High-temperature-resistant and engine oil-resistant sealant based on organic silicon-epoxy hybrid resin and preparation method of high-temperature-resistant and engine oil-resistant sealant

Abstract

The invention relates to a high-temperature-resistant engine oil-resistant sealant based on organic silicon-epoxy hybrid resin and a preparation method of the high-temperature-resistant engine oil-resistant sealant. The high-temperature-resistant engine oil-resistant sealant based on the organic silicon-epoxy hybrid resin is prepared from the following components in parts by weight: 100 parts of an organic silicon-epoxy hybrid polymer, 20 to 25 parts of modified boron nitride, 13 to 17 parts of modified silicon carbide, 8 to 10 parts of mica powder, 3 to 5 parts of graphene oxide, 25 to 30 parts of a curing agent, 0 to 13 parts of hydroxyl-terminated nitrile rubber and 1 to 2 parts of an antioxidant, according to the high-temperature-resistant engine oil-resistant sealant based on the organic silicon-epoxy hybrid resin and the preparation method thereof, the technical problem that the sealant in the prior art cannot meet the requirements of high temperature resistance, engine oil resistance and high cohesiveness at the same time is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sealants, and in particular to a high-temperature and oil-resistant sealant based on an organosilicon-epoxy hybrid resin and a preparation method thereof. Background Art

[0002] Flat sealants are widely used in automotive engine cylinder heads, transmission connectors, and high-temperature sealing rings in aircraft engines. In these applications, sealants are exposed to extreme temperatures and complex oil media (such as engine oil, lubricants, and fuel) for long periods of time, placing extremely stringent demands on the sealant's heat resistance, oil resistance, and interfacial bonding strength. Currently, most flat sealants on the market are anaerobic and silicone sealants, but anaerobic sealants have poor heat and oil resistance. Traditional silicone sealants, while offering excellent high-temperature resistance, also have poor oil resistance.

[0003] Invention patent CN114561049A discloses a high-low temperature resistant and oil-resistant sealing rubber material and its preparation method. The sealing rubber material has good oil medium resistance and can be used for a long time in an environment of -42°C to 140°C, but lacks long-term high temperature resistance verification of >250°C.

[0004] Invention patent CN116063981A discloses a high-temperature resistant anaerobic sealant with a functionalized cage-type silsesquioxane structure, its preparation method, and its application. The sealant prepared in this invention can withstand temperatures up to 350°C, but it does not address the sealant's poor oil resistance at high temperatures.

[0005] Therefore, in order to solve the above problems, the present invention urgently needs to provide a high temperature and oil resistant sealant based on silicone-epoxy hybrid resin and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin and a preparation method thereof, and to solve the technical problem that the sealant in the prior art cannot simultaneously meet the requirements of high-temperature resistance, oil resistance and high adhesion through the high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin and a preparation method thereof.

[0007] The present invention provides a high-temperature and oil-resistant sealant based on an organosilicon-epoxy hybrid resin. The sealant comprises, by weight, 100 parts of an organosilicon-epoxy hybrid polymer, 20-25 parts of modified boron nitride, 13-17 parts of modified silicon carbide, 8-10 parts of mica powder, 3-5 parts of graphene oxide, 25-30 parts of a curing agent, 0-13 parts of a hydroxyl-terminated nitrile rubber, and 1-2 parts of an antioxidant.

[0008] Preferably, the organosilicon-epoxy hybrid polymer is prepared by grafting hydroxyl-terminated polydimethylsiloxane with bisphenol A epoxy resin via a silane coupling agent.

[0009] Preferably, the silicone-epoxy hybrid polymer is prepared by the following steps:

[0010] According to parts by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane and 30-35 parts of bisphenol A epoxy resin are mixed under nitrogen protection, heated to 70-90° C., 2-3 parts of silane coupling agent are added dropwise, the temperature is raised to 120° C., and stirred for 3-4 hours to obtain a silicone-epoxy hybrid polymer.

[0011] Preferably, the modified boron nitride preparation steps include:

[0012] Add nano boron nitride powder into a reactor, heat it to 150°C in vacuum, dehydrate it for 2 hours, introduce perfluorooctyltriethoxysilane vapor into the reactor, and react it at 200°C for 4-6 hours to obtain modified boron nitride.

[0013] Preferably, the particle size of the nano boron nitride powder is 50 nm.

[0014] Preferably, the modified silicon carbide has a flaky structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1.

[0015] Preferably, the modified silicon carbide is obtained by wet ball milling grafting.

[0016] Preferably, the curing agent is methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methylhexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0017] Preferably, the mica powder is wet-process mica powder, and the particle size of the mica powder is 800-1250 mesh;

[0018] The diameter of graphene oxide sheets is 1-5 μm;

[0019] The acrylonitrile content in carboxyl-terminated nitrile rubber (CTBN) is greater than 22%;

[0020] The antioxidant is antioxidant 1010, and the purity of the antioxidant is ≥98%.

[0021] The present invention also provides a method for preparing a high-temperature and oil-resistant sealant based on the silicone-epoxy hybrid resin as described above, comprising the following steps:

[0022] Add the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raise the temperature to 70-90°C, add modified boron nitride, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add modified silicon carbide and mica powder, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add graphene oxide, and continue shearing until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80°C;

[0023] Cool the base material to 60℃, add hydroxy-terminated nitrile rubber, premix at low speed for 3-5 minutes, add curing agent and antioxidant, vacuum degassing, pre-cure at 70-90℃ for 50-70 minutes, heat to 140-160℃, and cure for 120-150 minutes.

[0024] The present invention provides a high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin and a preparation method thereof, which have the following improvements over the prior art:

[0025] 1. The high-temperature and oil-resistant sealant based on the organosilicon-epoxy hybrid resin provided by the present invention can be resistant to high temperatures and oil for a long time and has high bonding strength due to the mixture of organosilicon-epoxy hybrid polymer, modified boron nitride and modified silicon carbide. It can be used in industrial fields such as automobile engine cylinder heads, gearbox connectors, and high-temperature zone sealing rings of aircraft engines.

[0026] 2. The present invention provides a high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin. The silicone-epoxy hybrid polymer is prepared by grafting 100 parts of hydroxyl-terminated polydimethylsiloxane with bisphenol A epoxy resin through a silane coupling agent. The silane coupling agent acts as a molecular bridge, reacts with the epoxy resin through the epoxy group, and condenses the silanol end with the hydroxyl-terminated polydimethylsiloxane to construct a Si-O-Si and COC double network interpenetrating structure (IPN) through molecular entanglement to form a stable whole, effectively preventing the deformation or melting of a single material at high temperature, so that the material remains stable in a wider temperature range, and the heat resistance and toughness are simultaneously improved; in addition, the use of bisphenol A epoxy resin can improve the overall adhesion of the sealant.

[0027] 3. The high-temperature and oil-resistant sealant based on the silicone-epoxy hybrid resin provided by the present invention adopts the vapor deposition method to modify the nano-boron nitride with perfluorooctyltriethoxysilane, forming a single-molecule perfluoroalkyl layer on the surface of the nano-boron nitride, which can increase the contact angle from 35° to 152° (superoleophobicity) and triple the dispersion stability in engine oil (Zeta potential -52mV).

[0028] 4. The high-temperature and oil-resistant sealant based on the silicone-epoxy hybrid resin provided by the present invention adopts flaky silicon carbide to physically block the oil penetration path through its appearance design, thereby improving the oil resistance. Silicon carbide and modified boron nitride work synergistically, that is, modified boron nitride fills the gaps, and the layered structure of modified silicon carbide is used as a barrier to improve the permeability resistance, thereby solving the problems of the sealant's permeability resistance and bonding stability in a dynamic oil environment at 250°C. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] The present invention provides a high-temperature and oil-resistant sealant based on an organosilicon-epoxy hybrid resin. The sealant comprises, by weight, 100 parts of an organosilicon-epoxy hybrid polymer, 20-25 parts of modified boron nitride, 13-17 parts of modified silicon carbide, 8-10 parts of mica powder, 3-5 parts of graphene oxide, 25-30 parts of a curing agent, 0-13 parts of a hydroxyl-terminated nitrile rubber, and 1-2 parts of an antioxidant.

[0031] Specifically, the organosilicon-epoxy hybrid polymer is prepared by grafting hydroxyl-terminated polydimethylsiloxane with bisphenol A epoxy resin through a silane coupling agent.

[0032] Specifically, the preparation steps of silicone-epoxy hybrid polymer are:

[0033] According to parts by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane and 30-35 parts of bisphenol A epoxy resin are mixed under nitrogen protection, heated to 70-90° C., 2-3 parts of silane coupling agent are added dropwise, the temperature is raised to 120° C., and stirred for 3-4 hours to obtain a silicone-epoxy hybrid polymer.

[0034] Specifically, the steps for preparing modified boron nitride include:

[0035] Add nano boron nitride powder into a reactor, heat it to 150°C in vacuum, dehydrate it for 2 hours, introduce perfluorooctyltriethoxysilane vapor into the reactor, and react it at 200°C for 4-6 hours to obtain modified boron nitride.

[0036] Specifically, the particle size of the nano boron nitride powder is 50 nm.

[0037] Specifically, the modified silicon carbide has a flaky structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1.

[0038] Specifically, the modified silicon carbide is obtained by wet ball milling grafting.

[0039] Specifically, the wet ball milling grafting process is:

[0040] Silicon carbide and γ-aminopropyltriethoxysilane (KH-550) were added to a mixed solution of ethanol and water, ball-milled for 4 h (zirconia balls, ball-to-material ratio 5:1, rotation speed 300 rpm), dried at 120°C, and sieved (D50 = 15 μm); the mass ratio of silicon carbide to γ-aminopropyltriethoxysilane was 10:3; the mass ratio of ethanol to water was 9:1.

[0041] By modifying silicon carbide with KH-550, the epoxy group grafting amount reaches 1.8mmol / g (verified by titration); the shear strength of the resin-filler interface is improved.

[0042] Specifically, the curing agent is methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methylhexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0043] By compounding methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole in a ratio of 4:1, the curing speed can be increased and the conversion rate is high.

[0044] Specifically, the mica powder is wet-process mica powder with a particle size of 800-1250 mesh; the flake diameter of the graphene oxide is 1-5 μm; the acrylonitrile content in the carboxyl-terminated nitrile rubber (CTBN) is greater than 22%; and the antioxidant is antioxidant 1010 with an antioxidant purity of ≥98%.

[0045] The present invention also provides a method for preparing a high-temperature and oil-resistant sealant based on the silicone-epoxy hybrid resin as described above, comprising the following steps:

[0046] Add the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raise the temperature to 70-90°C, add modified boron nitride, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add modified silicon carbide and mica powder, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add graphene oxide, and continue shearing until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80°C;

[0047] Cool the base material to 60°C, add hydroxy-terminated nitrile rubber, premix at low speed for 3-5 minutes, add curing agent and antioxidant, vacuum degassing, control the endpoint viscosity at 24000-26000mPa·s (25°C), precure at 70-90°C for 50-70 minutes, heat to 140-160°C, and cure for 120-150 minutes.

[0048] The pressure of vacuum degassing is -0.09MPa to -0.1MPa, and the time of vacuum degassing is 30min to 50min.

[0049] The high-temperature and oil-resistant sealant based on the organosilicon-epoxy hybrid resin provided by the present invention can be resistant to high temperatures and oils for a long time and has high bonding strength due to the mixing of organosilicon-epoxy hybrid polymer, modified boron nitride and modified silicon carbide. It can be used in industrial fields such as automobile engine cylinder heads, transmission connectors, and high-temperature zone sealing rings of aircraft engines.

[0050] The present invention provides a high-temperature and oil-resistant sealant based on an organosilicon-epoxy hybrid resin. The organosilicon-epoxy hybrid polymer is prepared by grafting 100 parts of hydroxyl-terminated polydimethylsiloxane with bisphenol A epoxy resin via a silane coupling agent. The silane coupling agent acts as a molecular bridge, reacts with the epoxy resin via epoxy groups, and condenses the silanol ends with the hydroxyl-terminated polydimethylsiloxane to construct an interpenetrating Si-O-Si and COC double network (IPN) structure. The structure forms a stable whole through molecular entanglement, effectively preventing deformation or melting of a single material at high temperatures, allowing the material to remain stable over a wider temperature range, and simultaneously improving heat resistance and toughness. Furthermore, the use of bisphenol A epoxy resin can improve the overall adhesion of the sealant.

[0051] The high-temperature and oil-resistant sealant based on the organosilicon-epoxy hybrid resin provided by the present invention adopts the vapor deposition method to modify nano-boron nitride with perfluorooctyltriethoxysilane, forming a single-molecule perfluoroalkyl layer on the surface of the nano-boron nitride, which can increase the contact angle from 35° to 152° (superoleophobicity) and triple the dispersion stability in engine oil (Zeta potential -52mV).

[0052] The high-temperature and oil-resistant sealant based on the organosilicon-epoxy hybrid resin provided by the present invention adopts flaky silicon carbide to physically block the oil penetration path through its appearance design, thereby improving the oil resistance. The silicon carbide and modified boron nitride work synergistically, that is, the modified boron nitride fills the gaps, and the layered structure of the silicon carbide is used as a barrier to improve the permeation resistance, thereby solving the problems of the sealant's permeation resistance and bonding stability in a dynamic oil environment at 250°C.

[0053] Example 1

[0054] The high-temperature and oil-resistant sealant based on silicone-epoxy hybrid resin includes, by weight, 100 parts of silicone-epoxy hybrid polymer, 20 parts of modified boron nitride, 13 parts of modified silicon carbide, 8 parts of mica powder, 3 parts of graphene oxide, 25 parts of curing agent and 1.5 parts of antioxidant.

[0055] The preparation steps of high temperature resistant and oil resistant sealant are as follows:

[0056] 101) adding the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raising the temperature to 80° C., adding modified boron nitride, and high-speed shearing at 8000 rpm for 10-15 minutes, adding modified silicon carbide and mica powder, and high-speed shearing at 8000 rpm for 10 minutes, adding graphene oxide, and continuing shearing at 8000 rpm until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80° C.;

[0057] 102) Cool the base material to 60°C, add curing agent and antioxidant 1010, vacuum degassing, pre-cure at 80°C for 60 minutes, heat to 150°C, and cure for 120 minutes.

[0058] The pressure of vacuum degassing was -0.095 MPa, and the vacuum degassing time was 30 min.

[0059] Preparation steps of silicone-epoxy hybrid polymer:

[0060] According to parts by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane and 33 parts of bisphenol A epoxy resin were mixed under nitrogen protection, heated to 80°C, 2.5 parts of silane coupling agent were added dropwise, and the temperature was raised to 120°C at 5°C / min. The mixture was stirred for 3 hours (rotation speed 300 rpm) to obtain a silicone-epoxy hybrid polymer.

[0061] In this embodiment, the steps of preparing modified boron nitride include:

[0062] Nano boron nitride powder was added to a reactor, heated to 150°C under vacuum, and dehydrated for 2 hours. Perfluorooctyltriethoxysilane vapor was introduced into the reactor and reacted at 200°C for 4 hours to obtain modified boron nitride.

[0063] The particle size of the nano boron nitride powder in this embodiment is 50 nm.

[0064] The modified silicon carbide of this embodiment has a flaky structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1. The modified silicon carbide is obtained by wet ball milling grafting.

[0065] The curing agent of this embodiment is methyl hexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methyl hexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0066] The mica powder in this embodiment is wet-process mica powder with a particle size of 800-1250 mesh, purchased from Lingshou County Huajing Mica; the graphene oxide flake diameter is 1-5 μm, purchased from Ningbo Moxi Technology Co., Ltd.; the antioxidant is antioxidant 1010 with an antioxidant purity of ≥98%, purchased from BASF.

[0067] The properties of the high-temperature and oil-resistant sealant obtained in this example are shown in Table 1. The tensile strength and elongation at break were tested according to GB / T 528, using type 1 dumbbell specimens. The mass loss rate at 250°C (500 hours) was tested according to GB / T 1735, with curing at 250°C for 500 hours. The volume change in engine oil at 120°C (168 hours) was tested according to ASTM D471, using 15W-40 mineral engine oil, with curing at 120°C for 168 hours. The tensile shear strength and post-high-temperature tensile shear strength retention were tested according to GB / T 7124, using 45# steel as the substrate, which was sandblasted. The post-high-temperature tensile shear strength retention also required curing at 250°C for 24 hours.

[0068] Example 2

[0069] The high-temperature and oil-resistant sealant based on the silicone-epoxy hybrid resin includes, by weight, 100 parts of silicone-epoxy hybrid polymer, 25 parts of modified boron nitride, 17 parts of modified silicon carbide, 10 parts of mica powder, 5 parts of graphene oxide, 30 parts of curing agent and 2 parts of antioxidant.

[0070] The steps for preparing the high-temperature resistant and oil-resistant sealant in this embodiment are the same as those in Example 1.

[0071] The preparation steps of the organosilicon-epoxy hybrid polymer are the same as those in Example 1.

[0072] The preparation steps of modified boron nitride are the same as those in Example 1.

[0073] The particle size of the nano boron nitride powder in this embodiment is 50 nm.

[0074] The modified silicon carbide of this embodiment has a flake structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1.

[0075] The modified silicon carbide of this embodiment is obtained by wet ball milling grafting.

[0076] The curing agent of this embodiment is methyl hexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methyl hexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0077] The mica powder in this embodiment is wet-process mica powder, and the particle size of the mica powder is 800-1250 mesh; the diameter of the graphene oxide flakes is 1-5 μm; the antioxidant is antioxidant 1010, and the purity of the antioxidant is ≥98%.

[0078] The testing method for the high temperature and oil resistant sealant based on the organosilicon-epoxy hybrid resin obtained in this example is the same as that in Example 1. The performance is shown in Table 1.

[0079] Example 3

[0080] The high-temperature and oil-resistant sealant based on silicone-epoxy hybrid resin includes, by weight, 100 parts of silicone-epoxy hybrid polymer, 22 parts of modified boron nitride, 15 parts of modified silicon carbide, 9 parts of mica powder, 4 parts of graphene oxide, 28 parts of curing agent, 10 parts of terminal hydroxyl nitrile rubber and 1 part of antioxidant.

[0081] The preparation steps of high temperature resistant and oil resistant sealant are as follows:

[0082] 301) adding the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raising the temperature to 70° C., adding modified boron nitride, and high-speed shearing at 7000 rpm for 10 min, adding modified silicon carbide and mica powder, and high-speed shearing at 7000 rpm for 10 min, adding graphene oxide, and continuing shearing until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80° C.;

[0083] 302) Cool the base material to 60°C, add the hydroxy-terminated nitrile rubber, premix at low speed for 4 minutes, add the curing agent and antioxidant, degas in vacuum, precure at 70°C for 70 minutes, heat to 160°C, and cure for 150 minutes.

[0084] The pressure of vacuum degassing was -0.095 MPa, and the vacuum degassing time was 30 min.

[0085] Preparation steps of the organosilicon-epoxy hybrid polymer of this embodiment:

[0086] According to parts by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane and 35 parts of bisphenol A epoxy resin were mixed under nitrogen protection, heated to 90°C, 3 parts of silane coupling agent were added dropwise, the temperature was raised to 120°C, and stirred for 3.5 hours to obtain a silicone-epoxy hybrid polymer.

[0087] Specifically, the steps for preparing modified boron nitride include:

[0088] Add nano boron nitride powder into a reactor, heat it to 150°C in vacuum, dehydrate it for 2 hours, introduce perfluorooctyltriethoxysilane vapor into the reactor, and react it at 200°C for 6 hours to obtain modified boron nitride.

[0089] The particle size of the nano boron nitride powder in this embodiment is 50 nm.

[0090] The modified silicon carbide of this embodiment has a flake structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1.

[0091] The modified silicon carbide of this embodiment is obtained by wet ball milling grafting.

[0092] The curing agent of this embodiment is methyl hexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methyl hexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0093] The mica powder in this embodiment is wet-process mica powder with a particle size of 800-1250 mesh; the flake diameter of graphene oxide is 1-5 μm; the acrylonitrile content in the carboxyl-terminated nitrile rubber (CTBN) is greater than 22%; and the antioxidant is antioxidant 1010 with an antioxidant purity of ≥98%.

[0094] The testing method of the high temperature and oil resistant sealant based on the organosilicon-epoxy hybrid resin obtained in this example is the same as that in Example 1. The performance is shown in Table 1.

[0095] Example 4

[0096] The high-temperature and oil-resistant sealant based on silicone-epoxy hybrid resin includes, by weight, 100 parts of silicone-epoxy hybrid polymer, 22 parts of modified boron nitride, 15 parts of modified silicon carbide, 8 parts of mica powder, 3 parts of graphene oxide, 27 parts of curing agent, 7 parts of terminal hydroxyl nitrile rubber and 1 part of antioxidant.

[0097] The preparation steps of high temperature resistant and oil resistant sealant are as follows:

[0098] 401) adding the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raising the temperature to 90° C., adding modified boron nitride, and high-speed shearing at 9000 rpm for 10 min, adding modified silicon carbide and mica powder, and high-speed shearing at 9000 rpm for 10 min, adding graphene oxide, and continuing shearing until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80° C.;

[0099] 402) Cool the base material to 60°C, add the hydroxy-terminated nitrile rubber, premix at low speed for 5 minutes, add the curing agent and antioxidant, degas in vacuum, precure at 80°C for 50 minutes, heat to 160°C, and cure for 140 minutes.

[0100] The pressure of vacuum degassing was -0.095 MPa, and the vacuum degassing time was 30 min.

[0101] The steps for preparing the organosilicon-epoxy hybrid polymer are the same as those in Example 1.

[0102] The preparation steps of modified boron nitride are the same as those in Example 1.

[0103] The particle size of the nano boron nitride powder in this embodiment is 50 nm.

[0104] The modified silicon carbide of this embodiment has a flake structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:1.

[0105] The modified silicon carbide of this embodiment is obtained by wet ball milling grafting.

[0106] The curing agent of this embodiment is methyl hexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methyl hexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:1.

[0107] The mica powder in this embodiment is wet-process mica powder with a particle size of 800-1250 mesh; the flake diameter of graphene oxide is 1-5 μm; the acrylonitrile content in the carboxyl-terminated nitrile rubber (CTBN) is greater than 22%; and the antioxidant is antioxidant 1010 with an antioxidant purity of ≥98%.

[0108] The high temperature and oil resistant sealant based on the organosilicon-epoxy hybrid resin obtained in this example was tested in the same manner as in Example 1. The performance is shown in Table 1.

[0109] Comparative Example 1

[0110] The organic silicone sealant comprises, by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane, 1.5 parts of hexamethyldisilazane, 15 parts of fumed silica, 15 parts of boron nitride, 15 parts of silicon nitride, 8 parts of methyl tributylidene oxime silane, 0.5 parts of dibutyltin dilaurate and 2 parts of vinyltrimethoxysilane.

[0111] The preparation steps are:

[0112] D101) Hydroxyl-terminated polydimethylsiloxane was added to a planetary stirred tank and heated to 80°C; vacuum dehydration was performed (-0.09 MPa, 30 min); hexamethyldisilazane was added and stirred at low speed for 10 min; boron nitride was added in portions and dispersed at high speed (6000 rpm) for 20 min; silicon nitride was added and dispersed at high speed (6000 rpm) for 20 min; fumed silica was added in an amount of 5 parts each time and dispersed at high speed for 10 min each time;

[0113] D102) crosslinking system was added, the temperature was lowered to 40°C, and methyl tributylidene oxime silane, dibutyltin dilaurate, and vinyltrimethoxysilane were added; the mixture was stirred at a low speed (500 rpm) for 15 min under nitrogen protection; vacuum degassing (-0.09 MPa, 40 min) was performed, and the mixture was cured at 23°C / 50% RH to obtain a silicone sealant.

[0114] The testing method of the organosilicon sealant obtained in this comparative example is the same as that of Example 1, and the performance is shown in Table 1.

[0115] Comparative Example 1 is a traditional silicone sealant, in which boron nitride and silicon nitride are added to a hydroxyl-terminated polydimethylsiloxane system, but the boron nitride and silicon nitride are not modified. As can be seen from Table 1, the oil resistance and high temperature resistance of the silicone sealant obtained in Comparative Example 1 are much lower than those of Examples 1, 2, 3, and 4.

[0116] Comparative Example 2

[0117] The only difference between this comparative example and Example 1 is that unmodified boron nitride and unmodified silicon carbide are used.

[0118] The test method of the sealant obtained in this comparative example is the same as that of Example 1, and the performance is shown in Table 1.

[0119] In this comparative example, since the boron nitride is not modified, the surface of the boron nitride is lipophilic, and small molecule engine oil can more easily penetrate into the filler / resin cross section, and the boron nitride may even agglomerate inside, resulting in more significant swelling.

[0120] In this comparative example, since unmodified silicon carbide is added, the surface of silicon carbide contains hydrophilic groups (-OH), which have weak interface bonding with the hydrophobic resin (SERP), low stress transfer efficiency, and reduced tensile strength.

[0121] The modified silicon carbide used in Example 1 has a sheet structure with a diameter-to-thickness ratio of 10:1, which can extend the oil penetration path (the "maze effect" reduces the penetration rate by 3 times) and improve the overall oil resistance.

[0122] Modified silicon carbide, with KH-560 silane coupling agent grafted on the surface, forms a chemical bond with SERP to inhibit agglomeration.

[0123] Compared with Example 1, the volume change (%) of the 120°C engine oil (168h) in this comparative example is significantly increased.

[0124] Comparative Example 3

[0125] The only difference between this comparative example and Example 1 is that the curing agent is 25 parts of methylhexahydrophthalic anhydride (without adding EMI-24 imidazole accelerator).

[0126] The testing method of the organosilicon sealant obtained in this comparative example is the same as that of Example 1, and the performance is shown in Table 1.

[0127] The sealant obtained in Comparative Example 3 did not cure completely, with a DSC conversion rate of 72%. As can be seen in Table 1, using only the anhydride curing agent (MHHPA) without the imidazole accelerator resulted in a slow and difficult-to-complete cure reaction, especially at relatively low temperatures (80°C pre-curing). The lack of an accelerator resulted in an incomplete crosslinking network, significantly impacting overall performance.

[0128] Comparative Example 4

[0129] The epoxy adhesive comprises, by weight, 100 parts of bisphenol A epoxy resin, 85 parts of methyltetrahydrophthalic anhydride and 1 part of benzyldimethylamine.

[0130] The preparation steps include:

[0131] D401) Mix bisphenol A epoxy resin and methyltetrahydrophthalic anhydride at 60°C (500 rpm, 10 min); cool to 40°C, add benzyldimethylamine, and stir at low speed (300 rpm, 5 min) to avoid bubbles; cool to 25°C, and degas under vacuum at -0.09 MPa for 20 min.

[0132] D402) pre-curing at 120°C for 120 min, heating to 150°C at a rate of 2°C / min and curing for another 120 min to obtain epoxy adhesive.

[0133] The test method of the obtained epoxy adhesive is the same as that of Example 1, and the performance is shown in Table 1.

[0134] This comparative example is a traditional epoxy adhesive. As can be seen from Table 1, although the strength at room temperature is high, the high temperature resistance drops sharply due to molecular chain degradation, and its high temperature resistance and engine oil resistance are extremely poor.

[0135] Comparative Example 5

[0136] Compared with Example 1, this comparative example replaces the organosilicon-epoxy hybrid polymer with an equal amount of bisphenol A epoxy resin (according to the epoxy ratio in the organosilicon-epoxy hybrid polymer), and the other components and processes remain unchanged.

[0137] The data from Comparative Example 5 and Example 1 demonstrate that the interpenetrating network structure formed by the hydroxyl-terminated polydimethylsiloxane (PDMS) and bisphenol A epoxy resin in Example 1, via KH-560, is a key factor in improving both high-temperature and engine oil resistance. Pure epoxy resin systems, lacking high-energy Si-O-Si bonds and flexible siloxane chains, experience severe degradation and swelling in high-temperature engine oil environments.

[0138] Table 1 Performance parameters of high temperature and oil resistant sealants based on silicone-epoxy hybrid resins

[0139]

[0140]

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin, characterized by: Calculated by weight, the composition includes 100 parts of organosilicon-epoxy hybrid polymer, 20-25 parts of modified boron nitride, 13-17 parts of modified silicon carbide, 8-10 parts of mica powder, 3-5 parts of graphene oxide, 25-30 parts of curing agent, 0-13 parts of terminal hydroxyl nitrile rubber and 1-2 parts of antioxidant.

2. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: The organosilicon-epoxy hybrid polymer is prepared by grafting reaction of hydroxyl-terminated polydimethylsiloxane and bisphenol A epoxy resin through a silane coupling agent.

3. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 2, characterized in that: Preparation steps of silicone-epoxy hybrid polymer: According to parts by weight, 100 parts of hydroxyl-terminated polydimethylsiloxane and 30-35 parts of bisphenol A epoxy resin are mixed under nitrogen protection, heated to 70-90°C, 2-3 parts of silane coupling agent are added dropwise, the temperature is raised to 120°C, and stirred for 3-4 hours to obtain a silicone-epoxy hybrid polymer.

4. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: The preparation steps of modified boron nitride include: Add nano boron nitride powder into a reactor, heat it to 150°C in vacuum, dehydrate it for 2 hours, introduce perfluorooctyltriethoxysilane vapor into the reactor, and react it at 200°C for 4-6 hours to obtain modified boron nitride.

5. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 4, characterized in that: The particle size of the nano boron nitride powder is 50 nm.

6. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: The modified silicon carbide has a flake structure, and the diameter-to-thickness ratio of the modified silicon carbide is 10:

1.

7. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: Modified silicon carbide was obtained by wet ball milling grafting.

8. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: The curing agent is methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole, and the mass ratio of methylhexahydrophthalic anhydride to 2-ethyl-4-methylimidazole is 4:

1.

9. The high temperature and oil resistant sealant based on silicone-epoxy hybrid resin according to claim 1, characterized in that: The mica powder is wet-process mica powder with a particle size of 800-1250 mesh; The diameter of graphene oxide sheets is 1-5 μm; The acrylonitrile content in carboxyl-terminated nitrile rubber (CTBN) is greater than 22%; The antioxidant is antioxidant 1010, and the purity of the antioxidant is ≥98%.

10. A method for preparing a high-temperature and oil-resistant sealant based on a silicone-epoxy hybrid resin according to any one of claims 1 to 9, characterized in that: The steps include: Add the organosilicon-epoxy hybrid polymer to a high-speed shear emulsifier, raise the temperature to 70-90°C, add modified boron nitride, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add modified silicon carbide and mica powder, and high-speed shear at 7000-9000 rpm for 10-15 minutes, add graphene oxide, and continue shearing until the system is uniformly dispersed to obtain a base material, wherein the base material has a viscosity of 15000-20000 mPa·s at 80°C; Cool the base material to 60℃, add hydroxy-terminated nitrile rubber, premix at low speed for 3-5 minutes, add curing agent and antioxidant, vacuum degassing, pre-cure at 70-90℃ for 50-70 minutes, heat to 140-160℃, and cure for 120-150 minutes.

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