Graphene reinforced flame-retardant PE communication pipe and preparation process thereof

Abstract

The application provides a graphene reinforced flame-retardant PE communication pipe and a preparation process thereof, and the preparation raw materials include, by weight, 100-120 parts of high-density polyethylene, 4-8 parts of polyvinylidene fluoride, 2-4 parts of fluorine-containing acyl modified graphene, 10-20 parts of fluorine-containing silane coupling agent modified ammonium polyphosphate, 5-10 parts of polyolefin elastomer, 3-7 parts of maleic anhydride grafted high-density polyethylene, 0.5-1.5 parts of antioxidant, and 1-3 parts of lubricant. The PE communication pipe provided by the application has high-density polyethylene as a matrix, and has excellent mechanical strength, chemical corrosion resistance, flame retardancy, weather resistance, low-temperature impact resistance and other excellent performances.

Description

Technical Field

[0001] This invention relates to the field of communication tube technology, specifically to a graphene-reinforced flame-retardant PE communication tube and its manufacturing process. Background Technology

[0002] Communication pipelines are crucial carriers for information transmission and communication infrastructure. Polyethylene (PE) pipes are widely used in communication pipeline laying due to their advantages such as light weight, corrosion resistance, and ease of construction. Although ordinary polyethylene pipes possess certain mechanical properties and chemical stability, they still suffer from problems such as low mechanical strength and poor flame retardancy under long-term outdoor service and complex laying environments, making it difficult to meet the requirements of high-safety and high-durability communication pipelines.

[0003] In existing technologies, PE communication pipes are often modified by adding inorganic flame retardants and reinforcing fillers. However, inorganic fillers have poor interfacial compatibility with the polyethylene matrix, and are prone to agglomeration and uneven dispersion. This not only makes it difficult to synergistically improve the mechanical and flame retardant properties of the material, but also leads to a decrease in pipe processing fluidity and a deterioration in surface smoothness. At the same time, ordinary fillers lack effective interfacial bonding with the resin matrix, making the pipes prone to aging and degradation during long-term outdoor use. The inner wall friction coefficient is relatively high, and the low-temperature impact resistance is poor. The overall comprehensive performance is difficult to meet the engineering application requirements of high-safety and high-durability communication pipeline networks. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a graphene-reinforced flame-retardant PE communication tube and its manufacturing process.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a graphene-reinforced flame-retardant PE communication tube, the raw materials for which are prepared by weight include: 100-120 parts of high-density polyethylene, 4-8 parts of polyvinylidene fluoride, 2-4 parts of fluorinated acyl-modified graphene, 10-20 parts of fluorinated silane coupling agent-modified ammonium polyphosphate, 5-10 parts of polyolefin elastomer, 3-7 parts of maleic anhydride-grafted high-density polyethylene, 0.5-1.5 parts of antioxidant, and 1-3 parts of lubricant.

[0006] Using the above technical solution, high-density polyethylene (HDPE) serves as the matrix resin, providing the basic structure, mechanical strength, and chemical corrosion resistance for graphene-reinforced flame-retardant PE communication pipes. Polyvinylidene fluoride (PVDF) can interact with fluorinated segments on the surface of fluorinated acyl-modified graphene and fluorinated silane coupling agents-modified ammonium polyphosphate, resulting in fluorine-fluorine interactions and molecular chain entanglement, improving the dispersibility of fillers in the matrix and enhancing the pipe's weather resistance and corrosion resistance. Fluorinated acyl-modified graphene forms a physical barrier, contributing to improved mechanical strength and dimensional stability of the pipe, and the fluorinated segments can be utilized during the extrusion process. Enrichment of the inner surface of the pipe helps reduce the friction coefficient of the inner wall and the resistance of cable pulling; fluorinated silane coupling agent modified ammonium polyphosphate can improve its interfacial compatibility with the high-density polyethylene matrix and play a flame retardant role; polyolefin elastomer can improve the low-temperature impact resistance of the pipe; maleic anhydride grafted high-density polyethylene can improve the interfacial bonding force between inorganic fillers and high-density polyethylene matrix; antioxidants can inhibit the thermo-oxidative aging of resin during high-temperature processing and long-term use; lubricant can improve the melt flow of the system, reduce processing torque, and improve the surface finish of the pipe.

[0007] Preferably, the lubricant is one or two of polyethylene wax and calcium stearate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0008] Using the above technical solutions, polyethylene wax and calcium stearate can both improve the melt flow during the preparation of graphene-enhanced flame-retardant PE communication pipes, reduce processing torque, and improve the surface finish of the pipes; the antioxidant composed of hindered phenolic antioxidant (antioxidant 1010) and phosphite antioxidant (antioxidant 168) can inhibit the thermo-oxidative aging of high-density polyethylene and other resins during high-temperature processing and long-term use, thus extending the service life of the pipes.

[0009] Preferably, the raw materials for preparing the fluorinated acyl modified graphene include, by weight: 0.5-1.0 parts graphene oxide, 0.5-1.0 parts dopamine hydrochloride, 2-4 parts perfluorobutyryl chloride, 2-4 parts triethylamine, 150-250 parts anhydrous ethanol, and 200-300 parts deionized water.

[0010] Using the above technical solution, graphene oxide provides the basic sheet structure for fluorinated acyl-modified graphene, forming a physical isolation barrier; dopamine hydrochloride can undergo in-situ self-polymerization on the surface of graphene oxide to form a coating layer; perfluorobutyryl chloride can react with the coating layer formed by the polymerization of dopamine hydrochloride to graft fluorinated segments onto the surface of graphene oxide; triethylamine, as an acid-binding agent, can neutralize the hydrogen chloride generated by the reaction of perfluorobutyryl chloride with the coating layer, promoting the grafting reaction in the forward direction; anhydrous ethanol can be used as a dispersion medium for the reaction system to disperse the reaction products; deionized water can be used to disperse graphene oxide, providing a reaction environment for the in-situ self-polymerization of dopamine hydrochloride.

[0011] Preferably, the preparation method of the fluorinated acyl-modified graphene includes the following steps: 1) Add graphene oxide to deionized water and ultrasonically disperse it for 1-2 hours at an ultrasonic frequency of 40-50kHz and a power of 300-500W. Add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0-8.5, add dopamine hydrochloride, and stir the reaction at 200-300r / min at 30-40℃ for 14-18 hours to obtain polydopamine-coated graphene oxide. 2) The polydopamine-coated graphene oxide obtained in step 1) is subjected to plate and frame filter or vacuum filter, washed with deionized water 2-4 times, and then ultrasonically dispersed in anhydrous ethanol. Perfluorobutyryl chloride and triethylamine are added, and the reaction is carried out for 8-12 hours under nitrogen protection, 20-30℃ and stirring at 200-300r / min. 3) The product obtained in step 2) is subjected to plate and frame filtration or vacuum filtration, and washed 2-4 times each with anhydrous ethanol and deionized water. The resulting solid product is dried at 60-80℃ and vacuum degree -0.085~-0.095MPa for 20-24h to obtain fluorine-containing acyl modified graphene.

[0012] Using the above technical solution, the preparation method can uniformly disperse graphene oxide in deionized water, and dopamine hydrochloride undergoes in-situ self-polymerization on the surface of graphene oxide to form a polydopamine coating layer; perfluorobutyryl chloride can react with the polydopamine coating layer to achieve grafting of fluorinated segments on the surface of graphene oxide; subsequent filtration and washing steps can remove impurities in the reaction system, and drying steps can remove moisture and residual solvent from the solid product, finally obtaining fluorinated acyl-modified graphene.

[0013] Preferably, the raw materials for preparing the fluorinated silane coupling agent modified ammonium polyphosphate include, by weight: 20-30 parts of ammonium polyphosphate, 2-4 parts of dopamine hydrochloride, 5-10 parts of heptadecafluorodecyltrimethoxysilane, 0.1-0.3 parts of dibutyltin dilaurate, and 200-300 parts of anhydrous ethanol.

[0014] Using the above technical solution, ammonium polyphosphate serves as the basic component of the fluorinated silane coupling agent-modified ammonium polyphosphate, providing the acid source required for flame retardancy. Dopamine hydrochloride can undergo in-situ self-polymerization on the surface of ammonium polyphosphate to form a polydopamine coating. Heptadecafluorodecyltrimethoxysilane can undergo a condensation reaction with the polydopamine coating to achieve grafting of fluorinated silane segments onto the surface of ammonium polyphosphate. Dibutyltin dilaurate serves as a catalyst to promote the condensation reaction between the fluorinated silane coupling agent and the polydopamine coating. Anhydrous ethanol serves as a dispersion medium to ensure uniform dispersion of the raw materials, guaranteeing stable reaction and dispersion processes, ultimately yielding fluorinated silane coupling agent-modified ammonium polyphosphate.

[0015] Preferably, the preparation method of the fluorinated silane coupling agent modified ammonium polyphosphate includes the following steps: (1) Disperse ammonium polyphosphate in deionized water and stir at 200-300 r / min for 10-15 min. Then add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0-8.5, and then add dopamine hydrochloride. React at 30-40℃ and 200-300 r / min for 14-18 h to obtain polydopamine-coated ammonium polyphosphate. (2) The polydopamine-coated ammonium polyphosphate obtained in step (1) is subjected to plate and frame filter or vacuum filter, washed with deionized water 2-4 times, redispersed in anhydrous ethanol, and dibutyltin dilaurate and heptadecafluorodecyltrimethoxysilane are added. The mixture is reacted for 8-12 h under nitrogen protection, 60-80℃ and stirring at 200-300 r / min. (3) The product obtained in step (2) is subjected to plate and frame filter or vacuum filter, and washed 2-4 times with anhydrous ethanol and deionized water respectively. It is then dried at 60-70℃ and vacuum degree -0.085~-0.095MPa for 18-22h to obtain fluorinated silane coupling agent modified ammonium polyphosphate.

[0016] Using the above technical solution, this preparation method can uniformly disperse ammonium polyphosphate in deionized water. The tris(hydroxymethyl)aminomethane buffer solution can adjust the pH of the system to a suitable range. Dopamine hydrochloride undergoes in-situ self-polymerization on the surface of ammonium polyphosphate to form polydopamine-coated ammonium polyphosphate. Dibutyltin dilaurate can promote the condensation reaction between heptadecafluorodecyltrimethoxysilane and the polydopamine coating layer. Nitrogen protection can ensure the stable progress of the condensation reaction. Subsequent filtration and washing can remove unreacted impurities in the system, and drying can remove moisture and residual solvent, ensuring the purity and dispersibility of the product.

[0017] Preferably, the degree of polymerization of the ammonium polyphosphate is 900-1000, and the weight-average molecular weight of the polyvinylidene fluoride is 2 × 10⁻⁶. 5 Da.

[0018] Using the above technical solution, ammonium polyphosphate with a degree of polymerization of 900-1000 can stably provide the acid source required for flame retardancy. Its molecular structure ensures that it decomposes and releases ammonia gas and generates polyphosphoric acid at high temperatures, promoting dehydration of the substrate surface to form a dense carbon layer; the weight-average molecular weight is 2×10⁻⁶. 5 Da's polyvinylidene fluoride can form strong interfacial interactions with fluorinated segments on the surface of fluorinated acyl-modified graphene and fluorinated silane coupling agents-modified ammonium polyphosphate, promoting the dispersion of fillers in high-density polyethylene matrix. At the same time, it can decompose at high temperature to promote carbonization and improve the density of carbon layer.

[0019] This invention also provides a process for preparing a graphene-reinforced flame-retardant PE communication tube, comprising the following steps: S1. Dry high-density polyethylene at 80-90℃ for 4-6 hours, and vacuum dry fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate at 80-90℃ and vacuum degree -0.085~-0.095MPa for 2-4 hours respectively. S2. Add the dried high-density polyethylene, polyvinylidene fluoride, and polyolefin elastomer to a high-speed mixer and premix for 5-8 minutes at 70-80℃ and 1200-1400 r / min. Add maleic anhydride-grafted high-density polyethylene and continue mixing for 5-8 minutes. Then add fluorinated acyl-modified graphene and mix for 8-10 minutes at 90-100℃ and 1400-1600 r / min. Finally, add fluorinated silane coupling agent-modified ammonium polyphosphate, antioxidant, and lubricant, and mix for 5-10 minutes at 90-100℃ and 1000-1200 r / min to obtain the premix. S3. Add the premix obtained in step S2 to a twin-screw extruder for melt blending, extrusion granulation, and air cooling to obtain composite granules; S4. Add the composite granules obtained in step S3 into a single screw extruder, extrude them through a pipe die, and then pass the extruded pipe through a vacuum sizing box, a cooling water tank, and a traction machine in sequence. Finally, cut the pipe to a fixed length to obtain a graphene-reinforced flame-retardant PE communication pipe.

[0020] Using the above technical solution, this preparation process removes moisture from the raw materials by targeted drying of high-density polyethylene, fluorinated acyl-modified graphene, and fluorinated silane coupling agent-modified ammonium polyphosphate, ensuring the stability of subsequent processing. Mixing is carried out by controlling temperature and stirring speed in stages, ensuring uniform dispersion of the raw materials and improving the interfacial bonding between components. Uniform composite granules are obtained through melt blending and granulation using a twin-screw extruder. Then, through molding, cooling, traction, and fixed-length cutting using a single-screw extruder, a graphene-reinforced flame-retardant PE communication pipe with a complete structure and stable performance can be obtained. The orderly connection of each step ensures both processing fluidity and product molding quality, enabling the pipe's overall performance to meet the requirements of communication network engineering applications.

[0021] Preferably, in step S3, the extrusion process parameters of the twin-screw extruder are: zone 1 160-170℃, zone 2 175-185℃, zone 3 188-195℃, zone 4 195-200℃, zone 5 190-195℃, die head 185-190℃, screw speed 100-120r / min, and feed speed 15-25r / min.

[0022] By adopting the above technical solution, the temperature of zones one through five and the die head is gradually adjusted, which allows the premix to melt gradually during the extrusion process, ensuring melt uniformity. The reasonable matching of screw speed and feed speed can control the melt blending time and extrusion rate of the premix, ensuring that each component is fully mixed and uniformly dispersed, reducing interface defects. The synergistic effect of this set of extrusion process parameters can obtain composite granules with uniform performance and good processing properties, providing a stable raw material basis for subsequent pipe extrusion molding.

[0023] Preferably, in step S4, the temperatures of the single-screw extruder for pipe forming are: 170-180℃ in the feeding section, 185-195℃ in the compression section, 190-200℃ in the homogenization section, and 190-195℃ in the die; the screw speed is 30-50 r / min; and the traction speed is 1.5-2.0 m / min. The vacuum degree of the vacuum sizing box is -0.04 to -0.06 MPa, and the water temperature of the cooling water tank is 15-25℃.

[0024] By adopting the above technical solution, the composite granules can be fully melted and kept uniform, ensuring the quality of pipe forming; the reasonable matching of screw speed and traction speed can control the pipe forming rate and avoid forming defects; the vacuum setting of the vacuum sizing box can make the pipe shape regular, and the water temperature of the cooling water tank can quickly fix the pipe shape, ensuring that the prepared graphene-reinforced flame-retardant PE communication pipe has a regular shape and stable dimensions, meeting the usage requirements of communication pipes.

[0025] The beneficial effects of this invention are as follows: High-density polyethylene (HDPE) serves as the matrix resin, providing the basic structure, mechanical strength, and chemical corrosion resistance for graphene-reinforced flame-retardant PE communication pipes. Polyvinylidene fluoride (PVDF) can interact with fluorinated segments on the surface of fluorinated acyl-modified graphene and fluorinated silane coupling agents-modified ammonium polyphosphate, resulting in fluorine-fluorine interactions and molecular chain entanglement, improving the dispersibility of fillers in the matrix and enhancing the pipe's weather resistance and corrosion resistance. Fluorinated acyl-modified graphene forms a physical barrier, contributing to improved mechanical strength and dimensional stability of the pipe, and the fluorinated segments can be introduced into the pipe during extrusion processing. Surface enrichment helps reduce the friction coefficient of the inner wall of the pipe and reduce cable pulling resistance; fluorinated silane coupling agent modified ammonium polyphosphate can improve its interfacial compatibility with the high-density polyethylene matrix and play a flame retardant role; polyolefin elastomer can improve the low-temperature impact resistance of the pipe; maleic anhydride grafted high-density polyethylene can improve the interfacial bonding force between inorganic fillers and high-density polyethylene matrix; antioxidants can inhibit the thermo-oxidative aging of resin during high-temperature processing and long-term use; lubricant can improve the melt flow of the system, reduce processing torque, and improve the surface finish of the pipe. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0028] Table 1

[0029] Example 1: This embodiment provides a graphene-reinforced flame-retardant PE communication tube, which, by weight, comprises: 100 parts of high-density polyethylene with a weight-average molecular weight of 2 × 10⁻⁶. 5 The composition of Da includes 4 parts polyvinylidene fluoride, 2 parts fluorinated acyl-modified graphene, 10 parts fluorinated silane coupling agent modified ammonium polyphosphate, 5 parts polyolefin elastomer, 3 parts maleic anhydride-grafted high-density polyethylene, 0.5 parts antioxidant, and 1 part lubricant. The lubricant is polyethylene wax; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio.

[0030] The raw materials for preparing fluorinated acyl-modified graphene, by weight, include: 0.5 parts graphene oxide, 0.5 parts dopamine hydrochloride, 2 parts perfluorobutyryl chloride, 2 parts triethylamine, 150 parts anhydrous ethanol, and 200 parts deionized water.

[0031] The preparation method of fluorinated acyl-modified graphene includes the following steps: 1) Add graphene oxide to deionized water and ultrasonically disperse it for 1 hour at an ultrasonic frequency of 40 kHz and a power of 300 W. Add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0, add dopamine hydrochloride, and stir the reaction at 200 r / min at 30 °C for 14 hours to obtain polydopamine-coated graphene oxide. 2) The polydopamine-coated graphene oxide obtained in step 1) was subjected to plate and frame filter press, washed twice with deionized water, and then ultrasonically dispersed in anhydrous ethanol. Perfluorobutyryl chloride and triethylamine were added, and the reaction was carried out for 8 hours under nitrogen protection, 20°C and 200 r / min stirring. 3) The product obtained in step 2) was subjected to plate and frame filter press, and washed twice each with anhydrous ethanol and deionized water. The resulting solid product was dried at 60°C and vacuum degree -0.085MPa for 20h to obtain fluorinated acyl modified graphene.

[0032] The raw materials for preparing fluorinated silane coupling agent modified ammonium polyphosphate, by weight, include: 20 parts of ammonium polyphosphate with a degree of polymerization of 900, 2 parts of dopamine hydrochloride, 5 parts of heptadecafluorodecyltrimethoxysilane, 0.1 parts of dibutyltin dilaurate, and 200 parts of anhydrous ethanol.

[0033] The preparation method of ammonium polyphosphate modified with fluorinated silane coupling agent includes the following steps: (1) Disperse ammonium polyphosphate in deionized water and stir at 200 r / min for 10 min. Then add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0, and then add dopamine hydrochloride. React at 30℃ and 200 r / min for 14 h to obtain polydopamine-coated ammonium polyphosphate. (2) The polydopamine-coated ammonium polyphosphate obtained in step (1) was subjected to plate and frame filter press, washed twice with deionized water, redispersed in anhydrous ethanol, and dibutyltin dilaurate and heptadecafluorodecyltrimethoxysilane were added. The mixture was reacted for 8 h under nitrogen protection, 60 °C and stirring at 200 r / min. (3) The product obtained in step (2) was subjected to plate and frame filter press, washed twice with anhydrous ethanol and deionized water respectively, and dried for 18 h at 60 °C and vacuum degree -0.085 MPa to obtain ammonium polyphosphate modified with fluorinated silane coupling agent.

[0034] This embodiment also provides a fabrication process for a graphene-reinforced flame-retardant PE communication tube, including the following steps: S1. High-density polyethylene is dried at 80℃ for 4 hours, and fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate are vacuum dried at 80℃ and vacuum degree -0.085MPa for 2 hours respectively. S2. Add the dried high-density polyethylene, polyvinylidene fluoride, and polyolefin elastomer to a high-speed mixer and premix for 5 minutes at 70°C and 1200 rpm. Add maleic anhydride-grafted high-density polyethylene and continue mixing for 5 minutes. Then add fluorinated acyl-modified graphene and mix for 8 minutes at 90°C and 1400 rpm. Finally, add fluorinated silane coupling agent-modified ammonium polyphosphate, antioxidant, and lubricant, and mix for 5 minutes at 90°C and 1000 rpm to obtain the premix. S3. The premix obtained in step S2 is added to a twin-screw extruder for melt blending, extrusion granulation, and the process parameters are: zone 1 160℃, zone 2 175℃, zone 3 188℃, zone 4 195℃, zone 5 190℃, die head 185℃, screw speed 100r / min, feed speed 15r / min. The extruded strip is air-cooled and then granulated to obtain composite granules. S4. The composite granules obtained in step S3 are added to a single-screw extruder and extruded through a pipe die. The process parameters are: feeding section 170°C, compression section 185°C, homogenization section 190°C, die 190°C, screw speed 30 r / min, and traction speed 1.5 m / min. The extruded pipe passes through a vacuum sizing box with a vacuum degree of -0.04 MPa, a cooling water tank with a water temperature of 15°C, and a traction machine in sequence. Finally, it is cut to a fixed length to obtain a graphene-reinforced flame-retardant PE communication pipe.

[0035] Example 2: This embodiment provides a graphene-reinforced flame-retardant PE communication tube, which, by weight, comprises: 120 parts of high-density polyethylene with a weight-average molecular weight of 2 × 10⁻⁶. 5 The composition of Da includes 8 parts polyvinylidene fluoride, 4 parts fluorinated acyl-modified graphene, 20 parts fluorinated silane coupling agent modified ammonium polyphosphate, 10 parts polyolefin elastomer, 7 parts maleic anhydride-grafted high-density polyethylene, 1.5 parts antioxidant, and 3 parts lubricant. The lubricant is polyethylene wax; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio.

[0036] The raw materials for preparing fluorinated acyl-modified graphene, by weight, include: 1 part graphene oxide, 1 part dopamine hydrochloride, 4 parts perfluorobutyryl chloride, 4 parts triethylamine, 250 parts anhydrous ethanol, and 300 parts deionized water.

[0037] The preparation method of fluorinated acyl-modified graphene includes the following steps: 1) Add graphene oxide to deionized water and ultrasonically disperse it for 2 hours at an ultrasonic frequency of 50 kHz and a power of 500 W. Add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.5, add dopamine hydrochloride, and stir the reaction at 300 r / min at 40 °C for 18 hours to obtain polydopamine-coated graphene oxide. 2) The polydopamine-coated graphene oxide obtained in step 1) was filtered, washed 4 times with deionized water, and then ultrasonically dispersed in anhydrous ethanol. Perfluorobutyryl chloride and triethylamine were added, and the reaction was carried out for 12 h under nitrogen protection, 30 °C and 300 r / min stirring. 3) The product obtained in step 2) was filtered and washed 4 times each with anhydrous ethanol and deionized water. The resulting solid product was dried at 80°C and vacuum degree -0.095MPa for 24h to obtain fluorinated acyl modified graphene.

[0038] The raw materials for preparing fluorinated silane coupling agent modified ammonium polyphosphate, by weight, include: 30 parts of ammonium polyphosphate with a degree of polymerization of 1000, 4 parts of dopamine hydrochloride, 10 parts of heptadecafluorodecyltrimethoxysilane, 0.3 parts of dibutyltin dilaurate, and 300 parts of anhydrous ethanol.

[0039] The preparation method of ammonium polyphosphate modified with fluorinated silane coupling agent includes the following steps: (1) Disperse ammonium polyphosphate in deionized water and stir at 300 r / min for 15 min. Then add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.5, and then add dopamine hydrochloride. React at 40℃ and 300 r / min for 18 h to obtain polydopamine-coated ammonium polyphosphate. (2) The polydopamine-coated ammonium polyphosphate obtained in step (1) was filtered, washed 4 times with deionized water, redispersed in anhydrous ethanol, and dibutyltin dilaurate and heptadecafluorodecyltrimethoxysilane were added. The mixture was reacted for 12 h under nitrogen protection, 80 °C and 300 r / min stirring. (3) The product obtained in step (2) was filtered and washed 4 times each with anhydrous ethanol and deionized water. It was then dried at 70°C and vacuum degree -0.095MPa for 22h to obtain fluorinated silane coupling agent modified ammonium polyphosphate.

[0040] This embodiment also provides a fabrication process for a graphene-reinforced flame-retardant PE communication tube, including the following steps: S1. High-density polyethylene was dried at 90℃ for 6 hours, and fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate were vacuum dried at 90℃ and vacuum degree -0.095MPa for 4 hours respectively. S2. Add the dried high-density polyethylene, polyvinylidene fluoride, and polyolefin elastomer to a high-speed mixer and premix for 8 minutes at 80°C and 1400 r / min. Add maleic anhydride-grafted high-density polyethylene and continue mixing for 8 minutes. Then add fluorinated acyl-modified graphene and mix for 10 minutes at 100°C and 1600 r / min. Finally, add fluorinated silane coupling agent-modified ammonium polyphosphate, antioxidant, and lubricant, and mix for 10 minutes at 100°C and 1200 r / min to obtain the premix. S3. The premix obtained in step S2 is added to a twin-screw extruder for melt blending, extrusion granulation, and the process parameters are: zone 1 170℃, zone 2 185℃, zone 3 195℃, zone 4 200℃, zone 5 195℃, die head 190℃, screw speed 120r / min, feed speed 25r / min. The extruded strip is air-cooled and then granulated to obtain composite granules. S4. The composite granules obtained in step S3 are added to a single-screw extruder and extruded through a pipe die. The process parameters are: feeding section 180°C, compression section 195°C, homogenization section 200°C, die 195°C, screw speed 50 r / min, and traction speed 2.0 m / min. The extruded pipe passes through a vacuum sizing box with a vacuum degree of -0.06 MPa, a cooling water tank with a water temperature of 25°C, and a traction machine in sequence. Finally, it is cut to a fixed length to obtain a graphene-reinforced flame-retardant PE communication pipe.

[0041] Example 3: This embodiment provides a graphene-reinforced flame-retardant PE communication tube, which, by weight, comprises: 110 parts of high-density polyethylene with a weight-average molecular weight of 2×10⁻⁶. 5 The composition of Da includes 6 parts polyvinylidene fluoride, 3 parts fluorinated acyl-modified graphene, 15 parts fluorinated silane coupling agent modified ammonium polyphosphate, 7 parts polyolefin elastomer, 5 parts maleic anhydride-grafted high-density polyethylene, 1 part antioxidant, and 2 parts lubricant. The lubricant is a compound of polyethylene wax and calcium stearate in a 1:1 mass ratio; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a 1:1 mass ratio.

[0042] The raw materials for preparing fluorinated acyl-modified graphene, by weight, include: 0.7 parts graphene oxide, 0.7 parts dopamine hydrochloride, 3 parts perfluorobutyryl chloride, 3 parts triethylamine, 200 parts anhydrous ethanol, and 250 parts deionized water.

[0043] The preparation method of fluorinated acyl-modified graphene includes the following steps: 1) Add graphene oxide to deionized water and ultrasonically disperse it for 1.5 h at an ultrasonic frequency of 45 kHz and a power of 400 W. Add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.2, add dopamine hydrochloride, and stir the reaction at 250 r / min at 35 °C for 16 h to obtain polydopamine-coated graphene oxide. 2) The polydopamine-coated graphene oxide obtained in step 1) was filtered, washed three times with deionized water, and then ultrasonically dispersed in anhydrous ethanol. Perfluorobutyryl chloride and triethylamine were added, and the reaction was carried out for 10 h under nitrogen protection, 25 °C and 250 r / min stirring. 3) The product obtained in step 2) was filtered and washed three times each with anhydrous ethanol and deionized water. The resulting solid product was dried at 70°C and vacuum degree -0.09MPa for 22h to obtain fluorinated acyl modified graphene.

[0044] The raw materials for preparing fluorinated silane coupling agent modified ammonium polyphosphate, by weight, include: 25 parts of ammonium polyphosphate with a degree of polymerization of 950, 3 parts of dopamine hydrochloride, 7 parts of heptadecafluorodecyltrimethoxysilane, 0.2 parts of dibutyltin dilaurate, and 250 parts of anhydrous ethanol.

[0045] The preparation method of ammonium polyphosphate modified with fluorinated silane coupling agent includes the following steps: (1) Disperse ammonium polyphosphate in deionized water and stir at 250 r / min for 12 min. Then add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.2, and then add dopamine hydrochloride. React at 35℃ and 250 r / min for 16 h to obtain polydopamine-coated ammonium polyphosphate. (2) The polydopamine-coated ammonium polyphosphate obtained in step (1) was filtered, washed three times with deionized water, redispersed in anhydrous ethanol, and dibutyltin dilaurate and heptadecafluorodecyltrimethoxysilane were added. The mixture was reacted for 10 h under nitrogen protection, 70 °C and stirring at 250 r / min. (3) The product obtained in step (2) was filtered and washed three times each with anhydrous ethanol and deionized water. It was then dried for 20 h at 65 °C and a vacuum of -0.09 MPa to obtain ammonium polyphosphate modified with fluorinated silane coupling agent.

[0046] This embodiment also provides a fabrication process for a graphene-reinforced flame-retardant PE communication tube, including the following steps: S1. High-density polyethylene was dried at 85°C for 5 hours, and fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate were vacuum dried at 85°C and vacuum degree -0.09MPa for 3 hours respectively. S2. Add the dried high-density polyethylene, polyvinylidene fluoride, and polyolefin elastomer to a high-speed mixer and premix for 6 minutes at 75°C and 1300 r / min. Add maleic anhydride-grafted high-density polyethylene and continue mixing for 6 minutes. Then add fluorinated acyl-modified graphene and mix for 9 minutes at 95°C and 1500 r / min. Finally, add fluorinated silane coupling agent-modified ammonium polyphosphate, antioxidant, and lubricant, and mix for 7 minutes at 95°C and 1100 r / min to obtain the premix. S3. The premix obtained in step S2 is added to a twin-screw extruder for melt blending, extrusion granulation, and the process parameters are: zone 1 165℃, zone 2 180℃, zone 3 190℃, zone 4 198℃, zone 5 192℃, die head 188℃, screw speed 110r / min, feed speed 20r / min. The extruded strip is air-cooled and then granulated to obtain composite granules. S4. The composite granules obtained in step S3 are added to a single-screw extruder and extruded through a pipe die. The process parameters are: feeding section 175℃, compression section 190℃, homogenization section 195℃, die 192℃, screw speed 40r / min, and traction speed 1.8m / min. The extruded pipe passes through a vacuum sizing box with a vacuum degree of -0.05MPa, a cooling water tank with a water temperature of 20℃, and a traction machine in sequence. Finally, it is cut to a fixed length to obtain a graphene-reinforced flame-retardant PE communication pipe.

[0047] Comparative Example 1: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that no fluorinated acyl-modified graphene is added.

[0048] Comparative Example 2: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that no fluorinated silane coupling agent modified ammonium polyphosphate is added.

[0049] Comparative Example 3: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that maleic anhydride-grafted high-density polyethylene is not added.

[0050] Comparative Example 4: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that the fluorinated acyl-modified graphene is replaced with an equal amount of unmodified graphene oxide.

[0051] Comparative Example 5: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that the fluorinated silane coupling agent-modified ammonium polyphosphate is replaced with an equal amount of a physical mixture of ammonium polyphosphate and heptadecafluorodecyltrimethoxysilane, wherein the mass ratio of ammonium polyphosphate to heptadecafluorodecyltrimethoxysilane in the mixture is 4:1.

[0052] Comparative Example 6: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that polyvinylidene fluoride is replaced with an equal amount of high-density polyethylene.

[0053] Comparative Example 7: A graphene-reinforced flame-retardant PE communication tube and its preparation process are disclosed. The only difference between this tube and Example 3 is that no dopamine hydrochloride was added during the preparation of the fluorinated acyl-modified graphene (i.e., no polydopamine interlayer).

[0054] The communication tubing (uniform specifications: outer diameter 50mm, wall thickness 3mm) obtained in Examples 1-3 and Comparative Examples 1-7 were subjected to the following performance tests. Five parallel samples were tested for each group of samples, and the average value of the results was taken.

[0055] Tensile strength and elongation at break: Tested according to GB / T 8804.2-2023 "Determination of tensile properties of thermoplastic pipes - Part 2: Polyolefin pipes", using type II specimens and a test speed of 5 mm / min.

[0056] Notched impact strength (room temperature and -30℃): Tested according to "Determination of impact strength of plastic cantilever beam" (GB / T 1843-2008). The specimen was directly cut from the tube and the notch type was A.

[0057] Limiting oxygen index (LOI): determined according to the standard "Determination of flammability of plastics by oxygen index method - Part 2: Room temperature test" (GB / T2406.2-2009).

[0058] Vertical flammability rating (UL-94): Tested according to the "Vertical Method for Testing the Flammability of Plastics" (GB / T 2408-2021), with a sample thickness of 3 mm.

[0059] Inner wall friction coefficient: Tested according to "Determination of friction coefficient of plastics" (GB / T 10006-2021).

[0060] Volume resistivity: Tested according to the "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials" (GB / T 1410-2006), with a test voltage of 100V.

[0061] The results are shown in Tables 2 and 3.

[0062] Table 2 Test results of mechanical properties and flame retardant properties

[0063] Table 3. Test results of tribological and electrical insulation properties

[0064] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-7 are analyzed as follows: Comparative Example 1: Without the addition of fluorinated acyl-modified graphene, the tensile strength decreased from 30.6 MPa to 23.0 MPa (a decrease of 24.8%), the elongation at break decreased from 410% to 335% (a decrease of 18.3%), and the room-temperature notched impact strength decreased from 26.9 kJ / m. 2 Reduced to 20.8 kJ / m 2 (Decrease of 22.7%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2Reduced to 14.5 kJ / m 2 (A decrease of 31.0%), the limiting oxygen index decreased from 33.0% to 26.0% (a decrease of 21.2%), the UL-94 rating decreased from V-0 to V-1, the internal wall friction coefficient significantly increased from 0.072 to 0.148, and the volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 1.2×10 15 Ω·cm (reduction of 70.0%). The graphene sheets in this component can provide a physical barrier and significantly improve mechanical strength. Without them, an effective physical barrier and load-bearing network cannot be formed, resulting in a comprehensive decline in mechanical properties. At the same time, the barrier effect of the graphene condensed phase is weakened, heat transfer is accelerated, and the synergistic flame-retardant effect of the fluorine-containing low surface energy is lost, all of which contribute to the decline in flame-retardant performance.

[0065] Comparative Example 2: Ammonium polyphosphate modified without the addition of fluorinated silane coupling agent showed a decrease in tensile strength from 30.6 MPa to 27.6 MPa (a decrease of 9.8%), elongation at break from 410% to 380% (a decrease of 7.3%), and room temperature notched impact strength from 26.9 kJ / m. 2 Reduced to 23.9 kJ / m 2 (Decrease of 11.2%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2 Reduced to 17.5 kJ / m 2 (A decrease of 16.7%), limiting oxygen index decreased from 33.0% to 26.3% (a decrease of 20.3%), UL-94 rating decreased from V-0 to V-1, internal wall friction coefficient increased from 0.072 to 0.135 (an increase of 87.5%), and volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 3.6×10 15 Ω·cm (decrease of 10.0%). As a key acid source carrier in the intumescent flame retardant system, the absence of this component leads to a decrease in the compatibility between ammonium polyphosphate and the matrix, and uneven dispersion causes a reduction in mechanical properties. The absence of the acid source in the intumescent flame retardant system reduces char formation efficiency, resulting in a significant decrease in flame retardant performance. At the same time, the absence of fluorinated segments disrupts the integrity of the fluorinated low surface energy network, leading to a simultaneous decrease in both flame retardant performance and surface lubrication performance.

[0066] Comparative Example 3: High-density polyethylene grafted with maleic anhydride without the addition of maleic anhydride showed a decrease in tensile strength from 30.6 MPa to 24.2 MPa (a decrease of 20.9%), an decrease in elongation at break from 410% to 298% (a decrease of 27.3%), and an increase in room temperature notched impact strength from 26.9 kJ / m. 2 It dropped to 21.4 kJ / m 2 (Decrease of 20.4%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2 Reduced to 15.0 kJ / m 2(A decrease of 28.6%), the coefficient of friction of the inner wall increased from 0.072 to 0.078 (an increase of 8.3%), and the volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 2.6×10 15 Ω·cm (decreased by 35.0%). Maleic anhydride-grafted high-density polyethylene, as a reactive compatibilizer, has its maleic anhydride groups reacting chemically with the amino and hydroxyl groups on the surface of fluorinated acyl-modified graphene. After the deletion, the interfacial bonding force between the inorganic filler and the high-density polyethylene matrix decreases significantly, the stress transfer efficiency decreases, and the overall mechanical properties deteriorate; at the same time, the increase in interfacial defects leads to a decrease in electrical insulation performance.

[0067] Comparative Example 4: Replacing fluorinated acyl-modified graphene with an equal amount of unmodified graphene oxide reduced tensile strength from 30.6 MPa to 25.5 MPa (a decrease of 16.7%), elongation at break from 410% to 350% (a decrease of 14.6%), and room-temperature notched impact strength from 26.9 kJ / m. 2 Reduced to 22.4 kJ / m 2 (Decrease of 16.7%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2 Reduced to 15.8 kJ / m 2 (A decrease of 24.8%), limiting oxygen index decreased from 33.0% to 27.2% (a decrease of 17.6%), UL-94 rating decreased from V-0 to V-1, internal wall friction coefficient increased from 0.072 to 0.125 (an increase of 73.6%), and volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 1.8×10 15 Ω·cm (a decrease of 55.0%). The unmodified graphene oxide surface lacks a polydopamine interlayer and fluorinated graft chains, resulting in poor compatibility with the high-density polyethylene matrix, easy agglomeration leading to poor dispersion, inability to effectively transfer stress, and a significant decrease in mechanical properties. At the same time, it lacks the synergistic effect of high-temperature carbonization of polydopamine and the gas-phase dilution flame retardant effect of fluorinated segments, resulting in a significant reduction in flame retardant efficiency. Furthermore, without fluorinated segments participating in the construction of a low surface energy network, the friction coefficient of the inner wall increases significantly.

[0068] Comparative Example 5: Replacing the fluorinated silane coupling agent-modified ammonium polyphosphate with a physical mixture of ammonium polyphosphate and heptadecafluorodecyltrimethoxysilane resulted in a decrease in tensile strength from 30.6 MPa to 28.0 MPa (a decrease of 8.5%), elongation at break from 410% to 388% (a decrease of 5.4%), and room-temperature notched impact strength from 26.9 kJ / m. 2 Reduced to 24.3 kJ / m 2 (Decrease of 9.7%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2 Reduced to 17.8 kJ / m 2(A decrease of 15.2%), limiting oxygen index decreased from 33.0% to 26.7% (a decrease of 19.1%), UL-94 rating decreased from V-0 to V-1, internal wall friction coefficient increased from 0.072 to 0.116 (an increase of 61.1%), and volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 3.4×10 15 Ω·cm (decreased by 15.0%). Physical mixing cannot achieve chemical bonding between the fluorinated silane coupling agent and ammonium polyphosphate; the two are only physically adsorbed. During high-temperature processing, migration or desorption easily occurs, leading to uneven dispersion and interface defects, resulting in decreased mechanical properties. The lack of a chemically bonded structure weakens the synergistic effect of high-temperature carbonization of the polydopamine coating, reduces charring efficiency, and significantly decreases flame retardant performance. At the same time, the fluorinated component fails to be effectively anchored on the surface of ammonium polyphosphate, resulting in an incomplete low surface energy network and a significantly increased coefficient of friction.

[0069] Comparative Example 6: When polyvinylidene fluoride was replaced with an equal amount of high-density polyethylene, the notched impact strength at -30°C decreased from 21.0 kJ / m. 2 Reduced to 19.2 kJ / m 2 (A decrease of 8.6%), limiting oxygen index decreased from 33.0% to 29.5% (a decrease of 10.6%), UL-94 rating decreased from V-0 to V-1, internal wall friction coefficient increased from 0.072 to 0.124 (an increase of 72.2%), and volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 3.0×10 15 Ω·cm (decrease of 25.0%). Polyvinylidene fluoride (PVDF), as a fluorinated resin, forms strong interactions with the fluorinated segments in fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate. It is a key node in constructing a fluorinated low surface energy network. Its absence leads to the breakage of the interaction network between fluorinated components, significantly weakening the low surface energy effect and greatly increasing the internal wall friction coefficient. At the same time, the reduction of fluorine source weakens the gas phase dilution flame retardant effect, reduces the limiting oxygen index, and lowers the flame retardant rating.

[0070] Comparative Example 7: When preparing fluorinated acyl-modified graphene, dopamine hydrochloride was not added (i.e., no polydopamine interlayer). The tensile strength decreased from 30.6 MPa to 27.4 MPa (a decrease of 10.5%), the elongation at break decreased from 410% to 368% (a decrease of 10.2%), and the room-temperature notched impact strength increased from 26.9 kJ / m. 2 Reduced to 23.8 kJ / m 2 (Decrease of 11.5%), -30℃ notched impact strength decreased from 21.0 kJ / m. 2 Reduced to 17.4 kJ / m 2(A decrease of 17.1%), the limiting oxygen index decreased from 33.0% to 30.0% (a decrease of 9.1%), the UL-94 rating decreased from V-0 to V-1, the internal wall friction coefficient increased from 0.072 to 0.092 (an increase of 27.8%), and the volume resistivity increased from 4.0 × 10⁻⁶. 15 Ω·cm decreased to 3.1×10 15 Ω·cm (decreased by 22.5%). The absence of the polydopamine interlayer prevents the effective grafting of fluorinated alkyl acyl chlorides onto the graphene oxide surface, resulting in a significant decrease in grafting efficiency, poorer compatibility between graphene and the matrix interface, and uneven dispersion leading to a decline in mechanical properties. At the same time, the synergistic effect of polydopamine's own high-temperature carbonization to form a dense carbon layer is lost, reducing char formation efficiency and flame retardant properties. Furthermore, the density of fluorinated graft chains decreases, the low surface energy network is incomplete, and the coefficient of friction increases.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphene-reinforced flame-retardant PE communication tube, characterized in that, The raw materials for its preparation, by weight, include: 100-120 parts of high-density polyethylene, 4-8 parts of polyvinylidene fluoride, 2-4 parts of fluorinated acyl-modified graphene, 10-20 parts of fluorinated silane coupling agent-modified ammonium polyphosphate, 5-10 parts of polyolefin elastomer, 3-7 parts of maleic anhydride-grafted high-density polyethylene, 0.5-1.5 parts of antioxidant, and 1-3 parts of lubricant.

2. The graphene-reinforced flame-retardant PE communication tube according to claim 1, characterized in that, The lubricant is one or two of polyethylene wax and calcium stearate; the antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant.

3. The graphene-reinforced flame-retardant PE communication tube according to claim 1, characterized in that, The raw materials for preparing the fluorinated acyl-modified graphene, by weight, include: 0.5-1.0 parts of graphene oxide, 0.5-1.0 parts of dopamine hydrochloride, 2-4 parts of perfluorobutyryl chloride, 2-4 parts of triethylamine, 150-250 parts of anhydrous ethanol, and 200-300 parts of deionized water.

4. The graphene-reinforced flame-retardant PE communication tube according to claim 3, characterized in that, The preparation method of the fluorinated acyl-modified graphene includes the following steps: 1) Add graphene oxide to deionized water and ultrasonically disperse it for 1-2 hours at an ultrasonic frequency of 40-50kHz and a power of 300-500W. Add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0-8.5, add dopamine hydrochloride, and stir the reaction at 200-300r / min at 30-40℃ for 14-18 hours to obtain polydopamine-coated graphene oxide. 2) The polydopamine-coated graphene oxide obtained in step 1) is subjected to plate and frame filter or vacuum filter, washed with deionized water 2-4 times, and then ultrasonically dispersed in anhydrous ethanol. Perfluorobutyryl chloride and triethylamine are added, and the reaction is carried out for 8-12 hours under nitrogen protection, 20-30℃ and stirring at 200-300r / min. 3) The product obtained in step 2) is subjected to plate and frame filtration or vacuum filtration, and washed 2-4 times each with anhydrous ethanol and deionized water. The resulting solid product is dried at 60-80℃ and vacuum degree -0.085~-0.095MPa for 20-24h to obtain fluorine-containing acyl modified graphene.

5. The graphene-reinforced flame-retardant PE communication tube according to claim 1, characterized in that, The raw materials for preparing the fluorinated silane coupling agent modified ammonium polyphosphate, by weight, include: 20-30 parts of ammonium polyphosphate, 2-4 parts of dopamine hydrochloride, 5-10 parts of heptadecafluorodecyltrimethoxysilane, 0.1-0.3 parts of dibutyltin dilaurate, 200-300 parts of anhydrous ethanol, and 180-300 parts of deionized water.

6. The graphene-reinforced flame-retardant PE communication tube according to claim 5, characterized in that, The preparation method of the fluorinated silane coupling agent modified ammonium polyphosphate includes the following steps: (1) Disperse ammonium polyphosphate in deionized water and stir at 200-300 r / min for 10-15 min. Then add tris(hydroxymethyl)aminomethane buffer solution to adjust the pH to 8.0-8.5, and then add dopamine hydrochloride. React at 30-40℃ and 200-300 r / min for 14-18 h to obtain polydopamine-coated ammonium polyphosphate. (2) The polydopamine-coated ammonium polyphosphate obtained in step (1) is subjected to plate and frame filter or vacuum filter, washed with deionized water 2-4 times, redispersed in anhydrous ethanol, and dibutyltin dilaurate and heptadecafluorodecyltrimethoxysilane are added. The mixture is reacted for 8-12 h under nitrogen protection, 60-80℃ and stirring at 200-300 r / min. (3) The product obtained in step (2) is subjected to plate and frame filter or vacuum filter, and washed 2-4 times with anhydrous ethanol and deionized water respectively. It is then dried at 60-70℃ and vacuum degree -0.085~-0.095MPa for 18-22h to obtain fluorinated silane coupling agent modified ammonium polyphosphate.

7. The graphene-reinforced flame-retardant PE communication tube according to claim 5, characterized in that, The degree of polymerization of the ammonium polyphosphate is 900-1000.

8. A process for preparing a graphene-reinforced flame-retardant PE communication tube as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Dry high-density polyethylene at 80-90℃ for 4-6 hours, and vacuum dry fluorinated acyl-modified graphene and fluorinated silane coupling agent-modified ammonium polyphosphate at 80-90℃ and vacuum degree -0.085~-0.095MPa for 2-4 hours respectively. S2. Add the dried high-density polyethylene, polyvinylidene fluoride, and polyolefin elastomer to a high-speed mixer and premix for 5-8 minutes at 70-80℃ and 1200-1400 r / min. Add maleic anhydride-grafted high-density polyethylene and continue mixing for 5-8 minutes. Then add fluorinated acyl-modified graphene and mix for 8-10 minutes at 90-100℃ and 1400-1600 r / min. Finally, add fluorinated silane coupling agent-modified ammonium polyphosphate, antioxidant, and lubricant, and mix for 5-10 minutes at 90-100℃ and 1000-1200 r / min to obtain the premix. S3. Add the premix obtained in step S2 to a twin-screw extruder for melt blending, extrusion granulation, and air cooling to obtain composite granules; S4. Add the composite granules obtained in step S3 into a single screw extruder, extrude them through a pipe die, and then pass the extruded pipe through a vacuum sizing box, a cooling water tank, and a traction machine in sequence. Finally, cut the pipe to a fixed length to obtain a graphene-reinforced flame-retardant PE communication pipe.

9. The preparation process of the graphene-reinforced flame-retardant PE communication tube according to claim 8, characterized in that, In step S3, the extrusion process parameters of the twin-screw extruder are: Zone 1 160-170℃, Zone 2 175-185℃, Zone 3 188-195℃, Zone 4 195-200℃, Zone 5 190-195℃, Die head 185-190℃, screw speed 100-120r / min, and feed speed 15-25r / min.

10. The preparation process of the graphene-reinforced flame-retardant PE communication tube according to claim 8, characterized in that, In step S4, the temperatures of the single-screw extruder for pipe forming are as follows: feeding section 170-180℃, compression section 185-195℃, homogenization section 190-200℃, die 190-195℃; screw speed 30-50 r / min; traction speed 1.5-2.0 m / min; vacuum degree of vacuum sizing box -0.04~-0.06MPa; cooling water tank temperature 15-25℃.

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