EPDM (Ethylene-Propylene-Diene Monomer)-hydrogenated butyronitrile composite rubber pipeline as well as preparation method and application thereof

Abstract

The invention discloses an ethylene propylene diene monomer-hydrogenated butyronitrile composite rubber pipeline and a preparation method and application thereof, and belongs to the technical field of special pipeline materials.Anti-radiation filler is added into ethylene propylene diene monomer, and neutron capture and radiation shielding are achieved; hydrogenated butadiene-acrylonitrile rubber is used as an inner layer pipeline to bear fluid pressure impact and dynamically seal, and a pipeline of an integrated structure is formed between an inner layer rubber material and an outer layer rubber material through a peroxide vulcanization system and a maleic anhydride grafted ethylene propylene diene monomer compatibilizer under the co-vulcanization effect. According to the invention, the radiation-proof property of the outer layer rubber material and the high-strength and pressure-resistant property of the inner layer rubber material are complementary to each other, and the integrated combination of the three-layer structure is guaranteed through co-extrusion and an interface co-vulcanization cross-linked network, so that radiation shielding, damping energy consumption, corrosion resistance and high-pressure sealing are synchronously realized; the method is suitable for extreme working conditions such as nuclear power station radioactive drainage, cooling circulation pipe and chemical high-pressure slurry conveying.

Description

Technical Field

[0001] This invention relates to the field of special pipe materials technology, specifically to a ternary ethylene propylene diene monomer (EPDM)-hydrogenated nitrile butadiene rubber composite pipe, its preparation method, and its application. Background Technology

[0002] Nuclear power plant pipeline seawater discharge systems are exposed to extreme multi-factor coupled environments for a long time, including strong radiation fields such as gamma rays and neutron flux; highly corrosive seawater media such as chloride ions, dissolved oxygen, and microorganisms; severe dynamic loads such as water hammer and fluid pulsation; and various influences such as high temperature and high pressure cyclic conditions. Currently, nuclear power plant radioactive wastewater pipes are generally made of single materials such as ethylene propylene diene monomer (EPDM), hydrogenated nitrile butadiene rubber (HNBR), and fluororubber (FKM). These mainstream materials have significant shortcomings in meeting the aforementioned comprehensive requirements. While EPDM possesses excellent radiation resistance and seawater corrosion resistance, its tear strength and dynamic damping performance are significantly insufficient, making it prone to permanent deformation or seal failure under high-frequency water hammer impact. HNBR, while exhibiting excellent impact resistance and dynamic sealing reliability, experiences molecular chain breakage when the cumulative radiation dose exceeds the material's tolerance, leading to a decrease in elongation and failing to meet the long-term design life requirements of nuclear power plant pipes. FKM, while possessing outstanding chemical corrosion resistance, offers no advantage in radiation resistance or impact resistance and is also very expensive.

[0003] To balance various performance aspects, existing technologies have explored the use of EPDM blends with HNBR or simple laminated composite structures. However, due to the non-polar nature of EPDM and the polar nature of HNBR in the blends, thermodynamic incompatibility exists, leading to stress concentration weak points at the microscopic phase separation interface. Under irradiation, the phase interface preferentially cracks, and seawater infiltration along the interface accelerates corrosion. These defects expose nuclear power plant wastewater pipes to the risk of radioactive leakage, and the replacement frequency is more than three times higher than the design value. Summary of the Invention

[0004] This invention provides a EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe, its preparation method, and its application. It effectively solves the technical problem that the interface of existing composite materials prepared by blending EPDM rubber and hydrogenated nitrile butadiene rubber is easily penetrated by seawater, leading to cracking and corrosion, thus posing a risk of radioactive leakage to nuclear power plant wastewater pipes. Simultaneously, it provides a composite rubber material that combines the radiation resistance of EPDM rubber with the dynamic performance of hydrogenated nitrile butadiene rubber, and possesses a radiation-resistant interface, thereby meeting the stringent requirements of nuclear power facilities for safety, long service life, and adaptability to extreme environments.

[0005] The first objective of this invention is to provide a method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe, comprising the following steps: The mixture containing EPDM rubber and radiation-resistant filler is first mixed at 120℃~160℃, then cooled to ≤110℃, and a first peroxide vulcanization system and a first crosslinking agent are added for a second mixing to obtain the outer layer rubber compound.

[0006] The premix formed from hydrogenated nitrile rubber is subjected to intensive mixing at 120℃~160℃, then cooled to ≤110℃, and a second peroxide vulcanization system and a second crosslinking agent are added for a third mixing to obtain the inner layer rubber compound.

[0007] Both the first peroxide sulfidation system and the second peroxide sulfidation system are dicumyl peroxide or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0008] The outer and inner rubber layers are co-extruded in layers, forming an interfacial bonding zone between them. A compatibilizer and / or adhesive are injected into this interfacial bonding zone to obtain a composite structure pipe. The composite structure pipe is then co-vulcanized at 8MPa–20MPa and 150℃–170℃ to obtain a EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe. The compatibilizer is maleic anhydride-grafted EPDM rubber; the adhesive is boron-modified cyanoacrylate, a special silane coupling agent, a phenolic-epoxy resin system, or a radiation-resistant modified chloroprene rubber / phenolic resin mixed adhesive.

[0009] The hydrogenated nitrile butadiene rubber used in this invention was purchased from Lanzhou Petrochemical, China National Petroleum Corporation (CNPC), type NBR3305; the ethylene propylene diene monomer (EPDM) rubber was purchased from Mitsui Elastomers Co., Ltd., Sinopec, type 3092E; the maleic anhydride-grafted EPDM rubber used is described in existing literature: Study on AES / PC blends compatibilized with maleic anhydride-grafted EPDM rubber copolymers [J]. China Plastics, 2016, 30(05): 50-54. The boron-modified cyanoacrylate in the adhesive was purchased from Jiangsu Yangnong Chemical Co., Ltd., the special silane coupling agent was purchased from Chenguang New Materials, and the phenolic-epoxy resin system and the radiation-resistant modified chloroprene rubber / phenolic resin mixed adhesive were both purchased from Shanghai Huayi Resin Co., Ltd. The dicumyl peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane were both purchased from Jiangsu Daoming Chemical Co., Ltd.

[0010] In a preferred embodiment, the injection temperature is 80℃~100℃. To further improve interfacial adhesion, the injection of compatibilizer and / or adhesive into the interfacial bonding area needs to be carried out at a temperature of 80℃~100℃; otherwise, it will affect the bonding strength of the interfacial bonding area of ​​the EPDM-hydrogenated nitrile butadiene rubber composite material, thus leading to easy cracking.

[0011] In a preferred embodiment, when the adhesive is injected, the mass ratio of the EPDM rubber, hydrogenated nitrile rubber, and adhesive is 60–100:100–60:1–5; or, when the compatibilizer is injected, the mass ratio of the EPDM rubber to the compatibilizer is 100:1–3; or, when the compatibilizer and adhesive are injected, the mass ratio of the EPDM rubber, hydrogenated nitrile rubber, compatibilizer, and adhesive is 60–100:100–60:1–3:1–5. To ensure a stable bond strength between the inner and outer rubber layers, the amounts of EPDM rubber, hydrogenated nitrile butadiene rubber, compatibilizer, and adhesive are all limited. An imbalance in the amounts of the two main raw materials, EPDM rubber and hydrogenated nitrile butadiene rubber, will affect the bond strength of the interfacial bonding zone, impacting the corrosion and radiation resistance of both the inner and outer pipes. The amounts of compatibilizer and adhesive also negatively affect the bond strength of the interfacial bonding zone; insufficient amounts will not achieve the required bond strength, leading to cracking, while excessive amounts will also reduce the bond strength.

[0012] In a preferred embodiment, the mass ratio of EPDM rubber to hydrogenated nitrile butadiene rubber is 1-2:2-1; the mass ratio of EPDM rubber to radiation-shielding filler is 2:0.5-1.4; the mass ratio of EPDM rubber, the first peroxide vulcanization system, and the first co-crosslinking agent is 100:0.1-5:0.1-5; and the mass ratio of hydrogenated nitrile butadiene rubber, the second peroxide vulcanization system, and the second co-crosslinking agent is 100:0.1-5:0.1-5. To impart radiation-shielding properties to the outer rubber layer and increase the bonding strength of the interfacial bonding zone, insufficient radiation-shielding filler will not provide radiation protection, while excessive filler will affect the bonding strength of the outer pipe.

[0013] In a preferred embodiment, the radiation-shielding filler is selected from at least one of lead oxide, lead borate, boron carbide, boron nitride, lead tungstate, boron carbide / barium sulfate composite, gadolinium oxide, samarium oxide, and montmorillonite. All of the above radiation-shielding fillers can impart radiation-shielding properties to EPDM-hydrogenated nitrile butadiene rubber composite pipes. In subsequent embodiments of the present invention, barium sulfate / boron composite is preferably used as the radiation-shielding filler for performance description, wherein the mass ratio of boron carbide to barium sulfate in the boron carbide / barium sulfate composite is 1:1.

[0014] In a preferred embodiment, the hydrogenated nitrile butadiene rubber has an acrylonitrile content of 30%–50% and a hydrogenation degree ≥90%; the ethylene content of the EPDM rubber is 50%–70%, and the third monomer of the EPDM rubber is ethylene-ide-norbornene. To achieve a stable co-curing interface, the third monomer of the EPDM rubber, ethylene-ide-norbornene (ENB), as a diene third monomer, has extremely high reactivity of the double bonds on its side chain, far exceeding that of other types of third monomers. This significantly increases the vulcanization rate of EPDM, matching it with the vulcanization rate of HNBR, thereby achieving a stable co-curing interface.

[0015] Hydrogenated nitrile butadiene rubber (HNBR) is the direct contributor to the impact resistance and sealing function of pipelines. Higher acrylonitrile content improves oil and corrosion resistance, but reduces low-temperature elasticity. Therefore, an acrylonitrile content of 30%–50% balances the requirements for anti-swelling capacity and good elasticity in seawater environments. A hydrogenation degree of ≥90% (carbon-carbon double bonds in the main chain of hydrogenated saturated nitrile butadiene rubber) significantly improves its heat resistance, oxidation resistance, and ozone resistance. High hydrogenation is crucial for ensuring HNBR's long-term service life without aging in warm water environments. Reinforcing fillers such as carbon black or silica can significantly improve HNBR's tensile stress, tear strength, and abrasion resistance, which is essential for withstanding fluid erosion and potential solid particle wear. Appropriate plasticizers help improve the processing flowability of the rubber compound and optimize low-temperature performance. Peroxide vulcanization systems form CC crosslinks, with bond energies higher than the SS or CS bonds in sulfur vulcanization systems, resulting in superior heat resistance and compression set, and good compatibility with EPDM outer layers.

[0016] The outer layer of EPDM protects against external radiation and harsh environments. Ethylene content primarily affects crystallinity; a moderate content achieves a good balance between strength, elasticity, and processability. Higher ethylene content provides higher strength, but low-temperature performance decreases. The third monomer, ethylene-1,3-norbornene (ENB), provides the vulcanization active sites. Its double bonds on the side chain have extremely high reactivity, significantly increasing the vulcanization rate and matching it with the vulcanization rate of HNBR, which is key to achieving a stable co-vulcanization interface. Radiation-resistant filler: This is the core of the radiation resistance function. The filler reduces radiation damage to the polymer matrix by absorbing and scattering high-energy rays, such as gamma rays and neutrons.

[0017] In a preferred embodiment, the mixture further includes a first reinforcing filler, and after the first mixing is completed, the temperature is lowered to 120°C, and antioxidants and anti-ozone agents are added and mixed again; the premix further includes a second reinforcing filler, plasticizer, antioxidant and anti-ozone agent.

[0018] In a preferred embodiment, both the first and second co-crosslinking agents are triallyl isocyanurate or trimethylolpropane trimethacrylate, the first reinforcing filler is N550 carbon black, N660 carbon black, or silica, the second reinforcing filler is N330 carbon black, N550 carbon black, or silica, the plasticizer is polyester plasticizer TP-95, the antioxidant is ethoxyquinoline, and the anti-ozone agent is p-phenylenediamine. Triallyl isocyanurate is denoted as TAIC, and trimethylolpropane trimethacrylate is denoted as TMPTMA.

[0019] The triallyl isocyanurate was purchased from Hubei Shixing Chemical Co., Ltd.; the trimethylolpropane trimethacrylate was purchased from Hanfuxinyuan Technology Co., Ltd.; the N550 carbon black, N660 carbon black, and N330 carbon black were all purchased from Qingdao Sailulong (Germany); the polyester plasticizer TP-95 was purchased from Hubei Kewode Chemical Co., Ltd.; the antioxidant ethoxyquinoline was purchased from Shanghai Yuanye Biotechnology Co., Ltd.; the ozone-resistant agent p-phenylenediamine used in this invention is Nanjing Chemical Plant's antioxidant 4020.

[0020] The second objective of this invention is to provide a EPDM-hydrogenated nitrile butadiene composite rubber pipe, which is prepared by any of the above-described preparation methods. The EPDM-hydrogenated nitrile butadiene composite rubber pipe is an integrated composite structure pipe formed by an outer pipe, an interface bonding layer, and an inner pipe, wherein the thickness ratio of the outer pipe, the interface bonding layer, and the inner pipe is 5:0.1:5.

[0021] The third objective of this invention is to provide an application of the above-mentioned EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe in a nuclear power plant radioactive wastewater discharge system.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing an EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe. The method involves forming an outer layer rubber compound comprising EPDM rubber, radiation-shielding filler, and a first peroxide vulcanization system as active ingredients, and forming an inner layer rubber compound comprising hydrogenated nitrile butadiene rubber and a second peroxide vulcanization system. The outer and inner layers are co-extruded in layers, and a compatibilizer and / or adhesive are added to the interfacial bonding area formed between the outer and inner layers to obtain a composite structure pipe. The composite structure pipe is then co-vulcanized to obtain the EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe.

[0023] This invention incorporates radiation-shielding fillers into EPDM rubber to achieve neutron capture and radiation shielding. Hydrogenated nitrile butadiene rubber serves as the inner pipe layer to withstand fluid pressure impacts and provide dynamic sealing. An integrated pipe structure is formed between the inner and outer rubber layers through a first peroxide vulcanization system, a second peroxide vulcanization system, a compatibilizer, and / or an adhesive, under co-vulcanization. This invention achieves radiation shielding, energy damping, corrosion resistance, and high-pressure sealing simultaneously through the complementary material synergy of the radiation-shielding outer layer and the high-strength, pressure-resistant inner layer. Furthermore, the co-extrusion and interfacial co-vulcanization crosslinking network ensures the integrated bonding of the three layers. This makes it suitable for extreme conditions such as radioactive wastewater discharge from nuclear power plants, cooling circulation pipes, and high-pressure slurry transportation in chemical plants. Attached Figure Description

[0024] Figure 1 This is a three-dimensional schematic diagram of the EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe of the present invention, wherein 1 is the outer rubber layer formed mainly of EPDM rubber, 2 is the interface bonding area, and 3 is the inner rubber layer formed mainly of hydrogenated nitrile butadiene rubber.

[0025] Figure 2 The image shows the SEM image of the interface microstructure of the EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe of the present invention. In the image, 1 is the outer rubber layer formed mainly by EPDM rubber, 2 is the interface bonding area, and 3 is the inner rubber layer formed mainly by hydrogenated nitrile butadiene rubber. Detailed Implementation

[0026] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0027] The prior art mentioned in the background of this invention uses EPDM and HNBR blends or simple laminated composite structures. Because EPDM is non-polar while HNBR is polar, thermodynamic incompatibility exists, leading to stress concentration weak points at the microscopic phase separation interface. Under irradiation, the phase interface cracks preferentially, and seawater infiltration along the phase boundary accelerates corrosion. These defects expose nuclear power plant wastewater pipes to the risk of radioactive leakage, and the replacement frequency is more than three times higher than the design value. Based on the above technical problems, this invention provides a ternary ethylene propylene diene monomer (EPDM)-hydrogenated nitrile butadiene rubber (HNBR) composite rubber pipe, its preparation method, and its application.

[0028] The technical solution of the present invention will be analyzed and described in detail below.

[0029] This invention first provides a method for preparing EPDM-hydrogenated nitrile butadiene rubber composite pipes, comprising the following steps: The mixture containing EPDM rubber and radiation-resistant filler is first mixed at 120℃~160℃, then cooled to ≤110℃, and a first peroxide vulcanization system and a first crosslinking agent are added for a second mixing to obtain the outer layer rubber compound.

[0030] The premix formed from hydrogenated nitrile rubber is subjected to intensive mixing at 120℃~160℃, then cooled to ≤110℃, and a second peroxide vulcanization system and a second crosslinking agent are added for a third mixing to obtain the inner layer rubber compound.

[0031] Both the first peroxide sulfidation system and the second peroxide sulfidation system are dicumyl peroxide, denoted as DCP, or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, denoted as BIPB.

[0032] The outer and inner rubber layers are co-extruded in layers, forming an interfacial bonding region between them. A compatibilizer and / or adhesive are injected into this interfacial bonding region to obtain a composite structure pipe. The composite structure pipe is then co-vulcanized at 8MPa–20MPa and 150℃–170℃ to obtain a EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe. Figure 1 and Figure 2 As shown.

[0033] The compatibilizer is maleic anhydride-grafted EPDM-g-MAH; the adhesive is boron-modified cyanoacrylate, special silane coupling agent, phenolic-epoxy resin system, or radiation-resistant modified chloroprene rubber / phenolic resin mixed adhesive.

[0034] In the above technical solution, radiation-shielding fillers are added to EPDM rubber to achieve neutron capture and radiation shielding. Hydrogenated nitrile butadiene rubber is used as the inner layer of the pipe to withstand fluid pressure impact and provide dynamic sealing. A peroxide vulcanization system and maleic anhydride-grafted EPDM compatibilizer are used between the inner and outer rubber layers to form an integrated pipe structure under co-vulcanization. This invention achieves radiation shielding, energy damping, corrosion resistance, and high-pressure sealing simultaneously through the complementary material synergy of the radiation-shielding outer layer and the high-strength, pressure-resistant inner layer, and further ensures the integrated combination of the three layers through co-extrusion and interfacial co-vulcanization crosslinking network.

[0035] The strength of the interfacial bond directly determines the long-term reliability of the composite pipe. Under the action of the peroxide vulcanizing agent and the maleic anhydride-grafted EPDM-g-MAH compatibilizer, the co-vulcanized crosslinking network allows EPDM and HNBR to form a chemical co-crosslink at the interface. The polar groups of maleic anhydride (MAH) interact with the polar groups of HNBR, improving the compatibility of the two previously incompatible rubbers and resulting in an interfacial strength far exceeding that of physical adhesion. When the vulcanization rates of EPDM and HNBR are difficult to match, boron-modified cyanoacrylate or phenolic-epoxy resin system radiation-resistant adhesives are selected. These adhesives must remain stable under irradiation, without becoming embrittled or decomposing.

[0036] The mixing process temperature is controlled in stages: a high-temperature stage (120℃~160℃) ensures that the raw rubber is fully plasticized and the filler is evenly dispersed; a medium-temperature stage (~120℃) avoids excessive temperature that could cause decomposition and failure; and a low-temperature stage (≤110℃) prevents the peroxide vulcanizing agent from decomposing prematurely and scorching, ensuring the safety of subsequent processing.

[0037] In co-extrusion molding, since EPDM viscosity is typically higher than HNBR, extending the EPDM runner length increases its flow resistance, thereby ensuring that the two melt streams have similar pressure and flow velocity at the confluence point. When the EPDM runner length is 1.5–2.5:1 with the HNBR runner length, i.e., L... EPDM :L HNBR A ratio of 1.5 to 2.5:1 ensures a stable and smooth interface, preventing interlayer flow. Since the outer and inner layers have different flow rates, controlling the flow channel length effectively manages the risk of turbulent flow, achieving stable extrusion, ensuring interface quality, and maintaining the integrity of the layered structure. DDR is the ratio of the die cross-sectional area to the final product cross-sectional area, i.e., the draw ratio or traction ratio. Moderate draw, i.e., DDR > 1, is beneficial for molecular chain orientation, improving axial strength, eliminating the die expansion effect, and making product dimensions more accurate. Excessive DDR may lead to cracking. Vulcanization conditions during vulcanization molding, i.e., 150℃ to 170℃ and 8MPa to 20MPa, ensure complete decomposition of peroxides, thorough cross-linking reaction, and optimal physical and mechanical properties. High pressure suppresses bubbles that may be generated during vulcanization, such as moisture vaporization or residual air, improving density and ensuring tight adhesion between layers.

[0038] The technical effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0039] Example 1 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0040] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0041] S2, the outer layer rubber compound and the inner layer rubber compound are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber compound to the channel length of the inner layer rubber compound is 1.5:1. The melt temperature of the outer layer rubber compound is controlled at 130°C and the melt temperature of the inner layer rubber compound is controlled at 110°C. The inner and outer layers rubber compounds are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber into the interface bonding area formed by the outer and inner layers rubber compounds at 90°C to obtain the primary channel.

[0042] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0043] Example 2 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile butadiene rubber with an acrylonitrile content of 38% and a hydrogenation degree of 92%, 40 parts of N550 carbon black, 8 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0044] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0045] S2, the outer layer rubber and the inner layer rubber are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber to the channel length of the inner layer rubber is 1.5:1. The melt temperature of the outer layer rubber is controlled at 130°C and the melt temperature of the inner layer rubber is controlled at 110°C. The inner and outer layers rubber are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of boron-modified cyanoacrylate into the interface bonding area formed by the outer layer rubber and the inner layer rubber at 90°C to obtain the primary channel.

[0046] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0047] Example 3 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0048] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0049] S2, the outer layer rubber and the inner layer rubber are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber to the channel length of the inner layer rubber is 1.5:1. The melt temperature of the outer layer rubber is controlled at 130°C and the melt temperature of the inner layer rubber is controlled at 110°C. The inner and outer layers rubber are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber and 2 parts of boron-modified cyanoacrylate into the interface bonding area formed by the outer and inner layers rubber at 90°C to obtain the primary channel.

[0050] S3. The primary pipe is co-vulcanized at 15MPa and 165℃ for 30 minutes to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0051] Example 4 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0052] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 40 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0053] S2, the outer layer rubber compound and the inner layer rubber compound are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber compound to the channel length of the inner layer rubber compound is 1.5:1. The melt temperature of the outer layer rubber compound is controlled at 130°C and the melt temperature of the inner layer rubber compound is controlled at 110°C. The inner and outer layers rubber compounds are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber into the interface bonding area formed by the outer and inner layers rubber compounds at 90°C to obtain the primary channel.

[0054] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0055] Example 5 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile butadiene rubber with an acrylonitrile content of 50% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0056] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0057] S2, the outer layer rubber compound and the inner layer rubber compound are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber compound to the channel length of the inner layer rubber compound is 1.5:1. The melt temperature of the outer layer rubber compound is controlled at 130°C and the melt temperature of the inner layer rubber compound is controlled at 110°C. The inner and outer layers rubber compounds are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber into the interface bonding area formed by the outer and inner layers rubber compounds at 90°C to obtain the primary channel.

[0058] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0059] Example 6 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0060] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 50% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0061] S2, the outer layer rubber compound and the inner layer rubber compound are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber compound to the channel length of the inner layer rubber compound is 1.5:1. The melt temperature of the outer layer rubber compound is controlled at 130°C and the melt temperature of the inner layer rubber compound is controlled at 110°C. The inner and outer layers rubber compounds are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber into the interface bonding area formed by the outer and inner layers rubber compounds at 90°C to obtain the primary channel.

[0062] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0063] Example 7 A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 40 parts of N550 carbon black, 5 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0064] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 50 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0065] S2, the outer layer rubber compound and the inner layer rubber compound are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber compound to the channel length of the inner layer rubber compound is 1.5:1. The melt temperature of the outer layer rubber compound is controlled at 130°C and the melt temperature of the inner layer rubber compound is controlled at 110°C. The inner and outer layers rubber compounds are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of maleic anhydride-grafted EPDM rubber into the interface bonding area formed by the outer and inner layers rubber compounds at 90°C to obtain the primary channel.

[0066] S3. The primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 7mm, an outer layer thickness of 3mm, and a middle layer thickness of 0.1mm.

[0067] To further illustrate the technical effects of the present invention, comparative examples are also provided, as follows: Comparative Example 1 The difference compared to Example 1 is that EPDM rubber and hydrogenated nitrile rubber are blended.

[0068] A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. 100 parts of hydrogenated nitrile butadiene rubber with an acrylonitrile content of 42% and a hydrogenation degree of 95%, 100 parts of ethylene propylene diene monomer (EPDM) rubber with an ethylene content of 65% and ethylene-based norbornene as the third monomer, 70 parts of N550 carbon black, 10 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent are mixed at 120°C for 10 minutes, then cooled to 100°C, and 6 parts of DCP and 4 parts of TAIC are added and mixed for 6 minutes to obtain a mixed rubber compound.

[0069] S2, the mixed rubber compound is extruded at a melt temperature of 110°C and a die pressure of 14 bar to obtain a primary pipe.

[0070] S3, the primary pipe is co-vulcanized at 15MPa and 165℃ for 30min to obtain a EPDM-hydrogenated nitrile butadiene composite rubber pipe.

[0071] Comparative Example 2 The difference compared to Example 1 is that only EPDM rubber is used to prepare the pipe.

[0072] A method for preparing an EPDM rubber pipe includes the following steps: S1. Mix 100 parts of EPDM rubber with 65% ethylene content and ethyleneide norbornene as the third monomer, and 30 parts of N660 carbon black at 150°C for 8 minutes. Add 1.5 parts of antioxidant and 1 part of anti-ozone agent and mix at 120°C for 2 minutes. Then cool down to 110°C and add 2.5 parts of DCP and 1.5 parts of TAIC and mix for 5 minutes to obtain EPDM rubber compound.

[0073] S2, the EPDM rubber compound is extruded at a melt temperature of 110°C and a die pressure of 14 bar to obtain a primary pipe.

[0074] S3. The primary pipe is subjected to co-vulcanization treatment at atmospheric pressure and 165°C for 30 minutes to obtain EPDM rubber pipe.

[0075] Comparative Example 3 The difference compared to Example 1 is that the amount of radiation-resistant filler - boron carbide / barium sulfate composite - is increased.

[0076] A method for preparing a EPDM-hydrogenated nitrile butadiene rubber composite pipe includes the following steps: S1. Mix 100 parts of hydrogenated nitrile butadiene rubber with an acrylonitrile content of 30% and a hydrogenation degree of 92%, 40 parts of N550 carbon black, 8 parts of polyester plasticizer TP-95, 1.5 parts of antioxidant, and 1 part of anti-ozone agent at 120°C for 10 minutes, then cool to 100°C, add 3 parts of DCP and 2 parts of TAIC, and mix for 6 minutes to obtain the inner layer rubber compound.

[0077] 100 parts of ethylene propylene diene monomer (EPDM) rubber with 65% ethylene content and ethylene-ide norbornene as the third monomer, 80 parts of boron carbide / barium sulfate composite, and 30 parts of N660 carbon black were mixed at 150°C for 8 minutes. Then, 1.5 parts of antioxidant and 1 part of anti-ozone agent were added and mixed at 120°C for 2 minutes. The mixture was then cooled to 110°C and 2.5 parts of DCP and 1.5 parts of TAIC were added and mixed for 5 minutes to obtain the outer layer compound.

[0078] S2, the outer layer rubber and the inner layer rubber are fed into a dual-channel co-extrusion die respectively. The ratio of the channel length of the outer layer rubber to the channel length of the inner layer rubber is 1.5:1. The melt temperature of the outer layer rubber is controlled at 130°C and the melt temperature of the inner layer rubber is controlled at 110°C. The inner and outer layers rubber are extruded simultaneously with a die pressure of 14 bar. The draw ratio DDR=3 and the traction speed=1.5 times the extrusion rate are controlled. At the same time, an adhesive injection system is used to inject 2 parts of boron-modified cyanoacrylate into the interface bonding area formed by the outer layer rubber and the inner layer rubber at 90°C to obtain the primary channel.

[0079] S3, the primary pipe is co-vulcanized at 15MPa and 160℃ for 30min to form an integrated interface, resulting in a EPDM-hydrogenated nitrile butadiene composite rubber pipe with an inner layer thickness of 5mm, an outer layer thickness of 5mm, and a middle layer thickness of 0.1mm.

[0080] The performance of the EPDM-hydrogenated nitrile butadiene rubber composite rubber pipes prepared in Examples 1 to 7, Comparative Examples 1 and 3, and the EPDM rubber pipe prepared in Comparative Example 2 were tested, and the results are as follows.

[0081] Table 1. Performance Comparison of EPDM-Hydrogenated Nitrile Butadiene Rubber Composite Pipes of the Embodiments of the Present Invention Table 2. Performance comparison chart of the pipes in the comparative examples of the present invention. As shown in Tables 1 and 2, the radiation resistance dose-to-fracture of the pipes prepared in Examples 1 to 7 is all above 2.0 MGy, with Comparative Example 3 reaching 3.0 MGy, Example 3 at 2.7 MGy, and Example 2 at 2.5 MGy, significantly better than Comparative Example 1's 0.91 MGy and Comparative Example 2's 1.52 MGy. All examples added radiation-shielding filler to the outer layer, namely a boron carbide / barium sulfate composite, where boron carbide absorbs neutrons and barium sulfate shields gamma rays, synergistically improving radiation resistance. Comparative Example 3 used 80 parts of radiation-shielding filler in its outer layer rubber compound, resulting in stronger radiation resistance. In contrast, Comparative Example 1 was merely a simple blend, and Comparative Example 2 was a pure EPDM rubber pipe; neither adequately considered the rational addition and formulation combination of radiation-shielding filler, leading to poorer radiation resistance.

[0082] The dynamic sealing performance of Examples 1 to 3 and Comparative Example 3 was leak-free after 450,000 to 560,000 water hammer impacts, which is much higher than the failure of Comparative Example 1 after 250,000 impacts and the micro-leakage of Comparative Example 2 after 100,000 impacts. This is due to the integrated interface formed by the co-vulcanization and cross-linking of the inner and outer rubber materials and the precise injection of the adhesive in the examples. The layered structure design of the inner hydrogenated nitrile rubber is oil-resistant and the outer EPDM rubber is weather-resistant, which work together to resist water hammer impacts and enhance the sealing performance and impact resistance of the material under dynamic conditions.

[0083] The average weight gain rate of the pipes prepared in the examples was lower than that of the comparative examples. The lower the weight gain rate, the better the corrosion resistance. The weight gain rate of Example 1 was 2.25%, which was the best. Examples 1 and 3 had a hydrogenation degree of 95%, which provided stronger shielding ability against seawater penetration, with a weight gain rate of only 2.25% to 2.51%. Radiation-shielding fillers enhance the barrier effect, but excessive fillers, such as the 80 parts of radiation-shielding filler-boron carbide / barium sulfate composite in Comparative Example 3, can introduce interface defects, leading to an increase in corrosion weight gain, reaching 4.58%.

[0084] Example 3 exhibited the highest tensile strength at 26 MPa, compared to 23.5 MPa for Example 1, 22 MPa for Example 2, and 20 MPa for Comparative Example 3, all exceeding the 19 MPa of Comparative Example 1 and 15.2 MPa of Comparative Example 2. This is related to the degree of crosslinking of the materials, the reinforcing effect of the fillers, and the interfacial bonding strength. The reasonable mixing process and vulcanization conditions in the examples resulted in a good co-vulcanized crosslinked network structure at the interfacial bonding zone between the inner and outer rubber layers. Simultaneously, fillers such as carbon black played a reinforcing role, improving the tensile strength. In Example 3, the inner hydrogenated nitrile rubber contained 42% acrylonitrile and had a hydrogenation degree of 95%, indicating a superior formulation and optimal tensile strength.

[0085] Example 3 exhibited the highest interfacial bonding strength at 6.3 kN / m, compared to 5.2 kN / m in Example 1, 4.8 kN / m in Example 2, and 3.8 kN / m in Comparative Example 3. In Example 3, maleic anhydride-grafted EPDM rubber compatibilizer and boron-modified cyanoacrylate adhesive were precisely injected into the interfacial region during co-extrusion. The synergistic effect of the two adhesives significantly improved the interfacial bonding strength. In contrast, the other examples used only one adhesive, resulting in relatively lower interfacial bonding strengths. Comparative Examples 1 and 2 did not undergo any special interfacial treatment, and their interfacial bonding strength data are not listed. However, considering the overall performance, the poor interfacial bonding effect negatively impacted the overall performance.

[0086] The comparison between Example 4 and Example 1 verifies the influence of the amount of radiation shielding filler on the overall performance of the pipeline: when the filler amount is reduced from 50 parts to 40 parts, a decrease of 20%, the radiation resistance performance decreases from 2.0 MGy to 1.8 MGy, a decrease of 10%. This indicates that the boron carbide / barium sulfate composite directly contributes to the radiation shielding effect. Although the performance is slightly lower than that of Example 1, it verifies the necessity of the lower limit of the mass ratio of EPDM rubber to radiation shielding filler in the invention, which is 2:0.5-1.5, i.e., the filler amount ≥50 parts. Below this value, although the performance is usable, it is close to the critical point, and long-term reliability may be affected.

[0087] Example 5 verified the necessity of an upper limit on acrylonitrile content. A 50% acrylonitrile content optimizes seawater corrosion resistance, but compared to Example 1 and Comparative Example 3, the number of water hammer impacts decreases to 480,000. This is because the high acrylonitrile content reduces the low-temperature elasticity and flexibility of HNBR, thus decreasing its ability to resist dynamic impacts. The tensile strength increased from 23.1 MPa to 24.5 MPa. The high acrylonitrile content improved the material's strength, but at the cost of elasticity.

[0088] Example 6 validates the necessity of a lower limit for ethylene content. A 50% ethylene content reduces the tensile strength of EPDM from 23.1 MPa in Example 1 to 18.3 MPa. This is because the low ethylene content decreases the crystallinity and strength of the EPDM. The low ethylene content affects the rheological properties of the outer layer material, leading to a decrease in the interfacial bonding quality with the inner HNBR layer. The interfacial bonding strength decreases from 5.2 kN / m to 4.5 kN / m. Simultaneously, the low ethylene content reduces the crosslinking density of the EPDM, decreasing the material's resistance to radiation damage.

[0089] Example 7 verifies the impact of pipe thickness ratio on overall performance. Compared to Example 1, its radiation resistance decreased from 2.0 MGy to 1.7 MGy. This is because the outer layer thickness is insufficient, reducing the total amount of radiation-shielding filler and failing to provide adequate radiation shielding. However, the increased thickness of the inner HNBR layer improves the pipe's elasticity and sealing ability, making it more resistant to water hammer impact and enhancing dynamic sealing performance.

[0090] In summary, the embodiments of this invention achieve functional integration that the comparative example cannot match through layered composite design, interface compatibilization technology, and radiation-shielding filler. This integration includes radiation resistance, sealing, corrosion protection, and mechanical balance, solving the problems of interface weakening and limited functionality in the comparative example and verifying the necessity of the composite structure design. By optimizing material composition, such as the performance parameters of HNBR and EPDM, the amount of radiation-shielding filler, processing techniques such as mixing temperature and time, co-extrusion parameters, vulcanization conditions, and interface treatment methods, i.e., the type and amount of adhesive, the embodiments outperform the comparative example in terms of radiation resistance, dynamic sealing, seawater corrosion resistance, tensile strength, and interfacial bonding strength. Furthermore, different embodiments have their own advantages in specific performance aspects, depending on their targeted formulation and process adjustments.

[0091] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a ternary ethylene propylene diene monomer (EPDM)-hydrogenated nitrile butadiene rubber composite pipe, characterized in that, Includes the following steps: The mixture containing EPDM rubber and radiation-resistant filler is first mixed at 120℃~160℃, then cooled to ≤110℃, and a first peroxide vulcanization system and a first crosslinking agent are added for a second mixing to obtain the outer layer rubber compound. The premix formed from hydrogenated nitrile rubber is mixed at 120℃~160℃, cooled to ≤110℃, and then a second peroxide vulcanization system and a second crosslinking agent are added for a third mixing to obtain the inner layer rubber compound. Both the first peroxide sulfidation system and the second peroxide sulfidation system are dicumyl peroxide or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; The outer and inner rubber layers are co-extruded in layers, forming an interfacial bonding zone between them. A compatibilizer and / or adhesive are injected into this interfacial bonding zone to obtain a composite structure pipe. The composite structure pipe is then co-vulcanized at 8MPa–20MPa and 150℃–170℃ to obtain a EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe. The compatibilizer is maleic anhydride-grafted EPDM rubber; the adhesive is boron-modified cyanoacrylate, a special silane coupling agent, a phenolic-epoxy resin system, or a radiation-resistant modified chloroprene rubber / phenolic resin mixed adhesive.

2. The method for preparing the EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, The temperature at which the compatibilizer and / or adhesive are injected into the interfacial bonding region is 80°C to 100°C.

3. The method for preparing the EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, When the adhesive is injected, the mass ratio of the EPDM rubber, hydrogenated nitrile rubber and adhesive is 60-100:100-60:1-5; or, when the compatibilizer is injected, the mass ratio of the EPDM rubber and compatibilizer is 100:1-3; or, when the compatibilizer and adhesive are injected, the mass ratio of the EPDM rubber, hydrogenated nitrile rubber, compatibilizer and adhesive is 60-100:100-60:1-3:1-5.

4. The method for preparing the EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, The mass ratio of EPDM rubber to radiation-shielding filler is 2:0.5-1.4; the mass ratio of EPDM rubber, the first peroxide vulcanization system, and the first co-crosslinking agent is 100:0.1-5:0.1-5; and the mass ratio of hydrogenated nitrile rubber, the second peroxide vulcanization system, and the second co-crosslinking agent is 100:0.1-5:0.1-5.

5. The method for preparing the EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, The radiation shielding filler is selected from at least one of lead oxide, lead borate, boron carbide, boron nitride, lead tungstate, boron carbide / barium sulfate complex, gadolinium oxide, samarium oxide, and montmorillonite.

6. The method for preparing the EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, The hydrogenated nitrile butadiene rubber has an acrylonitrile content of 30% to 50% and a hydrogenation degree of ≥90%; the ethylene content of the EPDM rubber is 50% to 70%, and the third monomer of the EPDM rubber is ethylene-bis(norbornene).

7. The method for preparing EPDM-hydrogenated nitrile butadiene rubber composite pipe according to claim 1, characterized in that, The mixture also includes a first reinforcing filler. After the first mixing is completed, the temperature is lowered to 120°C, and antioxidants and anti-ozone agents are added and mixed again. The premix also includes a second reinforcing filler, plasticizer, antioxidant and anti-ozone agent.

8. The method for preparing the EPDM-hydrogenated nitrile butadiene composite rubber pipe according to claim 7, characterized in that, The first and second co-crosslinking agents are both triallyl isocyanurate or trimethylolpropane trimethacrylate, the first reinforcing filler is N550 carbon black, N660 carbon black or silica, the second reinforcing filler is N330 carbon black, N550 carbon black or silica, the plasticizer is polyester plasticizer TP-95, the antioxidant is ethoxyquinoline, and the anti-ozone agent is p-phenylenediamine.

9. A ternary ethylene propylene diene monomer (EPDM)-hydrogenated nitrile butadiene rubber composite rubber pipe, characterized in that, The EPDM-hydrogenated nitrile butadiene composite rubber pipe is prepared by the preparation method according to any one of claims 1 to 9. It is an integrated composite structure pipe formed by an outer pipe, an interface bonding layer and an inner pipe, wherein the thickness ratio of the outer pipe, the interface bonding layer and the inner pipe is 5:0.1:

5.

10. The application of the EPDM-hydrogenated nitrile butadiene rubber composite rubber pipe according to claim 9 in a nuclear power plant radioactive wastewater discharge system.

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