A low-temperature resistant and highly resilient EPDM seal, its preparation method and application

Abstract

This application relates to the field of rubber sealing materials technology, and discloses a low-temperature resistant and high-resilience EPDM seal, its preparation method, and its application. The low-temperature resistant and high-resilience EPDM seal of this application uses a rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanization activator, crosslinking agent, and antioxidant as raw materials. The rubber matrix includes EPDM and modified EPDM, with modified EPDM accounting for 8-35% of the total mass of the rubber matrix. The plasticizer is selected from at least one of epoxidized fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters. Furthermore, the composition and proportion of each raw material are specified. The preparation method involves mixing, vulcanization, primary vulcanization, and secondary vulcanization steps, enabling the low-temperature resistant and high-resilience EPDM seal of this application to possess both excellent low-temperature resistance and high resilience, and high-temperature resistance to compression deformation, thus meeting the long-term sealing requirements of new energy vehicle engine cooling systems under different regions and operating conditions.

Description

Technical Field

[0001] This application relates to the field of rubber sealing materials technology, and in particular to a low-temperature resistant and highly resilient EPDM seal, its preparation method, and its application. Background Technology

[0002] The cooling system of a new energy vehicle engine is a core component ensuring the normal operation of the engine, and its sealing performance directly affects the engine's operational stability and service life. Ethylene propylene diene monomer (EPDM) rubber, due to its excellent weather resistance, ozone resistance, and coolant resistance, has become the preferred material for sealing components in the cooling system of new energy vehicle engines.

[0003] However, existing EPDM seals have poor adaptability to high and low temperature environments, making it difficult to balance the elasticity retention at low temperatures and the resistance to compression deformation at high temperatures. Under long-term low or high temperature environments, the seals are prone to a decrease in low-temperature resilience or permanent compression deformation at high temperatures, resulting in poor adhesion between the seal and the sealing surface, a significant reduction in the sealing performance of the coolant, and leakage problems. This makes it impossible to meet the long-term sealing requirements of the cooling system of new energy vehicle engines under different regions and operating conditions.

[0004] To address the aforementioned issues, existing technologies improve the low-temperature performance of EPDM rubber by adding plasticizers. However, the addition of plasticizers can easily lead to a decline in the high-temperature performance of the rubber, resulting in problems such as high-temperature dissolution and migration, causing the material to harden and increase compression set. Other approaches involve adjusting the vulcanization process to increase the crosslinking density of the rubber. However, when the crosslinking density is too high, the internal structure becomes more compact, making it prone to hardening and brittleness at low temperatures, leading to a sharp decrease in elasticity. Therefore, simply adjusting the process has limited effect on improving the overall high and low temperature performance of the rubber. It is evident that existing technologies cannot fundamentally solve the technical challenge of simultaneously maintaining elasticity at low temperatures and resisting compression set at high temperatures. Summary of the Invention

[0005] To at least overcome one of the problems existing in the prior art, one objective of this invention is to provide a low-temperature resistant, high-resilience EPDM seal. This low-temperature resistant, high-resilience EPDM seal uses a rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanization activator, crosslinking agent, and antioxidant as raw materials. The rubber matrix includes EPDM and modified EPDM, with the modified EPDM accounting for 8-35% of the total mass of the rubber matrix. The plasticizer is selected from at least one of epoxidized fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters. Furthermore, the limitations on the composition and proportion of each raw material enable the low-temperature resistant, high-resilience EPDM seal of this application to possess both excellent low-temperature resistance and high resilience, and high-temperature resistance to compression deformation, thus meeting the long-term sealing requirements of new energy vehicle engine cooling systems under different regions and operating conditions. A second objective of this invention is to provide a method for preparing the low-temperature resistant, high-resilience EPDM seal. A third objective of this application is to provide applications of the low-temperature resistant, high-resilience EPDM seal.

[0006] Therefore, the present invention adopts the following technical solution: The first aspect of the present invention provides a low-temperature resistant and high-resilience EPDM seal, the raw material components of which include: a rubber matrix, carbon black, a plasticizer, a peroxide vulcanizing agent, a vulcanization activator, a crosslinking agent, and an antioxidant; the rubber matrix includes EPDM and modified EPDM, and the modified EPDM accounts for 8-35% of the total mass of the rubber matrix; the plasticizer is selected from at least one of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters.

[0007] The raw materials of the low-temperature resistant, high-resilience EPDM seal of this application utilize a composite system comprising EPDM and modified EPDM as the rubber matrix, with modified EPDM accounting for 8-35% of the total mass of the rubber matrix. Modified EPDM improves the compatibility between the rubber matrix and carbon black, plasticizers, etc., avoiding the defect of excessive molecular chain rigidity in pure EPDM at low temperatures. Epoxy fatty acid esters, epoxidized vegetable oils, or unsaturated fatty acid esters containing crosslinkable functional groups are selected as plasticizers. During peroxide vulcanization, these plasticizers participate in the crosslinking reaction through their epoxy groups or carbon-carbon double bonds, chemically bonding to the three-dimensional network of the rubber matrix. This fundamentally solves the industry problem of traditional small-molecule plasticizers easily migrating at high temperatures, leading to material hardening and brittleness. Simultaneously, the addition of a co-crosslinking agent significantly improves the crosslinking efficiency and density, forming a more complete and stable network structure. Through the synergistic effect of the above components, the low-temperature, high-resilience EPDM seal of this invention maintains excellent low-temperature elasticity while also possessing good high-temperature resistance to compression set, achieving a balance between high and low temperature performance over a wide temperature range.

[0008] Preferably, the ethylene content of the EPDM is 50-70 wt%. More preferably, the ethylene content of the EPDM is 55-70 wt%. Even more preferably, the ethylene content of the EPDM is 58-70 wt%.

[0009] Preferably, the method for modifying EPDM includes the following steps: EPDM is dissolved in an organic solvent, and grafting monomers and initiators are added. The mixture is reacted at 70-120°C for 1-6 hours. After precipitation and drying, modified EPDM is obtained. The grafting monomer is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and glycidyl methacrylate. The initiator is selected from at least one of dicumyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide, and anhydrous aluminum trichloride.

[0010] More preferably, the method for modifying EPDM includes the following steps: 100 parts by weight of EPDM are dissolved in 200 parts by weight of organic solvent, 3-10 parts by weight of graft monomer and 0.05-1 parts by weight of initiator are added, and the mixture is reacted at 70-120°C for 1-6 hours. After precipitation and drying, modified EPDM is obtained. The graft monomer is selected from at least one of vinyltrimethoxysilane and vinyltriethoxysilane. The initiator is selected from at least one of dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide, and anhydrous aluminum trichloride.

[0011] This preparation method facilitates the uniform introduction of polar groups from the grafted monomers into the EPDM backbone, avoiding local over-grafting or backbone degradation, thus ensuring the performance stability of the modified EPDM. At the same time, the modified EPDM prepared by this method enhances the interfacial bonding force between it and carbon black, and improves the flexibility and low-temperature crack resistance of the rubber molecular chain.

[0012] Preferably, the epoxy fatty acid ester is selected from at least one of epoxy methyl oleate, epoxy butyl oleate, and epoxy octyl stearate. More preferably, the epoxy fatty acid ester is selected from at least one of epoxy methyl oleate and epoxy octyl stearate.

[0013] Preferably, the epoxidized vegetable oil is selected from at least one of epoxidized soybean oil, epoxidized linseed oil, and epoxidized cottonseed oil. More preferably, the epoxidized vegetable oil is selected from at least one of epoxidized soybean oil and epoxidized linseed oil.

[0014] Preferably, the unsaturated fatty acid ester is selected from at least one of oleate, linoleate, and ricinoleate. More preferably, the unsaturated fatty acid ester is selected from at least one of oleate and ricinoleate.

[0015] Preferably, the plasticizer is composed of epoxy fatty acid esters, epoxidized vegetable oil, and unsaturated fatty acid esters; the weight ratio of the epoxy fatty acid esters, epoxidized vegetable oil, and unsaturated fatty acid esters in the plasticizer is (3~6):(2~5):(1.5~2). More preferably, the plasticizer is composed of epoxidized octyl stearate, epoxidized soybean oil, and ricinoleate; the weight ratio of the epoxidized octyl stearate, epoxidized soybean oil, and ricinoleate in the plasticizer is (3~6):(2~5):(1.5~2). Even more preferably, the weight ratio of the epoxidized octyl stearate, epoxidized soybean oil, and ricinoleate in the plasticizer is 5:3:1.5.

[0016] The plasticizer is composed of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters in a specific ratio. Epoxy fatty acid esters possess both good reactivity and plasticizing efficiency, serving as the primary plasticizer to provide fundamental properties. Epoxidized vegetable oils have a large molecular weight and good thermal stability, contributing to improved system pull-out resistance and high-temperature durability. Unsaturated fatty acid esters exhibit excellent low-temperature performance and can participate in cross-linking through carbon-carbon double bonds, fixing themselves to the rubber network. This improves high-temperature compression set resistance without compromising low-temperature elasticity, and even further enhances the overall performance of the seal by optimizing the network structure. Within this specific ratio range, the three components of the plasticizer work synergistically to promote an optimal balance in the seal's low-temperature elasticity, high-temperature compressive strength, and migration resistance.

[0017] Preferably, the carbon black is composed of a first carbon black and a second carbon black with different particle sizes, wherein the average particle size of the first carbon black is 40-60 nm and the average particle size of the second carbon black is 200-500 nm; the weight ratio of the first carbon black to the second carbon black is 1:(2.5-4). More preferably, the carbon black is composed of a first carbon black and a second carbon black with different particle sizes, wherein the average particle size of the first carbon black is 45-60 nm and the average particle size of the second carbon black is 300-500 nm; the weight ratio of the first carbon black to the second carbon black is 1:(2.5-3.5). Even more preferably, the carbon black is composed of a first carbon black and a second carbon black with different particle sizes, wherein the average particle size of the first carbon black is 45-60 nm and the average particle size of the second carbon black is 350-500 nm; the weight ratio of the first carbon black to the second carbon black is 1:3.

[0018] In this application, the first carbon black has a small particle size and a large specific surface area, resulting in good reinforcing effect and primarily providing mechanical properties such as tensile strength. The second carbon black has a large particle size, imparting good flexibility and low compressive deformation properties to the material, while having minimal impact on low-temperature dynamic properties. By using the larger-particle-size second carbon black as the main component, combined with the smaller-particle-size first carbon black, the material is ensured to maintain a stable reinforcing effect and resilience while possessing sufficient strength.

[0019] Preferably, the peroxide sulfide is selected from at least one of bis-tert-butylperoxyisopropylbenzene, diisopropylbenzene peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane. More preferably, the peroxide sulfide is selected from at least one of bis-tert-butylperoxyisopropylbenzene and diisopropylbenzene peroxide.

[0020] Preferably, the vulcanizing activator comprises zinc oxide and stearic acid in a weight ratio of (3~8):(0.5~2). More preferably, the vulcanizing activator comprises zinc oxide and stearic acid in a weight ratio of (4.5~8):(1~2). Even more preferably, the vulcanizing activator comprises zinc oxide and stearic acid in a weight ratio of (4.5~8):(1.5~2).

[0021] Preferably, the co-crosslinking agent is selected from at least one of triallyl isocyanurate, trimethylolpropane trimethacrylate, and triallyl cyanurate. More preferably, the co-crosslinking agent is selected from at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate.

[0022] Preferably, the antioxidant comprises amine antioxidants and imidazole antioxidants. More preferably, the amine antioxidant is selected from at least one of N-isopropyl-N'-phenyl-p-phenylenediamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine; and the imidazole antioxidant is selected from at least one of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and 2-mercaptomethylbenzimidazole zinc salt. Even more preferably, the antioxidant is a mixture of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and 2-mercaptomethylbenzimidazole zinc salt in a weight ratio of (0.5~1.5):1.

[0023] Preferably, in the raw materials of the low-temperature resistant and high-resilience EPDM seal, the weight ratio of rubber matrix, carbon black and plasticizer is 100:(35~50):(15~25).

[0024] Preferably, in the raw materials of the low-temperature resistant and high-resilience EPDM seal, the weight ratio of rubber matrix, carbon black, plasticizer and peroxide vulcanizing agent is 100:(35~50):(15~25):(3~8).

[0025] Preferably, in the raw materials of the low-temperature resistant and high-resilience EPDM seal, the weight ratio of rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent and vulcanizing activator is 100: (35~50): (15~25): (3~8): (3.5~7).

[0026] Preferably, in the raw materials of the low-temperature resistant and high-resilience EPDM seal, the weight ratio of rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanizing activator and crosslinking agent is 100: (35~50): (15~25): (3~8): (3.5~7): (2~5).

[0027] Preferably, in the raw materials of the low-temperature resistant and high-resilience EPDM seal, the weight ratio of rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanizing activator, crosslinking agent and antioxidant is 100: (35~50): (15~25): (3~8): (3.5~7): (2~5): (1~3).

[0028] In the raw material composition of the low-temperature resistant and high-resilience EPDM seal of this application, 35-50 parts by weight of carbon black provide sufficient reinforcement for the rubber compound; 15-25 parts by weight of plasticizer provides the required low-temperature elasticity while preventing high-temperature deformation caused by excessive plasticizer; 3-8 parts by weight of peroxide vulcanizing agent and 3.5-7 parts by weight of vulcanizing activator ensure smooth and efficient vulcanization and crosslinking, while also avoiding rubber embrittlement caused by excessive peroxide vulcanizing agent; and 2-5 parts by weight of crosslinking aid promote the formation of a dense and stable crosslinking network. The components work synergistically within the formulation range of this application, resulting in a low-temperature resistant and high-resilience EPDM seal with excellent low-temperature resistance, high resilience, and high-temperature resistance to compression deformation, meeting the long-term sealing requirements of new energy vehicle engine cooling systems under different regions and operating conditions.

[0029] A second aspect of the present invention provides a method for preparing a low-temperature resistant, high-resilience EPDM seal according to the first aspect of the present invention, comprising the following steps: S1. Mixing: Add EPDM, modified EPDM, carbon black, plasticizer, vulcanizing activator, and antioxidant to a mixer and mix, controlling the discharge temperature to 140~160℃ to obtain masterbatch. S2. Vulcanization: Adjust the temperature to 80~100℃, add peroxide vulcanizing agent and crosslinking agent, mix, sheet, and obtain compound rubber; S3. First-stage vulcanization: The compound rubber is vulcanized at 160~190℃ for 5~15 minutes to obtain a vulcanized semi-finished product; S4. Second-stage vulcanization: The vulcanized semi-finished product is subjected to second-stage vulcanization at 140~160℃ for 3~6h to obtain the low-temperature resistant and high-resilience EPDM seal.

[0030] Preferably, in step S1, the glue discharge temperature is 145~160℃.

[0031] Preferably, in step S3, the temperature of the first-stage vulcanization is 170~190℃, and the time is 8~15min. More preferably, in step S3, the temperature of the first-stage vulcanization is 175~190℃, and the time is 10~15min.

[0032] Preferably, in step S4, the temperature of the second-stage vulcanization is 140~160℃, and the time is 3~6h. More preferably, in step S4, the temperature of the second-stage vulcanization is 145~160℃, and the time is 4~6h. Even more preferably, in step S4, the temperature of the second-stage vulcanization is 150~160℃, and the time is 4.5~6h.

[0033] This application discloses a method for preparing low-temperature resistant, high-resilience EPDM seals, involving mixing, vulcanization, first-stage vulcanization, and second-stage vulcanization. The method incorporates optimized parameters. Specifically, in step S1, the mixing and discharge temperature is controlled at 140-160°C to ensure uniform dispersion of the modified EPDM's polar groups, plasticizers, carbon black, etc., within the rubber matrix, thus avoiding the risk of high-temperature degradation. In step S2, after adjusting the temperature to 80-100°C, peroxide vulcanizing agents and crosslinking aids are added, effectively preventing scorching during the preparation process and ensuring the safety of the mixed rubber during molding and processing. Step S3 involves adjusting the temperature to 160-190°C... A first-stage vulcanization process is performed at ℃ for 5-15 minutes to form a preliminary cross-linked network in the rubber matrix. This process ensures sufficient cross-linking density to impart high-temperature compression resistance to the seal while avoiding excessive cross-linking that restricts the low-temperature movement of molecular chains. Step S4 involves a second-stage vulcanization at 140-160℃ for 3-6 hours. This process ensures complete cross-linking and a more perfect and stable cross-linked network structure, minimizing compression set (improving high-temperature compression resistance). Simultaneously, it allows the plasticizer to fully bond into the three-dimensional network, removes residual small molecules, and eliminates internal stress, ensuring the long-term stability of low-temperature elasticity. Through the synergistic optimization of each step, the resulting low-temperature resistant, high-resilience EPDM seal achieves excellent low-temperature high resilience and high-temperature compression set resistance.

[0034] The third aspect of this application provides the application of a low-temperature resistant and high-resilience EPDM seal in the sealing of a cooling system for a new energy vehicle engine. The low-temperature resistant and high-resilience EPDM seal is the aforementioned low-temperature resistant and high-resilience EPDM seal, or is prepared by the aforementioned method.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The raw material components of this application include a rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanization activator, co-crosslinking agent, and antioxidant; wherein, the rubber matrix includes EPDM and modified EPDM, and modified EPDM accounts for 8-35% of the total mass of the rubber matrix; the plasticizer is selected from at least one of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters. Through the combined use of EPDM and modified EPDM, the polar groups introduced by the modified EPDM significantly improve the dispersibility of carbon black, etc., laying the foundation for excellent mechanical properties; the selection of epoxy fatty acid esters, epoxidized vegetable oils, or unsaturated fatty acid esters containing crosslinkable functional groups as plasticizers allows them to participate in the crosslinking reaction through epoxy groups or carbon-carbon double bonds during the peroxide vulcanization process, and be chemically bonded to the three-dimensional network structure of the rubber, solving the industry problem that traditional small molecule plasticizers easily migrate at high temperatures, causing the material to become hard and brittle; the addition of co-crosslinking agents further improves the crosslinking efficiency and crosslinking density, forming a more complete and stable network structure. Through the synergistic effect of the above components, the resulting low-temperature resistant and high-resilience EPDM seal possesses both excellent low-temperature resistance and high-temperature resistance to compression deformation. Its low-temperature shrinkage temperature TR10 is as low as -53.4℃, and the compression set after being compressed by 25% at 135℃ and held for 120 hours is as low as 12.4%. The tensile strength reaches 13.1MPa, and the tensile strength retention rate after heat aging is as high as 93.2%. This effectively solves the technical problem that existing EPDM seals cannot simultaneously achieve both low-temperature elasticity retention and high-temperature resistance to compression deformation.

[0036] 2) In the preparation method of the low-temperature resistant and high-resilience EPDM seal of this application, the steps of mixing, sulfur addition, first-stage vulcanization and second-stage vulcanization are carried out, and the preparation method parameters are optimized. The steps are simple and suitable for large-scale production, which helps to improve the stability and repeatability of the performance of the low-temperature resistant and high-resilience EPDM seal. Detailed Implementation

[0037] The present invention will be further described in detail below through specific embodiments, comparative examples and tables, but is not limited to all the discussions and data.

[0038] The EPDM raw rubber is sourced from Dow Chemical Company, USA, and is designated NORDEL™ IP 4570 with an ethylene content of 50 wt%. The carbon black N550 is sourced from Shanghai Liankangming Chemical Co., Ltd., with an average particle size of 40-48 nm. The carbon black N990 is sourced from Xinjiang Junxin Chemical Co., Ltd., with an average particle size of 280 nm.

[0039] Example of preparation of modified EPDM: Preparation Example 1: The preparation method of modified EPDM includes the following steps: 100g of EPDM raw rubber was dissolved in 200g of toluene and stirred until completely dissolved. Then, 5g of grafted monomer vinyltrimethoxysilane and 0.5g of initiator dicumyl peroxide were added. The system was heated to 95℃ under nitrogen protection and reacted at this temperature for 4h. After the reaction was completed, the reaction solution was poured into 2000mL of anhydrous ethanol to precipitate the solid product. After filtration, the obtained solid product was dried in a vacuum drying oven at 50~60℃ to constant weight to obtain modified EPDM.

[0040] Preparation Example 2: The preparation method of modified EPDM includes the following steps: 100g of EPDM raw rubber was dissolved in 200g of toluene and stirred until completely dissolved. Then, 8g of grafted monomer vinyltrimethoxysilane and 0.6g of initiator dicumyl peroxide were added. The system was heated to 95℃ under nitrogen protection and reacted at this temperature for 4h. After the reaction was completed, the reaction solution was poured into 2000mL of anhydrous ethanol to precipitate the solid product. After filtration, the obtained solid product was dried in a vacuum drying oven at 50~60℃ to constant weight to obtain modified EPDM.

[0041] Comparative examples of the preparation of modified EPDM: Preparation of Comparative Example 1: The preparation method of modified EPDM includes the following steps: 100g of EPDM raw rubber was dissolved in 200g of toluene and stirred until completely dissolved. Then, 12g of grafted monomer vinyltrimethoxysilane and 0.5g of initiator dicumyl peroxide were added. The system was heated to 95℃ under nitrogen protection and reacted at this temperature for 4h. After the reaction was completed, the reaction solution was poured into 2000mL of anhydrous ethanol to precipitate the solid product. After filtration, the obtained solid product was dried in a vacuum drying oven at 50~60℃ to constant weight to obtain modified EPDM.

[0042] Preparation of Comparative Example 2: The preparation method of modified EPDM includes the following steps: 100g of EPDM raw rubber was dissolved in 200g of toluene and stirred until completely dissolved. Then, 5g of grafted monomer vinyltrimethoxysilane and 0.5g of initiator dicumyl peroxide were added. The system was heated to 130℃ under nitrogen protection and reacted at this temperature for 4h. After the reaction was completed, the reaction solution was poured into 2000mL of anhydrous ethanol to precipitate the solid product. After filtration, the obtained solid product was dried in a vacuum drying oven at 50~60℃ to constant weight to obtain modified EPDM.

[0043] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this invention can be obtained from conventional commercial sources.

[0044] Examples of low-temperature resistant, high-resilience EPDM seals: A low-temperature resistant and highly resilient EPDM seal is prepared by the following steps: S1. Mixing: Preheat the internal mixer to 80~90℃ and set the speed to 40~50rpm. Add 100 parts by weight of EPDM and modified EPDM in sequence, of which the modified EPDM is 8~35 parts by weight. Mix for 1 minute until the rolls are completely covered. Then add 3.5~7 parts by weight of vulcanizing activator, 1~3 parts by weight of antioxidant, 35~50 parts by weight of carbon black, and 15~25 parts by weight of plasticizer in sequence. Carbon black and plasticizer are added in two batches. After each raw material is added, mix for 1~2 minutes until there is no obvious powder. Then increase the speed to 60r / min and continue mixing for 2~3 minutes. Monitor the temperature in real time. When the rubber compound temperature reaches 140~160℃, immediately discharge the rubber. The discharged masterbatch is thinly passed through the open mill 3 times and then sheeted and cooled. Let it stand for 24 hours. S2. Vulcanization: Put the cooled masterbatch into the open mill and pass cooling water through it. Control the roller temperature at 80~100℃, add 3~8 parts by weight of peroxide vulcanizing agent and 2~5 parts by weight of crosslinking agent, mix for 5~7 minutes, sheet out to make a compound with a thickness of 6~8mm, and let it stand for 12~24 hours. S3. First-stage vulcanization: After cutting the compound rubber, put it into the mold and place it in a flat vulcanizing machine with a temperature of 160~190℃ and a pressure of 15~20MPa for first-stage vulcanization for 5~15 minutes. Take it out and let it cool naturally to obtain the vulcanized semi-finished product. S4. Second-stage vulcanization: The vulcanized semi-finished product is placed in a forced-air drying oven at 140~160℃ for second-stage vulcanization for 3~6 hours, then removed and naturally cooled to obtain the low-temperature resistant and high-resilience EPDM seal.

[0045] Regarding step S1, in some specific embodiments, the total amount of EPDM and modified EPDM is 100 parts by weight, wherein the amount of modified EPDM can be 8 parts, 10 parts, 20 parts, 30 parts, or 35 parts; the amount of vulcanizing activator can be 3.5 parts, 5 parts, or 7 parts; the amount of antioxidant can be 1 part, 2 parts, or 3 parts; the amount of carbon black can be 35 parts, 40 parts, 45 parts, or 50 parts; and the amount of plasticizer can be 15 parts, 20 parts, or 25 parts. The discharge temperature can be 140°C, 145°C, 150°C, or 160°C. In some specific embodiments, the ethylene content of EPDM can be 50 wt%, 60 wt%, or 70 wt%. The plasticizer may be selected from at least one of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters; wherein, the epoxy fatty acid ester may be selected from at least one of epoxy methyl oleate, epoxy butyl oleate, and epoxy octyl stearate; the epoxidized vegetable oil may be selected from at least one of epoxidized soybean oil, epoxidized linseed oil, and epoxidized cottonseed oil; the unsaturated fatty acid ester may be selected from at least one of oleic acid esters, linoleic acid esters, and ricinoleic acid esters; the plasticizer may be composed of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters. The composition includes saturated fatty acid esters; in the plasticizer, the weight ratio of epoxy fatty acid esters, epoxidized vegetable oil, and unsaturated fatty acid esters can be 3:2:2, 4:3:1.5, 5:4:1.5, or 6:5:2; the plasticizer can be composed of epoxidized octyl stearate, epoxidized soybean oil, and ricinoleate, with the weight ratio of epoxidized octyl stearate, epoxidized soybean oil, and ricinoleate being 3:2:2, 4:3:1.5, 5:4:1.5, 5:3:1.5, or 6:5:2. The carbon black is composed of first carbon black and second carbon black with different particle sizes, wherein the average particle size of the first carbon black can be 40nm, 50nm, or 60nm, and the average particle size of the second carbon black can be 200nm, 300nm, 400nm, or 500nm; the weight ratio of the first carbon black and the second carbon black can be 1:2.5, 1:3, or 1:4. The vulcanizing activator includes zinc oxide and stearic acid in a weight ratio of 3:1, 5:2, 6:0.5, 7:1, or 8:1.5. The antioxidant includes amine antioxidants and imidazole antioxidants. The amine antioxidant can be selected from at least one of N-isopropyl-N'-phenyl-p-phenylenediamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine; the imidazole antioxidant can be selected from at least one of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and 2-mercaptomethylbenzimidazole zinc salt; the antioxidant can be 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and 2-mercaptomethylbenzimidazole zinc salt in a weight ratio of 0.5:1, 1:1, 1.2:1, or 1.5:1.

[0046] Regarding step S1, in some specific implementations, the method for modifying EPDM includes the following steps: 100 parts by weight of EPDM are dissolved in 200 parts by weight of organic solvent, and 3-10 parts by weight of grafting monomer and 0.05-1 parts by weight of initiator are added. The mixture is reacted at 70-120°C for 1-6 hours. After precipitation and drying, modified EPDM is obtained. The grafting monomer can be selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and glycidyl methacrylate. The initiator can be selected from at least one of dicumyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide, and anhydrous aluminum trichloride.

[0047] Regarding step S2, in some specific embodiments, the peroxide curing agent may be selected from at least one of bis-tert-butylperoxyisopropylbenzene, dicumyl peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane. The co-crosslinking agent may be selected from at least one of triallyl isocyanurate, trimethylolpropane trimethacrylate, and triallyl cyanurate. The amount of peroxide curing agent may be 3 parts, 5 parts, 6 parts, or 8 parts, and the amount of co-crosslinking agent may be 2 parts, 3 parts, 4 parts, or 5 parts.

[0048] Regarding step S3, in some specific implementations, the temperature of the first stage of vulcanization can be 160°C, 170°C, 185°C or 190°C, the pressure can be 15MPa, 17MPa or 20MPa, and the vulcanization time can be 5min, 10min or 15min.

[0049] Regarding step S4, in some specific implementations, the temperature of the second-stage vulcanization can be 140°C, 150°C, or 160°C, and the time can be 3h, 4h, 5h, or 6h. Example 1

[0050] A low-temperature resistant and highly resilient EPDM seal is prepared by the following steps: S1. Mixing: Preheat the internal mixer to 85°C and set the speed to 50 rpm. Add 80 g EPDM and 20 g modified EPDM from Preparation Example 1 in sequence, and mix for 1 min until the rolls are completely covered. Then add 6 g vulcanizing activator (5 g zinc oxide and 1 g stearic acid), 2 g antioxidant (1 g 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and 1 g... 2-Mercaptomethylbenzimidazole zinc salt), 40g carbon black (10g carbon black N550 and 30g carbon black N990), 19g plasticizer (10g octyl epoxy stearate, 6g epoxy soybean oil and 3g ricinoleate). Carbon black and plasticizer are added in two batches. After each raw material is added, the mixture is mixed for 1-2 minutes until there is no obvious powder. Then the speed is increased to 60r / min and the mixture is mixed for another 2-3 minutes. The temperature is monitored in real time. When the rubber compound temperature reaches 140-145℃, the rubber is discharged immediately. The discharged masterbatch is passed through a two-roll mill three times and then sheeted and cooled. It is then left to stand for 24 hours. S2. Vulcanization: Put the cooled masterbatch into the open mill and pass cooling water through it. Control the roller temperature at 85~90℃, add 5g of dicumyl peroxide and 4g of trimethylolpropane trimethacrylate, mix for 6min, sheet out to make a compound with a thickness of 6~8mm, and let it stand for 15h. S3. First-stage vulcanization: After cutting the compound rubber, put it into the mold and place it in a flat vulcanizing machine with a temperature of 170℃ and a pressure of 15MPa for first-stage vulcanization for 10 minutes. Take it out and let it cool naturally to obtain the vulcanized semi-finished product. S4. Second-stage vulcanization: The vulcanized semi-finished product is placed in a 150℃ forced-air drying oven for second-stage vulcanization for 6 hours, then removed and naturally cooled to obtain the low-temperature resistant and high-resilience EPDM seal. Example 2

[0051] The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that the modified EPDM in Preparation Example 1 is replaced by the modified EPDM in Preparation Example 2 in equal amounts. Example 3

[0052] The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Example 3, the amount of EPDM and the modified EPDM in Preparation Example 1 are 70g and 30g, respectively. Example 4

[0053] The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Example 4, the amount of plasticizer used is 17g, including 8g of octyl epoxy stearate, 6g of epoxy soybean oil and 3g of ricinoleate. Example 5

[0054] The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Example 5, the temperature of the first vulcanization is 185°C and the temperature of the second vulcanization is 160°C.

[0055] Comparative Example 1: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that the modified EPDM in Preparation Example 1 in Comparative Example 1 is replaced with the modified EPDM in Preparation Example 1.

[0056] Comparative Example 2: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that the modified EPDM in Preparation Example 1 in Comparative Example 2 is replaced by the modified EPDM in Preparation Example 2.

[0057] Comparative Example 3: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Comparative Example 3, the amount of EPDM and the amount of modified EPDM in Preparation Example 1 are 60g and 40g, respectively.

[0058] Comparative Example 4: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Comparative Example 4, the plasticizer is replaced by an equal amount of dioctyl sebacate.

[0059] Comparative Example 5: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that in Comparative Example 5, the amount of plasticizer used is 23g, including 14g of octyl epoxy stearate, 6g of epoxy soybean oil and 3g of ricinoleate.

[0060] Comparative Example 6: The preparation method of a low-temperature resistant and high-resilience EPDM seal is the same as that in Example 1, except that step S4, the two-stage vulcanization, is not included in Comparative Example 6.

[0061] Material performance testing: The low-temperature resistant, high-resilience EPDM seals of Examples 1-5 and Comparative Examples 1-6 were subjected to various performance tests, and the test methods are as follows: 1. Hardness (Shore A): Tested according to GB / T 531.2-2009 standard.

[0062] 2. Tensile strength and elongation at break: tested according to ASTM D412 standard.

[0063] 3. Low-temperature shrinkage temperature (TR10): Tested according to GB / T 7758-2020 standard.

[0064] 4. Compression set: Tested according to GB / T 7759.1-2015 standard (compress the sample by 25% at 135℃ and hold for 120h).

[0065] 5. Thermal aging tensile strength retention rate: After thermal aging (135℃ for 120h) according to GB / T 3512-2014 standard, the tensile strength after thermal aging is tested, and the thermal aging tensile strength retention rate is calculated according to the following formula: Thermal aging tensile strength retention rate = tensile strength after aging / tensile strength before aging × 100%.

[0066] The cured performance of the low-temperature resistant, high-resilience EPDM seals of Examples 1-5 and Comparative Examples 1-6 is shown in Table 1 below:

[0067] The low-temperature resistant, high-resilience EPDM seals in Examples 1-5 achieve excellent low-temperature resilience, high-temperature compression set, high mechanical strength, and heat aging resistance through the rational proportions and synergistic effects of various raw material components such as the rubber matrix, carbon black, plasticizer, and peroxide curing agent, particularly the specific proportion of modified EPDM in the total mass of the rubber matrix and the specific composition of the plasticizer. The results show that the low-temperature shrinkage temperature TR10 is as low as -53.4℃, the compression set after compression by 25% at 135℃ and held for 120 hours is as low as 12.4%, the tensile strength reaches 13.1 MPa, and the tensile strength retention rate after heat aging is as high as 93.2%. This meets the stringent requirements of new energy vehicle engine cooling system seals for low-temperature elasticity retention and high-temperature compression set resistance under different regions and operating conditions.

[0068] Compared with Example 1, Comparative Example 1 was prepared using the same method, except that the modified EPDM from Example 1 was replaced with the modified EPDM from Comparative Example 1. The results showed that although the low-temperature resistant, high-resilience EPDM seal of Comparative Example 1 had slightly higher hardness, its tensile strength decreased to 10.2 MPa, TR10 increased to -47.2℃ (5.1℃ higher than Example 1), compression set increased to 19.3%, and the strength retention rate after heat aging decreased to 82.7%. This may be because the excessive amount of grafted monomers introduced too many polar groups into the EPDM molecular chain, resulting in localized over-grafting, increased molecular chain rigidity, and possibly disrupted the original regular structure of EPDM. This reduced the compatibility between the modified EPDM and components such as carbon black and plasticizers, leading to an uneven crosslinking network and an inability to form a stable network structure. Ultimately, this resulted in a decrease in its low-temperature elasticity, mechanical properties, and high-temperature compression resistance.

[0069] Compared with Example 1, Comparative Example 2 was prepared using the same method, except that the modified EPDM from Example 1 was replaced with the modified EPDM from Comparative Example 2. The results showed that the low-temperature resistant, high-resilience EPDM seal of Comparative Example 2 exhibited a decline in all properties. Its tensile strength was only 9.8 MPa, TR10 increased to -45.6℃, compression set was as high as 22.7%, and the strength retention rate after thermal aging was only 79.5%. This may be because the reaction temperature during the preparation of the modified EPDM was too high, exceeding the upper temperature limit for the stability of the EPDM backbone, leading to partial thermo-oxidative degradation of the EPDM and localized chain breakage. This limited the effective grafting reaction, resulting in insufficient introduction of polar groups into the modified EPDM. Simultaneously, the degraded molecular chain segments could not form an effective cross-linking network, leading to a significant decrease in its mechanical properties, low-temperature elasticity, high-temperature compressibility, and thermal stability.

[0070] Compared with Example 1, Comparative Example 3 was prepared using the same method, except that the amounts of EPDM used in Comparative Example 3 and the modified EPDM used in Preparation Example 1 were 60g and 40g, respectively. The results showed that although the TR10 of the low-temperature resistant, high-resilience EPDM seal of Comparative Example 3 could reach -48.1℃, it was significantly higher than that of Example 1 by 4.2℃. Its tensile strength decreased to 11.3MPa, compression set increased to 18.1%, and the strength retention rate after heat aging decreased to 84.3%. This may be because the excessive amount of modified EPDM resulted in too many polar groups in the rubber matrix, enhanced intermolecular chain interactions, and increased rigidity of the crosslinking network. Simultaneously, the excessive modified EPDM disrupted the compatibility balance with the unmodified EPDM, leading to uneven dispersion of components such as carbon black and plasticizers, and decreased stability of the crosslinking network structure. Thus, while improving low-temperature elasticity to a limited extent, it severely damaged its high-temperature compression resistance and thermal stability.

[0071] Compared with Example 1, Comparative Example 4 was prepared using the same method, except that the plasticizer in Comparative Example 4 was replaced with an equal amount of dioctyl sebacate. The results showed that the TR10 of the low-temperature resistant, high-resilience EPDM seal of Comparative Example 4 increased to -46.3℃, the compression set increased to 21.6%, and the strength retention rate after heat aging decreased to 81.9%. This may be because dioctyl sebacate (DOS), as a traditional small-molecule plasticizer, does not contain crosslinkable functional groups such as epoxy groups or carbon-carbon double bonds. During peroxide vulcanization, it cannot participate in the crosslinking reaction and be chemically bonded to the three-dimensional rubber network, existing only in a physical blend form. During long-term use at high temperatures, DOS gradually migrates and precipitates, causing the rubber matrix to harden and become brittle, reducing the stability of the crosslinked network. Simultaneously, the loss of the plasticizer weakens the molecular chain mobility at low temperatures, ultimately resulting in insufficient low-temperature elasticity, high-temperature compression resistance, and heat aging performance.

[0072] Compared with Example 1, Comparative Example 5 was prepared using the same method, except that the amount of plasticizer used in Comparative Example 5 was 23g, including 14g of octyl epoxy stearate, 6g of epoxidized soybean oil, and 3g of ricinoleate. The results showed that the hardness (Shore A) of the low-temperature resistant, high-resilience EPDM seal of Comparative Example 5 decreased to 49HA, the tensile strength decreased to 10.7MPa, and the elongation at break increased to 585%. Although TR10 was slightly better than Example 1 due to sufficient total plasticizer content, its compression set significantly increased to 18.2%, and the strength retention after heat aging decreased to 85.4%. This may be because the proportion of epoxidized fatty acid esters (octyl epoxy stearate) in the plasticizer was too high, while the relative proportions of epoxidized vegetable oil and unsaturated fatty acid esters were insufficient. While epoxidized fatty acid esters exhibit high reactivity, excessive addition may lead to over-participation in cross-linking, increasing the rigidity or inhomogeneity of the cross-linked network and reducing its flexibility and elasticity. Simultaneously, the proportions of epoxidized vegetable oil and unsaturated fatty acid esters are relatively weakened, disrupting their synergistic effect. Although the total amount is within the limits of this application, the imbalance in the internal proportions prevents the system from forming a cross-linked network structure that is both flexible and dense. Ultimately, while maintaining certain low-temperature performance, high-temperature compressive strength and thermal stability are sacrificed, failing to achieve an optimal balance between low-temperature elasticity and high-temperature compressive strength.

[0073] Compared with Example 1, Comparative Example 6 was prepared using the same method, except that it did not include the two-stage vulcanization step S4, but only performed a single-stage vulcanization. The results showed that the low-temperature resistant, high-resilience EPDM seal of Comparative Example 6 exhibited a compression set as high as 24.9%, and its strength retention rate decreased to 86.2% after heat aging. This is likely because the lack of a two-stage vulcanization process prevented the complete cross-linking reaction of the rubber, resulting in a loose cross-linking network with a large number of residual small molecules. The internal stress was not eliminated, which not only prevented the plasticizer from fully bonding to the network, leading to easy plastic deformation of the cross-linking network at high temperatures and a sharp increase in compression set, but also accelerated the degradation of molecular chains during heat aging, ultimately causing a significant decrease in high-temperature performance and heat aging performance.

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A low-temperature resistant, high-resilience EPDM seal, characterized in that, Its raw material components include: rubber matrix, carbon black, plasticizer, peroxide vulcanizing agent, vulcanization activator, crosslinking agent and antioxidant; The rubber matrix includes EPDM and modified EPDM, and the modified EPDM accounts for 8-35% of the total mass of the rubber matrix; The plasticizer is selected from at least one of epoxy fatty acid esters, epoxidized vegetable oils, and unsaturated fatty acid esters.

2. The low-temperature resistant, high-resilience EPDM seal according to claim 1, characterized in that, The EPDM has an ethylene content of 50-70 wt%.

3. The low-temperature resistant, high-resilience EPDM seal according to claim 1, characterized in that, The method for modifying EPDM includes the following steps: EPDM was dissolved in an organic solvent, grafted monomers and initiators were added, and the mixture was reacted at 70~120℃ for 1~6 hours. After precipitation and drying, modified EPDM was obtained. The grafting monomer is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and glycidyl methacrylate.

4. The low-temperature resistant and high-resilience EPDM seal according to claim 1, characterized in that, The epoxy fatty acid ester is selected from at least one of epoxy methyl oleate, epoxy butyl oleate, and epoxy octyl stearate; And / or, the epoxidized vegetable oil is selected from at least one of epoxidized soybean oil, epoxidized linseed oil, and epoxidized cottonseed oil; And / or, the unsaturated fatty acid ester is selected from at least one of oleate, linoleate, and ricinoleate.

5. The low-temperature resistant, high-resilience EPDM seal according to claim 1, characterized in that, The plasticizer is composed of epoxy fatty acid ester, epoxidized vegetable oil and unsaturated fatty acid ester; the weight ratio of epoxy fatty acid ester, epoxidized vegetable oil and unsaturated fatty acid ester in the plasticizer is (3~6):(2~5):(1.5~2).

6. The low-temperature resistant, high-resilience EPDM seal according to claim 1, characterized in that, The carbon black is composed of a first carbon black and a second carbon black with different particle sizes. The average particle size of the first carbon black is 40~60nm, and the average particle size of the second carbon black is 200~500nm. In the carbon black, the weight ratio of the first carbon black to the second carbon black is 1:(2.5~4).

7. The low-temperature resistant, high-resilience EPDM seal according to claim 1, characterized in that, The peroxide sulfide agent is selected from at least one of bis-tert-butylperoxyisopropylbenzene, diisopropylbenzene peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; And / or, the vulcanizing activator comprises zinc oxide and stearic acid in a weight ratio of (3~8):(0.5~2); And / or, the co-crosslinking agent is selected from at least one of triallyl isocyanurate, trimethylolpropane trimethacrylate, and triallyl cyanurate; And / or, the antioxidants include amine antioxidants and imidazole antioxidants.

8. The low-temperature resistant, high-resilience EPDM seal according to any one of claims 1 to 7, characterized in that, Its raw materials include the following components in parts by weight: 100 parts of rubber matrix; 35-50 parts carbon black; Plasticizer 15-25 parts; Peroxide vulcanizing agent 3-8 parts; 3.5-7 parts of vulcanizing activator 2-5 parts of crosslinking agent; Anti-aging agent 1-3 parts.

9. A method for preparing a low-temperature resistant, high-resilience EPDM seal as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mixing: Add EPDM, modified EPDM, carbon black, plasticizer, vulcanizing activator, and antioxidant to a mixer and mix, controlling the discharge temperature to 140~160℃ to obtain masterbatch. S2. Vulcanization: Adjust the temperature to 80~100℃, add peroxide vulcanizing agent and crosslinking agent, mix, sheet, and obtain compound rubber; S3. First-stage vulcanization: The compound rubber is vulcanized at 160~190℃ for 5~15 minutes to obtain a vulcanized semi-finished product; S4. Second-stage vulcanization: The vulcanized semi-finished product is subjected to second-stage vulcanization at 140~160℃ for 3~6h to obtain the low-temperature resistant and high-resilience EPDM seal.

10. The application of a low-temperature resistant and high-resilience EPDM seal as described in any one of claims 1 to 8, or a low-temperature resistant and high-resilience EPDM seal prepared by the preparation method as described in claim 9, in the sealing of the cooling system of a new energy vehicle engine.

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