A ternary ethylene-propylene rubber composition, a method for preparing a finished product thereof, and an application thereof to an o-ring

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a ternary ethylene-propylene rubber material composition, a preparation method of a final rubber compound thereof and application of the final rubber compound in an O-shaped sealing ring. The ternary ethylene-propylene rubber material composition provided by the application comprises 100 parts of ternary ethylene-propylene rubber, 100-120 parts of carbon black, 10-20 parts of white carbon black, 1-4 parts of a coupling agent, 4-6 parts of zinc oxide, 1-3 parts of stearic acid, 1-5 parts of a plasticizer, 5-10 parts of a hardening resin, 3-6 parts of an antioxidant, 2-5 parts of a peroxide vulcanizing agent, 2-3 parts of an auxiliary cross-linking agent and 0.1-0.5 parts of an anti-scorching agent. The ternary ethylene-propylene rubber material composition provided by the application realizes synergistic improvement of various performances of the O-shaped sealing ring, such as high hardness, a wide temperature range, high pressure resistance, aging resistance and low compression permanent deformation, and meets the severe use conditions of an aviation-grade gas cylinder O-shaped sealing ring.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a EPDM rubber composition, a method for preparing the final compound, and its application in O-ring seals. Background Technology

[0002] The emergency escape slide gas cylinders on aircraft doors are crucial components of the airborne high-pressure gas supply system. Their accompanying O-rings, as key sealing elements, directly determine the reliability and safety of the cylinder seal. The aviation environment is extremely complex, alternating between the low temperatures at cruising altitudes above 10,000 meters and the ambient temperature inside the cabin. The gas cylinders endure pressures exceeding 20 MPa, placing extremely stringent and comprehensive performance requirements on the sealing materials: the material must possess extremely high hardness to resist structural deformation caused by high-pressure compression and meet the service conditions of the gas cylinder under high pressure; it must be able to adapt to the complex and wide temperature variations of high-altitude low temperatures and cabin environments during aviation; and it must also possess excellent anti-aging properties and low compression set to ensure that the O-ring's sealing performance does not deteriorate over long-term use, fundamentally eliminating safety hazards such as gas leaks.

[0003] Ethylene propylene diene monomer (EPDM) rubber is a preferred base material for aerospace-grade sealants due to its excellent weather resistance, aging resistance, and high and low temperature resistance. However, pure EPDM rubber has inherent problems such as low raw rubber strength, insufficient hardness, and poor processability, which cannot directly meet the high hardness and high pressure resistance requirements of aerospace-grade gas cylinder O-rings. Traditional EPDM sealants are mostly designed for civilian low-pressure, normal temperature, or general industrial scenarios, and generally suffer from low hardness (typical Shore A hardness is in the range of 50-80 degrees), high compression set, and poor high-pressure stability. Especially under pressure service conditions, high-temperature aging will exacerbate the irreversible deformation of EPDM gaskets. When the compression set exceeds 50% of the compression, the seal will lose its effective sealing function. Although low-temperature resistant EPDM sealing materials have been developed for the aerospace field in recent years, existing reports mostly focus on optimizing single properties, lacking a systematic solution for the synergistic improvement of multiple dimensions such as hardness, high pressure resistance, wide temperature range adaptability, aging resistance, and low compression set. Summary of the Invention

[0004] The purpose of this invention is to provide a EPDM rubber compound composition, a method for preparing the final compound, and its application in O-rings. The EPDM rubber compound composition provided by this invention achieves a synergistic improvement in various properties of O-rings, including high hardness, wide temperature range, high pressure resistance, aging resistance, and low compression set, meeting the stringent usage standards for aviation-grade gas cylinder O-rings.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a EPDM rubber composition comprising the following components in parts by weight: 100 parts EPDM rubber, 100-120 parts carbon black, 10-20 parts silica, 1-4 parts coupling agent, 4-6 parts zinc oxide, 1-3 parts stearic acid, 1-5 parts plasticizer, 5-10 parts hardening resin, 3-6 parts antioxidant, 2-5 parts peroxide vulcanizing agent, 2-3 parts crosslinking agent, and 0.1-0.5 parts scorching inhibitor; EPDM rubber in ML (1+4) 100℃ The Mooney viscosity under the specified conditions is ≥40 MU; the carbon black includes N330 and / or N375; the antioxidant includes p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD.

[0006] Preferably, the EPDM rubber is EPDM4045; the silica is precipitated silica; the coupling agent is silane coupling agent Si-69; and the plasticizer is paraffin oil or naphthenic oil.

[0007] Preferably, the hardening resin is a high-styrene resin, and the bound styrene content of the high-styrene resin is 55~70wt%.

[0008] Preferably, the mass ratio of the p-phenylenediamine antioxidant 4020 to the ketamine antioxidant RD is 2:1 to 3:1.

[0009] Preferably, the peroxide vulcanizing agent is peroxide DCP; the crosslinking agent is TAIC; and the scorching inhibitor is CTP.

[0010] This invention provides a method for preparing the final compound of the EPDM rubber composition described in the above technical solution, comprising the following steps: The EPDM rubber, zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant are mixed in one stage, and then discharged, pressed, cooled, and left to stand in sequence to obtain a one-stage compound. The first-stage compound, carbon black and plasticizer are mixed in two stages, and then discharged, pressed, cooled and left to stand in sequence to obtain the two-stage compound. The two-stage compound, peroxide vulcanizing agent, crosslinking agent and anti-scorching agent are mixed in three stages, and then discharged, pressed, cooled and stored in sequence to obtain the final compound of EPDM rubber composition.

[0011] This invention provides the application of the final compound of the EPDM rubber composition described in the above-described technical solution or the EPDM rubber composition prepared by the preparation method described in the above-described technical solution in the preparation of O-ring seals.

[0012] Preferably, the O-ring is an aviation-grade O-ring for gas cylinders.

[0013] This invention provides an O-ring seal, which is prepared by vulcanization of the final compound of the EPDM rubber composition described in the above technical solution.

[0014] Preferably, the vulcanization includes a first stage vulcanization and a second stage vulcanization performed sequentially; the pressure of the first stage vulcanization is 15~25MPa, the temperature is 160℃~180℃, and the time is 15~20min; the temperature of the second stage vulcanization is 120℃~150℃, and the time is 4~6h.

[0015] This invention provides a EPDM rubber composition comprising the following components in parts by weight: 100 parts EPDM rubber, 100-120 parts carbon black, 10-20 parts silica, 1-4 parts coupling agent, 4-6 parts zinc oxide, 1-3 parts stearic acid, 1-5 parts plasticizer, 5-10 parts hardening resin, 3-6 parts antioxidant, 2-5 parts peroxide vulcanizing agent, 2-3 parts co-crosslinking agent, and 0.1-0.5 parts scorching inhibitor; wherein the EPDM rubber is in ML... (1+4) 100℃ The Mooney viscosity under the specified conditions is ≥40 MU; the carbon black comprises N330 and / or N375; the antioxidant comprises p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD. Compared with the prior art, the present invention has the following beneficial effects: The EPDM rubber compound composition provided by this invention uses high Mooney viscosity EPDM rubber as its raw rubber system, combined with a high-structure carbon black (N330 and / or N375) and silica compound reinforcement system, and introduces a hardening resin to achieve a synergistic effect of high hardness and high pressure resistance. This results in a stable Shore A hardness of 90±2 degrees and a tensile strength ≥15MPa, effectively resisting extrusion deformation under high pressure (≥20MPa) service conditions. Simultaneously, the synergistic effect of silica and coupling agent ensures high hardness while also maintaining the rubber compound's elasticity and tear resistance (tear strength ≥25kN / m), avoiding the risk of brittle fracture of the sealing ring under high pressure.

[0016] This invention achieves performance retention across a wide temperature range by optimizing the formulation of the anti-aging system and using p-phenylenediamine antioxidant 4020 in synergy with ketone-amine antioxidant RD. The rubber compound maintains excellent performance stability across a wide temperature range, from -40℃ to 71℃. After aging in hot air at 71℃ for 24 hours, the tensile strength retention rate is ≥85%; after being placed at -40℃ for 24 hours, the elongation at break retention rate is ≥85%; and the brittle temperature is ≤-40℃, fully meeting the complex temperature requirements of alternating high-altitude low-temperature and cabin environments during aviation flight.

[0017] This invention employs a peroxide vulcanizing agent and a crosslinking agent to construct a highly efficient vulcanization system, generating stable CC crosslinking bonds. This imparts basic mechanical strength and structural stability to the O-ring, resulting in excellent long-term sealing reliability. Simultaneously, an anti-scorching agent effectively inhibits early vulcanization, extending the processing time of the rubber compound. Under the synergistic effect of the above components, the compression set of the rubber compound is ≤15% under conditions of 71℃×24h and 20MPa, significantly superior to traditional EPDM sealing compounds, ensuring that the sealing performance of the O-ring does not degrade under long-term high-pressure service.

[0018] This invention provides a method for preparing the final compound of the EPDM rubber compound composition described in the above technical solution. This invention employs a staged mixing process: first, EPDM rubber is mixed with zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant in a first-stage mixing process; then, it is mixed with carbon black and plasticizer in a second-stage mixing process; finally, it is mixed with peroxide vulcanizing agent, crosslinking agent, and scorching inhibitor in a low-temperature final mixing process. The stages are combined with a resting period, effectively adapting the reaction characteristics of each component of the rubber compound, avoiding problems such as premature decomposition of the vulcanizing agent or uneven dispersion of fillers during the high-temperature mixing stage, and fully ensuring the batch stability and reproducibility of the rubber compound performance.

[0019] In summary, the EPDM rubber composition provided by this invention is suitable for O-rings used in aerospace-grade gas cylinders. Using High Mooney EPDM as the main base material, the composition optimizes the overall performance of the rubber compound through the synergistic effect of its components by constructing a compounding and reinforcing system, optimizing the vulcanization system, and improving the anti-aging system. The rubber compound exhibits excellent properties such as high hardness (90), a wide temperature range of -40℃ to 71℃, and high pressure resistance (≥20MPa). It also possesses excellent anti-aging properties and low compression set characteristics, meeting the stringent standards for aerospace-grade gas cylinder O-rings. The accompanying staged temperature-controlled mixing method adapts to the reaction characteristics of each component, effectively ensuring the stability of the rubber compound's performance. Detailed Implementation

[0020] This invention provides a EPDM rubber composition comprising the following components in parts by weight: 100 parts EPDM rubber, 100-120 parts carbon black, 10-20 parts silica, 1-4 parts coupling agent, 4-6 parts zinc oxide, 1-3 parts stearic acid, 1-5 parts plasticizer, 5-10 parts hardening resin, 3-6 parts antioxidant, 2-5 parts peroxide vulcanizing agent, 2-3 parts crosslinking agent, and 0.1-0.5 parts scorching inhibitor; EPDM rubber in ML (1+4) 100℃ The Mooney viscosity under the specified conditions is ≥40 MU; the carbon black includes N330 and / or N375; the antioxidant includes p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD.

[0021] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well-known to those skilled in the art. Room temperature in this invention generally refers to a temperature between 15°C and 30°C, and is generally defined as 25°C.

[0022] The EPDM rubber composition provided by this invention comprises 100 parts by weight of EPDM rubber. In this invention, the EPDM rubber is in ML... (1+4) 100℃ The Mooney viscosity under the specified conditions is ≥40 MU, preferably 40~50 MU. In a specific embodiment of the present invention, the EPDM rubber is EPDM4045 (manufacturer: PetroChina Jilin Chemical, grade: J4045).

[0023] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 100-120 parts of carbon black, which may be 100, 110, or 120 parts in the examples. The carbon black includes N330 and / or N375, which may be N330 or N375 in the examples.

[0024] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 10-20 parts of silica, and in the examples, it can be 10, 15, or 20 parts. In the present invention, the silica is preferably precipitated silica.

[0025] Based on the mass fraction of the EPDM rubber, the EPDM rubber composition provided by this invention includes 1 to 4 parts of coupling agent, and in the examples, it can be 2, 3, or 4 parts. In this invention, the coupling agent is preferably the silane coupling agent Si-69.

[0026] Based on the mass fraction of the EPDM rubber, the EPDM rubber composition provided by the present invention includes 4 to 6 parts of zinc oxide, which may be 4.5, 5 or 5.5 parts in the examples.

[0027] Based on the mass fraction of the EPDM rubber, the EPDM rubber composition provided by the present invention includes 1 to 3 parts of stearic acid, which may be 1, 1.5 or 2 parts in the examples.

[0028] Based on the mass fraction of the EPDM rubber, the EPDM rubber composition provided by the present invention includes 1 to 5 parts of plasticizer, and in the examples, it can be 2, 3, or 4 parts. In the present invention, the plasticizer is preferably paraffin oil or naphthenic oil.

[0029] Based on the mass fraction of the EPDM rubber, the EPDM rubber composition provided by this invention includes 5-10 parts of hardening resin, which may be 5, 6, 7, 8, 9, or 10 parts in the embodiments. In this invention, the hardening resin is preferably a high-styrene resin. The bound styrene content of the high-styrene resin is preferably 55-70 wt%, more preferably 60-65 wt%.

[0030] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 3 to 6 parts of antioxidant, which may be 3, 3.5, 4, or 4.5 parts in the embodiments. In the present invention, the antioxidant preferably includes p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD. The mass ratio of p-phenylenediamine antioxidant 4020 to ketone amine antioxidant RD is preferably 2:1 to 3:1.

[0031] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 2 to 5 parts of peroxide vulcanizing agent, and in the examples, it can be 3, 4, or 5 parts. In the present invention, the peroxide vulcanizing agent is preferably DCP peroxide.

[0032] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 2-3 parts of a co-crosslinking agent, which may be 2, 2.5, or 3 parts in the examples. In the present invention, the co-crosslinking agent is preferably TAIC.

[0033] Based on the mass fraction of the EPDM rubber, the EPDM rubber compound composition provided by the present invention includes 0.1 to 0.5 parts of an anti-scorching agent, which may be 0.2, 0.3, or 0.4 parts in the embodiments. In the present invention, the anti-scorching agent is preferably CTP.

[0034] The EPDM rubber composition provided by this invention comprises: a raw rubber system using high Mooney EPDM 4045 as the main substrate, which has a stable molecular chain structure, excellent resistance to high and low temperatures and anti-aging properties, and high Mooney viscosity imparting high hardness and structural strength to the rubber compound, providing substrate support for high pressure resistance; a reinforcing system using high-structure carbon black (N330 / N375) and precipitated silica, with carbon black providing the main reinforcing effect to ensure high hardness and high pressure resistance of the rubber compound, and silica and coupling agent Si-69 enhancing the interfacial bonding force between the rubber compound and other components, the synergy of the two can ensure high hardness while also taking into account the elasticity and tear resistance of the rubber compound, avoiding brittleness under high pressure; and an anti-aging system using... The O-ring is formulated with p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD in a ratio of 2:1 to 3:1. Antioxidant 4020 effectively inhibits ozone, oxygen, and flexural cracking aging, while antioxidant RD enhances resistance to thermo-oxidative aging. The synergistic effect of these two agents allows the rubber compound to maintain excellent anti-aging properties within a wide temperature range of -40℃ to 71℃, extending the service life of the sealing ring. The vulcanization system uses peroxide DCP as the vulcanizing agent. DCP decomposes upon heating to generate highly reactive free radicals, which can abstract α-methylene hydrogen from the EPDM molecular chain, forming macromolecular free radicals that combine to generate stable CC crosslinking bonds, giving the O-ring its basic mechanical strength and structural stability. The co-crosslinking agent TAIC and DCP are also used. Free radical reactions can significantly increase crosslinking density and reduce main chain degradation; the anti-scorching agent CTP can effectively inhibit early vulcanization and extend the processing time of the rubber compound; the softening system: paraffin oil or naphthenic oil is selected as a plasticizer, which has good compatibility with EPDM rubber. Under the premise of ensuring high hardness of the rubber compound, it can effectively improve the processing fluidity of the rubber compound and avoid problems such as cracking and poor molding of the rubber compound during mixing and vulcanization.

[0035] This invention provides a method for preparing the final compound of the EPDM rubber composition described in the above technical solution, comprising the following steps: The EPDM rubber, zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant are mixed in one stage, and then discharged, pressed, cooled, and left to stand in sequence to obtain a one-stage compound. The first-stage compound, carbon black and plasticizer are mixed in two stages, and then discharged, pressed, cooled and left to stand in sequence to obtain the two-stage compound. The two-stage compound, peroxide vulcanizing agent, crosslinking agent and anti-scorching agent are mixed in three stages, and then discharged, pressed, cooled and stored in sequence to obtain the final compound of EPDM rubber composition.

[0036] This invention involves a primary mixing process of EPDM rubber, zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant, followed by sequential discharge, sheeting, cooling, and resting to obtain a primary compound. In this invention, the primary mixing is performed in an internal mixer. The preferred mixing speed is 30-50 r / min. Discharge is preferably performed when the temperature of the primary mixing reaches 110-120°C. The resulting compound is then sheeted using a sheeting machine. After sheeting, it is preferably cooled to room temperature by air cooling and then rested at room temperature for 12-24 hours.

[0037] After obtaining a primary compound, the present invention further involves a secondary compounding process with the primary compound, carbon black, and plasticizer, followed by sequential discharge, tableting, cooling, and resting to obtain a secondary compound. In this invention, the secondary compounding is performed in an internal mixer. The preferred mixing speed for the secondary compounding is 30-50 r / min. Discharge is preferably performed when the temperature of the secondary compounding reaches 120-130°C. The compound obtained from the secondary compounding is then tableted using a tableting machine. After tableting, it is preferably cooled to room temperature by air cooling and then rested at room temperature for a period of 12-24 hours.

[0038] After obtaining the two-stage compound, the present invention further involves a three-stage mixing process with the two-stage compound, peroxide vulcanizing agent, crosslinking agent, and anti-scorching agent. This is followed by sequential discharge, tableting, cooling, and resting to obtain the final EPDM rubber composition. In this invention, the three-stage mixing is performed in an internal mixer. The preferred mixing speed is 30-40 r / min. Discharge is preferably performed when the temperature reaches 80-100°C. The resulting compound is then tableted using a tableting machine. After tableting, it is preferably cooled to room temperature by air cooling and then rested at room temperature for 12-24 hours.

[0039] This invention provides the application of the final compound of the EPDM rubber composition described in the above-described technical solution or the EPDM rubber composition prepared by the preparation method described in the above-described technical solution in the preparation of O-rings. In this invention, the O-ring is preferably an O-ring for aerospace-grade gas cylinders.

[0040] This invention provides an O-ring seal, which is prepared by vulcanization of the final compound of the EPDM rubber composition described in the above technical solution.

[0041] In this invention, the vulcanization preferably includes a first stage vulcanization and a second stage vulcanization performed sequentially. The pressure of the first stage vulcanization is preferably 15-25 MPa, the temperature is preferably 160°C-180°C, and the time is preferably 15-20 min. The first stage vulcanization is preferably carried out in a flat vulcanizing machine. The second stage vulcanization is carried out in an oven. The temperature of the second stage vulcanization is preferably 120°C-150°C, and the time is preferably 4-6 h. After the second stage vulcanization is completed, the product obtained from the second stage vulcanization is preferably cooled to room temperature to obtain the O-ring seal.

[0042] The EPDM rubber composition for O-rings for aviation-grade gas cylinders provided by this invention has performance parameters that fully meet the requirements for use in aviation gas cylinders. The specific performance range is shown in Table 1.

[0043] Table 1 Performance parameters of the EPDM rubber composition provided by the present invention

[0044] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Examples 1-3 The formulations of the EPDM rubber compounds for O-rings used in aerospace-grade gas cylinders provided in Examples 1-3 are shown in Table 2, wherein the bound styrene content of the high-styrene resin is preferably 55-70 wt%. All components in Examples 1-3 are parts by weight. Table 2 Formulations of the EPDM rubber compositions provided in Examples 1-3

[0046] The preparation method of the final compound of the EPDM rubber composition provided in Examples 1-3 includes the following steps: Step 1, Preparation of primary compound: Ethylene propylene diene monomer (EPDM) rubber, zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant are put into an internal mixer and mixed at 40 r / min. When the mixing temperature reaches 110℃, the rubber is discharged. The mixture is then compressed into sheets by a sheeting machine and cooled to room temperature by air cooling. After standing at room temperature for 12 hours, the primary compound is obtained. Step 2, preparation of two-stage compound: The first-stage compound, carbon black and plasticizer are put into an internal mixer and mixed at a speed of 40 r / min. When the mixing temperature reaches 120℃, the compound is discharged, pressed into tablets by a tablet press, cooled to room temperature by air cooling, and left at room temperature for 12 hours to obtain the second-stage compound. Step 3, final rubber preparation: The two-stage compound rubber, peroxide vulcanizing agent, crosslinking agent and anti-scorching agent are put into the internal mixer and mixed at a low temperature of 30r / min. The mixing temperature is strictly controlled. When the temperature reaches 80℃, the rubber is discharged, pressed into tablets by a tablet press, cooled to room temperature by air cooling, and left to stand at room temperature for 12 hours to obtain the final rubber.

[0047] The above-mentioned final rubber compound was vulcanized and molded using a flat vulcanizing machine. The basic vulcanization process was vulcanization at 170℃ and 20MPa for 15 minutes. After vulcanization, it was vulcanized again in a 120℃ oven for 5 hours. After cooling to room temperature, an O-ring for aviation-grade gas cylinders was obtained.

[0048] The performance of the vulcanized EPDM rubber compound was tested according to national standards. The test standards were: GB / T531-2008 (hardness), GB / T528-2009 (tensile and breaking properties), GB / T529-2008 (tear strength), GB / T3512-2014 (hot air aging), GB / T7759-2015 (compression set), and GB / T1682-2014 (low temperature performance). The test results are shown in Table 3. Table 3 shows the performance test results of the EPDM rubber compositions provided in Examples 1-3.

[0049] The test results show that the EPDM rubber compounds prepared in Examples 1-3 of this invention meet and exceed the requirements for use of aviation-grade gas cylinder O-rings. The Shore A hardness is stable at 90±2, and the performance remains good under low temperature of -40℃ and high temperature of 71℃. The performance retention rate of the rubber compound after heat aging and low temperature placement is high, and the compression set is low. It completely solves the problems of low hardness, insufficient high pressure resistance and high compression set of traditional EPDM rubber compounds.

[0050] Comparative Example The formulations of the EPDM rubber compounds for the O-rings of aviation-grade gas cylinders provided in Comparative Examples 1-3 are shown in Table 4. All components in Comparative Examples 1-3 are parts by weight.

[0051] Table 4 Formulations of the EPDM rubber compositions provided in Comparative Examples 1-3

[0052] Comparative Example 1: Using EPDM rubber in ML (1+4) 100℃ The Mooney viscosity under the conditions was 30 MU, and the other conditions were the same as in Example 1.

[0053] Comparative Example 2: Based on Example 1, only the amount of high-styrene was reduced from 10 parts to 0 parts, while the other components and their amounts remained unchanged. This was used to verify the effect of high-styrene resin on the hardness properties of the rubber composition based on the carbon black / fumed silica reinforcing system.

[0054] Comparative Example 3: Based on Example 1, only the amount of carbon black N330 was reduced from 110 parts to 60 parts, while the other components and their amounts remained unchanged. This was used to verify the key role of the high amount of carbon black (100-120 parts) in achieving aerospace-grade high hardness of 90±2 degrees and high pressure resistance (≥20MPa).

[0055] The test results for the comparative examples are shown in Table 5: Table 5 shows the performance test results of the EPDM rubber compositions provided in Comparative Examples 1-3.

[0056] As can be seen from the above embodiments, the EPDM rubber composition for the aerospace-grade gas cylinder O-ring provided by the present invention, through formula optimization, takes into account the advantages of high hardness, high pressure resistance, wide temperature range, and low compression set. The prepared rubber compound has a Shore A hardness of 90, an applicable temperature of -40℃ to 71℃, and can withstand high pressure of over 20MPa. It also has excellent resistance to thermal oxygen and ozone aging, and a low compression set rate, which can fully meet the long-term sealing requirements of aerospace-grade gas cylinder O-rings under complex aerospace conditions.

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A EPDM rubber composition, characterized in that, The composition includes the following components in parts by weight: 100 parts EPDM rubber, 100-120 parts carbon black, 10-20 parts silica, 1-4 parts coupling agent, 4-6 parts zinc oxide, 1-3 parts stearic acid, 1-5 parts plasticizer, 5-10 parts hardening resin, 3-6 parts antioxidant, 2-5 parts peroxide vulcanizing agent, 2-3 parts crosslinking agent, and 0.1-0.5 parts scorching inhibitor. EPDM rubber in ML (1+4) 100℃ The Mooney viscosity under the specified conditions is ≥40 MU; the carbon black includes N330 and / or N375; the antioxidant includes p-phenylenediamine antioxidant 4020 and ketone amine antioxidant RD.

2. The EPDM rubber composition according to claim 1, characterized in that, The EPDM rubber is EPDM4045; the silica is precipitated silica; the coupling agent is silane coupling agent Si-69; and the plasticizer is paraffin oil or naphthenic oil.

3. The EPDM rubber composition according to claim 1, characterized in that, The hardening resin is a high-styrene resin, and the bound styrene content of the high-styrene resin is 55~70wt%.

4. The EPDM rubber composition according to claim 1, characterized in that, The mass ratio of p-phenylenediamine antioxidant 4020 to ketamine antioxidant RD is 2:1 to 3:

1.

5. The EPDM rubber composition according to claim 1, characterized in that, The peroxide vulcanizing agent is peroxide DCP; the crosslinking agent is TAIC; and the scorching inhibitor is CTP.

6. A method for preparing the final compound of the EPDM rubber composition according to any one of claims 1 to 5, characterized in that, Includes the following steps: The EPDM rubber, zinc oxide, stearic acid, silica, coupling agent, hardening resin, and antioxidant are mixed in one stage, and then discharged, pressed, cooled, and left to stand in sequence to obtain a one-stage compound. The first-stage compound, carbon black and plasticizer are mixed in two stages, and then discharged, pressed, cooled and left to stand in sequence to obtain the two-stage compound. The two-stage compound, peroxide vulcanizing agent, crosslinking agent and anti-scorching agent are mixed in three stages, and then discharged, pressed, cooled and stored in sequence to obtain the final compound of EPDM rubber composition.

7. The application of the final compound of the EPDM rubber composition according to any one of claims 1 to 5 or the EPDM rubber composition prepared by the preparation method according to claim 6 in the preparation of O-rings.

8. The application according to claim 7, characterized in that, The O-ring is an aviation-grade O-ring for gas cylinders.

9. An O-ring, characterized in that, It is prepared by vulcanization of the final compound of the EPDM rubber composition according to any one of claims 1 to 5.

10. The O-ring according to claim 9, characterized in that, The vulcanization process includes a first stage vulcanization and a second stage vulcanization in sequence; the pressure of the first stage vulcanization is 15~25MPa, the temperature is 160℃~180℃, and the time is 15~20min; the temperature of the second stage vulcanization is 120℃~150℃, and the time is 4~6h.

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