Low compression set perfluoroether rubber for high temperature sealing and method of making

Abstract

This invention discloses a low-compression-per-ether rubber for high-temperature sealing and its preparation method, belonging to the technical field of high-performance fluororubber materials. The perfluoroether rubber comprises perfluoroether rubber, a quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, 2-phenylbenzimidazole, spherical silica, a perfluoropolyether lubricant, a high-temperature reinforcing agent, a peroxide vulcanizing agent, a crosslinking aid, a heat-resistant stabilizer, and a processing dispersant. By constructing a quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modified structure and combining 2-phenylbenzimidazole and spherical silica to synergistically modify the perfluoroether rubber, this invention effectively reduces the Mooney viscosity and high-temperature compression set of the rubber compound, improves the material's high-temperature resilience, long-term sealing stability, and molding processing flow properties, and reduces weld lines and surface defects. It is suitable for sealing applications in high-temperature, high-corrosion, and high-cleanliness environments.

Description

Technical Field

[0001] This invention relates to the field of high-performance fluororubber materials technology, specifically to a low-compression-per-fluoroether rubber for high-temperature sealing and its preparation method. Background Technology

[0002] Perfluoroelastomer rubber is widely used in semiconductor, aerospace, chemical equipment and high-end sealing fields due to its excellent high temperature resistance, corrosion resistance, plasma resistance and chemical media resistance. It is especially suitable for the manufacture of sealing products in high temperature, high corrosion and high cleanliness environments.

[0003] While existing perfluoroelastomers (PFEs) possess high heat resistance, their strong molecular chain polarity and large intermolecular forces result in high Mooney viscosity and poor flowability. This leads to issues such as weld lines, uneven filling, and dimensional inconsistencies during molding, impacting the processing stability and yield of sealing products. Especially in the processing of complex sealing components, high Mooney viscosity further increases the probability of surface defects. Based on the existing disclosure, spherical silica materials can significantly reduce the Mooney value of PFEs, thereby improving flowability and reducing weld line defects.

[0004] On the other hand, when perfluoroether rubber seals are subjected to high-temperature compression conditions for a long time, they are prone to problems such as increased permanent compression deformation, decreased resilience and seal failure. Especially in high-temperature vulcanization and long-term thermal cycling environments, interfacial stress concentration is easily generated between traditional inorganic fillers and rubber matrix, which leads to a decrease in the stability of rubber network structure and thus affects the long-term sealing life of the material.

[0005] Most conventional reinforcing systems in existing technologies employ ordinary silica, carbon black, or a single silica-oxygen network structure, which have limited effectiveness in improving high-temperature compression set and cannot simultaneously achieve good processing flow properties, high-temperature resilience properties, and long-term sealing stability. Therefore, developing a perfluoroether rubber material that combines low Mooney processing performance, low compression set performance, and high-temperature sealing stability is of great significance. Summary of the Invention

[0006] To overcome the problems of high Mooney viscosity, poor processing flowability, large high-temperature compression set, and insufficient long-term sealing stability of perfluoroether rubber in the aforementioned background technology, the present invention aims to provide a low compression set perfluoroether rubber for high-temperature sealing and its preparation method. The present invention employs a quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier and 2-phenylbenzimidazole to synergistically construct a high-temperature resistant flexible network structure, and combines it with spherical silica, a high-temperature resistant reinforcing agent, and a perfluoropolyether lubrication system to synergistically modify the perfluoroether rubber matrix, thereby improving the rubber's flowability, high-temperature resilience, and sealing stability. The present invention can effectively reduce the Mooney viscosity and high-temperature compression set of perfluoroether rubber, improve the high-temperature sealing stability of the material, and reduce the generation of weld lines and surface defects during molding.

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

[0008] A high-temperature sealing low-compression-per-deformation perfluoroether rubber comprises the following raw materials in parts by weight: 100-160 parts of perfluoroether rubber; 15-60 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier; 2-15 parts of 2-phenylbenzimidazole; 10-50 parts of spherical silica; 1-10 parts of perfluoropolyether lubricant; 5-35 parts of high-temperature resistant reinforcing agent; 1-8 parts of peroxide vulcanizing agent; 1-10 parts of crosslinking aid; 1-8 parts of heat-resistant stabilizer; and 1-6 parts of processing dispersant. The quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier is an organic-inorganic hybrid network structure formed by hydrolysis, condensation, and synergistic reaction of tetraethoxysilane, vinyltriethoxysilane, tetraphenylphosphonium bromide, and 4-vinylphenylboronic acid.

[0009] Optionally, the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier comprises the following raw materials in parts by weight: 10-40 parts of tetraethoxysilane; 5-30 parts of vinyltriethoxysilane; 2-15 parts of tetraphenylphosphonium bromide; 2-20 parts of 4-vinylphenylboronic acid; and 30-120 parts of deionized water.

[0010] Optionally, the preparation method of the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier includes the following steps:

[0011] (1) Tetraethoxysilane and vinyltriethoxysilane were added to deionized water and mixed. A pre-hydrolysis reaction was carried out under stirring to obtain a silicon-oxygen precursor solution.

[0012] (2) Add 4-vinylphenylboronic acid to the silicon-oxygen precursor solution to carry out a synergistic reaction, so that the phenylboronic acid structure is dispersed in the silicon-oxygen network to obtain boric acid functionalized silicon-oxygen composite solution;

[0013] (3) Add tetraphenylphosphonium bromide to the boric acid functionalized silicon oxide composite solution to carry out ion synergistic modification reaction, and then dry it to obtain quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modified product.

[0014] Optionally, the reaction conditions for step (1) are: stirring speed of 300-800 rpm, pre-hydrolysis temperature of 40-75℃, reaction time of 1-5 h, and pH of the system of 3-6.

[0015] Optionally, the reaction conditions in step (2) are a synergistic reaction temperature of 45–85°C, a reaction time of 2–6 h, and a stirring speed of 400–900 rpm.

[0016] Optionally, the reaction conditions in step (3) are: ion-co-modification temperature of 50-90℃, reaction time of 2-8h, followed by drying treatment at 80-130℃ for 4-12h.

[0017] Optionally, the perfluoropolyether lubricant is a mixture of perfluoropolyether oil and polytetrafluoroethylene micro powder in a mass ratio of 5:1 to 20:1; the high-temperature reinforcing agent is a mixture of boron nitride and silicon carbide whiskers in a mass ratio of 1:1 to 5:1; the peroxide curing agent is a mixture of bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 1:1 to 4:1; the crosslinking aid is a mixture of triallyl isocyanurate and bismaleimide in a mass ratio of 1:1 to 3:1; the heat-resistant stabilizer is a mixture of magnesium oxide and cerium oxide in a mass ratio of 2:1 to 8:1; and the processing dispersant is a mixture of fluorosilicone modified polyether and zinc stearate in a mass ratio of 3:1 to 10:1.

[0018] Optionally, a method for preparing a low-compression-set perfluoroether rubber for high-temperature sealing, the method comprising the following steps:

[0019] S1, Perfluoroether rubber, quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, spherical silica and high-temperature reinforcing agent are added to a mixing equipment for premixing treatment, so that the spherical silica and synergistic modifier are dispersed in the perfluoroether rubber matrix to reduce the Mooney viscosity of the rubber compound and improve the molding flow performance, thus obtaining a premixed rubber compound;

[0020] S2, 2-phenylbenzimidazole, perfluoropolyether lubricant, heat stabilizer and processing dispersant are added to the premixed rubber compound for synergistic mixing, so that 2-phenylbenzimidazole is dispersed in the rubber network and the high temperature compression resilience is improved, and the modified compound is obtained.

[0021] S3 involves adding peroxide vulcanizing agent and crosslinking aid to the modified compound for final mixing, followed by compression molding, and then primary vulcanization and secondary high-temperature vulcanization treatment to reduce high-temperature compression set and reduce weld line defects in the product, resulting in a low compression set perfluoroether rubber for high-temperature sealing.

[0022] Optionally, the reaction conditions for step S1 are: a mixing temperature of 55–95°C, a mixing time of 15–40 min, and a mixing speed of 35–80 rpm; the reaction conditions for step S2 are: a co-mixing temperature of 70–120°C, a mixing time of 20–50 min, and a mixing speed of 40–90 rpm.

[0023] Optionally, the reaction conditions in step S3 are as follows: final refining temperature of 50–85°C and final refining time of 5–20 min; molding temperature of 170–210°C and molding time of 8–30 min; and a second-stage high-temperature vulcanization treatment at 250–320°C after the first vulcanization, with a vulcanization time of 6–24 h.

[0024] The beneficial effects of this invention are:

[0025] This invention constructs a quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modified structure, combining the high-temperature stability of the silicon-oxygen network with the association effect of quaternary phosphonium salt ions. This allows for the formation of a flexible network structure with buffering capacity under high-temperature compression conditions, thereby reducing internal stress concentration in rubber, improving the resilience of perfluoroether rubber under long-term high-temperature conditions, and effectively reducing compression set. Simultaneously, the phenylboronic acid structure in 4-vinylphenylboronic acid can synergistically restrict the silicon-oxygen network, improving the interfacial bonding stability between the modified structure and the perfluoroether rubber matrix, reducing filler agglomeration and interfacial detachment under high-temperature conditions, thus improving the material's thermal stability and long-term sealing stability. 2-Phenylenibimidazole has strong... The rigid aromatic heterocyclic structure and heat-resistant properties, when dispersed in the rubber matrix, can restrict the movement of rubber chain segments and improve the stability of the rubber network at high temperatures, enabling the material to maintain high resilience after high-temperature compression. Furthermore, the synergistic effect of spherical silica and the perfluoropolyether lubrication system can effectively reduce the Mooney viscosity of the rubber compound, improve its flow properties during molding, reduce weld lines and surface defects, and improve the molding integrity and product yield of complex structure seals. Therefore, the perfluoroether rubber prepared by this invention has excellent processing flow properties, low compression set, high-temperature sealing stability, and long-term thermal cycling stability, making it suitable for sealing applications in high-temperature, high-corrosion, and high-cleanliness environments. Attached Figure Description

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] Figure 1 The image shows a comparison of the infrared spectra of the silicon-oxygen precursor and the quaternary phosphonium salt-phenylboronic acid-silicon-oxygen synergistic modifier. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0029] Example 1: The purpose of this example is to obtain a low compression set perfluoroether rubber for high-temperature sealing with low Mooney viscosity and good processing flow properties.

[0030] S1, 10 parts of tetraethoxysilane and 5 parts of vinyltriethoxysilane were added to 30 parts of deionized water and pre-hydrolyzed at 40°C for 1 h under stirring at 300 rpm, with the pH of the system controlled at 3, to obtain a silicon-oxygen precursor solution; then 2 parts of 4-vinylphenylboronic acid were added to the silicon-oxygen precursor solution and stirred at 400 rpm for 2 h at 45°C to disperse the phenylboronic acid structure in the silicon-oxygen network, to obtain a boric acid-functionalized silicon-oxygen composite solution; then 2 parts of tetraphenylphosphonium bromide were added to the boric acid-functionalized silicon-oxygen composite solution and reacted at 50°C for 2 h, followed by drying at 80°C for 4 h to obtain a quaternary phosphonium salt-phenylboronic acid-silicon-oxygen synergistic modified product;

[0031] S2, 100 parts of perfluoroether rubber, 15 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, 10 parts of spherical silica, and 5 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers in a mass ratio of 1:1 are added to a mixing apparatus and mixed at 55°C and 35 rpm for 15 min to disperse the spherical silica and synergistic modifier in the perfluoroether rubber matrix, thus obtaining a premixed compound; then, 2 parts of 2-phenylbenzimidazole, 1 part of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder in a mass ratio of 5:1, 1 part of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide in a mass ratio of 2:1, and 1 part of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate in a mass ratio of 3:1 are added to the premixed compound and synergistically mixed at 70°C and 40 rpm for 20 min to obtain a modified compound;

[0032] S3, add 1 part of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 1:1 and 1 part of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 1:1 to the modified compound, and perform final mixing at 50°C for 5 min; then mold at 170°C for 8 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 250°C for 6 h to obtain a high-temperature sealing low compression set perfluoroether rubber.

[0033] Example 2: The purpose of this example is to obtain a high-temperature sealing low compression set perfluoroether rubber with optimal overall performance in terms of compression set, high-temperature sealing stability and processing flow.

[0034] S1, 25 parts of tetraethoxysilane and 18 parts of vinyltriethoxysilane were added to 75 parts of deionized water and pre-hydrolyzed at 58°C for 3 h under stirring at 550 rpm, with the pH of the system controlled at 5, to obtain a silicon-oxygen precursor solution; then 10 parts of 4-vinylphenylboronic acid were added to the silicon-oxygen precursor solution and stirred at 650 rpm for 4 h at 65°C to disperse the phenylboronic acid structure in the silicon-oxygen network, to obtain a boric acid-functionalized silicon-oxygen composite solution; then 8 parts of tetraphenylphosphonium bromide were added to the boric acid-functionalized silicon-oxygen composite solution and reacted at 70°C for 5 h, followed by drying at 105°C for 8 h to obtain a quaternary phosphonium salt-phenylboronic acid-silicon-oxygen synergistic modifier; Figure 1 Infrared spectral comparison results show that the unmodified silicon-oxygen precursor is mainly concentrated at 1110 cm⁻¹. -1 and 1035 cm -1 The presence of characteristic Si-O-Si absorption peaks nearby indicates the formation of a preliminary silicon-oxygen network structure in the system; after modification, the peak at 1605 cm⁻¹... -1 1510 cm -1 and 695 cm -1 The presence of significantly enhanced aromatic ring characteristic peaks nearby indicates that the tetraphenylphosphonium and 4-vinylphenylboronic acid structures have been successfully introduced into the system; simultaneously, at 1190 cm⁻¹... -1 The presence of a characteristic BOC absorption peak nearby indicates a synergistic effect between the phenylboronic acid structure and the silicon-oxygen network; after modification, the peak value is 1110 cm⁻¹. -1 and 1035 cm -1 The further enhancement of the absorption peak indicates that the system has formed a more stable organic-inorganic hybrid network structure;

[0035] S2, 130 parts of perfluoroether rubber, 35 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, 30 parts of spherical silica, and 20 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers at a mass ratio of 3:1 were added to a mixing apparatus and mixed at 75°C and 55 rpm for 28 min to disperse the spherical silica and synergistic modifier in the perfluoroether rubber matrix, thus obtaining a premixed compound; then, 8 parts of 2-phenylbenzimidazole, 5 parts of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder at a mass ratio of 10:1, 4 parts of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide at a mass ratio of 5:1, and 3 parts of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate at a mass ratio of 6:1 were added to the premixed compound and synergistically mixed at 95°C and 65 rpm for 35 min to obtain a modified compound;

[0036] S3, add 4 parts of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 2:1 and 5 parts of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 2:1 to the modified compound, and finally knead at 68°C for 12 min; then mold at 190°C for 18 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 290°C for 12 h to obtain a perfluoroether rubber with low compression set for high-temperature sealing.

[0037] Example 3: The purpose of this example is to obtain a low compression set perfluoroether rubber for high-temperature sealing with excellent high-temperature sealing stability and long-term thermal cycling stability.

[0038] S1, 40 parts of tetraethoxysilane and 30 parts of vinyltriethoxysilane were added to 120 parts of deionized water and pre-hydrolyzed at 75°C for 5 h under stirring at 800 rpm, with the pH of the system controlled at 6, to obtain a silicon-oxygen precursor solution; then 20 parts of 4-vinylphenylboronic acid were added to the silicon-oxygen precursor solution and stirred at 900 rpm for 6 h at 85°C to disperse the phenylboronic acid structure in the silicon-oxygen network, to obtain a boric acid-functionalized silicon-oxygen composite solution; then 15 parts of tetraphenylphosphonium bromide were added to the boric acid-functionalized silicon-oxygen composite solution and reacted at 90°C for 8 h, followed by drying at 130°C for 12 h to obtain a quaternary phosphonium salt-phenylboronic acid-silicon-oxygen synergistic modified product;

[0039] S2, 160 parts of perfluoroether rubber, 60 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, 50 parts of spherical silica, and 35 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers at a mass ratio of 5:1 were added to a mixing apparatus and mixed at 95°C and 80 rpm for 40 min to disperse the spherical silica and synergistic modifier in the perfluoroether rubber matrix, thus obtaining a premixed compound; then, 15 parts of 2-phenylbenzimidazole, 10 parts of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder at a mass ratio of 20:1, 8 parts of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide at a mass ratio of 8:1, and 6 parts of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate at a mass ratio of 10:1 were added to the premixed compound and synergistically mixed at 120°C and 90 rpm for 50 min to obtain a modified compound;

[0040] S3, add 8 parts of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 4:1 and 10 parts of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 3:1 to the modified compound, and finally knead at 85°C for 20 min; then mold at 210°C for 30 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 320°C for 24 h to obtain a perfluoroether rubber with low compression set for high-temperature sealing.

[0041] Comparative Example 1: The purpose of this comparative example is to verify the effect of the quaternary phosphonium salt structure in the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier on the high-temperature compression set properties of perfluoroether rubber.

[0042] S1, 25 parts of tetraethoxysilane and 18 parts of vinyltriethoxysilane were added to 75 parts of deionized water and pre-hydrolyzed at 58°C for 3 h under stirring at 550 rpm, with the pH of the system controlled at 5, to obtain a silicon-oxygen precursor solution; then 10 parts of 4-vinylphenylboronic acid were added to the silicon-oxygen precursor solution and stirred at 650 rpm for 4 h at 65°C to disperse the phenylboronic acid structure in the silicon-oxygen network, to obtain a boric acid-functionalized silicon-oxygen composite solution; then dried at 105°C for 8 h to obtain the phenylboronic acid-silicon-oxygen modified product;

[0043] S2, 130 parts of perfluoroether rubber, 35 parts of phenylboronic acid-siloxane modifier, 30 parts of spherical silica, and 20 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers at a mass ratio of 3:1 were added to a mixing apparatus and mixed at 75°C and 55 rpm for 28 min to disperse the spherical silica and modified structure in the perfluoroether rubber matrix, thus obtaining a premixed rubber compound; then, 8 parts of 2-phenylbenzimidazole, 5 parts of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder at a mass ratio of 10:1, 4 parts of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide at a mass ratio of 5:1, and 3 parts of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate at a mass ratio of 6:1 were added to the premixed rubber compound and synergistically mixed at 95°C and 65 rpm for 35 min to obtain a modified compound;

[0044] S3, add 4 parts of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 2:1 and 5 parts of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 2:1 to the modified compound, and finally grind at 68°C for 12 min; then mold at 190°C for 18 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 290°C for 12 h to obtain perfluoroether rubber for high-temperature sealing.

[0045] Comparative Example 2: The purpose of this comparative example is to verify the influence of the phenylboronic acid structure in the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modification structure on the high-temperature sealing stability of perfluoroether rubber.

[0046] S1, 25 parts of tetraethoxysilane and 18 parts of vinyltriethoxysilane were added to 75 parts of deionized water and pre-hydrolyzed at 58°C for 3 h under stirring at 550 rpm, with the pH of the system controlled at 5, to obtain a silicon-oxygen precursor solution; then 8 parts of tetraphenylphosphonium bromide were added to the silicon-oxygen precursor solution and reacted at 70°C for 5 h, followed by drying at 105°C for 8 h to obtain a quaternary phosphonium salt-silicon-oxygen modified product;

[0047] S2, 130 parts of perfluoroether rubber, 35 parts of quaternary phosphonium salt-siloxane modifier, 30 parts of spherical silica, and 20 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers at a mass ratio of 3:1 were added to a mixing apparatus and mixed at 75°C and 55 rpm for 28 min to disperse the spherical silica and modified structure in the perfluoroether rubber matrix, thus obtaining a premixed compound; then, 8 parts of 2-phenylbenzimidazole, 5 parts of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder at a mass ratio of 10:1, 4 parts of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide at a mass ratio of 5:1, and 3 parts of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate at a mass ratio of 6:1 were added to the premixed compound and synergistically mixed at 95°C and 65 rpm for 35 min to obtain a modified compound;

[0048] S3, add 4 parts of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 2:1 and 5 parts of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 2:1 to the modified compound, and finally grind at 68°C for 12 min; then mold at 190°C for 18 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 290°C for 12 h to obtain perfluoroether rubber for high-temperature sealing.

[0049] Comparative Example 3: The purpose of this comparative example is to verify the effect of 2-phenylbenzimidazole organic small molecules on the high-temperature compression resilience of perfluoroether rubber.

[0050] S1, 25 parts of tetraethoxysilane and 18 parts of vinyltriethoxysilane were added to 75 parts of deionized water and pre-hydrolyzed at 58°C for 3 h under stirring at 550 rpm, with the pH of the system controlled at 5, to obtain a silicon-oxygen precursor solution; then 10 parts of 4-vinylphenylboronic acid were added to the silicon-oxygen precursor solution and stirred at 650 rpm for 4 h at 65°C to disperse the phenylboronic acid structure in the silicon-oxygen network, to obtain a boric acid-functionalized silicon-oxygen composite solution; then 8 parts of tetraphenylphosphonium bromide were added to the boric acid-functionalized silicon-oxygen composite solution and reacted at 70°C for 5 h, followed by drying at 105°C for 8 h to obtain a quaternary phosphonium salt-phenylboronic acid-silicon-oxygen synergistic modifier;

[0051] S2, 130 parts of perfluoroether rubber, 35 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, 30 parts of spherical silica, and 20 parts of high-temperature resistant reinforcing agent formed by mixing boron nitride and silicon carbide whiskers at a mass ratio of 3:1 were added to a mixing apparatus and mixed at 75°C and 55 rpm for 28 min to disperse the spherical silica and synergistic modifier in the perfluoroether rubber matrix, thus obtaining a premixed compound; then, 5 parts of perfluoropolyether lubricant formed by mixing perfluoropolyether oil and polytetrafluoroethylene micro powder at a mass ratio of 10:1, 4 parts of heat-resistant stabilizer formed by mixing magnesium oxide and cerium oxide at a mass ratio of 5:1, and 3 parts of processing dispersant formed by mixing fluorosilicone modified polyether and zinc stearate at a mass ratio of 6:1 were added to the premixed compound and synergistically mixed at 95°C and 65 rpm for 35 min to obtain a modified compound;

[0052] S3, add 4 parts of peroxide vulcanizing agent formed by mixing bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 2:1 and 5 parts of crosslinking aid formed by mixing triallyl isocyanurate and bismaleimide in a mass ratio of 2:1 to the modified compound, and finally grind at 68°C for 12 min; then mold at 190°C for 18 min and perform a first vulcanization treatment, followed by a second-stage high-temperature vulcanization at 290°C for 12 h to obtain perfluoroether rubber for high-temperature sealing.

[0053] Performance testing:

[0054] 1. Compression set test

[0055] The perfluoroether rubbers prepared in the examples and comparative examples were cut into cylindrical sealing samples of the same size and placed at room temperature for 24 h before testing. Subsequently, the samples were placed in a compression fixture and compressed to 25% of their original thickness, and then placed in a 300°C high-temperature oven for 24 h to simulate the long-term pressure condition of perfluoroether rubber in a high-temperature sealing environment. After the treatment, the samples were taken out and allowed to recover at room temperature for 30 min. The thickness recovery of the samples was measured, and the compression set value was calculated to evaluate the rebound recovery ability and long-term sealing stability of the material after high-temperature compression.

[0056] 2. Mooney viscosity and processing flow properties test

[0057] The compound rubbers obtained in the examples and comparative examples were placed in a Mooney viscosity testing device and tested under specified preheating conditions. The changes in Mooney viscosity of the rubber compounds under high-temperature shear conditions were recorded. Simultaneously, complex-structure sealed samples were prepared from each group of rubber compounds under the same molding conditions. The integrity of the mold cavity filling, the number of weld lines, and the surface defects of the products were observed to evaluate the improvement effect of spherical silica and synergistic modified structures on the processing flow properties and molding stability of perfluoroether rubber. Based on the disclosed information, reducing Mooney viscosity helps to reduce weld lines and improve the product yield.

[0058] 3. High-temperature sealing stability performance test

[0059] The perfluoroether rubbers prepared in the examples and comparative examples were processed into O-ring seal samples and installed in a high-temperature sealing test device for long-term sealing tests under continuous high temperature and cyclic pressure conditions. During the test, the leakage at the sealing interface, the sealing failure time, and the surface changes of the seal were continuously recorded to evaluate the long-term sealing stability and thermal cycling performance of the material in a high-temperature environment.

[0060] 4. High-temperature rebound stability test

[0061] The perfluoroether rubbers prepared in the examples and comparative examples were processed into standard elasticity test specimens, and their initial rebound properties were measured at room temperature. Subsequently, the specimens were placed in a high-temperature environment of 280°C for 12 hours to simulate the long-term use environment of perfluoroether rubber under high-temperature sealing conditions. After the high-temperature treatment, the specimens were restored to room temperature and their rebound properties were measured again. At the same time, the presence of rebound lag, local hardening and elasticity decrease in the specimens were recorded to evaluate the improvement effect of the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modification structure and 2-phenylbenzimidazole on the high-temperature elasticity retention ability and long-term use stability of perfluoroether rubber.

[0062] Table 1 Performance test results of the examples and comparative examples

[0063] Group Compression permanent deformation / % Mooney viscosity / ML High temperature sealing duration / h High temperature rebound retention rate / % Example 1 19.6 61 420 82 Example 2 11.3 48 685 93 Example 3 14.8 56 610 89 Comparative Example 1 24.7 63 395 76 Comparative Example 2 22.9 60 438 79 Comparative Example 3 28.5 65 352 71

[0064] According to Table 1, the low compression set perfluoroether rubbers for high-temperature sealing prepared in Examples 1-3 are significantly better than the comparative examples in terms of compression set, Mooney viscosity, high-temperature sealing duration, and high-temperature rebound retention. This indicates that the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modification structure and 2-phenylbenzimidazole have a good synergistic reinforcing effect, which can effectively improve the high-temperature sealing stability and processing flow properties of perfluoroether rubber.

[0065] Among them, Example 2 exhibited the best overall performance, with a compression set of only 11.3%, significantly lower than Comparative Examples 1-3. This indicates that the synergistic modification structure formed by the quaternary phosphonium salt structure, phenylboronic acid structure, and silicon-oxygen network can effectively alleviate the stress concentration phenomenon inside the rubber under high-temperature compression conditions, while improving the resilience of the rubber network under long-term high-temperature conditions. In addition, Example 2 achieved a high-temperature resilience retention rate of 93%, indicating that the introduction of 2-phenylbenzimidazole can further improve the stability of rubber segments under high-temperature conditions and enhance the high-temperature elasticity retention of the material.

[0066] The Mooney viscosity of Example 2 was 48 ML, which was lower than that of other examples and comparative examples, indicating that the spherical silica and perfluoropolyether lubrication system can effectively improve the flow properties of the rubber compound during the molding process, thereby reducing weld lines and surface defects of the product; at the same time, its high-temperature sealing duration reached 685 h, indicating that the synergistic modified structure can improve the interfacial stability and thermal cycling stability of perfluoroether rubber in long-term high-temperature sealing environment.

[0067] Comparative Example 1, lacking the quaternary phosphonium salt ion synergistic structure formed by tetraphenylphosphonium bromide, resulted in a significant increase in compression set and a decrease in high-temperature rebound retention, indicating that the quaternary phosphonium salt structure plays an important role in the flexible buffering capacity of the rubber network. Comparative Example 2, lacking the 4-vinylphenylboronic acid structure, resulted in a decrease in the high-temperature sealing duration, indicating that the phenylboronic acid structure can improve the interfacial stability between the silicon-oxygen network and the rubber matrix. Comparative Example 3, lacking the addition of 2-phenylbenzimidazole, resulted in a significant decrease in high-temperature rebound performance and compression set performance, indicating that the organic small molecule structure can effectively improve the high-temperature stability of the rubber network.

[0068] In summary, this invention achieves a synergistic improvement in the processing flow properties, high-temperature resilience properties, and low compression set properties of perfluoroether rubber by constructing a quaternary phosphonium salt-phenylboronic acid-silica synergistic modified structure and combining it with a 2-phenylbenzimidazole, spherical silica, and perfluoropolyether lubrication system. The resulting material exhibits excellent high-temperature sealing stability and long-term thermal cycling performance.

Claims

1. A low compression set perfluoroether rubber for high temperature sealing, characterized by, The raw materials include the following parts by weight: 100-160 parts of perfluoroether rubber; 15-60 parts of quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier; 2-15 parts of 2-phenylbenzimidazole; 10-50 parts of spherical silica; 1-10 parts of perfluoropolyether lubricant; 5-35 parts of high-temperature resistant reinforcing agent; 1-8 parts of peroxide vulcanizing agent; 1-10 parts of crosslinking aid; 1-8 parts of heat-resistant stabilizer; and 1-6 parts of processing dispersant. The quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier is an organic-inorganic hybrid network structure formed by hydrolysis, condensation, and synergistic reaction of tetraethoxysilane, vinyltriethoxysilane, tetraphenylphosphonium bromide, and 4-vinylphenylboronic acid.

2. The high-temperature sealing low-compression-per-fluoroether rubber according to claim 1, characterized in that, The quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier comprises the following raw materials in parts by weight: 10-40 parts of tetraethoxysilane; 5-30 parts of vinyltriethoxysilane; 2-15 parts of tetraphenylphosphonium bromide; 2-20 parts of 4-vinylphenylboronic acid; and 30-120 parts of deionized water.

3. A low-compression-per-fluoroether rubber for high-temperature sealing according to claim 1 or 2, characterized in that, The preparation method of the quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier includes the following steps: (1) Tetraethoxysilane and vinyltriethoxysilane were added to deionized water and mixed. A pre-hydrolysis reaction was carried out under stirring to obtain a silicon-oxygen precursor solution. (2) Add 4-vinylphenylboronic acid to the silicon-oxygen precursor solution to carry out a synergistic reaction, so that the phenylboronic acid structure is dispersed in the silicon-oxygen network to obtain boric acid functionalized silicon-oxygen composite solution; (3) Add tetraphenylphosphonium bromide to the boric acid functionalized silicon oxide composite solution to carry out ion synergistic modification reaction, and then dry it to obtain quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modified product.

4. The high-temperature sealing low-compression-per-fluoroether rubber according to claim 3, characterized in that, The reaction conditions for step (1) are: stirring speed of 300-800 rpm, pre-hydrolysis temperature of 40-75℃, reaction time of 1-5 h, and pH of system of 3-6.

5. The high-temperature sealing low-compression-per-fluoroether rubber according to claim 3, characterized in that, The reaction conditions for step (2) are a synergistic reaction temperature of 45-85℃, a reaction time of 2-6 h, and a stirring speed of 400-900 rpm.

6. The high-temperature sealing low-compression-per-fluoroether rubber according to claim 3, characterized in that, The reaction conditions for step (3) are: ion synergistic modification temperature of 50-90℃, reaction time of 2-8 h, followed by drying treatment at 80-130℃ for 4-12 h.

7. The high-temperature sealing low-compression-per-fluoroether rubber according to claim 1, characterized in that, The perfluoropolyether lubricant is a mixture of perfluoropolyether oil and polytetrafluoroethylene micro powder in a mass ratio of 5:1 to 20:1; the high-temperature reinforcing agent is a mixture of boron nitride and silicon carbide whiskers in a mass ratio of 1:1 to 5:1; the peroxide curing agent is a mixture of bis(2,5-diphenylperoxide) and dicumyl peroxide in a mass ratio of 1:1 to 4:1; the crosslinking aid is a mixture of triallyl isocyanurate and bismaleimide in a mass ratio of 1:1 to 3:1; the heat-resistant stabilizer is a mixture of magnesium oxide and cerium oxide in a mass ratio of 2:1 to 8:1; and the processing dispersant is a mixture of fluorosilicone modified polyether and zinc stearate in a mass ratio of 3:1 to 10:

1.

8. A method for preparing a low-compression-per-fluoroether rubber for high-temperature sealing, characterized in that, The preparation method includes the following steps: S1, Perfluoroether rubber, quaternary phosphonium salt-phenylboronic acid-siloxane synergistic modifier, spherical silica and high-temperature reinforcing agent are added to a mixing equipment for premixing treatment, so that the spherical silica and synergistic modifier are dispersed in the perfluoroether rubber matrix to reduce the Mooney viscosity of the rubber compound and improve the molding flow performance, thus obtaining a premixed rubber compound; S2, 2-phenylbenzimidazole, perfluoropolyether lubricant, heat stabilizer and processing dispersant are added to the premixed rubber compound for synergistic mixing, so that 2-phenylbenzimidazole is dispersed in the rubber network and the high temperature compression resilience is improved, and the modified compound is obtained. S3 involves adding peroxide vulcanizing agent and crosslinking aid to the modified compound for final mixing, followed by compression molding, and then primary vulcanization and secondary high-temperature vulcanization treatment to reduce high-temperature compression set and reduce weld line defects in the product, resulting in a low compression set perfluoroether rubber for high-temperature sealing.

9. The method for preparing a low-compression-per-fluoroether rubber for high-temperature sealing according to claim 8, characterized in that, The reaction conditions for step S1 are: mixing temperature of 55-95℃, mixing time of 15-40 min, and mixing speed of 35-80 rpm; the reaction conditions for step S2 are: co-mixing temperature of 70-120℃, mixing time of 20-50 min, and mixing speed of 40-90 rpm.

10. The method for preparing a low-compression-per-fluoroether rubber for high-temperature sealing according to claim 8, characterized in that, The reaction conditions for step S3 are as follows: final refining temperature is 50-85℃, final refining time is 5-20 min; molding temperature is 170-210℃, molding time is 8-30 min; after the first vulcanization, a second-stage high-temperature vulcanization treatment is carried out at 250-320℃ for 6-24 h.

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