Semi-high temperature vulcanized high pressure variable performance EPDM material and preparation method thereof

Abstract

This invention discloses a semi-high temperature vulcanized high pressure variable EPDM material and its preparation method, belonging to the field of EPDM material technology. First, an antioxidant 4020 is reacted with glycidyl methacrylate to prepare a GMA-grafted antioxidant. Then, γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide are used to modify silica. Finally, the modified silica, GMA-grafted antioxidant, vinyltrimethoxysilane, EPDM raw rubber, EVM, reinforcing filler, vulcanization system, and other additives are mixed and vulcanized to obtain the EPDM material. This invention strengthens the interface by chemically bonding the filler and matrix and anchors the antioxidant to inhibit migration. While reducing the material's compression set, it solves the problems of weak filler-matrix interface bonding and easy antioxidant migration and extraction. It is suitable for automotive cooling pipes with stringent requirements for heat aging resistance, sealing performance, and media resistance.

Description

Technical Field

[0001] This invention belongs to the field of EPDM material technology, specifically a semi-high temperature vulcanized high pressure variable performance EPDM material and its preparation method. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber has become the core sealing and conveying material for automotive engine cooling pipes due to its excellent resistance to heat and oxygen aging, ozone, weathering and coolant. Cooling pipes serve in the harsh engine compartment environment for a long time, and the material must have extremely low compression set to maintain sealing reliability and ultra-long heat aging life.

[0003] Currently, to meet the stringent requirements for compression set in standards such as SAE J1638, the industry generally adopts peroxide vulcanization systems. This system provides a certain degree of thermal stability by forming carbon-carbon (CC) crosslinks, but it still has drawbacks: First, the crosslinked network of peroxides is highly rigid and lacks elastic recovery, making it difficult to improve compression set performance and meet the requirements for higher sealing reliability; second, the decomposition of peroxides requires high temperatures (usually >170℃) and the vulcanization rate is slow, resulting in low production efficiency, high energy consumption, and high costs; in addition, this system is sensitive to process conditions and impurities, and is easily affected by oxygen or certain components in the rubber compound, often resulting in uneven vulcanization or performance fluctuations.

[0004] Chinese patent application CN103834113A discloses a formulation and preparation method of EPDM material for use in products resistant to dynamic fatigue, which can effectively overcome the above-mentioned problems. This scheme employs a non-peroxidative effective vulcanization system with sulfur as the sulfur carrier and TMTD. This type of system can release active sulfur at relatively low temperatures, forming a cross-linked network dominated by single / disulfide bonds with better thermal stability, theoretically possessing both good compression set and high vulcanization efficiency.

[0005] However, when EPDM materials are directly applied to high-end cooling pipelines and other applications, a large amount of small-molecule antioxidants must be added to the formulation to ensure sufficient heat resistance and aging life. These small-molecule antioxidants are prone to migration, volatilization, or extraction by the medium under high temperatures and long-term immersion in coolant. This not only leads to a gradual decline in protective efficacy due to the continuous decrease in their effective concentration, but also the precipitated components may enter the coolant, potentially affecting the long-term operational stability of the system. Summary of the Invention

[0006] The purpose of this invention is to provide a semi-high temperature vulcanized high pressure variable performance EPDM material and its preparation method. By chemically bonding the filler and the matrix to strengthen the interface and anchoring the antioxidant to inhibit migration, it can significantly reduce compression set while effectively solving the problems of weak interface bonding and easy extraction of antioxidant. It is suitable for automotive cooling pipes with stringent requirements for heat aging life, sealing performance and media resistance.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A semi-high temperature vulcanized high pressure variable EPDM material, comprising the following components by mass parts:

[0009] The mixture contains 157-350 parts of masterbatch rubber, 4-8 parts of GMA grafting antioxidant, 2.8-3.2 parts of accelerator CZ, 1.3-1.7 parts of accelerator DM-75, 1.3-1.7 parts of vulcanizing agent DTDM-80, and 1-1.4 parts of accelerator TMTD.

[0010] Furthermore, the specific preparation steps of the GMA-grafted antioxidant are as follows:

[0011] Glycidyl methacrylate and antioxidant 4020 were added to a reaction vessel and reacted at 85-95℃ and 200-300r / min for 2-4h. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain the GMA grafted antioxidant.

[0012] Based on the epoxy-amine ring-opening reaction mechanism, under heating and stirring conditions, the epoxy group in the glycidyl methacrylate molecule undergoes a nucleophilic ring-opening reaction with the two primary amine groups (-NH2) in the antioxidant 4020 molecule in sequence to generate secondary amine bonds (-NH-) and hydroxyl groups (-OH). The resulting product is a structure of two GMA molecules grafted onto each antioxidant molecule, and finally a reactive GMA-grafted antioxidant with methacrylate double bonds retained at the end is obtained.

[0013] Furthermore, the mass ratio of glycidyl methacrylate to antioxidant 4020 is 73-90:69-85.

[0014] Furthermore, the specific preparation steps of the masterbatch are as follows:

[0015] Preheat the internal mixer to 80-100℃, add EPDM, and masticate for 1.5-2.5 minutes. Then, add stearic acid, indirect zinc oxide, calcium oxide, microcrystalline wax, mold release agent 935P, Borra carbon black N550, Borra carbon black N774, modified silica, calcined kaolin, silane coupling agent vinyltrimethoxysilane, and polyethylene glycol-4000 in sequence, mix, and cool to obtain the masterbatch.

[0016] Furthermore, the mass ratio of EPDM, EVM, stearic acid, indirect zinc oxide, calcium oxide, microcrystalline wax, release agent 935P, Borra carbon black N550, Borra carbon black N774, modified silica, calcined kaolin, vinyltrimethoxysilane, and polyethylene glycol-4000 is 60-100:12-20:0.5-2:5-10:2-5:0.5-6:1.5-9:40-80:30-60:5-15:10-50:2-8:1-5.

[0017] Furthermore, the mixing conditions are: mixing at 90-120℃ for 10-14 minutes.

[0018] Furthermore, the specific preparation steps for modified silica are as follows:

[0019] Add silica and deionized water to a reaction vessel, and add γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide at 50-80℃ and 200-400 r / min. React for 30-60 min. After the reaction is completed, filter, wash and dry to obtain modified silica.

[0020] Based on the hydrolysis-condensation reaction mechanism of silane coupling agents, under heating and stirring, the methoxy groups of MPTMS and Si-69 are first hydrolyzed into active silanol groups, which then condense with the silanol groups on the surface of silica to form stable siloxane bonds, thereby chemically grafting thiol groups and polysulfide segments onto the surface of silica to obtain modified silica.

[0021] Furthermore, the ratio of silica, deionized water, γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide is 80-120g: 0.8-1.5L: 0.5-2g: 0.5-2g.

[0022] This invention also provides a method for preparing a semi-high temperature vulcanized high pressure variable EPDM material, comprising the following steps:

[0023] Step 1: Using the epoxy-amine ring-opening grafting method, glycidyl methacrylate and antioxidant 4020 are used as raw materials to prepare GMA grafted antioxidant.

[0024] Step 2: Modify silica by co-modifying γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide to obtain modified silica.

[0025] Step 3: After mixing the modified silica, GMA grafted antioxidant, rubber matrix, and vulcanizing components, the mixture is vulcanized to obtain a semi-high temperature vulcanized high pressure modified EPDM material.

[0026] Furthermore, the specific steps for semi-high temperature vulcanized high pressure variable EPDM materials are as follows:

[0027] The masterbatch is rolled on a two-roll mill, and GMA grafted antioxidant, TMTD, CZ, DM-75 and DTDM-80 are added in sequence. The mixture is passed through a thin mill 5-6 times and sheeted to obtain the final rubber. The final rubber is left to stand at room temperature for 4-8 hours and then vulcanized to obtain a semi-high temperature vulcanized high pressure modified EPDM material.

[0028] Furthermore, the vulcanization conditions are 160-170℃ and 10-15MPa for 5-10 minutes.

[0029] The beneficial effects of this invention are:

[0030] 1. The high-performance EPDM material provided by this invention employs a non-peroxygen sulfur carrier vulcanization system and converts antioxidant 4020 into a reactive antioxidant capable of participating in crosslinking through GMA grafting. Simultaneously, silane synergistic modification imparts surface-active reaction sites to the silica. This invention permanently anchors the antioxidant to the rubber network through chemical bonding and constructs a robust filler-matrix interface. While achieving low compression set, it significantly inhibits the migration and extraction paths of the antioxidant, ensuring long-term stability of protective performance and solving the problem of premature degradation of material properties.

[0031] 2. This invention involves reacting glycidyl methacrylate (GMA) with antioxidant 4020 to introduce a methacrylate double bond that can participate in vulcanization at the end of the antioxidant molecule. This double bond allows the antioxidant to form a chemical bond with the EPDM molecular chain during vulcanization, thereby anchoring it in the three-dimensional rubber network. This not only fundamentally solves the problem of traditional small molecule antioxidants easily migrating, volatilizing, or being extracted and failing under high temperature and long-term immersion in coolant, ensuring the long-lasting and stable protective performance, but also, as an additional active crosslinking point, helps to improve the uniformity and density of the crosslinking network, producing a synergistic enhancement effect on improving the modulus and mechanical strength of the material, providing a core guarantee for the material to achieve an ultra-long service life at 120℃.

[0032] 3. This invention synergistically modifies silica using the silane coupling agent MPTMS and Si-69, grafting active groups such as thiol groups and polysulfide segments onto its surface. First, the active groups on the modified silica surface can directly participate in the cross-linking reaction of the sulfur carrier system during the vulcanization process, significantly enhancing the filler-matrix interface bonding, thereby improving the material's tensile stress, tear resistance, and abrasion resistance. Second, this strengthened interface indirectly produces auxiliary effects: on the one hand, the dense cross-linked network increases the migration resistance of small molecule antioxidants, delaying their precipitation; on the other hand, the stable interface reduces dynamic heat generation and lowers the migration driving force. While helping to solve the problem of antioxidant migration, it also improves the fatigue resistance of the material.

[0033] 4. During the vulcanization process of this invention, the vinyl groups at the ends of the vinyltrimethoxysilane molecules co-crosslink with the unsaturated points of the EPDM molecular chain and copolymerize with the methacrylate double bonds of the GMA grafted antioxidant. Simultaneously, it crosslinks with the thiol groups on the surface of the modified silica through the sulfur carrier system. The introduced vinyl elastomer EVM serves as a polar blending matrix. Its vinyl molecular chain forms crosslinking bonds with the active sulfur released from the sulfur carrier, and forms a uniform blending system with EPDM and modified silica through mechanical shearing and weak polar interactions. EVM compensates for the shortcomings of EPDM in resisting ethylene glycol coolant to adapt to the working conditions of automotive cooling pipes. As an important component of the three-dimensional network, it constructs an integrated EPDM-EVM-filler-antioxidant network with EPDM, GMA grafted antioxidant, and modified silica.

[0034] This synergistic effect, based on chemical bonding and physical blending, helps to improve the spatial uniformity and structural integrity of the crosslinked network. The polar groups of EVM inhibit the extraction of antioxidants by the coolant, and the synergistic crosslinking of EVM and EPDM optimizes the elastic recovery ability of the network, thereby optimizing compression set. At the same time, the enhanced network stability helps to reduce dynamic heat generation and improve fatigue resistance, thus ensuring the durability and reliability of the product under long-term harsh working conditions. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1: A semi-high temperature vulcanized high pressure variable EPDM material, prepared by the following steps:

[0037] S1: 81.6g of glycidyl methacrylate (GMA) and 77.1g of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (antioxidant 4020) were added to a reaction vessel and reacted for 3 hours at a temperature of 90℃ and a rotation speed of 250r / min. After the reaction was completed, the product was cooled to room temperature, filtered, washed and vacuum dried to obtain the GMA grafted antioxidant.

[0038] S2: Add 100g of silica and 1L of deionized water to a reaction vessel, heat and stir. When the temperature reaches 65℃ and the stirring speed is 200-400r / min, add 1g of γ-mercaptopropyltrimethoxysilane (MPTMS) and 1g of bis-(γ-triethoxysilylpropyl)tetrasulfide (Si-69). React under these temperature and stirring speed conditions for 45min. After the reaction is completed, filter the mixture and wash it with deionized water. Finally, place the filter cake at 100℃ and vacuum dry for 12h to obtain modified silica.

[0039] S3: Preheat the internal mixer to 90°C, add 80g of highly unsaturated ethylene propylene diene monomer (EPDM) and 16g of ethylene-vinyl acetate elastomer (EVM), and masticate for 2 minutes. Then, add 1.25g of stearic acid, 7.5g of indirect zinc oxide, 3.5g of calcium oxide, 3.25g of microcrystalline wax, 5.25g of release agent 935P, 60g of Borra carbon black N550, 45g of Borra carbon black N774, 10g of modified silica, 30g of calcined kaolin, 5g of silane coupling agent vinyltrimethoxysilane, and 3g of polyethylene glycol-4000. Mix at 110°C for 12 minutes. After ensuring that the fillers and additives are evenly dispersed, discharge the rubber to obtain the masterbatch.

[0040] S4: Wrap 253g of masterbatch rubber around the rollers on an open mill (roller temperature 50℃), and add 6g of GMA graft antioxidant, 1.2g of accelerator TMTD, 3g of accelerator CZ, 1.5g of accelerator DM-75 and 1.5g of vulcanizing agent DTDM-80 in sequence. Pass through the mill 5 times to ensure that the vulcanizing agent is evenly dispersed. Then, sheet the mixture to obtain the final rubber. After letting the final rubber rest at room temperature for 6 hours, place it in a preheated mold and vulcanize it for 7.5 minutes in a flat vulcanizing machine at 165℃ and 12.5MPa. Then, demold the mixture to obtain a semi-high temperature vulcanized high pressure modified EPDM material.

[0041] Example 2: A semi-high temperature vulcanized high pressure variable EPDM material, prepared by the following steps:

[0042] S1: 73g of glycidyl methacrylate (GMA) and 69g of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (antioxidant 4020) were added to a reaction vessel and reacted at 85℃ and 200r / min for 2h. After the reaction was completed, the product was cooled to room temperature, filtered, washed and vacuum dried to obtain GMA grafted antioxidant.

[0043] S2: Add 80g of silica and 0.8L of deionized water to a reaction vessel, heat and stir. When the temperature reaches 50℃ and the stirring speed is 200r / min, add 0.5g of γ-mercaptopropyltrimethoxysilane (MPTMS) and 0.5g of bis-(γ-triethoxysilylpropyl)tetrasulfide (Si-69). React under these temperature and stirring speed conditions for 30min. After the reaction is complete, filter the mixture and wash it with deionized water. Finally, place the filter cake in a vacuum dryer at 100℃ for 10h to obtain modified silica.

[0044] S3: Preheat the internal mixer to 80°C, add 60g of highly unsaturated ethylene propylene diene monomer (EPDM) and 12g of ethylene-vinyl acetate elastomer (EVM), and masticate for 1.5 min. Then add 0.5g of stearic acid, 5g of indirect zinc oxide, 2g of calcium oxide, 0.5g of microcrystalline wax, 1.5g of release agent 935P, 40g of Borra carbon black N550, 30g of Borra carbon black N774, 5g of modified silica, 10g of calcined kaolin, 2g of silane coupling agent vinyltrimethoxysilane, and 1g of polyethylene glycol-4000. Mix at 90°C for 10 min to ensure that the fillers and additives are evenly dispersed. Discharge the mixture and cool to room temperature to obtain the masterbatch.

[0045] S4: Place 157g of masterbatch on a two-roll mill (roll temperature 40℃), add 4g of GMA graft antioxidant, 1g of accelerator TMTD, 2.8g of accelerator CZ, 1.3g of accelerator DM-75 and 1.3g of vulcanizing agent DTDM-80 in sequence, pass through the mill 5 times to ensure uniform dispersion of the vulcanizing agent, and then sheet to obtain a final compound with a thickness of 2mm. After the final compound is left to stand at room temperature for 4 hours, it is placed in a preheated mold and vulcanized for 5 minutes in a flat vulcanizing machine at 160℃ and 10MPa. After demolding, a semi-high temperature vulcanized high pressure modified EPDM material is obtained.

[0046] Example 3: A semi-high temperature vulcanized high pressure variable EPDM material, prepared by the following steps:

[0047] S1: 90g of glycidyl methacrylate (GMA) and 85g of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (antioxidant 4020) were added to a reaction vessel and reacted at 95℃ and 300r / min for 4h. After the reaction was completed, the product was cooled to room temperature, filtered, washed and vacuum dried to obtain GMA grafted antioxidant.

[0048] S2: Add 120g of silica and 1.5L of deionized water to a reaction vessel, heat and stir. When the temperature reaches 80℃ and the stirring speed is 400r / min, add 2g of γ-mercaptopropyltrimethoxysilane (MPTMS) and 2g of bis-(γ-triethoxysilylpropyl)tetrasulfide (Si-69). React under these temperature and stirring speed conditions for 60min. After the reaction is completed, filter the mixture and wash it with deionized water. Finally, place the filter cake in a vacuum dryer at 100℃ for 14h to obtain modified silica.

[0049] S3: Preheat the internal mixer to 100℃, add 100g of highly unsaturated ethylene propylene diene monomer (EPDM) and 20g of ethylene-vinyl acetate elastomer (EVM), and masticate for 2.5min. Then add 2g of stearic acid, 10g of indirect zinc oxide, 5g of calcium oxide, 6g of microcrystalline wax, 9g of release agent 935P, 80g of Borra carbon black N550, 60g of Borra carbon black N774, 15g of modified silica, 50g of calcined kaolin, 8g of silane coupling agent vinyltrimethoxysilane, and 5g of polyethylene glycol-4000. Mix at 120℃ for 14min. After ensuring that the fillers and additives are evenly dispersed, discharge the rubber to obtain the masterbatch.

[0050] S4: Place 350g of masterbatch on a two-roll mill (roll temperature 60℃), add 8g of GMA grafted antioxidant, 1.4g of accelerator TMTD, 3.2g of accelerator CZ, 1.7g of accelerator DM-75, and 1.7g of vulcanizing agent DTDM-80 in sequence, and pass through the mill 6 times to ensure that the vulcanizing agent is evenly dispersed. Then, sheet the mixture to obtain the final compound. After letting the final compound stand at room temperature for 8 hours, place it in a preheated mold and vulcanize it in a flat vulcanizing machine at 170℃ and 15MPa for 10 minutes. Then, demold the mixture to obtain a semi-high temperature vulcanized high pressure modified EPDM material.

[0051] The raw materials used in Examples 1-3 of this application are all commercially available. Specifically, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (98%, antioxidant 4020), silica (200nm, gas phase method), stearic acid (used for synthesis), tetramethylthiuram disulfide (TMTD, 97%), and polyethylene glycol-4000 were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; glycidyl methacrylate (purity ≥97%), γ-mercaptopropyltrimethoxysilane (purity ≥95%), and bis-(γ-triethoxy) The following materials were purchased from Shanghai Aladdin Biochemical Co., Ltd.: propyltrimonium sulfide (purity ≥90%), indirect zinc oxide (metal content ≥99%, powder, particle size <5μm), calcium oxide (purity ≥98%), and microcrystalline wax (melting point 77-82℃); high unsaturated ethylene propylene diene monomer (EPDM) rubber (4725P) from Dow Nordel; Brønsted carbon black N550 and Brønsted carbon black N774 from Qingdao Newsenk New Material Co., Ltd.; and ethylene-vinyl acetate elastomer (EVM, Levapren) from Arlanx. ® 400 HV) was purchased from Arlanxon High Performance Elastomers (Changzhou) Co., Ltd.; N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was purchased from Ningbo Woyu Technology Co., Ltd.; dibenzothiazole disulfide (DM-75, 75% active ingredient) was purchased from Ningbo Aikem New Material Co., Ltd.; 4,4-dimorpholine disulfide (DTDM-80) was purchased from Hangzhou Dingyan Chemical Co., Ltd.; calcined kaolin (AR) was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; and release agent 935P was purchased from Dongguan Yuebang Rubber Technology Co., Ltd.

[0052] Comparative Example 1: Based on Example 1, step S1, the preparation of GMA grafted antioxidant, and step S2, the preparation of modified silica were omitted. In step S4, the GMA grafted antioxidant was replaced with ordinary antioxidant 4020, and the modified silica was replaced with ordinary silica. All other steps and parameters remained unchanged, and EPDM material was obtained.

[0053] Comparative Example 2: Based on Example 1, step S1, the preparation of GMA grafting antioxidant, was omitted, and the GMA grafting antioxidant in step S4 was replaced with ordinary antioxidant 4020. All other steps and parameters remained unchanged, and EPDM material was obtained.

[0054] Comparative Example 3: Based on Example 1, step S2, the preparation of modified silica, was omitted, and the modified silica in step S4 was replaced with ordinary silica. All other steps and parameters remained unchanged to obtain EPDM material.

[0055] The performance of the EPDM materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The vulcanization characteristics were tested according to GB / T 16584-1996 standard. Unvulcanized final rubber samples were tested using a rotorless vulcanizer at 165℃ for 60 minutes and an oscillation frequency of 1.67 Hz. The torque was continuously measured over time to obtain the scorch time (t). 10 ) and positive vulcanization time (t) 90 The longer the scorch time, the better the operational safety of the rubber compound during processing, and the less likely it is to undergo early vulcanization. The shorter the positive vulcanization time, the higher the vulcanization efficiency.

[0056] Tensile properties were determined in accordance with GB / T 528-2009 standard. The vulcanized rubber sheet was made into a standard dumbbell-shaped specimen and stretched uniformly at a rate of 500 mm / min on a tensile testing machine until the specimen broke. The maximum force value and the elongation at break were recorded during the test, and the tensile strength and elongation at break were calculated respectively. The higher the tensile strength, the stronger the load-bearing capacity of the material, and the higher the elongation at break, the better the toughness of the material.

[0057] The hardness was measured according to GB / T 531.1-2008 standard using a Shore A hardness tester. Multiple points were selected on the flat and clean surface of the vulcanized rubber sample. The hardness tester indenter was pressed vertically into the sample, the instantaneous hardness value was read, and the average value was calculated. The result was expressed as Shore A hardness.

[0058] Compression set is a key indicator for measuring the elastic recovery ability of rubber seals after long-term pressure. The test is conducted in accordance with the GB / T 7759.1-2015 standard. The vulcanized cylindrical sample is placed in a special fixture and compressed to 25% of its original thickness in a constant temperature chamber at 125℃. After holding for 22 hours, the sample is removed and cooled at room temperature for 30 minutes. The residual deformation is then measured and the compression set rate is calculated. The lower the value, the better the elastic recovery performance of the material and the stronger the sealing retention ability under long-term pressure conditions.

[0059] The coolant resistance performance is referenced to GB / T 1690-2010 standard. The sample is immersed in a 50% ethylene glycol aqueous solution at 125℃ for 70h, and its volume change rate and mechanical property retention rate are tested. The smaller the change rate, the better the resistance to media extraction and swelling.

[0060] Table 1 Performance test results of EPDM materials

[0061] As shown in Table 1, the semi-high temperature vulcanized high pressure variable EPDM materials prepared in Examples 1-3 of this invention exhibit excellent overall performance. These materials utilize a non-peroxide effective vulcanization system with TMTD as the sulfur carrier as the core, and introduce GMA grafting to synergistically modify the antioxidant and silane-modified silica, constructing a stable "interface-crosslinking-protection" synergistic structure. Regarding the vulcanization process, the positive vulcanization time (t) of the examples is [not specified in the original text]. 90 The significant shortening of the curvature indicates that the system has extremely high vulcanization efficiency in the semi-high temperature range of 160-170℃, and can quickly form a cross-linked network dominated by single / disulfide bonds with better thermal stability. Thus, it can achieve heat aging resistance performance close to or even better than that of traditional peroxide systems at relatively low vulcanization temperatures. In terms of sealing reliability, the compression set rate of the embodiment is as low as 17%-20%, which proves that the material has a high elastic recovery ability after long-term pressure. This excellent high-pressure deformation performance, combined with its good coolant resistance (low volume expansion rate and high tensile strength retention rate), fully meets the stringent requirements of automotive cooling pipes for sealing durability.

[0062] Comparative Example 1 used ordinary antioxidant 4020 and unmodified silica to replace the key modifying components. The test results showed that the comparative example had a lower vulcanization efficiency, poorer mechanical properties, higher compression set, and significant performance degradation in the coolant resistance test. Its tensile strength retention rate was low, and its volume expansion was significant. This result indicates that GMA grafted antioxidant and modified silica play a key role in improving the long-term protective properties and interfacial bonding strength of the material.

[0063] Comparative Example 2 lacked only the GMA grafted antioxidant but retained the modified silica. Its performance was better than Comparative Example 1 but significantly worse than the Example. In particular, its coolant resistance was still not up to standard and its compression set was too high. This shows that even if the interface is enhanced, if the antioxidant is not chemically anchored, it will still migrate and be lost in the high-temperature coolant, resulting in the failure of long-term protection. At the same time, it also proves that a stable interface itself makes a positive contribution to limiting the migration of small molecules and reducing compression set, but it cannot achieve the best effect on its own.

[0064] Comparative Example 3 lacked modified silica but retained GMA grafted antioxidant. Its performance was between that of the Example and Comparative Examples 1-2. Its coolant resistance was significantly better than that of Comparative Examples 1 and 2, confirming the effectiveness of the GMA grafted antioxidant in preventing extraction. However, its compression set was still higher than that of the Example, and its original tensile strength was also lower. This proves that modified silica is the key to building a strong interface, significantly reducing compression set, and improving mechanical strength. Without modified silica, even if the antioxidant is fixed, the overall network rigidity and elastic recovery ability of the material are still insufficient, and the optimal sealing and mechanical properties cannot be achieved.

[0065] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A semi-high temperature vulcanized high pressure variable performance EPDM material, characterized in that, It includes the following components by mass parts: The mixture contains 157-350 parts of masterbatch, 4-8 parts of GMA grafting antioxidant, 2.8-3.2 parts of accelerator CZ, 1.3-1.7 parts of accelerator DM-75, 1.3-1.7 parts of vulcanizing agent DTDM-80, and 1-1.4 parts of accelerator TMTD. The GMA grafted antioxidant is prepared by using glycidyl methacrylate and antioxidant 4020 as raw materials via an epoxy-amine ring-opening grafting method.

2. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 1, characterized in that, The specific preparation steps of the GMA-grafted antioxidant are as follows: Glycidyl methacrylate and antioxidant 4020 were added to a reaction vessel and reacted at 85-95℃ and 200-300r / min for 2-4h. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain the GMA grafted antioxidant.

3. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 2, characterized in that, The mass ratio of glycidyl methacrylate to antioxidant 4020 is 73-90:69-85.

4. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 1, characterized in that, The specific preparation steps of the masterbatch are as follows: Preheat the internal mixer to 80-100℃, add EPDM and EVM, and masticate for 1.5-2.5 minutes. Then, add stearic acid, indirect zinc oxide, calcium oxide, microcrystalline wax, mold release agent 935P, Borra carbon black N550, Borra carbon black N774, modified silica, calcined kaolin, silane coupling agent vinyltrimethoxysilane, and polyethylene glycol-4000 in sequence, mix, and cool to obtain the masterbatch.

5. The semi-high temperature vulcanized high pressure variable EPDM material according to claim 4, characterized in that, The mass ratio of EPDM, EVM, stearic acid, indirect zinc oxide, calcium oxide, microcrystalline wax, release agent 935P, Borra carbon black N550, Borra carbon black N774, modified silica, calcined kaolin, vinyltrimethoxysilane, and polyethylene glycol-4000 is 60-100:12-20:0.5-2:5-10:2-5:0.5-6:1.5-9:40-80:30-60:5-15:10-50:2-8:1-5.

6. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 4, characterized in that, The mixing conditions are as follows: mix at 90-120℃ for 10-14 minutes.

7. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 4, characterized in that, The specific preparation steps for the modified silica are as follows: Add silica and deionized water to a reaction vessel, and add γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide at 50-80℃ and 200-400 r / min. React for 30-60 min. After the reaction is completed, filter, wash and dry to obtain modified silica.

8. The semi-high temperature vulcanized high pressure variable performance EPDM material according to claim 7, characterized in that, The ratio of the amount of silica, deionized water, γ-mercaptopropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide is 80-120g: 0.8-1.5L: 0.5-2g: 0.5-2g.

9. A method for preparing a semi-high temperature vulcanized high pressure variable EPDM material as described in any one of claims 1-8, characterized in that, The specific steps are as follows: The masterbatch rubber is rolled on a two-mill, and GMA grafted antioxidant, TMTD, CZ, DM-75 and DTDM-80 are added in sequence. The mixture is passed through 5-6 times and sheeted to obtain the final rubber. The final rubber is left at room temperature for 4-8 hours and then vulcanized to obtain a semi-high temperature vulcanized high pressure modified EPDM material. The EPDM material has a compression set of ≤20% at 125°C.

10. The method for preparing a semi-high temperature vulcanized high pressure variable EPDM material according to claim 9, characterized in that, The vulcanization conditions are 160-170℃ and 10-15MPa for 5-10 minutes.

Images