High-strength integrated flexible composite pipe and preparation method thereof

Abstract

The invention relates to the field of composite pipes, in particular to a high-strength integrated flexible composite pipe and a preparation method thereof.The high-strength integrated flexible composite pipe is prepared from, by mass, 140-160 parts of modified high-density polyethylene, 125-145 parts of composite master batch, 410-420 parts of modified carbon fiber and the like. The novel composite pipe which is firm in interlayer combination, excellent in mechanical property and has multiple additional functions is successfully prepared by adopting an integrated continuous forming process, compared with the prior art, the product fundamentally improves the pain points that a traditional composite pipe is prone to layering and difficult to consider pressure resistance and flexibility at the same time, the multiple functions of static electricity resistance, bacterium resistance and the like are integrated, and the composite pipe is suitable for large-scale popularization and application. The manufacturing process is stable and efficient, and has wide application prospects in high-risk and severe environments such as oil and gas transportation, chemical pipelines and ocean engineering.

Description

Technical Field

[0001] This invention relates to the field of composite pipes, and more particularly to a high-strength integrated flexible composite pipe and its preparation method. Background Technology

[0002] High-strength integrated flexible composite pipe is an advanced tubular material made of high-molecular matrix resin, high-performance continuous fiber reinforcement and functional additives through a specific process. This type of pipe aims to achieve high strength, high pressure resistance and good axial flexibility at the same time, and is widely used in oil and gas transportation, industrial hydraulic pipelines, marine engineering and special fluid transmission.

[0003] With the increasing demands for lightweight, reliable, and adaptable equipment in various industrial sectors, the development of integrated flexible composite pipes that combine excellent mechanical properties, long service life, and efficient production processes has become an important development direction in this field.

[0004] In existing technologies, conventional fiber-reinforced thermoplastic composite pipes are mostly produced by layering and then composited. The interlayer bonding mainly relies on physical adhesion and simple polar compatibility, resulting in weak interfacial bonding. Under long-term alternating loads, interlayer delamination is prone to occur, becoming the root cause of structural failure. In order to improve strength, it is often necessary to significantly increase the amount of reinforcing fiber or the wall thickness, but this will sacrifice the flexibility of the pipe and lead to increased costs. In addition, traditional manufacturing processes usually carry out matrix modification, fiber treatment, winding molding and other processes in segments. The process is lengthy and the decay of interfacial activity over time will affect the final composite quality.

[0005] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a high-strength integrated flexible composite pipe and its preparation method. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a high-strength integrated flexible composite pipe and its preparation method, so as to solve the problems of weak interlayer bonding and performance imbalance in the prior art.

[0007] To achieve the above objectives, the present invention provides a high-strength integrated flexible composite pipe and its preparation method.

[0008] A high-strength integrated flexible composite pipe is composed of the following components in parts by weight: 140-160 parts of modified high-density polyethylene, 125-145 parts of composite masterbatch, 410-420 parts of modified carbon fiber, 90-110 parts of polyamide 6, 20-30 parts of modified polyolefin, and 5-10 parts of KH-550 treated nano-haloite clay. The modified high-density polyethylene is nano-silica modified high-density polyethylene; The composite masterbatch is composed of low-density polyethylene, graphene, and nano-titanium dioxide. The modified carbon fiber is ε-caprolactam modified carbon fiber; The modified polyolefin is a maleic anhydride-modified polyolefin.

[0009] Preferably, the preparation steps of the modified high-density polyethylene are as follows: Step A1: Add high-density polyethylene granules, maleic anhydride grafted polyethylene and antioxidant 1010 to a high-speed mixer, mix at 300-400 rpm for 2-4 minutes, heat to 55-65℃, increase the speed to 800-1000 rpm, mix for 6-8 minutes, and the mixing is complete to obtain the mixture. Step A2: Add KH-560 silane coupling agent and catalyst dibutyltin dilaurate to nano silica sol, heat to 20-30℃, stir for 20-30 minutes at a speed of 300-500 rpm, and after stirring is complete, a mixture is obtained; Step A3: Add the mixture and compound to a twin-screw extruder. The feeding section is 150-160℃, the melting section is 175-185℃, the pressure is reduced to -0.08MPa, the mixing reaction section and the discharge section are 190-200℃, the speed is 250-350rpm, the reaction is carried out for 2-4 minutes, the reaction is completed, the temperature is reduced to 20-40℃, the particle size is 2-4mm, and the product is dried to obtain modified high-density polyethylene.

[0010] The high-density polyethylene, model HD 5420GA, achieves a significant improvement in the rigidity, heat resistance, and dimensional stability of the matrix resin by forming a gradient interpenetrating network of nano-silica in the matrix, upgrading the macroscopic physical blending to microscopic topological entanglement. Simultaneously, the composite masterbatch, constructed with a titanate coupling agent, establishes a core-shell structure, realizing multifunctional integration. Its addition in masterbatch form ensures nanoscale dispersion within the matrix. Furthermore, this design endows the pipe's inner lining and outer protective layer with not only excellent mechanical strength but also multifunctional properties not found in traditional pipes, such as antistatic properties and long-lasting antibacterial self-cleaning, expanding its application scenarios.

[0011] Preferably, the mass ratio of high-density polyethylene particles, maleic anhydride-grafted polyethylene, and antioxidant 1010 in step A1 is 1:0.18-0.22:0.004-0.006. The mass ratio of KH-560 silane coupling agent, catalyst, and nano-silica sol in step A2 is 0.065-0.067:0.008-0.012:1; The mass ratio of the mixture to the liquid mixture in step A3 is 1:0.26-0.27.

[0012] Preferably, the composite masterbatch preparation steps are as follows: Step B1: Add the titanate coupling agent to anhydrous ethanol and stir for 4-6 minutes at a speed of 300-500 rpm to obtain a diluted coupling agent solution. Step B2: Add graphene and nano-titanium dioxide to a high-speed shear mill, mix for 2-4 minutes at a speed of 400-600 rpm, add coupling agent dilution, increase the speed to 2500-3500 rpm, shear for 10-20 minutes, after shearing is complete, dry to obtain nano-composite powder; Step B3: Add low-density polyethylene, nanocomposite powder, and dispersant polyethylene wax to a high-speed mixer, heat to 45-55℃, rotate at 300-500 rpm, stir for 2-4 minutes, increase the rotation speed to 900-1100 rpm, mix for 8-12 minutes, place in a twin-screw extruder, feed section 120-130℃, melt section 140-150℃, rotation speed 250-350 rpm, reduce pressure to -0.07MPa, mix and discharge sections 160-170℃, after the reaction is complete, cool to 25-35℃, particle size 2-3mm, dry to obtain composite masterbatch.

[0013] The low-density polyethylene is designated as LDPE 243H. Preferably, the mass ratio of the titanate coupling agent to anhydrous ethanol in step B1 is 1:8-10; The mass ratio of graphene, nano-titanium dioxide, and coupling agent dilution in step B2 is 0.37-0.39:0.48-0.52:1; The mass ratio of low-density polyethylene, nanocomposite powder and dispersant in step B3 is 3.38-3.4:1:0.13-0.14.

[0014] Preferably, the preparation steps of the modified carbon fiber are as follows: Step C1: In an air atmosphere, place the carbon fiber in a plasma treatment device with a gas flow rate of 20-40 L / min and a travel speed of 5-15 m / min. Immerse it in a 2.0% wt isocyanate-based silane coupling agent solution as an initiator and treat for 40-60 seconds. After treatment, dry and cure to obtain the treated fiber. Step C2: Under a nitrogen atmosphere, add metallic sodium to the ε-caprolactam monomer, heat to 110-120℃, rotate at 200-300 rpm, stir for 1-3 hours, add the treated fiber, continue for 4-8 minutes, cool to 5-15℃, and obtain modified carbon fiber.

[0015] Through plasma activation and silane coupling agent fixation of the initiator, polyamide 6 polymer is finally grown in situ on the fiber surface. This enables the reinforcing fiber and the subsequent active interface adhesive to achieve molecular-level fusion. At the same time, the modified polyolefin in the adhesive acts as a "molecular bridge". Its anhydride functional groups can react with both the polyamide 6 on the fiber surface and the irradiated activated polyethylene liner. With the "rivet" effect of nano-haloite clay, a multi-interface bonding mechanism is formed, which fundamentally solves the interlayer delamination problem caused by physical bonding in traditional composite pipes. It realizes a truly integrated structure, which enables the pipe to maintain structural integrity and reliability under harsh conditions such as high pressure and bending deformation.

[0016] Preferably, the mass ratio of carbon fiber to initiator in step C1 is 1:0.009-0.011; The mass ratio of sodium metal, ε-caprolactam monomer, and treated fiber in step C2 is 0.0003-0.0005:0.18-0.22:1.

[0017] Preferably, the preparation steps of the modified polyolefin are as follows: Polyolefin particles, maleic anhydride, initiator dicumyl peroxide, and antioxidant 10110 are added to a mixer at 300-400 rpm for 1-3 minutes. The temperature is then raised to 40-50℃, and the speed is increased to 800-1000 rpm for 5-8 minutes. Styrene is added and mixed for 2-3 minutes. The mixture is then placed in a twin-screw extruder at 120-130℃ in the feeding section, 140-160℃ in the melting section, and the pressure is reduced to -0.08MPa to -0.095MPa. The speed is 150-250 rpm, and the reaction and exhaust sections are at 165-175℃ for 2-3 minutes. After the reaction is complete, the mixture is cooled to 20-30℃, the particle size is 2-3 mm, and the mixture is dried to obtain modified polyolefin.

[0018] Preferably, the mass ratio of the polyolefin particles, maleic anhydride, initiator, antioxidant and styrene is 1:0.015-0.03:0.001-0.003:0.001-0.003:0.01-0.03.

[0019] A method for preparing a high-strength integrated flexible composite pipe, the method being as follows: Step S1: Add polyamide 6 powder to a mixed solvent of cresol and isopropanone, heat to 85-95℃, stir at 100-150 rpm for 2-3 hours, add modified polyolefin, increase the speed to 300-400 rpm, stir for 1.5-2.5 hours, add KH-550 treated nano halloysite clay, stir at 400-500 rpm for 30-50 minutes, increase the speed to 6000-8000 rpm, homogenize for 15-25 minutes, after homogenization is complete, cool to 35-45℃, filter, and obtain the adhesive solution; Step S2: Add the composite masterbatch and modified high-density polyethylene to a high-speed mixer at 400-600 rpm for 6-8 minutes. Then place the mixture in a single-screw extruder at 180-190°C in the feeding section and 195-205°C in the compression section, with a speed of 20-40 rpm. Cool the mixture to 90-110°C and use an electron beam energy of 1.5-2.5 MeV for 25-45 seconds to obtain the active pipe material. Step S3: Add modified fiber carbon to the adhesive solution, heat to 40-50℃, impregnate for 3-5 seconds, place on a winding machine, add active tube, heat to 80-100℃, hold for 20-30 seconds, then place in a mold, cool the front end to 20-40℃, hold for 20-40 seconds, heat the rear end to 220-240℃, hold for 1-3 minutes, the reaction is complete, cool to 15-30℃, traction force 30-50N, to obtain composite tube; By using an electron beam to irradiate the extruded inner liner tube online, mild cross-linking of the matrix and efficient activation of the surface are achieved simultaneously, creating optimal conditions for subsequent interfacial chemical reactions. Subsequently, the impregnated fibers are wound around the heated inner liner tube and immediately enter the integrated mold to complete curing, allowing the chemical reactions between the components to be completed efficiently within the optimal time and space window. In addition, this process is short and efficient, and through precise online control, it ensures the uniformity and stability of product quality. It integrates multiple traditionally independent processes into a continuous and automated process, which is the key to achieving high-performance products and reducing production costs.

[0020] In step S1, the mass ratio of polyamide 6, modified polyolefin, and KH-550 treated nano-haloite clay is 1:0.23-0.27:0.007-0.008. In step S1, the volume ratio of cresol to isopropanone in the mixed solvent is 7:3; The mass ratio of the composite masterbatch to the modified high-density polyethylene in step S2 is 1:13-17; In step S3, the mass ratio of modified carbon fiber, adhesive, and active tubing is 1.4-1.5:0.4-0.5:1.

[0021] The beneficial effects of this invention are: This invention provides a high-strength integrated flexible composite pipe and its preparation method. By constructing a novel composite material system and a unique interface design, and by adopting an integrated continuous molding process, this invention successfully prepares a new type of composite pipe with strong interlayer bonding, excellent mechanical properties, and multiple additional functions. Compared with the prior art, this product fundamentally improves the pain points of traditional composite pipes, such as easy delamination and difficulty in balancing pressure resistance and flexibility. At the same time, it achieves multi-functional integration such as antistatic and antibacterial properties. Its manufacturing process is stable and efficient, and it has broad application prospects in high-risk and harsh environments such as oil and gas transportation, chemical pipelines, and marine engineering. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a bar chart showing the results of the burst pressure test and the interlaminar shear strength test in this invention. Figure 2 The maximum load value F in the interlaminar shear strength test results of this invention. max A line graph; Figure 3 This is a bar chart of the ring stiffness test results in this invention; Figure 4 This is a bar chart showing the heat distortion temperature test results in this invention; Figure 5 This is a bar chart showing the antibacterial performance test results in this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] Example 1: Preparation of a modified high-density polyethylene S1: Add 100g of high-density polyethylene granules, 18g of maleic anhydride-grafted polyethylene and 0.4g of antioxidant 1010 to a high-speed mixer, mix at 300 rpm for 4 minutes, heat to 55℃, increase the speed to 1000 rpm and mix for 6 minutes. The mixing is complete, and the mixture is obtained. S2: Add 6.5g of KH-560 silane coupling agent and 0.8g of catalyst dibutyltin dilaurate to 100g of nano silica sol, heat to 20℃, stir for 30min at 300rpm, and after stirring is complete, a mixture is obtained. S3: Add 26g of the mixture and 100g of the mixture to a twin-screw extruder. The feeding section is 150℃, the melting section is 185℃, the pressure is reduced to -0.08MPa, the mixing reaction section and the discharge section are 190℃, the speed is 350rpm, the reaction is carried out for 2min, the reaction is completed, the temperature is reduced to 40℃, the particle size is 2-4mm, and the product is dried to obtain modified high-density polyethylene.

[0026] Example 2: Preparation of a modified high-density polyethylene S1: Add 100g of high-density polyethylene granules, 20g of maleic anhydride grafted polyethylene and 0.5g of antioxidant 1010 to a high-speed mixer, mix at 350rpm for 3min, heat to 60℃, increase the speed to 900rpm and mix for 7min. The mixing is complete, and the mixture is obtained. S2: Add 6.6g of KH-560 silane coupling agent and 1g of catalyst dibutyltin dilaurate to 100g of nano silica sol, heat to 25℃, stir for 25min at 400rpm, and after stirring is complete, a mixture is obtained. S3: Add 26.5g of the mixture and 100g of the mixture to a twin-screw extruder. The feeding section is 155℃, the melting section is 180℃, the pressure is reduced to -0.08MPa, the mixing reaction section and the discharge section are 195℃, the speed is 300rpm, the reaction is carried out for 3min, the reaction is completed, the temperature is reduced to 30℃, the particle size is 2-4mm, and the product is dried to obtain modified high-density polyethylene.

[0027] Example 3: Preparation of a modified high-density polyethylene S1: Add 100g of high-density polyethylene granules, 22g of maleic anhydride-grafted polyethylene and 0.6g of antioxidant 1010 to a high-speed mixer, mix at 400 rpm for 2 minutes, heat to 65℃, increase the speed to 800 rpm and mix for 8 minutes. The mixing is complete, and the mixture is obtained. S2: Add 6.7g of KH-560 silane coupling agent and 1.2g of catalyst dibutyltin dilaurate to 100g of nano silica sol, heat to 30℃, stir for 20min at 500rpm, and after stirring is complete, a mixture is obtained. S3: Add 27g of the mixture and 100g of the mixture to a twin-screw extruder. The feeding section is 160℃, the melting section is 175℃, the pressure is reduced to -0.08MPa, the mixing reaction section and the discharge section are 200℃, the speed is 250rpm, the reaction is carried out for 4min, the reaction is completed, the temperature is reduced to 20℃, the particle size is 2-4mm, and the product is dried to obtain modified high-density polyethylene.

[0028] Example 4: Preparation of a composite masterbatch S1: Add 100g of titanate coupling agent to 800g of anhydrous ethanol, stir for 4min at 500rpm to obtain a diluted coupling agent solution. S2: Add 37g of graphene and 48g of nano-titanium dioxide to a high-speed shearing machine, mix for 2 minutes at 600 rpm, add 100g of coupling agent dilution, increase the speed to 2500 rpm, shear for 20 minutes, and after shearing is complete, dry to obtain nano-composite powder. S3: Add 338g of low-density polyethylene, 100g of nanocomposite powder and 13g of dispersant polyethylene wax to a high-speed mixer, heat to 45℃, speed 500rpm, stir for 2min, increase speed to 1100rpm, mix for 8min, place in a twin-screw extruder, feed section 130℃, melt section 140℃, speed 350rpm, reduce pressure to -0.07MPa, mix section and discharge section 160℃, reaction complete, cool to 35℃, particle size 2-3mm, dry to obtain composite masterbatch.

[0029] Example 5: Preparation of a composite masterbatch S1: Add 100g of titanate coupling agent to 900g of anhydrous ethanol, stir for 5min at 400rpm to obtain a diluted coupling agent solution. S2: Add 38g of graphene and 50g of nano-titanium dioxide to a high-speed shearing machine, mix for 3 minutes at 500 rpm, add 100g of coupling agent dilution, increase the speed to 3000 rpm, shear for 15 minutes, and after shearing is complete, dry to obtain nano-composite powder. S3: Add 339g of low-density polyethylene, 100g of nanocomposite powder and 13.5g of dispersant polyethylene wax to a high-speed mixer, heat to 50℃, speed 400rpm, stir for 3min, increase speed to 1000rpm, mix for 10min, place in a twin-screw extruder, feed section 125℃, melt section 145℃, speed 300rpm, reduce pressure to -0.07MPa, mix section and discharge section 165℃, reaction complete, cool to 30℃, particle size 2-3mm, dry to obtain composite masterbatch.

[0030] Example 6: Preparation of a composite masterbatch S1: Add 100g of titanate coupling agent to 1000g of anhydrous ethanol, stir for 6 minutes at 300rpm to obtain a diluted coupling agent solution. S2: Add 39g of graphene and 52g of nano-titanium dioxide to a high-speed shearing machine, mix for 4 minutes at 400 rpm, add 100g of coupling agent dilution, increase the speed to 3500 rpm, shear for 10 minutes, and after shearing is complete, dry to obtain nano-composite powder. S3: Add 340g of low-density polyethylene, 100g of nanocomposite powder and 14g of dispersant polyethylene wax to a high-speed mixer, heat to 55℃, speed 300rpm, stir for 4min, increase speed to 900rpm, mix for 12min, place in a twin-screw extruder, feed section 120℃, melt section 150℃, speed 250rpm, reduce pressure to -0.07MPa, mixing section and discharge section 170℃, reaction complete, cool to 25℃, particle size 2-3mm, dry to obtain composite masterbatch.

[0031] Example 7: Preparation of a composite masterbatch S1: Add 100g of titanate coupling agent to 800g of anhydrous ethanol, stir for 4min at 500rpm to obtain a diluted coupling agent solution. S2: Add 37g of graphene, 48g of nano titanium dioxide, 3g of nano cerium oxide and 1.5g of ultraviolet absorber UV-326 to a high-speed shearing machine, mix for 2 minutes at 600 rpm, add 100g of coupling agent dilution, increase the speed to 2500 rpm, shear for 20 minutes, after shearing is complete, dry to obtain nanocomposite powder. S3: Add 338g of low-density polyethylene, 100g of nanocomposite powder and 13g of dispersant polyethylene wax to a high-speed mixer, heat to 45℃, speed 500rpm, stir for 2min, increase speed to 1100rpm, mix for 8min, place in a twin-screw extruder, feed section 130℃, melt section 140℃, speed 350rpm, reduce pressure to -0.07MPa, mix section and discharge section 160℃, reaction complete, cool to 35℃, particle size 2-3mm, dry to obtain composite masterbatch.

[0032] Example 8: Preparation of a modified carbon fiber S1: In an air atmosphere, 100g of carbon fiber is placed in a plasma treatment device with a gas flow rate of 20L / min and a travel speed of 15m / min. It is immersed in a 0.9g initiator and a 2.0%wt isocyanate-based silane coupling agent solution for 40s. After treatment, it is dried and cured to obtain the treated fiber. S2: Under a nitrogen atmosphere, 0.03g of metallic sodium was added to 18g of ε-caprolactam monomer, the temperature was raised to 110℃, the stirring speed was 300rpm, and the reaction was carried out for 1h. Then, 100g of the treated fiber was added, and the reaction was continued for 8min. The temperature was then lowered to 5℃ to obtain modified carbon fiber.

[0033] Example 9: Preparation of a modified carbon fiber S1: In an air atmosphere, 100g of carbon fiber is placed in a plasma treatment device with a gas flow rate of 30L / min and a travel speed of 10m / min. It is immersed in 1g of initiator and 2.0%wt isocyanate-based silane coupling agent solution for 50s. After treatment, it is dried and cured to obtain the treated fiber. S2: Under a nitrogen atmosphere, 0.04 g of metallic sodium was added to 20 g of ε-caprolactam monomer, the temperature was raised to 115 °C, the stirring speed was 250 rpm, and the reaction was carried out for 2 h. Then, 100 g of the treated fiber was added, and the reaction was continued for 6 min. The temperature was then lowered to 10 °C to obtain modified carbon fiber.

[0034] Example 10: Preparation of a modified carbon fiber S1: In an air atmosphere, 100g of carbon fiber is placed in a plasma treatment device with a gas flow rate of 40L / min and a travel speed of 5m / min. It is immersed in a 1.1g initiator and a 2.0%wt isocyanate-based silane coupling agent solution for 60s. After treatment, the fiber is dried and cured to obtain the treated fiber. S2: Under a nitrogen atmosphere, 0.05g of metallic sodium was added to 22g of ε-caprolactam monomer, the temperature was raised to 120℃, the stirring speed was 200rpm, and the reaction was carried out for 3h. Then, 100g of the treated fiber was added, and the reaction was continued for 4min. The temperature was then lowered to 15℃ to obtain modified carbon fiber.

[0035] Example 11: Preparation of a modified polyolefin 100g of polyolefin granules, 1.5g of maleic anhydride, 0.1g of initiator dicumyl peroxide, and 0.1g of antioxidant 10110 were added to a mixer and mixed at 300 rpm for 3 minutes. The temperature was then raised to 40°C, and the speed was increased to 1000 rpm for 5 minutes. 1g of styrene was added and mixed for 2 minutes. The mixture was then placed in a twin-screw extruder with the feeding section at 130°C, the melting section at 140°C, the pressure reduced to -0.095MPa, the speed at 150 rpm, and the reaction and exhaust sections at 175°C for 2 minutes. After the reaction was complete, the mixture was cooled to 30°C, the particle size was 2-3 mm, and the mixture was dried to obtain modified polyolefin.

[0036] Example 12: Preparation of a modified polyolefin 100g of polyolefin granules, 2g of maleic anhydride, 0.2g of initiator dicumyl peroxide, and 0.2g of antioxidant 10110 were added to a mixer and mixed at 350 rpm for 2 minutes. The temperature was then raised to 45°C, and the speed was increased to 900 rpm for 7 minutes. 2g of styrene was added and mixed for 2.5 minutes. The mixture was then placed in a twin-screw extruder with the feeding section at 125°C, the melting section at 150°C, the pressure reduced to -0.085MPa, the speed at 200 rpm, and the reaction and exhaust sections at 170°C for 2.5 minutes. After the reaction was complete, the mixture was cooled to 25°C, the particle size was 2-3 mm, and the mixture was dried to obtain modified polyolefin.

[0037] Example 13: Preparation of a modified polyolefin 100g of polyolefin granules, 3g of maleic anhydride, 0.3g of initiator dicumyl peroxide, and 0.3g of antioxidant 10110 were added to a mixer and mixed at 400 rpm for 1 min. The temperature was then raised to 50℃, and the speed was increased to 800 rpm for 8 min. 3g of styrene was added and mixed for 2 min. The mixture was then placed in a twin-screw extruder with the feeding section at 130℃, the melting section at 140℃, the pressure reduced to -0.095MPa, the speed at 150 rpm, and the reaction and exhaust sections at 175℃ for 2 min. After the reaction was complete, the mixture was cooled to 30℃, the particle size was 2-3 mm, and the mixture was dried to obtain modified polyolefin.

[0038] Example 14: A method for preparing a high-strength integrated flexible composite pipe S1: Add 100g of polyamide 6 powder to a mixed solvent of 140mL cresol and 60mL isoacetone, heat to 85℃, stir at 150rpm for 2h, add 23g of modified polyolefin (Example 11), increase the speed to 400rpm, stir for 1.5h, add 0.7g of KH-550 treated nano halloysite clay, stir at 400rpm for 50min, increase the speed to 6000rpm, homogenize for 25min, after homogenization is complete, cool to 35℃, filter, and obtain the adhesive solution; S2: Add 100g of composite masterbatch (Example 4) and 1300g of modified high-density polyethylene (Example 1) to a high-speed mixer, mix at 400rpm for 8min, place in a single-screw extruder, feed section 180℃, compression section 205℃, speed 20rpm, cool to 110℃, electron beam energy 1.5MeV, for 45s to obtain active pipe material; S3: Add 140g of modified fiber carbon (Example 8) to 40g of adhesive solution, heat to 40°C, impregnate for 5s, place on a winding machine, add 100g of active tube, heat to 80°C, hold for 30s, then place in a mold, cool the front end to 20°C, hold for 40s, heat the rear end to 220°C, hold for 3min, the reaction is complete, cool to 15°C, traction force 50N, to obtain composite tube.

[0039] Example 15: A method for preparing a high-strength integrated flexible composite pipe S1: Add 100g of polyamide 6 powder to a mixed solvent of 140mL cresol and 60mL isoacetone, heat to 90℃, stir at 125rpm for 2.5h, add 23g of modified polyolefin (Example 12), increase the speed to 350rpm, stir for 2h, add 0.75g of KH-550 treated nano halloysite clay, stir at 450rpm for 40min, increase the speed to 7000rpm, homogenize for 20min, after homogenization is complete, cool to 40℃, filter, and obtain the adhesive solution; S2: Add 100g of composite masterbatch (Example 5) and 1500g of modified high-density polyethylene (Example 2) to a high-speed mixer, mix at 500rpm for 7min, place in a single-screw extruder, feed section 185℃, compression section 200℃, speed 30rpm, cool to 100℃, electron beam energy 2MeV, for 35s to obtain active pipe material; S3: Add 145g of modified fiber carbon (Example 9) to 45g of adhesive solution, heat to 45°C, impregnate for 4s, place on a winding machine, add 100g of active tube, heat to 90°C, hold for 25s, then place in a mold, cool the front end to 30°C, hold for 30s, heat the rear end to 230°C, hold for 2min, the reaction is complete, cool to 25°C, traction force 40N, to obtain composite tube.

[0040] Example 16: A method for preparing a high-strength integrated flexible composite pipe S1: Add 100g of polyamide 6 powder to a mixed solvent of 140mL cresol and 60mL isoacetone, heat to 95℃, stir at 100rpm for 3h, add 27g of modified polyolefin (Example 13), increase the speed to 300rpm, stir for 2.5h, add 0.8g of KH-550 treated nano halloysite clay, stir at 400rpm for 50min, increase the speed to 6000rpm, homogenize for 25min, after homogenization is complete, cool to 35℃, filter, and obtain the adhesive solution; S2: Add 100g of composite masterbatch (Example 6) and 1700g of modified high-density polyethylene (Example 3) to a high-speed mixer, mix at 600rpm for 6min, place in a single-screw extruder, feed section 190℃, compression section 195℃, speed 40rpm, cool to 90℃, electron beam energy 2.5MeV, for 25s to obtain active pipe material; S3: Add 150g of modified fiber carbon (Example 10) to 50g of adhesive solution, heat to 50°C, impregnate for 3s, place on a winding machine, add 100g of active tube, heat to 100°C, hold for 20s, then place in a mold, cool the front end to 40°C, hold for 20s, heat the rear end to 240°C, hold for 1min, the reaction is complete, cool to 30°C, traction force 30N, to obtain composite tube.

[0041] Example 17: A method for preparing a high-strength integrated flexible composite pipe S1: Add 100g of polyamide 6 powder to a mixed solvent of 140mL cresol and 60mL isoacetone, heat to 85℃, stir at 150rpm for 2h, add 23g of modified polyolefin (Example 11), increase the speed to 400rpm, stir for 1.5h, add 0.7g of KH-550 treated nano-haloite clay and 3g of aluminum nitride nanowires, stir at 400rpm for 50min, increase the speed to 6000rpm, homogenize for 25min, after homogenization is complete, cool to 35℃, filter, and obtain the adhesive solution; S2: Add 100g of composite masterbatch (Example 7), 1300g of modified high-density polyethylene (Example 1), 6g of aluminum hypophosphite and 4g of zinc borate flame retardant synergist to a high-speed mixer, mix at 400rpm for 8min, place in a single-screw extruder, feed section 180℃, compression section 205℃, speed 20rpm, cool to 110℃, electron beam energy 1.5MeV, for 45s to obtain active pipe material; S3: Add 140g of modified fiber carbon (Example 8) to 40g of adhesive solution, heat to 40°C, impregnate for 5s, place on a winding machine, add 100g of active tube, heat to 80°C, hold for 30s, then place in a mold, cool the front end to 20°C, hold for 40s, heat the rear end to 220°C, hold for 3min, the reaction is complete, cool to 15°C, traction force 50N, to obtain composite tube.

[0042] Comparative Example 1: Compared with Example 14, this comparative example did not add nano-silica sol during the preparation of modified high-density polyethylene. All other steps and parameters were the same, and will not be repeated here. The final composite pipe was obtained.

[0043] Comparative Example 2: This comparative example differs from Example 14 only in that "modified polyolefin" is replaced with "polyolefin elastomer". All other steps and parameters are the same, and will not be repeated here. The final composite pipe is obtained.

[0044] Comparative Example 3: Compared with Example 14, this comparative example only did not omit the electron beam irradiation surface activation process in the preparation of modified fiber carbon. All other steps and parameters are the same, and will not be repeated here. The final composite tube is obtained.

[0045] Comparative Example 4: Compared with Example 14, this comparative example only did not add composite masterbatch during the preparation of the composite tube. All other steps and parameters were the same, and will not be repeated here. The final composite tube was obtained.

[0046] Performance testing: Explosive pressure test (test results as follows) Figure 1 (as shown) The test was conducted using a microcomputer-controlled pipe pressure burst tester, in accordance with the GB / T 15560-2020 testing standard. 1. Take the composite tubes of Examples 14-17 and Comparative Examples 1-4 respectively, cut the length (5±0.1)×nominal outer diameter, and place the samples at a temperature of 23±2℃ and a relative humidity of 50%±10% for 24 hours. 2. Install the sample on the fixture, inject clean water into the pipe sample, and at the same time open the exhaust valve to expel the air from the pipe. After there are no more air bubbles, close the exhaust valve, start the testing machine, pressurize at a rate of 0.5-1.0 MPa / s, and pressurize until the sample ruptures or the pressure gauge pointer shows its first drop. Record the highest pressure value, which is the burst pressure of the sample. Interlaminar shear strength test (test results as follows) Figure 1-2 (As shown) The universal testing machine was used in accordance with the GB / T 1450.1-2005 testing standard. 1. Take the composite tubes of Examples 14-17 and Comparative Examples 1-4 respectively, cut them into samples of 2.0mm×10.0mm×6.0mm, and place them at a temperature of 23±2℃ and a relative humidity of 50%±10% for 24 hours. 2. Place the specimen on the universal testing machine, adjust the support span Ls = 8mm, start the testing machine, maintain a constant speed of 2 ± 0.5mm / min, and record the maximum load value F. max (Unit: N); 3. Formula for calculating interlaminar shear strength (ILSS): ILSS: Interlaminar shear strength, in megapascals (MPa); F: Maximum load at specimen failure, in newtons (N); b: Specimen width, 10 mm, in millimeters (mm).

[0047] Table 1 Test Results of Examples and Comparative Examples Ring stiffness test (test results as follows) Figure 3 (As shown) The test was conducted using a pipe ring stiffness testing machine, in accordance with the GB / T 9647-2015 testing standard. 1. Cut samples of the composite tubes of Examples 14-17 and Comparative Examples 1-4 into lengths L=150mm, and place them at a temperature of 23±2℃ and a relative humidity of 50%±10% for 24 hours. 2. Place the sample in the sample forming machine and compress it at a constant speed of 5-10 mm / min until the vertical deformation of the inner diameter reaches 30%. Read the force value F (unit N) corresponding to the 3% vertical deformation of the pipe. 3. Formula for calculating ring stiffness (S): F: Force value corresponding to the ΔY deformation, N; ΔY: Deformation amount, 0.03×dm, mm; dm: Average outer diameter of the specimen, mm; L: Length of the specimen, m.

[0048] Heat distortion temperature test (test results as follows) Figure 4 (As shown) According to the GB / T 1634.2-2019 test standard, a heat distortion and Vicat softening point temperature measuring instrument was used. 1. Take the composite tubes of Examples 14-17 and Comparative Examples 1-4 respectively, cut them into samples with a length I=80±2.0mm, a width b=10.0±0.2mm, and a thickness h=4.0±0.2mm, and place them at a temperature of 23±2℃ and a relative humidity of 50%±10% for 88h. 2. Apply a bending normal stress of 0.45 MPa to the specimen and calculate the load force F (N): σ: 0.45MPa, b: specimen width (mm), h: specimen thickness (mm), L: support span, 64mm; 3. Place the sample on the support of the heat distortion instrument, apply the calculated load force F, immerse it in a hot oil bath, and heat it at a rate of 120±10℃ / h. When the deformation reaches 0.34mm, record the oil bath temperature, which is the heat distortion temperature (HDT). Surface resistivity test A high-resistance meter was used in accordance with the GB / T 1410-2006 testing standard. 1. Take the composite tubes of Examples 14-17 and Comparative Examples 1-4 respectively, cut them into 100×100mm pieces, and place them at a temperature of 23±2℃ and a relative humidity of 50%±10% for 24 hours. 2. Place the sample on the ground electrode, test the voltage 500V DC, charge for 60s, start the high resistance meter, and record the surface resistance Rx (Ω). 3. Formula for calculating surface resistivity ρs: Rx: Measured surface resistance value, Ω; D1: Diameter of measuring electrode, mm; D2: Inner diameter of protective electrode, mm; π: Pi; ln: Natural logarithm. Table 2 Test Results of Examples and Comparative Examples Antibacterial performance test (test results as follows) Figure 4 (As shown) According to the GB / T 31402-2023 testing standard, Escherichia coli was used as the test strain; 1. Experimental group: Take the composite tubes of Examples 14-17 and Comparative Examples 1-4 respectively, cut them into 50mm×50mm samples, soak them in 75% ethanol solution, and irradiate them with ultraviolet light for 30 minutes. Control group: 50mm×50mm ordinary high-density polyethylene sheets with smooth surfaces that have not undergone any antibacterial treatment; 2. Inoculate the bacterial strain into the culture medium, incubate at 37℃ and shake at 150 rpm for 24 hours, then dilute with sterile physiological saline to a final concentration of 1.0 × 10⁻⁶. 5 -4.0×10 5 CFU / mL; 3. Add 0.4 mL of Escherichia coli suspension to the sample, cover with a 40×40 mm sterile film, and incubate at 37℃ and 90% relative humidity for 24 h, then count the bacteria. 4. Calculation of antibacterial rate (R): B: Logarithm of the average viable bacterial concentration (lg[CFU / tablet]) after 24 hours of incubation for the negative control sample; C: Logarithm of the average viable bacterial concentration (lg[CFU / tablet]) after 24 hours of incubation for the test sample. Table 3. Antimicrobial test results of the examples and comparative examples Data Analysis: As can be seen from Tables 1-3, the high-strength integrated flexible composite pipe prepared by the present invention has higher burst pressure and interlaminar shear strength, better ring stiffness and heat distortion temperature, lower surface resistivity and significant antibacterial properties. In contrast, Comparative Example 1, due to the lack of introduction of nano-silica sol in the preparation of modified high-density polyethylene, resulted in significant deterioration of its burst pressure, ring stiffness, and heat distortion temperature. This was because the absence of nano-silica as a rigid particle to reinforce and pin the matrix made the material more prone to deformation and damage under internal and external pressure. At the same time, the nanoparticles failed to form a gradient interpenetrating network structure with the polymer matrix, which greatly weakened the stress transfer efficiency and the overall skeletal support. In addition, the thermal stability of the matrix resin decreased due to the lack of nanofiller, ultimately resulting in lower comprehensive mechanical properties and heat resistance of the pipe. In Comparative Example 2, the use of ordinary polyolefin elastomers instead of maleic anhydride-modified polyolefins resulted in a significant reduction in the interlaminar shear strength of the pipe, making it the weakest link in the structure. This is because the substitute lacks highly reactive maleic anhydride functional groups, failing to act as an effective "molecular bridge" between the fiber reinforcement and the polyethylene matrix. Furthermore, its physical compatibility is insufficient to resist interlaminar stress under harsh operating conditions, and it cannot form strong covalent bonds with the polyamide 6 on the fiber surface and the activated matrix. In addition, the chemical inertness of the interface renders the originally designed multiple bonding mechanisms ineffective, ultimately leading to a degradation of interlaminar bonding strength and severely impacting the structural integrity and long-term reliability of the pipe. Comparative Example 3, due to the elimination of the crucial electron beam irradiation surface activation process, resulted in insufficient interfacial reaction between the fiber, adhesive, and inner liner tube, leading to poor interlayer bonding strength and burst pressure. This was because the un-irradiated inner liner tube surface had high chemical inertness and insufficient reactive sites, which greatly limited the depth and efficiency of subsequent interfacial chemical reactions. At the same time, the bonding between the fiber and the matrix after impregnation still mainly relied on physical adsorption and mechanical interlocking. This bonding method is prone to relaxation and failure under long-term dynamic loads. In addition, the entire preparation process lost the key driving force for achieving molecular-level fusion within the "optimal time and space window," ultimately resulting in insufficient interfacial bonding strength and the inability to achieve a truly integrated composite structure. Comparative Example 4, due to the absence of composite masterbatch, resulted in the loss of the two core functions of antistatic and antibacterial properties in the prepared composite tube. At the same time, the mechanical and thermal properties also slightly declined. The direct reason is that the system lacks graphene to build a conductive network, resulting in a high surface resistivity and inability to leak charge. It also loses the photocatalytic activity of nano-titanium dioxide, making it unable to decompose bacterial organic matter. In addition, the composite masterbatch, as a carrier of functional fillers, can ensure the uniform dispersion and synergistic performance of nano-components in the matrix through its core-shell structure. Example 17, through the introduction of aluminum nitride nanowires and flame retardant synergists, along with functional enhancements to the composite masterbatch, resulted in a composite tube exhibiting the best performance among all examples in key properties such as burst pressure, ring stiffness, heat distortion temperature, and antibacterial rate. This is because aluminum nitride nanowires, as novel one-dimensional nanomaterials with high thermal conductivity and high modulus, further enhanced the mechanical properties and thermal stability of the matrix. While the addition of the flame retardant primarily aimed to improve flame retardancy, its good compatibility with the matrix and the synergistic effect of some nanoparticles also positively contributed to the material's rigidity and heat resistance. Furthermore, the optimized composite masterbatch not only retained the conductive and antibacterial functions of graphene and nano-titanium dioxide, but its other additives further improved the overall stability and weather resistance of the system. Ultimately, this example successfully achieved the most balanced and outstanding performance in terms of strength, rigidity, heat resistance, and functionality.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0050] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-strength integrated flexible composite pipe, characterized in that, It is composed of the following components in parts by weight: 140-160 parts of modified high-density polyethylene, 125-145 parts of composite masterbatch, 410-420 parts of modified carbon fiber, 90-110 parts of polyamide 6, 20-30 parts of modified polyolefin, and 5-10 parts of KH-550 treated nano-haloite clay. The modified high-density polyethylene is nano-silica modified high-density polyethylene; The composite masterbatch is composed of low-density polyethylene, graphene, and nano-titanium dioxide. The modified carbon fiber is ε-caprolactam modified carbon fiber; The modified polyolefin is a maleic anhydride-modified polyolefin.

2. The high-strength integrated flexible composite pipe according to claim 1, characterized in that, The preparation steps of the modified high-density polyethylene are as follows: Step A1: Add high-density polyethylene granules, maleic anhydride grafted polyethylene and antioxidant 1010 to a high-speed mixer and mix for 2-4 minutes. Heat to 55-65℃, increase the speed and mix for 6-8 minutes. Once mixing is complete, a mixture is obtained. Step A2: Add KH-560 silane coupling agent and catalyst dibutyltin dilaurate to nano silica sol, heat to 20-30℃, stir for 20-30 minutes, and after stirring is complete, a mixture is obtained; Step A3: Add the mixture and compound to a twin-screw extruder. The feeding section is 150-160℃, the melting section is 175-185℃, the pressure is reduced to -0.08MPa, the mixing reaction section and the discharge section are 190-200℃, and the reaction is carried out for 2-4 minutes. After the reaction is completed, the temperature is reduced to 20-40℃, the particle size is 2-4mm, and the product is dried to obtain modified high-density polyethylene.

3. The high-strength integrated flexible composite pipe according to claim 2, characterized in that, The mass ratio of high-density polyethylene particles, maleic anhydride-grafted polyethylene, and antioxidant 1010 in step A1 is 1:0.18-0.22:0.004-0.

006. The mass ratio of KH-560 silane coupling agent, catalyst, and nano-silica sol in step A2 is 0.065-0.067:0.008-0.012:1; The mass ratio of the mixture to the liquid mixture in step A3 is 1:0.26-0.

27.

4. The high-strength integrated flexible composite pipe according to claim 1, characterized in that, The preparation steps of the composite masterbatch are as follows: Step B1: Add the titanate coupling agent to anhydrous ethanol and stir for 4-6 minutes to obtain a diluted coupling agent solution; Step B2: Add graphene and nano-titanium dioxide to a high-speed shearing machine, mix for 2-4 minutes, add coupling agent dilution, increase the rotation speed, shear for 10-20 minutes, after shearing is complete, dry to obtain nano-composite powder; Step B3: Add low-density polyethylene, nanocomposite powder, and dispersant polyethylene wax to a high-speed mixer, heat to 45-55℃, stir for 2-4 minutes, increase the speed, mix for 8-12 minutes, place in a twin-screw extruder, feed section 120-130℃, melt section 140-150℃, speed 250-350 rpm, reduce pressure to -0.07MPa, mix and discharge sections 160-170℃, after the reaction is complete, cool to 25-35℃, particle size 2-3mm, dry to obtain composite masterbatch.

5. A high-strength integrated flexible composite pipe according to claim 4, characterized in that, The mass ratio of the titanate coupling agent to anhydrous ethanol in step B1 is 1:8-10; The mass ratio of graphene, nano-titanium dioxide, and coupling agent dilution in step B2 is 0.37-0.39:0.48-0.52:1; The mass ratio of low-density polyethylene, nanocomposite powder and dispersant in step B3 is 3.38-3.4:1:0.13-0.

14.

6. The high-strength integrated flexible composite pipe according to claim 1, characterized in that, The preparation steps of the modified carbon fiber are as follows: Step C1: In an air atmosphere, place the carbon fiber in a plasma treatment device with a gas flow rate of 20-40 L / min and a travel speed of 5-15 m / min. Immerse it in a 2.0% wt isocyanate-based silane coupling agent solution as an initiator and treat for 40-60 seconds. After treatment, dry and cure to obtain the treated fiber. Step C2: Under a nitrogen atmosphere, add metallic sodium to the ε-caprolactam monomer, heat to 110-120℃, rotate at 200-300 rpm, stir for 1-3 hours, add the treated fiber, continue for 4-8 minutes, cool to 5-15℃, and obtain modified carbon fiber.

7. A high-strength integrated flexible composite pipe according to claim 6, characterized in that, The mass ratio of carbon fiber to initiator in step C1 is 1:0.009-0.011; The mass ratio of sodium metal, ε-caprolactam monomer, and treated fiber in step C2 is 0.0003-0.0005:0.18-0.22:

1.

8. A high-strength integrated flexible composite pipe according to claim 1, characterized in that, The preparation steps of the modified polyolefin are as follows: Polyolefin particles, maleic anhydride, initiator dicumyl peroxide, and antioxidant 10110 are added to a mixer and mixed for 1-3 minutes. The temperature is raised to 40-50℃, the speed is increased, and the mixture is mixed for 5-8 minutes. Styrene is added and mixed for 2-3 minutes. The mixture is then placed in a twin-screw extruder with the feeding section at 120-130℃, the melting section at 140-160℃, the pressure reduced to -0.08MPa to -0.095MPa, the speed at 150-250rpm, and the reaction and exhaust sections at 165-175℃ for 2-3 minutes. After the reaction is complete, the mixture is cooled to 20-30℃, the particle size is 2-3mm, and the mixture is dried to obtain modified polyolefin.

9. A high-strength integrated flexible composite pipe according to claim 8, characterized in that, The mass ratio of the polyolefin particles, maleic anhydride, initiator, antioxidant and styrene is 1:0.015-0.03:0.001-0.003:0.001-0.003:0.01-0.

03.

10. A method for preparing a high-strength integrated flexible composite tube according to any one of claims 1-9, characterized in that, The preparation method is as follows: Step S1: Add polyamide 6 powder to a mixed solvent of cresol and isopropanone, heat to 85-95℃, stir for 2-3 hours, add modified polyolefin, increase the speed, stir for 1.5-2.5 hours, add KH-550 treated nano halloysite clay, stir at 500 rpm for 30-50 minutes, increase the speed, homogenize for 15-25 minutes, after homogenization is complete, cool to 35-45℃, filter, and obtain the adhesive solution; Step S2: Add the composite masterbatch and modified high-density polyethylene to a high-speed mixer and mix for 6-8 minutes. Then place it in a single-screw extruder with a feeding section of 180-190°C and a compression section of 195-205°C. Cool down to 90-110°C and use an electron beam energy of 1.5-2.5 MeV for 25-45 seconds to obtain the active pipe. Step S3: Add modified fiber carbon to the adhesive solution, heat to 40-50℃, impregnate for 3-5 seconds, place on a winding machine, add active tube, heat to 80-100℃, hold for 20-30 seconds, then place in a mold, cool the front end to 20-40℃, hold for 20-40 seconds, heat the rear end to 220-240℃, hold for 1-3 minutes, the reaction is complete, cool to 15-30℃, traction force 30-50N, to obtain composite tube; In step S1, the mass ratio of polyamide 6, modified polyolefin, and KH-550 treated nano-haloite clay is 1:0.23-0.27:0.007-0.

008. In step S1, the volume ratio of cresol to isopropanone in the mixed solvent is 7:3; The mass ratio of the composite masterbatch to the modified high-density polyethylene in step S2 is 1:13-17; In step S3, the mass ratio of modified carbon fiber, adhesive, and active tubing is 1.4-1.5:0.4-0.5:1.

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