Oil-resistant fluorine-containing rubber sealing element and preparation method thereof

Abstract

The invention discloses an oil-resistant fluorine-containing rubber sealing element and a preparation method thereof, and belongs to the technical field of fluorine-containing rubber, the oil-resistant fluorine-containing rubber sealing element is prepared by the following steps: stirring Na-montmorillonite and graphene oxide, performing ultrasonic treatment to obtain graphene intercalated montmorillonite powder, performing hydrophobic modification on the graphene intercalated montmorillonite powder through hydrothermal loaded CeO2 / ZrO2 nanoparticles and a titanate coupling agent, and then adding an antioxidant to obtain the oil-resistant fluorine-containing rubber sealing element. The preparation method comprises the following steps: modifying composite montmorillonite to obtain modified composite montmorillonite, then premixing the modified composite montmorillonite and F26 type fluorine-containing rubber to obtain composite fluorine-containing rubber, mixing the composite fluorine-containing rubber with fumed silica, a plasticizer F-20, active magnesium oxide, calcium hydroxide and phenolic resin SP-1055, and performing two-step vulcanization to obtain the oil-resistant fluorine-containing rubber sealing element. High tensile strength, excellent normal-temperature and high-temperature oil resistance, high tensile strength thermal aging retention rate and good sealing durability of the sealing element are realized.

Description

Technical Field

[0001] This invention relates to the field of fluororubber technology, and in particular to an oil-resistant fluororubber seal and its preparation method. Background Technology

[0002] Fluorinated rubber seals are high-end elastic sealing elements made from special fluororubber with fluorine atoms bonded to the carbon atoms of the molecular main chain or side chain. They are made through vulcanization and molding. They are designed for extreme working conditions in precision chemical equipment such as aerospace, petrochemical, and automotive engines and fuel systems. They can be used as static and dynamic sealing components to effectively block media such as fuel, lubricating oil, acid and alkali solvents, strong oxidants, and corrosive gases, prevent system leakage and intrusion of external impurities, and maintain the airtightness of equipment cavities and pipelines. They are the core components that ensure the continuous and stable operation of equipment under harsh working conditions.

[0003] General-purpose rubbers such as natural rubber, nitrile rubber, and chloroprene rubber have inherent defects such as narrow temperature range, weak resistance to strong chemical corrosion, susceptibility to swelling and degradation by solvents and oxidants, insufficient resistance to ozone and oxidative aging, and poor vacuum resistance. These inherent defects make it difficult to meet the sealing reliability requirements of extreme working conditions such as high temperature, strong corrosion, high oxidation, flammable and explosive media, high vacuum, and high-speed friction. In contrast, fluorine atoms have extremely high electronegativity and extremely high CF chemical bond energy. Through structural modification, the performance boundaries of general-purpose rubbers can be broken, endowing seals with excellent core properties such as high temperature resistance, chemical corrosion resistance, and aging resistance, making it the preferred base material for sealing under extreme working conditions.

[0004] A search revealed that Chinese patent CN114874571A discloses a fluororubber material and its preparation method. The method uses low Mooney ternary fluororubber TECNOFLON P 457 as the matrix, combined with specific barium sulfate filler, methyl fluorosilicone oil plasticizer, calcium hydroxide and magnesium oxide composite acid absorber, organosilicone and octadecylamine composite processing aid, and a composite vulcanization system composed of triallyl cyanurate, triallyl isocyanurate and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. The final material is obtained through multi-stage mixing, resting, remelting and step vulcanization processes.

[0005] The above-mentioned solutions improve the flexural fatigue resistance, elongation at break, and low-temperature resistance of fluororubber materials. However, the barium sulfate filler used only forms a weak bond with the fluororubber matrix through physical coating, lacking an anti-aging system and an efficient oil-resistant barrier structure. Under complex working conditions such as high temperature, coexistence of ozone, and complex oil phases (such as high-temperature oil immersion and multi-media mixing), it is easy to cause oxidative degradation of rubber molecular chains and ozone-induced microcracks. Furthermore, oil phase molecules can easily penetrate through the gaps between fillers and interfacial voids, causing the material to swell. As a result, the seals made from this material will experience problems such as reduced elongation, decreased oil resistance, and shortened service life after thermal aging. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing fluororubber seals in oil media, especially high-temperature oil media, which have insufficient oil resistance, poor sealing durability, low mechanical property retention rate and easy degradation of sealing performance under the combined effect of thermal aging and high-temperature oil erosion, making it difficult to meet the long-term use requirements of harsh high-temperature oil sealing conditions. Therefore, this invention proposes an oil-resistant fluororubber seal and its preparation method.

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

[0008] A method for preparing an oil-resistant fluorinated rubber seal includes the following steps:

[0009] Step 1: Sodium-based montmorillonite and graphene oxide are repeatedly stirred and sonicated to allow graphene oxide sheets to be physically inserted between the montmorillonite layers, resulting in graphene-intercalated montmorillonite powder.

[0010] Step 2: The graphene-intercalated montmorillonite powder is hydrothermally loaded with CeO2 / ZrO2 nanoparticles and a titanate coupling agent for hydrophobic modification to obtain modified composite montmorillonite.

[0011] Step 3: Premix the modified composite montmorillonite and F26 type fluorinated rubber to obtain composite fluorinated rubber, then mix it with fumed silica, plasticizer F-20, active magnesium oxide, calcium hydroxide and phenolic resin SP-1055 and vulcanize it in two steps to obtain oil-resistant fluorinated rubber seals.

[0012] Furthermore, the specific preparation steps for graphene-intercalated montmorillonite powder are as follows:

[0013] Sodium-based montmorillonite and deionized water were added to a three-necked flask and magnetically stirred for 20-24 hours, followed by sonication for 2-4 hours to obtain a montmorillonite dispersion. Graphene oxide was then added, and the mixture was stirred for another 20-24 hours and sonicated for 2-4 hours. The dispersion was then transferred to a glass evaporating dish and dried in a forced-air drying process at 55-65°C until it reached a viscous state. The mixture was sonicated for 2-4 hours and then freeze-dried at -70°C to -60°C until it reached a constant weight. The powder was then ground and passed through a 100-mesh sieve to obtain graphene-intercalated montmorillonite powder.

[0014] Furthermore, the ratio of sodium-based montmorillonite, deionized water, and graphene oxide is 250-350g: 25-40L: 250-350g.

[0015] Furthermore, the specific preparation steps of the modified composite montmorillonite are as follows:

[0016] The composite montmorillonite was added to anhydrous ethanol and ultrasonically stirred for 10-20 minutes. Then, a titanate coupling agent was added, and the mixture was reacted at 80-90℃ for 20-30 minutes. The mixture was filtered, washed, and dried to obtain the modified composite montmorillonite.

[0017] Furthermore, the ratio of composite montmorillonite, anhydrous ethanol, and titanate coupling agent is 400-600g: 20-50L: 80-120g.

[0018] Furthermore, the titanate coupling agent is any one of titanate coupling agents HY-201, KR-12, and KR-TTS.

[0019] Furthermore, the specific preparation steps of composite montmorillonite are as follows:

[0020] Graphene-intercalated montmorillonite powder and deionized water were added to a round-bottom flask and stirred for 20-24 hours. Cerium nitrate and zirconium oxynitrate were then added, and the mixture was stirred magnetically for another 5-7 hours. The mixture was then transferred to a reaction vessel and kept at 150-160℃ for 20-24 hours. After cooling to room temperature, the mixture was centrifuged for 10-20 minutes, washed, dried to constant weight, and transferred to a muffle furnace. The mixture was calcined at 500-600℃ for 5-7 hours and then cooled to room temperature to obtain composite montmorillonite.

[0021] Furthermore, the ratio of graphene intercalated montmorillonite powder, deionized water, cerium nitrate, and zirconium oxynitrate is 400-600g: 20-50L: 24-36g: 38.4-46.2g.

[0022] Furthermore, the specific preparation steps for composite fluororubber are as follows:

[0023] F26 type fluorinated rubber with a fluorine content of about 65-70% was added to ethyl acetate and magnetically stirred for 2-4 hours. Then, modified composite montmorillonite was added and stirred for 20-30 minutes. The mixture was then sonicated for 30-40 minutes, heated to 80-90℃, and stirred for another 1-2 hours. The mixture was then filtered and vacuum dried to constant weight to obtain composite fluorinated rubber.

[0024] Furthermore, the ratio of F26 type fluorinated rubber, ethyl acetate and modified composite montmorillonite is 1000-1200g: 20-22L: 400-480g.

[0025] Furthermore, the F26 type fluorinated rubber is any one of the fluorinated rubbers F2601, F2602 and F2606.

[0026] Furthermore, the specific preparation steps for oil-resistant fluorinated rubber seals are as follows:

[0027] After adjusting the open mill to 50-70℃ and the initial roll gap to 3-4mm, add the composite fluorinated rubber. After the rubber accumulates around the rolls, add fumed silica and plasticizer F-20. Mix evenly, then add active magnesium oxide and calcium hydroxide, and continue mixing until uniform. Then add phenolic resin SP-1055. Subsequently, adjust the roll gap to 0.5-1mm, pass through the thin mill 4-6 times, and then adjust to 2-3mm for sheeting. Let the mixed rubber stand for 24-48 hours to mature before use.

[0028] Apply the release agent evenly to the inner wall of the mold cavity, let it stand for 1-3 minutes to allow the release agent to form a film naturally, then add the mixed rubber into the mold, vulcanize at 170-180℃ and 15-17MPa for 10-20 minutes, and vulcanize again at 200-210℃ for 10-12 hours. Let it cool naturally to room temperature, remove the part, trim the edges, and obtain the oil-resistant fluorinated rubber seal.

[0029] Furthermore, the mass ratio of the composite fluororubber, fumed silica, plasticizer F-20, active magnesium oxide, calcium hydroxide, and phenolic resin SP-1055 is 1000-1200:150-200:50-80:30-50:60-80:15-25.

[0030] The present invention has the following beneficial effects:

[0031] 1. This invention involves inserting graphene oxide and CeO2 / ZrO2 nanoparticles into sodium-based montmorillonite, then modifying it with a titanate coupling agent to form a filler. This filler is premixed with F26 type fluorinated rubber and then co-processed with fumed silica and phenolic resin SP-1055 through vulcanization to prepare an oil-resistant fluorinated rubber seal. The intercalation of graphene oxide into the silicate layers of sodium-based montmorillonite expands and stabilizes the montmorillonite sheets, increasing their interlayer spacing and specific surface area. This provides a dispersion carrier for the graphene oxide, inhibits agglomeration, and facilitates subsequent nanoparticle composite formation. Cerium nitrate and zirconium oxynitrate hydrolyze in aqueous solution, releasing hydrogen ions to form an acidic system. This dissolves some metal cations from the montmorillonite, providing uniform dispersion sites for the CeO2 / ZrO2 nanoparticles generated from their decomposition. These nanoparticles are dispersed between the graphene intercalation layers and on the surface of the montmorillonite, providing secondary rigid support for the layered structure of the montmorillonite and improving the thermal stability and oil barrier properties of the filler. The monoalkoxy group of the titanate coupling agent chemically bonds with the active hydroxyl groups on the surface of the composite montmorillonite, forming a stable Ti-OM bond. This covalently grafts the long organic chain onto the filler surface, achieving hydrophobic modification of the composite montmorillonite and improving the dispersibility and interfacial compatibility between the filler and the hydrophobic fluororubber matrix. Pre-fusing the modified composite montmorillonite with F26 type fluororubber, the long organic chain of the titanate coupling agent exhibits good compatibility with the fluororubber matrix and forms chain segment entanglement, creating a stable organic-inorganic interface. Simultaneously, the layered structure of the modified composite montmorillonite forms a dense, overlapping barrier effect within the fluororubber matrix, further enhancing mechanical reinforcement and oil media barrier effects.

[0032] Composite fluororubber is mixed with fumed silica, plasticizer F-20, active magnesium oxide, calcium hydroxide, and phenolic resin SP-1055 using a temperature-controlled, thin-pass, and curing process on an open mill. Fumed silica and modified composite montmorillonite form fillers for synergistic reinforcement. Active magnesium oxide, calcium hydroxide, and CeO2 / ZrO2 nanoparticles achieve thermal stability synergy. Phenolic resin and the vulcanization system form a cross-linked network synergistically. The mixture is cured and molded through a warm-pressing process of primary and secondary vulcanization. The components form a dense composite system through chemical bonding, physical adsorption, and chain segment entanglement. With precise control of various process parameters, the seal achieves high tensile strength, excellent oil resistance at room temperature and high temperature, high tensile strength heat aging retention rate, and good sealing durability.

[0033] 2. The graphene-intercalated montmorillonite powder of this invention expands the silicate sheets of sodium-based montmorillonite through graphene oxide sheets, increasing their interlayer spacing and specific surface area, thus providing stable support for the montmorillonite sheets and preventing collapse. The layered structure of montmorillonite provides a dispersion carrier for graphene oxide and inhibits agglomeration. This powder possesses the natural layered media barrier potential of sodium-based montmorillonite and the mechanical and barrier enhancement properties brought by the high specific surface area of ​​graphene oxide. The expanded interlayer spacing and increased specific surface area provide space and sites for the subsequent in-situ uniform dispersion of CeO2 / ZrO2 nanoparticles.

[0034] 3. In this invention, composite montmorillonite is used to insert CeO2 / ZrO2 nanoparticles generated in the reaction into the interlayer of graphene-intercalated montmorillonite, which further enhances the layered barrier properties of montmorillonite and strengthens the barrier effect of the filler on oil molecules. In addition, the surface of composite montmorillonite retains abundant active hydroxyl sites, which provides a reaction basis for the subsequent chemical bonding modification of titanate coupling agents.

[0035] 4. In this invention, the modified composite montmorillonite achieves the transformation of the filler from hydrophilic to hydrophobic through the chemical bonding of the titanate coupling agent with the active hydroxyl groups on the surface of the composite montmorillonite; at the same time, the organic long chains grafted onto the surface of the filler by the coupling agent provide a structural basis for the subsequent stable combination with the rubber matrix through chemical bonding and physical entanglement. Detailed Implementation

[0036] 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.

[0037] Example 1: A method for preparing an oil-resistant fluorinated rubber seal, comprising the following steps:

[0038] S1: Add 250g of sodium-based montmorillonite and 25L of deionized water to a three-necked flask, stir magnetically at 350rpm for 20h, and then sonicate at 250W and 40kHz for 2h to obtain a montmorillonite dispersion. Add 250g of graphene oxide, continue stirring for 20h, and sonicate for 2h to promote the insertion of graphene oxide sheets into the montmorillonite molecular layers. Transfer to a glass evaporating dish, dry in a forced-air dryer at 55℃ until viscous, sonicate for 2h, and freeze-dry at -70℃ to constant weight. Grind with an agate mortar and pass through a 100-mesh sieve to obtain graphene-intercalated montmorillonite powder.

[0039] Graphene oxide enters the interlayered structure of montmorillonite through physical intercalation, using its layered structure to expand and stabilize the silicate sheets of montmorillonite, thereby forming graphene-intercalated montmorillonite powder with larger interlayer spacing and higher specific surface area.

[0040] S2: Add 400g of graphene-intercalated montmorillonite powder and 20L of deionized water to a round-bottom flask, stir at 350rpm for 20h, then add 24g of cerium nitrate and 38.4g of zirconium oxynitrate, continue magnetic stirring for 5h, transfer to a reaction vessel, keep at 150℃ for 20h, cool to room temperature, centrifuge at 8000rpm for 10min, wash 3 times with deionized water, then wash once with anhydrous ethanol, dry to constant weight at 90℃, transfer to a muffle furnace, calcine at 500℃ for 5h, cool to room temperature, and obtain composite montmorillonite.

[0041] Cerium nitrate and zirconium oxynitrate, as salts of strong acid and weak base, undergo hydrolysis to release hydrogen ions after dissolving in aqueous solution, making the system acidic. Under hydrothermal conditions, some metal cations in montmorillonite (such as Al)... 3+ Mg 2+ (etc.) are dissolved, while CeO2 and ZrO2 nanoparticles generated by the decomposition of cerium nitrate and zirconium oxynitrate are uniformly dispersed and composited in the interlayer structure of montmorillonite.

[0042] S3: Add 400g of composite montmorillonite to 20L of anhydrous ethanol, ultrasonically stir at 400rpm for 10min, then add 80g of titanate coupling agent HY-201, react at 80℃ for 20min, filter, wash the product three times with deionized water, then wash once with anhydrous ethanol, and dry at 90℃ for 8h to obtain modified composite montmorillonite.

[0043] The monoalkoxy group in the titanate coupling agent molecule undergoes a chemical bonding reaction with the active hydroxyl group on the surface of montmorillonite to form a stable Ti-OM bond (M is the metal ion on the surface of montmorillonite). At the same time, an organic hydrophobic film is formed on the surface of montmorillonite, which improves the dispersibility and interfacial compatibility in organic systems.

[0044] S4: Add 1000g of F26-type fluorinated rubber F2601 with a fluorine content of about 65% to 20L of ethyl acetate, stir magnetically at 60℃ for 2h, then add 400g of modified composite montmorillonite, stir at 400rpm for 20min, sonicate at 250W and 40kHz for 30min, raise the temperature to 80℃, and continue stirring for 1h to allow the modified composite montmorillonite to be fully adsorbed at the fluorinated rubber interface. Filter to remove excess solvent, and vacuum dry the product at 90℃ for 10h to obtain the composite fluorinated rubber.

[0045] One end of the titanate coupling agent molecule forms a chemical bond with the hydroxyl groups on the surface of montmorillonite through a hydrolysis-condensation reaction, while the other end, through its long organic chain, exhibits good compatibility, physical adsorption, and chain segment entanglement with the fluororubber matrix, forming a stable organic-inorganic interface.

[0046] S5: After adjusting the open mill to 50℃ and the initial roll gap to 3mm, add 1000g of composite fluorinated rubber. After the rubber accumulates around the rolls, add 150g of fumed silica and 50g of plasticizer F-20. Mix evenly, then add 30g of active magnesium oxide and 60g of calcium hydroxide. Continue mixing until even, then add 15g of phenolic resin SP-1055. Adjust the roll gap to 0.5mm, pass through the mill 4 times, then adjust to 2mm for sheeting. Let the mixed rubber stand for 24 hours to mature. Apply the release agent evenly to the inner wall of the mold cavity. Let it stand for 1 minute to allow the release agent to form a film naturally. Add the mixed rubber to the mold and vulcanize at 170℃ and 15MPa for 10 minutes. Vulcanize again at 200℃ for 10 hours. Let it cool naturally to room temperature, remove the part, and trim the edges to obtain an oil-resistant fluorinated rubber seal.

[0047] Example 2: A method for preparing an oil-resistant fluorinated rubber seal, comprising the following steps:

[0048] S1: Add 300g of sodium-based montmorillonite and 32.5L of deionized water to a three-necked flask, stir magnetically at 400rpm for 22h, and then sonicate at 300W and 50kHz for 3h to obtain a montmorillonite dispersion. Add 300g of graphene oxide, continue stirring for 22h, and sonicate for 3h to promote the insertion of graphene oxide sheets into the montmorillonite molecular layers. Transfer to a glass evaporating dish, dry in a forced-air dryer at 60℃ until viscous, sonicate for 3h, and freeze-dry at -65℃ to constant weight. Grind with an agate mortar and pass through a 100-mesh sieve to obtain graphene-intercalated montmorillonite powder.

[0049] S2: Add 500g of graphene-intercalated montmorillonite powder and 35L of deionized water to a round-bottom flask, stir at 400rpm for 22h, then add 30g of cerium nitrate and 42.3g of zirconium oxynitrate, continue magnetic stirring for 6h, transfer to a reaction vessel, keep at 155℃ for 22h, cool to room temperature, centrifuge at 8500rpm for 15min, wash 4 times with deionized water, then wash 2 times with anhydrous ethanol, dry to constant weight at 95℃, transfer to a muffle furnace, calcine at 550℃ for 6h, cool to room temperature, and obtain composite montmorillonite.

[0050] S3: Add 500g of composite montmorillonite to 35L of anhydrous ethanol, ultrasonically stir at 500rpm for 15min, then add 100g of titanate coupling agent HY-201, react at 85℃ for 25min, filter, wash the product with deionized water 4 times, then wash with anhydrous ethanol 2 times, and dry at 95℃ for 10h to obtain modified composite montmorillonite.

[0051] S4: Add 1100g of F26 type fluorinated rubber F2602 with a fluorine content of about 67.5% to 21L of ethyl acetate, stir magnetically at 65℃ for 3h, then add 440g of modified composite montmorillonite, stir at 500rpm for 25min, sonicate at 300W and 50kHz for 35min, raise the temperature to 85℃, and continue stirring for 1.5h to allow the modified composite montmorillonite to be fully adsorbed at the fluorinated rubber interface. Filter to remove excess solvent, and vacuum dry the product at 95℃ for 11h to obtain composite fluorinated rubber.

[0052] S5: After adjusting the open mill to 60℃ and the initial roll gap to 3.5mm, add 1100g of composite fluorinated rubber. After the rubber accumulates around the rolls, add 175g of fumed silica and 65g of plasticizer F-20. Mix evenly, then add 40g of active magnesium oxide and 70g of calcium hydroxide. Continue mixing until even. Then add 20g of phenolic resin SP-1055. Adjust the roll gap to 0.75mm, pass through the mill 5 times, and then adjust to 2.5mm for sheeting. Let the mixed rubber stand for 36 hours to mature. Apply the release agent evenly to the inner wall of the mold cavity. Let it stand for 2 minutes to allow the release agent to form a film naturally. Then add the mixed rubber to the mold and vulcanize at 175℃ and 16MPa for 15 minutes. Vulcanize again at 205℃ for 11 hours. Let it cool naturally to room temperature, remove the part, and trim the edges to obtain an oil-resistant fluorinated rubber seal.

[0053] Example 3: A method for preparing an oil-resistant fluorinated rubber seal, comprising the following steps:

[0054] S1: Add 350g of sodium-based montmorillonite and 40L of deionized water to a three-necked flask, stir magnetically at 450rpm for 24h, and then sonicate at 350W and 60kHz for 4h to obtain a montmorillonite dispersion. Then add 350g of graphene oxide, continue stirring for 24h, and sonicate for 4h to promote the insertion of graphene oxide sheets into the montmorillonite molecular layers. Transfer to a glass evaporating dish, dry in a forced-air dryer at 65℃ until it becomes viscous, sonicate for 4h, and freeze-dry at -60℃ to constant weight. Grind with an agate mortar and pass through a 100-mesh sieve to obtain graphene-intercalated montmorillonite powder.

[0055] S2: Add 600g of graphene-intercalated montmorillonite powder and 50L of deionized water to a round-bottom flask, stir at 450rpm for 24h, then add 36g of cerium nitrate and 46.2g of zirconium oxynitrate, continue magnetic stirring for 7h, transfer to a reaction vessel, keep at 160℃ for 24h, cool to room temperature, centrifuge at 9000rpm for 20min, wash 5 times with deionized water, then wash 3 times with anhydrous ethanol, dry to constant weight at 100℃, transfer to a muffle furnace, calcine at 600℃ for 7h, cool to room temperature, and obtain composite montmorillonite.

[0056] S3: Add 600g of composite montmorillonite to 50L of anhydrous ethanol, ultrasonically stir at 600rpm for 20min, then add 120g of titanate coupling agent HY-201, react at 90℃ for 30min, filter, wash the product 5 times with deionized water, then wash 3 times with anhydrous ethanol, and dry at 100℃ for 12h to obtain modified composite montmorillonite.

[0057] S4: Add 1200g of F2606, a fluorine-containing rubber of type F26 with a fluorine content of about 70%, to 22L of ethyl acetate. Stir magnetically at 70℃ for 4h. Then add 480g of modified composite montmorillonite. Stir at 600rpm for 30min. Sonicate at 350W and 60kHz for 40min. Raise the temperature to 90℃ and continue stirring for 2h to allow the modified composite montmorillonite to be fully adsorbed at the fluororubber interface. Filter to remove excess solvent. Dry the product under vacuum at 100℃ for 12h to obtain the composite fluorine-containing rubber.

[0058] S5: After adjusting the open mill to 70℃ and the initial roll gap to 4mm, add 1200g of composite fluorinated rubber. After the rubber accumulates around the rolls, add 200g of fumed silica and 80g of plasticizer F-20. Mix evenly, then add 50g of active magnesium oxide and 80g of calcium hydroxide. Continue mixing until even, then add 25g of phenolic resin SP-1055. Adjust the roll gap to 1mm, pass through the mill 6 times, then adjust to 3mm for sheeting. Let the mixed rubber stand for 48 hours to mature. Apply the release agent evenly to the inner wall of the mold cavity. Let it stand for 3 minutes to allow the release agent to form a film naturally. Add the mixed rubber to the mold and vulcanize at 180℃ and 17MPa for 20 minutes. Vulcanize again at 210℃ for 12 hours. Let it cool naturally to room temperature, remove the part, and trim the edges to obtain an oil-resistant fluorinated rubber seal.

[0059] Example 4: The difference from Example 1 is that the titanate coupling agent (HY-201) in step S3 is replaced with titanate coupling agent KR-12, while the other steps remain unchanged, and an oil-resistant fluorinated rubber seal is prepared.

[0060] Example 5: The difference from Example 1 is that the titanate coupling agent (HY-201) in step S3 is replaced with the titanate coupling agent KR-TTS, while the other steps remain unchanged, and an oil-resistant fluorinated rubber seal is prepared.

[0061] In Examples 1-3, sodium montmorillonite was selected from Lingshou County Maozhuo Building Materials Co., Ltd., with a mesh size of 325; graphene oxide was selected from Beijing Meiston Technology Development Co., Ltd., model SY-GO-S; cerium nitrate was selected from Shandong Haoshun Chemical Co., Ltd., CAS number 10294-41-4, model HS-448; zirconium oxynitrate was selected from Hubei Xinghengye Technology Co., Ltd., CAS number 13826-66-9; titanate coupling agent HY-201 was selected from Hubei Chengfeng Chemical Co., Ltd., CAS number 67691-13-8; titanate coupling agent KR-12 was selected from Wuhan Xinzhongxin Chemical Technology Co., Ltd., model 102; and titanate coupling agent KR-TTS was selected from Jinan Rongzheng Chemical Co., Ltd., model [missing information]. 105; F26 type fluorinated rubber (F2601, F2602 and F2606) is selected from Dongguan Weicai Plastic Raw Materials Co., Ltd., brand name Sanaifu; ethyl acetate is selected from Shandong Junguan Chemical Co., Ltd., CAS number 141-78-6; fumed silica is selected from Lingshou County Malin Mineral Products Processing Plant, model name GS-01; plasticizer F-20 is selected from Ningbo Qihuida Materials Technology Co., Ltd., brand name Baoli; activated magnesium oxide is selected from Haicheng Chengxin Microfine Stone Powder Factory, CAS number 1309-48-4; calcium hydroxide is selected from Jinan Jinyu Chemical Co., Ltd., CAS number 1305-62-0; phenolic resin SP-1055 is selected from Shenzhen Yoshida Chemical Co., Ltd.; the remaining raw materials are all commercially available products.

[0062] Comparative Example 1: The difference from Example 1 is that step S1 is omitted, and the graphene intercalated montmorillonite powder in step S2 is replaced with commercially available sodium-based montmorillonite. The remaining steps remain unchanged, and an oil-resistant fluorinated rubber seal is prepared.

[0063] Comparative Example 2: The difference from Example 1 is that step S2 is omitted, and the composite montmorillonite in step S3 is replaced with graphene intercalated montmorillonite powder prepared in step S1. The remaining steps remain unchanged, and an oil-resistant fluorinated rubber seal is prepared.

[0064] Comparative Example 3: The difference from Example 1 is that step S3 is omitted, and the modified composite montmorillonite in step S4 is replaced with the composite montmorillonite prepared in step S2. The remaining steps remain unchanged, and an oil-resistant fluorinated rubber seal is prepared.

[0065] The following performance tests were performed on the oil-resistant fluororubber seals prepared in Examples 1-3 and Comparative Examples 1-3:

[0066] Tensile strength: Referring to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", ring-shaped specimens were prepared and tested at room temperature. The tensile strength and elongation at break of the specimens were determined at a tensile rate of 500 mm / min. Tensile strength is the ratio of the maximum tensile force at break to the initial cross-sectional area of ​​the specimen, and elongation at break is the percentage of the gauge length elongation at break to the initial gauge length. Higher tensile strength and greater elongation at break indicate superior mechanical properties (tensile strength and toughness) of the material.

[0067] Aging resistance: Referring to GB / T 3512-2014 "Accelerated Aging and Heat Resistance Test of Vulcanized Rubber or Thermoplastic Rubber in Hot Air", Method A (cabinet-type hot air aging chamber, 5 air changes per hour) was used, with the aging temperature set at 200℃ and the time at 72h. After aging, the tensile strength was tested according to GB / T 528-2009, and the change rate of tensile strength was calculated. The calculation formula is: Tensile strength retention rate = (Tensile strength after aging / Initial tensile strength) × 100% (value < 100%, the higher the retention rate, the better the thermal stability).

[0068] Room temperature oil resistance: Referring to GB / T 1690-2010 "Test method for resistance to liquids of vulcanized rubber or thermoplastic rubber", a cylindrical standard specimen was prepared, immersed in IRM 903 standard oil, soaked at room temperature for 70 hours, removed and the surface oil stains were wiped off, and the volume change rate (ΔV%) and mass change rate (Δm%) were tested.

[0069] The calculation formula is: Volume change rate = (Volume after immersion - Initial volume) / Initial volume × 100%; Mass change rate = (Mass after immersion - Initial mass) / Initial mass × 100%; The smaller the absolute value of the change rate, the better the material's anti-swelling / shrinkage performance (oil resistance) in room temperature oil medium.

[0070] High-temperature oil resistance: Referring to GB / T 1690-2010 "Test Method for Liquid Resistance of Vulcanized Rubber or Thermoplastic Rubber", the same sample and oil as for room-temperature oil resistance are used, and the sample is immersed at 121℃ for 70 h (or the time can be adjusted as needed); the volume change rate (ΔV%) and mass change rate (Δm%) are tested and calculated, using the same formula as for room-temperature oil resistance. The smaller the absolute value of the change rate, the better the material's oil resistance (resistance to hot oil erosion) in high-temperature oil media.

[0071] Sealing durability: Referring to GB / T 7759.1-2015 "Determination of compression set of vulcanized rubber or thermoplastic rubber - Part 1: Under normal and high temperature conditions", a standard cylindrical specimen was used, the compression rate was set to 25%, and it was compressed at (175±1)℃ for 22h. After unloading, it was placed for 30 min, the thickness of the specimen after recovery was measured, and the compression set rate was calculated.

[0072] The calculation formula is: permanent compression deformation rate = (initial compression amount - recovery compression amount) / initial compression amount × 100%; initial compression amount = initial thickness × (1 - compression rate), recovery compression amount = original thickness - recovery thickness; the smaller the deformation rate, the better the material's shape recovery ability (sealing durability) after long-term pressure, and the longer the sealing life.

[0073] The results are shown in Table 1:

[0074] Table 1. Test Results of Oil-Resistant Fluoropolymer Rubber Seals

[0075] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (MPa) 18.2 20.5 22.3 12.5 15.8 13.6 Elongation at break (%) 305 328 345 205 255 225 Tensile strength after aging (MPa) 14.8 16.8 18.5 8.1 10.3 9.0 Tensile strength retention rate (%) 81.3 81.9 83.0 64.8 65.2 66.2 Oil resistance at room temperature (ΔV%) 4.5 4.1 3.5 10.2 7.5 8.8 Oil resistance at room temperature (Δm%) 3.8 3.3 2.9 8.5 6.2 7.3 High-temperature oil resistance (121℃, ΔV%) 5.4 5.0 4.5 12.5 8.8 9.6 High-temperature oil resistance (121℃, Δm%) 4.8 4.3 3.8 10.8 7.5 8.2 Sealing durability (compression set %) 14.1 13.2 12.1 25.5 20.3 22.7

[0076] As can be seen from Table 1, the oil-resistant fluorinated rubber seals prepared in Examples 1-3 of this invention are superior to Comparative Examples 1-3 in terms of tensile strength, elongation at break, tensile strength retention rate (aging resistance), room temperature oil resistance, high temperature oil resistance, and sealing durability (compression set).

[0077] In Comparative Example 1, the tensile strength, elongation at break, and tensile strength retention rate (aging resistance) decreased significantly. This may be because the montmorillonite was not intercalated with graphene oxide and was directly replaced with ordinary sodium-based montmorillonite. Its interlayer spacing is small and its specific surface area is low, which makes it impossible to form a stable intercalated structure. It is prone to lamellar aggregation and weak interfacial bonding with the fluororubber matrix, resulting in a significant reduction in mechanical load-bearing capacity and thermal aging stability.

[0078] In Comparative Example 2, the room temperature oil resistance, high temperature oil resistance, and sealing durability (compression set rate) were significantly reduced, and the tensile strength retention rate (aging resistance) was also reduced. This may be because the cerium nitrate and zirconium oxynitrate hydrothermal composite and calcination were not carried out. The montmorillonite layers lacked uniform dispersion and high-temperature stable support of CeO2 and ZrO2 nanoparticles, resulting in insufficient heat resistance and resistance to oil media erosion. It could not effectively block the penetration of oil molecules. At the same time, the material structure was prone to relaxation at high temperatures, leading to a significant decrease in oil resistance and sealing durability.

[0079] In Comparative Example 3, the tensile strength, elongation at break, room temperature oil resistance, high temperature oil resistance, and sealing durability (compression set) all decreased significantly. This may be because the composite montmorillonite was not modified to be hydrophobic by using a titanate coupling agent. The filler surface remained hydrophilic, resulting in poor interfacial compatibility with the hydrophobic fluororubber matrix. This led to agglomeration, interfacial debonding, and stress concentration, making it impossible to form a stable and continuous organic-inorganic interface structure. Consequently, the mechanical properties, oil resistance, and sealing resilience of the material were reduced.

[0080] 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 variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an oil-resistant fluorinated rubber seal, characterized in that, Includes the following steps: Step 1: Sodium-based montmorillonite and graphene oxide are stirred and ultrasonically treated to intercalate the graphene oxide sheets and sodium-based montmorillonite into graphene-intercalated montmorillonite powder. Step 2: Graphene-intercalated montmorillonite powder is hydrothermally loaded with CeO2 / ZrO2 nanoparticles and then hydrophobically modified with a titanate coupling agent to obtain modified composite montmorillonite. Step 3: Premix the modified composite montmorillonite and F26 type fluorinated rubber to obtain composite fluorinated rubber, then mix it with fumed silica, plasticizer F-20, active magnesium oxide, calcium hydroxide and phenolic resin SP-1055 and vulcanize it in two steps to obtain oil-resistant fluorinated rubber seals.

2. The method for preparing an oil-resistant fluorinated rubber seal according to claim 1, characterized in that, The specific preparation steps of the graphene-intercalated montmorillonite powder are as follows: Sodium-based montmorillonite and deionized water were added to a three-necked flask and magnetically stirred for 20-24 hours, followed by sonication for 2-4 hours to obtain a montmorillonite dispersion. Graphene oxide was then added, and the mixture was stirred for another 20-24 hours and sonicated for 2-4 hours. The dispersion was then transferred to a glass evaporating dish and dried at 55-65°C with forced air until it reached a viscous state. The mixture was sonicated for 2-4 hours and then freeze-dried at -70°C to -60°C until constant weight was achieved. The powder was then ground and passed through a 100-mesh sieve to obtain graphene-intercalated montmorillonite powder.

3. The method for preparing an oil-resistant fluorinated rubber seal according to claim 2, characterized in that, The ratio of sodium-based montmorillonite, deionized water, and graphene oxide is 250-350g: 25-40L: 250-350g.

4. The method for preparing an oil-resistant fluorinated rubber seal according to claim 1, characterized in that, The specific preparation steps of the modified composite montmorillonite are as follows: The composite montmorillonite was added to anhydrous ethanol and ultrasonically stirred for 10-20 minutes. Then, a titanate coupling agent was added, and the mixture was reacted at 80-90℃ for 20-30 minutes. The mixture was filtered, washed, and dried to obtain the modified composite montmorillonite.

5. The method for preparing an oil-resistant fluorinated rubber seal according to claim 4, characterized in that, The ratio of the composite montmorillonite, anhydrous ethanol and titanate coupling agent is 400-600g: 20-50L: 80-120g; The titanate coupling agent is any one of titanate coupling agent HY-201, titanate coupling agent KR-12 and titanate coupling agent KR-TTS.

6. The method for preparing an oil-resistant fluorinated rubber seal according to claim 5, characterized in that, The specific preparation steps of the composite montmorillonite are as follows: Graphene-intercalated montmorillonite powder and deionized water were added to a round-bottom flask and stirred for 20-24 hours. Cerium nitrate and zirconium oxynitrate were then added, and the mixture was stirred magnetically for another 5-7 hours. The mixture was then transferred to a reaction vessel and kept at 150-160℃ for 20-24 hours. After cooling to room temperature, the mixture was centrifuged for 10-20 minutes, washed, dried to constant weight, and transferred to a muffle furnace. The mixture was calcined at 500-600℃ for 5-7 hours and then cooled to room temperature to obtain composite montmorillonite.

7. The method for preparing an oil-resistant fluorinated rubber seal according to claim 6, characterized in that, The ratio of graphene-intercalated montmorillonite powder, deionized water, cerium nitrate, and zirconium oxynitrate is 400-600g: 20-50L: 24-36g: 38.4-46.2g.

8. The method for preparing an oil-resistant fluorinated rubber seal according to claim 1, characterized in that, The specific preparation steps of the composite fluorinated rubber are as follows: F26 type fluorinated rubber with a fluorine content of about 65-70% was added to ethyl acetate and magnetically stirred for 2-4 hours. Then, modified composite montmorillonite was added and stirred for 20-30 minutes. The mixture was then sonicated for 30-40 minutes, heated to 80-90℃, and stirred for 1-2 hours. The mixture was then filtered and vacuum dried to constant weight to obtain composite fluorinated rubber. The ratio of the F26 type fluorinated rubber, ethyl acetate and modified composite montmorillonite is 1000-1200g: 20-22L: 400-480g.

9. The method for preparing an oil-resistant fluorinated rubber seal according to claim 1, characterized in that, The specific preparation steps of the oil-resistant fluorinated rubber seal are as follows: After adjusting the open mill to 50-70℃ and the initial roll gap to 3-4mm, add the composite fluorinated rubber. After the rubber accumulates around the rolls, add fumed silica and plasticizer F-20. Mix evenly, then add active magnesium oxide and calcium hydroxide, and continue mixing until uniform. Then add phenolic resin SP-1055. Subsequently, adjust the roll gap to 0.5-1mm, pass through the thin mill 4-6 times, and then adjust to 2-3mm for sheeting. Let the mixed rubber stand for 24-48 hours to mature before use. Apply the release agent evenly to the inner wall of the mold cavity, let it stand for 1-3 minutes to allow the release agent to form a film naturally, then add the rubber compound into the mold, vulcanize at 170-180℃ and 15-17MPa for 10-20 minutes, and then vulcanize again at 200-210℃ for 10-12 hours. Allow it to cool naturally to room temperature, remove the part, trim the edges, and you will get an oil-resistant fluorinated rubber seal. The mass ratio of the composite fluorinated rubber, fumed silica, plasticizer F-20, active magnesium oxide, calcium hydroxide and phenolic resin SP-1055 is 1000-1200:150-200:50-80:30-50:60-80:15-25.

10. An oil-resistant fluororubber seal, characterized in that, It is prepared by the method for preparing an oil-resistant fluorinated rubber seal according to any one of claims 1-9.