A medium-resistant and aging-resistant multilayer fuel pipe and a preparation method thereof

Abstract

The application discloses a kind of media-resistant and anti-aging multilayer fuel pipe, including sequentially arranged from inside to outside inner layer, barrier layer, adhesive layer, braided layer and outer layer, inner layer is F-TPV fluorine-containing thermoplastic elastomer layer, barrier layer is FKM fluororubber layer, adhesive layer is ECO / CO fluorine-containing chloro ether rubber layer, braided layer is aramid reinforced layer, outer layer is AEM rubber layer, the thickness of outer layer is 1.2±0.2mm, for the pipe blank formed by inner layer, barrier layer, adhesive layer, braided layer, the thickness of outer layer is used to compensate to meet the thickness requirement of multilayer fuel pipe wall thickness 3.5mm.The application also discloses a kind of media-resistant and anti-aging multilayer fuel pipe of the preparation method as described above.Compared with prior art, solve the problem that the interlayer bonding force of existing multilayer fuel pipe is insufficient and the media-resistant, anti-aging performance is insufficient.

Description

Technical Field

[0001] This invention relates to the field of automotive fuel pipe manufacturing technology, and in particular to a multilayer fuel pipe that is resistant to media and aging and its preparation method. Background Technology

[0002] Fuel lines are a core component of a car's fuel supply system, responsible for the stable delivery of fuel from the fuel tank to the engine's fuel injection system. Modern car fuel lines generally employ a 3-5 layer composite structure, integrating the advantages of different materials to avoid the shortcomings of single materials while meeting environmental and safety standards.

[0003] Existing multi-layer fuel lines suffer from insufficient interlayer bonding and poor material compatibility, resulting in deficiencies in resistance to extreme environments, impermeability, and mechanical strength. Consequently, fuel lines have short service lives and low safety, making it difficult to meet the long-term use requirements under high temperature, high pressure, and highly corrosive media conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer fuel pipe that is resistant to media and aging, so as to solve the problems of insufficient interlayer bonding and insufficient resistance to media and aging in existing multilayer fuel pipes.

[0005] To achieve the above objectives, this invention discloses a multi-layer fuel pipe that is resistant to media and aging, comprising an inner layer, a barrier layer, an adhesive layer, a braided layer, and an outer layer arranged sequentially from the inside out. The inner layer is an F-TPV fluorinated thermoplastic elastomer layer with a thickness of not less than 0.25 mm. The barrier layer is an FKM fluororubber layer with a thickness of not less than 0.8 mm. The adhesive layer is an ECO / CO fluorinated chloroether rubber layer with a thickness of approximately 1.0 ± 0.2 mm. The braided layer is an aramid reinforcement layer. The outer layer is an AEM rubber layer with a thickness of 1.2 ± 0.2 mm. Based on the wall thickness of the pipe blank formed by the inner layer, barrier layer, adhesive layer, and braided layer, the thickness of the outer layer is used to compensate for the 3.5 mm wall thickness requirement of the multi-layer fuel pipe.

[0006] On the other hand, the present invention also discloses a method for preparing a multilayer fuel pipe that is resistant to media and aging as described above, comprising the following steps: S1. Raw material pretreatment: Take the raw material components of the inner layer and granulate them by melt blending to obtain inner layer granules. Take the raw material components of the barrier layer and add them to the internal mixer to mix and obtain barrier layer adhesive. Take the raw material components of the adhesive layer and add them to the internal mixer to mix and obtain adhesive layer adhesive. Take the raw material components of the outer layer and add them to the internal mixer to mix and obtain outer layer adhesive. S2. Tube blank forming: The inner layer granules are added to the inner layer extruder, the barrier layer adhesive is added to the barrier layer extruder, and the adhesive layer adhesive is added to the adhesive layer extruder. The inner layer extruder, the barrier layer extruder, and the adhesive layer extruder simultaneously extrude the melt through the three-layer co-extrusion die head and immediately enter the vacuum sizing sleeve to form a three-layer prefabricated tube blank in which the inner layer, the barrier layer, and the adhesive layer are concentrically arranged from the inside to the outside. The tube blank traction speed is 4 to 6 m / min. S3. Tube blank reinforcement: The three-layer precast tube blank with the adhesive layer surface in a semi-molten state is drawn through a horizontal high-speed braiding machine, and a braided layer is made on the surface of the three-layer precast tube blank using braiding fibers. S4. Outer layer coating: The outer layer adhesive is added to the outer layer single screw extruder. The coating die head of the outer layer single screw extruder is connected to the outlet of the horizontal high-speed braiding machine. The molten outer layer adhesive coats the braided layer and penetrates the braiding gap, forming a molten bond with the adhesive layer to form a five-layer composite tube blank. S5. Online vulcanization: The five-layer composite pipe blank undergoes online co-crosslinking vulcanization in a vulcanization box; S6. Cooling and shaping.

[0007] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In this invention, the inner layer in direct contact with fuel exhibits excellent high-temperature resistance and media resistance, while the barrier layer demonstrates strong chemical corrosion resistance and heat resistance. An adhesive layer enhances interlayer adhesion, and the introduced braided layer improves media resistance and aging resistance. Through the synergistic effect of multiple functional materials, the multi-layer fuel pipe achieves high-temperature resistance, high-pressure resistance, and resistance to strong acids and alkalis. Furthermore, the interlayer utilizes chemical co-crosslinking technology, increasing interfacial bonding strength by 50%, preventing delamination failure, and effectively improving the overall structural stability of the multi-layer fuel pipe.

[0008] 2. In this invention, during the preparation of the fuel pipe, the inner layer, barrier layer, and adhesive layer are simultaneously extruded through a three-layer co-extrusion die head to form a three-layer preform. After the three-layer preform is braided and covered with an outer layer, a five-layer composite pipe blank is obtained. Then, through online co-crosslinking vulcanization, chemical bonds are formed between the layers, and the interfacial bonding strength is increased by more than 50%, so that it does not delaminate after long-term use. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of a multi-layer fuel pipe that is resistant to media and aging.

[0011] Figure 2 This is a flowchart of a method for preparing a multilayer fuel pipe that is resistant to media and aging.

[0012] Legend: 1. Inner layer; 2. Barrier layer; 3. Adhesive layer; 4. Braided layer; 5. Outer layer. Detailed Implementation

[0013] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. Example 1

[0015] On the one hand, please refer to Figure 1 This invention discloses a multi-layer fuel pipe that is resistant to media and aging, comprising, from the inside out, an inner layer 1, a barrier layer 2, an adhesive layer 3, a braided layer 4, and an outer layer 5. The inner layer 1 is an F-TPV fluorinated thermoplastic elastomer layer with a thickness of not less than 0.25 mm, ensuring that the barrier layer thickness is ≥0.2 mm in the bending area of ​​the molded part. The barrier layer 2 is an FKM fluororubber layer with a thickness of not less than 0.8 mm, ensuring that the barrier layer thickness is ≥0.6 mm in the bending area of ​​the molded part. The adhesive layer 3 is ECO / CO The fluorinated chloroether rubber layer, the adhesive layer 3 has a thickness of approximately 1.0±0.2mm, the braided layer 4 is an aramid reinforcement layer, and the outer layer 5 is an AEM (ethylene-acrylate rubber) rubber layer with a thickness of 1.2±0.2mm. Based on the tube blank wall thickness formed by the inner layer 1, barrier layer 2, adhesive layer 3, and braided layer 4, the thickness of the outer layer 5 is used to compensate for the 3.5mm thickness requirement of the multi-layer fuel pipe wall thickness, that is, the thickness of the outer layer 5 = the multi-layer fuel pipe wall thickness - the tube blank wall thickness of the other four layers.

[0016] The inner layer 1 comprises the following raw material components by weight: 65-75 parts ETFE (ethylene-tetrafluoroethylene copolymer), 25-35 parts FKM (fluororubber), 2-4 parts acetylene black, 1.0-1.5 parts hindered phenolic antioxidant, 0.5-1.0 parts phosphite antioxidant, 0.3-0.8 parts zinc stearate, and 0.2-0.5 parts fluorine processing flow agent.

[0017] For the inner layer 1, which is in direct contact with fuel, a matrix resin of ETFE and FKM is used, and the fluororubber is of type VDF-HFP, which has the advantages of oil and alcohol resistance and low permeability. The addition of acetylene black achieves conductivity and antistatic properties. At the same time, hindered phenol antioxidants and phosphite antioxidants are used to improve anti-aging ability, giving the inner layer 1 excellent high temperature resistance and media resistance.

[0018] Take the raw material components of inner layer 1 according to the above proportions, and obtain inner layer raw material particles by melt blending and granulation. Specifically, a twin-screw extruder can be used for melt blending and granulation at a temperature of 260-300℃ and a speed of 220-280 rpm for 5-8 minutes, followed by water cooling, pelletizing, and drying.

[0019] Barrier layer 2 comprises the following raw material components by weight: 90-94 parts FKM, 3-5 parts calcium fluoride, 1-2 parts active magnesium oxide, 1.8-2.5 parts dicumyl peroxide (DCP), 0.6-1.0 parts triallyl isocyanurate (TAIC), and 0.5-1.0 parts amine antioxidant 4010NA.

[0020] FKM can specifically use VDF-HFP with medium to high fluorine content, and add calcium fluoride and active magnesium oxide as fillers to resist chemical corrosion. By adding a peroxide sulfidation system and antioxidants, its chemical corrosion resistance and heat resistance can be enhanced. Barrier layer 2, as the main barrier layer with a thickness of not less than 0.8 mm, has the advantages of extremely low fuel permeability, alcohol resistance, oil resistance, and high temperature resistance, and the wall thickness at the bending point is not less than 0.6 mm.

[0021] The adhesive layer 3 comprises the following raw material components by weight: 75-85 parts of ECO (epoxychloropropane-ethylene oxide copolymer), 15-25 parts of CO (epoxychloropropane homopolymer), 1.2-2.0 parts of triazine crosslinking agent (2,4,6-trimercapto-1,3,5-triazine), 1.0-1.5 parts of calcium-zinc composite stabilizer, 3-5 parts of liquid nitrile rubber (LNBR), 0.5-1.0 parts of antioxidant (MB), and 0.5-1.0 parts of microcrystalline wax.

[0022] The adhesive layer 3 matrix is ​​made of ECO / CO blend, with epoxy groups and ether bonds in the main chain. It is highly polar and has good interfacial compatibility with the FKM material of the barrier layer and the AEM material of the outer layer 5. It can form hydrogen bonds and share a "peroxide + triazine" crosslinking system to ensure adhesive strength. It is prepared with an environmentally friendly crosslinking agent that is lead-free, nickel-free and free of epoxy dimethyl propane (ETU). The oil-resistant additive liquid nitrile butadiene nitrile (LNBR) not only improves cold resistance, but also improves the processing fluidity of ECO / CO, enhances molecular interpenetration with FKM / AEM, strengthens adhesion, and effectively improves the interlayer adhesion of the multilayer fuel pipe.

[0023] The braided layer 4 is made of p-AR para-aramid fiber or m-AR meta-aramid fiber. The braiding material of the braided layer 4 is selected from p-AR para-aramid fiber or m-AR meta-aramid fiber to form a high-strength compression-resistant and impact-resistant skeleton. Alternatively, ultra-high temperature resistant POD (polyoxadiazole fiber) fiber can be used, which has excellent dimensional stability.

[0024] The outer layer 5 comprises the following raw material components by weight: 92-96 parts of AEM (ethylene-acrylate rubber), 1.2-1.8 parts of crosslinking agent DCP, 0.8-1.5 parts of UV stabilizer (UV-531), 2-4 parts of nano-SiO2, 1-2 parts of talc, and 0.3-0.6 parts of stearic acid.

[0025] The outer layer 5 uses AEM as the matrix and is produced by a guanidine-free crosslinking process. It does not contain pyrolysis products (such as o-toluidine), phosphate esters and / or halogenated flame retardants. It also adds UV stabilizers and abrasion-resistant fillers to improve weather resistance, heat resistance and protective properties.

[0026] On the other hand, please see Figure 2 The present invention also discloses a method for preparing a multilayer fuel pipe that is resistant to media and aging as described above, comprising the following steps: S1. Raw material pretreatment: Take the raw material components of inner layer 1 and granulate them by melt blending to obtain inner layer granules, i.e., F-TPV granules. Take the raw material components of barrier layer 2 and add them to an internal mixer to mix and obtain barrier layer rubber, i.e., FKM compound rubber. Take the raw material components of adhesive layer 3 and add them to an internal mixer to mix and obtain adhesive layer rubber, i.e., ECO compound rubber. Take the raw material components of outer layer 5 and add them to an internal mixer to mix and obtain outer layer rubber. S2. Tube blank forming: The inner layer granules are added to the inner layer extruder. Before adding the inner layer granules to the inner layer extruder, they are dried at 80℃ for 4 hours to remove moisture. The extruder temperature is 270~310℃ and the discharge speed is 6~9m / min. The barrier layer adhesive is added to the barrier layer extruder. Before adding the barrier layer adhesive, it is softened and preheated to 80℃. The extruder temperature is 190~220℃ and the discharge speed is 5~8m / min. The adhesive layer adhesive is added to the adhesive layer extruder. Before adding the adhesive layer adhesive, it is preheated to 75℃. The extruder temperature is 175~200℃ and the discharge speed is 4~7m / min. The inner layer extruder, barrier layer extruder, and adhesive layer extruder simultaneously extrude the melt through the three-layer co-extrusion die head and immediately enter the vacuum sizing sleeve to form a three-layer precast tube blank with inner layer 1, barrier layer 2, and adhesive layer 3 arranged concentrically from the inside to the outside. The tube blank traction speed is 4~6m / min. S3, tube blank reinforcement: The three-layer precast tube blank with the surface of the adhesive layer 3 in a semi-molten state is drawn through a horizontal high-speed braiding machine, and the braiding fiber is used to make the braided layer 4 on the surface of the three-layer precast tube blank; S4. Outer layer coating: The outer layer adhesive is preheated to 90°C and then added to the outer single-screw extruder. The coating die head of the outer single-screw extruder is connected to the outlet of the horizontal high-speed braiding machine and arranged coaxially. The extruder temperature is 185~210°C and the speed is 3.5~6m / min. The molten outer layer adhesive coats the braided layer 4 and penetrates the braiding gap, forming a molten bond with the adhesive layer 3 to form a five-layer composite tube blank. S5. Online vulcanization: The five-layer composite pipe blank is vulcanized online in a vulcanization box. At high temperature, the molecular chains of each layer of rubber / elastomer undergo co-crosslinking, and chemical bonds are formed between the layers to solve the delamination problem. S6. Cooling and Shaping: After vulcanization, the pipe body is first pulled through the air-cooling section and the water-cooling section in sequence. First, it is air-cooled for 4 to 6 minutes, from 80°C to 60°C, and then water-cooled for 8 to 12 minutes, from 60°C to room temperature. The slow cooling avoids interlayer cracking and pipe deformation caused by thermal expansion and contraction, and eliminates thermal stress.

[0027] The multi-layer fuel pipe, which has been cooled and shaped, can be cut to size as needed. The outer layer is laser-engraved with color codes and heat-fused with RFID tags to achieve intelligent identification of the pipeline, enabling error-proof installation in the later stage, with an installation accuracy of 100% and a positioning accuracy of ±0.05mm.

[0028] Working Principle: The inner layer 1, which directly contacts the fuel, exhibits excellent high-temperature resistance and media resistance. The barrier layer 2 possesses strong chemical corrosion resistance and heat resistance. The adhesive layer 3 enhances interlayer adhesion, and the introduced braided layer 4 improves media resistance and aging resistance. Through the synergy of multiple functional materials, the multi-layer fuel pipe achieves high-temperature resistance (250℃), high-pressure resistance (30MPa), and resistance to strong acids and alkalis. Furthermore, the interlayer utilizes chemical co-crosslinking technology, increasing the interfacial bonding strength by 50%, preventing delamination failure, and effectively improving the overall structural stability of the multi-layer fuel pipe. During the manufacturing process of the multi-layer fuel pipe, the inner layer 1, barrier layer 2, and adhesive layer 3 are simultaneously extruded through a three-layer co-extrusion die to form a three-layer preform. After braiding and outer layer coating, a five-layer composite preform is obtained. Online co-crosslinking and vulcanization then form chemical bonds between the layers, increasing the interfacial bonding strength by over 50%, ensuring no delamination during long-term use.

[0029] The working pressure of the multi-layer fuel pipe is increased by 40%, the burst pressure is ≥90MPa, the service life is extended, the performance retention rate is ≥90% after 2000h aging test, and the resistance to media is excellent. It shows no abnormalities after immersion in strong acid, strong alkali and organic solvent for 30 days. Example 2

[0030] Based on the above embodiments, this embodiment further improves upon the following technical solution: In step S3, before weaving on the horizontal high-speed braiding machine, annular grooves are processed on the semi-molten surface of the bonding layer 3 on the three-layer precast tube blank using a knurling wheel. The depth of the annular grooves is 50-100 μm and the spacing is 1-2 mm. Then, during the weaving process, the braiding fibers are pressed into the annular grooves by a pressure guide wheel with a pressure of 0.3-0.5 MPa.

[0031] The surface of the three-layer precast tube blank is roughened by knurling, so that the braided layer 4 and the adhesive layer 3 of the three-layer precast tube blank form a braided interlocking layer. This not only prevents the braided layer from slipping, but also facilitates the melting and penetration of the outer layer 5 into the braided mesh, forming a three-in-one structure of "outer layer adhesive - braided layer - adhesive layer", which strengthens the physical bond between layers and further improves the interlayer adhesion of the multi-layer fuel pipe. Example 3

[0032] Based on the above embodiments, this embodiment further improves upon the following technical solution: In step S5, the vulcanizing box is a segmented hot air vulcanizing box, which includes a shaping crosslinking section, an interlayer co-crosslinking section, and a stabilization section arranged sequentially along the conveying direction of the five-layer composite tube blank.

[0033] During the online vulcanization of the five-layer composite pipe blank, the temperature is controlled in stages within the vulcanization chamber to prevent overheating and degradation. The temperature of the shaping and cross-linking section is 150–160℃, where the five-layer composite pipe blank remains for 10–12 minutes to complete the initial cross-linking and fix the five-layer structure. Next, it enters the interlayer co-cross-linking section, where the temperature is 170–180℃, and the five-layer composite pipe blank remains for 25–30 minutes. During this section, the cross-linking agents (DCP, triazine) of the inner F-TPV layer, barrier layer FKM layer, adhesive layer ECO layer, and outer AEM layer of the five-layer composite pipe blank decompose simultaneously, and the interlayer molecular chains diffuse and covalently bond. Finally, it enters the stabilization section, where the temperature is 160℃ and the blank remains for 8–10 minutes to eliminate internal stress and stabilize the cross-linked structure.

[0034] Preferably, the internal air pressure of the vulcanizing chamber is higher than the external atmospheric pressure. During the vulcanization process, the internal air pressure of the vulcanizing chamber is a slight positive pressure of 0.05 MPa. At high temperatures, the materials of each layer are in a soft state. The slight pressure acts evenly on the outer wall of the tube, compacting the tiny gaps and air bubbles between the adhesive layer and the braided layer, and between the braided layer and the outer layer. This makes the interlayer bonding tighter, eliminates the risk of delamination, facilitates the penetration of crosslinking agent molecules and the formation of chemical bonds, and improves the interlayer peel strength.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-layer fuel pipe that is resistant to various media and aging, characterized in that, The system comprises, from the inside out, an inner layer, a barrier layer, an adhesive layer, a braided layer, and an outer layer. The inner layer is an F-TPV fluorinated thermoplastic elastomer layer with a thickness of not less than 0.25 mm. The barrier layer is an FKM fluororubber layer with a thickness of not less than 0.8 mm. The adhesive layer is an ECO / CO fluorinated chloroether rubber layer with a thickness of approximately 1.0 ± 0.2 mm. The braided layer is an aramid reinforcement layer. The outer layer is an AEM rubber layer with a thickness of 1.2 ± 0.2 mm. Based on the wall thickness of the tube blank formed by the inner layer, barrier layer, adhesive layer, and braided layer, the thickness of the outer layer is used to compensate for the 3.5 mm wall thickness requirement of the multi-layer fuel pipe.

2. The multi-layer fuel pipe with media resistance and aging resistance according to claim 1, characterized in that, The inner layer 1 comprises the following raw material components in parts by weight: 65-75 parts ETFE, 25-35 parts FKM, 2-4 parts acetylene black, 1.0-1.5 parts hindered phenolic antioxidant, 0.5-1.0 parts phosphite antioxidant, 0.3-0.8 parts zinc stearate, and 0.2-0.5 parts fluorine processing flow agent.

3. The multi-layer fuel pipe with resistance to media and aging as described in claim 1, characterized in that, The barrier layer comprises the following raw material components in parts by weight: 90-94 parts FKM, 3-5 parts calcium fluoride, 1-2 parts active magnesium oxide, 1.8-2.5 parts dicumyl peroxide, 0.6-1.0 parts triallyl isocyanurate, and 0.5-1.0 parts amine antioxidant 4010NA.

4. The multi-layer fuel pipe resistant to media and aging according to claim 1, characterized in that, The adhesive layer comprises the following raw material components in parts by weight: 75-85 parts ECO, 15-25 parts CO, 1.2-2.0 parts triazine crosslinking agent, 1.0-1.5 parts calcium-zinc composite stabilizer, 3-5 parts liquid nitrile rubber (LNBR), 0.5-1.0 parts antioxidant (MB), and 0.5-1.0 parts microcrystalline wax.

5. A multi-layer fuel pipe resistant to media and aging according to claim 1, characterized in that, The braided layer is made of p-AR para-aramid fiber or m-AR meta-aramid fiber.

6. The multi-layer fuel pipe resistant to media and aging according to claim 1, characterized in that, The outer layer comprises the following raw material components in parts by weight: 92-96 parts AEM, 1.2-1.8 parts crosslinking agent DCP, 0.8-1.5 parts UV stabilizer, 2-4 parts nano SiO2, 1-2 parts talc, and 0.3-0.6 parts stearic acid.

7. A method for preparing a multilayer fuel pipe that is resistant to media and aging as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Raw material pretreatment: Take the raw material components of the inner layer and granulate them by melt blending to obtain inner layer granules. Take the raw material components of the barrier layer and add them to the internal mixer to mix and obtain barrier layer adhesive. Take the raw material components of the adhesive layer and add them to the internal mixer to mix and obtain adhesive layer adhesive. Take the raw material components of the outer layer and add them to the internal mixer to mix and obtain outer layer adhesive. S2. Tube blank forming: The inner layer granules are added to the inner layer extruder, the barrier layer adhesive is added to the barrier layer extruder, and the adhesive layer adhesive is added to the adhesive layer extruder. The inner layer extruder, the barrier layer extruder, and the adhesive layer extruder simultaneously extrude the melt through the three-layer co-extrusion die head and immediately enter the vacuum sizing sleeve to form a three-layer prefabricated tube blank in which the inner layer, the barrier layer, and the adhesive layer are concentrically arranged from the inside to the outside. The tube blank traction speed is 4 to 6 m / min. S3. Tube blank reinforcement: The three-layer precast tube blank with the adhesive layer surface in a semi-molten state is drawn through a horizontal high-speed braiding machine, and a braided layer is made on the surface of the three-layer precast tube blank using braiding fibers. S4. Outer layer coating: The outer layer adhesive is added to the outer layer single screw extruder. The coating die head of the outer layer single screw extruder is connected to the outlet of the horizontal high-speed braiding machine. The molten outer layer adhesive coats the braided layer and penetrates the braiding gap, forming a molten bond with the adhesive layer to form a five-layer composite tube blank. S5. Online vulcanization: The five-layer composite pipe blank undergoes online co-crosslinking vulcanization in a vulcanization box; S6. Cooling and shaping.

8. The method for preparing the media-resistant and aging-resistant multilayer fuel pipe according to claim 7, characterized in that, In step S3, before weaving on the horizontal high-speed braiding machine, annular grooves are processed on the semi-molten surface of the bonding layer on the three-layer precast tube blank using a knurling wheel. The depth of the annular grooves is 50-100 μm and the spacing is 1-2 mm. Then, during the weaving process, the braiding fibers are pressed into the annular grooves by a pressure guide wheel.

9. The method for preparing the media-resistant and aging-resistant multilayer fuel pipe according to claim 7, characterized in that, In step S5, the vulcanizing box is a segmented hot air vulcanizing box, which includes a shaping crosslinking section, an interlayer co-crosslinking section, and a stabilization section arranged sequentially along the conveying direction of the five-layer composite tube blank.

10. The method for preparing the media-resistant and aging-resistant multilayer fuel pipe according to claim 9, characterized in that, In step S5, the air pressure inside the vulcanizing box is higher than the external atmospheric pressure.

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