Wear-resistant and magnetorheological fluid-resistant low-pressure variable HNBR seal and preparation method thereof

Abstract

This application relates to the field of sealing technology, and in particular to a wear-resistant and magnetorheological fluid-resistant low-pressure variable HNBR sealing component and its preparation method. It is prepared from the following raw materials in parts by weight: 100 parts hydrogenated nitrile rubber; 55-65 parts carbon black; 8.5-11 parts polytetrafluoroethylene micro powder; 8-12 parts phenyl plasticizer; 4-6 parts peroxide; 4-10 parts crosslinking synergist; and processing aid ≤8.5 parts. The hydrogenated nitrile rubber is composed of hydrogenated nitrile rubber A and hydrogenated nitrile rubber B; the acrylonitrile content of the hydrogenated nitrile rubber A is less than a certain percentage of the acrylonitrile content; the crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinylsiloxane. The above solution achieves a synergistic improvement in the three core properties of the sealing component: wear resistance, magnetorheological fluid resistance, and low compression set, while also ensuring excellent low-temperature adaptability and thermal shock stability, meeting the long-cycle and complex operating conditions requirements of magnetorheological dampers for new energy vehicles.

Description

Technical Field

[0001] This application relates to the field of sealing technology, and in particular to a wear-resistant and magnetorheological fluid low-pressure variable HNBR sealing element and its preparation method. Background Technology

[0002] Hydrogenated nitrile butadiene rubber (HNBR) is widely used as a core sealing material in the automotive, aerospace, and other fields due to its excellent oil resistance, heat resistance, and dynamic mechanical properties. However, with the development of new energy vehicles towards high performance, especially the widespread adoption of magnetorheological dampers (MRDs) in high-end models, unprecedentedly stringent requirements have been placed on internal seals. The magnetorheological fluid filled inside the MRD is not ordinary oil, but a suspension containing high concentrations and high hardness carbonyl iron powder. This special medium, combined with the extreme dynamic conditions of the high-frequency reciprocating motion of the damper, poses a severe challenge to the long-term reliability of traditional HNBR seals.

[0003] When existing HNBR seals are applied to magnetorheological dampers in new energy vehicles, their failure mode is not caused by a single factor, but rather exhibits a vicious cycle that gradually intensifies under the long-term coupling effect of chemical corrosion and physical vibration. First, there is the degradation of the material's fundamental properties caused by chemical corrosion. The seals, immersed in magnetorheological fluid for extended periods, are not only affected by the swelling effect of the base oil but also by the chemical erosion from iron powder surface-active substances and additives. This erosion leads to the slow degradation of the HNBR matrix and damage to its molecular chain structure, specifically manifested as a significant decrease in key mechanical properties such as tensile strength, tensile stress at a given elongation, and tear strength. This weakening of the material itself creates a vulnerability for subsequent physical damage.

[0004] Ultimately, the aforementioned hidden dangers evolved into a complete failure of sealing performance and loss of function. When the material strength is insufficient to support the necessary contact stress, and wear damages the original interference fit structure, the seals will be unable to effectively compensate for the dynamic gaps generated by vibration. Especially in low-temperature environments, the movement of rubber molecular chain segments is frozen, the material hardens, rebound lags, and the permanent compression deformation increases sharply, making it impossible for the seals to adhere to the piston rod in time during a cold start of the vehicle. This series of chain reactions ultimately leads to leakage of expensive magnetorheological fluid, loss of control of shock absorber damping force, and complete loss of suspension system function, severely affecting the vehicle's safety, handling, and service life.

[0005] In summary, existing HNBR sealing materials struggle to maintain a balance of strength, wear resistance, and sealing performance under the combined effects of magnetorheological fluid corrosion and long-term dynamic vibration, especially throughout their entire lifespan in extremely cold regions, where current technologies exhibit significant shortcomings. Therefore, developing an HNBR seal capable of withstanding magnetorheological fluid erosion, resisting hard particle wear, and maintaining low compressive permanent deformation over a wide temperature range is of paramount practical significance for improving the reliability and durability of shock absorption systems in new energy vehicles. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal and its preparation method.

[0007] In the first aspect, a wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal is made from the following raw materials in parts by weight: 100 parts of hydrogenated nitrile butadiene rubber; 55-65 parts carbon black; 8.5-11 parts of polytetrafluoroethylene micro powder; 8-12 parts of phenyl plasticizer; Peroxide 4-6 parts; 4-10 parts of cross-linking synergist Processing aids ≤ 8.5 parts; The hydrogenated nitrile butadiene rubber is composed of hydrogenated nitrile butadiene rubber A and hydrogenated nitrile butadiene rubber B; the acrylonitrile content of hydrogenated nitrile butadiene rubber A is less than the acrylonitrile content of hydrogenated nitrile butadiene rubber B; the crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane.

[0008] Hydrogenated nitrile butadiene rubber (HNBR) composed of HNBR A and HNBR B offers precise compatibility and complementary properties. HNBR A, with its low acrylonitrile content, enhances the low-temperature flexibility and resilience of the compound, preventing micro-gaps in seals at low temperatures. HNBR B, with its high acrylonitrile content, improves the compound's resistance to oil, magnetorheological fluids, and mechanical strength. Adding 55-65 parts of carbon black improves the compound's tensile strength, tear strength, and abrasion resistance, reducing physical damage to seals. Adding 8.5-11 parts of polytetrafluoroethylene (PTFE) micropowder reduces the coefficient of friction and enhances barrier properties and corrosion resistance. Adding 8-12 parts of phenyl plasticizer improves processing fluidity, enhances resistance to high and low temperatures and chemical media, and further improves flexibility and dimensional stability. Adding 4-6 parts of peroxide ensures full cross-linking of the compound, improving strength, abrasion resistance, and dimensional stability. Adding ≤8.5 parts of processing aids optimizes processing performance and ensures the overall performance stability of the seals. The crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinylsiloxane. Triallyl isocyanurate significantly improves the crosslinking efficiency of peroxides, promoting the full crosslinking of the adhesive to form a stable three-dimensional network structure, effectively reducing compression set, enhancing low-temperature flexibility, and improving the low-temperature resistance of the seals. The fluorinated vinylsiloxane introduces fluorine groups, strengthening the seals' resistance to magnetorheological fluid corrosion, resisting abrasive wear, improving the lubrication performance of the adhesive, and reducing frictional losses. Together, they synergistically enhance the crosslinking effect, reduce compression set, optimize low-temperature performance, improve the seals' wear resistance and resistance to magnetorheological fluid corrosion, promote thorough and uniform mixing of all raw material components, avoid performance shortcomings caused by component separation, and ultimately achieve a synergistic improvement in the three core properties of the seals: wear resistance, magnetorheological fluid resistance, and low compression set.

[0009] Preferably, the weight ratio of hydrogenated nitrile rubber A to hydrogenated nitrile rubber B is 7:3.

[0010] Hydrogenated nitrile butadiene rubber (NBR) A and hydrogenated NBR B are compounded at a weight ratio of 7:3 as the base compound. This allows for precise matching and complementarity of performance, ensuring the sealing reliability of the seals in low-temperature environments while enhancing their resistance to magnetorheological fluid corrosion. This lays a solid foundation for subsequent improvements in wear resistance and low compression set. The low acrylonitrile content of hydrogenated NBR A improves the low-temperature flexibility and resilience of the compound, preventing micro-gaps caused by the seals failing to keep up with piston rod surface fluctuations during cold starts, thus avoiding magnetorheological fluid leakage. The high acrylonitrile content of hydrogenated NBR B significantly improves the compound's resistance to oil and magnetorheological fluid media, enhances its resistance to corrosion by magnetorheological fluids, inhibits swelling, softening, or hardening of the material caused by magnetorheological fluids, and simultaneously increases the mechanical strength of the compound, providing structural support for the long-term service of the seals.

[0011] Preferably, the acrylonitrile content of the hydrogenated nitrile butadiene rubber A is ≤35%; and the acrylonitrile content of the hydrogenated nitrile butadiene rubber B is ≥36%.

[0012] Strictly controlling the acrylonitrile content of hydrogenated nitrile butadiene rubber (NBR) A to no more than 35% and the acrylonitrile content of hydrogenated NBR B to no less than 36% allows for precise performance matching and complementarity. Low-acrylonitrile NBR A improves the low-temperature flexibility and resilience of the compound, effectively mitigating issues such as frozen rubber molecular chains, material hardening, and insufficient rebound speed in low-temperature environments. This prevents micro-gaps caused by the seals failing to keep up with piston rod surface fluctuations during cold starts, leading to magnetorheological fluid leakage. High-acrylonitrile NBR B significantly enhances the compound's resistance to oil and magnetorheological fluid media, strengthens its resistance to magnetorheological fluid corrosion, inhibits swelling, softening, or hardening caused by magnetorheological fluids, and improves the compound's mechanical strength, providing structural support for the long-term service of the seals. The combined use of these two materials ensures the sealing reliability of the seals in low-temperature environments and strengthens their resistance to magnetorheological fluid corrosion, laying a solid foundation for subsequent improvements in wear resistance and low compression set performance.

[0013] Preferably, the crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane in a weight ratio of 1:(0.1-0.3).

[0014] Triallyl isocyanurate can significantly improve the crosslinking efficiency of peroxides, promote the full crosslinking of the compound to form a stable three-dimensional network structure, effectively reduce the compression set of the compound, and enhance the low-temperature flexibility of the compound, further improving the low-temperature resistance of the seal. Fluorinated vinylsiloxane can introduce fluorine groups into the system, strengthen the seal's resistance to corrosion by magnetorheological fluids, resist the abrasive wear of hard particles in the magnetorheological fluid, and improve the lubrication performance of the compound, helping to reduce the frictional loss between the seal and the piston rod. When the two are combined, they can synergistically improve the crosslinking effect, further reduce compression set and optimize the low-temperature performance. They can also significantly improve the wear resistance and magnetorheological fluid corrosion resistance of the seal through the introduction of fluorine groups, while effectively promoting the full and uniform mixing of various raw material components (especially polytetrafluoroethylene micro powder and HNBR compound), avoiding performance shortcomings caused by component separation, and ultimately achieving a synergistic improvement in the three core properties of the seal: wear resistance, magnetorheological fluid resistance and low compression set.

[0015] Preferably, the fluorinated vinylsiloxane is composed of the following raw materials in weight percentages: Vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane 5-10%; 1,2,2-Trifluorovinyltriphenylsilane 7-15%; Vinyl cage-type silsesquioxane 10-20%; The balance is 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane.

[0016] The vinyl groups of vinyl-terminated trifluoropropylmethyl-dimethyl copolymer siloxane, 1,2,2-trifluorovinyltriphenylsilane, and vinyl cage-like silsesquioxane can undergo co-crosslinking reactions with the unsaturated bonds on the molecular chains of hydrogenated nitrile butadiene rubber and triallyl isocyanurate during peroxide vulcanization, enhancing the stability of the crosslinking system. Vinyl cage-like silsesquioxane can improve the mechanical strength, abrasion resistance, and dimensional stability of rubber compounds, enhancing the ability of seals to resist long-term vibration and abrasion from hard particles in magnetorheological fluids. The fluorine groups of 1,2,2-trifluorovinyltriphenylsilane provide reinforcement. The formulation enhances the resistance to magnetorheological fluid corrosion and abrasion. The phenyl groups improve the rigidity and abrasion resistance of the rubber compound, reducing physical damage to the seal lip. 1,3-Bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane strengthens the bond between fillers and hydrogenated nitrile rubber, reduces compression set, blocks magnetorheological fluid penetration, and improves the compound's resistance to magnetorheological fluid corrosion. Vinyl-terminated trifluoropropylmethyl-dimethyl copolymer siloxane improves the seal's abrasion resistance, strengthens its resistance to magnetorheological fluid media, and reduces the compression set rate of the seal under high temperature and pressure. Overall, the crosslinking synergist formed by the fluorinated vinyl siloxane and triallyl isocyanurate in this formulation, in conjunction with other components, improves the seal's abrasion resistance, magnetorheological fluid resistance, and low compression set, mitigating the decline in strength, abrasion resistance, and sealing performance under complex operating conditions, and enhancing low-temperature tolerance and thermal shock adaptability.

[0017] Preferably, the vinyl cage-type silsesquioxane is acryloyloxypropyl-glycidyloxypropyl cage-type polysilsesquioxane / trinorbornene-isobutyl cage-type silsesquioxane.

[0018] Acryloyloxypropyl-glycidyloxypropyl cage-type polysilsesquioxane acts as a "nano-rigid node" and a "dual reaction anchor," while trinorbornene isobutyl cage-type silsesquioxane acts as an "ultra-highly active initiator / crosslinking center" and a "stress dissipation unit." Utilizing the high tensile properties of norbornene, it rapidly captures free radicals in the early stages of vulcanization to form dense crosslinking points. Its unique bicyclic structure can absorb impact energy. The binary compound of these two components, in synergy with other fluorinated / silicone crosslinking synergists, constructs a multifunctional hybrid crosslinking network in the HNBR matrix. This enables the seal to achieve a synergistic leap in four core properties: wear resistance, resistance to magnetorheological fluid corrosion, low-temperature resistance, and resistance to compression set. It fundamentally solves the problems of existing seals in new energy vehicle shock absorbers being subject to long-term magnetorheological fluid corrosion, high-frequency vibration wear, low-temperature start-up failure, and insufficient adaptability to thermal shock, significantly improving the service life and reliability of the product in new energy vehicle parts.

[0019] Preferably, the phenyl plasticizer is trioctyl trimellitate; the peroxide is DCP.

[0020] Trioctyl trimellitate, as a phenyl plasticizer, not only plays a conventional plasticizing role, improving the processing fluidity of the rubber compound and ensuring uniform mixing of various raw material components, but also enhances the high and low temperature resistance and chemical media resistance of the rubber compound by its benzene ring groups in its molecular structure. In particular, it enhances the rubber compound's resistance to swelling by magnetorheological fluids, reduces the impact of temperature fluctuations on the rubber compound's performance, and also helps to improve the rubber compound's flexibility and dimensional stability. DCP, as a peroxide, enables the composite HNBR rubber compound to undergo a full cross-linking reaction, forming a cross-linked network with a stable structure and excellent mechanical properties, further improving the rubber compound's strength, wear resistance, and dimensional stability, and enhancing the seals' ability to resist long-term vibration and magnetorheological fluid erosion.

[0021] Preferably, the processing aid is one or more of zinc oxide, stearic acid, and antioxidants.

[0022] Processing aids are one or more of zinc oxide, stearic acid, and antioxidants, which can optimize the mixing and molding performance of rubber compounds, reduce defects such as bubbles and delamination during processing, ensure uniform molding quality of seals, avoid weak points in the seals caused by processing defects, and ensure the overall stability of the seal performance.

[0023] Preferably, the antioxidant is antioxidant ZMTI and / or antioxidant 445.

[0024] Using antioxidants ZMTI and / or antioxidant 445 as antioxidants, in combination with other raw material components, can improve the anti-aging performance of seals, avoid the performance degradation of seals due to aging, and ensure the stability and reliability of seals during long-term use. Combined with other raw material components, it can achieve a synergistic improvement in the three core properties of seals: wear resistance, resistance to magnetorheological fluid, and low compression set, thus meeting the long-term and complex operating conditions requirements of magnetorheological dampers for new energy vehicles.

[0025] Secondly, a method for preparing a wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal is obtained by the following method: HNBR styropolymerization: Hydrogenated nitrile butadiene rubber A and hydrogenated nitrile butadiene rubber B are mixed and the roller temperature is controlled at 40-50℃. The mixture is then subjected to thin-pass plasticizing 2-3 times to soften it and reduce the Mooney viscosity, thus obtaining the mixed hydrogenated nitrile butadiene rubber. Additive premixing: Polytetrafluoroethylene (PTFE) micro powder, carbon black, and processing aids are mixed evenly to obtain mixture A, which is then set aside. The phenyl plasticizer is heated to 40-50℃ to obtain a pretreated phenyl plasticizer for later use. First stage of mixing: The mixed hydrogenated nitrile rubber is kneaded under pressure, and then phenyl plasticizer and mixture A are added in batches. After being mixed evenly, the rubber is discharged, milled, and cooled to obtain mixture B. Second stage of mixing: Mixture B is intensively mixed, then peroxide and crosslinking synergist are added. The intensive mixing temperature shall not exceed 90°C. Mix evenly to obtain compound C. Preforming: The mixed rubber compound C is extruded to form a preform blank, shaped by a mold, and then subjected to compression molding and vulcanization. The first stage of vulcanization is carried out at 160℃-175℃, with a pressure of 10-15MPa and a vulcanization time of 8-10 minutes to produce the preform. The preformed part undergoes a second stage of vulcanization and is baked at 145-155℃ to obtain the HNBR seal.

[0026] In the HNBR plasticizing stage, the roll temperature is controlled at 40-50℃ and thin-pass plasticizing is performed 2-3 times to soften hydrogenated nitrile rubber A and hydrogenated nitrile rubber B and reduce Mooney viscosity, facilitating subsequent processing. In the additive premixing stage, polytetrafluoroethylene powder, carbon black, and processing aids are mixed evenly to obtain mixture A. The phenyl plasticizer is heated to 40-50℃ to obtain pretreated phenyl plasticizer, which helps to evenly disperse the raw materials. In the first stage of mixing, the mixed hydrogenated nitrile rubber is kneaded under pressure and then the phenyl plasticizer and mixture A are added in batches to ensure thorough mixing of the components. In the second stage of mixing, mixture B is intensively kneaded and peroxide and crosslinking synergist are added. Furthermore, the mixing temperature does not exceed 90℃, which can promote the cross-linking reaction while avoiding excessive temperature affecting performance. In the pre-forming stage, through extrusion, mold shaping, compression molding vulcanization, and second-stage vulcanization, the seal can be formed and achieve the required performance. The final HNBR seal has excellent wear resistance, magnetorheological fluid corrosion resistance, and low compression set. It can effectively resist the abrasive wear of hard particles in the magnetorheological fluid, the chemical erosion of the magnetorheological fluid medium, and the problem of decreased strength and sealing performance caused by long-term vibration. At the same time, it has high low-temperature resistance and thermal shock stability, which can adapt to the complex working conditions of magnetorheological dampers for new energy vehicles.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. The base compound is composed of hydrogenated nitrile butadiene rubber (NBR) A and hydrogenated NBR B. These two materials complement each other, precisely adapting to different performance requirements. The low acrylonitrile content of hydrogenated NBR A effectively enhances the low-temperature flexibility and resilience of the compound, preventing the rubber molecular chains from freezing and the material from hardening in low-temperature environments. This allows the seals to quickly follow the surface fluctuations of the piston rod during vehicle cold starts, preventing magnetorheological fluid leakage. The high acrylonitrile content of hydrogenated NBR B significantly improves the compound's resistance to oil and magnetorheological fluid media, as well as its mechanical strength. It inhibits material swelling, softening, or hardening caused by magnetorheological fluids, providing robust structural support for the long-term stable service of the seals. 2. 8.5-11 parts by weight of polytetrafluoroethylene (PTFE) micropowder possesses excellent self-lubricating properties, wear resistance, and chemical stability. It forms a lubricating protective film on the surface of the seal, greatly reducing the coefficient of friction between the seal and the piston rod, and reducing abrasive wear. Simultaneously, it enhances the barrier properties and corrosion resistance of the adhesive to magnetorheological fluids, preventing the fluid from penetrating and damaging the internal structure of the adhesive. 8-12 parts by weight of phenyl plasticizer not only improves the processing fluidity of the adhesive, ensuring uniform mixing of all raw materials, but its phenyl ring groups also enhance the adhesive's resistance to high and low temperatures and its resistance to chemical media, reducing the impact of temperature fluctuations on the adhesive's properties, and further improving flexibility and dimensional stability, preventing the seal from deforming due to long-term vibration and temperature changes. 3. The crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinylsiloxane, which work together to achieve synergistic performance gains. Triallyl isocyanurate enhances the crosslinking efficiency of peroxides, promotes full crosslinking of the rubber compound to form a stable three-dimensional network structure, reduces compression set, and enhances low-temperature flexibility. Fluorinated vinylsiloxane introduces fluorine groups, strengthening the seal's resistance to magnetorheological fluid corrosion and wear, improving the lubrication performance of the rubber compound, and reducing frictional wear between the seal and the piston rod. The crosslinking synergistic effect with polytetrafluoroethylene micropowder further enhances wear resistance and magnetorheological fluid resistance; combined with phenyl plasticizer, it enhances the stability of the rubber compound at different temperatures; and working together with hydrogenated nitrile rubber, it optimizes the overall performance of the rubber compound, reduces compression set, ensures that the seal maintains reliable sealing force under complex working conditions, and comprehensively improves the overall performance of the seal. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments.

[0029] The source of raw materials; Hydrogenated nitrile butadiene rubber A: Therban® LT1707 (hydrogenated nitrile butadiene rubber); Hydrogenated nitrile butadiene rubber B: Therban® LT1757 (hydrogenated nitrile butadiene rubber); Carbon black N330; Polytetrafluoroethylene micro powder: Polymist®-F5A; The molecular structure of vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane is as follows: ; The molecular structure of 1,2,2-trifluorovinyltriphenylsilane is as follows: ; Acryloyloxypropyl-glycidyl oxypropyl cage-type polysilsesquioxane: Ecotion® POSS4029; The molecular structure of tri-norbornenylisobutyl cage-like silsesquioxane is as follows: ; The molecular structure of 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane is as follows: .

[0030] Example Example 1 A wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal is obtained by the following method: HNBR styropolymerization: Hydrogenated nitrile rubber A and hydrogenated nitrile rubber B are mixed in an internal mixer at a weight ratio of 70:30.

[0031] The surface temperature of the rollers in the mixing equipment is controlled between 40°C and 50°C.

[0032] The mixed rubber compound is subjected to thin-pass plasticizing three times. Thin-pass plasticizing refers to adjusting the roller gap to the minimum of 0.5 mm, allowing the rubber compound to pass through the roller gap, softening it under shear force, reducing Mooney viscosity, and initially mixing the two rubbers evenly to obtain a mixed hydrogenated nitrile rubber.

[0033] Additive premixing: Weigh out the polytetrafluoroethylene (PTFE) micro powder, carbon black, and processing aids and mix them evenly on a high-speed mixer at room temperature (speed 300 r / min, time 10 min) to ensure that each solid component is fully dispersed, and obtain mixture A for later use.

[0034] The phenyl plasticizer is heated to 50°C to reduce its viscosity, making it easier for the rubber to absorb quickly during the subsequent mixing process, thus obtaining a pretreated phenyl plasticizer for later use.

[0035] First stage of mixing: The mixed hydrogenated nitrile rubber is put into a mixer and kneaded under pressure for 3 minutes to soften it by wrapping it around the rollers.

[0036] During the mixing process, pretreated phenyl plasticizers are added in batches to fully impregnate the rubber macromolecular chains.

[0037] Add mixture A and continue pressurized mixing to ensure all powder and liquid components are evenly mixed with the rubber matrix. The total mixing time is usually controlled within 10 minutes, and the discharge temperature is controlled below 100℃ to prevent scorching.

[0038] After degassing, the rubber compound is further processed, rolled, and sheeted on an open mill, and then forced to cool to room temperature to obtain mixture B.

[0039] Second stage of mixing: Mixture B is put back into the internal mixer, and the temperature is controlled below 70°C.

[0040] Add peroxide and cross-linking synergist.

[0041] Mixing should be carried out under low-temperature conditions (the temperature of the mixing chamber must be strictly controlled not to exceed 90℃) to prevent premature decomposition of peroxides during the mixing process. The mixing time should be 4 minutes, allowing the solid additives to be completely dispersed without localized overheating.

[0042] After debinding, the mixture is passed through a two-roll mill again and sheeted to obtain the final compound C.

[0043] Preforming and vulcanization: The compound C is preformed using an extruder or a tablet press to form a preform of a specific shape.

[0044] The preform is placed in the mold cavity and subjected to compression molding vulcanization (one-stage vulcanization). The vulcanization conditions are: temperature 175℃, pressure 15MPa, and vulcanization time 600s. This stage allows the rubber compound to set within the mold and complete most of the cross-linking reaction, resulting in the preform.

[0045] The demolded preforms are placed in an oven for two-stage vulcanization (post-treatment vulcanization). They are baked at 150°C for 2 hours under normal pressure and hot air conditions. This step aims to eliminate low-molecular-weight substances produced by peroxide decomposition, stabilize the cross-linked network, and further improve the compression set performance (low-pressure deformation characteristics) of the seal, ultimately obtaining a wear-resistant and magnetorheological fluid-resistant HNBR seal.

[0046] The weight of the raw materials is as follows: 100 parts by weight of hydrogenated nitrile rubber; 65 parts carbon black; 8.5 parts of polytetrafluoroethylene micro powder; 12 parts of phenyl plasticizer; Peroxide 4 parts; 10 parts of cross-linking synergist; 8.5 parts of processing aids.

[0047] The weight ratio of hydrogenated nitrile butadiene rubber A to hydrogenated nitrile butadiene rubber B is 7:3. The phenyl plasticizer is trioctyl trimellitate; the peroxide is DCP. Processing aids consist of zinc oxide, stearic acid, and antioxidants in a weight ratio of 5:1:2.5. Antioxidants consist of antioxidant ZMTI and antioxidant 445 in a weight ratio of 1.5:1. The cross-linking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane in a weight ratio of 4:1; Fluorinated vinyl siloxanes are composed of the following raw materials by weight percentage: Vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane 8%; 12% 1,2,2-Trifluorovinyltriphenylsilane; Vinyl cage-like silsesquioxane (trinorbornene-isobutyl cage-like silsesquioxane) 5%; The balance is 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane (1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane to bring the total to 100%).

[0048] Example 2 The difference between Example 2 and Example 1 lies in the amount of raw materials used, as detailed below: 100 parts by weight of hydrogenated nitrile rubber; 60 parts carbon black; 5.8 parts of polytetrafluoroethylene micro powder; 10 parts of phenyl plasticizer; 5 parts peroxide; 8 parts of cross-linking synergist; 8.5 parts of processing aids.

[0049] The crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane in a weight ratio of 1:0.2; Fluorinated vinyl siloxanes are composed of the following raw materials by weight percentage: 10% vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane; 15% of 1,2,2-trifluorovinyltriphenylsilane; Vinyl cage-like silsesquioxane (trinorbornene-isobutyl cage-like silsesquioxane) 10%; The balance is 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane.

[0050] Example 3 The difference between Example 3 and Example 1 lies in the amount of raw materials used, as detailed below: 100 parts by weight of hydrogenated nitrile rubber; 55 parts carbon black; 8.5 parts of polytetrafluoroethylene micro powder; 8 parts of phenyl plasticizer; Peroxide 6 parts; 4 parts of cross-linking synergist; 8.5 parts of processing aids.

[0051] The crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane in a weight ratio of 1:0.3; Fluorinated vinyl siloxanes are composed of the following raw materials by weight percentage: 5% vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane; 1,2,2-Trifluorovinyltriphenylsilane 7%; Vinyl cage-like silsesquioxane (trinorbornene-isobutyl cage-like silsesquioxane) 20%; The balance is 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane. Example 4 The difference between Example 4 and Example 1 is that the vinyl cage-type silsesquioxane is replaced in equal amounts with 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane.

[0052] Example 5 The difference between Example 5 and Example 1 is that vinyl-terminated trifluoropropylmethyl-dimethyl copolymer siloxane is replaced in equal amounts with 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane.

[0053] Example 6 The difference between Example 6 and Example 1 is that the vinyl cage-type silsesquioxane is acryloyloxypropyl-glycidyloxypropyl cage-type polysilsesquioxane.

[0054] Example 7 The difference between Example 7 and Example 1 is that the vinyl cage-type silsesquioxane is composed of trinorbornene isobutyl cage-type silsesquioxane and acryloyloxypropyl-glycidyloxypropyl cage-type polysilsesquioxane in a weight ratio of 1:1.

[0055] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that polytetrafluoroethylene micro powder was replaced with carbon black in equal amounts.

[0056] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the crosslinking synergist is triallyl isocyanurate.

[0057] Performance testing 1) Basic performance table 1

[0058] If all of the above tests are passed, the basic performance is considered to be qualified.

[0059] 2) Resistance to corrosion by magnetorheological fluids Corrosion resistance of magnetorheological fluid: The seal was immersed in MRF-336AG magnetorheological fluid produced by LORD Corporation of the United States at 100°C for 48 hours. The retention rate of wear resistance and compression set were calculated.

[0060] The specific experimental data are shown in Table 2. Table 2. Experimental data of Examples 1-7 and Comparative Examples 1-2

[0061] In conjunction with Example 1 and Comparative Examples 1-2 and Table 2: The basic properties of Comparative Examples 1-2 were all qualified, and the basic properties of Example 1 were qualified (hardness: 70±5HA; density: 1.3±0.1g / cm³; tensile strength: ≥10MPa; elongation at break: ≥250%; TR10 (low temperature shrinkage): -30℃; compression set: temperature 125℃ / 24h / compression 25%, ≤25%; abrasion resistance: Akron abrasion volume ≤0.15cm³ / 1.61km). The abrasion resistance retention rate and compression set retention rate of Comparative Examples 1-2 were lower than those of Example 1, indicating that the crosslinking synergist, composed of triallyl isocyanurate and fluorinated vinyl siloxane, plays a synergistic role and further improves the overall performance of the seal.

[0062] The specific embodiments are merely explanations of this application and are not intended to limit it. Those skilled in the art can make modifications to these embodiments without contributing any inventive step after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal, characterized in that, It is prepared from the following raw materials in parts by weight: 100 parts of hydrogenated nitrile butadiene rubber; 55-65 parts carbon black; 8.5-11 parts of polytetrafluoroethylene micro powder; 8-12 parts of phenyl plasticizer; Peroxide 4-6 parts; Crosslinking synergist 4-10 parts; processing aid ≤8.5 parts; The hydrogenated nitrile butadiene rubber is composed of hydrogenated nitrile butadiene rubber A and hydrogenated nitrile butadiene rubber B; the acrylonitrile content of the hydrogenated nitrile butadiene rubber A is less than the acrylonitrile content of the other two types; the crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane.

2. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 1, characterized in that: The weight ratio of hydrogenated nitrile butadiene rubber A to hydrogenated nitrile butadiene rubber B is 7:

3.

3. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 1, characterized in that: The acrylonitrile content of the hydrogenated nitrile butadiene rubber A is ≤35%; the acrylonitrile content of the hydrogenated nitrile butadiene rubber B is ≥36%.

4. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 1, characterized in that: The crosslinking synergist is composed of triallyl isocyanurate and fluorinated vinyl siloxane in a weight ratio of 1:(0.1-0.3).

5. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 4, characterized in that, The fluorinated vinyl siloxane is composed of the following raw materials in weight percentages: Vinyl-terminated trifluoropropylmethyl-dimethyl copolysiloxane 5-10%; 1,2,2-Trifluorovinyltriphenylsilane 7-15%; Vinyl cage-type silsesquioxane 10-20%; The balance is 1,3-bis(3-methacryloyloxypropyl)tetra(trimethylsiloxy)disiloxane.

6. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 5, characterized in that: The vinyl cage-type silsesquioxane is acryloyloxypropyl-glycidyloxypropyl cage-type polysilsesquioxane / trinorbornene-isobutyl cage-type silsesquioxane.

7. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 1, characterized in that: The phenyl plasticizer is trioctyl trimellitate; the peroxide is DCP.

8. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 1, characterized in that: The processing aid is one or more of zinc oxide, stearic acid, and antioxidants.

9. The wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal according to claim 8, characterized in that: The antioxidant is antioxidant ZMTI and / or antioxidant 445.

10. A method for preparing a wear-resistant and magnetically resistant rheological fluid low-pressure variable HNBR seal as described in any one of claims 1-9, characterized in that, Obtained by the following method: HNBR styropolymerization: Hydrogenated nitrile butadiene rubber A and hydrogenated nitrile butadiene rubber B are mixed and the roller temperature is controlled at 40-50℃. The mixture is then subjected to thin-pass plasticizing 2-3 times to soften it and reduce the Mooney viscosity, thus obtaining the mixed hydrogenated nitrile butadiene rubber. Additive premixing: Polytetrafluoroethylene (PTFE) micro powder, carbon black, and processing aids are mixed evenly to obtain mixture A, which is then set aside. The phenyl plasticizer is heated to 40-50℃ to obtain a pretreated phenyl plasticizer for later use. First stage of mixing: The mixed hydrogenated nitrile rubber is kneaded under pressure, and then phenyl plasticizer and mixture A are added in batches. After being mixed evenly, the rubber is discharged, milled, and cooled to obtain mixture B. Second stage of mixing: Mixture B is intensively mixed, then peroxide and crosslinking synergist are added. The intensive mixing temperature shall not exceed 90°C. Mix evenly to obtain compound C. Preforming: The mixed rubber compound C is extruded to form a preform blank, shaped by a mold, and then subjected to compression molding and vulcanization. The first stage of vulcanization is carried out at 160℃-175℃, with a pressure of 10-15MPa and a vulcanization time of 8-10 minutes to produce the preform. The preformed part undergoes a second stage of vulcanization and is baked at 145-155℃ to obtain the HNBR seal.

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