduce the content of combustible free radicals, reduce the degree of gas-phase combustion, and improve the flame retardant properties of the material. At the same time, hydrazine groups can also capture and remove R·, RO·, and ROO· generated during aging, inhibit the attack of free radicals on chain segments, slow down chain segment breakage, and synergize with the ultraviolet light shielding ability of reduced graphene oxide to delay the aging process of the material. The double bonds on the side chains of polyvinyl chloride can form crosslinks with the double bonds on the modified reduced graphene oxide nanosheets, enhancing the mechanical properties of the material.

[0033] By comparison, Examples 1, 2, and 3 showed higher limiting oxygen index and tensile strength, and lower aging rate and corrosion resistance compared to Comparative Example 3. This indicates that the long-chain organic compounds grafted onto the surface of reduced graphene oxide sheets can hinder the aggregation between sheets, improve compatibility with the matrix, enhance the dispersibility of reduced graphene oxide in the matrix, and further enhance the material's anti-aging and corrosion resistance. The introduction of P and N flame-retardant elements and the rigid benzene ring structure into the long-chain organic compounds allows the PN system to release non-flammable gases during combustion, diluting the oxygen concentration and generating strong dehydrating substances that promote char formation, thereby improving... The material exhibits fire resistance and flame retardancy; the hydrazine group can capture free radicals generated during combustion, reducing the content of combustible free radicals, decreasing the degree of gas-phase combustion, and improving the flame retardant performance of the material; at the same time, the hydrazine group can also capture and remove R·, RO· and ROO· generated during aging, inhibiting the attack of free radicals on chain segments, slowing down chain segment breakage, and synergizing with the ultraviolet light shielding ability of reduced graphene oxide to delay the aging process of the material; the double bonds on the side chains of polyvinyl chloride can form crosslinks with the double bonds on the modified reduced graphene oxide nanosheets, enhancing the mechanical properties of the material.

[0034] By comparison, Examples 1, 2, and 3 showed higher limiting oxygen index, lower aging rate, and lower corrosion resistance than Comparative Example 4. This indicates that reduced graphene oxide has fewer functional groups on its surface, resulting in better ultraviolet light absorption and gas barrier capabilities. It can form a dense physical barrier, enhancing the material's anti-aging and corrosion resistance. At the same time, reduced graphene oxide can also serve as a char-forming framework, catalyzing the formation of a continuous, dense, and robust carbonaceous protective layer during combustion. This provides heat insulation, oxygen barrier, prevents the lower layer from continuing to burn, suppresses smoke release, and improves the material's fire resistance and flame retardancy.

[0035] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fire-retardant plastic, characterized in that, The fire-retardant plastic is prepared by mixing and reacting modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide. The modified polyvinyl chloride powder is prepared by reacting allyl hydrazine with polyvinyl chloride; The modified reduced graphene oxide nanosheets are prepared by reacting reduced graphene oxide nanosheets, allylphosphine dichloride, phosphorus oxychloride and 4,4-diaminodiphenylmethane.

2. A fire-retardant plastic and its preparation method, characterized in that, The preparation steps include the following: (1) Mix reduced graphene oxide nanosheets and acetonitrile at a mass ratio of 1:(290~310), disperse by ultrasonication for 1~3h, add triethylamine and 4,4-diaminodiphenylmethane at 1~3℃, add allylphosphine dichloride and phosphorus oxychloride at a uniform rate over 20~40min in a nitrogen atmosphere, continue ultrasonication for 55~65min, reflux at 45~55℃ for 23~25h, filter after cooling, wash with deionized water 3~5 times, and dry at 55~65℃ for 11~13h to obtain modified reduced graphene oxide nanosheets; (2) Mix allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide, stir at 75~85℃ and 200~400rpm for 1~3h, cool down to 20~30℃, add methanol until the mass of the precipitate remains unchanged, filter, dissolve with tetrahydrofuran, precipitate with methanol, filter, repeat the dissolution and precipitation 2~4 times, dry at 55~65℃ for 23~25h to obtain modified polyvinyl chloride; (3) Mix the modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide evenly, and mix and plasticize for 7-9 minutes using a two-roll mill at a mixing temperature of 170-180℃ and a roller speed ratio of 1:(1-2). Prepare samples at 170-180℃ using a 25t hydraulic flatbed press, and cut the samples using a universal sample preparation machine after cooling. Let the samples stand at 20-30℃ for 23-25 ​​hours to obtain fire-retardant plastic.

3. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, The amount of triethylamine added in step (1) is 6 to 7 times the mass of the reduced graphene oxide nanosheets.

4. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, The amount of 4,4-diaminodiphenylmethane added in step (1) is 1 to 3 times the mass of the reduced graphene oxide nanosheets.

5. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, The amount of allylphosphine dichloride added in step (1) is 0.2 to 0.4 times the mass of the reduced graphene oxide nanosheets.

6. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, The amount of phosphorus oxychloride added in step (1) is 1.1 to 1.2 times the mass of the reduced graphene oxide nanosheets.

7. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, The mixing of allyl hydrazine, triethylamine, polyvinyl chloride powder and N,N-dimethylformamide in step (2) is carried out at a mass ratio of 1:(0.3~0.4):(40~50):(260~280).

8. The fire-retardant plastic and its preparation method according to claim 2, characterized in that, In step (3), the modified polyvinyl chloride, modified reduced graphene oxide nanosheets, rare earth composite stabilizer, dioctyl phthalate and benzoyl peroxide are mixed in a mass ratio of 1:(0.03~0.05):(0.04~0.06):(0.04~0.06):(0.005~0.015).

Images