EPDM seal material for electronic water pump shaft seal and preparation method thereof

Abstract

The application discloses an EPDM sealing material for electronic water pump shaft seals and a preparation method thereof, and belongs to the technical field of rubber sealing materials. Double-bond modified hexagonal boron nitride and trifluoropropyltrimethoxysilane composite nanospheres are used as auxiliary reinforcing phases. The double-bond modified hexagonal boron nitride is a layered ceramic material with the characteristic of easy sliding. The trifluoropropyltrimethoxysilane composite nanospheres have a hollow structure and play a role similar to that of a ball bearing in the rubber matrix. The two can synergistically reduce the friction between the rubber molecular chains, so that the rubber molecular chains can more freely slide and deform under stress, can absorb stress at high and low temperatures, have good temperature impact resistance, and can adapt to the working requirements of electronic water pump shaft seals in cold northern regions.

Description

Technical Field

[0001] This invention belongs to the field of rubber seal technology, specifically EPDM sealing material for shaft seals of electronic water pumps and its preparation method. Background Technology

[0002] The electric water pump is a crucial component in an automotive thermal management system. It is typically driven and regulated by an electronic control unit (ECU) to circulate coolant. As a vital component of the electric water pump, the shaft seal places high demands on the performance of the sealing materials used.

[0003] Ethylene propylene diene monomer (EPDM) rubber is widely used in various sealing components due to its excellent aging resistance and chemical stability. Chinese patent application CN114702761A discloses a rubber material for sealing components that is resistant to ultra-high temperatures and low pressure deformation, and its preparation method. This method uses EPDM raw rubber with VNB as the third monomer and DCPD as the third monomer as the main materials, while also incorporating VMQ raw rubber. The three materials work synergistically to meet the standards of ultra-high temperature heat aging at 200℃ and high compression set at 200℃, as well as long-term high-temperature aging at 180℃ and high compression set at 180℃. It is particularly suitable for the shaft seal of electronic water pumps in automotive thermal management systems.

[0004] The above solutions share similarities with conventional solutions in that they all use carbon black as a reinforcing filler. Nanoscale carbon black particles can act as physical cross-linking points, improving the mechanical properties of rubber materials. However, the rigid particle properties of nano-carbon black and the strong interfacial constraints resulting from its high specific surface area significantly increase the glass transition temperature of rubber, causing it to transition from a highly elastic state to a glassy state earlier at low temperatures, thus losing its elasticity. Automotive thermal management systems also face the challenge of low-temperature operating conditions in cold northern environments. When the car starts, the temperature at the sealing components rises, which can cause stress-induced brittle fracture, thus affecting the stability of the EPDM sealing material. Summary of the Invention

[0005] The purpose of this invention is to provide EPDM sealing material for electronic water pump shaft seals and its preparation method. Double-bond modified hexagonal boron nitride and trifluoropropane-trimethoxysilane composite nanospheres are used as auxiliary reinforcing phases. Double-bond modified hexagonal boron nitride, as a layered ceramic material, has easy slip characteristics. The trifluoropropane-trimethoxysilane composite nanospheres have a hollow structure and act similarly to ball bearings in the rubber matrix. The two work synergistically to reduce friction between rubber molecular chains, allowing the rubber molecular chains to slip and deform more freely under stress. This enables the material to absorb stress at both high and low temperatures and provides good resistance to temperature shock, making it suitable for use in cold northern regions under high and low temperature shock conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The preparation method of EPDM sealing material for shaft seals of electronic water pumps includes the following steps:

[0008] Step 1: Hydrolyze γ-methacryloxypropyltrimethoxysilane to generate silanol groups, which then undergo a dehydration condensation reaction with the hydroxyl groups on the surface of hydroxylated hexagonal boron nitride to obtain double-bond modified hexagonal boron nitride.

[0009] Step 2: Using dicumyl peroxide as an initiator, grafting of EPDM rubber, modified hexagonal boron nitride, and 2-(1-styrene)benzofuran free radicals is initiated. Then, the furan groups undergo a Diels-Alder reaction with N,N'-(4,4'-methylenediphenyl)bismaleimide to form a thermally reversible covalent crosslinking network, thus obtaining modified EPDM rubber.

[0010] Step 3: Modified mesoporous silica nanospheres are obtained by reacting the carboxyl groups of the carboxyl hollow mesoporous silica nanoparticles with the amino groups of γ-aminopropyltriethoxysilane through an amidation reaction; trifluoropropanetrimethoxysilane composite nanospheres are obtained by condensing the silanol groups on the trifluoropropanetrimethoxysilane molecular chain with the silanol groups on the surface of the modified mesoporous silica nanospheres.

[0011] Step 4: The modified EPDM rubber is plasticized, then mixed with paraffin oil, zinc oxide, TMQ antioxidant, trifluoropropane-trimethoxysilane composite nanospheres, carbon black and polyethylene wax, and then sheeted. It is then mixed with dicumyl peroxide and triallyl isocyanurate, and sheeted again to obtain EPDM sealing material for electronic water pump shaft seals.

[0012] Furthermore, the mass ratio of modified EPDM rubber, paraffin oil, zinc oxide, TMQ antioxidant, trifluoropropane-trimethoxysilane composite nanospheres, carbon black, polyethylene wax, dicumyl peroxide, and triallyl isocyanurate is 100-110:12-14:5-7:1-2:25-27:30-35:3-4:7-8:2-4.

[0013] Furthermore, the specific preparation steps for double-bond modified hexagonal boron nitride are as follows:

[0014] Hydroxylated modified hexagonal boron nitride, ethanol, and deionized water were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. The pH was then adjusted to 4 with hydrochloric acid, and γ-methacryloyloxypropyltrimethoxysilane was added. The mixture was heated to 80-90℃ and stirred for 12-14 h. After centrifugation at 8000-9000 r / min for 3-5 min, the mixture was filtered. The precipitate was washed 2-4 times with deionized water and anhydrous ethanol, and then dried under vacuum at 60-80℃ for 1-2 h to obtain double-bond modified hexagonal boron nitride.

[0015] Furthermore, the ratio of hydroxylated modified hexagonal boron nitride, ethanol, deionized water and γ-methacryloyloxypropyltrimethoxysilane is 5-6g: 200-300mL: 100-120mL: 20-30mL.

[0016] Furthermore, the specific preparation steps for modified EPDM rubber are as follows:

[0017] Ethylene propylene diene monomer (EPDM) rubber, dicumyl peroxide, double-bond modified hexagonal boron nitride, 2-(1-styryl)benzofuran, and N,N'-(4,4'-methylenediphenyl)bismaleimide were added to a reaction vessel and heated to 170-180℃. The mixture was stirred at 60-70 r / min for 5-6 min. The product was then placed in a hot press and hot-pressed at 170-180℃ and 5-10 MPa for 5-7 min. After annealing at 60-70℃ for 1-2 h, the Diels-Alder reaction was allowed to proceed completely, yielding modified EPDM rubber.

[0018] Furthermore, the ratio of EPDM rubber, dicumyl peroxide, double-bond modified hexagonal boron nitride, 2-(1-styrene)benzofuran and N,N'-(4,4'-methylenediphenyl)bismaleimide is 100-110g: 1-1.2g: 3-4g: 10-12g: 1.4-1.6g.

[0019] Furthermore, the specific preparation steps of the modified mesoporous silica nanospheres are as follows:

[0020] Carboxyl-based hollow mesoporous silica nanoparticles and ethanol were added to a reaction vessel and stirred for 10-15 min at 20-25℃ and 500-600 r / min. Under a nitrogen atmosphere, N,N-diisopropylethylamine and O-benzotriazole-tetramethylurea hexafluorophosphate were added for activation for 3-5 min. Then, γ-aminopropyltriethoxysilane was added and the reaction was continued for 1-2 h. After filtration, the precipitate was washed 2-4 times with ethanol and isopropanol, respectively, and dried under vacuum at 60-70℃ for 24-26 h to obtain modified mesoporous silica nanospheres.

[0021] Furthermore, the ratio of carboxyl-containing hollow mesoporous silica nanoparticles, ethanol, N,N-diisopropylethylamine, O-benzotriazole-tetramethylurea hexafluorophosphate, and γ-aminopropyltriethoxysilane is 20-30 g: 1-1.2 L: 0.125-0.128 g: 0.1-0.2 g: 10-12 mL.

[0022] Furthermore, the specific preparation steps of the trifluoropropane-trimethoxysilane composite nanospheres are as follows:

[0023] Modified mesoporous silica nanospheres and a 50-60% (w / w) ethanol solution were added to a reaction vessel and stirred for 10-15 min at 20-25℃ and 500-600 r / min. Then, NaOH was added to adjust the pH to 8-9, followed by the addition of trifluoropropanetrimethoxysilane. The reaction was continued for 24-26 h. After filtration, the precipitate was washed 2-4 times with ethanol and deionized water, respectively, and then dried under vacuum at 60-70℃ for 24-26 h to obtain trifluoropropanetrimethoxysilane composite nanospheres.

[0024] Furthermore, the ratio of modified mesoporous silica nanospheres, ethanol solution, and trifluoropropanetrimethoxysilane is 5-7g:1-1.2L:2-4g.

[0025] Furthermore, the specific preparation steps for the EPDM sealing material used in the shaft seal of the electronic water pump are as follows:

[0026] Modified EPDM rubber was placed in a mixing chamber and plasticized at 60-70℃ for 45-50s. Then, paraffin oil, zinc oxide, TMQ antioxidant, trifluoropropane-trimethoxysilane composite nanospheres, and polyethylene wax were added and mixed for 450-550s until the temperature reached 150-155℃. The rubber was then discharged and sheeted. The temperature was lowered to 60-70℃, and dicumyl peroxide and triallyl isocyanurate were added and mixed for 200-220s until the temperature reached 105-110℃. The rubber was then discharged, and the product was passed through a two-roll mill 3-5 times before sheeting to obtain EPDM sealing material for electronic water pump shaft seals.

[0027] The beneficial effects of this invention are:

[0028] 1. The EPDM sealing material for electronic water pump shaft seals prepared in this invention uses double-bond modified hexagonal boron nitride and trifluoropropane-trimethoxysilane composite nanospheres as auxiliary reinforcing phases. Double-bond modified hexagonal boron nitride is a layered ceramic material with easy slippage characteristics, while trifluoropropane-trimethoxysilane composite nanospheres have a hollow structure and play a role similar to ball bearings in the rubber matrix. The two work together to reduce friction between rubber molecular chains, allowing the rubber molecular chains to slip and deform more freely under stress. It can absorb stress at high and low temperatures and has good resistance to temperature shock, making it suitable for the working requirements of electronic water pump shaft seals in cold northern regions.

[0029] 2. The double-bond modified hexagonal boron nitride and trifluoropropane-trimethoxysilane composite nanospheres of the present invention both contain a hydrophobic layer on their surface, which can effectively block the contact between water, cooling liquid ethylene glycol and rubber matrix. While increasing compatibility with rubber matrix, they can reduce the surface activity of oxygen-containing functional groups on the surface, reduce the degree of chemical reaction between the nanospheres and rubber matrix under high temperature and alkaline conditions, maintain the bonding point with rubber, and improve the service life of the seal.

[0030] 3. The trifluoropropane-trimethoxysilane composite nanospheres of the present invention have a trifluoropropane-trimethoxysilane layer on their surface that is not only a hydrophobic barrier layer, but also forms an interfacially compatible connecting phase with the rubber matrix and double-bond modified hexagonal boron nitride, thereby improving the interfacial bonding strength between the filler and the modified EPDM rubber.

[0031] 4. The modified EPDM rubber of the present invention contains a reversible crosslinking network, which can improve the uniformity of crosslinking points, inhibit compression set and stress relaxation, and significantly improve the service life of the seal. Furthermore, the double-bond modified hexagonal boron nitride of the present invention contains Lewis acid sites on its surface, which can catalyze the Diels-Alder reaction when 2-(1-styryl)benzofuran and N,N'-(4,4'-methylenediphenyl)bismaleimide undergo a Diels-Alder reaction, thereby increasing the degree of crosslinking. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: A method for preparing EPDM sealing material for an electronic water pump shaft seal, comprising the following steps:

[0034] S1: Add 5g of hydroxylated hexagonal boron nitride, 200mL of ethanol and 100mL of deionized water to a reaction vessel, stir for 20min at 20℃ and 500r / min, then adjust the pH to 4 with hydrochloric acid, add 20mL of γ-methacryloyloxypropyltrimethoxysilane, heat to 80℃, continue stirring for 12h, centrifuge at 8000r / min for 3min, filter, wash the precipitate twice with deionized water and anhydrous ethanol respectively, and dry under vacuum at 60℃ for 1h to obtain double bond modified hexagonal boron nitride.

[0035] S2: 100g of EPDM rubber, 1g of dicumyl peroxide, 3g of double-bond modified hexagonal boron nitride, 10g of 2-(1-styryl)benzofuran and 1.4g of N,N'-(4,4'-methylenediphenyl)bismaleimide were added to a reaction vessel and heated to 170℃. The mixture was stirred at 60r / min for 5min. The product was then placed in a hot press and hot-pressed at 170℃ and 5MPa for 5min. After annealing at 60℃ for 1h, the Diels-Alder reaction was allowed to proceed completely to obtain modified EPDM rubber.

[0036] S3: 20g of carboxyl-based hollow mesoporous silica nanoparticles and 1L of ethanol were added to a reaction vessel and stirred for 10min at 20℃ and 500r / min. Under a nitrogen atmosphere, 0.125g of N,N-diisopropylethylamine and 0.1g of O-benzotriazole-tetramethylurea hexafluorophosphate were added to activate the reaction for 3min. Then, 10mL of γ-aminopropyltriethoxysilane was added and the reaction was continued for 1h. The mixture was filtered, and the precipitate was washed twice with ethanol and isopropanol, respectively. The precipitate was dried under vacuum at 60℃ for 24h to obtain modified mesoporous silica nanospheres.

[0037] S4: Add 5g of modified mesoporous silica nanospheres and 1L of 50% ethanol solution to a reaction vessel, stir for 10min at 20℃ and 500r / min, then add NaOH to adjust the pH to 8, then add 2g of trifluoropropanetrimethoxysilane, continue the reaction for 24h, filter, wash the precipitate twice with ethanol and deionized water respectively, and dry under vacuum at 60℃ for 24h to obtain trifluoropropanetrimethoxysilane composite nanospheres.

[0038] S5: Place 100g of modified EPDM rubber in a mixing chamber and plasticize at 60℃ for 45s. Then add 12g of paraffin oil as a plasticizer, 5g of zinc oxide as an activator, 1g of TMQ antioxidant, 25g of trifluoropropane-trimethoxysilane composite nanospheres, 30g of carbon black, and 3g of polyethylene wax as a lubricant and mix for 450s until the temperature reaches 150℃. Then discharge the rubber and sheet the product. Cool the product to 60℃, add 7g of dicumyl peroxide as a vulcanizing agent and 2g of triallyl isocyanurate as an accelerator and mix for 200s until the temperature reaches 105℃. Then discharge the rubber and place the product in a two-roll mill. After passing through the mill three times at a roller temperature of 60℃ and a roller gap of 0.5mm, sheet the product to obtain EPDM sealing material for electronic water pump shaft seals.

[0039] Example 2: A method for preparing EPDM sealing material for an electronic water pump shaft seal, comprising the following steps:

[0040] S1: Add 5.5g of hydroxylated hexagonal boron nitride, 250mL of ethanol and 110mL of deionized water to a reaction vessel, stir for 25min at 22.5℃ and 550r / min, then adjust the pH to 4 with hydrochloric acid, add 25mL of γ-methacryloyloxypropyltrimethoxysilane, heat to 85℃, continue stirring for 13h, centrifuge at 8500r / min for 4min, filter, wash the precipitate three times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 70℃ for 1.5h to obtain double bond modified hexagonal boron nitride.

[0041] S2: 105g of EPDM rubber, 1.1g of dicumyl peroxide, 3.5g of double-bond modified hexagonal boron nitride, 11g of 2-(1-styrene)benzofuran and 1.5g of N,N'-(4,4'-methylenediphenyl)bismaleimide were added to a reaction vessel and heated to 175℃. The mixture was stirred at 65r / min for 5.5min. The product was then placed in a hot press and hot-pressed at 175℃ and 7.5MPa for 6min. The mixture was then annealed at 65℃ for 1.5h to ensure the Diels-Alder reaction was complete, thus obtaining modified EPDM rubber.

[0042] S3: 25g of carboxyl-based hollow mesoporous silica nanoparticles and 1.1L of ethanol were added to a reaction vessel and stirred for 12.5min at 22.5℃ and 550r / min. Under a nitrogen atmosphere, 0.1265g of N,N-diisopropylethylamine and 0.15g of O-benzotriazole-tetramethylurea hexafluorophosphate were added to activate the reaction for 4min. Then, 11mL of γ-aminopropyltriethoxysilane was added, and the reaction was continued for 1.5h. The mixture was filtered, and the precipitate was washed three times with ethanol and isopropanol, respectively. The precipitate was then dried under vacuum at 65℃ for 25h to obtain modified mesoporous silica nanospheres.

[0043] S4: 6g of modified mesoporous silica nanospheres and 1.1L of 55% ethanol solution were added to a reaction vessel and stirred for 12.5min at 22.5℃ and 550r / min. Then, NaOH was added to adjust the pH to 8.5, followed by the addition of 3g of trifluoropropanetrimethoxysilane. The reaction was continued for 25h. After filtration, the precipitate was washed three times with ethanol and three times with deionized water, and then dried under vacuum at 65℃ for 25h to obtain trifluoropropanetrimethoxysilane composite nanospheres.

[0044] S5: Place 105g of modified EPDM rubber in a mixing chamber and plasticize at 65℃ for 47.5s. Then add 13g of paraffin oil as a plasticizer, 6g of zinc oxide as an activator, 1.5g of TMQ antioxidant, 26g of trifluoropropane-trimethoxysilane composite nanospheres, 32.5g of carbon black, and 3.5g of polyethylene wax as a lubricant and mix for 500s until the temperature reaches 152.5℃. Remove the rubber and sheet the product. Cool the product to 65℃, add 7.5g of dicumyl peroxide as a vulcanizing agent and 3g of triallyl isocyanurate as an accelerator and mix for 210s until the temperature reaches 107.5℃. Remove the rubber and place the product in a two-roll mill. After passing through the mill four times at 65℃ and 0.75mm roller gap, sheet the product to obtain EPDM sealing material for electronic water pump shaft seals.

[0045] Example 3: A method for preparing EPDM sealing material for an electronic water pump shaft seal, comprising the following steps:

[0046] S1: Add 6g of hydroxylated hexagonal boron nitride, 300mL of ethanol and 120mL of deionized water to a reaction vessel, stir for 30min at 25℃ and 600r / min, then adjust the pH to 4 with hydrochloric acid, add 30mL of γ-methacryloyloxypropyltrimethoxysilane, heat to 90℃, continue stirring for 14h, centrifuge at 9000r / min for 5min, filter, wash the precipitate 4 times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 80℃ for 2h to obtain double bond modified hexagonal boron nitride.

[0047] S2: 110g of EPDM rubber, 1.2g of dicumyl peroxide, 4g of double-bond modified hexagonal boron nitride, 12g of 2-(1-styrene)benzofuran and 1.6g of N,N'-(4,4'-methylenediphenyl)bismaleimide were added to a reaction vessel and heated to 180℃. The mixture was stirred at 70r / min for 6min. The product was then placed in a hot press and hot-pressed at 180℃ and 10MPa for 7min. After annealing at 70℃ for 2h, the Diels-Alder reaction was completed to obtain modified EPDM rubber.

[0048] S3: 30g of carboxyl-based hollow mesoporous silica nanoparticles and 1.2L of ethanol were added to a reaction vessel and stirred for 15min at 25℃ and 600r / min. Under a nitrogen atmosphere, 0.128g of N,N-diisopropylethylamine and 0.2g of O-benzotriazole-tetramethylurea hexafluorophosphate were added to activate the reaction for 5min. Then, 12mL of γ-aminopropyltriethoxysilane was added and the reaction was continued for 2h. The mixture was filtered, and the precipitate was washed four times with ethanol and isopropanol, respectively. The precipitate was then dried under vacuum at 70℃ for 26h to obtain modified mesoporous silica nanospheres.

[0049] S4: 7g of modified mesoporous silica nanospheres and 1.2L of 60% ethanol solution were added to a reaction vessel and stirred for 15min at 25℃ and 600r / min. Then, NaOH was added to adjust the pH to 9, and then 4g of trifluoropropanetrimethoxysilane was added. The reaction was continued for 26h. After filtration, the precipitate was washed four times with ethanol and four times with deionized water, and then dried under vacuum at 70℃ for 26h to obtain trifluoropropanetrimethoxysilane composite nanospheres.

[0050] S5: Place 110g of modified EPDM rubber in a mixing chamber and plasticize at 70℃ for 50s. Then add 14g of paraffin oil as a plasticizer, 7g of zinc oxide as an activator, 2g of TMQ antioxidant, 27g of trifluoropropane-trimethoxysilane composite nanospheres, 35g of carbon black, and 4g of polyethylene wax as a lubricant and mix for 550s until the temperature reaches 155℃. Then discharge the rubber and sheet the product. Cool the product to 70℃, add 8g of dicumyl peroxide as a vulcanizing agent and 4g of triallyl isocyanurate as an accelerator and mix for 220s until the temperature reaches 110℃. Then discharge the rubber and place the product in a two-roll mill. After passing through the mill five times at 70℃ and 1mm roller gap, sheet the product to obtain EPDM sealing material for electronic water pump shaft seals.

[0051] Comparative Example 1: Based on Example 3, the trifluoropropane-trimethoxysilane composite nanospheres in step S5 were replaced with commercially available carbon black, while the other steps remained unchanged, to prepare EPDM sealing material for the shaft seal of an electronic water pump.

[0052] Comparative Example 2: Based on Example 3, the modified EPDM rubber in step S5 was replaced with the raw EPDM rubber in step S2, while the other steps remained unchanged, to prepare EPDM sealing material for the shaft seal of an electronic water pump.

[0053] Comparative Example 3: Based on Example 3, the trifluoropropane-trimethoxysilane composite nanospheres in step S5 were replaced with the modified mesoporous silica nanospheres prepared in step S3, while the other steps remained unchanged, to prepare EPDM sealing material for the shaft seal of an electronic water pump.

[0054] Sources of raw materials in the examples and comparative examples:

[0055] Carboxyl-based hollow mesoporous silica nanoparticles were purchased from Beijing Zhongke Keyou Nanotechnology Co., Ltd., with a particle size of 400 nm.

[0056] EPDM rubber was purchased from Sudali Plastics New Materials (Shanghai) Co., Ltd., item number: 4725P.

[0057] The paraffin oil was purchased from Hengshui Xuanqing Petroleum Technology Co., Ltd., CAS No.: 8012-95-1.

[0058] 2-(1-Styryl)benzofuran was purchased from Chemical BooK, CAS No.: 56426-70-1, molecular weight: 220.27.

[0059] N,N'-(4,4'-methylenediphenyl)bismaleimide was purchased from Wuhan Smike Biotechnology Co., Ltd., CAS No.: 13676-54-5.

[0060] O-benzotriazole-tetramethylurea hexafluorophosphate was purchased from Shanghai Hans Chemical Co., Ltd., CAS No.: 94790-37-1.

[0061] Trifluoropropane and trimethoxysilane were purchased from Chemical BooK, CAS No.: 429-60-7.

[0062] Dicumyl peroxide was purchased from Sigma-Aldrich, CAS No.: 80-43-3, molecular weight: 270.37.

[0063] Triallyl isocyanurate was purchased from Sigma-Aldrich, CAS No.: 1025-15-6, molecular weight: 249.27.

[0064] The specific preparation steps for hydroxylated hexagonal boron nitride are as follows:

[0065] 10g of hexagonal boron nitride powder with an average particle size of 500nm (Shanghai Pantian Powder Materials Co., Ltd., product number: PT-BN-500nm) was added to 1L of deionized water and sonicated at 300W for 2h to form a uniform dispersion. Then, 1mmol Tris was added and the pH of the dispersion was adjusted to 8.5 with hydrochloric acid. Then, 2g of dopamine hydrochloride was added and stirred at 25℃ and 500r / min for 4h. After centrifugation at 10000r / min for 5min, the solid product was collected and washed with deionized water until the supernatant was clear. The product was then vacuum dried at 60℃ for 12h to obtain hydroxylated hexagonal boron nitride.

[0066] The performance of the EPDM sealing materials for the shaft seals of electronic water pumps prepared in Examples 1-3 and Comparative Examples 1-3 was tested:

[0067] 1. Mechanical property testing: In accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", tensile tests were conducted at room temperature using a universal testing machine to test tensile strength and elongation at break. In addition, the EPDM sealing material for the shaft seal of the electronic water pump was placed in a 160℃ oven for a 3-day hot air aging test, and the tensile strength and elongation at break were retested.

[0068] 2. Low temperature resistance: Refer to GB / T 15256-2014 "Determination of low temperature brittleness of vulcanized rubber or thermoplastic rubber (multiple sample method)" to test the low temperature resistance of the sealing material, that is, the temperature at which 10% of the sealing material will undergo brittle fracture. The lower the value, the better the low temperature stability of the sealing material can maintain its anti-brittle fracture performance at lower temperatures.

[0069] 3. Temperature shock resistance: The EPDM sealing material for the electric water pump shaft seal was placed in a 160℃ oven for 3 days of hot air aging test. Then, in accordance with the standard GB / T 15256-2014 "Determination of low temperature brittleness of vulcanized rubber or thermoplastic rubber (multiple sample method)", the EPDM sealing material for the electric water pump shaft seal was treated at -20℃ for 4 cycles, and the strength retention rate was tested to evaluate the temperature shock resistance.

[0070] The results are shown in Table 1:

[0071] Table 1. Material Performance Test Table for EPDM Seals Used in Electronic Water Pump Shaft Seals

[0072] As shown in Table 1, the commercially available carbon black in Comparative Example 1 is a conventional reinforcing filler without the hollow structure of trifluoropropane-trimethoxysilane composite nanospheres. The commercially available carbon black is a rigid particle, which will significantly increase the glass transition temperature of EPDM rubber. Moreover, it lacks the stress absorption mechanism of the nanosphere ball bearing friction reduction. At low temperatures, the rubber molecular chains cannot slide freely, which easily leads to brittleness and extremely low heat aging strength retention. The oxygen-containing functional groups on the surface of carbon black have high activity, which easily reacts with the rubber matrix under high temperature alkaline coolant conditions, destroying the bonding point between the filler and the rubber. Furthermore, it lacks a hydrophobic barrier layer, and the ethylene glycol coolant can easily penetrate the rubber matrix, accelerating the molecular chain breakage and ultimately reducing the strength retention.

[0073] In Comparative Example 2, there is no thermal repair and no support from high crosslinking density: Ordinary EPDM rubber lacks a reversible crosslinking network of DA, which cannot improve the uniformity of crosslinking points, suppress compression set and stress relaxation, and has insufficient crosslinking density. The rubber molecular chain constraint is poor, and the mechanical properties and aging resistance are greatly reduced. Ordinary EPDM rubber lacks the lamellar slip toughening mechanism of double bond modified BN, and cannot effectively absorb stress at low temperatures. The molecular chain is prone to rigid breakage and cannot be adapted to ultra-low temperature working conditions in the north. Without the support of a high crosslinking density network, the rubber molecular chain is prone to depolymerization and breakage after thermal aging, which leads to cracking and deformation of the seals.

[0074] In Comparative Example 3, the modified mesoporous silica lacks a hydrophobic layer and interfacial bonding phase with trifluoropropane silane. Its bonding with the rubber matrix relies solely on physical adsorption, which prevents the formation of a ball bearing-type friction-reducing effect at low temperatures, increasing the risk of stress concentration. Without the hydrophobic barrier layer of trifluoropropane silane, ethylene glycol and water in the coolant can easily penetrate the rubber matrix. Furthermore, the high activity of oxygen-containing functional groups on the surface of the modified mesoporous silica makes it prone to chemical reactions with the rubber under high-temperature alkaline conditions, damaging the bond between the filler and the rubber and reducing the strength retention rate. Without the interfacial bonding of trifluoropropane silane, the modified mesoporous silica has poor compatibility with the double-bond modified hexagonal boron nitride and the rubber matrix phase.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. An EPDM sealing material for the shaft seal of an electronic water pump, characterized in that, The composition includes the following components by mass: 100-110 parts modified EPDM rubber, 12-14 parts paraffin oil, 5-7 parts zinc oxide, 1-2 parts TMQ antioxidant, 25-27 parts trifluoropropane-trimethoxysilane composite nanospheres, 30-35 parts carbon black, 3-4 parts polyethylene wax, 7-8 parts dicumyl peroxide and 2-4 parts triallyl isocyanurate; The modified EPDM rubber is prepared by free radical grafting of EPDM rubber, double bond modified hexagonal boron nitride and 2-(1-styrene)benzofuran, followed by a Diels-Alder reaction.

2. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 1, characterized in that, The specific preparation steps of the modified EPDM rubber are as follows: Ethylene propylene diene monomer (EPDM) rubber, dicumyl peroxide, double-bond modified hexagonal boron nitride, 2-(1-styryl)benzofuran, and N,N'-(4,4'-methylenediphenyl)bismaleimide were added to a reaction vessel and heated to 170-180℃. The mixture was stirred at 60-70 r / min for 5-6 min. The product was then placed in a hot press and hot-pressed at 170-180℃ and 5-10 MPa for 5-7 min, followed by annealing for 1-2 h to obtain modified EPDM rubber.

3. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 2, characterized in that, The ratio of the amounts of EPDM rubber, dicumyl peroxide, double-bond modified hexagonal boron nitride, 2-(1-styrene)benzofuran and N,N'-(4,4'-methylenediphenyl)bismaleimide is 100-110g: 1-1.2g: 3-4g: 10-12g: 1.4-1.6g.

4. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 2, characterized in that, The specific preparation steps for the double-bond modified hexagonal boron nitride are as follows: Hydroxylated modified hexagonal boron nitride, ethanol, and deionized water were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. The pH was then adjusted to 4 with hydrochloric acid, and γ-methacryloyloxypropyltrimethoxysilane was added. The mixture was heated to 80-90℃ and stirred for 12-14 h. After centrifugation at 8000-9000 r / min for 3-5 min, the mixture was filtered. The precipitate was washed 2-4 times with deionized water and anhydrous ethanol, and then dried under vacuum at 60-80℃ for 1-2 h to obtain double-bond modified hexagonal boron nitride.

5. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 4, characterized in that, The ratio of the amount of hydroxylated modified hexagonal boron nitride, ethanol, deionized water and γ-methacryloxypropyltrimethoxysilane is 5-6g: 200-300mL: 100-120mL: 20-30mL.

6. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 1, characterized in that, The specific preparation steps of the trifluoropropane-trimethoxysilane composite nanospheres are as follows: Modified mesoporous silica nanospheres and 50-60 wt% ethanol solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 10-15 min. Then, NaOH was added to adjust the pH to 8-9, followed by the addition of trifluoropropanetrimethoxysilane. The reaction was continued for 24-26 h. After filtration, washing, and vacuum drying, trifluoropropanetrimethoxysilane composite nanospheres were obtained.

7. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 6, characterized in that, The ratio of the modified mesoporous silica nanospheres, ethanol solution, and trifluoropropanetrimethoxysilane is 5-7g:1-1.2L:2-4g.

8. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 6, characterized in that, The specific preparation steps for the modified mesoporous silica nanospheres are as follows: Carboxyl-based hollow mesoporous silica nanoparticles and ethanol were added to a reaction vessel and stirred for 10-15 min at 20-25℃ and 500-600 r / min. Under a nitrogen atmosphere, N,N-diisopropylethylamine and O-benzotriazole-tetramethylurea hexafluorophosphate were added for activation for 3-5 min. Then, γ-aminopropyltriethoxysilane was added and the reaction was continued for 1-2 h. After filtration, the precipitate was washed 2-4 times with ethanol and isopropanol, respectively, and dried under vacuum at 60-70℃ for 24-26 h to obtain modified mesoporous silica nanospheres.

9. The EPDM sealing material for the shaft seal of an electronic water pump according to claim 8, characterized in that, The ratio of the carboxyl-based hollow mesoporous silica nanoparticles, ethanol, N,N-diisopropylethylamine, O-benzotriazole-tetramethylurea hexafluorophosphate, and γ-aminopropyltriethoxysilane is 20-30 g: 1-1.2 L: 0.125-0.128 g: 0.1-0.2 g: 10-12 mL.

10. The method for preparing EPDM sealing material for electronic water pump shaft seals according to claim 1, characterized in that, Includes the following steps: Modified EPDM rubber was placed in a mixing chamber and plasticized at 60-70℃ for 45-50s. Then, paraffin oil, zinc oxide, TMQ antioxidant, trifluoropropane-trimethoxysilane composite nanospheres, and polyethylene wax were added and mixed for 450-550s until the temperature reached 150-155℃. The rubber was then discharged and sheeted. The temperature was lowered to 60-70℃, and dicumyl peroxide and triallyl isocyanurate were added and mixed for 200-220s until the temperature reached 105-110℃. The rubber was then discharged, and the product was passed through a two-roll mill 3-5 times before sheeting to obtain EPDM sealing material for electronic water pump shaft seals.

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