High oil resistance and wide temperature range fluorosilicone rubber composite material, preparation method and application

Abstract

The application provides a high oil-resistant wide-temperature-range fluorosilicone rubber composite material, a preparation method and application, and belongs to the technical field of high polymer materials and silicone rubber. The sealing material is prepared through the mechanical blending method, so that the components are uniformly dispersed and interact with each other, and is prepared through high-temperature and high-pressure vulcanization. The prepared fluorosilicone rubber composite material has high hardness and modulus, and shows low compression permanent deformation rate. The oil resistance of the material is evaluated through the test oil conforming to the AMS3021 standard, and the result shows that the oil seal performance is excellent, and the fluorosilicone rubber composite material shows good application prospect in the combined sealing structure.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a high oil-resistant, wide-temperature-range fluorosilicone rubber composite material, its preparation method, and its application. Background Technology

[0002] In aircraft hydraulic systems, rubber-plastic composite seals are a common type of external dynamic seal, frequently used in the actuators of aircraft actuation systems. The rubber ring provides elastic preload, while the plastic slip ring directly contacts the moving shaft, forming the main working surface. During operation, under the combined effects of pre-compression and oil pressure, wear inevitably occurs on the contact surface of the seal. As the seal material is continuously depleted, the sealing effect decreases, leakage increases, and severe leakage can lead to system failure or even threaten flight safety. Therefore, the slip ring of a rubber-plastic composite seal is generally made of modified polytetrafluoroethylene (PTFE) with a low coefficient of friction. After wear, the elasticity provided by the rubber ring allows it to maintain a good fit with the shaft. For rubber seal materials, their primary function is to prevent hydraulic oil leakage. They not only need to be used long-term in the aviation hydraulic oil environment but also need to possess good high and low temperature resistance. If the seal fails and hydraulic oil leaks, it will cause many hazards, ranging from contaminating the aircraft environment and reducing the working capacity of hydraulic equipment and components to causing excessive power loss in the hydraulic system and potentially leading to aircraft accidents.

[0003] Currently, the main rubber materials used in hydraulic seals include nitrile rubber (NBR): NBR seals age rapidly during long-term operation at 135℃. Thermal expansion also increases the compression of the seal, leading to increased permanent deformation. At -55℃, low-temperature crystallization reduces the flexibility and elasticity of the rubber molecular chains, resulting in decreased seal reliability (Lei Haijun, Zhang Jizhong, Gong Wenfeng, et al. Wide temperature range resistance to 15℃). # Research on the properties of fluorosilicone rubber for aviation hydraulic oil [J]. Rubber Technology, 2022, 20(03): 122-125.); Fluororubber: Fluororubber is a binary and ternary elastomer composed of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene. Fluororubber belongs to carbon chain saturated polar rubber. Its high temperature resistance and oil resistance are the best among rubber materials, but its elasticity is poor, and its low temperature resistance and resistance to polar substances such as water are not ideal. Its brittle temperature is mostly between -20~-30℃ (Liu Li, Ma Tingchun, Li Shaoxiang, et al. Research progress on low temperature oil-resistant rubber [J]. Elastomers, 2008, (02): 69-74.); Fluoroether rubber: Fluoroether rubber introduces ether bonds into the side chain of fluororubber, which destroys the regularity of the molecular chain and increases the flexibility of the molecular chain, thereby improving its low temperature resistance. However, the low temperature shrinkage TR of fluoroether rubber is high. 10Although the performance drops to around -30℃ (Chen Yulin, Zhang Hao, Xu Enyun, et al. Research on aramid pulp reinforced carbon black / fluoroether rubber composites [J]. Rubber Industry, 2023, 70(12): 949-953), it still cannot meet the stringent conditions of high-altitude working temperature of -55℃ for aircraft. Perfluoroether rubber: Perfluoroether rubber is usually polymerized from a variety of monomers, including tetrafluoroethylene (TFE), third vulcanization point monomer (CSM) and perfluoroalkyl vinyl ether (PAVE / PAAVE). The introduction of vinyl ether makes the molecular chain of perfluoroether rubber more flexible, thereby greatly improving the low temperature resistance of the material. The minimum operating temperature of perfluoroether rubber drops to -45℃, which cannot meet the requirements of long-term oil-resistant sealing work in the extreme environment of aerospace. (Wang Baocheng, Zhang Bo, Wei Yuansi, et al. Research progress on perfluoroether rubber sealing materials [J / OL]. Lubrication and Sealing, 1-10 [2024-08-13]), and currently the price of perfluoroether rubber is high, with the price of raw rubber reaching tens of thousands of yuan per kilogram. The research and application of perfluoroether rubber still need further development.

[0004] Fluorosilicone rubber not only possesses the excellent high and low temperature properties of silicone rubber, but also, due to the introduction of fluorine, exhibits superior resistance to oils, solvents (including aliphatic, aromatic, and chlorinated solvents), and chemicals. Therefore, it is now widely used in the aircraft and aero-engine industries. Furthermore, fluorosilicone rubber is the only oil-resistant elastomer that can maintain its usability within a temperature range of -68℃ to 232℃.

[0005] In the structure of the combined sealing ring, the rubber ring needs to have a high preload on the plastic slip ring in order to provide a high uniform axial stress, achieve a high fit between the slip ring and the rotating shaft, and ensure the sealing function. Compared with nitrile rubber and fluoropolymer rubber, fluorosilicone rubber has lower mechanical properties such as modulus (usually characterized by 100% tensile stress) and hardness, which is why fluorosilicone rubber is less used in dynamic sealing applications (Lu Ming, An Xiaopeng, Pang Bo, et al. Comparative study on the adaptability of several rubber materials to aviation hydraulic seals [J]. Synthetic Materials Aging and Application, 2023, 52(06):22-23+132).

[0006] Therefore, a rubber material with high oil resistance, wide temperature range, and high modulus is needed to solve the above problems. Summary of the Invention

[0007] To address the aforementioned problems, a primary objective of this invention is to provide a high oil-resistant, wide-temperature-range fluorosilicone rubber composite material with excellent oil-resistant sealing performance, capable of long-term use in a wide temperature range of -55℃ to 200℃, and possessing high modulus.

[0008] To achieve the above objectives, the present invention provides a high oil-resistant wide-temperature-range fluorosilicone rubber composite material, which comprises the following raw materials in parts by weight: 100 parts of fluorosilicone rubber masterbatch, 5 to 20 parts of reinforcing filler, 0.5 to 2 parts of vulcanizing agent, and 0.5 to 3 parts of structure control agent.

[0009] Preferably, it further includes one or more of the following: 0.5 to 3 parts of processing aid, 0.5 to 3 parts of silane coupling agent, and 0.1 to 0.5 parts of vulcanizing agent.

[0010] Preferably, the fluorosilicone raw rubber is a fluorosilicone rubber prepared from a copolymer of 3,3,3-trifluoropropylmethylsiloxane units and methyl vinylsiloxane units, and the fluorosilicone rubber masterbatch is a fluorosilicone rubber masterbatch prepared by blending fluorosilicone raw rubber, inorganic fillers and silicone rubber.

[0011] Preferably, the reinforcing filler can be one or more of the following: precipitated silica VN3, fumed silica A200, fumed silica R974, carbon black N330, carbon black N550, carbon black N774, carbon black N990, clay, calcium carbonate, and nano-light calcium carbonate, with fumed silica A200 and fumed silica R974 being the most preferred. The preferred addition amount is 10-15 parts by weight. The precipitated silica VN3 has a specific surface area of ​​175 m². 2 / g; The average particle size of fumed silica A200 is 12nm, and the specific surface area is 175~225m². 2 / g; The average particle size of fumed silica R974 is 16nm, and the specific surface area is 90~190m². 2 / g; the particle size of carbon black N330 is 26~30nm; the particle size of carbon black N550 is 40~48nm; the particle size of carbon black N774 is 61~100nm; the particle size of carbon black N990 is 201~500nm.

[0012] Preferably, the vulcanizing agent is selected from at least one of benzoyl peroxide (DCP) and 2,4-dichlorobenzoyl peroxide (DCBP) 1,1-di-tert-butylperoxy-3,3,5-trimethoxycyclohexane (3M).

[0013] Preferably, the vulcanizing agent is at least one of triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC).

[0014] Preferably, the silane coupling agent is one or more of vinyltriethoxysilane (A151), 3-(methacryloyloxy)propyltrimethoxysilane (A174), and octyltriethoxysilane (A137) used in combination.

[0015] Another objective of this invention is to provide a method for preparing a high oil-resistant, wide-temperature-range fluorosilicone rubber composite material, the method comprising:

[0016] S1 Pretreatment: The structure control agent is added to the reinforcing filler and pre-mixed;

[0017] S2 compounding: The fluorosilicone rubber masterbatch and the pretreated reinforcing filler are placed in a kneader and kneaded under closed conditions for 10-25 minutes, with a kneader speed of 60-100 r / min and a temperature of 130-140℃. Then, the vulcanizing agent is added and the dispersion time is 10 minutes to obtain the compound.

[0018] S3 Secondary Mixing: After the rubber compound obtained in the kneader is taken out, a secondary mixing operation is performed on an open mixing mill. The secondary mixing operation includes thin-passing and triangular wrapping of the rubber compound on the open mixing mill, with a roller gap of 0.1~2mm, and the number of times is 1~2 times and 3~5 times respectively. Then the roller gap of the open mixing mill is increased to 1~2mm, and the rolling is performed 3~4 times to produce sheets.

[0019] S4 vulcanization: After secondary mixing, the compounded rubber is left at room temperature for 16 hours and then vulcanized. The vulcanization temperature is 170℃, the vulcanization time is 7 minutes, and the vulcanization pressure is 15MPa to obtain vulcanized rubber.

[0020] S5 Secondary vulcanization: The vulcanized rubber is subjected to secondary vulcanization treatment at a temperature of 200°C for 4 hours to obtain the fluorosilicone rubber composite material.

[0021] Preferably, in the S1 pretreatment step, a silane coupling agent and a structuring control agent are added together to the reinforcing filler and initially mixed; and / or, in the S2 mixing step, a processing aid is added to the fluorosilicone rubber masterbatch and the pretreated reinforcing filler and kneaded in a kneader; and / or, in the S2 mixing step, a vulcanizing agent is added along with a vulcanizing aid.

[0022] A third objective of this invention is to provide an application of a high oil-resistant, wide-temperature-range fluorosilicone rubber composite material in an oil-resistant rubber-plastic composite sealing structure. In this invention, this sealing system is primarily used in aerospace applications such as engine seals, fuel system seals, hydraulic system seals, and dynamic surface seals on aircraft.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The high oil-resistant, wide-temperature-range fluorosilicone rubber composite material provided by this invention utilizes the synergistic effect of its components, precisely controlling the proportions of each component to improve the overall performance of the fluorosilicone rubber. The modulus (tensile stress) and hardness of the material are enhanced, making it suitable for use in combined sealing structures. The material maintains a low compression set (compression set rate not exceeding 20%) under extreme high temperatures (175℃) and high-temperature oil-resistant environments (150℃ @ AMS3021 standard test oil), indicating excellent sealing performance. It also exhibits excellent low-temperature performance (low-temperature shrinkage temperature TR10 reaches -61.3℃), demonstrating its ability to operate stably for extended periods in extreme low-temperature environments (around -55℃) without losing elasticity or cracking due to excessively low temperatures. The rubber-plastic combined oil-resistant sealing structure made from this high oil-resistant, wide-temperature-range fluorosilicone rubber composite material can be applied to engine seals, fuel system seals, hydraulic system seals, and dynamic surface seals in aerospace applications. Detailed Implementation

[0025] The present invention will be further illustrated below with reference to actual examples, but the present invention is not limited to these embodiments.

[0026] In this invention, in order to realize the applicability of this rubber material to aviation hydraulic oil, the oil resistance test of this composite material uses an oil that conforms to the AMS3021 standard. This oil can test the rubber's ability to resist the penetration of diester polar compounds.

[0027] The fluorosilicone rubber masterbatch, vulcanizing agent, structure control agent, processing aid, reinforcing filler, silane coupling agent and vulcanization aid used are all commercially available products.

[0028] Fluorosilicone rubber masterbatch is prepared by blending fluorosilicone raw rubber, inorganic fillers and silicone rubber; the fluorosilicone raw rubber is selected from fluorosilicone rubber prepared by copolymerizing 3,3,3-trifluoropropylmethylsiloxane units and methyl vinylsiloxane units.

[0029] In the following examples and comparative examples, the vulcanizing agent 5-bis(tert-butylperoxy)hexane (DBPH) is abbreviated as vulcanizing agent DBPH, the co-vulcanizing agent triallyl isocyanate (TAIC) is abbreviated as co-vulcanizing agent TAIC, and the silane coupling agent vinyltriethoxysilane (A151) is abbreviated as silane coupling agent A151.

[0030] Hydroxyfluorosilicone oil was selected as the structure control agent in the examples and comparative examples.

[0031] Example 1

[0032] Its preparation method mainly includes the following steps:

[0033] S1 Pretreatment: Dry modification of the reinforcing filler fumed silica is carried out in advance, and the hydroxyl fluorosilicone oil, a structure control agent, is added to the reinforcing filler for premixing, so that the hydroxyl fluorosilicone oil is coated on the surface of the reinforcing filler.

[0034] S2 Mixing: First, knead the fluorosilicone rubber masterbatch in a kneader under closed conditions for 1 minute. Then, add the pretreated reinforcing filler in multiple batches. The kneader speed is set to 80 r / min, and the high-temperature kneading temperature is 130℃. The pretreated reinforcing filler is added in two stages. The first addition is 3 / 4 of the total reinforcing filler, which is mixed for 5 minutes. Then, the remaining reinforcing filler is added and mixed for 5 minutes. During both mixing processes, the top bolt is intermittently opened and held for 0.5 minutes before being closed. This lowers the temperature of the rubber compound inside the kneader. Then, the vulcanizing agent is added, and the mixture is kneaded for 2 minutes. The mixed rubber is then removed.

[0035] S3 Secondary Mixing: The extracted rubber compound is subjected to multiple thin-pass and triangular wrapping operations on an open-type rubber mixing mill with a roller gap of 0.1~2mm, for 1~2 times and 3~5 times respectively. Then, the roller gap of the open-type rubber mixing mill is increased to 1~2mm, and the rolls are rolled out 3~4 times.

[0036] S4 vulcanization: After the compounded rubber is placed at room temperature for 16 hours after secondary mixing, it is vulcanized using a flat vulcanizing apparatus. The vulcanization pressure is 15MPa, the vulcanization temperature is set to 170℃, and the vulcanization time is 7min.

[0037] S5 Secondary Vulcanization: The vulcanized rubber is subjected to secondary vulcanization at 200℃ for 4 hours in a blower dryer, and then used after being left at room temperature for 24 hours.

[0038] in,

[0039] Fluorosilicone rubber masterbatch: 100g;

[0040] Fumed silica A200 or R974: 13g;

[0041] Hydroxyfluorosilicone oil: 2.5g;

[0042] Vulcanizing agent DBPH: 1g.

[0043] Example 2

[0044] Following the preparation method and conditions of Example 1, the materials underwent pretreatment, mixing, secondary mixing, vulcanization, and secondary vulcanization. The difference in this embodiment is that the amount of fumed silica used as reinforcing filler is 10% by mass.

[0045] in,

[0046] Fluorosilicone rubber masterbatch: 100g;

[0047] Fumed silica A200 or R97: 10g;

[0048] Hydroxyfluorosilicone oil: 2g;

[0049] Vulcanizing agent DBPH: 1g.

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 2 is that the vulcanizing agent TAIC is added during the mixing process. In the S2 mixing step, the vulcanizing agent is added along with the vulcanizing agent. All other operating steps in this embodiment are the same as in Embodiment 2.

[0052] in,

[0053] Fluorosilicone rubber masterbatch: 100g;

[0054] Fumed silica A200 or R97: 10g;

[0055] Hydroxyfluorosilicone oil: 2g;

[0056] Vulcanizing agent DBPH: 1g;

[0057] TAIC (a vulcanizing agent): 0.1g.

[0058] Example 4

[0059] The preparation method mainly includes the following steps:

[0060] S1 Pretreatment: Dry modification of the reinforcing filler fumed silica is carried out in advance, and hydroxyl fluorosilicone oil is added to the reinforcing filler for premixing so that it is uniformly coated on the surface of the reinforcing filler.

[0061] S2 Mixing: First, knead the fluorosilicone rubber masterbatch and processing aid microcrystalline wax in a closed kneader for 1 minute. Then, add the treated reinforcing filler in multiple batches. The kneader speed is set to 80 r / min, and the high-temperature kneading temperature is 130℃. The filler is added in two stages. The first batch contains 3 / 4 of the total filler and is mixed for 5 minutes. Then, the remaining filler is added and mixed for 5 minutes. During both mixing processes, the top plug is intermittently opened and held for 0.5 minutes before being closed. This lowers the temperature of the rubber compound inside the kneader. Then, the vulcanizing agent is added, and the mixture is kneaded for 2 minutes. The mixed rubber is then removed.

[0062] S3 Secondary Mixing: The extracted rubber compound is subjected to multiple thin-pass and triangular wrapping operations on an open-type rubber mixing mill with a roller gap of 0.1~2mm, for 1~2 times and 3~5 times respectively. Then, the roller gap of the open-type rubber mixing mill is increased to 1~2mm, and the rolls are rolled out 3~4 times.

[0063] S4 vulcanization: After the mixed rubber compound is placed at room temperature for 16 hours, it is vulcanized using a flat vulcanizing apparatus. The vulcanization pressure is 15 MPa, the vulcanization temperature is set to 170℃, and the vulcanization time is 7 minutes.

[0064] S5 Secondary Vulcanization: The vulcanized rubber is subjected to secondary vulcanization at 200℃ for 4 hours in a blower dryer, and then used after being left at room temperature for 24 hours.

[0065] The difference between this embodiment and Embodiment 2 is that in this embodiment, the fluorosilicone rubber masterbatch and the processing aid microcrystalline wax are first mixed and dispersed during the mixing process.

[0066] in,

[0067] Fluorosilicone rubber masterbatch: 100g;

[0068] Fumed silica A200 or R97: 10g;

[0069] Hydroxyfluorosilicone oil: 2g;

[0070] Vulcanizing agent DBPH: 1g;

[0071] Microcrystalline wax: 2g.

[0072] Example 5

[0073] Its preparation method mainly includes the following steps:

[0074] S1 Pretreatment: Dry modification of the fumed silica used as a reinforcing filler is carried out in advance. The hydroxyl fluorosilicone oil, a structure control agent, is added to the reinforcing filler for preliminary mixing, so that the hydroxyl fluorosilicone oil coats the surface of the reinforcing filler.

[0075] S2 Mixing: First, knead the fluorosilicone rubber masterbatch in a closed kneader for 1 minute. Then, add the pretreated reinforcing filler in multiple batches. The kneader speed is set to 80 r / min, and the high-temperature kneading temperature is 130℃. The pretreated reinforcing filler is added in one step, and the mixing time is 5 minutes. During the mixing process, the top bolt is opened and held for 0.5 minutes before closing the top bolt. After the temperature of the rubber compound in the kneader is reduced, the vulcanizing agent is added, and kneading continues for 2 minutes. Then, the mixed rubber is removed.

[0076] S3 Secondary Mixing: The extracted rubber compound is subjected to multiple thin-pass and triangular wrapping operations on an open-type rubber mixing mill with a roller gap of 0.1~2mm, for 1~2 times and 3~5 times respectively. Then, the roller gap of the open-type rubber mixing mill is increased to 1~2mm, and the rolls are rolled out 3~4 times.

[0077] S4 vulcanization: After the mixed rubber compound is placed at room temperature for 16 hours, it is vulcanized using a flat vulcanizing apparatus. The vulcanization pressure is 15 MPa, the vulcanization temperature is set to 170℃, and the vulcanization time is 7 minutes.

[0078] S5 Secondary Vulcanization: The vulcanized rubber is subjected to secondary vulcanization at 200℃ for 4 hours in a blower dryer, and then used after being left at room temperature for 24 hours.

[0079] The difference between this embodiment and embodiment 2 is that the mixing step S2 in this embodiment uses a one-stage addition.

[0080] in,

[0081] Fluorosilicone rubber masterbatch: 100g;

[0082] Fumed silica A200 or R97: 10g;

[0083] Hydroxyfluorosilicone oil: 2g;

[0084] Vulcanizing agent DBPH: 1g.

[0085] Example 6

[0086] The difference between this embodiment and Embodiment 2 is that in the S1 pretreatment step, silane coupling agent A151 and structure control agent are added together to the reinforcing filler and mixed.

[0087] in,

[0088] Fluorosilicone rubber masterbatch: 100g;

[0089] Fumed silica A200 or R97: 10g;

[0090] 1g of silane coupling agent;

[0091] Hydroxyfluorosilicone oil: 1g;

[0092] Vulcanizing agent DBPH: 1g;

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 is that 8 parts by mass of fumed silica were added in the S1 pretreatment step of this comparative example.

[0095] in,

[0096] Fluorosilicone rubber masterbatch: 100g;

[0097] Fumed silica A200 or R97: 8g;

[0098] Hydroxyfluorosilicone oil: 1.5g;

[0099] Vulcanizing agent DBPH: 1g.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 2 is that the hydroxyl fluorosilicone oil, a structure control agent, is not added, and the S1 pretreatment step is not performed.

[0102] Fluorosilicone rubber masterbatch: 100g;

[0103] Fumed silica A200 or R97: 10g;

[0104] Vulcanizing agent DBPH: 1g.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 3 is that the mass fraction of the vulcanizing agent TAIC added to this comparative example is increased to 0.2 parts.

[0107] in,

[0108] Fluorosilicone rubber masterbatch: 100g;

[0109] Fumed silica A200 or R97: 10g;

[0110] Hydroxyfluorosilicone oil: 2g;

[0111] Vulcanizing agent DBPH: 1g;

[0112] TAIC (a vulcanizing agent): 0.2g.

[0113] Comparative Example 4

[0114] The difference between this comparative example and Example 3 is that the mass fraction of the vulcanizing agent TAIC added to this comparative example is increased to 0.3 parts.

[0115] in,

[0116] Fluorosilicone rubber masterbatch: 100g;

[0117] Fumed silica A200 or R97: 10g;

[0118] Hydroxyfluorosilicone oil: 2g;

[0119] Vulcanizing agent DBPH: 1g;

[0120] TAIC (a vulcanizing agent): 0.3g.

[0121] Comparative Example 5

[0122] The difference between this comparative example and Example 4 is that the processing aid is replaced with stearic acid.

[0123] Fluorosilicone rubber masterbatch: 100g;

[0124] Fumed silica A200 or R97: 10g;

[0125] Hydroxyfluorosilicone oil: 2g;

[0126] Vulcanizing agent DBPH: 1g;

[0127] Stearic acid: 2g.

[0128] Comparative Example 6

[0129] The difference between this comparative example and Example 4 is that the processing aids are replaced with stearic acid and zinc oxide.

[0130] Fluorosilicone rubber masterbatch: 100g;

[0131] Fumed silica A200 or R97: 10g;

[0132] Hydroxyfluorosilicone oil: 2g;

[0133] Vulcanizing agent DBPH: 1g;

[0134] Stearic acid: 2g;

[0135] Zinc oxide: 3g.

[0136] Comparative Example 7

[0137] The difference between this comparative example and Example 5 is that the kneader speed is set to 60 r / min during the mixing process, and the kneading temperature is 111℃.

[0138] in,

[0139] Fluorosilicone rubber masterbatch: 100g;

[0140] Fumed silica A200 or R97: 10g;

[0141] Hydroxyfluorosilicone oil: 2g;

[0142] Vulcanizing agent DBPH: 1g.

[0143] Comparative Example 8

[0144] The difference between this comparative example and Example 5 is that the kneader speed is set to 100 r / min during the mixing process, and the kneading temperature is 150°C.

[0145] in,

[0146] Fluorosilicone rubber masterbatch: 100g;

[0147] Fumed silica A200 or R97: 10g;

[0148] Hydroxyfluorosilicone oil: 2g;

[0149] Vulcanizing agent DBPH: 1g.

[0150] The pretreatment of hydroxyl fluorosilicone oil with silane coupling agent in S1 is to reduce the sliding of the rubber compound in the closed cavity during the kneading process, which would affect the kneading effect. Under the action of closed high temperature, it is beneficial to the sliding of hydroxyl fluorosilicone oil in the molecule and the combination of hydroxyl groups with inorganic fillers and rubber molecular chains, and it is beneficial to the dehydration and bonding effect of silane coupling agent on inorganic fillers.

[0151] The closed kneader in S2 mixes and disperses the base rubber, reinforcing fillers, processing aids, vulcanizing agents, and other auxiliaries (co-vulcanizing agents) to form a rubber composite compound. Strict temperature control is crucial during this process. Below 130℃, the dispersing effect of the structure control agent on the inorganic fillers is poor, and the fillers are prone to agglomeration. Between 130 and 140℃, the dispersibility of the inorganic fillers is effectively improved, resulting in a material with high performance. Above 140℃, the fluorosilicone rubber molecular chains are more prone to defects under high temperature and high shear, the torque within the closed cavity of the kneader increases sharply, the dispersibility of the inorganic fillers deteriorates, and the surface of the compound exhibits a larger particle texture, leading to a decline in material properties. The study revealed that, during the preparation process, materials prepared at a mixing temperature of 131℃ exhibited tensile strength increases of 11.5% and 18.4% compared to materials prepared at mixing temperatures of 111℃ and 150℃, respectively, and elongation at break increases of 12.0% and 14.8%, respectively. Furthermore, the two-stage addition of inorganic fillers resulted in a 5.7% increase in tensile strength and a 6.3% increase in elongation at break compared to a one-stage addition method. This indicates that appropriate mixing temperature, mixing time, and feeding methods contribute to improving material performance.

[0152] At the same time, it is necessary to strictly control the feeding sequence. The feeding sequence in the kneader is as follows: fluorosilicone rubber masterbatch, silicone rubber masterbatch or silicone rubber raw rubber or fluorosilicone rubber raw rubber, processing aids, inorganic nano-reinforcing fillers and structuring control agents, as well as silane coupling agents, vulcanizing agents and vulcanization aids.

[0153] In S3, the secondary mixing operation generally involves adjusting the roller gap of the compound to between 0.1mm and 2mm on an open mixing mill, and performing multiple thin passes, triangular wraps, and rolling operations on the compound to further disperse the filler.

[0154] In S4, the vulcanization process can employ any existing fluorosilicone rubber vulcanization process. Specifically, the vulcanization temperature can be 140~200℃, preferably 160~180℃; the vulcanization time can be 5~30min, preferably 5~10min. In one embodiment of the present invention, the vulcanization temperature is 170℃ and the vulcanization time is 7min.

[0155] In S5, the purpose of secondary vulcanization of the vulcanized rubber is to improve the vulcanization cross-linking structure and optimize material properties. Simultaneously, secondary vulcanization helps to remove gaseous byproducts and volatile substances generated during vulcanization, preventing them from affecting material properties. Studies have shown that after secondary vulcanization, the tensile strength of the material increased by 15.3%, while the elongation at break was only slightly reduced by 3%, indicating that secondary vulcanization significantly enhances the mechanical properties of the material. The secondary vulcanization temperature can be any temperature between 170 and 250°C, preferably 200 to 240°C, and the vulcanization time can be any condition between 2 and 8 hours, preferably 4 to 6 hours. In some embodiments of this invention, the secondary vulcanization temperature is 200°C, and the vulcanization time is 4 hours. A forced-air dryer is preferred as the heating instrument. Using a vacuum dryer may evaporate some small molecules from the material, leading to a decrease in material properties.

[0156] The fluorosilicone rubber composite materials prepared in Examples 1-6 and Comparative Examples 1-8 were tested.

[0157] The testing method is as follows:

[0158] Hardness: According to GB / T 531.1-2008, the test temperature is the standard laboratory temperature. A Shore A hardness tester, model BS61 Ⅱ, manufactured by Bareiss Instruments GmbH, Germany, is used to measure the hardness of vulcanized rubber. The sample thickness is at least 6 mm. The Shore A measurement position is at least 12 mm away from any edge. The standard spring test force is held for 3 seconds. Five measurements are taken at different positions on the sample, and the median value is taken.

[0159] Mechanical properties: According to GB / T 528-2009, the specimen is a dumbbell-shaped type 1 standard specimen (the narrow part is 6 mm wide), the test temperature is the standard laboratory temperature, and the mechanical properties of the dumbbell-shaped specimen are tested on an electronic universal testing machine (model AI-7000S1) produced by High-speed Rail Testing Instruments (Dongguan) Co., Ltd. The moving speed of the clamp is 500 mm / min, the number of specimens measured is 5, and the median of the measurement results is taken.

[0160] Compression set: In accordance with GB / T 7759.1-2015, cylindrical specimens with a diameter of (29.0±0.5) mm and a height of (12.5±0.5) mm were prepared and placed in a compression setter with a compression ratio of 25%. The compression set test was conducted in a hot air aging chamber (model GT-7017-EMU) produced by High-speed Rail Testing Instruments (Dongguan) Co., Ltd. The temperature of the hot air aging chamber was set to 175℃ and the test time was 22 hours. After the test, the specimens were allowed to recover at the standard laboratory temperature for (30±3) min, and then the compression set rate was tested. Three specimens were tested, and the median value of the test results was taken.

[0161] Solvent resistance: According to GB / T 1690-2010, GB / T 531.1-2008 and GB / T 7759.1-2015, the following specimens were prepared: (a) Shore A hardness test specimen; (b) a square specimen with a thickness of (2.0±0.2) mm and a side length of 25 mm; (c) a cylindrical specimen with a diameter of (29.0±0.5) mm and a height of (12.5±0.5) mm. The specimens were completely immersed in the test liquid in the test container and the solvent resistance was tested in a hot air aging chamber (model GT-7017-EMU) produced by High-speed Rail Testing Instruments (Dongguan) Co., Ltd. The temperature of the hot air aging chamber was set at 150℃, the test time was 70 hours, the test liquid was AMS 3021 test oil, and the number of specimens was 3. After the test, the specimens were left to stand at the standard laboratory temperature for 30 minutes, and then the Shore A hardness, volume change rate and compression set were tested.

[0162] The test results are shown in Tables 1 and 2. In the tables, " / " indicates that this performance has not been tested yet, and "-" indicates that the material has not met the conditions for testing this performance and there is no value.

[0163] Table 1 Performance data of fluorosilicone rubber composites in Examples 1-6

[0164]

[0165] Table 2 Performance data of fluorosilicone rubber composites of Comparative Examples 1-8

[0166]

[0167] Based on the material performance data of Examples 1-6 and Comparative Examples 1-8 in Table 1, it can be concluded that:

[0168] Analysis of Examples 1, 2, and Comparative Example 1 shows that the tensile stress of the material continuously increases with the addition of reinforcing filler content. When the filler content reaches 13 parts by mass, the modulus of the material meets the technical requirements for rubber rings used in rubber-plastic sealing composite structures. Mechanical properties also show that the compression set rate of the material continuously increases. This is because with the increase of filler content, the agglomeration of filler within the rubber matrix becomes more severe, leading to a decrease in resilience and a deterioration in compression set performance. However, this compression set rate remains at a low level, indicating that the sealing performance of the material is always guaranteed. Regarding the tensile strength of the material, although it can be seen that the tensile strength continuously decreases with the addition of filler content, considering the application scope of this invention—primarily for the preparation of sealing rings—tensile strength is not a key performance focus. Moreover, the tensile strength of this material is sufficient to ensure its normal operation. In the oil resistance test of the material in this invention, a novel test solvent (test oil conforming to AMS 3021 standard) was selected to test the oil resistance of the material. This test oil is highly polar and can be used as a reference test oil for the highly polar hydraulic oil or aviation fuel used in military aircraft in extreme low-temperature environments. This test method can better describe the oil resistance of the material in extreme environments. From the data in the table, it can be seen that the fluorosilicone rubber composite material of this invention has excellent oil resistance. After a long-term oil immersion test at 150℃@70h, the hardness of the material still remains at around -4, and the volume change rate still remains at around 5%. Furthermore, during the research, it was found that after the oil immersion test at 150℃@70h, the compression set of the material was 16%, which indicates that the material has excellent oil resistance and sealing performance.

[0169] Analysis of Example 2 and Comparative Example 2 shows that the elongation at break of the material decreased significantly after the removal of hydroxyl fluorosilicone oil from the system. This indicates that hydroxyl fluorosilicone oil plays an important role in improving the dispersibility of reinforcing fillers in the matrix and reducing the degree of agglomeration of reinforcing fillers in the matrix.

[0170] Analysis of Examples 3, 3, and 4 shows that the co-curing agent TAIC mainly plays a role in assisting crosslinking and promoting vulcanization within the system. As the content of TAIC increases, the modulus of the material continuously rises; however, excessive addition leads to an excessively low elongation at break. Example 3 satisfies the material's modulus requirements. Furthermore, compared to Example 1, the material prepared in this example exhibits reduced hardness, a significantly lower compression set, and better sealing performance. After high-temperature oil immersion testing, the material's hardness also shows a lower change.

[0171] Analysis of Examples 4, 5, and 6 shows that the addition of microcrystalline wax decreased the modulus of the material and increased the elongation at break, indicating that the microcrystalline wax acts as a small-molecule plasticizer in the matrix. However, in Comparative Examples 5 and 6, replacing the processing aid with stearic acid and using a combination of stearic acid and zinc oxide did not improve the dispersibility of the filler. Furthermore, after high-temperature vulcanization, the compression set of the material deteriorated sharply, and the sealing performance deteriorated significantly. This suggests that the stearic acid processing aid system may not be suitable for fluorosilicone rubber systems.

[0172] Analysis of the mixing and preparation methods of the materials in Examples 5, 7, and 8 reveals that at a rotor speed of 60 r / min, the mixing temperature in the closed chamber is 111°C. At this temperature, the in-situ modification effect of reinforcing fillers, structuring agents, and rubber matrix is ​​poor. At a rotor speed of 100 r / min, the mixing temperature in the closed chamber is 150°C. Under this temperature and high shear, the material may suffer structural damage, resulting in a decrease in the material's mechanical properties. The study found that at a rotor speed of 80 r / min, the mixing temperature in the closed chamber is 130°C, at which point the material exhibits optimal performance.

[0173] Compared with the prior art, the composite material provided by the present invention has the following advantages:

[0174] (1) The combination of bis(2,5) vulcanizing agent and TAIC co-vulcanizing agent has a significant effect on improving the three-dimensional network structure formed by vulcanization of rubber matrix.

[0175] (2) The addition of silane coupling agents is beneficial to optimizing the vulcanization crosslinking structure of materials. The molecular structure of some silane coupling agents consists of two parts: one end contains a functional group that can be hydrolyzed into a hydroxyl group (such as methoxy or ethoxy), and the other end contains an organic functional group (such as vinyl). In the rubber matrix, one end of the silane coupling agent can connect to the reinforcing filler to form a chemical or physical crosslinking; the other end combines with the rubber molecular chain through the addition reaction of vinyl to form a combined layer of organic matrix-silane coupling agent-inorganic matrix. On the one hand, it improves the dispersibility of the reinforcing filler in the rubber matrix and reduces the degree of filler aggregation. On the other hand, the silane coupling agent also increases the modulus of the material and optimizes the crosslinking structure.

[0176] (3) The reinforcing filler silica is pretreated with hydroxyl fluorosilicone oil. On the one hand, hydroxyl fluorosilicone oil plays a structural control role. The hydroxyl groups in hydroxyl fluorosilicone oil can form hydrogen bonds with the silanol groups on the silica surface and also form hydrogen bonds with the oxygen atoms on the fluorosilicone rubber molecular chain, which plays a bridging role and enhances the compatibility of the filler molecules in the rubber matrix, so that the silica can be better dispersed in the fluorosilicone rubber. At the same time, it shields some of the hydroxyl groups on the silica surface and reduces the agglomeration defect of silica. In addition, hydroxyl fluorosilicone oil acts as a plasticizer in the form of small molecules, reduces the interaction force between fluorosilicone rubber molecular chains, enhances the slippage of molecular chains, and thus improves the tensile and resilience of the material.

[0177] (4) In the preparation method, after adding the reinforcing filler treated with hydroxyl fluorosilicone oil and silane coupling agent to the kneader, it is mixed at 130~140℃ for 10min. The reinforcing filler is added in two parts. The first part is 3 / 4 of the total filler and mixed for 5min. Then the remaining filler is added and mixed for 5min. During the two mixing processes, the top plug is opened intermittently and held for 0.5min before closing the top plug, which helps to make the filler mix more uniformly.

[0178] (5) In the oil resistance test method of the present invention, the oil resistance of the material is tested in a high-temperature environment using a strong polar oil that meets the AMS 3021 standard test standard. This test method can better describe the performance of the material in extreme high temperature and polar oil medium environment, thereby more accurately evaluating the applicability of the material to aircraft.

[0179] In summary, the high oil resistance and wide temperature range fluorosilicone rubber composite material prepared by this invention exhibits excellent oil sealing performance and can be used for extended periods at temperatures ranging from -55℃ to 200℃, showing significant application potential in combined sealing structures. It is primarily used in aerospace applications such as engine seals, fuel system seals, hydraulic system seals, and dynamic surface seals for aircraft.

Claims

1. A high oil-resistant, wide-temperature-range fluorosilicone rubber composite material, characterized in that, The fluorosilicone rubber composite material is prepared from the following raw materials in parts by weight: 100 parts of fluorosilicone rubber masterbatch, 5 to 20 parts of reinforcing filler, 0.5 to 2 parts of vulcanizing agent, 0.5 to 3 parts of structure control agent, and 0.5 to 3 parts of processing aid, wherein the processing aid is microcrystalline wax; optionally, it also includes one or two of the following: 0.5 to 3 parts of silane coupling agent and 0.1 to 0.5 parts of vulcanizing agent. The high oil-resistant, wide-temperature-range fluorosilicone rubber composite material is prepared using the following method: S1 Pretreatment: The structure control agent is added to the reinforcing filler and pre-mixed; S2 compounding: Processing aids, fluorosilicone rubber masterbatch and pretreated reinforcing filler are placed in a kneader and kneaded under closed conditions for 10-25 minutes, kneader speed is 60-100 r / min, temperature is 130-140℃, then vulcanizing agent is added and dispersion time is 10 minutes to obtain compound. S3 Secondary Mixing: After the rubber compound obtained in the kneader is taken out, a secondary mixing operation is performed on an open mixing mill. The secondary mixing operation includes thin-passing and triangular wrapping of the rubber compound on the open mixing mill, with a roller gap of 0.1~2mm, and the number of times is 1~2 times and 3~5 times respectively. Then the roller gap of the open mixing mill is increased to 1~2mm, and the rolling is performed 3~4 times to produce sheets. S4 vulcanization: After secondary mixing, the compounded rubber is left at room temperature for 16 hours and then vulcanized. The vulcanization temperature is 170℃, the vulcanization time is 7 minutes, and the vulcanization pressure is 15MPa to obtain vulcanized rubber. S5 Secondary vulcanization: The vulcanized rubber is subjected to secondary vulcanization treatment at a temperature of 200°C for 4 hours to obtain the fluorosilicone rubber composite material.

2. The high oil resistance wide temperature range fluorosilicone rubber composite material according to claim 1, characterized in that, The fluorosilicone rubber masterbatch is a fluorosilicone rubber masterbatch prepared by blending fluorosilicone raw rubber, inorganic fillers and silicone rubber; the fluorosilicone raw rubber is selected from fluorosilicone rubber prepared by copolymerizing 3,3,3-trifluoropropylmethylsiloxane units and methyl vinylsiloxane units.

3. The high oil resistance wide temperature range fluorosilicone rubber composite material according to claim 1, characterized in that, The reinforcing filler is one or more of the following: precipitated silica VN3, fumed silica A200, fumed silica R974, carbon black N330, carbon black N550, carbon black N774, carbon black N990, clay, calcium carbonate, and nano-light calcium carbonate, added in a weight ratio of 10-15 parts.

4. The high oil resistance wide temperature range fluorosilicone rubber composite material according to claim 1, characterized in that, The vulcanizing agent is at least one of benzoyl peroxide (DCP), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH), 2,4-dichlorobenzoyl peroxide (DCBP), and 1,1-di-tert-butylperoxy-3,3,5-trimethoxycyclohexane (3M).

5. The high oil resistance wide temperature range fluorosilicone rubber composite material according to claim 1, characterized in that, The vulcanizing agent is at least one of triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC).

6. The high oil resistance wide temperature range fluorosilicone rubber composite material according to claim 1, characterized in that, The silane coupling agent is one or more of vinyltriethoxysilane (A151), 3-(methacryloyloxy)propyltrimethoxysilane (A174), and octyltriethoxysilane (A137).

7. A method for preparing a high oil-resistant, wide-temperature-range fluorosilicone rubber composite material as described in any one of claims 1 to 6, characterized in that, The preparation method includes: S1 Pretreatment: The structure control agent is added to the reinforcing filler and pre-mixed; S2 compounding: Processing aids, fluorosilicone rubber masterbatch and pretreated reinforcing filler are placed in a kneader and kneaded under closed conditions for 10-25 minutes, kneader speed is 60-100 r / min, temperature is 130-140℃, then vulcanizing agent is added and dispersion time is 10 minutes to obtain compound. S3 Secondary Mixing: After the rubber compound obtained in the kneader is taken out, a secondary mixing operation is performed on an open mixing mill. The secondary mixing operation includes thin-passing and triangular wrapping of the rubber compound on the open mixing mill, with a roller gap of 0.1~2mm, and the number of times is 1~2 times and 3~5 times respectively. Then the roller gap of the open mixing mill is increased to 1~2mm, and the rolling is performed 3~4 times to produce sheets. S4 vulcanization: After secondary mixing, the compounded rubber is left at room temperature for 16 hours and then vulcanized. The vulcanization temperature is 170℃, the vulcanization time is 7 minutes, and the vulcanization pressure is 15MPa to obtain vulcanized rubber. S5 Secondary vulcanization: The vulcanized rubber is subjected to secondary vulcanization treatment at a temperature of 200°C for 4 hours to obtain the fluorosilicone rubber composite material.

8. The preparation method according to claim 7, characterized in that, In the S1 pretreatment step, a silane coupling agent and a structuring control agent are added together to the reinforcing filler and initially mixed; and / or, in the S2 mixing step, a vulcanizing agent is added along with a vulcanizing aid.

9. The application of the high oil-resistant wide-temperature-range fluorosilicone rubber composite material according to any one of claims 1 to 6 in the oil-resistant sealing structure of rubber and plastic composites.

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